Novel Anti-inflammatory and Anti-fibrotic Agents for Diabetic Kidney Disease-From Bench to Bedside

Dysregulation of neutrophil extracellular traps (NETs)-related genes in the pathogenesis of diabetic kidney disease - Results from bioinformatics analysis and translational studies

The role of Neutrophil extracellular traps (NETs) in the immunopathogenesis of Diabetic Kidney Disease (DKD) remains elusive. We used a machine learning approach to identify differentially expressed genes (DEGs) associated with NETs in human DKD kidney biopsy datasets and validated the results using single-nucleus RNA sequencing datasets. The expressions of these candidate genes and related cytokines were verified in blood obtained from DKD patients. Three NETs-associated genes (ITGAM, ITGB2 and TLR7) were identified, which all showed significant upregulation in both glomerular and tubulointerstitial compartments in human DKD kidneys. DKD patients showed significantly higher number of activated neutrophils with increased ITGAM and ITGB2 expression, higher serum IL-6 but lower IL-10, compared to healthy controls (p all <0.01). This study suggests that dysregulation of NETs-associated genes ITGAM and ITGB2 are related to the pathogenesis of DKD, and may serve as novel diagnostic markers and therapeutic targets in DKD.

Fiery Connections: Macrophage-Mediated Inflammation, the Journey from Obesity to Type 2 Diabetes Mellitus and Diabetic Kidney Disease

The high prevalence of diabetes mellitus (DM) poses a significant public health challenge, with diabetic kidney disease (DKD) as one of its most serious consequences. It has become increasingly clear that type 2 DM (T2D) and the complications of DKD are not purely metabolic disorders. This review outlines emerging evidence related to the step-by-step contribution of macrophages to the development and progression of DKD in individuals who specifically develop T2D as a result of obesity. The macrophage is a prominent inflammatory cell that contributes to obesity, where adipocyte hypertrophy leads to macrophage recruitment and eventually to the expansion of adipose tissue. The recruited macrophages secrete proinflammatory cytokines, which cause systemic inflammation, glucose dysregulation, and insulin sensitivity, ultimately contributing to the development of T2D. Under such pathological changes, the kidney is susceptible to elevated glucose and thereby activates signaling pathways that ultimately drive monocyte recruitment. In particular, the early recruitment of proinflammatory macrophages in the diabetic kidney produces inflammatory cytokines/chemokines that contribute to inflammation and tissue damage associated with DKD pathology. Macrophage activation and recruitment are crucial inciting factors that also persist as DKD progresses. Thus, targeting macrophage activation and function could be a promising therapeutic approach, potentially offering significant benefits for managing DKD at all stages of progression.

Specific Alternation of Gut Microbiota and the Role of Ruminococcus gnavus in the Development of Diabetic Nephropathy

In this study, we aim to investigate the precise alterations in the gut microbiota during the onset and advancement of diabetic nephropathy (DN) and examine the impact of Ruminococcus gnavus (R. gnavus) on DN. Eight-week-old male KK-Ay mice were administered antibiotic cocktails for a duration of two weeks, followed by oral administration of R. gnavus for an additional eight weeks. Our study revealed significant changes in the gut microbiota during both the initiation and progression of DN. Specifically, we observed a notable increase in the abundance of Clostridia at the class level, higher levels of Lachnospirales and Oscillospirales at the order level, and a marked decrease in Clostridia_UCG-014 in DN group. Additionally, there was a significant increase in the abundance of Lachnospiraceae, Oscillospiraceae, and Ruminococcaceae at the family level. Moreover, oral administration of R. gnavus effectively aggravated kidney pathology in DN mice, accompanied by elevated levels of urea nitrogen (UN), creatinine (Cr), and urine protein. Furthermore, R. gnavus administration resulted in down-regulation of tight junction proteins such as Claudin-1, Occludin, and ZO-1, as well as increased levels of uremic toxins in urine and serum samples. Additionally, our study demonstrated that orally administered R. gnavus up-regulated the expression of inflammatory factors, including nucleotide-binding oligomerization domain-like receptor pyrin domain-containing protein 3 (NLRP3) and Interleukin (IL)-6. These changes indicated the involvement of the gut-kidney axis in DN, and R. gnavus may worsen diabetic nephropathy by affecting uremic toxin levels and promoting inflammation in DN.

Chlorogenic Acid Inhibits Progressive Pulmonary Fibrosis in a Diabetic Rat Model

Background

Chlorogenic acid (CGA) is known to have antifibrotic and hypoglycemic effects and may play a role in preventing diabetes-induced pulmonary fibrosis. This study aimed to determine the effect and optimum dose of CGA on diabetes-induced pulmonary fibrosis.

Methods

Thirty Wistar rats (two-month-old, 150-200 grams) were randomly divided into six groups, namely control, six weeks diabetes mellitus (DM1), eight weeks DM (DM2), and three DM2 groups (CGA1, CGA2, and CGA3) who received CGA doses of 12.5, 25, and 50 mg/Kg BW, respectively. After six weeks, CGA was administered intraperitoneally for 14 consecutive days. Lung tissues were taken for TGF-β1, CTGF, SMAD7, Collagen-1, and α-SMA mRNA expression analysis and paraffin embedding. Data were analyzed using one-way ANOVA and the Kruskal-Wallis test. P<0.05 was considered statistically significant.

Results

TGF-β1 expression in the CGA1 group (1.01±0.10) was lower than the DM1 (1.33±0.25, P=0.05) and DM2 (1.33±0.20, P=0.021) groups. α-SMA expression in the CGA1 group (median 0.60, IQR: 0.34-0.64) was lower than the DM1 (median 0.44, IQR: 0.42-0.80) and DM2 (median 0.76, IQR: 0.66-1.10) groups. Collagen-1 expression in the CGA1 group (0.75±0.13) was lower than the DM1 (P=0.24) and DM2 (P=0.26) groups, but not statistically significant. CTGF expression in CGA groups was lower than the DM groups (P=0.088), but not statistically significant. There was an increase in SMAD7 expression in CGA groups (P=0.286). Histological analysis showed fibrosis improvement in the CGA1 group compared to the DM groups.

Conclusion

CGA (12.5 mg/Kg BW) inhibited the expression of profibrotic factors and increased antifibrotic factors in DM-induced rats.

Dysregulated coagulation system links to inflammation in diabetic kidney disease

Diabetic kidney disease (DKD) is a significant contributor to end-stage renal disease worldwide. Despite extensive research, the exact mechanisms responsible for its development remain incompletely understood. Notably, patients with diabetes and impaired kidney function exhibit a hypercoagulable state characterized by elevated levels of coagulation molecules in their plasma. Recent studies propose that coagulation molecules such as thrombin, fibrinogen, and platelets are interconnected with the complement system, giving rise to an inflammatory response that potentially accelerates the progression of DKD. Remarkably, investigations have shown that inhibiting the coagulation system may protect the kidneys in various animal models and clinical trials, suggesting that these systems could serve as promising therapeutic targets for DKD. This review aims to shed light on the underlying connections between coagulation and complement systems and their involvement in the advancement of DKD.

Triptolide protects against podocyte injury in diabetic nephropathy by activating the Nrf2/HO-1 pathway and inhibiting the NLRP3 inflammasome pathway

Objectives: Diabetic nephropathy (DN) is the most common microvascular complication of diabetes mellitus. This study investigated the mechanism of triptolide (TP) in podocyte injury in DN.Methods: DN mouse models were established by feeding with a high-fat diet and injecting with streptozocin and MPC5 podocyte injury models were induced by high-glucose (HG), followed by TP treatment. Fasting blood glucose and renal function indicators, such as 24 h urine albumin (UAlb), serum creatinine (SCr), blood urea nitrogen (BUN), and kidney/body weight ratio of mice were examined. H&E and TUNEL staining were performed for evaluating pathological changes and apoptosis in renal tissue. The podocyte markers, reactive oxygen species (ROS), oxidative stress (OS), serum inflammatory cytokines, nuclear factor-erythroid 2-related factor 2 (Nrf2) pathway-related proteins, and pyroptosis were detected by Western blotting and corresponding kits. MPC5 cell viability and pyroptosis were evaluated by MTT and Hoechst 33342/PI double-fluorescence staining. Nrf2 inhibitor ML385 was used to verify the regulation of TP on Nrf2.Results: TP improved renal function and histopathological injury of DN mice, alleviated podocytes injury, reduced OS and ROS by activating the Nrf2/heme oxygenase-1 (HO-1) pathway, and weakened pyroptosis by inhibiting the nod-like receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome pathway. In vitro experiments further verified the inhibition of TP on OS and pyroptosis by mediating the Nrf2/HO-1 and NLRP3 inflammasome pathways. Inhibition of Nrf2 reversed the protective effect of TP on MPC5 cells.Conclusions: Overall, TP alleviated podocyte injury in DN by inhibiting OS and pyroptosis via Nrf2/ROS/NLRP3 axis.

Pathomechanisms of Diabetic Kidney Disease

The worldwide occurrence of diabetic kidney disease (DKD) is swiftly rising, primarily attributed to the growing population of individuals affected by type 2 diabetes. This surge has been transformed into a substantial global concern, placing additional strain on healthcare systems already grappling with significant demands. The pathogenesis of DKD is intricate, originating with hyperglycemia, which triggers various mechanisms and pathways: metabolic, hemodynamic, inflammatory, and fibrotic which ultimately lead to renal damage. Within each pathway, several mediators contribute to the development of renal structural and functional changes. Some of these mediators, such as inflammatory cytokines, reactive oxygen species, and transforming growth factor β are shared among the different pathways, leading to significant overlap and interaction between them. While current treatment options for DKD have shown advancement over previous strategies, their effectiveness remains somewhat constrained as patients still experience residual risk of disease progression. Therefore, a comprehensive grasp of the molecular mechanisms underlying the onset and progression of DKD is imperative for the continued creation of novel and groundbreaking therapies for this condition. In this review, we discuss the current achievements in fundamental research, with a particular emphasis on individual factors and recent developments in DKD treatment.

Salviolone protects against high glucose-induced proliferation, oxidative stress, inflammation, and fibrosis of human renal mesangial cells by upregulating membrane metalloendopeptidase expression

As one of complications of diabetes mellitus, diabetic nephropathy is related to renal dysfunction. Membrane metalloendopeptidase (MME) is associated with the pathogenesis of diabetic nephropathy and exerts a protective function in high glucose (HG)-treated podocytes. Salviolone, one of important bioactive components from Salvia miltiorrhiza, possesses an anti-inflammatory activity. However, the roles of salviolone in renal mesangial cell dysfunction under HG condition remain unknown. The targets of salviolone in diabetic nephropathy were predicted by bioinformatics analysis. Relative mRNA level of MME was detected by qPCR in HG-treated human renal mesangial cells (HRMCs). Cell viability was analyzed using CCK-8 assay. Cell proliferation was investigated by EdU staining. Oxidative stress was evaluated by detection of ROS generation and levels of oxidative stress-related biomarkers. The inflammatory cytokines and fibrosis-related biomarkers were examined by ELISA. Our results showed that MME expression was decreased in diabetic nephropathy and HG-treated HRMCs. Salviolone increased MME level in HG-treated HRMCs. Salviolone mitigated HG-induced HRMC proliferation by increasing MME expression. Salviolone attenuated HG-induced ROS generation, MDA level increase, and SOD activity decrease through upregulating MME expression. Moreover, salviolone suppressed HG-induced increase of levels of TNF-α, IL-1β, IL-6, fibronectin, and collagen IV through upregulating MME expression. In conclusion, salviolone attenuates proliferation, oxidative stress, inflammation, and fibrosis in HG-treated HRMCs through upregulating MME expression.

Aggravated renal fibrosis is positively associated with the activation of HMGB1-TLR2/4 signaling in STZ-induced diabetic mice

Diabetic kidney dysfunction is closely associated with renal fibrosis. Although the suppression of fibrosis is crucial to attenuate kidney damage, the underlying mechanisms remain poorly understood. In this study, renal injury in diabetic mice was induced by the intraperitoneal injection of streptozotocin (100 or 150 mg/kg) for 2 consecutive days. In the model mice, remarkable renal injury was observed, manifested by albuminuria, swelling of kidneys, and histopathological characteristics. The renal fibrosis was obviously displayed with high-intensity staining of fibrin, type IV collagen (Col IV), and fibronectin. The levels of Col IV and transforming growth factor-β1 were significantly increased in diabetic mice kidneys. The aggravated fibrotic process was associated with the overexpression of HMGB1, TLR2/4, and p-NF-κB. Furthermore, a high expression of F4/80 and CD14 indicated that macrophage infiltration was involved in perpetuating inflammation and subsequent fibrosis in the kidneys of diabetic mice. The results demonstrate that the severity of renal fibrosis is positively associated with the activation of HMGB1/TLR2/4 signaling in diabetes.

Interleukin-6 and Cardiovascular and Kidney Outcomes in Patients With Type 2 Diabetes: New Insights From CANVAS

OBJECTIVE

The inflammatory cytokine interleukin-6 (IL-6) is associated with cardiovascular (CV) and kidney outcomes in various populations. However, data in patients with type 2 diabetes are limited. We assessed the association of IL-6 with CV and kidney outcomes in the Canagliflozin Cardiovascular Assessment Study (CANVAS) and determined the effect of canagliflozin on IL-6.

RESEARCH DESIGN AND METHODS

Patients with type 2 diabetes at high CV risk were randomly assigned to canagliflozin or placebo. Plasma IL-6 was measured at baseline and years 1, 3, and 6. The composite CV outcome was nonfatal myocardial infarction, nonfatal stroke, or CV death; the composite kidney outcome was sustained ≥40% estimated glomerular filtration rate decline, end-stage kidney disease, or kidney-related death. Multivariable-adjusted Cox proportional hazards regression was used to estimate the associations between IL-6 and the outcomes. The effect of canagliflozin on IL-6 over time was assessed with a repeated-measures mixed-effects model.

RESULTS

The geometric mean IL-6 at baseline, available in 3,503 (80.2%) participants, was 1.7 pg/mL. Each doubling of baseline IL-6 was associated with 14% (95% CI 4, 24) and 21% (95% CI 1, 45) increased risk of CV and kidney outcomes, respectively. Over 6 years, IL-6 increased by 5.8% (95% CI 3.4, 8.3) in the placebo group. Canagliflozin modestly attenuated the IL-6 increase (absolute percentage difference vs. placebo 4.4% [95% CI 1.3, 9.9; P = 0.01]). At year 1, each 25% lower level of IL-6 compared with baseline was associated with 7% (95% CI 1, 22) and 14% (95% CI 5, 22) lower risks for the CV and kidney outcome, respectively.

CONCLUSIONS

In patients with type 2 diabetes at high CV risk, baseline IL-6 and its 1-year change were associated with CV and kidney outcomes. The effect of IL-6-lowering therapy on CV, kidney, and safety outcomes remains to be tested.

Etiopathogenesis of kidney disease in minority populations and an updated special focus on treatment in diabetes and hypertension

Diabetes and hypertension are the most common causes of chronic kidney disease (CKD) in the general population as well as in the Black and African American population, who also suffer from high rates of CKD and CKD progression compared to the White population. Progression of CKD can lead to kidney failure, and patients with progressive kidney disease have a high risk of premature mortality, particularly from cardiovascular disease. Screening for early detection of CKD is important as it facilitates the initiation of medications that have been shown to delay the progression of diabetes-related as well as non-diabetes-related CKD, and reduce rates of death from both kidney and cardiovascular disease. The potential adverse effects from use of some of the newer reno- and cardio-protective glucose-lowering medications, such as the sodium glucose cotransporter-2 inhibitors, may be effectively avoided with detailed patient education and monitoring by the healthcare provider. It is important to note that lifestyle modification including regular exercise, diet, and smoking cessation are first-line in the management of diabetes and hypertension. When CKD occurs, co-management by providers using a comprehensive strategy may avert early complications and facilitate appropriate early referral for nephrology specialty care.

MicroRNA-122-5p ameliorates tubular injury in diabetic nephropathy via FIH-1/HIF-1α pathway

Diabetes kidney disease (DKD) affects approximately one-third of diabetes patients, however, the specific molecular mechanism of DKD remains unclear, and there is still a lack of effective therapies. Here, we demonstrated a significant increase of microRNA-122-5p (miR-122-5p) in renal tubular cells in STZ induced diabetic nephropathy (DN) mice. Moreover, inhibition of miR-122-5p led to increased cell death and serve tubular injury and promoted DN progression following STZ treatment in mice, whereas supplementation of miR-122-5p mimic had kidney protective effects in this model. In addition, miR-122-5p suppressed the expression of factor inhibiting hypoxia-inducible factor-1 (FIH-1) in vitro models of DN. microRNA target reporter assay further verified FIH-1 as a direct target of miR-122-5p. Generally, FIH-1 inhibits the activity of HIF-1α. Our in vitro study further indicated that overexpression of HIF-1α by transfection of HIF-1α plasmid reduced tubular cell death, suggesting a protective role of HIF-1α in DN. Collectively, these findings may unveil a novel miR-122-5p/FIH-1/HIF-1α pathway which can attenuate the DN progression.