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Gene Passed by Mom Tied to Metabolic Syndrome

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THURSDAY, Oct. 21 (HealthDayNews) -- Genetic mutations passed down from mother to child may increase the chances for metabolic syndrome in adulthood, researchers report.

Metabolic syndrome is a collection of conditions that, when taken together, signal trouble. It is characterized by traits such as excessive belly fat, high cholesterol, insulin resistance and normal-high to high blood pressure. Recent studies have suggested that individuals with these traits are at increased risk for diabetes and heart disease.

"It's been known for a long time that high blood pressure and high cholesterol, along with several other metabolic traits, cluster in individual patients more often than would be expected by chance. But until now the explanation for this has been unclear," said study author Dr. Richard P. Lifton, a professor of genetics at Yale University.

His team's research into one family with unusually high rates of metabolic disease suggests that mutations in a maternally-passed gene may be at least partly to blame.

The finding won't lead to new treatments for hypertension, obesity or high cholesterol anytime soon, but it may open a window into the exact causes of each, Lifton said.

In a study appearing in the Oct. 21 online issue of Science, Lifton and his colleagues describe a family with an unusually high incidence of three seemingly linked conditions: high blood cholesterol, high blood pressure and a much rarer condition, hypomagnesemia (low blood levels of magnesium).

Focusing on hypomagnesemia, the researchers discovered that this rare condition was never passed from affected father to child. However, nearly 80 percent of children born to affected mothers inherited the problem.

This pointed to one type of gene as the culprit: mitochondrial DNA. Mitochondria are the cell's energy factories, producing all the energy your body requires.

And unlike other DNA, the DNA governing mitochondria are passed to offspring only via the mother.

"Because we get all of our mitochondria from our mothers and none from our fathers, that immediately suggested that we would find the causal mutation [for the metabolic cluster] in this mitochondrial gene," Lifton said.

Looking at that part of the maternal genome concerned with mitochondria, the researchers uncovered a genetic mutation they believe is responsible for this family's high incidence of unhealthy metabolic traits.

But the finding has implications far beyond this one clan, Lifton said.

Since mitochondrial function within human cells is known to decline with advancing age, scientists have long wondered if this regression might help explain why blood pressure, high cholesterol and other metabolic problems rise with age, too.

"Now, these results show for the first time that mutations in the mitochondrial gene can cause high blood pressure and high cholesterol," Lifton said.

He said its still "too early" to think about possible treatments for metabolic syndrome based on these findings. "That would really require a better understanding of the mechanism" linking impaired mitochondrial function and metabolic decline, he said.

However, once those mechanisms do become better understood, "treatments might be different, depending on whatever that answer is," he said.

Scientists have long used disease clusters within isolated families to shed light on illnesses that have the potential to touch entire populations, Lifton pointed out.

"By studying these very rare families, we begin to illuminate the basic pathways underlying common forms of disease," he said.

More information

To learn more about metabolic syndrome, head to the American Diabetes Association.

SOURCES: Richard P. Lifton, M.D., Ph.D., professor, genetics, Howard Hughes Medical Institute, Yale School of Medicine, New Haven, Conn.; Oct. 21, 2004, Science online
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