AQP7 and obesity due to melanocortin 4 receptor deficiency: In vitro experiments have confirmed that Apelin-13 significantly upregulates the expression of AQP7 in palmitic acid-treated hypertrophic adipocytes and reduces the accumulation of triglycerides in the cytoplasm, which could be reversed using the PI3K inhibitor LY294002 (61), suggesting that Apelin-13 might suppress lipid storage in hypertrophic adipocytes and thereby reduce obesity by upregulating AQP7 expression via the PI3K signaling pathway.