Central chronic apelin infusion decreases energy expenditure and thermogenesis in mice

Apelin is a bioactive peptide involved in the control of energy metabolism. In the hypothalamus, chronic exposure to high levels of apelin is associated with an increase in hepatic glucose production, and then contributes to the onset of type 2 diabetes. However, the molecular mechanisms behind deleterious effects of chronic apelin in the brain and consequences on energy expenditure and thermogenesis are currently unknown. We aimed to evaluate the effects of chronic intracerebroventricular (icv) infusion of apelin in normal mice on hypothalamic inflammatory gene expression, energy expenditure, thermogenesis and brown adipose tissue functions. We have shown that chronic icv infusion of apelin increases the expression of pro-inflammatory factors in the hypothalamus associated with an increase in plasma interleukin-1 beta. In parallel, mice infused with icv apelin exhibit a significant lower energy expenditure coupled to a decrease in PGC1alpha, PRDM16 and UCP1 expression in brown adipose tissue which could explain the alteration of thermogenesis in these mice. These data provide compelling evidence that central apelin contributes to the development of type 2 diabetes by altering energy expenditure, thermogenesis and fat browning.