Differential metabolic effects of casein and soy protein meals on skeletal muscle in healthy volunteers.
OBJECTIVE
Dietary protein intake is known to affect whole body and interorgan protein turnover. We examined if moderate-nitrogen and carbohydrate casein and soy meals have a different effect on skeletal muscle protein and amino acid kinetics in healthy young subjects.


METHODS
Muscle protein and amino acid kinetics were measured in the postabsorptive state and during 4-h enteral intake of isonitrogenous [0.21 g protein/(kg body weight. 4 h)] protein-based test meals, which contained either casein (CAPM; n = 12) or soy protein (SOPM; n = 10) in 2 separate groups. Stable isotope and muscle biopsy techniques were used to study metabolic effects.


RESULTS
The net uptake of glutamate, serine, histidine, and lysine across the leg was larger during CAPM than during SOPM intake. Muscle concentrations of glutamate, serine, histidine, glutamine, isoleucine and BCAA changed differently after CAPM and SOPM (P < 0.05). Muscle net protein breakdown decreased significantly (P < 0.05) to zero during feeding of both CAPM and SOPM, but differences in their (net) breakdown rates were not significant. Muscle protein synthesis was not different between CAPM and SOPM.


CONCLUSIONS
Moderate-nitrogen casein and soy protein meals differently alter leg amino acid uptake without a significant difference in influencing acute muscle protein metabolism.
Luiking
Yvette C
YC
Center for Translational Research in Aging & Longevity, Donald W. Reynolds Institute on Aging, University of Arkansas for Medical Sciences, Little Rock, AR 72205, USA.
Engelen
Mariëlle P K J
MP
Soeters
Peter B
PB
Boirie
Yves
Y
Deutz
Nicolaas E P
NE
D000596:Amino Acids / Q000493:pharmacokinetics; D000704:Analysis of Variance; D002364:Caseins / Q000008:administration & dosage* / Q000378:metabolism; D004044:Dietary Proteins / Q000008:administration & dosage* / Q000378:metabolism; D005260:Female; D006801:Humans; D007328:Insulin / Q000097:blood; D016014:Linear Models; D008297:Male; D009124:Muscle Proteins / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D016037:Single-Blind Method; D030262:Soybean Proteins / Q000008:administration & dosage* / Q000378:metabolism; D055815:Young Adult
D000596:Amino Acids; D002364:Caseins; D004044:Dietary Proteins; D007328:Insulin; D009124:Muscle Proteins; D030262:Soybean Proteins