Amelioration of effects of severe dietary copper deficiency by food restriction in rats

Copper deficiency: A potential model for determining the role of mitochondria in cardiac aging

Heart mitochondria experience age-related declines in cytochrome c oxidase (CCO) activity and increases in the generation of reactive oxygen species (ROS) that may contribute to loss of cardiac function and the development of disease that occur with advancing age. In a manner similar to aging, copper deficiency also suppresses heart CCO activity and has cardiovascular consequences related to increased peroxidation. Food restriction is often used as a tool to study oxidative mechanisms of aging and the present study examines the potential of copper deficiency to model the role of mitochondria in cardiac aging by determining if the effect of food restriction on CCO activity and oxidative stress in heart mitochondria parallels its effect on cardiac mitochondria during aging. Overall, copper deficiency severely inhibited CCO activity and increased both Mn superoxide dismutase (MnSOD) and glutathione peroxidase (GPX) in isolated heart mitochondria. However, a 20% reduction in food intake by copper-deficient rats increased CCO activity by 65% and decreased MnSOD activity by 25% but had no effect in rats fed adequate copper. Copper deficiency also reduced the carbonyl content of 80-100 kDa mitochondrial proteins, but the reduction in carbonyl content was unaffected by food restriction. Food restriction did, however, completely prevent the enlargement of cardiac mitochondria in copper-deficient rats. Together, these findings indicate that copper deficiency induces mitochondrial antioxidant enzyme activity and hypertrophy in cardiac tissue in response to reduced CCO activity and that food restriction may counteract these changes by reducing oxidative stress. Because the action of food restriction on CCO activity and mitochondrially generated oxidative stress are similar in copper deficiency and aging, copper deficiency may serve as a short-term model for studying the potential roles of mitochondria in cardiac aging.

Marginal zinc deficiency increases magnesium retention and impairs calcium utilization in rats

An experiment with rats was conducted to determine whether magnesium retention is increased and calcium utilization is altered by a marginal zinc deficiency and whether increased oxidative stress induced by a marginal copper deficiency exacerbated responses to a marginal zinc deficiency. Weanling rats were assigned to six groups of ten with dietary treatment variables of low zinc (5 mg/kg for 2 weeks and 8 mg/kg for 7 weeks), low copper (1.5 mg/kg), adequate zinc (15 mg/kg), and adequate copper (6 mg/kg). Two groups of rats were fed the adequate-zinc diet with low or adequate copper and pair-fed with corresponding rats fed the low-zinc diet. When compared to the pair-fed rats, marginal zinc deficiency significantly decreased the urinary excretion of magnesium and calcium, increased the concentrations of magnesium and calcium in the tibia, increased the concentration of magnesium in the kidney, and increased the urinary excretion of helical peptide (bone breakdown product). Marginal copper deficiency decreased extracellular superoxide dismutase and glutathione, which suggests increased oxidative stress. None of the variables responding to the marginal zinc deficiency were significantly altered by the marginal copper deficiency. The findings in the present experiment suggest that increased magnesium retention and impaired calcium utilization are indicators of marginal zinc deficiency.

The influence of ration size on copper homeostasis during sublethal dietary copper exposure in juvenile rainbow trout, Oncorhynchus mykiss

The influence of ration size on homeostasis and sublethal toxicity of copper (Cu) was assessed in rainbow trout (Oncorhynchus mykiss) during dietary Cu exposure in synthetic soft water. A constant dietary dose of 0.24 micromol Cu per g fish per day as CuSO(4).5H(2)O was delivered via diets containing 15.75, 7.87, and 5.24 micromol Cu g(-1) fed at 1.5, 3.0, and 4.5% wet body weight daily ration, respectively. Juvenile rainbow trout showed clear effects of ration but not Cu on growth suggesting that growth is hardly a sensitive endpoint for detection of sublethal dietary Cu exposure. All Cu-exposed fish accumulated the same total metal load when expressed on a per fish basis. This suggests that differences in tissue and whole-body Cu concentrations among the treatments reflected the differences in the fish size rather than total Cu accumulation, and demonstrate that absorption and accumulation of Cu from the gut during dietary exposure are independent of the food quantity in which the Cu is delivered. Fish fed a high ration exhibited greater mass-specific unidirectional uptake of waterborne Cu than fish fed a low ration indicating an increased need for Cu for growth processes in rapidly growing fish. Stimulated excretion of Cu was indicated by greater Cu accumulation in the bile of the Cu-exposed fish. Branchial Na(+), K(+)-ATPase was not affected by dietary Cu exposure or ration but gut Na(+), K(+)-ATPase activities showed stimulatory effects of increasing ration but not of Cu exposure. The 96-h LC50 for waterborne Cu (range 0.17-0.21 micromol l(-1) (10.52-13.20 microg l(-1)) was the same in all treatment groups indicating that ration size was unimportant and that dietary Cu did not induce an increase in tolerance to waterborne Cu. Taken together these results suggest that the nutritional status, fish size, and growth rates should be considered when comparing whole-body and tissue Cu concentration data for biomonitoring and risk assessment. Moreover, expressing the exposure as total metal dose rather than metal concentration in the diet is more appropriate.

Copper deficiency and cardiovascular disease: role of peroxidation, glycation, and nitration

Dietary copper deficiency causes a variety of cardiovascular deficits. Systemic effects include high blood pressure, enhancement of inflammation, anemia, reduced blood clotting, and possibly arteriosclerosis. Effects on specific organs or tissues include weakened structural integrity of the heart and blood vessels, impairment of energy use by the heart, reduced ability of the heart to contract, altered ability of blood vessels to control their diameter and grow, and altered structure and function of circulating blood cells. In some instances, the cause of a defect can be directly attributed to reduced activity of a specific copper-dependent enzyme. However, three nonspecific mechanisms of damage have been implicated in cardiovascular defects of copper deficiency. They are peroxidation, the interaction of oxygen-derived free radicals with lipids and proteins (possibly DNA); glycation, the nonenzymatic glycosylation of proteins; and nitration, the interaction of nitric oxide and its metabolites with peptides and proteins. Though independently these mechanisms present great potential for damage, the possibility that they may interact presents an added reason for concern. Furthermore, the fact that at least two of these mechanisms are associated with diabetes and aging suggests that copper deficiency may exacerbate deficits associated with these two conditions.Key words: copper, heart, circulation, peroxidation, glycation, nitric oxide.

Hepatic fructose-metabolizing enzymes and related metabolites: role of dietary copper and gender

The purpose of this study was to further examine the hypothesis that variations in hepatic fructose-metabolizing enzymes between males and females might account for the differences in the severity of copper (Cu) deficiency observed in fructose-fed male rats. Weanling rats of both sexes were fed high-fructose diets either adequate or deficient in copper for 45 days. Cu deficiency decreased sorbitol dehydrogenase activity and dihydroxyacetone phosphate levels and increased glyceraldehyde levels in both sexes. Gender effects were expressed by higher activities of glycerol 3-phosphate dehydrogenase and aldehyde dehydrogenase in male than in female rats and higher levels of dihydroxyacetone phosphate and fructose 1,6-diphosphate (F1,6DP) in female than in male rats. The interactions between dietary Cu and gender were as follows: alcohol dehydrogenase activities were higher in female rats and were further increased by Cu deficiency in both sexes; aldehyde dehydrogenase activities were decreased by Cu deficiency only in male rats; sorbitol levels were higher in male rats and were further increased by Cu deficiency in male rats; fructose 1-phosphate (F1P) levels were increased by Cu deficiency in both sexes, but to a greater extent in male rats; glyceraldehyde 3-phosphate levels were higher in female rats, but were decreased by Cu deficiency in female and increased in male rats. Though most of the examined hepatic fructose-metabolizing enzymes and metabolites showed great differences between rats fed diets either adequate or deficient in Cu, it is the activity of fructokinase and aldolase-B, and the concentrations of their common metabolites, F1P and notably F1,6DP, that could be in part responsible for differences in the severity of pathologies associated with Cu deficiency observed between female and male rats.

Early and advanced glycation end-products are increased in dietary copper deficiency

The hypothesis that nonenzymatic glycosylation of proteins (glycation) contributes to damage associated with dietary copper deficiency has depended largely on indirect evidence. Thus far, the observation of an elevated percentage of glycated hemoglobin in copper-deficient rats has provided the only direct evidence of an increase in glycation. We sought further direct evidence of increased glycation in copper deficiency. Male weanling rats were fed a copper-adequate (CuA, 6.4 mg Cu/kg diet) or copper-deficient diet (CuD, 0.4 mg Cu/kg diet) for 5 weeks. Rats fed the CuD diet were copper deficient as judged by depressed organ copper concentrations and a variety of indirect indices. Measurements of hemoglobin A(1) and serum fructosamine (both early glycation end-products) as well as serum pentosidine (an advanced glycation end-product) indicated that all three compounds were elevated in CuD rats relative to CuA rats. This finding further supports the view that glycation is enhanced and thus may contribute to defects associated with dietary copper deficiency.

Cardiovascular effects of dietary copper deficiency

Dietary copper deficiency may impair cardiovascular health by contributing to high blood pressure, enhancement of inflammation, anemia, reduced blood clotting and arteriosclerosis. The purpose of this review is to compile information on the numerous changes of the heart, blood and blood vessels that may contribute to these cardiovascular defects. These alterations include weakened structural integrity of the heart and blood vessels, impairment of the use of energy by the heart, reduced ability of the heart to contract, altered ability of blood vessels to control their diameter and to grow, and altered structure and function of circulating blood cells. The fundamental causes of these changes rest largely on reduced effectiveness of enzymes that depend on copper for their activity.

Benfluorex, a hypotriglyceridemic drug, reduces lipid peroxidation and alleviates adverse metabolic complications of copper deficiency

The pathologies associated with copper deficiency in rats fed fructose may be induced, in part, by hypertriglyceridemia and lipid peroxidation. Reducing triacylglycerol levels in plasma may result in lowering lipid peroxidation, which in turn could ameliorate metabolic effects resulting from the combination of fructose feeding and copper deficiency. Benfluorex, a hypolipidemic factor able to reduce hypertriglyceridemia, was administered to weanling male rats fed either copper-deficient (0.6 microgram Cu/g) or adequate (6.0 micrograms Cu/g) diets containing fructose as the sole dietary carbohydrate. In copper-deficient rats, benfluorex (50 micrograms.kg-1.d-1) reduced plasma triacylglycerols from 45 to 31 mg/dL, reduced lipid peroxidation by approximately 50%, and prevented the enlargements of heart and liver size and the atrophy of the pancreas, and ameliorated anemia. It is suggested that lipid peroxidation associated with hypertriglyceridemia may be responsible for the pathologies induced by the combination of fructose consumption and copper deficiency.