Obesity and the gut microbiota: does up-regulating colonic fermentation protect against obesity and metabolic disease?

Abstract

Obesity is now considered a major public health concern globally as it predisposes to a number of chronic human diseases. Most developed countries have experienced a dramatic and significant rise in obesity since the 1980s, with obesity apparently accompanying, hand in hand, the adoption of "Western"-style diets and low-energy expenditure lifestyles around the world. Recent studies report an aberrant gut microbiota in obese subjects and that gut microbial metabolic activities, especially carbohydrate fermentation and bile acid metabolism, can impact on a number of mammalian physiological functions linked to obesity. The aim of this review is to present the evidence for a characteristic "obese-type" gut microbiota and to discuss studies linking microbial metabolic activities with mammalian regulation of lipid and glucose metabolism, thermogenesis, satiety, and chronic systemic inflammation. We focus in particular on short-chain fatty acids (SCFA) produced upon fiber fermentation in the colon. Although SCFA are reported to be elevated in the feces of obese individuals, they are also, in contradiction, identified as key metabolic regulators of the physiological checks and controls mammals rely upon to regulate energy metabolism. Most studies suggest that the gut microbiota differs in composition between lean and obese individuals and that diet, especially the high-fat low-fiber Western-style diet, dramatically impacts on the gut microbiota. There is currently no consensus as to whether the gut microbiota plays a causative role in obesity or is modulated in response to the obese state itself or the diet in obesity. Further studies, especially on the regulatory role of SCFA in human energy homeostasis, are needed to clarify the physiological consequences of an "obese-style" microbiota and any putative dietary modulation of associated disease risk.

Shifts in microbiota species and fermentation products in a dietary model enriched in fat and sucrose

“…Our data agree with previous metagenomic analyses performed in diet-induced obese mice showing a bloom in the Erysipelotrichi class within the Firmicutes phylum (Fleissner et al, 2010Turnbaugh et al, 2008Turnbaugh et al, 2009;). In this context, it has been hypothesized that this group of bacteria could has the capacity to take up oligo-and monosaccharides from Western diets, such as glucose, fructose and sucrose, in order to produce ready to absorb short-chain fatty acids by their metabolism (Conterno et al, 2011). Moreover, these data should also consider the relevance of the increased body weight and possible metabolic changes related to the acquired overweight as a possible explanation for the increased Erysipelotrichi abundance.…”

A importância da microbiota no organismo humano e sua relação com a obesidade

“…A produção de SCFAs no cólon corresponde a 10% da energia diária requerida pelo homem e sua absorção é realizada através de difusão passiva ou via transportadores de ácidos mono-carboxílicos 19,20 .…”

Microbiota in Obesity

“…Enteroendocrine cells express the SCFA receptor and this gives the gut microbiota the opportunity to regulate host metabolism by induction of gut hormones released by L-cells especially glucagon-like peptide (GLP) and peptide YY (PYY) in response to GPCRs activation [14]. These hormones control satiety by regulating the production and release of digestive enzymes [18]. In addition to its effect on satiety, PYY decreases pancreatic secretions, suppresses gastric motility and slows gastric emptying thus enhancing digestion.…”