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. 2015 Nov 10;6:260.
doi: 10.3389/fphar.2015.00260. eCollection 2015.

Study of GABA in Healthy Volunteers: Pharmacokinetics and Pharmacodynamics

Free PMC article

Study of GABA in Healthy Volunteers: Pharmacokinetics and Pharmacodynamics

Junfeng Li et al. Front Pharmacol. .
Free PMC article


Preclinical studies show that GABA exerts anti-diabetic effects in rodent models of type 1 diabetes. Because little is known about its absorption and effects in humans, we investigated the pharmacokinetics and pharmacodynamics of GABA in healthy volunteers. Twelve subjects were subjected to an open-labeled, three-period trial involving sequential oral administration of placebo, 2 g GABA once, and 2 g GABA three times/day for 7 days, with a 7-day washout between each period. GABA was rapidly absorbed (Tmax: 0.5 ~ 1 h) with the half-life (t1/2) of 5 h. No accumulation was observed after repeated oral GABA administration for 7 days. Remarkably, GABA significantly increased circulating insulin levels in the subjects under either fasting (1.6-fold, single dose; 2.0-fold, repeated dose; p < 0.01) or fed conditions (1.4-fold, single dose; 1.6-fold, repeated dose; p < 0.01). GABA also increased glucagon levels only under fasting conditions (1.3-fold, single dose, p < 0.05; 1.5-fold, repeated dose, p < 0.01). However, there were no significant differences in the insulin-to-glucagon ratio and no significant change in glucose levels in these healthy subjects during the study period. Importantly, GABA significantly decreased glycated albumin levels in the repeated dosing period. Subjects with repeated dosing showed an elevated incidence of minor adverse events in comparison to placebo or the single dosing period, most notably transient discomforts such as dizziness and sore throat. However, there were no serious adverse events observed throughout the study. Our data show that GABA is rapidly absorbed and tolerated in human beings; its endocrine effects, exemplified by increasing islet hormonal secretion, suggest potential therapeutic benefits for diabetes.

Keywords: GABA; glucagon; glycated albumin; insulin; pharmacokinetics.


Figure 1
Figure 1
Concentration-time profiles of GABA. Individual concentration-time curves of GABA in the three periods (A, repeated dose period; B, single dose period; C, placebo period). Total concentration-time curves of GABA in the three periods, data are presented as geomean ± SE (D).
Figure 2
Figure 2
Concentration-time profiles of blood glucose, insulin and glucagon. The concentration-time curves of blood glucose, insulin, and glucagon in the three periods (A–C), data are expressed as percent variation of baseline and presented as mean±SE. **p < 0.01 vs. placebo. *p < 0.05 vs. placebo.
Figure 3
Figure 3
Profiles of glycated albumin. The glycated albumin levels on day 2, 15, and 23 are shown as mean ± SE. **p < 0.01 vs. placebo; ##p < 0.01 vs. single dose.

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