Iron metabolism in genetically obese (ob/ob) mice

Several reports in the clinical literature suggest that obese children may be at risk for developing iron deficiency. Here the absorption, retention, tissue distribution and tissue levels of iron were compared in lean (+/?) and obese (ob/ob) C57BL/6J mice to examine the impact of obesity on the iron status of this animal model. Obese mice absorbed and retained approximately twice as much 59Fe as lean mice after receiving a solution containing 1 mumol iron per os. This difference was independent of age, severity of obesity and mass of the gastrointestinal tract. Obese mice fed ad libitum had higher levels of 59Fe in blood and fat pads, but lower amounts of 59Fe in the skeletal-muscular system, than lean mice 6 d after subcutaneous injection of 1 mumol of the metal. At least 30% of carcass 59Fe was present in the liver of obese and lean mice 6 d after injection. Despite significantly lower concentrations of iron in liver and bone, blood hemoglobin and hematocrit were significantly higher in obese mice fed ad libitum than in lean mice at 10 wk of age. Plasma iron and transferrin were not affected by chronic obesity. Although several characteristics of iron metabolism differed in obese and lean mice, the results indicate that ob/ob mice were not iron deficient when fed a diet containing an adequate level of this micronutrient. The increased absorption of iron by obese mice probably represents an adaptive response that is required to supply additional micronutrient for the expanded blood volume in these animals.