Background: Glucose-dependent insulinotropic peptide (GIP) and glucagon-like peptide-1 (GLP-1) are incretin hormones that augment glucose-stimulated insulin secretion, promote pancreatic β-cell proliferation, neogenesis and inhibit β-cell apoptosis. Thus, they are excellent therapeutic targets against type 2 diabetes. Using a lymph fistula rat model, we studied the secretion of incretins into lymph. In adult rats, we found that GIP and GLP-1 concentrations in the fasting lymph were 132 ± 19 pg/ml and 31 ± 8 pM, respectively. After intraduodenal lipid infusion, their concentrations rose to 441 ± 144 pg/ml and 154 ± 23 pM, respectively.
Rationale: However, little is known about nutrient-stimulated secretion of GIP and GLP-1 in baby rats, whose gastrointestinal system and pancreatic β-cells are immature compared to adult rats.
Methods: Using our well-established lymph fistula model with conscious baby rats, just weaned (21 day after birth) and weighing 50-65 g, we assessed the secretion of GIP and GLP-1 in lymph after an intraduodenal challenge of lipid meal.
Results: Fasting GIP and GLP-1 levels were 295.4 ± 48.1 pg/ml and 59.6 ± 16.2 pM, respectively. After lipid infusion, GIP and GLP-1 levels increased to 1052 ± 90.1 pg/ml and 192.0 ± 19.7 pM respectively. Elevated incretin levels in baby rats (relative to adult animals) indicate possible involvement in the maturation of the enteroendocrine system and β-cells. This increase may be also important to ensure the adequate secretion of insulin to regulate blood glucose as the animals shift from a high-fat mother’s milk diet to a chow diet. Further studies are needed to determine the physiological role of the higher incretin levels in baby rats.
Conclusions: Lymph fistula baby rats can serve as an excellent model to study regulation of gut hormones by nutrient absorption at their early developmental stage. This model can also be used to study the influence of mother’s milk on the secretion of gut hormones and their impact on glucose and lipid metabolism in the newborn.
J. Qu: None. Q. Yang: None. C. Ko: None. M. Liu: None. D.D. Black: Advisory Panel; Self; Intercept Pharmaceuticals, Inc. P. Tso: None.
National Institutes of Health (DK59630)