Activated YAP causes renal damage of type 2 diabetic nephropathy

Yes-associated protein (YAP) is a critical factor of Hippo pathway. It can control organ size, regulate proliferation, differentiation, and apoptosis of cells, and mediate epithelial-mesenchymal transition and cell contact inhibition. It has gradually become a hot spot in the field of diabetic nephropathy (DN). Tea domain (TEAD) is a factor with a deoxyribose nucleic acid (DNA) binding domain, which combines with activated YAP to control the expression of their important target factor - connective tissue growth factor (CTGF).

We have investigated the role of YAP in type 2 diabetic nephropathy and evaluated the correlation between YAP and the progress of type 2 diabetic nephropathy. We have detected the expression of YAP, TEAD and CTGF in normal people (n=10) and patients with DN (n=51) by immunohistochemical and immunofluorescence staining and evaluated the relationship among clinical, pathologic data and YAP expression in type 2 diabetic nephropathy.

In kidneys of type 2 diabetic nephropathy, YAP, TEAD and CTGF were highly expressed in the nucleus of glomerular podocytes. In those healthy kidneys, however, all three of the above factors were mainly expressed in cytoplasm. Furthermore, the high expression of YAP in DN had relevance to increasing systolic blood pressure (SBP) (r=0.484, p=0.019), blood urea nitrogen (BUN) (r=0.522, p=0.032), creatinine (Cr) (r=0.496, p=0.031), progression of DN stage (r=0.647, p=0.001) and progression of DN pathologic classification (r=0.298, p=0.033). In addition, decreasing serum albumin (SAlb) (r=-0.656, p=0.001) and estimated glomerular filtration rate (eGFR) (r=-0.607, p=0.006) were also correlated with the high expression of YAP in DN.

High expression of YAP, TEAD and CTGF in kidney tissues suggested that YAP played a significant role in the renal damage of type 2 diabetic nephropathy. YAP that is correlated with SBP, BUN, Cr, DN stage, DN pathologic classification, SAlb and eGFR, suggested that inhibition of the activity of YAP might have the effect in delaying DN progression.