Animal experiments
All animal use was approved by the Animal Care and Ethical Committee of Nanjing Medical University. C57BL/6J mice [RRID: IMSR_JAX:000664] (male, 8-week old, 22 ± 2 g) were obtained from Animal Resource Center (Nanjing Medical University, Nanjing, China). Mice were housed under a 12 h light, 12 h dark cycle, with food and water freely accessible. After a 4-hour fast, STZ (Sigma-Aldrich, St. Louis, MO, USA) diluted in Na-citrate buffer (PH = 4.5) was injected intraperitoneally at a dose of 50 mg/kg for consecutive 5 days to destroy the islet beta cells of the mice. Hyperglycemia was defined as 2 consecutive random blood glucose readings of 16.7 mmol/L or higher.
For heparanase inhibition, OGT2115 (Tocris, Minneapolis, MN, USA) was dissolved in dimethyl sulfoxide (DMSO) and diluted to different concentrations with sterile water containing 5% Tween 80 and 30% PEG400. STZ mice received vehicle (sterile water containing 1% DMSO, 5% Tween 80, and 30% PEG400), a low OGT2115 dosage (3 mg/kg) or a higher dosage (10 mg/kg). OGT2115 and vehicle were subcutaneous injected daily for 4 weeks. The food intake, body weight gain and random blood glucose levels of the mice were followed up every week. All animal experiments were performed and analyzed through blinded experimenters. Each mouse in STZ or control group was numbered randomly within the weight range. After being divided randomly in each group, the animals were given their permanent number in the cages.
Intraperitoneal Glucose tolerance test (IPGTT) and insulin measurement
After the 4-week drug administration period, the animals were fasted for 12 hours and glucose (2 g/kg of body weight dissolved in saline) was intraperitoneally injected. Blood glucose was then measured from tail vein blood with a glucometer (Roche Diagnostics, Indianapolis, IN, USA) and test strips at 0, 30, 60, 90, and 120 min following the glucose injection. The results were displayed as a blood glucose curve and the area under the curve (AUC). Before and 30 min after glucose loading, additional blood samples were collected and serum insulin concentrations were measured using insulin ELISA kits (EZassay, Shenzhen, China).