Interleukin-4 inhibits the hypothalamic appetite control by modulating the insulin-AKT and JAK-STAT signaling in leptin mutant mice

Our previous research identified interleukin-4 (IL-4) as a key regulator of glucose/lipid metabolism, circulatory leptin levels, and insulin action, suggesting its potential as a therapeutic target for obesity and related complications. This study aimed to further elucidate the role of IL-4 in regulating hypothalamic appetite-controlling neuropeptides using leptin dysfunctional Leptin^145E/145E mice as the experimental model. IL-4 significantly reduces body weight, food intake, and serum glucose levels. Our data demonstrated that IL-4 exhibits multiple functions in regulating hypothalamic appetite control, including downregulating orexigenic agouti-related peptide and neuropeptide Y levels, promoting expression of anorexigenic proopiomelanocortin, alleviating microenvironmental hypothalamic inflammation, enhancing leptin and insulin pathway, and attenuating insulin resistance. Furthermore, IL-4 promotes uncoupling protein 1 expression of white adipose tissue (WAT), suggesting its role in triggering WAT-beige switch. In summary, this study uncovers novel function of IL-4 in mediating food-intake behaviors and metabolic efficiency by regulating hypothalamic appetite-control and WAT browning activities. These findings support the therapeutic potential of targeting hypothalamic inflammation and reducing adiposity through IL-4 intervention for tackling the pandemic increasing prevalence of obesity and associated metabolic disorders.