Abstract
To explore the involvement of oxidative stress in diabetic nephropathy, we examined serum ascorbic acid (AsA) and lipoperoxide (LPO) levels in patients with diabetes mellitus (DM, n=81) in relation to nephropathy assessed by various clinical parameters such as proteinuria, creatinine and albumin in serum, fasting blood glucose, and glycohemoglobin (HbAic) . Age-matched non-diabetics (n=15) were examined as controls. W e measured total, reduced and oxidized (dehydro-) forms of AsA. Diabetics were classified as normo-, micro-, macro-albuminuria and nephrotics. Diabetic patients with normoalbuminuria showed significantly lower AsA than non-diabetics (P<0.05) . Significant decrease of AsA was also found in diabetics with micro-, macro-albuminuria and nephrosis (p<0.001) . Although no significant difference in dehydro-AsA (DAsA) was seen among diabetics, the ratio of DAsA/ total AsA was tended to increase in relation to the protein content in urine, and this was significant in diabetic nephrosis (p<0.05) . AsA levels correlated with albumin concentration in sera of total diabetics (p<0.01), and the ratio of DAsA/TAsA was correlated with serum creatinine levels (p<0.05) . In contrast, we observed no significant relation between AsA and HbAIC. Our results suggest that serum AsA decreases in diabetics regardless of management of blood glucose and that AsA was decreased in association with severity of nephropathy. This may be due to oxidative stress. LPO in diabetics was elevated and the increment was associated with severity of nephropathy. W e could not, however, find a significant relation between AsA and LPO. Thus, serum AsA may not directly reflect the oxidative stress of lipoproteins.
