Grape antioxidant dietary fibre regulates intrinsic/extrinsic caspase activity balance and epithelial homeostasis in the colon

Background and Aim: Grape antioxidant dietary fibre (GADF) is a bioactive compound obtained from grape by-products, containing dietary fibre and polyphenols with antioxidant and biological activities. Previous studies have shown beneficial effects of GADF on intestinal health, including modulation of oxidative status, epithelial turnover and barrier function. As apoptosis is essential for epithelial renewal but excessive activation may impair epithelial integrity, this study aimed to investigate the effect of GADF supplementation on the balance between intrinsic and extrinsic apoptotic pathways and its association with epithelial apoptosis and mucosal integrity.

Methods: Animals were supplemented with GADF for 4 weeks. Proximal colon samples were collected for histological and molecular analyses. Apoptosis was evaluated by TUNEL staining, while mucosal architecture was assessed by H&E and PAS staining. Caspase-9 and caspase-8 activities were analysed, and the intrinsic/extrinsic apoptotic balance was calculated as ln(caspase-9/caspase-8). Statistical analyses included unpaired two-tailed Student’s t-test or Mann–Whitney U test, as appropriate. Pearson’s correlation coefficient was used for parametric correlations.

Results: GADF markedly reduced the intrinsic/extrinsic caspase activity balance, decreasing the caspase-9/caspase-8 ratio by 80.6% (p<0.001), indicating a lower relative contribution of intrinsic apoptotic signalling. This shift was accompanied by a 56.4% reduction in TUNEL-positive cells (p<0.01) and increased PAS staining (+21.9%, p<0.01), suggesting improved mucosal functional features. Mucosal thickness decreased by 14.4% (p<0.001). Caspase activity balance correlated with epithelial apoptosis and mucosal functional parameters, but not with mucosal thickness.

Conclusions: GADF preferentially modulates intrinsic apoptotic signalling by reducing the caspase-9/caspase-8 activity balance. This apoptotic reprogramming is associated with reduced epithelial apoptosis and preservation of mucosal functional features, supporting coordinated regulation of cell death and intestinal homeostasis