Excessive occupational exposure to Manganese (Mn) has been associated with clinical symptoms resembling idiopathic Parkinson’s disease (IPD), impairing cognitive and motor functions. Several studies point towards an involvement of the brain neurotransmitter system in Mn intoxication, which is hypothesized to be disturbed prior to onset of symptoms. Edited Magnetic Resonance Spectroscopy (MRS) offers the unique possibility to measure γ-amminobutyric acid (GABA) and other neurometabolites in vivo non-invasively in workers exposed to Mn. In addition, the property of Mn as Magnetic Resonance Imaging (MRI) contrast agent may be used to study Mn deposition in the human brain. In this study, using MRI, MRS, personal air sampling at the working place, work history questionnaires, and neurological assessment (UPDRS-III), the effects of chronic Mn exposure on the thalamic GABAergic system was studied in a group of welders (N = 39) with exposure to Mn fumes in a typical occupational setting. Two subgroups of welders with different exposure levels (Low: N = 26; mean air Mn = 0.13 ± 0.1 mg/m³; High: N = 13; mean air Mn = 0.23 ± 0.18 mg/m³), as well as unexposed control workers (N = 22, mean air Mn = 0.002 ± 0.001 mg/m³) were recruited. The group of welders with higher exposure showed a significant increase of thalamic GABA levels by 45% (p < 0.01, F(1,33) = 9.55), as well as significantly worse performance in general motor function (p < 0.01, F(1,33) = 11.35). However, welders with lower exposure did not differ from the controls in GABA levels or motor performance. Further, in welders the thalamic GABA levels were best predicted by past-12-months exposure levels and were influenced by the Mn deposition in the substantia nigra and globus pallidus. Importantly, both thalamic GABA levels and motor function displayed a non-linear pattern of response to Mn exposure, suggesting a threshold effect.

职业性过度接触锰（Mn）与特发性帕金森氏病（IPD）类似的临床症状相关，损害了认知和运动功能。多项研究指出，大脑神经递质系统参与了锰中毒，锰中毒被认为是在症状发作之前受到干扰的。编辑磁共振波谱（MRS）提供了一种独特的可能性，可以无创地在暴露于Mn的工人体内测量γ-氨基丁酸（GABA）和其他神经代谢产物。另外，Mn作为磁共振成像（MRI）造影剂的性质可用于研究人脑中Mn的沉积。在这项研究中，使用MRI，MRS，工作场所的个人空气采样，工作历史问卷和神经系统评估（UPDRS-III），在一组典型的职业环境中，在一组暴露于锰烟气的焊工（N = 39）中，研究了长期锰暴露对丘脑GABA能系统的影响。焊工分为两个小组，具有不同的暴露水平（低：N = 26；平均空气Mn = 0.13±0.1 mg / m³；高：N = 13；平均空气Mn = 0.23±0.18 mg / m ³），以及未暴露的对照工人（N = 22，平均空气Mn = 0.002±0.001 mg / m ^3））被招募。具有较高暴露水平的焊工组显示丘脑GABA水平显着提高了45％（p <0.01，F（1,33）= 9.55），并且在一般运动功能方面的表现也明显较差（p <0.01，F（ 1,33）= 11.35）。但是，较低暴露水平的焊工在GABA水平或运动性能方面与对照组无差异。此外，在焊工中，丘脑中的GABA水平最好通过过去12个月的暴露水平进行预测，并受黑质和苍白球中Mn沉积的影响。重要的是，丘脑的GABA水平和运动功能均表现出对锰暴露的非线性响应模式，表明存在阈值效应。