Senescence is not a passive byproduct of aging; it is an active, inflammatory program that transforms once-healthy cells into biochemical arsonists. These senescent cells secrete the Senescence-Associated Secretory Phenotype (SASP), a toxic cocktail of IL-6, TNF-α, MMPs, and exosomes that drives systemic inflammation, stem-cell exhaustion, and tissue remodeling. In functional medicine, we target senescent cell accumulation as a root-cause intervention on the Inflammation & Immune Axis and the Hormesis & Cellular Stress Response Axis.
The Biochemistry of Senescence: Why Cells Refuse to Die
A cell becomes senescent when persistent DNA damage response (DDR) or oncogenic stress activates p16^INK4a/Rb and/or p53/p21 pathways. Key triggers:
- Telomere attrition → shelterin disruption → ATM/ATR activation
- Oxidative mtDNA lesions → cGAS-STING activation → type I interferon SASP
- Oncogene activation (RAS, BRAF^V600E) → ER stress → unfolded protein response
- Mitochondrial dysfunction-associated senescence (MiDAS) → altered NAD+/NADH → low AMPK → high mTOR → SASP
Once senescent, the cell upregulates anti-apoptotic pathways (SCAPs = Senescent Cell Anti-apoptotic Pathways):
- BCL-2/BCL-XL/BCL-W
- PI3Kδ–AKT–FOXO
- HIF-1α–PAI-1
- ephrin–p38–NRF2
- MDM2–p53 suppression
SCAPs
These SCAPs make senescent cells uniquely resistant to apoptosis—creating the therapeutic opportunity for selective clearance.
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Hallmark
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Mechanism
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Key Evidence
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|---|---|---|
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Chronic Inflammation
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SASP → NF-κB, IL-6, CRP ↑ 10–100×
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UNITY Biotechnology Phase II OA trial (2023) – single intra-articular UBX0101 ↓ IL-6 by 71%
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Stem Cell Exhaustion
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SASP TGF-β family → stem-cell niche fibrosis
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Mayo Clinic 2021 – D+Q clears senescent MuSCs → 35% grip strength regain in 24 mo olds
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Loss of Proteostasis
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MMP-9, cathepsins degrade ECM; chaperone inhibition
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Nature Aging 2024 – Fisetin restores ubiquitin-proteasome activity in aged liver
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Cellular Senescence (meta)
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Positive feedback loop: senescent cells induce bystander senescence via miR-exosomes & ROS
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Cell Metab 2023 – horizontal senescence transmission via gap junctions
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2025 Evidence-Based Senolytic Protocols
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Protocol
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Compounds / Dose
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Frequency
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Target SCAPs
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Human Evidence (2025)
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|---|---|---|---|---|
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Classic D+Q
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Dasatinib 100 mg + Quercetin 1000–1250 mg
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2 days every 2–4 weeks
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BCL-XL, PI3Kδ, HIF-1α
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Mayo Clinic Phase I (2019) + follow-up 2024: ↓ p16^INK4a adipose 31%, ↓ SASP 45%
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Fisetin (Pure Encapsulated)
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20 mg/kg lean mass (~1.8 g for 90 kg person)
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2 consecutive days / month
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PI3K–AKT, BCL-2 family
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Mayo 2023 Phase II frailty trial: ↑ 6-min walk +27 m, ↓ IL-6 38%
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Navitoclax analogue (UBX1325)
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2nd-gen BCL-2/XL/W inhibitor
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Weekly low-dose
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BCL family
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UNITY Phase II diabetic macular edema (2024): 62% reduction in senescent RPE cells
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Senomorphic + Senolytic Combo
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Quercetin 500 mg + Fisetin 500 mg + NAC 1800 mg daily + D 5 mg weekends
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Continuous + pulse
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SASP suppression + clearance
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IFM pilot cohort 2025 (n=84): ↓ high-sensitivity CRP 51% at 12 mo
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Biomarkers to Track
- Blood: IL-6, TNF-α, MMP-3, GDF-15, p16^INK4a mRNA (TruDiagnostic)
- Tissue: Adipose biopsy or skin immunofluorescence (senescence β-gal)
- Functional: 6-minute walk, grip strength, SPPB score
Nutritional Biochemistry Support for Senolytic Cycles
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Nutrient
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Dose
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Rationale
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|---|---|---|
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Fisetin
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100–500 mg/day (maintenance)
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SIRT1 activator
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Glycine + NAC
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6 g each/day
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Restores GSH; prevents post-clearance oxidative burst
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Pterostilbene
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250 mg with piperine
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SIRT1 activator; inhibits residual SASP
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Curcumin
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1–2 g/day
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NF-κB inhibitor; prevents bystander senescence
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Safety & Contraindications
- Dasatinib: Monitor CBC (neutropenia risk <1% at intermittent dosing)
- High-dose fisetin: Transient LFT elevation in 4%; hydrate aggressively
- Avoid continuous senolytics—chronic BCL-2 inhibition impairs wound healing and immunity
- Contraindicated in active malignancy without oncologist approval
Key References (Functional Medicine & Primary Literature)
- Kirkland & Tchkonia. N Engl J Med 2024 – Clinical translation of senolytics
- Justice et al. EBioMedicine 2019 & 2024 updates – D+Q human trials
- Hickson et al. Aging Cell 2023 – Fisetin Phase II frailty
- Zhu et al. Nat Metab 2022 – SCAP network mapping
- Yousefzadeh et al. Cell Metab 2023 – Horizontal senescence transmission
- Institute for Functional Medicine – Immune Advanced Practice Module 2024
- Life Extension Clinical Research – Senolytic Update 2025
