Re-thinking diabetic nephropathy: Microalbuminuria is just a piece of the diagnostic puzzle

Renalase protects against podocyte injury by inhibiting oxidative stress and apoptosis in diabetic nephropathy

Diabetic nephropathy (DN) presents a significant public health challenge due to its high rate of incidence and severe health consequences. Renalase has been identified as having renal-protective properties. A key contributor to albuminuria in DN patients is podocyte loss. The function of Renalase in DN in relation to podocyte activity needs to be explored further. In this study, we assessed the therapeutic efficacy of Renalase by monitoring changes in urine protein levels and podocyte health in db/db mice. We also induced hyperglycemia (HG) to stimulate podocyte clone 5 (MPC5) cells to create a model of podocyte loss in DN. Through co-culturing these cells with Renalase or H2O2, we investigated the process by which Renalase prevents podocyte loss in vitro. In db/db mice, Renalase expression was significantly reduced, and adenoviral-mediated Renalase expression markedly alleviated DN symptoms and proteinuria. Furthermore, podocytopathy in db/db mice was significantly mitigated. In vitro, Renalase improved the expression of podocyte marker proteins, podocin, and nephrin, which are reduced by HG, as well as decreased oxidative stress and restrained apoptosis. Our findings suggest that Renalase can mitigate DN by reducing proteinuria through podocyte protection, potentially by inhibiting oxidative stress and apoptosis. These data suggest that Renalase may serve as a novel therapeutic agent in suppressing DN.

A semantic segmentation method to analyze retinal vascular parameters of diabetic nephropathy

Introduction

By using spectral domain optical coherence tomography (SD-OCT) to measure retinal blood vessels. The correlation between the changes of retinal vascular structure and the degree of diabetic nephropathy is analyzed with a full-pixel Semantic segmentation method.

Methods

A total of 120 patients with diabetic nephropathy who were treated in the nephrology department of Quzhou People's Hospital from March 2023 to March 2024 were selected and divided into three groups according to the urinary albumin creatinine ratio (UACR). The groups included simple diabetes group (UACR < 30 mg/g), microalbuminuria group (30 mg/g ≤ UACR <300 mg/g) and macroalbuminuria group (UACR ≥300 mg/g). SD-OCT was used to scan the arteries and veins in the superior temporal area B of the retina. The semantic segmentation method built into the SD-eye software was used to automatically identify the morphology and structure of the vessels and calculate the parameters of arteriovenous vessels. The parameters of arteriovenous vessels are as follows: outer diameter of the retinal artery (RAOD); inner diameter of the retinal artery (RALD); arterial wall thickness (AWT); arterial wall to lumen ratio (AWLR); cross sectional area of arterial wall (AWCSA); retinal vein outer diameter (RVOD); retinal vein inner diameter (RVLD); vein wall thickness (VWT); vein wall to lumen ratio (VWLR); cross sectional area of vein wall (VWCSA). Statistical analysis software was used to compare and analyze the parameters of retinal arteriovenous vessels of the three groups.

Results

The study revealed statistically significant differences in RAOD and RALD among the three groups (p < 0.05) with the RAOD and RALD of the macroalbuminuria group and microalbuminuria group being lower than those of the simple diabetes group. Conversely, there were no significant differences in AWT, AWLR and AWCSA among the three groups (p > 0.05). Additionally, the differences in RVOD and RVLD among the three groups were found to be statistically significant (p < 0.05) with the RVOD and RVLD of the simple diabetes group being lower than those of the microalbuminuria group and macroalbuminuria group. No significant differences were observed in VWT and VWL among the groups. Additionally, RVOD and RVLD were weakly associated with UACR (R = 0.247, p = 0.007; R = 0.210, p = 0.021). Full-pixel semantic segmentation method combined with OCT images is a new retinal vascular scanning technology, which can be used as a new method for early diagnosis of diabetic nephropathy. The structural changes of retinal vessels can be used to predict the severity of diabetic nephropathy during the development of diabetic nephropathy.

Linggui Zhugan Decoction Improves High Glucose-Induced Autophagy in Podocytes

OBJECTIVES

To explore the influence of Linggui Zhugan Decoction (LGZGD) on high glucose induced podocyte autophagy.

METHODS

LGZGD containing serum was prepared by intragastric administation of 4.2 g/kg (low dose), 8.4 g/kg (medium dose), and 12.6 g/kg (high dose) LGZGD into SD rats respectively. MPC5 and AB8/13 podocyte cells were treated with 60 mmol/L glucose to establish diabetic nephropathy podocyte model in vitro. Both podocytes were divided into control group, high glucose group, low dose LGZGD group, medium dose LGZGD group, and high dose LGZGD group, respectively. For the three LGZGD groups, before LGZGD intervention, podocytes were treated with 60 mmol/L glucose for 3 days. After treated with LGZGD containing serum, cells were collected to analyze cell migration using Transwell assay, proliferation using CCK8, apoptosis and cell cycle using flow cytometry, autophagosome formation using transmission electron microscopy, and expression levels of Beclin-1, Atg5, LC3II/I, and P62 proteins using Western blot.

RESULTS

Compared with the control group, the proliferation and migration of MPC5 and AB8/13 cells in the high glucose group slightly decreased, whereas these parameters restored after intervention with low and medium concentrations of LGZGD, with the medium dose LGZGD having the better effect (P < 0.05). Flow cytometry showed that the medium dose LGZGD group had a significantly lower apoptosis rate (P < 0.05) and higher survival rate (P > 0.05) compared to the high dose LGZGD group. High glucose arrested podocytes in G1 phase, whereas LGZGD shifted podocytes from being predominant in G1 phase to G2 phase. High dose LGZGD significanly reduced high glucose-increased autophagosome formation in both podocytes (P < 0.05). Western blot analysis showed that Beclin-1, Atg5, LC3II/I, and P62 expressions were increased in MPC5 cells treated with high glucose and reversed after adminstration of low and medium doses of LGZGD (P < 0.05).

CONCLUSIONS

LGZGD reduced apoptosis and enhanced autophagy in high glucose treated podocytes via regulating Beclin-1/LC3II/I/Atg5 expression.

Preclinical Detection of Early Glomerular Injury in Children with Kidney Diseases-Independently of Usual Markers of Kidney Impairment and Inflammation

Glomerular kidney diseases typically begin insidiously and can progress to end stage kidney failure. Early onset of therapy can slow down disease progression. Early diagnosis is required to ensure such timely therapy. The goal of our study was to evaluate protein biomarkers (BMs) for common nephropathies that have been described for children with Alport syndrome. Nineteen candidate BMs were determined by commercial ELISA in children with congenital anomalies of the kidneys and urogenital tract, inflammatory kidney injury, or diabetes mellitus. It is particularly essential to search for kidney disease BMs in children because they are a crucial target group that likely exhibits early disease stages and in which misleading diseases unrelated to the kidney are rare. Only minor differences in blood between affected individuals and controls were found. However, in urine, several biomarker candidates alone or in combination seemed to be promising indicators of renal injury in early disease stages. The BMs of highest sensitivity and specificity were collagen type XIII, hyaluronan-binding protein 2, and complement C4-binding protein. These proteins are unrelated to inflammation markers or to risk factors for and signs of renal failure. In conclusion, our study evaluated several strong candidates for screening for early stages of kidney diseases and can help to establish early nephroprotective regimens.

Role of Urinary Matrix Metalloproteinase-7 (MMP-7) as an Early Marker of Renal Dysfunction in Diabetic Individuals: A Cross-Sectional Study

BACKGROUND AND OBJECTIVES

The matrix metalloproteinase 7 (MMP-7) level gets heightened in the urine samples of diabetic individuals with impaired renal function. Renal biopsy is seldom offered because of its invasive nature. These concerns spurred the investigation of relationships between urine MMP-7 levels and the renal function of diabetic individuals. Studies exploring this aspect are scarce. We aimed to evaluate the glycemic and renal parameters of female and male individuals with or without type 2 diabetes mellitus (T2DM) or kidney disease. We also assessed the correlation of urine MMP-7 with various parameters.

METHODS

This prospective, analytical, cross-sectional study was conducted at Kalinga Institute of Medical Sciences (KIMS), Bhubaneswar, India, from February 2020 to January 2023. Female and male individuals 18-85 years of age diagnosed with either T2DM, hypertension, or kidney disease were assessed for their glycemic indices and renal parameters. Those with both renal disease and T2DM were placed in group A. The diabetic individuals without kidney disease constituted group B. People in group C had neither kidney disease nor T2DM. Patients in group D had kidney disease but were not diabetics. The parameters of the male and female participants in each of the four groups were assessed and compared, including: age, body mass index (BMI), fasting blood sugar (FBS), glycosylated hemoglobin (HbA1c), serum urea, serum creatinine, estimated glomerular filtration rate (eGFR), urine albumin, urine creatinine, urine albumin-creatinine ratio (ACR), serum sodium, serum potassium, and urine MMP-7 levels. Furthermore, we correlated urine MMP-7 with all these traits. We used R software (version 4.4.0, Vienna, Austria) for data analysis.

RESULTS

Two hundred eighty-seven (87.5%) of the 328 individuals we screened were eligible. Of them, group A had the maximum number (94) of participants, followed by B (75), C (65), and D (53). Males comprised 60.3% (n = 173) of the study population. The median age of the participants was 52.0 (44.0-61.1) years. The intergroup variations were statistically significant (p < 0.001) owing to their glycemic status and renal function. The gender-basis comparison of FBS and HbA1c yielded non-significant differences. On the contrary, assessment of the renal parameters revealed significant differences (p < 0.001) between females and males. The study population had a median urine MMP-7 level of 19.9 (1.1-50.5) µg/L. Significant associations with urine MMP-7 were found with serum creatinine (r = 0.91, p < 0.001), urine ACR (r = 0.86, p < 0.001), and eGFR (r = -0.84, p < 0.001).

CONCLUSION

Our study portrayed that male diabetics, in comparison to female diabetics, had greater levels of urine ACR, urine MMP-7, eGFR, and serum creatinine. Moreover, urine ACR, eGFR, and serum creatinine strongly correlated with the urine MMP-7 level.

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.

IGF1 and PPARG polymorphisms are associated with reduced estimated glomerular filtration rate in a cohort of children and adolescents with type 1 diabetes

INTRODUCTION

Several genetic loci have been associated with diabetic nephropathy; however, the underlying genetic mechanisms are still poorly understood, with no robust candidate genes identified yet.

AIM

We aimed to determine whether two polymorphisms, previously associated with renal decline, influence kidney impairment evaluating their association with markers of renal function in a pediatric population with type 1 diabetes (T1D).

MATERIAL AND METHODS

Renal function was evaluated by glomerular filtration rate (eGFR) and albumin-to-creatinine ratio (ACR) in a cohort of pediatric subjects with T1D (n = 278). Risk factors for diabetes complications (diabetes duration, blood pressure, HbA1c) were assessed. The IGF1 rs35767 and PPARG rs1801282 SNPs were genotyped by TaqMan RT-PCR system. An additive genetic interaction was calculated. Association analysis between markers of renal function and both SNPs or their additive interaction were performed.

RESULTS

Both SNPs showed a significant association with eGFR: the A allele of rs35767 or the C allele of rs1801282 were associated to reduced eGFR compared to G alleles. Multivariate regression analysis adjusted for age, sex, z-BMI, T1D duration, blood pressure and Hba1c values showed that the additive genetic interaction was independently associated with lower eGFR (β = -3.59 [-6.52 to -0.66], p = 0.017). No associations were detected between SNPs, their additive interaction and ACR.

CONCLUSIONS

These results provide new insight into the genetic predisposition to renal dysfunction, showing that two polymorphisms in IGF1 and PPARG genes can lead to a reduction in renal filtration rate leading these patients to be exposed to a higher risk of early renal complications.

Serum JKAP reflects Th2 and Th17 cell levels, and diabetic nephropathy risk and severity in diabetes mellitus patients

Objective: This study aimed to explore the potency of serum JKAP for estimating diabetic nephropathy risk in diabetes mellitus (DM) patients. Methods: Serum JKAP was detected in 212 DM patients. According to urinary albumin-to-creatinine ratio, DM patients were divided into normoalbuminuria, microalbuminuria and macroalbuminuria groups. Results: JKAP declined in the macroalbuminuria group versus normoalbuminuria group (p < 0.001). In DM patients, JKAP inversely correlated with Th17 cells (p < 0.001) but positively related to Th2 cells (p = 0.003). After adjustment, JKAP independently estimated lower risks of albuminuria (microalbuminuria + macroalbuminuria; odds ratio = 0.966, p < 0.001) and macroalbuminuria (odds ratio = 0.948; p = 0.002). Conclusion: Serum JKAP reflects increased Th2 cells, decreased Th17 cells, and lower diabetic nephropathy risk and severity in DM patients.

Diabetic Proteinuria Revisited: Updated Physiologic Perspectives

Albuminuria, a hallmark of diabetic nephropathy, reflects not only injury and dysfunction of the filtration apparatus, but is also affected by altered glomerular hemodynamics and hyperfiltration, as well as by the inability of renal tubular cells to fully retrieve filtered albumin. Albuminuria further plays a role in the progression of diabetic nephropathy, and the suppression of glomerular albumin leak is a key factor in its prevention. Although microalbuminuria is a classic manifestation of diabetic nephropathy, often progressing to macroalbuminuria or overt proteinuria over time, it does not always precede renal function loss in diabetes. The various components leading to diabetic albuminuria and their associations are herein reviewed, and the physiologic rationale and efficacy of therapeutic interventions that reduce glomerular hyperfiltration and proteinuria are discussed. With these perspectives, we propose that these measures should be initiated early, before microalbuminuria develops, as substantial renal injury may already be present in the absence of proteinuria. We further advocate that the inhibition of the renin-angiotensin axis or of sodium-glucose co-transport likely permits the administration of a normal recommended or even high-protein diet, highly desirable for sarcopenic diabetic patients.