The Important 0.1 Percent

(Nineteenth in a series of topical blogs based on chapter by chapter excerpts from Opiate Nation. Translation into most languages is available to the right.)

DNA sequences for any human is approximately 99.9 percent identical to every other human. That means that only 0.1 percent of our genetic makeup is unique to us. Genes are functional units of DNA that make up the human genome. But don’t be fooled into thinking that 0.1 percent variation is insignificant. It is nearly 3 billion base pairs of DNA which boils down to 3 million differences that determine our physical features like hair and eye color and health risks or protection from diseases such as heart disease, diabetes – and addiction. Genes influence the numbers and types of receptors in peoples’ brains, how quickly their bodies metabolize drugs, and how well they respond to different medications.

The National Institute of Drug Abuse (NIDA) reports that family studies that include identical twins, fraternal twins, adoptees, and siblings suggest that as much as half of a person’s risk of becoming addicted to nicotine, alcohol, or other drugs depends on his or her genetic makeup. Scientists estimate that genes – including the effects environmental factors have on a person’s gene expression, called epigenetics – account for between 40 and 60 percent of a person’s risk of addiction.

Epigenetics – epi meaning “above” – is the study of functional, and sometimes inherited, changes in the regulation of gene activity and expression that are not dependent on gene sequence. This means exposures or choices people make can actually “mark” (remodel) the structure of DNA at the cell level. So epigenetic regulatory systems enable the development of different cell types (e.g., skin, liver, or nerve cells) in response to the environment. These epigenetic marks can affect health and even the expression of the traits passed to children. For example, when a person uses cocaine, it can “mark” the DNA, increasing the production of proteins common in addiction which is believed to correspond with drug-seeking behaviors.

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GENETICS AND OPIOID VULNERABILITY

Addiction is recognized as a disease by scientists, and now, finally, by most of us. It is no longer considered a moral weakness except by some who, like The Emperor and his new clothes, can’t see their own “moral weakness” but only those of others. Enough said.

As DNA research gains new insights by the day, we are learning how our DNA codes are regulated which will help in opioid treatments and prevention. Tiny differences in a persons DNA called single-nucleotide polymorphisms, SNPs, can indicate whether we have a higher or lower risk for addiction. Some of us have an opioid receptor gene with a single building block change that protects us against substance dependence in general and opioid dependence in particular. This is why the ‘opioid euphoria’ I wrote about doesn’t happen for us. But for others, variations in genes for three dopamine receptors – signaling pleasure – cause increased risk for opioid addiction.

Exposure matters in genetic expression, even across generations, according to how our body’s cells read them. In a recent study of opioids in rats (cited in the Ohio Society of Addiction Medicine’s blog on May 31, where much of this article is referenced from) the parents exposure to opioids changed the way their offspring read their DNA code, lessening their susceptibility to opioid addiction. This shows how one generation’s experiences can change the destiny of the next generation and although it hasn’t been studied in human substance abuse, it has been seen in other complex diseases like obesity.

Research suggests that people born into a culture of drug use may be more inclined to get and stay sober. Epigenetic’s may play a role. How this effects individuals born into a family with addiction issues like alcoholism, drugs, smoking, gambling, etc. is still unclear. For some of us, we observed behavior in our parents or relatives and made a concerted effort to not repeat it. Although our genes may have given us tendencies towards an addiction, a strong repulsion steered us away from it – and in my case, a strong dependence on the Lord.For our son, had we known how many of our relatives had addiction issues and how much power the addictive genes had, we would have been less permissive with our son in regards to drinking at an early age – and certainly more proactive once he was addicted to opioids. It might have changed the outcome for his life. I pray this information will help you, your family, and friends avoid the heartbreak we have had to live with.