Adipose Tissue, Bile Acids, and Gut Microbiome Species Associated With Gallstones After Bariatric Surgery.

Several risk factors are associated with gallstone disease after bariatric surgery, but the underlying pathophysiological mechanisms of gallstone formation are unclear. We hypothesize that gallstone formation after bariatric surgery is induced by different pathways compared with gallstone formation in the general population, since postoperative formation occurs rapidly in patients who did not develop gallstones in preceding years. To identify both pathophysiological and potentially protective mechanisms against postoperative gallstone formation, we compared the preoperative fasting metabolome, fecal microbiome, and liver and adipose tissue transcriptome obtained before or during bariatric surgery of obese patients with and without postoperative gallstones. In total, 88 patients were selected from the BARIA longitudinal cohort study. Within this group, 32 patients had postoperative gallstones within 2 years. Gut microbiota metagenomic analyses showed group differences in abundance of 41 bacterial species, particularly abundance of Lactobacillaceae and Enterobacteriaceae in patients without gallstones. Subcutaneous adipose tissue transcriptomic analyses revealed four genes that were suppressed in gallstone patients compared with patients without gallstones. These baseline gene expression and gut microbiota composition differences might relate to protective mechanisms against gallstone formation after bariatric surgery. Moreover, baseline fasting blood samples of patients with postoperative gallstones showed increased levels of several bile acids. Overall, we revealed different genes and bacteria associated with gallstones than those previously reported in the general population, supporting the hypothesis that gallstone formation after bariatric surgery follows a different trajectory. Further research is necessary to confirm the involvement of the bile acids, adipose tissue activity, and microbial species observed here.

Lactose after Roux-en-Y gastric bypass for morbid obesity, is it a problem?

BACKGROUND: Roux-en-Y gastric bypass (RYGB) can cause multiple food intolerances and gastrointestinal complaints are frequently reported after dairy consumption. We aimed to determine the prevalence of lactose malabsorption and intolerance, and complaints associated with dairy consumption in daily life, before and after RYGB. METHOD: The lactose breath test (LBT) and lactose tolerance test (LTT) was performed in 84 patients awaiting RYGB surgery and 84 patients after surgery. Gastrointestinal symptoms at baseline and after testing were recorded. Lactose malabsorption was defined as a positive LBT and/or LTT. Lactose intolerance as a positive test combined with an increase of gastrointestinal complains. Dairy consumption in daily life and successive gastrointestinal complaints were registered via a questionnaire. Results of preoperative and postoperative patients were compared. RESULTS: Lactose malabsorption was present in 15 (17.9%) of the preoperative patients and in 25 (29.8%) of the postoperative patients (OR 2.46; 95%CI: 1.08-5.59; p = .03). Of the preoperative patients 6 (7.1%) patients met the criteria for lactose intolerance, compared to 8 (9.5%) patients in the postoperative group (OR 1.48; 95%CI 0.48-4.57; p = .50). Twelve (14.3%) preoperative patients indicated to have gastrointestinal complaints after dairy consumption in daily life versus 45 (53.6%) postoperative patients (p < .01). CONCLUSION: This study shows no increase in patients with proven lactose intolerance after RYGB compared to preoperative patients. Gastrointestinal complaints after dairy consumption in daily life were far more frequently reported by RYGB patients. It is unlikely that all reported gastrointestinal complaints are actually caused by lactose. Other ingredients in dairy, like fat, are possibly contributory.