Short-term strength training and the expression of myostatin and IGF-I isoforms in rat muscle and tendon: differential effects of specific contraction types

TY - JOUR

T1 - Short-term strength training and the expression of myostatin and IGF-I isoforms in rat muscle and tendon

T2 - differential effects of specific contraction types

AU - Heinemeier, K M

AU - Olesen, J L

AU - Schjerling, P

AU - Haddad, F

AU - Langberg, Henning

AU - Baldwin, K M

AU - Kjaer, M

PY - 2007

Y1 - 2007

N2 - In skeletal muscle, an increased expression of insulin like growth factor-I isoforms IGF-IEa and mechano-growth factor (MGF) combined with downregulation of myostatin is thought to be essential for training-induced hypertrophy. However, the specific effects of different contraction types on regulation of these factors in muscle are still unclear, and in tendon the functions of myostatin, IGF-IEa, and MGF in relation to training are unknown. Female Sprague-Dawley rats were subjected to 4 days of concentric, eccentric, or isometric training (n = 7-9 per group) of the medial gastrocnemius, by stimulation of the sciatic nerve during general anesthesia. mRNA levels for myostatin, IGF-IEa, and MGF in muscle and Achilles' tendon were measured by real-time RT-PCR. Muscle myostatin mRNA decreased in response to all types of training (2- to 8-fold) (P <0.05), but the effect of eccentric training was greater than concentric and isometric training (P <0.05). In tendon, myostatin mRNA was detected, but no changes were seen after exercise. IGF-IEa and MGF increased in muscle (up to 15-fold) and tendon (up to 4-fold) in response to training (P <0.01). In tendon no difference was seen between training types, but in muscle the effect of eccentric training was greater than concentric training for both IGF-IEa and MGF (P <0.05), and for IGF-IEa isometric training had greater effect than concentric (P <0.05). The results indicate a possible role for IGF-IEa and MGF in adaptation of tendon to training, and the combined changes in myostatin and IGF-IEa/MGF expression could explain the important effect of eccentric actions for muscle hypertrophy.

AB - In skeletal muscle, an increased expression of insulin like growth factor-I isoforms IGF-IEa and mechano-growth factor (MGF) combined with downregulation of myostatin is thought to be essential for training-induced hypertrophy. However, the specific effects of different contraction types on regulation of these factors in muscle are still unclear, and in tendon the functions of myostatin, IGF-IEa, and MGF in relation to training are unknown. Female Sprague-Dawley rats were subjected to 4 days of concentric, eccentric, or isometric training (n = 7-9 per group) of the medial gastrocnemius, by stimulation of the sciatic nerve during general anesthesia. mRNA levels for myostatin, IGF-IEa, and MGF in muscle and Achilles' tendon were measured by real-time RT-PCR. Muscle myostatin mRNA decreased in response to all types of training (2- to 8-fold) (P <0.05), but the effect of eccentric training was greater than concentric and isometric training (P <0.05). In tendon, myostatin mRNA was detected, but no changes were seen after exercise. IGF-IEa and MGF increased in muscle (up to 15-fold) and tendon (up to 4-fold) in response to training (P <0.01). In tendon no difference was seen between training types, but in muscle the effect of eccentric training was greater than concentric training for both IGF-IEa and MGF (P <0.05), and for IGF-IEa isometric training had greater effect than concentric (P <0.05). The results indicate a possible role for IGF-IEa and MGF in adaptation of tendon to training, and the combined changes in myostatin and IGF-IEa/MGF expression could explain the important effect of eccentric actions for muscle hypertrophy.

KW - Animals

KW - Female

KW - Gene Expression Regulation

KW - Hypertrophy

KW - Insulin-Like Growth Factor I

KW - Isometric Contraction

KW - Muscle Contraction

KW - Muscle, Skeletal

KW - Myostatin

KW - Physical Conditioning, Animal

KW - Protein Isoforms

KW - RNA, Messenger

KW - Random Allocation

KW - Rats

KW - Rats, Sprague-Dawley

KW - Tendons

KW - Transforming Growth Factor beta

U2 - 10.1152/japplphysiol.00866.2006

DO - 10.1152/japplphysiol.00866.2006

M3 - Journal article

C2 - 17038487

SN - 8750-7587

VL - 102

SP - 573

EP - 581

JO - Journal of Applied Physiology

JF - Journal of Applied Physiology

IS - 2

ER -