Lipids in Health and Disease

Background: The heart is rich in cardiolipin, a phospholipid acylated in four sites, predominately with linoleic acid. Whether or not aging alters the composition of cardiolipin acyl chains is controversial. We therefore measured the fatty acid concentration of cardiolipin in hearts of 4, 12 and 24 month old rats that consumed one diet, adequate in fatty acids for the duration of their life. Results: The concentration (nmol/g) of linoleic acid was decreased in 24 month old rats (3965 ± 617, mean ± SD) vs 4 month old rats (5525 ± 656), while the concentrations of arachidonic and docosahexaenoic acid were increased in 24 month old rats (79 ± 9 vs 178 ± 27 and 104 ± 16 vs 307 ± 68 for arachidonic and docosahexaenoic acids, 4 months vs 24 months, respectively). Similar changes were not observed in ethanolamine glycerophospholipids or plasma unesterified fatty acids, suggesting specificity of these effects to cardiolipin. Conclusion: These results demonstrate that cardiolipin remodeling occurs with aging, specifically an increase in highly unsaturated fatty acids. Background Cardiolipin (1'[1,2-diacyl-sn-glycero-3-phosphoryl]-3'[1",2"-diacyl-sn-glycero-3"-phosphoryl]-sn-glycerol; 1,3diphosphatidylglycerol) is a phospholipid found in particularly high concentrations in the heart. In mammalian cells, it is localized to the inner mitochondrial membrane [1] and is known for its unique and specific acyl structure. Cardiolipin, unlike other mammalian phospholipids, contains 4 stereospecifically numbered acyl groups. Heart cardiolipin is predominately acylated with linoleic acid [2]. The acyl specificity of cardiolipin is believed to occur via remodeling, as the enzymes responsible for its de novo synthesis are not acyl group specific [3,4]. Despite being discovered a relatively long time ago [5], fairly little is known about the function of cardiolipin, especially in mammalian cells. Several excellent reviews have summarized the known biochemistry and functions of cardiolipin which is thought to regulate several mitochondrial proteins [6-9]. It also is known that cardiolipin acyl chains vary greatly by species [10-13] and tissue, and can be modified by diet [14-17]. However, the functional significance of these changes is not known. It is controversial whether the acyl-chain composition of cardiolipin is altered with ageing. Several studies have reported that heart and liver total cardiolipin decreases with age [1820]. However, studies measuring the fatty acid composition (percent composition) of cardiolipin isolated from aged rat hearts has led to controversial findings, with one study [19] reporting no change in the acyl percent composition and another decreased linoleic and increased arachidonic acid percent compositions [20]. Published: 23 January 2006 Lipids in Health and Disease 2006, 5:2 doi:10.1186/1476-511X-5-2 Received: 30 November 2005 Accepted: 23 January 2006 This article is available from: http://www.lipidworld. com/content/5/1/2 © 2006 Lee et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.