The Mechanism Responsible For Exercise Combined With Alendronate Sodium In The Protection Against Ovariectomy-induced Osteoporosis Of Rats

ObjectiveTo observe the therapy effects of exercise (EX) combined with AlendronateSodium (FOX) on the treatment of ovariectomy-induced osteoporosis; then furtherresearch whether exercise can enhance the effects of Alendronate Sodium in theprotection against postmenopausal osteoporosis (PMOP) and its possible mechanism.MethodsNinety6months old female SD rats were randomly divided into2groups: sham(18rats) and ovariectomized group (72rats). Eight weeks after the ovariectomy,dual-energy x-ray absorptiometry (DEXA) scaned the bone mineral density (BMD) ofthe fourth lumbar vertebra, left femur and right femur. Then, the livingovariectomized rats were divided into4groups: ovariectomized model group (OVX),fosamax treatment group (OVX+FOX), exercise treatment group (OVX+EX), andexercise combined with fosamax treatment group (OVX+FOX+EX). Rats weretreated with1mg/kg fosamax intragastrically and/or exercise once a day for12weeks.1. DEXA scaned the BMD of the fourth lumbar vertebra, left femur and rightfemur again; Electromyogram (EMG) detected the Motor Nerve Conduction Velocity(MCV), motor distal latency (ML) and compound muscle action potential (CMAP) ofbilateral femoral nerve.2. ELISA analysed serum bone isoenzyme alkaline phosphatase (BALP),osteocalcin (BGP), carboxy terminal propeptideⅠprotection (PICP), tartrate-resistantacid phosphatase (TRAP), and type Ⅰcollagen cross-linked telopeptide (ICTP).3. Real time PCR detected the mRNA expression of osteoprotegerin (OPG) andthe receptor activator of nuclear factor kappa B ligand (RANKL) in rat bone tissue;western-blotting analysed the protein expression of p38, ERK, JNK, and c-Fos.4. ELISA analysed serum IL-1β, TNFα content; western-blotting analyzedNF-kappa B inhibitor IкB content in rat bone tissue. Results1. Twelve weeks after FOX and/or EX treatment towards ovariectomy rats,ovariectomized rats showed obviously lower BMD compared with sham group(P<0.05); FOX and/or EX can significantly increase BMD reduced by ovariectomy(P<0.05); BMD is significantly higher in the OVX+EX+FOX group than OVX+FOXor OVX+EX (P<0.05). However, no obvious difference was noticed betweenOVX+FOX and OVX+EX.2. Comapared to sham group, there was no distinct difference among the5groups inMCV. Neither ovariectomy nor FOX can significantly affect ML or CMAP. EX, EX+FOX canshorter ML compared to OVX (P<0.05) and ML is remarkablely shorter in OVX+FOX+EX thanFOX alone on the left femoral nerve (P<0.05). EX can improve CMAP on the right femoralnerve compared to OVX and CMAP is obviously higher in OVX+FOX+EX is than FOX alone(P<0.05).3. The serum BALP, BGP, PICP, TRAP, ICTP were significantly higher inovariectomized rats compared to sham group (P<0.05); FOX and/or EX cansignificantly reduce above parameters (P<0.05). OVX+EX+FOX group showed anobvious lowness than FOX or EX alone (P<0.05).4. Compared to sham group, TRANKL mRNA and protein expression weresignificantly increased (P<0.05); OPG mRNA and protein were remarkablely lower inOVX group (P<0.05); the TRANKL/OPG ratio obviously increased (P<0.05). FOXand/or EX can significantly reduce RANKL/OPG ratio (P<0.05). OVX+EX+FOXgroup showed obviously lower TRANKL/OPG ratio than FOX or EX alone (P<0.05).5. JNK phosphorylation level and c-Fos content were significantly increased inthe OVX group than sham in bone tissue (P<0.05); FOX and/or EX can significantlyinhibit the phosphorylation level of JNK and c-Fos content (P<0.05); however, nosignificant difference was observed among the OVX+FOX, OVX+EX, andOVX+FOX+EX.6. The serum IL-1β and TNFα level were significantly increased in OVX groupthan sham (P<0.05); FOX and/or EX can significantly reduce IL-1β and TNFα level (P<0.05); OVX+EX+FOX group showed obvious lower IL-1β and TNFα than FOXor EX alone (P<0.05).7. IκB phosphorylation level was remarkablely incread in OVX group than shamin bone tissue (P<0.05); FOX and/or EX can significantly inhibit the phosphorylationlevel of IκB (P<0.05); however, no significant difference was observed among theOVX+FOX, OVX+EX, and OVX+FOX+EX.ConclusionFosamax and exercise may inhibit IL-1β and TNFα expression through theIκB/NF-κB pathway induced by ovariectomy, and then induce the OPG expression,inhibit the RANKL expression in osteoblas and decrease the RANKL/OPG ratio, thusinhibit the JNK-c-fos signal pathway and at last restrain bone absorption effect ofosteoclast.