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RESEARCH UPDATE FIGHTING FAT


Scientists have discovered a new type of ‘beige fat’ cell that burns energy rather than storing excess calories


W


ith many people playing sport and exercising to control their weight, a recent study con- cerning body fat has grabbed


people’s attention. We all know too much fat is a bad thing. Yet studies into different types of fat – which burn en- ergy rather than store it – suggest that there might be new ways to tackle obe- sity. White ‘bad’ fat, is the type that stores


calories, and excess amounts of it cause people to put on weight. It’s found in abundance in obese people. Brown fat generates heat and burns


calories and has been linked to helping control weight. Brown fat dwindles with age – it was believed to only be pres- ent in children until researchers in 2009 found that it’s also active in up to 7.5 per cent of adults. But now a newer study* in the journal


Cell has reported the discovery of beige fat – a type of fat present in “most or all human beings” which has the ability to both store and burn calories.


BEIGE – THE NEW BROWN The existence of beige fat cells was first suggested in 2008 by Dr Bruce Spiegelman, a cell biologist at Har- vard Medical School. But it wasn’t until this recent study, conducted by Dr Spiegelman and scientists at Harvard’s Dana-Farber Cancer Institute, that it’s been possible to isolate the cells and de- termine their genetic profile. Beige fat cells, the scientists say, can


be found in humans in small deposits around the collarbone and spine. In this study, they cloned beige fat cells in mice to look at them more closely. The scientists discovered that beige


fat is similar to brown fat in some ways. Both contain iron, which gives them their distinct colour, and both have an abundance of mitochondria – a part of


A hormone produced by exercising muscles may stimulate cells to burn calories


the cell which can produce heat and burn calories. But there were also some significant


differences. Brown fats cells give off high levels of UCP1 a protein that mi- tochondria need to produce heat and burn calories. In comparison, beige fact cells usually express low levels of UCP1. However, beige fat can be stimulated to produce a lot of UCP1 when exposed irisin, a hormone released by muscles during exercise or when muscles shiver due to exposure to cold temperatures. It was also found that the cells differ


from each other genetically. Brown fat cells originate from muscle stem cells. In contrast, beige fat cells emerge from white fat cells – making it possible for them to store fat when levels of UCP1 are low, but burn it when muscles re- lease irisin through exercise.


FIGHTING OBESITY The study reports: “The therapeutic po- tential of both kinds of brown [brown


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and beige] fat cells is clear, as genetic manipulations in mice that create more brown or beige fat have strong anti- obesity and anti-diabetic actions.” It is hoped that these discoveries may


lead to new treatments in obesity. In- deed, Spiegelman has already set up a biotech company, Ember Therapeutics, in an attempt to develop irisin in a drug form to stimulate brown and beige fat cells to increase weight loss. However, this is still a very new field.


While more brown and beige fat cells are found in fit compared to sedentary people, for example, more research is needed to prove the two are directly linked. It’s believed that the effects of irisin may only be temporary but scien- tists don’t know this for sure yet.


*Spiegelman, Bruce M et al. Beige Adipocytes Are a Distinct Type of Thermogenic Fat Cell in Mouse and Human. Cell, Volume 150, Issue 2, p366-376. July 2012


Issue 1 2013 © cybertrek 2013


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