Smad3 deficiency promotes insulin secretion and protects against type 2 diabetes development in db/db mice. (A-C) Fasting serum insulin (A), Fasting blood glucose (B), and body weight (C) of five groups of mice (n ≥ 8 per group) from 4-32 weeks of age. Data are mean ± S.E.M. *p < 0.05, **p < 0.01, ***p < 0.001 vs. S3WT-db/m; #p < 0.05, ###p < 0.001 vs. S3WT-db/db; two-way ANOVA following Newman-Keuls multiple comparisons. (D-E) Blood glucose levels and area under curve (AUC) during intraperitoneal glucose tolerance test (IPGTT) (D) and intraperitoneal insulin tolerance test (IPITT) (E) at 20 weeks of age (n=5 per group). Data are mean ± S.E.M. ns, no significance, **p < 0.01, ****p < 0.0001 compared between groups as indicated. Statistical analysis was performed by one-way ANOVA, followed by multiple comparisons.