Deconstructing a Probiotic

Abstract

Biomedicine![Figure][1] CREDIT: F. YAN ET AL., J. CLIN. INVEST. 121 , 6 (2011) Despite aggressive marketing campaigns that highlight the beneficial effects of probiotics (therapeutics consisting of live microorganisms) on gastrointestinal health, in many cases the claimed benefits are made on the basis of limited or controversial clinical data. Moreover, there are far more hypotheses than experimental data on the molecular mechanisms by which probiotics alter gut homeostasis. A better understanding of these mechanisms could shed light on the disparate clinical data and perhaps even lead to more effective drugs that can substitute for living microbes. Studying Lactobacillus rhamnosus GG (LGG), which is used in yogurt as a nutritional supplement, Yan et al. found that this bacterium secretes a soluble protein, called p40, which prevents death of intestinal epithelial cells through activation of the epidermal growth factor receptor signaling pathway. In three mouse models of intestinal inflammation, administration of recombinant p40 (encased within special hydrogel beads to minimize its degradation) reduced disease symptoms in both a therapeutic and preventive setting. Whether p40 alone will show similar activity in humans without adverse side effects remains to be seen, but these results support the idea that the identification of the specific health-promoting factors made by probiotics is an avenue worth exploring. J. Clin. Invest. 121 , 10.1172/JCI44031 (2011). [1]: pending:yes