U.S. researchers said Tuesday that they have identified an enzyme that may play a central role in the development of obesity in mid-life.
In two groups of mice being fed high-fat foods, those who received an inhibitor that blocked the enzyme had a 40 percent decrease in weight gain compared with those that did not receive the drug.
The findings, published in the U.S. journal Cell Metabolism, could upend current notions about why people gain weight as they age, and could one day lead to more effective weight-loss medications.
”Our society attributes the weight gain and lack of exercise at mid-life (approximately 30 to 60 years) primarily to poor lifestyle choices and lack of will power, but this study shows that there is a genetic program driven by an overactive enzyme that promotes weight gain and loss of exercise capacity at mid-life,” said lead study author Jay H. Chung, head of the Laboratory of Obesity and Aging Research at the National Heart, Lung, and Blood Institute (NHLBI), part of the U.S. National Institutes of Health.
Researchers have known for years that losing weight and maintaining the capacity to exercise tend to get harder beginning between ages 30 to 40 — the start of mid-life.
In fact, it’s estimated that an average adult in America gains 30 pounds (13.6 kilograms) from age 20 to 50, even though food intake usually decreases during this period.
Scientists have developed new therapies for obesity, including fat-fighting pills, but many of those therapies have failed.
Chung and his associates searched for biochemical changes that occurred in middle-aged animals that are equivalent to 45 years in humans.
They found that an enzyme called DNA-dependent protein kinase, or DNA-PK, increases in activity with age.
他们发现随着年龄的增长，一种被称之为DNA依赖蛋白激酶（DNA-dependent protein kinase）的物质活性与日俱增。
Further work showed that DNA-PK promotes conversion of nutrients to fat and decreases the number of mitochondria, tiny organelles in the cells that turn fat into energy to fuel the body.
Mitochondria can be found in abundance among young people, but the numbers drop considerably in older people.
Researchers know that decreased mitochondria can promote obesity as well as loss of exercise capacity.