Jiyoung Kong

Effect of walking exercise on abdominal fat, insulin resistance and serum cytokines in obese women

[Purpose] The purpose of the study was to investigate the effect of 12-week walking exercise on abdominal fat, insulin resistance and serum cytokines in obese women. [Methods] Following baseline measurements, obese women (N = 20) who met obesity criterion of BMI at 25 kg/m2 or greater were randomly assigned to the control (n = 10) or exercise groups (n = 10). Women assigned to the exercise group participated in a walking exercise (with an intensity of 50-60% of predetermined VO2max, a frequency of 3 days per week and duration of 50-70 minutes targeting 400 kcal of energy expenditure per session) for 12 weeks, while women assigned to the control group maintained their sedentary lifestyle. After the 12-week walking intervention, post-test measurements were conducted using the same procedure as the baseline measurement. Analyses of variance with repeated measures were used to evaluate any significant time by group interactions for the measured variables. [Results] With respect to body fat parameters, significant time-by-group interactions were found in the abdominal subcutaneous (p = < 0.001) and visceral adipose tissues (p = 0.011). The exercise group had significant reductions in both subcutaneous and visceral adiposity, and the control group had no significant changes in those parameters. Similarly, there were significant time by group interactions in fasting glucose (p = 0.008), HOMA-IR (p = 0.029), serum TNF-α (p = 0.027), and IL-6 (p = 0.048) such that the exercise group had significant reductions in those parameters, with no such significant changes found in the control group. The exercise group also had a significant increase in serum adiponectin (p = 0.002), whereas the control group had no significant change in the parameter. [Conclusion] In summary, the current findings suggest that walking exercise can provide a safe and effective lifestyle strategy against abdominal obesity and serum insulin resistance markers in obese women.

Effect of aerobic exercise training on non-alcoholic fatty liver disease induced by a high fat diet in C57BL/6 mice

[Purpose] The aim of this study was to investigate the effects of aerobic exercise training on a high fat diet (HFD)-induced fatty liver and its metabolic complications in C57BL/6 mice. [Methods] Mice at 5-month old (n = 30) were randomly assigned to standard chow (SC + CON, n = 10) and high-fat diet (HFD, n = 20), and they were subjected to SC and HFD, respectively, for 23-week. After 15-week of HFD, mice in the HFD group were further assigned to HFD (HFD + CON, n = 10) or exercise training (HFD + EX, n = 10) groups. The HFD + EX mice were subjected to aerobic treadmill running during the last 8-week of the 23-week HFD course. Outcomes included hepatic steatosis, insulin resistance, and expression of genes involved in mitochondrial function and/or fatty oxidation as well as de novo lipogenesis and/or triacylglycerol (TAG) synthesis. [Results] Treadmill running ameliorated impaired glucose tolerance and insulin resistance secondary to the HFD. The beneficial effects of treadmill running were associated with enhanced molecular markers of mitochondrial function and/or fatty acids oxidation (i.e., PPARα and CPT1a mRNAs, pAMPK/AMPK, pACC, and SIRT1 protein) as well as suppressed expression of de novo lipogenesis and/or TAG synthesis (i.e., SREBP1c, lipin1 and FAS mRNAs) in the liver. [Conclusion] The current findings suggest that aerobic exercise training is an effective and non-pharmacological means to combat fatty liver and its metabolic complications in HFD-induced obese mice.

Roles of physical activity and cardiorespiratory fitness on sex difference in insulin resistance in late elementary years

[Purpose] Little is known about the potential role of lifestyle factors in sex differences in insulin resistance in late elementary school children. [Methods] In this cross-sectional study, we compared sex differences in Tanner scales, body fat, physical activity (PA) and fitness, and insulin resistance markers in elementary school children (boys, n = 69 and girls, n = 81) aged 12-13 years. Body composition was assessed with a standardized protocol. Cardiorespiratory fitness was measured as oxygen consumption during an incremental treadmill exercise. Fasting blood samples were collected for blood chemistry assays including lipids, glucose, insulin and homeostasis model assessment for insulin resistance (HOMA-IR), leptin, and adiponectin. Daily PA was measured with an accelerometer for 7 consecutive days, and they were classified as low-, moderate-, and vigorous-PA. Independent t-tests were used to compare mean differences in the measured variables between boys and girls. There were significant sex differences in Tanner scales, body mass index, percent body fat, and waist circumference (WC). [Results] Girls had significantly higher values in Tanner scales (p < 0.001) and percent body fat (p < 0.001) than boys. Boys had significantly higher values in body mass index (p = 0.019) and waist circumference (p < 0.001) than girls. Boys also had significantly higher values in VO2max (p < 0.001) and low (p < 0.001), moderate (p < 0.001), and vigorous (p < 0.001) PAs. With respect to metabolic risk factors, girls had significantly higher serum levels of triglycerides (p = 0.005), insulin (p < 0.001), and HOMA-IR (p < 0.001) and significantly lower high-density lipoprotein cholesterol (p = 0.015) than boys. [Conclusion] In summary, the current findings of the study showed that the increased risk for insulin resistance in girls over boys is associated with higher Tanner scale and percent body fat in conjunction with poor cardiorespiratory fitness and physical inactivity, suggesting that exercise intervention to promote physical activity and fitness is imperative for general health promotion of school children, with a special focus on girls.