Optical stimulation of mitochondria reduces blood glucose levels

Optical stimulation of mitochondria reduces blood glucose levels | 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 Optical stimulation of mitochondria reduces blood glucose levels Michael B Powner, Glen Jeffery This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3275287/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Mitochondria regulate metabolism, but solar light influences its rate. Red light increases mitochondrial membrane potentials and ATP production and may increase glucose demand. Here we show, with a glucose tolerance test, that red light exposure in normal subjects significantly reduces blood sugar levels. A 15 min exposure to 670 nm light, reduced the degree of blood glucose elevation following glucose intake by 27.7%, over 2 h. Maximum glucose spiking was reduced by 5.1%. Decreased blood glucose correlated with increased exhaled end-tidal CO 2 partial pressure at 1 h, indicating the mechanism includes an increased oxidation rate. Consequently, 670 nm light exposure can be used to reduce blood glucose spikes following meals. This may reduce damaging fluctuations of blood glucose on the body, a major risk factor for diabetic complications, offering a safe, non-invasive intervention for glucose management of diabetes at home. Biological sciences/Physiology Health sciences/Cardiology Photobiomodulation red light 670 nm mitochondria glucose oral glucose tolerance test human Figures Figure 1 Figure 2 Introduction Red light (~ 650–800 nm) stimulates mitochondrial respiration, shifting their metabolism. This photobiomodulation, alters cellular respiration rate, increases membrane potential, ATP production and subsequently reduces reactive oxygen species and inflammatory markers. [ 1 , 2 , 3 ] This results in improved sensory and motor function, including aged human colour perception. [ 4 , 5 , 6 ] 670 nm and other, longer wavelengths of red/near infra-red light are absorbed by the nanoscopic interfacial water layer surrounding mitochondrial ATP rotor pumps. [ 7 ] The energy transfer reduces water viscosity, allowing the rotor pump to achieve greater momentum, and increases ATP production. [ 7 ] An increase in ATP production rate requires more fuel. Glucose is the primary fuel source in animals and, as shown previously, systemic glucose concentrations decrease in an invertebrate model (bees) following a single 670 nm light exposure. [ 8 ] This result potentially has significance for human health, particularly in diabetes management and weight control. Here we have extended these findings from invertebrates into humans, demonstrating that a non-pharmaceutical, non-invasive, optical intervention can be used to support blood glucose level management. Results Participants were randomised into either a 670 nm group (n = 15), or placebo (no light) group (n = 15). All individuals undertook fasting oral glucose tolerance tests (OGTT), consuming 75g glucose in 150 ml of water. Capillary blood glucose levels were recorded by finger prick tests, and respired end-tidal carbon dioxide partial pressure (EtCO 2 ) was measured every 15 min for 2 h while at rest. For all individuals in both groups an initial baseline (control) OGTT was recorded. Within 7 days, a second OGTT was administered during which the 670 nm group received a 15 min light exposure of 40mW cm − 2 (28,800 J) across an area of 800 cm 2 of skin of the upper back starting 45 min prior to consuming glucose, with the light not turned on for the placebo group. Energies and timings of lights are consistent with previous studies. [ 9 ] Three comparisons were made between OGTTs for analysis. (1) The 670 nm and placebo intervention results were compared across the two subject populations. To ensure any results found were not caused by marked individual variabilities, paired within-participant comparisons were made between (2) the no 670 nm control against 670 nm exposure results and (3) no placebo control against placebo intervention results. Effect of red light on blood glucose parameters Following glucose loading in the OGTT, initial blood glucose levels over the first 30 min were similar in both 670 nm exposed and placebo interventions (Fig. 1 a). Blood glucose levels were always elevated above fasting levels following glucose consumption (Fig. 1 ). When comparing 670 nm against placebo interventions, 670 nm light reduced this elevation in blood glucose by 27.7% over the 2 h OGTT, as determined by area under the curve ( p = 0.0002 ) (Fig. 1 a). A repeated measures ANOVA confirmed a significant difference (p = 0.049) with post hoc analysis highlighting significant decreases found at specific time points of 45-, 60- and 90-min post-loading (Fig. 1 a). These relative decreases resulted in the absolute blood glucose level, not baselined to change from fasting level, being reduced by 7.3% ( p = 0.0061 ) between 670 nm and placebo interventions. The magnitude of this response following exposure of only a limited area of tissue, is likely the result of wider indirect metabolic upregulation, [ 10 ] potentially via distal mitochondrial communication. [ 11 ] Paired participant analyses confirmed this result. Within the 670 nm group, the elevation of blood glucose after loading was reduced by 26.3% ( p = 0.0008 ) following 670 nm exposure, with a significant effect found at 60 min post-loading and return to baseline at the final blood collection after 120 min (Fig. 1 b). Absolute blood glucose levels compared, without baselining to fasting levels, were decreased by 7.9% ( p = 0.0012 ). Within-participant data for the placebo group, comparing control visit and placebo intervention, showed no difference in blood glucose levels (Fig. 1 c). Here, we have also looked into the effect of 670 nm light on blood glucose spiking; maximum glucose levels reached, recorded in mmol/L, were reduced following 670 nm light exposure. Comparing 670 nm and placebo interventions revealed a reduction of 5.1% in the peak glucose concentration reached, down from 10.8 mmol/L to 10.2 mmol/L ( p = 0.0102 ) (Fig. 1 d). Separately, paired analysis within the 670 nm group gave a 7.5% reduction in maximum glucose peak level, down from 10.3 mmol/L to 9.5 mmol/L ( p = 0.0054 ), with no significant differences in maximum glucose level reached in the paired placebo group analysis (Fig. 1 d). These changes were obtained with only 15 minutes of exposure time over 800 cm 2 tissue area, accounting for approximately 4% of the skin surface area. [ 12 ] Effect of red light on exhaled carbon dioxide Reduced blood glucose levels may result from an increased glucose oxidation rate, or through an increased storage of the ingested glucose as glycogen. Increased oxidation would lead to increased CO 2 production and would be detectable through exhaled breath. Here, EtCO 2 increased during all the glucose tolerance test (Fig. 2 a-c), while participants were at rest, consistent with elevated carbohydrate intake. [ 13 ] No significant differences were observed between 670 nm and placebo groups (Fig. 1 a). However, a significant difference in EtCO 2 was observed 60 min post glucose loading when comparing 670 nm exposed participants against their no intervention control results (Fig. 2 b). This correlates with the first time point of significant reductions in blood glucose level (Fig. 1 b). No significant difference in breath rate was observed for any intervention. The observed change in CO 2 production is consistent with increased oxidation of glucose as a mechanism, supported by previous invertebrate experiments, where 670 nm exposure increased respired CO 2 volume [ 14 ] [see their Fig. 1 A], while not ruling out contribution from increased glucose storage. Discussion This study has shown that a single 15 min exposure to 670 nm light significantly reduces the amount of glucose loaded into the blood during a standard oral glucose tolerance test. While glucose is a vital nutrient, sustained high levels in the blood induce inflammation and insulin resistance in vascular endothelial cells. [ 15 ] A reduction in glucose loading after eating (post-prandial) is beneficial in those with impaired blood glucose homeostasis. However, the degree of post-prandial hyperglycaemia and other fluctuation in blood glucose levels may contribute to the pathogenesis of diabetic complications. [ 16 ] Fluctuations are more damaging than sustained hyperglycaemia, as an intermittent high glucose exposure further increases endothelial cell apoptosis rate. [ 17 ] Hence, clinical intervention routinely includes practices to minimise sharp fluctuations in blood glucose levels in diabetic patients. [ 18 ] We report that 670 nm exposure decreases maximum glucose levels reached post glucose challenge, and therefore offers an intervention to limit glucose spiking. The effect of red light exposure is consistent across species, [ 19 , 20 , 21 ] however the timing of onset has not been fully explored. Here, participants were exposed to red light 45 min prior to glucose loading, and blood glucose levels were significantly reduced 45 min post loading (Fig. 1 a), revealing that onset of the effect is within ~ 1.5 h. This is within the time frame of improved retinal function following red light exposure in aged human subjects. [ 6 ] Significant reduction in blood glucose was observed following local red light illumination of the body, rather than requiring whole body exposure. Red light exposure has been shown to have an abscopal effect [ 22 ] and results in systemic changes in cytokine expression in the blood [ 23 ]. It is likely that this systemic cytokine change may play a role in the marked widespread changes in blood glucose to a distal region of illumination. Alternatively, blood contains cell-free, respiratory competent, mitochondria [ 24 , 25 ] which may also be modulated by the red light and signal changes systemically as they circulate. 670 nm light increases ATP levels, [ 1 ] via increasing mitochondrial oxidative phosphorylation. [ 2 , 7 ] An increased facilitated diffusion rate of glucose into cells to meet increased intra-cellular demand by 670 nm absorption, is the likely mechanism that results in reduced blood glucose. Increased EtCO 2 levels observed in paired participant analysis of the 670 exposure group (Fig. 2 b), whilst the participants were at rest, could result from increased oxidation. However, stimulation of glucose incorporation into carbohydrate stores cannot be excluded as an alternative mechanism involved. Diabetes mellitus encompasses a group of etiologically different metabolic diseases and is characterised by impaired or loss of glucose homeostasis, leading to high blood glucose levels. It is the most common metabolic disorder worldwide and a major risk factor for cardiovascular disease. Type I diabetes results in elevated blood glucose levels due to reduced insulin secretion from a loss of pancreatic β-cells. While, the predominant form, Type II diabetes is typified by insulin insensitivity leading to a loss of insulin activation of cells in peripheral organs (particularly liver and skeletal muscle), resulting in reduced glucose uptake. [ 26 ] Concurrently, in Type II diabetes, pancreatic insulin secretion may be reduced and so is insufficient to meet the higher demand. [ 27 ] Glucose intolerance resulting in significantly elevated post-prandial blood glucose levels and elevated fasting glucose levels (5.6-7.0 mmol/L; American Diabetes Association, 6.1-7.0 mmol/L; World Health Organisation) often precedes Type II diabetes and is referred to as pre-diabetes. [ 28 ] People who are pre-diabetic are at five to six fold greater risk of developing Type II diabetes. Each of these three impaired metabolic states (Type I and Type II diabetes, and pre-diabetes) may benefit from photobiomodulation with 670 nm light to reduce post prandial blood glucose fluctuations that increase the risk of diabetic complications, such as nephropathy, retinopathy, or cardiovascular disease. [ 29 ] Mitochondrial oxidation rate peaks in the morning, coincident with the known surge of blood glucose. [ 30 ] Morning is the only time widow when 670 nm exposure is effective at manipulating mitochondrial function. [ 6 , 30 ] Hence, a brief exposure as a part of an early daily routine could be incorporated into normal life, supporting current recommended glucose control measures. Methods Study cohort This study was approved by City, University of London, School of Health and Psychological Sciences Research Ethics committee ( ETH2122-1596 ). We confirm that all research was performed in accordance with relevant guidelines/regulations, and that all participants gave informed consent to take part. This study was performed in accordance with the Declaration of Helsinki. Thirty healthy participants were recruited: 15 in the 670 nm group (mean age 41.1 ± 13.1 years), 15 in the placebo group (no light) (mean age 38.3 ± 13.7 years), with no known metabolic conditions and not taking medication known to effect metabolism. Oral glucose tolerance test and Blood glucose monitoring Participants fasted overnight, consuming only water for at least 10 hours prior to the oral glucose tolerance test (OGTT). An initial finger prick capillary blood glucose levels was measured using a blood glucose monitor (Kinetik Wellbeing, UK), a method with proven sensitivity vs venous glucose levels, for use in OGTT. [ 31 ] Forty-five minutes later an OGTT was performed. Participants consumed 75g glucose in water (total volume of 150ml), within 2 minutes. Following glucose consumption, further finger prick blood glucose concentrations were measured at 0 (fasted), 15, 30, 45, 60, 75, 90, 105, 120 min after administration of glucose solution. Respiratory measurements End-tidal partial pressure of carbon dioxide (EtCO 2 ) in expired gas, and breath rate were measured at the same time intervals as blood glucose (-45, 0, 15, 30, 45, 60, 75, 90, 105, 120 min after administration of glucose solution) via capnometry, using a PC-900B Hand Held SideStream EtCO2 monitor (PROACT medical, UK), and nasal cannula. Light exposure All participants undertook an OGTT on two separate occasions. During the first visit, they underwent an OGTT with a full set of glucose and respiration measurements without intervention (baseline measurements, control). Participants were randomised into the intervention group or the placebo group at the point of recruitment; during their second visit there was an intervention step added to the protocol. In the 670 nm group, immediately following initial blood glucose levels being recorded (-45 min), participants exposed a 800 cm 2 region of upper back to 670 nm light for 15 min at an intensity of 40mW cm − 2 (28,800 J). With a penetration depth of approximately 2 mm that would include the cells of the skin and underlying musculature [ 32 ] (including the trapezius). Light was delivered via LEDs; 670 nm was the peak wavelength, with a half power band of approximately 10 nm. The LED array was positioned 400 mm from the participants back, surrounded by a shield that rested on the participant’s skin, to prevent light leakage, and to blind the participant to which group they were randomised into. The placebo group underwent the same procedure, except the LED array was not switched on during their intervention OGTT. Statistical analysis The initial measurement at 0 min was used in analysis of change from fasting levels due to the variation in initial blood glucose concentration and EtCO 2 partial pressures between participants. Glucose loading in the blood over the 2 h OGTT was determined by measuring the area under the curve. This was carried out assuming linear lines between data points at sequential time intervals. For inter group comparisons (670 nm vs placebo), each intervention was first baselined against that groups control OGTT data and expressed relative to this for each participant. A repeated measures analysis of variance (ANOVA) using a general linear model with repeat measures, with post hoc Mann Whitney U test was used to test for significant difference between 670 nm and placebo interventions, while a post-hoc Wilcoxon Signed Rank Test was used for paired data analysis comparing intra-participant data (two tailed tests in each case, SPSS v25). Standard error of the mean was calculated for error bars. Declarations Acknowledgments The authors would like to thank Simon Grant and Ron Douglas for their productive comments in preparation of this manuscript. Author contributions MBP and GJ; project conception, study design, data collection, data analysis and interpretation, wrote the manuscript. Data availability statement The data that support the findings of this study are available through FigShare; 10.6084/m9.figshare.22665091. https://figshare.com/s/14144678e1c32f79cc32 References Begum, R. et al. . Near-infrared light increases ATP, extends lifespan and improves mobility in aged Drosophila melanogaster. Biology letters. 11(3):20150073 (2015). Kaynezhad, P., Tachtsidis, I., & Jeffery, G. Optical monitoring of retinal respiration in real time: 670 nm light increases the redox state of mitochondria. Experimental Eye Research 152 , 88–93 (2016). Hamblin, M. R. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS biophysics 4 (3), 337 (2017). Hu, D., Zhu, S., & Potas, J. R. Red LED photobiomodulation reduces pain hypersensitivity and improves sensorimotor function following mild T10 hemicontusion spinal cord injury. Journal of Neuroinflammation 13(1), 1–15 (2016). Weinrich, T. W., Hogg, C., & Jeffery, G. The temporal sequence of improved mitochondrial function on the dynamics of respiration, mobility, and cognition in aged Drosophila. Neurobiology of aging 70 , 140–147 (2018). Shinhmar, H., Hogg, C., Neveu, M. & Jeffery, G. Weeklong improved colour contrasts sensitivity after single 670 nm exposures associated with enhanced mitochondrial function. Scientific Reports 11(1):1–9 (2021). Sommer, A. P., Haddad, M. K. & Fecht, H. J. Light effect on water viscosity: implication for ATP biosynthesis. Scientific reports 5(1):1–6 (2015). Powner, M. B., & Jeffery, G. Systemic glucose levels are modulated by specific wavelengths in the solar light spectrum that shift mitochondrial metabolism. Plos one 17(11), e0276937 (2022). Fitzgerald, M. et. al. Red/near-infrared irradiation therapy for treatment of central nervous system injuries and disorders. Reviews in the Neurosciences 24(2), 205–226 (2013). Saliba, A. et al. Photobiomodulation mitigates diabetes-induced retinopathy by direct and indirect mechanisms: evidence from intervention studies in pigmented mice. PloS one 10(10), e0139003 (2015). Durieux, J., Wolff, S. & Dillin, A. The cell-non-autonomous nature of electron transport chain-mediated longevity. Cell 144(1), 79–91 (2011). Mosteller, R. D. Simplified calculation of body surface area. New England Journal of Medicine 317, 1098 (1987). Askanazi, J. et al. . Respiratory changes induced by the large glucose loads of total parenteral nutrition. JAMA, 243(14), 1444–1447 (1980). Powner, M. B., Priestley, G., Hogg, C. & Jeffery, G. Improved mitochondrial function corrects immunodeficiency and impaired respiration in neonicotinoid exposed bumblebees. Plos one 16 (8), e0256581 (2021). Kim, F. et al. Activation of IKKbeta by glucose is necessary and sufficient to impair insulin signaling and nitric oxide production in endothelial cells. J Mol Cell Cardiol. 39:327–334 (2005). Monnier, L. et al. Activation of oxidative stress by acute glucose fluctuations compared with sustained chronic hyperglycemia in patients with type 2 diabetes. JAMA 2006; 295:1681–1687 (2008). Quagliaro, L. et al . Intermittent high glucose enhances apoptosis related to oxidative stress in human umbilical vein endothelial cells. The role of protein kinase C and NAD(P)H-oxidase activation. Diabetes 52:2795–2804 (2003). Dandona, P. Minimizing glycemic fluctuations in patients with type 2 diabetes: approaches and importance. Diabetes technology & therapeutics, 19 (9), 498–506 (2017). Siqueira, R. C. et al . Short-Term Results of Photobiomodulation Using Light-Emitting Diode Light of 670 nm in Eyes with Age-Related Macular Degeneration. Photobiomodulation, Photomedicine, and Laser Surgery 39(9), 581–586 (2021). Begum, R., Powner, M. B., Hudson, N., Hogg, C. & Jeffery, G. Treatment with 670 nm light up regulates cytochrome C oxidase expression and reduces inflammation in an age-related macular degeneration model. PloS one 8 (2), e57828 (2013). Hamblin, M. R., Huang, Y. Y., & Heiskanen, V. Non-mammalian Hosts and Photobiomodulation: Do All Life‐forms Respond to Light?. Photochemistry and photobiology 95(1), 126–139 (2019). Johnstone, D. M., Mitrofanis, J., & Stone, J. Targeting the body to protect the brain: inducing neuroprotection with remotely-applied near infrared light. Neural regeneration research, 10(3), 349 (2015). Shinhmar, H., Hogg, C., & Jeffery, G. Exposure to long wavelength light that improves aged mitochondrial function shifts acute cytokine expression in serum and the retina. Plos one, 18(7), e0284172 (2023). Dache, Z. A. A. et al . Blood contains circulating cell free respiratory competent mitochondria. Faseb Journal, 34(3), 3616–3630 (2020). Song, X. et al . Existence of circulating mitochondria in human and animal peripheral blood. International Journal of Molecular Sciences, 21(6), 2122 (2020). McCarthy, M. I. Genomics, type 2 diabetes, and obesity. New England Journal of Medicine 363 (24), 2339–2350 (2010). McCarthy, M. I. & Zeggini, E. Genome-wide association studies in type 2 diabetes. Current diabetes reports 9 (2), 164–171 (2009). Tabák, A. G., Herder, C., Rathmann, W., Brunner, E. J. & Kivimäki, M. Prediabetes: a high-risk state for diabetes development. The Lancet 379 (9833), 2279–2290 (2012). Ceriello, A. Postprandial hyperglycemia and diabetes complications: is it time to treat?. Diabetes 54(1), 1–7 (2005). Shinhmar, H., Hoh Kam, J., Mitrofanis, J., Hogg, C. & Jeffery, G. Shifting patterns of cellular energy production (adenosine triphosphate) over the day and key timings for the effect of optical manipulation. Journal of Biophotonics 15(10), e202200093 (2022). Tan, A. Y. S. et al. . Self-administered oral glucose tolerance test with capillary glucose measurements for the screening of diabetes mellitus in high-risk adults: a feasibility study. BMJ Open Diabetes Research and Care 9 (2), e002556 (2021). Avci, P. et al.. Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. In Seminars in cutaneous medicine and surgery (Vol. 32, No. 1, p. 41). NIH Public Access (2013, March). Additional Declarations No competing interests reported. Cite Share Download PDF Status: Posted Version 1 posted 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. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-3275287","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":228314056,"identity":"74176281-2d81-41f5-90c7-e155d3188a9f","order_by":0,"name":"Michael B Powner","email":"","orcid":"","institution":"City, University of London","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Michael","middleName":"B","lastName":"Powner","suffix":""},{"id":228314057,"identity":"2c0e453e-103e-4432-81b0-820882da5f68","order_by":1,"name":"Glen Jeffery","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA4klEQVRIie2RsQrCMBCGDwS7FF0jDvERrgiCUIqPclJIF8HBRXAwky4+jL7BQYcufQBLF12cHOrWTVN1bjsK5lvuCPny/xAAi+U3IVj7Zjga4PI+6LZQUmWGy9XaToGPIqilImdwvTD5S8zuXkEQSBCKahWPIUQmNT3mi7EJCj0tFNcrGtTwUcaI+WJiinUIRKSblKhkeiJmaaVsmxUJoICJEc9upcRGaSiGHQgFU4iDVK0EYeLt3BvVp+wP84IpwF4Sn4pivZF9R2F9Sux+3hy922CLj5Ta4e/SdNVisVj+lhfpqUT3IKmTBwAAAABJRU5ErkJggg==","orcid":"","institution":"University College London","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Glen","middleName":"","lastName":"Jeffery","suffix":""}],"badges":[],"createdAt":"2023-08-18 12:14:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3275287/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3275287/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":42244013,"identity":"863f7c6a-f6ba-446b-9ba9-8078254398b3","added_by":"auto","created_at":"2023-08-28 14:10:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":55615,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eExposure to\u003c/strong\u003e \u003cstrong\u003e670 nm light reduces blood glucose levels\u003c/strong\u003e. (a) Capillary blood glucose concentrations were taken every 15 min for 2 h, following a fasted oral glucose tolerance test (OGTT). Exposure to 15 min of 670 nm light (28,800 J) (n= 15), starting 45 min prior to OGTT, significantly reduced blood glucose levels, from time point +45 min, compared to a placebo intervention (no light, n= 15). Area under the curve analysis shows a 27.7% reduction in mean glucose loading post glucose consumption (\u003cem\u003ep= 0.0002\u003c/em\u003e), while a repeated measures ANOVA confirms a significant difference between the two groups (\u003cem\u003ep= 0.049\u003c/em\u003e). Post hoc analysis conformed which specific time points showed differences (b) Glucose response within a single population, with and without 670 nm exposure; initially no 670 nm was given, and an OGTT carried out, subsequently they were re-tested and exposed to 670 nm. 670 nm in these individuals significantly reduced blood glucose loading of the blood. Area under the curve analysis showed a 26.3% reduction (\u003cem\u003ep= 0.0008\u003c/em\u003e) and this was confirmed by repeated measures ANOVA (\u003cem\u003ep\u0026lt;0.001\u003c/em\u003e). Reduced elevation was time dependent and observed after time point +60 min of the OGTT. (c) Glucose response within a single population was carried out as above for the placebo intervention; there were no significant differences found. (d) Maximum glucose levels reached were significantly reduced between 670 nm and placebo interventions. There was a significant reduction in maximum glucose level reached with 670 nm exposure, compared to the preceding control with no light exposure. There was no difference observed between the maximum OGTT result following placebo interventions compared to its preceding control. *; p\u0026lt; 0.05, **; p\u0026lt; 0.01, ***; p\u0026lt; 0.005, ns; not significant. Error bars are standard error of the mean. Statistical analysis: ANOVA using a general linear model with repeat measures, with post hoc Mann Whitney U test was used for between group analysis, and Wilcoxon Signed Rank Test for single participant (paired) analysis (all two tailed tests).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-3275287/v1/e64469a31bd4539193f6ab3c.png"},{"id":42244012,"identity":"2f5ea98c-43d5-426f-aa7c-3b419479a700","added_by":"auto","created_at":"2023-08-28 14:10:07","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":44756,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003e670 nm light increases exhaled carbon dioxide partial pressure\u003c/strong\u003e. End-tidal CO\u003csub\u003e2\u003c/sub\u003e (EtCO\u003csub\u003e2\u003c/sub\u003e) was recorded by side stream capnometry, every 15 min for 2 h, following a fasted oral glucose tolerance test. The expected increase in exhaled CO\u003csub\u003e2\u003c/sub\u003e partial pressure following glucose ingestion was observed across all four groups (a-c). No statistically significant difference was found between the 670 nm and Placebo intervention groups (\u003cem\u003ep= 0.21\u003c/em\u003e) (a). Within the 670 nm group, exposure to 15 min of 670 nm light (28,800 J) (n= 15), was found to induce a significant increase in EtCO\u003csub\u003e2\u003c/sub\u003e (ANOVA, \u003cem\u003ep= 0.03\u003c/em\u003e) (b). With post hoc analysis highlighted a statistically significant increase in EtCO\u003csub\u003e2\u003c/sub\u003e at 60 min, when compared against paired participant data recorded with no 670 nm light (b). *; p\u0026lt; 0.05. Error bars are standard error of the mean. Statistical analysis: ANOVA using a general linear model with repeat measures, with post hoc Mann Whitney U test was used for between group analysis, and Wilcoxon Signed Rank Test for single participant (paired) analysis (two tailed tests).\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-3275287/v1/1bdb848ff8a58eff86226552.png"},{"id":47245601,"identity":"66818806-af91-4dfa-b29f-de49f96aabf2","added_by":"auto","created_at":"2023-11-29 04:22:52","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":324562,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3275287/v1/ceca4290-61da-4345-9d25-ba4f6a8a2c1c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Optical stimulation of mitochondria reduces blood glucose levels","fulltext":[{"header":"Introduction","content":"\u003cp\u003eRed light (~\u0026thinsp;650\u0026ndash;800 nm) stimulates mitochondrial respiration, shifting their metabolism. This photobiomodulation, alters cellular respiration rate, increases membrane potential, ATP production and subsequently reduces reactive oxygen species and inflammatory markers. [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e, \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e] This results in improved sensory and motor function, including aged human colour perception. [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] 670 nm and other, longer wavelengths of red/near infra-red light are absorbed by the nanoscopic interfacial water layer surrounding mitochondrial ATP rotor pumps. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] The energy transfer reduces water viscosity, allowing the rotor pump to achieve greater momentum, and increases ATP production. [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] An increase in ATP production rate requires more fuel. Glucose is the primary fuel source in animals and, as shown previously, systemic glucose concentrations decrease in an invertebrate model (bees) following a single 670 nm light exposure. [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e] This result potentially has significance for human health, particularly in diabetes management and weight control. Here we have extended these findings from invertebrates into humans, demonstrating that a non-pharmaceutical, non-invasive, optical intervention can be used to support blood glucose level management.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eParticipants were randomised into either a 670 nm group (n\u0026thinsp;=\u0026thinsp;15), or placebo (no light) group (n\u0026thinsp;=\u0026thinsp;15). All individuals undertook fasting oral glucose tolerance tests (OGTT), consuming 75g glucose in 150 ml of water. Capillary blood glucose levels were recorded by finger prick tests, and respired end-tidal carbon dioxide partial pressure (EtCO\u003csub\u003e2\u003c/sub\u003e) was measured every 15 min for 2 h while at rest. For all individuals in both groups an initial baseline (control) OGTT was recorded.\u003c/p\u003e \u003cp\u003eWithin 7 days, a second OGTT was administered during which the 670 nm group received a 15 min light exposure of 40mW cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (28,800 J) across an area of 800 cm\u003csup\u003e2\u003c/sup\u003e of skin of the upper back starting 45 min prior to consuming glucose, with the light not turned on for the placebo group. Energies and timings of lights are consistent with previous studies. [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e] Three comparisons were made between OGTTs for analysis. (1) The 670 nm and placebo intervention results were compared across the two subject populations. To ensure any results found were not caused by marked individual variabilities, paired within-participant comparisons were made between (2) the no 670 nm control against 670 nm exposure results and (3) no placebo control against placebo intervention results.\u003c/p\u003e \u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003eEffect of red light on blood glucose parameters\u003c/h2\u003e \u003cp\u003eFollowing glucose loading in the OGTT, initial blood glucose levels over the first 30 min were similar in both 670 nm exposed and placebo interventions (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). Blood glucose levels were always elevated above fasting levels following glucose consumption (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). When comparing 670 nm against placebo interventions, 670 nm light reduced this elevation in blood glucose by 27.7% over the 2 h OGTT, as determined by area under the curve (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0002\u003c/em\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). A repeated measures ANOVA confirmed a significant difference (p\u0026thinsp;=\u0026thinsp;0.049) with post hoc analysis highlighting significant decreases found at specific time points of 45-, 60- and 90-min post-loading (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). These relative decreases resulted in the absolute blood glucose level, not baselined to change from fasting level, being reduced by 7.3% (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0061\u003c/em\u003e) between 670 nm and placebo interventions. The magnitude of this response following exposure of only a limited area of tissue, is likely the result of wider indirect metabolic upregulation, [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e] potentially via distal mitochondrial communication. [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]\u003c/p\u003e \u003cp\u003ePaired participant analyses confirmed this result. Within the 670 nm group, the elevation of blood glucose after loading was reduced by 26.3% (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0008\u003c/em\u003e) following 670 nm exposure, with a significant effect found at 60 min post-loading and return to baseline at the final blood collection after 120 min (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Absolute blood glucose levels compared, without baselining to fasting levels, were decreased by 7.9% (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0012\u003c/em\u003e). Within-participant data for the placebo group, comparing control visit and placebo intervention, showed no difference in blood glucose levels (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec).\u003c/p\u003e \u003cp\u003eHere, we have also looked into the effect of 670 nm light on blood glucose spiking; maximum glucose levels reached, recorded in mmol/L, were reduced following 670 nm light exposure. Comparing 670 nm and placebo interventions revealed a reduction of 5.1% in the peak glucose concentration reached, down from 10.8 mmol/L to 10.2 mmol/L (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0102\u003c/em\u003e) (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). Separately, paired analysis within the 670 nm group gave a 7.5% reduction in maximum glucose peak level, down from 10.3 mmol/L to 9.5 mmol/L (\u003cem\u003ep\u0026thinsp;=\u0026thinsp;0.0054\u003c/em\u003e), with no significant differences in maximum glucose level reached in the paired placebo group analysis (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed). These changes were obtained with only 15 minutes of exposure time over 800 cm\u003csup\u003e2\u003c/sup\u003e tissue area, accounting for approximately 4% of the skin surface area. [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eEffect of red light on exhaled carbon dioxide\u003c/h2\u003e \u003cp\u003eReduced blood glucose levels may result from an increased glucose oxidation rate, or through an increased storage of the ingested glucose as glycogen. Increased oxidation would lead to increased CO\u003csub\u003e2\u003c/sub\u003e production and would be detectable through exhaled breath. Here, EtCO\u003csub\u003e2\u003c/sub\u003e increased during all the glucose tolerance test (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea-c), while participants were at rest, consistent with elevated carbohydrate intake. [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] No significant differences were observed between 670 nm and placebo groups (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea). However, a significant difference in EtCO\u003csub\u003e2\u003c/sub\u003e was observed 60 min post glucose loading when comparing 670 nm exposed participants against their no intervention control results (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb). This correlates with the first time point of significant reductions in blood glucose level (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). No significant difference in breath rate was observed for any intervention. The observed change in CO\u003csub\u003e2\u003c/sub\u003e production is consistent with increased oxidation of glucose as a mechanism, supported by previous invertebrate experiments, where 670 nm exposure increased respired CO\u003csub\u003e2\u003c/sub\u003e volume [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e] [see their Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eA], while not ruling out contribution from increased glucose storage.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study has shown that a single 15 min exposure to 670 nm light significantly reduces the amount of glucose loaded into the blood during a standard oral glucose tolerance test. While glucose is a vital nutrient, sustained high levels in the blood induce inflammation and insulin resistance in vascular endothelial cells. [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e] A reduction in glucose loading after eating (post-prandial) is beneficial in those with impaired blood glucose homeostasis. However, the degree of post-prandial hyperglycaemia and other fluctuation in blood glucose levels may contribute to the pathogenesis of diabetic complications. [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e] Fluctuations are more damaging than sustained hyperglycaemia, as an intermittent high glucose exposure further increases endothelial cell apoptosis rate. [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e] Hence, clinical intervention routinely includes practices to minimise sharp fluctuations in blood glucose levels in diabetic patients. [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] We report that 670 nm exposure decreases maximum glucose levels reached post glucose challenge, and therefore offers an intervention to limit glucose spiking.\u003c/p\u003e \u003cp\u003eThe effect of red light exposure is consistent across species, [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e, \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] however the timing of onset has not been fully explored. Here, participants were exposed to red light 45 min prior to glucose loading, and blood glucose levels were significantly reduced 45 min post loading (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea), revealing that onset of the effect is within ~\u0026thinsp;1.5 h. This is within the time frame of improved retinal function following red light exposure in aged human subjects. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e] Significant reduction in blood glucose was observed following local red light illumination of the body, rather than requiring whole body exposure. Red light exposure has been shown to have an abscopal effect [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e] and results in systemic changes in cytokine expression in the blood [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. It is likely that this systemic cytokine change may play a role in the marked widespread changes in blood glucose to a distal region of illumination. Alternatively, blood contains cell-free, respiratory competent, mitochondria [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] which may also be modulated by the red light and signal changes systemically as they circulate.\u003c/p\u003e \u003cp\u003e670 nm light increases ATP levels, [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e] via increasing mitochondrial oxidative phosphorylation. [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e] An increased facilitated diffusion rate of glucose into cells to meet increased intra-cellular demand by 670 nm absorption, is the likely mechanism that results in reduced blood glucose. Increased EtCO\u003csub\u003e2\u003c/sub\u003e levels observed in paired participant analysis of the 670 exposure group (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb), whilst the participants were at rest, could result from increased oxidation. However, stimulation of glucose incorporation into carbohydrate stores cannot be excluded as an alternative mechanism involved.\u003c/p\u003e \u003cp\u003eDiabetes mellitus encompasses a group of etiologically different metabolic diseases and is characterised by impaired or loss of glucose homeostasis, leading to high blood glucose levels. It is the most common metabolic disorder worldwide and a major risk factor for cardiovascular disease. Type I diabetes results in elevated blood glucose levels due to reduced insulin secretion from a loss of pancreatic β-cells. While, the predominant form, Type II diabetes is typified by insulin insensitivity leading to a loss of insulin activation of cells in peripheral organs (particularly liver and skeletal muscle), resulting in reduced glucose uptake. [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e] Concurrently, in Type II diabetes, pancreatic insulin secretion may be reduced and so is insufficient to meet the higher demand. [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] Glucose intolerance resulting in significantly elevated post-prandial blood glucose levels and elevated fasting glucose levels (5.6-7.0 mmol/L; American Diabetes Association, 6.1-7.0 mmol/L; World Health Organisation) often precedes Type II diabetes and is referred to as pre-diabetes. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] People who are pre-diabetic are at five to six fold greater risk of developing Type II diabetes. Each of these three impaired metabolic states (Type I and Type II diabetes, and pre-diabetes) may benefit from photobiomodulation with 670 nm light to reduce post prandial blood glucose fluctuations that increase the risk of diabetic complications, such as nephropathy, retinopathy, or cardiovascular disease. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/p\u003e \u003cp\u003eMitochondrial oxidation rate peaks in the morning, coincident with the known surge of blood glucose. [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] Morning is the only time widow when 670 nm exposure is effective at manipulating mitochondrial function. [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e] Hence, a brief exposure as a part of an early daily routine could be incorporated into normal life, supporting current recommended glucose control measures.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eStudy cohort\u003c/h2\u003e \u003cp\u003eThis study was approved by City, University of London, School of Health and Psychological Sciences Research Ethics committee (\u003cem\u003eETH2122-1596\u003c/em\u003e). We confirm that all research was performed in accordance with relevant guidelines/regulations, and that all participants gave informed consent to take part. This study was performed in accordance with the Declaration of Helsinki. Thirty healthy participants were recruited: 15 in the 670 nm group (mean age 41.1\u0026thinsp;\u0026plusmn;\u0026thinsp;13.1 years), 15 in the placebo group (no light) (mean age 38.3\u0026thinsp;\u0026plusmn;\u0026thinsp;13.7 years), with no known metabolic conditions and not taking medication known to effect metabolism.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eOral glucose tolerance test and Blood glucose monitoring\u003c/h2\u003e \u003cp\u003e Participants fasted overnight, consuming only water for at least 10 hours prior to the oral glucose tolerance test (OGTT). An initial finger prick capillary blood glucose levels was measured using a blood glucose monitor (Kinetik Wellbeing, UK), a method with proven sensitivity vs venous glucose levels, for use in OGTT. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] Forty-five minutes later an OGTT was performed. Participants consumed 75g glucose in water (total volume of 150ml), within 2 minutes. Following glucose consumption, further finger prick blood glucose concentrations were measured at 0 (fasted), 15, 30, 45, 60, 75, 90, 105, 120 min after administration of glucose solution.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003eRespiratory measurements\u003c/h2\u003e \u003cp\u003eEnd-tidal partial pressure of carbon dioxide (EtCO\u003csub\u003e2\u003c/sub\u003e) in expired gas, and breath rate were measured at the same time intervals as blood glucose (-45, 0, 15, 30, 45, 60, 75, 90, 105, 120 min after administration of glucose solution) via capnometry, using a PC-900B Hand Held SideStream EtCO2 monitor (PROACT medical, UK), and nasal cannula.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003eLight exposure\u003c/h2\u003e \u003cp\u003eAll participants undertook an OGTT on two separate occasions. During the first visit, they underwent an OGTT with a full set of glucose and respiration measurements without intervention (baseline measurements, control). Participants were randomised into the intervention group or the placebo group at the point of recruitment; during their second visit there was an intervention step added to the protocol. In the 670 nm group, immediately following initial blood glucose levels being recorded (-45 min), participants exposed a 800 cm\u003csup\u003e2\u003c/sup\u003e region of upper back to 670 nm light for 15 min at an intensity of 40mW cm\u003csup\u003e\u0026minus;\u0026thinsp;2\u003c/sup\u003e (28,800 J). With a penetration depth of approximately 2 mm that would include the cells of the skin and underlying musculature [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e] (including the trapezius). Light was delivered via LEDs; 670 nm was the peak wavelength, with a half power band of approximately 10 nm. The LED array was positioned 400 mm from the participants back, surrounded by a shield that rested on the participant\u0026rsquo;s skin, to prevent light leakage, and to blind the participant to which group they were randomised into. The placebo group underwent the same procedure, except the LED array was not switched on during their intervention OGTT.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003eStatistical analysis\u003c/h2\u003e \u003cp\u003eThe initial measurement at 0 min was used in analysis of change from fasting levels due to the variation in initial blood glucose concentration and EtCO\u003csub\u003e2\u003c/sub\u003e partial pressures between participants. Glucose loading in the blood over the 2 h OGTT was determined by measuring the area under the curve. This was carried out assuming linear lines between data points at sequential time intervals. For inter group comparisons (670 nm vs placebo), each intervention was first baselined against that groups control OGTT data and expressed relative to this for each participant. A repeated measures analysis of variance (ANOVA) using a general linear model with repeat measures, with post hoc Mann Whitney U test was used to test for significant difference between 670 nm and placebo interventions, while a post-hoc Wilcoxon Signed Rank Test was used for paired data analysis comparing intra-participant data (two tailed tests in each case, SPSS v25). Standard error of the mean was calculated for error bars.\u003c/p\u003e \u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors would like to thank Simon Grant and Ron Douglas for their productive comments in preparation of this manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMBP and GJ; project conception, study design, data collection, data analysis and interpretation, wrote the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability statement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe data that support the findings of this study are available through FigShare;\u003c/p\u003e\n\u003cp\u003e10.6084/m9.figshare.22665091. \u003ca href=\"https://figshare.com/s/14144678e1c32f79cc32\"\u003ehttps://figshare.com/s/14144678e1c32f79cc32\u003c/a\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eBegum, R. \u003cem\u003eet al.\u003c/em\u003e. Near-infrared light increases ATP, extends lifespan and improves mobility in aged Drosophila melanogaster. Biology letters. 11(3):20150073 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKaynezhad, P., Tachtsidis, I., \u0026amp; Jeffery, G. Optical monitoring of retinal respiration in real time: 670 nm light increases the redox state of mitochondria. Experimental Eye Research \u003cem\u003e152\u003c/em\u003e, 88\u0026ndash;93 (2016).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHamblin, M. R. Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS biophysics \u003cem\u003e4\u003c/em\u003e(3), 337 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHu, D., Zhu, S., \u0026amp; Potas, J. R. Red LED photobiomodulation reduces pain hypersensitivity and improves sensorimotor function following mild T10 hemicontusion spinal cord injury. Journal of Neuroinflammation 13(1), 1\u0026ndash;15 (2016).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eWeinrich, T. W., Hogg, C., \u0026amp; Jeffery, G. The temporal sequence of improved mitochondrial function on the dynamics of respiration, mobility, and cognition in aged Drosophila. Neurobiology of aging \u003cem\u003e70\u003c/em\u003e, 140\u0026ndash;147 (2018).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShinhmar, H., Hogg, C., Neveu, M. \u0026amp; Jeffery, G. Weeklong improved colour contrasts sensitivity after single 670 nm exposures associated with enhanced mitochondrial function. Scientific Reports 11(1):1\u0026ndash;9 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSommer, A. P., Haddad, M. K. \u0026amp; Fecht, H. J. Light effect on water viscosity: implication for ATP biosynthesis. Scientific reports 5(1):1\u0026ndash;6 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePowner, M. B., \u0026amp; Jeffery, G. Systemic glucose levels are modulated by specific wavelengths in the solar light spectrum that shift mitochondrial metabolism. Plos one 17(11), e0276937 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eFitzgerald, M. \u003cem\u003eet. al.\u003c/em\u003e Red/near-infrared irradiation therapy for treatment of central nervous system injuries and disorders. Reviews in the Neurosciences 24(2), 205\u0026ndash;226 (2013).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSaliba, A. \u003cem\u003eet al.\u003c/em\u003ePhotobiomodulation mitigates diabetes-induced retinopathy by direct and indirect mechanisms: evidence from intervention studies in pigmented mice. PloS one 10(10), e0139003 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDurieux, J., Wolff, S. \u0026amp; Dillin, A. The cell-non-autonomous nature of electron transport chain-mediated longevity. Cell 144(1), 79\u0026ndash;91 (2011).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMosteller, R. D. Simplified calculation of body surface area. New England Journal of Medicine 317, 1098 (1987).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAskanazi, J. \u003cem\u003eet al.\u003c/em\u003e. Respiratory changes induced by the large glucose loads of total parenteral nutrition. JAMA, 243(14), 1444\u0026ndash;1447 (1980).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003ePowner, M. B., Priestley, G., Hogg, C. \u0026amp; Jeffery, G. Improved mitochondrial function corrects immunodeficiency and impaired respiration in neonicotinoid exposed bumblebees. Plos one \u003cem\u003e16\u003c/em\u003e(8), e0256581 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eKim, F. \u003cem\u003eet al.\u003c/em\u003e Activation of IKKbeta by glucose is necessary and sufficient to impair insulin signaling and nitric oxide production in endothelial cells. J Mol Cell Cardiol. 39:327\u0026ndash;334 (2005).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMonnier, L. \u003cem\u003eet al.\u003c/em\u003e Activation of oxidative stress by acute glucose fluctuations compared with sustained chronic hyperglycemia in patients with type 2 diabetes. \u003cem\u003eJAMA\u003c/em\u003e 2006; 295:1681\u0026ndash;1687 (2008).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eQuagliaro, L. \u003cem\u003eet al\u003c/em\u003e. Intermittent high glucose enhances apoptosis related to oxidative stress in human umbilical vein endothelial cells. The role of protein kinase C and NAD(P)H-oxidase activation. Diabetes 52:2795\u0026ndash;2804 (2003).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDandona, P. Minimizing glycemic fluctuations in patients with type 2 diabetes: approaches and importance. Diabetes technology \u0026amp; therapeutics, \u003cem\u003e19\u003c/em\u003e(9), 498\u0026ndash;506 (2017).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSiqueira, R. C. \u003cem\u003eet al\u003c/em\u003e. Short-Term Results of Photobiomodulation Using Light-Emitting Diode Light of 670 nm in Eyes with Age-Related Macular Degeneration. Photobiomodulation, Photomedicine, and Laser Surgery 39(9), 581\u0026ndash;586 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eBegum, R., Powner, M. B., Hudson, N., Hogg, C. \u0026amp; Jeffery, G. Treatment with 670 nm light up regulates cytochrome C oxidase expression and reduces inflammation in an age-related macular degeneration model. PloS one \u003cem\u003e8\u003c/em\u003e(2), e57828 (2013).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eHamblin, M. R., Huang, Y. Y., \u0026amp; Heiskanen, V. Non-mammalian Hosts and Photobiomodulation: Do All Life‐forms Respond to Light?. Photochemistry and photobiology 95(1), 126\u0026ndash;139 (2019).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eJohnstone, D. M., Mitrofanis, J., \u0026amp; Stone, J. Targeting the body to protect the brain: inducing neuroprotection with remotely-applied near infrared light. Neural regeneration research, 10(3), 349 (2015).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShinhmar, H., Hogg, C., \u0026amp; Jeffery, G. Exposure to long wavelength light that improves aged mitochondrial function shifts acute cytokine expression in serum and the retina. Plos one, 18(7), e0284172 (2023).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eDache, Z. A. A. \u003cem\u003eet al\u003c/em\u003e. Blood contains circulating cell free respiratory competent mitochondria. Faseb Journal, 34(3), 3616\u0026ndash;3630 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eSong, X. \u003cem\u003eet al\u003c/em\u003e. Existence of circulating mitochondria in human and animal peripheral blood. International Journal of Molecular Sciences, 21(6), 2122 (2020).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcCarthy, M. I. Genomics, type 2 diabetes, and obesity. New England Journal of Medicine \u003cem\u003e363\u003c/em\u003e(24), 2339\u0026ndash;2350 (2010).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eMcCarthy, M. I. \u0026amp; Zeggini, E. Genome-wide association studies in type 2 diabetes. Current diabetes reports \u003cem\u003e9\u003c/em\u003e(2), 164\u0026ndash;171 (2009).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTab\u0026aacute;k, A. G., Herder, C., Rathmann, W., Brunner, E. J. \u0026amp; Kivim\u0026auml;ki, M. Prediabetes: a high-risk state for diabetes development. The Lancet \u003cem\u003e379\u003c/em\u003e(9833), 2279\u0026ndash;2290 (2012).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eCeriello, A. Postprandial hyperglycemia and diabetes complications: is it time to treat?. Diabetes 54(1), 1\u0026ndash;7 (2005).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eShinhmar, H., Hoh Kam, J., Mitrofanis, J., Hogg, C. \u0026amp; Jeffery, G. Shifting patterns of cellular energy production (adenosine triphosphate) over the day and key timings for the effect of optical manipulation. Journal of Biophotonics 15(10), e202200093 (2022).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eTan, A. Y. S. \u003cem\u003eet al.\u003c/em\u003e. Self-administered oral glucose tolerance test with capillary glucose measurements for the screening of diabetes mellitus in high-risk adults: a feasibility study. BMJ Open Diabetes Research and Care \u003cem\u003e9\u003c/em\u003e(2), e002556 (2021).\u003c/span\u003e\u003c/li\u003e \u003cli\u003e\u003cspan\u003eAvci, P. \u003cem\u003eet al..\u003c/em\u003e Low-level laser (light) therapy (LLLT) in skin: stimulating, healing, restoring. In \u003cem\u003eSeminars in cutaneous medicine and surgery\u003c/em\u003e (Vol.\u0026nbsp;32, No. 1, p.\u0026nbsp;41). NIH Public Access (2013, March).\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"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":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Photobiomodulation, red light, 670 nm, mitochondria, glucose, oral glucose tolerance test, human","lastPublishedDoi":"10.21203/rs.3.rs-3275287/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3275287/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eMitochondria regulate metabolism, but solar light influences its rate. Red light increases mitochondrial membrane potentials and ATP production and may increase glucose demand. Here we show, with a glucose tolerance test, that red light exposure in normal subjects significantly reduces blood sugar levels. A 15 min exposure to 670 nm light, reduced the degree of blood glucose elevation following glucose intake by 27.7%, over 2 h. Maximum glucose spiking was reduced by 5.1%. Decreased blood glucose correlated with increased exhaled end-tidal CO\u003csub\u003e2\u003c/sub\u003e partial pressure at 1 h, indicating the mechanism includes an increased oxidation rate. Consequently, 670 nm light exposure can be used to reduce blood glucose spikes following meals. This may reduce damaging fluctuations of blood glucose on the body, a major risk factor for diabetic complications, offering a safe, non-invasive intervention for glucose management of diabetes at home.\u003c/p\u003e","manuscriptTitle":"Optical stimulation of mitochondria reduces blood glucose levels","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2023-08-28 14:10:03","doi":"10.21203/rs.3.rs-3275287/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"db62b367-ef6c-46e2-b110-7b6eb5d686d5","owner":[],"postedDate":"August 28th, 2023","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":24225005,"name":"Biological sciences/Physiology"},{"id":24225006,"name":"Health sciences/Cardiology"}],"tags":[],"updatedAt":"2023-11-29T04:14:45+00:00","versionOfRecord":[],"versionCreatedAt":"2023-08-28 14:10:03","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3275287","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3275287","identity":"rs-3275287","version":["v1"]},"buildId":"ehx78VzkSd0WSzXnipQa-","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}