Summary: Introduction: The gastrointestinal (GI) microbiome has emerged as a potential regulator of metabolism. However, the precise mechanisms of how microorganisms may influence physiology remain largely unknown. Interestingly, GI microorganisms, including methanogens, are localized within the same regions as the glucagon‐like peptide‐1 (GLP‐1) secreting L cells. GLP‐1 plays key roles appetite and glucose regulation. Furthermore, both methane and GLP‐1 levels are altered in obese humans with metabolic disease. We predict that high‐fat diet‐induced obesity alters the abundance of GI methanogens and that methane may play a role in the GLP‐1 secretory response from the L cell.Methods: To demonstrate this, GLP‐1 secretion response and faecal methanogens were examined in mice given a high‐fat diet for 14 weeks. In addition, the direct effect of methane on GLP‐1 secretion was assessed in two L‐cell models (NCI‐H716 and GLUTag).Results: High‐fat diet caused a significant increase in both GLP‐1 secretion and faecal methanogen content. There was a direct correlation between GLP‐1 secretion response and faecal methanogen levels. In L cells, methane stimulated GLP‐1 secretion and enhanced intracellular cAMP content.Conclusion: These results indicate that alterations in the methanogen communities occurring in obesity may play a vital role in directly enhancing GLP‐1 secretion, and that methane can directly stimulate the secretion of GLP‐1.

Circulating palmitic acid (PA) is increased in obesity and causes metabolic stress, leading to diabetes. This includes the impairment of the glucoregulatory hormone glucagon-like peptide-1 (GLP-1) secreted from intestinal L-cells. Recently, the anti-inflammatory gasotransmitter hydrogen sulfide (H₂S) has been implicated in the enhancement of GLP-1 secretion. We hypothesized that H₂S can reduce the oxidative stress caused by palmitate and play a protective role in L-cell function. This study was conducted on both human and mouse L-cells and a mouse model of Western diet (WD)-induced obesity. PA-induced L-cell stress was assessed using DCF-DA. H₂S was delivered using the donor GYY4137. C57BL/6 mice were fed either chow diet or PA-enriched WD for 20 weeks with ongoing measurements of glycemia and GLP-1 secretion. In both L-cell models, we demonstrated that PA caused an increase in reactive oxygen species (ROS). This ROS induction was partially blocked by the H₂S administration. In mice, the WD elevated body weight in both sexes and elevated fasting blood glucose and lipid peroxidation in males. Additionally, a single GYY4137 injection improved oral glucose tolerance in WD-fed male mice and also enhanced glucose-stimulated GLP-1 release. To conclude, H₂S reduces oxidative stress in GLP-1 cells and can improve glucose clearance in mice.

High-Intensity Interval Exercise (HIIE) has been shown to be more effective than moderate-intensity exercise for increasing acute lipid oxidation and lowering blood lipids during exercise and postprandially. Exercise in cold environments is also known to enhance lipid oxidation, however the immediate and long-term effects of HIIE exercise in cold are unknown. The purpose of this study was to examine the effects cold stress during HIIE on acute exercise metabolism and postprandial metabolism. Eleven recreationally active individuals (age: 23±3 years, weight: 80±9.7 kg, V̇O_2peak: 39.2±5.73 mL·kg^-1·min^-1) performed evening HIIE sessions (10x60s cycling, 90% V̇O_2peak interspersed with 90s active recovery, 30% V̇O_2peak) in thermoneutral (HIIE-TN, control; 21°C) and cold environments (HIIE-CO; 0°C), following a balanced crossover design. The following morning, participants consumed a high-fat meal. Indirect calorimetry was used to assess substrate oxidation, and venous blood samples were obtained to assess changes in noncellular metabolites. During acute exercise, lipid oxidation was 113% higher in HIIE-CO (p=0.002) without differences in V̇O₂ and EE (p≥0.162) between conditions. Postprandial V̇O₂, lipid and CHO oxidation, plasma insulin and triglyceride concentrations were not different between conditions (p>0.05). Postprandial blood LDL-C levels were higher in HIIE-CO two hours after the meal (p=0.003). Postprandial glucose AUC was 49% higher in HIIE-CO vs HIIE-TN (p=0.034). Under matched energy expenditure conditions, HIIE demonstrated higher lipid oxidation rates during exercise in the cold; but only marginally influenced postprandial lipid metabolism the following morning. In conclusion, HIIE in the cold seemed to be less favorable for postprandial lipid and glycemic responses.

Background: Obesity is a risk factor in the development of a variety of diseases including cardiovascular disease and type 2 diabetes. Circulating fatty acids (including palmitate) and protein glycation are both increased in obesity and diabetes and are known to cause metabolic stress. This includes the impairment of the glucoregulatory hormone glucagon-like peptide-1 (GLP-1) secreted from intestinal L-cells. Recently, the gastrointestinal microbiome has been implicated in the regulation of GLP-1. We believe that the bacterial metabolite hydrogen sulfide (H₂S) can play a protective role in L-cell metabolic stress. Methods: Our study was conducted on both human NCI H716 and mouse GLUTag GLP-1 secreting L-cells. L-cell stress was assessed using the total reactive oxygen species (ROS) dye DCF-DA. ROS levels were examined during incubation with palmitate (PA), glycated albumin (GA), and the bacterial gas donor GYY4137(H₂S). Next, GLP-1 secretion was measured after treating cells with PA and GA, along with H₂S using a GLP-1 ELISA. Results: We have demonstrated that elements of the obese physiological environment: PA and GA, cause an increase of reactive oxygen species (ROS) in L-cells. Specifically, 500μm PA and 200μg/mL GA caused a 75% and 50% increase in ROS generation, respectively. Furthermore, these treatments led to a 25% reduction of GLP-1 secretion in human L-cells. Finally, the microbial gas H₂S reduced basal and PA-induced ROS by nearly half. Conclusion: The microbial gas H₂S reduces metabolic stress in GLP-1 cells. This study will lay the foundation for future work exploring how bacterial products such as prebiotics and probiotics may be used as a treatment for complications associated with obesity and diabetes. Disclosure A. Mezouari: None. J. Gagnon: None. R. Nangia: None. Funding Natural Sciences and Engineering Research Council of Canada (RGPIN-2016-05905)

Background: Uterine smooth muscle tumors of uncertain malignant potential (STUMPs) are uncommon uterine neoplasms representing 1%–2% of uterine smooth muscle tumors. Recurrence after hysterectomy in postmenopausal patients has rarely been reported. Molecular alterations associated with recurrence remain poorly characterized. Methylthioadenosine phosphorylase (MTAP) deficiency has been described in sarcomas, but its role in STUMP remains poorly characterized. Case Presentation: A 61‐year‐old postmenopausal woman developed multifocal extrauterine recurrence affecting the rectus abdominis, vaginal cuff, peritoneum, small bowel, and abdominal wall 18 months after total abdominal hysterectomy with bilateral salpingo‐oophorectomy (TAH‐BSO) for presumed leiomyomas. The cumulative clinicopathologic findings were considered most consistent with recurrent STUMP, with one lesion exhibiting loss of MTAP expression. Retrospective review of the original hysterectomy specimen revealed previously unrecognized STUMP features, highlighting the diagnostic challenges at initial presentation. Conclusion: This case presents an unusual multifocal recurrence of STUMP following hysterectomy in a postmenopausal patient and reinforces the importance of long‐term surveillance, even after definitive surgical management. Focal MTAP loss was identified in one recurrent lesion and should be interpreted cautiously as a descriptive, hypothesis‐generating finding.