Correlations between serum concentration of three bone-derived factors and obesity and visceral fat accumulation in a cohort of middle aged men and women

Yiting Xu,Yuqian Bao,Yunfeng Xiao,Xiaoping Pan,Xingxing He,Xiaojing Ma

doi:10.1186/s12933-018-0786-9

Abstract

BackgroundThe aim of this study was 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.MethodsWe recruited 1179 people (aged 59.5 ± 6.2 years) from communities in Shanghai. Serum OCN levels were determined using an electrochemiluminescence immunoassay. Serum FGF23 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.ResultsSerum OCN levels were inversely correlated with body fat parameters, while FGF23 and NGAL were positively correlated (P < 0.05). After adjusting for confounders, waist circumference (W) and VFA had a closer relationship with serum OCN, FGF23, 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 FGF23 and/or NGAL levels, as well as with reduced OCN levels (all P < 0.05). In addition, serum OCN, FGF23, 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).ConclusionsCompared to the indicators of overall adiposity such as BMI or fat%, visceral adiposity indicators (W or VFA) were more closely related to serum OCN, FGF23 and NGAL levels. There was no interaction among the relationship of three bone-derived factors with visceral obesity, which revealed the independent relationship of endocrine function of skeleton with body fat.

Highlights

Osteoblasts, comprising 5% of all bone cells, are responsible for the subsequent replacement with new bone after removal of old or damaged bone
Lower serum OCN levels were observed in subjects with visceral obesity compared with subjects without this phenotype [18.3 (14.9–22.5) ng/mL versus 21.2 (16.8–26.1) ng/mL, P < 0.01], while serum FGF23 and neutrophil gelatinase-associated lipocalin (NGAL) levels were significantly elevated in subjects with visceral obesity [33.3 (26.7–40.0) pg/mL versus 36.3 (29.3–44.2) pg/mL, P < 0.01; 41.1 (29.6–55.9) ng/mL versus 50.0 (35.4–66.9) ng/mL, P < 0.01, respectively]
In conclusion, serum OCN levels were inversely correlated with body fat parameters, while serum FGF23 and NGAL levels were positively correlated

Summary

Introduction

Osteoblasts, comprising 5% of all bone cells, are responsible for the subsequent replacement with new bone after removal of old or damaged bone. Based on evidence that has accumulated in the past decade, biologically active factors which have endocrine function are secreted by osteoblasts and osteocytes, including osteocalcin (OCN) and fibroblast growth factor (FGF) 23 [2, 3]. Bone has recently been reported to be the predominant organ expressing lipocalin-2 (LCN-2), referred to neutrophil gelatinase-associated lipocalin (NGAL), secreted by osteoblasts and with at least tenfold higher expression levels in bone than in adipose tissue [4]. The aim of this study was 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

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