Limiting Mrs2-dependent mitochondrial Mg2+ uptake induces metabolic programming in prolonged dietary stress

The most abundant cellular divalent cations, Mg2+ (mM) and Ca2+ (nM-μM), antagonistically regulate divergent metabolic pathways with several orders of magnitude affinity preference, but the physiological significance of this competition remains elusive. In mice consuming a Western diet, genetic ablation of the mitochondrial Mg2+ channel Mrs2 prevents weight gain, enhances mitochondrial activity, decreases fat accumulation in the liver, and causes prominent browning of white adipose. Mrs2 deficiency restrains citrate efflux from the mitochondria, making it unavailable to support de novo lipogenesis. As citrate is an endogenous Mg2+ chelator, this may represent an adaptive response to a perceived deficit of the cation. Transcriptional profiling of liver and white adipose reveals higher expression of genes involved in glycolysis, β-oxidation, thermogenesis, and HIF-1α-targets, in Mrs2−/− mice that are further enhanced under Western-diet-associated metabolic stress. Thus, lowering mMg2+ promotes metabolism and dampens diet-induced obesity and metabolic syndrome. [Display omitted] •Mitochondrial Mg2+ channel Mrs2 rheostats MCU Ca2+ signals to maintain bioenergetic circuit•DNL precursor and cellular Mg2+ chelator citrate curbs HIF1α signal and oxidative metabolism•Lowering mMg2+ mitigates prolonged dietary-stress-induced obesity and metabolic syndrome•Mrs2 channel blocker CPACC reduces lipid accumulation and promotes browning and weight loss Madaris et al. show that limiting mitochondrial Mg2+ enhances bioenergetics in hepatocytes and thereby prevents Western-diet-induced NAFLD, microvascular rarefaction, and spontaneous tumor prevalence, and Mrs2 channel deletion reprograms whole-body energy metabolism that is driven by HIF1α transcriptional regulation in liver and adipose tissues in a citrate metabolite-dependent manner.