Epigenetic disturbances in obesity and diabetes: Epidemiological and functional insights

Role of Epigenetics and Metabolomics in Predicting Endothelial Dysfunction in Type 2 Diabetes

Type 2 diabetes (T2D) is a worldwide health problem and cardiovascular disease (CVD) is a leading cause of morbidity and mortality in T2D patients, making the prevention of CVD onset a major priority. It is therefore crucial to optimize diagnosis and treatment to reduce this burden. Endothelial dysfunction is one of the most important prognostic factors for CVD progression, thus novel approaches to identify the early phase of endothelial dysfunction may lead to specific preventive measures to reduce the occurrence of CVD. Nowadays, multiomics approaches have provided unprecedented opportunities to stratify T2D patients into endotypes, improve therapeutic treatment and outcome and amend the survival prediction. Among omics strategies, epigenetics and metabolomics are gaining increasing interest. Recently, a dynamic correlation between metabolic pathways and gene expression through chromatin remodeling, such as DNA methylation, has emerged, indicating new perspectives on the regulatory networks impacting cellular processes. Thus, a better understanding of epigenetic-metabolite relationships can provide insight into the physiological processes altered early in the endothelium that ultimately head to disease development. Here, recent studies on epigenetics and metabolomics related to CVD prevention potentially useful to identify disease biomarkers, as well as new therapies hopefully targeting the early phase of endothelial dysfunction are highlighted.

Integrative genomic analyses in adipocytes implicate DNA methylation in human obesity and diabetes

DNA methylation variations are prevalent in human obesity but evidence of a causative role in disease pathogenesis is limited. Here, we combine epigenome-wide association and integrative genomics to investigate the impact of adipocyte DNA methylation variations in human obesity. We discover extensive DNA methylation changes that are robustly associated with obesity (N = 190 samples, 691 loci in subcutaneous and 173 loci in visceral adipocytes, P < 1 × 10-7). We connect obesity-associated methylation variations to transcriptomic changes at >500 target genes, and identify putative methylation-transcription factor interactions. Through Mendelian Randomisation, we infer causal effects of methylation on obesity and obesity-induced metabolic disturbances at 59 independent loci. Targeted methylation sequencing, CRISPR-activation and gene silencing in adipocytes, further identifies regional methylation variations, underlying regulatory elements and novel cellular metabolic effects. Our results indicate DNA methylation is an important determinant of human obesity and its metabolic complications, and reveal mechanisms through which altered methylation may impact adipocyte functions.

Epigenetics in cancer development, diagnosis and therapy

Cancer is a dangerous disease and one of the leading causes of death in the world. In 2020, there were nearly 10 million cancer deaths and approximately 20 million new cases. New cases and deaths from cancer are expected to increase further in the coming years. To have a deeper insight into the mechanism of carcinogenesis, epigenetics studies have been published and received much attention from scientists, doctors, and patients. Among alterations in epigenetics, DNA methylation and histone modification are studied by many scientists. They have been reported to be a major contributor in tumor formation and are involved in metastasis. From the understanding of DNA methylation and histone modification, effective, accurate and cost-effective methods for diagnosis and screening of cancer patients have been introduced. Furthermore, therapeutic approaches and drugs targeting altered epigenetics have also been clinically studied and have shown positive results in combating tumor progression. Several cancer drugs that rely on DNA methylation inactivation or histone modification have been approved by the FDA for the treatment of cancer patients. In summary, epigenetics changes such as DNA methylation or histone modification are take part in tumor growth, and they also have great prospect to study diagnostic and therapeutic methods of this dangerous disease.

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

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

Independent phenotypic plasticity axes define distinct obesity sub-types

Studies in genetically 'identical' individuals indicate that as much as 50% of complex trait variation cannot be traced to genetics or to the environment. The mechanisms that generate this 'unexplained' phenotypic variation (UPV) remain largely unknown. Here, we identify neuronatin (NNAT) as a conserved factor that buffers against UPV. We find that Nnat deficiency in isogenic mice triggers the emergence of a bi-stable polyphenism, where littermates emerge into adulthood either 'normal' or 'overgrown'. Mechanistically, this is mediated by an insulin-dependent overgrowth that arises from histone deacetylase (HDAC)-dependent β-cell hyperproliferation. A multi-dimensional analysis of monozygotic twin discordance reveals the existence of two patterns of human UPV, one of which (Type B) phenocopies the NNAT-buffered polyphenism identified in mice. Specifically, Type-B monozygotic co-twins exhibit coordinated increases in fat and lean mass across the body; decreased NNAT expression; increased HDAC-responsive gene signatures; and clinical outcomes linked to insulinemia. Critically, the Type-B UPV signature stratifies both childhood and adult cohorts into four metabolic states, including two phenotypically and molecularly distinct types of obesity.

Differences in circulating obesity-related microRNAs in Austrian and Japanese men: A two-country cohort analysis

Background

The prevalence of obesity is higher in Western countries than in East Asian countries. It remains unknown whether microRNAs (miRNAs) are involved in the pathogenesis of the ethnic difference in obesity. The purpose of this study was to determine whether expression levels of circulating obesity-associated miRNAs are different in Europeans and Asians.

Methods

The subjects were middle-aged healthy male Austrians (n = 20, mean age of 49.9 years) and Japanese (n = 20, mean age of 48.7 years). Total miRNAs in serum from each subject were analyzed using the 3D-Gene miRNA Oligo chip. miRNAs that showed significant differences between the Austrian and Japanese groups were uploaded into Ingenuity Pathway Analysis (IPA).

Results

Among 16 miRNAs that were revealed to be associated with obesity in previous studies and showed expression levels that were high enough for a reasonable comparison, serum levels of 3 miRNAs displayed significant differences between the Austrian and Japanese groups: miR-125b-1-3p was significantly lower with a fold change of −2.94 and miR-20a-5p and miR-486–5p were significantly higher with fold changes of 1.73 and 2.38, respectively, in Austrians than in Japanese. In IPA including all 392 miRNAs that showed significant differences between Austrians and Japanese, three canonical pathways including leptin signaling in obesity, adipogenesis pathway and white adipose tissue browning pathway were identified as enriched pathways.

Conclusions

miRNAs are thought to be involved in the ethnic difference in the prevalence of obesity, which may in part be caused by different expression levels of miR-125b-1-3p, miR-20a-5p and miR-486–5p.

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Ethnic difference in circulating obesity-related microRNAs (miRs) were investigated.

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Levels of 2565 miRs in blood were compared between Austrians and Japanese.

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miR-125b-1-3p, −20a-5p and -486–5p levels were significantly different between them.

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Significant ethnic differences were found in blood levels of 392 miRs.

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These miRs target the molecules comprising obesity-related three canonical pathways.

DNMT3A and TET2; Potential Estimates of Generic DNA Methylation in Children and Adolescents with Obesity; Relation to Metabolic Dysregulation

INTRODUCTION

The role of DNA methylation in metabolic dysregulation is emerging. However, the functional role of methylation in obesity and metabolic dysregulation is poorly understood.

AIM

The aim of this study was to compare DNA methyltransferase-3A (DNMT3A) and ten-eleven translocase-2 (TET2) levels in children and adolescents with obesity to normal-weighed children and adolescents and to correlate them to various metabolic parameters.

METHODS

Fifty children and adolescents with obesity were compared to 50 matched normal-weighed children and adolescents. Participants underwent assessment for anthropometric measurements, Tanner staging, acanthosis nigricans, and mean blood pressure percentile on three different occasions. TET2, DNMT3A, fasting lipids, and insulin were measured with calculation of the homeostatic model assessment insulin resistance (HOMA-IR).

RESULTS

The median BMI SDS of the studied children and adolescents with obesity was 3.40, their mean TET2 was 178.40 ng/mL, and their mean DNMT3A was 2.18 ng/mL. TET2 is significantly lower (p = 0.009), while DNMT3A is significantly higher (p < 0.001) in children and adolescents with obesity than controls. Children and adolescents with obesity and insulin resistance have significantly lower TET2 (p = 0.012) and significantly higher DNMT3A (p = 0.013) than those without insulin resistance. Diastolic blood pressure percentile and HOMA-IR are positively correlated to DNMT3A (p < 0.001) and negatively correlated to TET-2 (p < 0.001). Multivariate logistic regression analysis revealed that TET2 and DNMT3A are independently associated with diastolic blood pressure percentile (p = 0.03 and p = 0.014, respectively) and HOMA-IR (p = 0.003 and p = 0.001, respectively).

CONCLUSIONS

Children and adolescents with obesity have significantly higher DNMT3A and significantly lower TET2 than controls. This is more evident in those having insulin resistance than those without. DNMT3A and TET2 are independently associated with systemic hypertension and insulin resistance in children with obesity.

Mechanisms for Improving Hepatic Glucolipid Metabolism by Cinnamic Acid and Cinnamic Aldehyde: An Insight Provided by Multi-Omics

Cinnamic acid (AC) and cinnamic aldehyde (AL) are two chemicals enriched in cinnamon and have been previously proved to improve glucolipid metabolism, thus ameliorating metabolic disorders. In this study, we employed transcriptomes and proteomes on AC and AL treated db/db mice in order to explore the underlying mechanisms for their effects. Db/db mice were divided into three groups: the control group, AC group and AL group. Gender- and age-matched wt/wt mice were used as a normal group. After 4 weeks of treatments, mice were sacrificed, and liver tissues were used for further analyses. Functional enrichment of differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) were performed using Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases. DEPs were further verified by parallel reaction monitoring (PRM). The results suggested that AC and AL share similar mechanisms, and they may improve glucolipid metabolism by improving mitochondrial functions, decreasing serotonin contents and upregulating autophagy mediated lipid clearance. This study provides an insight into the molecular mechanisms of AC and AL on hepatic transcriptomes and proteomes in disrupted metabolic situations and lays a foundation for future experiments.

Dietary Fiber Intake May Influence the Impact of FTO Genetic Variants on Obesity Parameters and Lipid Profile-A Cohort Study of a Caucasian Population of Polish Origin

Genetic and environmental factors play a key role in the development of obesity. The aim of this study was to explore the potential effect of fat mass and obesity-associated (FTO) rs3751812, rs8050136, rs9939609, rs6499640, rs8044769, and rs7190492 genotypes and dietary fiber intake on the obesity-related parameters and lipid profile in the Polish population. We selected 819 Polish Caucasian adult subjects (52.5% female and 47.5% male) for a final gene–diet interaction analysis, with mean BMI 28.5 (±6.6) kg/m². We performed measurements of anthropometric parameters, total body fat content and distribution, and blood glucose, insulin, and lipid concentrations. Daily fiber intake was analyzed based on 3-day food-intake diaries, and daily physical activity was evaluated based on the International Physical Activity Questionnaire—Long Form. Our study shows that carriers of the GG genotype (rs3751812), CC genotype (rs8050136), and GG genotype (rs6499640) presented lower hip circumference if daily fiber intake was above 18 g per day. Additionally, GG genotype (rs3751812) and CC genotype (rs8050136) carriers showed surprisingly higher total cholesterol and LDL-cholesterol levels when they were stratified to the group with higher than median fiber intake. The results of this study highlight that high-fiber diets may positively affect anthropometric parameters but may also worsen lipid profile dependent on the FTO genotype.

Epigenetic regulation of energy metabolism in obesity

Obesity has reached epidemic proportions globally. Although modern adoption of a sedentary lifestyle coupled with energy-dense nutrition is considered to be the main cause of obesity epidemic, genetic preposition contributes significantly to the imbalanced energy metabolism in obesity. However, the variants of genetic loci identified from large-scale genetic studies do not appear to fully explain the rapid increase in obesity epidemic in the last four to five decades. Recent advancements of next-generation sequencing technologies and studies of tissue-specific effects of epigenetic factors in metabolic organs have significantly advanced our understanding of epigenetic regulation of energy metabolism in obesity. The epigenome, including DNA methylation, histone modifications, and RNA-mediated processes, is characterized as mitotically or meiotically heritable changes in gene function without alteration of DNA sequence. Importantly, epigenetic modifications are reversible. Therefore, comprehensively understanding the landscape of epigenetic regulation of energy metabolism could unravel novel molecular targets for obesity treatment. In this review, we summarize the current knowledge on the roles of DNA methylation, histone modifications such as methylation and acetylation, and RNA-mediated processes in regulating energy metabolism. We also discuss the effects of lifestyle modifications and therapeutic agents on epigenetic regulation of energy metabolism in obesity.

Transcriptional characterization of subcutaneous adipose tissue in obesity affected women highlights metabolic dysfunction and implications for lncRNAs

Obesity is a complex disease with multifactorial causes, and its prevalence is becoming a serious health crisis. For this reason, there is a crucial need to identify novel targets and players. With this aim in mind, we analyzed via RNA-sequencing the subcutaneous adipose tissue of normal weight and obesity-affected women, highlighting the differential expression in the two tissues. We specifically focused on long non-coding RNAs, as 6 of these emerged as dysregulated in the diseased-tissue (COL4A2-AS2, RPS21-AS, PELATON, ITGB2-AS1, ACER2-AS and CTEPHA1). For each of them, we performed both a thorough in silico dissection and in vitro validation, to predict their function during adipogenesis. We report the lncRNAs expression during adipose derived stem cells differentiation to adipocytes as model of adipogenesis and their potential modulation by adipogenesis-related transcription factors (C/EBPs and PPARγ). Moreover, inhibiting CTEPHA1 expression we investigated its impact on adipogenesis-related transcription factors, showing its significative dysregulation of C/EBPα expression. Lastly, we dissected the subcellular localization, pathway involvement and disease-correlation for coding differentially expressed genes. Together, these findings highlight a transcriptional deregulation at the basis of obesity, impacted by both coding and long non-coding RNAs.

How Are Epigenetic Modifications Related to Cardiovascular Disease in Older Adults?

The rate of aging has increased globally during recent decades and has led to a rising burden of age-related diseases such as cardiovascular disease (CVD). At the molecular level, epigenetic modifications have been shown recently to alter gene expression during the life course and impair cellular function. In this regard, several CVD risk factors, such as lifestyle and environmental factors, have emerged as key factors in epigenetic modifications within the cardiovascular system. In this study, we attempted to summarized recent evidence related to epigenetic modification, inflammation response, and CVD in older adults as well as the effect of lifestyle modification as a preventive strategy in this age group. Recent evidence showed that lifestyle and environmental factors may affect epigenetic mechanisms, such as DNA methylation, histone acetylation, and miRNA expression. Several substances or nutrients such as selenium, magnesium, curcumin, and caffeine (present in coffee and some teas) could regulate epigenetics. Similarly, physical inactivity, alcohol consumption, air pollutants, psychological stress, and shift working are well-known modifiers of epigenetic patterns. Understanding the exact ways that lifestyle and environmental factors could affect the expression of genes could help to influence the time of incidence and severity of aging-associated diseases. This review highlighted that a healthy lifestyle throughout the life course, such as a healthy diet rich in fibers, vitamins, and essential elements, and specific fatty acids, adequate physical activity and sleep, smoking cessation, and stress control, could be useful tools in preventing epigenetic changes that lead to impaired cardiovascular function.

An Update on the Epidemiology of Type 2 Diabetes: A Global Perspective

Type 2 diabetes (T2D) is a public health burden associated with immense health care and societal costs, early death, and morbidity. Largely because of epidemiologic changes, including nutrition transitions, urbanization, and sedentary lifestyles, T2D is increasing in every region of the world, particularly in low-income and middle-income countries. This article highlights global trends in T2D and discusses the role of genes, early-life exposures, and lifestyle risk factors in the cause of T2D, with an emphasis on populations in current hotspots of the epidemic. It also considers potential impacts of the coronavirus disease 2019 pandemic and T2D prevention policies and action.

Role of long non-coding RNAs in adipogenesis: State of the art and implications in obesity and obesity-associated diseases

Obesity is an evolutionary, chronic, and relapsing disease that consists of a pathological accumulation of adipose tissue able to increase morbidity for high blood pressure, type 2 diabetes, metabolic syndrome, and obstructive sleep apnea in adults, children, and adolescents. Despite intense research over the last 20 years, obesity remains today a disease with a complex and multifactorial etiology. Recently, long non-coding RNAs (lncRNAs) are emerging as interesting new regulators as different lncRNAs have been found to play a role in early and late phases of adipogenesis and to be implicated in obesity-associated complications onset. In this review, we discuss the most recent advances on the role of lncRNAs in adipocyte biology and in obesity-associated complications. Indeed, more and more researchers are focusing on investigating the underlying roles that these molecular modulators could play. Even if a significant number of evidence is correlation-based, with lncRNAs being differentially expressed in a specific disease, recent works are now focused on deeply analyzing how lncRNAs can effectively modulate the disease pathogenesis onset and progression. LncRNAs possibly represent new molecular markers useful in the future for both the early diagnosis and a prompt clinical management of patients with obesity.

Differentially methylated regions (DMRs) in PON3 gene between responders and non-responders to a weight loss dietary intervention: a new tool for precision management of obesity

Differentially methylated regions (DMR) are genomic regions with different methylation status. The aim of this research was to identify DMRs in subjects with obesity that predict the response to a weight-loss dietary intervention and its association with metabolic variables. Based on the change in body mass index (BMI), 201 subjects with overweight and obesity were categorized in tertiles according to their response to a hypocaloric diet: Responders (R; n = 64) and Non-Responders (NR; n = 63). The R group lost 4.55 ± 0.91 BMI units (kg/m²) and the NR group lost 1.95 ± 0.73 kg/m² (p < 0.001). DNA methylation was analysed in buffy coat through a methylation array at baseline. DMRs were analysed using a function of ChAMP (Chip Analysis Methylation Pipeline) in R software. Baseline DNA methylation analysis between R and NR exhibited a DMR located at paraoxonase 3 gene (PON3) consisting of 13 CpG sites, eleven of them significantly hypermethylated in R. To analyse the implication of these 11 CpGs on weight loss, a z-score was performed as a measure of DMR methylation. This analysis showed a correlation between PON3 DNA methylation and BMI loss. This z-score negatively correlated with PON3 protein serum levels. Total paraoxonase activity in serum was not different between groups, but PON enzymatic activity positively correlated with oxidized LDL levels. The present study identified a DMR within PON3 gene that is related to PON3 protein levels in serum, and that could be used as a potential biomarker to predict the response to weight-loss dietary interventions.

ANGPTL8/Betatrophin Improves Glucose Tolerance in Older Mice and Metabolomic Analysis Reveals Its Role in Insulin Resistance in HepG2 Cells

BACKGROUND

Insulin resistance is a determining factor in the pathophysiology of type 2 diabetes mellitus (T2DM). Angiopoietin-like protein 8 (ANGPTL8, also known as betatrophin), associated with glucose homeostasis and lipid metabolism, has attracted attention. But its mechanism in glucose metabolism remains unclear. This study aimed to explore the effect of ANGPTL8/betatrophin on glucose tolerance in Kunming (KM) mice of different ages and metabolic profiles in insulin-resistant HepG2 cells. Our study may provide a new perspective of ANGPTL8/betatrophin in insulin resistance from the metabolic changes.

METHODS

Oral glucose tolerance test was performed in KM mice of different ages. Insulin concentration was measured by using a quantitative enzyme-linked immunosorbent assay (ELISA). ANGPTL8/betatrophin knockouts in HepG2 cells were established with clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated (Cas) protein 9 (CRISPR/Cas9) system. Cell counting kit-8 (CCK-8) assay was used to determine cell viability after gene knockout. The effect of ANGPTL8/betatrophin on the metabolomic changes was evaluated in high insulin-induced insulin-resistant HepG2 cells by an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method.

RESULTS

ANGPTL8/betatrophin improved glucose tolerance in older mice not by altering the concentration of insulin. Cell growth was affected in ANGPTL8/betatrophin knockout HepG2. Based on UPLC-MS/MS, compared with wild type insulin-resistant HepG2 cells, we identified 83 differential metabolites in ANGPTL8/betatrophin knockout HepG2 cells after high insulin induction. Among the 14 differential up-regulated metabolites, D-mannose had the highest fold change. In insulin-resistant HepG2 cells, ANGPTL8/betatrophin knockout exerted an effect on the amino acid metabolism, carbohydrate metabolism, metabolism of cofactors and vitamins, lipid metabolism, nucleotide metabolism, and genetic information processing pathway.

CONCLUSION

This study identified the effect of ANGPTL8/betatrophin on glucose tolerance in mice of different ages and metabolic profiles in insulin-resistant HepG2 cells. These findings may contribute to a new understanding of its role in glucose metabolism in the context of insulin resistance.

The Impact of lncRNAs in Diabetes Mellitus: A Systematic Review and In Silico Analyses

Long non-coding RNAs (lncRNAs) are non-coding transcripts that have emerged as one of the largest and diverse RNA families that regulate gene expression. Accumulating evidence has suggested a number of lncRNAs are involved in diabetes mellitus (DM) pathogenesis. However, results about lncRNA expressions in DM patients are still inconclusive. Thus, we performed a systematic review of the literature on the subject followed by bioinformatics analyses to better understand which lncRNAs are dysregulated in DM and in which pathways they act. Pubmed, Embase, and Gene Expression Omnibus (GEO) repositories were searched to identify studies that investigated lncRNA expression in cases with DM and non-diabetic controls. LncRNAs consistently dysregulated in DM patients were submitted to bioinformatics analysis to retrieve their target genes and identify potentially affected signaling pathways under their regulation. Fifty-three eligible articles were included in this review after the application of the inclusion and exclusion criteria. Six hundred and thirty-eight lncRNAs were differentially expressed between cases and controls in at least one study. Among them, six lncRNAs were consistently dysregulated in patients with DM (Anril, Hotair, Malat1, Miat, Kcnq1ot1, and Meg3) compared to controls. Moreover, these six lncRNAs participate in several metabolism-related pathways, evidencing their importance in DM. This systematic review suggests six lncRNAs are dysregulated in DM, constituting potential biomarkers of this disease.

Adipose Tissue Epigenetic Profile in Obesity-Related Dysglycemia - A Systematic Review

BACKGROUND

Obesity is a major risk factor for dysglycemic disorders, including type 2 diabetes (T2D). However, there is wide phenotypic variation in metabolic profiles. Tissue-specific epigenetic modifications could be partially accountable for the observed phenotypic variability.

SCOPE

The aim of this systematic review was to summarize the available data on epigenetic signatures in human adipose tissue (AT) that characterize overweight or obesity-related insulin resistance (IR) and dysglycemia states and to identify potential underlying mechanisms through the use of unbiased bioinformatics approaches.

METHODS

Original data published in the last decade concerning the comparison of epigenetic marks in human AT of individuals with metabolically unhealthy overweight/obesity (MUHO) versus normal weight individuals or individuals with metabolically healthy overweight/obesity (MHO) was assessed. Furthermore, association of these epigenetic marks with IR/dysglycemic traits, including T2D, was compiled.

RESULTS

We catalogued more than two thousand differentially methylated regions (DMRs; above the cut-off of 5%) in the AT of individuals with MUHO compared to individuals with MHO. These DNA methylation changes were less likely to occur around the promoter regions and were enriched at loci implicated in intracellular signaling (signal transduction mediated by small GTPases, ERK1/2 signaling and intracellular trafficking). We also identified a network of seven transcription factors that may play an important role in targeting DNA methylation changes to specific genes in the AT of subjects with MUHO, contributing to the pathogeny of obesity-related IR/T2D. Furthermore, we found differentially methylated CpG sites at 8 genes that were present in AT and whole blood, suggesting that DMRs in whole blood could be potentially used as accessible biomarkers of MUHO.

CONCLUSIONS

The overall evidence linking epigenetic alterations in key tissues such AT to metabolic complications in human obesity is still very limited, highlighting the need for further studies, particularly those focusing on epigenetic marks other than DNA methylation. Our initial analysis suggests that DNA methylation patterns can potentially discriminate between MUHO from MHO and provide new clues into why some people with obesity are less susceptible to dysglycemia. Identifying AT-specific epigenetic targets could also lead to novel approaches to modify the progression of individuals with obesity towards metabolic disease.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO, identifier CRD42021227237.

A Class I Histone Deacetylase Inhibitor Attenuates Insulin Resistance and Inflammation in Palmitate-Treated C2C12 Myotubes and Muscle of HF/HFr Diet Mice

Histone deacetylase (HDAC) inhibitors, which regulate gene expression by inhibiting the deacetylation of histones and nonhistone proteins, have been shown to exert a wide array of biological effects; these include anti-cancer, anti-obesity, and anti-diabetes effects, as well as cardiovascular-protective activity. However, the effects of class I HDAC inhibition on lipotoxicity in C2C12 myotubes and skeletal muscle tissue remain poorly understood. In this study, we investigated the molecular mechanism underlying the protective effect of class I HDAC inhibition under lipotoxic conditions, i.e., in palmitate (PA)-treated C2C12 myotubes and skeletal muscle tissue in high fat (HF)/high fructose (HFr) diet mice. PA treatment of C2C12 myotubes increased HDAC3 protein expression and impaired mitochondrial oxidation, resulting in increased mitochondrial ROS generation and an accumulation of intracellular triglycerides (TG). Prolonged exposure led to increased inflammatory cytokine expression and insulin resistance. In contrast, MS-275, a class I HDAC inhibitor, dramatically attenuated lipotoxicity, preventing PA-induced insulin resistance and inflammatory cytokine expression. Similar beneficial effects were also seen following HDAC3 knockdown. In addition, MS-275 increased the mRNA expression of peroxisome proliferator activator receptor γ-coactivator 1α (PGC1α) and mitochondrial transcription factor A (TFAM), which serve as transcriptional coactivators in the context of mitochondrial metabolism and biogenesis, and restored expression of peroxisome proliferator-activated receptor alpha (PPARα), medium-chain acyl-coenzyme A dehydrogenase (MCAD), enoyl-CoA hydratase, and 3-hydroxyacyl CoA dehydrogenase (EHHADH). In vivo, treatment of HF/HFr-fed mice with MS-275 ameliorated hyperglycemia, insulin resistance, stress signals, and TNF-α expression in skeletal muscle. Taken together, these results suggest that HDAC3 inhibition rather than HDAC1/2 inhibition by MS-275 protects against lipotoxicity in C2C12 myotubes and skeletal muscle, and may be effective for the treatment of obesity and insulin resistance.

Interactions Between Therapeutics for Metabolic Disease, Cardiovascular Risk Factors, and Gut Microbiota

With improved standards of living, the incidence of multiple metabolic disorders has increased year by year, especially major risk factors for cardiovascular disease such as hyperglycemia and hyperlipidemia, continues to increase. Emerging epidemiological data and clinical trials have shown the additional protective effects of some metabolic therapy drugs against cardiovascular diseases. A series of studies have found that these drugs may work by modulating the composition of gut microbiota. In this review, we provide a brief overview of the contribution of the gut microbiota to both metabolic disorders and cardiovascular diseases, as well as the response of gut microbiota to metabolic therapy drugs with cardiovascular benefits. In this manner, we link the recent advances in microbiome studies on metabolic treatment drugs with their cardiovascular protective effects, suggesting that intestinal microorganisms may play a potential role in reducing cardiovascular risk factors. We also discuss the potential of microorganism-targeted therapeutics as treatment strategies for preventing and/or treating cardiovascular disease and highlight the need to establish causal links between therapeutics for metabolic diseases, gut microbiota modulation, and cardiovascular protection.

The Impact of FTO Genetic Variants on Obesity and Its Metabolic Consequences is Dependent on Daily Macronutrient Intake

Numerous studies have identified the various fat mass and obesity-associated (FTO) genetic variants associated with obesity and its metabolic consequences; however, the impact of dietary factors on these associations remains unclear. The aim of this study was to evaluate the association between FTO single nucleotide polymorphisms (SNPs), daily macronutrient intake, and obesity and its metabolic consequences. From 1549 Caucasian subjects of Polish origin, genotyped for the FTO SNPs (rs3751812, rs8044769, rs8050136, and rs9939609), 819 subjects were selected for gene–diet interaction analysis. Anthropometric measurements were performed and total body fat content and distribution, blood glucose and insulin concentration during oral glucose tolerance test (OGTT), and lipid profile were determined. Macronutrient intake was analyzed based on three-day food records, and daily physical activity levels were evaluated using the International Physical Activity Questionnaire Long Form (IPAQ-LF). Our study shows that carriers of the GG genotype of rs3751812 presented lower body weight, body mass index (BMI), total body fat content, and hip and waist circumference and presented lower obesity-related markers if more than 48% of daily energy intake was derived from carbohydrates and lower subcutaneous and visceral fat content when energy intake derived from dietary fat did not exceed 30%. Similar results were observed for rs8050136 CC genotype carriers. We did not notice any significant differences in obesity markers between genotypes of rs8044769, but we did observe a significant impact of diet-gene associations. Body weight and BMI were significantly higher in TT and CT genotype carriers if daily energy intake derived from carbohydrates was less than 48%. Moreover, in TT genotype carriers, we observed higher blood glucose concentration while fasting and during the OGTT test if more than 18% of total energy intake was derived from proteins. In conclusion, our results indicate that daily macronutrient intake may modulate the impact of FTO genetic SNPs on obesity and obesity-related metabolic consequences.

The Molecular Mechanisms by Which Vitamin D Prevents Insulin Resistance and Associated Disorders

Numerous studies have shown that vitamin D deficiency is very common in modern societies and is perceived as an important risk factor in the development of insulin resistance and related diseases such as obesity and type 2 diabetes (T2DM). While it is generally accepted that vitamin D is a regulator of bone homeostasis, its ability to counteract insulin resistance is subject to debate. The goal of this communication is to review the molecular mechanism by which vitamin D reduces insulin resistance and related complications. The university library, PUBMED, and Google Scholar were searched to find relevant studies to be summarized in this review article. Insulin resistance is accompanied by chronic hyperglycaemia and inflammation. Recent studies have shown that vitamin D exhibits indirect antioxidative properties and participates in the maintenance of normal resting ROS level. Appealingly, vitamin D reduces inflammation and regulates Ca²⁺ level in many cell types. Therefore, the beneficial actions of vitamin D include diminished insulin resistance which is observed as an improvement of glucose and lipid metabolism in insulin-sensitive tissues.

Omics Biomarkers in Obesity: Novel Etiological Insights and Targets for Precision Prevention

PURPOSE OF REVIEW

Omics-based technologies were suggested to provide an advanced understanding of obesity etiology and its metabolic consequences. This review highlights the recent developments in "omics"-based research aimed to identify obesity-related biomarkers.

RECENT FINDINGS

Recent advances in obesity and metabolism research increasingly rely on new technologies to identify mechanisms in the development of obesity using various "omics" platforms. Genetic and epigenetic biomarkers that translate into changes in transcriptome, proteome, and metabolome could serve as targets for obesity prevention. Despite a number of promising candidate biomarkers, there is an increased demand for larger prospective cohort studies to validate findings and determine biomarker reproducibility before they can find applications in primary care and public health. "Omics" biomarkers have advanced our knowledge on the etiology of obesity and its links with chronic diseases. They bring substantial promise in identifying effective public health strategies that pave the way towards patient stratification and precision prevention.

Metabolic regulation of kisspeptin - the link between energy balance and reproduction

Hypothalamic kisspeptin neurons serve as the nodal regulatory centre of reproductive function. These neurons are subjected to a plethora of regulatory factors that ultimately affect the release of kisspeptin, which modulates gonadotropin-releasing hormone (GnRH) release from GnRH neurons to control the reproductive axis. The presence of sufficient energy reserves is critical to achieve successful reproduction. Consequently, metabolic factors impose a very tight control over kisspeptin synthesis and release. This Review offers a synoptic overview of the different steps in which kisspeptin neurons are subjected to metabolic regulation, from early developmental stages to adulthood. We cover an ample array of known mechanisms that underlie the metabolic regulation of KISS1 expression and kisspeptin release. Furthermore, the novel role of kisspeptin neurons as active players within the neuronal circuits that govern energy balance is discussed, offering evidence of a bidirectional role of these neurons as a nexus between metabolism and reproduction.

Myeloperoxidase As a Multifaceted Target for Cardiovascular Protection

Significance: Myeloperoxidase (MPO) is a heme peroxidase that is primarily expressed by neutrophils. It has the capacity to generate several reactive species, essential for its inherent antimicrobial activity and innate host defense. Dysregulated MPO release, however, can lead to tissue damage, as seen in several diseases. Increased MPO levels in circulation are therefore widely associated with conditions of increased oxidative stress and inflammation. Recent Advances: Several studies have shown a strong correlation between MPO and cardiovascular disease (CVD), through which elevated levels of circulating MPO are linked to poor prognosis with increased risk of CVD-related mortality. Accordingly, circulating MPO is considered a "high-risk" biomarker for patients with acute coronary syndrome, atherosclerosis, heart failure, hypertension, and stroke, thereby implicating MPO as a multifaceted target for cardiovascular protection. Consistently, recent studies that target MPO in animal models of CVD have demonstrated favorable outcomes with regard to disease progression. Critical Issues: Although most of these studies have established a critical link between circulating MPO and worsening cardiac outcomes, the mechanisms by which MPO exerts its detrimental effects in CVD remain unclear. Future Directions: Elucidating the mechanisms by which elevated MPO leads to poor prognosis and, conversely, investigating the beneficial effects of therapeutic MPO inhibition on alleviating disease phenotype will facilitate future MPO-targeted clinical trials for improving CVD-related outcomes.