Adaptations of the 3T3-L1 adipocyte lipidome to defective ether lipid catabolism upon alkylglycerol monooxygenase knockdown

Abstract

Little is known about the physiological role of alkylglycerol monooxygenase (AGMO), the only enzyme capable of cleaving the 1-O-alkyl ether bond of ether lipids. Expression and enzymatic activity of this enzyme can be detected in a variety of tissues including adipose tissue. This labile lipolytic membrane-bound protein uses tetrahydrobiopterin as a cofactor and mice with reduced tetrahydrobiopterin levels have alterations in body fat distribution and blood lipid concentrations. In addition, manipulation of AGMO in macrophages led to significant changes in the cellular lipidome, and alkylglycerolipids, the preferred substrates of AGMO, were shown to accumulate in mature adipocytes. Here, we investigated the roles of AGMO in lipid metabolism by studying 3T3-L1 adipogenesis. AGMO activity was induced over 11 days using an adipocyte differentiation protocol. We show that RNA interference-mediated knockdown of AGMO did not interfere with adipocyte differentiation or affect lipid droplet formation. Furthermore, lipidomics revealed that plasmalogen phospholipids were preferentially accumulated upon Agmo knockdown and a significant shift towards longer and more polyunsaturated acyl side chains of di- and triacylglycerols could be detected by mass spectrometry. Our results indicate that alkylglycerol catabolism has an influence not only on ether-linked species, but also on the degree of unsaturation in the massive amounts of triacylglycerols formed during in vitro 3T3-L1 adipocyte differentiation.