The aim of the present study was to investigate the protective effect of tacrolimus on early podocyte damage in rats with diabetic nephropathy (DN). A total of 38 normal male Sprague‑Dawley rats were randomly divided into four groups: Normal control group (group N; n=8), DN group (n=10), tacrolimus (FK506) treatment group (group F; n=10), benazepril (Lotensin) treatment group (group L; n=10). The rats in groups DN, F and L were administered with streptozotocin (STZ; 60 mg/kg) by intraperitoneal injection to establish the diabetic rat model. After 4 weeks, the diabetic rat model was established, and rats in the different groups were administered intragrastically with the respective drugs. Blood glucose (BS), body weight (BW) and 24‑h urine protein were detected every 4 weeks, serum creatinine (SCr), blood urea nitrogen (BUN) and kidney weight/body weight (KW/BW) were measured at the end of the 8 weeks of drug treatment. Renal pathological changes were observed under a light microscope and electron microscope. Expression of nephrin, which is a podocyte‑specific marker, was detected using western blot analysis. The results showed that the levels of SCr, BUN, KW/BW and 24‑h urine protein in groups D, F and L were significantly higher, compared with those in group N (P<0.05). No significant differences were found between groups F and L for the above indicators, with the exception of BS. However, all indices were significantly lower, compared with those in group DN (P<0.05). Renal pathological expression was normal in group N under light microscopy. There were significant increases in the glomerular volume, proliferative mesangial cells, width of the mesangial area and thickness of the basement membrane in group DN, however, all the above pathological characteristics were reduced in groups F and L, compared with group DN (P<0.05). No significant difference was found between groups F and L. A widened glomerular basement membrane, and disorder, widening and fusion of podocyte processes were observed under the electron microscope in group DN, however, these were reduced in groups F and L, compared with group DN (P<0.05). The results of the western blot analysis showed that the expression of nephrin decreased by 60.1% in group DN, compared with group N, and significant recovery in the expression of nephrin was observed in groups F and L (P<0.05). Tacrolimus reduced urinary protein and slowed the progression of DN, partially by recovering the protein expression of nephrin in the renal tissue of diabetic rats, and maintaining the integrity of the structure and function of podocytes.

Recent studies in animal models have revealed that mycophenolate mofetil (MMF) has certain protective effects against experimental diabetic nephropathy. The present study therefore aimed to investigate the hypothesis that diabetic nephropathy may be ameliorated by mycophenolate mofetil and benazepril treatment alone or in combination, and identify the potential underlying mechanisms in a rat model. Diabetes was induced in rats by a single intraperitoneal injection of streptozotocin. Rats were subsequently treated with benazepril, MMF or a combination of the two drugs, and blood glucose, normalized kidney weight, urine protein and serum creatinine were determined. The pathological changes in renal tissue were also observed. In addition, indices of epithelial mesenchymal transition, including α-smooth muscle actin (α-SMA) and transforming growth factor (TGF)-β1 expression, were examined. Normalized kidney weight, urine protein and serum creatinine levels were significantly improved in the diabetic rats treated with benazepril or mycophenolate mofetil, compared with those of rats in the untreated diabetic group. Pathological changes in the kidney were detected concurrently with increasing kidney weight and urinary albumin excretion, with a similar trend in variation among groups. In addition, the expression of epithelial mesenchymal transition indices, including α-SMA and TGF-β1, in the renal tubule interstitium were significantly decreased in the benazepril- and MMF-treated groups compared with those of the diabetic group. As expected, the aforementioned indices were markedly lower in the benazepril and MMF combined treatment group than those in the single medication groups. These data suggested that MMF may have a protective role in diabetic nephropathy, and that the underlying mechanism may be partially dependent upon the suppression of the epithelial mesenchymal transition. Furthermore, the combination of benazepril and MMF conferred enhanced efficacy over monotherapies in the treatment of diabetic nephropathy.