scholarly journals Lower recovery of muscle protein lost during starvation in old rats despite a stimulation of protein synthesis

1999 ◽  
Vol 277 (4) ◽  
pp. E608-E616 ◽  
Author(s):  
L. Mosoni ◽  
T. Malmezat ◽  
M. C. Valluy ◽  
M. L. Houlier ◽  
D. Attaix ◽  
...  
Keyword(s):  
Gene Expression ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Age Groups ◽  
Liver Protein ◽  
Protein Mass ◽  
Old Rats ◽  
Proteolytic Pathways ◽  
Lower Recovery

Sarcopenia could result from the inability of an older individual to recover muscle lost during catabolic periods. To test this hypothesis, we compared the capacity of 5-day-refed 12- and 24-mo-old rats to recover muscle mass lost after 10 days without food. We measured gastrocnemius and liver protein synthesis with the flooding-dose method and also measured nitrogen balance, 3-methylhistidine excretion, and the gene expression of components of proteolytic pathways in muscle comparing fed, starved, and refed rats at each age. We show that 24-mo-old rats had an altered capacity to recover muscle proteins. Muscle protein synthesis, inhibited during starvation, returned to control values during refeeding in both age groups. The lower recovery in 24-mo-old rats was related to a lack of inhibition of muscle proteolysis during refeeding. The level of gene expression of components of the proteolytic pathways did not account for the variations in muscle proteolysis at both ages. In conclusion, this study highlights the role of muscle proteolysis in the lower recovery of muscle protein mass lost during catabolic periods.

Effect of amino acids alone or with insulin on muscle and liver protein synthesis in adult and old rats

1993 ◽  
Vol 264 (4) ◽  
pp. E614-E620 ◽  
Author(s):  
L. Mosoni ◽  
M. L. Houlier ◽  
P. P. Mirand ◽  
G. Bayle ◽  
J. Grizard
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Male Rats ◽  
Liver Protein ◽  
Protein Mass ◽  
Age Related ◽  
Old Rats ◽  
Absolute Synthesis

This study was carried out to analyze age-related changes on amino acid and insulin effects on muscle and liver protein synthesis. Conscious male rats, aged 12 (adult) and 24 (old) mo, were infused for 90 min with either saline, amino acids, or amino acids with insulin and glucose. Protein synthesis was measured during the last 15 min of infusion (flooding dose of valine with L-[2,3,4-3H]valine). Gastrocnemius protein mass was 29% lower in old rats than in adults. However, basal muscle absolute synthesis rates were unchanged with age, and fractional synthesis rates (FSR) were increased. Amino acids significantly stimulated muscle FSR to a similar extent (18-20%) in adult (P < 0.01) and old rats (P = 0.03 when variability introduced by muscle atrophy was taken into account by a variance-covariance analysis). Insulin did not elicit any additional effect. Liver protein synthesis did not change with age or in response to infusions. We conclude that, despite an age-related loss of muscle proteins, capacity of muscle protein synthesis to be stimulated is preserved with age.

Altered response of protein synthesis to nutritional state and endurance training in old rats

1995 ◽  
Vol 268 (2) ◽  
pp. E328-E335 ◽  
Author(s):  
L. Mosoni ◽  
M. C. Valluy ◽  
B. Serrurier ◽  
J. Prugnaud ◽  
C. Obled ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Tibialis Anterior ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Marked Change ◽  
Treadmill Running ◽  
Liver Protein ◽  
Age Related ◽  
Old Rats ◽  
The Impact

This study was undertaken to determine whether the loss of muscle protein mass during aging could be explained by a reduced sensitivity of muscle protein synthesis to feeding and exercise. Male Wistar rats aged 12 and 24 mo were exercised by treadmill running for 4 mo. Protein synthesis was measured by the flooding dose method in tibialis anterior, soleus, and liver of conscious rested, trained rats and age-matched controls in the postprandial or in the postabsorptive state. No marked change with age could be detected in basal muscle protein synthesis. In contrast, protein synthesis was stimulated in adult but not in old rats by feeding in tibialis anterior and by exercise in soleus. In liver, protein synthesis was not modified by age but was stimulated by feeding and by exercise, which improved the response to feeding. We conclude that the impact of nutrition on muscle protein synthesis is blunted in old age, which could contribute to the age-related loss of nutrition-sensitive muscle proteins.

scholarly journals The effects of endotoxaemia on protein metabolism in skeletal muscle and liver of fed and fasted rats

1986 ◽  
Vol 235 (2) ◽  
pp. 329-336 ◽  
Author(s):  
M M Jepson ◽  
J M Pell ◽  
P C Bates ◽  
D J Millward
Keyword(s):  
Protein Synthesis ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Synthesis Rate ◽  
Liver Protein ◽  
Fractional Synthesis Rate ◽  
Protein Mass ◽  
Fractional Synthesis ◽  
Fasted Rats

The response of muscle and liver protein metabolism to either a single or three successive daily injections of an endotoxin (Escherichia coli lipopolysaccharide, serotype 0127 B8; 1 mg/ml, 0.3 mg/100 g body wt.) was studied in vivo in the fed rat, and at 24 and 30 h after endotoxin treatment during fasting. In the fed rats there was a catabolic response in muscle, owing to a 60-100% increase in muscle protein degradation rate, and a 52% fall in the synthesis rate. Although there was a 20% decrease in food intake, the decrease in protein synthesis was to some extent independent of this, since rats treated with endotoxin and fasted also showed a lower rate of muscle protein synthesis, which was in excess of the decrease caused by fasting alone. The mechanism of this decreased protein synthesis involved decreased translational activity, since in both fed and fasted rats there was a decreased rate of synthesis per unit of RNA. This occurred despite the fact that insulin concentrations were either maintained or increased, in the fasted rats, to those observed in fed rats. In the liver total protein mass was increased in the fed rats by 16% at 24 h, and the fractional synthesis rate at that time was increased by 35%. In rats fasted after endotoxin treatment the liver protein mass was not decreased as it was in the control fasted rats, and the fractional synthesis rate was increased by 22%. In both cases the increased synthesis rate reflected an elevated hepatic RNA concentration. The extent of this increase in hepatic protein synthesis was sufficient at one point to compensate for the fall in estimated muscle protein synthesis, so that the sum total in the two tissues was maintained.

scholarly journals The diurnal response of muscle and liver protein synthesis in vivo in meal-fed rats

1973 ◽  
Vol 136 (4) ◽  
pp. 935-945 ◽  
Author(s):  
P. J. Garlick ◽  
D. J. Millward ◽  
W. P. T. James
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Specific Radioactivity ◽  
Whole Body ◽  
Rat Tissues ◽  
Liver Protein ◽  
Protein Mass ◽  
Fractional Rate

1. The rate of protein synthesis in rat tissues was measured by constant intravenous infusion of [14C]tyrosine. A modification has been developed for the method of calculating the rate of protein synthesis in individual tissues from the specific radioactivity of the free and protein-bound amino acid in tissue at the end of the infusion. This technique gives greater accuracy and allows a greater choice of labelled amino acids. The specific radioactivity of free tyrosine in plasma was used to calculate the plasma tyrosine flux, an index of the rate of protein synthesis in the whole body. 2. Young male Wistar rats were allowed access to food for only 4h in every 24h. The tyrosine flux and the rate of protein synthesis in liver and muscle at different periods of time after a single feed were estimated. 3. The tyrosine flux did not alter after feeding nor even after starvation for 48h. 4. The average fractional rate of protein synthesis in muscle was 7.2%/day, i.e. the proportion of the protein mass which is replaced each day. The rate rose after eating and declined during starvation for 48h. In addition the rate of muscle protein synthesis correlated with the growth rate of the rat. 5. In liver the average fractional rate of protein synthesis was 50%/day. There was no change in the rate after eating nor after starvation for 48h. In contrast with muscle this suggests that the changes in protein mass were accompanied by changes in the rate of protein breakdown rather than synthesis.

Adaptation to prolonged starvation in the rat: curtailment of skeletal muscle proteolysis

1981 ◽  
Vol 241 (4) ◽  
pp. E321-E327 ◽  
Author(s):  
M. N. Goodman ◽  
M. A. McElaney ◽  
N. B. Ruderman
Keyword(s):  
Skeletal Muscle ◽  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Early Event ◽  
Body Protein ◽  
Fed State ◽  
Prolonged Starvation ◽  
Obese Rats ◽  
Old Rats

Previous studies have established that 16-wk-old nonobese and obese rats conserve body protein during prolonged starvation. To determine the basis for this, protein synthesis and degradation in skeletal muscle were evaluated in the isolated perfused hindquarters of these rats, in the fed state and when starved for 2, 5, 10, and 11 days. Rats aged 4 and 8 wk were used as a comparison. The results indicate that the response to starvation depends on several factors: the age of the rat, its degree of adiposity, and the duration of the fast. An early event in starvation was a decline in muscle protein synthesis. This occurred in all groups, albeit this reduction occurred more slowly in the older rats. A later response to starvation was an increase in muscle proteolysis. This occurred between 2 and 5 days in the 8-wk-old rats. In 16-wk-old rats it did not occur until between 5 and 10 days, and it was preceded by a period of decreased proteolysis. In 16-wk-old obese rats, a decrease in proteolysis persisted for upwards of 10 days and the secondary increase was not noted during the period of study. The data suggest that the ability of older and more obese rats to conserve body protein during starvation is due, in part, to a curtailment of muscle proteolysis. This adaptation seems to correlate with the availability of lipid fuels.

Enhanced response of muscle protein synthesis and plasma insulin to food intake in suckled rats

1993 ◽  
Vol 265 (2) ◽  
pp. R334-R340 ◽  
Author(s):  
T. A. Davis ◽  
M. L. Fiorotto ◽  
H. V. Nguyen ◽  
P. J. Reeds
Keyword(s):  
Protein Synthesis ◽  
Food Intake ◽  
Plasma Insulin ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Fed State ◽  
Fasting And Refeeding ◽  
Old Rats ◽  
Amino Acid Concentrations

To compare the sensitivity of muscle protein synthesis to food intake in neonatal and weaned rats, 5- and 16-day-old suckled rats and 28-day-old weaned rats were either fed, fasted for 8-10 h, or refed for 1-4 h after an 8-h fast. Protein synthesis was measured in vivo in soleus and plantaris muscles with a large dose of L-[4-3H]phenylalanine. In fed rats, fractional rates of protein synthesis (KS) decreased with age. Fasting decreased KS, and refeeding increased KS most in 5-day-old animals, less in 16-day-old rats, and least in 28-day-old rats. In 5-day-old rats, there were no differences in KS between soleus and plantaris muscles in the fed state and after fasting and refeeding; at 28 days, KS was higher in soleus than in plantaris in fed rats, and the soleus did not respond to fasting and refeeding. In rats at all three ages, the concentration of most plasma amino acids decreased during fasting; when 5-day-old rats were refed, plasma amino acid concentrations increased, but not to the levels in the fed state. Plasma insulin concentrations increased with age. Plasma insulin concentrations decreased more rapidly with fasting and increased more extensively with refeeding in 5-day-old rats than in older rats. These results suggest that muscle protein synthesis is more responsive to food intake in young suckled rats than in older suckled or weaned rats; this increased responsiveness is accompanied by greater changes in circulating insulin concentrations.

scholarly journals Glucocorticoid effects on insulin- and IGF-I-regulated muscle protein metabolism during aging

1998 ◽  
Vol 156 (1) ◽  
pp. 83-89 ◽  
Author(s):  
D Dardevet ◽  
C Sornet ◽  
I Savary ◽  
E Debras ◽  
P Patureau-Mirand ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Muscle Atrophy ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Recovery Period ◽  
Adult Rats ◽  
Igf I ◽  
Muscle Protein Metabolism ◽  
Old Rats

This study was performed to assess the effect of glucocorticoids (dexamethasone) on insulin- and IGF-I-regulated muscle protein metabolism in adult and old rats. Muscle atrophy occurred more rapidly in old rats, and recovery of muscle mass was impaired when compared with adults. Muscle wasting resulted mainly from increased protein breakdown in adult rat but from depressed protein synthesis in the aged animal. Glucocorticoid treatment significantly decreased the stimulatory effect of insulin and IGF-I on muscle protein synthesis in adult rats by 25.9 and 58.1% respectively. In old rats, this effect was even greater, being 49.3 and 100% respectively. With regard to muscle proteolysis, glucocorticoids blunted the anti-proteolytic action of insulin and IGF-I in both age groups. During the recovery period, adult rats reversed the glucocorticoid-induced resistance of muscle protein metabolism within 3 days, at which time old rats still exhibited the decrease in insulin-regulated proteolysis. In conclusion, the higher sensitivity of old rat muscle to glucocorticoids may in part result from the greater modification of the effects of insulin and IGF-I on muscle protein metabolism. These responses to glucocorticoids in old rats may be associated with the emergence of muscle atrophy with advancing age.

scholarly journals Postprandial Stimulation of Muscle Protein Synthesis in Old Rats Can Be Restored by a Leucine-Supplemented Meal

2002 ◽  
Vol 132 (1) ◽  
pp. 95-100 ◽  
Author(s):  
Dominique Dardevet ◽  
Claire Sornet ◽  
Gérard Bayle ◽  
Jacques Prugnaud ◽  
Corinne Pouyet ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Old Rats ◽  
Stimulation Of

Presence of low-grade inflammation impaired postprandial stimulation of muscle protein synthesis in old rats

2010 ◽  
Vol 21 (4) ◽  
pp. 325-331 ◽  
Author(s):  
Michèle Balage ◽  
Julien Averous ◽  
Didier Rémond ◽  
Cécile Bos ◽  
Estelle Pujos-Guillot ◽  
...  
Keyword(s):  
Protein Synthesis ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Low Grade ◽  
Old Rats ◽  
Low Grade Inflammation ◽  
Stimulation Of

scholarly journals Protein metabolism in the tumour-bearing mouse. Rates of protein synthesis in host tissues and in an Ehrlich ascites tumour at different stages in tumour growth

1989 ◽  
Vol 264 (3) ◽  
pp. 713-719 ◽  
Author(s):  
M N Lopes ◽  
P Black ◽  
A J Ashford ◽  
V M Pain
Keyword(s):  
Protein Synthesis ◽  
Food Intake ◽  
Protein Metabolism ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Liver Protein ◽  
Humoral Factors ◽  
Ascites Tumour ◽  
Ehrlich Ascites ◽  
Ehrlich Ascites Tumour

We have investigated the time course of the changes in protein metabolism in skeletal muscle and liver in mice during the progression of growth of an Ehrlich ascites tumour. The rate of protein synthesis in muscle begins to fall very rapidly, and the decrease is clearly established by the time the tumour first becomes visible at 4 days after implantation of the cells. Liver protein synthesis increases substantially, and protein breakdown in muscle increases, but the onset of both these changes occurs later than the fall in muscle protein synthesis. A decrease in food intake in these animals occurs very rapidly after introduction of the cells. The fractional rate of protein synthesis in the tumour cells falls from 73%/day at 5 days to 26%/day at 12 days after injection, but on an absolute basis the rate of protein synthesis in the tumour at 5 days of growth is very small compared with that in muscle and liver. These results are consistent with the notion that the initial effects on muscle protein synthesis and food intake are brought about by humoral factors rather than as direct consequences of the metabolic demands of the growing tumour.

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