Epigenetics of the Pathogenesis and Complications of Type 2 Diabetes Mellitus

Epigenetics and diabetic wound healing: Wilms tumor 1-associated protein as a therapeutic target

In this editorial, we highlight the study by Xiao et al. Despite progress in the management of diabetic foot ulcers (DFUs), impaired wound healing remains a significant clinical challenge. Recent studies have highlighted the critical role of epigenetic modifications in diabetic wound healing, with particular emphasis on DNA and RNA methylation pathways. This editorial discusses the findings of Xiao et al, who identified the Wilms tumor 1-associated protein (WTAP) - DNA methyltransferase 1 (DNMT1) axis as a pivotal regulator of endothelial dysfunction in DFUs. WTAP, a regulatory subunit of N6-methyladenosine (m6A) methyltransferase, is upregulated under high-glucose conditions and drives the excessive expression of DNMT1 via m6A modification. This contributes to impaired angiogenesis, reduced cell viability, and delayed wound closure. WTAP knockdown restored endothelial function and significantly improved wound healing in a diabetic mouse model. Furthermore, DNMT1 overexpression abrogated the benefits of WTAP suppression, confirming its downstream effector role. Thus, targeting the WTAP-DNMT1 axis provides a new avenue for DFU management. Moreover, epigenetic interventions that modulate both the m6A and RNA methylation pathways could restore endothelial function and enhance tissue repair in patients with diabetes.

High-Fat Diet and Metabolic Diseases: A Comparative Analysis of Sex-Dependent Responses and Mechanisms

Sex differences in metabolic disorders and susceptibility to chronic diseases induced by a high-fat diet (HFD) exhibit significant dimorphic characteristics. A long-standing male-centric bias in medical research and healthcare, predominantly focused on male physiological traits, has hindered the precise treatment of metabolic diseases in female patients. A comprehensive understanding of sex differences in metabolic health and their underlying mechanisms is crucial for advancing personalized health promotion and precision medicine. This review systematically elucidates sex-specific manifestations in high-fat diet-associated metabolic disorders: males predominantly develop visceral adiposity, insulin resistance, and dyslipidemia, accompanied by a significantly elevated risk of cardiovascular and metabolic syndromes. Premenopausal females maintain metabolic homeostasis through the estrogen-mediated optimization of glucose and lipid metabolism and oxidative stress buffering mechanisms, whereas postmenopausal-phase females experience dramatic metabolic vulnerability due to z loss of protective barriers. Furthermore, we emphasize multidimensional mechanistic interpretations of metabolic sexual dimorphism from perspectives including sex chromosome complement, sex hormone signaling pathways, epigenetic regulation, gut microbiota composition, and neuroendocrine dimorphism. This work provides critical theoretical foundations for rectifying unisex research paradigms and optimizing sex-specific early warning systems and precision therapeutic strategies for metabolic disorders.

High glucose induces DNA methyltransferase 1 dependent epigenetic reprogramming of the endothelial exosome proteome in type 2 diabetes

In response to hyperglycemia, endothelial cells (ECs) release exosomes with altered protein content and contribute to paracrine signalling, subsequently leading to vascular dysfunction in type 2 diabetes (T2D). High glucose reprograms DNA methylation patterns in various cell/tissue types, including ECs, resulting in pathologically relevant changes in cellular and extracellular proteome. However, DNA methylation-based proteome reprogramming in endothelial exosomes and associated pathological implications in T2D are not known. Hence, in the present study, we used Human umbilical vein endothelial cells (HUVECs), High Fat Diet (HFD) induced diabetic mice (C57BL/6) and clinical models to understand epigenetic basis of exosome proteome regulation in T2D pathogenesis . Exosomes were isolated by size exclusion chromatography and subjected to tandem mass tag (TMT) labelled quantitative proteomics and bioinformatics analysis. Immunoblotting was performed to validate exosome protein signature in clinically characterized individuals with T2D. We observed ECs cultured in high glucose and aortic ECs from HFD mouse expressed elevated DNA methyltransferase1 (DNMT1) levels. Quantitative proteomics of exosomes isolated from ECs treated with high glucose and overexpressing DNMT1 showed significant alterations in both protein levels and post translational modifications which were aligned to T2D associated vascular functions. Based on ontology and gene-function-disease interaction analysis, differentially expressed exosome proteins such as Thrombospondin1, Pentraxin3 and Cystatin C related to vascular complications were significantly increased in HUVECs treated with high glucose and HFD animals and T2D individuals with higher levels of glycated hemoglobin. These proteins were reduced upon treatment with 5-Aza-2'-deoxycytidine. Our study shows epigenetic regulation of exosome proteome in T2D associated vascular complications.

Targeting the Epigenetic Marks in Type 2 Diabetes Mellitus: Will Epigenetic Therapy Be a Valuable Adjunct to Pharmacotherapy?

Although genetic, environmental, and lifestyle factors largely contribute to type 2 diabetes mellitus (T2DM) risk, the role of epigenetics in its pathogenesis is now well established. The epigenetic mechanisms in T2DM mainly consist of DNA methylation, histone modifications and regulation by noncoding RNAs (ncRNAs). For instance, DNA methylation at CpG islands in the promoter regions of specific genes encoding insulin signaling and glucose metabolism suppresses these genes. Modulating the enzyme mediators of these epigenetic marks aims to restore standard gene expression patterns and improve glycemic control. In targeting these epigenetic marks, using epigenetic drugs such as DNA methyltransferase (DNAMT), histone deacetylase (HDAC) and histone acetyltransferase (HAT) inhibitors has led to variable success in humans and experimental murine models. Specifically, the United States' Food and Drug Administration (US FDA) has approved DNAMT inhibitors like 5-azacytidine and 5-aza-2'-deoxycytidine for use in diabetic retinopathy: a T2DM microvascular complication. These DNAMT inhibitors block the genes for methylation of mitochondrial superoxide dismutase 2 (SOD2) and matrix metallopeptidase 9 (MMP-9): the epigenetic marks in diabetic retinopathy. Traditional pharmacotherapy with metformin also have epigenetic effects in T2DM and positively alter disease outcomes when combined with epigenetic drugs like DNAMT and HDAC inhibitors, raising the prospect of using epigenetic therapy as a valuable adjunct to pharmacotherapy. However, introducing small interfering RNAs (siRNAs) in cells to silence specific target genes remains in the exploratory phase. Future research should focus on regulating gene expression in T2DM using long noncoding RNA (lncRNA) molecules, another type of ncRNA. This review discusses the epigenetics of T2DM and that of its macro- and microvascular complications, and the potential benefits of combining epigenetic therapy with pharmacotherapy for optimal results.

Current Updates on the Understanding of the Role of DNA Methylation on Obesity

Obesity is a condition in which there is an accumulation of excess body fat leading to a weight far above the normal range that poses significant health risks. According to WHO, 8 billion people in the world were obese in 2022. Consequently, obesity has become a pandemic with negative impacts on both global health and economies. Obesity is influenced by various factors including environmental influences, lifestyle choices, gut microbiota, genetic factors, and epigenetic mechanisms such as DNA methylation. DNA methylation can affect an individual's phenotype and condition without altering their DNA sequence. It is the most extensively studied epigenetic alteration and it plays an important part in controlling gene activity associated with obesity. Numerous studies have indicated that DNA methylation is implicated in obesity, thus this review aims to elaborate the roles of DNA methylation to inform the development of preventive measures for obesity.

Abnormal DNA methylation within HPA-axis genes years after paediatric critical illness

BACKGROUND

Critically ill children suffer from impaired physical/neurocognitive development 2 years later. Glucocorticoid treatment alters DNA methylation within the hypothalamus-pituitary-adrenal (HPA) axis which may impair normal brain development, cognition and behaviour. We tested the hypothesis that paediatric-intensive-care-unit (PICU) patients, sex- and age-dependently, show long-term abnormal DNA methylation within the HPA-axis layers, possibly aggravated by glucocorticoid treatment in the PICU, which may contribute to the long-term developmental impairments.

RESULTS

In a pre-planned secondary analysis of the multicentre PEPaNIC-RCT and its 2-year follow-up, we identified differentially methylated positions and differentially methylated regions within HPA-axis genes in buccal mucosa DNA from 818 former PICU patients 2 years after PICU admission (n = 608 no glucocorticoid treatment; n = 210 glucocorticoid treatment) versus 392 healthy children and assessed interaction with sex and age, role of glucocorticoid treatment in the PICU and associations with long-term developmental impairments. Adjusting for technical variation and baseline risk factors and correcting for multiple testing (false discovery rate < 0.05), former PICU patients showed abnormal DNA methylation of 26 CpG sites (within CRHR1, POMC, MC2R, NR3C1, FKBP5, HSD11B1, SRD5A1, AKR1D1, DUSP1, TSC22D3 and TNF) and three DNA regions (within AVP, TSC22D3 and TNF) that were mostly hypomethylated. These abnormalities were sex-independent and only partially age-dependent. Abnormal methylation of three CpG sites within FKBP5 and one CpG site within SRD5A1 and AKR1D1 was partly attributable to glucocorticoid treatment during PICU stay. Finally, abnormal methylation within FKBP5 and AKR1D1 was most robustly associated with long-term impaired development.

CONCLUSIONS

Two years after critical illness in children, abnormal methylation within HPA-axis genes was present, predominantly within FKBP5 and AKR1D1, partly attributable to glucocorticoid treatment in the PICU, and explaining part of the long-term developmental impairments. These data call for caution regarding liberal glucocorticoid use in the PICU.