Histone deacetylase (HDAC) inhibition as a novel treatment for diabetes mellitus

Can social adversity alter the epigenome, trigger oral disease, and affect future generations?

The nature versus nurture debate has intrigued scientific circles for decades. Although extensive research has established a clear relationship between genetics and disease development, recent evidence has highlighted the insufficiency of attributing adverse health outcomes to genetic factors alone. In fact, it has been suggested that environmental influences, such as socioeconomic position (SEP), may play a much larger role in the development of disease than previously thought, with extensive research suggesting that low SEP is associated with adverse health conditions. In relation to oral health, a higher prevalence of caries (tooth decay) exists among those of low SEP. Although little is known about the biological mechanisms underlying this relationship, epigenetic modifications resulting from environmental influences have been suggested to play an important role. This review explores the intersection of health inequalities and epigenetics, the role of early-life social adversity and its long-term epigenetic impacts, and how those living within the lower hierarchies of the socioeconomic pyramid are indeed at higher risk of developing diseases, particularly in relation to oral health. A deeper understanding of these mechanisms could lead to the development of targeted interventions for individuals of low SEP to improve oral health or identify those who are at higher risk of developing oral disease.

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.

Histone deacetylases and inhibitors in diabetes mellitus and its complications

Diabetes mellitus (DM) is a metabolic disorder characterized by hyperglycemia, with its prevalence linked to both genetic predisposition and environmental factors. Epigenetic modifications, particularly through histone deacetylases (HDACs), have been recognized for their significant influence on DM pathogenesis. This review focuses on the classification of HDACs, their role in DM and its complications, and the potential therapeutic applications of HDAC inhibitors. HDACs, which modulate gene expression without altering DNA sequences, are categorized into four classes with distinct functions and tissue specificity. HDAC inhibitors (HDACi) have shown efficacy in various diseases, including DM, by targeting these enzymes. The review highlights how HDACs regulate β-cell function, insulin sensitivity, and hepatic gluconeogenesis in DM, as well as their impact on diabetic cardiomyopathy, nephropathy, and retinopathy. Finally, we suggest that targeted histone modification is expected to become a key method for the treatment of diabetes and its complications. The study of HDACi offers insights into new treatment strategies for DM and its associated complications.

WNKs regulate mouse behavior and alter central nervous system glucose uptake and insulin signaling

Certain areas of the brain involved in episodic memory and behavior, such as the hippocampus, express high levels of insulin receptors and glucose transporter-4 (GLUT4) and are responsive to insulin. Insulin and neuronal glucose metabolism improve cognitive functions and regulate mood in humans. Insulin-dependent GLUT4 trafficking has been extensively studied in muscle and adipose tissue, but little work has demonstrated either how it is controlled in insulin-responsive brain regions or its mechanistic connection to cognitive functions. In this study, we demonstrate that inhibition of WNK (With-No-lysine (K)) kinases improves learning and memory in mice. Neuronal inhibition of WNK enhances in vivo hippocampal glucose uptake. Inhibition of WNK enhances insulin signaling output and insulin-dependent GLUT4 trafficking to the plasma membrane in mice primary neuronal cultures and hippocampal slices. Therefore, we propose that the extent of neuronal WNK kinase activity has an important influence on learning, memory and anxiety-related behaviors, in part, by modulation of neuronal insulin signaling.

Genetic and Epigenetic Aspects of Type 1 Diabetes Mellitus: Modern View on the Problem

Omics technologies accumulated an enormous amount of data that advanced knowledge about the molecular pathogenesis of type 1 diabetes mellitus and identified a number of fundamental problems focused on the transition to personalized diabetology in the future. Among them, the most significant are the following: (1) clinical and genetic heterogeneity of type 1 diabetes mellitus; (2) the prognostic significance of DNA markers beyond the HLA genes; (3) assessment of the contribution of a large number of DNA markers to the polygenic risk of disease progress; (4) the existence of ethnic population differences in the distribution of frequencies of risk alleles and genotypes; (5) the infancy of epigenetic research into type 1 diabetes mellitus. Disclosure of these issues is one of the priorities of fundamental diabetology and practical healthcare. The purpose of this review is the systemization of the results of modern molecular genetic, transcriptomic, and epigenetic investigations of type 1 diabetes mellitus in general, as well as its individual forms. The paper summarizes data on the role of risk HLA haplotypes and a number of other candidate genes and loci, identified through genome-wide association studies, in the development of this disease and in alterations in T cell signaling. In addition, this review assesses the contribution of differential DNA methylation and the role of microRNAs in the formation of the molecular pathogenesis of type 1 diabetes mellitus, as well as discusses the most currently central trends in the context of early diagnosis of type 1 diabetes mellitus.

Butyrate functions as a histone deacetylase inhibitor to protect pancreatic beta cells from IL-1β-induced dysfunction

Butyrate, a gut microbial metabolite, has beneficial effects on glucose homeostasis and has become an attractive drug candidate for type 2 diabetes (T2D). Recently, we showed that butyrate protects pancreatic beta cells against cytokine-induced dysfunction. In this study, we explored the underlying mechanisms of butyrate action. Pancreatic mouse islets were exposed to a non-cytotoxic concentration of interleukin-1β (IL-1β) for 10 days to mimic low-grade inflammation in T2D. Similar to the effect of butyrate, an isoform-selective histone deacetylase 3 (HDAC3) inhibitor normalized IL-1β-reduced glucose-stimulated insulin secretion and insulin content. In contrast, free fatty acid receptor 2 and 3 (FFAR2/3) agonists failed to normalize IL-1β-induced beta cell dysfunction. Furthermore, butyrate inhibited HDAC activity and increased the acetylation of histone H3 and H4 by 3- and 10-fold, respectively. Genome-wide analysis of histone H3 lysine 27 acetylation (H3K27ac) revealed that butyrate mainly increased H3K27ac at promoter regions (74%), while H3K27ac peaks regulated by IL-1β were more equally distributed at promoters (38%), introns (23%) and intergenic regions (23%). Gene ontology analysis showed that butyrate increased IL-1β-reduced H3K27ac levels near several genes related to hormone secretion and reduced IL-1β-increased H3K27ac levels near genes associated with inflammatory responses. Butyrate alone increased H3K27ac near many genes related to MAPK signaling, hormone secretion, and differentiation, and decreased H3K27ac at genes involved in cell replication. Together, these results suggest that butyrate prevents IL-1β-induced pancreatic islet dysfunction by inhibition of HDACs resulting in changes in H3K27ac levels at genes relevant for beta cell function and inflammatory responses.

Molecular mechanisms of diabetic heart disease: Insights from transcriptomic technologies

Over half a billion adults across the world have diabetes mellitus (DM). This has a wide-ranging impact on their health, including more than doubling their risk of major cardiovascular events, in comparison to age-sex matched individuals without DM. Notably, the risk of heart failure is particularly increased, even when coronary artery disease and hypertension are not present. Macro- and micro-vascular complications related to endothelial cell (EC) dysfunction are a systemic feature of DM and can affect the heart. However, it remains unclear to what extent these and other factors underpin myocardial dysfunction and heart failure linked with DM. Use of unbiased 'omics approaches to profile the molecular environment of the heart offers an opportunity to identify novel drivers of cardiac dysfunction in DM. Multiple transcriptomics studies have characterised the whole myocardium or isolated cardiac ECs. We present a systematic summary of relevant studies, which identifies common themes including alterations in both myocardial fatty acid metabolism and inflammation. These findings prompt further research focussed on these processes to validate potentially causal factors for prioritisation into therapeutic development pipelines.

Exosomes as biomarkers and therapy in type 2 diabetes mellitus and associated complications

Type 2 diabetes mellitus (T2DM) is one of the most prevalent metabolic disorders worldwide. However, T2DM still remains underdiagnosed and undertreated resulting in poor quality of life and increased morbidity and mortality. Given this ongoing burden, researchers have attempted to locate new therapeutic targets as well as methodologies to identify the disease and its associated complications at an earlier stage. Several studies over the last few decades have identified exosomes, small extracellular vesicles that are released by cells, as pivotal contributors to the pathogenesis of T2DM and its complications. These discoveries suggest the possibility of novel detection and treatment methods. This review provides a comprehensive presentation of exosomes that hold potential as novel biomarkers and therapeutic targets. Additional focus is given to characterizing the role of exosomes in T2DM complications, including diabetic angiopathy, diabetic cardiomyopathy, diabetic nephropathy, diabetic peripheral neuropathy, diabetic retinopathy, and diabetic wound healing. This study reveals that the utilization of exosomes as diagnostic markers and therapies is a realistic possibility for both T2DM and its complications. However, the majority of the current research is limited to animal models, warranting further investigation of exosomes in clinical trials. This review represents the most extensive and up-to-date exploration of exosomes in relation to T2DM and its complications.

The power of TOPMed imputation for the discovery of Latino-enriched rare variants associated with type 2 diabetes

AIMS/HYPOTHESIS

The Latino population has been systematically underrepresented in large-scale genetic analyses, and previous studies have relied on the imputation of ungenotyped variants based on the 1000 Genomes (1000G) imputation panel, which results in suboptimal capture of low-frequency or Latino-enriched variants. The National Heart, Lung, and Blood Institute (NHLBI) Trans-Omics for Precision Medicine (TOPMed) released the largest multi-ancestry genotype reference panel representing a unique opportunity to analyse rare genetic variations in the Latino population. We hypothesise that a more comprehensive analysis of low/rare variation using the TOPMed panel would improve our knowledge of the genetics of type 2 diabetes in the Latino population.

METHODS

We evaluated the TOPMed imputation performance using genotyping array and whole-exome sequence data in six Latino cohorts. To evaluate the ability of TOPMed imputation to increase the number of identified loci, we performed a Latino type 2 diabetes genome-wide association study (GWAS) meta-analysis in 8150 individuals with type 2 diabetes and 10,735 control individuals and replicated the results in six additional cohorts including whole-genome sequence data from the All of Us cohort.

RESULTS

Compared with imputation with 1000G, the TOPMed panel improved the identification of rare and low-frequency variants. We identified 26 genome-wide significant signals including a novel variant (minor allele frequency 1.7%; OR 1.37, p=3.4 × 10-9). A Latino-tailored polygenic score constructed from our data and GWAS data from East Asian and European populations improved the prediction accuracy in a Latino target dataset, explaining up to 7.6% of the type 2 diabetes risk variance.

CONCLUSIONS/INTERPRETATION

Our results demonstrate the utility of TOPMed imputation for identifying low-frequency variants in understudied populations, leading to the discovery of novel disease associations and the improvement of polygenic scores.

DATA AVAILABILITY

Full summary statistics are available through the Common Metabolic Diseases Knowledge Portal ( https://t2d.hugeamp.org/downloads.html ) and through the GWAS catalog ( https://www.ebi.ac.uk/gwas/ , accession ID: GCST90255648). Polygenic score (PS) weights for each ancestry are available via the PGS catalog ( https://www.pgscatalog.org , publication ID: PGP000445, scores IDs: PGS003443, PGS003444 and PGS003445).

PIMT Controls Insulin Synthesis and Secretion through PDX1

Pancreatic beta cell function is an important component of glucose homeostasis. Here, we investigated the function of PIMT (PRIP-interacting protein with methyl transferase domain), a transcriptional co-activator binding protein, in the pancreatic beta cells. We observed that the protein levels of PIMT, along with key beta cell markers such as PDX1 (pancreatic and duodenal homeobox 1) and MafA (MAF bZIP transcription factor A), were reduced in the beta cells exposed to hyperglycemic and hyperlipidemic conditions. Consistently, PIMT levels were reduced in the pancreatic islets isolated from high fat diet (HFD)-fed mice. The RNA sequencing analysis of PIMT knockdown beta cells identified that the expression of key genes involved in insulin secretory pathway, Ins1 (insulin 1), Ins2 (insulin 2), Kcnj11 (potassium inwardly-rectifying channel, subfamily J, member 11), Kcnn1 (potassium calcium-activated channel subfamily N member 1), Rab3a (member RAS oncogene family), Gnas (GNAS complex locus), Syt13 (synaptotagmin 13), Pax6 (paired box 6), Klf11 (Kruppel-Like Factor 11), and Nr4a1 (nuclear receptor subfamily 4, group A, member 1) was attenuated due to PIMT depletion. PIMT ablation in the pancreatic beta cells and in the rat pancreatic islets led to decreased protein levels of PDX1 and MafA, resulting in the reduction in glucose-stimulated insulin secretion (GSIS). The results from the immunoprecipitation and ChIP experiments revealed the interaction of PIMT with PDX1 and MafA, and its recruitment to the insulin promoter, respectively. Importantly, PIMT ablation in beta cells resulted in the nuclear translocation of insulin. Surprisingly, forced expression of PIMT in beta cells abrogated GSIS, while Ins1 and Ins2 transcript levels were subtly enhanced. On the other hand, the expression of genes, PRIP/Asc2/Ncoa6 (nuclear receptor coactivator 6), Pax6, Kcnj11, Syt13, Stxbp1 (syntaxin binding protein 1), and Snap25 (synaptosome associated protein 25) associated with insulin secretion, was significantly reduced, providing an explanation for the decreased GSIS upon PIMT overexpression. Our findings highlight the importance of PIMT in the regulation of insulin synthesis and secretion in beta cells.

Postmortem Brains from Subjects with Diabetes Mellitus Display Reduced GLUT4 Expression and Soma Area in Hippocampal Neurons: Potential Involvement of Inflammation

Diabetes mellitus (DM) is an important risk factor for dementia, which is a common neurodegenerative disorder. DM is known to activate inflammation, oxidative stress, and advanced glycation end products (AGEs) generation, all capable of inducing neuronal dysfunctions, thus participating in the neurodegeneration progress. In that process, disturbed neuronal glucose supply plays a key role, which in hippocampal neurons is controlled by the insulin-sensitive glucose transporter type 4 (GLUT4). We investigated the expression of GLUT4, nuclear factor NF-kappa B subunit p65 [NFKB (p65)], carboxymethyllysine and synapsin1 (immunohistochemistry), and soma area in human postmortem hippocampal samples from control, obese, and obese+DM subjects (41 subjects). Moreover, in human SH-SY5Y neurons, tumor necrosis factor (TNF) and glycated albumin (GA) effects were investigated in GLUT4, synapsin-1 (SYN1), tyrosine hydroxylase (TH), synaptophysin (SYP) proteins, and respective genes; NFKB binding activity in the SLC2A4 promoter; effects of increased histone acetylation grade by histone deacetylase 3 (HDAC3) inhibition. Hippocampal neurons (CA4 area) of obese+DM subjects displayed reduced GLUT4 expression and neuronal soma area, associated with increased expression of NFKB (p65). Challenges with TNF and GA decreased the SLC2A4/GLUT4 expression in SH-SY5Y neurons. TNF decreased SYN1, TH, and SYP mRNAs and respective proteins, and increased NFKB binding activity in the SLC2A4 promoter. Inhibition of HDAC3 increased the SLC2A4 expression and the total neuronal content of CRE-binding proteins (CREB/ICER), and also counterbalanced the repressor effect of TNF upon these parameters. This study revealed reduced postmortem human hippocampal GLUT4 content and neuronal soma area accompanied by increased proinflammatory activity in the brains of DM subjects. In isolated human neurons, inflammatory activation by TNF reduced not only the SLC2A4/GLUT4 expression but also the expression of some genes related to neuronal function (SYN1, TH, SYP). These effects may be related to epigenetic regulations (H3Kac and H4Kac status) since they can be counterbalanced by inhibiting HDAC3. These results uncover the improvement in GLUT4 expression and/or the inhibition of HDAC3 as promising therapeutic targets to fight DM-related neurodegeneration.

The Complex Interplay between Imbalanced Mitochondrial Dynamics and Metabolic Disorders in Type 2 Diabetes

Type 2 diabetes mellitus (T2DM) is a global burden, with an increasing number of people affected and increasing treatment costs. The advances in research and guidelines improve the management of blood glucose and related diseases, but T2DM and its complications are still a big challenge in clinical practice. T2DM is a metabolic disorder in which insulin signaling is impaired from reaching its effectors. Mitochondria are the "powerhouses" that not only generate the energy as adenosine triphosphate (ATP) using pyruvate supplied from glucose, free fatty acid (FFA), and amino acids (AA) but also regulate multiple cellular processes such as calcium homeostasis, redox balance, and apoptosis. Mitochondrial dysfunction leads to various diseases, including cardiovascular diseases, metabolic disorders, and cancer. The mitochondria are highly dynamic in adjusting their functions according to cellular conditions. The shape, morphology, distribution, and number of mitochondria reflect their function through various processes, collectively known as mitochondrial dynamics, including mitochondrial fusion, fission, biogenesis, transport, and mitophagy. These processes determine the overall mitochondrial health and vitality. More evidence supports the idea that dysregulated mitochondrial dynamics play essential roles in the pathophysiology of insulin resistance, obesity, and T2DM, as well as imbalanced mitochondrial dynamics found in T2DM. This review updates and discusses mitochondrial dynamics and the complex interactions between it and metabolic disorders.

Augmentation of Histone Deacetylase 6 Activity Impairs Mitochondrial Respiratory Complex I in Ischemic/Reperfused Diabetic Hearts

BACKGROUND

Diabetes augments activity of histone deacetylase 6 (HDAC6) and generation of tumor necrosis factor α (TNFα) and impairs the physiological function of mitochondrial complex I (mCI) which oxidizes reduced nicotinamide adenine dinucleotide (NADH) to nicotinamide adenine dinucleotide to sustain the tricarboxylic acid cycle and β-oxidation. Here we examined how HDAC6 regulates TNFα production, mCI activity, mitochondrial morphology and NADH levels, and cardiac function in ischemic/reperfused diabetic hearts.

METHODS

HDAC6 knockout, streptozotocin-induced type 1 diabetic, and obese type 2 diabetic db/db mice underwent myocardial ischemia/reperfusion injury in vivo or ex vivo in a Langendorff-perfused system. H9c2 cardiomyocytes with and without HDAC6 knockdown were subjected to hypoxia/reoxygenation injury in the presence of high glucose. We compared the activities of HDAC6 and mCI, TNFα and mitochondrial NADH levels, mitochondrial morphology, myocardial infarct size, and cardiac function between groups.

RESULTS

Myocardial ischemia/reperfusion injury and diabetes synergistically augmented myocardial HDCA6 activity, myocardial TNFα levels, and mitochondrial fission and inhibited mCI activity. Interestingly, neutralization of TNFα with an anti-TNFα monoclonal antibody augmented myocardial mCI activity. Importantly, genetic disruption or inhibition of HDAC6 with tubastatin A decreased TNFα levels, mitochondrial fission, and myocardial mitochondrial NADH levels in ischemic/reperfused diabetic mice, concomitant with augmented mCI activity, decreased infarct size, and ameliorated cardiac dysfunction. In H9c2 cardiomyocytes cultured in high glucose, hypoxia/reoxygenation augmented HDAC6 activity and TNFα levels and decreased mCI activity. These negative effects were blocked by HDAC6 knockdown.

CONCLUSIONS

Augmenting HDAC6 activity inhibits mCI activity by increasing TNFα levels in ischemic/reperfused diabetic hearts. The HDAC6 inhibitor, tubastatin A, has high therapeutic potential for acute myocardial infarction in diabetes.

Advanced Glycation End Products and Activation of Toll-like Receptor-2 and -4 Induced Changes in Aquaporin-3 Expression in Mouse Keratinocytes

Prolonged inflammation and impaired re-epithelization are major contributing factors to chronic non-healing diabetic wounds; diabetes is also characterized by xerosis. Advanced glycation end products (AGEs), and the activation of toll-like receptors (TLRs), can trigger inflammatory responses. Aquaporin-3 (AQP3) plays essential roles in keratinocyte function and skin wound re-epithelialization/re-generation and hydration. Suberanilohydroxamic acid (SAHA), a histone deacetylase inhibitor, mimics the increased acetylation observed in diabetes. We investigated the effects of TLR2/TLR4 activators and AGEs on keratinocyte AQP3 expression in the presence and absence of SAHA. Primary mouse keratinocytes were treated with or without TLR2 agonist Pam3Cys-Ser-(Lys)4 (PAM), TLR4 agonist lipopolysaccharide (LPS), or AGEs, with or without SAHA. We found that (1) PAM and LPS significantly upregulated AQP3 protein basally (without SAHA) and PAM downregulated AQP3 protein with SAHA; and (2) AGEs (100 µg/mL) increased AQP3 protein expression basally and decreased AQP3 levels with SAHA. PAM and AGEs produced similar changes in AQP3 expression, suggesting a common pathway or potential crosstalk between TLR2 and AGEs signaling. Our findings suggest that TLR2 activation and AGEs may be beneficial for wound healing and skin hydration under normal conditions via AQP3 upregulation, but that these pathways are likely deleterious in diabetes chronically through decreased AQP3 expression.

The mitigative effect of isorhamnetin against type 2 diabetes via gut microbiota regulation in mice

In order to demonstrate the effects of isorhamnetin (IH) on the symptoms of type 2 diabetes mellitus (T2DM) and the role of gut microbiota in this process, an T2DM mouse model was established via a high-fat diet and streptozotocin. After 6 weeks of IH intervention and diabetes phenotype monitoring, the mice were dissected. We detected blood indicators and visceral pathology. Contents of the cecum were collected for 16S rRNA sequencing and short chain fatty acid (SCFAs) detection. The results showed that after IH intervention, the body weight of type 2 diabetic mice was gradually stabilized, fasting blood glucose was significantly decreased, and food intake was reduced (P < 0.05). Isorhamnetin significantly increased the level of SCFAs and decreased the levels of blood lipids and inflammatory factors in mice (P < 0.05). 16S rRNA sequencing results showed that Lactobacillus were significantly decreased and Bacteroidales S24-7 group_norank were significantly increased (P < 0.05). Interestingly, gut microbiota was significantly correlated with inflammatory factors, blood lipids, and SCFAs (P < 0.05). Taken together, our data demonstrated that isorhamnetin could improve the diabetic effects in T2DM mice, which might be mediated by gut microbiota.

Exploring epigenetic reprogramming during central nervous system infection

Epigenetics involves the study of various modes of adaptable transcriptional regulation, contributing to cell identity, characteristics, and function. During central nervous system (CNS) infection, epigenetic mechanisms can exert pronounced control over the maturation and antimicrobial properties of nearly every immune cell type. Epigenetics is a relatively new field, with the first mention of these marks proposed only a half-century ago and a substantial body of immunological epigenetic research emerging only in the last few decades. Here, we review the best-characterized epigenetic marks and their functions as well as illustrate how various immune cell populations responding to CNS infection utilize these marks to organize their activation state and inflammatory processes. We also discuss the metabolic and clinical implications of epigenetic marks and the rapidly expanding set of tools available to researchers that are enabling elucidation of increasingly detailed genetic regulatory pathways. These considerations paint an intricate picture of inflammatory regulation, where epigenetic marks influence genetic, signaling, and environmental elements to orchestrate a tailored immunological response to the threat at hand, cementing epigenetics as an important player in immunity.

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.

Insoluble and Soluble Dietary Fibers from Kiwifruit (Actinidia deliciosa) Modify Gut Microbiota to Alleviate High-Fat Diet and Streptozotocin-Induced TYPE 2 Diabetes in Rats

This study aims to examine the anti-diabetic properties of insoluble and soluble dietary fibers from kiwifruit (KIDF and KSDF) in rats with type 2 diabetes mellitus (T2DM) resulting from a high-fat diet (HFD) and streptozotocin (STZ). Both KIDF and KSDF treatments for four weeks remarkably decreased body weight and increased satiety. In addition, the blood glucose level and circulatory lipopolysaccharide (LPS) content were decreased, while the insulin resistance, inflammatory status, and lipid profiles improved. These anti-diabetic effects might be related to the regulation of gut microbiota and increased SCFA content. The key microbial communities of KIDF and KSDF were different. Furthermore, the KIDF treatment increased the level of total SCFAs and isobutyric acid, while KSDF increased the levels of total SCFAs and butyric acid. The association between critical species and SCFA and between SCFA and biochemical parameters indicated that the mechanisms of KIDF and KSDF on T2DM might be different.

H19 inhibition increases HDAC6 and regulates IRS1 levels and insulin signaling in the skeletal muscle during diabetes

Background

Histone deacetylases (HDACs) that catalyze removal of acetyl groups from histone proteins, are strongly associated with several diseases including diabetes, yet the precise regulatory events that control the levels and activity of the HDACs are not yet well elucidated.

Methods

Levels of H19 and HDACs were evaluated in skeletal muscles of normal and diabetic db/db mice by Western Blot analysis. C2C12 cells were differentiated and transfected with either the scramble or H19 siRNA and the levels of HDACs and Prkab2, Pfkfb3, Srebf1, Socs2, Irs1 and Ppp2r5b were assessed by Western Blot analysis and qRT-PCR, respectively. Levels of H9, HDAC6 and IRS1 were evaluated in skeletal muscles of scramble/ H19 siRNA injected mice and chow/HFD-fed mice.

Results

Our data show that the lncRNA H19 and HDAC6 exhibit inverse patterns of expression in the skeletal muscle of diabetic db/db mice and in C2C12 cells, H19 inhibition led to significant increase in HDAC activity and in the levels of HDAC6, both at the transcript and protein levels. This was associated with downregulation of IRS1 levels that were prevented in the presence of the HDAC inhibitor, SAHA, and HDAC6 siRNA suggesting the lncRNA H19-HDAC6 axis possibly regulates cellular IRS1 levels. Such patterns of H19, HDAC6 and IRS1 expression were also validated and confirmed in high fat diet-fed mice where as compared to normal chow-fed mice, H19 levels were significantly inhibited in the skeletal muscle of these mice and this was accompanied with elevated HDAC6 levels and decreased IRS1 levels. In-vivo inhibition of H19 led to significant increase in HDAC6 levels and this was associated with a decrease in IRS1 levels in the skeletal muscle.

Conclusions

Our results suggest a critical role for the lncRNA H19-HDAC6 axis in regulating IRS1 levels in the skeletal muscle during diabetes and therefore restoring normal H19 levels might hold a therapeutic potential for the management of aberrant skeletal muscle physiology during insulin resistance and type 2 diabetes.

Short-Chain Fatty Acids Attenuate Renal Fibrosis and Enhance Autophagy of Renal Tubular Cells in Diabetic Mice Through the HDAC2/ULK1 Axis

BACKGRUOUND

This study investigated the effect of short-chain fatty acids (SCFAs) on diabetes in a mouse model.

METHODS

Autophagy in Akita mice and streptozocin (STZ)-induced diabetic C57BL/6 mice was determined by Western blots and immunohistochemistry (IHC). Western blots, IHC, hematoxylin and eosin staining, Masson staining, periodic acid-Schiff staining, and picrosirius red staining were conducted to detect whether autophagy and renal function improved in Akita mice and STZ-induced diabetic C57BL/6 mice after treatment of SCFAs. Western blots, IHC, and chromatin immunoprecipitation were performed to determine whether SCFAs affected diabetic mice via the histone deacetylase (HDAC2)/unc-51 like autophagy activating kinase 1 (ULK1) axis. Diabetic mice with kidney-specific knockout of HDAC2 were constructed, and IHC, Masson staining, and Western blots were carried out to detect whether the deletion of endogenous HDAC2 contributed to the improvement of autophagy and renal fibrosis in diabetic mice.

RESULTS

Reduced autophagy and severe fibrosis were observed in Akita mice and STZ-induced diabetic C57BL/6 mice. Increased autophagy and reduced renal cell fibrosis were found in SCFA-treated Akita diabetic mice and STZ-induced diabetic C57BL/6 mice. Diabetic mice treated with SCFAs had lower HDAC2 expression and more enriched binding of ULK1 promoter sequences to H3K27Ac. Endogenous knockout of HDAC2 caused enhanced autophagy and decreased renal fibrosis in diabetic mice treated with SCFAs.

CONCLUSION

SCFAs enhanced autophagy of renal tubular cells and attenuated renal fibrosis in diabetic mice through the HDAC2/ULK1 axis.

Proteomic Analysis of Serum Lysine Acetylation in Uyghur Patients With T2DM

Lysine acetylation is a reversible modification process after protein translation, which plays a key regulatory role in various metabolic diseases such as diabetes. The prevalence of type 2 diabetes mellitus (T2DM) in the Uyghur population is high, but the acetylation status of proteomics in Uyghur with T2DM is still unclear. Herein, we performed a quantitative proteomic study of lysine acetylation in T2DM patients using Tandem Mass Tags (TMTs) labeling, acetylation enrichment techniques, and high-resolution liquid chromatography-tandem mass spectrometry. We quantified 422 acetylation sites on 120 proteins, of which 347 sites of 103 proteins contained quantitative information. Compared with the control, we found that a total of eight acetylated sites within proteins were significantly differentially expressed with three upregulated and five downregulated, including histones H4 and H3.3C. Meanwhile, we completed bioinformatics analysis, including protein annotation, functional classification, functional enrichment, and cluster analysis, based on functional enrichment. In addition, the mRNA (ApoB-100, histones H4 and H3.3C) and protein (histones H4 and H3.3C) levels were verified through 60 samples. Besides, we also performed histone H4 chromatin immunoprecipitation analysis at the level of INS-1 cells. These could be potentially useful markers for the prediction of prediabetes and also provided a basis for the pathogenesis of T2DM.

Sodium butyrate potentiates insulin secretion from rat islets at the expense of compromised expression of β cell identity genes

Short-chain fatty acids (SCFAs) produced by the gut microbiota have been well demonstrated to improve metabolic homeostasis. However, the role of SCFAs in islet function remains controversial. In the present study, none of the sodium acetate, sodium propionate, and sodium butyrate (SB) displayed acute impacts on insulin secretion from rat islets, whereas long-term incubation of the three SCFAs significantly potentiated pancreatic β cell function. RNA sequencing (RNA-seq) revealed an unusual transcriptome change in SB-treated rat islets, with the downregulation of insulin secretion pathway and β cell identity genes, including Pdx1, MafA, NeuroD1, Gck, and Slc2a2. But these β cell identity genes were not governed by the pan-HDAC inhibitor trichostatin A. Overlapping analysis of H3K27Ac ChIP-seq and RNA-seq showed that the inhibitory effect of SB on the expression of multiple β cell identity genes was independent of H3K27Ac. SB treatment increased basal oxygen consumption rate (OCR), but attenuated glucose-stimulated OCR in rat islets, without altering the expressions of genes involved in glycolysis and tricarboxylic acid cycle. SB reduced the expression of Kcnj11 (encoding KATP channel) and elevated basal intracellular calcium concentration. On the other hand, SB elicited insulin gene expression in rat islets through increasing H3K18bu occupation in its promoter, without stimulating CREB phosphorylation. These findings indicate that SB potentiates islet function as a lipid molecule at the expense of compromised expression of islet β cell identity genes.

From natural products to HDAC inhibitors: An overview of drug discovery and design strategy

Histone deacetylases (HDACs) play a key role in the homeostasis of protein acetylation in histones and have recently emerged as a therapeutic target for numerous diseases. The inhibition of HDACs may block angiogenesis, arrest cell growth, and lead to differentiation and apoptosis in tumour cells. Thus, HDAC inhibitors (HDACi) have received increasing attention and many of which are developed from natural sources. In the past few decades, naturally occurring HDACi have been identified to have potent anticancer activities, some of which have demonstrated promising therapeutic effects on haematological malignancies. In this review, we summarized the discovery and modification of HDAC inhibitors from natural sources, novel drug design that uses natural products as parent nuclei, and dual target design strategies that combine HDAC with non-HDAC targets.

A Review on Epigenetic Inheritance of Experiences in Humans

If genetics defines the inheritance of DNA, epigenetics aims to regulate and make it adaptable. Epigenetic alterations include DNA methylation, chromatin remodelling, post-translational modifications of histone proteins and activity of non-coding RNAs. Several studies, especially in animal models, have reported transgenerational inheritance of epigenetic marks. However, evidence of transgenerational inheritance in humans via germline in the absence of any direct exposure to the driving external stimulus remains controversial. Most of the epimutations exist in relation with genetic variants. The present review looks at intergenerational and transgenerational inheritance in humans, (both father and mother) in response to diet, exposure to chemicals, stress, exercise, and disease status. If not transgenerational, at least intergenerational human studies could help to understand early processes of inheritance. In humans, female and male germline development follow separate paths of epigenetic events and both oocyte and sperm possess their own unique epigenomes. While DNA methylation alterations are reset during epigenetic reprogramming, non-coding RNAs via human sperm provide evidence of being reliable carriers for transgenerational inheritance. Human studies reveal that one mechanism of epigenetic inheritance cannot be applied to the complete human genome. Multiple factors including time, type, and tissue of exposure determine if the modified epigenetic mark could be transmissible and till which generation. Population-specific differences should also be taken into consideration while associating inheritance to an environmental exposure. A longitudinal study targeting one environmental factor, but different population groups should be conducted at a specific geographical location to pinpoint heritable epigenetic changes.

Advanced Bioinformatics Tools in the Pharmacokinetic Profiles of Natural and Synthetic Compounds with Anti-Diabetic Activity

Diabetes represents a major health problem, involving a severe imbalance of blood sugar levels, which can disturb the nerves, eyes, kidneys, and other organs. Diabes management involves several synthetic drugs focused on improving insulin sensitivity, increasing insulin production, and decreasing blood glucose levels, but with unclear molecular mechanisms and severe side effects. Natural chemicals extracted from several plants such as Gymnema sylvestre, Momordica charantia or Ophiopogon planiscapus Niger have aroused great interest for their anti-diabetes activity, but also their hypolipidemic and anti-obesity activity. Here, we focused on the anti-diabetic activity of a few natural and synthetic compounds, in correlation with their pharmacokinetic/pharmacodynamic profiles, especially with their blood-brain barrier (BBB) permeability. We reviewed studies that used bioinformatics methods such as predicted BBB, molecular docking, molecular dynamics and quantitative structure-activity relationship (QSAR) to elucidate the proper action mechanisms of antidiabetic compounds. Currently, it is evident that BBB damage plays a significant role in diabetes disorders, but the molecular mechanisms are not clear. Here, we presented the efficacy of natural (gymnemic acids, quercetin, resveratrol) and synthetic (TAK-242, propofol, or APX3330) compounds in reducing diabetes symptoms and improving BBB dysfunctions. Bioinformatics tools can be helpful in the quest for chemical compounds with effective anti-diabetic activity that can enhance the druggability of molecular targets and provide a deeper understanding of diabetes mechanisms.

Mof acetyltransferase inhibition ameliorates glucose intolerance and islet dysfunction of type 2 diabetes via targeting pancreatic α-cells

BACKGROUND

Previously, we reported that Mof was highly expressed in α-cells, and its knockdown led to ameliorated fasting blood glucose (FBG) and glucose tolerance in non-diabetic mice, attributed by reduced total α-cell but enhanced prohormone convertase (PC)1/3-positive α-cell mass. However, how Mof and histone 4 lysine 16 acetylation (H4K16ac) control α-cell and whether Mof inhibition improves glucose handling in type 2 diabetes (T2DM) mice remain unknown.

METHODS

Mof overexpression and chromatin immunoprecipitation sequence (ChIP-seq) based on H4K16ac were applied to determine the effect of Mof on α-cell transcriptional factors and underlying mechanism. Then we administrated mg149 to α-TC1-6 cell line, wild type, db/db and diet-induced obesity (DIO) mice to observe the impact of Mof inhibition in vitro and in vivo. In vitro, western blotting and TUNEL staining were used to examine α-cell apoptosis and function. In vivo, glucose tolerance, hormone levels, islet population, α-cell ratio and the co-staining of glucagon and PC1/3 or PC2 were examined.

RESULTS

Mof activated α-cell-specific transcriptional network. ChIP-seq results indicated that H4K16ac targeted essential genes regulating α-cell differentiation and function. Mof activity inhibition in vitro caused impaired α-cell function and enhanced apoptosis. In vivo, it contributed to ameliorated glucose intolerance and islet dysfunction, characterized by decreased fasting glucagon and elevated post-challenge insulin levels in T2DM mice.

CONCLUSION

Mof regulates α-cell differentiation and function via acetylating H4K16ac and H4K16ac binding to Pax6 and Foxa2 promoters. Mof inhibition may be a potential interventional target for T2DM, which led to decreased α-cell ratio but increased PC1/3-positive α-cells.

Changes in Stress-Mediated Markers in a Human Cardiomyocyte Cell Line under Hyperglycemia

Diabetes is a major risk factor for cardiovascular diseases, especially cardiomyopathy, a condition in which the smooth muscles of the heart become thick and rigid, affecting the functioning of cardiomyocytes, the contractile cells of the heart. Uncontrolled elevated glucose levels over time can result in oxidative stress, which could lead to inflammation and altered epigenetic mechanisms. In the current study, we investigated whether hyperglycemia can modify cardiac function by directly affecting these changes in cardiomyocytes. To evaluate the adverse effect of high glucose, we measured the levels of gap junction protein, connexin 43, which is responsible for modulating cardiac electric activities and Troponin I, a part of the troponin complex in the heart muscles, commonly used as cardiac markers of ischemic heart disease. AC16 human cardiomyocyte cells were used in this study. Under hyperglycemic conditions, these cells demonstrated altered levels of connexin 43 and Troponin-I after 24 h of exposure. We also examined hyperglycemia induced changes in epigenetic markers: H3K9me1, Sirtuin-1 (SIRT1), and histone deacetylase (HDAC)-2 as well as in inflammatory and stress-related mediators, such as heat shock protein (HSP)-60, receptor for advanced glycation end products (RAGE), toll-like receptor (TLR)-4, high mobility group box (HMGB)-1 and CXC chemokine receptor (CXCR)-4. Cardiomyocytes exposed to 25mM glucose resulted in the downregulation of HSP60 and SIRT1 after 48 h. We further examined that hyperglycemia mediated the decrease in the gap junction protein CX43, as well as CXC chemokine receptor CXCR4 which may affect the physiological functions of the cardiomyocytes when exposed to high glucose for 24 and 48 h. Upregulated expression of DNA-binding nuclear protein HMGB1, along with changes in histone methylation marker H3K9me1 have demonstrated hyperglycemia-induced damage to cardiomyocyte at 24 h of exposure. Our study established that 24 to 48 h of hyperglycemic exposure could stimulate stress-mediated inflammatory mediators in cardiomyocytes in vitro. These stress-related changes in hyperglycemia-induced cardiomyocytes may further initiate an increase in injury markers which eventually could alter the epigenetic processes. Therefore, epigenetic and inflammatory mechanisms in conjunction with alterations in a downstream signaling pathway could have a direct effect on the functionality of the cardiomyocytes exposed to high glucose during short and long-term exposures.

The Human Islet: Mini-Organ With Mega-Impact

This review focuses on the human pancreatic islet-including its structure, cell composition, development, function, and dysfunction. After providing a historical timeline of key discoveries about human islets over the past century, we describe new research approaches and technologies that are being used to study human islets and how these are providing insight into human islet physiology and pathophysiology. We also describe changes or adaptations in human islets in response to physiologic challenges such as pregnancy, aging, and insulin resistance and discuss islet changes in human diabetes of many forms. We outline current and future interventions being developed to protect, restore, or replace human islets. The review also highlights unresolved questions about human islets and proposes areas where additional research on human islets is needed.

Lactobacillus plantarum HAC01 ameliorates type 2 diabetes in high-fat diet and streptozotocin-induced diabetic mice in association with modulating the gut microbiota

Type 2 diabetes mellitus (T2DM) is a serious metabolic disorder that occurs worldwide; however, this condition can be managed with probiotics. We assessed the potential therapeutic effects of Lactobacillus plantarum HAC01 on hyperglycemia and T2DM and determined their potential mechanisms using mice with high-fat diet (HFD) and streptozotocin (STZ)-induced diabetes. The diabetic model was established with an HFD and 50 mg kg^-1 STZ. L. plantarum HAC01 was then administered for 10 weeks. Body weight, food and water intake, biochemical parameters, and homeostasis model assessment for insulin resistance (HOMA-IR) were measured. Oral glucose tolerance test and histological analysis were performed, and the glucose metabolism-related gene expression and signaling pathways in the liver were determined. Fecal microbiota and serum short-chain fatty acids (SCFAs) were also analyzed. L. plantarum HAC01 significantly lowered blood glucose and HbA1c levels and improved glucose tolerance and HOMA-IR. Additionally, it increased the insulin-positive β-cell area in islets and decreased the mRNA expression levels of phosphoenolpyruvate carboxykinase and glucose 6-phosphatase, which are associated with gluconeogenesis. L. plantarum HAC01 also increased the phosphorylation of AMPK and Akt, which are involved in glucose metabolism in the liver. Notably, L. plantarum HAC01 increased the Akkermansiaceae family and increased SCFAs in serum. L. plantarum HAC01 could alleviate hyperglycemia and T2DM by regulating glucose metabolism in the liver, protecting the islet β-cell mass, and restoring the gut microbiota and SCFAs. L. plantarum HAC01 may thus be an effective therapeutic agent for T2DM.

The Emerging Role of HDACs: Pathology and Therapeutic Targets in Diabetes Mellitus

Diabetes mellitus (DM) is one of the principal manifestations of metabolic syndrome and its prevalence with modern lifestyle is increasing incessantly. Chronic hyperglycemia can induce several vascular complications that were referred to be the major cause of morbidity and mortality in DM. Although several therapeutic targets have been identified and accessed clinically, the imminent risk of DM and its prevalence are still ascending. Substantial pieces of evidence revealed that histone deacetylase (HDAC) isoforms can regulate various molecular activities in DM via epigenetic and post-translational regulation of several transcription factors. To date, 18 HDAC isoforms have been identified in mammals that were categorized into four different classes. Classes I, II, and IV are regarded as classical HDACs, which operate through a Zn-based mechanism. In contrast, class III HDACs or Sirtuins depend on nicotinamide adenine dinucleotide (NAD+) for their molecular activity. Functionally, most of the HDAC isoforms can regulate β cell fate, insulin release, insulin expression and signaling, and glucose metabolism. Moreover, the roles of HDAC members have been implicated in the regulation of oxidative stress, inflammation, apoptosis, fibrosis, and other pathological events, which substantially contribute to diabetes-related vascular dysfunctions. Therefore, HDACs could serve as the potential therapeutic target in DM towards developing novel intervention strategies. This review sheds light on the emerging role of HDACs/isoforms in diabetic pathophysiology and emphasized the scope of their targeting in DM for constituting novel interventional strategies for metabolic disorders/complications.

The Roles of Dietary, Nutritional and Lifestyle Interventions in Adipose Tissue Adaptation and Obesity

The obesity and the associated non-communicable diseases (NCDs) are globally increasing in their prevalence. While the modern-day lifestyle required less ventilation of metabolic energy through muscular activities, this lifestyle transition also provided the unlimited accession to foods around the clock, which prolong the daily eating period of foods that contained high calorie and high glycemic load. These situations promote the high continuous flux of carbon substrate availability in mitochondria and induce the indecisive bioenergetic switches. The disrupted bioenergetic milieu increases the uncoupling respiration due to the excess flow of the substrate-derived reducing equivalents and reduces ubiquinones into the respiratory chain. The diversion of the uncoupling proton gradient through adipocyte thermogenesis will then alleviate the damaging effects of free radicals to mitochondria and other organelles. The adaptive induction of white adipose tissues (WAT) to beige adipose tissues (beAT) has shown beneficial effects on glucose oxidation, ROS protection and mitochondrial function preservation through the uncoupling protein 1 (UCP1)-independent thermogenesis of beAT. However, the maladaptive stage can eventually initiate with the persistent unhealthy lifestyles. Under this metabolic gridlock, the low oxygen and pro-inflammatory environments promote the adipose breakdown with sequential metabolic dysregulation, including insulin resistance, systemic inflammation and clinical NCDs progression. It is unlikely that a single intervention can reverse all these complex interactions. A comprehensive protocol that includes dietary, nutritional and all modifiable lifestyle interventions, can be the preferable choice to decelerate, stop, or reverse the NCDs pathophysiologic processes.

Redox Homeostasis in Pancreatic β-Cells: From Development to Failure

Redox status is a key determinant in the fate of β-cell. These cells are not primarily detoxifying and thus do not possess extensive antioxidant defense machinery. However, they show a wide range of redox regulating proteins, such as peroxiredoxins, thioredoxins or thioredoxin reductases, etc., being functionally compartmentalized within the cells. They keep fragile redox homeostasis and serve as messengers and amplifiers of redox signaling. β-cells require proper redox signaling already in cell ontogenesis during the development of mature β-cells from their progenitors. We bring details about redox-regulated signaling pathways and transcription factors being essential for proper differentiation and maturation of functional β-cells and their proliferation and insulin expression/maturation. We briefly highlight the targets of redox signaling in the insulin secretory pathway and focus more on possible targets of extracellular redox signaling through secreted thioredoxin1 and thioredoxin reductase1. Tuned redox homeostasis can switch upon chronic pathological insults towards the dysfunction of β-cells and to glucose intolerance. These are characteristics of type 2 diabetes, which is often linked to chronic nutritional overload being nowadays a pandemic feature of lifestyle. Overcharged β-cell metabolism causes pressure on proteostasis in the endoplasmic reticulum, mainly due to increased demand on insulin synthesis, which establishes unfolded protein response and insulin misfolding along with excessive hydrogen peroxide production. This together with redox dysbalance in cytoplasm and mitochondria due to enhanced nutritional pressure impact β-cell redox homeostasis and establish prooxidative metabolism. This can further affect β-cell communication in pancreatic islets through gap junctions. In parallel, peripheral tissues losing insulin sensitivity and overall impairment of glucose tolerance and gut microbiota establish local proinflammatory signaling and later systemic metainflammation, i.e., low chronic inflammation prooxidative properties, which target β-cells leading to their dedifferentiation, dysfunction and eventually cell death.

Type 1 diabetes mellitus as a disease of the β-cell (do not blame the immune system?)

Type 1 diabetes mellitus is believed to result from destruction of the insulin-producing β-cells in pancreatic islets that is mediated by autoimmune mechanisms. The classic view is that autoreactive T cells mistakenly destroy healthy ('innocent') β-cells. We propose an alternative view in which the β-cell is the key contributor to the disease. By their nature and function, β-cells are prone to biosynthetic stress with limited measures for self-defence. β-Cell stress provokes an immune attack that has considerable negative effects on the source of a vital hormone. This view would explain why immunotherapy at best delays progression of type 1 diabetes mellitus and points to opportunities to use therapies that revitalize β-cells, in combination with immune intervention strategies, to reverse the disease. We present the case that dysfunction occurs in both the immune system and β-cells, which provokes further dysfunction, and present the evidence leading to the consensus that islet autoimmunity is an essential component in the pathogenesis of type 1 diabetes mellitus. Next, we build the case for the β-cell as the trigger of an autoimmune response, supported by analogies in cancer and antitumour immunity. Finally, we synthesize a model ('connecting the dots') in which both β-cell stress and islet autoimmunity can be harnessed as targets for intervention strategies.

Zinc Metalloproteins in Epigenetics and Their Crosstalk

More than half a century ago, zinc was established as an essential micronutrient for normal human physiology. In silico data suggest that about 10% of the human proteome potentially binds zinc. Many proteins with zinc-binding domains (ZBDs) are involved in epigenetic modifications such as DNA methylation and histone modifications, which regulate transcription in physiological and pathological conditions. Zinc metalloproteins in epigenetics are mainly zinc metalloenzymes and zinc finger proteins (ZFPs), which are classified into writers, erasers, readers, editors, and feeders. Altogether, these classes of proteins engage in crosstalk that fundamentally maintains the epigenome's modus operandi. Changes in the expression or function of these proteins induced by zinc deficiency or loss of function mutations in their ZBDs may lead to aberrant epigenetic reprogramming, which may worsen the risk of non-communicable chronic diseases. This review attempts to address zinc's role and its proteins in natural epigenetic programming and artificial reprogramming and briefly discusses how the ZBDs in these proteins interact with the chromatin.

Valproic acid influences the expression of genes implicated with hyperglycaemia-induced complement and coagulation pathways

Because the liver plays a major role in metabolic homeostasis and secretion of clotting factors and inflammatory innate immune proteins, there is interest in understanding the mechanisms of hepatic cell activation under hyperglycaemia and whether this can be attenuated pharmacologically. We have previously shown that hyperglycaemia stimulates major changes in chromatin organization and metabolism in hepatocytes, and that the histone deacetylase inhibitor valproic acid (VPA) is able to reverse some of these metabolic changes. In this study, we have used RNA-sequencing (RNA-seq) to investigate how VPA influences gene expression in hepatocytes. Interesting, we observed that VPA attenuates hyperglycaemia-induced activation of complement and coagulation cascade genes. We also observe that many of the gene activation events coincide with changes to histone acetylation at the promoter of these genes indicating that epigenetic regulation is involved in VPA action.

Epigenetic Histone Modifications in the Pathogenesis of Diabetic Kidney Disease

Diabetic kidney disease (DKD), as the main complication of diabetes mellitus, is the primary cause of the end-stage renal disease (ESRD) and the most common chronic kidney disease. Overall, 30-40% of patients with type 1 and type 2 diabetes eventually develop DKD. Although some diabetes patients have intensified glycemic control, they still develop diabetic kidney disease. Current treatment methods can alleviate but do not markedly halt disease development, resulting in renal failure and severe complications, even contributing to elevated morbidity and mortality rates. DKD is a disease with interactions of genes and the environment. Emerging evidence indicates that DKD-associated key genes are also regulated by the epigenetic mechanism. Recently, increasing researches involving cells and experimental animals demonstrated that histone post-translational modifications can mediate gene expression, which correlated with diabetic kidney disease. Novel therapeutic strategies for epigenetic events could be beneficial for the early detection and treatment of DKD to prevent it from developing into end-stage renal disease (ESRD). In this review, we discuss prior findings in the field of histone modifications in DKD, especially histone acetylation and histone methylation. We then focus on recent developments in histone acetylation and methylation involved in the pathogenesis of DKD.

Prominent and emerging anti-diabetic molecular targets

Diabetes is on the rise across the globe affecting more than 463 million people and crucially increasing morbidities of diabetes-associated diseases. Urgent and immense actions are needed to improve diabetes prevention and treatment. Regarding the correlation of diabetes with many associated diseases, inhibition of the disease progression is more crucial than controlling symptoms. Currently, anti-diabetic drugs are accompanied by undesirable side-effects and target confined types of biomolecules. Thus, extensive research is demanding to identify novel disease mechanisms and molecular targets as probable candidates for effective treatment of diabetes. This review discusses the conventional molecule targets that have been applied for their therapeutic rationale in treatment of diabetes. Further, the emerging and prospective molecular targets for the future focus of library screenings are presented.

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.

Histone Deacetylase 3 Aggravates Type 1 Diabetes Mellitus by Inhibiting Lymphocyte Apoptosis Through the microRNA-296-5p/Bcl-xl Axis

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease characterized by immune-mediated destruction of pancreatic beta-cells. Multiple microRNAs (miRNAs) have been implicated in T1DM pathogenesis. Although histone deacetylase 3 (HDAC3) has been reported to be involved in T1DM, the underlying mechanisms remain to be further elucidated. This study was designed to investigate the potential regulatory role of Hdac3 on T1DM progression. The expression of miR-296-5p and B-cell leukemia-XL (BCL-XL) was determined using RT-qPCR and Western blot assay in peripheral blood mononuclear cells (PBMCs) of patients with T1DM, tumor necrosis factor-α (TNF-α)- and cycloheximide (CHX)-induced cell model, and streptozotocin (STZ)-induced rat model. The binding affinity between miR-296-5p and Bcl-xl was verified by using dual-luciferase reporter gene assay, and the binding between Hdac3 and the promoter region of miR-296-5p was validated using chromatin immunoprecipitation assay. Western blot analysis and flow cytometry were conducted to assess the apoptotic events of lymphocytes. miR-296-5p expression was downregulated while BCL-XL expression was upregulated in PBMCs of patients with T1DM. An adverse correlation was identified between miR-296-5p and Bcl-xl in mouse TE15 B lymphocytes. Bcl-xl was further validated to be targeted and negatively regulated by miR-296-5p in 293 T cells. Hdac3 inhibited miR-296-5p expression by binding to its promoter region. The effects of overexpressed Hdac3 on lymphocyte apoptosis was counterweighed via downregulation of Bcl-xl or upregulation of miR-296-5p, the mechanism of which was further validated in a rat model of DM. Taken together, the Hdac3-mediated upregulation of Bcl-xl via inhibiting miR-296-5p promoter activity enhanced the anti-apoptotic capacity of lymphocytes to accelerate the occurrence of T1DM.

Enhancer of Zeste Homolog 2 (EZH2) Mediates Glucolipotoxicity-Induced Apoptosis in β-Cells

Selective inhibition of histone deacetylase 3 (HDAC3) prevents glucolipotoxicity-induced β-cell dysfunction and apoptosis by alleviation of proapoptotic endoplasmic reticulum (ER) stress-signaling, but the precise molecular mechanisms of alleviation are unexplored. By unbiased microarray analysis of the β-cell gene expression profile of insulin-producing cells exposed to glucolipotoxicity in the presence or absence of a selective HDAC3 inhibitor, we identified Enhancer of zeste homolog 2 (EZH2) as the sole target candidate. β-Cells were protected against glucolipotoxicity-induced ER stress and apoptosis by EZH2 attenuation. Small molecule inhibitors of EZH2 histone methyltransferase activity rescued human islets from glucolipotoxicity-induced apoptosis. Moreover, EZH2 knockdown cells were protected against glucolipotoxicity-induced downregulation of the protective non-canonical Nuclear factor of kappa light polypeptide gene enhancer in B-cells (NFκB) pathway. We conclude that EZH2 deficiency protects from glucolipotoxicity-induced ER stress, apoptosis and downregulation of the non-canonical NFκB pathway, but not from insulin secretory dysfunction. The mechanism likely involves transcriptional regulation via EZH2 functioning as a methyltransferase and/or as a methylation-dependent transcription factor.

Epigenetic modification and therapeutic targets of diabetes mellitus

The prevalence of diabetes and its related complications are increasing significantly globally. Collected evidence suggested that several genetic and environmental factors contribute to diabetes mellitus. Associated complications such as retinopathy, neuropathy, nephropathy and other cardiovascular complications are a direct result of diabetes. Epigenetic factors include deoxyribonucleic acid (DNA) methylation and histone post-translational modifications. These factors are directly related with pathological factors such as oxidative stress, generation of inflammatory mediators and hyperglycemia. These result in altered gene expression and targets cells in the pathology of diabetes mellitus without specific changes in a DNA sequence. Environmental factors and malnutrition are equally responsible for epigenetic states. Accumulated evidence suggested that environmental stimuli alter the gene expression that result in epigenetic changes in chromatin. Recent studies proposed that epigenetics may include the occurrence of 'metabolic memory' found in animal studies. Further study into epigenetic mechanism might give us new vision into the pathogenesis of diabetes mellitus and related complication thus leading to the discovery of new therapeutic targets. In this review, we discuss the possible epigenetic changes and mechanism that happen in diabetes mellitus type 1 and type 2 separately. We highlight the important epigenetic and non-epigenetic therapeutic targets involved in the management of diabetes and associated complications.

Bifunctional HDAC Therapeutics: One Drug to Rule Them All?

Histone deacetylase (HDAC) enzymes play crucial roles in epigenetic gene expression and are an attractive therapeutic target. Five HDAC inhibitors have been approved for cancer treatment to date, however, clinical applications have been limited due to poor single-agent drug efficacy and side effects associated with a lack of HDAC isoform or complex selectivity. An emerging strategy aiming to address these limitations is the development of bifunctional HDAC therapeutics-single molecules comprising a HDAC inhibitor conjugated to another specificity targeting moiety. This review summarises the recent advancements in novel types of dual-targeting HDAC modulators, including proteolysis-targeting chimeras (PROTACs), with a focus on HDAC isoform and complex selectivity, and the future potential of such bifunctional molecules in achieving enhanced drug efficacy and therapeutic benefits in treating disease.

Roles of Epigenetic Modifications in the Differentiation and Function of Pancreatic β-Cells

Diabetes, a metabolic disease with multiple causes characterized by high blood sugar, has become a public health problem. Hyperglycaemia is caused by deficiencies in insulin secretion, impairment of insulin function, or both. The insulin secreted by pancreatic β cells is the only hormone in the body that lowers blood glucose levels and plays vital roles in maintaining glucose homeostasis. Therefore, investigation of the molecular mechanisms of pancreatic β cell differentiation and function is necessary to elucidate the processes involved in the onset of diabetes. Although numerous studies have shown that transcriptional regulation is essential for the differentiation and function of pancreatic β cells, increasing evidence indicates that epigenetic mechanisms participate in controlling the fate and regulation of these cells. Epigenetics involves heritable alterations in gene expression caused by DNA methylation, histone modification and non-coding RNA activity that does not result in DNA nucleotide sequence alterations. Recent research has revealed that a variety of epigenetic modifications play an important role in the development of diabetes. Here, we review the mechanisms by which epigenetic regulation affects β cell differentiation and function.

Isoform-specific characterization of class I histone deacetylases and their therapeutic modulation in pulmonary hypertension

Pharmacological modulation of class I histone deacetylases (HDAC) has been evaluated as a therapeutic strategy for pulmonary hypertension (PH) in experimental models of PH. However, information of their expression, regulation and transcriptional targets in human PH and the therapeutic potential of isoform-selective enzyme modulation are lacking. Comprehensive analysis of expression and regulation of class I HDACs (HDAC1, HDAC2, HDAC3 and HDAC8) was performed in cardiopulmonary tissues and adventitial fibroblasts isolated from pulmonary arteries (PAAF) of idiopathic pulmonary arterial hypertension (IPAH) patients and healthy donors. Cellular functions and transcriptional targets of HDAC enzymes were investigated. Therapeutic effects of pan-HDAC (Vorinostat), class-selective (VPA) and isoform-selective (CAY10398, Romidepsin, PCI34051) HDAC inhibitors were evaluated ex vivo (IPAH-PAAF, IPAH-PASMC) and in vivo (rat chronic hypoxia-induced PH and zebrafish angiogenesis). Our screening identifies dysregulation of class I HDAC isoforms in IPAH. Particularly, HDAC1 and HDAC8 were consistently increased in IPAH-PAs and IPAH-PAAFs, whereas HDAC2 and HDAC8 showed predominant localization with ACTA2-expressing cells in extensively remodeled IPAH-PAs. Hypoxia not only significantly modulated protein levels of deacetylase (HDAC8), but also significantly caused dynamic changes in the global histone lysine acetylation levels (H3K4ac, H3K9/K14ac and H3K27ac). Importantly, isoform-specific RNA-interference revealed that HDAC isoforms regulate distinct subset of transcriptome in IPAH-PAAFs. Reduced transcript levels of KLF2 in IPAH-PAAFs was augmented by HDAC8 siRNA and HDAC inhibitors, which also attenuated IPAH-associated hyperproliferation and apoptosis-resistance ex vivo, and mitigated chronic hypoxia-induced established PH in vivo, at variable degree. Class I HDAC isoforms are significantly dysregulated in human PAH. Isoform-selective HDAC inhibition is a viable approach to circumvent off-target effects.

Key Relevance of Epigenetic Programming of Adiponectin Gene in Pathogenesis of Metabolic Disorders

Background & Objective::

Significant health and social burdens have been created by the growth of metabolic disorders like type 2 diabetes mellitus (T2DM), atherosclerosis, and non-alcoholic steatohepatitis, worldwide. The number of the affected population is as yet rising, and it is assessed that until 2030, 4−5 million individuals will acquire diabetes. A blend of environmental, genetic, epigenetic, and other factors, such as diet, are accountable for the initiation and progression of metabolic disorders. Several researches have shown strong relevance of adiponectin gene and metabolic disorders. In this review, the potential influence of epigenetic mechanisms of adiponectin gene “ADIPOQ” on increasing the risk of developing metabolic disorders and their potential in treating this major disorder are discussed.

Results & Conclusion::

Various studies have postulated that a series of factors such as maternal High fat diet (HFD), oxidative stress, pro-inflammatory mediators, sleep fragmentation throughout lifetime, from gestation to old age, could accumulate epigenetic marks, including histone remodeling, DNA methylation, and microRNAs (miRNAs) that, in turn, alter the expression of ADIPOQ gene and result in hypoadiponectinemia which precipitates insulin resistance (IR) that in turn might induce or accelerate the onset and development of metabolic disorder. A better understanding of global patterns of epigenetic modifications and further their alterations in metabolic disorders will bestow better treatment strategies design.

Correction of Niemann-Pick type C1 trafficking and activity with the histone deacetylase inhibitor valproic acid

Niemann-Pick type C (NPC) disease is primarily caused by mutations in the NPC1 gene and is characterized by the accumulation of unesterified cholesterol and lipids in the late endosomal (LE) and lysosomal (Ly) compartments. The most prevalent disease-linked mutation is the I1061T variant of NPC1, which exhibits defective folding and trafficking from the endoplasmic reticulum to the LE/Ly compartments. We now show that the FDA-approved histone deacetylase inhibitor (HDACi) valproic acid (VPA) corrects the folding and trafficking defect associated with I1061T-NPC1 leading to restoration of cholesterol homeostasis, an effect that is largely driven by a reduction in HDAC7 expression. The VPA-mediated trafficking correction is in part associated with an increase in the acetylation of lysine residues in the cysteine-rich domain of NPC1. The HDACi-mediated correction is synergistically improved by combining it with the FDA-approved anti-malarial, chloroquine, a known lysosomotropic compound, which improved the stability of the LE/Ly-localized fraction of the I1061T variant. We posit that combining the activity of VPA, to modulate epigenetically the cellular acetylome, with chloroquine, to alter the lysosomal environment to favor stability of the trafficked I1061T variant protein can have a significant therapeutic benefit in patients carrying at least one copy of the I1061T variant of NPC1, the most common disease-associated mutation leading to NPC disease. Given its ability to cross the blood-brain barrier, we posit VPA provides a potential mechanism to improve the response to 2-hydroxypropyl-β-cyclodextrin, by restoring a functional NPC1 to the cholesterol managing compartment as an adjunct therapy.

Effects of Tributyrin Supplementation on Growth Performance, Insulin, Blood Metabolites and Gut Microbiota in Weaned Piglets

Simple Summary

In animal farming, alternatives to antibiotics are required due to the increase of antimicrobial resistance. In this contest, tributyrin showed the ability to promote gut health, to modulate gut microbiota and to improve protein digestibility, leading also to higher growth performance. However, although the mode of action of tributyrin on the intestinal epithelial cells has been partially explained, its effects on lipid and protein metabolism needs to be investigated. This paper provides information about the influence of tributyrin on production traits, blood parameters, faecal microbiota and faecal protein excretion in weaned piglets.

Abstract

The aim of this study was to investigate the effects of tributyrin supplementation on the production traits, the main metabolic parameters and gut microbiota in weaned piglets. One hundred and twenty crossbred piglets (Large White × Landrace) were randomly divided into two experimental groups (six pens each; 10 piglets per pen): the control group (CTRL), that received a basal diet, and the tributyrin group (TRIB) that received the basal diet supplemented with 0.2% tributyrin. The experimental period lasted 40 days. Production traits were measured at days 14, 28 and 40. A subset composed of 48 animals (n = 4 for each pen; n = 24 per group) was considered for the evaluation of serum metabolic parameters and hair cortisol by enzyme-linked immunosorbent assay (ELISA), and faecal microbiota by real-time polymerase chain reaction (PCR). Our results showed that the treatment significantly increased body weight (BW) at day 28 and day 40 (p = 0.0279 and p = 0.0006, respectively) and average daily gain (ADG) from day 28 to day 40 (p = 0.046). Gain to feed ratio (G:F) was significantly higher throughout the experimental period (p = 0.049). Even if the serum parameters were in the physiological range, albumin, albumin/globulin (A/G) ratio, glucose and high-density lipoproteins (HDL) fraction were significantly higher in the TRIB group. On the contrary, tributyrin significantly decreased the urea blood concentration (p = 0.0026), which was correlated with lean gain and feed efficiency. Moreover, serum insulin concentration, which has a regulatory effect on protein and lipid metabolism, was significantly higher in the TRIB group (p = 0.0187). In conclusion, this study demonstrated that tributyrin can be considered as a valid feed additive for weaned piglets.