Fatty Acid 2-Hydroxylase Mediates Diffusional Mobility of Raft-associated Lipids, GLUT4 Level, and Lipogenesis in 3T3-L1 Adipocytes

Lin Guo,Dequan Zhou,Kenneth M Pryse,Adewole L Okunade,Xiong Su

doi:10.1074/jbc.m110.119933

Abstract

Straight chain fatty acid alpha-oxidation increases during differentiation of 3T3-L1 adipocytes, leading to a marked accumulation of odd chain length fatty acyl moieties. Potential roles of this pathway in adipocyte differentiation and lipogenesis are unknown. Mammalian fatty acid 2-hydroxylase (FA2H) was recently identified and suggested to catalyze the initial step of straight chain fatty acid alpha-oxidation. Accordingly, we examined whether FA2H modulates adipocyte differentiation and lipogenesis in mature adipocytes. FA2H level markedly increases during differentiation of 3T3-L1 adipocytes, and small interfering RNAs against FA2H inhibit the differentiation process. In mature adipocytes, depletion of FA2H inhibits basal and insulin-stimulated glucose uptake and lipogenesis, which are partially rescued by the enzymatic product of FA2H, 2-hydroxy palmitic acid. Expression of fatty-acid synthase and SCD1 was decreased in FA2H-depleted cells, and levels of GLUT4 and insulin receptor proteins were reduced. 2-Hydroxy fatty acids are enriched in cellular sphingolipids, which are components of membrane rafts. Accelerated diffusional mobility of raft-associated lipids was shown to enhance degradation of GLUT4 and insulin receptor in adipocytes. Consistent with this, depletion of FA2H appeared to increase raft lipid mobility as it significantly accelerated the rates of fluorescence recovery after photobleaching measurements of lipid rafts labeled with Alexa 488-conjugated cholera toxin subunit B. Moreover, the enhanced recovery rates were partially reversed by treatment with 2-hydroxy palmitic acid. In conclusion, our findings document the novel role of FA2H in adipocyte lipogenesis possibly by modulation of raft fluidity and level of GLUT4.

Highlights

In addition to mitochondrial ␤-oxidation, fatty acids (FA)2 can be oxidized in peroxisomes, where they can undergo ␤
We explored whether increased fatty acid 2-hydroxylase (FA2H) is required for adipocyte differentiation
The fatty acid composition analysis shows the decrease of the percentage of monounsaturated fatty acids in TAG (Fig. 2B), which agrees with the decrease of SCD1 levels by FA2H siRNAs during differentiation (Fig. 1E)

Summary

Introduction

In addition to mitochondrial ␤-oxidation, fatty acids (FA)2 can be oxidized in peroxisomes, where they can undergo ␤-. Expression of fatty-acid synthase and SCD1 was decreased in FA2H-depleted cells, and levels of GLUT4 and insulin receptor proteins were reduced. We evaluated the importance of FA2H in regulating lateral mobility of raft-associated lipids, co-localization of GLUT4 with lysosomes and GLUT4 protein levels.

Results

Conclusion