Background/aim: A Significant number of patients with chronic obstructive pulmonary disease (COPD) exhibit skeletal muscle wasting and decreased capillary area formation which have been correlated to increased mortality. The current study aimed to determine the molecular mechanisms mediating decreased capillary formation in COPD.
Methods: Twenty-four COPD patients and twelve matching controls were recruited. COPD patients were divided into mild, moderate and severe groups according to GOLD (Global Initiative for Chronic Obstructive Lung Disease) criteria. Skeletal muscle biopsies were obtained from the tibialis anterior muscle. Fibre typing and capillary formation together with messenger RNA (mRNA) expression of hypoxia-inducible factors (HIF-1á and HIF-3á ), vascular endothelial growth factors (VEGF-A, -B and -C isoforms) and von Hippel Lindau (VHL) were determined. VHL expression and localization was further studied by immunohistochemistry.
Results: Skeletal muscle capillary formation was significantly decreased with ascending disease severity. Compared to controls, a tendency to mRNA overexpression of HIF-1á, HIF-3á and VEGF isoforms was observed at mild and moderate COPD that decreased at the severe stage. By contrast, skeletal muscle biopsies from COPD patients exhibited significant overexpression of VHL both on the mRNA and protein levels by immunohistochemistry. VHL protein was further determined to be localized to satellite cells.
Conclusions: Overexpression of VHL was identified in the skeletal muscle of patients with COPD. Increased VHL activity may exert a negative impact on transducing the hypoxic signal and may contribute to decreased capillarization in skeletal muscles of patients with COPD.
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