The Science of Longevity: Can We Slow or Reverse Aging?

The Hallmarks of Aging

López-Otín et al. (2013, updated 2023): 12 hallmarks of aging — genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis, disabled macroautophagy, deregulated nutrient sensing, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, altered intercellular communication, chronic inflammation, and dysbiosis. These hallmarks are interconnected: targeting one often affects others. Genomic instability: DNA damage accumulates from endogenous (ROS, replication errors) and exogenous (UV, chemicals) sources. Repair mechanisms (NHEJ, HR, BER, NER, MMR) become less efficient with age. Telomere attrition: protective chromosome caps shorten with each division — Hayflick limit (~50 divisions). Telomerase: active in stem cells and cancer cells, absent in most somatic cells. Epigenetic alterations: DNA methylation patterns change predictably with age — the basis of "epigenetic clocks" (Horvath clock, GrimAge, DunedinPACE).

Senolytics and Cellular Senescence

Cellular senescence: cells that stop dividing but refuse to die — accumulate with age and secrete inflammatory factors (SASP — Senescence-Associated Secretory Phenotype). SASP: a cocktail of cytokines, chemokines, proteases, and growth factors that drive chronic inflammation ("inflammaging") and promote age-related diseases. Senolytics: drugs that selectively kill senescent cells. Dasatinib + Quercetin (D+Q): the first senolytic combination (Baker lab, 2015), extended healthspan in mice by 36%. Unity Biotechnology: UBX1325 for age-related macular degeneration (Phase II). Rubedo Life Sciences: prodrug senolytics activated specifically in senescent cells. Human trials: UNITY, Mayo Clinic, and others testing senolytics for osteoarthritis, Alzheimer's, diabetic kidney disease, and IPF. Results so far: mixed — some signal in idiopathic pulmonary fibrosis, but challenges with specificity and side effects. Senomorphics: drugs that suppress SASP without killing cells — potentially safer (rapamycin, metformin).

Epigenetic Reprogramming

Yamanaka factors (2006, Nobel 2012): four transcription factors (Oct4, Sox2, Klf4, c-Myc) that reprogram adult cells to pluripotent stem cells. Partial reprogramming: brief expression of Yamanaka factors reverses aging markers WITHOUT dedifferentiation. Altos Labs ($3B, backed by Jeff Bezos): leading epigenetic reprogramming research. Calico (Google/Alphabet): ~$2.5 billion invested in understanding and intervening in aging. Turn Biotechnologies, Rejuvenate Bio, Life Biosciences: other major players. Mouse results: old mice regain youthful gene expression, improved organ function, extended lifespan. In vivo reprogramming: delivered via AAV vectors — improved vision in aged mice, muscle regeneration, organ rejuvenation. Risks: too much reprogramming → teratomas (tumors). Precision needed: just enough to rejuvenate, not enough to dedifferentiate. Epigenetic clocks: show 5-10 year age reversal in some interventions — but debate continues about whether clocks measure true biological aging or just correlate with it.

Drugs and Lifestyle Interventions

Rapamycin (sirolimus): mTOR inhibitor, extends lifespan in every organism tested (yeast, worms, flies, mice — 10-25%). Human trials: PEARL (Participatory Evaluation of Aging with Rapamycin for Longevity). Metformin: diabetes drug, epidemiological data suggests reduced cancer and cardiovascular risk. TAME trial (Targeting Aging with Metformin): 3,000 participants, results expected by 2027. GLP-1 agonists (semaglutide/Ozempic): beyond weight loss — cardiovascular protection, reduced inflammation, potential neurological benefits. NAD+ precursors (NMN, NR): restore declining NAD+ levels — modest evidence in humans, ongoing trials. Caloric restriction: 30% reduction extends lifespan 20-50% in rodents. CALERIE trial (humans): 12% restriction for 2 years slowed biological aging by 2-3% (DunedinPACE). Exercise: the most proven longevity intervention — 30 minutes/day moderate activity reduces all-cause mortality by 30%. Sleep: 7-9 hours consistently associated with lowest mortality risk. Longevity industry: $44 billion (2024) → projected $600 billion by 2035. The fundamental shift: aging increasingly treated as a treatable condition, not an inevitable decline.

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