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Aim. To present literature data on the metabolic and genetic mechanisms of impaired fatty acid (FA) synthesis in the development and progression of non-alcoholic fatty liver disease (NAFLD).General findings. NAFLD is a widespread disease progressing from steatosis to non-alcoholic steatohepatitis (NASH), increasing the risk of cirrhosis, liver failure and hepatocellular carcinoma. Progression of NAFLD and the development of NASH are closely related to lipid metabolism disorders caused not only by insufficient alimentary intake of fatty acids, but also by a decrease in the efficiency of their endogenous processing. The regulation of fatty acid metabolism involves enzymes desaturase (FADS1, FADS2) and elongase (ELOVL2 and ELOVL5) fatty acids. Desaturases are encoded by the FADS1 and FADS2 genes for fatty acid desaturases. Polymorphisms in the genes of fatty acid desaturases determine the effectiveness of PUFA endogenous processing. Violations in the activity of FADS1 and FADS2 and their genes are accompanied by dysregulation of the metabolic pathway involved in the biosynthesis of fatty acids. This leads to the damage of cell membranes, whose main components are represented by phospholipids. The progression of NAFLD is associated with the powerful toxicity of lipids released in the liver parenchyma upon the loss of the cell biomembrane integrity.Conclusions. Further research into the NAFLD genetic mechanisms regulating the metabolism of fatty acids appears to be promising for a deeper understanding of the pathogenesis of this multifactorial disease.

Background. Desaturase enzymes are involved in the formation of monoenoic acids from saturated fatty acids. One such enzyme is stearyl-CoA-desaturase (SCD1), which converts stearic acid to oleic acid. The aim of this work was to determine the effect of edible fats with different fatty acid compositions on SCD1 activity. Methods. High linoleic sunflower oil (HLSO), high oleic sunflower oil (HOSO) and palm oil (PO) were used. The rats were fed for 30 days with a semi-synthetic diet that did not contain any fats (FFD) and fat diets containing 5 % of each of the above oils. In animals, lipids were extracted from serum and liver and divided into 3 fractions: neutral lipids (NL), phospholipids (PL), and free fatty acids (FFA). The fatty acid composition of each fraction was determined by gas chromatography. The SCD18 activity was determined by the C18:1 n-9/C18:0 ‒ ratio, and the SCD16 activity was determined by the C16:1 n-7/C16:0 ratio. Results. A higher activity of SCD16 and SCD18 was found in the NL fraction, and the activity of SCD18 significantly exceeds that of SCD16. A decrease in the content of C16:0, C16:1 and C18:0 in the NL fraction of the liver and blood serum was shown. The activity of SCD16 in blood serum and liver decreases in rats fed fat diets­, while the activity of SCD18 does not decrease, and even increases with the consumption of HOSO.­ Conclusions. To determine the SCD1 activity, it is advisable to use the C18:1/C18:0 ratio in terms of the level of fatty acids in the NL fraction. Fatty diet inhibits SCD16 activity, and consumption of HOSO increases SCD18 activity.