Yoghurt that might stop a heart attack

10 Mar. Daily Telegraph

Our guts are home to a microscopic world and their contents may be a matter of life or death, reports Roger Highfield.

What does it mean to be human? It’s a deceptively simple question, but the answer is complex. The reason is that most of our cells are not human at all. We depend on a vast army of microbes to stay alive: a friendly “microbiome” that protects us against germs, breaks down food to release energy, and produces vitamins.

Your digestive system alone is home to roughly 100 trillion microbes about 10 times the number of cells in the major organs. A team co led by Prof Jeroen Raes of the Flemish Institute of Biotechnology has discovered that we all have one of three basic ecosystems of bugs in our guts but strangely, the type for each person is unrelated to their race, native country or diet.

They label these “enterotypes” the “bacteriodes”, “prevotella” and “ruminococcus”, to reflect the species of bug that dominate in each. People with a bacteriodes ecosystem, for example, have a bias towards bacteria that get most of their energy from carbohydrates and proteins.

This revelation has prompted much interest, because it could explain differences in our ability to digest food. A few years ago, Prof Jeffrey Gordon’s team at Washington University School of Medicine found that the intestines of obese people contain a slightly different repertoire of microbes when compared with slim people.

In the Flemish study, researchers found a similar correlation between obesity and the abundance of bacteria that extract energy rapidly from food.

Prof Jeremy Nicholson, of Imperial College London, doubts that the latest find is of huge biological significance, since the three enterotypes probably have similar roles and capabilities.

Yet he believes that one day, it might be possible to engineer enterotypes, which could be used (for example) to boost the number of calories extracted from poor diets by children in developing countries.

That is not to say that it will be easy. The human gut contains about 1,500 bacterial species, so tinkering with their ecology in a controlled way may be tricky.

Although there are products that claim to manipulate bacteria, such as prebiotics, which fuel certain microbes, and probiotics (such as yoghurt) that contain live bacteria, we still understand too little to do this reliably.

Yet recognition of the importance of the microbiome is growing.

It has already been linked to our understanding of obesity, allergies, diabetes and cancer – and in the past few days, a study has appeared by Prof John Baker at the Medical College of Wisconsin in Milwaukee that suggests that the types and levels of bacteria in a person’s gut may be used to predict the likelihood of their having a heart attack, too.

The find, Prof Baker believes, “is a revolutionary milestone” in the prevention and treatment of such attacks. As part of his experiments, he and his colleagues induced heart attacks in three separate groups of rats.

The first was fed a standard diet. The second was given the antibiotic vancomycin and the third fed a probiotic supplement containing Lactobacillus plantarum, a bacterium that suppresses the production of a hormone called leptin, which is linked to appetite and metabolism.

It turned out that the group treated with the antibiotic also showed decreased levels of leptin and that the two groups with lower leptin levels suffered less serious heart attacks, and recovered from them better.

“We may not be ready to prescribe yoghurt to prevent heart attacks, but this research does give us a much better understanding of how the microbiome affects our response to injury,” says Dr Gerald Weissmann, editor-in-chief of the journal in which the study appeared.

Prof Jeremy Pearson, associate medical director at the British Heart Foundation, stresses that more research will be required to show whether the dramatic changes in inflammatory molecules seen in the rats would apply to humans, too.

But few doubt that, in the not too distant future, we will get dramatic new insights into our health by studying the shadow world of our microbial passengers.