Abstract
Exogenous administration of islet amyloid polypeptide (IAPP) has been shown to inhibit both insulin and glucagon secretion. This study examined α-cell function in mice with β-cell specific overexpression of human IAPP (hIAPP) after an oral protein gavage (75 mg whey protein/mouse). Baseline glucagon levels were higher in transgenic mice (41±4.0 pg/mL, n=6) than in wildtype animals (19±5.1 pg/mL, n=5, P=.015). In contrast, the glucagon response to protein was impaired in transgenic animals (21±2.7 pg/mL in transgenic mice versus 38±5.7 pg/mL in wildtype mice at 15 minutes; P=.027). Baseline insulin levels did not differ between the groups, while the insulin response, as the glucagon response, was impaired after protein challenge (P=.018). Glucose levels were not different between the groups and did not change significantly after protein gavage. Acetaminophen was given through gavage to the animals (2 mg/mouse) to estimate gastric emptying. The plasma acetaminophen profile was similar in the two groups of mice. We conclude that disturbances in glucagon secretion exist in mice with β-cell specific overexpression of human IAPP, which are not secondary to changes in gastric emptying. The reduced glucagon response to protein challenge may reflect a direct inhibitory influence of hIAPP on glucagon secretion.
