Enhancement of beta-cell sensitivity to glucose by oral fat load.
Recent studies have demonstrated that 6 h infusions of lipid emulsion enhance insulin release, whereas 24 h infusions inhibit insulin secretion. How insulin release is modulated after oral fat loading has not yet been elucidated. 17 healthy fasting volunteers were subjected to 3 experiments in random order: test 1 was a frequently sampled i. v. glucose tolerance test (FSIVGTT, 0.3 g/kg glucose), test 2 began with the ingestion of 50 % sunflower oil (1.5 g/kg) followed by FSIVGTT 4 h later. Test 3 was identical to test 2 with i. v. addition of 100 U/kg heparin prior to FSIVGTT. Glucose and insulin data were analyzed by minimal model assumptions - glucose sensitivity of the beta-cells (Theta1), acute insulin response (AIR) (10 min), 3 h insulin release (Theta2), glucose threshold of insulin secretion (h), insulin degradation rate (n), peripheral insulin sensitivity (S(I)), and glucose-dependent glucose disposal (S(G)). After drinking the fat emulsion, FFAs increased to 0.8 +/- 0.3 mmol/l (test 2) and to 3.0 +/- 0.3 mmol/l (test 3). Moderately increased FFA concentrations were associated with elevation of Theta1 (test 1, control 335 +/- 157 vs. test 2: 859 +/- 612 pM x min x mM(-1), p = 0.030). At high plasma FFA levels and in the presence of heparin (test 3), Theta1 was reduced compared to test 2 and unchanged compared to test 1. Theta2 and h were elevated in both tests 2 and 3 compared to test 1. No changes of n, S(I) and S(G) were found. In conclusion, the ingestion of sunflower oil triglyceride emulsion resulted in a 60 % increase in plasma free fatty acids and enhanced the capacity of beta-cells to secrete insulin. Heparin-induced high levels of FFA further augmented the total insulin release and inhibited parameters of glucose responsiveness.
Wuesten
O
O
Division of Gastroenterology, Medical Clinic III, Justus Liebig University of Giessen, 35392 Giessen, Germany.
Balz
C H
CH
Kloer
H U
HU
Bretzel
R G
RG
Linn
T
T
D000273:Adipose Tissue / Q000378:metabolism; D000328:Adult; D004041:Dietary Fats / Q000008:administration & dosage*; D005217:Fat Emulsions, Intravenous / Q000008:administration & dosage; D005230:Fatty Acids, Nonesterified / Q000097:blood / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000494:pharmacology*; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood / Q000378:metabolism*; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects* / Q000378:metabolism; D007700:Kinetics; D008071:Lipoprotein Lipase / Q000378:metabolism; D008297:Male
D004041:Dietary Fats; D005217:Fat Emulsions, Intravenous; D005230:Fatty Acids, Nonesterified; D007328:Insulin; D008071:Lipoprotein Lipase; D005947:Glucose