Effect of experimental diabetes on the fatty acid composition, molecular species of phosphatidyl-choline and physical properties of hepatic microsomal membranes

Streptozotocin diabetes depresses Delta9, Delta6 and Delta5 fatty acid desaturases, decreasing arachidonic acid and increasing linoleic acid, but also unexpectedly increasing docosahexaenoic acid in the different phospholipids of liver microsomal lipids. 18.0/20:4n-6,16:0/20.4n-6 and 16:0/18:2n-6 are the predominant phosphatidyl choline (PC) molecular species in control rats, determining mainly PC contribution to the dynamic and biochemical properties of this bilayer. Diabetes decreases 20.4n-6 containing species and increases 18:2n-6 and 22:6n-3 containing species, maintaining the bulk dynamic properties in the hydrophobic interior of the bilayer, but changing its biochemical properties. The different dynamic parameters were measured by fluorometry using the probes 1,6-diphenyl-1,3,5-hexatriene (DPH), (4-trimethylammonium phenyl) 6-phenyl-1,3,5 (TMA-DPH) and 6-lauroyl-2,4-dimethyl aminonaphtalene (Laurdan). In the surrounding of the hydrophobic/hydrophilic interphase lipid molecules were less ordered and tightly packed in the diabetic samples, allowing a higher mobility of incorporated water molecules. The fact that diabetes decreases highly polyunsaturated acid of n-6 family but increases docosahexaenoic acid, indicates the necessity of re-evaluating its effect in human physiology. (C) 2000 Harcourt Publishers Ltd.