時尚雙語:有益脂肪可用於減肥

'Good' Fat Could Fight Obesity

Scientists believe they have identified a 'good' fat tissue that helps burn calories and may lead to new treatments for obesity.

Reporting in three different studies in this week's edition of the New England Journal of Medicine, researchers from Europe and the U.S. say they have identified a fat known as brown adipose tissue in adults and discovered that it plays a role in how the body expends energy.

'At the very least, we have identified that there is an entirely new way of approaching the obesity problem,' said Aaron Cypess, an author of one of the studies and an endocrinologist at Joslin Diabetes Center in Boston.

The brown tissue was thought to be present primarily in young children and generally disappeared with age. Even when the brown fat was found in adults, it was believed to play no role in how the body stores and expends energy.

The advent of high-tech medical imaging, however, has given researchers a new glimpse into the human body that reveals that not only is brown fat present in adults, but that it also is metabolically active. The studies combined images taken with positron-emission tomography, or PET machines, with those from computed tomography, or CT machines, to identify the brown fat.

Brown tissue helps to regulate body temperature by generating heat. In contrast, white adipose tissue stores energy. Obese people have too much of the white tissue.

Francesco Celi, an endocrinologist at the National Institute of Diabetes and Digestive and Kidney Diseases, said the findings may lead to the development of drugs that either help the body produce more of the brown fat or activate existing brown tissue. Treatments likely would take years.

Obesity drugs have proved difficult to develop, and only a few have entered the marketplace. Most focus on curbing appetite or how food is absorbed in the body. Last fall, Merck & Co. scrapped development of its anti-obesity drug taranabant because of side effects.

The findings of Dutch researchers published in the NEJM raise the possibility of nondrug treatments related to brown fat, Dr. Celi said.

The researchers from Maastricht University found that brown tissue can be activated quickly by exposing people to colder temperatures. In their experiment, volunteers were tested after resting on their back for two hours in a room with a temperature of 61 degrees.

'Taken together, these studies point to a potential 'natural' intervention to stimulate energy expenditure: turn down the heat and burn calories,' Dr. Celi wrote in an editorial accompanying the studies. In an interview, he said there is still much research to be done and that the body may compensate for the increase in energy expenditure by triggering a desire to eat more to boost energy intake.

The studies also found that brown fat was more common in women, younger patients and patients who were thin.

Dr. Cypess and colleagues at Joslin are investigating the use of an artificial protein commonly used in spine surgery to stimulate brown tissue. The protein, known as bone morphogenetic protein, or BMP, is used to spur bone growth. Research suggests it also helps create brown fat.

科學家們相信他們發現了一種幫助燃燒卡路里的“有益”脂肪組織，可能會產生治療肥胖症的新方法。

據本週《新英格蘭醫學期刊》(New England Journal of Medicine)刊登的三項不同的研究顯示，來自歐洲和美國的研究人員表示，他們在成人體內發現了一種被稱爲褐色脂肪組織的脂肪，對人體能量消耗有着重要作用。

其中一份研究報告的作者、波士頓喬士林糖尿病中心(Joslin Diabetes Center)的內分泌學家塞比斯(Aaron Cypess)說，我們至少發現了一種治療肥胖的全新方法。

褐色組織此前被認爲主要存在於兒童體內，通常會隨着年齡增長而消失。即便在成人體內發現褐色脂肪時，這種脂肪也被認爲和人體儲存與消耗能量沒有關係。

不過，高科技醫療成像技術的出現讓研究人員對人體有了新的瞭解：他們不僅在成人體內發現了褐色脂肪，而且還發現這種脂肪的新陳代謝很活躍。研究綜合使用了正電子發射斷層成象儀(PET)以及斷層掃描成象儀(CT)，以識別褐色脂肪。

褐色組織通過生成熱量幫助調節體溫。相比之下，白色脂肪組織存儲能量。肥胖症患者有過多的白色脂肪組織。

美國糖尿病、消化及腎臟疾病研究所(National Institute of Diabetes and Digestive and Kidney Diseases)的內分泌學家切利(Francesco Celi)說，這一發現可能有助於開發相關藥物，幫助人體生成更多褐色脂肪，或是激活現有的褐色組織。相關治療可能要耗時數年。

事實已經證明很難開發減肥藥，只有少量藥物進入市場。大多數減肥藥都專注於控制食慾或是遏制人體對食物的吸收。去年秋天，默克公司(Merck)由於副作用的原因放棄了開發減肥藥taranabant。

切利說，荷蘭研究人員在《新英格蘭醫學期刊》公佈的這一發現帶來了從褐色脂肪着手進行非藥物治療的可能性。

荷蘭馬斯垂剋大學(Maastricht University)的研究人員發現，人置身較低溫度下就可以迅速激活褐色脂肪。在實驗中，自願者在一個華氏61度（攝氏16度）的房間裏躺了兩個小時後進行測試。

切利在研究報告的附加評論中寫道，綜合來看，這些研究都指向了一種可能的自然干預療法，即通過降低熱量和燃燒卡路里來刺激能量消耗。他在採訪中表示，目前仍有很多研究需要做，人體可能會通過提高食慾以增加能量攝入，來彌補能量消耗的增加。

研究還發現，褐色脂肪在女性、年輕病人以及消瘦病人身上更爲常見。

喬士林糖尿病中心的塞比斯和同事正在研究一種人造蛋白質的使用，這種蛋白質常用於脊椎外科，用以刺激褐色組織。這種被稱爲骨形成蛋白(BMP)的人造蛋白質被用於刺激骨骼生長。研究顯示，它也有助於生成褐色脂肪。