Importance and effect of circulating mir-223 on cholesterol homeostasis and development of hypercholesterolemia

Hypercholesterolemia, which is characterized by high level of cholesterol in blood, is generally defined as presence of abnormal levels of lipoproteins responsible for cholesterol transport in blood. Disrupted cholesterol homeostasis enhances the risk of developing cardiovascular diseases such as atherosclerosis and coronary heart disease. miRNAs, which play a role in regulation in gene expression post-transcriptionally, are about 22 nucleotides in length, small, well preserved in the evolutionary process and non-coding RNA molecules. So far, hundreds of miRNAs have been identified in our genome. Some of these miRNAs that take part in gene regulation are stated to play a role in the protection of cholesterol transport, cholesterol metabolism and cholesterol homeostasis. It has been shown that miRNAs were detected in intracellular fluids at first and they can also be obtained from plasma samples, since they are highly stable after being found in extracellular fluids (eg serum, plasma, saliva, urine, amniotic fluid, tear, milk). Recent studies show that variability in the expression levels of circulating miRNA is associated with many diseases. One of these is cardiovascular diseases caused by impaired cholesterol homeostasis. In this study, we investigated whether circulating miR-223, which is considered to be effective in vivo and in vitro cholesterol homeostasis studies, could be considered as a biomarker for cholesterol homeostasis by examining hypercholesterolemic patients levels. As a result of the analysis, miR-223 levels in circulation were found to be down-regulated 2,003 fold in hypercholesterolemic patients compared to the control group. Total cholesterol, triglyceride and LDL values of patient and control groups were found to have a significant negative correlation with circulating miR-223 expressions. Decreased expressions of miR-223 in plasma were determined to be correlated with hypercholesterolemia.