汗腺神經支配之定量病理學研究

Abstract

於糖尿病周邊神經病變中，排汗功能障礙是使病人足部傷口進一步形成潰瘍的重要因素，然而尚未有報告明確說明汗腺神經支配與血糖控制的關聯。過去對於自主神經系統之研究以功能性評估為主，只有少數文獻證明自主神經病變之病理變化，亦即節後神經元之退化。本研究利用下肢末端之皮膚切片，以免疫染色技術標定蛋白基因產物 9.5 (protein gene product 9.5, PGP9.5)，並佐以剛果紅 (Congo-red) 組織染色界定汗腺範圍，研究汗腺神經支配與臨床自主神經病變症狀之關連。汗腺神經支配指數 (sweat gland innervation index, SGII) 係以電腦化的型態測量學方法分析神經與汗腺之面積 (computerized area-based morphometric analysis)，並將神經所占面積除以汗腺所占面積而得之百分比。參與本次研究之 42 位第二型糖尿病患 (男性 26 位，女性 16 位，年齡 56.64 ± 12.67 歲)，皆有對稱性之多發性神經病變，且表皮神經密度 (intraepidermal nerve fiber density, IENF density) 明顯減少 (0.82 ± 0.18 纖維/毫米)。於對照組之汗腺周圍，在光學顯微鏡及電子顯微鏡下皆可觀察到被 PGP9.5 所標定之神經纖維纏繞，於糖尿病患之汗腺周圍，纏繞的神經纖維則顯著減少甚至完全消失，顯示其支配汗腺之神經已退化。糖尿病人之 SGII 顯著少於性別與年齡相仿之對照組 (2.54% ± 1.87% vs. 4.68% vs. 1.51%, p < 0.0001)，42.86% 糖尿病人 SGII 低於正常值之第 5 百分位數。以複迴歸分析發現 SGII 與醣化血色素 (glycated hemoglobin, HbA1c) 有顯著相關 (p = 0.011)。有足部排汗功能障礙之病患，其 SGII 顯著低於排汗功能正常者 (0.82% ± 0.69% vs. 3.00% ± 1.81%, p = 0.0011)。以深呼吸時的心跳速率變異數 (heart rate variability during deep breathing) 為檢查方法，有心臟自主神經病變 (cardiac autonomic neuropathy, CAN) 的患者，其 SGII 也較心跳速率變異數正常的患者為低 (p = 0.0016)。由本實驗結果可知，汗腺神經退化是糖尿病周邊神經病變的顯著症狀，且與血糖控制具有相關性。皮膚切片為同時評估表皮與汗腺神經支配的簡便診斷工具。

In diabetic neuropathy, sudomotor dysfunction predisposing patients to skin wounds is a risk factor for foot ulceration. The relationship of sudomotor innervation and glycemic control, however, remains obscured. Previous assessments of the autonomic nervous system mainly depended on functional tests, and only a few studies documented the pathology of autonomic neuropathy, i.e., postganglionic nerve degeneration. To address these issues, we investigated sweat gland innervation and its clinical significance by performing skin biopsies of the distal leg and immunostaining of nerve fibers with anti-protein gene product 9.5 (PGP9.5) and counterstaining of sweat glands with Congo-red. A computerized area-based morphometric analysis was carried out to quantify the sweat gland innervation index (SGII), which was defined as the area of nerve fibers normalized to the area of sweat glands. We examined 42 type 2 diabetic patients (including 26 males and 16 females who were 56.64 ± 12.67 years old) with symmetrical length-dependent sensory neuropathy and reduced intraepidermal nerve fiber (IENF) density (0.82 ± 0.18 fibers/mm). In control subjects, PGP9.5(+) nerve terminals surrounded secretory coils of the sweat glands at the light- and electron-microscopic level. But these periglandular nerve terminals were either absent or markedly reduced in diabetic patients, indicating sudomotor nerve degeneration. Diabetic patients had lower values of the SGII compared to age- and gender-matched controls (2.54% ± 1.87% vs. 4.68% ± 1.51%, p < 0.0001), and the SGII was reduced in 42.86% of these patients. The SGII was correlated with glycated hemoglobin (HbA1C; p = 0.011) in a multiple linear-regression model. The SGII was lower in patients with anhidrosis of the feet compared to those with normal sweating of the feet (0.82% ± 0.69% vs. 3.00% ± 1.81%, p = 0.0011). Patients with cardiac autonomic neuropathy (CAN) according to a reduced heart rate variability during deep breathing had lower SGII values than those without CAN (p = 0.0016). In conclusion, sudomotor denervation is a significant presentation of diabetic neuropathy, and the SGII was associated with HbA1C. A skin biopsy offers a convenient assessment of sudomotor innervation and epidermal innervation.