Osmolarity and Glucose Differentially Regulate Aldose Reductase Activity in Cultured Mouse Podocytes

Abstract

Podocyte injury is associated with progression of many renal diseases, including diabetic nephropathy. In this study we examined whether aldose reductase (AR), the enzyme implicated in diabetic complications in different tissues, is modulated by high glucose and osmolarity in podocyte cells. AR mRNA, protein expression, and activity were measured in mouse podocytes cultured in both normal and high glucose and osmolarity for 6 hours to 5 days. Hyperosmolarity acutely stimulated AR expression and activity, with subsequent increase of AR expression but decrease of activity. High glucose also elevated AR protein level; however, this was not accompanied by respective enzyme activation. Furthermore, high glucose appeared to counteract the osmolarity-dependent activation of AR. In conclusion, in podocytes AR is modulated by high glucose and increased osmolarity in a different manner. Posttranslational events may affect AR activity independent of enzyme protein amount. Activation of AR in podocytes may be implicated in diabetic podocytopathy.

Status and Trends of the Association Between Diabetic Nephropathy and Diabetic Retinopathy From 2000 to 2021: Bibliometric and Visual Analysis

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The A allele of the rs759853 single nucleotide polymorphism in the AKR1B1 gene confers risk for diabetic kidney disease in patients with type 2 diabetes from a Brazilian population

“…Lewko and cols. (34) reported that AKR1B1 gene and protein expressions were elevated in mouse podocytes cultured with high glucose compared to cells cultured under normal glucose concentration. In kidneys from patients with and without DM, AKR1B1 activity was higher in glomeruli and small arteries of those patients with DKD compared to the non-DKD group (35).…”

Angiotensin II Modulates Podocyte Glucose Transport

“…For Western blot analysis, 30 μg of total protein was subjected to 8% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE). Proteins were then transferred to polyvinylidene difluoride (PVDF) Immobilion membranes (Millipore, Bedford, MA, USA) by a semidry blotting system (Hoefer Inc, MA, USA) as described previously ( 29 ). Primary antibodies reactive with the insulin receptor β subunit (1:400, rabbit polyclonal, Santa Cruz Biotechnology Inc., CA, USA) and to α-smooth muscle actin (1:2000, mouse monoclonal, Sigma-Aldrich, Poland) were used with secondary antibodies conjugated with alkaline phosphatase (goat anti–rabbit IgG and goat anti-mouse IgG, respectively, Santa Cruz Biotechnology Inc.) The complexes were visualized with 5-bromo-chloro-3-indolyl phosphate (BCIP) and nitro blue tetrazolium (NBT; Sigma-Aldrich, Poland) and photographed with a UVP BioImaging GDS-8000 system (UVP Inc., Upland, CA), using LabWorks 4.0 Image Acquisition and Analysis Software.…”