School of Health Sciences, Purdue University, West Lafayette, IN, United States.
School of Health Sciences, Purdue University, West Lafayette, IN, United States; Department of Public Health, Purdue University, West Lafayette, IN, United States.
Neurotoxicology. 2024 Sep;104:45-55. doi: 10.1016/j.neuro.2024.07.007. Epub 2024 Jul 11.
Inhalation of welding fumes can cause metal accumulation in the brain, leading to Parkinsonian-like symptoms. Metal accumulation and altered neurochemical profiles have been observed using magnetic resonance imaging (MRI) in highly exposed welders, being associated with decreased motor function and cognition. While MRI is impractical to use as a health risk assessment tool in occupational settings, toenail metal levels are easier to assess and have been demonstrated to reflect an exposure window of 7-12 months in the past. Yet, it is unclear whether toenail metal levels are associated with brain metal levels or changes in metabolism, which are the root of potential health concerns. This study investigates whether toenail manganese (Mn) and iron (Fe) levels, assessed at several time points, correlate with brain Mn and Fe levels, measured by MRI, as well as brain GABA, glutamate (Glu), and glutathione (GSH) levels, measured by Magnetic Resonance Spectroscopy (MRS), in seventeen Mn-exposed welders. Quantitative T1 and R2* MRI maps of the whole brain, along with GABA, Glu, and GSH MRS measurements from the thalamus and cerebellum were acquired at baseline (T0). Toenail clippings were collected at T0 and every three months after the MRI for a year to account for different exposure periods being reflected by toenail clippings and MRI. Spearman correlations of toenail metal levels were run against brain metal and metabolite levels, but no significant associations were found for Mn at any timepoint. Cerebellar GSH positively correlated with toenail Fe clipped twelve months after the MRI (p = 0.05), suggesting an association with Fe exposure at the time of the MRI. Neither thalamic GABA nor Glu correlated with toenail Fe levels. In conclusion, this study cannot support toenail Mn as a proxy for brain Mn levels or metabolic changes, while toenail Fe appears linked to brain metabolic alterations, underscoring the importance of considering other metals, including Fe, in studying Mn neurotoxicity.
吸入焊接烟尘会导致金属在大脑中积累，从而引发类似帕金森的症状。在高度暴露于焊接烟尘的焊工中，磁共振成像（MRI）观察到金属积累和神经化学特征的改变，与运动功能和认知能力下降有关。虽然 MRI 作为职业环境中的健康风险评估工具并不实用，但指甲金属水平更容易评估，并且已经证明可以反映过去 7-12 个月的暴露窗口。然而，指甲金属水平是否与大脑金属水平或代谢变化有关，这些都是潜在健康问题的根源，目前还不清楚。本研究调查了在 17 名锰暴露焊工中，多次评估的指甲锰（Mn）和铁（Fe）水平是否与 MRI 测量的大脑 Mn 和 Fe 水平以及磁共振波谱（MRS）测量的大脑 GABA、谷氨酸（Glu）和谷胱甘肽（GSH）水平相关。在基线（T0）时获得了整个大脑的定量 T1 和 R2* MRI 图谱，以及来自丘脑和小脑的 GABA、Glu 和 GSH MRS 测量值。在 MRI 后每三个月收集一次指甲碎屑，持续一年，以反映指甲碎屑和 MRI 所反映的不同暴露期。对指甲金属水平与大脑金属和代谢物水平进行了 Spearman 相关性分析，但在任何时间点都未发现 Mn 有显著相关性。小脑 GSH 与 MRI 后 12 个月时的指甲铁呈正相关（p = 0.05），表明 MRI 时与 Fe 暴露有关。丘脑 GABA 和 Glu 均与指甲 Fe 水平无关。总之，本研究不能支持指甲 Mn 作为大脑 Mn 水平或代谢变化的替代物，而指甲 Fe 似乎与大脑代谢改变有关，这凸显了在研究 Mn 神经毒性时考虑其他金属（包括 Fe）的重要性。
