Aging and glucose homeostasis in C57BL/6J male mice.

Age-dependent changes in glucose homeostasis were assessed in specific pathogen-free C57BL/6J male mice. Increased islet size and pancreatic insulin content in old (21-25-month-old) mice were associated with lower nonfasting plasma glucose levels and improved clearance of either an oral or an i.p. administered glucose load in comparison with young, mature (4-5-month-old) males. The almost twofold increase in islet size correlated with a twofold increase of glucose-stimulated insulin secretion from perifused islets from 25-month-old males compared with 5-month-old males. These aging male mice did not become obese, and there were no fibrotic changes associated with the hyperplastic islets observed in the old males. Thus, the findings that glucose tolerance did not deteriorate with age, coupled with the lack of evidence for impaired beta cell responsiveness to glucose in old males, suggest that deterioration in glucose homeostasis is not an inevitable consequence of aging in the mouse.