The Molecular Effects of Probiotics

Image credit: Ryan Pike,

Probiotics have been shown to produce significant health benefits, from relief of inflammatory bowel disease symptoms to reduction of allergic reactions. Our third report on the research presented at the National Academy of Sciences Colloquium “Microbes and Health” details recent evidence from van Baarlen and colleagues about how probiotics actually produce an effect on the human body. According to team leader, Dr. Michiel Kleerebezem, “the impact of probiotics at the molecular level in human mucosal tissues in vivo has remained unexplored for a long time. Nevertheless, specific clinical effects were measured consistently, which lacked a comprehensive molecular explanation or mechanistic insight. Our work provides molecular support for some of the clinical observations described for the probiotics we have studied.”

In the study Dr. Kleerebezem and his team looked at the reaction of the intestinal mucosa to three probiotic strains, Lactobacillus acidophilus, L. casei, and L. rhamnosus, which are all commercially available. Healthy volunteers were given either one of the three probiotics or a placebo control. After 6 hours biopsies were taken from the small intestine. RNA was then extracted and analyzed to examine the gene transcription activity occurring in response to the probiotics. The results indicated that the intestinal mucosa quickly produced a specific response to the presence of each bacterial strain. Responses to L. acidophilus included alteration in immune functioning, changes in the hormonal regulation of tissue growth and modulation of ion homeostasis. Similarly, L. casei altered the expression of immune system components but also caused an increase in the expression of genes regulating cellular proliferation and hormonal control of blood pressure. The mucosal response to L. rhamnosus resulted in up-regulation of genes involved in wound healing, immune responses and ion homeostasis. Comparison of these changes in gene expression with those produced by common pharmacological agents suggest that L. casei could be used to stimulate intestinal-muscle movement, reduce water retention and dampen down excessive immune responses. The effects of L. rhamnosus are similar to those produced by Na+/K+ ATPase inhibitors, amoebicides and intestinal muscle stimulators. In contrast, L. acidophilus has a gene transcription profile that is similar to some anti-hypertensives, antioxidants, anti-convulsants and aldosterone replacement therapies.

Overall, the research shows that probiotics can have beneficial effects on a range of regulatory processes within the body; however, the gene transcription responses showed great variation from person to person. As Dr. Kleerebezem says, the “proposed health-beneficial impacts of the consumption of probiotics may not be of equal functional value for all individuals. One conclusion we have clearly reached is that healthy humans are quite individual in terms of the molecular make-up of their tissue (including their intestinal mucosal tissues), which suggests that some individuals may benefit much more significantly from the consumption of probiotics compared to others. This aspect would support a more personalized application of probiotic supplementation to the diet, which is likely to enhance the health impact efficacy of these functional foods.”