Renoprotection of dapagliflozin in human renal proximal tubular cells via the inhibition of the high mobility group box 1‑receptor for advanced glycation end products‑nuclear factor‑κB signaling pathway

SGLT2 inhibitor improves the prognosis of patients with coronary heart disease and prevents in-stent restenosis

Coronary heart disease is a narrowing or obstruction of the vascular cavity caused by atherosclerosis of the coronary arteries, which leads to myocardial ischemia and hypoxia. At present, percutaneous coronary intervention (PCI) is an effective treatment for coronary atherosclerotic heart disease. Restenosis is the main limiting factor of the long-term success of PCI, and it is also a difficult problem in the field of intervention. Sodium-glucose cotransporter 2 (SGLT2) inhibitor is a new oral glucose-lowering agent used in the treatment of diabetes in recent years. Recent studies have shown that SGLT2 inhibitors can effectively improve the prognosis of patients after PCI and reduce the occurrence of restenosis. This review provides an overview of the clinical studies and mechanisms of SGLT2 inhibitors in the prevention of restenosis, providing a new option for improving the clinical prognosis of patients after PCI.

A Role for Sodium-Glucose Cotransporter 2 Inhibitors in the Treatment of Chronic Kidney Disease: A Mini Review

BACKGROUND

Sodium-glucose cotransport protein 2 (SGLT2) inhibitors, a new type of glucose-lowering drug, have been well proved in several clinical studies for their glucose-lowering and nephroprotective effects, and the nephroprotective effects include both indirect effects of metabolic improvement and direct effects, independent of glucose-lowering effects.

SUMMARY

In patients with diabetic kidney disease (DKD), several studies have demonstrated the potential nephroprotective mechanisms of SGLT2 inhibitors, and evidence of nephroprotective mechanisms in the non-DKD population is accumulating. Although the nephroprotective mechanism of SGLT2 inhibitors has not been fully elucidated, several laboratory studies have illustrated the mechanism underlying the effects of SGLT2 inhibitors at various aspects.

KEY MESSAGES

The purpose of this article is to review the mechanism of nephroprotective effect of SGLT2 inhibitors and to look forward to promising research in the future.

Tubular injury in diabetic kidney disease: molecular mechanisms and potential therapeutic perspectives

Diabetic kidney disease (DKD) is a chronic complication of diabetes and the leading cause of end-stage renal disease (ESRD) worldwide. Currently, there are limited therapeutic drugs available for DKD. While previous research has primarily focused on glomerular injury, recent studies have increasingly emphasized the role of renal tubular injury in the pathogenesis of DKD. Various factors, including hyperglycemia, lipid accumulation, oxidative stress, hypoxia, RAAS, ER stress, inflammation, EMT and programmed cell death, have been shown to induce renal tubular injury and contribute to the progression of DKD. Additionally, traditional hypoglycemic drugs, anti-inflammation therapies, anti-senescence therapies, mineralocorticoid receptor antagonists, and stem cell therapies have demonstrated their potential to alleviate renal tubular injury in DKD. This review will provide insights into the latest research on the mechanisms and treatments of renal tubular injury in DKD.

Renoprotective impact of Dapagliflozin and Mulberry extracts toward Fr-STZ induced diabetic nephropathy in rats: Biochemical and Molecular aspects.. [DOI: 10.21203/rs.3.rs-3186379/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Among the most typical reasons of end-stage renal disease (ESRD) is diabetic nephropathy (DN), which is also rated as a major microvascular complication of diabetes mellitus. The existent study looked at the impact of dapagliflozin, mulberry fruit and leaves extracts and their combination on the kidney of diabetic rats. To induce diabetic nephropathy, experimental rats were supplied with 10% fructose (Fr) in drinking water for the first two weeks. Each Fr-fed animal received an intraperitoneal injection of a low single dose of STZ (40 mg/kg) after being fasted for the whole night. Sixty albino rats were separated into six equivalent groups. Group I control rats, group II untreated diabetic rats, group III–VI are diabetic groups; received dapagliflozin for 4 weeks, mulberry fruit extract, mulberry leaves extract and combination of DAPA, MFE and MLE, respectively for 6 weeks. Untreated diabetic rats exhibited considerable rise in serum glucose, urea, creatinine, KIM-1, β2-MG, TNF-α, and TGβ1 levels compared to control rats, while treated diabetic ones manifested significant decrease in these measures in contrast to the untreated diabetic rats. Also, renal tissue IL-6, NF-κB and NADPH oxidase manifested significant increase in untreated diabetic rats, while treated groups revealed significant decline in comparison to the untreated one. DAPA and mulberry fruit and leaves extracts optimized IL-10 and renin expression in renal tissue. Histopathological picture of kidney, revealed significant improvement in rats received DAPA and mulberry extracts compared to untreated diabetic rats. It could be concluded that, DAPA, mulberry fruits and leaves extracts alleviated diabetic nephropathy complications. Therefore, combining these ingredients in a supplement may be promising for modulating diabetic nephropathy.

Ferroptosis: a new strategy for Chinese herbal medicine treatment of diabetic nephropathy

Diabetic nephropathy (DN) is a serious microvascular complication of diabetes. It has become a leading cause of death in patients with diabetes and end-stage renal disease. Ferroptosis is a newly discovered pattern of programmed cell death. Its main manifestation is the excessive accumulation of intracellular iron ion-dependent lipid peroxides. Recent studies have shown that ferroptosis is an important driving factor in the onset and development of DN. Ferroptosis is closely associated with renal intrinsic cell (including renal tubular epithelial cells, podocytes, and mesangial cells) damage in diabetes. Chinese herbal medicine is widely used in the treatment of DN, with a long history and definite curative effect. Accumulating evidence suggests that Chinese herbal medicine can modulate ferroptosis in renal intrinsic cells and show great potential for improving DN. In this review, we outline the key regulators and pathways of ferroptosis in DN and summarize the herbs, mainly monomers and extracts, that target the inhibition of ferroptosis.

DF-5 COMPOUND DELAYS DEVELOPMENT OF DIABETIC NEPHROPATHY IN RATS

Advanced glycation end-products play an important role in the development of diabetic complications, so slowing down of glycated proteins’ cross-links formation have been suggested as a potential therapeutic option for the treatment of vascular diabetic complications and preventing their progression.

The aim of the work was to assess the influence of novel anticrosslinking agent DF-5 on the renal advanced glycation end-products and collagen contents, body weight, blood glucose and glycated hemoglobin levels and the development of early renal disease in streptozotocin-induced diabetic rats.

Materials and methods. 40 male Sprague-Dawley rats were used in the study. Two months after inducing diabetes, the study substance was administered intragastrically once a day for 28 days (12.5 mg/kg). Measurements included the assessment of blood glucose and HbA1c levels, the evaluation of the renal function, and the results of histology and immunohistochemical staining of kidneys.

Results. A repeated intragastric administration of DF-5 for 30 days significantly reduced the level of HbA1c in the blood, but did not affect the level of fasting blood glucose. DF-5 compound significantly reduced proteinuria and prevented kidney damage in experimental animals by limiting damage of the glomeruli and tubules. It was found that DF-5 inhibits the progression of an early renal dysfunction in rats with streptozotocin-induced diabetic nephropathy. This was associated with a decreased accumulation of advanced glycation end-products in the kidney, accompanied by the improvement of both renal morphology and function.

Conclusion. The results obtained provide investigators with additional therapeutic options for the treatment of diabetic nephropathy and possibly other complications of diabetes.

SGLT2 inhibitors in the treatment of type 2 cardiorenal syndrome: Focus on renal tubules

The pathogenesis of type 2 cardiorenal syndrome (CRS) is mostly associated with reduced cardiac output, increased central venous pressure (CVP), activation of the renin-angiotensin-aldosterone system (RAAS), inflammation, and oxidative stress. As a drug to treat diabetes, sodium-glucose transporter 2 inhibitor (SGLT2i) has been gradually found to have a protective effect on the heart and kidney and has a certain therapeutic effect on CRS. In the process of chronic heart failure (CHF) leading to chronic renal insufficiency, the renal tubular system, as the main functional part of the kidney, is the first to be damaged, but this damage can be reversed. In this review, we focus on the protective mechanisms of SGLT2i targeting renal tubular in the treatment of CRS, including natriuresis and diuresis to relieve renal congestion, attenuate renal tubular fibrosis, improve energy metabolism of renal tubular, and slow tubular inflammation and oxidative stress. This may have beneficial effects on the treatment of CRS and is a direction for future research.

Toll-like receptors 2 and 4 stress signaling and sodium-glucose cotransporter-2 in kidney disease

Kidney disease is the 6th fastest-growing cause of death and a serious global health concern that urges effective therapeutic options. The inflammatory response is an initial reaction from immune and parenchymal cells in kidney diseases. Toll-like receptors (TLR) 2 and 4 are highly expressed by various kidney cells and respond to 'signaling danger' proteins, such as high mobility group box binding protein 1 (HMGB1) and prompt the progression of kidney disease by releasing inflammatory mediators. Burgeoning reports suggest that both SGLT2 and ER stress elevates TLR2/4 signaling via different axis. Moreover, SGLT2 signaling aggravates inflammation under the disease condition by promoting the NLR family pyrin domain-containing three inflammasomes and ER stress. Intriguingly, TLR2/4 downstream adaptors activate ER stress regulators. The above-discussed interactions imply that TLR2/4 does more than immune response during kidney disease. Here, we discuss in detail evidence of the roles and regulation of TLR2/4 in the context of a relationship between ER stress and SGLT2. Also, we highlighted different preclinical studies of SGLT2 inhibitors against TLR2/4 signaling in various kidney diseases. Moreover, we discuss the observational and interventional evidence about the relation between TLR2/4, ER stress, and SGLT2, which may represent the TLR2/4 as a potential therapeutic target for kidney disease.

Molecular Mechanisms Linking Empagliflozin to Renal Protection in the LLC-PK1 Model of Diabetic Nephropathy

Aims: Chronic diabetes complications, including diabetic nephropathy (DN), frequently result in end-stage renal failure. This study investigated empagliflozin (SGLT2i) effects on collagen synthesis, oxidative stress, cell survival, and protein expression in an LLC-PK1 model of DN. Methods: Combinations of high glucose (HG) and increasing empagliflozin concentrations (100 nM and 500 nM), as well as combinations of HG, H2O2, and empagliflozin, were used for cell culture treatment. The cell viability, glutathione (tGSH), ECM expression, and TGF-β1 concentration were measured. In addition, the protein expression of Akt, pAkt, GSK3, pGSK3, pSTAT3, and SMAD7 was determined. Results: The addition of both concentrations of empagliflozin to cells previously exposed to glucose and oxidative stress generally improved cell viability and increased GSH levels (p < 0.001, p < 0.05). In HG30/H2O2/Empa500-treated cells, significant increase in pSTAT3, pGSK3β, GSK3β, SMAD7, and pAKT levels (p < 0.001, p < 0.001, p < 0.05) was observed except for AKT. Lower drug concentrations did not affect the protein expression levels. Furthermore, empagliflozin treatment (100 nM and 500 nM) of HG30/H2O2-injured cells led to a decrease in TGF-β1 levels (p < 0.001). In cells exposed to oxidative stress and hyperglycemia, collagen production remained unchanged. Conclusion: Renoprotective effects of empagliflozin, in this LLC-PK1 cell model of DN, are mediated via activation of the Akt/GSK-3 signalling pathway, thus reducing oxidative stress-induced damage, as well as enhanced SMAD7 expression leading to downregulation of TGF-β1, one of the key mediators of inflammation and fibrosis.

Sodium-glucose Cotransporter Type 2 Inhibitors: A New Insight into the Molecular Mechanisms of Diabetic Nephropathy

Diabetic nephropathy is one of the chronic microvascular complications of diabetes and is a leading cause of end-stage renal disease. Fortunately, clinical trials have demonstrated that sodium-glucose cotransporter type 2 inhibitors could decrease proteinuria and improve renal endpoints and are promising agents for the treatment of diabetic nephropathy. The renoprotective effects of sodium-glucose cotransporter type 2 inhibitors cannot be simply attributed to their advantages in aspects of metabolic benefits, such as glycemic control, lowering blood pressure, and control of serum uric acid, or improving hemodynamics associated with decreased glomerular filtration pressure. Some preclinical evidence suggests that sodium-glucose cotransporter type 2 inhibitors exert their renoprotective effects by multiple mechanisms, including attenuation of oxidative and endoplasmic reticulum stresses, anti-fibrosis and anti-inflammation, protection of podocytes, suppression of megalin function, improvement of renal hypoxia, restored mitochondrial dysfunction and autophagy, as well as inhibition of sodium-hydrogen exchanger 3. In the present study, the detailed molecular mechanisms of sodium-glucose cotransporter type 2 inhibitors with the actions of diabetic nephropathy were reviewed, with the purpose of providing the basis for drug selection for the treatment of diabetic nephropathy.

The Pathophysiological Basis of Diabetic Kidney Protection by Inhibition of SGLT2 and SGLT1

SGLT2 inhibitors can protect the kidneys of patients with and without type 2 diabetes mellitus and slow the progression towards end-stage kidney disease. Blocking tubular SGLT2 and spilling glucose into the urine, which triggers a metabolic counter-regulation similar to fasting, provides unique benefits, not only as an anti-hyperglycemic strategy. These include a low hypoglycemia risk and a shift from carbohydrate to lipid utilization and mild ketogenesis, thereby reducing body weight and providing an additional energy source. SGLT2 inhibitors counteract hyperreabsorption in the early proximal tubule, which acutely lowers glomerular pressure and filtration and thereby reduces the physical stress on the filtration barrier, the filtration of tubule-toxic compounds, and the oxygen demand for tubular reabsorption. This improves cortical oxygenation, which, together with lesser tubular gluco-toxicity and improved mitochondrial function and autophagy, can reduce pro-inflammatory, pro-senescence, and pro-fibrotic signaling and preserve tubular function and GFR in the long-term. By shifting transport downstream, SGLT2 inhibitors more equally distribute the transport burden along the nephron and may mimic systemic hypoxia to stimulate erythropoiesis, which improves oxygen delivery to the kidney and other organs. SGLT1 inhibition improves glucose homeostasis by delaying intestinal glucose absorption and by increasing the release of gastrointestinal incretins. Combined SGLT1 and SGLT2 inhibition has additive effects on renal glucose excretion and blood glucose control. SGLT1 in the macula densa senses luminal glucose, which affects glomerular hemodynamics and has implications for blood pressure control. More studies are needed to better define the therapeutic potential of SGLT1 inhibition to protect the kidney, alone or in combination with SGLT2 inhibition.

High-mobility group box 1 (HMGB1) in COVID-19: extrapolation of dangerous liaisons

High-mobility group box 1 (HMGB1), a multifunctional nuclear protein, exists mainly within the nucleus of all mammal eukaryotic cells. It is actively secreted by the necrotic cells as a response to the inflammatory signaling pathway. HMGB1 binds to receptor ligands as RAGE, and TLR and becomes a pro-inflammatory cytokine with a robust capacity to trigger inflammatory response. It is a critical mediator of the pathogenesis of systemic inflammation in numerous inflammatory disorders. Release of HMGB1 is associated with different viral infections and strongly participates in the regulation of viral replication cycles. In COVID-19 era, high HMGB1 serum levels were observed in COVID-19 patients and linked with the disease severity, development of cytokine storm (CS), acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). SARS-CoV-2-induced cytolytic effect may encourage release of HMGB1 due to nuclear damage. Besides, HMGB1 activates release of pro-inflammatory cytokines from immune cells and up-regulation of angiotensin I-converting enzyme 2 (ACE2). Therefore, targeting of the HMGB1 pathway by anti-HMGB1 agents, such as heparin, resveratrol and metformin, may decrease COVID-19 severity. HMGB1 signaling pathway has noteworthy role in the pathogenesis of SARS-CoV-2 infections and linked with development of ALI and ARDS in COVID-19 patients. Different endogenous and exogenous agents may affect release and activation of HMGB1 pathway. Targeting of HMGB1-mediated TLR2/TLR4, RAGE and MAPK signaling, might be a new promising drug candidate against development of ALI and/or ARDS in severely affected COVID-19 patients.

A Novel Role of Dapagliflozin in Mitigation of Acetic Acid-Induced Ulcerative Colitis by Modulation of Monocyte Chemoattractant Protein 1 (MCP-1)/Nuclear Factor-Kappa B (NF-κB)/Interleukin-18 (IL-18)

Colon illnesses, particularly ulcerative colitis, are considered a major cause of death in both men and women around the world. The present study investigated the underlying molecular mechanisms for the potential anti-inflammatory effect of Dapagliflozin (DAPA) against ulcerative colitis (UC) induced by intracolonic instillation of 3% v/v acetic acid (AA). DAPA was administered to rats (1 mg/kg, orally) for two weeks during the treatment regimen. Interestingly, compared to the normal group, a marked increase in the index of colon/body weight, colon weight/colon length ratio, serum lactate dehydrogenase (LDH), and C-reactive protein (CRP), besides decrease in the serum total antioxidant capacity (TAC), were reported in the AA control group (p ˂ 0.05). Elevation in colon monocyte chemoattractant protein (MCP1), Interleukin 18 (IL-18), and inflammasome contents were also reported in the AA control group in comparison with the normal group. In addition, colon-specimen immunohistochemical staining revealed increased expression of nuclear factor-kappa B (NF-κB) and Caspase-3 with histopathological changes. Moreover, DAPA significantly (p ˂ 0.05) reduced the colon/body weight index, colon weight/colon length ratio, clinical evaluation, and macroscopic scoring of UC, and preserved the histopathological architecture of tissues. The inflammatory biomarkers, including colon MCP1, IL-18, inflammasome, Caspase-3, and NF-κB, were suppressed following DAPA treatment and oxidants/antioxidants hemostasis was also restored. Collectively, the present data demonstrate that DAPA represents an attractive approach to ameliorating ulcerative colitis through inhibiting MCP1/NF-κB/IL-18 pathways, thus preserving colon function. Antioxidant, anti-inflammatory, and anti-apoptotic properties of DAPA are implicated in its observed therapeutic benefits.

High mobility group box 1 and homocysteine as preprocedural predictors for contrast-induced acute kidney injury after percutaneous coronary artery intervention

PURPOSE

High mobility group box 1 (HMGB1) and homocysteine (Hcy) play important roles in contrast-induced acute kidney injury (CI-AKI). We compared HMGB1 to Hcy as preprocedural predictors for CI-AKI in coronary artery disease (CAD) patients after percutaneous coronary artery intervention (PCI).

METHODS

We included 257 eligible patients who were categorized into CI-AKI ( +) and CI-AKI ( -) group. The differences in clinical characteristics and biochemical indexes between two groups were analyzed.

RESULTS

We observed that thirty-eight (14.8%) of 257 eligible CAD patients developed CI-AKI. HMGB1 (14.65 [11.13-24.89] vs 10.88 [7.94-13.23], p < 0.001) and Hcy (14.07 [12.07-17.31] vs 12.09 [10.71-13.47], p < 0.001) increased significantly in CI-AKI ( +) group. Both age (r = 0.210, p = 0.001), serum creatinine (r = 0.509, p < 0.001), eGFR (r =  - 0.459, p < 0.001) and Hcy (r = 0.531, p < 0.001) were significantly correlated with HMGB1. Among all patients, HMGB1 (OR 1.181, 95% CI 1.081-1.290, p < 0.001) and Hcy (OR 1.260, 95% CI 1.066-1.489, p = 0.007) were independent predictors for the development of CI-AKI. We built the propensity score matching (PSM) using 38 pairs of patients. After adjustment, HMGB1 (OR 1.169, 95% CI 1.035-1.322, p = 0.012) and Hcy (OR 1.457, 95% CI 1.064-1.997, p = 0.019) were also independent predictors for the development of CI-AKI. Both HMGB1 (AUC: 0.704, 95% CI: 0.588-0.819, p = 0.002) and Hcy (AUC: 0.708, 95% CI: 0.593-0.823, p = 0.002) had predictive values for CI-AKI.

CONCLUSION

There is a significant positive association between HMGB1 and Hcy in CAD patients. Both HMGB1 and Hcy are potential preprocedural predictors of CI-AKI after PCI.

Role of Dendritic Cell in Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most significant microvascular complications in diabetic patients. DN is the leading cause of end-stage renal disease, accounting for approximately 50% of incident cases. The current treatment options, such as optimal control of hyperglycemia and elevated blood pressure, are insufficient to prevent its progression. DN has been considered as a nonimmune, metabolic, or hemodynamic glomerular disease initiated by hyperglycemia. However, recent studies suggest that DN is an inflammatory disease, and immune cells related with innate and adaptive immunity, such as macrophage and T cells, might be involved in its development and progression. Although it has been revealed that kidney dendritic cells (DCs) accumulation in the renal tissue of human and animal models of DN require activated T cells in the kidney disease, little is known about the function of DCs in DN. In this review, we describe kidney DCs and their subsets, and the role in the pathogenesis of DN. We also suggest how to improve the kidney outcomes by modulating kidney DCs optimally in the patients with DN.

Dapagliflozin Restores Impaired Autophagy and Suppresses Inflammation in High Glucose-Treated HK-2 Cells

Sodium-glucose cotransporter2 (SGLT2) inhibitors have a reno-protective effect in diabetic kidney disease. However, the detailed mechanism remains unclear. In this study, human proximal tubular cells (HK-2) were cultured in 5 mM glucose and 25 mM mannitol (control), 30 mM glucose (high glucose: HG), or HG and SGLT2 inhibitor, dapagliflozin-containing medium for 48 h. The autophagic flux was decreased, accompanied by the increased phosphorylation of S6 kinase ribosomal protein (p-S6RP) and the reduced phosphorylation of AMP-activated kinase (p-AMPK) expression in a HG condition. Compared to those of the control, dapagliflozin and SGLT2 knockdown ameliorated the HG-induced alterations of p-S6RP, p-AMPK, and autophagic flux. In addition, HG increased the nuclear translocation of nuclear factor-κB p65 (NF-κB) p65 and the cytoplasmic nucleotide-binding oligomerization domain-like receptor 3 (NLRP3), mature interleukin-1β (IL-1β), IL-6, and tumor necrosis factorα (TNFα) expression. Dapagliflozin, SGLT2 knockdown, and NF-κB p65 knockdown reduced the extent of these HG-induced inflammatory alterations. The inhibitory effect of dapagliflozin on the increase in the HG-induced nuclear translocation of NF-κB p65 was abrogated by knocking down AMPK. These data indicated that in diabetic renal proximal tubular cells, dapagliflozin ameliorates: (1) HG-induced autophagic flux reduction, via increased AMPK activity and mTOR suppression; and (2) inflammatory alterations due to NF-κB pathway suppression.

Protective effects of dapagliflozin against oxidative stress-induced cell injury in human proximal tubular cells

Elevated reactive oxygen species (ROS) in type 2 diabetes cause cellular damage in many organs. Recently, the new class of glucose-lowering agents, SGLT-2 inhibitors, have been shown to reduce the risk of developing diabetic complications; however, the mechanisms of such beneficial effect are largely unknown. Here we aimed to investigate the effects of dapagliflozin on cell proliferation and cell death under oxidative stress conditions and explore its underlying mechanisms. Human proximal tubular cells (HK-2) were used. Cell growth and death were monitored by cell counting, water-soluble tetrazolium-1 (WST-1) and lactate dehydrogenase (LDH) assays, and flow cytometry. The cytosolic and mitochondrial (ROS) production was measured using fluorescent probes (H2DCFDA and MitoSOX) under normal and oxidative stress conditions mimicked by addition of H₂O₂. Intracellular Ca²⁺ dynamics was monitored by FlexStation 3 using cell-permeable Ca²⁺ dye Fura-PE3/AM. Dapagliflozin (0.1–10 μM) had no effect on HK-2 cell proliferation under normal conditions, but an inhibitory effect was seen at an extreme high concentration (100 μM). However, dapagliflozin at 0.1 to 5 μM showed remarkable protective effects against H₂O₂-induced cell injury via increasing the viable cell number at phase G0/G1. The elevated cytosolic and mitochondrial ROS under oxidative stress was significantly decreased by dapagliflozin. Dapagliflozin increased the basal intracellular [Ca²⁺]_i in proximal tubular cells, but did not affect calcium release from endoplasmic reticulum and store-operated Ca²⁺ entry. The H₂O₂-sensitive TRPM2 channel seemed to be involved in the Ca²⁺ dynamics regulated by dapagliflozin. However, dapagliflozin had no direct effects on ORAI1, ORAI3, TRPC4 and TRPC5 channels. Our results suggest that dapagliflozin shows anti-oxidative properties by reducing cytosolic and mitochondrial ROS production and altering Ca²⁺ dynamics, and thus exerts its protective effects against cell damage under oxidative stress environment.

Mechanisms and Perspectives of Sodium-Glucose Co-transporter 2 Inhibitors in Heart Failure

Heart failure (HF) is a common complication or late-stage manifestation of various heart diseases. Numerous risk factors and underlying causes may contribute to the occurrence and progression of HF. The pathophysiological mechanisms of HF are very complicated. Despite accumulating advances in treatment for HF during recent decades, it remains an intractable clinical syndrome with poor outcomes, significantly reducing the quality of life and expectancy of patients, and imposing a heavy economic burden on society and families. Although initially classified as antidiabetic agents, sodium-glucose co-transporter 2 (SGLT2) inhibitors have demonstrated reduced the prevalence of hospitalization for HF, cardiovascular death, and all-cause death in several large-scale randomized controlled clinical trials. These beneficial effects of SGLT-2 inhibitors can be attributed to multiple hemodynamic, inflammatory and metabolic mechanisms, not only reducing the serum glucose level. SGLT2 inhibitors have been used increasingly in treatment for patients with HF with reduced ejection fraction due to their surprising performance in improving the prognosis. In addition, their roles and mechanisms in patients with HF with preserved ejection fraction or acute HF have also attracted attention. In this review article, we discuss the possible mechanisms and applications of SGLT2 inhibitors in HF.

Inhibitor of RAGE and glucose‑induced inflammation in bone marrow mesenchymal stem cells: Effect and mechanism of action

The occurrence and development of hyperglycemia‑induced inflammation is associated with increased expression of receptor for advanced glycation end products (RAGE) and inflammatory factors, including IL‑1β, TNF‑α and IL‑6. Previous studies have reported that the nucleotide‑binding oligomerization domain‑like receptor protein 3 (NLRP3) inflammasome interacts with thioredoxin‑interacting protein (TXNIP) and serves a crucial role in inflammation. FPS‑ZM1 has been identified as target inhibitor of RAGE and has been shown to exert an anti‑inflammatory effect in vitro. However, the underlying mechanism by which FPS‑ZM1 impacts high glucose (HG)‑induced inflammation in bone marrow mesenchymal stem cells (BMSCs) remains unclear. The present study explored the regulatory effect of FPS‑ZM1 on HG‑induced inflammation in BMSCs. Furthermore, the role of the TXNIP/NLRP3 inflammasome signaling pathway in the regulatory effects of FPS‑ZM1 on HG‑induced inflammation was studied. Cell viability was determined using Cell Counting Kit‑8 and western blotting was used to assess the protein expression levels of RAGE. ELISA was used to determine the levels of inflammatory markers. Reverse transcription‑quantitative PCR and western blotting were used to measure the mRNA and protein expression levels of TXNIP, caspase‑1, thioredoxin (TRX), NLRP3 and apoptosis‑related speck‑like protein containing CARD (ASC). The results revealed that in BMSCs, RAGE expression was stimulated by HG, an effect which was reversed by treatment with FPS‑ZM1. In addition, HG activated inflammatory factors, such as TNF‑α, IL‑1β and IL‑6; however, their levels were suppressed when cells were treated with FPS‑ZM1 or the TXNIP/NLRP3 pathway inhibitor, resveratrol (Res). Furthermore, FPS‑ZM1 inhibited the mRNA and protein expression levels of TXNIP, caspase‑1, NLRP3 and ASC, and promoted TRX expression, which was consistent with the effects of Res. These findings indicated that FPS‑ZM1 may attenuate HG‑induced inflammation in BMSCs. Furthermore, the TXNIP/NLRP3 inflammasome signaling pathway mediated the molecular mechanism underlying this effect.

Multiplex Bead Array Assay of a Panel of Circulating Cytokines and Growth Factors in Patients with Albuminuric and Non-AlbuminuricDiabetic Kidney Disease

A panel of cytokines and growth factors, mediating low-grade inflammation and fibrosis, was assessed in patients with type 2 diabetes (T2D) and different patterns of chronic kidney disease (CKD). Patients with long-term T2D (N = 130) were classified into four groups: no signs of CKD; estimated glomerular filtration rate (eGFR) <60 mL/min/1.73 m² without albuminuria; albuminuria and eGFR ≥60 mL/min/1.73 m²; albuminuria and eGFR <60 mL/min/1.73 m². Thirty healthy subjects were acted as control. Twenty-seven cytokines and growth factors were assessed in serum by multiplex bead array assay. Serum hs-CRP, urinary nephrin, podocine, and WFDC2 were measured by ELISA. Patients with T2D showed elevated IL-1Ra, IL-6, IL-17A, G-CSF, IP-10, MIP-1α, and bFGF levels; concentrations of IL-4, IL-12, IL-15, INF-γ, and VEGF were decreased. IL-6, IL-17A, G-CSF, MIP-1α, and bFGF correlated negatively with eGFR; IL-10 and VEGF demonstrated negative associations with WFDC2; no relationships with podocyte markers were found. Adjusted IL-17A and MIP-1α were predictors of non-albuminuric CKD, IL-13 predicted albuminuria with preserved renal function, meanwhile, IL-6 and hsCRP were predictors of albuminuria with eGFR decline. Therefore, albuminuric and non-albuminuric CKD in T2D patients are associated with different pro-inflammatory shifts in the panel of circulating cytokines.

Accelerated Kidney Aging in Diabetes Mellitus

With aging, the kidney undergoes inexorable and progressive changes in structural and functional performance. These aging-related alterations are more obvious and serious in diabetes mellitus (DM). Renal accelerated aging under DM conditions is associated with multiple stresses such as accumulation of advanced glycation end products (AGEs), hypertension, oxidative stress, and inflammation. The main hallmarks of cellular senescence in diabetic kidneys include cyclin-dependent kinase inhibitors, telomere shortening, and diabetic nephropathy-associated secretory phenotype. Lysosome-dependent autophagy and antiaging proteins Klotho and Sirt1 play a fundamental role in the accelerated aging of kidneys in DM, among which the autophagy-lysosome system is the convergent mechanism of the multiple antiaging pathways involved in renal aging under DM conditions. Metformin and the inhibitor of sodium-glucose cotransporter 2 are recommended due to their antiaging effects independent of antihyperglycemia, besides angiotensin-converting enzyme inhibitors/angiotensin receptor blockers. Additionally, diet intervention including low protein and low AGEs with antioxidants are suggested for patients with diabetic nephropathy (DN). However, their long-term benefits still need further study. Exploring the interactive relationships among antiaging protein Klotho, Sirt1, and autophagy-lysosome system may provide insight into better satisfying the urgent medical needs of elderly patients with aging-related DN.

Glyceraldehyde-Derived Pyridinium Evokes Renal Tubular Cell Damage via RAGE Interaction

Glyceraldehyde-derived advanced glycation end products (glycer-AGEs) contribute to proximal tubulopathy in diabetes. However, what glycer-AGE structure could evoke tubular cell damage remains unknown. We first examined if deleterious effects of glycer-AGEs on reactive oxygen species (ROS) generation in proximal tubular cells were blocked by DNA-aptamer that could bind to glyceraldehyde-derived pyridinium (GLAP) (GLAP-aptamer), and then investigated whether and how GLAP caused proximal tubular cell injury. GLAP-aptamer and AGE-aptamer raised against glycer-AGEs were prepared using a systemic evolution of ligands by exponential enrichment. The binding affinity of GLAP-aptamer to glycer-AGEs was measured with a bio-layer interferometry. ROS generation was evaluated using fluorescent probes. Gene expression was analyzed by reverse transcription-polymerase chain reaction (RT-PCR). GLAP-aptamer bound to glycer-AGEs with a dissociation constant of 7.7 × 10⁻⁵ M. GLAP-aptamer, glycer-AGE-aptamer, or antibodies directed against receptor for glycer-AGEs (RAGE) completely prevented glycer-AGE- or GLAP-induced increase in ROS generation, MCP-1, PAI-1, or RAGE gene expression in tubular cells. Our present results suggest that GLAP is one of the structurally distinct glycer-AGEs, which may mediate oxidative stress and inflammatory reactions in glycer-AGE-exposed tubular cells. Blockade of the interaction of GLAP-RAGE by GLAP-aptamer may be a therapeutic target for proximal tubulopathy in diabetic nephropathy.

Innate immunity in diabetic kidney disease

Increasing evidence suggests that renal inflammation contributes to the pathogenesis and progression of diabetic kidney disease (DKD) and that anti-inflammatory therapies might have renoprotective effects in DKD. Immune cells and resident renal cells that activate innate immunity have critical roles in triggering and sustaining inflammation in this setting. Evidence from clinical and experimental studies suggests that several innate immune pathways have potential roles in the pathogenesis and progression of DKD. Toll-like receptors detect endogenous danger-associated molecular patterns generated during diabetes and induce a sterile tubulointerstitial inflammatory response via the NF-κB signalling pathway. The NLRP3 inflammasome links sensing of metabolic stress in the diabetic kidney to activation of pro-inflammatory cascades via the induction of IL-1β and IL-18. The kallikrein-kinin system promotes inflammatory processes via the generation of bradykinins and the activation of bradykinin receptors, and activation of protease-activated receptors on kidney cells by coagulation enzymes contributes to renal inflammation and fibrosis in DKD. In addition, hyperglycaemia leads to protein glycation and activation of the complement cascade via recognition of glycated proteins by mannan-binding lectin and/or dysfunction of glycated complement regulatory proteins. Data from preclinical studies suggest that targeting these innate immune pathways could lead to novel therapies for DKD.

No Cytotoxic and Inflammatory Effects of Empagliflozin and Dapagliflozin on Primary Renal Proximal Tubular Epithelial Cells under Diabetic Conditions In Vitro

Gliflozins are inhibitors of the renal proximal tubular sodium-glucose co-transporter-2 (SGLT-2), that inhibit reabsorption of urinary glucose and they are able to reduce hyperglycemia in patients with type 2 diabetes. A renoprotective function of gliflozins has been proven in diabetic nephropathy, but harmful side effects on the kidney have also been described. In the current project, primary highly purified human renal proximal tubular epithelial cells (PTCs) have been shown to express functional SGLT-2, and were used as an in vitro model to study possible cellular damage induced by two therapeutically used gliflozins: empagliflozin and dapagliflozin. Cell viability, proliferation, and cytotoxicity assays revealed that neither empagliflozin nor dapagliflozin induce effects in PTCs cultured in a hyperglycemic environment, or in co-medication with ramipril or hydro-chloro-thiazide. Oxidative stress was significantly lowered by dapagliflozin but not by empagliflozin. No effect of either inhibitor could be detected on mRNA and protein expression of the pro-inflammatory cytokine interleukin-6 and the renal injury markers KIM-1 and NGAL. In conclusion, empa- and dapagliflozin in therapeutic concentrations were shown to induce no direct cell injury in cultured primary renal PTCs in hyperglycemic conditions.

Cardioprotection conferred by sodium-glucose cotransporter 2 inhibitors: a renal proximal tubule perspective

Sodium-glucose cotransporter 2 (SGLT2) inhibitors, also known as gliflozins, improve glycemia by suppressing glucose reuptake in the renal proximal tubule. Currently, SGLT2 inhibitors are primarily indicated as antidiabetic agents; however, their benefits extend far beyond glucose control. Cardiovascular outcome trials indicated that all studied SGLT2 inhibitors remarkably and consistently reduce cardiovascular mortality and hospitalization for heart failure (HF) in type 2 diabetes (T2D) patients. Nevertheless, the mechanisms underlying the unprecedented cardiovascular benefits of gliflozins remain elusive. Multiple processes that directly or indirectly improve myocardial performance may be involved, including the amelioration of proximal tubular dysfunction. Therefore, this paper provides a perspective on the potential cellular and molecular mechanisms of the proximal tubule that may, at least in part, mediate the cardioprotection conferred by SGLT2 inhibitors. Specifically, we focus on the effects of SGLT2 on extracellular volume homeostasis, including its plausible functional and physical association with the apical Na⁺/H⁺ exchanger isoform 3 as well as its complex and its possible bidirectional interactions with the intrarenal angiotensin system and renal sympathetic nervous system. We also discuss evidence supporting a potential benefit of gliflozins in reducing cardiovascular risk, attributable to their effect on proximal tubule handling of uric acid and albumin as well as in erythropoietin production. Unraveling the mechanisms behind the beneficial actions of SGLT2 inhibitors may not only contribute to a better understanding of the pathophysiology of cardiovascular diseases but also enable repurposing of gliflozins to improve the routine management of HF patients with or without T2D.

Canagliflozin, a sodium-glucose cotransporter 2 inhibitor, normalizes renal susceptibility to type 1 cardiorenal syndrome through reduction of renal oxidative stress in diabetic rats

AIMS/INTRODUCTION

Type 2 diabetes mellitus is a risk factor of acute kidney injury after myocardial infarction (MI), a form of cardiorenal syndrome. Recent clinical trials have shown that a sodium-glucose cotransporter 2 (SGLT2) inhibitor improved both cardiac and renal outcomes in patients with type 2 diabetes mellitus, but effects of an SGLT2 inhibitor on cardiorenal syndrome remain unclear.

MATERIALS AND METHODS

Type 2 diabetes mellitus (Otsuka Long-Evans Tokushima Fatty rats [OLETF]) and control (Long-Evans Tokushima Otsuka rats [LETO]) were treated with canagliflozin, an SGLT2 inhibitor, for 2 weeks. Renal tissues were analyzed at 12 h after MI with or without preoperative fasting.

RESULTS

Canagliflozin reduced blood glucose levels in OLETF, and blood β-hydroxybutyrate levels were increased by canagliflozin only with fasting. MI increased neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 protein levels in the kidney by 3.2- and 1.6-fold, respectively, in OLETF, but not in LETO. The renal messenger ribonucleic acid level of Toll-like receptor 4 was higher in OLETF than in LETO after MI, whereas messenger ribonucleic acid levels of cytokines/chemokines were not significantly different. Levels of lipid peroxides, nicotinamide adenine dinucleotide phosphate oxidase (NOX)2 and NOX4 proteins after MI were significantly higher in OLETF than in LETO. Canagliflozin with pre-MI fasting suppressed MI-induced renal expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in OLETF, together with reductions in lipid peroxides and NOX proteins in the kidney. Blood β-hydroxybutyrate levels before MI were inversely correlated with neutrophil gelatinase-associated lipocalin protein levels in OLETF. Pre-incubation with β-hydroxybutyrate attenuated angiotensin II-induced upregulation of NOX4 in NRK-52E cells.

CONCLUSIONS

The findings suggest that SGLT2 inhibitor treatment with a fasting period protects kidneys from MI-induced cardiorenal syndrome, possibly by β-hydroxybutyrate-mediated reduction of NOXs and oxidative stress, in type 2 diabetic rats.