There is mixed evidence regarding the influence of gut bacteria on health. Clinical interventional studies with several outcomes have been performed using different probiotic strains. In general, intervention with probiotics has shown positive influence on disease outcomes such as lowering BMI, blood glucose, or hyperlipidemia, but there are also negative studies. Interpretation of the pooled data has limitations due to heterogeneity in the length of interventions, administration form (capsules or fermented foods), bacteria strains and doses. The effects of probiotics on intestinal outcomes have been intensively investigated—for instance, probiotics prevent constipation by decreasing intestinal transit time. The gut-brain axis is an exciting field where probiotics could influence health by altering intestinal motility and absorption of nutrients or releasing metabolic signals into the blood of the host. Our research aims at identifying unique mechanisms that may explain the effect of gut bacteria/probiotics on health.
Probiotics have been shown to metabolise methyl groups during in vitro fermentation (in food industry) and produces S-adenosylmethionine (SAMe). S-adenosylmethionine is a key methyl donor produced from folate or betaine via C1-metabolism. SAMe constitutes a link between diet and DNA-synthesis, epigenetic changes, and neurotransmitter synthesis and catabolism. Alterations in SAMe have been reported in several human diseases such as depression, neurodegeneration, and cancer. We recently studied the effect of intervention with Lactobacillus helveticus R0052 and Bifidobacterium longum R0175 on one carbon (C1)-metabolism and monoamine neurotransmitters, two interrelated pathways disturbed in depression.
We conducted several set of experiments using animal models fed on a standard diet or on a methyl deficient diet followed by extensive metabolic studies on tissues, blood, feces, and urine samples. The results suggest that probiotics reduced the flow of methyl groups via betaine, increased liver methyl donor (S-adebnosylmethionine), and lower plasma dopamine. Multiple changes in one-carbon metabolism were seen in rats on a low-methyl diet, suggesting that at least some of the health effects of probiotics could be mediated by alterations in C1-metabolism and maybe regulated by diet contents of methyl donors. The present research has a high impact. Still, unless the results can be confirmed in human studies, no direct extrapolation is possible at this stage.
An intriguing field of research is to understand how probiotics can interfere with host metabolism and if this interference is dependent on the presence of dietary components. The progress of this intriguing field of research will transfer ‘gut feeling’ about probiotics into evidence-based interventions and will help us establish a causal link between gut bacteria-diet- and health. If a clear mechanism and interaction with the diet can be confirmed, the interventions with probiotics can be optimized to get a better outcome and minimize between-individuals variations in the diet.
*Probiotics’ impact on depression - Evaluating the influence on methyl groups and monoamines*
Dr Rima Obeid will be speaking in the Vitafoods Europe 2018 Education Programme on this topic. To register to attend, click here, where you can also view the entire Programme.