Researchers have found bacteria and bacterial components in human adipose tissue and other metabolic tissues, but they do not fully understand what the bacteria are doing there and what this has to do with the risk of developing disease. One researcher involved says that much more research is needed in this field.
Bacteria inside and on people strongly affect health. This applies to gut bacteria, which affect the development of such disorders as cardiovascular disease and obesity.
Bacteria on the skin, in the lungs, in the abdomen and in the nose also affect health. Some bacteria benefit health and others would preferably be eliminated completely.
In 2020, researchers discovered that adipose tissue contains bacteria and bacterial components .
How they got there and how this affects health is still unclear, but one researcher who helped to make the startling discovery advocates action.
Lucas Massier, Postdoctoral Fellow from the Karolinska Institutet in Stockholm, Sweden says that bacteria in adipose tissue may influence the development of many diseases, and researchers should therefore also study the importance of these bacteria and whether they might be targets for new treatments.
“This is a much-debated field that has not yet been well researched because it only opened up a decade ago. Now we need to figure out what to do to improve our knowledge,” he says.
Lucas Massier and colleagues have published a perspective article on the next steps in research on the role of bacteria in adipose tissue.
The article has been published in Nature Metabolism.
Not a random discovery
Two studies from 2020 found that bacteria probably have a role in human adipose tissue.
These first studies were met with scepticism, and other researchers speculated whether finding bacteria in human adipose tissue resulted from contamination in the studies and is not a natural phenomenon.
However, this speculation has since been largely rejected, and the current hypothesis posits that bacteria migrate from the gut to the adipose tissue without being able to explain how or why this happens.
“Some of the first studies in this field were very poorly executed, which made the results less credible. But we are now quite sure that bacteria have a role in adipose tissue, but we do not yet know what this involves,” says Lucas Massier.
May affect disease progression
These bacteria could play a role in fat metabolism in the body, just as gut bacteria do.
Perhaps the bacteria and the bacterial components in the adipose tissue influence the risk of obesity, metabolic disorders or cardiovascular diseases.
If this is the case, investigating whether manipulating the composition of the bacteria in the adipose tissue can influence the risk of developing these disorders could be relevant.
This is already being done for gut bacteria. Within this field, many experiments are taking place in which researchers try to change the composition of gut bacteria with the aim of reducing symptoms of disease or completely curing them.
“We have to assume that everything has a purpose and that the bacteria are not just in the adipose tissue by accident. The task now is to find out the reason,” says Lucas Massier.
Bacteria affect the metabolism of adipose tissue
Researchers have now taken the first steps towards improving understanding of the role of bacteria in adipose tissue in experiments with mice and in cell cultures in the laboratory.
These experiments have shown that the fat cells change their metabolic profile when they are exposed to bacteria, lipopolysaccharides from bacteria and bacterial DNA derived directly from the intestines.
The effect is often minimal, but it is measurable even at clinically relevant concentrations and often results in inflammation.
“However, whether this affects the development of obesity and diabetes is not yet known,” notes Lucas Massier.
He elaborates that everything may not be negative. Some bacteria or bacterial components may improve insulin sensitivity and thereby contribute to improving health.
Understanding which bacteria are beneficial in adipose tissue and which should preferably be eliminated to enable people to live as healthy and disease-free a life as possible is therefore relevant.
“This can improve understanding of the risk of developing metabolic disorders and whether some of these bacteria or their products might be targets for new treatments,” explains Lucas Massier.
Many more studies required
The purpose of the article in Nature Metabolism is to provide guidelines for future research in this field.
According to Lucas Massier, this research should include several experiments using animal models.
More functional cell studies should also be undertaken in which researchers investigate the exact role of the bacteria and bacterial components, both in the adipose tissue and in the cells in the tissue.
“We do not think that there is a specific tissue microbiome, but we are uncertain about the effects of the composition of bacteria and bacterial products. We need to investigate this further, so that in five years we can better understand the role of the bacteria in adipose tissue, how this affects health and whether this requires action,” concludes Lucas Massier.
“Tissue-resident bacteria in metabolic diseases: emerging evidence and challenges” has been published in Nature Metabolism. The research was supported by the Swedish Society for Medical Research, the Swedish Research Council, a Walter Benjamin Fellowship grant from the German Research Foundation and the Novo Nordisk Foundation through a Young Investigator Award.
