PROJECT SUMMARY/ABSTRACT While it has long been established that exercise training can have profound effects on systemic glucose homeostasis and skeletal muscle metabolism, more recent research has demonstrated that adipose tissues also play an important role in mediating the benefits of exercise on metabolic health. Studies supported by this award have shown that subcutaneous white adipose tissue (scWAT), the adipose tissue located beneath the skin, undergoes profound changes in gene and protein expression, structural architecture, and adipokine profile in response to exercise training, adaptations that play a strategic role in regulating systemic exercise- facilitated metabolic benefits. The signaling and intracellular mechanisms that control these important changes in scWAT phenotype and function are not known, but our preliminary data demonstrate that lactate and glycogen, two factors typically associated with skeletal muscle metabolism in response to exercise, also play fundamental roles in regulating exercise training effects on scWAT. In Specific Aim 1 lactate signaling through the G-protein receptor 81 (GPR81) and glycogen metabolism will be investigated as essential mediators of exercise training-induced adaptations to scWAT phenotype, and in turn, whole body systemic metabolism. Numerous approaches including genetically modified mouse models, physiological assessments, proteomics, RNAseq, and lipidomics will be used for this Aim. Specific Aims 2 and 3 will focus on visceral white adipose tissue (vWAT), the adipose depot that surrounds the internal organs under conditions of fuel over-abundance. While vWAT has been less studied in the context of molecular adaptations to training, our recently published multi-omics project investigating key metabolic tissues led to the discovery that under obese conditions, exercise training induces more profound cellular composition and transcriptomic changes in vWAT compared to scWAT. We also found that obesity and training significantly impact crosstalk between immune cells and adipose stem cells (ASCs) in vWAT. Given that exercise is a potent epigenetic modulator, we hypothesize that exercise training reverses the unfavorable responses to obesity by rewiring of the underlying epigenome of vWAT. In Specific Aim 2, single cell level open chromatin accessibility and lncRNA expression profiling in vWAT will be done to determine the epigenetic mechanisms mediating the effects of exercise training and obesity. In Aim 3, exercise training- and obesity-induced immune cell-ASC crosstalk using in vitro and in vivo models will be studied. This will include a focus on the putative interaction between amphiregulin, produced by type 2 innate lymphoid cells (ILC2s) with epidermal growth factor receptor of the ASCs, as this was the most striking interaction predicted by our in-silico single cell analysis. To complement our expertise in exercise science, adipose tissue biology, cell signaling, metabolism, and in vivo ...