Transgenic pigs are rich in healthy fats
14:52 27 March 2006
NewScientist.com news service
Jessica Marshall
Transgenic pigs enriched with omega-3 fatty acids could one day make pork sausages a healthy food choice.
Omega-3s are found at high concentrations in oily fish and foods like flax seeds. Another class of lipid, omega-6 fatty acids, is common in meat. The Western diet has become strongly skewed towards the consumption of omega-6 fatty acids over omega-3s, and this is believed to contribute to an increased incidence of heart disease, cancer, diabetes and other diseases.
In 2004, researchers created pigs that can convert their unhealthy omega-6 fatty acids into omega-3s, changing the ratio of omega-6 to omega-3 fats by fivefold. The team used cloning techniques to create piglets that produce an enzyme - originally from a nematode worm - that converts omega-6 fatty acids to omega-3s .
The latest study found that omega-3s made up an average of 8% of the total fat in the six transgenic piglets' muscles, compared with 1 to 2% in normal piglets.
Study co-author Jing Kang at Harvard Medical School in Boston, Massachusetts, US, believes the team can double the omega-3 concentration in subsequent efforts, bringing the levels close to those found in fish.
Pregnancy dilemma
Today’s omega-3 fatty acid supply is limited by depleted fishing stocks, he notes. In addition, eating fish poses a dilemma for pregnant women, who may be worried about mercury contamination, says co-author Yifan Dai of the University of Pittsburgh, Pennsylvania, US. “If we have a supply of omega-3 without mercury contamination, it will be the perfect supplement for the mother,” he says.
The researchers doubt the pork’s flavour would be significantly affected by the gene. But for the moment nobody can taste meat from the transgenic pigs without approval from the US’s regulatory authority, the Food and Drug Administration. In the meantime, the pigs will be bred and their offspring used for cardiovascular and other research. “My guess is that the transgenic pigs will be healthier, because they will have a better ratio of omega-3 to omega-6,” says Dai.
However, two recent studies cast doubt on the well-publicised benefits of omega-3 fatty acids. A recent review of studies suggested they may not help prevent cancer, and a review appearing in the British Medical Journal (DOI: 10.1136/bmj.38755.366331.2F) found no clear evidence that omega-3s decreased mortality or cardiovascular events.
But the new pigs would not make it healthy to eat unlimited amounts of bacon, Dai warns. Though omega-3s are made in muscle and organ tissues, the fat that streaks bacon would remain high in unhealthy saturated fat. For those who would prefer a drumstick or a burger, omega-3-boosted chickens and cows are in the pipeline, Kang says.
Journal reference: Nature Biotechnology (DOI: 10.1038/nbt1198)
基因轉殖豬富含健康的脂肪
富含Omega-3脂肪酸的基因轉殖豬將會使得豬臘腸成為健康的食物呢！的選擇。
（在此補充一小段介紹甚麼是 omega-3脂肪酸！！！）
Omega-3脂肪酸於多油的魚類和，食物如亞麻種子也有很高的濃度的含量，而另一種類的脂肪，Omega-6脂肪酸則通常存在於肉類。西式的飲食中大多食用Omega-6脂肪酸多於Omega-3脂肪酸，並且使得罹患心血管疾病、癌症、糖尿病等其他疾病的機率增加。
在2004年，研究者使用複製技術使得小豬製造一種原先來自於線蟲的酵素，該酵素可將Omega-6脂肪酸轉變成Omega-3脂肪酸的酵素，因此小豬可以將牠們身體中不健康的Omega-6脂肪酸轉變成Omega-3脂肪酸，轉變的比例可達五倍。
後期的研究發現，在六隻基因轉殖豬中，Omega-3脂肪酸大約佔全部脂肪的8%，而在一般的小豬中，Omega-3脂肪酸只佔全部脂肪的1~2%。
美國麻薩諸塞州波士頓哈佛醫學院的共筆者Jing Kang相信研究小組在其後的研究中能加倍Omega-3脂肪酸的濃度，將濃度提升到接近魚類中的含量。
造成懷孕時期的兩難困境
目前Omega-3脂肪酸的供應被限制於日漸消耗的漁獲中。且美國賓夕法尼亞州匹茲福堡大學的共筆者戴易義凡分(Yifan Dai，音譯)也說道，吃魚對於懷孕的婦女是一種進退兩難的情況，因為其中的汞含量令人感到憂心。”「若我們能提供不含汞的Omega-3，那這絕對是一種絕佳的補品。」她說。”
有些研究者認為基因的改變會影響豬肉的味道。，但目前由於沒有尚未得到美國食物與藥物流通控管理局的准許上市，所以還沒有人嚐試過這些基因轉殖豬的肉。但同時，這些基因轉殖豬依然在繁殖中，且他們的後代被可用來作為心血管及其他的研究。但戴義凡戴易分認為”「這些基因轉殖豬對我們來說會是更健康的，因為他們的Omega-3和Omega-6的比例可有更好調整更好些。”」
然而，目前有兩個研究對Omega-3脂肪酸益處的發表產生質疑。，其中一個研究是認為Omega-3脂肪酸對癌症的預防可能沒有幫助，而另一個在英國醫學藥日誌雜誌（British Medical Journal (DOI: 10.1136/bmj.38755.366331.2F)）中發表的研究發現，並沒有明確的證據證明Omega-3脂肪酸能降低死亡率或心血管疾病的發生。
此外，戴義凡戴易分也警告，毫無限制的大量食用這些新品種的豬所製成的培根並不會讓你更健康，。因為儘管Omega-3脂肪酸是在肌肉與器官組織被製造的，培根上所呈現的條紋油脂仍舊含有高含量不健康的飽和脂肪。，那對於這些人來說可能還比較寧願去吃雞腿或漢堡！而目前提高Omega-3脂肪酸含量的雞跟牛也正在研究中。
參考文獻
Jessica Marshall. 2006. Transgenic pigs are rich in healthy fats.
Nature Biotechnology (DOI: 10.1038/nbt1198)
Transgenic pigs are rich in healthy fats
- 14:52 27 March 2006
- NewScientist.com news service
- Jessica Marshall
Transgenic pigs enriched with omega-3 fatty acids could one day make pork sausages a healthy food choice.
Omega-3s are found at high concentrations in oily fish and foods like flax seeds. Another class of lipid, omega-6 fatty acids, is common in meat. The Western diet has become strongly skewed towards the consumption of omega-6 fatty acids over omega-3s, and this is believed to contribute to an increased incidence of heart disease, cancer, diabetes and other diseases.
In 2004, researchers created pigs that can convert their unhealthy omega-6 fatty acids into omega-3s, changing the ratio of omega-6 to omega-3 fats by fivefold. The team used cloning techniques to create piglets that produce an enzyme - originally from a nematode worm - that converts omega-6 fatty acids to omega-3s .
The latest study found that omega-3s made up an average of 8% of the total fat in the six transgenic piglets' muscles, compared with 1 to 2% in normal piglets.
Study co-author Jing Kang at Harvard Medical School in Boston, Massachusetts, US, believes the team can double the omega-3 concentration in subsequent efforts, bringing the levels close to those found in fish.
Pregnancy dilemma
Today’s omega-3 fatty acid supply is limited by depleted fishing stocks, he notes. In addition, eating fish poses a dilemma for pregnant women, who may be worried about mercury contamination, says co-author Yifan Dai of the University of Pittsburgh, Pennsylvania, US. “If we have a supply of omega-3 without mercury contamination, it will be the perfect supplement for the mother,” he says.
The researchers doubt the pork’s flavour would be significantly affected by the gene. But for the moment nobody can taste meat from the transgenic pigs without approval from the US’s regulatory authority, the Food and Drug Administration. In the meantime, the pigs will be bred and their offspring used for cardiovascular and other research. “My guess is that the transgenic pigs will be healthier, because they will have a better ratio of omega-3 to omega-6,” says Dai.
However, two recent studies cast doubt on the well-publicised benefits of omega-3 fatty acids. A recent review of studies suggested they may not help prevent cancer, and a review appearing in the British Medical Journal (DOI: 10.1136/bmj.38755.366331.2F) found no clear evidence that omega-3s decreased mortality or cardiovascular events.
But the new pigs would not make it healthy to eat unlimited amounts of bacon, Dai warns. Though omega-3s are made in muscle and organ tissues, the fat that streaks bacon would remain high in unhealthy saturated fat. For those who would prefer a drumstick or a burger, omega-3-boosted chickens and cows are in the pipeline, Kang says.
Journal reference: Nature Biotechnology (DOI: 10.1038/nbt1198)