中国北京地区绝经后汉族妇女雌激素受体基因多态性与骨密度的相关性研究
作者：关菁 戴兆亨 沈浣 田莉 高伯山 岳明刚
单位：北京大学人民医院妇产科，北京 100044
关键词：受体；雌激素；骨密度；绝经后期；限制性片段长度多态性
北京医科大学学报000608 [摘 要]目的：研究雌激素受体(estrogen receptor,ER)基因多态性在中国北京地区绝经后的汉族妇女中的分布及其与骨密度的相关性。方法：采用聚合酶链式反应-限制性片段长度多态性(PCR-restriction fragment length polymorphisms,PCR-RFLP)方法研究ER基因的Xba Ⅰ和Pvu Ⅱ酶切多态性，检测骨密度，通过方差分析探讨ER基因的多态性分布与骨密度的关系。结果：ER基因Pvu Ⅱ酶切多态性分布与桡骨松质骨以及桡骨密质骨的骨密度之间不存在相关性，而ER基因Xba Ⅰ酶切多态性分布与桡骨松质骨以及桡骨密质骨的骨密度之间存在相关性，XX基因型骨密度值最低，xx基因型骨密度值最高。结论：ER基因Xba Ⅰ酶切多态性分布与桡骨松质骨以及桡骨密质骨的骨密度之间显著相关(P<0.05)。本研究为探讨骨质疏松症在分子生物学范畴的发病机制及预防与预后提供了有益的依据。
, http://www.100md.com
[中图分类号]R322.65 [文献标识码]A
[文章编号]1000-1530(2000)06-0508-04
Study on the association of estrogen receptor genotypes with bone mineral density in Chinese postmenopausal Han women in Beijing
GUAN Jing，DAI Zhao-Heng，SHEN Huan，TIAN Li，GAO Bo-Shan，YUE Ming-Gang
(Department of Gynecology and Obstetrics,Peking University People's Hospital,Beijing 100044,China)
, 百拇医药
ABSTRACT Objective：To investigate the distribution of polymorphism of estrogen receptor (ER) gene in postmenopausal Han women in Beijing as well as its relationship with bone mineral density (BMD).Methods：Xba Ⅰ,and Pvu Ⅱ polymorphisms of ER gene were studied by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) and BMD were determined by DEXA (dual-energy X-ray absorptiometry).The relationship between BMD and polymorphism of ER gene was studied by variance analysis.Results：Pvu Ⅱ polymorphism of ER gene was not associated with BMD of spongy and compact bone of radius;while Xba Ⅰ polymorphism of ER gene was associated with BMD of spongy and compact bone of radius.The lowest BMD was found with XX genotype while the highest BMD was found with xx genotype.Conclusion:There is high correlation between of Xba Ⅰ polymorphism and BMD of spongy and compact bone of radius.Our study suggested some bases to explore the pathogenesis of osteoporosis and to prevent the development of osteoporosis.
, 百拇医药
KEY WORDS Receptors,estrogen;Bone density;Postmenopause;Restriction fragment length polymorphisms
Bone mineral density (BMD) is influenced by genetic and environmental factors.Studies showed that the vitamin D receptor (VDR) accounted for 75% of genetic factors of BMD[1],besides,estrogen receptor (ER) also influenced BMD.It was found that Xba Ⅰ and Pvu Ⅱ polymorphisms of ER had significant influences on BMD of Japanese,and that PPxx genotype was associated with low BMD[2].
, 百拇医药
The change of the single basic group of ER gene intron Ⅰ leads to the recognition of genes by restriction endonuclease Xba Ⅰ and Pvu Ⅱ respectively.Through the recognition of genes by endonuclease,different alleles of different individual ER's are differentiated.
In this research,we studied the relationship between BMD and polymorphism of ER gene among 99 healthy postmenopausal Chinese Han women by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).
, 百拇医药
1 CLINICAL MATERIALS AND METHODS
1.1 Subjects
99 healthy Beijing postmenopausal Han women between 49 and 55 years of age with no history of hormone replacement therapy (HRT) were studied.Women with diseases that affect BMD were excluded.
1.2 Methods
1.2.1 Bone Densitometry BMD was measured at spongy and compact bone of radius by dual-energy X-ray absorptiometry (Israel Dexa DX-10).
, 百拇医药
1.2.2 Isolation of Genomic DNA 2 ml peripheral blood was used to isolate DNA with Genomic DNA Purification kit (Promega) as recommended.The purified DNA was resolved in Tris EDTA (TE) buffer.
1.2.3 PCR Genomic DNA was amplified using polymerase chain reaction (PCR) with 10 mmol*L-1 Tris-HCl,50 mmol*L-1 KCl,2 mmol*L-1 MgCl2,200 μmol*L-1 dNTP (Takara) and 0.2 μmol*L-1 of each primer.The oligonucleotide primers used to determine the Xba Ⅰ and Pvu Ⅱ polymorphisms in the ER gene were:forward,5′- CTGCCACCCTATCTGTATCTTTTCCTATTCTCC- 3′;reverse,5′-TCTTTCTCTGCC-
, 百拇医药
ACCCTGGCGTCGATTATCTGA-3′[2].The conditions of PCR cycle were:denaturation at 94℃ for 5 min followed 30 circles of (1) denaturation at 94℃ for 30 s;(2) annealing at 62℃ for 40 s;(3) extension at 72℃ for 60 s;extension at 72℃ for 5 min was performed after PCR cycle[2].
1.2.4 Genotyping The PCR products of 1.3 kb fragments were digested with the Xba Ⅰ and Pvu Ⅱ restriction endonucleases (Takara) and separated on agarose gel.PP and XX,signifying the absence of restriction sites on both alleles,showed 1.3 kb fragment,and pp,signifying the presence of restriction sites on both alleles were digested into two fragments (0.85 kb and 0.45 kb).The cutting fragment of Xba Ⅰ polymorphism near the Pvu Ⅱ RFLP site revealed two fragments (0.9 kb and 0.4 kb) labeled as xx.
, http://www.100md.com
1.3 Statistical Analysis
To determine whether the proportions observed in our data were those to be expected in a random mating equilibrium population,they were explored using the χ2 method under the Hardy-Weinberg law[3].Distribution of characteristics in each genotype and the effect of the polymorphism of the ER gene on BMD of each skeletal site was evaluated with one-way ANOVA test[3].A Р value less than 0.05 was considered statistically significant.
, 百拇医药
2 RESULTS
2.1 The ERG polymorphism in northera Chinese postmenopausal Han women in Beijing
The ditribution of Pvu Ⅱ RFLP was:PP 13,Pp 61,pp 25.The ditribution of Xba Ⅰ RFLP was:XX 7,Xx 48,xx 44.In the combination of two RFLPs,all nine genotypes were detected in our data (Figure 1 and Table 1).
2.2 The ERG Pvu Ⅱ and Xba Ⅰ genotype of postmenopausal women in Beijing and the background material
, http://www.100md.com
The postmenopausal women's genotype and background materials were given in Table 2.There was no significant difference in age,age of menolipsis,height,and body weight among different groups.
2.3 The relationships between ERG Pvu Ⅱ polymorphism and BMD in postmenopausal women in Beijing
Through this study the distribution of Pvu Ⅱ polymorphism was not found to be related to radii spongy bone and compact bone (P>0.05,Table 3).
, 百拇医药
Figure 1 The results of electrophoresis for ER gene Pvu Ⅱ and Xba Ⅰ endonuclease digestion
Table 1 Genotypes at Pvu Ⅱ and Xba Ⅰ polymorphic sites Pvu Ⅱ genotypes
Xba Ⅰ genotypes
XX
Xx
xx
PP
4
7
, 百拇医药
2
Pp
2
35
24
pp
1
6
18
2.4 The relationships between the distribution of ER Xba Ⅰ polymorphism and BMD in postmenopausal women
It was found that the distribution of Xba Ⅰ polymorphism was significantly related to BMD of radii spongy bone and compact bone (P<0.05,Table 4)Table 2 The profile for the Pvu Ⅱ and Xba Ⅰ RFLP genotypes
, 百拇医药
Pvu Ⅱ
Xba Ⅰ
Genotypes
PP
Pp
pp
XX
Xx
xx
Number
13
61
25
, 百拇医药
7
48
44
Age(years)
53.06± 4.23
52.55±3.15
52.16±3.74
53.93±5.31
52.55±3.86
52.27±4.07
Height(cm)
160.1 ± 4.2
, 百拇医药
159.2 ±5.1
159.6 ±5.7
159.3 ±4.5
159.8 ±5.5
159.9 ±4.9
Weight(kg)
61.43±10.27
62.75±9.52
62.59±9.38
61.97±8.73
62.67±9.13
, 百拇医药
62.48±9.45
t/years
2.38± 0.98
2.52±1.14
2.83±1.03
2.71±0.82
2.49±1.07
2.66±1.18
t， duration since menopause.
Pvu Ⅱ genotypes：Age:F=0.20， P=0.82;Height:F=0.26， P=0.78； Weight:F=0.31， P=0.73； t/years F=0.45， P=0.64.
, 百拇医药
Xba Ⅰ genotypes：Age:F=0.39， P=0.68;Height:F=0.16， P=0.85； Weight:F=0.13， P=0.88； t/years F=0.71， P=0.50.Table 3 The relationships between ERG Pvu Ⅱ RFLP genotypes and BMD Bone of radius
PP
Pp
pp
n
F value
P value
Compact
, 百拇医药 -1.39±0.22
-1.36±0.25
-1.12±0.19
99
0.73
0.485
Spongy
-2.07±0.23
-2.05±0.34
-1.93±0.16
99
0.16
, 百拇医药
0.851
Table 4 The relationships between ERG Xba Ⅰ genotypes and BMD
Bone of radius
XX
Xx
xx
n
F value
P value
Compact
-1.55±0.37
, http://www.100md.com
-1.43±0.25
-0.95±0.24
99
3.92
0.023
Spongy
-2.54±0.38
-2.00±0.33
-1.74±0.16
99
3.20
0.045
, 百拇医药
3 DISSCUSSION
Osteoporosis is a dangerous disease with which patients have low bone content and are faced with high risk of bone fracture.It is quite popular in United States,Japan and China.Since the rapidly aging population is very prominent in China,people become more and more concerned with osteoporosis.For years,people had proved,through the study on one-egg twins and the researches on family disease of osteoporosis,that the genetic factor accounts for 60%-80% at BMD[4，5].Morrison et al[1] reported the close relationship between Vitamin D receptor (VDR) gene and BMD in 1994,followed by extensive researches in this field by other scientists.Recent studies had extended BMD gene analysis to other genes,such as interleukin-6 gene,and estrogen receptor gene——a hot point of the nearest studies[6].However the conclusions were different sometimes.Even though,theoretically polymorphism of ER gene is surely related to BMD in a certain degree.ER is mainly located in the nucleus of skeletogenous cells,and can act directly on skeletogenous cells.Estrogen can diffuse directly in cellular nucleus and combine with ER,and direct monitor of ER mRNA expression in normal skeletogenous cells can be achieved by RT-PCR analysis.Expression of ER depends on the existence of estrogen,for example ER mRNA expression is obviously reduced in an ovariectomized mouse,and is nearly up to normal level if the mouse receives estrogen treatment.This is also the genetic back ground for applying HRT on women sufferring from osteoporosis.The change in ER's quantity will directly influence its function,and the decrease will lead to the attenuation of the effect on skeletogenous cells,hence the reduction of bone content.Polymorphism of ER gene may have certain effect on ER's quantity.Therefore,theoretically there possibly exists certain relationships between polymorphism of genes and the change of bone content.
, 百拇医药
Present reports showed that PPxx genotype of Xba Ⅰ and Pvu Ⅱ RFLPs in Japanese were related to low BMD of vertebra[2];Korean ER genotype was not significantly related to BMD[3];and Belgian research findings also indicated that ER genotype was not related to BMD[7].Our study showed that BMD of radius spongy bone and cortical bone was not related to Pvu Ⅱ RFLPs of ER gene,but was significantly related to Xba Ⅰ RFLPs of ER gene.The disparity in the results might be explained by ethnic difference,which illustrated that the same genotype had different expressions in different races.
, 百拇医药
Alleles related study is one of the sensitive methods to determine the relevant sites of diseases.It explains not only the site information that relates with the occurrence of the disease but also some information of indecisive factors .The research on alleles relies on at least two factors:first,the genetic mutation rate should be low,such as ER gene complies with this requirement;second,research studies must be carried out in the same population as in our study all subjects were Beijing residents or from the same population.Due to the complexity of bone biology,the influence of bone's production and development by many factors,and the loss of bone content along with the aging population,we have to approve that osteoporosis is a multiple-factor and complicated pathologic process.Therefore,to exclude,to a maximum limit,the influence by other factors becomes the crux for the accuracy of the results of this experiment.For this reason,we selected subjects with small age gap (between 49 and 55 years old),a maximum menopause of 5 years,not much difference in diet habit,and none of them exceedingly fat or thin.So as to have a more scientific conclusion.
, 百拇医药
Although people had done a lot of research on polymorphism of ER gene,little is known about what a role had polymorphism of ER gene played in the occurrence of osteoporosis,and whether or not it joins the common activity together with other relevant genes.With the in-depth studies in this field,the solution to the above problems will enable us to face the ever-spreading osteoporosis in the future.
REFERENCES
1，Morrison NA,Qi JC,Tokita A,et al.Prediction of bone density from vitamin D receptor alleles[J].Nature,1994,367(6460):284-287
, 百拇医药
2，Kobayashi S,Inoue S,Hosoi T,et al.Association of bone mineral density with polymorphism of the estrogen receptor gene[J].J Bone Miner Res,1996,11(3):306-311
3，Han K,Choi J,Moon I,et al.Non-association of estrogen receptor genotypes with bone mineral density and bone turnover in Korean pre-,peri-,and postmenopausal women[J].Osteoporos Int,1999,9(4):290-295
4，Gosden JR,Middleton PG,Rout D.Localization of the human estrogen receptor gene to chromosome 6q24——q27 by in situ hybridization[J].Cytogenet Cell Genet,1986,43(3-4):218-220
, 百拇医药
5，Pocock NA,Eisman JA,Hopper JL,et al.Genetic determinants of bone mass in adults.A twin study[J].J Clin Invest,1987,80(3):706-710
6，Ponglikitmongkol M,Green S,Chambon P.Genomic organization of the human estrogen receptor gene[J].EMBO J,1988,7(11):3385-3388
7，Vandevyver C,Vanhoof J,Declerck K,et al.Lack of association between estrogen receptor genotypes and bone mineral density,fracture history,or muscle strength in elderly women[J].J Bone Miner Res,1999,14(9):1576-1582
Received：2000-05-18, 百拇医药
单位：北京大学人民医院妇产科，北京 100044
关键词：受体；雌激素；骨密度；绝经后期；限制性片段长度多态性
北京医科大学学报000608 [摘 要]目的：研究雌激素受体(estrogen receptor,ER)基因多态性在中国北京地区绝经后的汉族妇女中的分布及其与骨密度的相关性。方法：采用聚合酶链式反应-限制性片段长度多态性(PCR-restriction fragment length polymorphisms,PCR-RFLP)方法研究ER基因的Xba Ⅰ和Pvu Ⅱ酶切多态性，检测骨密度，通过方差分析探讨ER基因的多态性分布与骨密度的关系。结果：ER基因Pvu Ⅱ酶切多态性分布与桡骨松质骨以及桡骨密质骨的骨密度之间不存在相关性，而ER基因Xba Ⅰ酶切多态性分布与桡骨松质骨以及桡骨密质骨的骨密度之间存在相关性，XX基因型骨密度值最低，xx基因型骨密度值最高。结论：ER基因Xba Ⅰ酶切多态性分布与桡骨松质骨以及桡骨密质骨的骨密度之间显著相关(P<0.05)。本研究为探讨骨质疏松症在分子生物学范畴的发病机制及预防与预后提供了有益的依据。
, http://www.100md.com
[中图分类号]R322.65 [文献标识码]A
[文章编号]1000-1530(2000)06-0508-04
Study on the association of estrogen receptor genotypes with bone mineral density in Chinese postmenopausal Han women in Beijing
GUAN Jing，DAI Zhao-Heng，SHEN Huan，TIAN Li，GAO Bo-Shan，YUE Ming-Gang
(Department of Gynecology and Obstetrics,Peking University People's Hospital,Beijing 100044,China)
, 百拇医药
ABSTRACT Objective：To investigate the distribution of polymorphism of estrogen receptor (ER) gene in postmenopausal Han women in Beijing as well as its relationship with bone mineral density (BMD).Methods：Xba Ⅰ,and Pvu Ⅱ polymorphisms of ER gene were studied by polymerase chain reaction-restriction fragment length polymorphisms (PCR-RFLP) and BMD were determined by DEXA (dual-energy X-ray absorptiometry).The relationship between BMD and polymorphism of ER gene was studied by variance analysis.Results：Pvu Ⅱ polymorphism of ER gene was not associated with BMD of spongy and compact bone of radius;while Xba Ⅰ polymorphism of ER gene was associated with BMD of spongy and compact bone of radius.The lowest BMD was found with XX genotype while the highest BMD was found with xx genotype.Conclusion:There is high correlation between of Xba Ⅰ polymorphism and BMD of spongy and compact bone of radius.Our study suggested some bases to explore the pathogenesis of osteoporosis and to prevent the development of osteoporosis.
, 百拇医药
KEY WORDS Receptors,estrogen;Bone density;Postmenopause;Restriction fragment length polymorphisms
Bone mineral density (BMD) is influenced by genetic and environmental factors.Studies showed that the vitamin D receptor (VDR) accounted for 75% of genetic factors of BMD[1],besides,estrogen receptor (ER) also influenced BMD.It was found that Xba Ⅰ and Pvu Ⅱ polymorphisms of ER had significant influences on BMD of Japanese,and that PPxx genotype was associated with low BMD[2].
, 百拇医药
The change of the single basic group of ER gene intron Ⅰ leads to the recognition of genes by restriction endonuclease Xba Ⅰ and Pvu Ⅱ respectively.Through the recognition of genes by endonuclease,different alleles of different individual ER's are differentiated.
In this research,we studied the relationship between BMD and polymorphism of ER gene among 99 healthy postmenopausal Chinese Han women by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP).
, 百拇医药
1 CLINICAL MATERIALS AND METHODS
1.1 Subjects
99 healthy Beijing postmenopausal Han women between 49 and 55 years of age with no history of hormone replacement therapy (HRT) were studied.Women with diseases that affect BMD were excluded.
1.2 Methods
1.2.1 Bone Densitometry BMD was measured at spongy and compact bone of radius by dual-energy X-ray absorptiometry (Israel Dexa DX-10).
, 百拇医药
1.2.2 Isolation of Genomic DNA 2 ml peripheral blood was used to isolate DNA with Genomic DNA Purification kit (Promega) as recommended.The purified DNA was resolved in Tris EDTA (TE) buffer.
1.2.3 PCR Genomic DNA was amplified using polymerase chain reaction (PCR) with 10 mmol*L-1 Tris-HCl,50 mmol*L-1 KCl,2 mmol*L-1 MgCl2,200 μmol*L-1 dNTP (Takara) and 0.2 μmol*L-1 of each primer.The oligonucleotide primers used to determine the Xba Ⅰ and Pvu Ⅱ polymorphisms in the ER gene were:forward,5′- CTGCCACCCTATCTGTATCTTTTCCTATTCTCC- 3′;reverse,5′-TCTTTCTCTGCC-
, 百拇医药
ACCCTGGCGTCGATTATCTGA-3′[2].The conditions of PCR cycle were:denaturation at 94℃ for 5 min followed 30 circles of (1) denaturation at 94℃ for 30 s;(2) annealing at 62℃ for 40 s;(3) extension at 72℃ for 60 s;extension at 72℃ for 5 min was performed after PCR cycle[2].
1.2.4 Genotyping The PCR products of 1.3 kb fragments were digested with the Xba Ⅰ and Pvu Ⅱ restriction endonucleases (Takara) and separated on agarose gel.PP and XX,signifying the absence of restriction sites on both alleles,showed 1.3 kb fragment,and pp,signifying the presence of restriction sites on both alleles were digested into two fragments (0.85 kb and 0.45 kb).The cutting fragment of Xba Ⅰ polymorphism near the Pvu Ⅱ RFLP site revealed two fragments (0.9 kb and 0.4 kb) labeled as xx.
, http://www.100md.com
1.3 Statistical Analysis
To determine whether the proportions observed in our data were those to be expected in a random mating equilibrium population,they were explored using the χ2 method under the Hardy-Weinberg law[3].Distribution of characteristics in each genotype and the effect of the polymorphism of the ER gene on BMD of each skeletal site was evaluated with one-way ANOVA test[3].A Р value less than 0.05 was considered statistically significant.
, 百拇医药
2 RESULTS
2.1 The ERG polymorphism in northera Chinese postmenopausal Han women in Beijing
The ditribution of Pvu Ⅱ RFLP was:PP 13,Pp 61,pp 25.The ditribution of Xba Ⅰ RFLP was:XX 7,Xx 48,xx 44.In the combination of two RFLPs,all nine genotypes were detected in our data (Figure 1 and Table 1).
2.2 The ERG Pvu Ⅱ and Xba Ⅰ genotype of postmenopausal women in Beijing and the background material
, http://www.100md.com
The postmenopausal women's genotype and background materials were given in Table 2.There was no significant difference in age,age of menolipsis,height,and body weight among different groups.
2.3 The relationships between ERG Pvu Ⅱ polymorphism and BMD in postmenopausal women in Beijing
Through this study the distribution of Pvu Ⅱ polymorphism was not found to be related to radii spongy bone and compact bone (P>0.05,Table 3).
, 百拇医药
Figure 1 The results of electrophoresis for ER gene Pvu Ⅱ and Xba Ⅰ endonuclease digestion
Table 1 Genotypes at Pvu Ⅱ and Xba Ⅰ polymorphic sites Pvu Ⅱ genotypes
Xba Ⅰ genotypes
XX
Xx
xx
PP
4
7
, 百拇医药
2
Pp
2
35
24
pp
1
6
18
2.4 The relationships between the distribution of ER Xba Ⅰ polymorphism and BMD in postmenopausal women
It was found that the distribution of Xba Ⅰ polymorphism was significantly related to BMD of radii spongy bone and compact bone (P<0.05,Table 4)Table 2 The profile for the Pvu Ⅱ and Xba Ⅰ RFLP genotypes
, 百拇医药
Pvu Ⅱ
Xba Ⅰ
Genotypes
PP
Pp
pp
XX
Xx
xx
Number
13
61
25
, 百拇医药
7
48
44
Age(years)
53.06± 4.23
52.55±3.15
52.16±3.74
53.93±5.31
52.55±3.86
52.27±4.07
Height(cm)
160.1 ± 4.2
, 百拇医药
159.2 ±5.1
159.6 ±5.7
159.3 ±4.5
159.8 ±5.5
159.9 ±4.9
Weight(kg)
61.43±10.27
62.75±9.52
62.59±9.38
61.97±8.73
62.67±9.13
, 百拇医药
62.48±9.45
t/years
2.38± 0.98
2.52±1.14
2.83±1.03
2.71±0.82
2.49±1.07
2.66±1.18
t， duration since menopause.
Pvu Ⅱ genotypes：Age:F=0.20， P=0.82;Height:F=0.26， P=0.78； Weight:F=0.31， P=0.73； t/years F=0.45， P=0.64.
, 百拇医药
Xba Ⅰ genotypes：Age:F=0.39， P=0.68;Height:F=0.16， P=0.85； Weight:F=0.13， P=0.88； t/years F=0.71， P=0.50.Table 3 The relationships between ERG Pvu Ⅱ RFLP genotypes and BMD Bone of radius
PP
Pp
pp
n
F value
P value
Compact
, 百拇医药 -1.39±0.22
-1.36±0.25
-1.12±0.19
99
0.73
0.485
Spongy
-2.07±0.23
-2.05±0.34
-1.93±0.16
99
0.16
, 百拇医药
0.851
Table 4 The relationships between ERG Xba Ⅰ genotypes and BMD
Bone of radius
XX
Xx
xx
n
F value
P value
Compact
-1.55±0.37
, http://www.100md.com
-1.43±0.25
-0.95±0.24
99
3.92
0.023
Spongy
-2.54±0.38
-2.00±0.33
-1.74±0.16
99
3.20
0.045
, 百拇医药
3 DISSCUSSION
Osteoporosis is a dangerous disease with which patients have low bone content and are faced with high risk of bone fracture.It is quite popular in United States,Japan and China.Since the rapidly aging population is very prominent in China,people become more and more concerned with osteoporosis.For years,people had proved,through the study on one-egg twins and the researches on family disease of osteoporosis,that the genetic factor accounts for 60%-80% at BMD[4，5].Morrison et al[1] reported the close relationship between Vitamin D receptor (VDR) gene and BMD in 1994,followed by extensive researches in this field by other scientists.Recent studies had extended BMD gene analysis to other genes,such as interleukin-6 gene,and estrogen receptor gene——a hot point of the nearest studies[6].However the conclusions were different sometimes.Even though,theoretically polymorphism of ER gene is surely related to BMD in a certain degree.ER is mainly located in the nucleus of skeletogenous cells,and can act directly on skeletogenous cells.Estrogen can diffuse directly in cellular nucleus and combine with ER,and direct monitor of ER mRNA expression in normal skeletogenous cells can be achieved by RT-PCR analysis.Expression of ER depends on the existence of estrogen,for example ER mRNA expression is obviously reduced in an ovariectomized mouse,and is nearly up to normal level if the mouse receives estrogen treatment.This is also the genetic back ground for applying HRT on women sufferring from osteoporosis.The change in ER's quantity will directly influence its function,and the decrease will lead to the attenuation of the effect on skeletogenous cells,hence the reduction of bone content.Polymorphism of ER gene may have certain effect on ER's quantity.Therefore,theoretically there possibly exists certain relationships between polymorphism of genes and the change of bone content.
, 百拇医药
Present reports showed that PPxx genotype of Xba Ⅰ and Pvu Ⅱ RFLPs in Japanese were related to low BMD of vertebra[2];Korean ER genotype was not significantly related to BMD[3];and Belgian research findings also indicated that ER genotype was not related to BMD[7].Our study showed that BMD of radius spongy bone and cortical bone was not related to Pvu Ⅱ RFLPs of ER gene,but was significantly related to Xba Ⅰ RFLPs of ER gene.The disparity in the results might be explained by ethnic difference,which illustrated that the same genotype had different expressions in different races.
, 百拇医药
Alleles related study is one of the sensitive methods to determine the relevant sites of diseases.It explains not only the site information that relates with the occurrence of the disease but also some information of indecisive factors .The research on alleles relies on at least two factors:first,the genetic mutation rate should be low,such as ER gene complies with this requirement;second,research studies must be carried out in the same population as in our study all subjects were Beijing residents or from the same population.Due to the complexity of bone biology,the influence of bone's production and development by many factors,and the loss of bone content along with the aging population,we have to approve that osteoporosis is a multiple-factor and complicated pathologic process.Therefore,to exclude,to a maximum limit,the influence by other factors becomes the crux for the accuracy of the results of this experiment.For this reason,we selected subjects with small age gap (between 49 and 55 years old),a maximum menopause of 5 years,not much difference in diet habit,and none of them exceedingly fat or thin.So as to have a more scientific conclusion.
, 百拇医药
Although people had done a lot of research on polymorphism of ER gene,little is known about what a role had polymorphism of ER gene played in the occurrence of osteoporosis,and whether or not it joins the common activity together with other relevant genes.With the in-depth studies in this field,the solution to the above problems will enable us to face the ever-spreading osteoporosis in the future.
REFERENCES
1，Morrison NA,Qi JC,Tokita A,et al.Prediction of bone density from vitamin D receptor alleles[J].Nature,1994,367(6460):284-287
, 百拇医药
2，Kobayashi S,Inoue S,Hosoi T,et al.Association of bone mineral density with polymorphism of the estrogen receptor gene[J].J Bone Miner Res,1996,11(3):306-311
3，Han K,Choi J,Moon I,et al.Non-association of estrogen receptor genotypes with bone mineral density and bone turnover in Korean pre-,peri-,and postmenopausal women[J].Osteoporos Int,1999,9(4):290-295
4，Gosden JR,Middleton PG,Rout D.Localization of the human estrogen receptor gene to chromosome 6q24——q27 by in situ hybridization[J].Cytogenet Cell Genet,1986,43(3-4):218-220
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5，Pocock NA,Eisman JA,Hopper JL,et al.Genetic determinants of bone mass in adults.A twin study[J].J Clin Invest,1987,80(3):706-710
6，Ponglikitmongkol M,Green S,Chambon P.Genomic organization of the human estrogen receptor gene[J].EMBO J,1988,7(11):3385-3388
7，Vandevyver C,Vanhoof J,Declerck K,et al.Lack of association between estrogen receptor genotypes and bone mineral density,fracture history,or muscle strength in elderly women[J].J Bone Miner Res,1999,14(9):1576-1582
Received：2000-05-18, 百拇医药