1110-OR: ROCK1 Mediates the Anorexigenic Action of Melanocortin by Suppressing AMPK in MC4R-Expressing Neurons of the Paraventricular Nucleus

Introduction and Objective: The leptin-melanocortin pathway is a key hypothalamic circuit that maintains energy homeostasis and regulates food intake. We previously demonstrated that ROCK1 activation in POMC and AgRP neurons is required for leptin's metabolic effects on feeding and obesity. However, whether ROCK1 contributes to melanocortin action in melanocortin 4 receptor (MC4R) neurons remains unknown. We investigated the role of ROCK1 in MC4R-expressing neurons of the paraventricular hypothalamus (PVHMC4R) in body-weight homeostasis and melanocortin-induced satiety. Methods: To achieve site-specific ROCK1 suppression, we injected a Cre-dependent AAV-FlexON-shRNA-ROCK1-mCherry into the PVH of MC4R-Cre mice and confirmed that ROCK1 mRNA levels in PVHMC4R neurons were reduced by ~80%. Results: Selective suppression of ROCK1 in PVHMC4R neurons of MC4R-Cre mice results in a ~31% increase in body weight and adiposity compared with MC4R-Cre mice injected with control rAAV. This effect is most likely due to hyperphagia without changes in energy expenditure, accompanied by hyperinsulinemia, hyperleptinemia, and insulin resistance. Importantly, MC4R agonist MTII-induced food intake is impaired when ROCK1 is absent in MC4R-expressing neurons of the PVH, suggesting that ROCK1 is required for melanocortin action. Mechanistically, we found that ROCK1 physically binds to AMPK and inhibits its activation in the hypothalamus. In vitro studies further demonstrate that overexpression of an AMPK-S491A mutant prevents ROCK1 binding, indicating that Ser491 is a key regulatory site for the ROCK1-AMPK interaction. Conclusion: Our findings identify ROCK1 as a novel mediator of melanocortin's anorexigenic effects via inhibition of AMPK. Targeting ROCK1 in MC4R-expressing neurons of the PVH could offer a therapeutic strategy for obesity and its metabolic complications.