Please use this identifier to cite or link to this item:
|Title:||Quantification of hepatic transaldolase exchange activity and its effects on tracer measurements of indirect pathway flux in humans||Authors:||Jones, John G.
Delgado, Teresa C.
Caldeira, M. Madalena
|Issue Date:||2008||Citation:||Magnetic Resonance in Medicine. 59:2 (2008) 423-429||Abstract:||Exchange of hepatic glucose-6-phosphate (G6P) and glyceraldehyde-3-phosphate via transaldolase modifies hepatic G6P enrichment from glucose or gluconeogenic tracers. Transaldolase exchange was quantified in five healthy, fed subjects following an oral bolus of [1,2,3-13C3]glycerol (25-30 mg/kg) and paracetamol (10-12 mg/kg). 13C Isotopomers of hepatic G6P were quantified by 13C NMR spectroscopy of urinary glucuronide. [1,2,3-13C3]- and [4,5,6-13C3]glucuronide isotopomers, representing the conversion of [1,2,3-13C3]glycerol to G6P via dihydroxyacetone phosphate, were resolved from [1,2-13C2]- and [5,6-13C2]glucuronide 13C-isotopomers, derived from metabolism of [1,2,3-13C3]glycerol via pyruvate and phosphoenolpyruvate. Enrichment of [1,2,3-13C3]glucuronide was significantly less than that of [4,5,6-13C3]glucuronide (1.30 ± 0.57% versus 1.67 ± 0.42%, P < 0.05). Also, [1,2-13C2]glucuronide enrichment was significantly less than that of [5,6-13C2]glucuronide (0.28 ± 0.08% versus 0.36 ± 0.03%, P < 0.05). Transaldolase and triose phosphate isomerase exchange activities were estimated by applying the 13C-isotopomer data to a model of hepatic sugar phosphate metabolism. Triose phosphate isomerase exchange was ~99% complete and did not contribute significantly to the unequal 13C-isotopomer distributions of the glucuronide triose halves. Instead, this was attributable to 25 ± 23% of hepatic G6P flux undergoing transaldolase exchange. This results in substantial overestimates of indirect pathway contributions to hepatic glycogen synthesis with tracers such as [5-3H]glucose and 2H2O. Magn Reson Med, 2008. © 2008 Wiley-Liss, Inc.||URI:||http://hdl.handle.net/10316/8089||Rights:||openAccess|
|Appears in Collections:||FCTUC Ciências da Vida - Artigos em Revistas Internacionais|
Show full item record
Page view(s) 20526
checked on May 14, 2019
checked on May 14, 2019
Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.