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Insulin attenuates atrophy of unweighted soleus muscle by amplified inhibition of protein degradation.
- Source :
-
Metabolism: clinical and experimental [Metabolism] 1997 Jun; Vol. 46 (6), pp. 673-9. - Publication Year :
- 1997
-
Abstract
- Unweighting atrophy of immature soleus muscle occurs rapidly over the first several days, followed by slower atrophy coinciding with increased sensitivity to insulin of in vitro protein metabolism. This study determined whether this increased sensitivity might account for the diminution of atrophy after 3 days of tall-cast hindlimb suspension. The physiological significance of the increased response to insulin in unweighted muscle was evaluated by analyzing in vivo protein metabolism for day 3 (48 to 72 hours) and day 4 (72 to 96 hours) of unweighting in diabetic animals either injected with insulin or not treated. Soleus from nontreated diabetic animals showed a similar loss of protein during day 3 (-16.2%) and day 4 (-14.5%) of unweighting, whereas muscle from insulin-treated animals showed rapid atrophy (-14.5%) during day 3 only, declining to just -3.1% the next day. Since fractional protein synthesis was similar for both day 3 (8.6%/d) and day 4 (7.0%/d) of unweighting in insulin-treated animals, the reduction in protein loss must be accounted for by a slowing of protein degradation due to circulating insulin. Intramuscular (IM) injection of insulin (600 nmol/L) stimulated in situ protein synthesis similarly in 4-day unweighted (+56%) and weight-bearing (+90%) soleus, even though unweighted muscle showed a greater in situ response of 2-deoxy-[3H]glucose uptake to IM injection of either insulin (133 nmol/L) or insulin-like growth factor-I (IGF-I) (200 nmol/L) than control muscle. These findings suggest that unweighted muscle is selectively more responsive in vivo to insulin, and that the slower atrophy after 3 days of unweighting was due to an increased effect of insulin on inhibiting protein degradation.
- Subjects :
- Analysis of Variance
Animals
Atrophy
Deoxyglucose metabolism
Female
Injections, Intramuscular
Insulin administration & dosage
Muscle Proteins biosynthesis
Muscle, Skeletal drug effects
Rats
Rats, Sprague-Dawley
Weight-Bearing
Insulin pharmacology
Muscle Proteins metabolism
Muscle, Skeletal pathology
Muscle, Skeletal physiology
Subjects
Details
- Language :
- English
- ISSN :
- 0026-0495
- Volume :
- 46
- Issue :
- 6
- Database :
- MEDLINE
- Journal :
- Metabolism: clinical and experimental
- Publication Type :
- Academic Journal
- Accession number :
- 9186304
- Full Text :
- https://doi.org/10.1016/s0026-0495(97)90012-3