Gene-chip studies of adipogenesis-regulated microRNAs in mouse primary adipocytes and human obesity

Molecular targets for management of diabetes: Remodelling of white adipose to brown adipose tissue

Diabetes mellitus is a disorder characterised metabolic dysfunction that results in elevated glucose level in the bloodstream. Diabetes is of two types, type1 and type 2 diabetes. Obesity is considered as one of the major reasons intended for incidence of diabetes hence it turns out to be essential to study about the adipose tissue which is responsible for fat storage in body. Adipose tissues play significant role in maintaining the balance between energy stabilization and homeostasis. The three forms of adipose tissue are - White adipose tissue (WAT), Brown adipose tissue (BAT) and Beige adipose tissue (intermediate form). The amount of BAT gets reduced, and WAT starts to increase with the age. WAT when exposed to certain stimuli gets converted to BAT by the help of certain transcriptional regulators. The browning of WAT has been a matter of study to treat the metabolic disorders and to initiate the expenditure of energy. The three main regulators responsible for the browning of WAT are PRDM16, PPARγ and PGC-1α via various cellular and molecular mechanism. Presented review article includes the detailed elaborative aspect of genes and proteins involved in conversion of WAT to BAT.

Modulation of adipose tissue metabolism by exosomes in obesity

Obesity and its related metabolic complications represent a significant global health challenge. Central to this is the dysregulation of glucolipid metabolism, with a predominant focus on glucose metabolic dysfunction in the current research, whereas adipose metabolism impairment garners less attention. Exosomes (EXs), small extracellular vesicles (EVs) secreted by various cells, have emerged as important mediators of intercellular communication and have the potential to be biomarkers, targets, and therapeutic tools for diverse diseases. In particular, EXs have been found to play a role in adipose metabolism by transporting cargoes such as noncoding RNAs (ncRNA), proteins, and other factors. This review article summarizes the current understanding of the role of EXs in mediating adipose metabolism disorders in obesity. It highlights their roles in adipogenesis (encompassing adipogenic differentiation and lipid synthesis), lipid catabolism, lipid transport, and white adipose browning. The insights provided by this review offer new avenues for developing exosome-based therapies to treat obesity and its associated comorbidities.

New Mediators in the Crosstalk between Different Adipose Tissues

Adipose tissue is a multifunctional organ that regulates many physiological processes such as energy homeostasis, nutrition, the regulation of insulin sensitivity, body temperature, and immune response. In this review, we highlight the relevance of the different mediators that control adipose tissue activity through a systematic review of the main players present in white and brown adipose tissues. Among them, inflammatory mediators secreted by the adipose tissue, such as classical adipokines and more recent ones, elements of the immune system infiltrated into the adipose tissue (certain cell types and interleukins), as well as the role of intestinal microbiota and derived metabolites, have been reviewed. Furthermore, anti-obesity mediators that promote the activation of beige adipose tissue, e.g., myokines, thyroid hormones, amino acids, and both long and micro RNAs, are exhaustively examined. Finally, we also analyze therapeutic strategies based on those mediators that have been described to date. In conclusion, novel regulators of obesity, such as microRNAs or microbiota, are being characterized and are promising tools to treat obesity in the future.

Whole-body deletion of Endospanin 1 protects from obesity-associated deleterious metabolic alterations

The importance of the proper localization of most receptors at the cell surface is often underestimated, although this feature is essential for optimal receptor response. Endospanin 1 (Endo1) (also known as OBRGRP or LEPROT) is a protein generated from the same gene as the human leptin receptor and regulates the trafficking of proteins to the surface, including the leptin receptor. The systemic role of Endo1 on whole-body metabolism has not been studied so far. Here, we report that general Endo1-KO mice fed a high-fat diet develop metabolically healthy obesity with lipid repartitioning in organs and preferential accumulation of fat in adipose tissue, limited systematic inflammation, and better controlled glucose homeostasis. Mechanistically, Endo1 interacts with the lipid translocase CD36, thus regulating its surface abundance and lipid uptake in adipocytes. In humans, the level of Endo1 transcripts is increased in the adipose tissue of patients with obesity, but low levels rather correlate with a profile of metabolically healthy obesity. We suggest here that Endo1, most likely by controlling CD36 cell surface abundance and lipid uptake in adipocytes, dissociates obesity from diabetes and that its absence participates in metabolically healthy obesity.

Metabolic disorders affecting the liver and heart: Therapeutic efficacy of miRNA-based therapies?

Liver and heart disease are major causes of death worldwide. It is known that metabolic alteration causing type 2 diabetes (T2D) and Nonalcoholic fatty liver (NAFLD) coupled with a derangement in lipid homeostasis, may exacerbate hepatic and cardiovascular diseases. Some pharmacological treatments can mitigate organ dysfunctions but the important side effects limit their efficacy leading often to deterioration of the tissues. It needs to develop new personalized treatment approaches and recent progresses of engineered RNA molecules are becoming increasingly viable as alternative treatments. This review outlines the current use of antisense oligonucleotides (ASOs), RNA interference (RNAi) and RNA genome editing as treatment for rare metabolic disorders. However, the potential for small non-coding RNAs to serve as therapeutic agents for liver and heart diseases is yet to be fully explored. Although miRNAs are recognized as biomarkers for many diseases, they are also capable of serving as drugs for medical intervention; several clinical trials are testing miRNAs as therapeutics for type 2 diabetes, nonalcoholic fatty liver as well as cardiac diseases. Recent advances in RNA-based therapeutics may potentially facilitate a novel application of miRNAs as agents and as druggable targets. In this work, we sought to summarize the advancement and advantages of miRNA selective therapy when compared to conventional drugs. In particular, we sought to emphasise druggable miRNAs, over ASOs or other RNA therapeutics or conventional drugs. Finally, we sought to address research questions related to efficacy, side-effects, and range of use of RNA therapeutics. Additionally, we covered hurdles and examined recent advances in the use of miRNA-based RNA therapy in metabolic disorders such as diabetes, liver, and heart diseases.

Circulating MiRNAs Are Associated With Low-grade Systemic Inflammation and Leptin Levels in Older Adults

Inflammaging refers to the low-grade systemic inflammation that occurs with aging present in chronic non-communicable diseases. MicroRNAs (miRNAs) are potential biomarkers for these diseases in older adults. This study aimed to assess the expression of 21 circulating miRNAs and their associations with inflammatory biomarkers in older adults. This cross-sectional study was performed with 200 individuals participating in ISA-Nutrition. The systemic low-grade inflammation score (SIS) was calculated from the plasma concentration of 10 inflammatory biomarkers. Circulating miRNA expression was assessed using the Fluidigm method. Wilcoxon-Mann-Whitney test was employed to determine differences in SIS among groups distributed according to sex and presence of MetS. Spearman's correlation was used to estimate correlations among SIS, leptin levels, miRNA expression, and variables of interest. Analyses were performed using software R version 4.2.3, with a significance level of 0.05. The final sample consisted of 193 individuals with a mean age of 69.1 (SE = 0.5) years, being 64.7% individuals with metabolic syndrome (MetS). Positive correlations were observed between leptin concentration and metabolic risk factors, and leptin concentration was higher in individuals with MetS compared to those without MetS. The expression of 15 circulating miRNAs was negatively correlated with leptin concentration. GLMs showed negative associations between miRNAs (miR-15a, miR-16, miR-223, miR-363, miR-532), leptin, and/or SIS values; and only miR-21 showed positive association with SIS values. The results suggest the presence of peripheral leptin resistance associated with low-grade inflammation and plasma expression of miRNAs in older adults. These findings suggest the potential role of miRNAs as biomarkers for cardiometabolic risk.

Circulatory miRNAs as Correlates of Elevated Intra-Pancreatic Fat Deposition in a Mixed Ethnic Female Cohort: The TOFI_Asia Study

Ectopic lipid accumulation, including intra-pancreatic fat deposition (IPFD), exacerbates type 2 diabetes risk in susceptible individuals. Dysregulated circulating microRNAs (miRNAs) have been identified as correlating with clinical measures of pancreatitis, pancreatic cancer and type 1 diabetes. The aim of the current study was therefore to examine the association between circulating abundances of candidate miRNAs, IPFD and liver fat deposition as quantified using magnetic resonance imaging (MRI) and spectroscopy (MRS). Asian Chinese (n = 34; BMI = 26.7 ± 4.2 kg/m2) and European Caucasian (n = 34; BMI = 28.0 ± 4.5 kg/m2) females from the TOFI_Asia cohort underwent MRI and MRS analysis of pancreas (MR-%IPFD) and liver fat (MR-%liver fat), respectively, to quantify ectopic lipid deposition. Plasma miRNA abundances of a subset of circulatory miRNAs associated with IPFD and liver fat deposition were quantified by qRT-PCR. miR-21-3p and miR-320a-5p correlated with MR-%IPFD, plasma insulin and HOMA2-IR, but not MR-%liver fat. MR-%IPFD remained associated with decreasing miR-21-3p abundance following multivariate regression analysis. miR-21-3p and miR-320a were demonstrated to be negatively correlated with MR-%IPFD, independent of ethnicity. For miR-21-3p, this relationship persists with the inclusion of MR-%liver fat in the model, suggesting the potential for a wider application as a specific circulatory correlate of IPFD.

A transcriptomic and proteomic atlas of obesity and type 2 diabetes in cynomolgus monkeys

Obesity and type 2 diabetes (T2D) remain major global healthcare challenges, and developing therapeutics necessitates using nonhuman primate models. Here, we present a transcriptomic and proteomic atlas of all the major organs of cynomolgus monkeys with spontaneous obesity or T2D in comparison to healthy controls. Molecular changes occur predominantly in the adipose tissues of individuals with obesity, while extensive expression perturbations among T2D individuals are observed in many tissues such as the liver and kidney. Immune-response-related pathways are upregulated in obesity and T2D, whereas metabolism and mitochondrial pathways are downregulated. Moreover, we highlight some potential therapeutic targets, including SLC2A1 and PCSK1 in obesity as well as SLC30A8 and SLC2A2 in T2D. Our study provides a resource for exploring the complex molecular mechanism of obesity and T2D and developing therapies for these diseases, with limitations including lack of hypothalamus, isolated islets of Langerhans, longitudinal data, and body fat percentage.

Novel insights regarding the role of noncoding RNAs in diabetes

Diabetes mellitus (DM) is a group of metabolic disorders defined by hyperglycemia induced by insulin resistance, inadequate insulin secretion, or excessive glucagon secretion. In 2021, the global prevalence of diabetes is anticipated to be 10.7% (537 million people). Noncoding RNAs (ncRNAs) appear to have an important role in the initiation and progression of DM, according to a growing body of research. The two major groups of ncRNAs implicated in diabetic disorders are miRNAs and long noncoding RNAs. miRNAs are single-stranded, short (17–25 nucleotides), ncRNAs that influence gene expression at the post-transcriptional level. Because DM has reached epidemic proportions worldwide, it appears that novel diagnostic and therapeutic strategies are required to identify and treat complications associated with these diseases efficiently. miRNAs are gaining attention as biomarkers for DM diagnosis and potential treatment due to their function in maintaining physiological homeostasis via gene expression regulation. In this review, we address the issue of the gradually expanding global prevalence of DM by presenting a complete and up-to-date synopsis of various regulatory miRNAs involved in these disorders. We hope this review will spark discussion about ncRNAs as prognostic biomarkers and therapeutic tools for DM. We examine and synthesize recent research that used novel, high-throughput technologies to uncover ncRNAs involved in DM, necessitating a systematic approach to examining and summarizing their roles and possible diagnostic and therapeutic uses.

The Role of Epicardial Adipose Tissue-Derived MicroRNAs in the Regulation of Cardiovascular Disease: A Narrative Review

Cardiovascular diseases have been leading cause of death worldwide for many decades, and obesity has been acknowledged as a risk factor for cardiovascular diseases. In the present review, human epicardial adipose tissue-derived miRNAs reported to be differentially expressed under pathologic conditions are discussed and summarized. The results of the literature review indicate that some of the epicardial adipose tissue-derived miRNAs are believed to be cardioprotective, while some others show quite the opposite effects depending on the underlying pathologic conditions. Furthermore, they suggest that that the epicardial adipose tissue-derived miRNAs have great potential as both a diagnostic and therapeutic modality. Nevertheless, mainly due to highly limited availability of human samples, it is very difficult to make any generalized claims on a given miRNA in terms of its overall impact on the cardiovascular system. Therefore, further functional investigation of a given miRNA including, but not limited to, the study of its dose effect, off-target effects, and potential toxicity is required. We hope that this review can provide novel insights to transform our current knowledge on epicardial adipose tissue-derived miRNAs into clinically viable therapeutic strategies for preventing and treating cardiovascular diseases.

Developmental programming: Adipose depot-specific regulation of non-coding RNAs and their relation to coding RNA expression in prenatal testosterone and prenatal bisphenol-A -treated female sheep

Inappropriate developmental exposure to steroids is linked to metabolic disorders. Prenatal testosterone excess or bisphenol A (BPA, an environmental estrogen mimic) leads to insulin resistance and adipocyte disruptions in female lambs. Adipocytes are key regulators of insulin sensitivity. Metabolic tissue-specific differences in insulin sensitivity coupled with adipose depot-specific changes in key mRNAs, were previously observed with prenatal steroid exposure. We hypothesized that depot-specific changes in the non-coding RNA (ncRNA) - regulators of gene expression would account for the direction of changes seen in mRNAs. Non-coding RNA (lncRNA, miRNA, snoRNA, snRNA) from various adipose depots of prenatal testosterone and BPA-treated animals were sequenced. Adipose depot-specific changes in the ncRNA that are consistent with the depot-specific mRNA expression in terms of directionality of changes and functional implications in insulin resistance, adipocyte differentiation and cardiac hypertrophy were found. Importantly, the adipose depot-specific ncRNA changes were model-specific and mutually exclusive, suggestive of different regulatory entry points in this regulation.

Droplet Digital PCR Quantification of Selected Intracellular and Extracellular microRNAs Reveals Changes in Their Expression Pattern during Porcine In Vitro Adipogenesis

Extracellular miRNAs have attracted considerable interest because of their role in intercellular communication, as well as because of their potential use as diagnostic and prognostic biomarkers for many diseases. It has been shown that miRNAs secreted by adipose tissue can contribute to the pathophysiology of obesity. Detailed knowledge of the expression of intracellular and extracellular microRNAs in adipocytes is thus urgently required. The system of in vitro differentiation of mesenchymal stem cells (MSCs) into adipocytes offers a good model for such an analysis. The aim of this study was to quantify eight intracellular and extracellular miRNAs (miR-21a, miR-26b, miR-30a, miR-92a, miR-146a, miR-148a, miR-199, and miR-383a) during porcine in vitro adipogenesis using droplet digital PCR (ddPCR), a highly sensitive method. It was found that only some miRNAs associated with the inflammatory process (miR-21a, miR-92a) were highly expressed in differentiated adipocytes and were also secreted by cells. All miRNAs associated with adipocyte differentiation were highly abundant in both the studied cells and in the cell culture medium. Those miRNAs showed a characteristic expression profile with upregulation during differentiation.

MicroRNA Expression Profiling Using Agilent One-Color Microarray

MicroRNA (miRNA) expression profiling is an important tool to identify miRNA regulation in physiological or pathological states. This technique has a large number of molecular diagnostic applications, including cancer, cardiovascular and autoimmune diseases, and forensics. To date, a multitude of high-throughput genomic approaches have been developed. Here, we focus on miRNA expression profiling by microarray using SurePrint technology, providing a description of both the workflow and methods for expression profiling by Agilent One-Color Microarray.

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

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

Urinary Exosomal MicroRNAs as Biomarkers for Obesity-Associated Chronic Kidney Disease

The early detection of chronic kidney disease (CKD) is key to reducing the burden of disease and rising costs of care. This need has spurred interest in finding new biomarkers for CKD. Ideal bi-omarkers for CKD should be: easy to measure; stable; reliably detected, even when interfering substances are present; site-specific based on the type of injury (tubules vs. glomeruli); and its changes in concentration should correlate with disease risk or outcome. Currently, no single can-didate biomarker fulfills these criteria effectively, and the mechanisms underlying kidney fibrosis are not fully understood; however, there is growing evidence in support of microRNA-mediated pro-cesses. Specifically, urinary exosomal microRNAs may serve as biomarkers for kidney fibrosis. In-creasing incidences of obesity and the recognition of obesity-associated CKD have increased interest in the interplay of obesity and CKD. In this review, we provide: (1) an overview of the current scope of CKD biomarkers within obese individuals to elucidate the genetic pathways unique to obesi-ty-related CKD; (2) a review of microRNA expression in obese individuals with kidney fibrosis in the presence of comorbidities, such as diabetes mellitus and hypertension; (3) a review of thera-peutic processes, such as diet and exercise, that may influence miR-expression in obesity-associated CKD; (4) a review of the technical aspects of urinary exosome isolation; and (5) future areas of research.

Green tea epigallocatechin gallate suppresses 3T3-L1 cell growth via microRNA-143/MAPK7 pathways

Green tea epigallocatechin gallate (EGCG) and microRNA (miRNA) molecules modulate obesity. Nevertheless, it is still unknown whether EGCG modulates fat cell growth via miRNA-related signaling. In this study, white preadipocytes were used to examine whether the antimitogenic effect of EGCG on fat cells is regulated by the miR-143/MAPK7 pathway. We showed that EGCG upregulated the levels of miR-143, but not miR-155, in 3T3-L1 preadipocytes. Moreover, EGCG downregulated MAPK7 mRNA and protein levels time- and dose-dependently. MAPK7 expression increased during 3T3-L1 cell proliferation. miR-143 overexpression in the absence of EGCG mimicked the effects of EGCG to suppress preadipocyte growth and MAPK7 expression, whereas knockdown of miR-143 antagonized the EGCG-altered levels of miR-143, MAPK7, and pERK1/2 and reversed the EGCG-inhibited cell growth. These findings suggest that EGCG inhibits 3T3-L1 cell growth via miR-143/MAPK7 pathway.

A Physiological Approach to Inflammatory Markers in Obesity

Obesity is one of the most critical health problems all over the world; it is associated with metabolic dysfunction and overnutrition. Changes in the physiological function of adipose tissue, leading to altered secretion of adipocytokines, inflammatory mediators release, and chronic low-grade inflammation, are seen in obesity. Macrophages, neutrophils, CD4+ and CD8+ T cells, B cells, natural killer T (NKT) cells, eosinophils, mast cells, and adipocytes are involved in the inflammatory response that occurs during obesity. Various inflammatory markers are released from these cells. In this chapter, we will mention inflammatory mechanisms and markers of obesity.

Adipose tissue-specific ablation of Ces1d causes metabolic dysregulation in mice

Carboxylesterase 1d (Ces1d) is a crucial enzyme with a wide range of activities in multiple tissues. It has been reported to localize predominantly in ER. Here, we found that Ces1d levels are significantly increased in obese patients with type 2 diabetes. Intriguingly, a high level of Ces1d translocates onto lipid droplets where it digests the lipids to produce a unique set of fatty acids. We further revealed that adipose tissue-specific Ces1d knock-out (FKO) mice gained more body weight with increased fat mass during a high fat-diet challenge. The FKO mice exhibited impaired glucose and lipid metabolism and developed exacerbated liver steatosis. Mechanistically, deficiency of Ces1d induced abnormally large lipid droplet deposition in the adipocytes, causing ectopic accumulation of triglycerides in other peripheral tissues. Furthermore, loss of Ces1d diminished the circulating free fatty acids serving as signaling molecules to trigger the epigenetic regulations of energy metabolism via lipid-sensing transcriptional factors, such as HNF4α. The metabolic disorders induced an unhealthy microenvironment in the metabolically active tissues, ultimately leading to systemic insulin resistance.

An adipose lncRAP2-Igf2bp2 complex enhances adipogenesis and energy expenditure by stabilizing target mRNAs

lncRAP2 is a conserved cytoplasmic lncRNA enriched in adipose tissue and required for adipogenesis. Using purification and in vivo interactome analyses, we show that lncRAP2 forms complexes with proteins that stabilize mRNAs and modulate translation, among them Igf2bp2. Surveying transcriptome-wide Igf2bp2 client mRNAs in white adipocytes reveals selective binding to mRNAs encoding adipogenic regulators and energy expenditure effectors, including adiponectin. These same target proteins are downregulated when either Igf2bp2 or lncRAP2 is downregulated, hindering adipocyte lipolysis. Proteomics and ribosome profiling show this occurs predominantly through mRNA accumulation, as lncRAP2-Igf2bp2 complex binding does not impact translation efficiency. Phenome-wide association studies reveal specific associations of genetic variants within both lncRAP2 and Igf2bp2 with body mass and type 2 diabetes, and both lncRAP2 and Igf2bp2 are suppressed in adipose depots of obese and diabetic individuals. Thus, the lncRAP2-Igf2bp2 complex potentiates adipose development and energy expenditure and is associated with susceptibility to obesity-linked diabetes.

Identification and Functional Verification Reveals that miR-195 Inhibiting THRSP to Affect Fat Deposition in Xinyang Buffalo

The buffalo population is extensive in China, but its meat quality is relatively inferior. Therefore, improving meat quality should be one of the breeding goals. microRNAs (miRNAs) play an essential regulatory role in the post-transcriptional expression of genes. Some studies have reported their function regulating genes related to fat deposition and adipocyte differentiation in cattle, but there is limited reports in buffalo. We performed small RNA transcriptome sequencing of Xinyang buffalo adipose tissue between calves and adults in this study. As a result, 282 mature miRNAs were significantly differentially expressed, and co-expression analysis showed that 454 miRNAs were significantly associated with developmental stages. Target gene identification, GO (gene ontology) annotation, and KEGG analysis of miRNAs showed that miR-195, miR-192, and miR-24-3p could target key genes for lipogenesis and thus regulate adipose deposition and differentiation. Among them, miR-195 was significantly upregulated in adipose tissue and induced adipocytes of adult buffaloes, and its overexpression significantly inhibited lipid accumulation in primary adipocytes. Dual-luciferase reporter gene analysis showed that miR-195 reduced the expression of thyroid hormone response protein (THRSP) by targeting its 3′ untranslated terminal region, suggesting that miR-195 may inhibit lipid accumulation in adipocytes by regulating THRSP. The results confirmed the reliability of predictive screening of miRNAs and provided theoretical support for buffalo fattening.

miR-21 mimic blocks obesity in mice: A novel therapeutic option

MicroRNAs (miRNAs) are promising drug targets for obesity and metabolic disorders. Recently, miRNA mimics are providing a unique mechanism of action that guides the process for drug development and sets out the context of their therapeutic application. miRNA (miR)-21 expression in white adipose tissue (WAT) has been associated with obesity. We aimed to analyze miR-21 expression levels in relation to diabetes and obesity to determine the effect that miR-21 mimic has on processes involved in WAT functionality, to dissect the underlying molecular mechanisms, and to study the potential therapeutic application of the miR-21 mimic against obesity. We found higher miR-21 levels in WAT from non-diabetic obese compared to normoweight humans and mice. Moreover, in 3T3-L1 adipocytes, miR-21 mimic affect genes involved in WAT functionality regulation and significantly increase the expression of genes involved in browning and thermogenesis. Interestingly, in vivo treatment with the miR-21 mimic blocked weight gain induced by a high-fat diet in obese mice, without modifying food intake or physical activity. This was associated with metabolic enhancement, WAT browning, and brown adipose tissue (AT) thermogenic programming through vascular endothelial growth factor A (VEGF-A), p53, and transforming growth factor β1 (TGF-β1) signaling pathways. Our findings suggest that miR-21 mimic-based therapy may provide a new opportunity to therapeutically manage obesity and consequently, its associated alterations.

Identification of core gene in obese type 2 diabetes patients using bioinformatics analysis

Objectives Adipocytes and adipocyte lipid metabolism are closely related with obesity and type 2 diabetes, but the molecular mechanism still needs further investigation. The aim of this study is to discover the adipocyte genes and pathways involved in obesity and type 2 diabetes using bioinformatics analysis.

Methods The GSE27951 gene expression profile was obtained. Software and online tools (STRING, Cytoscape, BioGPS, CTD, and FunRich) were used to identify core genes.21 human subcutaneous adipose samples, with 10 from type 2 diabetic patients and 11 from normal controls, were included in these analyses.

Results 184 differentially expressed genes (DEGs) including 42 up-regulated genes and 142 down-regulated genes were found to be enriched in metabolism, receptor activity, collagen type IV and glutamine biosynthesis I pathway by using the enrichment analysis. Seven hub genes were identified from the PPI network using various software (Cytoscape, STRING, BioGPS, and CTD). Four core genes (COL4A2, ACACB, GLUL, and CD36) were found to be highly expressed in subcutaneous adipose tissue of obese patients accompanying type 2 diabetes.

Conclusion COL4A2, ACACB, GLUL and CD36 might be the core molecular biomarkers of obesity in patients with or without type 2 diabetes.

microRNAs in Human Adipose Tissue Physiology and Dysfunction

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

miR-F4-C12 Functions on the Regulation of Adipose Accumulation by Targeting PIK3R1 in Castrated Male Pigs

Simple Summary

MicroRNAs play crucial roles in regulating adipogenesis and fat storage; their role in regulating castrated male pig adipose growth is worth elucidating. Four nine-fold differentially expressed miRNAs were selected to investigate their functions on the regulation of adipose development based on our previous study. In 3T3-L1 cells and backfat tissues of castrated and intact male pigs, miR-F4-C12 was identified as involved in the adipose development using qRT-PCR and oil O staining. PIK3R1 was proposed by the TargetScan, miRDB and starBase as a target of miR-F4-C12 and verified through a dual-luciferase reporter assay and Western blot. These results revealed that miR-F4-C12 may regulate adipose accumulation in castrated male pigs by targeting PIK3R1. Our data provide a valuable foundation to understand the molecular mechanisms involved in adipose tissue metabolism to castration-induced sex hormone deficiency.

Abstract

MicroRNAs (miRNAs) constitute small regulatory molecules for a wide array of biological activities (18~24 nucleotides in length), including adipogenesis and adipose deposition. Their effect is, however, incompletely defined in inducing fat accumulation in castrated male pigs. Based on our study, four nine-times miRNAs were selected to examine their functions in adipose formation activities. In 3T3-L1 cells and backfat tissues of castrated and intact male pigs, miR-F4-C12 was identified as a factor in adipose development utilizing quantitative real-time PCR (qRT-PCR). Further, miR-F4-C12 was identified to promote fat development, suggesting that miR-F4-C12 was involved in adipogenesis. Moreover, phosphoinositide-3-kinase regulatory subunit 1 (PIK3R1) was proposed by the TargetScan, miRDB and starBase as a target of miR-F4-C12 and verified through a two-luciferase reporter assay. The over-expression of miR-F4-C12 dramatically decreases the PIK3R1 protein level in 3T3-L1 cells. The mRNA and protein levels of PIK3R1 in castrated pigs are reduced relative to intact pigs, providing further evidence that PIK3R1 is involved in regulating adipose accumulation. These results suggest that miR-F4-C12 involves adipose development and may regulate subcutaneous adipose tissue accumulation by targeting PIK3R1 in castrated male pigs.

Sex-Dependent Changes of miRNA Levels in the Hippocampus of Adrenalectomized Rats Following Acute Corticosterone Administration

We explored sex-biased effects of the primary stress glucocorticoid hormone corticosterone on the miRNA expression profile in the rat hippocampus. Adult adrenalectomized (ADX) female and male rats received a single corticosterone (10 mg/kg) or vehicle injection, and after 6 h, hippocampi were collected for miRNA, mRNA, and Western blot analyses. miRNA profiling microarrays showed a basal sex-biased miRNA profile in ADX rat hippocampi. Additionally, acute corticosterone administration triggered a sex-biased differential expression of miRNAs derived from genes located in several chromosomes and clusters on the X and 6 chromosomes. Putative promoter analysis unveiled that most corticosterone-responsive miRNA genes contained motifs for either direct or indirect glucocorticoid actions in both sexes. The evaluation of transcription factors indicated that almost 50% of miRNA genes sensitive to corticosterone in both sexes was under glucocorticoid receptor regulation. Transcription factor-miRNA regulatory network analyses identified several transcription factors that regulate, activate, or repress miRNA expression. Validated target mRNA analysis of corticosterone-responsive miRNAs showed a more complex miRNA-mRNA interaction network in males compared to females. Enrichment analysis revealed that several hippocampal-relevant pathways were affected in both sexes, such as neurogenesis and neurotrophin signaling. The evaluation of selected miRNA targets from these pathways displayed a strong sex difference in the hippocampus of ADX-vehicle rats. Corticosterone treatment did not change the levels of the miRNA targets and their corresponding tested proteins. Our data indicate that corticosterone exerts a sex-biased effect on hippocampal miRNA expression, which may engage in sculpting the basal sex differences observed at higher levels of hippocampal functioning.

Non-Coding RNAs: Novel Players in Insulin Resistance and Related Diseases

The rising prevalence of metabolic diseases related to insulin resistance (IR) have stressed the urgent need of accurate and applicable tools for early diagnosis and treatment. In the last decade, non-coding RNAs (ncRNAs) have gained growing interest because of their potential role in IR modulation. NcRNAs are variable-length transcripts which are not translated into proteins but are involved in gene expression regulation. Thanks to their stability and easy detection in biological fluids, ncRNAs have been investigated as promising diagnostic and therapeutic markers in metabolic diseases, such as type 2 diabetes mellitus (T2D), obesity and non-alcoholic fatty liver disease (NAFLD). Here we review the emerging role of ncRNAs in the development of IR and related diseases such as obesity, T2D and NAFLD, and summarize current evidence concerning their potential clinical application.

Mechanisms linking endoplasmic reticulum (ER) stress and microRNAs to adipose tissue dysfunction in obesity

Over accumulation of lipids in adipose tissue disrupts metabolic homeostasis by affecting cellular processes. Endoplasmic reticulum (ER) stress is one such process affected by obesity. Biochemical and physiological alterations in adipose tissue due to obesity interfere with adipose ER functions causing ER stress. This is in line with increased irregularities in other cellular processes such as inflammation and autophagy, affecting overall metabolic integrity within adipocytes. Additionally, microRNAs (miRNAs), which can post-transcriptionally regulate genes, are differentially modulated in obesity. A better understanding and identification of such miRNAs could be used as novel therapeutic targets to fight against diseases. In this review, we discuss ways in which ER stress participates as a common molecular process in the pathogenesis of obesity-associated metabolic disorders. Moreover, our review discusses detailed underlying mechanisms through which ER stress and miRNAs contribute to metabolic alteration in adipose tissue in obesity. Hence, identifying mechanistic involvement of miRNAs-ER stress cross-talk in regulating adipose function during obesity could be used as a potential therapeutic approach to combat chronic diseases, including obesity.

Assessing the Contribution of Relative Macrophage Frequencies to Subcutaneous Adipose Tissue

Background: Macrophages play an important role in regulating adipose tissue function, while their frequencies in adipose tissue vary between individuals. Adipose tissue infiltration by high frequencies of macrophages has been linked to changes in adipokine levels and low-grade inflammation, frequently associated with the progression of obesity. The objective of this project was to assess the contribution of relative macrophage frequencies to the overall subcutaneous adipose tissue gene expression using publicly available datasets.

Methods: Seven publicly available microarray gene expression datasets from human subcutaneous adipose tissue biopsies (n = 519) were used together with TissueDecoder to determine the adipose tissue cell-type composition of each sample. We divided the subjects in four groups based on their relative macrophage frequencies. Differential gene expression analysis between the high and low relative macrophage frequencies groups was performed, adjusting for sex and study. Finally, biological processes were identified using pathway enrichment and network analysis.

Results: We observed lower frequencies of adipocytes and higher frequencies of adipose stem cells in individuals characterized by high macrophage frequencies. We additionally studied whether, within subcutaneous adipose tissue, interindividual differences in the relative frequencies of macrophages were reflected in transcriptional differences in metabolic and inflammatory pathways. Adipose tissue of individuals with high macrophage frequencies had a higher expression of genes involved in complement activation, chemotaxis, focal adhesion, and oxidative stress. Similarly, we observed a lower expression of genes involved in lipid metabolism, fatty acid synthesis, and oxidation and mitochondrial respiration.

Conclusion: We present an approach that combines publicly available subcutaneous adipose tissue gene expression datasets with a deconvolution algorithm to calculate subcutaneous adipose tissue cell-type composition. The results showed the expected increased inflammation gene expression profile accompanied by decreased gene expression in pathways related to lipid metabolism and mitochondrial respiration in subcutaneous adipose tissue in individuals characterized by high macrophage frequencies. This approach demonstrates the hidden strength of reusing publicly available data to gain cell-type-specific insights into adipose tissue function.

Functions of amyloid precursor protein in metabolic diseases

Amyloid precursor protein (APP) is a transmembrane precursor protein that is widely expressed in the central nervous system and peripheral tissues in the liver and pancreas, adipose tissue, and myotubes. APP can be cleaved by proteases in two different ways to produce a variety of short peptides, each with different physiological properties and functions. APP peptides generated by non-amyloidogenic processing can positively influence metabolism, while the peptides produced by amyloidogenic processing have the opposite effects. Here, we summarize the regulatory effects of APP and its cleavage peptides on metabolism in the central nervous system and peripheral tissues. In addition, abnormal expression and function of APP and APP-derived peptides are associated with metabolic diseases, such as type 2 diabetes, obesity, non-alcoholic fatty liver disease, and cardiovascular disease, and cancers. Pharmacological intervention of APP function or reduction of the production of peptides derived from amyloidogenic processing may be effective strategies for the prevention and treatment of Alzheimer's disease, and they may also provide new guidance for the treatment of metabolic diseases.

D-Mannose Inhibits Adipogenic Differentiation of Adipose Tissue-Derived Stem Cells via the miR669b/MAPK Pathway

The adipogenic differentiation of adipose tissue-derived stem cells (ADSCs) plays an important role in the process of obesity and host metabolism. D-Mannose shows a potential regulating function for fat tissue expansion and glucose metabolism. To explore the mechanisms through which D-mannose affects the adipogenic differentiation of adipose-derived stem cells in vitro, we cultured the ADSCs with adipogenic medium inducement containing D-mannose or glucose as the control. The adipogenic differentiation specific markers Pparg and Fabp4 were determined by real-time PCR. The Oil Red O staining was applied to measure the lipid accumulation. To further explore the mechanisms, microarray analysis was performed to detect the differences between glucose-treated ADSCs (G-ADSCs) and D-mannose-treated ADSCs (M-ADSCs) in the gene expression level. The microarray data were further analyzed by a Venn diagram and Gene Set Enrichment Analysis (GSEA). MicroRNA inhibitor transfection was used to confirm the role of key microRNA. Results. D-Mannose intervention significantly inhibited the adipogenic differentiation of ADSCs, compared with the glucose intervention. Microarray showed that D-mannose increased the expression of miR669b, which was an inhibitor of adipogenesis. In addition, GSEA and western blot suggested that D-mannose suppressed the adipogenic differentiation via inhibiting the MAPK pathway and further inhibited the expression of proteins related to glucose metabolism and tumorigenesis. Conclusion. D-Mannose inhibits adipogenic differentiation of ADSCs via the miR669b/MAPK signaling pathway and may be further involved in the regulation of glucose metabolism and the inhibition of tumorigenesis.

Does microRNA Perturbation Control the Mechanisms Linking Obesity and Diabetes? Implications for Cardiovascular Risk

Metabolic disorders such as obesity and type 2 diabetes (T2D) are considered the major risk factors for the development of cardiovascular diseases (CVD). Although the pathological mechanisms underlying the mutual development of obesity and T2D are difficult to define, a better understanding of the molecular aspects is of utmost importance to identify novel therapeutic targets. Recently, a class of non-coding RNAs, called microRNAs (miRNAs), are emerging as key modulators of metabolic abnormalities. There is increasing evidence supporting the role of intra- and extracellular miRNAs as determinants of the crosstalk between adipose tissues, liver, skeletal muscle and other organs, triggering the paracrine communication among different tissues. miRNAs may be considered as risk factors for CVD due to their correlation with cardiovascular events, and in particular, may be related to the most prominent risk factors. In this review, we describe the associations observed between miRNAs expression levels and the most common cardiovascular risk factors. Furthermore, we sought to depict the molecular aspect of the interplay between obesity and diabetes, investigating the role of microRNAs in the interorgan crosstalk. Finally, we discussed the fascinating hypothesis of the loss of protective factors, such as antioxidant defense systems regulated by such miRNAs.

Protein Arginine Methyltransferase PRMT5 Regulates Fatty Acid Metabolism and Lipid Droplet Biogenesis in White Adipose Tissues

The protein arginine methyltransferase 5 (PRMT5) is an emerging regulator of cancer and stem cells including adipogenic progenitors. Here, a new physiological role of PRMT5 in adipocytes and systemic metabolism is reported. Conditional knockout mice were generated to ablate the Prmt5 gene specifically in adipocytes (Prmt5AKO). The Prmt5AKO mice exhibit sex- and depot-dependent progressive lipodystrophy that is more pronounced in females and in visceral (than subcutaneous) white fat. The lipodystrophy and associated energy imbalance, hyperlipidemia, hepatic steatosis, glucose intolerance, and insulin resistance are exacerbated by high-fat-diet. Mechanistically, Prmt5 methylates and releases the transcription elongation factor SPT5 from Berardinelli-Seip congenital lipodystrophy 2 (Bscl2, encoding Seipin) promoter, and Prmt5AKO disrupts Seipin-mediated lipid droplet biogenesis. Prmt5 also methylates Sterol Regulatory Element-Binding Transcription Factor 1a (SREBP1a) and promotes lipogenic gene expression, and Prmt5AKO suppresses SREBP1a-dependent fatty acid metabolic pathways in adipocytes. Thus, PRMT5 plays a critical role in regulating lipid metabolism and lipid droplet biogenesis in adipocytes.

The Role of microRNAs in Metabolic Syndrome-Related Oxidative Stress

Oxidative stress (OxS) is the cause and the consequence of metabolic syndrome (MetS), the incidence and economic burden of which is increasing each year. OxS triggers the dysregulation of signaling pathways associated with metabolism and epigenetics, including microRNAs, which are biomarkers of metabolic disorders. In this review, we aimed to summarize the current knowledge regarding the interplay between microRNAs and OxS in MetS and its components. We searched PubMed and Google Scholar to summarize the most relevant studies. Collected data suggested that different sources of OxS (e.g., hyperglycemia, insulin resistance (IR), hyperlipidemia, obesity, proinflammatory cytokines) change the expression of numerous microRNAs in organs involved in the regulation of glucose and lipid metabolism and endothelium. Dysregulated microRNAs either directly or indirectly affect the expression and/or activity of molecules of antioxidative signaling pathways (SIRT1, FOXOs, Keap1/Nrf2) along with effector enzymes (e.g., GPx-1, SOD1/2, HO-1), ROS producers (e.g., NOX4/5), as well as genes of numerous signaling pathways connected with inflammation, insulin sensitivity, and lipid metabolism, thus promoting the progression of metabolic imbalance. MicroRNAs appear to be important epigenetic modifiers in managing the delicate redox balance, mediating either pro- or antioxidant biological impacts. Summarizing, microRNAs may be promising therapeutic targets in ameliorating the repercussions of OxS in MetS.

MicroRNAs and obesity-induced endothelial dysfunction: key paradigms in molecular therapy

The endothelium plays a pivotal role in maintaining vascular health. Obesity is a global epidemic that has seen dramatic increases in both adult and pediatric populations. Obesity perturbs the integrity of normal endothelium, leading to endothelial dysfunction which predisposes the patient to cardiovascular diseases. MicroRNAs (miRNAs) are short, single-stranded, non-coding RNA molecules that play important roles in a variety of cellular processes such as differentiation, proliferation, apoptosis, and stress response; their alteration contributes to the development of many pathologies including obesity. Mediators of obesity-induced endothelial dysfunction include altered endothelial nitric oxide synthase (eNOS), Sirtuin 1 (SIRT1), oxidative stress, autophagy machinery and endoplasmic reticulum (ER) stress. All of these factors have been shown to be either directly or indirectly caused by gene regulatory mechanisms of miRNAs. In this review, we aim to provide a comprehensive description of the therapeutic potential of miRNAs to treat obesity-induced endothelial dysfunction. This may lead to the identification of new targets for interventions that may prevent or delay the development of obesity-related cardiovascular disease.

Dysregulation of Amyloid Precursor Protein Impairs Adipose Tissue Mitochondrial Function and Promotes Obesity

Mitochondrial function in white adipose tissue (WAT) is an important yet understudied aspect in adipocyte biology. Here, we report a role for amyloid precursor protein (APP) in compromising WAT mitochondrial function through a high-fat diet (HFD)-induced, unconventional mis-localization to mitochondria that further promotes obesity. In humans and mice, obese conditions significantly induce APP production in WAT and its enrichment in mitochondria. Mechanistically, a HFD-induced dysregulation of signal recognition particle subunit 54c is responsible for the mis-targeting of APP to adipocyte mitochondria. Mis-localized APP blocks the protein import machinery, leading to mitochondrial dysfunction in WAT. Adipocyte-specific and mitochondria-targeted APP overexpressing mice display increased body mass and reduced insulin sensitivity, along with dysfunctional WAT due to a dramatic hypertrophic program in adipocytes. Elimination of adipocyte APP rescues HFD-impaired mitochondrial function with significant protection from weight gain and systemic metabolic deficiency. Our data highlights an important role of APP in modulating WAT mitochondrial function and obesity-associated metabolic dysfunction.

Gene Expression Profiling of MicroRNAs in HPV-Induced Warts and Normal Skin

: Infection with the human papillomavirus (HPV) is a common occurrence among the global population, with millions of new cases emerging on an annual basis. Dysregulated microRNA (miRNA) expression is increasingly being identified to play a role in a number of different diseases, especially in the context of high-risk HPV infection. The present study investigated the miRNA expression profiles of warts induced by low-risk HPV. In warts, miR-27b, miR-24-1, miR-3654, miR-647, and miR-1914 were downregulated while miR-612 was upregulated compared to normal skin. Using miRTargetLink Human, experimentally supported evidence was obtained showing that miR-27b targeted the vascular endothelial growth factor C (VEGFC) and CAMP-responsive element binding protein 1 (CREB1) genes. The VEGFC and CREB1 genes have been reported to be involved in tumorigenesis and wart formation, respectively. Similarly, the oxidized low-density lipoprotein receptor 1 (OLR1) gene, which plays an important role in the humoral immunity of the skin, and the plexin D1 (PLXND1) gene, which is highly expressed in tumor vasculature, were both found to be common targets of miR-27b, miR-1914, and miR-612.

Over-expression of miR-34c leads to early-life visceral fat accumulation and insulin resistance

Overweight children and adolescents are at high risk for adult and late life obesity. This report investigates some underlying mechanisms contributing to obesity during early life in an animal model. We generated a strain of transgenic mice, cU2, overexpressing human microRNA 34c, a microRNA functionally implicated in adipogenesis. Male and female cU2 mice exhibit significant weight gain, accompanied by marked increase in abdominal fat mass and metabolic abnormalities, including reduction of both glucose clearance rate and insulin sensitivity, as early as two months of age. Adipogenesis derailment at this early age is suggested by decreased expression of adiponectin, the fat mass and obesity-associated gene, and the adiponectin receptor R1, coupled with a reduction of the brown fat biomarker PAT2 and the adipogenesis inhibitor SIRT1. Notably, adiponectin is an important adipokine and an essential regulator of glucose and fatty acid homeostasis. cU2 mice may provide a crucial animal model for investigating the role of miR-34c in early onset insulin resistance and visceral fat mass increase, contributing to accelerated body weight gain and metabolic disorders. Intervention in this dysregulation may open a new preventive strategy to control early-life weight gain and abnormal insulin resistance, and thus prevalent adult and late life obesity.

MicroRNAs in Obesity and Related Metabolic Disorders

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

Impact of obesity on breast cancer recurrence and minimal residual disease

BACKGROUND

Obesity is associated with an increased risk of breast cancer recurrence and cancer death. Recurrent cancers arise from the pool of residual tumor cells, or minimal residual disease (MRD), that survives primary treatment and persists in the host. Whether the association of obesity with recurrence risk is causal is unknown, and the impact of obesity on MRD and breast cancer recurrence has not been reported in humans or in animal models.

METHODS

Doxycycline-inducible primary mammary tumors were generated in intact MMTV-rtTA;TetO-HER2/neu (MTB/TAN) mice or orthotopic recipients fed a high-fat diet (HFD; 60% kcal from fat) or a control low-fat diet (LFD; 10% kcal from fat). Following oncogene downregulation and tumor regression, mice were followed for clinical recurrence. Body weight was measured twice weekly and used to segregate HFD mice into obese (i.e., responders) and lean (i.e., nonresponders) study arms, and obesity was correlated with body fat percentage, glucose tolerance (measured using intraperitoneal glucose tolerance tests), serum biomarkers (measured by enzyme-linked immunosorbent assay), and tissue transcriptomics (assessed by RNA sequencing). MRD was quantified by droplet digital PCR.

RESULTS

HFD-Obese mice weighed significantly more than HFD-Lean and LFD control mice (p < 0.001) and had increased body fat percentage (p < 0.001). Obese mice exhibited fasting hyperglycemia, hyperinsulinemia, and impaired glucose tolerance, as well as decreased serum levels of adiponectin and increased levels of leptin, resistin, and insulin-like growth factor 1. Tumor recurrence was accelerated in HFD-Obese mice compared with HFD-Lean and LFD control mice (median relapse-free survival 53.0 days vs. 87.0 days vs. 80.0 days, log-rank p < 0.001; HFD-Obese compared with HFD-Lean HR 2.52, 95% CI 1.52-4.16; HFD-Obese compared with LFD HR 2.27, 95% CI 1.42-3.63). HFD-Obese mice harbored a significantly greater number of residual tumor cells than HFD-Lean and LFD mice (12,550 ± 991 vs. 7339 ± 2182 vs. 4793 ± 1618 cells, p < 0.001).

CONCLUSION

These studies provide a genetically engineered mouse model for study of the association of diet-induced obesity with breast cancer recurrence. They demonstrate that this model recapitulates physiological changes characteristic of obese patients, establish that the association between obesity and recurrence risk is causal in nature, and suggest that obesity is associated with the increased survival and persistence of residual tumor cells.

Osteogenesis depends on commissioning of a network of stem cell transcription factors that act as repressors of adipogenesis

Mesenchymal (stromal) stem cells (MSCs) constitute populations of mesodermal multipotent cells involved in tissue regeneration and homeostasis in many different organs. Here we performed comprehensive characterization of the transcriptional and epigenomic changes associated with osteoblast and adipocyte differentiation of human MSCs. We demonstrate that adipogenesis is driven by considerable remodeling of the chromatin landscape and de novo activation of enhancers, whereas osteogenesis involves activation of preestablished enhancers. Using machine learning algorithms for in silico modeling of transcriptional regulation, we identify a large and diverse transcriptional network of pro-osteogenic and antiadipogenic transcription factors. Intriguingly, binding motifs for these factors overlap with SNPs related to bone and fat formation in humans, and knockdown of single members of this network is sufficient to modulate differentiation in both directions, thus indicating that lineage determination is a delicate balance between the activities of many different transcription factors.

MicroRNAs and other non-coding RNAs in adipose tissue and obesity: emerging roles as biomarkers and therapeutic targets

Obesity is a metabolic condition usually accompanied by insulin resistance (IR), type 2 diabetes (T2D), and dyslipidaemia, which is characterised by excessive fat accumulation and related to white adipose tissue (WAT) dysfunction. Enlargement of WAT is associated with a transcriptional alteration of coding and non-coding RNAs (ncRNAs). For many years, big efforts have focused on understanding protein-coding RNAs and their involvement in the regulation of adipocyte physiology and subsequent role in obesity. However, diverse findings have suggested that a dysfunctional adipocyte phenotype in obesity might be also dependent on specific alterations in the expression pattern of ncRNAs, such as miRNAs. The aim of this review is to update current knowledge on the physiological roles of miRNAs and other ncRNAs in adipose tissue function and their potential impact on obesity. Therefore, we examined their regulatory role on specific WAT features: adipogenesis, adipokine secretion, inflammation, glucose metabolism, lipolysis, lipogenesis, hypoxia and WAT browning. MiRNAs can be released to body fluids and can be transported (free or inside microvesicles) to other organs, where they might trigger metabolic effects in distant tissues, thus opening new possibilities to a potential use of miRNAs as biomarkers for diagnosis, prognosis, and personalisation of obesity treatment. Understanding the role of miRNAs also opens the possibility of using these molecules on individualised dietary strategies for precision weight management. MiRNAs should be envisaged as a future therapeutic approach given that miRNA levels could be modulated by synthetic molecules (f.i. miRNA mimics and inhibitors) and/or specific nutrients or bioactive compounds.

Diabetes in Pregnancy and MicroRNAs: Promises and Limitations in Their Clinical Application

Maternal diabetes is associated with an increased risk of complications for the mother and her offspring. The latter have an increased risk of foetal macrosomia, hypoglycaemia, respiratory distress syndrome, preterm delivery, malformations and mortality but also of life-long development of obesity and diabetes. Epigenetics have been proposed as an explanation for this long-term risk, and microRNAs (miRNAs) may play a role, both in short- and long-term outcomes. Gestation is associated with increasing maternal insulin resistance, as well as β-cell expansion, to account for the increased insulin needs and studies performed in pregnant rats support a role of miRNAs in this expansion. Furthermore, several miRNAs are involved in pancreatic embryonic development. On the other hand, maternal diabetes is associated with changes in miRNA both in maternal and in foetal tissues. This review aims to summarise the existing knowledge on miRNAs in gestational and pre-gestational diabetes, both as diagnostic biomarkers and as mechanistic players, in the development of gestational diabetes itself and also of short- and long-term complications for the mother and her offspring.

A Network Biology Approach for Assessing the Role of Pathologic Adipose Tissues in Insulin Resistance Using Meta-analysis of Microarray Datasets

Background

The role of adipose tissue in Insulin resistance (IR) and Type 2 Diabetes (T2D) has well been received in the biomedical community; being a precursor of T2D, identification of the molecular basis of IR is therefore, vital to elucidate T2D- pathogenesis and meta-analysis of previously conducted microarray studies provides an inexpensive approach to achieve this end.

Methods

In this study, we have carried out a statistical meta-analysis of 157 microarray datasets from five independent studies and identified a meta-signature of 1,511 genes; their functional meaning was elucidated by integrated pathways-analysis. Further, a protein-protein interaction network was constructed and key genes along with their high confidence transcriptional- and epigenetic-mediators were identified using a network biology approach.

Results

Various inflammation- and immune system-related pathways such as TGF-β signaling, IL7 signaling, Neutrophil degranulation, and Chemokine signaling etc. were enriched in sick adipose tissues; identified transcription factors, and microRNAs were also found to regulate processes relevant to IR/T2D pathophysiology.

Conclusion

This study endorses the development of effective bioinformatics workflow and further grants an indication for the acceptance of adiposopathy as the root mechanistic pathology that poses risk for development of type 2 diabetes; concept of adipospathy in place of metabolic syndrome will open the possibility to design drugs, those will ameliorate adipose functions and hence proved to be more effective against Type 2 Diabetes.

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

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

A computational biology approach of a genome-wide screen connected miRNAs to obesity and type 2 diabetes

OBJECTIVE

Obesity and type 2 diabetes (T2D) arise from the interplay between genetic, epigenetic, and environmental factors. The aim of this study was to combine bioinformatics and functional studies to identify miRNAs that contribute to obesity and T2D.

METHODS

A computational framework (miR-QTL-Scan) was applied by combining QTL, miRNA prediction, and transcriptomics in order to enhance the power for the discovery of miRNAs as regulative elements. Expression of several miRNAs was analyzed in human adipose tissue and blood cells and miR-31 was manipulated in a human fat cell line.

RESULTS

In 17 partially overlapping QTL for obesity and T2D 170 miRNAs were identified. Four miRNAs (miR-15b, miR-30b, miR-31, miR-744) were recognized in gWAT (gonadal white adipose tissue) and six (miR-491, miR-455, miR-423-5p, miR-132-3p, miR-365-3p, miR-30b) in BAT (brown adipose tissue). To provide direct functional evidence for the achievement of the miR-QTL-Scan, miR-31 located in the obesity QTL Nob6 was experimentally analyzed. Its expression was higher in gWAT of obese and diabetic mice and humans than of lean controls. Accordingly, 10 potential target genes involved in insulin signaling and adipogenesis were suppressed. Manipulation of miR-31 in human SGBS adipocytes affected the expression of GLUT4, PPARγ, IRS1, and ACACA. In human peripheral blood mononuclear cells (PBMC) miR-15b levels were correlated to baseline blood glucose concentrations and might be an indicator for diabetes.

CONCLUSION

Thus, miR-QTL-Scan allowed the identification of novel miRNAs relevant for obesity and T2D.

Implications of publicly available genomic data resources in searching for therapeutic targets of obesity and type 2 diabetes

Obesity and type 2 diabetes (T2D) are two major conditions that are related to metabolic disorders and affect a large population. Although there have been significant efforts to identify their therapeutic targets, few benefits have come from comprehensive molecular profiling. This limited availability of comprehensive molecular profiling of obesity and T2D may be due to multiple challenges, as these conditions involve multiple organs and collecting tissue samples from subjects is more difficult in obesity and T2D than in other diseases, where surgical treatments are popular choices. While there is no repository of comprehensive molecular profiling data for obesity and T2D, multiple existing data resources can be utilized to cover various aspects of these conditions. This review presents studies with available genomic data resources for obesity and T2D and discusses genome-wide association studies (GWAS), a knockout (KO)-based phenotyping study, and gene expression profiles. These studies, based on their assessed coverage and characteristics, can provide insights into how such data can be utilized to identify therapeutic targets for obesity and T2D.