Probiotic or synbiotic alters the gut microbiota and metabolism in a randomised controlled trial of weight management in overweight adults.

The gut microbiota contributes to host energy metabolism, and altered gut microbiota has been associated with obesity-related metabolic disorders. We previously reported that a probiotic alone or together with a prebiotic controls body fat mass in healthy overweight or obese individuals in a randomised, double-blind, placebo controlled clinical study (ClinicalTrials.gov NCT01978691). We now aimed to investigate whether changes in the gut microbiota may be associated with the observed clinical benefits. Faecal and plasma samples were obtained from a protocol compliant subset (n=134) of participants from a larger clinical study where participants were randomised (1:1:1:1) into four groups: (1) placebo, 12 g/d microcrystalline cellulose; (2) Litesse® Ultra™ polydextrose (LU), 12 g/day; (3) Bifidobacterium animalis subsp. lactis 420™ (B420), 1010 cfu/d in 12 g microcrystalline cellulose; (4) LU+B420, 1010 cfu/d of B420 in 12 g/d LU for 6 months of intervention. The faecal microbiota composition and metabolites were assessed as exploratory outcomes at baseline, 2, 4, 6 months, and +1 month post-intervention and correlated to obesity-related clinical outcomes. Lactobacillus and Akkermansia were more abundant with B420 at the end of the intervention. LU+B420 increased Akkermansia, Christensenellaceae and Methanobrevibacter, while Paraprevotella was reduced. Christensenellaceae was consistently increased in the LU and LU+B420 groups across the intervention time points, and correlated negatively to waist-hip ratio and energy intake at baseline, and waist-area body fat mass after 6 months treatment with LU+B420. Functional metagenome predictions indicated alterations in pathways related to cellular processes and metabolism. Plasma bile acids glycocholic acid, glycoursodeoxycholic acid, and taurohyodeoxycholic acid and tauroursodeoxycholic acid were reduced in LU+B420 compared to Placebo. Consumption of B420 and its combination with LU resulted in alterations of the gut microbiota and its metabolism, and may support improved gut barrier function and obesity-related markers.

Contribution of volatiles to the antifungal effect of Lactobacillus paracasei in defined medium and yogurt.

Lactic acid bacteria with antifungal properties can be used to control spoilage of food and feed. Previously, most of the identified metabolites have been isolated from cell-free fermentate of lactic acid bacteria with methods suboptimal for detecting possible contribution from volatiles to the antifungal activity. The role of volatile compounds in the antifungal activity of Lactobacillus paracasei DGCC 2132 in a chemically defined interaction medium (CDIM) and yogurt was therefore investigated with a sampling technique minimizing volatile loss. Diacetyl was identified as the major volatile produced by L. paracasei DGCC 2132 in CDIM. When the strain was added to a yogurt medium diacetyl as well as other volatiles also increased but the metabolome was more complex. Removal of L. paracasei DGCC 2132 cells from CDIM fermentate resulted in loss of both volatiles, including diacetyl, and the antifungal activity towards two strains of Penicillium spp. When adding diacetyl to CDIM or yogurt without L. paracasei DGCC 2132, marked inhibition was observed. Besides diacetyl, the antifungal properties of acetoin were examined, but no antifungal activity was observed. Overall, the results demonstrate the contribution of diacetyl in the antifungal effect of L. paracasei DGCC 2132 and indicate that the importance of volatiles may have been previously underestimated.