Why Dysbiosis, SIBO, Hydrogen Sulfide Intolerance, MCAS, and Long COVID May All Be Downstream of a Single Event — The NAD⁺/CD38 drain: how inflammation steals the cell's energy currency

There is one more leak in the system that ties the whole picture together, and it centers on NAD⁺ — the molecule that carries electrons into the electron transport chain and powers the cell's repair and longevity enzymes (the sirtuins). In a healthy cell, NAD⁺ is abundant. But chronic inflammation drives up an enzyme called CD38, an NAD⁺-consuming enzyme expressed heavily on activated immune cells. CD38 chews through NAD⁺ at a ferocious rate. As inflammation persists, the NAD⁺ pool drains. The consequences ripple straight back into everything we've discussed: less NAD⁺ means less fuel for the electron transport chain — exactly when the chain is already crippled by iron-sulfur damage; less NAD⁺ means the sirtuins (NAD⁺-dependent enzymes that maintain mitochondrial health and tune metabolism) go quiet, removing one of the cell's main repair programs; less NAD⁺ deepens the metabolic shift away from oxidative phosphorylation — the very shift that started the oxia-dysbiosis loop. So inflammation doesn't just damage the machinery; it simultaneously drains the currency the machinery runs on. The CD38/NAD⁺ axis is the financial side of the collapse, while the peroxynitrite/iron-sulfur axis is the structural side. They fail together, and they fail in the same direction.