**2.2.1 Materials and methods**

All experiments were performed using Hartley male guinea pigs with a body weight of 500- 600 g. Experimental protocols followed the Principals of Laboratory Animal Care and were approved by the Ethics Committee of Toho University School of Medicine. Until experiments began, guinea pigs were housed in groups of three in metabolism cages in a temperature-controlled room with a 12h light/dark cycle. They had free access to tap water and guinea pig chow.

Under intra-abdominal anaesthesia (pentobarbital sodium 30mg/Kg), streptozotocin (STZ) was administrated to 12 guinea pigs intra-abdominally. After 4 weeks, a glucose tolerance test (50% glucose, 1g/Kg, intra-abdominal route) was performed. Impaired glucose tolerance (IGT) was defined as a blood glucose level of more than 300 mg/dl after 3 hrs. Six control guinea pigs had intra-abdominal saline only.

Fig. 2. Changes in Concentrations of Serum DHEA

Blood samples were taken from intra-orbital vessels after 12 hrs starvation. Serum DHEA, DHEA-S, fasting plasma glucose (FPG) and serum c-peptide were measured in each group at four time points: before STZ administration; after 4 weeks; after 8 weeks; and after 12 weeks. Simultaneously glucose tolerance tests were performed. From 15 weeks of STZ administration DHEA-S(Mylis) (20mg/Kg) was administrated via the intra-abdominal route three times per week in three IGT group guinea pigs and three control group animals. After 4 weeks, 8 weeks and 12 weeks of DHEA-S administration, blood samples were taken by the same method and glucose tolerance tests were also performed.

Data are expressed as mean±SD. Statistical analysis was performed using ANOVA with Bonferroni's correction. A value of p<0.05 was considered statistically significant.
