Acetyl-L-carnitine chemical in blood connected to depression

A group of researchers from Stanford in collaboration with other universities have found that in humans a low level of acetyl-L-carnitine or L-acetyle carnitine in blood could be a predictor of the duration and severity of depression.

Researchers led by Natalie Rasgon professor of psychiatry and behavioral sciences at Stanford, in collaboration with colleagues from different centres have shown that this chemical is connected to depression.

Acetyl-L-carnitine is not only produced naturally in the body but is also available in supermarkets and marketed as a health food nutritional supplement. The team noted that individuals who have an early onset of depression and those who are resistant to depression treatment have typically lower blood levels of acetyl-L-carnitine. The results from this unique study were published this week in the latest issue of the Proceedings of the National Academy of Sciences.

Image Credit: Kan_chana / Shutterstock
Image Credit: Kan_chana / Shutterstock

There is existing animal research that connects low levels of this chemical and depression but this is the first time that the same has been proven in humans. This could pave the way for new depression treatments as well feel researchers. Acetyl-L-carnitine itself or drugs that enhance this chemical in blood could be the new class of antidepressants that have fewer side effects and may be faster acting than the existing antidepressants feel the researchers.

Rasgon called this new research, “an exciting addition to our understanding of the mechanisms of depressive illness.” She said that as a clinical psychiatrist she has been treating many people with depression which is one of the leading forms of mood disorders in the United States. At any given time it affects around 8 to 10 percent of the general population and one in four person is likely to have experienced depressive illness at least at some point in their lives. Rasgon explained that depression remains one of the leading causes for absenteeism from work and suicide. In addition pharmacological treatments are useful for only around half of the sufferers and in these individuals the drugs may have side effects that make many individuals stop taking them.

The study was co led by Dr. Bruce McEwen, professor and chief of the Laboratory of Neuroendocrinology at The Rockefeller University in New York City and Carla Nasca, PhD, a postdoctoral scholar in McEwen’s lab. Dr. Nasca has led the animal studies previously that show that depression like behaviour is connected with deficiency of acetyl-L-carnitine explained Dr. McEwen. In these animals of the laboratory that showed depressive symptoms, when the chemical was orally or intravenously administered, the symptoms regressed and normal behaviour was restored he said. Further the animals treated with acetyl-L-carnitine were responsive to the chemical within a few days as opposed to a few weeks that are taken for any antidepressant to show effects on symptoms. He said however that it is too early to start using the chemical as a treatment for depression as the dose, duration of use and frequency of usage needs to be studied in details.

Nasca’s experiments have shown that acetyl-L-carnitine is a crucial mediator of the metabolism of fat in the body and production of energy. This plays an important role in the brain and prevents the excessive firing of the nerve cells in the hippocampus and the frontal cortex in the brain. For this new study in humans Nasca recruited men and women aged between 20 and 70 years who were diagnosed with depression. Some experienced episodes of acute depression and had to be admitted to Weill Cornell Medicine or Mount Sinai School of Medicine for immediate management. All the participants were screened using questionnaires and detailed medical histories from them were obtained. Their blood samples were collected. From the diagnostic tools that are normally used to detect depression, 28 individuals were diagnosed to have moderate depression while 43 were diagnosed with severe depression.

The participants of the study were compared to 45 individuals who were matched in terms of age, sex and other parameters but did not have depression. The levels of acetyl-L-carnitine in blood of those with depression was found to be significantly lower than those without depression. Regardless of age and gender, this connection held true. Among those who had most severe depression and had been resistant to treatment or those who had been detected with depression early in life, the levels of acetyl-L-carnitine were found to be the lowest. Patients with a childhood history of neglect, poverty, abuse or exposure to violent activities also had lower levels of this chemical, the researchers noted.

Rasgon too warned people against self-medicating themselves with this nutritional supplement yet. “We have many previous examples of how nutritional supplements widely available over the counter and unregulated by the Food and Drug Administration — for example, omega-3 fatty acids or various herbal substances — are touted as panaceas for you-name-it, and then don’t pan out,” she said. As of now the chemical remains a major biomarker that could predict depression and its severity and that is a big step she said.

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