Submitted to: Trace Elements in Man and Animals International Symposium
Publication Type: Proceedings
Publication Acceptance Date: May 7, 1999
Publication Date: N/A
Interpretive Summary: Altered metabolism of sugar, as commonly occurs in diabetes and aging, may increase blood sugar. This can lead to the undesirable binding of sugar to proteins (termed glycation) that causes damage to the proteins and may alter their function. We have shown previously that this altered sugar binding may be the cause of problems associated with dietary copper deficiency. To date, however, the only direct evidence that altered sugar binding occurs in copper deficiency has been the observation of an elevated percentage of sugar bound to the blood protein hemoglobin. The purpose of the present study was to look for stronger evidence of sugar binding by proteins in copper deficiency by measuring the concentration of another protein containing bound sugar as well as a compound that represents protein that has been destroyed by sugar binding. We found that two such compounds were elevated in copper-deficient rats, thus further confirming the occurrence of a harmful enhanced binding of sugar to proteins in dietary copper deficiency. This information will be useful to scientists interested in the biochemistry of copper deficiency and to consumers interested in nutrition as it relates to diabetes and aging.
Technical Abstract: The hypothesis that nonenzymatic glycosylation of proteins (glycation) contributes to damage associated with dietary copper deficiency has depended largely on indirect evidence. Observation of an elevated percentage of glycated hemoglobin in copper-deficient rats has thus far 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 five weeks. Rats fed CuD diet were copper deficient as judged by depressed liver copper concentration, reduced body weight, elevated heart weight to body weight ratio and reduced hematocrit. Hemoglobin A1 and serum fructosamine (both early glycation end-products) were elevated in copper-deficient rats (by 60% and 26%, respectively). Serum pentosidine (an advanced glycation end- product) was undetectable in copper-adequate rats and found at a concentration of 6.4 pmol/mg protein in copper-deficient rats. This finding further supports the view that glycation is enhanced and thus may contribute to defects associated with dietary copper deficiency.