Figure 1.
(A) Percentage of diabetic mice achieving normoglycemia after 7 weeks of treatment with vehicle, PSN632408, sitagliptin, and PSN632408 combined with sitagliptin.
Normoglycemia was not achieved in vehicle-treated diabetic mice. By contrast, 32% (6 of 19) PSN632408-treated mice, 36% (5 of 14) sitagliptin-treated mice, and 59% (13 of 22) PSN632408 plus sitagliptin-treated mice achieved normoglycemia between 6 and 7 weeks (P<0.05, vs. PSN632408 alone or sitagliptin alone). (B) Pretreatment and posttreatment blood glucose levels in diabetic mice with restored normoglycemia (nonfasting blood glucose level <200 mg/dL) after treatment for 7 weeks. Posttreatment blood glucose levels were significantly reduced compared with pretreatment blood glucose levels in these mice (P<0.01).
Figure 2.
Active GLP-1 levels in plasma of mice 30 minutes after treatment with PSN632408, sitagliptin, or PSN632408 and sitagliptin combination (n = 7 to 8 mice per group).
Plasma GLP-1 levels were significantly higher in mice treated with PSN632408 and sitagliptin combination than in mice treated with PSN632408 alone, (p<0.05).
Figure 3.
(A) OGTT in non-diabetic control mice and diabetic mice treated with vehicle, and those that achieved normoglycemia after 7 weeks treatment with PSN632408, sitagliptin, or PSN632408 and sitagliptin combination (n = 5 mice per group).
Blood glucose levels in mice treated with PSN632408 and sitagliptin combination were significantly lower than in mice treated with PSN632408 alone at 45 minutes and at 90 minutes (p<0.01) and in mice treated with sitagliptin alone at 90 minutes (p<0.01). (B) Blood glucose AUC0–120 in mice treated with PSN632408, sitagliptin, or PSN632408 and sitagliptin combination was significantly lower than in mice treated with vehicle (P<0.01).
Figure 4.
(A) Confocal images represent insulin (red) immunostained pancreas sections from diabetic mice treated with vehicle, PSN632408, sitagliptin, or PSN632408 plus sitagliptin.
(B) Quantification of β-cell mass in the pancreases of non-diabetic control mice and diabetic mice with restored normoglycemia after 7 weeks of treatment with PSN632408, sitagliptin, or PSN632408 and sitagliptin combination (3 to 4 mice per group). β-Cell mass was significantly higher in mice treated with PSN632408 and sitagliptin combination than in mice treated with PSN632408 alone or sitagliptin alone (P<0.05).
Figure 5.
(A) Immunostaining of insulin (red), BrdU (yellow), and DAPI (blue) in pancreas sections from BrdU treated non-diabetic control mice and diabetic mice with restored normoglycemia after 7 weeks of treatment with PSN632408, sitagliptin, or PSN632408 combined with sitagliptin.
White arrows indicate insulin/BrdU/DAPI co-positive cells. (B) The percentage of insulin/BrdU co-positive cells among total insulin positive cells was significantly higher in mice treated with PSN632408 and sitagliptin combination than in mice treated with PSN632408 alone (p<0.01, n = 4 to 6 mice per group).
Figure 6.
(A) Immunostaining of insulin (red), Ki67 (green), and DAPI (blue) in pancreas sections from non-diabetic control mice and diabetic mice with restored normoglycemia after 7 weeks treatment with PSN632408, sitagliptin, or PSN632408 combined with sitagliptin.
White arrows indicate insulin/Ki67/DAPI co-positive cells. (B) The percentage of insulin/Ki67 co-positive cells among total insulin positive cells was significantly higher in mice treated with PSN632408 and sitagliptin combination than in mice treated with PSN632408 alone or sitagliptin alone (p<0.01, n = 4 to 6 mice per group).
Figure 7.
(A) Immunostaining of insulin (red), BrdU (yellow) and DAPI (blue) in pancreas sections from BrdU-treated non-diabetic control mice and diabetic mice with restored normoglycemia after 7 weeks treatment with PSN632408, sitagliptin, or PSN632408 combined with sitagliptin.
White arrows indicate insulin/DAPI co-positive pancreatic duct cells. Green arrows indicate insulin/BrdU/DAPI co-positive pancreatic duct cells. (B) Immunostaining of insulin (red), CK19 (green), BrdU (yellow), and DAPI (blue) in pancreas sections from these mice. Red arrow indicates CK19/BrdU co-positive pancreatic duct cells. White arrows indicate insulin/CK19 co-positive pancreatic duct cells. (C) The percentage of ducts with insulin/CK19 co-positive cells was significantly increased in mice treated with PSN632408 alone or PSN632408 and sitagliptin combination compared with non-diabetic control mice (p<0.05, n = 3 to 6 mice per group).
Figure 8.
(A) Immunostaining of glucagon (green), BrdU (yellow), and DAPI (blue) in pancreas sections from BrdU-terated non-diabetic control mice and diabetic mice with restored normoglycemia after 7 weeks treatment with PSN632408, sitagliptin, or PSN632408 combined with sitagliptin.
White arrows indicate glucagon/BrdU/DAPI co-positive cells. (B) The percentage of glucagon/BrdU/DAPI co-positive cells among total glucagon positive cells was significantly increased in mice treated with PSN632408 and sitagliptin combination compared with mice treated with PSN632408 alone or sitagliptin alone (p<0.05, n = 3 to 5 mice per group). (C) Immunostaining of amylase (green), BrdU (red), and DAPI (blue) in pancreas sections from BrdU-treated non-diabetic control mice and diabetic mice with restored normoglycemia after 7 weeks treatment with PSN632408, sitagliptin, or PSN632408 combined with sitagliptin.