A whole-grain diet reduces peripheral insulin resistance and improves glucose kinetics in obese adults: A randomized-controlled trial.
Steven K Malin, Emily L Kullman, Amanda R Scelsi, Jacob M Haus, Julianne Filion, Mangesh R Pagadala, Jean-Philippe Godin, Sunil Kochhar, Alastair B Ross, John P Kirwan
Author Information
Steven K Malin: Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
Emily L Kullman: Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
Amanda R Scelsi: Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
Jacob M Haus: Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
Julianne Filion: Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
Mangesh R Pagadala: Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States.
Jean-Philippe Godin: Analytical Sciences Department, Nestlé Research Center, Lausanne, Switzerland.
Sunil Kochhar: Analytical Sciences Department, Nestlé Research Center, Lausanne, Switzerland.
Alastair B Ross: Analytical Sciences Department, Nestlé Research Center, Lausanne, Switzerland.
John P Kirwan: Department of Pathobiology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States; Metabolic Research Center, Endocrinology and Metabolism Institute, Cleveland Clinic, Cleveland, OH, United States. Electronic address: kirwanj@ccf.org.
BACKGROUND: Whole-grain intake is associated with lower risk of type 2 diabetes but the mechanisms are unclear. PURPOSE: We tested the hypothesis that a WG diet reduces insulin resistance and improves glucose use in individuals at risk for type 2 diabetes compared with an isocaloric-matched refined-grain diet. METHODS: A double-blind, randomized, controlled, crossover trial of 14 moderately obese adults (Age, 38 ± 2 y; BMI, 34.0 ± 1.1 kg/m). Insulin resistance and glucose metabolism was assessed using an oral glucose tolerance test combined with isotopic tracers of [6,6-H]-glucose and [U-C]-glucose, and indirect calorimetry. Peripheral and hepatic insulin resistance was assessed as 1/(rate of disposal/insulin), and endogenous glucose rates of appearance (R) iAUC × insulin iAUC, respectively. Both diets met ADA nutritional guidelines and contained either whole-grain (50 g per 1000 kcal) or equivalent refined-grain. All food was provided for 8 wk. with an 8-10 wk. washout period between diets. RESULTS: Post-prandial glucose tolerance, peripheral insulin sensitivity, and metabolic flexibility (insulin-stimulated - fasting carbohydrate oxidation) improvements were greater after whole-grain compared to the refined-grain diet (P < 0.05). Compared to baseline, body fat (~2 kg) and hepatic R insulin resistance was reduced by both diets, while fasting glucose and exogenous glucose-meal were unchanged after both interventions. Changes in peripheral insulin resistance and metabolic flexibility correlated with improved glucose tolerance (P < 0.05). CONCLUSION: Whole-grains reduced diabetes risk and the mechanisms appear to work through reduced post-prandial blood glucose and peripheral insulin resistance that were statistically linked to enhanced metabolic flexibility.
