Gut microbes and their metabolites play crucial roles in the pathogenesis of diabetic kidney disease (DKD). However, which one and how specific gut-derived metabolites affect the progression of DKD remain largely unknown. This study aimed to investigate the potential roles of indole-3-propionic acid (IPA), a microbial metabolite of tryptophan, in DKD. Metagenomic sequencing was performed to analyze the microbiome structure in DKD. Metabolomics screening and validation were conducted to identify characteristic metabolites associated with DKD. The protective effect of IPA on DKD glomerular endothelial cells (GECs) was assessed through in vivo and in vitro experiments. Further validation via western blot, immunoprecipitation, gene knockout, and site-directed mutation elucidated the mechanism of IPA on mitochondrial injury. Alterations in gut microbial community structure and dysregulated tryptophan metabolism were evident in DKD mice. Serum IPA levels were significantly reduced in DKD patients and correlated with fasting blood glucose, HbA1c, urine albumin-to-creatinine ratio (UACR), and estimated glomerular filtration rate (eGFR). IPA supplementation ameliorated albuminuria, bolstered the integrity of the glomerular filtration barrier, and mitigated mitochondrial impairments in GECs. Mechanistically, IPA hindered SIRT1 phosphorylation-mediated ubiquitin-proteasome degradation, restoring SIRT1's role in promoting PGC-1α deacetylation and nuclear translocation, thereby upregulating genes associated with mitochondrial biosynthesis and antioxidant defense. Our findings underscore the potential of the microbial metabolite IPA to attenuate DKD progression, offering novel insights and potential therapeutic strategies for its management.

Elevated circulating trimethylamine N-oxide (TMAO) concentrations have been observed in patients with chronic kidney disease (CKD). We aimed to systematically estimate and quantify the association between TMAO concentrations and kidney function. The PubMed, EMBASE, Cochrane Library, Scopus, and Web of Science databases were systematically searched from 1995 to 1 June, 2020, for clinical studies on circulating TMAO concentrations and kidney function indicators. We used R software to conduct meta-analyses of the extracted data. A cumulative meta-analysis was applied to test whether health status affected the pooled effect value. Meta-regression and subgroup analyses were performed to identify possible sources of heterogeneity. Ultimately, we included a total of 32 eligible clinical studies involving 42,062 participants. In meta-analyses of continuous-outcome variables, advanced CKD was associated with a 67.9 μmol/L (95% CI: 52.7, 83.2; P < 0.01) increase in TMAO concentration, and subjects with high concentrations of TMAO had a 12.9 mL/(min·1.73 m²) (95% CI: −16.6, −9.14; P < 0.01) decrease in glomerular filtration rate (GFR). In meta-analyses of the correlations, TMAO was strongly inversely correlated with GFR [Fisher's z-transformed correlation coefficient (ZCOR): −0.45; 95% CI: −0.58, −0.32; P < 0.01] and positively associated with the urine albumin-to-creatinine ratio (UACR; ZCOR: 0.26; 95% CI: 0.08, 0.43; P < 0.01), serum creatinine (sCr; ZCOR: 0.43; 95% CI: 0.28, 0.58; P < 0.01), urine albumin excretion rate (UAER; ZCOR: 0.06; 95% CI: 0.04, 0.09; P < 0.01), blood urea (ZCOR: 0.50; 95% CI: 0.29, 0.72; P < 0.01), blood uric acid (ZCOR: 0.32; 95% CI: 0.25, 0.38; P < 0.01), and serum cystatin C (CysC; ZCOR: 0.47, 95% CI: 0.44, 0.51; P < 0.01). This is the first systematic review and meta-analysis to reveal a negative association between circulating TMAO concentrations and kidney function.

Purpose: Numerous clinical studies have explored sodium–glucose cotransporter 2 inhibitor (SGLT2i) in patients with chronic heart failure (CHF), with or without type 2 diabetes mellitus (T2DM), and SGLT2i were proved to significantly reduce CHF hospitalization, cardiovascular death, cardiovascular mortality, all-cause mortality and myocardial infarction in patients with or without T2DM. However, only a limited few have investigated the effects of SGLT-2i on HF disease-specific health status and cardiac function. This meta-analysis aims to assess the effects of SGLT2i on disease-specific health status and cardiac function in CHF patients. Methods: A comprehensive search was conducted of trials by searching in PubMed, EMBASE, CENTRAL, Scopus, and Web of Science, and two Chinese databases (CNKI and Wanfang), Clinical Trials (http://www.clinicaltrials.gov) were also searched. Results: A total of 18 randomized controlled trials (RCTs) involving 23,953 participants were included in the meta-analysis. The effects of SGLT2 inhibitors were compared with control or placebo groups in CHF with or without T2DM. The SGLT2 inhibitors group exhibited a significant reduction in pro b-type natriuretic peptide (NT-proBNP) levels by 136.03 pg/ml (95% confidence interval [CI]: −253.36, − 18.70; P = 0.02). Additionally, a greater proportion of patients in the SGLT2 inhibitors group showed a ≥ 20% decrease in NT-proBNP (RR = 1.45, 95% CI [0.92, 2.29], p = 0.072). However, no statistically significant difference was observed for the effects on B-type natriuretic peptide (BNP). The use of SGLT-2 inhibitors led to a noteworthy improvement in LVEF by 2.79% (95% CI [0.18, 5.39];P = 0.036). In terms of health status, as assessed by the Kansas City Cardiomyopathy Questionnaire (KCCQ) and 6-minute walk distance, SGLT2 inhibitors led to a significant improvement in KCCQ clinical summary (KCCQ-CS) score (WMD = 1.7, 95% CI [1.67, 1.73], P < 0.00001), KCCQ overall summary (KCCQ-OS) score (WMD = 1.73, 95% CI [0.94, 2.52], P < 0.00001), and KCCQ total symptom (KCCQ-TS) score (WMD = 2.88, 95% CI [1.7, 4.06], P < 0.00001). Furthermore, the occurrence of KCCQ-CS and KCCQ-OS score increases ≥ 5 points had relative risks (RR) of 1.25 (95% CI [1.11, 1.42], P < 0.00001) and 1.15 (95% CI [1.09, 1.22], P < 0.00001), respectively. Overall, SGLT2 inhibitors increased the 6-minute walk distance by 23.98 m (95% CI [8.34, 39.62]; P = 0.003) compared to control/placebo from baseline. Conclusions: The SGLT2 inhibitors treatment offers an effective strategy for improving NT-proBNP levels, Kansas City Cardiomyopathy Questionnaire scores and 6-minute walk distance in CHF with or without T2DM. These findings indicate that SGLT2i improve cardiac function and health status in CHF with or without T2DM, and provide valuable guidance for clinicians making treatment decisions for patients with CHF.

Diabetic kidney disease (DKD) is a major microvascular complication of diabetes mellitus (DM) and is closely associated to programmed cell death. However, the complex mechanisms of necroptosis, an alternative cell death pathway, in DKD pathogenesis are yet to be elucidated. This study indicates that necroptosis is involved in DKD induced by high glucose (HG) both in vivo and in vitro. HG intervention led to the activation of RIPK1/RIPK3/MLKL signaling, resulting in renal tissue necroptosis and proinflammatory activation in streptozotocin/high-fat diet- (STZ/HFD-) induced diabetic mice and HG-induced normal rat kidney tubular cells (NRK-52E). We further found that in HG-induced NRK-52E cell, necroptosis might, at least partly, depend on the levels of reactive oxygen species (ROS). Meanwhile, ROS participated in necroptosis via a positive feedback loop involving the RIPK1/RIPK3 pathway. In addition, blocking RIPK1/RIPK3/MLKL signaling by necrostatin-1 (Nec-1), a key inhibitor of RIPK1 in the necroptosis pathway, or antioxidant N-acetylcysteine (NAC), an inhibitor of ROS generation, could effectively protect the kidney against HG-induced damage, decrease the release of proinflammatory cytokines, and rescue renal function in STZ/HFD-induced diabetic mice. Inhibition of RIPK1 effectively decreased the activation of RIPK1-kinase-/NF-κB-dependent inflammation. Collectively, we demonstrated that high glucose induced DKD via renal tubular epithelium necroptosis, and Nec-1 or NAC treatment downregulated the RIPK1/RIPK3/MLKL pathway and finally reduced necroptosis, oxidative stress, and inflammation. Thus, RIPK1 may be a therapeutic target for DKD.

Chronic high‐dose alcohol consumption impairs bone remodeling, reduces bone mass, and increases the risk of osteoporosis and bone fracture. However, the mechanisms underlying alcohol‐induced osteoporosis are yet to be elucidated. In this study, we showed that excess intake of ethyl alcohol (EtOH) resulted in osteopenia and osteoblast necroptosis in mice that led to necrotic lesions and reduced osteogenic differentiation in bone marrow mesenchymal stem cells (BMMSCs). We found that EtOH treatment led to the activation of the RIPK1/RIPK3/MLKL signaling, resulting in increased osteoblast necroptosis and decreased osteogenic differentiation and bone formation both in vivo and in vitro. We further discovered that excessive EtOH treatment‐induced osteoblast necroptosis might partly depend on reactive oxygen species (ROS) generation; concomitantly, ROS contributed to necroptosis of osteoblasts through a positive feedback loop involving RIPK1/RIPK3. In addition, blocking of the RIPK1/RIPK3/MLKL signaling by necrostatin‐1 (Nec‐1), a key inhibitor of RIPK1 kinase in the necroptosis pathway, or antioxidant N‐acetylcysteine (NAC), an inhibitor of ROS, could decrease the activation of osteoblast necroptosis and ameliorate alcohol‐induced osteopenia both in vivo and in vitro. Collectively, we demonstrated that chronic high‐dose alcohol consumption induced osteopenia via osteoblast necroptosis and revealed that RIPK1 kinase may be a therapeutic target for alcohol‐induced osteopenia.

Background. Chronic hyperglycemia‐induced inflammation is recognized as the most important pathophysiological process in diabetic kidney disease (DKD). As maresin 1 (MaR1) is an extensive anti‐inflammatory lipid mediator, the present study investigated the protective role of MaR1 in the pathogenesis of DKD and its clinical relevance. Methods. Serum MaR1 concentrations were analyzed in 104 subjects with normal glucose tolerant, type 2 diabetes (T2DM), or DKD. Streptozotocin (STZ) together with high fat diet was used to induce male C57BL/6 J mice into diabetic mice which were treated with MaR1. Human renal tubule epithelial cells (HK‐2 cells) were treated by high glucose for glucotoxicity cell model and transfected with LGR6 siRNA for knockdown with MaR1 added，and detected oxidative stress and inflammatory related factors. Results. Serum MaR1 concentrations were significant decreased in T2DM with or without kidney disease compared with normal participant and were lowest in patients with DKD. Serum MaR1 concentrations were negatively correlated with hemoglobin A1c (HbA1c), duration of diabetes, urinary albumin to creatinine ratio (UACR), neutrophil, and neutrophil‐lymphocyte ratio and were positively correlated with high‐density lipoprotein‐cholesterol (HDL‐C) and estimated glomerular filtration rate (eGFR). In mouse model, MaR1 injection alleviated hyperglycemia, UACR and the pathological progression of DKD. Interestingly, the renal expression of LGR6 was down‐regulated in DKD and high glucose treated HK‐2 cells but up‐regulated by MaR1 treatment. Mechanistically, MaR1 alleviated inflammation via LGR6‐mediated cAMP‐SOD2 antioxidant pathway in DKD mice and high glucose treated HK‐2 cells. Conclusions. Our study demonstrates that decreased serum MaR1 levels were correlated with the development of DKD. MaR1 could alleviate DKD and glucotoxicity‐induced inflammation via LGR6‐mediated cAMP‐SOD2 antioxidant pathway. Thus, our present findings identify MaR1 as a predictor and a potential therapeutic target for DKD.