Marginal thiamine deficiency increases oxidative markers in the plasma and selected tissues in F344 rats

A moderate thiamine deficiency that does not affect weight gain or produce the classical signs of thiamine deficiency may have adverse health effects. We assessed the effect of marginally thiamine-deficient diets by measuring the effects of the diets on an enzyme marker for thiamine adequacy and markers for plasma and tissue exposure to potential endogenous carbonyl toxins. Five groups of male F344 rats were fed an AIN76-based diet containing thiamine at 2, 2.9, 5.2, 11, or 18 mg/kg diet. The animals were killed at 70 days by carbon dioxide inhalation, and cardiac blood, liver, colon, and brain samples were obtained. Erythrocytes were analyzed for transketolase activity; plasma for glyoxal, methylglyoxal, hydroimidazolone, nitrotyrosine, and protein carbonyl adducts; and tissue extracts for the 3 protein adducts. Thiamine pyrophosphate–dependent transketolase activity was inversely correlated with dietary thiamine of less than 5.2 mg/kg diet. Plasma methylglyoxal and protein adduct concentrations also increased significantly at dietary thiamine levels or at thiamine level of less than 2.6 mg/kg diet. The brain, liver, and colon showed similar trends, with evident tissue specificity. Diets marginally deficient in thiamine increase the endogenous formation of carbonyl products at thiamine levels only slightly below the requirement levels, 4 mg/kg diet (0.25 mg/kJ diet).