Decrease of microRNA-122 causes hepatic insulin resistance by inducing protein tyrosine phosphatase 1B, which is reversed by licorice flavonoid

Caloric Restriction Induces MicroRNAs to Improve Mitochondrial Proteostasis

Both caloric restriction (CR) and mitochondrial proteostasis are linked to longevity, but how CR maintains mitochondrial proteostasis in mammals remains elusive. MicroRNAs (miRNAs) are well known for gene silencing in cytoplasm and have recently been identified in mitochondria, but knowledge regarding their influence on mitochondrial function is limited. Here, we report that CR increases miRNAs, which are required for the CR-induced activation of mitochondrial translation, in mouse liver. The ablation of miR-122, the most abundant miRNA induced by CR, or the retardation of miRNA biogenesis via Drosha knockdown significantly reduces the CR-induced activation of mitochondrial translation. Importantly, CR-induced miRNAs cause the overproduction of mtDNA-encoded proteins, which induces the mitochondrial unfolded protein response (UPR^mt), and consequently improves mitochondrial proteostasis and function. These findings establish a physiological role of miRNA-enhanced mitochondrial function during CR and reveal miRNAs as critical mediators of CR in inducing UPR^mt to improve mitochondrial proteostasis.

•

CR increases miRNA biogenesis and the global expression of miRNAs in mitochondria

•

miRNAs are critical for CR-induced activation of mitochondrial translation

•

CR-induced miRNAs cause overproduction of mtDNA-encoded proteins and induce UPR^mt

Associations of blood levels of trace elements and heavy metals with metabolic syndrome in Chinese male adults with microRNA as mediators involved

Metabolic syndrome (MetS) is a global health problem with an increasing prevalence. However, effects of trace elements and heavy metals on MetS and the mechanism underlying this effect are poorly understood. A preliminary cross-sectional study was conducted in 2015. Significantly higher blood concentrations of lead (Pb), cadmium (Cd), copper (Cu), and selenium (Se) were observed in the MetS group. With a priori adjustment for age, the concentration of Cu and Se in the blood was associated with a 2.56 - fold [95% confidence interval (CI), 1.11, 5.92] and 3.31 - fold (95% CI, 1.4, 7.82) increased risk of MetS, respectively. Moreover, increased blood Se concentrations were associated with body mass index (BMI) [odds ratio (OR): 2.56; 95% CI, 1.11, 5.93], high blood pressure [for both systolic and diastolic blood pressures (SBP and DBP); OR: 3.82; 95% CI, 1.47, 7.31 for SBP and OR: 2.56; 95% CI, 1.18, 5.59 for DBP], and hypertriglyceridemia (OR: 3.3; 95% CI, 1.51, 7.2). In addition, the expression of miR-21-5p, miR-122-5p, and miR-146a-5p was significantly higher in subjects with MetS than those without MetS. Increased expression of miR-21-5p was significantly associated with increased SBP (β = 5.28; 95% CI, 0.63, 9.94) and DBP (β = 4.17; 95% CI, 0.68, 7.66). Moreover, Cu was positively associated with miR-21-5p (β = 3.02; 95% CI, 0.07, 5.95), whereas Se was positively associated with miR-122-5p (β = 2.7; 95% CI, 0.64, 4.76). The bootstrapping mediation models indicated that miR-21-5p partially mediated the relationships between Cu level and SBP/DBP. This study suggested that Cu and Se were both associated with MetS, and miR-21-5p participated in the development of MetS associated with Cu.

Natural products in licorice for the therapy of liver diseases: Progress and future opportunities

Liver diseases related complications represent a significant source of morbidity and mortality worldwide, creating a substantial economic burden. Oxidative stress, excessive inflammation, and dysregulated energy metabolism significantly contributed to liver diseases. Therefore, discovery of novel therapeutic drugs for the treatment of liver diseases are urgently required. Licorice is one of the most commonly used herbal drugs in Traditional Chinese Medicine for the treatment of liver diseases and drug-induced liver injury (DILI). Various bioactive components have been isolated and identified from the licorice, including glycyrrhizin, glycyrrhetinic acid, liquiritigenin, Isoliquiritigenin, licochalcone A, and glycycoumarin. Emerging evidence suggested that these natural products relieved liver diseases and prevented DILI through multi-targeting therapeutic mechanisms, including anti-steatosis, anti-oxidative stress, anti-inflammation, immunoregulation, anti-fibrosis, anti-cancer, and drug-drug interactions. In the current review, we summarized the recent progress in the research of hepatoprotective and toxic effects of different licorice-derived bioactive ingredients and also highlighted the potency of these compounds as promising therapeutic options for the treatment of liver diseases and DILI. We also outlined the networks of underlying molecular signaling pathways. Further pharmacology and toxicology research will contribute to the development of natural products in licorice and their derivatives as medicines with alluring prospect in the clinical application.

High-throughput sequencing of small RNAs and analysis of differentially expressed microRNAs associated with high-fat diet-induced hepatic insulin resistance in mice

Background

Hepatic insulin resistance (IR) plays a crucial role in the development of many metabolic diseases, such as type 2 diabetes. MicroRNAs (miRNAs) are involved in the pathogenesis of IR and related diseases; however, studies of miRNAs in hepatic IR are limited.

Method

In this study, we adopted a high-throughput sequencing approach to construct small RNA libraries in the livers of normal mice and high-fat diet-induced hepatic IR mice.

Results

Through analysis of data, 107 known and 56 novel miRNAs were identified as differentially expressed miRNAs between the two groups. Additionally, bioinformatics methods were used to predict targets of the differentially expressed miRNAs and to explore the potential downstream Gene Ontology categories and Kyoto Encyclopedia of Genes and Genomes pathways. Meanwhile, some differentially expressed miRNAs (miR-34a-5p, miR-149-5p, miR-335-3p, miR-10b-5p, miR-1a-3p, miR-411-5p, and miR-592-5p) were validated by quantitative-time PCR, and their potential target genes related to IR or glycolipid metabolism were also predicted and presented in this study.

Conclusion

Taken together, our results defined miRNA expression signature that may lead to hepatic IR in mice, and the findings provided a foundation for future studies to further explore the effects and underlying mechanisms of the miRNAs and their target genes in the pathogenesis of hepatic IR and related diseases.

Electronic supplementary material

The online version of this article (10.1186/s12263-019-0630-1) contains supplementary material, which is available to authorized users.

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.

miR-125a-5p ameliorates hepatic glycolipid metabolism disorder in type 2 diabetes mellitus through targeting of STAT3

Glycolipid metabolic disorder is an important cause for the development of type 2 diabetes mellitus (T2DM). Clarification of the molecular mechanism of metabolic disorder and exploration of drug targets are crucial for the treatment of T2DM.

Methods: We examined miR-125a-5p levels in palmitic acid-induced AML12 cells and the livers of type 2 diabetic rats and mice, and then validated its target gene. Through gain- and loss-of-function studies, the effects of miR-125a-5p via targeting of STAT3 on regulating glycolipid metabolism were further illustrated in vitro and in vivo.

Results: We found that miR-125a-5p was significantly decreased in the livers of diabetic mice and rats, and STAT3 was identified as the target gene of miR-125a-5p. Overexpression of miR-125a-5p in C57BL/6 mice decreased STAT3 level and downregulated the expression levels of p-STAT3 and SOCS3. Consequently, SREBP-1c-mediated lipogenesis pathway was inhibited, and PI3K/AKT pathway was activated. Moreover, silencing of miR-125a-5p significantly increased the expression levels of STAT3, p-STAT3 and SOCS3, thus activating SREBP-1c pathway and suppressing PI3K/AKT pathway. Therefore, hyperglycemia, hyperlipidemia and decreased liver glycogen appeared in C57BL/6 mice. In palmitic acid-induced AML12 cells, miR-125a-5p mimic markedly increased glucose consumption and uptake and decreased the accumulation of lipid droplets by regulating STAT3 signaling pathway. Consistently, miR-125a-5p overexpression obviously inhibited STAT3 expression in diabetic KK-Ay mice, thereby decreasing blood glucose and lipid levels, increasing hepatic glycogen content, and decreasing accumulation of hepatic lipid droplets in diabetic mice. Furthermore, inhibition of miR-125a-5p in KK-Ay mice aggravated glycolipid metabolism dysfunction through regulating STAT3.

Conclusions: Our results confirmed that miR-125a-5p should be considered as a regulator of glycolipid metabolism in T2DM, which can inhibit hepatic lipogenesis and gluconeogenesis and elevate glycogen synthesis by targeting STAT3.

MicroRNAs and type 2 diabetes mellitus: Molecular mechanisms and the effect of antidiabetic drug treatment

The incidence of type 2 diabetes mellitus (T2DM), the most prevalent metabolic disease, is rapidly growing worldwide. T2DM has several underlying causes involved in its development. In recent decades, there is compelling evidence demonstrating that microRNAs (miRs) are implicated in the pathophysiology of T2DM. miRs are small non-coding RNAs which serve as endogenous gene regulators by binding to specific sequences in RNA and modifying gene expression toward up- or down-regulation. T2DM occurrence and complications may be influenced by increasing or decreasing the activity of some miRs. In the present narrative review, we comment on four molecular pathways/mechanisms that mediate the link between T2DM and different forms of miRs. These mechanisms include involvement of miRs in beta cells development, insulin sensitivity/resistance, insulin production/secretion and insulin signaling. The effects of antidiabetic drugs on miRs are also discussed.

Emerging role of nutrition and the non-coding landscape in type 2 diabetes mellitus: A review of literature

With the advent of recent advances in molecular techniques and whole genome sequencing, we have come to know that the non-coding landscape (including non-coding RNAs, tRNAs and even telomeres) plays a major role in the regulation of cellular processes. Furthermore, the deregulation of this landscape has been found to contribute to and even bring about the pathogenesis of a large number of diseases. One of such diseases is diabetes mellitus (type 2 specifically) whose incidence rate and global burden is constantly increasing. Nutrition has been proven to be a key player in the development, onset and control of type 2 diabetes mellitus. Additionally, non-coding DNA based molecular markers are emerging as biomarkers of T2D, susceptibility, and perhaps dietary supplements can modulate non-coding DNA based markers expression and function in T2D management. In this review, we provide a brief overview of the developmental origins and genetics of type 2 diabetes mellitus, how each component of the non-coding landscape contributes to the development and progression of the disease and finally we discuss how dietary interventions modulate the non-coding landscape in T2D.

Protein Tyrosine Phosphatase 1B Inhibition and Glucose Uptake Potentials of Mulberrofuran G, Albanol B, and Kuwanon G from Root Bark of Morus alba L. in Insulin-Resistant HepG2 Cells: An In Vitro and In Silico Study

Type II diabetes mellitus (T2DM) is the most common form of diabetes and has become a major health problem across the world. The root bark of Morus alba L. is widely used in Traditional Chinese Medicine for treatment and management of diabetes. The aim of the present study was to evaluate the enzyme inhibitory potentials of three principle components, mulberrofuran G (1), albanol B (2), and kuwanon G (3) in M. alba root bark against diabetes, establish their enzyme kinetics, carry out a molecular docking simulation, and demonstrate the glucose uptake activity in insulin-resistant HepG2 cells. Compounds 1–3 showed potent mixed-type enzyme inhibition against protein tyrosine phosphatase 1B (PTP1B) and α-glucosidase. In particular, molecular docking simulations of 1–3 demonstrated negative binding energies in both enzymes. Moreover, 1–3 were non-toxic up to 5 µM concentration in HepG2 cells and enhanced glucose uptake significantly and decreased PTP1B expression in a dose-dependent manner in insulin-resistant HepG2 cells. Our overall results depict 1–3 from M. alba root bark as dual inhibitors of PTP1B and α-glucosidase enzymes, as well as insulin sensitizers. These active constituents in M. alba may potentially be utilized as an effective treatment for T2DM.

Hepatic miR-125b inhibits insulin signaling pathway by targeting PIK3CD

Insulin resistance is often characterized as the most critical factor contributing to the development of (T2D) type 2 diabetes. MicroRNAs (miRNAs) are endogenous non-coding short single-stranded RNAs that function as negative regulators in many physiological and pathological processes. The objective of this study was to evaluate the roles of miR-125b in the regulation of insulin sensitivity in hepatocytes. We found that hepatic miR-125b levels were significantly increased in the patients with type 2 diabetes, high fat diet (HFD) mice, ob/ob and db/db mice. In vitro, miR-125b was also significantly up-regulated in tumor necrosis factor-alpha- (TNF-α) and glucosamine-induced insulin resistance conditions. Furthermore, miR-125b overexpression impaired the insulin signaling pathway in HepG2 cells, L02c cells, and primary hepatocytes. Inhibition of miR-125b improved insulin sensitivity, especially in insulin-resistant cells induced by either TNF-α or glucosamine. We demonstrated that miR-125b targeted the 3'-untranslated region (3'-UTR) of phosphoinositide 3-kinase catalytic subunit delta (PIK3CD) mRNA. The hepatic PIK3CD protein levels were markedly decreased in patients with type 2 diabetes, HFD, ob/ob, and db/db mice. Inhibition of PIK3CD markedly attenuated the improvement of insulin sensitivity induced by miR-125b inhibitors. More importantly, overexpressing miR-125b in mice causes insulin resistance and impairs glucose homeostasis. Together, these findings indicate that miR-125b inhibits insulin sensitivity by targeting PIK3CD in hepatocytes, supporting hepatic miR-125b, or PIK3CD are potential therapeutic target of insulin resistance.

The Potential and Action Mechanism of Polyphenols in the Treatment of Liver Diseases

Liver disease, involving a wide range of liver pathologies from fatty liver, hepatitis, and fibrosis to cirrhosis and hepatocellular carcinoma, is a serious health problem worldwide. In recent years, many natural foods and herbs with abundant phytochemicals have been proposed as health supplementation for patients with hepatic disorders. As an important category of phytochemicals, natural polyphenols have attracted increasing attention as potential agents for the prevention and treatment of liver diseases. The striking capacities in remitting oxidative stress, lipid metabolism, insulin resistance, and inflammation put polyphenols in the spotlight for the therapies of liver diseases. It has been reported that many polyphenols from a wide range of foods and herbs exert therapeutic effects on liver injuries via complicated mechanisms. Therefore, it is necessary to have a systematical review to sort out current researches to help better understand the potentials of polyphenols in liver diseases. In this review, we aim to summarize and update the existing evidence of natural polyphenols in the treatment of various liver diseases by in vitro, in vivo, and clinical studies, while special attention is paid to the action mechanisms.

Crosstalk Between the Unfolded Protein Response, MicroRNAs, and Insulin Signaling Pathways: In Search of Biomarkers for the Diagnosis and Treatment of Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a metabolic disorder that is characterized by functional defects in glucose metabolism and insulin secretion. Its complex etiology and multifaceted nature have made it difficult to design effective therapies for early diagnosis and treatment. Several lines of evidence indicate that aberrant activation of the unfolded protein response (UPR) in response to endoplasmic reticulum (ER) stress impairs the β cell's ability to respond to glucose and promotes apoptosis. Elucidating the molecular mechanisms that govern β cell dysfunction and cell death can help investigators design therapies to halt or prevent the development of T2DM. Early diagnosis of T2DM, however, warrants additionally the identification of potential biomarkers. MicroRNAs (miRNAs) are key regulators of transcriptional processes that modulate various features of insulin signaling, such as insulin sensitivity, glucose tolerance, and insulin secretion. A deeper understanding of how changes in patterns of expression of miRNAs correlate with altered glucose metabolism can enable investigators to develop methods for the early diagnosis and treatment of T2DM. The first part of this review examines how altered expression of specific UPR pathway proteins disrupts ER function and causes β cell dysfunction, while the second part discusses the potential role of miRNAs in the diagnostic and treatment of T2DM.

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.

Nutriepigenomics and malnutrition

Epigenetics is defined as the modulation of gene expression without changes to the underlying DNA sequence. Epigenetic alterations, as a consequence of in utero malnutrition, may play a role in susceptibility to develop adulthood diseases and inheritance. However, the mechanistic link between epigenetic modifications and abnormalities in nutrition remains elusive. This review provides an update on the association of suboptimal nutritional environment and the high propensity to produce adult-onset chronic illnesses with a particular focus on modifications in genome functions that occur without alterations to the DNA sequence. We will mention the drivers of the phenotype and pattern of epigenetic markers set down during the reprogramming along with novel preventative and therapeutic strategies. New knowledge of epigenetic alterations is opening a gate toward personalized medicine.

Apigenin, a modulator of PPARγ, attenuates HFD-induced NAFLD by regulating hepatocyte lipid metabolism and oxidative stress via Nrf2 activation

Lipid metabolic disorders and oxidative stress in the liver are key steps in the progression of nonalcoholic fatty liver disease (NAFLD), which is a major risk factor for the development of metabolic syndrome. To date, no pharmacological treatment for this condition has been approved. Our previous study has found that the food-derived compound apigenin (Api) significantly attenuates obesity-induced metabolic syndrome by acting as a peroxisome proliferator-activated receptor gamma modulator (PPARM). Herein, a high fat diet (HFD) induced NAFLD model was used to dig out whether Api had the effect on NAFLD. The results showed that Api had obvious effect in restraining NAFLD progression, including attenuating HFD induced lipid accumulation and oxidative stress in vivo. As a PPARM, although Api did significantly inhibit the expression of PPARγ target genes encoding the protein associated with lipid metabolism, it had no obvious activating effect on PPARγ. Interestingly, we found that Api promoted Nrf2 into the nucleus, thereby markedly activating Nrf2 to inhibit the lipid metabolism related genes and increase the oxidative stress related genes. Further Nrf2 knockdown/knockout and overexpression experiments showed that Api regulating PPARγ target genes was dependent on Nrf2 activation and the activation of Nrf2 counteracted the activation effect of PPARγ by Api. Importantly, we also found that Api might bind with Nrf2 via auto dock and ITC assay. Therefore, our results indicate that Api ameliorates NAFLD by a novel regulating mode of Nrf2 and PPARγ in inhibiting lipid metabolism and oxidative stress abnormity.

Emerging Roles for MicroRNAs in Diabetic Microvascular Disease: Novel Targets for Therapy

Chronic, low-grade systemic inflammation and impaired microvascular function are critical hallmarks in the development of insulin resistance. Accordingly, insulin resistance is a major risk factor for type 2 diabetes and cardiovascular disease. Accumulating studies demonstrate that restoration of impaired function of the diabetic macro- and microvasculature may ameliorate a range of cardiovascular disease states and diabetes-associated complications. In this review, we focus on the emerging role of microRNAs (miRNAs), noncoding RNAs that fine-tune target gene expression and signaling pathways, in insulin-responsive tissues and cell types important for maintaining optimal vascular homeostasis and preventing the sequelae of diabetes-induced end organ injury. We highlight current pathophysiological paradigms of miRNAs and their targets involved in regulating the diabetic microvasculature in a range of diabetes-associated complications such as retinopathy, nephropathy, wound healing, and myocardial injury. We provide an update of the potential use of circulating miRNAs diagnostically in type I or type II diabetes. Finally, we discuss emerging delivery platforms for manipulating miRNA expression or function as the next frontier in therapeutic intervention to improve diabetes-associated microvascular dysfunction and its attendant clinical consequences.

Lipid overload during gestation and lactation can independently alter lipid homeostasis in offspring and promote metabolic impairment after new challenge to high-fat diet

Background

Nutritional status in early life is critically involved in the metabolic phenotype of offspring. However the changes triggered by maternal consumption of high-fat diet (HFD) in pre- or postnatal period should be better understood. Here we evaluated whether maternal HFD consumption during gestation and lactation could differently affect liver miR-122 and miR-370 expression leading to metabolic damages observed in offspring. Moreover, we investigate whether early overnutrition program offspring to more harmful response to HFD in later life.

Methods

Female mice were fed either a standard chow (SC) diet or a HFD three weeks before and during mating, gestation and/or lactation. Offspring were evaluated on the delivery day (d0), in a cross-fostering model at day 28 (d28) and in adult life, after a re-challenge with a HFD (d82).

Results

In vitro analysis using liver cell line showed that palmitate could induced decrease in miR-122 and increase in miR-370 expression. Newborn pups (d0) from obese dams showed a decrease in lipid oxidation markers (Cpt1a and Acadvl), an increase in triacylglycerol synthesis markers (Agpat and Gpam), as well as lower miR-122 and higher miR-370 hepatic content that was inversely correlated to maternal serum NEFA and TAG. Pups fostered to SC dams presented an increase in body weight and Agpat/Gpam expression at d28 compared to pups fostered to HFD dams and an inverse correlation was observed between miR-122 hepatic expression and offspring serum TAG. In adult life (d82), the reintroduction of HFD resulted in higher body weight gain and hepatic lipid content. These effects were accompanied by impairment in lipid and glucose metabolism, demonstrated by reduced Cpt1a/Acadvl and increased Agpat/Gpam expression, lower glucose tolerance and insulin sensitivity.

Conclusion

Our data suggest that both gestational and lactation overnutrition results in metabolic changes that can permanently alter lipid homeostasis in offspring. The presence of fatty acids in maternal blood and milk seem to be responsible for modulating the expression of miR-122 and miR-370, which are involved in liver metabolism. These alterations significantly increase susceptibility to obesity and ectopic lipid accumulation and lead to a more harmful response to HFD in offspring.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-017-0168-4) contains supplementary material, which is available to authorized users.

Lipid overload during gestation and lactation can independently alter lipid homeostasis in offspring and promote metabolic impairment after new challenge to high-fat diet

BACKGROUND

Nutritional status in early life is critically involved in the metabolic phenotype of offspring. However the changes triggered by maternal consumption of high-fat diet (HFD) in pre- or postnatal period should be better understood. Here we evaluated whether maternal HFD consumption during gestation and lactation could differently affect liver miR-122 and miR-370 expression leading to metabolic damages observed in offspring. Moreover, we investigate whether early overnutrition program offspring to more harmful response to HFD in later life.

METHODS

Female mice were fed either a standard chow (SC) diet or a HFD three weeks before and during mating, gestation and/or lactation. Offspring were evaluated on the delivery day (d0), in a cross-fostering model at day 28 (d28) and in adult life, after a re-challenge with a HFD (d82).

RESULTS

In vitro analysis using liver cell line showed that palmitate could induced decrease in miR-122 and increase in miR-370 expression. Newborn pups (d0) from obese dams showed a decrease in lipid oxidation markers (Cpt1a and Acadvl), an increase in triacylglycerol synthesis markers (Agpat and Gpam), as well as lower miR-122 and higher miR-370 hepatic content that was inversely correlated to maternal serum NEFA and TAG. Pups fostered to SC dams presented an increase in body weight and Agpat/Gpam expression at d28 compared to pups fostered to HFD dams and an inverse correlation was observed between miR-122 hepatic expression and offspring serum TAG. In adult life (d82), the reintroduction of HFD resulted in higher body weight gain and hepatic lipid content. These effects were accompanied by impairment in lipid and glucose metabolism, demonstrated by reduced Cpt1a/Acadvl and increased Agpat/Gpam expression, lower glucose tolerance and insulin sensitivity.

CONCLUSION

Our data suggest that both gestational and lactation overnutrition results in metabolic changes that can permanently alter lipid homeostasis in offspring. The presence of fatty acids in maternal blood and milk seem to be responsible for modulating the expression of miR-122 and miR-370, which are involved in liver metabolism. These alterations significantly increase susceptibility to obesity and ectopic lipid accumulation and lead to a more harmful response to HFD in offspring.

MicroRNA Regulatory Networks as Biomarkers in Obesity: The Emerging Role

Even though it is a pandemic health problem worldwide, the pathogenesis of obesity is poorly understood. Recently, emerging studies verified that microRNAs (miRNAs) are involved in complicated metabolic processes including adipocyte differentiation, fat cell formation (adipogenesis), obesity-related insulin resistance and inflammation. Many regulatory networks have been identified in murine adipose tissue, but those in human adipose tissue are not as well known. In addition, miRNAs have been detected in circulation, and thus may be usable as diagnostic indicators. MiRNAs may play an important part in regulating metabolic functions in adipose tissues and, by extension, obesity and its associated disorders. Consequently, they may be potential candidates for therapeutic targets and biomarkers.

RESISTIN INHIBITS GLUCOSE-STIMULATED INSULIN SECRETION THROUGH MIR-494 BY TARGET ON STXBP5

Aims

Resistin has been reported to impair the pancreatic beta cells and associated with insulin resistance. MicroRNAs (miRNAs) are short, endogenously produced non-coding ribonucleotides that bind mRNAs and function mainly as negative regulators in mammals. MiRNAs have been implicated in many diseases, including insulin resistance and diabetes. A considerable body of evidence has indicated an important function for miRNAs in insulin secretion. The current study was designed to investigate the effects of miR-494 in the reductions in insulin secretion attributable to resistin.

Methods

Insulin secretion was determined by ELISA, and expressions of genes were identified using quantitative RT-PCR (qRT-PCR) or Western blot analysis.

Results

Insulin secretion was significantly reduced by resistin. Overexpression of miR-494 inhibited insulin secretion both in diet culture and high glucose medium in MIN6 cell lines. MiR-494 down-regulated the protein level of STXBP5 by pairing with sites in the 3'UTR.

Conclusion

miR-494 is involved in the insulin secretion regulated by resistin via its effects on STXBP5 in MIN6 cells.

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.

Xylobiose, an Alternative Sweetener, Ameliorates Diabetes-Related Metabolic Changes by Regulating Hepatic Lipogenesis and miR-122a/33a in db/db Mice

Type 2 diabetes is a major public health concern worldwide. Xylobiose (XB) consists of two molecules of d-xylose and is a major disaccharide in xylooligosaccharides that are used as prebiotics. We hypothesized that XB could regulate diabetes-related metabolic and genetic changes via microRNA expression in db/db mice. For six weeks, C57BL/KsJ-db/db mice received 5% XB as part of the total sucrose content of their diet. XB supplementation improved glucose tolerance with reduced levels of OGTT AUC, fasting blood glucose, HbA1c, insulin, and HOMA-IR. Furthermore, XB supplementation decreased the levels of total triglycerides, total cholesterol, and LDL-C. The expression levels of miR-122a and miR-33a were higher and lower in the XB group, respectively. In the liver, expressions of the lipogenic genes, including, fatty acid synthase (FAS), peroxisome proliferator activated receptor γ (PPARγ), sterol regulatory element-binding protein-1C (SREBP-1C), sterol regulatory element-binding protein-2 (SREBP-2), acetyl-CoA carboxylase (ACC), HMG-CoA reductase (HMGCR), ATP-binding cassette transporter G5/G8 (ABCG5/8), cholesterol 7 alpha-hydroxylase (CYP7A1), and sterol 12-alpha-hydroxylase (CYP8B1), as well as oxidative stress markers, including superoxide dismutase 1 (SOD1), superoxide dismutase 2 (SOD2), glutathione peroxidase (GPX), and catalase, were also regulated by XB supplementation. XB supplementation inhibited the mRNA expressions levels of the pro-inflammatory cytokines, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, interleukin (IL)-6, and monocyte chemoattractant protein (MCP)-1, as well as phosphorylation of c-Jun N-terminal kinase/stress activated protein kinase (JNK/SAPK), p38 mitogen-activated protein kinases (MAPK), and extracellular signal-regulated kinases 1/2 (ERK1/2). These data demonstrate that XB exhibits anti-diabetic, hypolipogenic, and anti-inflammatory effects via regulation of the miR-122a/33a axis in db/db mice.

Recent advances in the development of protein tyrosine phosphatase 1B inhibitors for Type 2 diabetes

Diabetes mellitus is the most serious and prevalent metabolic disorders worldwide, complications of which can decrease significantly the quality of life and contribute to premature death. Resistance to insulin is a predominant pathophysiological factor of Type 2 diabetes (T2D). Protein tyrosine phosphatase 1B (PTP1B) is an important negative factor of insulin signal and a potent therapeutic target in T2D patients. This review highlights recent advances (2012-2015) in research related to the role of PTP1B in signal transduction processes implicated in pathophysiology of T2D, and novel PTP1B inhibitors with an emphasis on their chemical structures and modes of action.

Gα12 overexpressed in hepatocellular carcinoma reduces microRNA-122 expression via HNF4α inactivation, which causes c-Met induction

MicroRNA-122 (miR-122) is implicated as a regulator of physiological and pathophysiological processes in the liver. Overexpression of Gα₁₂ is associated with overall survival in patients with hepatocellular carcinoma (HCC). Array-based miRNA profiling was performed on Huh7 stably transfected with activated Gα₁₂ to find miRNAs regulated by the Gα₁₂ pathway; among them, miR-122 was most greatly repressed. miR-122 directly inhibits c-Met expression, playing a role in HCC progression. Gα₁₂ destabilized HNF4α by accelerating ubiquitination, impeding constitutive expression of miR-122. miR-122 mimic transfection diminished the ability of Gα₁₂ to increase c-Met and to activate ERK, STAT3, and Akt/mTOR, suppressing cell proliferation with augmented apoptosis. Consistently, miR-122 transfection prohibited tumor cell colony formation and endothelial tube formation. In a xenograft model, Gα₁₂ knockdown attenuated c-Met expression by restoring HNF4α levels, and elicited tumor cell apoptosis but diminished Ki67 intensities. In human HCC samples, Gα₁₂ levels correlated to c-Met and were inversely associated with miR-122. Both miR-122 and c-Met expression significantly changed in tumor node metastasis (TNM) stage II/III tumors. Moreover, changes in Gα₁₂ and miR-122 levels discriminated recurrence-free and overall survival rates of HCC patients. Collectively, Gα₁₂ overexpression in HCC inhibits MIR122 transactivation by inactivating HNF4α, which causes c-Met induction, contributing to cancer aggressiveness.

Parallel expression profiling of hepatic and serum microRNA-122 associated with clinical features and treatment responses in chronic hepatitis C patients

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate a variety of biological processes. Recently, human liver-specific miRNA miR-122 has been reported to facilitate hepatitis C virus (HCV) replication in liver cells. HCV is one of the leading causes of liver diseases worldwide. In Pakistan, the estimated prevalence is up to 10%. Here, we report hepatic and serum miR-122 expression profiling from paired liver and serum samples from treatment-naive chronic hepatitis C (CHC) patients and controls. We aimed to elucidate the biomarker potential of serum miR-122 for monitoring disease progression and predicting end treatment response (ETR). Hepatic miR-122 levels were significantly down-regulated in CHC patients. A significant inverse correlation was observed between hepatic and serum miR-122 levels, indicating that serum miR-122 levels reflect HCV-associated disease progression. Both hepatic and serum miR-122 were significantly correlated (P < 0.05) with several clinicopathological features of CHC. Receiver operator curve analysis showed that serum miR-122 had superior discriminatory ability even in patients with normal alanine transaminase levels. Multivariate logistic regression analysis highlighted pre-treatment serum miR-122 levels as independent predictors of ETR. In conclusion, serum miR-122 holds the potential to serve as a promising biomarker of disease progression and ETR in CHC patients.

Helicobacter pylori infection causes hepatic insulin resistance by the c-Jun/miR-203/SOCS3 signaling pathway

BACKGROUND

Epidemiological studies have indicated that patients with chronic Helicobacter pylori infection have an increased risk of developing type 2 diabetes mellitus, but the underlying mechanisms remain largely unknown. This study aimed to investigate whether H. pylori infection contributes to the development of insulin resistance, as well as the underlying mechanisms both in vivo and in vitro.

METHODS

The effect of H. pylori infection on glucose metabolism was evaluated in humans and mouse models. The role of the c-Jun/miR-203/suppressor of cytokine signaling 3 (SOCS3) pathway in H. pylori-induced insulin resistance was determined in vitro and was validated in vivo.

RESULTS

Average fasting glucose levels were increased in patients (P = 0.012) and mice (P = 0.004) with H. pylori infection. Diabetic mice with H. pylori infection showed impaired glucose metabolism and insulin tolerance and hyperinsulinemia. Furthermore, H. pylori infection impaired insulin signaling in primary hepatocytes. H. pylori infection could upregulate SOCS3, a well-known insulin signaling inhibitor, by downregulating miR-203. SOCS3 overexpression interfered with insulin signaling proteins, and knockdown of SOCS3 alleviated H. pylori-induced impairment of insulin signaling. The transcription factor c-Jun, which affects gene expression, was induced by H. pylori infection and suppressed miR-203 expression.

CONCLUSIONS

Our results demonstrated that H. pylori infection induced hepatic insulin resistance by the c-Jun/miR-203/SOCS3 signaling pathway and provide possible implications with regard to resolving insulin resistance.

Function and clinical potential of microRNAs in hepatocellular carcinoma

MicroRNAs (miRNAs) are small non-coding RNAs involved in the initiation and progression of several types of human cancer, including hepatocellular carcinoma (HCC), which is one of the most common types of cancer and the third leading cause of cancer-related mortality worldwide. Mounting evidence has demonstrated that miRNAs play a vital role in HCC, hepatitis, alcoholic liver disease, liver cell development and the metabolic functions of the liver. The aim of the present review was to summarize the most recent findings on the functions of miRNAs in the liver and discuss their potential roles in the diagnosis, prognosis and treatment of HCC.

MicroRNAs in obesity-associated disorders

The emergence of a worldwide obesity epidemic has dramatically increased the prevalence of insulin resistance and metabolic syndrome, predisposing individuals to a greater risk for the development of non-alcoholic fatty liver disease, type II diabetes and atherosclerotic cardiovascular diseases. Current available pharmacological interventions combined with diet and exercise-based managements are still poorly effective for weight management, likely in part due to an incomplete understanding of regulatory mechanisms and pathways contributing to the systemic metabolic abnormalities under disturbed energy homeostasis. MicroRNAs, small non-coding RNAs that regulate posttranscriptional gene expression, have been increasingly described to influence shifts in metabolic pathways under various obesity-related disease settings. Here we review recent discoveries of the mechanistic role that microRNAs play in regulating metabolic functions in liver and adipose tissues involved in obesity associated disorders, and briefly discusses the potential candidates that are being pursued as viable therapeutic targets.

Regulation of RPTPα-c-Src signalling pathway by miR-218

Receptor protein tyrosine phosphatase alpha (RPTPα), an activator of Src family kinases, is found significantly overexpressed in human cancer tissues. However, little is known about the regulation of RPTPα expression. miRNAs target multiple genes and play important roles in many cancer processes. Here, we identified a miRNA, miR-218 that binds directly to the 3'-UTR of RPTPα. Ectopic overexpression of miR-218 decreased RPTPα protein leading to decreased dephosphorylation of c-Src and decreased tumour growth in vitro and in vivo. A feedback loop between c-Src and miR-218 was revealed where c-Src inhibits transcription of SLIT2, which intronically hosts miR-218. These results show a novel regulatory pathway for RPTPα-c-Src signalling.

The emerging role of microRNAs and nutrition in modulating health and disease

Understanding the molecular mechanisms that inform how diet and dietary supplements influence health and disease is an active research area. One such mechanism concerns the role of diet in modulating the activity and function of microRNAs (miRNAs). miRNAs are small noncoding RNA molecules that are involved in posttranscriptional gene silencing and have been shown to control gene expression in diverse biological processes including development, differentiation, cell proliferation, metabolism, and inflammation as well as in human diseases. Recent evidence described in this review highlights how dietary factors may influence cancer, cardiovascular disease, type 2 diabetes mellitus, obesity, and nonalcoholic fatty liver disease through modulation of miRNA expression. Additionally, circulating miRNAs are emerging as putative biomarkers of disease, susceptibility, and perhaps dietary exposure. Research needs to move beyond associations in cells and animals to understanding the direct effects of diet and dietary supplements on miRNA expression and function in human health and disease.

The function of miRNAs and their potential as therapeutic targets in burn-induced insulin resistance (review)

Burns are common accidental injuries. The main clinical manifestations of severe burn injury are insulin resistance and high metabolism. Insulin resistance results in hyperglycemia, which may lead to skeletal muscle wasting and suspended wound healing. It also elevates the risk of infection and sepsis. Studies have indicated that insulin receptor (IR) and insulin receptor substrate 1 (IRS1) are essential factors involved in the regulation of blood glucose levels. Moreover, the suppression of the IR/IRS1 signaling pathway results in insulin resistance. Recent studies have also indicated that miRNAs, which are small non-coding RNAs consisting of 20-23 nucleotides, target the 3'-untranslated region (3'-UTR) of IRS1 mRNA and attenuate protein translation. miRNAs also play an important role in the development of type II diabetes (T2D) and obesity-induced insulin resistance. In the present review, we discuss the involvement of miRNAs in burn-induced insulin resistance through the targeting of the IR/IRS1 signaling pathway. We also discuss the possibility of miRNAs a novel therapeutic target in insulin resistance in burn patients.

Nck1 depletion induces activation of the PI3K/Akt pathway by attenuating PTP1B protein expression

Background

Activation of the PI3K/Akt pathway mediates crucial cellular functions regulated by receptor tyrosine kinases, such as cell growth, proliferation, survival and metabolism. Previously, we reported that the whole-body knockout of the Src homology domain-containing adaptor protein Nck1 improves overall glucose homeostasis and insulin-induced activation of the PI3K/Akt pathway in liver of obese mice. The aim of the current study is to elucidate the mechanism by which Nck1 depletion regulates hepatic insulin signaling.

Results

Here, we demonstrate that Nck1 regulates the activation of the PI3K/Akt pathway in a protein tyrosine phosphatase 1B (PTP1B)-dependent mechanism. Indeed, depletion of Nck1 by siRNA in HepG2 cells enhances PI3K-dependent basal and growth factor-induced Akt activation. In accordance, primary hepatocytes isolated from Nck1^−/− mice also display enhanced Akt activation in response to insulin. Activation of the PI3K/Akt pathway in Nck1-depleted HepG2 cells relies on higher levels of tyrosine-phosphorylated proteins and correlates with decreased PTP1B levels. Interestingly, Nck1 and PTP1B in cells are found in a common molecular complex and their interaction is dependent on the SH3 domains of Nck1. Finally, Nck1 depletion in HepG2 cells neither affects PTP1B gene transcription nor PTP1B protein stability, suggesting that Nck1 modulates PTP1B expression at the translational level.

Conclusion

Our study provides strong evidence supporting that the adaptor protein Nck1 interacts with PTP1B and also regulates PTP1B expression. In this manner, Nck1 plays a role in regulating the PI3K/Akt pathway.

Isoliquiritigenin is a potent inhibitor of NLRP3 inflammasome activation and diet-induced adipose tissue inflammation

Inflammasome activation initiates the development of many inflammatory diseases, including obesity and type 2 diabetes. Therefore, agents that target discrete activation steps could represent very important drugs. We reported previously that ILG, a chalcone from Glycyrrhiza uralensis, inhibits LPS-induced NF-κB activation. Here, we show that ILG potently inhibits the activation of NLRP3 inflammasome, and the effect is independent of its inhibitory potency on TLR4. The inhibitory effect of ILG was stronger than that of parthenolide, a known inhibitor of the NLRP3 inflammasome. GL, a triterpenoid from G. uralensis, had similar inhibitory effects on NLRP3 activity, but high concentrations of GL were required. In contrast, activation of the AIM2 inflammasome was inhibited by GL but not by ILG. Moreover, GL inhibited NLRP3- and AIM2-activated ASC oligomerization, whereas ILG inhibited NLRP3-activated ASC oligomerization. Low concentrations of ILG were highly effective in IAPP-induced IL-1β production compared with the sulfonylurea drug glyburide. In vivo analyses revealed that ILG potently attenuated HFD-induced obesity, hypercholesterolemia, and insulin resistance. Furthermore, ILG treatment improved HFD-induced macrovesicular steatosis in the liver. Finally, ILG markedly inhibited diet-induced adipose tissue inflammation and IL-1β and caspase-1 production in white adipose tissue in ex vivo culture. These results suggest that ILG is a potential drug target for treatment of NLRP3 inflammasome-associated inflammatory diseases.

MicroRNAs: the fine modulators of liver development and function

MicroRNAs are a class of small non-coding RNAs involved in the transcriptional and post-transcriptional regulation of gene expression. The function of miRNAs in liver disease including hepatocellular carcinoma (HCC), hepatitis, and alcoholic liver disease, have been widely studied and extensively reviewed. Increasing evidence demonstrates that miRNAs also play a critical role in normal liver development and in the fine-tuning of fundamental biological liver processes. In this review, we highlight the most recent findings on the role of miRNAs in liver specification and differentiation, liver cell development, as well as in the many metabolic functions of the liver, including glucose, lipid, iron and drug metabolism. These findings demonstrate an important role of miRNAs in normal liver development and function. Further researches will be needed to fully understand how miRNAs regulate liver generation and metabolic function, which should then lead to greater insights in liver biology and perhaps open up the possibility to correct errors that cause liver diseases or metabolic disorders.

Significance of serum and hepatic microRNA-122 levels in patients with non-alcoholic fatty liver disease

BACKGROUND & AIMS

Non-alcoholic fatty liver disease (NAFLD) is believed to be a type of metabolic syndrome. MicroRNA-122 (miR-122) is the most abundant microRNA in the liver and is an important factor for the metabolism of glucose and lipids. In the present study, we examined the correlation between the hepatic and serum miR-122 expression levels and the clinicopathological factors of patients with NAFLD.

METHODS

We extracted the total RNA, along with preserved miRNAs, from liver biopsy samples of 67 patients with NAFLD. In 52 of these 67 patients, the total RNA was extracted from serum. The miR-122 that was obtained by quantitative reverse transcription-polymerase chain reaction was quantified using TaqMan MicroRNA assays.

RESULTS

A significant correlation was detected between serum and hepatic miR-122 expression (correlation coefficient, 0.461; P=0.005). Patients with mild steatosis (<33%) showed significantly lower levels of hepatic miR-122 compared with patients with severe steatosis (>33%) (hepatic miR-122: mild/severe=2.158±1.786/4.836±7.506, P=0.0473; serum miR-122: mild/severe=0.002±0.005/0.007±0.001, P=0.0491). Moreover, hepatic and serum miR-122 levels were significantly higher in patients with mild fibrosis than in those with severe fibrosis (hepatic miR-122: mild/severe=5.201±7.275/2.394±1.547, P=0.0087; serum miR-122: mild/severe=0.008±0.011/0.002±0.004, P=0.0191).

CONCLUSIONS

We found that the hepatic and serum miR-122 levels were associated with hepatic steatosis and fibrosis. The serum miR-122 level can be a useful predictive marker of liver fibrosis in patients with NAFLD.

Gα12 gep oncogene deregulation of p53-responsive microRNAs promotes epithelial-mesenchymal transition of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has a poor prognosis owing to aggressive phenotype. Gα12 gep oncogene product couples to G-protein-coupled receptors, whose ligand levels are frequently increased in tumor microenvironments. Here, we report Gα12 overexpression in human HCC and the resultant induction of zinc-finger E-box-binding homeobox 1 (ZEB1) as mediated by microRNA deregulation. Gα12 expression was higher in HCC than surrounding non-tumorous tissue. Transfection of Huh7 cell with an activated mutant of Gα12 (Gα12QL) deregulated microRNA (miRNA or miR)-200b/a/429, -194-2/192 and -194-1/215 clusters in the miRNome. cDNA microarray analyses disclosed the targets affected by Gα12 gene knockout. An integrative network of miRNAs and mRNA changes enabled us to predict ZEB1 as a key molecule governed by Gα12. Decreases of miR-200a/b, -192 and -215 by Gα12 caused ZEB1 induction. The ability of Gα12 to decrease p53 levels, as a result of activating protein-1 (AP-1)/c-Jun-mediated mouse double minute 2 homolog induction, contributed to transcriptional deregulation of the miRNAs. Gα12QL induced ZEB1 and other epithelial-mesenchymal transition markers with fibroblastoid phenotype change. Consistently, transfection with miR-200b, -192 or -215 mimic prevented the ability of Gα12QL to increase tumor cell migration/invasion. In xenograft studies, sustained knockdown of Gα12 decreased the overall growth rate and average volume of tumors derived from SK-Hep1 cell (mesenchymal-typed). In HCC patients, miR-192, -215 and/or -200a were deregulated with microvascular invasion or growth advantage. In the HCC samples with higher Gα12 level, a correlation existed in the comparison of relative changes of Gα12 and ZEB1. In conclusion, Gα12 overexpressed in HCC causes ZEB1 induction by deregulating p53-responsive miRNAs, which may facilitate epithelial-mesenchymal transition and growth of liver tumor. These findings highlight the significance of Gα12 upregulation in liver tumor progression, implicating Gα12 as an attractive therapeutic target.

Autophagy and microRNA dysregulation in liver diseases

Autophagy is a catabolic process through which organelles and cellular components are sequestered into autophagosomes and degraded via fusion with lysosomes. Autophagy plays a role in many physiological processes, including stress responses, energy homeostasis, elimination of cellular organelles, and tissue remodeling. In addition, autophagy capacity changes in various disease states. A series of studies have shown that autophagy is strictly controlled to maintain homeostatic balance of energy metabolism and cellular organelle and protein turnover. These studies have also shown that this process is post-transcriptionally controlled by small noncoding microRNAs that regulate gene expression through complementary base pairing with mRNAs. Conversely, autophagy regulates the expression of microRNAs. Therefore, dysregulation of the link between autophagy and microRNA expression exacerbates the pathogenesis of various diseases. In this review, we summarize the roles of autophagy and microRNA dysregulation in the course of liver diseases, with the aim of understanding how microRNAs modify key autophagic effector molecules, and we discuss how this dysregulation affects both physiological and pathological conditions. This article may advance our understanding of the cellular and molecular bases of liver disease progression and promote the development of strategies for pharmacological intervention.

MicroRNA-122 triggers mesenchymal-epithelial transition and suppresses hepatocellular carcinoma cell motility and invasion by targeting RhoA

The loss of microRNA-122 (miR-122) expression is strongly associated with increased invasion and metastasis, and poor prognosis of hepatocellular carcinoma (HCC), however, the underlying mechanisms remain poorly understood. In the present study, we observed that miR-122 over-expression in HCC cell lines Sk-hep-1 and Bel-7402 triggered the mesenchymal-epithelial transition (MET), as demonstrated by epithelial-like morphological changes, up-regulated epithelial proteins (E-cadherin, ZO-1, α-catenin, occludin, BVES, and MST4), and down-regulated mesenchymal proteins (vimentin and fibronectin). The over-expression of miRNA-122 also caused cytoskeleton disruption, RhoA/Rock pathway inactivation, enhanced cell adhesion, and suppression of migration and invasion of Sk-hep-1 and Bel-7402 cells, whereas, these effects could be reversed through miR-122 inhibition. Additional studies demonstrated that the inhibition of wild-type RhoA function induced MET and inhibited cell migration and invasion, while RhoA over-expression reversed miR-122-induced MET and inhibition of migration and invasion of HCC cells, suggesting that miR-122 induced MET and suppressed the migration and invasion of HCC cells by targeting RhoA. Moreover, our results demonstrated that HNF4α up-regulated its target gene miR-122 that subsequently induced MET and inhibited cell migration and invasion, whereas miR-122 inhibition reversed these HNF4α-induced phenotypes. These results revealed functional and mechanistic links among the tumor suppressors HNF4α, miR-122, and RhoA in EMT and invasive and metastatic phenotypes of HCC. Taken together, our study provides the first evidence that the HNF4α/miR-122/RhoA axis negatively regulates EMT and the migration and invasion of HCC cells.

Possible involvement of food texture in insulin resistance and energy metabolism in male rats

Food texture is known to affect energy metabolism. Although feeding with soft pellets (SP) or via a tube is known to cause increases in body weight, it is unclear how different food textures influence energy metabolism. In this study, we investigated the effects of two different food textures on energy balance and glucose and lipid metabolism in male Wistar rats. The rats were fed SP or control pellets (CP) on a 3-h restricted feeding schedule for 14 weeks and their energy intake, body weight, and energy expenditure were examined. The levels of gastrointestinal hormones, glucose and insulin, were investigated at pre-, mid, and post-feeding. Glucose tolerance and insulin tolerance tests were conducted, and the expressions of molecules involved in the insulin signaling system or lipogenesis in the liver were examined. Histological investigation of pancreatic islets was carried out using anti-insulin and anti-Ki-67 antibodies. Furthermore, the expression in the liver and circulating blood of microRNA-33 (miR-33), which regulates insulin receptor substance 2, was examined. There were no significant differences in energy intake, body weight, or gastrointestinal hormone levels between the SP and CP rats; however, the SP rats showed glucose intolerance and insulin resistance with disruption of insulin signaling. Increases in lipogenic factors and miR-33 expression were also found in the SP rats. The numbers of insulin-positive areas and Ki-67-positive cells of SP rats were significantly increased. This study shows that a soft food texture causes diabetes without obesity, so differences in food texture may be an important factor in type 2 diabetes.

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.

Maternal high-fat diet consumption modulates hepatic lipid metabolism and microRNA-122 (miR-122) and microRNA-370 (miR-370) expression in offspring

Maternal consumption of a high-fat diet (HFD) during pregnancy and lactation is closely related to hepatic lipid accumulation, insulin resistance and increased serum cytokine levels in offspring and into their adulthood. MicroRNA (miRNA) have been implicated in cholesterol biosynthesis and fatty acid metabolism. We evaluated the modulation of hepatic fatty acid synthesis (de novo), β-oxidation pathways, and miRNA-122 (miR-122) and miRNA-370 (miR-370) expression in recently weaned offspring (day 28) of mouse dams fed a HFD (HFD-O) or a standard chow (SC-O) during pregnancy and lactation. Compared with SC-O mice, HFD-O mice weighed more, had a larger adipose tissue mass and were more intolerant to glucose and insulin (P< 0·05). HFD-O mice also presented more levels of serum cholesterol, TAG, NEFA and hepatic IκB kinase and c-Jun N-terminal kinase phosphorylation compared with SC-O mice (P< 0·05). Protein levels of fatty acid synthase, acetyl-CoA carboxylase and 3-hydroxy-3-methylglutaryl-CoA reductase were similar in HFD-O and SC-O mice, whereas expression levels of SCD1 mRNA and protein were more abundant in HFD-O mice than in SC-O mice (P< 0·05). Interestingly, mRNA expression levels of the β-oxidation-related genes ACADVL and CPT1 were decreased in HFD-O mice (P< 0·05). Furthermore, the expression of miR-122 was reduced but that of miR-370 was increased in HFD-O mice compared with that in SC-O mice (P< 0·05). Changes in hepatic lipid metabolism were accompanied by increased mRNA content of AGPAT1 and TAG deposition in HFD-O mice (P< 0·05). Taken together, the present results strongly suggest that maternal consumption of a HFD affects the early lipid metabolism of offspring by modulating the expression of hepatic β-oxidation-related genes and miRNA that can contribute to metabolic disturbances in adult life.

MiRNA-145 is involved in the development of resistin-induced insulin resistance in HepG2 cells

BACKGROUND

Resistin is associated with insulin resistance, and determining its developmental and molecular mechanisms may help the development of novel treatments. MicroRNAs (miRNAs) are involved in many physiological and pathological processes as negative regulators. However, it remains unclear whether miRNAs play a role in resistin-induced insulin resistance. We performed mouse liver miRNA microarrays to analyze the differences in expression between resistin-treated and control mice. Resistin upregulated miR-145 both in vivo and in vitro. Therefore, we aimed to study whether miR-145 played a role in resistin-induced insulin resistance.

METHODS AND RESULTS

We transfected HepG2 cells, and used miR-145 mimics and inhibitors to assess the role of miR-145 in resistin-induced insulin resistance. The overexpression of miR-145 inhibited glucose uptake in HepG2 cells, diminished the phosphorylation of Akt and IRS-1, and induced insulin resistance in hepatocytes. Next, a study of transcriptional regulation revealed that p65 was essential for the upregulation of miR-145 by resistin, and chromatin immunoprecipitation (ChIP) confirmed that p65 could bind to the promoter region of miR-145.

CONCLUSION

miR-145 plays a role in the development of resistin-induced insulin resistance via the p65 pathway.

MicroRNAs as potential biomarkers in diseases and toxicology

MiRNAs (microRNAs) are single-stranded non-coding RNAs of approximately 21-23 nucleotides in length whose main function is to inhibit gene expression by interfering with mRNA processes. MicroRNAs suppress gene expression by affecting mRNA (messenger RNAs) stability, targeting the mRNA for degradation, or both. In this review, we have examined how microRNA expression could be altered following exposure to chemicals and how they could represent appropriate tissue and more interestingly circulating biomarkers. Among the key questions before using the microRNA for evaluation of risk toxicity, it remains still to clarify how they could be causally involved in the adverse effects and how stable their changes are.

Metabolic consequences of microRNA-122 inhibition in rainbow trout, Oncorhynchus mykiss

Background

MicroRNAs (miRNAs) are small regulatory molecules which post-transcriptionally regulate mRNA stability and translation. Several microRNAs have received attention due to their role as key metabolic regulators. In spite of the high evolutionary conservation of several miRNAs, the role of miRNAs in lower taxa of vertebrates has not been studied with regard to metabolism. The liver-specific and highly abundant miRNA-122 is one of the most widely studied miRNA in mammals, where it has been implicated in the control of hepatic lipid metabolism. Following our identification of acute postprandial, nutritional and endocrine regulation of hepatic miRNA-122 isomiRNA expression in rainbow trout, we used complementary in silico and in vivo approaches to study the role of miRNA-122 in rainbow trout metabolism. We hypothesized that the role of miRNA-122 in regulating lipid metabolism in rainbow trout is conserved to that in mammals and that modulation of miRNA-122 function would result in altered lipid homeostasis and secondarily altered glucose homeostasis, since lipogenesis has been suggested to act as glucose sink in trout.

Results

Our results show that miRNA-122 was functionally inhibited in vivo in the liver. Postprandial glucose concentrations increased significantly in rainbow trout injected with a miRNA-122 inhibitor, and this effect correlated with decreases in hepatic FAS protein abundance, indicative of altered lipogenic potential. Additionally, miRNA-122 inhibition resulted in a 20% decrease in plasma cholesterol concentration, an effect associated with increased expression of genes involved in cholesterol degradation and excretion.

Conclusions

Overall evidence suggests that miRNA-122 may have evolved in early vertebrates to support liver-specific metabolic functions. Nevertheless, our data also indicate that metabolic consequences of miRNA-122 inhibition may differ quantitatively between vertebrate species and that distinct direct molecular targets of miRNA-122 may mediate metabolic effects between vertebrate species, indicating that miRNA-122 - mRNA target relationships may have undergone species-specific evolutionary changes.