MicroRNA-494, upregulated by tumor necrosis factor-α, desensitizes insulin effect in C2C12 muscle cells

Dietary modulation of microRNAs in insulin resistance and type 2 diabetes

The prevalence of type 2 diabetes is increasing worldwide. Various molecular mechanisms have been proposed to interfere with the insulin signaling pathway. Recent advances in proteomics and genomics indicate that one such mechanism involves the post-transcriptional regulation of insulin signaling by microRNA (miRNA). These noncoding RNAs typically induce messenger RNA (mRNA) degradation or translational repression by interacting with the 3' untranslated region (3'UTR) of target mRNA. Dietary components and patterns, which can either enhance or impair the insulin signaling pathway, have been found to regulate miRNA expression in both in vitro and in vivo studies. This review provides an overview of the current knowledge of how dietary components influence the expression of miRNAs related to the control of the insulin signaling pathway and discusses the potential application of these findings in precision nutrition.

The Interplay Between Cytokines and MicroRNAs to Regulate Metabolic Disorders

Metabolic disorders represent significant public health challenges worldwide. Emerging evidence suggests that cytokines and microRNAs (miRNAs) play crucial roles in the pathogenesis of metabolic disorders by regulating various metabolic processes, including insulin sensitivity, lipid metabolism, and inflammation. This review provides a comprehensive overview of the intricate interplay between cytokines and miRNAs in the context of metabolic disorders, including obesity, type 2 diabetes, and cardiovascular diseases. We discuss how dysregulation of cytokine-miRNA networks contributes to the development and progression of metabolic disorders and explore the therapeutic potential of targeting these interactions for disease management.

The role of miR-143/miR-145 in the development, diagnosis, and treatment of diabetes

Objectives

Diabetes mellitus [DM], is a multifaceted metabolic disease, which has become a worldwide threat to human wellness. Over the past decades, an enormous amount of attention has been devoted to understanding how microRNAs [miRNAs], a class of small non-coding RNA regulators of gene expression at the post-transcriptional level, are tied to DM pathology. It has been demonstrated that miRNAs control insulin synthesis, secretion, and activity. This review aims to provide an evaluation of the use of miR-143 and miR-145 as biomarkers for the diagnosis and prognosis of diabetes.

Methods

The use of miR-143 and miR-145 as biomarkers for the diagnosis and prognosis of diabetes has been studied, and research that examined this link was sought after in the literature. In addition, we will discuss the cellular and molecular pathways of insulin secretion regulation by miR-143/145 expression and finally their role in diabetes.

Results

In the current review, we emphasize recent findings on the miR-143/145 expression profiles as novel DM biomarkers in clinical studies and animal models and highlight recent discoveries on the complex regulatory effect and functional role of miR-143/145 expression in DM.

Conclusion

A novel clinical treatment that alters the expression and activity of miR-143/miR-145 may be able to return cells to their natural state of glucose homeostasis, demonstrating the value of using comprehensive miRNA profiles to predict the beginning of diabetes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01317-y.

Regulation and mechanism of action of miRNAs on insulin resistance in skeletal muscles

The term "insulin resistance" is commonly understood as a decrease in the response of insulin-sensitive tissues to insulin at its sufficient concentration, leading to chronic compensatory hyperinsulinemia. Type 2 diabetes mellitus is based on mechanisms consisting in the development of resistance to insulin in target cells (hepatocytes, adipocytes, skeletal muscle cells), resulting in the termination of an adequate response of these tissues to interaction with insulin. Since in healthy people 75-80% of glucose is utilized by skeletal muscle, it is more likely that the main cause of insulin resistance is impaired insulin-stimulated glucose utilization by skeletal muscle. With insulin resistance, skeletal muscles do not respond to insulin at its normal concentration, thereby determining an increase in glucose levels and a compensatory increase in insulin production in response to this. Despite many years of studying diabetes mellitus (DM) and insulin resistance, the molecular genetic basis for the development of these pathological conditions is still the subject of numerous studies. Recent studies point to the involvement of microRNAs (miRNAs) as dynamic modifiers in the pathogenesis of various diseases. MiRNAs are a separate class of RNA molecules that play a key role in the post-transcriptional regulation of gene expression. Recent studies have shown that miRNAs dysregulation in DM is closely related to miRNAs regulatory abilities in skeletal muscle insulin resistance. This gave grounds to consider an increase or decrease in the expression of individual microRNAs in muscle tissue and consider them as new biomarkers for diagnosing and monitoring insulin resistance and promising directions for targeted therapy. This review presents the results of scientific studies examining the role of miRNAs in skeletal muscle insulin resistance.

Estrogen Receptor Subtypes Elicit a Distinct Gene Expression Profile of Endothelial-Derived Factors Implicated in Atherosclerotic Plaque Vulnerability

In the presence of established atherosclerosis, estrogens are potentially harmful. MMP-2 and MMP-9, their inhibitors (TIMP-2 and TIMP-1), RANK, RANKL, OPG, MCP-1, lysyl oxidase (LOX), PDGF-β, and ADAMTS-4 play critical roles in plaque instability/rupture. We aimed to investigate (i) the effect of estradiol on the expression of the abovementioned molecules in endothelial cells, (ii) which type(s) of estrogen receptors mediate these effects, and (iii) the role of p21 in the estrogen-mediated regulation of the aforementioned factors. Human aortic endothelial cells (HAECs) were cultured with estradiol in the presence or absence of TNF-α. The expression of the aforementioned molecules was assessed by qRT-PCR and ELISA. Zymography was also performed. The experiments were repeated in either ERα- or ERβ-transfected HAECs and after silencing p21. HAECs expressed only the GPR-30 estrogen receptor. Estradiol, at low concentrations, decreased MMP-2 activity by 15-fold, increased LOX expression by 2-fold via GPR-30, and reduced MCP-1 expression by 3.5-fold via ERβ. The overexpression of ERα increased MCP-1 mRNA expression by 2.5-fold. In a low-grade inflammation state, lower concentrations of estradiol induced the mRNA expression of MCP-1 (3.4-fold) and MMP-9 (7.5-fold) and increased the activity of MMP-2 (1.7-fold) via GPR-30. Moreover, p21 silencing resulted in equivocal effects on the expression of the abovementioned molecules. Estradiol induced different effects regarding atherogenic plaque instability through different ERs. The balance of the expression of the various ER subtypes may play an important role in the paradoxical characterization of estrogens as both beneficial and harmful.

RNA sequencing reveals potential interacting networks between the altered transcriptome and ncRNome in the skeletal muscle of diabetic mice

For a global epidemic like Type 2 diabetes mellitus (T2DM), while impaired gene regulation is identified as a primary cause of aberrant cellular physiology; in the past few years, non-coding RNAs (ncRNAs) have emerged as important regulators of cellular metabolism. However, there are no reports of comprehensive in-depth cross-talk between these regulatory elements and the potential consequences in the skeletal muscle during diabetes. Here, using RNA sequencing, we identified 465 mRNAs and 12 long non-coding RNAs (lncRNAs), to be differentially regulated in the skeletal muscle of diabetic mice and pathway enrichment analysis of these altered transcripts revealed pathways of insulin, FOXO and AMP-activated protein kinase (AMPK) signaling to be majorly over-represented. Construction of networks showed that these pathways significantly interact with each other that might underlie aberrant skeletal muscle metabolism during diabetes. Gene-gene interaction network depicted strong interactions among several differentially expressed genes (DEGs) namely, Prkab2, Irs1, Pfkfb3, Socs2 etc. Seven altered lncRNAs depicted multiple interactions with the altered transcripts, suggesting possible regulatory roles of these lncRNAs. Inverse patterns of expression were observed between several of the deregulated microRNAs (miRNAs) and the differentially expressed transcripts in the tissues. Towards validation, overexpression of miR-381-3p and miR-539-5p in skeletal muscle C2C12 cells significantly decreased the transcript levels of their targets, Nfkbia, Pik3r1 and Pi3kr1, Cdkn2d, respectively. Collectively, the findings provide a comprehensive understanding of the interactions and cross-talk between the ncRNome and transcriptome in the skeletal muscle during diabetes and put forth potential therapeutic options for improving insulin sensitivity.

MiR-494-mediated Effects on the NF-κB Signaling Pathway Regulate Lipopolysaccharide-Induced Acute Kidney Injury in Mice

OBJECTIVE

To explore the effects of miR-494 inhibition through the NF-κB signaling pathway on lipopolysaccharide (LPS)-induced acute kidney injury (AKI) mouse model.

METHODS

The AKI mice induced by LPS were treated with miR-494 antagomir, and the kidney parameters and indicators of oxidative stress were detected. HE and TUNEL staining were performed to observe the kidney histopathology and the apoptosis in renal tubular epithelial cells (RTECs), respectively. The ROS level was measured using dihydroethidium (DHE) staining. In addition, qRT-PCR, western blotting, immunohistochemistry (IHC), and ELISA were also used to detect gene or protein expression.

RESULTS

LPS-induced AKI mice injected with the miR-494 antagomir showed reduced blood urea nitrogen (BUN) and serum creatinine (Cr) with improved kidney histopathology. The expression levels of p-IKKα/β, p-IκBα and p65 NF-κB in the nucleus were increased in kidney tissues from the LPS-induced AKI mice, and they were decreased by the miR-494 antagomir. Moreover, the results of IHC showed that the miR-494 antagomir downregulated p65 NF-κB in kidney tissues from the LPS-induced AKI mice, accompanied by decreased levels of TNF-α, IL-1β, IL-6, MDA, NO, and ROS but increased levels of SOD and GSH. In addition, the LPS-induced AKI mice had increased apoptosis in RTECs, as well as increased Caspase-3 and Bax and decreased Bcl-2, which were reversed by the miR-494 antagomir.

CONCLUSIONS

The inhibition of miR-494 could reduce inflammatory responses and improve oxidative stress in kidney tissues from LPS-induced AKI mice by blocking the NF-κB pathway accompanying by reduced apoptosis in RTECs.

Efficient and modified 2-NBDG assay to measure glucose uptake in cultured myotubes

Under type-2 diabetes, insulin resistance develops in skeletal muscles as a key defect and to study the disorder, its manifestation, and possible solution, measurement of glucose uptake is a fundamental necessity. Of various approaches (i.e. scintillation counting, flow cytometry, fluorometry and spectrophotometry) fluorescent labelled glucose analogue, 2-NBDG solution is the most popular one. Although 2-NBDG based assay is the most widely used approach in various cells including skeletal muscle, even then all available protocols possess huge variability which impacts the overall data reproducibility. Moreover, starvation (use of glucose/serum free medium), one of the prerequisite condition for glucose uptake assay, itself induces stress specifically during longer pre-incubation periods and alters muscle cell metabolism and morphology, but the fact has not been duly considered. Therefore in the present article, using specific skeletal muscle cells i.e. C2C12 myotubes, we have re-established the conditions like pre-incubation time period, concentrations of insulin, glucose and serum/BSA while maintaining the cultured myotubes in morphologically healthy state. Our lab standardized protocols were observed to be effective in studying insulin resistance condition induced by diverse stresses (oxidative & inflammation) in myotubes. Comparative study conducted with already established protocols demonstrates that the present method is more efficient, effective and better improvised for studying glucose uptake in C2C12.

Effects of physical activity on cell-to-cell communication during type 2 diabetes: A focus on miRNA signaling

Type 2 diabetes (TD2) is a progressive disease characterized by hyperglycemia that results from alteration in insulin secretion, insulin resistance, or both. A number of alterations involving different tissues and organs have been reported to the development and the progression of T2D, and more relevantly, through cell-to-cell communication pathways. Recent studies demonstrated that miRNAs are considerably implicated to cell-to-cell communication during T2D. Physical activity (PA) is associated with decreasing risks of developing T2D and acts as insulin-like factor. Cumulative evidence suggests that this effect could be mediated in part through improving insulin sensitivity in T2D and obese patients and modulating miRNAs synthesis and release in healthy patients. Therefore, the practice of PA should ideally be established before the initiation of T2D. This review describes cell-to-cell communications involved in the pathophysiology of T2D during PA.

MicroRNA-494-3p inhibits formation of fast oxidative muscle fibres by targeting E1A-binding protein p300 in human-induced pluripotent stem cells

MYOD-induced microRNA-494-3p expression inhibits fast oxidative myotube formation by downregulating myosin heavy chain 2 (MYH2) in human induced pluripotent stem cells (hiPSCs) during skeletal myogenesis. However, the molecular mechanisms regulating MYH2 expression via miR-494-3p remain unknown. Here, using bioinformatic analyses, we show that miR-494-3p potentially targets the transcript of the E1A-binding protein p300 at its 3'-untranslated region (UTR). Myogenesis in hiPSCs with the Tet/ON-myogenic differentiation 1 (MYOD1) gene (MyoD-hiPSCs) was induced by culturing them in doxycycline-supplemented differentiation medium for 7 days. p300 protein expression decreased after transient induction of miR-494-3p during myogenesis. miR-494-3p mimics decreased the levels of p300 and its downstream targets MYOD and MYH2 and myotube formation efficiency. p300 knockdown decreased myotube formation efficiency, MYH2 expression, and basal oxygen consumption rate. The binding of miR-494-3p to the wild type p300 3'-UTR, but not the mutated site, was confirmed using luciferase assay. Overexpression of p300 rescued the miR-494-3p mimic-induced phenotype in MyoD-hiPSCs. Moreover, miR-494-3p mimic reduced the levels of p300, MYOD, and MYH2 in skeletal muscles in mice. Thus, miR-494-3p might modulate MYH2 expression and fast oxidative myotube formation by directly regulating p300 levels during skeletal myogenesis in MyoD-hiPSCs and murine skeletal muscle tissues.

Expression patterns and prognostic value of miR-210, miR-494, and miR-205 in middle-aged and old patients with sepsis-induced acute kidney injury

Septic patients suffer a 'cytokine storm' from proinflammatory cytokines, chemokines and other inflammatory mediators, resulting in acute kidney injury (AKI) and death. The purpose of the present study was to determine the expression patterns of microRNA-210 (miR-210), miR-494, and miR-205 in middle-aged and old patients with sepsis-induced AKI and to evaluate their association with patient prognosis. Serum blood urea nitrogen (BUN), creatinine (Cr) and cystatin C levels were determined in peripheral venous blood collected from 110 patients with sepsis-induced AKI and 110 healthy controls. The expression profile of 30 miRNAs was analyzed by TaqMan low-density array (TLDA) in plasma samples from patients and controls. Association of miRNAs with prognosis and survival of patients was analyzed by Spearman's rank correlation coefficient, Cox multivariate analysis, and ROC curve analysis. TILDA analysis showed 11 upregulated and 11 downregulated miRNAs in patients with sepsis-induced AKI. MiR-210 and miR-494 were the most upregulated and miR-205 was the most downregulated miRNA. High expression of miR-210 and miR-494 was positively correlated with BUN, Cr and cystatin C levels of patients, while low expression of miR-205 was negatively correlated. MiR-210 and miR-494 expression was significantly decreased and miR-205 expression was increased in survivors with sepsis-induced AKI (28-day survival, n = 68) vs. non-survivors (n = 42). BUN, Cr, and miR-205 were independent risk factors for prognosis in sepsis-induced AKI. Our study showed the predictive value of miR-210, miR-494, and miR-205 in prognosis and survival of patients with sepsis-induced AKI. MiR-205 is an independent risk factor for sepsis-induced AKI and its decreased expression is associated with shorter patient survival.

MicroRNAs as Regulators of Insulin Signaling: Research Updates and Potential Therapeutic Perspectives in Type 2 Diabetes

The insulin signaling pathway is composed of a large number of molecules that positively or negatively modulate insulin specific signal transduction following its binding to the cognate receptor. Given the importance of the final effects of insulin signal transduction, it is conceivable that many regulators are needed in order to tightly control the metabolic or proliferative functional outputs. MicroRNAs (miRNAs) are small non-coding RNA molecules that negatively modulate gene expression through their specific binding within the 3′UTR sequence of messenger RNA (mRNA), thus causing mRNA decoy or translational inhibition. In the last decade, miRNAs have been addressed as pivotal cellular rheostats which control many fundamental signaling pathways, including insulin signal transduction. Several studies demonstrated that multiple alterations of miRNAs expression or function are relevant for the development of insulin resistance in type 2 diabetes (T2D); such alterations have been highlighted in multiple insulin target organs including liver, muscles, and adipose tissue. Indirectly, miRNAs have been identified as modulators of inflammation-derived insulin resistance, by controlling/tuning the activity of innate immune cells in insulin target tissues. Here, we review main findings on miRNA functions as modulators of insulin signaling in physiologic- or in T2D insulin resistance- status. Additionally, we report the latest hypotheses of prospective therapies involving miRNAs as potential targets for future drugs in T2D.

RETRACTED: MicroRNA-494 inhibition alleviates acute lung injury through Nrf2 signaling pathway via NQO1 in sepsis-associated acute respiratory distress syndrome

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. Concern was raised about the reliability of the Western blot results in Figures 5G,H+I, which appear to have a similar phenotype as many other publications, as detailed here: https://pubpeer.com/publications/7C9483B2551952AD53CCFCE206C4EB; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. The journal requested that the corresponding author comment on these concerns and provide the raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

miR‑188 suppresses tumor progression by targeting SOX4 in pediatric osteosarcoma

microRNA‑188 (miR‑188) acts as a tumor suppressor in various types of human cancer, including glioma, oral squamous cell carcinoma and hepatocellular carcinoma. However, the function and mechanism of miR‑188 in pediatric osteosarcoma (OS) have yet to be investigated. In the present study reverse transcription‑quantitative polymerase chain reaction revealed that miR‑188 expression was significantly downregulated in pediatric OS tissues and cell lines. miR‑188 overexpression markedly suppressed OS cell proliferation, migration and invasion, and induced cellular apoptosis. An in vivo assay demonstrated that miR‑188 overexpression inhibited tumor growth. miR‑188 targeted SOX4 to regulate its expression. miR‑188 expression was inversely correlated with SOX4 in pediatric OS tissues. SOX4 restoration abrogated the inhibitory effects of miR‑188 on OS cells. The results of the present study indicated that miR‑188 suppressed pediatric OS progression by targeting SOX4.

The Destiny of Glucose from a MicroRNA Perspective

Glucose serves as a primary, and for some tissues the unique, fuel source in order to generate and maintain the biological functions. Hyperglycemia is a hallmark of type 2 diabetes and is the direct consequence of perturbations in the glucose homeostasis. Insulin resistance, referred to as a reduced response of target tissues to the hormone, contributes to the development of hyperglycemia. The molecular mechanisms responsible for the altered glucose homeostasis are numerous and not completely understood. MicroRNAs (miRNAs) are now recognized as regulators of the lipid and glucose metabolism and are involved in the onset of metabolic diseases. Indeed, these small non-coding RNA molecules operate in the RNA silencing and posttranscriptional regulation of gene expression and may modulate the levels of kinases and enzymes in the glucose metabolism. Therefore, a better characterization of the function of miRNAs and a deeper understanding of their role in disease may represent a fundamental step toward innovative treatments addressing the causes, not only the symptoms, of hyperglycemia, using approaches aimed at restoring either miRNAs or their specific targets. In this review, we outline the current understanding regarding the impact of miRNAs in the glucose metabolism and highlight the need for further research focused on altered key kinases and enzymes in metabolic diseases.

MicroRNAs and altered metabolism of clear cell renal cell carcinoma: Potential role as aerobic glycolysis biomarkers

BACKGROUND

Warburg Effect is a metabolic switch that occurs in most of cancer cells but its advantages are not fully understood. This switch is known to happen in renal cell carcinoma (RCC), which is the most common solid cancer of the adult kidney. RCC carcinogenesis is related to pVHL loss and Hypoxia Inducible Factor (HIF) activation, ultimately leading to the activation of several genes related to glycolysis. MicroRNAs (miRNAs) regulate gene expression at a post-transcriptional level and are also deregulated in several cancers, including RCC.

SCOPE OF REVIEW

This review focuses in the miRNAs that direct target enzymes involved in glycolysis and that are deregulated in several cancers. It also reviews the possible application of miRNAs in the improvement of clinical patients' management.

MAJOR CONCLUSIONS

Several miRNAs that direct target enzymes involved in glycolysis are downregulated in cancer, strongly influencing the Warburg Effect. Due to this strong influence, FDG-PET can possibly benefit from measurement of these miRNAs. Restoring their levels can also bring an improvement to the current therapies.

GENERAL SIGNIFICANCE

Despite being known for almost a hundred years, the Warburg Effect is not fully understood. MiRNAs are now known to be intrinsically connected with this effect and present an opportunity to understand it. They also open a new door to improve current diagnosis and prognosis tests as well as to complement current therapies. This is urgent for cancers like RCC, mostly due to the lack of an efficient screening test for early relapse detection and follow-up and the development of resistance to current therapies.

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.

Infections: A Possible Risk Factor for Type 2 Diabetes

Diabetes mellitus is one of the biggest challenges to human health globally, with an estimated 95% of the global diabetic population having type 2 diabetes. Classical causes for type 2 diabetes, such as genetics and obesity, do not account for the high incidence of the disease. Recent data suggest that infections may precipitate insulin resistance via multiple mechanisms, such as the proinflammatory cytokine response, the acute-phase response, and the alteration of the nutrient status. Even pathogen products, such as lipopolysaccharide and peptidoglycans, can be diabetogenic. Therefore, we argue that infections that are known to contribute to insulin resistance should be considered as risk factors for type 2 diabetes.

MicroRNAs-Mediated Regulation of Skeletal Muscle GLUT4 Expression and Translocation in Insulin Resistance

The solute carrier family 2 facilitated glucose transporter member 4 (GLUT4) plays a key role in the insulin-induced glucose uptake by muscle and adipose tissues. In prediabetes and diabetes, GLUT4 expression/translocation has been detected as reduced, participating in mechanisms that impair glycemic control. Recently, a class of short endogenous noncoding RNAs named microRNAs (miRNAs) has been increasingly described as involved in the posttranscriptional epigenetic regulation of gene expression. The present review focuses on miRNAs potentially involved in the expression of GLUT4 expression, and proteins related to GLUT4 and translocation in skeletal muscle, seeking to correlate them with insulin resistance and diabetes. So far, miR-21a-5p, miR-29a-3p, miR-29c-3p, miR-93-5p, miR-106b-5p, miR-133a-3p, miR-133b-3p, miR-222-3p, and miR-223-3p have been reported to directly and/or indirectly regulate the GLUT4 expression; and their expression is altered under diabetes-related conditions. Besides, some miRNAs that have been linked to the expression of proteins involved in GLUT4 translocation machinery in muscle could also impact glucose uptake. That makes these miRNAs promising targets for preventive and/or therapeutic approaches, which could improve glycemic control, thus deserving future new investigations.

Bacterial and cytokine mixtures predict the length of gestation and are associated with miRNA expression in the cervix

AIM

Bacterial vaginosis may lead to preterm birth through epigenetic programming of the inflammatory response, specifically via miRNA expression.

METHODS

We quantified bacterial 16S rRNA, cytokine mRNA and 800 miRNA from cervical swabs obtained from 80 women at 16-19 weeks' gestation. We generated bacterial and cytokine indices using weighted quantile sum regression and examined associations with miRNA and gestational age at delivery.

RESULTS & DISCUSSION

Each decile of the bacterial and cytokine indices was associated with shorter gestations (p < 0.005). The bacterial index was associated with miR-494, 371a, 4286, 185, 320e, 888 and 23a (p < 0.05). miR-494 remained significant after false discovery rate correction (q < 0.1). The cytokine index was associated with 27 miRNAs (p < 0.05; q < 0.01).

CONCLUSION

Future investigation into the role of bacterial vaginosis- and inflammation-associated miRNA and preterm birth is warranted.

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.

MicroRNA-665 suppressed the invasion and metastasis of osteosarcoma by directly inhibiting RAB23

MicroRNAs (miRNAs) are small, short and noncoding RNAs that regulate gene expression posttranscriptionally. Increasing evidences have demonstrated that deregulated expression of miRNAs is found in osteosarcoma. In this study, we demonstrated that miR-665 was downregulated in osteosarcoma tissues compared to non-tumorous tissues. The overall survival (OS) of osteosarcoma patients with low miR-665 expression was lower than that of these patients with high miR-665 expression. Ectopic expression of miR-665 suppressed the osteosarcoma cell proliferation, EMT and invasion. We identified Rab23 as a direct target gene of miR-665. Rab23 was downregulated in osteosarcoma tissues and cell lines. The expression of miR-665 was inversely associated with the expression of Rab23 in the osteosarcoma tissues. These results suggested that miR-665 acted as a tumor suppressor gene in the development of osteosarcoma.

TNF-α induces vascular insulin resistance via positive modulation of PTEN and decreased Akt/eNOS/NO signaling in high fat diet-fed mice

BACKGROUND

High fat diet (HFD) induces insulin resistance in various tissues, including the vasculature. HFD also increases plasma levels of TNF-α, a cytokine that contributes to insulin resistance and vascular dysfunction. Considering that the enzyme phosphatase and tension homologue (PTEN), whose expression is increased by TNF-α, reduces Akt signaling and, consequently, nitric oxide (NO) production, we hypothesized that PTEN contributes to TNF-α-mediated vascular resistance to insulin induced by HFD. Mechanisms underlying PTEN effects were determined.

METHODS

Mesenteric vascular beds were isolated from C57Bl/6J and TNF-α KO mice submitted to control or HFD diet for 18 weeks to assess molecular mechanisms by which TNF-α and PTEN contribute to vascular dysfunction.

RESULTS

Vasodilation in response to insulin was decreased in HFD-fed mice and in ex vivo control arteries incubated with TNF-α. TNF-α receptors deficiency and TNF-α blockade with infliximab abolished the effects of HFD and TNF-α on insulin-induced vasodilation. PTEN vascular expression (total and phosphorylated isoforms) was increased in HFD-fed mice. Treatment with a PTEN inhibitor improved insulin-induced vasodilation in HFD-fed mice. TNF-α receptor deletion restored PTEN expression/activity and Akt/eNOS/NO signaling in HFD-fed mice.

CONCLUSION

TNF-α induces vascular insulin resistance by mechanisms that involve positive modulation of PTEN and inhibition of Akt/eNOS/NO signaling. Our findings highlight TNF-α and PTEN as potential targets to limit insulin resistance and vascular complications associated with obesity-related conditions.

Sesquiterpenes from Baizhu Stimulate Glucose Uptake by Activating AMPK and PI3K

Baizhu, the dried rhizome of Atractylodes Macrocephala Koidz (Compositae), is one of the most important traditional Chinese herbal medicines. Baizhu is generally used to treat digestive disorders and diabetes in Asian countries. This study investigates the activity of two sesquiterpenes isolated from Baizhu, atractylenolide I (AT-I) and atractylenolide II (AT-II), for their effects on glucose uptake in mouse skeletal muscle C2C12 cells, and the corresponding mechanism. These compounds show a significant stimulatory effect on glucose uptake in C2C12 myotubes. Both AT-I and AT-II significantly increased GLUT4 but not GLUT1 protein levels, and promoted GLUT4 translocation to the plasma membrane. The increased glucose uptake induced by these compounds is associated with activation of AMP-activated protein kinase (AMPK) and PI3K/Akt pathways in these cells. Further studies have indicated that AT-I and AT-II ameliorate TNF-[Formula: see text]-induced insulin resistance in C2C12 myotubes. In summary, our findings highlight the insulin mimetic activity of Baizhu in myotubes, and provide insights into the action mechanism underlying these effects. Our findings may also prove highly relevant to the development of novel therapeutic applications for these compounds.

Circulating miRNAs as intercellular messengers, potential biomarkers and therapeutic targets for Type 2 diabetes

miRNAs have emerged as key epigenetic regulators of metabolism. Their deregulation contributes to metabolic abnormalities, proposing their potential role as therapeutic targets for Type 2 diabetes. The exciting finding that miRNAs exist in the bloodstream suggests that circulating miRNAs may act in a hormone-like fashion. Despite the fact that significant progress has been made in understanding circulating miRNAs, this topic is full of complexities and many questions remain unanswered. The goal of this review is to bring together up-to-date knowledge about circulating miRNAs and their role as intercellular communicators as well as potential biomarkers and therapeutic targets in metabolic diseases, providing examples of possible clinical applications for circulating miRNAs in diabetes and cardiovascular complications.

RNA Profiling in Human and Murine Transplanted Hearts: Identification and Validation of Therapeutic Targets for Acute Cardiac and Renal Allograft Rejection

Acute cellular rejection (ACR) is the adverse response of the recipient's immune system against the allogeneic graft. Using human surveillance endomyocardial biopsies (EMBs) manifesting ACR and murine allogeneic grafts, we profiled implicated microRNAs (miRs) and mRNAs. MiR profiling showed that miR-21, -142-3p, -142-5p, -146a, -146b, -155, -222, -223, and -494 increased during ACR in humans and mice, whereas miR-149-5p decreased. mRNA profiling revealed 70 common differentially regulated transcripts, all involved in immune signaling and immune-related diseases. Interestingly, 33 of 70 transcripts function downstream of IL-6 and its transcription factor spleen focus forming virus proviral integration oncogene (SPI1), an established target of miR-155, the most upregulated miR in human EMBs manifesting rejection. In a mouse model of cardiac transplantation, miR-155 absence and pharmacological inhibition attenuated ACR, demonstrating the causal involvement and therapeutic potential of miRs. Finally, we corroborated our miR signature in acute cellular renal allograft rejection, suggesting a nonorgan specific signature of acute rejection. We concluded that miR and mRNA profiling in human and murine ACR revealed the shared significant dysregulation of immune genes. Inflammatory miRs, for example miR-155, and transcripts, in particular those related to the IL-6 pathway, are promising therapeutic targets to prevent acute allograft rejection.

Micro-RNA Binding Site Polymorphisms in the WFS1 Gene Are Risk Factors of Diabetes Mellitus

The absolute or relative lack of insulin is the key factor in the pathogenesis of diabetes mellitus. Although the connection between loss of function mutations of the WFS1 gene and DIDMOAD-syndrome including diabetes mellitus underpins the significance of wolframin in the pathogenesis, exact role of WFS1 polymorphic variants in the development of type 1 and type 2 diabetes has not been discovered yet. In this analysis, 787 patients with diabetes and 900 healthy people participated. Genotyping of the 7 WFS1 SNPs was carried out by TaqMan assays. Association study was performed by χ2-test in combination with correction for multiple testing. For functional analysis, the entire 3' UTR of the WFS1 gene was subcloned in a pMIR-Report plasmid and relative luciferase activities were determined. Linkage disequilibrium analysis showed a generally high LD within the investigated region, however the rs1046322 locus was not in LD with the other SNPs. The two miR-SNPs, rs1046322 and rs9457 showed significant association with T1DM and T2DM, respectively. Haplotype analysis also confirmed the association between the 3' UTR loci and both disease types. In vitro experiments showed that miR-185 reduces the amount of the resulting protein, and rs9457 miRSNP significantly influences the rate of reduction in a luciferase reporter assay. Genetic variants of the WFS1 gene might contribute to the genetic risk of T1DM and T2DM. Furthermore demonstrating the effect of rs9457 in binding of miR-185, we suggest that the optimal level of wolframin protein, potentially influenced by miR-regulation, is crucial in normal beta cell function.

MicroRNAs as regulators of metabolic disease: pathophysiologic significance and emerging role as biomarkers and therapeutics

The prevalence of overweight and obesity in developed and developing countries has greatly increased the risk of insulin resistance and type 2 diabetes mellitus. It is evident from human and animal studies that obesity alters microRNA (miRNA) expression in metabolically important organs, and that miRNAs are involved in changes to normal physiology, acting as mediators of disease. miRNAs regulate multiple pathways including insulin signaling, immune-mediated inflammation, adipokine expression, adipogenesis, lipid metabolism, and food intake regulation. Thus, miRNA-based therapeutics represent an innovative and attractive treatment modality, with non-human primate studies showing great promise. In addition, miRNA measures in plasma or bodily fluids may be used as disease biomarkers and predictors of metabolic disease in humans. This review analyzes the role of miRNAs in obesity and insulin resistance, focusing on the miR-17/92, miR-143-145, miR-130, let-7, miR-221/222, miR-200, miR-223, miR-29 and miR-375 families, as well as miRNA changes by relevant tissue (adipose, liver and skeletal muscle). Further, the current and future applications of miRNA-based therapeutics and diagnostics in metabolic disease are discussed.

The MicroRNA-217 Functions as a Potential Tumor Suppressor in Gastric Cancer by Targeting GPC5

Gastric cancer (GC) is one of the most common malignancies worldwide. Emerging evidence has shown that aberrant expression of microRNAs (miRNAs) plays important roles in cancer progression. However, little is known about the potential role of miR-217 in GC. In this study, we investigated the role of miR-217 on GC cell proliferation and invasion. The expression of miR-217 was down-regulated in GC cells and human GC tissues. Enforced expression of miR-217 inhibited GC cells proliferation and invasion. Moreover, Glypican-5 (GPC5), a new ocncogene, was identified as the potential target of miR-217. In addition, overexpression of miR-217 impaired GPC5-induced promotion of proliferation and invasion in GC cells. In conclusion, these findings revealed that miR-217 functioned as a tumor suppressor and inhibited the proliferation and invasion of GC cells by targeting GPC5, which might consequently serve as a therapeutic target for GC patients.

Application of microRNAs in diabetes mellitus

MicroRNAs (miRNAs) are small molecules negatively regulating gene expression by diminishing their target mRNAs. Emerging studies have shown that miRNAs play diverse roles in diabetes mellitus. Type 1 diabetes (T1D) and T2D are two major types of diabetes. T1D is characterized by a reduction in insulin release from the pancreatic β-cells, while T2D is caused by islet β-cell dysfunction in response to insulin resistance. This review describes the miRNAs that control insulin release and production by regulating cellular membrane electrical excitability (ATP:ADP ratio), insulin granule exocytosis, insulin synthesis in β-cells, and β-cell fate and islet mass formation. This review also examines miRNAs involved the insulin resistance of liver, fat, and skeletal muscle, which change insulin sensitivity pathways (insulin receptors, glucose transporter type 4, and protein kinase B pathways). This review discusses the potential application of miRNAs in diabetes, including the use of gene therapy and therapeutic compounds to recover miRNA function in diabetes, as well as the role of miRNAs as potential biomarkers for T1D and T2D.