Blood glucose meter

In order to establish diabetic model, streptozotocin (STZ, Sigma, St. Louis, MO, USA) injection was applied. Male Sprague–Dawley (SD) rats (weight 200–240 g) received intraperitoneal injection of STZ (35 mg/kg) for 3 days [31 (link)]. Blood glucose levels were tested by blood glucose meter (Lifescan, Inc., Milpitas, CA, USA) one week following STZ injection. Animals with glucose levels ≥16.6 mmol/L were considered as diabetic. Diabetic rats received standard food for 4 weeks and then randomized into the following 4 groups (n = 15): (1) DM group: diabetic rats without any treatment; (2) DM + U50,488H group: diabetic rats that received daily treatment of U50,488H (Biomol, Plymouth Meeting, PA, USA) at 1 mg/kg for 4 weeks; (3) DM + vehicle group: diabetic rats that received only saline daily for 4 weeks; (4) DM + nor-BNI group: diabetic rats that received daily treatment of nor-BNI (Sigma, St. Louis, MO, USA) at 0.5 mg/kg for 4 weeks. Age-matched normal rats that received only saline daily (n = 15) were used as non-diabetic controls (CON). All experiments were conducted under the National Institutes of Health Guidelines on the Use of Laboratory Animal and were approved by the Fourth Military Medical University Committee on Animal Care.

Male Balb/cbyJ mice, 4-5 weeks old, were obtained from the National Laboratory Animal Center (National Science Council, Taipei City, Taiwan). All animals were handled according to the guidelines of the Instituted Animal Care and Use Committee of Chung Shan Medical University (IACUC, CSMU) for the care and use of laboratory animals. Mice were housed on a 12 h light/dark cycle. After adaptation for one week, mice were fed with high fat (60% calories) diet for 2 weeks. Then, diabetes was induced by intraperitoneal injection of streptozotocin (STZ, Sigma, St. Louis, MO, USA) for five days continuously at 40 mg/kg in citrate buffer (0.1 M citric acid, pH 4.5) after a 4 h fasting as described previously [24 (link), 25 (link)]. Blood glucose level was monitored on day 10 from the tail vein by using a blood glucose meter (Lifescan Inc. Milpitas, CA, USA). Mice with fasting blood glucose level ≥180 mg/dL were used for this study.

Postprandial blood glucose and body weight of mice were monitored weekly during the period of salidroside treatment. For the measurement of postprandial blood glucose levels, food was removed for 2 h as previously described [29 (link)], then blood samples from the tail vein were collected and the glucose levels were measured by a blood glucose meter (LifeScan Inc., Milpitas, CA). Serum insulin levels and the homeostasis model assessment-insulin resistance (HOMA-IR) index were determined as previously described [30 (link)].