Over 70% of the human immune system resides within the gut-associated lymphoid tissue (GALT). Disruption of the intestinal epithelial barrier and loss of microbial taxonomic diversity drive systemic subclinical inflammation.
Short-Chain Fatty Acids (SCFAs) as Epigenetic Modulators
Bacterial fermentation of non-digestible prebiotic dietary fibers yields key short-chain fatty acids:
- Butyrate: Primary energy source for colonocytes; acts as a potent histone deacetylase (HDAC) inhibitor, promoting Foxp3 expression and regulatory T-cell (Treg) differentiation.
- Propionate: Regulates hepatic gluconeogenesis and satiety peptide signaling via FFAR2/FFAR3 receptors.
- Acetate: Readily crosses the blood-brain barrier and modulates microglial activation states.
Intestinal Permeability & Lipopolysaccharide (LPS) Translocation
When tight junction proteins (Claudins, Occludin, ZO-1) degrade, bacterial endotoxins (LPS) translocate into systemic circulation. Circulating LPS binds Toll-like receptor 4 (TLR4) on macrophages and endothelial cells, triggering systemic NF-kB activation and chronic vascular inflammation.