The use of stable isotope tracer techniques to measure muscle protein fractional synthesis rate (FSR) has been well established and widely used. The most common method that has been utilized so far is a primed constant infusion (CI) method, which requires 3–4 h of tracer infusion. However, recently our group has developed a bolus injection (BI) method, which requires an injection of bolus of tracer and can be completed within 1 h. In this study, we compared calf (gastrocnemius) muscle protein FSR measured using these two different methods — CI and BI.
FSRs were measured in eight people (5 men and 3 women; age: 62.3 ± 6.9 years (mean ± SD); body weight: 75.4 ± 21.5 kg) at basal, postabsorptive state using L-[ring-2H5]-phenylalanine. In the CI protocol, a primed continuous infusion was given for 4 h, and muscle biopsies were taken at 120 and 240 min; in the BI, a bolus injection of the tracer was given at 0 min and biopsies were taken at 5 and 60 min. Tracer enrichments in blood and muscle tissue were determined by gas chromatography–mass spectrometry. Data are expressed as mean ± SE; t-test, linear regression and Levene Median equal variance test analyses were performed.
CI FSR was 0.066 ± 0.006%/h, whereas BI FSR was 0.058 ± 0.008%/h, p = NS. The linear regression analysis showed a significant relationship between BI and CI, p = 0.038. The intra-class correlation coefficient was 0.83. The standard deviation of the differences in the measurements was 0.015%/h. The Levene Median equal variance test demonstrated no difference in variance between the CI and BI measurements (p = 0.722).
No difference could be detected in calf muscle protein FSR measured by CI and BI methods; the BI method can be used for the measurement of muscle protein FSR in humans.
Abbreviations:BI (bolus method), CI (constant infusion method), FD (flooding dose), FBR (fractional breakdown rate), FSR (fractional synthesis rate), GC-MS (gas chromatography–mass spectrometry), PAD (peripheral arterial disease)
To read this article in full you will need to make a payment
Purchase one-time access:Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
One-time access price info
- For academic or personal research use, select 'Academic and Personal'
- For corporate R&D use, select 'Corporate R&D Professionals'
Subscribe:Subscribe to Metabolism - Clinical and Experimental
Already a print subscriber? Claim online access
Already an online subscriber? Sign in
Register: Create an account
Institutional Access: Sign in to ScienceDirect
- Isotopic tracers in metabolic research: principles and practice of kinetic analysis.Wiley-Liss, New Jersey2005
- Measurement of protein synthesis in human tissues by the flooding method.Curr Opin Clin Nutr Metab Care. 1998; 1: 455-460
- Assessment of the mathematical issues involved in measuring the fractional synthesis rate of protein using the flooding dose technique.Clin Sci. 1993; 84: 177-183
- Comparison of constant infusion and flooding dose techniques to measure muscle protein synthesis rate in dogs.J Nutr. 1992; 122: 878-887
- Effects of flooding amino acids on incorporation of labeled amino acids into human muscle protein.Am J Physiol. 1998; 275: E73-E78
- Measurement of muscle protein fractional synthesis and breakdown rates from a pulse tracer injection.Am J Physiol. 2002; 283: E753-E764
- Minimal whey protein with carbohydrate stimulates muscle protein synthesis following resistance exercise in trained young men.Appl Physiol Nutr Metab. 2007; 32: 1132-1138
- Amino acids stimulate leg muscle protein synthesis in peripheral arterial disease.J Vasc Surg. 2007; 45: 554-560
- Use of a heated superficial hand vein as an alternative site for the measurement of amino acid concentrations and for the study of glucose and alanine kinetics in man.Metabolism. 1981; 30: 936-940
- Stable isotope tracer analysis by GC-MS, including quantification of isotopomer effects.Am J Physiol. 1992; 263: E584-E596
- Methods for measuring tissue protein breakdown rate in vivo.Curr Opin Clin Nutr Metab Care. 2005; 8: 534-537
- Measurement of the rate of protein synthesis in muscle of postabsorptive young men by injection of a “flooding dose” of [1-13C]leucine.Clin Sci (Lond). 1989; 77: 329-336
- Resistance exercise increases AMPK activity and reduces 4E-BP1 phosphorylation and protein synthesis in human skeletal muscle.J Physiol. 2006; 576: 613-624
- Resistance exercise maintains skeletal muscle protein synthesis during bed rest.J Appl Physiol. 1997; 82: 807-810
- Protein synthesis rates in human muscles: neither anatomical location nor fibre-type composition are major determinants.J Physiol. 2005; 563: 203-211
- Effect of weight loss on the rate of muscle protein synthesis during fasted and fed conditions in obese older adults.Obesity. 2012; 20: 1780-1786
- Human muscle protein turnover—why is it so variable?.J Appl Physiol. 2011; 110: 480-491
Published online: September 26, 2014
Accepted: September 20, 2014
Received: July 18, 2014
© 2014 Elsevier Inc. Published by Elsevier Inc. All rights reserved.