MicroRNA-218 targets adiponectin receptor 2 to regulate adiponectin signaling

MicroRNA regulation of AMPK in nonalcoholic fatty liver disease

Obesity-associated nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease and is the leading cause of liver failure and death. The function of AMP-activated protein kinase (AMPK), a master energy sensor, is aberrantly reduced in NAFLD, but the underlying mechanisms are not fully understood. Increasing evidence indicates that aberrantly expressed microRNAs (miRs) are associated with impaired AMPK function in obesity and NAFLD. In this review, we discuss the emerging evidence that miRs have a role in reducing AMPK activity in NAFLD and nonalcoholic steatohepatitis (NASH), a severe form of NAFLD. We also discuss the underlying mechanisms of the aberrant expression of miRs that can negatively impact AMPK, as well as the therapeutic potential of targeting the miR-AMPK pathway for NAFLD/NASH.

Adiponectin, the adiponectin paradox, and Alzheimer's Disease: Is this association biologically plausible?

Dementia, especially Alzheimer's Disease (AD) and vascular dementia, is a major public health problem that continues to expand in both economically emerging and hegemonic countries. In 2017, the World Alzheimer Report estimated that over 50 million people were living with dementia globally. Metabolic dysfunctions of brain structures such as the hippocampus and cerebral cortex have been implicated as risk factors for dementia. Several well-defined metabolic risk factors for AD include visceral obesity, chronic inflammation, peripheral and brain insulin resistance, type 2 diabetes mellitus (T2DM), hypercholesterolemia, and others. In this review, we describe the relationship between the dysmetabolic mechanisms, although still unknown, and dementia, particularly AD. Adiponectin (ADPN), the most abundant circulating adipocytokine, acts as a protagonist in the metabolic dysfunction associated with AD, with unexpected and intriguing dual biological functions. This contradictory role of ADPN has been termed the adiponectin paradox. Some evidence suggests that the adiponectin paradox is important in amyloidogenic evolvability in AD. We present cumulative evidence showing that AD and T2DM share many common features. We also review the mechanistic pathways involving brain insulin resistance. We discuss the importance of the evolvability of amyloidogenic proteins (APs), defined as the capacity of a system for adaptive evolution. Finally, we describe potential therapeutic strategies in AD, based on the adiponectin paradox.

microRNAs in Human Adipose Tissue Physiology and Dysfunction

In recent years, there has been a large amount of evidence on the role of microRNA (miRNA) in regulating adipose tissue physiology. Indeed, miRNAs control critical steps in adipocyte differentiation, proliferation and browning, as well as lipolysis, lipogenesis and adipokine secretion. Overnutrition leads to a significant change in the adipocyte miRNOME, resulting in adipose tissue dysfunction. Moreover, via secreted mediators, dysfunctional adipocytes may impair the function of other organs and tissues. However, given their potential to control cell and whole-body energy expenditure, miRNAs also represent critical therapeutic targets for treating obesity and related metabolic complications. This review attempts to integrate present concepts on the role miRNAs play in adipose tissue physiology and obesity-related dysfunction and data from pre-clinical and clinical studies on the diagnostic or therapeutic potential of miRNA in obesity and its related complications.

MicroRNAs, Parkinson's Disease, and Diabetes Mellitus

Parkinson’s disease (PD) is a neurodegenerative disorder that affects 1% of the population over the age of 60. Diabetes Mellitus (DM) is a metabolic disorder that affects approximately 25% of adults over the age of 60. Recent studies showed that DM increases the risk of developing PD. The link between DM and PD has been discussed in the literature in relation to different mechanisms including mitochondrial dysfunction, oxidative stress, and protein aggregation. In this paper, we review the common microRNA (miRNA) biomarkers of both diseases. miRNAs play an important role in cell differentiation, development, the regulation of the cell cycle, and apoptosis. They are also involved in the pathology of many diseases. miRNAs can mediate the insulin pathway and glucose absorption. miRNAs can also regulate PD-related genes. Therefore, exploring the common miRNA biomarkers of both PD and DM can shed a light on how these two diseases are correlated, and targeting miRNAs is a potential therapeutic opportunity for both diseases.

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.

The cross-talk between adipokines and miRNAs in health and obesity-mediated diseases

BACKGROUND

Multiple studies have revealed a direct correlation between obesity and the development of multiple comorbidities, including metabolic diseases, cardiovascular disorders, chronic inflammatory disease, and cancers. However, the molecular mechanism underlying the link between obesity and the progression of these diseases is not completely understood. Adipokines are factors that are secreted by adipocytes and play a key role in whole body homeostasis. Collaboratively, miRNAs are suggested to have key functions in the development of obesity and obesity-related disorders. Based on recently emerging evidence, obesity leads to the dysregulation of both adipokines and obesity-related miRNAs. In the present study, we described the correlations between obesity and its related diseases that are mediated by the mutual regulatory effects of adipokines and miRNAs.

METHODS

We reviewed current knowledge of the modulatory effects of adipokines on miRNAs activity and their relevant functions in pathological conditions and vice versa.

RESULTS

Our research reveals the ability of adipokines and miRNAs to control the expression and activity of the other class of molecules, and their effects on obesity-related diseases.

CONCLUSIONS

This study may help researchers develop a roadmap for future investigations and provide opportunities to develop new therapeutic and diagnostic methods for treating obesity-related diseases.

MicroRNAs in Obesity and Related Metabolic Disorders

Metabolic disorders are characterized by the inability to properly use and/or store energy. The burdens of metabolic disease, such as obesity or diabetes, are believed to arise through a complex interplay between genetics and epigenetics predisposition, environment and nutrition. Therefore, understanding the molecular mechanisms for the onset of metabolic disease will provide new insights for prevention and treatment. There is growing concern about the dysregulation of micro-RNAs (miRNAs) in metabolic diseases. MiRNAs are short non-coding RNA molecules that post-transcriptionally repress the expression of genes by binding to untranslated regions and coding sequences of the target mRNAs. This review aims to provide recent data about the potential involvement of miRNAs in metabolic diseases, particularly obesity and type 2 diabetes.

Sustained Intermittent Hypoxemia Induces Adiponectin Oligomers Redistribution and a Tissue-Specific Modulation of Adiponectin Receptor in Mice

Introduction: Hypoxemia is a critical component of several respiratory diseases and is known to be involved in the processes underlying co-morbidities associated to such disorders, notably at the cardiovascular level. Circulating level of Adiponectin (Ad), known as a metabolic regulator and cardio-protective hormone was previously suggested to be reduced by hypoxia but consequences of such variation are unclear. The evaluation of the specific effect of hypoxemia on Ad forms and receptors could improve the understanding of the involvement of Ad axis in hypoxemia-related diseases.

Methods: Ad-pathway components were investigated in a murine model of sustained intermittent hypoxemia (FiO₂ 10%, 8 h/day, 35 days).

Results: Sustained intermittent hypoxemia (SIH) induced a redistribution of Ad multimers in favor of HMW forms, without change in total plasmatic level. Mice submitted to hypoxia also exhibited tissue-specific modification of adiporeceptor (AdipoR) protein level without mRNA expression change. A decreased AdipoR2 abundance was observed in skeletal muscle and heart whereas AdipoR1 level was only reduced in muscle. No change was observed in liver regarding AdipoR. Lipid profile was unchanged but glucose tolerance increased in hypoxemic mice.

Conclusion: Sustained intermittent hypoxemia, per se, modify Ad oligomerization state as well as AdipoR protein abundance in a tissue-specific way. That suggests alteration in Ad-dependant pathways in pathological conditions associated to SIH. Investigation of Ad-pathway components could therefore constitute useful complementary criteria for the clustering of patients with hypoxemia-related diseases and management of co-morbidities, as well as to develop new therapeutic strategies.

Potential role of microRNAs in the regulation of adipocytes liposecretion and adipose tissue physiology

Adipose tissue is a dynamic endocrine organ playing a pivotal role in metabolism modulation. Adipocytes differentiation requires a highly orchestrated series of changes of gene expression in precursor cells. At the same time, white mature adipocytes are plastic cells able to reversibly transdifferentiate toward fibroblast-like cells via the liposecretion process, returning back to a non-committed status of the cells. In particular, adipose tissue microenvironment along with external signaling molecules such as adipokines, cytokines and growth factors can regulate adipocytes physiology through complex molecular networks. MicroRNAs (miRNAs), a type of non-coding RNA, acting as fine regulators of biological processes and their expression is sensible to the environment and cellular status changes. MiRNAs are thought to play a pivotal role in regulating the physiology of adipose tissue as well as in the development of obesity and associated metabolic disturbances, although the underlying mechanisms have not been identified so far. Elucidating the molecular mechanisms orchestrating adipose tissue biology is required to better characterize obesity and its associated diseases. In this respect, the review aims to analyze the microRNAs potentially involved in adipogenesis highlighting their role in the process of liposecretion, adipocyte proliferation, and adipokines secretion. The role of microRNAs in the development of obesity and obesity-associated disorders is also discussed.

Differential microRNA expression profiles and bioinformatics analysis between young and aging spontaneously hypertensive rats

MicroRNAs (miRNAs/miRs) serve a role as important regulators in cardiac hypertrophy. The present study aimed to reveal the differential expression profile of miRNAs between young and aging spontaneously hypertensive rats (SHRs) and studied the functional annotation of predicted targets. Briefly, 3-month-old and 12-month-old SHRs (n=3/group) were subjected to echocardiography, histopathological analysis and dihydroethidium staining. Subsequently, small RNA sequencing and data processing was conducted to identify the differentially expressed miRNAs between these two groups. Eight significantly upregulated miRNAs were validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR), followed by in silico target gene prediction. Functional annotation analysis of the predicted targets was performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. As a result, significantly impaired left ventricular diastolic function was detected in the 12-month-old SHRs, alongside increased myocyte cross-sectional area and percentage area of fibrosis, elevated reactive oxygen species production and reduced microvessel density (P<0.05). Compared with the 3-month-old SHRs, 21 miRNAs were significantly upregulated and five miRNAs were downregulated in 12-month-old rats (P<0.05). Eight upregulated, remodeling-associated miRNAs, including rno-miR-132-3p, rno-miR-182, rno-miR-208b-3p, rno-miR-212-3p, rno-miR-214-3p, rno-miR-218a-5p, rno-miR-221-3p and rno-miR-222-3p, underwent bioinformatics analysis. The target genes were significantly enriched in 688 GO terms and 39 KEGG pathways, including regulation of peptidyl-tyrosine phosphorylation, regulation of protein serine/threonine kinase activity, adrenergic signaling in cardiomyocytes, ErbB signaling pathway, mTOR signaling pathway, FoxO signaling pathway, Ras signaling pathway, insulin secretion, adipocytokine signaling pathway, HIF-1 signaling pathway, Rap1 signaling pathway, VEGF signaling pathway and TNF signaling pathway. Collectively, the present study identified a dysregulated miRNA profile in aging SHRs, which targeted numerous signaling pathways associated with cardiac hypertrophy, autophagy, insulin metabolism, angiogenesis and inflammatory response.

Hypoxia-inducible microRNA-218 inhibits trophoblast invasion by targeting LASP1: Implications for preeclampsia development

Preeclampsia (PE) is a major contributor to maternal morbidity and mortality. However, the molecular mechanisms underlying PE progression are not well characterized. Here, we investigated the role of miR-218 in PE development. The expression of miR-218 and its host genes SLIT2 and SLIT3 was up-regulated in preeclamptic placentae compared to normal placentae. miR-218 expression was induced by hypoxia and decreased after knockdown of HIF-1α in an extravillous trophoblast cell line (HTR-8/SVneo). Chromatin immunoprecipitation assays showed direct binding of HIF-1α to the promoters of SLIT2 and SLIT3. Bioinformatics analysis identified LASP1 as a direct target of miR-218. Overexpression of miR-218 repressed the expression of LASP1 at both the mRNA and protein level. Meanwhile, miR-218 repressed the activity of a luciferase reporter containing the 3'-untranslated region of the LASP1 gene. Furthermore, expression of LASP1 rescued the inhibitory effect of miR-218 on HTR-8/SVneo cell invasion. Together, these results indicated that miR-218 contributes to PE by targeting LASP1 to inhibit trophoblast invasion.

Adiponectin Receptors Are Less Sensitive to Stress in a Transgenic Mouse Model of Alzheimer's Disease

Background: Adiponectin and leptin are implicated in the initiation and pathomechanism of Alzheimer's disease (AD). The serum concentrations of these adipokines has been extensively studied in AD, however little is known about their receptors in this disease. Objective: We developed a novel approach to examine whether the receptors of adiponectin (AdipoR1 and -R2) and/or leptin (LepR) can contribute to AD pathomechanism. To achieve this, we investigated the effect of both genetic and environmental factors associated with AD on the expression of these receptors. Method: We used C57BL/6J (WT) and APP(swe)/Presen(e9d)1 (AD) mice. Both strains were exposed to restraint stress (RS) daily for 6h over different time periods. Then, we measured the mRNA expression of AdipoR1, AdipoR2 and LepR and the level of AdipoR1 and AdipoR2 proteins in the hippocampal and prefrontal cortical areas of each mouse. Results: We detected brain region specific transcriptomic changes of adiponectin receptors induced by APP and PS1 transgenes. Both acute and chronic RS caused significant elevations in AdipoR1 mRNA expression in the hippocampus of WT mice. In the prefrontal cortex, the mRNA expression of AdipoR1 followed a biphasic course. In AD mice, RS did not promote any changes in the expression of AdipoR1 mRNA and AdipoR1 protein levels. AdipoR2 mRNA in AD animals, however, showed a significant increase in the prefrontal cortex during RS. Regarding AdipoR1 and AdipoR2 mRNA and protein expression, relevant changes could be measured during stress exposure in both brain areas. Furthermore, stress exposed groups exhibited little change in LepR mRNA expression. Conclusion: Our findings indicate that carrying the transgenes associated with AD induces modification in the expression of both adiponectin receptors. In the case of a normal genetic background, these receptors also appear to be sensitive to environmental factors, while in a genetically determined AD model less response to stress stimuli could be observed. The results suggest that modification of adipokine receptors could also be considered in the therapeutic approach to AD.

A Series of microRNA in the Chromosome 14q32.2 Maternally Imprinted Region Related to Progression of Non-Alcoholic Fatty Liver Disease in a Mouse Model

Background & Aims

Simple steatosis (SS) and non-alcoholic steatohepatitis (NASH) are subtypes of non-alcoholic fatty liver disease (NAFLD), and the pathogenic differences between SS and NASH remain unclear. MicroRNAs (miRNAs) are endogenous, non-coding, short RNAs that regulate gene expression. The aim of this study was to use animal models and human samples to examine the relationship between miRNA expression profiles and each type of NAFLD (SS and NASH).

Methods

DD Shionogi, Fatty Liver Shionogi (FLS) and FLS ob/ob mice were used as models for normal control, SS and NASH, respectively. Microarray analysis and real-time PCR were used to identify candidate NAFLD-related miRNAs. Human serum samples were used to examine the expression profiles of these candidate miRNAs in control subjects and patients with SS or NASH.

Results

Fourteen miRNAs showed clear expression differences among liver tissues from SS, NASH, and control mice with good reproducibility. Among these NAFLD candidate miRNAs, seven showed similar expression patterns and were upregulated in both SS and NASH tissues; these seven candidate miRNAs mapped to an miRNA cluster in the 14q32.2 maternally imprinted region delineated by delta-like homolog 1 and type III iodothyronine deiodinase (Dlk1-Dio3 mat). Software-based predictions indicated that the transforming growth factor-β pathway, insulin like growth factor-1 and 5' adenosine monophosphate activated protein kinase were potential targets of theses Dlk1-Dio3 mat NAFLD candidate miRNAs. In addition, serum samples from patients with SS or NASH differed markedly with regard to expression of the putative Dlk1-Dio3 mat miRNAs, and these differences accurately corresponded with NAFLD diagnosis.

Conclusion

The expression profiles of seven miRNAs in 14q32.2 mat have high potential as biomarkers for NAFLD and for improving future research on the pathogenesis and treatment of NASH.