Plasma glucose (A, C, and E) and insulin (G) concentrations, the area under the glucose curve against baseline (0 min, AUC) (B, D, and F), and HOMA-IR (H) in the OLETF and LETO rats fed the standard and high fat diets in response to an oral glucose load (2 g/kg body weight). Oral glucose tolerance tests were performed at 2 (A and B), 8 (C and D), and 15 weeks (E-G) after the start of feeding the experimental diets. Each value represents mean ± SEM, n = 9. Means without a common letter differ, P < 0.05. P values estimated by repeated measure 2 way ANOVA and 2-way ANOVA were (A) < 0.01 for strain, < 0.01 for diet, < 0.01 for time, 0.07 for strain x diet, < 0.01 for strain x time, < 0.01 for diet x time, and < 0.01 for strain x diet x time, (B) < 0.01 for strain, < 0.01 for diet, and 0.10 for strain x diet, (C) < 0.01 for strain, < 0.01 for diet, < 0.01 for time, < 0.01 for strain x diet, < 0.01 for strain x time, < 0.01 for diet x time, and < 0.01 for strain x diet x time, (D) < 0.01 for strain, < 0.01 for diet, and < 0.01 for strain x diet, (E) < 0.01 for strain, < 0.01 for diet, < 0.01 for time, < 0.01 for strain x diet, < 0.01 for strain x time, < 0.01 for diet x time, and < 0.01 for strain x diet x time, (F) < 0.01 for strain, < 0.01 for diet, and < 0.01 for strain x diet, (G) < 0.01 for strain, < 0.01 for diet, < 0.01 for time, 0.07 for strain x diet, < 0.01 for strain x time, < 0.01 for diet x time, and < 0.01 for strain x diet x time, and (H) < 0.01 for strain, < 0.01 for diet, and 0.10 for strain x diet.