Urine metabolic profile in rats with arterial hypertension of different genesis.

The diversity of pathogenetic mechanisms underlying arterial hypertension leads to the necessity to devise a personalized approach to the diagnosis and treatment of the disease. Metabolomics is one of the promising methods for personalized medicine, as it provides a comprehensive understanding of the physiological processes occurring in the body. The metabolome is a set of low-molecular substances available for detection in a sample and representing intermediate and final products of cell metabolism. Changes in the content and ratio of metabolites in the sample mark the corresponding pathogenetic mechanisms by highlighting them, which is especially important for such a multifactorial disease as arterial hypertension. To identify metabolomic markers for hypertensive conditions of different origins, three forms of arterial hypertension (AH) were studied: rats with hereditary AH (ISIAH rat strain); rats with AH induced by L-NAME administration (a model of endothelial dysfunction with impaired NO production); rats with AH caused by the administration of deoxycorticosterone in combination with salt loading (hormone-dependent form - DOCA-salt AH). WAG rats were used as normotensive controls. 24-hour urine samples were collected from all animals and analyzed by quantitative NMR spectroscopy for metabolic profiling. Then, potential metabolomic markers for the studied forms of hypertensive conditions were identified using multivariate statistics. Analysis of the data obtained showed that hereditary stress-induced arterial hypertension in ISIAH rats was characterized by a decrease in the following urine metabolites: nicotinamide and 1-methylnicotinamide (markers of inflammatory processes), N- acetylglutamate (nitric oxide cycle), isobutyrate and methyl acetoacetate (gut microbiota). Pharmacologically induced forms of hypertension (the L-NAME and DOCA+NaCl groups) do not share metabolomic markers with hereditary AH. They are differentiated by N,N-dimethylglycine (both groups), choline (the L-NAME group) and 1-methylnicotinamide (the group of rats with DOCA-salt hypertension).

Metabolic profile of blood serum in experimental arterial hypertension.

The etiology of essential hypertension is intricate, since it employs simultaneously various body systems related to the regulation of blood pressure in one way or another: the sympathetic nervous system, renin-angiotensin-aldosterone and hypothalamic-pituitary-adrenal systems, renal and endothelial mechanisms. The pathogenesis of hypertension is influenced by a variety of both genetic and environmental factors, which determines the heterogeneity of the disease in human population. Hence, there is a need to perform research on experimental models - inbred animal strains, one of them being ISIAH rat strain, which is designed to simulate inherited stress-induced arterial hypertension as close as possible to primary (or essential) hypertension in humans. To determine specific markers of diseases, various omics technologies are applied, including metabolomics, which makes it possible to evaluate the content of low-molecular compounds - amino acids, lipids, carbohydrates, nucleic acids fragments - in biological samples available for clinical analysis (blood and urine). We analyzed the metabolic profile of the blood serum of male ISIAH rats with a genetic stress-dependent form of arterial hypertension in comparison with the normotensive WAG rats. Using the method of nuclear magnetic resonance spectroscopy (NMR spectroscopy), 56 metabolites in blood serum samples were identified, 18 of which were shown to have significant interstrain differences in serum concentrations. Statistical analysis of the data obtained showed that the hypertensive status of ISIAH rats is characterized by increased concentrations of leucine, isoleucine, valine, myo-inositol, isobutyrate, glutamate, glutamine, ornithine and creatine phosphate, and reduced concentrations of 2-hydroxyisobutyrate, betaine, tyrosine and tryptophan. Such a ratio of the metabolite concentrations is associated with changes in the regulation of glucose metabolism (metabolic markers - leucine, isoleucine, valine, myo-inositol), of nitric oxide synthesis (ornithine) and catecholamine pathway (tyrosine), and with inflammatory processes (metabolic markers - betaine, tryptophan), all of these changes being typical for hypertensive status. Thus, metabolic profiling of the stress-dependent form of arterial hypertension seems to be an important result for a personalized approach to the prevention and treatment of hypertensive disease.

Toward Gene Therapy of Hypertension: Experimental Study on Hypertensive ISIAH Rats.

TiO2-based nanocomposites were prepared to deliver oligonucleotides into cells. The nanocomposites were designed by the immobilization of polylysine-containing oligonucleotides on TiO2-nanoparticles (TiO2·PL-DNA). We showed for the first time the possibility of using the proposed nanocomposites for treatment of hypertensive disease by introducing them into hypertensive ISIAH rats developed as a model of stress-sensitive arterial hypertension. The mRNA of the gene encoding angiotensin I-converting enzyme (ACE1) involved in the synthesis of angiotensin II was chosen as a target. Administration (intraperitoneal injection and inhalation) of the nanocomposite showed a significant (by 20-30 mm Hg) decrease in systolic blood pressure when the nanocomposite contained the ACE1 gene-targeted oligonucleotide. When using the oligonucleotide with a random sequence, no effect was observed. Further development and improvement of the inhalation nanocomposite drug delivery to systemic hypertensive disease treatment promises new possibilities for clinical practice.

Stress-sensitive arterial hypertension, haemodynamic changes and brain metabolites in hypertensive ISIAH rats: MRI investigation.

NEW FINDINGS: What is the central question of this study? Stress-sensitive arterial hypertension is considered to be controlled by changes in central and peripheral sympathetic regulating mechanisms, which eventually result in haemodynamic alterations and blood pressure elevation. Therefore, study of the early stages of development of hypertension is of particular interest, because it helps in understanding the aetiology of the disease. What is the main finding and its importance? Non-invasive in vivo investigation in ISIAH rats demonstrated that establishment of sustainable stress-sensitive hypertension is accompanied by a decrease in prefrontal cortex activity and mobilization of hypothalamic processes, with considerable correlations between haemodynamic parameters and individual metabolite ratios. The study of early development of arterial hypertension in association with emotional stress is of great importance for better understanding of the aetiology and pathogenesis of the hypertensive disease. Magnetic resonance imaging (MRI) was applied to evaluate the changes in haemodynamics and brain metabolites in 1- and 3-month-old inherited stress-induced arterial hypertension (ISIAH) rats (10 male rats) with stress-sensitive arterial hypertension and in control normotensive Wistar Albino Glaxo (WAG) rats (eight male rats). In the 3-month-old ISIAH rats, the age-dependent increase in blood pressure was associated with increased blood flow through the renal arteries and decreased blood flow in the lower part of the abdominal aorta. The renal vascular resistance in the ISIAH rats decreased during ageing, although at both ages it remained higher than the renal vascular resistance in WAG rats. An integral metabolome portrait demonstrated that development of hypertension in the ISIAH rats was associated with an attenuation of the excitatory and energetic activity in the prefrontal cortex, whereas in the WAG rats the opposite age-dependent changes were observed. In contrast, in the hypothalamus of 3-month-old ISIAH rats, an increase in energetic activity and prevalence of excitatory over inhibitory neurotransmitters was noticed. The blood flow through the main arteries showed a positive correlation with glutamate and glutamine levels in the hypothalamus and a negative correlation with the hypothalamic GABA level. The blood pressure values were positively correlated with hypothalamic choline levels. Thus, the early development of stress-sensitive hypertension in the ISIAH rats is accompanied by considerable changes both in brain metabolite ratios and in the parameters of blood flow through the main arteries.

Parameters of Blood Flow in Great Arteries in Hypertensive ISIAH Rats with Stress-Dependent Arterial Hypertension.

Magnetic resonance angiography was used to examine blood flow in great arteries of hypertensive ISIAH and normotensive Wistar rats. In hypertensive ISIAH rats, increased vascular resistance in the basin of the abdominal aorta and renal arteries as well as reduced fraction of total renal blood flow were found. In contrast, blood flow through both carotid arteries in ISIAH rats was enhanced, which in suggests more intensive blood supply to brain regulatory centers providing enhanced stress reactivity of these rats characterized by stress-dependent arterial hypertension.