Production of conjugated linoleic acid (CLA)
by the human gut microbiota: effect of inulin on microbial
composition and CLA concentration in a human intestinal model
Ilaria Carafa
1, Domenico Masuero
1, Urska Vrhovsek
1, Giovanni Bittante
2, Elena Franciosi
1, Kieran M. Tuohy
11 Department of Food Quality and Nutrition, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy 2 Department of Agronomy, Food, Natural Resources, Animals, and Environment (DAFNAE), University of Padova, Legnaro (PD), Italy
Introduction
Conjugated linoleic acids (CLAs) show a number of putative health-promoting activities including carcinogenic, anti-adipogenic, anti-diabetogenic, anti-inflammatory and antioxidant actions. CLAs are naturally produced by ruminal bacteria and several studies demonstrate that various lactobacilli and bifidobacteria are also able to produce CLAs in vitro from linoleic acid (LA). However, the ability of the human gut microbiota to produce CLA is less extensively studied. Our hypothesis is that the human gut microbiota is able to convert LA to CLA, and that the readily fermentable fiber inulin would positively modulate the growth of CLA-producing bacteria and, consequently increase the CLA content in the intestine.
Materials and methods
The capability of the fecal microbiota from five healthy donors to produce CLAs was tested in anaerobic batch cultures for 48 hours at pH 5.5 and 6.5. Test treatments were linoleic acid (LA; 1 mg/mL) + bovine serum albumin (BSA; 0.2 mg/mL), and LA (1 mg/mL) + BSA (0.2 mg/mL) + inulin (1%, w/v) compared to a control BSA (0.2 mg/mL) fermentation. The microbial composition was analyzed 0, 24 and 48 hours after starting the fermentation by 16S rRNA gene Illumina MiSeq sequencing (V3-V4 region). CLAs were quantified by Ultra performance liquid chromatography - tandem mass spectrometer (UPLC-MS/MS) and bi-dimensional gas chromatography (GC x GC).
Results
The inclusion of LA+BSA+inulin at pH 5.5 significantly increased the relative abundance of Collinsella aerofaciens (p<0.05), and tended to increase the relative abundance of bifidobacteria and lactic acid bacteria (LAB). LA+BSA+inulin at both pH 5.5 and 6.5 reduced the relative abundance of Parabacteroides, Bilophila, Clostridia and Enterobacteriaceae (p<0.05).
The concentration of CLA, in particular the isomer cis9,trans11 C18:2, was higher in the LA+BSA+inulin group at pH 5.5 after 24 and 48 hours (p< 0.05) fermentation.
24h c9,t11 CLA
Mean Mean±SE Mean±1,96*SE
BSA BSA-LA-Inul BSA-LA
Tesi -2 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 c 9 ,t 1 1 C L A 48h c9,t11 CLA
BSA BSA-LA-Inul BSA-LA
Tesi -5 0 5 10 15 20 25 30 35 40 45 c9,t1 1 CLA m g/g o f fat ty ac id m g/g o f fat ty ac id * -6 -5 -4 -3 -2 -1 0 1 2 3 4 PC1: 43.27% -6 -4 -2 0 2 4 6 8 10 F a c to r 2 : 3 2 .9 2 % c11,t13 CLA -1,0 -0,5 0,0 0,5 1,0 PC1 : 43.27% -1,0 -0,5 0,0 0,5 1,0 P C 2 : 3 2 .9 2 % palmitic acid (E)-octadec-10-enoic acid oleic acid vaccenic acid linoleic acid c9,t11 CLA t10,c12 CLA c9,c11 CLA c10,t12 CLA t9,t11 CLA P C2:
PCA after 48 h fermentation at pH 5.5
The PCA shows a clear separation of the LA+BSA+inulin group, in particular the isomer cis9,trans11 C18:2, was higher in the LA+BSA+inulin group at pH 5.5 after 24 and 48 hours (p< 0.05) fermentation.
Conclusions:
The data show that the treatment LA+BSA+inulin at pH 5.5 induce substantial changes in microbiota composition, including bifidogenesis and CLA production in a human intestinal microbiota model. The increase of bifidobacteria and LAB, which have previously been shown in vitro to produce CLA, may also be involved in CLA production under simulated cecal microbiome. These preclinical observations warrant confirmation in suitably designed animal and human mechanistic studies.
BSA
LA+BSA+inulin
