HIGH-FRUCTOSE INTAKE SIGNIFICANTLY REDUCES KIDNEY COPPER CONCENTRATIONS IN DIABETIC, ISLET TRANSPLANTED RATS

Trace element status is known to be altered in the diabetic state, alt hough the factors affecting trace element homeostasis in this conditio n are not well understood. The authors examined the effects of a high fructose diet (40% wt:wt) vs a control diet on the copper (Cu), zinc ( Zn), and iron (Fe) concentrations in the kidney, plasma, and red blood cells of islet transplanted (TX) and sham-operated (SHAM) rats. Male, Wistar Furth rats made diabetic by streptozotocin injection (55 mg/kg , iv) were given an intraportal islet transplant (1000 islets); contro l animals were sham-injected, sham-operated (SHAM). Rats within TX and SHAM groups were assigned to either a high fructose diet(40% fructose , 25% cornstarch, FR) or a purified control diet (33% cornstarch, 33% dextrose, CNTL) containing identical amounts of mineral mixture for a period of 6 wk. Kidney Cu concentration was significantly elevated amo ng hyperglycemic TX-CNTL rats (224 +/- 25 nmol/g wet wt), but was mark edly reduced in hyperglycemic TX-FR rats (109 +/- 14 nmol/g) relative to normoglycemic controls. This occurred in spite of similar levels of glucose, insulin (fed and fasted), insulin secretory capacity, body w eight, and food intake in the TX-CNTL and TX-FR groups. Among the subg roup of rats with normal glucose levels post-TX, kidney Cu levels norm alized and were unaffected by dietary treatment (normaglycemic TX-CNTL = 60 +/- 5 nmol/g; normoglycemic TX-FR = 40 +/- 2 nmol/g). Kidney Cu concentrations also were unaffected by fructose feeding in SHAM animal s (CNTL, 60 +/- 4 nmol/g and FR, 51 +/- 5 nmol/g). Kidney Zn and Fe co ncentrations were similar among the treatment groups. Plasma and red b lood cell (RBC) Cu, Zn, and Fe concentrations were also similar among the groups. Since fructose feeding led to a substantial reduction of k idney Cu concentrations in the presence of hyperglycemia, the authors suggest that this model can be useful in examining effects of altered kidney Cu, accumulation in the diabetic animal.