Update on GLUT4 Vesicle Traffic: A Cornerstone of Insulin Action

A comprehensive view of muscle glucose uptake: regulation by insulin, contractile activity, and exercise

Skeletal muscle is the main site of glucose deposition in the body during meals and the major glucose utilizer during physical activity. Although in both instances the supply of glucose from the circulation to the muscle is of paramount importance, in most conditions the rate-limiting step in glucose uptake, storage, and utilization is the transport of glucose across the muscle cell membrane. This step is dependent upon the translocation of the insulin- and contraction-responsive glucose transporter GLUT4 from intracellular storage sites to the sarcolemma and T tubules. Here, we first analyze how glucose can traverse the capillary wall into the muscle interstitial space. We then review the molecular processes that regulate GLUT4 translocation in response to insulin and muscle contractions and the methodologies utilized to unravel them. We further discuss how physical activity and inactivity, respectively, lead to increased and decreased insulin action in muscle and touch upon sex differences in glucose metabolism. Although many key processes regulating glucose uptake in muscle are known, the advent of newer and bioinformatics tools has revealed further molecular signaling processes reaching a staggering level of complexity. Much of this molecular mapping has emerged from cellular and animal studies and more recently from application of a variety of -omics in human tissues. In the future, it will be imperative to validate the translatability of results drawn from experimental systems to human physiology.

TBC1D30 regulates proinsulin and insulin secretion and is the target of a genomic association signal for proinsulin

AIMS/HYPOTHESIS

Components of the insulin processing and secretion pathways remain incompletely understood. Here, we examined a genome-wide association study (GWAS) signal for plasma proinsulin levels. Lead GWAS variant rs150781447-T encodes an Arg279Cys substitution in TBC1 domain family member 30 (TBC1D30), but no role for this protein in insulin processing or secretion has been established previously. This study aimed to evaluate whether TBC1D30 drives the GWAS association signal by determining whether TBC1D30 is involved in proinsulin secretion and, if so, to examine the effects of variant alleles and potential mechanisms.

METHODS

Using CRISPR/Cas9 genome editing to create double-strand breaks and prime editing to install substitutions in INS1 832/13 insulinoma cells, we generated clonal cell lines with altered TBC1D30, as well as homozygous and heterozygous lines carrying the lead GWAS variant. We characterised lines by Sanger sequencing, quantitative PCR and ELISAs to measure glucose-stimulated proinsulin and insulin secretion. We also tested the effects of TBC1D30 knockdown on proinsulin and insulin secretion in human islets. We further assessed TBC1D30's contribution to secretory pathways by examining the effects of altered gene function on intracellular proinsulin and insulin content and insulin localisation, and by identifying potential proteins that interact with TBC1D30 using affinity purification mass spectrometry.

RESULTS

Compared with mock-edited cells, cell lines with reduced TBC1D30 expression or altered Rab GTPase-activating protein (RabGAP) domain had significantly more secreted proinsulin, 1.8- and 2.6-fold more than controls, respectively. Similarly, cells expressing the variant substitution demonstrated increased proinsulin secretion. Cell lines with a partial deletion of a critical functional domain showed 1.8-fold higher expression of Tbc1d30 and at least 2.0-fold less secreted proinsulin. Cells with altered RabGAP domain sequence also demonstrated, to a lesser extent, changes in secreted insulin levels. TBC1D30 knockdown in human islets resulted in increased insulin secretion with no significant effect on proinsulin secretion. The effects of altered TBC1D30 on mislocalisation of insulin, intracellular proinsulin and insulin content and the identities of interacting proteins are consistent with a role for TBC1D30 in proinsulin and insulin secretion.

CONCLUSIONS/INTERPRETATION

These findings suggest that effects on TBC1D30 are responsible for the GWAS signal and that TBC1D30 plays a critical role in the secretion of mature insulin.

The role of ERK1/2 signaling in diabetes: pathogenic and therapeutic implications

ERK1/2 (extracellular signal-regulated kinase 1/2) is an important member of the MAPK (mitogen-activated protein kinase) family and is widely involved in many biological processes such as cell proliferation, differentiation, apoptosis and migration. After activation by phosphorylation, ERK1/2 can be transferred into the nucleus and directly or indirectly affect the activity of transcription factors, thereby regulating gene expression. More and more studies have shown that ERK1/2 plays an important role in diabetes and its complications, such as insulin secretion, islet β cell function, diabetic cardiomyopathy, diabetic nephropathy, renal fibrosis, lipogenesis, diabetic vasculopathy, etc. These effects reveal the complexity and diversity of the ERK1/2 signaling pathway in the pathogenesis of diabetes, and its activation and inhibition mechanisms in multiple physiological and pathological processes provide potential targets for diabetes treatment. The purpose of this mini-review is to explore the key role of ERK1/2 in diabetes and the progress of research on targeted inhibitors of ERK1/2, which provides new strategies for the treatment of diabetes.

Marine N-3 Fatty Acids Mitigate Hyperglycemia in Prediabetes by Improving Muscular Glucose Transporter 4 Translocation and Glucose Homeostasis

Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) have been proposed to benefit cardiometabolic health. However, the relationship between the intake of DHA and EPA and type 2 diabetes (T2D) risk remains equivocal, and the effects of DHA and EPA on skeletal muscle, the primary organ for glucose metabolism, merit further investigation. Here, we show that habitual fish oil supplementation was associated with a 9% lower T2D risk and significantly interacted with variants at GLUT4 in a prospective cohort of 48,358 people with prediabetes. Muscular metabolome analysis in the animal study revealed that DHA and EPA altered branched-chain amino acids, creatine, and glucose oxidation-related metabolites, concurrently with elevated muscular glycogen synthase and pyruvate dehydrogenase contents that promoted glucose disposal. Further myotube investigation revealed that DHA and EPA promoted muscular GLUT4 translocation by elevating Rab GTPases and target-SNARE expression. Together, DHA and EPA supplementation provides a promising approach for T2D prevention through targeting muscular glucose homeostasis, including enhancing GLUT4 translocation, glycogen synthesis, and aerobic glycolysis.

Compromised Peroxisome Proliferator-Activated Receptor γ-Mediated Impaired Placental Glucose Transport Via the Phosphatidylinositol 3-Kinase/Protein Kinase B Signaling Pathway Is Associated With Fetal Growth Restriction

Fetal growth restriction (FGR) is a condition in which a fetus cannot grow to its full potential during pregnancy. It is a leading cause of perinatal mortality and morbidity. However, the underlying etiology remains elusive. Here, we report that peroxisome proliferator-activated receptor γ (PPARγ) is inactivated in the trophoblasts of the human placenta of FGR-complicated pregnancies. In the FGR placentas, p-PI3KTyr458 and p-AKTSer473 levels were also lowered. Additionally, there was a reduction in GLUT3 and GLUT4 levels in the cell membrane. Consistently, FGR patients showed decreased glucose concentrations in both the placenta and umbilical cord blood compared with that in normal pregnancy. In mouse models, deletion of Pparg in trophoblasts and reduced uterine perfusion pressure surgery successfully induced FGR and replicated these changes. Modulating PPARγ activity using rosiglitazone or GW9662 in BeWo cells, a model of syncytiotrophoblasts, resulted in the activation or inhibition of the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, as well as the promotion or reduction of membrane translocation of GLUT3 and GLUT4, ultimately affecting glucose uptake in trophoblast cells. MK-2206 blocked these regulatory effects of rosiglitazone in BeWo cells. Furthermore, the administration of rosiglitazone encapsulated in placenta-targeting nanoparticles improved the growth and development of fetal mice in the reduced uterine perfusion pressure group. In summary, PPARγ in trophoblast cells orchestrates the translocation of GLUT3 and GLUT4 to the cellular membrane via the phosphatidylinositol 3-kinase/protein kinase B signaling pathway, thereby regulating cellular glucose uptake and transport. Dysfunctions in this mechanism are strongly associated with FGR. Therefore, targeted activation of PPARγ in the placenta may be a potentially efficacious intrauterine intervention for FGR.

The interrelated roles of RAB family proteins in the advancement of neoplastic growth

Rab Proteins, A Subfamily Of The Ras Superfamily Of Small Gtpases, Are Critical Regulators Of Intracellular Vesicular Trafficking, Which Is Intricately Linked To Various Cellular Processes. These Proteins Play Essential Roles Not Only In Maintaining Cellular Homeostasis But Also In Mediating The Complex Interplay Between Cancer Cells and Their Microenvironment. Rab Proteins Can Act As Either Oncogenic Factors Or Tumor Suppressors, With Their Functions Highly Dependent On The Cellular Context. Mechanistic Studies Have Revealed That Rab Proteins Are Involved In A Variety Of Processes, Including Vesicular Transport, Tumor Microenvironment Regulation, Autophagy, Drug Resistance, and Metabolic Regulation, and Play Either A Promotional Or Inhibitory Role In Cancer Development. Consequently, Targeting Rab Gtpases To Restore Dysregulated Vesicular Transport Systems May Offer A Promising Therapeutic Strategy To Inhibit Cancer Progression. However, It Is Equally Important To Consider The Potential Risks Of Disrupting Rab Functions, As Their Roles Are Highly Context-Dependent and May Have Opposing Effects In Different Malignancies. This Review Focuses On The Multifaceted Involvement Of Rab Family Proteins In Cancer Progression Underscores Their Importance As Potential Therapeutic Targets and Underscores The Need For A Deeper Understanding Of Their Complex Roles In Tumorigenesis.

AKT activation triggers Rab14-mediated ADAM10 translocation to the cell surface in human aortic endothelial cells

AKT (protein kinase B) activation reduces the harmful effects of advanced glycation end products (AGEs); however, the protective mechanisms remain unknown. In cultured human aortic endothelial cells (HAECs), we investigated how AKT signaling suppresses AGEs-induced intercellular adhesion molecule-1 (ICAM-1) expression. AGEs of bovine serum albumin (AGE-BSA) increased ICAM-1 expression, but this effect was abolished by pretreatment with the AKT activator SC79. SC79 activated AKT1, AKT2, and AKT3, translocated a disintegrin and metalloprotease 10 (ADAM10) to the cell surface, and induced ectodomain shedding of the receptor for AGEs (RAGE). In contrast, GI 254023X-mediated ADAM10 inhibition and siRNA-mediated ADAM10 knockdown both prevented SC79-induced RAGE ectodomain shedding. On the other hand, MK-2206, a pan-AKT inhibitor, and siRNA-mediated knockdown of AKT1, AKT2, or AKT3 prevented SC79-induced ADAM10 cell surface translocation and RAGE ectodomain shedding. Notably, Rab14 was co-immunoprecipitated with ADAM10. Following SC79 treatment, Rab14 moved to the cell surface, whereas siRNA-mediated Rab14 knockdown prevented SC79 from promoting ADAM10 cell surface translocation and RAGE ectodomain shedding and abolished SC79's ability to inhibit AGE-BSA-induced ICAM-1 expression. In conclusion, upon activation of all three isoforms, AKT suppresses AGE-BSA-induced ICAM-1 expression by inducing ADAM10-mediated RAGE ectodomain shedding. This occurs because AKT signaling boosts Rab14-dependent ADAM10 cell surface translocation.

PDHA1 Alleviates Myocardial Ischemia-Reperfusion Injury by Improving Myocardial Insulin Resistance During Cardiopulmonary Bypass Surgery in Rats

OBJECTIVE

Cardiopulmonary bypass (CPB) is a requisite technique for thoracotomy in advanced cardiovascular surgery. However, the consequent myocardial ischemia-reperfusion injury (MIRI) is the primary culprit behind cardiac dysfunction and fatal consequences post-operation. Prior research has posited that myocardial insulin resistance (IR) plays a vital role in exacerbating the progression of MIRI. Nonetheless, the exact mechanisms underlying this phenomenon remain obscure.

METHODS

We constructed pyruvate dehydrogenase E1 α subunit (PDHA1) interference and overexpression rats and used ascending aorta occlusion in an in vivo model of CPB-MIRI. We devised an in vivo model of CPB-MIRI by constructing rat models with both pyruvate dehydrogenase E1α subunit (PDHA1) interference and overexpression through ascending aorta occlusion. We analyzed myocardial glucose metabolism and the degree of myocardial injury using functional monitoring, biochemical assays, and histological analysis.

RESULTS

We discovered a clear downregulation of glucose transporter 4 (GLUT4) protein content expression in the CPB I/R model. In particular, cardiac-specific PDHA1 interference resulted in exacerbated cardiac dysfunction, significantly increased myocardial infarction area, more pronounced myocardial edema, and markedly increased cardiomyocyte apoptosis. Notably, the opposite effect was observed with PDHA1 overexpression, leading to a mitigated cardiac dysfunction and decreased incidence of myocardial infarction post-global ischemia. Mechanistically, PDHA1 plays a crucial role in regulating the protein content expression of GLUT4 on cardiomyocytes, thereby controlling the uptake and utilization of myocardial glucose, influencing the development of myocardial insulin resistance, and ultimately modulating MIRI.

CONCLUSION

Overall, our study sheds new light on the pivotal role of PDHA1 in glucose metabolism and the development of myocardial insulin resistance. Our findings hold promising therapeutic potential for addressing the deleterious effects of MIRI in patients.

Multiomics profiling of DNA methylation, microRNA, and mRNA in skeletal muscle from monozygotic twin pairs discordant for type 2 diabetes identifies dysregulated genes controlling metabolism

BACKGROUND

A large proportion of skeletal muscle insulin resistance in type 2 diabetes (T2D) is caused by environmental factors.

METHODS

By applying multiomics mRNA, microRNA (miRNA), and DNA methylation platforms in biopsies from 20 monozygotic twin pairs discordant for T2D, we aimed to delineate the epigenetic and transcriptional machinery underlying non-genetic muscle insulin resistance in T2D.

RESULTS

Using gene set enrichment analysis (GSEA), we found decreased mRNA expression of genes involved in extracellular matrix organization, branched-chain amino acid catabolism, metabolism of vitamins and cofactors, lipid metabolism, muscle contraction, signaling by receptor tyrosine kinases pathways, and translocation of glucose transporter 4 (GLUT4) to the plasma membrane in muscle from twins with T2D. Differential expression levels of one or more predicted target relevant miRNA(s) were identified for approximately 35% of the dysregulated GSEA pathways. These include miRNAs with a significant overrepresentation of targets involved in GLUT4 translocation (miR-4643 and miR-548z), signaling by receptor tyrosine kinases pathways (miR-607), and muscle contraction (miR-4658). Acquired DNA methylation changes in skeletal muscle were quantitatively small in twins with T2D compared with the co-twins without T2D. Key methylation and expression results were validated in muscle, myotubes, and/or myoblasts from unrelated subjects with T2D and controls. Finally, mimicking T2D-associated changes by overexpressing miR-548 and miR-607 in cultured myotubes decreased expression of target genes, GLUT4 and FGFR4, respectively, and impaired insulin-stimulated phosphorylation of Akt (Ser473) and TBC1D4.

CONCLUSIONS

Together, we show that T2D is associated with non- and epigenetically determined differential transcriptional regulation of pathways regulating skeletal muscle metabolism and contraction.

Skeletal muscle cystathionine γ-lyase deficiency promotes obesity and insulin resistance and results in hyperglycemia and skeletal muscle injury upon HFD in mice

OBJECTIVES

The objective of this study was to investigate whether skeletal muscle cystathionine γ-lyase (CTH) contributes to high-fat diet (HFD)-induced metabolic disorders using skeletal muscle Cth knockout (CthΔskm) mice.

METHODS

The CthΔskm mice and littermate Cth-floxed (Cthf/f) mice were fed with either HFD or chow diet for 13 weeks. Metabolomics and transcriptome analysis were used to assess the impact of CTH deficiency in skeletal muscle.

RESULTS

Metabolomics coupled with transcriptome showed that CthΔskm mice displayed impaired energy metabolism and some signaling pathways linked to insulin resistance (IR) in skeletal muscle although the mice had normal insulin sensitivity. HFD led to reduced CTH expression and impaired energy metabolism in skeletal muscle in Cthf/f mice. CTH deficiency and HFD had some common pathways enriched in the aspects of amino acid metabolism, carbon metabolism, and fatty acid metabolism. CthΔskm+HFD mice exhibited increased body weight gain, fasting blood glucose, plasma insulin, and IR, and reduced glucose transporter 4 and CD36 expression in skeletal muscle compared to Cthf/f+HFD mice. Impaired mitochondria and irregular arrangement in myofilament occurred in CthΔskm+HFD mice. Omics analysis showed differential pathways enriched between CthΔskm mice and Cthf/f mice upon HFD. More severity in impaired energy metabolism, reduced AMPK signaling, and increased oxidative stress and ferroptosis occurred in CthΔskm+HFD mice compared to Cthf/f+HFD mice.

DISCUSSION

Our results indicate that skeletal muscle CTH expression dysregulation contributes to metabolism disorders upon HFD.

Chicken GLUT4 function via enhancing mitochondrial oxidative phosphorylation and inhibiting ribosome pathway in skeletal muscle satellite cells

Glucose Transporter 4 (GLUT4) is a crucial protein facilitating glucose uptake and metabolism across cell membranes in mammals. However, information on GLUT4 in birds has historically been limited. In this study, we investigated the dynamic expression profile of chicken GLUT4 using real-time quantitative PCR (RT-qPCR) and examined its potential effects and mechanisms via GLUT4 overexpression and RNA sequencing (RNA-seq) in chicken primary skeletal muscle satellite cells (CP-SMSCs). Our results demonstrated that chicken GLUT4 is differentially expressed across tissues, with predominant expression in skeletal muscles, and across developmental stages of CP-SMSCs, with notable upregulation during the phases of cell proliferation and early differentiation. Notably, 0.1 μM insulin for 60 min significantly elevated the expression of GLUT4 in CP-SMSCs (P < 0.05). GLUT4 overexpression in CP-SMSCs promoted cell proliferation, as evidenced by Cell Counting Kit-8 (CCK-8) (P < 0.05) and 5-Ethynyl-2'-Deoxyuridine (EDU) assays (P < 0.05), and enhanced glucose consumption following 0.1 μM insulin treatment (P < 0.05). However, it inhibited glucose consumption 12 h after the addition of 5 g/L glucose (P < 0.05). After overexpressing GLUT4, we identified 302 differentially expressed genes (DEGs) in CP-SMSCs, with 134 upregulated and 168 downregulated. These DEGs are primarily enriched in pathways such as oxidative phosphorylation, ribosome, cardiac muscle contraction, ATP metabolic processes, and mitochondrial protein complexes. Specifically, in the enriched oxidative phosphorylation pathway, the upregulated DEGs (12) encode mitochondrial proteins, while the downregulated DEGs (6) are nuclear genome-derived. The ribosomal pathway is predominantly inhibited, accompanying with the downregulation of the translocase of outer mitochondrial membrane 7 (TOMM7)/translocase of inner mitochondrial membrane 8 (TIMM8A) complex responsible for mitochondrial protein transport, and a reduction in 28S (LOC121106978) and 18S (LOC112533601) ribosomal rRNAs. In conclusion, chicken GLUT4 is dynamically modulated during development and acts as an insulin responder that significantly regulates cellular glucose uptake and cell proliferation. This regulation occurs mainly through enhancing the mitochondrial oxidative phosphorylation and inhibiting ribosomal pathway.

Type 2 diabetes mellitus in adults: pathogenesis, prevention and therapy

Type 2 diabetes (T2D) is a disease characterized by heterogeneously progressive loss of islet β cell insulin secretion usually occurring after the presence of insulin resistance (IR) and it is one component of metabolic syndrome (MS), and we named it metabolic dysfunction syndrome (MDS). The pathogenesis of T2D is not fully understood, with IR and β cell dysfunction playing central roles in its pathophysiology. Dyslipidemia, hyperglycemia, along with other metabolic disorders, results in IR and/or islet β cell dysfunction via some shared pathways, such as inflammation, endoplasmic reticulum stress (ERS), oxidative stress, and ectopic lipid deposition. There is currently no cure for T2D, but it can be prevented or in remission by lifestyle intervention and/or some medication. If prevention fails, holistic and personalized management should be taken as soon as possible through timely detection and diagnosis, considering target organ protection, comorbidities, treatment goals, and other factors in reality. T2D is often accompanied by other components of MDS, such as preobesity/obesity, metabolic dysfunction associated steatotic liver disease, dyslipidemia, which usually occurs before it, and they are considered as the upstream diseases of T2D. It is more appropriate to call "diabetic complications" as "MDS-related target organ damage (TOD)", since their development involves not only hyperglycemia but also other metabolic disorders of MDS, promoting an up-to-date management philosophy. In this review, we aim to summarize the underlying mechanism, screening, diagnosis, prevention, and treatment of T2D, especially regarding the personalized selection of hypoglycemic agents and holistic management based on the concept of "MDS-related TOD".

The pivotal role of glucose transporter 1 in diabetic kidney disease

Diabetes mellitus (DM) is a significant public health problem. Diabetic kidney disease (DKD) is the most common complication of DM, and its incidence has been increasing with the increasing prevalence of DM. Given the association between DKD and mortality in patients with DM, DKD is a significant burden on public health resources. Despite its significance in DM progression, the pathogenesis of DKD remains unclear. Aberrant glucose uptake by cells is an important pathophysiological mechanism underlying DKD renal injury. Glucose is transported across the bilayer cell membrane by a glucose transporter (GLUT) located on the cell membrane. Multiple GLUT proteins have been identified in the kidney, and GLUT1 is one of the most abundantly expressed isoforms. GLUT1 is a crucial regulator of intracellular glucose metabolism and plays a key pathological role in the phenotypic changes in DKD mesangial cells. In an attempt to understand the pathogenesis of DKD better, we here present a review of studies on the role of GLUT1 in the development and progression of DKD.

Study of the Effects of Deuterium-Depleted Water on the Expression of GLUT4 and Insulin Resistance in the Muscle Cell Line C2C12

Deuterium-depleted water (DDW) is used in the treatment of many diseases, including cancer and diabetes. To detect the effect of DDW on gene expression and activation of the insulin-responsive transporter GLUT4 as a mechanism for improving the pathology of diabetes, we investigated the GLUT4 expression and glucose uptake at various concentrations of DDW using the myoblast cell line C2C12 differentiated into myotubes. GLUT4 gene expression significantly increased under deuterium depletion, reaching a maximum value at a deuterium concentration of approximately 50 ppm, which was approximately nine times that of natural water with a deuterium concentration of 150 ppm. GLUT4 protein also showed an increase at similar DDW concentrations. The membrane translocation of GLUT4 by insulin stimulation reached a maximum value at a deuterium concentration of approximately 50-75 ppm, which was approximately 2.2 times that in natural water. Accordingly, glucose uptake also increased by up to 2.2 times at a deuterium concentration of approximately 50 ppm. Drug-induced insulin resistance was attenuated, and the glucose uptake was four times higher in the presence of 10 ng/mL TNF-α and three times higher in the presence of 1 μg/mL resistin at a deuterium concentration of approximately 50 ppm relative to natural water. These results suggest that DDW promotes GLUT4 expression and insulin-stimulated activation in muscle cells and reduces insulin resistance, making it an effective treatment for diabetes.

Deciphering the role of classical oestrogen receptor in insulin resistance and type 2 diabetes mellitus: From molecular mechanism to clinical evidence

The biological actions of oestrogen are mediated by the oestrogen receptor α or β (ERα or ERβ), which are members of a broad nuclear receptor superfamily. Numerous in vivo and in vitro studies have demonstrated that loss of circulating oestrogen modulated by classical ERα and ERβ led to rapid changes in pancreatic β-cell and islet function, GLUT4 expression, insulin sensitivity and glucose tolerance, dysfunctional lipid homeostasis, oxidative stress, and inflammatory cascades. Remarkably, 17β-oestradiol (E2) can completely reverse these effects. This review evaluates the current understanding of the protective role of classical ER in critical pathways and molecular mechanisms associated with insulin resistance and type 2 diabetes mellitus (T2DM). It also examines the effectiveness of menopausal hormone therapy (MHT) in reducing the risk of developing T2DM in menopausal women. Clinical trials have shown the protective effects of MHT on glucose metabolism, which may be useful to treat T2DM in perimenopausal women. However, there are concerns about E2's potential side effects of obesity and hyperlipidaemia in menopausal women. Further studies are warranted to gain understanding and find other oestrogen alternatives for treatment of insulin resistance and T2DM in postmenopausal women.

Unlocking liver health: Can tackling myosteatosis spark remission in metabolic dysfunction-associated steatotic liver disease?

Myosteatosis is highly prevalent in metabolic dysfunction-associated steatotic liver disease (MASLD) and could reciprocally impact liver function. Decreasing muscle fat could be indirectly hepatoprotective in MASLD. We conducted a review to identify interventions reducing myosteatosis and their impact on liver function. Non-pharmacological interventions included diet (caloric restriction or lipid enrichment), bariatric surgery and physical activity. Caloric restriction in humans achieving a mean weight loss of 3% only reduces muscle fat. Lipid-enriched diet increases liver fat in human with no impact on muscle fat, except sphingomyelin-enriched diet which reduces both lipid contents exclusively in pre-clinical studies. Bariatric surgery, hybrid training (resistance exercise and electric stimulation) or whole-body vibration in human decrease both liver and muscle fat. Physical activity impacts both phenotypes by reducing local and systemic inflammation, enhancing insulin sensitivity and modulating the expression of key mediators of the muscle-liver-adipose tissue axis. The combination of diet and physical activity acts synergistically in liver, muscle and white adipose tissue, and further decrease muscle and liver fat. Several pharmacological interventions (patchouli alcohol, KBP-089, 2,4-dinitrophenol methyl ether, adipoRon and atglistatin) and food supplementation (vitamin D or resveratrol) improve liver and muscle phenotypes in pre-clinical studies by increasing fatty acid oxidation and anti-inflammatory properties. These interventions are effective in reducing myosteatosis in MASLD while addressing the liver disease itself. This review supports that disturbances in inter-organ crosstalk are key pathophysiological mechanisms involved in MASLD and myosteatosis pathogenesis. Focusing on the skeletal muscle might offer new therapeutic strategies to treat MASLD by modulating the interactions between liver and muscles.

Depletion of TBC1D4 Improves the Metabolic Exercise Response by Overcoming Genetically Induced Peripheral Insulin Resistance

The Rab-GTPase-activating protein (RabGAP) TBC1D4 (AS160) represents a key component in the regulation of glucose transport into skeletal muscle and white adipose tissue (WAT) and is therefore crucial during the development of insulin resistance and type 2 diabetes. Increased daily activity has been shown to be associated with improved postprandial hyperglycemia in allele carriers of a loss-of-function variant in the human TBC1D4 gene. Using conventional Tbc1d4-deficient mice (D4KO) fed a high-fat diet, we show that moderate endurance exercise training leads to substantially improved glucose and insulin tolerance and enhanced expression levels of markers for mitochondrial activity and browning in WAT from D4KO animals. Importantly, in vivo and ex vivo analyses of glucose uptake revealed increased glucose clearance in interscapular brown adipose tissue and WAT from trained D4KO mice. Thus, chronic exercise is able to overcome the genetically induced insulin resistance caused by Tbc1d4 depletion. Gene variants in TBC1D4 may be relevant in future precision medicine as determinants of exercise response.

ARTICLE HIGHLIGHTS

A narrative review on the mechanism of natural flavonoids in improving glucolipid metabolism disorders

Glucolipid metabolism disorder (GLMD) is a complex chronic disease characterized by glucose and lipid metabolism disorders with a complex and diverse etiology and rapidly increasing incidence. Many studies have identified the role of flavonoids in ameliorating GLMD, with mechanisms related to peroxisome proliferator-activated receptors, nuclear factor kappa-B, AMP-activated protein kinase, nuclear factor (erythroid-derived 2)-like 2, glucose transporter type 4, and phosphatidylinositol-3-kinase/protein kinase B pathway. However, a comprehensive summary of the flavonoid effects on GLMD is lacking. This study reviewed the roles and mechanisms of natural flavonoids with different structures in the treatment of GLMD reported globally in the past 5 years and provides a reference for developing flavonoids as drugs for treating GLMD.

RAB31 in glioma-derived endothelial cells promotes glioma cell invasion via extracellular vesicle-mediated enrichment of MYO1C

Extracellular vesicles (EV), important messengers in intercellular communication, can load and transport various bioactive components and participate in different biological processes. We previously isolated glioma human endothelial cells (GhECs) and found that GhECs, rather than normal human brain endothelial cells (NhECs), exhibit specific enrichment of MYO1C into EVs and promote the migration of glioma cells. In this study, we explored the mechanism by which MYO1C is secreted into EVs. We report that such secretion is dependent on RAB31, RAB27B, and FAS. When expression of RAB31 increases, MYO1C is enriched in secretory EVs. Finally, we identified an EV export mechanism for MYO1C that promotes glioma cell invasion and is dependent on RAB31 in GhECs. In summary, our data indicate that the knockdown of RAB31 can reduce enrichment of MYO1C in extracellular vesicles, thereby attenuating the promotion of glioma cell invasion by GhEC-EVs.

Biochemical Toxicological Study of Insulin Overdose in Rats: A Forensic Perspective

Due to nonspecific pathological changes and the rapid degradation of insulin in postmortem blood samples, the identification of the cause of death during insulin overdose has always been a difficulty in forensic medicine. At present, there is a lack of studies on the toxicological changes and related mechanisms of an insulin overdose, and the specific molecular markers of insulin overdose are still unclear. In this study, an animal model of insulin overdose was established, and 24 SD rats were randomly divided into a control group, insulin overdose group, and a recovery group (n = 8). We detected the biochemical changes and analyzed the toxicological mechanism of an insulin overdose. The results showed that after insulin overdose, the rats developed irregular convulsions, Eclampsia, Opisthotonos, and other symptoms. The levels of glucose, glycogen, and C-peptide in the body decreased significantly, while the levels of lactate, insulin, and glucagon increased significantly. The decrease in plasma K+ was accompanied by the increase in skeletal muscle K+. The PI3K-AKT signaling pathway was significantly activated in skeletal muscle, and the translocation of GLUT4/Na+-K+-ATPase to sarcolemma was significantly increased. Rare glycogenic hepatopathy occurred in the recovery group after insulin overdose. Our study showed that insulin overdose also plays a role in skeletal muscle cells, mainly through the PI3K-Akt signaling pathway. Therefore, the detection of signaling pathway proteins of the skeletal muscle cell membrane GLUT4 and Na+-K+-ATPase has a certain auxiliary diagnostic value for forensic insulin overdose identification. Glycogen detection in the liver and skeletal muscle is important for the diagnosis of insulin overdose, but it still needs to be differentiated from other causes of death. Skeletal muscle has great potential for insulin detection, and the ratio of insulin to the C-peptide (I:C) can determine whether an exogenous insulin overdose is present.

A Novel Role for DOC2B in Ameliorating Palmitate-Induced Glucose Uptake Dysfunction in Skeletal Muscle Cells via a Mechanism Involving β-AR Agonism and Cofilin

Diet-related lipotoxic stress is a significant driver of skeletal muscle insulin resistance (IR) and type 2 diabetes (T2D) onset. β2-adrenergic receptor (β-AR) agonism promotes insulin sensitivity in vivo under lipotoxic stress conditions. Here, we established an in vitro paradigm of lipotoxic stress using palmitate (Palm) in rat skeletal muscle cells to determine if β-AR agonism could cooperate with double C-2-like domain beta (DOC2B) enrichment to promote skeletal muscle insulin sensitivity under Palm-stress conditions. Previously, human T2D skeletal muscles were shown to be deficient for DOC2B, and DOC2B enrichment resisted IR in vivo. Our Palm-stress paradigm induced IR and β-AR resistance, reduced DOC2B protein levels, triggered cytoskeletal cofilin phosphorylation, and reduced GLUT4 translocation to the plasma membrane (PM). By enhancing DOC2B levels in rat skeletal muscle, we showed that the deleterious effects of palmitate exposure upon cofilin, insulin, and β-AR-stimulated GLUT4 trafficking to the PM and glucose uptake were preventable. In conclusion, we revealed a useful in vitro paradigm of Palm-induced stress to test for factors that can prevent/reverse skeletal muscle dysfunctions related to obesity/pre-T2D. Discerning strategies to enrich DOC2B and promote β-AR agonism can resist skeletal muscle IR and halt progression to T2D.

Insulin resistance induced by long-term hyperinsulinemia abolishes the effects of acute insulin exposure on cell-surface nicotinic acetylcholine receptor levels and actin cytoskeleton morphology

Using CHO-K1/A5 cells, a clonal cell line that robustly expresses adult muscle-type nicotinic acetylcholine receptor (nAChR), we explored whether insulin resistance in these mammalian cells affects cell-surface expression of the nAChR, its endocytic internalization, and actin cytoskeleton integrity. Acute nanomolar insulin stimulation resulted in a slow increase in nAChR cell-surface levels, reaching maximum levels at ∼1 h. Long periods of insulin incubation caused CHO-K1/A5 cells to become insulin resistant, as previously observed with several other cell types. Furthermore, long-term insulin treatment abolished the effects of short-term insulin exposure on cell-surface nAChR levels, suggestive of a desensitization phenomenon. It also affected the kinetics of ligand-induced nAChR internalization. Since the integrity of the cortical actin cytoskeleton affects nAChR endocytosis, we also studied the effects of long-term insulin treatment on this meshwork. We found that it significantly affected the cortical actin morphology of CHO-K1/A5 cells and the response of the actin cytoskeleton to a subsequent short-term insulin stimulus. Overall, the present results show for the first time the effects of insulin signaling on cell-surface nAChR expression and actin cytoskeleton-associated internalization.

LRRK2 negatively regulates glucose tolerance via regulation of membrane translocation of GLUT4 in adipocytes

Epidemiological studies have shown that abnormalities of glucose metabolism are involved in leucine-rich repeat kinase 2 (LRRK2)-associated Parkinson's disease (PD). However, the physiological significance of this association is unclear. In the present study, we investigated the effect of LRRK2 on high-fat diet (HFD)-induced glucose intolerance using Lrrk2-knockout (KO) mice. We found for the first time that HFD-fed KO mice display improved glucose tolerance compared with their wild-type (WT) counterparts. In addition, high serum insulin and leptin, as well as low serum adiponectin resulting from HFD in WT mice were improved in KO mice. Using western blotting, we found that Lrrk2 is highly expressed in adipose tissues compared with other insulin-related tissues that are thought to be important in glucose tolerance, including skeletal muscle, liver, and pancreas. Lrrk2 expression and phosphorylation of its kinase substrates Rab8a and Rab10 were significantly elevated after HFD treatment in WT mice. In cell culture experiments, treatment with a LRRK2 kinase inhibitor stimulated insulin-dependent membrane translocation of glucose transporter 4 (Glut4) and glucose uptake in mouse 3T3-L1 adipocytes. We conclude that increased LRRK2 kinase activity in adipose tissue exacerbates glucose tolerance by suppressing Rab8- and Rab10-mediated GLUT4 membrane translocation.

Polymorphism and expression of the HMGA1 gene and association with tail fat deposition in Hu sheep

Hu sheep is an excellent short fat-tailed breed in China. Fat deposition in Hu sheep tail affects carcass quality and consumes a lot of energy, leading to an increase in feed cost. The objective of this study was to analyze the effects of HMGA1 polymorphism on tail fat weight in Hu sheep. Partial coding and non-coding sequences of HMGA1 were amplified with PCR and single nucleotide polymorphisms (SNP) of HMGA1 in 1163 Hu sheep were detected using DNA sequencing and KASPar technology. RT-qPCR analysis was performed to test HMGA1 expression in different tissues. The results showed that the expression of HMGA1 was higher in the duodenum, liver, spleen, kidney, and lung than in the heart, muscle, rumen, tail fat, and lymph. A mutation, g.5312 C > T, was detected in HMGA1; g.5312 C > T was significantly associated with tail fat weight, relative weight of tail fat (body weight), and relative weight of tail fat (carcass) (p < 0.05). The tail fat weight of the TT genotype was remarkably higher than that of the CC and TC genotypes. Therefore, HMGA1 can be used as a genetic marker for marker-assisted selection of tail fat weight in Hu sheep.

Palmitate-induced insulin resistance causes actin filament stiffness and GLUT4 mis-sorting without altered Akt signalling

Skeletal muscle insulin resistance, a major contributor to type 2 diabetes, is linked to the consumption of saturated fats. This insulin resistance arises from failure of insulin-induced translocation of glucose transporter type 4 (GLUT4; also known as SLC2A4) to the plasma membrane to facilitate glucose uptake into muscle. The mechanisms of defective GLUT4 translocation are poorly understood, limiting development of insulin-sensitizing therapies targeting muscle glucose uptake. Although many studies have identified early insulin signalling defects and suggest that they are responsible for insulin resistance, their cause-effect has been debated. Here, we find that the saturated fat palmitate (PA) causes insulin resistance owing to failure of GLUT4 translocation in skeletal muscle myoblasts and myotubes without impairing signalling to Akt2 or AS160 (also known as TBC1D4). Instead, PA altered two basal-state events: (1) the intracellular localization of GLUT4 and its sorting towards a perinuclear storage compartment, and (2) actin filament stiffness, which prevents Rac1-dependent actin remodelling. These defects were triggered by distinct mechanisms, respectively protein palmitoylation and endoplasmic reticulum (ER) stress. Our findings highlight that saturated fats elicit muscle cell-autonomous dysregulation of the basal-state machinery required for GLUT4 translocation, which 'primes' cells for insulin resistance.

AMPKγ3 Controls Muscle Glucose Uptake in Recovery From Exercise to Recapture Energy Stores

Exercise increases muscle glucose uptake independently of insulin signaling and represents a cornerstone for the prevention of metabolic disorders. Pharmacological activation of the exercise-responsive AMPK in skeletal muscle has been proven successful as a therapeutic approach to treat metabolic disorders by improving glucose homeostasis through the regulation of muscle glucose uptake. However, conflicting observations cloud the proposed role of AMPK as a necessary regulator of muscle glucose uptake during exercise. We show that glucose uptake increases in human skeletal muscle in the absence of AMPK activation during exercise and that exercise-stimulated AMPKγ3 activity strongly correlates to muscle glucose uptake in the postexercise period. In AMPKγ3-deficient mice, muscle glucose uptake is normally regulated during exercise and contractions but impaired in the recovery period from these stimuli. Impaired glucose uptake in recovery from exercise and contractions is associated with a lower glucose extraction, which can be explained by a diminished permeability to glucose and abundance of GLUT4 at the muscle plasma membrane. As a result, AMPKγ3 deficiency impairs muscle glycogen resynthesis following exercise. These results identify a physiological function of the AMPKγ3 complex in human and rodent skeletal muscle that regulates glucose uptake in recovery from exercise to recapture muscle energy stores.

ARTICLE HIGHLIGHTS

Exercise-induced activation of AMPK in skeletal muscle has been proposed to regulate muscle glucose uptake in recovery from exercise. This study investigated whether the muscle-specific AMPKγ3-associated heterotrimeric complex was involved in regulating muscle glucose metabolism in recovery from exercise. The findings support that exercise-induced activation of the AMPKγ3 complex in human and mouse skeletal muscle enhances glucose uptake in recovery from exercise via increased translocation of GLUT4 to the plasma membrane. This work uncovers the physiological role of the AMPKγ3 complex in regulating muscle glucose uptake that favors replenishment of the muscle cellular energy stores.

Dissecting the Interrelationship between COVID-19 and Diabetes Mellitus

COVID-19 disease, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has led to enormous morbidity and mortality worldwide. After gaining entry into the human host, the virus initially infects the upper and lower respiratory tract, subsequently invading multiple organs, including the pancreas. While on one hand, diabetes mellitus (DM) is a significant risk factor for severe COVID-19 infection and associated death, recent reports have shown the onset of DM in COVID-19-recovered patients. SARS-CoV-2 infiltrates the pancreatic islets and activates stress response and inflammatory signaling pathways, impairs glucose metabolism, and consequently leads to their death. Indeed, the pancreatic autopsy samples of COVID-19 patients reveal the presence of SARS-CoV-2 particles in β-cells. The current review describes how the virus enters the host cells and activates an immunological response. Further, it takes a closer look into the interrelationship between COVID-19 and DM with the aim to provide mechanistic insights into the process by which SARS-CoV-2 infects the pancreas and mediates dysfunction and death of endocrine islets. The effects of known anti-diabetic interventions for COVID-19 management are also discussed. The application of mesenchymal stem cells (MSCs) as a future therapy for pancreatic β-cells damage to reverse COVID-19-induced DM is also emphasized.

Insulin alleviates murine colitis through microbiome alterations and bile acid metabolism

BACKGROUND

Insulin has been reported to exhibit anti-inflammatory activities in the context of bowel inflammation. However, the role of the interaction between insulin and the microbiota in gut health is unclear. Our goal was to investigate the mechanism of action of insulin in bowel inflammation and the relationship between insulin and the gut microbiota.

METHODS

We used acute and chronic murine models of inflammatory bowel disease (IBD) to evaluate whether insulin influences the progression of colitis. Colonic tissues, the host metabolome and the gut microbiome were analyzed to investigate the relationship among insulin treatment, the microbiome, and disease. Experiments involving antibiotic (Abx) treatment and fecal microbiota transplantation (FMT) confirmed the association among the gut microbiota, insulin and IBD. In a series of experiments, we further defined the mechanisms underlying the anti-inflammatory effects of insulin.

RESULTS

We found that low-dose insulin treatment alleviated intestinal inflammation but did not cause death. These effects were dependent on the gut microbiota, as confirmed by experiments involving Abx treatment and FMT. Using untargeted metabolomic profiling and 16S rRNA sequencing, we discovered that the level of the secondary bile acid lithocholic acid (LCA) was notably increased and the LCA levels were significantly associated with the abundance of Blautia, Enterorhadus and Rumi-NK4A214_group. Furthermore, LCA exerted anti-inflammatory effects by activating a G-protein-coupled bile acid receptor (TGR5), which inhibited the polarization of classically activated (M1) macrophages.

CONCLUSION

Together, these data suggest that insulin alters the gut microbiota and affects LCA production, ultimately delaying the progression of IBD.

Impaired Insulin Signaling Mediated by the Small GTPase Rac1 in Skeletal Muscle of the Leptin-Deficient Obese Mouse

Insulin-stimulated glucose uptake in skeletal muscle is mediated by the glucose transporter GLUT4. The small GTPase Rac1 acts as a switch of signal transduction that regulates GLUT4 translocation to the plasma membrane following insulin stimulation. However, it remains obscure whether signaling cascades upstream and downstream of Rac1 in skeletal muscle are impaired by obesity that causes insulin resistance and type 2 diabetes. In an attempt to clarify this point, we investigated Rac1 signaling in the leptin-deficient (Lepob/ob) mouse model. Here, we show that insulin-stimulated GLUT4 translocation and Rac1 activation are almost completely abolished in Lepob/ob mouse skeletal muscle. Phosphorylation of the protein kinase Akt2 and plasma membrane translocation of the guanine nucleotide exchange factor FLJ00068 following insulin stimulation were also diminished in Lepob/ob mice. On the other hand, the activation of another small GTPase RalA, which acts downstream of Rac1, by the constitutively activated form of Akt2, FLJ00068, or Rac1, was partially abrogated in Lepob/ob mice. Taken together, we conclude that insulin-stimulated glucose uptake is impaired by two mechanisms in Lepob/ob mouse skeletal muscle: one is the complete inhibition of Akt2-mediated activation of Rac1, and the other is the partial inhibition of RalA activation downstream of Rac1.

Research progress into adipose tissue macrophages and insulin resistance

In recent years, there has been an increasing incidence of metabolic syndrome, type 2 diabetes, and cardiovascular events related to insulin resistance. As one of the target organs for insulin, adipose tissue is essential for maintaining in vivo immune homeostasis and metabolic regulation. Currently, the specific adipose tissue mechanisms involved in insulin resistance remain incompletely understood. There is increasing evidence that the process of insulin resistance is mostly accompanied by a dramatic increase in the number and phenotypic changes of adipose tissue macrophages (ATMs). In this review, we discuss the origins and functions of ATMs, some regulatory factors of ATM phenotypes, and the mechanisms through which ATMs mediate insulin resistance. We explore how ATM phenotypes contribute to insulin resistance in adipose tissue. We expect that modulation of ATM phenotypes will provide a novel strategy for the treatment of diseases associated with insulin resistance.

Alternative glucose uptake mediated by β-catenin/RSK1 axis under stress stimuli in mammalian cells

Cells adapt to stress conditions by increasing glucose uptake as cytoprotective strategy. The efficiency of glucose uptake is determined by the translocation of glucose transporters (GLUTs) from cytosolic vesicles to cellular membranes in many tissues and cells. GLUT translocation is tightly controlled by the activation of Tre-2/BUB2/CDC16 1 domain family 4 (TBC1D4) via its phosphorylation. The mechanisms of glucose uptake under stress conditions remain to be clarified. In this study, we surprisingly found that glucose uptake is apparently increased for the early response to three stress stimuli, glucose starvation and the exposure to lipopolysaccharide (LPS) or deoxynivalenol (DON). The stress-induced glucose uptake was mainly controlled by the increment of β-catenin level and the activation of RSK1. Mechanistically, β-catenin directly interacted with RSK1 and TBC1D4, acting as the scaffold protein to recruit activated RSK1 to promote the phosphorylation of TBC1D4. In addition, β-catenin was further stabilized due to the inhibition of GSK3β kinase activity which is caused by activated RSK1 phosphorylating GSK3β at Ser9. In general, this triple protein complex consisting of β-catenin, phosphorylated RSK1, and TBC1D4 were increased in the early response to these stress signals, and consequently, further promoted the phosphorylation of TBC1D4 to facilitate the translocation of GLUT4 to the cell membrane. Our study revealed that the β-catenin/RSK1 axis contributed to the increment of glucose uptake for cellular adaption to these stress conditions, shedding new insights into cellular energy utilization under stress.

Measurement of GLUT4 Traffic to and from the Cell Surface in Muscle Cells

Elevated blood glucose following a meal is cleared by insulin-stimulated glucose entry into muscle and fat cells. The hormone increases the amount of the glucose transporter GLUT4 at the plasma membrane in these tissues at the expense of preformed intracellular pools. In addition, muscle contraction also increases glucose uptake via a gain in GLUT4 at the plasma membrane. Regulation of GLUT4 levels at the cell surface could arise from alterations in the rate of its exocytosis, endocytosis, or both. Hence, methods that can independently measure these traffic parameters for GLUT4 are essential to understanding the mechanism of regulation of membrane traffic of the transporter. Here, we describe cell population-based assays to measure the steady-state levels of GLUT4 at the cell surface, as well as to separately measure the rates of GLUT4 endocytosis and endocytosis. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Measuring steady-state cell surface GLUT4myc Basic Protocol 2: Measuring steady-state cell surface GLUT4-HA Basic Protocol 3: Measuring GLUT4myc endocytosis Basic Protocol 4: Measuring GLUT4myc exocytosis.

PICK1-Deficient Mice Maintain Their Glucose Tolerance During Diet-Induced Obesity

Context

Metabolic disorders such as obesity represent a major health challenge. Obesity alone has reached epidemic proportions, with at least 2.8 million people worldwide dying annually from diseases caused by overweight or obesity. The brain-metabolic axis is central to maintain homeostasis under metabolic stress via an intricate signaling network of hormones. Protein interacting with C kinase 1 (PICK1) is important for the biogenesis of various secretory vesicles, and we have previously shown that PICK1-deficient mice have impaired secretion of insulin and growth hormone.

Objective

The aim was to investigate how global PICK1-deficient mice respond to high-fat diet (HFD) and assess its role in insulin secretion in diet-induced obesity.

Methods

We characterized the metabolic phenotype through assessment of body weight, composition, glucose tolerance, islet morphology insulin secretion in vivo, and glucose-stimulated insulin secretion ex vivo.

Results

PICK1-deficient mice displayed similar weight gain and body composition as wild-type (WT) mice following HFD. While HFD impaired glucose tolerance of WT mice, PICK1-deficient mice were resistant to further deterioration of their glucose tolerance compared with already glucose-impaired chow-fed PICK1-deficient mice. Surprisingly, mice with β-cell-specific knockdown of PICK1 showed impaired glucose tolerance both on chow and HFD similar to WT mice.

Conclusion

Our findings support the importance of PICK1 in overall hormone regulation. However, importantly, this effect is independent of the PICK1 expression in the β-cell, whereby global PICK1-deficient mice resist further deterioration of their glucose tolerance following diet-induced obesity.

Mustn1 ablation in skeletal muscle results in increased glucose tolerance concomitant with upregulated GLUT expression in male mice

Glucose homeostasis is closely regulated to maintain energy requirements of vital organs and skeletal muscle plays a crucial role in this process. Mustn1 is expressed during embryonic and postnatal skeletal muscle development and its function has been implicated in myogenic differentiation and myofusion. Whether Mustn1 plays a role in glucose homeostasis in anyway remains largely unknown. As such, we deleted Mustn1 in skeletal muscle using a conditional knockout (KO) mouse approach. KO mice did not reveal any specific gross phenotypic alterations in skeletal muscle. However, intraperitoneal glucose tolerance testing (IPGTT) revealed that 2-month-old male KO mice had significantly lower glycemia than their littermate wild type (WT) controls. These findings coincided with mRNA changes in genes known to be involved in glucose metabolism, tolerance, and insulin sensitivity; 2-month-old male KO mice had significantly higher expression of GLUT1 and GLUT10 transporters, MUP-1 while OSTN expression was lower. These differences in glycemia and gene expression were statistically insignificant after 4 months. Identical experiments in female KO and WT control mice did not indicate any differences at any age. Our results suggest a link between Mustn1 expression and glucose homeostasis during a restricted period of skeletal muscle development/maturation. While this is an observational study, Mustn1's relationship to glucose homeostasis appears to be more complex with a possible connection to other key proteins such as GLUTs, MUP-1, and OSTN. Additionally, our data indicate temporal and sex differences. Lastly, our findings strengthen the notion that Mustn1 plays a role in the metabolic capacity of skeletal muscle.

microRNA-96 targets the INS/AKT/GLUT4 signaling axis: Association with and effect on diabetic retinopathy

Background

miR-96-5p is a highly expressed microRNA in the retina of subjects with diabetes. The INS/AKT/GLUT4 signaling axis is the main cell signaling pathway of glucose uptake in cells. Here, we investigated the role of miR-96-5p in this signaling pathway.

Methods

Expression levels of miR-96-5p and its target genes were measured under high glucose conditions, in the retina of streptozotocin-induced diabetic mice, in the retina of AAV-2-eGFP-miR-96 or GFP intravitreal injected mice and in the retina of human donors with diabetic retinopathy (DR). MTT, wound healing, tube formation, Western blot, TUNEL, angiogenesis assays and hematoxylin-eosin staining of the retinal sections were performed.

Results

miR-96-5p expression was increased under high glucose conditions in mouse retinal pigment epithelial (mRPE) cells, in the retina of mice receiving AAV-2 carrying miR-96 and STZ-treated mice. Expression of the miR-96-5p target genes related to the INS/AKT/GLUT4 signaling pathway was reduced following miR-96-5p overexpression. mmu-miR-96-5p expression decreased cell proliferation and thicknesses of retinal layers. Cell migration, tube formation, vascular length, angiogenesis, and TUNEL-positive cells were increased.

Conclusions

In in vitro and in vivo studies and in human retinal tissues, miR-96-5p regulated the expression of the PIK3R1, PRKCE, AKT1, AKT2, and AKT3 genes in the INS/AKT axis and some genes involved in GLUT4 trafficking, such as Pak1, Snap23, RAB2a, and Ehd1. Because disruption of the INS/AKT/GLUT4 signaling axis causes advanced glycation end product accumulation and inflammatory responses, the inhibition of miR-96-5p expression could ameliorate DR.

Glucose transporter 4: Insulin response mastermind, glycolysis catalyst and treatment direction for cancer progression

The glucose transporter family (GLUT) consists of fourteen members. It is responsible for glucose homeostasis and glucose transport from the extracellular space to the cell cytoplasm to further cascade catalysis. GLUT proteins are encoded by the solute carrier family 2 (SLC2) genes and are members of the major facilitator superfamily of membrane transporters. Moreover, different GLUTs also have their transporter kinetics and distribution, so each GLUT member has its uniqueness and importance to play essential roles in human physiology. Evidence from many studies in the field of diabetes showed that GLUT4 travels between the plasma membrane and intracellular vesicles (GLUT4-storage vesicles, GSVs) and that the PI3K/Akt pathway regulates this activity in an insulin-dependent manner or by the AMPK pathway in response to muscle contraction. Moreover, some published results also pointed out that GLUT4 mediates insulin-dependent glucose uptake. Thus, dysfunction of GLUT4 can induce insulin resistance, metabolic reprogramming in diverse chronic diseases, inflammation, and cancer. In addition to the relationship between GLUT4 and insulin response, recent studies also referred to the potential upstream transcription factors that can bind to the promoter region of GLUT4 to regulating downstream signals. Combined all of the evidence, we conclude that GLUT4 has shown valuable unknown functions and is of clinical significance in cancers, which deserves our in-depth discussion and design compounds by structure basis to achieve therapeutic effects. Thus, we intend to write up a most updated review manuscript to include the most recent and critical research findings elucidating how and why GLUT4 plays an essential role in carcinogenesis, which may have broad interests and impacts on this field.

Role of Hydroxytyrosol and Oleuropein in the Prevention of Aging and Related Disorders: Focus on Neurodegeneration, Skeletal Muscle Dysfunction and Gut Microbiota

Aging is a multi-faceted process caused by the accumulation of cellular damage over time, associated with a gradual reduction of physiological activities in cells and organs. This degeneration results in a reduced ability to adapt to homeostasis perturbations and an increased incidence of illnesses such as cognitive decline, neurodegenerative and cardiovascular diseases, cancer, diabetes, and skeletal muscle pathologies. Key features of aging include a chronic low-grade inflammation state and a decrease of the autophagic process. The Mediterranean diet has been associated with longevity and ability to counteract the onset of age-related disorders. Extra virgin olive oil, a fundamental component of this diet, contains bioactive polyphenolic compounds as hydroxytyrosol (HTyr) and oleuropein (OLE), known for their antioxidant, anti-inflammatory, and neuroprotective properties. This review is focused on brain, skeletal muscle, and gut microbiota, as these systems are known to interact at several levels. After the description of the chemistry and pharmacokinetics of HTyr and OLE, we summarize studies reporting their effects in in vivo and in vitro models of neurodegenerative diseases of the central/peripheral nervous system, adult neurogenesis and depression, senescence and lifespan, and age-related skeletal muscle disorders, as well as their impact on the composition of the gut microbiota.

Aqueous extract of Sanghuangporus baumii induces autophagy to inhibit cervical carcinoma growth

Sanghuangporus baumii, an edible fungus rich in heteropolysaccharides, has been found to have some anti-cervical cancer effects. In the current study, the effects of an aqueous extract of S. baumii on cervical cancer were investigated in a U14 cervical carcinoma cell implanted female Kunming mouse model. An aqueous extract of S. baumii (SHWE) was administered to tumor-bearing mice by gavage for 21 days. SHWE treatment significantly inhibited tumor growth by 67.4% at a dose of 400 mg per kg bodyweight. Transcriptomic results showed that the expression of key genes GABARAP, VMP1, VAMP8 and STX17 which are involved in the autophagy pathway was regulated after SHWE treatment, suggesting that SHWE may induce autophagy in tumors. The results were further confirmed by measuring the LC3II/LC3I ratio using western blotting. Moreover, some differentially expressed genes were involved in the insulin signaling pathway, implying that SHWE induced autophagy by disturbing glucose uptake and utilization in tumors. The analysis of the gut microbiota indicated that SHWE treatment stimulated the proliferation of Akkermansia, a well-known probiotic that presented benefits in metabolic regulation and cancer therapy. In conclusion, SHWE administration modified the gut microbiota, disturbed the glucose metabolism and induced autophagy in tumors, and then inhibited the development of cervical carcinoma in vivo.

Enhanced protein acetylation initiates fatty acid-mediated inhibition of cardiac glucose transport

Fatty acids (FAs) rapidly and efficiently reduce cardiac glucose uptake in the Randle cycle or glucose-FA cycle. This fine-tuned physiological regulation is critical to allow optimal substrate allocation during fasted and fed states. However, the mechanisms involved in the direct FA-mediated control of glucose transport have not been totally elucidated yet. We previously reported that leucine and ketone bodies, other cardiac substrates, impair glucose uptake by increasing global protein acetylation from acetyl-CoA. As FAs generate acetyl-CoA as well, we postulated that protein acetylation is enhanced by FAs and participates in their inhibitory action on cardiac glucose uptake. Here, we demonstrated that both palmitate and oleate promoted a rapid increase in protein acetylation in primary cultured adult rat cardiomyocytes, which correlated with an inhibition of insulin-stimulated glucose uptake. This glucose absorption deficit was caused by an impairment in the translocation of vesicles containing the glucose transporter GLUT4 to the plasma membrane, although insulin signaling remained unaffected. Interestingly, pharmacological inhibition of lysine acetyltransferases (KATs) prevented this increase in protein acetylation and glucose uptake inhibition induced by FAs. Similarly, FA-mediated inhibition of insulin-stimulated glucose uptake could be prevented by KAT inhibitors in perfused hearts. To summarize, enhanced protein acetylation can be considered as an early event in the FA-induced inhibition of glucose transport in the heart, explaining part of the Randle cycle.NEW & NOTEWORTHY Our results show that cardiac metabolic overload by oleate or palmitate leads to increased protein acetylation inhibiting GLUT4 translocation to the plasma membrane and glucose uptake. This observation suggests an additional regulation mechanism in the physiological glucose-FA cycle originally discovered by Randle.

Regulation of De Novo Lipid Synthesis by the Small GTPase Rac1 in the Adipogenic Differentiation of Progenitor Cells from Mouse White Adipose Tissue

White adipocytes act as lipid storage, and play an important role in energy homeostasis. The small GTPase Rac1 has been implicated in the regulation of insulin-stimulated glucose uptake in white adipocytes. Adipocyte-specific rac1-knockout (adipo-rac1-KO) mice exhibit atrophy of subcutaneous and epididymal white adipose tissue (WAT); white adipocytes in these mice are significantly smaller than controls. Here, we aimed to investigate the mechanisms underlying the aberrations in the development of Rac1-deficient white adipocytes by employing in vitro differentiation systems. Cell fractions containing adipose progenitor cells were obtained from WAT and subjected to treatments that induced differentiation into adipocytes. In concordance with observations in vivo, the generation of lipid droplets was significantly attenuated in Rac1-deficient adipocytes. Notably, the induction of various enzymes responsible for de novo synthesis of fatty acids and triacylglycerol in the late stage of adipogenic differentiation was almost completely suppressed in Rac1-deficient adipocytes. Furthermore, the expression and activation of transcription factors, such as the CCAAT/enhancer-binding protein (C/EBP) β, which is required for the induction of lipogenic enzymes, were largely inhibited in Rac1-deficient cells in both early and late stages of differentiation. Altogether, Rac1 is responsible for adipogenic differentiation, including lipogenesis, through the regulation of differentiation-related transcription.

Molecular and Physiological Functions of PACAP in Sweat Secretion

Sweat plays a critical role in human body, including thermoregulation and the maintenance of the skin environment and health. Hyperhidrosis and anhidrosis are caused by abnormalities in sweat secretion, resulting in severe skin conditions (pruritus and erythema). Bioactive peptide and pituitary adenylate cyclase-activating polypeptide (PACAP) was isolated and identified to activate adenylate cyclase in pituitary cells. Recently, it was reported that PACAP increases sweat secretion via PAC1R in mice and promotes the translocation of AQP5 to the cell membrane through increasing intracellular [Ca²⁺] via PAC1R in NCL-SG3 cells. However, intracellular signaling mechanisms by PACAP are poorly clarified. Here, we used PAC1R knockout (KO) mice and wild-type (WT) mice to observe changes in AQP5 localization and gene expression in sweat glands by PACAP treatment. Immunohistochemistry revealed that PACAP promoted the translocation of AQP5 to the lumen side in the eccrine gland via PAC1R. Furthermore, PACAP up-regulated the expression of genes (Ptgs2, Kcnn2, Cacna1s) involved in sweat secretion in WT mice. Moreover, PACAP treatment was found to down-regulate the Chrna1 gene expression in PAC1R KO mice. These genes were found to be involved in multiple pathways related to sweating. Our data provide a solid basis for future research initiatives in order to develop new therapies to treat sweating disorders.

Long noncoding RNA ENST00000436340 promotes podocyte injury in diabetic kidney disease by facilitating the association of PTBP1 with RAB3B

Dysfunction of podocytes has been regarded as an important early pathologic characteristic of diabetic kidney disease (DKD), but the regulatory role of long noncoding RNAs (lncRNAs) in this process remains largely unknown. Here, we performed RNA sequencing in kidney tissues isolated from DKD patients and nondiabetic renal cancer patients undergoing surgical resection and discovered that the novel lncRNA ENST00000436340 was upregulated in DKD patients and high glucose-induced podocytes, and we showed a significant correlation between ENST00000436340 and kidney injury. Gain- and loss-of-function experiments showed that silencing ENST00000436340 alleviated high glucose-induced podocyte injury and cytoskeleton rearrangement. Mechanistically, we showed that fat mass and obesity- associate gene (FTO)-mediated m6A induced the upregulation of ENST00000436340. ENST00000436340 interacted with polypyrimidine tract binding protein 1 (PTBP1) and augmented PTBP1 binding to RAB3B mRNA, promoted RAB3B mRNA degradation, and thereby caused cytoskeleton rearrangement and inhibition of GLUT4 translocation to the plasma membrane, leading to podocyte injury and DKD progression. Together, our results suggested that upregulation of ENST00000436340 could promote podocyte injury through PTBP1-dependent RAB3B regulation, thus suggesting a novel form of lncRNA-mediated epigenetic regulation of podocytes that contributes to the pathogenesis of DKD.

Anemoside B4 Exerts Hypoglycemic Effect by Regulating the Expression of GLUT4 in HFD/STZ Rats

Anemoside B4 (B4) is a saponin that is extracted from Pulsatilla chinensis (Bge.), and Regel exhibited anti-inflammatory, antioxidant, antiviral, and immunomodulatory activities. However, its hypoglycemic activity in diabetes mellitus has not been evaluated. Here, we explored the effect of B4 on hyperglycemia and studied its underlying mechanism of lowering blood glucose based on hyperglycemic rats in vivo and L6 skeletal muscle cells (L6) in vitro. The rats were fed a high-fat diet (HFD) for one month, combined with an intraperitoneal injection of 60 mg/kg streptozotocin (STZ) to construct the animal model, and the drug was administrated for two weeks. Blood glucose was detected and the proteins and mRNA were expressed. Our study showed that B4 significantly diminished fasting blood glucose (FBG) and improved glucose metabolism. In addition, B4 facilitated glucose utilization in L6 cells. B4 could enhance the expression of glucose transporter 4 (GLUT4) in rat skeletal muscle and L6 cells. Mechanistically, B4 elevated the inhibition of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathways. Furthermore, we confirmed the effect of B4 on glucose uptake involved in the enhancement of GLUT4 expression in part due to PI3K/AKT signaling by using a small molecule inhibitor assay and constructing a GLUT4 promoter plasmid. Taken together, our study found that B4 ameliorates hyperglycemia through the PI3K/AKT pathway and promotes GLUT4 initiation, showing a new perspective of B4 as a potential agent against diabetes.

Undaria pinnatifida (Wakame) Intake Ameliorates High-Fat Diet-Induced Glucose Intolerance via Promoting GLUT4 Expression and Membrane Translocation in Muscle

Type 2 diabetes mellitus (T2DM), a lifestyle-related disease, is developed due to eating habits and decreased physical activity. Diabetes also increases the risk of cancer and major neurodegenerative diseases; controlling the onset of diabetes helps prevent various illnesses. Eating seaweed, such as Undaria pinnatifida (wakame), is a part of the Asian food culture. Therefore, we analyzed the antidiabetic effect of wakame intake using the high-fat diet-induced diabetes mouse model. Furthermore, we analyzed the effect of wakame extract on the cell membrane translocation of glucose transporter-4 (GLUT4) and activation of insulin signal molecules, such as AKT and AMPK, in insulin-sensitive tissues. Differentiated C2C12 cells were incubated with wakame components. The membrane translocation of GLUT4 and phosphorylation of AKT and AMPK were investigated with immunofluorescence staining and Western blotting, respectively. Also, male C57BL/6J mice were fed the normal diet (ND), high-fat diet (HFD), ND with 1% wakame powder (ND + W), or HFD with 1% wakame powder (HFD + W). We evaluated the effect of wakame intake on high-fat diet-induced glucose intolerance using an oral glucose tolerance test. Moreover, we analyzed insulin signaling molecules, such as GLUT4, AKT, and AMPK, in muscle using Western blotting. GLUT4 membrane translocation was promoted by wakame components. Also, GLUT4 levels and AKT and AMPK phosphorylation were significantly elevated by wakame components in C2C12 cells. In addition, the area under the curve (AUC) of the HFD + W group was significantly smaller than that of the HFD group. Furthermore, the level of GLUT4 in the muscle was increased in the wakame intake group. This study revealed that various wakame components exerted antidiabetic effects on the mice on a high-fat diet by promoting glucose uptake in the skeletal muscle, enhancing GLUT4 levels, and activating AKT and AMPK.

Tinosporaside from Tinospora cordifolia Encourages Skeletal Muscle Glucose Transport through Both PI-3-Kinase- and AMPK-Dependent Mechanisms

The stem of Tinospora cordifolia has been traditionally used in traditional Indian systems of medicine for blood sugar control, without the knowledge of the underlying mechanism and chemical constitution responsible for the observed anti-diabetic effect. In the present study, Tinosporaside, a diterpenoid isolated from the stem of T. cordifolia, was investigated for its effects on glucose utilization in skeletal muscle cells, which was followed by determining the anti-hyperglycemic efficacy in our diabetic db/db mice model. We found that tinosporaside augmented glucose uptake by increasing the translocation of GLUT4 to the plasma membrane in L6 myotubes, upon prolonged exposure for 16 h. Moreover, tinosporaside treatment significantly increased the phosphorylation of protein kinase B/AKT (Ser-473) and 5' AMP-activated protein kinase (AMPK, Thr-172). These effects were abolished in the presence of the wortmannin and compound C. Administration of tinosporaside to db/db mice improved glucose tolerance and peripheral insulin sensitivity associated with increased gene expression and phosphorylation of the markers of phosphoinositide 3-kinases (PI3Ks) and AMPK signaling in skeletal muscle tissue. The findings revealed that tinosporaside exerted its antidiabetic efficacy by enhancing the rate of glucose utilization in skeletal muscle, mediated by PI3K- and AMPK-dependent signaling mechanisms.

Endosomal trafficking in metabolic homeostasis and diseases

The global prevalences of obesity and type 2 diabetes mellitus have reached epidemic status, presenting a heavy burden on society. It is therefore essential to find novel mechanisms and targets that could be utilized in potential treatment strategies and, as such, intracellular membrane trafficking has re-emerged as a regulatory tool for controlling metabolic homeostasis. Membrane trafficking is an essential physiological process that is responsible for the sorting and distribution of signalling receptors, membrane transporters and hormones or other ligands between different intracellular compartments and the plasma membrane. Dysregulation of intracellular transport is associated with many human diseases, including cancer, neurodegeneration, immune deficiencies and metabolic diseases, such as type 2 diabetes mellitus and its associated complications. This Review focuses on the latest advances on the role of endosomal membrane trafficking in metabolic physiology and pathology in vivo, highlighting the importance of this research field in targeting metabolic diseases.

Aerobic exercise ameliorates insulin resistance in C57BL/6 J mice via activating Sestrin3

Skeletal muscle insulin resistance (IR) is closely linked to hyperglycemia and metabolic disorders. Regular exercise enhances insulin sensitivity in skeletal muscle, but its underlying mechanisms remain unknown. Sestrin3 (SESN3) is a stress-inducible protein that protects against obesity-induced hepatic steatosis and insulin resistance. Regular exercise training is known to increase SESN3 expression in skeletal muscle. The purpose of this study was to explore whether SESN3 mediates the metabolic effects of exercise in the mouse model of high-fat diet (HFD)-induced IR. SESN3^-/- mice exhibited severer body weight gain, ectopic lipid accumulation, and dysregulation of glucose metabolism after long-term HFD feeding compared with the wild-type (WT) mice. Moreover, we found that SESN3 deficiency weakened the effects of exercise on reducing serum insulin levels and improving glucose tolerance in mice. Exercise training increased pAKT-S473 and GLUT4 expression, accompanied by enhanced pmTOR-S2481 (an indicator of mTORC2 activity) in WT quadriceps that were less pronounced in SESN3^-/- mice. SESN3 overexpression in C2C12 myotubes further confirmed that SESN3 played an important role in skeletal muscle glucose metabolism. SESN3 overexpression increased the binding of Rictor to mTOR and pmTOR-S2481 in C2C12 myotubes. Moreover, SESN3 overexpression resulted in an elevation of glucose uptake and a concomitant increase of pAKT-S473 in C2C12 myotubes, whereas these effects were diminished by downregulation of mTORC2 activity. Taken together, SESN3 is a crucial protein in amplifying the beneficial effects of exercise on insulin sensitivity in skeletal muscle and systemic glucose levels. SESN3/mTORC2/AKT pathway mediated the effects of exercise on skeletal muscle insulin sensitivity.

Chicken GLUT4 undergoes complex alternative splicing events and its expression in striated muscle changes dramatically during development

Glucose transporter protein 4 (GLUT4) plays an important role in regulating insulin-mediated glucose homeostasis in mammals. Until now, studies on GLUT4 have focused on mammals mostly, while chicken GLUT4 has been rarely investigated. In this study, chicken GLUT4 mRNA sequences were obtained by combining conventional amplification, 5'- and 3'- rapid amplification of cDNA ends technique (RACE), then bioinformatics analysis on its genomic structure, splicing pattern, subcellular localization prediction and homologous comparisons were carried out. In addition, the distribution of GLUT4 was detected by RT-qPCR in bird's liver and striated muscles (cardiac muscle, pectoralis and leg muscle) at different ages, including embryonic day 14 (E14), E19, 7-day-old (D7), D21 and D49 (n = 3-4). Results showed that chicken GLUT4 gene produced at least 14 transcripts (GenBank accession No: OP491293-OP491306) through alternative splicing and polyadenylation, which predicted encoding 12 types of amino acid (AA) sequences (with length ranged from 65 AA to 519 AA). These proteins contain typical major facilitator superfamily domain of glucose transporters with length variations, sharing a common sequence of 59 AA, and were predicted to have distinct subcellular localization. The dominant transcript (named as T1) consists of 11 exons with an open reading frame being predicted encoding 519 AA. In addition, analyzing on the spatio-temporal expression of chicken GLUT4 showed it dominantly expressed in pectoralis, leg muscles and cardiac muscle, and the mRNA level of chicken GLUT4 dramatically fluctuated with birds' development in cardiac muscle, pectoralis and leg muscles, with the level at D21 significantly higher than that at E14, E19, and D49 (P < 0.05). These data indicated that chicken GLUT4 undergoes complex alternative splicing events, and GLUT4 expression level in striated muscle was subjected to dynamic regulation with birds' development. Results indicate these isoforms may play overlapping and distinct roles in chicken.

Control of cell metabolism by the epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) triggers the activation of many intracellular signals that control cell proliferation, growth, survival, migration, and differentiation. Given its wide expression, EGFR has many functions in development and tissue homeostasis. Some of the cellular outcomes of EGFR signaling involve alterations of specific aspects of cellular metabolism, and alterations of cell metabolism are emerging as driving influences in many physiological and pathophysiological contexts. Here we review the mechanisms by which EGFR regulates cell metabolism, including by modulation of gene expression and protein function leading to control of glucose uptake, glycolysis, biosynthetic pathways branching from glucose metabolism, amino acid metabolism, lipogenesis, and mitochondrial function. We further examine how this regulation of cell metabolism by EGFR may contribute to cell proliferation and differentiation and how EGFR-driven control of metabolism can impact certain diseases and therapy outcomes.

MICAL1 facilitates pancreatic cancer proliferation, migration, and invasion by activating WNT/β-catenin pathway

Background

MICAL1 is involved in the malignant processes of several types of cancer; however, the role of MICAL1 in pancreatic cancer (PC) has not been well-characterized. This study aimed to investigate the expression and function of MICAL1 in PC.

Methods

RT-qPCR and immunohistochemistry were used to detect MICAL1 expression in PC and adjacent nontumor tissues. Cell Counting Kit-8, EdU, clone formation, wound healing, and Transwell assays as well as animal models were used to investigate the effects of overexpression or inhibition of MICAL1 expression on the proliferation, invasion, and metastasis of PC cells. RNA-seq was used to explore the main pathway underlying the functions of MICAL1. Proteomics, mass spectrometry, and co-immunoprecipitation assays were used to investigate the interaction of proteins with MICAL1. Rescue experiments were conducted to validate these findings.

Results

Both MICAL1 mRNA and protein levels were upregulated in PC tissues compared with matched adjacent nontumor tissues. The expression level of MICAL1 was associated with the proliferative and metastatic status of PC. Repression of MICAL1 significantly inhibited PC cell growth, migration, and invasion in vitro and in vivo. RNA sequencing analysis indicated that MICAL1 was closely correlated with the WNT pathway. Overexpression of MICAL1 (1) promoted the phosphorylation of TBC1D1 at the Ser660 site, (2) facilitated the distribution of FZD7 on the cytomembrane, (3) inhibited the degradation of FZD7 in the lysosome, and (4) activated the WNT pathway.

Conclusions

MICAL1 was upregulated in PC and involved in stimulating the progression of PC cells by activating the WNT/β-catenin signaling pathway. Therefore, MICAL1 is a potential therapeutic target for PC.