二甲基甲醯胺（N,N-dimethylformamide, DMF）為一種水溶性與脂溶性良好的有機溶劑，廣泛用於各種工業製程。DMF於體內會代謝形成N-methylformamide（NMF）及N-acetyl-S-(N-methylcarbamoryl)cysteine（AMCC）於尿中排出；過去文獻指出此為造成DMF健康效應之肝毒性與男性生殖傷害主要來源，其中又以AMCC為長期暴露之毒性指標。近來研究指出肝毒性與男性生殖傷害可能與粒線體膜電位（m）、粒線體DNA（mitochondrial DNA, mtDNA）功能缺陷相關，如mtDNA 4,977-bp斷損突變（mtDNA4977）及mtDNA copy number，然而至今未有DMF造成m或mtDNA損害之相關研究。本研究目的為（1）受DMF暴露後，m、mtDNA4977及mtDNA copy number之變化情形；（2）評估不同DMF暴露劑量與m、∆mtDNA4977及mtDNA copy number變化的劑量反應關係；（3）比較及探討不同生物樣本分析結果之意義與差異。本研究首先選取13名職業暴露DMF男性勞工與13名年齡、工作年資配對之對照組，進行血液樣本∆mtDNA4977及mtDNA copy number分析。研究結果顯示DMF暴露組之相對ΔmtDNA4977量較對照組顯著為高（p<0.001）；若進一步依暴露程度（高於DMF法規容許濃度10 ppm與低於10 ppm）做分組比較，發現差異亦達顯著（p=0.014）。在尿中生物指標AMCC高濃度組（> 40 mg/L）之相對ΔmtDNA4977量較低濃度組（≤ 40 mg/L）顯著為高（p=0.042）；而另一生物指標NMF則無統計上顯著差異。在mtDNA copy number方面，其變化趨勢與ΔmtDNA4977相似，但只有尿中NMF達顯著差異（p=0.011）。本研究另外選取9名職業暴露DMF之男性勞工與9名年齡配對之對照組，進行其精液樣本之m、∆mtDNA4977及mtDNA copy number變化情形分析。研究結果顯示，DMF暴露組之m正常比例顯著低於對照組（p<0.001）；經暴露程度做分組比較後，DMF高濃度分組亦顯著低於對照組（p=0.009），但NMF高濃度組僅與低濃度組達邊際顯著差異（p=0.068）。而在∆mtDNA4977及mtDNA copy number分析方面，研究結果與血液樣本之變化趨勢相同，但唯有DMF暴露組與對照組間之mtDNA copy number及DMF高濃度組與低濃度組間之∆mtDNA4977達顯著差異（p=0.004及p=0.026），而DMF暴露組與對照組間之∆mtDNA4977則僅達邊際顯著差異（p=0.070）。因此，本研究結論為長期DMF職業暴露可能會造成勞工精子細胞∆Ψm下降，同時亦會引起精液與血液樣本之mtDNA copy number變化及增加∆mtDNA4977發生的比率。建議未來研究應納入更多有效樣本數，以做更深入之探討。

N,N-dimethylformamide (DMF) has been widely used in industries because of its extensive miscibility with water and solvents. Its health effects include hepatotoxicity and male reproductoxicity, possibly linked with mitochondrial membrane potential (∆Ψm), mitochondrial DNA 4,977-bp deletion (ΔmtDNA4977) and mitochondrial DNA (mtDNA) copy number. The relationship between DMF exposure and ∆Ψm or mtDNA alterations, however, has not been postulated yet. The purpose of this study was to investigate the association of ∆Ψm, ΔmtDNA4977 and mtDNA copy number with DMF exposure and to explore the association of the DMF-derived ∆Ψm and mtDNA alterations with exposure to the airborne DMF and two urinary DMF biomarkers of N-methylformamide (NMF) and N-acetyl-S-(N-methylcarbamoryl) cysteine (AMCC). Firstly, 13 DMF-exposed workers and 13 age-seniority-matched control workers (all male) in a synthetic leather factory were recruited. The analyses of ΔmtDNA4977 and mtDNA copy number in blood cells were achieved on each participant. We found the frequencies of relative ΔmtDNA4977 in DMF-exposed group were significantly higher than those in the control group (p<0.001). Moreover, elevation in the proportion of ΔmtDNA4977 of individuals with exposure exceeding the permissible exposure limit (PEL) of A-DMF and the biological exposure index (BEI) of urinary AMCC (U-AMCC) levels was significantly higher than those not (p=0.014 and p=0.042, respectively). No significant findings were observed, however, for the urinary NMF (U-NMF). In the comparisons on relative mtDNA copy number frequency, on the other hand, only U-NMF showed the significantly difference between those exceeding and not exceeding (p=0.011), but not in the comparisons with A-DMF and U-AMCC. Secondly, for the semen samples, 9 DMF-exposed male workers and 9 age-matched controls were selected to analyze the ∆Ψm, ΔmtDNA4977 and mtDNA copy number. We found the percentage of ∆Ψm normality in DMF-exposed group was significantly lower than that in control group (p<0.001). Moreover, the elevation in the percentage of ∆Ψm normality of individuals with exposure exceeding the PEL of A-DMF was also significantly lower than that not (p=0.009). In the analyses of ΔmtDNA4977 and mtDNA copy number for the sperm, the alteration trends were the same as for the blood cells. Thus, we concluded that long-term exposure to DMF might cause the alteration of ∆Ψm in semen samples and the alterations of mtDNA in semen and blood samples, and a further study with more subjects involved is warranted.

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