Effects of zinc deficiency on the fatty acid composition and metabolism in rats fed a fat-free diet

The effects of dietary zinc deficiency (ZD) on the composition and metabolism of the fatty acyl chains of phospholipids in rat liver were investigated with a fat-free diet. The levels of (n−9) fatty acids such as 18∶1 and 20∶3(n−9) in liver phospholipids (PL) were significantly lower in ZD-rats (19.4% and 5.4%, respectively) than in PF-rats (25.2 and 8.3%). On the other hand, the level of (n−6) acids such as 18∶2 and 20∶4 were higher in ZD-rats (3.3 and 19.1%, respectively) than in PF-rats (2.1 and 14.9%). In order to study the metabolism of fatty acids in vivo,¹⁴C-18∶0 or¹⁴C-18∶2 was intravenously injected, and then the conversion to the respective metabolite was examined. After the injection of¹⁴C-18∶0, the radioactivity was found in 18∶0 (49.3% of the total), 18∶1 (33.2%), and 20∶3 (n−9) (9.1%) in liver PL in PF-rats at 24h. In ZD-rats, the radioactivity was dramatically lower in 18∶1 (23.5%) and 20∶ (n−9) (3.6%), suggesting that the conversion of 18∶0 to 18∶1 and 20∶3 (n−9) was strongly inhibited in ZD-rats. When¹⁴C-18∶2 was injected, the radioactivity was mainly found in 18∶2, 20∶3(n−6), and 20∶4. The radioactivity in 20∶4 in ZD-rats was slightly higher than that in control rats. These results indicate that zinc deficiency affects the fatty acid metabolism in liver, in particular, it causes a reduction in δ9 desaturase activity, when rats are fed a fat-free diet.