Molecular Mechanisms of Diabetic Kidney Disease

TGF-β: elusive target in diabetic kidney disease

Transforming growth factor-beta (TGF-β), a cytokine with near omnipresence, is an integral part of many vital cellular processes across the human body. The family includes three isoforms: Transforming growth factor-beta 1, 2, and 3. These cytokines play a significant role in the fibrosis cascade. Diabetic kidney disease (DKD), a major complication of diabetes, is increasing in prevalence daily, and the classical diagnosis of diabetes is based on the presence of albuminuria. The occurrence of nonalbuminuric DKD has provided new insight into the pathogenesis of this disease. The emphasis on multifactorial pathways involved in developing DKD has highlighted some markers associated with tissue fibrosis. In diabetic nephropathy, TGF-β is significantly involved in its pathology. Its presence in serum and urine means that it could be a diagnostic tool while its regulation provides potential therapeutic targets. Completely blocking TGF-β signaling could reach untargeted regions and cause unanticipated effects. This paper reviews the basic details of TGF-β as a cytokine, its role in DKD, and updates on research carried out to validate its candidacy.

Diagnostic value of serum TGF-β1 and CysC in type 2 diabetic kidney disease: a cross-sectional study

Background

Diabetic kidney disease (DKD) is one of the common microvascular complications of diabetes. The exploration of serum biomarkers holds promise for improving the efficiency and accuracy of early DKD diagnosis. This study aims to investigate the diagnostic value of transforming growth factor-β1 (TGF-β1) and cystatin C (CysC) in DKD patients.

Methods

A total of 126 patients with type 2 diabetes mellitus (T2DM) diagnosed at Dongzhimen Hospital, Beijing University of Chinese Medicine, between May 2021 and March 2023 were enrolled. Patients were categorized based on proteinuria levels and estimated glomerular filtration rate (eGFR). Correlation analyses were conducted to examine the relationships between serum TGF-β1, CysC, and clinical parameters. Logistic regression was applied to identify correlation factors for DKD and renal function impairment in T2DM patients. Furthermore, receiver operating characteristic (ROC) curve analysis was performed to assess diagnostic efficacy.

Results

Significant differences in TGF-β1 and CysC levels were observed across groups with varying proteinuria levels. CysC was positively correlated with TGF-β1 (r = 0.640, p < 0.001). TGF-β1 has been associated with proteinuria levels in T2DM patients. Each unit increase in TGF-β1 was associated with a 1.122-fold and 1.470-fold higher odds of the presence of microalbuminuria and proteinuria, respectively, in the normal proteinuria (NP) group. TGF-β1 and CysC showed varying diagnostic performance. TGF-β1 better distinguished microalbuminuria group (MP) from NP, while CysC alone was less effective. T2DM patients with impaired renal function exhibited significantly higher CysC and TGF-β1 levels compared to those with normal renal function. CysC emerged as an associated factor of renal function decline (OR = 2.255, p = 0.008). CysC demonstrated superior diagnostic efficacy compared to TGF-β1 in predicting renal function impairment (AUC = 0.974).

Conclusion

CysC and TGF-β1 can serve as potential biomarkers for assessing renal impairment and proteinuria in T2DM patients. Their combined evaluation demonstrates diagnostic value and clinical application potential.

Inflammation in glomerular diseases

The structural and functional integrity of glomerular cells is critical for maintaining normal kidney function. Glomerular diseases, which involve chronic histological damage to the kidney, are related to injury to glomerular cells such as endothelial cells, mesangial cells (MCs), and podocytes. When faced with pathogenic conditions, these cells release pro-inflammatory cytokines such as chemokines, inflammatory factors, and adhesion factors. These substances interact with glomerular cells through specific inflammatory pathways, resulting in damage to the structure and function of the glomeruli, ultimately causing glomerular disease. Although the role of inflammation in chronic kidney diseases is well known, the specific molecular pathways that result in glomerular diseases remain largely unclear. For a long time, it has been believed that only immune cells can secrete inflammatory factors. Therefore, targeted therapies against immune cells were considered the first choice for treating inflammation in glomerular disease. However, emerging research indicates that non-immune cells such as glomerular endothelial cells, MCs, and podocytes can also play a role in renal inflammation by releasing inflammatory factors. Similarly, targeted therapies against glomerular cells should be considered. This review aims to uncover glomerular diseases related to inflammation and pathways in glomerular inflammation, and for the first time summarized that non-immune cells in the glomerulus can participate in glomerular inflammatory damage by secreting inflammatory factors, providing valuable references for future strategies to prevent and treat glomerular diseases. More importantly, we emphasized targeted glomerular cell therapy, which may be a key direction for the future treatment of glomerular diseases.

High-Resolution Untargeted Metabolomics Reveals Alternate-Day Fasting May Attenuate Diabetic Kidney Disease Progression in BTBR ob/ob Mice by Affecting the HCA, IPA and Reducing Inflammation

Diabetic kidney disease (DKD) is one of the most severe complications of diabetes mellitus, with limited effective therapeutic interventions. Alternate-day fasting (ADF) shows potential in treating DKD, though its mechanisms are not fully understood. In this study, BTBR ob/ob mice underwent 12 weeks of ADF, and high-resolution untargeted metabolomics were performed to uncover the underlying mechanisms. After 12 weeks of ADF, the BTBR ob/ob mice exhibited weight loss, lower blood glucose and LDL-C levels, reduced 24-h urinary protein excretion, and decreased renal collagen deposition. A total of 44 metabolites were differentially expressed, with 25 up-regulated and 19 down-regulated. Notably, hyocholic acid (HCA) and indole-3-propionic acid (IPA), both products of intestinal bacteria, can modulating inflammation were differentially expressed. Furthermore, the kidneys of BTBR ob/ob mice showed significantly lower NF-κB pathway activity and reduced inflammation after 12 weeks of ADF. This study indicates that ADF may alleviate DKD progression by modulating HCA, IPA, and decreasing inflammation.

Tirzepatide alleviates oxidative stress and inflammation in diabetic nephropathy via IL-17 signaling pathway

Oxidative stress (OS) and inflammation play essential roles in the development of diabetic nephropathy (DN). Tirzepatide (TZP) has a protective effect in diabetes. However, its underlying mechanism in DN remains unclear. DN model mice were induced by intraperitoneal injection of streptozotocin (STZ; 60 mg/kg), followed by administration of different doses of TZP (3 and 10 nmol/kg) via intraperitoneal injection for 8 weeks. The effects of TZP on DN were evaluated by detecting DN-related biochemical indicators, kidney histopathology, apoptosis, OS, and inflammation levels. Additionally, to further reveal the potential mechanism, we investigated the role of TZP in modulating the IL-17 pathway. TZP reduced serum creatinine (sCR), blood urea nitrogen (BUN), and advanced glycosylation end products (AGEs) levels, while simultaneously promoting insulin secretion in diabetic mice. Additionally, TZP attenuated tubular and glomerular injury and reduced renal apoptosis levels. Further studies found that TZP increased the levels of SOD and CAT, and decreased MDA. Meanwhile, TZP also reduced the expression of pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in both mouse serum and kidney homogenates. TZP effectively inhibited the IL-17 pathway, and subsequent intervention with an IL-17 pathway agonist (IL-17A) reversed the suppressive effects of TZP on OS and inflammation. TZP can improve DN by inhibiting OS and inflammation through the suppression of the IL-17 pathway.

Targeting ferroptosis as a prospective therapeutic approach for diabetic nephropathy

Diabetic nephropathy (DN) is a severe complication of diabetes mellitus, causing a substantive threat to the public, which receives global concern. However, there are limited drugs targeting the treatment of DN. Owing to this, it is highly crucial to investigate the pathogenesis and potential therapeutic targets of DN. The process of ferroptosis is a type of regulated cell death (RCD) involving the presence of iron, distinct from autophagy, apoptosis, and pyroptosis. A primary mechanism of ferroptosis is associated with iron metabolism, lipid metabolism, and the accumulation of ROS. Recently, many studies testified to the significance of ferroptosis in kidney tissue under diabetic conditions and explored the drugs targeting ferroptosis in DN therapy. Our review summarized the most current studies between ferroptosis and DN, along with investigating the significant processes of ferroptosis in different kidney cells, providing a novel target treatment option for DN.

Unveiling the utility of artificial intelligence for prediction, diagnosis, and progression of diabetic kidney disease: an evidence-based systematic review and meta-analysis

OBJECTIVE

The purpose of this study was to conduct a systematic investigation of the potential of artificial intelligence (AI) models in the prediction, detection of diagnostic biomarkers, and progression of diabetic kidney disease (DKD). In addition, we compared the performance of non-logistic regression (LR) machine learning (ML) models to conventional LR prediction models.

METHODS

Until January 30, 2024, a comprehensive literature review was conducted by investigating databases such as Medline (via PubMed) and Cochrane. Research that is inclusive of AI or ML models for the prediction, diagnosis, and progression of DKD was incorporated. The area under the Receiver Operating Characteristic Curve (AUROC) served as the principal outcome metric for assessing model performance. A meta-analysis was performed utilizing MedCalc statistical software to calculate pooled AUROC and assess the performance differences between LR and non-LR models.

RESULTS

A total of 57 studies were included in the meta-analysis. The pooled AUROC of AI or ML model was 0.84 (95% CI = 0.81-0.86, p < 0.0001) for analyzing prediction of DKD, 0.88 (95%CI = 0.84-0.92, p < 0.0001) for detecting diagnostic biomarkers, and 0.80 (95% CI = 0.77-0.82, p < 0.0001) for analyzing progression of DKD. The pooled AUROC of LR and non-LR ML models exhibited no significant differences across all categories (p > 0.05), except for the random forest (RF) model, which displayed a statistically significant increase in predictive accuracy compared to LR for DKD occurrence (p < 0.04).

CONCLUSION

ML models showed solid DKD prediction effectiveness, with pooled AUROC values over 0.8, suggesting good performance. These data demonstrated that non-LR and LR models perform similarly in overall CKD management, but the RF model outperforms the LR model, particularly in predicting the occurrence of DKD. These findings highlight the promise of AI technologies for better DKD management. To improve model reliability, future study should include extended follow-up periods as well as external validation.

Exercise as a therapeutic approach to alleviate diabetic kidney disease: mechanisms, clinical evidence and potential exercise prescriptions

Diabetic kidney disease (DKD) is a global and severe complication that imposes a significant burden on individual health, families, and society. Currently, the main treatment approaches for DKD include medication, blood glucose control, protein-restricted diet, and blood pressure management, all of which have certain limitations. Exercise, as a non-pharmacological intervention, has attracted increasing attention. This review introduces the mechanisms and clinical evidence of exercise on DKD, and proposes potential exercise prescriptions. Exercise can improve blood glucose stability related to DKD and the renin-angiotensin-aldosterone system (RAAS), reduce renal oxidative stress and inflammation, enhance the crosstalk between muscle and kidneys, and improve endothelial cell function. These mechanisms contribute to the comprehensive improvement of DKD. Compared to traditional treatment methods, exercise has several advantages, including safety, effectiveness, and no significant side effects. It can be used as an adjunct therapy to medication, blood glucose control, protein-restricted diet, and blood pressure management. Despite the evident benefits of exercise in DKD management, there is still a lack of large-scale, long-term randomized controlled trials to provide more evidence and develop exercise guidelines for DKD. Healthcare professionals should actively encourage exercise in DKD patients and develop personalized exercise plans based on individual circumstances.

Evaluation of the Effect of an α-Adrenergic Blocker, a PPAR-γ Receptor Agonist, and a Glycemic Regulator on Chronic Kidney Disease in Diabetic Rats

Diabetic nephropathy (DN) is a globally widespread complication of diabetes mellitus (DM). Research indicates that pioglitazone and linagliptin mitigate the risk of DN by reducing inflammation, oxidative stress, and fibrosis. The role of tamsulosin in DN is less studied, but it may contribute to reducing oxidative stress and inflammatory responses. The protective effects of combining pioglitazone, linagliptin, and tamsulosin on the kidneys have scarcely been investigated. This study examines the individual and combined effects of these drugs on DN in Wistar rats. Diabetic rats were treated with tamsulosin, pioglitazone, and linagliptin for six weeks. We assessed food and water intake, estimated glomerular filtration rate (eGFR), histological markers, urea, creatinine, glucose, NF-κB, IL-1, IL-10, TGF-β, and Col-IV using immunofluorescence and qPCR. The DN group exhibited hyperglycaemia, reduced eGFR, and tissue damage. Tamsulosin and linagliptin improved eGFR, decreased urinary glucose, and repaired tissue damage. Pioglitazone and its combinations restored serum and urinary markers and reduced tissue damage. Linagliptin lowered serum creatinine and tissue injury. In conclusion, tamsulosin, linagliptin, and pioglitazone demonstrated renoprotective effects in DN.

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.

Prediabetes and CKD: Does a causal relationship exist

The relationship between diabetes and the development of kidney complications is well known, but the understanding of prediabetes and insulin resistance with impaired kidney function has been scarcely assessed. Various factors could explain this phenomenon, from the lack of standardization in the definitions of prediabetes, to the erratic and inconsistent evidence in large-scale epidemiological and cohort studies. It seems that the pathophysiological pathway of prediabetes could be related to inflammation and neurohormonal hyperactivation, factors present even before the onset of diabetes, which might be the main drivers of glomerular hyperfiltration, albuminuria, and impaired glomerular filtration rate. It is possible that existing treatments for the management of diabetes, as metformin or SGLT2 inhibitors may also be useful in patients with prediabetes with evidence of functional and structural kidney damage. The purpose of this review is to summarize the evidence regarding the relationship between prediabetes (preDM) and the development of CKD.

Upregulation of Metrnl improves diabetic kidney disease by inhibiting the TGF-β1/Smads signaling pathway: A potential therapeutic target

PURPOSE

This study comprises an investigation of the role of meteorin-like (Metrnl) in an experimental model of diabetic kidney disease (DKD).

METHODS

Twenty-four db/db mice were randomly assigned to one of the following groups: DKD, DKD + Metrnl-/-, and DKD + Metrnl+/+. Plasma Metrnl concentrations were measured using ELISA. Kidney tissues were examined via western blotting, qRT-PCR, and immunohistochemistry to determine the expression levels of inflammatory factors. Electron microscopy was employed to observe stained kidney sections.

RESULTS

Compared with the NC group, FBG, BW, and UACR were elevated in the DKD and Metrnl-/- groups, with severe renal pathological injury, decreased serum Metrnl concentration, decreased renal Metrnl expression, and increased expression levels of TNF-α, TGF-β1, TGF-R1, pSmad2, pSmad3, and α-SMA. In contrast, the Metrnl+/+ group showed decreased FBG and UACR, BUN, TC and TG, increased HDL-C and serum Metrnl concentration, increased renal Metrnl expression, and decreased expression of TNF-α, TGF-β1, TGF-R1, pSmad2, pSmad3, and α-SMA, compared to the DKD and Metrnl-/- groups. A Pearson bivariate correlation analysis revealed a negative correlation between UACR and Metrnl, and a positive correlation between UACR and TGF-β1.

CONCLUSION

Upregulation of renal Metrnl expression can improve renal injury by downregulating the expression of molecules in the TGF-β1/Smads signaling pathway in the renal tissues of type 2 diabetic mice; and by reducing the production of fibrotic molecules such as α-SMA.

Autophagy alterations in obesity, type 2 diabetes, and metabolic dysfunction-associated steatotic liver disease: the evidence from human studies

Autophagy is an evolutionarily conserved process that plays a pivotal role in the maintenance of cellular homeostasis and its impairment has been implicated in the pathogenesis of various metabolic diseases including obesity, type 2 diabetes (T2D), and metabolic dysfunction-associated steatotic liver disease (MASLD). This review synthesizes the current evidence from human studies on autophagy alterations under these metabolic conditions. In obesity, most data point to autophagy upregulation during the initiation phase of autophagosome formation, potentially in response to proinflammatory conditions in the adipose tissue. Autophagosome formation appears to be enhanced under hyperglycemic or insulin-resistant conditions in patients with T2D, possibly acting as a compensatory mechanism to eliminate damaged organelles and proteins. Other studies have proposed that prolonged hyperglycemia and disrupted insulin signaling hinder autophagic flux, resulting in the accumulation of dysfunctional cellular components that can contribute to β-cell dysfunction. Evidence from patients with MASLD supports autophagy inhibition in disease progression. Nevertheless, given the available data, it is difficult to ascertain whether autophagy is enhanced or suppressed in these conditions because the levels of autophagy markers depend on the overall metabolism of specific organs, tissues, experimental conditions, or disease duration. Owing to these constraints, determining whether the observed shifts in autophagic activity precede or result from metabolic diseases remains challenging. Additionally, autophagy-modulating strategies are shortly discussed. To conclude, more studies investigating autophagy impairment are required to gain a more comprehensive understanding of its role in the pathogenesis of obesity, T2D, and MASLD and to unveil novel therapeutic strategies for these conditions.

The Combined Effects of the Most Important Dietary Patterns on the Incidence and Prevalence of Chronic Renal Failure: Results from the US National Health and Nutrition Examination Survey and Mendelian Analyses

BACKGROUND

We aimed to comprehensively assess the relationship of specific dietary patterns and various nutrients with chronic kidney disease (CKD) and its progression.

METHODS

The observational study data were from the NHANES 2005-2020. We calculated four dietary pattern scores (healthy eating index 2020 (HEI-2020), dietary inflammatory index (DII), alternative mediterranean diet (aMed), and dietary approaches to stop hypertension (DASH)) and the intakes of various nutrients and defined CKD, CKD-very high risk, and kidney dialysis. Associations between dietary patterns and nutrients and disease were assessed by means of two logistic regression models. Two-sample MR was performed with various food and nutrients as the exposure and CKD, kidney dialysis as the outcome. Sensitivity analyses were conducted to verify the reliability of the results.

RESULTS

A total of 25,167 participants were included in the analyses, of whom 4161 had CKD. HEI-2020, aMed, and DASH were significantly negatively associated with CKD and CKD-very high risk at higher quartiles, while DII was significantly positively associated. A higher intake of vitamins and minerals may reduce the incidence and progression of CKD to varying degrees. The MR results, corrected for false discovery rates, showed that a higher sodium intake was associated with a higher prevalence of CKD (OR: 3.91, 95%CI: 2.55, 5.99).

CONCLUSIONS

Adhering to the three dietary patterns of HEI-2020, aMed, and DASH and supplementing with vitamins and minerals benefits kidney health.

Serum cell division cycle 42 reflects the development and progression of diabetic nephropathy in patients with diabetes mellitus

Cell division cycle 42 (CDC42) regulates podocyte apoptosis to take part in the development and progression of diabetic nephropathy (DN), but currently the clinical evidence is limited. The aim of the present study was to investigate the capability of serum CDC42 expression level to estimate the development and progression of DN in patients with diabetes mellitus (DM). Patients with type 2 DM (n=306) were enrolled and divided into normoalbuminuria (n=185), microalbuminuria (n=72) and macroalbuminuria (n=49) groups based on the urinary albumin-to-creatinine ratio. Serum CDC42 was measured in all subjects using enzyme-linked immunosorbent assay. The median (interquartile range) CDC42 in patients with DM was 0.461 (0.314-0.690) ng/ml (range, 0.087-1.728 ng/ml). CDC42 was positively associated with the estimated glomerular filtration rate (P<0.001), but negatively correlated with body mass index, systolic blood pressure, hemoglobin A1c, serum creatine, serum uric acid and C reactive protein (all P<0.050). CDC42 levels were lowest in the macroalbuminuria group, followed by the microalbuminuria group, and were highest in the normoalbuminuria group (P<0.001). CDC42 indicated that it was a favorable estimator for the presence of albuminuria [area under the curve (AUC), 0.792; 95% confidence interval (CI), 0.736-0.848] and macroalbuminuria (AUC, 0.845; 95% CI, 0.775-0.915). By analyses in four different multivariate logistic regression models, increased CDC42 was independently associated with the presence of microalbuminuria (all P<0.001), macroalbuminuria (most P<0.001) and microalbuminuria + macroalbuminuria (all P<0.001). Serum CDC42 level negatively correlated with microalbuminuria and macroalbuminuria in patients with DM, suggesting its ability for estimating the development and progression of DN.

Hyperglycemia - A culprit of podocyte pathology in the context of glycogen metabolism

Prolonged disruption in the balance of glucose can result in metabolic disorders. The kidneys play a significant role in regulating blood glucose levels. However, when exposed to chronic hyperglycemia, the kidneys' ability to handle glucose metabolism may be impaired, leading to an accumulation of glycogen. Earlier studies have shown that there can be a significant increase in glucose storage in the form of glycogen in the kidneys in diabetes. Podocytes play a crucial role in maintaining the integrity of filtration barrier. In diabetes, exposure to elevated glucose levels can lead to significant metabolic and structural changes in podocytes, contributing to kidney damage and the development of diabetic kidney disease. The accumulation of glycogen in podocytes is not a well-established phenomenon. However, a recent study has demonstrated the presence of glycogen granules in podocytes. This review delves into the intricate connections between hyperglycemia and glycogen metabolism within the context of the kidney, with special emphasis on podocytes. The aberrant storage of glycogen has the potential to detrimentally impact podocyte functionality and perturb their structural integrity. This review provides a comprehensive analysis of the alterations in cellular signaling pathways that may potentially lead to glycogen overproduction in podocytes.

Immunogenicity, Safety, and Efficacy of Influenza Vaccine in T2DM and T2DM with Chronic Kidney Disease

Patients with Type 2 diabetes mellitus (T2DM) and Chronic Kidney Disease (CKD) face an increased risk of morbidity and mortality after influenza infection. Several studies have shown that the influenza vaccine effectively prevents morbidity and mortality in T2DM patients. However, there has been limited research aimed at assessing the effectiveness of the trivalent influenza vaccine in T2DM-CKD patients. This study aimed to identify Geometric Mean Titers (GMTs), seroprotection, seroconversion, safety, and efficacy. This open-label clinical trial was conducted at AMC Hospital in Bandung, West Java, Indonesia between June 2021 and July 2022. The study subjects consisted of 41 T2DM and 26 T2DM-CKD patients who were administered the trivalent influenza vaccine. There was a significant difference in the average age, with the T2DM-CKD patients being older. Median titers post-vaccination for the B/Washington virus were higher in the T2DM patients compared to the T2DM-CKD patients, and this difference was statistically significant. A majority, comprising 75.6% of the T2DM and 80.8% of the T2DM-CKD patients monitored post-influenza-vaccination, did not experience any adverse reactions. The most common reaction was the sensation of fever, with incidence rates of 12.2% in the T2DM patients and 15.4% in the T2DM-CKD patients. Furthermore, we observed that the incidence of Influenza-like Illness was highest at 7.3% in the T2DM patients and 7.7% in the T2DM-CKD patients. The trivalent influenza vaccine demonstrated equivalent safety and effectiveness in both groups.

Total flavonoids of Astragalus protects glomerular filtration barrier in diabetic kidney disease

BACKGROUND

Diabetic kidney disease (DKD) is a prevalent complication of diabetes and the leading cause of end-stage renal disease. Recent evidence suggests that total flavonoids of Astragalus (TFA) has promising effects on diabetes; however, its influence on DKD and the underlying mechanism remains unclear.

METHODS

In this study, we induced the DKD model using streptozotocin (STZ) in male C57BL/6J mice and utilized glomerular endothelial cell (GEC) lines for in vitro investigations. We constructed a network pharmacology analysis to understand the mechanism of TFA in DKD. The mechanism of TFA action on DKD was investigated through Western blot analysis and multi-immunological methods.

RESULTS

Our findings revealed that TFA significantly reduced levels of urinary albumin (ALB). Network pharmacology and intracellular pathway experiments indicated the crucial involvement of the PI3K/AKT signaling pathway in mediating these effects. In vitro experiments showed that TFA can preserve the integrity of the glomerular filtration barrier by inhibiting the expression of inflammatory factors TNF-alpha and IL-8, reducing oxidative stress.

CONCLUSION

Our findings demonstrated that TFA can ameliorates the progression of DKD by ameliorating renal fibrosis and preserving the integrity of the kidney filtration barrier. These results provide pharmacological evidence supporting the use of TFA in the treatment of kidney diseases.

Apigenin analogs as α-glucosidase inhibitors with antidiabetic activity

This study investigated the inhibitory potential of a series of synthesized compounds (L1-L27) on α-glucosidase. Among them, compound L22 showed significant inhibitory effect. Through enzymatic kinetics studies, we demonstrated that L22 acts via a non-competitive inhibition mode with a Ki value of 2.61 μM, highlighting its high affinity for the enzyme. Molecular docking studies revealed the formation of hydrogen bonds between L22 and α-glucosidase and diverse interactions with neighboring amino acid residues. Furthermore, molecular dynamics simulations confirmed the stability of the L22-α-glucosidase complex. In a mouse model of type 2 diabetes, treatment with L22 significantly lowered fasting blood glucose levels, and reduced insulin resistance, suggesting its potential as a therapeutic agent for type 2 diabetes. Furthermore, L22 showed a protective effect against oxidative stress in the liver and alleviated liver and pancreatic abnormalities. These results provide valuable insights into the mechanism of action of L22 and its potential applications to treat type 2 diabetes, and improve liver health.

The effect of hypothyroidism on the risk of diabetes and its microvascular complications: a Mendelian randomization study

Context

Several observational studies have found that hypothyroidism is associated with diabetes and its microvascular complications. However, the cause and effect have not been clarified.

Objective

The aim of the study was to examine the causality of such associations by a Mendelian randomization study.

Methods

Two-sample Mendelian randomization analysis was conducted to investigate the associations. Summary statistics for hypothyroidism were from the UK Biobank, and diabetes and its microvascular complications were from the largest available genome-wide association studies. MR-Egger, weighted median, inverse variance weighted, simple mode and weighted mode were used to examine the causal associations, and several sensitivity analyses were used to assess pleiotropy.

Results

Inverse variance weighted estimates suggested that hypothyroidism was associated with type 1 diabetes and type 1 diabetes with renal complications (β= 9.059926, se= 1.762903, P = 2.76E-07 and β= 10.18375, se= 2.021879, P = 4.73E-07, respectively) but not type 2 diabetes and type 2 diabetes with renal complications. In addition, hypothyroidism was positively associated with severe nonproliferative diabetic retinopathy and proliferative diabetic retinopathy (β= 8.427943, se= 2.142493, P = 8.36E-05 and β= 3.100939, se= 0.74956, P=3.52E-05, respectively).

Conclusions

The study identified the causal roles of hypothyroidism in diabetes and its microvascular complications. Hypothyroidism can lead to type 1 diabetes, type 1 diabetes with renal complications, severe nonproliferative diabetic retinopathy and proliferative diabetic retinopathy.

Potential application of Klotho as a prognostic biomarker for patients with diabetic kidney disease: a meta-analysis of clinical studies

Background

Diabetic kidney disease (DKD) is a serious diabetic complication and the performance of serum Klotho in DKD's prognostic evaluation is controversial.

Objective

To assess the association of serum Klotho with adverse kidney and non-kidney clinical outcomes in patients with DKD.

Design

Clinical studies regarding the relationship of serum Klotho with DKD were included. Study quality was assessed using the Newcastle-Ottawa scale. Subgroup and sensitive analyses were performed to search for the source of heterogeneity.

Data sources and methods

We comprehensively searched PubMed, Embase, Web of Science, and Cochrane library databases up to 27 September 2022. The associations of Klotho with albuminuria, such as the urinary albumin creatinine ratio (UACR), kidney outcomes such as persistent albuminuria, estimated glomerular filtration rate decline, and non-kidney outcomes such as diabetic retinopathy, cardiovascular morbidity, and mortality, were evaluated. The indicators, such as the correlation coefficient (r), odds ratio (OR), relative risk, and hazard ratio, were retrieved or calculated from the eligible studies.

Results

In all, 17 studies involving 5682 participants fulfilled the inclusion criteria and were included in this meta-analysis. There was no significant association of serum Klotho with UACR in DKD patients [summary r, -0.28 (-0.55, 0.04)] with high heterogeneity. By contrast, a strong association was observed regarding serum Klotho with kidney outcomes [pooled OR, 1.60 (1.15, 2.23)], non-kidney outcomes [pooled OR, 2.78 (2.11, 3.66)], or combined kidney and non-kidney outcomes [pooled OR, 1.96 (1.45, 2.65)] with moderate heterogeneity. Subgroup analysis indicated that age, study design, and the estimated glomerular filtration rate may be the sources of heterogeneity.

Conclusion

A decreased serum Klotho level is possibly associated with an increased risk of developing kidney and non-kidney clinical outcomes in DKD patients; thus, Klotho may be a possible biomarker to predict DKD clinical outcomes. Additional studies are needed to clarify and validate Klotho's prognostic value.

Research progress on the hypoglycemic activity and mechanisms of natural polysaccharides

The incidence of diabetes, as a metabolic disease characterized by high blood sugar levels, is increasing every year. The predominantly western medicine treatment is associated with certain side effects, which has prompted people to turn their attention to natural active substances. Natural polysaccharide is a safe and low-toxic natural substance with various biological activities. Hypoglycemic activity is one of the important biological activities of natural polysaccharides, which has great potential for development. A systematic review of the latest research progress and possible molecular mechanisms of hypoglycemic activity of natural polysaccharides is of great significance for better understanding them. In this review, we systematically reviewed the relationship between the hypoglycemic activity of polysaccharides and their structure in terms of molecular weight, monosaccharide composition, and glycosidic bonds, and summarized underlying molecular mechanisms the hypoglycemic activity of natural polysaccharides. In addition, the potential mechanisms of natural polysaccharides improving the complications of diabetes were analyzed and discussed. This paper provides some valuable insights and important guidance for further research on the hypoglycemic mechanisms of natural polysaccharides.

MAGI2 ameliorates podocyte apoptosis of diabetic kidney disease through communication with TGF-β-Smad3/nephrin pathway

Podocytes, the key component of the glomerular filtration barrier (GFB), are gradually lost during the progression of diabetic kidney disease (DKD), severely compromising kidney functionality. The molecular mechanisms regulating the survival of podocytes in DKD are incompletely understood. Here, we show that membrane-associated guanylate kinase inverted 2 (MAGI2) is specifically expressed in renal podocytes, and promotes podocyte survival in DKD. We found that MAGI2 expression was downregulated in podocytes cultured with high-glucose in vitro, and in kidneys of db/db mice as well as DKD patients. Conversely, we found enforced expression of MAGI2 via AAV transduction protected podocytes from apoptosis, with concomitant improvement of renal functions. Mechanistically, we found that MAGI2 deficiency induced by high glucose levels activates TGF-β signaling to decrease the expression of anti-apoptotic proteins. These results indicate that MAGI2 protects podocytes from cell death, and can be harnessed therapeutically to improve renal function in diabetic kidney disease.

Regulation of renal lipid deposition in diabetic nephropathy on morroniside via inhibition of NF-KB/TNF-a/SREBP1c signaling pathway

Morroniside (MOR), a cyclic enol ether terpene glycoside isolated from Cornus officinalis, has been shown to inhibit lipid accumulation, although the mechanism of action is uncertain. The aim of this study was to investigate the potential pathways by which MOR affects renal lipid deposition in diabetic nephropathy (DN). In vitro and in vivo experiments were performed using the PA-induced HK-2 cell model and a KKAy animal model, respectively. Network pharmacological analysis was used to identify potential MOR signaling pathways for DN therapy, with results verified via Western blotting and immunofluorescence experiments. The effect of MOR on lipid metabolism was investigated using BODIPY 493/503 staining. Our results indicate that MOR significantly reduces lipid accumulation both in vitro and in vivo. According to network pharmacology studies, the NF-κB/TNF-α/SREBP1c signaling pathway may be the mechanism of action of MOR in DN. MOR was found to inhibit this pathway by reducing the phosphorylation of NF-κB p65 and the expression of TNF-α and SREBP1c, similar to the effects of Bay11-7082. Additionally, MOR significantly inhibited the expression of lipid factors such as ACC, FAS, and SCD1. In conclusion, MOR can regulate the disruption of lipid metabolism in DN and reduce renal lipid deposition via suppression of the NF-κB/TNF-α/SREBP1c signaling pathway.

Protective effect of eriodictyol against hyperglycemia-induced diabetic nephropathy in rats entails antioxidant and anti-inflammatory effects mediated by activating Nrf2

The pathogenesis of diabetic nephropathy (DN) involves cellular activation of oxidative stress and inflammation. Eriodictyol is a citrus-derived flavonoid with multiple pharmacological and protective effects in various conditions. The protective role of Eriodictyol against diabetes and diabetic nephropathy is less investigated. The current research aimed to explore the role of eriodictyol in protecting against DN prompted by streptozotocin in male rats and investigate some possible mechanisms of action. Diabetes was brought about in rats by an i.p injection of a lone dose (65 mg/kg). Five groups of rats were included (n = 8 each) as control (non-diabetic), eriodictyol (20 mg/kg, orally), STZ-diabetic, STZ + eriodictyol (20 mg/kg, orally), and STZ + eriodictyol (20 mg/kg, orally) + ML385 (30 µg/kg, i.p.). Kidney histology and the levels of some markers of kidney function, renal oxidative stress, and renal inflammation were analyzed in all groups of rats. Treatment with eriodictyol prevented the damage in the renal glomeruli and tubules and reduced renal immune cell infiltration in STZ-treated animals. It also spiked urinary creatinine excretion and reduced urine volume and urinary levels of albumin, monocyte chemoattractant protein 1 (MCP-1), urinary kidney injury molecule-1 (KIM-1), and nephrin in these diabetic rats. In addition, eriodictyol stimulated the nuclear protein accumulation of Nrf2 and boosted the expression of superoxide dismutase (SOD), glutathione (GSH), heme oxygenase-1 (HO-1), and catalase (CAT) in the diabetic rat kidneys. In concomitance, it reduced the nuclear levels of NF-κB and levels of interleukine-6 (IL-6), malondialdehyde (MDA), and tumor necrosis factor-α (TNF-α) and attenuated the reduction in renal ATP levels and the increase in the mitochondria transition pore opening (mtTPT). However, the administration of eriodictyol did not affect rats' body weights and fasting glucose and insulin levels but significantly reduced serum levels of cholesterol, triglycerides, LDL-c, and oxidized LDL-c (ox-LDL-c). In conclusion, eriodictyol prevents STZ-induced nephropathy by a hypolipidemic effect and concomitant antioxidant and anti-inflammatory effects mediated by activating Nrf2/NF-κB/antioxidant axis.

The role of autophagy in the treatment of type II diabetes and its complications: a review

Type II diabetes mellitus (T2DM) is a chronic metabolic disease characterized by prolonged hyperglycemia and insulin resistance (IR). Its incidence is increasing annually, posing a significant threat to human life and health. Consequently, there is an urgent requirement to discover effective drugs and investigate the pathogenesis of T2DM. Autophagy plays a crucial role in maintaining normal islet structure. However, in a state of high glucose, autophagy is inhibited, resulting in impaired islet function, insulin resistance, and complications. Studies have shown that modulating autophagy through activation or inhibition can have a positive impact on the treatment of T2DM and its complications. However, it is important to note that the specific regulatory mechanisms vary depending on the target organ. This review explores the role of autophagy in the pathogenesis of T2DM, taking into account both genetic and external factors. It also provides a summary of reported chemical drugs and traditional Chinese medicine that target the autophagic pathway for the treatment of T2DM and its complications.

Insulin and the kidneys: a contemporary view on the molecular basis

Insulin is a hormone that is composed of 51 amino acids and structurally organized as a hexamer comprising three heterodimers. Insulin is the central hormone involved in the control of glucose and lipid metabolism, aiding in processes such as body homeostasis and cell growth. Insulin is synthesized as a large preprohormone and has a leader sequence or signal peptide that appears to be responsible for transport to the endoplasmic reticulum membranes. The interaction of insulin with the kidneys is a dynamic and multicenter process, as it acts in multiple sites throughout the nephron. Insulin acts on a range of tissues, from the glomerulus to the renal tubule, by modulating different functions such as glomerular filtration, gluconeogenesis, natriuresis, glucose uptake, regulation of ion transport, and the prevention of apoptosis. On the other hand, there is sufficient evidence showing the insulin receptor's involvement in renal functions and its responsibility for the regulation of glucose homeostasis, which enables us to understand its contribution to the insulin resistance phenomenon and its association with the progression of diabetic kidney disease.

Sitagliptin Mitigates Diabetic Nephropathy in a Rat Model of Streptozotocin-Induced Type 2 Diabetes: Possible Role of PTP1B/JAK-STAT Pathway

Diabetic nephropathy (DN) is a microvascular complication of diabetes mellitus. This study examined the therapeutic effects of sitagliptin, a dipeptidyl peptidase inhibitor, on DN and explored the underlying mechanism. Male Wistar albino rats (n = 12) were intraperitoneally administered a single dose of streptozotocin (30 mg/kg) to induce diabetes. Streptozotocin-treated and untreated rats (n = 12) were further divided into normal control, normal sitagliptin-treated control, diabetic control, and sitagliptin-treated diabetic groups (n = 6 in each). The normal and diabetic control groups received normal saline, whereas the sitagliptin-treated control and diabetic groups received sitagliptin (100 mg/kg, p.o.). We assessed the serum levels of DN and inflammatory biomarkers. Protein tyrosine phosphatase 1 B (PTP1B), phosphorylated Janus kinase 2 (P-JAK2), and phosphorylated signal transducer activator of transcription (P-STAT3) levels in kidney tissues were assessed using Western blotting, and kidney sections were examined histologically. Sitagliptin reduced DN and inflammatory biomarkers and the expression of PTP1B, p-JAK2, and p-STAT3 (p < 0.001) and improved streptozotocin-induced histological changes in the kidney. These results demonstrate that sitagliptin ameliorates inflammation by inhibiting DPP-4 and consequently modulating the PTP1B-related JAK/STAT axis, leading to the alleviation of DN.

Novel Biomarkers of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a highly prevalent condition worldwide. It represents one of the most common complications arising from diabetes mellitus (DM) and is the leading cause of end-stage kidney disease (ESKD). Its development involves three fundamental components: the hemodynamic, metabolic, and inflammatory axes. Clinically, persistent albuminuria in association with a progressive decline in glomerular filtration rate (GFR) defines this disease. However, as these alterations are not specific to DKD, there is a need to discuss novel biomarkers arising from its pathogenesis which may aid in the diagnosis, follow-up, therapeutic response, and prognosis of the disease.

Single Nucleotide Polymorphisms of the RAC1 Gene as Novel Susceptibility Markers for Neuropathy and Microvascular Complications in Type 2 Diabetes

Single nucleotide polymorphisms (SNP) in the RAC1 (Rac family small GTPase 1) gene have recently been linked to type 2 diabetes (T2D) and hyperglycemia due to their contribution to impaired redox homeostasis. The present study was designed to determine whether the common SNPs of the RAC1 gene are associated with diabetic complications such as neuropathy (DN), retinopathy (DR), nephropathy, angiopathy of the lower extremities (DA), and diabetic foot syndrome. A total of 1470 DNA samples from T2D patients were genotyped for six common SNPs by the MassArray Analyzer-4 system. The genotype rs7784465-T/C of RAC1 was associated with an increased risk of DR (p = 0.016) and DA (p = 0.03) in males, as well as with DR in females (p = 0.01). Furthermore, the SNP rs836478 showed an association with DR (p = 0.005) and DN (p = 0.025) in males, whereas the SNP rs10238136 was associated with DA in females (p = 0.002). In total, three RAC1 haplotypes showed significant associations (FDR < 0.05) with T2D complications in a sex-specific manner. The study's findings demonstrate, for the first time, that the RAC1 gene's polymorphisms represent novel and sex-specific markers of neuropathy and microvascular complications in type 2 diabetes, and that the gene could be a new target for the pharmacological inhibition of oxidative stress as a means of preventing diabetic complications.

Pediatric Diabetic Nephropathy: Novel Insights from microRNAs

Diabetic nephropathy (DN) represents the most common microvascular complication in patients with diabetes. This progressive kidney disease has been recognized as the major cause of end-stage renal disease with higher morbidity and mortality. However, its tangled pathophysiology is still not fully known. Due to the serious health burden of DN, novel potential biomarkers have been proposed to improve early identification of the disease. In this complex landscape, several lines of evidence supported a critical role of microRNAs (miRNAs) in regulating posttranscriptional levels of protein-coding genes involved in DN pathophysiology. Indeed, intriguing data showed that deregulation of certain miRNAs (e.g., miRNAs 21, -25, -92, -210, -126, -216, and -377) were pathogenically linked to the onset and the progression of DN, suggesting not only a role as early biomarkers but also as potential therapeutic targets. To date, these regulatory biomolecules represent the most promising diagnostic and therapeutic options for DN in adult patients, while similar pediatric evidence is still limited. More, findings from these elegant studies, although promising, need to be deeper investigated in larger validation studies. In an attempt to provide a comprehensive pediatric overview in the field, we aimed to summarize the most recent evidence on the emerging role of miRNAs in pediatric DN pathophysiology.

Upregulation of miR145 and miR126 in EVs from Renal Cells Undergoing EMT and Urine of Diabetic Nephropathy Patients

Diabetic nephropathy (DN) is a severe kidney-related complication of type 1 and type 2 diabetes and the most frequent cause of end-stage kidney disease. Extracellular vesicles (EVs) present in the urine mainly derive from the cells of the nephron, thus representing an interesting tool mirroring the kidney's physiological state. In search of the biomarkers of disease progression, we here assessed a panel of urinary EV miRNAs previously related to DN in type 2 diabetic patients stratified based on proteinuria levels. We found that during DN progression, miR145 and miR126 specifically increased in urinary EVs from diabetic patients together with albuminuria. In vitro, miRNA modulation was assessed in a model of TGF-β1-induced glomerular damage within a three-dimensional perfusion system, as well as in a model of tubular damage induced by albumin and glucose overload. Both renal tubular cells and podocytes undergoing epithelial to mesenchymal transition released EVs containing increased miR145 and miR126 levels. At the same time, miR126 levels were reduced in EVs released by glomerular endothelial cells. This work highlights a modulation of miR126 and miR145 during the progression of kidney damage in diabetes as biomarkers of epithelial to mesenchymal transition.

Bisacurone attenuates diabetic nephropathy by ameliorating oxidative stress, inflammation and apoptosis in rats

BACKGROUND

Diabetes nephropathy (DN) is a serious diabetic problem that may progress to renal failure. The root of Curcuma longa L., often known as turmeric, provides various health benefits. Bisacurone is a bioactive terpenoid found in small amounts in turmeric that possesses anti-inflammatory and antioxidant properties. The present study focuses on the potential protective effects of bisacurone against DN via reducing renal inflammation, oxidative stress, and apoptosis.

METHODS

Type 2 diabetes was created in rats by feeding them a high-fat/high-sugar diet for 8 weeks, followed by a low dose of streptozotocin and Bisacurone (50 and 100 μg/kg bisacurone) given for 4 weeks.

RESULTS

In diabetic rats, bisacurone reduced hyperglycemia, protected against body weight (BW) loss, lowered renal markers, reduced lipid profile alterations and avoided histological abnormalities. Bisacurone treatment reduced oxidative stress by decreasing malondialdehyde (MDA) levels while enhancing antioxidant defenses through superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) levels. Furthermore, bisacurone treatment activated the renal Nrf2/Keap1 signaling pathway but attenuated the high levels of NFκB p65, TNF-α, IL-1β, IL-6, Cox2, and iNOS. Bisacurone also reduced Bax, caspase-3, caspase-9 and cytochrome c but increased Bcl-2 in the kidneys of diabetic rats.

CONCLUSION

In the present study, bisacurone reduces DN by reducing hyperglycemia, oxidative stress, inflammation, and apoptosis, while also increasing Nrf2/HO-1 signaling.