Glycated Albumin Is a More Useful Glycation Index than HbA1c for Reflecting Renal Tubulopathy in Subjects with Early Diabetic Kidney Disease

Glucagon-Like Peptide 1 Receptor Agonist Improves Renal Tubular Damage in Mice with Diabetic Kidney Disease

PURPOSE

This study aims to investigate the renal protective effect of glucagon-like peptide 1 receptor agonist (GLP-1RA) on improving renal tubular damage in diabetic kidney disease (DKD) and to explore the potential mechanism of GLP-1RA on renal tubular protection.

METHODS

Long-acting GLP-1RA was used to treat DKD mice for 12 weeks. The label-free quantitative proteomic analysis of renal proteins was conducted to explore the differentially expressed proteins (DEPs) in the renal tissues of the control, DKD and GLP-1RA groups. The DEPs and markers of renal tubular injury were verified by qPCR in vivo and in vitro. The expression of glucagon-likepeptide-1 receptor (GLP-1R) in renal tubules was determined by immunofluorescence staining.

RESULTS

GLP-1RA treatment significantly improved the tubular damages in kidney tissues of DKD mice and mTEC cells stimulated by high glucose (HG). Proteomics analysis revealed that 30 proteins in kidney tissue were differentially expressed among three groups. Seminal vesicle secretory protein 6 (SVS6) was the most differentially expressed protein in kidney tissues among three groups of mice. The expression changes of Svs6 mRNA in vitro and in vivo detected by qPCR were consistent with the results of proteomic analysis. Furthermore, reduction of Svs6 expression by SVS6 siRNA could attenuate HG-stimulated tubular injury in mTEC cells. Immunofluorescence staining also found that GLP-1R was widely expressed in renal tubules in vitro and in vivo.

CONCLUSION

GLP-1RA significantly improved renal tubular damage in DKD mice. SVS6 may be a potential therapeutic target for GLP-1RA in the treatment of DKD.

Diabetic Kidney Disease, Cardiovascular Disease and Non-Alcoholic Fatty Liver Disease: A New Triumvirate?

Non-alcoholic fatty liver disease is a highly prevalent disease worldwide with a renowned relation to cardiovascular disease and chronic kidney disease. These diseases share a common pathophysiology including insulin resistance, oxidative stress, chronic inflammation, dysbiosis and genetic susceptibilities. Non-alcoholic fatty liver disease is especially prevalent and more severe in type 2 diabetes. Patients with non-alcoholic fatty liver disease should have liver fibrosis assessment in order to identify those at the highest risk of adverse outcomes so that appropriate management strategies can be implemented. Early diagnosis and treatment of non-alcoholic fatty liver disease could ameliorate the burden of cardiovascular disease and chronic kidney disease.

Use of glycated albumin for the identification of diabetes in subjects from northeast China

BACKGROUND

Metabolic memory is important for the diagnosis and treatment of diabetes in the early stage, and in maintaining blood glucose concentrations within the normal range. The clinical diagnosis of diabetes mellitus is currently made using fasting plasma glucose, 2 h-plasma glucose (2h-PG) during a 75 g oral glucose tolerance test, and hemoglobin A1c (HbA1c) level. However, the fasting plasma glucose test requires fasting, which is a barrier to screening, and reproducibility of the 2h-PG level is poor. HbA1c is affected by a shortened red blood cell lifespan. In patients with anemia and hemoglobinopathies, the measured HbA1c levels may be inaccurate. Compared with HbA1c, glycated albumin (GA) is characterized by more rapid and greater changes, and can be used to diagnose new-onset diabetes especially if urgent early treatment is required, for example in gestational diabetes. In this study, we provided cutoff values for GA and evaluated its utility as a screening and diagnostic tool for diabetes in a large high-risk group study.

AIM

To evaluate the utility of GA in identifying subjects with diabetes in northeast China, and to assess the diagnostic accuracy of the proposed GA cutoff in the diagnosis of diabetes mellitus.

METHODS

This cross-sectional study included 1935 subjects, with suspected diabetes or in high-risk groups, from 2014 to 2015 in the Second Affiliated Hospital of Harbin Medical University (Harbin, China). The use of GA to identify diabetes was investigated using the area under the receiver operating characteristic curve (AUC). The GA cutoffs were derived from different 2h-PG values with hemoglobin A1c cutoffs used as a calibration curve.

RESULTS

The GA cutoff for the diagnosis of diabetes mellitus was 15.15% from the receiver operating characteristic (ROC) curve. ROC analysis demonstrated that GA was an efficient marker for detecting diabetes, with an AUC of 90.3%.

CONCLUSION

Our study supports the use of GA as a biomarker for the diagnosis of diabetes.

Hepatic fibrosis is associated with total proteinuria in Korean patients with type 2 diabetes

The association between non-alcoholic fatty liver disease (NAFLD) and diabetic kidney disease assessed using either albuminuria or proteinuria remains controversial. This study aimed to investigate the association between hepatic steatosis or fibrosis and albuminuria or proteinuria in Korean patients with type 2 diabetes mellitus (T2D).We enrolled 1108 patients with T2D and categorized as 3 groups; non-proteinuria (NP), isolated non-albumin proteinuria (iNAP), and albuminuria. Urinary albumin and protein levels were assessed as urinary albumin-to-creatinine ratio (uACR) and urinary protein-to-creatinine ratio (uPCR), respectively. Hepatic steatosis and fibrotic burden were assessed using the NAFLD liver fat score, Fibrosis-4 calculator (FIB-4) index, and NAFLD fibrosis score (NFS).The prevalence of significant steatosis was similar among groups (NP: 74.6% vs iNAP: 70.3% vs albuminuria: 79.9%, P = .085). The prevalence of significant fibrosis was significantly higher in the iNAP (18.7%) and albuminuria (16.5%) groups than in the NP group (9.5%, P = .001). Both uPCR and uACR showed a correlation with NFS (uPCR: r = 0.123, P < .001; uACR: r = 0.064, P = .033). In multivariate logistic regression analysis, uPCR ≥150 mg/g was found to have a stronger association with hepatic fibrosis than uACR ≥30 mg/g (adjusted odds ratio 1.55 [95% CI 1.03-2.33] vs adjusted odds ratio 1.16 [95% CI, 0.72-1.87]).In conclusion, patients with iNAP and albuminuria had a higher prevalence of hepatic fibrosis than those without proteinuria. Total proteinuria was associated with advanced liver fibrosis, whereas albuminuria was related to hepatic steatosis.

Glycated Plasma Proteins as More Sensitive Markers for Glycemic Control in Type 1 Diabetes

PURPOSE

Glycated hemoglobin (HbA1c) is used clinically for diagnosis and therapeutic management of diabetes. However, HbA1c reflects average blood glucose level over a long period. The aim of this study is to look for short period, more sensitive protein markers that correlate better with glycemic level.

EXPERIMENTAL DESIGN

The glycated proteome of human plasma from type 1 diabetic individuals with good and poor (n = 20 each) glycemic control are analyzed using an online two-dimensional proteomics approach. Selected glycated peptides are further validated for their potential as candidate biomarkers using parallel reaction monitoring.

RESULTS

305 glycated peptides are quantified and 290 are significantly increased in samples with poor glycemic control. 76 of the 88 selected glycated peptides have receiver operating characteristic area under curve (AUC) values greater than 0.8. Six validated glycated peptides with high AUC show high correlation with HbA1c and have higher fold changes between poor and good glycemic control than HbA1c. The parent proteins have half-lives shorter than HbA1c.

CONCLUSIONS AND CLINICAL RELEVANCE

Using an advanced proteomics platform for protein glycation analysis, glycated peptides and proteins are identified that are promising as more sensitive, shorter term indicators of glycemic control in diabetic patients than the commonly used HbA1c.

Empagliflozin reduces high glucose-induced oxidative stress and miR-21-dependent TRAF3IP2 induction and RECK suppression, and inhibits human renal proximal tubular epithelial cell migration and epithelial-to-mesenchymal transition

Proximal tubular epithelial cells (PTEC) in the S1 segment of the kidney abundantly express sodium-glucose co-transporters (SGLT) that play a critical role in whole body glucose homeostasis. We recently reported suppression of RECK (Reversion Inducing Cysteine Rich Protein with Kazal Motifs), a membrane anchored endogenous MMP inhibitor and anti-fibrotic mediator, in the kidneys of db/db mice, a model of diabetic kidney disease (DKD), as well as in high glucose (HG) treated human kidney proximal tubule cells (HK-2). We further demonstrated that empagliflozin (EMPA), an SGLT2 inhibitor, reversed these effects. Little is known regarding the mechanisms underlying RECK suppression under hyperglycemic conditions, and its rescue by EMPA. Consistent with our previous studies, HG (25 mM) suppressed RECK expression in HK-2 cells. Further mechanistic investigations revealed that HG induced superoxide and hydrogen peroxide generation, oxidative stress-dependent TRAF3IP2 upregulation, NF-κB and p38 MAPK activation, inflammatory cytokine expression (IL-1β, IL-6, TNF-α, and MCP-1), miR-21 induction, MMP2 activation, and RECK suppression. Moreover, RECK gain-of-function inhibited HG-induced MMP2 activation and HK-2 cell migration. Similar to HG, advanced glycation end products (AGE) induced TRAF3IP2 and suppressed RECK, effects that were inhibited by EMPA. Importantly, EMPA treatment ameliorated all of these deleterious effects, and inhibited epithelial-to-mesenchymal transition (EMT) and HK-2 cell migration. Collectively, these findings indicate that hyperglycemia and associated AGE suppress RECK expression via oxidative stress/TRAF3IP2/NF-κB and p38 MAPK/miR-21 induction. Furthermore, these results suggest that interventions aimed at restoring RECK or inhibiting SGLT2 have the potential to treat kidney inflammatory response/fibrosis and nephropathy under chronic hyperglycemic conditions, such as DKD.

Association of urinary acidification function with the progression of diabetic kidney disease in patients with type 2 diabetes

OBJECTIVE

Although diabetic kidney disease (DKD) has been considered as a glomerulocentric disease in the past few decades, growing evidence demonstrated that tubular damage was indispensable in its pathogenesis and progression. This study was designed to investigate the association of urinary acidification dysfunction with the progression of DKD in type 2 diabetic patients.

METHODS

Here the urinary acidification functions were measured from 80 participants with renal biopsy-proven DKD. The different kinds of renal tubular transportation dysfunction were analyzed, including the dysfunction of bicarbonate reabsorption, titratable acid secretion, and ammonium secretion. In addition, patients were followed up for 17 (interquartile range, 11-32) months to evaluate the effect of urinary acidification dysfunction in the progression of DKD.

RESULTS

The most common urinary acidification dysfunction was the disorder of ammonium secretion, accounting for 53.75%. The more proteinuria excretion and the lower glomerular filtration rate (GFR) were observed in the urinary titratable acid disorder group than the normal group, and the same results were obtained for ammonium secretion disorder. Urine titratable acid was positively correlated with eGFR whereas it was inversely correlated with proteinuria, serum creatinine, and BUN. Moreover, 24 h urine protein, serum creatinine, BUN and cystatin C increased from DKD stage II to stage IV, whereas the eGFR and urine titratable acid decreased in the same way. Furthermore, Kaplan-Meier analysis and Cox regression showed that the disorder of titratable acid was an independent risk factor for DKD progression.

CONCLUSIONS

The dysfunction of urinary titratable acid is a potential biomarker for the severity of proteinuria, eGFR and glomerular lesions in patients with DKD. Moreover, the titratable acid disorder is an independent risk factor of the DKD progression.

Glucometabolic characteristics and higher vascular complication risk in Korean patients with type 2 diabetes with non-albumin proteinuria

OBJECTIVE

We investigated the clinical relevance of non-albumin proteinuria (NAP) in Korean patients with type 2 diabetes (T2D).

RESEARCH DESIGN AND METHODS

We enrolled 883 T2D patients who had both their urinary albumin-to-creatinine ratio (uACR) and protein-to-creatinine ratio (uPCR) measured. We classified the patients into non-proteinuria (NP; uPCR <150 mg/g and uACR <30 mg/g), isolated NAP (iNAP; uPCR ≥150 mg/g and uACR <30 mg/g), and albuminuria (uACR ≥30 mg/g) groups. The associations between uPCR, uACR, and several indices of glucose metabolism were investigated.

RESULTS

The glucometabolic pathophysiology of iNAP (96 [10.9%]) group was more associated with a decrease in homeostatic model assessment (HOMA)-beta value (aOR 1.89 [95% CI, 1.21-2,96]) than with an increase in HOMA-insulin resistance (aOR 1.29 [95% CI, 0.83-2.01]). uPCR ≥150 mg/g was also found to have more consistent and stronger association with vascular complications than uACR ≥30 mg/g (aOR 1.44 [95% CI, 1.03-2.02] vs. 1.26 [95% CI, 0.89-1.79]).

CONCLUSIONS

The nephropathy of iNAP may be mainly attributed to decreased beta cell function. Furthermore, uPCR might be a more sensitive urinary biomarker than uACR for the detection of vascular complications in T2D patients.

Increasing waist circumference is associated with decreased levels of glycated albumin

BACKGROUND

Glycated albumin (GA) levels are affected by body fat and its distribution. We explored the association of waist circumference (WC) with GA and to assess the extent to which WC influences GA.

METHODS

We recruited 1799 subjects (age 26-82 y) from communities. GA was determined using the enzyme method, and glycated hemoglobin A_1c (HbA_1c) was detected using high-performance liquid chromatography.

RESULTS

Subjects with central obesity had lower GA and GA/HbA_1c than those without (both P < .01). GA and GA/HbA_1c were negatively correlated with central obesity (both P < .01), whereas HbA_1c was not correlated (P = .833). In the euglycemic and hyperglycemic subpopulations, GA and GA/HbA_1c showed decreasing trends as WC levels increased (both P for trends <0.01). WC was a significant negative determinant of GA (P < .05). In the hyperglycemic subpopulation, the GA value decreased by approximately 0.15% for each 5 cm increment in WC regardless of the presence of central obesity.

CONCLUSIONS

The GA value was reduced by approximately 0.15% for each 5 cm increment in WC, suggesting that more attention should be paid to actual blood glucose underestimated by GA in obese people.