High-fat diet exacerbates experimental colitis by inhibiting lysosomal function via the STAT3-TFEB Axis

An elevated risk for inflammatory bowel disease (IBD) has been linked to the intake of high-fat diet (HFD), yet the underlying molecular mechanisms remain unclear. The lysosome and the macroautophagy/autophagy-lysosome pathway (ALP) are critical for maintaining the intestinal epithelial barrier. By employing both an in vivo model of dextran sulfate sodium (DSS)-induced colitis in mice and an in vitro model using lipopolysaccharide (LPS)-treated NCM460 cells, we established that HFD in vivo and palmitic acid (PA) in vitro profoundly impair epithelial barrier function and amplify inflammation, which was linked to the suppression of lysosomal function and the ALP. Mechanistically, HFD in vivo and PA in vitro activated STAT3 (p-STAT3[Y705]) under DSS- and LPS-associated inflammatory stress, respectively. This led to a dual suppression of TFEB: on the one hand, activated STAT3 directly bound to the TFEB promoter to inhibit its transcription; on the other hand, it facilitated the lysosomal recruitment of MTOR and activated MTORC1, which promoted TFEB phosphorylation (p-TFEB[S211]) and hindered its nuclear translocation. This cascade resulted in lysosomal membrane permeabilization (LMP), loss of acidification, and impaired degradative function. Intestinal epithelial-specific knockout of Stat3 or pharmacological activation of TFEB restored lysosomal function, repaired the epithelial barrier, and ameliorated colitis. Conversely, rectal administration of AAV9-shTfeb reversed the protective effects conferred by stat3 knockout. Our study reveals that HFD in vivo and PA in vitro disrupt lysosomal function and the intestinal barrier through the STAT3-TFEB axis, suggesting this signaling pathway as a promising avenue for intervention in diet-associated IBD.Abbreviations: AB-PAS: Alcian blue-periodic acid-Schiff; ALP: autophagy-lysosome pathway; CD: Crohn disease; ChIP: chromatin immunoprecipitation; CLEAR: coordinated lysosomal expression and regulation; DSS: dextran sulfate sodium; HFD: high-fat diet; IBD: inflammatory bowel disease; IF: immunofluorescence; IHC: immunohistochemistry; LAMP: lysosome associated membrane protein; LGALS3/Gal3: galectin 3; LMP: lysosomal membrane permeabilization; LPS: lipopolysaccharide; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MTOR: mechanistic target of rapamycin kinase; MTORC1: mechanistic target of rapamycin kinase complex 1; PA: palmitic acid; RRAG: Ras-related GTP binding; RRAG-CA: constitutively active RRAG GTPase; RT-qPCR: reverse transcription quantitative PCR; SQSTM1/p62: sequestosome 1; STAT3: signal transducer and activator of transcription 3; TA1: TFEB activator 1; TEM: transmission electron microscopy; TFEB: transcription factor EB; TJ: tight junction; TUNEL: terminal deoxynucleotidyl transferase dUTP nick-end labeling; UC: ulcerative colitis; WB: western blot; WT: wild-type.