Academic journal article Iranian Journal of Public Health

Cardioprotective Effect of High Intensity Interval Training and Nitric Oxide Metabolites (NO^suv 2^^sup -^, NO^sub 3^^sup -^)

Academic journal article Iranian Journal of Public Health

Cardioprotective Effect of High Intensity Interval Training and Nitric Oxide Metabolites (NO^suv 2^^sup -^, NO^sub 3^^sup -^)

Article excerpt

Introduction

Cardiovascular diseases are still the main cause of mortality all over of the world. Therefore, cardioprotection is one of the most important criteria in recent decades. In patients who survive acute myocardial infarction (AMI), the amount of damaged myocardium due to ischemia (infract size) largely predicts the mortality rate of patients. Thus, it is commonly held that a significant decline in myocardial infarction decreases the morbidity and mortality. Preconditioning (PC) is one of the main approaches to decrease myocardial infarction (1). Ischemic preconditioning (IPC) refers to a brief period of ischemia protecting the heart against prolonged episodes of ischemia (2). Despite the considerable protective effects of IPC, it is not applicable in the clinic. Regular exercise training is one of the most efficient PC methods.

Exercise protects myocardium against ischemia reperfusion (IR) injury (3). However, the mechanism nism of these protective functions known to date. Several mechanisms have been examined concerning the cardioprotective effects of exercise training. NO makes a greater contribution to cardiovascular health than was expected before. NO is both a trigger (through endothelial NOS) and a mediator (through iNOS) of delayed ischemic preconditioning (4). Moreover, NO has several physiological properties that highlights it as the cardioprotective signaling molecule that is potentially involved in myocardial I/R injury (5-8). ENOS-deficient rats ran a distance 60% less than that of their same-age counterparts in the control group (8). Considering the cardioprotective effects of NO and its instability, some researchers have conducted more studies on the NO effects and its metabolites, nitrite and nitrate. Nitric oxide amounts decrease in endothelial dysfunction (9). Exercise training, especially high intensity interval training (HIIT) may restore NO concentration and its metabolites to a normal range and decrease vascular disorders (10). NO concentration decreases during ischemia and reversely the plasma levels of the NO metabolites increase during exercise in both rodents and human (11, 12).

Increased levels of NO metabolites during exercise may contribute to cardiac protection against IR injury. Since there is limited evidence on the role of nitrite and nitrate in exercise-induced cardioprotection, the present study aimed to address the variations in the plasma levels of nitric oxide metabolites following eight weeks of HIIT and its cardioprotective effects during IR injury in adult male rats.

Materials and Methods

Research samples

A number of 44 male Wistar rats, 3 - 4 months, were prepared from Iranian Pasteur Research Center and used in the present study. The rats were kept in the 12:12 light-dark cycle at 50% moisture and a temperature of 22±30 C. They were kept in cages containing 4 rats per unit and had free access to food.

The ethical codes of treating laboratory animals, set by the Iranian Society for Supporting Laboratory Animals Used for Scientific Purposes, were strictly followed in the present study. The University of Tehran approved the treating and handling method, the training program and the sampling type of animals conducted in the present study.

Allowing the animals to adapt to their new environment for a week, they were divided into 4 groups including HIIT (n=8), HIIT+IR program (n=14), control (n=8), and control+IR program (n=14).

Exercise Training program

The training program was developed based on previous protocols (13, 14) and the researchers' experiences. During the first week, the animals were introduced into the training program by walking and then running on the treadmill at different speeds. Then, they performed 8 weeks of progressive exercise training. Every session consisted of one hour exercise training performed in three stages:

· Warm-up: running for 6 minutes at 50-60% VO2max

· Main training: 7 intervals of 7-minute running at 5-200 slope consisting of 4-minute running at 80-100% VO2max and 3minute running at 50-60% VO2max

· Cool-down: running for 5 minutes at 5060% VO2max

The control group did not perform any exercise training whatsoever. …

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