title: Relationship between fat-free mass and urinary excretion of creatinine and 3-methylhistidine in adult humans.
abstract: The urinary excretion of endogenous creatinine (CRTN) and 3-methylhistidine (3-MH) has been proposed as a predictor of fat-free mass (FFM) in healthy subjects. In this study, we report the relationship between FFM, estimated by densitometry plus deuterium dilution, and daily urinary excretion of CRTN and 3-MH in a sample of 20 healthy adult subjects of both sexes. 3-MH and CRTN were measured in 2 days of urine collection, which followed 4 days of meat-free diet. Meat-free diet was maintained throughout the period of urine collection. The mean of 2 days of excretion of 3-MH was 237.7 +/- 87.3 (SD) and 138.9 +/- 31.2 mumol/day in men and women, respectively. The mean CRTN excretion was 1.51 +/- 0.22 and 0.98 +/- 0.15 g/day in men and women, respectively. CRTN excretion was found well associated with FFM (R2 = 0.89; P < 0.0001), whereas 3-MH was lightly associated with FFM (R2 = 0.33; P < 0.01). Residuals from the regression of 3-MH vs. FFM were found to be correlated with CRTN excretion and FFM (R2 = 0.57 and 0.67, respectively), suggesting that muscularity and the absolute amount of lean mass are relevant for the error in predicting FFM from 3-MH excretion. Data confirm that urinary CRTN excretion can be an expedient indirect method for evaluating body composition in healthy adult subjects. Data also suggest that the relationship between 3-MH and FFM is complex, limiting the possibility of predicting body composition from the excretion of this metabolite.
authors.affiliation: Unit of Human Nutrition, National Institute of Nutrition, Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Virgili
authors.forename: G
authors.initials: G
authors.lastname: Maiani
authors.forename: Z H
authors.initials: ZH
authors.lastname: Zahoor
authors.forename: D
authors.initials: D
authors.lastname: Ciarapica
authors.forename: A
authors.initials: A
authors.lastname: Raguzzini
authors.forename: A
authors.initials: A
authors.lastname: Ferro-Luzzi
mesh_terms: D000328:Adult; D001823:Body Composition / Q000502:physiology*; D001834:Body Water / Q000502:physiology; D001835:Body Weight / Q000502:physiology; D003404:Creatinine / Q000652:urine*; D017666:Deuterium Oxide; D004032:Diet; D014676:Diet, Vegetarian; D005260:Female; D006801:Humans; D008297:Male; D008762:Methylhistidines / Q000652:urine*; D012115:Residual Volume
chemical_list: D008762:Methylhistidines; D003404:Creatinine; D017666:Deuterium Oxide; C028118:3-methylhistidine