title: Intestinal Methanobrevibacter smithii but not total bacteria is related to diet-induced weight gain in rats.
abstract: It is increasingly understood that gastrointestinal (GI) methanogens, including Methanobrevibacter smithii, influence host metabolism.
  
  
  OBJECTIVE
  Therefore, we compared M. smithii colonization and weight gain in a rat model under different dietary conditions.
  
  
  METHODS
  Sprague-Dawley rats were inoculated with M. smithii or vehicle (N = 10/group), fed normal chow until day 112 postinoculation, high-fat chow until day 182, then normal chow until day 253. Thereafter, five rats from each group were fed high-fat and normal chow until euthanasia.
  
  
  RESULTS
  Both groups exhibited M. smithii colonization, which increased following inoculation only for the first 9 days. Change to high-fat chow correlated with significant increases in weight (P < 0.00001) and stool M. smithii (P < 0.01) in all rats, with stool M. smithi decreasing on return to normal chow. Rats switched back to high-fat on day 253 further increased weight (P < 0.001) and stool M. smithii (P = 0.039). Euthanasia revealed all animals had higher M. smithii, but not total bacteria, in the small intestine than in the colon. Rats switched back to high-fat chow had higher M. smithii levels in the duodenum, ileum, and cecum than those fed normal chow; total bacteria did not differ in any bowel segment. Rats which gained more weight had more bowel segments colonized, and the lowest weight recorded was in a rat on high-fat chow which had minimal M. smithii colonization.
  
  
  CONCLUSIONS
  We conclude that M. smithii colonization occurs in the small bowel as well as in the colon, and that the level and extent of M. smithii colonization is predictive of degree of weight gain in this animal model.
authors.affiliation: Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Cedars-Sinai Medical Center, Los Angeles, California, USA.
authors.forename: Ruchi
authors.initials: R
authors.lastname: Mathur
authors.forename: Gene
authors.initials: G
authors.lastname: Kim
authors.forename: Walter
authors.initials: W
authors.lastname: Morales
authors.forename: Jaekyu
authors.initials: J
authors.lastname: Sung
authors.forename: Emily
authors.initials: E
authors.lastname: Rooks
authors.forename: Venkata
authors.initials: V
authors.lastname: Pokkunuri
authors.forename: Stacy
authors.initials: S
authors.lastname: Weitsman
authors.forename: Gillian M
authors.initials: GM
authors.lastname: Barlow
authors.forename: Christopher
authors.initials: C
authors.lastname: Chang
authors.forename: Mark
authors.initials: M
authors.lastname: Pimentel
mesh_terms: D000818:Animals; D004032:Diet; D059305:Diet, High-Fat; D007421:Intestine, Small / Q000378:metabolism / Q000382:microbiology*; D041581:Methanobrevibacter / Q000254:growth & development / Q000302:isolation & purification*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015430:Weight Gain