Metabolic and Molecular Subacute Effects of a Single Moderate-Intensity Exercise Bout, Performed in the Fasted State, in Obese Male Rats

Abstract

Introduction and objectives: Obesity represents a major global public health problem. Its etiology is multifactorial and includes poor dietary habits, such as hypercaloric and hyperlipidic diets (HFDs), physical inactivity, and genetic factors. Regular exercise is, per se, a tool for the treatment and prevention of obesity, and recent studies suggest that the beneficial effects of exercise can be potentiated by the fasting state, thus potentially promoting additional effects. Despite the significant number of studies showing results that corroborate such hypothesis, very few have evaluated the effects of fasted-state exercise in overweight/obese populations. Therefore, the aim of this study was to evaluate the subacute effects (12 h after conclusion) of a single moderate-intensity exercise bout, performed in either a fed or an 8 h fasted state, on serum profile, substrate-content and heat shock pathway-related muscle protein immunocontent in obese male rats. Methods: Male Wistar rats received a modified high-fat diet for 12 weeks to induce obesity and insulin resistance. The animals were allocated to four groups: fed rest (FER), fed exercise (FEE), fasted rest (FAR) and fasted exercise (FAE). The exercise protocol was a 30 min session on a treadmill, with an intensity of 60% of VO₂max. The duration of the fasting period was 8 h prior to the exercise session. After a 12 h recovery, the animals were killed and metabolic parameters of blood, liver, heart, gastrocnemius and soleus muscles were evaluated, as well as SIRT1 and HSP70 immunocontent in the muscles. Results: HFD induced obesity and insulin resistance. Soleus glycogen concentration decreased in the fasted groups and hepatic glycogen decreased in the fed exercise group. The combination of exercise and fasting promoted a decreased concentration of serum total cholesterol and triglycerides. In the heart, combination fasting plus exercise was able to decrease triglycerides to control levels. In the soleus muscle, both fasting and fasting plus exercise were able to decrease triglyceride concentrations. In addition, heat shock protein 70 and sirtuin 1 immunocontent increased after exercise in the gastrocnemius and soleus muscles. Conclusions: An acute bout of moderate intensity aerobic exercise, when realized in fasting, may induce, in obese rats with metabolic dysfunctions, beneficial adaptations to their health, such as better biochemical and molecular adaptations that last for at least 12 h. Considering the fact that overweight/obese populations present an increased risk of cardiovascular events/diseases, significant reductions in such plasma markers of lipid metabolism are an important achievement for these populations.

Keywords: aerobic exercise; fasting; inflammation; metabolism; obesity.

Figure 1

Total body mass (A) of the rats during the treatment with high-fat diet. Oral glucose tolerance test (OGTT) (B) and OGTT incremental area under the curve (IAUC) (C) on the 11th week of treatment. Intraperitoneal glucose tolerance test (IPGTT) (D) and IPGTT incremental area under the curve (IAUC) (E) on the 11th week of treatment. Data were analyzed by two-way ANOVA (Bonferroni post hoc), one-way ANOVA (Bonferroni post hoc) or Student’s t test. Results were considered different when p < 0.05. Letters represent significant differences between weeks. * significant difference between experimental groups.

Figure 2

Concentration of glucose (A) and total proteins (B) in the serum at the end of the experimental treatment. Animal groups: fed rest (FER), fed exercise (FEE), fasted rest (FAR) and fasted exercise (FAE). Data were analyzed by two-way ANOVA (Bonferroni post hoc) or Kruskal-Wallis test. Results were considered different when p < 0.05. Letters represent significant differences between each experimental group.

Figure 3

Glycogen concentration in the gastrocnemius (A), soleus (B), liver (C) and heart (D) of the rats at the end of the experimental treatment. Animal groups: fed rest (FER), fed exercise (FEE), fasted rest (FAR) and fasted exercise (FAE). Data were analyzed by two-way ANOVA (Bonferroni post hoc) or Kruskal-Wallis test. Results were considered different when p < 0.05. * significant difference between fed and fasted groups. Letters represent significant differences between each experimental group.

Figure 4

Lactate concentration in the serum (A), liver (B), gastrocnemius (C) and soleus (D) muscles at the end of the experimental treatment. Animal groups: fed rest (FER), fed exercise (FEE), fasted rest (FAR) and fasted exercise (FAE).

Figure 5

Concentration of lipids in the tissues. Serum total cholesterol (A). Triglycerides in the serum (B), liver (C), heart (D), gastrocnemius (E) and soleus (F) muscles at the end of the experimental treatment. Animal groups: fed rest (FER), fed exercise (FEE), fasted rest (FAR) and fasted exercise (FAE). Data were analyzed by two-way ANOVA (Bonferroni post hoc) or Kruskal-Wallis test. Results were considered different when p < 0.05. # Represents significant difference between rest and exercised groups. Letters represent significant differences between each experimental group.

Figure 6

Protein immunocontent at the end of the experimental treatment. Heat shock protein 70 (HSP70) in the gastrocnemius (A) and soleus (B) muscles. Sirtuin 1 (SIRT1) in the gastrocnemius (C) and soleus (D) muscles. Data were analyzed by two-way ANOVA followed by Bonferroni post hoc. Results were considered different when p < 0.05. # Represents significant difference between rest and exercised groups.