Gender differences in plasma ghrelin and its relations to body composition and bone - an opposite-sex twin study.
BACKGROUND
Ghrelin, a peptide hormone that plays a role in the regulation of appetite and body adiposity, may also play a role in bone metabolism.


OBJECTIVE
We used the opposite-sex twin model to study associations of plasma ghrelin levels with measures of bone mass and body composition, and determine how such associations were influenced by gender and age.


METHODS
We measured total plasma ghrelin by radioimmunoassay (RIA) and bone mass/body composition parameters by dual energy X-ray absorptiometry in 79 pairs of opposite sex twins (n = 158 subjects). To examine the effect of age, the study population was divided by median age into two groups: under 51.2 years (38 pairs) and over 51.2 years (41 pairs).


RESULTS
Women had higher plasma ghrelin levels than men (median 1063 vs. 869 ng/l, P < 0.01). Age was a significant predictor of plasma ghrelin levels after adjustment for gender, fat mass and body size. In the older age group, plasma ghrelin levels were inversely associated with fat mass measures in men and women, but there were gender differences in the nature of these associations. In women, plasma ghrelin correlated inversely with body mass index (BMI, r = -0.32), total fat mass (r = -0.30) and fat mass/lean mass ratio (r = -0.42), whereas in men associations with abdominal fat mass (r = -0.31) and fat distribution index (r = -0.33) were observed. Plasma ghrelin was associated with alcohol consumption in older men and women. In the obese subgroup (BMI > 30) no significant gender differences in plasma ghrelin were found. Plasma ghrelin levels were not significantly associated with bone mineral density (BMD) generally, except for hip BMD in younger women (r = -0.39).


CONCLUSIONS
Plasma ghrelin levels are associated with age, gender, alcohol intake and fat mass measures but only weakly to bone mass measures.
Makovey
Joanna
J
Institute of Bone and Joint Research, Kolling Institute, Royal North Shore Hospital, University of Sydney, Sydney, Australia. jmakovey@med.usyd.edu.au
Naganathan
Vasi
V
Seibel
Markus
M
Sambrook
Philip
P
D015502:Absorptiometry, Photon; D050154:Adiposity; D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000428:Alcohol Drinking; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology*; D005260:Female; D054439:Ghrelin; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010384:Pelvic Bones / Q000503:physiopathology; D036361:Peptide Hormones / Q000097:blood*; D012044:Regression Analysis; D012727:Sex Characteristics; D014429:Twins, Dizygotic / Q000097:blood* / Q000502:physiology
D054439:Ghrelin; D036361:Peptide Hormones