Influence of genetic obesity on tissue concentrations of zinc, copper, manganese and iron in mice.

The concentrations (micrograms/gram dry wt) of four essential trace metals in various tissues from C57BL/6J lean (+/?) and obese (ob/ob) mice were determined. Lower concentrations of zinc were found in liver, femur, small intestine and muscle from obese mice than in those from lean mice at 22 wk of age. The concentrations of copper in liver, femur, small intestine, muscle and testes, iron in liver, femur, muscle and plasma, and manganese in liver, femur and small intestine from adult obese mice were also significantly below the concentrations present in tissues from age-matched lean mice. Hepatic concentrations of zinc, copper and manganese in obese mice were also lower than those in lean mice when the different amounts of neutral lipid in obese and lean liver were considered. In contrast with the trend towards lower concentrations of trace metals in tissues from adult obese mice, plasma zinc and copper levels and ceruloplasmin activity were higher in adult obese mice than in lean controls. The effect of genetic obesity on tissue trace metals concentrations was similar in male and female mice. Several tissues from young (5-6 wk of age) obese mice also had lower concentrations of the trace metals than age-matched lean mice, although the differences were not as great as in adults. These data demonstrate that chronic obesity in the genetically obese (ob/ob) mouse is associated with lower concentrations, but not necessarily lower total quantities, of several inorganic micronutrients in tissues. The possibility tht chronic obesity alters the nutritional requirements for these trace metals is discussed.