#70–David Sinclair, PhD: How cellular reprogramming could slow our aging clock, & the latest on NAD

Resveratrol occurs naturally in red wine, grape skins, and Japanese knotweed — but at concentrations hundreds to thousands of times lower than the therapeutic dose. A typical glass of red wine contains 0.3–1 mg of resveratrol; Sinclair's 1,000 mg dose is roughly 1,000x a glass of wine. Fat co-ingestion increases absorption because resveratrol is lipophilic and is absorbed via chylomicrons in the lymphatic system, largely bypassing hepatic first-pass metabolism that would otherwise metabolize it.

At 1,000 mg/day NR, a placebo-controlled human trial showed muscle NAD+ rose — suggesting that at high enough doses, NR does escape hepatic capture and reach peripheral tissues. Mitochondrial markers of activity paradoxically went down in that study, though Sinclair speculates this could reflect improved mitochondrial efficiency. NMN may have advantages over NR: it is one step closer to NAD+ and some data suggests it has a distinct gut-transporter pathway that partially bypasses microbiome degradation.

The metformin plus exercise interaction was highlighted in a paper suggesting metformin blunts muscle hypertrophy and aerobic adaptation in older adults who exercise. Sinclair's protocol — take it on travel/sedentary days, skip it on workout days — is an n=1 attempt to capture the longevity signal while preserving exercise adaptation. Sinclair states he has also trialed rapamycin but does not take it regularly.

Sinclair frames fasting as a 'pulse your biological stress' intervention — the adversity activates survival circuits (sirtuins, AMPK, mTOR suppression) that maintain the epigenome, but only if followed by full recovery. The metaphor he uses is that sirtuin proteins are 'first responders' — if you keep sending them on emergencies (constant DNA break repair from poor lifestyle) they cannot return to maintaining the epigenome. Fasting creates the biochemical conditions (low NAD+/NADH drain, elevated AMPK) that let sirtuins do their maintenance job rather than constantly being diverted to emergency DNA repair.

Sinclair and Attia discuss the ideal experiment: longitudinal Horvath clock measurements before and after extended fasting, rapamycin dosing cycles, or NAD+ supplementation. Sinclair proposes on-air: baseline measurement, then extended fast (7 days), then re-measure. This would be the cleanest test of whether fasting genuinely slows the deep methylation clock or only affects upstream markers. Commercial testing companies offering methylation-age tests had already emerged at the time of recording.

Attia describes being curious whether his pulsatile rapamycin protocol shows up on the Horvath clock — whether the intermittent mTOR inhibition is actually moving the deep methylation clock or only the superficial biomarkers. The ITP study showed rapamycin extends mouse lifespan more robustly than resveratrol or NR in normal lean mice, making it the benchmark comparator for other longevity interventions.

Sinclair's team chose the eye for practical reasons: it is immune-privileged, existing AAV-based gene therapies for eye diseases are already FDA-approved (e.g., SPARK Therapeutics' RPE65 therapy for retinal dystrophy costs in the high hundreds of thousands), and the eye tolerates viral delivery well. Two readouts confirmed vision restoration: a behavioral test (mouse tracks moving lines of decreasing thickness on a screen) and objective electrophysiological measurement of signal amplitude in the occipital cortex. Steve Horvath's methylation clock confirmed that treated cells measured younger by epigenetic age. Hundreds of genes that had drifted with aging — including olfactory receptor genes inexplicably expressed in the retina of old mice — reset toward the young pattern after reprogramming.

The clock records every lifestyle insult: packs per day smoked matched the medical record, not the patient's self-report. By implication, the clock also records every protective behavior — fasting, exercise, calorie restriction. Commercial methylation-age testing companies had begun to emerge at the time of this episode, and Sinclair and Attia discuss using longitudinal samples to track whether interventions are working directionally even if month-to-month precision is insufficient. Sinclair notes he was fasting at the time of recording ('having not eaten in a couple of days') specifically to slow his clock.

The NR → NMN → NAD+ pathway requires two enzymatic steps inside cells. NR enters via a specific transporter; NMN adds a phosphate group; NAD+ is the final product. When a sirtuin deacetylates a target protein, it consumes one NAD+ and releases NAM plus O-acetyl-ADP-ribose. If you simultaneously boost NAD+ precursors and accumulate NAM, you push the gas and the brake at the same time. A 2019 Princeton study (Rabinowitz lab) found that oral NR was largely captured by the liver, with minimal NR leaving hepatocytes — though a separate study at 1,000 mg/day showed intramuscular NAD+ also rose, suggesting dose-dependent spillover past hepatic first pass.

Kirkland's experiment: a tiny dab of senescent cells implanted into the peritoneal cavity of young mice caused premature aging across the whole organism — higher blood sugar and multiple signs of systemic aging. This demonstrates that senescent burden is not a passive marker but an active driver. The question of whether partial reprogramming can rescue a cell that has already clicked into senescence (versus one that is merely identity-confused but not yet zombie) remains open. Sinclair's guess: pre-senescent identity loss is likely reversible; fully committed senescence may require a different approach (senolytics like dasatinib + quercetin).

Resveratrol acts like a 'molecular glue' between SIRT1 and a specific motif on its substrate protein — the enzyme undergoes a conformational bend at an 'elbow' region. The mutation creates a stiff elbow that prevents this bending, eliminating resveratrol sensitivity without otherwise disrupting enzyme function. Both resveratrol and the more potent synthetic STACs (sirtuin-activating compounds) like SRT2104 were blocked by the same mutation, confirming a shared binding site. The ITP study (independent life-testing consortium) found that resveratrol did not extend lifespan in healthy lean mice — consistent with the hypothesis that sirtuins must already be overtaxed (as in obese or aged animals) for NAD+/resveratrol restoration to matter.

Sinclair describes this at the time of recording: he is fasting ('having not eaten in a couple of days') explicitly to activate his sirtuins. His framing of metformin timing follows the same logic — avoid it on heavy exercise days so as not to suppress the mitochondrial biogenesis signal. The principle generalizes to rapamycin: 'I wouldn't take rapamycin suddenly if I was exercising because it's gonna tell the cell to hunker down and not grow and you may not even heal after exercise.' The optimal protocol is alternating stress (fasting, heavy exercise, cold exposure) with full recovery rather than chronic mild suppression.