O. G GilevaIzhevsk State Medical Academy , Russian Federation
Title: Biochemical markers of liver damage on a fructose-induced diet in rats.
Relevance: An increased content of fructose as a common source of carbohydrates in food products leads to a violation of metabolic processes in the body, which may be associated with the biochemical characteristics of fructose metabolism. The result of this is an increase in the risk of developing obesity, diabetes mellitus, cardiovascular diseases, as well as liver diseases induced by the formation of oxidative stress against the background of changes in lipid and carbohydrate metabolism. Destructive processes in the liver may indicate an increase in the content of the main markers of hepatocyte cytolysis: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), lactate dehydrogenase (LDH).
Goal of the work: Create an experimental model for the development of inflammatory processes in the liver under the influence of a fructose-induced diet.
Materials and methods: The study was conducted on 50 male rats weighing 250-300 g. The animals were divided into experimental and control groups of 25 animals each. Rats of the control group received a balanced vivarium diet, animals of the experimental group received a diet containing 60% fructose, 20% protein, 14% fiber, 6% fat for 35 days. From day 36 to day 60, the rats were on a standard vivarium diet. On the 60th day, the formation of metabolic abnormalities in the long term was assessed. The animals were weighed and taken out of the experiment on an empty stomach by decapitation under short-term ether anesthesia on the 21st (n=16), 35th (n=16), 60th (n=18) days of the experiment. Blood was collected in tubes and centrifuged at 3000 rpm for 15 min. In the resulting serum, the content of glucose, total cholesterol (TC), low-density lipoproteins (LDL), triglycerides (TG), insulin, activity of ALT, AST, ALP, LDH were determined. Biochemical studies were performed on an AU-480 automatic analyzer (Beckman Coulter, USA) using reagents from the same manufacturer. The insulin content was determined on a StatFax-2100 enzyme immunoassay analyzer (Awareness Technology, USA) using a set of reagents from Vector-best LLC, Russia. Insulin resistance indices were calculated using the formulas: HOMA = (glucose *insulin)/22.5; CARO = glucose/insulin; de Ritis coefficient - according to the ratio of AST to ALT.
Results and discussion: During the study, there was a tendency to increase the concentration of glucose in the blood serum of rats with a significant increase on the 21st and 60th day of the experiment by 1.18 and 1.21 times, respectively, and cholesterol on the 35th day of the experiment, 1.59 times relative to the control. The insulin concentration significantly increased throughout the experiment, exceeding the control values by 1.5, 1.7 and 1.9 times on the 21st, 35th and 60th day of the experiment. Insulin resistance indices also differed from control values, which may indicate the formation of insulin resistance. The content of LDL increased statistically significantly during the entire experiment by 2.58, 2.41 and 3.47 times compared with the control on the 21st, 35th and 60th day of the experiment, respectively. These changes may be associated with excessive accumulation of fructose conversion products - acetyl-coenzyme A (Acyl-CoA) due to its special metabolism. Increased synthesis of Acyl-CoA contributes to excessive synthesis of free fatty acids, followed by TG and transport forms of LDL. This can lead to activation of the free-radical oxidation reaction in hepatocytes and increased formation of free radicals, which, interacting with lipids, carbohydrates and amino acids, form their primary oxidation products. Such reactions can serve as an initiating factor in the destruction of liver cells with the release of liver-specific enzymes into the bloodstream. During the experiment, there was an increase in the activity of hepatocyte cytolysis markers with a significant increase: ALT by 69.8 and 99% on the 35th and 60th day of the experiment; AST by 18.2, 28.5 and 30.8%, ALP by 38.3, 43.6 and 78.7%, LDH by 76.8, 119 and 149.6% by the 21st, 35th and the 60th day of the experiment, respectively, compared with the control. A decrease in the de Ritis coefficient confirms the activation of cytolytic processes in the liver.
Conclusion: Thus, the fructose-induced diet increases the content of specific rat liver enzymes (ALT, AST, ALP, LDH) against the background of disturbances in lipid and carbohydrate metabolism with an increase in the concentrations of cholesterol, TG, LDL, as well as glucose and insulin, and the formation of insulin resistance. The reason for the initiation of cytolytic processes in hepatocytes may be free-radical oxidation of protein-lipid complexes and activation of inflammatory reactions against the background of increased consumption of fructose.
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