A chemical switch that tells cells when to burn fat and when to store it has been discovered in mice, paving the way for new drugs that could one day be used to control obesity and cholesterol.

Scientists at the Salk Institute in La Jolla, California, have identified a receptor in mouse cells that supervises how fat is used in the body and influences the ease with which mice put on weight.

If a similar regulator exists in human beings, which is likely, it would be a promising target for drugs that stimulate the burning of fat to fight the developed world's growing obesity epidemic. Genes that carry the blueprint for receptor, PPARd, could also help to explain why some people seem to eat what they like and remain thin, while others find that every extra calorie goes straight on to the waistline.

Experiments revealed that when PPARd was stimulated, mice used up fat deposits and lost weight, while mice with low PPARd activity were prone to obesity.

Mice with a highly active version weighed about 20 per cent less than normal mice at birth, and 35 per cent less at the age of one. The active receptor also protected mice against obesity when fed a high-calorie and high-fat diet. The findings are published today in the journal Cell.

科学家近日在老鼠体内发现一种化学变化，能够表明细胞在什么时候燃烧脂肪，又在什么时候对脂肪进行储存。这一发现也许能够帮助人们进一步研制控制脂肪和胆固醇的药品。

加利福尼亚拉霍拉沙克研究所的科学家发现在老鼠的细胞中有一种感受体，负责调度分配体内的脂肪，当老鼠因为安逸而体重增加时，这一感受提也能发挥相应的作用。

如果在人类体内也能有这样一种调节器，或者利用药物来达到调节的目的，也许就能解决全球范围内愈演愈烈的肥胖问题了。构成这一名为PPARd的感受体的基因的存在，也能从某种程度上解释为什么有的人并不忌口却仍能保持身材，而有的人却仿佛摄入的所有热量都立刻囤积在了腰上。

实验显示，当PPARd受到刺激，老鼠就会消耗体内囤积的脂肪，从而使体重下降。而PPARd不活跃的老鼠则比较肥胖。

体内这一物质活跃的老鼠在出生时体重就比普通老鼠轻约20%，到一岁时则要轻35%左右。体内感受体活跃的老鼠即便吃大量高热量高脂肪的食物，也不容易发胖。这一研究结果刊登在4月18日的《细胞》杂志上。