Changes in the Fatty Acid Composition of Brain and Liver Phospholipids from Rats Fed Fat-Free Diet

Ivančica Delaš¹*, Milivoj Popović¹, Tomislav Petrović¹, Frane Delaš² and Davor Ivanković<sup>1

1</sup>School of Medicine, [alata 3, HR-10 000 Zagreb, Croatia
²Faculty of Food Technology and Biotechnology, Pierottijeva 6, HR-10 000 Zagreb, Croatia

Article history:
Received July 23, 2007
Accepted December 4, 2007

Key words:
fat-free diet, phospholipids, liver, brain, rat, phospholipase A₂

Summary:
This study has been undertaken with the aim of elucidating the effect of a fat-free diet (FFD), which is known to be deficient in essential fatty acids (EFA), on the composition of fatty acids in the brain and liver glycerophospholipids of rats. Changes in the stereochemical distribution of fatty acids linked to the sn-1 or sn-2 position were of special interest. Two groups of animals were fed either the control diet (CD) or the FFD for two weeks. From the total lipid extracts of the brain and liver tissues, phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol+phosphatidylserine (PI+PS) fractions were separated by column and thin layer chromatography (TLC). After digestion with phospholipase A₂ (PLA₂), fatty acids from the sn-1 and sn-2 positions were separately converted into methyl esters and analyzed by gas chromatography. In animals fed FFD, the relative levels of unsaturated fatty acids increased in the sn-1 position of the PI+PS fraction in both liver and brain tissues, as well as in the PE fraction from the brain tissue. In other fractions no statistically significant differences were found. When the levels of particular fatty acids were evaluated, significant decreases in the amounts of palmitic (PA, 16:0), stearic (SA, 18:0), and nervonic (NA, 24:1n-9) acids, and/or significant increases of eicosenoic (ENA, 20:1n-9), arachidonic (AA, 20:4n-6) and docosahexaenoic (DHA, 22:6n-3) acids were detected in some fractions. It can be concluded that in the brain and liver glycerophospholipids of rats fed FFD, the EFAs lacking in the diet were moderately substituted by endogenously synthesized unsaturated fatty acids.

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