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First published online September 19, 2008
Journal of Experimental Biology 211, 3195-3204 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.019968

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Systematic differences in membrane acyl composition associated with varying body mass in mammals occur in all phospholipid classes: an analysis of kidney and brain

Jessica R. Nealon^1,2, Stephen J. Blanksby³, Todd W. Mitchell^1,2 and Paul L. Else^1,2,*

¹ Metabolic Research Centre, University of Wollongong, Wollongong, New South Wales, Australia 2522
² School of Health Sciences, University of Wollongong, Wollongong, New South Wales, Australia 2522
³ School of Chemistry, University of Wollongong, Wollongong, New South Wales, Australia 2522

^* Author for correspondence (e-mail: pelse{at}uow.edu.au)

Accepted 17 July 2008

The acyl composition of membrane phospholipids in kidney and brain of mammals of different body mass was examined. It was hypothesized that reduction in unsaturation index (number of double bonds per 100 acyl chains) of membrane phospholipids with increasing body mass in mammals would be made-up of similar changes in acyl composition across all phospholipid classes and that phospholipid class distribution would be regulated and similar in the same tissues of the different-sized mammals. The results of this study supported both hypotheses. Differences in membrane phospholipid acyl composition (i.e. decreased omega-3 fats, increased monounsaturated fats and decreased unsaturation index with increasing body size) were not restricted to any specific phospholipid molecule or to any specific phospholipid class but were observed in all phospholipid classes. With increase in body mass of mammals both monounsaturates and use of less unsaturated polyunsaturates increases at the expense of the long-chain highly unsaturated omega-3 and omega-6 polyunsaturates, producing decreases in membrane unsaturation. The distribution of membrane phospholipid classes was essentially the same in the different-sized mammals with phosphatidylcholine (PC) and phosphatidylethanolamine (PE) together constituting 91% and 88% of all phospholipids in kidney and brain, respectively. The lack of sphingomyelin in the mouse tissues and higher levels in larger mammals suggests an increased presence of membrane lipid rafts in larger mammals. The results of this study support the proposal that the physical properties of membranes are likely to be involved in changing metabolic rate.

Key words: fatty acids, lipids, lipid head group, metabolism, mass spectrometry, phospholipids, glycerophospholipids, lipid class, lipid rafts, ESI–MS, basal metabolic rate, lipidomics

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