GPAT3 deficiency alleviates insulin resistance and hepatic steatosis in a mouse model of severe congenital generalized lipodystrophy

Berardinelli-Seip congenital lipodystrophy type 2 (BSCL2) is the most severe form of human lipodystrophy and is caused by loss-of-function mutations in the BSCL2/seipin gene. Exactly how seipin may regulate adipogenesis remains unclear. A recent study in vitro suggested that seipin may function to inhibit the activity of glycerol-3-phosphate acyltransferases (GPATs), and increased GPAT activity may be responsible for the defective adipogenesis under seipin deficiency. Here we generated Seipin(-/-)Gpat3(-/-) mice, which had mild but significant recovery of white adipose tissue mass over Seipin(-/-) mice. The mass of brown adipose tissue (BAT) of the Seipin(-/-)Gpat3(-/-) mice was almost completely restored to normal level. Importantly, the Seipin(-/-)Gpat3(-/-) mice showed significant improvement in liver steatosis and insulin sensitivity over Seipin(-/-) mice, which is attributable to the increased BAT mass and to the enhanced browning of the subcutaneous fat of the Seipin(-/-)Gpat3(-/-) mice. Together, our results establish a functional link between seipin and GPAT3 in vivo and suggest that GPAT inhibitors may have beneficial effects on BSCL2 patients.