WNT Inhibitory Activity of Malus Pumila miller cv Annurca and Malus domestica cv Limoncella Apple Extracts on Human Colon-Rectal Cells Carrying Familial Adenomatous Polyposis Mutations

Abstract

Inhibitors of the Wingless-related Integration site (WNT)/β-catenin pathway have recently been under consideration as potential chemopreventive agents against Familial Adenomatous Polyposis (FAP). This autosomal-dominant syndrome is caused by germline mutations in the gene coding for the protein APC and leads to hyperactivation of the WNT/β-catenin signaling pathway, uncontrolled intestinal cell proliferation and formation of adenocarcinomas. The aim of the present work was to: (i) test, on in vitro cultures of cells carrying FAP mutations and on ex vivo biopsies of FAP patients, the WNT inhibitory activity of extracts from two common southern Italian apples, Malus pumila Miller cv. ‘Annurca’ and Malus domestica cv ‘Limoncella’; (ii) identify the mechanisms underpinning their activities and; (iii) evaluate their potency upon gastrointestinal digestion. We here show that both Annurca and Limoncella apple extracts act as WNT inhibitors, mostly thanks to their polyphenolic contents. They inhibit the pathway in colon cells carrying FAP mutations with active dilutions falling in ranges close to consumer-relevant concentrations. Food-grade manufacturing of apple extracts increases their WNT inhibitory activity as result of the conversion of quercetin glycosides into the aglycone quercetin, a potent WNT inhibitor absent in the fresh fruit extract. However, in vitro simulated gastrointestinal digestion severely affected WNT inhibitory activity of apple extracts, as result of a loss of polyphenols. In conclusion, our results show that apple extracts inhibit the WNT pathway in colon cells carrying FAP mutations and represent a potential nutraceutical alternative for the treatment of this pathology. Enteric coating is advisable to preserve the activity of the extracts in the colon-rectal section of the digestive tract.

Annurca Apple Polyphenols Ignite Keratin Production in Hair Follicles by Inhibiting the Pentose Phosphate Pathway and Amino Acid Oxidation

“…The Polyphenolic fraction of Annurca contains hundreds of different metabolites [ 26 , 53 ]. The activity of most of the polyphenols contained in AAE is drastically reduced when they are isolated from the extract and used as pure molecules [ 54 ]. AAE phytocomplex seems to represent the perfect environment where polyphenols can exert their biological function.…”

“…The phytocomplex probably acts chemically, by protecting apple metabolites from oxidation and degradation. Recent evidences may suggest that the phytocomplex may as well act biologically by activating and deactivating specific cellular pathways, ultimately augmenting the efficacy of the active metabolites [ 54 ]. In this scenario, the need to follow hundreds of compounds simultaneously increases the complexity of any study aiming at the identification of the mechanism of action of nutraceuticals.…”

Induction of Hair Keratins Expression by an Annurca Apple-Based Nutraceutical Formulation in Human Follicular Cells

“…As protein oxidation can be associated with an increased susceptibility to proteases, the antioxidant potential of AMS can be an important player for the keratinization process [52]. Moreover, based primarily on the polyphenolic pool of the Annurca apple extract, it has recently been suggested that there is a biological interference with the WNT signaling, which deserves further investigations according to its critical role in hair cell specification and development [53].…”

Chemopreventive Potential of Apple Pulp Callus Against Colorectal Cancer Cell Proliferation and Tumorigenesis

“…6,7 Apples or apple products (apple juice, extracts, dehydrated apples) could exert biological effects to prevent or reduce the proliferation of colorectal cancer, both in in vitro and in vivo models and in case-control studies, by which the risk of colorectal cancer risk resulted inversely correlated with the number of consumed apples. [8][9][10][11][12][13] Those beneficial effects have been attributed to the apple's bioactive molecule mixture, which is more effective than a single bioactive molecule in exerting their biological activities. [14][15][16] We have demonstrated that a specific apple is particularly rich in polyphenols and that its juice leads to the strongest antiproliferative activity against breast cancer cells, in comparison to the five other apple varieties, suggesting that polyphenols play an important role.…”