Longitudinal assessment of auditory and ocular dysfunction associated with hyperglycemia in Zucker diabetic fatty rats

Longitudinal assessment of auditory and ocular dysfunction associated with hyperglycemia in Zucker diabetic fatty rats | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Longitudinal assessment of auditory and ocular dysfunction associated with hyperglycemia in Zucker diabetic fatty rats Jin Li, Bo Liu This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8675794/v1 This work is licensed under a CC BY 4.0 License Status: Under Revision Version 1 posted 12 You are reading this latest preprint version Abstract Diabetic retinopathy is a well-recognized microvascular complication of diabetes mellitus; however, diabetes-associated auditory dysfunction remains less well characterized, particularly with respect to its longitudinal progression. In this study, we performed a longitudinal assessment of ocular and auditory function in Zucker Diabetic Fatty (ZDF) rats and examined their relationships with chronic hyperglycemia. Forty male ZDF (fa/fa) rats and thirty-two age-matched control rats (fa/–) were evaluated at 12, 20, 28, and 36 weeks of age. Ocular changes were assessed using slit-lamp microscopy and fluorescein fundus angiography, while auditory function was evaluated using auditory brainstem response (ABR) testing across frequencies from 4 to 32 kHz. Fasting blood glucose levels were monitored throughout the study. ZDF rats developed sustained hyperglycemia from 12 weeks of age onward. Elevated ABR thresholds were first observed at high frequencies (32 kHz) at 12 weeks, followed by progressive involvement of mid frequencies (16 and 24 kHz) at 20 weeks and all tested frequencies (4–32 kHz) at 28–36 weeks. Retinal vascular leakage and cataract formation increased with disease duration. Fasting blood glucose levels showed strong positive associations with ABR thresholds across all frequencies (r = 0.72–0.85, p < 0.01) and with cataract severity. These findings show that chronic hyperglycemia in ZDF rats is accompanied by progressive auditory and ocular dysfunction, providing longitudinal functional evidence of multisystem sensory impairment in a diabetic animal model. Health sciences/Diseases Health sciences/Endocrinology Health sciences/Medical research Diabetes mellitus Hearing impairment Auditory brainstem response Diabetic retinopathy Cataract Microangiopathy Zucker diabetic fatty rat Figures Figure 1 Figure 2 Figure 3 1. Introduction Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia resulting from defects in insulin secretion, insulin resistance, or both. Chronic hyperglycemia leads to progressive microvascular and neural damage, causing complications such as retinopathy, nephropathy, and neuropathy. Among these, diabetic retinopathy (DR) affects nearly one-third of diabetic patients and remains a leading cause of vision loss worldwide[ 1 ]. Despite its high prevalence and clinical burden, diabetic ocular disease has been extensively studied. Nevertheless, the selection of animal models that accurately replicate human pathology is crucial for translational research. Emerging evidence suggests that diabetic microangiopathy and metabolic dysregulation also affect the auditory system. Our previous study[ 2 ] reported a 67.3% prevalence of tinnitus and hearing loss in diabetic patients. A recent meta-analysis[ 3 ] revealed similar rates ranging from 40.6% to 71.9%, consistent with our findings. While diabetic hearing loss (DHL) receives less attention than DR or nephropathy, it significantly impairs patients’ communication, cognition, and quality of life. The Zucker Diabetic Fatty (ZDF) rat is a widely used model of type 2 diabetes, featuring obesity, insulin resistance, and spontaneous hyperglycemia, which closely mirrors human metabolic dysfunction[ 4 ]. Studies[ 5 , 6 ]have demonstrated microvascular injury, oxidative stress, mitochondrial dysfunction, and neurodegeneration in both the retina and cochlea of diabetic animals, contributing to cataracts, DR, and sensorineural hearing loss. Owing to its sensitivity, reproducibility, and noninvasiveness, auditory testing is ideal for detecting early diabetic complications[ 2 ]. However, few longitudinal studies have simultaneously assessed the temporal progression of ocular and auditory deficits in the same diabetic model. Investigating the temporal relationships among hyperglycemia, ocular abnormalities, and hearing loss can provide insights into shared mechanisms of diabetic systemic complications and inform preventive strategies. This study aimed to systematically evaluate ocular and auditory functional changes in ZDF rats and age-matched controls at multiple time points. Cataracts and retinal pathology were assessed using slit-lamp examination and fluorescein angiography, while hearing thresholds were measured by auditory brainstem response (ABR). We further analyzed correlations between fasting blood glucose levels and sensory impairments to elucidate the mechanisms underlying diabetes-related sensory dysfunction. 2. Materials and Methods 2.1 Animals Forty male Zucker Diabetic Fatty (ZDF, fa/fa) rats and thirty-two age-matched control rats (fa/-) were obtained from Vital River Laboratory Animal Technology Co., Ltd. (Beijing, China). All experiments were approved by the Capital Medical University Animal Ethics Committee (Approval No. AEEI-2018-211) and conducted in accordance with the NIH Guide for the Care and Use of Laboratory Animals (2006). Rats were randomly assigned to four age groups (12, 20, 28, and 36 weeks). Auditory brainstem response (ABR) testing was performed at 8 weeks of age to establish baseline hearing thresholds. At each time point, slit-lamp microscopy, fluorescein fundus angiography, and ABR were conducted under 1% pentobarbital sodium anesthesia (0.6 mL/100 g, i.p.). At the end of the experimental procedures, rats were euthanized humanely under deep anesthesia. Deep anesthesia was induced by intraperitoneal administration of 1% pentobarbital sodium (1.5 mL/100 g, i.p). Death was confirmed by the absence of respiratory movements and cardiac activity prior to tissue disposal. All procedures were performed in accordance with institutional and national guidelines for the care and use of laboratory animals. 2.2 Blood Glucose Measurement Fasting blood glucose was measured every two weeks using a glucometer with tail vein samples collected after a 12-hour fast. 2.3 Slit-Lamp Examination After pupil dilation with 1% tropicamide, lens opacity was examined using a slit-lamp microscope (Haag-Streit AG, USA) and graded as follows: Grade 0 : clear lens without vacuoles; Grade 1 : anterior vacuoles covering less than 50% of the lens surface; Grade 2 : partial vacuole loss with cortical opacity; Grade 3 : cortical and nuclear opacity; Grade 4 : mature cataract. 2.4 Fluorescein Angiography Rats without cataracts underwent fundus fluorescein angiography using the OPTO-RIS imaging system (Optoprobe, Canada). Following anesthesia, rats received an intraperitoneal injection of 0.1 mL of 2.5% sodium fluorescein (Wuzhou Pharmaceutical Co., China). Images were captured after injection to assess retinal vascular leakage intensity. 2.5 Auditory Brainstem Response (ABR) Testing Rats were placed supine on a temperature-controlled platform. Subdermal electrodes were positioned at the vertex (active recording), ipsilateral mastoid (reference), and contralateral mastoid (ground). Measurements were conducted using the SmartEP system (TDT Rz6, Intelligent Hearing Systems, Miami, FL, USA) inside a soundproof chamber. Tone-burst stimuli at frequencies of 4, 8, 16, 24, and 32 kHz (39.1 clicks/s) were generated, with 2-cycle rise/fall times and 16 ms analysis windows (averaged over 1,024 sweeps). The sound intensity started at 90 dB SPL and decreased in 10 dB steps, followed by 5 dB steps. The minimum stimulus intensity eliciting a visible wave II was defined as the threshold. 3. Results 3.1 Blood Glucose At 8 weeks, no significant differences in average blood glucose levels were observed between the experimental and control groups. The experimental group exhibited significantly elevated blood glucose compared to the control group at all subsequent time points (12, 20, 28, and 36 weeks) (Table 1 ). Table 1 Comparison of blood glucose values between the experimental group and the control group. Diabetes group (n = 20) Control group (n = 16) P -value 8 weeks# 4.95 ± 0.28 4.91 ± 0.12 >0.05 12 weeks# 15.23 ± 6.69 5.05 ± 0.23 < 0.001*** 20 weeks# 22.19 ± 3.39 6 ± 0.55 < 0.001*** 28 weeks# 27.13 ± 5.53 6.05 ± 0.64 < 0.001*** 36 weeks# 32.83 ± 1.49 6.98 ± 0.75 < 0.001*** *P < 0.05, ***P < 0.001。 #blood glucose values(mmol/l) 3.2 Ophthalmic complications Early microvascular lesions in the experimental group primarily included retinal vascular leakage and microangiomas. As the disease progressed, cataract formation became the predominant ophthalmic complication (Fig. 1 A). Figure 1 B illustrates the retinal vascular leakage across groups. Ophthalmic complications were defined as the presence of retinal vascular leakage or cataracts graded I-IV. The number of eyes with complications in the experimental group showed a significant increase at 12, 20, 28, and 36 weeks compared to controls (Table 2 ). Additionally, cataract severity in the experimental group progressively worsened at all time points (Fig. 1 C). The correlation between fasting blood glucose and cataract severity is shown in Fig. 1 D, demonstrating a positive association between hyperglycemia and ocular pathology. These findings indicate that ophthalmic complications in ZDF rats exhibit a progressive deterioration with disease duration. Table 2 Comparison of the number of eyeballs with ophthalmic complications between the experimental group and the control group. Eyes Number in diabetes group (n = 40) Eyes Number in control group (n = 32) P -value 12 weeks OC n (%), RVL n (%), CF n (%) 20 (50), 20 (50),0(0) 0 (0), 0 (0), 0 (0) 0.001* 20 weeks OC n (%), RVL n (%), CF n (%) 32 (80),8(20),24(60) 0 (0), 0 (0), 0 (0) < 0.001 *** 28 weeks OC n (%), RVL n (%), CF n (%) 36 (90),8(20),28(70) 4 (12.5), 4 (12.5), 0 (0) < 0.001 *** 36 weeks OC n (%), RVL n (%), CF n (%) 40 (100),0(0),40(100) 8 (25), 4 (12.5), 4 (12.5) < 0.001 *** Ophthalmic complications: OC, Retinal Vascular Leakage: RVL, Cataract Formation: CF. *P < 0.05, ***P < 0.001。 3.3 Auditory Function Baseline ABR thresholds at 8 weeks showed no significant differences between groups. At 12 weeks, the experimental group displayed elevated thresholds at 32 kHz. By 20 weeks, ABR thresholds increased at 4, 16, 24, and 32 kHz. At 28–36 weeks, significant threshold shifts occurred across all tested frequencies (4–32 kHz) (Fig. 2 ). This progression, which involves a transition from high-frequency hearing loss to pan-frequency impairment, mimics the clinical pattern observed in diabetic hearing loss. 3.4 Correlation Between Blood Glucose and ABR Thresholds Fasting glucose levels were strongly and positively correlated with ABR thresholds at all frequencies (4–32 kHz) (Fig. 3 ), indicating that auditory dysfunction severity parallels hyperglycemic progression. 4. Discussion In this longitudinal study, we characterized the temporal progression of auditory and ocular dysfunction in Zucker Diabetic Fatty (ZDF) rats, a widely used model of type 2 diabetes mellitus. By integrating repeated functional assessments with metabolic monitoring, we observed that sustained elevations in fasting blood glucose were accompanied by progressive impairments in both auditory and visual systems. These findings provide longitudinal functional evidence that chronic metabolic dysregulation is associated with multisystem sensory dysfunction in a diabetic animal model. A notable observation was the early elevation of auditory brainstem response (ABR) thresholds at high frequencies, which emerged as early as 12 weeks of age. This functional change occurred concurrently with the appearance of retinal vascular leakage, suggesting that auditory and retinal alterations may develop in parallel during the early stages of diabetes. The preferential involvement of high-frequency hearing at earlier time points is consistent with clinical and experimental observations indicating that the basal region of the cochlea is particularly susceptible to metabolic and vascular stress. This corroborates clinical observations that high-frequency sensorineural hearing loss often precedes or parallels early diabetic retinopathy[ 7 , 8 ]. A critical finding of this study was the sequential progression of auditory dysfunction, characterized by a distinct frequency-dependent pattern. The initial detection of significant hearing loss exclusively at 32 kHz as early as 12 weeks underscores the heightened susceptibility of the basal cochlear turn to diabetic injury. The basal cochlear turn, crucial for high-frequency sound processing, is metabolically demanding and highly dependent on stria vascularis microcirculation, rendering it susceptible to systemic metabolic stress[ 5 ]. The extension of hearing impairment to mid frequencies by 20 weeks, followed by pan-frequency involvement at 28–36 weeks, indicates a time-dependent pattern of cochlear degeneration. Such progression is compatible with a base-to-apex distribution of cochlear pathology along the tonotopic gradient and accords with clinical evidence in diabetes, where sensorineural hearing loss commonly begins at high frequencies and progressively involves lower frequencies as disease duration increases[ 9 ]. The underlying process is likely driven by the cumulative effects of diabetes-related microvascular impairment, chronic oxidative stress, and gradual neural degeneration, leading to increasingly diffuse cochlear injury[ 10 ]. This pattern of progression supports the use of frequency-dependent changes as a basis for staging diabetic hearing loss and for defining windows for early intervention. The robust positive correlation between fasting glucose levels and ABR thresholds furthers the hypothesis that hyperglycemia-driven metabolic perturbations are pivotal to cochlear dysfunction. The progression of canonical diabetic microvascular pathology, characterized by basement membrane thickening, endothelial injury, pericyte loss, and capillary rarefaction[ 11 ], is driven by chronic hyperglycemia. These pathological changes may contribute to impaired cochlear perfusion and disruption of the endocochlear potential[ 12 ]. These changes likely initiate downstream damage to hair cells and spiral ganglion neurons, culminating in progressive sensorineural hearing loss[ 13 ]. Parallel to cochlear dysfunction, ZDF rats exhibited progressive ocular abnormalities, including retinal vascular leakage and cataract formation. Fluorescein angiography delineated retinal microvascular leakage, an early marker of diabetic retinopathy, indicative of blood–retinal barrier breakdown, endothelial compromise, and pericyte dropout[ 14 ]. Our results demonstrate that cataract onset in ZDF rats occurred at 20 weeks of age, Cataract development strongly correlated with hyperglycemia, reflecting osmotic stress via the polyol pathway, oxidative injury, and protein glycation[ 15 ]. With both incidence and severity escalating progressively thereafter. The presence of lens opacities obstructed retinal evaluation via fluorescein angiography, precluding longitudinal monitoring of diabetes‑induced microvascular changes in the retina with this imaging modality. Therefore, the progression of ocular complications in ZDF rats was assessed by quantifying cataract development as a surrogate measure. In contrast, owing to its noninvasive characteristics and high sensitivity, ABR provided a stable, noninvasive, and repeatable functional measure that remained feasible throughout the disease course, highlighting its utility for longitudinal monitoring when ocular imaging is compromised. The solid correlation between glycemic load and the severity of both cataract and hearing loss validates cumulative hyperglycemia as a primary driver of multisystem sensory degeneration [16] . The concurrent progression of auditory and ocular dysfunction observed in this study suggests that multiple sensory systems may be similarly affected during chronic diabetes. While the present findings do not establish shared mechanisms, they are consistent with the concept that systemic metabolic dysregulation is associated with widespread functional alterations [ 17 , 18 ]. Our results validate the ZDF rat as an effective model for studying diabetes-induced sensory organ dysfunction. The model replicates key features of human diabetic retinopathy and hearing loss, including early microvascular deficits, progressive degeneration, and strong dependence on glycemic load[ 19 ], which supports its utility for preclinical testing of interventions targeting metabolic stress, oxidative injury, or microvascular protection. While this longitudinal investigation systematically delineates the temporal progression and reciprocal relationships among hyperglycemia, cataractogenesis, and auditory deterioration, thereby demonstrating their coordinated progression within a diabetic model, the study nevertheless exhibits several limitations that warrant further scholarly inquiry. The lack of histological confirmation requires detailed histological analyses of the stria vascularis, cochlear microvasculature, and retinal vessels to establish structural correlates of the observed functional decline. In addition, molecular investigations quantifying oxidative stress, mitochondrial dysfunction, inflammatory cytokine profiles, and AGE-RAGE signaling pathways are essential to advance mechanistic understanding. The protective roles of SIRT1- and SIRT3-dependent pathways warrant further investigation in future studies, as these mechanisms were not directly examined in the present work [ 20 , 21 ]. Finally, intervention studies are necessary to evaluate the efficacy of glycemic control strategies, antioxidant therapies, mitochondrial stabilizers, and vasoprotective agents in preventing or reversing sensory degeneration. Recent findings on DACRAs (Dual Amylin and Calcitonin Receptor Agonists), such as KBP-336, demonstrate improved glycemic regulation and attenuation of diabetes-induced cognitive impairment in ZDF rats, highlighting potential therapeutic strategies for sensory complications[ 22 ]. 5. Conclusion This longitudinal study demonstrates that progressive hyperglycemia in ZDF rats is associated with early and parallel deterioration of auditory and visual function. Hearing impairment, detected using ABR, emerged concurrently with retinal microvascular abnormalities and progressed in a frequency-dependent manner. These findings support auditory dysfunction as a sensitive, noninvasive functional indicator of diabetes-associated sensory involvement and highlight the potential translational value of auditory assessment for monitoring systemic diabetic complications. Declarations 6.Acknowledgments We appreciate Beijing Institute of Otolaryngology, Key Laboratory of Otolaryngology Head and Neck Surgery for providing equipment for this research. 7.Author contributions J.L. designed the study, performed the experiments, analyzed the data, and drafted the manuscript.B.L. supervised the study, contributed to the study design and data interpretation, and critically revised the manuscript. All authors reviewed and approved the final version of the manuscript. 8. Data availability statement All data supporting the findings of this study are available within the paper 9.Disclosure statement No potential conflicts of interest relevant to this article were reported. 10.Funding This study was supported by The Capital Health Research and Development of Special (No. 2018-1-1091). References Seo, H., Park, S. & Song, M. Diabetic retinopathy: mechanisms, current therapies, and emerging strategies. Cells 14 , 376 (2025). https://doi.org/10.3390/cells14050376 Li, J., Zhang, Y., Fu, X., Bi, J., Li, Y., Liu, B. & Zhang, L. Alteration of auditory function in type 2 diabetic and pre-diabetic patients. Acta Otolaryngol. 138 , 542–547 (2018). https://doi.org/10.1080/00016489.2017.1422084 Caballero Borrego, M. & Andujar Lara, I. Type 2 diabetes mellitus and hearing loss: a PRISMA systematic review and meta-analysis. Otolaryngol. Head Neck Surg. 173 , 1041–1053 (2025). https://doi.org/10.1002/ohn.1346 Al-Awar, A., Kupai, K., Veszelka, M. et al. Experimental diabetes mellitus in different animal models. J. Diabetes Res. 2016 , 9051426 (2016). https://doi.org/10.1155/2016/9051426 Meyer zum Gottesberge, A., Massing, T., Sasse, A. et al. Zucker diabetic fatty rats, a model for type 2 diabetes, develop an inner ear dysfunction that can be attenuated by losartan treatment. Cell Tissue Res. 362 , 307–315 (2015). https://doi.org/10.1007/s00441-015-2215-7 Szabó, K., Énzsöly, A., Dékány, B. et al. Histological evaluation of diabetic neurodegeneration in the retina of Zucker diabetic fatty rats. Sci. Rep. 7 , 8891 (2017). https://doi.org/10.1038/s41598-017-09068-6 Bainbridge, K. E., Hoffman, H. J. & Cowie, C. C. Diabetes and hearing impairment in the United States: audiometric evidence from the National Health and Nutrition Examination Survey, 1999–2004. Ann. Intern. Med. 149 , 1–10 (2008). https://doi.org/10.7326/0003-4819-149-1-200807010-00231 Akinpelu, O. V., Mujica-Mota, M. & Daniel, S. J. Is type 2 diabetes mellitus associated with alterations in hearing? A systematic review and meta-analysis. Laryngoscope 124 , 767–776 (2014). https://doi.org/10.1002/lary.24354 Lee, H. J., Yoo, S. G., Lee, S. J. et al. Association between HbA1c and hearing loss: a tertiary care center-based study. Sci. Rep. 13 , 18409 (2023). https://doi.org/10.1038/s41598-023-44909-7 Lee, J. H., Park, S., Perez-Flores, M. C. et al. Early functional alterations in membrane properties and neuronal degeneration are hallmarks of progressive hearing loss in NOD mice. Sci. Rep. 9 , 12128 (2019). https://doi.org/10.1038/s41598-019-48376-x Yau, J. W. Y., Rogers, S. L., Kawasaki, R. et al. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care 35 , 556–564 (2012). https://doi.org/10.2337/dc11-1909 Forbes, J. M. & Cooper, M. E. Mechanisms of diabetic complications. Physiol. Rev. 93 , 137–188 (2013). https://doi.org/10.1152/physrev.00045.2011 Fukushima, H., Cureoglu, S., Schachern, P. A. et al. Effects of type 2 diabetes mellitus on cochlear structure in humans. Arch. Otolaryngol. Head Neck Surg. 132 , 934–939 (2006). https://doi.org/10.1001/archotol.132.9.934 Chong, D. D., Das, N. & Singh, R. P. Diabetic retinopathy: screening, prevention, and treatment. Cleve. Clin. J. Med. 91 , 503–510 (2024). https://doi.org/10.3949/ccjm.91a.24028 Obrosova, I. G. Increased sorbitol pathway activity generates oxidative stress in tissue sites for diabetic complications. Antioxid. Redox Signal. 7 , 1543–1552 (2005). https://doi.org/10.1089/ars.2005.7.1543 Brownlee, M. Biochemistry and molecular cell biology of diabetic complications. Nature 414 , 813–820 (2001). https://doi.org/10.1038/414813a Lin, Y., Shen, J., Li, D. et al. miR-34a contributes to diabetes-related cochlear hair cell apoptosis via SIRT1/HIF-1α signaling. Gen. Comp. Endocrinol. 246 , 63–70 (2017). https://doi.org/10.1016/j.ygcen.2017.02.017 García-Díez, E., López-Oliva, M. E., Caro-Vadillo, A. et al. Supplementation with a cocoa–carob blend, alone or in combination with metformin, attenuates diabetic cardiomyopathy, cardiac oxidative stress and inflammation in Zucker diabetic rats. Antioxidants 11 , 432 (2022). https://doi.org/10.3390/antiox11020432 Iizuka, S., Suzuki, W., Tabuchi, M. et al. Diabetic complications in a new animal model (TSOD mouse) of spontaneous non-insulin-dependent diabetes mellitus with obesity. Exp. Anim. 54 , 71–83 (2005). https://doi.org/10.1538/expanim.54.71 Kume, S., Haneda, M., Kanasaki, K. et al. Silent information regulator 2 (SIRT1) attenuates oxidative stress-induced mesangial cell apoptosis via p53 deacetylation. Free Radic. Biol. Med. 40 , 2175–2182 (2006). https://doi.org/10.1016/j.freeradbiomed.2006.02.014 Brown, K. D., Maqsood, S., Huang, J. et al. Activation of SIRT3 by the NAD⁺ precursor nicotinamide riboside protects from noise-induced hearing loss. Cell Metab. 20 , 1059–1068 (2014). https://doi.org/10.1016/j.cmet.2014.11.003 Larsen, A. T., Mohamed, K. E., Petersen, E. A. et al. The insulin sensitizer KBP-336 prevents diabetes-induced cognitive decline in Zucker diabetic fatty rats. J. Prev. Alzheimers Dis. 11 , 1122–1131 (2024). https://doi.org/10.14283/jpad.2024.74 Additional Declarations No competing interests reported. Cite Share Download PDF Status: Under Revision Version 1 posted Editorial decision: Revision requested 04 May, 2026 Reviews received at journal 03 May, 2026 Reviews received at journal 30 Apr, 2026 Reviewers agreed at journal 25 Apr, 2026 Reviewers agreed at journal 24 Apr, 2026 Reviews received at journal 23 Apr, 2026 Reviewers agreed at journal 23 Apr, 2026 Reviewers invited by journal 02 Mar, 2026 Editor assigned by journal 02 Mar, 2026 Editor invited by journal 20 Feb, 2026 Submission checks completed at journal 26 Jan, 2026 First submitted to journal 26 Jan, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-8675794","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":600102606,"identity":"931f36db-74d3-4e7e-aaf1-6ca54584be6f","order_by":0,"name":"Jin Li","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAz0lEQVRIiWNgGAWjYJCCAww8Egxs7M0HHyRU2JCghY/nWLLBgzNpJFglJ5GjJvmw7RBhlboz0h8eYJCxyGNjyGGrSGA7wMDf3p2AV4vZjYQEkMOK2RjOHruRwHOHQeLM2Q2EtBwAaUlsY+xLu5Eg8YzBQCKXkJbEBogWZh6zggSDw8RoSWaAaGHjMWNISCBGy5lnUC08bMkSCQfSeAj75Xj64w+MPXWJ8+c/Pvjx5z8bOf72XvxaQID5bw+Cw0NQOQT8IFLdKBgFo2AUjEwAAGwsSXtrpyBjAAAAAElFTkSuQmCC","orcid":"","institution":"Beijing TongRen Hospital, Capital Medical University","correspondingAuthor":true,"prefix":"","firstName":"Jin","middleName":"","lastName":"Li","suffix":""},{"id":600102607,"identity":"a11adf86-e33a-422d-8c45-73cfc02f5391","order_by":1,"name":"Bo Liu","email":"","orcid":"","institution":"Beijing TongRen Hospital, Capital Medical University","correspondingAuthor":false,"prefix":"","firstName":"Bo","middleName":"","lastName":"Liu","suffix":""}],"badges":[],"createdAt":"2026-01-23 06:39:53","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8675794/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8675794/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":103989485,"identity":"9f1e2efb-f6b6-44e0-b158-0027af192d9f","added_by":"auto","created_at":"2026-03-05 11:12:02","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":518125,"visible":true,"origin":"","legend":"\u003cp\u003eOphthalmic complications in ZDF and control rats. A: aceg and i shows direct visual observation, and bdfh and j shows slit-lamp examination. a and b, lens turbidity of 0, clear lenses and no vacuoles present; c and d, turbidity of 1, vacuoles cover half the surface of the anterior pole; e and f, turbidity of 2, some vacuoles have disappeared and a hazy cortex; g and h, turbidity of 3, hazy cortex and dense nuclear opacity; i and j, turbidity of 4, a mature cataract is observed. B: k and m, normal Fundus fluorescein angiography in rats; l and n, Fundus fluorescein angiography showing retinal leakage. C: Differences in lens turbidity between the experimental group and the control group at the indicated time points. *\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05, *** \u003cem\u003eP\u003c/em\u003e \u0026lt; 0.001. D: The relationship between blood glucose and cataract severity in ZDF rats.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8675794/v1/aac719ebc1532177bb6bc803.png"},{"id":103989486,"identity":"f5345250-7d6f-4c3b-8d21-ea1fdbe11bdf","added_by":"auto","created_at":"2026-03-05 11:12:03","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":152369,"visible":true,"origin":"","legend":"\u003cp\u003eHearing loss in ZDF and control rats: Differences in the TB-ABR threshold values at different ages between the experimental group and the control group. TB-ABR was tested at 4, 8, 16, 24, and 32 kHz. *\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.05, ***\u003cem\u003eP\u003c/em\u003e \u0026lt; 0.001.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8675794/v1/33c61066911aca95ba301c51.png"},{"id":103989504,"identity":"76af9989-315d-4b08-9ea1-fa54a1dc1c16","added_by":"auto","created_at":"2026-03-05 11:12:15","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":97711,"visible":true,"origin":"","legend":"\u003cp\u003eCorrelation of ABR threshold and average blood glucose value in ZDF rats. The average blood glucose level of ZDF rats correlated significantly with the average threshold of TB-ABR at 4, 8, 16, 24 and 32kHz (1=0.957, P\u0026lt;0.001; 1=0.795, P\u0026lt;0.001; 1= 0.843, P \u0026lt; 0.001; 1= 0.942, P \u0026lt; 0.001; 1 = 0.963, P \u0026lt; 0.001; 1= 0.998, P\u0026lt;0.001)\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8675794/v1/34f1dfcae1f9a957a3324527.png"},{"id":103989534,"identity":"d7b65bc7-7f65-42e0-bebd-29aa68a56cfa","added_by":"auto","created_at":"2026-03-05 11:12:24","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1439079,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8675794/v1/37f8abe4-dead-42f0-a16c-a7191f63ee54.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Longitudinal assessment of auditory and ocular dysfunction associated with hyperglycemia in Zucker diabetic fatty rats","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eDiabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia resulting from defects in insulin secretion, insulin resistance, or both. Chronic hyperglycemia leads to progressive microvascular and neural damage, causing complications such as retinopathy, nephropathy, and neuropathy. Among these, diabetic retinopathy (DR) affects nearly one-third of diabetic patients and remains a leading cause of vision loss worldwide[\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Despite its high prevalence and clinical burden, diabetic ocular disease has been extensively studied. Nevertheless, the selection of animal models that accurately replicate human pathology is crucial for translational research.\u003c/p\u003e \u003cp\u003eEmerging evidence suggests that diabetic microangiopathy and metabolic dysregulation also affect the auditory system. Our previous study[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e] reported a 67.3% prevalence of tinnitus and hearing loss in diabetic patients. A recent meta-analysis[\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] revealed similar rates ranging from 40.6% to 71.9%, consistent with our findings. While diabetic hearing loss (DHL) receives less attention than DR or nephropathy, it significantly impairs patients\u0026rsquo; communication, cognition, and quality of life.\u003c/p\u003e \u003cp\u003eThe Zucker Diabetic Fatty (ZDF) rat is a widely used model of type 2 diabetes, featuring obesity, insulin resistance, and spontaneous hyperglycemia, which closely mirrors human metabolic dysfunction[\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Studies[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]have demonstrated microvascular injury, oxidative stress, mitochondrial dysfunction, and neurodegeneration in both the retina and cochlea of diabetic animals, contributing to cataracts, DR, and sensorineural hearing loss. Owing to its sensitivity, reproducibility, and noninvasiveness, auditory testing is ideal for detecting early diabetic complications[\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eHowever, few longitudinal studies have simultaneously assessed the temporal progression of ocular and auditory deficits in the same diabetic model. Investigating the temporal relationships among hyperglycemia, ocular abnormalities, and hearing loss can provide insights into shared mechanisms of diabetic systemic complications and inform preventive strategies.\u003c/p\u003e \u003cp\u003eThis study aimed to systematically evaluate ocular and auditory functional changes in ZDF rats and age-matched controls at multiple time points. Cataracts and retinal pathology were assessed using slit-lamp examination and fluorescein angiography, while hearing thresholds were measured by auditory brainstem response (ABR). We further analyzed correlations between fasting blood glucose levels and sensory impairments to elucidate the mechanisms underlying diabetes-related sensory dysfunction.\u003c/p\u003e"},{"header":"2. Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1 Animals\u003c/h2\u003e \u003cp\u003eForty male Zucker Diabetic Fatty (ZDF, fa/fa) rats and thirty-two age-matched control rats (fa/-) were obtained from Vital River Laboratory Animal Technology Co., Ltd. (Beijing, China). All experiments were approved by the Capital Medical University Animal Ethics Committee (Approval No. AEEI-2018-211) and conducted in accordance with the NIH Guide for the Care and Use of Laboratory Animals (2006). Rats were randomly assigned to four age groups (12, 20, 28, and 36 weeks). Auditory brainstem response (ABR) testing was performed at 8 weeks of age to establish baseline hearing thresholds. At each time point, slit-lamp microscopy, fluorescein fundus angiography, and ABR were conducted under 1% pentobarbital sodium anesthesia (0.6 mL/100 g, i.p.). At the end of the experimental procedures, rats were euthanized humanely under deep anesthesia. Deep anesthesia was induced by intraperitoneal administration of 1% pentobarbital sodium (1.5 mL/100 g, i.p). Death was confirmed by the absence of respiratory movements and cardiac activity prior to tissue disposal. All procedures were performed in accordance with institutional and national guidelines for the care and use of laboratory animals.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2 Blood Glucose Measurement\u003c/h2\u003e \u003cp\u003eFasting blood glucose was measured every two weeks using a glucometer with tail vein samples collected after a 12-hour fast.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3 Slit-Lamp Examination\u003c/h2\u003e \u003cp\u003eAfter pupil dilation with 1% tropicamide, lens opacity was examined using a slit-lamp microscope (Haag-Streit AG, USA) and graded as follows: \u003cb\u003eGrade 0\u003c/b\u003e: clear lens without vacuoles; \u003cb\u003eGrade 1\u003c/b\u003e: anterior vacuoles covering less than 50% of the lens surface; \u003cb\u003eGrade 2\u003c/b\u003e: partial vacuole loss with cortical opacity; \u003cb\u003eGrade 3\u003c/b\u003e: cortical and nuclear opacity; \u003cb\u003eGrade 4\u003c/b\u003e: mature cataract.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4 Fluorescein Angiography\u003c/h2\u003e \u003cp\u003eRats without cataracts underwent fundus fluorescein angiography using the OPTO-RIS imaging system (Optoprobe, Canada). Following anesthesia, rats received an intraperitoneal injection of 0.1 mL of 2.5% sodium fluorescein (Wuzhou Pharmaceutical Co., China). Images were captured after injection to assess retinal vascular leakage intensity.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5 Auditory Brainstem Response (ABR) Testing\u003c/h2\u003e \u003cp\u003eRats were placed supine on a temperature-controlled platform. Subdermal electrodes were positioned at the vertex (active recording), ipsilateral mastoid (reference), and contralateral mastoid (ground). Measurements were conducted using the SmartEP system (TDT Rz6, Intelligent Hearing Systems, Miami, FL, USA) inside a soundproof chamber. Tone-burst stimuli at frequencies of 4, 8, 16, 24, and 32 kHz (39.1 clicks/s) were generated, with 2-cycle rise/fall times and 16 ms analysis windows (averaged over 1,024 sweeps). The sound intensity started at 90 dB SPL and decreased in 10 dB steps, followed by 5 dB steps. The minimum stimulus intensity eliciting a visible wave II was defined as the threshold.\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e3.1 Blood Glucose\u003c/h2\u003e \u003cp\u003eAt 8 weeks, no significant differences in average blood glucose levels were observed between the experimental and control groups. The experimental group exhibited significantly elevated blood glucose compared to the control group at all subsequent time points (12, 20, 28, and 36 weeks) (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e).\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of blood glucose values between the experimental group and the control group.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eDiabetes group (n\u0026thinsp;=\u0026thinsp;20)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eControl group (n\u0026thinsp;=\u0026thinsp;16)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e8 weeks#\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e4.95\u0026thinsp;\u0026plusmn;\u0026thinsp;0.28\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e4.91\u0026thinsp;\u0026plusmn;\u0026thinsp;0.12\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026gt;0.05\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12 weeks#\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e15.23\u0026thinsp;\u0026plusmn;\u0026thinsp;6.69\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e5.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.23\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20 weeks#\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e22.19\u0026thinsp;\u0026plusmn;\u0026thinsp;3.39\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e6\u0026thinsp;\u0026plusmn;\u0026thinsp;0.55\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e28 weeks#\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e27.13\u0026thinsp;\u0026plusmn;\u0026thinsp;5.53\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e6.05\u0026thinsp;\u0026plusmn;\u0026thinsp;0.64\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e36 weeks#\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e32.83\u0026thinsp;\u0026plusmn;\u0026thinsp;1.49\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e6.98\u0026thinsp;\u0026plusmn;\u0026thinsp;0.75\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e*P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, ***P\u0026thinsp;\u0026lt;\u0026thinsp;0.001。 #blood glucose values(mmol/l)\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e3.2 Ophthalmic complications\u003c/h2\u003e \u003cp\u003eEarly microvascular lesions in the experimental group primarily included retinal vascular leakage and microangiomas. As the disease progressed, cataract formation became the predominant ophthalmic complication (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA). Figure\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eB illustrates the retinal vascular leakage across groups. Ophthalmic complications were defined as the presence of retinal vascular leakage or cataracts graded I-IV. The number of eyes with complications in the experimental group showed a significant increase at 12, 20, 28, and 36 weeks compared to controls (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). Additionally, cataract severity in the experimental group progressively worsened at all time points (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eC). The correlation between fasting blood glucose and cataract severity is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eD, demonstrating a positive association between hyperglycemia and ocular pathology. These findings indicate that ophthalmic complications in ZDF rats exhibit a progressive deterioration with disease duration.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eComparison of the number of eyeballs with ophthalmic complications between the experimental group and the control group.\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"4\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eEyes Number in diabetes group (n\u0026thinsp;=\u0026thinsp;40)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eEyes Number in control group (n\u0026thinsp;=\u0026thinsp;32)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003eP\u003c/em\u003e-value\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e12 weeks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOC n (%), RVL n (%), CF n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e20 (50), 20 (50),0(0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0), 0 (0), 0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.001*\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e20 weeks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOC n (%), RVL n (%), CF n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e32 (80),8(20),24(60)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e0 (0), 0 (0), 0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003cp\u003e***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e28 weeks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOC n (%), RVL n (%), CF n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e36 (90),8(20),28(70)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e4 (12.5), 4 (12.5), 0 (0)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003cp\u003e***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e36 weeks\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003eOC n (%), RVL n (%), CF n (%)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e40 (100),0(0),40(100)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003e8 (25), 4 (12.5), 4 (12.5)\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e\u0026lt;\u0026thinsp;0.001\u003c/p\u003e \u003cp\u003e***\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003eOphthalmic complications: OC, Retinal Vascular Leakage: RVL, Cataract Formation: CF.\u003c/td\u003e\u003c/tr\u003e \u003ctr\u003e\u003ctd colspan=\"4\"\u003e*P\u0026thinsp;\u0026lt;\u0026thinsp;0.05, ***P\u0026thinsp;\u0026lt;\u0026thinsp;0.001。\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e3.3 Auditory Function\u003c/h2\u003e \u003cp\u003eBaseline ABR thresholds at 8 weeks showed no significant differences between groups. At 12 weeks, the experimental group displayed elevated thresholds at 32 kHz. By 20 weeks, ABR thresholds increased at 4, 16, 24, and 32 kHz. At 28\u0026ndash;36 weeks, significant threshold shifts occurred across all tested frequencies (4\u0026ndash;32 kHz) (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003e). This progression, which involves a transition from high-frequency hearing loss to pan-frequency impairment, mimics the clinical pattern observed in diabetic hearing loss.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e3.4 Correlation Between Blood Glucose and ABR Thresholds\u003c/h2\u003e \u003cp\u003eFasting glucose levels were strongly and positively correlated with ABR thresholds at all frequencies (4\u0026ndash;32 kHz) (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e), indicating that auditory dysfunction severity parallels hyperglycemic progression.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eIn this longitudinal study, we characterized the temporal progression of auditory and ocular dysfunction in Zucker Diabetic Fatty (ZDF) rats, a widely used model of type 2 diabetes mellitus. By integrating repeated functional assessments with metabolic monitoring, we observed that sustained elevations in fasting blood glucose were accompanied by progressive impairments in both auditory and visual systems. These findings provide longitudinal functional evidence that chronic metabolic dysregulation is associated with multisystem sensory dysfunction in a diabetic animal model.\u003c/p\u003e \u003cp\u003eA notable observation was the early elevation of auditory brainstem response (ABR) thresholds at high frequencies, which emerged as early as 12 weeks of age. This functional change occurred concurrently with the appearance of retinal vascular leakage, suggesting that auditory and retinal alterations may develop in parallel during the early stages of diabetes. The preferential involvement of high-frequency hearing at earlier time points is consistent with clinical and experimental observations indicating that the basal region of the cochlea is particularly susceptible to metabolic and vascular stress. This corroborates clinical observations that high-frequency sensorineural hearing loss often precedes or parallels early diabetic retinopathy[\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. A critical finding of this study was the sequential progression of auditory dysfunction, characterized by a distinct frequency-dependent pattern. The initial detection of significant hearing loss exclusively at 32 kHz as early as 12 weeks underscores the heightened susceptibility of the basal cochlear turn to diabetic injury. The basal cochlear turn, crucial for high-frequency sound processing, is metabolically demanding and highly dependent on stria vascularis microcirculation, rendering it susceptible to systemic metabolic stress[\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe extension of hearing impairment to mid frequencies by 20 weeks, followed by pan-frequency involvement at 28\u0026ndash;36 weeks, indicates a time-dependent pattern of cochlear degeneration. Such progression is compatible with a base-to-apex distribution of cochlear pathology along the tonotopic gradient and accords with clinical evidence in diabetes, where sensorineural hearing loss commonly begins at high frequencies and progressively involves lower frequencies as disease duration increases[\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The underlying process is likely driven by the cumulative effects of diabetes-related microvascular impairment, chronic oxidative stress, and gradual neural degeneration, leading to increasingly diffuse cochlear injury[\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. This pattern of progression supports the use of frequency-dependent changes as a basis for staging diabetic hearing loss and for defining windows for early intervention.\u003c/p\u003e \u003cp\u003eThe robust positive correlation between fasting glucose levels and ABR thresholds furthers the hypothesis that hyperglycemia-driven metabolic perturbations are pivotal to cochlear dysfunction. The progression of canonical diabetic microvascular pathology, characterized by basement membrane thickening, endothelial injury, pericyte loss, and capillary rarefaction[\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e], is driven by chronic hyperglycemia. These pathological changes may contribute to impaired cochlear perfusion and disruption of the endocochlear potential[\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. These changes likely initiate downstream damage to hair cells and spiral ganglion neurons, culminating in progressive sensorineural hearing loss[\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eParallel to cochlear dysfunction, ZDF rats exhibited progressive ocular abnormalities, including retinal vascular leakage and cataract formation. Fluorescein angiography delineated retinal microvascular leakage, an early marker of diabetic retinopathy, indicative of blood\u0026ndash;retinal barrier breakdown, endothelial compromise, and pericyte dropout[\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Our results demonstrate that cataract onset in ZDF rats occurred at 20 weeks of age, Cataract development strongly correlated with hyperglycemia, reflecting osmotic stress via the polyol pathway, oxidative injury, and protein glycation[\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. With both incidence and severity escalating progressively thereafter. The presence of lens opacities obstructed retinal evaluation via fluorescein angiography, precluding longitudinal monitoring of diabetes‑induced microvascular changes in the retina with this imaging modality. Therefore, the progression of ocular complications in ZDF rats was assessed by quantifying cataract development as a surrogate measure. In contrast, owing to its noninvasive characteristics and high sensitivity, ABR provided a stable, noninvasive, and repeatable functional measure that remained feasible throughout the disease course, highlighting its utility for longitudinal monitoring when ocular imaging is compromised.\u003c/p\u003e \u003cp\u003eThe solid correlation between glycemic load and the severity of both cataract and hearing loss validates cumulative hyperglycemia as a primary driver of multisystem sensory degeneration\u003csup\u003e[16]\u003c/sup\u003e. The concurrent progression of auditory and ocular dysfunction observed in this study suggests that multiple sensory systems may be similarly affected during chronic diabetes. While the present findings do not establish shared mechanisms, they are consistent with the concept that systemic metabolic dysregulation is associated with widespread functional alterations [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eOur results validate the ZDF rat as an effective model for studying diabetes-induced sensory organ dysfunction. The model replicates key features of human diabetic retinopathy and hearing loss, including early microvascular deficits, progressive degeneration, and strong dependence on glycemic load[\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e], which supports its utility for preclinical testing of interventions targeting metabolic stress, oxidative injury, or microvascular protection.\u003c/p\u003e \u003cp\u003eWhile this longitudinal investigation systematically delineates the temporal progression and reciprocal relationships among hyperglycemia, cataractogenesis, and auditory deterioration, thereby demonstrating their coordinated progression within a diabetic model, the study nevertheless exhibits several limitations that warrant further scholarly inquiry. The lack of histological confirmation requires detailed histological analyses of the stria vascularis, cochlear microvasculature, and retinal vessels to establish structural correlates of the observed functional decline. In addition, molecular investigations quantifying oxidative stress, mitochondrial dysfunction, inflammatory cytokine profiles, and AGE-RAGE signaling pathways are essential to advance mechanistic understanding. The protective roles of SIRT1- and SIRT3-dependent pathways warrant further investigation in future studies, as these mechanisms were not directly examined in the present work [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Finally, intervention studies are necessary to evaluate the efficacy of glycemic control strategies, antioxidant therapies, mitochondrial stabilizers, and vasoprotective agents in preventing or reversing sensory degeneration. Recent findings on DACRAs (Dual Amylin and Calcitonin Receptor Agonists), such as KBP-336, demonstrate improved glycemic regulation and attenuation of diabetes-induced cognitive impairment in ZDF rats, highlighting potential therapeutic strategies for sensory complications[\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e"},{"header":"5. Conclusion","content":"\u003cp\u003eThis longitudinal study demonstrates that progressive hyperglycemia in ZDF rats is associated with early and parallel deterioration of auditory and visual function. Hearing impairment, detected using ABR, emerged concurrently with retinal microvascular abnormalities and progressed in a frequency-dependent manner. These findings support auditory dysfunction as a sensitive, noninvasive functional indicator of diabetes-associated sensory involvement and highlight the potential translational value of auditory assessment for monitoring systemic diabetic complications.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e6.Acknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eWe appreciate Beijing Institute of Otolaryngology, Key Laboratory of Otolaryngology Head and Neck Surgery for providing equipment for this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e7.Author contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eJ.L. designed the study, performed the experiments, analyzed the data, and drafted the manuscript.B.L. supervised the study, contributed to the study design and data interpretation, and critically revised the manuscript. All authors reviewed and approved the final version of the manuscript.\u003c/p\u003e\n\u003cp\u003e8. \u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll data supporting the findings of this study are available within the paper\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e9.Disclosure statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo potential conflicts of interest relevant to this article were reported.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e10.Funding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study was supported by The Capital Health Research and Development of Special (No. 2018-1-1091).\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eSeo, H., Park, S. \u0026amp; Song, M. Diabetic retinopathy: mechanisms, current therapies, and emerging strategies. \u003cem\u003eCells\u003c/em\u003e\u003cstrong\u003e14\u003c/strong\u003e, 376 (2025). https://doi.org/10.3390/cells14050376\u003c/li\u003e\n\u003cli\u003eLi, J., Zhang, Y., Fu, X., Bi, J., Li, Y., Liu, B. \u0026amp; Zhang, L. Alteration of auditory function in type 2 diabetic and pre-diabetic patients. \u003cem\u003eActa Otolaryngol.\u003c/em\u003e\u003cstrong\u003e138\u003c/strong\u003e, 542\u0026ndash;547 (2018). https://doi.org/10.1080/00016489.2017.1422084\u003c/li\u003e\n\u003cli\u003eCaballero Borrego, M. \u0026amp; Andujar Lara, I. Type 2 diabetes mellitus and hearing loss: a PRISMA systematic review and meta-analysis. \u003cem\u003eOtolaryngol. Head Neck Surg.\u003c/em\u003e\u003cstrong\u003e173\u003c/strong\u003e, 1041\u0026ndash;1053 (2025). https://doi.org/10.1002/ohn.1346\u003c/li\u003e\n\u003cli\u003eAl-Awar, A., Kupai, K., Veszelka, M. \u003cem\u003eet al.\u003c/em\u003e Experimental diabetes mellitus in different animal models. \u003cem\u003eJ. Diabetes Res.\u003c/em\u003e\u003cstrong\u003e2016\u003c/strong\u003e, 9051426 (2016). https://doi.org/10.1155/2016/9051426\u003c/li\u003e\n\u003cli\u003eMeyer zum Gottesberge, A., Massing, T., Sasse, A. \u003cem\u003eet al.\u003c/em\u003e Zucker diabetic fatty rats, a model for type 2 diabetes, develop an inner ear dysfunction that can be attenuated by losartan treatment. \u003cem\u003eCell Tissue Res.\u003c/em\u003e\u003cstrong\u003e362\u003c/strong\u003e, 307\u0026ndash;315 (2015). https://doi.org/10.1007/s00441-015-2215-7\u003c/li\u003e\n\u003cli\u003eSzab\u0026oacute;, K., \u0026Eacute;nzs\u0026ouml;ly, A., D\u0026eacute;k\u0026aacute;ny, B. \u003cem\u003eet al.\u003c/em\u003e Histological evaluation of diabetic neurodegeneration in the retina of Zucker diabetic fatty rats. \u003cem\u003eSci. Rep.\u003c/em\u003e\u003cstrong\u003e7\u003c/strong\u003e, 8891 (2017). https://doi.org/10.1038/s41598-017-09068-6\u003c/li\u003e\n\u003cli\u003eBainbridge, K. E., Hoffman, H. J. \u0026amp; Cowie, C. C. Diabetes and hearing impairment in the United States: audiometric evidence from the National Health and Nutrition Examination Survey, 1999\u0026ndash;2004. \u003cem\u003eAnn. Intern. Med.\u003c/em\u003e\u003cstrong\u003e149\u003c/strong\u003e, 1\u0026ndash;10 (2008). https://doi.org/10.7326/0003-4819-149-1-200807010-00231\u003c/li\u003e\n\u003cli\u003eAkinpelu, O. V., Mujica-Mota, M. \u0026amp; Daniel, S. J. Is type 2 diabetes mellitus associated with alterations in hearing? A systematic review and meta-analysis. \u003cem\u003eLaryngoscope\u003c/em\u003e\u003cstrong\u003e124\u003c/strong\u003e, 767\u0026ndash;776 (2014). https://doi.org/10.1002/lary.24354\u003c/li\u003e\n\u003cli\u003eLee, H. J., Yoo, S. G., Lee, S. J. \u003cem\u003eet al.\u003c/em\u003e Association between HbA1c and hearing loss: a tertiary care center-based study. \u003cem\u003eSci. Rep.\u003c/em\u003e\u003cstrong\u003e13\u003c/strong\u003e, 18409 (2023). https://doi.org/10.1038/s41598-023-44909-7\u003c/li\u003e\n\u003cli\u003eLee, J. H., Park, S., Perez-Flores, M. C. \u003cem\u003eet al.\u003c/em\u003e Early functional alterations in membrane properties and neuronal degeneration are hallmarks of progressive hearing loss in NOD mice. \u003cem\u003eSci. Rep.\u003c/em\u003e\u003cstrong\u003e9\u003c/strong\u003e, 12128 (2019). https://doi.org/10.1038/s41598-019-48376-x\u003c/li\u003e\n\u003cli\u003eYau, J. W. Y., Rogers, S. L., Kawasaki, R. \u003cem\u003eet al.\u003c/em\u003e Global prevalence and major risk factors of diabetic retinopathy. \u003cem\u003eDiabetes Care\u003c/em\u003e\u003cstrong\u003e35\u003c/strong\u003e, 556\u0026ndash;564 (2012). https://doi.org/10.2337/dc11-1909\u003c/li\u003e\n\u003cli\u003eForbes, J. M. \u0026amp; Cooper, M. E. Mechanisms of diabetic complications. \u003cem\u003ePhysiol. Rev.\u003c/em\u003e\u003cstrong\u003e93\u003c/strong\u003e, 137\u0026ndash;188 (2013). https://doi.org/10.1152/physrev.00045.2011\u003c/li\u003e\n\u003cli\u003eFukushima, H., Cureoglu, S., Schachern, P. A. \u003cem\u003eet al.\u003c/em\u003e Effects of type 2 diabetes mellitus on cochlear structure in humans. \u003cem\u003eArch. Otolaryngol. Head Neck Surg.\u003c/em\u003e\u003cstrong\u003e132\u003c/strong\u003e, 934\u0026ndash;939 (2006). https://doi.org/10.1001/archotol.132.9.934\u003c/li\u003e\n\u003cli\u003eChong, D. D., Das, N. \u0026amp; Singh, R. P. Diabetic retinopathy: screening, prevention, and treatment. \u003cem\u003eCleve. Clin. J. Med.\u003c/em\u003e\u003cstrong\u003e91\u003c/strong\u003e, 503\u0026ndash;510 (2024). https://doi.org/10.3949/ccjm.91a.24028\u003c/li\u003e\n\u003cli\u003eObrosova, I. G. Increased sorbitol pathway activity generates oxidative stress in tissue sites for diabetic complications. \u003cem\u003eAntioxid. Redox Signal.\u003c/em\u003e\u003cstrong\u003e7\u003c/strong\u003e, 1543\u0026ndash;1552 (2005). https://doi.org/10.1089/ars.2005.7.1543\u003c/li\u003e\n\u003cli\u003eBrownlee, M. Biochemistry and molecular cell biology of diabetic complications. \u003cem\u003eNature\u003c/em\u003e\u003cstrong\u003e414\u003c/strong\u003e, 813\u0026ndash;820 (2001). https://doi.org/10.1038/414813a\u003c/li\u003e\n\u003cli\u003eLin, Y., Shen, J., Li, D. \u003cem\u003eet al.\u003c/em\u003e miR-34a contributes to diabetes-related cochlear hair cell apoptosis via SIRT1/HIF-1\u0026alpha; signaling. \u003cem\u003eGen. Comp. Endocrinol.\u003c/em\u003e\u003cstrong\u003e246\u003c/strong\u003e, 63\u0026ndash;70 (2017). https://doi.org/10.1016/j.ygcen.2017.02.017\u003c/li\u003e\n\u003cli\u003eGarc\u0026iacute;a-D\u0026iacute;ez, E., L\u0026oacute;pez-Oliva, M. E., Caro-Vadillo, A. \u003cem\u003eet al.\u003c/em\u003e Supplementation with a cocoa\u0026ndash;carob blend, alone or in combination with metformin, attenuates diabetic cardiomyopathy, cardiac oxidative stress and inflammation in Zucker diabetic rats. \u003cem\u003eAntioxidants\u003c/em\u003e\u003cstrong\u003e11\u003c/strong\u003e, 432 (2022). https://doi.org/10.3390/antiox11020432\u003c/li\u003e\n\u003cli\u003eIizuka, S., Suzuki, W., Tabuchi, M. \u003cem\u003eet al.\u003c/em\u003e Diabetic complications in a new animal model (TSOD mouse) of spontaneous non-insulin-dependent diabetes mellitus with obesity. \u003cem\u003eExp. Anim.\u003c/em\u003e\u003cstrong\u003e54\u003c/strong\u003e, 71\u0026ndash;83 (2005). https://doi.org/10.1538/expanim.54.71\u003c/li\u003e\n\u003cli\u003eKume, S., Haneda, M., Kanasaki, K. \u003cem\u003eet al.\u003c/em\u003e Silent information regulator 2 (SIRT1) attenuates oxidative stress-induced mesangial cell apoptosis via p53 deacetylation. \u003cem\u003eFree Radic. Biol. Med.\u003c/em\u003e\u003cstrong\u003e40\u003c/strong\u003e, 2175\u0026ndash;2182 (2006). https://doi.org/10.1016/j.freeradbiomed.2006.02.014\u003c/li\u003e\n\u003cli\u003eBrown, K. D., Maqsood, S., Huang, J. \u003cem\u003eet al.\u003c/em\u003e Activation of SIRT3 by the NAD⁺ precursor nicotinamide riboside protects from noise-induced hearing loss. \u003cem\u003eCell Metab.\u003c/em\u003e\u003cstrong\u003e20\u003c/strong\u003e, 1059\u0026ndash;1068 (2014). https://doi.org/10.1016/j.cmet.2014.11.003\u003c/li\u003e\n\u003cli\u003eLarsen, A. T., Mohamed, K. E., Petersen, E. A. \u003cem\u003eet al.\u003c/em\u003e The insulin sensitizer KBP-336 prevents diabetes-induced cognitive decline in Zucker diabetic fatty rats. \u003cem\u003eJ. Prev. Alzheimers Dis.\u003c/em\u003e\u003cstrong\u003e11\u003c/strong\u003e, 1122\u0026ndash;1131 (2024). https://doi.org/10.14283/jpad.2024.74\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Diabetes mellitus, Hearing impairment, Auditory brainstem response, Diabetic retinopathy, Cataract, Microangiopathy, Zucker diabetic fatty rat","lastPublishedDoi":"10.21203/rs.3.rs-8675794/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8675794/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eDiabetic retinopathy is a well-recognized microvascular complication of diabetes mellitus; however, diabetes-associated auditory dysfunction remains less well characterized, particularly with respect to its longitudinal progression. In this study, we performed a longitudinal assessment of ocular and auditory function in Zucker Diabetic Fatty (ZDF) rats and examined their relationships with chronic hyperglycemia.\u003c/p\u003e\n\u003cp\u003eForty male ZDF (fa/fa) rats and thirty-two age-matched control rats (fa/–) were evaluated at 12, 20, 28, and 36 weeks of age. Ocular changes were assessed using slit-lamp microscopy and fluorescein fundus angiography, while auditory function was evaluated using auditory brainstem response (ABR) testing across frequencies from 4 to 32 kHz. Fasting blood glucose levels were monitored throughout the study.\u003c/p\u003e\n\u003cp\u003eZDF rats developed sustained hyperglycemia from 12 weeks of age onward. Elevated ABR thresholds were first observed at high frequencies (32 kHz) at 12 weeks, followed by progressive involvement of mid frequencies (16 and 24 kHz) at 20 weeks and all tested frequencies (4–32 kHz) at 28–36 weeks. Retinal vascular leakage and cataract formation increased with disease duration. Fasting blood glucose levels showed strong positive associations with ABR thresholds across all frequencies (r = 0.72–0.85, p \u0026lt; 0.01) and with cataract severity.\u003c/p\u003e\n\u003cp\u003eThese findings show that chronic hyperglycemia in ZDF rats is accompanied by progressive auditory and ocular dysfunction, providing longitudinal functional evidence of multisystem sensory impairment in a diabetic animal model.\u003c/p\u003e","manuscriptTitle":"Longitudinal assessment of auditory and ocular dysfunction associated with hyperglycemia in Zucker diabetic fatty rats","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-05 11:11:13","doi":"10.21203/rs.3.rs-8675794/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-05-04T07:40:59+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-03T04:11:43+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-30T05:11:28+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"85513002128700193462758929668214939370","date":"2026-04-25T18:24:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"227191272850518533503187012120057045550","date":"2026-04-24T05:45:49+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-23T20:17:50+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"247938069561731209017216364335391051859","date":"2026-04-23T20:14:18+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-02T12:44:06+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-02T12:36:47+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"","date":"2026-02-20T11:27:57+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-01-26T23:24:41+00:00","index":"","fulltext":""},{"type":"submitted","content":"Scientific Reports","date":"2026-01-26T23:20:30+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"scientific-reports","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"scirep","sideBox":"Learn more about [Scientific Reports](http://www.nature.com/srep/)","snPcode":"","submissionUrl":"","title":"Scientific Reports","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Scientific Reports","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"45781ed7-716d-47cb-bd5d-fd634a415c2c","owner":[],"postedDate":"March 5th, 2026","published":true,"recentEditorialEvents":[{"type":"decision","content":"Revision requested","date":"2026-05-04T07:40:59+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-05-03T04:11:43+00:00","index":165,"fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-30T05:11:28+00:00","index":164,"fulltext":""}],"rejectedJournal":[],"revision":"","amendment":"","status":"in-revision","subjectAreas":[{"id":63858413,"name":"Health sciences/Diseases"},{"id":63858414,"name":"Health sciences/Endocrinology"},{"id":63858415,"name":"Health sciences/Medical research"}],"tags":[],"updatedAt":"2026-05-04T07:53:33+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-05 11:11:13","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8675794","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8675794","identity":"rs-8675794","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}