A DXA study of muscle-bone relationships in the whole body and limbs of 2,512 normal men and pre- and post-menopausal women

RICARDO FRANCISCO CAPOZZA; GUSTAVO ROBERTO COINTRY (COMPARTIENDO PRIMERA AUTORÍA CON DR. CAPOZZA); PABLO CURE RAMIREZ; JOSÉ LUIS FERRETTI; CARLOS CURE CURE

BONE

Elsevier

Lugar: Nueva York; Año: 2004 vol. 35 p. 283 - 295

8756-3282

A whole-body DXA study of 1,450 healthy Caucasian individuals [Ferretti et al; Bone 22:683,1998] found that mineral mass, either crude (BMC) or statistically adjusted to fat mass (FM-adj.BMC) correlated linearly with lean mass (LM, proportional to muscle mass). The results showed similar slopes but decreasing intercepts (ordinate values) in the order: pre-MP women > men > post-MP women > children. This supports the hypothesis that sex hormones and related factors influence the control of bone status by muscle strength in all species. Now we further study those relationships in 2,512 healthy Hispanic adults (307 men, 753 pre-MP women, 1,452 post-MP women), including separate determinations in their upper and lower limbs. The slopes of the BMC or FM-adj.BMC vs LM relationships were parallel in all the studied regions. However, region-related differences were found between the ordinates of the curves. In the whole body, the crude-BMC/LM relationships showed the same ordinate differences as previously observed. In the lower limbs, those differences were smaller in magnitude but highly significant, showing the order: pre-MP women > men = post-MP women. In the upper limbs, the decreasing ordinate order was: men > pre-MP women > post-MP women. After fat-adjustment of the BMC, order in both limbs was: men > pre-MP women > post-MP women. Parallelism of the curves was maintained in all cases. LM had a larger independent influence on these results than FM, body weight, or age. The parallelism of the curves supports the idea that a common biomechanical control of bones by muscles occurs in humans. Results suggest that sex-hormone-associated differences in DXA-assessed muscle-bone proportionality in humans could vary according to the region studied. This could be related to the different weight-bearing nature of the musculoskeletal structures studied. Besides the obvious anthropometric associations, FM would exert a mechanical effect as a component of body weight, evident in the lower limbs, while muscle contractions would induce a more significant, dynamical effect in both lower and upper limbs. Muscles seem to exert a larger influence than FM, body weight and age on BMC in the whole body and lower limbs, regardless of the gender and reproductive status of the individual. The muscle-bone relationships studied may provide a rationale for a future differential diagnosis between disuse-related and other types of osteopenia.