The Role of the Brain in Glucose Regulation

Growing evidence suggests that the brain plays an important role in the regulation of glucose homeostasis. The brain continuously sense and integrates autonomic, hormonal and nutrient-related signals that convey information about both long-term energy stores (e.g., insulin and leptin), and short-term nutrient availability including glucose, fatty acids and gut- or liver-derived hormones such as glucagon-like peptide-1 and members of the fibroblast growth factor family (FGF). In response, the brain coordinates behavioral, autonomic, and neuroendocrine responses that regulate hepatic glucose production (HGP) and peripheral glucose uptake, thereby maintaining euglycemia across a range of physiological and environmental conditions.
During states of acute energy deficit, such as hypoglycemia, or chronic energy deficiency, such as leptin deficiency, the brain triggers adaptive responses to increase fuel availability for the CNS while conserving energy. These responses include increased feeding, enhanced HGP driven by elevated glucagon and corticosterone secretion via activation of the hypothalamus–pituitary adrenal (HPA) axis, and suppression of energy‑expensive processes such as growth and reproduction through inhibition of the hypothalamus pituitary–thyroid (HPT) axis. Work from our group and others demonstrates that neurons within the hypothalamic ventromedial nucleus (VMN) are both necessary and sufficient to mediate adaptive counterregulatory responses (CRR) to hypoglycemia and restore low blood glucose levels back to the normal range.
Similar adaptive responses to hypoglycemia are observed in models of genetic or acquired leptin deficiency. Our work further shows that central leptin administration normalizes diabetic hyperglycemia in ob/ob mice, and in insulin-deficient diabetes mellitus (uDM), independent of effects on body weight and food intake, highlighting the therapeutic potential of targeting CNS pathways. Supporting this, our findings further show that a single injection of FGF1 directly into the brain induces sustained diabetes remission in rodent models of T2D without altering food intake, body weight, or causing hypoglycemia. This effect is mediated, in part, via inhibition of AgRP neurons in the arcuate nucleus, whose hyperactivity drives hyperglycemia independently of obesity or hyperphagia. Moreover, chronic AgRP inactivation in ob/ob mice replicates the anti-diabetic effects of FGF1, highlighting a discrete hypothalamic circuit capable of sustaining long-term glucose homeostasis. Collectively, this work supports the CNS as a central regulator of glucose metabolism and identify the brain as a promising target for novel diabetes therapies.