Timing of vagal stimulation affects postprandial lipid metabolism in humans.
BACKGROUND
Vagal stimulation combined with an oral fat load enhances postprandial lipemia in animals and humans.


OBJECTIVE
We assessed whether the observed postprandial increase in plasma lipids could be explained by changes in exogenous (chylomicron) or endogenous (VLDL) lipid metabolism and whether the timing of vagal stimulation in relation to fat intake was important.


METHODS
Vagal stimulation was achieved by using the modified sham feeding (MSF) technique, in which food is tasted and chewed but not swallowed. Seven healthy men consumed an oral fat load (50 g) on one occasion (control protocol). On 2 other occasions, they consumed an oral fat load combined with MSF of an appetizing meal. MSF was performed for either 1 h before or 1 h after the oral fat load. Blood was collected for 7 h and was analyzed for hormones and metabolites.


RESULTS
The postprandial triacylglycerol response differed significantly (P < 0.001) between the 3 protocols. Both MSF studies resulted in significantly higher plasma pancreatic polypeptide concentrations compared with the control. Compared with MSF for 1 hour after fat intake, MSF for 1 h before fat intake resulted in significantly higher plasma insulin concentrations (P = 0.013), a more rapid rise in chylomicron triacylglycerol concentrations (P = 0.04), and higher VLDL triacylglycerol and apoliprotein B-100 concentrations.


CONCLUSIONS
Vagal stimulation enhanced postprandial lipemia via effects on both chylomicron and VLDL metabolism. MSF before fat intake had more dramatic effects on postprandial lipemia than did MSF after fat intake, possibly because of increased parasympathetic activity at the time of ingestion.
Robertson
M Denise
MD
Oxford Centre for Diabetes, Endocrinology and Metabolism, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, United Kingdom. denise.robertson@oxlip.ox.ac.uk
Mason
Andrew O
AO
Frayn
Keith N
KN
D000328:Adult; D053299:Apolipoprotein B-100; D001055:Apolipoproteins B / Q000097:blood; D001786:Blood Glucose / Q000032:analysis; D002914:Chylomicrons / Q000097:blood; D004041:Dietary Fats / Q000008:administration & dosage; D005502:Food; D006801:Humans; D007700:Kinetics; D008055:Lipids / Q000097:blood*; D008079:Lipoproteins, VLDL / Q000097:blood; D008297:Male; D010191:Pancreatic Polypeptide / Q000097:blood; D013997:Time Factors; D014280:Triglycerides / Q000097:blood; D014630:Vagus Nerve / Q000502:physiology*
D053299:Apolipoprotein B-100; D001055:Apolipoproteins B; D001786:Blood Glucose; D002914:Chylomicrons; D004041:Dietary Fats; D008055:Lipids; D008079:Lipoproteins, VLDL; D014280:Triglycerides; D010191:Pancreatic Polypeptide