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Skeletal muscle fiber‐type, enzyme activity, and angiogenesis are altered in exercise trained mice deficient in muscle VEGF
Author(s) -
Olfert I.M.,
Giuliano P.,
Howlett R.A,
Breen E.C.,
Wagner P.D.
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a815-a
Subject(s) - endocrinology , skeletal muscle , medicine , treadmill , angiogenesis , chemistry , endurance training , vascular endothelial growth factor , muscle hypertrophy , muscle fibre , vegf receptors
Vascular endothelial growth factor (VEGF) is required for maintaining capillary number in adult mouse skeletal muscle. Muscle capillarity and endurance exercise capacity is reduced in cre/loxP mediated muscle VEGF knock‐out (myoVEGF−/−) mice. To test the importance of myocyte VEGF in exercise training, we accessed muscle adaptations to exercise training in myoVEGF−/− and wild‐type (WT) mice following a 6‐week training regime. Training consisted of 1‐hr treadmill run, 5‐d/wk, where myoVEGF−/− and WT mice ran at the same absolute speed/incline and work intensity gradually increased from 10 m/min, 0° incline (wk 1) to 22 m/min, 10° incline (wk 6). In WT mice, testing of maximal running speed increased following training (33.5 ± 1.2 to 36.3 ± 1.4 m/min, p<0.05, mean±SEM), but only small, non‐significant, rises in capillary‐to‐fiber ratio, C:F (1.24 ± 0.18 to 1.40 ± 0.25, p=n.s.) and capillary density, CD (36 ± 5 to 56 ±9 #/mm 2 , p=0.10) were seen in the gastrocnemius muscle. Fiber type composition remained unaltered. In myoVEGF−/−, training did not alter maximal running speed tests (23.0 ± 1.2 to 24.6 ± 1.1 m/min), C:F (0.65 ± 0.10 to 0.61 ± 0.07), or CD (22 ± 2 to 29 ± 3 #/mm 2 ); however, % of type IIA fibers tended to decrease (81 ± 4% to 72 ± 3%, p=0.07) while % of type IIB fibers increased (12 ± 4% to 23 ± 3%, p<0.05). Type I fibers (6 ±1% to 5 ± 1%) were unchanged. Phosphofructokinase (PFK) enzyme activity was greater in myoVEGF−/− than WT (86.7±5.1 vs. 72.3±3.7 mmol/kg/min, p<0.05) muscle. These data suggest that myoVEGF−/− mice have a greater reliance on glycolytic metabolism during exercise; and that in the absence of muscle VEGF, the potential for skeletal muscle angioadaptation to physical training is lost. Funding AHA 0365103Y, NIH 17731, Parker B. Francis Foundation.