LAUSR

Introduction The global arginine bioavailability ratio (GABR) is used to estimate arginine supply. Arginine is precursor to nitric oxide (NO) that has been suggested to play a role in major depressive disorder (MDD). NO also participates in neuronal, inflammatory and cardioprotective functions. Objectives To compare GABR between: – D patients and non-depressed controls; – remitted and non-remitted MDD patients; – baseline and follow-up within remitted and non-remitted MDD groups. Aims To investigate the role of NO production in MDD. Methods The sample comprised 99 MDD patients and 253 non-depressed controls (Beck Depression Inventory scores < 10) aged 20–71 years. Altogether, 78 patients returned for the follow-up; 33 were remitted and 45 non-remitted. GABR was calculated from serum levels of arginine, citrulline and ornithine, which were analysed using ultra-performance liquid chromatography. Differences between the study groups were examined using logistic regression adjusted for age, gender, smoking, alcohol use, physical exercise and glycated haemoglobin. The follow-up regression analyses were adjusted for age, gender and physical exercise. Results Lowered GABR was associated with belonging to the MDD group (OR 0.13, 95% CI 0.03–0.50). Exclusion of participants using anti-depressants that were associated with measured metabolites did not change the results. Over the follow-up period, the remitted and non-remitted groups both showed an increase in GABR (Z = –.53, P < 0.001 and Z = –3.00, P = 0.003, respectively). Conclusions Decreased GABR may characterise MDD. This could affect neuronal, immunological and cardioprotective functions of NO. Disclosure of interest The authors have not supplied their declaration of competing interest.