MON-719 Alterations in Diaphragm Neuromuscular Junctions and Associated Mesenchymal Cells in Obesity-associated Respiratory Dysfunction

Abstract Disclosure: J.A. Syed: None. S. Patterson: None. J. Yang: None. M. Woo: None. E.D. Buras: None. Introduction and objective: Pulmonary disorders impact 40-80% of individuals with obesity and include dyspnea on exertion, which reduces exercise tolerance, and obesity hypoventilation syndrome (OHS), which doubles 5-year mortality rate. Type 2 diabetes independently contributes to increased risk of chronic respiratory disorders, with phenic neuropathy implicated in the pathogenesis. Fibro-adipogenic progenitors (FAPs) are muscle mesenchymal cells recently shown to be critical for maintenance of neuromuscular junctions (NMJs). Notably, an FAP subpopulation marked by Hsd11b1 and Mme expression, geographically associates with NMJs, suggesting a functional link. Our previous work demonstrated high fat diet feeding to significantly alter diaphragm FAP profiles; however, the impact of obesity and diabetes on diaphragm NMJ-associated FAPs remains uninvestigated. Methods: We evaluated this in a model of long-standing obesity/ type 2 diabetes by subjecting mice to a 12-month diet-induced obesity (DIO) protocol beginning at 2-months old, analyzing diaphragm NMJ morphology by confocal microscopy and FAP profiles by single cell RNA sequencing (scRNA-seq). Results: 12-month DIO mice developed respiratory dysfunction, as indicated by whole body plethysmography (tidal volume reduction during hypoxic and hypercapnic challenges) and non-invasive ultrasound (reduced diaphragm excursion amplitude). NMJs of DIO mice exhibited an abnormal crumpled morphology and increased peri-NMJ extracellular matrix deposition. Hsd11b1/ Mme-expressing NMJ-associated FAPs assumed a fibro-inflammatory phenotype with enhanced expression of the genes encoding NF-kB, interleukin-6, and fibronectin. Conclusions: These data demonstrate that alterations in respiratory function and diaphragm NMJ architecture correspond with the emergence of fibro-inflammatory NMJ-associated FAPs in a model of long-term obesity and type 2 diabetes. Presentation: Monday, July 14, 2025