Mechanistic insight of diabetic nephropathy and its pharmacotherapeutic targets: An update

Tangshenning Attenuates High Glucose-Induced Podocyte Injury via Restoring Autophagy Activity through Inhibiting mTORC1 Activation

Diabetic nephropathy (DN) is a microvascular complication of diabetes mellitus (DM) and the most common cause of death in diabetic patients. DN progression is associated with podocyte damage due to reduced autophagy caused by mTORC1 activation. Tangshenning (TSN) has been shown to reduce proteinuria, protect renal function, and reduce podocyte damage. Still, the effect of TSN on the autophagic activity of podocytes remains unclear. Herein, in vitro experiments using a high glucose-induced podocyte injury model were performed. Results showed that TSN treatment enhanced the weakened nephrin expression and autophagic activity of podocytes and inhibited the mTORC1 pathway (p-mTOR, mTOR, p-p70S6K, p70S6K, ULK1, and 4EBP1) under high glucose conditions. Furthermore, the mTORC1 activator (siRNA-TSC2) partially inhibited the above beneficial effects of TSN, suggesting that mTORC1 was the target of TSN to regulate autophagy. In summary, TSN reduces podocyte damage induced by high glucose via inhibiting mTORC1 pathway and downstream targets and restoring podocyte autophagy.

Dual-Specificity Phosphatases and Kidney Diseases

BACKGROUND

Dual-specificity phosphatases (DUSPs) belong to the family of protein tyrosine phosphatases, which can dephosphorylate both serine/threonine and tyrosine residues. During the past decades, DUSPs have been implicated in various physiological and pathological activities. Besides mitogen-activated protein kinases (MAPKs) as the main substrates, other protein and nonprotein substrates can also be dephosphorylated by DUSPs. Aberrant regulations of DUSPs have been found in various diseases such as cancer, neurological disorders, and kidney diseases, suggesting the involvement of DUSPs in the pathogenesis of diseases.

SUMMARY

In this review, we summarize the general characteristics of DUSPs and the research progress made in the field of kidney diseases, including diabetic nephropathy, hypertensive nephropathy, chronic kidney disease, acute kidney injury, and lupus nephritis. As the main biochemical function of DUSPs is to dephosphorylate MAPKs activity, decreased DUSPs are found in kidney disease models, whereas forced DUSPs expression reverses the disease presentation, which was proved by using transgenic or gene knockout model.

KEY MESSAGES

Mounting evidence demonstrates that DUSPs have essential physiological and pathological functions in kidney disease. Fully understanding the functions and mechanisms of DUSPs in kidney disease contributes to their clinical application in translation medicine.

Eight Differential miRNAs in DN Identified by Microarray Analysis as Novel Biomarkers

BACKGROUND

Diabetic nephropathy (DN) is the common cause of renal diseases such as end-stage renal disease (ESRD) and chronic kidney disease (CKD). Various diagnostic applications and treatment methods are used for clinical but remain some prognosis issues. To avoid morbidity and mortality related to DN, early detection of disease complications as well as targeted therapeutic strategies is essential. Considerable evidence indicates that non-coding RNA plays a vital role in the biological processes of various diseases, used as biomarkers and therapeutic targets. And the most known ncRNAs are the microRNAs (miRNAs), long noncoding RNAs (lncRNAs), and circular RNAs (circRNAs).

MATERIALS AND METHODS

Our study aimed to identify potential prognostic ncRNAs involved in DN by bioinformatics analysis and validated expression levels through quantitative polymerase chain reaction (qPCR) and GEO database. Our research focuses on differential expression miRNAs (DEmiRNAs) in DN and their interactions with critical genes.

RESULTS

We identified 8 up-regulated DEmiRNAs, including miR-103a-2-5p, miR-297, miR-548x-3p, miR-604, miR-644a, miR-1256, miR-3911 and miR-5047 finally. We further validated these miRNAs in a murine model.

CONCLUSION

Identifying these up-regulated genes and elucidating these miRNAs regulatory network will contribute to a better understanding of the molecular mechanism of DN and how they can be used as new biomarkers and potential therapeutic targets for DN.

Gastrodin inhibits high glucose‑induced inflammation, oxidative stress and apoptosis in podocytes by activating the AMPK/Nrf2 signaling pathway

Diabetic nephropathy (DN) is a serious and common complication of type 1 and 2 diabetes. Gastrodin has been reported to suppress high glucose (HG)-induced inflammation and oxidative stress in vivo and in vitro. However, the effect of gastrodin on DN has not been fully elucidated. The present study aimed to investigate the underlying mechanism involved in the effect of gastrodin on podocyte injury caused by DN. Cell viability was evaluated using Cell Counting Kit-8 assay and secretion levels of TNF-α, IL-1β and IL-6 were measured using ELISA. The levels of malondialdehyde, activities of lactate dehydrogenase and superoxide dismutase were quantified using corresponding assay kits. Additionally, cell apoptosis was analyzed by TUNEL assay, whilst protein expressions related to inflammation, apoptosis and the 5'-AMP-activated protein kinase (AMPK)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway were measured by western blot analysis. The results showed that gastrodin increased the viability of MPC5 cells following HG stimulation. Gastrodin also alleviated HG-induced inflammation, oxidative stress and apoptosis in MPC5 cells. Furthermore, gastrodin promoted activation of the AMPK/Nrf2 pathway in MPC5 cells. Treatment with the AMPK inhibitor, compound C, reversed the inhibitory effects of gastrodin on inflammation, oxidative stress and cell apoptosis. To conclude, treatment of MPC5 cells with gastrodin can attenuate HG-induced inflammation, oxidative stress and cell apoptosis by activating the AMPK/Nrf2 signaling pathway. Results from the current study suggest that gastrodin can be used as an effective therapeutic agent against HG-induced podocyte injury in DN.

Discovery of caffeoylisocitric acid as a Keap1-dependent Nrf2 activator and its effects in mesangial cells under high glucose

Diabetic nephropathy (DN) is one of the severe microvascular complications of diabetes mellitus. Oxidative stress resulting from aberrant metabolism of glucose mediates renal inflammation and fibrosis in the progression of DN. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor regulating the expression of antioxidant enzymes. Activating Nrf2 will give a promising therapy for DN. To discover novel Nrf2 activators, we have investigated caffeoylisocitric acid using mesangial cells under high glucose. The results showed at 10 μM, caffeoylisocitric acid significantly inhibited the self-limited proliferation of mesangial cells induced by high glucose. Further assessments have disclosed caffeoylisocitric acid mitigated oxidative stress, inflammation and accumulation of extracellular matrix resulting from high glucose via inactivating MAPK signalling. Meanwhile activation of Nrf2 was observed and involved in these effects through the interaction between Keap1 and caffeoylisocitric acid to disrupt Keap1-Nrf2 complex. Therefore, caffeoylisocitric acid is a promising Nrf2 activator targeting DN.

Fucoxanthin regulates Nrf2 signaling to decrease oxidative stress and improves renal fibrosis depending on Sirt1 in HG-induced GMCs and STZ-induced diabetic rats

Diabetic nephropathy (DN) is one of the major microvascular complications of diabetes. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a crucial cellular defense factor to cope with oxidative stress. Silent information regulator T1 (Sirt1) is a deacetylase with antioxidative stress activity. Fucoxanthin is a marine-derived carotenoid. This study was conducted to investigate whether fucoxanthin could alleviate oxidative stress by activating Sirt1/Nrf2 signaling to alleviate DN. In streptozotocin-induced diabetic rats, fucoxanthin treatment effectively improved renal function, alleviated glomerulosclerosis. Fucoxanthin reversed the decreased protein levels of Sirt1 and Nrf2 in the kidney of diabetic rats and glomerular mesangial cells cultured in high glucose. Conversely, EX527, a Sirt1 inhibitor, counteracted the effect of fucoxanthin on the expression of Nrf2. Furthermore, in vivo and vitro results showed that fucoxanthin treatment reversed the low expression and activity of superoxide dismutase and heme oxygenase 1, depending on Sirt1 activation. Our results suggest that fucoxanthin improves diabetic kidney function and renal fibrosis by activating Sirt1/Nrf2 signaling to reduce oxidative stress.

TGF-β1 is involved in senescence-related pathways in glomerular endothelial cells via p16 translocation and p21 induction

p16 inhibits cyclin-dependent kinases and regulates senescence-mediated arrest as well as p21. Nuclear p16 promotes G1 cell cycle arrest and cellular senescence. In various glomerular diseases, nuclear p16 expression is associated with disease progression. Therefore, the location of p16 is important. However, the mechanism of p16 trafficking between the nucleus and cytoplasm is yet to be fully investigated. TGF-β1, a major cytokine involved in the development of kidney diseases, can upregulate p21 expression. However, the relationship between TGF-β1 and p16 is poorly understood. Here, we report the role of podocyte TGF-β1 in regulating the p16 behavior in glomerular endothelial cells. We analyzed podocyte-specific TGF-β1 overexpression mice. Although p16 was found in the nuclei of glomerular endothelial cells and led to endothelial cellular senescence, the expression of p16 did not increase in glomeruli. In cultured endothelial cells, TGF-β1 induced nuclear translocation of p16 without increasing its expression. Among human glomerular diseases, p16 was detected in the nuclei of glomerular endothelial cells. In summary, we demonstrated the novel role of podocyte TGF-β1 in managing p16 behavior and cellular senescence in glomeruli, which has clinical relevance for the progression of human glomerular diseases.

CircTLK1 Downregulation Attenuates High Glucose-Induced Human Mesangial Cell Injury by Blocking the AKT/NF-κB Pathway Through Sponging miR-126-5p/miR-204-5p

Diabetic nephropathy (DN) is the main cause of end-stage renal disease. Circular RNA hsa_circ_0004442 (circTLK1) accelerates the progression of renal cell carcinoma. However, the role of circTLK1 in DN pathogenesis is indistinct. The expression of circTLK1, microRNA-126-5p (miR-126-5p), and microRNA-204-5p (miR-204-5p) was tested by quantitative real-time polymerase chain reaction. The levels of interleukin-6 and interleukin-1β were measured by enzyme-linked immunosorbent assay. The levels of reactive oxygen species and malondialdehyde and the activity of superoxide dismutase were determined with corresponding kits. Several protein levels were evaluated with western blotting. The relationship between circTLK1 and miR-126-5p/miR-204-5p was verified by dual-luciferase reporter assay. CircTLK1 was highly expressed in DN patient's serum and high-glucose (HG)-treated human mesangial cells. Functionally, circTLK1 inhibition reduced HG-induced inflammation, oxidative stress, and ECM accumulation in human mesangial cells. CircTLK1 was verified as a sponge for miR-126-5p and miR-204-5p, which were downregulated in DN patient's serum and HG-treated human mesangial cells. Both miR-126-5p and miR-204-5p upregulation decreased inflammation, oxidative stress, and ECM accumulation in HG-treated human mesangial cells and circTLK1 silencing-mediated influence on HG-induced human mesangial cell injury was overturned by miR-126-5p or miR-204-5p inhibition. Moreover, circTLK1 knockdown blocked the AKT/NF-κB pathway by sponging miR-126-5p/miR-204-5p. CircTLK1 downregulation alleviated HG-induced inflammation, oxidative stress, and ECM accumulation through blocking the AKT/NF-κB pathway via sponging miR-126-5p/miR-204-5p, providing a new mechanism to comprehend the pathogenesis of DN.

The Multiple Roles of Fibroblast Growth Factor in Diabetic Nephropathy

Diabetic nephropathy (DN) is a common microvascular complication in the late stages of diabetes. Currently, the etiology and pathogenesis of DN are not well understood. Even so, available evidence shows its development is associated with metabolism, oxidative stress, cytokine interaction, genetic factors, and renal microvascular disease. Diabetic nephropathy can lead to proteinuria, edema and hypertension, among other complications. In severe cases, it can cause life-threatening complications such as renal failure. Patients with type 1 diabetes, hypertension, high protein intake, and smokers have a higher risk of developing DN. Fibroblast growth factor (FGF) regulates several human processes essential for normal development. Even though FGF has been implicated in the pathological development of DN, the underlying mechanisms are not well understood. This review summarizes the role of FGF in the development of DN. Moreover, the association of FGF with metabolism, inflammation, oxidative stress and fibrosis in the context of DN is discussed. Findings of this review are expected to deepen our understanding of DN and generate ideas for developing effective prevention and treatments for the disease.

Dietary natural products as a potential inhibitor towards advanced glycation end products and hyperglycemic complications: A phytotherapy approaches

Natural products exist in various natural foods such as plants, herbs, fruits, and vegetables. Furthermore, marine life offers potential natural products with significant biological activity. The biochemical reaction is known as advanced glycation end products (AGEs) occurs in the human body. On the other hand, foods are capable of a wide range of processing conditions resulting in the generation of exogenous AGEs adducts. Protein glycation and the formation of advanced glycation end products both contribute to the pathogenesis of hyperglycemic complications. AGEs also play a pivotal role in microvascular and macrovascular complications progression by receptors for advanced glycation end products (RAGE). RAGE activate by AGEs leads to up-regulation of transcriptional factor NF-kB and inflammatory genes. Around the globe, researchers are working in various approaches for therapeutical implications on controlling AGEs mediated disease complications. In this regard, one of the potential promising agents observed with a wide range of AGEs inhibition by food-derived natural products. Current biotechnological tools have been turned to natural products or phytochemicals to manufacture the molecules without compromising their functionality. Metabolic engineering and bioinformatics perspectives have recently enabled the generation of a few potent metabolites with anti-diabetic activity. As the primary focus, this review article will also discuss multidisciplinary approaches that emphasize current advances in anti-diabetic therapeutic action and future perspectives of natural products.

Effects of Psoralea corylifolia L. seed extract on AGEs-induced cell proliferation and fibrotic factor expression in mesangial cells

Diabetic nephropathy is a microvascular complication of diabetes that is characterized by mesangial expansion and thickening of the glomerular basement membrane. The production of advanced glycation end products (AGEs) increases in diabetic patients. Activation of the receptor of AGE (RAGE) signaling pathway induces mesangial expansion via the reactive oxygen species (ROS)-mediated production of pro-inflammatory and extracellular matrix molecules. The Psoralea corylifolia L. seed (PCS) is a widely used herbal medicine with various biological activities. The current study investigated the effect of PCS extract on mesangial cell proliferation and the RAGE signaling pathway in SV40 MES 13 cells. SV40 MES 13 cells were harvested after treatment with various concentrations of PCS extract at 10 µg/ml AGEs for 24 h. The results revealed that the PCS extract inhibited AGEs-induced mesangial cell proliferation and cyclin protein expression in a concentration-dependent manner. In addition, the AGEs-induced expression of fibrotic factors, such as transforming growth factor β, fibronectin and collagen, was reduced in mesangial cells after exposure to the PCS extract. The PCS extract also reduced RAGE expression and inhibited the expression of its downstream signaling pathways, such as NADPH oxidase, intracellular ROS and phospho-NF-κB. In conclusion, the data suggested that the PCS extract attenuated AGEs-induced renal mesangial cell proliferation and fibrosis via the suppression of oxidative stress and the downregulation of inflammatory and fibrotic factor expression.

A Comprehensive Review of Neuronal Changes in Diabetics

There has been an exponential rise in diabetes mellitus (DM) cases on a global scale. Diabetes affects almost every system of the body, and the nervous system is no exception. Although the brain is dependent on glucose, providing it with the energy required for optimal functionality, glucose also plays a key role in the regulation of oxidative stress, cell death, among others, which furthermore contribute to the pathophysiology of neurological disorders. The variety of biochemical processes engaged in this process is only matched by the multitude of clinical consequences resulting from it. The wide-ranging effects on the central and peripheral nervous system include, but are not limited to axonopathies, neurodegenerative diseases, neurovascular diseases, and general cognitive impairment. All language search was conducted on MEDLINE, COCHRANE, EMBASE, and GOOGLE SCHOLAR till September 2021. The following search strings and Medical Subject Headings (MeSH terms) were used: "Diabetes Mellitus," "CNS," "Diabetic Neuropathy," and "Insulin." We explored the literature on diabetic neuropathy, covering its epidemiology, pathophysiology with the respective molecular pathways, clinical consequences with a special focus on the central nervous system and finally, measures to prevent and treat neuronal changes. Diabetes is slowly becoming an epidemic, rapidly increasing the clinical burden on account of its wide-ranging complications. This review focuses on the neuronal changes occurring in diabetes such as the impact of hyperglycemia on brain function and structure, its association with various neurological disorders, and a few diabetes-induced peripheral neuropathic changes. It is an attempt to summarize the relevant literature about neuronal consequences of DM as treatment options available today are mostly focused on achieving better glycemic control; further research on novel treatment options to prevent or delay the progression of neuronal changes is still needed.

Telmisartan Mitigates High-Glucose-Induced Injury in Renal Glomerular Endothelial Cells (rGECs) and Albuminuria in Diabetes Mice

Diabetic nephropathy (DN) is a common and severe complication of diabetes, impacting millions of people worldwide. High concentrations of serum glucose-associated injury of renal glomerular endothelial cells (rGECs) are involved in the DN pathogenesis. We found that exposure to high glucose increased the expression of angiotensin II type 1 receptor (AT1R) in human rGECs (hrGECs). To block the increased AT1R level, we used the newly developed antagonist Telmisartan. This study investigated whether Telmisartan possessed a beneficial effect against high-glucose-induced insults in hrGECs and explored the underlying mechanism. Our findings indicate that Telmisartan ameliorated high-glucose-induced mitochondrial dysfunction by increasing mitochondrial membrane potential. Also, Telmisartan attenuated oxidative stress by reducing the levels of two oxidative stress biomarkers 8-hydroxy-2 deoxyguanosine (8-OHDG) and malondialdehyde (MDA). Further, we found that Telmisartan prevented high-glucose-induced expression of NADPH oxidase 2 (NOX-2). Interestingly, exposure to high glucose resulted in the increased endothelial permeability of renal glomerular endothelial cells, which was mitigated by treatment with Telmisartan. Mechanistically, these effects are mediated by the MLCK/MLC-2/occludin signaling pathway. In the leptin-deficient db/db diabetic mouse model, we proved that Telmisartan treatment ameliorated the reduction of occludin and albuminuria. In conclusion, our findings demonstrate that Telmisartan possesses protective effects on high-glucose-induced injury to renal glomerular endothelial cells; its antagonizing of AT1R could be a potential therapeutic target in diabetic nephropathy.

Efficacy and safety of acupuncture combined with Chinese Herbal Medicine for diabetic nephropathy: A protocol for systematic review and meta-analysis

BACKGROUND

Diabetic nephropathy (DN) is one of the most serious complications in the development of diabetes mellitus, which has become the main cause of end-stage renal disease and one of the main causes of death in diabetic patients. With the prevalence of diabetes, the number of patients at risk for developing DN is increasing, with 20-40 percent of all patients with diabetes at risk for developing DN. Acupuncture and Chinese herbal medicine treatments are often combined to treat DN; however, there has been no meta-analysis on their synergistic effects. Therefore, we aimed to perform a systematic review and meta-analysis to estimate the effectiveness of acupuncture combined with Chinese herbal medicine for DN treatment.

METHODS

Nine electronic databases were retrieved for this study. The English databases mainly retrieved PubMed, Web of Science, Embase, AMED, and the Cochrane Library, while the CNKI, VIP, CBM, and Wanfang databases were used to retrieve the Chinese literature. There is no definite time limit for the retrieval literature, and the languages are limited to Chinese and English. We will consider articles published between database initiation and August 2021. We used Review Manager 5.4, provided by the Cochrane Collaborative Network for statistical analysis. Clinical randomized controlled trials related to acupuncture combined with Chinese herbal medicine for DN were included in this study. Research selection, data extraction, and research quality assessments were independently completed by two researchers. We then assessed the quality and risk of the included studies and observed the outcome measures.

RESULTS

This study provides a high-quality synthesis to assess the effectiveness and safety of acupuncture combined with Chinese herbal medicine for treating DN.

CONCLUSION

This systematic review will provide evidence to determine whether acupuncture combined with Chinese herbal medicine is an effective and safe intervention for patients with DN.

ETHICS AND DISSEMINATION

The protocol of the systematic review does not require ethical approval because it does not involve humans. This article will be published in peer-reviewed journals and presented at relevant conferences.

REGISTRATION NUMBER

INPLASY202180018.

Microcracks on the Rat Root Surface Induced by Orthodontic Force, Crack Extension Simulation, and Proteomics Study

Root resorption is a common complication during orthodontic treatment. Microcracks occur on the root surface after an orthodontic force is applied and may be related to the root resorption caused by the orthodontic process. However, the mechanisms underlying root resorption induced by microcracks remain unclear. In this study, a rat orthodontic model was used to investigate the biological mechanisms of root resorption caused by microcracks. First, the first molar was loaded with 0.5-N orthodontic force for 7 days, and microcracks were observed on the root apex surface using a scanning electron microscope. Second, to describe the mechanical principle resulting in microcracks, a finite element model of rat orthodontics was established, which showed that a maximum stress on the root apex can cause microcrack extension. Third, after 7 days of loading in vivo, histological observation revealed that root resorption occurred in the stress concentration area and cementoclasts appeared in the resorption cavity. Finally, proteomics analysis of the root apex area, excluding the periodontal ligament, revealed that the NOX2, Aifm1, and MAPK signaling pathways were involved in the root resorption process. Microcrack extension on the root surface increases calcium ion concentrations, alters the proteins related to root resorption, and promotes cementoclast formation.

Chemical Constituents from the Rhizome of Ligusticum chuanxiong Hort. and Their Nrf2 Inducing Activity

The rhizome of Ligusticum chuanxiong Hort. has been widely used for the therapy of diabetic nephropathy (DN) in traditional Chinese medicine (TCM). The nuclear transcription factor erythroid 2-related factor (Nrf2) is a potential target for treating DN. The purpose of this research was to study the chemical constituents from the rhizome of L. chuanxiong, evaluate their Nrf2 inducing activity, and find the molecules with potential therapeutic effect against DN. In this study, two new phthalides (1-2) along with twenty-seven known constituents were obtained from the rhizome of L. chuanxiong. Their structures were elucidated through various spectroscopic methods. Twelve constituents, including eight phthalides (2, 5, 6,10-13, 14) and four other compounds (17, 18, 20,28), stimulated NAD(P)H: quinone reductase (QR) activity, suggesting that these bioactive constituents were potential Nrf2 activators. Among the isolated compounds, phthalide levistolide A (LA, 14) upregulated the protein levels of Nrf2, NQO1, and γ-GCS in a dose-dependent manner. Our results implied that the clinical application of the rhizome of L. chuanxiong as an anti-DN drug in TCM might be attributed to the Nrf2 inducing effect of phthalides. Thus, phthalides is a group of promising leading molecules for discovering anti-DN agents.

Flavonoids on diabetic nephropathy: advances and therapeutic opportunities

With the advances in biomedical technologies, natural products have attracted substantial public attention in the area of drug discovery. Flavonoids are a class of active natural products with a wide range of pharmacological effects that are used for the treatment of several diseases, in particular chronic metabolic diseases. Diabetic nephropathy is a complication of diabetes with a particularly complicated pathological mechanism that affects at least 30% of diabetic patients and represents a great burden on public health. A large number of studies have shown that flavonoids can alleviate diabetic nephropathy. This review systematically summarizes the use of common flavonoids for the treatment of diabetic nephropathy. We found that flavonoids play a therapeutic role in diabetic nephropathy mainly by regulating oxidative stress and inflammation. Nrf-2/GSH, ROS production, HO-1, TGF-β1 and AGEs/RAGE are involved in the process of oxidative stress regulation. Quercetin, apigenin, baicalin, luteolin, hesperidin, genistein, proanthocyanidin and eriodictyol were found to be capable of alleviating oxidative stress related to the aforementioned factors. Regarding inflammatory responses, IL-1, IL-6β, TNF-α, SIRT1, NF-κB, and TGF-β1/smad are thought to be essential. Quercetin, kaempferol, myricetin, rutin, genistein, proanthocyanidin and eriodictyol were confirmed to influence the above targets. As a result, flavonoids promote podocyte autophagy and inhibit the overactivity of RAAS by suppressing the upstream oxidative stress and inflammatory pathways, ultimately alleviating DN. The above results indicate that flavonoids are promising drugs for the treatment of diabetic nephropathy. However, due to deficiencies in the effect of flavonoids on metabolic processes and their lack of structural stability in the body, further research is required to address these issues.

Omarigliptin ameliorated high glucose-induced nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome activation through activating adenosine monophosphate-activated protein kinase α (AMPKα) in renal glomerular endothelial cells

Diabetic nephropathy (DN) is a complication of diabetes that induces the development of end-stage renal disease (ESRD). The pathogenesis of DN is reported to be closely related to the activation of the NOD-like receptor 3 (NLRP3) inflammasome in renal glomerular endothelial cells. Omarigliptin is a novel dipeptidyl peptidase-4 (DPP-4) inhibitor developed for the management of type II diabetes, it has been recently reported to possess a significant anti-inflammatory property. This study aims to explore the potential therapeutic effects of Omarigliptin on DN. We established an in vitro injury model in human renal glomerular endothelial cells (HrGECs) using high glucose (HG). The severe cytotoxicity and increased oxidative stress in HrGECs induced by HG were pronouncedly reversed by the introduction of Omarigliptin. Furthermore, the activated NLRP3 inflammasome and the excessive production of interleukin 18 (IL-18) and interleukin 1β (IL-1β) in HrGECs induced by incubation with HG were pronouncedly reversed by the introduction of Omarigliptin, accompanied by the activation of the AMPK/mTOR signaling pathway. After the co-administration of the adenosine monophosphate-activated protein kinase α (AMPKα) inhibitor, compound C, the protective effects of Omarigliptin against HG-induced NLRP3 inflammasome activation and production of pro-inflammatory factors were dramatically abolished. Taken together, our data revealed that Omarigliptin ameliorated HG-induced inflammation in renal glomerular endothelial cells through suppressing NLRP3 inflammasome activation mediated by AMPKα.

New progress in drugs treatment of diabetic kidney disease

Diabetic kidney disease (DKD) is not only one of the main complications of diabetes, but also the leading cause of the end-stage renal disease (ESRD). The occurrence and development of DKD have always been a serious clinical problem that leads to the increase of morbidity and mortality and the severe damage to the quality of life of human beings. Controlling blood glucose, blood pressure, blood lipids, and improving lifestyle can help slow the progress of DKD. In recent years, with the extensive research on the pathological mechanism and molecular mechanism of DKD, there are more and more new drugs based on this, such as new hypoglycemic drugs sodium-glucose cotransporter 2 (SGLT2) inhibitors, glucagon-like peptide-1 (GLP-1) inhibitors, and dipeptidyl peptidase-4 (DPP-4) inhibitors with good efficacy in clinical treatment. Besides, there are some newly developed drugs, including protein kinase C (PKC) inhibitors, advanced glycation end product (AGE) inhibitors, aldosterone receptor inhibitors, endothelin receptor (ETR) inhibitors, transforming growth factor-β (TGF-β) inhibitors, Rho kinase (ROCK) inhibitors and so on, which show positive effects in animal or clinical trials and bring hope for the treatment of DKD. In this review, we sort out the progress in the treatment of DKD in recent years, the research status of some emerging drugs, and the potential drugs for the treatment of DKD in the future, hoping to provide some directions for clinical treatment of DKD.

Signaling Pathways Involved in Diabetic Renal Fibrosis

Diabetic kidney disease (DKD), as the most common complication of diabetes mellitus (DM), is the major cause of end-stage renal disease (ESRD). Renal interstitial fibrosis is a crucial metabolic change in the late stage of DKD, which is always considered to be complex and irreversible. In this review, we discuss the pathological mechanisms of diabetic renal fibrosis and discussed some signaling pathways that are closely related to it, such as the TGF-β, MAPK, Wnt/β-catenin, PI3K/Akt, JAK/STAT, and Notch pathways. The cross-talks among these pathways were then discussed to elucidate the complicated cascade behind the tubulointerstitial fibrosis. Finally, we summarized the new drugs with potential therapeutic effects on renal fibrosis and listed related clinical trials. The purpose of this review is to elucidate the mechanisms and related pathways of renal fibrosis in DKD and to provide novel therapeutic intervention insights for clinical research to delay the progression of renal fibrosis.

Early Renoprotective Effect of Ruxolitinib in a Rat Model of Diabetic Nephropathy

Diabetic kidney disease (DKD) is still one of the unresolved major complications of diabetes mellitus, which leads ultimately to end-stage renal disease in both type 1 and type 2 diabetes patients. Available drugs that suppress the renin-angiotensin system have partially minimized the disease impact. Yet, there is an unmet need for new therapeutic interventions to protect the kidneys of diabetic patients. In DN, glomerular sclerosis and tubulointerstitial fibrosis are mediated through several pathways, of which JAK/STAT is a key one. The current study explored the potential renoprotective effect of the JAK1/JAK2 inhibitor ruxolitinib (at doses of 0.44, 2.2, and 4.4 mg·kg^-1) compared to that of enalapril at a dose of 10 mg·kg^-1, in a rat model of streptozotocin-induced diabetes mellitus over 8 weeks. The effect of ruxolitinib was assessed by determining urinary albumin/creatinine ratio, serum level of cystatin, and levels of TGF-β1, NF-κB, and TNF-α in renal tissue homogenates by biochemical assays, the glomerular sclerosis and tubulointerstitial fibrosis scores by histological analysis, and fibronectin, TGF-β1, and Vimentin levels by immunohistochemical staining with the respective antibodies. Our results revealed a significant early favorable effect of a two-week ruxolitinib treatment on the renal function, supported by a decline in the proinflammatory biomarkers of DKD. This pre-clinical study suggests that the renoprotective effect of ruxolitinib in the long term should be investigated in animals, as this drug may prove to be a potential option for the treatment of diabetic kidney disease.

Circular RNA expression profile in transgenic diabetic mouse kidneys

Background

Diabetic nephropathy is one of the most important complications in patients with diabetes. The etiology and pathogenesis of diabetic nephropathy remain unclear. Several studies have indicated that circular RNAs (circRNAs) play crucial regulatory roles in numerous human diseases and normal physiology; however, to date, no study has focused on the comprehensive expression profile of circRNAs in the kidneys of diabetic mice. Therefore, we aimed to identify differentially expressed circRNAs in diabetic mouse kidneys to explore the possible roles of dysregulated circRNAs in diabetic nephropathy development.

Results

Diabetic BKS-Lepr^em2Cd479/Nju (BKS-DB/Nju) mice and their nondiabetic wild-type littermates of C57BL/KsJ wild-type (WT) mice were used as experimental animals. Among all circRNAs identified by high-throughput RNA sequencing, four circRNAs were upregulated and ten were downregulated in diabetic mouse kidneys compared to those in nondiabetic mouse kidneys. After verification using quantitative reverse transcriptase polymerase chain reaction assays, we found that circR_1084, circR_182, circR_4, circR_50, circR_596, circR_897, and circR_203 were downregulated, whereas circR_627, circR_628, circR_735, and circR_801 were upregulated in the renal tissues of 8- and 16-week-old BKS-DB/Nju mice compared to those in WT mice.

Conclusion

We studied the circRNA expression profile in the kidneys of diabetic mice. Differentially expressed circRNAs may be useful as candidate biomarkers for diabetic nephropathy. Collectively, our results provide a novel theoretical basis for further investigation of the regulatory roles of circRNA in the etiology and pathogenesis of diabetic nephropathy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s11658-021-00270-z.

Overexpression of lipoic acid synthase gene alleviates diabetic nephropathy of Leprdb/db mice

INTRODUCTION

Diabetic nephropathy (DN) develops in about 40% of patients with type 2 diabetes and remains the leading cause of end-stage renal disease. The mechanisms of DN remain to be elucidated. Oxidative stress is thought to be involved in the development of DN but antioxidant therapy has produced conflicting results. Therefore, we sought to define the role of antioxidant in retarding the development of DN in this study.

RESEARCH DESIGN AND METHODS

We generated a new antioxidant/diabetes mouse model, Lias^H/HLepr^db/db mice, by crossing db/db mice with Lias^H/H mice, which have overexpressed Lias gene (~160%) compared with wild type, and also correspondingly increased endogenous antioxidant capacity. The new model was used to investigate whether predisposed increased endogenous antioxidant capacity was able to retard the development of DN. We systemically and dynamically examined main pathological alterations of DN and antioxidant biomarkers in blood and kidney mitochondria.

RESULTS

Lias^H/HLepr^db/db mice alleviated major pathological alterations in the early stage of DN, accompanied with significantly enhanced antioxidant defense. The model targets the main pathogenic factors by exerting multiple effects such as hypoglycemic, anti-inflammation, and antioxidant, especially protection of mitochondria.

CONCLUSION

The antioxidant animal model is not only very useful for elucidating the underlying mechanisms of DN but also brings insight into a new therapeutic strategy for clinical applications.

The Emerging Role of HDACs: Pathology and Therapeutic Targets in Diabetes Mellitus

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into four different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting novel interventional strategies for metabolic disorders/complications.

Based on Network Pharmacology and Molecular Docking to Explore the Underlying Mechanism of Huangqi Gegen Decoction for Treating Diabetic Nephropathy

Background

Huangqi Gegen decoction (HGD), a Chinese herb formula, has been widely used to treat diabetic nephropathy in China, while the pharmacological mechanisms are still unclear. Therefore, the present study aims to explore the underlying mechanism of HGD for treating diabetic nephropathy (DN).

Materials and Methods

Traditional Chinese Medicine Systems Pharmacology Database (TCMSP), UniProt, and SwissTargetPrediction databases were used to search the active ingredients and potential targets of HGD. In addition, multiple disease-related databases were used to collect DN-related targets. Common targets of the protein-protein interaction (PPI) network were established using the STRING database. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the DAVID database. At last, AutoDockVina was used to conduct molecular docking verification for the core components and targets.

Results

A total of 27 active ingredients and 354 putative identified target genes were screened from HGD, of which 99 overlapped with the targets of DN and were considered potential therapeutic targets. Further analysis showed that the HGD activity of quercetin, formononetin, kaempferol, isorhamnetin, and beta-sitosterol ingredients is possible through VEGFA, IL6, TNF, AKT1, and TP53 targets involved in TNF, toll-like receptors, and MAPK-related pathways, which have anti-inflammatory, antiapoptosis, antioxidation, and autophagy effects, relieve renal fibrosis and renal cortex injury, and improve renal function, thus delaying the development of DN. The molecular docking results showed that quercetin, formononetin, kaempferol, isorhamnetin, beta-sitosterol had a good binding activity with VEGFA, IL6, TNF, AKT1, and TP53.

Conclusion

This study demonstrated that HGD might take part in the treatment of DN through multicomponent, multitarget, and multichannel combined action.

Diabetic nephropathy: A twisted thread to unravel

Diabetic nephropathy (DN), a persistent microvascular problem of diabetes mellitus is described as an elevated level of albumin excretion in urine and impaired renal activity. The morbidity and mortality of type-1 diabetics and type-2 diabetics due to end stage renal disease is also a result of the increased prevalence of DN. DN typically occurs as a consequence of an association among metabolic and hemodynamic variables, activating specific pathways leading to renal injury. According to current interventions, intensive glucose regulation decreases the threat of DN incidence and growth, and also suppressing the renin-angiotensin system (RAS) is a significant goal for hemodynamic and metabolism-related deformities in DN. However, the pathogenesis of DN is multifactorial so novel approaches other than glucose and blood pressure control are required for treatment. This review briefly summarizes the reported pathogenesis of DN, current interventions for its treatment, and possible novel interventions to unweave the thread of DN.

Comparative effects of incretin-based therapy on early-onset diabetic nephropathy in rats: Role of TNF-α, TGF-β and c-caspase-3

AIMS

Diabetic nephropathy, a major threat to diabetic patients, is considered as the main reason for end-stage renal disease. Fortunately, incretin-based therapy has been aroused as considerable source to attenuate diabetic renal damage. This study aimed to investigate whether superior protective effects on the progression of diabetic kidney are exerted by glucagon-like peptide-1 analog, exenatide, or dipeptidyl peptidase-4 inhibitor, sitagliptin.

MATERIALS AND METHODS

Male Wistar rats were fed high-fat diet for 2 weeks followed by injection of low dose streptozotocin to induce type 2 diabetes mellitus. Four weeks after induction of diabetes, diabetic rats were administered vehicle, exenatide (5 μg/kg/day, SC) or sitagliptin (10 mg/kg/day, orally) for 4 weeks.

KEY FINDINGS

Different incretin mimetic agents improved renal function as evident by significant decreases in serum creatinine and urea levels with decline in urinary microalbuminuria and marked improvement in histological alterations. Both treated diabetic rats also exhibited a significant improvement in metabolic intolerance with more pronounced effect of exenatide on glucose regulation. Ameliorated renal oxidative stress alongside significant downregulation in transforming growth factor-beta, tumor necrosis factor-alpha and cleaved-caspase-3 protein expressions in renal tissues were recorded in treated diabetic rats.

SIGNIFICANCE

Administration of either exenatide or sitagliptin showed ameliorative effects on early diabetic nephropathy without notable differences between their renal protective effects. However, further clinical studies are still required to ensure their comparative promising effects on the management of renal complication of diabetes.

Therapeutic Potential of Polyphenols in the Management of Diabetic Neuropathy

Diabetic neuropathy (DN) is a common and serious diabetes-associated complication that primarily takes place because of neuronal dysfunction in patients with diabetes. Use of current therapeutic agents in DN treatment is quite challenging because of their severe adverse effects. Therefore, there is an increased need of identifying new safe and effective therapeutic agents. DN complications are associated with poor glycemic control and metabolic imbalances, primarily oxidative stress (OS) and inflammation. Various mediators and signaling pathways such as glutamate pathway, activation of channels, trophic factors, inflammation, OS, advanced glycation end products, and polyol pathway have a significant contribution to the progression and pathogenesis of DN. It has been indicated that polyphenols have the potential to affect DN pathogenesis and could be used as potential alternative therapy. Several polyphenols including kolaviron, resveratrol, naringenin, quercetin, kaempferol, and curcumin have been administered in patients with DN. Furthermore, chlorogenic acid can provide protection against glutamate neurotoxicity via its hydrolysate, caffeoyl acid group, and caffeic acid through regulating the entry of calcium into neurons. Epigallocatechin-3-gallate treatment can protect motor neurons by regulating the glutamate level. It has been demonstrated that these polyphenols can be promising in combating DN-associated damaging pathways. In this article, we have summarized DN-associated metabolic pathways and clinical manifestations. Finally, we have also focused on the roles of polyphenols in the treatment of DN.

LncRNA lnc-ISG20 promotes renal fibrosis in diabetic nephropathy by inducing AKT phosphorylation through miR-486-5p/NFAT5

Long non‐coding RNA (lncRNA) lnc‐ISG20 has been found aberrantly up‐regulated in the glomerular in the patients with diabetic nephropathy (DN). We aimed to elucidate the function and regulatory mechanism of lncRNA lnc‐ISG20 on DN‐induced renal fibrosis. Expression patterns of lnc‐ISG20 in kidney tissues of DN patients were determined by RT‐qPCR. Mouse models of DN were constructed, while MCs were cultured under normal glucose (NG)/high glucose (HG) conditions. The expression patterns of fibrosis marker proteins collagen IV, fibronectin and TGF‐β1 were measured with Western blot assay. In addition, the relationship among lnc‐ISG20, miR‐486‐5p, NFAT5 and AKT were analysed using dual‐luciferase reporter assay and RNA immunoprecipitation. The effect of lnc‐ISG20 and miR‐486/NFAT5/p‐AKT axis on DN‐associated renal fibrosis was also verified by means of rescue experiments. The expression levels of lnc‐ISG20 were increased in DN patients, DN mouse kidney tissues and HG‐treated MCs. Lnc‐ISG20 silencing alleviated HG‐induced fibrosis in MCs and delayed renal fibrosis in DN mice. Mechanistically, miR‐486‐5p was found to be a downstream miRNA of lnc‐ISG20, while miR‐486‐5p inhibited the expression of NFAT5 by binding to its 3'UTR. NFAT5 overexpression aggravated HG‐induced fibrosis by stimulating AKT phosphorylation. However, NFAT5 silencing reversed the promotion of in vitro and in vivo fibrosis caused by lnc‐ISG20 overexpression. Our collective findings indicate that lnc‐ISG20 promotes the renal fibrosis process in DN by activating AKT through the miR‐486‐5p/NFAT5 axis. High‐expression levels of lnc‐ISG20 may be a useful indicator for DN.

Cudrania tricuspidata Root Extract Prevents Methylglyoxal-Induced Inflammation and Oxidative Stress via Regulation of the PKC-NOX4 Pathway in Human Kidney Cells

Diabetic nephropathy is a microvascular complication induced by diabetes, and methylglyoxal (MGO) is a reactive carbonyl species causing oxidative stress that contributes to the induction of inflammatory response in kidney cells. Cudrania tricuspidata (CT), cultivated in Northeast Asia, has been used as traditional medicine for treating various diseases, including neuritis, liver damage, and cancer. In this study, we determined whether a CT root extract (CTRE) can prevent MGO-induced reactive oxygen species (ROS) production and inflammation and assessed underlying mechanisms using a kidney epithelial cell line, HK-2. We observed that CTRE inhibited MGO-induced ROS production. Additionally, CTRE ameliorated the activation of MGO-induced inflammatory signaling pathways such as p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), and c-JUN N-terminal kinase (JNK). Consistent with these results, expressions of p-nuclear factor-kappa B (NFκB) and inflammatory cytokines, tumor necrosis factor-α, interleukin- (IL-) 1β, and IL-6, were decreased when compared with MGO-only exposed HK-2 cells. CTRE alleviated the MGO-induced decrease in nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and antioxidant enzyme mRNA expressions. MGO induced the expression of NADPH oxidase 4 (NOX4); CTRE pretreatment inhibited this induction. Further studies revealed that the NOX4 expression was inhibited owing to the suppression of MGO-induced protein kinase C (PKC) activation following CTRE treatment. Collectively, our data suggest that CTRE attenuates MGO-induced inflammation and oxidative stress via inhibition of PKC activation and NOX4 expression, as well as upregulating the Nrf2-antioxidant enzyme pathway in HK-2 cells.

Ginkgo Biloba Extract EGB761 Ameliorates the Extracellular Matrix Accumulation and Mesenchymal Transformation of Renal Tubules in Diabetic Kidney Disease by Inhibiting Endoplasmic Reticulum Stress

The study is aimed at investigating the effects of Ginkgo biloba extract EGB761 on renal tubular damage and endoplasmic reticulum stress (ERS) in diabetic kidney disease (DKD). A total of 50 C57BL/6 N mice were randomly divided into the normal group, DKD group, DKD+EGB761 group (36 mg/kg), and DKD+4-phenylbutyrate (4-PBA) group (1 g/kg). The DKD model was replicated by high-fat diet combined with intraperitoneal injection of streptozotocin (STZ). Renal tubular epithelial cells (HK-2) were divided into the control group, high-glucose group (30 mmol/L), EGB761 group (40 mg/L, 20 mg/L, 10 mg/L), TM group, and TM+4-PBA group. After 8 weeks of administration, expressions of serum creatinine (Scr), blood urea nitrogen (BUN), 24 h urinary protein (24 h Pro), fasting blood glucose (FBG), β 2-microglobulin (β 2-MG), and retinol binding protein 4 (RBP4) of mice were tested. The pathological changes of renal tissue were observed. The expressions of extracellular matrix (ECM) accumulation and epithelial-mesenchymal transition (EMT) markers α-smooth muscle actin (α-SMA), E-cadherin, fibronectin, and collagen IV, as well as the ERS markers GRP78 and ATF6, were tested by Western blot, qPCR, immunohistochemistry, or immunofluorescence. EGB761 could decrease the Scr, BUN, 24 h Pro, and FBG levels in the DKD group, alleviate renal pathological injury, decrease urine β 2-MG, RBP4 levels, and decrease the expression of α-SMA, collagen IV, fibronectin, and GRP78, as well as ATF6, while increase the expression of E-cadherin. These findings demonstrate that EGB761 can improve renal function, reduce tubular injury, and ameliorate ECM accumulation and EMT in DKD kidney tubules, and the mechanism may be related to the inhibition of ERS.

Increased dishevelled associated activator of morphogenesis 2, a new podocyte-associated protein, in diabetic nephropathy

BACKGROUND

Previously, by using proteomic analysis and RNA sequencing in isolated glomeruli, we identified several novel differentially expressed proteins in human and mouse diabetic nephropathy (DN) versus controls, including dishevelled associated activator of morphogenesis 2 (DAAM2). DAAM2 binds the Wnt effector Dvl. We aimed to study possible contributions of DAAM2 to DN.

METHODS

We assessed DAAM2 by immunostaining in non-cancer regions of human nephrectomy (Nx), DN and normal donor kidney tissues. We also examined DAAM2 in DN mice (db/db eNOS-/-) and Nx mice. DN mice treated with angiotensin-converting enzyme inhibitor (ACEI), dipeptidyl peptidase 4 inhibitor (DPP4I) or vehicle were compared. DAAM2 was knocked down in primary cultured podocytes by small interfering RNA to study its effects on cell function.

RESULTS

In normal human glomeruli, DAAM2 was expressed only on podocytes. DAAM2 expression was increased in both Nx and DN versus normal donors. Podocyte DAAM2 expression was increased in DN and Nx mouse models. Glomerular DAAM2 expression correlated with glomerular size and was decreased significantly by ACEI while DPP4I only numerically reduced DAAM2. In primary cultured podocytes, knockdown of DAAM2 enhanced adhesion, slowed migration, activated Wnt-β-catenin signaling and downregulated mammalian target of rapamycin complex 1 (mTORC1) and Rho activity.

CONCLUSIONS

Podocyte DAAM2 is upregulated in both Nx and DN, which could be contributed to by glomerular hypertrophy. We hypothesize that DAAM2 regulates podocyte function through the mTORC1, Wnt/β-catenin and Rho signaling pathways.

Polydatin-loaded chitosan nanoparticles ameliorates early diabetic nephropathy by attenuating oxidative stress and inflammatory responses in streptozotocin-induced diabetic rat

In various developed countries, diabetic nephropathy (DN) is the principal cause of end-stage kidney disease and a main reason of injury and mortality in individuals with renal morbidity worldwide. Polydatin (POL) has been evaluated as a potential antioxidant, anti-inflammatory and a nephroprotective agent. In spite of this, the possible benefits and protective effects of POL on early diabetic nephropathy are not quite clarified. For the effective clearance from the body besides safe drug delivery, biodegradable nanoparticles have interesting attraction. This work was designed to evaluate the positive effect and possible mechanisms of Polydatin-loaded Chitosan-Nanoparticles (POL-NPs) on early DN in streptozotocin-induced diabetic rats. Followed the induction of diabetes, rats classified into four groups, diabetic control and diabetic rats treated daily and orally with; POL, Polydatin-loaded chitosan-Nanoparticles (POL-NPs), plus normal control rats. Our findings showed that diabetic group presented a significant high level of the blood glucose, blood glycosylated hemoglobin (HbA1c), serum insulin, renal function related parameters, renal Advanced glycation-end products (AGEs) and lipid peroxidation level compared to normal control rats, while serum albumin level and the activities of renal antioxidant enzymes were significantly decreased. Moreover, in the kidney of diabetic rat mRNA expression of nuclear factor-kappa B (NF-κB) and cyclooxygenase-2 (Cox-2) were up-regulated. Besides, increase in serum levels of pro-inflammatory cytokines (TNF-α, IL-6 and IL-18) and decrease in anti-inflammatory cytokine (IL-10). POL and POL-NPs supplementation were significantly attenuate the above-mention results and returned the normal equilibrium between pro- and anti-inflammatory cytokines. In conclusion, POL and POL-NPs have antidiabetic effect, suppresses oxidative stress and mitigates renal inflammation through inhibition of NF-κB in diabetic kidney in early progressive DN.

Metformin regulates inflammation and fibrosis in diabetic kidney disease through TNC/TLR4/NF-κB/miR-155-5p inflammatory loop

BACKGROUND

Type 2 diabetes mellitus (T2DM) is significantly increasing worldwide, and the incidence of its complications is also on the rise. One of the main complications of T2DM is diabetic kidney disease (DKD). The glomerular filtration rate (GFR) and urinary albumin creatinine ratio (UACR) increase in the early stage. As the disease progresses, UACR continue to rise and GFR begins to decline until end-stage renal disease appears. At the same time, DKD will also increase the incidence and mortality of cardiovascular and cerebrovascular diseases. At present, the pathogenesis of DKD is not very clear. Therefore, exploration of the pathogenesis of DKD to find a treatment approach, so as to delay the development of DKD, is essential to improve the prognosis of DKD.

AIM

To detect the expression of tenascin-C (TNC) in the serum of T2DM patients, observe the content of TNC in the glomerulus of DKD rats, and detect the expression of TNC on inflammatory and fibrotic factors in rat mesangial cells (RMCs) cultured under high glucose condition, in order to explore the specific molecular mechanism of TNC in DKD and bring a new direction for the treatment of DKD.

METHODS

The expression level of TNC in the serum of diabetic patients was detected by enzyme-linked immunosorbent assay (ELISA), the protein expression level of TNC in the glomerular area of DKD rats was detected by immunohistochemistry, and the expression level of TNC in the rat serum was detected by ELISA. Rat glomerular mesangial cells were cultured. Following high glucose stimulation, the expression levels of related proteins and mRNA were detected by Western blot and polymerase chain reaction, respectively.

RESULTS

ELISA results revealed an increase in the serum TNC level in patients with T2DM. Increasing UACR and hypertension significantly increased the expression of TNC (P < 0.05). TNC expression was positively correlated with glycosylated haemoglobin (HbA1c) level, body mass index, systolic blood pressure, and UACR (P < 0.05). Immunohistochemical staining showed that TNC expression in the glomeruli of rats with streptozotocin-induced diabetes was significantly increased compared with normal controls (P < 0.05). Compared with normal rats, serum level of TNC in diabetic rats was significantly increased (P < 0.05), which was positively correlated with urea nitrogen and urinary creatinine (P < 0.05). The levels of TNC, Toll-like receptor-4 (TLR4), phosphorylated nuclear factor-κB p65 protein (Ser536) (p-NF-κB p65), and miR-155-5p were increased in RMCs treated with high glucose (P < 0.05). The level of TNC protein peaked 24 h after high glucose stimulation (P < 0.05). After TNC knockdown, the levels of TLR4, p-NF-κB p65, miR-155-5p, connective tissue growth factor (CTGF), and fibronectin (FN) were decreased, revealing that TNC regulated miR-155-5p expression through the TLR4/NF-κB p65 pathway, thereby regulating inflammation (NF-κB p65) and fibrosis (CTGF and FN) in individuals with DKD. In addition, metformin treatment may relive the processes of inflammation and fibrosis in individuals with DKD by reducing the levels of the TNC, p-NF-κB p65, CTGF, and FN proteins.

CONCLUSION

TNC can promote the occurrence and development of DKD. Interfering with the TNC/TLR4/NF-κB p65/miR-155-5p pathway may become a new target for DKD treatment.

Myricitrin, a Glycosyloxyflavone in Myrica esculenta Bark Ameliorates Diabetic Nephropathy via Improving Glycemic Status, Reducing Oxidative Stress, and Suppressing Inflammation

The present study evaluated the therapeutic potential of myricitrin (Myr), a glycosyloxyflavone extracted from Myrica esculenta bark, against diabetic nephropathy. Myr exhibited a significant hypoglycemic effect in high fat-fed and a single low-dose streptozotocin-induced type 2 diabetic (T2D) rats. Myr was found to improve glucose uptake by the skeletal muscle via activating IRS-1/PI3K/Akt/GLUT4 signaling in vitro and in vivo. Myr significantly attenuated high glucose (HG)-induced toxicity in NRK cells and in the kidneys of T2D rats. In this study, hyperglycemia caused nephrotoxicity via endorsing oxidative stress and inflammation resulting in the induction of apoptosis, fibrosis, and inflammatory damages. Myr was found to attenuate oxidative stress via scavenging/neutralizing oxidative radicals and improving endogenous redox defense through Nrf-2 activation in both in vitro and in vivo systems. Myr was also found to attenuate diabetes-triggered renal inflammation via suppressing NF-κB activation. Myr inhibited hyperglycemia-induced apoptosis and fibrosis in renal cells evidenced by the changes in the expressions of the apoptotic and fibrotic factors. The molecular docking predicted the interactions between Myr and different signal proteins. An in silico absorption, distribution, metabolism, excretion, and toxicity (ADMET) study predicted the drug-likeness character of Myr. Results suggested the possibility of Myr to be a potential therapeutic agent for diabetic nephropathy in the future.

Enteropeptidase inhibition improves kidney function in a rat model of diabetic kidney disease

AIM

To examine the effects of an enteropeptidase inhibitor, SCO-792, on kidney function in rats.

MATERIALS AND METHODS

The pharmacological effects of SCO-792 were evaluated in Wistar fatty (WF) rats, a rat model of diabetic kidney disease (DKD).

RESULTS

Oral administration of SCO-792 increased faecal protein content and improved glycaemic control in WF rats. SCO-792 elicited a rapid decrease in urine albumin-to-creatinine ratio (UACR). SCO-792 also normalized glomerular hyperfiltration and decreased fibrosis, inflammation and tubular injury markers in the kidneys. However, pioglitazone-induced glycaemic improvement had no effect on kidney variables. Dietary supplementation of amino acids (AAs), which bypass the action of enteropeptidase inhibition, mitigated the effect of SCO-792 on UACR reduction, suggesting a pivotal role for enteropeptidase. Furthermore, autophagy activity in the glomerulus, which is impaired in DKD, was elevated in SCO-792-treated rats. Finally, a therapeutically additive effect on UACR reduction was observed with a combination of SCO-792 with irbesartan, an angiotensin II receptor blocker.

CONCLUSIONS

This study is the first to demonstrate that enteropeptidase inhibition is effective in improving disease conditions in DKD. SCO-792-induced therapeutic efficacy is likely to be independent of glycaemic control and mediated by the regulation of AAs and autophagy. Taken together with a combination effect of irbesartan, SCO-792 may be a novel therapeutic option for patients with DKD.

O-GlcNAcylation Suppresses the Ion Current IClswell by Preventing the Binding of the Protein ICln to α-Integrin

O-GlcNAcylation is a post-translational modification of proteins that controls a variety of cellular processes, is chronically elevated in diabetes mellitus, and may contribute to the progression of diabetic complications, including diabetic nephropathy. Our previous work showed that increases in the O-GlcNAcylation of cellular proteins impair the homeostatic reaction of the regulatory volume decrease (RVD) after cell swelling by an unknown mechanism. The activation of the swelling-induced chloride current IClswell is a key step in RVD, and ICln, a ubiquitous protein involved in the activation of IClswell, is O-GlcNAcylated. Here, we show that experimentally increased O-GlcNAcylation of cellular proteins inhibited the endogenous as well as the ICln-induced IClswell current and prevented RVD in a human renal cell line, while decreases in O-GlcNAcylation augmented the current magnitude. In parallel, increases or decreases in O-GlcNAcylation, respectively, weakened or stabilized the binding of ICln to the intracellular domain of α-integrin, a process that is essential for the activation of IClswell. Mutation of the putative YinOYang site at Ser67 rendered the ICln-induced IClswell current unresponsive to O-GlcNAc variations, and the ICln interaction with α-integrin insensitive to O-GlcNAcylation. In addition, exposure of cells to a hypotonic solution reduced the O-GlcNAcylation of cellular proteins. Together, these findings show that O-GlcNAcylation affects RVD by influencing IClswell and further indicate that hypotonicity may activate IClswell by reducing the O-GlcNAcylation of ICln at Ser67, therefore permitting its binding to α-integrin. We propose that disturbances in the regulation of cellular volume may contribute to disease in settings of chronically elevated O-GlcNAcylation, including diabetic nephropathy.

Bioactive Agent Discovery from the Natural Compounds for the Treatment of Type 2 Diabetes Rat Model

Diabetes mellitus is a well-known chronic metabolic disease that poses a long-term threat to human health and is characterized by a relative or absolute lack of insulin, resulting in hyperglycemia. Type 2 diabetes mellitus (T2DM) typically affects many metabolic pathways, resulting in β-cell dysfunction, insulin resistance, abnormal blood glucose levels, inflammatory processes, excessive oxidative reactions, and impaired lipid metabolism. It also leads to diabetes-related complications in many organ systems. Antidiabetic drugs have been approved for the treatment of hyperglycemia in T2DM; these are beneficial for glucose metabolism and promote weight loss, but have the risk of side effects, such as nausea or an upset stomach. A wide range of active components, derived from medicinal plants, such as alkaloids, flavonoids, polyphenol, quinones, and terpenoids may act as alternative sources of antidiabetic agents. They are usually attributed to improvements in pancreatic function by increasing insulin secretions or by reducing the intestinal absorption of glucose. Ease of availability, low cost, least undesirable side effects, and powerful pharmacological actions make plant-based preparations the key player of all available treatments. Based on the study of therapeutic reagents in the pathogenesis of humans, we use the appropriate animal models of T2DM to evaluate medicinal plant treatments. Many of the rat models have characteristics similar to those in humans and have the advantages of ease of genetic manipulation, a short breeding span, and access to physiological and invasive testing. In this review, we summarize the pathophysiological status of T2DM rat models and focus on several bioactive compounds from herbal medicine with different functional groups that exhibit therapeutic potential in the T2DM rat models, in turn, may guide future approach in treating diabetes with natural drugs.

Discovery of polypodiside as a Keap1-dependent Nrf2 activator attenuating oxidative stress and accumulation of extracellular matrix in glomerular mesangial cells under high glucose

Diabetic nephropathy (DN) is a severe microvascular complication of diabetes mellitus. High glucose has resulted in oxidative stress and following renal fibrosis as the crucial nodes of this disease. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor regulating transcription of many antioxidant genes and suppressing synthesis of extracellular matrix. To discover Nrf2 activators targeting DN, we have evaluated polypodiside using cell-based assays. The results showed polypodiside inhibited the high glucose-induced self-limited proliferation of glomerular meangial cells. Activation of Nrf2 and enhanced transcription to antioxidant response elements were observed in the presence of polypodiside. Oxidative stress and accumulation of extracellular matrix induced by high glucose in glomerular meangial cells have been ameliorated by polypodiside. Further investigations revealed the effects of polypodiside on glomerular meangial cells were associated with activation of Nrf2. Co-immunoprecipitation of Nrf2 disclosed polypodiside disrupted the Kelch-like ECH-associated protein-1 (Keap1)-Nrf2 interaction. Molecular docking elucidated polypodiside could enter the Nrf2 binding cavity of Keap1 via interacting with the residues encompassing that cavity. These findings indicate polypodiside is a Keap1-dependent Nrf2 activator affording the catabatic effects against oxidative stress and accumulation of extracellular matrix in glomerular meangial cells under high glucose.

Suppression of Inflammatory Cytokines Expression with Bitter Melon (Momordica Charantia) in TNBS-instigated Ulcerative Colitis

Background and Objective

This study was aimed to elucidate the molecular mechanism of Momordica charantia (MCh), along with a standard drug prednisolone, in a rat model of colitis induced by trinitrobenzene sulfonic acid (TNBS).

Methods

After the induction of the experimental colitis, the animals were treated with MCh (4 g/kg/day) for 14 consecutive days by intragastric gavage. The colonic tissue expression levels of C-C motif chemokine ligand 17 (CCL-17), interleukin (IL)-1β, IL-6, IL-23, interferon-γ (IFN-γ), nuclear factor kappa B (NF-kB), and tumor necrosis factor-α (TNF-α), were determined at both mRNA and protein levels to estimate the effect of MCh. Besides, colonic specimens were analyzed histopathologically after staining with hematoxylin and eosin.

Results

The body weights from TNBS-instigated colitis rats were found to be significantly lower than untreated animals. Also, the IFN-γ, IL-1β, IL-6, Il-23, TNF-α, CCL-17, and NF-kB mRNA and protein levels were increased significantly from 1.86-4.91-fold and 1.46-5.50-fold, respectively, in the TNBS-instigated colitis group as compared to the control. Both the MCh and prednisolone treatment significantly reduced the bodyweight loss. It also restored the induced colonic tissue levels of IL-1β, IL-6, IFN-γ, and TNF-α to normal levels seen in untreated animals. These results were also supported with the histochemical staining of the colonic tissues from both control and treated animals.

Conclusion

The presented data strongly suggests that MCh has the anti-inflammatory effect that might be modulated through vitamin D metabolism. It is the right candidate for the treatment of UC as an alternative and complementary therapeutics.

Oligo-Fucoidan Improves Diabetes-Induced Renal Fibrosis via Activation of Sirt-1, GLP-1R, and Nrf2/HO-1: An In Vitro and In Vivo Study

Fucoidan extracted from brown algae has multiple beneficial functions. In this study, we investigated the effects of low-molecular-weight fucoidan (oligo-FO) on renal fibrosis under in vitro and in vivo diabetic conditions, and its molecular mechanisms. Advanced glycation product (AGE)-stimulated rat renal proximal tubular epithelial cells (NRK-52E) and diabetic mice induced by high-fat diet and intraperitoneal injection of streptozotocin and nicotinamide were used. Oligo-FO treatment significantly inhibited anti-high mobility group box 1 (HMGB1)/RAGE/ anti-nuclear factor-kappa B (NF-κB)/transforming growth factor-β1 (TGF-β1)/TGF-β1R/Smad 2/3/fibronectin signaling pathway and HIF-1α activation in AGE-stimulated NRK-52E cells. Conversely, the expression and activity of Sirt-1; the levels of ubiquitin-specific peptidase 22 (USP22), p-AMPK, glucagon-like peptide-1 receptor (GLP-1R), and heme oxygenase-1 (HO-1); and Nrf2 activation were remarkably increased by oligo-FO in AGE-stimulated cells. However, the above effects of oligo-FO were greatly diminished by inhibiting Sirt-1, HO-1, or GLP-1R activity. Similar changes of these pro-fibrotic genes in the kidney and a marked attenuation of renal injury and dysfunction were observed in oligo-FO-treated diabetic mice. These findings indicated that the inhibitory effects of the oligo-FO on diabetes-evoked renal fibrosis are mediated by suppressing TGF-β1-activated pro-fibrogenic processes via Sirt-1, HO-1, and GLP-1R dependence. Collectively, fucoidan-containing foods or supplements may be potential agents for ameliorating renal diseases due to excessive fibrosis.

AMPK allostery: A therapeutic target for the management/treatment of diabetic nephropathy

Diabetic nephropathy (DN) is a chronic complication of diabetes mellitus (DM) with approximately 30-40% of patients with DM developing nephropathy, and it is the leading cause of end-stage renal diseases and diabetic morbidity. The pathogenesis of DN is primarily associated with irregularities in the metabolism of glucose and lipid leading to hyperglycemia-induced oxidative stress, which has been a major target together with blood pressure regulation in the control of DN progression. However, the regulation of 5' adenosine monophosphate-activated protein kinase (AMPK), a highly conserved protein kinase for maintaining energy balance and cellular growth and repair has been implicated in the development of DM and its complications. Therefore, targeting AMPK pathway has been explored as a therapeutic strategy for the treatment of diabetes and its complication, although most of the mechanisms have not been fully elucidated. In this review, we discuss the structure of AMPK relevant to understanding its allosteric regulation and its role in the pathogenesis and progression of DN. We also identify therapeutic agents that modulate AMPK and its downstream targets with their specific mechanisms of action in the treatment of DN.

Systemic inhibition of miR-451 increases fibrotic signaling and diminishes autophagic response to exacerbate renal damage in Tallyho/Jng mice

miRNAs provide fine tuning of gene expression via inhibition of translation. miR-451 has a modulatory role in cell cycling via downregulation of mechanistic target of rapamycin. We aimed to test whether chronic systemic inhibition of miR-451 would enhance renal fibrosis (associated with deranged autophagy). Adult TallyHo/Jng mice (obese insulin resistant) were randomized to two treatment groups to receive either miR-451 inhibition [via a locked nucleic acid construct] or a similar scrambled locked nucleic acid control for 8 wk. All mice were fed a high-fat diet (60% kcal from fat) ad libitum and humanely euthanized after 12 wk. Kidneys and blood were collected for analysis. Renal expression of miR-451 was sixfold lower in inhibitor-treated mice compared with control mice. miR-451 inhibition increased kidney weight and collagen and glycogen deposition. Blood chemistry revealed significantly higher Na⁺ and anion gap (relative metabolic acidosis) in inhibitor-treated mice. Western blot analysis and immunohistochemistry of the kidney revealed that the inhibitor increased markers of renal injury and fibrosis, e.g., kidney injury molecule 1, neutrophil gelatinase-associated lipocalin, transforming growth factor-β, 14-3-3 protein-ζ, mechanistic target of rapamycin, AMP-activated protein kinase-α, calcium-binding protein 39, matrix metallopeptidase-9, and the autophagy receptor sequestosome 1. In contrast, the inhibitor reduced the epithelial cell integrity marker collagen type IV and the autophagy markers microtubule-associated protein 1A/1B light chain 3B and beclin-1. Taken together, these results support a protective role for miR-451 in reducing renal fibrosis by enhancing autophagy in obese mice.

Gynura divaricata exerts hypoglycemic effects by regulating the PI3K/AKT signaling pathway and fatty acid metabolism signaling pathway

OBJECTIVES

The study aimed to examine the anti-diabetic effects of Gynura divaricata (GD) and the underlying mechanism.

METHODS

Information about the chemical compositions of GD was obtained from extensive literature reports. Potential target genes were predicted using PharmMapper and analyzed using Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO). To validate the results from bioinformatics analyses, an aqueous extract of GD was administered to type 2 diabetic rats established by feeding a high-fat and high-sugar diet followed by STZ injection. Key proteins of the PI3K/AKT signaling pathway and fatty acid metabolism signaling pathway were investigated by immunoblotting.

RESULTS

The blood glucose of the rats in the GD treatment group was significantly reduced compared with the model group without treatment. GD also showed activities in reducing the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), and creatinine (CREA). The levels of urine sugar (U-GLU) and urine creatinine (U-CREA) were also lowered after treatment with GD. Bioinformatics analysis showed that some pathways including metabolic pathways, insulin resistance, insulin signaling pathway, PPAR signaling pathway, bile secretion, purine metabolism, etc. may be regulated by GD. Furthermore, GD significantly increased the protein expression levels of PKM1/2, p-AKT, PI3K p85, and GLUT4 in the rat liver. In addition, the expression levels of key proteins in the fatty acid metabolism signaling pathway including AMPK, p-AMPK, PPARα, and CPT1α were significantly upregulated. The anti-apoptotic protein BCL-2/BAX expression ratio in rats was significantly upregulated after GD intervention. These results were consistent with the bioinformatics analysis results.

CONCLUSIONS

Our study suggests that GD can exert hypoglycemic effects in vivo by regulating the genes at the key nodes of the PI3K/AKT signaling pathway and fatty acid metabolism signaling pathway.

Isobavachalcone ameliorates diabetic nephropathy in rats by inhibiting the NF-κB pathway

Isobavachalcone (ISO) exhibits good anti-inflammatory activity. We evaluated the renoprotective effects of ISO against diabetic nephropathy (DN). Diabetic rats established by the single injection of streptozotocin (STZ) were orally treated with ISO. The levels of serum creatinine (Scr), blood urea nitrogen (BUN), and 24 hr urinary protein were measured. In this study, ISO effectively ameliorated renal damage by reducing BUN, Scr, and 24 hr urinary protein and also improved kidney pathological appearances. ISO prevented STZ-caused apoptosis in the glomerular tissue in vivo and blocked the high glucose (HG)-induced growth inhibitory effect in human renal glomerular endothelial cells in vitro. Moreover, ISO reduced pro-inflammatory mediator production and blocked the NF-κB pathway in the damaged renal tissues and HG-treated HRGEC cells. Taken together, the results of this study indicate that ISO consumption might have significant beneficial effects on the DN and this action might be correlated with the modulation of the NF-κB pathway. PRACTICAL APPLICATIONS: ISO is an active compound from the dried ripe fruit of Psoralea corylifolia L. seed, which is traditionally served as a food ingredient in Asia. In this investigation, we observed the beneficial effects of ISO on a murine model with DN. Further research revealed that the protective action of ISO might be connected with its weak hypoglycaemic and notable anti-inflammatory effects. Our research data suggest that ISO-enriched food might be a good choice for people suffering from DN.

The Effects of Salvianolate Combined With Western Medicine on Diabetic Nephropathy: A Systematic Review and Meta-Analysis

Background

Salvianolate, a compound mainly composed of salvia magnesium acetate, is extracted from the Chinese herb Salvia miltiorrhiza. Because of its biological activity, easy quality control and certain efficacy, salvianolate is widely used in treating ischemic cardiocerebral vascular disease, liver damage, renal injury, diabetes, and its complications. Particularly, it has potential protective effects on diabetic nephropathy (DN).

Objective

This meta-analysis aimed to evaluate the efficacy and safety of salvianolate when combined with western medicine in patients affected with DN.

Methods

We searched Pubmed, Web of Science, the Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Data knowledge service platform (Wanfang Data), Chinese Scientific Journal Database (VIP), and China Biology Medicine Disc (SinoMed) for randomized controlled trials (RCTs) of salvianolate in combination with western medicine on DN, including results from the foundation of each database until November 30, 2019. Two reviewers independently performed literature screening, data extraction, and quality evaluation. This meta-analysis was carried out using RevMan5.3 software.

Results

From the 12 RCTs, 1,030 patients from China were involved. Compared with single-use western medicine, the combination of salvianolate and western medicine for the treatment of DN could reduce levels of serum creatinine (Scr) [MD=-16.53, 95% CI (-28.79, -4.27), P=0.008], blood urea nitrogen (BUN) [MD=-1.40, 95% CI (-2.17, -0.62), P=0.0004], urinary albumin excretion rate (UARE) [SMD=-1.84, 95% CI (-2.70, -0.98), P < 0.0001], 24-hour urinary protein (24h Upro) [MD=-0.37, 95% CI (-0.47, -0.26), P < 0.00001], albumin-to-creatinine ratio (ACR) [SMD=-1.43, 95% CI (-2.64, -0.23), P=0.02], hypersensitive C-reactive protein (hs-CRP) [MD=-5.69, 95% CI (-7.09, -4.29), P < 0.00001], interleukin-6 (IL-6) [MD=-12.53, 95% CI (-18.55, -6.52), P < 0.0001], malondialdehyde (MDA) [SMD=-2.05, 95% CI (-3.67, -0.43), P=0.01], as well as improve clinical efficacy [RR=1.21, 95% CI (1.12,1.31), P < 0.00001], and increase superoxide dismutase (SOD) levels [SMD=1.12, 95% CI (0.86,1.38), P < 0.00001]. No increase in the occurrence of serious adverse events were observed in the treatment group compared with the control group.

Conclusion

This study indicated that salvianolate combined with western medicine contributes to protecting renal function, inhibiting inflammation, and exhibiting anti-oxidative properties, thereby improving clinical efficacy. Thus, salvianolate can be considered as a potential complementary therapy for DN patients. However, due to the low quality of methodology and small sample sizes, more rigorous and larger trials are essential to validate our results.

Ibrolipim attenuates early-stage nephropathy in diet-induced diabetic minipigs: Focus on oxidative stress and fibrogenesis

It is well-recognized that hyperlipidemia and lipid peroxidation contribute to the progression of diabetic nephropathy (DN), which is associated with oxidative stress (OS) and fibrotic lesions. Ibrolipim, a specific lipoprotein lipase activator, has been proved to reduce hyperglycemia and hyperlipidemia, suppress renal lipid deposition, and also protect renal damage. However, the underlying mechanisms of its renoprotective effect are not clearly elaborated. Herein, the present study was to identify whether the putative mechanism of Ibrolipim was related to OS and fibrogenesis in diabetic minipigs fed by high-sucrose and high-fat diet (HSFD) with or without Ibrolipim for 5 months. Compared with the normal control diet, nutrient stress induced by HSFD caused moderate glomerulosclerosis and tubulointerstitial fibrosis, and promoted renal ultrastructural and functional abnormalities. These abnormalities were correlated with renal OS and fibrogenesis characterized by the increased levels of reactive oxygen species (ROS), malondialdehyde, hydroxyproline, collagen type Ⅳ alpha 1 and fibronectin, and decreased contents of reduced glutathione and total antioxidant capacity in kidneys. Ibrolipim significantly ameliorated these abnormalities in HSFD-fed minipigs. In addition, Ibrolipim diminished HSFD-induced nicotinamide-adenine dinucleotide phosphate oxidase-4 activation to reduce ROS production, and enhanced the expression and activity of antioxidant enzymes (i.e. superoxide dismutase 1, catalase and glutathione peroxidase 1) to increase ROS elimination, resulting in obvious suppression of renal OS. Meanwhile, Ibrolipim not only inhibited the upregulation of transforming growth factor-β1 but also partially reversed the downregulation of matrix metalloproteinase 2, and then prevented extracellular matrix (ECM) accumulation. Taken together, Ibrolipim exhibits anti-oxidative and anti-fibrotic effects via modulating the rebalance of renal ROS and ECM metabolism, and ultimately attenuates the progression of nephropathy in diet-induced diabetic minipigs.

Artemisinin attenuates early renal damage on diabetic nephropathy rats through suppressing TGF-β1 regulator and activating the Nrf2 signaling pathway

AIM

The present study aims to investigate the protective effects of artemisinin (ATZ) on early renal damage in experimental diabetic rats and its probable mechanism.

METHODS

Models of diabetic nephropathy (DN) rats was established utilizing streptozotocin (STZ)-injection intraperitoneally (55 mg/kg) method. All rats were subsequently divided into normal control group, model group and ATZ (25, 50, 75 mg/kg) group randomly. Biochemical parameters including body weight, kidney index, blood glucose, 24 h UAER, Scr, BUN, T-SOD, GSH-Px and MDA were comprehensively determined after 8-week consecutive administrations. HE and PAS stainings were performed to observe the histopathological alterations of kidney. Western blot was conducted to detect the expressions of TGF-β1, Nrf2, HQ-1 and NQO1.

KEY FINDINGS

ATZ at three concentrations in ATZ group significantly increased the body weight. Biochemical parameters altered significantly between model group and ATZ group. Moreover, ATZ inhibited TGF-β1 protein expression and activated the Nrf2 signaling pathway. Pathological histology results revealed the alterations including mesangial cells proliferation, thickness of glomerular capillary basement membrane, extracellular matrix (ECM) and the 24 h UAER. Western blot analysis demonstrated the increase of antioxidant proteins HO-1 and NQO1 and Nrf2-related proteins.

SIGNIFICANCE

ATZ could reduce early renal oxidative stress damage in DN rats by inhibiting TGF-β1 protein expression in kidney tissues as well as activating the Nrf2 signaling pathway and enhancing the expression of antioxidant proteins, thereby exerting the protective effects on DN kidney. The current study is the first report of ATZ on attenuating effects on kidney of DN rats, which could lay solid theoretical foundations on clinical application of ATZ to treat DN.