Somatic concerns, depressive traits, atherosclerosis and the incidence of cardiovascular disease in ageing Finnish men

Serum levels of carnosine may be associated with the duration of MDD episodes

BACKGROUND

Major depressive disorder (MDD) is a recurrent disorder that incurs a high societal burden. However, the etiology of MDD remains unclear. The functioning of several systems associated with the etiopathogenesis of MDD, such as inflammatory and stress systems, is partially modulated by the dipeptide carnosine.

METHODS

The study comprised 99 MDD patients and 253 non-depressed controls aged 20-71 years. Fasting serum samples were analyzed using ultra-performance liquid chromatography coupled to mass spectrometry to determine the serum levels of carnosine and its constituent, histidine. We compared these metabolites in three different settings: 1) MDD patients vs. non-depressed controls and 2) remitted vs. non-remitted MDD patients, as well as 3) changes in the metabolite levels during the follow-up period within a) the remitted group and b) the non-remitted group. In addition, we assessed the possible effect of medications on the measured metabolites.

RESULTS

We observed higher serum levels of carnosine in the MDD group compared to the control group at baseline (OR = 1.895, 95%CI = 1.223-2.937, p = 0.004). Elevated serum levels of carnosine were also associated with a longer duration of the depressive episode (Z = 0.406, p = 0.001). However, the use of any antipsychotic medication (n = 36) was associated with lowered carnosine levels (p = 0.010 for use vs. non-use). At the follow-up, remitted and non-remitted participants displayed no significant differences in their carnosine levels (Z = -0.14, p = 0.891) or histidine (Z = -1.39 p = 0.164).

CONCLUSIONS

An increase in circulating carnosine may characterize depressive episodes and may represent a protective homeostatic reaction against MDD-related oxidative stress and inflammation.

Global arginine bioavailability ratio is decreased in patients with major depressive disorder

BACKGROUND

Major depressive disorder (MDD) is characterized by increased oxidative and nitrosative stress. We compared nitric oxide metabolism, i.e., the global arginine bioavailability ratio (GABR) and related serum amino acids, between MDD patients and non-depressed controls, and between remitted and non-remitted MDD patients.

METHODS

Ninety-nine MDD patients and 253 non-depressed controls, aged 20-71 years, provided background data via questionnaires. Fasting serum samples were analyzed using ultra-performance liquid chromatography coupled to mass spectrometry to determine the serum levels of ornithine, arginine, citrulline, and symmetric and asymmetric dimethylarginine. GABR was calculated as arginine divided by the sum of ornithine plus citrulline. We compared the above measures between: 1) MDD patients and controls, 2) remitted (n=33) and non-remitted (n = 45) MDD patients, and 3) baseline and follow-up within the remitted and non-remitted groups.

RESULTS

Lower arginine levels (OR 0.98, 95% CI 0.97-0.99) and lower GABR (OR 0.13, 95% CI 0.03-0.50) were associated with the MDD vs. the non-depressed group after adjustments for potential confounders. The remitted group showed a decrease in GABR, arginine, and symmetric dimethylarginine, and an increase in ornithine after the follow-up compared with within-group baseline values. The non-remitted group displayed an increase in arginine and ornithine levels and a decrease in GABR. No significant differences were recorded between the remitted and non-remitted groups.

LIMITATIONS

The MDD group was not medication-free.

CONCLUSIONS

Arginine bioavailability may be decreased in MDD. This could impair the production of nitric oxide, and thus add to oxidative stress in the central nervous system.