Challenging the conventional wisdom on diabetic nephropathy: Is microalbuminuria the earliest event?

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.

Screening candidate diagnostic biomarkers for diabetic kidney disease

BACKGROUND

There are big differences in treatments and prognosis between diabetic kidney disease (DKD) and non-diabetic renal disease (NDRD). However, DKD patients couldn't be diagnosed early due to lack of special biomarkers. Urine is an ideal non-invasive sample for screening DKD biomarkers. This study aims to explore DKD special biomarkers by urinary proteomics.

MATERIALS AND METHODS

According to the result of renal biopsy, 142 type 2 diabetes mellitus (T2DM) patients were divided into 2 groups: DKD (n = 83) and NDRD (n = 59). Ten patients were selected from each group to define urinary protein profiles by label-free quantitative proteomics. The candidate proteins were further verifyied by parallel reaction monitoring (PRM) methods (n = 40). Proteins which perform the same trend both in PRM and proteomics were verified by enzyme-linked immunosorbent assays (ELISA) with expanding the sample size (n = 82). The area under the receiver operating characteristic curve (AUC) was used to evaluate the accuracy of diagnostic biomarkers.

RESULTS

We identified 417 peptides in urinary proteins showing significant difference between DKD and NDRD. PRM verification identified C7, SERPINA4, IGHG1, SEMG2, PGLS, GGT1, CDH2, CDH1 was consistent with the proteomic results and p < 0.05. Three potential biomarkers for DKD, C7, SERPINA4, and gGT1, were verified by ELISA. The combinatied SERPINA4/Ucr and gGT1/Ucr (AUC = 0.758, p = 0.001) displayed higher diagnostic efficiency than C7/Ucr (AUC = 0.632, p = 0.048), SERPINA4/Ucr (AUC = 0.661, p = 0.032), and gGT1/Ucr (AUC = 0.661, p = 0.029) respectively.

CONCLUSIONS

The combined index SERPINA4/Ucr and gGT1/Ucr can be considered as candidate biomarkers for diabetic nephropathy after adjusting by urine creatinine.

Nomogram for the prediction of crescent formation in IgA nephropathy patients: a retrospective study

BACKGROUND

The 2017 Oxford classification of immunoglobulin A nephropathy (IgAN) recently reported that crescents could predict a worse renal outcome. Early prediction of crescent formation can help physicians determine the appropriate intervention, and thus, improve the outcomes. Therefore, we aimed to establish a nomogram model for the prediction of crescent formation in IgA nephropathy patients.

METHODS

We retrospectively analyzed 200 cases of biopsy-proven IgAN patients. Least absolute shrinkage and selection operator(LASSO) regression and multivariate logistic regression was applied to screen for influencing factors of crescent formation in IgAN patients. The performance of the proposed nomogram was evaluated based on Harrell's concordance index (C-index), calibration plot, and decision curve analysis.

RESULTS

Multivariate logistic analysis showed that urinary protein ≥ 1 g (OR = 3.129, 95%CI = 1.454-6.732), urinary red blood cell (URBC) counts ≥ 30/ul (OR = 3.190, 95%CI = 1.590-6.402), mALBU ≥ 1500 mg/L(OR = 2.330, 95%CI = 1.008-5.386), eGFR < 60ml/min/1.73m2(OR = 2.295, 95%CI = 1.016-5.187), Serum IgA/C3 ratio ≥ 2.59 (OR = 2.505, 95%CI = 1.241-5.057), were independent risk factors for crescent formation. Incorporating these factors, our model achieved well-fitted calibration curves and a good C-index of 0.776 (95%CI [0.711-0.840]) in predicting crescent formation.

CONCLUSIONS

Our nomogram showed good calibration and was effective in predicting crescent formation risk in IgAN patients.

Diabetic kidney disease in pediatric patients: A current review

In the last decades, a significant increase in the incidence of diabetic kidney disease (DKD) was observed concomitant with rising diabetes mellitus (DM) incidence. Kidney disease associated with DM in children and adolescents is represented by persistent albuminuria, arterial hypertension, progressive decline in estimated glomerular filtration rate to end-stage renal disease and increased cardiovascular and all-cause morbidity and mortality of these conditions. In medical practice, the common and still the “gold standard” marker for prediction and detection of diabetic kidney involvement in pediatric diabetes is represented by microalbuminuria screening even if it has low specificity to detect early stages of DKD. There are some known limitations in albuminuria value as a predictor biomarker for DKD, as not all diabetic children with microalbuminuria or macroalbuminuria will develop end-stage renal disease. As tubular damage occurs before the glomerular injury, tubular biomarkers are superior to the glomerular ones. Therefore, they may serve for early detection of DKD in both type 1 DM and type 2 DM. Conventional and new biomarkers to identify diabetic children and adolescents at risk of renal complications at an early stage as well as renoprotective strategies are necessary to delay the progression of kidney disease to end-stage kidney disease. New biomarkers and therapeutic strategies are discussed as timely diagnosis and therapy are critical in the pediatric diabetic population.

Lipotoxic Proximal Tubular Injury: A Primary Event in Diabetic Kidney Disease

The pathogenesis of diabetic nephropathy is a complex process that has a great relationship with lipotoxicity. Since the concept of “nephrotoxicity” was proposed, many studies have confirmed that lipotoxicity plays a significant role in the progression of diabetic nephropathy and causes various renal dysfunction. This review will make a brief summary of renal injury caused by lipotoxicity that occurs primarily and predominantly in renal tubules during diabetic progression, further leading to glomerular dysfunction. The latest research suggests that lipotoxicity-mediated tubular injury may be a major event in diabetic nephropathy.

Hirudin Reduces the Expression of Markers of the Extracellular Matrix in Renal Tubular Epithelial Cells in a Rat Model of Diabetic Kidney Disease Through the Hypoxia-Inducible Factor-1α (HIF-1α)/Vascular Endothelial Growth Factor (VEGF) Signaling Pathway

BACKGROUND This study aimed to investigate the effects of hirudin on the production of extracellular matrix (ECM) factors by renal tubular epithelial cells in a rat model of diabetic kidney disease (DKD) and HK-2 human renal tubule epithelial cells. MATERIAL AND METHODS Sprague-Dawley rats were divided into the normal control group (n=10), the normal control+hirudin group (n=10), the DKD model group (n=12) and the DKD+hirudin group (n=12). At the end of the study, renal histopathology was undertaken, and the expression of type IV collagen, fibronectin, hypoxia-inducible factor-1alpha (HIF-1alpha), and vascular endothelial growth factor (VEGF) were evaluated using immunohistochemistry, Western blot, and quantitative real-time polymerase chain reaction (qRT-PCR). HK-2 cells were cultured in glucose and treated with hirudin. Protein and mRNA expression of fibronectin, type IV collagen, HIF-1alpha, and VEGF were evaluated following knockdown or overexpression of HIF-1alpha. RESULTS Hirudin significantly improved renal function in the rat model of DKD (P<0.01), and significantly down-regulated the expression of fibronectin, type IV collagen, HIF-1alpha, and VEGF proteins (P<0.05). The expression of ECM associated proteins was increased in HK-2 cells treated with high glucose and reduced in the high glucose+shRNA HIF-1alpha group (P<0.05). Compared with the control group, the expression of ECM associated proteins was increased in the HIF-1alpha over-expressed group, and decreased following treatment with hirudin (P<0.05). CONCLUSIONS Hirudin reduced the expression of markers of ECM by inhibiting the HIF-1alpha/VEGF signaling pathway in DKD renal tubular epithelial cells.

Ipragliflozin Ameliorates Endoplasmic Reticulum Stress and Apoptosis through Preventing Ectopic Lipid Deposition in Renal Tubules

BACKGROUND

Chronic kidney disease (CKD) and non-alcoholic steatohepatitis (NASH) are major health burdens closely related to metabolic syndrome. A link between CKD and NASH has been assumed; however, the underlying mechanism is still unknown. Ectopic lipid deposition (ELD) in the hepatocyte results in endoplasmic reticulum (ER) stress, which plays an important role in the development of steatohepatitis. ELD is also assumed to play a role in the development of kidney injury. We aimed to investigate the role of ELD and ER stress in the development of CKD, and evaluate the efficacy of a sodium glucose cotransporter-2 inhibitor, ipragliflozin.

METHODS

Male FLS-ob/ob mice that closely imitate the pathophysiology of NASH were treated with vehicle or ipragliflozin. Metabolic characteristics, histology of the kidney, ER stress, and apoptotic signals were evaluated.

RESULTS

The serum triglyceride was significantly lower in mice treated with ipragliflozin. Ipragliflozin reduced ELD in renal tubules. Ipragliflozin also reduced the expression levels of GRP78 and CHOP, apoptotic cells, and interstitial fibrosis.

CONCLUSIONS

ELD induced kidney injury through ER stress. Ipragliflozin improved the pathogenesis of CKD by reducing ELD and ER stress in NASH-model mice. Our results suggest ipragliflozin has therapeutic effect on CKD in NASH.