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

Full Abstract

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.

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Author information

Author/s: Heinemeier, K M (KM); Olesen, J L (JL); Schjerling, P (P); Haddad, F (F); Langberg, H (H); Baldwin, K M (KM); Kjaer, M (M);

Affiliation: Institute of Sports Medicine, Bispebjerg Hospital-Bldg. 8, 1st Floor, 23 Bispebjerg Bakke, DK-2400 Copenhagen NV, Denmark. katjaheinemeier(-atsign-)hotmail.com

Journal and publication information

Publication Type: Comparative Study; Journal Article; Research Support, Non-U.S. Gov't

Journal: Journal of applied physiology (Bethesda, Md. : 1985) (J Appl Physiol), published in United States. (Language: eng)

Reference: 2007-Feb; vol 102 (issue 2) : pp 573-81

Dates: Created 2007/02/07; Completed 2007/03/22; Revised 2008/11/21;

PMID: 17038487, status: MEDLINE (last retrieval date: 12/26/2008)

Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.

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MeSH headings (categories)

This article was linked to the MESH Headings shown below.

Animals
Female
Gene Expression Regulation
Hypertrophy
Insulin-Like Growth Factor I - genetics; metabolism
Isometric Contraction - physiology
Muscle Contraction - physiology
Muscle, Skeletal - metabolism; pathology
Myostatin

Myostatin
Physical Conditioning, Animal - physiology
Protein Isoforms - genetics; metabolism
RNA, Messenger - metabolism
Random Allocation
Rats
Rats, Sprague-Dawley
Tendons - metabolism
Transforming Growth Factor beta - genetics; metabolism

Associated Chemicals: Gdf8 protein, rat (0) ; Myostatin (0) ; Protein Isoforms (0) ; RNA, Messenger (0) ; Transforming Growth Factor beta (0) ; Insulin-Like Growth Factor I (67763-96-6)

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