Adiposity, gut microbiota and faecal short chain fatty acids are linked in adult humans

Abstract

Background/Objectives:High dietary fibre intakes may protect against obesity by influencing colonic fermentation and the colonic microbiota. Though, recent studies suggest that increased colonic fermentation contributes to adiposity. Diet influences the composition of the gut microbiota. Previous research has not evaluated dietary intakes, body mass index (BMI), faecal microbiota and short chain fatty acid (SCFA) in the same cohort. Our objectives were to compare dietary intakes, faecal SCFA concentrations and gut microbial profiles in healthy lean (LN, BMI⩽25) and overweight or obese (OWOB, BMI>25) participants.Design:We collected demographic information, 3-day diet records, physical activity questionnaires and breath and faecal samples from 94 participants of whom 52 were LN and 42 OWOB.Results:Dietary intakes and physical activity levels did not differ significantly between groups. OWOB participants had higher faecal acetate (P=0.05), propionate (P=0.03), butyrate (P=0.05), valerate (P=0.03) and total short chain fatty acid (SCFA; P=0.02) concentrations than LN. No significant differences in Firmicutes to Bacteroides/Prevotella (F:B) ratio was observed between groups. However, in the entire cohort, Bacteroides/Prevotella counts were negatively correlated with faecal total SCFA (r=−0.32, P=0.002) and F:B ratio was positively correlated with faecal total SCFA (r=0.42, P<0.0001). Principal component analysis identified distinct gut microbiota and SCFA–F:B ratio components, which together accounted for 59% of the variation. F:B ratio loaded with the SCFA and not with the microbiota suggesting that SCFA and F:B ratio vary together and may be interrelated.Conclusions:The results support the hypothesis that colonic fermentation patterns may be altered, leading to different faecal SCFA concentrations in OWOB compared with LN humans. More in-depth studies looking at the metabolic fate of SCFA produced in LN and OWOB participants are needed in order to determine the role of SCFA in obesity.

High relative abundance of firmicutes and increased TNF-α levels correlate with obesity in children

“…9,10,20 However, several studies in adults have found an increase of Bacteroidetes, 21,22 less proportion of Firmicutes, unaltered Bacteroidetes ratio, 23 or no differences in the proportions between these two phyla with the obesity degree. 24,25 In the present study, we found a high relation of Firmicutes/Bacteroidetes in obese children which is consistent with other studies. 7,[26][27][28] These controversial results could be explained by lifestyles, ethnic groups, 29,30 geographic origin 23 and even by the different experimental, bioinformatics and cohort selection methodologies used.…”

The intestinal microbiota, energy balance, and malnutrition: emphasis on the role of short-chain fatty acids

“…Although some studies did not find a difference in F:B ratio [73], or even found an inverse F:B ratio [74], they did find significantly more SCFAs in obese subjects compared with lean subjects [73,74]. Fernandes et al [73] also found that the amount of fecal SCFAs did positively correlate to the F:B ratio and found an inverse association between Bacteroidetes and body mass index (BMI). Moreover, a progressive increase in Bacteroidetes was associated with voluntary weight loss in a dietary intervention study following 12 obese subjects over the course of a year [5].…”

“…Furthermore, an increase in the Firmicutes:Bacteroidetes (F:B) ratio has been associated with obesity in mice [32,72] and humans [25,71]. Although some studies did not find a difference in F:B ratio [73], or even found an inverse F:B ratio [74], they did find significantly more SCFAs in obese subjects compared with lean subjects [73,74]. Fernandes et al [73] also found that the amount of fecal SCFAs did positively correlate to the F:B ratio and found an inverse association between Bacteroidetes and body mass index (BMI).…”

Prenatal androgen exposure causes hypertension and gut microbiota dysbiosis

“…129 −131 After absorption, SCFAs are processed in the liver for use in gluconeogenesis and lipogenesis. 132 −135 Interestingly, dietary supplementation with SCFAs has been shown in rodents to promote a switch from lipid synthesis to oxidation and to protect against obesity and insulin resistance. 38 , 39 Bacteria from the family Enterobacteriaceae , particularly Escherichia coli , have been associated with increased systemic lipopolysaccharides 136 , increased risk of obesity, inflammation, reduced glomerular filtration rate, increased serum cystatin C and insulin resistance.…”