Insulin hypersensitivity in mice lacking the V1b vasopressin receptor.
We have reported that [Arg(8)]-vasopressin-stimulated insulin release is blunted in islet cells isolated from V1b receptor-deficient (V1bR(-/-)) mice. In this study, we used V1bR(-/-) mice to examine the physiological role of the V1b receptor in regulating blood glucose levels in vivo, and we found that the fasting plasma glucose, insulin and glucagon levels were lower in V1bR(-/-) mice than in wild-type (V1bR(+/+)) mice. Next, we evaluated glucose tolerance by performing an intraperitoneal glucose tolerance test (GTT). The plasma glucose and insulin levels during the GTT were lower in V1bR(-/-) mice than in V1bR(+/+) mice. An insulin tolerance test (ITT) revealed that, after insulin administration, plasma glucose levels were lower in V1bR(-/-) mice than in V1bR(+/+) mice. In addition, a hyperinsulinaemic-euglycaemic clamp study showed that the glucose infusion rate was increased in V1bR(-/-) mice, indicating that insulin sensitivity was enhanced at the in vivo level in V1bR(-/-) mice. Furthermore, we found that the V1b receptor was expressed in white adipose tissue and that insulin-stimulated phosphorylation of Akt as an important signaling molecule was increased in adipocytes isolated from V1bR(-/-) mice. Thus, the blockade of the V1b receptor could result, at least in part, in enhanced insulin sensitivity by altering insulin signalling in adipocytes.
Fujiwara
Yoko
Y
Department of Pharmacology, National Research Institute for Child Health and Development, 2-10-1 Okura, Setagaya-ku, Tokyo 157 8535, Japan.
Hiroyama
Masami
M
Sanbe
Atsushi
A
Aoyagi
Toshinori
T
Birumachi
Jun-Ichi
J
Yamauchi
Junji
J
Tsujimoto
Gozoh
G
Tanoue
Akito
A
D017667:Adipocytes / Q000378:metabolism; D000818:Animals; D001786:Blood Glucose / Q000502:physiology*; D015870:Gene Expression; D005934:Glucagon / Q000097:blood; D005951:Glucose Tolerance Test; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017483:Receptors, Vasopressin / Q000502:physiology*
D001786:Blood Glucose; D007328:Insulin; D017483:Receptors, Vasopressin; D005934:Glucagon; D051057:Proto-Oncogene Proteins c-akt