Passage 6
Scientists have developed a slimming drug that successfully suppresses appetite and results in a dramatic loss of weight without any apparent ill effects.The drug interferes with appetite control and prevents the build-up of fatty tissue.More importantly，the drug appears to prevent a serious decline metabolic rate—causing tiredness and lethargy—which is typically associated with living on a starvation diet.As a result，mice taking the drug lost 45 percent more weight than mice fed the same amount of food，which compensate for the lack of food by becoming more sluggish.
The scientists，from the Johns Hopkins University in Baltimore，said that C75 is likely to produce a similar effect on humans because appetite control in the brain is thought to be based largely on the same chemical pathways as those in mice.“We are not claiming to have found the fabled weight-loss drug.What we have found，using C75，is a major path- way in the brain that the body uses naturally in regulating appetite at least in mice，”said Francis Kuhajda，a pathologist and senior team member.“We badly need effective drugs for weight loss.Obesity is a huge problem.We’re hoping to explore the possibilities of this new pathway，”he said.
Discovering a biochemical pathway in the brain that controls appetite raises new prospects for eloping slimming aids.Research on leptin，a hormone produced in fatty tissue for controlling fat deposits，has so far failed to produce the expected slimming drug break-through.The latest study，published in the journal Science，showed that even moderate doses of C75 produced a significant loss of appetite，which returned to normal after a few months.
The scientists believe that C75，which they produced synthetically in the laboratory，binds to an enzyme called fatty acid synthase，which is involved in storing excess food intake as fat.Inhibiting enzyme causes a build-up of a chemical in the liver which acts as a precursor to fat deposition.This precursor is thought to have an indirect effect on the brain，causing appetite suppression.
Normally，when animals fast，a hormone called neuropeptide Y increases sharply in the appetite control centers of the brain，stimulating the desire for food.However，when animals are given C75，levels of this hormone fall，leading to a loss of interest in food.Dr.Kuhajda said discovering that C75 has no effect on metabolic rate is one of the most significant findings of the study.“If you try to lose weight by starving，your metabolism slows down after a few days，”he said.“It’s a survival mechanism that sabotages many diets.We see this in fasting mice.Yet metabolic rate in the C75-treated mice doesn’t slow down at all.”Further animals studies will be needed before C75 could be tested on humans.
26.Living on a starvation diet may result in____.
A.a dramatic loss of weight without any ill effects
B.a long-term loss of interest in eating
C.a slowdown of fat deposition
D.fatigue and inactivity
27.The scientists from the Johns Hopkins University said that C75，the slimming drug proved effective in mice，is likely to work on humans because____.
A.the chemical pathway responsible for appetite control in humans is believed to be the same as that in mice
B.it is a major pathway in the brain which is activated to regulate appetite
C.it is especially effective in the battle against obesity
D.its effect has also been proved by human studies(https://www.daowen.com)
28.Leptin____.
A.refers to a new biochemical pathway in the brain that controls appetite
B.raises new prospects for developing slimming drugs
C.is a hormone produced in fatty tissue for controlling fat build-up
D.has turned to a breakthrough in the search for effective slimming drugs
29.The newly-found slimming drug can successfully suppress appetite because____.
A.C75 made synthetically in the laboratory works effectively on human body
B.fatty acid sythase is involved in storing excess food intake as fat
C.C75 inhibits the activity of an enzyme called fatty acid synthase
D.it increases a hormone called neuropeptide Y in the appetite-control centers of the brain
30.What is the most remarkable about the new slimming drug C75？
A.It successfully suppresses appetite.
B.It encourages the scientists to study slimming drugs from new perspectives.
C.It generates a new hormone that may prove to be the key to overweight.
D.It doesn’t affect the metabolic rate，a survival mechanism in living beings.