TABLE 2.

Actions of GIP and GLP-1 that affect blood glucose levels

	GIP	GLP-1
Islets
Insulin secretion	↑	↑
Insulin synthesis	↑	↑
Insulin, glucokinase and GLUT2 expression	↑	↑
Glucagon secretion	↑	↓ (indirect)
Somatostatin secretion	↑	↑ (indirect)
β cell proliferation	↑	↑
β cell apoptosis	↓	↓
Sweet taste modulator	—	Yes
Gastrointestinal tract
Gastric emptying	—	↓
Gastric acid secretion	↓	↓
Motility	—	↓
Central nervous system
Food intake	—	↓
Satiety	—	↑
Muscle
Glucose uptake	—	↑
Liver
Glucose production	↓ (indirect)	↓ (indirect)

↑, increase; ↓, decrease; —, no effect or not reported.