The adipokine tartrate-resistant acid phosphatase 5a in serum correlates to adipose tissue expansion in obesity

Purpose: Tartrate-resistant acid phosphatase (TRAP) exists as two isoforms, 5a and 5b. TRAP 5a is elevated in adipose tissue of obese women, interacts with pre-adipocytes and is linked to insulin-sensitive hyperplastic obesity when overexpressed in mice. The aim of this study was to investigate the relation between serum TRAP 5a, adiposity indices and metabolic syndrome risk markers in lean and obese women, using a newly developed TRAP 5a-specific ELISA.
Materials and methods: A TRAP 5a sandwich ELISA was optimized using TRAP 5a-specific monoclonal antibodies and tested in sera of healthy males. TRAP 5a levels were quantitated in sera from healthy males and lean and obese women.
Results: Serum TRAP 5a protein levels were lower in obese women in comparison with lean. In obese, but not in lean women, serum TRAP 5a correlated positively to % fat mass, BMI, waist- and hip circumference, waist-to-hip ratio and PAI, while no correlations to serum leptin, HOMA, glucose, insulin, FFA, HDL, TG, APO-A1 and APO-B were observed.
Conclusions: TRAP 5a serum levels correlated positively to anthropometric obesity parameters but not to metabolic syndrome risk factors, indicating that serum TRAP 5a is associated with pathological adipose tissue expansion.

研究目的：酒石酸抗性酸性磷酸酶（Tartrate-resistant acid phosphatase, TRAP）存在5a和5b两种同工型。TRAP 5a在肥胖女性的脂肪组织中表达升高，可与前脂肪细胞相互作用，在小鼠体内过表达时与胰岛素敏感性增生型肥胖存在关联。本研究旨在采用新开发的TRAP 5a特异性酶联免疫吸附测定（ELISA）法，探究瘦体型与肥胖女性血清TRAP 5a水平、肥胖指标及代谢综合征风险标志物之间的关联。
材料与方法：本研究使用TRAP 5a特异性单克隆抗体优化了TRAP 5a夹心ELISA法，并在健康男性血清中完成了方法学验证。对健康男性、瘦体型及肥胖女性的血清样本进行了TRAP 5a水平定量检测。
研究结果：与瘦体型女性相比，肥胖女性的血清TRAP 5a蛋白水平更低。在肥胖女性（而非瘦体型女性）中，血清TRAP 5a水平与体脂百分比、体重指数（BMI）、腰围、臀围、腰臀比及PAI呈正相关；未观察到其与血清瘦素、稳态模型评估（HOMA）、葡萄糖、胰岛素、游离脂肪酸（FFA）、高密度脂蛋白（HDL）、甘油三酯（TG）、载脂蛋白A1（APO-A1）及载脂蛋白B（APO-B）存在相关性。
结论：血清TRAP 5a水平与人体测量学肥胖相关参数呈正相关，但与代谢综合征风险因子无显著关联，提示血清TRAP 5a与病理性脂肪组织扩张存在相关性。