Causal role of genetically predicted impairment of branched-chain amino acid catabolism on insulin secretion and insulin resistance in type 2 diabetes.

Branched chain amino acids (BCAA) are important signaling molecules that are strongly related to type 2 diabetes (T2D), but the data linking BCAAs to reduced insulin sensitivity (IS) in youth is conflicting. This complex relationship of BCAAs with IS and glycemia may be further confounded by metformin that potentially alters BCAA synthesis and transport via gut mechanisms. Therefore, we compared: (1) BCAAs in 20 youth with T2D pre-metformin to 10 normal glucose tolerant (NGT) age/BMI-matched controls and (2) the change in BCAAs after 3 months of metformin in 8 youth with T2D. Fasting BCAAs were measured with nuclear magnetic resonance spectroscopy and IS and oral disposition index (oDI) calculated during a multi-sample 75g OGTT. Compared to NGT, youth with T2D had higher BCAAs and hemoglobin A1c (HbA1c) but lower IS and oDI (Table). Higher total BCAAs pre-metformin correlated with HbA1c (r=0.6, P<0.001,), inversely correlated with oDI (r= -0.5, P=0.02,), but not with IS or BMI (r=0.2, P>0.2). Metformin decreased HbA1c and increased leucine and isoleucine (Table), but there was no change in BMI, IS or valine (all P>0.05). In youth, higher BCAAs were related to lower β-cell function relative to IS and worse glycemia. Although metformin improved glycemia, BCAAs were paradoxically increased suggesting that BCAAs may not be a useful treatment biomarker or indicator of changes in metabolic status. Disclosure A. Meyers: None. C.K. Cravalho: None. A. Villalobos-Perez: None. S. Matta: None. L. Mabundo: None. A.B. Courville: None. M.L. Sampson: None. J.D. Otvos: Employee; Self; LabCorp. S.T. Chung: None. Funding National Institutes of Health (to S.T.C., L.M., A.B.C.)

As the essential amino acids, branched-chain amino acid (BCAA) from diets is indispensable for health. BCAA supplementation is often recommended for patients with consumptive diseases or healthy people who exercise regularly. Latest studies and ours reported that elevated BCAA level was positively correlated with metabolic syndrome, diabetes, thrombosis and heart failure. However, the adverse effect of BCAA in atherosclerosis (AS) and its underlying mechanism remain unknown. Here, we found elevated plasma BCAA level was an independent risk factor for CHD patients by a human cohort study. By employing the HCD-fed ApoE−/− mice of AS model, ingestion of BCAA significantly increased plaque volume, instability and inflammation in AS. Elevated BCAA due to high dietary BCAA intake or BCAA catabolic defects promoted AS progression. Furthermore, BCAA catabolic defects were found in the monocytes of patients with CHD and abdominal macrophages in AS mice. Improvement of BCAA catabolism in macrophages alleviated AS burden in mice. The protein screening assay revealed HMGB1 as a potential molecular target of BCAA in activating proinflammatory macrophages. Excessive BCAA induced the formation and secretion of disulfide HMGB1 as well as subsequent inflammatory cascade of macrophages in a mitochondrial-nuclear H2O2 dependent manner. Scavenging nuclear H2O2 by overexpression of nucleus-targeting catalase (nCAT) effectively inhibited BCAA-induced inflammation in macrophages. All of the results above illustrate that elevated BCAA promotes AS progression by inducing redox-regulated HMGB1 translocation and further proinflammatory macrophage activation. Our findings provide novel insights into the role of animo acids as the daily dietary nutrients in AS development, and also suggest that restricting excessive dietary BCAA consuming and promoting BCAA catabolism may serve as promising strategies to alleviate and prevent AS and its subsequent CHD.

Disclosure: A. Gattu: None. M. Tanzer: None. T. Yaron: None. L. Cantley: None. C.R. Kahn: None. Hepatic insulin resistance is central to type 2 diabetes (T2D). Understanding the cellular drivers underlying insulin resistance in the liver is challenging since, in vivo, this can be due to cell-intrinsic defects in insulin signaling, as well as the effects of multiple circulating factors that can modify insulin signaling. Here, we have utilized inducible pluripotent stem cells (iPS) from 8 control and 8 T2D patients differentiated in vitro into hepatocytes (iHeps) to dissect the cell-intrinsic defects in hepatic insulin resistance. We find that following stimulation with insulin, T2D iHeps displayed “pathway-selective insulin resistance,” in which insulin failed to suppress gene expression of critical gluconeogenic enzymes (PCK1, G6PC) but continued to stimulate expression of the lipogenic enzymes (FASN, ACACA). This was associated with a 1.5-fold higher level of insulin stimulation of C[1]4 acetate into lipids, i.e., de novo lipogenesis. Immunoblotting analysis showed T2D iHeps exhibited a 50% reduction in phosphorylation of the insulin receptor IRY[1][1]35 and ∼ 30% reductions in AKTT308, GSK3αS2[1]/GSK3βS9, and FOXO1T24/FOXO3aT32 in T2D following insulin stimulation for 10 minutes. To define the full spectrum of alterations in signaling in iHeps, we used unbiased LC-MS/MS-based phosphoproteomics. This revealed alterations in 987 insulin-regulated phosphosphorylations that had increased phosphorylation after insulin treatment and alterations in 723 sites for which insulin decreased phosphorylation (with a |fold-change| >1.5 and adj. p < 0.05). These alterations were of two types: 43% of the altered insulin-regulated phosphosites showed reduced or “impaired” insulin regulation, but 57% of the phosphosites displayed new or significantly increased insulin-regulated phosphorylations in T2D, i.e., “emergent” signaling. The impaired signaling in T2D included losses in the insulin receptor signaling cascade, Rho-GTPase pathway, Notch-HLH, and anti-viral mechanisms of IFN-stimulated genes. In contrast, emergent signaling included other components of the Rho-GTPase pathway, metabolism of RNA, membrane trafficking, and chromatin-modifying enzymes. Using an AI-based kinase-substrate association analysis, we found that the deficiencies in signaling represented reduced actions of kinases AKT2, AKT3, PKCθ, CHK2, PHKG2, and/or STK32C kinases, while the emergent changes represented increases in ROCK1, ROCK2, MST4 and/or BCKDK kinase activity. In summary, phosphoproteomic analyses of iHeps revealed a comprehensive insulin signaling network disrupted in insulin resistance in the liver in T2D, which underlies the etiology of insulin resistance. These alterations can be ascribed to changes in the activity of two classes of upstream kinases, representing potential new targets for treating T2D. Presentation: 6/1/2024

Objective: The associations between different types of diabetes, characterized by distinct pathophysiology and genetic architecture, and pancreatic ductal adenocarcinoma (PDAC) risk are not fully understood. We investigated associations of genetic susceptibility to type 2 diabetes (T2D), its eight mechanistic clusters and type 1 diabetes (T1D) using Mendelian randomization (MR) and maturity-onset diabetes of the young (MODY) pathway/gene-set analysis with PDAC risk. Method: Using summary-level genome-wide association statistics for T2D (242, 283 cases, 1, 569, 734 controls), T1D (18, 942 cases, 501, 638 controls), and PDAC (10, 244 cases and 360, 535 controls) in individuals of European ancestry, we conducted two-sample MR to examine associations of genetic susceptibility to T2D and T1D with PDAC risk, using single nucleotide polymorphisms (SNP) significantly associated with T2D, eight mechanistic TD2 clusters (i.e., β-cell dysfunction with a positive or negative association with proinsulin, residual glycaemic, body fat, metabolic syndrome, obesity, lipodystrophy, and liver and lipid metabolism), and T1D identified from published genome-wide association studies (P<5×10-8) as instrumental variables. We also assessed associations of genetic susceptibility to PDAC risk with T2D and T1D using reverse MR. We used MR-RAPS method as the primary analysis approach complemented with sensitivity analyses using MR-IVW, weighted-median, MR-Egger, MR-PRESSO and MR-PIVW. We applied the Summary-based Adaptive Rank Truncated Product (sARTP) method to evaluate the associations for PDAC and the MODY gene set, which consists of 26 genes identified from the Kyoto Encyclopedia of Genes and Genomes (KEGG) database. Results: Genetic susceptibility to T2D (MR-RAPS: OR=1.10; 95% CI 1.05-1.14), particularly the obesity (OR=1.28; 95% CI 1.15-1.42) and lipodystrophy (OR=1.25; 95% CI 1.04-1.50) clusters, was associated with PDAC risk. T1D showed no association with PDAC risk (OR=1.01; 95% CI 0.99-1.02). Reverse MR found no evidence that genetic susceptibility to PDAC risk was associated with T2D or T1D (P>0.05). Sensitivity analyses using other MR methods supported these findings, with no evidence of pleiotropic effects (MR-Egger intercept P>0.05). The MODY gene-set was significantly associated with PDAC risk (P=2.5×10-6), with HNF1A, HNF1B, FOXA3, HNF4A, and HNF4G as the top five contributing genes. Conclusion: Our findings support a role of T2D, particularly the obesity and lipodystrophy clusters, in PDAC risk. Additionally, the genomic susceptibility regions of MODY were significantly associated with PDAC. Citation Format: Ting Zhang, Xing Hua, Chirayu Mohindroo, Xiaoyu Wang, PanScan and PanC4 Consortium, Brian M. Wolpin, Harvey A. Risch, Laufey T. Amundadottir, Alison P. Klein, Kai Yu, Haoyu Zhang, Rachael Z. Stolzenberg-Solomon. Different types of diabetes and pancreatic ductal adenocarcinoma risk: A Mendelian randomization and pathway/gene-set analysis [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 6209.

BackgroundGenetic susceptibility to type 2 diabetes (T2D) is multifactorial. A growing number of genes have been identified as risk factors for T2D across multiple ethnicities in trans-ancestry meta-analysis of large-scale genome-wide association studies. Few studies have looked at these genes in Sub-Saharan African populations. This study was undertaken to look for associations between T2D and single nucleotide polymorphisms (SNPs) in a number of the top candidate genes in a selected Sudanese population.MethodsA total 240 T2D cases and 128 unrelated healthy control subjects were included in this study. Age, sex, weight and height were recorded, blood pressure and biochemical profiles of glucose and lipids were analysed. Single nucleotide polymorphism (SNP) genotyping was performed using the Sequenom MassARRAY® system. Fourteen SNPs were selected across 7 genes: CAPN10 (rs2975760 and rs5030952), PPARG (rs17036314 and rs1801282), IGF2BP2 (rs4402960 and rs1470579), CDKAL1 (rs9465871), HHEX (rs1111875), TCF7L2 (rs7903146, rs11196205 and rs12255372), and KCNJ11 (rs5215, rs1800467 and rs5219). Allelic and haplotype association analyses were performed under additive models in PLINK. P ≤ 0.007 (=0.05/7 genes) was the P-value required to achieve correction for multiple testing.ResultsA significant genetic association between the SNPs rs7903146 (odds ratio 1.69, 95 % confidence interval 1.21–2.38, P = 0.002) and rs12255372 (odds ratio 1.70, 95 % confidence interval 1.20–2.41, P = 0.003) at TCF7L2 and T2D was found in Sudanese population. These associations were retained after adjusting for age, sex and BMI (e.g. rs7903146: odds ratio 1.70, Padj:age/sex/BMI = 0.005). The strongest haplotype association (odds ratio 2.24; Padj:age/sex/BMI = 0.0003) comprised the two point haplotype T_C across rs7903146 and rs11196205. Stepwise logistic regression demonstrated that SNP rs7903146 added significant main effects to rs11196205 or rs12255372, whereas the reverse was not true, indicating that the main effect for association with T2D in this population is most strongly tagged by SNP rs7903146. Adjusted analyses also provided support for protection from T2D associated with minor alleles at SNPs rs2975760 at CAPN10 (odds ratio 0.44, 95 % confidence interval 0.20-0.97, Padj:age/sex/BMI = 0.042) and rs1111876 at HHEX (odds ratio 0.60, 95 % confidence interval 0.39- 0.93, Padj:age/sex/BMI = 0.022).ConclusionsMultiethnic associations between T2D and SNPs at TCF7L2, CAPN10 and HHEX extend to Sub-Saharan Africa, specifically Sudan.

Hepatic insulin resistance is central to type 2 diabetes (T2D), fatty liver disease, and metabolic syndrome. To identify the fundamental, cell-autonomous defects underlying hepatic insulin resistance in T2D, we have used inducible human pluripotent stem (iPS) cells derived from 16 individuals with and without T2D differentiated to hepatocytes (iHeps) and studied in vitro. Consistent with pathway selective insulin resistance, we find that insulin failed to suppress gene expression of critical gluconeogenic enzymes (PCK1, G6PC) but continued to stimulate increased expression of the lipogenic enzymes, fatty acid synthase and acetyl Co-A carboxylase 1 in T2D iHeps. iHeps from T2D also displayed reduced insulin receptor tyrosine phosphorylation and reduced phosphorylation through the IRS/Akt pathway. Global phosphoproteomics in control and T2D iHeps identified 378 unique phosphosites regulated by insulin, and many dysregulated phosphosites within the classical insulin signaling pathway (IRS, AKT1/2, GSK3, FOXO1, RPS6KB1, TSC2) and components of gene transcription regulation, membrane trafficking, Rho-GTPases, vesicle transport. Using a kinome-wide data set created with synthetic peptide libraries to profile almost all functional known human serine/threonine kinases, we found the alterations in insulin signaling mapped to AKT, P70S6K, P90S6K, RSK, PKCτ, and SGK kinases. Thus, iHeps from T2D patients show pathway-selective insulin resistance with a loss of suppression of gluconeogenesis by insulin yet persistent activation of lipogenesis, even in vitro, in the absence of any circulating factor exposure. T2D iHeps also show a dysregulated phosphorylation network that provides new clues to the kinases whose action is altered in T2D and hepatic insulin resistance. Disclosure A.Gattu: None. A.Krook: None. J.R.Zierath: None. M.Mann: None. C.Kahn: None. Funding National Institutes of Health (T32DK007260-46)

Introduction: Few studies have reported that whether elevated plasma branched-chain amino acids (BCAA) level is causally related to atherosclerosis (AS) and the mechanism involved. Methods: First, the plasma BCAA level of 258 atherosclerotic cardiovascular disease (ASCVD) patients and 188 normal people was measured. Second, plaque volume, stability and inflammation of AS mice were evaluated. Third, we assayed BCAA level, catabolism-promoting genes and inflammation in the circulating monocytes of ASCVD patients and abdominal macrophages of AS mice. Fourth, inflammation and macrophage polarization were evaluated in BCAA catabolic deficient RAW 264.7 cells. Finally, mitochondrial hydrogen peroxide (mtH 2 O 2 ), nuclear H 2 O 2 and High mobility group box 1 (HMGB1) levels in RAW 264.7 cells were measured and RAW 264.7 cells-overexpressing catalase targeted to mitochondria (MCAT), nucleus (NCAT) and HMGB1KD RAW 264.7 cells were built to detect their effect on macrophage polarization. Results: First, we found that plasma BCAA level was an independent risk factor of ASCVD. Second, we also found plasma BCAA level was elevated in AS mice, which led to the increase of plaque volume and instability, as well as inflammation. The growth of plaque instability was characterized by increased macrophage amounts and decreased smooth muscle cells (SMCs) and collagen contents. Conversely, when plasma BCAA level was lowered, the above phenomena could be reversed. Third, elevated plasma BCAA level resulting from BCAA catabolic defect occurred in the monocytes of ASCVD patients and the abdominal macrophages of AS mice, which increased inflammatory response by promoting the polarization of macrophages toward M1 phenotype. Fourth, elevated BCAA level-mediated macrophage polarization toward M1 phenotype was regulated by increasing mtH 2 O 2 level to induce secretion of HMGB1 by increasing nuclear H 2 O 2 level. Finally, the improvement of BCAA catabolism of macrophages alleviated AS progression in mice. Conclusions: Our data demonstrates that elevated plasma BCAA level is an independent risk factor of ASCVD and promotes AS progression, indicating that plasma BCAA level might be a therapeutic target for ASCVD.

The branched chain amino acids (BCAA), leucine, isoleucine and valine, are essential for mammals, and they play a positive role in exercise capacity, muscle development, and a lean body phenotype. BCAA supplementation is commonly paired with exercise in order to promote muscle growth, increase resistance to fatigue and reduce muscle soreness. Conversely, elevated serum BCAA is strongly and positively correlated with the development of insulin resistance, coronary heart disease, and type II diabetes, and is predictive of patient response to therapeutics and intervention outcomes. We have previously shown that defective BCAA catabolism in mice impaired glucose metabolism in the heart and increased susceptibility to stress-induced cardiac damage. In this study we sought to determine the effects of elevated BCAA levels on skeletal muscle performance and response to exercise training using mouse models with systemically elevated BCAA levels. Here we assess the hypothesis that defective BCAA catabolism negatively impacts exercise capacity and endurance through deregulation of substrate utilization in the skeletal muscle using a mouse model with systemically elevated BCAA levels. Impairment of BCAA catabolism due to the deletion of mitochondrial-localized protein phosphatase 2C (PP2Cm), a key enzyme in activating BCAA catabolism, leads to elevated BCAA levels in mice. To study this, PP2Cm-knock out (KO) mice and their littermate controls were subjected to high-intensity and low-intensity exercise capacity tests via forced treadmill running. PP2Cm-KO mouse has a 20% reduction in exercise capacity. Reduced exercise capacity positively correlated with elevated serum BCAA levels. Additionally, KO animals supplemented with BCAAs demonstrated elevated serum succinate, alanine and glutamate levels, which are metabolic markers of physiological stress. We conclude that the inability to catabolize BCAAs has a negative effect on exercise capacity and endurance.

The branched chain amino acids (BCAA), leucine, isoleucine and valine, are essential for mammalians, and they play a positive role in exercise capacity, muscle development, and a lean body phenotype. BCAA supplementation is commonly paired with exercise in order to promote muscle growth, increase resistance to fatigue and reduce muscle soreness. On the other hand, elevated serum BCAA is strongly and positively correlated with the development of insulin resistance, coronary heart disease, and type II diabetes, and is predictive of patient response to therapeutics and intervention outcomes. We have previously shown that defective BCAA catabolism in mice impaired glucose metabolism in the heart and increased susceptibility to stress-induced cardiac damage. In this study we sought to determine the effects of elevated BCAA levels on skeletal muscle performance and response to exercise training using mouse models with systemically elevated BCAA levels. Supplementation of BCAA (1.5mg/g bodyweight/day, ratio of Leu:Ile:Val = 1.5:0.8:1) was administered to mice with impairment of BCAA catabolism due to the deletion of mitochondrial-localized protein phosphatase 2C (KO), a key enzyme in activating BCAA catabolism, and their littermate controls (CON). Mice were subjected to one week of daily exercise training via forced treadmill running and an exercise capacity test was performed at the beginning and end of training. Baseline maximum running time was decreased in the KO compared to CON (mean 73.4 and 82.5 min, respectively). One week of training resulted in increased exercise capacity in CON with an attenuated increase in KO mice (mean 136 and 112 min, respectively). BCAA supplementation did not further improve exercise capacity in CON (mean 131 min) and abrogated the response to training in KO (mean 70.1 min). Reduced exercise capacity positively correlated with elevated serum BCAA levels. Additionally, KO supplemented with BCAAs demonstrated elevated serum succinate, alanine and glutamate levels, which are metabolic markers of physiological stress. We conclude that short term supplementation of BCAA has no benefit for exercise capacity and accumulation of BCAAs has a negative effect on endurance exercise capacity.

Non-alcoholic fatty liver disease (NAFLD) is likely to be associated with elevated plasma branched-chain amino acids (BCAAs) and may precede the development of type 2 diabetes (T2D). We hypothesized that BCAAs may be involved in the pathogenesis of T2D attributable to NAFLD and determined the extent to which plasma BCAAs influence T2D development in NAFLD. We evaluated cross-sectional associations of NAFLD with fasting plasma BCAAs (nuclear magnetic resonance spectroscopy), and prospectively determined the extent to which the influence of NAFLD on incident T2D is attributable to BCAA elevations. In the current study, 5791 Prevention of REnal and Vascular ENd-stage Disease (PREVEND) cohort participants without T2D at baseline were included. Elevated fatty liver index (FLI) ≥60, an algorithm based on triglycerides, gamma-glutamyltransferase, body mass index (BMI) and waist circumference, was used as proxy of NAFLD. Elevated FLI ≥ 60 was present in 1671 (28.9%) participants. Cross-sectionally, BCAAs were positively associated with FLI ≥ 60 (β = 0.208, p < 0.001). During a median follow-up of 7.3 years, 276 participants developed T2D, of which 194 (70.2%) had an FLI ≥ 60 (log-rank test, p < 0.001). Cox regression analyses revealed that both FLI ≥60 (hazard ratio (HR) 3.46, 95% CI 2.45–4.87, p < 0.001) and higher BCAA levels (HR 1.19, 95% CI 1.03–1.37, p = 0.01) were positively associated with incident T2D. Mediation analysis showed that the association of FLI with incident T2D was in part attributable to elevated BCAAs (proportion mediated 19.6%). In conclusion, both elevated FLI and elevated plasma BCAA levels are associated with risk of incident T2D. The association of NAFLD with T2D development seems partly mediated by elevated BCAAs.

ObjectiveWe employed Mendelian randomization to explore the effects of genetic predisposition to type 2 diabetes (T2D), hyperglycemia, insulin resistance, and pancreatic β-cell dysfunction on risk of stroke subtypes and related cerebrovascular phenotypes.MethodsWe selected instruments for genetic predisposition to T2D (74,124 cases, 824,006 controls), HbA1c levels (n = 421,923), fasting glucose levels (n = 133,010), insulin resistance (n = 108,557), and β-cell dysfunction (n = 16,378) based on published genome-wide association studies. Applying 2-sample Mendelian randomization, we examined associations with ischemic stroke (60,341 cases, 454,450 controls), intracerebral hemorrhage (1,545 cases, 1,481 controls), and ischemic stroke subtypes (large artery, cardioembolic, small vessel stroke), as well as with related phenotypes (carotid atherosclerosis, imaging markers of cerebral white matter integrity, and brain atrophy).ResultsGenetic predisposition to T2D and higher HbA1c levels were associated with higher risk of any ischemic stroke, large artery stroke, and small vessel stroke. Similar associations were also noted for carotid atherosclerotic plaque, fractional anisotropy, a white matter disease marker, and markers of brain atrophy. We further found associations of genetic predisposition to insulin resistance with large artery and small vessel stroke, whereas predisposition to β-cell dysfunction was associated with small vessel stroke, intracerebral hemorrhage, lower gray matter volume, and total brain volume.ConclusionsThis study supports causal effects of T2D and hyperglycemia on large artery and small vessel stroke. We show associations of genetically predicted insulin resistance and β-cell dysfunction with large artery and small vessel stroke that might have implications for antidiabetic treatments targeting these mechanisms.Classification of EvidenceThis study provides Class II evidence that genetic predisposition to T2D and higher HbA1c levels are associated with a higher risk of large artery and small vessel ischemic stroke.

Empirical investigations have identified associations between elevated branched-chain amino acids (BCAAs) levels and an increased incidence of hypertensive disorders of pregnancy (HDP). The aim of this study is to rigorously explore the causal linkage between BCAAs concentrations and the risk of developing HDP. A bidirectional Mendelian randomization (MR) analysis was conducted to ascertain the causal relationship between BCAAs levels and the risk of HDP. Instrumental genetic variables derived from the genome-wide association studies of serum BCAAs levels – encompassing total BCAAs, leucine, isoleucine and valine from the UK Biobank, and HDP data (16,417 cases and 213,893 controls) from the FinnGen consortium – were utilized. We conducted inverse-variance weighted, MR-Egger, simple mode, and weighted MR estimates. To assess the heterogeneity and potential presence of horizontal pleiotropy among the instrumental variables, Cochran Q statistic and the MR-Egger intercept were employed. Simultaneously, transcriptomic data were utilized in conjunction with machine learning to identify key genes through which BCAAs influence HDP. Single-cell techniques were employed to analyze the major cell populations. The forward MR analysis indicated a significant positive correlation between the levels of total BCAAs (OR: 1.300, 95% CI: 1.117–1.462; P < .0001), leucine (OR: 1.096, 95% CI: 1.123–1.505; P < .0001), and valine (OR: 1.299, 95% CI: 1.141–1.478; P < .0001) with the risk of HDP. Isoleucine levels (OR: 1.266, 95% CI: 1.054–1.521; P = .012) demonstrated a positive association with HDP risk that did not reach statistical significance after Bonferroni correction. The reverse analysis revealed no causal effect of HDP on the levels of total BCAAs (OR: 0.992, 95% CI: 0.967–1.018; P = .543), leucine (OR: 1.005, 95% CI: 0.973–1.039; P = .750), isoleucine (OR: 1.000, 95% CI: 0.974–1.026; P = .973), and valine (OR: 0.988, 95% CI: 0.962–1.014; P = .354). Transcriptomic analysis identified MCCC2 and BCAT2 as key genes through which BCAAs affect the occurrence of HDP, and these genes are predominantly expressed in endothelial cells. We provide robust evidence Our findings suggest that HDP was associated with an increased level of BCAAs, and the effects may be related to the expression levels of MCCC2 and BCAT2 in endothelial cells.

Background: Despite the achievements of genome-wide association studies (GWAS), the genetic mechanisms that predispose individuals to type 2 diabetes (T2D) and its cardiovascular (CV) complications remain poorly understood. The prevalence of T2D is three to six times higher among South Asian Indians compared to Europeans. High-throughput metabolite profiling techniques have advanced rapidly, evolving from focusing on single-gene/single-metabolite associations to a genome-wide/metabolome-wide approach. However, data is limited on non-white populations. We conducted an integrated genome-wide lipidomic analysis and Mendelian randomization (MR) to identify gene variants associated with lipid metabolites and determine the causal relationships between circulating lipid species and T2D, as well as CV risk factors, using a discovery cohort of Asian Indian Diabetic Heart Study (AIDHS) (3871) and validation cohorts comprising over 1.14 million European and South Asian Individuals from multiple independent studies. Methods: Untargeted lipidomic analysis was performed on blood samples of AIDHS individuals using liquid chromatography and high-resolution mass spectrometry (LC-MS/MS). We analyzed the association of 269 metabolites with T2D and CVD by conducting a metabolome-GWAS using genotyped and imputed data from 20,006,524 variants in discovery and replication cohorts. Results: Our study identified 261 SNP-metabolite associations of genome-wide significance, of which 59 association signals (p ranging from 8.4×10 −8 to 1.8×10 -18 ) were from genes involved in atherosclerosis, fatty acid biosynthesis, inflammation, insulin signaling, and apoptosis pathways. Two-sample MR and sensitivity analysis using independent of 1,141,060 individuals from European and South Asian populations from the UK Biobank, DIAGRAM, DIAMANT, and Australia, identified species of fatty acids, PC, and LPCs contributing to increased or decreased risk for T2D and CVD. Conclusion: In this first metabolome-GWAS in Asian Indians, we report new mQTLs beyond FADS1/2 associated with lipid subclasses not reported previously. MR analysis in independent datasets identified new molecular signatures of circulating lipid and fatty acid metabolism that are causally associated with inflammation and vascular ischemic disease in dysregulated insulin metabolism and T2D. Funding: The AIDHS study was supported by NIH grants R01DK082766 and R01DK118427 (NIDDK) and grants from the Presbyterian Health Foundation of Oklahoma.

Alteration of various metabolites has been linked to type 2 diabetes (T2D) and insulin resistance. However, identifying significant associations between metabolites and tissue-specific phenotypes requires a multi-omics approach. In a cohort of 42 subjects with different levels of glucose tolerance (normal, prediabetes and T2D) matched for age and body mass index, we calculated associations between parameters of whole-body positron emission tomography (PET)/magnetic resonance imaging (MRI) during hyperinsulinemic euglycemic clamp and non-targeted metabolomics profiling for subcutaneous adipose tissue (SAT) and plasma. Plasma metabolomics profiling revealed that hepatic fat content was positively associated with tyrosine, and negatively associated with lysoPC(P-16:0). Visceral adipose tissue (VAT) and SAT insulin sensitivity (Ki), were positively associated with several lysophospholipids, while the opposite applied to branched-chain amino acids. The adipose tissue metabolomics revealed a positive association between non-esterified fatty acids and, VAT and liver Ki. Bile acids and carnitines in adipose tissue were inversely associated with VAT Ki. Furthermore, we detected several metabolites that were significantly higher in T2D than normal/prediabetes. In this study we present novel associations between several metabolites from SAT and plasma with the fat fraction, volume and insulin sensitivity of various tissues throughout the body, demonstrating the benefit of an integrative multi-omics approach.

Disruption of BCATm in Mice Leads to Increased Energy Expenditure Associated with the Activation of a Futile Protein Turnover Cycle