Molecular Stability of Brain Plasmalogens in a Fat Free Diet

Jasna Dovhanj¹, Ivančica Delaš², Fritz Paltauf³ and Milivoj Popović²*

¹School of Medicine, University »Josip Juraj Strossmayer«, Osijek, Department of Chemistry and Biochemistry, Huttlerova 4, HR – 31 000 Osijek, Croatia
²School of Medicine, University of Zagreb, Department of Chemistry and Biochemistry, Šalata 3, HR – 10 000 Zagreb, Croatia
³Institut für Biochemie und Lebensmittelchemie der Technischen Universität, Petersgasse 12, A-8010 Graz, Austria

Article history:
Received February 24, 2000
Accepted May 17, 2000

Key words:
fat-free diet, plasmalogens, brain, rat

Summary:
Fat free diet (FFD) affects specifically structures of particular lipid molecules. The effect of short-term (two-week) diet on rat brain plasmalogens is reported in this paper. Two groups of eight animals (Wistar strain, average body weight 180 g) were on two different diets: the control diet (CD) was actually a standard rat chaw, while the fat free diet (FFD) was prepared in our own laboratory. Both diets were isoenergetic (CD 15.74 kJ; FFD 15.10 kJ). The average body weight gain was 4 %. For CD the mass of brain was 692.7 and for FFD 891.3 mg. Total phosphate/protein ratio (TP/P) of the brain tissue was 48.7/100 in CD and 33.2/100 in FFD, indicating the inhibited biosynthesis of phospholipids. The majority of plasmalogens in brain is associated with the phosphatidylethanolamine (PE) lipids. Plasmenyl-phosphatydilethanolamine (Pla-PE) comprised 58.3 % in CD and 59.7 % in FFD of total PE. Following effects of FFD on Pla-PE fatty acid composition were noticed: (i) increased content of palmitoleic acid (+3.45 %), (ii) increased content of stearic (+8.22 %) with decreased content of oleic acid (–6.02 %), (iii) decreased content of essential fatty acids (–12.55 %) and (iv) decreased content of polyunsaturated fatty acids followed by a simultaneous increase of eicosatrienoic acid content (+6.21 %) and a decrease of docosahexaenoic acid content (–8.47 %). The overall effect of FFD caused a moderate saturation of Pla-PE fatty acids (F_u/–7.39). The analysis of the aldehydogenic moiety of the Pla-PE resulted in: (i) no essential changes in the amount of total aldehydes of the PE lipids (CD 58.3 %, FFD 59.7 %); (ii) the alkenyl chain was composed of C 16, C 18 and C 20 homologues, while C 18 and C 20 homologues comprised almost 70 % of total aldehydes, (iii) no essential changes neither of the total amount of C 18 homologue (CD 59.4 %, FFD 64.1 %), nor of the ratio of cis-trans C 18 isomers were found, and finally (iv) the amount of C 20 homologue remained almost unchanged (CD 4.05 %, FFD 4.23 %). All of the represented data indicate very slight modulations of the Pla-PE molecule affected by a FFD and support the already recognized idea that plasmalogens are one of the most important stabilizers of the structure of biological membranes.

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