The Expression Of BMP-2and Its Inhibitor Noggin In The Early Stage Of Streptozotocin-induced Type1Diabetic Rat

ObjectiveTo establish the model of type1diabetic rats, observe the bone biochemical indices and bone mineral density (BMD), investigate the relationship between the bony metabolic disturbance and the expression of bone morphogenetic protein2(BMP-2) and Noggin of the femur.Methods1. Animals and Induction of diabetesSix to eight weeks old female Wistar rats strain were purchased. Rats were divided into a control group (group C, n=18) and a diabetic group (group D, n=18). Experimental diabetes was induced by a single intraperitoneal injection of streptozotocin (STZ,60mg/kg). Animals in group C were received the same volume of the citrate buffer only. Three days after induction of diabetes, rats with glucose levels>16.7mmol/L were selected into the diabetic group. The animals were killed at weeks1,2and4.2. Sample collectionThe animals were killed under anaesthesia with ketamine hydrochloride. The blood sample was obtained from the inferior vena cava. After the removing of muscle and tendons, the femurs was used for quantitative real-time PCR,western blot and BMD analyses. 3. Blood and bone measurements(1) Serum levels of insulin, BALP, OC, PTH and CT was measured using a Rat Insulin ELISA kit, Rat BALP ELISA kit, Rat OC ELISA kit, Rat PTH ELISA kit and Rat CT ELISA kit. The blood glucose was assayed by the blood glucose meter trace.(2) The right distal femur, after the removing of muscle and tendons, was used for the quantitative real-time PCR and western blot, to detect the mRNA and protein expression of the BMP-2and Noggin.(3) The BMD of the left femur was measured by DXA.Results1. General parameters:Diabetics rats showed significantly elevated glucose concentration and markedly reduced body weight than control group at weeks1,2and4(P<0.05). The serum insulin concentration decreased in the diabetic group (P<0.05).2. Biochemical analysis:Serum levels of BALP in the diabetic group increased significantly than the control group at2and4weeks (P<0.05), however, levels of PTH and CT in the diabetic were similar to the control group during the course of the study. Serum OC concentration in the diabetic group decreased significantly than the control group at1,2and4weeks (P<0.05)3. Expression of BMP-2and Noggin mRNA in the distal femur:The levels of BMP-2mRNA were significantly decreased to49%of the control value at week4(P<0.01); however, the expression of Noggin mRNA in diabetic rats were significantly increased to1.5-fold the control value at week4(P<0.01).4. Levels of BMP-2and Noggin protein in the distal femur:The levels of BMP-2protein in diabetic rats decreased to64%of the control value at week4. The level of Noggin protein in diabetic rats increased to1.5-fold the control value at week4(P<0.01)5. Bone densitometry measurements:The BMD of the total area of the femur in diabetic rats was significantly reduced at week4compared to the control group ( P<0.05).ConclusionThe expression of BMP-2was decreased in the bone in the early stage of type1diabetes, however, the expression of Noggin increased. It suggests the imbalance between BMP-2and Noggin to be involved in type1diabetes induced osteopenia.