Mitochondrial function is not affected by renal morphological changes in diabetic Goto-Kakizaki rat

Renal disease is a common complication of diabetes mellitus. The pathogenesis of diabetic nephropathy is not well understood, but hyperglycemia seems to be a crucial factor. Recent evidence indicates that the overproduction of reactive oxygen species, observed in both clinical and experimental diabetes, and mitochondrial dysfunction are key factors in pathogenic process. The objective of this investigation was to test the hypothesis of whether hyperglycemia could affect kidney morphology and mitochondrial bioenergetics as well as susceptibility to oxidative stress in 12-month-old diabetic Goto-Kakizaki (GK) rats, a model of type 2 diabetes mellitus. We observed that there were no significant differences in the kidney respiratory function and phosphorylation capacity between GK and age-matched control Wistar rats. Mitochondria from kidneys of diabetic rats were equally susceptible to in vitro oxidative damage as those from normal rats, while coenzyme Q and alpha-tocopherol concentrations were similar in both types of preparations. However, the kidney of GK rats presented in most glomerulus a capillary basement membrane thickening with mesangial widening, in evolution to segmental glomerular sclerosis, and, in some interlobular arteries, excessive deposition of PAS-positive material at the tunica intima. The results show that the mild prolonged hyperglycemia and the kidney structural changes observed in GK rats are not sufficient to cause renal dysfunction and were not associated with functional and biochemical alterations in mitochondria.