Effective Delivery of Endogenous Antioxidants Ameliorates Diabetic Nephropathy

Reactive Oxygen Species-Mediated Diabetic Heart Disease: Mechanisms and Therapies

Significance: Diabetic heart disease (DHD) is the primary cause of mortality in people with diabetes. A significant contributor to the development of DHD is the disruption of redox balance due to reactive oxygen species (ROS) overproduction resulting from sustained high glucose levels. Therapies specifically focusing on the suppression of ROS will hugely benefit patients with DHD. Recent Advances: In addition to the gold standard pharmacological therapies, the recent development of gene therapy provides an exciting avenue for developing new therapeutics to treat ROS-mediated DHD. In particular, microRNAs (miRNAs) are gaining interest due to their crucial role in several physiological and pathological processes, including DHD. Critical Issues: miRNAs have many targets and differential function depending on the environment. Therefore, a proper understanding of the function of miRNAs in specific cell types and cell states is required for the successful application of this technology. In the present review, we first provide an overview of the role of ROS in contributing to DHD and the currently available treatments. We then discuss the newer gene therapies with a specific focus on the role of miRNAs as the causative factors and therapeutic targets to combat ROS-mediated DHD. Future Directions: The future of miRNA therapeutics in tackling ROS-mediated DHD is dependent on a complete understanding of how miRNAs behave in different cells and environments. Future research should also aim to develop conditional miRNA therapeutic platforms capable of switching on and off in response to disruptions in the redox state. Antioxid. Redox Signal. 36, 608-630.

Mouse metallothionein-1 and metallothionein-2 are not biologically interchangeable in an animal model of multiple sclerosis, EAE

Mouse metallothionein-1 and 2 (MT1 and MT2) are often considered physiologically equivalent, because they are normally regulated coordinately by a wide range of stimuli, and it is assumed that in vivo they will be normally fully loaded with zinc(ii) (Zn7-MT1/2), although other metal ions, such as copper(i), may be eventually found as well. However, mouse MT2, in contrast to MT1, exhibits a preference for Zn(ii) coordination in comparison to that for Cu(i), which might underlie putatively different biological functions for these two mammalian isoforms. We have characterized the effects of exogenously administered mouse MT1 and MT2, and of transgenic Mt1 overexpression, in an animal model of multiple sclerosis (MS), experimental autoimmune encephalomyelitis (EAE), by active immunization with MOG35-55 peptide. Mice treated daily with MT2 showed a significant amelioration of the clinical course, with decreased peak and cumulative scores and delayed onset of EAE. In contrast, treatment with MT1 or its transgenic overexpression only caused a non-significant trend. MT2 treatment preserved better the myelin of the spinal cord, and the pattern of leukocyte infiltrates and gene expression are compatible with an inhibitory effect on neuroinflammation. Splenocytes from these animals in culture responded adequately to MOG35-55 peptide, but a bias for a Th2 profile seemed to be present in the MT2-treated mice. Interestingly, MT1 but not MT2 decreased the number of cytokines in the serum. The present results indicate that mouse MT1 and MT2 are not biologically interchangeable in the EAE model.

Mitochondria transfer from mesenchymal stem cells structurally and functionally repairs renal proximal tubular epithelial cells in diabetic nephropathy in vivo

The underlying therapeutic mechanism of renal tubular epithelium repair of diabetic nephropathy (DN) by bone marrow-derived mesenchymal stem cells (BM-MSCs) has not been fully elucidated. Recently, mitochondria (Mt) transfer was reported as a novel action of BM-MSCs to rescue injured cells. We investigated Mt transfer from systemically administered BM-MSCs to renal proximal tubular epithelial cells (PTECs) in streptozotocin (STZ)-induced diabetic animals. BM-MSCs also transferred their Mt to impaired PTECs when co-cultured in vitro, which suppressed apoptosis of impaired PTECs. Additionally, BM-MSC-derived isolated Mt enhanced the expression of mitochondrial superoxide dismutase 2 and Bcl-2 expression and inhibited reactive oxygen species (ROS) production in vitro. Isolated Mt also inhibited nuclear translocation of PGC-1α and restored the expression of megalin and SGLT2 under high glucose condition (HG) in PTECs. Moreover, isolated Mt directly injected under the renal capsule of STZ rats improved the cellular morphology of STZ-PTECs, and the structure of the tubular basement membrane and brush border in vivo. This study is the first to show Mt transfer from systemically administered BM-MSCs to damaged PTECs in vivo, and the first to investigate mechanisms underlying the potential therapeutic effects of Mt transfer from BM-MSCs in DN.

Renoprotective effect of JinQi-JiangTang tablet on high-fat diet and low-dose streptozotocin-induced type 2 diabetic rats

JinQi-JiangTang tablet (JQ), a traditional Chinese patent medicine, have been commonly applied to clinical therapy in type 2 diabetic patients. The present study was undertaken to investigate the renoprotective effect of JQ on type 2 diabetic rats. The type 2 diabetic rat model was successfully induced by a high-fat and high-sugar diet combined with a single low-dose of streptozotocin. Intervention with JQ could significantly diminish the body weight loss, reduce the levels of fasting blood glucose, 24 hour urinary protein, blood urea nitrogen and serum creatinine in STZ-induced diabetic rats. JQ improved the creatinine clearance in diabetic rats. What's more, the levels of total cholesterol, triglyceride and low-density lipoprotein cholesterol were markedly reduced following JQ treatment, while the level of high-density lipoprotein cholesterol was elevated. Moreover, JQ significantly improved the activity of superoxide dismutase, catalase and glutathione peroxidase, whereas decreased the level of lipid peroxidation malondialdehyde in renal tissue of diabetic rats. Furthermore, immunohistochemical analysis showed that JQ significantly downregulated the expression of Bax, Caspase-3 and Cytochrome c and upregulated Bcl-2 protein expression in the renal tissue of diabetic rats, which was considered as the major pathogeneses of apoptosis. These data demonstrated that JQ exhibited a renoprotective effect through blood glucose control, alleviating lipid metabolism, anti-oxidative stress and anti-apoptosis activities.

JinQi-JiangTang tablet (JQ), a traditional Chinese patent medicine, have been commonly applied to clinical therapy in type 2 diabetic patients.

Implications of impaired zinc homeostasis in diabetic cardiomyopathy and nephropathy

Impaired zinc homeostasis is observed in diabetes mellitus (DM2) and its complications. Zinc has a specific role in pancreatic β-cells via insulin synthesis, storage, and secretion. Intracellular zinc homeostasis is tightly controlled by zinc transporters (ZnT and Zip families) and metallothioneins (MT) which modulate the uptake, storage, and distribution of zinc. Several investigations in animal models demonstrate the protective role of MT in DM2 and its cardiovascular or renal complications, while a copious literature shows that a common polymorphism (R325W) in ZnT8, which affects the protein's zinc transport activity, is associated with increased DM2 risk. Emerging studies highlight a role of other zinc transporters in β-cell function, suggesting that targeting them could make a possible contribution in managing the hyperglycemia in diabetic patients. This article summarizes the current findings concerning the role of zinc homeostasis in DM2 pathogenesis and development of diabetic cardiomyopathy and nephropathy and suggests novel therapeutic targets. © 2017 BioFactors, 43(6):770-784, 2017.

Metallothioneins and renal ageing

BACKGROUND

Human lifespan is increasing continuously and about one-third of the population >70 years of age suffers from chronic kidney disease. The pathophysiology of the loss of renal function with ageing is unclear.

METHODS

We determined age-associated gene expression changes in zero-hour biopsies of deceased donor kidneys without laboratory signs of impaired renal function, defined as a last serum creatinine >0.96 mg/dL in females and >1.18 mg/dL in males, using microarray technology and the Significance Analysis of Microarrays routine. Expression changes of selected genes were confirmed by quantitative polymerase chain reaction and in situ hybridization and immunohistochemistry for localization of respective mRNA and protein. Functional aspects were examined in vitro.

RESULTS

Donors were classified into three age groups (<40, 40-59 and >59 years; Groups 1, 2 and 3, respectively). In Group 3 especially, genes encoding for metallothionein (MT) isoforms were more significantly expressed when compared with Group 1; localization studies revealed predominant staining in renal proximal tubular cells. RPTEC/TERT1 cells overexpressing MT2A were less susceptible towards cadmium chloride-induced cytotoxicity and hypoxia-induced apoptosis, both models for increased generation of reactive oxygen species.

CONCLUSIONS

Increased expression of MTs in the kidney with ageing might be a protective mechanism against increased oxidative stress, which is closely related to the ageing process. Our findings indicate that MTs are functionally involved in the pathophysiology of ageing-related processes.

Identification of cysteinylated transthyretin, a predictive biomarker of treatment response to partially hydrolyzed guar gum in type 2 diabetes rats, by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry

Recent evidence has indicated that total fiber intake is inversely related to type 2 diabetes risk. The present study aimed to investigate the effects of chronic administration of partially hydrolyzed guar gum (PHGG), a water-soluble dietary fiber, on the occurrence of diabetes and its complications, fatty liver and nephropathy. We also identified predictive serum biomarkers of treatment response to PHGG by mass spectroscopy-based proteomic analysis using Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a good model of human non-insulin-dependent diabetes mellitus. In this study, at 5 weeks of age, OLETF rats and control strain Long-Evans Tokushima Otsuka (LETO) rats were fed a control diet or a high-fiber diet (5% PHGG) for 57 weeks. Body weight, food intake, oral glucose tolerance test, plasma insulin levels, and urine glucose and protein levels were regularly measured. Oral glucose tolerance tests (OGTT) and storage of serum in a deep freezer were conducted at the beginning of the experiment and every 4 weeks after overnight fasting during the experiments. PHGG treatment affected neither meal patterns nor the body weight of OLETF and LETO rats. Repeated measure analysis of variance revealed significant differences in fasting plasma glucose and plasma glucose at 2 h after OGTT between control OLETF (OLETF-C) rats and OLETF rats treated with PHGG (OLETF-F). The glucose response determined by the area under the curve of OGTT was significantly greater in OLETF-C rats than that in OLETF-F rats at 25 weeks of age. HOMA-IR, an index of insulin resistance, increased at 25 weeks of age in OLETF-C rats, while this increase was significantly inhibited in OLETF-F rats. At 62 weeks of age, PHGG treatment significantly improved hepatic steatosis as well as renal mesangial matrix accumulation in OLETF rats. To identify the risk marker for diabetes mellitus by SELDI-TOF MS, we collected sera from 21-week-old individuals. Among the 12 specific peaks that were risk marker candidates for diabetes mellitus, the m/z 13,720 peak was identified as that of cysteinylated transthyretin by sequencing of four tryptic peptides using tandem mass spectrometry and peak distribution around the m/z 13,720 peak in the SELDI-TOF spectra. In conclusion, we found that chronic treatment with PHGG improved insulin resistance, delayed the onset of diabetes, and inhibited the development of diabetic complications, as well as identified cysteinylated transthyretin as a predictive biomarker of treatment response to PHGG in OLETF rats.

The role of DJ-1/Nrf2 pathway in the pathogenesis of diabetic nephropathy in rats

Diabetic nephropathy (DN) is one of the most common chronic complications of diabetes, which is associated with an increased oxidative stress induced by hyperglycemia and alterations in DJ-1/NF-E2-related factor-2 (Nrf2) pathway. In the present study, we investigated the role and the proper time nodes of DJ-1/Nrf2 pathway in the pathogenesis of DN. Diabetes mellitus (DM) model of rats was induced by intraperitoneal injection of streptozotocin (STZ) on male Sprague-Dawley (SD) rats. Then, the diabetic rats were divided into 4, 8 and 12 weeks groups. As early at 4 weeks of diabetes, renal histologic evaluation score, cystatin C (Cys C), β2-microglobulin (β2-MG) and malondialdehyde (MDA) levels were increased, and total antioxidative capacity (T-AOC) level was decreased as compared with that in the control group. The protein expressions of DJ-1, NF-E2-related factor-2 (Nrf2) and heme oxygenase-1 (HO-1) were upregulated compared with the control group from 4 weeks and further increased with the progression of DM. The protein expressions of DJ-1, Nrf2 and HO-1 in renal tissues have good line correlations with renal histologic evaluation score, respectively. Taken together, these results suggested that the activation of DJ-1/Nrf2 pathway was involved in the pathogenesis of diabetic nephropathy in rats.