The mammalian brain fundamentally relies on precise lipid homeostasis to maintain structural integrity and complex neural signaling. Emerging evidence positions lipid metabolism reprogramming not merely as a secondary pathological byproduct but as a core initiating driver of age-related neurodegenerative diseases. This review systematically evaluates the mechanisms of cerebral lipid dyshomeostasis during brain aging, highlighting glial cells as the central mediators of this pathological cascade. We comprehensively dissect the age-associated “lipid drift”, emphasizing apolipoprotein E (APOE)-induced cholesterol transport defects and lipid raft pathology, the accumulation of lipid droplets that triggers microglial metabolic stress (LDAMs), and ceramide-driven neuronal apoptosis coupled with the exosome-mediated propagation of pathogenic proteins. Furthermore, we map these aberrant lipid networks to specific pathological signatures in Alzheimer’s, Parkinson’s, and demyelinating diseases. Finally, we critically evaluate promising therapeutic interventions, including nutritional strategies, LXR/RXR agonists, and nanotechnology-enabled delivery systems designed to bypass the blood–brain barrier. By integrating high-throughput lipidomics for early diagnostic biomarker discovery, we underscore the translational imperative of restoring cerebral lipid homeostasis as a disease-modifying strategy for neurodegeneration.

The prevention and treatment of cardiovascular disease (CVD) are undergoing a paradigm shift from a lipid-centric approach to a holistic metabolic perspective. Central to this evolution is the gut–fat–heart axis, a sophisticated three-dimensional communication network that integrates neural, endocrine, and immunometabolic signaling to regulate systemic lipid homeostasis. This manuscript systematically explores how the gut microbiota acts as a “metabolic organ” to remotely control host health through the production of bioactive metabolites and the modulation of molecular communication networks. At the physiological level, microbial products such as short-chain fatty acids (SCFAs) and modified bile acids regulate energy balance and lipid synthesis via the FXR-FGF15/19 axis and G protein-coupled receptors. Furthermore, gut hormones like GLP-1 and neuro-reflex pathways involving the vagus nerve provide rapid control over postprandial lipid clearance and feeding behavior. Conversely, pathological dysbiosis triggers the accumulation of harmful metabolites, such as trimethylamine N-oxide (TMAO) and lipopolysaccharides (LPS), which drive lipotoxicity, vascular inflammation, and “dysfunctional HDL” formation. These processes accelerate the progression of atherosclerosis, heart failure, and metabolic syndrome. Finally, the article outlines promising clinical translation strategies, including the development of TMA lyase inhibitors, next-generation probiotics, and the use of phytochemicals to reshape the microbial landscape. By decoding the molecular dialogues within the gut–fat–heart axis, this research provides a novel strategic vantage point for the integrated management of cardiovascular–kidney–metabolic (CKM) syndrome.