Growth hormone receptor (GHR) in AgRP neurons regulates thermogenesis in aged mice in a sex-specific manner

Abstract

AbstractEvidence for hypothalamic regulation of energy homeostasis and thermoregulation in brown adipose tissue (BAT) during aging has been well recognized, yet the central molecular mediators involved in this process are poorly understood. The arcuate hypothalamus (ARC), orexigenic agouti-related peptide (AgRP) neurons control nutrient intake, energy homeostasis, and BAT thermogenesis. To determine the roles of growth hormone receptor (GHR) signaling in the AgRP neurons we used mice with the AgRP-specific GHR deletion (AgRPΔGHR). We found that female AgRPΔGHRmice were resistant to temperature adaptation, and their body core temperature remained significantly lower when held at 10°C, 22°C, or 30°C, compared to control mice. Low body core temperature in female AgRPΔGHRmice has been associated with significant reductions inUcp1andPgc1αexpression in the BAT. Further, neuronal activity in AgRP in response to cold exposure was blunted in AgRPΔGHRfemales, while the number of Fos+AgRP neurons was increased in control females exposed to cold. Global transcriptome from BAT identified increased expression of genes related to immune responses and chemokine activity and decreased expression of genes involved in triglycerides synthesis and metabolic pathways in AgRPΔGHRfemales. Importantly, these were the same genes that are downregulated by thermoneutrality in control mice but not in the AgRPΔGHRanimals. Collectively, these data demonstrate a novel circuit of thermal regulation between the hypothalamic AgRP-GHR and BAT and provide insight into the brain systems that are critical for the thermogenic vitality of the elderly.