Mouse Maternal High-Fat Intake Dynamically Programmed mRNA m⁶A Modifications in Adipose and Skeletal Muscle Tissues in Offspring

Exercise promotes skeletal muscle growth in adolescents via modulating Mettl3-mediated m6A methylation of MyoD in muscle satellite cells

BACKGROUND

Exercise exerts positive impacts on skeletal muscle health and homeostasis. Emerging evidence suggests that m6A methylation is involved in various physiological processes. However, the impact of exercise on adolescent skeletal muscle growth and the underlying epigenetic mechanisms remain poorly understood.

METHODS

The lower-limb skeletal muscles were harvested from exercise and control groups to compare the skeletal muscle growth in adolescents. mRNA sequencing was conducted to explore the mechanisms underlying enhanced skeletal muscle growth following exercise. The effects and mechanisms of Mettl3-mediated m6A methylation on adolescent skeletal muscle growth were investigated using muscle satellite cell (MuSC)-specific Mettl3 knockout (KO) mice. The potential function of MyoD for skeletal muscle growth in adolescents was explored by phenotypes after overexpression and evaluation of in vivo myogenesis. Additionally, the effects of the methyl donor betaine on adolescent skeletal muscle growth were investigated in vitro and in vivo.

RESULTS

Exercise could promote skeletal muscle growth in adolescents. Sequencing data analysis and confirmation assays uncovered that exercise significantly increased Mettl3-mediated m6A methylation and elevated the expression levels of activation marker MyoD in MuSCs. Establishment of MuSC-specific Mettl3 KO mice further demonstrated that Mettl3-mediated m6A methylation in MyoD contributed to skeletal muscle growth during adolescence. Mettl3-mediated m6A methylation regulated MyoD mRNA stability at the posttranscriptional level in MuSCs, with a functional site at 234 bp A. Increased expression of MyoD could contribute to myogenesis of adolescent MuSCs. Furthermore, the methyl donor betaine could enhance MyoD expression, contributing to MuSCs activation and skeletal muscle growth in adolescents by boosting m6A methylation levels.

CONCLUSIONS

Exercise promoted skeletal muscle growth in adolescents through facilitating MyoD mRNA stability of MuSCs in a Mettl3-mediated m6A-dependent manner. The methyl donor betaine could be a potential alternative to exercise for promoting adolescent skeletal muscle growth by directly augmenting the global levels of m6A methylation. These findings may provide a theoretical foundation for encouraging daily fitness exercise and ensuring healthy growth in adolescents.

The maternal lifestyle in pregnancy: Implications for foetal skeletal muscle development

The world is facing a global nutrition crisis, as evidenced by the rising incidence of metabolic disorders such as obesity, insulin resistance and chronic inflammation. Skeletal muscle is the largest tissue in humans and plays an important role in movement and host metabolism. Muscle fibre formation occurs mainly during the embryonic stage. Therefore, maternal lifestyle, especially nutrition and exercise during pregnancy, has a critical influence on foetal skeletal muscle development and the subsequent metabolic health of the offspring. In this review, the influence of maternal obesity, malnutrition and micronutrient intake on foetal skeletal muscle development is systematically summarized. We also aim to describe how maternal exercise shapes foetal muscle development and metabolic health in the offspring. The role of maternal gut microbiota and its metabolites on foetal muscle development is further discussed, although this field is still in its 'infancy'. This review will provide new insights to reduce the global crisis of metabolic disorders and highlight current gaps to promote further research.

Inhibitor of FTO, Rhein, Restrains the Differentiation of Myoblasts and Delays Skeletal Muscle Regeneration

N6-methyladenosine (m6A) is a crucial RNA modification affecting skeletal muscle development. Rhein, an anti-inflammatory extract, inhibits FTO, a key demethylase in m6A metabolism. Our study showed that during muscle fiber formation, FTO and ALKBH5 expression increased while m6A levels decreased. After muscle injury, FTO and ALKBH5 expression initially rose but later fell, while m6A levels initially dropped and then recovered. Inhibition of FTO by Rhein reduced MyHC and MyoG expression, indicating myoblast differentiation suppression. In a mouse model, Rhein decreased MyHC expression and muscle fiber cross-sectional area, delaying muscle regeneration. Rhein's ability to increase RNA m6A modification delays skeletal muscle remodeling post-injury, suggesting a new medicinal application for this plant extract.

Toxic effects of triclosan on hepatic and intestinal lipid accumulation in zebrafish via regulation of m6A-RNA methylation

Triclosan (TCS), recognized as an endocrine disruptor, has raised significant concerns due to its widespread use and potential health risks. To explore the impact of TCS on lipid metabolism, both larval and adult zebrafish were subjected to acute and chronic exposure to TCS. Through analyzes of biochemical and physiological markers, as well as Oil Red O (ORO) and hematoxylin and eosin (H&E) staining, our investigation revealed that TCS exposure induced hepatic and intestinal lipid accumulation in larval and adult zebrafish, leading to structural damage and inflammatory responses in these tissues. The strong affinity of TCS with PPARγ and subsequent pathway activation indicate that PPARγ pathway plays a crucial role in TCS-induced lipid buildup. Furthermore, we observed a decrease in m6A-RNA methylation levels in the TCS-treated group, which attributed to the increased activity of the demethylase FTO and concurrent suppression of the methyltransferase METTL3 gene expression by TCS. The alteration in methylation dynamics is identified as a potential underlying mechanism behind TCS-induced lipid accumulation. To address this concern, we explored the impact of folic acid-a methyl donor for m6A-RNA methylation-on lipid accumulation in zebrafish. Remarkably, folic acid administration partially alleviated lipid accumulation by restoring m6A-RNA methylation. This restoration, in turn, contributed to a reduction in inflammatory damage observed in both the liver and intestines. Additionally, folic acid partially mitigates the up-regulation of PPARγ and related genes induced by TCS. These findings carry substantial implications for understanding the adverse effects of environmental pollutants such as TCS. They also emphasize the promising potential of folic acid as a therapeutic intervention to alleviate disturbances in lipid metabolism induced by environmental pollutants.

Update on N6-methyladenosine methylation in obesity-related diseases

Obesity is a chronic metabolic disease that is closely related to type 2 diabetes mellitus, cardiovascular diseases, nonalcoholic fatty liver disease, obstructive sleep apnea, and osteoarthritis. The prevalence of obesity is increasing rapidly every year and is recognized as a global public health problem. In recent years, the role of epigenetics in the development of obesity and related diseases has been recognized and is currently a research hotspot. N6-methyladenosine (m6A) methylation is the most abundant epigenetic modification in the eukaryotic RNA, including mRNA and noncoding RNA. Several studies have shown that the m6A modifications in the target mRNA and the corresponding m6A regulators play a significant role in lipid metabolism and are strongly associated with the pathogenesis of obesity-related diseases. In this review, the latest research findings regarding the role of m6A methylation in obesity and related metabolic diseases are summarized. The authors' aim is to highlight evidence that suggests the clinical utility of m6A modifications and the m6A regulators as novel early prediction biomarkers and precision therapeutics for obesity and obesity-related diseases.

Maternal Prepregnancy 5-Hydroxytryptamine Exposure Affects the Early Development of the Fetus

In recent decades, the increasing incidence of depression has contributed to an increase in the use of serotonergic drugs, such as antidepressants, which predisposes humans to serotonin syndrome. Serotonin syndrome is caused by elevated serotonin levels in the central and peripheral nervous systems. It has been well documented that the development of offspring can be affected by maternal exposure to environmental challenges, such as stress, diseases, or an unhealthy diet during pregnancy. Serotonin, also called 5-hydroxytryptamine (5-HT), is widely expressed in the female reproductive system and plays an important role in the development of follicles and embryos. However, whether the suffering of the mother from serotonin syndrome before pregnancy affects fetal development is still uncertain. In the present study, to explore the effect of maternal prepregnancy 5-HT exposure on the fetus, intraperitoneal injection of 5-HT was used to change maternal prepregnancy 5-HT levels. It was found that maternal prepregnancy 5-HT exposure significantly reduced the body weight and liver weight and the levels of estrogen and progesterone in female mice. Although there was no significant difference in the cleavage rate and blastocyst rate between the 5-HT and control groups, maternal prepregnancy 5-HT exposure increased the percentage of embryo resorption, decreased placental weight, and led to placental inflammation at E13.5. Notably, 5-HT exposure caused weight loss in the offspring at 2 weeks. These results suggested that maternal prepregnancy 5-HT exposure could affect the development of the offspring, which was partly caused by reduced hormonal secretion and placental inflammation.

Impact of Nutrition on Age-Related Epigenetic RNA Modifications in Rats

Nutrition plastically modulates the epigenetic landscape in various tissues of an organism during life via epigenetic changes. In the present study, to clarify whether this modulation involves RNA methylation, we evaluated global RNA methylation profiles and the expression of writer, reader, and eraser genes, encoding for enzymes involved in the RNA methylation. The study was carried out in the heart, liver, and kidney samples from rats of different ages in response to a low-calorie diet. We found that, although each tissue showed peculiar RNA methylation levels, a general increase in these levels was observed throughout the lifespan as well as in response to the six-month diet. Similarly, a prominent remodeling of the expression of writer, reader, and eraser genes emerged. Our data provide a comprehensive overview of the role exerted by diet on the tissue-specific epigenetic plasticity of RNA according to aging in rats, providing the first evidence that methylation of RNA, similarly to DNA methylation, can represent an effective biomarker of aging. What is more, the fact that it is regulated by nutrition provides the basis for the development of targeted approaches capable of guaranteeing the maintenance of a state of good health.

Roles of RNA Modifications in Diverse Cellular Functions

Chemical modifications of RNA molecules regulate both RNA metabolism and fate. The deposition and function of these modifications are mediated by the actions of writer, reader, and eraser proteins. At the cellular level, RNA modifications regulate several cellular processes including cell death, proliferation, senescence, differentiation, migration, metabolism, autophagy, the DNA damage response, and liquid-liquid phase separation. Emerging evidence demonstrates that RNA modifications play active roles in the physiology and etiology of multiple diseases due to their pervasive roles in cellular functions. Here, we will summarize recent advances in the regulatory and functional role of RNA modifications in these cellular functions, emphasizing the context-specific roles of RNA modifications in mammalian systems. As m6A is the best studied RNA modification in biological processes, this review will summarize the emerging advances on the diverse roles of m6A in cellular functions. In addition, we will also provide an overview for the cellular functions of other RNA modifications, including m5C and m1A. Furthermore, we will also discuss the roles of RNA modifications within the context of disease etiologies and highlight recent advances in the development of therapeutics that target RNA modifications. Elucidating these context-specific functions will increase our understanding of how these modifications become dysregulated during disease pathogenesis and may provide new opportunities for improving disease prevention and therapy by targeting these pathways.

N6-Methyladenosine-Related Gene Signature Associated With Monocyte Infiltration Is Clinically Significant in Gestational Diabetes Mellitus

OBJECTIVE

The objective of this study was to reveal the potential crosstalk between immune infiltration and N⁶- methyladenosine (m⁶A) modification in the placentas of patients with gestational diabetes mellitus (GDM), and to construct a model for the diagnosis of GDM.

METHODS

We analyzed imbalanced immune infiltration and differentially expressed m⁶A-related genes (DMRGs) in the placentas of patients with GDM, based on the GSE70493 dataset. An immune-related DMRG signature, with significant classifying power and diagnostic value, was identified using a least absolute shrinkage and selection operator (LASSO) regression. Based on the selected DMRGs, we developed and validated a nomogram model using GSE70493 and GSE92772 as the training and validation sets, respectively.

RESULTS

Infiltration of monocytes was higher in GDM placentas than in control samples, while the infiltration of macrophages (M1 and M2) in GDM placentas was lower than in controls. A total of 14 DMRGs were strongly associated with monocyte infiltration, seven of which were significant in distinguishing patients with GDM from normal controls. These genes were CD81, CFH, FABP5, GBP1, GNG11, IL1RL1, and SLAMF6. The calibration curve, decision curve, clinical impact curve, and receiver operating characteristic curve showed that the nomogram recognized GDM with high accuracy in both the training and validation sets.

CONCLUSIONS

Our results provide clues that crosstalk between m⁶A modification and immune infiltration may have implications in terms of novel biomarkers and therapeutic targets for GDM.

Splice variants of metabolic nuclear receptors: Relevance for metabolic disease and therapeutic targeting

Metabolic nuclear receptors are ligand-activated transcription factors which control a wide range of metabolic processes and signaling pathways in response to nutrients and xenobiotics. Targeting these NRs is at the forefront of our endeavours to generate novel treatment options for diabetes, metabolic syndrome and fatty liver disease. Numerous splice variants have been described for these metabolic receptors. Structural changes, as a result of alternative splicing, lead to functional differences among NR isoforms, resulting in the regulation of different metabolic pathways by these NR splice variants. In this review, we describe known splice variants of FXR, LXRs, PXR, RXR, LRH-1, CAR and PPARs. We discuss their structure and functions, and elaborate on the regulation of splice variant abundance by nutritional signals. We conclude that NR splice variants pose an intriguing new layer of complexity in metabolic signaling, which needs to be taken into account in the development of treatment strategies for metabolic diseases.

Regulation of RNA N6-methyladenosine modification and its emerging roles in skeletal muscle development

N6-methyladenosine (m6A) is one of the most widespread and highly conserved chemical modifications in cellular RNAs of eukaryotic genomes. Owing to the development of high-throughput m6A sequencing, the functions and mechanisms of m6A modification in development and diseases have been revealed. Recent studies have shown that RNA m6A methylation plays a critical role in skeletal muscle development, which regulates myoblast proliferation and differentiation, and muscle regeneration. Exploration of the functions of m6A modification and its regulators provides a deeper understanding of the regulatory mechanisms underlying skeletal muscle development. In the present review, we aim to summarize recent breakthroughs concerning the global landscape of m6A modification in mammals and examine the biological functions and mechanisms of enzymes regulating m6A RNA methylation. We describe the interplay between m6A and other epigenetic modifications and highlight the regulatory roles of m6A in development, especially that of skeletal muscle. m6A and its regulators are expected to be targets for the treatment of human muscle-related diseases and novel epigenetic markers for animal breeding in meat production.

Comprehensive analysis of the transcriptome-wide m6A methylome in invasive malignant pleomorphic adenoma

Background

Invasive malignant pleomorphic adenoma (IMPA) is a highly invasive parotid gland tumor and lacks effective therapy. N6-Methyladenosine (m⁶A) is the most prevalent post-transcriptional modification of mRNAs in eukaryotes and plays an important role in the pathogenesis of multiple tumors. However, the significance of m⁶A-modified mRNAs in IMPA has not been elucidated to date. Hence, in this study, we attempted to profile the effect of IMPA in terms of m⁶A methylation in mRNA.

Methods

Methylated RNA immunoprecipitation with next-generation sequencing (MeRIP-seq) and RNA sequencing (RNA-seq) were utilized to acquire the first transcriptome-wide profiling of the m⁶A methylome map in IMPA followed by bioinformatics analysis.

Results

In this study, we obtained m⁶A methylation maps of IMPA samples and normal adjacent tissues through MeRIP-seq. In total, 25,490 m⁶A peaks associated with 13,735 genes were detected in the IMPA group, whereas 33,930 m⁶A peaks associated with 18,063 genes were detected in the control group. Peaks were primarily enriched within coding regions and near stop codons with AAACC and GGAC motifs. Moreover, functional enrichment analysis demonstrated that m⁶A-containing genes were significantly enriched in cancer and metabolism relevant pathways. Furthermore, we identified a relationship between the m⁶A methylome and the RNA transcriptome, indicating a mechanism by which m⁶A modulates gene expression.

Conclusions

Our study is the first to provide comprehensive and transcriptome-wide profiles to determine the potential roles played by m⁶A methylation in IMPA. These results may open new avenues for in-depth research elucidating the m⁶A topology of IMPA and the molecular mechanisms governing the formation and progression of IMPA.

Epigenetic regulation of adipose tissue expansion and adipogenesis by N6 -methyladenosine

Obesity, defined as excessive fat accumulation, is strongly associated with metabolic diseases and cancer, and its prevalence is rising worldwide. Thus, understanding the molecular mechanism of adipogenesis is of fundamental significance. Epigenetic modifications play important roles in regulating adipogenesis. N⁶ -methyladenosine (m⁶ A), the most prevalent and abundant mRNA modification in eukaryotic cells, modulates multiple aspects of RNA metabolism, including mRNA stability, translation, splicing and export. Recent studies indicate that m⁶ A methylation plays important roles in modulating gene expression and signal pathways in various physiologic processes and diseases. Notably, the significant function and regulatory mechanisms of m⁶ A in adipogenesis are now emerging. In this review, we summarize recent studies that elucidate the vital roles of m⁶ A modifications in regulating adipogenesis and adipose tissue expansion. Furthermore, we highlight the nutritional regulation of m⁶ A methylation and adipogenesis, which may prove a novel therapeutic strategy to fight against obesity.

Fusaric acid decreases p53 expression by altering promoter methylation and m6A RNA methylation in human hepatocellular carcinoma (HepG2) cells

Fusaric acid (FA) is a food-borne mycotoxin that mediates toxicity with limited information on its epigenetic properties. p53 is a tumour suppressor protein that regulates cell cycle arrest and apoptotic cell death. The expression of p53 is regulated transcriptionally by promoter methylation and post-transcriptionally by N-6-methyladenosine (m6A) RNA methylation. We investigated the effect of FA on p53 expression and its epigenetic regulation via promoter methylation and m6A RNA methylation in human hepatocellular carcinoma (HepG2) cells. HepG2 cells were treated with FA [0, 25, 50, 104, and 150 µg/ml; 24 h] and thereafter, DNA, RNA, and protein was isolated. Promoter methylation and expression of p53 was measured using qPCR and Western blot. RNA immuno-precipitation was used to determine m6A-p53 levels. The expression of m6A methyltransferases (METTL3 and METTL14), demethylases (FTO and ALKBH5), and readers (YTHDF1-3 and YTHDC2) were measured using qPCR. FA induced p53 promoter hypermethylation (p < 0.0001) and decreased p53 expression (p < 0.0001). FA decreased m6A-p53 levels (p < 0.0001) by decreasing METTL3 (p < 0.0001) and METTL14 (p < 0.0001); and suppressed expression of YTHDF1 (p < 0.0001), YTHDF3 (p < 0.0001), and YTHDC2 (p < 0.0001) that ultimately reduced p53 translation (p < 0.0001). Taken together, the data shows that FA epigenetically decreased p53 expression by altering its promoter methylation and m6A RNA methylation in HepG2 cells. This study reveals a mechanism for p53 regulation by FA and provides insight into future therapeutic interventions.

Resveratrol Attenuates High-Fat Diet Induced Hepatic Lipid Homeostasis Disorder and Decreases m6A RNA Methylation

Purpose: N 6-methyladenosine (m6A) mRNA methylation is affected by dietary factors and associated with lipid metabolism; however, whether the regulatory role of resveratrol in lipid metabolism is involved in m6A mRNA methylation remains unknown. Here, the objective of this study was to investigate the effect of resveratrol on hepatic lipid metabolism and m6A RNA methylation in the liver of mice. Methods: A total of 24 male mice were randomly allocated to LFD (low-fat diet), LFDR (low-fat diet + resveratrol), HFD (high-fat diet), and HFDR (high-fat diet + resveratrol) groups for 12 weeks (n = 6/group). Final body weight of mice was measured before sacrificing. Perirhemtric fat, abdominal and epididymal fat, liver tissues, and serum were collected at sacrifice and analyzed. Briefly, mice phenotype, lipid metabolic index, and m6A modification in the liver were assessed. Results: Compared to the HFD group, dietary resveratrol supplementation reduced the body weight and relative abdominal, epididymal, and perirhemtric fat weight in high-fat-exposed mice; however, resveratrol significantly increased average daily feed intake in mice given HFD. The amounts of serum low-density lipoprotein cholesterol (LDL), liver total cholesterol (TC), and triacylglycerol (TAG) were significantly decreased by resveratrol supplementation. In addition, resveratrol significantly enhanced the levels of peroxisome proliferator-activated receptor alpha (PPARα), peroxisome proliferator-activated receptor beta/delta (PPARβ/δ), cytochrome P450, family 4, subfamily a, polypeptide 10/14 (CYP4A10/14), acyl-CoA oxidase 1 (ACOX1), and fatty acid-binding protein 4 (FABP4) mRNA and inhibited acyl-CoA carboxylase (ACC) mRNA levels in the liver. Furthermore, the resveratrol in HFD increased the transcript levels of methyltransferase like 3 (METTL3), alkB homolog 5 (ALKBH5), fat mass and obesity associated protein (FTO), and YTH domain family 2 (YTHDF2), whereas it decreased the level of YTH domain family 3 (YTHDF3) and m6A abundance in mice liver. Conclusion: The beneficial effect of resveratrol on lipid metabolism disorder under HFD may be due to decrease of m6A RNA methylation and increase of PPARα mRNA, providing mechanistic insights into the function of resveratrol in alleviating the disturbance of lipid metabolism in mice.

Novel Insights into Adipogenesis from the Perspective of Transcriptional and RNA N6-Methyladenosine-Mediated Post-Transcriptional Regulation

Obesity is a critical risk factor causing the development of metabolic diseases and cancers. Its increasing prevalence worldwide has aroused great concerns of the researchers on adipose development and metabolic function. During adipose expansion, adipogenesis is a way to store lipids as well as to avoid lipotoxicity in other tissues, and may be an approach to offset the negative metabolic effects of obesity. In this Review, the transcriptional regulation of adipogenesis is outlined to characterize numerous biological processes in research on the determination of adipocyte fate and regulation of adipogenic differentiation. Notably, one of the post-transcriptional modifications of mRNA, namely, N6-methyladenosine (m6A), has been recently found to play a role in adipogenesis. Here, the roles of m6A-related enzymes and proteins in adipogenesis, with a particular focus on how these m6A-related proteins function at different stages of adipogenesis, are mainly discussed. The Review also highlights the coordination role of the transcriptional and post-transcriptional (RNA m6A methylation) regulation in adipogenesis and related biological processes. In this context, a better understanding of adipogenesis at both the transcriptional and post-transcriptional levels may facilitate the development of novel strategies to improve metabolic health in obesity.

Multifaceted Functions and Novel Insight Into the Regulatory Role of RNA N6-Methyladenosine Modification in Musculoskeletal Disorders

RNA modifications have emerged as key regulators of transcript expression in diverse physiological and pathological processes. As one of the most prevalent types of RNA modifications, N⁶-methyladenosine (m⁶A) has become the highlight in modulation of various diseases through interfering RNA splicing, translation, nuclear export, and decay. In many cases, the detailed functions of m⁶A in cellular processes and diseases remain unclear. Notably, recent studies have determined the relationship between m⁶A modification and musculoskeletal disorders containing osteosarcoma, osteoarthritis, rheumatoid arthritis, osteoporosis, etc. Herein, this review comprehensively summarizes the recent advances of m⁶A modification in pathogenesis and progression of musculoskeletal diseases. Specifically, the underlying molecular mechanisms, detection technologies, regulatory functions, clinical implications, and future perspectives of m⁶A in musculoskeletal disorders are discussed, with the aim to provide a novel insight into their association.

Emerging role of m6 A RNA methylation in nutritional physiology and metabolism

N6 -methyladenine (m6 A) is the most prevalent type of internal RNA methylation in eukaryotic mRNA and plays critical roles in regulating gene expression for fundamental cellular processes and diverse physiological functions. Recent evidence indicates that m6 A methylation regulates physiology and metabolism, and m6 A has been increasingly implicated in a variety of human diseases, including obesity, diabetes, metabolic syndrome and cancer. Conversely, nutrition and diet can modulate or reverse m6 A methylation patterns on gene expression. In this review, we summarize the recent progress in the study of the m6 A methylation mechanisms and highlight the crosstalk between m6 A modification, nutritional physiology and metabolism.

Acupuncture Targeting SIRT1 in the Hypothalamic Arcuate Nucleus Can Improve Obesity in High-Fat-Diet-Induced Rats with Insulin Resistance via an Anorectic Effect

OBJECTIVE

To investigate the anorexigenic and anti-obesity effectiveness of electroacupuncture (EA) on high-fat-diet-induced (HFDI) obese rats with insulin resistance (IR) and to reveal the possible mechanisms of EA affecting SIRT1 (silent mating type information regulation 2 homolog 1) in the central nervous system (CNS).

METHODS

We divided 60 rats into 6 groups. All interventions, including EA and intracerebroventricular administration, were performed after 8 weeks of model establishment. We tested obesity phenotypes like body weight (BW) gain; food intake; and IR levels including glucose infusion rate, intraperitoneal insulin tolerance test (IPITT), and intraperitoneal glucose tolerance test (IPGTT) during treatment. We detected protein expression and microscopic locations in hypothalamic SIRT1, the transcription factor FOXO1 (forkhead box protein O1), acetylated FOXO1 (Ac-FOXO1), pro-opiomelanocortin (POMC), and neuropeptide Y (NPY) via Western blotting and immunofluorescence, and monitored gene expression by real-time polymerase chain reaction.

RESULTS

Like the SIRT1 agonist, EA suppressed BW gain and IR levels in obese rats, but this was only partially blocked by the SIRT1 antagonist. EA could upregulate protein expression of hypothalamic SIRT1 and downregulate the acetylation level of FOXO1 in the hypothalamic arcuate nucleus (ARC), which decreased gene expression of NPY and increased that of POMC. The agonist targeted the hypothalamic SIRT1 gene, unlike EA, which targeted posttranscriptional regulation.

CONCLUSION

EA could improve obesity in HFDI rats with IR via its anorectic effect. This effect targeted posttranscriptional regulation of the SIRT1 gene, which induced upregulation of ARC FOXO1 deacetylation and mediated the gene expression of POMC and NPY.

Maternal conjugated linoleic acid alters hepatic lipid metabolism via the AMPK signaling pathway in chick embryos

The effects of maternal conjugated linoleic acid (CLA) on embryonic development and hepatic lipid metabolism were investigated in chick embryos. A total of 180 Arbor Acres female broiler breeders (36 wk old) were randomly divided into the following 3 dietary treatment groups: a basic diet (control), a basic diet containing 0.5% CLA (CLA1), and a basic diet containing 1.0% CLA (CLA2). The females were fed for 8 wk, and the eggs from each group were collected and hatched during the last 2 wk. The results showed that the addition of dietary CLA increased the broken egg rate and reduced the fertilization rate and the egg hatchability (P < 0.05). CLA enrichment decreased the polyunsaturated and monounsaturated fatty acids and increased the saturated fatty acids in the yolk sac (P < 0.05). The yolk sac weight, body weight, and body length had a linear decrease with CLA supplementation (P < 0.05). In the developing chick embryo (at E14) and newly hatched chick (D0), the serum triglyceride concentration decreased with maternal CLA supplementation and was accompanied by a reduction in subcutaneous adipose tissue deposition. In addition, maternal CLA supplementation mediated the hepatic lipid metabolism by decreasing the mRNA expression of sterol regulatory element-binding proteins-1c (SREBP-1c), fatty acid synthase and acetyl-CoA carboxylase, and increasing the mRNA expression of adenosine 5'-monophosphate-activated protein kinase α (AMPKα), peroxisome proliferator-activated receptors α (PPARα), liver fatty acid-binding protein, adipose triglyceride lipase and carnitine palmitoyltransferase in embryonic chick livers (P < 0.05). A drop in SREBP-1c protein expression and an increase in the protein expression of p-AMPKα and PPARα were also observed in the liver of chick embryo (P < 0.05). In conclusion, maternal CLA supplementation regulated the fatty acid composition in the yolk sac, and mediated embryonic chick development and hepatic lipometabolism, and these effects may be related to the AMPK pathway. These findings suggest the potential ability of maternal CLA supplementation to reduce fat deposition in chick embryos.

Resveratrol and Curcumin Improve Intestinal Mucosal Integrity and Decrease m6A RNA Methylation in the Intestine of Weaning Piglets

N 6-Methyladenosine (m6A) is the most prevalent modification on eukaryotic messenger RNA (mRNA). Resveratrol and curcumin, which can exert many health-protective effects, may have a relationship with m6A RNA methylation. We hypothesized that the combination of resveratrol and curcumin could affect growth performance, intestinal mucosal integrity, m6A RNA methylation, and gene expression in weaning piglets. One hundred and eighty piglets weaned at 28 ± 2 days were fed a control diet or supplementary diets (300 mg/kg of antibiotics; 300 mg/kg of each resveratrol and curcumin; 100 mg/kg of each resveratrol and curcumin; 300 mg/kg of resveratrol; 300 mg/kg of curcumin) for 28 days. The results showed that the combination of resveratrol and curcumin improved growth performance and enhanced intestinal mucosal integrity and functions in weaning piglets. Resveratrol and curcumin also increased intestinal antioxidative capacity and mRNA expression of tight junction proteins. Furthermore, resveratrol and curcumin decreased the content of m6A and decreased the enrichment of m6A on the transcripts of tight junction proteins and on heme oxygenase-1 in the intestine. Our findings indicated that the combination of resveratrol and curcumin increased growth performance, enhanced intestine function, and protected piglet health, which may be associated with changes in m6A methylation and gene expression, suggesting that curcumin and resveratrol may be a potential natural alternative to antibiotics.

Comprehensive analysis of differences of N6-methyladenosine RNA methylomes between high-fat-fed and normal mouse livers

Aim: To assess the m⁶A methylome in mouse fatty liver induced by a high-fat diet (HFD). Materials & methods: MeRIP-seq was performed to identify differences in the m⁶A methylomes between the normal liver and fatty liver induced by an HFD. Results: As compared with the control group, the upmethylated coding genes upon feeding an HFD were primarily enriched in processes associated with lipid metabolism, while genes with downmethylation were enriched in processes associated with metabolism and translation. Furthermore, many RNA-binding proteins that potentially bind to differentially methylated m⁶A sites were mainly annotated in processes of RNA splicing. Conclusion: These findings suggest that differential m⁶A methylation may act on functional genes through RNA-binding proteins to regulate the metabolism of lipids in fatty liver disease.

Maternal heat stress regulates the early fat deposition partly through modification of m6A RNA methylation in neonatal piglets

It is known that heat stress induces various physiological challenges in livestock production including changes in lipid metabolism. However, the molecular mechanism of how heat stress regulates lipid metabolism at the mRNA level is still largely unknown. N6-methyl-adenosine (m6A) is the most common and abundant modification on RNA molecules present in eukaryotes, which affects almost all aspects of RNA metabolism and thus gives us the hint that it may participate in changes of gene expression of lipid metabolism during heat stress. Therefore, the purpose of the present study was to investigate the effect of heat stress on fat metabolism in 21-day Large White × Landrace piglets from sows challenged by heat stress from day 85 of gestation until day 21 of lactation. We measured the expression of heat shock proteins (HSPs), genes associated with lipid metabolism, m6A-related enzymes, and m6A levels in abdominal fat and liver of offspring piglets. Our results showed that high ambient temperature significantly increased the expression of HSP70 (P < 0.01) in both liver and abdominal fat and upregulated HSP27 in the liver (P < 0.05). Additionally, genes involved in fat metabolism such as ACACA, FASN, DGAT1, PPAR-γ, SREBP-1c, and FABP4 were upregulated in abdominal fat in the experimental group challenged by high ambient temperature. In the liver, heat stress increased the mRNA expression of DGAT1, SREBP-1c, and CD36 and decreased ATGL and CPT1A expression (P < 0.05). The m6A level was higher in the heat stress group compared with the control group in the liver and abdominal fat of offspring piglets (P < 0.01). Notably, heat stress also increased gene expression of METTL14, WTAP, FTO, and YTHDF2 (P < 0.05) in both abdominal fat and liver. The protein abundances of METTL3, METTL14, and FTO were upregulated after heat stress in abdominal fat (P < 0.05) but not in the liver. Although there was no difference in the protein abundance of YTHDF2 in abdominal fat, its level was increased in the liver (P < 0.05). In conclusion, our findings showed that heat stress increased expression of genes involved in lipogenesis, which provided scientific evidence to the observation of increased fatness in pigs under heat stress. We also demonstrated a possible mechanism that m6A RNA modification may be associated with these changes in lipid metabolism upon heat stress.

Curcumin Attenuates Lipopolysaccharide-Induced Hepatic Lipid Metabolism Disorder by Modification of m6 A RNA Methylation in Piglets

N⁶ -methyladenosine (m⁶ A) regulates gene expression and affects cellular metabolism. In this study, we checked whether the regulation of lipid metabolism by curcumin is associated with m⁶ A RNA methylation. We investigated the effects of dietary curcumin supplementation on lipopolysaccharide (LPS)-induced liver injury and lipid metabolism disorder, and on m⁶ A RNA methylation in weaned piglets. A total of 24 Duroc × Large White × Landrace piglets were randomly assigned to control, LPS, and CurL (LPS challenge and 200 mg/kg dietary curcumin) groups (n = 8/group). The results showed that curcumin reduced the increase in relative liver weight as well as the concentrations of aspartate aminotransferase and lactate dehydrogenase induced by LPS injection in the plasma and liver of weaning piglets (p < 0.05). The amounts of total cholesterol and triacylglycerols were decreased by curcumin compared to that by the LPS injection (p < 0.05). Additionally, curcumin reduced the expression of Bcl-2 and Bax mRNA, whereas it increased the p53 mRNA level in the liver (p < 0.05). Curcumin inhibited the enhancement of SREBP-1c and SCD-1 mRNA levels induced by LPS in the liver. Notably, dietary curcumin affected the expression of METTL3, METTL14, ALKBH5, FTO, and YTHDF2 mRNA, and increased the abundance of m⁶ A in the liver of piglets. In conclusion, the protective effect of curcumin in LPS-induced liver injury and hepatic lipid metabolism disruption might be due to the increase in m⁶ A RNA methylation. Our study provides mechanistic insights into the effect of curcumin in protecting against hepatic injury during inflammation and metabolic diseases.

Circadian Clock Regulation of Hepatic Lipid Metabolism by Modulation of m6A mRNA Methylation

Transcriptional regulation of circadian rhythms is essential for lipid metabolic homeostasis, disruptions of which can lead to metabolic diseases. Whether N6-methyladenosine (m6A) mRNA methylation impacts circadian regulation of lipid metabolism is unclear. Here, we show m6A mRNA methylation oscillations in murine liver depend upon a functional circadian clock. Hepatic deletion of Bmal1 increases m6A mRNA methylation, particularly of PPaRα. Inhibition of m6A methylation via knockdown of m6A methyltransferase METTL3 decreases PPaRα m6A abundance and increases PPaRα mRNA lifetime and expression, reducing lipid accumulation in cells in vitro. Mechanistically, YTHDF2 binds to PPaRα to mediate its mRNA stability to regulate lipid metabolism. Induction of reactive oxygen species both in vitro and in vivo increases PPaRα transcript m6A levels, revealing a possible mechanism for circadian disruption on m6A mRNA methylation. These data show that m6A RNA methylation is important for circadian regulation of downstream genes and lipid metabolism, impacting metabolic outcomes.

Epigenetic modification of nucleic acids: from basic studies to medical applications

The epigenetic modification of nucleic acids represents one of the most significant areas of study in the field of nucleic acids because it makes gene regulation more complex and heredity more complicated, thus indicating its profound impact on aspects of heredity, growth, and diseases. The recent characterization of epigenetic modifications of DNA and RNA using chemical labelling strategies has promoted the discovery of these modifications, and the newly developed single-base or single-cell resolution mapping strategies have enabled large-scale epigenetic studies in eukaryotes. Due to these technological breakthroughs, several new epigenetic marks have been discovered that have greatly extended the scope and impact of epigenetic modifications in nucleic acids over the past few years. Because epigenetics is reversible and susceptible to environmental factors, it could potentially be a promising direction for clinical medicine research. In this review, we have comprehensively discussed how these epigenetic marks are involved in disease, including the pathogenesis, prevention, diagnosis and treatment of disease. These findings have revealed that the epigenetic modification of nucleic acids has considerable significance in various areas from methodology to clinical medicine and even in biomedical applications.

Aldosterone is involved in the pathogenesis of obesity-related glomerulopathy through activation of Wnt/β-catenin signaling in podocytes

Obesity-related glomerulopathy (ORG) is morphologically characterized by glomerulomegaly with or without observable focal segmental glomerulosclerosis under light microscope, with decreased podocyte density and number, and with increased foot‑process width observed under electron microscope. The severity of podocyte injury is correlated with the degree of proteinuria and renal dysfunction. However, the pathogenesis of ORG is not well understood. The aim of the present study was to explore the possible pathogenic role of aldosterone (ALDO) in ORG. In the in vivo animal experiments, body weight, Lee's obesity index, abdominal fat index, urinary protein excretion, average glomerular diameter were significantly increased, the mRNA and protein expression of podocyte‑associated molecules including nephrin, podocin, podoplanin and podocalyxin were significantly reduced, and the Wnt/β‑catenin signaling pathway was activated in ORG model mice compared with the Control mice, whereas the administration of spironolactone significantly ameliorated these effects. In the in vitro experiments on cultured podocytes, the mRNA and protein expression levels of the aforementioned podocyte‑associated molecules were significantly downregulated and the Wnt/β‑catenin signaling pathway was activated following ALDO stimulation, whereas eplerenone significantly attenuated all the above effects. Dickkopf‑related protein 1 (DKK1), an inhibitor of Wnt/β‑catenin signaling pathway, also reduced the effects of ALDO exposure on the expression of podocyte‑associated molecules. The present study hypothesized that ALDO may be involved in the pathogenesis of ORG through the activation of Wnt/β‑catenin signaling pathway in podocytes.

Maternal conjugated linoleic acid modulates TAG metabolism in adult rat offspring

Conjugated linoleic acid (CLA) might regulate the lipid depots in liver and adipose tissue. As there is an association between maternal nutrition, fat depots and risk of offspring chronic disease, the aim was to investigate the effect of maternal CLA consumption on TAG regulation and some inflammatory parameters in adult male rat offspring receiving or not receiving CLA. Female Wistar rats were fed control (C) or CLA-supplemented (1 %, w/w) diets during 4 weeks before and throughout pregnancy and lactation. After weaning, male offspring of CLA rats were fed C or CLA diets (CLA/C and CLA/CLA groups, respectively), whereas C male rat offspring were fed a C diet (C/C group) for 9 weeks. Serum TAG levels were increased in the CLA/CLA and CLA/C groups, associated with a reduction of lipoprotein lipase activity and weights of adipose tissue. The liver TAG levels were decreased in the CLA/CLA group, related to a significant reduction of fatty acid synthase (FAS), acetyl-CoA carboxylase (ACC) and glucose-6-phosphate dehydrogenase enzyme activities, as well as to the mRNA levels of FAS, ACC, stearoyl-CoA desaturase-1 and sterol regulatory element-binding protein-1c. Even though normal TAG levels were found in the liver of CLA/C rats, a reduction of lipogenesis was also observed. Thus, these results demonstrated a programming effect of CLA on the lipid metabolic pathways leading to a preventive effect on the TAG accretion in adipose tissue and the liver of male rat offspring. This knowledge could be important to develop some dietary strategies leading to a reduced incidence of obesity and fatty acid liver disease in humans.