Induction of Delta 9-fatty acyl desaturation in rainbow trout (Oncorhynchus mykiss) liver by dietary manipulation

Abstract

Hepatic stearoyl Δ9-fatty acyl desaturation was demonstrated to be modulated in trout by dietary manipulation. Desaturation was very low in hepatocytes isolated from the livers of starved fish with only 2% of [1-14c]18:0 converted to Δ9-desaturase products (18:1n-9 and 20:1n-9). After 6 weeks of feeding a commercial (fish oil-containing) pelleted trout diet, 50% of the radioactivity from [1-14c]18:0 was converted to Δ9-desaturase products. Another period of starvation, after the 6-week feeding period, reduced Δ9-desaturation with only 4–5% of radioactivity from [1-14c]18:0 being converted to Δ9-desaturase products in hepatocytes. Subsequent refeeding produced a much more rapid induction of Δ9-desaturation with the activity significantly increased after only 3 days refeeding and the activity restored to the level before starvation after only 1 week of refeeding. The fatty acid composition of the diet appeared to be less important to the induction of hepatic Δ9-desaturation than the overall nutritional status because Δ9-desaturation in livers of fish fed a high saturated fatty acid diet, comprising 96% palmitic acid (16:0), was similar to that of fish fed a fish oil-containing diet.