Oxidative stress in mice is dependent on the free glucose content of the diet

In animals, chronic intake of diets with high proportions of rapidly absorbable glucose promotes the development of insulin resistance. High levels of glucose can produce permanent chemical alterations in proteins and lipid peroxidation. delta-Aminolevulinate dehydratase (delta-ALA-D) is a sulfhydryl-containing enzyme essential for all aerobic organisms and is highly sensitive to the presence of pro-oxidants elements. The heme synthetic pathway is impaired in porphyria and a frequent coexistence of diabetes mellitus and porphyria disease has been reported in humans and experimental animal models, which can be casually linked to the delta-ALA-D inhibition found in diabetics. The present study was designed to evaluate the effect of two different diets, a high glucose (HG) diet and a high starch (HS) diet, on lipid peroxidation levels in different tissues (brain, liver, and kidney) and on delta-ALA-D activity (from liver and kidney) in mice. Plasma glucose and triglyceride levels were significantly higher in mice fed HG than in mice fed HS (P < 0.02 and P < 0.03, respectively). Thiobarbituric acid reactive species (TBA-RS) content was significantly increased in kidney and liver from HG diet-fed mice when compared with animals fed HS diets (P < 0.001). Hepatic delta-ALA-D activity of HG diet-fed animals was significantly lower than that of HS diet-fed animals (P < 0.01). The results of this study support the hypothesis that consumption of a diet with high free glucose can promote the development of oxidative stress that we tentatively attribute to hyperglycemia.