Experimental study on precaution osteoporosis by the increase of cerebrospinal fluid leptin level on rabbit model / 中华骨科杂志

ABSTRACT

Objective To explore effect of increasing cerebrospinal fluid (CSF) leptin level by administration from the foramen magnum to the cerebellum medulla oblongata pool in osteoporosis in rabbit model established by ovariectomy (OVX) and methylprednisolones.Methods According to certain inclusion and exclusion criteria,30 adult rabbits which were healthy 5-month-old female New Zealand white rabbits with the same batch and weight were divided into 5 groups (n=6) with random number table,including control group,normal saline group,Low dose group,middle dose group and high dose group.The animal model of osteoporosis (OP) was established 8 weeks after ovariectomy (bilateral ovarian resection) and intramuscular injection of methylprednisolone daily for 8 consecutive weeks in all groups.The control group were only simulated puncture and didn't inject any drugs or normal saline,the normal saline group were intracerebroventricular (ICV) injection with NS and Low,Middle and High dose group injected with low,middle and high dose of leptin respectively at 0,3,7 days after OVX.Before (0 week) and 4,8 weeks after the operation,the measure of dual energy X-ray absorptiometry was done on all the rabbits femur and bone mineral density (BMD) was delivered.Before (0 week) and 4,8 weeks after the first administration,leptin in cerebrospinal fluid (CSF) and serum growth hormone (GH),insulin growth factor 1 (IGF-1) and osteocalcin (OT/BGP) were tested with Enzyme linked immunosorbent assay and serum calcium,phosphorus and alkaline phosphatase (ALP) with automatic biochemical analyzer (ACA).The rabbits were sacrificed and the thalamus and femoral neck were harvested to test the expression of leptin receptor (LEPR) in thalamus and bone morphogenetic protein-2 (BMP-2) and type Ⅰ collagen (Col Ⅰ) at 8 weeks after the first administration.Results Compared with the control group and NS group,the cerebrospinal fluid (CSF) leptin concentration of leptin administration groups kept in a higher level significantly at 4 and 8 weeks after leptin administration,it was positively correlated with the concentration of administration.After administration 4 and 8 weeks,the bone mineral density (BMD) of leptin administration groups were not significantly lower than that of non-administration groups,and the high dose group was unchanged.The serum osteocalcin/bone glad protein (OT/BGP) concentration of leptin administration groups decreased more significantly compared with the non-administration groups at 4 weeks after leptin administration;and it rebounded more significantly than the non-administration groups and low dose group rebounded more significantly than other non-administration groups at 8 weeks.The concentration of serum growth hormone (GH) of 5 groups showed a downward trend at 4 and 8 weeks,the serum GH concentration of leptin administration groups decreased more significantly than the non-administration groups.The concentration of serum insulin-like growth IGF-1 of 5 groups were decreased significantly at 4 weeks,and the serum IGF-1 concentration of control and low dose groups were significantly higher than other 3 groups at 8weeks.Compared with the non-administration groups,the concentration of serum Calcium of leptin administration groups were increased more obvious,and it was positively correlated with the concentration of administration.Serum phosphorus of 5 groups were decreased at 4 weeks and elevated at 8 weeks;there was no difference among the groups.Serum ALP showed a continuous downward trend,and the middle dose group decreased significantly compared with other groups at 4 and 8 weeks.RTPCR results showed that the BMP-2 and Col Ⅰ mRNA expression increased and positively correlated with leptin administration concentration at 8weeks.Conclusion The increase of cerebrospinal fluid leptin level can promote the bone metabolism,reduce bone loss and precaution the occurrence of osteoporosis in rabbit model caused by OVX and methylprednisolone,and it was positively correlated with the concentration of administration.That provides a new method for the prevention and treatment of osteoporosis in rabbit model.