Manganese status, gut endogenous losses of manganese, and antioxidant enzyme activity in rats fed varying levels of manganese and fat

Abstract

We hypothesized that manganese deficient animals fed high vs moderate levels of polyunsaturated fat would either manifest evidence of increased oxidative stress or would experience compensatory changes in antioxidant enzymes and/or shifts in manganese utilization that result in decreased endogenous gut manganese losses. Rats (females in Study 1, males in Study 2,n = 8/treatment) were fed diets that contained 5 or 20% corn oil by weight and either 0.01 or 1.5 μmol manganese/g diet. In study 2,⁵⁴Mn complexed to albumin was injected into the portal vein to assess gut endogenous losses of manganese. The manganese deficient rats:

• 1. Had 30–50% lower liver, tibia, kidney, spleen, and pancreas manganese concentrations than manganese adequate rats;

• 2. Conserved manganese through ≈70-fold reductions in endogenous fecal losses of manganese;

• 3. Had lower heart manganese superoxide dismutase (MnSOD) activity; and

• 4. Experienced only two minor compensatory changes in the activity of copper-zinc superoxide dismutase (CuZnSOD) and catalase.

Gut endogenous losses of manganese tended to account for a smaller proportion of absorbed manganese in rats fed high-fat diets; otherwise fat intake had few effects on tissue manganese concentrations.