Psych Setback: New Study Demolishes Genetic Link to Depression
A new analysis has strongly refuted a previous claim that a certain genetic mutation could predispose people toward clinical depression.
The meta-analysis, conducted by researchers from the U.S. National Institute of Mental Health and published in the Journal of the American Association, reviewed the results of 14 separate studies on a total of 14,250 people, 1,769 of whom had suffered from clinical depression, also known as major depression.
A widely reported 2003 study, published in the journal Science, found that people with a specific variant of a gene involved in serotonin transport were predisposed to develop major depression, but only if they had a history of stressful life events.
The neurotransmitter serotonin is believed to play an important role in depression, hence the popularity of the antidepressant drug class of selective serotonin reuptake inhibitors.
But the new study failed to find any connection with that gene. It did find that regardless of genetics, people with a history of stressful life events were 41 percent more likely to develop clinical depression.
“For an initial study that hadn’t been replicated, [the Science study] was published to much acclaim,” said research Kathleen Ries Merikangas said. “If it had been replicated, it was an important finding [but] geneticists have been uniformly skeptical from the beginning.”
The interplay between genes and the environment is much more complex in mental illness than in other forms of sickness, said Keith A. Young of Texas A&M Health Science Center.
As many as 40 different genes may play a role in serotonin activity alone, Merikangas noted.
“Mental disorders are the most complex of all diseases,” she said. “We’re learning more about how genes can control the different biologic pathways in the brain, but more importantly, how that brain is wired to respond to environmental factors. We’re at the very primitive stages of knowledge.”
Epigenetics discoveries challenge outdated medical beliefs about DNA, inheritance and gene expression
t is widely accepted in scientific circles that organisms inherit DNA from their predecessors through a process known as hard inheritance — so named because changes in the nucleotide sequence of the passed-on DNA is rare and only happens through random mutation — but soft inheritance, or the affect of non-genetic factors on DNA, is emerging as a new science that overrides hard genetics.
In a study published in the May issue of Nature Reviews Genetics, Eric Richards, Ph.D. proposed that changes such as alternative DNA packaging and small chemical additions to DNA bases that prevent the expression can be passed on and should be considered soft inheritance.
Richards, professor of biology at Washington University in St. Louis, analyzed past studies of epigenetics — a Greek term meaning “above and beyond the gene” — and evolution, and found that there is evidence in both the plant and animal kingdoms that supports the notion of soft inheritance.
One of the mechanisms Richards points to is known as DNA methylation, or the chemical modification of the DNA chemical subunit cytosine. Studies have shown that a lack of proper DNA methylation can cause developmental problems in higher organisms, including stunted growth in plants and death in mice.
Richards has also studied epigentics’ effect on DNA packaging, noting that DNA that is “loosely wrapped” around proteins is easier to access. This, along with the location of DNA within the nucleus, presents another factor that affects the regulation of gene expression.
Such theories, Richards said, tend to provoke a negative reaction from his peers who remain steeped in outmoded beliefs about DNA.
“Epigenetics as soft inheritance in mammals puts us on a slippery slope that many people don’t want to visit,” he said.
The reaction was similar for the theories of pre-Darwinian evolutionist Jean-Baptiste Lamarck, who believed that the environment plays an important role in organisms’ acquisition of evolutionary characteristics. Shore birds, for example, acquired long legs by constantly trying to stretch their legs and lift themselves out of the water, Lamarck believed. But many of Lamarck’s theories are now being shows to be surprisingly correct, decades later.
“When most biologists hear the name Lamarck or the term soft inheritance, the reaction is, ‘Oh my God, here we go again,’” Richards said. “But from a molecular biology point of view there is a mechanism to do soft inheritance, and epigenetic inheritance can be construed as a form soft inheritance. That’s all I’m saying.”
“The really heretical thing to say is that the environment could be pushing the epigenetic information in a direction that is beneficial,” he said. “This is the more extreme variation of soft inheritance that raises the hackles.”
One such hackle-raising study observed the epigenetic changes in mice hybrids from diet in a field Richards refers to as “nutritional epigenomics.” In the study, researchers attempted to affect the DNA methylation of pregnant mice through varying levels of folate and B vitamins.
“The idea was: If you pump these pregnant moms up with these dietary supplements, you might be able to skew the DNA methylation patterns, and thus skew the way the mice come out at the end of the day, and it works,’” Richards said. “In this particular instance that says what you’re getting fed in the womb influences your phenotype; physical and physiological attributes.”
“These findings are revolutionizing our understanding about the role of nutrition and other environmental factors in human health. What they are showing,” added Mike Adams, a holistic nutritionist, “is that your health is certainly not controlled entirely by your genes. Nutrition, it turns out, affects the way your genetic code is expressed. As a result, nutrition and other environmental factors determine your health just as much as your genetic code.”
According to a separate study, early grooming and nurturing of rat pups by their mothers affected the methylation of a glucocorticoid receptor gene, found in the hippocampus in the brain. This nurturing apparently activates the glucocorticoid receptor and provides the pups with an enhanced ability to handle stress later on in their lives. Richards said the process appears to be brought on by changes in DNA methylation through changes in DNA packaging.
“These studies do not demonstrate inheritance between generations, but they do show that the early nutritional environment in the mice and early behavioral environment in the rat studies can change the DNA packaging on the genome, and that that is ‘remembered’ in the cell divisions that make the rest of the organism, ” Richards said. “But this is not from one generation to another. No one has shown that yet.”
Richards said that more extreme variations of soft inheritance would require that it be proven, one way or another, whether environment can induce an inheritable epigenetic change in an organism.
“Certainly, nobody has shown that an epigenetically induced beneficial or adaptive change has been inherited,” Richard admitted, but he pointed out that there was also no reason to discount the idea of epigenetic inheritance.
“The big questions to resolve are how many epigenetic changes are induced by the environment, what types of phenotypes result from these changes, and how many of these epigenetic changes are inherited,” he said.
Dr. Dean Ornish, head of the Preventive Medicine Research Institute in Sausalito, California, is a well-known author advocating lifestyle changes to improve health. Dr. Ornish is also affiliated with the University of California at San Francisco. He recently reported on the Gene Expression Modulation by Intervention with Nutrition and Lifestyle (GEMINAL) study. This study indicated that making positive changes in one’s diet, exercise, and stress management can affect more than a person’s weight. Dr. Ornish’s study was published in the June 16, 2008 edition of the journal Proceedings of the National Academy of Sciences.
The study followed 30 men who had opted out of conventional treatment for low-risk prostate cancer. The men decided, before they were recruited to take part in the study, not to undergo treatments such as surgery, radiation, or hormone therapy normally advocated for the disease. The men were closely monitored for tumor progression through the duration of the study.
Instead, for three months, they made changes in their lifestyle: They ate a diet rich in fruits, vegetables, whole grains, legumes and soy products. They exercised moderately, walking for half an hour a day. Each day they spent an hour practicing stress management methods such as meditation. Additionally, the men participated in support group sessions.
As the study progressed, the men lost weight, lowered their blood pressure and cholesterol, and generally saw improvements in their health. Previous studies gave evidence of lowered prostate-specific antigen (PSA) levels with dietary changes.
Biopsies taken at the beginning and end of the study demonstrated some more significant changes. About 500 genes evidenced changes in activity at the end of the study. 48 disease preventing genes were turned on. 453 genes which promote disease, like breast and prostate cancers, were turned off.
Dr. Ornish expressed excitement over the results in a Reuters interview. The implications of this study go beyond men and prostate cancer. People are not doomed by their genetics. They can make positive changes fairly quickly. In three months, genetic changes can be made through the choices we make in food, exercise, and the way we handle stress.
This is an area of study that merits further investigation, the researchers concluded
The relationship between unhealthy eating and the development of disease is undeniable. When most people get a cancer diagnosis their doctors are quick to prescribe drugs and harsh treatments such as radiation, chemotherapy, and surgery. All of these treatments have a harrowing effect on the body opening it up to a whole host of other problems.
US Physicians Group Endorses Medical Marijuana Transcending political controversy and stigma surrounding the subject, the second largest physician group in the country has endorsed the use, reclassification, and further study of medicinal marijuana.
Cancer Alternative Treatments Digest Part 29 / Marijuana for pain management Cannabis reduced pain intensity and unpleasantness equally. Thus, as with opioids, cannabis does not rely on a relaxing or tranquilizing effect, but rather reduces both the core component of nociception (nerve pain) and the emotional aspect of the pain experience to an equal degree.
Cancer Alternative Treatments Digest Part 25 / Hemp Oil Extract The current restrictions against hemp were put in place and maintained, not because hemp is evil or harmful, but for big money to make more big money, while we suffer and die needlessly. Look at a proposal such as this; if we were allowed to grow hemp in our back yards and cure our own illnesses, what do you think the reaction of the pharmaceutical industry would be to such a plan?
In a survey of 79 oncologists from McGill University Cancer Center in Canada, 64 said they would not consent to treatment with Cisplatin, a common chemotherapy drug, while 58 oncologists said they would reject all the current trials being carried out by their establishment. Why? "The ineffectiveness of chemotherapy and its unacceptable degree of toxicity." Philip Day, Cancer: Why We're Still Dying to Know the Truth
Loading...
