Assessing the In Vitro Effects of Carrot Pomace Extract on Intestinal Epithelium Integrity and Functions

Carrot processing for juice generates substantial pomace residues rich in bioactive compounds, which represent both an environmental challenge and an unexploited resource. This study investigated the protective effects of a polyphenolic extract derived from carrot pomace (CP) against Escherichia coli lipopolysaccharide (LPS)-induced damage. For that, we used IPEC-1 (Intestinal Porcine Epithelial Cells) as an in vitro model of the intestinal epithelium. The total phenolic content of the CP polyphenolic extract (CPE) was 1.017 mg GAE/mL, with flavan-3-ols (epicatechin, catechin, epigallocatechin) accounting for 71.3% of that value. Before being exposed to LPS (10 μg/mL) for 24 h, the cells were pre-treated with CP extract (20.34 µg and 10.17 µg polyphenols/mL of extract corresponding to 1/50 and 1/100 dilution) for 4 h. Epithelial renewal (cell viability, cell proliferation and apoptosis), monolayer/barrier integrity (TEER, FD4 permeability, LDH release), as well as epithelial functionality (synthesis of pro-inflammatory cytokines: TNF-α, IL-1β, IL-6, reactive oxygen species (ROS), nitric oxide (NO) production), MAPK signalling and mitochondrial morphology and function were assessed. The results showed that CP extract had no cytotoxic effects and successfully counteracted LPS-induced loss of cell viability and proliferation. The pre-treatment with CPE at both dilutions significantly reduced LPS-induced apoptosis and cell death. Barrier integrity was preserved with TEER values maintained near baseline: -0.43% and -0.24% for 1/50 and 1/100 dilutions of CPE vs. -53.47% at 72 h for LPS alone, and paracellular FD4 passage was restored to control levels. At the molecular level, CP extract reduced pro-inflammatory cytokine gene expression (IL-6 by 40%, TNF-α by 50-56%) and suppressed LPS-induced MAPK activation by 62.9% and 46.5%, for 1/50 and 1/100 dilutions of CPE, respectively. The pre-treatment of cells with CP extract normalised LPS-induced ROS production and protected mitochondrial morphology and function. These in vitro findings demonstrate that CP extract exerts a protective effect on intestinal epithelial cells, acting through anti-inflammatory, antioxidant and barrier-preserving mechanisms. This supports the hypothesis for valorisation of carrot agro-industrial by-products as functional feed additives for promoting intestinal health. Further in vivo studies are needed to validate this hypothesis and to establish the concentration/rate of inclusion of carrot by-products to achieve the maximal positive effects.