Effect of different training mode on Interleukin-6 (IL-6) and C-reactive protein (CRP) in type 2 diabetes mellitus (T2DM) patients.

PURPOSE: This study was carried out to investigate the effects of different training modes on IL-6 and CRP in patients with type 2 diabetes mellitus (T2DM).
METHODS: The subjects consisted of 16 middle-aged women with type 2 diabetes mellitus (T2DM), all of whom had no other complications. The 16 subjects were randomly assigned to two experimental groups: the circuit training group (CTG, n = 8) and aerobic training group (ATG, n = 8). Based on measured THR (target heart rate) for maximum oxygen consumption rate, the circuit training group (CTG) exercised at 60% intensity, 60 min/day, 5 sets, 3 days/week for 12 weeks. Based on measured THR (target heart rate) for maximum oxygen consumption rate, the aerobic training group (ATG) exercised at 60% intensity (which was increased gradually in weeks 4, 7, and 10) 60 min/day, 3 days/week for 12 weeks.
RESULTS: The results are as follows. Significant decreases in the post training values of weight, % Fat, BMI, IL-6 and CRP (p < .05) were observed in the CTG compared to pre-training. However, there were no differences in the physical characteristic and blood inflammatory factors between the groups (ATG & CTG).
CONCLUSION: In conclusion, the results of this study suggest that circuit training (CT) may be considered as an effective training mode for helping to decrease the blood inflammatory factors (IL-6 and CRP) in patients with type 2 diabetes mellitus (T2DM).

RCT Entities:   Population Interventions Outcomes

INTRODUCTION

Weight loss and physical activity are effective for the prevention of metabolic syndrome (MS) and type 2 diabetic mellitus (T2DM) [1]. In addition, chronic low levels of inflammatory factors are associated with obesity and sedentary lifestyle, and are independent risk factors for T2DM and cardiovascular disease (CVD) [2].

Exercise training is known to be inversely related to increased levels of pro-inflammatory markers and promotion of insulin resistance. The steady movement of muscles also induces anti-inflammatory effects [3].

Atherosclerosis and coronary heart disease are associated with elevated levels of interleukin 6 (IL-6), C-reactive protein (CRP) and tumor necrosis factor (TNF-α). Elevation of the inflammatory factors IL-6 and CRP in T2DM with metabolic dysfunction [4-6], MS or obesity play a key role in insulin resistance [7]. Chronic low-level inflammatory factors ncrease the levels of cytokines and CRP. Conversely, physical activity increases the levels of anti-inflammatory cytokine [3]. Recently, this cytokine has been called myokine because it is released from skeletal muscles, as well as endocrine tissues [3,8]. The levels of cytokines tend to be elevated more at higher intensity in acute exercise [9]; however, it was proven that the levels are reduced by regular aerobic training [2,10].

Of the many training modes, aerobic training has generally been recommended for patients with T2DM. However, the American Diabetes Association [11] and American College of Sports Medicine [12] recently suggested that a combination of aerobic and resistance training is more effective for managing diabetes. Thus, the effects of combined resistance and aerobic training have also been studied [13,14], and combined training was proven to be effective for reducing plasma cytokine levels, similar to the effects of aerobic training. When only resistance training was conducted 3 days per week for 12 weeks [15] or 3 days per week for 40 weeks [16], the plasma cytokine levels (IL-6, CRP) were not significantly reduced. Another mode of training, circuit training, consists of an alternating series of aerobic and resistance exercises, and is proven to have effects for improvement of physical fitness and promotion of health [17]. Moreover, there are differences between circuit training and combined training. While aerobic training proceeds with resistance training in the combined training, circuit training involves both aerobic and resistance exercises, and prevents boredom by mixing the two up [13]. Accordingly, circuit training is able to compensate for the disadvantages of resistance or aerobic training. In this regard, it is thought to be difficult for diabetes patients to perform combined training because different two types of exercises should be done during the training. However, resistance training can contribute to improving the impaired glucose tolerance (IGT) and insulin sensitivity in T2DM patients, and low-intensity resistance exercise is recommended in circuit training [18]. Through this training, muscle strength and cardiovascular endurance can be improved at the same time. Therefore, it was determined that circuit training would be appropriate for patients with T2DM, and it was selected for examination in the present study [19]. The advantages of circuit training are also thought to influence inflammatory factors. However, few studies have been done on the effects of circuit and aerobic training on inflammatory factors, compared to single or combined training.

The present study aimed to suggest an effective exercise mode for T2DM patients by identifying the effects on inflammatory factors according to two different training modes: 12 weeks of moderate-intensity circuit and aerobic training.

METHODS

Subjects

Of the female T2DM patients who were admitted to D University Hospital, 16 patients who understood the purpose of the study and agreed to participate were randomly selected. They were asked to choose their preferred training program between the two different training programs offered (circuit and the aerobic training). The inclusion criteria for this study were as follows: (1) patients without severe disease or other serious complications of diabetes, (2) patients with HbA1c ranging from 7 to 10%, (3) patients without renal dysfunction, and (4) patients with fasting blood glucose levels of 200 mg/dl or less. The patients were divided into two groups: the circuit training group (CTG, n = 8) and the aerobic training group (ATG, n = 8). The physical characteristics of the patients are described in Table 1.

Table 1.

Comparison of characteristics between baseline and after 12 weeks of exercise training

Variable	CTG(n = 8)		ATG(n = 8)		F-value	P-value
	Baseline	12 weeks	Baseline	12 weeks
Age (yrs)	51.00 ± 1.38		52.50 ± 1.82		-	-
Height (cm)	156.90 ± 1.74		155.09 ± 1.87		-	-
Weight (Kg)	57.17 ± 5.49	55.15 ± 6.65[☦]	58.65 ± 5.25	58.17 ± 4.61	.403	a: .546
					8.737	b: <.021
					8.828	c: < .021
Fat (%)	28.95 ± 2.39	27.00 ± 3.04[☦]	29.78 ± 2.68	29.67 ± 2.33	1.324	a: .288
					5.592	b: < .050
					2.564	c: .153
BMI (Kg-m-2)	24.61 ± 2.42	23.11 ± 2.26[☦]	25.92 ± 2.97	25.45 ± 2.46	2.688	a: .145
					7.698	b: < .028
					1.887	c: .212

Values are mean ± S.D.

;Baseline vs. 12Weeks (* p< .05)

CTG: Circuit exercise group

ATG: Aerobic exercise group

a: groups, b: time, c: groups × time interaction

Anthropometric assessment and body fat measurement

For height, weight, BMI and body fat assessment, measurements were carried out at rest using a body composition analyzer (Venus 5.5, Jawon Medical), before and after the 12-week training program. Body mass index (BMI) is defined as the weight in kilograms divided by the square of the height in meters.

Maximal-graded treadmill exercise test (maximal-GTX) and 12 weeks of circuit and aerobic training program

The maximal-graded treadmill exercise test (maximal-GTX) is one of the treadmill (Model Q65, Quinton Co, U.S.A) exercise tests designed by Bruce (1973). Herein, the subjects began with 3 minutes of treadmill exercise at 1.7 mph (mile per hour) and at a) gradient of 10%. At three minute intervals, the incline of the treadmill was increased by 2%, and the speed was also increased to 2.5 mph, 3.4 mph, 4.2mph and then 5.0 mph.

Peake et al. (2005) reported that the intensity of exercise contributing to the effective reduction of plasma cytokine was 60% VO2max [20]. In this study, the maximal oxygen consumption rate (VO2max) was measured in all patients during the maximal-GTX with the Bruce protocol. Based on the measured maximal oxygen consumption rate, the target heart rate (THR) corresponding to 60% VO2max was calculated for each participant [21].

The circuit training group (CTG) wore a Polar heart rate monitor and exercised at a THR corresponding to 60% VO2max for 60 minutes per day, 3 days per week, for 12 weeks. The circuit training program began with a 10-minute warm-up, and the main workout consisted of 5 sets at 12 RM (Repetition Maximum), carried out in the order of Step walking, Pull down, Abdominal, Walking, Leg curl, Leg extension, Cycle ergometer and Arm curl. Each exercise was performed for 30 seconds and interspersed with 10-second rest periods. A total of 5 sets with 2 minutes of rest between the sets were carried out for 40 minutes. Finally, cool-down exercise (stretching) was performed for 10 minutes. Completion of the circuit training program took a total of 60 minutes, and hypoglycemia did not occur during the exercise.

The aerobic training group (ATG) also wore a Polar heart rate monitor and exercised at a THR corresponding to 60% VO2max for 60 minutes per day, 3 days per week, for 12 weeks. Warm-up and cool-down exercises were performed for 20 minutes, and a walking exercise, the main workout, was carried out on an eight-lane (450 m) track as follows: For weeks 1-3, the walking was performed at a speed of 5.4 km/h for 40 minutes (walking session 1). For weeks 4-6, the walking was done at a speed of 5.7 km/h for 40 minutes (walking session 2). For weeks 7-9 weeks, the participants walked at a speed of 6.0 km/h for 40 minutes (walking session 3). For weeks 10-12 weeks, the exercise was carried out at a speed of 6.3 km/h for 40 minutes (walking session 4). In summary, the walking speed was increased by 0.3 km/h in three week intervals during the training program. In addition, GXT was conducted every three weeks and the THR corresponding to 60% VO2max was re-set according to the results and applied to the program. It took a total of 60 minutes to complete the walking exercise program, including the warm-up and cool-down exercises. Both training groups (CTG, ATG) performed GTX every 3 weeks, and the THR for both groups was modified based on the results .