Brief communicationRoux-en-Y gastric bypass surgery in rats alters gut microbiota profile along the intestine☆
Introduction
Recent studies examined the association between changes in intestinal microbial diversity in obese rodents and humans; some bacterial groups were associated with changes in the nutritional status. Obesity was associated with higher Firmicutes and lower Bifidobacterium spp., Bacteroides-related bacteria and Lactobacillus spp. in comparison with the lean counterparts [1], [2], [3], [4]. Interestingly, weight loss achieved by dieting was able to reverse those changes [5]. Furthermore, nutrients with prebiotic properties induced qualitative changes in the composition of the gastrointestinal microbiota and peptide release (e.g., glucagon-like peptide-1 (GLP-1)) similar to those seen after dieting. In diet-induced obese and type 2 diabetic (T2DM) mice the release of gut peptides induced by treatment with prebiotics improved glucose and lipid metabolism as well as systemic inflammation [6].
Roux-en-Y gastric bypass (RYGB) is currently, the most effective strategy for long term weight loss maintenance. RYGB significantly reduces body weight, improves T2DM and changes the postprandial enteric endocrine responses.
Gut microbiota analysis of fecal samples from humans and rats after RYGB suggested that the reduction of Firmicutes and Bacteroidetes may partly explain the weight loss and beneficial effects on metabolism and inflammation associated with the RYGB surgery [7], [8], [9]. Liou [10] confirmed these findings and also showed that cecal transplants from mice after RYGB to unoperated germ free mice decreased the body weight and adiposity compared to recipients of microbiota from sham-operated mice.
There are currently no data on the impact of gut microbiota on the hormonal and metabolic changes associated with RYGB. In most of the human and rodent studies investigating the ecology and activity of intestinal microbiota, fecal or cecal samples have been used. However, these may not be representative of the microbiome in RYGB where the intestine is surgically manipulated into three discrete sections which may each contribute to distinct metabolic signals compared to feces that represents a amalgamate of the microbiome from the intestine as a whole. Therefore, we assessed the bacterial composition in the different anatomically corresponding intestinal segments after RYGB or sham surgery.
Section snippets
Subjects and housing
Sixteen male Wistar rats (Harlan Laboratories Inc., Blackthorn, UK; Elevage Janvier, Le-Genest-St. Isle, France) were individually housed under a 12 h/12 h light–dark cycle at a room temperature of 21 ±2 °C. Water and standard chow were available ad libitum. All experiments were approved by the Veterinary Office of the Canton Zurich, Switzerland. All rats were given one week of acclimatization before being randomized to RYGB (n = 8) or sham-operation (n = 8). After surgery, rats received Ensure
Results and discussion
Average presurgical body weight of rats was 430 ± 4 g. Seven days after surgery, sham-operated controls weighed significantly more compared with gastric bypass rats (sham: 370 ± 9 g vs. bypass: 450 ± 6 g, p < 0.001). Body weight changes for both groups are shown in Fig. 2.
Total bacterial content was significantly increased in the alimentary limb and common channel after RYGB compared to sham rats. In the cecum after RYGB the changes in the microbial ecology were similar to that seen after prebiotic
Conclusions
In conclusion, these data are critical because they accurately represent how RYGB surgery may affect microbial communities in different intestinal segments after surgery. Because most changes in gut microbiota were independent from weight loss, we conclude that other mechanisms than weight loss per se seem to be responsible for the alteration of the intestinal microbial population after RYGB surgery.
Postsurgical modulations of the gastrointestinal microbial community, e.g. the bypass of the
Disclosure
The authors declare no conflict of interests.
Melania Osto (MO) was supported by the Swiss National Research Foundation (SNF) — Ambizione-Nachwuchsförderungskredit and the Olga Mayenfisch Research Foundation, Grant Nr. 35111013.
Kathrin Abegg (KA) was supported by the Forschungskredit of the University of Zurich.
Marco Bueter (MB) was supported by the SNF.
Patrice D. Cani (PDC) was supported by the FRS-FNRS (Fond de la Recherche Scientifique) in Belgium.
Thomas A. Lutz (TAL) was supported by the SNF
Author contribution
MO; TAL: study concept and design;
MO; KA; MB: acquisition of data;
MO; PDC; TAL: analysis and interpretation of data;
MO; TAL: drafting of the manuscript.
MB; CWR; PDC; TAL: critical revision of the manuscript for important intellectual content.
Acknowledgements
We would like to thank PDC who is a Research Associate from the FRS-FNRS.
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