Pathogenesis and novel treatment from the mouse model of type 2 diabetic nephropathy

Exercise in Diabetic Nephropathy: Protective Effects and Molecular Mechanism

Diabetic nephropathy (DN) is a serious complication of diabetes, and its progression is influenced by factors like oxidative stress, inflammation, cell death, and fibrosis. Compared to drug treatment, exercise offers a cost-effective and low-risk approach to slowing down DN progression. Through multiple ways and mechanisms, exercise helps to control blood sugar and blood pressure and reduce serum creatinine and albuminuria, thereby alleviating kidney damage. This review explores the beneficial effects of exercise on DN improvement and highlights its potential mechanisms for ameliorating DN. In-depth understanding of the role and mechanism of exercise in improving DN would pave the way for formulating safe and effective exercise programs for the treatment and prevention of DN.

SLC30A7 has anti-oxidant stress effects in high glucose-induced apoptosis via the NFE2L2/HMOX1 signal transduction pathway

AIMS

Apoptosis and oxidant stress are known to be involved in the pathogenesis of diabetic kidney disease (DKD). We have previously reported that zinc transporter 7 in SLC30 family (SLC30A7) inhibits apoptosis in rat peritoneal mesothelial cells under high glucose (HG) conditions. In the current study, we aimed to investigate whether SLC30A7 had effect for anti-oxidant stress in renal tubular epithelial cells under HG.

METHODS

SLC30A7 in HG-induced apoptosis in a normal rat kidney tubular epithelial cell line (NRK-52E cells)/kidneys of STZ-induced diabetic mice was examined and the activity of nuclear factor erythroid 2-related factor 2 (NFE2L2) was further analyzed by using real time RT-PCR, siRNA and Western blot protocols.

RESULTS

SLC30A7 was found to be up-regulated, while NFE2L2 was activated in kidneys of STZ-induced diabetic mice and HG-induced apoptosis of NRK-52E cells. Knock-down of SLC30A7 with siRNA protocol resulted in lower intracellular free zinc levels in the cells and decreased zinc distribution in the Golgi apparatus. Furthermore, knock-down of NFE2L2 down-regulated its target HMOX1 gene expression, decreased SLC30A7 activity but increased HG-induced apoptosis.

CONCLUSION

The current study provides new evidence that SLC30A7 has anti-oxidant stress effects in HG-induced apoptosis via the NFE2L2/HMOX1 signal transduction pathway.

Pectin-Lyase-Modified Ginseng Extract and Ginsenoside Rd Inhibits High Glucose-Induced ROS Production in Mesangial Cells and Prevents Renal Dysfunction in db/db Mice

Diabetes increases the incidence rate of chronic renal disease. Pectin-lyase-modified ginseng (GS-E3D), with enhanced ginsenoside Rd content, has been newly developed. In this study, renal protective roles of GS-E3D in type-2 diabetic db/db mice were investigated. The generation of reactive oxygen species (ROS) induced by high glucose (25 mM) was reduced by ES-E3D (75%) and ginsenoside Rd (60%). Diabetic db/db mice received 100 or 250 mg/kg/day of GS-E3D daily via oral gavage for 6 weeks. Albuminuria and urinary 8-hydroxy-2'-deoxyguanosine (8-OhdG, an oxidative stress marker) levels were increased in db/db mice and the levels recovered after GS-E3D treatment. In renal tissues, TUNEL-positive cells were decreased after GS-E3D treatment, and the increased apoptosis-related protein expressions were restored after GS-E3D treatment. Therefore, GS-E3D has a potent protective role in diabetes-induced renal dysfunction through antioxidative and antiapoptotic activities. These results may help patients to select a dietary supplement for diabetes when experiencing renal dysfunction.

Effects of Dexmedetomidine on the RhoA /ROCK/ Nox4 Signaling Pathway in Renal Fibrosis of Diabetic Rats

Objective

To investigate the effects and mechanisms of dexmedetomidine (Dex) on model rats of diabetic nephropathy (DN).

Methods

Rats were divided into NC, model, Dex-L (1μg/ kg), Dex-M (5μg/kg) and Dex-H (10μg/kg) groups. Rats in all groups except in the NC group were injected with streptozotocin (STZ) combined with right nephrectomy. Rats in Dex (1, 5 and 10μg/kg) groups received gavage with Dex (1, 5 and 10μg/kg). After 4 weeks, rats were sacrificed and kidneys were collected. HE staining was performed for a renal injury. Masson staining was applied to detect the fibrotic accumulation in rat kidney. Radioimmunoassay was used to test the renal function. Immunohistochemical method was used to detect protein expressions of RhoA, p-MYPT and Nox4 in rat kidney.

Results

Compared with the NC group, the levels of urine microalbumin in protein, α1-MG and β2-MG, renal fibrotic accumulation, RhoA, p-MYPT, Nox4 and α-SMA in model group increased significantly (P＜0.001, respectively). Compared with the model group, Dex low, medium and high groups improved the deposition of renal fiber in rats, inhibited the expression levels of microalbumin, α1-MG and β2-MG in urine and decreased expression of RhoA, p-MYPT, Nox4 and α-SMA proteins (P＜0.05, P＜0.01).

Conclusion

Dex is possible to inhibit the expression of α-SMA and renal fibrous substance deposition in rat kidney via RhoA/ROCK/Nox4 signaling pathway, thereby reducing early kidney damage in model rats.

PFOA and PFOS promote diabetic renal injury in vitro by impairing the metabolisms of amino acids and purines

BACKGROUND

Environmental pollutants, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), are common surfactants in various consumer products. Epidemiological studies have demonstrated the association of diabetic kidney diseases with PFOA and PFOS. However, mechanisms of metabolic alterations involved are still unclear.

METHODS

Considering their involvement of glomerular hemodynamics, rat mesangial cells (MCs) are used as an in vitro model of diabetic kidney diseases for exposure to PFOS/PFOA under diabetic condition. Non-targeted metabolomics studies based on liquid chromatography-high resolution mass spectrometry were conducted to determine how PFOA/PFOS promoted fibrotic and proinflammatory responses in the MCs under diabetic condition.

RESULTS

Exposure of PFOA/PFOS (10 μM) increased oxidative stress and the levels of fibrotic and proinflammatory markers in MCs under diabetic condition. We demonstrated for the first time that PFOA and PFOS altered amino acid biosynthesis, citrate cycle, and purine metabolism in MCs under diabetic condition. Compared with diabetic condition, the exposure of PFOA and PFOS under diabetic condition more significantly altered the levels of 13 intracellular metabolites, including L-tyrosine, L-phenylalanine, L-arginine, L-tryptophan, AMP, ADP, UMP, inosine, and hypoxanthine, which have been reported to be related to kidney injury. In addition, PFOA/PFOS treatment significantly altered the expression levels of key enzymes involved in these metabolisms. Treatment with L-tyrosine, L-phenylalanine, L-arginine, and L-tryptophan reduced the levels of fibrotic and inflammatory markers induced by PFOA/PFOS.

CONCLUSION

Our results suggest that under diabetic condition, exposure of PFOA or PFOS aggravated diabetic kidney injury in vitro by impairing metabolisms of amino acids and purines to induce more fibrosis and inflammation in MCs.

Long-Term Intensive Lifestyle Intervention Promotes Improvement of Stage III Diabetic Nephropathy

BACKGROUND Diabetic nephropathy (DN) is a potentially fatal complication of diabetes mellitus. While lifestyle changes can reduce diabetes risk, it is unclear whether improved lifestyle can slow or reverse DN progression. This study evaluated whether an intensive lifestyle intervention (IL-I) targeting weight loss and inflammation through increased physical activity and reduced caloric intake can delay DN progression. MATERIAL AND METHODS Patients were randomly divided into 2 groups. Both groups received diet and exercise guidelines, but one (IL-I) received more frequent external support than the other (control). We compared markers of metabolic and cardiovascular health, redox status, inflammation, and renal function between groups at 3 and 6 months. Metabolic and cardiovascular metrics included BMI, blood pressure, blood glycosylated hemoglobin (HbA1c), and serum HDL-cholesterol. Redox status was evaluated by serum superoxide dismutase (SOD) and the lipid oxidation product malondialdehyde (MDA), while inflammation was assessed by serum concentrations of IL-6 and TNF-alpha. Renal function was assessed by urine/serum 8-OHdG, albumin: creatinine ratio (ACR), and the renal fibrosis marker TGF-ß1. RESULTS Both groups demonstrated initial BMI reduction, lower HbA1c, and higher HDL-cholesterol, but changes were significantly larger in the IL-I group at 6 months. Blood pressure at 6 months was reduced only in the IL-I group. The IL-I group also achieved a greater sustained SOD increase and MDA reduction. Finally, only the IL-I group demonstrated significant reductions in urine ACR, serum/urine 8-OHdG, and plasma TGF-ß1. These indicators deteriorated after IL-I was stopped. CONCLUSIONS Lifestyle changes including exercise and diet can delay renal damage and promote improvement from DN.

Renoprotective effect of Zhenwu decoction against renal fibrosis by regulation of oxidative damage and energy metabolism disorder

Zhenwu decoction (ZWD) is a promising traditional Chinese prescription against renal fibrosis, while its underlying mechanism remains unclear. Rat model of renal fibrosis were established and divided into control group, model group, ZWD treatment group and enalapril maleate treatment group. Metabolic profiles on serum samples from each group were acquired by using ultra performance liquid chromatography coupled with quadrupole time-of-flight high-resolution mass spectrometry. Metabolomics combined with molecular biology were comparatively conducted on samples of various groups. Fifteen potential biomarkers were identified and these biomarkers are mainly phospholipids and fatty acids. The results showed renal fibrosis was associated with oxidative damage and energy metabolism disorder. The results of histopathology, biochemistry and metabolomics demonstrated that ZWD exhibited an efficient renoprotective effect by alleviating oxidative stress, increasing energy metabolism and regulating fibrotic cytokines. This study provided scientific support for the research and development of new drugs from traditional Chinese medicine.

A causal link between oxidative stress and inflammation in cardiovascular and renal complications of diabetes

Chronic renal and vascular oxidative stress in association with an enhanced inflammatory burden are determinant processes in the development and progression of diabetic complications including cardiovascular disease (CVD), atherosclerosis and diabetic kidney disease (DKD). Persistent hyperglycaemia in diabetes mellitus increases the production of reactive oxygen species (ROS) and activates mediators of inflammation as well as suppresses antioxidant defence mechanisms ultimately contributing to oxidative stress which leads to vascular and renal injury in diabetes. Furthermore, there is increasing evidence that ROS, inflammation and fibrosis promote each other and are part of a vicious connection leading to development and progression of CVD and kidney disease in diabetes.

Rhein lysinate protects renal function in diabetic nephropathy of KK/HlJ mice

The purpose of the present study was to assess the protective effects of rhein lysinate (RHL) in a KK/HlJ mouse model of diabetic nephropathy (DN) and to explore its mechanism of action. A total of 4 groups were established: C57BL/J control, the KK/HlJ model and 25 and 50 mg/kg/day RHL-treated KK/HlJ groups. The KK/HlJ mouse model of DN was established by streptozotocin injection, followed by maintenance on a specific diet. The albumin-to-creatinine ratio (ACR) was determined at 5 weeks and at 16 weeks, the kidneys were harvested, and morphological examination and immunohistochemical analysis were performed. The levels of malondialdehyde (MDA), as well as superoxide dismutase (SOD) and glutathione peroxidase (GSH-px) activities in the kidneys were measured using appropriate assay kits. The expression of inflammatory factors and associated proteins was analyzed using western blot analysis. At 5 weeks, the levels of ACR in KK/HlJ mice were increased, which was inhibited by treatment with RHL. Treatment with RHL (50 mg/kg/day) decreased the body weight of KK/HlJ mice. Compared with the C57BL/J control, the KK/HlJ model mice had a significantly lower activity of SOD and GSH-px in the kidneys, but had significantly higher levels of MDA. Treatment of KK/HlJ mice with RHL significantly increased the activities SOD and GSH-px, and reduced the MAD level in the kidneys. Renal tubular epithelial cell edema was observed in KK/HlJ mice but not in C57BL/J mice. RHL decreased the incidence of renal tubular epithelial cell edema and significantly decreased the expression of TNF-α and IL-6 as well as the expression and phosphorylation of NF-κB in the kidneys. Therefore, DN is associated with the expression of inflammatory factors, renal tubular epithelial cell edema and renal dysfunction in KK/HlJ mice. RHL improves renal function by decreasing kidney inflammation.

Disease-syndrome combination modeling: metabolomic strategy for the pathogenesis of chronic kidney disease

Conventional disease animal models have limitations on the conformity to the actual clinical situation. Disease-syndrome combination (DS) modeling may provide a more efficient strategy for biomedicine research. Disease model and DS model of renal fibrosis in chronic kidney disease were established by ligating the left ureter and by ligating unilateral ureteral combined with exhaustive swimming, respectively. Serum metabolomics was conducted to evaluate disease model and DS model by using ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Potential endogenous biomarkers were identified by multivariate statistical analysis. There are no differences between two models regarding their clinical biochemistry and kidney histopathology, while metabolomics highlights their difference. It is found that abnormal sphingolipid metabolism is a common characteristic of both models, while arachidonic acid metabolism, linolenic acid metabolism and glycerophospholipid metabolism are highlighted in DS model. Metabolomics is a promising approach to evaluate experiment animal models. DS model are comparatively in more coincidence with clinical settings, and is superior to single disease model for the biomedicine research.

Endothelial Progenitor Cells in Diabetic Microvascular Complications: Friends or Foes?

Despite being featured as metabolic disorder, diabetic patients are largely affected by hyperglycemia-induced vascular abnormality. Accumulated evidence has confirmed the beneficial effect of endothelial progenitor cells (EPCs) in coronary heart disease. However, antivascular endothelial growth factor (anti-VEGF) treatment is the main therapy for diabetic retinopathy and nephropathy, indicating the uncertain role of EPCs in the pathogenesis of diabetic microvascular disease. In this review, we first illustrate how hyperglycemia induces metabolic and epigenetic changes in EPCs, which exerts deleterious impact on their number and function. We then discuss how abnormal angiogenesis develops in eyes and kidneys under diabetes condition, focusing on “VEGF uncoupling with nitric oxide” and “competitive angiopoietin 1/angiopoietin 2” mechanisms that are shared in both organs. Next, we dissect the nature of EPCs in diabetic microvascular complications. After we overview the current EPCs-related strategies, we point out new EPCs-associated options for future exploration. Ultimately, we hope that this review would uncover the mysterious nature of EPCs in diabetic microvascular disease for therapeutics.

New molecular insights in diabetic nephropathy

Diabetes mellitus represents one of the major causes of functional kidney impairment. The review highlights the most significant steps made over the last decades in understanding the molecular basis of diabetic nephropathy (DN), which may provide reliable biomarkers for early diagnosis and prognosis, along with new molecular targets for personalized medicine. There is an increased interest in developing new therapeutic strategies to slow DN progression for improving patients' quality of life and reducing all-cause morbidity and disease-associated mortality. It is highly important to have a science-based medical attitude when facing diabetic patients with associated comorbidities and risk of rapid evolution toward end-stage renal disease. The data discussed herein were mainly from MEDLINE and PubMed articles published in English from 1990 to 2015 and from up-to-date. The search term was "diabetic nephropathy and oxidative stress".

G protein-coupled receptors: potential therapeutic targets for diabetic nephropathy

Diabetic nephropathy, a lethal microvascular complication of diabetes mellitus, is characterized by progressive albuminuria, excessive deposition of extracellular matrix, thickened glomerular basement membrane, podocyte abnormalities, and podocyte loss. The G protein-coupled receptors (GPCRs) have attracted considerable attention in diabetic nephropathy, but the specific effects have not been elucidated yet. Likewise, abnormal signaling pathways are closely interrelated to the pathologic process of diabetic nephropathy, despite the fact that the mechanisms have not been explored clearly. Therefore, GPCRs and its mediated signaling pathways are essential for priority research, so that preventative strategies and potential targets might be developed for diabetic nephropathy. This article will give us comprehensive overview of predominant GPCR types, roles, and correlative signaling pathways in diabetic nephropathy.

Non-Alcoholic Fatty Liver Disease Is a Risk Factor for the Development of Diabetic Nephropathy in Patients with Type 2 Diabetes Mellitus

Background

Non-alcoholic fatty liver disease (NAFLD) is prevalent in individuals with type 2 diabetes mellitus (T2DM). Diabetic nephropathy (DN) is also associated with T2DM. However, little is known about the interaction between these conditions in patients with T2DM.

Objective

To examine the association between NAFLD and DN in patients with T2DM.

Methods

This retrospective study included patients seen between January 2006 and July 2014.T2DM patients were divided into two groups based on NAFLD status (with NAFLD = group A; without = group B). The cumulative incidence of DN and chronic kidney disease (CKD) staging were compared between the two groups. Liver fat content was examined in some patients. Associations among NAFLD, other factors,and DN were analyzed by the additive interaction method.

Results

Cumulative incidence of DN in patients from group A (58.58%) was higher than in group B (37.22%) (P = 0.005). In both groups, the number of DN patients with CKD stage 1 was greater than the number of patients with stages 2–5. Increased liver fat content was associated with increased occurrence of severe and mild albuminuria and decreased glomerular filtration rate (GFR). There were positive correlations between NAFLD and insulin resistance index (HOMA-IR), free fatty acids (FFA), tumor necrosis factor-α (TNF-α), omentin-1, visceral fat area, homocysteine (HCY), and serum uric acid (UA).

Conclusion

NAFLD might be a risk factor for DN. Elevated liver fat content could be associated with higher DN burden.

Renin-Angiotensin-Aldosterone System Blockade in Diabetic Nephropathy. Present Evidences

Diabetic Kidney Disease (DKD) is the leading cause of chronic kidney disease in developed countries and its prevalence has increased dramatically in the past few decades. These patients are at an increased risk for premature death, cardiovascular disease, and other severe illnesses that result in frequent hospitalizations and increased health-care utilization. Although much progress has been made in slowing the progression of diabetic nephropathy, renal dysfunction and the development of end-stage renal disease remain major concerns in diabetes. Dysregulation of the renin-angiotensin-aldosterone system (RAAS) results in progressive renal damage. RAAS blockade is the cornerstone of treatment of DKD, with proven efficacy in many arenas. The theoretically-attractive option of combining these medications that target different points in the pathway, potentially offering a more complete RAAS blockade, has also been tested in clinical trials, but long-term outcomes were disappointing. This review examines the “state of play” for RAAS blockade in DKD, dual blockade of various combinations, and a perspective on its benefits and potential risks.

Diabetic nephropathy: What does the future hold?

The consensus management of diabetic nephropathy (DN) in 2015 involves good control of glycaemia, dyslipidaemia and blood pressure (BP). Blockade of the renin-angiotensin-aldosterone system using angiotensin-converting enzyme inhibitors, angiotensin-2 receptor blockers or mineralocorticoid inhibitors are key therapeutic approaches, shown to be beneficial once overt nephropathy is manifest, as either, or both, of albuminuria and loss of glomerular filtration rate. Some significant additional clinical benefits in slowing the progression of DN was reported from the Remission clinic experience, where simultaneous intensive control of BP, tight glycaemic control, weight loss, exercise and smoking cessation were prioritised in the management of DN. This has not proved possible to translate to more conventional clinical settings. This review briefly looks over the history and limitations of current therapy from landmark papers and expert reviews, and following an extensive PubMed search identifies the most promising clinical biomarkers (both established and proposed). Many challenges need to be addressed urgently as in order to obtain novel therapies in the clinic; we also need to examine what we mean by remission, stability and progression of DN in the modern era.

Additive protection by LDR and FGF21 treatment against diabetic nephropathy in type 2 diabetes model

The onset of diabetic nephropathy (DN) is associated with both systemic and renal changes. Fibroblast growth factor (FGF)-21 prevents diabetic complications mainly by improving systemic metabolism. In addition, low-dose radiation (LDR) protects mice from DN directly by preventing renal oxidative stress and inflammation. In the present study, we tried to define whether the combination of FGF21 and LDR could further prevent DN by blocking its systemic and renal pathogeneses. To this end, type 2 diabetes was induced by feeding a high-fat diet for 12 wk followed by a single dose injection of streptozotocin. Diabetic mice were exposed to 50 mGy LDR every other day for 4 wk with and without 1.5 mg/kg FGF21 daily for 8 wk. The changes in systemic parameters, including blood glucose levels, lipid profiles, and insulin resistance, as well as renal pathology, were examined. Diabetic mice exhibited renal dysfunction and pathological abnormalities, all of which were prevented significantly by LDR and/or FGF21; the best effects were observed in the group that received the combination treatment. Our studies revealed that the additive renal protection conferred by the combined treatment against diabetes-induced renal fibrosis, inflammation, and oxidative damage was associated with the systemic improvement of hyperglycemia, hyperlipidemia, and insulin resistance. These results suggest that the combination treatment with LDR and FGF21 prevented DN more efficiently than did either treatment alone. The mechanism behind these protective effects could be attributed to the suppression of both systemic and renal pathways.

Autophagy-Lysosome Pathway in Renal Tubular Epithelial Cells Is Disrupted by Advanced Glycation End Products in Diabetic Nephropathy

It has been suggested that autophagy protects renal tubular epithelial cells (TECs) from injury in diabetic nephropathy (DN). However, the manner in which the autophagy-lysosome pathway is changed in this state remains unclear. In this study of DN, we investigated the autophagic activity and lysosomal alterations in vivo and in vitro. We found that autophagic vacuoles and SQSTM1-positive proteins accumulated in TECs from patients with DN and in human renal tubular epithelial cell line (HK-2 cells) treated with advanced glycation end products (AGEs), the important factors that involved in the pathogenesis of DN. In HK-2 cells, exposure to AGEs caused a significant increase in autophagosomes but a marked decrease in autolysosomes, and the lysosomal turnover of LC3-II was not observed, although LC3-II puncta were co-localized with the irregular lysosomal-associated membrane protein1 granules after AGEs treatment. Furthermore, lysosomal membrane permeabilization was triggered by AGEs, which likely resulted in a decrease in the enzymatic activities of cathepsin B and cathepsin L, the defective acidification of lysosomes, and suppression of the lysosomal degradation of DQ-ovalbumin. Oxidative stress evoked by AGEs-receptor for AGE interaction likely played an important role in the lysosomal dysfunction. Additionally, ubiquitinated proteins were co-localized with SQSTM1-positive puncta and accumulated in HK-2 cells after exposure to AGEs, indicating blocked degradation of SQSTM1-positive and ubiquitinated aggregates. Taken together, the results show that lysosomal membrane permeabilization and lysosomal dysfunction are triggered by AGEs, which induce autophagic inactivation in TECs from patients with DN. Disruption of the autophagy-lysosome pathway should be focused when studying the mechanisms underlying DN.

Angiotensin I converting enzyme inhibitory peptides obtained after in vitro hydrolysis of pea (Pisum sativum var. Bajka) globulins

Pea seeds represent a valuable source of active compounds that may positively influence health. In this study, the pea globulins were digested in vitro under gastrointestinal condition and potentially bioaccessible angiotensin I converting enzyme (ACE) inhibitory peptides were identified. The degree of hydrolysis after pepsin, 14.42%, and pancreatin, 30.65%, were noted. The peptides with the highest ACE inhibitory properties were separated using ion exchange chromatography on DEAE-cellulose. Thirteen peptides fractions were obtained but only four showed potential antihypertensive properties. The highest inhibitory activity was determined for the fraction F8 (IC50 = 0.0014 mg/mL). This fraction was separated on Sephadex G10 and two peptide fractions were obtained. The peptides fraction (B) with the highest ACE inhibitory activity (IC50 = 0.073 mg/mL) was identified by ESI-MS/MS. The sequences of ACE inhibitory peptides were GGSGNY, DLKLP, GSSDNR, MRDLK, and HNTPSR. Based on Lineweaver-Burk plots for the fraction B, the kinetic parameters as K m, Vmax, and K i and mode of inhibition were determined. This fraction belongs to uncompetitive inhibitor of ACE activity. The seeds of pea are the source of precursor protein, which releases the ACE inhibitory peptides as a result of enzymatic hydrolysis.