Insulin deficiency induces rat renal mesangial cell dysfunction via activation of IGF-1/IGF-1R pathway

Human umbilical cord mesenchymal stem cells attenuate diabetic nephropathy through the IGF1R-CHK2-p53 signalling axis in male rats with type 2 diabetes mellitus

Diabetes mellitus (DM) is a disease syndrome characterized by chronic hyperglycaemia. A long-term high-glucose environment leads to reactive oxygen species (ROS) production and nuclear DNA damage. Human umbilical cord mesenchymal stem cell (HUcMSC) infusion induces significant antidiabetic effects in type 2 diabetes mellitus (T2DM) rats. Insulin-like growth factor 1 (IGF1) receptor (IGF1R) is important in promoting glucose metabolism in diabetes; however, the mechanism by which HUcMSC can treat diabetes through IGF1R and DNA damage repair remains unclear. In this study, a DM rat model was induced with high-fat diet feeding and streptozotocin (STZ) administration and rats were infused four times with HUcMSC. Blood glucose, interleukin-6 (IL-6), IL-10, glomerular basement membrane, and renal function were examined. Proteins that interacted with IGF1R were determined through coimmunoprecipitation assays. The expression of IGF1R, phosphorylated checkpoint kinase 2 (p-CHK2), and phosphorylated protein 53 (p-p53) was examined using immunohistochemistry (IHC) and western blot analysis. Enzyme-linked immunosorbent assay (ELISA) was used to determine the serum levels of 8-hydroxydeoxyguanosine (8-OHdG). Flow cytometry experiments were used to detect the surface markers of HUcMSC. The identification of the morphology and phenotype of HUcMSC was performed by way of oil red "O" staining and Alizarin red staining. DM rats exhibited abnormal blood glucose and IL-6/10 levels and renal function changes in the glomerular basement membrane, increased the expression of IGF1 and IGF1R. IGF1R interacted with CHK2, and the expression of p-CHK2 was significantly decreased in IGF1R-knockdown cells. When cisplatin was used to induce DNA damage, the expression of p-CHK2 was higher than that in the IGF1R-knockdown group without cisplatin treatment. HUcMSC infusion ameliorated abnormalities and preserved kidney structure and function in DM rats. The expression of IGF1, IGF1R, p-CHK2, and p-p53, and the level of 8-OHdG in the DM group increased significantly compared with those in the control group, and decreased after HUcMSC treatment. Our results suggested that IGF1R could interact with CHK2 and mediate DNA damage. HUcMSC infusion protected against kidney injury in DM rats. The underlying mechanisms may include HUcMSC-mediated enhancement of diabetes treatment via the IGF1R-CHK2-p53 signalling pathway.

Role of microRNA-505 during tumor progression and metastasis

Late diagnosis of cancer in advanced stages due to the lack of screening methods is considered as the main cause of poor prognosis and high mortality rate among these patients. Therefore, it is necessary to investigate the molecular tumor biology in order to introduce biomarkers that can be used in cancer screening programs and early diagnosis. MicroRNAs (miRNAs) have key roles in regulation of the cellular pathophysiological processes. Due to the high stability of miRNAs in body fluids, they are widely used as the non-invasive tumor markers. According to the numerous reports about miR-505 deregulation in a wide range of cancers, we investigated the role of miR-505 during tumor progression. It was shown that miR-505 mainly has the tumor suppressor functions through the regulation of signaling pathways, chromatin remodeling, and cellular metabolism. This review has an effective role in introducing miR-505 as a suitable marker for the early cancer diagnosis.

Monocarboxylate transporter 4 promotes the migration of non‑cancerous L929 fibroblast cells by activating the IGF1/IGF1R/PIK3R3/SGK1 axis

The tumor microenvironment (TME) and Warburg effect are critical for the regulation of tumor metastasis. The monocarboxylate transporter (MCT) family members, particularly MCT4, which is encoded by the solute carrier family 16 member 3 gene, play an important role in the regulation of the TME and mediation of the Warburg effect by transporting lactate out of cancer cells. Migration and invasion are two key features of metastasis. Few studies have investigated the mechanism by which MCT4 promotes cell migration, and the suggested mechanisms by which MCT4 promotes migration vary in different tumor cell models. The purpose of the present study was to use non-cancerous cells as a research model to investigate the specific mechanism underlying the promotion of migration by MCT4. In a previous study, murine L929 cells overexpressing human MCT4 (MCT4-L929 cells) were generated and MCT4 was demonstrated to promote the migration and invasion of these non-cancerous cells. In the present study, MCT4-L929 cells and control-L929 cells were used to investigate the potential pathways and mechanisms through which MCT4 promotes cell migration. RNA sequencing analysis revealed 872 differentially expressed genes, comprising 337 and 535 upregulated and downregulated genes, respectively, in the MCT4-L929 cells. Reverse transcription-quantitative analysis and western blotting revealed that MCT4 overexpression increased the transcription and protein levels of insulin-like growth factor 1 (IGF1). In a wound healing assay, the migration of exogenous mouse IGF1-treated control-L929 cells was similar to that of MCT4-L929 cells. Additionally, the inhibition of IGF1 receptor (IGF1R) or serum/glucocorticoid regulated kinase 1 (SGK1), a downstream protein in the IGF1 and phosphoinositide 3-kinase PI3K regulatory subunit 3 (PIK3R3) pathways, in MCT4-L929 cells mitigated the cell migration-promoting effect of MCT4. These novel findings suggest that MCT4 may promote the migration of L929 fibroblast cells via activation of the IGF1/IGF1R/PIK3R3/SGK1 axis.

Uncovering the mechanism of resveratrol in the treatment of diabetic kidney disease based on network pharmacology, molecular docking, and experimental validation

BACKGROUND

Diabetic kidney disease (DKD) has been the leading cause of chronic kidney disease in developed countries. Evidence of the benefits of resveratrol (RES) for the treatment of DKD is accumulating. However, comprehensive therapeutic targets and underlying mechanisms through which RES exerts its effects against DKD are limited.

METHODS

Drug targets of RES were obtained from Drugbank and SwissTargetPrediction Databases. Disease targets of DKD were obtained from DisGeNET, Genecards, and Therapeutic Target Database. Therapeutic targets for RES against DKD were identified by intersecting the drug targets and disease targets. GO functional enrichment analysis, KEGG pathway analysis, and disease association analysis were performed using the DAVID database and visualized by Cytoscape software. Molecular docking validation of the binding capacity between RES and targets was performed by UCSF Chimera software and SwissDock webserver. The high glucose (HG)-induced podocyte injury model, RT-qPCR, and western blot were used to verify the reliability of the effects of RES on target proteins.

RESULTS

After the intersection of the 86 drug targets and 566 disease targets, 25 therapeutic targets for RES against DKD were obtained. And the target proteins were classified into 6 functional categories. A total of 11 cellular components terms and 27 diseases, and the top 20 enriched biological processes, molecular functions, and KEGG pathways potentially involved in the RES action against DKD were recorded. Molecular docking studies showed that RES had a strong binding affinity toward PPARA, ESR1, SLC2A1, SHBG, AR, AKR1B1, PPARG, IGF1R, RELA, PIK3CA, MMP9, AKT1, INSR, MMP2, TTR, and CYP2C9 domains. The HG-induced podocyte injury model was successfully constructed and validated by RT-qPCR and western blot. RES treatment was able to reverse the abnormal gene expression of PPARA, SHBG, AKR1B1, PPARG, IGF1R, MMP9, AKT1, and INSR.

CONCLUSIONS

RES may target PPARA, SHBG, AKR1B1, PPARG, IGF1R, MMP9, AKT1, and INSR domains to act as a therapeutic agent for DKD. These findings comprehensively reveal the potential therapeutic targets for RES against DKD and provide theoretical bases for the clinical application of RES in the treatment of DKD.

AG1024, an IGF-1 receptor inhibitor, ameliorates renal injury in rats with diabetic nephropathy via the SOCS/JAK2/STAT pathway

Insulin-like-growth factor-1 (IGF-1) is the ligand for insulin-like growth factor-1 receptor (IGF-1R), and the roles of IGF-1/IGF-1R in diabetic nephropathy (DN) are well-characterized previously. However, the biological functions of AG1024 (an IGF-1R inhibitor) in DN remain unknown. This study investigates the roles and related mechanisms of AG-1024 in DN. The experimental DN was established via intraperitoneal injection of streptozotocin, and STZ-induced diabetic rats were treated with AG1024 (20 mg/kg/day) for 8 weeks. The 24 h proteinuria, blood glucose level, serum creatinine, and blood urea nitrogen were measured for biochemical analyses. The increase in 24 h proteinuria, blood glucose level, serum creatinine, and blood urea of DN rats were conspicuously abated by AG1024. After biochemical analyses, the renal tissue specimens were collected, and as revealed by hematoxylin and eosin staining and Masson staining, AG-1024 mitigated typical renal damage and interstitial fibrosis in DN rats. Then, the anti-inflammatory effect of AG-1024 was assessed by western blotting and ELISA. Mechanistically, AG-1024 upregulated SOCS1 and SOCS3 expression and decreased phosphorylated JAK2, STAT1, and STAT3, as shown by western blotting. Collectively, AG-1024 (an IGF-1R inhibitor) ameliorates renal injury in experimental DN by attenuating renal inflammation and fibrosis via the SOCS/JAK2/STAT pathway.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

The Interplay of NEAT1 and miR-339-5p Influences on Mesangial Gene Expression and Function in Various Diabetic-Associated Injury Models

Mesangial cells (MCs), substantial cells for architecture and function of the glomerular tuft, take a key role in progression of diabetic kidney disease (DKD). Despite long standing researches and the need for novel therapies, the underlying regulatory mechanisms in MCs are elusive. This applies in particular to long non-coding RNAs (lncRNA) but also microRNAs (miRNAs). In this study, we investigated the expression of nuclear paraspeckle assembly transcript 1 (NEAT1), a highly conserved lncRNA, in several diabetes in-vitro models using human MCs. These cells were treated with high glucose, TGFβ, TNAα, thapsigargin, or tunicamycin. We analyzed the implication of NEAT1 silencing on mesangial cell migration, proliferation, and cell size as well as on mRNA and miRNA expression. Here, the miRNA hsa-miR-339-5p was not only identified as a potential interaction partner for NEAT1 but also for several coding genes. Furthermore, overexpression of hsa-miR-339-5p leads to a MC phenotype comparable to a NEAT1 knockdown. In-silico analyses also underline a relevant role of NEAT1 and hsa-miR-339-5p in mesangial physiology, especially in the context of DKD.

Increased activity of the metalloproteinase PAPP-A promotes diabetes-induced glomerular hypertrophy

BACKGROUND

Diabetic nephropathy (DN) is a serious complication of diabetes and a common cause of end stage renal failure. Insulin-like growth factor (IGF)-signaling has been implicated in DN, but is mechanistically poorly understood. Here, we assessed the activity of the metalloproteinase PAPP-A, an activator of IGF activity, and its possible interaction with the endogenous PAPP-A inhibitors stanniocalcin (STC)-1 and -2 in the mammalian kidney under normal and hyperglycemic conditions.

METHODS AND RESULTS

Immunohistochemistry demonstrated that PAPP-A, its proteolytic substrate IGF binding protein-4, STC1 and STC2 are present in the human kidney. Endogenous inhibited complexes of PAPP-A (PAPP-A:STC1 and PAPP-A:STC2) were demonstrated in media conditioned by human mesangial cells (HMCs), suggesting that PAPP-A activity is regulated by the STCs in kidney tissue. A method for the selective detection of active PAPP-A in tissue was developed and a significant increase in glomerular active PAPP-A in human diabetic kidney relative to normal was observed. In DN patients, the estimated glomerular filtration rate correlated with PAPP-A activity. In diabetic mice, glomerular growth was reduced when PAPP-A activity was antagonized by adeno-associated virus-mediated overexpression of STC2.

CONCLUSION

We propose that PAPP-A activity in renal tissue is precisely balanced by STC1 and STC2. An imbalance in this equilibrium causing increased PAPP-A enzymatic activity potentially contributes to the development of DN, and thus, therapeutic targeting of PAPP-A activity may represent a novel strategy for its treatment.

Correlation analysis of serum IGF-1 and IL-6 and urinary albumin/creatinine ratio in patients with type 2 diabetic kidney disease

OBJECTIVES

Diabetic kidney disease (DKD) is one of the most common chronic complications in diabetic patients, and there are major limitations in its pathological diagnosis. This study's objectives were to examine the changes in serum insulin-like growth factor-1 (IGF-1) and interleukin-6 (IL-6) levels in DKD patients with various urinary albumin/creatinine ratio (ACR) and to evaluate the utility of these two biological markers in the clinical diagnosis of the condition.

METHODS

We chose 80 type 2 diabetic patients as the experimental group and 20 healthy normal participants as the control group. The experimental group was split into three groups based on the ACR range: diabetes without nephropathy group (ACR < 30 mg/g), microalbuminuric group (30 < ACR < 300 mg/g), and macroalbuminuric group (ACR > 300 mg/g). The levels of serum IL-6 and IGF-1 were assessed in each trial participant.

RESULTS

Serum IGF-1 was higher in the experimental group than in the control group (P < 0.01), and serum IL-6 levels were also higher than in the control group (P < 0.001). In DKD patients, serum levels of IL-6 and IGF-1 tended to rise when ACR levels rose. By Pearson correlation analysis, serum IGF-1 and IL-6 were positively correlated with ACR (r = 0.765 and r = 0.651, all P < 0.001) and negatively correlated with eGFR (r = -0.389 and r = -0.364, all P < 0.01). Additionally, the receiver operating characteristic (ROC) characteristic curve showed that the area under the curve (AUC) values for serum IGF-1 and IL-6 were 0.9056 and 0.7850, respectively, while the AUR value for both combined was 0.9367.

CONCLUSION

Serum IGF-1 and IL-6 levels can be used to diagnose DKD, and the combined analysis of these two indicators can improve the sensitivity and specificity of the disease diagnosis.

P2X7 receptor-nitric oxide interaction mediates apoptosis in mouse immortalized mesangial cells exposed to high glucose

INTRODUCTION

Diabetes mellitus (DM) is a chronic disease characterized by hyperglycemia that leads to diabetic nephropathy (DN). We showed that P2X7, a purinergic receptor, was highly expressed in DM; however, when oxidative stress was controlled, renal NO recovered, and the activation of this receptor remained significantly reduced. The aim of this study was to assess the influence of NO on the P2X7 and apoptosis in mouse immortalized mesangial cells (MiMC) cultured in high glucose (HG) medium.

METHODS

MiMCs were cultured with DMEM and exposed to normal glucose (NG), mannitol (MA), or HG. Cell viability was assessed by an automated counter. Supernatants were collected for NO quantification, and proteins were extracted for analysis of NO synthases (iNOS and eNOS), caspase-3, and P2X7.

RESULTS

Cell viability remained above 90% in all groups. There was a significant increase in the proliferation of cells in HG compared to MA and NG. NO, iNOS, caspase-3, and P2X7 were significantly increased in HG compared to NG and MA, with no changes in eNOS. We observed that there was a strong and significant correlation between P2X7 and NO.

DISCUSSION

The main finding was that the production of NO by iNOS was positively correlated with the increase of P2X7 in MCs under HG conditions, showing that there is a common stimulus between them and that NO interacts with the P2X7 pathway, contributing to apoptosis in experimental DM. These findings could be relevant to studies of therapeutic targets for the prevention and/or treatment of hyperglycemia-induced kidney damage to delay DN progression.

IGF-1/IGF-1R blockade ameliorates diabetic kidney disease through normalizing Snail1 expression in a mouse model

This study investigated the role of insulin-like growth factor-1/insulin-like growth factor-1 receptor (IGF-1/IGF-1R) in the genesis and progression of diabetic kidney disease (DKD) in a streptozotocin (STZ)-induced mouse diabetes model. We showed elevated IGF-1 expression in the DKD kidneys after 16 wk of diabetic onset. Intraperitoneal administration of IGF-1R inhibitor (glycogen synthase kinase-3β, GSK4529) from week 8 to week 16 postdiabetes induction ameliorated urinary albumin excretion and kidney histological changes due to diabetes, including amelioration of glomerulomegaly, inflammatory infiltration, and tubulointerstitial fibrosis. The GSK4529 treatment also attenuated alterations in renal tubular expression of E-cad and matrix protein fibronectin. Moreover, renal fibrosis in DKD (without treatment) was associated with Snail1 overexpression that was effectively prevented by IGF-1R inhibition. Further experiments in cultured renal epithelial cells (NRK) showed that IGF-1 silencing reproduced in vivo effects of IGF-1R inhibition with markedly attenuated Snail1 expression and near normalization of the Ecad1 and fibronectin expression pattern. Further Snail1 silencing prevented high-glucose-induced changes without affecting IGF-1 expression, consistent with Snail1 acting downstream to IGF-1. The antifibrotic effects were also shown with benazepril or insulin treatment but to a much lesser degree. In summary, in STZ-induced diabetic mice, activation of IGF-1 in diabetic kidneys induces fibrogenesis through Snail1 upregulation. The diabetes-related histological and functional changes, as well as fibrogenesis, can be attenuated by IGF-1/IGF-1R inhibition.

Catalpol in Diabetes and its Complications: A Review of Pharmacology, Pharmacokinetics, and Safety

This review aimed to provide a general view of catalpol in protection against diabetes and diabetic complications, as well as its pharmacokinetics and safety concerns. The following databases were consulted with the retrieval of more than 100 publications through June 2019: PubMed, Chinese National Knowledge Infrastructure, WanFang Data, and web of science. Catalpol exerts an anti-diabetic effect in different animal models with an oral dosage ranging from 2.5 to 200 mg/kg in rats and 10 to 200 mg/kg in mice. Besides, catalpol may prevent the development of diabetic complications in kidney, heart, central nervous system, and bone. The underlying mechanism may be associated with an inhibition of inflammation, oxidative stress, and apoptosis through modulation of various cellular signaling, such as AMPK/PI3K/Akt, PPAR/ACC, JNK/NF-κB, and AGE/RAGE/NOX4 signaling pathways, as well as PKCγ and Cav-1 expression. The pharmacokinetic profile reveals that catalpol could pass the blood-brain barrier and has a potential to be orally administrated. Taken together, catalpol is a well-tolerated natural compound with promising pharmacological actions in protection against diabetes and diabetic complications via multi-targets, offering a novel scaffold for the development of anti-diabetic drug candidate. Further prospective and well-designed clinical trials will shed light on the potential of clinical usage of catalpol.

MiR-505 suppressed the growth of hepatocellular carcinoma cells via targeting IGF-1R

Hepatocellular carcinoma (HCC) is one of the most common cancers globally. An increasing body of evidence has demonstrated the critical function of microRNAs (miRNAs) in the initiation and progression of human cancers. Here, we showed that miR-505 was down-regulated in HCC tissues and cell lines. Reduced expression of miR-505 was significantly correlated with the worse prognosis of HCC patients. Overexpression of miR-505 suppressed the proliferation, colony formation and induced apoptosis of both HepG2 and Huh7 cells. Further mechanism study uncovered that miR-505 bound the 3'-untranslated region (3'-UTR) of the insulin growth factor receptor (IGF-1R) and inhibited the expression of IGF-1R in HCC cells. The down-regulation of IGF-1R by miR-505 further suppressed the phosphorylation of AKT at the amino acid S473. Consistently, the abundance of glucose transporter (GLUT) 1 (GLUT1) was reduced with the overexpression of miR-505. Down-regulation of GLUT1 by miR-505 consequently attenuated the glucose uptake, lactate production and ATP generation of HCC cells. Collectively, our results demonstrated the tumor suppressive function of miR-505 possibly via inhibiting the glycolysis of HCC cells. These findings suggested miR-505 as an interesting target for designing anti-cancer strategy in HCC.

Knockdown of IGF-1R Triggers Viral RNA Sensor MDA5- and RIG-I-Mediated Mitochondrial Apoptosis in Colonic Cancer Cells

The important role of insulin-like growth factor-1 receptor (IGF-1R) in tumorigenesis has been well established. The classical model involves IGF-1R binding to IGF-1/2, the following activation of PI3K-Akt-signaling cascades, driving cell proliferation and apoptosis inhibition. Here we report a new signal transduction pathway of IGF-1R in the intestinal epithelium. Using heterozygous knockout mice (Igf1r^+/-), we analyzed the expressions of viral RNA sensors MDA5 and RIG-I in the intestinal epithelium. Igf1r^+/- mice exhibited higher MDA5 and RIG-I than wild-type (WT) mice, indicating that knockdown of IGF-1R could trigger MDA5 and RIG-I. IGF-1R knockdown-triggered MDA5 and RIG-I were further investigated in human colonic cancer cells. Increased MDA5 and RIG-I were clearly seen in the cytoplasm in cancer cells as well as normal human colonic cells with silenced IGF-1R. Notably, the upregulations of MDA5 and RIG-I was not affected by blockage of the PI3K-Akt pathway with LY294002. These results suggested a new signal transduction pathway of IGF-1R. Importantly, IGF-1R knockdown-triggered MDA5 and RIG-I resulted in colorectal cancer apoptosis through activation of the mitochondrial pathway. These in vitro observations were evidenced in the azoxymethane (AOM)-dextran sulfate sodium (DSS) colorectal cancer model of mice. In conclusion, knockdown of IGF-1R triggers viral RNA sensor MDA5- and RIG-I-mediated mitochondrial apoptosis in cancer cells.

Ramipril can alleviate the accumulation of renal mesangial matrix in rats with diabetic nephropathy by inhibiting insulin-like growth factor-1

Purpose

To investigate the impact of Ramipril (RAM) on the expressions of insulin-like growth factor-1 (IGF-1) and renal mesangial matrix (RMM) in rats with diabetic nephropathy (DN).

Methods

The Sprague Dawley rats were divided into normal control (NC) group (n = 12), DN group (n = 11), and DN+RAM group (n = 12). The ratio of renal weight to body weight (RBT), fasting blood glucose (FBG), HbA1c, 24-h urine protein (TPU), blood urea nitrogen (BUN), creatinine (Cr), renal pathological changes, the levels of IGF-1, fibronectin (FN), type IV collagen (Col-IV), and matrix metalloproteinases (MMP)-2 were compared among the groups.

Results

Compared with NC group, the RBT, FBG, HbA1c, TPU, BUN, Cr, and RMM in DN group were significantly increased (P < 0.05), the IGF-1, FN, and Col-IV were significantly upregulated (P < 0.05), while MMP was significantly downregulated (P < 0.05). Compared with DN group, the indexes except for the FBG and HbA1c in DN+RAM group were significantly improved (P < 0.05), among which IGF-1 exhibited significant positive correlation with TPU(r=0.937), FN(r=0.896) and Col-IV(r=0.871), while significant negative correlation with MMP-2 (r=-0.826) (P<0.05).

Conclusion

RAM may protect the kidneys by suppressing IGF-1 and mitigating the accumulation of RMM.

SND p102 promotes extracellular matrix accumulation and cell proliferation in rat glomerular mesangial cells via the AT1R/ERK/Smad3 pathway

SND p102 was first described as a transcriptional co-activator, and subsequently determined to be a co-regulator of Pim-1, STAT6 and STAT5. We previously reported that SND p102 expression was increased in high glucose-treated mesangial cells (MCs) and plays a role in the extracellular matrix (ECM) accumulation of MCs by regulating the activation of RAS. In this study, we further examined the roles of SND p102 in diabetic nephropathy (DN)-induced glomerulosclerosis. Rats were injected with STZ (50 mg/kg, ip) to induce diabetes. MCs or isolated glomeruli were cultured in normal glucose (NG, 5.5 mmol/L)- or high glucose (HG, 25 mmol/L)-containing DMEM. We found that SND p102 expression was significantly increased in the diabetic kidneys, as well as in HG-treated isolated glomeruli and MCs. In addition, HG treatment induced significant fibrotic changes in MCs evidenced by enhanced protein expression of TGF-β, fbronectin and collagen IV, and significantly increased the proliferation of MCs. We further revealed that overexpression of SND p102 significantly increased the protein expression of angiotensin II (Ang II) type 1 receptor (AT1R) in MCs by increasing its mRNA levels via directly targeting the AT1R 3'-UTR, which resulted in activation of the ERK/Smad3 signaling and subsequently promoted the up-regulation of fbronectin, collagen IV, and TGF-β in MCs, as well as the cell proliferation. These results demonstrate that SND p102 is a key regulator of AT1R-mediating ECM synthesis and cell proliferation in MCs. Thus, small molecule inhibitors of SND p102 may be a novel therapeutic strategy for DN.

Inflammation-activated CXCL16 pathway contributes to tubulointerstitial injury in mouse diabetic nephropathy

Inflammation and lipid disorders play crucial roles in synergistically accelerating the progression of diabetic nephropathy (DN). In this study we investigated how inflammation and lipid disorders caused tubulointerstitial injury in DN in vivo and in vitro. Diabetic db/db mice were injected with 10% casein (0.5 mL, sc) every other day for 8 weeks to cause chronic inflammation. Compared with db/db mice, casein-injected db/db mice showed exacerbated tubulointerstitial injury, evidenced by increased secretion of extracellular matrix (ECM) and cholesterol accumulation in tubulointerstitium, which was accompanied by activation of the CXC chemokine ligand 16 (CXCL16) pathway. In the in vitro study, we treated HK-2 cells with IL-1β (5 ng/mL) and high glucose (30 mmol/L). IL-1β treatment increased cholesterol accumulation in HK-2 cells, leading to greatly increased ROS production, ECM protein expression levels, which was accompanied by the upregulated expression levels of proteins in the CXCL16 pathway. In contrast, after CXCL16 in HK-2 cells was knocked down by siRNA, the IL-1β-deteriorated changes were attenuated. In conclusion, inflammation accelerates renal tubulointerstitial lesions in mouse DN via increasing the activity of CXCL16 pathway.

PROTECTIVE EFFECT OF INSULIN TREATMENT ON EARLY RENAL CHANGES IN STREPTOZOTOCIN-INDUCED DIABETIC RATS

OBJECTIVES

Chronic kidney disease is a progressive complication of diabetes mellitus (DM). This study aimed to analyse early renal changes in streptozotocin induced diabetic rats and demonstrate the effect of early treatment with insulin on kidney's histology.

METHODS

30 male-adult Sprague-Dawley rats were included in the study. Diabetes was induced in 24 of the rats by a single injection of 65 mg/kg streptozotocin dissolved in saline. 5 units/day NPH insulin injection was started to 10 rats as treatment group and 11 rats were followed untreated. 6 rats constituted the control group. Induction of diabetes failed in 3 animals and 3 untreated rats died during the study. After 21 days, all rats were sacrificed and their kidneys were removed to obtain histological sections to be evaluated by light microscopy.

RESULTS

Ten treated and 8 untreated diabetic rats and 6 healthy controls, totally 24 rats completed the study. There was a significant weight loss in treated and untreated diabetic groups and a weight gain in the control group (p<0.05). Final blood glucose levels were significantly higher in untreated diabetic group when compared to treated diabetic and control groups and higher in treated diabetic group when compared to control group. Histological analysis of kidney sections showed normal morphology in control group. Changes like increased mesangium, tubular atrophy and tubules with dilated lumen and irregular cell shapes were found in the untreated group whereas, glomerulus and mesangium showed similar morphology with control group with a few changes in tubules, in insulin-treated group.

CONCLUSION

In DM, renal changes start at an early point and it is possible to prevent/delay those changes at this point with early intervention of insulin treatment.

c-Myc promotes renal fibrosis by inducing integrin αv-mediated transforming growth factor-β signaling

Fibrogenesis involves the activation of renal fibroblasts upon kidney injury. However, the mechanisms underlying renal fibroblast activation are poorly characterized. c-Myc is a predominant oncogene encoding a pleiotropic transcription factor that participates in the regulation of various genes, including genes vital for regulating the cell cycle, cell proliferation, and apoptosis. Here we tested whether renal fibrosis in unilateral ureteral obstruction and folic acid-induced renal fibrosis mouse models are associated with the overexpression of c-Myc. Transforming growth factor-β (TGF-β) has been identified as a key mediator of renal fibrosis, and it is secreted in an inactive form as a complex with latency-associated peptide and latent TGF-β-binding proteins. Five αv-containing integrins with different β -subunits can activate TGF-β, and consistent with this we found that c-Myc bound directly to the promoter of integrin αv in renal fibroblasts activating its transcription. This, in turn, induced activation of TGF-β signaling. Pharmacological blockade of c-Myc attenuated renal fibrosis in vivo in the ureteral obstruction and folic acid-treated mouse models and inhibited the proliferation and activation of renal fibroblasts in vitro. Thus, c-Myc overexpression stimulated proliferation and activation of renal fibroblasts by inducing integrin αv -mediated TGF-β signaling. Hence, targeting c-Myc may have clinical utility in the treatment of renal fibrosis.

The impact of insulin resistance on the kidney and vasculature

Insulin resistance is a systemic disorder that affects many organs and insulin-regulated pathways. The disorder is characterized by a reduced action of insulin despite increased insulin concentrations (hyperinsulinaemia). The effects of insulin on the kidney and vasculature differ in part from the effects on classical insulin target organs. Insulin causes vasodilation by enhancing endothelial nitric oxide production through activation of the phosphatidylinositol 3-kinase pathway. In insulin-resistant states, this pathway is impaired and the mitogen-activated protein kinase pathway stimulates vasoconstriction. The action of insulin on perivascular fat tissue and the subsequent effects on the vascular wall are not fully understood, but the hepatokine fetuin-A, which is released by fatty liver, might promote the proinflammatory effects of perivascular fat. The strong association of salt-sensitive arterial hypertension with insulin resistance indicates an involvement of the kidney in the insulin resistance syndrome. The insulin receptor is expressed on renal tubular cells and podocytes and insulin signalling has important roles in podocyte viability and tubular function. Renal sodium transport is preserved in insulin resistance and contributes to the salt-sensitivity of blood pressure in hyperinsulinaemia. Therapeutically, renal and vascular insulin resistance can be improved by an integrated holistic approach aimed at restoring overall insulin sensitivity and improving insulin signalling.