Skeletal muscle G6PDH activity is altered in pre-diabetic individuals. (A) G6PDH activity in vastus lateralis muscle of obese insulin sensitive (IS; n = 17), obese insulin resistant (IR; n = 21), and obese pre-diabetic individuals (Pre; n = 24). (B) G6PDH activity in vastus lateralis muscle of IS (n = 17), IR (n = 21), and Pre (stratified for normal fasting glucose (NFG; n = 13) and impaired fasting glucose (IFG; n = 11) levels). (C) Correlation between basal vastus lateralis muscle G6PDH activity and fasting blood glucose levels in IS, IR, and Pre (n = 62). (D) Correlation between basal vastus lateralis muscle G6PDH activity and fasting glucose:fasting insulin levels in IS, IR, and Pre (n = 62). (E) Correlation between basal vastus lateralis muscle G6PDH activity and blood glucose levels 2 h following a 75 g oral glucose tolerance test (OGTT) in IS, IR, and Pre (n = 62). Data are presented as a scatter plot (bar denotes mean ± S.D) and were analyzed using a one-way ANOVA (A, B), or linear regression analysis (C–E). **p < 0.01 vs. IS and IR; †p < 0.05 vs. Pre NFG.