Highlights
- •Human gut microbiota ferments prebiotics, such as inulin, into short-chain fatty acids.
- •Short-chain fatty acids have positive effects on human metabolism.
- •Fat oxidation increased after inulin ingestion in human overweight to obese subjects.
- •13C-labeled inulin was microbially fermented into 13C-labeled short-chain fatty acids.
- •Replacing digestible carbohydrates with inulin may favor human substrate metabolism.
Abstract
Background and Aims
Human gut microbiota play an important role in maintaining human health. Dietary fibers,
i.e. prebiotics, are fermented by human gut microbiota into the short-chain fatty
acids (SCFAs) acetate, propionate, and butyrate. SCFAs promote fat oxidation and improve
metabolic health. Therefore, the prebiotic inulin might be an effective dietary strategy
to improve human metabolism. We aimed to investigate the acute metabolic effects of
ingesting inulin compared with digestible carbohydrates and to trace inulin-derived
SCFAs using stable isotope tracer methodology.
Methods
In a double-blind, randomized, placebo-controlled crossover design, 14 healthy, overweight
to obese men consumed a high-fat milkshake containing A) 24 g inulin of which 0.5 g
was U-13C-inulin (INU) or B) 24 g maltodextrin placebo (PLA), with a wash-out period of at
least five days. Fat oxidation was measured via an open-circuit ventilated hood and
blood samples were collected up to 7 h after ingestion. Plasma, breath, and fecal
samples were collected, and appetite and satiety scores were assessed.
Results
Fat oxidation increased in the early postprandial phase (0−3 h), and both plasma glucose
and insulin were lower after INU ingestion compared with PLA (all P < 0.05). Plasma free fatty acids were higher in the early, and lower in the late
postprandial period after INU ingestion. Inulin was fermented into SCFAs as indicated
by higher plasma acetate concentrations after INU compared with PLA (P < 0.05). In addition, we found continuous increases in plasma 13C-SCFA enrichments (P < 0.05 from t = 120 onwards) and breath 13CO2 enrichments after INU intake. There were no effects on plasma triglycerides, free
glycerol, satiety hormones GLP-1 and PYY, and appetite and satiety scores.
Conclusions
Ingestion of the prebiotic inulin improves fat oxidation and promotes SCFA production
in overweight to obese men. Overall, replacing digestible carbohydrates with the fermentable
inulin may favor human substrate metabolism.
Clinical Trial Registry
The trial was registered at clinicaltrials.gov under number NCT02009670.
Abbreviations:
AMPK (adenosine monophosphate (AMP)-activated protein kinase), CHO (carbohydrate), DP (degree of polymerization), FFA (free fatty acid), GLP-1 (glucagon-like peptide-1), GPR (G-coupled protein receptor), iAUC (incremental area under the curve), INU (inulin treatment (0.5 g 13C-labeled inulin combined with 23.5 g unlabeled inulin)), MPE (mole percent excess), PLA (placebo treatment), PYY (peptide YY), SCFA (short-chain fatty acid), VAS (Visual Analogue Scale)Keywords
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Article info
Publication history
Published online: June 25, 2018
Accepted:
June 24,
2018
Received:
February 24,
2018
Identification
Copyright
© 2018 Elsevier Inc. All rights reserved.
