Pharmacogenetics of bone treatments: the VDR and ERalpha gene story

Bone Fracture Incidence in Postmenopausal Women: Results of a 10 Year Follow Up in a RAC-OST-POL Study of rs1544410, rs7975232 and rs731236 Polymorphisms

BACKGROUND

The clinical significance of the genetic influence of vitamin D receptor polymorphisms has still not been well-analyzed.

OBJECTIVES

To verify whether rs1544410, rs7975232 and rs731236 polymorphisms are associated with a higher 10-year fracture risk in postmenopausal women.

METHODS

The study group was a subset of a pre-defined population as part of the broader epidemiological research called the RAC-OST-POL Study and consisted of 358 postmenopausal women, chosen randomly from Racibórz (Poland) inhabitants (mean baseline age 65 ± 6.9 years, BMI 31.2 ± 5.5 kg/m2). From all participants' medical history, data concerning co-morbidities, fracture history, the medication used, parental history of bone fractures, cigarettes and alcohol use were taken at baseline. Moreover, rs1544410, rs7975232 and rs731236 polymorphisms were analyzed. Next, over the following 10 years, participants were contacted once a year and questioned concerning new fractures events and their circumstances.

RESULTS

We did not find statistically significant main effects on the fracture incidence of single-polymorphism variants. However, there were some significant findings dependent on the co-existence of these polymorphisms and medical factors. Women with a positive history of parental fracture and configuration of CC rs7975232, AA rs731236 and CC rs1544410 had a higher fracture incidence. The risk of bone fracture was also significantly higher in the group of heterozygotes of AC rs7975232 if their BMI value was in the categories of normal weight or overweight, or if they were treated with calcium or vitamin D.

CONCLUSIONS

Polymorphisms of rs1544410, rs7975232 and rs731236 are connected with the fracture incidence in postmenopausal women. Nevertheless, its influence should be considered with co-existing clinical factors, especially paternal fracture history, prior fracture, BMI value, any osteoporotic treatment or calcium/vit. D supplementation.

Vitamin D, Bone Metabolism, and Fracture Risk in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among premenopausal women. PCOS may have reproductive, metabolic, cardiovascular, and psychological implications. Vitamin D deficit is often encountered in PCOS women and may contribute to the pathophysiology of this disorder. As of the key role of vitamin D in bone and mineral metabolism, and because the vitamin D status appears to be closely linked with the PCOS manifestations including insulin resistance, obesity, ovulatory and menstrual irregularities, oxidative stress and PTH elevation, hypovitaminosis D may directly and indirectly via the different facets of PCOS impair bone health in these women. Although limited data are available on life-long fracture risk in women with PCOS, the importance of preserving bone health in youth and adults to prevent osteoporosis and related fractures is also recognized in PCOS women. Evidence of the association between vitamin D and the clinical hallmarks of PCOS are summarized and discussed. Vitamin D arises as a cornerstone in women with PCOS and contributes to the pathophysiological link between PCOS and bone metabolism.

Clinical and molecular studies related to bone metabolism in patients with congenital adrenal hyperplasia

Patients with congenital adrenal hyperplasia (CAH) due to 21-hydroxylase deficiency need glucocorticoid (GC) therapy, which alters bone mineral metabolism. We analyze clinical and biochemical parameters and different polymorphisms of candidate genes associated with bone mineral density (BMD) in CAH patients. The CAH patients treated with GC and healthy controls were studied. Anthropometric parameters, biochemical markers of bone turnover, and BMD were evaluated. Polymerase chain reaction technique was used to genotype different candidate genes. The 192-192 genotype frequency (IGF-I) was lower in poorly controlled patients than that from controls. In CAH patients, FF genotype (vitamin D receptor, VDR) correlated with lower lumbar spine BMD and there was a significant association between the 0-0 genotype (IGF-I) and high values of β-CrossLaps and a low total BMD. This study contributes to understanding of the association of genetic determinants of BMD with the variable response to GC treatment in CAH patients and demonstrates the usefulness of these genetic polymorphisms.

Small-molecule hormones: molecular mechanisms of action

Small-molecule hormones play crucial roles in the development and in the maintenance of an adult mammalian organism. On the molecular level, they regulate a plethora of biological pathways. Part of their actions depends on their transcription-regulating properties, exerted by highly specific nuclear receptors which are hormone-dependent transcription factors. Nuclear hormone receptors interact with coactivators, corepressors, basal transcription factors, and other transcription factors in order to modulate the activity of target genes in a manner that is dependent on tissue, age and developmental and pathophysiological states. The biological effect of this mechanism becomes apparent not earlier than 30-60 minutes after hormonal stimulus. In addition, small-molecule hormones modify the function of the cell by a number of nongenomic mechanisms, involving interaction with proteins localized in the plasma membrane, in the cytoplasm, as well as with proteins localized in other cellular membranes and in nonnuclear cellular compartments. The identity of such proteins is still under investigation; however, it seems that extranuclear fractions of nuclear hormone receptors commonly serve this function. A direct interaction of small-molecule hormones with membrane phospholipids and with mRNA is also postulated. In these mechanisms, the reaction to hormonal stimulus appears within seconds or minutes.

Skeletal effects of vitamin D supplementation in postmenopausal black women

Black women have lower serum 25-hydroxyvitamin D (25[OH]D) levels and higher parathyroid hormone (PTH) levels than white peers but lower bone turnover, suggesting skeletal resistance to PTH. Our objective was to determine if vitamin D supplementation (1,000 IU/day) would prevent bone loss and whether vitamin D receptor (VDR) polymorphisms modify the response. We performed a 2-year randomized, controlled, double-blind study of 1,000 IU vitamin D(3) vs. placebo in postmenopausal black women with serum 25(OH)D levels <20 ng/mL (n = 103). Measurements of 25(OH)D, PTH, and bone turnover were evaluated at baseline and 3, 6, 12, 18, and 24 months. DNA was extracted from peripheral blood leukocytes, and genotyping was conducted using standard techniques. Spine and hip bone mineral density (BMD) was measured at baseline and every 6 months. Serum 25(OH)D increased 11 ng/mL with vitamin D supplementation (p < 0.001), with no change in the placebo group. Vitamin D supplementation produced a significant decline in PTH at 3 months only, with no differences in bone turnover between placebo and vitamin D at any time point. Two-year changes in BMD were not significantly different between placebo- and vitamin D-treated black women at any skeletal site. Despite similar elevations in 25(OH)D, femoral neck BMD was only responsive to vitamin D supplementation in FF subjects (n = 47), not Ff/ff subjects (n = 31). Vitamin D supplementation does not appear to influence bone loss in black women. However, in the FF polymorphism of the VDR gene group, vitamin D supplementation may retard the higher rate of bone loss.

Review of osteoporosis pharmacotherapy for geriatric patients

BACKGROUND

Fractures are a significant problem in geriatric patients, and understanding the evidence for benefit and possible harm of osteoporosis treatments is critical to appropriate management of this patient population.

OBJECTIVE

The purpose of this article was to review the evidence and treatment considerations related to use of the approved osteoporosis treatments in the United States across the continuum of ages in the geriatric population.

METHODS

MEDLINE and the Web of Science were searched to find English-language articles published from 2000 through July 2009. Search terms included: practice guideline, osteoporosis, calcium, vitamin D, pharmacoeconomics, ethnicity, and treatment. The generic names of each of the osteoporosis treatments approved in the United States were searched to find relevant clinical trials and randomized controlled trials (RCTs). Pivotal trials that included fracture data or focused specifically on elderly patients (> or = 60 years of age) were selected. Bibliographies in the identified articles were searched for additional articles, and the prescribing information for each of the approved treatments was reviewed.

RESULTS

Many osteoporosis studies have a mean patient age >60 years, but data for older patients are limited. Subanalyses of older patient groups have found risedronate to be beneficial for vertebral fractures in patients aged 70 to 79 years (absolute risk reduction [ARR], 8.4%; P < 0.001) and teriparatide to be beneficial for both vertebral (ARR, 6.4%; P < 0.05) and new nonvertebral fragility fractures (ARR, 9.9%; P < 0.05) in women aged > or = 75 years. However, no RCTs of geriatric patients who were either nonambulatory or had multiple comorbidities were identified in the literature.

CONCLUSIONS

Evidence indicates that the osteoporosis treatments currently available in the United States are beneficial for treating osteoporosis in geriatric patients. However, data are limited for the oldest patients (> or = 80 years) and those with significant comorbidities. Because of the limited availability of data for geriatric patients with significant comorbidities, the properties of the various agents, including efficacy, tolerability, and potential contraindications, should be considered carefully for each geriatric patient.

Age-specific effects of estrogen receptors' polymorphisms on the bone traits in healthy fertile women: the BONTURNO study

BACKGROUND

Skeletal characteristics such as height (Ht), bone mineral density (BMD) or bone turnover markers are strongly inherited. Common variants in the genes encoding for estrogen receptor alpha (ESR1) and beta (ESR2) are proposed as candidates for influencing bone phenotypes at the population level.

METHODS

We studied 641 healthy premenopausal women aged 20-50 years (yrs) participating into the BONTURNO study. Exclusion criteria were irregular cyclic menses, low trauma fracture, metabolic bone or chronic diseases. Serum C-telopeptide of type I collagen (CTX), osteocalcin (OC), and N-terminal propeptide of type I procollagen (P1NP) were measured in all enrolled subjects, who underwent to lumbar spine (LS), total hip (TH) and femoral neck (FN) BMD evaluation by DXA. Five hundred seventy Caucasian women were genotyped for ESR1 rs2234693 and rs9340799 and ESR2 rs4986938 polymorphisms.

RESULTS

Although no genotype differences were found in body parameters, subjects with combined ESR1 CCGG plus ESR2 AA-AG genotype were taller than those with opposite genotype (P = 0.044). Moreover, ESR1 rs2234693 genotypes correlated with family history of osteoporosis (FHO) and hip fracture (FHF) (P < 0.01), while ESR2 AA-AC genotypes were strongly associated with FHF (OR 2.387, 95% CI 1.432-3.977; P < 0.001).When clustered by age, 20-30 yrs old subjects, having at least one ESR1 rs2234693 C allele presented lower LS- (P = 0.008) and TH-BMD (P = 0.047) than TT genotypes. In 41-50 yrs age, lower FN-BMD was associated with ESR2 AA (P = 0.0180) subjects than in those with the opposite genotype. ESR1 rs2234693 and rs9340799 and ESR2 rs4986938 polymorphisms did not correlate with age-adjusted values of OC, CTX and P1NP.

CONCLUSION

These findings support the presence of age-specific effects of ESR1 and ESR2 polymorphisms on various skeletal traits in healthy fertile women.