Glucose tolerance is associated with differential expression of microRNAs in skeletal muscle: results from studies of twins with and without type 2 diabetes.
OBJECTIVE
We aimed to identify microRNAs (miRNAs) associated with type 2 diabetes and risk of developing the disease in skeletal muscle biopsies from phenotypically well-characterised twins.


METHODS
We measured muscle miRNA levels in monozygotic (MZ) twins discordant for type 2 diabetes using arrays. Further investigations of selected miRNAs included target prediction, pathway analysis, silencing in cells and association analyses in a separate cohort of 164 non-diabetic MZ and dizygotic twins. The effects of elevated glucose and insulin levels on miRNA expression were examined, and the effect of low birthweight (LBW) was studied in rats.


RESULTS
We identified 20 miRNAs that were downregulated in MZ twins with diabetes compared with their non-diabetic co-twins. Differences for members of the miR-15 family (miR-15b and miR-16) were the most statistically significant, and these miRNAs were predicted to influence insulin signalling. Indeed, miR-15b and miR-16 levels were associated with levels of key insulin signalling proteins, miR-15b was associated with the insulin receptor in non-diabetic twins and knockdown of miR-15b/miR-16 in myocytes changed the levels of insulin signalling proteins. LBW in twins and undernutrition during pregnancy in rats were, in contrast to overt type 2 diabetes, associated with increased expression of miR-15b and/or miR-16. Elevated glucose and insulin suppressed miR-16 expression in vitro.


CONCLUSIONS
Type 2 diabetes is associated with non-genetic downregulation of several miRNAs in skeletal muscle including miR-15b and miR-16, potentially targeting insulin signalling. The paradoxical findings in twins with overt diabetes and twins at increased risk of the disease underscore the complexity of the regulation of muscle insulin signalling in glucose homeostasis.
Steno Diabetes Center, Gentofte, Denmark, jette.bork.jensen@sund.ku.dk.
Jette
J
Bork-Jensen
Camilla
C
Scheele
Daniel V
DV
Christophersen
Emma
E
Nilsson
Martin
M
Friedrichsen
Denise S
DS
Fernandez-Twinn
Louise G
LG
Grunnet
Thomas
T
Litman
Kim
K
Holmstrøm
Birgitte
B
Vind
Kurt
K
Højlund
Henning
H
Beck-Nielsen
Jørgen
J
Wojtaszewski
Susan E
SE
Ozanne
Bente K
BK
Pedersen
Pernille
P
Poulsen
Allan
A
Vaag
D000368:Aged; D000704:Analysis of Variance; D003718:Denmark; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D015536:Down-Regulation; D005260:Female; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D008297:Male; D035683:MicroRNAs / Q000378:metabolism*; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000378:metabolism*; D015398:Signal Transduction; D014430:Twins, Monozygotic
D007328:Insulin; D035683:MicroRNAs