The Geroscience Hypothesis: Biological Aging as a Malleable Driver of Multimorbidity

Aging and chronic diseases are no longer viewed as separate processes but as different manifestations of accumulated cellular damage. The geroscience hypothesis states that biological aging is malleable and that modifying its drivers will slow the progression of aging while preventing multiple chronic conditions.

The intracellular signalling pathways that respond to nutritional status (mTOR, insulin pathways) or stress (autophagy, chaperones) have been identified as both determinants of lifespan and causal factors in diseases as diverse as cancer and Alzheimer’s disease. This convergence is what makes aging a “source” rather than merely a “context” for disease.

Twelve Molecular Hallmarks That Bridge Aging to Specific Pathologies

The 12 established hallmarks of aging serve as mechanistic bridges between chronological time and clinical pathology. Each hallmark has been experimentally shown to drive specific disease processes when accentuated and to delay disease when therapeutically targeted.

Inflammaging: The NF-κB/NLRP3 Axis Driving Cardiovascular and Neurodegenerative Disease

Inflammaging — chronic, low-grade systemic inflammation associated with aging — acts as a central pathogenic driver that promotes tissue dysfunction by activating NF-κB and NLRP3 signalling. It impairs cellular quality control and accelerates the progression of both cardiovascular and neurodegenerative diseases.

In the cardiovascular system, inflammaging mediates a transition from physiological repair to maladaptive remodelling. Chronic inflammation increases vascular permeability and promotes LDL oxidation — key early events in atherogenesis. Persistent NLRP3 inflammasome signalling increases ROS production and triggers monocyte transformation into foam cells, leading to plaque formation and instability. NF-κB-mediated cytokine production facilitates leukocyte adhesion and induces vascular stiffness through excessive collagen deposition and elastin reorganisation. This persistent inflammatory state is a significant factor in heart failure with preserved ejection fraction (HFpEF).

In the central nervous system, inflammaging disrupts the homeostasis of resident immune cells. Aging microglia exhibit dysregulated autophagy, leading to impaired debris clearance and sustained chronic neuroinflammation. Neuroinflammation promotes the accumulation and transmission of α-synuclein in Parkinson’s disease and Tau protein in Alzheimer’s disease; specifically, microglial NF-κB activation drives Tau seeding and toxicity. In amyotrophic lateral sclerosis (ALS), genomic instability and cytoplasmic DNA leakage activate the cGAS-STING pathway, triggering motor neuron death.

Autophagy–Neuroinflammation Crosstalk: Divergent Pathways in Alzheimer’s vs. Parkinson’s Disease

In both Alzheimer’s and Parkinson’s disease, a pathological feedback loop exists where chronic neuroinflammation impairs autophagic flux while undegraded toxic protein aggregates further stimulate pro-inflammatory signalling. The primary difference lies in the specific aggregates that disrupt cellular quality control and the distinct pathways — lysosomal versus mitophagic — that serve as the initial site of failure.

Gerotherapeutic Interventions: From mTOR Inhibition to Senolytic Clearance

The strongest support for aging as the source of other diseases comes from studies where targeting aging processes ameliorates multiple distinct pathologies. Three classes of intervention dominate the evidence corpus.

Metformin targets multiple aging-related mechanisms. While used primarily for type 2 diabetes, metformin activates AMPK, inhibits mTORC1, suppresses NLRP3 inflammasome activation, and promotes chaperone-mediated autophagy. Clinical data show reduced all-cause mortality and a lower incidence of cancer and cardiovascular disease. The TAME (Targeting Aging with Metformin) trial is currently under way to test metformin as an aging intervention directly, and a parallel trial (NCT05093959) evaluates it in older patients with HFpEF.

Rapamycin inhibits the mTOR pathway and has been shown to extend lifespan and improve cardiac function and immune response in multiple animal models — even when administered late in life. Partial mTORC1 inhibition in aged rats counteracts muscle mass decline. The hyperactivation of mTORC1 is linked to impaired autophagy and sarcopenia, making mTOR a hub target in the geroscience network.

Senolytics selectively eliminate senescent cells by targeting their anti-apoptotic pathways (Bcl-2 family). Dasatinib and quercetin (D+Q) have demonstrated efficacy in reversing established vasomotor dysfunction, reducing osteoporosis, and alleviating frailty in mice. In a pilot study of patients with idiopathic pulmonary fibrosis, D+Q treatment over three weeks yielded clinically meaningful gains in physical function despite no change in lung capacity.

Emerging Mechanisms: NAD+ Decline, CD38, and the cGAS-STING Axis in Aging Pathology

The BioSkepsis research landscape synthesis identifies an emerging phase of geroscience research (2022–2025) that expands the original nine hallmarks to twelve, emphasises immunometabolic drift, and maps inter-organ axes such as the gut–bone–brain interaction.

CD38 and NAD+ depletion. CD38 is identified as the primary NADase that depletes tissue NAD+ levels during aging. Pharmacological inhibition of CD38 (e.g., with apigenin or 78c) restores intracellular NAD+ levels and SIRT3 activity, subsequently reducing mitochondrial ROS. In clinical settings, the NAD+ precursor nicotinamide riboside (NR) induced transcriptional upregulation of mitochondrial and lysosomal processes in Parkinson’s patients within one month.

cGAS-STING in ALS. In amyotrophic lateral sclerosis, the accumulation of genomic instability and subsequent leakage of DNA into the cytoplasm activates the cGAS-STING pathway, triggering a cytokine response that results in motor neuron death. This positions genomic instability as a direct inflammatory trigger in neurodegeneration — not just in cancer.

E3 ubiquitin ligases as chaperones. Certain E3 ubiquitin ligases such as TRIM11 exhibit chaperone-like activity that increases the solubility of Tau, facilitating its clearance via the ubiquitin–proteasome or autophagic systems. This represents a convergence of the proteostasis and senescence hallmarks at the level of specific druggable protein targets.

Biases and Caveats: Model Organism Divergence and the Lifespan–Aging Rate Distinction

The BioSkepsis evidence corpus flags critical distinctions that temper the geroscience narrative.

Model organism divergence. Much foundational aging evidence relies on mice, where cancer accounts for 70–90% of natural deaths. Pro-longevity effects in rodents may therefore reflect direct anti-cancer mechanisms rather than a genuine slowing of the general aging rate. Interventions may extend life by purely inhibiting lethal, species-specific pathologies without affecting non-lethal aging markers like hair greying or skin thinning.

Biological age variation. Individuals age at different rates across different organ systems. Biological age is a more accurate predictor of disease risk than chronological age — but the implication is that not all pro-longevity interventions necessarily slow the aging rate of every tissue equally.

Regulatory hurdles. While biomarkers like the epigenetic clock (DunedinPACE) can detect changes in aging rates within two years of caloric restriction, the FDA does not yet recognise aging as a clinical indication. This creates a translational bottleneck for geroscience-derived therapies despite strong preclinical support.

Recency bias. The surge in publications between 2022 and 2025 has introduced high-resolution data (scRNA-seq) that clarifies cell-type-specific roles but often lacks the long-term longitudinal validation found in older, established evidence clusters.

Three Phases of Geroscience Evidence Evolution: From Hallmark Definition to Network Medicine

The BioSkepsis landscape synthesis maps the maturation of aging research into three distinct phases.

Early phase (2009–2015): Hallmark definition and interventional proof-of-concept. This period centred on foundational mechanisms: telomere attrition, genomic instability, and nutrient sensing. Key benchmarks included the demonstration that rapamycin could extend lifespan in genetically heterogeneous mice when administered late in life, and the discovery of senolytics — drugs like dasatinib and quercetin that selectively clear senescent cells to alleviate frailty.

Stable phase (2016–2021): Geroscience frameworks and multi-hallmark intersections. Researchers established formal clinical trial frameworks such as the TAME trial to move beyond single-disease paradigms. Evidence solidified around the role of metabolic sensors like AMPK and SIRT1 in modulating autophagy and mitochondrial function. This phase also demonstrated that aging hallmarks — immunosenescence and inflammaging — significantly dictate the severity of infections like COVID-19.

Emerging phase (2022–2025): Network expansion and critical synthesis. The hallmarks expanded from nine to twelve, adding disabled macroautophagy, chronic inflammation, and dysbiosis. Research now emphasises immunometabolic drift and inter-organ axes such as the gut–bone–brain interaction. “Osteosarcopenia” emerged as a bridge condition where bone and muscle deterioration synergise via shared inflammatory pathways. Critical perspectives simultaneously questioned whether rodent lifespan extension is a valid proxy for slowed organismal aging.

Who Benefits from Citation-Grounded Aging–Disease Research Synthesis

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