Combined MMF and insulin therapy prevents renal injury in experimental diabetic rats

Comparison of the effects of levocetirizine and losartan on diabetic nephropathy and vascular dysfunction in streptozotocin-induced diabetic rats

This work was designed to investigate the effects of levocetirizine, a histamine H1 receptor antagonist, on diabetes-induced nephropathy and vascular disorder, in comparison to an angiotensin II receptor antagonist, losartan. Diabetes was induced in male Sprague Dawley rats by a single intraperitoneal injection of streptozotocin (50mg/kg). Diabetic rats were divided into three groups; diabetic, diabetic-levocetirizine (0.5mg/kg/day) and diabetic-losartan (25mg/kg/day). Treatments were started two weeks following diabetes induction and continued for additional eight weeks. At the end of the experiment, urine was collected and serum was separated for biochemical measurements. Tissue homogenates of kidney and aorta were prepared for measuring oxidative stress, nitric oxide (NO), transforming growth factor-β1 (TGF-β1) and tumor necrosis factor-α (TNF-α). Moreover, histological analyses were conducted and aortic vascular reactivity was investigated. Levocetirizine improved renal function in diabetic rats (evidenced by mitigation of diabetes-induced changes in kidney to body weight ratio, serum albumin, urinary proteins and creatinine clearance). Moreover, levocetirizine attenuated the elevated renal levels of TNF-α and TGF-β1, ameliorated renal oxidative stress and restored NO bioavailability in diabetic kidney. These effects were comparable to or surpassed those produced by losartan. Moreover, levocetirizine, similar to losartan, reduced the enhanced responsiveness of diabetic aorta to phenylephrine. Histological evaluation of renal and aortic tissues further confirmed the beneficial effects of levocetirizine on diabetic nephropathy and revealed a greater attenuation of diabetes-induced vascular hypertrophy by levocetirizine than by losartan. In conclusion, levocetirizine may offer comparable renoprotective effect to, and possibly superior vasculoprotective effects than, losartan in streptozotocin-diabetic rats.

Renal injury induced in alloxan diabetic rats. Role of Mycophenolate Mofetil as therapeutic agent

BACKGROUND

Renal injury may develop in uncontrolled chronic hyperglycemia due to increased oxidative stress and release of pro-inflammatory mediators, leading to diabetic complications.

METHODS

Mycophenolate Mofetil (MMF) is an immunosuppressant drug, an inhibitor of inosine monophosphate dehydrogenase (IMPDH), relevant to inflammation processes. MMF effect was tested in alloxan-diabetic rats on selected parameters like oxidative stress, gene expression of tumor necrosis factor-α (TNF-α) and transforming growth factor-β1 (TGF-β1), in relation to microalbuminuria and renal function.

RESULTS

We found that the onset of microalbuminuria preceded the increase in serum glucose after alloxan treatment. Gene expression of TNF-α and TGF-β1 showed gradual increase after one and two weeks of alloxan administration as compared to the normal group. MMF administration decreased the gene expression of TNF-α and TGF-β1 in kidney tissues, serum glucose, fructosamine, urea, creatinine, C-reactive protein, malondialdehyde, urinary microalbumin and total protein. Histological examination of kidney tissues showed significant improvement in MMF treated rats as compared to diabetic control.

CONCLUSIONS

MMF modulated renal injury of alloxan diabetic rats. Collective data may support its therapeutic effect but further clinical trials may be requested.

Superior renoprotective effects of the combination of breviscapine with enalapril and its mechanism in diabetic rats

Breviscapine is a flavonoid extracted from a Chinese herb Erigeron breviscapus, previously it was shown that treatment with breviscapine attenuated renal injury in the diabetic rats. The purpose of this study was to investigate whether breviscapine combined with enalapril (an ACE inhibitor) have superior renoprotective effects against diabetic nephropathy. Rats were randomly separated into five groups: control, diabetes, diabetes treated with enalapril, diabetes treated with breviscapine, or diabetes treated with combined enalapril with breviscapine. Twenty-four hours urinary AER and the levels of 3-NT in renal tissue and MDA in renal tissue and urine as well as activities and expression of PKC in renal tissue were determined, and renal tissue morphology were observed by light microscopy after 8 weeks. Expression of TGFβ1 protein was performed by immunohistochemistry method. Increased AER and kidney pathologic injury were attenuated by treatment with either enalapril or breviscapine and further reduced by the combination of the two. Elevated 3-NT in renal tissue and MDA levels in renal tissue and urine were reduced by enalapril or breviscapine and, more effectively, by combined enalapril with breviscapine. PKC activities and expression were higher in renal tissue in diabetic rats than those of the control group, which were reduced by both monotherapies, and further abrogated by combination therapy in both cases. Overexpression of TGFβ1 protein observed in the glomeruli and tubulointerstitium of diabetic rats was attenuated by enalapril or breviscapine to a similar lever and further reduced by the combination of the two. The combination of enalapril and breviscapine confers superiority over monotherapies on renoprotection, which mechanism may be at least partly correlated with synergetic suppression on increased oxidative stress and PKC activities as well as overexpression of TGFβ1 in renal tissue.

Mechanisms of diabetic complications

It is increasingly apparent that not only is a cure for the current worldwide diabetes epidemic required, but also for its major complications, affecting both small and large blood vessels. These complications occur in the majority of individuals with both type 1 and type 2 diabetes. Among the most prevalent microvascular complications are kidney disease, blindness, and amputations, with current therapies only slowing disease progression. Impaired kidney function, exhibited as a reduced glomerular filtration rate, is also a major risk factor for macrovascular complications, such as heart attacks and strokes. There have been a large number of new therapies tested in clinical trials for diabetic complications, with, in general, rather disappointing results. Indeed, it remains to be fully defined as to which pathways in diabetic complications are essentially protective rather than pathological, in terms of their effects on the underlying disease process. Furthermore, seemingly independent pathways are also showing significant interactions with each other to exacerbate pathology. Interestingly, some of these pathways may not only play key roles in complications but also in the development of diabetes per se. This review aims to comprehensively discuss the well validated, as well as putative mechanisms involved in the development of diabetic complications. In addition, new fields of research, which warrant further investigation as potential therapeutic targets of the future, will be highlighted.