Recent studies have revealed that exercise has favorable effects on hyperglycemia, hypercholesterolemia and hypertension (HT). Related with this fact, regular exercise has been reported to reduce the risk of diabetes mellitus (DM), HT, obesity, cardiovascular diseases, and metabolic syndrome (Kraemer and Castracane, 2007). However, data acquired from exercise studies involving either humans or animals have yet to constitute consensus. The relation between physical exercise and hormone concentrations, on one hand, and the mechanism of action of exercise, on the other, has not been completely clarified. Moreover, the number of studies demonstrating the beneficial effects of exercise and the amount of drug research which could decrease the negative effects of it on the body are still unsatisfactory.

In order to understand whether alone and together exercise and caffeic acid phenethyl ester (CAPE) has an effect on obesity and weight control, we investigated the leptin, resistin, lipid parameters (triglyceride [TG] and total cholesterol levels [TC], HDL-C, LDL-C), and body weights in rat model.

Leptin, one of the markers in the present study, is a hormone secreted from adipocytes, which suppresses food intake by acting on the hypothalamus through negative feedback mechanisms and increases energy expenditure. It has been reported that short-term training sessions (<12 weeks) do not have an impact on leptin levels so long as they do not reduce fat mass, while long-term training sessions (>12 weeks) decrease leptin levels (Kraemer and Castracane, 2007). This decrease takes places in conjunction with the decrease in fat mass. Gutin et al., 1999 assessed the leptin levels in obese children after an exercise program and observed that leptin levels in the group, comprising 24 girls and 10 boys, were reduced following a 4-month exercise program. Pasman et al., 1998 carried out a moderate exercise program with middle-aged obese men, using a very low-calorie diet. This exercise program continued for 4 months at 3-4 times per week, and a significant decrease was observed in the leptin levels (Reseland et al., 2001).

Another adipokine substance used in the present study is a recently discovered hormone called resistin, which is found abundantly in and excreted from adipocytes. It is significantly related to obesity and type 2 diabetes. Jung et al., 2008 observed a decrease in resistin levels pursuant to a 12-week exercise program and a low-calorie diet, and stated that this decrease was related to weight loss.

The possible protective effects of CAPE on leptin, resistin, and lipid parameters in groups with/without exercise were observed in the present study. CAPE has been used for many years as a traditional type of active composite of propolis extract. Recently, studies have revealed CAPE to have anti-inflammatory, antioxidant, immunumodulator, antimycotic, and anticarcinogenic characteristics (Gurel et al., 2004; Hepsen et al., 1997; Ilhan et al., 1999; Orhan et al., 1999; Uz et al., 2002).

It has been demonstrated that at a concentration of CAPE at 10 µmol/kg concentration completely blocks production of ROS and xanthine and xanthine oxidase system (XO) and also reduces malondialdehyde level secondary to polyunsaturate fatty acid oxidation (Yilmaz et al., 2004). CAPE inhibits protein tyrozin kinase, cyclooxigenase (non-spesifically) and suppresses activity of lipooxigenase and so it has been show that CAPE prevents lipid peroxidation (Koltuksuz et al., 1999; Ozer et al., 2005). Antiinflammatory activity of CAPE is equal to diclofenac and hydrocortisone (Koksel et al., 2006). CAPE is a potent and specific inhibitor of activation of nuclear transcription factor NF-θºB by TNF-α (Natarajan et al., 1996). In addition to this, CAPE is a lipooxygenase inhibitor with antioxidant properties (Natarajan et al. , 1996; Sud'ina et al., 1993). However, there have been no studies about effects of CAPE on leptin, resistin, and lipid parameters in groups with/without exercise. Therefore, the possible protective effects of CAPE on leptin, resistin and lipid parameters in groups with/without exercise were observed in the present study.

In the study, a total of 40 Sprague-Dawley male rats were used in 4 groups of 10 rats each. The groups were arranged as Group 1S (sedentary + 40% ethanol (2ml·kg^-1·day^-1, intraperitoneally-i.p.), Group 2E (exercise + ethanol), Group 3C (sedentary + CAPE (10 µmol·kg^-1·day^-1, i.p.) and Group 4CE (exercise + CAPE). A 1-week exercise familiarization program was conducted as a preliminary study. Afterwards, the rats prone to exercise were allocated to exercise groups, while the other rats, not prone to exercise, were allocated to sedentary groups. The study was approved by Experimental Animals Ethics Committee of Selcuk University (SUDAM).

In the long-term treadmill, exercise program was performed as a) 10 m·min^-1, 20 m·min^-1 and 25 m·min^-1 jogging for ten minutes on the 1^st, 2^nd and 3^rd days, respectively; b) 25 m·min^-1 jogging for 20 minutes on the 4^th day; and c) 30 minutes jogging for 25 m·min^-1 on the 5^th day.

Following the exercise schedule, ethanol was administered to the rats in Group 1S for 6 weeks. The rats in Group 2E underwent 6 weeks of exercise. The rats in Group 3C were supplemented with CAPE i.p. throughout 6 weeks. The rats in Group 4CE underwent 6 weeks of exercise and were also supplemented with CAPE.

CAPE (Sigma C8221) was purchased from the Sigma Company, dissolved in 40% ethanol and administered to the rats in Groups 3E and 4CE. For 45 minutes over 6 weeks, a 25 m·min^-1 jogging program was applied. After the final exercise session, all the rats in each group were anesthetized with ketamine hydrochloride (50 mg·kg^-1) + xylazine HCL (5 mg·kg^-1) administered i.p. 24 hours. Blood samples were collected in sterile tubes without anticoagulant. After centrifugation (1500 g, 10 minutes, 4°C), sera were carefully harvested and stored at -20°C until analysis. After blood sampling, animals were sacrified by decapitation.

Leptin concentrations were determined by the ELISA technique with commercially available reagents (USBiological (BioAssay Elisa kit, catalogue no:L1670-30J, USA). Resistin concentrations were determined by the ELISA technique with commercially available reagents (BioVendor, Catalogue no:RD391016200R, USA). Triglyceride, total cholesterol and HDL-C were measured with colorimetric methods in Dimension Xpand auto analyzer (Dade Behring, Siemens, USA) using original Dade Behring reagents. LDL-C values were calculated according to the Friedewald formula: LDL-C= Total cholesterol-[(triglyceride/5)+ HDL]. Lipid parameters were expressed in mg/dL. All analysis was performed in Biochemistry Department of Medical Faculty of Selcuk University.

Statistical tests were carried out using SPSS for Windows 10.0. Distribution characteristics were tested with the Shapiro-Wilk test. Due to the fact that the group distributions bear non-parametric characteristics, the multiplex group comparisons were assessed by the Kruskal-Wallis test, and the Mann-Whitney U test was then administered for paired comparisons. Furthermore, the intra-group comparisons of each group regarding their pre- and post-exercise weights were performed by the Wilcoxon Signed Rank Test. Results were given as Mean ± SD, and p < 0.05 was assumed as statistically significant.

The results are presented in Table 1 as Mean ± SD values. Table 2 presents data related to the weight parameters of the rats.

When Group 2E and Group 3C were compared in terms of cholesterol values, a significant increase was observed in Group 3C compared with Group 2E (p < 0.01). When Group 3C and Group 4CE were compared in terms of triglyceride values, a significant increase respectively was found in Group 3C compared with Group 4CE (p < 0.01), and in Group 3C compared with Group 2E (p < 0.01). Also, weight gain accompanied the increase in triglyceride levels. It was concluded that triglyceride and cholesterol levels decreased to a considerable extent in the exercise groups and concluded that TG and TC were therefore substantially affected by exercise (Table 1).

When groups supplemented with CAPE were compared with the other groups in terms of leptin, resistin and lipid parameters, it was concluded that CAPE alone was not effective on these parameters (Table 1).

When Group 3C and Group 4CE were compared in terms of HDL cholesterol values, the HDL values displayed significant differences and were lower in Group 4CE (p < 0.05) (Table 1). However, post-exercise body weights of all the animal groups increased compared with their pre-exercise body weights, and a considerably significant weight increase was observed (p = 0.005) (Table 2).

Obesity is associated with resistance to the actions of leptin, resistin, lipid parameters and insulin via mechanisms that are not yet fully understood. Therefore, the aim of this study was to investigate the effects of exercise, diet and CAPE on leptin, resistin, lipid parameters, and body weight.

Pomerants et al., 2006 investigated the serum leptin levels after acute aerobic exercise of 60 males at different stages of adolescence. The study results revealed no change in leptin level after acute exercise. In a study by Kim et al., 2008, a group of 17 overweight male children were compared with a control group (n = 9). The exercise group undertook a 12-week exercise program of 30 minutes walking 2 days a week and 50 minutes on a running band 2 days a week. The leptin levels of the exercise group showed a significant decrease compared to the control group (p < 0.05), and reduced leptin levels were determined in the exercise group at the end of the 12-week exercise program in comparison to the beginning. Zoladz et al., 2005 formed a model of 8 healthy non-smoking young males undertook moderate exercise and gave blood samples five minutes before exercise, during exercise, and after exercise. Leptin levels were measured in the blood samples. The hypothesis of these researchers was that plasma leptin and ghrelin levels resulting from hunger and exercise may affect the cardiovascular response. Based on the findings of Zoladz et al., 2005 in the acute exercise model the leptin levels have been shown not to have been affected. Rämson et al., 2008 researched plasma leptin levels during intensive exercise by 8 trained male skiers. The 4-week exercise program consisted of the following: familiarization exercises in week 1, an increase in exercise intensity in weeks 2 and 3, and, in week 4, a decreased of exercise intensity to that of week 1. The exercise was carried out for 2 hours a day, 6 days a week. Two hours before starting the exercise, a carbohydrate-rich meal was eaten by the skiers. At the end of the first, second and fourth weeks, fasting blood samples were taken before, 5 minutes after and 30 minutes after the exercise. The leptin levels during exercise of the second and third week were statistically significantly low compared to the levels before and after exercise (p < 0.05). Kyriazis et al., 2007 applied a single 60-minute moderate exercise session to sedentary obese males and no difference was determined in the measurements of leptin levels taken 24 and 48 hours after exercise. This showed that a single 60-minute moderate exercise session did not affect the leptin levels by any significant amount. Koch et al., 2010 demonstrated that leptin resistance, which occurs in obesity, reduces the hypothalamic response to insulin and thereby impairs peripheral glucose homeostasis, contributing to the development of type 2 diabetes. In a study by Cui et al., 2011, leptin repletion resulted in a reversal of the suppression of uncoupling protein 1 levels in brown adipose tissue, indicating an additional role for reducing body fat and leptin during peak lactation. Arikan et al., 2008 measured plasma leptin levels of athletes doing weight training, and the leptin levels of the control group were found to be higher than those of the athletes (p < 0.01). This study demonstrated that the sedentary control group had higher leptin levels compared with the exercise group. Kelly et al., 2007 could not find any difference between the levels of blood adipokines such as leptin and resistin in a sedentary group and in a group of 19 obese children involved in an 8-week aerobic exercise program. They concluded that 8-week exercise alone does not make any significant difference in leptin and resistin levels. Murakami et al., 2007 also evaluated blood leptin levels of two obese groups, both subject to diet restriction but only one following an exercise program. This study revealed that after a 60-minute aerobic exercise program three days a week for 12 weeks, leptin levels decreased after exercise in both groups (p < 0.001, p<0.004), and this decrease was higher in the group with the combination of diet restriction and exercise. This demonstrates that diet restriction is effective on leptin levels and that, when diet restriction is accompanied by exercise, this effect becomes more evident. Christ et al., 2006 administered a 3-hour exercise program to 11 healthy athletes and measured leptin levels by taking blood samples at 15, 45, 80, 110, 130 and 180 minutes. A decrease was determined in the leptin concentrations (p < 0.03) after a 3-hour exercise session. Similar to the above-mentioned study results, the present study revealed a significant decrease in leptin levels at the end of the exercise program. It was concluded that exercise has a considerable effect on leptin levels.

Kondo et al., 2006 investigated the effect of exercise on the adipokine levels in the circulation of young obese women. Eight young obese students underwent a 30-60 minute exercise program 4-5 days a week for 7 months, and 8 control students did not perform any exercise. The body weight and leptin levels of the obese participants were found to be considerably higher than those in the control group (p < 0.01). Exercise reduced body weight and leptin levels (p < 0.05) and increased HDL-C levels (p < 0.05) in the obese participants. No significant change was found in TC and TG levels. The study concluded that changes in leptin levels in the circulation contribute to the adjustment of metabolic condition via exercise and that this can be used as an indicator in evaluating the exercise treatment. Kondo et al., 2006 also stated that the evident decrease in both body weight and leptin levels in the circulation suggests that exercise may affect metabolic condition and that this effect can be used as an indicator in evaluating the effects of exercise. Levin et al. (2004) measured weight loss and plasma leptin levels in 42 male rats at the end of a 6-week exercise program. In exercise group, a weight loss of 33% and a decrease of 35% in leptin levels were determined. They also showed that calorie restriction together with exercise is more effective than exercise alone. Kondo et al., 2006 and Levin et al. (2004), Jung et al., 2008 concluded that combined exercise and sibutramine application decreased leptin, resistin, TC, TG and body weight. In that study, the exercise was performed not alone but accompanied by sibutramine, a pharmacological agent that acts as a weight regulator by providing an artificial saturation sensation. Therefore, it is possible that the evident decrease in leptin level resulted from exercise. In conformity with the above-mentioned study results, the present study determined that triglyceride, total cholesterol, HDL-C, LDL-C and leptin values in exercise groups decreased considerably. It was concluded that exercise is effective against various diseases, such as cardiovascular diseases caused by lipid parameters in human and animals.

In recent years there has been some controversy about the physiological role of the effect of resistin on obesity and insulin resistance in mice, rats and humans (McTernan et al., 2006). Therefore, resistin was selected together with leptin as the other marker substance in the present study. The present study’s conformities to and contrasts with previous studies on resistin, exercise and obesity are discussed below.

Pagano et al., 2005 reported that there was a relationship between resistin concentrations and adiposity, which showed that the amount of circulating resistin was related to obesity. In a study by Borst et al., 2005 of visceral skeletal muscle taken from rats, the increase observed in insulin response was most probably due to resistin and IL levels. This suggested that the source of resistin release could be visceral fatty tissue. Moreover, a decrease in serum resistin level caused by removal of visceral fat may play a role in the reversal of insulin resistance. Jung et al., 2008 stated that exercise and sibutramine application decreased resistin levels, and like Jung et al., 2008, Kadoglou et al., 2007 reported that 45-60-minutes of exercise 4 times a week for 16 weeks decreased resistin levels. However, certain studies such as Giannopoulou et al., 2005, Kelly et al., 2007, Rokling-Anderson et al. (2007), Shadid et al., 2006, Monzillo et al., 2003 and Jamurta et al. (2006), have reported the contrary result that exercise does not affect resistin levels. As in these study results, in our chronic exercise model, resistin levels were determined to remain unaffected. Gouni et al. (2008) measured serum leptin, resistin and lipid levels after 14 days of simvastatin and ezetimibe treatment on healthy people. In that study, people were divided into three groups: Group 1S received only statin, Group 2E received only ezetimibe and Group 3C received both. A significant decrease was observed in LDL-C levels, while no significant change was found in leptin and resistin levels. Jung et al., 2008 also investigated the change of adipocytokines before and after weight loss in obese subjects. Sibutramine treatment was administered along with a 12-week exercise program on 28 obese patients who were attending obesity clinics and were on calorie-restricted diets. At the end of 12 weeks, similar to the present study results, total cholesterol (p < 0.001) and triglyceride (p < 0. 007) levels were reported to have decreased. In the present study, when Group 2E and Group 3C were compared in terms of total cholesterol values respectively, a significant increase (p < 0.01) was observed in Group 3C compared with Group 2E, and a significant increase (p < 0.05) was observed in Group 3C compared with Group 4CE. With respect to triglyceride values, when Group 3C and Group 4CE were compared, a significant increase (p < 0.01) was observed in Group 3C compared with Group 4CE, and a significant increase (p < 0.01) was observed in Group 3C compared with Group 2E. Weight gain accompanied the increase in the triglyceride levels. It was concluded that triglyceride and total cholesterol decreased in the exercise groups to a considerable extent and that TG and TC were substantially affected by exercise. When Group 3C and Group 4CE were compared with respect to HDL-C values, they were found to be significantly lower in Group 4CE (p < 0.05).

As a result, in the present study, it was determined that exercise and CAPE caused no significant change in resistin levels. The exercise was substantially effective on leptin and lipid parameters. When pre- and post-exercise body weights of all animal groups were compared, in all groups, a significant weight gain was observed (p = 0.005, despite the exercise). This result was thought to arise from the without diet restriction in the rats.

Our study revealed that CAPE was not effective on weight control, lipid parameters, and adipokine substances such as leptin and resistin, but that exercise was considerably effective on leptin and lipid parameters. However, exercise alone was not sufficient to lose weight and can be effective in weight control only when accompanied by a restricted diet. Exercise with a restricted diet will be especially useful for people with diseases of the heart-circulatory system, high cholesterol and obesity to continue their lives in a healthy way.