Improved blood glucose disposal and altered insulin secretion patterns in adenosine A1 receptor knockout mice

Yang GK, Fredholm BB, Kieffer TJ, Kwok YN. Improved blood glucose disposal and altered insulin secretion patterns in adenosine A(1) receptor knockout mice. Am J Physiol Endocrinol Metab 303: E180-E190, 2012. First published May 1, 2012; doi:10.1152/ajpendo.00050.2012.-Type 2 diabetes mellitus (T2DM) is characterized by the inability of the pancreatic beta-cells to secrete enough insulin to meet the demands of the body. Therefore, research of potential therapeutic approaches to treat T2DM has focused on increasing insulin output from beta-cells or improving systemic sensitivity to circulating insulin. In this study, we examined the role of the A1 receptor in glucose homeostasis with the use of A1 receptor knockout mice (A(1)R(-/-)). A(1)R(-/-) mice exhibited superior glucose tolerance compared with wild-type controls. However, glucose-stimulated insulin release, insulin sensitivity, weight gain, and food intake were comparable between the two genotypes. Following a glucose challenge, plasma glucagon levels in wild-type controls decreased, but this was not observed in A(1)R(-/-) mice. In addition, pancreas perfusion with oscillatory glucose levels of 10-min intervals produced a regular pattern of pulsatile insulin release with a 10-min cycling period in wild-type controls and 5 min in A(1)R(-/-) mice. When the mice were fed a high-fat diet (HFD), both genotypes exhibited impaired glucose tolerance and insulin resistance. Increased insulin release was observed in HFD-fed mice in both genotypes, but increased glucagon release was observed only in HFD-fed A(1)R(-/-) mice. In addition, the regular patterns of insulin release following oscillatory glucose perfusion were abolished in HFD-fed mice in both genotypes. In conclusion, A1 receptors in the pancreas are involved in regulating the temporal patterns of insulin release, which could have implications in the development of glucose intolerance seen in T2DM.