Influence of exogenous melatonin on the oxidative status and the state of peroxidation of proteins in a rat model of alimentary obesity

Abstract

Not only lipids, but also proteins are exposed to the action of reactive oxygen species (ROS). Oxidative modification of proteins (PBS) leads to a change in their native conformation with the formation of large aggregates, it causes inactivation of enzymes, disrupts the metabolism and functioning of cells. In addition, there is a growing interest in studying the hormone of the pineal gland called melatonin, as well as its synthetic analogues as the leading protection factors in the oxidative stress conditioned by disturbed physiological rhythms, including obesity. The peculiarities of protein peroxidation in the case of alimentary obesity, as well as the conditions affecting to this process, in contrast to lipid peroxidation (LPO), have not been studied sufficiently, that has determined the purpose of this study. Aim. To evaluate the effect of exogenous melatonin on the oxidative status and features of PBS in rats with alimentary obesity. Methods. The study was conducted on 27 white Wistar male rats with body weight 160–180 grams. Animals were divided into 3 series of 9 rats in each: 1 series – intact animals; 2 series – animals with alimentary obesity, followed by the introduction of 0,9% sodium chloride solution in a volume of 2 ml for 12 days; 3 series – animals with alimentary obesity followed by melatonin administration at a dose of 2 mg / kg rats for 12 days. Alimentary obesity was reproduced by feeding animals with high-calorie carbohydrate-fatty food, consisting of a laboratory feed "Assortment Agro" (42.5%), butter (25%) and sweet condensed milk (32.5%) for seven weeks. The maximum physical working capacity and resistance of rats to severe hypobaric hypoxia were determined. PBS was determined by the method of R. Levine in the modification of E.E. Dubinina. In addition, the lipid peroxidation marker – TBA-reactive products (malonic dialdehyde MDA) was determined. Results. It has been established that the PBS in alimentary obesity is not specific, it is reflected in the increase in the areas of absorption of light from both the visible and ultraviolet of aldehyde and ketondinitrophenylhydrazones. In parallel with this, there was a marked increase in the concentration of TBA-reactive products in the blood serum in this pathology, as well as a significant decrease in the resistance of rats to hypobaric hypoxic hypoxia and maximum physical activity. The daily administration of a 2 mg/kg melatonin suspension to rats with alimentary obesity for 12 days leads to a significant decrease in the concentration of TBA-reactive products, however, the PBS is not significantly affected. Conclusion. Alimentary obesity in rats, simulated by the maintenance of animals on a high-calorie carbohydrate-fat diet, leads to an increase in the proportion of visceral fat in the body, an increase in the activity of PBS in the form of an increase in the level of carbonyl derivatives, a significant increase in the concentration of MDA, and a significant decrease in the stability of rats to hypobaric hypoxic hypoxia and maximum physical activity. When a melatonin suspension was administered at a dose of 2 mg/kg for 12 days, a stable high level of carbonyl derivatives was observed, in comparison with the intact series, which was explained by the need to use a greater concentration of the drug to increase its exposure time, which requires further study.

Keywords

• obesity
• oxidative stress
• protein peroxidation
• melatonin