Key that lets in COVID to rampage through your

The virus works by locking on to receptors found on cells . . . and being overweight (or a man) means you could be more at risk

Every week the alarming truth about the Covid-19 coronavirus is becoming clearer. Some of us are much more likely to die from it than others, and the key reasons are just beginning to be unravelled by scientists.

For most fit and healthy people, the risk is small to non-existent; but for others, the possibility of dying once infected is frightening. While there have been just two deaths among children aged under 15 in the UK, there have been more than 30,000 in those aged over 60.

We now know that being overweight, with its associated problems of type 2 diabetes, high blood pressure and heart disease, substantially increases the danger of not surviving the infection — thought to be as a result of a weakened immune system.

If you combine this with the additional risk of age-related decline in the immune system, the danger is even greater.

But now it seems there is another sinister element to the story which might explain why deaths in men outnumber those in women by two to one, why overweight people are badly affected, why some minority ethnic groups may be at higher risk of complications and possibly why smokers seem to be protected from catching the infection (and why they fare badly if they do get it).

evidence is emerging of the role of a cell receptor called ACe2, which Covid-19 attaches to in order to infect our healthy cells. It’s thought that the more of these receptors you have, the more entry points there are for the virus.

The ACe2 receptor was found to be the main entry point for the potentially lethal severe acute respiratory syndrome (SArS) virus, of which this new coronavirus is the latest version. The receptors are found on cells in the nose lining, the lungs, pancreas, kidneys and gut, and in the lining of blood vessels, in the heart muscle and circulating on cells in the blood.

The variety of locations could help explain why those people with Covid-19 have suffered such a wide range of different symptoms, from loss of a sense of taste and smell to stomach problems such as diarrhoea and post-infection heart problems.

The normal role of the ACe2 receptor is in blood pressure control. It sits on our cells and is activated by a chemical messenger in our blood: if blood pressure is high, the receptor causes blood vessels to dilate.

It works alongside another blood pressure regulatory compound simply called ACe (this is not a receptor but an enzyme) which causes blood vessels to constrict. Together, ACe2 and ACe keep blood pressure levels regulated. It’s this system that ACe inhibitors — drugs for high blood pressure and heart failure taken by 15 per cent of all adults in Britain — are designed to target, blocking the enzyme and preventing blood pressure rising.

OBESITY MEANS MORE ‘ENTRY POINTS’

The Covid-19 coronavirus is designed to fasten itself on to ACe2 receptors like a key opening a lock. It then gets into the cell and re-programs it to make multiple copies of the virus.

It then destroys these exhausted cells and billions of copies of the virus are released, which then infect other cells around the body.

This process causes a clog-up of dead and decaying cells and an associated immune reaction (which leads to the symptoms of the disease). For those with high levels of ACe2 receptors, there are many more entry points for the virus, so more chance of severe disease and worse outcomes.

Now studies have highlighted groups who have more ACe2 receptors, and those who have fewer. An investigation published last week in The Journal of the American Medical Association, by doctors at Mount Sinai hospital in New york, showed four-year-old children had fewer ACe2 receptors in their noses than older adults.

And it seems people with high blood pressure and heart disease produce more of these receptors as their bodies struggle to cope with a malfunctioning system. An international study published this month in the european heart Journal looked at ACe2 receptor levels in 1,485 men and 537 women with heart failure — a major cause of high blood pressure. In men, ACe2 receptors were circulating in higher volumes in cells found in their blood and even in the testes.

Another study, published last week in the journal Obesity, found that overweight people with the lung condition chronic obstructive pulmonary disease (COPD), which is linked to damage caused by smoking, ‘have more of the receptor or entry points required for coronavirus infection in their lungs’, said the lead author Dr Andrew higham, a researcher in the division of infection, immunity and respiratory medicine at the

University of Manchester. ‘This means these patients may be at a greater risk of developing Covid-19 due to increased opportunities for infection.’ There are 1.2million

Britons with COPD. It is clear that fat cells, too, produce more ACe2 receptors. ‘The more fat you have, the more ACe2 receptors you’ve got,’ says Professor Sanjay