Insulin Regulates a Broad Network of Gene Expression in the Brain to Regulated Brain Metabolism and Neurotransmission

Impaired insulin signaling in brain leads to both metabolic and behavioral abnormalities. To understand the role of insulin on gene expression in the brain, we performed hyperinsulinemic-euglycemic clamps using physiological doses of insulin in C57BL/6 mice, and after 3 hours collected different brain regions and analyzed their transcriptomes by RNA Seq. In response to peripheral insulin, 1851 genes were up- or down-regulated in the hypothalamus by at least 50% (all P < 0.01). Other regions showed different responses with 205 genes significantly regulated by ≥ 50% in hippocampus and 131 regulated in nucleus accumbens. Insulin upregulated the pathway for very long chain fatty acyl-CoA synthesis in all three regions, but most insulin responsive genes were region specific. Thus, in hypothalamus, insulin modulated metabolism by suppressing the glycolysis and pentose phosphate pathway, while increasing expression of genes in the pyruvate dehydrogenase complex and cholesterol biosynthesis. Conversely, mice with streptozotocin diabetes displayed decreased expression of genes involved in the regulation of pyruvate dehydrogenase complex, very long-chain fatty acyl-CoA and cholesterol biosynthesis in hypothalamus, all of which were normalized by exogenous insulin. In addition, insulin regulated many genes in the hypothalamus involved in neurotransmission, including enhancing the expression of multiple GABA-A receptor subunits and suppressing many neuropeptides. Based on the transcriptional signature, changes in gene expression by insulin involve neurons, astrocytes, oligodendrocytes, microglia and endothelial cells. In summary, peripherally administered insulin rapidly and potently regulates expression of genes involved in neurotransmission, neuromodulation and brain metabolism, especially in the hypothalamus. This helps reroute substrate carbons to the biogenesis of plasma membrane for neuronal and glial function and synaptic remodeling. Disclosure W. Cai: None. T.M. Batista: None. R. Garcia Martin: None. A. Ramirez: None. M. Konishi: None. B.T. O'Neill: None. J.K. Kim: None. C. Kahn: Advisory Panel; Self; MedImmune. Board Member; Self; Kaleido Biosciences. Consultant; Self; AntriaBio, Inc., Cobalt Therapeutics, Flagship Pioneering. Research Support; Self; Alnylam.