Expression of microRNAs: potential molecular link between obesity, diabetes and cancer

Association between diabetes and cancer. Current mechanistic insights into the association and future challenges

Compelling pieces of epidemiological, clinical, and experimental research have demonstrated that Diabetes mellitus (DM) is a major risk factor associated with increased cancer incidence and mortality in many human neoplasms. In the pathophysiology context of DM, many of the main classical actors are relevant elements that can fuel the different steps of the carcinogenesis process. Hyperglycemia, hyperinsulinemia, metabolic inflammation, and dyslipidemia are among the classic contributors to this association. Furthermore, new emerging actors have received particular attention in the last few years, and compelling data support that the microbiome, the epigenetic changes, the reticulum endoplasmic stress, and the increased glycolytic influx also play important roles in promoting the development of many cancer types. The arsenal of glucose-lowering therapeutic agents used for treating diabetes is wide and diverse, and a growing body of data raised during the last two decades has tried to clarify the contribution of therapeutic agents to this association. However, this research area remains controversial, because some anti-diabetic drugs are now considered as either promotors or protecting elements. In the present review, we intend to highlight the compelling epidemiological shreds of evidence that support this association, as well as the mechanistic contributions of many of these potential pathological mechanisms, some controversial points as well as future challenges.

An Epidemiological Systematic Review with Meta-Analysis on Biomarker Role of Circulating MicroRNAs in Breast Cancer Incidence

Breast cancer (BC) is a multifactorial disease caused by an interaction between genetic predisposition and environmental exposures. MicroRNAs are a group of small non-coding RNA molecules, which seem to have a role either as tumor suppressor genes or oncogenes and seem to be related to cancer risk factors. We conducted a systematic review and meta-analysis to identify circulating microRNAs related to BC diagnosis, paying special attention to methodological problems in this research field. A meta-analysis was performed for microRNAs analyzed in at least three independent studies where sufficient data to make analysis were presented. Seventy-five studies were included in the systematic review. A meta-analysis was performed for microRNAs analyzed in at least three independent studies where sufficient data to make analysis were presented. Seven studies were included in the MIR21 and MIR155 meta-analysis, while four studies were included in the MIR10b metanalysis. The pooled sensitivity and specificity of MIR21 for BC diagnosis were 0.86 (95%CI 0.76-0.93) and 0.84 (95%CI 0.71-0.92), 0.83 (95%CI 0.72-0.91) and 0.90 (95%CI 0.69-0.97) for MIR155, and 0.56 (95%CI 0.32-0.71) and 0.95 (95%CI 0.88-0.98) for MIR10b, respectively. Several other microRNAs were found to be dysregulated, distinguishing BC patients from healthy controls. However, there was little consistency between included studies, making it difficult to identify specific microRNAs useful for diagnosis.

LncRNA MALAT1 Regulates Hyperglycemia Induced EMT in Keratinocyte via miR-205

Epithelial-to-mesenchymal transition (EMT) is critical to cutaneous wound healing. When skin is injured, EMT activates and mobilizes keratinocytes toward the wound bed, therefore enabling re-epithelialization. This process becomes dysregulated in patients with diabetes mellitus (DM). Long non-coding RNAs (lncRNAs) regulate many biological processes. LncRNA-metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) influences numerous cellular processes, including EMT. The objective of the current study is to explore the role of MALAT1 in hyperglycemia (HG)-induced EMT. The expression of MALAT1 was found to be significantly upregulated, while the expression of miR-205 was downregulated in diabetic wounds and high-glucose-treated HaCaT cells. The initiation of EMT in HaCaT cells from hyperglycemia was confirmed by a morphological change, the increased expression of CDH2, KRT10, and ACTA2, and the downregulation of CDH1. The knockdown of MALAT1 was achieved by transfecting a small interfering RNA (SiRNA). MALAT1 and miR-205 were found to modulate HG-induced EMT. MALAT1 silencing or miR-205 overexpression appears to attenuate hyperglycemia-induced EMT. Mechanistically, MALAT1 affects HG-induced EMT through binding to miR-205 and therefore inducing ZEB1, a critical transcription factor for EMT. In summary, lncRNA MALAT1 is involved in the hyperglycemia-induced EMT of human HaCaT cells. This provides a new perspective on the pathogenesis of diabetic wounds.

MicroRNA biomarkers of type 2 diabetes: evidence synthesis from meta-analyses and pathway modelling

AIMS/HYPOTHESIS

MicroRNAs are being sought as biomarkers for the early identification of type 2 diabetes. This study aimed to synthesise the evidence from microRNA-type 2 diabetes association studies and microRNA-regulated type 2 diabetes pathway delineation studies that met stringent quality criteria to identify and validate microRNAs of both statistical and biological significance as type 2 diabetes biomarkers.

METHODS

Eligible controlled studies on microRNA expression profiling of type 2 diabetes were retrieved from PubMed, ScienceDirect and Web of Science. MicroRNA-regulated type 2 diabetes pathway delineation studies were conducted by integrating and cross-verifying the data from miRTarBase, TransmiR, miRecords, TargetScanHuman, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and the Retraction Watch database. Before meta-analysis, quality assessment was performed according to the corresponding reporting guidelines for evidence-based medicine. To select the most statistically significant microRNAs, we conducted extensive meta-analyses according to the latest methodology. Subgroup and sensitivity analyses were carried out to further examine the microRNA candidates for their tissue specificity and blood fraction specificity and the robustness of the evidence. Signalling pathway impact analysis of dysregulated microRNAs identified from meta-analyses was performed to select biologically significant microRNAs that were enriched in our newly built microRNA-regulated pathways.

RESULTS

Of the 404 differentially expressed microRNAs identified in the 156 controlled profiling studies with a combined sample size of >15,000, only 60 were both consistently and significantly dysregulated in human type 2 diabetes. No microRNAs were both consistently and significantly dysregulated in multiple tissues according to subgroup analyses. In total, 58 microRNAs were found to be robust in sensitivity analyses. A total of 1966 pathway delineation studies were identified, including 3290 microRNA-target interactions, which were further combined with KEGG pathways, producing 225 microRNA-regulated pathways. Impact analysis found that 16 dysregulated microRNAs identified from extensive meta-analyses were statistically significantly enriched in the augmented KEGG type 2 diabetes pathway.

CONCLUSIONS/INTERPRETATION

Sixteen microRNAs met the criteria for biomarker selection. In terms of both significance and relevance, the order of priority for verification of these microRNAs is as follows: miR-29a-3p, miR-221-3p, miR-126-3p, miR-26a-5p, miR-503-5p, miR-100-5p, miR-101-3p, mIR-103a-3p, miR-122-5p, miR-199a-3p, miR-30b-5p, miR-130a-3p, miR-143-3p, miR-145-5p, miR-19a-3p and miR-311-3p.

REGISTRATION

PROSPERO registration number CRD42017081659.

Renal Cell Cancer and Obesity

Cancers are a frequent cause of morbidity and mortality. There are many risk factors for tumours, including advanced age, personal or family history of cancer, some types of viral infections, exposure to radiation and some chemicals, smoking and alcohol consumption, as well as obesity. Increasing evidence suggest the role of obesity in the initiation and progression of various cancers, including renal cell carcinoma. Since tumours require energy for their uncontrollable growth, it appears plausible that their initiation and development is associated with the dysregulation of cells metabolism. Thus, any state characterised by an intake of excessive energy and nutrients may favour the development of various cancers. There are many factors that promote the development of renal cell carcinoma, including hypoxia, inflammation, insulin resistance, excessive adipose tissue and adipokines and others. There are also many obesity-related alterations in genes expression, including DNA methylation, single nucleotide polymorphisms, histone modification and miRNAs that can promote renal carcinogenesis. This review focuses on the impact of obesity on the risk of renal cancers development, their aggressiveness and patients’ survival.

MicroRNA biomarkers of type 2 diabetes: A protocol for corroborating evidence by computational genomics and meta-analyses

BACKGROUND

Few microRNAs were found consistently dysregulated in type 2 diabetes (T2D) that would gain confidence from Big Pharma to develop diagnostic or therapeutic biomarkers. This study aimed to corroborate evidence from eligible microRNAs-T2D association studies according to stringent quality criteria covering both biological and statistical significance in T2D for biomarker development.

METHODS AND ANALYSES

Controlled microRNA expression profiling studies on human with T2D will be retrieved from PubMed, ScienceDirect, and Embase for selecting the statistically significant microRNAs according to pre-specified search strategies and inclusion criteria. Multiple meta-analyses with restricted maximum-likelihood estimation and empirical Bayes estimation under the random-effects model will be conducted by metafor package in R. Subgroup and sensitivity analyses further examine the microRNA candidates for their disease specificity, tissue specificity, blood fraction specificity, and statistical robustness of evidence. Biologically relevant microRNAs will then be selected through genomic database corroboration. Their association with T2D is further measured by area under the curve (AUC) of receive operating characteristic (ROC). Meta-analysis of AUC of potential biomarkers will also be conducted. Enrichment analysis on potential microRNA biomarkers and their target genes will be performed by iPathwayGuide and clusterProfiler, respectively. The corresponding reporting guidelines will be used to assess the quality of included studies according to their profiling methods (microarray, RT-PCR, and RNA-Seq).

ETHICS AND DISSEMINATION

No ethics approval is required since this study does not include identifiable personal patient data.

PROTOCOL REGISTRATION NUMBER

CRD42017081659.

Nutritive implications of dietary microRNAs: facts, controversies, and perspectives

As a group of non-coding RNA molecules, microRNAs have recently become more well-known due to their pivotal role in gene regulation. A large number of endogenous microRNAs naturally occur in the human body, and some of them act as regulatory targets of diet and its components. The wide presence of microRNAs in various food materials has inspired food scientists and nutritionists to explore their nutritive and bioactive significance. This article comprehensively reports updated insights into the accessibility, stability, absorbability, and bioactivity of dietary microRNAs by combining the current knowledge into figures and tables for reader's convenience. As one frontier in food science and nutrition, the research platform on dietary microRNAs is imperfect and even defective as indicated by the inconsistent and even contradictory results concluded by different investigations. The pros and cons as well as the limitations of current investigations have been critically discussed with attention chiefly paid to experimental designs and protocols. Moreover, future research directions have been recommended. Thus, this paper may not only provide a quick glance at the state-of-the-art of dietary microRNAs but also guide further research to clarify the present controversies and make the results more credible and persuasive.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Alteration of the esophageal microbiota in Barrett's esophagus and esophageal adenocarcinoma

The incidence of esophageal adenocarcinoma (EAC) has increased in recent decades, and its 5-year survival rate is less than 20%. As a well-established precursor, patients with Barrett's esophagus (BE) have a persistent risk of progression to EAC. Many researchers have already identified some factors that may contribute to the development of BE and EAC, and the identified risks include gastroesophageal reflux (GER), male sex, older age, central obesity, tobacco smoking, Helicobacter pylori (H. pylori) eradication, and the administration of proton pump inhibitors (PPIs) and antibiotics. The human gut harbors trillions of microorganisms, the majority of which are bacteria. These microorganisms benefit the human host in many ways, such as helping in digestion, assisting in the synthesis of certain vitamins, promoting the development of the gastrointestinal immune system, regulating metabolism and preventing invasion by specific pathogens. In contrast, microbial dysbiosis may play important roles in various diseases, such as inflammation and cancers. The composition of the microbiota located in the normal esophagus is relatively conserved without distinct microbial preferences in the upper, middle and lower esophagus. Six major phyla constitute the esophageal microbiota, including Firmicutes, Bacteroides, Actinobacteria, Proteobacteria, Fusobacteria and TM7, similar to the oral microbiota. Streptococcus dominates the esophageal microbiota. However, the microbiota varies in different esophageal diseases compared to that in the healthy esophagus. The type I microbiota, which is primarily composed of gram-positive bacteria, is closely associated with the normal esophagus, while type II microbiota has enriched gram-negative bacteria and is mainly associated with the abnormal esophagus. These increased gram-negative anaerobes/microaerophiles include Veillonella, Prevotella, Haemophilus, Neisseria, Granulicatella and Fusobacterium, many of which are associated with BE. The microbial diversity in the esophagus is decreased in EAC patients, and Lactobacillus fermentum is enriched compared to that in controls and BE patients. Furthermore, the microbiota may be associated with BE and EAC by interacting with their risk factors, including central obesity, GER, H. pylori, administration of PPIs and antibiotics. Therefore, a large gap in research must be bridged to elucidate the associations among these factors. Some studies have already proposed several potential mechanisms by which the microbiota participates in human carcinogenesis by complicated interactions with the human host immune system and signaling pathways. The activation of the LPS-TLR4-NF-κB pathway may contribute to inflammation and malignant transformation. This exciting field of gastrointestinal microbiota allows us to unravel the mystery of carcinogenesis from another perspective. Further studies are needed to explore whether the microbiota changes before or after disease onset, to improve our understanding of the pathogenesis, and to find novel targets for prevention, diagnosis and therapy, which could offer more cost-effective and relatively safe choices.

The emerging role of epigenetic modifiers in repair of DNA damage associated with chronic inflammatory diseases

At sites of chronic inflammation epithelial cells are exposed to high levels of reactive oxygen species (ROS), which can contribute to the initiation and development of many different human cancers. Aberrant epigenetic alterations that cause transcriptional silencing of tumor suppressor genes are also implicated in many diseases associated with inflammation, including cancer. However, it is not clear how altered epigenetic gene silencing is initiated during chronic inflammation. The high level of ROS at sites of inflammation is known to induce oxidative DNA damage in surrounding epithelial cells. Furthermore, DNA damage is known to trigger several responses, including recruitment of DNA repair proteins, transcriptional repression, chromatin modifications and other cell signaling events. Recruitment of epigenetic modifiers to chromatin in response to DNA damage results in transient covalent modifications to chromatin such as histone ubiquitination, acetylation and methylation and DNA methylation. DNA damage also alters non-coding RNA expression. All of these alterations have the potential to alter gene expression at sites of damage. Typically, these modifications and gene transcription are restored back to normal once the repair of the DNA damage is completed. However, chronic inflammation may induce sustained DNA damage and DNA damage responses that result in these transient covalent chromatin modifications becoming mitotically stable epigenetic alterations. Understanding how epigenetic alterations are initiated during chronic inflammation will allow us to develop pharmaceutical strategies to prevent or treat chronic inflammation-induced cancer. This review will focus on types of DNA damage and epigenetic alterations associated with chronic inflammatory diseases, the types of DNA damage and transient covalent chromatin modifications induced by inflammation and oxidative DNA damage and how these modifications may result in epigenetic alterations.

Obesity impacts the regulation of miR-10b and its targets in primary breast tumors

BACKGROUND

Obesity increases breast cancer (BC) risk in post-menopausal women by mostly unknown molecular mechanisms which may partly be regulated by microRNAs (miRNAs).

METHODS

We isolated RNA from paired benign and malignant biopsies from 83 BC patients and determined miRNA profiles in samples from 12 women at the extremes of the BMI distribution by RNA-seq. Candidates were validated in all samples. Associations between miR-10b expression and validated target transcript levels, and effects of targeted manipulation of miR-10b levels in a primary BC cell line on proliferation and invasion potential, were explored.

RESULTS

Of the 148 miRNAs robustly expressed in breast tissues, the levels of miR-21, miR-10b, miR-451a, miR-30c, and miR-378d were significantly associated with presence of cancer. Of these, miR-10b showed a stronger down-regulation in the tumors of the obese subjects, as opposed to the lean. In ductal but not lobular tumors, significant inverse correlations were observed between the tumor levels of miR-10b and miR-30c and the mRNA levels of cancer-relevant target genes SRSF1, PIEZO1, MAPRE1, CDKN2A, TP-53 and TRA2B, as well as tumor grade. Suppression of miR-10b levels in BT-549 primary BC-derived cells increased cell proliferation and invasive capacity, while exogenous miR-10b mimic decreased invasion. Manipulation of miR-10b levels also inversely affected the mRNA levels of miR-10b targets BCL2L11, PIEZO1 and NCOR2.

CONCLUSIONS

Our findings suggest that miR-10b may be a mediator between obesity and cancer in post-menopausal women, regulating several known cancer-relevant genes. MiR-10b expression may have diagnostic and therapeutic implications for the incidence and prognosis of BC in obese women.

Physiological markers and multimorbidity: A systematic review

Background:

Multimorbidity is the co-occurrence of two or more diseases in the same individual. One method to identify this condition at an early stage is the use of specific markers for various combinations of morbidities. Nonetheless, evidence related to physiological markers in multimorbidity is limited.

Objective:

The aim was to perform a systematic review to identify physiological markers associated with multimorbidity.

Design:

Articles available on PubMed, Register of Controlled Trials, Academic Search Premier, CINAHL, Scopus, SocINDEX, Web of Science, LILACS, and SciELO, from their inception to May 2018, were systematically searched and reviewed. The project was registered in PROSPERO under the number CRD42017055522.

Results:

The systematic search identified 922 papers. After evaluation, 18 articles were included in the full review reporting at least one physiological marker in coexisting diseases or which are strongly associated with the presence of multimorbidity in the future. Only five of these studies examined multimorbidity in general, identifying five physiological markers associated with multimorbidity, namely, dehydroepiandrosterone sulfate (DHEAS), interleukin 6 (IL-6), C-reactive protein (CRP), lipoprotein (Lp), and cystatin C (Cyst-C).

Conclusions:

There is a paucity of studies related to physiological markers in multimorbidity. DHEAS, IL-6, CRP, Lp, and Cyst-C could be the initial focus for further investigation of physiological markers related to multimorbidity.

Glucagon Like Peptide 1 and MicroRNA in Metabolic Diseases: Focusing on GLP1 Action on miRNAs

Glucagon like peptide 1 (GLP1) is an incretin hormone released from the enteroendocrine L-type cells of the lower gastrointestinal tract. The active isoforms of GLP1 are rapidly degraded (<2 min) by protease dipeptidyl peptidase-4 (DPP-4) after their release. Among its functions, GLP1 exerts a pivotal role in regulating glucose and lipid metabolism. In particular, GLP1 increases glucose stimulated insulin secretion, functional pancreatic β-cell mass and decreases glucagon secretion from pancreatic α-cells. GLP1 can also be a regulator of lipid and lipoprotein metabolism ameliorating diabetic dyslipidemia, liver steatosis, and promoting satiety. Interestingly, it has been found that GLP1 and GLP1 agonists can modulate the expression of different microRNAs (miRNAs), a ~22 nucleotides small non-coding RNAs, key modulators of protein expression. In particular, in pancreas, GLP1 increases the expression levels of miRNA-212 and miRNA-132, stimulating insulin secretion. Similarly, GLP1 decreases miRNA-338 levels, leading to an increase of pancreatic β-cell function, followed by an improvement of diabetic conditions. Moreover, GLP1 modulation of miRNAs expression in the liver regulates hepatic lipid storage. Indeed, GLP1 down-regulates miRNA-34a and miRNA-21 and up-regulates miRNA-200b and miRNA-200c expression in liver, reducing intra hepatic lipid accumulation and liver steatosis. Clinical and pre-clinical studies, discussed in this review, suggest that modulation of GLP1/miRNAs pathway may be a useful and innovative therapeutic strategy for prevention and treatment of metabolic disorders, such as diabetes mellitus and liver steatosis.

Role of MicroRNA Regulation in Obesity-Associated Breast Cancer: Nutritional Perspectives

Breast cancer is the most common malignancy diagnosed in women, and the incidence of breast cancer is increasing every year. Obesity has been identified as one of the major risk factors for breast cancer progression. The mechanisms by which obesity contributes to breast cancer development is not yet understood; however, there are a few mechanisms counted as potential producers of breast cancer in obesity, including insulin resistance, chronic inflammation and inflammatory cytokines, adipokines, and sex hormones. Recent emerging evidence suggests that alterations in microRNA (miRNA) expressions are found in several diseases, including breast cancer and obesity; however, miRNA roles in obesity-linked breast cancer are beginning to unravel. miRNAs are thought to be potential noninvasive biomarkers for diagnosis and prognosis of cancer patients with comorbid conditions of obesity as well as therapeutic targets. Recent studies have evidenced that nutrients and other dietary factors protect against cancer and obesity through modulation of miRNA expressions. Herein, we summarize a comprehensive overview of up-to-date information related to miRNAs and their molecular targets involved in obesity-associated breast cancer. We also address the mechanisms by which dietary factors modulate miRNA expression and its protective roles in obesity-associated breast cancer. It is hoped that this review would provide new therapeutic strategies for the treatment of obesity-associated breast cancer to reduce the burden of breast cancer.

An unbiased silencing screen in muscle cells identifies miR-320a, miR-150, miR-196b, and miR-34c as regulators of skeletal muscle mitochondrial metabolism

OBJECTIVE

Strategies improving skeletal muscle mitochondrial capacity are commonly paralleled by improvements in (metabolic) health. We and others previously identified microRNAs regulating mitochondrial oxidative capacity, but data in skeletal muscle are limited. Therefore, the present study aimed to identify novel microRNAs regulating skeletal muscle mitochondrial metabolism.

METHODS AND RESULTS

We conducted an unbiased, hypothesis-free microRNA silencing screen in C2C12 myoblasts, using >700 specific microRNA inhibitors, and investigated a broad panel of mitochondrial markers. After subsequent validation in differentiated C2C12 myotubes, and exclusion of microRNAs without a human homologue or with an adverse effect on mitochondrial metabolism, 19 candidate microRNAs remained. Human clinical relevance of these microRNAs was investigated by measuring their expression in human skeletal muscle of subject groups displaying large variation in skeletal muscle mitochondrial capacity.

CONCLUSION

The results show that that microRNA-320a, microRNA-196b-3p, microRNA-150-5p, and microRNA-34c-3p are tightly related to in vivo skeletal muscle mitochondrial function in humans and identify these microRNAs as targets for improving mitochondrial metabolism.

Association between hyperinsulinemia and increased risk of cancer death in nonobese and obese people: A population-based observational study

Obesity, metabolic syndrome and type 2 diabetes are associated with cancer-related mortality. We assessed whether hyperinsulinemia is a risk factor for cancer death in nonobese people without diabetes. We conducted a prospective cohort study using data from the National Health and Nutrition Examination Survey 1999-2010 and followed up the participants until December 31, 2011. For the primary analysis of cancer mortality, we used Cox proportional hazard models to estimate hazard ratios (HRs) in the participants with hyperinsulinemia and those without. Hyperinsulinemia was defined as a fasting insulin level of ≥10 μU/mL. To identify causes of deaths, the International Classification of Diseases, Tenth Revision codes were used. This study included 9,778 participants aged 20 years or older without diabetes or a history of cancer: 6,718 nonobese participants (2,057 with hyperinsulinemia [30.6%]) and 3,060 obese participants (2,303 with hyperinsulinemia [75.3%]). A total of 99.9% completed follow-up. Among all study participants, cancer mortality was significantly higher in those with hyperinsulinemia than in those without hyperinsulinemia (adjusted HR 2.04, 95% CI 1.24-3.34, p = 0.005). Similarly, among nonobese participants, multivariable analysis showed that cancer mortality was significantly higher in those with hyperinsulinemia than in those without (adjusted HR 1.89, 95% CI 1.07-3.35, p = 0.02). Considering that nonobese people with hyperinsulinemia were at higher risk of cancer mortality than those without hyperinsulinemia, improvement of hyperinsulinemia may be an important approach for preventing cancer regardless of the presence or absence of obesity.

Obesity Downregulates MicroRNA-126 Inducing Capillary Rarefaction in Skeletal Muscle: Effects of Aerobic Exercise Training

Background. We investigated the effects of exercise training (ET) on miR-126 levels and skeletal muscle angiogenesis in obese Zucker rats. Results. Zucker rats were randomly assigned to sedentary and swimming-trained groups: lean sedentary (LS) and trained (LTR); obese sedentary (OB) and trained (OBTR). The OB group displayed capillary rarefaction compared with the LS group. In contrast, ET increased the capillary/fiber ratio by 38% in the LTR group and normalized capillary rarefaction in the OBTR group. VEGF, PI3K, and eNOS levels were reduced in the skeletal muscle of the OB group. ET normalized VEGF, PI3K, and eNOS levels in OBTR, contributing to vascular network homeostasis. PI3KR2 inhibits PI3K, a key mediator of the VEGF signaling pathway. Obesity decreased miR-126 and increased PI3KR2 levels compared with the LS group. However, ET normalized miR-126 levels in the OBTR group versus the LS group and decreased expression of PI3KR2. Conclusion. Our findings show that obesity leads to skeletal muscle capillary rarefaction, which is regulated by decreased miR-126 levels and increased PI3KR2. Inversely, ET normalizes miR-126 levels and VEGF signaling and should be considered an important therapeutic strategy for vascular disorders.

Leptin and insulin up-regulate miR-4443 to suppress NCOA1 and TRAF4, and decrease the invasiveness of human colon cancer cells

Background

Obesity is a risk factor for colorectal cancer (CRC). Normal and tumor cells respond to metabolic hormones, such as leptin and insulin. Thus, obesity-associated resistance to these hormones likely leads to changes in gene expression and behavior of tumor cells. However, the mechanisms affected by leptin and insulin signaling in CRC cells remain mostly unknown.

Methods

We hypothesized that microRNAs (miRNAs) are involved in the regulation of tumorigenesis-related gene expression in CRC cells by leptin and insulin. To test this hypothesis, miRNA levels in the CRC-derived cell lines HCT-116, HT-29 and DLD-1 were profiled, following leptin and insulin treatment. Candidate miRNAs were validated by RT-qPCR. Predicted miRNA targets with known roles in cancer, were validated by immunoblots and reporter assays in HCT-116 cells. Transfection of HCT-116 cells with candidate miRNA mimic was used to test in vitro effects on proliferation and invasion.

Results

Of ~800 miRNAs profiled, miR-4443 was consistently up-regulated by leptin and insulin in HCT-116 and HT-29, but not in DLD-1, which lacked normal leptin receptor expression. Dose response experiments showed that leptin at 100 ng/ml consistently up-regulated miR-4443 in HCT-116 cells, concomitantly with a significant decrease in cell invasion ability. Transfection with miR-4443 mimic decreased invasion and proliferation of HCT-116 cells. Moreover, leptin and miR-4443 transfection significantly down-regulated endogenous NCOA1 and TRAF4, both predicted targets of miR-4443 with known roles in cancer metastasis. miR-4443 was found to directly regulate TRAF4 and NCOA1, as validated by a reporter assay. The up-regulation of miR-4443 by leptin or insulin was attenuated by the inhibition of MEK1/2.

Conclusions

Our findings suggest that miR-4443 acts in a tumor-suppressive manner by down-regulating TRAF4 and NCOA1 downstream of MEK-C/EBP-mediated leptin and insulin signaling, and that insulin and/or leptin resistance (e.g. in obesity) may suppress this pathway and increase the risk of metastatic CRC.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-016-2938-1) contains supplementary material, which is available to authorized users.

Tumour biology of obesity-related cancers: understanding the molecular concept for better diagnosis and treatment

Obesity continues to be a major global problem. Various cancers are related to obesity and proper understanding of their aetiology, especially their molecular tumour biology is important for early diagnosis and better treatment. Genes play an important role in the development of obesity. Few genes such as leptin, leptin receptor encoded by the db (diabetes), pro-opiomelanocortin, AgRP and NPY and melanocortin-4 receptors and insulin-induced gene 2 were linked to obesity. MicroRNAs control gene expression via mRNA degradation and protein translation inhibition and influence cell differentiation, cell growth and cell death. Overexpression of miR-143 inhibits tumour growth by suppressing B cell lymphoma 2, extracellular signal-regulated kinase-5 activities and KRAS oncogene. Cancers of the breast, uterus, renal, thyroid and liver are also related to obesity. Any disturbance in the production of sex hormones and insulin, leads to distortion in the balance between cell proliferation, differentiation and apoptosis. The possible mechanism linking obesity to cancer involves alteration in the level of adipokines and sex hormones. These mediators act as biomarkers for cancer progression and act as targets for cancer therapy and prevention. Interestingly, many anti-cancerous drugs are also beneficial in treating obesity and vice versa. We also reviewed the possible link in the mechanism of few drugs which act both on cancer and obesity. The present review may be important for molecular biologists, oncologists and clinicians treating cancers and also pave the way for better therapeutic options.

The Obesity-Breast Cancer Conundrum: An Analysis of the Issues

Breast cancer develops over a timeframe of 2-3 decades prior to clinical detection. Given this prolonged latency, it is somewhat unexpected from a biological perspective that obesity has no effect or reduces the risk for breast cancer in premenopausal women yet increases the risk for breast cancer in postmenopausal women. This conundrum is particularly striking in light of the generally negative effects of obesity on breast cancer outcomes, including larger tumor size at diagnosis and poorer prognosis in both pre- and postmenopausal women. This review and analysis identifies factors that may contribute to this apparent conundrum, issues that merit further investigation, and characteristics of preclinical models for breast cancer and obesity that should be considered if animal models are used to deconstruct the conundrum.

Food derived microRNAs

Foods provide fats, carbohydrates, and proteins as well as vitamins, minerals and trace elements. These dietary factors may influence cellular processes by regulating endogenous microRNA expression. MicroRNAs are non-coding regulatory molecules which affect gene expression at the post transcriptional level. It has been shown that plant and animal derived foods also contain microRNA. Yet, it is unclear if and to what extent plant and animal food derived microRNAs are absorbed by mammals. Thus, future studies need to better address absorption, tissue distribution and function of dietary plant and animal derived microRNAs in the context of human health and disease.

miRNA-30e regulates abnormal differentiation of small intestinal epithelial cells in diabetic mice by downregulating Dll4 expression

OBJECTIVES

Depression of the Notch/Hes1 pathway has been reported to play a role in abnormal differentiation of intestinal epithelial cells (IECs) in diabetes mellitus (DM). However, the mechanism by which this pathway influences IEC differentiation has remained unclear. In this study, we have investigated the role of microRNAs (miRNAs) in regulating the Notch/Hes1 pathway in IECs of DM mice.

MATERIALS AND METHODS

Integrated comparative miRNA microarray technology was used to determine the expression profile of miRNAs in IECs of DM mice. After bioinformatic analysis, an miRNA with altered expression levels, miRNA-30e, was identified as a candidate for regulating the Notch pathway in DM. A luciferase reporter assay confirmed that miRNA-30e targeted 3'-UTR of the Notch gene. The role of miRNA-30e in regulating Notch signalling was then explored by up- and downregulating its expression in vitro and in vivo.

RESULTS

Abnormal differentiation of IECs in DM mice was associated with reduced activity of the Dll4/NICD/Hes1 signal pathway. Based on bioinformatic analyses, increased expression of miRNA-30e was identified as a potential candidate for regulating Notch signalling. miRNA-30e targeted the 3'-UTR of Dll4 and downregulated Dll4 expression in primary IECs and IEC-6 cells. Exogenous miRNA-30e reduced activity of the Dll4/NICD/Hes1 pathway, and induced abnormal differentiation of IECs in normal mice. Conversely, treatment with miRNA-30e antagonist upregu-lated activity of the Dll4/NICD/Hes1 pathway in vivo, and normalized IEC differentiation in DM mice.

CONCLUSIONS

Increased levels of miRNA-30e downregulated activity of the Dll4/NICD/Hes1 signalling pathway by targeting the 3'-UTR of Dll4, which contributed to abnormal differentiation in small intestinal epithelia of DM mice.

Interplay Between Metabolism and Oncogenic Process: Role of microRNAs

Cancer is a complex disease that arises from the alterations in the composition and regulation of several genes leading to the disturbances in signaling pathways, resulting in the dysregulation of cell proliferation and death as well as the ability of transformed cells to invade the host tissue and metastasize. It is increasingly becoming clear that metabolic reprograming plays a critical role in tumorigenesis and metastasis. Therefore, targeting this phenotype is considered as a promising approach for the development of therapeutics and adjuvants. The process of metabolic reprograming is linked to the activation of oncogenes and/or suppression of tumor suppressor genes, which are further regulated by microRNAs (miRNAs) that play important roles in the interplay between oncogenic process and metabolic reprograming. Looking at the advances made in the recent past, it appears that the translation of knowledge from research in the areas of metabolism, miRNA, and therapeutic response will lead to paradigm shift in the management of this disease.

The Role of microRNAs in Mitochondria: Small Players Acting Wide

MicroRNAs (miRNAs) are short, single-stranded, non-coding RNA molecules that act as post-transcriptional gene regulators. They can inhibit target protein-coding genes, through repressing messenger RNA (mRNA) translation or promoting their degradation. miRNAs were initially found to be originated from nuclear genome and exported to cytosol; where they exerted most of their actions. More recently, miRNAs were found to be present specifically in mitochondria; even originated there from mitochondrial DNA, regulating in a direct manner genes coding for mitochondrial proteins, and consequently mitochondrial function. Since miRNAs are recognized as major players in several biological processes, they are being considered as a key to better understand, explain, and probably prevent/cure not only the pathogenesis of multifactorial diseases but also mitochondrial dysfunction and associated diseases. Here we review some of the molecular mechanisms purported for miRNA actions in several biological processes, particularly the miRNAs acting in mitochondria or in mitochondria-related mechanisms.

MicroRNA expression altered by diet: can food be medicinal?

As the link between metabolism and major disease processes becomes more well-defined, the identification of key molecular targets is leading to new therapeutic strategies. As a result, small non-coding RNA molecules that regulate gene expression via epigenetic alterations, microRNAs have been identified as regulators of these metabolic processes. In the last decade, dietary interventions have been used to change metabolism and to potentially alter disease progression and clinical outcomes. These interventions have been linked, at a molecular level, to microRNAs. This review will summarize the role of various dietary strategies on the expression of several microRNA families.

MicroRNAs in pathogenesis of breast cancer: Implications in diagnosis and treatment

MicroRNAs (miRNAs) are small non-coding RNAs generated by a two-step complex process and are post transcriptional negative regulators of their target mRNAs. Dysregulation of many of these miRNAs has been associated with tumorigenesis in various cancers including breast cancer. Aberrantly high expression of specific miRNAs in breast cancer cells is demonstrated to be linked with inhibition of tumor suppressor genes and promote tumorigenesis. They are classified as oncogenic miRNAs. However, the tumor suppressor miRNAs are downregulated in breast cancer cells, since their major targets are oncogenic mRNAs. Understanding mechanism of action of specific miRNAs in breast cancer cells can be utilized to develop newer anti-cancer therapies. Recently, newer techniques are also developed to detect abundance of specific miRNA in the blood plasma samples and can be used in early diagnosis or prognosis in breast cancer. In this review article, we have discussed several miRNAs dysregulated in breast cancer and their therapeutic potential.

Diabetes and cancer: two diseases with obesity as a common risk factor

There is a growing body of evidence to support a connection between diabetes (predominantly type 2), obesity and cancer. Multiple meta-analyses of epidemiological data show that people with diabetes are at increased risk of developing many different types of cancers, along with an increased risk of cancer mortality. Several pathophysiological mechanisms for this relationship have been postulated, including insulin resistance and hyperinsulinaemia, enhanced inflammatory processes, dysregulation of sex hormone production and hyperglycaemia. In addition to these potential mechanisms, a number of common risk factors, including obesity, may be behind the association between diabetes and cancer. Indeed, obesity is associated with an increased risk of cancer and diabetes. Abdominal adiposity has been shown to play a role in creating a systemic pro-inflammatory environment, which could result in the development of both diabetes and cancer. Here, we examine the relationship between diabetes, obesity and cancer, and investigate the potential underlying causes of increased cancer risk in individuals with diabetes. Current treatment recommendations for reducing the overall disease burden are also explored and possible areas for future research are considered.

Mechanisms of obesity-induced gastrointestinal neoplasia

Obesity is among the fastest growing diseases worldwide; treatment is inadequate, and associated disorders, including gastrointestinal cancers, have high morbidity and mortality. An increased understanding of the mechanisms of obesity-induced carcinogenesis is required to develop methods to prevent or treat these cancers. In this report, we review the mechanisms of obesity-associated colorectal, esophageal, gastric, and pancreatic cancers and potential treatment strategies.

MicroRNA 375 mediates palmitate-induced enteric neuronal damage and high-fat diet-induced delayed intestinal transit in mice

BACKGROUND & AIMS

A high-fat diet (HFD) can cause serious health problems, including alteration of gastrointestinal transit, the exact mechanism of which is not clear. Several microRNAs (miRNAs) are involved in energy homeostasis, lipid metabolism, and HFD-induced weight gain. We investigated the role of miRNAs in HFD-induced damage to the enteric nervous system.

METHODS

Male mice were fed a HFD (60% calories from fat) or regular diets (18% calories from fat) for 11 weeks. Mice on regular diets and HFDs were given intraperitoneal injections of Mir375 inhibitor or a negative control. Body weights, food intake, stool indices, and gastrointestinal transit (following Evans blue gavage) were measured. An enteric neuronal cell line (immorto-fetal enteric neuronal) and primary enteric neurons were used for in vitro studies.

RESULTS

HFD delayed intestinal transit, which was associated with increased apoptosis and loss of colonic myenteric neurons. Mice fed a low-palmitate HFD did not develop a similar phenotype. Palmitate caused apoptosis of enteric neuronal cells associated with mitochondrial dysfunction and endoplasmic reticulum stress. Palmitate significantly increased the expression of Mir375 in vitro; transfection of cells with a Mir375 inhibitor prevented the palmitate-induced enteric neuronal cell apoptosis. Mir375 expression was increased in myenteric ganglia of mice fed HFD and associated with decreased levels of Mir375 target messenger RNAs, including Pdk1. Systemic injection of a Mir375 inhibitor for 5 weeks prevented HFD-induced delay in intestinal transit and morphologic changes.

CONCLUSIONS

HFDs delay colonic transit, partly by inducing apoptosis in enteric neuronal cells. This effect is mediated by Mir375 and is associated with reduced levels of Pdk1. Mir375 might be targeted to increase survival of enteric neurons and gastrointestinal motility.

High-throughput sequencing of microRNAs in peripheral blood mononuclear cells: identification of potential weight loss biomarkers

Introduction

MicroRNAs (miRNAs) are being increasingly studied in relation to energy metabolism and body composition homeostasis. Indeed, the quantitative analysis of miRNAs expression in different adiposity conditions may contribute to understand the intimate mechanisms participating in body weight control and to find new biomarkers with diagnostic or prognostic value in obesity management.

Objective

The aim of this study was the search for miRNAs in blood cells whose expression could be used as prognostic biomarkers of weight loss.

Methods

Ten Caucasian obese women were selected among the participants in a weight-loss trial that consisted in following an energy-restricted treatment. Weight loss was considered unsuccessful when <5% of initial body weight (non-responders) and successful when >5% (responders). At baseline, total miRNA isolated from peripheral blood mononuclear cells (PBMC) was sequenced with SOLiD v4. The miRNA sequencing data were validated by RT-PCR.

Results

Differential baseline expression of several miRNAs was found between responders and non-responders. Two miRNAs were up-regulated in the non-responder group (mir-935 and mir-4772) and three others were down-regulated (mir-223, mir-224 and mir-376b). Both mir-935 and mir-4772 showed relevant associations with the magnitude of weight loss, although the expression of other transcripts (mir-874, mir-199b, mir-766, mir-589 and mir-148b) also correlated with weight loss.

Conclusions

This research addresses the use of high-throughput sequencing technologies in the search for miRNA expression biomarkers in obesity, by determining the miRNA transcriptome of PBMC. Basal expression of different miRNAs, particularly mir-935 and mir-4772, could be prognostic biomarkers and may forecast the response to a hypocaloric diet.

The role of microRNAs in breast cancer migration, invasion and metastasis

MicroRNAs (miRNAs) are a major class of small, noncoding RNA molecules that regulate gene expression by targeting mRNAs to trigger either translational repression or mRNA degradation. They have recently been more widely investigated due to their potential role as targets for cancer therapy. Many miRNAs have been implicated in several human cancers, including breast cancer. miRNAs are known to regulate cell cycle and development, and thus may serve as useful targets for exploration in anticancer therapeutics. The link between altered miRNA signatures and breast cancer development and metastasis can be observed either through the loss of tumor suppressor miRNAs, such as let-7s, miR-30a/31/34a/125s/200s/203/205/206/342 or the overexpression of oncogenic miRNAs, such as miR-10b/21/135a/155/221/222/224/373/520c in breast cancer cells. Some of these miRNAs have also been validated in tumor specimens of breast cancer patients, underscoring their potential roles in diagnostics, as well as targets for novel therapeutics for breast cancer. In this review article, we will provide an overview and update of our current understanding of the mode of action of several of these well characterized miRNAs in breast cancer models. Therefore, better understanding of the gene networks orchestrated by these miRNAs may help exploit the full potential of miRNAs in regards to cancer diagnosis, treatment, and therapeutics.

Mitochondria and Oxidative Stress in the Cardiorenal Metabolic Syndrome

Mitochondria play a fundamental role in the maintenance of normal structure, function, and survival of tissues. There is considerable evidence for mitochondrial dysfunction in association with metabolic diseases including insulin resistance, obesity, diabetes, and the cardiorenal metabolic syndrome. The phenomenon of reactive oxygen species (ROS)-induced ROS release through interactions between cytosolic and mitochondrial oxidative stress contributes to a vicious cycle of enhanced oxidative stress and mitochondrial dysfunction. Activation of the cytosolic and mitochondrial NADPH oxidase system, impairment of the mitochondrial electron transport, activation of p66shc pathway-targeting mitochondria, endoplasmic reticular stress, and activation of the mammalian target of the rapamycin-S6 kinase pathway underlie dysregulation of mitochondrial dynamics and promote mitochondrial oxidative stress. These processes are further modulated by acetyltransferases including sirtuin 1 and sirtuin 3, the former regulating nuclear acetylation and the latter regulating mitochondrial acetylation. The regulation of mitochondrial functions by microRNAs forms an additional layer of molecular control of mitochondrial oxidative stress. Alcohol further exacerbates mitochondrial oxidative stress induced by overnutrition and promotes the development of metabolic diseases.

MicroRNA, nutrition, and cancer prevention

MicroRNA (miRNA) are small noncoding RNA molecules that are involved in post-transcriptional gene silencing. Alterations in miRNA expression are observed in and may underlie many different human diseases, including cancer. In fact, miRNA have been shown to affect the hallmarks of cancer, including sustaining proliferative signaling, evading growth suppressors, resisting cell death, enabling replicative immortality, inducing angiogenesis, and activating invasion and metastasis. Genetic and epigenetic alterations may explain aberrant miRNA expression in cancer cells and may also contribute to cancer risk. It is now thought that by circulating through the bloodstream, miRNA can exert their effects at distant sites as well as within the cells of origin. Recent evidence suggests that nutrients and other bioactive food components protect against cancer through modulation of miRNA expression. Moreover, dietary factors have been shown to modify miRNA expression and their mRNA targets in various cancer processes, including apoptosis, cell cycle regulation, differentiation, inflammation, angiogenesis, and metastasis as well as pathways in stress response. Herein, we provide a brief overview of dietary modulation of miRNA expression and its potential role in cancer prevention. Understanding the affect of dietary factors on miRNA expression and function may provide insight on prevention strategies to reduce the burden of cancer.