Effect of chronic wheel running on the fatty acid composition of rat serum lipids

Introduction

Although there are many studies addressing the effect of chronic exercise on the fatty acid composition of serum lipids, there is no agreement as to the effect of exercise, probably because of the near uniqueness of each of these studies in terms of type of exercise, species, lipid class and diet of the animals or humans examined. Therefore, the purpose of this study was to aid in reaching a consensus on this controversial topic by examining the effects of long-term wheel running on the fatty acid composition of non-esterified fatty acids (NEFA), phospholipids (PL), triacylglycerols (TG), 1,2-diacylglycerols (DG) and cholesterol esters (CE) in rat serum.

Methods

Male Wistar rats were divided randomly into a trained (n = 20) and an untrained group (n = 14). The members of the trained group exercised ad libitum for 8 weeks in cages equipped with a wheel. Upon completion of the training period, the eleven most active trained animals (having run, on average, over 2 km/d) and the untrained animals were decapitated and their blood was collected. The fatty acid composition of NEFA, PL, TG, DG and CE was determined by a combination of thin-layer chromatography and gas chromatography as both concentrations and percentages. Additionally, the serum levels of high-density lipoprotein cholesterol (HDLC) and total cholesterol (TC) were measured spectrophotometrically. Differences between untrained and trained animals were examined by two-tailed unpaired Student’s t tests. To determine the meaningfulness of the effect of exercise on fatty acid composition, effect sizes were calculated as the difference between means divided by the SD of the untrained group.

Results

The concentrations of all fatty-acid bearing lipid classes except CE were significantly lower in the trained animals compared to the untrained ones. Specifically, the concentrations of NEFA, PL, TG and DG were lower by 24.8, 10.6, 24.5 and 36.4%, respectively, in the trained animals. We found several significant differences between the two groups regarding the concentrations and percentages of individual fatty acids in all lipid classes, with most appearing in NEFA, PL and DG. Furthermore, the differences between trained and untrained rats were generally dependent on lipid class. TC and HDLC concentrations were not affected significantly by training, but their ratio (considered an atherogenic index) decreased significantly by 9.3% in the trained rats.

Discussion/Conclusions

Judging from the magnitude of the effect sizes and the percentage differences between trained and untrained animals, there were many large effects of chronic exercise on the fatty acid composition of serum lipids. In addition, the adaptive capacity of the fatty acid profile of serum lipids to wheel running was generally lipid class-dependent, both qualitatively and quantitatively. In conclusion, long-term wheel running modified the fatty acid profile of NEFA, PL, TG, DG and CE in rat serum, and could thus be considered as a modulator of the fatty acid composition of serum lipids.