Total body skeletal muscle mass: estimation by creatine (methyl-d3) dilution in humans

Current methods for clinical estimation of total body skeletal muscle mass have significant limitations. We tested the hypothesis that creatine ( methyl-d3) dilution (D3-creatine) measured by enrichment of urine D3-creatinine reveals total body creatine pool size, providing an accurate estimate of total body skeletal muscle mass. Healthy subjects with different muscle masses [ n = 35: 20 men (19–30 yr, 70–84 yr), 15 postmenopausal women (51–62 yr, 70–84 yr)] were housed for 5 days. Optimal tracer dose was explored with single oral doses of 30, 60, or 100 mg D3-creatine given on day 1. Serial plasma samples were collected for D3-creatine pharmacokinetics. All urine was collected through day 5. Creatine and creatinine (deuterated and unlabeled) were measured by liquid chromatography mass spectrometry. Total body creatine pool size and muscle mass were calculated from D3-creatinine enrichment in urine. Muscle mass was also measured by magnetic resonance imaging (MRI), dual-energy x-ray absorptiometry (DXA), and traditional 24-h urine creatinine. D3-creatine was rapidly absorbed and cleared with variable urinary excretion. Isotopic steady-state of D3-creatinine enrichment in the urine was achieved by 30.7 ± 11.2 h. Mean steady-state enrichment in urine provided muscle mass estimates that correlated well with MRI estimates for all subjects ( r = 0.868, P < 0.0001), with less bias compared with lean body mass assessment by DXA, which overestimated muscle mass compared with MRI. The dilution of an oral D3-creatine dose determined by urine D3-creatinine enrichment provides an estimate of total body muscle mass strongly correlated with estimates from serial MRI with less bias than total lean body mass assessment by DXA.

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Total-body creatine pool size and skeletal muscle mass determination by creatine-(methyl-d3) dilution in rats

Journal of Applied Physiology ◽

10.1152/japplphysiol.00122.2012 ◽

2012 ◽

Vol 112 (11) ◽

pp. 1940-1948 ◽

Cited By ~ 39

Author(s):

Stephen A. Stimpson ◽

Scott M. Turner ◽

Lisa G. Clifton ◽

James C. Poole ◽

Hussein A. Mohammed ◽

...

Keyword(s):

Skeletal Muscle ◽

Steady State ◽

Lean Body Mass ◽

Muscle Mass ◽

Body Mass ◽

Skeletal Muscle Mass ◽

The Body ◽

Pool Size ◽

Tracer Dose ◽

Total Body

There is currently no direct, facile method to determine total-body skeletal muscle mass for the diagnosis and treatment of skeletal muscle wasting conditions such as sarcopenia, cachexia, and disuse. We tested in rats the hypothesis that the enrichment of creatinine-( methyl-d3) (D3-creatinine) in urine after a defined oral tracer dose of D3-creatine can be used to determine creatine pool size and skeletal muscle mass. We determined 1) an oral tracer dose of D3-creatine that was completely bioavailable with minimal urinary spillage and sufficient enrichment in the body creatine pool for detection of D3-creatine in muscle and D3-creatinine in urine, and 2) the time to isotopic steady state. We used cross-sectional studies to compare total creatine pool size determined by the D3-creatine dilution method to lean body mass determined by independent methods. The tracer dose of D3-creatine (<1 mg/rat) was >99% bioavailable with 0.2–1.2% urinary spillage. Isotopic steady state was achieved within 24–48 h. Creatine pool size calculated from urinary D3-creatinine enrichment at 72 h significantly increased with muscle accrual in rat growth, significantly decreased with dexamethasone-induced skeletal muscle atrophy, was correlated with lean body mass ( r = 0.9590; P < 0.0001), and corresponded to predicted total muscle mass. Total-body creatine pool size and skeletal muscle mass can thus be accurately and precisely determined by an orally delivered dose of D3-creatine followed by the measurement of D3-creatinine enrichment in a single urine sample and is promising as a noninvasive tool for the clinical determination of skeletal muscle mass.

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Somatotype, Body Composition and Explosive Power of Athlete and Non-Athlete

LASE Journal of Sport Science ◽

10.1515/ljss-2016-0023 ◽

2014 ◽

Vol 5 (1) ◽

pp. 26-34

Author(s):

Saha Sukanta

Keyword(s):

College Students ◽

Skeletal Muscle ◽

Body Composition ◽

Body Weight ◽

Lean Body Mass ◽

Muscle Mass ◽

Body Mass ◽

Body Fat ◽

Skeletal Muscle Mass ◽

Explosive Power

Abstract The aim of this study was to identify the effect of somatotype and body composition variables on leg explosive power of college level men students. The sample consisted of 500 young college students, divided into two groups: athletes (N= 250) undergoing Bachelor of Physical Education course whose mean age 23.86 ± 0.36 years; and non-athletes (N= 250) college students who do not take part regular physical activities and mean age 22.16 ± 0.88 years. The somatotype was assessed using the Heath & Carter method. Assessing body composition of the subject various anthropometric measurements were taken. Sargent vertical jump test was used to measure leg explosive power. The measures were compared between the two groups using the Student t-test for independent samples. The two groups differed significantly (p≤0.01) in terms of body weight, % body fat, lean body mass, % skeletal muscle mass and somatotype. The findings of the present study showing that athlete have higher mean values in leg explosive power (p≤0.01) than non-athlete. The leg explosive power was positively significantly (p≤0.01) correlated with % skeletal muscle mass, lean body mass, mesomorphy and ectomorphy components of somatotype; on the other hand body weight, height, % body fat, body surface area and endomorphy component of somatotype significantly (p≤0.01) negatively correlated. In conclusion, somatotype and body composition variables are important factors in determining leg explosive power.

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