Evidence for greater production of colonic short-chain fatty acids in overweight than lean humans

Abstract

BackgroundShort-chain fatty acids (SCFA) are produced by colonic microbiota from dietary carbohydrates and proteins that reach the colon. It has been suggested that SCFA may promote obesity via increased colonic energy availability. Recent studies suggest obese humans have higher faecal SCFA than lean, but it is unclear if this difference is due to increased SCFA production or reduced absorption.ObjectivesTo compare rectal SCFA absorption, dietary intake and faecal microbial profile in lean (LN) versus overweight and obese (OWO) individuals.DesignEleven (11) LN and 11 OWO individuals completed a 3-day diet record, provided a fresh faecal sample and had SCFA absorption measured using the rectal dialysis bag method. The procedures were repeated after two weeks.ResultsAge-adjusted faecal SCFA concentration was significantly higher in OWO than LN (81.3 ± 7.4 vs. 64.1 ± 10.4 mmol/kg, P = 0.023). SCFA absorption (24.4 ± 0.8 vs 24.7 ± 1.2%, respectively, P =0.787) and dietary intakes were similar between the groups, except for a higher fat intake in OWO. However, fat intake did not correlate with SCFAs or bacterial abundance. OWO had higher relative Firmicutes abundance (83.1 ± 4.1 vs 69.5 ± 5.8%, respectively, P = 0.008) and a higher Firmicutes:Bacteriodetes ratio (P = 0.023) than LN. There was a positive correlation between Firmicutes and faecal SCFA within the whole group (r =0.507, P =0.044), with a stronger correlation after adjusting for available carbohydrate (r = 0.615, P =0.005).ConclusionsThe higher faecal SCFA in OWO subjects is not due to differences in SCFA absorption or diet. Our results are consistent with the hypothesis that OWO subjects produce more colonic SCFA than LN due to differences in colonic microbiota. However, further studies are needed to prove this.

Effects of dietary inulin on bacterial growth, short-chain fatty acid production and hepatic lipid metabolism in gnotobiotic mice

“…There are ambiguous data about the effect of dietary fiber and SCFA on obesity development. While a systematic review published in 2011 [28] reports a slight but significant decrease of body weight (1.3%) with higher dietary fiber intake, recent literature data show a positive correlation between SCFA and obesity [9]. The positive effect of dietary fibers on obesity development is often correlated with a reduced appetite and thereby a decreased energy intake.…”

“…Consistent with this, several studies revealed that obese individuals have significantly higher fecal SCFA concentrations than lean individuals. Since this was not due to changes in the colonic absorption rate or dietary intake, it is taken as evidence for a higher production of SCFA in overweight individuals [9,10]. In apparent contrast to that, other results show a negative correlation between cecal SCFA production and obesity, and they suggest a protective effect of SCFA against dietinduced weight gain [11,12].…”

Short Chain Fatty Acids Prevent High-fat-diet-induced Obesity in Mice by Regulating G Protein-coupled Receptors and Gut Microbiota

“…However, no consistent conclusions have been reached on changes of gut SCFA production in obesity. It has been demonstrated that fecal SCFA concentrations in rodent models of genetic obesity and overweight adult humans are higher than those of their lean counterparts, indicating an increased microbial energy harvest in obesity222327. However, in diet-induced obese mice fed a HFD with 45% calories from fat, reduced fecal SCFA (acetate and propionate) concentrations have been reported28.…”

Gut microbiota and glucometabolic alterations in response to recurrent partial sleep deprivation in normal-weight young individuals

“…Both animal and human studies indicate that cholesterol synthesis and other liver functions can be influenced by gut-derived SCFAs, even over short time scales [60], [61], [62], [63]. Bacteria producing SCFAs are less abundant in obesity and T2DM [6], but, strikingly, some studies found higher fecal SCFA concentrations in obese subjects [10], [64]. Evidence suggests that supplementation with these molecules may impact insulin sensitivity and energy expenditure in mice and humans [65], [66].…”