Effect of amygdalin on fracture healing in osteoporosis rats
Objective To investigate the effect of amygdalin(AD)on fracture healing in osteoporotic(OP)rats and its possible mechanism.Methods SD rats were randomly divided into sham group,model group,inhibitor group and low,medium,high dose experimental groups,12 rats in each group.The OP rat model was established by bilateral ovariectomy.After the model was successfully established,rats in low,medium and high dose experimental groups were intraperitoneally injected with 0.1,0.5 and 1.0 mg·kg-1 AD;the inhibitor group was intraperitoneally injected with 5.0 mg·kg-1 H-89[cyclic adenosine monophosphate/protein kinase A/cyclic adenosine monophosphate response element binding protein(cAMP/PKA/CREB)pathway inhibitor]+1.0 mg·kg-1 AD;sham group and model group were intraperitoneally injected with the same amount of 0.9%NaCl,once a day for 90 days.Micro-computer tomography was applied to observe the microstructure of the epiphysis in rats;the biomechanical status of femur was evaluated by orthopedic biomechanical test;the contents of serum osteocalcin(OC),C-terminal telopeptides of type Ⅰ collagen(CTX-Ⅰ),bone morphogenetic protein 2(BMP-2)and cAMP were detected by enzyme-linked immunosorbent assay(ELISA);the level of oxidative stress products in rat serum was detected by kit;Western blot was used to detect the expression of alkaline phosphatase(ALP)and cAMP/PKA/CREB signaling pathway protein(p-PKA/PKA,p-CREB/CREB)in rat bone tissue.Results The bone mineral density of sham group,model group and low,medium,high dose experimental groups,inhibitor group were(251.54±15.41),(135.82±10.92),(173.57±12.65),(204.31±14.48),(235.62±11.37)and(187.83±13.64)mg·cm-3;the contents of cAMP were(0.85±0.06),(0.20±0.03),(0.34±0.07),(0.48±0.09),(0.81±0.12)and(0.57±0.06)μmol·L-1;the expression of p-PKA/PKA were 0.96±0.08,0.06±0.02,0.35±0.04,0.67±0.07,0.94±0.09 and 0.37±0.05;p-CREB/CREB protein were 0.92±0.12,0.04±0.01,0.28±0.03,0.59±0.06,0.91±0.10 and 0.29±0.04,respectively.There were significant differences in the above indexes between sham group and model group,between low,medium,high dose experimental groups and model group,between inhibitor group and high dose experimental group(all P<0.05).Conclusion AD can reduce oxidative stress,promote fracture healing and alleviate OP symptoms in rats.The mechanism may be related to the activation of cAMP/PKA/CREB signaling pathway.