Abstract
The aim of the present study was to investigate the time and intensity dependent effects of exercise on the heart components of the lipolytic complex. Wistar rats ran on a treadmill with the speed of 18 m/min for 30 min (M30) or 120 min (M120) or with the speed of 28 m/min for 30 min (F30). The mRNA and protein expressions of the compounds adipose triglyceride lipase (ATGL), comparative gene identification-58 (CGI-58), G0/G1 switch gene 2 (G0S2), hormone sensitive lipase (HSL) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) were examined by real-time PCR and Western blot, respectively. Lipid content of free fatty acids (FFA), diacylglycerols (DG) and triacylglycerols (TG) were estimated by gas liquid chromatography. We observed virtually no changes in the left ventricle lipid contents and only minor fluctuations in its ATGL mRNA levels. This was in contrast with its right counterpart i.e., the content of TG and DG decreased in response to both increased duration and intensity of a run. This occurred in tandem with increased mRNA expression for ATGL, CGI-58 and decreased expression of G0S2. It is concluded that exercise affects behavior of the components of the lipolytic system and the lipid content in the heart ventricles. However, changes observed in the left ventricle did not mirror those in the right one.
Highlights
It is widely known that a sedentary lifestyle and the increased consumption of a high-calorie Western diet contributes to the development of serious metabolic dysfunctions, which have, in the present day, reached proportions of global epidemics [1,2]
We investigated the impact of treadmill running on the gene and protein expression of Adipose triglyceride lipase (ATGL), comparative gene identification-58 (CGI-58), G0S2 and hormone sensitive lipase (HSL), as well as on lipids content (TG, DG and Free fatty acid (FFA)) and their fatty acid composition, in the heart ventricles
If a moderate intensity exercise continues for a long time, the reliance on fatty acids for energy provisions dominates, as evidenced by lower values of the respiratory quotient (RQ = 0.7) [23]
Summary
It is widely known that a sedentary lifestyle and the increased consumption of a high-calorie Western diet contributes to the development of serious metabolic dysfunctions (i.e., obesity, metabolic syndrome and type 2 diabetes), which have, in the present day, reached proportions of global epidemics [1,2]. During instances of increased metabolic demand, triglycerides (TG) stored in lipid droplets of adipocytes undergo lipolysis into fatty acids (FA) and glycerol that are released into the circulation. Even up to 60% of FA entering cardiomyocytes are first esterified to TG and directed towards oxidation [4] This indicates that TG stored in the form of intracellular lipid droplets constitute an accessible energy reservoir and regulate the delivery of FA to cardiomyocytes. Aside from their role as metabolic substrates, FA activate signaling molecules such as peroxisome proliferator-activated receptors (PPARs), that in turn increase the expression of proteins involved in fat metabolism [3]. The incorporation of the blood borne FA into TG protects cardiomyocytes against an excessive intracellular FA accumulation and prevents their toxic effects [7]
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