Not all fat is created equal

Why is it that fat stored in one part of the body has different health implications to fat stored somewhere else? According to researchers from the Garvan Institute of Medical Research and CSIRO, that’s just the way it’s been programmed.

The research team recently compared fat cells from under the skin and from the harmful fat inside the abdomen. In the process, they created what is claimed to be the first comprehensive genomic map revealing features that appear to ‘hardwire’ different types of fat early in cell development. Their work has been published in the journal Scientific Reports.

Fat can be harmful or largely benign, depending on where in the body it is located. ‘Subcutaneous’ fat sits underneath the skin to store energy and is generally harmless. Meanwhile, accumulation of ‘visceral’ fat, located in the abdomen, including around the liver, stomach and intestines, promotes inflammation and metabolic disturbances, and is associated with health complications such as type 2 diabetes and heart disease. This is despite the fact that, when compared with other cell types in the body, visceral and subcutaneous fat cells are very similar to each other in their function.

“It has been unclear why fat cells, which appear so similar, are associated with such different health outcomes,” said Professor Katherine Samaras, Head of the Clinical Obesity, Nutrition and Adipose Biology lab at Garvan and a co-author on the study.

Seeking answers, Prof Samaras and her colleagues isolated the fat-storing cells from visceral and subcutaneous fat biopsies from three individuals. The team compared the fat cells’ epigenomes, the chemical tags attached to DNA that control how genes are read and their transcriptomes — the genetic output of the cell.

By creating a comprehensive genomic map, the researchers discovered a number of fundamental epigenetic differences linked to changed genetic output between the cells in subcutaneous and visceral fat. Furthermore, the team discovered these differences arise early in cell development and are likely present in the precursor cells from which fat cells arise. This finding indicates that despite the fat cells’ similar appearance, fat cells become hardwired early to be harmful or non-harmful.

“Our analysis revealed epigenetic differences that may control different genes being turned on in subcutaneous and visceral fat cells that could contribute to their different properties and health effects,” said lead author Dr Stephen Bradford, from Garvan and CSIRO. This demonstrates that the epigenome can provide a view into the differences of cells that seem very similar.

The findings may guide future research to uncover the drivers of harm arising from fat build-up in different parts of the body, as well as further insight into the development of fat as well as other cell types in future. And given that some other cell types have their own health risks, any further understanding of their development could be very valuable indeed.

Image credit: ©stock.adobe.com/au/dementevajulia

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