A range of common health problems could be caused by gene faults in aging mitochondria - the 'powerhouses' of the cell - US scientists say. The team, based at Yale University School of Medicine, say their findings could help explain 'metabolic syndrome' - a combination of high blood pressure, high blood cholesterol, obesity and insulin resistance. Together, these symptoms increase the risk of type II diabetes, heart disease and stroke.
The researchers studied a large, extended family in which many female members were affected by high blood pressure, high cholesterol or low magnesium levels. The team, who published their work in the journal Science, studied 142 women in the family, half of whom had all three conditions. Since no male relatives were affected, the scientists suspected that a gene found in the mitochondria might be responsible. Mitochondria are inherited solely through the maternal line, since those present in the sperm are packed into the tail, which falls off after fertilisation and so does not contribute anything to the fertilised egg.
Mitochondria contain around 35 of the estimated 25,000 genes that make up the human genome, the rest of which are located in the cell nucleus. The researchers found that the affected women had a mitochondrial gene mutation that interferes with the mitochondria's ability to make proteins. None of the unaffected members of the family had inherited the mutation. However, many of the younger affected women had low magnesium levels, but not high cholesterol or high blood pressure. This suggests that other factors such as diet are involved in triggering the conditions.
Team leader Richard Lifton said there had been no previous reports of a common genetic link between the three conditions studied. He thinks that similar mitochondria faults could trigger metabolic syndrome in the general population. However, he told BBC News Online that despite linking the traits to the mitochondrial defect, 'there remains a complex black box in between', adding 'we don't know the mechanism that links the two'. UK cardiovascular expert Hugh Watkins, of Oxford University, said that the new research 'doesn't answer the big questions, but it does give us a place to start looking'.