Volume 28, Issue 8 (11-2021)                   RJMS 2021, 28(8): 1-10 | Back to browse issues page

Research code: IAUK162271914
Ethics code: IAUK162271914
Clinical trials code: IAUK162271914

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Islamic Azad University, Kermanshah, Iran , delavar2009@iauksh.ac.ir
Abstract:   (1941 Views)
Background & Aims: In recent years, the issue of weight regulation, energy balance and energy homeostasis, appetite and food intake has always been a major topic of discussion among exercise physiology researchers. On the other hand, due to the close relationship between obesity and various factors related to the regulation of appetite and role of some peptides, many researchers interested to find better understanding on this field. Energy balance regulation is a complex issue and several mechanisms are involved in weight regulation; including genetic, physiological and behavioral factors. The hypothalamus is an important part of the brain that plays an important role in energy balance by secreting neuropeptides and various chemical transmitters. The hypothalamus exerts this regulatory action through two sets of signals. The activity of a group of signals reduces body fat, including serotonin and leptin, while another group of signals increase body fat and this action is done through an appetizing neuropeptide such as neuropeptide Y. Leptin is a peptide  hormone that is mainly synthesized and released by subcutaneous fat cells in a fixed, pulsating manner with a peak secretion at midnight .Leptin levels are highly correlated with circadian rhythms and sleep status. Leptin levels increase during the biological night and peak during the biological morning. In conclusion, it seems that the issue of regulating energy balance and eating behavior or appetite, affected by various neuro-hormonal factors. Exercise intervention is also considered as one of the effective factors in creating a negative energy balance and starting the process of reducing excess body fat. Numerous studies have been performed on the effect of aerobic exercise on weight loss and improvement of some neuro-hormonal factors affecting the regulation of energy balance, but in many of these studies there are conflicting results. One of the less discussed topics is the circadian rhythm and changes in some neuro-hormonal factors at different times of day. The aim of this research was to study effect of circadian rhythm on response of neuropeptide Y and leptin to eight weeks of aerobic training with moderate intensity in non-athlete obese young men.
Methods: In a quasi-experimental study with pretest-posttest design, 36 non-athlete obese young men with means of age 25.4±3.3 years, weight 98.3±7.7 kg and body mass index 31.8±1.1 kg/m2 were selected purposely and available. Prior to participation, all subjects read and signed informed, voluntary consent forms. The subjects divided randomly into three equal groups (n=12) of control, morning training and evening training. Training intervention was performed during eight weeks, three sessions and with an intensity of 60-75 percent of maximum heart rate. The aerobic training program started in the first week with an intensity of 60% of the maximum heart rate and then every two weeks the aerobic training was increased by 5%. Each session consisted of 10 minutes warming-up, 40 minutes interval aerobic training and 10 minutes cooling-down. During exercise, the heart rates of subjects were monitored using a Polar heart rate monitor. The morning training and evening training groups, performed aerobic training program at 10 am and 5 pm respectively. During the exercise intervention, the subjects used a similar diet and were prohibited from taking any medications or supplements. Before and after training intervention, blood sampling was performed at 10 hours fasting state. Plasma levels of neuropeptide Y and leptin were analyzed using validated ELISA kits. Data were analyzed by using one-way analysis of variance and at significant level at p<0.05.
Results: The finding of this study indicated that eight weeks of aerobic training intervention in morning and evening caused to significant decrease in plasma levels of leptin (p=0.03) and significant increase in plasma levels of neuropeptide Y (p=0.0001).In comparison between morning and evening training, the changes of Leptin levels (p=0.02) and neuropeptide Y levels (p=0.0001) was more in evening training.
Conclusion: Circadian rhythms are a set of endogenous autonomous oscillators that act to coordinate the body's internal clock in a 24-h day/night cycles and allow different organisms to have adaptation to fluctuating environment. The circadian rhythms are stimulated by the daily changes of light and are followed by hormonal fluctuations; especially the hormones involved in the discussion of appetite. According to the results of this study, eight weeks of aerobic training with moderate intensity causes to changes in plasma levels of neuropeptide Y and leptin hormones, so that these changes in evening training were more than morning training. The lowest concentration of leptin is at noon and the highest is at midnight. This is due to the effects of insulin on leptin and increased glomerular filtration in the morning. It is not yet clear how these circadian rhythm changes affect the role of leptin in weight control. A further decrease in leptin levels in the evening training group is probably related to lower baseline leptin levels at that time. Several mechanisms increase neuropeptide Y. Neuropeptide Y is sensitive to blood glucose and is activated by decreases in blood glucose levels. Aerobic exercise reduces muscle glycogen stores and increases glucose uptake by active muscles. lowering blood glucose levels is significantly associated with increased appetite. Decreases in blood glucose stimulates the secretion of neuropeptide Y. Another mechanism of increase in neuropeptide Y levels is its negative association with leptin levels. As some studies have shown, under positive energy balance conditions, high leptin levels are associated with suppression of neuropeptide Y expression. The results of the present study showed that a decrease in plasma levels of leptin was associated with an increase in plasma levels of neuropeptide Y. In addition, previous investigations have shown that Cortisol and growth hormone are among the most important hormones affecting the increase of leptin levels that are affected by the circadian rhythm. This is probably an explanation for the significant increase in neuropeptide Y levels in the evening training group. One of the limitations of the present study was the lack of evaluation of hormones such as cortisol, insulin and growth hormone, which fluctuate under the influence of circadian rhythms. In conclusion it seems that eight weeks of aerobic training with moderate intensity may have positive effects on changes in neuropeptide Y and leptin hormones involved in the discussion of appetite. These changes seem to be more in the evening training.
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Type of Study: Research | Subject: Exercise Physiology

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