RETRACTED ARTICLE: Obesity-associated gut microbiota is enriched in Lactobacillus reuteri and depleted in Bifidobacterium animalis and Methanobrevibacter smithii

TLDR

Obesity is linked to alterations in gut microbiota, notably reduced Bacteroidetes, and certain Lactobacillus and Bifidobacterium strains have been implicated in weight regulation. The study aimed to confirm reported gut microbiota changes and assess whether specific Lactobacillus or Bifidobacterium species associate with obesity or lean status. Stool samples from 68 obese and 47 control subjects were analyzed by quantitative PCR and selective culture to quantify Firmicutes, Bacteroidetes, Methanobrevibacter smithii, Lactococcus lactis, Bifidobacterium animalis, and seven Lactobacillus species. Bifidobacterium animalis and Methanobrevibacter smithii were linked to normal weight, whereas Lactobacillus reuteri was associated with obesity, indicating species‑level gut microbiota composition correlates with body weight and highlighting the first human evidence of Lactobacillus‑obesity association, though findings warrant cautious interpretation.

Abstract

Obesity is associated with increased health risk and has been associated with alterations in bacterial gut microbiota, with mainly a reduction in Bacteroidetes, but few data exist at the genus and species level. It has been reported that the Lactobacillus and Bifidobacterium genus representatives may have a critical role in weight regulation as an anti-obesity effect in experimental models and humans, or as a growth-promoter effect in agriculture depending on the strains. To confirm reported gut alterations and test whether Lactobacillus or Bifidobacterium species found in the human gut are associated with obesity or lean status, we analyzed the stools of 68 obese and 47 controls targeting Firmicutes, Bacteroidetes, Methanobrevibacter smithii, Lactococcus lactis, Bifidobacterium animalis and seven species of Lactobacillus by quantitative PCR (qPCR) and culture on a Lactobacillus-selective medium. In qPCR, B. animalis (odds ratio (OR)=0.63; 95% confidence interval (CI) 0.39–1.01; P=0.056) and M. smithii (OR=0.76; 95% CI 0.59–0.97; P=0.03) were associated with normal weight whereas Lactobacillus reuteri (OR=1.79; 95% CI 1.03–3.10; P=0.04) was associated with obesity. The gut microbiota associated with human obesity is depleted in M. smithii. Some Bifidobacterium or Lactobacillus species were associated with normal weight (B. animalis) while others (L. reuteri) were associated with obesity. Therefore, gut microbiota composition at the species level is related to body weight and obesity, which might be of relevance for further studies and the management of obesity. These results must be considered cautiously because it is the first study to date that links specific species of Lactobacillus with obesity in humans.