Abstract
Context: Glucagon-like peptide-1 (GLP-1) agonists control postprandial glucose and lipid excursion in type 2 diabetes; however, the mechanisms are unclear.
Objective: To determine the mechanisms of postprandial lipid and glucose control with lixisenatide (GLP-1 analog) in type 2 diabetes.
Design: Randomized, double-blind, cross-over study.
Setting: Centre for Diabetes, Endocrinology, and Research, Royal Surrey County Hospital, Guildford, United Kingdom.
Patients: Eight obese men with type 2 diabetes [age, 57.3 +/- 1.9 years; body mass index, 30.3 +/- 1.0 kg/m(2); glycosylated hemoglobin, 66.5 +/- 2.6 mmol/mol (8.2% +/- 0.3%)].
Interventions: Two metabolic studies, 4 weeks after lixisenatide or placebo, with cross-over and repetition of studies.
Main Outcome Measures: Study one: very-low-density lipoprotein (VLDL) and chylomicron (CM) triacylglycerol (TAG) kinetics were measured with an IV bolus of [H-2(5)]glycerol in a 12-hour study, with hourly feeding. Oral [C-13]triolein, in a single meal, labeled enterally derived TAG. Study two: glucose kinetics were measured with [U-C-13]glucose in a mixed-meal (plus acetaminophen to measure gastric emptying) and variable IV [6,6-H-2(2)]glucose infusion.
Results: Study one: CM-TAG (but not VLDL-TAG) pool-size was lower with lixisenatide (P = 0.046). Lixisenatide reduced CM [C-13]oleate area under the curve (AUC)(60-480min) concentration (P = 0.048) and increased CM-TAG clearance, with no effect on CM-TAG production rate. Study two: postprandial glucose and insulin AUC(0-240min) were reduced with lixisenatide (P = 0.0051; P < 0.05). Total glucose production (P = 0.015), rate of glucose appearance from the meal (P = 0.0098), and acetaminophen AUC(0-360min) (P = 0.006) were lower with lixisenatide than with placebo.
Conclusions: Lixisenatide reduced [C-13]oleate concentrations, derived from a single meal in CM-TAG and glucose rate of appearance from the meal through delayed gastric emptying. However, daylong CM production, measured with repeated meal feeding, was not reduced by lixisenatide and decreased CM-TAG concentration resulted from increased CM-TAG clearance.