Response of Muscle Protein Synthesis to the Infusion of Insulin-like Growth Factor-I and Fasting in Young Chickens

This study determined whether rates of protein synthesis increase after acute resistance exercise in skeletal muscle from severely diabetic rats. Previous studies consistently show that postexercise rates of protein synthesis are elevated in nondiabetic and moderately diabetic rats. Severely diabetic rats performed acute resistance exercise ( n= 8) or remained sedentary ( n = 8). A group of nondiabetic age-matched rats served as controls ( n = 9). Rates of protein synthesis were measured 16 h after exercise. Plasma glucose concentrations were >500 mg/dl in the diabetic rats. Rates of protein synthesis (nmol phenylalanine incorporated ⋅ g muscle−1 ⋅ h−1, means ± SE) were not different between exercised (117 ± 7) and sedentary (106 ± 9) diabetic rats but were significantly ( P < 0.05) lower than in sedentary nondiabetic rats (162 ± 9) and in exercised nondiabetic rats (197 ± 7). Circulating insulin concentrations were 442 ± 65 pM in nondiabetic rats and 53 ± 11 and 72 ± 19 pM in sedentary and exercised diabetic rats, respectively. Plasma insulin-like growth factor I concentrations were reduced by 33% in diabetic rats compared with nondiabetic rats, and there was no difference between exercised and sedentary diabetic rats. Muscle insulin-like growth factor I was not affected by resistance exercise in diabetic rats. The results show that there is a critical concentration of insulin below which rates of protein synthesis begin to decline in vivo. In contrast to previous studies using less diabetic rats, severely diabetic rats cannot increase rates of protein synthesis after acute resistance exercise.

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Differential effect of sepsis on ability of leucine and IGF-I to stimulate muscle translation initiation

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00132.2004 ◽

2004 ◽

Vol 287 (4) ◽

pp. E721-E730 ◽

Cited By ~ 40

Author(s):

Charles H. Lang ◽

Robert A. Frost

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Growth Factor ◽

Translation Initiation ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Insulin Like Growth Factor ◽

Factor I ◽

Growth Factor I ◽

Signaling Components

Polymicrobial sepsis impairs skeletal muscle protein synthesis, which results from impairment in translation initiation under basal conditions. The purpose of the present study was to test the hypothesis that sepsis also impairs the anabolic response to amino acids, specifically leucine (Leu). Sepsis was induced by cecal ligation and puncture, and 24 h later, Leu or saline (Sal) was orally administered to septic and time-matched nonseptic rats. The gastrocnemius was removed 20 min later for assessment of protein synthesis and signaling components important in peptide-chain initiation. Oral Leu increased muscle protein synthesis in nonseptic rats. Leu was unable to increase protein synthesis in muscle from septic rats, and synthetic rates remained below those observed in nonseptic + Sal rats. In nonseptic + Leu rats, phosphorylation of eukaryotic initiation factor (eIF)4E-binding protein 1 (4E-BP1) in muscle was markedly increased compared with values from time-matched Sal-treated nonseptic rats. This change was associated with redistribution of eIF4E from the inactive eIF4E·4E-BP1 to the active eIF4E·eIF4G complex. In septic rats, Leu-induced phosphorylation of 4E-BP1 and changes in eIF4E distribution were completely abrogated. Sepsis also antagonized the Leu-induced increase in phosphorylation of S6 kinase 1 and ribosomal protein S6. Sepsis attenuated Leu-induced phosphorylation of mammalian target of rapamycin and eIF4G. The ability of sepsis to inhibit anabolic effects of Leu could not be attributed to differences in plasma concentrations of insulin, insulin-like growth factor I, or Leu between groups. In contrast, the ability of exogenous insulin-like growth factor I to stimulate the same signaling components pertaining to translation initiation was not impaired by sepsis. Hence, sepsis produces a relatively specific Leu resistance in skeletal muscle that impairs the ability of this amino acid to stimulate translation initiation and protein synthesis.

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Relationship of Insulin-Like Growth Factor-I to Muscle Protein Synthesis in Fasted Chicks.

Japanese poultry science ◽

10.2141/jpsa.35.263 ◽

1998 ◽

Vol 35 (5) ◽

pp. 263-270 ◽

Cited By ~ 5

Author(s):

Kazumi KITA ◽

Takako SHIBATA ◽

M.AMAN YAMAN ◽

Michael A. CONLON ◽

Takeshi SASAKI ◽

...

Keyword(s):

Protein Synthesis ◽

Growth Factor ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Insulin Like Growth Factor ◽

Factor I ◽

Growth Factor I ◽

Relationship Of

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Muscle protein synthesis rate is altered in response to a single injection of insulin-like growth factor-I in seven-day-old Leghorn chicks

Poultry Science ◽

10.1093/ps/81.10.1543 ◽

2002 ◽

Vol 81 (10) ◽

pp. 1543-1547 ◽

Cited By ~ 18

Author(s):

MA Conlon ◽

K Kita

Keyword(s):

Protein Synthesis ◽

Growth Factor ◽

Single Injection ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Synthesis Rate ◽

Protein Synthesis Rate ◽

Insulin Like Growth Factor ◽

Factor I ◽

Muscle Protein Synthesis Rate

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Insulin-like growth factor-I and more potent variants restore growth of diabetic rats without inducing all characteristic insulin effects

Biochemical Journal ◽

10.1042/bj2910781 ◽

1993 ◽

Vol 291 (3) ◽

pp. 781-786 ◽

Cited By ~ 13

Author(s):

F M Tomas ◽

S E Knowles ◽

P C Owens ◽

C S Chandler ◽

G L Francis ◽

...

Keyword(s):

Growth Factor ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Treated Group ◽

Diabetic Rats ◽

Insulin Like Growth Factor ◽

Igf Binding Proteins ◽

Factor I ◽

Igf I ◽

Growth Factor I

The effects of graded doses of insulin-like growth factor-I (IGF-I) and two variants which bind poorly to IGF-binding proteins were investigated in 160 g streptozotocin-induced diabetic rats. The two variants were the truncated form, des(1-3)IGF-I, and another with arginine at residue 3 and an N-terminal extension, termed LR3-IGF-I. The peptides were infused via mini-osmotic pumps. Reference groups received either vehicle or insulin (30 i.u. per day). Treatment led to a marked dose-dependent increase in growth rate and nitrogen balance. The highest dose (695 micrograms/day) of IGF-I increased body weight by 48.1 +/- 1.7 g/7 days, compared with 11.0 +/- 2.8 g/7 days for the vehicle-treated group. The two variants were 2.5-3 times more potent than IGF-I in restoring growth. The insulin-treated group gained more weight (64.5 +/- 1.6 g/7 days), but the added gain was fat (92.5 +/- 4.8 g of fat/kg carcass wet wt., compared with 32.2 +/- 2.1 for all other groups) rather than protein. All peptides increased muscle protein-synthesis rates and RNA levels by up to 50%, with IGF-I the least potent. These high doses of IGFs did not decrease either the glucosuria or the daily excretion rate of N tau-methyl-histidine (N tau-MH). On the other hand, insulin treatment markedly decreased both glucosuria (from 82.7 +/- 5.4 to 4.5 +/- 3.3 mmol/day) and N tau-MH excretion (from 9.3 +/- 0.3 to 7.1 +/- 0.4 mumol/day per kg). This experiment shows that, although IGF-I and variants can restore growth in diabetic rats, other insulin-dependent metabolic processes in liver, muscle and adipose tissue are not restored.

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Insulin-like growth factor I accelerates protein synthesis in skeletal muscle during sepsis

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1995.269.5.e977 ◽

1995 ◽

Vol 269 (5) ◽

pp. E977-E981 ◽

Cited By ~ 24

Author(s):

C. V. Jurasinski ◽

T. C. Vary

Keyword(s):

Protein Synthesis ◽

Growth Factor ◽

Peptide Chain ◽

Translational Efficiency ◽

Insulin Like Growth Factor ◽

Recombinant Human Insulin ◽

Chain Initiation ◽

Factor I ◽

Igf I ◽

Growth Factor I

Sepsis causes an inhibition of protein synthesis in gastrocnemius that is resistant to the anabolic effects of insulin. The purpose of the present studies was to investigate the effect of recombinant human insulin-like growth factor I (IGF-I) on protein synthesis during a 30-min perfusion of the isolated rat hindlimb from septic rats. Inclusion of IGF-I (1 or 10 nM) in the perfusate stimulated protein synthesis in gastrocnemius of septic rats 2.5-fold and restored rates of protein synthesis to those observed in control rats. The stimulation of protein synthesis did not result from an increase in the RNA content but was correlated with a 2.5-fold increase in the translational efficiency. The enhanced translational efficiency was accompanied by a 33 and 55% decrease in the abundance of free 40S and 60S ribosomal subunits, respectively, indicating that IGF-I accelerated peptide-chain initiation relative to elongation/termination. These studies provide evidence that IGF-I can accelerate protein synthesis in gastrocnemius during chronic sepsis by reversing the sepsis-induced inhibition of peptide-chain initiation.

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Insulin-like growth factor I preserves host lean tissue mass in cancer cachexia

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1992.262.3.r426 ◽

1992 ◽

Vol 262 (3) ◽

pp. R426-R431 ◽

Cited By ~ 2

Author(s):

E. H. Ng ◽

C. S. Rock ◽

D. D. Lazarus ◽

L. Stiaino-Coico ◽

L. L. Moldawer ◽

...

Keyword(s):

Growth Factor ◽

Muscle Protein ◽

Insulin Like Growth Factor ◽

Skeletal Muscle Protein ◽

Lean Tissue ◽

Tissue Mass ◽

Fischer 344 ◽

Factor I ◽

Igf I ◽

Growth Factor I

Insulin-like growth factor I (IGF-I) has been implicated in the regulation and maintenance of skeletal muscle protein balance and thus may be of potential benefit in attenuating the cancer-cachectic process. To examine this hypothesis, 47 sham or tumor-implanted Fischer 344 rats were randomized to receive either continuous subcutaneous IGF-I (220 or 400 micrograms/day) or saline as control. In the tumor-bearing (TB) population, IGF-I-treated groups showed a dose-dependent increase in host weight gain (P less than 0.05), final carcass weight (P less than 0.05), and gastrocnemius muscle weights (P less than 0.05) and protein contents (0.50 +/- 0.02, 0.40 +/- 0.01, and 0.52 +/- 0.03 g/100 g host wt, for non-TB saline, TB saline, and TB 400 mg IGF-I groups, respectively; P less than 0.01, IGF-I vs. saline). Similar increases in muscle RNA and DNA contents (P less than 0.01) were induced by IGF-I treatment (P less than 0.05). IGF-I treatment in this rat sarcoma model significantly reduced the proportion of aneuploid cells in the tumor (aneuploid-to-diploid ratio: TB saline 1.1 +/- 0.2 vs. TB IGF-I 0.5 +/- 0.1; P less than 0.05). IGF-I treatment attenuated host muscle protein and lean tissue depletion without stimulation of tumor growth. The tumor aneuploid population was reduced in response to IGF-I treatment. Thus IGF-I may be a potential therapeutic agent in cancer-induced cachexia.

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Changes in protein metabolism of ovine primary muscle cultures on treatment with growth hormone, insulin, insulin-like growth factor I or epidermal growth factor

Journal of Endocrinology ◽

10.1677/joe.0.1120087 ◽

1987 ◽

Vol 112 (1) ◽

pp. 87-96 ◽

Cited By ~ 60

Author(s):

J. M. M. Harper ◽

J. B. Soar ◽

P. J. Buttery

Keyword(s):

Growth Hormone ◽

Protein Synthesis ◽

Growth Factor ◽

Epidermal Growth Factor ◽

Insulin Like Growth Factor ◽

Factor I ◽

Muscle Cultures ◽

Epidermal Growth ◽

Growth Factor I ◽

High Concentrations

ABSTRACT Methods for the primary culture of muscle cells from fetal sheep were developed which gave high yields of cells. Myoblasts were grown in vitro, and allowed to fuse to form contractile multinucleate myotubes; these could be maintained in a good condition for at least 2 weeks. Protein turnover in these differentiated cultures was examined for sensitivity to each of four potentially anabolic peptide hormones and growth factors: insulin, insulin-like growth factor I (somatomedin C), epidermal growth factor and growth hormone. Insulin was found to have no effect except at high concentrations (1 μmol/l), compatible with its role as a somatomedin analogue. Insulin-like growth factor I was active at lower levels (1 nmol/l) but the cultures were not as responsive to it as were primary rat muscle cultures or differentiated L6 cells, which were tested in similar experiments. The maximum stimulation of protein synthesis observed with the ruminant system was only 16%. Epidermal growth factor was highly anabolic for primary cultures from sheep muscle, and the cells were very sensitive to it, half-maximal stimulation of protein synthesis being seen with concentrations as low as 20 pmol/l. No effects of bovine growth hormone were seen in the ovine system. However, an inhibition of protein breakdown was found with high concentrations (0·1 μmol/l) in the L6 rat myoblast cell line. It was found that the culture conditions used could affect the observed responses of protein synthesis and degradation, despite withdrawal of serum from the incubation media 22 h before testing. J. Endocr. (1987) 112, 87–96

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Insulin-like growth factor I exerts growth hormone- and insulin-like actions on human muscle protein metabolism

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1994.267.2.e331 ◽

1994 ◽

Vol 267 (2) ◽

pp. E331-E336 ◽

Cited By ~ 21

Author(s):

D. A. Fryburg

Keyword(s):

Growth Hormone ◽

Growth Factor ◽

Muscle Protein ◽

Muscle Metabolism ◽

Insulin Like Growth Factor ◽

Factor I ◽

Igf I ◽

Muscle Protein Metabolism ◽

Growth Factor I ◽

Forearm Muscle

The effect of a 6-h intra-arterial infusion of recombinant human (rh) insulin-like growth factor I (IGF-I) on forearm muscle metabolism was studied in 19 postabsorptive subjects. Forearm glucose, lactate, and phenylalanine (Phe) balances, as well as estimates of protein degradation (Phe Ra) and synthesis (Phe Rd) were measured before and at 3 and 6 h into an infusion of rhIGF-I at a dose of 1.8 (n = 6), 6.0 (n = 8), or 10.0 (n = 5) micrograms.kg-1.h-1. In response to intra-arterial IGF-I, deep venous IGF-I rose by 55, 141, and 315%, respectively (all P < 0.01), and forearm blood flow accelerated by 75 (1.8 microgram), 213 (6.0 micrograms), and 159% (10.0 micrograms; all P < 0.02). No change in forearm glucose uptake was observed at the lowest dose, whereas four- to sixfold increases were observed at both the 6 and 10 micrograms.kg-1.h-1 doses (both P < 0.02). Forearm Phe balance shifted positively at all three doses by 27 +/- 6, 48 +/- 7, and 51 +/- 9 nmol.min-1 x 100 ml-1, respectively (all P < 0.01). At all three doses, Phe Rd increased comparably by 49-74% (all P < 0.05). At the 6.0 and 10.0 but not the 1.8 microgram.kg-1.h-1 dose, Phe Ra decreased by approximately 45% (P < 0.02). Forearm muscle metabolism was also studied in the contralateral non-IGF-infused arm at these three doses. Despite increases in deep venous IGF-I up to 517 ng/ml due to recirculating IGF-I (10.0 micrograms.kg-1.h-1 dose), contralateral forearm muscle glucose, lactate, or Phe handling did not change. In conclusion, intra-arterial IGF-I exhibits growth hormone-like effects at all doses tested, whereas the insulin-like effects are observed at higher doses; these effects appear dependent on the route of administration.

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Effects of insulin-like growth factor-I, insulin, and leucine on protein turnover and ubiquitin ligase expression in rainbow trout primary myocytes

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00516.2009 ◽

2010 ◽

Vol 298 (2) ◽

pp. R341-R350 ◽

Cited By ~ 56

Author(s):

Beth M. Cleveland ◽

Gregory M. Weber

Keyword(s):

Protein Synthesis ◽

Rainbow Trout ◽

Growth Factor ◽

Protein Degradation ◽

Ubiquitin Ligase ◽

Protein Turnover ◽

Insulin Like Growth Factor ◽

Factor I ◽

Igf I ◽

Growth Factor I

The effects of insulin-like growth factor-I (IGF-I), insulin, and leucine on protein turnover and pathways that regulate proteolytic gene expression and protein polyubiquitination were investigated in primary cultures of 4-day-old rainbow trout myocytes. Supplementing media with 100 nM IGF-I increased protein synthesis by 13% ( P < 0.05) and decreased protein degradation by 14% ( P < 0.05). Treatment with 1 μM insulin increased protein synthesis by 13% ( P < 0.05) and decreased protein degradation by 17% ( P < 0.05). Supplementing media containing 0.6 mM leucine with an additional 2.5 mM leucine did not increase protein synthesis rates but reduced rates of protein degradation by 8% ( P < 0.05). IGF-I (1 nM–100 nM) and insulin (1 nM-1 μM) independently reduced the abundance of ubiquitin ligase mRNA in a dose-dependent manner, with maximal reductions of ∼70% for muscle atrophy F-box (Fbx) 32, 40% for Fbx25, and 25% for muscle RING finger-1 (MuRF1, P < 0.05). IGF-I and insulin stimulated phosphorylation of FOXO1 and FOXO4 ( P < 0.05), which was inhibited by the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor wortmannin, and decreased the abundance of polyubiquitinated proteins by 10–20% ( P < 0.05). Supplementing media with leucine reduced Fbx32 expression by 25% ( P < 0.05) but did not affect Fbx25 nor MuRF1 transcript abundance. Serum deprivation decreased rates of protein synthesis by 60% ( P < 0.05), increased protein degradation by 40% ( P < 0.05), and increased expression of all ubiquitin ligases. These data suggest that, similar to mammals, the inhibitory effects of IGF-I and insulin on proteolysis occur via P I3-kinase/protein kinase B signaling and are partially responsible for the ability of these compounds to promote protein accretion.

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