Child Abuse Linked to Adolescent Obesity

December 7, 2016 · Posted in Risk Factors · Comment 

child abuse linked to adolescent obesityNew research clarifies how trauma in early life can lead to obesity in adolescence. In a study of 160 young people between the ages of 9 and 15, researcher Janitza Montalvo-Ortiz and colleagues identified seven sites in the genome where DNA methylation predicted body mass index (BMI) in adolescence. The researchers also collected information on family traumas that occurred during the participants’ childhoods and found that DNA methylation and family trauma such as child abuse interacted to predict BMI.

Epigenetics describes the ways life experiences can change how easily DNA is turned on or off. While the genes coded by DNA sequences one inherits from one’s parents never change, the structure of DNA can change. DNA methylation is one type of epigenetic change that refers to the addition of methyl groups to promoter regions of DNA in response to life events.

In this research, which was presented at the 2016 meeting of the Society of Biological Psychiatry, Montalvo-Ortiz and colleagues found that the site of DNA methylation with the strongest link to BMI in adolescence was a gene called MAP2K3. This gene had previously been linked to obesity, but this is the first time DNA methylation at this site has been linked to both obesity and childhood trauma. Other relevant gene sites where DNA methylation occurred include ANKRD2, CPXM2, NUBPL, and RFK.

Early Experiences Have Lasting Effects on DNA

October 28, 2015 · Posted in Genetics, Risk Factors · Comment 

nurse visits family

It is well established that certain early experiences can affect a person’s risk of developing a mental illness. Adversity in childhood, including abuse or the loss of a parent, is a risk factor not only for diagnosis of a mood disorder, but also for a more difficult course of illness. This may occur through epigenetic means. Epigenetics refers to a process by which environmental factors can change the way that DNA is transcribed, for example through the addition of methyl groups to strands of DNA. This tends to inhibit DNA from being transcribed and producing protein growth factors and other neurochemicals that are important for development.

A study by Kieran J. O’Donnell and colleagues presented at the 2015 meeting of the Society of Biological Psychiatry investigated whether epigenetics play a role in the success of a parenting intervention called the Nurse Family Partnership. Participants were 27-year-olds born to women who had received the intervention or a control intervention. Genome-wide DNA methylation was measured in the 188 participants’ blood.

Analysis of the blood revealed that the Nurse Family Partnership intervention was associated with DNA methylation at 1015 sites across 593 genes. Some of these sites were enriched for certain neurodevelopmental processes. Maltreatment in childhood was also associated with methylation at 1552 sites across 878 genes.

Editor’s Note: The take-home message of this landmark study is that maltreatment in childhood exerts lasting effects on the genome via epigenetic mechanisms, but early positive intervention also exerts lasting epigenetic effects, which likely have a normalizing impact.

Types of Epigenetic Modifications

January 3, 2014 · Posted in Genetics, Theory · Comment 

DNA strandWe sometimes refer to epigenetics, a process by which the environment impacts not your inherited genes (based on the DNA nucleotides that encode amino acids to be sequenced in the production of proteins), but how easy it is to activate gene transcription or repress gene transcription.

There are various epigenetic modifications that can occur. Sometimes acetyl or methyl groups are added to DNA or the histones around which DNA is wound.

1. DNA Methylation (usually repressive)

2. Histone Methylation (usually repressive)

3. Histone Acetylation (usually activating)

4. DNA hydroxymethylation

5. Micro RNAs (si-mRNA) (repressing or activating)

6. Nucleosome remodeling by chromatin regulatory enzymes. If the histone spools around which DNA is wrapped are moved further apart, this is activating. If the histones are moved closer together, this is repressing.

Childhood Adversity and Epigenetic Pockmarks

August 19, 2013 · Posted in Risk Factors · Comment 

Neglected lonely childMaltreatment in childhood may have a lasting impact on health through epigenetics. Epigenetics refers to the idea that events and substances in the environment can affect the structure of DNA by adding chemicals (often methyl or acetyl groups) onto DNA and histones (structures around which DNA is wound) in such a way that the DNA is more or less likely to be transcribed and activated to produce new proteins. Thus our DNA is shaped not only by the genetic inheritance we receive from our parents, but also by events in the environment (which do not alter the sequence of DNA but can influence how easily the DNA gets turned on to produce proteins in our bodies.)

A 2013 study by Divya Mehta et al. published in the Proceedings of the National Academy of Sciences analyzed the childhood backgrounds of adult patients with PTSD and found that patients’ profiles of disease-related gene expression and DNA methylation in blood differed greatly depending on whether or not they had experienced abuse in childhood. Adults who had been abused as children were about twice as likely to show patterns of DNA methylation accompanying their PTSD-related changes in gene expression.

The implication of this research is that childhood trauma can leave a kind of epigenetic pockmark on a person’s DNA, affecting the way the DNA produces proteins, potentially for the rest of that person’s life.

Rats Exposed to Jet Fuel Pass Epigenetic Changes on to Third Generation

April 8, 2013 · Posted in Risk Factors · Comment 

rat

A recent study of rats showed that exposure to hydrocarbons (jet fuel JP-8) can bring about disease not just in the rats who were exposed, but also in subsequent generations. Epigenetics is the study of how environmental events or biochemical changes can affect the structure of DNA, e.g. by attaching extra methyl groups. (These kinds of “epimutations” are separate from the inherited genetic makeup we receive from our parents, but new evidence suggests that some can be passed on to future generations.)

When first generation female rats were exposed to jet fuel, third generation rats showed 33 different examples of DNA methylation as well as obesity.

Previous research has shown similar signs of transgenerational transmission of disease resulting from first generation exposure to chemicals such as bisphenol A, phthalates, dioxins, and pesticide mixtures.

Depression Associated with Increased DNA Methylation

March 25, 2013 · Posted in Risk Factors · Comment 

DNA

Epigenetics is an emerging field where researchers are studying the ways environmental events and biochemical changes can affect the structure of DNA. Chemicals such as methyl groups can accumulate on DNA (a process called methylation), which usually results in suppression of genes in that area. DNA is tightly wound around proteins called histones, which can also be methylated or acetylated (when acetyl groups accumulate) based on events in the environment, including stressors and drug use. The environmental events do not change the genetic inheritance people receive from their parents, but instead change the ease with which genes are transcribed (or switched on).

At the 2012 meeting of the Society of Biological Psychiatry, Dr. Yurong Xin et al. presented an abstract that indicates that depressed patients may have much more DNA methylation at CpG sites on genes. CpG sites occur in many genes and refer to a place where a cytosine and a guanine (two of the four building blocks of DNA) sit next to each other on the same strand of DNA (the ‘p’ refers to the chemical bond between the two). CpG sites can become methylated. Xin and colleagues measured 27,578 CpG sites across 14,000 genes in the human genome. They found an eightfold increase in DNA methylation at these CpG sites in depressed patients compared to controls.

Editor’s Note: Previous research has found that early life experiences like psychosocial stress can lead to epigenetic changes. The new findings by Dr. Xin indicate that DNA methylation may occur and accumulate across the lifespan and suggests that DNA methylation may be associated with the emergence and progression of depression. Future treatments for depression could target this DNA hypermethylation, but determining how to do that selectively without affecting normal functioning may be a challenge.