Aromatase in bone cell: association with osteoporosis in postmenopausal women

Metabolic associated fatty liver disease and bone mineral density: a cross-sectional study of the National Health and Nutrition Examination Survey 2017-2018

This research is a cross-sectional study based on the participants aged 50 years and older from National Health and Nutrition Examination Survey (NHANES) database. The metabolic associated fatty liver disease (MAFLD) population has higher BMD and a lower risk of osteoporosis than those without MAFLD.

INTRODUCTION

MAFLD is a new definition presented by panel of experts based on non-alcoholic fatty liver disease in 2020. However, the link between MAFLD and bone mineral density (BMD) is uncertain. Thus, the present study aimed to investigate the relationship between MAFLD and BMD.

METHODS

This cross-sectional study included subjects aged ≥ 50 years from the National Health and Nutrition Examination Survey 2017-2018. Multivariate linear regression models were performed to investigate the association between MAFLD and BMD. Moreover, the relationship between MAFLD and osteoporosis was assessed using multiple logistic regression models.

RESULTS

Finally, 817 participants (non-MAFLD, n = 436; MAFLD, n = 381) were included in the final analysis. The results demonstrated that participants with MAFLD showed higher femoral BMDs than those without MAFLD, especially among males aged ≥ 50 years and females aged ≥ 65 years. Moreover, the results showed that obese men (BMI ≥ 30 kg/m²) with MAFLD had higher femoral BMDs than the control group according to subgroup analyses stratified by BMI, but this trend was not present in women. In addition, multiple logistic regression models showed that participants with MAFLD had no increased risks of osteoporosis.

CONCLUSION

The present study found that the MAFLD population has higher BMD and a lower risk of osteoporosis than those without MAFLD. Because the present study was a cross-sectional study, we could not identify the cause-effect relation between MAFLD and BMD. Therefore, additional research needs to be performed to explore the influences of MAFLD on bone metabolism in the future.

Protective Role of DHEAS in Age-related Changes in Bone Mass and Fracture Risk

PURPOSE

Dehydroepiandrosterone sulfate (DHEAS) from the adrenal cortex substantially decreases with age, which may accelerate osteoporosis. However, the association of DHEAS with bone mineral density (BMD) and fracture is inconclusive. We conducted a Mendelian randomization (MR) analysis to investigate the role of DHEAS in age-related changes in BMD and fracture risk.

METHODS

Single nucleotide polymorphisms (SNPs) associated with serum DHEAS concentrations were used as instrumental variables (4 SNPs for main analysis; 4 SNPs for men and 5 SNPs for women in sex-related analysis). Summary statistics were obtained from relevant genome-wide association studies.

RESULTS

A log-transformed unit (µmol/L) increase in serum DHEAS concentrations was associated with an SD increase in estimated BMD at the heel (estimate, 0.120; 95% CI, 0.081-0.158; P = 9 × 10-10), and decreased fracture (odds ratio, 0.989; 95% CI, 0.981-0.996; P = 0.005), consistent with dual-energy X-ray absorptiometry-derived BMD at the femoral neck and lumbar spine. Their associations remained even after adjusting for height, body mass index, testosterone, estradiol, sex hormone-binding globulin, and insulin-like growth factor 1. The association of DHEAS with fracture remained after adjusting for falls, grip strength, and physical activity but was attenuated after adjusting for BMD. The MR-Bayesian model averaging analysis showed BMD was the top mediating factor for association of DHEAS with fracture. The association between DHEAS and BMD was observed in men but not in women.

CONCLUSION

DHEAS was associated with increased BMD and decreased fracture. DHEAS may play a protective role in decreasing fracture risk, mainly by increasing bone mass.

Estrogen deficiency - a central paradigm in age-related impaired healing?

Wound healing is a dynamic biological process achieved through four sequential, overlapping phases; hemostasis, inflammation, tissue proliferation and remodeling. For effective wound healing, all four phases must occur in the appropriate order and time frame. It is well accepted that the wound healing process becomes disrupted in the elderly, increasing the propensity of non-healing wound states that can lead to substantial patient morbidity and an enormous financial burden on healthcare systems. Estrogen deprivation in the elderly has been identified as the key driver of age-related delayed wound healing in both genders, with topical and systemic estrogen replacement reversing the detrimental effects of aging on wound repair. Evidence suggests estrogen deprivation may contribute to the development of chronic wound healing states in the elderly but research in this area is somewhat limited, warranting further investigations. Moreover, although the beneficial effects of estrogen on cutaneous healing have been widely explored, the development of estrogen-based treatments to enhance wound repair in the elderly have yet to be widely exploited. This review explores the critical role of estrogen in reversing age-related impaired healing and evaluates the prospect of developing more focused novel therapeutic strategies that enhance wound repair in the elderly via activation of specific estrogen signaling pathways in regenerating tissues, whilst leaving non-target tissues largely unaffected.

Impact of Dehydroepiandrosterone (DHEA) on Bone Mineral Density and Bone Mineral Content in a Rat Model of Male Hypogonadism

Objectives: The present study examined the effect DHEA (dehydroepiandrosterone) on bone mineral content (BMC) and bone mineral density (BMD) and biomarkers of bone remodeling in orchidectomized male rats. Material and Methods: A total of 32 male rats were divided equally into four groups (n = 8): (i) control group (C), (ii) control treated with DHEA (Control + DHEA), (iii) orchidectomized (ORCH) group that underwent bilateral orchidectomy and (iv) orchidectomized (ORCH) rats treated with DHEA (ORCH+DHEA). DHEA treatment started 4 weeks after orchidectomy and continued for 12 weeks. After 12 weeks the bone mineral density (BMD) and bone mineral content (BMC) were assayed in the tibia and femur of the right hind limb of each rat. We also measured the serum levels of the bone turnover markers deoxypyridinoline (Dpd), N-telopeptide of type I collagen (NTx), alkaline phosphatase (ALP), tartrate-resistant acid phosphatase 5b (TRAP-5b) and osteocalcin (OC) as well as receptor activator of nuclear factor kappa B (RANK) and osteoprotegerin (OPG). Results: Orchidectomy in rats caused significant reduction in BMD, BMC, serum levels of testosterone, PTH (parathyroid hormone), OPG, OC and ALP with significant rise in serum levels of TRAP-5B, RANK, Dpd and NTx1 (p < 0.05). On the other hand, DHEA therapy for 12 weeks caused significant improvement in all studied parameters except NTx1 (p < 0.05). Conclusions: DHEA corrected hypogonadism-induced osteoporosis in male rats probably via inhibiting osteoclastogenesis, stimulating the activity of osteoblasts and stimulating the secretion of PTH and testosterone.

Bone mineral density in women with deep infiltrating endometriosis who have undergone early bilateral oophorectomy

OBJECTIVE

To study bone mineral density (BMD) in women with and without pelvic deep infiltrating endometriosis (DIE) who underwent early bilateral oophorectomy (BO).

METHODS

A case-control study was performed in 83 women who underwent early BO before the age of 45 years, 31 for DIE and 52 for another clinical condition. All the women answered a standardized computer-assisted questionnaire to record their clinical and historical data and were medically examined. Lumbar spine and femoral neck BMDs were measured by dual-energy X-ray absorptiometry after early BO. Simultaneously, serum calcium, intact parathyroid, 25-hydroxyvitamin D, and cross-linked C-telopeptide were also measured. Unadjusted and adjusted odds ratios (with 95% confidence intervals [CI]) for endometriosis were calculated using logistic regression.

RESULTS

The mean lumbar spine and femoral neck BMDs were significantly higher in women who underwent early BO for DIE than in those who underwent early BO for another clinical condition. After adjusting for age at BMD measurement, years since menopause, age at menarche and body mass index, odds ratio for endometriosis associated with a 1-SD increase in lumbar spine and femoral neck BMD was 2.59 (95% CI: 1.45-4.62) and 2.16 (95% CI: 1.23-3.81), respectively.

CONCLUSION

Higher lumbar spine and femoral neck BMDs are associated with an increase in the likelihood of pelvic DIE in women who underwent early BO. This might be expected to the extent that endometriosis is itself associated with enhanced estrogen status, although further studies are needed to confirm such a hypothesis. These findings suggest that BMD measurement could contribute to the hormonal management of surgical menopause in women with DIE.

Unveiling the Pharmacological Mechanisms of Eleutheroside E Against Postmenopausal Osteoporosis Through UPLC-Q/TOF-MS-Based Metabolomics

Postmenopausal osteoporosis (PMOP) is a common metabolic bone disease in postmenopausal women in the Worldwide, and seriously affects the quality of life of middle-aged and elderly women. Therefore, there is an urgent need to discover a highly effective drug for PMOP treatment. In this study, ultra-high performance liquid tandem quadrupole time-of-flight mass spectrometry (UPLC-Q/TOF-MS) was used to analyze the urine metabolic profiling and potential biomarkers, the relevant metabolic network of PMOP rats, and further to evaluate the intervention effect of Eleutheroside E (EE) against PMOP. Using multivariate statistical analysis combined with UPLC-Q/TOF-MS, a total of 27 biomarkers were identified, which related with 16 metabolic pathways, mainly involving steroidogenesis, beta oxidation of very long chain fatty acids, glutathione metabolism, carnitine synthesis, estrone metabolism, oxidation of branched chain fatty acids, etc. After treatment of EE, these biomarkers were markedly regulated, mainly involving steroid hormone biosynthesis, arachidonic acid metabolism, primary bile acid biosynthesis, indicating that EE had the therapeutic effect on PMOP. This study identified the potential urine metabolic markers and related metabolic pathways of the PMOP, explained the metabolic effect and pharmacological mechanisms of EE against PMOP, and provided a basis for the pharmacological study of EE.

Contributions of Dickkopf-1 to Obesity-Induced Bone Loss and Marrow Adiposity

Low bone strength in overweight individuals is a significant medical problem. One important determinant of mesenchymal stem cell fate into osteoblasts or adipocytes is the Wnt signaling pathway. We recently showed that Dickkopf‐1 (DKK1), a potent Wnt inhibitor, is upregulated in obese mice. In this study, we investigated the role of DKK1 in the pathogenesis of obesity‐induced bone loss using global and tissue‐specific KO mice. Obesity was induced in 8‐week‐old male mice with an inducible global (Rosa26‐CreERT2) or osteoprogenitor‐ (Osx–Cre‐) specific deletion of Dkk1 with a high‐fat diet (HFD) containing 60% fat. After 12 weeks, body weight, bone volume, bone fat mass, and bone turnover were assessed. Dkk1^fl/fl;Rosa26‐CreERT2 mice experienced a similar increase in body weight and white fat pads as control mice. A HFD significantly reduced trabecular bone mass and the bone formation rate in Cre‐ mice and Dkk1^fl/fl;Rosa26‐CreERT2 mice. Interestingly, Dkk1^fl/fl;Rosa26‐CreERT2 mice were protected from HFD‐induced cortical bone loss. Furthermore, a HFD was associated with increased bone marrow fat in the femur, which was less pronounced in Dkk1^fl/fl;Rosa26‐CreERT2 mice. Mice with an osteoprogenitor‐specific Dkk1 deletion showed similar results as the global knockout, showing a protection against HFD‐induced cortical bone loss and an accumulation of bone marrow fat, but a similar decrease in trabecular bone volume. In summary, DKK1 appears to contribute distinctly to cortical, but not trabecular bone loss in obesity. © 2020 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

Recent Advances in Anti-Aging Medicine

A rapidly aging population in Korea has led to increased attention in the field of anti-aging medicine. The purpose of anti-aging medicine is to slow, stop, or reverse the aging process and its associated effects, such as disability and frailty. Anti-aging medicine is emerging as a growing industry, but many supplements or protocols are available that do not have scientific evidence to support their claims. In this review, the mechanisms of action and the clinical implications of anti-aging interventions were examined and explained. Calorie restriction mimetics define compounds that imitate the outcome of calorie restriction, including an activator of AMP protein kinase (metformin), inhibitor of growth hormone/insulin-like growth factor-1 axis (pegvisomant), inhibitor of mammalian target of rapamycin (rapamycin), and activator of the sirtuin pathway (resveratrol). Hormonal replacement has also been widely used in the elderly population to improve their quality of life. Manipulating healthy gut microbiota through prebiotic/probiotics or fecal microbiota transplantation has significant potential in anti-aging medicine. Vitamin D is expected to be a primary anti-aging medicine in the near future due to its numerous positive effects in the elderly population.

A High Serum Cortisol/DHEA-S Ratio Is a Risk Factor for Sarcopenia in Elderly Diabetic Patients

Context

Elderly patients with type 2 diabetes mellitus (T2DM) have a high prevalence of frailty and/or sarcopenia. Sarcopenia is thought to be related to discordant secretions of the adrenal hormones cortisol and dehydroepiandrosterone (DHEA), as well as the sulfate ester of DHEA (DHEA-S). The current study sought to evaluate the risk factors for sarcopenia in elderly patients with T2DM.

Design and Patients

We enrolled 108 consecutive elderly patients aged ≥65 years with T2DM (mean age, 76.2 ± 7.3 years; 43.5% males). Sarcopenia was assessed and diagnosed based on the Asian version of the diagnostic criteria regarding muscular strength, physical function, and muscle mass. We assessed various physical parameters, blood tests, and atherosclerosis markers and statistically determined the risk factors for sarcopenia.

Results

Multiple regression analysis showed that the independent risk factors for sarcopenia were a serum cortisol/DHEA-S ratio ≥0.2, diastolic blood pressure <70 mm Hg, Hb concentration <13 g/dL, and an ankle brachial index <1.0. The strongest risk factor for sarcopenia was a serum cortisol/DHEA-S ratio ≥0.2. An increase in the serum cortisol/DHEA-S ratio reflected higher cortisol values and lower DHEA-S values in patients with sarcopenia compared with those in nonsarcopenic patients. The concentrations of cortisol and DHEA-S, as well as the cortisol/DHEA-S ratio, changed in accordance with the severity of sarcopenia.

Conclusions

A relative increase in cortisol may reflect the presence of stress and stimulate muscle catabolism, whereas a relative decrease in DHEA-S may cause a decrease in the anabolic action of DHEA on muscle; the combination of these factors may lead to sarcopenia.

A comprehensive overview on osteoporosis and its risk factors

Osteoporosis is a bone disorder with remarkable changes in bone biologic material and consequent bone structural distraction, affecting millions of people around the world from different ethnic groups. Bone fragility is the worse outcome of the disease, which needs long term therapy and medical management, especially in the elderly. Many involved genes including environmental factors have been introduced as the disease risk factors so far, of which genes should be considered as effective early diagnosis biomarkers, especially for the individuals from high-risk families. In this review, a number of important criteria involved in osteoporosis are addressed and discussed.

Effects of androgen and progestin on the proliferation and differentiation of osteoblasts

Osteoporosis is liable to affect patients with gonadal hormone deficiency, and a supplement of androgens may be used to increase bone density of patients with osteoporosis. Since the androgens currently used may cause severe side effects, it is useful to investigate the effect of other androgens and progestin on bone improvement. The aim of the current study was to investigate the effects of pregnenolone (Preg), androstenedione (AD), etiocholanolone (Etio), androsterone (An), nandrolone (NA) and testosterone (T) on the proliferation and differentiation of osteoblasts for potential clinical applications. Human osteoblasts were cultured and treated with androgens and progestin, including Preg, AD, Etio, An, NA, and T, at concentrations of 0, 10^-10, 10^-8, 10^-6 and 10^-5 mol/l. The levels of cell proliferation, alkaline phosphatase (ALP) activity and osteocalcin content were measured and assessed. Preg, AD, Etio, An, and T at concentrations of 10^-10 and/or 10^-8 mol/l significantly improved osteoblast proliferation. NA at concentrations of 10^-10, 10^-8, 10^-6 and 10^-5 mol/l also significantly improved osteoblast proliferation. Preg, AD, Etio, An, NA, and T significantly increased ALP activity and osteocalcin content. The present study demonstrated, for the first time, that Preg, AD, Etio, An, and NA could improve the proliferation and differentiation of osteoblasts in vitro.

Role of dihydrotestosterone in whole-body energy utilization during acute running exercise in mice

PURPOSE

Dihydrotestosterone (DHT) plays an important role in various processes that utilize energy, including fat and carbohydrate oxidation. The purpose of this study was to determine the effect of inhibiting DHT formation during mid-intensity running exercise on energy expenditure and fat and carbohydrate oxidation in the whole body using a calorimetric chamber.

METHODS

Twelve ICR adult male mice, 9 weeks of age, were randomized into two groups: CON (n = 6, no treatment with exercise) and CONIN (n = 6, DHT inhibitor treatment with exercise, SRD5A1A2 is an enzyme involved in the metabolism of free testosterone into DHT). Inhibitor was administered to the CONIN group intraperitoneally, while the CON group was treated with vehicle (corn oil 2 mg/kg). After 3 days of administration of the inhibitor or vehicle, exercise was performed at 60-70% VO2max for 30 min on a treadmill in a calorimetric chamber. The O2 uptake, CO2 production, carbohydrate and fat oxidation, and respiratory exchange ratio (RER) during 30-min exercise were measured using a calorimeter.

RESULTS

During a single bout of exercise, the CONIN group showed a significantly higher area under the curve (AUC) of O2 uptake and CO2 production from 20 min into exercise than the CON group (p < 0.001). The CONIN group showed a significantly higher AUC for carbohydrate oxidation from 20 min into exercise than the CON group (p < 0.001), whereas no difference was found in fat oxidation between groups (p = 0.067). The CONIN group had a significantly higher AUC of RER from 20 min into exercise than the CON group (p < 0.001).

CONCLUSION

We observed increased energy consumption at the later phase of 30-min moderate-intensity treadmill running when DHT production was inhibited. Furthermore, when DHT production during exercise was inhibited, whole-body fat utilization was inhibited and carbohydrate oxidation was substantially increased at the later phase of exercise compared to in the control group. Therefore, changes in DHT concentration in the body during exercise may be involved in whole-body fat utilization, suggesting that DHT may be an important factor affecting endurance exercise capacity.

Dehydroepiandrosterone and Bone

In humans, dehydroepiandrosterone (DHEA), secreted mainly from the adrenal cortex, and its sulfate ester, DHEAS, are the most abundant circulating steroids. DHEA/DHEAS possess pleiotropic effects in human aging, bone, metabolic diseases, neurologic function/neurodegenerative diseases, cancer, immune system and disorders, cardiovascular diseases, diabetes, muscle function, sexual dysfunction, and other health conditions. The age-related reduced levels of DHEA and DHEAS are associated with bone mineral density measures of osteopenia and osteoporosis. Clinical, epidemiological, and experimental studies indicate that DHEA replacement therapy may be beneficial for bone health through its inhibition of skeletal catabolic IL-6 and stimulation of osteoanabolic IGF-I-mediated mechanisms. Studies with primary cultures of human bone marrow-derived mesenchymal stem cells (hMSCs) were used to show that DHEA stimulates osteoblastogenesis. The in vitro stimulation of both osteoblastogenesis and IGF-I gene expression by DHEA in hMSCs requires IGF-I receptor, PI3K, p38 MAPK, or p42/44 MAPK signaling pathways. The in vitro inhibition of IL-6 secretion in hMSCs by DHEA was more consistent and extensive than by estradiol or dihydrotestosterone. In summary, evidence from us and others indicates that DHEA may be useful for treating bone diseases through its inhibition of skeletal catabolic IL-6 and stimulation of anabolic IGF-I-mediated mechanisms.

Local estrogen axis in the human bone microenvironment regulates estrogen receptor-positive breast cancer cells

BACKGROUND

Approximately 70% of all breast cancers express the estrogen receptor, and are regulated by estrogen. While the ovaries are the primary source of estrogen in premenopausal women, most breast cancer is diagnosed following menopause, when systemic levels of this hormone decline. Estrogen production from androgen precursors is catalyzed by the aromatase enzyme. Although aromatase expression and local estrogen production in breast adipose tissue have been implicated in the development of primary breast cancer, the source of estrogen involved in the regulation of estrogen receptor-positive (ER+) metastatic breast cancer progression is less clear.

METHODS

Bone is the most common distant site of breast cancer metastasis, particularly for ER+ breast cancers. We employed a co-culture model using trabecular  bone tissues obtained from total hip replacement (THR) surgery specimens to study ER+ and estrogen receptor-negative (ER-) breast cancer cells within the human bone microenvironment. Luciferase-expressing ER+ (MCF-7, T-47D, ZR-75) and ER- (SK-BR-3, MDA-MB-231, MCF-10A) breast cancer cells were cultured directly on bone tissue fragments or in bone tissue-conditioned media, and monitored over time with bioluminescence imaging (BLI). Bone tissue-conditioned media were generated in the presence vs. absence of aromatase inhibitors, and testosterone. Bone tissue fragments were analyzed for aromatase expression by immunohistochemistry.

RESULTS

ER+ breast cancer cells were preferentially sustained in co-cultures with bone tissues and bone tissue-conditioned media relative to ER- cells. Bone fragments analyzed by immunohistochemistry revealed expression of the aromatase enzyme. Bone tissue-conditioned media generated in the presence of testosterone had increased estrogen levels and heightened capacity to stimulate ER+ breast cancer cell proliferation. Pretreatment of cultured bone tissues with aromatase inhibitors, which inhibited estrogen production, reduced the capacity of conditioned media to stimulate ER+ cell proliferation.

CONCLUSIONS

These results suggest that a local estrogen signaling axis regulates ER+ breast cancer cell viability and proliferation within the bone metastatic niche, and that aromatase inhibitors modulate this axis. Although endocrine therapies are highly effective in the treatment of ER+ breast cancer, resistance to these treatments reduces their efficacy. Characterization of estrogen signaling networks within the bone microenvironment will identify new strategies for combating metastatic progression and endocrine resistance.

The effect of estrogen on tendon and ligament metabolism and function

Tendons and ligaments are crucial structures inside the musculoskeletal system. Still many issues in the treatment of tendon diseases and injuries have yet not been resolved sufficiently. In particular, the role of estrogen-like compound (ELC) in tendon biology has received until now little attention in modern research, despite ELC being a well-studied and important factor in the physiology of other parts of the musculoskeletal system. In this review we attempt to summarize the available information on this topic and to determine many open questions in this field.

Role of RUNX2 in Breast Carcinogenesis

RUNX2 is a transcription factor playing the major role in osteogenesis, but it can be involved in DNA damage response, which is crucial for cancer transformation. RUNX2 can interact with cell cycle regulators: cyclin-dependent kinases, pRB and p21Cip1 proteins, as well as the master regulator of the cell cycle, the p53 tumor suppressor. RUNX2 is involved in many signaling pathways, including those important for estrogen signaling, which, in turn, are significant for breast carcinogenesis. RUNX2 can promote breast cancer development through Wnt and Tgfβ signaling pathways, especially in estrogen receptor (ER)-negative cases. ERα interacts directly with RUNX2 and regulates its activity. Moreover, the ERα gene has a RUNX2 binding site within its promoter. RUNX2 stimulates the expression of aromatase, an estrogen producing enzyme, increasing the level of estrogens, which in turn stimulate cell proliferation and replication errors, which can be turned into carcinogenic mutations. Exploring the role of RUNX2 in the pathogenesis of breast cancer can lead to revealing new therapeutic targets.

Bu-Shen-Ning-Xin Decoction ameliorated the osteoporotic phenotype of ovariectomized mice without affecting the serum estrogen concentration or uterus

INTRODUCTION

Bu-Shen-Ning-Xin Decoction (BSNXD), a traditional Chinese medicinal composition, has been used as a remedy for postmenopausal osteoporosis, but its effects on bone metabolism and the uterus have not been reported.

PURPOSE

We aimed to determine the respective effects of BSNXD on the bones and the uterus of ovariectomized (OVX) mice to evaluate the efficacy and safety of this herbal formula.

MATERIALS AND METHODS

Postmenopausal osteoporosis animal models that were generated by ovariectomy were treated with BSNXD. Dual-energy X-ray absorptiometry was performed to analyze the bone mineral density, and histomorphometric analysis was performed to measure the parameters related to bone metabolism. Calcein labeling was performed to detect bone formation. The uteruses from the mice were weighed, and the histomorphometry was analyzed. Drug-derived serum was prepared to assess the 17-β-estradiol concentration via enzyme immunoassay.

RESULTS

BSNXD administration ameliorated the osteoporotic phenotype of OVX mice, as evidenced by an increase in the bone mineral density and bone volume; these effects could not be abolished by the administration of the aromatase inhibitor letrozole. Moreover, BSNXD had no effect on the serum estrogen concentration or uterus.

CONCLUSION

These results suggest that BSNXD has ameliorating effects on bone loss due to estrogen deprivation without affecting the peripheral blood estrogen concentration or the uterus in OVX mice.

The association between serum dehydroepiandrosterone Sulphate (DHEA-S) level and bone mineral density in Korean men

CONTEXT

Many lines of evidence indicate that dehydroepiandrosterone (DHEA) plays a distinct role in bone metabolism and that its sulphated form (DHEA-S), which is easily measured in blood, may be a potential biomarker of osteoporosis-related phenotypes. However, most previous epidemiologic studies focused on postmenopausal women and reported conflicting results.

OBJECTIVE

We aimed to investigate the association between the serum DHEA-S level and bone mass in men.

DESIGN AND METHODS

This large cross-sectional study included 1089 healthy Korean men who participated in a routine health screening examination. Bone mineral density (BMD) at the lumbar spine, total femur, femur neck, and trochanter and serum DHEA-S level were obtained in all subjects.

RESULTS

After adjustment for age, body mass index, lifestyle factors and serum levels of calcium, phosphorus, testosterone, 25-OH-vitamin D3 and cortisol, higher serum DHEA-S concentrations were associated with higher BMD values at all skeletal sites. Consistently, compared to the subjects in the highest DHEA-S quartile (Q4), those in the lowest DHEA-S quartile (Q1) showed significantly lower BMD values. Multiple logistic regression analyses revealed that the odds ratios for the risk of lower BMD (T-score <-1) increased in a dose-dependent manner across decreasing DHEA-S quartiles and the odds for the risk of lower BMD were 2·59-fold higher in Q1 than in Q4.

CONCLUSION

These findings support previous evidences that DHEA-S has favourable effects on bone mass in men and suggest that a low serum DHEA-S level may be a potential risk factor for male osteoporosis.

Aromatase enzyme expression in acromegaly and its possible relationship with disease prognosis

The purpose of this study was to evaluate aromatase enzyme expression in growth hormone (GH) secreting adenomas and comparison with prolactinomas, nonfunctional adenomas, and normal pituitary tissues. Also the impact of its expression on clinical and prognostic features was evaluated. 38 acromegaly, 26 prolactinoma, and 31 nonfunctional pituitary adenoma and 11 normal pituitary gland samples from autopsies were included. Aromatase and estrogen receptor-alpha (ERα) were evaluated by Immunohistochemical method; demographic, pre- and postoperative features of the patients were noted. Aromatase was expressed in varying degrees in all cases in study including controls. Aromatase expression in patients with acromegaly was significantly higher than patients with prolactinoma, nonfunctional adenoma, and controls (p = 0.04, p = 0.01 and p < 0.001, respectively). Taken together two functional adenoma groups, prolactinoma and acromegaly, aromatase expression was negatively correlated with ER-alpha (p = 0.02, r = -0.34). Also, Ki-67 immunohistochemical results were negatively correlated with aromatase expression (p = 0.03, r = -0.27) while positively correlated with ER expression (p < 0.01). Consistent with the growing evidence about testosterone effect on pituitary functions, aromatase expression was found to be higher in GH-secreting pituitary adenoma. Aromatase was expressed in all pituitary tissues including autopsy samples; however, it was highest in patients with acromegaly. In patients with acromegaly and prolactinoma, aromatase expression was negatively correlated with Ki-67 score, and also it was higher in patients with complete postoperative remission than without remission. Therefore, aromatase expression may be a good prognostic marker predominantly in acromegaly.

Transcriptional control of local estrogen formation by aromatase in the breast

Aromatase is the critical enzyme that converts androgens to estrogens. It is frequently highly expressed in the tumour bearing breast of women diagnosed with estrogen receptor positive tumours, resulting in dramatically increased local estrogen production to drive tumour progression. Expression of aromatase is regulated primarily at the transcriptional level of its encoding gene CYP19A1, located on chromosome 15 of the human genome. A characteristic feature of CYP19A1 expression is its use of alternative promoters to regulate transcription in a tissue-specific manner. In breast cancer, the increase in aromatase expression is mediated via higher expression of the distal adipose-specific promoter I.4 and a switch to the preferential use of proximal promoters I.3 and II. This results in a net increase of CYP19A1 transcripts in tumour-bearing breast up to 3-4-fold higher than normal breast. Current aromatase inhibitors - whilst efficacious - exhibit significant side effects that reduce patient compliance. Understanding the transcription factors and signalling pathways that control aromatase expression will lead to opportunities to develop breast-specific inhibitors with an improved side-effects profile. This article is part of a Special Issue entitled 'Essential role of DHEA'.

Off-label use of hormones as an antiaging strategy: a review

Given demographic evolution of the population in modern societies, one of the most important health care needs is successful aging with less frailty and dependency. During the last 20 years, a multitude of anti-aging practices have appeared worldwide, aiming at retarding or even stopping and reversing the effects of aging on the human body. One of the cornerstones of anti-aging is hormone replacement. At present, women live one third of their lives in a state of sex-hormone deficiency. Men are also subject to age-related testosterone decline, but andropause remains frequently under-diagnosed and under-treated. Due to the decline of hormone production from gonads in both sexes, the importance of dehydroepiandrosterone (DHEA) in steroid hormone production increases with age. However, DHEA levels also decrease with age. Also, growth hormone age-associated decrease may be so important that insulin growth factor-1 levels found in elderly individuals are sometimes as low as those encountered in adult patients with established deficiency. Skin aging as well as decreases in lean body mass, bone mineral density, sexual desire and erectile function, intellectual activity and mood have all been related to this decrease of hormone production with age. Great disparities exist between recommendations from scientific societies and actual use of hormone supplements in aging and elderly patients. In this article, we review actual data on the effects of age related hormone decline on the aging process and age-related diseases such as sarcopenia and falls, osteoporosis, cognitive decline, mood disorders, cardiovascular health and sexual activity. We also provide information on the efficiency and safety of hormone replacement protocols in aging patients. Finally, we argue on future perspectives of such protocols as part of everyday practice.

A review of age-related dehydroepiandrosterone decline and its association with well-known geriatric syndromes: is treatment beneficial?

Dehydroepiandrosterone (DHEA) and its sulfate ester are the most abundant steroids in humans. DHEA levels fall with age in men and women, reaching values sometimes as low as 10%-20% of those encountered in young individuals. This age-related decrease suggests an "adrenopause" phenomenon. Studies point toward several potential roles of DHEA, mainly through its hormonal end products, making this decline clinically relevant. Unfortunately, even if positive effects of DHEA on muscle, bone, cardiovascular disease, and sexual function seem rather robust, extremely few studies are large enough and/or long enough for conclusions regarding its effects on aging. Moreover, because it has been publically presented as a "fountain of youth" equivalent, over-the-counter preparations lacking pharmacokinetic and pharmacodynamic data are widely used worldwide. Conceptually, supplementing a pre-hormone is extremely interesting, because it would permit the human organism to adequately use it throughout long periods, increasing or decreasing end products according to his needs. Nevertheless, data on the safety profile of long-term DHEA supplementation are still lacking. In this article, we examine the potential relation between low DHEA levels and well-known age-related diseases, such as sarcopenia, osteoporosis, dementia, sexual disorders, and cardiovascular disease. We also review risks and benefits of existing protocols of DHEA supplementation.

(1)H NMR metabolic profiling analysis offers evaluation of Nilestriol treatment in ovariectomised rats

Nilestriol (NIL) has been applied to treat menopausal dysfunctions, yet its mechanism has remained unknown. To understand the relationship between the changes in homeostatic metabolites and ovarian oestrogen deficiency syndromes after NIL treatment, proton Nuclear Magnetic Resonance ((1)H NMR)-based metabonomic technologies were used to analyse a rat model of oestrogen deficiency. An orthogonal partial least-squares regression (OPLS) differentiation model was used on 12-week metabolic analyses of ovariectomised (OVX) rats treated or mock treated with NIL. Furthermore, data analysis using Chenomx software quantified results to identify the most significantly altered metabolite concentrations, allowing for metabolic explanations of the effects of NIL therapies. In this study, PLS results revealed that there are considerably distinct differences between treatment groups. Additionally, a total of 45 metabolites shown to have a high variation between groups were selected for target quantification. Using a one-way LSD ANOVA analysis, 32 metabolite concentrations were significantly altered in the OVX group. A total of 21 metabolites were altered significantly in the NIL-treatment group but later returned to normal. According to the OPLS VIP calculation, the metabolites most affected by NIL treatment were mostly involved in insulin resistance. In addition, abnormal concentration changes in lactate in the NIL-treatment group and 3-indoxylsulfate in the OVX group were observed. To our knowledge, this study is the first to address the molecular mechanism of NIL from a metabonomic perspective, and, more specifically, to establish a catalogue of endo-molecular changes effected by NIL in the regulation of oestrogen deficiency disorder.

Effects of obesity on bone mass and quality in ovariectomized female Zucker rats

Obesity and osteoporosis are two chronic conditions that have been increasing in prevalence. Despite prior data supporting the positive relationship between body weight and bone mineral density (BMD), recent findings show excess body weight to be detrimental to bone mass, strength, and quality. To evaluate whether obesity would further exacerbate the effects of ovariectomy on bone, we examined the tibiae and fourth lumbar (L4) vertebrae from leptin receptor-deficient female (Lepr(fa/fa)) Zucker rats and their heterozygous lean controls (Lepr(fa/+)) that were either sham-operated or ovariectomized (Ovx). BMD of L4 vertebra was measured using dual-energy X-ray absorptiometry, and microcomputed tomography was used to assess the microstructural properties of the tibiae. Ovariectomy significantly (P < 0.001) decreased the BMD of L4 vertebrae in lean and obese Zucker rats. Lower trabecular number and greater trabecular separation (P < 0.001) were also observed in the tibiae of lean- and obese-Ovx rats when compared to sham rats. However, only the obese-Ovx rats had lower trabecular thickness (Tb.Th) (P < 0.005) than the other groups. These findings demonstrated that ovarian hormone deficiency adversely affected bone mass and quality in lean and obese rats while obesity only affected Tb.Th in Ovx-female Zucker rats.

Coadministration of anastrozole sustains therapeutic testosterone levels in hypogonadal men undergoing testosterone pellet insertion

INTRODUCTION

Current U.S. Food and Drug Administration-approved therapies for hypogonadism involve testosterone (T) replacement. Testosterone pellets (TP) require a minor office procedure every 3 to 4 months. The need for repeated insertions increases the likelihood of a complication. Anastrozole (AZ) is an aromatase inhibitor that has been used off-label for the treatment of male hypogonadism. AZ increases T levels by lowering serum estradiol (E2) levels and increasing gonadotropin (GTP) levels.

AIM

We hypothesized that the concomitant use of AZ with TP insertions would sustain therapeutic T levels and increase the interval between TP insertions.

METHODS

Men treated with TP for hypogonadism at an academic center were offered AZ (1 mg/day) at the time of TP reinsertion as a way of potentially decreasing the frequency of TP insertions. Total T (TT), free T (FT), sex hormone binding globulin, E2, luteinizing hormone (LH), and follicle-stimulating hormone FSH levels were obtained prior to T replacement and at 6 and 15 weeks from TP insertion. Men were re-implanted at 16 weeks if their TT levels were less than 350 ng/dL and their symptoms recurred. We retrospectively reviewed our records of men who underwent TP, TP, and AZ from 2011 to 2012. Demographics, TT, FT, LH, FSH, and E2 levels were recorded. Data were analyzed with anova and a Tukey's test.

MAIN OUTCOME MEASURE

TT level at 6, 15, or >15 weeks from TP insertion.

RESULTS

Thirty-eight men with 65 insertions were analyzed. The TP AZ group had significantly higher TT and FT levels than the TP group at >120 days (P < 0.05). The TP group had significantly higher E2 levels at all time points (P < 0.01). GTP levels remained stable in the TP AZ group. Average time to reinsertion in TP AZ was 198 days vs. 128 days in the TP group.

CONCLUSION

Men on TP AZ maintain therapeutic T levels longer than men on TP alone and have significantly less GTP suppression.

Genetic polymorphism at Val80 (rs700518) of the CYP19A1 gene is associated with aromatase inhibitor associated bone loss in women with ER + breast cancer

PURPOSE

Polymorphisms in the CYP19A1 (aromatase) gene have been reported to influence disease-free survival and the incidence of musculoskeletal complaints in patients taking aromatase inhibitors (AIs) for estrogen receptor positive (ER+) breast cancer. Bone loss and fractures are well-recognized complications from AI therapy. The objective of this study is to determine the influence of polymorphisms in the CYP19A1 gene on bone loss among patients taking aromatase inhibitors for ER+ breast cancer.

PATIENTS AND METHODS

The subjects consisted of 97 postmenopausal women with ER+ breast cancer who were initiated on third-generation AIs. Bone mineral density (BMD) was measured by dual energy X-ray absorptiometry at baseline and at 6 and 12 months. Twenty-four hour urine N-telopeptide (NTX) was measured by Elisa and serum estradiol was measured by ultrasensitive radioimmunoassay at baseline, and at 6 months. Genotyping was done by Taqman SNP allelic discrimination assay.

RESULTS

Women with the AA genotype for the rs700518 (G/A at Val(80)) developed significant bone loss at the lumbar spine and the total hip at 12 months relative to patients carrying the G allele (GA/GG); both p = 0.03. There was a borderline greater increase in urinary NTX in those with the AA genotype compared to patients with the G allele, p = 0.05; but no significant difference in changes in estradiol levels among the genotypes.

CONCLUSION

Patients with the AA genotype for the rs700518 polymorphism in the CYP19A1 gene are at risk for AI-associated bone loss and deserve close follow-up during long-term AI therapy.

The interrelationship between bone and fat: from cellular see-saw to endocrine reciprocity

The number of mature osteoblasts and marrow adipocytes in bone is influenced by the differentiation of the common mesenchymal progenitor cell towards one phenotype and away from the other. Consequently, factors which promote adipogenesis not only lead to fatty marrow but also inhibit osteoblastogenesis, resulting in decreased osteoblast numbers, diminished bone formation and, potentially, inadequate bone mass and osteoporosis. In addition to osteoblast and bone adipocyte numbers being influenced by this skewing of progenitor cell differentiation towards one phenotype, mature osteoblasts and adipocytes secrete factors which may evoke changes in the cell fate and function of each other. This review examines the endogenous factors, such as PPAR-γ2, Wnt, IGF-1, GH, FGF-2, oestrogen, the GP130 signalling cytokines, vitamin D and glucocorticoids, which regulate the selection between osteoblastogenesis and adipogenesis and the interrelationship between fat and bone. The role of adipokines on bone, such as adiponectin and leptin, as well as adipose-derived oestrogen, is reviewed and the role of bone as an energy regulating endocrine organ is discussed.

Dehydroepiandrosterone treatment effects on weight, bone density, bone metabolism and mood in women suffering from anorexia nervosa-a pilot study

We investigated the effects of the administration of dehydroepiandrosterone (DHEA) on weight, bone metabolism, bone density and clinical mood symptoms in outpatient Anorexia Nervosa (AN) patients. AN patients (n=26) were double-blindly randomized to receive DHEA (100mg) or placebo for 6 months. Outcome measures were bone mineral density (BMD) and bone mineral content (BMC) measured by dual energy X-ray absorptiometry (DXA) and metabolism indexes, steroid hormones, and mood and eating disorder symptoms measured at baseline and at the 3 and 6 months follow-up visits. Mood and eating disorder symptoms were assessed monthly by the Beck Depression Inventory, Eating Disorder Inventory and Clinical Global Improvement Scales. No treatment or treatment by time interaction was observed for any bone density measures. Deoxypiridinolyne (DPD) was positively correlated with weight (P=0.02). An increase in body mass index (BMI) in the DHEA group was significantly higher at 4 months compared to the control group (P=0.05). Improvement of mood was significantly correlated with weight only in the DHEA group. Despite a significant decrease in DPD, no improvement in bone mineral density was detected. However, patients treated with DHEA benefited from a significant increase in BMI, which was positively correlated with improvement in mood.

Effect of DHEA supplementation on serum IGF-1, osteocalcin, and bone mineral density in postmenopausal, glucocorticoid-treated women

PURPOSE

DHEA therapy increases bone formation in postmenopausal women. We have found only a few reports of dehydroepiandrosterone replacement therapy in women receiving long-term glucocorticoid medication. The purpose of this study was to establish whether DHEA replacement therapy may be useful in the treatment of steroid-induced osteoporosis in postmenopausal women.

MATERIALS AND METHODS

Nineteen women, aged 50-78 years, treated at least for three years with average daily doses of more than 7.5 mg prednisone, with T-score L2/L4<-1.5 and bisphosphonates intolerance, were enrolled to the study. For the first year of the study the patients were given calcium, vitamin D3 and thiazide diuretics. For another year the patients received orally micronized DHEA 25-50 mg daily. Before the study, after twelve months of Calcium/D3 therapy, then after six weeks and six months of DHEA therapy, serum concentrations of DHEAS, androstenedione, testosterone, estradiol, FSH, IGF-1 and osteocalcin were assessed. Bone mineral density (BMD) in lumbar spine and femoral neck was measured before the treatment, after a year on Calcium/D3 and after six and twelve months of DHEA replacement therapy.

RESULTS

In all treated women, DHEA significantly increased serum DHEAS, androstenedione and testosterone concentrations. A significant elevation of serum IGF-1 and osteocalcin concentrations was found as early as after six weeks of DHEA treatment. A significant increase of bone mineral density in the lumbar spine and femoral neck was observed after six and twelve months of DHEA treatment.

CONCLUSION

Our results suggest a beneficial role of DHEA replacement therapy in the treatment of steroid-induced osteoporosis.

Increased 2-hydroxylation of estrogen is associated with lower body fat and increased lean body mass in postmenopausal women

Menopause is associated with changes in bone, muscle and fat mass. The importance of postmenopausal estrogen metabolism in bone health has been established. However, its relationship to body composition in postmenopausal women remains undetermined. The objective of this study is to determine the association between estrogen metabolism and body composition in postmenopausal women. This is a cross sectional study of 97 postmenopausal Caucasian women, 49-80 y.o., ≥1 year from the last normal menstrual period or those who have had oophorectomy. Inactive [2-hydroxyestrone (2OHE(1))] and active [16α-hydroxyestrone (16α-OHE(1))] urinary metabolites of estrogen were measured by ELISA. The whole and regional body composition was measured by DXA. We have found that both 2OHE(1), and 2OHE(1)/16α-OHE(1) ratio were negatively correlated with % total fat, and % truncal fat but positively correlated with % total lean mass. Comparing the fat and lean parameters of body composition according to tertiles of 2OHE(1) and 2OHE(1)/16αOHE(1) ratio showed that subjects in the lowest tertiles, had the highest % total fat, and % truncal fat and the lowest % total lean mass. Multiple regression analysis also showed 2OHE(1) and calcium intake as statistically significant predictors of all body composition parameters. In conclusion, in postmenopausal women, an increase in the metabolism of estrogen towards the inactive metabolites is associated with lower body fat and higher lean mass than those with predominance of the metabolism towards the active metabolites.

Estrogen receptor dependent gene expression by osteoblasts - direct, indirect, circumspect, and speculative effects

Hormone activated estrogen receptors (ERs) have long been appreciated as potent mediators of gene expression in female reproductive tissues. These highly targeted responses likely evolved from more elemental roles in lower organisms, in agreement with their widespread effects in the cardiovascular, immunological, central nervous, and skeletal tissue systems. Still, despite intense investigation, the multiple and often perplexing roles of ERs retain significant attention. In the skeleton, this in part derives from apparently opposing effects by ER agonists on bone growth versus bone remodeling, and in younger versus older individuals. The complexity associated with ER activation can also derive from their interactions with other hormone and growth factor systems, and their direct and indirect effects on gene expression. We propose that part of this complexity results from essential interactions between ERs and other transcription factors, each with their own biochemical and molecular intricacies. Solving some of the many questions that persist may help to achieve better, or better directed, use of agents that can drive ER activation in focused and possibly tissue restricted ways.

Tissue physiology and pathology of aromatase

Aromatase is expressed in multiple tissues, indicating a crucial role for locally produced oestrogens in the differentiation, regulation and normal function of several organs and processes. This review is an overview of the role of aromatase in different tissues under normal physiological conditions and its contribution to the development of some oestrogen-related pathologies.

Blockade of transforming growth factor-beta (TGFβ) signaling inhibits osteoblastic tumorigenesis by a novel human prostate cancer cell line

BACKGROUND

The skeleton is the most common site of prostate cancer metastasis, which often results in osteoblastic lesions. The role of transforming growth factor-beta (TGFβ) signaling in prostate cancer-induced osteoblastic metastasis is not clear. We investigated the role of TGFβ signaling in prostate cancer-induced bone metastasis using a novel human prostate cancer cell line, PacMetUT1.

METHODS

We injected PacMetUT1/Luc-GFP cells in male nude mice by intracardiac and intratibia injections and then investigated the effect of TGFβ signaling abrogation on osteoblastic tumor growth and incidence in vivo by using fluorescence and bioluminescence imaging analysis and quantifying bone and tumor volume by histomorphometry analysis. Osteoclasts were counted using TRAP assay.

RESULTS

Osteoblastic bone metastasis in skull, rib, and femur was detected after 10-16 weeks of intracardiac injection of the PacMetUT1 cells. Stable knockdown of TGFβ1 with an shRNA resulted in decreased tumor incidence and bone formation when the cells were directly injected into the tibiae. Systemic administration of either a small inhibitor of TGFβ type I receptor kinase or a pan TGFβ binding protein (BG(E) RII) also decreased bone tumor growth and osteoblastic bone formation in vivo after 7 weeks of treatment.

CONCLUSIONS

Our results for the first time indicate that blockade of TGFβ signaling in the PacMetUT1 model significantly inhibits osteoblastic bone formation and tumor incidence. Thus, TGFβ signaling pathway may be a viable target for the prevention and treatment of prostate cancer-induced bone metastasis.

Aromatase activity and bone loss in men

Aromatase is a specific component of the cytochrome P450 enzyme system responsible for the transformation of androgen precursors into estrogens. This enzyme is encoded by the CYP19A1 gene located at chromosome 15q21.2, that is, expressed in ovary and testis, but also in many extraglandular sites such as the placenta, brain, adipose tissue, and bone. The activity of aromatase regulates the concentrations of estrogens with endocrine, paracrine, and autocrine effects on target issues including bone. Importantly, extraglandular aromatization of circulating androgen precursors is the major source of estrogen in men. Clinical and experimental evidences clearly indicate that aromatase activity and estrogen production are necessary for longitudinal bone growth, the attainment of peak bone mass, pubertal growth spurt, epiphyseal closure, and normal bone remodeling in young individuals. Moreover, with aging, individual differences in aromatase activity may significantly affect bone loss and fracture risk in men.

Aromatase activity and bone loss

Aromatase is a specific component of the cytochrome P450 enzyme system that is responsible for the transformation of C19 androgen precursors into C18 estrogenic compounds. This enzyme is encoded by the CYP19A1 gene located at chromosome 15q21.2, that is expressed in ovary and testis not only but also in many extraglandular sites such as the placenta, brain, adipose tissue, and bone. The regulation of the level and activity of aromatase determines the levels of estrogens that have endocrine, paracrine, and autocrine effects on target issues including bone. Importantly, extraglandular aromatization of circulating androgen precursors is the major source of estrogen not only in men (since only 15% of circulating estradiol is released directly by the testis) but also in women after the menopause. Several lines of clinical and experimental evidence now clearly indicate that aromatase activity and estrogen production are necessary for longitudinal bone growth, attainment of peak bone mass, the pubertal growth spurt, epiphyseal closure, and normal bone remodeling in young individuals. Moreover, with aging, individual differences in aromatase activity and thus in estrogen levels may significantly affect bone loss and fracture risk in both genders.

Steroid hormone metabolizing enzymes in benign and malignant human bone tumors

IMPORTANCE IN THE FIELD: Primary bone tumors are considered as (sex steroid) hormone-dependent tumors. Osteosarcoma, osteoblastoma and bone cysts are preferentially found in males, while giant cell tumors are more common in females. Indeed, bone tumor development and progression are influenced by sex steroid hormones derived from in situ synthesis in bone cells.

AREAS COVERED IN THIS REVIEW

This review describes intracrine mechanisms for local formation of the biologically most active estrogen, 17beta-estradiol (E2), from circulating steroid precursors through the 'aromatase' (aromatization of androgens) and the 'sulfatase' (conversion of inactive estrone-sulfate) pathway.

WHAT THE READER WILL GAIN

The reader gains knowledge on both pathways and the enzymes, which contribute to the in situ availability of active hormones, namely 3beta-hydroxysteroid dehydrogenases, 17beta-hydroxysteroid dehydrogenases, aromatase, steroid sulfatases and sulfotransferases. An overview is given and the expression and function of these enzymes in bone tumors are discussed.

TAKE HOME MESSAGE

Knowledge on pathways for the in situ formation of E2 in bone cells may allow the identification of potential targets for i) novel endocrine therapeutic options in primary bone tumors and ii) future preventive interventions.

The gene for aromatase, a rate-limiting enzyme for local estrogen biosynthesis, is a downstream target gene of Runx2 in skeletal tissues

The essential osteoblast-related transcription factor Runx2 and the female steroid hormone estrogen are known to play pivotal roles in bone homeostasis; however, the functional interaction between Runx2- and estrogen-mediated signaling in skeletal tissues is minimally understood. Here we provide evidence that aromatase (CYP19), a rate-limiting enzyme responsible for estrogen biosynthesis in mammals, is transcriptionally regulated by Runx2. Consistent with the presence of multiple Runx2 binding sites, the binding of Runx2 to the aromatase promoter was demonstrated in vitro and confirmed in vivo by chromatin immunoprecipitation assays. The bone-specific aromatase promoter is activated by Runx2, and endogenous aromatase gene expression is upregulated by Runx2 overexpression, establishing the aromatase gene as a target of Runx2. The biological significance of the Runx2 transcriptional control of the aromatase gene is reflected by the enhanced estrogen biosynthesis in response to Runx2 in cultured cells. Reduced in vivo expression of skeletal aromatase gene and low bone mineral density are evident in Runx2 mutant mice. Collectively, these findings uncover a novel link between Runx2-mediated osteoblastogenic processes and the osteoblast-mediated biosynthesis of estrogen as an osteoprotective steroid hormone.

The effect of anti epileptic drug therapy on serum 25-hydroxyvitamin D and parameters of calcium and bone metabolism--a longitudinal study

BACKGROUND

Chronic antiepileptic drug use is associated with bone loss. We sought to assess the longitudinal effect of antiepileptic drug on serum 25-hydroxyvitamin D [25(OH)D] levels and bone mineral metabolism markers.

METHODS

Patients in the emergency services or those in neurology outpatient department with history of seizure were characterized and included in the study prospectively. Daily dietary intake of calories, calcium, phosphorus and phytates were characterized by dietary recall method. Base line bone mineral parameters - serum calcium, phosphorus, alkaline phosphatase (SAP), tartrate resistant acid phosphatase (TRACP), 25(OH)D levels, parathyroid hormone (PTH) and urinary calcium creatinine ratio (Ca.Cr), urinary calcium/kg/bodyweight (BW) and phosphate excretion index (PEI) were determined. Patients on AED therapy with normal 25(OH)D levels were followed up and were re-evaluated at the end of 6 months.

RESULTS

The daily dietary calcium intake of the subjects was lower than the RDA (Recommended Dietary Allowance) by ICMR (Indian Council of Medical Research). The diet was high in phytates. Two-thirds of the recruited subjects were vitamin D deficient. Subjects with normal 25(OH)D levels at base line showed a significant fall of 25(OH)D levels, urinary calcium, urinary calcium/kg/BW and TRACP levels at the end of 6 months irrespective of the AED used or the plasma level of AED.

CONCLUSIONS

Hypovitaminosis D is common in our population. Subjects with normal 25(OH)D levels, irrespective of the type of antiepileptic medications even at sub-therapeutic serum levels of the drug, went into 25(OH)D deficiency and insufficiency states. Theoretically it can be worthwhile to supplement calcium and vitamin D even before initiation of antiepileptic therapy.

Sex hormone and neuroendocrine aspects of the metabolic syndrome

We discuss the recent advances in the knowledge that the sex steroids testosterone (T), estradiol and dehydroepiandrosterone sulphate (DHEA-S) are involved in the development of visceral obesity and of the metabolic syndrome. Cross talk between leptin and the androgen receptor (AR) in the hypothalamus as well as the peripheral conversion of DHEA and T to estrone, estradiol and dihydrotestosterone (DHT) in adipocytes and hepatocytes play important roles in the metabolic syndrome in men. Finally, we discuss the development of new drugs, selective AR modulators, for treating the metabolic syndrome in men.

The multiple roles of estrogens and the enzyme aromatase

Aromatase is the enzyme that catalyzes the last step of estrogen biosynthesis. It is expressed in many tissues such as the gonads, brain and adipose tissue. The regulation of the level and activity of aromatase determines the levels of estrogens that have endocrine, paracrine and autocrine effects on tissues. Estrogens play many roles in the body, regulating reproduction, metabolism and behavior. In the brain, cell survival and the activity of neurons are affected by estrogens and hence aromatase.

Alternative 5'-untranslated first exons of the mouse Cyp19A1 (aromatase) gene

The human aromatase gene (CYP19A1) has eleven tissue-specific untranslated first exons, while only three have been described in the mouse Cyp19A1 namely brain-, ovary- and testis-specific exons 1. The present study aims to elucidate the complete structure of the mouse Cyp19A1 gene. We detected aromatase transcripts in mouse bone, aorta, hypothalamus, adipose, gonads and placenta, but not nulliparous mammary fat pad. BestFit algorithm analysis against the human CYP19A1 has identified ten putative first exons upstream of mouse Cyp19A1. Based on these putative sequences, we were able to design specific primers for RT-PCR and detected for the first time, the presence of exons I.4 and I.3 in murine fat and gonads, respectively. These are novel 5'UTRs of mouse Cyp19A1. Using RT-PCR and 5' RACE, we confirmed the expression of exon 1f in the hypothalamus and proximal exon P2 in the ovary. The testis-specific exon 1 begins 217bp further upstream than previously reported. Putative exons 2a, I.5, I.7, I.6 and I.2 were not detected in mouse tissues. Therefore, we showed that mouse Cyp19A1 contains more tissue-specific first exons than previously thought and displays a similar genomic organization to human CYP19A1.