V. Tashchuk ¹, L. Vlasyk ², H. Khrebtii ¹

¹ Bukovinian State Medical University, Chernivtsi, Ukraine

² “L.I. Medved’s Research Center of Preventive Toxicology, Food and Chemical Safety, Ministry of Health, Ukraine (State Enterprise)”, Kyiv, Ukraine

ABSTRACT. Hypertension is the most common cardiovascular disease that most researchers consider as a state of endothelial dysfunction, which is accompanied by the constriction of smooth muscle of the vessels, increased resistance to left ventricular ejection, and predisposition to atherosclerosis. The disturbance of the endothelial function of the vessels is pathogenetically associated with the development of insulin resistance, which is observed in a significant number of patients with arterial hypertension and underlies the metabolic syndrome. L-arginine (α-amino-δ-guanidinovaleric acid) is a conventionally irreplaceable amino acid that is an active and versatile cellular regulator of many vital functions of the body. L-arginine is a substrate for NO-synthase, an enzyme that catalyzes the synthesis of NO in endothelial cells. Results of the study demonstrated that the combination of combination antihypertensive therapy lisinopril and amlodipine and lipid-lowering therapy with atorvastatin and gradual introduction of L-arginine intravenously, orally in patients with hypertension and concomitant insulin resistance improves endothelial function of blood vessels, namely a statistically significant increase in endothelium dependent vasodilatation, in comparison with the group of patients whose treatment scheme included only lisinopril, amlodipine and atorastatyn. In the treatment of L-arginine drugs for three months, we note a significant decrease in the НOMA-index and triglyceride levels compared with the group of patients receiving baseline treatment, indicating an improvement in carbohydrate and lipid metabolism.

Key Words: hypertension, insulin resistance, L-arginine, endothelial dysfunction, lipid metabolism.

Introduction. Arterial hypertension (AH) is the most common cardiovascular disease, which most researchers consider as a state of endothelial dysfunction, accompanied by the constriction of the smooth muscle of the vessels, increased left ventricular ejection resistance, and predisposition to atherosclerosis [1]. Impairment of the endothelial function of the vessels is pathogenetically associated with the development of insulin resistance (IR), which is observed in a huge number of patients with AH and is the basis of metabolic syndrome [3, 5]. L-arginine (α-amino-δ-guanidinovaleric acid) is a conventionally essential amino acid that is an active and diverse cellular regulator of many vital functions of the body. L-arginine is a substrate for NO-synthase, an enzyme that catalyses the synthesis of NO in endothelial cells [2].

Objective. Study of the effect of the natural precursor of nitric oxide - L-arginine on the functional state of the endothelium of blood vessels, as well as on carbohydrate and lipid metabolism in patients with arterial hypertension and concomitant insulin resistance.

Materials and methods. The basis of this study was the results of examination of 37 patients with stage II AH (according to the recommendations of the Ukrainian Association of Cardiologists, 2008), 0-I stage chronic heart failure (CHF), functional classes (FC) I-II, aged 60–88 years (mean age was (77.3 + 0.8) years) and concomitant insulin resistance. All patients were males.

For the diagnostics of insulin resistance, HOMA (Homeostasis model assessment) index was used, which has been determined by the following formula:

HOMA = fasting blood insulin level (mU/mL), multiplied by fasting blood glucose level (mmol/L) and divided by 22.5. HOMA index below 2.77 was considered as the normal level [4].

Endothelium-dependent vasodilation (EDVD) was determined using D. Celermajer test. An assessment of the flow-induced vasodilation was performed by measuring the diameter of the artery in reactive hyperaemia phase (after vascular decompression). EDVD was defined as the ratio of the magnitude of change in the diameter of the brachial artery after a test with reactive hyperaemia to its value at rest. The normal reaction of the brachial artery was considered to be dilation against the background of reactive hyperaemia test with more than 10 % of the baseline values. Endothelium-independent vasodilation (EIVD) was calculated as the ratio of the change in the diameter of the artery after receiving nitroglycerin to the baseline values. Also, in all observation groups, we measured the rate of blood flow in the brachial artery at rest and at the background of reactive hyperaemia test (V, m/s).

According to the planned study design, all patients with stage II AH received combined antihypertensive therapy with angiotensin-converting enzyme inhibitor lisinopril at a dose of 5–20 mg/day and calcium antagonist amlodipine at a dose of 2.5 to 10 mg/day and hypolipidaemic therapy with atorvastatin 10 mg/day.

Among patients with AH, a separate group of patients (19 patients) was allocated, which, in addition to the above-mentioned treatment regimen, received additional infusion and oral presentations of L-arginine. During 12–14 days (during the hospital stay) patients were infused daily with 100 mL of 4.2 % L-arginine hydrochloride solution. After discharge from the hospital, patients orally took 20 mL of oral presentation of L-arginine (4 g L-arginine) twice daily 40 minutes before meals. Treatment course with infusion and oral presentations was 3 months (90 days). Efficacy was evaluated 3 months after the initiation of the prescribed treatment.

Statistical processing of the study results was performed using methods of variation statistics with StatSoft “Statistica” v. 6.0. The overwhelming number of parameters had an abnormal distribution (the type of distribution was determined using the Shapiro-Wilk test), so we used non-parametric statistics methods. Study results are presented as the median and interquartile range (25–75 percentiles). The difference of p < 0,05 was regarded as statistically probable.

Discussion. Characteristics of endothelial function of the vessels in the examined patients before and after three months of background therapy (lisinopril + amlodipine + atorvastatin) and therapy with additional involvement of L-arginine (lisinopril + amlodipine + atorvastatin + L-arginine) is shown in Table. 1.

Table 1

Changes in the parameters of endothelial function of blood vessels over time in patients with arterial hypertension and insulin resistance under exposure to the different treatment regimens

Notes:

1. Designations: EDVD — endothelium-dependent vasodilation; EIVD — endothelium-independent vasodilation; V — blood flow rate in the brachial artery; RHT — reactive hyperaemia test.
2. p(b-3) — significance of the results upon comparison of the baseline value of parameters and value after 3 months, calculated by Wilcoxon test.
3. p — significance of differences in the rate of distribution of signs, calculated by χ2 test.

It should be noted that the examined patients had shown a marked impairment of the endothelial function of the vessels in the form of a significant reduction in EDVD with the formation of a vasoconstrictor response to a reactive hyperaemia test. EDVD was decreased in all groups of examined patients. It should be noted that impairment of the normal vasodilating reaction to nitroglycerin in patients with AH and IR makes it possible that impaired response of smooth vascular cells and nitrate vasodilators participates in the development of endothelial dysfunction. Some researchers explain this by the development of early “ageing” of vessels in patients with IR with a change in vascular cytoarchitectonics [5].

In patients with AH and concomitant IR, EDVD have significantly improved under exposure to different therapies just after 3 months of follow-up. After 3 months, EDVD in allocated groups of patients under the exposure to background treatment regimen increased by 63.1 %, and with an additional prescription of L-arginine — by 97.9 %.

Changes in the main parameters of carbohydrate metabolism under the effect of antihypertensive therapy with lisinopril and amlodipine and hypolipidaemic therapy with atorvastatin and regimen with additional prescription of L-arginine to the background therapy are given in Table 2.

Table 2

Changes in the parameters of carbohydrate metabolism over time in patients with arterial hypertension and insulin resistance under exposure to the different treatment regimens

Notes:

1. Designations: НОМА (Homeostasis model assessment) – index used to define insulin resistance.
2. *<0,05 — significance of the results upon comparison of the value of parameters for the 3rd month according to the baseline value, calculated by Wilcoxon test.
3. p — significance of differences of changes of parameters over time between allocated groups of patients for the 3rd month, evaluated by χ2 test.

The results of the study of changes in the carbohydrate metabolism under the exposure to different regimens of combined antihypertensive and hypolipidaemic therapy showed a significant decrease in HOMA index after 3 months of treatment only in patients with AH and insulin resistance, with the additional inclusion of L-arginine to the treatment regimen (p < 0.05). Changes in glucose and insulin levels over time in the allocated groups of patients with AH did not significantly differ and did not lead to a significant decrease in the above parameters within 3 months of follow-up.

Changes in the lipid spectrum of blood under the exposure to three months of therapy with the additional involvement of L-arginine are shown in Table 3.

Table 3

Changes in the parameters of lipid metabolism over time in patients with arterial hypertension and insulin resistance under exposure to the different treatment regimens

Notes:

1. Designations: C — cholesterol; TG — triglycerides; HDL — high-density lipoproteins; LDL — low-density lipoproteins; VLDL — very low-density lipoproteins.
2. p(b-3) — significance of the results upon comparison of the baseline value of parameters and value after 3 months, calculated by Wilcoxon test.
3. p — significance of differences in the rate of distribution of signs, calculated by χ2 test.

In all patients with AH and IR, there was a significant improvement in the test parameters of lipid profiles under the exposure to hypolipidaemic therapy with atorvastatin after 3 months of treatment. However, in the group of patients with the additional inclusion of L-arginine to the treatment regimen, there was a significant reduction in triglycerides level (p = 0.028).

Detected changes of increase in EDVD, decrease of the HOMA index and triglyceride levels over time with additional involvement of L-arginine, a substrate for NO-synthase, to the combined antihypertensive and hypolipidaemic treatment, can lend evidence that endothelial dysfunction is not only a “cornerstone” of AH progression but also the development of metabolic displacements that accompany it.

Conclusion

1. The combination of combined antihypertensive therapy with lisinopril and amlodipine and hypolipidaemic therapy with atorvastatin and the gradual administration of intravenous and oral L-arginine in the treatment of patients with arterial hypertension and concomitant insulin resistance contributed to improved endothelial function of the blood vessels, namely: statistically significant increase in endothelium-dependent vasodilation, compared with a group of patients whose treatment regimen included only lisinopril, amlodipine and atorvastatin.
2. In the treatment of L-arginine presentations for three months, we note a significant decrease in the HOMA index and triglyceride levels compared with the group of patients receiving background treatment regimen, indicating an improvement in carbohydrate and lipid metabolism.

Prospects for further studies are to compare the efficiency of treatment regimens with the inclusion of L-arginine presentations in patients with other cardiovascular conditions, such as coronary artery disease, with the determination of the most optimal therapy.

REFERENCES

1. Stres i khvoroby systemy krovoobihu / za red. V.M. Kovalenka, V.M. Kornackoho // DU”Nacionalnyi naukovyi centr ”Instytut kardiolohii imeni akad. M.D. Strazheska”. — Kyiv, 2015. — S. 354.

2. Arginine supplementation for improving maternal and neonatal outcomes in hypertensive disorder of pregnancy: a systematic review / S. Gui, J. Jia, X. Niu [et al.] // J. Renin Angiotensin Aldosterone Syst. — 2014.—№15(1). — R. 88–96.

3. Endothelial Dysfunction and Vascular Disease — A Thirthieth Anniversary Update / P.M. Vanhoutte, H. Shimokawa, M. Feletou, E.H. Tang / Acta Physiol (Oxf). — 2015. — №26. — R. 101–111.

4. HOMA-IR is associated with significant angiographic coronary artery disease in non-diabetic, nonobese individuals: a cross-sectional study / M. Mossmann, M.V. Wainstein, S.C. Gon3alves [et al.] // Diabetol. Metab. Syndr. — 2015. — №14. — R. 87–100.

5. The study of markers of endothelial dysfunction in metabolic syndrome / A.K. Ahirwar, A. Jain, A. Singh [et al.] // Horm Mol Biol Clin Investig. — 2015. — №24(3). — R. 131–136.

Надійшла до редакції 16.04.2019 р.