Preventive effects of nucleoprotein supplementation combined with intermittent loading on capillary regression induced by hindlimb unloading in rat soleus muscle.

Ryosuke Nakanishi,Yusuke Hirayama,Hidemi Fujino,Noriaki Maeshige

doi:10.14814/phy2.13134

Abstract

Physical inactivity leads to muscle atrophy and capillary regression in the skeletal muscle. Intermittent loading during hindlimb unloading attenuates the muscle atrophy, meanwhile the capillary regression in the skeletal muscle is not suppressed. Nucleoprotein has antioxidant capacity and may prevent capillary regression. Therefore, we assessed the combined effects of intermittent loading with nucleoprotein supplementation on capillary regression induced by hindlimb unloading. Five groups of rats were assigned: control (CON), 7 days hindlimb unloading (HU), HU plus nucleoprotein supplementation (HU + NP), intermittent loading during HU (HU + IL), and intermittent loading combined with nucleoprotein supplementation during HU (HU + IL + NP). Seven days HU resulted in decrease in capillary number‐to‐fiber number (C/F) ratio accompanied with disuse‐associated changes in fetal liver kinase‐1 (Flk‐1), a proangiogenesis factor, and thrombospondin‐1 (TSP‐1), an antiangiogenesis factor, in the soleus muscle. In addition, citrate synthase (CS) activity was decreased and protein level of superoxide dismutase (SOD)‐2 was increased. Neither nucleoprotein supplementation nor intermittent loading prevented the decrease in the C/F ratio, whereas nucleoprotein supplementation combined with intermittent loading prevented the regression of capillary during unloading. Moreover, the levels of Flk‐1, TSP‐1, and SOD‐2 protein and the CS activity were maintained up to control levels. These results suggested that nucleoprotein supplementation combined with intermittent loading was effective to prevent capillary regression induced by muscle atrophy.

Highlights

Capillaries play a critical role in deliver of oxygen and nutrients to skeletal muscle, and have remarkable plasticity (Olfert and Birot 2011)
Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society
The decrease in capillary numberto-fiber number (C/F) ratio was prevented by the combined treatment (HU + IL + NP) other treatments (HU + NP and hindlimb unloading (HU) + IL) did not prevent the decrease in C/F ratio (Fig. 1F)

Summary

Introduction

Capillaries play a critical role in deliver of oxygen and nutrients to skeletal muscle, and have remarkable plasticity (Olfert and Birot 2011). It is well established that the decrease in physical activity leads to capillary regression (Kano et al 2000; Fujino et al 2005; Roudier et al 2010; Olfert and Birot 2011). The capillary regression induced by hindlimb unloading (HU) is regulated by the imbalance between pro- and anti-angiogenic signals: a decrease in fetal liver kinase-1 (Flk-1) and an increase in thrombospondin-1 (TSP-1) (Roudier et al 2010).

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Conclusion