Modulation of human intestinal microbiota in a clinical trial by consumption of a ß-D-glucan-enriched extract obtained from Lentinula edodes.

PURPOSE: The aim of this study was to evaluate the hypocholesterolemic, immune- and microbiota-modulatory effect of a mushroom extract in hypercholesterolemic subjects. METHODS: A randomized, controlled, double-blind, and parallel clinical trial was carried out with subjects from 18 to 65 years old (n = 52) with untreated mild hypercholesterolemia. Volunteers consumed a ß-D-glucan-enriched (BGE) mixture (10.4 g/day) obtained from shiitake mushrooms (Lentinula edodes) ensuring a 3.5 g/day of fungal ß-D-glucans or a placebo incorporated in three different commercial creams. RESULTS: This mixture showed hypocholesterolemic activities in vitro and in animal studies. After eight weeks intervention, no significant differences in lipid- or cholesterol-related parameters were found compared to placebo subjects as well as before and after the BGE mixture administration. No inflammatory or immunomodulatory responses were noticed and no changes in IL-1ß, IL-6, TNF-α or oxLDL were recorded. However, consumption of the BGE mixture was safe and managed to achieve the dietary fibre intake recommended as cardiovascular protective diet. Moreover, the BGE mixture modulated the colonic microbiota differently compared to placebo. Microbial community composition varied from before to after the intervention with several genera being positively or negatively correlated with some biomarkers related to cholesterol metabolism. CONCLUSION: These results suggested a relation between cholesterol metabolism, microbiota and BGE administration. Nevertheless, the precise significance of this differential modulation was not fully elucidated and requires further studies.

Effect of Selenium-Enriched Agaricus bisporus (Higher Basidiomycetes) Extracts, Obtained by Pressurized Water Extraction, on the Expression of Cholesterol Homeostasis Related Genes by Low-Density Array.

Culinary-medicinal mushrooms are able to lower blood cholesterol levels in animal models by different mechanisms. They might impair the endogenous cholesterol synthesis and exogenous cholesterol absorption during digestion. Mushroom extracts, obtained using pressurized water extractions (PWE) from Agaricus bisporus basidiomes, supplemented or not supplemented with selenium, were applied to HepG2 cell cultures to study the expression of 19 genes related to cholesterol homeostasis by low-density arrays (LDA). Only the PWE fractions obtained at 25°C showed 3-hydroxy-3-methylglutaryl-CoA reductase (HMGCR) inhibitory activity. Besides the enzymatic inhibition, PWE extracts may downregulate some of the key genes involved in the cholesterol homeostasis, such as the squalene synthase gene (FDFT1), since its mRNA expression falls by one third of its initial value. In summary, A. bisporus extracts may also modulate biological cholesterol levels by molecular mechanisms further than the enzymatic way previously reported.