Reduced peripheral availability of tryptophan and increased activation of the kynurenine pathway and cortisol correlate with major depression and suicide.

Objectives: Patients affected by major depression (MDD) are at high risk of suicide. The metabolism of tryptophan (Trp) along the serotonin (5-HT) and kynurenine (Kyn) pathways was found dysfunctional in MDD and in suicide. However, a clear biological framework linking dysfunctions in Trp metabolism via 5-HT and Kyn, cortisol, and the activities of tryptophan and indoleamino 2,3-dioxygenase (TDO, IDO) enzymes has not been yet clarified in MDD with or without suicidal behaviours.Methods: We analysed peripheral markers of Trp via 5-HT and Kyn pathways, Kyn/Trp ratio as a measure of TDO/IDO activities, cortisol, and psychopathology in 73 non-suicidal and 56 suicidal MDD patients, and in 40 healthy controls.Results: Plasma Trp levels were lower and the ratio Kyn/Trp higher in suicidal MDD than in non-suicidal MDD patients and controls. Trp levels and the ratio Kyn/Trp correlated with suicidal ideation, and cortisol with the Kyn/Trp ratio. Finally, Trp levels discriminated controls from non-suicidal and suicidal MDD patients, and also non-suicidal from suicidal MDD patients.Conclusions: Reduced availability of Trp for 5-HT synthesis and increased activation of the Kyn pathway and cortisol correlate with depression and suicide. Low plasma Trp levels may be a biomarker of MDD and suicide in MDD.

The association between altered lipid profile and suicide attempt among Tunisian patients with schizophrenia.

BACKGROUND: There have been many studies on psychiatric disorders, but very little is known about the biology of suicide with schizophrenia. In the present study, we are looking for a possible connection between altered lipid profile and suicidal behavior in schizophrenic Tunisian patients. METHODS: Assay of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c), and triglycerides (TG) has been done for 126 schizophrenic patients with and without suicide attempts and 131 healthy controls recruited in the University Hospital of Monastir. RESULTS: TC and LDL-c levels were significantly higher in schizophrenic patients compared to controls. TC was significantly lower in schizophrenic patients with suicide attempt compared to those without suicide attempt. Depending to the sonority of suicide attempt, TC was significantly lower in patients with recent suicide attempt compared to those with lifetime suicide attempt and without suicide attempt (p < 0.001), and no significant differences between TG, LDL-c, and HDL-c were noted. CONCLUSIONS: Results of this study showed that TC levels in schizophrenic patients after a recent suicide attempt are significantly lower than in patients without suicide attempt and with lifetime suicide attempts. TC can be one of biological markers defined suicidal risk for schizophrenic patients.