Lutfi Mohamed Faisal, Elhakeem Ramaze Farouke
Department of Physiology, Faculty of Medicine and Health Sciences, Al-Neelain University, Khartoum, Sudan.
PLoS One. 2016 Jul 21;11(7):e0159820. doi: 10.1371/journal.pone.0159820. eCollection 2016.
Previous studies reported increased risk of cardiac events in subjects with fasting blood glucose (FBG) levels lower than the diagnostic threshold of diabetes mellitus. However, whether increased cardiac events in those with upper normal FBG is secondary to the shift of their cardiac sympathovagal balance towards sympathetic predominance is unknown.
To assess the association between FBG levels and cardiac autonomic modulation (CAM) in euglycaemic healthy subjects based on heart rate variability (HRV) derived indices.
The study enrolled 42 healthy young adults. Following sociodemographic and clinical assessment, blood samples were collected to measure FBG levels. Five minutes ECG recordings were performed to all participants to obtain frequency domain HRV measurements, namely the natural logarithm (Ln) of total power (LnTP), very low frequency (LnVLF), low frequency (LnLF) and high frequency (LnHF), low frequency/ high frequency ratio (LnLF/HF), normalized low frequency (LF Norm) and high frequency (HF Norm).
FBG levels correlated positively with LnHF (r = 0.33, P = 0.031) and HF Norm (r = 0.35, P = 0.025) and negatively with LF Norm (r = -0.35, P = 0.025) and LnLF/HF (r = -0.33, P = 0.035). LnHF and HF Norm were significantly decreased in subjects with the lower (4.00 (1.34) ms2/Hz and 33.12 (11.94) n.u) compared to those with the upper FBG quartile (5.64 (1.63) ms2/Hz and 49.43 (17.73) n.u, P = 0.013 and 0.032 respectively). LF Norm and LnLF/HF were significantly increased in subjects with the lower (66.88 (11.94) n.u and 0.73 (0.53)) compared to those with the higher FBG quartile (50.58 (17.83) n.u and 0.03 (0.79), P = 0.032 and 0.038 respectively).
The present study is the first to demonstrate that rise of blood glucose concentration, within physiological range, is associated with higher parasympathetic, but lower sympathetic CAM. Further researches are needed to set out the glycemic threshold beyond which further increase in glucose level readjusts sympathovagal balance towards sympathetic predominance again.
既往研究报道，空腹血糖（FBG）水平低于糖尿病诊断阈值的受试者发生心脏事件的风险增加。然而，FBG处于正常上限的人群发生心脏事件增加是否继发于心交感迷走神经平衡向交感神经优势的转变尚不清楚。
基于心率变异性（HRV）衍生指标，评估血糖正常的健康受试者中FBG水平与心脏自主神经调节（CAM）之间的关联。
本研究纳入了42名健康的年轻成年人。在进行社会人口统计学和临床评估后，采集血样以测量FBG水平。对所有参与者进行5分钟的心电图记录，以获得频域HRV测量值，即总功率的自然对数（LnTP）、极低频（LnVLF）、低频（LnLF）和高频（LnHF）、低频/高频比值（LnLF/HF）、标准化低频（LF Norm）和标准化高频（HF Norm）。
FBG水平与LnHF（r = 0.33，P = 0.031）和HF Norm（r = 0.35，P = 0.025）呈正相关，与LF Norm（r = -0.35，P = 0.025）和LnLF/HF（r = -0.33，P = 0.035）呈负相关。与FBG处于上四分位数的受试者相比，FBG处于下四分位数的受试者（4.00（1.34）ms2 / Hz和33.12（11.94）n.u）的LnHF和HF Norm显著降低（分别为5.64（1.63）ms2 / Hz和49.43（17.73）n.u，P = 0.013和0.032）。与FBG处于较高四分位数的受试者相比，FBG处于较低四分位数的受试者（66.88（11.94）n.u和0.73（0.53）） 的LF Norm和LnLF/HF显著升高（分别为50.58（17.83）n.u和0.03（0.79），P = 0.032和0.038）。
本研究首次表明，在生理范围内血糖浓度升高与较高的副交感神经活性但较低的交感神经CAM相关。需要进一步的研究来确定血糖阈值，超过该阈值血糖水平的进一步升高会再次使交感迷走神经平衡重新调整为交感神经优势。
