title: Wholegrain barley β-glucan fermentation does not improve glucose tolerance in rats fed a high-fat diet.
abstract: Fermentation of oat and barley β-glucans is believed to mediate in part their metabolic health benefits, but the exact mechanisms remain unclear. In this study, we sought to test the hypothesis that barley β-glucan fermentation raises circulating incretin hormone levels and improves glucose control, independent of other grain components. Male Sprague-Dawley rats (n = 30) were fed a high-fat diet for 6 weeks and then randomly allocated to 1 of 3 dietary treatments for 2 weeks. The low- (LBG, 0% β-glucan) and high- (HBG, 3% β-glucan) β-glucan diets contained 25% wholegrain barley and similar levels of insoluble dietary fiber, available carbohydrate, and energy. A low-fiber diet (basal) was included for comparison. Immediately prior to the dietary intervention, gastric emptying rate (using the (13)C-octanoic breath test) and postprandial glycemic response of each diet were determined. At the end of the study, circulating gut hormone levels were determined; and a glucose tolerance test was performed. The rats were then killed, and indices of cecal fermentation were assessed. Diet did not affect live weight; however, the HBG diet, compared to basal and LBG, reduced food intake, tended to slow gastric emptying, increased cecal digesta mass and individual and total short-chain fatty acid pools, and lowered digesta pH. In contrast, circulating levels of glucose, insulin, gastric-inhibitory peptide, and glucagon-like peptide-1, and glucose tolerance were unaffected by diet. In conclusion, wholegrain barley β-glucan suppressed feed intake and increased cecal fermentation but did not improve postprandial glucose control or insulin sensitivity.
authors.affiliation: Commonwealth Scientific & Industrial Research Organisation (CSIRO) Food and Nutrition Flagship, Australia. Electronic address: damien.belobrajdic@csiro.au.
authors.forename: Damien P
authors.initials: DP
authors.lastname: Belobrajdic
authors.affiliation: CSIRO Agriculture Flagship, Canberra, Australia, 2601. Electronic address: steve.jobling@csiro.au.
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Jobling
authors.affiliation: Commonwealth Scientific & Industrial Research Organisation (CSIRO) Food and Nutrition Flagship, Australia. Electronic address: matthew.morell@csiro.au.
authors.forename: Matthew K
authors.initials: MK
authors.lastname: Morell
authors.affiliation: Institute of Plant Science and Resources, Okayama University, Kurashiki 710-0046, Japan. Electronic address: staketa@rib.okayama-u.ac.jp.
authors.forename: Shin
authors.initials: S
authors.lastname: Taketa
authors.affiliation: Commonwealth Scientific & Industrial Research Organisation (CSIRO) Food and Nutrition Flagship, Australia. Electronic address: tony.bird@csiro.au.
authors.forename: Anthony R
authors.initials: AR
authors.lastname: Bird
mesh_terms: D000818:Animals; D001786:Blood Glucose; D002432:Cecum / Q000382:microbiology*; D059305:Diet, High-Fat / Q000009:adverse effects*; D004043:Dietary Fiber / Q000008:administration & dosage; D004435:Eating / Q000187:drug effects*; D005285:Fermentation / Q000187:drug effects*; D005749:Gastric Inhibitory Polypeptide / Q000378:metabolism; D052216:Glucagon-Like Peptide 1 / Q000378:metabolism; D005951:Glucose Tolerance Test; D001467:Hordeum / Q000737:chemistry*; D007328:Insulin / Q000097:blood; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D047071:beta-Glucans / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D001786:Blood Glucose; D004043:Dietary Fiber; D007328:Insulin; D047071:beta-Glucans; D005749:Gastric Inhibitory Polypeptide; D052216:Glucagon-Like Peptide 1
keywords: Barley; Glycemic index; Incretin; SCFA; Satiety; Wholegrain; β-Glucan