NAD+ decline is not just metabolic—it's a signaling failure that triggers the aging cascade

NAD+ drops 50% by age 50. We know this hurts mitochondrial function and sirtuin activity. But the deeper story may be signaling.

High NAD+ in youth maintains the "youthful state" through sirtuins and PARPs. When NAD+ falls, cells receive a molecular signal that it's time to senesce. The metabolic dysfunction is downstream of the signaling decision.

If true, NAD+ precursors don't just fuel mitochondria—they reset the developmental clock.