The relationship of serum osteocalcin concentration to insulin secretion, sensitivity, and disposal with hypocaloric diet and resistance training.
BACKGROUND
Bone has recently been described as exhibiting properties of an endocrine organ by producing osteocalcin that increases insulin sensitivity and secretion in animal models.


OBJECTIVE
We aimed to evaluate circulating osteocalcin in association with insulin sensitivity and insulin secretion in three different studies in nondiabetic subjects: one cross-sectional study in 149 men (using minimal model), and two longitudinal studies in two independent groups (one formed by 26 women, and the other by 9 men and 11 women), after a mean of 7.3 and 16.8% weight loss, and after a mean of 8.7% weight loss plus regular exercise.


RESULTS
In the cross-sectional study, circulating osteocalcin was associated with insulin sensitivity, mainly in lean subjects, and with insulin secretion (only in lean subjects). A mean of 16.8%, but not 7.3% weight loss, led to significant increases in circulating osteocalcin. However, a mean of 8.7% weight loss plus regular exercise led to the more pronounced effects on the serum osteocalcin concentration, which increased in parallel to reduced visceral fat mass, unchanged thigh muscle mass, and increased leg strength and force. The postintervention serum levels of osteocalcin were associated with both insulin sensitivity (r = 0.49; P = 0.03) and fasting triglycerides (r = -0.54; P = 0.01). The change in visceral fat was the parameter that best predicted the change in serum osteocalcin, once age, body mass index, and insulin sensitivity changes were controlled for (P = 0.002).


CONCLUSIONS
Circulating osteocalcin could mediate the role of bone as an endocrine organ in humans.
Department of Diabetes, Institut d'Investigació Biomédica de Girona, CIBER Fisiopatología de la Obesidad y Nutrición CB06/03/010, 17007 Girona, Catalonia, Spain. uden.jmfernandezreal@htrueta.scs.es
Jose Manuel
JM
Fernández-Real
Mikel
M
Izquierdo
Francisco
F
Ortega
Esteban
E
Gorostiaga
Javier
J
Gómez-Ambrosi
Jose Maria
JM
Moreno-Navarrete
Gema
G
Frühbeck
Cristina
C
Martínez
Fernando
F
Idoate
Javier
J
Salvador
Lluis
L
Forga
Wifredo
W
Ricart
Javier
J
Ibañez
D000328:Adult; D000368:Aged; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D002149:Energy Intake; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D000078790:Insulin Secretion; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood*; D055070:Resistance Training; D015431:Weight Loss
D007328:Insulin; D015675:Osteocalcin