Glossary of Aging Research Terms

Harmful compounds formed when proteins or fats combine with sugars. AGEs accumulate with age and contribute to inflammation, oxidative stress, and tissue damage.

A serine/threonine protein kinase central to the PI3K/AKT pathway, regulating cell survival, growth, and metabolism. Modulation of AKT activity influences lifespan in model organisms.

A cellular energy sensor that promotes autophagy, mitochondrial biogenesis, and metabolic health. AMPK activation mimics some benefits of caloric restriction.

An evolutionary theory proposing that genes beneficial early in life may have harmful effects later, contributing to aging. This trade-off shapes the evolution of lifespan.

Programmed cell death that removes damaged or unnecessary cells. Dysregulated apoptosis contributes to aging and age-related disease.

A protein kinase that responds to DNA double-strand breaks, activating cell cycle checkpoints and DNA repair. ATM deficiency accelerates aging phenotypes.

A kinase that detects DNA replication stress and single-strand breaks, coordinating DNA repair and cell cycle arrest. ATR signaling is crucial for genomic stability.

A cellular recycling process that degrades damaged organelles and proteins. Autophagy declines with age and its restoration extends lifespan in multiple species.

A measure of physiological aging that may differ from chronological age. Assessed using epigenetic clocks, biomarkers, and functional tests.

A measurable indicator of biological state or condition. Aging biomarkers include DNA methylation patterns, inflammatory markers, and functional capacity measures.

Medications that slow bone loss by inhibiting osteoclast activity. Used to treat osteoporosis and reduce fracture risk in aging populations.

A nematode worm widely used in aging research due to its short lifespan, genetic tractability, and conserved aging pathways. Many longevity interventions were first discovered in C. elegans.

A clinical trial demonstrating that moderate caloric restriction in humans improves cardiometabolic health and slows biological aging without malnutrition.

A state of stable growth arrest where cells remain metabolically active but cease dividing. Senescent cells accumulate with age and secrete harmful factors via the SASP.

Molecular chaperones assist in protein folding and prevent aggregation. Heat shock proteins (HSPs) are key chaperones that decline with age, impairing proteostasis.

The complex of DNA and proteins that forms chromosomes. Chromatin structure changes with age, affecting gene expression and genomic stability.

The concept that interventions can delay disease onset, compressing the period of illness toward the end of life and extending healthspan relative to lifespan.

A gene-editing technology enabling precise modification of DNA sequences. CRISPR is used in aging research to study gene function and develop potential therapies.

The formation of chemical bonds between proteins or DNA molecules, causing tissue stiffening and functional decline. AGEs are a major source of crosslinking in aging.

Signaling proteins that mediate immune and inflammatory responses. Pro-inflammatory cytokines increase with age, contributing to inflammaging.

A tyrosine kinase inhibitor that acts as a senolytic drug, selectively clearing senescent cells. Often combined with quercetin in aging research and clinical trials.

An evolutionary theory proposing that organisms allocate limited resources between reproduction and somatic maintenance, with aging resulting from insufficient investment in repair.

The cellular mechanisms that detect and repair DNA damage. DDR efficiency declines with age, leading to accumulation of genomic damage and cellular dysfunction.

An epigenetic modification involving addition of methyl groups to DNA, regulating gene expression. DNA methylation patterns change predictably with age, forming the basis of epigenetic clocks.

The fruit fly, a model organism in aging research offering rapid generation time, genetic tools, and conserved aging mechanisms. Many longevity genes were first identified in Drosophila.

A blood-based biomarker measuring the pace of aging, developed from the Dunedin longitudinal study. DunedinPACE predicts future health outcomes and tracks aging rate.

A plate-based assay technique for detecting and quantifying proteins, antibodies, or hormones. Widely used to measure biomarkers in aging research.

Cellular stress caused by accumulation of misfolded proteins in the ER. ER stress activates the unfolded protein response and increases with age.

A measurable outcome used to assess intervention efficacy in clinical trials. Aging research endpoints include mortality, disease incidence, and functional decline.

Changes in gene expression without altering DNA sequence, including DNA methylation and histone modifications. Epigenetic alterations are a hallmark of aging.

A predictive model using DNA methylation patterns to estimate biological age. Multiple epigenetic clocks exist, including Horvath, Hannum, GrimAge, and PhenoAge.

Selective autophagy of endoplasmic reticulum components. ER-phagy maintains ER homeostasis and protein quality control, declining with age.

The structural network of proteins and molecules surrounding cells. ECM stiffening and altered composition contribute to tissue aging and dysfunction.

A flavonoid with senolytic properties found in fruits and vegetables. Fisetin reduces senescent cell burden and extends healthspan in mice.

A family of transcription factors regulating stress resistance, autophagy, and metabolism. FOXO activation extends lifespan across multiple species and is inhibited by insulin/IGF-1 signaling.

A clinical syndrome of decreased physiological reserve and vulnerability to stressors. Frailty increases with age and predicts adverse health outcomes.

An early theory proposing that cumulative oxidative damage from free radicals causes aging. While oversimplified, oxidative stress remains relevant to aging biology.

Accumulation of DNA damage, mutations, and chromosomal abnormalities. Genomic instability is a primary hallmark of aging and contributes to cancer and cellular dysfunction.

An interdisciplinary field studying the biological mechanisms of aging and their relationship to age-related diseases. Geroscience aims to target aging itself as a therapeutic strategy.

An epigenetic clock that predicts mortality and healthspan using DNA methylation and plasma protein levels. GrimAge strongly correlates with age-related disease risk.

A peptide hormone regulating growth and metabolism. Reduced GH/IGF-1 signaling extends lifespan in model organisms, though optimal levels in humans remain debated.

The twelve fundamental biological processes driving 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.

The number of times a normal cell can divide before entering senescence, typically 40-60 divisions for human cells. Named after Leonard Hayflick, this limit relates to telomere shortening.

The period of life spent in good health, free from chronic disease and disability. Extending healthspan, not just lifespan, is the primary goal of geroscience.

A transcription factor that activates heat shock proteins in response to proteotoxic stress. HSF1 activity declines with age, impairing stress resistance.

Chaperone proteins induced by cellular stress that assist in protein folding and prevent aggregation. HSP expression decreases with age, contributing to proteostasis decline.

Tightly packed chromatin associated with gene silencing. Loss of heterochromatin structure with age leads to aberrant gene expression and genomic instability.

Chemical changes to histone proteins that regulate chromatin structure and gene expression. Histone modification patterns change with age as part of epigenetic alterations.

A dose-response phenomenon where low doses of stress stimulate beneficial adaptive responses. Exercise, fasting, and some compounds may extend lifespan through hormetic mechanisms.

The first multi-tissue epigenetic clock, developed by Steve Horvath, using DNA methylation at 353 CpG sites to estimate biological age across diverse tissues.

The variation in time intervals between heartbeats, reflecting autonomic nervous system function. HRV declines with age and predicts mortality risk.

A hormone with structural similarity to insulin that promotes growth and metabolism. Reduced IGF-1 signaling extends lifespan in model organisms by activating stress resistance pathways.

Age-related decline in immune function, characterized by reduced naive T cells, increased memory cells, and chronic inflammation. Immunosenescence increases infection susceptibility and vaccine inefficacy.

Chronic, low-grade inflammation that increases with age. Inflammaging contributes to most age-related diseases and is driven by senescent cells, immune dysfunction, and gut dysbiosis.

A conserved pathway regulating growth, metabolism, and lifespan. Reduced IIS extends lifespan across species by activating FOXO transcription factors and stress resistance mechanisms.

A National Institute on Aging program testing compounds for lifespan extension in genetically heterogeneous mice across three sites. The ITP has validated several pro-longevity interventions including rapamycin and acarbose.

A stress-activated protein kinase involved in inflammation, apoptosis, and metabolism. JNK inhibition extends lifespan in some model organisms.

Short-lived fish species used in aging research, particularly the African turquoise killifish. Their compressed lifespan and vertebrate biology make them valuable models for studying aging interventions.

An indigestible aggregate of oxidized proteins and lipids that accumulates in lysosomes with age, particularly in post-mitotic cells. Lipofuscin accumulation impairs cellular function.

A theoretical point where life-extending therapies advance faster than aging occurs, enabling indefinite lifespan extension. Popularized by Aubrey de Grey.

Age-related decline in protein quality control mechanisms, leading to accumulation of damaged and aggregated proteins. Loss of proteostasis is a hallmark of aging.

An organelle containing enzymes that degrade cellular waste. Lysosomal function declines with age, impairing autophagy and cellular clearance.

The primary form of autophagy, involving sequestration of cytoplasmic material in double-membrane vesicles (autophagosomes) for lysosomal degradation. Macroautophagy declines with age.

An analytical technique that measures mass-to-charge ratios of molecules. Used in aging research for proteomics, metabolomics, and biomarker discovery.

A cluster of conditions including obesity, insulin resistance, hypertension, and dyslipidemia that increase disease risk and accelerate aging.

A diabetes medication that activates AMPK and shows promise as a geroprotector. Metformin is being tested in the TAME trial for effects on aging and age-related disease.

The community of microorganisms inhabiting the body, particularly the gut. Microbiome composition changes with age (dysbiosis) and influences immune function and metabolism.

Small non-coding RNA molecules that regulate gene expression post-transcriptionally. MicroRNA profiles change with age and influence aging processes.

Age-related decline in mitochondrial quality and function, leading to reduced energy production and increased oxidative stress. Mitochondrial dysfunction is a hallmark of aging.

A stress response pathway that detects and responds to mitochondrial protein folding defects. UPRmt activation can extend lifespan through hormetic mechanisms.

Selective autophagy of mitochondria. Mitophagy removes damaged mitochondria and is essential for maintaining mitochondrial quality. Mitophagy declines with age.

A protein kinase that senses nutrients and regulates growth, metabolism, and autophagy. mTOR inhibition by rapamycin extends lifespan in multiple species and is a validated longevity intervention.

One of two mTOR complexes, sensitive to rapamycin and nutrients. mTORC1 inhibition promotes autophagy, stress resistance, and longevity.

The second mTOR complex, less sensitive to acute rapamycin treatment. mTORC2 regulates cell survival and cytoskeletal organization.

A coenzyme essential for metabolism and cellular energy production. NAD+ levels decline with age, and restoration through precursors like NMN or NR shows promise for healthspan extension.

A long-lived rodent exhibiting exceptional resistance to cancer and age-related disease. Naked mole-rats maintain proteostasis and show minimal functional decline with age, making them valuable models for aging research.

The rate-limiting enzyme in NAD+ biosynthesis from nicotinamide. NAMPT activity declines with age, contributing to NAD+ depletion.

A form of programmed necrosis that releases inflammatory signals. Necroptosis increases with age and contributes to chronic inflammation.

A transcription factor regulating immune and inflammatory responses. Chronic NF-κB activation drives inflammaging and age-related disease.

A NAD+ precursor that boosts NAD+ levels when supplemented. NMN administration improves metabolic function and shows anti-aging effects in animal studies.

A cell signaling pathway regulating cell fate, proliferation, and differentiation. Notch signaling changes with age and affects stem cell function.

A NAD+ precursor similar to NMN that elevates NAD+ levels. NR supplementation shows metabolic benefits and is being tested in human trials.

A transcription factor regulating antioxidant and detoxification responses. Nrf2 activation protects against oxidative stress and extends lifespan in some models.

An imbalance between reactive oxygen species production and antioxidant defenses. While oxidative stress contributes to aging, simple antioxidant supplementation has shown limited efficacy.

A cyclin-dependent kinase inhibitor that enforces cellular senescence. p16 expression increases with age and serves as a senescence biomarker.

A cyclin-dependent kinase inhibitor that induces cell cycle arrest in response to stress. p21 mediates senescence and DNA damage responses.

A tumor suppressor protein that responds to cellular stress by inducing cell cycle arrest, DNA repair, or apoptosis. p53 activity increases with age but can contribute to stem cell exhaustion.

Surgical joining of two organisms to create shared circulation. Heterochronic parabiosis (old-young pairing) reveals circulating factors that influence aging and rejuvenation.

The first stage of human testing, evaluating safety and dosing in a small group. Phase I trials establish basic safety profiles for aging interventions.

The second stage of clinical testing, assessing efficacy and side effects in a larger group. Phase II trials provide preliminary evidence of therapeutic benefit.

Large-scale trials comparing a new intervention to standard treatment. Phase III trials generate definitive evidence for regulatory approval.

An epigenetic clock predicting mortality and age-related phenotypes using DNA methylation and clinical biomarkers. PhenoAge captures biological aging better than chronological age.

An enzyme in the insulin/IGF-1 signaling pathway that activates AKT. Reduced PI3K/AKT signaling extends lifespan in model organisms.

A rare genetic disorder causing accelerated aging in children. Studying progeria reveals mechanisms of normal aging and potential therapeutic targets.

The maintenance of protein homeostasis through synthesis, folding, trafficking, and degradation. Proteostasis networks decline with age, leading to protein aggregation and dysfunction.

A flavonoid with senolytic and antioxidant properties. Quercetin is often combined with dasatinib to clear senescent cells in research and clinical trials.

An mTOR inhibitor that robustly extends lifespan across species. Rapamycin promotes autophagy, enhances immune function, and delays age-related disease in animal models.

Chemically reactive molecules containing oxygen, produced during metabolism. While excessive ROS causes damage, moderate levels serve signaling functions and may mediate hormetic benefits.

Cellular senescence triggered by telomere shortening after repeated divisions. Replicative senescence limits the proliferative capacity of cells.

A polyphenol that activates sirtuins and shows anti-aging effects in some model organisms. Human efficacy remains uncertain despite early promise.

A technique for quantifying gene expression across the transcriptome. RNA-seq reveals age-related changes in gene expression and identifies therapeutic targets.

Age-related loss of muscle mass and strength. Sarcopenia increases fall risk, metabolic dysfunction, and mortality.

The collection of inflammatory cytokines, growth factors, and proteases secreted by senescent cells. The SASP drives chronic inflammation and tissue dysfunction in aging.

An agent that selectively eliminates senescent cells. Senolytic drugs like dasatinib and quercetin extend healthspan and reduce age-related pathology in animal models.

An agent that suppresses the harmful SASP of senescent cells without killing them. Senomorphics may complement senolytics in aging interventions.

Techniques for analyzing gene expression or epigenetic state in individual cells. Single-cell sequencing reveals cellular heterogeneity and aging-related changes in cell populations.

An NAD+-dependent deacetylase that regulates metabolism, stress resistance, and gene expression. SIRT1 activation mimics some benefits of caloric restriction and extends lifespan in model organisms.

Additional members of the sirtuin family with diverse cellular roles. SIRT3 regulates mitochondrial metabolism, while SIRT6 maintains genomic stability and is strongly associated with longevity.

A polyamine that induces autophagy and shows life-extending effects. Spermidine levels decline with age, and supplementation improves cardiovascular function.

Age-related decline in stem cell number and function, reducing tissue regenerative capacity. Stem cell exhaustion is a hallmark of aging affecting multiple tissues.

A proposed clinical trial testing whether metformin delays aging and age-related disease in older adults. TAME aims to validate aging as a treatable condition.

An enzyme that adds DNA sequences to telomeres, counteracting shortening. Telomerase is active in stem cells and most cancer cells but repressed in somatic cells.

Protective DNA-protein structures at chromosome ends that shorten with each cell division. Telomere attrition limits replicative capacity and is a hallmark of aging.

Progressive shortening of telomeres with age and cellular replication. Telomere attrition triggers replicative senescence and is one of the primary hallmarks of aging.

The original name for mTOR, derived from its discovery as the target of rapamycin. TOR pathways are conserved across evolution and regulate growth and lifespan.

A major protein degradation pathway that tags proteins with ubiquitin for proteasomal destruction. UPS function declines with age, contributing to loss of proteostasis.

A cellular stress response activated by accumulation of misfolded proteins in the endoplasmic reticulum. UPR capacity declines with age, impairing proteostasis.

Maximal oxygen consumption during exercise, a measure of cardiovascular fitness. VO2 max declines with age and strongly predicts mortality risk.

A premature aging disorder caused by mutations in the WRN helicase gene. Werner syndrome provides insights into normal aging mechanisms and genomic stability.

A pathway regulating cell proliferation, differentiation, and tissue homeostasis. Wnt signaling changes with age and affects stem cell function and regeneration.

A hypothesis proposing that stress response pathways can be activated by consuming plant compounds produced under stress. Polyphenols like resveratrol may work through xenohormetic mechanisms.