Objective: Analysis of the relationship between adiponectin, interleukin-18 (IL-18) and ghrelin and bone mineral density (BMD), in a group of women that had undergone a gastric- bypass for morbid obesity a year before.
Methods: Forty-one morbidly obese patients aged 46 +/- 9 years and with an initial body mass index of 49.5 +/- 7.6 were included in the study and a gastric by-pass operation was performed in all of them. Anthropometric variables, body composition measured with dual energy X-ray absorptiometry (DEXA) and plasma concentrations of parathormone (PTH), 25(OH) vitamin D, insulin growth factor (IGF-I), adiponectin, IL-18 and ghrelin were determined before and a year after surgery. BMD was evaluated with DEXA 12 months after bariatric surgery.
Results: A year after surgery 36.2% of inicial body weight was lost and this was associated with an improvement of the inflammatory profile reflected by a significant reduction of IL-18 and a increase of adiponectin plasma concentrations. In the univariate analysis BMD inversely correlated with age (r = -0.287, p = 0.008) and with lean mass (r = 0.318, p = 0.043) but not with adiponectin, IL-18 and ghrelin concentrations. PTH showed a positive correlation with weight (r = 0.362, p = 0.03), lean mass (r = 0.372, p = 0.039), and a negative association with plasma concentrations of calcium (r = -0.48, p = 0.003) and 25(OH) vitamin D (r = -0.44, p = 0.014). Plasma 25(OH) vitamin D correlated negatively with the sum of fat mass and lean mass measured with DEXA (r = -0.210, p = 0.043). In the multiple regression analysis BMD remained associated only with lean mass (beta = 0.193, p = 0.016).
Conclusions: Our study does not support the existance of a direct effect of adipose tissue on bone metabolism through the secretion of adiponectin. The absence of association between inflammatory cytokine IL-18 and ghrelin with BMD also argues against their implication in bone regulation.