The Central Role of Glucokinase in Glucose Homeostasis: A Perspective 50 Years After Demonstrating the Presence of the Enzyme in Islets of Langerhans

Discovery of liver-selective glucokinase activators comprising N-(4-alkylthiazol-2-yl)benzamides and N-(3-alkyl-1,2,4-thiadiazol-5-yl)benzamides for the treatment of metabolic disorders

Glucokinase ("GK") plays a critical role in regulating glucose homeostasis within the body. Proof-of-concept animal models demonstrated that small molecule GK activation enhances glucose uptake and utilization by various tissues, including liver and pancreas. Accordingly, glucokinase activators ("GKAs") were extensively explored as a potential therapy for carbohydrate metabolism disorders. Yet in clinical trials, mechanism-based hypoglycemia was often observed when GK was activated in both liver and pancreas. One ameliorative approach was to pursue hepatocentric GKAs. Described herein is a series of liver selective GKAs based on N-(4-alkylthiazol-2-yl)benzamide and N-(3-alkyl-1,2,4-thiadiazol-5-yl)benzamide pharmacophores. Optimization efforts revealed that enhanced liver selectivity could be achieved by replacing diethylphosphonate group (compound 1) with a dimethylphosphinate (compound 3). Due to mutagenicity of a putative aminoheterocycle metabolite of 3, subsequent amines were triaged using SOS chromotest. Efforts ultimately led to identification of thiazole-based compounds 11-13, which exhibited significant glucose lowering in acute DIO ("diet-induced obese") mouse OGTT ("oral glucose tolerance test") studies. However, insulin secretion was observed at higher doses, and thus the desired therapeutic window between efficacy and insulin secretion was not achieved. Thiadiazole-based compounds were then explored to assess whether this modification could obviate the insulin secretion observed with the thiazole series. Several thiadiazoles were discovered with exceptionally high liver selectivity and drug liver concentrations when evaluated in mouse pharmacokinetic studies. Compounds 17-19 and 20-22 were advanced into acute DIO OGTT studies, but were inactive. Notably, a relatively higher degree of plasma protein binding was observed for the non-efficacious vs. efficacious compounds.

Genetic evidence for the effects of glucokinase activation on frailty-related outcomes: A Mendelian randomisation study

AIMS

We aimed to use the Mendelian randomisation (MR) design to investigate the potential causal effects of glucokinase (GK) activation on frailty-related outcomes and to explore the potential mediating effects of metabolic and inflammatory biomarkers.

MATERIALS AND METHODS

Seventeen independent single-nucleotide polymorphisms (SNPs) located within the GCK gene and significantly correlated with the glycated haemoglobin (HbA1c) level were used as genetic proxies for the effect of GK activation. We employed two-sample MR analysis to assess the relationship between genetically proxied GK activation and multifactorial frailty-related outcomes (frailty index, grip strength, walking pace, appendicular lean mass [ALM] and telomere length) We also explored the potential mediating effects using two-step MR.

RESULTS

Genetically proxied GK activation was significantly associated with a lower frailty index (beta: -0.161 per 1% decrease in HbA1c level due to GK activation, 95% confidence interval: -0.282 to -0.040, false discovery rate-adjusted p = 0.011). Additionally, GK activation showed significant associations with increased grip strength, higher ALM, faster walking pace and longer telomere length. GK activation also demonstrated a significant indirect effect on total grip strength and telomere length by reducing C-reactive protein levels (proportion of mediation: 6.79% to 8.21%).

CONCLUSION

Our study provides genetic evidence supporting the causal effects of GK activation on lowering the risk of frailty. These findings suggest that GK activators (GKAs) may aid in the management of frailty and sarcopaenia in people with diabetes; however, future randomized controlled trials are necessary to validate these results and establish their clinical applicability.

Liver and intestine transcriptome analysis reveals molecular mechanisms of phytase-driven nutrient utilization and metabolic regulation in hybrid catfish

The use of phytase in aquafeeds has gained increasing attention as a strategy to enhance nutritional value and mitigate the adverse effects of phytic acid, especially for diets containing plant-based ingredients. Notwithstanding examples of phytase-induced phenotypic changes, the molecular mechanisms underlying phytase supplementation are not well understood. The present study evaluated the effects of phytase on the transcriptomic profiles in the liver and intestine, as well as on growth, feed conversion ratio (FCR), and hematological parameters of Jubilee × D&B hybrid catfish. Over a 140-day feeding trial, phytase supplementation (2500 phytase units/kg diet) significantly improved growth, FCR, red blood cell count, hematocrit, and total cell count in the blood compared with fish fed the basal diet. By comparing the transcriptomic profiles of phytase-supplemented and control fish, we identified a distinct gene expression profile relative to controls. This profile was characterized by differentially expressed genes (DEGs) associated with mineral metabolism (including iron), energy homeostasis, protein synthesis, carbohydrate and lipid metabolism, and immune response. The putative roles of key DEGs, including their interactions in different metabolic pathways, are discussed. The current study explains the benefits of phytase supplementation on hybrid catfish performance on the molecular level, uncovers the transcriptomic mechanisms controlling these benefits, and provides valuable information for customized functional feeds in aquaculture.

Sugar-sensing swodkoreceptors and swodkocrine signaling

Sugars are one of the major metabolites and are essential for nucleic acid synthesis and energy production. In addition, sugars can act as signaling molecules. To study sugar signaling at the systemic level, there is an urgent need to systematically identify sugar-sensing proteins and nucleic acids. I propose the terms "swodkoreceptor" and "swodkocrine signaling," derived from the Polish word "słodki" meaning "sweet," to comprise all sugar-sensing proteins and signaling events, respectively, regardless of their cellular location and signaling domains. This proposal is intended to facilitate the inclusion of proteins such as the Escherichia coli LacI repressor as an allolactose receptor, human glucokinase regulatory protein (GCKR) as a fructose receptor, and other sugar-binding based allosterically regulated enzymes and transcription factors as sugar-sensing receptors. In addition, enzyme-interacting proteins whose interaction state is regulated by sugar binding have also been proposed as sugar receptors. The systemic study of protein- and nucleic-acid-based swodkoreceptors may help to identify organelle-specific swodkoreceptors and to also address receptor duality. The study of intra- and inter-organism swodkocrine signaling and its crosstalk with gasocrine signaling may help to understand the etiology of diseases due to dysregulation in sugar homeostasis and signaling.

Case Report: New insights about clinical manifestations of patients with GCK genetic variants

GCK-MODY is a genetic condition characterized by alterations in the GCK gene, which can include several types of inactivating genetic variants - ranging from missense and nonsense variants, and splice site variants, to small and large deletions and insertions in the gene. This disorder primarily affects glucose homeostasis and usually presents in heterozygous individuals. Although GCK-MODY is a well-studied condition, some variant carriers may manifest symptoms that deviate from the typical disease phenotype. Our study identified two Brazilian patients with GCK-MODY carrying novel frameshift variants, one of whom presented atypical manifestations of the disease. The patient is a 14-year-old male harboring a variant c.398del; p.(Phe133SerfsTer7) in the GCK gene. He presented with the typical clinical features of GCK-MODY, including mild and stable fasting hyperglycemia, however, he also presented a history of polyuria and polydipsia, which are unusual symptoms of the disease. These symptoms could be associated with the more severe impact of a frameshift variant. However, we did not observe the same unusual phenotype in our second patient, who is a 15-year-old normal-weight female. At the age of 8, she was diagnosed with diabetes mellitus. The patient with the p.(Val335ArgfsTer124) variant presented with mild, stable hyperglycemia, a characteristic feature of the disease. In this study, we present two cases of novel frameshift variants in GCK and review other reports in the literature that have shown patients with atypical manifestations of the disease and highlight the importance of a comprehensive characterization of the phenotypic spectrum caused by GCK-MODY variants.

Physiological Fatty Acid-Stimulated Insulin Secretion and Redox Signaling Versus Lipotoxicity

Significance: Type 2 diabetes as a world-wide epidemic is characterized by the insulin resistance concomitant to a gradual impairment of β-cell mass and function (prominently declining insulin secretion) with dysregulated fatty acids (FAs) and lipids, all involved in multiple pathological development. Recent Advances: Recently, redox signaling was recognized to be essential for insulin secretion stimulated with glucose (GSIS), branched-chain keto-acids, and FAs. FA-stimulated insulin secretion (FASIS) is a normal physiological event upon postprandial incoming chylomicrons. This contrasts with the frequent lipotoxicity observed in rodents. Critical Issues: Overfeeding causes FASIS to overlap with GSIS providing repeating hyperinsulinemia, initiates prediabetic states by lipotoxic effects and low-grade inflammation. In contrast the protective effects of lipid droplets in human β-cells counteract excessive lipids. Insulin by FASIS allows FATP1 recruitment into adipocyte plasma membranes when postprandial chylomicrons come late at already low glycemia. Future Directions: Impaired states of pancreatic β-cells and peripheral organs at prediabetes and type 2 diabetes should be revealed, including the inter-organ crosstalk by extracellular vesicles. Details of FA/lipid molecular physiology are yet to be uncovered, such as complex phenomena of FA uptake into cells, postabsorptive inactivity of G-protein-coupled receptor 40, carnitine carrier substrate specificity, the role of carnitine-O-acetyltransferase in β-cells, and lipid droplet interactions with mitochondria. Antioxid. Redox Signal. 42, 566-622.

Stimulus-Secretion Coupling Mechanisms of Glucose-Induced Insulin Secretion: Biochemical Discrepancies Among the Canonical, ADP Privation, and GABA-Shunt Models

Integration of old and recent experimental data consequences is needed to correct and help improve the hypothetical mechanism responsible for the stimulus-secretion coupling mechanism of glucose-induced insulin secretion. The main purpose of this review is to supply biochemical considerations about some of the metabolic pathways implicated in the process of insulin secretion. It is emphasized that glucose β-cells' threshold to activate secretion (5 mM) might depend on the predominance of anaerobic glycolysis at this basal glucose concentration. This argues against the predominance of phosphoenolpyruvate (PEP) over mitochondrial pyruvate oxidation for the initiation of insulin secretion. Full quantitative and qualitative reproduction, except the threshold effect, of glucose-induced insulin release by a permeable methylated analog of succinic acid indicates that mitochondrial metabolism is enough for sustained insulin secretion. Mitochondrial PEP generation is skipped if the GABA-shunt pathway is exclusively coupled to the citric acid cycle, as proposed in the "GABA-shunt" model of stimulus-secretion coupling. Strong or maintained depolarization by KCl or sulfonylureas might induce the opening of β-cells Cx36 hemichannels, allowing the loss of adenine nucleotides and other metabolites, mimicking the effect of an excessive mitochondrial ATP demand. A few alterations of OxPhos (Oxidative Phosphorylation) regulation in human T2D islets have been described, but the responsible mechanism(s) is (are) not yet known. Finally, some experimental data arguing as proof of the relative irrelevance of the mitochondrial function in the insulin secretion coupling mechanism for the initiation and/or sustained stimulation of hormone release are discussed.

Nicotinamide riboside and nicotinamide mononucleotide facilitate NAD+ synthesis via enterohepatic circulation

Decreased nicotinamide adenine dinucleotide (oxidized form) (NAD+) levels are reportedly associated with several aging-related disorders. Thus, supplementation with NAD+ precursors, such as nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR), exhibits beneficial effects against these disorders. However, the in vivo metabolic pathways of NMN and NR remain to be elucidated. In this study, we comprehensively analyzed the fate of orally and intravenously administered NMN and NR in mice using NAD+ metabolomics. We found that only a small portion of orally administered NMN and NR was directly absorbed from the small intestine and that most of them underwent gut microbiota-mediated deamidation and conversion to nicotinic acid (NA). Moreover, intravenously administered NMN and NR were rapidly degraded into nicotinamide and secreted to bile followed by deamidation to NA by gut microbiota. Thus, enterohepatic circulated NA is preferentially used in the liver. These findings showed that NMN and NR are indirectly converted to NAD+ via unexpected metabolic pathways.

Astrocyte glucose-6-phosphatase-Beta regulates ventromedial hypothalamic nucleus glucose counterregulatory neurotransmission and systemic hormone profiles

Brain astrocytes generate free glucose at the conclusion of glycogenolysis or gluconeogenesis by glucose-6-phosphatase-beta (Glc-6-Pase-β) hydrolytic action. Astrocytes shape ventromedial hypothalamic nucleus (VMN) control of glucose counterregulation via lactate provision, yet possible effects of astrocyte endogenous glucose production are unknown. Current research investigated eu- and hypoglycemic patterns of VMN neuron counterregulatory neurotransmitter marker protein expression and counterregulatory hormone secretion following in vivo VMN astrocyte Glc-6-Pase-β gene-knockdown. Gene-silencing caused reductions in VMN astrocyte Glc-6-Pase-β protein expression and tissue glycogen and glucose content. Hypoglycemic suppression (dorsomedial VMN; VMNdm) or augmentation (ventrolateral VMN; VMNvl) of glycogen involves Glc-6-Pase-β -independent versus -dependent mechanisms, respectively. siRNA pretreatment reversed hypoglycemic down-regulation of VMNdm glucose levels and intensified up-regulated VMNvl glucose accumulation. Glc-6-Pase-β gene-knockdown correspondingly suppressed or enhanced baseline expression of glutamate decarboxylase65/67 (GAD) and neuronal nitric oxide synthase (nNOS), protein markers for the counterregulation-inhibiting or -enhancing neurochemicals γ-aminobutyric acid and nitric oxide. Glc-6-Pase-β siRNA pretreatment did not alter hypoglycemic suppression of VMN GAD protein but reversed (VMNdm) or amplified (VMNvl) nNOS up-regulation. VMN Glc-6-Pase-β gene-silencing attenuated hypoglycemic patterns of corticosterone and growth hormone secretion and enhanced glucagon release. In summary, data provide unique evidence that VMN Glc-6-Pase-β activity affects glucose counterregulation. Outcomes document astrocyte Glc-6-Pase-β control of VMN glucose and glycogen accumulation as well as VMN neuron counterregulatory neurotransmission. Further research is warranted to identify Glc-6-Pase-β - mediated adjustments in astrocyte glucose metabolism that affect VMN GABAergic and/or nitrergic signaling within the brain glucostatic circuitry.

Exploring proinsulin proteostasis: insights into beta cell health and diabetes

Proinsulin misfolding is central to diabetes. This review examines the cellular mechanisms regulating proinsulin proteostasis in pancreatic β-cells, encompassing genetic factors such as insulin gene mutations, and exploring the roles of endoplasmic reticulum (ER) stress and the unfolded protein response (UPR), ER redox balance, mitochondrial function, and the influence of extrinsic factors. Mutations in the INS gene, particularly those affecting cysteine residues, impair folding and disulfide bond formation, often exhibiting dominant-negative effects on the wild-type proinsulin. The importance of ER quality control mechanisms, including chaperones and oxidoreductases, in facilitating proper folding and degradation of misfolded proinsulin is emphasized. Disruptions in these systems, due to genetic mutations, ER stress, or impaired ER-to-Golgi trafficking, lead to proinsulin accumulation and β-cell dysfunction. The unfolded protein response (UPR), especially the PERK and IRE1α-XBP1 pathways, emerges as a central regulator of protein synthesis and ER stress management. The review also discusses the role of mitochondrial health, ER redox state, and extrinsic factors such as diet and medications in influencing proinsulin proteostasis. Finally, the structural insights from NMR and molecular dynamics simulations are discussedhighlighting the dynamics of misfolding and underscoring the importance of disulfide bonds. These mechanistic insights suggest innovative strategies targeting thiol/disulfide redox systems in cells to mitigate protein misfolding diseases including diabetes.

Glucokinase: from allosteric glucose sensing to disease variants

Human glucokinase (GCK) functions as a glucose sensor in the pancreas and liver, where GCK activity regulates insulin secretion and glycogen synthesis, respectively. GCK's low affinity for glucose and the sigmoidal substrate dependency of enzymatic turnover enables it to act as a sensor that makes cells responsive to changes in circulating glucose levels. Its unusual kinetic properties are intrinsically linked to the enzyme's conformational dynamics. Accordingly, genetic variants that alter the dynamics or other aspects of GCK function are linked to three glucose homeostasis diseases. In this review, we describe the enzyme GCK, focusing on its role as a glucose sensor, its unusual kinetic properties, and recent large-scale efforts to assess GCK variant effects.

Ventromedial hypothalamic nucleus neuronal nitric oxide knockdown effects on GABAergic neuron metabolic sensor and transmitter marker gene expression in the male rat

The diffusible gas nitric oxide (NO) and amino acid γ-gamma-aminobutyric acid (GABA) exert contrary effects on glucose counterregulation in the male rat, but how these neurochemical signals integrate within ventromedial hypothalamic nucleus (VMN) neural circuitries remains unclear. Female rat dorsomedial (VMNdm) and ventrolateral (VMNvl) GABAergic neurons express neuronal nitric oxide synthase (nNOS) mRNA; notably these subpopulations exhibit dissimilar nNOS transcriptional responses to insulin-induced hypoglycemia (IIH). Here, nNOS gene knockdown tools were used to examine whether one or both VMN GABA neuron groups may be a target for nitrergic control of basal and hypoglycemic counterregulatory hormone secretion in the male. Data show that VMN nNOS gene knockdown respectively up- or down-regulated counterregulatory hormone profiles in eu- versus hypoglycemic male rats. Single-cell multiplex qPCR analysis of laser-catapult-microdissected GABA neurons showed that IIH elevated nNOS gene expression in GABA neurons from each VMN division, yet nNOS siRNA pretreatment attenuated distinctive IIH-associated transmitter marker gene expression patterns in VMNdm versus VMNvl GABAergic neurons. nNOS gene silencing had similar effects on glucokinase and glucose transporter gene responses to IIH in each GABA neuron subpopulation but elicited division-specific effects on mRNA encoding 5-AMP-activated protein kinase (AMPK) alpha/catalytic subunits and the lactate membrane receptor GPR81/HCAR1. Current findings provide original evidence that VMN NO may impose bi-directional, glucose status-contingent control of counterregulatory hormone outflow in the male rat. Data moreover imply that during IIH, NO may control distinctive sources of metabolic sensory regulatory stimuli in VMNdm versus VMNvl GABA neurons and may shape unique counterregulation-controlling neurochemical transmission by each cell population.

The role of glucose-6-phosphatase activity in glucose homeostasis and its potential for diabetes therapy

Glucose-6-phosphatase catalytic subunit (G6PC)1 and G6PC2 are crucial for glucose metabolism, regulating processes like glycolysis, gluconeogenesis, and glycogenolysis. Despite their structural and functional similarities, G6PC1 and G6PC2 exhibit distinct tissue-specific expression patterns, G6P hydrolysis kinetics, and physiological functions. This review provides a comprehensive overview of their enzymology and distinct roles in glucose homeostasis. We examine how inactivating mutations in G6PC1 lead to glycogen storage disease, and how elevated G6PC1 and G6PC2 expression can affect the incidence of diabetic complications, risk for type 2 diabetes mellitus (T2DM) and various cancers. We also discuss the potential of inhibiting G6PC1 and G6PC2 to protect against complications from elevated blood glucose levels, and highlight drug development efforts targeting G6PC1 and G6PC2, and the therapeutic potential of inhibitors for disease prevention.

Multi-Omics Sequencing Dissects the Atlas of Seminal Plasma Exosomes from Semen Containing Low or High Rates of Sperm with Cytoplasmic Droplets

Sperm cytoplasmic droplets (CDs) are remnants of cytoplasm that can cause a number of problems if it not shed from the sperm after ejaculation. Exosomes can rapidly bind to sperm, but it is not clear whether exosomes can affect the migration and shedding of CDs. We first extracted and characterized seminal plasma exosomes from boar semen containing sperm with low or high rates of CDs. Then, the transcriptomic and proteomic detection of these exosomes were performed to analyze the differences between the two groups of seminal plasma exosomes. The results revealed that 486 differentially expressed genes (DEGs), 40 differentially expressed proteins (DEPs), and 503 differentially expressed lncRNAs (DElncRNAs) were identified between the low CD rate group and high CD rate group. Integrative multi-omics analysis showed that exosome components may affect migration and shedding of cytoplasmic droplets by influencing cytoskeletal regulation and insulin signaling, including regulation of the actin cytoskeleton, ECM-receptor interaction, axon guidance, insulin secretion, and the insulin signaling pathway. Overall, our study systematically revealed the DEGs, DEPs, and DElncRNAs in seminal plasma exosomes between low CD rate semen and high CD rate semen, which will help broaden our understanding of the complex molecular mechanisms involved in the shedding of CDs.

Bambusa vulgaris leaf extract inhibits the inflammatory and oxidative pathways in streptozotocin-induced diabetic rats

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional and medicinal plant treatments for diabetes mellitus (DM) include Bambusa vulgaris (Shrad.), but little is known about the mechanism.

AIM OF THE STUDY

This study investigated the antioxidant and hepatoprotective effects of B. vulgaris.

MATERIALS AND METHODS

DM was induced by intraperitoneal injection of streptozotocin (60 mg/kg). Thirty (30) male Wistar rats were then divided into six groups: control; diabetic control; metformin (100 mg/kg); 50, 100, and 200 mg/kg of B. vulgaris (BV) treated. Fasting blood glucose and weights of rats were monitored at three-day intervals and sacrifice was done after twenty-one days. The activities of SOD, CAT, and liver marker enzymes were investigated. The expressions of insulin-sensitive (TGR5, GLP-1), pro-inflammatory cytokines (TNF-α, IL-1β, IL-6, ICAM), and antioxidant genes (SOD, CAT) were investigated using RT-PCR. Schrödinger suites and Auto-Dock Vina were used for docking B. vulgaris phytocompounds identified from works of literature with TGR-5. The liver's histology was also assessed.

RESULTS

BV increased antioxidant activities and reduced liver marker activities in the serum. BV downregulated the expressions of genes associated with inflammation and upregulated antioxidant and insulin-sensitive genes relative to diabetic control. BV regenerated the liver architectural tissue degenerated by inflammation due to STZ. B. vulgaris phytocompounds like farobin A (-11.493 kcal/mol), orientin (-12.296 kcal/mol), and rutin (-12.581 kcal/mol) have better binding energy with TGR5 than metformin (-1.961 kcal/mol).

CONCLUSION

The hepatoprotective and ameliorative effect of B. vulgaris in DM could be due to its ability to boost antioxidant status and insulin secretion and reduce inflammation.

Modern-Day Therapeutics and Ongoing Clinical Trials against Type 2 Diabetes Mellitus: A Narrative Review

OBJECTIVES

Diabetes Mellitus (DM) is a global health concern that affects millions of people globally. The present review aims to narrate the clinical guidelines and therapeutic interventions for Type 2 Diabetes Mellitus (T2DM) patients. Furthermore, the present work summarizes the ongoing phase 1/2/3 and clinical trials against T2DM.

METHODS

A meticulous and comprehensive literature review was performed using various databases, such as PubMed, MEDLINE, Clinical trials database (https://clinicaltrials.gov/), and Google Scholar, to include various clinical trials and therapeutic interventions against T2DM.

RESULTS

Based on our findings, we concluded that most T2DM-associated clinical trials are interventional. Anti-diabetic therapeutics, including insulin, metformin, Dipeptidyl Peptidase-4 (DPP-4) inhibitors, Glucagon-Like Peptide-1 Receptor Agonists (GLP-1RAs), and Sodium- Glucose cotransporter-2 (SGLT-2) inhibitors are frontline therapeutics being clinically investigated. Currently, the therapeutics in phase IV clinical trials are mostly SGLT-2 inhibitors, implicating their critical contribution to the clinical management of T2DM.

CONCLUSION

Despite the success of T2DM treatments, a surge in innovative treatment options to reduce diabetic consequences and improve glycemic control is currently ongoing. More emphasis needs to be on exploring novel targeted drug candidates that can offer more sustained glycemic control.

G6PC2 controls glucagon secretion by defining the set point for glucose in pancreatic α cells

Elevated glucagon concentrations have been reported in patients with type 2 diabetes (T2D). A critical role for α cell-intrinsic mechanisms in regulating glucagon secretion was previously established through genetic manipulation of the glycolytic enzyme glucokinase (GCK) in mice. Genetic variation at the glucose-6-phosphatase catalytic subunit 2 (G6PC2) locus, encoding an enzyme that opposes GCK, has been reproducibly associated with fasting blood glucose and hemoglobin A1c. Here, we found that trait-associated variants in the G6PC2 promoter are located in open chromatin not just in β but also in α cells and documented allele-specific G6PC2 expression of linked variants in human α cells. Using α cell-specific gene ablation of G6pc2 in mice, we showed that this gene plays a critical role in controlling glucose suppression of amino acid-stimulated glucagon secretion independent of alterations in insulin output, islet hormone content, or islet morphology, findings that we confirmed in primary human α cells. Collectively, our data demonstrate that G6PC2 affects glycemic control via its action in α cells and possibly suggest that G6PC2 inhibitors might help control blood glucose through a bihormonal mechanism.

Exploring Phytochemicals as Potential Inhibitors of Cancer Cell Metabolic Pathways: A Computational Study

OBJECTIVE

The objective of this study is to explore the therapeutic potential of phytochemicals in cancer cell metabolism by investigating their ability to inhibit key molecular targets involved in tumor growth and drug resistance.

METHODS

We evaluated specific phytochemicals against critical cancer-related targets such as GLS1, CKα, MGLL, IDH1, PDHK1, and PHGDH. Molecular docking methods were used to understand the binding interactions between phytochemicals and their selected targets. ADME (absorption, distribution, metabolism, and excretion) analysis and molecular dynamics (MD) simulations were conducted to assess pharmacokinetic properties and ligand-protein interaction dynamics, respectively. MM-PBSA (molecular mechanics Poisson-Boltzmann surface area) calculations were utilized to estimate binding free energies.

RESULTS

Molecular dynamics simulations demonstrate that phytochemicals like EGCG, Diosgenin, Withaferin A, and Celastrol exhibit stable binding to their respective targets, suggesting potential therapeutic benefits. Specifically, EGCG shows strong and non-toxic binding affinity with GLS1, making it a promising candidate for cancer treatment.

CONCLUSION

Our study underscores the potential of phytochemicals as effective inhibitors of cancer cell metabolism. The stable binding interactions highlight promising avenues for developing innovative cancer therapies. Further experimental investigations are warranted to validate these findings and advance the development of hybrid phytochemical-based treatments for combating chemoresistance.

In silico design of dehydrophenylalanine containing peptide activators of glucokinase using pharmacophore modelling, molecular dynamics and machine learning: implications in type 2 diabetes

Diabetes represents a significant global health challenge associated with substantial healthcare costs and therapeutic complexities. Current diabetes therapies often entail adverse effects, necessitating the exploration of novel agents. Glucokinase (GK), a key enzyme in glucose homeostasis, primarily regulates blood glucose levels in hepatocytes and pancreatic cells. Unlike other hexokinases, GK exhibits unique kinetic properties, such as a high Km and lack of feedback inhibition, allowing it to function as a glucose sensor Glucokinase activators (GKAs) have emerged as promising candidates for managing type-2 diabetes by allosterically enhancing GK activity. Despite initial promise, existing GKAs face significant safety concerns, driving the need for compounds with improved safety profiles. This study introduces a novel chemical scaffold within the GKA landscape: peptide-based GKAs incorporating non-standard amino acid residues such as α,β-dehydrophenylalanine (ΔPhe/ΔF). A virtual library containing 3,368,000 peptides was constructed and screened using a hybrid pharmacophore, namely DHRR (D: donor; H: hydrogen; R: aromatic ring). Molecular docking and molecular dynamics simulations assisted in identifying three peptides, Pep-11, Pep-15, and Pep-16, which depicted stable binding at the allosteric site of Glucokinase. These peptides were synthesized using a combination of solid and solution phase synthesis methods. In vitro enzymatic activity of glucokinase was increased by at least 1.5 times in the presence of these peptides. Several machine learning algorithms were explored as alternatives to conventional in-silico methods for predicting GK activity. Regression and tree-based algorithms outperformed other methods, with the logistic regression and random forest classifiers both achieving an ROC-AUC of 0.98.

Effects of glucokinase haploinsufficiency on the pancreatic β-cell mass and function of long-term high-fat, high-sucrose diet-fed mice

AIMS/INTRODUCTION

We previously showed that glucokinase haploinsufficiency improves the glucose tolerance of db/db mice by preserving pancreatic β-cell mass and function. In the present study, we aimed to determine the effects of glucokinase haploinsufficiency on the β-cell mass and function of long-term high-fat, high-sucrose (HFHS) diet-fed mice.

MATERIALS AND METHODS

Four-week-old male glucokinase haploinsufficient (Gck+/-) mice and 4-week-old male wild-type (Gck+/+) mice (controls) were each divided into two groups: an HFHS diet-fed group and a normal chow-fed group, and the four groups were followed until 16, 40 or 60 weeks-of-age. Their glucose tolerance, glucose-stimulated insulin secretion and β-cell mass were evaluated. In addition, islets were isolated from 40-week-old mice, and the expression of key genes was compared.

RESULTS

Gck+/-HFHS mice had smaller compensatory increases in β-cell mass and glucose-stimulated insulin secretion than Gck+/+HFHS mice, and their glucose tolerance deteriorated from 16 to 40 weeks-of-age. However, their β-cell mass and glucose-stimulated insulin secretion did not decrease between 40 and 60 weeks-of-age, but rather, tended to increase, and there was no progressive deterioration in glucose tolerance. The expression of Aldh1a3 in pancreatic islets, which is high in several models of diabetes and is associated with an impairment in β-cell function, was high in Gck+/+HFHS mice, but not in Gck+/-HFHS mice.

CONCLUSIONS

Glucokinase haploinsufficiency prevents the progressive deterioration of pancreatic β-cell mass/function and glucose tolerance in long-term HFHS diet-fed mice.

Reconsidering lactate disallowance in pancreatic β cells

Lactate synthesis via lactate dehydrogenase A (LDHA), traditionally considered to be a 'disallowed' function in pancreatic β cells, is redefined by Cuozzo et al. who find that lactate produced by β cells regulates fasting insulin secretion via LDHB. The metabolic sources, fates, and relevance of β cell lactate are further examined.

Evaluation of the anti-diabetic and anti-inflammatory potentials of curcumin nanoparticle in diabetic rat induced by streptozotocin

Background

Natural materials are frequently good options for drug development, regardless of their source. It has been demonstrated that curcumin boosts antioxidant capacity and guards against diabetic disorders.

Aim

The current study aimed to evaluate the possible anti-inflammatory and anti-diabetic effects of curcumin-NPs (Cur-NPs) in streptozotocin-induced diabetic rats.

Methods

Four groups of rats were randomly selected; (1) standard control group, (2) Cur-NPs group was given the regular food of rats along with 5 mg/kg of Cur-NPs daily, (3) Diabetic rats in the STZ group served as the positive control, and (4) Included in the STZ~Cur-NPs group were diabetic rats receiving Cur-NPs (5 mg/kg/day).

Results

After receiving Cur-NPs treatment for 6 weeks, the levels of glucose, tumor necrosis factor alpha TNF-alpha, interlukin1 β (IL1β), interlukin-4, interlukin-6, interlukin-10, MDA, and NO in the diabetic animals were significantly reduced. Simultaneously, the levels of insulin, CAT, GPx, GSH, and SOD were significantly increased, approaching the levels of the corresponding healthy animals. Similarly, insulin secretion increased in the islet β-cells as shown by immunohistochemical analysis, indicating improved glycaemic control and eventual glucose commitment to glycolysis; its processes for scavenging free radicals and acting as an antioxidant may explain this behavior.

Conclusion

As a result, our findings aid in the potential characterization and creation of novel therapeutic agents that prevent diabetes.

In Vivo Glucose Transporter-2 Regulation of Dorsomedial Versus Ventrolateral VMN Astrocyte Metabolic Sensor and Glycogen Metabolic Enzyme Gene Expression in Female Rat

Astrocyte glycogenolysis shapes ventromedial hypothalamic nucleus (VMN) regulation of glucostasis in vivo. Glucose transporter-2 (GLUT2), a plasma membrane glucose sensor, controls hypothalamic primary astrocyte culture glycogen metabolism in vitro. In vivo gene silencing tools and single-cell laser-catapult-microdissection/multiplex qPCR techniques were used here to examine whether GLUT2 governs dorsomedial (VMNdm) and/or ventrolateral (VMNvl) VMN astrocyte metabolic sensor and glycogen metabolic enzyme gene profiles. GLUT2 gene knockdown diminished astrocyte GLUT2 mRNA in both VMN divisions. Hypoglycemia caused GLUT2 siRNA-reversible up-regulation of this gene profile in the VMNdm, but down-regulated VMNvl astrocyte GLUT2 transcription. GLUT2 augmented baseline VMNdm and VMNvl astrocyte glucokinase (GCK) gene expression, but increased (VMNdm) or reduced (VMNvl) GCK transcription during hypoglycemia. GLUT2 imposed opposite control, namely stimulation versus inhibition of VMNdm or VMNvl astrocyte 5'-AMP-activated protein kinase-alpha 1 and -alpha 2 gene expression, respectively. GLUT2 stimulated astrocyte glycogen synthase (GS) gene expression in each VMN division. GLUT2 inhibited transcription of the AMP-sensitive glycogen phosphorylase (GP) isoform GP-brain type (GPbb) in each site, yet diminished (VMNdm) or augmented (VMNvl) astrocyte GP-muscle type (GPmm) mRNA. GLUT2 enhanced VMNdm and VMNvl glycogen accumulation during euglycemia, and curbed hypoglycemia-associated VMNdm glycogen depletion. Results show that VMN astrocytes exhibit opposite, division-specific GLUT2 transcriptional responsiveness to hypoglycemia. Data document divergent GLUT2 control of GCK, AMPK catalytic subunit, and GPmm gene profiles in VMNdm versus VMNvl astrocytes. Ongoing studies seek to determine how differential GLUT2 regulation of glucose and energy sensor function and glycogenolysis in each VMN location may affect local neuron responses to hypoglycemia.

Conserved glucokinase regulation in zebrafish confirms therapeutic utility for pharmacologic modulation in diabetes

Glucokinase (GCK) is an essential enzyme for blood glucose homeostasis. Because of its importance in glucose metabolism, GCK is considered an attractive target for the development of antidiabetic drugs. However, a viable therapeutic agent has still to emerge, prompting efforts to improve understanding of the complex regulation and biological effects of GCK. Using the vertebrate organism zebrafish, an attractive model to study metabolic diseases and pharmacological responses, we dissected the complexities of gck regulation and unraveled effects of Gck modulation. We found that while gck expression in zebrafish islet cells is constitutive, gck expression in the liver is regulated by nutritional status, confirming similarity to the mammalian system. A combination of transgenic gck reporter lines and our diabetes model, the pdx1 mutant, allowed monitoring of gck expression under pathological conditions, revealing reduced gck expression and activity in the liver, which was unresponsive to nutrient stimulation, and decreased expression in the islet due to the reduced number of β-cells. Gck activation substantially ameliorated hyperglycemia in pdx1 mutants, without inducing oxidative stress responses in liver or islet. In-depth characterization of Gck activity and regulation at the cellular level in a whole-organism diabetes model clarifies its applicability as a drug target for therapies.

Unraveling the impaired incretin effect in obesity and type 2 diabetes: Key role of hyperglycemia-induced unscheduled glycolysis and glycolytic overload

Glucagon-like peptide-1 (GLP-1) agonists and GLP-1 and glucose-dependent insulinotropic polypeptide (GIP) co-agonists are major treatment options for subjects with obesity and patients with type 2 diabetes mellitus (T2DM). They counter without addressing the mechanistic cause of the impaired incretin effect associated with obesity and T2DM. Incretin effect impairment is characterized by decreased secretion of incretins from enteroendocrine cells and incretin resistance of pancreatic β-cells. It is linked to hyperglycemia. We present evidence that subversion of the gating of glucose entry into glycolysis, mainly by glucokinase (hexokinase-4), during persistent hyperglycemia in enteroendocrine cells, pancreatic β- and α-cells and appetite-regulating neurons contributes to the biochemical mechanism of the impaired incretin effect. Unscheduled glycolysis and glycolytic overload thereby produced decreases cell signalling of incretin secretion to glucose and other secretion stimuli and incretin receptor responses. This mechanism provides a guide for development of alternative therapies targeting recovery of the impaired incretin effect.

Identification of small molecule glucokinase activators for the treatment of diabetes based on plants from the traditional Chinese medicine: In silico analysis

Mutations in glucokinase (GCK) can either enhance or inhibit insulin secretion, leading to different forms of diabetes, including gestational diabetes. While many glucokinase activators (GKAs) have been explored as treatments, their long-term effectiveness has often been unsatisfactory. However, recent interest has surged with the introduction of dorzagliatin and TTP399. This study investigates the efficacy of four previously studied compounds (Swertiamarin, Apigenin, Mangiferin, and Tatanan A) in activating GCK using computational methods. Initial molecular docking revealed binding affinities ranging from -6.7 to -8.6 kcal/mol. The compounds were then evaluated for drug-likeness and pharmacokinetic properties. Re-docking studies were performed for validation. Based on their favorable binding affinities and compliance with Lipinski's rule and ADMET criteria, three compounds (Swertiamarin, Apigenin, and Tatanan A) were selected for molecular dynamics (MD) simulations. MD simulations demonstrated that Swertiamarin showed excellent stability, as indicated by analyses of RMSD, RMSF, radius of gyration (Rg), hydrogen bonding, and principal component analysis (PCA). These results suggest that Swertiamarin holds promise for further investigation in in vivo and clinical settings to evaluate its potential in enhancing GCK activity and treating diabetes. This study assessed the potential of four compounds as GCK activators using molecular docking, pharmacokinetic profiling, and MD simulations. Swertiamarin, in particular, showed significant stability and adherence to drug-likeness criteria, making it a promising candidate for further research in combating diabetes.

Glucokinase (GCK) in diabetes: from molecular mechanisms to disease pathogenesis

Glucokinase (GCK), a key enzyme in glucose metabolism, plays a central role in glucose sensing and insulin secretion in pancreatic β-cells, as well as glycogen synthesis in the liver. Mutations in the GCK gene have been associated with various monogenic diabetes (MD) disorders, including permanent neonatal diabetes mellitus (PNDM) and maturity-onset diabetes of the young (MODY), highlighting its importance in maintaining glucose homeostasis. Additionally, GCK gain-of-function mutations lead to a rare congenital form of hyperinsulinism known as hyperinsulinemic hypoglycemia (HH), characterized by increased enzymatic activity and increased glucose sensitivity in pancreatic β-cells. This review offers a comprehensive exploration of the critical role played by the GCK gene in diabetes development, shedding light on its expression patterns, regulatory mechanisms, and diverse forms of associated monogenic disorders. Structural and mechanistic insights into GCK's involvement in glucose metabolism are discussed, emphasizing its significance in insulin secretion and glycogen synthesis. Animal models have provided valuable insights into the physiological consequences of GCK mutations, although challenges remain in accurately recapitulating human disease phenotypes. In addition, the potential of human pluripotent stem cell (hPSC) technology in overcoming current model limitations is discussed, offering a promising avenue for studying GCK-related diseases at the molecular level. Ultimately, a deeper understanding of GCK's multifaceted role in glucose metabolism and its dysregulation in disease states holds implications for developing targeted therapeutic interventions for diabetes and related disorders.

Etiology of the Neonatal Hypoglycemias

To provide a more appropriate foundation for dealing with the problem of hypoglycemia in newborn infants, this article focuses on the mechanisms which underlie the various forms of neonatal hypoglycemia and discusses their implications for newborn care. Evidence indicates that all of the major forms of neonatal hypoglycemia are the result of hyperinsulinism due to dysregulation of pancreatic islet insulin secretion. Based on these observations, the authors propose that routine measurement of B-hydroxybutyrate should be considered an essential part of glucose monitoring in newborn infants.

Glucose Transporters Are Key Components of the Human Glucostat

Mouse models are extensively used in metabolic studies. However, inherent differences between the species, notably their blood glucose levels, hampered data translation into clinical settings. In this study, we confirmed GLUT1 to be the predominantly expressed glucose transporter in both adult and fetal human β-cells. In comparison, GLUT2 is detected in a small yet significant subpopulation of adult β-cells and is expressed to a greater extent in fetal β-cells. Notably, GLUT1/2 expression in INS+ cells from human stem cell-derived islet-like clusters (SC-islets) exhibited a closer resemblance to that observed in fetal islets. Transplantation of primary human islets or SC-islets, but not murine islets, lowered murine blood glucose to the human glycemic range, emphasizing the critical role of β-cells in establishing species-specific glycemia. We further demonstrate the functional requirements of GLUT1 and GLUT2 in glucose uptake and insulin secretion through chemically inhibiting GLUT1 in primary islets and SC-islets and genetically disrupting GLUT2 in SC-islets. Finally, we developed a mathematical model to predict changes in glucose uptake and insulin secretion as a function of GLUT1/2 expression. Collectively, our findings illustrate the crucial roles of GLUTs in human β-cells, and identify them as key components in establishing species-specific glycemic set points.

ARTICLE HIGHLIGHTS

Dorzagliatin: A Breakthrough Glucokinase Activator Coming on Board to Treat Diabetes Mellitus

Dorzagliatin, an innovative dual-acting allosteric oral glucokinase activator that targets glucose homeostasis and insulin resistance, has gained approval for treating type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). The effectiveness of existing antidiabetic treatments in enhancing beta cell (β-cell) activity is restricted. Currently, there are no satisfactory medications available to address the fundamental deficiency in glucose sensing for glucokinase-maturity-onset diabetes of the young (GCK-MODY), which is caused by mutations in the glucokinase gene; researchers have embarked on glucokinase activators. Dorzagliatin enhances the affinity of glucokinase for glucose and glucose-sensing capacity, improves β-cell function, and reduces insulin resistance. Two phase 3 studies, an adjunct trial of dorzagliatin with metformin for T2DM patients and a monotherapy trial for drug-naïve T2DM patients, are key clinical trials that have shown a favorable safety and tolerability profile. They also demonstrated a rapid, sustained reduction in glycated hemoglobin (HbA1c) and a significant decrease in postprandial blood glucose. This review will summarize the substantial clinical evidence supporting the safety and efficacy of dorzagliatin in treating diabetes mellitus (DM) and clarify the molecular mechanisms underlying its action.

Biochemical and metabolic characterization of a G6PC2 inhibitor

Three glucose-6-phosphatase catalytic subunits, that hydrolyze glucose-6-phosphate (G6P) to glucose and inorganic phosphate, have been identified, designated G6PC1-3, but only G6PC1 and G6PC2 have been implicated in the regulation of fasting blood glucose (FBG). Elevated FBG has been associated with multiple adverse clinical outcomes, including increased risk for type 2 diabetes and various cancers. Therefore, G6PC1 and G6PC2 inhibitors that lower FBG may be of prophylactic value for the prevention of multiple conditions. The studies described here characterize a G6PC2 inhibitor, designated VU0945627, previously identified as Compound 3. We show that VU0945627 preferentially inhibits human G6PC2 versus human G6PC1 but activates human G6PC3. VU0945627 is a mixed G6PC2 inhibitor, increasing the Km but reducing the Vmax for G6P hydrolysis. PyRx virtual docking to an AlphaFold2-derived G6PC2 structural model suggests VU0945627 binds two sites in human G6PC2. Mutation of residues in these sites reduces the inhibitory effect of VU0945627. VU0945627 does not inhibit mouse G6PC2 despite its 84% sequence identity with human G6PC2. Mutagenesis studies suggest this lack of inhibition of mouse G6PC2 is due, in part, to a change in residue 318 from histidine in human G6PC2 to proline in mouse G6PC2. Surprisingly, VU0945627 still inhibited glucose cycling in the mouse islet-derived βTC-3 cell line. Studies using intact mouse liver microsomes and PyRx docking suggest that this observation can be explained by an ability of VU0945627 to also inhibit the G6P transporter SLC37A4. These data will inform future computational modeling studies designed to identify G6PC isoform-specific inhibitors.

Elucidation of the beneficial role of co-fermented whole grain quinoa and black barley with Lactobacillus on rats fed a western-style diet via a multi-omics approach

Long-term consumption of Western-style diet (WSD) can lead to metabolic disorders and dysbiosis of gut microbiota, presenting a critical risk factor for various chronic conditions such as fatty liver disease. In the present study, we investigated the beneficial role of co-fermented whole grain quinoa and black barley with Lactobacillus kisonensis on rats fed a WSD. Male Sprague-Dawley (SD) rats, aged six weeks and weighing 180 ± 10 g, were randomly assigned to one of three groups: the normal control group (NC, n = 7), the WSD group (HF, n = 7), and the WSD supplemented with a co-fermented whole grain quinoa with black barley (FQB) intervention group (HFF, n = 7). The findings indicated that FQB was effective in suppressing body weight gain, mitigating hepatic steatosis, reducing perirenal fat accumulation, and ameliorating pathological damage in the livers and testicular tissues of rats. Additionally, FQB intervention led to decreased levels of serum uric acid (UA), aspartate aminotransferase (AST), and alanine aminotransferase (ALT). These advantageous effects can be ascribed to the regulation of FQB on gut microbiota dysbiosis, which includes the restoration of intestinal flora diversity, reduction of the F/B ratio, and promotion of probiotics abundance, such as Akkermansia and [Ruminococcus] at the genus level. The study employed the UPLC-Q-TOF-MSE technique to analyze metabolites in fecal and hepatic samples. The findings revealed that FQB intervention led to a regression in the levels of specific metabolites in feces, including oxoadipic acid and 20a, 22b-dihydroxycholesterol, as well as in the liver, such as pyridoxamine, xanthine and xanthosine. The transcriptome sequencing of liver tissues revealed that FQB intervention modulated the mRNA expression of specific genes, including Cxcl12, Cidea, and Gck, known for their roles in anti-inflammatory and anti-insulin resistance mechanisms in the context of WSD. Our findings indicate that co-fermented whole-grain quinoa with black barley has the potential to alleviate metabolic disorders and chronic inflammation resulting from the consumption of WSD.

Impaired GK-GKRP interaction rather than direct GK activation worsens lipid profiles and contributes to long-term complications: a Mendelian randomization study

BACKGROUND

Glucokinase (GK) plays a key role in glucose metabolism. In the liver, GK is regulated by GK regulatory protein (GKRP) with nuclear sequestration at low plasma glucose level. Some GK activators (GKAs) disrupt GK-GKRP interaction which increases hepatic cytoplasmic GK level. Excess hepatic GK activity may exceed the capacity of glycogen synthesis with excess triglyceride formation. It remains uncertain whether hypertriglyceridemia associated with some GKAs in previous clinical trials was due to direct GK activation or impaired GK-GKRP interaction.

METHODS

Using publicly available genome-wide association study summary statistics, we selected independent genetic variants of GCKR and GCK associated with fasting plasma glucose (FPG) as instrumental variables, to mimic the effects of impaired GK-GKRP interaction and direct GK activation, respectively. We applied two-sample Mendelian Randomization (MR) framework to assess their causal associations with lipid-related traits, risks of metabolic dysfunction-associated steatotic liver disease (MASLD) and cardiovascular diseases. We verified these findings in one-sample MR analysis using individual-level statistics from the Hong Kong Diabetes Register (HKDR).

RESULTS

Genetically-proxied impaired GK-GKRP interaction increased plasma triglycerides, low-density lipoprotein cholesterol and apolipoprotein B levels with increased odds ratio (OR) of 14.6 (95% CI 4.57-46.4) per 1 mmol/L lower FPG for MASLD and OR of 2.92 (95% CI 1.78-4.81) for coronary artery disease (CAD). Genetically-proxied GK activation was associated with decreased risk of CAD (OR 0.69, 95% CI 0.54-0.88) and not with dyslipidemia. One-sample MR validation in HKDR showed consistent results.

CONCLUSIONS

Impaired GK-GKRP interaction, rather than direct GK activation, may worsen lipid profiles and increase risks of MASLD and CAD. Development of future GKAs should avoid interfering with GK-GKRP interaction.

Importance of Michaelis Constants for Cancer Cell Redox Balance and Lactate Secretion-Revisiting the Warburg Effect

Cancer cells metabolize a large fraction of glucose to lactate, even under a sufficient oxygen supply. This phenomenon-the "Warburg Effect"-is often regarded as not yet understood. Cancer cells change gene expression to increase the uptake and utilization of glucose for biosynthesis pathways and glycolysis, but they do not adequately up-regulate the tricarboxylic acid (TCA) cycle and oxidative phosphorylation (OXPHOS). Thereby, an increased glycolytic flux causes an increased production of cytosolic NADH. However, since the corresponding gene expression changes are not neatly fine-tuned in the cancer cells, cytosolic NAD+ must often be regenerated by loading excess electrons onto pyruvate and secreting the resulting lactate, even under sufficient oxygen supply. Interestingly, the Michaelis constants (KM values) of the enzymes at the pyruvate junction are sufficient to explain the priorities for pyruvate utilization in cancer cells: 1. mitochondrial OXPHOS for efficient ATP production, 2. electrons that exceed OXPHOS capacity need to be disposed of and secreted as lactate, and 3. biosynthesis reactions for cancer cell growth. In other words, a number of cytosolic electrons need to take the "emergency exit" from the cell by lactate secretion to maintain the cytosolic redox balance.

Novel Therapeutics for Type 2 Diabetes Mellitus-A Look at the Past Decade and a Glimpse into the Future

Cardiovascular disease (CVD) and kidney disease are the main causes of morbidity and mortality in type 2 diabetes mellitus (T2DM). Globally, the incidence of T2DM continues to rise. A substantial increase in the burden of CVD and renal disease, alongside the socioeconomic implications, would be anticipated. Adopting a purely glucose-centric approach focusing only on glycemic targets is no longer adequate to mitigate the cardiovascular risks in T2DM. In the past decade, significant advancement has been achieved in expanding the pharmaceutical options for T2DM, with novel agents such as the sodium-glucose cotransporter type 2 (SGLT2) inhibitors and glucagon-like peptide receptor agonists (GLP-1 RAs) demonstrating robust evidence in cardiorenal protection. Combinatorial approaches comprising multiple pharmacotherapies combined in a single agent are an emerging and promising way to not only enhance patient adherence and improve glycemic control but also to achieve the potential synergistic effects for greater cardiorenal protection. In this review, we provide an update on the novel antidiabetic agents in the past decade, with an appraisal of the mechanisms contributing to cardiorenal protection. Additionally, we offer a glimpse into the landscape of T2DM management in the near future by providing a comprehensive summary of upcoming agents in early-phase trials.

Glucose transporter-2 regulation of VMN GABA neuron metabolic sensor and transmitter gene expression

Glucose transporter-2 (GLUT2) monitors cellular glucose uptake. Astrocyte GLUT2 controls glucose counterregulatory hormone secretion. In vivo gene silencing and laser-catapult-microdissection tools were used here to investigate whether ventromedial hypothalamic nucleus (VMN) GLUT2 may regulate dorsomedial (VMNdm) and/or ventrolateral (VMNvl) γ-aminobutyric acid (GABA) neurotransmission to control this endocrine outflow in female rats. VMN GLUT2 gene knockdown suppressed or stimulated hypoglycemia-associated glutamate decarboxylase (GAD)1 and GAD2 mRNA expression in VMNdm versus VMNvl GABAergic neurons, respectively. GLUT2 siRNA pretreatment also modified co-expressed transmitter marker gene profiles in each cell population. VMNdm GABA neurons exhibited GLUT2 knockdown-sensitive up-regulated 5'-AMP-activated protein kinase-alpha1 (AMPKα1) and -alpha2 (AMPKα2) transcripts during hypoglycemia. Hypoglycemic augmentation of VMNvl GABA neuron AMPKα2 was refractory to GLUT2 siRNA. GLUT2 siRNA blunted (VMNdm) or exacerbated (VMNvl) hypoglycemic stimulation of GABAergic neuron steroidogenic factor-1 (SF-1) mRNA. Results infer that VMNdm and VMNvl GABA neurons may exhibit divergent, GLUT2-dependent GABA neurotransmission patterns in the hypoglycemic female rat. Data also document differential GLUT2 regulation of VMNdm versus VMNvl GABA nerve cell SF-1 gene expression. Evidence for intensification of hypoglycemic hypercorticosteronemia and -glucagonemia by GLUT2 siRNA infers that VMN GLUT2 function imposes an inhibitory tone on these hormone profiles in this sex.

Targeting Protein Kinases to Protect Beta-Cell Function and Survival in Diabetes

The prevalence of diabetes is increasing worldwide. Massive death of pancreatic beta-cells causes type 1 diabetes. Progressive loss of beta-cell function and mass characterizes type 2 diabetes. To date, none of the available antidiabetic drugs promotes the maintenance of a functional mass of endogenous beta-cells, revealing an unmet medical need. Dysfunction and apoptotic death of beta-cells occur, in particular, through the activation of intracellular protein kinases. In recent years, protein kinases have become highly studied targets of the pharmaceutical industry for drug development. A number of drugs that inhibit protein kinases have been approved for the treatment of cancers. The question of whether safe drugs that inhibit protein kinase activity can be developed and used to protect the function and survival of beta-cells in diabetes is still unresolved. This review presents arguments suggesting that several protein kinases in beta-cells may represent targets of interest for the development of drugs to treat diabetes.

Sex-Dimorphic Effects of Hypoglycemia on Metabolic Sensor mRNA Expression in Ventromedial Hypothalamic Nucleus-Dorsomedial Division (VMNdm) Growth Hormone-Releasing Hormone Neurons

Growth hormone-releasing hormone (Ghrh) neurons in the dorsomedial ventromedial hypothalamic nucleus (VMNdm) express the metabolic transcription factor steroidogenic factor-1 and hypoglycemia-sensitive neurochemicals of diverse chemical structures, transmission modes, and temporal signaling profiles. Ghrh imposes neuromodulatory control of coexpressed transmitters. Multiple metabolic sensory mechanisms are employed in the brain, including screening of the critical nutrient glucose or the energy currency ATP. Here, combinatory laser-catapult-microdissection/single-cell multiplex qPCR tools were used to investigate whether these neurons possess molecular machinery for monitoring cellular metabolic status and if these biomarkers exhibit sex-specific sensitivity to insulin-induced hypoglycemia. Data show that hypoglycemia up- (male) or downregulated (female) Ghrh neuron glucokinase (Gck) mRNA; Ghrh gene silencing decreased baseline and hypoglycemic patterns of Gck gene expression in each sex. Ghrh neuron glucokinase regulatory protein (Gckr) transcript levels were respectively diminished or augmented in hypoglycemic male vs female rats; this mRNA profile was decreased by Ghrh siRNA in both sexes. Gene transcripts encoding catalytic alpha subunits of the energy monitor 5-AMP-activated protein kinase (AMPK), i.e., Prkaa1 and 2, were increased by hypoglycemia in males, yet only the former mRNA was hypoglycemia-sensitive in females. Ghrh siRNA downregulated baseline and hypoglycemia-associated Prkaa subunit mRNAs in males but elicited divergent changes in Prkaa2 transcripts in eu- vs hypoglycemic females. Results provide unique evidence that VMNdm Ghrh neurons express the characterized metabolic sensor biomarkers glucokinase and AMPK and that the corresponding gene profiles exhibit distinctive sex-dimorphic transcriptional responses to hypoglycemia. Data further document Ghrh neuromodulation of baseline and hypoglycemic transcription patterns of these metabolic gene profiles.

LONP1 regulation of mitochondrial protein folding provides insight into beta cell failure in type 2 diabetes

Proteotoxicity is a contributor to the development of type 2 diabetes (T2D), but it is unknown whether protein misfolding in T2D is generalized or has special features. Here, we report a robust accumulation of misfolded proteins within the mitochondria of human pancreatic islets in T2D and elucidate its impact on β cell viability. Surprisingly, quantitative proteomics studies of protein aggregates reveal that human islets from donors with T2D have a signature more closely resembling mitochondrial rather than ER protein misfolding. The matrix protease LonP1 and its chaperone partner mtHSP70 were among the proteins enriched in protein aggregates. Deletion of LONP1 in mice yields mitochondrial protein misfolding and reduced respiratory function, ultimately leading to β cell apoptosis and hyperglycemia. Intriguingly, LONP1 gain of function ameliorates mitochondrial protein misfolding and restores human β cell survival following glucolipotoxicity via a protease-independent effect requiring LONP1-mtHSP70 chaperone activity. Thus, LONP1 promotes β cell survival and prevents hyperglycemia by facilitating mitochondrial protein folding. These observations may open novel insights into the nature of impaired proteostasis on β cell loss in the pathogenesis of T2D that could be considered as future therapeutic targets.

Recent drug development of dorzagliatin, a new glucokinase activator, with the potential to treat Type 2 diabetes: A review study

Type 2 diabetes mellitus (T2DM) is a complicated disease related to metabolism that results from resistance to insulin and sustained hyperglycemia. Traditional antidiabetic drugs cannot meet the demand of different diabetes patients for reaching the glycemic targets; thus, the identification of new antidiabetic drugs is urgently needed for the treatment of T2DM to enhance glycemic control and the prognosis of patients suffering from T2DM. Recently, glucokinase (GK) has attracted much attention and is considered to be an effective antidiabetic agent. Glucokinase activators (GKA) represented by dorzagliatin could activate GK and mimic its function that triggers a counter-regulatory response to blood glucose changes. Dorzagliatin has shown great potential for glycemic control in diabetic patients in a randomized, double-blind, placebo-controlled Phase 3 trial (SEED study) and had a favorable safety profile and was well tolerated (DAWN study). In the SEED study, dorzagliatin significantly reduced glycosylated hemoglobin (HbA1c) by 1.07% and postprandial blood glucose by 2.83 mol/L, showing the great potential of this drug to control blood glucose in diabetic patients, with good safety and good tolerance. An extension of the SEED study, the DREAM study, confirmed that dorzagliatin monotherapy significantly improved 24-h glucose variability and increased time in range (TIR) to 83.7% over 46 weeks. Finally, the clinical study of dorzagliatin combined with metformin (DAWN study) confirmed that dorzagliatin could significantly reduce HbA1c by 1.02% and postprandial blood glucose by 5.45 mol/L. The current review summarizes the development of GK and GKA, as well as the prospects, trends, applications, and shortcomings of these treatments, especially future directions of clinical studies of dorzagliatin.

Clinical investigation of glucokinase activators for the restoration of glucose homeostasis in diabetes

As a sensor, glucokinase (GK) controls glucose homeostasis, which progressively declines in patients with diabetes. GK maintains the equilibrium of glucose levels and regulates the homeostatic system set points. Endocrine and hepatic cells can both respond to glucose cooperatively when GK is activated. GK has been under study as a therapeutic target for decades due to the possibility that cellular GK expression and function can be recovered, hence restoring glucose homeostasis in patients with type 2 diabetes. Five therapeutic compounds targeting GK are being investigated globally at the moment. They all have distinctive molecular structures and have been clinically shown to have strong antihyperglycemia effects. The mechanics, classification, and clinical development of GK activators are illustrated in this review. With the recent approval and marketing of the first GK activator (GKA), dorzagliatin, GKA's critical role in treating glucose homeostasis disorder and its long-term benefits in diabetes will eventually become clear.

Hyperglycemia facilitates EV71 replication: Insights into miR-206-mediated regulation of G3BP2 promoting EV71 IRES activity

Background: Neurotropic virus infections actively manipulate host cell metabolism to enhance virus neurovirulence. Although hyperglycemia is common during severe infections, its specific role remains unclear. This study investigates the impact of hyperglycemia on the neurovirulence of enterovirus 71 (EV71), a neurovirulent virus relying on internal ribosome entry site (IRES)-mediated translation for replication. Methods: Utilizing hSCARB2-transgenic mice, we explore the effects of hyperglycemia in EV71 infection and elucidate the underlying mechanisms. Results: Remarkably, administering insulin alone to reduce hyperglycemia in hSCARB2-transgenic mice results in a decrease in brainstem encephalitis and viral load. Conversely, induced hyperglycemia exacerbates neuropathogenesis, highlighting the pivotal role of hyperglycemia in neurovirulence. Notably, miR-206 emerges as a crucial mediator induced by viral infection, with its expression further heightened by hyperglycemia and concurrently repressed by insulin. The use of antagomiR-206 effectively mitigates EV71-induced brainstem encephalitis and reduces viral load. Mechanistically, miR-206 facilitates IRES-driven virus replication by repressing the stress granule protein G3BP2. Conclusions: Novel therapeutic approaches against severe EV71 infections involve managing hyperglycemia and targeting the miR-206-stress granule pathway to modulate virus IRES activity.

Should Glucokinase be Given a Chance in Diabetes Therapeutics? A Clinical-Pharmacological Review of Dorzagliatin and Lessons Learned So Far

Despite advances in the management of type 2 diabetes mellitus (T2DM), one-third of patients with diabetes do not achieve the desired glycemic goal. Considering this inadequacy, many agents that activate glucokinase have been investigated over the last two decades but were withdrawn before submission for marketing permission. Dorzagliatin is the first glucokinase activator that has been granted approval for T2DM, only in China. As overstimulation of glucokinase is linked with pathophysiological disturbances such as fatty liver and cardiovascular issues and a loss of therapeutic efficacy with time. This review aims to highlight the benefits of glucokinase activators vis-à-vis the risks associated with chronic enzymatic activation. We discuss the multisystem disturbances expected with chronic activation of the enzyme, the lessons learned with glucokinase activators of the past, the major efficacy and safety findings with dorzagliatin and its pharmacological properties, and the status of other glucokinase activators in the pipeline. The approval of dorzagliatin in China was based on the SEED and the DAWN trials, the major pivotal phase III trials that enrolled patients with T2DM with a mean glycosylated hemoglobin of 8.3-8.4%, and a mean age of 53-54.5 years from multiple sites in China. Patients with uncontrolled diabetes, cardiac diseases, organ dysfunction, and a history of severe hypoglycemia were excluded. Both trials had a randomized double-blind placebo-controlled phase of 24 weeks followed by an open-label phase of 28 weeks with dorzagliatin. Drug-naïve patients with T2DM with a disease duration of 11.7 months were enrolled in the SEED trial while the DAWN trial involved patients with T2DM with a mean duration of 71.5 months and receiving background metformin therapy. Compared with placebo, the decline in glycosylated hemoglobin at 24 weeks was more with dorzagliatin with an estimated treatment difference of - 0.57% in the SEED trial and - 0.66% in the DAWN trial. The desired glycosylated hemoglobin (< 7%) was also attained at more than two times higher rates with dorzagliatin. The glycemic improvement was sustained in the SEED trial but decreased over 52 weeks in the DAWN trial. Hyperlipidemia was observed in 12-14% of patients taking dorzagliatin versus 9-11% of patients receiving a placebo. Additional adverse effects noticed over 52 weeks with dorzagliatin included an elevation in liver enzymes, hyperuricemia, hyperlacticacidemia, renal dysfunction, and cardiovascular disturbances. Considering the statistically significant improvement in glycosylated hemoglobin with dorzagliatin in patients with T2DM, the drug may be given a chance in treatment-naïve patients with a shorter disease history. However, with the waning therapeutic efficacy witnessed in patients with long-standing diabetes, which was also one of the potential concerns with previously tested molecules, extended studies involving patients with chronic and uncontrolled diabetes are needed to comment upon the long-term therapeutic performance of dorzagliatin. Likewise, evidence needs to be generated from other countries, patients with organ dysfunction, a history of severe hypoglycemia, cardiac diseases, and elderly patients before extending the use of dorzagliatin. Apart from monitoring lipid profiles, long-term safety studies of dorzagliatin should involve the assessment of serum uric acid, lactate, renal function, liver function, and cardiovascular parameters.

Molecular docking, pharmacokinetic prediction and molecular dynamics simulations of tankyrase inhibitor compounds with the protein glucokinase, induced in the development of diabetes

GCK is a protein that plays a crucial role in the sensing and regulation of glucose homeostasis, which associates it with disorders of carbohydrate metabolism and the development of several pathologies, including gestational diabetes. This makes GCK an important therapeutic target that has aroused the interest of researchers to discover GKA that are simultaneously effective in the long term and free of side effects. TNKS is a protein that interacts directly with GCK; recent studies have shown that it inhibits GCK action, which affects glucose detection and insulin secretion. This justifies our choice of TNKS inhibitors as ligands to test their effects on the GCK-TNKS complex. For this purpose, we investigated the interaction of the GCK-TNKS complex with 13 compounds (TNKS inhibitors and their analogues) using the molecular docking approach as a first step, after which the compounds that generated the best affinity scores were evaluated for drug similarity and pharmacokinetic properties. Subsequently, we selected the six compounds that generated high affinity and that were in accordance with the parameters of the drug rules as well as pharmacokinetic properties to ensure a molecular dynamics study. The results allowed us to favor the two compounds (XAV939 and IWR-1), knowing that even the tested compounds (TNKS 22, (2215914) and (46824343)) produced good results that can also be exploited. These results are therefore interesting and encouraging, and they can be exploited experimentally to discover a treatment for diabetes, including gestational diabetes.Communicated by Ramaswamy H. Sarma.

Tetrahydropalmatine from medicinal plants activates human glucokinase to regulate glucose homeostasis

Many synthetic glucokinase activators (GKAs), modulating glucokinase (GK), an important therapeutic target in diabetes have failed to clear clinical trials. In this study, an in silico structural similarity search with differing scaffolds of reference GKAs have been used to identify derivatives from natural product databases. Ten molecules with good binding score and similar interactions to that in the co-crystallized GK as well good activation against recombinant human GK experimentally were identified. Tetrahydropalmatine, an alkaloid present in formulations and drugs from medicinal plants, has not been explored as an antidiabetic agent and no information regarding its mechanism of action or GK activation exists. Tetrahydropalmatine activates GK with EC50 value of 71.7 ± 17.9 μM while lowering the S0.5 (7.1 mM) and increasing Vmax (9.22 μM/min) as compared to control without activator (S0.5 = 10.37 mM; Vmax = 4.8 μM/min). Kinetic data (α and β values) suggests it to act as mixed, nonessential type activator. Using microscale thermophoresis, Kd values of 3.8 μM suggests a good affinity for GK. In HepG2 cell line, the compound potentiated the uptake of glucose and maintained glucose homeostasis by increasing the expression of GK, glycogen synthase, and insulin receptor genes and lowering the expression of glucokinase regulatory protein (GKRP) and glucagon. Tetrahydropalmatine at low concentrations could elicit a good response by reducing expression of GKRP, increasing expression of GK while also activating it. Thus, it could be used alone or in combination as therapeutic drug as it could effectively modulate GK and alter glucose homeostasis.

Whole transcriptome sequencing analyses of islets reveal ncRNA regulatory networks underlying impaired insulin secretion and increased β-cell mass in high fat diet-induced diabetes mellitus

AIM

Our study aims to identify novel non-coding RNA-mRNA regulatory networks associated with β-cell dysfunction and compensatory responses in obesity-related diabetes.

METHODS

Glucose metabolism, islet architecture and secretion, and insulin sensitivity were characterized in C57BL/6J mice fed on a 60% high-fat diet (HFD) or control for 24 weeks. Islets were isolated for whole transcriptome sequencing to identify differentially expressed (DE) mRNAs, miRNAs, IncRNAs, and circRNAs. Regulatory networks involving miRNA-mRNA, lncRNA-mRNA, and lncRNA-miRNA-mRNA were constructed and functions were assessed through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses.

RESULTS

Despite compensatory hyperinsulinemia and a significant increase in β-cell mass with a slow rate of proliferation, HFD mice exhibited impaired glucose tolerance. In isolated islets, insulin secretion in response to glucose and palmitic acid deteriorated after 24 weeks of HFD. Whole transcriptomic sequencing identified a total of 1324 DE mRNAs, 14 DE miRNAs, 179 DE lncRNAs, and 680 DE circRNAs. Our transcriptomic dataset unveiled several core regulatory axes involved in the impaired insulin secretion in HFD mice, such as miR-6948-5p/Cacna1c, miR-6964-3p/Cacna1b, miR-3572-5p/Hk2, miR-3572-5p/Cckar and miR-677-5p/Camk2d. Additionally, proliferative and apoptotic targets, including miR-216a-3p/FKBP5, miR-670-3p/Foxo3, miR-677-5p/RIPK1, miR-802-3p/Smad2 and ENSMUST00000176781/Caspase9 possibly contribute to the increased β-cell mass in HFD islets. Furthermore, competing endogenous RNAs (ceRNA) regulatory network involving 7 DE miRNAs, 15 DE lncRNAs and 38 DE mRNAs might also participate in the development of HFD-induced diabetes.

CONCLUSIONS

The comprehensive whole transcriptomic sequencing revealed novel non-coding RNA-mRNA regulatory networks associated with impaired insulin secretion and increased β-cell mass in obesity-related diabetes.

Towards a comprehensive understanding of the muscle proteome in Schizothorax labiatus: Insights from seasonal variations, metabolic responses, and reproductive signatures in the River Jhelum

Proteomics is a very advanced technique used for defining correlations, compositions and activities of hundreds of proteins from organisms as well as effectively used in identifying particular proteins with varying peptide lengths and amino acid counts. In the present study, an endeavour has been put forth to create muscle proteome expression of snow trout, Schizothorax labiatus. Liquid chromatography-mass spectrometry (LC-MS) using label free quantification (LFQ) technique has extensively been carried out to explore changes in protein metabolism and its composition to discriminate across species, clarify functions and pinpoint protein biomarkers from organisms. In LFQ technique, the abundances of proteins are determined based on the signal intensities of their corresponding peptides in mass spectrometry. The main benefit of using this method is that it doesn't require pre-labelling proteins with isotopic tags, which streamlines the experimental procedure and gets rid of any bias that might have been caused by the labelling process. LFQ techniques frequently offer a wider dynamic range, making it possible to detect and quantify proteins over a broad range of abundances obtained from the complex biological materials including fish muscle. The results of proteomic analysis could provide an insight in understanding about how various proteins are expressed in response to environmental challenges. For proteomic study, two different weight groups of S. labiatus were taken from River Jhelum based on biological, physiological and logistical factors. These groups corresponded to different life stages, such as younger size and adults/brooders in order to capture potential variations in the muscle proteome related to growth and development. The proteomic analysis of S. labiatus depicted that an overall of 220 proteins in male and 228 in female fish of group 1 were noted. However, when male and female S. labiatus were examined based on spectral count and peptide abundance using ProteinLynx Global Software, a total of 10 downregulated and 32 upregulated proteins were found. In group 2 of S. labiatus, a total of 249 proteins in male and 301 in female fish were documented. When the two genders of S. labiatus were likened to one another by LFQ technique, a total of 41 downregulated and 06 upregulated proteins were identified. The variability in the protein numbers between two fish weight groups reflected biological differences, influenced by factors such as age, developmental stages, physiological condition and reproductive activities. During the study, it was observed that S. labiatus exhibited downregulated levels of proteins that were involved in feeding and growth. The contributing factors to this manifestation could be explained by lower feeding and metabolic activity of fish and decreased food availability during winter in River Jhelum. Contrarily, the fish immune response proteins were found to be significantly over-expressed in S. labiatus, indicating that the environment was more likely to undergo increased microbial infection, pollution load and anthropogenic activities. In addition, it was also discovered that there was an upregulated expression of the reproductive proteins in S. labiatus, which could be linked to the fish's pre-spawning time as the fish used in this study was collected in the winter season which is the pre-spawning period of the fish. Therefore, the present study would be useful in obtaining new insights regarding the molecular makeup of species, methods of adaptation and reactions to environmental stresses. This information contributes to our understanding of basic science and may have applications in environmental monitoring, conservation and preservation of fish species.

Post-Translational Modifications and Diabetes

Diabetes and its associated complications have increasingly become major challenges for global healthcare. The current therapeutic strategies involve insulin replacement therapy for type 1 diabetes (T1D) and small-molecule drugs for type 2 diabetes (T2D). Despite these advances, the complex nature of diabetes necessitates innovative clinical interventions for effective treatment and complication prevention. Accumulative evidence suggests that protein post-translational modifications (PTMs), including glycosylation, phosphorylation, acetylation, and SUMOylation, play important roles in diabetes and its pathological consequences. Therefore, the investigation of these PTMs not only sheds important light on the mechanistic regulation of diabetes but also opens new avenues for targeted therapies. Here, we offer a comprehensive overview of the role of several PTMs in diabetes, focusing on the most recent advances in understanding their functions and regulatory mechanisms. Additionally, we summarize the pharmacological interventions targeting PTMs that have advanced into clinical trials for the treatment of diabetes. Current challenges and future perspectives are also provided.

RFX6 Maintains Gene Expression and Function of Adult Human Islet α-Cells

Mutations in the gene encoding the transcription factor regulatory factor X-box binding 6 (RFX6) are associated with human diabetes. Within pancreatic islets, RFX6 expression is most abundant in islet α-cells, and α-cell RFX6 expression is altered in diabetes. However, the roles of RFX6 in regulating gene expression, glucagon output, and other crucial human adult α-cell functions are not yet understood. We developed a method for selective genetic targeting of human α-cells and assessed RFX6-dependent α-cell function. RFX6 suppression with RNA interference led to impaired α-cell exocytosis and dysregulated glucagon secretion in vitro and in vivo. By contrast, these phenotypes were not observed with RFX6 suppression across all islet cells. Transcriptomics in α-cells revealed RFX6-dependent expression of genes governing nutrient sensing, hormone processing, and secretion, with some of these exclusively expressed in human α-cells. Mapping of RFX6 DNA-binding sites in primary human islet cells identified a subset of direct RFX6 target genes. Together, these data unveil RFX6-dependent genetic targets and mechanisms crucial for regulating adult human α-cell function.

ARTICLE HIGHLIGHTS

The aryl hydrocarbon receptor in β-cells mediates the effects of TCDD on glucose homeostasis in mice

OBJECTIVE

Chronic exposure to persistent organic pollutants (POPs) is associated with increased incidence of type 2 diabetes, hyperglycemia, and poor insulin secretion in humans. Dioxins and dioxin-like compounds are a broad class of POPs that exert cellular toxicity through activation of the aryl hydrocarbon receptor (AhR). We previously showed that a single high-dose injection of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, aka dioxin; 20 μg/kg) in vivo reduced fasted and glucose-stimulated plasma insulin levels for up to 6 weeks in male and female mice. TCDD-exposed male mice were also modestly hypoglycemic and had increased insulin sensitivity, whereas TCDD-exposed females were transiently glucose intolerant. Whether these effects are driven by AhR activation in β-cells requires investigation.

METHODS

We exposed female and male β-cell specific Ahr knockout (βAhrKO) mice and littermate Ins1-Cre genotype controls (βAhrWT) to a single high dose of 20 μg/kg TCDD and tracked the mice for 6 weeks.

RESULTS

Under baseline conditions, deleting AhR from β-cells caused hypoglycemia in female mice, increased insulin secretion ex vivo in female mouse islets, and promoted modest weight gain in male mice. Importantly, high-dose TCDD exposure impaired glucose homeostasis and β-cell function in βAhrWT mice, but these phenotypes were largely abolished in TCDD-exposed βAhrKO mice.

CONCLUSION

Our study demonstrates that AhR signaling in β-cells is important for regulating baseline β-cell function in female mice and energy homeostasis in male mice. We also show that β-cell AhR signaling largely mediates the effects of TCDD on glucose homeostasis in both sexes, suggesting that the effects of TCDD on β-cell function and health are driving metabolic phenotypes in peripheral tissues.