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Epigenetic clocks provide powerful tools for estimating health and lifespan but their ability to predict brain degeneration and neuronal damage during the aging process is unknown. In this study, we use GrimAge, an epigenetic clock correlated to several blood plasma proteins, to longitudinally investigate brain cellular microstructure in axonal white matter from a cohort of healthy aging individuals. A specific focus was made on white matter hyperintensities, a visible neurological manifestation of small vessel disease, and the axonal pathways throughout each individual's brain affected by their unique white matter hyperintensity location and volume. 98 subjects over 55 years of age were scanned at baseline with 41 returning for a follow-up scan 2 years later. Using diffusion MRI lesionometry, we reconstructed subject-specific networks of affected axonal tracts and examined the diffusion cellular microstructure composition of these areas, both at baseline and longitudinally, for evidence of cellular degeneration. A chronological age-adjusted version of GrimAge was significantly correlated with baseline WMH volume and markers of neuronal decline, indicated by increased extracellular free water, increased intracellular signal, and decreased axonal signal within WMH. By isolating subject-specific axonal regions "lesioned" by crossing through a WMH, age-adjusted GrimAge was also able to predict longitudinal development of similar patterns of neuronal decline throughout the brain. This study is the first to demonstrate WMH lesionometry as a subject-specific precision imaging technique to study degeneration in aging and the first to establish a relationship between accelerated epigenetic GrimAge and brain cellular microstructure in humans., (© 2024 The Author(s). Aging Cell published by Anatomical Society and John Wiley & Sons Ltd.)

The role of lipoprotein (a) (Lp[a]) in the development of obstructive coronary artery disease (CAD) and high-risk plaque (HRP) in primary prevention patients with stable chest pain is unknown. We sought to evaluate the relation of Lp(a), independent of low-density lipoprotein cholesterol (LDL-C), with the presence of obstructive CAD and HRP to improve understanding of the residual risk imparted by Lp(a) on CAD. We performed a secondary analysis in Prospective Multicenter Imaging Study for Evaluation of Chest Pain (PROMISE) Trial participants who had coronary computed tomographic angiography (CTA) performed and Lp(a) data available. Lp(a) concentration was analyzed as a binary variable, with elevated Lp(a) defined as ≥50 mg/100 ml. "Stenosis ≥50%" was defined as ≥50% coronary artery stenosis in any epicardial vessel, and "stenosis ≥70%" was defined as ≥70% coronary artery stenosis in any epicardial vessel and/or ≥50% left main coronary artery stenosis. HRP was defined as presence of plaque on CTA imaging with evidence of positive remodeling, low computed tomography attenuation, or napkin-ring sign. Multivariate logistic regression models were constructed to evaluate the association between Lp(a) and the outcomes of obstructive CAD and HRP stratified by LDL-C ≥100 versus <100 mg/100 ml. Of the 1,815 patients who underwent CTA and had Lp(a) data available, those with elevated Lp(a) were more commonly women and Black than those with lower Lp(a). Elevated Lp(a) was associated with stenosis ≥50% (odds ratio 1.57, 95% confidence interval 1.14 to 2.15, p = 0.005) and stenosis ≥70% (odds ratio 2.05, 95% confidence interval 1.34 to 3.11, p = 0.0008) in the multivariate models, and this relation was not modified by LDL-C ≥100 versus <100 mg/100 ml (interaction p >0.4). Elevated Lp(a) was not associated with HRP when adjusted for obstructive CAD. This study of patients without known CAD found that elevated Lp(a) ≥50 mg/100 ml was independently associated with the presence of obstructive CAD regardless of controlled versus uncontrolled LDL-C but was not independently associated with HRP when stenosis ≥50% or ≥70% was accounted for. Further research is warranted to delineate the role of Lp(a) in the residual risk for atherosclerotic cardiovascular disease that patients may have despite optimal LDL-C lowering., Competing Interests: Declaration of competing interest Dr. Shah reports research grants from Amgen, Janssen, Eli Lily, Novartis, and National Institutes of Health, and service as a consultant/advisor for Merck, Amgen, Norvartis, and New Amsterdam Pharma. Dr. Ferencik reports consulting fees from Cleerly, HeartFlow, Elucid, Siemens Healthineers, and BioMarin, and stock options from Elucid, and is a member of an advisory board for Cleerly. Dr. Lu reports research funding to his institution from the American Heart Association, AstraZeneca, Ionis, Johnson & Johnson Innovation, Kowa Pharmaceuticals America, MedImmune, National Academy of Medicine, National Heart, Lung, and Blood Institute, and Risk Management Foundation of the Harvard Medical Institutions outside the submitted work. Dr. Foldyna reports research grants from National Institutes of Health/National Heart, Lung, and Blood Institute (R01HL170877, 5P30DK040561), AstraZeneca, Cleerly Health, MedImmune, and MedTrace. Dr. Pagidipati reports research support from Alnylam, Amgen, Bayer, Boehringer Ingelheim (Ingelheim, Germany), Eggland's Best, Eli Lilly (Esperion), Novartis, Novo Nordisk, Merck; service on consultation/advisory panels for Amgen, Bayer, Boehringer Ingelheim, CRISPR Therapeutics, Eli Lilly, AstraZeneca, Merck, Novartis, and Novo Nordisk; service as an Executive Committee member for trials sponsored by Novo Nordisk and by Amgen and by AstraZeneca; service on a Data and Safety Monitoring Board for trials sponsored by Johnson & Johnson and Novartis; and service on a medical advisory board for Miga Health. The remaining authors have no competing interests to declare., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Objectives: To determine the relationship between lipoprotein particle size/number with hepatic steatosis (HS), given its association with traditional lipoproteins and coronary atherosclerosis., Methods: Individuals with available CT data and blood samples enrolled in the PROMISE trial were studied. HS was defined based on CT attenuation. Lipoprotein particle size/number were measured by nuclear magnetic resonance spectroscopy. Principal components analysis (PCA) was used for dimensionality reduction. The association of PCA factors and individual lipoprotein particle size/number with HS were assessed in multivariable regression models. Associations were validated in an independent cohort of 59 individuals with histopathology defined HS., Results: Individuals with HS (n=410/1,509) vs those without (n=1,099/1,509), were younger (59±8 vs 61±8 years) and less often females (47.6 % vs 55.9 %). All PCA factors were associated with HS: factor 1 (OR:1.36, 95 %CI:1.21-1.53), factor 3 (OR:1.75, 95 %CI:1.53-2.02) and factor 4 (OR:1.49; 95 %CI:1.32-1.68) were weighted heavily with small low density lipoprotein (LDL) and triglyceride-rich (TRL) particles, while factor 2 (OR:0.86, 95 %CI:0.77-0.97) and factor 5 (OR:0.74, 95 %CI:0.65-0.84) were heavily loaded with high density lipoprotein (HDL) and larger LDL particles. These observations were confirmed with the analysis of individual lipoprotein particles in PROMISE. In the validation cohort, association between HS and large TRL (OR: 8.16, 95 %CI:1.82-61.98), and mean sizes of TRL- (OR: 2.82, 95 %CI:1.14-9.29) and HDL (OR:0.35, 95 %CI:0.13-0.72) were confirmed., Conclusions: Large TRL, mean sizes of TRL-, and HDL were associated with radiographic and histopathologic HS. The use of lipoprotein particle size/number could improve cardiovascular risk assessment in HS., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 Published by Elsevier B.V.)

While chronological age is a strong predictor for health-related risk factors, it is an incomplete metric that fails to fully characterize the unique aging process of individuals with different genetic makeup, neurodevelopment, and environmental experiences. Recent advances in epigenomic array technologies have made it possible to generate DNA methylation-based biomarkers of biological aging, which may be useful in predicting a myriad of cognitive abilities and functional brain network organization across older individuals. It is currently unclear which cognitive domains are negatively correlated with epigenetic age above and beyond chronological age, and it is unknown if functional brain organization is an important mechanism for explaining these associations. In this study, individuals with accelerated epigenetic age (i.e. AgeAccelGrim) performed worse on tasks that spanned a wide variety of cognitive faculties including both fluid and crystallized intelligence (N = 103, average age = 68.98 years, 73 females, 30 males). Additionally, fMRI connectome-based predictive models suggested a mediating mechanism of functional connectivity on epigenetic age acceleration-cognition associations primarily in medial temporal lobe and limbic structures. This research highlights the important role of epigenetic aging processes on the development and maintenance of healthy cognitive capacities and function of the aging brain., (© 2024. The Author(s).)

Background The interplay between branched-chain amino acid (BCAA) metabolism, an important pathway in adiposity and cardiometabolic disease, and visceral adipose depots such as hepatic steatosis (HS) and epicardial adipose tissue is unknown. We leveraged the PROMISE clinical trial with centrally adjudicated coronary computed tomography angiography imaging to determine relationships between adipose depots, BCAA dysregulation, and coronary artery disease (CAD). Methods and Results The PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) trial randomized 10 003 outpatients with stable chest pain to computed tomography angiography versus standard-of-care diagnostics. For this study, we included 1798 participants with available computed tomography angiography data and biospecimens. Linear and logistic regression were used to determine associations between a molar sum of BCAAs measured by nuclear magnetic resonance spectroscopy with body mass index, adipose traits, and obstructive CAD. Mendelian randomization was then used to determine if BCAAs are in the causal pathway for adipose depots or CAD. The study sample had a mean age of 60 years (SD, 8.0), body mass index of 30.6 (SD, 5.9), and epicardial adipose tissue volume of 57.3 (SD, 21.3) cm 3 /m 2 ; 27% had HS, and 14% had obstructive CAD. BCAAs were associated with body mass index (multivariable beta 0.12 per SD increase in BCAA [95% CI, 0.08-0.17]; P =4×10 -8 ). BCAAs were also associated with HS (multivariable odds ratio [OR], 1.46 per SD increase in BCAAs [95% CI, 1.28-1.67]; P =2×10 -8 ), but BCAAs were associated only with epicardial adipose tissue volume (odds ratio, 1.18 [95% CI, 1.07-1.32]; P =0.002) and obstructive CAD (OR, 1.18 [95% CI, 1.04-1.34]; P =0.009) in univariable models. Two-sample Mendelian randomization did not support the role of BCAAs as within the causal pathways for HS or CAD. Conclusions BCAAs have been implicated in the pathogenesis of cardiometabolic diseases, and adipose depots have been associated with the risk of CAD. Leveraging a large clinical trial, we further establish the role of dysregulated BCAA catabolism in HS and CAD, although BCAAs did not appear to be in the causal pathway of either disease. This suggests that BCAAs may serve as an independent circulating biomarker of HS and CAD but that their association with these cardiometabolic diseases is mediated through other pathways.

This study examined struggles to establish autonomy and relatedness with peers in adolescence and early adulthood as predictors of advanced epigenetic aging assessed at age 30. Participants ( N = 154; 67 male and 87 female) were observed repeatedly, along with close friends and romantic partners, from ages 13 through 29. Observed difficulty establishing close friendships characterized by mutual autonomy and relatedness from ages 13 to 18, an interview-assessed attachment state of mind lacking autonomy and valuing of attachment at 24, and self-reported difficulties in social integration across adolescence and adulthood were all linked to greater epigenetic age at 30, after accounting for chronological age, gender, race, and income. Analyses assessing the unique and combined effects of these factors, along with lifetime history of cigarette smoking, indicated that each of these factors, except for adult social integration, contributed uniquely to explaining epigenetic age acceleration. Results are interpreted as evidence that the adolescent preoccupation with peer relationships may be highly functional given the relevance of such relationships to long-term physical outcomes.

Oxytocin (OT), the brain's most abundant neuropeptide, plays an important role in social salience and motivation. Clinical trials of the efficacy of OT in autism spectrum disorder (ASD) have reported mixed results due in part to ASD's complex etiology. We investigated whether genetic and epigenetic variation contribute to variable endogenous OT levels that modulate sensitivity to OT therapy. To carry out this analysis, we integrated genome-wide profiles of DNA-methylation, transcriptional activity, and genetic variation with plasma OT levels in 290 participants with ASD enrolled in a randomized controlled trial of OT. Our analysis identified genetic variants with novel association with plasma OT, several of which reside in known ASD risk genes. We also show subtle but statistically significant association of plasma OT levels with peripheral transcriptional activity and DNA-methylation profiles across several annotated gene sets. These findings broaden our understanding of the effects of the peripheral oxytocin system and provide novel genetic candidates for future studies to decode the complex etiology of ASD and its interaction with OT signaling and OT-based interventions. LAY SUMMARY: Oxytocin (OT) is an abundant chemical produced by neurons that plays an important role in social interaction and motivation. We investigated whether genetic and epigenetic factors contribute to variable OT levels in the blood. To this, we integrated genetic, gene expression, and non-DNA regulated (epigenetic) signatures with blood OT levels in 290 participants with autism enrolled in an OT clinical trial. We identified genetic association with plasma OT, several of which reside in known autism risk genes. We also show statistically significant association of plasma OT levels with gene expression and epigenetic across several gene pathways. These findings broaden our understanding of the factors that influence OT levels in the blood for future studies to decode the complex presentation of autism and its interaction with OT and OT-based treatment., (© 2023 The Authors. Autism Research published by International Society for Autism Research and Wiley Periodicals LLC.)

BACKGROUND More than half of major adverse cardiovascular events (MACE) occur in the absence of obstructive coronary artery disease and are often attributed to the rupture of high-risk coronary atherosclerotic plaque (HRP). Blood-based biomarkers that associate with imaging-defined HRP and predict MACE are lacking. METHODS AND RESULTS Nuclear magnetic resonance-based lipoprotein particle profiling was performed in the biomarker substudy of the PROMISE (Prospective Multicenter Imaging Study for Evaluation of Chest Pain) trial (N=4019) in participants who had stable symptoms suspicious for coronary artery disease. Principal components analysis was used to reduce the number of correlated lipoproteins into uncorrelated lipoprotein factors. The association of lipoprotein factors and individual lipoproteins of significantly associated factors with core laboratory determined coronary computed tomographic angiography features of HRP was determined using logistic regression models. The association of HRP-associated lipoproteins with MACE was assessed in the PROMISE trial and validated in an independent coronary angiography biorepository (CATHGEN [Catheterization Genetics]) using Cox proportional hazards models. Lipoprotein factors composed of high-density lipoprotein (HDL) subclasses were associated with HRP. In these factors, large HDL (odds ratio [OR], 0.70 [95% CI, 0.56-0.85]; P <0.001) and medium HDL (OR, 0.84 [95% CI, 0.72-0.98]; P =0.028) and HDL size (OR, 0.82 [95% CI, 0.69-0.96]; P =0.018) were associated with HRP in multivariable models. Medium HDL was associated with MACE in PROMISE (hazard ratio [HR], 0.76 [95% CI, 0.63-0.92]; P =0.004), which was validated in the CATHGEN biorepository (HR, 0.91 [95% CI, 0.88-0.94]; P <0.001). CONCLUSIONS Large and medium HDL subclasses and HDL size inversely associate with HRP features, and medium HDL subclasses inversely associate with MACE in PROMISE trial participants. These findings may aid in the risk stratification of individuals with chest pain and provide insight into the pathobiology of HRP. REGISTRATION URL: https://clinicaltrials.gov; Unique identifier: NCT01174550.

Heart failure with reduced ejection fraction (HFrEF) is increasingly treated with medications for type 2 diabetes mellitus (T2DM). Whether metabolic derangements in HFrEF and T2DM are associated with differential outcomes remains unclear. Therefore, understanding molecular pathways in HFrEF and T2DM and their effects on clinical endpoints is important. The FIGHT trial randomized 300 individuals with HFrEF and a recent HF hospitalization to liraglutide (a GLP-1 receptor agonist) versus placebo to assess effects on mortality, HF rehospitalization, and 6-month change in NT-ProBNP. Although the trial showed no clinical benefit of liraglutide, the trial population was highly enriched for individuals with T2DM. Sixty metabolites were quantified via mass spectrometry in plasma from 254 FIGHT participants (N = 147 (57.9%) with T2DM). Principal components analysis reduced the high number of correlated metabolites into uncorrelated factors. The association of factor levels with 90-day changes in 6-min walk distance (6MWD) and NT-proBNP, and with time to mortality or HF hospitalization were evaluated. There were no changes in metabolite factors according to treatment assignment. However, in analyses stratified by T2DM status, changes in five plasma metabolite factors correlated with changes in functional outcomes beyond adjustment: factor 2 (branched-chain amino acids [BCAA]) correlated with changes in NT-proBNP (ρ = - 0.291, p = 4 × 10 -4 ) and 6MWD (ρ= 0.265, p = 0.011); factor 1 (medium-chain acylcarnitines;  ρ = 0.220, p = 0.008), factor 4 (long-chain dicarboxylacylcarnitines; ρ = 0.191, p = 0.019), factor 5 (long-chain acylcarnitines; ρ = 0.198, p = 0.017), and factor 8 (urea cycle metabolites; ρ = - 0.239, p = 4 × 10 -3 ), correlated with change in NT-proBNP. Factor 4 was associated with time-to-event (HR = 1.513 [95% CI 1.208-1.896], p = 3 × 10 -4 ) with a trend towards stronger prognostic effect in T2DM (T2DM: p = 1 × 10 -3 , non-T2DM: p = 0.1). We identified metabolites of BCAA, urea cycle and fatty acid metabolism as biomarkers of HFrEF outcomes, with observed differences in HFrEF patients with T2DM. Such biomarkers might enable future diagnostic or therapeutic interventions in individuals with HFrEF and T2DM.Trial Registration: Clinicaltrials.gov. Identifier: NCT01800968. First posted: February 28, 2013., (© 2022. The Author(s).)

Aims: This study was designed to assess links between lifetime levels of marijuana use and accelerated epigenetic aging., Design: Prospective longitudinal study, following participants annually from age 13 to age 30., Setting and Participants: A community sample of 154 participants recruited from a small city in the Southeastern United States., Measurements: Participants completed annual assessments of marijuana use from age 13 to age 29 and provided blood samples that yielded two indices of epigenetic aging (DNAmGrimAge and DunedinPoAm) at age 30. Additional covariates examined included history of cigarette smoking, anxiety and depressive symptoms, childhood illness, gender, adolescent-era family income, and racial/ethnic minority status., Findings: Lifetime marijuana use predicted accelerated epigenetic aging, with effects remaining even after covarying cell counts, demographic factors and chronological age (β's = 0.32 & 0.27, p's < 0.001, 95% CI's = 0.21-0.43 & 0.16-0.39 for DNAmGrimAge and DunedinPoAm, respectively). Predictions remained after accounting for cigarette smoking (β's = 0.25 & 0.21, respectively, p's < 0.001, 95% CI's = 0.14-0.37 & 0.09-0.32 for DNAmGrimAge and DunedinPoAm, respectively). A dose-response effect was observed and there was also evidence that effects were dependent upon recency of use. Effects of marijuana use appeared to be fully mediated by hypomethylation of a site linked to effects of hydrocarbon inhalation (cg05575921)., Conclusions: Marijuana use predicted epigenetic changes linked to accelerated aging, with evidence suggesting that effects may be primarily due to hydrocarbon inhalation among marijuana smokers. Further research is warranted to explore mechanisms underlying this linkage., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Background: Experimental studies and small clinical trials have suggested that treatment with intranasal oxytocin may reduce social impairment in persons with autism spectrum disorder. Oxytocin has been administered in clinical practice to many children with autism spectrum disorder., Methods: We conducted a 24-week, placebo-controlled phase 2 trial of intranasal oxytocin therapy in children and adolescents 3 to 17 years of age with autism spectrum disorder. Participants were randomly assigned in a 1:1 ratio, with stratification according to age and verbal fluency, to receive oxytocin or placebo, administered intranasally, with a total target dose of 48 international units daily. The primary outcome was the least-squares mean change from baseline on the Aberrant Behavior Checklist modified Social Withdrawal subscale (ABC-mSW), which includes 13 items (scores range from 0 to 39, with higher scores indicating less social interaction). Secondary outcomes included two additional measures of social function and an abbreviated measure of IQ., Results: Of the 355 children and adolescents who underwent screening, 290 were enrolled. A total of 146 participants were assigned to the oxytocin group and 144 to the placebo group; 139 and 138 participants, respectively, completed both the baseline and at least one postbaseline ABC-mSW assessments and were included in the modified intention-to-treat analyses. The least-squares mean change from baseline in the ABC-mSW score (primary outcome) was -3.7 in the oxytocin group and -3.5 in the placebo group (least-squares mean difference, -0.2; 95% confidence interval, -1.5 to 1.0; P = 0.61). Secondary outcomes generally did not differ between the trial groups. The incidence and severity of adverse events were similar in the two groups., Conclusions: This placebo-controlled trial of intranasal oxytocin therapy in children and adolescents with autism spectrum disorder showed no significant between-group differences in the least-squares mean change from baseline on measures of social or cognitive functioning over a period of 24 weeks. (Funded by the National Institute of Child Health and Human Development; SOARS-B ClinicalTrials.gov number, NCT01944046.)., (Copyright © 2021 Massachusetts Medical Society.)

Background: Whether differences in circulating long chain acylcarnitines (LCAC) are seen in heart failure (HF) patients with and without diabetes mellitus (DM), and whether these biomarkers report on exercise capacity and clinical outcomes, remains unknown. The objective of the current study was to use metabolomic profiling to identify biomarkers that report on exercise capacity, clinical outcomes, and differential response to exercise in HF patients with and without DM., Methods: Targeted mass spectrometry was used to quantify metabolites in plasma from participants in the heart failure: a controlled trial investigating outcomes of exercise training (HF-ACTION) trial. Principal components analysis was used to identify 12 uncorrelated factors. The association between metabolite factors, diabetes status, exercise capacity, and time to the primary clinical outcome of all-cause mortality or all-cause hospitalization was assessed., Results: A total of 664 participants were included: 359 (54%) with DM. LCAC factor levels were associated with baseline exercise capacity as measured by peak oxygen consumption (beta 0.86, p  =  2 × 10 -7 , and were differentially associated in participants with and without DM (beta 1.58, p  =  8  ×  10 -8 vs. 0.67, p  =  9  ×  10 -4 , respectively; p value for interaction  =  0.012). LCAC levels changed to a lesser extent in participants with DM after exercise (mean ∆ 0.09, p  =  0.24) than in those without DM (mean ∆ 0.16, p  =  0.08). In univariate and multivariate modeling, LCAC factor levels were associated with time to the primary outcome (multivariate HR 0.80, p  =  2.74  ×  10 -8 ), and were more strongly linked to outcomes in diabetic participants (HR 0.64, p  =  3.21  ×  10 -9 v. HR 0.90, p  =  0.104, p value for interaction  =  0.001). When analysis was performed at the level of individual metabolites, C16, C16:1, C18, and C18:1 had the greatest associations with both exercise capacity and outcomes, with higher levels associated with worse outcomes. Similar associations with time to the primary clinical outcome were not found in a control group of patients without HF from the CATHeterization GENetics (CATHGEN) study., Conclusions: LCAC biomarkers are associated with exercise status and clinical outcomes differentially in HF patients with and without DM. Impaired fatty acid substrate utilization and mitochondrial dysfunction both at the level of the skeletal muscle and the myocardium may explain the decreased exercise capacity, attenuated response to exercise training, and poor clinical outcomes seen in patients with HF and DM. Trial Registration clinicaltrials.gov Identifier: NCT00047437., (© 2021. The Author(s).)

Lymphoblastoid cell lines (LCLs) are generated by transforming primary B cells with Epstein-Barr virus (EBV) and are used extensively as model systems in viral oncology, immunology, and human genetics research. In this study, we characterized single-cell transcriptomic profiles of five LCLs and present a simple discrete-time simulation to explore the influence of stochasticity on LCL clonal evolution. Single-cell RNA sequencing (scRNA-seq) revealed substantial phenotypic heterogeneity within and across LCLs with respect to immunoglobulin isotype; virus-modulated host pathways involved in survival, activation, and differentiation; viral replication state; and oxidative stress. This heterogeneity is likely attributable to intrinsic variance in primary B cells and host-pathogen dynamics. Stochastic simulations demonstrate that initial primary cell heterogeneity, random sampling, time in culture, and even mild differences in phenotype-specific fitness can contribute substantially to dynamic diversity in populations of nominally clonal cells., Competing Interests: ES, EB, EH, JZ, SG, JB, SG, CC, ML No competing interests declared, JD Joanne Dai is affiliated with Amgen Inc, The author has no financial interests to declare., (© 2021, SoRelle et al.)

The MIR137 locus is a replicated genetic risk factor for schizophrenia. The risk-associated allele is reported to increase miR-137 expression and miR-137 overexpression alters synaptic transmission in mouse hippocampus. We investigated the cellular mechanisms underlying these observed effects in mouse hippocampal neurons in culture. First, we correlated the risk allele to expression of the genes in the MIR137 locus in human postmortem brain. Some evidence for increased MIR137HG expression was observed, especially in hippocampus of the disease-associated genotype. Second, in mouse hippocampal neurons, we confirmed previously observed changes in synaptic transmission upon miR-137 overexpression. Evoked synaptic transmission and spontaneous release were 50% reduced. We identified defects in release probability as the underlying cause. In contrast to previous observations, no evidence was obtained for selective synaptic vesicle docking defects. Instead, ultrastructural morphometry revealed multiple effects of miR-137 overexpression on docking, active zone length and total vesicle number. Moreover, proteomic analyses of neuronal protein showed that expression of Syt1 and Cplx1, previously reported as downregulated upon miR-137 overexpression, was unaltered. Immunocytochemistry of synapses overexpressing miR-137 showed normal Synaptotagmin1 and Complexin1 protein levels. Instead, our proteomic analyses revealed altered expression of genes involved in synaptogenesis. Concomitantly, synaptogenesis assays revealed 31% reduction in synapse formation. Taken together, these data show that miR-137 regulates synaptic function by regulating synaptogenesis, synaptic ultrastructure and synapse function. These effects are plausible contributors to the increased schizophrenia risk associated with miR-137 overexpression.

Oxidative phosphorylation within mitochondria is the main source of aerobic energy for neuronal functioning, and the key genes are located in mitochondrial DNA. Deficits in oxidative phosphorylation functioning have been reported for schizophrenia, but efforts in the identification of genetic markers within the mitochondrial DNA that predispose to schizophrenia have been limited. We genotyped a set of mitochondrial SNPs using Illumina HumanExome arrays and tested for association in the Swedish schizophrenia sample (N> 10,000). We developed a novel approach for mitochondrial DNA imputation in order to increase the number of common SNPs available for association analysis. The most significant findings were for the mitochondrial SNPs C15452A (GRCh38.p10; rs527236209; p = 0.007; gene MT-CYB; defining haplogroup JT); A11251G (rs869096886; p = 0.007; gene MT-ND4; defining haplogroup JT), and T4216C (rs1599988; p = 0.008, gene MT-ND1, defining haplogroup R2'JT). We also conducted rare variant burden analyses and obtained a p-value of 0.007. For multimarker haplotypes analysis, the most significant finding was for the J group (OR: 0.86, p = 0.02). We conducted the largest association study of mitochondrial DNA variants and schizophrenia but did not find an association that survived multiple testing correction. Analysis of a larger sample is required and will allow a better understanding of the role of mitochondria in schizophrenia.