Quantitative comparison of pathways of hepatic glycogen repletion in fed and fasted humans
- Yale Univ. School of Medicine, New Haven, CT (USA)
The effect of fasting vs. refeeding on hepatic glycogen repletion by the direct pathway, i.e., glucose----glucose 6-phosphate (G-6-P)----glycogen, was determined. Acetaminophen was administered during an infusion of glucose labeled with (1-13C)- and (6-14C)glucose into four healthy volunteers after an overnight fast and into the same subjects 4 h after breakfast. 13C enrichments in C-1 and C-6 of glucose formed from urinary acetaminophen glucuronide compared with enrichments in C-1 and C-6 of plasma glucose provided an estimate of glycogen formation by the direct pathway. The specific activity of glucose from the glucuronide compared with the specific activity of the plasma glucose, along with the percentages of 14C in C-1 and C-6 of the glucose from the glucuronide, also provided an estimate of the amount of glycogen formed by the direct pathway. The estimates were similar. Those from (6-14C)glucose would have been higher than from (1-13C)glucose if the pentose cycle contribution to overall glucose utilization had been significant. After an overnight fast, during the last hour of infusion, 49 +/- 3% of the glycogen formed was formed via the direct pathway. After breakfast, at similar plasma glucose and insulin concentrations, the percentage increased to 69 +/- 7% (P less than 0.02). Thus the contributions of the pathways to hepatic glycogen formation depend on the dietary state of the individual. For a dietary regimen in which individuals consume multiple meals per day containing at least a moderate amount of carbohydrates most glycogen synthesis occurs by the direct pathway.
- OSTI ID:
- 6369421
- Journal Information:
- American Journal of Physiology; (USA), Journal Name: American Journal of Physiology; (USA) Vol. 259; ISSN 0002-9513; ISSN AJPHA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
BODY
CARBOHYDRATES
CARBON 13
CARBON 14 COMPOUNDS
CARBON ISOTOPES
DIGESTIVE SYSTEM
EVEN-ODD NUCLEI
FASTING
GLANDS
GLUCOSE
GLYCOGEN
HEXOSES
ISOTOPE APPLICATIONS
ISOTOPE DILUTION
ISOTOPES
LABELLED COMPOUNDS
LIGHT NUCLEI
LIVER
METABOLISM
MONOSACCHARIDES
NUCLEI
ORGANIC COMPOUNDS
ORGANS
POLYSACCHARIDES
SACCHARIDES
STABLE ISOTOPES
SYNTHESIS
TRACER TECHNIQUES