Short Telomeres Associated with Family Risk of Bipolar Disorder

September 13, 2017 · Posted in Genetics, Risk Factors · Comment 

telomeres

Telomeres are bits of genetic material at the end of each strand of DNA that protect chromosomes as they replicate. Short telomeres have been linked to aging and a variety of medical and psychiatric diseases. Stress and depressive episodes can shorten telomeres, while treatment with lithium can lengthen them.

Telomere length is a heritable trait, and a 2017 study by researcher Timothy R. Powell and colleagues suggests that shorter telomeres are a familial risk factor for bipolar disorder.

The study, published in the journal Neuropsychopharmacology, compared the telomere lengths of 63 people with bipolar disorder, 74 of their immediate relatives (49 of whom had no lifetime psychiatric illness, while the other 25 had a different mood disorder), and 80 unrelated people with no psychiatric illness. The well relatives of the people with bipolar disorder had shorter telomeres than the unrelated healthy volunteers.

Relatives (both well and not) and people with bipolar disorder who were not being treated with lithium both had shorter telomeres than people with bipolar disorder who were being treated with lithium.

Another finding was that longer telomeres were linked to greater volume of the left and right hippocampus, and improved verbal memory on a test of delayed recall. This study provides more evidence that taking lithium increases the volume of the hippocampus and has neuroprotective benefits for people with bipolar disorder.

Levels of Amino Acid Proline Interact with COMT Genotype to Affect Negative Symptoms

May 24, 2017 · Posted in Course of Illness, Genetics, Neurobiology · Comment 

DNAIn a 2016 article, researcher Catherine L. Clelland and colleagues reported that a patient’s levels of the amino acid proline interact with their genetic profile to influence the seriousness of their negative symptoms. Negative symptoms of schizophrenia and bipolar disorder include flat affect and lack of volition and can be some of the hardest symptoms to treat.

High levels of proline in the central nervous system have been linked to schizophrenia. Proline is a precursor to the neurotransmitter glutamate, and high proline levels have been found to alter glutamate and dopamine signaling in mice. This is one of the factors affecting negative symptoms.

The other factor affecting negative symptoms is the COMT gene. The enzyme catechol-o-methlyl transferase (COMT) metabolizes dopamine in the prefrontal cortex. There are several common versions of the gene for COMT. The most efficient is known as val-158-val, identifying that the gene has two valine amino acids at position 158. People with high proline levels and the val-158-val version of the COMT gene had fewer negative symptoms than people with high proline levels and another version of the gene, val-158-met (indicating one valine and one methionine amino acid at position 158).

Clelland and colleagues hypothesized that high proline levels may actually counteract the dopamine shortages common in the prefrontal cortex in people with the val-158-val genotype of COMT, which is more efficient at breaking down dopamine in this region.

The mood stabilizer valproate increases proline levels. In the study, which was published in Translational Psychiatry, people with schizophrenia and the val-val genotype had fewer negative symptoms when treated with valproate than those with the val-met genotype who received the same treatment.

Early Cannabis Use and BDNF Gene Variant Increase Psychosis Risk

May 3, 2017 · Posted in Genetics, Risk Factors · Comment 

Teen smoking marijuanaNormal variations in genes can affect risk of mental illness. One gene that has been implicated in psychosis risk is known as BDNF. It controls production of brain-derived neurotrophic factor, a protein that protects neurons and is important for learning and memory. Another important gene is COMT, which controls production of the enzyme catechol-O-methyltransferase, which breaks down neurotransmitters such as dopamine in the brain.

Several forms of these genes appear in the population. These normal variations in genes are known as polymorphisms. Certain polymorphisms have been linked to disease risk. A study by Anna Mané and colleagues published in the Journal of Psychiatric Research in 2017 explored links between COMT and BDNF polymorphisms, cannabis use, and age at first episode of psychosis.

Mané and colleagues found that among 260 Caucasians being treated for a first episode of psychosis, the presence of a BDNF polymorphism known as val-66-met and a history of early cannabis use were associated with younger age at psychosis onset.

The val-66-met version of BDNF occurs in 25-35% of the population. It functions less efficiently than a version called val-66-val.

The researchers also found that males were more likely to have used cannabis at a young age.

Editor’s Note: In the general population, marijuana use doubles the risk of developing psychosis. Previous data had indicated that the risk was higher for those with a COMT polymorphism known as val-158-val that leads to more efficient metabolism of dopamine in the prefrontal cortex. The resulting deficits in dopamine increase vulnerability to psychosis compared to people with the val-158-met version of the COMT gene.

The new study by Mané and colleagues suggests that a common form of BDNF may be associated with an earlier onset of psychosis. Bottom line: Pot is dangerous for young users and can induce psychosis, particularly in people at genetic risk. Pot may be legal in many places, but heavy use in young people remains risky for mental health and cognitive functioning.

The company Genomind offers genetic testing for BDNF and COMT variants as part of a routine panel.

In Rats, Mother’s Exercise Habits Affect Those of Offspring

October 10, 2016 · Posted in Genetics · Comment 

mothers who exercise more have offspring who exercise moreA recent study suggests that when a mother rat exercises during pregnancy, her offspring will exercise more too.

In the study, published by Jesse D. Eclarinel and colleagues in The FASEB Journal, pregnant mother rats were placed in cages that each contained an exercise wheel. One group had access to a working wheel on which they could run. The other group had the same wheel, but it was locked so that they couldn’t use it for running. Daughters of the rats who ran during pregnancy ran more in adulthood (both at 60 days and 300 days after birth) than daughters of the rats who couldn’t run during pregnancy.

While it is a mystery why this occurs, it is consistent with other data about the ways that a parent’s experiences can influence the next generation, even when the offspring don’t grow up with the parents.

For example, father rats conditioned to associate a specific smell with fear of an electric shock have offspring that also fear that smell (but not other smells).

Drug use is another example. Father rats given access to cocaine have offspring that are less interested in cocaine. Interestingly, father rats exposed to marijuana have offspring that are more interested in opiates.

Experiences with drugs or stress are thought to affect the next generation via ‘epigenetic’ marks on ova or sperm. These marks change the way DNA is packaged, with long-lasting effects on behavior and chemistry. Most marks from a mother’s or father’s experiences are erased at the time of conception, but some persist and affect the next generation.

The nature versus nurture debate is getting more and more complicated. Parents can influence offspring in a number of ways: 1) genetics; 2) epigenetics in the absence of contact between parent and offspring after birth; 3) epigenetic effects of behavioral contact—that is, parents’ caring and warmth versus abuse and neglect can affect offspring’s DNA expression too. All these are in addition to any purely behavioral influence a parent may have on their offspring via discipline, teaching, being a role model, etc.

Editor’s Note: The moral of the story is, choose your parents wisely, or behave wisely if you yourself become a parent.

DNA Repair Plays Role in Brain Development, Cancer, and Aging

September 5, 2016 · Posted in Genetics · Comment 

DNA repair

DNA has several ways of repairing itself. Serious damage, including breaks to both strands of the double helix and problems with replication, prompt a process known as DNA damage repair, or DDR. Researcher Stephen J. Elledge of Harvard Medical School won the 2015 Albert Lasker Basic Medical Research Award for his findings about DDR. He summarized these findings in a September article in the journal JAMA.

DDR occurs because of DNA’s remarkable self-awareness. Through the DDR process, DNA can detect when it has been damaged and prompt the right kind of repair. When damage occurs, DDR allows for the activation of enzymes that can remodel DNA to maintain the integrity of the genome.

When DDR pathways are activated, they can alter more than 1000 different proteins. DDR can affect immune function, blood and bone marrow, viral response, cancer, aging, and brain development.

Mutations in components of the DDR pathway can lead to problems with brain development, including Seckel syndrome (characterized by dwarfism, brain and facial abnormalities, and mental retardation) and ataxia telangiectasia (loss of control of bodily movements along with weakened immune system).

DDR is particularly relevant to cancer, since properly functioning DDR promotes a stable genome. Classic cancer treatments such as radiation and chemotherapy also rely on DDR to prompt cell death.

DDR also plays a role in aging. When we get older or have certain illnesses, telomeres, bits of material at the end of DNA strands that protect the DNA during replication, get shorter. This prompts DDR to engage in tumor prevention measures, either killing off the cells or changing them into what’s called senescent cells. Senescent cells prevent tumors, but their accumulation is associated with chronic inflammation, aging, and age-related diseases.

Editor’s Note: You can protect your telomeres and possibly hold off the age-related effects of DDR. Healthy diet, exercise, meditation, goal setting, and making positive contributions to society all help maintain telomere length. Lithium treatment also directly increases telomere length.

In Rats, Dad’s Cocaine Use Affects Son’s Spatial Memory

July 14, 2016 · Posted in Genetics, Neurobiology · Comment 

cocaine use affects offspring's spatial memory

Evidence is mounting that certain behaviors by parents can leave marks on their sperm or eggs that are passed on to their offspring in a process called epigenetics. In a recent study by researcher Mathieu Wimmer and colleagues, male rats that were exposed to cocaine for 60 days (the time it takes for sperm to develop fully) had male offspring who showed diminished short- and long-term spatial memory compared to the offspring of male rats that were not exposed to cocaine. Female offspring were not affected in this way.

The spatial tasks the offspring rats completed depended heavily on the hippocampus. Wimmer and colleagues believe that cocaine use in the fathers decreased the amount of a brain chemical called d-serine in the offspring. D-serine plays a role in memory formation and the brain’s ability to form synaptic connections. Injecting the offspring of rats who were exposed to cocaine with d-serine before the spatial memory tasks normalized the rats’ performance.

Over-Pruning of Synapses May Explain Schizophrenia

April 15, 2016 · Posted in Genetics, Neurobiology · Comment 

over-pruning of synapses in schizophrenia

A gene that plays a role in the pruning of synapses has been linked to schizophrenia. The gene encodes an immune protein called complement component 4 (C4), which may mediate the pruning of synapses, the connections between neurons. Researchers led by Aswin Sekar found that in mice, C4 was responsible for the elimination of synapses. The team linked gene variants that lead to more production of C4A proteins to excessive pruning of synapses during adolescence, the period during which schizophrenia symptoms typically appear. This may explain why the brains of people with schizophrenia have fewer neural connections. The researchers hope that future therapies may target the genetic roots of the illness rather than simply treating its symptoms.

Memory Activates Epigenetic Changes in Mice Brain Cells

April 4, 2016 · Posted in Genetics, Neurobiology · Comment 

epigenetic changes to mouse brain cells

In a 2015 article in Nature Neuroscience, Stefan Bonn and André Fischer reported that when mice were prompted to use their long-term memory to recognize a specific environment, epigenetic changes occurred in their neurons and glia. Epigenetic changes refer to chemical alterations in DNA or histones (which give DNA structure) that increase or decrease the expression of certain genes. Sometimes environmental factors lead to a methyl or acetyl group joining a strand of DNA or histones, changing how easily the genes are turned on or off.

When the mice used their long-term memory, the main change that occurred was DNA methylation in their neurons. There were also changes to histones that were linked to memory acquisition but resulted in few changes in gene expression. The DNA methylation changes, on the other hand, changed neural pathways, leading to “rewiring” of the brain.

Link Between Childhood Trauma and Difficult Course of Bipolar Disorder Clarified

November 9, 2015 · Posted in Genetics, Risk Factors · Comment 

Trauma in childhood linked to course of bipolar disorder

A collaboration between Norwegian and French researchers led by Bruno Etain has clarified the pathway by which childhood trauma is linked to worse outcomes among people with bipolar disorder. The researchers, who presented their work in a poster at the 2015 meeting of the Society of Biological Psychiatry, replicated earlier findings by this editor (Robert Post) that patients who experienced trauma as a child had a more adverse course of bipolar disorder. Etain and colleagues found a link between childhood trauma and an earlier age of onset of bipolar disorder, rapid cycling, suicide attempts, and cannabis misuse.

The researchers identified more than 550 patients with bipolar disorder, who answered questionnaires about their history of bipolar disorder and childhood trauma. Their DNA was also analyzed, and the researchers found that the effect of childhood trauma on age of onset was mediated by the presence of common genetic variants in proteins related to stress (the serotonin transporter) and immune function (Toll-like receptors). They also found that the traits of mood lability (or moodiness) and impulsivity mediated the effects of trauma on clinical outcomes.

The lasting epigenetic effects of child maltreatment and adversity noted in the above abstract are consistent with a large literature showing more epigenetic effects in these individuals than in controls. While genetics are important, the impact of the environment is also substantial.

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.

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