Abstract Background: Fetal metabolic programming imposed by maternal obesity and impaired glucose tolerance predisposes the offspring to metabolic disease and beta cell dysfunction as adults. The aim of this study was to assess the whole pancreas RNA changes in neonatal offspring exposed to fetal programming. Methods: The outcome of fetal programming on offspring was tested using the selectively bred Diet Induced Obese (DIO) and the Diet Resistant (DR) strains. DIO and DR rats were fed either chow or high fat, high sucrose (high energy, HE) diet during gestation and the differences in pancreas RNA expression at two days after birth were measured by microarray. Pancreas sections were stained and analyzed for alpha and beta cell numbers. Neonatal islets were treated with cytotoxic cytokines and RNA measured by RT-Q-PCR. Results: Morphometric analyses revealed significant differences in alpha and beta cell numbers per pancreas or per islet by HE diet. Microarray analyses revealed 11 fold downregulation of the long noncoding RNA Bsr in whole pancreas by HE feeding of DIO rat dams. MicroRNAs from the same locus, the Dlk1- Dio3 imprinted region, were also decreased by HE diet. Moreover, treatment of isolated neonatal islets with inflammatory cytokines, IL-1β and IFN-γ, led to reduction of Bsr transcript in a time and dose dependent manner. Conclusions: Our data suggest that fetal programming of Bsr may play a role in beta cell dysfunction in obesity and type 2 diabetes.
Abstract MicroRNA (miRNA)-375 is highly expressed in the pancreatic endocrine islets. Maintaining appropriate miR-375 levels is very important for beta cell development, function and proliferation. The aim of the current study was to investigate the regulation and localization of miR-375 in rat perinatal pancreas at embryonic day 20 (E20), postnatal day 0 (D0) and day 2 (D2). Expression levels of miR-375 were measured by in situ hybridization on fixed neonatal rat pancreas. Interestingly, while miR-375 was detectable at robust levels at all three time points, the major site of expression of miR-375 at D0 and D2 was in pancreatic exocrine cells. Our data show that miR-375 has a dynamic change of expression in pancreatic exocrine tissue during the perinatal period. Moreover, these findings indicate that pancreatic endocrine cells may not always be the major source of expression of miR-375 in pancreas. We suggest that the marked change of miR-375 levels in exocrine cells following birth could regulate processes involved in the adaptation of the exocrine pancreas to digestion of external nutrients derived from milk.
AbstractCombined immuno-FISH offers an important tool for understanding the localization of mature microRNAs with reference to other proteins within the same cell. This procedure has been previously demonstrated by our team and the method has been described earlier [1, 2].
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.
MicroRNAs (miRNAs) are endogenous single-stranded non-coding RNAs of about ~ 22 nucleotides which suppress gene expression by selectively binding to the 3' non coding region (3'-UTR) of specific messenger RNAs through base-pairing.There are now more than 1600 human miRNAs annotated in the miRNA registry (http://microrna.sanger.ac.uk), but, at the moment, very few miRNAs have been well characterized and most of their roles remain unknown.miRNAs derive from transcripts that fold back on themselves to form distinctive hairpin structures, whereas the other types of endogenous small RNAs derive either from much longer hairpins that give rise to a greater diversity of small RNAs (siRNAs), or from bimolecular RNA duplexes (siRNAs), or from precursors without any suspected doublestranded character (piRNAs).The key step to understanding more about the possible functions of microRNA is to identify their mRNA targets.Recent studies have supported a role of miRNAs in the initiation and progression of human malignancies.Several groups have studied the global miRNA expression in cancer patients and found that miRNAs show different patterns of expression in normal and tumor tissues.The involvement of miRNAs in human cancer is probably due to the fact that >50% of miRNA genes are located at chromosomal regions, such as fragile sites or common break point sites, and regions of deletion or amplification that are generally altered in human tumors.Experimental evidence has shown that miRNA expression profiles enable the classification of poorly characterized human tumors that cannot be accurately classified using only the mRNA expression patterns.As a result, the miRs involved in the oncogenic transformation process are being investigated as novel biomarkers of disease detection and prognosis as well as potential therapeutic targets for human cancers.The aim of this review is to provide a general background regarding current knowledge about miRNA involvement in human pancreatic cancer and in the regulation of glucose metabolism.
MicroRNAs belong to a family of small (~23 nt) non-coding RNAs that mediate posttranscriptional gene silencing. They are emerging as important new regulators of differentiation and development. Knowledge of their role in pancreas and islet development, may help in developing a regenerative therapy for diabetes mellitus, a metabolic disorder affecting hundreds of millions of people worldwide. In this minireview, we summarize the latest evidence of the role these new regulators play in islet lineage development, aiming to attract more research into this important developmental regulators.
noncodingrnas (ncrnas) is a large class of structurally and functionally diverse rna molecules that do not code for any protein. One of the most significant discoveries in the past 2 decades has been the identification of small regulatory noncoding rnas; micrornas (also referred to as “mirnas” or “mirs”). The discovery of micrornas and the understanding of regulatory mechanisms that they offer in “fine tuning” the adaptation and presentation of individual genomes is overwhelming. Originally described in animals by Victor ambros [1] and Gary ruvkin [2] in 1993, micrornas have now been recognized to impact human health in numerous ways. Discovery of such regulatory molecules have assigned a critical role to the originally thought “junk Dna”. Bacteria and other prokaryotic organisms have the least amount of non-coding (“junk”) Dna as compared to the more evolved species. This “junk Dna” was believed to have accumulated over several centuries of evolution as a result of evolutionary modifications, transposons as well as parasite and viral infections. Following completion of the human genome project in 2001, it was revealed that only up to 2% of our genome codes for all the proteins that make up our bodies. This was very interesting as humans, having developed complex physiologies, were believed to carry many more protein-coding genes. Instead, it was discovered that insects have twice as many protein-coding genes (~13,500) than yeast (~6,000) and that increase in cell number or complexity is not related to number of protein-coding genes. There are 19,000 protein-coding genes in C. elegans, for its 959-cell body plan as compared to similar number (~22,000) of protein-coding genes in humans for ~10 trillion cells. One major difference between slugs and humans is the relative proportion of non-coding Dna. It is now demonstrated that ncrnas can influence the expression of over 30% of proteincoding genes and play important homeostatic roles to regulate gene expression during development and disease. Today, it is well known that micrornas play an important role in normal development of endocrine pancreas and may also regulate progression of diabetes and its complications. The number of publications related to micrornas and Diabetes have increased significantly over the last 10 years (Figure 1a). The importance of these publications in understanding other biologies has also greatly increased based on a high citation rate of these articles (Figure 1a). a number of grant applications and
Ever since the discovery of small non-coding RNAs, microRNAs have been identified to play a critical role in development and function of pancreatic insulin-producing beta cells.Research carried out until now demonstrates that microRNAs can specifically target key pancreatic transcription factors and signalling molecules.This in turn may influence changes in insulin production and secretion.microRNAs are also identified in insulin target organs that are altered as a result of hyperglycemia and insulin resistance.Recent studies demonstrate that microRNAs are not only confined to cells but are also detected in biological fluids including serum, plasma and urine.These data indicate that miRNAs may be looked upon having a dual role, as biomarkers and as regulators of disease.We review the existing literature in understanding the role of microRNAs in development, function and death of pancreatic beta cells as well as in the development of metabolic disease.We discuss the possible mechanisms that contribute to identifying the role of microRNAs as sensitive and efficient biomarkers to predict the progression of diabetes.Understanding tissue-specific microRNA signatures and their role as a cause or effect of diabetes would provide more information on progression of this disease.
Sangiao-Alvarellos et al., 2014, have also shown that miR-200a regulate the IRS2 expression [3].Taken together these results suggest that miR-200a may play an important role in energy metabolism by regulating leptin and insulin signalling.The expression levels of IRS2 and ObRb are reduced in the Ob/Ob mice and blocking the miR-200a by intracerebro-ventricular (ICV) infusion of anti miR-200a restores the expression of both IRS2 and ObRb.Blocking of miR-200a in mice, results in increased insulin receptor expression and mRNA coding for POMC and Neuropeptide Y.The anti mir-200a also causes the reduction of the body weight gain in the Ob/Ob mice however the reduced body weight was not accompanied by reduced food intake suggesting that the restoration is not complete and may be the satiation signalling is probably not regulated by miR-200a.Similarly the insulin glucose tolerance test also indicates that the recovery is not complete in the Ob/Ob mice after blocking of miR-200a.Over expression of miR-200a pre miRNA in the neuroblastoma cells SH-SY5Y causes the reduction of IRS2 and ObRb mRNA and protein expression.Further, they have also shown that over expression of pre-miR-200a decreases the phosphorylation of Stat3, ERK1/2 and Akt which causes the impairment of leptin and insulin signalling pathway in human neuroblastoma cell line.Apart from hypothalamic effects of miR-200a Creptin et al also showed that blocking of miR-200a in hypothalamus results in the significant increase in the expression of IRS-2 and IR in the liver of ob/ob mice.Caravalheira et al proposed that there is cross-talk between the insulin and leptin signaling in Rat hypothalamus indicating that glucose homeostatsis or metabolism and food intake go hand in hand [4].While the levels of miR-200b/c is increased in diabetic kidney disease [5] but that of miR-200a is increased [6], mice suggesting a more complex regulatory network regulating miR-200 gene family and its interaction with glucose metabolism and obesity [7].Hence a detailed study to establish the relation between expression of miR-200a/b/c and their effect on the insulin and leptin signalling is required.
Angiogenesis is the pathological process of forming new blood vessels from pre-existing vessels. It is one of the main features of many conditions such as cancer and inflammatory diseases. MicroRNAs (miRNAs) are small non-coding RNAs that regulate post-transcriptional gene expression. Recent studies have suggested that miRNAs play a significant role in angiogenesis. The study from Wang et al reported a novel angiomiR, miRNA-329, and its negative correlation with CD 146 expression in angiogenesis. These in vitro and in vivo studies introduce an appealing new way of treating angiogenesis by targeting CD146.
