Abstract

BACKGROUND
Diabetic nephropathy is one of the most serious complications in diabetes mellitus, and it is the leading cause of end stage renal disease. It has been reported that angiotensin converting enzyme inhibitor (ACEi) reduces the vascular endothelial growth factor (VEGF) expression, and so it plays an important role in reducing the renal damage. Peroxisome proliferator activated receptor-gamma (PPAR-gamma) agonist is known to reduce insulin resistance in type 2 diabetic patients. In the previous study, PPAR-gamma agonist was shown to lower VEGF expression in the retina, but it increased the plasma VEGF level. Alpha-lipoic acid (alpha-LA), which is an antioxidant, lowers the increased level of VEGF in retina as well. The precise role of PPAR-gamma agonist and alpha-LA on renal VEGF expression in diabetic nephropathy is still uncertain. We studied the effect of PPAR-gamma agonist, angiotensin II receptor blocker (ATIIRB) and alpha-LA on the renal VEGF expression in diabetic rats. METHODS: We used 60 Sprague-Dawley male rats, those were 8 weeks old and weighted about 300 g each as the study subjects. Among them, 48 rats were chosen and injected with streptozotocin (70 mg/kg) into peritoneal cavity to induce diabetes mellitus. The rast were than divided into 5 groups. Group I was a normal control group (n=12), group II was diabetic control group (n=12), group III was diabetic group that was given with PPAR-gamma agonist (n=12), group IV was the diabetic group that was given ATIIRB (n=12), and group V was the diabetic rats that were given alpha-LA (n=12). We measured their body weight, blood glucose levels, 24 hour urine protein and albumin levels at the baseline, the 8th and the 16th weeks of the experiment. On the 16th weeks of our experiment we extracted the kidneys to measure the glomerular volume, the optical density of the VEGF staining and VEGF mRNA expression. RESULTS: At the beginning of the study, the 5 groups all showed similar 24 hour urine albumin levels. At the 8th week, group II showed an increased urine albumin level of 143.4 +/- 117.2 mg/day; this was greater than that of group IV (60.7+/-30.6 mg/day) (p<0.05). The glomerular volume and optical densities of VEGF expression were significantly reduced in group III, IV and V compared to group II. For group IV and V, the renal VEGF mRNA expression was significantly lower than that of group II, but group III showed no significant difference. from group II. CONCLUSION: Angiotensin II receptor blocker delayed the progression of diabetic nephropathy. PPAR-gamma agonist and alpha-lipoic acid did not have any protective effect against the progression of diabetic nephropathy in spite of the decreased VEGF expression noted in this study.

• Keywords: Diabetes mellitus;Diabetic nephropathy;VEGF;Angiotensin II receptor blocker;Peroxisome proliferator activated receptor-gamma agonist;alpha-Lipoic acid;