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Body weight is a significant predictor of bone mass. Hormonal factors such as sex hormones, insulin, leptin and adiponectin are thought to play a role in the mechanisms controlling the association of body weight and fat mass with bone mass. However, contradictory results have been reported for the association between serum adipocytokines and bone mineral density (BMD). We therefore examined whether the serum adipocytokine and ghrelin levels, markers of fat metabolism, are associated with BMD in male adults. For 80 male adults (average age 54·5 ± 6·4 years; average body mass index (BMI) 24·4 ± 2·5 kg/m2), the correlations between serum resistin, leptin, adiponectin and ghrelin levels with BMD were investigated. Among the adipocytokines, serum resistin levels were negatively correlated with lumbar spine BMD ( r =  –0·237, P = 0·05). After adjustment was made for age and BMI, log-transformed serum leptin showed a significant negative correlation with lumbar spine BMD, which was not seen on bivariate analysis ( r =  –0·237, P = 0·039). Femoral neck BMD was marginally associated only with serum adiponectin levels ( r =  –0·226, P = 0·062). In multiple regression analyses, among the adipokines, only resistin was a significant determinant of lumbar spine BMD, although the variance was small ( R2 = 0·256). Serum ghrelin levels were not correlated with the BMD of either body site. Serum resistin level showed a significant negative correlation with lumbar spine BMD, although the variance was small. Further studies are needed to elucidate the role of adipocytokines in bone metabolism. [ABSTRACT FROM AUTHOR]

Osteoporosis is a growing health problem in males as well as in females. Sex hormones and insulin-like growth factor-I (IGF-I) have been shown to be the major determinants in male bone metabolism. Osteoprotegerin (OPG) is a recently identified cytokine that acts as a decoy receptor for the receptor activator of NF-κB ligand (RANKL). OPG and RANKL have been shown to be important regulators of osteoclastogenesis. However, the relationship between the OPG-RANKL system and male bone status in human populations are unclear. Thus, the aim of this study was to investigate the relationship between the OPG-RANKL system and bone mineral metabolism in males.Serum concentrations of OPG, RANKL, oestradiol, total testosterone and IGF-I and bone mineral density (BMD) were measured in 80 Korean males aged 42–70 (mean age, 54·5 year). Enzyme-linked immunosorbent assays were used to determine the serum concentrations of OPG and RANKL. Serum concentrations of oestradiol, total testosterone, IGF-I and bone turnover markers were determined using standard methods. BMD at the lumbar spine and femoral neck were measured by dual energy X-ray absorptiometry.We observed a significant negative correlation between the serum OPG levels and lumbar spine BMD (r =−0·259,P < 0·05) in Spearman correlation analysis. Serum OPG levels and RANKL/OPG ratios were found to be significantly correlated to the serum osteocalcin levels (r =− 0·254,P < 0·05;r = 0·264,P < 0·05) in Spearman correlation analysis. Serum OPG levels were found to be negatively correlated with serum oestradiol levels (r =−0·319,P < 0·01) in Spearman correlation analysis. In addition, a significant positive correlation was found between serum RANKL/OPG ratios and oestradiol levels (r = 0·374,P < 0·001) in Spearman correlation analysis. In contrast, Serum total testosterone and IGF-I levels were not correlated with serum OPG levels or RANKL to OPG ratios in Spearman correlation analysis. In a multiple regression analysis, age, body mass index (BMI), and serum OPG levels were identified as a significant predictor for lumbar spine BMD, and age, BMI, serum OPG and RANKL levels for femoral neck BMD. In another multiple regression analysis, only serum oestradiol level was identified as a significant predictor for serum OPG or RANKL levels. In contrast, Serum total testosterone and IGF-I levels were not correlated with serum OPG or RANKL levels in multiple regression analysis.Our data show that the circulating OPG-RANKL system is associated with bone metabolism in the male populations. Also, our data suggest that OPG and RANKL may be mediators of the effects of oestradiol in male bone metabolism. [ABSTRACT FROM AUTHOR]

Osteoprotegerin (OPG) is a recently identified cytokine that acts as a decoy receptor for the RANK ligand. Moreover, OPG has been shown to be an important inhibitor of osteoclastogenesis in animal models. However, the relationship between circulating OPG levels and female bone status in human populations is unclear. In this study we undertook to investigate the relationship between circulating OPG levels and bone mineral metabolism in healthy women. Our subjects were 287 women aged 37–73 years (mean age 51·5 years). The serum concentrations of OPG were determined by enzyme-linked immunosorbent assay (ELISA). The biochemical markers of bone turnover and FSH were measured using standard methods. Bone mineral densities at the lumbar spine and femoral neck were measured by dual-energy X-ray absorptiometry. Postmenopausal women had a significantly higher mean value of serum OPG than premenopausal women (1358·5 ± 32·5 pg/ml vs. 1228·8 ± 33·3 pg/ml, P < 0·01). Serum OPG levels were positively correlated with age ( r = 0·169, P < 0·01), as were urine deoxypyridinoline levels ( r = 0·133, P < 0·05) and serum FSH levels ( r = 0·187, P < 0·01) in a bivariate correlation analyses. In a multiple regression analysis, only urine calcium excretion was identified as a significant predictor for serum OPG levels. Circulating OPG levels were found to be associated with urine calcium excretion and menopause in healthy women. Our observations suggest that circulating OPG levels reflect an antiresorptive activity in bone, and they are related to endogenous oestrogen levels. [ABSTRACT FROM AUTHOR]