OBESE ADIPOSE TISSUE EXTRACELLULAR VESICLES ACTIVATE FATTY ACID OXIDATION TO DRIVE COLONIC STEMNESS

Introduction: Patients with obesity and mouse models of obesity exhibit abnormalities in intestinal epithelial cells, including altered barrier function and enhanced stemness. Adipose tissue (AT) is the largest endocrine organ secreting cytokines, hormones, and extracellular vesicles (EVs). AT cellular composition and secretion is strikingly altered during obesity, including increased EV release. EVs are lipid membrane-enclosed, nanometer sized vesicles released by cells that carry molecular cargo (protein, mRNA, other cytoplasmic components) to recipient cells, resulting in intra-organ communication. High fat diet (HFD)-induced obesity in mice can enhance stemness of Lgr5+ intestinal stem cells (ISCs), altering homeostasis of the crypt niche. However, modulation of ISCs directly by EVs secreted from AT remains unknown. Here, we aim to characterize EV cargo from obese and non-obese AT and demonstrate the role of obese adipose-derived EVs in altering colonic ISC function. Methods: As a mouse model of obesity, C57BL6 (WT) mice were fed a purified HFD containing 45% kcal fat or a purified matched diet containing 10% kcal fat from 4-20 weeks of age. Visceral AT was cultured ex vivo and EVs were isolated by differential centrifugation. Mouse obese (OB-EVs) and non-obese adipose EVs (N-OB-EVs) were characterized by Nanosight Tracking Analysis, transmission electron microscopy (TEM), and proteomic Panther analysis and Ingenuity Pathway Analysis (IPA). Colon organoids (colonoids) were cultured from WT mice for 2 days and then treated with N-OB-EVs or OB-EVs 10^7 or 10^8 EVs/ml every 2 days in exosome-free media for 7 days. To inhibit fatty acid (FA) b-oxidation (FAO), colonoids were treated with 100 mM etomoxir (ETX) or vehicle during EV treatment. Seahorse XF Mito Stress Test was conducted to analyze metabolism. Colonoids formed/crypt, regeneration capacity, and gene expression markers of ISCs were measured to determine stemness. Additionally, ability of EVs to sustain colonoid formation during reduced Wnt3α culturing conditions was measured. Results: Compared to N-OB-EVs, OB-EVs were significantly enriched with proteins associated with FA metabolism, with a significant upregulation of ACADL (log2(FC) = 5.492), an enzyme responsible for FAO (Fig. 1A-D). Colonoids treated with OB-EVs exhibited increased exogenous ACADL protein expression (Fig. 1E), survival, growth, and persistence of stem/progenitor function, which were abolished by ETX (Fig. 2). OB-EVs enhanced colonoid formation during reduced Wnt3α conditions. Conclusions: These results suggest that the contents of obese adipose EVs are poised to fuel FAO and to promote obesity-induced alterations in colonic ISCs. We identify alteration of metabolism as a key mechanism of adipose-to-intestinal tissue communication elicited by EVs, thereby influencing basal colonic ISC homeostasis during obesity.