6509 IGF-1 receptor and insulin receptor in LepRb neurons coordinates body growth, reproduction, and metabolism

Abstract Disclosure: M. Wang: None. J.W. Hill: None. Growth and reproduction are tightly linked. Growth hormone (GH) deficiency results in a profound suppression of postnatal growth accompanied by severely delayed puberty and reproductive senescence, while GH excess is correlated with the reverse. The specific mechanism underlying this delay is undefined. Although leptin receptor (LepRb)-expressing neurons are known to link body growth and reproduction, the role of insulin-like growth factor 1 receptor (IGF1R) signaling in LepRb neuron function is unknown. Previous studies have shown that IGF-1 and insulin can bind to each other’s receptor, permitting IGF-1 signaling in the absence of IGF1R. Therefore, we created mice lacking IGF1R exclusively in LepRb neurons (IGF1RLepRb mice) and mice simultaneously lacking IGF1R and IR in LepRb neurons (IGF1R/IRLepRb mice) to test if IGF1R and insulin receptor (IR) cooperatively regulate metabolic and reproductive functions. IGF1RLepRb and IGF1R/IRLepRb mice displayed delayed onset of puberty and impaired fertility in both sexes, which suggested that both IGF1R and IR in LepRb neurons are required for normal reproduction. Additionally, we found transient growth retardation in IGF1RLepRb and IGF1R/IRLepRb mice. Loss of IGF1R in LepRb neurons led to lower serum IGF-1 and GH levels in male mice and impaired trabecular and cortical bone development in mice of both sexes. Only transient and mild changes were noticed in the body weight. However, we found IGF1R and IR in LepRb neurons jointly regulate body mass composition, energy homeostasis and glucose homeostasis, as shown by elevated fat mass composition, low energy expenditure and low physical activity in IGF1R/IRLepRb mice. Taken together, these studies identify the unique and cooperative role of LepRb IGF1R and IRs in the regulation of body growth, reproduction, and metabolism. Presentation: 6/3/2024