<i>Akkermansia muciniphila</i> abundance is lower in severe obesity, but its increased level after bariatric surgery is not associated with metabolic health improvement

Abstract

The gut bacterial species <i>Akkermansia muciniphila</i> is associated with a healthier clinical profile. The purpose of this study was to determine the association between <i>A. muciniphila</i> and glucose homeostasis in patients undergoing bariatric surgery (BS): gastric banding (GB) or Roux-en-Y gastric bypass (RYGB). This nonrandomized prospective study included 65 women with severe obesity. Longitudinal analysis included subjects for whom <i>A. muciniphila</i> data were available at follow-up [1, 3, and 12 mo; GB (<i>n</i> = 10) or RYGB (<i>n</i> = 11)]. Glucose homeostasis markers were measured under fasting conditions (glucose, insulin, and HbA1c) or during an oral glucose tolerance test. Fecal microbiota was analyzed using shotgun metagenomics, and <i>A. muciniphila</i> relative abundance was assessed with 16S rRNA quantitative PCR. <i>A. muciniphila</i> relative abundance was significantly lower in severe obesity [mean body mass index, 45.7 kg/m² (SD 5.4)] than in moderate obesity [33.2 kg/m² (SD 3.8)] but not associated with glucose homeostasis markers. A significant increase in <i>A. muciniphila</i> relative abundance after RYGB was not correlated with metabolic improvement. Baseline <i>A. muciniphila</i> abundance was correlated with bacterial gene richness and was highest in the high-richness Ruminococcaceae enterotype. <i>A. muciniphila</i> increased in relative abundance after BS in patients with low baseline <i>A</i>. <i>muciniphila</i> abundance, especially those with a <i>Bacteroides</i> type 2 enterotype classification. Although decreased in severe obesity, relative abundance of <i>A. muciniphila</i> was not associated with glucose homeostasis before or after BS. A certain level of <i>A. muciniphila</i> abundance might be required to observe a beneficial link to health. The severity of obesity and gut dysbiosis may partly explain the discrepancy with previous findings in less obese populations.