Tuesday, 5 February 2013

Fighting obesity with stem cells

Researchers from the Ottawa Hospital Research Institute released a study today where they present their findings on adult muscle stem cells (AMSCs) and how they can be triggered to turn into brown fat, one of the two types of fat found in the human body. Unlike white fat (white adipose tissue), brown fat is a form of "good fat" with many implications in the treatment of obesity.

The research team was led by Michael A. Rudnicki, who in 2007 was also the first to prove the existence of adult skeletal muscle cells. In the new study, Rudnicki shows that AMSCs have the capacity to differentiate into not only muscle fibres but brown adipose tissue-cells as well.

Brown fat, in the case of humans, is mainly found in infants. It's prime function is heat generation without requiring shivering. Brown fat cells contain higher amounts of mitochondria than white fat cells do and require more oxygen as well. Several studies have found a link between higher amounts of brown fat and a smaller chance of presenting with obesity.

Image showing the prime location of brown fat in adults
PET scan showing the main locations of brown fat, the upper chest and neck
The researchers have identified that the presence of a small gene regulator called microRNA-133 (or miR-133) induces stem cells to turn into muscle fibres. However, it's absence induces them into becoming brown fat. 

During the study, the researchers injected their mouse model with an agent called Oligonucleotide (ASO) which reduces the amounts of MiR-133. This, resulted in higher amounts of brown fat cells which in turn protected the mice from obesity. The mice also presented with an improved ability to process glucose and an increased production of heat from the whole body. 

Rudnicki believes that his team discovery is very important in the "battle against obesity".  The ASO agent is already under human clinical examination in non obesity-related conditions. However, an ASO-based treatment for obesity is still years away. Dr. Rudnicki adds that he and his team are very excited with the results, however the findings are only the first step and there is much more research needed before an actual ASO treatment is released.

Obesity is a medical condition in which patients have accumulated excess amounts of body fat. This excess amounts of fat have an adverse effect on their health, leading to reduced life expectancy and/or increased health problems. The condition may be the result of one, or a combination, of the following:
  • "Bad" Genes
  • Increased food consumption
  • Increased alcohol consumption
  • Lack of exercise
  • A symptom of a condition like Hypothyroidism, Cushing's syndrome and growth hormone deficiency

Portrait of an obese man
Portrait of an obese man
A documentary on obesity

Yin, H., Pasut, A., Soleimani, V., Bentzinger, C., Antoun, G., Thorn, S., Seale, P., Fernando, P., van IJcken, W., Grosveld, F., Dekemp, R., Boushel, R., Harper, M., & Rudnicki, M. (2013). MicroRNA-133 Controls Brown Adipose Determination in Skeletal Muscle Satellite Cells by Targeting Prdm16 Cell Metabolism, 17 (2), 210-224 DOI: 10.1016/j.cmet.2013.01.004

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