The Impaired Growth Induced by Zinc Deficiency in Rats Is Associated with Decreased Expression of the Hepatic Insulin-like Growth Factor I and Growth Hormone Receptor Genes

Abstract

This study was conducted to determine whether dietary zinc status affects the expression of the insulin-like growth factor I and growth hormone receptor/growth hormone binding protein genes in the liver of growing rats. Weanling male Sprague-Dawley rats were randomly allotted to zinc-deficient, pair-fed or ad libitum-fed dietary treatments and fed diets containing no added zinc for 14 d. Zinc acetate was added to the deionized, distilled water (30 mg/L) provided to pair-fed and ad libitum-fed rats. As expected, zinc deficiency significantly reduced growth rate by 60% and was associated with a significantly lower serum insulin-like growth factor I concentration (46 and 67% lower than pair-fed and ad libitum-fed rats, respectively). The reduction in serum insulin-like growth factor I concentration was associated with a decrease in insulin-like growth factor I gene expression. The abundance of the 7.5-kb insulin-like growth factor I mRNA transcript in zinc-deficient and pair-fed rats was 14 and 31% that of the ad libitum-fed rats. The 0.8-1.2-kb insulin-like growth factor I transcript also was significantly lower in the zinc-deficient and pair-fed rats. In contrast, the abundance of the 1.8-kb insulin-like growth factor I transcript was unaffected by zinc deficiency. The growth hormone receptor mRNA levels of zinc-deficient and pair-fed rats were 17 and 50% and their growth hormone binding protein mRNA levels were 46 and 65% those of the ad libitum-fed rats. In summary, zinc deficiency markedly decreases expression of the insulin-like growth factor I and growth hormone receptor genes.(ABSTRACT TRUNCATED AT 250 WORDS)