Ghrelin Brain-Gut Pathway Discovered to Control Sugar and Fat Metabolism

Ghrelin, often called the "hunger hormone," plays a crucial role in regulating appetite and energy balance. While its effects on metabolism are well-established, the precise neural circuits linking central ghrelin signaling in the brain to peripheral metabolic control have remained incompletely understood. This study specifically aimed to elucidate the ghrelin fiber projections from the hypothalamic arcuate nucleus (ARC) to the dorsal vagal complex (DVC) and their functional impact on glycolipid metabolism.

Activation of ghrelin projections from the ARC to the DVC significantly improved metabolic health in mice. Chemogenetic activation of ARC-DVC ghrelin neurons led to a 28% reduction in fasting blood glucose levels and a 35% improvement in glucose tolerance (measured by AUC) compared to control groups (p<0.01). Furthermore, these interventions resulted in a 22% decrease in liver triglyceride accumulation and a 15% reduction in circulating LDL cholesterol levels (p<0.05). Conversely, specific inhibition of these ghrelin pathways exacerbated metabolic dysfunction, leading to a 20% increase in fasting glucose and impaired insulin sensitivity by 25% (p<0.05). The study also observed a 1.8-fold increase in GLUT4 expression (a glucose transporter) in skeletal muscle and a 2.1-fold decrease in hepatic SREBP-1c mRNA (a key regulator of lipid synthesis), indicating enhanced glucose uptake and reduced lipid synthesis, respectively.