Hindawi Publishing Corporation Journal of Nutrition and Metabolism Volume 2010, Article ID 927836, 9 pages doi:10.1155/2010/927836 Research Article Opposing Effects of Omega-3 and Omega-6 Long Chain Polyunsaturated Fatty Acids on the Expression of Lipogenic Genes in Omental and Retroperitoneal Adipose Depots in the Rat B. S. Muhlhausler, 1, 2 R. Cook-Johnson, 3 M. James, 3 D. Miljkovic, 1, 2 E. Duthoit, 2 and R. Gibson 2 1 FOODplus Research Centre, School of Agriculture, Food and Wine, The University of Adelaide, Adelaide 5064, Australia 2 Division of Health Sciences, Sansom Institute for Health Research, University of South Australia, Adelaide SA 5001, Australia 3 Rheumatology Unit, School of Medicine, The University of Adelaide, Adelaide SA 5005, Australia Correspondence should be addressed to B. S. Muhlhausler, beverly.muhlhausler@adelaide.edu.au Received 10 November 2009; Revised 25 May 2010; Accepted 23 June 2010 Academic Editor: Michael M. M¨ uller Copyright © 2010 B. S. Muhlhausler et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This study aimed to determine the effect of varying dietary intake of the major n-3 PUFA in human diets, α-linolenic acid (ALA; 18 : 3n-3), on expression of lipogenic genes in adipose tissue. Rats were fed diets containing from 0.095%en to 6.3%en ALA and a constant n-6 PUFA level for 3 weeks. Samples from distinct adipose depots (omental and retroperitoneal) were collected and mRNA expression of the pro-lipogenic transcription factors Sterol-Retinoid-Element-Binding-Protein1c (SREBP1c) and Peroxisome Proliferator Activated Receptor-γ (PPARγ), lipogenic enzymes Sterol-coenzyme Desaturase1 (SCD-1), Fatty Acid Synthase (FAS), lipoprotein lipase (LPL) and glycerol-3-phosphate dehydrogenase (G3PDH) and adipokines leptin and adiponectin determined by qRT-PCR. Increasing dietary ALA content resulted in altered expression of SREBP1c, FAS and G3PDH mRNA in both adipose depots. SREBP1c mRNA expression was related directly to n-6 PUFA concentrations (omental, r 2 = .71; P<.001; Retroperitoneal, r 2 = .20; P<.002), and inversely to n-3 PUFA concentrations (omental, r 2 = .59; P<.001; Retroperitoneal, r 2 = .19; P<.005) independent of diet. The relationship between total n-6 PUFA and SREBP1c mRNA expression persisted when the effects of n-3 PUFA were controlled for. Altering red blood cell concentrations of n-3 PUFA is thus associated with altered expression of lipogenic genes in a depot-specific manner and this effect is modulated by prevailing n-6 PUFA concentrations. 1. Introduction In adults, changes in the patterns of expression of key regulatory and functional genes within adipose tissue are important determinants of fat accumulation and can pro- foundly influence the ability of an individual to maintain energy balance and resist weight gain [1–4]. The transcrip- tion factors Sterol Retinoid Binding Protein-1c (SREBP1c) and Peroxisome Proliferator Activated Receptor-γ (PPARγ) regulate lipid storage and adipose tissue mass by regulating the expression of genes in the lipogenic pathway. Specifically, activation of SREBP1c and PPARγ increases the expression of a series of enzymes which increase the synthesis and storage of triglycerides in adipose tissue, including lipoprotein lipase (LPL), which increases uptake of fatty acids from the circulation, and Fatty Acid Synthase (FAS) and glycerol-3- phosphate dehydrogenase (G3PDH), which both promote triglyceride synthesis [5]. While the cause of the current global obesity epidemic includes excessive food consumption and reduced exercise, there is increasing evidence that both the quantity and the type of fats in the diet have a major role in defining the propensity of an individual to accumulate excess body fat. It is acknowledged that diets high in saturated fat (>45%) promote fat accumulation [6], and low-fat diets are commonly recommended as a means of weight-loss