We previously reported that Hibiscus sabdariffa polyphenol extracts (HPE) are beneficial for diabetic nephropathy. Since an epithelial to mesenchymal transition (EMT) is critical in renal fibrosis, the present study aimed to investigate whether HPE could prevent EMT of tubular cells. Treatment of HPE reduced angiotensin II receptors (AT)-1 and transforming growth factor β1 (TGF-β1) evoked by high glucose and recovered the increased vimentin and decreased E-cadherin. HPE decreased fibronectin, thus avoiding EMT and accompanying fibrosis. AT-1 was upstream to TGF-β1, while there were recruitment signals between AT-1 and TGF-β1. Scan electron microscopy (SEM) and immunohistochemistry (IHC) revealed that the interacting filaments of tubular cells disappeared when treated with high glucose, and type IV collagen of tubulointerstitial decreased in diabetic kidneys. Treatment of HPE recovered morphological changes of cell junction and basement membrane. We suggest that HPE has the potential to be an adjuvant for diabetic nephropathy by regulating AT-1/TGF-β1 and EMT.
