Gene expression profiles during beta cell maturation and after IL-1beta exposure reveal important roles of Pdx-1 and Nkx6.1 for IL-1beta sensitivity.
OBJECTIVE
Maturation of the beta cells in the islets of Langerhans is dependent upon sequential activation of different transcription factors such as Pdx-1 and Nkx6.1. This maturation is associated with an acquired sensitivity to cytokines and may eventually lead to type 1 diabetes. The aims of this study were to characterise changes in mRNA expression during beta cell maturation as well as after interleukin-1beta (IL-1beta) exposure.


METHODS
Transcriptome analyses were performed on two phenotypes characterised as a glucagon-producing pre-beta-cell phenotype (NHI-glu), which matures to an IL-1beta-sensitive insulin-producing beta cell phenotype (NHI-ins). Beta cell lines over-expressing Pdx-1 or Nkx6.1, respectively, were used for functional characterisation of acquired IL-1beta sensitivity.


RESULTS
During beta cell maturation 98 fully annotated mRNAs changed expression levels. Of these, 50 were also changed after 24 h of IL-1beta exposure. In addition, 522 and 197 fully annotated mRNAs, not affected by maturation, also changed expression levels following IL-1beta exposure of the beta cell and the pre-beta-cell phenotype, respectively. Beta cell maturation was associated with an increased expression of Nkx6.1, whereas both Pdx-1 and Nkx6.1 expression were decreased following IL-1beta exposure. Over-expression of Nkx6.1 or Pdx-1 in cell lines resulted in a significantly increased sensitivity to IL-1beta.


CONCLUSIONS
These results suggest that the final beta cell maturation accompanied by increased IL-1beta sensitivity is, in part, dependent upon the expression of genes regulated by Pdx-1 and Nkx6.1. Future classification of the genes regulated by these transcription factors and changed during beta cell maturation should elucidate their role in the acquired sensitivity to IL-1beta and may be helpful in identifying new targets for intervention/prevention strategies.
Nielsen
K
K
Steno Diabetes Center, Niels Steensensvej 2, 2820, Gentofte, Denmark.
Kruhøffer
M
M
Orntoft
T
T
Sparre
T
T
Wang
H
H
Wollheim
C
C
Jørgensen
M C
MC
Nerup
J
J
Karlsen
A E
AE
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects*; D018398:Homeodomain Proteins / Q000235:genetics*; D007375:Interleukin-1 / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology*; D016381:Islets of Langerhans Transplantation; D018075:RNA, Complementary / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic
D017931:DNA Primers; D018398:Homeodomain Proteins; D007375:Interleukin-1; C491327:Nkx6-1 protein, rat; D018075:RNA, Complementary; D012333:RNA, Messenger; D015534:Trans-Activators; C084010:pancreatic and duodenal homeobox 1 protein