Sufferers of major depressive disorder (MMD) have reduced arginine bioavailability, which is known to be an independent risk factor of cardiovascular disease, according to a new study from the University of Eastern Finland.
Arginine is an amino acid that the body uses to produce nitric oxide, which, in turn, is a nervous system and immune defence mediator that also plays a role in vascular regulation. The global arginine bioavailability ration (GABR) is an indicator of the body’s arginine levels and has previously been used to measure the body’s capacity to produce nitric oxide.
The study showed that people suffering from MDD have reduced bioavailability.
Lead author of the study and doctoral student Toni Ali-Sisto said: “It is possible that depression-induced inflammatory responses lead to reduced arginine levels.
“This may result in insufficient production of nitric oxide for the needs of the nervous system and circulation. However, we don’t know yet what exactly causes reduced arginine bioavailability in people with depression.”
Studying the depressive mind
The study involved 99 adults diagnosed with major depressive disorder and 253 non-depressed controls. The concentration of three amino acids – arginine, citrulline and ornithine – were analysed from their fasting glucose samples.
This data was used to calculate their GABRs. Symmetric and asymmetric dimethylarginine concentrations were also measured, as they both play a role in the production of nitric oxide.
The study also analysed if these concentrations changed in people with depression during eight-month follow-ups.
“Although our study shows that people with depression have reduced arginine bioavailability, this doesn’t mean that taking an arginine supplement would protect against depression. That’s an area for further research,” Ali-Sisto says.
“Arginine bioavailability was slightly higher in people who had recovered from depression than in people who remained depressed. However, a more extensive set of data and a longer follow-up period are necessary for estimating arginine’s role in depression recovery.”
What did the study find?
It was found that people with depression had weaker arginine bioavailability than their non-depressed controls.
The were no significant differences found in the symmetric and asymmetric dimethylarginine concentrations. The use of anti-depressants or anti-psychotics did not affect the concentrations, either.
Results were published in Journal of Affective Disorders.
