Sunday, January 29, 2012

Exercise in a bottle?

Could scientists have finally found the key ingredient for an "exercise drug?" A recently discovered hormone seems to play a role in turning unhealthy "white" fat into calorie-burning "brown" fat. The hormone is named Irisin and, in mice at least, it seems to do what we've only known exercise to be able to accomplish. Brown adipose tissue (BAT) or brown fat is one of two types of fat or adipose tissue (the other being white adipose tissue) found in mammals. I’m not sure how that is possible since if the embryology is investigated it shows that BAT is related to skeletal muscle not white fat.

Brown fat is especially abundant in new born babies and in hibernating mammals. Its primary function is to generate body heat in animals or new born babies that do not shiver. In contrast to white adipocytes (fat cells), which contain a single lipid droplet, brown adipocytes contain numerous smaller droplets and a much higher number of mitochondria, which contain iron and make it brown.

In neonates), brown fat, which then makes up about 5% of the body mass and is located on the back, along the upper half of the spine and toward the shoulders, is of great importance to avoid lethal cold (hypothermia is a major death risk for premature neonates). Numerous factors make infants more susceptible to cold than adults:

 The higher ratio of body surface (proportional to heat loss) to body volume (proportional to heat production). Heat production in brown fat provides a baby with an alternative means of heat regulation.

 It was believed that after infants grow up, most of the mitochondria (which are responsible for the brown colour) in brown adipose tissue disappear, and the tissue becomes similar in function and appearance to white fat. However, more recent research has shown that brown fat is related not to white fat, but to skeletal muscle.

Further, recent studies using Positron Emission Tomography scanning of adult humans have shown that it is still present in adults in the upper chest and neck. The remaining deposits become more visible (increasing tracer uptake, that is, more metabolically active) with cold exposure and less visible if an adrenergic beta blocker is given before the scan. The recent study could lead to a new method of weight loss, since brown fat takes calories from normal fat and burns it. Brown fat cells and muscle cells both seem to be derived from the same stem cells in the embryo. Researchers found that both muscle and brown fat cells expressed the same muscle factor Myf5, whereas white fat cells did not. This suggested that muscle cells and fat cells were both derived from the same stem cell. Furthermore, muscle cells that were cultured with the transcription factor PRDM16 were converted into brown fat cells, and brown fat cells without PRDM16 were converted into muscle cells – How cool is that!?

Getting back to this miracle drug- in the lab, researchers at the Dana-Farber Cancer Institute found that when mice spent three weeks doing free-wheel running, their irisin levels increased 65 percent.  With more irisin, the mice developed more brown fat, the desirable fat that helps the body expend energy (rather than the unattractive white kind).

Could this hormone, if developed into a drug for humans, be the answer to our growing obesity and diabetes epidemics? Why can’t we just exercise people?

Any way I've decided to look like this which is going to take some hard
exercise work but I am determined! Except I would like more anatomical looking boobs - my natural boobs are fine (I think).

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