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NAD+, mitochondrial function, hormesis, aging biomarkers, sirtuin pathways
Biological age differs from chronological age. This hub covers evidence-based strategies for extending healthspan: NAD+, sirtuin activators, mitochondrial biogenesis, intermittent fasting, temperature hormesis, and biological age biomarkers (DNAm, telomere length). Sources: Cell, Nature Aging, Cell Metabolism.
Last reviewed: 2026-06-01 · Dr. V. Pereligyn
Age-related progressive loss of skeletal muscle mass and strength. EWGSOP2 diagnostic threshold: grip strength below 27 kg in men and 16 kg in women, confirmed by low muscle mass (ASMI below 7.0 and 5.5 kg/m²). Prevalence is 10–16% after age 65 and doubles every decade, associated with falls, disability, and all-cause mortality.
A state in which DNAm-clock epigenetic age exceeds chronological age by more than 5 years (AgeAccel above +5). PhenoAge and GrimAge phenotypic markers reliably predict cardiovascular and oncologic mortality independent of chronological age. Found in 20–25% of adults, associated with smoking, obesity, chronic inflammation, and insulin resistance.
Age-dependent decline of intracellular nicotinamide adenine dinucleotide by 40–60% by age 60 relative to young adults. Laboratory threshold: whole-blood NAD+ below 25 µM or NAD+/NADH ratio below 5. Associated with CD38 activation, PARP hyperactivation under DNA damage, reduced SIRT1 and SIRT3 sirtuin activity, and mitochondrial dysfunction.
Decline in mitochondrial bioenergetic efficiency: loss of membrane potential, increased ROS output, and reduction of mtDNA copy number by more than 30% from age-matched reference. Diagnostic criteria include resting lactate above 2.2 mmol/L, GDF-15 above 1200 pg/mL, and reduced VO2max. Underlies sarcopenia, neurodegeneration, and metabolic syndrome.
Progressive attrition of terminal TTAGGG repeats by 50–100 base pairs per year. Critical threshold is below 5 kb in leukocytes, corresponding to the Hayflick replicative senescence limit. Accelerated shortening (over 70 bp/year) is associated with cardiovascular mortality, idiopathic pulmonary fibrosis, and predisposition to myelodysplastic syndromes.
| Marker | Reference | What it means |
|---|---|---|
| DNAm epigenetic age (Horvath/PhenoAge/GrimAge) | AgeAccel from -3 to +3 years | AgeAccel above +5 years independently predicts all-cause and cardiovascular mortality; GrimAge is the most accurate lifespan predictor. |
| Leukocyte telomere length (LTL) | 5.5–9.5 kb (age-dependent) | Values below the 10th age-adjusted percentile indicate accelerated replicative aging and elevated coronary artery disease risk. |
| Whole-blood NAD+ | 25–55 µM | Concentration below 25 µM indicates substrate deficiency for sirtuins and PARP, justifying precursor supplementation. |
| NAD+/NADH ratio | 5–10 (individual) | A ratio below 5 reflects redox imbalance and impaired respiratory chain complex I function. |
| mtDNA copy number (mtDNA-CN) | 80–250 copies/cell (PBMC) | Reduction over 30% from age-matched reference correlates with sarcopenia, insulin resistance, and all-cause mortality. |
| GDF-15 | below 1200 pg/mL | Cytokine of mitochondrial stress; levels above 1800 pg/mL are an independent predictor of mortality and frailty. |
| hsCRP | below 1.0 mg/L | Inflammaging marker; 1.0–3.0 mg/L indicates intermediate risk, above 3.0 mg/L indicates high cardiovascular event risk. |
Nicotinamide riboside (NR) 300–1000 mg/day and nicotinamide mononucleotide (NMN) 250–900 mg/day orally raise whole-blood NAD+ by 40–90% within 4–8 weeks by bypassing the NAMPT-limited salvage pathway. Evidence quality: confirmed double-blind RCTs (Martens 2018, Yoshino 2021, Yi 2023) demonstrate bioavailability and safety, while clinical endpoints (muscle strength, insulin sensitivity) show modest effects; no human lifespan data exist. [1][2][3]
Resveratrol 150–500 mg/day and pterostilbene 50–250 mg/day activate SIRT1, primarily through AMPK-mediated NAD+ elevation, mimicking caloric restriction signaling. Evidence quality: predominantly mechanistic and animal data (Howitz 2003, Baur 2006); human RCTs (Timmers 2011) show improved metabolic parameters in obesity but no confirmed mortality effect. Pterostilbene has superior bioavailability (~80% vs 20%) and a 105-minute half-life. [1][2][3]
A 16:8 (TRE) or 5:2 protocol induces AMPK, autophagy via mTORC1 suppression, and ketogenesis. Cold exposure at 11–15°C for 2–3 minutes or sauna at 80–90°C for 15–30 minutes 3–4 times weekly activates UCP1-dependent thermogenesis and HSP70/HSP90. Evidence quality: the Laukkanen RCT (2015, n=2315) shows a 40% reduction in all-cause mortality with 4–7 sauna sessions weekly; TRE data are mainly metabolic biomarkers (de Cabo and Mattson 2019). [1][2][3]
Fisetin 20 mg/kg for 2 days monthly or quercetin 1000 mg with dasatinib 100 mg for 2 days every 2–4 weeks selectively eliminates senescent cells by inhibiting BCL-2/BCL-XL anti-apoptotic pathways. Evidence quality: robust preclinical data (Yousefzadeh 2018, Xu 2018) with 36% lifespan extension in mice; phase I/II pilot RCTs in humans (Hickson 2019, IPF) confirm safety and SASP-marker reduction, but clinical outcomes and an optimal regimen for healthy individuals remain unestablished. [1][2][3]
Intermittent senolytic protocol using the flavonoid fisetin: 100 mg/kg body weight orally for 3 consecutive days, once monthly (Yousefzadeh et al., EBioMedicine 2018). The dosing is pulsed rather than continuous — senescent cells (SnCs) accumulate slowly, so chronic suppression is unnecessary and theoretically counterproductive for tissue regeneration. Biomarkers: PBMC p16INK4a expression, SASP panel (IL-6, IL-8, MMP-3) at baseline and 4 weeks post-cycle. Contraindications: active malignancy, pregnancy, warfarin (CYP interactions). Combinations such as dasatinib + quercetin (D+Q) remain off-label and require clinical supervision; fisetin monotherapy has a more favorable safety profile. [1][2][3]
Male 47, presenting with reduced exercise tolerance, morning fatigue, recovery >48 h post-training. Baseline: whole-blood NAD+ 18 µM (reference 30-50), HOMA-IR 2.4, hs-CRP 1.8 mg/L, VO2max 32 mL/kg/min. Intervention: NMN 500 mg/day oral, fasting, 12 weeks; training and diet held constant. At 12 weeks: NAD+ 36 µM (+100%), HOMA-IR 1.6 (-33%), hs-CRP 0.9 mg/L (-50%), VO2max 36 mL/kg/min (+12%). Subjective recovery shortened to 24 h; morning alertness normalized by week 6. No adverse events. This case illustrates reversibility of age-related NAD+ decline in the context of subclinical insulin resistance, with concordant improvement in inflammation and aerobic capacity.
Female 52, postmenopausal, family history of CAD. Baseline: ApoB 110 mg/dL, LDL-C 158 mg/dL, Lp(a) 22 nmol/L, coronary calcium score 0, BMI 27.4, BP 132/84. Patient declined statin therapy. Intervention over 6 months: Mediterranean dietary pattern with saturated fat <7%, psyllium soluble fiber 10 g/day, bergamot extract 1000 mg/day, resistance training 3×/week, weight loss 5.2 kg. At 6 months: ApoB 70 mg/dL (-36%), LDL-C 92 mg/dL (-42%), Lp(a) unchanged, hs-CRP 2.1→0.7 mg/L, BP 118/76. PCSK9 inhibitor deferred. Case demonstrates attainment of target ApoB <80 mg/dL through non-pharmacological means in primary prevention.
Both precursors effectively raise blood NAD+ but through different pathways. NR (300–600 mg/day) has a longer RCT history and official FDA GRAS status. NMN (250–500 mg/day) is theoretically one step closer to NAD+ but passes through the NRK1 route after dephosphorylation. Head-to-head trials show no clinically meaningful difference. The choice depends on availability and tolerability.
Yes, DNA methylation epigenetic clocks are available: Horvath (2013), PhenoAge (2018), and GrimAge (2019). GrimAge is considered the best mortality predictor. Test cost is 250–500 USD; the sample is saliva or blood. An alternative is phenotypic age from 9 routine biomarkers (albumin, creatinine, glucose, CRP, lymphocytes, MCV, RDW, ALP, WBC), available from standard biochemistry.
A 16:8 protocol is safe when muscle mass is preserved and sarcopenia is absent. After age 65, extended fasting (over 24 hours) accelerates muscle loss and is contraindicated below ASMI threshold. Baseline albumin, prealbumin, and grip strength must be checked first. Fasting is contraindicated in type 1 diabetes, eating disorders, and during sulfonylurea therapy.
Regular cold immersion activates the noradrenergic response, UCP1 thermogenesis, and raises adiponectin. RCTs by van Marken Lichtenbelt show improved insulin sensitivity and brown fat activation. No human lifespan data exist. Sauna has stronger evidence: 4–7 sessions per week reduce mortality by 40% (Laukkanen, n=2315). A combined sauna-cold protocol is recommended.
Most supported: metformin (TAME trial ongoing), low-dose rapamycin (mechanistic), NAD+ precursors, omega-3 EPA/DHA, vitamin D3 in deficiency, creatine 5 g/day for sarcopenia. Resveratrol and senolytics have strong preclinical but weak clinical data. The key point: correcting a confirmed deficiency and normalizing metabolic parameters yields more benefit than trendy supplements.
Both markers independently predict mortality, but the effect is cumulative. VO2max above the 80th age percentile reduces all-cause mortality by 80% compared to the lowest quartile (Mandsager 2018, n=122,007). Grip strength below 26 kg in men and 16 kg in women is an independent mortality predictor. Optimally: 150 minutes of aerobic exercise plus resistance training 2–3 times weekly, with annual VO2max and grip strength monitoring.
Horvath (2013) tracks chronological age and has low clinical sensitivity to interventions. PhenoAge (Levine, 2018) adds phenotypic markers (CRP, albumin, creatinine) and correlates with mortality risk. GrimAge (Lu, 2019) was trained on time-to-death and is the strongest healthspan predictor. DunedinPACE (Belsky, 2022) measures pace of aging (years per year) and is most sensitive to short-term interventions (12-24 weeks). For protocol monitoring use DunedinPACE plus GrimAge; reserve Horvath for cross-sectional baseline rather than tracking change.
Caloric restriction (CR, -25%) has long-term RCT support: CALERIE-2 (2 years, n=218) showed reduced DunedinPACE and improved cardiometabolic markers. Intermittent fasting (TRE 16:8, 14:10) in head-to-head RCTs (Lowe, JAMA IM 2020; Liu, NEJM 2022) produced equivalent weight loss but no metabolic advantage over isocaloric diets. Bottom line: CR has stronger biomarker-of-aging evidence, while TRE offers better adherence. A moderate CR plus TRE 14:10 combination is a reasonable compromise.
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