Novel Mechanisms for Exercise Training Effects on Glucose Homeostasis

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PROJECT SUMMARY/ABSTRACT Regular physical activity is essential for overall health, including beneficial effects to improve whole-body metabolic homeostasis and insulin sensitivity: adaptations that are critical for people with diabetes. While these benefits of exercise training are well described, the underlying cellular and molecular mechanisms are not well understood. The concept that exercise stimulates tissue-to-tissue communication to improve overall metabolic health has emerged as an important area of scientific investigation. Exercise is a complex physiological stimulus that regulates numerous molecules, signaling networks and tissues, and we hypothesize that all of these adaptations contribute to mediating the beneficial effects of physical exercise on health. Studies supported by this award have shown that exercise-induced adaptations to subcutaneous adipose tissue (scWAT) play a fundamental role in this process. In the next phase of this project we propose to use mouse models to investigate three critical areas of exercise and adipose tissue biology, all of which are based on our compelling preliminary or published studies. Specific Aim 1 is based on our findings suggesting that the mechanism for the beneficial role of exercise-trained scWAT on metabolism involves the secretion and biological actions of multiple exercise-induced adipokines. We discovered that TGF-β2 is one such exercise- specific adipokine, and demonstrated that TGF-β2 is regulated by lactate and has profound effects on tissue and systemic metabolism. One goal of Specific Aim 1 is to elucidate the cellular signaling mechanisms regulating this novel exercise-induced lactate-TGF-β2 axis. Given the potential clinical significance of exercise-regulated adipokines, another goal of Aim 1 is to elucidate the complete exercise-regulated scWAT secretome. In Specific Aim 2, we will investigate CRISP1, another newly identified exercise-regulated adipokine. Importantly, our preliminary data show that CRISP1 is regulated by a lactate-independent mechanism and has beneficial effects on tissue and systemic metabolism. In addition, CRISP1 appears to be sex-specific, only increasing with exercise in male mice, and in Aim 2 we will investigate underlying mechanisms for sex-specific adaptations to scWAT. Specific Aim 3 will investigate exercise regulation of “lipokines”, signaling lipids that are a new class of molecules shown to have metabolic effects. We discovered that 12,13-diHOME is a novel lipokine increased by both exercise and exercise training, released from brown adipose tissue, and functions to increase skeletal muscle fatty acid metabolism. Specific Aim 3 will study the metabolic consequences of exercise-regulated 12,13-diHOME. This innovative project should lead to a new paradigm in which exercise-stimulated circulating factors derived from adipose tissues function to regulate the beneficial effects of exercise on health. These studies have the potential to define novel biologics to aid in the treatment of obesity, type 2 diabetes, and other metabolic diseases.