Microarray analysis of genes with impaired insulin regulation in the skeletal muscle of type 2 diabetic patients indicates the involvement of basic helix-loop-helix domain-containing, class B, 2 protein (BHLHB2).
OBJECTIVE
One of the major processes by which insulin exerts its multiple biological actions is through gene expression regulation. Thus, the identification of transcription factors affected by insulin in target tissues represents an important challenge. The aim of the present study was to gain a greater insight into this issue through the identification of transcription factor genes with insulin-regulated expression in human skeletal muscle.


METHODS
Using microarray analysis, we defined the sets of genes modulated during a 3 h hyperinsulinaemic-euglycaemic clamp (2 mU min(-1) kg(-1)) in the skeletal muscle of insulin-sensitive control volunteers and in moderately obese insulin-resistant type 2 diabetic patients.


RESULTS
Of the 1,529 and 1,499 genes regulated during the clamp in control and diabetic volunteers, respectively, we identified 30 transcription factors with impaired insulin-regulation in type 2 diabetic patients. Analysis of the promoters of the genes encoding these factors revealed a possible contribution of the transcriptional repressor basic helix-loop-helix domain-containing, class B, 2 protein (BHLHB2), insulin regulation of which is strongly altered in the muscle of diabetic patients. Gene ontology analysis of BHLHB2 target genes, identified after BHLHB2 overexpression in human primary myotubes, demonstrated that about 10% of the genes regulated in vivo during hyperinsulinaemia are potentially under the control of this repressor. The data also suggested that BHLHB2 is situated at the crossroads of a complex transcriptional network that is able to modulate major metabolic and biological pathways in skeletal muscle, including the regulation of a cluster of genes involved in muscle development and contraction.


CONCLUSIONS
We have identified BHLHB2 as a potential novel mediator of insulin transcriptional action in human skeletal muscle.
Rome
S
S
INRA 1235, INSERM 870, INSA-Lyon, Régulations Métaboliques Nutrition et Diabète, Université de Lyon, Oullins, 69600, France. srome@univ-lyon1.fr
Meugnier
E
E
Lecomte
V
V
Berbe
V
V
Besson
J
J
Cerutti
C
C
Pesenti
S
S
Granjon
A
A
Disse
E
E
Clement
K
K
Lefai
E
E
Laville
M
M
Vidal
H
H
D000328:Adult; D020029:Base Pairing; D051792:Basic Helix-Loop-Helix Proteins / Q000502:physiology*; D001786:Blood Glucose / Q000032:analysis; D003924:Diabetes Mellitus, Type 2 / Q000235:genetics* / Q000503:physiopathology; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005260:Female; D005786:Gene Expression Regulation; D018398:Homeodomain Proteins / Q000502:physiology*; D006801:Humans; D007328:Insulin / Q000097:blood / Q000235:genetics / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology*; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D014158:Transcription, Genetic
D051792:Basic Helix-Loop-Helix Proteins; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D018398:Homeodomain Proteins; D007328:Insulin; D012313:RNA; C107989:BHLHE40 protein, human