Genetic and dietary cues are known drivers of obesity, yet how they converge at the molecular level is incompletely understood. Here we show that PPARγ supports hypertrophic expansion of adipose tissue via transcriptional control of LPCAT3, an endoplasmic reticulum (ER)-resident O-acyltransferase that selectively enriches diet-derived omega-6 polyunsaturated fatty acids (n-6 PUFAs) in the membrane lipidome. In mice fed a high-fat diet, lowering membrane n-6 PUFA levels through genetic or dietary interventions results in aberrant adipose triglyceride (TG) turnover, ectopic fat deposition and insulin resistance. Additionally, we detail a non-canonical adaptive response in ‘lipodystrophic’ Lpcat3–/– adipose tissues that engages a futile lipid cycle to increase metabolic rate and offset lipid overflow to ectopic sites. Live-cell imaging, lipidomics and molecular dynamics simulations reveal that adipocyte LPCAT3 activity enriches n-6 arachidonate in the phosphatidylethanolamine (PE)-dense ER–lipid droplet interface. Functionally, this localized PE remodelling optimizes TG storage by driving the formation of large droplets that exhibit greater resistance to adipose TG lipase activity. These findings highlight the PPARγ–LPCAT3 axis as a mechanistic link between dietary n-6 PUFA intake, adipose expandability and systemic energy balance. Dietary n-6 PUFAs enhance adipose tissue expandability through the PPARγ–LPCAT3 membrane remodelling axis.

OBJECTIVE:Sex differences in adipose tissue impact metabolic health, but the underlying molecular mechanisms remain unclear. We previously identified a female-specific chr17 trans-eQTL hotspot regulating mitochondrial gene expression in gonadal white adipose tissue (gWAT). Here, we tested whether iWAT contributes comparably to sex differences in mitochondrial function and futile cycling. METHODS:We analyzed iWAT and gWAT from male and female mice across 58 genetically diverse Hybrid Mouse Diversity Panel (HMDP) strains fed a high-fat, high-sucrose diet. We assessed mitochondrial DNA (mtDNA), oxidative phosphorylation (OXPHOS) and futile cycle gene expression, performed genetic mapping, and measured respiration. RESULTS:In gWAT, females showed higher mtDNA, OXPHOS expression, and a female-specific chr17 trans-eQTL, correlating with metabolic traits. In contrast, iWAT lacked this hotspot and showed higher mtDNA, OXPHOS expression, and respiration in males. Lipid cycling genes (Lipe, Mgll, Pnpla2) were elevated in male iWAT, while Mpc1, Mpc2, and Pck1 were enriched in female gWAT. Ucp1 was higher in female gWAT but not sex-biased in iWAT. Alpl (TNAP), key creatine cycling gene, was upregulated in females in both depots, particularly in iWAT. CONCLUSIONS:Female gWAT shows genetically driven mitochondrial regulation linked to metabolic protection, whereas male iWAT has higher mitochondrial content, OXPHOS expression, and respiration. Elevated lipolytic enzymes in male iWAT suggest greater FFA release, while higher pyruvate import and glyceroneogenesis genes in female gWAT favor FFA recycling. Alpl upregulation in females indicates sex-biased UCP1-independent thermogenesis. These depot- and sex-specific signatures reflect distinct metabolic strategies and highlight the need to consider both in adipose research.

BACKGROUND:In genetic studies with the Hybrid Mouse Diversity Panel, we previously identified a chromosome 9 locus for atherosclerosis. We now identify NNMT (nicotinamide N-methyltransferase), an enzyme that degrades nicotinamide, as the causal gene in the locus and show that the underlying mechanism involves salvage of nicotinamide to nicotinamide adenine dinucleotide (NAD). METHODS:Gain/loss of function studies in macrophages were performed to examine the role of NAD levels in macrophage proliferation and apoptosis in atherosclerosis. RESULTS:Global inhibition of NNMT using an antisense oligonucleotide reduced atherosclerosis lesion area 5- to 10-fold in both male and female mice on a hyperlipidemic background. Selective inhibition of NNMT in liver and adipose, the major tissues expressing high levels of the enzyme, using siRNA (small interfering RNA), had little or no effect on atherosclerosis. Therefore, we hypothesized that levels of NAD in macrophages might contribute. This was confirmed by showing that transplantation with bone marrow from Nnmt knockout mice resulted in reduced lesional macrophage proliferation, increased macrophage apoptosis, and reduced atherosclerosis. Consistent with this conclusion, reduced expression of macrophage CD38, an enzyme that degrades NAD, reduced both macrophage proliferation and atherosclerosis. Moreover, cultured macrophages from heterozygous Nnmt knockout mice exhibited reduced proliferation, increased apoptosis, and an increased NAD/NADH (nicotinamide adenine dinucleotide, reduced) ratio. CONCLUSIONS:These findings reveal a role for nicotinamide salvage and NAD turnover in macrophage proliferation and survival in the context of atherosclerosis.

BACKGROUND:Heart failure with preserved ejection fraction (HFpEF) has overtaken heart failure with reduced ejection fraction as the leading type of heart failure globally and is marked by high morbidity and mortality rates, yet with only a single approved pharmacotherapy: SGLT2i (sodium-glucose co-transporter 2 inhibitor). A prevailing theory for the mechanism underlying SGLT2i is nutrient deprivation signaling, of which ketogenesis is a hallmark. However, it is unclear whether the canonical ketogenic enzyme, HMGCS2 (3-hydroxy-3-methylglutaryl-coenzyme A synthase 2), plays any cardiac role in HFpEF pathogenesis or therapeutic response. METHODS:We used human myocardium, human HFpEF and heart failure with reduced ejection fraction transcardiac blood sampling, an established murine model of HFpEF, ex vivo Langendorff perfusion, stable isotope tracing in isolated cardiomyocytes, targeted metabolomics, proteomics, lipidomics, and a novel cardiomyocyte-specific conditional HMGCS2-deficient model that we generated. RESULTS:We demonstrate, for the first time, the intrinsic capacity of the human heart to produce ketones via HMGCS2. We found that increased acetylation of HMGCS2 led to a decrease in the enzyme's specific activity. However, this was overcome by an increase in the steady-state levels of protein. Oxidized form of nicotinamide adenine dinucleotide repletion restored HMGCS2 function via deacetylation, increased fatty acid oxidation, and rescued cardiac function in HFpEF. Critically, using a conditional, cardiomyocyte-specific HMGCS2 knockdown murine model, we revealed that the oxidized form of nicotinamide adenine dinucleotide is unable to rescue HFpEF in the absence of cardiomyocyte HMGCS2. CONCLUSIONS:The canonical ketogenic enzyme, HMGCS2, mediates the therapeutic effects of the oxidized form of nicotinamide adenine dinucleotide repletion in HFpEF by restoring normal lipid metabolism and mitochondrial function.

Importance:Plasma levels of the gut microbiota-dependent metabolite trimethylamine N-oxide (TMAO) are associated with prevalent abdominal aortic aneurysms (AAA) in humans and fostering of AAA progression in animal models; therapeutic targeting of TMAO production blocks AAA progression and rupture in multiple mouse models. A blood biomarker that identifies individuals at risk for incident AAA development, accelerated AAA expansion, or recommendation for surgical AAA repair could be an asset for risk stratification. Objective:To determine whether TMAO is associated with risk for AAA development, rapid AAA expansion, and risk for recommended surgical intervention. Design, Setting, and Participants:This was a prospective cohort study using 2 independent clinical cohorts undergoing aorta imaging surveillance: a European cohort and a US cohort. Included in this study were patients undergoing serial imaging surveillance of the aorta and long-term outcome monitoring. Patients were recruited from single-center studies in Uppsala, Sweden, and Cleveland, Ohio. Study data were analyzed from October 2023 to May 2025. Exposures:Plasma TMAO concentrations measured by stable isotope dilution liquid chromatography with tandem mass spectrometry. Main Outcomes and Measures:The association of TMAO levels with AAA risk, fast-growing AAA (≥4.0 mm per year), and recommended surgical intervention (≥4.0 mm per year or ≥5.5 cm diameter). Results:The European cohort included 237 individuals (median [IQR] age, 65 [65-73] years; 211 male [89.0%]), and the US cohort included 658 individuals (median [IQR] age, 63 [57-70] years; 523 male [79.5%]). In the European cohort, elevated circulating TMAO was significantly associated with AAA risk independent of traditional risk factors and kidney function. Moreover, elevated TMAO predicted both greater risk for fast-growing AAA (adjusted odds ratio [aOR], 2.75; 95% CI, 1.20-6.79) and recommended surgical intervention (aOR, 2.67; 95% CI, 1.24-6.09). Similar patterns were observed in the US cohort and the combined European and US cohort, with heightened circulating TMAO corresponding with significantly increased adjusted risk for fast-growing AAA (US cohort: aOR, 2.71; 95% CI, 1.53-4.80; combined cohort: aOR, 2.30; 95% CI, 1.47-3.62) and recommended surgical intervention (US cohort: aOR, 2.73; 95% CI, 1.56-4.80; combined cohort: aOR, 2.41; 95% CI, 1.55-3.74). Addition of TMAO to base models containing traditional cardiovascular risk factors resulted in significant improvement in both risk estimation for fast-growing AAA and predicting recommended surgical intervention. Conclusion and Relevance:Results of this cohort study suggest that elevated circulating TMAO levels were associated with increased risk of AAA and identified patients at heightened risk for fast-growing AAA and recommended surgical intervention. TMAO may help identify individuals who may benefit from more frequent surveillance imaging and early surgical intervention to prevent aortic dissection or rupture.

BACKGROUND:Ovarian cancer (OC) poses a significant challenge for conventional chimeric antigen receptor-engineered T (CAR-T) cell therapy, due to frequent recurrence linked to tumor heterogeneity, platinum resistance, immune evasion, and an immunosuppressive tumor microenvironment (TME). METHODS:Here, we analyze primary OC patient samples and identify a unique opportunity for allogeneic CAR-NKT (AlloCAR-NKT) cells to concurrently attack OC tumor cells and their TME. Leveraging stem cell gene engineering and a clinically guided culture method, we achieve robust generation of AlloCAR-NKT cells at high yield and purity. FINDINGS:Compared to conventional CAR-T cells, AlloCAR-NKT cells demonstrate superior anti-OC efficacy, showcasing multiple OC-targeting mechanisms, focused tumor homing, and pronounced TME modulation. AlloCAR-NKT cells also exhibit a high safety profile with reduced cytokine release syndrome. Additionally, these cells do not induce graft-versus-host disease and resist host immune-cell-mediated allorejection. CONCLUSIONS:These findings underscore the unique efficacy and safety advantages, as well as the off-the-shelf potential of AlloCAR-NKT cell therapy for OC. FUNDING:Major funding was provided by the California Institute for Regenerative Medicine (CIRM).

A better understanding of genetic architecture will help enhance precision medicine and clinical care. Towards this end, we investigate sex-stratified analyses for several traits in the Hybrid Mouse Diversity Panel (HMDP) and UK Biobank to assess trait polygenicity and identify contributing loci. By comparing allelic effect directions in males and females, we hypothesize that non-associated loci should show random effect directions across sexes. Instead, we observe strong concordance in effect direction, even among alleles lacking nominal statistical significance. Our findings suggest hundreds of loci influence each mouse trait and thousands affect each human trait, including traits with no significant loci under conventional approaches. We also detect patterns consistent with spurious widespread epistasis. These results highlight the value of sex-stratified analyses in uncovering novel loci, suggest a method for identifying biologically relevant associations beyond statistical thresholds, and caution that pervasive main effects may produce misleading epistatic signals.

Background: Circulating glycine levels have been associated with reduced risk of coronary artery disease (CAD) in humans but these associations have not been observed in all studies. We evaluated whether the relationship between glycine levels and atherosclerosis was causal using genetic analyses in humans and feeding studies in mice. Methods: Serum glycine levels were evaluated for association with risk of CAD in the UK Biobank. Genetic determinants of glycine levels were identified through a genome-wide association study (GWAS) and used to evaluate the causal relationship between glycine and risk of CAD by Mendelian randomization (MR). A dietary supplementation study was carried out with atherosclerosis-prone apolipoprotein E deficient (ApoE−/−) mice to determine the effects of increased circulating glycine levels on cardiometabolic traits and aortic lesion formation. Results: Among 105,718 UK Biobank subjects, elevated serum glycine levels were associated with significantly reduced risk of prevalent CAD (Quintile 5 vs. Quintile 1 OR = 0.76, 95% CI 0.67–0.87; p < 0.0001) and incident CAD (Quintile 5 vs. Quintile 1 HR = 0.70, 95% CI 0.65–0.77; p < 0.0001) after adjustment for age, sex, ethnicity, anti-hypertensive and lipid-lowering medications, blood pressure, kidney function, and diabetes. A GWAS meta-analysis with 230,947 subjects identified 61 loci for glycine levels, of which 26 were novel. MR analyses provided modest evidence that genetically elevated glycine levels were causally associated with reduced systolic blood pressure and risk of type 2 diabetes, but did not provide significant evidence for an association with decreased risk of CAD. Glycine supplementation in mice had no effects on cardiometabolic traits or atherosclerotic lesion development. Conclusions: While expanding the genetic architecture of glycine metabolism, MR analyses and in vivo feeding studies did not provide evidence that the clinical association of this amino acid with atherosclerosis represents a causal relationship.

Air pollution exposure enhances the risk of cardiovascular morbidity and mortality. Epidemiological studies provide strong evidence of a link between exposure to ambient particulate matter with aerodynamic diameter< 2.5 µm (PM2.5) and development of cardiovascular and metabolic disorders. We have shown that inhaled ultrafine particles (UFP) or whole diesel exhaust (DE), enriched in UFP, induce cardiometabolic effects, including dyslipidemia and hepatic steatosis. However, the pathogenic mechanisms remain unknown. We recently demonstrated that exposure to ambient particulate in the ultrafine-size range altered the gut microbiota composition in various animal models, with a potential to induce systemic effects. Thus, we hypothesized that sub-chronic inhalation exposure to DE leads to gut dysbiosis and altered gut-derived metabolites, likely responsible for some of the metabolic effects. Male apolipoprotein E-/- (ApoE-/-) mice, exposed to inhaled DE vs. filtered air (FA) (6 h/day, 5 days/week for 16 weeks) displayed alterations in cecal microbiota composition, which associated with elevated plasma cholesterol and triglycerides, as well as hepatic triglycerides and oxidized lipids. DE exposure upregulated hepatic mRNA and protein levels of 12-lipoxygenase (Alox12), together with significantly reduced fecal acetate levels, correlating with changes in lipids and cecal microbiota composition. Metabolic effects were recapitulated in HepG2 cells treated with DE particles, including elevated Alox12 mRNA levels and decreased respiration in isolated mitochondria. Supplementation with gut-derived short chain fatty acid acetate reversed these effects in cells. In conclusion, inhaled DE induced gut microbiome dysbiosis, lipid peroxidation and triglyceride accumulation, likely via mitochondrial dysfunction, which was rescued in cells by acetate supplementation.

Background: Senescence, a state of permanent cell cycle arrest, is a complex cellular phenomenon closely affiliated with age-related diseases and pathological fibrosis. Cellular senescence is now recognized as a significant contributor to organ fibrosis, largely driven by transforming growth factor beta (TGF-β) signaling, such as in metabolic dysfunction-associated steatohepatitis (MASH), idiopathic pulmonary fibrosis (IPF), chronic kidney disease (CKD), and myocardial fibrosis, which can lead to heart failure, cystic fibrosis, and fibrosis in pancreatic tumors, to name a few. MASH is a progressive inflammatory and fibrotic liver condition that has reached pandemic proportions, now considered the largest non-viral contributor to the need for liver transplantation. Methods: We previously studied Oxy210, an anti-fibrotic and anti-inflammatory, orally bioavailable, oxysterol-based drug candidate for MASH, using APOE*3-Leiden.CETP mice, a humanized hyperlipidemic mouse model that closely recapitulates the hallmarks of human MASH. In this model, treatment of mice with Oxy210 for 16 weeks caused significant amelioration of the disease, evidenced by reduced hepatic inflammation, lipid deposition, and fibrosis, atherosclerosis and adipose tissue inflammation. Results: Here we demonstrate increased hepatic expression of senescence-associated genes and senescence-associated secretory phenotype (SASP), correlated with the expression of pro-fibrotic and pro-inflammatorygenes in these mice during the development of MASH that are significantly inhibited by Oxy210. Using the HepG2 human hepatocyte cell line, we demonstrate the induced expression of senescent-associated genes and SASP by TGF-β and inhibition by Oxy210. Conclusions: These findings further support the potential therapeutic effects of Oxy210 mediated in part through inhibition of senescence-driven hepatic fibrosis and inflammation in MASH and perhaps in other senescence-associated fibrotic diseases.

Kidney fibrosis determines clinical outcomes in individuals with chronic kidney disease (CKD). The stoichiometric ratio of collagens in renal scar differs from that of healthy kidney extracellular matrix (ECM), but the functional importance of altered collagen types in injured kidneys remains unclear. Using human population studies, we show that circulating protein and renal mRNA amounts of collagen V A1 (COL5A1) exhibited associations with kidney disease and incident CKD risk. We show that Col5a1 regulates the degree of postinjury fibrosis and renal function. Mice with conditionally knocked out Col5a1 ( Col5a1 CKO) exhibited decreased renal function and greater renal fibrosis after dietary adenine- or ureteric obstruction–mediated kidney injury. Renal fibroblasts in Col5a1 CKO animals up-regulated the profibrotic αvβ3 integrin. Inhibition of αvβ3 signaling with a small molecule, cilengitide, rescued postinjury renal function in Col5a1 CKO animals. Using the hybrid mouse diversity panel that comprises 100 diverse inbred strains of mice, we observed that gene expression of Col5a1 after injury exhibited genetic variation across 100 strains. Strains with low Col5a1 expression after injury exhibited worse renal function compared with animals that had higher degrees of expression. We next measured Col5a1 expression in peripheral blood mononuclear cells in mice to identify nonresponder strains that did not have increased Col5a1 expression after kidney injury. We observed that administration of cilengitide in nonresponder strains significantly rescued postinjury renal fibrosis and function. These studies point to the feasibility of precision medicine approaches to target Col5a1 for enhancing renal repair.

UbiA prenyltransferase domain containing 1 (Ubiad1) has the potential to affect cholesterol and phospholipid levels in different cell types. We previously identified Ubiad1 as a candidate gene for regulating subcutaneous fat pad weight in a mouse genome-wide association study. Here we evaluated the relationship between Ubiad1 and obesity-related traits in cohorts of humans and mice, and in Ubiad1+/− mice fed a high-fat diet. In both humans and mice, adipose tissue Ubiad1 mRNA expression correlated negatively with adiposity and positively with mitochondria-related genes. To determine the role of Ubiad1 in high-fat diet-induced obesity, we disrupted the Ubiad1 gene in mice. Deletion of Ubiad1 was embryonically lethal in C57BL/6 N mice, preventing analysis of adult Ubiad1−/− mice. Thus, male and female Ubiad1+/+ and Ubiad1+/− mice were fed high-fat diet for 10 weeks, with no difference in weight gain and adipose tissue organ weights observed between the genotypes. Analysis of liver mRNA expression revealed that Ubiad1 heterozygosis (Ubiad1+/−) altered several pathways involved in lipid metabolism. Detailed lipid quantification with HPLC-qTOF/MS showed increased levels of hepatic ceramides in female Ubiad1+/− mice, whereas phosphatidylglycerols, phosohatidylinositol and lysophosphatidylethanolamines were reduced in male Ubiad1+/− mice. Our findings reveal sex-specific effects of Ubiad1 expression on hepatic lipid metabolism.

Population studies have revealed associations between host genetic and gut microbiome in humans and mice. However, the molecular bases for how host genetic variation impacts the gut microbial community and bacterial metabolic niches remain largely unknown. We leveraged 90 inbred hyperlipidemic mouse strains from the hybrid mouse diversity panel (HMDP), previously studied for a variety of cardio-metabolic traits. Metagenomic analysis of cecal DNA followed by genome-wide association analysis identified genomic loci that were associated with microbial enterotypes in the gut. Among these, we detected a genetic locus surrounding multiple amylase genes that were associated with abundances of Firmicutes (Lachnospiraceae family) and Bacteroidetes (Muribaculaceae family) taxa encoding distinct starch and sugar degrading capabilities. The genetic variants at the amylase gene locus were associated with distinct gut microbial communities (enterotypes) with different predicted metabolic capacities for carbohydrate degradation. Mendelian randomization analysis revealed host phenotypes, including liver fibrosis and plasma HDL-cholesterol levels, that were associated with gut microbiome enterotypes. This work reveals novel relationships among host genetic variation, gut microbial enterotypes, and host metabolic traits and supports the notion that variation of host amylase may represent a key determinant of gut microbiome in mice.

BACKGROUND:Trimethylamine-N-oxide (TMAO) has been significantly linked to atherosclerosis via several mechanisms, but its direct effect on the atherosclerosis-prone vasculature remains unclear. The objective of this study was to characterize the cell type-dependent and independent effects of TMAO on key vascular cell types involved in atherosclerosis progression in vivo. METHODS:We performed single-cell RNA-sequencing on aortic athero-prone regions of female Ldlr-/- mice fed normal laboratory, high-cholesterol, or high-cholesterol+TMAO diets for 3 months to identify which aortic cell types, differentially expressed genes, and biological pathways are affected by TMAO. We also modeled cell-cell communications and intracellular gene regulatory networks to identify gene networks perturbed by TMAO feeding. Key genes and pathways were validated using human vascular smooth muscle cells (vSMCs) exposed to TMAO. Changes in fibrous cap thickness, macrophage content, and collagen deposition in response to TMAO were measured with immunostaining and histology and quantified. RESULTS:Our single-cell RNA-sequencing analysis revealed that TMAO supplementation upregulated apoptotic gene signatures and downregulated extracellular matrix (ECM) organization and collagen formation genes in a subset of atherosclerosis-specific modulated vSMCs. We also identified degradation of the ECM as a top pathway for vSMC-derived macrophage differentially expressed genes in response to TMAO. Network analyses supported that macrophage-vSMC communication mediates ECM remodeling. Using human smooth muscle cells exposed to TMAO in vitro, we confirmed the direct effect of TMAO on regulating collagen and apoptotic genes. In agreement with the changes in these pathways that affect plaque stability, we observed a significant decrease in fibrous cap thickness and collagen deposition in mice supplemented with TMAO. CONCLUSIONS:Our results reveal the effects of TMAO on vSMCs to promote apoptosis and decrease ECM formation and on macrophage-mediated ECM degradation to, in concert enhance atherosclerotic plaque instability.

Background and aims: We previously reported that Oxy210, an oxysterol-based drug candidate, exhibits antifibrotic and anti-inflammatory properties. We also showed that, in mice, it ameliorates hepatic hallmarks of non-alcoholic steatohepatitis (NASH), including inflammation and fibrosis, and reduces adipose tissue inflammation. Here, we aim to investigate the effects of Oxy210 on atherosclerosis, an inflammatory disease of the large arteries that is linked to NASH in epidemiologic studies, shares many of the same risk factors, and is the major cause of mortality in people with NASH. Methods: Oxy210 was studied in vivo in APOE*3-Leiden.CETP mice, a humanized mouse model for both NASH and atherosclerosis, in which symptoms are induced by consumption of a high fat, high cholesterol “Western” diet (WD). Oxy210 was also studied in vitro using two cell types that are important in atherogenesis: human aortic endothelial cells (HAECs) and macrophages treated with atherogenic and inflammatory agents. Results: Oxy210 reduced atherosclerotic lesion formation by more than 50% in hyperlipidemic mice fed the WD for 16 weeks. This was accompanied by reduced plasma cholesterol levels and reduced macrophages in lesions. In HAECs and macrophages, Oxy210 reduced the expression of key inflammatory markers associated with atherosclerosis, including interleukin-1 beta (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), chemokine (C-C motif) ligand 2 (CCL2), vascular cell adhesion molecule-1 (VCAM-1), and E-Selectin. In addition, cholesterol efflux was significantly enhanced in macrophages treated with Oxy210. Conclusions: These findings suggest that Oxy210 could be a drug candidate for targeting both NASH and atherosclerosis, as well as chronic inflammation associated with the manifestations of metabolic syndrome.

The role of gut microbe-derived metabolites in the development of metabolic syndrome (MetS) remains unclear. This study aimed to evaluate the associations of gut microbe-derived metabolites and MetS traits in the cross-sectional Metabolic Syndrome In Men (METSIM) study. The sample included 10,194 randomly related men (age 57.65 ± 7.12 years) from Eastern Finland. Levels of 35 metabolites were tested for associations with 13 MetS traits using lasso and stepwise regression. Significant associations were observed between multiple MetS traits and 32 metabolites, three of which exhibited particularly robust associations. N-acetyltryptophan was positively associated with Homeostatic Model Assessment for Insulin Resistant (HOMA-IR) (β = 0.02, p = 0.033), body mass index (BMI) (β = 0.025, p = 1.3 × 10−16), low-density lipoprotein cholesterol (LDL-C) (β = 0.034, p = 5.8 × 10−10), triglyceride (0.087, p = 1.3 × 10−16), systolic (β = 0.012, p = 2.5 × 10−6) and diastolic blood pressure (β = 0.011, p = 3.4 × 10−6). In addition, 3-(4-hydroxyphenyl) lactate yielded the strongest positive associations among all metabolites, for example, with HOMA-IR (β = 0.23, p = 4.4 × 10−33), and BMI (β = 0.097, p = 5.1 × 10−52). By comparison, 3-aminoisobutyrate was inversely associated with HOMA-IR (β = −0.19, p = 3.8 × 10−51) and triglycerides (β = −0.12, p = 5.9 × 10−36). Mendelian randomization analyses did not provide evidence that the observed associations with these three metabolites represented causal relationships. We identified significant associations between several gut microbiota-derived metabolites and MetS traits, consistent with the notion that gut microbes influence metabolic homeostasis, beyond traditional risk factors.

Introduction: Our groups have previously identified trimethylamine N-oxide (TMAO) as a risk factor for cardiovascular diseases (CVD). In humans, elevated plasma TMAO levels are associated with a ~2.5-fold increased risk for major adverse cardiac events, such as death, myocardial infarction, and stroke. Bacterial metabolism of dietary choline (and L-carnitine) in the intestine leads to an intermediate, trimethylamine (TMA), which is absorbed from the gut and oxidized primarily by the hepatic flavin-containing monooxygenase 3 (FMO3) to generate TMAO. Hypothesis: We hypothesize that decreased TMAO generation caused by FMO3 deficiency in mice leads to decreased circulating TMAO levels and atherosclerosis. Approach and Results: We generated FMO3 knockout (KO) mouse on a C57BL/6J background via CRISPR/Cas9 technology. We then crossed the FMO3KO mice with LDL receptor knockout (LDLRKO) mice to generate FMO3 heterozygous (FMO3Het)/LDLRKO mice and FMO3KO/LDLRKO mice for the study. Female FMO3Het/LDLRKO and FMO3KO/LDLRKO mice were fed a 1% choline, a TMAO precursor, and 0.5% cholesterol diet for 3 months to increase circulating TMAO and total cholesterol levels. After diet feeding, FMO3KO/LDLRKO mice had 51% lower TMAO levels compared to FMO3Het/LDLRKO mice (18.3 μM vs. 38.3 μM, p < 0.0001), but no effects on plasma lipids, glucose, or insulin levels. Most notably, atherosclerotic lesion at the aortic root was decreased by 24% (p < 0.01) in the FMO3KO/LDLRKO mice as compared to the FMO3Het/LDLRKO mice. The mRNA levels of inflammatory genes, such as Cox2 and E-selectin, in the aorta were significantly decreased by more than 50% in FMO3KO/LDLRKO mice when compared to the control mice. Western blot analysis revealed decreased NF-κB activation in the aorta samples of the FMO3KO/LDLRKO mice as compared to those of the controls, suggesting reduced inflammation in the former. We also measured circulating IL-6 and TNF-α levels but did not observe any differences in plasma levels of these inflammatory biomarkers. Conclusions: Taken together, our data demonstrate that Fmo3 deficiency reduces TMAO levels and aortic lesion development in the context of an appropriate pro-atherogenic diet that contains also high levels of a TMAO precursor. These results also suggest that one mechanism for the pro-atherogenic effects of TMAO is through localized upregulation of inflammatory pathways at the level of the vessel wall, which do not necessarily manifest systemically.

BackgroundAn association between gut microbes and cardiovascular disease (CVD) has been established, but the underlying mechanisms remain largely unknown.MethodsWe conducted a secondary analysis of the cross-sectional data obtained from the Metabolic Syndrome in Men (METSIM) population-based cohort of 10,194 Finnish men (age = 57.65 ± 7.12 years). We tested the levels of circulating gut microbe-derived metabolites as predictors of CVD, ischemic cerebrovascular accident (CVA), and myocardial infarction (MI). The Kaplan–Meier method was used to estimate the time from the participants' first outpatient clinic visit to the occurrence of adverse outcomes. The associations between metabolite levels and the outcomes were assessed using Cox proportional hazard models.ResultsDuring a median follow-up period of 200 months, 979 participants experienced CVD, 397 experienced CVA, and 548 experienced MI. After adjusting for traditional risk factors and correcting for multiple comparisons, higher plasma levels of succinate [quartile 4 vs. quartile 1; adjusted hazard ratio, aHR = 1.30, (confidence interval (CI), 1.10–1.53) p = 0.0003, adjusted p = 0.01] were significantly associated with the risk of CVD. High plasma levels of ursodeoxycholic acid (UDCA) (quartile 3 vs. quartile 1); [aHR = 1.68, (CI, 1.26–2.2); p = 0.0003, adj. p = 0.01] were associated with a higher risk of CVA. Furthermore, as a continuous variable, succinate was associated with a 10% decrease in the risk of CVD [aHR = 0.9; (CI, 0.84–0.97); p = 0.008] and a 15% decrease in the risk of MI [aHR = 0.85, (CI, 0.77–0.93); p = 0.0007].ConclusionGut microbe-derived metabolites, succinate, and ursodeoxycholic acid were associated with CVD, MI, and CVA, respectively. Regulating the gut microbes may represent a potential therapeutic target for modulating CVD and CVA.

PURPOSE:Bone is susceptible to fluctuations in iron homeostasis, as both iron deficiency and overload are linked to poor bone strength in humans. In mice, however, inconsistent results have been reported, likely due to different diet setups or genetic backgrounds. Here, we assessed the effect of different high and low iron diets on bone in six inbred mouse strains (C57BL/6J, A/J, BALB/cJ, AKR/J, C3H/HeJ, and DBA/2J). METHODS:Mice received a high (20,000 ppm) or low-iron diet (∼10 ppm) after weaning for 6-8 weeks. For C57BL/6J males, we used two dietary setups with similar amounts of iron, yet different nutritional compositions that were either richer ("TUD study") or poorer ("UCLA study") in minerals and vitamins. After sacrifice, liver, blood and bone parameters as well as bone turnover markers in the serum were analyzed. RESULTS:Almost all mice on the UCLA study high iron diet had a significant decrease of cortical and trabecular bone mass accompanied by high bone resorption. Iron deficiency did not change bone microarchitecture or turnover in C57BL/6J, A/J, and DBA/2J mice, but increased trabecular bone mass in BALB/cJ, C3H/HeJ and AKR/J mice. In contrast to the UCLA study, male C57BL/6J mice in the TUD study did not display any changes in trabecular bone mass or turnover on high or low iron diet. However, cortical bone parameters were also decreased in TUD mice on the high iron diet. CONCLUSION:Thus, these data show that cortical bone is more susceptible to iron overload than trabecular bone and highlight the importance of a nutrient-rich diet to potentially mitigate the negative effects of iron overload on bone.