24 September 2010

Epigenetic Link To Body Mass Index Found

First, cold viruses are implicated as playing a major role in obesity. Now, another study of 74 adults over the age of 57 years old, is finding that epigenetics ("changes in gene activity that do not involve mutations to DNA, but manage to survive through cell replication . . [and] govern gene expression") play an important role in obesity.

So, what is your epigenome again?

Though most of your epigenome is static and determined at birth, a small subset changes over time, and these changes are now being ascribed to environment factors and even behavior — whether you smoke, feel stressed or eat an unhealthy diet, for instance. Some scientists argue that epigenetic changes — the most common type is known as DNA methylation — can be passed onto future generations.

And, what exactly did the researchers find?

The team began by mapping 4.5 million areas of the human genome. Of the 4.5 million locations, researchers found that 227 were distinct between people — like an epigenetic fingerprint. Two-thirds of those distinct locations remained constant over time, but one-third changed over the course of the 11-year study. Feinberg attributes these changes to environmental and behavioral influences. . . . [S]ome of the genetic methylation that occurred over the course of the study — involving the expression of 13 genes — was in fact related to BMI.

Multiple observations:

1. All but one in 19,823 areas of the epiggenome studies were exactly the same in 74 different subjects. The part of a person's epigenome that differs from person to person could be described in a shorthand notation that would fit in a couple of text messages. Indeed, since there are far fewer than 40 different possible values at any distinct epigenome location studied, and it is likely that not all possible combinations may actually manifest themselves, one could probably devise a code that would describe a person's entire epigenome in a single text message.

2. The parts of the epigenome relevant to BMI are a small subset of the total variable portion of the epigenome studied. This could be described with a code about the length of the typical e-mail password.

3. It is possible to distinguish between epigenomic profiles that people are basically stuck with and can't change through behavior, and those that your environment can change.

4. From a potential medical perspective, changing someone's epigenome is probably easier than changing someone's genes.

5. This study is one more nail in the coffin of the conventional wisdom, common among physicians and other people who deal with obesity problemes professionally, that obesity is a simple product of how many calories you eat per day and how much you exercise.

6. Knowledge of the particular role played by the genes whose activity is epigenetically influenced in ways linked to BMI helps us understand the biochemistry of obesity and may suggest novel approaches to controlling obesity with drugs or diet.

7. Testing of BMI relevant epigenetic locations may make it possible to profile people's natural tendencies with regard to obesity and learn which approaches work best with different kinds of obesity.

8. It is possible that cold virus infections linked to obesity have a mechanism that changes someone's epigenome. Knowing the mechanism by which cold virus infections can lead to obesity would allow researchers to know which treatments would be or would not be likely to be effective.

No comments: