Whole Grain Oats Improve Insulin Sensitivity and Plasma Cholesterol Profile and Modify Gut Microbiota Composition in C57BL/6J Mice

Background: Whole grain consumption reduces the risk of major chronic diseases. It is not clear how whole grains exert their beneficial effects. Objective: The aim was to compare the physiologic effects of whole grain oat (WGO) flour with low bran oat (LBO) flour. Methods: Two AIN-93G-based diets were formulated with either WGO or LBO flour. Five-week-old male C57BL/6J mice were fed LBO (n = 11) and WGO (n = 13) diets for 8 wk. Cecal microbiota was profiled by pyrosequencing of the 16S ribosomal RNA gene. Data are reported as means +/- SEMs or antilogs of the mean (mean - SEM, mean + SEM). Results: The weight gain was 14.6% less in the WGO group during week 7 (P = 0.04). WGO improved insulin sensitivity as reflected by significantly lower plasma insulin [1500 (1370, 1650) ng/L vs. 2340 (2090, 2620) ng/L; P = 0.006], C-peptide (3980 +/- 548 ng/L vs. 7340 +/- 1050 ng/L; P = 0.007), and homeostasis model assessment-estimated insulin resistance (21.4 +/- 2.3 vs. 34.7 +/- 4.9; P = 0.03). Plasma total cholesterol was 9.9% less and non-HDL cholesterol was 11% less in the WGO group. A comparison of relative abundance indicated Prevotellaceae, Lactobacillaceae, and Alcaligenaceae families were 175.5% (P = 0.03), 184.5% (P = 0.01), and 150.0% (P = 0.004), respectively, greater in the WGO group and Clostridiaceae and Lachnospiraceae families were 527% (P = 0.004) and 62.6% (P = 0.01), respectively, greater in the LBO group. Cecal microbiota composition predicts 63.9% variation in plasma insulin and 88.9% variation in plasma non-HDL cholesterol. Conclusions: In mice, WGOs improved insulin sensitivity and plasma cholesterol profile compared with LBOs, and the effects were associated with the changes in cecal microbiota composition. Increasing WGO consumption may help improve insulin sensitivity and dyslipidemia in chronic diseases.