ABSTRACT
Background: Mitochondrial (Mito) dysfunction in IBD reduces mucosal O2 consumption and increases O2 delivery to the microbiome. Increased enteric O2 promotes blooms of facultative anaerobes (eg. Proteobacteria ) and restricts obligate anaerobes (eg. Firmicutes ). Dysbiotic metabolites negatively affect host metabolism and immunity. Our novel compound (AuPhos) upregulates intestinal epithelial cell (IEC) mito function, attenuates colitis and corrects dysbiosis in humanized Il10-/- mice. We posit that AuPhos corrects IBD-associated dysbiotic metabolism. Methods: Primary effect of AuPhos on mucosal Mito respiration and healing process was studied in ex vivo treated human colonic biopsies and piroxicam-accelerated (Px) Il10-/- mice. Secondary effect on microbiome was tested in DSS-colitis WT B6 and germ-free 129.SvEv WT or Il10-/- mice reconstituted with human IBD stool (Hu- Il10-/- ). Mice were treated orally with AuPhos (10- or 25- mg/kg; q3d) or vehicle, stool samples collected for fecal lipocalin-2 (f-LCN2) assay and microbiome analyses using 16S rRNA sequencing. AuPhos effect on microbial metabolites was determined using untargeted global metabolomics. AuPhos-induced hypoxia in IECs was assessed by Hypoxyprobe-1 staining in sections from pimonidazole HCl-infused DSS-mice. Effect of AuPhos on enteric oxygenation was assessed by E. coli Nissle 1917 WT (aerobic respiration-proficient) and cytochrome oxidase (cydA) mutant (aerobic respiration-deficient). Results: Metagenomic (16S) analysis revealed AuPhos reduced relative abundances of Proteobacteria and increased blooms of Firmicutes in uninflamed B6 WT, DSS-colitis, Hu-WT and Hu- Il10-/- mice. AuPhos also increased hypoxyprobe-1 staining in surface IECs suggesting enhanced O2 utilization. AuPhos-induced anaerobiosis was confirmed by a significant increase in cydA mutant compared to WT (O2-utlizing) E.coli . Ex vivo treatment of human biopsies with AuPhos showed significant increase in Mito mass, and complexes I and IV. Further, gene expression analysis of AuPhos-treated biopsies showed increase in stem cell markers (Lgr4, Lgr5, Lrig1), with concomitant decreases in pro-inflammatory markers (IL1ß,MCP1, RankL). Histological investigation of AuPhos-fed Px- Il10-/- mice showed significantly decreased colitis score in AuPhos-treated Px- Il10-/- mice, with decrease in mRNA of pro-inflammatory cytokines and increase in Mito complexes ( ND5 , ATP6 ). AuPhos significantly altered microbial metabolites associated with SCFA synthesis, FAO, TCA cycle, tryptophan and polyamine biosynthesis pathways. AuPhos increased pyruvate, 4-hydroxybutyrate, 2-hydroxyglutarate and succinate, suggesting an upregulation of pyruvate and glutarate pathways of butyrate production. AuPhos reduced IBD-associated primary bile acids (BA) with concomitant increase in secondary BA (SBA). AuPhos treatment significantly decreased acylcarnitines and increased L-carnitine reflective of enhanced FAO. AuPhos increases TCA cycle intermediates and creatine, energy reservoir substrates indicating enhanced OxPHOS. Besides, AuPhos also upregulates tryptophan metabolism, decreases Kynurenine and its derivatives, and increases polyamine biosynthesis pathway (Putresceine and Spermine). Conclusion: These findings indicate that AuPhos-enhanced IEC mitochondrial function reduces enteric O2 delivery, which corrects disease-associated metabolomics by restoring short-chain fatty acids, SBA, AA and IEC energy metabolism.
ABSTRACT
BACKGROUND: Altered prandial glycemic response after Roux-en-Y gastric bypass (RYGB) is exaggerated in patients with post-RYGB hypoglycemia. Increased contribution of glucagon-like peptide 1 (GLP-1) to prandial insulin secretion plays a key role in developing hypoglycemia after RYGB, but the role of nonhormonal gut factors remains unknown. Here, the effect of vagal activation on prandial bile acid (BA) composition in relation to glucose, insulin and gut hormone responses was examined in a small size group of nondiabetic subjects after RYGB with intact gallbladder compared to nonoperated controls. METHODS: Concentrations of blood glucose, hormones, and BAs were measured in two RYGB subjects with documented hypoglycemia (HGB), three asymptomatic RYGB-treated subjects (AGB), and four nonoperated controls with intact gallbladders during a meal-tolerance test with (MTT-Sham) and without (MTT) preceding modified sham feeding (chew and spit). KEY RESULTS: Meal ingestion raised serum total BAs in RYGB-treated subjects without any effect in nonoperated controls. Modified sham feeding similarly increased meal-induced responses of conjugated BAs (CBAs) in all subjects (p < 0.05 compared to MTT alone), whereas unconjugated BAs (UBAs), mainly deoxycholic and chenodeoxycholic acid, were raised only in the HGB group (p < 0.001 for interaction). Prandial UBAs had an inverse correlation with glucose nadir (r = -0.75, p < 0.05) and were directly associated with ISR and GLP-1 during MTT-Sham. CONCLUSIONS & INFERENCES: In this small cohort, vagal activation by modified sham feeding increases prandial CBAs in both operated and nonoperated subjects but enhances UBAs only in patients with documented post-RYGB hypoglycemia. Our findings highlight a potential role for nonhormonal gut factors, such as BA and gut microbiome, in glucose abnormalities after RYGB.
