Misawa Sonoko, Kuwabara Satoshi, Ogawara Kazue, Kitano Yukiko, Yagui Kazuo, Hattori Takamichi
Department of Neurology, Chiba University School of Medicine, 1-8-1 Inohana, Chuo-ku, Chiba 260-8670, Japan.
Clin Neurophysiol. 2004 Nov;115(11):2525-9. doi: 10.1016/j.clinph.2004.06.008.
To investigate the effects of hyperglycemia on axonal excitability in human diabetics. Diabetic nerve dysfunction is partly associated with the altered polyol pathway and Na+-K+ ATPase activity, probably resulting in a decrease in the trans-axonal Na+ gradient and reduced nodal Na+ currents.
Threshold tracking was used to measure the relative refractory periods (RPs) of median motor axons in 58 diabetic patients, 45 normal subjects, and 12 patients with non-diabetic axonal neuropathy. In diabetic patients, the relationship of RPs with hemoglobin A1c (HbA1c) levels was analyzed.
The mean RP was similar for diabetics and normal controls as a group, but was longer in patients with non-diabetic neuropathy than in normal controls (P=0.02). Diabetic patients with good glycemic control (HbA1c levels <7%) had longer RPs than patients with poorer glycemic control and normal controls (P=0.01). RP was longest at the HbA1c level of 6%, gradually decreasing and reaching a plateau at the HbA1c level of 8-9%.
Hyperglycemia shortens RPs, possibly because metabolic abnormalities lead to reduced nodal Na+ currents, and thereby to a lower inactivation of Na+ channels when generating an action potential.
RP measurements could provide new insights into the ionic pathophysiology of human diabetic neuropathy.
研究高血糖对糖尿病患者轴突兴奋性的影响。糖尿病神经功能障碍部分与多元醇途径改变及钠钾ATP酶活性有关，这可能导致轴突跨膜钠梯度降低和结区钠电流减少。
采用阈值跟踪法测量58例糖尿病患者、45例正常受试者和12例非糖尿病性轴索性神经病患者正中运动轴突的相对不应期（RP）。分析糖尿病患者中RP与糖化血红蛋白（HbA1c）水平的关系。
糖尿病患者组和正常对照组的平均RP相似，但非糖尿病性神经病患者的RP比正常对照组更长（P = 0.02）。血糖控制良好（HbA1c水平<7%）的糖尿病患者的RP比血糖控制较差的患者和正常对照组更长（P = 0.01）。RP在HbA1c水平为6%时最长，随后逐渐下降，在HbA1c水平为8 - 9%时达到平台期。
高血糖会缩短RP，可能是因为代谢异常导致结区钠电流减少，从而在产生动作电位时钠通道失活降低。
RP测量可为人类糖尿病性神经病的离子病理生理学提供新的见解。
