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

Abstract

BackgroundMajor 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. MethodsThe 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. ResultsWe 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). ConclusionsAn increase in circulating carnosine may characterize depressive episodes and may represent a protective homeostatic reaction against MDD-related oxidative stress and inflammation.