Age-related changes in neurotransmitter systems contribute to declines in cognitive, emotional, and motor function, yet the biological mechanisms linking these changes to aging are not completely understood. Epigenetic regulation offers a promising framework to bridge this gap. DNA methylation-based biomarkers of biological aging (i.e., epigenetic clocks) capture cumulative and dynamic aspects of biological aging that may reflect vulnerability in neural systems beyond chronological age. However, whether these indices track with the integrity of neurotransmitter systems has not been systematically examined. This scoping review synthesizes evidence across human studies to evaluate how epigenetic aging processes influence neurotransmitter gene regulation and system function across the lifespan. We included 109 studies spanning 2005–2026. GABAergic genes (GAD1, GABRA2) showed the most consistent and reproducible age-related promoter hypermethylation across the cortex, inversely correlated with mRNA expression and corroborated by MRS evidence of cortical GABA decline. Dopaminergic and serotonergic evidence during normative aging was sparse; most epigenetic data in these systems came from disease cohorts. Histone modifications converged on neurotransmission and synaptic-plasticity loci, predominantly in Alzheimer’s disease tissue. Subcortical and brainstem nuclei central to monoaminergic and cholinergic systems remain under-investigated for normative aging epigenetic processes. Environmental and social determinants, socioeconomic status, childhood adversity, and chronic stress, were consistently associated with accelerated peripheral epigenetic aging, but brain-specific data are scarce.

Background: Hepatocellular carcinoma (HCC) develops predominantly from chronic liver injury, with diet representing a clinically actionable yet mechanistically complex modulator of hepatic carcinogenesis. Despite advances in immunotherapy, long-term survival remains poor, underscoring the need for complementary preventive and adjunctive strategies. Methods: We conducted a narrative review of epidemiological, experimental, and clinical literature on dietary patterns, polyphenols, and non-polyphenol nutraceuticals for HCC prevention and management, with a focus on underlying molecular and cellular mechanisms. Results: Dietary polyphenols and selected nutraceuticals exert pleiotropic effects on signaling pathways implicated in HCC, including NF-κB, STAT3, TGF-β/SMAD, PI3K/AKT, and Wnt/β-catenin, while modulating hepatic stellate cell activation, immune cell polarization, and microbiome-derived metabolites. Preclinical studies suggest that some compounds may enhance antitumor immunity and sensitize tumors to systemic therapies; however, clinical translation is constrained by limited bioavailability, pharmacokinetic variability, formulation heterogeneity, and a lack of high-quality trials. Conclusions: This review highlights the potential of dietary patterns and nutraceuticals in HCC prevention and as adjunctive therapies. It outlines key translational priorities, including etiologic stratification, biomarker-driven trial design, and rigorous safety evaluation.

Background/Objectives: Glioblastoma (GBM) is the most lethal primary brain malignancy in adults, with a median overall survival of approximately 15 months. Temozolomide (TMZ) resistance develops in virtually all patients, and no second-line regimen has improved outcomes over the past two decades. The DNA methyltransferase inhibitor decitabine (DAC) has attracted interest as a chemosensitizer, but whether it directly reverses the TMZ-resistance transcriptome or operates through distinct, complementary mechanisms has not been tested at multi-omics resolution. Methods: We performed an integrative six-layer multi-omics analysis across five public GEO datasets (bulk RNA-seq, EPIC 850K methylation, and 21,676 single cells) re-purposed from studies conducted for unrelated aims, formally tested DAC-mediated reversal of the TMZ-resistance transcriptome across 11,707 genes, mapped pharmacogenomic targets with DGIdb v5, and built an exploratory, hypothesis-generating 11-gene prognostic model internally validated in TCGA-GBM (n = 166) and externally tested in the independent CPTAC-GBM cohort (n = 96). Results: DAC reprogrammed transcription across 1114–1882 differentially expressed genes per cohort and reactivated 146 direct epigenetic targets, identifying INPP5D/SHIP1 as the top-ranked direct epigenetic-reactivation target. Genome-wide reversal analysis across 11,707 co-detected genes showed a negligible effect (Spearman ρ = 0.073), but single-cell analysis revealed significant per-cell attenuation of MES-like and stem-like programs (Δ = −0.071 and −0.135, respectively; both p < 0.001). The 11-gene risk model achieved a Harrell’s C-index of 0.706 (apparent); after correcting for the two-stage gene selection with a full-pipeline bootstrap, the optimism-corrected C-index was 0.63, and external validation in an independent cohort (CPTAC-GBM, n = 96) showed only near-chance discrimination (C-index 0.55), indicating that the signature does not generalize and is exploratory. Pharmacogenomic mapping yielded 734 unique therapeutic agents (230 FDA-approved) across 69 druggable targets after excluding AR. Most of these agents are not GBM-directed, so this catalog-level mapping is hypothesis-generating rather than a set of therapeutic recommendations. Conclusions: DAC does not broadly reverse the TMZ-resistant transcriptome but acts through three complementary mechanisms: epigenetic reactivation of INPP5D/SHIP1, cancer-testis-antigen and type I interferon induction, and per-cell attenuation of mesenchymal–stem-like transcriptional intensity, supporting hypotheses for rationally designed DAC-based combination therapy in TMZ-resistant GBM.