Alteration in faecal bile acids, gut microbial composition and diversity after laparoscopic sleeve gastrectomy

Background Laparoscopic sleeve gastrectomy (LSG) is a well established treatment for severe obesity and type 2 diabetes. Although the gut microbiota is linked to the efficacy of LSG, the underlying mechanisms remain elusive. The effect of LSG for morbid obesity on the gut microbiota and bile acids was assessed here. Methods Severely obese subjects who were candidates for LSG were included and followed until 6 months after surgery. The composition and abundance of the microbiota and bile acids in faeces were assessed by 16S ribosomal RNA sequencing, quantitative PCR and liquid chromatography-mass spectrometry. Results In total, 28 patients with a mean(s.d.) BMI of 44 center dot 2(6 center dot 6) kg/m(2) were enrolled. These patients had achieved excess weight loss of 53 center dot 2(19 center dot 0) per cent and showed improvement in metabolic diseases by 6 months after LSG, accompanied by an alteration in the faecal microbial community. The increase in alpha-diversity and abundance of specific taxa, such as Rikenellaceae and Christensenellaceae, was strongly associated with reduced faecal bile acid levels. These changes had a significant positive association with excess weight loss and metabolic alterations. However, the total number of faecal bacteria was lower in patients before (mean(s.d.) 10 center dot 26(0 center dot 36) log(10) cells per g faeces) and after (10 center dot 39(0 center dot 29) log(10) cells per g faeces) operation than in healthy subjects (10 center dot 83(0 center dot 27) log(10) cells per g faeces). Conclusion LSG is associated with a reduction in faecal bile acids and greater abundance of specific bacterial taxa and alpha-diversity that may contribute to the metabolic changes.