Obesity, Epigenetics and a Wild Card

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DNA methylation is one of several epigenetic processes that cells can use to control gene expression by switching genes off. Apparently, we can influence the impact of DNA methylation by avoiding sugar and stress, and by getting enough quality sleep, and probably through a multitude of other means that we don’t even know about yet.

As Bailey Kirkpatrick says:

Perhaps even more intriguing is the discovery that certain epigenetic marks may be maintained and passed on through generations, known as transgenerational epigenetic inheritance. Ultimately, the inconsistent evidence indicates to us that the molecular mechanisms by which these tags are inherited have yet to be understood. Currently, the evidence points to more questions than answers.

Not long ago, a large international study found that high BMI subjects had DNA methylation tags “at more than 200 areas on the genome.” Also, “the researchers showed that the epigenetic changes occurred as a result of being overweight.” In other words, “alterations in DNA methylation are predominantly the consequence of adiposity, rather than the cause.”

The thing is, these changes can be passed along to the innocently unsuspecting next generation. This might be good to keep in mind, for any parent who blames a child for being fat. There is reason to suspect that the “sins of the fathers” (an expression from the King James Bible) might be responsible for the next generation’s woes, through epigenetic transmission.

The markers are, writes Eric Boodman, “like Post-it notes stuck onto the DNA telling a cell whether or not it should express a specific gene.” He reports on a study of six obese men who underwent weight-loss surgery:

By comparing sperm from before and after the surgery, they could see that the dramatic shift in a man’s weight also changed the epigenetic tags in his reproductive cells.

After centuries of the onus for everything falling on mothers, the accountability of fathers has become a real issue. For instance, a study of obese fathers showed that “The microRNA signatures of the father’s sperm and his daughter’s breast tissue was changed… [M]ammary gland development was altered and there was an increased risk of breast cancer in their daughters.”

Prepare for a shock

New and potentially explosive research from Serbia has found, as the title of a PLOS article has it, “Evidence for host genetic regulation of altered lipid metabolism in experimental toxoplasmosis supported with gene data mining results.” The parasite Toxoplasma gondii, spread by rats and mice via cats, is present in one-third of humans worldwide. The infection can exist in either acute or chronic form, and is suspected of contributing to mental health disorders such as schizophrenia. Affected fetuses can develop neurological and ocular diseases.

In the quoted study:

The results showed that acute infection was associated with a decrease in Chl content in both the liver and periphery (brain, peripheral lymphocytes), and a decrease in Chl reverse transport… We propose that the observed changes in Chl metabolism are part of the host defense response.

The liver plays a crucial role in lipid metabolism, which affects a person’s vulnerability to obesity and diabetes. The thing about T. gondii is, it can’t synthesize the cholesterol it needs, “and thus depends on uptake of host Chl for its own development.”

According to the study:

In acute infection, the host responds by an attempt to deprive the parasite of Chl, necessary for tachyzoite proliferation and development. The influence of T. gondii infection on Chl metabolism may have a significance beyond this immediate effect, as Chl influences various key physiological processes such as role in the metabolism of lipid soluble vitamins, synthesis of sex hormones etc.

Is it such an absurd idea that this widespread parasitic infection might have something to do with the obesity epidemic? One barrier to complete understanding is simply the immense number of variables that must be accounted for.

A person has about 20,000 genes. They act in different combinations, and an awful lot of traumas can happen to DNA that are capable of influencing the expression of those genes.

Another problem is that people get hold of one bit of news, and go crazy jumping to conclusions. It will take an incredible amount of research to sort out what is going on, and then more research to figure out what can be done about it.

Your responses and feedback are welcome!

Source: “Epigenetics: Avoiding the Pull of Pseudoscientific Nonsense,” WhatIsEpigenetics.com, 11/03/15
Source: “Being Overweight Adds Distinct Epigenetic Marks to DNA,” WhatIsEpigenetics.com, 12/27/16
Source: “A father’s sperm could predict whether his child will be obese,” StatNews.com, 12/03/15
Source: “Overweight Fathers May Epigenetically Increase Their Daughters’ Risk of Breast Cancer,” WhatIsEpigenetics.com, 07/05/16
Source: “Evidence for host genetic regulation of altered lipid metabolism in experimental toxoplasmosis supported with gene data mining results,” PLOS.org, 05/01/17
Photo credit: Flavio via Visualhunt/CC BY

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