Parenteral Linoleic and γ-Linolenic Acids Ameliorate the Gross Effects of Zinc Deficiency

Abstract

Zinc deficiency and essential fatty acid deficiency in rats have gross effects which are very similar. Zinc, prostaglandin E₁, and dihomo-γ-linolenic acid (prostaglandin E₁ precursor) all have very similar effects on rat vascular smooth muscle. Zinc deficiency has no consistent effect on tissue zinc or zinc enzymes. These observations suggest that the mechanism by which zinc deficiency affects growth and metabolism may be via inhibition of prostaglandin synthesis from essential fatty acids. This hypothesis was examined using zinc deficient rats supplemented with oils containing various concentrations of essential fatty acids. Male Wistar rats were maintained on a zinc deficient diet for 5 weeks and supplemented daily with one of three oils containing different concentrations of essential fatty acids: olive oil (mainly oleic acid), safflower oil (mainly linoleic acid), or evening primrose oil (mainly linoleic and γ-linolenic acids). The olive oil treated rats did not benefit from this treatment in any respect. Dermal lesions were actually worse in this group than in the untreated zinc deficient rats. Safflower oil supplementation significantly inhibited the development of dermal lesions but was of only marginal benefit with respect to growth. Evening primrose oil supplementation also blocked the development of dermal lesions and restored growth to 50% of control. It is suggested that a primary defect of zinc deficiency is to inhibit essential fatty acid metabolism to prostaglandins either by blocking linoleic acid desaturation to γ-linolenic acid or by inhibiting mobilization of dihomo-γ-linolenic acid from tissue membrane stores.