BackgroundPatients with major depressive disorder (MDD) have a high risk of suicide. Many pathophysiological factors involved in MDD and suicide such us a low cholesterol levels have been associated with MDD and increased vulnerability to suicide. In this study, we investigate the relation between lipid parameters and suicide risk in patients with MDD.MethodsPlasma levels of total cholesterol, triglycerides, and high-density lipoprotein cholesterol (HDL-c) and low-density lipoprotein cholesterol (LDL-c) were determined in 160 patients meeting the DSM-IV-TR criteria for MDD (110 patients without suicidal behavior and 52 suicidal attempters) and 151 healthy controls.ResultsA significant decrease in plasma cholesterol levels was observed in the group of suicidal depressive patients compared to those without suicidal behavior (p < 0.001). For the other lipid levels (triglycerides, HDL cholesterol, and LDL cholesterol), there were no significant differences between suicidal and non-suicidal patients.ConclusionsOur study showed a significant decrease in plasma cholesterol levels in suicidal patients. This result support the hypothesis of the association of low plasma cholesterol level and suicidal behavior in patients with major depressive disorder.

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.

BackgroundThere 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.MethodsAssay 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.ResultsTC 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.ConclusionsResults 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.

Background: The increased degradation of tryptophan (Trp) along the kynurenine (Kyn) pathway due to inflammation and/or activation of the hypothalamic-pituitary–adrenal (HPA) axis has been reported among the biological factors involved in the pathophysiology of major depressive disorder (MDD) and suicide. However, the interaction among these multiple factors is not yet completely clarified. Method: We studied plasma levels of Trp, Kyn, cortisol and proinflammatory cytokines (IL-1, IL-6, IL-12, IL-20) and calculated the ratio Kyn/Trp as an index of the breakdown of Trp into Kyn in 31 suicidal MDD patients and 67 non-suicidal MDD patients. Result: We confirmed that suicidal MDD patients have reduced plasma Trp, higher Kyn and Kyn/Trp ratio, and no difference in cortisol levels than non-suicidal MDD patients. IL-1 and IL-12 levels were significantly higher in suicidal MDD than in non-suicidal MDD (p=0.034 and p=0.023, respectively), whereas Il-6 and IL-20 levels were equal in the two groups. The Kyn/Trp ratio was positively correlated with a pro-inflammatory cytokines index (r=0.309, p=0.002) and cortisol (r=0.368, p=0.001). Notably, the variance in the Kyn/Trp ratio explained by the model, including both cortisol and inflammatory parameters as dependent variables, substantially improved compared with the models in which the two parameters were considered separately. Conclusion: These findings show that both cortisol and proinflammatory cytokines are involved in the enhanced breakdown of Trp into Kyn occurring in suicidal MDD patients, thus adding new knowledge on the biological mechanisms leading to the activation of the Kyn pathway in MDD and suicide.

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