環境毒素、成藥恐引發胎兒自閉症 | 台灣環境資訊協會-環境資訊中心

環境毒素、成藥恐引發胎兒自閉症

2014年04月14日
摘譯自2014年4月9日ENS加拿大,安大略省,多倫多報導;姜唯編譯;蔡麗伶審校

英國約克大學的研究人員發現,腦部脂質分子濃度的異常,會影響早期胎兒腦部兩條主要神經路徑的交互作用,進而可能導致自閉症。

科學家進一步研究發現,環境因子可能影響這些脂質分子的濃度,例如某些化妝品和成藥中的化學成分。

科學家發現,環境因子可能引發胎兒自閉症。(圖:Bianca de Blok)

自閉症系譜疾病 恐為環境毒素引發

「我們發現,當一種叫做前列腺素E2(PGE2)的脂質分子在腦部的濃度異常時,便會影響Wnt蛋白的功能,可能影響胚胎早期的發展。」約克大學自閉症研究聯盟成員、健康學院教授Dorota Crawford解釋。

前列腺素E2是一種生物活性脂肪酸,屬天然脂質衍生物,和健康人體正常運作有關。約克大學研究人員在論文中寫道,「異常的PGE2信號和神經系統的疾病有關。」

「來自細胞外的刺激,如免疫和感染性物質、汞和鉛等環境毒素,以及含有米索前列醇和丙戊酸的藥物,都可能讓特定生物合成路徑異常分泌PGE2,改變細胞信號傳遞,進而影響睡眠、發燒、發炎和疼痛等生理反應。」

「藥物、毒素或感染物質等環境因素增加了氧化壓力,導致脂質過氧化和免疫反應,干擾了PGE2信號傳遞;這些都和自閉症譜系疾病(ASD)有關。」

自閉症病例增加 不全是因診斷進步

自閉症是一種腦部發展的主要疾病,輕微的症狀包括不斷重複某些行為,嚴重者可能出現社交行為和語言能力的缺失。自閉症好發於男孩,機率是女孩的4倍,而且發生機率越來越高,根據美國疾病預防與管制局2010年的資料,每68個孩童就有1個有自閉症。

此外,研究者也寫道:「越來越多證據顯示環境因子可能引發ASD等神經發育障礙疾病,亟需瞭解潛在的外在原因和可能的作用機制。」

Crawford說,基因在演化過程中變化並不顯著,即使遺傳因素是自閉症的主因,脂肪酸攝取不足、接觸感染物質、化學物質或藥物等外在因素仍可能造成基因表現改變,導致自閉症。

「從統計數據可以看到警訊。自閉症發生機率已從兩年前的88之1增加了30%。也許我們不能再單純地把自閉症發生機率增加歸因於診斷工具的進步或是病識感增加了。」

Autism Triggered in the Womb by ‘Environmental Factors’
TORONTO, Ontario, Canada, April 9, 2014 (ENS)

Autism can be triggered by abnormal levels of lipid molecules in the brain that affect the interaction between two key neural pathways in early brain development in the womb, researchers at York University have learned.

The scientists discovered that environmental causes such as exposure to chemicals in some cosmetics and common over-the-counter medications can affect the levels of these lipids.

Autism is a primary disorder of brain development with symptoms ranging from mild to severe and including repetitive behavior, deficits in social interaction, and impaired language. It is four times more prevalent in boys than in girls and the incidence continues to rise.

The U.S. Center for Disease Control and Prevention estimates that 1 in 68 children now has autism, based on data from 2010.

“We have found that the abnormal level of a lipid molecule called Prostaglandin E2 in the brain can affect the function of Wnt proteins. It is important because this can change the course of early embryonic development,” explained Professor Dorota Crawford in the Faculty of Health and a member of the York Autism Alliance Research Group.

Prostaglandin E2 (PGE2) is a bioactive fatty acid, a natural lipid-derived molecule involved in healthy, normal functioning of the human body. The York University researchers write, “Abnormal PGE2 signalling has been associated with pathologies of the nervous system.”

“Extracellular stimuli such as immunological and infectious agents, environmental toxins such as mercury and lead, and exposure to drugs including misoprostol and valproic acid can trigger the local production of PGE2 via specific biosynthetic pathways, resulting in altered cell signal transmission that modulates biological functions such as sleep, fever, inflammation, and pain,” the authors state.

In addition, the study published Monday in the journal “Cell Communication and Signaling,” states, “Increasing evidence for the contribution of environmental factors in the etiology of neurodevelopmental disorders like ASD [autism spectrum disorder] has prompted urgency to reveal their potential exogenous causes and underlying mechanisms.”

“Environmental factors like exposure to drugs, toxins or infectious agents cause disruptions in PGE2 signalling by increasing the levels of oxidative stress, consequent lipid peroxidation, and the immunological response; these factors and consequences that disturb normal PGE2 signalling have all been linked to ASD,” the study states.

According to Crawford, genes do not undergo significant changes in evolution, so even though genetic factors are the main cause, environmental factors such as insufficient dietary supplementations of fatty acids, exposures to infections, various chemicals or drugs can change gene expression and contribute to autism.

“The statistics are alarming. It’s 30 percent higher than the previous estimate of 1 in 88 children, up from only two years earlier. Perhaps we can no longer attribute this rise in autism incidence to better diagnostic tools or awareness of autism,” said Crawford.

※ 全文及圖片詳見:ENS