Diseases of Western lifestyle linked to single genetic defect

A single genetic defect inherited solely from mothers may play a key role in a range of disorders linked to a Western lifestyle, such as high blood pressure and obesity.

A single genetic defect inherited solely from mothers may play a key role in a range of disorders linked to a Western lifestyle, such as high blood pressure and obesity.

The discovery comes from a study of an extended family in the United States, which has given scientists an insight into the root cause of potentially lethal diseases of middle age.

Medical researchers have found that a genetic defect passed on through the family contributes to an array of "metabolic disorders". This is the first time scientists have identified a single genetic mutation responsible for several metabolic abnormalities.

It is well known that certain metabolic disorders exacerbated by lifestyle, such as high blood pressure, have a strong genetic component. But this study suggests that the root causes could lie not in the genes of chromosomes, in the cell nucleus, but in the genes of the mitochondria - the microscopic power houses of the cell, outside the nucleus. Mitochondria and their genes are inherited solely from the mother.

Scientists led by Richard Lifton of Yale University Medical School in New Haven, Connecticut, found that a single change in the mitochondrial DNA of the American family was responsible for all their metabolic disorders.

Professor Lifton said that the discovery meant that many of the most common diseases in Western people could be due to the interaction between lifestyle and genes of the mitochondria. He said: "Epidemiological studies over the last 20 years have shown that hypertension, high cholesterol, high triglycerides, low magnesium, diabetes, insulin resistance and obesity tend to cluster with one another.

"But not everybody who has any one of these traits has all of the others. This finding raises the possibility that all features of the metabolic syndrome may be attributable to altered mitochondrial function."

He added: "We studied 142 relatives. When we looked at the pattern of these [diseases], we found there was an excess of affected individuals on the maternal lineage." The scientists discovered a small but critical mutation in the mitochondrial DNA of the affected relatives.

"There has never before been a report of a common genetic link among any of the three traits we found - low magnesium, hypertension and high cholesterol," the professor said.

The study, published in the journal Science, shows that the type of disorder appears to occur randomly among those who carry the same mutation. This means there must be interaction between the defective gene and the environment.