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 variat ions in hepatic fructose-metabolizing enzymes between males and females mig ht account for the differences in the severity of copper (Cu) deficiency ob served 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 defi ciency decreased sorbitol dehydrogenase activity and dihydroxyacetone phosp hate levels and increased glyceraldehyde levels in both sexes. Gender effec ts were expressed by higher activities of gylcerol 3-phosphate dehydrogenas e and aldehyde dehydrogenase in male than in female rats and higher levels of dihydroxyacetone phosphate and fructose 1,6-diphosphate (F1,6DP) in fema le than in male rats. The interactions between dietary Cu and gender were a s follows: alcohol dehydrogenase activities were higher in female rats and were further increased by Cu deficiency in both sexes; aldehyde dehydrogena se activities were decreased by Cu deficiency only in male rats; sorbitol l evels were higher in male rats and were further increased by Cu deficiency in male rats; fructose 1-phosphate (F1P) levels were increased by Cu defici ency 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 defic iency in female and increased in male rats. Though most of the examined hep atic fructose-metabolizing enzymes and metabolites showed great differences between rats fed diets either adequate or deficient in Cu, it is the activ ity 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 ob served between female and male rats. (J. Nutr. Biochem. 11: 374-381, 2000) (C) Elsevier Science Inc. 2000. All rights reserved.