The Genetic and Life Style Determinants of Bone Mass of Young Greek Males
Condition: Osteoporosis
MeSH terms: Osteoporosis
Study type: Observational

Summary: 
      The genetic bases of peak bone mass in males, as determinants of an individual's risk of
      developing osteoporotic fractures in old age and their interaction with dietary and lifestyle
      factors are still poorly understood.

      Our objective was to examine the relative contribution of genetic and environmental variables
      to the regulation of peak bone mass in a population-based cohort of young healthy men,
      focusing on the BsmI polymorphism of vitamin D receptor (VDR)gene and the AluI polymorphism
      of calcitonin receptor (CTR)gene.
    

Detailed description: 
      Material and Methods

      Subjects

      In this cross-sectional study, 301 Greek healthy young men, aged 16-35 were selected during
      gradational examinations for the Greek Armed forces. Men who were treated with
      corticosteroids, anticonvulsants, or anticoagulants or who suffered from hypogonadism,
      kidney, liver, thyroid and gastrointestinal disease or diabetes mellitus were excluded from
      the study.

      Approval by the hospital ethics committee and informed consent were obtained. Height and body
      weight were measured with the subjects in sportswear, standing barefoot on a fixed
      stadiometer and on a standard clinical balance. Height was recorded in centimetres and weight
      in kilograms. The stadiometer and scale were routinely monitored for accuracy and precision.
      Body mass index (BMI) was calculated as weight/height 2 .

      Dietary Evaluation

      Current dietary factors (calcium, proteins, alcohol, coffee and tea intake), were assessed
      using a food frequency questionnaire validated in the MEDOS study, and completed with an
      interview. Calcium intake was estimated considering milk, yogurt and cheese consumption.
      Protein intake was estimated by taking into account the consumption of meat and fish per
      week. Tea and coffee consumption was also taken into account.

      Nondieter factors were investigated using a questionnaire

      Physical was quantified as hours of sports activities per week (defined as taking part in
      organized sport for at least 12 months). Smoking behaviour was coded as 'yes' (daily smoking)
      or 'no', and sunlight exposure when there was exposure in places abroad during the previous 3
      months. Duration of immobilizations was also coded as 'less' or 'more than 1 month' (in
      majority, due to fractures caused by high energy trauma).

      Genetic analyses

      Genomic DNA was extracted from peripheral blood leukocytes with a DNA extraction kit
      (Puregene DNA isolation kit, Gentra Systems Inc., Munich, Germany). Polymorphisms in the CTR
      and VDR genes were determined by polymerase chain reaction (PCR) as previously described
      using Taq DNA polymerase (Takara, Tokyo, Japan), and thermal cycler (PCR Primus 96 plus-MWG
      AG BIOTECH). 4Î¼l of CTR-PCR product were digested with AluI (New England Biolabs, UK) and 2
      Î¼l of VDR-PCR product were digested with BsmI (New England Biolabs, UK) according to
      manufacturerâ€™s instructions. AluI restriction digest yielded DNA fragments of 120/108-bp
      (TT), 228/120/108-bp (TC) and 228-bp (CC) and BsmI restriction digest yielded DNA fragments
      of 1200/650-bp (bb), 1850/1200/650-bp (Bb) and 1850-bp (BB), which were visualized using a 3%
      and 1% agarose gel respectively stained with ethidium bromide.

      BMD Measurements

      Distal BMC (dBMC), distal BMD (dBMD) and ultradistal BMD (udBMD) at the radius were measured
      by single X-ray absorptiometry (Osteometer DTX-100, Denmark). Additionally, there were
      assessments of the corresponding geometrical areas, such as radial area (RadAr), ulnar area
      (UlnAr) and ultradistal area (udAr). BMD is expressed as grams/cm2; BMC is expressed in grams
      and Area as cm2 The in vivo precision for the BMD and BMC measurements in our laboratory was
      1-5%.

      Statistical Analysis

      Descriptive statistics were determined for all variables. All variables are sufficiently
      represented using the mean value (mean) and standard deviation (SD).

      Univariate analysis was performed using the two-sample Student's test or Welch-test (in a
      case of unequal SDs) and the model of one-way analysis of variance with no repeated
      measurements (pairwise multiple comparisons were analysed using the Tukey test). Analysis of
      covariance (ANCOVA) used the bone values (BMC, BMD, Area) as dependent variables, the VDR and
      CTR polymorphisms as factors and age, weight and height as covariates. Furthermore, multiple
      stepwise regression analysis was used to determine significant predictors of BMD. All tests
      are two sided; P<0, 05 was defined as significant. All data analysis was performed using the
      Statistical Package for Social Sciences (version 10.0) software (SPSS Inc., Chicago, IL).
    

Observational model: Defined Population
Time perspective: Other
Keywords: Peak Bone Mass; Male; Genetic Polymorphisms