Figure 2.

Microbes influence taste perception through the immune system and hormones. The microbial element, lipopolysaccharide (LPS), can induce inflammatory processes and hormone secretion that have local and systemic effects. Lingual LPS administration (top left) triggers a TLR response of inflammatory cytokine (TNF-α, INF-γ and IL-10) secretion and apoptosis of taste bud cells. LPS in the gut lumen (bottom center) interacts with TLRs to induces cytokine secretion (TNF-α, INF-γ and IL-6) into the blood stream that spreads to taste bud cells and alters tastant receptor expression and therefore taste thresholds. LPS also interacts with Enteroendocrine cells (EEC) (bottom left) stimulating release of gut hormones (CCK, PYY, GLP-1) that enter systemic circulation. These hormones are known to act as gustatory signaling molecules in taste bud cells. Microbial-induced taste responses (bottom right) might trigger a direct vagal mechanism to the brain.