Insights into the molecular mechanism for type 2 diabetes susceptibility at the KCNQ1 locus from temporal changes in imprinting status in human islets

Population-scale skeletal muscle single-nucleus multi-omic profiling reveals extensive context specific genetic regulation

Skeletal muscle, the largest human organ by weight, is relevant to several polygenic metabolic traits and diseases including type 2 diabetes (T2D). Identifying genetic mechanisms underlying these traits requires pinpointing the relevant cell types, regulatory elements, target genes, and causal variants. Here, we used genetic multiplexing to generate population-scale single nucleus (sn) chromatin accessibility (snATAC-seq) and transcriptome (snRNA-seq) maps across 287 frozen human skeletal muscle biopsies representing 456,880 nuclei. We identified 13 cell types that collectively represented 983,155 ATAC summits. We integrated genetic variation to discover 6,866 expression quantitative trait loci (eQTL) and 100,928 chromatin accessibility QTL (caQTL) (5% FDR) across the five most abundant cell types, cataloging caQTL peaks that atlas-level snATAC maps often miss. We identified 1,973 eGenes colocalized with caQTL and used mediation analyses to construct causal directional maps for chromatin accessibility and gene expression. 3,378 genome-wide association study (GWAS) signals across 43 relevant traits colocalized with sn-e/caQTL, 52% in a cell-specific manner. 77% of GWAS signals colocalized with caQTL and not eQTL, highlighting the critical importance of population-scale chromatin profiling for GWAS functional studies. GWAS-caQTL colocalization showed distinct cell-specific regulatory paradigms. For example, a C2CD4A/B T2D GWAS signal colocalized with caQTL in muscle fibers and multiple chromatin loop models nominated VPS13C, a glucose uptake gene. Sequence of the caQTL peak overlapping caSNP rs7163757 showed allelic regulatory activity differences in a human myocyte cell line massively parallel reporter assay. These results illuminate the genetic regulatory architecture of human skeletal muscle at high-resolution epigenomic, transcriptomic, and cell state scales and serve as a template for population-scale multi-omic mapping in complex tissues and traits.

The CEBPA-FGF21 regulatory network may participate in the T2DM-induced skeletal muscle atrophy by regulating the autophagy-lysosomal pathway

AIMS

Recent years have witnessed an increasing research interest in the roles of transcription factor (TF)-gene regulatory network in type 2 diabetes mellitus (T2DM). Thus, we sought to characterize the mechanistic insights based on the TF-gene regulatory network in skeletal muscle atrophy in T2DM.

METHODS

Differentially expressed TFs (DETFs) and mRNAs (DEmRNAs) were obtained in T2DM-related gene expression profiles (GSE12643, GSE55650, GSE166502, and GSE29221), followed by WGCNA, and GO and KEGG enrichment analyses. Next, the iRegulon plug-in unit of Cytoscape software was used to construct a TF-mRNA regulatory network. Besides, RT-qPCR and ChIP-seq were utilized to measure the expression of CEBPA and FGF21 in the skeletal muscle tissues or cells of T2DM rat models. At last, the effect of overexpression of FGF21 on the autophagy-lysosomal pathway was examined in skeletal muscle cells of T2DM rats.

RESULTS

Totally, 12 DETFs and 102 DEmRNAs were found in the skeletal muscle tissues of T2DM samples. The DEmRNAs were mainly enriched in the autophagy-lysosomal pathway. CEBPA affected the skeletal muscle atrophy in T2DM by regulating 5 target genes via the autophagy-lysosomal pathway. CEBPA could target FGF21. In addition, the expression of CEBPA was elevated, while the expression of FGF21 was diminished in the skeletal muscle tissues or cells of T2DM rats. The CEBPA-FGF21 regulatory network promoted skeletal muscle atrophy in T2DM by activating the autophagy-lysosomal pathway.

CONCLUSION

The CEBPA-FGF21 regulatory network may participate in the T2DM-induced skeletal muscle atrophy by regulating the autophagy-lysosomal pathway. Thus, our study provides interesting targets for prevention of skeletal muscle atrophy in T2DM.

Suppression of P2X7R by Local Treatment Alleviates Acute Gouty Inflammation

Objective

Gout is the most common inflammatory arthritis associated with interleukin-1β (IL-1β) accumulation during exacerbation. In this study, we aimed to clarify whether potassium channel antagonists attenuate local inflammation in mice with monosodium urate (MSU)-induced gout.

Methods

We cultured human macrophage THP-1 cells and evaluated the molecular levels of both IL-1β and potassium channels stimulated with MSU and/or potassium channel antagonists. Acute gout models were generated in IL-1β luciferase transgenic male mice using synovium-like subcutaneous air pouches with MSU injection. Their luciferase activities were monitored following potassium channel blocker treatment using the IVIS Spectrum CT imaging system. The lavages and tissues were extracted from their air pouches, followed by cell counting and pathological analysis.

Results

MSU stimulation increased the gene expression levels of pro-IL-1β, P2x7r and Kv1.3, whereas the expression of Kcnq1 was decreased in phorbol 12-myristate 13-acetate-induced THP-1 cells. Both high and low concentrations of the P2x7 receptor inhibitor adenosine 5'-triphosphate (ATP) derivative periodate oxidized ATP (oATP) decreased the production of IL-1β in the supernatant of THP-1 cells. The sixth hour was the peak time of IL-1β luciferase activity after MSU intervention in vivo. oATP ameliorated the synovial IL-1β luciferase activity, reduced inflammatory cell infiltration and alleviated the erosive damage in the cartilage.

Conclusion

The anti-inflammatory properties of potassium channel inhibitors, especially of oATP, might point to new strategies for local anti-inflammatory therapy for acute gout.

Sex differences in the influence of type 2 diabetes (T2D)-related genes, parental history of T2D, and obesity on T2D development: a case-control study

BACKGROUND

This study investigated the effect of sex and age at type 2 diabetes (T2D) diagnosis on the influence of T2D-related genes, parental history of T2D, and obesity on T2D development.

METHODS

In this case-control study, 1012 T2D cases and 1008 healthy subjects were selected from the Diabetes in Mexico Study database. Participants were stratified by sex and age at T2D diagnosis (early, ≤ 45 years; late, ≥ 46 years). Sixty-nine T2D-associated single nucleotide polymorphisms were explored and the percentage contribution (R²) of T2D-related genes, parental history of T2D, and obesity (body mass index [BMI] and waist-hip ratio [WHR]) on T2D development was calculated using univariate and multivariate logistic regression models.

RESULTS

T2D-related genes influenced T2D development most in males who were diagnosed early (R² = 23.5%; females, R² = 13.5%; males and females diagnosed late, R² = 11.9% and R² = 7.3%, respectively). With an early diagnosis, insulin production-related genes were more influential in males (76.0% of R²) while peripheral insulin resistance-associated genes were more influential in females (52.3% of R²). With a late diagnosis, insulin production-related genes from chromosome region 11p15.5 notably influenced males while peripheral insulin resistance and genes associated with inflammation and other processes notably influenced females. Influence of parental history was higher among those diagnosed early (males, 19.9%; females, 17.5%) versus late (males, 6.4%; females, 5,3%). Unilateral maternal T2D history was more influential than paternal T2D history. BMI influenced T2D development for all, while WHR exclusively influenced males.

CONCLUSIONS

The influence of T2D-related genes, maternal T2D history, and fat distribution on T2D development was greater in males than females.

Regenerative medicine: current research and perspective in pediatric surgery

The field of regenerative medicine, encompassing several disciplines including stem cell biology and tissue engineering, continues to advance with the accumulating research on cell manipulation technologies, gene therapy and new materials. Recent progress in preclinical and clinical studies may transcend the boundaries of regenerative medicine from laboratory research towards clinical reality. However, for the ultimate goal to construct bioengineered transplantable organs, a number of issues still need to be addressed. In particular, engineering of elaborate tissues and organs requires a fine combination of different relevant aspects; not only the repopulation of multiple cell phenotypes in an appropriate distribution but also the adjustment of the host environmental factors such as vascularisation, innervation and immunomodulation. The aim of this review article is to provide an overview of the recent discoveries and development in stem cells and tissue engineering, which are inseparably interconnected. The current status of research on tissue stem cells and bioengineering, and the possibilities for application in specific organs relevant to paediatric surgery have been specifically focused and outlined.

Identification of Potentially Functional Circular RNA/Long Noncoding RNA-MicroRNA-mRNA Regulatory Networks Associated with Vascular Injury in Type 2 Diabetes Mellitus by Integrated Microarray Analysis

This research is aimed at figuring out the potential circular RNA (circRNA)/long noncoding RNA- (lncRNA-) microRNA- (miRNA-) mRNA regulatory networks associated with a vascular injury in type 2 diabetes mellitus (T2DM). Differentially expressed genes (DEGs) screened in T2DM-related expression datasets were intersected with genes associated with vascular injury in T2DM to obtain candidate DEGs, followed by the construction of an interaction network of DEGs. The upstream miRNAs of candidate genes were predicted by mirDIP, miRWalk, and DIANA TOOLS databases, and the upstream lncRNAs/circRNAs of miRNAs by DIANA-LncBase/circBank database, followed by the construction of circRNA/lncRNA-miRNA-mRNA regulatory networks. Peripheral blood was attained from T2DM patients with macroangiopathy for clinical validation of expression and correlation of key factors. Differential analysis screened 37 candidate DEGs correlated with vascular injury in T2DM. Besides, MAPK3 was a core gene associated with vascular injury in T2DM. Among the predicted upstream miRNAs of MAPK3, miR-4270, miR-92a-2-5p, miR-423-5p, and miR-613 ranked at the top according to binding scores. The upstream lncRNAs and circRNAs of the 4 miRNAs were further predicted, obtaining 11 candidate lncRNAs and 3 candidate circRNAs. Moreover, KCNQ1OT1, circ_0020316, and MAPK3 were upregulated, but miR-92a-2-5p was downregulated in the peripheral blood of T2DM patients with macroangiopathy. Mechanistically, KCNQ1OT1 and circ_0020316 bound to miR-92a-2-5p that inversely targeted MAPK3. Collectively, KCNQ1OT1/circ_0020316-miR-92a-2-5p-MAPK3 coexpression regulatory networks might promote vascular injury in T2DM.

Syndromic forms of congenital hyperinsulinism

Congenital hyperinsulinism (CHI), also called hyperinsulinemic hypoglycemia (HH), is a very heterogeneous condition and represents the most common cause of severe and persistent hypoglycemia in infancy and childhood. The majority of cases in which a genetic cause can be identified have monogenic defects affecting pancreatic β-cells and their glucose-sensing system that regulates insulin secretion. However, CHI/HH has also been observed in a variety of syndromic disorders. The major categories of syndromes that have been found to be associated with CHI include overgrowth syndromes (e.g. Beckwith-Wiedemann and Sotos syndromes), chromosomal and monogenic developmental syndromes with postnatal growth failure (e.g. Turner, Kabuki, and Costello syndromes), congenital disorders of glycosylation, and syndromic channelopathies (e.g. Timothy syndrome). This article reviews syndromic conditions that have been asserted by the literature to be associated with CHI. We assess the evidence of the association, as well as the prevalence of CHI, its possible pathophysiology and its natural course in the respective conditions. In many of the CHI-associated syndromic conditions, the mechanism of dysregulation of glucose-sensing and insulin secretion is not completely understood and not directly related to known CHI genes. Moreover, in most of those syndromes the association seems to be inconsistent and the metabolic disturbance is transient. However, since neonatal hypoglycemia is an early sign of possible compromise in the newborn, which requires immediate diagnostic efforts and intervention, this symptom may be the first to bring a patient to medical attention. As a consequence, HH in a newborn or infant with associated congenital anomalies or additional medical issues remains a differential diagnostic challenge and may require a broad genetic workup.

The transcriptomic and epigenetic alterations in type 2 diabetes mellitus patients of Chinese Tibetan and Han populations

BACKGROUND

Due to the distinctive living environment, lifestyle, and diet, the Tibetan community in China has the lowest prevalence of T2DM and prediabetes among numerous ethnic groups, while Han community shows the highest statistic. In this study, we aim to conclude the clinical manifestations of both Tibetan and Han T2DM patients and their association with transcriptomic and epigenetic alterations.

METHODS

A cross-sectional study including 120 T2DM patients from Han and Tibetan ethnic groups were conducted between 2019 to 2021 at the Hospital of Chengdu University of Traditional Chinese Medicine. The various clinical features and laboratory tests were recorded and analyzed between the two groups. The genome-wide methylation pattern and RNA expression were determined by Reduced Representation Bisulfite Sequencing (RBBS) and Poly (A) RNA sequencing (RNA-seq) from leucocytes of peripheral blood samples in 6 Han and 6 Tibetan patients. GO analysis and KEGG analysis were conducted in differentially expressed genes and those with differentially methylated regions.

RESULTS

Compared to Han, Tibetan T2DM individuals intake more coarse grains, meat and yak butter, but less refined grains, vegetables and fruit. They also showed increased BMI, Hb, HbA1c, LDL, ALT, GGT and eGFR, and decreased level of BUN. Among the 12 patients in the exploratory cohort, we identified 5178 hypomethylated and 4787 hypermethylated regions involving 1613 genes in the Tibetan group. RNA-seq showed a total of 947 differentially expressed genes (DEGs) between the two groups, with 523 up-regulated and 424 down-regulated in Tibetan patients. By integrating DNA methylation and RNA expression data, we identified 112 DEGs with differentially methylated regions (overlapping genes) and 14 DEGs with promoter-related DMRs. The functional enrichment analysis demonstrated that the overlapping genes were primarily involved in metabolic pathways, PI3K-Akt signaling pathway, MAPK signaling pathway, pathways in cancer and Rap1 signaling pathway.

CONCLUSION

Our study demonstrates the clinical characteristics of T2DM differ subtly between various ethnic groups that may be related to epigenetic modifications, thus providing evidence and ideas for additional research on the genetic pattern of T2DM.

Molecular hallmarks of long non-coding RNAs in aging and its significant effect on aging-associated diseases

Aging is linked to the deterioration of many physical and cognitive abilities and is the leading risk factor for Alzheimer's disease. The growing aging population is a significant healthcare problem globally that researchers must investigate to better understand the underlying aging processes. Advances in microarrays and sequencing techniques have resulted in deeper analyses of diverse essential genomes (e.g., mouse, human, and rat) and their corresponding cell types, their organ-specific transcriptomes, and the tissue involved in aging. Traditional gene controllers such as DNA- and RNA-binding proteins significantly influence such programs, causing the need to sort out long non-coding RNAs, a new class of powerful gene regulatory elements. However, their functional significance in the aging process and senescence has yet to be investigated and identified. Several recent researchers have associated the initiation and development of senescence and aging in mammals with several well-reported and novel long non-coding RNAs. In this review article, we identified and analyzed the evolving functions of long non-coding RNAs in cellular processes, including cellular senescence, aging, and age-related pathogenesis, which are the major hallmarks of long non-coding RNAs in aging.

Generation of Isogenic hiPSCs with Targeted Edits at Multiple Intronic SNPs to Study the Effects of the Type 2 Diabetes Associated KCNQ1 Locus in American Indians

The top genetic association signal for type 2 diabetes (T2D) in Southwestern American Indians maps to intron 15 of KCNQ1, an imprinted gene. We aim to understand the biology whereby variation at this locus affects T2D specifically in this genomic background. To do so, we obtained human induced pluripotent stem cells (hiPSC) derived from American Indians. Using these iPSCs, we show that imprinting of KCNQ1 and CDKN1C during pancreatic islet-like cell generation from iPSCs is consistent with known imprinting patterns in fetal pancreas and adult islets and therefore is an ideal model system to study this locus. In this report, we detail the use of allele-specific guide RNAs and CRISPR to generate isogenic hiPSCs that differ only at multiple T2D associated intronic SNPs at this locus which can be used to elucidate their functional effects. Characterization of these isogenic hiPSCs identified a few aberrant cell lines; namely cell lines with large hemizygous deletions in the putative functional region of KCNQ1 and cell lines hypomethylated at the KCNQ1OT1 promoter. Comparison of an isogenic cell line with a hemizygous deletion to the parental cell line identified CDKN1C and H19 as differentially expressed during the endocrine progenitor stage of pancreatic-islet development.

Genome-Wide DNA Methylation in Policemen Working in Cities Differing by Major Sources of Air Pollution

DNA methylation is the most studied epigenetic mechanism that regulates gene expression, and it can serve as a useful biomarker of prior environmental exposure and future health outcomes. This study focused on DNA methylation profiles in a human cohort, comprising 125 nonsmoking city policemen (sampled twice), living and working in three localities (Prague, Ostrava and Ceske Budejovice) of the Czech Republic, who spent the majority of their working time outdoors. The main characterization of the localities, differing by major sources of air pollution, was defined by the stationary air pollution monitoring of PM2.5, B[a]P and NO₂. DNA methylation was analyzed by a genome-wide microarray method. No season-specific DNA methylation pattern was discovered; however, we identified 13,643 differentially methylated CpG loci (DML) for a comparison between the Prague and Ostrava groups. The most significant DML was cg10123377 (log₂FC = −1.92, p = 8.30 × 10⁻⁴) and loci annotated to RPTOR (total 20 CpG loci). We also found two hypomethylated loci annotated to the DNA repair gene XRCC5. Groups of DML annotated to the same gene were linked to diabetes mellitus (KCNQ1), respiratory diseases (PTPRN2), the dopaminergic system of the brain and neurodegenerative diseases (NR4A2). The most significant possibly affected pathway was Axon guidance, with 86 potentially deregulated genes near DML. The cluster of gene sets that could be affected by DNA methylation in the Ostrava groups mainly includes the neuronal functions and biological processes of cell junctions and adhesion assembly. The study demonstrates that the differences in the type of air pollution between localities can affect a unique change in DNA methylation profiles across the human genome.

Stem Cell-Derived β Cells: A Versatile Research Platform to Interrogate the Genetic Basis of β Cell Dysfunction

Pancreatic β cell dysfunction is a central component of diabetes progression. During the last decades, the genetic basis of several monogenic forms of diabetes has been recognized. Genome-wide association studies (GWAS) have also facilitated the identification of common genetic variants associated with an increased risk of diabetes. These studies highlight the importance of impaired β cell function in all forms of diabetes. However, how most of these risk variants confer disease risk, remains unanswered. Understanding the specific contribution of genetic variants and the precise role of their molecular effectors is the next step toward developing treatments that target β cell dysfunction in the era of personalized medicine. Protocols that allow derivation of β cells from pluripotent stem cells, represent a powerful research tool that allows modeling of human development and versatile experimental designs that can be used to shed some light on diabetes pathophysiology. This article reviews different models to study the genetic basis of β cell dysfunction, focusing on the recent advances made possible by stem cell applications in the field of diabetes research.

Human and rat skeletal muscle single-nuclei multi-omic integrative analyses nominate causal cell types, regulatory elements, and SNPs for complex traits

Skeletal muscle accounts for the largest proportion of human body mass, on average, and is a key tissue in complex diseases and mobility. It is composed of several different cell and muscle fiber types. Here, we optimize single-nucleus ATAC-seq (snATAC-seq) to map skeletal muscle cell-specific chromatin accessibility landscapes in frozen human and rat samples, and single-nucleus RNA-seq (snRNA-seq) to map cell-specific transcriptomes in human. We additionally perform multi-omics profiling (gene expression and chromatin accessibility) on human and rat muscle samples. We capture type I and type II muscle fiber signatures, which are generally missed by existing single-cell RNA-seq methods. We perform cross-modality and cross-species integrative analyses on 33,862 nuclei and identify seven cell types ranging in abundance from 59.6% to 1.0% of all nuclei. We introduce a regression-based approach to infer cell types by comparing transcription start site-distal ATAC-seq peaks to reference enhancer maps and show consistency with RNA-based marker gene cell type assignments. We find heterogeneity in enrichment of genetic variants linked to complex phenotypes from the UK Biobank and diabetes genome-wide association studies in cell-specific ATAC-seq peaks, with the most striking enrichment patterns in muscle mesenchymal stem cells (∼3.5% of nuclei). Finally, we overlay these chromatin accessibility maps on GWAS data to nominate causal cell types, SNPs, transcription factor motifs, and target genes for type 2 diabetes signals. These chromatin accessibility profiles for human and rat skeletal muscle cell types are a useful resource for nominating causal GWAS SNPs and cell types.

The role of long non-coding RNAs in the regulation of pancreatic beta cell identity

Type 2 diabetes (T2D) is a widespread disease affecting millions in every continental population. Pancreatic β-cells are central to the regulation of circulating glucose, but failure in the maintenance of their mass and/or functional identity leads to T2D. Long non-coding RNAs (lncRNAs) represent a relatively understudied class of transcripts which growing evidence implicates in diabetes pathogenesis. T2D-associated single nucleotide polymorphisms (SNPs) have been identified in lncRNA loci, although these appear to function primarily through regulating β-cell proliferation. In the last decade, over 1100 lncRNAs have been catalogued in islets and the roles of a few have been further investigated, definitively linking them to β-cell function. These studies show that lncRNAs can be developmentally regulated and show highly tissue-specific expression. lncRNAs regulate neighbouring β-cell-specific transcription factor expression, with knockdown or overexpression of lncRNAs impacting a network of other key genes and pathways. Finally, gene expression analysis in studies of diabetic models have uncovered a number of lncRNAs with roles in β-cell function. A deeper understanding of these lncRNA roles in maintaining β-cell identity, and its deterioration, is required to fully appreciate the β-cell molecular network and to advance novel diabetes treatments.

Epigenetic age prediction

Advanced age is the main common risk factor for cancer, cardiovascular disease and neurodegeneration. Yet, more is known about the molecular basis of any of these groups of diseases than the changes that accompany ageing itself. Progress in molecular ageing research was slow because the tools predicting whether someone aged slowly or fast (biological age) were unreliable. To understand ageing as a risk factor for disease and to develop interventions, the molecular ageing field needed a quantitative measure; a clock for biological age. Over the past decade, a number of age predictors utilising DNA methylation have been developed, referred to as epigenetic clocks. While they appear to estimate biological age, it remains unclear whether the methylation changes used to train the clocks are a reflection of other underlying cellular or molecular processes, or whether methylation itself is involved in the ageing process. The precise aspects of ageing that the epigenetic clocks capture remain hidden and seem to vary between predictors. Nonetheless, the use of epigenetic clocks has opened the door towards studying biological ageing quantitatively, and new clocks and applications, such as forensics, appear frequently. In this review, we will discuss the range of epigenetic clocks available, their strengths and weaknesses, and their applicability to various scientific queries.

Novel Reclassification of Adult Diabetes Is Useful to Distinguish Stages of β-Cell Function Linked to the Risk of Vascular Complications: The DOLCE Study From Northern Ukraine

Background

Presently, persons with diabetes are classified as having type 1 (T1D) or type 2 diabetes (T2D) based on clinical diagnosis. However, adult patients exhibit diverse clinical representations and this makes treatment approaches challenging to personalize. A recent Scandinavian study proposed a novel classification of adult diabetes into five clusters based on disease pathophysiology and risk of vascular complications. The current study aimed to characterize new subgroups of adult diabetes using this strategy in a defined population from northern Ukraine.

Methods

We analyzed 2,140 patients with established diabetes from the DOLCE study (n = 887 with new-onset diabetes and n = 1,253 with long duration). We used the k-means approach to perform clustering analyses using BMI, age at onset of diabetes, HbA_1c, insulin secretion (HOMA2-B), and insulin resistance (HOMA2-IR) indices and glutamic acid decarboxylase antibodies (GADA) levels. Risks of macro- (myocardial infarction or stroke) and microvascular [retinopathy, chronic kidney disease (CKD) and neuropathy] complications and associations of genetic variants with specific clusters were studied using logistic regression adjusted for age, sex, and diabetes duration.

Results

Severe autoimmune diabetes (SAID, 11 and 6%) and severe insulin-deficient diabetes (SIDD, 25 and 14%) clusters were twice as prevalent in patients with long-term as compared to those with new-onset diabetes. Patients with long duration in both SAID and SIDD clusters had highest risks of proliferative retinopathy, and elevated risks of CKD. Long-term insulin-resistant obese diabetes 1 (IROD1) subgroup had elevated risks of CKD, while insulin-resistant obese diabetes 2 (IROD2) cluster exhibited the highest HOMA2-B, lowest HbA_1c, and lower prevalence of all microvascular complications as compared to all other clusters. Genetic analyses of IROD2 subgroup identified reduced frequency of the risk alleles in the TCF7L2 gene as compared to all other clusters, cumulatively and individually (p = 0.0001).

Conclusion

The novel reclassification algorithm of patients with adult diabetes was reproducible in this population from northern Ukraine. It may be beneficial for the patients in the SIDD subgroup to initiate earlier insulin treatment or other anti-diabetic modalities to preserve β-cell function. Long-term diabetes cases with preserved β-cell function and lower risk for microvascular complications represent an interesting subgroup of patients for further investigations of protective mechanisms.

A 3D system to model human pancreas development and its reference single-cell transcriptome atlas identify signaling pathways required for progenitor expansion

Human organogenesis remains relatively unexplored for ethical and practical reasons. Here, we report the establishment of a single-cell transcriptome atlas of the human fetal pancreas between 7 and 10 post-conceptional weeks of development. To interrogate cell–cell interactions, we describe InterCom, an R-Package we developed for identifying receptor–ligand pairs and their downstream effects. We further report the establishment of a human pancreas culture system starting from fetal tissue or human pluripotent stem cells, enabling the long-term maintenance of pancreas progenitors in a minimal, defined medium in three-dimensions. Benchmarking the cells produced in 2-dimensions and those expanded in 3-dimensions to fetal tissue identifies that progenitors expanded in 3-dimensions are transcriptionally closer to the fetal pancreas. We further demonstrate the potential of this system as a screening platform and identify the importance of the EGF and FGF pathways controlling human pancreas progenitor expansion.

From single-cell transcriptome analyses to defining culture media for spheroids, the authors provide a census of information to understand the development of human pancreatic progenitors. This approach identifies signalling pathways (EGF and FGF) regulating progenitor proliferation.

GPR119 agonists: Novel therapeutic agents for type 2 diabetes mellitus

Diabetes mellitus type 2 (T2D) is a group of genetically heterogeneous metabolic disorders whose frequency has gradually risen worldwide. Diabetes mellitus Type 2 (T2D) has started to achieve a pandemic level, and it is estimated that within the next decade, cases of diabetes might get double due to increase in aging population. Diabetes is rightly called the 'silent killer' because it has emerged to be one of the major causes, leading to renal failure, loss of vision; besides cardiac arrest in India. Thus, a clinical requirement for the oral drug molecules monitoring glucose homeostasis appears to be unmet. GPR119 agonist, a family of G-protein coupled receptors, usually noticed in β-cells of pancreatic as well as intestinal L cells, drew considerable interest for type 2 diabetes mellitus (T2D). GPR119 monitors physiological mechanisms that enhance homeostasis of glucose, such as glucose-like peptide-1, gastrointestinal incretin hormone levels, pancreatic beta cell-dependent insulin secretion and glucose-dependent insulinotropic peptide (GIP). In this manuscript, we have reviewed the work done in the last five years (2015-2020) which gives an approach to design, synthesize, evaluate and study the structural activity relationship of novel GPR119 agonist-based lead compounds. Our article would help the researchers and guide their endeavours in the direction of strategy and development of innovative, effective GPR119 agonist-based compounds for the management of diabetes mellitus type 2.

DNA Methylation Patterning and the Regulation of Beta Cell Homeostasis

Pancreatic beta cells play a central role in regulating glucose homeostasis by secreting the hormone insulin. Failure of beta cells due to reduced function and mass and the resulting insulin insufficiency can drive the dysregulation of glycemic control, causing diabetes. Epigenetic regulation by DNA methylation is central to shaping the gene expression patterns that define the fully functional beta cell phenotype and regulate beta cell growth. Establishment of stage-specific DNA methylation guides beta cell differentiation during fetal development, while faithful restoration of these signatures during DNA replication ensures the maintenance of beta cell identity and function in postnatal life. Lineage-specific transcription factor networks interact with methylated DNA at specific genomic regions to enhance the regulatory specificity and ensure the stability of gene expression patterns. Recent genome-wide DNA methylation profiling studies comparing islets from diabetic and non-diabetic human subjects demonstrate the perturbation of beta cell DNA methylation patterns, corresponding to the dysregulation of gene expression associated with mature beta cell state in diabetes. This article will discuss the molecular underpinnings of shaping the islet DNA methylation landscape, its mechanistic role in the specification and maintenance of the functional beta cell phenotype, and its dysregulation in diabetes. We will also review recent advances in utilizing beta cell specific DNA methylation patterns for the development of biomarkers for diabetes, and targeting DNA methylation to develop translational approaches for supplementing the functional beta cell mass deficit in diabetes.

Genetic basis and identification of candidate genes for wooden breast and white striping in commercial broiler chickens

Wooden breast (WB) and white striping (WS) are highly prevalent and economically damaging muscle disorders of modern commercial broiler chickens characterized respectively by palpable firmness and fatty white striations running parallel to the muscle fiber. High feed efficiency and rapid growth, especially of the breast muscle, are believed to contribute to development of such muscle defects; however, their etiology remains poorly understood. To gain insight into the genetic basis of these myopathies, a genome-wide association study was conducted using a commercial crossbred broiler population (n = 1193). Heritability was estimated at 0.5 for WB and WS with high genetic correlation between them (0.88). GWAS revealed 28 quantitative trait loci (QTL) on five chromosomes for WB and 6 QTL on one chromosome for WS, with the majority of QTL for both myopathies located in a ~ 8 Mb region of chromosome 5. This region has highly conserved synteny with a portion of human chromosome 11 containing a cluster of imprinted genes associated with growth and metabolic disorders such as type 2 diabetes and Beckwith-Wiedemann syndrome. Candidate genes include potassium voltage-gated channel subfamily Q member 1 (KCNQ1), involved in insulin secretion and cardiac electrical activity, lymphocyte-specific protein 1 (LSP1), involved in inflammation and immune response.

Long non-coding RNA-regulated pathways in pancreatic β cells: Their role in diabetes

Long non-coding RNAs (lncRNAs) are transcripts of more than 200 nucleotides that have not coding potential, but act as gene expression regulators through several molecular mechanisms. Several studies have identified tons of lncRNAs that are expressed in pancreatic β cells and many of them have been shown to have β cell-specific expression, suggesting a potential role in the regulation of basal β cell functions. Indeed, accumulating evidence based on numerous studies, has highlighted the implication of lncRNAs in the regulation of pancreatic β cell differentiation and proliferation, insulin synthesis and secretion, and apoptosis. In addition, several lncRNAs have shown to be implicated in pancreatic β cell dysfunction linked to different types of diabetes, including type 1 and type 2 diabetes, and monogenic forms of the disease. Pathogenic conditions linked to diabetes (inflammation or lipoglucotoxicity, for example) dysregulate the expression of several lncRNAs, suggesting that changes in lncRNA may alter potentially important pathways for β cell function, and eventually leading to β cell dysfunction and diabetes development. In this sense, functional characterization of some lncRNAs has demonstrated that these non-coding molecules participate in the regulation of several crucial pathways at the pancreatic β cell level, and dysregulation of these pathways leads to pathogenic phenotypes. In this review, we provide an overview of the action mechanisms of functionally characterized lncRNAs in healthy β cells and describe the contribution of some diabetes-associated lncRNAs to pancreatic β cell failure.

Human Pluripotent Stem Cells to Model Islet Defects in Diabetes

Diabetes mellitus is characterized by elevated levels of blood glucose and is ultimately caused by insufficient insulin production from pancreatic beta cells. Different research models have been utilized to unravel the molecular mechanisms leading to the onset of diabetes. The generation of pancreatic endocrine cells from human pluripotent stem cells constitutes an approach to study genetic defects leading to impaired beta cell development and function. Here, we review the recent progress in generating and characterizing functional stem cell-derived beta cells. We summarize the diabetes disease modeling possibilities that stem cells offer and the challenges that lie ahead to further improve these models.

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.

The role of DNA methylation in the pathogenesis of type 2 diabetes mellitus

Diabetes mellitus (DM) is a chronic condition characterised by β cell dysfunction and persistent hyperglycaemia. The disorder can be due to the absence of adequate pancreatic insulin production or a weak cellular response to insulin signalling. Among the three types of DM, namely, type 1 DM (T1DM), type 2 DM (T2DM), and gestational DM (GDM); T2DM accounts for almost 90% of diabetes cases worldwide.

Epigenetic traits are stably heritable phenotypes that result from certain changes that affect gene function without altering the gene sequence. While epigenetic traits are considered reversible modifications, they can be inherited mitotically and meiotically. In addition, epigenetic traits can randomly arise in response to environmental factors or certain genetic mutations or lesions, such as those affecting the enzymes that catalyse the epigenetic modification. In this review, we focus on the role of DNA methylation, a type of epigenetic modification, in the pathogenesis of T2DM.

From Genetic Association to Molecular Mechanisms for Islet-cell Dysfunction in Type 2 Diabetes

Genome-wide association studies (GWAS) have identified over 400 signals robustly associated with risk for type 2 diabetes (T2D). At the vast majority of these loci, the lead single nucleotide polymorphisms (SNPs) reside in noncoding regions of the genome, which hampers biological inference and translation of genetic discoveries into disease mechanisms. The study of these T2D risk variants in normoglycemic individuals has revealed that a significant proportion are exerting their disease risk through islet-cell dysfunction. The central role of the islet is also demonstrated by numerous studies, which have shown an enrichment of these signals in islet-specific epigenomic annotations. In recent years the emergence of authentic human beta-cell lines, and advances in genome-editing technologies coupled with improved protocols differentiating human pluripotent stem cells into beta-like cells has opened up new opportunities for T2D disease modeling. Here we review the current understanding on the genetic basis of T2D focusing on approaches, which have facilitated the identification of causal variants and their effector transcripts in human islets. We will present examples of functional studies based on animal and conventional cellular systems and highlight the potential of novel stem cell-based T2D disease models.

Interplay of Placental DNA Methylation and Maternal Insulin Sensitivity in Pregnancy

The placenta participates in maternal insulin sensitivity changes during pregnancy; however, mechanisms remain unclear. We investigated associations between maternal insulin sensitivity and placental DNA methylation markers across the genome. We analyzed data from 430 mother-offspring dyads in the Gen3G cohort. All women underwent 75-g oral glucose tolerance tests at ∼26 weeks of gestation; we used glucose and insulin measures to estimate insulin sensitivity (Matsuda index). At delivery, we collected samples from placenta (fetal side) and measured DNA methylation using Illumina EPIC arrays. Using linear regression models to quantify associations at 720,077 cytosine-guanine dinucleotides (CpGs), with adjustment for maternal age, gravidity, smoking, BMI, child sex, and gestational age at delivery, we identified 188 CpG sites where placental DNA methylation was associated with Matsuda index (P < 6.94 × 10^-8). Among genes annotated to these 188 CpGs, we found enrichment in targets for miRNAs, in histone modifications, and in parent-of-origin DNA methylation including the H19/MIR675 locus (paternally imprinted). We identified 12 known placenta imprinted genes, including KCNQ1 Mendelian randomization analyses revealed five loci where placenta DNA methylation may causally influence maternal insulin sensitivity, including the maternally imprinted gene DLGAP2. Our results suggest that placental DNA methylation is fundamentally linked to the regulation of maternal insulin sensitivity in pregnancy.

Long Non-Coding RNAs as Key Modulators of Pancreatic β-Cell Mass and Function

Numerous studies have sought to decipher the genetic and other mechanisms contributing to β-cell loss and dysfunction in diabetes mellitus. However, we have yet to fully understand the etiology of the disease or to develop satisfactory treatments. Since the majority of diabetes susceptibility loci are mapped to non-coding regions within the genome, understanding the functions of non-coding RNAs in β-cell biology might provide crucial insights into the pathogenesis of type 1 (T1D) and type 2 (T2D) diabetes. During the past decade, numerous studies have indicated that long non-coding RNAs play important roles in the maintenance of β-cell mass and function. Indeed, lncRNAs have been shown to be involved in controlling β-cell proliferation during development and/or β-cell compensation in response to hyperglycaemia. LncRNAs such as TUG-1 and MEG3 play a role in both β-cell apoptosis and function, while others sensitize β-cells to apoptosis in response to stress signals. In addition, several long non-coding RNAs have been shown to regulate the expression of β-cell-enriched transcription factors in cis or in trans. In this review, we provide an overview of the roles of lncRNAs in maintaining β-function and mass, and discuss their relevance in the development of diabetes.

Silencing of KCNQ1OT1 Decreases Oxidative Stress and Pyroptosis of Renal Tubular Epithelial Cells

BACKGROUND

Long noncoding RNAs (lncRNAs) can regulate the progression of DN. This research aimed to study the effect of lncRNA KCNQ1OT1 on the oxidative stress and pyroptosis of the renal tubular epithelial cells induced by high glucose (HG).

METHODS

RT-qPCR analysis detected the KCNQ1OT1 expression in serum with DN and HG-induced HK-2 cells, detect the expression of NLRP3, cleaved-caspase1, P-caspase1, IL-1β, p-IL-1β and GSDMD-N in HG-induced HK-2 cells, and confirm the transfection effects. The expression of NLRP3, cleaved-caspase1, P-caspase1, IL-1β, p-IL-1β and GSDMD-N in HG-induced HK-2 cells was also analyzed by Western blot analysis. ELISA assay detected the levels of TNF-α, IL-6 and MCP-1. The levels of ROS, MDA and SOD were determined by respective ELISA kits and ROS was also detected by the ROS assay kit (containing DCFH-DA).

RESULTS

We found that KCNQ1OT1 was increased in the plasma of patients with DN and HG-induced HK-2 cells and KCNQ1OT1 interference could decrease the inflammation, oxidative stress and pyroptosis of HG-induced HK-2 cells. In addition, KCNQ1OT1 directly targets miR-506-3p. MiR-506-3p was downregulated in the plasma of patients with DN and HG-induced HK-2 cells and KCNQ1OT1 interference promoted the expression of miR-506-3p. MiR-506-3p overexpression suppressed the inflammation, oxidative stress and pyroptosis of HG-induced HK-2 cells.

CONCLUSION

This study demonstrated that downregulation of KCNQ1OT1 inhibited the inflammation, oxidative stress and pyroptosis of HG-induced HK-2 cells by up-regulating the expression of miR-506-3p, which provide new insights into the treatment of DN.

Genomic imprinting disorders: lessons on how genome, epigenome and environment interact

Genomic imprinting, the monoallelic and parent-of-origin-dependent expression of a subset of genes, is required for normal development, and its disruption leads to human disease. Imprinting defects can involve isolated or multilocus epigenetic changes that may have no evident genetic cause, or imprinting disruption can be traced back to alterations of cis-acting elements or trans-acting factors that control the establishment, maintenance and erasure of germline epigenetic imprints. Recent insights into the dynamics of the epigenome, including the effect of environmental factors, suggest that the developmental outcomes and heritability of imprinting disorders are influenced by interactions between the genome, the epigenome and the environment in germ cells and early embryos.

Epigenetics and Type 2 Diabetes Risk

PURPOSE OF REVIEW

The influence of environmental factors on type 2 diabetes (T2D) risk is now well recognized and highlights the contribution of epigenetic mechanisms. This review will focus on the role of epigenetic factors in the risk and pathogenesis of T2D.

RECENT FINDINGS

Epigenetic dysregulation has emerged as a key mechanism underpinning the pathogenesis of T2D and its complications. Environmental variations, including alterations in lifestyle, nutrition, and metabolic demands during prenatal and postnatal life can induce epigenetic changes that may impact glucose homeostasis and the function of different metabolic organs. Accumulating data continues to uncover the specific pathways that are epigenetically dysregulated in T2D, providing an opportunity for therapeutic targeting. Environmental changes can disrupt specific epigenetic mechanisms underlying metabolic homeostasis, thus contributing to T2D pathogenesis. Such epigenetic changes can be transmitted to the next generation, contributing to the inheritance of T2D risk. Recent advances in epigenome-wide association studies and epigenetic editing tools present the attractive possibility of identifying epimutations associated with T2D, correcting specific epigenetic alterations, and designing novel epigenetic biomarkers and interventions for T2D.

Genetic polymorphisms associated with pediatric-onset type 2 diabetes: A family-based transmission disequilibrium test and case-control study

BACKGROUND AND OBJECTIVE

Genetics play a very strong role in the development of pediatric-onset type 2 diabetes (T2D); however, little information exists about specific common single nucleotide polymorphisms (SNPs) associated with T2D in this age group. The aim of the study was to analyze the association and parental transmission of 64 obesity-related SNPs with pediatric-onset T2D in Mexican families.

METHODS

A total of 57 pedigrees containing 171 probands with pediatric-onset T2D and 119 unrelated controls older than 18 years were included. The participants were genotyped for 64 polymorphisms. Association of each variant with pediatric-onset T2D was analyzed through a parent-offspring transmission disequilibrium test (TDT) and in a case-control comparison by χ² analysis.

RESULTS

Five SNPs exhibited associations with pediatric-onset T2D in the combined case-parent trio and case-control analysis: LINGO/rs10968576 (odds ratio [OR] 1.82, P = 0.003), POC5/rs2112347 (OR 1.96, P = 2.4E-5), RPS10-NUDT3/rs206936 (OR 1.40, P = 0.023), GLIS3/rs7034200 (OR 2.34, P = 1.2E-6), and VEGFA/rs6905288 (OR 1.58, P = 0.015). The first three were also associated with obesity status. The SNPs POC5/rs2112347 and RPS10-NUDT3/rs206936 were significantly associated through the maternal allele and GLIS3/rs7034200 through the paternal allele (P < 0.05).

CONCLUSIONS

These findings suggest that certain SNPs associated with obesity and other metabolic traits may also be involved in risk of pediatric-onset T2D in Mexican families. We also identified preferential transmission of parental alleles in some variants.

Treating prediabetes: why and how should we do it?

Prediabetes is the subclinical impairment in fasting plasma glucose, impaired glucose tolerance or both. The degree of impairment is between euglycemia and the hyperglycemia of type 2 diabetes (T2DM). Prediabetes is not considered benign, because it is a risk factor for T2DM but is also associated with micro and macrovascular complications. Lifestyle interventions including diet and exercise are first-line treatments. Medications can also play a role, as randomized controlled trials of biguanides (metformin) alpha-glucosidase inhibitors (Acarbose), inhibitors of pancreatic lipase (Orlistat), PPAR-gamma agonists (Rosiglitazone, Pioglitazone), meglitinides (Nateglinide) and GLP-1 receptor agonists (Liraglutide) have all shown benefits. Bariatric surgery is another efficacious means of preventing T2DM in patients with prediabetes and obesity. Prediabetes in its various guises is a risk factor for the future development T2DM and diabetic complications. Importantly the prediabetic state is amenable to interventions that prevent/delay transition to overt T2DM. Knowledge gaps exist regarding how best to make prognostication highly sensitive and specific as to which patient will develop T2DM. Moreover, understanding of phenotype specific pathophysiology may add value to funding appropriate interventions for patients with prediabetes. Management of patients with prediabetes should be individualized based on the algorithms that predict phenotype specific risk and allow for the use of phenotype tailored interventions.

Role of lncRNAs in aging and age-related diseases

Aging is progressive physiological degeneration and consequently declined function, which is linked to senescence on both cellular and organ levels. Accumulating studies indicate that long noncoding RNAs (lncRNAs) play important roles in cellular senescence at all levels-transcriptional, post-transcriptional, translational, and post-translational. Understanding the molecular mechanism of lncRNAs underlying senescence could facilitate interpretation and intervention of aging and age-related diseases. In this review, we describe categories of known and novel lncRNAs that have been involved in the progression of senescence. We also identify the lncRNAs implicated in diseases arising from age-driven degeneration or dysfunction in some representative organs and systems (brains, liver, muscle, cardiovascular system, bone pancreatic islets, and immune system). Improved comprehension of lncRNAs in the aging process on all levels, from cell to organismal, may provide new insights into the amelioration of age-related pathologies and prolonged healthspan.

Patterns of differential gene expression in a cellular model of human islet development, and relationship to type 2 diabetes predisposition

AIMS/HYPOTHESIS

Most type 2 diabetes-associated genetic variants identified via genome-wide association studies (GWASs) appear to act via the pancreatic islet. Observed defects in insulin secretion could result from an impact of these variants on islet development and/or the function of mature islets. Most functional studies have focused on the latter, given limitations regarding access to human fetal islet tissue. Capitalising upon advances in in vitro differentiation, we characterised the transcriptomes of human induced pluripotent stem cell (iPSC) lines differentiated along the pancreatic endocrine lineage, and explored the contribution of altered islet development to the pathogenesis of type 2 diabetes.

METHODS

We performed whole-transcriptome RNA sequencing of human iPSC lines from three independent donors, at baseline and at seven subsequent stages during in vitro islet differentiation. Differentially expressed genes (q < 0.01, log2 fold change [FC] > 1) were assigned to the stages at which they were most markedly upregulated. We used these data to characterise upstream transcription factors directing different stages of development, and to explore the relationship between RNA expression profiles and genes mapping to type 2 diabetes GWAS signals.

RESULTS

We identified 9409 differentially expressed genes across all stages, including many known markers of islet development. Integration of differential expression data with information on transcription factor motifs highlighted the potential contribution of REST to islet development. Over 70% of genes mapping within type 2 diabetes-associated credible intervals showed peak differential expression during islet development, and type 2 diabetes GWAS loci of largest effect (including TCF7L2; log2FC = 1.2; q = 8.5 × 10-10) were notably enriched in genes differentially expressed at the posterior foregut stage (q = 0.002), as calculated by gene set enrichment analyses. In a complementary analysis of enrichment, genes differentially expressed in the final, beta-like cell stage of in vitro differentiation were significantly enriched (hypergeometric test, permuted p value <0.05) for genes within the credible intervals of type 2 diabetes GWAS loci.

CONCLUSIONS/INTERPRETATION

The present study characterises RNA expression profiles during human islet differentiation, identifies potential transcriptional regulators of the differentiation process, and suggests that the inherited predisposition to type 2 diabetes is partly mediated through modulation of islet development.

DATA AVAILABILITY

Sequence data for this study has been deposited at the European Genome-phenome Archive (EGA), under accession number EGAS00001002721.

DNA methylation landscapes in the pathogenesis of type 2 diabetes mellitus

Although genetic variations and environmental factors are vital to the development and progression of type 2 diabetes mellitus (T2DM), emerging literature suggest that epigenetics, especially DNA methylation, play a key role in the pathogenesis of T2DM by affecting insulin secretion of pancreatic β cells and the body’s resistance to insulin. Previous studies have elucidated how DNA methylation interacted with various factors in T2DM pathogenesis. This review summarized the role of related methylation genes in insulin-sensitive organs, such as pancreatic islets, skeletal muscle, liver, brain and adipose tissue, as well as peripheral blood cells, comparing the tissue similarity and specificity of methylated genes, aiming at a better understanding of the pathogenesis of T2DM and providing new ideas for the personalized treatment of this metabolism-associated disease.

A systematic analysis highlights multiple long non-coding RNAs associated with cardiometabolic disorders

Genome-wide association studies (GWAS) have identified many susceptibility loci for cardiometabolic disorders. Most of the associated variants reside in non-coding regions of the genome including long non-coding RNAs (lncRNAs), which are thought to play critical roles in diverse biological processes. Here, we leveraged data from the available GWAS meta-analyses on lipid and obesity-related traits, blood pressure, type 2 diabetes, and coronary artery disease and identified 179 associated single-nucleotide polymorphisms (SNPs) in 102 lncRNAs (p-value < 2.3 × 10^-7). Of these, 55 SNPs, either the lead SNP or in strong linkage disequilibrium with the lead SNP in the related loci, were selected for further investigations. Our in silico predictions and functional annotations of the SNPs as well as expression and DNA methylation analysis of their lncRNAs demonstrated several lncRNAs that fulfilled predefined criteria for being potential functional targets. In particular, we found evidence suggesting that LOC157273 (at 8p23.1) is involved in regulating serum lipid-cholesterol. Our results showed that rs4841132 in the second exon and cg17371580 in the promoter region of LOC157273 are associated with lipids; the lncRNA is expressed in liver and associates with the expression of its nearby coding gene, PPP1R3B. Collectively, we highlight a number of loci associated with cardiometabolic disorders for which the association may act through lncRNAs.

Pancreatic β-Cell Electrical Activity and Insulin Secretion: Of Mice and Men

The pancreatic β-cell plays a key role in glucose homeostasis by secreting insulin, the only hormone capable of lowering the blood glucose concentration. Impaired insulin secretion results in the chronic hyperglycemia that characterizes type 2 diabetes (T2DM), which currently afflicts >450 million people worldwide. The healthy β-cell acts as a glucose sensor matching its output to the circulating glucose concentration. It does so via metabolically induced changes in electrical activity, which culminate in an increase in the cytoplasmic Ca2+ concentration and initiation of Ca2+-dependent exocytosis of insulin-containing secretory granules. Here, we review recent advances in our understanding of the β-cell transcriptome, electrical activity, and insulin exocytosis. We highlight salient differences between mouse and human β-cells, provide models of how the different ion channels contribute to their electrical activity and insulin secretion, and conclude by discussing how these processes become perturbed in T2DM.

From Sea to Shining Sea and the Great Plains to Patagonia: A Review on Current Knowledge of Diabetes Mellitus in Hispanics/Latinos in the US and Latin America

The past two decades have witnessed many advances in the prevention, treatment, and control of diabetes mellitus (DM) and its complications. Increased screening has led to a greater recognition of type 2 diabetes mellitus (type 2 DM) and prediabetes; however, Hispanics/Latinos, the largest minority group in the US, have not fully benefited from these advances. The Hispanic/Latino population is highly diverse in ancestries, birth places, cultures, languages, and socioeconomic backgrounds, and it populates most of the Western Hemisphere. In the US, the prevalence of DM varies among Hispanic/Latino heritage groups, being higher among Mexicans, Puerto Ricans, and Dominicans, and lower among South Americans. The risk and prevalence of diabetes among Hispanics/Latinos are significantly higher than in non-Hispanic Whites, and nearly 40% of Hispanics/Latinos with diabetes have not been formally diagnosed. Despite these striking facts, the representation of Hispanics/Latinos in pharmacological and non-pharmacological clinical trials has been suboptimal, while the prevalence of diabetes in these populations continues to rise. This review will focus on the epidemiology, etiology and prevention of type 2 DM in populations of Latin American origin. We will set the stage by defining the terms Hispanic, Latino, and Latin American, explaining the challenges identifying Hispanics/Latinos in the scientific literature and databases, describing the epidemiology of diabetes-including type 2 DM and gestational diabetes mellitus (GDM)-and cardiovascular risk factors in Hispanics/Latinos in the US and Latin America, and discussing trends, and commonalities and differences across studies and populations, including methodology to ascertain diabetes. We will discuss studies on mechanisms of disease, and research on prevention of type 2 DM in Hispanics/Latinos, including women with GDM, youth and adults; and finalize with a discussion on lessons learned and opportunities to enhance research, and, consequently, clinical care oriented toward preventing type 2 DM in Hispanics/Latinos in the US and Latin America.

Two missense mutations in KCNQ1 cause pituitary hormone deficiency and maternally inherited gingival fibromatosis

Familial growth hormone deficiency provides an opportunity to identify new genetic causes of short stature. Here we combine linkage analysis with whole-genome resequencing in patients with growth hormone deficiency and maternally inherited gingival fibromatosis. We report that patients from three unrelated families harbor either of two missense mutations, c.347G>T p.(Arg116Leu) or c.1106C>T p.(Pro369Leu), in KCNQ1, a gene previously implicated in the long QT interval syndrome. Kcnq1 is expressed in hypothalamic GHRH neurons and pituitary somatotropes. Co-expressing KCNQ1 with the KCNE2 β-subunit shows that both KCNQ1 mutants increase current levels in patch clamp analyses and are associated with reduced pituitary hormone secretion from AtT-20 cells. In conclusion, our results reveal a role for the KCNQ1 potassium channel in the regulation of human growth, and show that growth hormone deficiency associated with maternally inherited gingival fibromatosis is an allelic disorder with cardiac arrhythmia syndromes caused by KCNQ1 mutations.

Nutrient sensing in pancreatic islets: lessons from congenital hyperinsulinism and monogenic diabetes

Pancreatic beta cells sense changes in nutrients during the cycles of fasting and feeding and release insulin accordingly to maintain glucose homeostasis. Abnormal beta cell nutrient sensing resulting from gene mutations leads to hypoglycemia or diabetes. Glucokinase (GCK) plays a key role in beta cell glucose sensing. As one form of congenital hyperinsulinism (CHI), activating mutations of GCK result in a decreased threshold for glucose-stimulated insulin secretion and hypoglycemia. In contrast, inactivating mutations of GCK result in diabetes, including a mild form (MODY2) and a severe form (permanent neonatal diabetes mellitus (PNDM)). Mutations of beta cell ion channels involved in insulin secretion regulation also alter glucose sensing. Activating or inactivating mutations of ATP-dependent potassium (K_ATP ) channel genes result in severe but completely opposite clinical phenotypes, including PNDM and CHI. Mutations of the other ion channels, including voltage-gated potassium channels (K_v 7.1) and voltage-gated calcium channels, also lead to abnormal glucose sensing and CHI. Furthermore, amino acids can stimulate insulin secretion in a glucose-independent manner in some forms of CHI, including activating mutations of the glutamate dehydrogenase gene, HDAH deficiency, and inactivating mutations of K_ATP channel genes. These genetic defects have provided insight into a better understanding of the complicated nature of beta cell fuel-sensing mechanisms.

Increased identification of novel variants in type 2 diabetes, birth weight and their pleiotropic loci

BACKGROUND

Clinical and epidemiological findings point to an association between type 2 diabetes (T2D) and low birth weight. However, the nature of the relationship is largely unknown. The aim of this study was to identify novel single nucleotide polymorphisms (SNPs) in T2D and birth weight, and their pleiotropic loci.

METHODS

A pleiotropy-informed conditional false discovery rate (cFDR) method was applied to two independent genome-wide association studies (GWAS) summary statistics of T2D (n = 149 821) and birth weight (n = 26 836).

RESULTS

A conditional Q-Q plot showed strong enrichment of genetic variants in T2D conditioned on different levels of association with birth weight. 133 T2D-associated SNPs, including 120 novel SNPs, were identified with a significance threshold of cFDR < 0.05; 13 significant birth weight-associated SNPs, including 12 novel SNPs (cFDR < 0.05) were identified. Conjunctional cFDR (ccFDR) analysis identified nine pleiotropic loci, including seven novel loci, shared by both T2D and birth weight (ccFDR < 0.05). Two novel SNPs located at the CDK5 regulatory subunit-associated protein 1-like 1 (CDKAL1; rs1012635; cFDR < 0.05) and adenylate cyclase 5 (ADCY5; rs4677887; cFDR < 0.05) genes are of note. These two genes increase the risk of T2D and low birth weight through the pathway of the "fetal insulin hypothesis."

CONCLUSION

Several pleiotropic loci were identified between T2D and birth weight by leveraging GWAS results. The results make it possible to explain a greater proportion of trait heritability and improve our understanding of the shared pathophysiology between T2D and birth weight.

Role of DNA Methylation in Type 2 Diabetes Etiology: Using Genotype as a Causal Anchor

Several studies have investigated the relationship between genetic variation and DNA methylation with respect to type 2 diabetes, but it is unknown if DNA methylation is a mediator in the disease pathway or if it is altered in response to disease state. This study uses genotypic information as a causal anchor to help decipher the likely role of DNA methylation measured in peripheral blood in the etiology of type 2 diabetes. Illumina HumanMethylation450 BeadChip data were generated on 1,018 young individuals from the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort. In stage 1, 118 unique associations between published type 2 diabetes single nucleotide polymorphisms (SNPs) and genome-wide methylation (methylation quantitative trait loci [mQTLs]) were identified. In stage 2, a further 226 mQTLs were identified between 202 additional independent non-type 2 diabetes SNPs and CpGs identified in stage 1. Where possible, associations were replicated in independent cohorts of similar age. We discovered that around half of known type 2 diabetes SNPs are associated with variation in DNA methylation and postulated that methylation could either be on a causal pathway to future disease or could be a noncausal biomarker. For one locus (KCNQ1), we were able to provide further evidence that methylation is likely to be on the causal pathway to disease in later life.

Genetic and epigenetic mechanisms underlying arsenic-associated diabetes mellitus: a perspective of the current evidence

Chronic exposure to arsenic has been associated with the development of diabetes mellitus (DM), a disease characterized by hyperglycemia resulting from dysregulation of glucose homeostasis. This review summarizes four major mechanisms by which arsenic induces diabetes, namely inhibition of insulin-dependent glucose uptake, pancreatic β-cell damage, pancreatic β-cell dysfunction and stimulation of liver gluconeogenesis that are supported by both in vivo and in vitro studies. Additionally, the role of polymorphic variants associated with arsenic toxicity and disease susceptibility, as well as epigenetic modifications associated with arsenic exposure, are considered in the context of arsenic-associated DM. Taken together, in vitro, in vivo and human genetic/epigenetic studies support that arsenic has the potential to induce DM phenotypes and impair key pathways involved in the regulation of glucose homeostasis.

DNA methylation signatures in peripheral blood strongly predict all-cause mortality

DNA methylation (DNAm) has been revealed to play a role in various diseases. Here we performed epigenome-wide screening and validation to identify mortality-related DNAm signatures in a general population-based cohort with up to 14 years follow-up. In the discovery panel in a case-cohort approach, 11,063 CpGs reach genome-wide significance (FDR<0.05). 58 CpGs, mapping to 38 well-known disease-related genes and 14 intergenic regions, are confirmed in a validation panel. A mortality risk score based on ten selected CpGs exhibits strong association with all-cause mortality, showing hazard ratios (95% CI) of 2.16 (1.10–4.24), 3.42 (1.81–6.46) and 7.36 (3.69–14.68), respectively, for participants with scores of 1, 2–5 and 5+ compared with a score of 0. These associations are confirmed in an independent cohort and are independent from the ‘epigenetic clock'. In conclusion, DNAm of multiple disease-related genes are strongly linked to mortality outcomes. The DNAm-based risk score might be informative for risk assessment and stratification.

DNA methylation is modulated by environmental factors and has a role in many complex diseases. Here, the authors find that methylation at specific DNA sites is associated with all-cause mortality, and a methylation-based risk score may be informative for risk assessment and stratification.

Differentiation of Diabetes by Pathophysiology, Natural History, and Prognosis

The American Diabetes Association, JDRF, the European Association for the Study of Diabetes, and the American Association of Clinical Endocrinologists convened a research symposium, "The Differentiation of Diabetes by Pathophysiology, Natural History and Prognosis" on 10-12 October 2015. International experts in genetics, immunology, metabolism, endocrinology, and systems biology discussed genetic and environmental determinants of type 1 and type 2 diabetes risk and progression, as well as complications. The participants debated how to determine appropriate therapeutic approaches based on disease pathophysiology and stage and defined remaining research gaps hindering a personalized medical approach for diabetes to drive the field to address these gaps. The authors recommend a structure for data stratification to define the phenotypes and genotypes of subtypes of diabetes that will facilitate individualized treatment.

A variation in KCNQ1 gene is associated with repaglinide efficacy on insulin resistance in Chinese Type 2 Diabetes Mellitus Patients

Repaglinide is an insulin secretagogue that often exhibits considerable interindividual variability in therapeutic efficacy. The current study was designed to investigate the impact of KCNQ1 genetic polymorphism on the efficacy of repaglinide and furthermore to identify the potential mechanism of action in patients with type 2 diabetes. A total of 305 patients and 200 healthy subjects were genotyped for the KCNQ1 rs2237892 polymorphism, and 82 patients with T2DM were randomized for the oral administration of repaglinide for 8 weeks. HepG2 cells were incubated with repaglinide in the absence or presence of a KCNQ1 inhibitor or the pcDNA3.1-hKCNQ1 plasmid, after which the levels of Akt, IRS-2 and PI(3)K were determined. Our data showed that repaglinide significantly decreased HOMA-IR in patients with T2DM. Furthermore, the level of HOMA-IR was significantly reduced in those patients with CT or TT genotypes than CC homozygotes. The KCNQ1 inhibitor enhanced repaglinide efficacy on insulin resistance, with IRS-2/PI(3)K/Akt signaling being up-regulated markedly. As in our clinical experiment, these data strongly suggest that KCNQ1 genetic polymorphism influences repaglinide response due to the pivotal role of KCNQ1 in regulating insulin resistance through the IRS-2/PI(3)K/Akt signaling pathway. This study was registered in the Chinese Clinical Trial Register on May 14, 2013. (No. ChiCTR-CCC13003536).