MED13cTg heart ventricles and epididymal fat

The heart requires a continuous supply of energy but has little capacity for energy storage and thus relies on exogenous metabolic sources. We previously showed that cardiac MED13 modulates systemic energy homeostasis in mice. Here we sought to define the extra-cardiac tissue(s) that respond to cardiac MED13 signaling. We show that cardiac over-expression of MED13 in transgenic (MED13cTg) mice confers a lean phenotype that is associated with increased lipid uptake, beta-oxidation and mitochondrial content in white adipose tissue (WAT) and liver. Cardiac expression of MED13 decreases metabolic gene expression and metabolite levels in heart and liver but enhances them in WAT. Although exhibiting increased energy expenditure in the fed state, MED13cTg mice metabolically adapt to fasting. Furthermore, MED13cTg hearts oxidize fuel that is readily available, rendering them more efficient in the fed state. Parabiosis experiments in which circulations of wild-type and MED13cTg mice are joined, reveal that circulating factor(s) in MED13cTg mice promote enhanced metabolism and leanness. These findings demonstrate that MED13 acts within the heart to promote systemic energy expenditure in extra-cardiac energy depots and point to an unexplored metabolic communication system between the heart and other tissues. Overall design: n=3 for each genotype and organ

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Baskin KK, Grueter CE, Kusminski CM, Holland WL, Bookout AL, Satapati S, Kong YM, Burgess SC, Malloy CR, Scherer PE, Newgard CB, Bassel-Duby R, Olson EN