Could a simple blood test predict a person’s risk of dying from heart disease or cancer?
Reporting in an early online publication of the Journal of the American Medical Association and at the European Society of Cardiology Congress, Johan Arnlov and his colleagues say that a certain enzyme that is measured in the blood may be linked to both heart disease and cancer, and therefore could serve as an early predictor of who is mostly likely to die from these diseases.
In the study, which involved nearly 2,000 people enrolled in two separate long-term trials, Arnlov’s team measured the levels of cathepsin S, an enzyme involved in breaking up proteins. They then tracked these volunteers for up to 12.5 years, and found that those with the highest levels of cathepsin S were more likely to die than those with lower, or about half those levels.
What is unique about the study is that it’s the first to identify a marker associated with both heart disease and cancer, two of the leading killers of American adults. The effect remained strong even after the scientists adjusted for other factors that can contribute to heart- and cancer-related death, such as age, blood pressure, history of heart disease, diabetes and cholesterol levels.
Arnlov decided to focus on cathepsin S because previous studies have linked the enzyme to atheroslcerosis, or the buildup and hardening of the arteries that increase the risk of heart disease. In animal studies, mice without the gene for cathepsin S developed less heart disease, and, interestingly, less cancer, compared with those animals that had the gene. Early studies in people have also showed that obese individuals tend to have higher levels of cathepsin S, and that if they lose weight, their levels go down.
“Cathepsin S is involved in several processes in the body,” says Arnlov. “It is involved in the immune system, in regulating how [foreign material] is presented to the immune system, and it is highly expressed in [fat] tissue. It is involved in several crucial steps in the atherosclerotic process as well as in tumorgenesis.”
But, he says, it’s not clear exactly how cathepsin S might contribute to either heart disease or cancer. Nor is it obvious yet which tissues are producing the enzyme and whether there is a normal or healthy level. For example, the enzyme appears to be involved in inflammation, which can make plaques in the blood vessels unstable and trigger a heart attack, but it does not seem to be affected by levels of other inflammatory factors that have been linked to heart disease risk, such as C-reactive protein, or CRP.
“To be honest, we don’t know really what circulating levels of cathepsin S reflect,” says Arnlov. “We can’t be sure in what tissues it originates; we have no idea. So further studies need to elucidate what the circulating levels of cathepsin S really [mean].”
He says it’s too early to know whether cathepsin S can be useful in predicting who is at greatest risk of having heart disease, or whether levels of the enzyme in the blood can even become an early warning for cancer. But already pharmaceutical companies are targeting cathepsin S with compounds that block its activity. Those studies will likely provide answers to some critical questions about whether the enzyme really can be a biological crystal ball.
A blood test to determine how fast someone is ageing has been shown to work on a population of wild birds, the first time the ageing test has been used successfully on animals living outside a laboratory setting.
The test measures the average length of tiny structures on the tips of chromosomes called telomeres which are known to get shorter each time a cell divides during an organism’s lifetime.
Telomeres are believed to act like internal clocks by providing a more accurate estimate of a person’s true biological age rather than their actual chronological age.
This has led some experts to suggest that telomere tests could be used to estimate not only how fast someone is ageing, but possibly how long they have left to live if they die of natural causes.
Telomere tests have been widely used on experimental animals and at least one company is offering a £400 blood test in the UK for people interested in seeing how fast they are ageing based on their average telomere length.
Now scientists have performed telomere tests on an isolated population of songbirds living on an island in the Seychelles and found that the test does indeed accurately predict an animal’s likely lifespan.
“We saw that telomere length is a better indicator of life expectancy than chronological age. So by measuring telomere length we have a way of estimating the biological age of an individual – how much of its life it has used up,” said David Richardson of the University of East Anglia.
The researchers tested the average telomere lengths of a population of 320 Seychelles Warblers living on the remote Cousin Island, which ornithologists have studied for 20 years, documenting the life history of each bird.
“Our results provide the first clear and unambiguous evidence of a relationship between telomere length and mortality in the wild, and substantiate the prediction that telomere length and shortening rate can act as an indicator of biological age further to chronological age,” says the study published in the journal Molecular Ecology.
Studying an island population of wild birds was important because there were no natural predators and little migration, meaning that the scientists could accurately study the link between telomere length and a bird’s natural lifespan.
“We wanted to understand what happens over an entire lifetime, so the Seychelles warbler is an ideal research subject. They are naturally confined to an isolated tropical island, without any predators, so we can follow individuals throughout their lives, right into old age,” Dr Richardson said.
“We investigated whether, at any given age, their telomere lengths could predict imminent death. We found that short and rapidly shortening telomeres were a good indication that the bird would die within a year,” he said.
“We also found that individuals with longer telomeres had longer life spans overall. It used to be thought that telomere shortening occurred at a constant rate in individuals, and that telomere length could act as an internal clock to measure the chronological age of organisms in the wild,” Dr Richardson said.
“However while telomeres do shorten with chronological age, the rate at which this happens differs between individuals of the same age. This is because individuals experience different amounts of biological stress due to the challenges and exertions they face in life. Telomere length can be used as a measure of the amount of damage an individual has accumulated over its life,” he added.
Source :www.independent.co.uk/
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