Muscle protein turnover in broiler chickens: effects of high ambient temperatures and dietary protein intake

The present experiments4 were undertaken to investigate the effects of environmental temperatures on growth, abdominal fat content, rate of muscle protein turnover, and heat production in tube-fed intact male broiler chickens. Plasma concentrations of thyroxine (T4), triiodothyronine (T3), and corticosterone (CTC) were also examined. Chicks (15d old) were kept at different environmental temperatures (16,19,22,25,28,31, and 34°) and given the experimental diet (200g crude protein/kg, 13·;57M/kg metabolizable energy) by tube three times daily throughout the 12d experimental period. In the hot conditions, except for 34°, body-weight gain was significantly higher than in the cold conditions. Thus, food conversion ratios (food: gain ratios) were lower when the birds were exposed to the hot conditions other than 34°. Likewise, abdominal fat content was significantly increased, and heat production was lower in the groups kept under the hot conditions other than 34°. The rate of skeletal muscle protein turnover and plasma concentration of CTC were decreased when the birds were exposed to hot conditions other than 34°. suggesting a role of CTC in the regulation of muscle protein turnover. Plasma concentrations of T4 and T3 were significantly decreased as environmental temperature increased. These results clearly show that plasma concentrations of thyroid hormones and CTC are associated with accelerated muscle protein turnover and heat production.

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Whole-body leucine and muscle protein kinetics in rats fed varying protein intakes

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1984.246.5.e444 ◽

1984 ◽

Vol 246 (5) ◽

pp. E444-E451 ◽

Cited By ~ 6

Author(s):

B. C. Laurent ◽

L. L. Moldawer ◽

V. R. Young ◽

B. R. Bistrian ◽

G. L. Blackburn

Keyword(s):

Dietary Protein ◽

Protein Intake ◽

Muscle Protein ◽

Specific Radioactivity ◽

Rectus Muscle ◽

Whole Body ◽

Dietary Protein Intake ◽

Body Protein ◽

Leucine Kinetics ◽

Ad Libitum

Whole-body leucine kinetics and rectus muscle synthetic rates were evaluated in postabsorptive rats fed semipurified diets that varied in the casein content. Rats were allowed to consume ad libitum a 2% casein diet or were pair-fed or ad libitum-fed 6, 20, or 40% casein diets for 14 days. After overnight starvation, rates of whole-body leucine kinetics and rectus muscle synthetic rates were determined with a 2-h constant intravenous infusion of L-[1-14C]leucine. The postabsorptive response to inadequate protein intakes included a significant reduction in the release of leucine from whole-body protein degradation as well as subsequent reutilization for protein synthesis. In contrast, dietary protein intake at levels greater than required for maximal growth were not associated with any increases in leucine incorporation into whole-body protein or muscle fractional synthetic rates. Rates of whole-body leucine oxidation based on plasma leucine specific radioactivities underestimated total oxidation by 22-27%, and this was relatively constant as the protein component of the diet was varied. In addition, the muscle acid-soluble leucine specific radioactivity was similar to the plasma alpha-ketoisocaproate enrichment, regardless of dietary protein intake.

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Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00060.2005 ◽

2005 ◽

Vol 289 (4) ◽

pp. E678-E683 ◽

Cited By ~ 52

Author(s):

Douglas R. Bolster ◽

Matthew A. Pikosky ◽

P. Courtney Gaine ◽

William Martin ◽

Robert R. Wolfe ◽

...

Keyword(s):

Skeletal Muscle ◽

Protein Synthesis ◽

Endurance Exercise ◽

Dietary Protein ◽

Protein Intake ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Dietary Protein Intake ◽

Skeletal Muscle Protein ◽

Skeletal Muscle Protein Synthesis

This investigation evaluated the physiological impact of different dietary protein intakes on skeletal muscle protein synthesis postexercise in endurance runners. Five endurance-trained, male runners participated in a randomized, crossover design diet intervention, where they consumed either a low (0.8 g/kg; LP)-, moderate (1.8 g/kg; MP)-, or high (3.6 g/kg; HP)-protein diet for 4 wk. Diets were designed to be eucaloric with carbohydrate, fat, and protein approximating 60, 30, and 10%; 55, 30, and 15%; and 40, 30, and 30% for LP, MP, and HP, respectively. Substrate oxidation was assessed via indirect calorimetry at 3 wk of the dietary interventions. Mixed-muscle protein fractional synthetic rate (FSR) was measured after an endurance run (75 min at 70% V̇o2 peak) using a primed, continuous infusion of [2H5]phenylalanine. Protein oxidation increased with increasing protein intake, with each trial being significantly different from the other ( P < 0.01). FSR after exercise was significantly greater for LP (0.083%/h) and MP (0.078%/h) than for HP (0.052%/h; P < 0.05). There was no difference in FSR between LP and MP. This is the first investigation to establish that habitual dietary protein intake in humans modulates skeletal muscle protein synthesis after an endurance exercise bout. Future studies directed at mechanisms by which level of protein intake influences skeletal muscle turnover are needed.

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Effect of dietary protein on hepatic mitochondrial function and cardiac muscle protein turnover in uremic rats

Nutrition Research ◽

10.1016/s0271-5317(85)80020-8 ◽

1985 ◽

Vol 5 (1) ◽

pp. 65-79

Author(s):

Robert S. Tyzbir ◽

Arthur S. Kunin ◽

Deborah E. Hewett ◽

Jean R. Hewitt

Keyword(s):

Cardiac Muscle ◽

Mitochondrial Function ◽

Dietary Protein ◽

Protein Turnover ◽

Muscle Protein ◽

Muscle Protein Turnover

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Influence of Dietary Protein Intake on Whole-Body Protein Turnover in Humans

Diabetes Care ◽

10.2337/diacare.14.12.1189 ◽

1991 ◽

Vol 14 (12) ◽

pp. 1189-1198 ◽

Cited By ~ 57

Author(s):

P. J. Garlick ◽

M. A. McNurlan ◽

P. E. Ballmer

Keyword(s):

Dietary Protein ◽

Protein Turnover ◽

Protein Intake ◽

Whole Body ◽

Dietary Protein Intake ◽

Body Protein

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Muscle Protein Turnover in Sex-Linked Dwarf and Normal Broiler Chickens ,

Poultry Science ◽

10.3382/ps.0652082 ◽

1986 ◽

Vol 65 (11) ◽

pp. 2082-2089 ◽

Cited By ~ 6

Author(s):

S.J. JONES ◽

M.D. JUDGE ◽

E.D. ABERLE

Keyword(s):

Protein Turnover ◽

Broiler Chickens ◽

Muscle Protein ◽

Muscle Protein Turnover

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Muscle Protein Turnover and Tenderness in Broiler Chickens Fed Cimaterol

Journal of Animal Science ◽

10.2527/jas1989.67102646x ◽

1989 ◽

Vol 67 (10) ◽

pp. 2646 ◽

Cited By ~ 27

Author(s):

J. B. Morgan ◽

S. J. Jones ◽

C. R. Calkins

Keyword(s):

Protein Turnover ◽

Broiler Chickens ◽

Muscle Protein ◽

Muscle Protein Turnover

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The role of dietary protein in optimizing muscle mass, function and health outcomes in older individuals

British Journal Of Nutrition ◽

10.1017/s0007114512002590 ◽

2012 ◽

Vol 108 (S2) ◽

pp. S88-S93 ◽

Cited By ~ 71

Author(s):

Robert R. Wolfe

Keyword(s):

Protein Synthesis ◽

Health Outcomes ◽

Muscle Mass ◽

Dietary Protein ◽

Protein Intake ◽

Muscle Protein ◽

Muscle Protein Synthesis ◽

Dietary Protein Intake ◽

Older Individuals ◽

And Function

The determination of whether increased dietary protein can positively affect health outcomes is hindered by the absence of prospective, randomized trials directly addressing this issue in which all pertinent variables are controlled. Consequently, we can only address the question deductively by considering the support for the rationale underlying the notion of a beneficial effect of increased dietary protein intake. With regard to health outcomes, we have focused on older individuals. Muscle mass and function are progressively lost with aging, so that by the age of 60 many individuals have reached a threshold where function begins to be affected. An association between reduced muscle mass and strength and unfavourable health outcomes is more likely to be revealed in individuals who have significant decrements in muscle mass and strength. In this article support for the rationale underlying the notion of a beneficial effect of increased dietary protein intake is considered. Dietary protein intake, and the resulting increased availability of plasma amino acids, stimulates muscle protein synthesis. If all other variables are controlled, increased muscle protein synthesis leads to improved muscle mass, strength and function over time. Increased muscle mass, strength and function are related to improved health outcomes in older individuals. Since adverse effects of reasonable increases in protein intake above the recommended dietary allowance (RDA) of 0·8 g protein/kg/day have not been reported, it is reasonable to conclude that the optimal protein intake for an older individual is greater than the RDA.

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