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

Developments in the connection between epithelial‑mesenchymal transition and endoplasmic reticulum stress (Review)

Endoplasmic reticulum stress (ERS) and epithelial‑mesenchymal transition (EMT) have important roles in fibrosis and tumour development. Moderate ERS activates cellular defence mechanisms in response to noxious stimuli; however, sustained or overly strong ERS induces apoptosis. In this disease process, EMT induces epithelial cells to acquire the ability to migrate and invade. Reportedly, ERS directly or indirectly regulates EMT processes through multiple mechanisms (such as key transcription factors, signalling pathways, ferroptosis, autophagy and oxidative stress), and both processes form a complex network of interactions. Given the critical roles of ERS and EMT in disease, targeted intervention of these two processes has emerged as a potential therapeutic strategy. In the present study, the molecular interaction mechanism of ERS and EMT was systematically explored, research progress in fibrotic and neoplastic diseases was reviewed and the potential application prospects of related targeted therapies were examined, which may provide new ideas for the development of drugs to reverse fibrosis and treat tumours.

Endoplasmic reticulum stress and unfolded protein response in renal lipid metabolism

The endoplasmic reticulum (ER) is a crucial cellular organelle involved in protein synthesis, folding, modification, and transport. Exposure to internal and external stressors can induce endoplasmic reticulum stress (ERS), leading to abnormal protein folding and ER malfunction. This stress can disrupt lipid synthesis, metabolism, and transport processes. Fatty acid oxidation is the primary energy source for the renal system. When energy intake exceeds the storage capacity of adipose tissue, lipids accumulate abnormally in non-adipose tissues, including kidneys, liver, and pancreas. Lipids accumulate in the kidneys of nearly all cell types, including thylakoid membranous, pedunculated, and proximal renal tubular epithelial cells. Intracellular free fatty acids can significantly disrupt renal lipid metabolism, contributing to ischemia-reperfusion acute kidney injury, diabetic nephropathy, renal fibrosis, and lupus nephritis. Consequently, this study delineated the primary signaling pathways and mechanisms of the ERS-induced unfolded protein response, explored the mechanistic link between ERS and lipid metabolism, and elucidated its role in renal lipid metabolism. This study aimed to offer new perspectives on managing and treating renal disorders.

Polyethylene glycol loxenatide protects diabetic kidneys by inhibiting GRP78/PERK/eIF2α pathway, and improves cardiac injury by suppressing TLR4/NF-κB inflammatory pathway

BACKGROUND

Cardiovascular and renal complications of type 2 diabetes are the main causes of death in diabetic patients. Clinical studies have found that polyethylene glycol loxenatide (PEG-Loxe), a GLP-1 analog widely used to treat type 2 diabetes, boosts renal and cardiac functions in diabetic patients. However, its mechanism of action remains to be elucidated.

METHODS

Using injury models of HK-2 human renal proximal tubular epithelial cells and H9C2 rat myocardial cells, as well as db/db mouse models of type 2 diabetes, this study assessed the protective effects of PEG-Loxe on T2DM mice kidneys and hearts and revealed their mechanisms of action.

RESULTS

PEG-Loxe treatment significantly reduced the contents of serum creatinine, urea nitrogen, and 24 h urine protein, alleviated glomerular injury and inflammatory reaction, markedly elevated cardiac left ventricular ejection fraction (LVEF) and fractional shortening (LVFS) levels, diminished pathological injuries in cardiac tissues, and improved renal and cardiac functions in db/db mice. In addition, PEG-Loxe considerably decreased the GRP78 mRNA and protein expressions of GRP78, p-eIF2α, ATF4, and CHOP in the kidneys of T2DM mice, inhibited GRP78/PERK/eIF2α pathway-related proteins in HK-2 cells cultured in high glucose concentrations, subdued renal endoplasmic reticulum stress, and eased renal injury in T2DM mice. PEG-Loxe also obstructed the TLR4/NF-κB inflammatory pathway and myocardial apoptosis and mitigated cardiac trauma in T2DM by reducing TLR4, MyD88, and p-NF-κBp65 protein expressions in cardiac tissues. The H9C2 cell experiment further confirmed PEG-Loxe's ability to protect the cardiovascular system of T2DM patients by inhibiting the TLR4/NF-κB inflammatory pathway and lessening LDH and CK-MB levels.

CONCLUSION

We showed that PEG-Loxe could decrease renal stress response and improve renal injury in T2DM by inhibiting endoplasmic reticulum stress via the GRP78/PERK/eIF2α pathway. Additionally, PEG-Loxe could hinder the TLR4/NF-κB inflammatory pathway and myocardial apoptosis and boost cardiac function, thus exerting protective effects on the cardiovascular system in T2DM.

Diphenyl diselenide protects against diabetic kidney disease through modulating gut microbiota dysbiosis in streptozotocin-induced diabetic rats

Introduction

Diphenyl diselenide (DPDS) ameliorates nephropathy in streptozotocin (STZ)-induced type 1 diabetic rats by inhibiting oxidative stress and inflammatory reactions. However, it has not been clarified whether DPDS alleviates type 1 diabetic kidney disease (DKD) is related to the inhibition of extracellular matrix (ECM) production and the regulation of intestinal flora disorder.

Methods

The present study investigated the effects of DPDS on ECM generation in the kidney and intestinal microflora composition in feces. The rats were orally administered DPDS or metformin for eight weeks. Various indices were measured to assess the severity of renal injury. After euthanizing the rats, oxidative stress markers in serum and kidney were assessed using biochemical methods, and the expressions of ECM-related proteins in kidney were analyzed using Western blot. Additionally, 16S rRNA high-throughput sequencing was used to evaluate the diversity and composition of the intestinal flora in feces.

Results

The results showed DPDS and metformin improved the DKD in STZ rats, as evidenced by decreased blood glucose, BUN, urine volume, urine microalbumin, urinary β2 microglobulin, and improvement of renal pathological morphology. Furthermore, DPDS intervention markedly reduced the protein expression of α-SMA, COI Ⅳ, FN, and vimentin in the kidneys. Besides, DPDS not only improved dyslipidemia in STZ diabetic rats, but also enhanced the activities of antioxidant enzymes, decreased the level of MDA in serum and kidney, and regulated the expression of proteins related to the Nrf2/Keap1 signaling pathway in the kidney. Moreover, we found that DPDS could selectively improve the relative abundance of probiotics as well as the diversity of flora, thus ameliorating the intestinal microbial composition of the STZ rats, significantly regulating the intestinal microbial homeostasis.

Discussion

Overall, DPDS inhibited ECM production and improved renal pathological changes, which may be related to reducing oxidative stress damage in the kidney and improving intestinal flora imbalance, providing data support for the further development and application of DPDS in DKD.

DMDD, isolated from Averrhoa carambola L., ameliorates diabetic nephropathy by regulating endoplasmic reticulum stress-autophagy crosstalk

BACKGROUND

Studies have shown that Averrhoa carambola L. possesses therapeutic potential for diabetes and related complications. However, the specific beneficial effects and molecular mechanisms of 2-dodecyl-6-meth-oxycyclohexa-2,5-diene-1,4-dione (DMDD) isolated from Averrhoa carambola L. on diabetic nephropathy (DN) require further investigation.

METHODS

80 C57BL/6 J male mice were subjected to a 1-week adaptive feeding, followed by a high-fat diet and intraperitoneal injection of 100 mg/kg streptozotocin (STZ) to construct an in vivo DN model. Additionally, human renal proximal tubular epithelial cells (HK-2) induced by high glucose (HG) were used as an in vitro DN model. The expression levels of epithelial-mesenchymal transition (EMT), endoplasmic reticulum stress (ERS), and autophagy-related proteins in renal tubular cells were detected by Western Blot, flow cytometry, immunofluorescence, and enzyme-linked immunosorbent assay (ELISA) staining. Transcriptome analysis revealed was conducted to elucidate the specific mechanism of by which DMDD mitigates DN by inhibiting ERS and autophagy. HK-2 cells were transfected with IRE1α overexpression lentivirus to reveal the role of IRE1α overexpression in HG-induced HK-2.

RESULTS

The experimental data showed that DMDD significantly reduced blood glucose levels and improved renal pathological alterations in DN mice. Additionally, DMDD inhibited the calcium (Ca2+) pathway, manifested by decreased autophagosome formation and downregulation of LC3II/I, Beclin-1, and ATG5 expression. Moreover, in HG-induced HK-2 cells, DMDD suppressed the overexpression of GRP78, CHOP, LC3II/I, Beclin1, and ATG5. Notably, IRE1α overexpression significantly increased autophagy incidence; however, DMDD treatment subsequently reduced the expression of LC3II/I, Beclin1, and ATG5.

CONCLUSION

DMDD effectively inhibits excessive ERS and autophagy, thereby reducing renal cell apoptosis through the IRE1α pathway and Ca 2+ pathway.

The molecular mechanisms of ginkgo (Ginkgo biloba) activity in signaling pathways: A comprehensive review

BACKGROUND

One of the most unique plants that have ever grown on the planet is Ginkgo biloba L., a member of the Ginkgoaceae family with no close living relatives. The existence of several differently structured components of G. biloba has increased the chemical variety of herbal therapy. Numerous studies that investigated the biochemical characteristics of G. biloba suggest this plant as a potential treatment for many illnesses.

PURPOSE

Review the molecular mechanisms involved in the signaling pathways of G. biloba activity in varied circumstances and its potential as a novel treatment for various illnesses.

METHODS

Studies focusing on the molecular processes and signaling pathways of compounds and extracts of G. biloba were found and summarized using the proper keywords and operators from Google Scholar, PubMed, Web of Science, and Scopus without time restrictions.

RESULTS

G. biloba exerts its effects through its anti-inflammatory, anti-apoptotic, anti-cancer, neuroprotective, cardioprotective, hepatoprotective, antiviral, antibacterial, pulmoprotective, renoprotective, anti-osteoporosis, anti-melanogenic, retinoprotective, otoprotective, adipogenic, and anti-adipogenic properties. The most important mechanisms involved in these actions are altering the elevation of ROS formation, inhibiting NADPH oxidases activation, altering the expression of antioxidant enzymes, downregulating MAPKs (p38 MAPK and ERK, and JNK) and AP-1, increasing cAMP, inactivating Stat5, activating the AMPK signaling pathway, affecting Stat3/JAK2, NF-κB, Nrf-2, mTOR, HGF/c-Met, Wnt/β-catenin and BMP signaling pathways, and changing the mitochondrial transmembrane potential, the Bax/Bcl-2 ratio, the release of Cyc from mitochondria to cytosol, the protein cleavage of caspases 3, 7, 8, 9, and 12, poly (ADP-ribose) polymerase, and MMPs levels.

CONCLUSIONS

G. biloba and its components have gained attention in recent years for their therapeutic benefits, such as their anti-inflammatory, antioxidant, anti-apoptotic, and apoptotic effects. By understanding their molecular mechanisms and signaling pathways, potential novel medicines might be developed in response to the rising public desire for new therapies.

Effects and safety of Ginkgo biloba on blood metabolism in type 2 diabetes mellitus: a systematic review and meta-analysis

Background

There has existed controversy regarding the use of Ginkgo biloba (GKB) for blood metabolism among type 2 diabetes mellitus(T2DM) patients, and we tried to analyze the effects and safety of GKB on T2DM patients.

Methods

We conducted a literature search between January 2003 and December 2022 of seven online databases (PubMed, Scopus, Embase, Google Scholar, Web of Sciences, Cochrane Library, and China National Knowledge Infrastructure). A systematic literature review and meta-analysis were performed to compare the effects and safety of GKB among T2DM patients. Four groups of parameters were extracted and analyzed: hemorheology parameters, lipid profile, glycemic control markers, and adverse events.

Results

In the end, 13 eligible articles with 11 indicators among 1573 patients were included. In the hemorheology parameters section, GKB showed significantly lower plasma viscosity (PV) (SMD=-0.91, 95%CI [-1.45, -0.36], P<0.01) and hematocrit (Hct) (SMD=-0.60, 95%CI [-0.97, -0.24], P<0.01) than the control group. GKB shoed higher velocity of the dorsalis pedis artery (VDPA) (SMD=0.51, 95%CI [0.26, 0.76], P<0.01) and ankle brachial index (ABI) (SMD=0.71, 95%CI [0.32, 1.10], P<0.01) than the control. In both the lipid profile and glycemic control markers sections, we did not find any difference between GKB and control groups, including total cholesterol (TC), triglyceride (TG), low-density lipoprotein (LDL), high-density lipoprotein (HDL), hemoglobin A1c (HbA1c), and fasting serum glucose (FSG). In addition, we saw no difference in adverse events (AE). The sensitivity analysis and funnel plot showed that the results in this research were robust and had no publication bias.

Conclusion

In conclusion, GKB might safely reduce the risk of peripheral arterial or even systemic cardiovascular disease. However, GKB did not directly improve lipid and blood glucose levels in T2DM patients.

Systematic review registration

https://inplasy.com/, identifier INPLASY202350096.

IKVAV peptide-containing hydrogel decreases fibrous scar after spinal cord injury by inhibiting fibroblast migration and activation

Fibrous scar is one of the major factors that hinder functional recovery in patients with spinal cord injury (SCI). Studies have shown that the laminin α1 peptide chain ile-les-val-ala-Val (IKVAV) promoted axonal growth and motor function recovery in rats after SCI. However, whether IKVAV could ameliorate SCI via reducing the formation of fibrous scar was not clear. A SCI model was constructed by transecting the rat spinal cord with a scalpel and implanting poly (N-propan-2-ylprop-2-enamide) (PNIPAM)-b-poly (AC-PEG-COOH) (PNPP) or PNIPAM-b-poly (AC-PEG-IKVAV) (PNPP-IKVAV) hydrogel. 14 days later hematoxylin-eosin staining and immunohistochemical staining were used to assess the effect of PNPP-IKVAV on scar formation. The effect of PNPP-IKVAV on endoplasmic reticulum (ER) stress was investigated by immunohistochemical staining. NIH-3T3 cells were used for in vitro scratching experiments and a transforming growth factor 1 (TGF-β1) activation model was constructed to assess the role of PNPP-IKVAV. In this study, PNPP-IKVAV inhibited fibroblast migration and suppressed TGF-β1 activation and ER stress (ERS) to reduce the extracellular matrix secretion by fibroblasts.

The role of Chinese herbal medicine in the treatment of diabetic nephropathy by regulating endoplasmic reticulum stress

Diabetic nephropathy (DN), a prevalent microvascular complication of diabetes mellitus, is the primary contributor to end-stage renal disease in developed countries. Existing clinical interventions for DN encompass lifestyle modifications, blood glucose regulation, blood pressure reduction, lipid management, and avoidance of nephrotoxic medications. Despite these measures, a significant number of patients progress to end-stage renal disease, underscoring the need for additional therapeutic strategies. The endoplasmic reticulum (ER) stress response, a cellular defense mechanism in eukaryotic cells, has been implicated in DN pathogenesis. Moderate ER stress can enhance cell survival, whereas severe or prolonged ER stress may trigger apoptosis. As such, the role of ER stress in DN presents a potential avenue for therapeutic modulation. Chinese herbal medicine, a staple in Chinese healthcare, has emerged as a promising intervention for DN. Existing research suggests that some herbal remedies may confer renoprotective benefits through the modulation of ER stress. This review explores the involvement of ER stress in the pathogenesis of DN and the advancements in Chinese herbal medicine for ER stress regulation, aiming to inspire new clinical strategies for the prevention and management of DN.

Endoplasmic reticulum stress in diabetic kidney disease: adaptation and apoptosis after three UPR pathways

Diabetes kidney disease (DKD) is one of the common chronic microvascular complications of diabetes, which has become the most important cause of modern chronic kidney disease beyond chronic glomerulonephritis. The endoplasmic reticulum is one of the largest organelles, and endoplasmic reticulum stress (ERS) is the basic mechanism of metabolic disorder in all organs and tissues. Under the stimulation of stress-induced factors, the endoplasmic reticulum, as a trophic receptor, regulates adaptive and apoptotic ERS through molecular chaperones and three unfolded protein reaction (UPR) pathways, thereby regulating diabetic renal damage. Therefore, three pathway factors have different expressions in different sections of renal tissues. This study deeply discussed the specific reagents, animals, cells, and clinical models related to ERS in DKD, and reviewed ERS-related three pathways on DKD with glomerular filtration membrane, renal tubular reabsorption, and other pathological lesions of different renal tissues, as well as the molecular biological mechanisms related to the balance of adaption and apoptosis by searching and sorting out MeSH subject words from PubMed database.

Endoplasmic reticulum stress-triggered ferroptosis via the XBP1-Hrd1-Nrf2 pathway induces EMT progression in diabetic nephropathy

Diabetic nephropathy (DN) is characterized by tubulointerstitial fibrosis caused by epithelial-mesenchymal transition (EMT) of renal tubular epithelial cells. Although ferroptosis promotes DN development, the specific pathological process that is affected by ferroptosis in DN remains unclear. Herein, EMT-related changes, including increased α-smooth muscle actin (α-SMA) and Vimentin expression and decreased E-cadherin expression, were observed in the renal tissues of streptozotocin-induced DN mice and high glucose-cultured human renal proximal tubular (HK-2) cells. Treatment with ferrostatin-1 (Fer-1) ameliorated these changes and rescued renal pathological injury in diabetic mice. Interestingly, endoplasmic reticulum stress (ERS) was activated during EMT progression in DN. Inhibiting ERS improved the expression of EMT-associated indicators and further rescued the characteristic changes in ferroptosis caused by high glucose, including reactive oxygen species (ROS) accumulation, iron overload, increased lipid peroxidation product generation, and reduced mitochondrial cristae. Moreover, overexpression of XBP1 increased Hrd1 expression and inhibited NFE2-related factor 2 (Nrf2) expression, which could enhance cell susceptibility to ferroptosis. Co-immunoprecipitation (Co-IP) and ubiquitylation assays indicated that Hrd1 interacted with and ubiquitinated Nrf2 under high-glucose conditions. Collectively, our results demonstrated that ERS triggers ferroptosis-related EMT progression through the XBP1-Hrd1-Nrf2 pathway, which provides new insights into potential mechanisms for delaying EMT progression in DN.

Translation Animal Models of Diabetic Kidney Disease: Biochemical and Histological Phenotypes, Advantages and Limitations

Animal models play a crucial role in studying the pathogenesis of diseases, developing new drugs, identifying disease risk markers, and improving means of prevention and treatment. However, modeling diabetic kidney disease (DKD) has posed a challenge for scientists. Although numerous models have been successfully developed, none of them can encompass all the key characteristics of human DKD. It is essential to choose the appropriate model according to the research needs, as different models develop different phenotypes and have their limitations. This paper provides a comprehensive overview of biochemical and histological phenotypes, modeling mechanisms, advantages and limitations of DKD animal models, in order to update relevant model information and provide insights and references for generating or selecting the appropriate animal models to fit different experimental needs.

Ginkgo biloba extract attenuates cisplatin-induced renal interstitial fibrosis by inhibiting the activation of renal fibroblasts through down-regulating the HIF-1α/STAT3/IL-6 pathway in renal tubular epithelial cells

BACKGROUND

Activation of renal fibroblasts into myofibroblasts plays an important role in promoting renal interstitial fibrosis (RIF). Ginkgo biloba extract (EGb) can alleviate RIF induced by cisplatin (CDDP).

PURPOSE

To elucidate the effect of EGb treatment on cisplatin-induced RIF and reveal its potential mechanism.

METHODS

The two main active components in EGb were determined by high-performance liquid chromatography (HPLC) analysis. Rats were induced by CDDP and then treated with EGb, 2ME2 (HIF-1α inhibitor) or amifostine. After HK-2 cells and HIF-1α siRNA HK-2 cells were treated with CDDP, EGb or amifostine, the conditioned medium from each group was cultured with NRK-49F cells. The renal function of rats was detected. The renal damage and fibrosis were evaluated by H&E and Masson trichrome staining. The IL-6 content in the cell medium was detected by ELISA. The expression levels of indicators related to renal fibrosis and signaling pathway were examined by western blotting and qRT-PCR.

RESULTS

HPLC analysis showed that the contents of quercetin and kaempferol in EGb were 36.0 μg/ml and 45.7 μg/ml, respectively. In vivo, EGb and 2ME2 alleviated renal damage and fibrosis, as well as significantly decreased the levels of α-SMA, HIF-1α, STAT3 and IL-6 in rat tissues induced by CDDP. In vitro, the levels of HIF-1α, STAT3 and IL-6 were significantly increased in HK-2 cells and HIF-1α siRNA HK-2 cells induced by CDDP. Notably, HIF-1α siRNA significantly decreased the levels of HIF-1α, STAT3 and IL-6 in HK-2 cells, as well as the IL-6 level in medium from HK-2 cells. Additionally, the α-SMA level in NRK-49F cells was significantly increased after being cultured with conditioned medium from HK-2 cells or HIF-1α siRNA HK-2 cells exposed to CDDP. Furthermore, exogenous IL-6 increased the α-SMA level in NRK-49F cells. Importantly, the expression levels of the above-mentioned indicators were significantly decreased after the HK-2 cells and HIF-1α siRNA HK-2 cells were treated with EGb.

CONCLUSION

This study revealed that EGb improves CDDP-induced RIF, and the mechanism may be related to its inhibition of the renal fibroblast activation by down-regulating the HIF-1α/STAT3/IL-6 pathway in renal tubular epithelial cells.

Role of endoplasmic reticulum stress and autophagy in the transition from acute kidney injury to chronic kidney disease

Acute kidney injury (AKI) and chronic kidney disease (CKD) are global health concerns with increasing rates in morbidity and mortality. Transition from AKI-to-CKD is common and requires awareness in the management of AKI survivors. AKI-to-CKD transition is a main risk factor for the development of cardiovascular disease and progression to end-stage kidney disease. The mechanisms driving AKI-to-CKD transition are being explored to identify potential molecular and cellular targets for renoprotective drug interventions. Endoplasmic reticulum (ER) stress and autophagy are involved in the process of AKI-to-CKD transition. Excessive ER stress results in the persistent activation of unfolded protein response, which is an underneath cause of kidney cell death. Moreover, ER stress modulates autophagy and vice-versa. Autophagy is a degradation defensive mechanism protecting cells from malfunction. However, the underlying pathological mechanism involved in this interplay in the context of AKI-to-CKD transition is still unclear. In this review, we discuss the crosstalk between ER stress and autophagy in AKI, AKI-to-CKD transition, and CKD progression. In addition, we explore possible therapeutic targets that can regulate ER stress and autophagy to prevent AKI-to-CKD transition to improve the long-term prognosis of AKI survivors.

Metformin Ameliorates Epithelial-Mesenchymal Transition of Renal Tubular Epithelial Cells in Diabetes by Increasing Vitamin D Receptor Expression

BACKGROUND

Metformin is used as a first-line drug for the treatment of type 2 diabetes. Epithelial-mesenchymal transition (EMT) plays a significant role in the development of renal tubular damage in diabetic kidney disease. However, the underlying mechanisms of EMT in diabetic kidney disease are unclear and how to inhibit this process remains to be explored.

METHODS

C57 mice were randomly divided into four groups, including the normal control group (NC group), the Type 2 diabetes group (T2DM group), the metformin group (MET group), and glibenclamide group (GLIB). Fasting blood glucose (FBG), glycated hemoglobin (HbA1c), urinary albumin, RBP, PCX, and creatinine were measured. Renal pathology was observed with HE staining. Molecular mechanism of VDR expression are regulated by metformin through wound healing assay, and Western blot analysis of VDR, Ecad, and SMA in HK2 cells.

RESULTS

In animal experiments, compared with the NC group, the T2DM group showed decreased body weight, increased levels of FBG, HbA1c, UAlb/UCR, URBP/UCR, and UPCX/UCR, decreased levels of VDR protein and mRNA expression in renal tissues (P < 0.05), and significantly increased renal pathological damage in mice in the T2DM group. Compared with the T2DM group, mice in the GLIB and MET groups had higher body weight and lower FBG, HbA1c, UAlb/UCR, URBP/UCR, and UPCX/UCR (P < 0.05). In addition, renal pathological damage was significantly reduced in the MET group compared to the GLIB group. In HK2 cells, high glucose promoted the reduction of VDR and the development of EMT compared to the NC group. In addition, we found that Metformin can up-regulate VDR and inhibit EMT.

CONCLUSION

Our study shows that the renoprotective effect of metformin is independent of glycemic control and metformin is involved in the progression of EMT by regulating VDR expression.

Sirtuin Family and Diabetic Kidney Disease

Diabetes mellitus (DM) is gradually attacking the health and life of people all over the world. Diabetic kidney disease (DKD) is one of the most common chronic microvascular complications of DM, whose mechanism is complex and still lacks research. Sirtuin family is a class III histone deacetylase with highly conserved NAD⁺ binding domain and catalytic functional domain, while different N-terminal and C-terminal structures enable them to bind different deacetylated substrates to participate in the cellular NAD⁺ metabolism. The kidney is an organ rich in NAD⁺ and database exploration of literature shows that the Sirtuin family has different expression localization in renal, cellular, and subcellular structures. With the progress of modern technology, a variety of animal models and reagents for the Sirtuin family and DKD emerged. Machine learning in the literature shows that the Sirtuin family can regulate pathophysiological injury mainly in the glomerular filtration membrane, renal tubular absorption, and immune inflammation through various mechanisms such as epigenetics, multiple signaling pathways, and mitochondrial function. These mechanisms are the key nodes participating in DKD. Thus, it is of great significance for target therapy to study biological functions of the Sirtuin family and DKD regulation mechanism in-depth.

Glucagon-Like Peptide 1 Receptor Agonist Improves Renal Tubular Damage in Mice with Diabetic Kidney Disease

PURPOSE

This study aims to investigate the renal protective effect of glucagon-like peptide 1 receptor agonist (GLP-1RA) on improving renal tubular damage in diabetic kidney disease (DKD) and to explore the potential mechanism of GLP-1RA on renal tubular protection.

METHODS

Long-acting GLP-1RA was used to treat DKD mice for 12 weeks. The label-free quantitative proteomic analysis of renal proteins was conducted to explore the differentially expressed proteins (DEPs) in the renal tissues of the control, DKD and GLP-1RA groups. The DEPs and markers of renal tubular injury were verified by qPCR in vivo and in vitro. The expression of glucagon-likepeptide-1 receptor (GLP-1R) in renal tubules was determined by immunofluorescence staining.

RESULTS

GLP-1RA treatment significantly improved the tubular damages in kidney tissues of DKD mice and mTEC cells stimulated by high glucose (HG). Proteomics analysis revealed that 30 proteins in kidney tissue were differentially expressed among three groups. Seminal vesicle secretory protein 6 (SVS6) was the most differentially expressed protein in kidney tissues among three groups of mice. The expression changes of Svs6 mRNA in vitro and in vivo detected by qPCR were consistent with the results of proteomic analysis. Furthermore, reduction of Svs6 expression by SVS6 siRNA could attenuate HG-stimulated tubular injury in mTEC cells. Immunofluorescence staining also found that GLP-1R was widely expressed in renal tubules in vitro and in vivo.

CONCLUSION

GLP-1RA significantly improved renal tubular damage in DKD mice. SVS6 may be a potential therapeutic target for GLP-1RA in the treatment of DKD.

Fibrosis, the Bad Actor in Cardiorenal Syndromes: Mechanisms Involved

Cardiorenal syndrome is a term that defines the complex bidirectional nature of the interaction between cardiac and renal disease. It is well established that patients with kidney disease have higher incidence of cardiovascular comorbidities and that renal dysfunction is a significant threat to the prognosis of patients with cardiac disease. Fibrosis is a common characteristic of organ injury progression that has been proposed not only as a marker but also as an important driver of the pathophysiology of cardiorenal syndromes. Due to the relevance of fibrosis, its study might give insight into the mechanisms and targets that could potentially be modulated to prevent fibrosis development. The aim of this review was to summarize some of the pathophysiological pathways involved in the fibrotic damage seen in cardiorenal syndromes, such as inflammation, oxidative stress and endoplasmic reticulum stress, which are known to be triggers and mediators of fibrosis.

NADH/NAD+ Redox Imbalance and Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a common and severe complication of diabetes mellitus. If left untreated, DKD can advance to end stage renal disease that requires either dialysis or kidney replacement. While numerous mechanisms underlie the pathogenesis of DKD, oxidative stress driven by NADH/NAD⁺ redox imbalance and mitochondrial dysfunction have been thought to be the major pathophysiological mechanism of DKD. In this review, the pathways that increase NADH generation and those that decrease NAD⁺ levels are overviewed. This is followed by discussion of the consequences of NADH/NAD⁺ redox imbalance including disruption of mitochondrial homeostasis and function. Approaches that can be applied to counteract DKD are then discussed, which include mitochondria-targeted antioxidants and mimetics of superoxide dismutase, caloric restriction, plant/herbal extracts or their isolated compounds. Finally, the review ends by pointing out that future studies are needed to dissect the role of each pathway involved in NADH-NAD⁺ metabolism so that novel strategies to restore NADH/NAD⁺ redox balance in the diabetic kidney could be designed to combat DKD.