Normal blood glucose but impaired glucose tolerance in BG4KO mice. A: BG4KO mice (black bars) have fed and fasting blood glucose concentrations and fed and fasting plasma insulin concentrations similar to those of WT (white bar), Lox (horizontal lines), and Cre (slanted lines) mice. B: BG4KO mice had fed and fasting blood insulin concentrations similar to those of the control groups. C: Intraperitoneal GTTs (2 mg/kg) were performed in 12-week-old male mice fed normal chow. BG4KO mice (black triangles) had significantly higher excursions in blood glucose compared with WT (white circles), Lox (black circles), and Cre (white triangles) mice, where indicated. D: No difference in blood glucose was observed between BG4KO and the control mice during an insulin tolerance test. *P = 0.006 (repeated-measures ANOVA) vs. WT, Lox, and Cre mice. Data are expressed as the mean ± SEM (n = 6–17 mice per group).