Exercise-induced expression of angiogenic growth factors in skeletal muscle and in capillaries of healthy and diabetic mice

Background. Diabetes has negative, and exercise training positive, effects on the skeletal muscle vasculature, but the mechanisms are not yet fully understood. In the present experiment the effects of running exercise on the mRNA expression of pro- and antiangiogenic factors were studied in healthy and diabetic skeletal muscle. The responses in capillaries and muscle fibers, collected from the muscle with laser capture microdissection, were also studied separately. Methods. Healthy and streptozotocin-induced diabetic mice were divided into sedentary and exercise groups. Exercise was a single bout of 1 h running on a treadmill. Gastrocnemius muscles were harvested 3 h and 6 h post exercise, and angiogenesis-related gene expressions were analyzed with real-time PCR. In addition to muscle homogenates, capillaries and muscle fibers were collected from the muscle with laser capture microdissection method and analyzed for vascular endothelial growth factor-A (VEGF-A) and thrombospondin-1 (TSP-1) mRNA expression. Results. Of the proangiogenic factors, VEGF-A and VEGF receptor-2 (VEGFR-2) mRNA expression increased significantly (P < 0.05) in healthy skeletal muscle 6 h post exercise. VEGF-B also showed a similar trend (P = 0.08). No significant change was observed post exercise in diabetic muscles in the expression of VEGF-A, VEGFR-2 or VEGF-B. The expression of angiogenesis inhibitor TSP-1 and angiogenic extracellular matrix protein Cyr61 were significantly increased in diabetic muscles (P < 0.05–0.01). Capillary mRNA expression resembled that in the muscle homogenates, however, the responses were greater in capillaries compared to muscle homogenates and pure muscle fibers. Conclusion. The present study is the first to report the effects of a single bout of exercise on the expression of pro- and antiangiogenic factors in diabetic skeletal muscle, and it provides novel data about the separate responses in capillaries and muscle fibers to exercise and diabetes. Diabetic mice seem to have lower angiogenic responses to exercise compared to healthy mice, and they show markedly increased expression of angiogenesis inhibitor TSP-1. Furthermore, exercise-induced VEGF-A expression was shown to be greater in capillaries than in muscle fibers.peerReviewe

Seasonal and annual changes in physical performance capacity of elite athletes

Seasonal and annual changes in physical performance characteristics of 10 female and 28 male cross-country skiers, 5 male nordic combination skiers and 7 male skijumpers were studied. Following parameters were investigated on most of the athletes: maximal oxygen uptake (maxVo₂) in leg and arm work, vertical running velocity (Vv), total isometric leg force (TLF), percentage of slow twitch muscle fibers (%ST fibers) and succinate dehydrogenase activity (SDH) in m. vastus lateralis. The measurements were made between the spring of 1973 and winter of 1976. The yearly measurement times were spring (the beginning of the basic training period), autumn (a change from the basic training period to special training period of each event) and winter (competitive season). The maxVo₂ of the cross-country skier groups increased by 4,7 - 9.9 % from spring to winter and by 3.1 - 4.6 % annually. In arm work maxVo₂ of the same subjects increased by 5.6 - 13.8 % from spring to winter and by 4.2 - 5.9 % annually. The nordic combination skiers increased annually their maxVo₂ in leg by 1.7 % and in arm work by 5.7 %. The SDH activity of the male and female skiers increased by 32.7 % and 40.3 % from spring to winter and the annual increases were 29.8 % and 16.2 %, respectively. The nordic combination skiers increased their SDH activity by 42.5 % annually. The TLF of the nordic combination skiers and ski4umners increased annually by 24.8 % and 29.1 % and the annual increases in Vv were 16.1 % and 8.3 %, respectively. Annual increases in maxVo2, SDH activity, Vv and TLF were not related to the initial level in each parameter. The %ST fibers of no groups changed during the investigation period. Instead, the annual increases in maxVo₂ were positively related to %ST fibers

Anaerobic performance capacity in athletes

Neuromuscular and anaerobic performance characteristics in 89 athletes and 31 reference subjects were studied. The main parameters were vertical velocity (Vᵥ) and muscular power (MP) during running up the stairs, total and relative isometric leg force, blood lactate after maximal treadmill running, percentage of fast twitch fibers (%FT fibers), lactate dehydrogenase activity (LDH) and creatine phosphokinase (CPK) in m. vastus lateralis (VL) and in some cases in m. gastrocnemius and m. deltoideus. Vᵥ and MP were recorded highest among power athletes (running 100-400m, jumping, throwing), ice hockey players and speed skaters. Total and relative leg forces of the power athletes, canoeists, ice hockey players, skijumpers and alpine skiers were highest. Power athletes, 800m runners, canoeists and alpine skiers had highest and almost equal blood lactate concentrations. Power athletes had 63% FT fibers in m. VL but it did not differ significantly from the mean value of reference subjects. The relative leg force, vertical velocity and blood lactate correlated significantly with %FT fibers in m. VL of the male athletes. Vertical velocity demonstrated significant correlations also with LDH and CPK. The athletes and their sport events could not be classified systematically into. The parameters studied seemed to divide the athletes and their sport events into neuromuscular, anaerobic and aerobic types. The specific needs of the different sport events might have masked the expected characteristics of energy and power utilization. However, a high %FT fibers might be a prerequisite for a success-full athletes in "power events"