MicroRNA profiling reveals new potential modulators of insulin-resistance and cardiovascular risk in type 2 diabetes

Background: Type 2 Diabetes (T2DM) is a chronic disease characterized
by an inadequate beta-cell response to the progressive insulin
resistance. The tiny mechanism(s) underlying insulin-resistance and
increased atherosclerosis burden in T2DM patients are not fully
understood. MicroRNAs (miRNAs) are short (20–22 nucleotides of
length), endogenous, non-coding, RNAs representing a new class of
regulators of gene expression. Remarkably, they are found in all cell
type and their presence is clearly detectable in peripheral blood.
Currently miRNAs involvement has been demonstrated in many
diseases such as cancer, inflammatory and cardiovascular diseases.
However, the role of miRNAs in T2DM in humans is not fully elucidated,
thus aim of this study was to investigate the plasma miRNAs
profile of diabetic patients.
Materials and Methods: Blood samples were collected from 11
diabetic patients and 11 matched control patients. T2DM diagnosis
was formulated according currently available American Diabetes
Association guidelines. We enrolled only drug-naı¨ve patients before
starting specific treatment. Patients with active inflammatory diseases,
chronic kidney disease and cancer were excluded. RNA was extracted
according with previously validated methods, quantified and pooled
and a wide microRNA expression profiling was performed (miRNome).
Then, some of the miRNAs that were differently expressed
between two groups were validated by RealTime-PCR (RT-PCR).
Data analyses were performed with deltadelta Ct method. Finally,
bioinformatics was used in order to identify the potential targets of
these miRNAs.
Results: Microarray analysis showed that 4 miRNAs were upregulated
whereas 21 miRNAs were downregulated in diabetic patients.
Interestingly, RT-PCR validation confirmed a significant downregulation
of let-7a (p = 0.023) and let-7f (p = 0.049). Moreover, we
found a significant upregulation of miR-326 (p = 0.006). Furthermore,
an interesting trend supporting down-regulation of miR-16,
miR-21 and let-7 g in diabetic patients was found, despite these
values did not reach statistical significance probably due the small
study population. In silico analysis of predicted targets confirmed that
these miRNAs may modulate genes greatly involved in insulin-signaling
(including Adiponectin, IGF-1 receptor and others),
endothelial function (including PTEN) and linked to cardiovascular
risk (including VLDL receptor, TGF-beta).
Conclusion: This study demonstrated that diabetes is associated with
a modulation of the expression of plasma miRNA that are involved in
insulin resistance and endothelial function. Further studies on these specific miRNAs’ targets are required to understand the molecular
read-out of this modulation. If confirmed, these findings will contribute
to improve our knowledge on diabetes pathophysiology and
lead to the identification of new innovative therapeutic strategies for
T2DM.