Overview on the effects of progestins on bone

Antiosteoporotic effect of Hemidesmus indicus Linn. on ovariectomised rats

PHARMACOLOGICAL RELEVANCE

Root of Hemidesmus indicus (L). R. Br., an herbal drug of India is traditionally used to prevent or treat female hormonal disturbance related disorders and assuaging symptoms of menopausal conditions.

AIM OF THE STUDY

Lack of scientific data for potential use in bone loss, the present study was undertaken to investigate the effects of ethanol extract of Hemidesmus indicus root for osteoporosis in ovariectomised rats.

MATERIALS AND METHODS

Thirty wistar female rats were randomly divided into five groups. One group was sham operated and other four groups were undergone dorsal ovariectomy (OVX). After four weeks of post-operative recovery, three OVX groups, viz. Group1, Group2 and Group3 were treated for ninety days with standard raloxifene (RLX) 1mg/kg/day, Hemidesmus indicus root extract (HIRE) 100mg/kg/day and HIRE 200mg/kg/day respectively. Sham and OVX control groups were fed with equal 1% vehicle volume. Serum and urine biochemistry (alkaline phosphatase, tartrate resistant acid phosphatase, triglyceride, total cholesterol, calcium, phosphorous and hydroxyproline), weight of body, uterus and vagina, femur parameters, three point bending of tibia and fourth lumbar vertebra compression were examined. Furthermore, bone architecture and uterine hypertrophy were examined by histopathological studies.

RESULTS

Application of HIRE has increased bone strength and restored bone turnover markers such as alkaline phosphatase, tartrate resistant acid phosphatase and hydroxyproline moreover, improved femur parameters indicated mineralized bones, similar to the results observed with raloxifene treatment. Histopathology studies showed fibrocartilaginous proliferation of trabecular bone and absence of uterine hypertrophy.

CONCLUSION

The results strongly suggest that HIRE prevents bone loss in OVX induced osteoporosis without estrogen like side effects. It might be a potential remedy like raloxifene for postmenopausal or estrogen deficiency caused osteoporosis.

Aging and bone health in Singaporean Chinese pre-menopausal and postmenopausal women

OBJECTIVE

The study evaluated relationships between menopausal statuses, hormone replacement therapy (HRT), body mass index (BMI), percent body fat (PBF), and exercise with osteoporosis and bone mineral density (BMD) in Singaporean women.

STUDY DESIGN

This is a cross-sectional study.

MAIN OUTCOME MEASURES

The spine BMD, and femoral neck BMD as well as the prevalence of osteoporosis are the main outcome measures studied.

RESULTS

Age, BMI, PBF and exercise intensity were independently associated with spine and femoral neck BMD. Women with higher BMI and lower PBF had higher BMD and lower prevalence of osteoporosis. Postmenopausal women without HRT had lower BMD and higher prevalence of osteoporosis while those on HRT had similar BMD and prevalence of osteoporosis as premenopausal women.

CONCLUSION

This study shows that BMI and PBF are powerful predictors of BMD. Osteoporosis is site-specific in the Singapore population, being higher in the femoral neck than in the lumbar spine. The bone status after menopause may not be worse than that dictated by age alone and both ERT and E/PRT could sustain the BMD to levels corresponding to those of women a decade younger. A strategy to improve bone health should include dieting and physical exercise program that focuses on selectively reducing fat mass and increasing lean mass.

The effect of pregnancy on orthodontic tooth movement in rats

Introduction: The purpose of this study was to investigate the effect of pregnancy on orthodontic tooth movement in Wistar rats. Material and Methods: Forty eight female three-month old Wistar rats with an average weight of 250±25 gr were selected and randomly divided into two experimental (pregnant) and control groups (non-pregnant). Maxillary central incisors were tipped distally by insertion of springs exerting 30g force. Two, seven and fourteen days after spring insertion animals were sacrificed. Then the mesioincisal distance between maxillary incisors were measured. Subsequently, histological sections were prepared to count osteoclasts under a light microscope. The data on the extent of orthodontic tooth movement, and the number of osteoclasts were analyzed by independent sample t-test. Results: The results indicated that 2,7 and 14 days after force application there was no significant difference in orthodontic tooth movement between experimental and control groups (p>0.05). The number of osteoclasts were significantly lower in the experimental group 7 and 14 days after spring insertion (p<0.05). Conclusion: Pregnancy may decrease the amount of tooth movement in the linear phase but it is not statistically significant. The number of osteoclasts is significantly decreased during pregnancy.

Key words:Pregnancy, rat, orthodontic tooth movement, osteoclast.

The effect of oral contraceptives on orthodontic tooth movement in rat

INTRODUCTION

The purpose of this study was to investigate the effect of ethinyl estradiol/norgestrel - used in some oral contraceptives- on orthodontic tooth movement in Wistar rats.

MATERIAL AND METHODS

Forty eight female three-month old Wistar rats with an average weight of 250 ± 25 gr were divided into two experimental and control groups. One week prior to appliance insertion and during the appliance therapy period, 100 mcg/kg/day of ethinyl estradiol and 1 mg/kg/days of norgestrel were administered to the experimental group by gavage; meanwhile the control group received an equivalent volume of Sodium Chloride 0.9 % (Saline). Maxillary central incisors were tipped distally by insertion of springs exerting 30 g force. Two, seven and fourteen days after spring insertion animals were sacrificed. The mesioincisal distance between maxillary incisors were measured. Subsequently, histological sections were prepared for histomorphometric studies.

RESULTS

14 days after force application the orthodontic tooth movement was significantly lower in the experimental group (p<0.05). The number of osteoclasts were significantly lower in the experimental group 2, 7 and 14 days after spring insertion (p<0.05).

CONCLUSION

Ethinyl estradiol/norgestrel (oral contraceptives) can significantly decrease the amount of tooth movement in the linear phase.

Long-term effects of progestins on bone quality and fractures

The effects of progestins on the quality of bone and their influence on the risk of fractures are reviewed. Data discussed are based on experimental studies in vivo that generally lasted for longer than one year. Information is given on the background of osteoporosis and on several means of inducing changes in bone quality. In young women who start using oral contraceptives based on progestins alone shortly after pubertal development, a significant decrease in bone quality has been documented. World Health Organization experts have concluded that this is not a real argument for restrictions on the use of these contraceptives. In postmenopausal women, no evidence has been found for a bone-protective or an estrogen-antagonistic effect of progestins. A wide range of estrogens have been used that have shown positive effects on bone, which are not antagonized by progestins. The therapeutic use of high-dose megestrol acetate may result in marked negative effects on bone, leading to severe osteoporosis, possibly due to the inherent glucocorticoid activity of this progestin. Other pharmacotherapeutic agents that can be used in postmenopausal therapy, and that clearly have beneficial effects on bone, are discussed.

Gene polymorphisms involved in the regulation of bone quality

Osteoporotic fractures in subjects at advanced age constitute a tremendous and growing problem. Established lifestyle risk factors can explain only a modest proportion of the liability to osteoporotic fractures. Bone mineral density (BMD) is considered the best established risk factor for osteoporotic fractures. The importance of genetic factors in the quality of bone is substantial, but no consensus exists yet on the genes that are involved. However, concomitant diseases, balance disorders and lifestyle habits are more important for fractures in elderly subjects. The abundance of common sequence variations, so-called polymorphisms, in the human genome and their high frequency in the population have made them targets to explain variation in the risk. Some genes have been identified that appear to be involved in the regulation of bone mass and in the pathogenesis of osteoporosis. Among these are those coding for the two estrogen receptors (ERalpha and ERbeta), the androgen receptor (AR) and the vitamin D receptor (VDR). In addition, enzymes involved in the biogenesis of estrone and estradiol have attracted attention as well as polymorphisms in the regulatory region of the type I collagen gene, COLIA1, affecting the binding site for the transcription factor Specificity protein 1 (Sp1). Although evidence suggests that the quality of bone is determined to a large extent by genetic factors, research so far has not been able to unequivocally identify genes involved in this matter. Over the last years a large number of studies have pointed to the variability in many genes and their relation with BMD, bone-related symptoms or specific therapies. The findings emphasize the complexity of the genetics of bone mass and bone loss.

Pharmacology of estrogens and progestogens: influence of different routes of administration

This review comprises the pharmacokinetics and pharmacodynamics of natural and synthetic estrogens and progestogens used in contraception and therapy, with special consideration of hormone replacement therapy. The paper describes the mechanisms of action, the relation between structure and hormonal activity, differences in hormonal pattern and potency, peculiarities in the properties of certain steroids, tissue-specific effects, and the metabolism of the available estrogens and progestogens. The influence of the route of administration on pharmacokinetics, hormonal activity and metabolism is presented, and the effects of oral and transdermal treatment with estrogens on tissues, clinical and serum parameters are compared. The effects of oral, transdermal (patch and gel), intranasal, sublingual, buccal, vaginal, subcutaneous and intramuscular administration of estrogens, as well as of oral, vaginal, transdermal, intranasal, buccal, intramuscular and intrauterine application of progestogens are discussed. The various types of progestogens, their receptor interaction, hormonal pattern and the hormonal activity of certain metabolites are described in detail. The structural formulae, serum concentrations, binding affinities to steroid receptors and serum binding globulins, and the relative potencies of the available estrogens and progestins are presented. Differences in the tissue-specific effects of the various compounds and regimens and their potential implications with the risks and benefits of hormone replacement therapy are discussed.