Summary
We examined the effects of exogenous and endogenous GIP on plasma triglyceride levels
in rats, pretreated with a fat-enriched diet, during intraduodenal infusion of a lipid
test meal (Lipomul, 8 ml/h). Following the fat load the plasma triglyceride levels
increased nearly linearly from a fasting value of 0.621 ± 0.031 mmol/l to 3.32 ± 0.403
mmol/l at 150 min. Simultaneously, the plasma GIP levels rose from 47.1 ± 5.1 at fasting
to a peak value of 268.4 ± 32.2 pmol/l at 120 min. When porcine GIP was infused intravenously
during the fat load, the plasma triglyceride increments were significantly smaller
(control 1.64 ± 0.264 mmol/l versus 0.949 ± 0.114 mmol/l during GIP infusion at 60
min; p < 0.002). GIP infusion in the absence of the fat load did not change fasting
triglyceride levels.
The effect of endogenous GIP was investigated by neutralization of GIP by injection
of GIP antiserum (0.3 ml). Rats pretreated with the antiserum exhibited a significantly
greater triglyceride increment late in the time course of the fat load. These data
demonstrate that exogenous and endogenous GIP are able to lower the plasma triglyceride
response to a fat load. Both, inhibition of fat absorption or stimulation of triglyceride
uptake by peripheral tissues may be responsible for the GIP effects. The gut peptide
GIP seems to represent an important hormonal regulator of postprandial triglyceride
response.
Key words
Gastric Inhibitory Polypeptide - Triglyceride - Metabolism - Chylomicrons - Rats
