Suzuki E, Yasuda K, Yasuda K, Miyazaki S, Takeda N, Inouye H, Omawari N, Miura K
Department of Internal Medicine, Gifu University, School of Medicine, Japan.
J Lab Clin Med. 1994 Nov;124(5):627-37.
To define the existence of intracellular hydration caused by metabolic derangements in the excised sciatic nerves of diabetic rats quantitatively, relaxation times (T1, T2) and fraction of intracellular water content were measured with 1H-nuclear magnetic resonance (NMR) spectroscopy in normal rats (control group, n = 10), streptozotocin (STZ)-induced (50 mg/kg, i.v.) diabetic rats (DM group, n = 10), STZ-induced diabetic rats treated with an aldose reductase inhibitor (ARI, Epalrestat, 100 mg/kg) (ARI group, n = 8), and STZ-induced diabetic rats treated with insulin (insulin group, n = 4). For selective measurement of intracellular relaxation times, the inversion recovery (IR) method for conventional T1 and Carr-Purcell-Meiboom-Gill method for T2 were used with an aqueous chemical shift reagent, 10 mmol/L dysprosium triethylenetetramine-N,N,N',N",N"',N"'-hexaacetic acid, resulting in distinct separation of intracellular (Schwann cell, axon, endothelial cell, and pericyte) and extracellular waters under the isotonic condition of the rat sciatic nerves. Furthermore, a new method of driven-equilibrium single-pulse observation of T1 (DESPOT) was used for rapid measurement of T1 for the purpose of clinical application on magnetic resonance imaging (MRI). T1 values measured by the DESPOT and IR methods were significantly correlated (p < 0.001). Total and intracellular water contents, sorbitol contents, and relaxation times of the sciatic nerve taken from the DM group were significantly elevated (p < 0.01), while myoinositol (p < 0.01) and extracellular water (p < 0.05) contents were significantly decreased as compared with the control group. Both insulin and ARI treatments significantly improved relaxation times as compared with those in the DM group (p < 0.05-0.01). Relaxation times correlated positively with total water (T1, p < 0.05-0.01; T2, p < 0.01), intracellular water (T1, p < 0.001; T2, p < 0.001), and sorbitol (T1, p < 0.001; T2, p < 0.001) contents of the excised nerve. Sorbitol content correlated positively with total and intracellular water contents (p < 0.01) but negatively with extracellular water content (p < 0.05). These findings indicated that sorbitol itself and/or secondary sodium accumulation caused by an increase in sorbitol may be a major contributor to the increase in intracellular hydration and prolonged relaxation times associated with hyperglycemia, which are reversible with insulin or ARI treatment. It was also suggested that rapid T1 measurement would provide new insights into the pathogenesis of human diabetic neuropathy as a non-invasive evaluation method on MRI.
为了定量确定糖尿病大鼠坐骨神经中代谢紊乱引起的细胞内水合作用的存在，采用氢核磁共振（NMR）光谱法测量了正常大鼠（对照组，n = 10）、链脲佐菌素（STZ）诱导（50 mg/kg，静脉注射）的糖尿病大鼠（糖尿病组，n = 10）、用醛糖还原酶抑制剂（ARI，依帕司他，100 mg/kg）治疗的STZ诱导糖尿病大鼠（ARI组，n = 8）以及用胰岛素治疗的STZ诱导糖尿病大鼠（胰岛素组，n = 4）的弛豫时间（T1、T2）和细胞内水含量分数。为了选择性测量细胞内弛豫时间，使用传统T1的反转恢复（IR）方法和T2的Carr-Purcell-Meiboom-Gill方法，并使用10 mmol/L三乙烯四胺-N，N，N'，N"，N'"，N'"-六乙酸镝这种水性化学位移试剂，在大鼠坐骨神经等渗条件下实现细胞内（雪旺细胞、轴突、内皮细胞和周细胞）和细胞外水的明显分离。此外，为了在磁共振成像（MRI）上进行临床应用而快速测量T1（驱动平衡单脉冲T1观测法，DESPOT），采用了一种新方法。通过DESPOT和IR方法测量的T1值显著相关（p < 0.001）。与对照组相比，糖尿病组坐骨神经的总水和细胞内水含量、山梨醇含量以及弛豫时间显著升高（p < 0.01），而肌醇（p < 0.01）和细胞外水（p < 0.05）含量显著降低。与糖尿病组相比，胰岛素和ARI治疗均显著改善了弛豫时间（p < 0.05 - 0.01）。弛豫时间与切除神经的总水（T1，p < 0.05 - 0.01；T2，p < 0.01）、细胞内水（T1，p < 0.001；T2，p < 0.001）和山梨醇（T1，p < 0.001；T2，p < 0.001）含量呈正相关。山梨醇含量与总水和细胞内水含量呈正相关（p < 0.01），但与细胞外水含量呈负相关（p < 0.05）。这些发现表明，山梨醇本身和/或山梨醇增加引起的继发性钠积累可能是细胞内水合作用增加以及与高血糖相关的弛豫时间延长的主要原因，胰岛素或ARI治疗可使其逆转。还表明，快速T1测量作为MRI上的一种非侵入性评估方法，将为人类糖尿病神经病变的发病机制提供新的见解。
