New DNA Test Can Predict Childhood Obesity. Has Gene Screening Gone Too Far?

by jeeg 31. March 2014 22:15

Scientific advances promise less-invasive ways to screen for diseases in unborn children. But are we on the road to an age of 'designer babies'?

Will your child become obese one day? Finding out may be as easy as testing your youngster's blood. But this type of testing is raising concerns about how far science should go to detect genetic conditions and diseases—and the ethics of giving that information to expectant parents.

Researchers at the Universities of Southampton, Exeter, and Plymouth in the U.K. have successfully used a DNA-reading blood test to examine the number of epigenetic switches that turn on the PGC1a gene, which controls the body’s fat-storage activity. The scientists conducted the blood test on 5-year-old children and found that it indicated which children would have high body fat and which would have low body fat as they aged.

DNA methylation, which regulates how genes function from an early age, causes epigenetic switches to turn on. A DNA methylation rating of 10 percent in a 5-year-old child was linked to up to 12 percent more body fat by the time the child reached 14 years of age. Results depended also on gender, physical-activity level, and the age the child reached puberty.

Graham Burdge, a professor at the University of Southampton, said the test is in the preliminary stages, but it may help adults manage their young children's weight and encourage them to use available resources—such as a dietician—if needed.

“The test needs further development, including testing in a larger group of children,” said Burdge.

If a blood test to gauge obesity is in development now, perhaps one to test babies in utero isn’t far off, he said.

Burdge said that researchers have published findings showing that a variation in DNA methylation in the umbilical cord can predict an unborn child's tendency to be obese by the age of 9. Would women want to know this information during their pregnancies, and, moreover, would such testing even be safe?

Technology, Ethics, and Public Health

This news comes not long after a February US Food and Drug Administration meeting to consider whether testing mitochondrial manipulation technology on humans is safe. The technology is used to prevent mitochondrial diseases in children and to boost fertility in older women. It is done by combining DNA from three individuals and involves removing the nuclear DNA from an egg with mitochondrial abnormalities, and then putting that nuclear DNA in a donor egg that has had its DNA removed.

Ricki Lewis, Ph.D., an author and genetic counselor based in New York, said she doesn’t believe the procedure is necessary and would rather see the energy spent helping to treat those living with genetic diseases.

She expects the FDA to announce in the fall whether the first phase of a clinical trial will begin, but she does not think it will be approved.

Jeremy E. Gruber, president of the Council for Responsible Genetics, dubs this procedure the “three-parent baby” method. “Right now, genetic testing is being used for inherited conditions, but the recent controversies over an emerging technique, mitochondrial replacement, could change that,” he said. 

Gruber said that the test has not yet been proven safe and needs more research. If approved, it would be the first instance of human genetic engineering. 

“While in this case it is designed for therapeutic reasons, the FDA has already suggested it could be used as a fertility treatment, and it opens the door for future enhancement applications since there is a complete lack of ethical framework and regulation in this area,” Gruber said.

Another view on the matter comes from Dr. Serena Chen, director of the reproductive endocrinology division of the Department of Obstetrics and Gynecology at Saint Barnabas Medical Center in New Jersey.

“To say that this procedure is creating ‘three-parent babies’ is misleading and irresponsible," Chen said.

The focus of the technology is preventing mitochondrial disease, said Chen, whereas the concept of “designer babies” is about nuclear genetic mutation (selecting for certain traits in a child, such as brown hair or blue eyes). “None of these traits are related to mitochondria as far as we know,” Chen noted.

While changing the nuclear genome is something that scientists are not close to, Chen said, they are at the point where they can detect genetic diseases and chromosomal abnormalities in embryos used for in-vitro fertilization by using preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS). They can then manipulate the outcome of a pregnancy by implanting only healthy, normal embryos in a woman's uterus. PGD and PGS seem like a “much more humane and medically safer approach” to avoiding genetic disease, she said. “This is a new way of selecting for a healthy pregnancy. The old way was to detect an abnormal pregnancy then terminate.” 

Today's Genetic-Testing Landscape

Gruber noted that some prenatal genetic testing is normal, including tests to screen for Down syndrome. Screening is also done based on individual risk factors, as is the case if a woman has a family history of genetic conditions or has a particular ethnic background that could increase her risk.

Tests for noninvasive prenatal genetic diagnosis (NIPD) have been growing in popularity. NIPD enables doctors to test fetal DNA in the mother’s blood. This is much less invasive than other procedures, such as amniocentesis.

“At this very new stage in its use, it’s still usually coupled with a confirmatory more-invasive test and is only being used for high-risk pregnancies,” he said. Gruber added that many companies are rushing to market the tests, and he anticipates that in the future it will be a standard of care to perform whole genome sequencing to look at a child's entire genetic code before he or she is born. 

Whole genome sequencing is already being considered as a possible substitute for the more limited types of newborn gene screening, Gruber said.

Kristen Fischer, Healthline News


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