Renato J. Ferretti

The severity of copper deficiency in rats is determined by the type of dietary carbohydrate.

Abstract The purpose of this investigation was to study the interaction between copper and dietary carbohydrates on clinical and enzymatic indices associated with copper deficiency. Copper deficiency was produced in rats by feeding diets adequate in all nutrients including selenium and chromium, but marginal in copper (1.2 μg/g diet) containing 62% of either starch, fructose, or glucose. During the fifth week, the fructose of the copper-deficient diet (20 rats) was replaced by either starch (10 rats) or by glucose (10 rats). The experiment was terminated after 11 weeks. Copper deficiency in rats fed fructose significantly lowered body weight and hematocrit, but increased liver weight, blood urea nitrogen, ammonia, cholesterol, and triglycerides when compared to rats fed starch or glucose. The copper metalloenzyme, superoxide dismutase, the selenoenzyme, glutathione peroxidase, and hepatic ATP were decreased in the copper-deficient rats fed fructose as compared to copper-deficient rats fed starch or glucose. These results indicate that fructose may be the dietary component which has a deleterious effect on copper and selenium status. Changing the type of dietary carbohydrate in copper-deficient rats from fructose to either starch or glucose ameliorated the severity of the deficiency. The protective effects were more pronounced with starch than with glucose.

Interaction between dietary carbohydrate and copper nutriture on lipid peroxidation in rat tissues.

The effects of the interactions between dietary carbohydrates and copper deficiency on superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities and their roles in peroxidative pathways were investigated. Weanling rats were fed diets deficient in copper and containing either 62% starch, fructose, or glucose. Decreased activity of SOD was noted in all rats fed the copper-deficient diets regardless of the nature of dietary carbohydrate. However, the decreased activity was more pronouced in rats fed fructose. Feeding the fructose diets decreased the activity of GSH-Px by 25 and 50% in the copper-supplemented and copper-deficient rats, respectively, compared to enzyme activities in rats fed similar diets containing either starch or glucose. The decreased SOD and GSH-Px activities in rats fed the fructose diet deficient in copper were associated with increased tissue per-oxidation and decreased hepatic adenosine triphosphate (ATP). When the fructose in the diet of copper-deficient rats was replaced with either starch or glucose, tissue SOD and GSH-Px activities were increased and these increases in enzyme activity were associated with a tendency toward reduced mitochondrial peroxidation when compared to the corre-sponding values for rats fed fructose throughout the experiment Dietary fructose aggrevated the symptoms associated with copper deficiency, but starch or glucose ameliorated them. The protective effects were more pronounced with starch than with glucose.

Effects of different dietary carbohydrates on hepatic enzymes of copper-deficient rats.

Abstract The present study was undertaken to measure the activities of several hepatic enzymes of regulatory importance in the pathways of lipogenesis and gluconeogenesis in rats fed diets marginally deficient in copper (1.2 μg Cu/g of diet) and containing either fructose, glucose, or starch as the carbohydrate sources. Although all copper-deficient rats exhibited the characteristic signs of copper deficiency, they were more pronounced in rats fed the diet containing fructose. Except for the activity of phosphoenolpyruvate carboxykinase which was unaffected either by copper deficiency or by the type of dietary carbohydrate, the hepatic activities of glucose-6-phosphate dehydrogenase, malic enzyme, L-α-glycerophosphate dehydrogenase and fructose 1,6-diphosphatase were unaffected by copper deficiency but were affected by the type of carbohydrate in the diet. Fructose produced the greatest increase in enzymatic activities, whereas starch produced the least activity and glucose induced an intermediate effect. These results indicate that the deleterious effects of a fructose diet deficient in copper on biochemical and physiological indices could not be due to an immediate metabolite of fructose. However, the involvement of a subsequent metabolite of fructose in the mechanism of copper utilization and/or requirement cannot be excluded.