Intestinal metabolic activity of mice fed a high-fat diet supplemented with wheat bran and Lactobacillus fermentum

Abstract

In recent years there has been an increase of people diagnosed metabolic syndrome (MS), due to a greater consumption of high-fat diets and a sedentary lifestyle, among other factors. Incorporation of bran fibers and probiotics in diet modifies intestinal microbiota (IM) and exerts beneficial effects on the health of individuals. Lactobacillus fermentum CRL1446 (Lf) is a strain with feruloyl esterase (FE) activity, which increases the bioavailability of ferulic acid (FA) at the intestinal level. FA is a phenolic compound present in vegetable fibers (esterified) with proven antioxidant, hypoglycemic and lipid-lowering activity, which can be used in different metabolic diseases. This work aimed to evaluate the effect of oral administration of Lf on IM and intestinal metabolic activity of mice with MS induced by a high-fat diet and supplemented with wheat bran (HFD+WB). Male Swiss albino mice 6 weeks old (N=24) were separated into 3 groups and fed for 14 weeks. Groups were as follows: (1) Control group, mice receiving water and normal diet; (2) MS group, mice receiving water and HFD+WB; (3) MS+Lf group, mice receiving Lf suspension (dose: 108 cells/day) and HFD+WB. Stools from all groups were stored for metagenomics analysis. Animals were sacrificed and intestines were removed. Microbial metabolic activity was evaluated in colon contents by determining: (1) Intestinal FE activity: methylferulate was used as substrate and the FA released was quantified by HPLC; (2) Presence of metabolites derived from FA: detection was carried out by HPLC-MS; (3) Short-chain fatty acids (SCFA): acetic, propionic and butyric acids were quantified by HPLC. Relative abundance of Bacteroidetes was lower in MS group (31.2%) with respect to control group (85.8%), while in MS+Lf group Bacteroidetes increased (59.05%) compared to MS group. On the other hand, the proportion of Firmicutes was 12.75% in control group and it increased in MS group (55.05%); however, in MS+Lf group it was observed a decreased abundance of Firmicutes (36.05%). Intestinal FE activity was reduced (42%) in MS group compared to control group. Supplementation with Lf increased intestinal FE activity in MS+Lf group by 46%, compared to MS group. In all groups, dihydroferulic acid, 3,4-dihydroxyphenylpropionic acid and 3-hydroxyphenylpropionic acid (HPPA) were detected. A lower abundance of HPPA was observed in MS group compared to control, and an increase was found in MS+Lf group. Results showed a reduction in levels of all SCFA in MS group with respect to control. MS+Lf group showed no differences in acetic and propionic acid concentrations with respect to MS group, but an increase in concentration of butyric acid was observed. Results obtained suggest that supplementation with Lf enhanced the beneficial effects of a diet rich in bran, increasing the microbial metabolic activity at intestinal level in individuals suffering MS.