MicroRNAs in diabetes - are they perpetrators in disguise or just epiphenomena?

MicroRNAs (miRNA) are non-coding RNAs, the majority of which are 22 nucleotide in size. They regulate gene transcription and control more than 50% of the mammalian genome. Although functional significance and targets of several miRNAs are yet to be identified, they may be regarded as controller of cellular physiology and function. Through such regulation they play vital roles in normal and diseased states. In the context of diabetes and chronic diabetic complications, recent research has identified alterations of a significant number of miRNAs. However, in a complex chronic disease like diabetes, multiple transcripts may also change in a temporal fashion depending on the disease progression and activation of counter-regulatory mechanisms. Hence, it is also possible that some miRNA changes may not be causally related to the disease pathogenesis and represent epiphenomena. To date, over 500 studies have addressed the role of miRNAs in the pathogenesis of type 1 and type 2 diabetes and chronic diabetic complications. Majority of the altered miRNAs appear to have pathogenetic roles. In this review, we have tried to identify alterations of specific miRNAs and the pathways they may regulate. We have also tried to identify whether some of these miRNA alterations may form basis of potential treatments.