Increased 2-hydroxylation of estrogen in women with a family history of osteoporosis

An LC-MS/MS Methodological Framework for Steroid Hormone Measurement from Human Serum

Estrogens and androgens are important regulators of sexual development and physiological processes in men and women, acting on numerous organs throughout the body. Moreover, they can contribute to a variety of pathologies, including osteoporosis, cancer, and cardiovascular and neurologic diseases. Analysis of estrogens and androgens in biological samples has been commonly performed using immunoassays for many years. However, these assays are suboptimal, as there is cross-reactivity with similar analytes, and they have moderate specificity and sensitivity. Thus, there is a clinical need to develop highly sensitive and specific methods for the accurate measurement of estrogen and androgen concentrations. Herein, we describe the development of three liquid chromatography coupled tandem mass spectrometry-based methods that incorporate the use of a Triple Quadrupole Mass Spectrometer for quantitative measurement of endogenous concentrations of various steroid hormones in human serum samples: (1) the simultaneous measurement of testosterone, androstenedione, and cortisol, (2) dehydroepiandrosterone (DHEA), and (3) 17β-estradiol (E₂). The use of derivatizing reagents, Girard's reagent P and dansyl chloride, allowed for significant gains in sensitivity in the analysis of DHEA and E2, respectively, relative to the underivatized analyte. These procedures proved efficient and adequately sensitive for steroid hormone analysis in extracted patient sera samples from older men and postmenopausal women, providing reliable data down to low nanogram/ml and sub-nanogram/ml levels. Moreover, utilizing the combination of highly specific mass transitions associated with these analytes and their respective internal deuterated standards provided a high degree of specificity to the identity of these hormones.

Steroids-specific target library for steroids target prediction

Steroids exist universally and play critical roles in various biological processes. Identifying potential targets of steroids is of great significance in studying their physiological and biochemical activities, the side effects and for drug repurposing. Herein, aiming at more precise steroids targets prediction, a steroids-specific target library integrating 3325 PDB or homology modeling structures categorized into 196 proteins was built by considering chemical similarity from DrugBank and biological processes from KEGG. The main properties of this library include: (1) It was manually prepared and checked to eliminate mistakes. (2) The library enriched the possible steroids targets and could decrease the false positives of structure-based target screening for steroids. (3) The ranking by protein name instead of PDB ID could make the screening more efficiency and precise. (4) Protein flexibility was taken into account partially by the different active conformations through the structural redundancy of each category of protein, which leads to more accurate prediction. The case studies of glycocholic acid and 24-epibrassinolide proved its powerful predictive accuracy. In summary, our strategy to build the steroids-specific protein library for steroids target prediction is a promising approach and it provides a novel idea for the target prediction of small molecules.

The anti-estrogenic activity of indole-3-carbinol in neonatal rat osteoblasts is associated with the estrogen receptor antagonist 2-hydroxyestradiol

PURPOSE

To gain new insight into the roles of cruciferous vegetable-derived bioactive phytochemicals in bone cells, we investigated the effects of indole-3-carbinol (I3C) on cell proliferation and differentiation in estradiol (E2)-exposed calvarial osteoblasts that were obtained from neonatal rats.

METHODS

Osteoblast activity was assessed by analyzing cellular DNA, cell-associated osteocalcin (OC) levels and alkaline phosphatase (AP) activity. We also examined [(3)H]-estrone (E1) metabolism and estrogen-agonistic and estrogen-antagonistic activities of 2-hydroxy (OH) E1 and 2-OHE2 and their capacity to displace [(3)H]-E2 at ER binding sites using competition studies.

RESULTS

I3C did not affect on cellular DNA, OC levels or AP activity. However, I3C completely inhibited E2-induced increases in cell proliferation and differentiation in neonatal rat osteoblasts. Metabolic studies demonstrated that I3C promoted the conversion of [(3)H]-E1 to 2-OHE1 and 2-OHE2 and those higher rates of conversion (twofold-threefold) were archived when a higher dose of I3C was applied. Proliferation and differentiation studies showed that 2-OHE2 but not 2-OHE1 inhibited E2-induced increases in cell proliferation and differentiation via an ER-mediated mechanism. Likewise, Esr1 was expressed at high level than Esr2. 2-OHE1 showed no activity or affinity for ER.

CONCLUSIONS

This study is the first to show that a bioactive compound derived from cruciferous vegetables, I3C, abolishes the E2-mediated stimulation of cell activities including, proliferation and differentiation, in rat osteoblasts and increases the 2-hydroxylation of E1, resulting in the formation of inactive and anti-estrogenic metabolites. These results suggest that in neonatal rat osteoblasts, the anti-estrogenic effect of I3C is mediated by 2-OHE2 through ER-α.

Simultaneous Quantitation of Estradiol and Estrone in Serum Using Liquid Chromatography Mass Spectrometry

Accurate measurement of the endogenous estrogens, estrone (E1) and estradiol (E2), is important in the clinical diagnosis and monitoring of multiple disorders. Typically, given the efficacy and low cost, radioimmunoassays (RIA) and enzyme-linked immunoassays (EIA) are used to quantify these hormones in biological samples. Unfortunately, at low levels these assays lack the necessary sensitivity and specificity for diagnosis of certain disorders in adult and pediatric endocrinology and oncology. In response to this need, we developed a fast and sensitive high performance liquid chromatography negative electrospray ionization tandem mass spectrometry (LC-MS/MS) method to measure serum estrone (E1) and estradiol (E2) without chemical derivatization. Samples are spiked with a stable isotopic carbon thirteen ((13)C) labeled internal standard and the estrogens are isolated by liquid-liquid extraction (LLE) with hexane:Methyl-tert-butyl ether (MTBE) (9:1). Following centrifugation and dry down samples are reconstituted with deionized water, and separated on a C18 reverse phase column. The analytes are quantified using a six point calibration curve with a linearity of 2.6-625 pg/ml and with a variability of less than 8 % across analytical range.

Comparison of liquid chromatography-microchip/mass spectrometry to conventional liquid chromatography-mass spectrometry for the analysis of steroids

The feasibility of a microfluidic-based liquid chromatography-electrospray ionization/mass spectrometric system (HPLC-Chip/ESI/MS) was studied and compared to a conventional narrow-bore liquid chromatography-electrospray ionization/mass spectrometric (LC-ESI/MS) system for the analysis of steroids. The limits of detection (LODs) for oxime derivatized steroids, expressed as concentrations, were slightly higher with the HPLC-Chip/MS system (50-300 pM) using an injection volume of 0.5 μL than with the conventional LC-ESI/MS (10-150 pM) using an injection volume of 40 μL. However, when the LODs are expressed as injected amounts, the sensitivity of the HPLC-Chip/MS system was about 50 times higher than with the conventional LC-ESI/MS system. The results indicate that the use of HPLC-Chip/MS system is clearly advantageous only in the analysis of low-volume samples. Both methods showed good linearity and good quantitative and chromatographic repeatability. In addition to the instrument comparisons with oxime derivatized steroids, the feasibility of the HPLC-Chip/MS system in the analysis of non-derivatized and oxime derivatized steroids was compared. The HPLC-Chip/MS method developed for non-derivatized steroids was also applied to the quantitative analysis of 15 mouse plasma samples.

Dietary calcium intake is associated with less gain in intra-abdominal adipose tissue over 1 year

Calcium intake is reported to enhance weight loss with a preferential loss in trunk fat. Discrepant findings exist as to the effects of calcium intake on longitudinal changes in total fat mass and central fat deposition. Therefore, the purpose of this study was to determine associations between dietary calcium intake and 1-year change in body composition and fat distribution, specifically intra-abdominal adipose tissue (IAAT). A total of 119 healthy, premenopausal women were evaluated at baseline and 1 year later. Average dietary calcium was determined via 4-day food records. Total fat was determined by dual-energy X-ray absorptiometry (DXA) and subcutaneous abdominal adipose tissue (SAAT) and IAAT by computed tomography. Over the study period, participants' reported daily calcium and energy intakes were 610.0 ± 229.9 mg and 1,623.1 ± 348.5 kcal, respectively. The mean change in weight, total fat, IAAT, and SAAT was 4.9 ± 4.4 kg, 5.3 ± 4.0 kg, 7.7 ± 19.5 cm(2), and 49.3 ± 81.1 cm(2), respectively. Average calcium intake was significantly, inversely associated with 1-year change in IAAT (standardized β: -0.23, P < 0.05) after adjusting for confounding variables. For every 100 mg/day of calcium consumed, gain in IAAT was reduced by 2.7 cm(2). No significant associations were observed for average calcium intake with change in weight, total fat, or SAAT. In conclusion, dietary calcium intake was significantly associated with less gain in IAAT over 1 year in premenopausal women. Further investigation is needed to verify these findings and determine the calcium intake needed to exert beneficial effects on fat distribution.

Liquid chromatography-tandem mass spectrometry applications in endocrinology

Liquid chromatography-tandem mass spectrometry (LC-MS/MS) has been recognized as a primary methodology for the accurate analysis of endogenous steroid hormones in biological samples. This review focuses on the use of LC-MS/MS in clinical laboratories to assist with the diagnosis of diverse groups of endocrine and metabolic diseases. Described analytical methods use on-line and off-line sample preparation and analytical derivatization to enhance analytical sensitivity, specificity, and clinical utility. Advantages of LC-MS/MS as an analytical technique include high specificity, possibility to simultaneously measure multiple analytes, and the ability to assess the specificity of the analysis in every sample. All described analytical methods were extensively validated, utilized in routine diagnostic practice, and were applied in a number of clinical and epidemiological studies, including a study of the steroidogenesis in ovarian follicles.

Bone mineral density and prediction of non-osteoporotic disease

It is widely recognized that bone mineral density (BMD) is one of the best predictors of osteoporotic fractures. Sex hormone status clearly affects bone either directly or indirectly and a longer estrogen exposure appears to be a major determinant of postmenopausal BMD. Accordingly, several studies have led to the hypothesis that BMD might represent a marker of the accumulated lifetime exposure of estrogen and therefore be used as a predictor factor of the risk of other postmenopausal conditions such as breast cancer or cardiovascular diseases (CVD). With regard to the risk of breast cancer, there is evidence that different surrogate markers of lifetime exposure to estrogen are associated with an increased risk for breast cancer. Most of these markers are the opposite of those for the risk of fracture. Furthermore, several studies have also reported that women with higher BMD have an increased risk of breast cancer compared to women with lower BMD. On the other hand, postmenopausal women with osteoporosis are at increased risk for acute cardiovascular events and mortality independently of age and cardiovascular risk factors. BMD has been shown to inversely correlate with surrogate markers of CVD including aortic calcifications and atherosclerosis. The underlying mechanisms of such a relationship are not fully understood. Several plausible molecular links are serum lipids, pro-inflammatory cytokines or the RANK/RANK ligand/osteoprotegerin system. Interestingly, all of these factors are modulated by estrogens. It could thus be hypothesized that the intensity of postmenopausal estrogen deficiency could be also the common pathogenic factor between atherosclerosis and osteoporosis.

High sensitivity measurement of estrone and estradiol in serum and plasma using LC-MS/MS

Measurement of low concentrations of estrogens, encountered in pre-pubertal children, men, and postmenopausal women, is important for numerous clinical applications. We describe a method for high sensitivity analysis of estrogens that uses two-dimensional chromatographic separation and tandem mass spectrometry detection. Aliquots of serum or plasma samples are combined with stable isotope-labeled internal standard and estrogens are extracted with methyl t-butyl ether. The solvent is evaporated, estrogens derivatized to form dansyl derivatives, and the samples are analyzed. Quantitation is performed using triple quadrupole mass spectrometer equipped with electrospray ion source using positive ion mode ionization and multiple reaction monitoring acquisition.

Effects of dietary calcium compared with calcium supplements on estrogen metabolism and bone mineral density

BACKGROUND

High calcium intake has been associated with both high bone mineral density (BMD) and high urinary estrogen metabolites. However, the role of dietary calcium and calcium supplements on estrogen metabolism and BMD remains unknown.

OBJECTIVE

The objective was to investigate the importance of the source of calcium intake on estrogen metabolism and BMD.

DESIGN

The average total daily calcium intake from supplements and diet, urinary estrogen metabolites, and spine and proximal femur BMD were studied in 168 healthy postmenopausal white women.

RESULTS

Women who obtained calcium primarily from the diet or from both the diet and supplements had significantly (P=0.03) lower ratios of nonestrogenic to estrogenic metabolites (2-hydroxyestrone 1/16 alpha-hydroxyestrone) than did those who obtained calcium primarily from supplements. Adjusted BMD z scores were significantly greater in the subjects who obtained calcium primarily from the diet or from both the diet and supplements than in those who obtained calcium primarily from calcium supplements at the spine (P=0.012), femoral neck (P=0.02), total femur (P=0.003), and intertrochanter (P=0.005). This difference was evident especially in those who obtained calcium primarily from the diet, whose total calcium intake was lower than that in those who obtained calcium primarily from supplements.

CONCLUSION

Calcium from dietary sources is associated with a shift in estrogen metabolism toward the active 16 alpha-hydroxyl metabolic pathway and with greater BMD and thus may produce more favorable effects in bone health in postmenopausal women than will calcium from supplements.

Estrogen metabolism modulates bone density in men

Estrogen is a critical hormone for bone homeostasis in men, but no information is available on the role of estrogen metabolism among men. The aim of this study was to evaluate the effect of estrogen hydroxylation on male bone mineral density (BMD). Participants consisted of 61 healthy Caucasian males (mean age 66.6 +/- 1.0 years). Urinary estrogen metabolites were measured by enzyme-linked immunosorbent assay, serum estradiol by ultrasensitive radioimmunoassay, sex hormone binding globulin by radioimmunoassay, and BMD of the lumbar spine and the proximal femur by dual-energy X-ray absorptiometry. Active estrogen metabolites, 16alpha-hydroxyestrone (16alphaOHE(1)) and estriol (E(3)), positively correlated with adjusted BMD in all regions of the proximal femur (all P < 0.05) but not at the lumbar spine, and those in the highest tertile of urinary 16alphaOHE(1 )had the highest BMD. Free estradiol index (FEI) also positively correlated with BMD of the total hip, femoral neck, and intertrochanter (all P < 0.05), while there was no correlation between BMD with inactive metabolites (2-hydroxyestrone and 2-methoxyestrone) and serum testosterone. Multiple regression analysis showed 16alphaOHE(1), FEI, and body mass index are important independent predictors of BMD in all regions of the proximal femur. Estrogen metabolism may modulate BMD in men. Increased urinary 16alphaOHE(1) and E(3) levels are associated with high BMD at the proximal femur, and 16alphaOHE(1) appears to be a major determinant of BMD among the metabolites evaluated.