Abstract
BackgroundChanging dietary fatty acid composition in modern diet influences the prevalence of obesity. Increasing evidences suggest favorable effects of n-3 PUFA for protecting against obesity and the metabolic syndrome. However, the regulation of n-3 PUFA in adipose is still unclear. Thus, this study addressed metabolism of different dietary fats in the adipose tissue of porcine model.MethodsEight-week-old cross-bred pigs were randomly assigned to three groups and fed a 2% fat diet for 30 days from either soybean oil (SBO), docosahexaenoic acid (DHA) or beef tallow. An in vitro experiment was conducted in which linoleic acid (LA), DHA or oleic acid (OA) were added to represent the major fatty acid in the SBO-, DHA- or BT- diets, respectively. Adipocytes size and lipid metabolism related genes were analyzed.ResultsPlasma triacylglycerol (TAG) was lower in DHA- than in BT-fed pigs, and the product of lipolysis, glycerol was highest in BT-fed pigs. In addition, expression of the lipolytic genes, adipose triglyceride lipase and hormone sensitive lipase was higher in BT-fed pigs and with OA treatment in vitro. DHA promoted protein kinase A activity in pigs without affecting lipolytic genes. Adipocyte cell sizes, TAG content and expression of lipogenic-related genes including, adipose differentiated related protein (ADRP) and diacylglycerol acyltransferase 1 (DGAT1) were elevated by DHA in vivo and in vitro, indicating DHA promoted adipogenesis to trap TAG in adipose tissue. Fatty acid β-oxidation genes were increased in the DHA-fed pigs.ConclusionThis effect was partly explained by the effect of DHA to promote adipogenesis to trap TAG in adipocytes and also increase expression of genes involved in adipocyte fatty acid oxidation. Therefore, our results suggest a direct effect of DHA on adipocyte metabolism, resulting in TAG turnover and fatty acid dissipation to facilitate plasma lipid uptake from the circulation.
Highlights
Changing dietary fatty acid composition in modern diet influences the prevalence of obesity
The current study shows that consumption of docosahexaenoic acid (DHA) as the major fatty acid in the diet resulted in lower plasma TAG and increased expression of lipogenic genes in the Subcutaneous adipose tissues (SCAT)
DHA is known as a Proliferator-activated receptor γ (PPARγ) ligand, it is similar to the TZD family of drugs (PPARγ agonists), and our data confirm the gene expression results of Ranganathan et al [60]
Summary
Changing dietary fatty acid composition in modern diet influences the prevalence of obesity. Dietary fatty acid (FA) composition is an important factor in weight control because the intake of saturated fatty acids is linked to increased risk for obesity [2,3,4]. Dietary polyunsaturated fatty acids (PUFA) suppress the metabolic syndrome phenotype by lowering plasma triacylglycerols (TAGs). The serum TAG lowering by the n-3 series of fatty acids is demonstrated in obese children compared to age-matched lean controls [9]. Diets with a lower ratio of n-3 to n-6 fatty acids may lead to the pathology of metabolic syndrome in children [11], and consumption of a low dose of n-3 PUFA (1 g of n-3 PUFA/day) is associated with a reduction in plasma TAG in humans [12]. The benefits of n-3 PUFA have been well documented, the underlying mechanisms involving adipocytes have not been clearly elucidated
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