Exercise Induces White Adipose Tissue Browning Across the Weight Spectrum in Humans

While the effect of exercise on white adipose tissue browning and metabolic improvement in rodents is clear, there are few studies in humans with inconclusive results. Thus, the aim of the study was to assess whether an exercise intervention promotes subcutaneous adipose tissue browning in humans, and whether this response is associated with metabolic improvement in three groups of individuals defined by body mass index (BMI) (kg/m²). Sedentary adult subjects with different BMI were enrolled in a 12-week bicycle-training program (3 times per week, intensity 70-80% HRmax). Brown and beige gene expression in subcutaneous adipose tissue (scWAT) biopsies, and serum glucose, insulin, lipid, adipokine, and myokine levels were compared before and after the exercise intervention. Thirty-three non-diabetic subjects (mean age 30.4 ± 4.6 years; 57.57% female; 13 normal weight, 10 overweight and 10 with obesity) completed the exercise intervention. Without any significant change in body composition, exercise improved several metabolic parameters, most notably insulin resistance and particularly in the overweight group. Circulating adiponectin, apelin, and irisin exercise-induced changes predicted 60% of the insulin sensitivity improvement. After exercise UCP1, TBX1, CPT1B scWAT expression significantly increased, along with P2RX5 significant positive staining. These changes are compatible with scWAT browning, however, they were not associated with glucose metabolism improvement. In conclusion, 12-weeks of exercise training produced brown/beige gene expression changes in abdominal scWAT of non-diabetic individuals with different BMI, which did not contribute to the metabolic improvement. However, this result should not be interpreted as a lack of effect of browning on metabolic parameters. These findings suggest that a bigger effect is needed and should not preclude the development of more effective strategies of browning. Furthermore, exercise-induced changes in adiponectin, apelin, and irisin predicted insulin sensitivity improvement, supporting the important role of adipokines and myokines in metabolism homeostasis.

[Effectiveness of two aerobic exercise programs in the treatment of metabolic syndrome: a preliminary study]

The effectiveness of two aerobic exercise programs on the modification of the metabolic syndrome (MS) components and its influence in reducing cardiovascular risk was evaluated in 16 sedentary women (30-66 years old). Patients were randomly divided into two exercise groups: continuous training (CE: 45 minutes at 65-70% of heart rate reserve or HRR) or interval training (IE: 5 x 3 minute intervals at 80-85% HRR with two minutes of active recovery at 65-70% HRR), and each participant gave previous informed consent. The components of MS were assessed according to the criteria for women of the National Cholesterol Education/Third Treatment Adult Panel, and cardiovascular risk factors at baseline and 16 weeks later. Data analyses were performed with the Wilcoxon signed test and the Mann-Whitney U-test (SPSS v. 12.0 Windows: p < 0.05). Both exercise programs were effective in the modification of a number of MS components (triglycerides, systolic/diastolic blood pressure), however IE had a higher percentage of patients without MS diagnosis at the end of the study (62.5%). The CE improved the physical fitness by increasing the VO₂peak and METs and decreasing heart rate recovery, which is reflected on the reduction of cardiovascular risk.

[Decrease of liver fat content by aerobic exercise or metformin therapy in overweight or obese women]

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is characterized by high intrahepatic triglyceride level. It is associated with an increased prevalence of cardiovascular disease, independently of underlying cardiometabolic risk factors. Metformin is used as a pharmacological treatment; the adherence is low because of the presence of adverse effects. Aerobic exercise could be an alternative therapy, but its effectiveness compared with metformin has not been established in the treatment of NAFLD. The aim of this study was to establish the effectiveness of aerobic exercise and its influence in reducing cardiovascular risk in overweight or obese women with NAFLD.

MATERIAL AND METHODS

Sedentary women 25-60 years old with body mass index (BMI) > 24.9 kg/m2 and liver fat content < 50 HU, were randomly divided into two parallel groups: exercise group (EG) or metformin group (MG). The EG performed an aerobic exercise program of 60 min/5 days/ week at 60-85% of heart rate reserve; the MG took 1 g/day of metformin each morning. The duration of the intervention was 12 weeks. The liver fat content, metabolic and cardiorespiratory- fitness parameters were evaluated at the beginning and end of the program. The study complied with the Helsinki ethics codes for human research.

RESULTS

The study included a sample of 16 women, with 8 per group. The treatments modified the liver fat content by 14.6% (CI95% 0.92, 28.36) and 10.37% (CI95% -1.74, 22.48) for the EG and MG, respectively. In the EG, the insulin levels and HOMA-IR decreased (P < 0.05), and the cardiovascular fitness improved.

CONCLUSIONS

An aerobic exercise program of 12 weeks with a volume training of 300 min/week and a moderate to vigorous intensity (60-85% VO2peak) modified the liver fat content and improved cardiovascular risk factors during the intervention. Exercise contributed to a holistic approach by modifying a number of the components of metabolic syndrome, cardiorespiratory-fitness, and cardiovascular risk.