Project description:Induced pluripotent stem cells (iPSCs), upon differentiation into somatic cell types, offer the ability to model the genetic states of tissues in the individuals from whom the iPSCs were derived. A recent study used a multiethnic cohort of healthy individuals to derive iPSCs and iPSC-hepatocytes and perform gene expression and expression quantitative trait locus analyses, identifying causal genes and variants linked to blood lipid levels.2 We sought to use the same cohort of iPSC lines to generate a similar resource with iPSC-cardiomyocytes and make the results available to the community.
Project description:Tetrahydrobiopterin (BH4) is an essential cofactor for several metabolic enzymes, including the aromatic amino acid hydroxylases, alkylglycerol mono-oxygenase and NO synthases. BH4 deficiency due to an autosomal recessive defect in its biosynthetic enzyme 6-pyruvoyltetrahydropterin synthase (PTPS, encoded by the PTS gene) leads to a variant form of hyperphenylalaninemia concomitant with severe deficiency of brain monoamine neurotransmitters. In contrast, augmentation of BH4 by pharmacological supplementation or stimulation of its biosynthesis is thought to correct eNOS dysfunction, to protect from (cardio) vascular disease and/or to prevent from abdominal obesity and development of the metabolic syndrome. We have previously reported that complete Pts knock-out (ko) mice die after birth (Elzaouk et al JBC 2003). Here we generated a murine Pts-knock-in (ki) allele expressing a PTPS-p.Arg15Cys mutant enzyme with low residual activity (12% of wild-type in vitro) and investigated heterozygous Pts-ko/wt, homozygous Pts-ki/ki and compound heterozygous Pts-ki/ko mutant mice. All mice were viable and, depending on the severity of the Pts alleles, exhibited up to 90% reduction of PTPS activity in liver and brain tissues concomitant with high neopterin, but neither an elevation of blood L-Phe, nor a decrease in brain monoamine neurotransmitters dopamine or serotonin. Upon a standard systemic and comprehensive phenotyping of Pts-ki/ki mice, we found alterations in energy metabolites with reduced body mass, higher fat content, lower lean mass, and increased blood glucose and cholesterol in mutant animals. Furthermore, heterozygous Pts-ko/wt and/or homozygous Pts-ki/ki mice exhibited increased body weight and elevated intra-abdominal fat tissue when fed with normal chow or high fat diet. We conclude that a reduced BH4-biosynthetic activity in mice leads to abnormal body fat distribution and abdominal obesity potentially through a mildly compromised eNOS function.
Project description:Body fat distribution is a heritable risk factor for cardiovascular and metabolic disease. In humans, rare Inhibin beta E (INHBE, activin E) loss-of-function variants are associated with lower waist-to-hip ratio and protection from type 2 diabetes. Hepatic fatty acid sensing promotes INHBE expression during fasting and in obese individuals, yet it is unclear how the hepatokine activin E governs body shape and energy metabolism. Here, we uncover activin E as a negative feedback regulator of adipose lipolysis that restrains excessive fat breakdown during fasting. By suppressing β-agonist-induced lipolysis, activin E promotes visceral fat accumulation, adipocyte hypertrophy and contributes to adipose dysfunction in mice. Mechanistically, we demonstrate that activin E elicits its effect on adipose tissue through ACVR1C, activating SMAD2/3 signaling and suppressing PPARG target genes. Conversely, loss of activin E or ACVR1C increases fat utilization, lowers adiposity and drives gene signatures indicative of healthy adipose function. Our studies identify activin E-ACVR1C as metabolic rheostat promoting liver-adipose crosstalk to preserve fat mass during prolonged fasting, a mechanism that is maladaptive in obese individuals.
Project description:It is recognized that higher height and weight are associated with higher risk of atrial fibrillation or flutter (AF) but it is unclear whether risk of AF is related to body fat, body fat location, or lean body mass.This article reports the Danish population-based prospective cohort Diet, Cancer and Health study conducted among 55,273 men and women 50-64 years of age at recruitment. The associations between bioelectrical impedance derived measures of body composition and combinations of anthropometric measures of body fat distribution and risk of an incident record of AF in the Danish Registry of Patients were investigated.During follow-up (median 13.5 years) AF developed in 1,669 men and 912 women. Higher body fat at any measured location was associated with higher risk of AF. The adjusted hazard ratio (HR) per 1 sex-specific standard deviation (SD) increment in body fat mass was 1.29 (95% confidence interval [CI], 1.24-1.33). Higher lean body mass was also associated with a higher risk of AF. The adjusted HR for 1 sex-specific SD increment was 1.40 (95% CI, 1.35-1.45).Higher body fat and higher lean body mass were both associated with higher risk of AF.