Background and Objectives
Rebaudioside A, a steviol glycoside, is deglycosylated by intestinal microflora prior to the absorption of steviol and conjugation to steviol glucuronide. While glucose-lowering properties are observed for rebaudioside A in mice, they have been attributed to the metabolites steviol and steviol glucuronide. We aimed to characterize the pharmacokinetic and pharmacodynamic properties of rebaudioside A and its metabolites in patients with early-onset type 2 diabetes mellitus (T2DM).
This randomized, placebo-controlled, open-label, two-way crossover trial was performed in subjects with T2DM on metformin or no therapy at the University Hospitals Leuven, Belgium. Following oral rebaudioside A (3 g), plasma concentrations of rebaudioside A, steviol and steviol glucuronide were determined. The effect on glucose homeostasis was examined by an oral glucose tolerance test (OGTT) performed 19 h following rebaudioside A administration, i.e. the presumed time of maximal steviol and steviol glucuronide concentrations. The primary pharmacodynamic endpoint was the difference in area under the blood glucose concentration–time curve during the first 2 h of the OGTT (AUCGlucose(0–2h)) for rebaudioside A vs. placebo.
In total, 30 subjects [63.5 (57.8–69.0) years of age, 86.7% male] completed the trial. Rebaudioside A was detected as early as 1 h after administration in nearly all subjects. As expected, steviol and steviol glucuronide reached their maximal concentrations at 19.5 h following rebaudioside A administration. Rebaudioside A did not lower the AUCGlucose(0–2h) compared to placebo (− 0.7 (95% CI − 22.3; 20.9) h·mg/dL, P = 0.95). Insulin and C-peptide concentrations were also comparable between both conditions (P > 0.05).
Rebaudioside A is readily absorbed after oral administration and metabolized to steviol and steviol glucuronide. However, no effect on glucose nor insulin or C-peptide excursion was observed during the OGTT at the time of maximal metabolite concentrations. Thus, no antidiabetic properties of rebaudioside A could be observed in patients with T2DM after single oral use.