{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,22]],"date-time":"2026-10-22T22:08:59Z","timestamp":1792706939893,"version":"4.5.0"},"reference-count":31,"publisher":"American Physiological Society","issue":"1","funder":[{"DOI":"10.13039\/100004330","name":"GlaxoSmithKline (GSK)","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100004330","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Journal of Applied Physiology"],"published-print":{"date-parts":[[2018,1,1]]},"abstract":"<jats:p>\n                    A noninvasive method to estimate muscle mass based on creatine ( methyl-d\n                    <jats:sub>3<\/jats:sub>\n                    ) (D\n                    <jats:sub>3<\/jats:sub>\n                    -creatine) dilution using fasting morning urine was evaluated for accuracy and variability over a 3- to 4-mo period. Healthy older (67- to 80-yr-old) subjects ( n = 14) with muscle wasting secondary to aging and four patients with chronic disease (58\u201376 yr old) fasted overnight and then received an oral 30-mg dose of D\n                    <jats:sub>3<\/jats:sub>\n                    -creatine at 8 AM ( day 1). Urine was collected during 4 h of continued fasting and then at consecutive 4- to 8-h intervals through day 5. Assessment was repeated 3\u20134 mo later in 13 healthy subjects and 1 patient with congestive heart failure. Deuterated and unlabeled creatine and creatinine were measured using liquid chromatography\u2013tandem mass spectrometry. Total body creatine pool size and muscle mass were calculated from D\n                    <jats:sub>3<\/jats:sub>\n                    -creatinine enrichment in urine. Muscle mass was also measured by whole body MRI and 24-h urine creatinine, and lean body mass (LBM) was measured by dual-energy X-ray absorptiometry (DXA). D\n                    <jats:sub>3<\/jats:sub>\n                    -creatinine urinary enrichment from day 5 provided muscle mass estimates that correlated with MRI for all subjects ( r\u2009=\u20090.88, P &lt; 0.0001), with less bias [difference from MRI\u2009= \u22123.00\u2009\u00b1\u20092.75 (SD) kg] than total LBM assessment by DXA, which overestimated muscle mass vs. MRI (+22.5\u2009\u00b1\u20093.7 kg). However, intraindividual variability was high with the D\n                    <jats:sub>3<\/jats:sub>\n                    -creatine dilution method, with intrasubject SD for estimated muscle mass of 2.5 kg vs. MRI (0.5 kg) and DXA (0.8 kg). This study supports further clinical validation of the D\n                    <jats:sub>3<\/jats:sub>\n                    -creatine method for estimating muscle mass.\n                  <\/jats:p>\n                  <jats:p>\n                    NEW &amp; NOTEWORTHY Measurement of creatine ( methyl-d\n                    <jats:sub>3<\/jats:sub>\n                    ) (D\n                    <jats:sub>3<\/jats:sub>\n                    -creatine) and D\n                    <jats:sub>3<\/jats:sub>\n                    -creatinine excretion in fasted morning urine samples may be a simple, less costly alternative to MRI or dual-energy X-ray absorptiometry (DXA) to calculate total body muscle mass. The D\n                    <jats:sub>3<\/jats:sub>\n                    -creatine enrichment method provides estimates of muscle mass that correlate well with MRI, and with less bias than DXA. However, intraindividual variability is high with the D\n                    <jats:sub>3<\/jats:sub>\n                    -creatine method. Studies to refine the spot urine sample method for estimation of muscle mass may be warranted.\n                  <\/jats:p>","DOI":"10.1152\/japplphysiol.00455.2016","type":"journal-article","created":{"date-parts":[[2017,8,31]],"date-time":"2017-08-31T21:11:56Z","timestamp":1504213916000},"page":"1-9","source":"Crossref","is-referenced-by-count":64,"title":["Creatine (\n                    <i>methyl<\/i>\n                    -d\n                    <sub>3<\/sub>\n                    ) dilution in urine for estimation of total body skeletal muscle mass: accuracy and variability vs. MRI and DXA"],"prefix":"10.1152","volume":"124","author":[{"given":"Richard V.","family":"Clark","sequence":"first","affiliation":[{"name":"Muscle Metabolism Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ann C.","family":"Walker","sequence":"additional","affiliation":[{"name":"Muscle Metabolism Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Ram R.","family":"Miller","sequence":"additional","affiliation":[{"name":"Muscle Metabolism Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Robin L.","family":"O\u2019Connor-Semmes","sequence":"additional","affiliation":[{"name":"Muscle Metabolism Discovery Performance Unit, GlaxoSmithKline, Research Triangle Park, North Carolina"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eric","family":"Ravussin","sequence":"additional","affiliation":[{"name":"Pennington Biomedical Research Center, Baton Rouge, Louisiana"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"William T.","family":"Cefalu","sequence":"additional","affiliation":[{"name":"Pennington Biomedical Research Center, Baton Rouge, Louisiana"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"24","reference":[{"key":"B1","doi-asserted-by":"publisher","DOI":"10.2165\/00007256-199418040-00005"},{"key":"B2","doi-asserted-by":"publisher","DOI":"10.1177\/0148607111417448"},{"key":"B3","doi-asserted-by":"publisher","DOI":"10.1016\/j.nutres.2015.09.003"},{"key":"B4","doi-asserted-by":"publisher","DOI":"10.1093\/gerona\/glv129"},{"key":"B5","doi-asserted-by":"publisher","DOI":"10.1016\/S0140-6736(86)90837-8"},{"key":"B6","doi-asserted-by":"publisher","DOI":"10.1016\/j.jocd.2015.05.063"},{"key":"B7","doi-asserted-by":"publisher","DOI":"10.1111\/j.1532-5415.2009.02366.x"},{"key":"B8","doi-asserted-by":"publisher","DOI":"10.1093\/gerona\/glu023"},{"key":"B9","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00045.2014"},{"key":"B10","doi-asserted-by":"publisher","DOI":"10.1002\/jcsm.12082"},{"key":"B11","doi-asserted-by":"publisher","DOI":"10.1378\/chest.92.5.883"},{"key":"B12","doi-asserted-by":"publisher","DOI":"10.1172\/JCI104929"},{"key":"B13","doi-asserted-by":"publisher","DOI":"10.1136\/jcp.18.1.74"},{"key":"B14","doi-asserted-by":"publisher","DOI":"10.1042\/cs0810249"},{"key":"B15","doi-asserted-by":"publisher","DOI":"10.1152\/ajpendo.1994.266.5.E725"},{"key":"B16","doi-asserted-by":"publisher","DOI":"10.1042\/cs0830367"},{"key":"B17","doi-asserted-by":"publisher","DOI":"10.1093\/ajcn\/37.3.478"},{"key":"B18","doi-asserted-by":"publisher","DOI":"10.1093\/ajcn\/50.5.1167"},{"key":"B20","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00260.2004"},{"key":"B21","doi-asserted-by":"publisher","DOI":"10.1093\/ajcn\/76.2.378"},{"key":"B22","doi-asserted-by":"publisher","DOI":"10.1152\/jappl.1970.28.3.264"},{"key":"B23","doi-asserted-by":"publisher","DOI":"10.4155\/bio.13.323"},{"key":"B24","doi-asserted-by":"publisher","DOI":"10.1007\/s12603-011-0049-x"},{"key":"B25","doi-asserted-by":"publisher","DOI":"10.2165\/00003088-200342060-00005"},{"key":"B26","doi-asserted-by":"publisher","DOI":"10.1152\/physiolgenomics.00157.2007"},{"key":"B27","doi-asserted-by":"publisher","DOI":"10.1046\/j.1365-201X.1998.0298f.x"},{"key":"B28","doi-asserted-by":"publisher","DOI":"10.1007\/s13539-013-0110-1"},{"key":"B29","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00122.2012"},{"key":"B30","doi-asserted-by":"publisher","DOI":"10.1080\/02841860802130001"},{"key":"B31","doi-asserted-by":"publisher","DOI":"10.1093\/rheumatology\/39.3.293"},{"key":"B32","doi-asserted-by":"publisher","DOI":"10.1152\/physrev.2000.80.3.1107"}],"container-title":["Journal 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