Obesity-related glomerulopathy is associated with elevated WT1 expression in podocytes.

BACKGROUND: The prevalence of obesity is increasing worldwide at an alarming rate. In addition to the increased incidence of cardiovascular and metabolic diseases, obesity is the most potent risk factor for developing chronic kidney disease (CKD). Although systemic events such as hemodynamic factors, metabolic effects, and lipotoxicity were implicated in the pathophysiology of obesity-related glomerulopathy (ORG) and kidney dysfunction, the precise mechanisms underlying the association between obesity and CKD remain unexplored. METHODS: In this study, we employed spontaneous WNIN/Ob rats to investigate the molecular events that promote ORG. Further, we fed a high-fat diet to mice and analyzed the incidence of ORG. Kidney functional parameters, micro-anatomical manifestations, and podocyte morphology were investigated in both experimental animal models. Gene expression analysis in the rodents was compared with human subjects by data mining using Nephroseq and Kidney Precision Medicine Project database. RESULTS: WNIN/Ob rats were presented with proteinuria and several glomerular deformities, such as adaptive glomerulosclerosis, decreased expression of podocyte-specific markers, and effacement of podocyte foot process. Similarly, high-fat-fed mice also showed glomerular injury and proteinuria. Both experimental animal models showed increased expression of podocyte-specific transcription factor WT1. The altered expression of putative targets of WT1 such as E-cadherin, podocin (reduced), and α-SMA (increased) suggests elevated expression of WT1 in podocytes elicits mesenchymal phenotype. Curated data from CKD patients revealed increased expression of WT1 in the podocytes and its precursors, parietal epithelial cells. CONCLUSION: WT1 is crucial during nephron development and has minimal expression in adult podocytes. Our study discovered elevated expression of WT1 in podocytes in obesity settings. Our analysis suggests a novel function for WT1 in the pathogenesis of ORG; however, the precise mechanism of WT1 induction and its involvement in podocyte pathobiology needs further investigation.

Age-related neuronal damage by advanced glycation end products through altered proteostasis.

Aging is a main risk factor for many diseases including neurodegenerative disorders. Numerous theories and mechanisms including accumulation of advanced glycation end products (AGEs) have been put forward in explaining brain aging. However, a focused study on the status of AGEs in the brain during progressive aging in connection with interrelated cellular processes like ubiquitin-proteasome system (UPS), unfolded protein response, autophagy-lysosome system and apoptosis is lacking. In this study, we investigated the levels of AGEs in the brain of 5-, 10-, 15- and 20-months old WNIN rats. Endoplasmic reticulum (ER) stress response, UPS components, autophagy flux, neurotrophic and presynaptic markers along with cell death markers were analyzed by immunoblotting. The neuronal architecture was analyzed by H&E and Nissl staining. The results demonstrated progressive accumulation of AGEs in the brain during aging. Adaptive ER stress response was observed by 10-months while maladaptive ER stress response was seen at 15- and 20-months of age along with impaired UPS and autophagy, and perturbations in neuronal growth factors. All these disturbances intensify with age to further exaggerate cell death mechanisms. There was a shrinkage of the cell size with aging and Congo-red staining revealed ß-amyloid accumulation in higher ages. Together these results suggest that progressive accumulation of AGEs with aging in the brain may lead to neuronal damage by affecting ER homeostasis, UPS, autophagic flux, and neuronal growth factors.

Circulating levels of Hsp27 in microvascular complications of diabetes: Prospects as a biomarker of diabetic nephropathy.

AIM: Heat shock protein 27 (Hsp27) is a small heat shock protein known to protect the cells from apoptosis under stress. In the present study, we determined the plasma Hsp27 levels in type 2 diabetes subjects without and with microvascular complications- diabetic retinopathy (DRe), diabetic nephropathy (DNe), and diabetic neuropathy (DNu) to understand if it could serve as a marker for these complications. METHODS: This is a hospital-based case-control study with 754 subjects including 247 controls, 195 subjects with diabetes, 123 with DRe, 80 with DNe and 109 with DNu. Plasma Hsp27 levels were measured by ELISA. RESULTS: The mean plasma Hsp27 was higher in the DNe group (631.5±355.2) compared to the control (496.55±308.54), diabetes (523.41±371.01), DRe (494.60±391.48) and DNu (455.21±319.74) groups with a p-value of 0.018. Receiver operating characteristic (ROC) curve analysis of Hsp27 in DNe group showed an area under the curve (AUC) of 0.617. Spearman correlation analysis shows a positive correlation of plasma Hsp27 with serum creatinine (p=0.053, r-value 0.083). Gender, age and BMI did not affect the plasma Hsp27 levels. CONCLUSION: The plasma Hsp27 levels in the DNe group are higher compared to the control and other complications, thereby it could be explored to be used as a potential biomarker of DNe.

Ellagic acid inhibits non-enzymatic glycation and prevents proteinuria in diabetic rats.

The formation of advanced glycation end products (AGEs) is a characteristic feature of diabetic tissues and accumulation of these products has been implicated in the pathogenesis of micro- and macrovascular complications of diabetes including diabetic nephropathy (DN). Compelling evidence suggests that AGEs mediate progressive alteration in the renal architecture and loss of renal function whereas inhibitors of AGEs prevent the progression of experimental DN. We have investigated the potential of ellagic acid (EA), a polyphenol present abundantly in fruits and vegetables, to prevent in vivo accumulation of AGE and to ameliorate renal changes in diabetic rats. Streptozotocin-induced diabetic rats were fed with either 0.2% or 2% of EA in the diet for 12 weeks. Dietary supplementation of EA to diabetic rats prevented the glycation mediated RBC-IgG-cross-links and HbA1c accumulation. EA inhibited the accumulation of N-carboxymethyl lysine (CML), a predominant AGE in the diabetic kidney. Further, EA also prevented the AGE-mediated loss of expression of podocyte slit diaphragm proteins: nephrin and podocin. By inhibiting CML formation, EA improved renal function in rats as evidenced by urinary albumin and creatinine levels. In conclusion, EA inhibited AGE accumulation in the diabetic rat kidney and ameliorated AGE-mediated pathogenesis of DN.

Hyperglycemia induced expression, phosphorylation, and translocation of αB-crystallin in rat skeletal muscle.

αB-Crystallin (αBC) is a member of the small heat shock protein family that responds to a variety of stress and prevents the aggregation of partially unfolded proteins. Chronic hyperglycemia created during diabetes results in skeletal muscle atrophy and leads to diabetic myopathy. The aim of this study was to investigate the role of αBC under chronic hyperglycemia in rat skeletal muscle. Diabetes was induced in Wistar rats by a single i.p injection of streptozotocin and maintained for a period of 12 weeks at the end of which the animals were sacrificed and the muscle was collected. The protein levels of αBC and its phosphorylation status in gastrocnemius muscle were analyzed by immunoblotting. The translocation of phosphorylated αBC was analyzed by detergent solubility assay, co-immunoprecipitation (Co-IP), and immunohistochemistry. The cell death was analyzed by TUNEL assay and by apoptotic markers. The interaction of αBC with Bax was analyzed by Co-IP. Chronic hyperglycemia significantly increased the protein levels of αBC and its phosphorylation at S59 by activation of p38 mitogen-activated protein kinase (p38MAPK) and at S45 by activation of the extracellular regulated protein kinase 1/2 (ERK1/2). Further, phosphorylated αBC translocated and interacted with desmin indicating that phosphorylated αBC forms might be involved in protection of sarcomere structures from disruption in chronic hyperglycemia. Further, Co-IP studies showed an impaired interaction of αBC with Bax which could be one of the possible factors for increased cell death as evidenced by TUNEL assay in diabetic muscle. These results suggest that an increased expression, phosphorylation, translocation of αBC, and its involvement in apoptosis might play a significant role in maintenance of cytoskeletal architecture and protection of cells from apoptosis in diabetic skeletal muscle.