Tissue zinc and copper levels in diabetic C57BL/KsJ (db/db) mice fed a zinc-deficient diet: lack of evidence for specific depletion of tissue zinc stores.

We investigated whether the decreased femur zinc concentrations reported in genetically obese diabetic db/db C57BL/KsJ mice reflected an increased propensity to zinc deficiency by determining zinc concentrations in tissues from 18-19-wk-old db/db and control mice following ad libitum feeding of a zinc-deficient diet (2 mg/kg) or restricted or ad libitum feeding of a zinc-adequate diet (20 mg/kg) for 12 wk. Although hepatic and renal zinc concentrations of db/db mice fed the zinc-deficient diet tended to be lower than in any other experimental group when expressed on a dry weight basis, zinc concentrations in these tissues were either not different from or greater than those of their nondiabetic controls when expressed on an ash weight basis, i.e., relative to all mineral constituents of these organs. Hepatic and renal copper concentrations of the diabetic db/db mice were either not different from or greater than those of their controls on an ash weight basis. Femur zinc concentrations of diabetic db/db mice fed zinc-adequate diets were lower than those of their controls on a dry weight basis but were not different from their controls on an ash weight basis. We found proportionately lower dry zinc, calcium and magnesium concentrations in femurs of the db/db mice fed a nonpurified diet than in femurs of their db/m and m/m controls. These findings suggest that the low femur zinc concentration reported in the diabetic db/db mouse probably reflects a generalized decrease in bone mineral content rather than a specific depletion of tissue zinc stores.