MicroRNA-425 controls lipogenesis and lipolysis in adipocytes

Deciphering adipose development: Function, differentiation and regulation

The overdevelopment of adipose tissues, accompanied by excess lipid accumulation and energy storage, leads to adipose deposition and obesity. With the increasing incidence of obesity in recent years, obesity is becoming a major risk factor for human health, causing various relevant diseases (including hypertension, diabetes, osteoarthritis and cancers). Therefore, it is of significance to antagonize obesity to reduce the risk of obesity-related diseases. Excess lipid accumulation in adipose tissues is mediated by adipocyte hypertrophy (expansion of pre-existing adipocytes) or hyperplasia (increase of newly-formed adipocytes). It is necessary to prevent excessive accumulation of adipose tissues by controlling adipose development. Adipogenesis is exquisitely regulated by many factors in vivo and in vitro, including hormones, cytokines, gender and dietary components. The present review has concluded a comprehensive understanding of adipose development including its origin, classification, distribution, function, differentiation and molecular mechanisms underlying adipogenesis, which may provide potential therapeutic strategies for harnessing obesity without impairing adipose tissue function.

Defining the activity of pro-reparative extracellular vesicles in wound healing based on miRNA payloads and cell type-specific lineage mapping

Small extracellular vesicles (EVs) are released by cells and deliver biologically active payloads to coordinate the response of multiple cell types in cutaneous wound healing. Here we used a cutaneous injury model as a donor of pro-reparative EVs to treat recipient diabetic obese mice, a model of impaired wound healing. We established a functional screen for microRNAs (miRNAs) that increased the pro-reparative activity of EVs and identified a down-regulation of miR-425-5p in EVs in vivo and in vitro associated with the regulation of adiponectin. We tested a cell type-specific reporter of a tetraspanin CD9 fusion with GFP to lineage map the release of EVs from macrophages in the wound bed, based on the expression of miR-425-5p in macrophage-derived EVs and the abundance of macrophages in EV donor sites. Analysis of different promoters demonstrated that EV release under the control of a macrophage-specific promoter was most abundant and that these EVs were internalized by dermal fibroblasts. These findings suggested that pro-reparative EVs deliver miRNAs, such as miR-425-5p, that stimulate the expression of adiponectin that has insulin-sensitizing properties. We propose that EVs promote intercellular signaling between cell layers in the skin to resolve inflammation, induce proliferation of basal keratinocytes, and accelerate wound closure.

Adipocyte-derived exosomal miR-22-3p modulated by circadian rhythm disruption regulates insulin sensitivity in skeletal muscle cells

Circadian rhythm disruption leads to dysregulation of lipid metabolism, which further drive the occurrence of insulin resistance (IR). Exosomes are natural carrier systems that advantageous for cell communication. In the present study, we aimed to explore whether and how the exosomal microRNAs (miRNAs) in circulation participate in modulating skeletal muscle IR induced by circadian rhythm disruption. In the present study, 24-h constant light (12-h light/12-h light, LL) was used to establish the mouse model of circadian rhythm disruption. Bmal1 interference was used to establish the cell model of circadian rhythm disruption. And in clinical experiments, we chose a relatively large group of rhythm disturbance-shift nurses. We showed that LL-induced circadian rhythm disruption led to increased body weight and visceral fat volume, as well as occurrence of IR in vivo. Furthermore, exosomal miR-22-3p derived from adipocytes in the context of circadian rhythm disruption induced by Bmal1 interference could be uptaken by skeletal muscle cells to promote IR occurrence in vitro. Moreover, miR-22-3p in circulation was positively correlated with the clinical IR-associated factors. Collectively, these data showed that exosomal miR-22-3p in circulation may act as potential biomarker and therapeutic target for skeletal muscle IR, contributing to the prevention of diabetes in the context of rhythm disturbance.

Bioinformatics Analysis of miR-181a and Its Role in Adipogenesis, Obesity, and Lipid Metabolism Through Review of Literature

The miRNAs regulate various biological processes in the mammalian body system. The role of miR-181a in the development, progression, and expansion of cancers is well-documented. However, the role of miR-181a in adipogenesis; lipid metabolism; obesity; and obesity-related issues such as diabetes mellitus needs to be explored. Therefore, in the present study, the literature was searched and bioinformatics tools were applied to explore the role of miR-181a in adipogenesis. The list of adipogenic and lipogenic target genes validated through different publications were extracted and compiled. The network and functional analysis of these target genes was performed through in-silico analysis. The mature sequence of miR-181a of different species were extracted from and were found highly conserved among the curated species. Additionally, we also used various bioinformatics tools such as target gene extraction from Targetscan, miRWalk, and miRDB, and the list of the target genes from these different databases was compared, and common target genes were predicted. These common target genes were further subjected to the enrichment score and KEGG pathways analysis. The enrichment score of the vital KEGG pathways of the target genes is the key regulator of adipogenesis, lipogenesis, obesity, and obesity-related syndromes in adipose tissues. Therefore, the information presented in the current review will explore the regulatory roles of miR-181a in fat tissues and its associated functions and manifestations.

Naringin reduces fat deposition by promoting the expression of lipolysis and β-oxidation related genes

AIMS

Naringin, a flavonoid present in citrus fruits, has been known for the capacity to reduce lipid synthesis and anti-inflammatory. In this study, we investigated whether naringin increases lipolysis and fatty acid β-oxidation to change fat deposition.

METHODS

In in vivo experiment, obese adult mice (20-weeks-old, n = 18) were divided into control group fed with normal diet and naringin-treated group fed with naringin-supplemented diet (5 g/kg) for 60 days, respectively. In in vitro experiment, differentiated 3T3-L1 adipocytes were treated for four days with or without naringin (100 µg/mL).

RESULTS

Supplementing naringin significantly reduced the body weight, abdominal fat weight, blood total cholesterol content of mice, but did not affect food intake. In addition, naringin decreased levels of pro-inflammatory factors in adipose tissue including interleukin-1β (IL-1β), interleukin-6 (IL-6), and monocyte chemotactic protein 1 (MCP-1). Naringin increased the expression of AMP-activated protein kinase (AMPK), a key factor in cellular energy metabolism, and raised the ratio of p-AMPK/AMPK in mouse liver tissue. The protein expression of hormone-sensitive lipase (HSL), phospho-HSL563 (p-HSL563), p-HSL563/HSL, and adipocyte triglyceride lipase (ATGL) was significantly increased in the adipose tissue of naringin-treated mice. Furthermore, naringin enhanced the expression of fatty acid β-oxidation genes, including carnitine palmitoyl transferase 1 (CPT1), uncoupling protein 2 (UCP2), and acyl-coenzyme A oxidase 1 (AOX1) in mouse adipose tissue. In in vitro experiment, similar findings were observed in differentiated 3T3-L1 adipocytes with naringin treatment. The treatment remarkably reduced intracellular lipid content, increased the number of mitochondria and promoted the gene expression of HSL, ATGL, CPT1, AOX1, and UCP2 and the phosphorylation of HSL protein.

CONCLUSION

Naringin reduced body fat in obese mice and lipid content in differentiated 3T3-L1 adipocytes, which was associated with enhanced AMPK activation and upregulation of the expression of the lipolytic genes HSL, ATGL, and β-oxidation genes CPT1, AOX1, and UCP2.

AMP-activated protein kinase is a key regulator of obesity-associated factors

An imbalance between caloric intake and energy expenditure leads to obesity. Obesity is an important risk factor for the development of several metabolic diseases including insulin resistance, metabolic syndrome, type 2 diabetes mellitus, and cardiovascular disease. So, controlling obesity could be effective in the improvement of obesity-related diseases. Various factors are involved in obesity, such as AMP-activated protein kinases (AMPK), silent information regulators, inflammatory mediators, oxidative stress parameters, gastrointestinal hormones, adipokines, angiopoietin-like proteins, and microRNAs. These factors play an important role in obesity by controlling fat metabolism, energy homeostasis, food intake, and insulin sensitivity. AMPK is a heterotrimeric serine/threonine protein kinase known as a fuel-sensing enzyme. The central role of AMPK in obesity makes it an attractive molecule to target obesity and related metabolic diseases. In this review, the critical role of AMPK in obesity and the interplay between AMPK and obesity-associated factors were elaborated.

Screening of key miRNAs related with the differentiation of subcutaneous adipocytes and the validation of miR-133a-3p functional significance in goats

OBJECTIVE

Adipocyte differentiation is regulated by a variety of functional genes and noncoding RNAs. However, the role of miRNAs in lipid deposition of goat white adipose tissue is still unclear. Therefore, this study revealed the miRNA expression profile in goat subcutaneous adipocytes by sRNA-seq.

METHODS

The miRNA expressed in goat subcutaneous preadipocytes and the mature adipocytes were sequenced by sRNA-seq. The differentially expressed miRNAs (DEm) were screened and gene ontology (GO) and Kyoto encyclopedia for genes and genomes (KEGG) analyses were performed. Gain-of-function and loss-of-function combined with oil red O staining, Bodipy staining, and quantitative reverse-transcription polymerase chain reaction (qPCR) were utilized to determine the effect of miR-133a-3p on adipocyte differentiation.

RESULTS

A total of 218 DEm were screened out. The target genes of these DEm were significantly enriched in GO items such as biological regulation and in KEGG terms such as FAK signaling pathway and MAPK signaling pathway. qPCR verified that the expression trend of miRNA was consistent with miRNA-seq. The gain-of-function or loss-of-function of miR-133a-3p showed that it promoted or inhibited the accumulation of lipid droplets, and CCAAT enhancer binding protein α (C/EBPα) and C/EBPβ were extremely significantly up-regulated or down-regulated respectively (p<0.01), the loss-of-function also led to a significant down-regulation of peroxisome proliferator activated receptor gamma (PPARγ) (p<0.01).

CONCLUSION

This study successfully identified miRNAs expression patterns in goat subcutaneous adipocytes, and functional identification indicates that miR-133a-3p is a positive regulator of the differentiation process of goat subcutaneous adipocytes. Our results lay the foundation for the molecular mechanism of lipid deposition in meat-source goats from the perspective of miRNA.

Bta-miR-6517 promotes proliferation and inhibits differentiation of pre-adipocytes by targeting PFKL

The proliferation and differentiation of pre-adipocytes are regulated by microRNAs (miRNAs) and other factors. In this study, the potential functions of bta-miR-6517 in the regulation of pre-adipocyte proliferation and differentiation were explored. The qRT-PCR, oil red O staining and CCK-8 assay were used to evaluate the role of bta-miR-6517. Further, the target gene of bta-miR-6517 was identified using bioinformatics analysis, dual-luciferase reporter system and qRT-PCR system. The results found that the overexpression of bta-miR-6517 promoted the expression of proliferation marker genes and substantially increased the adipocyte proliferation vitality in the CCK-8 assay, whereas suppressing of bta-miR-6517 had the opposite effect. Overexpression bta-miR-6517 suppressed the expression of adipogenic genes, which inhibited lipid accumulation, whereas suppressing of bta-miR-6517 had the opposite effect. Furthermore, the dual-fluorescent reporter experiment results demonstrated that bta-miR-6517 directly targeted phosphofructokinase, liver type (PFKL). When bta-miR-6517 was either overexpressed or suppressed, it negatively regulated PFKL. In conclusion, we observed that bta-miR-6517 promoted adipocyte proliferation and inhibited differentiation by targeting PFKL.

Stool microRNA profiles reflect different dietary and gut microbiome patterns in healthy individuals

OBJECTIVES

MicroRNA (miRNA) profiles have been evaluated in several biospecimens in relation to common diseases for which diet may have a considerable impact. We aimed at characterising how specific diets are associated with the miRNome in stool of vegans, vegetarians and omnivores and how this is reflected in the gut microbial composition, as this is still poorly explored.

DESIGN

We performed small RNA and shotgun metagenomic sequencing in faecal samples and dietary recording from 120 healthy volunteers, equally distributed for the different diets and matched for sex and age.

RESULTS

We found 49 miRNAs differentially expressed among vegans, vegetarians and omnivores (adj. p <0.05) and confirmed trends of expression levels of such miRNAs in vegans and vegetarians compared with an independent cohort of 45 omnivores. Two miRNAs related to lipid metabolism, miR-636 and miR-4739, were inversely correlated to the non-omnivorous diet duration, independently of subject age. Seventeen miRNAs correlated (|rho|>0.22, adj. p <0.05) with the estimated intake of nutrients, particularly animal proteins, phosphorus and, interestingly, lipids. In omnivores, higher Prevotella and Roseburia and lower Bacteroides abundances than in vegans and vegetarians were observed. Lipid metabolism-related miR-425-3p and miR-638 expression levels were associated with increased abundances of microbial species, such as Roseburia sp. CAG 182 and Akkermansia muciniphila, specific of different diets. An integrated analysis identified 25 miRNAs, 25 taxa and 7 dietary nutrients that clearly discriminated (area under the receiver operating characteristic curve=0.89) the three diets.

CONCLUSION

Stool miRNA profiles are associated with specific diets and support the role of lipids as a driver of epigenetic changes and host-microbial molecular interactions in the gut.

Liver Kinase B1 Regulates Remodeling of the Tumor Microenvironment in Triple-Negative Breast Cancer

Liver kinase B1 (LKB1) is a potent tumor suppressor that regulates cellular energy balance and metabolism as an upstream kinase of the AMP-activated protein kinase (AMPK) pathway. LKB1 regulates cancer cell invasion and metastasis in multiple cancer types, including breast cancer. In this study, we evaluated LKB1’s role as a regulator of the tumor microenvironment (TME). This was achieved by seeding the MDA-MB-231-LKB1 overexpressing cell line onto adipose and tumor scaffolds, followed by the evaluation of tumor matrix-induced tumorigenesis and metastasis. Results demonstrated that the presence of tumor matrix enhanced tumorigenesis in both MDA-MB-231 and MDA-MB-231-LKB1 cell lines. Metastasis was increased in both MDA-MB-231 and -LKB1 cells seeded on the tumor scaffold. Endpoint analysis of tumor and adipose scaffolds revealed LKB1-mediated tumor microenvironment remodeling as evident through altered matrix protein production. The proteomic analysis determined that LKB1 overexpression preferentially decreased all major and minor fibril collagens (collagens I, III, V, and XI). In addition, proteins observed to be absent in tumor scaffolds in the LKB1 overexpressing cell line included those associated with the adipose matrix (COL6A2) and regulators of adipogenesis (IL17RB and IGFBP4), suggesting a role for LKB1 in tumor-mediated adipogenesis. Histological analysis of MDA-MB-231-LKB1-seeded tumors demonstrated decreased total fibril collagen and indicated decreased stromal cell presence. In accordance with this, in vitro condition medium studies demonstrated that the MDA-MB-231-LKB1 secretome inhibited adipogenesis of adipose-derived stem cells. Taken together, these data demonstrate a role for LKB1 in regulating the tumor microenvironment through fibril matrix remodeling and suppression of adipogenesis.

Differential regulatory roles of microRNAs during intramuscular adipogenesis in Chinese Guizhou Congjiang Xiang pigs

Intramuscular fat development is regulated by a series of complicated processes, with non-coding RNA (ncRNA) such as microRNA (miRNA) having a critical role during intramuscular preadipocyte proliferation and differentiation in pigs. In the present study, the miRNA expression profiles of intramuscular preadipocytes from the longissimus dorsi muscle of Chinese Guizhou Congjiang Xiang pigs were detected by RNA-seq during various differentiation stages, namely, day 0 (D0), day 4 (D4), and day 8 (D8). A total of 67, 95, and 16 differentially expressed (DE) miRNAs were detected between D4 and D0, D8 and D0, and D8 and D4, respectively. According to gene ontology and Kyoto Encyclopedia of Genes analysis, target genes of DE miRNAs were enriched in categories and pathways related to lipid metabolic process, lipid biosynthetic process, as well as the PI3K-Akt, AMPK, and MAPK signalling pathways. Notably, miR-148a-3p was differentially expressed, with highest expressed abundance in D0, D4, and D8. Overexpression of miR-148a-3p in intramuscular preadipocytes increased cell proliferation and differentiation, and decreased apoptosis, in comparison to the knockdown of miR-148a-3p in intramuscular preadipocytes. Luciferase activity assays, quantitative polymerase-chain reaction, and western blot analysis confirmed that miR-148a-3p regulated adipogenesis by repressing PPARGC1A expression. Accordingly, the effect of miR-148a-3p mimic was attenuated by overexpression of PPARGC1A intramuscular preadipocytes. Furthermore, miR-148a-3p promoted intramuscular preadipocyte differentiation by inhibiting the AMPK/ACC/CPT1C signalling pathway. Taken together, we identified expression profiles of miRNAs in intramuscular preadipocytes and determined that miR-148a-3p acted as a promoter of adipogenesis.

DAPK1 Interacts with the p38 isoform MAPK14, Preventing its Nuclear Translocation and Stimulation of Bone Marrow Adipogenesis

Bone marrow (BM) adipose tissue (BMAT), a unique adipose depot, plays an important role in diseases such as osteoporosis and bone metastasis. Precise control of mesenchymal stem cell (MSC) differentiation is critical for BMAT formation and regeneration. Here, we show that death associated protein kinase 1 (DAPK1) negatively regulates BM adipogenesis in vitro and in vivo. Prx1 creDapk1 loxp/loxp mice showed more adipocytes in the femur than Dapk1 loxp/loxp mice. Further mechanistic analyses revealed that DAPK1 inhibits p38 mitogen-activated protein kinase (MAPK) signaling in the nucleus by binding the p38 isoform MAPK14, decreasing p38 nuclear activity, which subsequently inhibits BM adipogenesis. The inhibitory effect of DAPK1 against MAPK14 was independent of its kinase activity. In addition, the decreased DAPK1 was observed in the BM-MSCs of ageing mice. Our results reveal a previously undescribed function for DAPK1 in the regulation of adipogenesis, and may also reveal the underlying mechanism of BMAT formation in ageing.

An Update in Epigenetics in Metabolic-Associated Fatty Liver Disease

Metabolic-associated fatty liver disease (MAFLD) is characterized by hepatic steatosis accompanied by one of three features: overweight or obesity, T2DM, or lean or normal weight with evidence of metabolic dysregulation. It is distinguished by excessive fat accumulation in hepatocytes, and a decrease in the liver's ability to oxidize fats, the accumulation of ectopic fat, and the activation of proinflammatory pathways. Chronic damage will keep this pathophysiologic cycle active causing progression from hepatic steatosis to cirrhosis and eventually, hepatocarcinoma. Epigenetics affecting gene expression without altering DNA sequence allows us to study MAFLD pathophysiology from a different perspective, in which DNA methylation processes, histone modifications, and miRNAs expression have been closely associated with MAFLD progression. However, these considerations also faced us with the circumstance that modifying those epigenetics patterns might lead to MAFLD regression. Currently, epigenetics is an area of great interest because it could provide new insights in therapeutic targets and non-invasive biomarkers. This review comprises an update on the role of epigenetic patterns, as well as innovative therapeutic targets and biomarkers in MAFLD.

Identification of the interactions between specific genetic polymorphisms and nutrient intake associated with general and abdominal obesity in middle-aged adults

BACKGROUND & AIMS

Comprehensive understanding of gene-diet interactions is necessary to establish proper dietary guidelines to prevent and manage general and abdominal obesity. We investigated the role of genetic variants and their interactions with general and abdominal obesity-associated nutrients using a largescale genome-wide association study of Korean adults.

METHODS

A total of 50,808 participants from a Korean genome and epidemiology study were included. Dietary intake was assessed using a food frequency questionnaire. Obesity was defined as a body mass index ≥25 kg/m². Abdominal obesity (AO) was defined as waist circumference ≥90 cm and 80 cm in males and females, respectively. Dietary nutrient intake was classified based on Korean Dietary Reference Intakes (DRIs). Odds ratios and 95% confidence intervals were calculated after adjusting for age, sex, exercise, smoking, alcohol drinking, total energy consumption, PC1, and PC2.

RESULTS

Among the individuals consuming fat (%) above DRI, carriers of Ca binding protein 39 (CAB39)- rs6722579 minor allele (A) have a higher risk of AO than those not carrying the SNP (odds ration [OR] = 3.73, p-value = 2.05e-07; interaction p-value = 1.80e-07). Among the individuals consuming vitamin C above DRI, carriers of carboxypeptidase Q (CPQ)- rs59465035 minor allele (T) have a lower risk of AO than those without that SNP (OR = 0.89, p-value = 1.44e-08; interaction p-value = 9.50e-06). The genetic association with obesity was stronger among individuals with a genetic variant rs4130113 near GHR gene region in those consume folate above DRI and with a genetic variant rs5760920 near CRYBB2 gene region in those consume vitamin B2 above DRI.

CONCLUSION

Our study results suggested that interactions of specific polymorphisms at loci and certain nutrients may influence obesity and abdominal obesity.

Adipocyte-Specific Inhibition of Mir221/222 Ameliorates Diet-Induced Obesity Through Targeting Ddit4

MicroRNAs expressed in adipocytes are involved in transcriptional regulation of target mRNAs in obesity, but miRNAs critically involved in this process is not well characterized. Here, we identified upregulation of miR-221-3p and miR-222-3p in the white adipose tissues in C57BL/6 mice fed with high fat-high sucrose (HFHS) chow by RNA sequencing. Mir221 and Mir222 are paralogous genes and share the common seed sequence and Mir221/222AdipoKO mice fed with HFHS chow demonstrated resistance to the development of obesity compared with Mir221/222flox/y . Ddit4 is a direct target of Mir221 and Mir222, and the upregulation of Ddit4 in Mir221/222AdipoKO was associated with the suppression of TSC2 (tuberous sclerosis complex 2)/mammalian target of rapamycin complex 1 (mTORC1)/S6K (ribosomal protein S6 kinase) pathway. The overexpression of miR-222-3p linked to enhanced adipogenesis, and it may be a potential candidate for miRNA-based therapy.

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.

Let-7a induces metabolic reprogramming in breast cancer cells via targeting mitochondrial encoded ND4

BACKGROUND AND OBJECTIVES

MicroRNA (miRNA) that translocate from the nucleus to mitochondria are referred to as mitochondrial microRNA (mitomiR). Albeit mitomiRs have been shown to modulate gene expression, their functional impact within mitochondria is unknown. The main objective of this study is to investigate whether the mitochondrial genome is regulated by miR present inside the mitochondria.

METHODS AND RESULTS

Here, we report mitomiR let-7a regulates mitochondrial transcription in breast cancer cells and reprogram the metabolism accordingly. These effects were mediated through the interaction of let-7a with mtDNA, as studied by RNA pull-down assays, altering the activity of Complex I in a cell line-specific manner. Our study, for the first time, identifies the role of mitomiR (let-7a) in regulating the mitochondrial genome by transcriptional repression and its contribution to regulating mitochondrial metabolism of breast cancer cells.

CONCLUSION

These findings uncover a novel mechanism by which mitomiR regulates mitochondrial transcription.

A Review of miRNAs as Biomarkers and Effect of Dietary Modulation in Obesity Associated Cognitive Decline and Neurodegenerative Disorders

There has been a progressive increase in the prevalence of obesity and its comorbidities such as type 2 diabetes and cardiovascular diseases worldwide. Recent studies have suggested that the crosstalk between adipose tissue and central nervous system (CNS), through cellular mediators and signaling pathways, may causally link obesity with cognitive decline and give rise to neurodegenerative disorders. Several mechanisms have been proposed in obesity, including inflammation, oxidative stress, insulin resistance, altered lipid and cholesterol homeostasis, which may result in neuroinflammation, altered brain insulin signaling, amyloid-beta (Aβ) deposition and neuronal cell death. Since obesity is associated with functional and morphological alterations in the adipose tissues, the resulting peripheral immune response augments the development and progression of cognitive decline and increases susceptibility of neurodegenerative disorders, such as Alzheimer's Disease (AD) and Parkinson's Disease (PD). Studies have also elucidated an important role of high fat diet in the exacerbation of these clinical conditions. However, the underlying factors that propel and sustain this obesity associated cognitive decline and neurodegeneration, remains highly elusive. Moreover, the mechanisms linking these phenomena are not well-understood. The cumulative line of evidence have demonstrated an important role of microRNAs (miRNAs), a class of small non-coding RNAs that regulate gene expression and transcriptional changes, as biomarkers of pathophysiological conditions. Despite the lack of utility in current clinical practices, miRNAs have been shown to be highly specific and sensitive to the clinical condition being studied. Based on these observations, this review aims to assess the role of several miRNAs and aim to elucidate underlying mechanisms that link obesity with cognitive decline and neurodegenerative disorders. Furthermore, this review will also provide evidence for the effect of dietary modulation which can potentially ameliorate cognitive decline and neurodegenerative diseases associated with obesity.

MicroRNA-489-3p promotes adipogenesis by targeting the Postn gene in 3T3-L1 preadipocytes

AIMS

Accumulating evidence indicates that a number of microRNAs (miRNAs) serve as essential regulators during adipogenesis and adipolysis in humans and animals and play critical roles in the development of fat tissue. In this study, we aimed to determine the functional role and underlying regulatory mechanism of microRNA-489-3p (miR-489) in adipocytes.

MATERIALS AND METHODS

The expression patterns of miR-489 in mice were measured by qRT-PCR. Overexpression and knockdown of miR-489 by mimic and inhibitor transfections in 3T3-L1 preadipocytes revealed the regulatory effect of miR-489 on cellular proliferation and differentiation and energy turnover. Furthermore, RNA-seq, bioinformatics prediction, and dual luciferase reporter assays were used to identify the direct target of miR-489.

KEY FINDINGS

The results showed that miR-489 was highly expressed in the visceral fat tissue of adult mice, and obese mice exhibited higher levels of miR-489 than normal mice. Overexpression of miR-489 suppressed proliferation but promoted adipogenic differentiation and lipid accumulation in the cells. Mitochondrial oxidation also fluctuated in the cells due to the high expression of miR-489. Notably, knockdown of miR-489 did not have a strong opposing effect on the cells. Periostin (Postn) was identified as a direct target gene for miR-489, and silencing the Postn gene similarly stimulated adipogenesis and differentiation of adipocytes.

SIGNIFICANCE

miR-489 provides a strong driving force for adipogenesis metabolism and adipocyte differentiation by targeting the Postn gene. This result may contribute to the treatment of obesity.

RNA-Seq Reveals Function of Bta-miR-149-5p in the Regulation of Bovine Adipocyte Differentiation

Intramuscular fat is a real challenge for the experts of animal science to improve meat quality traits. Research on the mechanism of adipogenesis provides invaluable information for the improvement of meat quality traits. This study investigated the effect of bta-miR-149-5p and its underlying mechanism on lipid metabolism in bovine adipocytes. Bovine adipocytes were differentiated and transfected with bta-miR-149-5p mimics or its negative control (NC). A total of 115 DEGs including 72 upregulated and 43 downregulated genes were identified in bovine adipocytes. The unigenes and GO term biological processes were the most annotated unigene contributor parts at 80.08%, followed by cellular component at 13.4% and molecular function at 6.7%. The KEGG pathways regulated by the DEGs were PI3K-Akt signaling pathway, calcium signaling pathway, pathways in cancer, MAPK signaling pathway, lipid metabolism/metabolic pathway, PPAR signaling pathway, AMPK signaling pathway, TGF-beta signaling pathway, cAMP signaling pathway, cholesterol metabolism, Wnt signaling pathway, and FoxO signaling pathway. In addition to this, the most important reactome enrichment pathways were R-BTA-373813 receptor CXCR2 binding ligands CXCL1 to 7, R-BTA-373791 receptor CXCR1 binding CXCL6 and CXCL8 ligands, R-BTA-210991 basigin interactions, R-BTA-380108 chemokine receptors binding chemokines, R-BTA-445704 calcium binding caldesmon, and R-BTA-5669034 TNFs binding their physiological receptors. Furthermore, the expression trend of the DEGs in these pathways were also exploited. Moreover, the bta-miR-149-5p significantly (p < 0.01) downregulated the mRNA levels of adipogenic marker genes such as CCND2, KLF6, ACSL1, Cdk2, SCD, SIK2, and ZEB1 in bovine adipocytes. In conclusion, our results suggest that bta-miR-149-5p regulates lipid metabolism in bovine adipocytes. The results of this study provide a basis for studying the function and molecular mechanism of the bta-miR-149-5p in regulating bovine adipogenesis.

MiR-99b-5p Attenuates Adipogenesis by Targeting SCD1 and Lpin1 in 3T3-L1 Cells

The number and distribution of adipocytes directly affect the quality of livestock meat products. The analysis of the adipogenesis mechanism is the basis for improving meat quality. The formation of adipocytes is regulated by many factors, including a class of endogenous small RNAs, named microRNA (miRNA). Previous studies have shown that miRNAs could affect adipogenesis by post-transcriptional regulation of target genes. In our study, a decreased miR-99b-5p expression level was found in the adipose tissue of obese mice. Overexpression of miR-99b-5p could increase cell proliferation by promoting the cell cycle while inhibiting cell differentiation. In addition, interference with miR-99b-5p obtained the opposite result. Furthermore, the proteomics sequencing analysis screened 1154 differentially expressed proteins, which are closely related to adipocyte differentiation and fatty acid metabolism. In addition, the results of the dual-luciferase test showed that miR-99b-5p can directly target the proteins SCD1 and Lpin1 with significantly different expression levels in proteomic sequencing. Then, this result was verified at the level of mRNA and protein in a further study. Collectively, these results suggested that miR-99b-5p may be a target for improving meat quality.

MiR-25-3p regulates the differentiation of intramuscular preadipocytes in goat via targeting KLF4

Adipocyte differentiation, which plays an important role in fat deposition, involves a complex molecular mechanism. MicroRNAs (miRNAs) are essential in this progress. Here, we showed that miR-25-3p expression had increased during goat intramuscular preadipocyte differentiation, which peaked at day 3. Using liposome transfection and qRT-PCR techniques, we found that knocking down miR-25-3p reduced the accumulation of lipid droplets by downregulating or upregulating the expression of LPL, PPARγ, AP2, SREBP1, and C/EBPβ but upregulating the expression of KLF4. Overexpression of miR-25-3p results in the opposite. Furthermore, the dual luciferase assay showed that overexpression of miR-25-3p significantly inhibited luciferase activity of KLF4. These results showed that miR-25-3p has a binding site within the 3′-UTR of KLF4 mRNA. Together, these findings indicate that miR-25-3p is a positive regulator of intramuscular preadipocyte differentiation via targeting to KLF4 in goats.

New insights of Krüppel-like transcription factors in adipogenesis and the role of their regulatory neighbors

Obesity is a serious public health problem associated with predisposition to develop metabolic diseases. Over the past decade, several studies in vitro and in vivo have shown that the activity of Krüppel-like factors (KLFs) regulates adipogenesis, adipose tissue function and metabolism. Comprehension of both the origin and development of adipocytes and of adipose tissue could provide new insights into therapeutic strategies to contend against obesity and related metabolic diseases. This review focus on the transcriptional role that KLF family members play during adipocyte differentiation, describes their main interactions and the mechanisms involved in this fine-tuned developmental process. We also summarize new findings of the involvement of several effectors that modulate KLFs expression during adipogenesis, including growth factors, circadian clock proteins, interleukins, nuclear receptors, protein kinases and importantly, microRNAs. Thus, KLFs regulation by these factors and emerging molecules might constitute a potential therapeutic target for anti-obesity intervention.

Non-Coding and Regulatory RNAs as Epigenetic Remodelers of Fatty Acid Homeostasis in Cancer

Cancer cells commonly display metabolic fluctuations. Together with the Warburg effect and the increased glutaminolysis, alterations in lipid metabolism homeostasis have been recognized as a hallmark of cancer. Highly proliferative cancer cells upregulate de novo synthesis of fatty acids (FAs) which are required to support tumor progression by exerting multiple roles including structural cell membrane composition, regulators of the intracellular redox homeostasis, ATP synthesis, intracellular cell signaling molecules, and extracellular mediators of the tumor microenvironment. Epigenetic modifications have been shown to play a crucial role in human development, but also in the initiation and progression of complex diseases. The study of epigenetic processes could help to design new integral strategies for the prevention and treatment of metabolic disorders including cancer. Herein, we first describe the main altered intracellular fatty acid processes to support cancer initiation and progression. Next, we focus on the most important regulatory and non-coding RNAs (small noncoding RNA-sncRNAs-long non-coding RNAs-lncRNAs-and other regulatory RNAs) which may target the altered fatty acids pathway in cancer.

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.

Intestinal Lipid Metabolism Genes Regulated by miRNAs

MicroRNAs (miRNAs) crucial roles in translation repression and post-transcriptional adjustments contribute to regulate intestinal lipid metabolism. Even though their actions in different metabolic tissues have been elucidated, their intestinal activity is yet unclear. We aimed to investigate intestinal miRNA-regulated lipid metabolism-related genes, by creating an intestinal-specific Dicer1 knockout (Int-Dicer1 KO) mouse model, with a depletion of microRNAs in enterocytes. The levels of 83 cholesterol and lipoprotein metabolism-related genes were assessed in the intestinal mucosa of Int-Dicer1 KO and Wild Type C57BL/6 (WT) littermates mice at baseline and 2 h after an oral lipid challenge. Among the 18 genes selected for further validation, Hmgcs2, Acat1 and Olr1 were found to be strong candidates to be modulated by miRNAs in enterocytes and intestinal organoids. Moreover, we report that intestinal miRNAs contribute to the regulation of intestinal epithelial differentiation. Twenty-nine common miRNAs found in the intestines were analyzed for their potential to target any of the three candidate genes found and validated by miRNA-transfection assays in Caco-2 cells. MiR-31-5p, miR-99b-5p, miR-200a-5p, miR-200b-5p and miR-425-5p are major regulators of these lipid metabolism-related genes. Our data provide new evidence on the potential of intestinal miRNAs as therapeutic targets in lipid metabolism-associated pathologies.

Differentially Expressed miRNA-Gene Targets Related to Intramuscular Fat in Musculus Longissimus Dorsi of Charolais × Holstein F2-Crossbred Bulls

Intramuscular fat (IMF) is a meat quality indicator associated with taste and juiciness. IMF deposition, influenced by genetic and non-genetic factors, occurs through a transcriptionally coordinated process of adipogenesis. MicroRNAs (miRNAs) are transcriptional regulators of vital biological processes, including lipid metabolism and adipogenesis. However, in bovines, limited data on miRNA profiling and association with divergent intramuscular fat content, regulated exclusively by genetic parameters, have been reported. Here, a microarray experiment was performed to identify and characterize the miRNA expression pattern in the Musculus longissimus dorsi of F₂-cross (Charolais × German Holstein) bulls with high and low IMF. A total of 38 differentially expressed miRNAs (DE miRNAs), including 33 upregulated and 5 downregulated (corrected p-value ≤ 0.05, FC ≥ ±1.2), were reported. Among DE miRNAs, the upregulated miRNAs miR-105a/b, miR-695, miR-1193, miR-1284, miR-1287-5p, miR-3128, miR-3178, miR-3910, miR-4443, miR-4445 and miR-4745, and the downregulated miRNAs miR-877-5p, miR-4487 and miR-4706 were identified as novel fat deposition regulators. DE miRNAs were further analyzed, along with previously identified differentially expressed genes (DEGs) from the same samples and predicted target genes, using multiple bioinformatic approaches, including target prediction tools and co-expression networks, as well as Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment. We identified DE miRNAs and their gene targets associated with bovine intramuscular adipogenesis, and we provide a basis for further functional investigations.

The Proliferation and Differentiation of Adipose-Derived Stem Cells in Neovascularization and Angiogenesis

Neovascularization and angiogenesis are vital processes in the repair of damaged tissue, creating new blood vessel networks and increasing oxygen and nutrient supply for regeneration. The importance of Adipose-derived Mesenchymal Stem Cells (ASCs) contained in the adipose tissue surrounding blood vessel networks to these processes remains unknown and the exact mechanisms responsible for directing adipogenic cell fate remain to be discovered. As adipose tissue contains a heterogenous population of partially differentiated cells of adipocyte lineage; tissue repair, angiogenesis and neovascularization may be closely linked to the function of ASCs in a complex relationship. This review aims to investigate the link between ASCs and angiogenesis/neovascularization, with references to current studies. The molecular mechanisms of these processes, as well as ASC differentiation and proliferation are described in detail. ASCs may differentiate into endothelial cells during neovascularization; however, recent clinical trials have suggested that ASCs may also stimulate angiogenesis and neovascularization indirectly through the release of paracrine factors.

Bta-miR-149-5p inhibits proliferation and differentiation of bovine adipocytes through targeting CRTCs at both transcriptional and posttranscriptional levels

MicroRNAs are small, single stranded, and noncoding RNAs that have been proven to be potent regulators of adipogenesis. However, the role of bta-miR-149-5p in regulating bovine adipogenesis is still unclear. Expression profiling in different stages of adipogenesis revealed that bta-miR-149-5p was enriched in the proliferation stage, and also on Day 9 of differentiation in bovine adipocytes. Our gain of function study showed that bta-miR-149-5p can negatively regulate both bovine adipocyte proliferation and differentiation. Overexpression of bta-miR-149-5p suppressed the expression of proliferation marker genes at both the messenger RNA (mRNA) and protein levels, markedly decreased the percentage of S-phase cells, decreased the number of EdU-stained cells, and substantially reduced adipocyte proliferation vitality in the cell count assay. Collectively, these findings elucidated that bta-miR-149-5p inhibits adipocyte proliferation. Furthermore, overexpression of bta-miR-149-5p also suppressed the expression of adipogenic genes at both the mRNA and protein levels, inhibited lipid accumulation, and reduced the secretion of adiponectin in bovine adipocytes. Furthermore, a luciferase activity assay explored how bta-miR-149-5p targeted CRTCs (CRTC1 and CRTC2) directly. This targeting was further validated by the mRNA and protein level expression of CRTC1 and CRTC2, which were down regulated by bta-miR-149-5p overexpression. Moreover, bta-miR-149-5p indirectly targeted CRTC1 and CRTC2 through regulating their key transcription factors. Overexpression of bta-miR-149-5p suppressed the expression of SMAD3, while enriched the expression of NRF1, which are the key transcription factors and proven regulators of CRTC1. Overexpression of bta-miR-149-5p also repressed the expression of C/EBPγ, XBP1, INSM1, and ZNF263, which are the key regulators of CRTCs, at both the mRNA and protein levels. These findings suggest that bta-miR-149-5p is a negative regulator of CRTC1 and CRTC2 both at transcriptional and posttranscriptional level. Taken together, these findings suggest that bta-miR-149-5p can regulate adipogenesis, which implies that bta-miR-149-5p could be a target for increasing intramuscular fat in beef cattle.

Obesity, Insulin Resistance, and Colorectal Cancer: Could miRNA Dysregulation Play A Role?

Obesity is associated with insulin resistance and low-grade inflammation. Insulin resistance is a risk factor for cancer. A recent chapter in epigenetics is represented by microRNAs (miRNAs), which post-transcriptionally regulate gene expression. Dysregulated miRNA profiles have been associated with diseases including obesity and cancer. Herein we report dysregulated miRNAs in obesity both in animal models and in humans, and we also document dysregulated miRNAs in colorectal cancer (CRC), as example of an obesity-related cancer. Some of the described miRNAs are found to be similarly dysregulated both in obesity, insulin resistance (IR), and CRC. Thus, we present miRNAs as a potential molecular link between obesity and CRC onset and development, giving a new perspective on the role of miRNAs in obesity-associated cancers.

microRNA-16-5p promotes 3T3-L1 adipocyte differentiation through regulating EPT1

Adipogenesis is an organized process of cellular differentiation by which pre-adipocytes differentiate towards mature adipocytes. miR-16-5p has been reported to be involved in cell proliferation, apoptosis, differentiation and angiogenesis. However little is known about miR-16-5p functional role in 3T3-L1 adipocyte differentiation. In this study, we found that miRNA-16-5p was significantly upregulated during 3T3-L1 preadipocytes differentiation towards mature adipocytes. Over-expression of miRNA-16-5p promoted mature adipocytes specific genes expression and fat droplet accumulation in vitro and in vivo. Meanwhile we have identified EPT1 as the target gene of miRNA-16-5p. Taken together, our data provided evidence to support that miRNA-16-5p promotes adipocyte differentiation by suppressing EPT1.