Scottish scientists have traced the origins of a type of fat known as a “silent killer” which they hope could help lead to new treatments.
The researchers in Edinburgh found that visceral fat - which builds up dangerously around organs, even in people who do not appear overweight - could be traced back to a single type of cell in the developing embryo.
They hope the findings could lead to ways of stopping the body building up this “bad” fat around organs.
The body contains two main kinds of fat - subcutaneous fat which sits directly beneath the skin providing energy and insulation, and visceral fact which forms in deposits around the vital organs including the heart and intestines.
Research has shown that high levels of visceral fat are linked to a higher risk of cancer, Type 2 diabetes, cardiovascular disease and Alzheimer’s, while subcutaneous fat is thought to be protective.
But scientists have struggled to understand where the two fats originate.
Now researchers from the Medical Research Council’s Human Genetics Unit at Edinburgh University have helped pinpoint the source, which they hope could have important implications for the future understanding of obesity and its causes of ill-health.
Using genetically modified mice, the researchers showed that up to 80 per cent of visceral fat in the body could be traced back to a single type of cell found in the developing embryo in the womb.
These early fat cells expressed a gene called Wt1, which was not found in subcutaneous fat cells.
The researchers, writing in the journal Nature Cell Biology, said this suggested that the two types of fat came from different sources.
Cells expressing the Wt1 gene were also found in the visceral fat of adult mice, with these cells continuing to make more fat cells throughout life.
The highest number of these cells were found in fat deposits around the heart and stomach - the riskiest places to carry excess fat.
The scientists suggested that understanding how it may be possible to control these cells could lead to treatments that help stop the body from laying down more “bad” fat around the organs.
In some cases, even slim people can have dangerously high levels of visceral fat which is not visible from their appearance. It is also present in people who are overweight.
Professor Stephen Hill, chair of the MRC’s molecular and cellular medicine board, which funded the work, said: “Visceral fat can be a silent killer because it’s possible to have a lot of it without looking fat on the outside.
“Studies like this one are important because they help us to understand how our genes and other biological factors are involved in regulating visceral fat, so that in future we can devise new ways to prevent or treat the devastating consequences of obesity.”
Lead researcher Dr You-Ying Chau said their findings should help lead to treatments to combat bad fat, but this could take some time.
“If we could find a way to control the regulation of these cells, we might be able to stop the body laying down any more bad fat around the organs.
“However, it will take many more years of research before we get there,” she said.
The researchers also found that visceral fat, like the organs it surrounds, had its own protective membrane called a mesothelium, which also contained the Wt1 gene and could also act as a source of visceral fat.
Professor Nick Hastie, leader of the research team and Director of the MRC Human Genetics Unit, added: “We found strong evidence for the existence of a mesothelium, which was a big surprise because nobody thought this membrane existed in fat.
“It seems that not only does the mesothelium help produce the cells that make the fat, it also surrounds the fat, making it into a neat little organ.”