Introduction: Dietary bioactive compounds are increasingly recognized for their role in regulating epithelial homeostasis and preventing abnormal cell proliferation. Among them, polyphenol-rich byproducts of winemaking have demonstrated antiproliferative effects in various tissues, including the colon, by modulating oxidative stress, inflammation, and cell cycle control. Grape Antioxidant Dietary Fibre (GADF) is a natural product that combines high amounts of dietary fibre and phenolic antioxidants obtained by a patent procedure from red grape pomace (Vitis vinifera, var Cencibel). In this study, we studied GADF's effect on proximal colonic epithelium proliferation and its molecular mechanisms in healthy rats.
Methods: Male Wistar rats were randomly assigned to control (Standard diet) or GADF-fed groups (5% w/w GADF replacing cellulose in an isoenergetic diet) for four weeks. Proximal colonic tissues were collected, and cytosolic and nuclear extracts were obtained. Immunohistochemistry and Western blot were conducted to assess proliferation and cell cycle markers. All procedures were approved by the Animal Care Committee of Universidad Complutense de Madrid (EU Directive 86/609/EEC).
Results: A significantly lower percentage of proliferating cell nuclear antigen (PCNA)-positive nuclei in Lieberkühn’s crypts was observed in GADF-fed rats compared to controls (-30.71%, p<0,0001). GADF also induced a 24-fold increase in p53 phosphorylation at Ser392 (p < 0.0001), with localization in both the nucleus and cytoplasm. In parallel, GADF upregulated the expression of the cyclin-dependent kinase inhibitors p21^Cip1/Waf1 and p27^Kip1 by 35% and 25% (both p<0.001) and downregulated cyclin D1 and cyclin E by 26% and 17% (p<0.01), respectively.
Conclusions: This study provides novel insights into the molecular mechanisms by which GADF modulates epithelial cell dynamics in the healthy colon. By inducing a p53-dependent G1/S cell cycle arrest, GADF effectively limits epithelial proliferation, supporting its role as a promising chemopreventive dietary component for maintaining colonic health and reducing early risk factors associated with colorectal cancer.
