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Uncoupling Metabolic Health from Thermogenesis via BCAA Flux in Brown Fat

ABSTRACT: Brown adipose tissue (BAT) is best known for thermogenesis. Whereas numerous studies in rodents found tight associations between the metabolic benefits of BAT and enhanced wholebody energy expenditure, emerging evidence in humans suggests that BAT is protective against Type 2 diabetes independent of body-weight. The underlying mechanism for this dissociation remained unclear. Here, we report that impaired mitochondrial flux of branched-chain amino acids (BCAA) in BAT, by deleting mitochondrial BCAA carrier (MBC, encoded by Slc25a44), was sufficient to cause systemic insulin resistance without affecting whole-body energy expenditure or body-weight. We found that brown adipocytes catabolized BCAAs in the mitochondria as essential nitrogen donors for the biosynthesis of glutamate, N-acetylated amino acids, and one of the products, glutathione. BAT-selective impairment in mitochondrial BCAA flux led to elevated oxidative stress and insulin resistance in the liver, accompanied by reduced levels of BCAA-derived metabolites in the circulation. In turn, supplementation of glutathione restored insulin sensitivity of BAT-specific MBC knockout mice. Notably, a high-fat diet rapidly impaired BCAA catabolism and the synthesis of BCAA-nitrogen derived metabolites in the BAT, while cold-induced BAT activity is coupled with an active synthesis of these metabolites. Together, the present work uncovers a mechanism through which brown fat controls metabolic health independent of thermogenesis via BCAA-derived nitrogen carriers acting on the liver.

ORGANISM(S): Mus Musculus (mouse)

SUBMITTER: Shingo Kajimura

PROVIDER: PXD043813 | JPOST Repository | Tue Mar 05 00:00:00 GMT 2024

REPOSITORIES: jPOST

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Project description:The global prevalence of obesity is increasing across age and gender. The rising burden of obesity in young people contributes to the early emergence of type 2 diabetes. Having one parent obese is an independent risk factor for childhood obesity. While the detrimental impact of diet-induced maternal obesity on offspring is well established, the extent of the contribution of obese fathers is unclear, as is the role of non-genetic factors in the casual pathway. Here we show that paternal high fat diet exposure programmed Î²-cell âdysfunctionâ in their F1 female offspring. Chronic high fat diet consumption in Sprague Dawley fathers led to increased body weight, adiposity, impaired glucose tolerance and insulin sensitivity. Relative to controls, their female offspring had lower body weight at day-1, increased pubertal growth rate, impaired insulin secretion and glucose tolerance, in the absence of obesity or increased adiposity. Paternal high fat diet was observed to alter gene expression of pancreatic islet genes in adult female offspring (P < 0.001); affected functional clusters includes calcium ion binding, insulin, apoptosis, Wnt and cell cycle organ/system development. This is the first reported study in mammals describing non-genetic, intergenerational transmission of metabolic sequelae of high fat diet from father to offspring. These findings support a role of fathers in metabolic programming of offspring and form a framework for further studies. F0 founders were male Sprague Dawley rats, divided into two groups, high fat (HF) and control. The HF fathers were given commercially prepared high-fat pellets (43% as fat); while the controls ate standard laboratory chow (9% as fat). The two groups of fathers had distinct phenotype; the HF fathers were significantly heavier with increased adiposity, they were also glucose intolerant and insulin resistant. At 15 weeks of age, fathers were mated with normal females consuming chow, to generate the F1 offspring. Only female offspring were studied. Female offspring were weaned unto standard laboratory chow at 3 weeks. At 6 and 12 weeks, intraperitoneal glucose tolerance test (IpGTT) was performed to measure blood glucose and insulin profile; at 11 weeks, intraperitoneal insulin tolerance test was done. The body weight and adiposity of these offspring were not different between the two groups. The HF offspring had glucose intolerance and impaired glucose-induced insulin response, mainly at the acute phase, observed since 6 weeks. The IpITT was not different between groups. At 13 weeks, islets were harvested from the two groups of offspring.

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Uncoupling Metabolic Health from Thermogenesis via BCAA Flux in Brown Fat

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