Estrogen effects on skeletal muscle insulin-like growth factor 1 and myostatin i

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Exp Biol Med (Maywood). 2007 Nov;232(10):1314-25.

Estrogen effects on skeletal muscle insulin-like growth factor 1 and

myostatin in ovariectomized rats.

Tsai WJ, McCormick KM, Brazeau DA, Brazeau GA.

Department of Pharmaceutical Sciences, School of Pharmacy and

Pharmaceutical Sciences, 517 Hochstetter Hall, North Campus,

University at Buffalo, Amherst, New York 14260.

Previous work showed that estrogen replacement attenuates muscle

growth in immature rats. The present study examined muscle insulin-

like growth factor-1 (IGF-1) and myostatin expression to determine

whether these growth regulators might be involved in mediating

estrogen's effects on muscle growth. IGF-1 and myostatin message and

protein expression in selected skeletal muscles from 7-week-old sham-

ovariectomized (SHAM) and ovariectomized rats that received

continuous estrogen (OVX/E2) or solvent vehicle (OVX/CO) from an

implant for 1 week or 5 weeks was measured.

In the 1-week study, ovariectomy increased IGF-1 mRNA expression in

fast extensor digitorum longus and gastrocnemius muscles; the

increase was reversed by estrogen replacement. A similar trend was

observed in the slow soleus muscle, although the change was not

statistically significant. In contrast to mRNA, muscle IGF-1 protein

expression was not different between SHAM and OVX/ CO animals in the

1-week study.

One week of estrogen replacement significantly decreased IGF-1

protein level in all muscles examined. Myostatin mRNA expression was

not different among the 1-week treatment groups. One week of

estrogen replacement significantly increased myostatin protein in

the slow soleus muscle but not the fast extensor digitorum longus

and gastrocnemius muscles. There was no treatment effect on IGF-1

and myostatin expression in the 5-week study; this finding suggested

a transient estrogen effect or upregulation of a compensatory

mechanism to counteract the estrogen effect observed at the earlier

time point.

This investigation is the first to explore ovariectomy and estrogen

effects on skeletal muscle IGF-1 and myostatin expression. Results

suggest that reduced levels of muscle IGF-1 protein may mediate

estrogen's effect on growth in immature, ovariectomized rats.

Increased levels of muscle myostatin protein may also have a role in

mediating estrogen's effects on growth in slow but not fast skeletal

muscle.