Deuterated Creatine Dilution to Assess Muscle Mass (D3-Cr Muscle Mass) in Humans: Methods, Early Results, and Future Directions
This chapter describes the operational aspects of the deuterated creatine (D3-Cr) dilution protocol including the methods for administering the timed dose and urine collection and calculation of creatine (Cr) pool size and muscle mass. The D3-Cr dilution method provides a direct measurement of Cr pool size which is used to calculate muscle mass. The excretion of creatinine and measurement of D3-Crn enrichment in urine provides an opportunity to “sample” the intra-myocellular enrichment of D3-Cr and determine the dilution of the oral D3-Cr label in the whole-body Cr pool in skeletal muscle. The most challenging part of the D3-Cr dilution protocol is the timing of the dose and subsequent fasting urine collection. Use of height to standardize lean mass measure to body size avoids the problems particular to dual energy x-ray absorptiometry and other compartment models. D3-Cr muscle mass/weight is therefore the recommended approach to analyze data.
