Metabolic and Behavioral Effects of Zinc Deficiency in Rats

Disruptions in the regulation of food intake and metabolism can result in obesity or anorexia. It is clear that zinc deficiency results in anorexia and previous research suggests the existence of alterations in energy efficiency and metabolism. Zinc deficiency results in changes in neuropeptides that regulate energy intake and expenditure. Numerous diagnostic conditions also result in anorexia and wasting, similar to that of zinc deficiency. However, the mechanism underlying these abnormalities remains unknown, and the behavioral and metabolic effects of zinc deficiency have not been fully established. Therefore, the purpose of this work is to fully characterize the behavioral and metabolic consequences of zinc deficiency and its association with anxiety, and to suggest mechanisms underlying the anorexia associated with zinc deficiency and other clinical conditions. Despite differences in locomotor activity between zinc deficient(ZD, zinc, ad lib) and pair-fed (PF, 28 ppm zinc, amount consumed by ZD), there were no differences in MR, RQ or BMR. This suggests a greater metabolic cost of activity may exist in ZD. Contrary to previous studies, this work shows a decrease in consummatory food intake with zinc deficiency without evidence of alterations in appetitive motivational behaviors. This suggests that zinc deficiency alters the hedonic impact of food reward, but not the motivation to seek food. The data presented here also suggests an anxiogenic effect associated with zinc deficiency, which may be involved in the hedonic changes in food intake. Furthermore, this work suggests that alterations of the opioid reward system may be involved in the anorexia and anxiety-like behaviors produced by zinc deficiency.