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Randomized Controlled Trial
. 2019 Apr;63(7):e1800967.
doi: 10.1002/mnfr.201800967. Epub 2019 Mar 20.

A Whole-Grain Diet Increases Glucose-Stimulated Insulin Secretion Independent of Gut Hormones in Adults at Risk for Type 2 Diabetes

Steven K Malin  1   2 , Emily L Kullman  1   3 , Amanda R Scelsi  1 , Jean-Philippe Godin  4 , Alastair B Ross  5 , John P Kirwan  1   6
Affiliations
Randomized Controlled Trial

A Whole-Grain Diet Increases Glucose-Stimulated Insulin Secretion Independent of Gut Hormones in Adults at Risk for Type 2 Diabetes

Steven K Malin et al. Mol Nutr Food Res. 2019 Apr.

Abstract

Introduction: The effect of whole-grain (WG) versus refined-grain (RG) diets on glucose-stimulated insulin secretion (GSIS) and β-cell function is unclear.

Methods: In a double-blind crossover randomized controlled trial, 13 prediabetic adults (37.2 ± 1.8 y, BMI: 33.6 ± 1.4 kg m-2 , 2 h glucose: 146.9 ± 11.6 mg dL-1 ) are provided isocaloric-matched WG and RG diets for 8-weeks each, with an 8-10 week washout between diets. Glucose, insulin, and C-peptide are studied over 240 min following a 75 g OGTT. Incretins (GLP-1 and GIP), PYY, and total ghrelin are assessed at 0, 30, and 60 min. Mixed-meal diets for carbohydrate (54%), fat (28%), and protein (18%) contain either WG (50 g/1000 kcal) or equivalent RG.

Results: Both diets induce fat loss (≈2 kg). While neither diet impacts early phase GSIS, the WG diet increases total GSIS (iAUC of C-peptide0-240 /Glc0-240 , p = 0.02) and β-cell function (disposition index; GSIS × insulin sensitivity, p = 0.02). GIP and PYY are unaltered by either diet, but GLP-1 is higher at 30 min following RG versus WG (p = 0.04). Ghrelin levels are higher at 60 min of the OGTT following both interventions (p = 0.01).

Conclusion: A WG-rich diet increases β-cell function independent of gut hormones in adults with prediabetes.

Keywords: alkylresorcinols; glucose tolerance; insulin; low-glycemic diet; obesity.

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Conflict of interest statement

CONFLICTS OF INTEREST

JPG is employed by Nestlé, while the remaining authors report no conflict of interest.

Figures

Figure 1.
Figure 1.
Effect of Whole-Grain and Refined-Grain Diets on Glucose-Stimulated Insulin Secretion. Data are reported as mean ± SEM. Compared to Pre, *P<0.05 using Paired t-tests. †P<0.05 using ANCOVA. Post-test total phase disposition index (DI) tended to be higher after WG compared with RG P=0.09 using Paired t-tests, although glucose-stimulated insulin secretion (GSIS) early phase did not (P=0.57). Whole-grain (WG); Refined grain (RG).
Figure 2.
Figure 2.
Effect of Whole-Grain and Refined-Grain Diets on Gut Hormones. Glucagon-like peptide 1 (GLP-1; A), Glucose-dependent insulinotropic polypeptide (GIP; B), peptide tyrosine-tyrosine (PYY; C) and total ghrelin (D) are shown. No post-test differences existed for any outcome using Paired t-tests, except for GLP-1 being higher after RG vs. WG (P=0.055). Data are reported as mean ± SEM. *P<0.05 for WG vs. RG, #P<0.05 for main effect of test. Whole-grain (WG); Refined grain (RG).
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