Prostaglandins, Leukotrienes and Essential Fatty Acids 78 (2008) 73–79 Sex, but not maternal protein or folic acid intake, determines the fatty acid composition of hepatic phospholipids, but not of triacylglycerol, in adult rats G.C. Burdge a, , J.L. Slater-Jefferies b , R.A. Grant a , W.-S. Chung a , A.L. West a , K.A. Lillycrop c , M.A. Hanson b , P.C. Calder a a Institute of Human Nutrition, Institute of Developmental Sciences Building, University of Southampton, Southampton General Hospital, Tremona Road, Southampton SO16 6YD, UK b Centre for the Developmental Origins of Health and Disease, University of Southampton, Southampton SO16 6YD, UK c Development and Cell Biology, University of Southampton, Southampton SO16 7PX, UK Received 12 July 2007; received in revised form 26 October 2007; accepted 31 October 2007 Abstract The aim of the study was to investigate whether the protein and folic acid content of the maternal diet and the sex of the offspring alter the polyunsaturated fatty acid content of hepatic phospholipids and triacylglycerol (TAG). Pregnant rats were fed diets containing 18% or 9% protein with either 1 or 5 mg/kg folic acid. Maternal diet did not alter hepatic lipid composition in the adult offspring. Data from each maternal dietary group were combined and reanalysed. The proportion of 18:0, 20:4n-6 and 22:6n-3 in liver phospholipids was higher in females than in males, while hepatic TAG composition did not differ between sexes. D5 Desaturase expression was higher in females than in males. Neither D5 nor D6 desaturase expression was related to polyunsaturated fatty acid concentrations. These results suggest that sex differences in liver phospholipid fatty acid composition may reflect primary differences in the specificity of phospholipid biosynthesis. r 2007 Elsevier Ltd. All rights reserved. 1. Introduction Polyunsaturated fatty acids (PUFA), in particular arachidonic acid (20:4n-6) and docosahexaenoic acid (22:6n-3), are important structural components of mem- brane phospholipids and are required for normal cell function [1,2]. In the liver, PUFA may also be incorpo- rated into transport pools such as phospholipids and triacylglycerol (TAG), which are destined for secretion into the circulation in very low-density lipoprotein. Thus hepatic lipid metabolism is central to ensuring supply of PUFA to other tissues [3,4]. It is important therefore to understand the processes that determine the concentra- tions of PUFA in hepatic lipid pools. The 18 carbon essential fatty acid (EFA) precursors of 20:4n-6 and 22:6n-3, linoleic acid (18:2n-6) or a-linolenic acid (18:3n-3) are relatively abundant in the diets of humans and laboratory animals, which suggests that conversion of these EFAs to the longer-chain forms may be important for maintaining concentrations of 20:4n-6 and 22:6n-3 in cell membranes. The pathway for this molecular trans- formation involves the activities of D6 and D5 desaturase, elongases and peroxisomal b-oxidation [5]. This process appears to be at best limited in men but is higher in women [6–8]. This may explain higher 22:6n-3 concentra- tion in blood lipids [9,10] in women than in men, which is possibly due to a positive effect of oestrogen [7,11,12]. Plasma and liver phospholipid 20:4n-6 concentrations are higher in female rats than in males, and they can be manipulated by testosterone or oestrogen administration, but are abolished by gonadectomy [13–16]. This may be ARTICLE IN PRESS www.elsevier.com/locate/plefa 0952-3278/$ - see front matter r 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.plefa.2007.10.028 Corresponding author. Tel.: +44 23 80798663; fax: +44 23 80795255. E-mail address: g.c.burdge@soton.ac.uk (G.C. Burdge).