MAIT Cell Activation and Glucose Homeostasis

Intraperitoneal glucose tolerance and intraperitoneal insulin tolerance tests were performed as reported previously [34 (link)]. Briefly, for the glucose tolerance test, the mice were injected with glucose (2 mg/g body weight) intraperitoneally, and for the insulin tolerance test, with human insulin (1.0 and 1.5 mU/g body weight for the NC- and HFD-fed mice, respectively). Blood samples were collected from the tail vein before and 15, 30, 60, 90, and 120 min after the glucose or insulin injection. Blood glucose levels were measured with the StatStrip (NIPRO, Tokyo, Japan), and serum insulin levels with a mouse insulin enzyme–linked immunosorbent assay (ELISA) kit (Morinaga Ultra-Sensitive Mouse/Rat Insulin ELISA Kit; MORINAGA, Yokohama, Japan). To evaluate the effects of activation of TCR signaling on glucose tolerance, 5-OP-RU, a specific ligand for the MAIT cell TCR, was injected 24 h before the insulin tolerance test. The 5-OP-RU was prepared by incubating an aliquot of 3.6 mM 5-A-RU in DMSO with three volumes of 1 mM methylglyoxal in water at 37 °C for 30 min.