Leucine supplementation improves glucose and insulin homeostasis and prevents overt diabetes in RCS10 mice. A: Plasma glucose levels in the fed (or after 3 hour refed), basal (after five hour of food and leucine deprivation), and fast states in the control and leucine-treated RCS10 mice after 4 or 8 months of leucine-treatment. B: Plasma insulin levels in the refed, basal, and fast states in the control and leucine-treated mice at the end of 8 month study. C: Plasma concentrations of leucine and other amino acids after 3 hour-refeeding. D: The relationship between HbA1c levels and plasma glucose levels after the refeeding. There was a significant correlation between the two parameters (F = 29.46, p < 0.001), which fits the following equation (refed glu = -284 + 69.58x HbA1c, Standard error of estimation is 80.245). E: The relationship between HbA1c levels and plasma insulin levels after 3 hr refeeding. There was no statistically significant correlation between HbA1c levels and refed plasma insulin levels at the end of 8 month treatment. Beta cell decompensation was evident in the mice with overt diabetes (HbA1c > 9%, circled). * and ** indicate p < 0.05 and 0.01, control vs. leucine-treated, respectively, n = 7.