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

Riikka Kivelä,Veikko Vihko,Maarit Lehti,Heikki Kainulainen,Sanni Jalava,Mika Silvennoinen

doi:10.1186/1475-2840-7-13

Abstract

BackgroundDiabetes 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.MethodsHealthy 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.ResultsOf 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.ConclusionThe 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.

Highlights

IntroductionExercise training positive, effects on the skeletal muscle vasculature, but the mechanisms are not yet fully understood
Diabetes has negative, and exercise training positive, effects on the skeletal muscle vasculature, but the mechanisms are not yet fully understood
Exerciseinduced vascular endothelial growth factor-A (VEGF-A) expression was shown to be greater in capillaries than in muscle fibers

Summary

Introduction

Exercise training positive, effects on the skeletal muscle vasculature, but the mechanisms are not yet fully understood. Angiogenesis, the growth of new blood vessels from pre-existing ones, is controlled by complex pathways with both pro- and antiangiogenic factors [3] Both type 1 and type 2 diabetes have been shown to affect angiogenic growth factors and inhibitors in skeletal muscle [4,5]. In our previous study streptozotocin-induced diabetes decreased the mRNA levels of several proangiogenic proteins and increased those of antiangiogenic ones in mouse skeletal muscle [4]. This change in the balance between stimulators and inhibitors may be one of the reasons for the markedly increased risk for peripheral cardiovascular complications in diabetes. In healthy skeletal muscle several animal and human studies have shown increased VEGF-A expression after acute exercise [16,17,18] or electrical stimulation [19,20]

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