High-fructose feeding of streptozotocin-diabetic rats is associated with increased cataract formation and increased oxidative stress in the kidney

We examined the effects of high-fructose (FR) feeding on the development of diabetic complications in the lens and the kidney of streptozotocin (STZ)- diabetic rats. Male Wistar Furth rats were treated with one of two doses of STZ (HIGH STZ, 55 mg/kg body weight; MOD STZ, 35 mg/kg body weight) or veh icle alone (SHAM) and were then assigned to a control (CNTL) or 400 g FR/kg diet for 12 weeks. At the end of the study, body weight, plasma glucose an d insulin concentrations differed among STZ groups (HIGH v. MOD v. SHAM, P< 0.001) but did not differ due to diet. Plasma FR concentrations were signif icantly higher in FR-fed v. CNTL-fed groups (P<0.0001) and in HIGH-STZ grou ps v. MOD-STZ and SHAM groups (P<0.0004 and P<0.0001 respectively). Focal l ength variability of the lens, a quantitative measure of cataract formation , was increased in the HIGH STZ, FR group compared with the HIGH STZ, CNTL group (P<0.01). The concentration of H2O2 in kidney microsomes was signific antly higher in HIGH STZ, FR rats v. HIGH STZ, CNTL rats (P<0.01). Microalb uminuria was not observed in any of the groups examined, and there was no e vidence of extensive histological damage in the kidney from any rats. Under conditions of severe hyperglycaemia, high FR intake promotes the developme nt of cataracts in the lens of the eye, and results in increased concentrat ions of substances indicative of oxidative stress in the kidney. Although F R has been suggested as a carbohydrate source for diabetics, a high FR diet coupled with hyperglycaemia produces effects that may promote some of the complications associated with diabetes.