The gut microbiota as an environmental factor that regulates fat storage

Abstract

New therapeutic targets for noncognitive reductions in energy intake, absorption, or storage are crucial given the worldwide epidemic of obesity. The gut microbial community (microbiota) is essential for processing dietary polysaccharides. We found that conventionalization of adult germ-free (GF) C57BL͞6 mice with a normal microbiota harvested from the distal intestine (cecum) of conventionally raised animals produces a 60% increase in body fat content and insulin resistance within 14 days despite reduced food intake. Studies of GF and conventionalized mice revealed that the microbiota promotes absorption of monosaccharides from the gut lumen, with resulting induction of de novo hepatic lipogenesis. Fasting-induced adipocyte factor (Fiaf), a member of the angiopoietin-like family of proteins, is selectively suppressed in the intestinal epithelium of normal mice by conventionalization. Analysis of GF and conventionalized, normal and Fiaf knockout mice established that Fiaf is a circulating lipoprotein lipase inhibitor and that its suppression is essential for the microbiota-induced deposition of triglycerides in adipocytes. Studies of Rag1؊͞؊ animals indicate that these host responses do not require mature lymphocytes. Our findings suggest that the gut microbiota is an important environmental factor that affects energy harvest from the diet and energy storage in the host.symbiosis ͉ nutrient processing ͉ energy storage ͉ adiposity ͉ fastinginduced adipose factor

Genes involved in obesity: Adipocytes, brain and microflora

“…Along the same lines Bäckhed et al (2004), recently reported that germ-free mice re-colonized with normal microbiota rapidly develop a 60% increase in body fat mass associated with insulinresistance, despite reduced food intake. As expected (Maffei et al, 1995), these mice present increased leptin levels, proportional to the increase of body fat.…”

Probiotics – do they have a role in the pig industry?

“…A novel role in regulating fat storage has been recently ascribed to microbiota by recent studies, a promotion of monosaccharides absorption from the gut resulting in induction of de novo hepatic lipogenesis has been shown by comparing germ-free mice with conventionalised mice (Bä ckhed et al, 2004). Furthermore, an increased capacity to harvest energy from the diet has been observed by comparing gut microbiota of obese and lean mice (Turnbaugh et al, 2006).…”

Implication de la flore intestinale dans le métabolisme énergétique

“…Plusieurs études américaines émanant du laboratoire de J. Gordon ont suggéré l'implication de la flore intestinale dans la régulation de l'homéostasie énergétique [11]. Il y a quelques années, F. Backhed et ses collaborateurs ont mis en évidence le fait suivant : de jeunes souris élevées de façon classique possèdent -malgré un apport alimentaire en calories moins important -une masse adipeuse plus développée (+ 40 %) que celle des souris exemptes de flore intestinale (souris axéniques) [12]. Dans le même ordre d'idée, les auteurs ont démontré que les souris dépourvues de flore intestinale à la naissance, puis colonisées avec une flore intestinale émanant de souris normales, développent davantage de masse grasse (environ + 60 %) et présentent une diminution de la sensibilité à l'insuline deux semaines après l'instauration de la flore.…”

“…La diminution de l'expression de FIAF observée chez les souris colonisées, participerait à l'accumulation de lipides dans le tissu adipeux. Ces expériences ont démontré pour la première fois que les bactéries intestinales pouvaient réguler le stockage d'énergie chez l'hôte qu'elles colonisent [12] ( Figure 1). …”