Do genetic factors explain associations between muscle strength, lean mass, and bone density? A twin study

Area of Science:

• Human physiology
• Genetics
• Bone health

Background:

• The relationship between muscle strength, lean mass, and bone mineral density (BMD) is complex.
• Understanding the genetic versus environmental contributions to these associations is crucial for targeted interventions.

Purpose of the Study:

• To investigate the extent to which genetic factors determine the associations between lean mass, muscle strength, and bone mineral density (BMD) in adult females.
• To quantify the heritability of lean mass and femoral neck BMD and their shared genetic influences.

Main Methods:

• Utilized a twin study design with 56 monozygotic (MZ) and 56 dizygotic (DZ) female twin pairs.
• Assessed bone mineral density (BMD) at the femoral neck, lean mass, muscle strength, fat mass, and height.
• Employed within-pair difference analyses and cross-trait cross-twin correlations to estimate genetic and environmental influences.

Main Results:

• Lean mass was significantly associated with femoral neck BMD, independent of fat mass and height.
• Same-trait correlations for BMD and lean mass were substantially higher in MZ twins compared to DZ twins, suggesting genetic influence.
• Genetic factors were estimated to account for 60-80% of the individual variances in both femoral neck BMD and lean mass.
• Over 50% of the covariance between lean mass and femoral neck BMD was attributed to shared genetic factors.

Conclusions:

• The association between greater lean mass and greater bone mineral density (BMD) is largely determined by genetic factors.
• Genes regulating body size appear to play a significant role in the coordinated regulation of muscle mass and bone density.
• These findings highlight the substantial genetic underpinnings of musculoskeletal health and the interplay between muscle and bone.