Abstract
Physical exercise improves learning and memory abilities by increasing the levels of several growth factors in the hippocampus. One growth factor, vascular endothelial growth factor (VEGF), is primarily produced in the muscles and not only increases in the periphery during exercise but can also cross the blood-brain barrier. The aim of this study is to investigate the effects of regular aerobic chronic exercise on different types of muscle fibers and the relationships between learning/memory and muscle induced-VEGF. Following a one-week adaptation period, male rats underwent treadmill training at a speed of 8 m/min for 30 min daily, 3 days a week for 6 weeks. Memory functions were evaluated using the Morris water maze. VEGF, superoxide dismutase (SOD), glutathione peroxidase (GPx), and malondialdehyde (MDA) levels were measured in type 1 and type 2 muscle fibers and VEGF levels were also measured in the hippocampus. Exercise positively affected both learning and memory and also increased VEGF levels in both muscle fiber types. Muscle VEGF levels positively correlate with hippocampal learning and hippocampal VEGF levels. Exercise reduced both SOD and MDA levels in type 1 and type 2 muscle fibers, whereas GPx levels decreased only in type 2 muscle fibers. Our findings suggest that regular aerobic exercise elevates VEGF levels and diminishes oxidative stress in both fiber types. Exercise-induced VEGF levels in both type 1 and 2 muscle fibers appear to be associated with the positive effect of exercise on learning and memory function and is accompanied by an increase in VEGF levels in the hippocampus. Further research is needed to elucidate the exact mechanism by which fiber type-specific VEGF mediates hippocampal neurogenesis and angiogenesis. Physical exercise improves learning and memory abilities by increasing the levels of several growth factors in the hippocampus. One growth factor, vascular endothelial growth factor (VEGF), is primarily produced in the muscles and not only increases in the periphery during exercise but can also cross the blood-brain barrier. The aim of this study is to investigate the effects of regular aerobic chronic exercise on different types of muscle fibers and the relationships between learning/memory and muscle induced-VEGF. Following a one-week adaptation period, male rats underwent treadmill training at a speed of 8 m/min for 30 min daily, 3 days a week for 6 weeks. Memory functions were evaluated using the Morris water maze. VEGF, superoxide dismutase (SOD), glutathione peroxidase (GPx), and malondialdehyde (MDA) levels were measured in type 1 and type 2 muscle fibers and VEGF levels were also measured in the hippocampus. Exercise positively affected both learning and memory and also increased VEGF levels in both muscle fiber types. Muscle VEGF levels positively correlate with hippocampal learning and hippocampal VEGF levels. Exercise reduced both SOD and MDA levels in type 1 and type 2 muscle fibers, whereas GPx levels decreased only in type 2 muscle fibers. Our findings suggest that regular aerobic exercise elevates VEGF levels and diminishes oxidative stress in both fiber types. Exercise-induced VEGF levels in both type 1 and 2 muscle fibers appear to be associated with the positive effect of exercise on learning and memory function and is accompanied by an increase in VEGF levels in the hippocampus. Further research is needed to elucidate the exact mechanism by which fiber type-specific VEGF mediates hippocampal neurogenesis and angiogenesis.
Highlights
Many aspects of the health benefits of exercise are known, such as those in endocrine and cardiovascu‐ lar systems, as well as metabolic and developmental functions (Hughes et al, 1993; Ostergard et al, 2006; Labonte‐Lemoyne et al, 2017; Lin and Lee, 2018)
The aim of this study is to investigate the relationship between hippocampus‐de‐ pendent memory function and fiber type‐specific vascular endothelial growth factor (VEGF) levels and to determine if antioxidant status depends on muscle fiber type in exercised rats
We demonstrated that regular aerobic exercise enhanced the memory performance of rats, elevated the VEGF levels in both fiber types and in hippocampal tissue, and reduced antioxidant and lipid peroxidation levels in type 1 and type 2 muscle fibers
Summary
Many aspects of the health benefits of exercise are known, such as those in endocrine and cardiovascu‐ lar systems, as well as metabolic and developmental functions (Hughes et al, 1993; Ostergard et al, 2006; Labonte‐Lemoyne et al, 2017; Lin and Lee, 2018). Skeletal muscle fibers, which are classified by myosin heavy‐chain iso‐ form expression, are basically divided into two types: type 1 (oxidative) and type 2 (glycolytic) fibers. Type 1 fibers have a slow contraction speed and predominant‐ ly use oxidative metabolism for energy production, while type 2 fibers are fast‐twitch and use glycolytic metabolism (Qaisar et al, 2016). Oxidative fibers have greater capillary densities than glycolytic fibers (Cherwek et al, 2000). Regular aerobic exercise leads to many adaptive changes in skeletal muscles to increase utilization of oxygen and energy substrates, such as increasing vascularization to achieve better perfusion of the muscle, fiber type transformation and mitochondrial biogenesis (Yan et al, 2011)
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