Pro-inflammatory cytokines are associated with podocyte damage and proximal tubular dysfunction in the early stage of diabetic kidney disease in type 2 diabetes mellitus patients

Diagnostic Value and Mechanism of Action of Serum miR-1281 Involved in T2DM and Complications of DKD

OBJECTIVE

To research the diagnostic value and mechanism of miR-1281 involved in type 2 diabetes mellitus (T2DM) and diabetic kidney disease (DKD).

METHODS

One hundred and eighteen patients with T2DM (68 DKD patients) and 35 healthy individuals were included. Fasting venous blood and one-time morning urine were collected for biochemical testing. RT-qPCR detected miR-1281 expression, ROC curve assessed the diagnostic value of miR-1281 for T2DM and DKD, and logistic regression predicted risk factors affecting the progression of DKD. ELISA analysed inflammatory cytokine expression, and Pearson correlation assessed its relevance to miR-1281. CCK8 detected cell proliferation and flow cytometry recorded apoptosis.

RESULTS

miR-1281 was upregulated in T2DM patients and increased more significantly in DKD patients. The ROC curves indicated that miR-1281 had diagnostic value in predicting T2DM and DKD, and miR-1281 was closely related to the pathological characteristics of DKD patients. The logistic results showed that increased miR-1281 expression was a risk factor for DKD progression. ELISA showed that inflammatory cytokines (IL-6, IL-18, TNF-α) were significantly increased in patients with T2DM, and Pearson correlation analysis indicated a positive correlation between miR-1281 and inflammatory cytokine expression. The high-glucose environment promoted cell proliferation, decreased apoptosis, and increased inflammatory factor levels, but transfection of the miR-1281 inhibitor resisted the adverse effects of the high-glucose environment on cells.

CONCLUSION

miR-1281 promotes glomerular cell proliferation, inhibits apoptosis, and increases the level of intracellular inflammation, leading to impaired renal function in T2DM patients.

Targeting senescence to prevent diabetic kidney disease: Exploring molecular mechanisms and potential therapeutic targets for disease management

BACKGROUND/AIMS

As a microvascular complication, diabetic kidney disease is the leading cause of chronic kidney disease and end-stage renal disease worldwide. While the underlying pathophysiology driving transition of diabetic kidney disease to renal failure is yet to be fully understood, recent studies suggest that cellular senescence is central in disease development and progression. Consequently, understanding the molecular mechanisms which initiate and drive senescence in response to the diabetic milieu is crucial in developing targeted therapies that halt progression of renal disease.

METHODS

To understand the mechanistic pathways underpinning cellular senescence in the context of diabetic kidney disease, we reviewed the literature using PubMed for English language articles that contained key words related to senescence, inflammation, fibrosis, senescence-associated secretory phenotype (SASP), autophagy, and diabetes.

RESULTS

Aberrant accumulation of metabolically active senescent cells is a notable event in the progression of diabetic kidney disease. Through autocrine- and paracrine-mediated mechanisms, resident senescent cells potentiate inflammation and fibrosis through increased expression and secretion of pro-inflammatory cytokines, chemoattractants, recruitment of immune cells, myofibroblast activation, and extracellular matrix remodelling. Compounds that eliminate senescent cells and/or target the SASP - including senolytic and senomorphics drugs - demonstrate promising results in reducing the senescent cell burden and associated pro-inflammatory effect.

CONCLUSIONS

Here we evidence the link between senescence and diabetic kidney disease and highlight underlying molecular mechanisms and potential therapeutic targets that could be exploited to delay disease progression and improve outcomes for individuals with the disease. Trials are now required to translate their therapeutic potential to a clinical setting.

Canonical effects of cytokines on glomerulonephritis: A new outlook in nephrology

Glomerulonephritis (GN) is an important cause of renal inflammation resulting from kidney-targeted adaptive and innate immune responses and consequent glomerular damage. Given the lack of autoantibodies, immune complexes, or the infiltrating immune cells in some forms of GN, for example, focal segmental glomerulosclerosis and minimal change disease, along with paraneoplastic syndrome and a special form of renal involvement in some viral infections, the likeliest causative scenario would be secreted factors, mainly cytokine(s). Since cytokines can modulate the inflammatory mechanisms, severity, and clinical outcomes of GN, it is rational to consider the umbrella term of cytokine GN as a new outlook to reclassify a group of previously known GN. We focus here, particularly, on cytokines that have the central "canonical effect" in the development of GN.

Mechanistic Insights Into Redox Damage of the Podocyte in Hypertension

Podocytes are specialized cells within the glomerular filtration barrier, which are crucial for maintaining glomerular structural integrity and convective ultrafiltration. Podocytes exhibit a unique arborized morphology with foot processes interfacing by slit diaphragms, ladder-like, multimolecular sieves, which provide size and charge selectivity for ultrafiltration and transmembrane signaling. Podocyte dysfunction, resulting from oxidative stress, dysregulated prosurvival signaling, or structural damage, can drive the development of proteinuria and glomerulosclerosis in hypertensive nephropathy. Functionally, podocyte injury leads to actin cytoskeleton rearrangements, foot process effacement, dysregulated slit diaphragm protein expression, and impaired ultrafiltration. Notably, the renin-angiotensin system plays a pivotal role in podocyte function, with beneficial AT2R (angiotensin receptor 2)-mediated nitric oxide (NO) signaling to counteract AT1R (angiotensin receptor 1)-driven calcium (Ca2+) influx and oxidative stress. Disruption of this balance contributes significantly to podocyte dysfunction and drives albuminuria, a marker of kidney damage and overall disease progression. Oxidative stress can also lead to sustained ion channel-mediated Ca2+ influx and precipitate cytoskeletal disorganization. The complex interplay between GPCR (G-protein coupled receptor) signaling, ion channel activation, and redox injury pathways underscores the need for additional research aimed at identifying targeted therapies to protect podocytes and preserve glomerular function. Earlier detection of albuminuria and podocyte injury through routine noninvasive diagnostics will also be critical in populations at the highest risk for the development of hypertensive kidney disease. In this review, we highlight the established mechanisms of oxidative stress-mediated podocyte damage in proteinuric kidney diseases, with an emphasis on a hypertensive renal injury. We will also consider emerging therapies that have the potential to selectively protect podocytes from redox-related injury.

Propionate and butyrate counteract renal damage and progression to chronic kidney disease

BACKGROUND

Short-chain fatty acids (SCFAs), mainly acetate, propionate and butyrate, are produced by gut microbiota through fermentation of complex carbohydrates that cannot be digested by the human host. They affect gut health and can contribute at the distal level to the pathophysiology of several diseases, including renal pathologies.

METHODS

SCFA levels were measured in chronic kidney disease (CKD) patients (n = 54) at different stages of the disease, and associations with renal function and inflammation parameters were examined. The impact of propionate and butyrate in pathways triggered in tubular cells under inflammatory conditions was analysed using genome-wide expression assays. Finally, a pre-clinical mouse model of folic acid-induced transition from acute kidney injury to CKD was used to analyse the preventive and therapeutic potential of these microbial metabolites in the development of CKD.

RESULTS

Faecal levels of propionate and butyrate in CKD patients gradually reduce as the disease progresses, and do so in close association with established clinical parameters for serum creatinine, blood urea nitrogen and the estimated glomerular filtration rate. Propionate and butyrate jointly downregulated the expression of 103 genes related to inflammatory processes and immune system activation triggered by tumour necrosis factor-α in tubular cells. In vivo, the administration of propionate and butyrate, either before or soon after injury, respectively, prevented and slowed the progression of damage. This was indicated by a decrease in renal injury markers, the expression of pro-inflammatory and pro-fibrotic markers, and recovery of renal function over the long term.

CONCLUSIONS

Propionate and butyrate levels are associated with a progressive loss of renal function in CKD patients. Early administration of these SCFAs prevents disease advancement in a pre-clinical model of acute renal damage, demonstrating their therapeutic potential independently of the gut microbiota.

Pharmacological Nephroprotection in Chronic Kidney Disease Patients with Type 2 Diabetes Mellitus-Clinical Practice Position Statement of the Polish Society of Nephrology

Both chronic kidney disease (CKD) and type 2 diabetes (T2D) are modern epidemics worldwide and have become a severe public health problem. Chronic kidney disease progression in T2D patients is linked to the need for dialysis or kidney transplantation and represents the risk factor predisposing to serious cardiovascular complications. In recent years, important progress has occurred in nephroprotective pharmacotherapy in CKD patients with T2D. In the current position paper, we described a nephroprotective approach in CKD patients with T2D based on the five following pillars: effective antihyperglycemic treatment, SGLT2 inhibitor or semaglutide, antihypertensive therapy, use of RASi (ARB or ACEi), and in selected patients, finerenone, as well as sodium bicarbonate in patients with metabolic acidosis. We thought that the current statement is comprehensive and up-to-date and addresses multiple pathways of nephroprotection in patients with CKD and T2D.

Clinico-demographic and biochemical correlation of inflammatory gene expression in pediatric nephrotic syndrome

BACKGROUND

Nephrotic syndrome (NS) is a common kidney disease in children. While Steroid-Sensitive Nephrotic Syndrome (SSNS) is frequently observed, Steroid-Resistant Nephrotic Syndrome (SRNS) has a poor prognosis and often leads to chronic kidney disease. The pathogenesis of SRNS is complex, with immunological modulation of T helper subtypes 1 and 2 cytokines increasing susceptibility to the disease. Currently, no established biomarkers can accurately predict SRNS. However, a group of cytokines might serve as potential indicators of responsiveness, aiding in the identification of patients with SRNS. The discovery of these cytokines as novel biomarkers for early diagnosis could greatly benefit patients. This includes preventing the adverse effects of glucocorticoid treatment and enabling a timely transition to more effective therapeutic alternatives.

METHODS

This study aims to investigate the association between the gene expression patterns of cytokines, including IL-2, IL-4, IL-5, IL-6, IL-9, IL-10, IL-13, IL-17A, NF-κB, and TNFα, in healthy participants (n = 100), SSNS patients (n = 100), and SRNS patients (n = 100). Using qRT-PCR, followed by Receiver-operating characteristic analysis, the study assesses their potential as biomarkers. Additionally, clinicodemographic data were analyzed, and bioinformatic analyses such as coexpression analysis, gene enrichment, pathway analysis, and Cytoscape were performed to enhance our understanding of the inflammatory cascade initiating podocyte injury in NS.

RESULTS

The results of our study suggest that specific candidate genes, including IL-2, IL-5, IL-6, IL-9, IL-17A, IL-10, IL-13, and TNFα, exhibit upregulation and hold significant importance, with an Area Under the Curve value of 0.9.

CONCLUSION

These genes have the potential to serve as valuable prognostic and management tools for NS, forming a promising panel of inflammatory gene biomarkers. Furthermore, conducting an extensive analysis that integrates cytokine genes with their respective targeted microRNAs could offer deeper insights into the pathogenesis of the disease.

Biomarkers of chronic kidney disease in older individuals: navigating complexity in diagnosis

Chronic kidney disease (CKD) in older individuals is a matter of growing concern in the field of public health across the globe. Indeed, prevalence of kidney function impairment increases with advancing age and is often exacerbated by age-induced modifications of kidney function, presence of chronic diseases such as diabetes, hypertension, and cardiovascular disorders, and increased burden related to frailty, cognitive impairment and sarcopenia. Accurate assessment of CKD in older individuals is crucial for timely intervention and management and relies heavily on biomarkers for disease diagnosis and monitoring. However, the interpretation of these biomarkers in older patients may be complex due to interplays between CKD, aging, chronic diseases and geriatric syndromes. Biomarkers such as serum creatinine, estimated glomerular filtration rate (eGFR), and albuminuria can be significantly altered by systemic inflammation, metabolic changes, and medication use commonly seen in this population. To overcome the limitations of traditional biomarkers, several innovative proteins have been investigated as potential, in this review we aimed at consolidating the existing data concerning the geriatric aspects of CKD, describing the challenges and considerations in using traditional and innovative biomarkers to assess CKD in older patients, highlighting the need for integration of the clinical context to improve biomarkers' accuracy.

Reactive oxygen species impair Na+ transport and renal components of the renin-angiotensin-aldosterone system after paraquat poisoning

Paraquat (1,1'-dimethyl-4,4'-bipyridyl dichloride) is an herbicide widely used worldwide and officially banned in Brazil in 2020. Kidney lesions frequently occur, leading to acute kidney injury (AKI) due to exacerbated reactive O2 species (ROS) production. However, the consequences of ROS exposure on ionic transport and the regulator local renin-angiotensin-aldosterone system (RAAS) still need to be elucidated at a molecular level. This study evaluated how ROS acutely influences Na+-transporting ATPases and the renal RAAS. Adult male Wistar rats received paraquat (20 mg/kg; ip). After 24 h, we observed body weight loss and elevation of urinary flow and serum creatinine. In the renal cortex, paraquat increased ROS levels, NADPH oxidase and (Na++K+)ATPase activities, angiotensin II-type 1 receptors, tumor necrosis factor-α (TNF-α), and interleukin-6. In the medulla, paraquat increased ROS levels and NADPH oxidase activity but inhibited (Na++K+)ATPase. Paraquat induced opposite effects on the ouabain-resistant Na+-ATPase in the cortex (decrease) and medulla (increase). These alterations, except for increased serum creatinine and renal levels of TNF-α and interleukin-6, were prevented by 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (tempol; 1 mmol/L in drinking water), a stable antioxidant. In summary, after paraquat poisoning, ROS production culminated with impaired medullary function, urinary fluid loss, and disruption of Na+-transporting ATPases and angiotensin II signaling.

Association between neutrophil-to-lymphocyte ratio and diabetic kidney disease in type 2 diabetes mellitus patients: a cross-sectional study

Aims

This investigation examined the possibility of a relationship between neutrophil-to-lymphocyte ratio (NLR) and diabetic kidney disease (DKD) in type 2 diabetes mellitus (T2DM) patients.

Methods

Adults with T2DM who were included in the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2020 were the subjects of the current cross-sectional investigation. Low estimated glomerular filtration rate (eGFR) (< 60 mL/min/1.73 m2) or albuminuria (urinary albumin-to-creatinine ratio (ACR) ≥ 30 mg/g) in T2DM patients were the diagnostic criteria for DKD. Weighted multivariable logistic regression models and generalized additive models were used to investigate the independent relationships between NLR levels with DKD, albuminuria, and low-eGFR. Additionally, we examined the relationships between DKD, albuminuria, and low-eGFR with other inflammatory markers, such as the aggregate index of systemic inflammation (AISI), systemic immune-inflammation index (SII), system inflammation response index (SIRI), and platelet-to-lymphocyte ratio (PLR) and monocyte-to-lymphocyte ratio (MLR). Their diagnostic capabilities were evaluated and contrasted using receiver operating characteristic (ROC) curves.

Results

44.65% of the 7,153 participants who were recruited for this study were males. DKD, albuminuria, and low-eGFR were prevalent in 31.76%, 23.08%, and 14.55% of cases, respectively. Positive correlations were seen between the NLR with the prevalences of DKD, albuminuria, and low-eGFR. Subgroup analysis and interaction tests revealed that the associations of NLR with DKD, albuminuria, and low-eGFR were not significantly different across populations. In addition, MLR, SII and SIRI showed positive associations with the prevalence of DKD. ROC analysis discovered that when compared to other inflammatory markers (MLR, PLR, SII, SIRI, and AISI), NLR may demonstrate more discriminatory power and accuracy in assessing the risk of DKD, albuminuria, and low-eGFR.

Conclusion

Compared to other inflammatory markers (MLR, PLR, SII, SIRI, and AISI), NLR may serve as the more effective potential inflammatory marker for identifying the risk of DKD, albuminuria, and low-eGFR in US T2DM patients. T2DM patients with elevated levels of NLR, MLR, SII, and SIRI should be closely monitored for their potential risk to renal function.

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.

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.

Potential Role and Expression Level of Urinary CXCL8 in Different Stages of Incipient Diabetic Nephropathy with Undiminished Creatinine Clearance: A Pilot Study

Background

Diabetic nephropathy (DN) is one of the most devastating microvascular complications of diabetes, with a high prevalence and poor prognosis. Early intervention is crucial to improve the outcomes of DN. CXCL8 is related to podocyte damage in incipient DN; however, the role and expression level of CXCL8 have never been elucidated, especially in those with undiminished creatinine clearance.

Methods

Consecutive inpatients with type 2 diabetes were included in this study. Patients were assigned into four groups based on the Mogensen stage, reflecting pathological features through clinical manifestations: non-DN group, hyperfiltration group, microalbuminuria group and overt DN group. Clinical and laboratory data were retrospectively collected and analyzed. Urinary CXCL8 (uCXCL8) was measured using an enzyme-linked immunosorbent assay (ELISA) method and adjusted for urinary creatinine (Cr) from the same urine sample.

Results

In total, 88 eligible consecutive inpatients with type 2 diabetes were included in this study. uCXCL8 was differentially expressed in different stages of incipient DN; it decreased in the hyperfiltration phase of incipient DN (1.40±1.01 pg/μmol Cr) and was highly expressed in patients in the microalbuminuria stage (5.01±4.01 pg/μmol Cr). uCXCL8 was positively correlated with age, diabetes course, cystatin C and urinary albuminuria-to-creatinine ratio, but negatively correlated with estimated glomerular filtration rate (P<0.05). uCXCL8 was a risk factor for classic DN after adjusting for age, diabetes course and cystatin C (OR=1.17, 95% CI 0.98-1.4, P=0.045).

Conclusion

CXCL8 played an important role in the progression of incipient DN. The unique expression profile of uCXCL8 may provide a reference for understanding the prognosis and mechanisms of incipient DN progression. uCXCL8 was an independent risk factor for the development of classic DN.

Mitochondrial DNA Changes in Blood and Urine Display a Specific Signature in Relation to Inflammation in Normoalbuminuric Diabetic Kidney Disease in Type 2 Diabetes Mellitus Patients

Mitochondrial dysfunction is an important mechanism contributing to the development and progression of diabetic kidney disease (DKD). Mitochondrial DNA (mtDNA) levels in blood and urine were evaluated in relation to podocyte injury and proximal tubule (PT) dysfunction, as well as to a specific inflammatory response in normoalbuminuric DKD. A total of 150 type 2 diabetes mellitus (DM) patients (52 normoalbuminuric, 48 microalbuminuric, and 50 macroalbuminuric ones, respectively) and 30 healthy controls were assessed concerning the urinary albumin/creatinine ratio (UACR), biomarkers of podocyte damage (synaptopodin and podocalyxin), PT dysfunction (kidney injury molecule-1 (KIM-1) and N-acetyl-β-(D)-glucosaminidase (NAG)), and inflammation (serum and urinary interleukins (IL-17A, IL-18, and IL-10)). MtDNA-CN and nuclear DNA (nDNA) were quantified in peripheral blood and urine via qRT-PCR. MtDNA-CN was defined as the ratio of the number of mtDNA/nDNA copies via analysis of the CYTB/B2M and ND2/B2M ratio. Multivariable regression analysis provided models in which serum mtDNA directly correlated with IL-10 and indirectly correlated with UACR, IL-17A, and KIM-1 (R² = 0.626; p < 0.0001). Urinary mtDNA directly correlated with UACR, podocalyxin, IL-18, and NAG, and negatively correlated with eGFR and IL-10 (R² = 0.631; p < 0.0001). Mitochondrial DNA changes in serum and urine display a specific signature in relation to inflammation both at the podocyte and tubular levels in normoalbuminuric type 2 DM patients.

Vitamin D and Diabetic Kidney Disease

Vitamin D is a hormone involved in many physiological processes. Its active form, 1,25(OH)₂D₃, modulates serum calcium-phosphate homeostasis and skeletal homeostasis. A growing body of evidence has demonstrated the renoprotective effects of vitamin D. Vitamin D modulates endothelial function, is associated with podocyte preservation, regulates the renin-angiotensin-aldosterone system, and has anti-inflammatory effects. Diabetic kidney disease (DKD) is a leading cause of end-stage kidney disease worldwide. There are numerous studies supporting vitamin D as a renoprotector, potentially delaying the onset of DKD. This review summarizes the findings of current research on vitamin D and its role in DKD.

Role of renal tubular programed cell death in diabetic kidney disease

The pathogenic mechanism of diabetic kidney disease (DKD) is involved in various functions; however, its inadequate characterisation limits the availability of effective treatments. Tubular damage is closely correlated with renal function and is thought to be the main contributor to the injury observed in early DKD. Programed cell death (PCD) occurs during the biological development of the living body. Accumulating evidence has clarified the fundamental role of abnormalities in tubular PCD during DKD pathogenesis. Among PCD types, classical apoptosis, autophagic cell death, and pyroptosis are the most studied and will be the focus of this review. Our review aims to elucidate the current knowledge of the mechanism of DKD and the potential therapeutic potential of drugs targeting tubular PCD pathways in DKD.

Chemiluminescence Immunoassay Method of Urinary Liver Fatty-acid-binding Protein as a Promising Candidate for Kidney Disease

Liver fatty acid binding protein (L-FABP) is an intercellular lipid chaperone protein that selectively combines with unsaturated free fatty acids and transports them to mitochondria or peroxisomes. L-FABP is a promising biomarker for the early detection of renal diseases in humans. Herein a chemiluminescence method (CLIA) was demonstrated to measure the level of urinary L-FABP in the urinary samples. An anti-(L-FABP)-magnetic beads complex was prepared to capture the analyte target. Sensitivity, precision, accuracy, interference effect, high-dose hook effect of the developed assay were evaluated. Under the suitable experimental parameters, the established method have a wide linear range (0.01-10 ng/mL) and also showed a sufficiently low limit of detection of 0.0060 ng/mL. Besides, the satisfactory recoveries of the method in the urinary were ranged from 97.74%-112.32%, which was well within the requirement of clinical analysis. Furthermore, this proposed method has been successfully applied to the clinical determination of L-FABP in patients who have been diagnosed with kidney disease. The results showed that CLIA could accurately and rapidly determine the urinary level of L-FABP with high-throughput, which could be useful as a new tool to predict complications in patients with kidney disease. The clinical trial was approved by Shuyang Hospital of Traditional Chinese Medicine Ethics Committee: 20,210,202-001 at February 2, 2021.

Association of Neutrophil-to-Lymphocyte Ratio and Platelet-to-Lymphocyte Ratio with Diabetic Kidney Disease in Chinese Patients with Type 2 Diabetes: A Cross-Sectional Study

Purpose

The neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) have been extensively studied in a variety of diseases. However, research on their relationship with diabetic kidney disease (DKD) is limited. The aim of our study was to investigate the association between these two indicators and renal function in Chinese patients with type 2 diabetes and assess whether they can serve as predictors of DKD.

Methods

This cross-sectional study enrolled 655 Chinese patients with type 2 diabetes. Subjects were divided into three groups according to the urinary albumin-to-creatinine ratio (UACR). The differences in the NLR and PLR among the groups and their correlation with renal function were analyzed. Logistic regression analysis was used to analyze independent risk factors for DKD, and receiver operating characteristic (ROC) curves were used to assess the predictive values of the NLR and PLR for the disease.

Results

The NLR and PLR were significantly different among the three groups, and they increased with increasing levels of albuminuria. Pearson's correlation analysis showed that the NLR and PLR were positively correlated with the UACR but negatively correlated with the estimated glomerular filtration rate (eGFR) (p<0.001). Logistic regression analysis showed that these two indicators were independent risk factors for DKD (p<0.001). The results of ROC curve analysis suggested that the NLR (AUC=0.794; 95% CI, 0.760-0.827; p<0.001) and PLR (AUC=0.665; 95% CI, 0.623-0.706, p<0.001) had important diagnostic value for DKD.

Conclusion

The NLR and PLR were closely associated with renal function among Chinese patients with type 2 diabetes, and high NLR and PLR values may serve as predictors of DKD.

Inhibition of the glycogen synthase kinase 3β-hypoxia-inducible factor 1α pathway alleviates NLRP3-mediated pyroptosis induced by high glucose in renal tubular epithelial cells

NEW FINDINGS

What is the central question of this study? Activation of the glycogen synthase kinase 3 β (GSK-3β)-hypoxia-inducible factor 1 α (HIF-1α) pathway results in stimulation of pyroptosis under high glucose, and exerts actions in a number renal diseases: does this pathway have a role in renal tubular epithelial cells? What is the main finding and its importance? Down-regulation of GSK-3β can inhibit pyroptosis of renal tubular epithelial cells induced by high glucose and this may be related to down-regulation of HIF-1α. This role of the GSK-3β-HIF-1α pathway has not previously been reported and identifies a potential new therapeutic target in diabetic nephropathy.

ABSTRACT

Diabetic nephropathy (DN) is not only one of the main complications of diabetes, but also has a high incidence rate and a high mortality rate. Glycogen synthase kinase 3 β (GSK-3β) and hypoxia-inducible factor 1 α (HIF-1α) have been demonstrated to influence DN by regulating pyroptosis. This study aimed to investigate the effect of the GSK-3β-HIF-1α pathway on pyroptosis of high-glucose (HG)-induced renal tubular cells. Mouse renal proximal tubular epithelial cells (TKPT cells) were induced by HG to simulate DN cell and we transfected TKPT cells with GSK-3β knockdown lentivirus. Western blot analysis confirmed the transfection effects and detected the expression of GSK-3β, HIF-1α, Nod-like receptor protein 3 (NLRP3), cleaved-caspase-1, pro-caspase-1, gasdermin D (GSDMD) and GSDMD-N. The expression of GSDMD-N and HIF-1α were also verified by immunofluorescence. The levels of interleukin (IL)-1β and IL-18 were measured by enzyme linked immunosorbent assay. Flow cytometric analysis determined the apoptosis rate. Results showed that HIF-1α expression was increased in HG-induced TKPT cells, and GSK-3β knockdown could decrease the levels of NLRP3, cleaved-caspase-1, GSDMD-N and HIF-1α, verified by immunofluorescence. Moreover, GSK-3β knockdown suppressed the expression of IL-1β and IL-18, and reduced the apoptosis rate. Lithium chloride (LiCl) interference could cause the same changes as GSK-3β knockdown for HG-induced TKPT cells, and dimethyloxallyl glycine could reverse the effect of GSK-3β-knockdown interference. Our studies definitively demonstrate that the GSK-3β-HIF-1α signalling pathway mediates HG-stimulated pyroptosis in renal tubular epithelial cells and that down-regulation of GSK-3β inhibited HG-induced pyroptosis by inhibiting the expression of HIF-1α. These findings suggest a new potential target for the treatment of DN.

Diphenyl Diselenide Alleviates Tert-Butyl Hydrogen Peroxide-Induced Oxidative Stress and Lipopolysaccharide-Induced Inflammation in Rat Glomerular Mesangial Cells

Hyperglycemia, oxidative stress, and inflammation play key roles in the onset and development of diabetic complications such as diabetic nephropathy (DN). Diphenyl diselenide (DPDS) is a stable and simple organic selenium compound with anti-hyperglycemic, anti-inflammatory, and anti-oxidative activities. Nevertheless, in vitro, the role and molecular mechanism of DPDS on DN remains unknown. Therefore, we investigated the effects of DPDS on tert-butyl hydrogen peroxide (t-BHP)-induced oxidative stress and lipopolysaccharide (LPS)-induced inflammation in rat glomerular mesangial (HBZY-1) cells and explored the underlying mechanisms. DPDS attenuated t-BHP-induced cytotoxicity, concurrent with decreased intracellular ROS and MDA contents and increased SOD activity and GSH content. Moreover, DPDS augmented the protein and mRNA expression of Nrf2, HO-1, NQO1, and GCLC in t-BHP-stimulated HBZY-1 cells. In addition, DPDS suppressed LPS-induced elevations of intracellular content and mRNA expression of interleukin (IL)-6, IL-1β and TNF-α. Furthermore, LPS-induced NFκB activation and high phosphorylation of JNK and ERK1/2 were markedly suppressed by DPDS in HBZY-1 cells. In summary, these data demonstrated that DPDS improves t-BHP-induced oxidative stress by activating the Nrf2/Keap1 pathway, and also improves LPS-induced inflammation via inhibition of the NFκB/MAPK pathways in HBZY-1 cells, suggesting that DPDS has the potential to be developed as a candidate for the prevention and treatment of DN.

Therapeutic Potential of Photobiomodulation for Chronic Kidney Disease

Chronic kidney disease (CKD) is a growing global public health problem. The implementation of evidence-based clinical practices only defers the development of kidney failure. Death, transplantation, or dialysis are the consequences of kidney failure, resulting in a significant burden on the health system. Hence, innovative therapeutic strategies are urgently needed due to the limitations of current interventions. Photobiomodulation (PBM), a form of non-thermal light therapy, effectively mitigates mitochondrial dysfunction, reactive oxidative stress, inflammation, and gut microbiota dysbiosis, all of which are inherent in CKD. Preliminary studies suggest the benefits of PBM in multiple diseases, including CKD. Hence, this review will provide a concise summary of the underlying action mechanisms of PBM and its potential therapeutic effects on CKD. Based on the findings, PBM may represent a novel, non-invasive and non-pharmacological therapy for CKD, although more studies are necessary before PBM can be widely recommended.

Ras guanine nucleotide-releasing protein-4 promotes renal inflammatory injury in type 2 diabetes mellitus

INTRODUCTION

Ras guanine nucleotide-releasing protein-4 (RasGRP4) is an activator of Ras protein, which plays significant roles in both the inflammatory response and immune activation. This study determined the role of RasGRP4 in diabetic kidney disease (DKD) progression.

METHODS

CRISPR/Cas9 technology was used to establish RasGRP4 knockout (KO) mice. Diabetes was induced by a high-fat diet combined with five consecutive daily intraperitoneal injections of streptozotocin (60 mg/kg) in C57BL/6J wild-type (WT) mice and RasGRP4 KO mice. Hematoxylin and eosin, periodic acid-Schiff, and Masson's trichrome staining were used to observe the histology of pathological injury. Immunohistochemical staining was used to analyze inflammatory cell infiltration. Quantitative PCR and Western blotting were used to detect the expression of inflammatory mediators and the activation of signaling pathways in renal tissues. In vitro cell co-culture experiments were performed to explore the interactions between peripheral blood mononuclear cells (PBMCs) and glomerular endothelial cells (GEnCs).

RESULTS

RasGRP4 KO mice developed less severe diabetic kidney injury compared to WT mice, exhibiting lower proteinuria, reduced CD3+ T lymphocyte and F4/80+ macrophage infiltration, less inflammatory mediator expression including interleukin 6, tumor necrosis alpha, intercellular adhesion molecule-1, and vascular cell adhesion molecule-1, and lower expression levels of critical signal transduction molecules in the NLR family pyrin domain-containing 3 inflammasome and mitogen-activated protein kinase (MAPK)/nuclear factor kappa B (NF-κB) signaling pathways in the diabetic kidney. In vitro experiments showed that the adhesion function of PBMCs of RasGRP4 KO mice was reduced compared to that of WT mice. Moreover, the expression of adhesion molecules and critical signal transduction molecules in the NLRP3 inflammasome and MAPK/NF-κB signaling pathways in GEnCs was stimulated by the supernatant of PBMCs, which were derived from RasGRP4 KO mice treated with high glucose and were also significantly reduced compared to those derived from WT mice.

CONCLUSION

RasGRP4 promotes the inflammatory injury mediated by PBMCs in diabetes, probably by regulating the interaction between PBMCs and GEnCs and further activating the NLRP3 inflammasome and MAPK/NF-κB signaling pathways.

Rack1 regulates pro-inflammatory cytokines by NF-κB in diabetic nephropathy

Diabetic nephropathy (DN) is one of the chronic microvascular diseases of diabetes. Studies revealed that inflammation is involved in the development of DN. However, its mechanisms are not fully clear. Here, we screened DN-related mRNAs by RNA sequencing in the renal tissues of db/db DN mice and normal control mice. The Swiss-Model, ZDOCK 3.0.2 and PyMOL 2.3.2 were applied for bioinformatics analysis. In total, we obtained 6,820 mRNAs that were dysexpressed in DN. Among them, Receptor for Activated C Kinase 1 (Rack1) was focused on for its high fold changes and high values of fragments per kilobase million (FPKM) in both two groups (FPKM >100). Moreover, Rack1 was highly expressed in DN in vivo and in vitro. Results displayed that the expressions of pro-inflammatory cytokines Mcp-1 and Tnf-α were increased when Rack1 was overexpressed in cells cultured with low glucose while the expressions of Mcp-1 and Tnf-α were decreased when Rack1 was silenced in cells cultured with high glucose. Furthermore, results showed that the established DN inflammatory factor nuclear factor NF-kappa-B (NF-κB) was regulated by Rack1 via the direct interaction between Rack1 and NF-κB subunits P50 and P65. In summary, this identified Rack1 could play an important role in the inflammation of DN via NF-κB, which can provide new insight for DN research.

High-Resolution Tandem Mass Spectrometry Identifies a Particular Ganglioside Pattern in Early Diabetic Kidney Disease of Type 2 Diabetes Mellitus Patients

Considering the valuable information provided by glycosphingolipids as molecular markers and the limited data available for their detection and characterization in patients suffering from Type 2 diabetic kidney disease (DKD), we developed and implemented a superior method based on high-resolution (HR) mass spectrometry (MS) and tandem MS (MS/MS) for the determination of gangliosides in the urine of DKD patients. This study was focused on: (i) testing of the HR MS and MS/MS feasibility and performances in mapping and sequencing of renal gangliosides in Type 2 DM patients; (ii) determination of the changes in the urine gangliosidome of DKD patients in different stages of the disease-normo-, micro-, and macroalbuminuria-in a comparative assay with healthy controls. Due to the high resolution and mass accuracy, the comparative MS screening revealed that the sialylation status of the ganglioside components; their modification by O-acetyl, CH3COO-, O-fucosyl, and O-GalNAc; as well as the composition of the ceramide represent possible markers for early DKD detection, the assessment of disease progression, and follow-up treatment. Moreover, structural investigation by MS/MS demonstrated that GQ1d(d18:1/18:0), GT1α(d18:1/18:0) and GT1b(d18:1/18:0) isomers are associated with macroalbuminuria, meriting further investigation in relation to their role in DKD.

Usefulness of urinary tubule injury markers for predicting progression of renal dysfunction in patients with type 2 diabetes and albuminuria: The Fukuoka Diabetes Registry

AIMS

We prospectively investigated the association of urinary tubule injury markers with estimated glomerular filtration rate (eGFR) decline in Japanese patients with type 2 diabetes.

METHODS

Urinary kidney injury molecule 1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), liver-type fatty-acid-binding protein (L-FABP), and urinary albumin-to creatinine ratio (UACR) were measured in 2,685 participants with type 2 diabetes. Renal outcomes were ≥ 30% decline in eGFR from the baseline and annual eGFR decline for 5 years.

RESULTS

In normoalbuminuric participants, no tubular markers were associated with ≥ 30% decline in eGFR or annual eGFR changes. In those with UACR ≥ 30 mg/gCr, hazard ratios for ≥ 30% eGFR decline were 1.37 (95% confident interval (CI) 1.07-1.75) for urinary KIM-1 (>1.5 µg/gCr), 1.46 (95% CI 1.13-1.66) for urinary NGAL (>16.4 µg/gCr), and 1.26 (95% CI 0.94-1.66) for urinary L-FABP (>12.5 µg/gCr), 2.61 (95% CI 1.64-4.17) for the combination of 3 tubular markers above the cutoff after multivariable adjustments including UACR and eGFR.

CONCLUSIONS

The current study demonstrated that urinary tubule injury markers and their combination were significant predictors for the future eGFR decline in those with type 2 diabetes and albuminuria independently of UACR and eGFR. Urinary tubular markers may be useful to identify high-risk patients with albuminuria.

Clonal hematopoiesis of indeterminate potential and diabetic kidney disease: a nested case-control study

Introduction

The disease trajectory of diabetic kidney disease (DKD) shows a high interindividual variability not sufficiently explained by conventional risk factors. Clonal hematopoiesis of indeterminate potential (CHIP) is a proposed novel cardiovascular risk factor. Increased kidney fibrosis and glomerulosclerosis were described in mouse models of CHIP. Here, we aim to analyze whether CHIP affects the incidence or progression of DKD.

Methods

A total of 1419 eligible participants of the PROVALID Study were the basis for a nested case-control (NCC) design. A total of 64 participants who reached a prespecified composite endpoint within the observation period (initiation of kidney replacement therapy, death from kidney failure, sustained 40% decline in estimated glomerular filtration rate or sustained progression to macroalbuminuria) were identified and matched to 4 controls resulting in an NCC sample of 294 individuals. CHIP was assessed via targeted amplicon sequencing of 46 genes in peripheral blood. Furthermore, inflammatory cytokines were analyzed in plasma via a multiplex assay.

Results

The estimated prevalence of CHIP was 28.91% (95% CI 22.91%–34.91%). In contrast to other known risk factors (albuminuria, hemoglobin A1c, heart failure, and smoking) and elevated microinflammation, CHIP was not associated with incident or progressive DKD (hazard ratio [HR] 1.06 [95% CI 0.57–1.96]).

Conclusions

In this NCC study, common risk factors as well as elevated microinflammation but not CHIP were associated with kidney function decline in type 2 diabetes mellitus.

Involvement of Inflammasome Components in Kidney Disease

Inflammasomes are multiprotein complexes with an important role in the innate immune response. Canonical activation of inflammasomes results in caspase-1 activation and maturation of cytokines interleukin-1β and -18. These cytokines can elicit their effects through receptor activation, both locally within a certain tissue and systemically. Animal models of kidney diseases have shown inflammasome involvement in inflammation, pyroptosis and fibrosis. In particular, the inflammasome component nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) and related canonical mechanisms have been investigated. However, it has become increasingly clear that other inflammasome components are also of importance in kidney disease. Moreover, it is becoming obvious that the range of molecular interaction partners of inflammasome components in kidney diseases is wide. This review provides insights into these current areas of research, with special emphasis on the interaction of inflammasome components and redox signalling, endoplasmic reticulum stress, and mitochondrial function. We present our findings separately for acute kidney injury and chronic kidney disease. As we strictly divided the results into preclinical and clinical data, this review enables comparison of results from those complementary research specialities. However, it also reveals that knowledge gaps exist, especially in clinical acute kidney injury inflammasome research. Furthermore, patient comorbidities and treatments seem important drivers of inflammasome component alterations in human kidney disease.

Update on pathogenesis and diagnosis flow of normoalbuminuric diabetes with renal insufficiency

In recent decades, the prevalence of diabetic kidney disease has remained stable and appears to be a wide heterogeneity. Normoalbuminuric diabetes with renal insufficiency, which is characterized by a decline in the glomerular filtration rate in the absence of albuminuria, has been identified as an albuminuria-independent phenotype of diabetic kidney disease. Epidemiological data demonstrate that normoalbuminuric phenotype is prevalent. Compared to albuminuric phenotype, normoalbuminuric phenotype has distinct clinical characteristics and a wide heterogeneity of pathological features. Currently, the pathogenesis of normoalbuminuric phenotype remains unclear. Additionally, the flow of diagnosing normoalbuminuric phenotype is not perfect. In this article, we review the latest studies addressing the epidemiology, clinical characteristics, and pathology of normoalbuminuric phenotype. Based on the studies of clinical features and renal histopathologic changes, we attempt to propose an underlying pathogenesis model and a flow chart for diagnosing normoalbuminuric phenotype.

Review of early circulating biomolecules associated with diabetes nephropathy - Ideal candidates for early biomarker array test for DN

BACKGROUND

Diabetic nephropathy (DN) is one of the catastrophic complications of type 2 diabetes mellitus (T2DM). 45% of DN patients progressed to End Stage Renal Disease (ESRD) which robs casualties of the quality of live. The challenge in early diagnosis of DN is it is asymptomatic in the early phase. Current gold standard test for screening and diagnosis of DN are nonspecific and are not sensitive in detecting DN early enough and subsequently monitor renal function during management and intervention plans. Recent studies reported various biomolecules which are associated with the onset of DN in T2DM using cutting-edge technologies. These biomolecules could be potential early biomarkers for DN. This review selectively identified potential early serum biomolecules which are potential candidates for developing an Early Biomarker Array Test for DN.

METHODS

An advanced literature search was conducted on 4 online databases. Search terms used were "Diabetes Mellitus, Type 2", "Diabetic nephropathy", "pathogenesis" and "early biomarker. Filters were applied to capture articles published from 2010 to 2020, written in English, human or animal models and focused on serum biomolecules associated with DN.

RESULTS

Five serum biomolecules have been evidently described as contributing pivotal roles in the pathophysiology of DN. MiR-377, miR-99b, CYP2E1, TGF-β1 and periostin are potential candidates for designing an early biomarker array for screening and diagnosis of early stages of DN. The five shortlisted biomolecules originates from endogenous biochemical processes which are specific to the progressive pathophysiology of DN.

CONCLUSION

miR-377, miR-99b, CYP2E1, TGF-β1 and periostin are potential candidate biomolecules for diagnosing DN at the early phases and can be developed into a panel of endogenous biomarkers for early detection of DN in patients with T2DM. The outcomes of this study will be a stepping stone towards planning and developing an early biomarker array test for diabetic nephropathy. The proposed panel of early biomarkers for DN has potential of stratifying the stages of DN because each biomolecule appears at distinct stages in the pathophysiology of DN.

Tubular injury in diabetic ketoacidosis: Results from the diabetic kidney alarm study

OBJECTIVE

Glomerular injury is a recognized complication of diabetic ketoacidosis (DKA), yet the tubular lesions are poorly understood. The aim of this prospective study was to evaluate the presence and reversibility of tubular injury during DKA in children with type 1 diabetes (T1D).

RESEARCH DESIGN AND METHODS

Blood and urine samples were collected from 40 children with DKA (52% boys, mean age 11 ± 4 years, venous pH 7.2 ± 0.1, glucose 451 ± 163 mg/dL) at three timepoints: 0-8 and 12-24 h after starting insulin, and 3 months after discharge. Mixed-effects models evaluated the changes in tubular injury markers over time (neutrophil gelatinase-associated lipocalin [NGAL], kidney injury molecule 1 [KIM-1], and interleukin 18 [IL-18]). We also evaluated the relationships among the tubular injury biomarkers, copeptin, a vasopressin surrogate, and serum uric acid (SUA).

RESULTS

Serum NGAL, KIM-1, and IL-18 were highest at 0-8 h (306.5 ± 45.9 ng/mL, 128.9 ± 10.1 pg/mL, and 564.3 ± 39.2 pg/mL, respectively) and significantly decreased over 3 months (p = 0.03, p = 0.01, and p < 0.001, respectively). There were strong relationships among increases in copeptin and SUA and rises in tubular injury biomarkers. At 0-8 h, participants with acute kidney injury (AKI) [17%] showed significantly higher concentrations of tubular injury markers, copeptin, and SUA.

CONCLUSIONS

DKA was characterized by tubular injury, and the degree of injury associated with elevated copeptin and SUA. Tubular injury biomarkers, copeptin and SUA may be able to predict AKI in DKA.

Adiponectin receptor agonist AdipoRon ameliorates renal inflammation in diet-induced obese mice and endotoxin-treated human glomeruli ex vivo

AIMS/HYPOTHESIS

Chronic low-grade inflammation with local upregulation of proinflammatory molecules plays a role in the progression of obesity-related renal injury. Reduced serum concentration of anti-inflammatory adiponectin may promote chronic inflammation. Here, we investigated the potential anti-inflammatory and renoprotective effects and mechanisms of action of AdipoRon, an adiponectin receptor agonist.

METHODS

Wild-type DBA/2J mice were fed with high-fat diet (HFD) supplemented or not with AdipoRon to model obesity-induced metabolic endotoxaemia and chronic low-grade inflammation and we assessed changes in the glomerular morphology and expression of proinflammatory markers. We also treated human glomeruli ex vivo and human podocytes in vitro with AdipoRon and bacterial lipopolysaccharide (LPS), an endotoxin upregulated in obesity and diabetes, and analysed the secretion of inflammatory cytokines, activation of inflammatory signal transduction pathways, apoptosis and migration.

RESULTS

In HFD-fed mice, AdipoRon attenuated renal inflammation, as demonstrated by reduced expression of glomerular activated NF-κB p65 subunit (NF-κB-p65) (70%, p < 0.001), TNFα (48%, p < 0.01), IL-1β (51%, p < 0.001) and TGFβ (46%, p < 0.001), renal IL-6 and IL-4 (21% and 20%, p < 0.05), and lowered glomerular F4/80-positive macrophage infiltration (31%, p < 0.001). In addition, AdipoRon ameliorated HFD-induced glomerular hypertrophy (12%, p < 0.001), fibronectin accumulation (50%, p < 0.01) and podocyte loss (12%, p < 0.001), and reduced podocyte foot process effacement (15%, p < 0.001) and thickening of the glomerular basement membrane (18%, p < 0.001). In cultured podocytes, AdipoRon attenuated the LPS-induced activation of the central inflammatory signalling pathways NF-κB-p65, c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (p38-MAPK) (30%, 36% and 22%, respectively, p < 0.001), reduced the secretion of TNFα (32%, p < 0.01), and protected against podocyte apoptosis and migration. In human glomeruli ex vivo, AdipoRon reduced the LPS-induced secretion of inflammatory cytokines IL-1β, IL-18, IL-6 and IL-10.

CONCLUSIONS/INTERPRETATION

AdipoRon attenuated the renal expression of proinflammatory cytokines in HFD-fed mice and LPS-stimulated human glomeruli, which apparently contributed to the amelioration of glomerular inflammation and injury. Mechanistically, based on assays on cultured podocytes, AdipoRon reduced LPS-induced activation of the NF-κB-p65, JNK and p38-MAPK pathways, thereby impelling the decrease in apoptosis, migration and secretion of TNFα. We conclude that the activation of the adiponectin receptor by AdipoRon is a potent strategy to attenuate endotoxaemia-associated renal inflammation.

The IL-8-CXCR1/2 axis contributes to diabetic kidney disease

AIMS/HYPOTHESIS

Inflammation has a major role in diabetic kidney disease. We thus investigated the role of the IL-8-CXCR1/2 axis in favoring kidney damage in diabetes.

METHODS

Urinary IL-8 levels were measured in 1247 patients of the Joslin Kidney Study in type 2 diabetes (T2D). The expression of IL-8 and of its membrane receptors CXCR1/CXCR2 was quantified in kidney tissues in patients with T2D and in controls. The effect of CXCR1/2 blockade on diabetic kidney disease was evaluated in db/db mice.

RESULTS

IL-8 urinary levels were increased in patients with T2D and diabetic kidney disease, with the highest urinary IL-8 levels found in the patients with the largest decline in glomerular filtration rate, with an increased albumin/creatine ratio and the worst renal outcome. Moreover, glomerular IL-8 renal expression was increased in patients with T2D, as compared to controls. High glucose elicits abundant IL-8 secretion in cultured human immortalized podocytes in vitro. Finally, in diabetic db/db mice and in podocytes in vitro, CXCR1/2 blockade mitigated albuminuria, reduced mesangial expansion, decreased podocyte apoptosis and reduced DNA damage.

CONCLUSIONS/INTERPRETATION

The IL-8- CXCR1/2 axis may have a role in diabetic kidney disease by inducing podocyte damage. Indeed, targeting the IL-8-CXCR1/2 axis may reduce the burden of diabetic kidney disease.

The role of inflammation in diabetic kidney disease

Diabetic kidney disease (DKD) has been the leading cause of chronic kidney disease for over 20 years. Yet, over these two decades, the clinical approach to this condition has not much improved beyond the administration of glucose-lowering agents, renin-angiotensin-aldosterone system blockers for blood pressure control, and lipid-lowering agents. The proportion of diabetic patients who develop DKD and progress to end-stage renal disease has remained nearly the same. This unmet need for DKD treatment is caused by the complex pathophysiology of DKD, and the difficulty of translating treatment from bench to bed, which further adds to the growing argument that DKD is not a homogeneous disease. To better capture the full spectrum of DKD in our design of treatment regimens, we need improved diagnostic tools that can better distinguish the subgroups within the condition. For instance, DKD is typically placed in the broad category of a non-inflammatory kidney disease. However, genome-wide transcriptome analysis studies consistently indicate the inflammatory signaling pathway activation in DKD. This review will utilize human data in discussing the potential for redefining the role of inflammation in DKD. We also comment on the therapeutic potential of targeted anti-inflammatory therapy for DKD.

Kidney Diseases: The Age of Molecular Markers

Kidney diseases are conditions that increase the morbidity and mortality of those afflicted. Diagnosis of these conditions is based on parameters such as the glomerular filtration rate (GFR), measurement of serum and urinary creatinine levels and equations derived from these measurements (Wasung, Chawla, Madero. Clin Chim Acta 438:350-357, 2015). However, serum creatinine as a marker for measuring renal dysfunction has its limitations since it is altered in several other physiological situations, such as in patients with muscle loss, after intense physical exercise or in people on a high protein diet (Riley, Powers, Welch. Res Q Exerc Sport 52(3):339-347, 1981; Juraschek, Appel, Anderson, Miller. Am J Kidney Dis 61(4):547-554, 2013). Besides the fact that serum creatinine is a marker that indicates glomerular damage, it is necessary the discovery of new biomarkers that reflect not only glomerular damage but also tubular impairment. Recent advances in Molecular Biology have led to the generation or identification of new biomarkers for kidney diseases such as: Acute Kidney Failure (AKI), chronic kidney disease (CKD), nephritis or nephrotic syndrome. There are recent markers that have been used to aid in diagnosis and have been shown to be more sensitive and specific than classical markers, such as neutrophil gelatinase associated lipocalin (NGAL) or kidney injury molecule-1 (KIM-1) (Wasung, Chawla, Madero. Clin Chim Acta 438:350-357, 2015; George, Gounden. Adv Clin Chem 88:91-119, 2019; Han, Bailly, Abichandani, Thadhani, Bonventre. Kidney Int 62(1):237-244, 2002; Fontanilla, Han. Expert Opin Med Diagn 5(2):161-173, 2011). However, early diagnostic biomarkers are still necessary to assist the intervention and monitor of the progression of these conditions.

New Potential Biomarkers for Chronic Kidney Disease Management-A Review of the Literature

The prevalence of chronic kidney disease (CKD) is increasing worldwide, and the mortality rate continues to be unacceptably high. The biomarkers currently used in clinical practice are considered relevant when there is already significant renal impairment compromising the early use of potentially successful therapeutic interventions. More sensitive and specific biomarkers to detect CKD earlier on and improve patients' prognoses are an important unmet medical need. The aim of this review is to summarize the recent literature on new promising early CKD biomarkers of renal function, tubular lesions, endothelial dysfunction and inflammation, and on the auspicious findings from metabolomic studies in this field. Most of the studied biomarkers require further validation in large studies and in a broad range of populations in order to be implemented into routine CKD management. A panel of biomarkers, including earlier biomarkers of renal damage, seems to be a reasonable approach to be applied in clinical practice to allow earlier diagnosis and better disease characterization based on the underlying etiologic process.

Metformin Protects against Podocyte Injury in Diabetic Kidney Disease

Metformin is the most commonly prescribed drug for treating type 2 diabetes mellitus (T2D). Its mechanisms of action have been under extensive investigation, revealing that it has multiple cellular targets, either direct or indirect ones, via which it regulates numerous cellular pathways. Diabetic kidney disease (DKD), the serious complication of T2D, develops in up to 50% of the individuals with T2D. Various mechanisms contribute to the development of DKD, including hyperglycaemia, dyslipidemia, oxidative stress, chronic low-grade inflammation, altered autophagic activity and insulin resistance, among others. Metformin has been shown to affect these pathways, and thus, it could slow down or prevent the progression of DKD. Despite several animal studies demonstrating the renoprotective effects of metformin, there is no concrete evidence in clinical settings. This review summarizes the renoprotective effects of metformin in experimental settings. Special emphasis is on the effects of metformin on podocytes, the glomerular epithelial cells that are central in maintaining the glomerular ultrafiltration function.

Lipid deposition and metaflammation in diabetic kidney disease

A critical link between metabolic disorders and a form of low-grade systemic and chronic inflammation has been recently established and named 'Metaflammation'. Metaflammation has been recognized as a key mediator of both microvascular and macrovascular complications of diabetes and as a significant contributor to the development of diabetic kidney disease (DKD). The goal of this review is to summarize the contribution of diabetes-induced inflammation and the related signaling pathways to diabetic complications, with a particular focus on how innate immunity and lipid metabolism influence each other.

Astragalus membranaceus Injection Suppresses Production of Interleukin-6 by Activating Autophagy through the AMPK-mTOR Pathway in Lipopolysaccharide-Stimulated Macrophages

Astragalus membranaceus (AM), used in traditional Chinese medicine, has been shown to enhance immune functions, and recently, its anti-inflammatory effects were identified. However, the mechanisms of action remain unclear. Most studies have shown that autophagy might be involved in the immune response of the body, including inflammation. Here, we developed an inflammatory model by stimulating macrophages with lipopolysaccharides (LPS) to explore the anti-inflammatory effect and mechanisms of AM injection from the perspective of the regulation of autophagy. Immunoblot, immunofluorescence, and ELISA were used to determine the effects of AM injection on the production of interleukin-6 (IL-6) and alterations of autophagy markers. It was found that AM injection reduced the expression of IL-6 in LPS-stimulated macrophages and reversed the LPS-induced inhibition of cellular autophagy. After treatment with inhibitors of signaling pathways, it was shown that LPS downregulated autophagy and upregulated the production of IL-6 in macrophages via the protein kinase B (Akt)/mammalian target of rapamycin (mTOR) pathway. AM injection reversed the effects of LPS by activating the AMP-activated protein kinase (AMPK) instead of inhibiting Akt. These results were further confirmed by testing activators and siRNA silencing of AMPK. Hence, these 2 distinct signaling molecules appear to exert opposite effects on mTOR, which integrates information from multiple upstream signaling pathways, negatively regulating autophagy. In addition, we demonstrated that autophagy might play a key role in regulating the production of IL-6 by testing activators and inhibitors of autophagy and siRNA silencing of ATG5. These findings showed that AM injection might enhance autophagy by activating AMPK and might further play a repressive effect on the LPS-stimulated expression of IL-6. This study explored the relationship between autophagy, signaling pathways, and the production of inflammatory factors in a model of endotoxin infection and treatment with AM injection.