MiR-206 is expressed in pancreatic islets and regulates glucokinase activity

Hyperglycemia facilitates EV71 replication: Insights into miR-206-mediated regulation of G3BP2 promoting EV71 IRES activity

Background: Neurotropic virus infections actively manipulate host cell metabolism to enhance virus neurovirulence. Although hyperglycemia is common during severe infections, its specific role remains unclear. This study investigates the impact of hyperglycemia on the neurovirulence of enterovirus 71 (EV71), a neurovirulent virus relying on internal ribosome entry site (IRES)-mediated translation for replication. Methods: Utilizing hSCARB2-transgenic mice, we explore the effects of hyperglycemia in EV71 infection and elucidate the underlying mechanisms. Results: Remarkably, administering insulin alone to reduce hyperglycemia in hSCARB2-transgenic mice results in a decrease in brainstem encephalitis and viral load. Conversely, induced hyperglycemia exacerbates neuropathogenesis, highlighting the pivotal role of hyperglycemia in neurovirulence. Notably, miR-206 emerges as a crucial mediator induced by viral infection, with its expression further heightened by hyperglycemia and concurrently repressed by insulin. The use of antagomiR-206 effectively mitigates EV71-induced brainstem encephalitis and reduces viral load. Mechanistically, miR-206 facilitates IRES-driven virus replication by repressing the stress granule protein G3BP2. Conclusions: Novel therapeutic approaches against severe EV71 infections involve managing hyperglycemia and targeting the miR-206-stress granule pathway to modulate virus IRES activity.

The Role of MicroRNA-206 in the Regulation of Diabetic Wound Healing via Hypoxia-Inducible Factor 1-Alpha

Successful wound healing in diabetic patients is hindered by dysregulated miRNA expression. This study aimed to investigate the abnormal expression of miRNAs in diabetic wound healing and the potential therapeutic role of modulating the miR-206/HIF-1α pathway. MicroRNA assays were used to identify differentially expressed miRNAs in diabetic wound sites and adjacent areas. In vitro models and a rat diabetic model were established to evaluate the effects of miR-206 on HIF-1α regulation and wound healing. The study revealed differential expression of miR-206 in diabetic wound tissues, its interaction with HIF-1α, and the inhibitory effect of miR-206 on cell growth under high glucose conditions. Modulating the miR-206/HIF-1α pathway using miR-206 antagomir promoted HIF-1α, CD34, and VEGF expression, ultimately enhancing diabetic wound healing.

Circulating miR-206, miR-181b, and miR-21 as promising biomarkers in hypothyroidism and their relationship to related hyperlipidemia and hepatic steatosis

Background: Thyroid hormones (THs) signaling has profound effects on many physiological processes. The regulation of THs signaling in various tissues involves the action of microRNAs (miRNAs) on thyroid deiodinases and receptors. THs regulate the expression of certain miRNAs and their target messenger RNAs (mRNAs) in various tissues and cells. The modulation of miRNA levels by THs affects their functions in processes such as liver lipid metabolism, skin physiology, and muscle and heart performance. Aim: This research aimed to investigate miR-181b, miR-206, and miR-21 in the serum of patients with subclinical and overt hypothyroidism to determine their possible role in the diagnosis of the disease and their relationship to clinical disorders related to hypothyroidism. Methods: This study included ninety participants, divided evenly into three groups as follows: patients with overt hypothyroidism diagnosed clinically, radiologically, and by investigation, subclinical hypothyroid patients, and healthy volunteers. The patients had a thorough medical history and underwent a clinical examination. Laboratory tests included plasma cholesterol, LDL, HDL, TGs, liver and renal function tests, CBC, fasting insulin, HOMA-IR, HbA1c, TSH, and free T4. The serum levels of miR-21, miR-206, and miR-181b were measured using qRT-PCR. Results: miR-206 and miR-181b levels were higher in the subclinical group, followed by the hypothyroid and control groups. For miR-21, there was a significantly lower mean value in both the hypothyroid and subclinical groups than in the control group, with no difference between the two groups. Both miR-206 and miR-181b showed a significant negative association with albumin and free T4 levels and a significant direct association with GGT, ALT, AST, creatinine, uric acid, TGs, TC, LDL, TSH, thyroid volume, and CAP score. The same correlation pattern was observed for miR-181b, except that it was not significantly correlated with the TGs. For miR-21 levels, there was a significant positive correlation with albumin, free T4 level, and kPa score and a negative correlation with GGT, ALT, AST, creatinine, uric acid, HOMA-IR, HbA1c, TC, LDL, TSH, and CAP score. Cases with F1 kPa score and S2 CAP scores had significantly higher averages for miR-206 and miR-181b, with a p-value of 0.05. Moreover, miR-21 levels were significantly lower in the S2 CAP score group. Conclusion: These miRNAs (miR-206, miR-181b, and miR-21) may be used as diagnostic biomarkers for hypothyroidism. They may be used as therapeutic targets to control dyslipidemia and hepatic steatosis during hypothyroid disease.

Ube4A maintains metabolic homeostasis and facilitates insulin signaling in vivo

OBJECTIVE

Defining the regulators of cell metabolism and signaling is essential to design new therapeutic strategies in obesity and NAFLD/NASH. E3 ubiquitin ligases control diverse cellular functions by ubiquitination-mediated regulation of protein targets, and thus their functional aberration is associated with many diseases. The E3 ligase Ube4A has been implicated in human obesity, inflammation, and cancer. However, its in vivo function is unknown, and no animal models are available to study this novel protein.

METHODS

A whole-body Ube4A knockout (UKO) mouse model was generated, and various metabolic parameters were compared in chow- and high fat diet (HFD)-fed WT and UKO mice, and in their liver, adipose tissue, and serum. Lipidomics and RNA-Seq studies were performed in the liver samples of HFD-fed WT and UKO mice. Proteomic studies were conducted to identify Ube4A's targets in metabolism. Furthermore, a mechanism by which Ube4A regulates metabolism was identified.

RESULTS

Although the body weight and composition of young, chow-fed WT and UKO mice are similar, the knockouts exhibit mild hyperinsulinemia and insulin resistance. HFD feeding substantially augments obesity, hyperinsulinemia, and insulin resistance in both sexes of UKO mice. HFD-fed white and brown adipose tissue depots of UKO mice have increased insulin resistance and inflammation and reduced energy metabolism. Moreover, Ube4A deletion exacerbates hepatic steatosis, inflammation, and liver injury in HFD-fed mice with increased lipid uptake and lipogenesis in hepatocytes. Acute insulin treatment resulted in impaired activation of the insulin effector protein kinase Akt in liver and adipose tissue of chow-fed UKO mice. We identified the Akt activator protein APPL1 as a Ube4A interactor. The K63-linked ubiquitination (K63-Ub) of Akt and APPL1, known to facilitate insulin-induced Akt activation, is impaired in UKO mice. Furthermore, Ube4A K63-ubiquitinates Akt in vitro.

CONCLUSION

Ube4A is a novel regulator of obesity, insulin resistance, adipose tissue dysfunction and NAFLD, and preventing its downregulation may ameliorate these diseases.

Glimepiride Compared to Liraglutide Increases Plasma Levels of miR-206, miR-182-5p, and miR-766-3p in Type 2 Diabetes Mellitus: A Randomized Controlled Trial

BACKGRUOUND

Diabetes is a chronic disease with several long-term complications. Several glucose-lowering drugs are used to treat type 2 diabetes mellitus (T2DM), e.g., glimepiride and liraglutide, in which both having different modes of action. Circulating microRNAs (miRNAs) are suggested as potential biomarkers that are associated with the disease development and the effects of the treatment. In the current study we evaluated the effect of glimepiride, liraglutide on the expression of the circulating miRNAs.

METHODS

The present study is a post hoc trial from a previously randomized control trial comparing liraglutide versus glimepiride both in combination with metformin in subjects with T2DM, and subclinical heart failure. miRNAs were determined in the subjects' serum samples with next generation sequencing. Expression patterns of the circulating miRNAs were analyzed using bioinformatic univariate and multivariate analyses (clinical trial registration: NCT01425580).

RESULTS

Univariate analyses show that treatment with glimepiride altered expression of three miRNAs in patient serum, miR-206, miR-182-5p, and miR-766-3p. Both miR-182-5p and miR-766-3p were also picked up among the top contributing miRNAs with penalized regularised logistic regressions (Lasso). The highest-ranked miRNAs with respect to Lasso coefficients were miR-3960, miR-31-5p, miR-3613-3p, and miR-378a-3p. Liraglutide treatment did not significantly influence levels of circulating miRNAs.

CONCLUSION

Present study indicates that glucose-lowering drugs differently affect the expression of circulating miRNAs in serum in individuals with T2DM. More studies are required to investigate possible mechanisms by which glimepiride is affecting the expression of circulating miRNAs.

Therapeutic Potential of miRNAs for Type 2 Diabetes Mellitus: An Overview

MicroRNA(miRNA)s have been identified as an emerging class for therapeutic interventions mainly due to their extracellularly stable presence in humans and animals and their potential for horizontal transmission and action. However, treating Type 2 diabetes mellitus using this technology has yet been in a nascent state. MiRNAs play a significant role in the pathogenesis of Type 2 diabetes mellitus establishing the potential for utilizing miRNA-based therapeutic interventions to treat the disease. Recently, the administration of miRNA mimics or antimiRs in-vivo has resulted in positive modulation of glucose and lipid metabolism. Further, several cell culture-based interventions have suggested beta cell regeneration potential in miRNAs. Nevertheless, few such miRNA-based therapeutic approaches have reached the clinical phase. Therefore, future research contributions would identify the possibility of miRNA therapeutics for tackling T2DM. This article briefly reported recent developments on miRNA-based therapeutics for treating Type 2 Diabetes mellitus, associated implications, gaps, and recommendations for future studies.

Visceral Adipose Tissue E2F1-miRNA206/210 Pathway Associates with Type 2 Diabetes in Humans with Extreme Obesity

Objective: Up-regulated expression of transcription-factor E2F1 in human visceral adipose tissue (VAT) characterizes a dysmetabolic obesity sub-phenotype. An E2F1-miRNA network has been described in multiple cancers. Here we investigated whether elevated VAT-E2F1 in obesity is associated with VAT-miRNA alterations similar to, or distinct from, those described in cancer. Furthermore, we assessed if E2F1-associated miRNA changes may contribute to the link between high- VAT-E2F1 and a dysmetabolic obesity phenotype. Methods: We assembled a cohort of patients with obesity and high-VAT-E2F1, matched by age, sex, ±BMI to patients with low-VAT-E2F1, with and without obesity (8 patients/groupX3 groups). We performed Nanostring©-based miRNA profiling of VAT samples from all 24 patients. Candidate E2F1-related miRNAs were validated by qPCR in an independent cohort of patients with extreme obesity, with or without type-2-diabetes (T2DM) (n = 20). Bioinformatic tools and manipulation of E2F1 expression in cells were used to establish the plausibility of the functional VAT-E2F1-miRNA network in obesity. Results: Among n = 798 identified miRNAs, 17 were differentially expressed in relation to E2F1 and not to obesity itself. No evidence for the cancer-related E2F1-miRNA network was identified in human VAT in obesity. In HEK293-cells, overexpression/downregulation of E2F1 correspondingly altered the expression of miRNA-206 and miRNA-210-5p, two miRNAs with reported metabolic functions consistent with those of E2F1. In VAT from both cohorts, the expression of both miRNA-206 and 210-5p intercorrelated, and correlated with the expression of E2F1. In cohort 1 we did not detect significant associations with biochemical parameters. In cohort 2 of patients with extreme obesity, all those with high VAT-E2F1 showed a diabetes-complicated obesity phenotype and higher expression of miRNA-206 and miRNA-210-5p, which also correlated with fasting glucose levels (both miRNAs) and fasting insulin (miRNA-210-5p). Conclusions: Whilst the previously described cancer-related E2F1-miRNA network does not appear to operate in VAT in obesity, miRNAs-206 and 210-5p may link high-E2F1 expression in VAT with diabetes-complicated extreme obesity phenotype.

Neuroendocrine microRNAs linked to energy homeostasis: future therapeutic potential

The brain orchestrates whole-body metabolism through an intricate system involving interneuronal crosstalk and communication. Specifically, a key player in this complex circuitry is the hypothalamus that controls feeding behaviour, energy expenditure, body weight and metabolism, whereby hypothalamic neurons sense and respond to circulating hormones, nutrients, and chemicals. Dysregulation of these neurons contributes to the development of metabolic disorders, such as obesity and type 2 diabetes. The involvement of hypothalamic microRNAs, post-transcriptional regulators of gene expression, in the central regulation of energy homeostasis has become increasingly apparent, although not completely delineated. This review summarizes current evidence demonstrating the regulation of feeding-related neuropeptides by brain-derived microRNAs as well as the regulation of specific miRNAs by nutrients and other peripheral signals. Moreover, the involvement of microRNAs in the central nervous system control of insulin, leptin, and estrogen signal transduction is examined. Finally, the therapeutic and diagnostic potential of microRNAs for metabolic disorders will be discussed and the regulation of brain-derived microRNAs by nutrients and other peripheral signals is considered. Demonstrating a critical role of microRNAs in hypothalamic regulation of energy homeostasis is an innovative route to uncover novel biomarkers and therapeutic candidates for metabolic disorders.

Connexins and Glucose Metabolism in Cancer

Connexins are a family of transmembrane proteins that regulate diverse cellular functions. Originally characterized for their ability to mediate direct intercellular communication through the formation of highly regulated membrane channels, their functions have been extended to the exchange of molecules with the extracellular environment, and the ability to modulate numerous channel-independent effects on processes such as motility and survival. Notably, connexins have been implicated in cancer biology for their context-dependent roles that can both promote or suppress cancer cell function. Moreover, connexins are able to mediate many aspects of cellular metabolism including the intercellular coupling of nutrients and signaling molecules. During cancer progression, changes to substrate utilization occur to support energy production and biomass accumulation. This results in metabolic plasticity that promotes cell survival and proliferation, and can impact therapeutic resistance. Significant progress has been made in our understanding of connexin and cancer biology, however, delineating the roles these multi-faceted proteins play in metabolic adaptation of cancer cells is just beginning. Glucose represents a major carbon substrate for energy production, nucleotide synthesis, carbohydrate modifications and generation of biosynthetic intermediates. While cancer cells often exhibit a dependence on glycolytic metabolism for survival, cellular reprogramming of metabolic pathways is common when blood perfusion is limited in growing tumors. These metabolic changes drive aggressive phenotypes through the acquisition of functional traits. Connections between glucose metabolism and connexin function in cancer cells and the surrounding stroma are now apparent, however much remains to be discovered regarding these relationships. This review discusses the existing evidence in this area and highlights directions for continued investigation.

Mechanisms Driving Palmitate-Mediated Neuronal Dysregulation in the Hypothalamus

The hypothalamus maintains whole-body homeostasis by integrating information from circulating hormones, nutrients and signaling molecules. Distinct neuronal subpopulations that express and secrete unique neuropeptides execute the individual functions of the hypothalamus, including, but not limited to, the regulation of energy homeostasis, reproduction and circadian rhythms. Alterations at the hypothalamic level can lead to a myriad of diseases, such as type 2 diabetes mellitus, obesity, and infertility. The excessive consumption of saturated fatty acids can induce neuroinflammation, endoplasmic reticulum stress, and resistance to peripheral signals, ultimately leading to hyperphagia, obesity, impaired reproductive function and disturbed circadian rhythms. This review focuses on the how the changes in the underlying molecular mechanisms caused by palmitate exposure, the most commonly consumed saturated fatty acid, and the potential involvement of microRNAs, a class of non-coding RNA molecules that regulate gene expression post-transcriptionally, can result in detrimental alterations in protein expression and content. Studying the involvement of microRNAs in hypothalamic function holds immense potential, as these molecular markers are quickly proving to be valuable tools in the diagnosis and treatment of metabolic disease.

Molecular Mechanisms of Nutrient-Mediated Regulation of MicroRNAs in Pancreatic β-cells

Pancreatic β-cells within the islets of Langerhans respond to rising blood glucose levels by secreting insulin that stimulates glucose uptake by peripheral tissues to maintain whole body energy homeostasis. To different extents, failure of β-cell function and/or β-cell loss contribute to the development of Type 1 and Type 2 diabetes. Chronically elevated glycaemia and high circulating free fatty acids, as often seen in obese diabetics, accelerate β-cell failure and the development of the disease. MiRNAs are essential for endocrine development and for mature pancreatic β-cell function and are dysregulated in diabetes. In this review, we summarize the different molecular mechanisms that control miRNA expression and function, including transcription, stability, posttranscriptional modifications, and interaction with RNA binding proteins and other non-coding RNAs. We also discuss which of these mechanisms are responsible for the nutrient-mediated regulation of the activity of β-cell miRNAs and identify some of the more important knowledge gaps in the field.

Targeting microRNAs with thymoquinone: a new approach for cancer therapy

Cancer is a global disease involving transformation of normal cells into tumor types via numerous mechanisms, with mortality among all generations, in spite of the breakthroughs in chemotherapy, radiotherapy and/or surgery for cancer treatment. Since one in six deaths is due to cancer, it is one of the overriding priorities of world health. Recently, bioactive natural compounds have been widely recognized due to their therapeutic effects for treatment of various chronic disorders, notably cancer. Thymoquinone (TQ), the most valuable constituent of black cumin seeds, has shown anti-cancer characteristics in a wide range of animal models. The revolutionary findings have revealed TQ's ability to regulate microRNA (miRNA) expression, offering a promising approach for cancer therapy. MiRNAs are small noncoding RNAs that modulate gene expression by means of variation in features of mRNA. MiRNAs manage several biological processes including gene expression and cellular signaling pathways. Accordingly, miRNAs can be considered as hallmarks for cancer diagnosis, prognosis and therapy. The purpose of this study was to review the various molecular mechanisms by which TQ exerts its potential as an anti-cancer agent through modulating miRNAs.

Glucokinase activation as antidiabetic therapy: effect of nutraceuticals and phytochemicals on glucokinase gene expression and enzymatic activity

Diabetes represents an important public health problem. Recently, new molecular targets have been identified and exploited to treat this disease. Due to its pivotal role in glucose homeostasis, glucokinase (GCK) is a promising target for the development of novel antidiabetic drugs; however, pharmacological agents that modulate GCK activity have been linked to undesirable side-effects, limiting its use. Interestingly, plants might be a valuable source of new therapeutic compounds with GCK-activating properties and presumably no adverse effects. In this review, we describe biochemical characteristics related to the physiological and pathological importance of GCK, as well as the mechanisms involved in its regulation at different molecular levels. Posteriorly, we present a compendium of findings supporting the potential use of nutraceuticals and phytochemicals in the management of diabetes through modulation of GCK expression and activity. Finally, we propose critical aspects to keep in mind when designing experiments to evaluate GCK modulation properly.

MicroRNA, Diabetes Mellitus and Colorectal Cancer

Diabetes mellitus (DM) is an endocrinological disorder that is due to either the pancreas not producing enough insulin, or the body does not respond appropriately to insulin. There are many complications of DM such as retinopathy, nephropathy, and peripheral neuropathy. In addition to these complications, DM was reported to be associated with different cancers. In this review, we discuss the association between DM and colorectal cancer (CRC). CRC is the third most commonly diagnosed cancer worldwide that mostly affects older people, however, its incidence and mortality are rising among young people. We discuss the relationship between DM and CRC based on their common microRNA (miRNA) biomarkers. miRNAs are non-coding RNAs playing important functions in cell differentiation, development, regulation of cell cycle, and apoptosis. miRNAs can inhibit cell proliferation and induce apoptosis in CRC cells. miRNAs also can improve glucose tolerance and insulin sensitivity. Therefore, investigating the common miRNA biomarkers of both DM and CRC can shed a light on how these two diseases are correlated and more understanding of the link between these two diseases can help the prevention of both DM and CRC.

Roles of Noncoding RNAs in Islet Biology

The discovery that most mammalian genome sequences are transcribed to ribonucleic acids (RNA) has revolutionized our understanding of the mechanisms governing key cellular processes and of the causes of human diseases, including diabetes mellitus. Pancreatic islet cells were found to contain thousands of noncoding RNAs (ncRNAs), including micro-RNAs (miRNAs), PIWI-associated RNAs, small nucleolar RNAs, tRNA-derived fragments, long non-coding RNAs, and circular RNAs. While the involvement of miRNAs in islet function and in the etiology of diabetes is now well documented, there is emerging evidence indicating that other classes of ncRNAs are also participating in different aspects of islet physiology. The aim of this article will be to provide a comprehensive and updated view of the studies carried out in human samples and rodent models over the past 15 years on the role of ncRNAs in the control of α- and β-cell development and function and to highlight the recent discoveries in the field. We not only describe the role of ncRNAs in the control of insulin and glucagon secretion but also address the contribution of these regulatory molecules in the proliferation and survival of islet cells under physiological and pathological conditions. It is now well established that most cells release part of their ncRNAs inside small extracellular vesicles, allowing the delivery of genetic material to neighboring or distantly located target cells. The role of these secreted RNAs in cell-to-cell communication between β-cells and other metabolic tissues as well as their potential use as diabetes biomarkers will be discussed. © 2020 American Physiological Society. Compr Physiol 10:893-932, 2020.

Circulating miR-330-3p in Late Pregnancy is Associated with Pregnancy Outcomes Among Lean Women with GDM

Gestational Diabetes Mellitus (GDM) is characterised by insulin resistance accompanied by reduced beta-cell compensation to increased insulin demand, typically observed in the second and third trimester and associated with adverse pregnancy outcomes. There is a need for a biomarker that can accurately monitor status and predict outcome in GDM, reducing foetal-maternal morbidity and mortality risks. To this end, circulating microRNAs (miRNAs) present themselves as promising candidates, stably expressed in serum and known to play crucial roles in regulation of glucose metabolism. We analysed circulating miRNA profiles in a cohort of GDM patients (n = 31) and nondiabetic controls (n = 29) during the third trimester for miRNA associated with insulin-secretory defects and glucose homeostasis. We identified miR-330-3p as being significantly upregulated in lean women with GDM compared to nondiabetic controls. Furthermore, increased levels of miR-330-3p were associated with better response to treatment (diet vs. insulin), with lower levels associated with exogenous insulin requirement. We observed miR-330-3p to be significantly related to the percentage of caesarean deliveries, with miR-330-3p expression significantly higher in spontaneously delivered GDM patients. We report this strong novel association of circulating miR-330-3p with risk of primary caesarean delivery as a pregnancy outcome linked with poor maternal glycaemic control, strengthening the growing body of evidence for roles of diabetes-associated miRNAs in glucose homeostasis and adaptation to the complex changes related to pregnancy.

miR-149 Negative Regulation of mafA Is Involved in the Arsenite-Induced Dysfunction of Insulin Synthesis and Secretion in Pancreatic Beta Cells

Chronic exposure to arsenic, a potent environmental oxidative stressor, is associated with the incidence of diabetes. However, the mechanisms for arsenite-induced reduction of insulin remain largely unclear. After CD1 mice were treated with 20 or 40 ppm arsenite in the drinking water for 12 months, the mice showed reduced fasting insulin levels, a depression in glucose clearance, and lower insulin content in the pancreas. The levels of glucose-stimulated insulin secretion (GSIS) in pancreatic β-cells isolated from arsenite-exposed mice were low compared with those for control mice. Immunohistochemistry studies showed that arsenite exposure resulted a reduction of insulin content in the pancreas of mice. Exposure of Min6 cells, a pancreatic beta cell line, to low levels of arsenite led to lower GSIS in a dose- and time-dependent fashion. Since microRNAs (miRNAs) are involved in pancreatic β-cell function and the pathogenesis of diabetes, we hypothesized that arsenite exposure activates miR-149, decreases insulin transcription factor v-maf musculoaponeurotic fibrosarcoma oncogene homolog A (mafA), and induces an insulin synthesis and secretion disorder. In arsenite-exposed Min6 cells, mafA activity was lowered by the increase of its target miRNA, miR-149. Luciferase assays illustrated an interaction between miR-149 and the mafA 3' untranslated region. In Min6 cells transfected with an miR-149 inhibitor, arsenite did not regulate GSIS and mafA expression. In control cells, however, arsenite decreased GSIS or mafA expression. Our results suggest that low levels of arsenite affect β-cell function and regulate insulin synthesis and secretion by modulating mafA expression through miR-149.

microRNA-206 modulates the hepatic expression of the organic anion-transporting polypeptide 1B1

BACKGROUND & AIMS

The organic anion-transporting polypeptide 1B1 (OATP1B1) is an anion exchanger expressed at the hepatocyte sinusoidal membrane, which mediates the uptake of several endogenous metabolites and drugs. OATP1B1 expression level and activity are major sources of inter-patient variability of pharmacokinetics and pharmacodynamics of several drugs. Besides the genotype, factors that contribute to the inter-individual variability in OATP1B1 expression level are practically unknown. The aim of this work was to uncover novel epigenetic mechanisms of OATP1B1 regulation.

METHODS

A functional screening strategy to assess the effect of microRNAs on the uptake of estrone-3-sulphate, an OATP1B1 substrate, into human hepatocellular carcinoma (Huh-7) cells was used. microRNA-206 (miR-206) expression in human liver tissues was measured by real-time RT-PCR. OATP1B1 expression in Huh-7 and in human liver tissues was assessed by real-time RT-PCR, Western blotting and immunostaining. The mRNA-miRNA interaction was assessed by reporter assay.

RESULTS

miR-206 mimic repressed mRNA and protein expression of OATP1B1 in Huh-7 cells. The intracellular accumulation of estrone-3-sulphate was reduced by 30% in cells overexpressing miR-206. The repressive effect of miR-206 on the activity of the firefly luciferase gene 2 under the control of the OATP1B1 3' untranslated region was lost upon deletion of the predicted miR-206 binding site. Hepatic miR-206 level negatively correlated with OATP1B1 mRNA and protein levels extracted from normal human liver tissues.

CONCLUSIONS

miR-206 exerts a suppressive effect on OATP1B1 expression by an epigenetic mechanism. Individuals with high hepatic levels of miR-206 appear to display lower level of OATP1B1.

Comprehensive transcriptional profiling of aging porcine liver

Background

Aging is a major risk factor for the development of many diseases, and the liver, as the most important metabolic organ, is significantly affected by aging. It has been shown that the liver weight tends to increase in rodents and decrease in humans with age. Pigs have a genomic structure, with physiological as well as biochemical features that are similar to those of humans, and have therefore been used as a valuable model for studying human diseases. The molecular mechanisms of the liver aging of large mammals on a comprehensive transcriptional level remain poorly understood. The pig is an ideal model animal to clearly and fully understand the molecular mechanism underlying human liver aging.

Methods

In this study, four healthy female Yana pigs (an indigenous Chinese breed) were investigated: two young sows (180-days-old) and two old sows (8-years-old). High throughput RNA sequencing was performed to evaluate the expression profiles of messenger RNA, long non-coding RNAs, micro RNAs, and circular RNAs during the porcine liver aging process. Gene Ontology (GO) analysis was performed to investigate the biological functions of age-related genes.

Results

A number of age-related genes were identified in the porcine liver. GO annotation showed that up-regulated genes were mainly related to immune response, while the down-regulated genes were mainly related to metabolism. Moreover, several lncRNAs and their target genes were also found to be differentially expressed during liver aging. In addition, the multi-group cooperative control relationships and constructed circRNA-miRNA co-expression networks were assessed during liver aging.

Conclusions

Numerous age-related genes were identified and circRNA-miRNA co-expression networks that are active during porcine liver aging were constructed. These findings contribute to the understanding of the transcriptional foundations of liver aging and also provide further references that clarify human liver aging at the molecular level.

Glycogen Synthase Kinase 3 Beta Controls Presenilin-1-Mediated Endoplasmic Reticulum Ca²⁺ Leak Directed to Mitochondria in Pancreatic Islets and β-Cells

Background/Aims

In pancreatic β-cells, the intracellular Ca²⁺ homeostasis is an essential regulator of the cells’ major functions. The endoplasmic reticulum (ER) as interactive intracellular Ca²⁺ store balances cellular Ca²⁺. In this study basal ER Ca²⁺ homeostasis was evaluated in order to reveal potential β-cell-specificity of ER Ca²⁺ handling and its consequences for mitochondrial Ca²⁺, ATP and respiration.

Methods

The two pancreatic cell lines INS-1 and MIN-6, freshly isolated pancreatic islets, and the two non-pancreatic cell lines HeLA and EA.hy926 were used. Cytosolic, ER and mitochondrial Ca²⁺ and ATP measurements were performed using single cell fluorescence microscopy and respective (genetically-encoded) sensors/dyes. Mitochondrial respiration was monitored by respirometry. GSK3β activity was measured with ELISA.

Results

An atypical ER Ca²⁺ leak was observed exclusively in pancreatic islets and β-cells. This continuous ER Ca²⁺ efflux is directed to mitochondria and increases basal respiration and organellar ATP levels, is established by GSK3β-mediated phosphorylation of presenilin-1, and is prevented by either knockdown of presenilin-1 or an inhibition/knockdown of GSK3β. Expression of a presenlin-1 mutant that mimics GSK3β-mediated phosphorylation established a β-cell-like ER Ca²⁺ leak in HeLa and EA.hy926 cells. The ER Ca²⁺ loss in β-cells was compensated at steady state by Ca²⁺ entry that is linked to the activity of TRPC3.

Conclusion

Pancreatic β-cells establish a cell-specific ER Ca²⁺ leak that is under the control of GSK3β and directed to mitochondria, thus, reflecting a cell-specific intracellular Ca²⁺ handling for basal mitochondrial activity.

MicroRNA profiling of diabetic atherosclerosis in a rat model

OBJECTIVE

The incidence of diabetic atherosclerosis (DA) is increasing worldwide. The study aim was to identify differentially expressed microRNAs (DE-miRs) potentially associated with the initiation and/or progression of DA, thereby yielding new insights into this disease.

METHODS

Matched iliac artery tissue samples were isolated from 6 male rats with or without DA. The Affymetrix GeneChip microRNA 4.0 Array was used to detect miRs. Differential expression between atherosclerotic group and non-atherosclerotic group samples was analyzed using the Gene-Cloud of Biotechnology Information platform. Targetscan and miRanda were then used to predict targets of DE-miRs. Functions and pathways were identified for significantly enriched candidate target genes and a DE-miR functional regulatory network was assembled to identify DA-associated core target genes.

RESULTS

A total of nine DE-miRs (rno-miR-206-3p, rno-miR-133a-5p, rno-miR-133b-3p, rno-miR-133a-3p, rno-miR-325-5p, rno-miR-675-3p, rno-miR-411-5p, rno-miR-329-3p, and rno-miR-126a-3p) were identified, all of which were up-regulated and together predicted to target 3349 genes. The target genes were enriched in known functions and pathways related to lipid and glucose metabolism. The functional regulatory network indicated a modulatory pattern of these metabolic functions with DE-miRs. The miR-gene network suggested arpp19 and MDM4 as possible DA-related core target genes.

CONCLUSION

The present study identified DE-miRs and miRNA-gene networks enriched for lipid and glucose metabolic functions and pathways, and arpp19 and MDM4 as potential DA-related core target genes, suggesting DE-miRs and/or arpp19 and MDM4 could act as potential diagnostic markers or therapeutic targets for DA.

Expression of miR-206 in human islets and its role in glucokinase regulation

Inappropriate insulin secretion from β-cells is considered as an early sign of impaired glucose tolerance and type 2 diabetes (T2D). Glucokinase (GCK) is an important enzyme that regulates glucose metabolism and ensures that the normal circulating glucose concentrations are maintained. GCK expression is induced by glucose and regulated via transcription factors and regulatory proteins. Recently, microRNA-206 (miR-206) was reported to regulate GCK and alter glucose tolerance in normal and high-fat diet-fed mice. Although the study findings have implications for human diabetes, studies in human islets are lacking. Here, we analyze human islets from individuals without or with T2D, using TaqMan-based real-time qPCR at the tissue (isolated islet) level as well as at single cell resolution, to assess the relationship between miR-206 and GCK expression in normal and T2D human islets. Our data suggest that, unlike mouse islets, human islets do not exhibit any correlation between miR-206 and GCK transcripts. These data implicate the need for further studies aimed toward exploring its potential role(s) in human islets.

MicroRNAs in islet hormone secretion

Pancreatic islet hormone secretion is central in the maintenance of blood glucose homeostasis. During development of hyperglycaemia, the β-cell is under pressure to release more insulin to compensate for increased insulin resistance. Failure of the β-cells to secrete enough insulin results in type 2 diabetes (T2D). MicroRNAs (miRNAs) are short non-coding RNA molecules suitable for rapid regulation of the changes in target gene expression needed in β-cell adaptations. Moreover, miRNAs are involved in the maintenance of α-cell and β-cell phenotypic identities via cell-specific, or cell-enriched expression. Although many of the abundant miRNAs are highly expressed in both cell types, recent research has focused on the role of miRNAs in β-cells. It has been shown that highly abundant miRNAs, such as miR-375, are involved in several cellular functions indispensable in maintaining β-cell phenotypic identity, almost acting as "housekeeping genes" in the context of hormone secretion. Despite the abundance and importance of miR-375, it has not been shown to be differentially expressed in T2D islets. On the contrary, the less abundant miRNAs such as miR-212/miR-132, miR-335, miR-130a/b and miR-152 are deregulated in T2D islets, wherein the latter three miRNAs were shown to play key roles in regulating β-cell metabolism. In this review, we focus on β-cell function and describe miRNAs involved in insulin biosynthesis and processing, glucose uptake and metabolism, electrical activity and Ca²⁺ -influx and exocytosis of the insulin granules. We present current status on miRNA regulation in α-cells, and finally we discuss the involvement of miRNAs in β-cell dysfunction underlying T2D pathogenesis.

Effects of thymoquinone on liver miRNAs and oxidative stress in Ehrlich acid mouse solid tumor model

We investigated the effects of thymoquinone (TQ) on the expression of liver microRNAs (miRNAs), liver histopathology and oxidative stress in Ehrlich acid solid tumor model induced mice. We used 24 male BALB/c mice divided randomly into three groups. Control (C) group mice were injected intraperitoneally (i.p.) with 0.5 ml saline for four weeks. Tumor (T) group mice were injected i.p. with 0.5 ml saline for four weeks, then Ehrlich acid tumor cells were injected subcutaneously into the neck to induce solid tumor formation. TQ (T + Tq) group mice injected i.p. with 10 mg/kg TQ for four weeks, then Ehrlich acid tumor cells were injected subcutaneously into the neck of the mice in this group to induce solid tumor formation. At the end of the study, liver from all groups were removed for histopathological and miRNAs analysis, and oxidative stress measurement. We found that the expression of miR-206b-3p was up-regulated and the oxidative stress and necrosis increased in the liver tissue of mice with Ehrlich acid solid tumor. TQ application decreased the oxidative stress, prevented necrosis, increased regeneration and down-regulated the expression of miR-206b-3p in the liver tissue.

Do skeletal muscle-secreted factors influence the function of pancreatic β-cells?

Skeletal muscle is an endocrine organ that secretes a variety of compounds including proteins (myokines), metabolites, microRNAs (miRNAs), and exosomes, many of which are regulated by exercise and play important roles in endocrine signaling. Interorgan communication via muscle-secreted factors therefore provides a novel area for investigation and implicates the importance of skeletal muscle in the pathophysiology of metabolic diseases such as type 2 diabetes (T2D). Given that underlying molecular mechanisms of T2D are subject of ongoing research, in light of new evidence it is probable that interorgan cross-talk between skeletal muscle and pancreatic β-cells plays an important part. To date, the number of studies published in this field provide the basis of this review. Specifically, we discuss current experimental evidence in support for a role of skeletal muscle to β-cell cross-talk, paying particular attention to muscle-secreted factors including myokines, metabolites, miRNAs, and factors contained within exosomes that influence the function and/or the survival of β-cells in health and disease. In reviewing this evidence, we provide an update on the list of known muscle-secreted factors that have potential to influence the function and/or survival of β-cells under normal and diabetic conditions. We also report limitations of current cross-talk methods and discuss future directions in this growing field.

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.

The adverse effects of perinatal exposure to nonylphenol on carbohydrate metabolism in male offspring rats

BACKGROUND

We sought to investigate the adverse effects of perinatal exposure to nonylphenol (NP) on carbohydrate metabolism of male offspring rats.

METHODS

Thirty-two healthy pregnant Sprague Dawley rats were randomly divided into four groups, control normal diet group (C), NP normal diet group (NPN), control high-energy diet group (CH), and NP high-energy diet group (NPH). Both of the control groups were received a gavage of corn oil and the NP-groups were received NP (200 mg/kg/day) from gestational days 6 to post-natal day (PND) 21. The concentrations of NP in pancreatic tissues were measured by high-performance liquid chromatography (HPLC). The key genes of glucose metabolism expression were detected by reverse transcription-polymerase chain reaction (RT-PCR). The pancreatic tissues were stained with hematoxylin/eosin (HE).

RESULTS

On PND 1, the body weights of male pups in the NPN and NPH groups were lower than those of the CH group (p = 0.012 and 0.001, respectively). On PND 30, the body weight of male pups from the NPH group was elevated compared with the C group (p = 0.019), while the body weights of male pups in the NPN and NPH groups were elevated compared to the CH group (p = 0.034 and 0.004, respectively). On PND 60, the body weights of NPN and NPH pups were higher than those in the C (p < 0.001) and CH groups (p < 0.001). The levels of fasting blood glucose (FBG) were increased significantly in the animals treated with NP compared to control animals (F = 29.14, p < 0.001). The FBG levels in the treatment groups are ranked as follows: NPH > NPN > CH > C (p < 0.05). The concentrations of NP in pancreas tissues in both the NPN (2045.0 ± 130.1 μg/L) and NPH groups (2038.0 ± 104.2 μg/L) were higher than those in the C (499.5 ± 27.4 μg/L) and CH groups (494.2 ± 22.4 μg/L; p < 0.05). Morphological examination of tissues from rats exposed to NP shown that the NP-treated groups appeared to have a higher degree of inflammatory injury, edema, and focal necrotic cells in the pancreatic tissues. Compared with C group, expression of glucokinase (GCK) was down-regulated, while Uncoupling protein-2 (UCP-2) was up-regulated in the NP-treated groups (F_GCK = 218.89, p < 0.001; F_UCP-2 = 18.82, p < 0.001).

CONCLUSIONS

Prenatal exposure to NP could induce glucose metabolism disorder in male F1 rats, which may be due to the fact that NP induces abnormal expression patterns of GCK and UCP-2.

MicroRNAs as stress regulators in pancreatic beta cells and diabetes

Background

MicroRNAs have emerged as important regulatory non-coding RNAs that tune cellular responses to physiological perturbations and disease conditions. An increasing body of literature underlines the important roles of miRNA function in pancreatic β-cells in response to metabolic, genetic and inflammatory stress. Lessons from genetic loss- and gain-of-function studies have implicated several highly expressed and evolutionary conserved miRNAs in stress signal modulation, resolution and buffering, thereby forming stabilizing miRNA networks that preserve β-cell differentiation, function, proliferation and cell survival.

Scope of Review

This review will summarize our current knowledge of how biologically relevant miRNAs regulate stress responses in pancreatic β-cells, discuss the challenges and opportunities associated with using secreted miRNAs as biomarkers and forecast how mechanistic knowledge of miRNA function can be exploited in developing miRNA-based therapeutics.

Major Conclusions

miRNAs play important roles in the function, differentiation, proliferation, and survival of pancreatic β-cells. Many miRNA families that are regulated by metabolic, genetic, and inflammatory stressors have been found to coordinate the adaptive responses of β-cells in vivo in conditions such as obesity and diabetes.

The Role of miRNAs in Common Inflammatory Arthropathies: Osteoarthritis and Gouty Arthritis

MicroRNAs (miRNAs) are small, non-coding RNA species that are highly evolutionarily conserved, from higher invertebrates to man. Up to 1000 miRNAs have been identified in human cells thus far, where they are key regulators of the expression of numerous targets at the post-transcriptional level. They are implicated in various processes, including cell differentiation, metabolism, and inflammation. An expanding list of miRNAs is known to be involved in the pathogenesis of common, non-autoimmune inflammatory diseases. Interestingly, osteoarthritis (OA) is now being conceptualized as a metabolic disease, as there is a correlation among hyperuricemia and metabolic syndrome (MetS). Experimental evidence suggests that metabolic deregulation is a commonality between these different pathological entities, and that miRNAs are key players in the modulation of metabolic routes. In light of these findings, this review discusses the role of miRNAs in OA and gouty arthritis, as well as the possible therapeutic targetability of miRNAs in these diseases.

Glucose enhances rat islet function via stimulating CART expression

Cocaine- and amphetamine-regulated transcript (CART) is an anorexigenic peptide widely expressed in the central and peripheral nervous systems, as well as in endocrine cells. CART is markedly upregulated in the β-cells of several rodent models of type-2 diabetes. The stimulatory effect of exogenous CART peptide on insulin secretion is cAMP dependent. Glucose is the most important regulator of islet function. However, the role of CART in glucose-potentiated insulin secretion remains unclear. Here, our results showed that glucose time- and dose-dependently elicited CART mRNA expression in rat islets. Both the glucokinase agonist GKA50 and the long-acting GLP-1 analogue exendin-4 increased CART mRNA expression. The protein kinase A (PKA) inhibitor H89 and the inactivation of cAMP response element-binding protein (CREB) suppressed forskolin-stimulated CART mRNA expression. Furthermore, CART overexpression amplified insulin secretion from rat islets in response to glucose and forskolin, and ameliorated dexamethasone-impaired insulin secretion. These findings suggest that islet-derived CART is involved, at least in part, in high glucose-potentiated pancreatic β-cell function.

Loss of Sodium/Hydrogen Exchanger NHA2 Exacerbates Obesity- and Aging-Induced Glucose Intolerance in Mice

We previously demonstrated that the sodium/hydrogen exchanger NHA2, also known as NHEDC2 or SLC9B2, is critical for insulin secretion by β–cells. To gain more insights into the role of NHA2 on systemic glucose homeostasis, we studied the impact of loss of NHA2 during the physiological aging process and in the setting of diet-induced obesity. While glucose tolerance was normal at 2 months of age, NHA2 KO mice displayed a significant glucose intolerance at 5 and 12 months of age, respectively. An obesogenic high fat diet further exacerbated the glucose intolerance of NHA2 KO mice. Insulin levels remained similar in NHA2 KO and WT mice during aging and high fat diet, but fasting insulin/glucose ratios were significantly lower in NHA2 KO mice. Peripheral insulin sensitivity, measured by insulin tolerance tests and hyperinsulinemic euglycemic clamps, was unaffected by loss of NHA2 during aging and high fat diet. High fat diet diminished insulin secretion capacity in both WT and NHA2 KO islets and reduced expression of NHA2 in WT islets. In contrast, aging was characterized by a gradual increase of NHA2 expression in islets, paralleled by an increasing difference in insulin secretion between WT and NHA2 KO islets. In summary, our results demonstrate that loss of the sodium/hydrogen exchanger NHA2 exacerbates obesity- and aging-induced glucose intolerance in mice. Furthermore, our data reveal a close link between NHA2 expression and insulin secretion capacity in islets.