The protective PLCG2 variants delay Alzheimer’s disease onset age in APOE ε4 carriers

The protective PLCG2 variants delay Alzheimer’s disease onset age in APOE ε4 carriers | medRxiv /* */ /* */ <!-- <!-- /*! * yepnope1.5.4 * (c) WTFPL, GPLv2 */ (function(a,b,c){function d(a){return"[object Function]"==o.call(a)}function e(a){return"string"==typeof a}function f(){}function g(a){return!a||"loaded"==a||"complete"==a||"uninitialized"==a}function h(){var a=p.shift();q=1,a?a.t?m(function(){("c"==a.t?B.injectCss:B.injectJs)(a.s,0,a.a,a.x,a.e,1)},0):(a(),h()):q=0}function i(a,c,d,e,f,i,j){function k(b){if(!o&&g(l.readyState)&&(u.r=o=1,!q&&h(),l.onload=l.onreadystatechange=null,b)){"img"!=a&&m(function(){t.removeChild(l)},50);for(var d in y[c])y[c].hasOwnProperty(d)&&y[c][d].onload()}}var j=j||B.errorTimeout,l=b.createElement(a),o=0,r=0,u={t:d,s:c,e:f,a:i,x:j};1===y[c]&&(r=1,y[c]=[]),"object"==a?l.data=c:(l.src=c,l.type=a),l.width=l.height="0",l.onerror=l.onload=l.onreadystatechange=function(){k.call(this,r)},p.splice(e,0,u),"img"!=a&&(r||2===y[c]?(t.insertBefore(l,s?null:n),m(k,j)):y[c].push(l))}function j(a,b,c,d,f){return q=0,b=b||"j",e(a)?i("c"==b?v:u,a,b,this.i++,c,d,f):(p.splice(this.i++,0,a),1==p.length&&h()),this}function k(){var a=B;return a.loader={load:j,i:0},a}var l=b.documentElement,m=a.setTimeout,n=b.getElementsByTagName("script")[0],o={}.toString,p=[],q=0,r="MozAppearance"in l.style,s=r&&!!b.createRange().compareNode,t=s?l:n.parentNode,l=a.opera&&"[object Opera]"==o.call(a.opera),l=!!b.attachEvent&&!l,u=r?"object":l?"script":"img",v=l?"script":u,w=Array.isArray||function(a){return"[object Array]"==o.call(a)},x=[],y={},z={timeout:function(a,b){return b.length&&(a.timeout=b[0]),a}},A,B;B=function(a){function b(a){var a=a.split("!"),b=x.length,c=a.pop(),d=a.length,c={url:c,origUrl:c,prefixes:a},e,f,g;for(f=0;f<d;f++)g=a[f].split("="),(e=z[g.shift()])&&(c=e(c,g));for(f=0;f<b;f++)c=x[f](c);return c}function g(a,e,f,g,h){var i=b(a),j=i.autoCallback;i.url.split(".").pop().split("?").shift(),i.bypass||(e&&(e=d(e)?e:e[a]||e[g]||e[a.split("/").pop().split("?")[0]]),i.instead?i.instead(a,e,f,g,h):(y[i.url]?i.noexec=!0:y[i.url]=1,f.load(i.url,i.forceCSS||!i.forceJS&&"css"==i.url.split(".").pop().split("?").shift()?"c":c,i.noexec,i.attrs,i.timeout),(d(e)||d(j))&&f.load(function(){k(),e&&e(i.origUrl,h,g),j&&j(i.origUrl,h,g),y[i.url]=2})))}function h(a,b){function c(a,c){if(a){if(e(a))c||(j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}),g(a,j,b,0,h);else if(Object(a)===a)for(n in m=function(){var b=0,c;for(c in a)a.hasOwnProperty(c)&&b++;return b}(),a)a.hasOwnProperty(n)&&(!c&&!--m&&(d(j)?j=function(){var a=[].slice.call(arguments);k.apply(this,a),l()}:j[n]=function(a){return function(){var b=[].slice.call(arguments);a&&a.apply(this,b),l()}}(k[n])),g(a[n],j,b,n,h))}else!c&&l()}var h=!!a.test,i=a.load||a.both,j=a.callback||f,k=j,l=a.complete||f,m,n;c(h?a.yep:a.nope,!!i),i&&c(i)}var i,j,l=this.yepnope.loader;if(e(a))g(a,0,l,0);else if(w(a))for(i=0;i (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];var j=d.createElement(s);var dl=l!='dataLayer'?'&l='+l:'';j.src='//www.googletagmanager.com/gtm.js?id='+i+dl;j.type='text/javascript';j.async=true;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-P4HH5NV'); Skip to main content Home About Submit ALERTS / RSS Search for this keyword Advanced Search The protective PLCG2 variants delay Alzheimer’s disease onset age in APOE ε 4 carriers View ORCID Profile Heli Jeskanen , View ORCID Profile Sami Heikkinen , Inka Kervinen , Jenni Lehtisalo , Tiia Ngandu , Roosa-Maria Willman , Jessica Rosa , View ORCID Profile Dorit Hoffmann , FinnGen , View ORCID Profile Ville Leinonen , View ORCID Profile Annakaisa Haapasalo , View ORCID Profile Mari Takalo , View ORCID Profile Henna Martiskainen , View ORCID Profile Mikko Hiltunen doi: https://doi.org/10.1101/2025.09.22.25336304 Heli Jeskanen 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Heli Jeskanen Sami Heikkinen 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Sami Heikkinen Inka Kervinen 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site Jenni Lehtisalo 2 Department of Public Health, Lifestyles and Living Environments Unit, Finnish Institute for Health and Welfare (THL) , Helsinki, Finland 3 Institute of Clinical Medicine/Neurology, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site Tiia Ngandu 2 Department of Public Health, Lifestyles and Living Environments Unit, Finnish Institute for Health and Welfare (THL) , Helsinki, Finland 4 Division of Clinical Geriatrics, Center for Alzheimer Research, Care Sciences and Society (NVS), Karolinska Institutet , Stockholm, Sweden Find this author on Google Scholar Find this author on PubMed Search for this author on this site Roosa-Maria Willman 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site Jessica Rosa 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site Dorit Hoffmann 5 A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland ; Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Dorit Hoffmann FinnGen Find this author on Google Scholar Find this author on PubMed Search for this author on this site Ville Leinonen 7 Department of Neurosurgery, Kuopio University Hospital , Kuopio, Finland 8 Institute of Clinical Medicine – Neurosurgery, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Ville Leinonen Annakaisa Haapasalo 5 A. I. Virtanen Institute for Molecular Sciences, University of Eastern Finland ; Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Annakaisa Haapasalo Mari Takalo 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Mari Takalo Henna Martiskainen 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Henna Martiskainen Mikko Hiltunen 1 Institute of Biomedicine, University of Eastern Finland , Kuopio, Finland Find this author on Google Scholar Find this author on PubMed Search for this author on this site ORCID record for Mikko Hiltunen For correspondence: mikko.hiltunen{at}uef.fi Abstract Full Text Info/History Metrics Supplementary material Data/Code Preview PDF ABSTRACT INTRODUCTION We investigated the impact of protective PLCG2 -P522R and PLCG2 -3’UTR variants, and the TREM2 -R62H risk variant on Alzheimer’s disease (AD) onset age in relation to APOE ε4 status. Plasma-based biomarkers of the different variants were also explored. METHODS Kaplan-Meier and survival analyses were performed using FinnGen genotype and clinical endpoint data to assess the onset ages of AD, anxiety, and type 2 diabetes. Plasma biomarkers related to metabolism and inflammation were analyzed in 145 FINGER cohort participants. RESULTS PLCG2 -P522R and PLCG2 -3’UTR variants delayed AD onset, including among APOE ε 4 carriers. PLCG2 -P522R carriers showed elevated plasma ghrelin levels. TREM2 -R62H variant associated with an earlier onset of AD in APOE ε 4 carriers. DISCUSSION Protective PLCG2 variants may mitigate APOE ε 4-mediated risk of AD, which coincide with increased plasma levels of ghrelin. These findings highlight the further need to explore biomarkers and mechanisms associated with the protective variants in relation to APOE ε 4. 1 INTRODUCTION Genetic studies have identified a protective P522R variant in the PLCG2 gene ( PLCG2 -P522R; rs72824905 C>G), which decreases the risk of Alzheimer’s disease (AD) and increases longevity ( 1 – 4 ). PLCG2 -P522R, which potentiates PLCγ2 function, mediates several beneficial effects on microglia function in in vivo and in vitro models ( 5 – 10 ). Moreover, recent findings have revealed that neuronal downregulation of PLCG2 impairs synaptic function and triggers AD-related alterations, suggesting that changes in PLCγ2 levels and subsequent functions also within neurons are significant in the context of AD ( 5 ). PLCγ2 works downstream of triggering receptor expressed on myeloid cells 2 (TREM2) ( 11 ). TREM2 is selectively expressed in microglia and it plays a key role in modulating the cell survival, phagocytosis, and inflammatory responses ( 3 , 11 , 12 ). In TREM2 gene, several AD associated risk increasing variants have been recognized, such as R47H and R62H ( 1 , 13 – 15 ). These variants impair TREM2 functions leading to reduced microglial activation and clearance of β-amyloid, which exacerbates the disease pathology ( 3 , 11 , 12 ). It has been suggested that when compared to non-carriers, these variants do not differ in clinical presentation of the AD at baseline but they exhibit faster cognitive decline ( 13 ). Here, we investigated the effects of the protective PLCG2 -P522R and PLCG2- 3’UTR (rs4243226 A>G) variants on the onset age of AD individually and in relation to apolipoprotein E ε4 ( APOE ε 4) allele in the large FinnGen cohort originating from Finland ( 16 ). Furthermore, to identify potential biomarkers associated with the protective PLCG2 variants, we assessed the effects of the two variants on the plasma levels of common metabolic and inflammatory markers within the well-established FINGER intervention cohort ( 17 ). Here, we show that the protective PLCG2 -P522R variant delays AD onset age among APOE ε 4 carriers as well as associates with increased plasma levels of ghrelin, which is known to exert anti-inflammatory effects, metabolic regulation, and cognitive enhancement. Furthermore, we show that the PLCG2 -3’UTR variant delays the AD onset age among APOE ε4 carriers and in contrast, TREM2 -R62H leads to earlier onset of AD. 2 RESULTS 2.1 Protective PLCG2 variants exhibit minimal linkage disequilibrium Carriership of PLCG2 -P522R (rs72824905 C>G) showed the expected protective effect against AD in FinnGen (OR=0.55, 95% CI: 0.40-0.77, p=3.83×10 −4 ). Furthermore, we identified a common variant in the 3’UTR of PLCG2 (rs4243226 A>G, allele frequency: 0.7), which was associated with a significantly decreased risk of AD (OR=0.92, 95% CI: 0.90-0.95, p=2.55×10 −8 ). Linkage disequilibrium (LD) metrics revealed r 2 and D’ values of 0.0004 and 0.85, indicating a minimal correlation between the two variants despite the high degree of allelic co-segregation. 2.2 PLCG2 variants delay the onset age of AD To study AD onset timing and risk, we used Kaplan-Meier survival curves to illustrate differences in onset age, while the Cox proportional hazards model estimated the risk of developing AD between the genotypes. Based on the survival analyses, PLCG2 -P522R (CG or GG) significantly delayed AD onset age as compared to non-carriers (CC) in FinnGen ( Fig. 1A ). Cox analysis revealed that PLCG2 -P522R associated with a reduced risk by 42% of developing AD (HR=0.58, 95% CI: 0.42-0.82, p=0.00167). Additionally, male sex associated with an increased risk of AD (HR=1.09, 95% CI: 1.05-1.13, p=8.99×10 −7 ). The PLCG2 -P522R associated with a delayed onset of AD both in females and males (Supp. Fig. 1A-B). In the APOE genotype - stratified analysis with sex as a covariate, PLCG2 -P522R decreased the risk of AD in the APOE ε3/4 group by 46% (HR=0.54, 95% CI: 0.32-0.91, p=0.022, Fig. 1B ). The sex did not significantly affect the AD age of onset among the APOE ε3/4 carriers. However, male sex increased the risk of having AD within in APOE ε3/3 carriers (HR=1.20, 95% CI: 1.14-1.27, p=3.7×10 −12 , Supp. Fig. 1C-D). Within the APOE ε4/4 group, the PLCG2 -P522R variant or sex did not significantly affect the AD onset age as compared to non-carrier AD patients ( Fig. 1B and Supp. Fig. 1C-D). Cox regression analysis of PLCG2 -3’UTR revealed that this common variant (AG or GG) decreased the risk of AD by 11-16% as compared to non-carriers (AA) ( Fig. 1C ). There were no significant differences between sexes with respect to PLCG2 -3’UTR (Supplementary Table 1, Supp. Fig. 1E-F). According to APOE genotype-stratified analysis using sex as a covariate, the PLCG2 -3’UTR variant did not significantly affect the AD onset age within the APOE ε3/3 group. Conversely, PLCG2 -3’UTR moderately increased the AD onset age among homozygous PLCG2 -3’UTR carriers as compared to non-carriers within the APOE ε3/4 group (HR=0.83, 95% CI: 0.76-0.91, p=4.32×10 −5 , Fig. 1D ). Sex did not affect the AD onset age in the APOE ε3/4 group (Supp. Fig. 1G-H). Interestingly, the homozygosity of PLCG2 -3’UTR (GG) delayed the AD onset age in the APOE ε4/4 carriers (HR=0.87, 95% CI: 0.78-0.96, p=0.0091, Fig. 1D ). Furthermore, when sex effects were studied separately in APOE ε4/4 carriers, the PLCG2 -3’UTR exerted a protective effect only in female AD patients who were either heterozygous (HR=0.74, 95% CI: 0.58-0.94, p=0.016) or homozygous (HR=0.65, 95% CI: 0.51-0.83, p=0.00051) (Supp. Fig. 1G-H) for the PLCG2 -3’UTR variant. Download figure Open in new tab Figure 1. Protective PLCG2 -P522R delays the onset age of Alzheimer’s disease. To investigate the impact of the PLCG2 -P522R variant on AD onset, Kaplan-Meier curves on FinnGen endpoint data were utilized, with the focus on APOE ε 3- and APOE ε 4-carrying individuals >50 years of age. The curves illustrate the AD-free time in years, starting from age 50 until the AD diagnosis or the end of follow-up for the non-carrier group. Shaded area indicates 95% confidence intervals. A) PLCG2 -P522R compared to non-carriers in FinnGen “ALZHEIMER” endpoint. B) PLCG2 -P522R carriers compared to non-carriers in FinnGen “ALZHEIMER” endpoint with APOE ε 4 allele count. C) PLCG2 -3’UTR carriers compared to non-carriers in FinnGen “ALZHEIMER” endpoint. D) PLCG2 -3’UTR carriers compared to non-carriers in FinnGen “ALZHEIMER” endpoint with APOE ε 4 allele count. E) TREM2 -R62H carriers compared to non-carriers in FinnGen “ALZHEIMER” endpoint. F) TREM2 -R62H carriers compared to non-carriers in FinnGen “ALZHEIMER” endpoint with APOE ε 4 allele count. G) PLCG2 -P522R carriers compared to non-carriers in “ANY DEATH” endpoint. H) PLCG2 -P522R carriers compared to non-carriers with APOE ε 4 in “ANY DEATH” endpoint. APOE : ε3/3=33, ε3/4=34 and ε4/4=44 2.3 TREM2 -R62H variant carriers show earlier onset of AD Given that biologically PLCγ2 functions downstream of the TREM2 receptor, we also investigated the effects of the AD risk-increasing variant TREM2 -R62H (rs143332484 C>T, OR=1.21, 95% CI: 1.04-1.40, p=1.3×10 −3 ). The TREM2 -R62H (AF=0.0078) is more common in the Finnish population than the more widely known TREM2 -R47H (AF=0.00045) AD risk variant ( 15 , 18 ). No significant differences in the AD onset age were found between TREM2 -R62H carriers (CT or TT) and non-carriers (CC) using the Cox model ( Fig. 1E , Supplementary Table 2). Also, no differences were observed between females and males (Supp. Fig. 2A-B). In the APOE genotype-stratified analysis with sex as covariate, TREM2 -R62H did not affect the AD onset age among the APOE ε3/3 carriers ( Fig. 1F ). Male sex increased the risk of AD to a similar extent as observed in the PLCG2 -P522R and APOE ε3/3-carrying individuals (Supp. Fig. 2C-D). TREM2 -R62H increased the risk of AD by 23% (HR=1.24, 95% CI: 1.01-1.52, p=0.04, Fig. 1F ) among the APOE ε3/4 group. Sex did not influence the AD onset age in APOE ε3/4 carriers. Among the APOE ε4/4 carriers, TREM2 -R62H decreased the AD onset age only in males (HR=1.80, 95% CI: 1.015-3.19, p=0.04, Supp. Fig. 2C-D). 2.4 PLCG2 -P522R variant does not increase longevity but protects against anxiety As the PLCG2 -P522R variant has been associated with longevity ( 1 , 3 ), we investigated the FinnGen endpoint ‘Any Death’ to assess if the carriers lived longer than the non-carriers. However, we did not find any difference between the carriers and non-carriers ( Fig. 1G ). Also, there were no differences in APOE genotype-stratified analysis nor between sexes ( Fig. 1H , Supp. Fig. 2E-H). Previously, some PLCG2 hypermorphic mutations have been reported to associate with an increased risk of autoimmune diseases ( 19 ). Thus, we examined whether homozygous PLCG2 -P522R carriers exhibited signs of autoimmune diseases but found no significant associations. This observation highlights the beneficial nature of the PLCG2 -P522R variant as opposed to strong hypermorphic mutations in PLCG2 ( 20 , 21 ). In our recent study, we observed an anxiety phenotype in mice harboring the PLCG2 -P522R ( 9 ). Accordingly, we investigated if an association with anxiety can be detected in FinnGen in the individuals carrying the protective PLCG2 -P522R. Unexpectedly, PLCG2 -P522R delayed the onset age of anxiety as compared to non-carriers ( Fig. 2A ). Notably, this effect was observed in female but not in male PLCG2 -P522R carriers ( Fig. 2A-C ). Download figure Open in new tab Figure 2. PLCG2 -P522R is protective against anxiety. To investigate the impact of the PLCG2-P522R variant on anxiety onset, Kaplan-Meier curves on FinnGen endpoint data were utilized. The curves illustrate the anxiety-free time in years. The x-axis indicates the age at the first diagnosis for cases and the age at the end of follow-up for the non-carrier group. Shaded area indicates 95% confidence interval. A) All carriers and non-carriers, B) only females, and C) only males in “ANXIETY” endpoint. 2.5 PLCG2 -P522R variant carriers have increased plasma levels of ghrelin To identify potential biomarkers associated with the PLCG2 and TREM2 variants, we analyzed 40 metabolism and inflammation-related markers in plasma samples of 145 FINGER cohort individuals ( 17 , 22 , 23 ). Significantly higher levels of ghrelin and visfatin were detected in PLCG2 -P522R carriers as compared to non-carriers or carriers of PLCG2 -3’UTR or TREM2 -R62H variants ( Fig. 3A-B ). Since ghrelin and leptin jointly regulate energy metabolism, we also examined plasma leptin levels ( 24 ). No significant differences were observed in the leptin levels between PLCG2 -P522R and non-carriers ( Fig. 3C ). APOE genotype nor sex affected the levels of ghrelin or visfatin (Supp. Fig. 3A-E). However, males showed lower leptin levels than females (Supp. Fig. 3F). When ghrelin levels were tested using multilinear regression model adjusted by age, sex, and APOE genotype, the PLCG2 -P522R was the only statistically significant effector (Supplementary Table 3). In a similar analysis, there were no statistically significant differences in the levels of visfatin or leptin (Supplementary Table 4-5). Due to the fact that ghrelin is known to increase appetite and affect peripheral metabolism ( 25 ), we investigated the waist circumference, BMI, and waist-to-height ratio of the PLCG2 and TREM2 variant carriers. No significant differences in these parameters between the genotypes were observed ( Fig. 3D-F ). Furthermore, levels of plasma C-reactive protein (CRP), an indicator of inflammation, remained unaffected at baseline and during seven-year follow-up measurements between the carriers and controls (Supp Fig. 4). Interestingly, when screening metabolism-associated endpoints, PLCG2 -P522R was found to decrease the onset age of type 2 diabetes (T2D), but only in males ( Fig. 4A-C ). Download figure Open in new tab Figure 3. Protective PLCG2 -P522R carriers have higher plasma ghrelin levels compared to controls, TREM2 -R62H, and PLCG2 -3’UTR carriers. A) Ghrelin, B) Visfatin, and C) Leptin levels in peripheral plasma samples from the FINGER cohort. D) Waist circumference, E) BMI, and F) Waist-to-height ratio of FINGER individuals. n(control)=53-56, n(P522R)=5-7, n(R62H)=10-18, and n(3’UTR)=60-63. ANOVA, Tukey’s post hoc test. Mean±SD. *<0.05, **<0.01 Download figure Open in new tab Figure 4. The PLCG2 -P522R-carrying males have a higher risk of type 2 diabetes. To investigate the impact of the PLCG2 -P522R variant on T2D onset, Kaplan-Meier curves on FinnGen endpoint data were utilized. These curves illustrate the T2D-free time in years. The x-axis indicates the age at the first diagnosis for cases and the age at the end of follow-up for the non-carrier group. Shaded area indicates 95% confidence interval. A) PLCG2 -P522R FinnGen individuals as well as B) only females and C) only males in “T2D_WIDE” endpoint. 3 MATERIALS AND METHODS This study was conducted in accordance with the ethical principles outlined in the Declaration of Helsinki. 3.1 Participants FinnGen phenotype information and clinical endpoints are based on national health registries, including hospital discharge, prescription medication purchase, and cancer registers. A list of endpoints can be found from https://www.finngen.fi/en/researchers/clinical-endpoints and they can be explored at https://risteys.finngen.fi/ . We have utilized information from 493,563 individuals from the FinnGen data release R12 in the analyses. In G6_ALZHEIMER endpoint, 319,783 individuals older than 50 years with APOE ε3/3, ε3/4, and ε4/4 genotypes were selected to investigate the effects of APOE ε 4 on the different variant carriers on the Kaplan-Meier curves and cox analysis. In other endpoints presented in this study, all carriers of the PLCG2 -P522R, PLCG2 -3’UTR, and TREM2 -R62H variants regardless of age were included. The FinnGen Study combines genome data with digital health data based on national health registers ( 16 ). FinnGen includes samples that have been collected from the Finnish biobanks as well as legacy samples, which are from previous research cohorts that has been transferred to the biobanks. The individuals in FinnGen have given written informed consent for biobank research based on the Finnish Biobank Act. Separate research cohorts that have been collected before the Finnish biobank Act (September 2013) and start of FinnGen (August 2017), have been collected based on study-specific consents and later transferred to the Finnish biobanks after approved by the Finnish Medicine Agency Fimea. LD metrics were done in the Sisu (v4.2) imputation panel used in FinnGen. All FinnGen study subjects have undergone genome-wide genotyping. Most of the subjects have been genotyped using FinnGen ThermoFisher Axiom custom array. Approximately 70,000 subjects have been genotyped with various Illumina GWAS arrays as they originate primarily from the National Institute of Health and Welfare biobank samples that were genotyped before FinnGen. Approximately 21 million variants per individual were imputed using Finnish whole-genome reference SISu v4.2 (approximately 8,700 individuals). All genotype data is in the human genome build GRCh38/hg38. The genotype probability threshold in FinnGen was set to 0.8 for all the genotypes investigated. The FINGER cohort characteristics ( 23 ) and study design ( 22 ) have been described previously ( 26 ). Individuals who have dementia or substantial cognitive impairment have been excluded. Here, we only utilized data from participants aged 60-78 years carrying PLCG2- P522R (n=7), PLCG2 -3’UTR (n=63), or TREM2 -R62H (n=19), and non-carriers (n=56), who did not carry any of the investigated variants. The sex distribution among non-carriers was similar to variant carriers. As PLCG2 -3’UTR is a common variant, all the PLCG2 -P522R and TREM2 -R62H individuals also carry the PLCG2 -3’UTR. Plasma biomarkers at the baseline and CRP values during one-, five-, and seven-year follow-up were used in the analysis. Forty plasma biomarkers were measured using Bioplex human diabetes 10-plex (BioRad, 10010747) assay multiplexed with adiponectin and adipsin as well as cytokine targets: eotaxin, G-CSF, GM-CSF, IFN-2Rα, IFN-γ, IL-10, IL12(p40), IL-12(p70), IL-13, IL-15, IL-1β, IL-2, IL-3, IL-4, IL5, IL-6, IL-7, IL-8, IP-10, MCP-1, MIP-1α, MIP-1β, IL-1ra, RANTES, TNF-α, TNF-β, VEGF, IL-1, and IL-17. FINGER ( 22 ) individuals were genotyped using Illumina Global Screening Assay and imputed with TOPMed reference panel as described previously by Bellenguez et al. ( 1 ). 3.2 FinnGen endpoints Endpoint information can be found in the FinnGen and FinRegistery data portal Risteys ( https://risteys.finngen.fi/ , read 16.09.2025): AD was defined as a diagnosis in the hospital discharge or cause of death registries with the ICD codes G30 (ICD-10) or 3310 (ICD-9). The remaining individuals were considered as controls. T2D was defined as a diagnosis in the hospital discharge or cause of death registries with the ICD codes E11 (ICD-10) or 250.A (ICD-9). The remaining individuals were considered as controls. Individuals with pancreatitis were removed from both cases and controls. Anxiety was defined as a diagnosis in the hospital discharge or cause of death registries with the ICD codes F41.2, F41.3, F41.8, F41.9 (ICD-10), 3000A (ICD-9), or 3000 (ICD-8). The remaining individuals, excluding those with neurotic, stress-related and somatoform disorders were considered as controls. 3.3 Statistical analysis Kaplan-Meier curves were generated using R and survminer package (v 0.5.0). Also, survival analyses were performed in R using survival package (v 3.8.3). Based on the time dependence of the tested variables, cox proportional hazard model or extended cox model was used. Model fit was tested using Schoenfeld residuals. Separate APOE ε3/3, ε3/4, and ε4/4 groups were created to analyze the effects of APOE ε 4 because the cox models nor the extended cox models proportional hazard assumption were met. APOE ε3/3 and APOE ε3/4 groups were analyzed using the cox model, including sex as covariate. APOE ε4/4 group was further divided into females and males, and the groups were then separately analyzed using the cox model. The dose-dependent effects of the variants were investigated by comparing the HRs of the different groups. Differences in BMI between genotypes were tested using Two-Way ANOVA and Tukey’s post hoc test using R (4.5.0). Two-way ANOVA for biomarker data was performed in GraphPad Prism (v 10.4.2.633). Outliers from the data were identified using ROUT (Q=1%) and excluded from the analysis and figures. Multiple regression analyses of ghrelin, leptin, and visfatin were done in SPSS (v 29.0.0.0) adjusting for age, sex, and APOE ε 4 carrier status. CRP levels > 10 were considered as a sign of acute inflammation and were excluded. Differences in the CRP levels over time were tested using Linear Mixed effects model using lme4 (v 1.1-37) and lmerTest (v 3.1-3) packages in R (4.4.1). Data are presented as mean ± standard deviation (SD) or standard error of the mean (SEM). 4 DISCUSSION We and others have previously characterized the molecular mechanisms of the protective PLCG2 -P522R variant in various models ( 6 – 10 ). Building on this, we here examined the effects of the protective PLCG2 -P522R variant using FinnGen ( 16 ) and explored the potential plasma-based biomarkers in the FINGER cohort ( 22 , 23 , 26 ). Alongside PLCG2 -P522R variant, we examined the newly identified common protective PLCG2 -3’UTR variant and TREM2 -R62H risk variant. Both PLCG2 variants were associated with a delayed AD onset, also among APOE ε 4 carriers, with the PLCG2 -3’UTR variant showing a weaker, yet significant, effect. In contrast, TREM2 -R62H variant was linked to an earlier AD onset in APOE ε 4 carriers. Unfortunately, the low number of variant carriers limited the analysis of PLCG2 and TREM2 variant interaction. Furthermore, we observed increased plasma ghrelin levels in the PLCG2 -P522R variant carriers compared to non-carriers. Altogether, the obtained results strengthen the notion that the PLCG2 protective variants may alleviate the effects of APOE ε 4, the strongest genetic AD risk factor and the neuroprotective effects may derive partly from increased ghrelin levels. The protective PLCG2 -P522R variant delayed the AD onset age in APOE ε3/4 carriers, but not APOE ε4/4 carriers, when compared to non-carriers. APOE ε 4 is known to disrupt lipid homeostasis and immune response and to cause mitochondrial dysfunction ( 27 – 30 ), while PLCG2 -P522R variant exerts opposing effects ( 7 , 9 ). These findings suggest that PLCG2 -P522R variant can mitigate the APOE ε 4-mediated risk of AD in individuals carrying one ε4 allele. In vivo studies have shown decreased and a more compact β-amyloid plaque area in Plcg 2-P522R mouse brain, proposing a possible mechanism by which the Plcg 2-P522R variant may render β-amyloid plaques less toxic to the surrounding neurons ( 9 , 10 ). Also, it was recently demonstrated that the PLCG2 -P522R variant enhances immune responsiveness ( 31 ). Conversely, loss-of-function variants in PLCG2 have been shown to impair synaptic function ( 5 ). These findings suggest that enhanced PLCG2 -P522R-related mechanisms in both microglia and neurons may contribute to its protective effects. Although the PLCG2 -3’UTR variant has a similar impact on the age of onset of Alzheimer’s disease as the PLCG2 -P522R variant, the molecular mechanism underlying its protective effects remain to be elucidated. TREM2 is one of the key receptors modulating PLCγ2 activity ( 12 , 32 , 33 ). Importantly, TREM2 variants associate with an increased risk of AD ( 15 , 18 , 34 – 36 ). TREM2 deficiency leads to impaired microglial response to β-amyloid plaques, accumulation of the lipid droplets, and increased β-amyloid load in the brain ( 11 , 37 ). In this study we investigated whether the TREM2 -R62H variant has opposite effects on the AD onset and biomarkers as compared to the PLCG2 -P522R variant. We found that the TREM2- R62H variant decreases the onset age of AD, especially in the APOE ε4 carriers. Given that APOE ε4 is the most well know genetic risk factor for AD, it is important to understand its complex interactions with other genetic variants, including TREM2 and PLCG2 , when considering new therapies for AD ( 13 , 14 , 38 ). In our present study, TREM2 -R62H variant significantly increases the risk of AD only when APOE ε4 is also present. This differs from Thomassen et al. ( 38 ) results, which showed that TREM2 -R62H variant significantly increases the risk of AD also in APOE ε3/3 carriers. This suggests that TREM2 -R62H variant might have population specific effects. They also reported that male APOE ε 4/4 individuals with the TREM2 -R62H variant had higher risk of having AD as compared to females, suggesting that TREM2 -R62H has sex-dependent effect. Given that TREM2 activation may mitigate the harmful effects of APOE ε4, this underscores the importance of developing novel therapies targeting components of the TREM2 pathway, such as PLCγ2, which hold significant promise as potential treatment strategies for AD. This is especially needed among individuals with increased risk of AD owing to APOE ε4 background, which are not fully eligible for disease-modifying treatments, such as lecanemab ( 39 ). Additionally, a deeper understanding of how sex influences AD risk across different genotypes is essential for developing effective therapeutic strategies. Ghrelin, a neuroprotective hormone secreted by cells in the stomach, plays a key role in regulating the appetite and energy balance of the body ( 24 , 40 , 41 ). It binds to growth hormone secretagogue receptor (GHS-R), and it has been shown to protect neurons from β-amyloid-induced toxicity, reduce tau phosphorylation, and enhance synaptic plasticity ( 40 – 43 ). Despite its therapeutic potential, the role of ghrelin in AD pathology remains poorly understood. The PLCG2 -P522R variant carriers showed elevated plasma levels of ghrelin and visfatin compared to non-carriers and carriers of the other investigated variants. This is an interesting finding, as elevated ghrelin levels are known to exert anti-inflammatory effects, metabolic regulation, and promote cognitive enhancement ( 40 , 42 , 44 ). Importantly, BMI or waist circumference of the PLCG2 -P522R variant carriers did not differ from the controls or carriers of the other investigated variants, although a slight trend towards a decrease was detected in the waist circumference among the PLCG2 -P522R-carrying females as compared to PLCG2 -3’UTR or TREM2 -R62H variant carriers and non-carriers. It has been shown that ghrelin can pass through the blood-brain barrier, directly affecting brain cells ( 43 , 45 – 47 ). Thus, elevated ghrelin levels in the PLCG2 -P522R variant carriers could contribute to reduced inflammation and enhanced cognition, which are crucial in the context of neurodegeneration. In contrast, leptin levels remained unchanged in carriers of the protective PLCG2 -P522R variant, suggesting that the hunger signal remains active. Supporting this observation, we previously demonstrated that aged knock-in mice homozygous for the Plcg2 -P522R weighed less compared to their wild-type counterparts ( 9 ). Whether ghrelin elevation is a direct effect of PLCG2 -P522R variant remains thus far unknown. Also, the role of visfatin is ambiguous as it has been shown to have a positive correlation with ghrelin only in metabolic syndrome or T2D ( 48 , 49 ). Here, we showed an earlier onset age of T2D in males but not in female PLCG2 -P522R variant carriers. Additionally, onset of anxiety was delayed in females, suggesting sex-specific effects, consistent with prior findings ( 7 ). While therapies aimed at increasing ghrelin levels may offer benefits in neurodegeneration, it should be considered that they could also disrupt the natural metabolic balance and increase the risk of severe adverse effects. Interestingly, ghrelin may polarize microglia to an anti-inflammatory M2 type ( 50 ) and reduce the number of inflammatory M1 type microglia in cerebral ischemic injury ( 51 ). Given this background, the protective effects of PLCG2 -P522R variant could be linked to increased ghrelin levels, which subsequently could drive microglia polarization more towards an anti-inflammatory type. What makes this finding intriguing is that microglia lack the GHSR, the primary receptor for ghrelin ( 52 – 54 ). Yet, ghrelin treatment has been shown to suppress inflammatory response and reduce reactive oxygen species production in microglial cells ( 52 , 53 ). Furthermore, ghrelin has also been shown to act as a mitochondrional mediator and enhance mitochondrial fitness upon inflammation in macrophages ( 55 ). While the precise mechanisms underlying the effects of ghrelin on microglial signaling remain unclear, these observations suggest the involvement of GHSR–independent pathways. Hence, ghrelin could affect microglia functions indirectly by modulating other brain cell types that do express the GHSR, such as neurons ( 52 , 53 , 56 ) and astrocytes ( 57 ). Moreover, the beneficial role of ghrelin in the central nervous system has been widely discussed, including enhanced cognition ( 45 , 58 – 60 ). However, there is still a lack of direct evidence on whether ghrelin or its active form acyl ghrelin can influence microglial metabolism or if the effects are mediated by the interaction of ghrelin with insulin signaling pathways or through neuronal pathways. In conclusion, future studies should explore the mechanisms of how the protective PLCG2 variants may mitigate APOE ε 4-related impairments as it may offer new therapeutic avenues for a vast number of AD patients. Related to this, ghrelin shows an intriguing promise in modulating neurodegenerative processes, but its underlying effects, especially in APOE ε 4 carriers, require further investigations in experimental models as well as human cohorts. Data Availability All data produced in the present study are available upon reasonable request to the authors https://risteys.finngen.fi/ SOURCES OF FUNDING The work was supported by the Doctoral Programme in Molecular Medicine of the University of Eastern Finland (HJ, IK, and RMW); Research Council of Finland grants 355604 (HM), 339767 (VL), 360445 (AH), 338182 (MH); Sigrid Jusélius Foundation (AH, VL, MH); Kuopio University Hospital VTR Fund (VL); The Strategic Neuroscience Funding of the University of Eastern Finland (AH, MH); Jane and Aatos Erkko Foundation (MH), Faculty of Health Sciences of University of Eastern Finland (MH), and Alzheimer’s Association (ADSF-24-1284326-C, MH). DISCLOSURES Authors have nothing to disclose. SUPPLEMENTARY MATERIAL FinnGen Banner updated April2025_0.xlsx Supplementary_Figures.pdf Supplementary_Tables.pdf ACKNOWLEDGEMENTS We wish to thank the participants and investigators of the FINGER and FinnGen cohorts. Footnotes ↵ 6 A full list of authors and their affiliations at the supplementary file of the manuscript REFERENCES 1. ↵ Bellenguez C , Küçükali F , Jansen IE , Kleineidam L , Moreno-Grau S , Amin N , et al. New insights into the genetic etiology of Alzheimer’s disease and related dementias . Nature genetics . 2022 Apr 1 ; 54 ( 4 ): 412 – 36 . OpenUrl CrossRef PubMed 2. Conway OJ , Carrasquillo MM , Wang X , Bredenberg JM , Reddy JS , Strickland SL , et al. ABI3 and PLCG2 missense variants as risk factors for neurodegenerative diseases in Caucasians and African Americans . Mol Neurodegener . 2018 Oct 11 ; 13 : 53 . OpenUrl CrossRef PubMed 3. ↵ Sims R , ARUK Consortium , Gerad/Perades , CHARGE , Adgc , EADI , Van Der Lee SJ , Naj AC , Bellenguez C , et al. Rare coding variants in PLCG2, ABI3, and TREM2 implicate microglialmediated innate immunity in Alzheimer’s disease . Nat Genet . 2017 Sep ; 49 ( 9 ): 1373 – 84 . OpenUrl CrossRef PubMed 4. ↵ van der Lee SJ , Conway OJ , Jansen I , Carrasquillo MM , Kleineidam L , van den Akker E , et al. A nonsynonymous mutation in PLCG2 reduces the risk of Alzheimer’s disease, dementia with Lewy bodies and frontotemporal dementia, and increases the likelihood of longevity . Acta Neuropathol . 2019 ; 138 ( 2 ): 237 – 50 . OpenUrl CrossRef PubMed 5. ↵ Coulon A , Rabiller F , Takalo M , Roy A , Martiskainen H , Siedlecki-Wullich D , et al. Neuronal downregulation of PLCG2 impairs synaptic function and elicits Alzheimer disease hallmarks [Internet] . bioRxiv ; 2024 [cited 2025 Jun 6]. p. 2024.04.29.591575 . Available from: https://www.biorxiv.org/content/10.1101/2024.04.29.591575v1 6. ↵ Solomon S , Sampathkumar NK , Carre I , Mondal M , Chennell G , Vernon AC , et al. Heterozygous expression of the Alzheimer’s disease-protective PLCγ2 P522R variant enhances Aβ clearance while preserving synapses . Cell Mol Life Sci . 2022 Jul 27 ; 79 ( 8 ): 453 . OpenUrl CrossRef PubMed 7. ↵ Staley HA , Jernigan JE , Bolen ML , Titus AM , Neighbarger N , Cole C , et al. Alzheimer’s diseaseassociated protective variant Plcg2-P522R modulates peripheral macrophage function in a sex-dimorphic manner . J Neuroinflammation . 2024 Nov 1 ; 21 : 280 . OpenUrl PubMed 8. Takalo M , Wittrahm R , Wefers B , Parhizkar S , Jokivarsi K , Kuulasmaa T , et al. The Alzheimer’s disease-associated protective Plcγ2-P522R variant promotes immune functions . Mol Neurodegeneration . 2020 Dec ; 15 ( 1 ): 52 . OpenUrl 9. ↵ Takalo M , Jeskanen H , Rolova T , Kervinen I , Hellén M , Heikkinen S , et al. The protective PLCγ2-P522R variant mitigates Alzheimer’s disease-associated pathologies by enhancing beneficial microglial functions . J Neuroinflammation . 2025 Mar 5 ; 22 ( 1 ): 64 . OpenUrl PubMed 10. ↵ Tsai AP , Dong C , Lin PBC , Oblak AL , Viana Di Prisco G , Wang N , et al. Genetic variants of phospholipase C-γ2 alter the phenotype and function of microglia and confer differential risk for Alzheimer’s disease . Immunity . 2023 Sep ; 56 ( 9 ): 2121 - 2136 .e6. OpenUrl CrossRef PubMed 11. ↵ Keren-Shaul H , Spinrad A , Weiner A , Matcovitch-Natan O , Dvir-Szternfeld R , Ulland TK , et al. A Unique Microglia Type Associated with Restricting Development of Alzheimer’s Disease . Cell . 2017 Jun 15 ; 169 ( 7 ): 1276 - 1290 .e17. OpenUrl CrossRef PubMed 12. ↵ Andreone BJ , Przybyla L , Llapashtica C , Rana A , Davis SS , Van Lengerich B , et al. Alzheimer’sassociated PLCγ2 is a signaling node required for both TREM2 function and the inflammatory response in human microglia . Nat Neurosci . 2020 Aug ; 23 ( 8 ): 927 – 38 . OpenUrl PubMed 13. ↵ Dijkstra JIR , Vermunt L , Venkatraghavan V , Ozhegov G , Coomans EM , Ossenkoppele R , et al. TREM2 risk variants and associated endophenotypes in alzheimer’s disease . Alzheimer’s Research & Therapy . 2025 Mar 6 ; 17 ( 1 ): 57 . OpenUrl 14. ↵ Lu Y , Liu W , Wang X. TREM2 variants and risk of Alzheimer’s disease: a meta-analysis . Neurol Sci . 2015 Oct 1 ; 36 ( 10 ): 1881 – 8 . OpenUrl PubMed 15. ↵ Guerreiro R , Wojtas A , Bras J , Carrasquillo M , Rogaeva E , Majounie E , et al. TREM2 Variants in Alzheimer’s Disease . New England Journal of Medicine . 2013 Jan 10 ; 368 ( 2 ): 117 – 27 . OpenUrl CrossRef PubMed Web of Science 16. ↵ Kurki MI , Karjalainen J , Palta P , Sipilä TP , Kristiansson K , Donner KM , et al. FinnGen provides genetic insights from a well-phenotyped isolated population . Nature . 2023 Jan ; 613 ( 7944 ): 508 – 18 . OpenUrl CrossRef PubMed 17. ↵ Ngandu T , Lehtisalo J , Solomon A , Levälahti E , Ahtiluoto S , Antikainen R , et al. A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): a randomised controlled trial . The Lancet . 2015 Jun 6 ; 385 ( 9984 ): 2255 – 63 . OpenUrl CrossRef 18. ↵ Jonsson T , Stefansson H , Steinberg S , Jonsdottir I , Jonsson PV , Snaedal J , et al. Variant of TREM2 Associated with the Risk of Alzheimer’s Disease . N Engl J Med . 2013 Jan 10 ; 368 ( 2 ): 107 – 16 . OpenUrl CrossRef PubMed Web of Science 19. ↵ Baysac K , Sun G , Nakano H , Schmitz EG , Cruz AC , Fisher C , et al. PLCG2-associated immune dysregulation (PLAID) comprises broad and distinct clinical presentations related to functional classes of genetic variants . Journal of Allergy and Clinical Immunology . 2024 Jan 1 ; 153 ( 1 ): 230 – 42 . OpenUrl 20. ↵ Zhou Q , Lee GS , Brady J , Datta S , Katan M , Sheikh A , et al. A Hypermorphic Missense Mutation in PLCG2, Encoding Phospholipase Cγ2, Causes a Dominantly Inherited Autoinflammatory Disease with Immunodeficiency . Am J Hum Genet . 2012 Oct 5 ; 91 ( 4 ): 713 – 20 . OpenUrl CrossRef PubMed 21. ↵ Martín-Nalda A , Fortuny C , Rey L , Bunney TD , Alsina L , Esteve-Solé A , et al. Severe Autoinflammatory Manifestations and Antibody Deficiency Due to Novel Hypermorphic PLCG2 Mutations . J Clin Immunol . 2020 ; 40 ( 7 ): 987 – 1000 . OpenUrl CrossRef PubMed 22. ↵ Kivipelto M , Solomon A , Ahtiluoto S , Ngandu T , Lehtisalo J , Antikainen R , et al. The Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER): Study design and progress . Alzheimer’s & Dementia . 2013 ; 9 ( 6 ): 657 – 65 . OpenUrl 23. ↵ Ngandu T , Lehtisalo J , Levälahti E , Laatikainen T , Lindström J , Peltonen M , et al. Recruitment and Baseline Characteristics of Participants in the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER)—A Randomized Controlled Lifestyle Trial . International Journal of Environmental Research and Public Health . 2014 Sep ; 11 ( 9 ): 9345 – 60 . OpenUrl 24. ↵ Espinoza García AS , Martínez Moreno AG , Reyes Castillo Z. The role of ghrelin and leptin in feeding behavior: Genetic and molecular evidence . Endocrinología, Diabetes y Nutrición (English ed) . 2021 Nov 1 ; 68 ( 9 ): 654 – 63 . OpenUrl 25. ↵ Gray DSM , Page LC , Tong J. Ghrelin Regulation of Glucose Metabolism . Journal of neuroendocrinology . 2019 Apr 3 ; 31 ( 7 ): e12705 . OpenUrl PubMed 26. ↵ Ngandu T , Lehtisalo J , Solomon A , Levälahti E , Ahtiluoto S , Antikainen R , et al. A 2 year multidomain intervention of diet, exercise, cognitive training, and vascular risk monitoring versus control to prevent cognitive decline in at-risk elderly people (FINGER): a randomised controlled trial . The Lancet . 2015 Jun 6 ; 385 ( 9984 ): 2255 – 63 . OpenUrl CrossRef 27. ↵ Hellén M , Weert I , Müller SA , Räsänen N , Kettunen P , Lehtonen Š , et al. Inflammationinduced lysosomal dysfunction in human iPSC-derived microglia is exacerbated by APOE 4/4 genotype . Journal of Neuroinflammation . 2025 Jun 2 ; 22 ( 1 ): 147 . OpenUrl PubMed 28. Lin YT , Seo J , Gao F , Feldman HM , Wen HL , Penney J , et al. APOE4 causes widespread molecular and cellular alterations associated with Alzheimer’s disease phenotypes in human iPSC-derived brain cell types . Neuron . 2018 Jun 27 ; 98 ( 6 ): 1141 - 1154 .e7. OpenUrl CrossRef PubMed 29. Pires M , Rego AC . Apoe4 and Alzheimer’s Disease Pathogenesis—Mitochondrial Deregulation and Targeted Therapeutic Strategies . Int J Mol Sci . 2023 Jan 1 ; 24 ( 1 ): 778 . OpenUrl PubMed 30. ↵ Sienski G , Narayan P , Bonner JM , Kory N , Boland S , Arczewska AA , et al. APOE4 disrupts intracellular lipid homeostasis in human iPSC-derived glia . Sci Transl Med . 2021 Mar 3 ; 13 ( 583 ): eaaz4564 . OpenUrl FREE Full Text 31. ↵ Diks AM , Teodosio C , de Mooij B , Groenland RJ , Naber BAE , de Laat IF , et al. Carriers of the p.P522R variant in PLCγ2 have a slightly more responsive immune system . Molecular Neurodegeneration . 2023 Apr 20 ; 18 ( 1 ): 25 . OpenUrl PubMed 32. ↵ Ulland TK , Colonna M. TREM2 — a key player in microglial biology and Alzheimer disease . Nat Rev Neurol . 2018 Nov ; 14 ( 11 ): 667 – 75 . OpenUrl CrossRef PubMed 33. ↵ Krasemann S , Madore C , Cialic R , Baufeld C , Calcagno N , Fatimy RE , et al. The TREM2-APOE pathway drives the transcriptional phenotype of dysfunctional microglia in neurodegenerative diseases . Immunity . 2017 Sep 19 ; 47 ( 3 ): 566 . OpenUrl CrossRef PubMed 34. ↵ Huang M , Wang D , Xu Z , Xu Y , Xu X , Ma Y , et al. Lack of Genetic Association Between TREM2 and Alzheimer’s Disease in East Asian Population . Am J Alzheimers Dis Other Demen . 2015 Sep ; 30 ( 6 ): 541 – 6 . OpenUrl CrossRef PubMed 35. Jiang T , Tan L , Chen Q , Tan MS , Zhou JS , Zhu XC , et al. A rare coding variant in TREM2 increases risk for Alzheimer’s disease in Han Chinese . Neurobiology of Aging . 2016 Jun 1 ; 42 : 217.e1 – 217.e3 . OpenUrl CrossRef PubMed 36. ↵ Jin SC , Benitez BA , Karch CM , Cooper B , Skorupa T , Carrell D , et al. Coding variants in TREM2 increase risk for Alzheimer’s disease . Hum Mol Genet . 2014 Nov 1 ; 23 ( 21 ): 5838 – 46 . OpenUrl CrossRef PubMed 37. ↵ McQuade A , Coburn M , Tu CH , Hasselmann J , Davtyan H , Blurton-Jones M. Development and validation of a simplified method to generate human microglia from pluripotent stem cells . Mol Neurodegeneration . 2018 Dec ; 13 ( 1 ): 67 . OpenUrl 38. ↵ Thomassen JQ , Hampton L , Ulms B , Grenier-Boley B , Heikkinen S , Garcia P , et al. APOE stratified genome-wide association studies provide novel insights into the genetic etiology of Alzheimers’s disease [Internet] . medRxiv ; 2025 [cited 2025 Jun 9]. p. 2025.05.07.25327065 . Available from: https://www.medrxiv.org/content/10.1101/2025.05.07.25327065v1 39. ↵ Yan L , Zhang L , Xu Z , Luo Z. A real-world disproportionality analysis of FDA adverse event reporting system (FAERS) events for lecanemab . Front Pharmacol . 2025 ; 16 : 1559447 . OpenUrl PubMed 40. ↵ Thomas AS , Sassi M , Angelini R , Morgan AH , Davies JS . Acylation, a Conductor of Ghrelin Function in Brain Health and Disease . Front Physiol . 2022 Jun 30 ; 13 : 831641 . OpenUrl PubMed 41. ↵ Cowley MA , Smith RG , Diano S , Tschöp M , Pronchuk N , Grove KL , et al. The distribution and mechanism of action of ghrelin in the CNS demonstrates a novel hypothalamic circuit regulating energy homeostasis . Neuron . 2003 Feb 20 ; 37 ( 4 ): 649 – 61 . OpenUrl CrossRef PubMed Web of Science 42. ↵ Kent BA , Beynon AL , Hornsby AKE , Bekinschtein P , Bussey TJ , Davies JS , et al. The orexigenic hormone acyl-ghrelin increases adult hippocampal neurogenesis and enhances pattern separation . Psychoneuroendocrinology . 2015 Jan ; 51 : 431 – 9 . OpenUrl CrossRef PubMed 43. ↵ Rhea EM , Salameh TS , Gray S , Niu J , Banks WA , Tong J. Ghrelin transport across the blood– brain barrier can occur independently of the growth hormone secretagogue receptor . Mol Metab . 2018 Sep 24 ; 18 : 88 – 96 . OpenUrl PubMed 44. ↵ Walker A , Rivera P , Wang Q , Chuang JC , Tran S , Osborne-Lawrence S , et al. The P7C3 class of neuroprotective compounds exerts antidepressant efficacy in mice by increasing hippocampal neurogenesis . Mol Psychiatry . 2015 Apr ; 20 ( 4 ): 500 – 8 . OpenUrl CrossRef PubMed 45. ↵ Russo C , Valle MS , Russo A , Malaguarnera L. The Interplay between Ghrelin and Microglia in Neuroinflammation: Implications for Obesity and Neurodegenerative Diseases . Int J Mol Sci . 2022 Nov 3 ; 23 ( 21 ): 13432 . OpenUrl CrossRef PubMed 46. Banks WA , Tschöp M , Robinson SM , Heiman ML . Extent and Direction of Ghrelin Transport Across the Blood-Brain Barrier Is Determined by Its Unique Primary Structure . The Journal of Pharmacology and Experimental Therapeutics . 2002 Aug 1 ; 302 ( 2 ): 822 – 7 . OpenUrl Abstract / FREE Full Text 47. ↵ Diano S , Farr SA , Benoit SC , McNay EC , da Silva I , Horvath B , et al. Ghrelin controls hippocampal spine synapse density and memory performance . Nat Neurosci . 2006 Mar ; 9 ( 3 ): 381 – 8 . OpenUrl CrossRef PubMed Web of Science 48. ↵ Abushahla HS , Bulatova N , Kasabri V , Naffa R. Correlates of ghrelin and visfatin in metabolic syndrome patients with and without prediabetes . Int J Diabetes Dev Ctries . 2019 Jan 1 ; 39 ( 1 ): 82 – 93 . OpenUrl 49. ↵ Ahmed MB , Ismail MIA , Meki ARM . Relation of Osteoprotegerin, Visfatin and Ghrelin to Metabolic Syndrome in Type 2 Diabetic Patients . Int J Health Sci (Qassim) . 2015 Apr ; 9 ( 2 ): 127 – 39 . OpenUrl PubMed 50. ↵ Guo Y , Zhao J , Liu X , Lu P , Liang F , Wang X , et al. Ghrelin Induces Ferroptosis Resistance and M2 Polarization of Microglia to Alleviate Neuroinflammation and Cognitive Impairment in Alzheimer’s Disease . J Neuroimmune Pharmacol . 2025 Jan 11 ; 20 ( 1 ): 6 . OpenUrl PubMed 51. ↵ Tian R , Mao G. Ghrelin reduces cerebral ischemic injury in rats by reducing M1 microglia/macrophages . Eur J Histochem . 2022 Jan 12 ; 66 ( 1 ): 3350 . OpenUrl PubMed 52. ↵ Lee JY , Yune TY . Ghrelin Inhibits Oligodendrocyte Cell Death by Attenuating Microglial Activation . Endocrinol Metab . 2014 Sep 25 ; 29 ( 3 ): 371 – 8 . OpenUrl 53. ↵ Moon M , Kim HG , Hwang L , Seo JH , Kim S , Hwang S , et al. Neuroprotective Effect of Ghrelin in the 1-Methyl-4-Phenyl-1,2,3,6-Tetrahydropyridine Mouse Model of Parkinson’s Disease by Blocking Microglial Activation . Neurotox Res . 2009 May 1 ; 15 ( 4 ): 332 – 47 . OpenUrl CrossRef PubMed Web of Science 54. ↵ Kojima M , Hosoda H , Date Y , Nakazato M , Matsuo H , Kangawa K. Ghrelin is a growthhormone-releasing acylated peptide from stomach . Nature . 1999 Dec ; 402 ( 6762 ): 656 – 60 . OpenUrl CrossRef PubMed Web of Science 55. ↵ Corrêa da Silva F , Aguiar C , Pereira JAS , de Brito Monteiro L , Davanzo GG , Codo AC , et al. Ghrelin effects on mitochondrial fitness modulates macrophage function . Free Radical Biology and Medicine . 2019 Dec 1 ; 145 : 61 – 6 . OpenUrl PubMed 56. ↵ Xu H , Li Y , Liu R , Wu L , Zhang C , Ding N , et al. Protective effects of ghrelin on brain mitochondria after cardiac arrest and resuscitation . Neuropeptides . 2019 Aug 1 ; 76 : 101936 . OpenUrl PubMed 57. ↵ Fuente-Martín E , García-Cáceres C , Argente-Arizón P , Díaz F , Granado M , Freire-Regatillo A , et al. Ghrelin Regulates Glucose and Glutamate Transporters in Hypothalamic Astrocytes . Sci Rep . 2016 Mar 30 ; 6 : 23673 . OpenUrl PubMed 58. ↵ Poher AL , Tschöp MH , Müller TD . Ghrelin regulation of glucose metabolism . Peptides . 2018 Feb ; 100 : 236 – 42 . OpenUrl CrossRef PubMed 59. Reich N , Hölscher C. Acylated Ghrelin as a Multi-Targeted Therapy for Alzheimer’s and Parkinson’s Disease . Front Neurosci . 2020 Dec 14 ; 14 : 614828 . OpenUrl PubMed 60. ↵ Stark R , Ashley SE , Andrews ZB . AMPK and the neuroendocrine regulation of appetite and energy expenditure . Molecular and Cellular Endocrinology . 2013 Feb 25 ; 366 ( 2 ): 215 – 23 . OpenUrl CrossRef PubMed View the discussion thread. Back to top Previous Next Posted September 25, 2025. Download PDF Supplementary Material Data/Code Email Thank you for your interest in spreading the word about medRxiv. NOTE: Your email address is requested solely to identify you as the sender of this article. Your Email * Your Name * Send To * Enter multiple addresses on separate lines or separate them with commas. You are going to email the following The protective PLCG2 variants delay Alzheimer’s disease onset age in APOE ε4 carriers Message Subject (Your Name) has forwarded a page to you from medRxiv Message Body (Your Name) thought you would like to see this page from the medRxiv website. Your Personal Message CAPTCHA This question is for testing whether or not you are a human visitor and to prevent automated spam submissions. Share The protective PLCG2 variants delay Alzheimer’s disease onset age in APOE ε 4 carriers Heli Jeskanen , Sami Heikkinen , Inka Kervinen , Jenni Lehtisalo , Tiia Ngandu , Roosa-Maria Willman , Jessica Rosa , Dorit Hoffmann , FinnGen , Ville Leinonen , Annakaisa Haapasalo , Mari Takalo , Henna Martiskainen , Mikko Hiltunen medRxiv 2025.09.22.25336304; doi: https://doi.org/10.1101/2025.09.22.25336304 Share This Article: Copy Citation Tools The protective PLCG2 variants delay Alzheimer’s disease onset age in APOE ε 4 carriers Heli Jeskanen , Sami Heikkinen , Inka Kervinen , Jenni Lehtisalo , Tiia Ngandu , Roosa-Maria Willman , Jessica Rosa , Dorit Hoffmann , FinnGen , Ville Leinonen , Annakaisa Haapasalo , Mari Takalo , Henna Martiskainen , Mikko Hiltunen medRxiv 2025.09.22.25336304; doi: https://doi.org/10.1101/2025.09.22.25336304 Citation Manager Formats BibTeX Bookends EasyBib EndNote (tagged) EndNote 8 (xml) Medlars Mendeley Papers RefWorks Tagged Ref Manager RIS Zotero Tweet Widget Facebook Like Google Plus One Subject Area Genetic and Genomic Medicine Subject Areas All Articles Addiction Medicine (568) Allergy and Immunology (863) Anesthesia (300) Cardiovascular Medicine (4436) Dentistry and Oral Medicine (444) Dermatology (382) Emergency Medicine (608) Endocrinology (including Diabetes Mellitus and Metabolic Disease) (1509) Epidemiology (15229) Forensic Medicine (30) Gastroenterology (1124) Genetic and Genomic Medicine (6600) Geriatric Medicine (668) Health Economics (997) Health Informatics (4538) Health Policy (1368) Health Systems and Quality Improvement (1613) Hematology (542) HIV/AIDS (1264) Infectious Diseases (except HIV/AIDS) (15916) Intensive Care and Critical Care Medicine (1103) Medical Education (623) Medical Ethics (146) Nephrology (667) Neurology (6599) Nursing (346) Nutrition (998) Obstetrics and Gynecology (1144) Occupational and Environmental Health (957) Oncology (3333) Ophthalmology (974) Orthopedics (369) Otolaryngology (420) Pain Medicine (436) Palliative Medicine (130) Pathology (663) Pediatrics (1693) Pharmacology and Therapeutics (691) Primary Care Research (711) Psychiatry and Clinical Psychology (5447) Public and Global Health (9232) Radiology and Imaging (2198) Rehabilitation Medicine and Physical Therapy (1370) Respiratory Medicine (1196) Rheumatology (593) Sexual and Reproductive Health (712) Sports Medicine (530) Surgery (712) Toxicology (99) Transplantation (289) Urology (265) (function(){function c(){var b=a.contentDocument||a.contentWindow.document;if(b){var d=b.createElement('script');d.innerHTML="window.__CF$cv$params={r:'a00ec302cb270708',t:'MTc3OTY1MTUxNw=='};var a=document.createElement('script');a.src='/cdn-cgi/challenge-platform/scripts/jsd/main.js';document.getElementsByTagName('head')[0].appendChild(a);";b.getElementsByTagName('head')[0].appendChild(d)}}if(document.body){var a=document.createElement('iframe');a.height=1;a.width=1;a.style.position='absolute';a.style.top=0;a.style.left=0;a.style.border='none';a.style.visibility='hidden';document.body.appendChild(a);if('loading'!==document.readyState)c();else if(window.addEventListener)document.addEventListener('DOMContentLoaded',c);else{var e=document.onreadystatechange||function(){};document.onreadystatechange=function(b){e(b);'loading'!==document.readyState&&(document.onreadystatechange=e,c())}}}})();