Puerarin Attenuated Early Diabetic Kidney Injury through Down-Regulation of Matrix Metalloproteinase 9 in Streptozotocin-Induced Diabetic Rats

Diabetic nephropathy (DN) is a serious complication and it leads to kidney failure. The endothelial nitric oxide synthases (eNOS) seems to be involved in the development and progression of DN. The Puerarin is a well-known Chinese traditional formula, which is widely used in clinical practice for the treatment of kidney disease. The present study was designed to investigate the renal protective effects of Puerarin on streptozotocin (STZ)-induced diabetic rats. Thirty Sprague-Dawley (SD) male rats were divided into three groups at random. The diabetic group and the Puerarin-treated group were intraperitoneally injected with STZ 65 mg/kg and the Puerarin-treated rats were intraperitoneally injected Puerarin 100 mg/kg/day for 4 weeks. The results showed the Puerarin could improve body weight, blood sugar, BUN and SCr levels, and reduce ultrastructural changes of kidney in diabetic rats. It also attenuated eNOS expression in glomerular endothelial cells and tubular cells of diabetic rats with Puerarin treatment (p50.05). The Puerarin had significant renal-protective effects for the diabetic nephropathy, possibly through regulating eNOS expression, and it may be used as a potential therapeutic reagent.

The prevalence of diabetes and co-morbid diseases, especially in developing countries, may have already exceeded estimates. Accumulating reports indicate considerable underpinnings in the mechanisms of the aetiopathogenesis of metabolic syndrome, bipolar disorder, epilepsy and, recently, substance addiction. Continuing evidence incriminates dysfunction in genetic, mitochondrial and inflammatory cascade mechanisms as contributory factors to the dysregulation of neurotrophic, serotonergic, dopaminergic, adrenergic, glutamatergic, GABAergic and autophagic pathways. There may also be co-incident dysregulation of the global anti-oxidant network, the endogenous digitalis system, the vasopressin signalling and the hypothalamo-pituitary-adrenal axis. Nuclear factor-kappa B (NF-kappa B) signaling and reactive oxygen species lead to activation of the mammalian target of rapamycin complex I (mTORCI) and this process may be central to the aetiopathogenesis of drug addiction, obesity, foetal programming, diabetes mellitus, epilepsy and bipolar disorder. Antiglycaemics such as cannabinoid CB2 agonists, metformin, artesunate and valproate; insulin-mimetics such as glucagon-like peptide-I (GLP-I) and its analogues; phytomedicines from garlic and curcumin are now shown to exhibit neuroprotective effects. These agents which may down-regulate inflammatory cytokines, upregulate endothelial nitric oxide (eNOS) and peroxisome proliferator-activated receptor alpha (PPAR-α) signalling, attenuate mitochondrial dysfunction, enhance the actions of glucagon-like peptide-I (GLP-I), inhibit mTOR, NF-kappa B, interleukin-I β and glycogen synthase kinase-3 β stand to be of benefit in these illnesses which demonstrate considerable overlay in their aetopathogenic mechanisms. Underpinnings and bidirectional relationships between the metabolic syndrome and mental health disorders may pave way for common new fronts to drug development in translational cardiovascular psychiatry and neurology.

Abstract. Insufficient matrix metalloproteinase (MMP)-9 and MMP-2 is considered to be a contributor of extracellular matrix (ECM) accumulation in diabetic nephropathy (DN). C-peptide can reverse fibrosis, thus exerting a beneficial effect on DN. Whether C-peptide induces MMP-9 and MMP-2 to reverse ECM accumulation is not clear. In the present study, in order to determine ECM metabolism, rat mesangial cells were treated with high glucose (HG) and C-peptide intervention, then the early and late effects of C-peptide on HG-affected MMP-9 and MMP-2 were evaluated. Firstly, it was confirmed that HG mainly suppressed MMP-9 expression levels. Furthermore, C-peptide treatment induced MMP-9 expression at 6 h and suppressed it at 24 h, revealing the early dual effects of C-peptide on MMP-9 expression. Subsequently, significant increase in MMP-9 expression at 72, 96 and 120 h C-peptide treatment was observed. These changes in MMP-9 protein content confirmed its expression changes following late C-peptide treatment. Furthermore, at 96 and 120 h C-peptide treatment reversed the HG-inhibited MMP-9 secretion, further indicating the late induction effect of C-peptide on MMP-9. The present results demonstrated that C-peptide exerted a late induction effect on MMP-9 in HG-stimulated rat mesangial cells, which may be associated with the underlying mechanism of C-peptide's reversal effects on DN. IntroductionDiabetic nephropathy (DN), the leading cause of end stage renal disease, is the major cause of mortality in type 1 diabetes mellitus (DM) and the second most severe complications in type 2 diabetes (1,2). Deposition of extracellular matrix (ECM) in mesangial areas is a feature of DN, and mesangial cells have been proposed to be the determinant of ECM accumulation (3,4). However, the mechanism underlying ECM accumulation in DN is not fully clarified.Matrix metalloproteinases (MMPs) are a family of zinc-dependent endopeptidases that can degrade numerous types of ECM components (5,6). Among others, MMP-2 basally expresses while MMP-9 is an inducible enzyme, both of which primarily degrade types-I and -IV collagen and laminin, major components of ECM (7-9). Generally, MMP-2 and MMP-9 are involved in tumor metastasis (6,10). Furthermore, it has been shown that insufficient MMP-2 and MMP-9 may be a contributor of ECM accumulation in DN (11). However, the expression levels of MMP-2 and MMP-9 in DN remain controversial, and even short-and long-term hyperglycemia may exert differential effects (8,(12)(13)(14). As an inducible enzyme, MMP-9 may be more easily affected in patients with DN (15). Therefore, the changes of MMP-2, and particularly MMP-9, for high glucose (HG) stimulation require clarification.C-peptide is the linker between the A-chain and B-chain of insulin. Lack of C-peptide along with insulin is the primary feature of type 1 DM and late stage of type 2 DM (16). C-peptide has been found to have unique beneficial effects on DN, attenuating glomerular and tubular injury (17)(18)(19). Physiological concentration of C-peptide ca...