A single food bolus stimulates albumin synthesis in growing piglets.
BACKGROUND
A stable isotope tracer method to quantify the synthesis of proteins of hepatic origin in response to feeding is described. The response of albumin synthesis on one mixed meal in a piglet model was investigated and the intragastric and intravenous administration modes of 13C-valine were compared.


METHODS
The fasting and postprandial fractional synthesis rates (FSRs) of albumin in 15 piglets were measured while infusion rates of 13C-valine were changed in anticipation of the increased appearance of the tracee after a single liquid food bolus (30 mL/kg infant formula). 13C-valine enrichments in albumin hydrolysates at regular time intervals were determined with gas chromatography-combustion isotope ratio mass spectrometry.


RESULTS
The intravenous mode (n = 8) showed constant plasma alpha-ketoisovalerate tracer-to-tracee ratios (coefficient of variation range: 1-8%), and a 27% increase in albumin FSR after the food bolus (mean FSR +/- standard error [SE]: fasting 14.4% +/- 1.6% vs. postprandial 18.3% +/- 2.2% per day; P < 0.005). In the intragastric mode (n = 7), albumin FSR calculated from the mean precursor values increased 32% after feeding (fasting 14.6% +/- 1.5% vs. postprandial 19.3% +/- 1.6% per day; P = 0.005), despite absence of constant alpha-ketoisovalerate enrichment (coefficient of variation range: 15-31%). The FSRs were not significantly different between both infusion modes.


CONCLUSIONS
A mixed food bolus increases albumin FSR in growing piglets by approximately 30%, irrespective of the tracer administration route. The concept of anticipated precursor steady state is applicable to study changes of hepatic protein synthesis after a single meal. The intragastric mode of tracer administration can be applied as a less invasive method to measure tissue specific protein synthesis in children.
de Meer
K
K
Laboratory for Metabolic Diseases, University Medical Centre Utrecht, The Netherlands. k.demeer@azvu.nl
Smolders
H C
HC
Meesterburrie
J
J
de Sain-van der Velden
M
M
Voorbij
H A
HA
Okken
A
A
Reijngoud
D J
DJ
Kulik
W
W
D000818:Animals; D002247:Carbon Isotopes; D004044:Dietary Proteins / Q000494:pharmacology; D004435:Eating / Q000502:physiology*; D005215:Fasting / Q000502:physiology; D005260:Female; D007262:Infusions, Intravenous; D007441:Intubation, Gastrointestinal; D007553:Isotope Labeling / Q000379:methods; D008099:Liver / Q000378:metabolism*; D023421:Models, Animal; D019518:Postprandial Period / Q000502:physiology; D011498:Protein Precursors / Q000378:metabolism*; D011897:Random Allocation; D012709:Serum Albumin / Q000096:biosynthesis* / Q000378:metabolism; D013552:Swine; D013997:Time Factors; D014633:Valine / Q000008:administration & dosage / Q000493:pharmacokinetics
D002247:Carbon Isotopes; D004044:Dietary Proteins; D011498:Protein Precursors; D012709:Serum Albumin; D014633:Valine