Forty-five SD rats (3 months old, 200 ± 20 g) were obtained from the Department of Experimental Animals in China Medical University (Animal Certificate Number: SCXK (Liaoning) 2008-0005). Fifteen rats grew as control while other thirty rats were established T2DOP model. The model rats were given a high-fat feed and 12 h/day water for 2 months. Then streptozotocin was intraperitoneally injected at 30 mg/kg. Seventy-two hours later, the model was successfully established when insulin sensitivity index decreased and fasting plasma glucose exceeded 7.8 mmol/L. Then all rats continue grew 3 months to cause osteoporosis. Thirty model rats were divided into two groups. One was fifteen T2DOP rats only, and other was fifteen T2DOP rats with deferoxamine (DFO) treatment (60 mg/kg/day, intraperitoneally inject, last for the last 1 month).

Eight-week-old specific-pathogen-free Sprague Dawley rats weighing 220 ± 20 g were purchased from China Medical University, Department of Experimental Animals. A total of 60 rats were used to determine the targets of bone histomorphometry; 45 rats were used to establish a diabetic model, and remaining 15 rats were divided into a control group. The diabetic rats were divided into three groups (n = 15 each) treated with intraperitoneal injection of high-dose melatonin (50 mg/kg, HMT group), intraperitoneal injection of low-dose melatonin (10 mg/kg, LMT group), and a control T2DM group.

The mice were fed a standard pellet diet (mice maintenance diet; Tengxin Biotechnology Co., Ltd) and distilled water ad libitum and kept at a 12-h lightdark cycle, a temperature of 23 to 25 and a relative humidity of 50% ± 5%. Mice were divided into four groups: control (Ctrl), ferric ammonium citrate (FAC), ART and combined treatment (FAC + ART). FAC (Sigma-Aldrich; 40 mg/kg) were injected intraperitoneally every 3 days for 8 weeks. ART group mice were administered 50 mg/kg by oral gavage every other day for 8 weeks.