A putative causal relationship between vitamin D status and glucose metabolism and a direct effect of vitamin D on cardiac autonomic function (CAF) have been suggested. We hypothesized that vitamin D binding protein (DBP), as a transporter of vitamin D, might also influence CAF and the overall metabolic risk. The present study aims to assess the relationship between DBP and CAF and metabolic status in a high-risk population with prediabetes. A total of 174 subjects (mean age 49.1±12.9 years, mean body mass index 30.2±6.2 kg/m2) were divided into 2 groups according to glucose tolerance: 48 with normal glucose tolerance and 126 with prediabetes. Glucose tolerance was assessed during oral glucose tolerance test, applying 2006 World Health Organization criteria. Fasting and postload glucose and immunoreactive insulin were measured (homeostatic model assessment of insulin resistance and homeostatic model assessment of β-cell function were calculated). Anthropometric indexes, blood pressure, hemoglobin A1c, creatinine, lipids, high-sensitivity C-reactive protein, total 25-hydroxyvitamin D, DBP (free 25-hydroxyvitamin D was calculated), and intact parathormone were measured. Body composition was estimated by impedance analysis (InBody 720), whereas tissue advanced glycation end products were assessed by skin autofluorescence (AGE Reader, DiagnOptics, the Netherlands). CAF was evaluated by АNX-3.0 system, applying standard autonomic tests. DBP was found to be elevated in women, as well as in the presence of cardiac autonomic dysfunction and metabolic syndrome. DBP was related to parasympathetic activity in both sexes and in prediabetes; to body fat in women and in prediabetes; and to age and high-density lipoprotein cholesterol in men. Vitamin D deficiency was established in 40.8% of the studied cohort. These results support the hypothesis that DBP is associated with CAF and some metabolic parameters in prediabetes.

中文翻译：

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维生素D结合蛋白与糖尿病前期心脏自主神经功能和代谢状态有关

已经提出维生素 D 状态与葡萄糖代谢之间的推定因果关系以及维生素 D 对心脏自主神经功能 (CAF) 的直接影响。我们假设维生素 D 结合蛋白 (DBP) 作为维生素 D 的转运蛋白，也可能影响 CAF 和整体代谢风险。本研究旨在评估糖尿病前期高危人群中 DBP 和 CAF 与代谢状态之间的关系。共有 174 名受试者（平均年龄 49.1±12.9 岁，平均体重指数 30.2±6.2 kg/m2）根据葡萄糖耐量分为 2 组：48 名葡萄糖耐量正常，126 名糖尿病前期。在口服葡萄糖耐量试验期间评估葡萄糖耐量，应用 2006 年世界卫生组织标准。测量空腹和负荷后葡萄糖和免疫反应性胰岛素（计算胰岛素抵抗的稳态模型评估和 β 细胞功能的稳态模型评估）。测量人体测量指标、血压、血红蛋白 A1c、肌酐、血脂、高敏 C 反应蛋白、总 25-羟基维生素 D、DBP（计算游离 25-羟基维生素 D）和完整的甲状旁腺激素。通过阻抗分析（InBody 720）评估身体成分，而通过皮肤自发荧光（AGE Reader，DiagnOptics，荷兰）评估组织晚期糖基化终产物。CAF 由 АNX-3.0 系统评估，应用标准自主测试。发现女性以及存在心脏自主神经功能障碍和代谢综合征的 DBP 升高。DBP 与两性和糖尿病前期的副交感神经活动有关；女性和糖尿病前期的体脂；以及男性的年龄和高密度脂蛋白胆固醇。40.8% 的研究队列中存在维生素 D 缺乏症。这些结果支持 DBP 与 CAF 和糖尿病前期的一些代谢参数相关的假设。