High dosage of Exendin-4 increased early insulin secretion in differentiated beta cells from mouse embryonic stem cells.
OBJECTIVE
To investigate early insulin release (EIR) and late insulin release (LIR) upon glucose challenge as well as important insulin signaling factors in differentiated insulin-producing cells from embryonic stem cells(ESCs).


METHODS
A recently published protocol was modified by increasing the concentration of Exendin-4 (from 0.1 nmol/L to 10 nmol/L) together with an additional 5-day culture in low glucose (5.5 mmol/L) medium after differentiation. Gene expression profile, insulin content, C-peptide, EIR and LIR were determined.


RESULTS
Compared to a lower concentration of Exendin-4 (0.1 nmol/L), a higher concentration of Exendin-4 (10 nmol/L) increased glucose-responsive insulin secretion, especially EIR. Moreover, 10 nmol/L Exendin-4 increased the expression of the following genes: insulin 1, Pdx-1 (an important transcription factor, newly recognized insulin signaling factors), Epac1 and Epac2 (exchange proteins directly activated by cAMP 1 and 2), and sulfonylurea receptor 1 (SUR1, the subunit of the K(ATP) channel).


CONCLUSIONS
According to current knowledge, our modified protocol with a higher concentration of Exendin-4 (10 nmol/L) together with an additional 5-day 5.5 mmol/L glucose culture after differentiation improved the efficiency of differentiation toward the beta cell phenotype, which was possibly the result of stimulated expression of Pdx-1, Epac 1, and Epac 2, which in turn inhibited the K(ATP) channel through combination with SUR1, leading to increased EIR upon glucose challenge.
Li
Hua
H
Department of Anatomy, Li Ka Shing Faculty of Medicine, University of Hong Kong, Hong Kong SAR, China.
Lam
Amy
A
Xu
Ai-min
AM
Lam
Karen Sl
KS
Chung
Sookja Kim
SK
D000818:Animals; D002096:C-Peptide / Q000378:metabolism; D002454:Cell Differentiation; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000166:cytology*; D000077270:Exenatide; D020869:Gene Expression Profiling; D005947:Glucose / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology*; D007328:Insulin / Q000378:metabolism*; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D051379:Mice; D010455:Peptides / Q000494:pharmacology*; D010641:Phenotype; D014688:Venoms / Q000494:pharmacology*
D002096:C-Peptide; D007004:Hypoglycemic Agents; D007328:Insulin; D010455:Peptides; D014688:Venoms; D000077270:Exenatide; D005947:Glucose