Time-dependent biological decline organized via the López-Otín 2023 hallmarks-of-aging framework and its tripartite classification: 5 primary hallmarks (genomic instability, telomere attrition, epigenetic alterations, loss of proteostasis,…
Aging Biology
Aging biology
The study of the progressive, time-dependent functional decline of biological systems — from biomolecules through cells, tissues, organs,…
Hallmarks of aging (López-Otín 2023)
López-Otín, Blasco, Partridge, Serrano, Kroemer (Cell 2023) update to the original Cell 2013 hallmarks. Twelve interlocking cellular and…
Aging-hallmark tripartite classification
López-Otín 2013/2023 partition of the twelve hallmarks into three functional tiers by causal role. **Primary hallmarks** (genomic…
Primary hallmark: genomic instability
Aging cells accumulate somatic mutations, gross chromosomal rearrangements, aneuploidy, mtDNA mutations, and persistent DNA damage. Drivers…
Primary hallmark: telomere attrition
Linear chromosome ends shorten ~50-100 bp per division because of the end-replication problem and lack of telomerase in most somatic cells.…
Primary hallmark: epigenetic alterations
Age-associated, non-sequence changes in chromatin state: global DNA-methylation drift (CpG hypomethylation with local hypermethylation at…
Primary hallmark: loss of proteostasis
Age-related decline in the protein quality control network: reduced chaperone capacity (HSP70, HSP90, HSP60), impaired…
Primary hallmark: disabled macroautophagy
López-Otín 2023 addition — autophagic flux declines with age across most tissues. Macroautophagy clears damaged organelles (mitochondria,…
Antagonistic hallmark: deregulated nutrient sensing
The four principal nutrient-sensing pathways — insulin/IGF-1 signaling (IIS), mTOR, AMPK, and sirtuins — become dysregulated with age.…
Antagonistic hallmark: mitochondrial dysfunction
Age-related decline in mitochondrial respiratory capacity, ETC complex abundance, and mtDNA integrity; accumulation of mtDNA heteroplasmy…
Antagonistic hallmark: cellular senescence
Stable cell-cycle arrest triggered by telomere dysfunction, DNA damage, oncogenic stress, or other insults — with the senescence-associated…
Integrative hallmark: stem cell exhaustion
Progressive decline in tissue-resident stem cell number, self-renewal capacity, and regenerative output. Hematopoietic stem cells show…
Integrative hallmark: altered intercellular communication
Age-associated dysregulation of hormonal, neural, and immunological signaling between cells and tissues. Includes chronic low-grade…
Integrative hallmark: chronic inflammation (inflammaging)
Franceschi 2000 'inflammaging' — a low-grade, sterile, chronic pro-inflammatory state that accumulates with age in the absence of overt…
Integrative hallmark: dysbiosis
López-Otín 2023 addition — age-associated perturbation of the gut microbiome toward reduced diversity, loss of short-chain-fatty-acid…
mTOR–rapamycin longevity axis
mTORC1 integrates nutrient, growth-factor, and energy signals to drive anabolic programmes (protein synthesis, lipogenesis, ribosome…
Sirtuin–NAD⁺ aging axis
The seven mammalian sirtuins (SIRT1-7) are NAD⁺-dependent deacylases / ADP-ribosyltransferases controlling chromatin, metabolic, and…
Insulin/IGF-1 longevity signaling
The first genetic longevity pathway identified: *C. elegans* daf-2 (insulin/IGF-1 receptor homologue) loss-of-function doubles lifespan,…
Caloric restriction longevity intervention
Reduction of caloric intake by 20-40% without malnutrition — the oldest and most cross-species-validated longevity intervention. McCay 1935…
Horvath epigenetic aging clock
Horvath 2013 (Genome Biology): a weighted combination of DNA-methylation levels at 353 CpG sites predicts chronological age across most…
Hayflick limit
Hayflick & Moorhead 1961: normal human diploid fibroblasts undergo a finite number of population doublings (~50) in culture before entering…
Senolytic pharmacology
Small molecules that selectively kill senescent cells by exploiting their anti-apoptotic dependency (senescent cells upregulate…
Geroscience hypothesis
Kennedy, Berger, Brunet, Campisi, Cuervo, Epel, Franceschi, Lithgow, Morimoto, Pessin, Rando, Richardson, Rogina, Sierra, Lamming 2014…
p16-INK4a senescence biomarker
CDKN2A-encoded cyclin-dependent-kinase inhibitor p16-INK4a accumulates with age in nearly every mammalian tissue — among the most…
Heterochronic parabiosis
Surgical joining of the circulatory systems of a young and an old animal, allowing exchange of blood-borne factors. Pioneered by Clive…
Klotho anti-aging factor
Kuro-o et al. 1997 (Nature): a single mouse mutation producing a dramatically accelerated-aging phenotype (short lifespan, atherosclerosis,…
Progeria syndromes as natural accelerated-aging experiments
Monogenic disorders recapitulating aspects of accelerated aging provide clean causal tests of the primary hallmarks. Hutchinson-Gilford…
Yamanaka partial reprogramming rejuvenation
Full Yamanaka-factor (OSKM: Oct4, Sox2, Klf4, c-Myc) expression reverts differentiated cells to iPSCs (Takahashi & Yamanaka 2006).…