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Recently, there have been some reports that changes in serum lipid composition may be related to suicide, major depression and immune-inflammatory responses. Findings from our laboratory suggest that major depression is accompanied by reduced formation of cholesteryl esters and perhaps by impairment of reverse cholesterol transport. The latter is reportedly accompanied by lower serum high-density lipoprotein cholesterol (HDL-C). The aim of this study was to examine whether (i) major depression is accompanied by lower serum HDL-C or by abnormal levels of serum total cholesterol, triglycerides, low-density lipoprotein-C (LDL-C) or vitamin E, (ii) suicidal attempts are related to lower serum HDL-C and (iii) there are significant associations between serum HDL-C and immune/inflammatory markers. A total of 36 subjects with major depression, of whom 28 patients showed treatment resistance, as well as 28 normal control subjects, had blood sampled for the assay of the above lipids, serum zinc (Zn), albumin (Alb) and flow cytometric determination of the T-helper/T-suppressor (CD4+/CD8+) T-cell ratio. In total, 28 depressed subjects had repeated measures of these variables both before and after treatment with antidepressants. Serum HDL-C and total cholesterol, as well as the HDL-C/cholesterol ratio, were significantly lower in subjects with major depression than in normal controls. Serum HDL-C levels were significantly lower in depressed men who had at some time made serious suicidal attempts than in those without such suicidal behaviour. Treatment with antidepressants for 5 weeks did not significantly alter either serum HDL-C or other lipid variables. Serum HDL-C levels were significantly and negatively correlated with the (CD4+/CD8+) T-cell ratio, and positively correlated with serum Alb and Zn. These results suggest that (i) lower serum HDL-C levels are a marker for major depression and suicidal behaviour in depressed men, (ii) lower serum HDL-C levels are probably induced by the immune/inflammatory response in depression and (iii) there is impairment of reverse cholesterol transport from the body tissues to the liver.

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Previous research has revealed that major depression is accompanied by disorders in excitatory amino acids, e.g. glutamate and aspartate, and alterations in serum levels of other amino acids, e.g. serine, glycine and taurine. The aim of the present study was to examine serum levels of aspartate, asparagine, glutamate, glutamine, serine, glycine, threonine, histidine, alanine, taurine and arginine in major depression patients with treatment-resistant depression (TRD). No significant differences in the serum concentrations of any of the above amino acids could be found between patients with and without TRD and normal controls. Non-responders to treatment with antidepressants during a period of 5 weeks were characterized by significantly lower serum levels of aspartate, asparagine, serine, threonine and taurine. A 5-week period of treatment with antidepressants significantly reduced the serum levels of aspartate, glutamate and taurine, and significantly increased the serum concentrations of glutamine. The results suggest that alterations in serum levels of aspartate, asparagine, serine, threonine and taurine may predict the subsequent response to treatment with antidepressants, and that the latter may modulate serum levels of excitatory amino acids and taurine.