Hypothesis

We propose that administering recombinant human growth hormone in short, nocturnal pulses aligned with endogenous slow‑wave sleep GHRH surges will raise serum IGF-1 to levels comparable with exercise training in older adults, yet will not provoke insulin resistance or other metabolic adverse effects.

Mechanistic Rationale

• GH pulsatility preserves hepatic STAT5 signaling while limiting SOCS induction – Continuous GH exposure drives sustained JAK2-STAT5 activation that upregulates suppressors of cytokine signaling (SOCS2/3), which blunt insulin receptor substrate phosphorylation and promote hepatic insulin resistance. In contrast, intermittent GH spikes allow SOCS proteins to degrade between pulses, maintaining insulin signaling fidelity. This principle is supported by rodent models where pulsatile GH restores insulin sensitivity despite elevated IGF-1[[https://www.frontiersin.org/journals/genetics/articles/10.3389/fgene.2021.667355/full]].
• Exercise‑like IGF-1 production via hepatic IGF‑1 gene transcription – Nocturnal GH pulses amplify the natural sleep‑associated IGF‑1 surge, stimulating hepatic IGF‑1 synthesis without the chronic elevation seen with daily injections. Exercise raises IGF‑1 through a similar pulsatile pattern, which explains its metabolic safety[[https://pmc.ncbi.nlm.nih.gov/articles/PMC5938552/]].
• Decoupling from inflammaging‑driven insulin resistance – By avoiding constant GH receptor activation, the hypothesis reduces GH‑induced SOCS-mediated interference with insulin signaling, allowing the anti‑inflammatory benefits

Hypothesis

Aged retinal pigment epithelium (RPE) releases mitochondria-derived extracellular vesicles (EVs) loaded with oxidized mitochondrial DNA (mtDNA). These EVs act as damage‑associated molecular patterns that bind mannose‑binding lectin (MBL) and activate the lectin complement pathway, generating C3 convertase, C3 deposition, and downstream membrane attack complex (MAC) formation. The resulting complement activity amplifies reactive oxygen species (ROS) production, creating a feed‑forward loop that drives RPE dysfunction. Enhancing mitophagy reduces EV release, thereby lowering lectin‑pathway activation and breaking the redox‑complement loop while preserving C3’s essential opsonophagocytic functions.

Rationale

• Oxidative stress can directly activate complement components, leading to C3 deposition and MAC formation that further increase ROS and mitochondrial damage [1].
• In aged mouse retinas, C3 accumulates in the sub‑RPE space by 12 months, marking sites of ongoing injury [2].
• C3‑deficient aged mice show preserved retinal thickness, better electroretinogram b‑wave amplitudes, reduced 4‑HNE, and heightened autophagy (higher LC3B‑II/I, lower p62) [2], indicating that loss of C3 mitigates the deleterious arm of the loop.
• Paradoxically, complete C3 loss worsens pathology in the absence of regulatory proteins (CFH⁻/⁻.C3⁻/⁻ mice exhibit more photoreceptor loss, Bruch’s membrane thickening, and amyloid

Background

The convergence of senolytic and metabolic interventions has shown synergistic lifespan extension in mice, exemplified by rapamycin plus acarbose achieving up to 36.6% median lifespan increase [2]. However, clinical translation is hampered by off-target toxicity of potent senolytics such as navitoclax, which causes thrombocytopenia [1]. Emerging strategies use senomorphics to suppress the senescence-associated secretory phenotype (SASP) before senolytic exposure to reduce inflammatory toxicity [1].

Hypothesis

We propose that short-term pretreatment with rapamycin acts as a senomorphic that remodels lysosomal function and increases the expression of specific endocytic receptors on senescent cells, thereby enhancing the uptake and cytotoxic efficiency of subsequently administered senolytics while permitting lower drug doses and reducing off-target effects.

Testable Predictions

1. In vitro, human fibroblasts rendered senescent by irradiation will show increased lysosomal activity (measured by LysoTracker fluorescence) and upregulated expression of the mannose-6-phosphate receptor (M6PR) after 24 h rapamycin treatment (10 nM).
2. Co‑culture of these pre‑treated senescent cells with navitoclax will result in a ≥2‑fold increase in Annexin V‑positive cells compared with navitoclax alone, an effect blocked by chloroquine pretreatment.
3. In aged mice, intermittent rapamycin (5 mg/kg, i.p., 3 days/week) administered 48 h prior to a sub‑therapeutic dose of navitoclax (25 mg/kg) will achieve senescent cell clearance comparable to full‑dose navitoclax (50 mg/kg

Hypothesis

Age‑associated decline in the eukaryotic initiation factor 2B (eIF2B) complex, rather than PERK kinase activity, creates a translational bottleneck that prevents ATF4 protein accumulation despite phosphorylated eIF2α in senescent satellite cells. Restoring eIF2B activity will bypass this block, re‑establish the PERK‑ATF4‑autophagy axis, and rescue muscle regeneration.

Rationale

Recent work shows that PERK/eIF2α signaling is intact in aged muscle but ATF4 protein fails to accumulate【4】. This points to a defect downstream of eIF2α‑P, specifically in the ribosome reinitiation step that depends on eIF2B‑mediated GTP‑GDP exchange on eIF2. eIF2B activity declines with age in several tissues, and its inhibition reproduces the translational block seen in senescence【1】【2】. Moreover, the PERK arm is essential for satellite cell survival, differentiation and regeneration【3】, whereas IRE1 deletion does not affect regeneration, underscoring the non‑redundant role of PERK‑ATF4 output.

We hypothesize that age‑related oxidative stress or inflammatory signaling modifies eIF2B subunits (e.g., via phosphorylation of the ε subunit) reducing its guanine‑nucleotide exchange activity. Consequently, even when eIF2α is phosphorylated, ternary complex formation is insufficient to allow ribosomes to bypass the upstream ORFs of ATF4 mRNA, blocking its translation.

Predictions

1. In satellite cells isolated from old mice, eIF2B activity (measured by GDP‑GTP exchange assay) will be lower than in young cells, while PERK phosphorylation and eIF2α‑P levels remain comparable.
2. Pharm

Intermittent pulses of gut‑derived microbial metabolites activate the enteric nervous system (ENS) to trigger a systemic hormetic response that upregulates repair pathways without inducing chronic inflammation.

Microbial metabolites such as short‑chain fatty acids (SCFAs) and tryptamine derivatives fluctuate rhythmically with feeding cycles. These molecules stimulate afferent fibers of the vagus and spinal ENS, leading to coordinated release of acetylcholine and serotonin in the gut wall. The resulting neurochemical signal travels to the hypothalamus and peripheral tissues, where it transiently activates AMPK, SIRT1, and HSF1 in a pattern that mimics classic hormetic stressors (e.g., exercise, fasting). Because the signal is brief and followed by a recovery window, downstream effectors—FOXO transcription factors, Nrf2, and mitophagy machinery—are phosphorylated and then allowed to reset, preventing the pathway exhaustion seen with constant agonist exposure.

We hypothesize that this ENS‑mediated metabolite rhythm provides the constitutive low‑amplitude threat signal described in the seed idea, keeping repair networks primed. In the absence of such pulses, repair pathways drift toward basal activity, accelerating accumulation of lipofuscin and mitochondrial damage; conversely, excessive or continuous metabolite exposure drives maladaptive stress, mimicking the insulin resistance observed with continuous rapamycin dosing.

Testable predictions: 1. Germ‑free mice colonized with a strain that produces a rhythmic SCFA pulse (e.g., engineered Lactobacillus releasing butyrate

Hypothesis

It's known that senescent immune cells in gut‑associated lymphoid tissue secrete SASP factors that reshape the luminal microbiome toward LPS‑rich taxa, which in turn fuels systemic inflammaging and microglial activation. We hypothesize that targeted depletion of LPS‑producing bacteria with gut‑restricted bacteriophages will interrupt this loop, reduce circulating endotoxin, lower senescence‑associated cytokine production, and restore neuroimmune homeostasis.

Rationale

Aging immune cells accumulate in Peyer’s patches and mesenteric lymph nodes, where they release IL‑6, TNF‑α and IL‑1β that alter epithelial mucus secretion and antimicrobial peptide patterns. This creates a niche favoring Enterobacteriaceae and other LPS‑rich anaerobes. Elevated LPS translocates across a compromised barrier, triggering TLR4 signaling on peripheral monocytes and brain microglia, which amplifies SASP production in a feed‑forward circuit. Breaking the microbial arm should therefore dampen the immune senescence driver.

Predictions

• Aged mice receiving oral LPS‑specific phage will show a >50 % reduction in fecal LPS‑encoding gene copies within 7 days.
• Plasma TNF‑α, IL‑6 and IL‑1β will decline to levels comparable to young controls after 2 weeks.
• Flow cytometry of splenic and cerebral CD8⁺ T cells will reveal a ≥30 % decrease in p16^INK4a^‑positive senescent cells.
• Microbiome sequencing will reveal a relative increase in butyrate‑producing Clostridia and a decrease in Proteobacteria.
• Behavioral assays (sucrose preference, forced swim) will demonstrate improved mood‑l

Hypothesis

Iron availability in colonic crypts operates as a bistable regulator of TET enzyme activity, creating two epigenetically distinct stem‑cell states: a youthful state with low Wnt‑gene methylation and an aged state exhibiting ACCA drift. Restoration of intracellular iron(II) not only reactivates TET demethylation but also triggers a butyrate‑dependent upregulation of ferroportin (FPN), exporting excess iron and preventing re‑accumulation of oxidative stress that drives further drift.

Mechanistic Basis

• Iron(II) is a cofactor for TET enzymes; its loss in aging crypts reduces 5‑mC oxidation, allowing DNMT‑mediated hypermethylation of Wnt regulators (see iron‑TET link) [3].
• Butyrate, a bacterial fermentation product, inhibits HDACs, increasing transcription of the iron‑export gene FPN and the iron‑storage gene ferritin light chain (FTL) via heightened histone acetylation at their promoters.
• Elevated FPN exports cytosolic iron(II), lowering the labile iron pool and reducing Fenton‑mediated ROS that would otherwise oxidize TET cofactors and promote DNMT3B activity.
• Thus, a butyrate‑iron feedback loop can lock crypts in a low‑methylation, low‑ROS state, reversing ACCA drift.

Testable Predictions

1. Crypts isolated from proximal colon (higher butyrate exposure) will show higher FPN expression, higher labile iron(II), and lower ACCA‑associated methylation than distal crypts.
2. Acute iron chelation with deferoxamine in colonic organoids will increase TET activity and decrease methylation at the 15 CRC‑associated CpG sites within 72 h.
3. Supplementa

Hypothesis

Chronic elevation of mitochondrial UDP‑GlcNAc flux drives O‑GlcNAcylation of the mitochondrial chaperone HSP60, reducing its ability to refold imported proteins and thereby promoting aggregation of client proteins such as α‑synuclein and misfolded metabolic enzymes in cardiomyocytes and neurons.

Rationale

• The hexosamine biosynthetic pathway (HBP) supplies UDP‑GlcNAc that fuels O‑GlcNAc transferase (OGT) activity in the mitochondrial matrix when the pyrimidine nucleotide carrier pnc1 transports UDP‑GlcNAc across the inner membrane [3].
• Mitochondrial OGT mislocalization in diabetic hearts correlates with respiratory dysfunction [3].
• HSP60 is a matrix‑localized chaperone essential for folding of mitochondrial proteins; its activity is known to be modulated by post‑translational modifications, yet O‑GlcNAcylation of HSP60 has not been reported.
• O‑GlcNAc cycling influences α‑synuclein aggregation and autophagy‑lysosome flux [4], linking HBP flux to proteostasis failure.
• Aging activates HBP genes and promotes extracellular matrix GAG accumulation, suggesting a feed‑forward loop where increased flux exacerbates protein aggregation [6].

Mechanistic Insight

We propose that O‑GlcNAcylation of HSP60 occurs on serine/threonine residues within its apical domain, sterically hindering ATP binding and substrate interaction. This modification would shift HSP60 from a high‑affinity foldi

Aging tissues accumulate dysfunctional cells not because they are actively pruned but because surveillance systems collapse. In the brain, neurons suffer oxidative damage and impaired protein clearance while microglial phagocytosis wanes; in the colon, DNA mismatch repair‑deficient (dMMR) clones evade immune elimination and expand, creating field cancerization. Both failures share a metabolic hinge: declining NAD+ levels reduce sirtuin activity and increase PARP consumption, leading to hyperacetylation of FOXO3 and NF‑κB p65. Hyperacetylated FOXO3 cannot drive autophagic gene expression in neurons, allowing damaged proteins to persist. Hyperacetylated p65 sustains a chronic inflammatory state that exhausts CD8+ T cells and compromises their cytotoxic granule release in the colonic mucosa. Consequently, the same NAD+ deficit simultaneously weakens neuronal quality control and immune surveillance, permitting the buildup of metabolically expensive, weakly connected neurons and hypermutated dMMR epithelial clones.

Testable prediction: Restoring NAD+ in aged mice will reinstate FOXO3‑dependent autophagy in neurons and restore CD8+ T cell cytotoxicity against dMMR clones, reducing both neuronal loss and clonal expansion. Experimentally, 24‑month‑old C57BL/6 mice receive nicotinamide riboside (NR) or vehicle for 12 weeks. Brain sections are stained for NeuN, LC3‑II, and 4‑HNE to quantify neuronal survival, autophagic flux, and oxidative damage. Colon tissues are immunostained for MLH1 loss (dMMR marker), CD8, granzyme B, and γH2AX to assess clone burden, T cell infiltration, cyto

Hypothesis

Aging induces epigenetic reprogramming of intestinal stem cells (ISCs) that selectively silences tight‑junction genes (TJP1/OCLN) and activates the pore‑forming claudin‑2 (CLDN2) promoter, thereby establishing a self‑reinforcing loop of barrier dysfunction and systemic inflammaging.

Mechanistic Rationale

• DNA methylation as a primary regulator: In aged ISCs, increased activity of DNA methyltransferase 1 (DNMT1) leads to hypermethylation of CpG islands in the promoters of TJP1 and OCLN, reducing their transcription. Concurrently, loss of methylation at specific enhancer regions of CLDN2 enhances its expression, creating a “leaky” phenotype.
• Link to inflammaging: Elevated serum IFN‑γ and IL‑6 in older individuals further upregulate DNMT1 via STAT1/STAT3 signaling, creating a feed‑forward loop where cytokine exposure deepens epigenetic silencing of barrier genes.
• Reversibility through TET activation: Vitamin C or low‑dose 5‑azacytidine can stimulate ten‑eleven translocation (TET) enzymes, promoting demethylation of TJP1/OCLN promoters and restoring transcription, while also suppressing CLDN2 expression.
• Connection to CB₁ signaling: The same epigenetic machinery regulates CNR1 (CB₁ receptor) promoters; colonic CNR1 remains unmethylated with age, explaining preserved CB₁ expression in the colon but loss in the small intestine where DNMT1 activity is higher.

Testable Predictions

1. Methylation‑expression correlation: In human intestinal biopsies from young (<30 yr) and old (>70 yr) donors, bisulfite sequencing will show significa

Hypothesis: Combined oral supplementation with urolithin A (UA) and spermidine will synergistically lower senescence biomarkers in human immune cells by coupling UA-driven mito-phagy with spermidine-stimulated bulk autophagy, resulting in enhanced lysosomal clearance and attenuated senescence-associated secretory phenotype.

Mechanistic basis: UA activates the AMPK-SIRT1-PGC-1alpha axis, which promotes PINK1/Parkin-mediated removal of damaged mitochondria and stimulates mitochondrial biogenesis[1]. AMPK activation also phosphorylates ULK1, initiating autophagosome formation. Spermidine inhibits the acetyltransferase EP300, leading to increased acetylation of histone H3 at autophagy-gene promoters and to deacetylation of essential autophagy proteins such as ATG5 and ATG7, thereby amplifying general autophagosome synthesis[2]. Both pathways converge on the lysosomal transcription factor TFEB: SIRT1-dependent deacetylation increases TFEB nuclear localization, while EP300 inhibition prevents TFEB acetylation-driven inactivation, together boosting lysosomal biogenesis and acidification. Elevated lysosomal capacity accelerates degradation of mito-phagy cargos and cytosolic protein aggregates, reducing oxidative stress and DNA damage that drive p16^INK4a and p21^CIP1 expression. Lower mitochondrial ROS also dampens NF-kappaB signaling, curbing the secretion of IL-6, TNF-alpha and other SASP factors.

Testable prediction: In a randomized, double-blind, placebo-controlled study of adults aged 65-80, participants receiving UA (1 g/day) plus spermidine (5 mg/day) for 12 weeks will

Hypothesis

In the aged zona reticularis, protein aggregates are not inert waste but a dynamic reservoir that sequesters misfolded steroidogenic enzymes (e.g., CYP17A1, 3β‑HSD) into a thermodynamically stable state. This sequestration prevents soluble oligomers from inhibiting residual activity while preserving a pool of enzyme that can be refolded when proteostatic capacity is transiently boosted. Thus, aggregates function as a buffered depot that sustains DHEA output until stress‑responsive chaperones or disaggregases are recruited.

Mechanistic Basis

• Chronic oxidative stress in the zona reticularis promotes partial unfolding of CYP17A1, generating aggregation‑prone intermediates.
• When chaperone (Hsp70, Hsp90) and proteasome activities decline, the cell redirects these intermediates into amyloid‑like aggregates via small heat shock proteins (HspB1, HspB5) that act as nucleators.
• The aggregated conformation buries exposed hydrophobic surfaces, reducing soluble oligomer toxicity.
• Localized ATP‑dependent disaggregase complexes (Hsp110‑Hsp70‑Hsp40) can transiently associate with aggregates, pulling out individual monomers for refolding without fully dissolving the depot.
• This cycle creates a steady‑state where a fraction of enzyme remains active, another fraction is safely stored, and a third fraction is being repaired.

Testable Predictions

1. Pharmacological enhancement of disaggregase activity (e.g., with Hsp110 inducers) will increase soluble CYP17A1 levels and DHEA secretion in aged adrenal slices, but only if aggregate turnover is not overwhelmed. 2

Hypothesis\nNAD+ decline does not merely reflect damage; it actively amplifies the senescence‑associated secretory phenotype (SASP) by suppressing SIRT1 deacetylase activity, thereby unleashing NF‑κB‑driven transcription of pro‑inflammatory cytokines and CD38. This creates a feed‑forward loop where rising CD38 consumes more NAD+, further inhibiting SIRT1 and sustaining SASP.\n\n## Mechanistic Rationale\nSIRT1 requires NAD+ to deacetylate p65 NF‑κB, keeping it transcriptionally quiet. When NAD+ falls, p65 remains acetylated, NF‑κB translocates to the nucleus, and drives expression of IL‑6, IL‑8, and CD38 itself [1][2]. Senescent cells already secrete SASP factors that induce CD38 [2]; low NAD+ deepens this signal by removing SIRT1’s brake. Concurrently, PARP1 hyperactivation—triggered by accumulating DNA damage—competes for the dwindling NAD+ pool, lowering SIRT1 activity even further [3]. The net effect is a metabolic‑inflammatory circuit that converts NAD+ loss from a passive biomarker into an active driver of chronic inflammation.\n\n## Testable Predictions\n1. Pharmacological elevation of NAD+ (e.g., NMN) in old mice will reduce SASP factor secretion and lower CD38 expression in tissues, independent of senescent‑cell clearance.\n2. SIRT1 overexpression in senescent cells will blunt NF‑κB activation and decrease CD38 transcription even when NAD+ is low.\n3. Simultaneous inhibition of CD38 and activation of SIRT1 will synergistically lower circulating IL‑6 and improve metabolic readouts more than either intervention alone.\n\n## Experimental Design\n- Animal cohorts

Chronic NSAID use reduces prostaglandin E2 (PGE2) signaling, which in turn diminishes mitochondrial citrate export and ATP‑citrate lyase (ACLY) activity, lowering nuclear acetyl‑CoA pools. Reduced acetyl‑CoA limits histone acetylation, especially H3K27ac, and shifts the epigenetic landscape toward a pattern seen in accelerated aging. This hypothesis predicts that long‑term NSAID users will show higher epigenetic age (e.g., GrimAge) and lower nuclear acetyl‑CoA/H3K27ac levels compared with age‑matched non‑users, independent of underlying pain status.

Mechanistic Rationale

• PGE2 binds EP2/EP4 receptors → Gs → ↑cAMP → PKA activation → phosphorylation and activation of ACLY in cytosol and nucleus.
• Active ACLY cleaves citrate to acetyl‑CoA + oxaloacetate, feeding cytosolic and nuclear acetyl‑CoA pools.
• Nuclear acetyl‑CoA is the substrate for histone acetyltransferases (p300/CBP) that deposit H3K27ac at enhancers of DNA‑damage‑response and metabolic genes.
• Reduced H3K27ac leads to tighter chromatin, diminished transcription of repair genes, and increased recruitment of DNA methyltransferases (DNMT3A/B) at CpG islands.
• The resulting epigenetic drift mirrors clocks such as GrimAge, which weigh methylation at sites linked to smoking, plasma proteins, and aging‑related phenotypes.

Experimental Design

1. Cohort assembly – Recruit three groups of adults aged 50‑75: (i) chronic NSAID users (≥6 months daily ibuprofen or celecoxib), (ii) pain‑matched controls using acetaminophen (non‑COX‑2 inhibitor), and (iii) healthy controls with no regular analgesic use. Target

Hypothesis: Intermittent hormetic stimuli trigger a transient increase in chondroitin sulfate C6‑sulfation (C6S) mediated by the sulfotransferase CHST11, which alters the negative charge density of the hippocampal extracellular matrix [1]. This charge shift modulates local electric fields, thereby tuning the voltage‑dependence of nearby Na⁺ and Ca²⁺ channels and adjusting neuronal excitability toward a protective, low‑firing state [2]. Repeated cycles of sulfation increase and subsequent depletion during recovery create a structural memory that sustains improved mitochondrial function and suppresses senescence markers (p16^INK4a, SASP) [3]. With advancing age, basal CHST11 activity declines and the ECM becomes locked in a low‑C6S/high‑C4S state, reducing matrix negative charge, depolarizing resting potentials, and promoting hyperexcitability‑driven calcium overload that feeds into inflammaging [4][5][6]. Thus, the health benefits of hormesis depend on the capacity to remodel ECM sulfation patterns; loss of this plasticity converts a protective signal into a maladaptive, age‑associated ECM signature [7].

Testable predictions: (1) In young mice, intermittent fasting or exercise will raise hippocampal C6S/C4S ratios within 6 h, returning to baseline after 24 h of recovery; (2) Pharmacological inhibition of CHST11 (e.g., with D‑6‑O‑sulfate) will block the hormetic rise in C6S and abolish the associated improvements in spatial memory and mitochondrial respiration; (3) Aged mice supplemented with a CHST11‑activating peptide will show restored C6S enrichment, reduced hipp

Hypothesis

In aging vocal folds, chronic subclinical inflammation creates a siege‑like metabolic state that constitutively activates autophagy transcriptional programs while lysosomal dysfunction blocks flux completion. This mismatch forces the cell to rationally dismantle non‑essential biosynthetic machinery—particularly ER‑associated ribosomes and rough endoplasmic reticulum—through selective ER‑phagy, thereby reducing synthesis of extracellular matrix proteins (collagen, elastin) and accelerating the fibro‑fatty atrophy seen in presbyphonia. Mitochondrial ribosomes are spared to preserve ATP for survival.

Mechanistic Rationale

• Transcription‑flux uncoupling: Cholesterol depletion and aging‑related TFEB/FOXO dysregulation increase ATG gene transcription 1 2 but lysosomal acidification and cathepsin activity decline, yielding high LC3‑II puncta with accumulated p62—a signature of incomplete autophagy.
• Selective cargo preference: Inflammation‑induced muscle atrophy shows preferential autophagy of ER and cytosolic ribosomes while sparing mitochondrial ribosomes 4; we hypothesize a similar hierarchy in vocal fold fibroblasts where ER‑phagy receptors (e.g., FAM134B, SEC62) are up‑regulated, targeting the secretory pathway responsible for ECM protein production.
• Energetic triage: By consuming ER membranes and ribosomes, the cell liberates amino acids and lipids for immediate energy needs, sustaining b

Background

Cardiac involvement in systemic sclerosis (SSc) remains a leading cause of mortality, yet early detection of myocardial fibrosis is challenging. Current biomarkers (troponin, BNP) detect injury late. Myeloid-derived growth factor (MYDGF), secreted by bone marrow-derived monocytes and macrophages under inflammatory stress, has emerged as a cardioprotective mediator whose circulating levels paradoxically decline during active fibrotic remodeling. Periostin, a matricellular protein produced by activated cardiac fibroblasts, exists in multiple splice variants with differential profibrotic potency.

Hypothesis

We propose that the trajectory slope of serum soluble MYDGF decline, combined with the ratio of periostin splice variants (exon 17-containing/exon 21-containing) measured in peripheral blood, predicts subclinical myocardial fibrosis progression in SSc 8–20 weeks before cardiac MRI native T1 mapping values exceed the pathological threshold.

Mechanistic Rationale

1. MYDGF consumption model: In early myocardial fibrosis, activated cardiac fibroblasts and infiltrating macrophages consume MYDGF locally as an endogenous anti-fibrotic signal, reducing circulating levels before structural damage becomes imageable.
2. Periostin isoform switching: The exon 17-containing periostin variant preferentially activates αVβ3/αVβ5 integrin-mediated TGF-β signaling in cardiac fibroblasts, while exon 21-containing variants have reduced profibrotic activity. A rising exon17/exon21 ratio reflects active fibroblast polarization toward pathological matrix depositio

Hypothesis

KDM5 demethylases act as a chromatin‑based brake that prevents the age‑associated spread of H3K27me3 from peak to inter‑peak regions at glycolytic gene promoters. By binding to high‑H3K4me3, accessible chromatin through its JmjC catalytic domain and C5HC2 zinc finger, KDM5 maintains a locally permissive environment that limits PRC2 activity. When KDM5 function is compromised—either by loss of demethylase activity or disruption of its scaffolding interface—PRC2 gains access to these loci, leading to ectopic H3K27me3 deposition, transcriptional silencing of glycolytic enzymes, and the metabolic decline observed in aged Drosophila. This model directly links the divergent roles of KDM5 in cancer (where its overexpression promotes immune evasion) and aging (where its loss of function drives metabolic dysfunction) through a shared mechanism: regulation of the H3K4me3/H3K27me3 balance at bivalent domains.

Testable Predictions

1. Genetic perturbation – Knocking down KDM5 (via RNAi or CRISPR) in young adult flies will recapitulate the aged H3K27me3 drift profile, increasing inter‑peak signal by ~9% at glycolytic promoters without altering global H3K4me3 levels.

2. Pharmacological inhibition – Treatment with a selective KDM5 inhibitor (e.g., CPI-455) will produce the same epigenetic shift as genetic loss, and the effect will be rescued by concomitant PRC2 knock‑down, indicating epistatic relationship.

3. Chromatin context dependence – Mutating the C5HC2 zinc finger while preserving the JmjC domain will still cause H3K27me3 redistribution, confi

Hypothesis

Age‑related decline in gut epithelial mitochondrial function releases mitochondrial DNA (mtDNA) into the intestinal lumen and circulation, where it acts as a damage‑associated molecular pattern (DAMP) that activates the cGAS‑STING pathway in brain microglia, driving neuroinflammation independently of classic LPS or SCFA mechanisms.

Rationale

• The gut‑brain axis in aging is a bidirectional loop where dysbiosis, barrier leak, and microglial activation reinforce each other [1] [2].
• Current models emphasize microbial metabolites (CML, LPS, SCFAs) and cytokine signaling (CNTF/JAK/STAT3) as the main routes to microglial activation [1].
• However, aged gut epithelium shows accumulated mitochondrial dysfunction, increased ROS, and mtDNA damage [3]. Extracellular mtDNA is a potent DAMP that engages cytosolic cGAS, producing cGAMP and activating STING‑TBK1‑IRF3 signaling, leading to type‑I IFN production and inflammasome priming [4].
• If gut‑derived mtDNA reaches the brain via circulation or vagal afferents, it could directly stimulate microglia, bypassing the need for peripheral cytokine surges.

Novel Mechanistic Insight

We propose that mitochondrial stress in enterocytes triggers the