Phenotypes in Depression and Molecular Levels

In clinical studies, major depressive disorder has had four specifiers, including melancholic feature, atypical feature, catatonic feature, and postpartum onset. In the future, we should investigate the distributions of the four specifiers of depression among patients with physical illness and discuss which biological markers could link the depressive disorder and the physical illness. 

Lipid Profile Levels in Patients with Major Depression with Melancholic Feature, Atypical Feature, Catatonic 

Although there are papers that discuss the relationships between cholesterol, lipid profiles, and major depression [34-39], there are few data that discuss the association between lipid profiles and depressive disorders with different phenotypes. Huang and Chen investigated the correlation between serum lipid, lipoprotein concentration, and major depressive disorder in patients evaluated for general health screening [41]. They found that analysis of covariance after age adjustment revealed significant differences in patients with melancholic feature and patients with atypical feature in serum concentrations of TG and VLDL in men and HDL in women [41]. However, there are still no reports that discuss the relationships between lipid profiles and major depression with postpartum onset or catatonic feature. In the future, large sample numbers will be needed to clarify the clinical differences in this field. 

In addition to the studies of clinical biological changes in lipid profile levels in patients with major depression, the mechanism of lipid metabolism should be noted and discussed [133], In past studies, the main plasma lipid transport forms have been free fatty acids, triglycerides, and cholesteryl esters. 

Free fatty acids, derived primarily from adipocyte triglycerides, are transported as a physical complex with plasma albumin. Triglycerides and cholesteryl esters are transported in the core of plasma lipoproteins [134], Deliconstantinos observed the physical state of the Na+/K+-ATPase lipid microenvironment as it changed from a liquid-crystalline form to a gel phase [135], The studies concerning the albumin-cholesterol complex, its behavior, and its role in the structure of biomembranes provided important new clues as to the role of this fascinating molecule in normal and pathological states [135]. 

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