The Single Molecule Driving Both Your SIBO and Your MCAS (And Why Nothing Has Worked) — What succinate does, and why it changes everything

Succinate is a normal intermediate in the energy cycle inside every mitochondrion. In a healthy cell, it appears for a fraction of a second and is immediately consumed by an enzyme called succinate dehydrogenase. You shouldn&#8217;t see much of it floating around. But when mitochondria are stressed &#8212; by hydrogen sulfide overload from sulfate-reducing bacteria, by chronic inflammation, by the metabolite &#8220;itaconate&#8221; that your own immune cells produce during infection, or just by running out of the cofactors required to keep the cycle moving &#8212; succinate dehydrogenase gets blocked. Succinate piles up. It can&#8217;t stay in the mitochondrion. It gets dumped into the cell, then out of the cell, and into the surrounding tissue. And once it&#8217;s there, succinate does three things at once. This is the part you need to understand, because it is the explanation you have been waiting for. The first thing succinate does is reach a receptor called SUCNR1. SUCNR1 sits on three cell types you should recognize: tuft cells (sentinel cells in your gut wall that watch for parasites and microbial trouble), mast cells (the cells your MCAS doctor has been trying to calm down), and certain immune cells. When succinate hits SUCNR1 on a tuft cell, the tuft cell releases IL-25, which activates a class of immune cells called ILC2s, which release IL-13, which causes the gut to e