Hormone Injections Induce Weight Loss
For the first time, injections of the hormone leptin have been shown to curb appetite and induce weight loss in a human, a new study says.
Scientists caused a stir four years ago when they announced that leptin could lead to weight loss in mice, but until now, a direct role in human obesity had not been confirmed.
The findings by doctors at Addenbrooke's Hospital in Cambridge, England, provide important clues as researchers try to decipher the genetic and environmental factors in obesity. The work could lead to medical treatments for some forms of the condition.
Leptin is a protein produced by fat cells. It is supposed to signal the brain to stop eating, but the signal does not get through properly in some overweight people.
The study published in today's edition of the New England Journal of Medicine involved a severely overweight 9-year-old girl who suffered from a rare genetic defect in which her body produced virtually no leptin.
At the age of 6, the girl was so overweight that doctors performed liposuction on her legs to increase her mobility. She was constantly hungry and became disruptive when denied food. In 1997, when the girl was 9 and weighed 208 pounds, doctors began administering daily injections of leptin.
Within a week of treatment, the girl's appetite had diminished significantly. After a year of injections, she had lost 36 pounds, and 95 percent of that weight was fat. She also began to show signs of early puberty--an interesting side effect because other people with this congenital defect also have experienced stunted reproductive development.
In an accompanying editorial in the journal, Michael Rosenbaum and Rudolph L. Leibel of the Columbia University College of Physicians and Surgeons wrote that many factors besides leptin affect weight, and people should not conclude that leptin injections would make losing weight easy.
Leptin is being tested in ordinary cases of obesity as an appetite suppressant. Preliminary findings from one study indicate that it is not a miracle cure, but shows some promise when combined with diet and exercise.
Cocaine's Chemistry And Addictive Power
Cocaine may be one of the toughest addictions to cure because it triggers a buildup of a protein that persists in the brain and stimulates genes that intensify the craving for the drug, new research suggests.
Scientists at the Yale School of Medicine were able to isolate the long-lived protein, called Delta-FosB, and show that it triggered addiction when released to a specific area of the brains of genetically engineered mice.
The protein (pronounced fawz-bee) is not produced in the brain until addicts have used cocaine several times, or even for several years. But once the buildup begins, the need for the drug becomes overpowering and the user's behavior becomes increasingly compulsive.
The study, published today in the journal Nature, indicates genetics is less a factor in addiction than prolonged drug use, said Alan Leshner, director of the National Institute on Drug Abuse, which funded part of the study.
Nestler and his colleagues combined genetic and biochemical research to isolate the Delta-FosB protein and the area of the brain it affected, then did behavioral studies on the mice.