Zinc deficiency changes preferred macronutrient intake in subpopulations of Sprague-Dawley outbred rats and reduces hepatic pyruvate kinase gene expression

Macronutrient selection patterns of male rats were analyzed using a 3-choice macronutrient selection system providing either adequate (+Zn) or deficient (-Zn) levels of zinc (30 or 1 mg Zn/kg), In study 1, rats were provided +Zn and -Zn diets for 28 d. All rats preferred carbohydrate (>50% carbohydrate intake) at the onset, consuming an average of 71% carbohydrate (cho), 17% protein (pro), and 12% fat, By the end of the study, 25% of the -Zn rats switched preference from cho to fat, whereas no +Zn rats changed, In study 2, -Zn rats preferring fat increased their total intake to normal levels, but only 50% reverted to carbohydrate preference after 35 d of zinc repletion, Hypothalamic concentrations of galanin were measured in groups of +Zn and -Zn cho-and fat-preferring rats, Galanin, which may be regulated with fat intake, was not different in -Zn rats preferring fat vs, -Zn rats preferring cho, Galanin concentrations were higher in +Zn than in -Zn rats (P < 0.05) and higher in +Zn rats preferring fat than in +Zn rats preferring cho (P < 0.05), Hepatic pyruvate kinase (PK) mRNA concentrations were related to cho preference, regardless of zinc status. When PK mRNA levels were measured in rats consuming a single AIN-93-based diet, PK mRNA levels were significantly reduced by zinc deficiency (P < 0.05), Because PK is highly regulated by insulin, the effect of insulin may be. reduced by zinc deficiency, making it more difficult for -Zn rats to catabolize dietary cho. This may explain why some -Zn rats switched from preferring cho to fat after developing zinc deficiency.