Chapters authored
The Synergistic Contribution of Lactobacillus and Dietary Phytophenols in Host Health
Phytophenols are found ubiquitously among all plants. They are important in diets rich in fruits and vegetables because these compounds provide health benefits to the host, ultimately decreasing the incidence of chronic diseases. These compounds act as natural antioxidants and provide anti-inflammatory, antiviral, antibiotic, and antineoplastic properties. Reactive oxygen species (ROS) are produced under normal physiological functions, and low/moderate levels are required for cellular turnover and signaling. However, when ROS levels become too high, oxidative stress can occur. Phytophenols quench ROS and ultimately avoid the damaging effects ROS elicit on the cell. The highest source of bioavailable phytophenols comes from our diet as a component usually esterified in plant fiber. For phytophenols to be absorbed by the body, they must be released by esterases, or other related enzymes. The highest amount of esterase activity comes from the gastrointestinal (GI) microbiota; therefore, the host requires the activity of mutualistic bacteria in the GI tract to release absorbable phytophenols. For this reason, mutualistic bacteria have been investigated for beneficial properties in the host. Our laboratory has begun studying the interaction of Lactobacillus johnsonii N6.2 with the host since it was found to be negatively correlated with type 1 diabetes (T1D). Analyses of this strain have revealed two important characteristics: (1) It has the ability to release phytophenols from dietary fiber through the secretion of two strong cinnamoyl esterases and (2) L. johnsonii also has the ability to generate significant amounts of H2O2, controlling the activity of indoleamine 2,3-dioxygenase (IDO), an immunomodulatory enzyme.
Part of the book: Probiotics and Prebiotics in Human Nutrition and Health
A Network of Physiological Interactions Modulating GI Homeostasis: Probiotics, Inflammasome, mTOR
The gastrointestinal surface is in constant interaction with various exogenous molecules. Exogenous components are discriminated in the GI context, as good, in case of nutrients and fibers, and bad, when they negatively affect host integrity. During this tolerogenic process, they also train the host’s immune system. The immune system is a morpho-physiologic unit driven by immune cells with the assistance of commensal organisms. Several species of commensal microorganisms have been used for centuries as probiotics due to their beneficial effects on human health. Lowering local levels of pro-inflammatory cytokines has a systemic effect, which is one of the fundamental characteristics associated with probiotics. Still, the primary mechanisms wiring those regulatory circuits as a unit remain unclear. Modulation of the innate immune system, via regulation of inflammasome assembly is emerging as a critical driver of this interaction. Stimulation of toll like receptors (TLR) and inner cell sensors like NLRP3 connect probiotics with essential host systems. In this context, the mTOR-regulated circuits, an intricate network modulating a cascade of protein phosphorylations, could be an important channel connecting host metabolism and probiotics crosstalk.
Part of the book: Probiotics