The Effects of Circuit Resistance Training on Inflammatory Status, Insulin Resistance and Body Composition in Overweight Adolescent Boys

he adverse consequences of overweight/obesity among adolescents are obvious (1). Obesity triggers a systemic inflammatory condition in which the balance between pro-and anti-inflammatory cytokine production is disrupted and resulted T 1. PhD. of Exercise Physiology, Faculty of Sport Sciences, University of Mazandaran, Babolsar, Mazandaran, Iran. 2. Associate Professor of Exercise Physiology, Faculty of Sport Sciences, University of Mazandaran, Babolsar, Mazandaran, Iran. 3. Associate Professor of Exercise Physiology, Faculty of Sport Sciences, University of Mazandaran, Babolsar, Mazandaran, Iran.


Introduction
he adverse consequences of overweight/obesity among adolescents are obvious (1). Obesity triggers a in the increased and decreased pro-and antiinflammatory cytokine production respectively (2,3,4). Low-grade inflammation connects obesity to some severe diseases such as metabolic syndrome and type 2 diabetes mellitus (T2DM) (5,6). Cytokines are secreted by a variety of immune and non-immune cells (7)(8)(9)(10)(11) and considered as the index of inflammation (12,13). Interleukin-4 (IL-4) and interleukin-13 (IL-13) are involved in modulating energy metabolism (14). IL-4 delays lipid accumulation, leading to reduced body fat and weight gain (15)(16)(17)(18)(19). An inverse relationship between IL-4 and weight gain is proposed (15). Moreover, IL-4 is considered as the trigger of signal for insulin action, thereby regulating the insulin signaling pathways (19). IL-13 performs a variety of functions, including restoring glucose homeostasis and limiting inflammation (20). The favorable effects of exercise on inflammation are demonstrated, showing an inverse relationship between exercise and inflammatory condition (21)(22)(23). Exercise induced improvements to body composition improve the inflammatory status and health risk factors (24). The influence of exercise training over inflammatory indicators is associated with the alterations of body composition induced by anti-inflammatory effects of exercise training (25,26). Resistance exercise training (RET) is recommended as an effective option to treat obesity for adolescents (27)(28)(29)(30)(31). However, the anti-inflammatory effect of RET on cytokine responses has not been given attention enough and is unclear. Unlike the pro-inflammatory cytokines, exercise-induced alterations in the antiinflammatory cytokines are less identified. Few available studies have used RT as a muscle-damaging exercise protocol to induce inflammation (12,32,33). In addition to this, most of the data regarding the IL-4 and IL-13 is derived from protein/mRNA of these cytokines in response to exercise training (34) and there is a lack of evidence on the circulating alterations of these cytokines in response to exercise training. Therefore, this study was designed to assess the effects of a six-week weight loss circuit resistance training protocol on inflammatory status, insulin resistance and body composition in overweight adolescent boys.

Materials and Methods
Twenty out of 100 overweight adolescent boys (aged: 18.5 (±1) years, weight: 81.1 (±4.5) kg, body mass index: 27.7 (±0.7) kg/m 2 ) announced their preparation to take apart in this study. All of the students were informed of the study through announcements distributed to all high school in the area (Abdanan County, Ilam Province, Iran). Prior to the commencement of the trial, the written consents of both participants and their parents were obtained through a meeting in which all details of the study were shared in depth with them. The anthropometric and serum variables of all of the subjects were determined at the baseline and at the end of the study. The subjects were randomly and equally assigned into the circuit resistance training (CRT; n= 10) and control (CG; n= 10) groups. The CRT group performed a weight-loss protocol 3 days/week for 6 weeks.

Anthropometric and serum measurements
The stature, body weight (BW) and body mass index (BMI) of all the subjects were measured by an electronic scale (model Seca 763, made in Germany, with the precision of 50g) in the health center of the physical education group of the education department. The body fat percentage (BF%) was determined by the slim guide skinfold caliper and Jackson and Pollack's three points formula (triceps brachii, abdomen and thigh) (35). To measure the serum levels of glucose, insulin, IL-4 and IL-13, the amount of nearly 10 cc blood were taken from each individual in a fasting sate. After being separated, the serum of each person was stored at -20 0 C for future analysis. Analysis of IL-4 (Cat No. 950.020.096, Diaclone, French), IL-13 (Cat No. 850.080.096, Diaclone, French) concentrations was performed using ELISA kits from Diaclone company with the minimum detectable concentration of 0.7 pg/Ml, 1.5 pg/Ml respectively. The intra-and interassay variations were less than 5% and 10% for both IL-4 and IL-13. Analysis of insulin concentrations was performed using ELISA kits from Accubind (Monobind Inc., Lake Forest, CA, USA) with sensitivity of 0.75µlU/mL, intra-assay variability was 4.3 to 8.3%. Serum concentrations of glucose were measured by photometric method (Pars Azmun Company Kits, Iran). Insulin resistance index (IRI) was calculated using the homeostasis model assessment (HOMA). IRI= (fasting insulin [µ U/mL] × fasting glucose [mmol/L]) / 22.5 (36). The two time-points considered for determining the anthropometric and serum variables of all of the subjects were 24 hours before the beginning and 24-28 hours after the ending of study in a fasting state at the same time at 8 o'clock in the morning. Tables 1 and 2 depict the anthropometric characteristics, HOMA-IR and IL-4, IL-13 respectively.

Circuit Resistance Training Protocol
The CRT group performed a nine-exercise protocol (9 different work-outs) 3 days a week for 6 weeks in which the principal muscle groups were involved. The protocol consisted of chest press, leg press, shoulder press, seated rows, leg extension, triceps extension, leg curl, biceps curl and sit-up. Each exercise included 8-12 repetitions at the workload of 60% of the subjects' one repetition maximum (1RM). Each session consisted of three circuits and in each circuit 9 movements which were previously mentioned were done one after another. The duration of each movement was 30 seconds (8-12 repetitions), the duration of resting between two consecutive movements was 30 seconds and the duration of resting between the two circuits was considered to be 120 seconds. Each session lasted 50-55 minutes. The principle of overload was designed after each three weeks of training. In this study the Brzycki formula was used to calculate the 1RM (37).

Statistical analysis
The distribution of variables was assessed by Kolmogorov-Smirnov test. The Paired T-test was used for determining the possible changes in each group after 6 weeks. Moreover, to compare groups, we calculated the difference (after-before) for each group and tested it by independent T-test. The SPSS version 16.0 was used to analyze the data and the significance level was considered at 5 %.

Ethical considerations
This study was approved by the Ethics Committee of the University of Mazandaran with the code of 2269045.

Results
BW (P-value= 0.54), BMI (P-value= 0.17) and BF% (P-value= 0.096) of the subjects in the CRT group showed insignificantly decreased changes compared with pre-training values whereas those of the subjects in the CG showed significantly increased changes compared with pre-training values. Moreover, significant changes were found fort the changes of BW (P-value= 0.005), BMI (P-value= 0.001) and BF% (P-value= 0.003) between groups (table 1). The serum levels of glucose (P-value= 0.33), insulin (P-value= 0.64) and HOMA-IR (P-value= 0.63) showed insignificantly decreased changes compared with pre-training values whereas that of glucose (P-value= 0.002) of the subjects in the CG showed a significantly increased change compared with pre-training value. Moreover, no significant changes were found for the changes of glucose (P-value= 0.61), insulin (P-value= 0.24) and HOMA-IR (P-value= 0.23) between groups (table 1). The serum levels of IL-4 (P-value= 0.68) and IL-13 (P-value= 0.21) showed insignificantly increased changes compared with pre-training values following 6 weeks of training whereas for the control group, IL-4 (P-value= 0.44) and IL-13 (P-value= 0.46) showed insignificantly Downloaded from ijdo.ssu.ac.ir at 4:30 IRDT on Thursday April 9th 2020 IRANIAN JOURNAL OF DIABETES AND OBESITY, VOLUME 11, NUMBER 2, SUMMER 2019 decreased changes compared with pre-training values. Moreover, no significant changes were found for the changes of IL-4 (P-value= 0.38) and IL-13 (P-value= 0.15) between groups (table 2).

Discussion
This study suggested that although six weeks of CRT failed to induce meaningful antiinflammatory cytokine responses, and to improve body composition and HOMA-IR in overweight adolescent boys, but had protective effects on inflammatory status, HOMA-IR and body composition and prevented them from being deteriorated when compared with those of control group (tables 1& 2). Exercise  training directs the production of cytokines towards an anti-inflammatory state in diverse organs such as skeletal muscle and adipose tissue (38). RET showed to be connected with decreased systemic inflammation related to diseases such as insulin resistance and obesity (39). Some studies have indicated the antiinflammatory effects of RET in different populations including overweight adults (40), elderly individuals (41) (45). One of the mechanisms related to the anti-inflammatory effects of exercise training is fat reduction (46). Excess fat mass, especially visceral fat is considered as a major risk factor for systemic inflammation (47). It's been suggested that exercise training exerts a positive reducing effect on the inflammatory condition through directing the secretion of cytokines towards an anti-inflammatory state leading to reduce the amount of adipose tissue (38,48). Consequently, it's probable that alterations in the inflammatory state of cytokines lead to confirmed health advantages of exercise training. There are studies with conflicting results assessing if the antiinflammatory effect of exercise training is linked to body fat, some of which suggest a relationship (49), whereas the other studies indicate no relationship (50). IL-4 is suggested to be inversely proportional to weight gain and adiposity (15). In the current study, compared to subjects in the control group, subjects in the training group had insignificantly decreased BW, BMI, BF% values and insignificantly increased serum levels of IL-4 which indicates the protective effect of CRT. It might be concluded that six weeks of CRT has not been able to increase IL-4 enough so as to significantly decrease BW, BMI and BF%. Another variable investigated in this study was HOMA-IR. The proposed CRT protocol had no significant effect on HOMA-IR within overweight adolescent boys. RET has been reported to enhance insulin sensitivity by lowering systemic inflammation and increasing glucose uptake by muscle cells (51).These results may, to some extent, be due to an improved body composition and increased muscle mass (52). The discrepancies regarding the effectiveness of RET on inflammatory response, body composition and metabolic profile could be interpreted in various ways including, the variety of RET interventions, training variables such as intensity, duration, volume and metabolic condition of participants. It remains unclear if a higher intensity or longer duration of the proposed CRT protocol would result in significant anti-inflammatory cytokine responses, improvements to body composition and metabolic profile within overweight adolescent boys. There are some limitations to be considered in the current research. There is Limited data regarding the effect of CRT on antiinflammatory cytokine responses, in particular IL-4 and IL-13 that emphasizes the necessity for more researches into these cytokines. In the present study, the dietary intakes of the participants were not monitored, and they were simply asked to have their routine dietary regimens. Another issue is that the posttraining sampling time taken at 24-28 hours after the last session of CRT is the major issue that may interfere with the chronic effect of CRT on inducing an anti-inflammatory cytokine response. Due to the residual effects of the last session of exercise can last up to 72 hours, the future studies need to clarify this issue by determining the time course secretion of these anti-inflammatory cytokines in response to CRT. Finally, the sample size of this study was rather small, and further studies with larger numbers of subjects should be undertaken in the future.

Conclusions
This study suggested that although six weeks of CRT failed to induce a meaningful antiinflammatory cytokine responses, and to improve body composition and HOMA-IR in overweight adolescent boys, but had protective effects on inflammatory status, HOMA-IR and body composition and prevented them from being deteriorated.