Features of Pathogenetic Mechanisms of Skin Hyperpigmentation: A One-Moment Cross-Sectional Research

Abstract

Introduction 
Despite the uniqueness of the melanin pigment system, where the final outcome of pigmentation is formed through the interaction of two types of cells (melanocytes and keratinocytes), researchers have made certain progress in partially understanding the mechanisms of melanogenesis and patient therapy. Undoubtedly, the most significant clinical implications pertain to pigmentation disorders primarily associated with melanin.

Objective of the Research
To study the levels of lipoproteins of various classes in patients with hyperkeratosis and their role in the formation of skin hyperpigmentation.

Methods
The research involved 50 women living in Rostov-on-Don, average age 42.3±1.1 years, divided into two groups: 25 people with skin hyperpigmentation, average age 41.52±1.68 years, undergoing treatment in the dermatology department; 25 people - practically healthy (PH) individuals - during medical examinations, average age 43.57±1.43 years. The content of total cholesterol (TC), triacylglycerides (TG), HDL was determined by the enzymatic colorimetric method using the ChronolabAG kits (Switzerland), LDL - by the turbidimetric method, very low density lipoproteins (VLDL) - by the calculated TG/5 method. Statistical processing of the obtained data was performed using Microsoft Office Excel 2007 (Microsoft Corp., USA) and Statistica 10.0 (StatSoft Inc, USA). The data are presented as M±m, where M is the mean value of the feature, m is the mean error of the feature, and also as an expression of the frequency of occurrence of the feature in absolute values (n) and percentages (%). The significance of differences between subgroups was assessed using 
Student's T-criterion. Correlation analysis was performed to determine the relationships between different parameters. The threshold level of statistical significance was p < 0.05. The Mann-Whitney criterion was used for comparative analysis of absolute differences in samples.

Results
During the study of the metabolic features of lipoprotein metabolism in patients with hyperpigmentation, an increase in the level of individual lipoprotein classes was noted compared to the control group. The level of total cholesterol, TG, LDL, VLDL was statistically significantly increased, and a tendency towards a decrease in HDL was revealed. Thus, the content of TC in patients with hyperpigmentation was statistically significantly different from the control, by 18.64% (p = 0.148), which suggests that cholesterol is used to build cell membranes. Against this background, a higher content of TG was noted - by 18.1% (p = 0.393), which are obviously used to maintain cell energy costs. It should be noted that the concentrations of atherogenic fractions of VLDL, LDL in hyperpigmentation were higher than in the control: VLDL - by 18.13% (p = 0.352) and LDL - by 44.93% (p = 0.044). Which is obviously associated with increased cholesterol esters entering the epidermal tissue. However, HDL values tended to decrease in the main group compared to the control.

Conclusion
It was found that patients with hyperpigmentation have statistically significantly increased levels of individual lipoprotein classes, such as LDL, VLDL, as well as TG and TC. This is probably an indicator of the constant need of cells to synthesize membrane lipids and maintain increased cellular metabolism, which is necessary for increased regeneration of the epidermis. Further study of the level of blood plasma lipoproteins and analysis of changes in their fractions will reveal the pathogenetic mechanisms of skin hyperpigmentation, as well as reveal the predictors that contribute to its formation.