Hypercorticism and Manganese Metabolism in Brown Adipose Tissue of the Obese Mouse

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Abstract
In ob/ob mice, we showed previously that brown adipose tissue (BAT) has an abnormally low manganese (Mn) content associated with low Mn-superoxide dismutase (MnSOD) and succinate dehydrogenase (SDH) activities. These anomalies can be corrected partially by supplementing the diet with Mn. The present work was designed to find out whether the hypercorticism of the obese mouse plays a role in this anomalous Mn metabolism in BAT. Mn content and MnSOD and SDH activities were determined in BAT from control and adrenalectomized (ADX) obese mice and from control and corticosterone-supplemented lean mice. Adrenalectomy of the obese mouse restored BAT Mn content, SDH activity and lipid peroxidative activity to normal but had little effect on MnSOD activity. Corticosteroid supplementation in the lean mouse did not reproduce the anomalies of Mn metabolism found in the untreated obese mouse. These results show that hypercorticism alone is not responsible for the anomalies of Mn metabolism. It is possible that the hyperinsulinemia of the obese mouse is involved in this process since adrenalectomy corrected hyperinsulinemia in the obese mouse, but corticosteroid supplementation of the lean mouse did not reproduce the high plasma insulin levels or the anomalies in body composition typical of the untreated obese mouse.