Everyone is familiar with having a “gut instinct” or feeling “sick to the stomach”. Now scientists are viewing those metaphors in a new light after the emergence of a new approach to tackling obesity.
It centres on startling discoveries about a network of hundreds of millions of neurons that links our brains to our guts.
Known as the enteric nervous system (ENS), the first hints of its existence were found by the Greek anatomist Galen about 2,000 years ago. Since then, it has become clear that it is far more than just another bit of the body’s wiring.
Even primitive forms of life that barely possess anything like a brain have analogues of the ENS, pointing to its vital importance to organisms.
Research has now shown that the ENS is a neural super network, allowing signals to flow from the brain to our gut and vice versa – linking our health, mood and thoughts to our stomachs.
Such is the sophistication of the link that some researchers now talk of the ENS as being the body’s “second brain”.
And that is making it a prime target in the search for ways of tackling obesity.
With about two thirds of people in the UAE now classed as overweight or obese, the need for answers has never been more urgent.
Hospitals in the country are increasingly being called upon to carry out bariatric operations such as sleeve gastrectomies, in which surgeons remove up to three quarters of a patient’s stomach in an effort to reduce obesity.
But as this newspaper reported last week, doctors in the UAE are now warning that rapid weight loss through such radical surgery is no panacea: as many as a quarter of patients go on to gain weight later in life.
In any case, there is no hope of hospitals being able to meet the ever-growing demand.
Yet studies of bariatric surgery revealed an intriguing link with the ENS. It turns out that such operations affect the so-called vagus nerve, a key part of the circuitry connecting the ENS to the brain.
Now researchers are investigating how to trigger the same effect on the vagus nerve but without radical surgery.
Starting from the base of the brain and passing through most of the major organs, the vagus nerve acts like a “service door” into the ENS.
That has led doctors to explore its potential as a means of influencing conditions ranging from depression and migraines to inflammatory diseases such as rheumatoid arthritis.
The idea is to send electrical impulses through the vagus nerve, thus tweaking the behaviour of specific organs by remote control.
And it has been shown to work with some conditions: so-called vagal nerve stimulation (VNS) is being used by some patients to control epilepsy.
Now the same approach is being investigated as a means of treating obesity. Researchers have shown that the vagus nerve plays a key role in the hunger response – although exactly how that happens remains unclear.
Even so, by blocking its signals using tiny impulses supplied electronically, it may be possible to stop the vagus nerve from telling the brain that it is time to eat.
Last year the US Food and Drug Administration (FDA) approved a device developed by EnteroMedics in Minnesota that put this theory to the test.
More than 200 patients with a body mass index of at least 35 took part in a trial of a small VNS device implanted in their abdomen using keyhole surgery.
The study found that, after a year, those fitted with the device typically lost about 9 per cent more of their excess weight than those given a sham device. More than a third of those with the device lost at least 25 per cent of their excess weight.
Some of those taking part reported some side effects but these were deemed acceptable by the FDA to grant approval, subject to the company carrying out more research.
The current issue of the journal Obesity Surgery carries an update of research into the device – and the results remain encouraging.
Those fitted with the device lost about a third of their excess weight over the course of a year, with a quarter of the patients losing at least 50 per cent. Again, the side effects were minor.
Meanwhile, researchers at Imperial College London are working on a smarter version of VNS that triggers blocking signals only when the hunger hormones are present. The device is being prepared for clinical trials in human volunteers and could be on the market within five years.
But this device will still have to be implanted surgically. The ideal solution would be a VNS device that works through the skin.
There is hope that this may soon be possible. In its wandering path from the brain to the various organs, the vagus nerve passes through the neck and into the ear canal, providing more accessible points for applying electrical impulses.
In 2010, electroCore, a New Jersey medical technology company, developed a device for treating migraines that delivers electrical impulses to the so-called afferent fibres in the vagus nerve that run from various organs into the brain.
Clinical trials of the device showed that applying the device to a specific point on the neck for five minutes produced significant pain relief in about 50 per cent of migraine patients, and complete pain relief in about 20 per cent, along with no serious side effects.
Last month Britain’s National Institute for Health and Care Excellence approved the company’s device for treating migraine.
Now the same idea is being pursued as a simple, non-surgical means of altering the vagus nerve’s influence on hunger.
Researchers at the University Hospital of Saint-Etienne in France are now recruiting patients for a trial of a VNS device that sits inside the ear and can block excess hunger signals from the stomach.
The trial will compare the effectiveness of using the technique for an hour, four times a day, in 50 people. A similar number of people will be fitted with a sham device.
Results are expected over the next year or so, and they will attract interest from more than just obesity researchers. For if the results are positive, they could herald the start of a whole new approach to medicine.
That is enough to give any medical researcher butterflies.
Robert Matthews is a visiting professor of science at Aston University, Birmingham. His new book, Chancing It: The Laws of Chance - And What They Mean for You, is out now