Relationship Between Dietary Sterols and Gut Microbiota: A Review

Abstract

Cholesterol intestinal absorption differs markedly from that of plant sterols; whereas the cholesterol absorption rate is high (30–60%) for total plant sterols it is low (2–3%). Non‐absorbed sterols reach the colon, where the microbiota interacts with them. Non‐absorbed cholesterol biotransformation has been widely studied by in vitro fermentation assays using gut microbiota from human feces and pure cultures of enteric microorganisms. A great variety of sterols and its metabolites have been detected, which allows establishing two pathways for cholesterol microbial degradation to coprostanol. However, biotransformation studies of plant sterols are scarce and its microbial transformation pathway remains to be fully clarified. Furthermore, the sterol contents in feces are highly variable among individuals, due to specific microbiota and especially dietary factors. However, no standardized methodology has been developed for sterols and their metabolites determination in feces. Studies on sterol excretion values, microbial transformation, and sterol determination methodology have been reviewed. Given that cholesterol metabolites can contribute to the development of colon cancer and that information about plant sterols biotransformation is scarce, this review contributes to improve the knowledge of the sterol implication in the gut microbiota and of PS impact in the colonic microbiota metabolization of cholesterol. Practical Applications: It has been suggested that the metabolites produced during the biotransformation of cholesterol have pro‐carcinogenic activity within colon. In addition, it has been indicated that the intake of high doses of plant sterols can attenuate or decrease this biotransformation. However, it is still unknown if the microbial metabolites of plant sterols have the same effect as those of animal origin. In order to shed light on the aforementioned aspects, all the information about the dietary sterols biotransformation and their impact on gut microbiota have been compiled. In addition, the sterols contents in feces and their methodologic analysis have also been reviewed. This review offers a broad view on the interaction between dietary sterols and gut microbiota, which can help to the better understand the relationship between microbiota and sterols for future research studies. This review presents the impact of dietary sterol on gut microbiota and microbial transformation of dietary sterols.

Gut microbes from the phylogenetically diverse genusEubacteriumand their various contributions to gut health

“…[158][159][160] An additional third pathway has also been identified which involves isomerization of cholesterol to allocholesterol, which can be reduced to coprostanol by Eubacterium ATCC21-403 and 408 species. 161 The final pathway is, however, poorly studied.…”

Microbial Reduction of Cholesterol to Coprostanol: An Old Concept and New Insights

“…The mechanism of cholesterol conversion to coprostanol was investigated and three major pathways were proposed [38,[55][56][57][58]. The first one is a direct, stereospecific reduction of the 5,6-double bond of cholesterol, without an intermediate formation of a ketone at C3 (Figure 2) [59,60].…”

“…D8) incubated with labeled cholesterol allowed for the production of cholestenone and coprostanone intermediates, demonstrating that this microbial pathway involved at least three steps [45,61,62]. The third pathway consisted of the isomerization of cholesterol to allocholesterol, which can be reduced to coprostanol by Eubacterium ATCC21, 408, and 403 species [38,57,58]. However, few data exist regarding this last bacterial metabolic pathway.…”

Impact of a Plant Sterol- and Galactooligosaccharide-Enriched Beverage on Colonic Metabolism and Gut Microbiota Composition Using anIn VitroDynamic Model

“…The relative abundance of the genera during the fermentation of the beverage is shown in intermediates. 12 Besides, a direct pathway has been suggested for coprostanol formation. 37 In the present study, the non-detection of sterol intermediate metabolites .…”

“…Eubacterium have only been reported, in the studies carried out several years ago with isolated cultures, to be cholesterol-reducing bacteria related to the direct as well as indirect routes for cholesterol metabolism. 12,[41][42][43] An absence of Eubacterium spp., the only species associated with the PS biotransformation pathway, 12,44 was observed in the present study, being suggestive of the involvement of other bacterial species in the PS metabolization pathway.…”