Urinary tubular biomarkers as predictors of kidney function decline, cardiovascular events and mortality in microalbuminuric type 2 diabetic patients

Extracellular matrix turnover proteins as risk markers in people with type 2 diabetes and microalbuminuria

BACKGROUND

This post-hoc study investigated whether biomarkers reflecting extracellular matrix (ECM) turnover predicted cardiovascular disease (CVD), mortality, and progression of diabetic kidney disease (DKD) in individuals with type 2 diabetes (T2D) and microalbuminuria.

METHODS

Serum levels of specific ECM turnover biomarkers were assessed in 192 participants with T2D and microalbuminuria from an observational study conducted at Steno Diabetes Center Copenhagen from 2007 to 2008. Endpoints included CVD events, mortality, and DKD progression, defined as decline in estimated glomerular filtration rate (eGFR) of >30 %.

RESULTS

Participants had a mean age of 59 years, with 75 % males. Over a median follow-up of 4.9 to 6.3 years, the study recorded 38 CVD events, 24 deaths, and 40 DKD events. Elevated levels of a degradation fragment of collagen type I (C1M) were associated with an increased risk of >30 % eGFR decline, although this association was not independent of other risk factors. No significant associations were found between other ECM turnover biomarkers and DKD progression, mortality, or CVD risk.

CONCLUSION

Elevated C1M levels were linked to DKD progression in individuals with T2D and microalbuminuria, but not independently of other risk factors. None of the ECM turnover biomarkers were associated with CVD or mortality.

Urinary non-albumin protein-creatinine ratio is an independent predictor of mortality in patients with type 2 diabetes: a retrospective cohort study

Albuminuria is a well-known predictor of chronic kidney disease in patients with type 2 diabetes mellitus (DM). However, proteinuria is associated with chronic complications in patients without albuminuria. In this retrospective cohort study, we explored whether non-albumin proteinuria is associated with all-cause mortality and compared the effects of non-albumin proteinuria on all-cause mortality between patients with and without albuminuria. We retrospectively collected data from patients with type 2 DM for whom we had obtained measurements of both urinary albumin-to-creatinine ratio (UACR) and urinary protein-to-creatinine ratio (UPCR) from the same spot urine specimen. Urinary non-albumin protein-creatinine ratio (UNAPCR) was defined as UPCR-UACR. Of the 1809 enrolled subjects, 695 (38.4%) patients died over a median follow-up of 6.4 years. The cohort was separated into four subgroups according to UACR (30 mg/g) and UNAPCR (120 mg/g) to examine whether these indices are associated with all-cause mortality. Compared with the low UACR and low UNAPCR subgroup as the reference group, multivariable Cox regression analyses indicated no significant difference in mortality in the high UACR and low UNAPCR subgroup (hazard ratio [HR] 1.189, 95% confidence interval [CI] 0.889-1.589, P = 0.243), but mortality risks were significantly higher in the low UACR and high UNAPCR subgroup (HR 2.204, 95% CI 1.448-3.356, P < 0.001) and in the high UACR with high UNAPCR subgroup (HR 1.796, 95% CI 1.451-2.221, P < 0.001). In the multivariable Cox regression model with inclusion of both UACR and UNAPCR, UNAPCR ≥ 120 mg/g was significantly associated with an increased mortality risk (HR 1.655, 95% CI 1.324-2.070, P < 0.001), but UACR ≥ 30 mg/g was not significantly associated with mortality risk (HR 1.046, 95% CI 0.820-1.334, P = 0.717). In conclusion, UNAPCR is an independent predictor of all-cause mortality in patients with type 2 DM.

Association between continuous glucose monitoring-derived glycemic control indices and urinary biomarkers of diabetic kidney disease: Hyogo Diabetes Hypoglycemia Cognition Complications study

AIMS

Glomerular damage and proximal tubular damage play an important role in the pathogenesis of diabetic kidney disease. This study aimed to investigate the relationship between the urinary markers of proximal tubular injury, including urinary liver-type fatty acid-binding protein-to-creatinine ratio (uL-FABP/Cr) and urinary N-acetyl-β-D-glucosaminidase-to-creatinine ratio (uNAG/Cr), and glycemic control status.

METHODS

This cross-sectional study included 245 and 39 patients with type 2 diabetes mellitus (T2DM) and non-T2DM (NDM), respectively. The participants of this study were fitted with retrospective CGM, and glycemic control indices, such as time in range (TIR) and glycemia risk index (GRI), were calculated.

RESULTS

The results were presented as medians (interquartile ranges). The uL-FABP/Cr was significantly higher in the microalbuminuria than in the normo-albuminuria group [4.2 (2.7-7.1) and 2.2 (1.4-3.4) μg/gCr, respectively, P < 0.001], while the uNAG/Cr in the normo-albuminuria group [6.3 (4.5-10.1) U/gCr] was significantly higher than that in the NDM group [5.3 (3.8-6.3) U/gCr, P = 0.048] but significantly lower than that in the microalbuminuria group [9.2 (6.4-11.1) U/gCr, P = 0.004]. The multivariate logistic regression analysis indicated that CGM-derived TIR was significantly associated with the urinary albumin-to-creatinine ratio [uAlb/Cr, odds ratio (OR) 0.985, 95% confidence interval (CI) 0.971-0.998, P = 0.029] and uNAG/Cr (OR 0.973, 95% CI 0.957-0.989, P = 0.001) independent of renal function. GRI was similarly associated with uAlb/Cr and uNAG/Cr.

CONCLUSION

The findings of this study indicated that uNAG/Cr was elevated before albuminuria development and was associated with CGM-derived TIR and GRI.

Precision prognostics for cardiovascular disease in Type 2 diabetes: a systematic review and meta-analysis

BACKGROUND

Precision medicine has the potential to improve cardiovascular disease (CVD) risk prediction in individuals with Type 2 diabetes (T2D).

METHODS

We conducted a systematic review and meta-analysis of longitudinal studies to identify potentially novel prognostic factors that may improve CVD risk prediction in T2D. Out of 9380 studies identified, 416 studies met inclusion criteria. Outcomes were reported for 321 biomarker studies, 48 genetic marker studies, and 47 risk score/model studies.

RESULTS

Out of all evaluated biomarkers, only 13 showed improvement in prediction performance. Results of pooled meta-analyses, non-pooled analyses, and assessments of improvement in prediction performance and risk of bias, yielded the highest predictive utility for N-terminal pro b-type natriuretic peptide (NT-proBNP) (high-evidence), troponin-T (TnT) (moderate-evidence), triglyceride-glucose (TyG) index (moderate-evidence), Genetic Risk Score for Coronary Heart Disease (GRS-CHD) (moderate-evidence); moderate predictive utility for coronary computed tomography angiography (low-evidence), single-photon emission computed tomography (low-evidence), pulse wave velocity (moderate-evidence); and low predictive utility for C-reactive protein (moderate-evidence), coronary artery calcium score (low-evidence), galectin-3 (low-evidence), troponin-I (low-evidence), carotid plaque (low-evidence), and growth differentiation factor-15 (low-evidence). Risk scores showed modest discrimination, with lower performance in populations different from the original development cohort.

CONCLUSIONS

Despite high interest in this topic, very few studies conducted rigorous analyses to demonstrate incremental predictive utility beyond established CVD risk factors for T2D. The most promising markers identified were NT-proBNP, TnT, TyG and GRS-CHD, with the highest strength of evidence for NT-proBNP. Further research is needed to determine their clinical utility in risk stratification and management of CVD in T2D.

Combined detection of urinary biomarkers noninvasively predicts extent of renal injury in patients with early diabetic kidney disease with kidney qi deficiency syndrome: A retrospective investigation

Incipient diagnosis and noninvasive forecasts using urinary biomarkers are important for preventing diabetic kidney disease (DKD) progression, but they are also controversial. Previous studies have shown a potential relationship between urinary tubular biomarkers (UTBs) and traditional Chinese medicine (TCM) syndrome in patients with DKD. Thus, we further evaluated the clinical significance of combined detection of urinary biomarkers in noninvasively predicting the extent of renal damage in patients with early DKD with kidney qi deficiency syndrome, and preliminarily explored the potential biological link between UTBs and TCM syndrome in DKD. We categorized 92 patients with Type 2 diabetes mellitus into three groups as follows: 20 patients with normoalbuminuria, 50 patients with microalbuminuria, and 22 patients with macroalbuminuria. We found that, in all groups, 24 hr urinary albumin (24hUAlb) and urinary albumin-to-creatinine ratio (UACR) showed stepwise and significant increases. Urinary cystatin C (UCysC), urinary N-acetyl-β-d-glucosaminidase (UNAG), and urinary retinol-binding protein (URBP) synchronously increased gradually, consistent with the degree of albuminuria in all groups. Moreover, 24hUAlb and UACR were positively correlated with UCysC, UNAG, and URBP, respectively. In 72 patients with Type 2 DKD with albuminuria, a positive correlation was observed between UNAG and URBP, UCysC was also positively correlated with UNAG and URBP, respectively. Additionally, TCM syndrome distributional characteristics in all patients were consistent with clinical manifestations of kidney qi deficiency syndrome. Therefore, the combined detection of UCysC, UNAG, URBP, and UAlb may be used as a practical clinical technique to noninvasively forecast the extent of renal injury in patients with early Type 2 DKD with kidney qi deficiency syndrome. UTBs may be one of the biological bases of the specific TCM syndromes in DKD.

Precision Prognostics for Cardiovascular Disease in Type 2 Diabetes: A Systematic Review and Meta-analysis

Background Precision medicine has the potential to improve cardiovascular disease (CVD) risk prediction in individuals with type 2 diabetes (T2D). Methods We conducted a systematic review and meta-analysis of longitudinal studies to identify potentially novel prognostic factors that may improve CVD risk prediction in T2D. Out of 9380 studies identified, 416 studies met inclusion criteria. Outcomes were reported for 321 biomarker studies, 48 genetic marker studies, and 47 risk score/model studies. Results Out of all evaluated biomarkers, only 13 showed improvement in prediction performance. Results of pooled meta-analyses, non-pooled analyses, and assessments of improvement in prediction performance and risk of bias, yielded the highest predictive utility for N-terminal pro b-type natriuretic peptide (NT-proBNP) (high-evidence), troponin-T (TnT) (moderate-evidence), triglyceride-glucose (TyG) index (moderate-evidence), Genetic Risk Score for Coronary Heart Disease (GRS-CHD) (moderate-evidence); moderate predictive utility for coronary computed tomography angiography (low-evidence), single-photon emission computed tomography (low-evidence), pulse wave velocity (moderate-evidence); and low predictive utility for C-reactive protein (moderate-evidence), coronary artery calcium score (low-evidence), galectin-3 (low-evidence), troponin-I (low-evidence), carotid plaque (low-evidence), and growth differentiation factor-15 (low-evidence). Risk scores showed modest discrimination, with lower performance in populations different from the original development cohort. Conclusions Despite high interest in this topic, very few studies conducted rigorous analyses to demonstrate incremental predictive utility beyond established CVD risk factors for T2D. The most promising markers identified were NT-proBNP, TnT, TyG and GRS-CHD, with the highest strength of evidence for NT-proBNP. Further research is needed to determine their clinical utility in risk stratification and management of CVD in T2D.

Acylcarnitines: Can They Be Biomarkers of Diabetic Nephropathy?

Diabetic nephropathy (DN), one of the most serious microvascular complications of diabetes mellitus (DM), may progress to end-stage renal disease (ESRD). Current biochemical biomarkers, such as urinary albumin excretion rate (UAER), have limitations for early screening and monitoring of DN. Recent studies have identified some metabolites as candidate biomarkers for early detection of DN. In this review, we summarize the role of dysregulated acylcarnitines (AcylCNs) in DN pathophysiology. Lower abundance of short- and medium-chain AcylCNs and higher long-chain AcylCNs often occurred in DM with normal albuminuria and microalbuminuria, compared with advanced stages of DN. The increase of long-chain AcylCNs was supposed to be an adaptive compensation in fat acids (FAs) oxidation in the early stage of DN. Conversely, the decrease of long-chain AcylCNs was due to incomplete oxidation of FAs in advanced stage of DN. Thus, AcylCNs may serve as sensitive biomarkers in predicting the risk of DN.

Novel Cardiovascular Risk Factors in Patients with Diabetic Kidney Disease

Patients with diabetic kidney disease (DKD) are at very high risk for cardiovascular events. Only part of this increased risk can be attributed to the presence of diabetes mellitus (DM) and to other DM-related comorbidities, including hypertension and obesity. The identification of novel risk factors that underpin the association between DKD and cardiovascular disease (CVD) is essential for risk stratification, for individualization of treatment and for identification of novel treatment targets.In the present review, we summarize the current knowledge regarding the role of emerging cardiovascular risk markers in patients with DKD. Among these biomarkers, fibroblast growth factor-23 and copeptin were studied more extensively and consistently predicted cardiovascular events in this population. Therefore, it might be useful to incorporate them in risk stratification strategies in patients with DKD to identify those who would possibly benefit from more aggressive management of cardiovascular risk factors.

Diabetic kidney disease: new clinical and therapeutic issues. Joint position statement of the Italian Diabetes Society and the Italian Society of Nephrology on "The natural history of diabetic kidney disease and treatment of hyperglycemia in patients with type 2 diabetes and impaired renal function"

Aims

This joint document of the Italian Diabetes Society and the Italian Society of Nephrology reviews the natural history of diabetic kidney disease (DKD) in the light of the recent epidemiological literature and provides updated recommendations on anti-hyperglycemic treatment with non-insulin agents.

Data Synthesis

Recent epidemiological studies have disclosed a wide heterogeneity of DKD. In addition to the classical albuminuric phenotype, two new albuminuria-independent phenotypes have emerged, i.e., “nonalbuminuric renal impairment” and “progressive renal decline”, suggesting that DKD progression toward end-stage kidney disease (ESKD) may occur through two distinct pathways, albuminuric and nonalbuminuric. Several biomarkers have been associated with decline of estimated glomerular filtration rate (eGFR) independent of albuminuria and other clinical variables, thus possibly improving ESKD prediction. However, the pathogenesis and anatomical correlates of these phenotypes are still unclear. Also the management of hyperglycemia in patients with type 2 diabetes and impaired renal function has profoundly changed during the last two decades. New anti-hyperglycemic drugs, which do not cause hypoglycemia and weight gain and, in some cases, seem to provide cardiorenal protection, have become available for treatment of these individuals. In addition, the lowest eGFR safety thresholds for some of the old agents, particularly metformin and insulin secretagogues, have been reconsidered.

Conclusions

The heterogeneity in the clinical presentation and course of DKD has important implications for the diagnosis, prognosis, and possibly treatment of this complication. The therapeutic options for patients with type 2 diabetes and impaired renal function have substantially increased, thus allowing a better management of these individuals.

Novel Urinary Glycan Biomarkers Predict Cardiovascular Events in Patients With Type 2 Diabetes: A Multicenter Prospective Study With 5-Year Follow Up (U-CARE Study 2)

Background: Although various biomarkers predict cardiovascular event (CVE) in patients with diabetes, the relationship of urinary glycan profile with CVE in patients with diabetes remains unclear.

Methods: Among 680 patients with type 2 diabetes, we examined the baseline urinary glycan signals binding to 45 lectins with different specificities. Primary outcome was defined as CVE including cardiovascular disease, stroke, and peripheral arterial disease.

Results: During approximately a 5-year follow-up period, 62 patients reached the endpoint. Cox proportional hazards analysis revealed that urinary glycan signals binding to two lectins were significantly associated with the outcome after adjustment for known indicators of CVE and for false discovery rate, as well as increased model fitness. Hazard ratios for these lectins (+1 SD for the glycan index) were UDA (recognizing glycan: mixture of Man5 to Man9): 1.78 (95% CI: 1.24–2.55, P = 0.002) and Calsepa [High-Man (Man2–6)]: 1.56 (1.19–2.04, P = 0.001). Common glycan binding to these lectins was high-mannose type of N-glycans. Moreover, adding glycan index for UDA to a model including known confounders improved the outcome prediction [Difference of Harrel's C-index: 0.028 (95% CI: 0.001–0.055, P = 0.044), net reclassification improvement at 5-year risk increased by 0.368 (0.045–0.692, P = 0.026), and the Akaike information criterion and Bayesian information criterion decreased from 725.7 to 716.5, and 761.8 to 757.2, respectively].

Conclusion: The urinary excretion of high-mannose glycan may be a valuable biomarker for improving prediction of CVE in patients with type 2 diabetes, and provides the rationale to explore the mechanism underlying abnormal N-glycosylation occurring in patients with diabetes at higher risk of CVE.

Trial Registration: This study was registered with the University Hospital Medical Information Network on June 26, 2012 (Clinical trial number: UMIN000011525, URL: https://upload.umin.ac.jp/cgi-open-bin/ctr_e/ctr_view.cgi?recptno=R000013482).

The ratio and difference of urine protein-to-creatinine ratio and albumin-to-creatinine ratio facilitate risk prediction of all-cause mortality

The role of the difference and ratio of albuminuria (urine albumin-to-creatinine ratio, uACR) and proteinuria (urine protein-to-creatinine ratio, uPCR) has not been systematically evaluated with all-cause mortality. We retrospectively analyzed 2904 patients with concurrently measured uACR and uPCR from the same urine specimen in a tertiary hospital in Taiwan. The urinary albumin-to-protein ratio (uAPR) was derived by dividing uACR by uPCR, whereas urinary non-albumin protein (uNAP) was calculated by subtracting uACR from uPCR. Conventional severity categories of uACR and uPCR were also used to establish a concordance matrix and develop a corresponding risk matrix. The median age at enrollment was 58.6 years (interquartile range 45.4-70.8). During the 12,391 person-years of follow-up, 657 deaths occurred. For each doubling increase in uPCR, uACR, and uNAP, the adjusted hazard ratios (aHRs) of all-cause mortality were 1.29 (95% confidence interval [CI] 1.24-1.35), 1.12 (1.09-1.16), and 1.41 (1.34-1.49), respectively. For each 10% increase in uAPR, it was 1.02 (95% CI 0.98-1.06). The linear dose-response association with all-cause mortality was only observed with uPCR and uNAP. The 3 × 3 risk matrices revealed that patients with severe proteinuria and normal albuminuria had the highest risk of all-cause mortality (aHR 5.25, 95% CI 1.88, 14.63). uNAP significantly improved the discriminative performance compared to that of uPCR (c statistics: 0.834 vs. 0.828, p-value = 0.032). Our study findings advocate for simultaneous measurements of uPCR and uACR in daily practice to derive uAPR and uNAP, which can provide a better mortality prognostic assessment.

Plasma trimethylamine N-oxide and its metabolic precursors and risk of mortality, cardiovascular and renal disease in individuals with type 2-diabetes and albuminuria

AIMS

The trimethylamine N-oxide (TMAO) pathway is related to intestinal microbiota and has been associated to risk of cardiovascular disease (CVD). We investigated associations between four plasma metabolites in the TMAO pathway and risk of all-cause mortality, CVD and deterioration in renal function in individuals with type 2-diabetes (T2D) and albuminuria.

MATERIALS AND METHODS

Plasma concentrations of TMAO, choline, carnitine, and betaine were measured by liquid chromatography-tandem mass spectrometry at baseline in 311 individuals with T2D and albuminuria. Information on all-cause mortality and fatal/non-fatal CVD during follow-up was obtained from registries. The association of each metabolite, and a weighted sum score of all four metabolites, with the endpoints were examined. Serum creatinine was measured at follow-up visits and the renal endpoint was defined as eGFR-decline of ≥30%. Associations were analysed using proportional hazards models adjusted for traditional risk factors.

RESULTS

Baseline mean(SD) age was 57.2(8.2) years and 75% were males. Follow-up was up to 21.9 years (median (IQR) follow-up 6.8 (6.1-15.5) years for mortality and 6.5 (5.5-8.1) years for CVD events). The individual metabolites and the weighted sum score were not associated with all-cause mortality (n = 106) or CVD (n = 116) (adjusted p≥0.09). Higher choline, carnitine and the weighted sum score of the four metabolites were associated with higher risk of decline in eGFR (n = 106) (adjusted p = 0.001, p = 0.03 and p<0.001, respectively).

CONCLUSIONS

In individuals with T2D and albuminuria, higher choline, carnitine and a weighted sum of four metabolites from the TMAO pathway were risk markers for deterioration in renal function during long-term follow-up. Metabolites from the TMAO pathway were not independently related to risk of all-cause mortality or CVD.

Calcitriol attenuates renal tubular epithelial cells apoptosis via inhibiting p38MAPK signaling in diabetic nephropathy

AIMS

To observe the effect of calcitriol on tubular epithelial cells apoptosis in diabetic nephropathy (DN) and to explore the possible mechanism of its renal protection.

METHODS

In vivo, DN rats established by streptozocin (STZ) were treated with or without calcitriol by gavage. Rats were killed at 18 weeks after treatment. In vitro, HK-2 cells were cultured in high glucose with or without 1,25-dihydroxyvitamin D3. In some experiments, P38MAPK activator anisomycin was applied to incubate HK-2 cells. Cell apoptosis was detected by TUNEL or Annexin V-FITC/PI staining with flow cytometry. Immunohistochemical staining was used to observe the expression of VDR in kidney. Protein expression of cleaved caspase-3, Bax, Bcl-2, VDR, pp38MAPK and p38MAPK was assessed by western blotting.

RESULT

Calcitriol treatment ameliorated the severity of proteinuria and reduced renal tubular epithelial cells apoptosis in DN rats. In addition, calcitriol treatment significantly increased renal VDR expression and reduced the expression of p-p38MAPK in rats. In vitro, 1,25-dihydroxyvitamin D3 decreased the apoptotic rate of HK-2 cells induced by high glucose. In accord with the results from animal study, 1,25-dihydroxyvitamin D3 increased VDR expression, but decreased p-p38MAPK expression in HK-2 cells. Moreover, P38MAPK activator anisomycin blocked the anti-apoptotic effect of 1,25-dihydroxyvitamin D3 on HK-2 cells.

CONCLUSIONS

Calcitriol attenuates renal tubular cells apoptosis via VDR activation which inhibits p38MAPK signaling in DN rats.

Assessment of urinary NGAL for differential diagnosis and progression of diabetic kidney disease

OBJECTIVE

Chronic kidney disease (CKD) related to diabetes has become more common than glomerulonephritis in recent years. Given the inefficient and difficult identification of diabetic kidney disease (DKD) from non-diabetic kidney disease (NDKD) as well as a result of emerging evidence supporting a role for tubular involvement in DKD, we aimed to investigate the utility of urinary neutrophil gelatinase-associated lipocalin (uNGAL) in the differential diagnosis and predictive value of DKD from NDKD.

METHODS

Data for 100 type 2 diabetic patients with CKD at our center from June 2016 to August 2019 were reviewed. All the patients were categorized into 2 groups by the renal biopsy results: DKD and NDKD. Urinary NGAL levels were normalized by urinary creatinine and calculated as uNGAL/creatinine ratios (uNCR). The independent factors of the occurrence of DKD and the diagnostic implications of uNCR were explored by logistic regression and receiver-operating characteristic (ROC) curve analysis. In addition, we analyzed the relationship between uNCR and proteinuria in patients with DKD by Pearson test and linear regression. Kaplan-Meier survival analysis was performed to assess the prospective association of uNCR with the renal outcome.

RESULTS

Significantly higher levels of uNCR were observed in patients with DKD when compared to those with NDKD (28.65 ng/mg vs 27.47 ng/mg, p< .001). uNCR was identified as an independent risk factor for the occurrence of DKD in diabetic patients with CKD (odds ratio [OR] = 1.020; 95%CI = [1.001-1.399], p = .042). The optimal cutoff value of uNCR for predicting DKD was 60.685 ng/mg with high specificity (90.5%) but relatively low sensitivity (55.7%). In Pearson test, uNCR was positively correlated with proteinuria, serum creatine, blood urea nitrogen, duration of diabetes, interstitial inflammation score and global sclerosis, whereas it was inversely correlated with eGFR, hemoglobin, serum albumin and 25-hydroxy vitamin D. Furthermore, in a fully adjusted model including eGFR, serum albumin and total cholesterol, the group with uNCR>60.685 ng/mg was associated with 7.595 times higher likelihood of nephrotic-range proteinuria compared to the group with uNCR≤60.685 ng/mg. In the Kaplan-Meier survival analysis, the event-free survival probability in patients with uNCR>60.685 ng/mg was significantly lower than those with uNCR≤60.685 ng/mg (p = .048).

CONCLUSIONS

uNCR might serve as a potential tool for identifying cases in which there was a high clinical suspicion of DKD and that in whom confirmatory biopsy could be considered, and the best predictive cutoff value of normalized uNCR for DKD diagnosis was 60.685 ng/mg. Type 2 diabetic patients with increased level of uNCR had higher risk to nephrotic-range proteinuria and worse renal outcome.

Neutrophil Gelatinase-Associated Lipocalin and Retinol-Binding Protein-4 as Biomarkers for Diabetic Kidney Disease

AIMS

This study was designed to evaluate the conflicting association between 2 tubular protein markers including neutrophil gelatinase-associated lipocalin (NGAL) and retinol-binding protein-4 (RBP-4) with albuminuria and glomerular filtration rate (GFR) and calculate the accuracy of the role of NGAL and RBP-4 in diagnosis of diabetic nephropathy (DN) in patients with type2 diabetes.

METHODS

This is a cross-sectional study that included 133 patients with type 2 diabetes. There were 3 diabetic study groups with normoalbuminuria, moderately increased albuminuria, severely increased albuminuria, and non-diabetic control group without any renal disease. We analyzed the difference of urinary NGAL (uNGAL) and RBP-4 between nondiabetics and diabetics, as well as within the diabetic group. We also assessed the association between albuminuria and NGAL and RBP-4.

RESULTS

The urinary levels of NGAL and RBP-4 were higher in patients with type 2 diabetes compared to nondiabetics as well as in albuminuric diabetics compared to nonalbuminuric patients with diabetes (p value <0.001). These 2 proteins were higher in patients with severely increased albuminuria compared to patients with moderately increased albuminuria, even after adjustment for other metabolic factors (all p < 0.01). Moreover, areas under the curve of NGAL and RBP-4 for the diagnosis of chronic kidney disease were 80.6 and 74.6%, respectively.

CONCLUSION

uNGAL and RBP-4 are potential markers of tubular damage that may increase before the onset of glomerular markers such as albuminuria and GFR in patients with type 2 diabetes. Therefore, these markers can be used as complementary measurements to albuminuria and GFR in the earlier diagnosis of DN.

Diabetic kidney diseases revisited: A new perspective for a new era

BACKGROUND

Globally, diabetic kidney disease (DKD) is the leading cause of end-stage renal disease. As the most common microvascular complication of diabetes, DKD is a thorny, clinical problem in terms of its diagnosis and management. Intensive glucose control in DKD could slow down but not significantly halt disease progression. Revisiting the tremendous advances that have occurred in the field would enhance recognition of DKD pathogenesis as well as improve our understanding of translational science in DKD in this new era.

SCOPE OF REVIEW

In this review, we summarize advances in the understanding of the local microenvironmental changes in diabetic kidneys and discuss the involvement of genetic and epigenetic factors in the pathogenesis of DKD. We also review DKD prevalence changes and analyze the challenges in optimizing the diagnostic approaches and management strategies for DKD in the clinic. As we enter the era of 'big data', we also explore the possibility of linking systems biology with translational medicine in DKD in the current healthcare system.

MAJOR CONCLUSION

Newer understanding of the structural changes of diabetic kidneys and mechanisms of DKD pathogenesis, as well as emergent research technologies will shed light on new methods of dealing with the existing clinical challenges of DKD.

Diabetic kidney disease: New clinical and therapeutic issues. Joint position statement of the Italian Diabetes Society and the Italian Society of Nephrology on "The natural history of diabetic kidney disease and treatment of hyperglycemia in patients with type 2 diabetes and impaired renal function"

AIMS

This joint document of the Italian Diabetes Society and the Italian Society of Nephrology reviews the natural history of diabetic kidney disease (DKD) in the light of the recent epidemiological literature and provides updated recommendations on anti-hyperglycemic treatment with non-insulin agents.

DATA SYNTHESIS

Recent epidemiological studies have disclosed a wide heterogeneity of DKD. In addition to the classical albuminuric phenotype, two new albuminuria-independent phenotypes have emerged, i.e., "nonalbuminuric renal impairment" and "progressive renal decline", suggesting that DKD progression toward end-stage kidney disease (ESKD) may occur through two distinct pathways, albuminuric and nonalbuminuric. Several biomarkers have been associated with decline of estimated glomerular filtration rate (eGFR) independent of albuminuria and other clinical variables, thus possibly improving ESKD prediction. However, the pathogenesis and anatomical correlates of these phenotypes are still unclear. Also the management of hyperglycemia in patients with type 2 diabetes and impaired renal function has profoundly changed during the last two decades. New anti-hyperglycemic drugs, which do not cause hypoglycemia and weight gain and, in some cases, seem to provide cardiorenal protection, have become available for treatment of these individuals. In addition, the lowest eGFR safety thresholds for some of the old agents, particularly metformin and insulin secretagogues, have been reconsidered.

CONCLUSIONS

The heterogeneity in the clinical presentation and course of DKD has important implications for the diagnosis, prognosis, and possibly treatment of this complication. The therapeutic options for patients with type 2 diabetes and impaired renal function have substantially increased, thus allowing a better management of these individuals.

High Serum Uric Acid Is Associated with Tubular Damage and Kidney Inflammation in Patients with Type 2 Diabetes

Background

Uric acid presents different roles in an organism. High serum uric acid concentrations may induce inflammatory pathways and promote kidney damage through different mechanisms. Therefore, this study investigated the association among high serum uric acid concentrations, renal tubular damage, and renal inflammation assessed via estimation of urinary kidney injury molecule-1 (KIM-1) and inflammatory cytokines in patients with type 2 diabetes (T2D).

Methods

Urinary concentrations of KIM-1, IL-1, IL-6, IL-10, and TNF-alpha, as well as other biochemical parameters, were assessed in 125 patients with T2D who were grouped into two groups based on the serum uric acid levels (<6.0 mg/dL and ≥6.0 mg/dL). Patients were also stratified according to the tertiles of serum uric acid concentrations.

Results

Urinary KIM-1, IL-1, IL-6, and TNF-alpha were higher in patients with serum uric acid concentrations ≥ 6.0 mg/dL. However, the differences between the groups were not statistically significant when the urinary values of KIM-1 and cytokines were normalized by the urinary creatinine concentration. Serum uric acid concentrations were significantly associated with urinary KIM-1 (values normalized by urinary creatinine concentration) and urinary TNF-alpha (absolute values and values normalized by urinary creatinine concentration), independent of the body mass index (BMI) and estimated glomerular filtration rate (eGFR).

Conclusions

High serum uric acid concentrations were associated with high urinary KIM-1 levels accompanied by the increase of urinary proinflammatory cytokines in patients with T2D. However, normalization of urinary markers by urine creatinine concentration seems to influence the profile of the results.

Renal injury after uninephrectomy in male and female intrauterine growth-restricted aged rats

Epidemiological studies report an inverse association between birth weight and risk for kidney disease that may differ between males and females, but studies investigating this association are limited. This study tested the hypothesis that male intrauterine growth-restricted offspring in a model of low birth weight induced by placental insufficiency in the rat exhibit enhanced renal injury in response to a persistent secondary renal insult while female growth-restricted offspring are protected. For this study, control offspring from sham-operated dams and growth-restricted offspring from reduced uterine perfusion dams underwent uninephrectomy or a sham procedure at 18 months of age. One month later, urinary markers of renal injury, renal function, and histological damage were measured. Results were analyzed using 2-way ANOVA. Male and female offspring were assessed separately. Proteinuria and urinary neutrophil gelatinase-associated lipocalin were significantly elevated in male growth-restricted offspring exposed to uninephrectomy when compared to male uninephrectomized control. Urinary kidney injury marker-1 was elevated in male uninephrectomized growth-restricted offspring relative to male sham growth-restricted but not to male uninephrectomized controls. Likewise, urinary neutrophil gelatinase-associated lipocalin was elevated in female uninephrectomized growth-restricted offspring but only when compared to female sham growth-restricted offspring. Markers of renal function including glomerular filtration rate and serum creatinine were impaired after uninephrectomy in female offspring regardless of birth weight. Histological parameters did not differ between control and growth-restricted offspring. Collectively, these studies suggest that both male and female growth-restricted offspring demonstrate susceptibility to renal injury following uninephrectomy; however, only male growth-restricted offspring exhibited an increase in renal markers of injury in response to uninephrectomy relative to same-sex control counterparts. These findings further suggest that urinary excretion of protein, kidney injury marker-1, and neutrophil gelatinase-associated lipocalin may be early markers of kidney injury in growth-restricted offspring exposed to a secondary renal insult such as reduction in renal mass.