2.4. Intraperitoneal glucose and insulin tolerance tests (IGTT & IPITT)

This has been done on the first 6 rats/group. IGTT and IPITT were performed as previously described by others (Wong and Sul, 2010). By the end of the last day of the experiment (day 7), all rats have fasted, for 12 h and then exposed to IPTT, in brief, glucose solution (1 g/kg) was injected (i.p) into each rat and then blood samples were withdrawn at 0.0, 15, 30, 60, 120 min. Then all rats were brought back to their special cages with free access to food and water. The next day, IPITT was conducted after 5 h fasting where each animal was injected with 0.75U/kg insulin and blood samples were withdrawn over the same time intervals for 1 h. For both tests, 200 µl of blood was collected each time into EDTA-supplied tubes and centrifuged (1200g/5 min/room temperature) to collect plasma which was further stored at −20 °C and used later to measure fasting glucose and insulin levels using the commercially available kits (Cat. No. 10009582, Cayman chemicals, USA and Cat No. ELR-Insulin-1, ga, USA, respectively).