MicroRNA-29a-c decrease fasting blood glucose levels by negatively regulating hepatic gluconeogenesis

MicroRNA-29-mediated cross-talk between metabolic organs in the pathogenesis of diabetes mellitus and its complications: A narrative review

Diabetes mellitus (DM) is a heterogeneous group of disorders characterized by hyperglycemia. Microribonucleic acids (microRNAs) are noncoding RNA molecules synthesized in the nucleus, modified, and exported to the extracellular environment to bind to their complementary target sequences. It regulates protein synthesis in the targeted cells by inhibiting translation or triggering the degradation of the target messenger. MicroRNA-29 is one of noncoding RNA that can be secreted by adipose tissue, hepatocytes, islet cells, and brain cells. The expression level of the microRNA-29 family in several metabolic organs is regulated by body weight, blood concentrations of inflammatory mediators, serum glucose levels, and smoking habits. Several experimental studies have demonstrated the effect of microRNA-29 on the expression of target genes involved in glucose metabolism, insulin synthesis and secretion, islet cell survival, and proliferation. These findings shed new light on the role of microRNA-29 in the pathogenesis of diabetes and its complications, which plays a vital role in developing appropriate therapies. Different molecular pathways have been proposed to explain how microRNA-29 promotes the development of diabetes and its complications. However, to the best of our knowledge, no published review article has summarized the molecular mechanism of microRNA-29-mediated initiation of DM and its complications. Therefore, this narrative review aims to summarize the role of microRNA-29-mediated cross-talk between metabolic organs in the pathogenesis of diabetes and its complications.

Small extracellular vesicles from young plasma reverse age-related functional declines by improving mitochondrial energy metabolism

Recent investigations into heterochronic parabiosis have unveiled robust rejuvenating effects of young blood on aged tissues. However, the specific rejuvenating mechanisms remain incompletely elucidated. Here we demonstrate that small extracellular vesicles (sEVs) from the plasma of young mice counteract pre-existing aging at molecular, mitochondrial, cellular and physiological levels. Intravenous injection of young sEVs into aged mice extends their lifespan, mitigates senescent phenotypes and ameliorates age-associated functional declines in multiple tissues. Quantitative proteomic analyses identified substantial alterations in the proteomes of aged tissues after young sEV treatment, and these changes are closely associated with metabolic processes. Mechanistic investigations reveal that young sEVs stimulate PGC-1α expression in vitro and in vivo through their miRNA cargoes, thereby improving mitochondrial functions and mitigating mitochondrial deficits in aged tissues. Overall, this study demonstrates that young sEVs reverse degenerative changes and age-related dysfunction, at least in part, by stimulating PGC-1α expression and enhancing mitochondrial energy metabolism.

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family in physiological and pathophysiological process and diseases

Peroxisome proliferator-activated receptor gamma coactivator-1 (PGC-1) family (PGC-1s), consisting of three members encompassing PGC-1α, PGC-1β, and PGC-1-related coactivator (PRC), was discovered more than a quarter-century ago. PGC-1s are essential coordinators of many vital cellular events, including mitochondrial functions, oxidative stress, endoplasmic reticulum homeostasis, and inflammation. Accumulating evidence has shown that PGC-1s are implicated in many diseases, such as cancers, cardiac diseases and cardiovascular diseases, neurological disorders, kidney diseases, motor system diseases, and metabolic disorders. Examining the upstream modulators and co-activated partners of PGC-1s and identifying critical biological events modulated by downstream effectors of PGC-1s contribute to the presentation of the elaborate network of PGC-1s. Furthermore, discussing the correlation between PGC-1s and diseases as well as summarizing the therapy targeting PGC-1s helps make individualized and precise intervention methods. In this review, we summarize basic knowledge regarding the PGC-1s family as well as the molecular regulatory network, discuss the physio-pathological roles of PGC-1s in human diseases, review the application of PGC-1s, including the diagnostic and prognostic value of PGC-1s and several therapies in pre-clinical studies, and suggest several directions for future investigations. This review presents the immense potential of targeting PGC-1s in the treatment of diseases and hopefully facilitates the promotion of PGC-1s as new therapeutic targets.

MicroRNA-29a Compromises Hepatic Adiposis and Gut Dysbiosis in High Fat Diet-Fed Mice via Downregulating Inflammation

SCOPE

miR-29a expression patterns influence numerous physiological phenomena. Of note, upregulation of miR-29a ameliorates high-fat diet (HFD)-induced liver dysfunctions in mice. However, the miR-29a effect on gut microbiome composition and HFD-induced gut microbiota changes during metabolic disturbances remains unclear. The study provides compelling evidence for the protective role of miR-29a in gut barrier dysfunction and steatohepatitis.

METHODS AND RESULTS

miR-29a overexpressed mice (miR-29aTg) are bred to characterize intestinal, serum biochemical, and fecal microbiota profiling features compared to wild-type mice (WT). Mice are fed an HFD for 8 months to induce steatohepatitis, and intestinal dysfunction is determined via histopathological analysis. miR-29aTg has better lipid metabolism capability that decreases total cholesterol and triglyceride levels in serum than WT of the same age. The study further demonstrates that miR-29aTg contributes to intestinal integrity by maintaining periodic acid Schiff positive cell numbers and diversity of fecal microorganisms. HFD-induced bacterial community disturbance and steatohepatitis result in more severe WT than miR-29aTg. Gut microorganism profiling reveals Lactobacillus, Ruminiclostridium_9, and Lachnoclostridium enrichment in miR-29aTg and significantly decreases interleukin-6 expression in the liver and intestinal tract.

CONCLUSION

This study provides new evidence that sheds light on the host genetic background of miR-29a, which protects against steatohepatitis and other intestinal disorders.

The role of microRNAs in the molecular link between circadian rhythm and autism spectrum disorder

Circadian rhythm regulates physiological cycles of awareness and sleepiness. Melatonin production is primarily regulated by circadian regulation of gene expression and is involved in sleep homeostasis. If the circadian rhythm is abnormal, sleep disorders, such as insomnia and several other diseases, can occur. The term 'autism spectrum disorder (ASD)' is used to characterize people who exhibit a certain set of repetitive behaviors, severely constrained interests, social deficits, and/or sensory behaviors that start very early in life. Because many patients with ASD suffer from sleep disorders, sleep disorders and melatonin dysregulation are attracting attention for their potential roles in ASD. ASD is caused by abnormalities during the neurodevelopmental processes owing to various genetic or environmental factors. Recently, the role of microRNAs (miRNAs) in circadian rhythm and ASD have gained attraction. We hypothesized that the relationship between circadian rhythm and ASD could be explained by miRNAs that can regulate or be regulated by either or both. In this study, we introduced a possible molecular link between circadian rhythm and ASD. We performed a thorough literature review to understand their complexity.

Coronarin A modulated hepatic glycogen synthesis and gluconeogenesis via inhibiting mTORC1/S6K1 signaling and ameliorated glucose homeostasis of diabetic mice

Promotion of hepatic glycogen synthesis and inhibition of hepatic glucose production are effective strategies for controlling hyperglycemia in type 2 diabetes mellitus (T2DM), but agents with both properties were limited. Herein we report coronarin A, a natural compound isolated from rhizomes of Hedychium gardnerianum, which simultaneously stimulates glycogen synthesis and suppresses gluconeogenesis in rat primary hepatocytes. We showed that coronarin A (3, 10 μM) dose-dependently stimulated glycogen synthesis accompanied by increased Akt and GSK3β phosphorylation in rat primary hepatocytes. Pretreatment with Akt inhibitor MK-2206 (2 μM) or PI3K inhibitor LY294002 (10 μM) blocked coronarin A-induced glycogen synthesis. Meanwhile, coronarin A (10 μM) significantly suppressed gluconeogenesis accompanied by increased phosphorylation of MEK, ERK1/2, β-catenin and increased the gene expression of TCF7L2 in rat primary hepatocytes. Pretreatment with β-catenin inhibitor IWR-1-endo (10 μM) or ERK inhibitor SCH772984 (1 μM) abolished the coronarin A-suppressed gluconeogenesis. More importantly, we revealed that coronarin A activated PI3K/Akt/GSK3β and ERK/Wnt/β-catenin signaling via regulation of a key upstream molecule IRS1. Coronarin A (10, 30 μM) decreased the phosphorylation of mTOR and S6K1, the downstream target of mTORC1, which further inhibited the serine phosphorylation of IRS1, and subsequently increased the tyrosine phosphorylation of IRS1. In type 2 diabetic ob/ob mice, chronic administration of coronarin A significantly reduced the non-fasting and fasting blood glucose levels and improved glucose tolerance, accompanied by the inhibited hepatic mTOR/S6K1 signaling and activated IRS1 along with enhanced PI3K/Akt/GSK3β and ERK/Wnt/β-catenin pathways. These results demonstrate the anti-hyperglycemic effect of coronarin A with a novel mechanism by inhibiting mTORC1/S6K1 to increase IRS1 activity, and highlighted coronarin A as a valuable lead compound for the treatment of T2DM.

Triptolide protects human retinal pigment epithelial ARPE-19 cells against high glucose-induced cell injury by regulation of miR-29b/PTEN

Oxidative stress and inflammation are necessary pathogenic factors contributing to the aetiology of diabetic retinopathy (DR). Triptolide (TPL) is derived from the traditional Chinese herb lei gong teng with anti-inflammatory, immunosuppressive and antitumor activities. This article was developed to examine the effect of TPL on DR. ARPE-19 cells were pre-treated with TPL and then stimulated by high glucose (HG). We found that TPL treatment enhanced cell viability, decreased apoptosis and ROS production in HG-treated RPE cells. MiR-29b was low-expressed in HG-treated cells, but TPL raised its expression. In addition, the protective activity of TPL towards ARPE-19 cells was attenuated when miR-29b was reduced. By utilising bioinformatics evaluation, PTEN was predicted as a downstream target of miR-29b. Also, TPL obstructed PI3K/AKT signalling pathways in HG-treated ARPE-19 Cells. Taken together, TPL secured ARPE-19 cells from HG-induced oxidative damage via regulating miR-29b/PTEN axis.

Fatty acids homeostasis during fasting predicts protection from chemotherapy toxicity

Fasting exerts beneficial effects in mice and humans, including protection from chemotherapy toxicity. To explore the involved mechanisms, we collect blood from humans and mice before and after 36 or 24 hours of fasting, respectively, and measure lipid composition of erythrocyte membranes, circulating micro RNAs (miRNAs), and RNA expression at peripheral blood mononuclear cells (PBMCs). Fasting coordinately affects the proportion of polyunsaturated versus saturated and monounsaturated fatty acids at the erythrocyte membrane; and reduces the expression of insulin signaling-related genes in PBMCs. When fasted for 24 hours before and 24 hours after administration of oxaliplatin or doxorubicin, mice show a strong protection from toxicity in several tissues. Erythrocyte membrane lipids and PBMC gene expression define two separate groups of individuals that accurately predict a differential protection from chemotherapy toxicity, with important clinical implications. Our results reveal a mechanism of fasting associated with lipid homeostasis, and provide biomarkers of fasting to predict fasting-mediated protection from chemotherapy toxicity.

Fasting has been reported to protect from chemotherapy-associated toxicity. Here, the authors show that fatty acid profiles in erythrocyte membranes and gene expression from peripheral blood mononuclear cells are associated to the fasting-mediated benefits during cancer treatment in mice and patients.

The microRNA-29 family - role in metabolism and metabolic disease

The microRNA-29a family members miR-29a-3p, miR-29b-3p and miR-29c-3p are ubiquitously expressed and consistently increased in various tissues and cell types in conditions of metabolic disease; obesity, insulin resistance and type 2 diabetes. In pancreatic beta cells, miR-29a is required for normal exocytosis, but increased levels are associated with impaired beta cell function. Similarly, in liver miR-29 species are higher in models of insulin resistance and type 2 diabetes, and either knock-out or depletion using a microRNA inhibitor improves hepatic insulin resistance. In skeletal muscle, miR-29 upregulation is associated with insulin resistance and altered substrate oxidation, and similarly, in adipocytes over-expression of miR-29a leads to insulin resistance. Blocking miR-29a using nucleic acid antisense therapeutics show promising results in preclinical animal models of obesity and type 2 diabetes, although the widespread expression pattern of miR-29 family members complicates the exploration of single target tissues. However, in fibrotic diseases, such as in late complications of diabetes and metabolic disease (diabetic kidney disease, non-alcoholic steatohepatitis), miR-29 expression is suppressed by TGFβ allowing increased extracellular matrix collagen to form. In the clinical setting circulating levels of miR-29a and miR-29b are consistently increased in type 2 diabetes and in gestational diabetes, and are also possible prognostic markers for deterioration of glucose tolerance. In conclusion, miR-29 plays an essential role in various organs relevant to intermediary metabolism and its upregulation contribute to impaired glucose metabolism, while it suppresses fibrosis development. Thus, a correct balance of miR-29a levels seems important for cellular and organ homeostasis in metabolism.

Role of non-coding RNAs on liver metabolism and NAFLD pathogenesis

Obesity and type 2 diabetes are major contributors to the growing prevalence of non-alcoholic fatty liver disease (NAFLD), a chronic liver condition characterized by accumulation of fat in individuals without a significant amount of alcohol intake. The NAFLD spectrum ranges from simple steatosis (early stages, known as NAFL), to non-alcoholic steatohepatitis (NASH), which can progress to fibrosis and cirrhosis or hepatocellular carcinoma. Obesity, type 2 diabetes, and NAFLD are strongly associated with insulin resistance. In the liver, insulin resistance increases hepatic glucose output, lipogenesis, and VLDL secretion, leading to a combination of hyperglycemia and hypertriglyceridemia. Aberrant gene expression is a hallmark of insulin resistance. Non-coding RNAs (ncRNAs) have emerged as prominent regulators of gene expression that operate at the transcriptional, post-transcriptional, and post-translational levels. In the last couple of decades a wealth of studies have provided evidence that most processes of liver metabolism are orchestrated by ncRNAs. This review focuses on the role of microRNAs, long non-coding RNAs and circular RNAs as coordinators of hepatic function, as well as the current understanding on how their dysregulation contributes to abnormal metabolism and pathophysiology in animal models of insulin resistance and NAFLD. Moreover, ncRNAs are emerging as useful biomarkers that may be able to discriminate between the different stages of NAFLD. The potential of ncRNAs as therapeutic drugs for NAFLD treatment and as biomarkers is discussed.

Genistein Alleviates High-Fat Diet-Induced Obesity by Inhibiting the Process of Gluconeogenesis in Mice

Genistein is an isoflavone phytoestrogen that has been shown to improve obesity; however, the underlying molecular mechanisms involved therein have not been clearly elucidated. In this study, we administered genistein to high-fat diet-induced obese mice to investigate its effect on hepatic gluconeogenesis. The results showed that genistein treatment significantly inhibited body weight gain, hyperglycemia, and adipose and hepatic lipid deposition in high-fat diet-induced obese mice. Glucose tolerance test (GTT), insulin tolerance test (ITT) and pyruvate tolerance test (PTT) showed that genistein treatment significantly inhibited gluconeogenesis and improved insulin resistance in obese mice. In addition, this study also found that genistein could promote the expression of miR-451 in vitro and in vivo, and the dual-luciferase reporter system showed that G6pc (glucose-6-phosphatase) may be a target gene of miR-451. Both genistein treatment and in vivo injection of miR-451 agomir significantly inhibited gluconeogenesis and inhibited the expression of G6pc and Gk (glycerol kinase, a known target gene of miR-451). In conclusion, genistein may inhibit gluconeogenesis in obese mice by regulating the expression of Gk and G6pc through miR-451. These results may provide insights into the functions of miR-451 and food-derived phytoestrogens in ameliorating and preventing gluconeogenesis-related diseases.

Differences in Liver microRNA profiling in pigs with low and high feed efficiency

Feed cost is the main factor affecting the economic benefits of pig industry. Improving the feed efficiency (FE) can reduce the feed cost and improve the economic benefits of pig breeding enterprises. Liver is a complex metabolic organ which affects the distribution of nutrients and regulates the efficiency of energy conversion from nutrients to muscle or fat, thereby affecting feed efficiency. MicroRNAs (miRNAs) are small non-coding RNAs that can regulate feed efficiency through the modulation of gene expression at the post-transcriptional level. In this study, we analyzed miRNA profiling of liver tissues in High-FE and Low-FE pigs for the purpose of identifying key miRNAs related to feed efficiency. A total 212~221 annotated porcine miRNAs and 136~281 novel miRNAs were identified in the pig liver. Among them, 188 annotated miRNAs were co-expressed in High-FE and Low-FE pigs. The 14 miRNAs were significantly differentially expressed (DE) in the livers of high-FE pigs and low-FE pigs, of which 5 were downregulated and 9 were upregulated. Kyoto Encyclopedia of Genes and Genomes analysis of liver DE miRNAs in high-FE pigs and low-FE pigs indicated that the target genes of DE miRNAs were significantly enriched in insulin signaling pathway, Gonadotropin-releasing hormone signaling pathway, and mammalian target of rapamycin signaling pathway. To verify the reliability of sequencing results, 5 DE miRNAs were randomly selected for quantitative reverse transcription-polymerase chain reaction (qRT-PCR). The qRT-PCR results of miRNAs were confirmed to be consistent with sequencing data. DE miRNA data indicated that liver-specific miRNAs synergistically acted with mRNAs to improve feed efficiency. The liver miRNAs expression analysis revealed the metabolic pathways by which the liver miRNAs regulate pig feed efficiency.

Contributions of microRNAs to Peripheral Insulin Sensitivity

An extensive literature base combined with advances in sequencing technologies demonstrate microRNA levels correlate with various metabolic diseases. Mechanistic studies also establish microRNAs regulate central metabolic pathways and thus play vital roles in maintaining organismal energy balance and metabolic homeostasis. This review highlights research progress on the roles and regulation of microRNAs in the peripheral tissues that confer insulin sensitivity. We discuss sequencing technologies used to comprehensively define the target spectrum of microRNAs in metabolic disease that complement studies reporting physiologic roles for microRNAs in the regulation of glucose and lipid metabolism in animal models. We also discuss the emerging roles of exosomal microRNAs as endocrine signals to regulate lipid and carbohydrate metabolism.

Molecular Mechanisms and Epigenetic Regulation in Diabetic Cardiomyopathy

Diabetes mellitus (DM) is an important lifestyle disease. Type 2 diabetes is one of the prime contributors to cardiovascular diseases (CVD) and diabetic cardiomyopathy (DbCM) and leads to increased morbidity and mortality in patients with DM. DbCM is a typical cardiac disease, characterized by cardiac remodeling in the presence of DM and in the absence of other comorbidities such as hypertension, valvular diseases, and coronary artery disease. DbCM is associated with defective cardiac metabolism, altered mitochondrial structure and function, and other physiological and pathophysiological signaling mechanisms such as oxidative stress, inflammation, myocardial apoptosis, and autophagy. Epigenetic modifiers are crucial players in the pathogenesis of DbCM. Thus, it is important to explore the role of epigenetic modifiers or modifications in regulating molecular pathways associated with DbCM. In this review, we have discussed the role of various epigenetic mechanisms such as histone modifications (acetylation and methylation), DNA methylation and non-coding RNAs in modulating molecular pathways involved in the pathophysiology of the DbCM.

Epigenetic Mechanisms of Endocrine-Disrupting Chemicals in Obesity

The incidence of obesity has dramatically increased over the last decades. Recently, there has been a growing interest in the possible association between the pandemics of obesity and some endocrine-disrupting chemicals (EDCs), termed “obesogens”. These are a heterogeneous group of exogenous compounds that can interfere in the endocrine regulation of energy metabolism and adipose tissue structure. Oral intake, inhalation, and dermal absorption represent the major sources of human exposure to these EDCs. Recently, epigenetic changes such as the methylation of cytosine residues on DNA, post-translational modification of histones, and microRNA expression have been considered to act as an intermediary between deleterious effects of EDCs and obesity development in susceptible individuals. Specifically, EDCs exposure during early-life development can detrimentally affect individuals via inducing epigenetic modifications that can permanently change the epigenome in the germline, enabling changes to be transmitted to the next generations and predisposing them to a multitude of diseases. The purpose of this review is to analyze the epigenetic alterations putatively induced by chemical exposures and their ability to interfere with the control of energy metabolism and adipose tissue regulation, resulting in imbalances in the control of body weight, which can lead to obesity.

Changes in PGC-1α-Dependent Mitochondrial Biogenesis Are Associated with Inflexible Hepatic Energy Metabolism in the Offspring Born to Dexamethasone-Treated Mothers

In the present study we investigated the participation of hepatic peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1α) in the metabolic programming of newborn rats exposed in utero to dexamethasone (DEX). On the 21st day of life, fasted offspring born to DEX-treated mothers displayed increased conversion of pyruvate into glucose with simultaneous upregulation of PEPCK (phosphoenolpyruvate carboxykinase) and G6Pase (glucose-6-phosphatase). Increased oxidative phosphorylation, higher ATP/ADP ratio and mitochondrial biogenesis and lower pyruvate levels were also found in the progeny of DEX-treated mothers. On the other hand, the 21-day-old progeny of DEX-treated mothers had increased hepatic triglycerides (TAG) and lower CPT-1 activity when subjected to short-term fasting. At the mechanistic level, rats exposed in utero to DEX exhibited increased hepatic PGC-1α protein content with lower miR-29a-c expression. Increased PGC-1α content was concurrent with increased association to HNF-4α and NRF1 and reduced PPARα expression. The data presented herein reveal that changes in the transcription machinery in neonatal liver of rats born to DEX-treated mothers leads to an inflexible metabolic response to fasting. Such programming is hallmarked by increased oxidative phosphorylation of pyruvate with impaired FFA oxidation and hepatic TAG accumulation.

Differential expression of micro RNA-29 family in non-diabetic adults of diabetic and non-diabetic parents

OBJECTIVE

MicroRNAs are known to regulate 60% of genes at post translational level. MicroRNAs including Micro RNA-29 family play a vital role in cellular activities and have validate role in numerous metabolic disorders inclusive of diabetes mellitus and its complications. While micro RNA profile changes years before the occurrence of disease. This cross-sectional study was conducted in non-diabetic adults of diabetic and non-diabetic parents to explore the early changes in expression of micro RNA-29 family as it can be served as early biomarker of type 2 diabetes in non-diabetic adults. This study was conducted from January 2019 to January 2021. Micro RNA was extracted from plasma of 50 participants and expression was compared through qPCR. While data was analyzed through SPSS version 21.0.

RESULTS

29a and 29b had lower expression in participants with family history of DM compared to those having no family history of DM (P < 0.0001). While micro RNA 29c was found to be significantly higher in participants with positive family history of type 2 diabetes as compared to those without family history of diabetes (P = 0.001).

tRNA-derived fragment tRF Lys-CTT-010 promotes triple-negative breast cancer progression by regulating glucose metabolism via G6PC

tRNA-derived fragments (tRFs) are a novel class of small non-coding RNAs (sncRNAs) whose biological roles are not well defined. Here, using multiple approaches, we investigated its role in human triple-negative breast cancer (TNBC). Our genome-wide transcriptome analysis of sncRNAs revealed that tRF Lys-CTT-010 was significantly increased in human TNBC. It promoted TNBC proliferation and migration. It also closely associated with starch and sucrose metabolism pathways (KEGG analysis) and positively regulated the expression of glucose-6-phosphatase catalytic subunit (G6PC), one of the related genes in the pathway. G6PC, a complex of glucose-6-phosphatase in gluconeogenesis and glycogenolysis, is upregulated in human TNBC samples. Further studies demonstrated that overexpression of G6PC in tRF Lys-CTT-010 inhibitor transfected TNBC cell lines can reverse malignant biological behavior and knockdown of G6PC in TNBC cell lines inhibited tumor progression and reversed the oncogenic function of tRF Lys-CTT-010. In addition, tRF Lys-CTT-010 interacted with G6PC to regulate cellular lactate production and glycogen consumption, resulting in cell survival and proliferation. Thus, fine-tuneing glucose metabolism and the tRF Lys-CTT-010 /G6PC axis may provide a therapeutic target for TNBC treatment.

MicroRNA-mediated regulation of glucose and lipid metabolism

In animals, systemic control of metabolism is conducted by metabolic tissues and relies on the regulated circulation of a plethora of molecules, such as hormones and lipoprotein complexes. MicroRNAs (miRNAs) are a family of post-transcriptional gene repressors that are present throughout the animal kingdom and have been widely associated with the regulation of gene expression in various contexts, including virtually all aspects of systemic control of metabolism. Here we focus on glucose and lipid metabolism and review current knowledge of the role of miRNAs in their systemic regulation. We survey miRNA-mediated regulation of healthy metabolism as well as the contribution of miRNAs to metabolic dysfunction in disease, particularly diabetes, obesity and liver disease. Although most miRNAs act on the tissue they are produced in, it is now well established that miRNAs can also circulate in bodily fluids, including their intercellular transport by extracellular vesicles, and we discuss the role of such extracellular miRNAs in systemic metabolic control and as potential biomarkers of metabolic status and metabolic disease.

Personalized Nutrition Approach in Pregnancy and Early Life to Tackle Childhood and Adult Non-Communicable Diseases

The development of childhood and adult non-communicable diseases (NCD) is associated with environmental factors, starting from intrauterine life. A new theory finds the roots of epigenetic programming in parental gametogenesis, continuing during embryo development, fetal life, and finally in post-natal life. Maternal health status and poor nutrition are widely recognized as implications in the onset of childhood and adult diseases. Early nutrition, particularly breastfeeding, also plays a primary role in affecting the health status of an individual later in life. A poor maternal diet during pregnancy and lack of breastfeeding can cause a nutrient deficiency that affects the gut microbiota, and acts as a cofactor for many pathways, impacting the epigenetic controls and transcription of genes involved in the metabolism, angiogenesis, and other pathways, leading to NCDs in adult life. Both maternal and fetal genetic backgrounds also affect nutrient adsorption and functioning at the cellular level. This review discusses the most recent evidence on maternal nutrition and breastfeeding in the development of NCD, the potentiality of the omics technologies in uncovering the molecular mechanisms underlying it, with the future prospective of applying a personalized nutrition approach to prevent and treat NCD from the beginning of fetal life.

Adulthood blood levels of hsa-miR-29b-3p associate with preterm birth and adult metabolic and cognitive health

Preterm birth (PTB) is associated with increased risk of type 2 diabetes and neurocognitive impairment later in life. We analyzed for the first time the associations of PTB with blood miRNA levels in adulthood. We also investigated the relationship of PTB associated miRNAs and adulthood phenotypes previously linked with premature birth. Blood MicroRNA profiling, genome-wide gene expression analysis, computer-based cognitive testing battery (CANTAB) and serum NMR metabolomics were performed for Young Finns Study subjects (aged 34-49 years, full-term n = 682, preterm n = 84). Preterm birth (vs. full-term) was associated with adulthood levels of hsa-miR-29b-3p in a fully adjusted regression model (p = 1.90 × 10^-4, FDR = 0.046). The levels of hsa-miR-29b-3p were down-regulated in subjects with PTB with appropriate birthweight for gestational age (p = 0.002, fold change [FC] = - 1.20) and specifically in PTB subjects with small birthweight for gestational age (p = 0.095, FC = - 1.39) in comparison to individuals born full term. Hsa-miR-29b-3p levels correlated with the expressions of its target-mRNAs BCL11A and CS and the gene set analysis results indicated a target-mRNA driven association between hsa-miR-29b-3p levels and Alzheimer's disease, Parkinson's disease, Insulin signaling and Regulation of Actin Cytoskeleton pathway expression. The level of hsa-miR-29b-3p was directly associated with visual processing and sustained attention in CANTAB test and inversely associated with serum levels of VLDL subclass component and triglyceride levels. In conlcusion, adult blood levels of hsa-miR-29b-3p were lower in subjects born preterm. Hsa-miR-29b-3p associated with cognitive function and may be linked with adulthood morbidities in subjects born preterm, possibly through regulation of gene sets related to neurodegenerative diseases and insulin signaling as well as VLDL and triglyceride metabolism.

Quercetin‑conjugated superparamagnetic iron oxide nanoparticles modulate glucose metabolism-related genes and miR-29 family in the hippocampus of diabetic rats

Quercetin (QC) is a dietary bioflavonoid that can be conjugated with nanoparticles to facilitate its brain bioavailability. We previously showed that quercetin-conjugated superparamagnetic iron oxide nanoparticles (QCSPIONs) reduced the level of blood glucose in diabetic rats. Glucose transporters (GLUTs), insulin-like growth factor-1 (IGF-1), and microRNA-29 (miR-29) play a critical role in brain glucose homeostasis. In the current study, we examined the effects of QCSPION on the expression of glucose metabolism-related genes, and the miR-29 family as a candidate regulator of glucose handling in the hippocampus of diabetic rats. Our in silico analyses introduce the miR-29 family as potential regulators of glucose transporters and IGF-1 genes. The expression level of the miR-29 family, IGF-1, GLUT1, GLUT2, GLUT3, and GLUT4 were measured by qPCR. Our results indicate that diabetes significantly results in upregulation of the miR-29 family and downregulation of the GLUT1, 2, 3, 4, and IGF-1 genes. Interestingly, QCSPIONs reduced miR-29 family expression and subsequently enhanced GLUT1, 2, 3, 4, and IGF-1expression. In conclusion, our findings suggest that QCSPION could regulate the expression of the miR-29 family, which in turn increases the expression of glucose transporters and IGF-1, thereby reducing diabetic complications.

MicroRNAs as regulators, biomarkers and therapeutic targets in liver diseases

MicroRNAs (miRNAs) are small, non-coding RNAs that post-transcriptionally regulate gene expression by binding to specific mRNA targets and promoting their degradation and/or translational inhibition. miRNAs regulate both physiological and pathological liver functions. Altered expression of miRNAs is associated with liver metabolism dysregulation, liver injury, liver fibrosis and tumour development, making miRNAs attractive therapeutic strategies for the diagnosis and treatment of liver diseases. Here, we review recent advances regarding the regulation and function of miRNAs in liver diseases with a major focus on miRNAs that are specifically expressed or enriched in hepatocytes (miR-122, miR-194/192), neutrophils (miR-223), hepatic stellate cells (miR-29), immune cells (miR-155) and in circulation (miR-21). The functions and target genes of these miRNAs are emphasised in alcohol-associated liver disease, non-alcoholic fatty liver disease, drug-induced liver injury, viral hepatitis and hepatocellular carcinoma, as well liver fibrosis and liver failure. We touch on the roles of miRNAs in intercellular communication between hepatocytes and other types of cells via extracellular vesicles in the pathogenesis of liver diseases. We provide perspective on the application of miRNAs as biomarkers for early diagnosis, prognosis and assessment of liver diseases and discuss the challenges in miRNA-based therapy for liver diseases. Further investigation of miRNAs in the liver will help us better understand the pathogeneses of liver diseases and may identify biomarkers and therapeutic targets for liver diseases in the future.

Expression of miRNA-29 in Pancreatic β Cells Promotes Inflammation and Diabetes via TRAF3

Type 2 diabetes mellitus (T2DM) is recognized as a chronic, low-grade inflammatory disease characterized by insulin resistance and pancreatic β cell dysfunction; however, the underlying molecular mechanism remains unclear. Here, we report a key β cell-macrophage crosstalk pathway mediated by the miRNA-29-TNF-receptor-associated factor 3 (TRAF3) axis. β cell-specific transgenic miR-29a/b/c mice are predisposed to develop glucose intolerance and insulin resistance when fed a high-fat diet (HFD). The metabolic effect of β cell miR-29 is largely mediated through macrophages because either depletion of macrophages or reconstitution with miR-29-signaling defective bone marrow improves metabolic parameters in the transgenic mice. Mechanistically, our data show that miR-29 promotes the recruitment and activation of circulating monocytes and macrophages and, hence, inflammation, via miR-29 exosomes in a TRAF3-dependent manner. Our results demonstrate the ability of β cells to modulate the systemic inflammatory tone and glucose homeostasis via miR-29 in response to nutrient overload.

Honokiol Alleviates Methionine-Choline Deficient Diet-Induced Hepatic Steatosis and Oxidative Stress in C57BL/6 Mice by Regulating CFLAR-JNK Pathway

Background

Honokiol (HNK) has been reported to possess various beneficial effects in the context of metabolic disorders, including fatty liver, insulin resistance, and oxidative stress which are closely related to nonalcoholic steatohepatitis (NASH), however with no particular reference to CFLAR or JNK.

Methods

C57BL/6 mice were fed methionine-choline-deficient (MCD) diet and administered simultaneously with HNK (10 and 20 mg/kg once a day, ig) for 6 weeks, and NCTC1469 cells were pretreated, respectively, by oleic acid (OA, 0.5 mmol/L) plus palmitic acid (PA, 0.25 mmol/L) for 24 h, and adenovirus-down Cflar for 24 h, then exposed to HNK (10 and 20 μmol/L) for 24 h. Commercial kits, H&E, MT, ORO staining, RT-qPCR, and Western blotting were used to detect the biomarkers, hepatic histological changes, and the expression of key genes involved in NASH.

Results

The in vivo results showed that HNK suppressed the phosphorylation of JNK (pJNK) by activating CFLAR; enhanced the mRNA expression of lipid metabolism-related genes Acox, Cpt1α, Fabp5, Gpat, Mttp, Pparα, and Scd-1; and decreased the levels of hepatic TG, TC, and MDA, as well as the levels of serum ALT and AST. Additionally, HNK enhanced the protein expression of oxidative stress-related key regulatory gene NRF2 and the activities of antioxidases HO-1, CAT, and GSH-Px and decreased the protein levels of prooxidases CYP4A and CYP2E1. The in vivo effects of HNK on the expression of CLFAR, pJNK, and NRF2 were proved by the in vitro experiments. Moreover, HNK promoted the phosphorylation of IRS1 (pIRS1) in both tested cells and increased the uptake of fluorescent glucose 2-NBDG in OA- and PA-pretreated cells.

Conclusions

HNK ameliorated NASH mainly by activating the CFLAR-JNK pathway, which not only alleviated fat deposition by promoting the efflux and β-oxidation of fatty acids in the liver but also attenuated hepatic oxidative damage and insulin resistance by upregulating the expression of NRF2 and pIRS1.

Circulating exosomal microRNAs as potential biomarkers of hepatic injury and inflammation in a murine model of glycogen storage disease type 1a

Most patients affected by glycogen storage disease type 1a (GSD1a), an inherited metabolic disorder caused by mutations in the enzyme glucose-6-phosphatase-α (G6Pase-α), develop renal and liver complications, including the development of hepatocellular adenoma/carcinoma. The purpose of this study was to identify potential biomarkers of the pathophysiology of the GSD1a-affected liver. To this end, we used the plasma exosomes of a murine model of GSD1a, the LS-G6pc ^{-/ -} mouse, to uncover the modulation in microRNA expression associated with the disease. The microRNAs differentially expressed between LS-G6pc ^-/- and wild-type mice, LS-G6pc ^-/- mice with hepatocellular adenoma and LS-G6pc ^-/- mice without adenoma, and LS-G6pc ^-/- mice with amyloidosis and LS-G6pc ^-/- mice without amyloidosis were identified. Pathway analysis demonstrated that the target genes of the differentially expressed microRNA were significantly enriched for the insulin signaling pathway, glucose and lipid metabolism, Wnt/β-catenin, telomere maintenance and hepatocellular carcinoma, and chemokine and immune regulation signaling pathways. Although some microRNAs were common to the different pathologic conditions, others were unique to the cancerous or inflammatory status of the animals. Therefore, the altered expression of several microRNAs is correlated with various pathologic liver states and might help to distinguish them during the progression of the disease and the development of late GSD1a-associated complications.

MiR-542-5p Inhibits Hyperglycemia and Hyperlipoidemia by Targeting FOXO1 in the Liver

PURPOSE

This research was designed to investigate how miR-542-5p regulates the progression of hyperglycemia and hyperlipoidemia.

MATERIALS AND METHODS

An in vivo model with diabetic db/db mice and an in vitro model with forskolin/dexamethasone (FSK/DEX)-induced primary hepatocytes and HepG2 cells were employed in the study. Bioinformatics analysis was conducted to identify the expression of candidate miRNAs in the liver tissues of diabetic and control mice. H&E staining revealed liver morphology in diabetic and control mice. Pyruvate tolerance tests, insulin tolerance tests, and intraperitoneal glucose tolerance test were utilized to assess insulin resistance. ELISA was conducted to evaluate blood glucose and insulin levels. Red oil O staining showed lipid deposition in liver tissues. Luciferase reporter assay was used to depict binding between miR-542-5p and forkhead box O1 (FOXO1).

RESULTS

MiR-542-5p expression was under-expressed in the livers of db/db mice. Further in vitro experiments revealed that FSK/DEX, which mimics the effects of glucagon and glucocorticoids, induced cellular glucose production in HepG2 cells and in primary hepatocytes cells. Notably, these changes were reversed by miR-542-5p. We found that transcription factor FOXO1 is a target of miR-542-5p. Further in vivo study indicated that miR-542-5p overexpression decreases FOXO1 expression, thereby reversing increases in blood glucose, blood lipids, and glucose-related enzymes in diabetic db/db mice. In contrast, anti-miR-542-5p exerted an adverse influence on blood glucose and blood lipid metabolism, and its stimulatory effects were significantly inhibited by sh-FOXO1 in normal control mice.

CONCLUSION

Collectively, our results indicated that miR-542-5p inhibits hyperglycemia and hyperlipoidemia by targeting FOXO1.

Regulatory Mechanisms of Mitochondrial Function and Cardiac Aging

Aging is a major risk factor for cardiovascular diseases (CVDs), the major cause of death worldwide. Cardiac myocytes, which hold the most abundant mitochondrial population, are terminally differentiated cells with diminished regenerative capacity in the adult. Cardiomyocyte mitochondrial dysfunction is a characteristic feature of the aging heart and one out of the nine features of cellular aging. Aging and cardiac pathologies are also associated with increased senescence in the heart. However, the cause and consequences of cardiac senescence during aging or in cardiac pathologies are mostly unrecognized. Further, despite recent advancement in anti-senescence therapy, the targeted cell type and the effect on cardiac structure and function have been largely overlooked. The unique cellular composition of the heart, and especially the functional properties of cardiomyocytes, need to be considered when designing therapeutics to target cardiac aging. Here we review recent findings regarding key factors regulating cell senescence, mitochondrial health as well as cardiomyocyte rejuvenation.

Resveratrol Upregulates mmu-miR-363-3p via the PI3K-Akt Pathway to Improve Insulin Resistance Induced by a High-Fat Diet in Mice

PURPOSE

This study aimed to investigate how resveratrol (RSV) improves high-fat diet (HFD)-induced hepatic insulin resistance in mice via microRNA (miRNA) mmu-miR-363-3p in vitro and in vivo.

MATERIALS AND METHODS

C57BL/6J mice were fed a HFD for 8 weeks to establish an insulin resistance model. The model mice were treated or not with RSV for 6 weeks. Differential miRNA expression in mouse liver tissues was analyzed by high-throughput sequencing. Mouse HepG2 cells were treated with palmitic acid (PA) to establish a cell model of insulin resistance. HepG2 cells were transfected with mmu-miR-363-3p inhibitor or mimic, and the expression of PI3K-Akt signaling pathway-related proteins was analyzed.

RESULTS

Based on the high-throughput sequencing analysis, mmu-miR-363-3p was identified as a major miRNA involved in the action of RSV on insulin resistance. Based on KEGG pathway enrichment analysis, PI3K-Akt signaling was found to be significantly enriched among differentially expressed miRNAs, and this pathway is closely related to insulin resistance. RSV treatment reduced the expression of FOXO1 and G6PC, which are downstream of the PI3K-Akt pathway. In the cell model, mmu-miR-363-3p inhibitor significantly suppressed p-Akt and p-PI3K levels, but enhanced those of FOXO1 and G6PC. In contrast, mmu-miR-363-3p mimic significantly enhanced the p-Akt and p-PI3K levels, but suppressed FOXO1 and G6PC expression, which was similar to the effect of RSV.

CONCLUSION

RSV improves insulin resistance by upregulating miRNA mmu-miR-363-3p via the PI3K-Akt pathway.

Hepatic microRNA Expression by PGC-1α and PGC-1β in the Mouse

The fine-tuning of liver metabolism is essential to maintain the whole-body homeostasis and to prevent the onset of diseases. The peroxisome proliferator-activated receptor-γ coactivators (PGC-1s) are transcriptional key players of liver metabolism, able to regulate mitochondrial function, gluconeogenesis and lipid metabolism. Their activity is accurately modulated by post-translational modifications. Here, we showed that specific PGC-1s expression can lead to the upregulation of different microRNAs widely implicated in liver physiology and diseases development and progression, thus offering a new layer of complexity in the control of hepatic metabolism.

Micro-RNA-27a/b negatively regulates hepatic gluconeogenesis by targeting FOXO1

In the context of hepatic insulin resistance, hepatic gluconeogenesis is abnormally increased, which results in increased hepatic glucose production and hyperglycemia, but the underlying mechanisms remain to be fully elucidated. Micro-RNAs (miRNAs) have been identified as critical regulators of diabetes and other metabolic disorders. In this study, we found that the expressions of miRNA-27 family members miRNA-27a and miRNA-27b (miR-27a/b) decreased significantly in the livers of diabetic mice. Moreover, the levels of miR-27a/b increased in the serum of patients with type 2 diabetes. Our present results showed that inhibition of miR-27a/b expression led to increased hepatic protein levels of glucose-6-phosphatase and phosphoenolpyruvate carboxykinase and enhanced hepatic gluconeogenesis in vitro and in vivo. Overexpression of miR-27a/b suppressed hepatic glucose output and alleviated hyperglycemia in diabetic mice. Further study revealed that forkhead box O1 (FOXO1) is a downstream target of miR-27a/b. Taken together, we found novel evidence suggesting that miR-27a/b contributes to hepatic gluconeogenesis through targeting FOXO1 and provided novel mechanistic insight into the pathophysiology of insulin resistance.

Silibinin ameliorates hepatic lipid accumulation and oxidative stress in mice with non-alcoholic steatohepatitis by regulating CFLAR-JNK pathway

Non-alcoholic steatohepatitis (NASH) is a chronic metabolic syndrome and the CFLAR-JNK pathway can reverse the process of NASH. Although silibinin is used for the treatment of NASH in clinical, its effect on CFLAR-JNK pathway in NASH remains unclear. This study aimed to investigate the effect of silibinin on CFLAR-JNK pathway in NASH models both in vivo and in vitro. The in vivo study was performed using male C57BL/6 mice fed with methionine- choline-deficient diet and simultaneously treated with silibinin for 6 weeks. The in vitro study was performed by using mouse NCTC-1469 cells which were respectively pretreated with oleic acid plus palmitic acid, and adenovirus-down Cflar for 24 h, then treated with silibinin for 24 h. After the drug treatment, the key indicators involved in CFLAR-JNK pathway including hepatic injury, lipid metabolism and oxidative stress were determined. Silibinin significantly activated CFLAR and inhibited the phosphorylation of JNK, up-regulated the mRNA expression of Pparα, Fabp5, Cpt1α, Acox, Scd-1, Gpat and Mttp, reduced the activities of serum ALT and AST and the contents of hepatic TG, TC and MDA, increased the expression of NRF2 and the activities of CAT, GSH-Px and HO-1, and decreased the activities and expression of CYP2E1 and CYP4A in vivo. These effects were confirmed by the in vitro experiments. Silibinin prevented NASH by regulating CFLAR-JNK pathway, and thereby on one hand promoting the β-oxidation and efflux of fatty acids in liver to relieve lipid accumulation, and on the other hand inducing antioxidase activity (CAT, GSH-Px and HO-1) and inhibiting pro-oxidase activity (CYP2E1 and CYP4A) to relieve oxidative stress.

Hepatic miR-181b-5p Contributes to Glycogen Synthesis Through Targeting EGR1

BACKGROUND/AIM

The miR-181 family plays an important role in the regulation of various cellular functions. However, whether miR-181b-5p mediates hepatic insulin resistance remains unknown. In this study, we investigated the effect of miR-181b-5p on the regulation of hepatic glycogen synthesis.

METHODS

The miR-181b-5p levels in the livers of diabetic mice were detected by real-time PCR. The glycogen levels and AKT/GSK pathway activation were examined in human hepatic L02 cells and HepG2 cells transfected with miR-181b-5p mimic or inhibitor. The potential target genes of miR-181b-5p were evaluated using a luciferase reporter assay and Western blot analysis. EGR1-specific siRNA and pCMV-EGR1 were used to further determine the role of miR-181b-5p in hepatic glycogen synthesis in vitro. Hepatic inhibition of miR-181b-5p in mice was performed using adeno-associated virus 8 (AAV8) vectors by tail intravenous injection.

RESULTS

The miR-181b-5p levels were significantly decreased in the serum and livers of diabetic mice as well as the serum of type 2 diabetes patients. Importantly, inhibition of miR-181b-5p expression impaired the AKT/GSK pathway and reduced glycogenesis in hepatocytes. Moreover, upregulation of miR-181b-5p reversed high-glucose-induced suppression of glycogenesis. Further analysis revealed that early growth response 1 (EGR1) was a downstream target of miR-181b-5p. Silencing of EGR1 expression rescued miR-181b-5p inhibition-reduced AKT/GSK pathway activation and glycogenesis in hepatocytes. Hepatic inhibition of miR-181b-5p led to insulin resistance in C57BL/6 J mice.

CONCLUSION

We demonstrated that miR-181b-5p contributes to glycogen synthesis by targeting EGR1, thereby regulating PTEN expression to mediate hepatic insulin resistance.

Circulating miR-29b positively correlates with non-alcoholic fatty liver disease in a Chinese population

OBJECTIVE

Early screening of non-alcoholic fatty liver disease (NAFLD) is of great significance for the early detection and intervention in NAFLD. MicroRNAs (miRNAs) are important regulators of metabolic diseases including NAFLD. The aim of this study was to investigate the association of serum miR-29a-c with NAFLD in a Chinese population.

METHODS

Participants were divided into four groups based on the presence or absence of NAFLD and/or type 2 diabetes mellitus (T2DM). Quantitative polymerase chain reaction analysis was performed to quantify serum level of miR-29a-c. The association of miR-29a-c with NAFLD was evaluated.

RESULTS

Serum miR-29b, but not miR-29a or miR-29c, was positively associated with NAFLD (odds ratio [OR] 2.04 [1.16- 3.58], P = 0.013). Additionally, age, serum triglyceride and fasting plasma glucose (FPG) levels were independently associated with miR-29b (β ± standard error [SE] = 0.004 ± 0.002, P = 0.019 for age; β ± SE = 0.110 ± 0.054, P = 0.042 for triglyceride; and β ± SE = 0.389 ± 0.161, P = 0.016 for FPG). MiR-29b level was positively correlated with intrahepatic lipid content (β ± SE = 6.055 ± 2.630, P = 0.024) after adjusted for age, sex, and body mass index.

CONCLUSIONS

Serum miR-29b was associated with intrahepatic lipid content and NAFLD in a Chinese population-based study.

Down-regulation of MicroRNA-592 in obesity contributes to hyperglycemia and insulin resistance

Background

Many studies have demonstrated that microRNAs, a class of small and non-coding RNA molecules, play an important role in the regulation of glucose and lipid homeostasis. In the present study, we sought to investigate the function of miR-592 in the development of obesity-associated metabolic disorders, including hyperglycemia andinsulin resistance.

Methods

The expression levels of miR-592 were measured in the liver of obese mice and humans by quantitative reverse transcription PCR. Loss- and gain-of function experiments were employed to explore the metabolic function of miR-592 using locked nucleic acids and adenovirus in lean and obese mice, respectively. The molecular target of miR-592 was determined by western blotting and luciferase reporter assays.

Findings

We found a significant decreased expression of miR-592 in the liver of obese mice and humans. Inhibition of miR-592 led to elevated blood glucose levels, enhanced gluconeogenesis and reduced insulin sensitivity in lean mice. In contrast, adenovirus-mediated overexpression of hepatic miR-592 improved metabolic disorders in obese mice. Mechanistically, we found that the transcription factor forkhead box O1 (FOXO1) is a direct target gene of miR-592 to mediate its metabolic functions. miR-592 was able to inhibit the mRNA and protein expression of FOXO1 by binding to its 3′-untranslated region.

Interpretations

Our findings demonstrate that obesity-associated down-regulation of miR-592 plays an important role in the progression of metabolic diseases. Restoration of hepatic miR-592 could improve glucose and lipid metabolism in obese mice.

Fund

This work is supported by the National Key Research and Development Program of China (No. 2016YFC1304805 to Dr. Chen), Natural Science Foundation of China (No. 81771574 to Dr. Wu), Shanghai Science Foundation (No. 18ZR1437800 to Dr. Li), Science and Technology Commission of Shanghai Municipality (Nos.18dz2304400 and 15,411,970,700 to Dr. Yang).

Urinary miRNA-29a-3p levels are associated with metabolic parameters via regulation of IGF1 in patients with metabolic syndrome

Circulating microRNAs (miRNAs or miRs) have been demonstrated to serve as diagnostic and prognostic biomarkers in metabolic syndrome (MetS). The role of urinary miRNAs in MetS diagnosis remains unknown. Here, elevated miR-29a-3p levels were observed in urine samples of patients with MetS compared with control subjects using a microarray analysis (n=4/group) and validation via reverse transcription-quantitative polymerase chain reaction (n=40/group). Associations between urinary miR-29a-3p levels and parameters associated with metabolism, such as adiposity, insulin resistance, lipid profiles and hepatic enzymes were further assessed. Multiple linear regression analyses revealed that urinary miR-29a-3p levels were independently correlated with fasting insulin (β=0.561; P<0.001), high density lipoprotein-cholesterol (β=0.242; P<0.001) and body mass index (β=-0.141; P<0.05). The area under the receiver operating characteristic curve was 0.776 and miR-29a-3p had a diagnostic value for MetS with 68.2% sensitivity and 77.3% specificity. Furthermore, insulin-like growth factor 1 was identified as a target of miR-29a-3p by searching bioinformatics databases and was validated by dual-luciferase reporter and western blot assays. In conclusion, elevated urinary miR-29a-3p levels were positively associated with MetS and demonstrated to have a potential value as biomarkers in the diagnosis of MetS. The findings provided a better understanding of the role of urinary miRNAs in pathogenesis of MetS.

Characterization of miRNA profiles in the mammary tissue of dairy cattle in response to heat stress

Background

MicroRNAs (miRNAs) are a class of small noncoding RNAs that play important roles in the regulation of gene expression. However, the role of miRNAs in bovine mammary gland responses to heat stress is not well understood.

Results

In the present study, we performed a deep RNA sequencing analysis to identify miRNAs associated with the heat stress potential of the bovine mammary gland. We identified 27 miRNAs that were differentially expressed significantly between the mammary tissue of Holstein cattle heat stress and normal conditions. Twenty miRNAs had higher expression in the mammary tissue of heat-stressed Holstein cattle. The seven highest differentially expressed candidate miRNAs (bta-miR-21-5p, bta-miR-99a-5p, bta-miR-146b, bta-miR-145, bta-miR-2285 t, bta-miR-133a, and bta-miR-29c) identified by deep RNA sequencing were additionally evaluated by stem-loop qPCR. Enrichment analyses for targeted genes revealed that the major differences between miRNAs expression in the mammary gland of heat-stressed versus control were associated with the regulation of Wnt, TGF-β, MAPK, Notch, and JAK-STAT.

Conclusions

These data indicated that the differentially expressed miRNAs identified in this study may act as dominant regulators during heat stress. We might reduce heat stress damage of Holstein cows by up-regulating or down-regulating these differentially expressed miRNAs.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5298-1) contains supplementary material, which is available to authorized users.

Gluconeogenesis in Cancer: Function and Regulation of PEPCK, FBPase, and G6Pase

Cancer cells display a high rate of glycolysis in the presence of oxygen to promote proliferation. Gluconeogenesis, the reverse pathway of glycolysis, can antagonize aerobic glycolysis in cancer via three key enzymes - phosphoenolpyruvate carboxykinase (PEPCK), fructose-1,6-bisphosphatase (FBPase), and glucose-6-phosphatase (G6Pase). Recent studies have revealed that, in addition to metabolic regulation, these enzymes also play a role in signaling, proliferation, and the cancer stem cell (CSC) tumor phenotype. Multifaceted regulation of PEPCK, FBPase, and G6Pase through transcription, epigenetics, post-translational modification, and enzymatic activity is observed in different cancers. We review here the function and regulation of key gluconeogenic enzymes and new therapeutic opportunities.

Hepatic c-Jun regulates glucose metabolism via FGF21 and modulates body temperature through the neural signals

Objective

c-Jun, a prominent member of the activator protein 1 (AP-1) family, is involved in various physiology processes such as cell death and survival. However, a role of hepatic c-Jun in the whole-body metabolism is poorly understood.

Methods

We generated liver-specific c-Jun knock-out (c-jun^△li) mice to investigate the effect of hepatic c-Jun on the whole-body physiology, particularly in blood glucose and body temperature. Primary hepatocytes were also used to explore a direct regulation of c-Jun in gluconeogenesis.

Results

c-jun^△li mice showed higher hepatic gluconeogenic capacity compared with control mice, and similar results were obtained in vitro. In addition, fibroblast growth factor 21 (FGF21) expression was directly inhibited by c-Jun knockdown and adenovirus-mediated hepatic FGF21 over-expression blocked the effect of c-Jun on gluconeogenesis in c-jun^△li mice. Interestingly, c-jun^△li mice also exhibited higher body temperature, with induced thermogenesis and uncoupling protein 1 (UCP1) expression in brown adipose tissue (BAT). Furthermore, the body temperature became comparable between c-jun^△li and control mice at thermoneutral temperature (30 °C). Moreover, the activity of sympathetic nervous system (SNS) was increased in c-jun^△li mice and the higher body temperature was inhibited by beta-adrenergic receptor blocker injection. Finally, the activated SNS and increased body temperature in c-jun^△li mice was most likely caused by the signals from the brain and hepatic vagus nerve, as the expression of c-Fos (the molecular marker of neuronal activation) was changed in several brain areas controlling body temperature and body temperature was decreased by selective hepatic vagotomy.

Conclusions

These data demonstrate a novel function of hepatic c-Jun in the regulation of gluconeogenesis and body temperature via FGF21 and neural signals. Our results also provide novel insights into the organ crosstalk in the regulation of the whole-body physiology.

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Liver-specific inactivation of c-Jun increased gluconeogenesis via decreasing FGF21 expression.

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Liver-specific inactivation of c-Jun increased body temperature by promoting thermogenesis in BAT.

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Hepatic c-Jun modulates body temperature via regulating sympathetic nervous system activity and vagus nerve.

Let-7b acts as a tumor suppressor in osteosarcoma via targeting IGF1R

MicroRNAs serve crucial functions in cancer progression by inhibiting the translation of target genes and causing mRNA degradation. However, the underlying regulatory mechanism of Let-7b in osteosarcoma (OS) has not, to the best of our knowledge, been comprehensively elucidated. The aim of the present study was to investigate the function of Let-7b in OS and clarify the regulation of insulin-like growth factor 1 receptor (IGF1R) by Let-7b. It was observed that Let-7b was significantly downregulated in OS tissues and cell lines compared with the matched adjacent non-tumorous tissues and human normal osteoblastic cell line hFOB 1.19. Overexpression of Let-7b significantly inhibited the proliferation and invasion of U2OS and SAOS-2 cells. A luciferase reporter assay validated that IGF1R was a downstream and functional target of Let-7b. Let-7b was also able to decrease the expression levels of IGF1R protein. Functional studies revealed that the antitumor effect of Let-7b was probably due to targeting and suppressing IGF1R expression. Furthermore, in OS tissues, IGF1R was identified to be significantly upregulated and negatively correlated with Let-7b levels. In conclusion, the results of the present study indicated that Let-7b suppresses OS cellular proliferation and invasion via targeting IGF1R. A novel candidate prognostic factor was identified and it is suggested that the Let-7b/IGF1R axis may represent a novel anti-metastasis therapeutic target in OS.

Role of miR29c in goose fatty liver is mediated by its target genes that are involved in energy homeostasis and cell growth

Background

A short period of overfeeding can lead to severe hepatic steatosis in the goose, which is physiological, suggesting that geese, as a descendent of a migrating ancestor, may have evolutionally developed a unique mechanism that operates in contrast to the mechanism underlying pathological fatty liver in humans or other mammals. In this study, we report that suppression of miR29c and upregulation of its target genes in goose fatty liver vs. normal liver could be part of a unique mechanism that contributes to the regulation of energy homeostasis and cell growth.

Results

Our data showed that miR29c expression was comprehensively inhibited in energy homeostasis-related tissues (the liver, fat and muscle) of overfed vs. normally fed geese, which is different from miR29c induction that occurs in tissues of the diabetic rat. To address the function of miR29c, three predicted target genes (i.e., Insig1, Sgk1 and Col3a1) that participate in energy homeostasis or cell growth were validated by a dual-fluorescence reporter system and other in vitro assays. Importantly, expression of Insig1, Sgk1 and Col3a1 was upregulated in goose fatty liver. In line with these observations, treatment of goose hepatocytes with high glucose or palmitate suppressed the expression of miR29c but induced the expression of the target genes, suggesting that hyperglycemia and hyperlipidemia, at least partially, contribute to the suppression of miR29c and induction of the target genes in goose fatty liver. In addition, pharmacological assays indicated that RFX1 was a transcription factor involved in the expression of miR29c.

Conclusions

This study suggests that miR29c may play a role in the regulation of energy homeostasis and tissue growth via its target genes, contributing to the tolerance of the goose to severe hepatic steatosis.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1653-3) contains supplementary material, which is available to authorized users.

lncRNA MEG3 promotes hepatic insulin resistance by serving as a competing endogenous RNA of miR-214 to regulate ATF4 expression

MicroRNA (miR)-214 has been demonstrated to suppress gluconeogenesis by targeting activating transcription factor 4 (ATF4), which regulates gluconeogenesis by affecting the transcriptional activity of forkhead box protein O1 (FoxO1). Our previous study revealed that the upregulation of maternally expressed gene 3 (MEG3), a long noncoding RNA, enhanced hepatic insulin resistance via increased FoxO1 expression. The present study aimed to explore whether miR-214 and ATF4 were involved in the MEG3-mediated increase of FoxO1 expression. MEG3, miR-214 and ATF4 expression were examined by reverse transcription quantitative polymerase chain reaction and western blot analysis. The interaction among MEG3, miR-214 and ATF4 was analysed using the luciferase reporter assay. MEG3-targeting small interference RNAs were injected into high-fat diet (HFD)-fed mice to verify the role of MEG3 in hepatic insulin resistance in vivo. MEG-3 and ATF4 were demonstrated to be upregulated and miR-214 was indicated to be downregulated in the livers of HFD-fed and ob/ob mice. In mouse primary hepatocytes, palmitate time-dependently increased MEG3 and ATF4 but decreased miR-214 expression levels. Furthermore, MEG3 served as a competing endogenous RNA (ceRNA) for miR-214 to facilitate ATF4 expression, while miR-214 inhibition and ATF4 overexpression reversed the MEG3 knockdown-mediated decrease in the expression of FoxO1 and FoxO1-downstream targets phosphoenolpyruvate carboxykinase and glucose-6-phosphatase catalytic subunit. In HFD-fed mice, MEG3 knockdown substantially improved impaired glucose and insulin tolerance, while down-regulating HFD-induced ATF4 expression and upregulating HFD-suppressed miR-214 expression. In conclusion, MEG3 promoted hepatic insulin resistance by serving as a ceRNA of miR-214 to facilitate ATF4 expression. These data provide insight into the molecular mechanism of MEG3 involvement in the development of type 2 diabetes mellitus.

The microRNA-29/PGC1α regulatory axis is critical for metabolic control of cardiac function

Different microRNAs (miRNAs), including miR-29 family, may play a role in the development of heart failure (HF), but the underlying molecular mechanisms in HF pathogenesis remain unclear. We aimed at characterizing mice deficient in miR-29 in order to address the functional relevance of this family of miRNAs in the cardiovascular system and its contribution to heart disease. In this work, we show that mice deficient in miR-29a/b1 develop vascular remodeling and systemic hypertension, as well as HF with preserved ejection fraction (HFpEF) characterized by myocardial fibrosis, diastolic dysfunction, and pulmonary congestion, and die prematurely. We also found evidence that the absence of miR-29 triggers the up-regulation of its target, the master metabolic regulator PGC1α, which in turn generates profound alterations in mitochondrial biogenesis, leading to a pathological accumulation of small mitochondria in mutant animals that contribute to cardiac disease. Notably, we demonstrate that systemic hypertension and HFpEF caused by miR-29 deficiency can be rescued by PGC1α haploinsufficiency, which reduces cardiac mitochondrial accumulation and extends longevity of miR-29–mutant mice. In addition, PGC1α is overexpressed in hearts from patients with HF. Collectively, our findings demonstrate the in vivo role of miR-29 in cardiovascular homeostasis and unveil a novel miR-29/PGC1α regulatory circuitry of functional relevance for cell metabolism under normal and pathological conditions.

To combat diseases, we first need to gain knowledge on how cells function at the molecular level to maintain normal physiology. One great scientific achievement of the last decade was the identification of thousands of small regulatory RNA molecules, called microRNAs. Strikingly, each microRNA has the potential to fine-tune the expression of hundreds of target genes depending on the spatiotemporal context. Therefore, defects in key microRNAs can contribute to the development of diseases. In the present work, we characterize the role for miR-29 in cardiac function in a mouse model. We found that mice deficient for miR-29 develop life-threatening cardiometabolic alterations that subsequently cause heart failure with diastolic dysfunction and systemic hypertension. We also demonstrate that these pathological phenotypes originate in part by the anomalous up-regulation of the transcriptional coactivator PGC1α, which can lead to mitochondrial hyperplasia in the heart. Genetic removal of one copy of PGC1α significantly attenuated the severity of the cardiovascular phenotype observed in miR-29–deficient mice. In addition, we show that PGC1α expression is misregulated in heart failure patients, suggesting that the implementation of miR-29 replacement therapy could potentially be used to treat these fatal pathologies.

Effects of fasting and refeeding on protein and glucose metabolism in Arctic charr

Refeeding, following a period of food deprivation will often lead to compensatory growth. Although many studies have focused on molecular mechanisms behind this accelerated growth response in fish, little is known on the roles of protein and metabolism. We also assessed, for the first time, the potential roles of miRNAs in regulating compensatory growth. Artcic charr, Salvelinus alpinus, a northern freshwater species, was deprived of food for 101 days and then fed to satiety for 126 days. The refeeding period resulted in compensatory growth, with a partial compensation of body mass. The feed deprivation period lead to a decrease in hepatosomatic index (HSI) and intestinal somatic index (ISI). HSI and ISI were then gradually replenished during early refeeding, following a lag phase prior to the compensatory growth response. mRNA transcripts regulating protein degradation via the autophagy pathway (Cathepsin D and Cathepsin L) in muscle were upregulated during feed restriction and downregulated after refeeding, which could allow for greater protein accretion in muscle, facilitating compensatory growth. Transcript levels from the ubiquitin proteasome pathway (Mafbx and Murf1) and the calpain system (Calpain 7 and Calpastatin) suggested that these pathways were not involved in regulating compensatory growth. Furthermore, we've shown that miRNAs (miR-29a and miR-223) could be involved in fish glycogen homeostasis during the early stages of refeeding. These findings provide a deeper understanding of the molecular mechanisms regulating growth in fish.

MicroRNA‑152 regulates insulin secretion and pancreatic β cell proliferation by targeting PI3Kα

An increasing number of microRNAs (miRNAs/miRs) are reported to have important roles in diabetes. Glucose‑stimulated insulin secretion and pancreatic β cell proliferation are essential in the control of metabolic disorder, however, the underlying molecular mechanisms remain unclear. The present study investigated the function of miR‑152 in diabetes. The results of reverse transcription‑quantitative polymerase chain reaction demonstrated that miR‑152 levels in the blood were markedly reduced in patients with diabetes compared with nondiabetic controls. In addition, a high blood glucose concentration was significantly associated with reduced miR‑152 expression. Furthermore, overexpression of miR‑152 using miR‑152 mimics promoted the proliferation of INS‑1 and MIN6 cells, as determined by an MTT assay, in addition to insulin secretion, while knockdown of miR‑152 using an inhibitor led to the opposite effects. Phosphatidylinositol 3‑kinase (PI3K) signaling has been reported to inhibit insulin secretion, however, the regulation of PI3K in the pancreatic β cell is poorly understood. The present study identified that PI3K catalytic subunit α (PI3Kα) was a direct target gene of miR‑152 using a luciferase reporter assay, and miR‑152 inhibited the expression of PI3Kα at the protein level, which was determined by western blotting. Therefore, the regulation of insulin secretion and pancreatic β cell proliferation may occur via the miR‑152/PI3Kα axis. The overexpression of PI3Kα in INS‑1 and MIN6 cells partially reduced the effects of miR‑152 overexpression on insulin secretion. Consistently, PI3Kα levels were reduced in murine pancreatic islets following treatment with 20 mM glucose, and increased in blood samples from patients with diabetes compared with healthy individuals. In conclusion, the results of the present study demonstrate that miR‑152 may have an important role in pancreatic β cell function, and established an association between miR‑152 and the PI3Kα axis. Therefore, targeting PI3Kα may be a potential therapeutic option for diabetes.

microRNA-205-5p is a modulator of insulin sensitivity that inhibits FOXO function

Objectives

Hepatic insulin resistance is a hallmark of type 2 diabetes and obesity. Insulin receptor signaling through AKT and FOXO has important metabolic effects that have traditionally been ascribed to regulation of gene expression. However, whether all the metabolic effects of FOXO arise from its regulation of protein-encoding mRNAs is unknown.

Methods

To address this question, we obtained expression profiles of FOXO-regulated murine hepatic microRNAs (miRNAs) during fasting and refeeding using mice lacking Foxo1, 3a, and 4 in liver (L-Foxo1,3a, 4).

Results

Out of 439 miRNA analyzed, 175 were differentially expressed in Foxo knockouts. Their functions were associated with insulin, Wnt, Mapk signaling, and aging. Among them, we report a striking increase of miR-205-5p expression in L-Foxo1,3a,4 knockouts, as well as in obese mice. We show that miR-205-5p gain-of-function increases AKT phosphorylation and decreases SHIP2 in primary hepatocytes, resulting in FOXO inhibition. This results in decreased hepatocyte glucose production. Consistent with these observations, miR-205-5p gain-of-function in mice lowered glucose levels and improved pyruvate tolerance.

Conclusions

These findings reveal a homeostatic miRNA loop regulating insulin signaling, with potential implications for in vivo glucose metabolism.

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A comprehensive analysis of Foxo-dependent miRNA.

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miRNAs recapitulate the transcriptional effects of Foxo on insulin signaling.

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Foxo regulates miRNA transcription during the fasting/refeeding transition.

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miR205 regulates insulin sensitivity through a homeostatic loop with Foxo.

MiR-29 family members interact with SPARC to regulate glucose metabolism

MicroRNA (miR)-29 family members have been reported to play important regulatory roles in metabolic disease. We used TargetScan to show that "secreted protein acidic rich in cysteine" (SPARC) is a target of the miR-29s. SPARC is a multifunctional secretory protein involved in a variety of biological activities, and SPARC dysregulation is associated with a wide range of obesity-related disorders, including type 2 diabetes mellitus (T2DM). We explored whether miR-29s played roles in glucose metabolism and whether miR-29s directly targeted SPARC. We also examined the effect of SPARC on glucose metabolism and how the association of miR-29s with SPARC affected glucose metabolism. We found that overexpression of miR-29s reduced glucose uptake and GLUT4 levels; that miR-29 directly targeted SPARC, resulting in degradation of SPARC-encoding mRNA and reduction in the SPARC protein level; that SPARC increased glucose uptake and GLUT4 levels; that shRNA-mediated knockdown of SPARC reduced GLUT4 protein levels in 3T3-L1 adipocytes; that miR-29s reduced glucose uptake and GLUT4 levels; and that miR-29s inhibited glucose uptake by suppressing SPARC synthesis. Thus, the miR-29 family negatively regulates glucose metabolism by inhibiting SPARC expression.

The long non-coding RNA Gm10768 activates hepatic gluconeogenesis by sequestering microRNA-214 in mice

Overactivated hepatic gluconeogenesis contributes to the pathogenesis of metabolic disorders, including type 2 diabetes. Precise control of hepatic gluconeogenesis is thus critical for maintaining whole-body metabolic homeostasis. Long non-coding RNAs (lncRNAs) have been shown to play key roles in diseases by regulating diverse biological processes, but the function of lncRNAs in maintaining normal physiology, particularly glucose homeostasis in the liver, remains largely unexplored. We identified a novel liver-enriched long non-coding RNA, Gm10768, and examined its expression patterns under pathophysiological conditions. We further adopted gain- and loss-of-function strategies to explore the effect of Gm10768 on hepatic glucose metabolism and the possible molecular mechanism involved. Our results showed that the expression of Gm10768 was significantly increased in the liver of fasted mice and was induced by gluconeogenic hormonal stimuli. Functionally, overexpression of Gm10768 activated hepatic gluconeogenesis in a cell-autonomous manner. In contrast, depletion of Gm10768 suppressed hepatic glucose production both in vitro and in vivo Adenovirus-mediated hepatic knockdown of Gm10768 improved glucose tolerance and hyperglycemia of diabetic db/db mice. Mechanistically, Gm10768 sequestrated microRNA-214 (miR-214) to relieve its suppression on activating transcription factor 4 (ATF4), a positive regulator of hepatic gluconeogenesis. Taken together, we identified Gm10768 as a new lncRNA activating hepatic gluconeogenesis through antagonizing miR-214 in mice.

The role of microRNAs in glucocorticoid action

Glucocorticoids (GCs) are steroids with profound anti-inflammatory and immunomodulatory activities. Synthetic GCs are widely used for managing chronic inflammatory and autoimmune conditions, as immunosuppressants in transplantation, and as anti-tumor agents in certain hematological cancers. However, prolonged GC exposure can cause adverse effects. A detailed understanding of GCs' mechanisms of action may enable harnessing of their desirable actions while minimizing harmful effects. Here, we review the impact on the GC biology of microRNAs, small non-coding RNAs that post-transcriptionally regulate gene expression. Emerging evidence indicates that microRNAs modulate GC production by the adrenal glands and the cells' responses to GCs. Furthermore, GCs influence cell proliferation, survival, and function at least in part by regulating microRNA expression. We propose that the beneficial effects of GCs may be enhanced through combination with reagents targeting specific microRNAs.