Interaction between carotenoids and the intestinal microbiota and its impact on functinal properties

Abstract

Noncommunicable diseases (NCDs) are responsible for 41 million deaths annually and can be linked to unhealthy dietary habits, prompting various nutrition and health organizations to advocate for regular fruit and vegetable consumption. Carotenoids and their metabolites are associated with positive health benefits and are the most prevalent lipid-soluble phytochemicals in the human diet, found in small amounts in human blood, and susceptible to oxidation and isomerization reactions. In nature, carotenoids have reduced bioavailability, leading to their accumulation in the colon, which is colonized by a diverse population of microorganisms playing crucial roles in digestion, and maintaining intestinal health. The bioavailability of these compounds can be influenced by various factors, highlighting the significance of the intestinal microbiota in their absorption and metabolism. The diet plays a fundamental role in the regulation of the microbiota, which can affect the effectiveness of carotenoids' action. However, the specific interaction between carotenoids and intestinal microbiota is not well-documented yet and lacks clear evidence. To better understand the possible interaction between carotenoids and the intestinal microbiota, three carotenoids (beta()-carotene, lutein, and lycopene), a mixture of these pigments, and the algae Osmundea pinnatifida (as a source of carotenoids) were subjected to an in vitro simulation of the gastrointestinal digestion. After the characterization of the impact of this process on each tested condition, the digested carotenoids were evaluated on fresh human faecal samples from volunteer donors via fermentation to assess the effect on the intestinal microbiota's metabolic and population dynamics. The digestion of the carotenoids in the tested conditions, in a general way, originated different types of carotenoids along the gastrointestinal tract (GIT), being -carotene the only condition in which was identified the absorption of a carotene (2.49%). No carotenoids were detected in O. pinnatifida, which suggests that in a complex matrix like algae, carotenoids may be compromised in their bioaccessibility without prior lysis treatment of the algae. The intestinal microbiota composition was analysed, being demonstrated that the Bacteroidota, Bacillota, Pseudomonadota, and Actinomycetota are the main phyla present and that carotenoids stimulated the increase of the relative abundance (RA) of Lachnospiraceae family and the decrease of Lactobacillus, Enterococcus, Streptococcus and Bifidobacterium genera which was consistent with the previous studies. In general, the production of short-chain fatty acids (SCFAs) was also stimulated in the presence of carotenoids, which once again corroborates results obtained in previous studies and supports the positive role of these pigments in intestinal health. In terms of functional properties, the tested carotenoid solutions presented considerable antioxidant and antidiabetic activities, being the highest values obtained for lutein in the fraction absorbed and for the mixture of carotenoids in the fraction retained in the intestine. Finally, it was demonstrated the antimutagenic effect of these carotenoid samples regardless of the concentration and also the absence of cytotoxicity even when applied at the highest concentrations.

Date of Award	10 Oct 2023
Original language	English
Awarding Institution	Universidade Católica Portuguesa
Supervisor	Marta Coelho (Supervisor), Ana Maria Gomes (Co-Supervisor) & Maria Manuela Pintado (Co-Supervisor)