Combined influence of low mineral and lean body massess (DXA) on the propensity to “osteoporotic” fractures after menopause

RICARDO FRANCISCO CAPOZZA; CARLOS CURE CURE; GUSTAVO ROBERTO COINTRY; MARGARITA META; PABLO CURE RAMIREZ; JOERN RITTWEGER; JOSÉ LUIS FERRETTI

Colonia (Alemania)

Workshop; VI INTERNATIONAL WORKSHOP FOR MUSCULOSKELETAL & NEURONAL INTERACTIONS; 2008

International Society of Musculoskeletal & Neuronal Interactions (ISMNI)

Combined influence of low mineral and lean body massess (DXA) on the propensity to “osteoporotic” fractures after menopause      In whole-body studies with DXA [Ferretti; Bone 22:683,1998, n = 1,450] we had shown that the densitometric mineral mass, either crude (BMC) or statistically adjusted to fat mass (FA-BMC) in order to avoid any fat interference with its determination, correlated linearly with the lean mass (LM) showing similar slopes but decreasing intercepts in the order: pre-MP women > men > post-MP women > children. This evidenced 1. the homogeneous control of bone status by muscle strength in the species through the bone mechanostat, and 2. the interaction of sex hormones with that regulation. Now we aim to expand that evidence by studying a large sample of 3,000 normal, Caucasic and Hispanic Columbian men and pre- and post-MP women, including also determinations of the same variables in the upper and lower limbs.    In all the studied regions the slopes of the BMC or FA-BMC vs LM relationships were always parallel. However, interesting region-related differences were found between the intercepts of the curves. In the whole body the crude-BMC/ LM relationships showed the same intercept differences as previously observed (pre-MP women > men > post-MP women). In the lower limbs these differences were less significant and showed the order: pre-MP women > men = post-MP women. In the upper limbs they showed very clearly the decreasing order: men > pre-MP women > post-MP women. After fat-adjustment of the BMC, the order of the intercept magnitude in the limbs was always men > pre-MP women > post-MP women, the differences being much more significant for the upper than the lower limbs. In the upper limbs the slopes of the correlation curves between the FA-BMC and the LM were very low and statistically nonsignificant.    Assuming that LM is proportional to muscle mass, and that the fat adjustment of the BMC renders this variable a more reliable indicator of the bone status than its crude values, results suggest that the sex-hormone-induced differences in the DXA-assessed muscle-bone proportionality in humans would vary noticeably according to the region studied, perhaps in connection with the weight-bearing nature of the musculoskeletal structures in question.