Aims: This study was designed to investigate the interrelationships between three bone-derived factors [serum osteocalcin (OCN), fibroblast growth factor (FGF) 23, and neutrophil gelatinase-associated lipocalin (NGAL) levels] and body fat content and distribution, in order to reveal the potential endocrine function of bone in the development of obesity.
Methods: We recruited 1179 people (aged 59.5 ± 6.2 years) from communities in Shanghai. Serum OCN levels were determined using an electrochemiluminescence immunoassay, and thus serum FGF-23 and NGAL levels were determined using a sandwich enzyme-linked immunosorbent assay. The abdominal fat distribution, including visceral fat area (VFA), was assessed by magnetic resonance imaging. Visceral obesity was defined as a VFA ≥ 80 cm2.
Results: Serum OCN levels were inversely correlated with body fat parameters, while FGF-23 and NGAL were positively correlated (P < 0.05). After adjusting for confounders, waist circumference (W) and VFA had a closer relationship with serum OCN, FGF-23, and NGAL levels than body mass index (BMI) and body fat percentage (fat%, all P < 0.05). The risk of visceral obesity significantly increased with higher FGF-23 and/or NGAL levels, as well as with reduced OCN levels (all P < 0.05). In addition, serum OCN, FGF-23, and NGAL levels were independently associated with visceral obesity (all P < 0.01). The relationships persisted among subjects with normal glucose tolerance or subjects with hyperglycaemia (both P < 0.05).
Conclusions: Compared to overall adiposity, visceral adiposity was more closely related to serum OCN, FGF-23 and NGAL levels. There was no interaction among the relationship of three bone-derived factors with visceral obesity, which suggested the independent relationship of endocrine function of skeleton with body fat.
Y. Bao: None. Y. Xu: None. X. Ma: None. X. Pan: None. X. He: None. Y. Xiao: None.