Chronic intermittent hypoxia induces changes on the expression and activity of neprilysin (EC 3.4.24.11) in the brain of rats

The Impact of Intermittent Hypoxia on Metabolism and Cognition

Intermittent hypoxia (IH), one of the primary pathologies of sleep apnea syndrome (SAS), exposes cells throughout the body to repeated cycles of hypoxia/normoxia that result in oxidative stress and systemic inflammation. Since SAS is epidemiologically strongly correlated with type 2 diabetes/insulin resistance, obesity, hypertension, and dyslipidemia included in metabolic syndrome, the effects of IH on gene expression in the corresponding cells of each organ have been studied intensively to clarify the molecular mechanism of the association between SAS and metabolic syndrome. Dementia has recently been recognized as a serious health problem due to its increasing incidence, and a large body of evidence has shown its strong correlation with SAS and metabolic disorders. In this narrative review, we first outline the effects of IH on the expression of genes related to metabolism in neuronal cells, pancreatic β cells, hepatocytes, adipocytes, myocytes, and renal cells (mainly based on the results of our experiments). Next, we discuss the literature regarding the mechanisms by which metabolic disorders and IH develop dementia to understand how IH directly and indirectly leads to the development of dementia.

CHANGE OF INDICES OF THE AMINO ACID COMPOSITION OF RATS’ HEARTS AT ARTIFICIAL HYPOBIOSIS

A series of unsolved questions in such sciences as: medicine, veterinary, biology still exist in the modern world. One of them is a search for new promising ways of anaesthetization, at which it would be unnecessary to use apparatuses as an “artificial heart”, “artificial ventilation of lungs” at short-term surgical interventions. Just artificial hypobiosis may become one of such methods. Main conditions for creation are a synchronous effect of such factors as hypoxia, hypercapnia, hypothermia. That is why for confirming the safety of this method in pre-clinical studies with a further perspective of using at clinical ones, it is necessary to study the mechanism of an effect and influence of the hypobiotic condition on the homeostasis of the living organism in detail. Rats are the best research object in this case. Just they have a similar physiological structure of such organs as a heart. An urgent question about changes that take place in the amino acid composition under the hypobiotic effect still be unexplained. That is why the aim of the study was to investigate amino acid changes of the rat heart under condition of artificial hypobiosis. White outbred male rats with mass 180–200 g were used in the experiments. The animals were divided in groups: control (intact) and experimental: the condition of artificial hypobiosis (first group) and 24 hours after release from artificial hypobiosis (second group). The number of animals in each group n=5. The experiments were conducted according to requirements of “The European convention about protection of vertebral animals, used with experimental or other scientific aims” (Strasbourg, France 1985), by general ethical principles of experiments with animals, approved by the First national congress of Ukraine on bioethics (2001). As a result of the conducted studies, a little decrease of several amino acids under condition of artificial hypobiosis was demonstrated. First of all, a decrease of such amino acids as aminosuccinic, glutamic, isoleucine, leucine, lysine, arginine was observed in rats’ hearths under artificial hypobiosis. There was also demonstrated an increase of the level of these amino acids in rats’ hearts after 24 hours after release from it.

INDICATORS OF THE ELEMENT RANGE OF RAT’S BLOOD IN TERM ARTIFICIAL HYPOBYOSIS

The promising method of anesthesia and anesthesia is the state of artificial hypobiosis. Hypercapnia is a prerequisite for creating an artificial carbon dioxide hypobiosis, along with hypoxia and hypothermia. Adhering to the conditions under which the state of artificial carbon dioxide hypobiosis is created, animals reduce the level and intensity of metabolic processes both in the body as a whole and in separate organs. In order to investigate the safety of the hypobiological state and evaluate its applicability in clinical practice, it is necessary to investigate the functional characteristics of the blood. One of the most important indicators is the change of elemental composition. After all, the set of micro-and macro-elements is involved in the enzymatic reactions of the organism, its metabolic processes. Therefore, the aim of the study was to investigate the elemental changes in the blood of rats for artificial hypobiosis. In experiments, white non-breeding male rats weighing 180–200 g were used, which were maintained under standard vivarium conditions. Animals were divided into 2 groups: control and experimental (the state of artificial hypobiosis). Each group had 7 animals. Measurement of the content of macro- and micronutrients was carried out using a mass spectrometric ionization method in an inductively coupled plasma on an IRIS Interband II XSP device manufactured by Thermo Scientific, USA. The results of the study were processed and presented using the methods of statistical analysis, namely: the method of descriptive statistics; Shapiro-Wielka's criterion for choosing a statistical criterion for comparing groups; Student's criterion; Mann-Whitney's criterion. Results of evaluation of dynamics in the experimental (hypobiotic) group using the criterion of sign-marks of Wilcoxon. As a result of the studies, increased levels of Sodium, Ferrum, Calcium were observed, while the content of Nickel and Barium reduced. The results of the analysis of the dynamics of blood parameters in the experimental group by the methods of descriptive statistics showed significant changes in such elements as: Potassium, Sodium, Ferrum, Calcium, Magnesium. The heterogeneity of the results of the experimental and control groups according to the Mann-Whitney criterion was demonstrated in the following elements: Potassium, Sodium, Ferrum, Calcium, Chromium, Strontium.