The effects of long-term moderate exercise and Western-type diet on oxidative/nitrosative stress, serum lipids and cytokines in female Sprague Dawley rats

Abstract

Purpose: Regular exercise reduces obesity and the risk of cardiovascular disease. However, health-promoting benefits of physical activity are commonly associated with increased inflammation and oxidative stress. Here, we tested whether constant moderate exercise is able to prevent or attenuate the oxidative/nitrosative stress, inflammation, and serum lipids in lean and obese rats.

Methods: Four-month-old female Sprague Dawley rats received standard or a high-fat diet. Animals were subjected to a physical activity protocol, consisting of 30 min forced treadmill exercise for 5 consecutive days per week during 10 months. Baseline and sedentary (non-exercised) rats were used as controls. Lipids, oxidized low-density lipoprotein cholesterol, nitric oxide metabolites, and pro- and anti-inflammatory markers were measured in blood collected upon euthanasia.

Results: At variance to young baseline control rats, 14-month-old animals fed normal diet had increased plasma lipid levels, including total cholesterol and triglycerides, which were further elevated in rats that consumed a high-fat diet. While treadmill exercise did not lower the amount of serum lipids in standard diet group, forced physical activity reduced non-high-density lipoprotein cholesterol in response to high-fat diet feeding. Exercised rats fed standard diet or high-fat diet had lower abundancy of nitric oxide metabolites, which coincided with increased levels of oxidized low-density lipoprotein cholesterol. Accordingly, the amount of nitric oxide metabolites correlated inversely with oxidized low-density lipoprotein cholesterol and homo-arginine. Exercise significantly reduced inflammatory cytokines in high-fat diet fed rats only.

Conclusion: Our study suggests that regular exercise alters the equilibrium between oxidative and anti-oxidative compounds and reduces pro-inflammatory cytokines.

Keywords: Long-term moderate exercise; Nitric oxide; Nitric oxide synthase; Oxidized LDL; Sprague Dawley rats; Western-type diet.

Fig. 1

The experimental design. One-hundred and twenty young female Sprague Dawley rats were randomly allocated into 5 groups, each consisting of 24 animals. The animals in the baseline control group were euthanized after the acclimatization period. The remain of ninety-six animals were divided in a 1:1 ratio and fed ND or HFD and subjected to a 10-month study protocol as follows: half of the rats fed ND or HFD performed 30-min running exercise sessions on a treadmill. Six animals (2 vs. 4 rats fed ND and HFD, respectively) died prior to the end of the study and eighteen more (2 vs. 16 rats under ND and HFD) had to be excluded due to the development of tumours

Fig. 2

Box and Whisker Blot of the body weight (a) and the lipid profile (b–f) after the 10 months study period. **p < 0.01 compared to appropriate sedentary control group; ^#p < 0.05, ^##p < 0.01, ^###p < 0.001 compared to appropriate normal diet control group; ^£££p < 0.001 compared to baseline control group. The study groups have been abbreviated as follows: baseline group (BL), control normal diet (coND), exercise normal diet (exeND), control high fat diet (coHFD) and exercise high-fat diet (exeHFD)

Fig. 3

Box and Whisker Blot of oxidized LDL (a). ***p < 0.001 compared to appropriate sedentary control group; ^£££p < 0.001 compared to baseline control group. Box and Whisker Blot of nitric oxide metabolites (b). ***p < 0.001 compared to appropriate sedentary control group; ^##p < 0.01, ^###p < 0.001 compared to appropriate normal diet control group; ^£££p < 0.001 compared to baseline control group. Box and Whisker Blot of homo-arginine and ADMA (c–d). ***p < 0.001 compared to appropriate sedentary control group; ^#p < 0.05, ^##p < 0.01 compared to appropriate normal diet control group; ^£££p < 0.001 compared to baseline control group

Fig. 4

Simple Scatter Dot Plot of the linear regression analysis with r = − 0.640 and p = 0.000 between oxidized LDL-C and nitric oxide metabolites (a) and r = − 0.453 and p = 0.000 between h-arg and nitric oxide metabolites (b)

Fig. 5

Box and Whisker Blot of the panel of cytokines and chemokines (a–f). *p < 0.05, **p < 0.01 compared to appropriate sedentary control group; ^#p < 0.05 compared to appropriate normal diet control group. ^£p < 0.05, ^££p < 0.01, ^£££p < 0.001 compared to baseline control group

Fig. 6

Box and Whisker Blot of IGF-1 (a), adiponectin (b) and leptin (c). *p < 0.05 compared to appropriate sedentary control group; ^#p < 0.05, ^##p < 0.01, ^###p < 0.001 compared to appropriate normal diet control group. ^£p < 0.05, ^£££p < 0.001 compared to baseline control group