Impaired insulin-regulated membrane aminopeptidase translocation to the plasma membrane in adipocytes of Otsuka Long Evans Tokushima Fatty rats.
Insulin-regulated membrane aminopeptidase (IRAP) translocates to the plasma membrane with glucose transporter-4 (GLUT4) on insulin stimulation. However, this may be impaired in patients at risk of diabetes. Recently a novel technique has been developed to assess cell surface IRAP activity dynamically using a fluorogenic membrane impermeable substrate. In this study we measured the cell surface IRAP activity and 3-O-[methyl-14C]-D-Glucose uptake in adipocytes isolated from Otsuka Long Evans Tokushima Fatty rats (OLETF), developed as a model of type 2 diabetes mellitus, to evaluate whether the translocation of GLUT4/IRAP vesicles is affected. On the addition of insulin, the cell surface IRAP activity promptly increased to reach equilibrium in a hormone dose-dependent manner. OLETF rats showed significantly lower equilibrium activity than control rats (P<0.01). Time to reach the equilibrium was also significantly longer in the OLETF case, and adipocytes isolated from OLETF rats demonstrated both a delay and a reduction in 3-O-[methyl-14C]-D-Glucose uptake. This impairment in all parameters was alleviated by treatment with pioglitazone. Continuous measurement of cell surface IRAP activity allowed accurate evaluations of GLUT4/IRAP vesicle translocation and of the establishment of defects in OLETF rats.
Takeuchi
Mikihito
M
Department of Obstetrics and Gynaecology, Nagoya University Graduate School of Medicine, Japan.
Itakura
Atsuo
A
Okada
Mayumi
M
Mizutani
Shigehiko
S
Kikkawa
Fumitaka
F
D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D010122:Cystinyl Aminopeptidase / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy / Q000378:metabolism*; D051275:Glucose Transporter Type 4 / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D000077205:Pioglitazone; D051381:Rats; D020334:Rats, Inbred OLETF; D045162:Thiazolidinediones / Q000494:pharmacology
D051275:Glucose Transporter Type 4; D007004:Hypoglycemic Agents; D007328:Insulin; C495694:Slc2a4 protein, rat; D045162:Thiazolidinediones; D010122:Cystinyl Aminopeptidase; C105964:leucyl-cystinyl aminopeptidase; D000077205:Pioglitazone