Objective      To determine the effects and potential mechanisms of insulin-like growth factor-1 (IGF-1) on osteoporosis in diabetic rats.       Methods      Thirty male SD rats (with an age of 3 months and weight of 220 to 250 g) were randomly assigned into control group (naive rats administered with PBS)

diabetic group (diabetic rats received PBS)

and IGF-1 group (diabetic rats received IGF-1). After SD diabetic rats were induced by intraperitoneal injection of streptozotocin

PBS or 1 mg/(kg·d) IGF-1 was given to the rats from the corresponding groups for 3 months. Then the tibial bone density was calculated with the aid of X-ray photography

the serum level of bone alkaline phosphatase (BALP) was detected

the contents of tibial calcium and phosphonium were measured for the weight ratio of tibial ash to tibial bone

and the expression of tibial bone morphogenetic protein-2 (BMP-2) was detected by Western blotting and immunohistochemical assay.       Results       In the control

diabetic and IGF-1 groups

the BALP level was 2.42±0.56

1.54±0.41 and 2.18±0.62 ng/L respectively; the calcium content was 5.89±1.21

5.41±0.75 and 5.75±1.05 mol/L respectively; the phosphonium content was 3.78±0.56

3.21±0.47 and 3.67±0.41 mol/L respectively; the ratio of tibial ash to tibial bone was (67.21±0.81)%

(63.13±0.63)% and (65.81±0.21)% respectively. The serum level of BALP

the expression of BMP-2

the contents of calcium and phosphonium

the weight ratio of tibial ash to tibial bone

and the tibial bone density were decreased in diabetic group compared with control group (P0.05). While

the IGF-1 group showed increased BALP level

up-regulated tibial BMP-2

increased contents of tibial calcium and phosphonium

increased weight ratio of tibial ash to tibial bone

and improved tibial bone density compared to diabetic group (P0.05).       Conclusion        IGF-1 enhances the tibial contents of tibial calcium and phosphonium

increase weight ratio of tibial ash to tibial bone

and inhibit osteoporosis in diabetic rats. These alterations may result from IGF-1 enhancing the level of BALP and up-regulating BMP-2 in the tibia.