Lipid Metabolism-Signaling Crosstalk in Metabolic Disease and Aging: Mechanisms and Therapeutic Targets

Lipid metabolism and lipid-derived signaling together ensure cellular and systemic homeostasis. Their dysregulation causes obesity, type 2 diabetes, cardiovascular disease, NAFLD/MASH, and neurodegeneration throughout life. This review integrates central pathways, such as ACC-FASN-mediated de novo lipogenesis, lipid-droplet lipolysis, and mitochondrial and peroxisomal β-oxidation, and their regulation by insulin-PI3K-Akt, glucagon-cAMP-PKA, SREBPs, PPARs, and AMPK. We emphasize the mechanisms by which bioactive lipids like diacylglycerols, ceramides, eicosanoids, and endocannabinoids serve as second messengers linking nutrient state to insulin signaling, inflammation, and stress response; pathologic accumulation of these species enhances insulin resistance and lipotoxicity. Aging disrupts these axes via diminished catecholamine-stimulated lipolysis, defective fatty-acid oxidation, mitochondrial failure, and adipose depot redistribution, facilitating ectopic fat and postprandial dyslipidemia. We suggest a pathway-to-phenotype paradigm that connects lipid species and tissue environment to clinical phenotypes, allowing for mechanism-to-intervention alignment. Therapeutic avenues range from lipid lowering for atherogenic risk to novel agents targeting ACLY, ACC, FASN, CPT1, and nuclear receptors, with precision lifestyle intervention in diet and exercise. Translation is still heterogeneous because of isoform-dependent effects, safety trade-offs, and inconsistent adherence. We prioritize harmonization of lipidomics with multi-omics for stratifying patients, enriching responders, and bridging gaps between mechanistic understanding and clinical outcome, with focus on age-sensitive prevention and treatment for lipid-mediated metabolic disease.