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

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-peptide 0-240 /Glc 0-240 , 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).

β Cell dysfunction during progression of metabolic syndrome to type 2 diabetes

“…Earlier clinical reports and recent clinical deep phenotyping in the RISE study in adults and youth in prediabetes or early T2DM indicate a large spectrum of insulin secretory capacity, basal insulin secretion, and glucose-stimulated insulin secretion responses, as well as heterogeneous responses to interventions with insulin replacement, weight loss, and exercise (43,44). Two recent studies provide clinical proof of concept that intervening at the behavioral level of MetS/prediabetes using short-term diet or exercise augments glucose-stimulated insulin secretion in human subjects (79,80). These studies support the idea that early intervention is critical to our ability to prevent or delay the progression to T2DM, but they also highlight the heterogeneity of these responses within different patients and the need to better understand particular islet compositions, β cell population compositions, and the respective responses of these heterogeneous cell populations.…”

Nutritional Strategies in Prediabetes: A Scoping Review of Recent Evidence

“…These studies demonstrated whole grains to be superior to refined grains, with the most notable benefits being better glucose- and insulin-related parameters such as FPG, HbA1c, glucose metabolism, insulin level, insulin sensitivity as well as insulin resistance [ 19 , 23 , 57 ]. The rate of progression to T2DM and weight loss also demonstrated positive outcomes in favor of the whole grain group [ 57 , 77 ]. Furthermore, plasma inflammatory markers were also reduced in the study by de Mello et al [ 56 ].…”

“…Thirty of 52 studies (57.7%) that investigated changes in weight and/or BMI, reported significant improvement postintervention [ 17 , 22 , 24 , 26 , 27 , 29 , 31 , 32 , 33 , 40 , 43 , 58 , 59 , 61 , 65 , 71 , 74 , 77 , 84 , 87 , 88 , 90 , 93 , 98 , 99 , 101 , 102 , 109 , 110 , 111 ]. Similar proportions of statistically significant findings were observed for the waist and hip circumferences and/or waist-to-hip ratio (17/32 studies, 53.1%) [ 17 , 18 , 24 , 26 , 32 , 33 , 38 , 58 , 61 , 62 , 84 , 87 , 88 , 101 , 102 , 108 , 109 ] as well as systolic and diastolic blood pressure (16/31 studies, 51.6%) [ 17 , ...…”

“…Similar proportions of statistically significant findings were observed for the waist and hip circumferences and/or waist-to-hip ratio (17/32 studies, 53.1%) [ 17 , 18 , 24 , 26 , 32 , 33 , 38 , 58 , 61 , 62 , 84 , 87 , 88 , 101 , 102 , 108 , 109 ] as well as systolic and diastolic blood pressure (16/31 studies, 51.6%) [ 17 , 31 , 32 , 38 , 40 , 62 , 86 , 87 , 88 , 93 , 98 , 102 , 104 , 108 , 109 , 111 ]. Fat mass, fat-free mass and/or percent body fat were detailed by 22 studies, of which 15 (68.2%) demonstrated positive outcomes [ 17 , 18 , 29 , 67 , 69 , 71 , 74 , 77 , 93 , 98 , 101 , 102 , 109 , 110 , 111 ].…”

Lifestyle and glycemic health 5 years postpartum in obese and non-obese high diabetes risk women

“…The non-obese women had overall a higher HFII indicating a healthier diet compared to obese participants. They also consumed less snacks and more whole grain products, which have been suspected to improve the function of beta cells [ 21 ], and there was a trend toward lower consumption of red meats, generally associated with lower diabetes risk [ 22 ]. The HFII of non-obese women, however, was not associated with glycemic health 5 years postpartum.…”