Dissection of Insulin-Dependent Pathways in Skeletal Muscle under Physiological and Diabetic Conditions

Abstract

Insulin signaling regulates growth and metabolism, in part, by regulation of gene expression. To gain more insight into transcriptional pathways activated by physiological levels of insulin in vivo we performed euglycemic insulin clamp in mice at low (4 mU.kg-1.min-1) and high (12 mU.kg-1.min-1) concentrations of insulin and analyzed changes in gene expression in skeletal muscle by RNA-sequencing. At 3 h, low insulin regulated 451 genes while high insulin regulated 1771 genes by at least 1.5-fold (FDR<0.25). Interestingly, the most up regulated pathways in muscle were potential targets of estrogen-related receptor alpha (Esrra) and were related to TCA cycle and oxidative phosphorylation, while the most suppressed genes were targets of FoxO1 involved in autophagy. Insulin also inhibited the expression of over 40 genes involved in mRNA processing/splicing, mostly within the U2 ribonucleoprotein complex, which regulates the assembly and catalytic activity of the spliceosome. To determine how these insulin-dependent pathways might be altered in diabetes, we intersected the clamp gene expression data with gene expression data in streptozotocin (STZ) or high fat diet (HFD) obesity-induced diabetes focusing on genes oppositely regulated by insulin and diabetes. This approach revealed 93 insulin-regulated genes that were dysregulated in STZ and HFD muscle. Most related to TCA cycle and oxidative phosphorylation, however, changes in mRNAs involved in RNA processing/splicing also overlapped in HFD samples, thus indicating potential insulin resistance-specific gene expression signatures. Together these data demonstrate that insulin is a potent regulator of gene expression in vivo altering mRNA diversity through both changes in expression and dysregulation of the spliceosome, with the latter being most prominent in states of insulin resistance. These differences provide unique targets for therapeutic approaches to type 1 and type 2 diabetes involving muscle. Disclosure T.M. Batista: None. R. Garcia Martin: None. W. Cai: None. S. Suk: None. H. Noh: None. J.K. Kim: None. C. Kahn: Advisory Panel; Self; CohBar, ERX Therapeutics, AntriaBio, Inc.. Board Member; Self; Kaleio Biosciences.