Identification of microRNAs with a role in glucose stimulated insulin secretion by expression profiling of MIN6 cells

Crosstalk between microRNA and inflammation; critical regulator of diabetes

A growing body of evidence indicates that microRNAs (miRNAs may be used as biomarkers for the diagnosis, prognosis, and treatment of diabetes, given their changed expression profile as the disease progresses. There is growing interest in using individual miRNAs or whole miRNA clusters linked to diabetes as therapeutic targets because of their abnormal expression and functioning. In diabetes, miRNAs are also involved in inflammatory and immunological responses. Additionally, the inflammatory response controls the generation, processing, and stability of pre- or mature miRNAs and miRNA biogenesis. With a comprehensive grasp of molecular biological activities and the signaling axis, this review emphasizes the critical functions of miRNAs in inflammatory and immunological processes in diabetes. We further emphasized the potential role of these miRNAs in controlling inflammation associated with diabetes. This assessment will direct the shift from many studies to practical applications for tailored diabetes treatment and assist in identifying new therapeutic targets and approaches.

A Review of micro RNAs changes in T2DM in animals and humans

Type 2 diabetes mellitus (T2DM) and its associated complications have become a crucial public health concern in the world. According to the literature, chronic inflammation and the progression of T2DM have a close relationship. Accumulated evidence suggests that inflammation enhances the insulin secretion lost by islets of Langerhans and the resistance of target tissues to insulin action, which are two critical features in T2DM development. Based on recently highlighted research that plasma concentration of inflammatory mediators such as tumor necrosis factor α and interleukin-6 are elevated in insulin-resistant and T2DM, and it raises novel question marks about the processes causing inflammation in both situations. Over the past few decades, microRNAs (miRNAs), a class of short, noncoding RNA molecules, have been discovered to be involved in the regulation of inflammation, insulin resistance, and T2DM pathology. These noncoding RNAs are specifically comprised of RNA-induced silencing complexes and regulate the expression of specific protein-coding genes through various mechanisms. There is extending evidence that describes the expression profile of a special class of miRNA molecules altered during T2DM development. These modifications can be observed as potential biomarkers for the diagnosis of T2DM and related diseases. In this review study, after reviewing the possible mechanisms involved in T2DM pathophysiology, we update recent information on the miRNA roles in T2DM, inflammation, and insulin resistance.

Hypoglycemia, Vascular Disease and Cognitive Dysfunction in Diabetes: Insights from Text Mining-Based Reconstruction and Bioinformatics Analysis of the Gene Networks

Hypoglycemia has been recognized as a risk factor for diabetic vascular complications and cognitive decline, but the molecular mechanisms of the effect of hypoglycemia on target organs are not fully understood. In this work, gene networks of hypoglycemia and cardiovascular disease, diabetic retinopathy, diabetic nephropathy, diabetic neuropathy, cognitive decline, and Alzheimer's disease were reconstructed using ANDSystem, a text-mining-based tool. The gene network of hypoglycemia included 141 genes and 2467 interactions. Enrichment analysis of Gene Ontology (GO) biological processes showed that the regulation of insulin secretion, glucose homeostasis, apoptosis, nitric oxide biosynthesis, and cell signaling are significantly enriched for hypoglycemia. Among the network hubs, INS, IL6, LEP, TNF, IL1B, EGFR, and FOS had the highest betweenness centrality, while GPR142, MBOAT4, SLC5A4, IGFBP6, PPY, G6PC1, SLC2A2, GYS2, GCGR, and AQP7 demonstrated the highest cross-talk specificity. Hypoglycemia-related genes were overrepresented in the gene networks of diabetic complications and comorbidity; moreover, 14 genes were mutual for all studied disorders. Eleven GO biological processes (glucose homeostasis, nitric oxide biosynthesis, smooth muscle cell proliferation, ERK1 and ERK2 cascade, etc.) were overrepresented in all reconstructed networks. The obtained results expand our understanding of the molecular mechanisms underlying the deteriorating effects of hypoglycemia in diabetes-associated vascular disease and cognitive dysfunction.

The MicroRNA Landscape of Acute Beta Cell Destruction in Type 1 Diabetic Recipients of Intraportal Islet Grafts

Ongoing beta cell death in type 1 diabetes (T1D) can be detected using biomarkers selectively discharged by dying beta cells into plasma. microRNA-375 (miR-375) ranks among the top biomarkers based on studies in animal models and human islet transplantation. Our objective was to identify additional microRNAs that are co-released with miR-375 proportionate to the amount of beta cell destruction. RT-PCR profiling of 733 microRNAs in a discovery cohort of T1D patients 1 h before/after islet transplantation indicated increased plasma levels of 22 microRNAs. Sub-selection for beta cell selectivity resulted in 15 microRNAs that were subjected to double-blinded multicenter analysis. This led to the identification of eight microRNAs that were consistently increased during early graft destruction: besides miR-375, these included miR-132/204/410/200a/429/125b, microRNAs with known function and enrichment in beta cells. Their potential clinical translation was investigated in a third independent cohort of 46 transplant patients by correlating post-transplant microRNA levels to C-peptide levels 2 months later. Only miR-375 and miR-132 had prognostic potential for graft outcome, and none of the newly identified microRNAs outperformed miR-375 in multiple regression. In conclusion, this study reveals multiple beta cell-enriched microRNAs that are co-released with miR-375 and can be used as complementary biomarkers of beta cell death.

Extracellular vesicles and their role in gestational diabetes mellitus

Gestational diabetes mellitus (GDM) is a complex disorder that is defined by glucose intolerance with onset during pregnancy. The incidence of GDM is increasing worldwide. Pregnancies complicated with GDM have higher rates of maternal and fetal morbidity with short- and long-term consequences, including increased rates of cardiovascular disease and type II diabetes for both the mother and offspring. The pathophysiology of GDM still remains unclear and there has been interest in the role of small extracellular vesicles (sEVs) in the maternal metabolic adaptations that occur in pregnancy and GDM. Small EVs are nanosized particles that contain bioactive content, including miRNAs and proteins, which are released by cells to provide cell-to-cell communication. Pregnancy induces an increase in total and placental-secreted sEVs across gestation, with a further increase in sEV number and changes in the protein and miRNA composition of these sEVs in GDM. Research has suggested that these sEVs have an impact on maternal adaptations during pregnancy, including targeting the pancreas, skeletal muscle and adipose tissue. Consequently, this review will focus on the differences in total and placental sEVs in GDM compared to normal pregnancy, the role of sEVs in the pathophysiology of GDM and their clinical application as potential GDM biomarkers.

The Predominant microRNAs in β-cell Clusters for Insulin Regulation and Diabetic Control

micro (mi)-RNAs are vital regulators of multiple processes including insulin signaling pathways and glucose metabolism. Pancreatic β-cells function is dependent on some miRNAs and their target mRNA, which together form a complex regulative network. Several miRNAs are known to be directly involved in β-cells functions such as insulin expression and secretion. These small RNAs may also play significant roles in the fate of β-cells such as proliferation, differentiation, survival and apoptosis. Among the miRNAs, miR-7, miR-9, miR-375, miR-130 and miR-124 are of particular interest due to being highly expressed in these cells. Under diabetic conditions, although no specific miRNA profile has been noticed, the expression of some miRNAs and their target mRNAs are altered by posttranscriptional mechanisms, exerting diverse signs in the pathobiology of various diabetic complications. The aim of this review article is to discuss miRNAs involved in the process of stem cells differentiation into β-cells, resulting in enhanced β-cell functions with respect to diabetic disorders. This paper will also look into the impact of miRNA expression patterns on in vitro proliferation and differentiation of β-cells. The efficacy of the computational genomics and biochemical analysis to link the changes in miRNA expression profiles of stem cell-derived β-cells to therapeutically relevant outputs will be discussed as well.

Identification of stress-related microRNA biomarkers in type 2 diabetes mellitus: A systematic review and meta-analysis

BACKGROUND

Many studies have investigated microRNAs (miRNAs) in the detection of type 2 diabetes mellitus (T2DM). Herein, the dysregulated direction of stress-related miRNAs used as biomarkers of T2DM are summarized and analyzed.

METHODS

PubMed, EMBASE, ISI Web of Science, and three Chinese databases were searched for case-control miRNA profiling studies about T2DM. A meta-analysis under a random effect was performed. Subgroup analysis was conducted based on different tissues and species. Sensitivity analysis was conducted to confirm the robustness among studies. The effect size was pooled using ln odds ratios (ORs), 95% confidence intervals (95% CIs), and P-values.

RESULTS

The present meta-analysis included 39 case-control studies with a total of 494 miRNAs. Only 33 miRNAs were reported in three or more studies and, of these, 18 were inconsistent in their direction of dysregulation. Two significantly dysregulated miRNAs (let-7 g and miR-155) were identified in the meta-analysis. Four miRNAs (miR-142-3p, miR-155, miR-21, and miR-34c-5p) were dysregulated in patients with T2DM, whereas five miRNAs (miR-146a, miR-199a-3p, miR-200b, miR-29b and miR-30e) were dysregulated in animal models of diabetes. In addition, two dysregulated miRNAs (miR-146a and miR-21) were highly cornea specific and heart specific. In sensitivity analysis, only miR-155 was still significantly dysregulated after removing studies with small sample sizes.

CONCLUSIONS

The present meta-analysis revealed that 16 stress-related miRNAs were significantly dysregulated in T2DM. MiR-148b, miR-223, miR-130a, miR-19a, miR-26b and miR-27b were selected as potential circulating biomarkers of T2DM. In addition, miR-146a and miR-21 were identified as potential tissue biomarkers of T2DM.

Role of miRNAs in the pathogenesis of T2DM, insulin secretion, insulin resistance, and β cell dysfunction: the story so far

Diabetes, the most common endocrine disorder, also known as a silent killer disease, is characterized by uncontrolled hyperglycemia. According to the International Diabetes Federation, there were 451 million people with diabetes mellitus worldwide in 2017. It is a multifactorial syndrome caused by genetic as well as environmental factors. Noncoding RNAs, especially the miRNAs, play a significant role in the development as well as the progression of the disease. This is on account of insulin resistance or defects in β cell function. Various miRNAs including miR-7, miR-9, miR-16, miR-27, miR-24, miR-29, miR-124a, miR-135, miR-130a, miR-144, miR-181a, and miR-375 and many more have been associated with insulin resistance and other pathogenic conditions leading to the development of the disease. These miRNAs play significant roles in various pathways underlying insulin resistance such as PI3K, AKT/GSK, and mTOR. The main target genes of these miRNAs are FOXO1, FOXA2, STAT3, and PTEN. The miRNAs carry out important functions in insulin target tissues like the adipose tissue, liver, and muscle. MiRNAs miR-9, miR-375, and miR-124a, are also associated with the secretion of insulin from pancreatic cells. There is an interplay between the miRNAs and pancreatic cell growth, especially the miRNAs affecting development and proliferation of these cells. Most of the miRNAs target more than one gene which not only justifies their use as biomarkers but also their therapeutic potential. The current review has been compiled with an aim to discuss the role of various miRNAs involved in various pathogenic mechanisms including insulin resistance, insulin secretion, and the β cell dysfunction.

miRNA Dysregulation in the Development of Non-Alcoholic Fatty Liver Disease and the Related Disorders Type 2 Diabetes Mellitus and Cardiovascular Disease

According to the World Health Organization, the continuing surge in obesity pandemic creates a substantial increase in incidences of metabolic disorders, such as non-alcoholic fatty liver disease (NAFLD), type 2 diabetes mellitus, and cardiovascular disease. MicroRNAs (miRNAs) belong to an evolutionarily conserved class of short (20-22 nucleotides in length) and single-stranded non-coding RNAs. In mammals, miRNAs function as critical post-transcriptional negative regulators involved not only in many biological processes but also in the development of many diseases such as NAFLD and comorbidities. More recently, it has been described that cells can secrete miRNAs in extracellular vesicles, transported by body fluids, and uptaken by other tissues regulating gene expression. Therefore, this could be a mechanism of signaling involved not only in physiological pathways but also in the development of diseases. The association of some miRNA expression profiles with certain disorders has made them very interesting molecules for diagnosis, prognosis, and disease management. The finding of specific miRNA signatures to diagnose NAFLD and related diseases could anticipate the risk of development of related complications and, actually, it is the driving force of present health strategies worldwide. In this review, we have included latest advances in knowledge about the miRNAs involved in the development of NAFLD and related diseases and examined how this knowledge could be used to identify new non-invasive biomarkers and new pharmacological interventions.

MicroRNA-410 participates in the pathological process of postmenopausal osteoporosis by downregulating bone morphogenetic protein-2

The present study aimed to investigate bone morphogenetic protein (BMP)-2 and microRNA (miR)-410 expression and the mechanism of regulation in serum and CD¹⁴⁺ peripheral blood mononuclear cells (PBMCs) from postmenopausal osteoporosis patients and model mice. A total of 26 patients with postmenopausal osteoporosis were included in the experimental group and 29 age-matched healthy subjects were included in the control group. A total of 60 mice were divided into sham and ovariectomized (OVX) groups. Following surgery, 28 mice remained in the sham and 25 mice remained in OVX group. BMP-2 protein expression in serum and CD¹⁴⁺ PBMCs from patients and model mice was determined using ELISA and western blotting, respectively. Reverse transcription-quantitative polymerase chain reaction assays were performed to determine miR-410 and BMP-2 mRNA levels in serum and CD¹⁴⁺ PBMCs from patients and model mice. Dual luciferase reporter assays were used to identify direct interactions between miR-410 and BMP-2 mRNA. Compared with the control group, BMP-2 mRNA and protein expression in serum and CD¹⁴⁺ PBMCs from patients with postmenopausal osteoporosis and model mice were significantly decreased. miR-410 levels in serum and CD¹⁴⁺ PBMCs from patients with postmenopausal osteoporosis and model mice were significantly increased when compared with the control group. Dual luciferase reporter assays revealed that BMP-2 was a target gene of miR-410. The current study demonstrated that decreased BMP-2 expression in serum and CD¹⁴⁺ PBMCs from patients with postmenopausal osteoporosis was associated with the upregulation of miR-410. These results suggest that miR-410 may participate in the pathological process of postmenopausal osteoporosis by downregulating BMP-2.

MicroRNA expression profile in plasma from type 1 diabetic patients: Case-control study and bioinformatic analysis

AIMS

To investigate a miRNA expression profile in plasma of type 1 diabetes (T1DM) patients and control subjects and analyze the putative pathways involved.

METHODS

Expressions of 48 miRNAs were analyzed in plasma of 33 T1DM patients and 26 age-and-gender-matched controls using Stem-loop RT-PreAmp PCR and TaqMan Low Density Arrays (Thermo Fisher Scientific). Five dysregulated miRNAs were then chosen for validation in an independent sample of 27 T1DM patients and 14 controls, using RT-qPCR. Bioinformatic analyses were performed to determine in which pathways these miRNAs are involved.

RESULTS

Nine miRNAs were differentially expressed between recently-diagnosed T1DM patients (<5 years of diagnosis) and controls. No differences were observed between patients with ≥5 years of diagnosis and controls. After validation in an independent sample of T1DM patients, miR-103a-3p, miR-155-5p, miR-200a-3p, and miR-210-3p were confirmed as being upregulated in recently-diagnosed T1DM patients compared with controls or patients with ≥5 years of diagnosis. Moreover, miR-146a-5p was downregulated in recently-diagnosed T1DM patients compared with the other groups. These five miRNAs regulate several genes from innate immune system-, MAPK-, apoptosis-, insulin- and cancer-related pathways.

CONCLUSION

Five miRNAs are dysregulated in recently-diagnosed T1DM patients and target several genes involved in pathways related to T1DM pathogenesis, thus representing potential T1DM biomarkers.

MicroRNA Expression Analysis of In Vitro Dedifferentiated Human Pancreatic Islet Cells Reveals the Activation of the Pluripotency-Related MicroRNA Cluster miR-302s

β-cell dedifferentiation has been recently suggested as an additional mechanism contributing to type-1 and to type-2 diabetes pathogenesis. Moreover, several studies demonstrated that in vitro culture of native human pancreatic islets derived from non-diabetic donors resulted in the generation of an undifferentiated cell population. Additional evidence from in vitro human β-cell lineage tracing experiments, demonstrated that dedifferentiated cells derive from β-cells, thus representing a potential in vitro model of β-cell dedifferentiation. Here, we report the microRNA expression profiles analysis of in vitro dedifferentiated islet cells in comparison to mature human native pancreatic islets. We identified 13 microRNAs upregulated and 110 downregulated in islet cells upon in vitro dedifferentiation. Interestingly, among upregulated microRNAs, we observed the activation of microRNA miR-302s cluster, previously defined as pluripotency-associated. Bioinformatic analysis indicated that miR-302s are predicted to target several genes involved in the control of β-cell/epithelial phenotype maintenance; accordingly, such genes were downregulated upon human islet in vitro dedifferentiation. Moreover, we uncovered that cell–cell contacts are needed to maintain low/null expression levels of miR-302. In conclusion, we showed that miR-302 microRNA cluster genes are involved in in vitro dedifferentiation of human pancreatic islet cells and inhibits the expression of multiple genes involved in the maintenance of β-cell mature phenotype.

miR-758-3p: a blood-based biomarker that's influence on the expression of CERP/ABCA1 may contribute to the progression of obesity to metabolic syndrome

Due to increasing prevalence of obesity, a simple method or methods for the diagnosis of metabolic syndrome are urgently required to reduce the risk of associated cardiovascular disease, diabetes and cancer. This study aimed to identify a miRNA biomarker that may distinguish metabolic syndrome from obesity and to investigate if such a miRNA may have functional relevance for metabolic syndrome.

52 adults with clinical obesity (n=26) or metabolic syndrome (n=26) were recruited. Plasma specimens were procured from all and were randomly designated to discovery and validation cohorts. miRNA discovery profiling was performed, using array technology, on plasma RNA. Validation was performed by quantitative polymerase chain reaction. The functional effect of miR-758-3p on its predicted target, cholesterol efflux regulatory protein/ATP-binding cassette transporter, was investigated using HepG2 liver cells.

Custom miRNA profiling of 25 miRNAs in the discovery cohort found miR-758-3p to be detected in the obese cohort but undetected in the metabolic syndrome cohort. miR-758-3p was subsequently validated as a potential biomarker for metabolic syndrome by quantitative polymerase chain reaction. Bioinformatics analysis identified cholesterol efflux regulatory protein/ATP-binding cassette transporter as miR-758-3p’s predicted target. Specifically, mimicking miR-758-3p in HepG2 cells suppressed cholesterol efflux regulatory protein/ATP-binding cassette transporter protein expression; conversely, inhibiting miR-758-3p increased cholesterol efflux regulatory protein/ATP-binding cassette transporter protein expression.

miR-758-3p holds potential as a blood-based biomarker for distinguishing progression from obesity to metabolic syndrome and as a driver in controlling cholesterol efflux regulatory protein/ATP-binding cassette transporter expression, indicating it potential role in cholesterol control in metabolic syndrome.

Identification of microRNAs and genes associated with hyperandrogenism in the follicular fluid of women with polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disease, which is characterized by hyperandrogenism (HA), chronic anovulation, polycystic ovaries, insulin resistance, and obesity. At present, the mechanism by which PCOS/HA occurs has not been fully elucidated, thus, the mechanisms behind and interventions for HA in PCOS are current hot topics in research. MiRNAs have recently been shown to serve as diagnostic or prognostic biomarkers in patients with cancer. Thus, we are currently focused on studying the altered expression of miRNAs in follicular fluid and their correlation with HA in PCOS. Illumina deep sequencing technology was used to explore different miRNAs in the follicular fluid of women with PCOS/HA and in the follicular fluid of women in a control group. Target prediction databases were then used to analyse the target genes of different expressed miRNAs, and GO analysis and the KEGG pathway database were used to identify the functions and the main biochemical and signalling pathways of differentially expressed target genes. The expression levels of 263 miRNAs were significantly different (>2-fold up-regulated or <0.5-fold down-regulated, P < 0.05) between the two groups of women. For example, the expression levels of miRNA (200a-3p, 10b-3p, 200b-3p, 29c-3p, 99a-3p, and 125a-5p) were significantly increased, while there was a decreased expression of miR-105-3p in PCOS patients with respect to the control. Literature has shown that the above seven miRNAs were associated with HA in PCOS. Furthermore, 31 770 genes were predicted to be targets of the 263 differentially expressed microRNAs. GO analysis and the KEGG pathway database showed involvement of these target genes in HA in PCOS. These results suggest the presence of differentially expressed miRNAs in the follicular fluid of women with PCOS/HA versus women in the control group. The potential role of these microRNAs was elucidated using bioinformatics tools and was found to be involved in the regulation of different pathways, biological functions, and cellular components underlying PCOS. The results of this research may reveal new mechanisms of PCOS/HA and suggest potential treatment targets.

microRNA-503 contribute to pancreatic beta cell dysfunction by targeting the mTOR pathway in gestational diabetes mellitus

Loss of pancreatic β cells is involved in pathogenesis of gestational diabetes mellitus (GDM). Recently, several studies have elucidated the connection between microRNAs (miRNAs) and diabetes mellitus (DM), but the role of miRNAs in GDM remains unclear. The aim of this study was to evaluate the potential functions of miRNAs in GDM and to investigate the underlying mechanisms of action. First, we explored the expression profile of miRNAs in placenta tissue from GDM patients using microarray. Validation analysis was performed in peripheral blood specimens using quantitative reverse transcription PCR (qRT-PCR). Then the role and regulating mechanism of miR-503 in weaken the function of pancreatic β cell was investigated. We found that miR-503 was markedly upregulated in placenta tissue from GDM patients, as elevated in peripheral blood specimens, and the high level was positively correlated to blood glucose concentration. Knockdown of miR-503 enhanced insulin secretion of pancreatic β-cells, promoted cell proliferation and protected cells from apoptosis, whereas overexpression of miR-503 showed the opposite effects. Furthermore, mammalian target of rapamycin (mTOR) was identified as a direct target of miR-503 and mTOR silencing could reverse the improving effects of miR-503 knockdown on insulin secretion and pancreatic β-cells proliferation. High expression of miR-503 in peripheral blood may be acted as a diagnosis biomarker of GDM. MiR-503 regulated functions of pancreatic β-cells by targeting the mTOR pathway, suggesting that targeting miR-503/mTOR axis could serve as a novel therapeutic target for GDM.

miR-204 is associated with an endocrine phenotype in human pancreatic islets but does not regulate the insulin mRNA through MAFA

miR-204 has been proposed to modulate insulin expression in human pancreatic islets by regulating the expression of the MAFA transcript, and in turn insulin transcription. We investigated miR-204 expression in pancreatic endocrine tumors (PET), a panel of human tissues, tissues derived from pancreatic islet purification, and in induced pluripotent stem cells (iPSCs) differentiated towards a pancreatic endocrine phenotype by quantitative real time RT-PCR or droplet digital PCR (ddPCR). In addition, we evaluated the effect of miR-204 up- or down-regulation in purified human islets and in the EndoC-βH1 cell line, as an experimental model of human pancreatic β cells. Our results confirm that miR-204 was enriched in insulin producing PET, in β cells within healthy pancreatic islets, and highly expressed in EndoC-βH1 cells. Moreover, in iPSCs miR-204 increased stepwise upon stimulated differentiation to insulin producing cells. However, up- or down-regulation of miR-204 in human islets and in EndoC-βH1 cells resulted in modest and not significant changes of the MAFA and INS mRNAs measured by ddPCR or c-peptide release. Our data confirm the association of miR-204 with a β cell endocrine phenotype in human pancreatic islets, but do not support its direct role in regulating the levels of insulin mRNA through MAFA.

Interplay between miRNAs and human diseases

MicroRNAs (miRNAs) are endogenous, non-coding RNAs, which have evoked a great deal of interest due to their importance in many aspects of homeostasis and diseases. MicroRNAs are stable and are essential components of gene regulatory networks. They play a crucial role in healthy individuals and their dysregulations have also been implicated in a wide range of diseases, including diabetes, cardiovascular disease, kidney disease, and cancer. This review summarized the current understanding of interactions between miRNAs and different diseases and their role in disease diagnosis and therapy.

MicroRNA Dysregulation in Aging and Pathologies of the Skeletal Muscle

Skeletal muscle is one of the biggest organs of the body with important mechanistic and metabolic functions. Muscle homeostasis is controlled by environmental, genetic, and epigenetic factors. Indeed, MiRNAs, small noncoding RNAs robust regulators of gene expression, have and have been shown to regulate muscle homeostasis on several levels: through controlling myogenesis, muscle growth (hypertrophy) and atrophy, as well as interactions of muscle with other tissues. Given the large number of MiRNA target genes and the important role of MiRNAs in most physiological processes and various diseases, MiRNAs may have an enormous potential as therapeutic targets against numerous disorders, including pathologies of muscle. The purpose of this review is to present the current knowledge of the role of MiRNAs in skeletal muscle homeostasis and pathologies and the potential of MiRNAs as therapeutics for skeletal muscle wasting, with particular focus on the age- and disease-related loss of muscle mass and function.

Role of miRNAs in the pathogenesis and susceptibility of diabetes mellitus

MicroRNAs (miRNAs) are noncoding RNAs of ~22 nucleotides that regulate gene expression post-transcriptionally by binding to the 3' untranslated region of messenger RNA (mRNAs), resulting in inhibition of translation or mRNA degradation. miRNAs have a key role in fine-tuning cellular functions such as proliferation, differentiation and apoptosis, and they are involved in carcinogenesis, glucose homeostasis, inflammation and other biological processes. In this review, we focus on the role of miRNAs in the pathophysiology of the metabolic disease and diabetes mellitus, the hallmark of which is hyperglycemia caused by defective insulin secretion and/or action. A growing number of studies have revealed the association between miRNAs and the processes of insulin production and secretion in pancreatic β cells. In addition, aberrant expression of miRNAs in skeletal muscle, adipose tissue and liver has also been reported. Intriguingly, the tumor suppressor p53 has been implicated in the pathogenesis of diabetes in association with a number of miRNAs, suggesting that a p53/miRNA pathway might be a therapeutic target. Moreover, data from genome-wide association studies have revealed that several miRNA target sequences overlap type 2 diabetes susceptibility loci. Finally, the recent discovery of circulating miRNAs associated with diabetes onset/progression suggests the potential use of miRNAs as biomarkers.

MicroRNAs in Type 1 Diabetes: Complex Interregulation of the Immune System, β Cell Function and Viral Infections

Since the discovery of the first mammalian microRNA (miRNA) more than two decades ago, a plethora of miRNAs has been identified in humans, now amounting to more than 2500. Essential for post-transcriptional regulation of gene networks integral for developmental pathways and immune response, it is not surprising that dysregulation of miRNAs is often associated with the aetiology of complex diseases including cancer, diabetes and autoimmune disorders. Despite massive expansion of small RNA studies and extensive investigation in diverse disease contexts, the role of miRNAs in type 1 diabetes has only recently been explored. Key studies using human islets have recently implicated virus-induced miRNA dysregulation as a pivotal mechanism of β cell destruction, while the interplay between miRNAs, the immune system and β cell survival has been illustrated in studies using animal and cellular models of disease. The role of specific miRNAs as major players in immune system homeostasis highlights their exciting potential as therapeutics and prognostic biomarkers of type 1 diabetes.

MicroRNA-463-3p/ABCG4: A new axis in glucose-stimulated insulin secretion

OBJECTIVE

Glucose-stimulated insulin secretion (GSIS) is known to be essential in the control of metabolic fuel homeostasis, though the molecular mechanisms involved remain unclear.

METHODS

MicroRNA (miRNA)-463-3p and ATP-binding cassette A4 (ABCG4) expression was analyzed by real-time PCR, and the potential role of miRNA-463-3p or ABCG4 was evaluated by overexpressing or silencing such miRNA or genes.

RESULTS

The miRNA-463-3p inhibited GSIS without affecting cell viability. Further, mechanistic studies demonstrated that ABCG4 was a direct target of microRNA-463-3p and, to this effect, that ABCG4 played an important role in GSIS. The targeting was relevant in pancreatic islet β-cells, where GSIS through the miRNA-463-3p/ABCG4 axis was observed. Interestingly, in type 2 diabetes human pancreatic islets, expression of miRNA-463-3p and insulin was upregulated and ABCG4 downregulated compared with nondiabetic controls, and their expression levels were closely correlated.

CONCLUSIONS

The findings collectively establish a link between GSIS and the miRNA-463-3p/ABCG4 axis and represent a promising target for future diabetes mellitus treatments.

MicroRNA expression profiles in patients with acute Crimean Congo hemorrhagic fever reveal possible adjustments to cellular pathways

Several viral diseases are associated with altered microRNA (miRNA) expression, which can provide vital information about how cellular pathways respond to infection. However, the miRNA profile of Crimean Congo Hemorrhagic Fever (CCHFV) infections are not known. To address this gap, we performed real-time PCR-based miRNA analysis in individuals with acute Crimean Congo Hemorrhagic Fever (CCHFV) infections, with the goal of identifying pathways that might be associated with this disease. Peripheral blood mononuclear cells were analysed in eight individuals with detectable viral RNA and compared to five healthy subjects. A total of 106 differentially expressed miRNAs were identified, of which 19 miRNAs were either fivefold prominently up- or down-regulation. Several miRNAs associated with cytokine expression, some of which were previously associated with Dengue and Hantavirus infections were revealed. Moreover, possible mechanisms related to secretion of adhesion molecules and viral escape from innate immunity were identified. Pathway enrichment analyses further revealed the putative involvement of TNF-alfa, TGF-beta, MAPK, WNT, and neurotrophin signaling pathways in disease pathogenesis. J. Med. Virol. 89:417-422, 2017. © 2016 Wiley Periodicals, Inc.

Hyperglycemia-induced changes in miRNA expression patterns in epicardial adipose tissue of piglets

MicroRNAs (miRNAs) are a class of molecular posttranscriptional regulators found to participate in numerous biological mechanisms, such as adipogenesis, fat deposition, or glucose metabolism. Additionally, a detailed analysis on the molecular and cellular mechanisms of miRNA-related effects on metabolism leads to developing novel diagnostic markers and therapeutic approaches. To identify miRNA whose activity changed in epicardial adipose tissue in piglets during hyperglycemia, we analyzed the different miRNA expression patterns between control and hyperglycemia groups. The microarray analysis selected three differentially expressed microRNAs as potential biomarkers: hsa-miR-675-5p, ssc-miR-193a-3p, and hsa-miR-144-3p. The validation of miRNA expression with real-time PCR indicated an increased expression levels of ssc-miR-193a-3p and miR-675-5p, whereas the expression level of hsa-miR-144-3p was lower in epicardial adipose tissue in response to hyperglycemia (P<0.01). The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses suggested that these miRNAs differentially expressed between hyperglycemic and control piglets are involved in insulin, adipocytokine, and phosphatidylinositol 3-kinase-Akt signaling pathways, and development of type 2 diabetes as well. The results suggested that hyperglycemia can significantly affect the expression patterns of miRNA in porcine adipose tissue.

MicroRNAs as regulators of beta-cell function and dysfunction

In the last decade, there has been an explosion in both the number of and knowledge about miRNAs associated with both type 1 and type 2 diabetes. Even though we are presently in the initial stages of understanding how this novel class of posttranscriptional regulators are involved in diabetes, recent studies have demonstrated that miRNAs are important regulators of the islet transcriptome, controlling apoptosis, differentiation and proliferation, as well as regulating unique islet and beta-cell functions and pathways such as insulin expression, processing and secretion. Furthermore, a large number of miRNAs have been linked to diabetogenic processes induced by elevated levels of glucose, free fatty acids and inflammatory cytokines. Thus, miRNAs are novel therapeutic targets with the potential of protecting the beta-cell, and there is proof of principle that miRNA antagonists, so-called antagomirs, are effective in vivo for other disorders. miRNAs are exported out of cells in exosomes, raising the intriguing possibility of cell-to-cell communication between distant tissues via miRNAs and that miRNAs can be used as biomarkers of beta-cell function, mass and survival. The purpose of this review is to provide a status on how miRNAs control beta-cell function and viability in health and disease.

Uptake of dietary milk miRNAs by adult humans: a validation study

Breast milk is replete with nutritional content as well as nucleic acids including microRNAs (miRNAs). In a recent report, adult humans who drank bovine milk appeared to have increased circulating levels of miRNAs miR-29b-3p and miR-200c-3p. Since these miRNAs are homologous between human and cow, these results could be explained by xeno-miRNA influx, endogenous miRNA regulation, or both. More data were needed to validate the results and explore for additional milk-related alterations in circulating miRNAs. Samples from the published study were obtained, and 223 small RNA features were profiled with a custom OpenArray, followed by individual quantitative PCR assays for selected miRNAs. Additionally, small RNA sequencing (RNA-seq) data obtained from plasma samples of the same project were analyzed to find human and uniquely bovine miRNAs. OpenArray revealed no significantly altered miRNA signals after milk ingestion, and this was confirmed by qPCR. Plasma sequencing data contained no miR-29b or miR-200c reads and no intake-consistent mapping of uniquely bovine miRNAs. In conclusion, the results do not support transfer of dietary xenomiRs into the circulation of adult humans.

Multiple microRNAs within the 14q32 cluster target the mRNAs of major type 1 diabetes autoantigens IA-2, IA-2β, and GAD65

Islet antigen (IA)-2, IA-2β, and glutamate decarboxylase (GAD65) are major autoantigens in type 1 diabetes (T1D). Autoantibodies to these autoantigens appear years before disease onset and are widely used as predictive markers. Little is known, however, about what regulates the expression of these autoantigens. The present experiments were initiated to test the hypothesis that microRNAs (miRNAs) can target and affect the levels of these autoantigens. Bioinformatics was used to identify miRNAs predicted to target the mRNAs coding IA-2, IA-2β, and GAD65. RNA interference for the miRNA processing enzyme Dicer1 and individual miRNA mimics and inhibitors were used to confirm the effect in mouse islets and MIN6 cells. We show that the imprinted 14q32 miRNA cluster contains 56 miRNAs, 32 of which are predicted to target the mRNAs of T1D autoantigens and 12 of which are glucose-sensitive. Using miRNA mimics and inhibitors, we confirmed that at least 7 of these miRNAs modulate the mRNA levels of the T1D autoantigens. Dicer1 knockdown significantly reduced the mRNA levels of all 3 autoantigens, further confirming the importance of miRNAs in this regulation. We conclude that miRNAs are involved in regulating the expression of the major T1D autoantigens.

Differential expression of miRNAs and their relation to active tuberculosis

The aim of this work was to screen miRNA signatures dysregulated in tuberculosis to improve our understanding of the biological role of miRNAs involved in the disease. Datasets deposited in publically available databases from microarray studies on infectious diseases and malignancies were retrieved, screened, and subjected to further analysis. Effect sizes were combined using the inverse-variance model and between-study heterogeneity was evaluated by the random effects model. 35 miRNAs were differentially expressed (12 up-regulated, 23 down-regulated; p < 0.05) by combining 15 datasets of tuberculosis and other infectious diseases. 15 miRNAs were found to be significantly differentially regulated (7 up-regulated, 8 down-regulated; p < 0.05) by combining 53 datasets of tuberculosis and malignancies. Most of the miRNA signatures identified in this study were found to be involved in immune responses and metabolism. Expression of these miRNA signatures in serum samples from TB subjects (n = 11) as well as healthy controls (n = 10) was examined by TaqMan miRNA array. Taken together, the results revealed differential expression of miRNAs in TB, but available datasets are limited and these miRNA signatures should be validated in future studies.

A novel function of microRNA 130a-3p in hepatic insulin sensitivity and liver steatosis

MicroRNAs (miRNAs) are endogenous, noncoding, short, single-stranded RNAs that are evolutionarily conserved and believed to play a role in controlling a variety of biological processes. The roles of miRNAs in insulin resistance and liver steatosis, however, are largely unknown. The objective of this study was to evaluate the roles of miR-130a in the regulation of insulin sensitivity and liver steatosis. In our current study, we observed that overexpression of miR-130a-3p increases insulin signaling in both HepG2 cells and primary mouse hepatocytes, and silencing of miR-130a-3p has the opposite effects. However, miR-130a-5p has no effect in the regulation of insulin signaling. Consistently, whole-body and hepatic insulin sensitivity are improved in mice injected with adenoviruses that overexpress miR-130a-3p. Furthermore, we provided evidence showing that growth factor receptor-bound protein 10 is required for miR-130a-3p-regulated insulin sensitivity. On the other hand, we observed that expression of miR-130a-3p is decreased in the livers of db/db mice and that adenovirus-mediated overexpression of miR-130a-3p reverses insulin resistance and liver steatosis, the latter of which is achieved via suppressing fatty acid synthase expression in these mice. This study identifies a novel function for hepatic miR-130a-3p in the regulation of insulin sensitivity and liver steatosis.

MicroRNA-410 regulated lipoprotein lipase variant rs13702 is associated with stroke incidence and modulated by diet in the randomized controlled PREDIMED trial

BACKGROUND

MicroRNAs have emerged as important epigenetic regulators in cardiovascular diseases (CVDs). Using an observational meta-analysis design, we previously characterized a gain-of-function microRNA-410 target site polymorphism (rs13702T>C) in the 3'untranslated region of the lipoprotein lipase (LPL) gene. The C allele was associated with lower triglycerides, and this association was modulated by fat intake.

OBJECTIVES

We aimed to extend our findings by assessing the interaction between the rs13702 polymorphism and fat intake on triglycerides at baseline and longitudinally by using a dietary intervention design. We also examined as a primary outcome the association of this variant with CVD incidence and its modulation by the Mediterranean diet (MedDiet).

DESIGN

We studied 7187 participants in the PREDIMED (Prevención con Dieta Mediterránea) randomized trial that tested a MedDiet intervention compared with a control diet, with a median 4.8-y follow-up. LPL polymorphisms and triglycerides were determined and CVD assessed. Gene-diet interactions for triglycerides were analyzed at baseline (n = 6880) and after a 3-y intervention (n = 4131). Oxidative stress parameters were investigated in a subsample.

RESULTS

The rs13702T>C polymorphism was strongly associated with lower triglycerides in C allele carriers and interacted synergistically with dietary monounsaturated (P = 0.038) and unsaturated fat intake (P = 0.037), decreasing triglycerides at baseline. By 3 y, we observed a gene-diet interaction (P = 0.025) in which the C allele was associated with a greater reduction in triglycerides after intervention with MedDiet, high in unsaturated fat. Although the polymorphism was associated with lower stroke risk (HR: 0.74; 95% CI: 0.57, 0.97; P = 0.029 per C allele), this association reached statistical significance only in the MedDiet intervention (HR: 0.58; 95% CI: 0.37, 0.91; P = 0.019 in C compared with TT carriers), not in the control group (HR: 0.94; 95% CI: 0.55, 1.59; P = 0.805).

CONCLUSION

We report a novel association between a microRNA target site variant and stroke incidence, which is modulated by diet in terms of decreasing triglycerides and possibly stroke risk in rs13702 C allele carriers after a high-unsaturated fat MedDiet intervention.

A rare SNP in pre-miR-34a is associated with increased levels of miR-34a in pancreatic beta cells

Changes in the levels of specific microRNAs (miRNAs) can reduce glucose-stimulated insulin secretion and increase beta-cell apoptosis, two causes of islet dysfunction and progression to type 2 diabetes. Studies have shown that single nucleotide polymorphisms (SNPs) within miRNA genes can affect their expression. We sought to determine whether miRNAs, with a known role in beta-cell function, possess SNPs within the pre-miRNA structure which can affect their expression. Using published literature and dbSNP, we aimed to identify miRNAs with a role in beta-cell function that also possess SNPs within the region encoding its pre-miRNA. Following transfection of plasmids, encoding the pre-miRNA and each allele of the SNP, miRNA expression was measured. Two rare SNPs located within the pre-miRNA structure of two miRNA genes important to beta-cell function (miR-34a and miR-96) were identified. Transfection of INS-1 and MIN6 cells with plasmids encoding pre-miR-34a and the minor allele of rs72631823 resulted in significantly (p < 0.05) higher miR-34a expression, compared to cells transfected with plasmids encoding the corresponding major allele. Similarly, higher levels were also observed upon transfection of HeLa cells. Transfection of MIN6 cells with plasmids encoding pre-miR-96 and each allele of rs41274239 resulted in no significant differences in miR-96 expression. A rare SNP in pre-miR-34a is associated with increased levels of mature miR-34a. Given that small changes in miR-34a levels have been shown to cause increased levels of beta-cell apoptosis this finding may be of interest to studies looking at determining the effect of rare variants on type 2 diabetes susceptibility.

Time-dependent expression profiles of microRNAs and mRNAs in rat milk whey

Functional RNAs, such as microRNA (miRNA) and mRNA, are present in milk, but their roles are unknown. To clarify the roles of milk RNAs, further studies using experimental animals such as rats are needed. However, it is unclear whether rat milk also contains functional RNAs and what their time dependent expression profiles are. Thus, we prepared total RNA from whey isolated from rat milk collected on days 2, 9, and 16 postpartum and analyzed using microarrays and quantitative PCR. The concentration of RNA in colostrum whey (day 2) was markedly higher than that in mature milk whey (days 9 and 16). Microarray analysis detected 161 miRNAs and 10,948 mRNA transcripts. Most of the miRNAs and mRNA transcripts were common to all tested milks. Finally, we selected some immune- and development-related miRNAs and mRNAs, and analysed them by quantitative PCR (in equal sample volumes) to determine their time-dependent changes in expression in detail. Some were significantly more highly expressed in colostrum whey than in mature milk whey, but some were expressed equally. And mRNA expression levels of some cytokines and hormones did not reflect the protein levels. It is still unknown whether RNAs in milk play biological roles in neonates. However, our data will help guide future in vivo studies using experimental animals such as rats.

MicroRNAs -the next generation therapeutic targets in human diseases

MicroRNAs (miRNAs), an abundant class of ~22-nucleotide non-coding RNAs, regulate the expression of genes at post transcriptional level. MiRNAs are important regulators of eukaryotic gene expression and therefore implicated in a wide range of biological processes. The miRNA-related genetic alterations are possibly more implicated human diseases than currently appreciated. Genetic variants in miRNA target sites, called miRNA genes are identified to be associated with human diseases. This review discusses about the role of micro-RNA genes in various human diseases such as neurodegenerative disorders, cardio-vascular diseases, and metabolic disorders, and how they can be targeted as a new therapeutic tool in future with reference to drug discoveries/ development.

Identifying common and specific microRNAs expressed in peripheral blood mononuclear cell of type 1, type 2, and gestational diabetes mellitus patients

Background

Regardless the regulatory function of microRNAs (miRNA), their differential expression pattern has been used to define miRNA signatures and to disclose disease biomarkers. To address the question of whether patients presenting the different types of diabetes mellitus could be distinguished on the basis of their miRNA and mRNA expression profiling, we obtained peripheral blood mononuclear cell (PBMC) RNAs from 7 type 1 (T1D), 7 type 2 (T2D), and 6 gestational diabetes (GDM) patients, which were hybridized to Agilent miRNA and mRNA microarrays. Data quantification and quality control were obtained using the Feature Extraction software, and data distribution was normalized using quantile function implemented in the Aroma light package. Differentially expressed miRNAs/mRNAs were identified using Rank products, comparing T1DxGDM, T2DxGDM and T1DxT2D. Hierarchical clustering was performed using the average linkage criterion with Pearson uncentered distance as metrics.

Results

The use of the same microarrays platform permitted the identification of sets of shared or specific miRNAs/mRNA interaction for each type of diabetes. Nine miRNAs (hsa-miR-126, hsa-miR-1307, hsa-miR-142-3p, hsa-miR-142-5p, hsa-miR-144, hsa-miR-199a-5p, hsa-miR-27a, hsa-miR-29b, and hsa-miR-342-3p) were shared among T1D, T2D and GDM, and additional specific miRNAs were identified for T1D (20 miRNAs), T2D (14) and GDM (19) patients. ROC curves allowed the identification of specific and relevant (greater AUC values) miRNAs for each type of diabetes, including: i) hsa-miR-1274a, hsa-miR-1274b and hsa-let-7f for T1D; ii) hsa-miR-222, hsa-miR-30e and hsa-miR-140-3p for T2D, and iii) hsa-miR-181a and hsa-miR-1268 for GDM. Many of these miRNAs targeted mRNAs associated with diabetes pathogenesis.

Conclusions

These results indicate that PBMC can be used as reporter cells to characterize the miRNA expression profiling disclosed by the different diabetes mellitus manifestations. Shared miRNAs may characterize diabetes as a metabolic and inflammatory disorder, whereas specific miRNAs may represent biological markers for each type of diabetes, deserving further attention.

miRNA-30a-5p-mediated silencing of Beta2/NeuroD expression is an important initial event of glucotoxicity-induced beta cell dysfunction in rodent models

AIMS/HYPOTHESIS

The loss of beta cell function is a critical factor in the development of type 2 diabetes. Glucotoxicity plays a major role in the progressive deterioration of beta cell function and development of type 2 diabetes mellitus. Here we demonstrate that microRNA (miR)-30a-5p is a key player in early-stage glucotoxicity-induced beta cell dysfunction.

METHODS

We performed northern blots, RT-PCR and western blots in glucotoxicity-exposed primary rat islets and INS-1 cells. We also measured glucose-stimulated insulin secretion and insulin content. In vivo approaches were used to evaluate the role of miR-30a-5p in beta cell dysfunction.

RESULTS

miR-30a-5p expression was increased in beta cells after exposure to glucotoxic conditions, and exogenous miR-30a-5p overexpression also induced beta cell dysfunction in vitro. miR-30a-5p directly suppressed expression of Beta2/NeuroD (also known as Neurod1) by binding to a specific binding site in its 3'-untranslated region. After restoration of Beta2/NeuroD expression by knockdown miR-30a-5p or transfection of the Beta2/NeuroD gene, beta cell dysfunction, including decreased insulin content, gene expression and glucose-stimulated insulin secretion, recovered. Glucose tolerance and beta cell dysfunction improved on direct injection of Ad-si30a-5p into the pancreas of diabetic mice.

CONCLUSIONS/INTERPRETATION

Our data demonstrate that miR-30a-5p-mediated direct suppression of Beta2/NeuroD gene expression is an important initiation step of glucotoxicity-induced beta cell dysfunction.

Bovine milk contains microRNA and messenger RNA that are stable under degradative conditions

We previously reported that microRNA (miRNA) is present in human breast milk. Recently, other groups have reported that bovine milk also contains miRNA; however, these reports are few. We therefore investigated bovine milk miRNA using microarray and quantitative PCR analyses to identify the differences between colostrum and mature milk. The RNA concentration in a colostrum whey fraction was higher than that in a mature milk whey fraction. In total, 102 miRNA were detected in bovine milk by microarray analysis (100 in colostrum and 53 in mature milk; 51 were common to both). Among these miRNA, we selected several immune- and development-related miRNA, including miR-15b, miR-27b, miR-34a, miR-106b, miR-130a, miR-155, and miR-223. These miRNA were detected in bovine milk by quantitative PCR, and each of these miRNA was significantly more highly expressed in colostrum than in mature milk. We also confirmed the presence of some mRNA in bovine milk. Nevertheless, synthesized miRNA spiked in the raw milk whey were degraded, and naturally existing miRNA and mRNA in raw milk were resistant to acidic conditions and RNase treatment. The RNA molecules in milk were stable. We also detected miRNA and mRNA in infant formulas purchased from Japanese markets. It is still unknown whether milk-derived RNA molecules play biological roles in infants; however, if milk-derived RNA do show functions in infants, our data will help guide future studies.

Procyanidins modulate microRNA expression in pancreatic islets

Procyanidins modulate glucose metabolism, partly due to its effects on pancreas. Given the role of microRNAs (miRNAs) in the regulation of diabetes and the fact that flavonoids modulate miRNAs in other tissues, we hypothesized that procyanidins might target miRNAs in the pancreas. We investigated the miRNA expression profile in pancreatic islets isolated from rats treated with a daily dose of grape seed procyanidin extract (GSPE) (25 mg/kg of body weight) for 45 days. The miRWalk database identified putative target genes of these miRNAs. We found that GSPE altered significantly the expression of miR-1249, miR-483, miR-30c-1*, and miR-3544. In silico prediction studies suggested that ion transport and response to glucose are among the regulated pathways. As a conclusion, this is the first study showing that procyanidins can also exert their bioactivity on pancreatic islets by modifying the miRNA expression pattern.

Gain-of-function lipoprotein lipase variant rs13702 modulates lipid traits through disruption of a microRNA-410 seed site

Genome-wide association studies (GWAS) have identified hundreds of genetic variants that are associated with lipid phenotypes. However, data supporting a functional role for these variants in the context of lipid metabolism are scarce. We investigated the association of the lipoprotein lipase (LPL) variant rs13702 with plasma lipids and explored its potential for functionality. The rs13702 minor allele had been predicted to disrupt a microRNA (miR) recognition element (MRE) seed site (MRESS) for the human microRNA-410 (miR-410). Furthermore, rs13702 is in linkage disequilibrium (LD) with several SNPs identified by GWAS. We performed a meta-analysis across ten cohorts of participants that showed a statistically significant association of rs13702 with triacylglycerols (TAG) (p = 3.18 × 10(-42)) and high-density lipoprotein cholesterol (HDL-C) (p = 1.35 × 10(-32)) with each copy of the minor allele associated with 0.060 mmol/l lower TAG and 0.041 mmol/l higher HDL-C. Our data showed that an LPL 3' UTR luciferase reporter carrying the rs13702 major T allele was reduced by 40% in response to a miR-410 mimic. We also evaluated the interaction between intake of dietary fatty acids and rs13702. Meta-analysis demonstrated a significant interaction between rs13702 and dietary polyunsaturated fatty acid (PUFA) with respect to TAG concentrations (p = 0.00153), with the magnitude of the inverse association between dietary PUFA intake and TAG concentration showing -0.007 mmol/l greater reduction. Our results suggest that rs13702 induces the allele-specific regulation of LPL by miR-410 in humans. This work provides biological and potential clinical relevance for previously reported GWAS variants associated with plasma lipid phenotypes.

From cellular senescence to age-associated diseases: the miRNA connection

Cellular senescence has evolved from an in-vitro model system to study aging in vitro to a multifaceted phenomenon of in-vivo importance as senescent cells in vivo have been identified and their removal delays the onset of age-associated diseases in a mouse model system. From the large emerging class of non-coding RNAs, miRNAs have only recently been functionally implied in the regulatory networks that are modified during the aging process. Here we summarize examples of similarities between the differential expression of miRNAs during senescence and age-associated diseases and suggest that these similarities might emphasize the importance of senescence for the pathogenesis of age-associated diseases. Understanding such a connection on the level of miRNAs might offer valuable opportunities for designing novel diagnostic and therapeutic strategies.

Transcriptional and translational regulation of cytokine signaling in inflammatory β-cell dysfunction and apoptosis

Disease is conventionally viewed as the chaotic inappropriate outcome of deranged tissue function resulting from aberrancies in cellular processes. Yet the patho-biology of cellular dysfunction and death encompasses a coordinated network no less sophisticated and regulated than maintenance of homeostatic balance. Cellular demise is far from passive subordination to stress but requires controlled coordination of energy-requiring activities including gene transcription and protein translation that determine the graded transition between defensive mechanisms, cell cycle regulation, dedifferentiation and ultimately to the activation of death programmes. In fact, most stressors stimulate both homeostasis and regeneration on one hand and impairment and destruction on the other, depending on the ambient circumstances. Here we illustrate this bimodal ambiguity in cell response by reviewing recent progress in our understanding of how the pancreatic β cell copes with inflammatory stress by changing gene transcription and protein translation by the differential and interconnected action of reactive oxygen and nitric oxide species, microRNAs and posttranslational protein modifications.

MicroRNAs in insulin resistance and obesity

MicroRNAs (miRNAs) are a class of short, single-stranded non-protein coding gene products which can regulate the gene expression through post-transcriptional inhibition of messenger RNA (mRNA) translation. They are known to be involved in many essential biological processes including development, insulin secretion, and adipocyte differentiation. miRNAs are involved in complex metabolic processes, such as energy and lipid metabolism, which have been studied in the context of diabetes and obesity. Obesity, hyperlipidemia (elevated levels of blood lipids), and insulin resistance are strongly associated with the onset of type 2 diabetes. These conditions are also associated with aberrant expression of multiple essential miRNAs in pancreatic islets of Langerhans and peripheral tissues, including adipose tissue. A thorough understanding of the physiological role these miRNAs play in these tissues, and changes to their expression under pathological conditions, will allow researchers to develop new therapeutics with the potential to correct the aberrant expression of miRNAs in type 2 diabetes and obesity.

Post-transcriptional regulation in metabolic diseases

Post-transcriptional gene regulation by microRNAs (miRNAs) and RNA-binding proteins (RBPs) is central to many biological functions. Aberrant gene expression patterns underlie many metabolic diseases that represent major public health concerns and formidable therapeutic challenges. Several studies have established a number of post-transcriptional regulators implicated in metabolic diseases such as diabetes and obesity. In addition, emerging knowledge of metabolically active and insulin-sensitive organs, such as the pancreas, liver, muscle and adipose compartment, is rapidly expanding the panel of potential therapeutic targets for the treatment of metabolic diseases. Here, we review our current understanding of miRNAs and RBPs that affect glucose and lipid homeostasis, and their roles in normal physiology and metabolic disorders, especially type 2 diabetes and obesity.

miRNA-125b regulates TNF-α production in CD14+ neonatal monocytes via post-transcriptional regulation

Neonates, although deficient in cell immunity, frequently reveal sepsis with augmented proinflammatory reactions. Here, we found that neonatal monocytes produced significantly higher TNF-α mRNA and protein than adult monocytes. Assessment of the transcriptional factor found no significant difference of NF-κB p65 level between neonatal and adult monocytes. Addition of Act D to access the half-life of TNF-α mRNA revealed no significant difference of the LPS-induced TNF-α mRNA half-life between them, whereas CHX increased neonatal TNF-α mRNA significantly. This suggests that a post-transcriptional mechanism involves the augmentation of TNF-α production by neonatal monocytes. To examine whether miRNA was involved in the post-transcriptional regulation, differential displays of miRNA array between neonatal and adult MNCs were performed, along with the discovery of hsa-miR-103, hsa-miR-125b, hsa-miR-130a, hsa-miR-454-3p, and hsa-miR-542-3p, which were greater than a twofold decrease or increase after LPS treatment for 4 h. The functional validation identified that miR-125b decreased significantly in association with higher TNF-α expression by neonatal monocytes after LPS stimulation. Transfection of the miR-125b precursor into neonatal monocytes significantly repressed the TNF-α mRNA and protein expression, suggesting that miR-125b negatively regulates TNF-α expression in neonatal monocytes. Modulation of miRNA expression may be used to regulate TNF-α production in newborns with altered proinflammatory reactions.

miRNAs and diabetes mellitus

Diabetes is a chronic disease that manifests when insulin production by the pancreas is insufficient or when the body cannot effectively utilize the secreted insulin. The onset of diabetes often goes undetected until the later stages where subsequent glucose accumulation in the system (hyperglycemia) is observed. Over time, it leads to serious multi-organ damage, especially to the nerves and blood vessels. The WHO reports that approximately 346 million people worldwide are diagnosed with diabetes. With no cure available, long-term medical care for diabetes has become a global economic challenge globally. Hence, there is a need to explore novel early biomarkers and therapeutics for diabetes. One such potential molecule is the miRNAs. miRNAs are endogenous, noncoding RNAs that predominantly inhibit gene expression. Compelling evidence showed that altered miRNA expressions are linked to pathological conditions, including diabetes manifestation. This review focuses on the implications of miRNAs in diabetes and their related complications.

Increased expression of miR-325-3p by urocortin 2 and its involvement in stress-induced suppression of LH secretion in rat pituitary

Urocortin 2 (Ucn2) is a member of the corticotropin releasing factor (CRF) peptide family, which binds to CRF type 2 receptor. We previously reported on expression of Ucn2 in proopiomelanocortin cells of rat pituitary and its inhibitory action on LH secretion. We also demonstrated that Ucn2 is involved in the mechanism underlying immobilization-induced suppression of LH secretion; the details remain unclear. Here, we found that Ucn2 increased the expression of miR-325-3p, one of three microRNAs with predicted sequence for binding to LH β-subunit 3'-untranslated region (3'-UTR) in monolayer cultured rat anterior pituitary cells, and that miR-325-3p was expressed in LH cells of the anterior pituitary. Immobilization also increased miR-325-3p expression in the anterior pituitary, and its increase was blocked by pretreatment with anti-Ucn2 IgG. Overexpression of miR-325-3p in cultured pituitary cells significantly suppressed intracellular contents and secretion of LH, while miR-325-3p knockdown blocked Ucn2-induced suppression of intracellular contents and secretion of LH. Coexpression of miR-325-3p with LH β-subunit 3'-UTR-fused luciferase vector significantly suppressed luciferase activity compared with that of mock transfectants. These results suggest that miR-325-3p is involved in immobilization-induced suppression of LH translation and secretion and that Ucn2 plays a role in the increase in miR-325-3p expression.