Protein expression profile of human renal mesangial cells under high glucose

Mendelian randomization analysis reveals causal relationships between circulating cell traits and renal disorders

Purpose

The aim of this study was to investigate the causal relationships between circulating cell traits and risk of renal disorders.

Methods

We applied a comprehensive two-sample Mendelian randomization (MR) analysis. Single nucleotide polymorphisms (SNPs) from publicly available genome-wide association studies (GWAS) databases were utilized. Genetically predicted instrumental variables of human blood cell traits were extracted from Blood Cell Consortium (BCX) while data on renal diseases was obtained from Finngen consortium. The primary MR analysis was conducted using the inverse variance weighted (IVW) method, with the weighted median (WM) and MR-Egger models used as additional methods. Sensitivity analyses, including MR-PRESSO, radial regression and MR-Egger intercept were conducted to detect outliers and assess horizontal pleiotropy. We further utilized the leave-one-out analysis to assess the robustness of the results. Causal associations were considered significant based on false rate correction (FDR), specifically when the IVW method provided a pFDR < 0.05.

Results

Our results demonstrated that both white blood cell (WBC) count (OR = 1.50, 95% CI = 1.10-2.06, pFDR = 0.033, pIVW = 0.011) and lymphocyte count (OR = 1.50, 95% CI = 1.13-1.98, pFDR = 0.027, pIVW = 0.005) were causally associated with a higher risk of IgA nephropathy. Furthermore, WBC count was identified as a significant genetic risk factor for renal malignant neoplasms (OR = 1.23, 95% CI = 1.06-1.43, pFDR = 0.041, pIVW = 0.007). Additionally, an increased level of genetically predicted eosinophils was found to be causally associated with a higher risk of diabetic nephropathy (OR = 1.21, 95% CI = 1.08-1.36, pFDR = 0.007, pIVW = 0.001). No evidence of pleiotropy was determined.

Conclusion

Our findings provide evidence of causal associations of circulating WBC count, lymphocyte count and IgA nephropathy, WBC count and renal malignant neoplasms, and eosinophil count and diabetic nephropathy. These results have the potential to contribute to the development of novel diagnostic options and therapeutic strategies for renal disorders.

Early urinary biomarkers of diabetic nephropathy in type 1 diabetes mellitus show involvement of kallikrein-kinin system

BACKGROUND

Additional urinary biomarkers for diabetic nephropathy (DN) are needed, providing early and reliable diagnosis and new insights into its mechanisms. Rigorous selection criteria and homogeneous study population may improve reproducibility of the proteomic approach.

METHODS

Long-term type 1 diabetes patients without metabolic comorbidities were included, 11 with sustained microalbuminuria (MA) and 14 without MA (nMA). Morning urine proteins were precipitated and resolved by 2D electrophoresis. Principal component analysis (PCA) and Projection to latent structures discriminatory analysis (PLS-DA) were adopted to assess general data validity, to pick protein fractions for identification with mass spectrometry (MS), and to test predictive value of the resulting model.

RESULTS

Proteins (n = 113) detected in more than 90% patients were considered representative. Unsupervised PCA showed excellent natural data clustering without outliers. Protein spots reaching Variable Importance in Projection score above 1 in PLS (n = 42) were subjected to MS, yielding 33 positive identifications. The PLS model rebuilt with these proteins achieved accurate classification of all patients (R2X = 0.553, R2Y = 0.953, Q2 = 0.947). Thus, multiple earlier recognized biomarkers of DN were confirmed and several putative new biomarkers suggested. Among them, the highest significance was met in kininogen-1. Its activation products detected in nMA patients exceeded by an order of magnitude the amount found in MA patients.

CONCLUSIONS

Reducing metabolic complexity of the diseased and control groups by meticulous patients' selection allows to focus the biomarker search in DN. Suggested new biomarkers, particularly kininogen fragments, exhibit the highest degree of correlation with MA and substantiate validation in larger and more varied cohorts.

Role of HSP60 (HSPD1) in diabetes-induced renal tubular dysfunction: regulation of intracellular protein aggregation, ATP production, and oxidative stress

Because underlying mechanisms of diabetic nephropathy/tubulopathy remained poorly understood, we aimed to define a key protein involving in hyperglycemia-induced renal tubular dysfunction. All altered renal proteins identified from previous large-scale proteome studies were subjected to global protein network analysis, which revealed heat shock protein 60 (HSP60, also known as HSPD1) as the central node of protein-protein interactions. Functional validation was performed using small interfering RNA (siRNA) to knock down HSP60 (siHSP60). At 48 h after exposure to high glucose (HG) (25 mM), Madin-Darby canine kidney (MDCK) renal tubular cells transfected with controlled siRNA (siControl) had significantly increased level of HSP60 compared to normal glucose (NG) (5.5 mM), whereas siHSP60-transfected cells showed a dramatically decreased HSP60 level. siHSP60 modestly increased intracellular protein aggregates in both NG and HG conditions. Luciferin-luciferase assay showed that HG modestly increased intracellular ATP, and siHSP60 further enhanced such an increase. OxyBlot assay showed significantly increased level of oxidized proteins in HG-treated siControl-transfected cells, whereas siHSP60 caused marked increase of oxidized proteins under the NG condition. However, the siHSP60-induced accumulation of oxidized proteins was abolished by HG. In summary, our data demonstrated that HSP60 plays roles in regulation of intracellular protein aggregation, ATP production, and oxidative stress in renal tubular cells. Its involvement in HG-induced tubular cell dysfunction was most likely via regulation of intracellular ATP production.-Aluksanasuwan, S., Sueksakit, K., Fong-ngern, K., Thongboonkerd, V. Role of HSP60 (HSPD1) in diabetes-induced renal tubular dysfunction: regulation of intracellular protein aggregation, ATP production, and oxidative stress.

1,4-Dihydropyridine derivatives without Ca2+-antagonist activity up-regulate Psma6 mRNA expression in kidneys of intact and diabetic rats

Impaired degradation of proteins by the ubiquitin-proteasome system (UPS) is observed in numerous pathologies including diabetes mellitus (DM) and its complications. Dysregulation of proteasomal degradation might be because of altered expression of genes and proteins involved in the UPS. The search for novel compounds able to normalize expression of the UPS appears to be a topical problem. A novel group of 1,4-dihydropyridine (1,4-DHP) derivatives lacking Ca2+-antagonists activities, but capable to produce antidiabetic, antioxidant and DNA repair enhancing effects, were tested for ability to modify Psma6 mRNA expression levels in rat kidneys and blood in healthy animals and in rats with streptozotocin (STZ) induced DM. Psma6 gene was chosen for the study, as polymorphisms of its human analogue are associated with DM and cardiovascular diseases. 1,4-DHP derivatives (metcarbatone, etcarbatone, glutapyrone, J-9-125 and AV-153-Na) were administered per os for three days (0.05 mg/kg and/or 0.5 mg/kg). Psma6 gene expression levels were evaluated by quantitative PCR. Psma6 expression was higher in kidneys compared to blood. Induction of diabetes caused increase of Psma6 expression in kidneys, although it was not changed in blood. Several 1,4-DHP derivatives increased expression of the gene both in kidneys and blood of control and model animals, but greater impact was observed in kidneys. The observed effect might reflect coupling of antioxidant and proteolysis-promoting activities of the compounds.

Proteomic analysis of the kidney filtration barrier--Problems and perspectives

Diseases of the glomerular filter of the kidney are a leading cause of end-stage renal failure. The kidney filter is localized within the renal glomeruli, small microvascular units that are responsible for ultrafiltration of about 180 liters of primary urine every day. The renal filter consists of three layers, fenestrated endothelial cells, glomerular basement membrane, and the podocytes, terminally differentiated, arborized epithelial cells. This review demonstrates the use of proteomics to generate insights into the regulation of the renal filtration barrier at a molecular level. The advantages and disadvantages of different glomerular purification methods are examined, and the technical limitations that have been significantly improved by in silico or biochemical approaches are presented. We also comment on phosphoproteomic studies that have generated considerable molecular-level understanding of the physiological regulation of the kidney filter. Lastly, we conclude with an analysis of urinary exosomes as a potential filter-derived resource for the noninvasive discovery of glomerular disease mechanisms.