D3-Creatine Dilution to Assess Muscle Mass

Etiquetas de revisión

Datos neutrales que nuestra revisión registró sobre cómo se hizo este estudio. Describen el método, nunca si nos gusta el resultado.

Cómo se estudió

Diseño

Estudio de cohortes (indexado por PubMed)

Estudiado en

Personas

Resultado principal

Marcadores de salud y funcionamiento

Quién lo pagó

Financiación

Financiación no declarada

Publicación

Publicado

2018-09-12 · J Gerontol A Biol Sci Med Sci · vol. 74 · número 6 · págs. 842–843

Editorial

Oxford University Press

Citado

16 citas · más que el 76% de estudios similares · 1.0× el promedio de su campo

Referencias

15 trabajos

Acceso

Lectura gratuita

Áreas de investigación

Nutrition and Health in Aging · Body Composition Measurement Techniques · Muscle metabolism and nutrition

Palabras clave

Creatine, Dilution, Muscle mass, Medicine, Physical medicine and rehabilitation, Internal medicine, Physics

MeSH

humans, creatine, incidence, prospective studies, accidental falls, aged, male, mobility limitation, physical functional performance

1 autor

• Laura A Schaap🇳🇱 · autor de correspondenciaVrije Universiteit Amsterdam

Texto inicial

El texto original del estudio, en el idioma en que se publicó.

Este estudio se publicó sin resumen, como suele pasar con las cartas de investigación y los reportes breves. Así empieza; el texto completo se puede leer gratis.

In this issue of the Journal of Gerontology, Cawthon and colleagues (1) report on D3-creatine dilution, a novel method to assess muscle mass in human populations, finding a more robust association with function in older men in the osteoporosis in men (MrOs) cohort study than has been seen with dual-energy x-ray absorptiometry (DXA). Previous studies have relied on DXA to assess sarcopenia. Health ABC used both DXA and cross-sectional thigh and abdominal computed tomography (CT) scanning to determine how body composition relates to disability. Using various analytic approaches, fat mass and muscle strength were found to be most strongly related to physical function (2), and strength was more strongly related to mortality than muscle mass (3). Though muscle mass clearly declines with age in longitudinal analysis (4,5) it has been difficult to identify an independent association of a single measure of lean mass with health outcomes. Although limited to a study in older men, this report by Cawthon illustrates the issues with the ability of DXA to quantify muscle mass and validates the D3-creatine approach. Muscle mass assessment methods have had significant issues with cost, accuracy, and radiation dose. Methods in use include CT scanning to assess muscle cross-sectional area, magnetic resonance imaging (MRI, areal and whole body), bioelectric impedance (BIA), and DXA of appendicular fat-free (lean) mass (ALM). DXA is currently most widely used in research and the clinic because of its low radiation dose and lower cost. It also has the advantage of accurately assessing bone and fat mass. Several groups have developed sarcopenia metrics that include DXA ALM (6–8). In contrast to DXA, deuterated creatine (D3-creatine) assesses muscle mass directly. D3-creatine is a stable isotope that is given orally in water and distributes to the muscle compartment. The creatine is digested, absorbed, and transported into muscle against a gradient and is metabolized irreversibly into creatinine which is excreted in the urine. Enrichment of labeled creatinine in the urine is related to skeletal muscle labelled creatine enrichment and whole body (skeletal muscle) creatine pool size, thus muscle mass. This relationship has been validated against independent measures of muscle mass in rats (9) and validated against whole-body magnetic resonance imaging (MRI) in men and women across a range of ages (10). In the Clark methods article (10), the D3-creatine was compared with DXA ALM as well as MRI and 24-hour creatinine, showing that DXA ALM was biased toward higher values for lean mass at higher body weights when compared with MRI or D3-creatine. With aging, fat infiltrates muscle, and this important feature of aging is not detected by DXA, since intermuscular and intramuscular fat are read as lean mass. In obesity, fat mass is increased in all fat depots including intermuscular and intramuscular fat, leading to bias in the assessment of DXA ALM. Of critical importance, muscle and fat are related to function in opposite directions, thus the role of muscle mass for function is essentially partly canceled by fat when DXA is used to define muscle mass. By isolating contractile muscle mass from noncontractile components including fat, the D3-creatine assessment is not only an accurate method to assess muscle mass but is less biased by obesity and aging than DXA ALM. This may be especially important in women who have a larger relative amount of body fat for size compared with men. The D3-creatine method will require additional validation in women, but is likely to be as accurate as in men. The field of sarcopenia has not come to consensus as to the optimal way to consider adiposity and body size when defining sarcopenia in an individual. Muscle mass is always related to total body size and adiposity and, as noted previously, differs substantially between men and women. Different approaches to adjust for adiposity and body size exist and involve either correction for height, body mass or BMI. Each of these approaches has a different effect on the classification of low muscle mass, and subsequently, on the association with health outcomes (11). For example, when ALM is divided by height squared, the lowest values of this measure will be found in relatively thin subjects with low fat mass. On the contrary, when ALM is divided by a measure of weight or BMI, lower values will be present in heavier subjects who have relatively more fat mass. This is in line with Table 1 of the present report, which shows that those with a higher D3-creatine/body mass have a lower percent body fat, while those with a lower D3-creatine/body mass have a higher percent body fat. The different effects of various adiposity adjustments need to be carefully considered when interpreting associations between muscle mass metrics with outcomes. In the present report, several analytic approaches to adjust for adiposity were compared in the MrOs cohort. The primary approach presented adjusted the D3-creatine value for muscle mass by dividing muscle mass by total body mass (weight). This approach provided the strongest association with function. The results of this approach were compared with the results of DXA ALM divided by height squared in Figure 2. However, a direct comparison between these muscle mass metrics on outcomes is difficult, as explained earlier. A better interpretable comparison could involve D3-creatine/body mass and DXA ALM/body mass, which is presented in the supplementary tables. Although the odds for poor function remain strongest for D3-creatine/body mass, the differences with DXA ALM/body mass are smaller, and associations point in the same direction. On the other hand, poor associations were found when D3-creatine was divided by height squared. Further inspection of the supplementary tables shows strong inverse associations of percentage body fat (measured by DXA) with function. These findings clearly show that the use various analytic approaches to adjust for adiposity yield different results for associations with function. The findings of these secondary analyses presented in the supplementary tables are very informative and show the importance of adiposity in the association between muscle mass and outcomes. Overall, the findings of the report by Cawthon and colleagues suggest that DXA is very useful for qualifying body fat but less suitable for the estimation of lean mass. Conversely, the D3-creatine is an accurate measure of muscle mass but it does not give us information about the location and distribution of fat. Several studies of CT scan and MRI (5,12) suggest that these methods can distinguish between fat and muscle better than DXA, but more work is needed to define the role of these imaging modalities in classifying an individual as sarcopenic or sarcopenic obese. Given that intramuscular, intermuscular, and subcutaneous fat depots (2,13,14), each have unique contributions to health outcomes in older adults, I can only conclude that a combination of multiple methods is needed to fully describe body composition. The D3-creatine dilution method is clearly well validated in men as a method that is isolating the impact of muscle mass on function. Future work should include D3-creatine along with measures of adiposity to better determine ideal body composition in health and with aging.

Texto vía OpenAlex. Los derechos de autor siguen siendo de los autores o la editorial.

Confianza de la comunidad

Cargando…

¿Cuánto confías en los hallazgos de este estudio?

Comentarios

¿Algo está mal aquí?

Señala este estudio si su información, etiquetas o financiación parecen incorrectas. Un editor revisa cada señalamiento.