Scientists Find How Glycine Is Linked To Depression, Mood-Related Disorders

The inhibitory effect of a common amino acid found in our body – glycine – may be contributing to depression, anxiety and other mood-related disorders in some people, scientists say. The findings could be a game changer in depression treatments.

Depression is a common mental disorder that affects around 3.8% of the world's population. It is a growing health concern that is estimated to cause an economic burden of around $326 billion annually in the United States.

A team of scientists from Herbert Wertheim UF Scripps Institute for Biomedical Innovation and Technology, Florida, who started the research to understand the functioning of brain cell receptors made the accidental discovery of the amino acid's link with depression.

The researchers first identified a receptor, called GPR158, in 2018. In a follow-up study, the team found that mice that lacked the gene for the receptor showed resilience to stress. This discovery suggested that GPR158 can be a therapeutic target. They were awaiting further research to find the signal source.

The breakthrough came after scientists evaluated the structure of GPR158 and determined that the signaling molecule was the amino acid glycine.

When glycine sends the signal, GPR158 binds to the amino acid that acts as an inhibitor and not an activator in the cells. Scientists noticed that glycine could send a "slow-down" signal to the brain, which can contribute to depression and anxiety.

The inhibitory effect of glycine is a crucial discovery in formulating future antidepressants that can act faster. The study "improves understanding of the biological causes of major depression and could accelerate efforts to develop new, faster-acting medications for such hard-to-treat mood disorders," said neuroscientist Kirill Martemyanov, corresponding author of the study. "Most medications for people with depression take weeks before they kick in, if they do at all. New and better options are really needed."

Glycine is sold as a nutritional supplement to improve mood and sleep. This is because of its ability to act differently in different cell types. Glycine acts in complex ways, sending slow-down signals in certain cell types while sending excitatory signals in others.

So, more research is needed to understand how the body maintains the right balance of the amino acid and how brain cell activity is affected by it.

"We are in desperate need of new depression treatments. If we can target this with something specific, it makes sense that it could help. We are working on it now," Martemyanov added.