Serotonin… a word that brings to mind a commercial that might show our happy brain neurons bouncing serotonin between them.
There is a lot more to this molecule than most of us realize! This article covers how the body makes and transports serotonin and the needed receptors to complete its pathway. I’ll explain the genetic variants that impact the serotonergic system and then go through diet, supplement, and lifestyle changes that impact serotonin.
What does serotonin do?
In the brain, serotonin acts in several ways:
- as a neurotransmitter, sending a chemical message between neurons.
- as the precursor molecule for melatonin
- in sleep quality, including sleep hallucinations[ref][ref]
But there is more to serotonin than just its impact on the brain.
About 90% of serotonin is made in the gut and helps to regulate motility.[ref] Serotonin also regulates other functions such as; bone mass, cardiovascular health, the endocrine system, and appetite.
Serotonin is also important in energy metabolism, heart rate, cell growth, and immunity.[ref]
Some researchers believe that imbalances in serotonin may play a role in depression or anxiety. Common antidepressants include SSRIs (selective serotonin reuptake inhibitors) and are thought to increase serotonin levels in the brain. Although, the method through which they work is still not completely understood.[ref]
Another link between serotonin and depression is that serotonin modulates immune function.[ref] Increased inflammation is implicated in causing major depressive disorder for some.
Recent animal research shows that one reason that SSRIs may not work for everyone is due to increased inflammation. The study showed that in inflammatory situations, histamine is upregulated and SSRIs act in off-target actions on histamine instead of increasing serotonin. In this study, decreasing histamine levels increased the SSRI effectiveness.[ref] (Read more about histamine and check your histamine intolerance genes.)
Serotonin Synthesis and Transport:
Like most signaling molecules and neurotransmitters, serotonin first needs to be created (synthesized), then it needs to be transported, and finally the signal needs to be received by a cellular receptor.
Synthesis: Serotonin, also known as 5-hydroxytryptamine or 5-HT, is synthesized from the amino acid tryptophan using tryptophan hydroxylase. The TPH1 and TPH2 genes encode the tryptophan hydroxylase enzymes.
Transport: Serotonin is transported by SLC6A4, which is also known as SERT or sodium-dependent serotonin transporter.
Receptors: Serotonin receptors on the cell membrane, HTR1A, HTR1B, and HTR2A receive the serotonin signal.
All of these work in concert: from the creation of serotonin from amino acids to the transport of serotonin to the receptors that are necessary to receive this chemical messenger.
Serotonin Syndrome: Too much serotonin
Ultimately, balance is the key to serotonin. Too much serotonin can result in serotonin syndrome. Symptoms include restlessness, confusion, shivering, diarrhea, and, potentially, death.[ref]
Serotonin syndrome is usually caused by drugs such as MAOIs or SSRIs that affect the rate of serotonin break down.[ref]
Genetic Variants that Change Serotonin Levels:
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Related Genes and Topics:
Bipolar Disorder, Depression, Circadian Clock Genes
New research shows that depression and bipolar disorder are linked to changes or disruption in circadian genes. Some people carry genetic variants in the circadian genes that make them more susceptible to circadian disruption.
Tryptophan is an amino acid that the body uses to make serotonin and melatonin. Genetic variants can impact the amount of tryptophan that is used for serotonin. This can influence mood, sleep, neurotransmitters, and immune response.