Heritable and nutritional influences on bone mineral mass

Whole Genome Sequencing Unravels New Genetic Determinants of Early-Onset Familial Osteoporosis and Low BMD in Malta

Background: Osteoporosis is a skeletal disease with a strong genetic background. The study aimed to identify the genetic determinants of early-onset familial osteoporosis and low bone mineral density (BMD) in a two-generation Maltese family. Methods: Fifteen relatives aged between 28–74 years were recruited. Whole genome sequencing was conducted on 12 relatives and shortlisted variants were genotyped in the Malta Osteoporotic Fracture Study (MOFS) for replication. Results: Sequential variant filtering following a dominant inheritance pattern identified rare missense variants within SELP, TGF-β2 and ADAMTS20, all of which were predicted to be likely pathogenic and participate in osteoimmunology. TGF-β2 c.1136C>T was identified in five individuals from the MOFS in heterozygosity, four of whom had osteopenia/osteoporosis at the lumbar spine and hip, and/or had sustained a low-trauma fracture. Heterozygosity for the ADAMTS20 c.4090A>T was accompanied by lower total hip BMD (p = 0.018) and lower total serum calcium levels in MOFS (p < 0.01), recapitulating the findings from the family. Women carrying at least one copy of the alternative allele (TC/CC) for SELP c.2177T>C exhibited a tendency for lower lumbar spine BMD and/or wrist fracture history relative to women with TT genotype. Conclusions: Our findings suggest that the identified variants, alone or in combination, could be causal factors of familial osteoporosis and low BMD, requiring replication in larger collections.

Prenatal calcium and vitamin D intake, and bone mass in later life

The aging population will result in an increasing burden of osteoporotic fractures, necessitating the identification of novel strategies for prevention. There is increasing recognition that factors in utero may influence bone mineral accrual, and, thus, osteoporosis risk. The role of calcium and vitamin D has received much attention in recent years, and in this review, we will survey available studies relating maternal calcium and vitamin D status during pregnancy to offspring bone development. The evidence base supporting a positive influence on intrauterine skeletal growth appears somewhat stronger for maternal 25(OH)-vitamin D concentration than for calcium intake, and the available data point toward the need for high-quality randomized controlled trials in order to inform public health policy. It is only with such a rigorous approach that it will be possible to delineate the optimal strategy for vitamin D supplementation in pregnancy in relation to offspring bone health.

Association between regulating synaptic membrane exocytosis 2 gene polymorphisms and degenerative lumbar scoliosis

Degenerative lumbar scoliosis (DLS) is a spinal deformity that develops after skeletal maturity and progresses with age. In contrast to adolescent idiopathic scoliosis, the genetic association of DLS has not yet been elucidated. The purpose of this study was to investigate the association between regulating synaptic membrane exocytosis 2 (RIMS2, OBOE) gene polymorphisms and DLS. Two coding single-nucleotide polymorphisms [rs2028945 (Gln1200Gln) and rs10461 (Ala1327Ala)] of RIMS2 were selected and genotyped by direct sequencing. As a result, the rs10461 was associated with DLS in allele frequencies (P=0.008) and genotype distributions (P=0.006 in the codominant model, 0.018 in the dominant model and 0.029 in the recessive model). In the analysis of haplotypes, two haplotypes exhibited significant differences between the control and DLS groups (CC haplotype, P=0.009 in the codominant model, 0.038 in the dominant model and 0.030 in the recessive model; CT haplotype, P=0.041 in the codominant model and 0.021 in the dominant model). These findings suggest that RIMS2 may be associated with the development of DLS.

Assessing bone health in children and adolescents

During normal childhood and adolescence, the skeleton undergoes tremendous change. Utilizing the processes of modeling and remodeling, the skeleton acquires its adult configuration and ultimately achieves peak bone mass. Optimization of peak bone mass requires the proper interaction of environmental, dietary, hormonal, and genetic influences. A variety of acute and chronic conditions, as well as genetic polymorphisms, are associated with reduced bone density, which can lead to an increased risk of fracture both in childhood and later during adulthood. Bone densitometry has an established role in the evaluation of adults with bone disorders, and the development of suitable reference ranges for children now permits the application of this technology to younger individuals. We present a brief overview of the factors that determine bone density and the emerging role of bone densitometry in the assessment of bone mass in growing children and adolescents.

FokI and BsmI polymorphisms of the vitamin D receptor gene and bone mineral density in a random Bulgarian population sample

Numerous studies on vitamin D receptor (VDR) gene polymorphisms differ with conflicting data in various populations. We studied the association of FokI and BsmI polymorphisms in the gene encoding the vitamin D receptor with bone mineral density (BMD) in 219 persons of Bulgarian nationality. The calculated relative risk (RR) for low bone mineral density is higher for FokI marker (3.14) compared to BsmI marker (2.44). The etiological factor (EF), which shows association between polymorphisms investigated and illness on populational level, is defined as EF = 0.51 for FokI marker and EF = 0.42 for BsmI marker. Because of this we conclude that FokI and BsmI polymorphisms are closely related to low BMD at the forearm and lumbar spine. Both polymorphisms are useful genetic markers in determining BMD and osteoporosis risk. Further studies of larger cohorts and in ethnically diverse subgroups are necessary.

A 2-year prospective study on the effects of depot medroxyprogesterone acetate on bone mass-response to estrogen and calcium therapy in individual users

The primary aim of this prospective 2-year follow-up study was to investigate the effect of depot medroxyprogesterone acetate (DMPA) on the maintenance of bone mass in women aged 30-45 years. The effects of estrogen or calcium substitution during the second year of follow-up was investigated in seven DMPA users with a high annual bone loss during the first year. The bone mass of 35 users of DMPA and 10 women without hormonal contraception was investigated using peripheral quantitative computed tomography. The baseline cortical and trabecular bone mass (TBM) and the annual change was not different in DMPA users and controls. Over 24 months we measured an increase in TBM of 0.6% and a decrease in cortical bone mass of 0.1% in exposed women. Some but not all of the DMPA users with a bone loss during the first year could be successfully treated with estradiol or calcium. In conclusion, we did not observe an accelerated bone loss in DMPA users aged 30-45 years.

A functional polymorphic variant in the interleukin-6 gene promoter associated with low bone resorption in postmenopausal women

OBJECTIVE

To examine functional interleukin-6 (IL-6) -174 G-->C allelic variants in relation to bone turnover and bone mineral density (BMD) in postmenopausal women.

METHODS

Four hundred thirty-four healthy women living in the community (mean +/- SD age 71.7 +/- 5.7 years) were genotyped for the IL-6 -174 G-->C polymorphism. Serum levels of C-telopeptide of type I collagen (CTx), a marker of bone resorption, and osteocalcin (OC), a marker of bone formation, were determined. BMD at the hip and forearm was measured by dual-energy x-ray absorptiometry.

RESULTS

CTx levels differed significantly (P = 0.006) among IL-6 genotypes (mean +/- SEM 0.275 +/- 0.02 ng/ml, 0.325 +/- 0.01 ng/ml, and 0.356 +/- 0.02 ng/ml in women with the CC genotype [n = 68], the GC genotype [n = 204], and the GG genotype [n = 162], respectively). Compared with the GG group, age-adjusted odds ratios for high bone resorption were 0.65 (95% confidence interval [95% CI] 0.41-1.0, P = 0.06) and 0.37 (95% CI 0.18-0.73, P = 0.0047) in GC and CC subjects, respectively. In contrast, OC levels did not differ by genotype. BMD at the hip and forearm was 1.5-5% higher in CC subjects compared with GG subjects (P not significant). When the cohort was divided according to the median age (70.5 years), BMD was significantly decreased in older compared with younger postmenopausal women with the GG and GC genotypes (-9.6% on average; P < 0.01), but not in those with the CC genotype (-5.1% on average; P not significant).

CONCLUSION

Compared with the GC and GG IL-6 -174 G-->C genotypes, the CC genotype is associated with lower bone resorption and lesser decrease in bone mass in older postmenopausal women. These results suggest that IL-6 -174 G-->C alleles may be significant determinants of the risk for osteoporosis in elderly subjects.

A prospective study on the effects of depot medroxyprogesterone acetate on trabecular and cortical bone after attainment of peak bone mass

OBJECTIVE

To study the annual change of bone mass in women aged 30-45 years being treated with depot medroxyprogesterone acetate (DMPA) in order to evaluate whether the bone mass depends on the duration of DMPA use or the oestradiol level.

DESIGN

Prospective longitudinal study over an interval of 12 months.

SETTING

A family planning centre of a university hospital.

PATIENTS

Thirty-six current users of DMPA.

INTERVENTIONS

Injection of 150 mg DMPA every 12 weeks.

MEASUREMENTS

Bone mass was measured at the distal radius by peripheral quantitative computed tomography (reproducibility 0.3%).

RESULTS

Mean annual changes (SD) in trabecular and cortical bone mass were 0.06 (1.6%) [P = 0.8] and -0.26% (0.6) [P < 0.04]. The decrease in cortical bone mass was not significant because the changes were within the precision error of the method used for the measurements. Duration of DMPA use and oestradiol levels were not associated to the bone parameters.

CONCLUSION

We did not find a negative impact of DMPA on the bone mass of premenopausal women aged 30-45 years.