Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Mar 23;7(1):374.
doi: 10.1038/s41598-017-00515-y.

Clinically Applicable GABA Receptor Positive Allosteric Modulators Promote ß-Cell Replication

Affiliations
Free PMC article

Clinically Applicable GABA Receptor Positive Allosteric Modulators Promote ß-Cell Replication

Jide Tian et al. Sci Rep. .
Free PMC article

Abstract

A key goal of diabetes research is to develop treatments to safely promote human ß-cell replication. It has recently become appreciated that activation of γ-aminobutyric acid receptors (GABA-Rs) on ß-cells can promote their survival and replication. A number of positive allosteric modulators (PAMs) that enhance GABA's actions on neuronal GABAA-Rs are in clinical use. Repurposing these GABAA-R PAMs to help treat diabetes is theoretically appealing because of their safety and potential to enhance the ability of GABA, secreted from ß-cells, or exogenously administered, to promote ß-cell replication and survival. Here, we show that clinically applicable GABAA-R PAMs can increase significantly INS-1 ß-cell replication, which is enhanced by exogenous GABA application. Furthermore, a GABAA-R PAM promoted human islet cell replication in vitro. This effect was abrogated by a GABAA-R antagonist. The combination of a PAM and low levels of exogenous GABA further increased human islet cell replication. These findings suggest that PAMs may potentiate the actions of GABA secreted by islet ß-cells on GABAA-Rs and provide a new class of drugs for diabetes treatment. Finally, our findings may explain a past clinical observation of a GABAA-R PAM reducing HbA1c levels in diabetic patients.

Conflict of interest statement

D.L.K. and J.T. are inventors of GABA-related patents. D.L.K. serves on the Scientific Advisory Board of Diamyd Medical. The authors have no competing financial interest. Drs Daniel Kaufman and Jide Tian are guarantors of this work and, as such, had full access to all the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Figures

Figure 1
Figure 1
The structure of AP-3.
Figure 2
Figure 2
(A) GAD enzymatic activity in INS-1 cells. The GAD enzymatic activity within homogenates was assessed using a standard CO2 trapping assay as described in Methods. Data shown are mean CPM + /− SEM from a representative assay from three experiments. (B) Effect of PAMs on INS-1 cell proliferation. INS-1 cells were cultured with the indicated PAM at a dose range of 10−9 to 10−6 M and assessed for their proliferation. Data shown are the average rate of proliferation relative to that of cultures with media alone (designated as 1). INS-1 cells were treated with alprazolam (C), midazolam (D), clonazepam (E), or AP-3 (F) at the indicated concentrations along with a dose range of GABA. Control cultures were incubated with GABA alone at the indicated concentration (solid lines). ††††p < 0.001 versus control cultures with medium alone. *p < 0.05, **p < 0.01, ***p < 0.001 versus cultures with the same dose of GABA, determined by Student T test. G) INS-1 cells were cultured with GABA (0.3 mM) and midazolam or clonazepam (100 nM) with, or without, the TSPO inhibitor PK11195 (1 µM) for 48 hrs.
Figure 3
Figure 3
Alprazolam enhances human islet cell replication. Fresh human islets were treated in triplicate with the indicated dosage of GABA, together with, or without, the indicated PAM as described in Methods. Data shown are the average rate of proliferation relative to that of cultures with medium alone (designated as 1). N = three independent studies. *p < 0.05, determined by Student T test.
Figure 4
Figure 4
Treatment with bicuculline ablates the ability of alprazolam to enhance islet cell replication. Human islets were incubated with alprazolam (100 nM) together with a standard dose range of bicuculline (0–50 uM). Data shown are the average rate of proliferation relative to that of cultures with medium alone (designated as 1).
Figure 5
Figure 5
Alprazolam enhances GABA’s ability to promote human islet cell replication. Human islets were incubated with a dose range of GABA together with alprazolam (100 ng/ml) for 4 days in the presence of 3H thymidine. Data shown are the average rate of proliferation relative to that of cultures with medium alone (designated as 1) in a representative study. N = two independent studies with triplicate cultures. The results were very similar in both studies. ††p < 0.01 and †††p < 0.001for GABA, or GABA + alprazolam vs. control medium alone; *p < 0.05 and ***P < 0.01 for GABA + alprazolam vs. GABA alone, determined by Student T-test.

Similar articles

See all similar articles

Cited by 6 articles

See all "Cited by" articles

References

    1. Braun M, et al. Gamma-aminobutyric acid (GABA) is an autocrine excitatory transmitter in human pancreatic beta-cells. Diabetes. 2010;59:1694–1701. doi: 10.2337/db09-0797. - DOI - PMC - PubMed
    1. Ligon B, Yang J, Morin SB, Ruberti MF, Steer ML. Regulation of pancreatic islet cell survival and replication by gamma-aminobutyric acid. Diabetologia. 2007;50:764–773. doi: 10.1007/s00125-007-0601-8. - DOI - PubMed
    1. Soltani N, et al. GABA exerts protective and regenerative effects on islet beta cells and reverses diabetes. Proc Natl Acad Sci USA. 2011;108:11692–11697. doi: 10.1073/pnas.1102715108. - DOI - PMC - PubMed
    1. Tian J, et al. GABA regulates both the survival and replication of human ß-cells. Diabetes. 2013;62:3760–3765. doi: 10.2337/db13-0931. - DOI - PMC - PubMed
    1. Prud’homme, G. J. et al. GABA Protects Human Islet Cells Against the Deleterious Effects of Immunosuppressive Drugs and Exerts Immunoinhibitory Effects Alone. Transplantation. doi:10.1097/TP.0b013e31829c24be (2013). - PubMed

Publication types

MeSH terms

Feedback