Regulation of PTEN/AKT/FAK pathways by PPARγ impacts on fibrosis in diabetic nephropathy

Renal tubular epithelial-to-mesenchymal transition (EMT) and tubulointerstitial fibrosis (TIF) are important pathological features of diabetic nephropathy (DN). However, the regulatory mechanism underlying EMT and TIF are still unclear. Previous studies showed that the decrease in the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) was closely related to the aggravation of DN, but no published study showed how PTEN participated in the regulation of EMT and TIF. In this study, the rat proximal tubular epithelial cells (NRK52E) and C57BL mice and human kidney tissues were used as the research objects to investigate the mechanism underlying the regulatory effect of peroxisome proliferator-activated receptors gamma (PPAR gamma) on PTEN and its influence on EMT and TIF, the regulation of PTEN's dual activity of lipid phosphatase/protein phosphatase by the serine threonine protein kinase B(AKT)/focal adhesion kinase (FAK) signaling pathway, and the role of PTEN in EMT and TIF. The results showed that PPAR gamma regulated the expression of PTEN at a transcriptional level and further regulated EMT and TIF. This dual activity could regulate the phosphorylation level of AKT and FAK and also affect FAK transcription. However, the 129 mutant of PTEN (PTEN-G129E) lost the lipid phosphatase activity, and its protein phosphatase activity was involved only in EMT and renal fibrosis through regulating FAK phosphorylation. This study systematically elucidated the role of PPAR gamma/PTEN/AKT/FAK signaling pathway in EMT and TIF during the pathogenesis of DN.