Targeting FABP4 Improves Healthy Aging by Rejuvenating Liver Metabolism

Introduction: Aging is characterized by progressive metabolic dyshomeostasis that increases morbidity and mortality. Solutions for optimizing healthy aging are challenged by lacking appropriate biomarkers. Moreover, druggable targets to rejuvenate the aging-associated metabolic phenotypes remain unavailable. Methods: Proteomics analysis was performed in a cohort of young and elderly adults. Circulating levels of insulin-like growth factor 1 (IGF-1) and fatty acid binding protein 4 (FABP4) were evaluated by ELISA. FABP4 was silenced in elderly mice by adeno-associated virus. Metabolic activities were measured by metabolic cages. Cognitive function was evaluated by Morris water maze. Glucose and lipid metabolism were evaluated by biochemistry assays with blood samples. RNA-seq in mouse liver was performed for transcriptome analysis. Results: Among 9 aging-sensitive proteins shared by both male and female, FABP4 was identified as a reliable aging biomarker in both human and mouse. Silencing FABP4 in elderly mice significantly rejuvenated the aging-associated decline in metabolic activities. FABP4 knockdown reversed the aging-associated metabolic disorders by promoting degradation of cholesterol and fatty acids, while suppressing gluconeogenesis. Transcriptome analysis revealed a restoration of the pro-aging gene reprogramming towards inflammation and metabolic disorders in the liver after FABP4 knockdown. FABP4 overexpression promoted human LO2 cell senescence. Moreover, administration of an FABP4 inhibitor BMS309403 delivered metabolic benefits in elderly mice. Conclusion: Our findings demonstrate FABP4 as a reliable aging biomarker as well as a practicable target to improve healthy aging in the elderly. Keywords: Aging; Biomarkers; FABP4; Metabolic disorders; Rejuvenation; Senescence. Overall design: All animals were housed in a constant environment (room temperature, 24 ± 3 °C; room humidity,55 ± 5%) with a standard 12-h light/12-h dark cycle. Mice were fed with normal chow and with free access to water. A total of thirty 14-month-old male WT mice were randomly divided into two groups as the following: (1) mice injected with AAV9-shRNA-Fabp4 by tail vein and sWAT in situ injection with a dose of 4×10^11 viral genomes, n=15; (2) mice injected with AAV9-shRNA-Neg with the same way and same amount, n=15. The above animals were kept until 20-month-old after AAV injection for sundry experiments. A group of 8-week-old WT mice were regarded as young control group (n=15). The mice were anaesthetized with inhalational anaesthetic and euthanized by cervical dislocation. Liver were immediately dissected and stored at -80°C. Three independent biological replicate samples from Young or Old group were used for RNA extraction. RNA-seq was completed by Novogene.