NEW ORLEANS, Nov. 13 – A natural gene variation that is already linked to high blood pressure may also predispose those who inherit it to obesity, according to a study reported today at the American Heart Association’s Scientific Sessions 2000.
The discovery could lead to new approaches to prevent high blood pressure and obesity.
German researchers found that people who inherit two copies of the gene, one from each parent, have a high risk of obesity. However, exercising for two hours or more a week appears to block the genetic tendency. “This underscores that obesity is not only a genetic disease, but that certain genes – in connection with environmental or behavioral factors – can increase the likelihood of obesity,” says lead author Achim Gutersohn, M.D., of the University of Essen in Essen, Germany. “However, such inherited factors can be countered by a healthy lifestyle.”
He notes that the gene variation, called the GNB3 825T allele, is a “thrifty genotype.” He speculates that the once-beneficial gene arose early in human history, when a high level of physical activity was the norm, to help our ancestors in hunter-gatherer societies survive periods of low food supplies. But the gene variation now has become detrimental in industrialized countries where less physical activity is demanded.
The German team linked the 825T allele to obesity after studying 1,291 young, healthy, white volunteers – average age, 29.8 years. “We conducted this study to better understand why the GNB3 825T allele is associated with an increased cardiovascular risk,” Gutersohn says.
Earlier studies had associated the gene variation with high blood pressure, particularly in people with left ventricular hypertrophy, a thickening of the heart muscle that can be life threatening. Animal and laboratory cell studies have also shown that increased activation of G protein, a messenger system within cells, leads to a greater production of fat cells.
Gutersohn and his colleagues measured the height and weight of the 532 women and 759 men who took part in the study and gathered information on the participants’ socioeconomic status, diets and physical activity. Examination of their DNA, obtained from blood samples, revealed whether or not a volunteer carried the 825T allele.
“One significant finding of our study is the strong effect of the gene in white individuals with a sedentary lifestyle,” Gutersohn says. “Our findings show that individuals who have inherited two copies of the 825T allele have a high risk of obesity if they do not participate in regular physical activity.” Dr. Gutersohn and colleagues at the University of Essen also provided estimates of how often the 825T allele occurs in several racial groups by analyzing the genes of 1,153 anonymous individuals from five population groups – Australian aborigines, Japanese, Chinese, black Africans and black Americans. They found it was most common in black Africans and black Americans.
Combining the 825T allele data from these groups with that from the white volunteers allowed the team to estimate the frequency with which the gene variation occurs among different racial populations. Gutersohn says the estimated frequency showed that at least one copy of the allele was carried by 71.4 to 87.8 percent of black Africans and black Americans; 43.1 to 49.0 percent of Asians; and 25.1 to 29.6 percent of Caucasians.
The researchers believe the 825T allele holds great potential as a genetic screening tool to identify people at risk of obesity-related diseases. This would allow physicians to initiate preventive treatments long before symptoms appeared.
Co-authors are Rainer Mueller, M.D., and Winfried Siffert, M.D.
NR00-1181 (SS2000/Gutersohn)