Selective reduction of Δ6 and Δ5 desaturase activities but not Δ9 desaturase in micropigs chronically fed ethanol

This study investigated the mechanism by which chronic ethanol feeding reduces arachidonate and other highly unsaturated fatty acids in pig liver phospholipids. Five micropigs were fed a diet providing 89 kcal/kg body wt for 12 mo, with ethanol and fat as 40 and 34% of energy, respectively. Five control pigs were pairfed corn starch instead of ethanol. The activities of Δ6 and Δ5 desaturases (expressed as microsomal conversion of precursor to product) in liver from ethanol-fed pigs were reduced to less than half that of controls, whereas the activity of Δ9 desaturase was unaffected in the ethanol group. Δ5 Desaturase activity showed positive correlation with the abundance of its products in liver total phospholipids and microsomes in the ethanol group, but not in the controls. Correlation between Δ6 desaturase activity and its products showed similar pattern to that of Δ5 desaturase, but did not reach statistical significance. No difference was observed between the two groups in coenzyme A concentration in the liver. These results suggest that the selective reduction of Δ6 and Δ5 desaturase activities, not the microsomal electron transport system, are directly responsible for the altered profile of liver phospholipids.