MIN6 Cells Research Articles

Identifying and validating the key regulatory transcription factor YY1 in the aging process of pancreatic beta cells based on bioinformatics.

The aging of pancreatic beta cells is closely associated with various diseases, such as impaired glucose tolerance, yet the underlying regulatory mechanisms remain unclear. In this study, we screened young and aged mouse pancreatic beta cells' high-throughput sequencing data from the GEO public database. Utilizing bioinformatics techniques, we identified the key regulatory factor YY1 in the aging process of pancreatic islets. We observed a significant decrease in the expression of YY1 in a D-gal-induced mouse model of pancreatic aging and an H2O2-induced MIN6 cell model of aging. Moreover, both vivo and vitro models, we found that the YY1 agonist eudesmin (EDN) improved glucose intolerance in mice, alleviated aging of pancreatic beta cells, and downregulated the expression of cell cycle protein P21. Mechanistically, we discovered that EDN inhibited the P38/JNK MAPK pathway in aging cells. In summary, our study confirms the regulatory role of the transcription factor YY1 in the aging process of pancreatic beta cells. This finding may provide a new approach for the clinical treatment of pancreatic aging-related diseases such as impaired glucose tolerance or diabetes.

Ligandrol Ameliorates High-Fat Diet- and Streptozotocin-Induced Type 2 Diabetes Mellitus and Prevents Pancreatic Islets Degeneration.

Androgen therapy has been shown to alleviate type 2 diabetes mellitus (T2DM) but is also associated with severe side effects such as prostate cancer. The present study aims to identify the best hit selective androgen receptor (AR) modulator by in silico studies and then investigates its antidiabetic effects in high-fat diet- and streptozotocin (STZ)-induced T2DM male rat model. Molecular docking and molecular dynamics (MD) studies were carried out using Maestro 13.1 and Desmond (2023-2024). Cytotoxicity and insulin secretion were measured in MIN6 cell lines. T2DM was induced using high-fat diet (HFD) for 4 weeks, followed by single STZ (40 mg/kg, intraperitoneally). OneTouch Ultra glucometer was used to measure fasting blood glucose. Gene expression was determined using reverse transcription polymerase chain reaction. Histopathology was carried out using hematoxylin and eosin stain. Through molecular docking, we identify ligandrol as a potential hit. Ligandrol showed a good binding affinity (-10.74 kcal/mol). MD showed that ligandrol is stable during the 100 ns simulation. Ligandrol increases insulin secretion in a dose-dependent manner in vitro in 2 h. Ligandrol (0.3 and 1 mg/kg, orally) significantly decreased the body weight and fasting blood glucose levels compared with the HFD and STZ group. Gene expression showed that ligandrol significantly increased the AR-targeted gene, neurogenic differentiation 1, compared with the HFD and STZ group. Histopathological staining studies showed that ligandrol prevents pancreatic islet degeneration compared with the HFD and STZ group. Our findings suggest that ligandrol's protective effect on pancreatic islets leading to its antidiabetic effect occurs through the activation of AR.

Long-Lasting Exendin-4-Coated Gold Nanoparticles: Synthesis and In Vivo Evaluation of Hypoglycemic Activity

Background: Gold nanoparticles (NPs) have drawn great attention in the area of biomedical research with their relatively safe and versatile properties. This study aimed to synthesize long-lasting exendin-4-coated gold NPs (EX-ABD-AFF-GoldNPs) and evaluate their anti-diabetic effects in vivo. Methods: In the present study, EX-ABD-AFF-GoldNPs were synthesized using a simple one-step aqueous reduction method. The physical characterization of the prepared particles verified the successful formation of the EX-ABD-AFF-GoldNPs through dynamic light scattering (DLS), transmission electron microscopy (TEM), ultraviolet–visible (UV-VIS) light spectroscopy, and Fourier transform infrared spectroscopy (FTIR). The anti-hyperglycemic and anti-obesity effects were assessed in high-fat diet (HFD)-fed obese diabetic mice. Additionally, pharmacokinetics (PK) and biodistribution studies were performed to verify the long-lasting properties. Results: The EX-ABD-AFF-GoldNPs were conglomerates of smaller globular-shaped particles, and the average size was 110(±14) nm, based on the TEM images. Safety assessments using Min6, HepG2, and B16F10 cell lines demonstrated low cytotoxicity, with over 80% cell viability up to the highest tested concentration of 150 μg/mL (as EX-ABD-AFF). Notably, the animal studies showed that the EX-ABD-AFF-GoldNPs exhibited significant hypoglycemic activity, comparable to the EX-ABD-AFF, in the HFD-fed mice. A 4-week treatment with EX-ABD-AFF-GoldNPs produced similar reductions in blood glucose and body weight to the EX-ABD-AFF, without any apparent toxicity. Furthermore, the PK and biodistribution study results confirmed the long-lasting properties (plasma half-life: 43.6 h) of the particles. Conclusions: Overall, this study demonstrated that the preparation of therapeutic protein-loaded gold NPs is feasible and, despite their much larger size compared with the protein, EX-ABD-AFF-GoldNPs can be successfully absorbed through the subcutaneous route and show nearly equivalent hypoglycemic activity to the EX-ABD-AFF protein. Finally, this study showed that long-lasting properties could be acquired by only coating EX-ABD-AFF onto gold NPs.

Sesamol Alleviated Lipotoxicity-Induced Dysfunction in MIN6 Cells via Facilitating Cellular Senescence Caused by Endoplasmic Reticulum Stress.

Obesity is found to be a significant risk factor for type 2 diabetes mellitus (T2DM), attributed to lipotoxicity-induced β-cell dysfunction. However, the specific mechanism involved in the process remains incompletely unclarified. The current study demonstrated lipotoxicity resulted in the activation of ER stress, which increased the protein level of TXNIP, thereby inducing senescence-assiciated dysfunction in MIN6 cells under high fat environment. And we also found sesamol, a natural functional component extracted from sesame, was able to alleviate senescence-associated β-cell dysfunction induced by lipotoxicity by inhibiting ER stress and TXNIP. Our findings provided novel insights into senescence-related T2DM and propose innovative therapeutic approaches for utilizing sesamol in the treatment of T2DM in the obese elderly population.

Evaluation of anti-diabetic effects of Glimepiride/metformin cocrystal

Emerging data suggest that cocrystal of two compounds may have a different pharmacological effect from two compounds alone or their physical combination. Glimepiride (Gli) and metformin (Met) are two types of anti-diabetic drugs. Previously we generated the glimepiride/metformin cocrystal (GM). In this study, we evaluated the anti-diabetic effects of GM and explored the underlying mechanisms. Our result showed that GM reduced the blood glucose and HbA1c levels in db/db mice, and low doses of GM can achieve the hypoglycemic effect as Gli or Met alone, and high dose of GM was better than Gli and Met alone in improving the pathological changes of liver. In vivo studies showed that GM activated AMPK and STAT3 signaling, downregulated TXNIP expression and upregulated MaFA expression. Moreover, GM promoted the secretion of insulin in pancreas of db/db mice and in high glucose-treated INS-1 and MIN-6 cells. Together, GM possesses slightly better anti-diabetic effects than Met or Gli alone in db/db mice, and the mechanism of GM protecting β-cell dysfunction induced by glucotoxicity may be associated with activation of the AMPK/TXNIP/MaFA pathway.

The general glycan profiling of Dendrobium officinale and their protective effects on MIN6 cells via ERK signaling pathway

Based on structural elucidation of natural and hydrolyzed glycans, the general glycans profiling of D. officinale were unequivocally established for the first time as follows: [Display omitted] The results indicated that the structure of D. officinale glycans with low degree of polymerization (DP ≤ 22) was linear α-D-1,4-glucan, whereas the structure of glycans with high degree of polymerization (DP > 24) was linear acetylated 1,4-glucomannan. The content of acetyl groups and mannose to glucose (M/G) ratio increased with the degree of polymerization of D. officinale glycans. In addition, this study showed that natural D. officinale glycans protected pancreatic β-cell damage induced by glucotoxicity through the extracellular signal–regulated kinase (ERK)1/2 pathway.

Terazosin, a repurposed GPR119 agonist, ameliorates mitophagy and β-cell function in NAFPD by inhibiting MST1-Foxo3a signalling pathway.

GPR119 agonists are being developed to safeguard the function of pancreatic β-cells, especially in the context of non-alcoholic fatty pancreas disease (NAFPD) that is closely associated with β-cell dysfunction. This study aims to employ a drug repurposing strategy to screen GPR119 agonists and explore their potential molecular mechanisms for enhancing β-cell function in the context of NAFPD. MIN6 cells were stimulated with palmitic acid (PA), and a NAFPD model was established in GPR119-/- mice fed with a high-fat diet (HFD). Terazosin, identified through screening, was utilized to assess its impact on enhancing β-cell function via the MST1-Foxo3a pathway and mitophagy. Terazosin selectively activated GPR119, leading to increased cAMP and ATP synthesis, consequently enhancing insulin secretion. Terazosin administration improved high blood glucose, obesity, and impaired pancreatic β-cell function in NAFPD mice. It inhibited the upregulation of MST1-Foxo3a expression in pancreatic tissue and enhanced damaged mitophagy clearance, restoring autophagic flux, and improving mitochondrial quantity and structure in β-cells. Nevertheless, GPR119 deficiency negated the positive impact of terazosin on pancreatic β-cell function in NAFPD mice and abolished its inhibitory effect on the MST1-Foxo3a pathway. Terazosin activates GPR119 on the surface of pancreatic β-cells, enhancing mitophagy and alleviating β-cell dysfunction in the context of NAFPD by suppressing the MST1-Foxo3a signalling pathway. Terazosin could be considered a priority treatment for patients with concomitant NAFPD and hypertension.

Novel human PDX1 Asn196Thr variant causes pancreas agenesis and reduces the generation of duodenal enteroendocrine cells

Abstract Introduction/Objective Pancreatic and duodenal homeobox 1 (PDX1) is a well-studied transcription factor required for pancreas organogenesis. PDX1 mutations are associated with the development of diabetes. An 8-month-old female patient with previously uncharacterized compound heterogeneous PDX1 missense mutations (Thr151Met and Asn196Thr) was identified in this study. The patient has permanent neonatal diabetes, pancreas hypoplasia, and a malformed gallbladder. Methods/Case Report PDX1 Thr151Met and Asn196Thr variants in the patient were identified by next-generation sequencing gene panel and confirmed by Sanger sequencing. To examine how the mutations affect PDX1 functions in vitro, we expressed mouse Pdx1 Thr152Met and Asn197Thr, homologous to human PDX1 Thr151Met and Asn196Thr, respectively, in mouse insulinoma MIN6 cells and human embryonic kidney 293T cells and examined protein localization, protein stability, DNA binding, and protein-protein interaction. We also generated embryonic day 18 mouse embryos carrying Pdx1 Asn197Thr missense mutation using CRISPR/Cas9 to examine its roles in the development of the pancreas and other digestive organs in vivo. Results (if a Case Study enter NA) We found that the Pdx1 Asn197Thr variant, but not Thr152Met, altered its nuclear localization and disrupted PDX1-Onecut 1 interaction. Neither variant significantly affected PDX1 protein stability, but both reduced PDX1 binding to the Pdx1 gene promoter. Importantly, we found that the Pdx1 Asn197Thr variant caused pancreas agenesis and a reduction in the generation of enteroendocrine cells in the proximal duodenum in mouse models. Conclusion Our data indicated that the PDX1 Asn196Thr variant impairs its DNA binding and protein-protein interaction, causing pancreas agenesis and a reduction in the generation of duodenal enteroendocrine cells.

7880 The Role Of PTHrP In Glucose Metabolism And Insulin Secretion

Abstract Disclosure: I.M. Max-Harry: None. N. Kantake: None. C.S. Nunemaker: None. T.J. Rosol: None. Insulin and glucagon are the two most important hormones for blood glucose homeostasis. Identifying the key players in their regulation will contribute greatly towards combatting types 1 and 2 diabetes. Parathyroid Hormone-related protein (PTHrP), a protein expressed by pancreatic beta cells, has been implicated in various developmental and physiological roles, but particularly, PTHrP increases beta-cell proliferation and insulin secretion in pancreatic islets. Incubating mouse pancreatic islets and Min6 cells with 10nM exogenous PTHrP showed a significant increase in both insulin secretion (for islets, PTHrP: 865.4ng/ml ± 77.66, con: 498.5ng/ml ± 40.63, p=0.024, n=4) and glucagon secretion (PTHrP: 20.87pmol/l ± 3.776, con: 8.798pmol/l ± 1.616, p= 0.068, n=3) after 24hours. In order to further investigate the effects observed, min6 cells were transiently transfected to overexpress PTHrP, and a glucose-stimulated insulin secretion (GSIS) assay was carried out with 2mM and 20mM glucose. The results showed a reduction in basal insulin secretion at 2mM glucose and an increase in insulin secretion at 20mM glucose for the PTHrP transfected cells. PTHrP improved the stimulation index of Min6 cells (PTHrP: 2.279 ± 0.2056, con: 1.659 ± 0.1386, p= 0.03, n=6) and enhanced their sensitivity to glucose. Preliminary proliferation assays showed that cells transfected with PTHrP have increased proliferation and a protection from cell death when incubated in serum-free media. This study, in addition to our previously published research showing that a lack of intact PTHrP leads to islet dysfunction, revealed that PTHrP may be crucial to appropriate glucose sensitivity of beta cells. Further studies are being carried out to understand the mechanism behind these effects and the genes/proteins involved in the regulation of insulin secretion by PTHrP. Presentation: 6/1/2024

9317 Diabetogenic Stress-Mediated Beta Cell Extracellular Vesicle:Autophagy Pathway Crosstalk

Abstract Disclosure: A. Roy: None. G. Ariyaratne: None. A. Matveyenko: None. N. Javeed: None. Diabetogenic stressors including elevated free fatty acids (lipotoxicity), low-grade systemic inflammation, and proteotoxicity are central to the development of Type 2 Diabetes (T2D). Due to their high protein synthetic burden, β-cells employ autophagy and endo/lysosomal pathways to reduce protein aggregates, and protect β-cell mass and function. Recently, extracellular vesicles (EVs; 30-150 nm sized nanoparticles) have been shown to work in tandem with autophagy to facilitate cellular adaptation and intercellular communication. As diabetogenic stressors have been shown to perturb autophagy via lysosomal defects, our group has noted enhanced EV secretion. Thus, we hypothesize that diabetogenic factors enhance EV secretion through activation of an EV-based secretory autophagy pathway and that re-balancing of both pathways could improve β-cell function in T2D. To test this, MIN6 cells were exposed to free fatty acid palmitate (PAL; 24h), or pro-inflammatory cytokines IL-1β, TNFα, and IFNγ (CYTO; 48h). Expression of autophagic markers, LC3 and p62 were increased in CYTO and PAL conditions suggesting defects in auto/lysosomal function. Upon PAL/CYTO treatment in MIN6 cells, conditioned media EVs were isolated using differential ultracentrifugation. We noted enhanced protein expression of LC3-II and p62 in PAL- and cytoEVs, suggesting a diversion of immature autophagosome components into EVs due to lysosomal inhibition. To restore balance between autophagy:EV flux, we used EV biogenesis inhibitor, GW4869 (GW; 24h) or autophagy inducer, rapamycin (Rapa; 24h) on MIN6 cells exposed to PAL or CYTO. Isolated EVs were subjected to Nanoparticle Tracking Analysis (NTA) which showed a significant reduction in EV concentration with GW or Rapa addition (p<.05). Isolated mouse islet exposed to CYTO+GW/Rapa or PAL+GW/Rapa showed significant improvements in glucose stimulated insulin secretion (vs. CYTO or PAL; p<.05). Taken together, these data implicate activation of EV-based secretory autophagy in response to diabetogenic stressors and thus, potential targets to improve functional β-cell mass. Presentation: 6/2/2024

7260 Nuclear Corepressor 1 (NCoR1) plays important role in the regulation of insulin gene transcription in mouse Min6 pancreatic beta cells

Abstract Disclosure: H. Shimizu: None. Y. Horibata: None. I. Amano: None. M.J. Ritter: None. M. Ohyama: None. M. Domae: None. H. Sugimoto: None. A.N. Hollenberg: None. Background: Nuclear Corepressor 1 (NCoR1) is a transcriptional corepressor which has been recognized as an important player in the regulation of hepatic lipogenesis and hematopoiesis in mouse embryo. NCoR1 is also widely expressed in mouse insulin sensitive organs, for instance adipocyte, skeletal muscle, and hepatocytes. Mouse genetic deletion strategies of either NCoR1 or SMRT(NCoR2; an ortholog corepressor of NCoR1) demonstrated that each corepressor effects the insulin sensitivity in the tissues. However, the role of each corepressor in pancreatic beta cell is not still elucidated. Methods: To clarify this, we took the gene-targeting strategy for NCoR1 using CRISPR Cas-9 and made the pancreatic beta Min6 clone which lacks NCoR1 protein (Min6-NCoR1KO; NKO cells). For this study, wild type Min6 cells (WT) and NKO cells were cultured in the Dulbecco's DMEM medium with 10% fetal bovine serum for 4-5 days, and the expression analyses compared between two cell types were performed. Results: Both comprehensive proteomics and following expression analyses compared between WT and NKO cells demonstrated that NKO cells have significantly lower expression level of insulin (INS-1 and INS-2), accompanied with high expression of histone deacetylase 6 (HDAC6). For further analyses, we also made the Min6 clone which lacks SMRT(Min6-SMRTKO; SKO cells). Interestingly, SKO cell had higher insulin and lower HDAC6 levels, accompanied with significant up-regulation of NCoR1. Conclusion: Taken together, these data indicate that NCoR1 has dominant effects in the regulation of both histone deacetylation and insulin gene transcription in Min6 cells. Further investigations for the function of NCoR1 in the insulin gene transcription observed in Min6 cells will be needed. Presentation: 6/2/2024

12614 Induction Of Gpt2 During Metabolic Stress Is Associated With Reduced Incretin Responsiveness And Decreased β-cell Resilience To Metabolic Stress

Abstract Disclosure: S. Sen: None. A.V. Rozo: None. M. Haemmerle: None. J. Roman: None. A.V. Scota: None. J.A. Christine: None. E.M. Morrow: None. S.A. Tersey: None. C.B. Newgard: None. N.M. Doliba: None. D.A. Stoffers: None. Elevated blood glucose and lipids compromise pancreatic β-cell survival and function, but the underlying molecular mechanisms are ill-understood. We previously found that mitochondrial glutamate-pyruvate transaminase 2 (GPT2) is induced by ER and glucolipotoxic (GLT) stress. Here, we find that islets from type 2 diabetic donors exhibited markedly elevated levels of GPT2 compared to those of non-diabetic donors. GLT stress induced GPT2 in MIN6 cells, primary murine, and human non-diabetic islets. We generated β-cell specific Gpt2-deficient (Gpt2βKO) and Gpt2 floxed control (Gpt2f/f) mice to study the in vivo role of Gpt2 in β-cells. Intraperitoneal (IP) glucose tolerance (GTT) of Gpt2βKO mice was minimally affected on chow diet; therefore, we placed Gpt2f/f and Gpt2βKO mice on 45 kcal% high-fat and matched control diets. At 1 week, HFD-fed Gpt2βKO mice exhibited reduced β-cell death, measured by droplet digital PCR of circulating unmethylated preproinsulin DNA and by TUNEL analysis. Over 37 weeks, HFD-fed Gpt2βKO mice showed lower random blood glucose similar to Gpt2f/f mice under a control diet. While IPGTT was modestly improved in HFD-fed Gpt2βKO compared to HFD-fed Gpt2f/f mice, insulin secretion was not enhanced. Remarkably, oral glucose administration markedly improved glucose tolerance and enhanced insulin secretion of control- and HFD-fed Gpt2βKO mice compared to Gpt2f/f mice, while GLP-1 and GIP levels were unaltered, suggesting enhanced incretin action on the β-cell. Indeed, Gpt2βKO mice (under both control and high-fat diets) were more responsive to administration of GLP1R agonist Exendin-4 (Ex4) than Gpt2f/f mice. Isolated Gpt2βKO islets secreted more insulin when stimulated by Ex4 and GIP but not acetylcholine. Perifusion assay revealed markedly enhanced insulin secretion of Gpt2βKO islets in response to a stepwise exposure to increasing Ex4 doses, indicating enhanced incretin sensitivity. Metabolic flux analysis of Gpt2βKO and Gpt2f/f islets exposed to uniformly labeled glucose (U-13C glucose) under low (2.8mM), high (12mM) glucose, and high glucose with Ex4 conditions revealed elevated levels of key TCA cycle intermediates in Gpt2βKO islets under high glucose and high glucose+Ex4 conditions, indicating increased TCA cycle flux that likely enhances insulin secretion. Gpt2βKO mice had higher β cell mass than Gpt2f/f littermates under control diet and HFD feeding. Bulk islet RNA-seq from Gpt2f/f and Gpt2βKO mice exposed to GLT revealed upregulation of genes responsible for cell cycle and division pathways and downregulation of apoptosis and ER stress genes, consistent with enhanced survival of Gpt2βKO islets under stress conditions. In summary, β-cell GPT2 is increased during metabolic stress and T2D. Its deficiency induces a metabolic reprogramming that improves incretin sensitivity and protects pancreatic β-cells from metabolic stress. Presentation: 6/2/2024

8010 Potent MSB-61 as Type 1 Diabetes (T1D) therapy: mechanism of action in insulin secretion

Abstract Disclosure: N. Ajmal: None. M. Bogart: None. K. Corbin: None. P. Khan: None. M. Shafqat: None. S. Bergmeier: None. G. Gu: None. X. Tong: None. C.S. Nunemaker: None. Type 1 diabetes (T1D) is a chronic autoimmune disorder caused by proinflammatory cytokines (Interleukin 1-beta; IL1-β, Tumor Necrosis Factor-alpha; TNF-α, and Interferon-gamma; IFN-ϒ) from immune cells that destroy insulin-producing beta cells in pancreatic islets and lead to hyperglycemia. The development of possible treatments to cure T1D is needed besides intensive insulin therapy that does not halt disease progression. We have identified a small molecule called MSB-61 that can protect islet cells from endoplasmic reticulum stressors (66% protection) and cytokines (33% protection) as measured by propidium iodide in islets isolated from mice using 50uM MSB-61. Importantly, we observed large increases in insulin secretion during overnight exposure to 50uM MSB-61. Insulin secretion began to increase in response to MSB-61 at ∼4h, reaching a plateau at ∼8h of greater than 4-fold insulin release compared to controls. The Kegg pathway analysis of RNA-seq data on MSB-61 suggested that multiple genes upregulated by MSB-61 are involved in insulin secretion through an amplifying pathway that includes cAMP/PKA and Pi3k/Akt signaling cascades. Based on RNA sequencing data, this study aimed to test MSB-61 for identifying pathway by which it potentiates insulin secretion. Islets from CD-1 mice and mouse insulinoma Min-6 cell lines were used to test amplifying pathways by using cAMP/PKA and Pi3k/Akt analogs and antagonists with and without MSB-61, and overnight insulin secretion and insulin content will be measured by enzyme-linked immunosorbent assay (ELISA). MSB-61 showed no potential effects on insulin secretion when tested for Pi3k/Akt pathway in the presence of analogs and antagonists such as 740-Y-P and wortmannin. It further suggests MSB-61 might potentiate insulin secretion through the cAMP/PKA pathway, which is still under investigation. RNA sequencing analysis of mouse islets showed several genes that belong to Ras family member-2 and have GTPase activity. Genes with GTPase activity will be further investigated to help identify if MSB-61 stimulates insulin secretion through an amplifying pathway involving the cAMP/PKA downstream signaling cascade. Identifying the mechanism of action and signaling pathway by which MSB-61 potentiates insulin secretion will open new ways of identifying T1D therapeutic interventions that would help replace standard insulin therapy. Presentation: 6/3/2024

Structural and quantitative characterization of membrane N-glycans from MIN6 mouse pancreatic beta cells using liquid chromatography-quadrupole-Orbitrap tandem mass spectrometry

MIN6, a mouse pancreatic beta cell line, is used in diabetes research, and the cellular N-glycoproteins in membrane are important in regulating the metabolism of insulin secretion. However, the identities of N-glycans in MIN6 cells are yet to be fully elucidated. In this study, the structures of N-glycans were analyzed using liquid chromatography-electrospray ionization-higher energy collisional dissociation-tandem mass spectrometry. The abundances (%) of each N-glycan relative to the total N-glycans (100 %) were also obtained. Fifty N-glycans (with relative abundance of each > 0.5 %) were obtained, revealing 22 bisecting N-acetylglucosamine (GlcNAc; associated with cell adhesion and growth; sum of relative abundance of each: 27.1 %), 21 core-fucosylated (associated with glucose sensing and insulin secretion regulation; 28.3 %), and 16 sialylated (N-acetylneuraminic acid; related to the expression of glucose transporters and diabetes;15.5 %) N-glycans. Membranes contained higher bisecting GlcNAc and core-fucosylation, similar sialylation, but less high-mannosylation than the lysate (the cellular contents). Notably, all bisecting GlcNAc N-glycans were categorized into structures with (16.6 %) or without (10.5 %) core-fucosylation and with (6.9 %) or without (20.2 %) sialylation. The bisecting GlcNAc structures were not found in human islets; moreover, sialylation levels were 6.9 times higher than for human islets. These structural characteristics of N-glycans affect their cell adhesion and distribution through homologous interactions between beta cells, leading to increased insulin secretion efficiency. This study is the first to identify the structures and quantities of 50 N-glycans in MIN6 cell membranes that may play an important role in regulating the functions of pancreatic beta cells.

CNPAS2 induced β cell dysfunction by regulating KANK1 expression in type 2 diabetes.

Diabetes mellitus type 2 (T2DM) is formed by defective insulin secretion with the addition of peripheral tissue resistance of insulin action. It has been affecting over 400 million people all over the world. To explore the pathogenesis of T2DM and to develop and implement new prevention and treatment strategies for T2DM. Receiver operating characteristic (ROC) curve analysis was used to conduct diagnostic markers. The expression level of genes was determined by reverse transcription-PCR as well as Western blot. Cell proliferation assays were performed by cell counting kit-8 (CCK-8) tests. At last, T2DM mice underwent Roux-en-Y gastric bypass surgery. We found that NPAS2 was significantly up-regulated in islet β cell apoptosis of T2DM. The ROC curve revealed that NPAS2 was capable of accurately diagnosing T2DM. NPAS2 overexpression did increase the level of KANK1. In addition, the CCK-8 test revealed knocking down NPAS2 and KANK1 increased the proliferation of MIN6 cells. At last, we found that gastric bypass may treat type 2 diabetes by down-regulating NPAS2 and KANK1. This study demonstrated that NPAS2 induced β cell dysfunction by regulating KANK1 expression in type 2 diabetes, and it may be an underlying therapy target of T2DM.

SRSF2 is essential for maintaining pancreatic beta-cell identity and regulating glucose homeostasis in mice

Diabetes is characterized by decreased beta-cell mass and islet dysfunction. The splicing factor SRSF2 plays a crucial role in cell survival, yet its impact on pancreatic beta cell survival and glucose homeostasis remains unclear. We observed that the deletion of Srsf2 specifically in beta cells led to time-dependent deterioration in glucose tolerance, impaired insulin secretion, decreased islet mass, an increased number of alpha cells, and the onset of diabetes by the age of 10 months in mice. Single-cell RNA sequencing (scRNA-seq) analyses revealed that, despite an increase in populations of unfolded protein response (UPR)-activated and undifferentiated beta cells within the SRSF2_KO group, there was a notable decrease in the expression of UPR-related and endoplasmic reticulum (ER)-related genes, accompanied by a loss of beta-cell identity. This suggests that beta cells have transitioned from an adaptive phase to a maladaptive phase in islets of 10-month-old SRSF2_KO mice. Further results demonstrated that deletion of SRSF2 caused decreased proliferation in beta cells within 3-month-old islets and Min6 cells. These findings underscore the essential role of SRSF2 in controlling beta-cell proliferation and preserving beta-cell function in mice.

An insight into the role of ESIPT/TICT-based antioxidant flavone analogues in fluoro-probing diabetes-induced viscosity changes: a unified experimental and theoretical endeavour.

Potent antioxidants, like 3-hydroxy flavones, attracted considerable attention due to their excited state intramolecular proton transfer (ESIPT)-based fluorescence behaviour. This article is an interesting demonstration of a series of synthetic 3-hydroxy flavone analogues having high antioxidant activity as molecular rotor-like viscosity probes. Among these flavone analogues, 4'-N,N-dimethylamino-3-hydroxy flavone (3) is the most potent one, showing the twisted intramolecular charge transfer (TICT)-dependent fluoroprobing activity toward the blood viscosity changes associated with diabetes and free fatty acids (FFA)-induced nuclear viscosity changes of MIN6 cells. The TICT dynamics of (3), which instigates its viscosity probing activity, was comprehended with the help of DFT-based computational studies. Abnormal cellular viscosity changes are the pathological traits for various diseases, and non-toxic flavone-based viscosity probes can be useful for diagnosing such pathological conditions.

MiR-146a-5p mediates inflammation-induced β cell mitochondrial dysfunction and apoptosis

We previously showed that miR-146a-5p is upregulated in pancreatic islets treated with pro-inflammatory cytokines. Others have reported that miR-146a-5p overexpression is associated with β cell apoptosis and impaired insulin secretion. However, the molecular mechanisms mediating these effects remain elusive. To investigate the role of miR-146a-5p in β cell function, we developed stable MIN6 cell lines to either overexpress or inhibit the expression of miR-146a-5p. Monoclonal cell populations were treated with pro-inflammatory cytokines (IL-1β, IFNγ, and TNFα) to model type 1 diabetes (T1D) in vitro. We found that overexpression of miR-146a-5p increased cell death under conditions of inflammatory stress and led to mitochondrial membrane depolarization, whereas inhibition of miR-146a-5p reversed these effects. Additionally, inhibition of miR-146a-5p increased insulin secretion, mitochondrial DNA copy number, respiration rate, and ATP production Further, RNA sequencing data showed enrichment of pathways related to insulin secretion, apoptosis, and mitochondrial function when the expression levels of miR-146a-5p were altered. Finally, a temporal increase in miR-146a-5p expression levels and a decrease in mitochondria function markers was observed in islets derived from NOD mice. Collectively, these data suggest that miR-146a-5p may promote β cell dysfunction and death during inflammatory stress by suppressing mitochondrial function.

MiR-146a-5p mediates inflammation-induced β cell mitochondrial dysfunction and apoptosis.

We previously showed that miR-146a-5p is upregulated in pancreatic islets treated with pro-inflammatory cytokines. Others have reported that miR-146a-5p overexpression is associated with β cell apoptosis and impaired insulin secretion. However, the molecular mechanisms mediating these effects remain elusive. To investigate the role of miR-146a-5p in β cell function, we developed stable MIN6 cell lines to either overexpress or inhibit the expression of miR-146a-5p. Monoclonal cell populations were treated with pro-inflammatory cytokines (IL-1β, IFNγ, and TNFα) to model type 1 diabetes (T1D) in vitro. We found that overexpression of miR-146a-5p increased cell death under conditions of inflammatory stress and led to mitochondrial membrane depolarization, whereas inhibition of miR-146a-5p reversed these effects. Additionally, inhibition of miR-146a-5p increased insulin secretion, mitochondrial DNA copy number, respiration rate, and ATP production Further, RNA sequencing data showed enrichment of pathways related to insulin secretion, apoptosis, and mitochondrial function when the expression levels of miR-146a-5p were altered. Finally, a temporal increase in miR-146a-5p expression levels and a decrease in mitochondria function markers was observed in islets derived from NOD mice. Collectively, these data suggest that miR-146a-5p may promote β cell dysfunction and death during inflammatory stress by suppressing mitochondrial function.

Irisin alleviates the pyroptosis of β cells in T2DM by inhibiting NLRP3 inflammasome through regulating miR-19b-3p/SOCS3/STAT3 axis mediated autophagy.

The purpose of this study was to analyze the mechanism by which irisin affects β-cell pyroptosis in type 2 diabetes mellitus (T2DM). The in vivo T2DM model was established by raised with high-fat diet and intraperitoneally injection of streptozocin. Min6 cells were divided into four groups: negative control (NC), high glucose (HG), HG + irisin, and HG + irisin+3-MA. The cell viability was determined by CCK-8 assay. Dual-luciferase gene reporter assay was conducted to confirm the binding between miR-19b-3p and SOCS3. The expression level of FNDC5 and GSDMD was visualized using the immunofluorescence assay. The protein level of FNDC5, Beclin1, LC3II/I, NLRP3, cleaved-caspase-1, GSDMD-N, STAT3, p-STAT3, and SOCS3 was determined by Western blotting. The secretion of irisin, lactate dehydrogenase (LDH), and insulin was checked by ELISA. In vivo results showed that pathological changes in islet tissues with declined number of β cells, elevated FBG value, decreased FIN and HOMA-β value, elevated autophagy-associated proteins expressions, and activated NLRP3 signaling in T2DM mice, which were dramatically reversed by FNDC5 overexpression. Furthermore, the declined level of miR-19b-3p and p-STAT3, as well as the upregulation of SOCS3, was greatly rescued by FNDC5 overexpression. The in vitro data confirmed the binding site between SOCS3 and miR-19b-3p. SOCS3 was downregulated and p-STAT3 was upregulated in miR-19b-3p mimic-treated Min6 cells. In HG-stimulated Min6 cells, the elevated cell viability, increased production of insulin, decreased release of LDH, and inactivated NLRP3 signaling induced by irisin were abolished by miR-19b-3p inhibitor and STAT3 inhibitor. The increased level of autophagy-related proteins and activated SOCS3/STAT3 axis induced by irisin in HG-stimulated Min6 cells were abolished by miR-19b-3p inhibitor. The inhibitory effect of irisin against NLRP3 signaling in HG-stimulated Min6 cells was abrogated by 3-MA. In conclusion, irisin alleviated the pyroptosis of β cells in T2DM by inhibiting NLRP3 signaling through miR-19b-3p/SOCS3/STAT3 axis mediated autophagy.