Actions of Short-Term Fasting on Human Skeletal Muscle Myogenic and Atrogenic Ge

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Ann Nutr Metab. 2006 Aug 24;50(5):476-481

Actions of Short-Term Fasting on Human Skeletal Muscle Myogenic and

Atrogenic Gene Expression.

Larsen AE, Tunstall RJ, Carey KA, G, Kambadur R, Crowe TC,

Cameron- D.

School of Exercise and Nutrition Sciences, Deakin University,

Burwood, Australia.

Background: Skeletal muscle mass is governed by multiple IGF-1-

sensitive positive regulators of muscle-specific protein synthesis

(myogenic regulatory factors which includes myoD, myogenin and Myf5)

and negative regulators, including the atrogenic proteins myostatin,

atrogin-1 and muscle ring finger 1 (MuRF-1). The coordinated control

of these myogenic and atrogenic factors in human skeletal muscle

following short-term fasting is currently unknown.

Method: Healthy adults (n = 6, age 27.6 years) undertook a 40-hour

fast. Skeletal muscle biopsy (vastus lateralis) and venous blood

samples were taken 3, 15 and 40 h into the fast after an initial

standard high-carbohydrate meal. Gene expression of the myogenic

regulator factors (myoD, myogenin and Myf5) and the atrogenic factors

(myostatin, atrogin-1 and MuRF-1) were determined by real-time PCR

analysis. Plasma myostatin and IGF-1 were determined by ELISA.

Results: There were no significant alterations in either the positive

or negative regulators of muscle mass at either 15 or 40 h, when

compared to gene expression measured 3 h after a meal. Similarly,

plasma myostatin and IGF-1 were also unaltered at these times.

Conclusions: Unlike previous observations in catabolic and cachexic

diseased states, short-term fasting (40 h) fails to elicit marked

alteration of the genes regulating both muscle-specific protein

synthesis or atrophy. Greater periods of fasting may be required to

initiate coordinated inhibition of myogenic and atrogenic gene

expression.