α-Linolenic acid suppresses cholesterol and triacylglycerol biosynthesis pathway by suppressing SREBP-2, SREBP-1a and-1c expression

alpha-Linolenic acid (ALA), a major fatty acid in flaxseed oil, has multiple functionalities such as anti-cardiovascular and anti-hypertensive activities. In this study, we investigated the effects of ALA on lipid metabolism and studied the possible mechanisms of its action in differentiated 3T3-L1 adipocytes using DNA microarray analysis. From a total of 34,325 genes in the DNA chip, 87 genes were down-regulated and 185 genes were up-regulated at least twofold in differentiated 3T3-L1 adipocyte cells treated with 300 mu M ALA for a week, 5-12 days after induction of cell differentiation, compared to ALA-untreated 3T3-L1 adipocytes (control). From the Reactome analysis results, eight lipid metabolism-related genes involved in cholesterol and triacylglycerol biosynthesis pathway and lipid transport were significantly down-regulated by ALA treatment. Furthermore, ALA significantly decreased the mRNA expressions of sterol regulatory element binding protein (SREBP)-2, SREBP-1a, SREBP-1c and fatty acid synthase (FAS) in 3T3-L1 adipocyte cells. On the other hand, the average levels of the gene expressions of carnitine palmitoyltransferase 1a (CPT-1a) and leptin in 300 mu M ALA treatment were increased by 1.7- and 2.9-fold, respectively, followed by an increase in the intracellular ATP content. These results show that ALA is likely to inhibit cholesterol and fatty acid biosynthesis pathway by suppressing the expression of transcriptional factor SREBPs. Furthermore, ALA promotes fatty acid oxidation in 3T3-L1 adipocytes, thereby increasing its health benefits.