Frontiers in Diabetic Kidney Disease: Introduction

Non-invasive metabolic biomarkers for early diagnosis of diabetic nephropathy: Meta-analysis of profiling metabolomics studies

AIM

Diabetic nephropathy (DN) is one of the worst complications of diabetes. Despite a growing number of DN metabolite profiling studies, most studies are suffering from inconsistency in their findings. The main goal of this meta-analysis was to reach to a consensus panel of significantly dysregulated metabolites as potential biomarkers in DN.

DATA SYNTHESIS

To identify the significant dysregulated metabolites, meta-analysis was performed by "vote-counting rank" and "robust rank aggregation" strategies. Bioinformatics analyses were performed to identify the most affected genes and pathways. Among 44 selected studies consisting of 98 metabolite profiles, 17 metabolites (9 up-regulated and 8 down-regulated metabolites), were identified as significant ones by both the meta-analysis strategies (p-value<0.05 and OR>2 or <0.5) and selected as DN metabolite meta-signature. Furthermore, enrichment analyses confirmed the involvement of various effective biological pathways in DN pathogenesis, such as urea cycle, TCA cycle, glycolysis, and amino acid metabolisms. Finally, by performing a meta-analysis over existing time-course studies in DN, the results indicated that lactic acid, hippuric acid, allantoin (in urine), and glutamine (in blood), are the topmost non-invasive early diagnostic biomarkers.

CONCLUSION

The identified metabolites are potentially involved in diabetic nephropathy pathogenesis and could be considered as biomarkers or drug targets in the disease.

PROSPERO REGISTRATION NUMBER

CRD42020197697.

Determinants of Diabetic Nephropathy among Diabetic Patients in General Public Hospitals of Tigray, Ethiopia, 2018/19

BACKGROUND

Diabetic nephropathy is real damage resulting from having uncontrolled diabetes mellitus. Unmanaged diabetic nephropathy is one of the most leading causes of kidney failure. There is a scarcity of information on the determinants of diabetic nephropathy among diabetes mellitus patients in Ethiopia. Identification of the determinants can help devise a strategy to properly address the disease and its consequences. Therefore, this study was designed to assess the determinants of diabetic nephropathy among diabetes mellitus patients.

METHODS

Unmatched case-control study design with 168 cases and 672 controls with a mean age of 45.18 and 62.12, respectively, participated in the study. An interviewer-administered questionnaire was employed for data collection, and a systematic sampling technique was used to select the study participants. Data were entered into Epi data and exported to SPSS for data clarification and analysis. Binary logistic regression analysis was carried out to check the level of association between diabetic nephropathy and the independent variables.

RESULTS

Comorbidity (AOR: 4.96 at 95 CI: 1.77-13.87), hypertension (AOR: 6.33, 95% CI: 2.51-16.02), poor glycemic control (AOR: 3.27, 95% CI: 1.31, 8.21), age (AOR: 1.14, 95%: 1.09-1.19), duration with diabetes mellitus since diagnosis (AOR: 1.83, 95 CI: 1.62-2.06), and nonadherence to diabetic medication (AOR: 3.3, 95% CI: 1.34, 8.15), diet (AOR: 5.96, 95%: 1.92-18.54), and exercise (AOR: 5.60, 95% CI: 1.94-16.21) were the determinants of diabetic nephropathy.

CONCLUSION

Adherence to medication, diet, and exercise should be empowered to achieve glycemic control and to prevent diabetic nephropathy. More attention has to be also given for old aged diabetic patients, long duration since diagnosis of diabetes mellitus, hypertension, and other comorbidities.

Urine NGAL as an early biomarker for diabetic kidney disease: accumulated evidence from observational studies

Objectives: Urine neutrophil gelatinase-associated lipocalin (NGAL) was found to increase in diabetic kidney disease (DKD). However, the clinical value of urine NGAL as diagnostic indicators in DKD remains to be clarified. Methods: Relevant studies were systematically retrieved from PubMed, Embase, Web of Science, and the Cochrane Library. Stratified analyses and regression analyses were performed. Results: Fourteen studies with 1561 individuals were included in our analysis, including 1204 cross-sectional participants and 357 cohort participants. For the cross-sectional studies, the pooled sensitivity and specificity of NGAL in the diagnosis of DKD were 0.82 (95% confidence interval (CI): 0.75-0.87) and 0.81 (95% CI: 0.68-0.90), respectively. The pooled diagnostic odds ratio was 19 (95% CI: 11-33), and the overall area under the curve was 0.88 (95% CI: 0.84-0.90). For the cohort studies, the pooled sensitivity and specificity of NGAL in the diagnosis of DKD were 0.96 (95% CI: 0.91-0.98) and 0.89 (95% CI: 0.84-0.92), respectively. The overall area under the curve was 0.98, indicating good discriminative ability of NGAL as biomarkers for DKD. Conclusions: Urine NGAL, as the early diagnostic marker of DKD, might have the high diagnostic value, especially in cohort studies.

Empagliflozin attenuates diabetic tubulopathy by improving mitochondrial fragmentation and autophagy

We examined the effects of empagliflozin, a selective inhibitor of Na⁺-glucose cotransporter 2, on mitochondrial quality control and autophagy in renal tubular cells in a diabetic environment in vivo and in vitro. Human renal proximal tubular cells (hRPTCs) were incubated under high-glucose conditions. Diabetes was induced with streptozotocin in male C57BL/6J mice. Improvements in mitochondrial biogenesis and balanced fusion-fission protein expression were noted in hRPTCs after treatment with empagliflozin in high-glucose media. Empagliflozin also increased autophagic activities in renal tubular cells in the high-glucose environment, which was accompanied with mammalian target of rapamycin inhibition. Moreover, reduced mitochondrial reactive oxygen species production and decreased apoptotic and fibrotic protein expression were observed in hRPTCs after treatment with empagliflozin, even in the hyperglycemic circumstance. Importantly, empagliflozin restored AMP-activated protein kinase-α phosphorylation and normalized levels of AMP-to-ATP ratios in hRPTCs subjected to a high-glucose environment, which suggests the way that empagliflozin is involved in mitochondrial quality control. Empagliflozin effectively suppressed Na⁺-glucose cotransporter 2 expression and ameliorated renal morphological changes in the kidneys of streptozotocin-induced diabetic mice. Electron microscopy analysis showed that mitochondrial fragmentation was decreased and 8-hydroxy-2'-deoxyguanosine content was low in renal tubular cells of empagliflozin treatment groups compared with those of the diabetic control group. We suggest one mechanism related to the renoprotective actions of empagliflozin, which reverse mitochondrial dynamics and autophagy.

Clinical efficacy and safety of Tripterygium wilfordii Hook in the treatment of diabetic kidney disease stage IV: A meta-analysis of randomized controlled trials

BACKGROUND

The present study aims to evaluate the clinical efficacy and safety of Tripterygium wilfordii Hook (TwH) combined with angiotensin receptor blockers/ACE inhibitors (ARB/ACEI) in the treatment of diabetic kidney disease (DKD) stage IV.

METHODS

We searched China National Knowledge Internet (CNKI), the Chinese Biomedical Database, Embase and PubMed for articles about TwH combined with ARB/ACEI in treating DKD stage IV and set the study inclusion and elimination standards.

RESULTS

A total of 22 randomized controlled trials (RCTs) with 1414 participants were collected for detailed evaluation. The meta-analysis results suggested that compared with the controls, the combined group showed significant effects in reducing 24-h urinary protein [mean difference (MD) = -0.87, 95% confidence interval (CI) = (-1.03, -0.71)], raising serum albumin [MD = 4.14, 95% CI (3.43, 4.85)] and the total efficiency [odds ratio (OR) = 4.84, 95% CI (3.33, 7.03)], with no statistical difference in serum creatinine between both groups [MD = -3.02, 95% CI (-6.40, 0.37), P > .05]. However, the risk of adverse reactions increased by 8% [Risk Difference (RD) = 0.08, 95% CI (0.05, 0.11)] in the combination.

CONCLUSIONS

TwH combined with ARB/ACEI in the treatment of DKD stage IV is superior to the monotherapy of ARB/ACEI.

Identification of candidate microRNA biomarkers in diabetic nephropathy: a meta-analysis of profiling studies

AIMS

The aim was to perform a meta-analysis on the miRNA expression profiling studies in diabetic nephropathy (DN) to identify candidate diagnostic biomarkers.

METHODS

A comprehensive literature search was done in several databases and 53 DN miRNA expression studies were selected. To identify significant DN-miR meta-signatures, two meta-analysis methods were employed: vote-counting strategy and the robust rank aggregation method. The targets of DN-miRs were obtained and a gene set enrichment analysis was carried out to identify the pathways most strongly affected by dysregulation of these miRNAs.

RESULTS

We identified a significant miRNA meta-signature common to both meta-analysis approaches of three up-regulated (miR-21-5p, miR-146a-5p, miR-10a-5p) and two down-regulated (miR-25-3p and miR-26a-5p) miRNAs. Besides that, subgroup analyses divided and compared the differentially expressed miRNAs according to species (human and animal), types of diabetes (T1DN and T2DN) and tissue types (kidney, blood and urine). Enrichment analysis confirmed that DN-miRs supportively target functionally related genes in signaling and community pathways in DN.

CONCLUSION

Five highly significant and consistently dysregulated miRNAs were identified, and future studies should focus on discovering their potential effect on DN and their clinical value as DN biomarkers and therapeutic mediators.

Inflammatory Mechanisms as New Biomarkers and Therapeutic Targets for Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of CKD and end-stage kidney disease (ESKD) worldwide. Approximately 30-40% of people with diabetes develop this microvascular complication, placing them at high risk of losing kidney function as well as of cardiovascular events, infections, and death. Current therapies are ineffective for arresting kidney disease progression and mitigating risks of comorbidities and death among patients with DKD. As the global count of people with diabetes will soon exceed 400 million, the need for effective and safe treatment options for complications such as DKD becomes ever more urgent. Recently, the understanding of DKD pathogenesis has evolved to recognize inflammation as a major underlying mechanism of kidney damage. In turn, inflammatory mediators have emerged as potential biomarkers and therapeutic targets for DKD. Phase 2 clinical trials testing inhibitors of monocyte-chemotactic protein-1 chemokine C-C motif-ligand 2 and the Janus kinase/signal transducer and activator of transcription pathway, in particular, have produced promising results.

Albuminuria, serum creatinine, and estimated glomerular filtration rate as predictors of cardio-renal outcomes in patients with type 2 diabetes mellitus and kidney disease: a systematic literature review

BACKGROUND

Albuminuria, elevated serum creatinine and low estimated glomerular filtration rate (eGFR) are pivotal indicators of kidney decline. Yet, it is uncertain if these and emerging biomarkers such as uric acid represent independent predictors of kidney disease progression or subsequent outcomes among individuals with type 2 diabetes mellitus (T2DM). This study systematically examined the available literature documenting the role of albuminuria, serum creatinine, eGFR, and uric acid in predicting kidney disease progression and cardio-renal outcomes in persons with T2DM.

METHODS

Embase, MEDLINE, and Cochrane Central Trials Register and Database of Systematic Reviews were searched for relevant studies from January 2000 through May 2016. PubMed was searched from 2013 until May 2016 to retrieve studies not yet indexed in the other databases. Observational cohort or non-randomized longitudinal studies relevant to albuminuria, serum creatinine, eGFR, uric acid and their association with kidney disease progression, non-fatal cardiovascular events, and all-cause mortality as outcomes in persons with T2DM, were eligible for inclusion. Two reviewers screened citations to ensure studies met inclusion criteria.

RESULTS

From 2249 citations screened, 81 studies were retained, of which 39 were omitted during the extraction phase (cross-sectional [n = 16]; no outcome/measure of interest [n = 13]; not T2DM specific [n = 7]; review article [n = 1]; editorial [n = 1]; not in English language [n = 1]). Of the remaining 42 longitudinal study publications, biomarker measurements were diverse, with seven different measures for eGFR and five different measures for albuminuria documented. Kidney disease progression differed substantially across 31 publications, with GFR loss (n = 9 [29.0%]) and doubling of serum creatinine (n = 5 [16.1%]) the most frequently reported outcome measures. Numerous publications presented risk estimates for albuminuria (n = 18), serum creatinine/eGFR (n = 13), or both combined (n = 6), with only one study reporting for uric acid. Most often, these biomarkers were associated with a greater risk of experiencing clinical outcomes.

CONCLUSIONS

Despite the utility of albuminuria, serum creatinine, and eGFR as predictors of kidney disease progression, further efforts to harmonize biomarker measurements are needed given the disparate methodologies observed in this review. Such efforts would help better establish the clinical significance of these and other biomarkers of renal function and cardio-renal outcomes in persons with T2DM.

Effect of breviscapine injection on clinical parameters in diabetic nephropathy: A meta-analysis of randomized controlled trials

Diabetic nephropathy (DN) is currently a major public health problem worldwide. The objective of the present study was to evaluate the clinical effect of breviscapine injections in patients with DN. A meta-analysis was performed using the following databases to obtain published reports in any language: PubMed/MEDLINE, Embase, China National Knowledge Infrastructure, Chinese Evidence-Based Medicine, Wanfang Digital Periodicals, Chinese Academic Journals Full-text Database, Chinese Biological and Medical Database, China Doctoral and Masters Dissertations Full-text Database and the Chinese Proceedings of Conference Full-text Database. Two assessors independently reviewed each trial. A total of 35 randomized controlled trials, which performed studies on a total of 2,320 patients (1,188 in treatment groups and 1,132 in control groups), were included in the present meta-analysis. Data were analyzed using Stata version 11.0 for Windows. The results from the analysis demonstrated that breviscapine injections have greater therapeutic effects in patients with DN in comparison with the control group, including renal protective effects (reducing urine protein, serum creatinine and blood urea nitrogen) and adjustment for dyslipidemia (affecting levels of cholesterol, triglycerides and high density lipoproteins). These effects indicate that breviscapine injections are beneficial to patients with DN. Further studies are required to determine the mechanisms underlying the therapeutic effects of breviscapine.

Clinical verification of a novel urinary microRNA panal: 133b, -342 and -30 as biomarkers for diabetic nephropathy identified by bioinformatics analysis

BACKGROUND

Because microvascular disease is one of the major drivers of diabetic complications, early detection of diabetic nephropathy (DN) by assessing the expression of exosomal microRNAs (miRNAs) in DN patients and healthy controls, may be of clinical value. The aim of this study wasto identify a novel miRNA panel of DN by combining bioinformatics analysis of miRNA databases and clinical verification to evaluate the significance of this panel as urine biomarkers for type 2 diabetic nephropathy (T2DN).

PATIENTS AND METHODS

Public miRNA databases e.g miro-Ontology and miRWalk were analyzed and a novel panel of 3 microRNAs was retrieved. Meanwhile, combinatorial target prediction algorithms were applied. Multiple case-matched normal were examined by quantative RT-PCR for differential expression in urine exosomes from 210 participants, and the three identified miRNAs were validated as DN biomarkers.

RESULTS

We found urinary exosomalmiR-133b, miR-342, and miR-30a were expressed at significantly elevated levels in T2DN patients (P<0.001) compared to normal. Furthermore, high-level expression of the 3 miRNAs was associated withHbA1c,systolic-diastolic blood pressure, LDL, serum creatinine, urinary albumin creatinine ratio and estimated glomerular filtration rate(eGFR). Moreover, 39.3%, 19.6% and 17.9% of patients with normo-albuminuria had positive (miR-133b, miR-342 and miR-30a, respectively); indicating the possibility of molecular changes in these patients before onset of albuminuria.

CONCLUSION

We have identified novel urinary exosomal miRNA biomarkers of DN which were altered not only in micro and macroalbuminuric groups but also in some normoalbuminuria cases prior to albuminuria.

Urinary biomarkers for early diabetic nephropathy: beyond albuminuria

Diabetic nephropathy (DN) is the most common cause of end-stage kidney disease in the USA and accounts for a significant increase in morbidity and mortality in patients with diabetes. Early detection is critical in improving clinical management. Although microalbuminuria is regarded as the gold standard for diagnosing the onset of DN, its predictive powers are limited. Consequently, great efforts have been made in recent years to identify better strategies for the detection of early stages of DN and progressive kidney function decline in diabetic patients. Here, we review the various urinary biomarkers that have emerged from these studies which hold promise as more sensitive diagnostic tools for the earlier detection of diabetic kidney disease and the prediction of progression to end-stage kidney disease. A number of key biomarkers present in the urine have been identified that reflect kidney injury at specific sites along the nephron, including glomerular/podocyte damage and tubular damage, oxidative stress, inflammation and activation of the intrarenal renin-angiotensin system. We also describe newer approaches, including urinary microRNAs, which are short noncoding mRNAs that regulate gene expression, and urine proteomics, that can be used to identify potential novel biomarkers in the development and progression of diabetic kidney disease.

Proteomic profile in glomeruli of type-2 diabetic KKAy mice using 2-dimensional differential gel electrophoresis

Background

Diabetic nephropathy (DN) is a leading cause of end-stage renal disease. To search for glomerular proteins associated with early-stage DN, glomeruli of spontaneous type 2 diabetic KKAy mice were analyzed by 2-dimensional differential gel electrophoresis (2D-DIGE).

Material/Methods

Glomeruli of 20-week spontaneous type 2 diabetic KKAy mice and age-matched C57BL/6 mice were isolated by kidney perfusion with magnetic beads. Proteomic profiles of glomeruli were investigated by using 2D-DIGE and matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. Western blot analysis was used to confirm the results of proteomics. Immunohistochemical and semi-quantitative analysis were used to confirm the differential expression of prohibitin and annexin A2 in glomeruli.

Results

We identified 19 differentially expressed proteins – 17 proteins were significantly up-regulated and 2 proteins were significantly down-regulated in glomeruli of diabetic KKAy mice. Among them, prohibitin and annexin A2 were up-regulated and Western blot analysis validated the same result in proteomics. Immunohistochemical analysis also revealed up-regulation of prohibitin and annexin A2 in glomeruli of KKAy mice.

Conclusions

Our findings suggest that prohibitin and annexin A2 may be associated with early-stage DN. Further functional research might help to reveal the pathogenesis of DN.