caa a22 4500 388097396 CHVBK 20180307125307.0 cr unu---uuuuu 161130e199911 xx s 000 0 eng 10.1017/S0029665199001275 doi S0029665199001275 pii (NATIONALLICENCE)cambridge-10.1017/S0029665199001275 Landau Bernard R. Departments of Medicine, Biochemistry, and Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4951, USA Quantifying the contribution of gluconeogenesis to glucose production in fasted human subjects using stable isotopes [Elektronische Daten] [Bernard R. Landau] The contribution of gluconeogenesis to glucose production is estimated from the enrichment of the H bound to C-5 of glucose relative to either that bound to C-2 of glucose or the enrichment in body water on ingesting 2H2O in the fasted state. Contributions of all gluconeogenic substrates are included in the estimate and the limitation of an uncertain precursor enrichment removed. The half-life of 2H2O in body water precludes a repeat study for many weeks. Glycogen cycling could result in underestimation, but there is evidence that glycogen cycling does not occur in liver in the fasted state. Gluconeogenesis has been estimated by mass-isotopomer-distribution analyses, usually by administering 13C-labelled glycerol. Underestimates emphasize the major limitation of the method, i.e. the need to assume a single enrichment of the precursor pool. Estimates of gluconeogenesis from isotopomer distribution in arterial-blood glucose and lactate on infusing [U-13C6] glucose are unreliable, as a proportion of the glucose is formed from glycerol and from amino acids not converted to glucose via pyruvate. Loss of label in the Krebs cycle and relying on enrichment of arterial-blood lactate as a measure of hepatic pyruvate further add to the uncertainty. Estimates of the rate of gluconeogenesis by NMR are obtained by subtraction of the rate of glycogenolysis determined by NMR from the rate of glucose production. Estimates are then the mean rate for the period over which glycogen contents are measured. Technical considerations can limit the accuracy of analyses and result in overestimates. The Nutrition Society 2H-labelled water nationallicence Gluconeogenesis nationallicence Stable isotopes nationallicence NMR nationallicence Mass-isotopomer analysis nationallicence Proceedings of the Nutrition Society Cambridge University Press 58/4(1999-11), 963-972 0029-6651 58:4<963 1999 58 PNS https://doi.org/10.1017/S0029665199001275 text/html Onlinezugriff via DOI 1 conference jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0029665199001275 text/html Onlinezugriff via DOI NATIONALLICENCE 100 1- Landau Bernard R. Departments of Medicine, Biochemistry, and Nutrition, Case Western Reserve University School of Medicine, Cleveland, OH 44106-4951, USA NATIONALLICENCE 773 0- Proceedings of the Nutrition Society Cambridge University Press 58/4(1999-11), 963-972 0029-6651 58:4<963 1999 58 PNS CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge