牛奶中的農藥與低神經元密度有關


  【24drs.com】根據一篇新研究,1980年代初期在牛奶中發現該年代之前使用的一種農藥,可能和巴金森氏症患者腦部的神經退化結果有關。
  
  這篇由日本大津滋賀醫科大學Robert Abbott 博士所領銜的研究,線上發表於12月9日的神經學期刊。
  
  他解釋,之前認為攝取乳製品和巴金森氏症有關,不過原因未知。有機氯農藥也被認為與巴金森氏症有關,我們的研究結果認為,牛奶中的農藥和巴金森氏症者的神經退化可能有關。
  
  這篇研究提到的農藥—環氧化七氯(heptachlor epoxide) —目前在西方世界已不再使用,但是,Abbott 博士強調,這是一個非常持久的化學藥品,會被土壤與水吸收,在環境中停留數年。所以它會出現在魚類和牛乳中,它最近在許多國家被發現,大多是在較少控制的發展中國家。
  
  他還指出,這篇研究已經超越了使用這一特定殺蟲劑的廣泛影響。
  
  我們知道,巴金森氏症患者的飲食很重要。現在,我們發現,飲食和黑質的神經退化有關,更重要的是,多年前的飲食習慣和後來的腦部變化有關,這表示,要防止這些變化發生的所需時間相當長。
  
  另外,我們要對我們所飲所食有所認識。這篇研究探討牛奶,但是,我們該考慮的不只是牛奶。宏觀背景是,這項研究認為,腦部因巴金森氏症而發生變化時,多年之前的環境因素依舊有影響。我們吃的、喝的、呼吸的一切,都會影響多年後的腦部情況。
  
  為了進行本篇研究,來自夏威夷的449名日裔美籍男性(平均年齡54歲)參與檀香山亞洲老化研究,追蹤超過30年,直到死亡,死後進行屍檢。
  
  牛奶攝取資料蒐集期間為1965-1968年,屍檢是在1992-2004年間進行,測量黑質的神經元密度。研究者也檢測116名男性之腦組織的環氧化七氯值。這個農藥在1980年代之前被廣泛用於夏威夷,且在1980年代初期於夏威夷供應的牛奶中的含量過高。
  
  結果顯示,喝大量牛奶(>16盎司/天)之非抽菸者的神經元密度最低,Abbott 博士指出,之前有研究認為抽菸與巴金森氏症風險較低有關。
  
  排除路易氏體失智症或巴金森氏症案例之後,校正所有人的神經元密度,喝大量牛奶(>16盎司/天)者的背內側象限值,比喝較少量者低41.5% (P = .001)。對於曾經在某個時間點抽菸者,喝牛奶和神經元較少無關。
  
  喝最多牛奶的人之中,90%的腦中測出環氧化七氯殘留,沒有喝牛奶者則是有63%測出。
  
  Abbott博士指出,這篇研究有若干假設。他表示,牛奶攝取量是在1960年代報告,我們假設牛奶攝取模式在往後幾年會是相同的。我們並沒有測量牛奶中的環氧化七氯量,所以,我們無法確切地說牛奶有被農藥汙染,但是,那些喝最多牛奶者的腦部屍檢發現,腦中有這個農藥。
  
  他指出,研究的重要訊息是,在巴金森氏症被診斷之前,我們可以預測腦中重要區域的細胞死亡和巴金森氏症有關,我們也可以追蹤在這狀況下所見的神經元退化。
  
  紐約州紐約市哥倫比亞大學Karen Marder醫師、北卡羅萊納州三角研究園區、國家環境健康科學研究中心的Honglei Chen醫師在編輯評論中指出,雖然牛奶遭受環氧化七氯汙染是這些研究結果的合理解釋,但是,這篇研究沒有直接顯示腦中的環氧化七氯是來自牛奶而非其他來源。
  
  他們指出,這篇研究認為環氧化七氯汙染是夏威夷最常喝牛奶者的巴金森氏症風險比較高的罪魁禍首,但是,它並未在其他世代提供攝取牛奶或乳製品與巴金森氏症之關聯的良好解釋 ,而且,牛奶污染的證據不足。
  
  但是,編輯們結論指出,這篇研究為流行病學研究如何探討巴金森氏症的因果機轉設定了一個良好範本,應該鼓勵這種以終身方式追蹤探討、揭開神經退行性疾病之複雜過程的方法。
  
  資料來源:http://www.24drs.com/
  
  Native link:Pesticide in Milk Linked to Lower Neuron Density

Pesticide in Milk Linked to Lower Neuron Density

By Sue Hughes
Medscape Medical News

A pesticide used before the early 1980s and found in milk at that time may be associated with neurodegenerative findings in the brain characteristic of Parkinson's disease, according to a new study.

The study, published online in Neurology on December 9, was led by Robert Abbott, PhD, Shiga University of Medical Science in Otsu, Japan.

"Consumption of dairy products has been linked to Parkinson's disease before but a reason for this is not known," he explained to Medscape Medical News. "Organochlorine pesticides have also been linked to Parkinson's. Our results suggest that pesticides in the milk may be related to the neurodegeneration seen in Parkinson's."

This pesticide in this study — heptachlor epoxide — is not used anymore in the western world, but Dr Abbott stressed that it is a very persistent chemical that is absorbed into the soil and water and stays in the environment for many years.

"So it can still end up in fish and milk. It has recently been detected in several countries and is probably more prevalent in developing countries, where there are fewer controls," he said.

Long Window of Opportunity

He also makes the point that this study has wider implications beyond the use of this one particular pesticide.

"We know diet is important in Parkinson's. We have now shown that diet is linked to neurodegeneration in the substantia nigra, and more importantly, dietary habits many years earlier are linked to later changes in the brain," he said. "This suggests there is a long window of opportunity where it may be possible to prevent these changes from occurring."

He added: "The other message is that we need to be aware of what we are eating and drinking. This study has looked at milk but it is not just milk we should think about. The big picture is that this study suggests an environmental factor can predate brain changes typical of Parkinson's long before the condition ever develops. What we eat/drink/breathe may affect what happens in our brains years later."

For the study, 449 Japanese-American men (average age, 54 years) from Hawaii who participated in the Honolulu-Asia Aging Study were followed for more than 30 years until death, after which autopsies were performed.

Milk intake data were collected from 1965 to 1968. Postmortem examinations were conducted between 1992 and 2004. Neuron density counts in the substantia nigra were measured. The researchers also tested brain tissue from 116 men for levels of heptachlor epoxide, which was used extensively in Hawaii before the 1980s and was found at excessively high levels in the milk supply in Hawaii in the early 1980s.

Results showed that neuron density was lowest in nonsmokers who consumed high amounts of milk (>16 oz/day). Dr Abbott noted that smoking has previously been associated with a lower risk for Parkinson's.

After removing cases of Parkinson's or dementia with Lewy bodies, adjusted neuron density in all but the dorsomedial quadrant was 41.5% lower for milk intake greater than 16 oz/day vs lesser intake (P = .001). For persons who were smokers at any point, there was no association between milk intake and loss of neurons.

Among those who drank the most milk, residues of heptachlor epoxide were found in 90% of brains as compared with 63% of those who consumed no milk.

Assumptions

Dr Abbott noted that several assumptions were made in this study.

"The consumption of milk was reported in the 1960s, and we are assuming the pattern of milk consumption would have stayed the same in the years ahead," he said. "And we didn't measure levels of heptachlor epoxide in the milk, so we can't actually say for sure that the milk was contaminated with the pesticide, but brains at autopsy did contain this pesticide at higher amounts in the patients who drank the most milk."

He added: "The important messages from our study are that we can predict cell death in critical regions of the brain associated with Parkinson's before the condition is diagnosed and that dietary factors can predate the clinical symptoms of Parkinson's and can track with the neurodegeneration seen in the condition."

In an accompanying editorial, Honglei Chen, MD, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, and Karen Marder, MD, Columbia University, New York, New York, point out that although contamination of milk with heptachlor is a reasonable explanation for the findings, the study did not directly show that the brain heptachlor was from milk rather than from other sources.

They add that the current study makes heptachlor contamination a plausible culprit for higher Parkinson's disease risk among frequent milk drinkers in Hawaii, but it may not offer a good explanation for the association of milk or dairy consumption and Parkinson's in other cohorts where evidence of milk contamination is lacking.

But the editorialists conclude that the study "sets an excellent example of how epidemiologic studies can contribute to the search for causal mechanisms underlying PD [Parkinson's disease]," adding that "this life-course approach to unveiling the complicated process of neurodegeneration should be encouraged."

The study was supported by a contract and grants from the National Institute on Aging; by a contract from the National Heart, Lung, and Blood Institute; by a grant from the National Institute of Neurological Disorders and Stroke; by a grant from the United States Department of the Army; by the Office of Research and Development, Medical Research Service, Department of Veterans Affairs; by the Kuakini Medical Center; and in part by the Intramural Research Program of the National Institute on Aging. The authors have disclosed no relevant financial relationships.

Neurology. Published online December 9, 2015.

    
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