Correlation between faecal microbial community structure and cholesterol-to-coprostanol conversion in the human gut

Abstract

Intensity of the cholesterol-to-coprostanol conversion in the intestine, as assessed by the coprostanol-to-cholesterol ratio in faeces, was found highly variable among 15 human volunteers, ranging from absent to almost complete cholesterol conversion. The number of coprostanoligenic bacteria in the same faecal samples, as estimated by the most probable number method, was found to be less than 10(6) cellsg-1 of fresh stools in the low-to-inefficient converters and at least 10(8) cellsg-1 of fresh stools in the highest converters, indicating that the population level of cultivable faecal coprostanoligenic bacteria correlated with the intensity of cholesterol-to-coprostanol conversion in the human gut. Microbial communities of the samples were profiled by temporal temperature gradient gel electrophoresis (TTGE) of bacterial 16S rRNA gene amplicons. Dendrogram analysis of the TTGE profiles using the Pearson product moment correlation coefficient and a unweighted pair group method with arithmetic averages (UPGMA) algorithm clearly separated banding patterns from low-to-inefficient and high converters in two different clusters suggesting a relationship between TTGE profiles and coprostanoligenic activity. Principal components analysis further demonstrated that a large subset of bands rather than some individual bands contributed to this clustering.

Differences in gut microbiota activity (antimicrobials, potential mutagens, and sterols) according to diet

“…Higher amounts of lactic acid bacteria (lactobacilli+bifi dobacteria 10 8 -10 10 cell/g faeces) were observed in case of samples with higher sterol conversion (conversion 85-90%). This fi nding agrees with the data in literature that the level of cholesterol reducing bacteria must be at least 10 6 cell/g of wet stool for effi cient conversion of cholesterol in the human gut, while a population of more than 10 8 cell/g of wet stool leads to nearly complete conversion (VEIGA et al, 2005). Taking into account that most of isolated bacterial converters belong to Bacteroidetes, whose number was low (on average 10 3 cell/g faeces) in studied faecal samples, these data correlate well.…”

Bacteroides sp. Strain D8, the First Cholesterol-Reducing Bacterium Isolated from Human Feces

“…In a previous study, we established that the population level of cultivable fecal coprostanoligenic bacteria correlated with the intensity of cholesterol-to-coprostanol conversion in the human gut. Indeed, we found that populations containing less than 10 6 , between 10 6 and 10 8 , and more than 10 8 coprostanoligenic bacteria/g (wet weight) of stool are associated with inefficient, intermediate, and high cholesterol conversion patterns, respectively (38). In the present study, fecal communities belonging to the Bacteroides-Porphyromonas-Prevotella group from 11 humans with different cholesterol conversion patterns were profiled by TTGE of amplified 16S rRNA gene fragments in order to estimate the incidence of Bacteroides sp.…”

“…Standard tests of cholesterol-to-coprostanol reducing activity were carried out in standard brain medium (SBM) (pH 7.2 to 7.4), which was derived from the medium described by Brinkley et al (7) and contained the following components (per liter): 20 g lyophilized calf brain, 10 g Casitone, 10 g yeast extract, 5 g KH 2 PO 4 , and 0.5 g sodium thioglycolate. Where indicated below, activity was also assayed in a basal cholesterol (BC) medium (pH 7.5) derived from the medium described by Ren et al (31) and containing (per liter) 10 g Casitone, 10 g yeast extract, 5 g sodium pyruvate, 0.5 g sodium thioglycolate, 1 g CaCl 2 · 2H 2 O, 0.2 g cholesterol, and 1.0 g lecithin, as well as in brain heart infusion-yeast extract-hemin (BHI-YH) medium (pH 7.4) enriched with cholesterol (38) and containing (per liter) 10 g brain heart infusion (Difco), 10 g yeast extract, 10 ml of a 0.1% hemin solution (Sigma-Aldrich Chimie), 0.5 g L-cysteine (Sigma-Aldrich Chimie), 0.2 g cholesterol, and 1 g lecithin. Agar (14 g/liter) was added to BHI-YH medium when required.…”

“…Total DNA was extracted for PCRtemporal temperature gradient gel electrophoresis (TTGE) as previously described (15) from 0.2-g frozen and thawed stool aliquots which had been obtained from 11 healthy human subjects and for which we had previously assessed the population level of cultivable coprostanoligenic bacteria and the cholesterolto-coprostanol ratio (38). The concentration and integrity of the nucleic acids were determined visually by electrophoresis on a 1% agarose gel containing ethidium bromide.…”

“…1) by intestinal microorganisms was established during the 1930s (8). It was subsequently reported that the efficiency of microbial cholesterol-to-coprostanol conversion in human populations was bimodal, with a majority of high converters and a minority of low or inefficient converters (38,40). This bacterial metabolism proceeds according to two pathways (4,31), one involving the intermediate formation of 4-cholesten-3-one and coprostanone and the other involving the direct conversion of cholesterol into coprostanol through reduction of the 5-6 double bond.…”