The Same Barrier Collapses Everywhere: Why Dysbiosis Causes ADHD, Brain Fog, Anxiety, Depression, and Chronic Fatigue Simultaneously—And Why You Can't Treat Them Separately The Discovery That Changes — Part 3: The Microglial Revolution—How Dysbiosis Arrests Brain Immune Development

The Stunted Microglia Phenomenon Here&#8217;s one of the most remarkable findings in recent neuroscience: mice raised without any microbiota (germ-free mice) develop microglia that remain stunted, immature, and dysfunctional even weeks after birth. These microglia look morphologically different: Reduced branching Enlarged soma Impaired surveillance capacity Exaggerated pro-inflammatory responses to inflammatory stimuli But here&#8217;s the stunning part: administering a single mixture of acetate, propionate, and butyrate via drinking water to germ-free mice rescues normal microglial maturation within days. Not probiotics. Not complex microbiota. Just the three SCFAs. The Mechanism: FFAR2 &#8594; Tregs &#8594; Microglial Education The pathway works like this: Step 1: SCFA-FFAR2 activation in the gut Acetate, propionate, butyrate bind FFAR2 (GPR43) on intestinal epithelial cells and enteroendocrine cells Also bind FFAR2/3 on vagal afferent neurons that innervate the hepatic portal vein (where SCFAs accumulate) Step 2: Treg differentiation in gut-associated lymphoid tissue FFAR2 activation on enteroendocrine cells increases GLP-1 and other hormone secretion These hormones signal through dendritic cells Dendritic cells drive Foxp3+ regulatory T cell (Treg) differentiation from naive CD4+ T cells SCFAs also directly enhance Treg differentiation through HDAC inhibition and increased