Insulin In Mice Research Articles

Network pharmacology and transcriptomics explore the therapeutic effects of Ermiao Wan categorized formulas for diabetes in mice

Ermiao wan (EMW) is a classical traditional Chinese medicine formula, with two modified versions including Sanmiao wan (SMW) and Simiao wan (FMW). These Ermiao wan categorized formulas (ECFs) are traditionally used to treat gouty arthritis and hyperuricemia. However, their potential benefits and mechanisms on diabetes remain to be explored. This study aims to investigate the overall effects and biological differences of ECFs in high fat diet (HFD)-fed mice based on network pharmacology and transcriptomics. ECFs significantly reduced body weight, improved oral glucose tolerance, decreased fat accumulation, and lowered serum insulin and inflammatory cytokine levels in HFD-fed mice. FMW had better efficacy than EMW and SMW. Network pharmacology analysis revealed that ECFs targeted functional modules associated with chronic inflammation, lipid metabolism, and glucose metabolism. Transcriptome results also showed ECFs could inhibit genes associated with inflammation and upregulated some genes in lipid metabolism. Comprehensive analysis and QPCR verification indicated the beneficial effects of ECFs on diabetes might be attributed to the regulation of Ddit3, Ccl2, Esr1, and Cyp7a1. This study provides a theoretical basis for the clinical use of ECFs.

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

PARN Maintains RNA Stability to Regulate Insulin Maturation and GSIS in Pancreatic β Cells.

Diabetes, a metabolic disorder characterized by hyperglycemia, underscores the importance of normal pancreatic β-cell development and function in maintaining glucose homeostasis. Poly(A)-specific ribonuclease (PARN) serves as the principal regulator of messenger RNA (mRNA) stability, yet its specific role in pancreatic β cells remains unclear. This study utilizes mice with targeted PARN deficiency in β cells to elucidate this role. Notably, Parn conditional knockout mice present unaltered β-cell development and insulin sensitivity but reduced glucose-stimulated insulin secretion (GSIS). The observed outcomes are corroborated in NIT-1 cells. Furthermore, transcriptomic analyses reveal aberrant mRNA expression of genes crucial for insulin secretion in PARN-deficient β cells. Insights from linear amplification of complementary DNA ends and sequencing and coimmunoprecipitation experiments reveal an interaction between PARN and polypyrimidine tract-binding protein 1 (PTBP1), regulating the RNA stability of solute carrier family 30, member 8 (Slc30a8) and carbohydrate sulfotransferase 3 (Chst3). Interference with either PARN or PTBP1 disrupts this stability. These data indicate that PARN deficiency hampers GSIS and insulin maturation by destabilizing Slc30a8 and Chst3 RNAs. These findings provide compelling evidence indicating that PARN is a potential therapeutic target for enhancing insulin maturation and secretion.

An orally administered glucose-responsive polymeric complex for high-efficiency and safe delivery of insulin in mice and pigs.

Contrary to current insulin formulations, endogenous insulin has direct access to the portal vein, regulating glucose metabolism in the liver with minimal hypoglycaemia. Here we report the synthesis of an amphiphilic diblock copolymer comprising a glucose-responsive positively charged segment and polycarboxybetaine. The mixing of this polymer with insulin facilitates the formation of worm-like micelles, achieving highly efficient absorption by the gastrointestinal tract and the creation of a glucose-responsive reservoir in the liver. Under hyperglycaemic conditions, the polymer triggers a rapid release of insulin, establishing a portal-to-peripheral insulin gradient-similarly to endogenous insulin-for the safe regulation of blood glucose. This insulin formulation exhibits a dose-dependent blood-glucose-regulating effect in a streptozotocin-induced mouse model of type 1 diabetes and controls the blood glucose at normoglycaemia for one day in non-obese diabetic mice. In addition, the formulation demonstrates a blood-glucose-lowering effect for one day in a pig model of type 1 diabetes without observable hypoglycaemia, showing promise for the safe and effective management of type 1 diabetes.

Deciphering the Molecular Dance: Exploring the Dynamic Interplay Between Mouse Insulin B9-23 Peptides and their Variants.

Type 1 diabetes results from the autoimmune destruction of pancreatic insulin-producing β-cells, primarily targeted by autoreactive T cells that recognize insulin B9-23 peptides as antigens. Using drift tube ion mobility spectrometry-mass spectrometry, transmission electron microscopy, and two-dimensional infrared spectroscopy, we characterized mouse insulin 1 B9-23 (Ins1 B9-23), insulin 2 B9-23 (Ins2 B9-23), along with two of their mutants, Ins2 B9-23 Y16A and Ins2 B9-23 C19S. Our findings indicate that Ins1 B9-23 and the Ins2 Y16A mutant exhibit rapid fibril formation, whereas Ins2 B9-23 and the Ins2 C19S mutant show slower fibrillization and a structural rearrangement from globular protofibrils to fibrillar aggregates. These differences in aggregation behaviors also manifest in interactions with (-)epigallocatechin gallate (EGCG), a canonical amyloid inhibitor. EGCG effectively disrupts the fibrils formed by Ins1 B9-23 and the Y16A mutant. However, it proves ineffective in preventing fibril formation of Ins2 B9-23 and the C19S mutant. These results establish a strong correlation between the aggregation behaviors of these peptides and their divergent effects on anti-islet autoimmunity.

Consistent Delivery of Adeno-Associated Virus via Lateral Tail-Vein Injection in Adult Mice.

Many disorders affect multiple organs or involve different regions of the body, so it is critical to deliver therapeutics systemically to target the affected cells located in different sites. Intravenous injection is a widely used systemic delivery route in preclinical studies that assess treatments intended for body-wide administration. In adult mice, it involves the intravenous administration of the therapeutic agent into the mouse's lateral tail veins. When mastered, tail-vein injections are safe and fast, and only require simple and commonly available tools. However, tail-vein injections are technically challenging and require extensive training and continuous practice to ensure the accurate delivery of the intended dose. Here we describe a detailed, optimized, lateral tail-vein injection protocol that we have developed based on our experience and on recommendations that had been previously reported by other groups. Other than the mouse restrainers and insulin syringes, this protocol requires only reagents and equipment that are readily available in most labs. We found that following this protocol results in consistently successful intravenous delivery of adeno-associated virus (AAV) into the tail veins of unsedated 7-9 week-old mice. Additionally, we describe the optimized protocols for the histological detection of fluorescent reporter proteins and vector genome per diploid genome (vg/dg) quantification used to assess AAV transduction and biodistribution. The goal of this protocol is to aid experimenters in easily performing tail-vein injections successfully and consistently, which can reduce the practice time needed to master the technique.

Effects of a high-fat diet on cognition and brain distribution of intranasal insulin in E3 and E4 male and female mice

There are genetic and environmental risk factors that contribute to the development of cognitive decline in Alzheimer’s disease (AD). Some of these include the genetic predisposition of the apolipoprotein E4 genotype, consuming a high-fat diet (HFD), and the female sex. Brain insulin receptor resistance and deficiency have also been shown to be associated with AD and cognitive impairment. Intranasal (INL) insulin enhances cognition in AD, but the response varies due to genotype, diet, and sex. We investigated here the combination of these risk factors in a humanized mouse model, expressing E3 or E4, following a HFD in males and females on cognitive performance and the brain distribution of insulin following INL delivery. The HFD had a negative effect on survival in male mice only, requiring sex to be collapsed. We found many genotype, diet, and genotype x diet effects in anxiety-related tasks. We further found beneficial effects of INL insulin in our memory tests, with the most important findings showing a beneficial effect of INL insulin in mice on a HFD. We found insulin distribution throughout the brain after INL delivery was largely unaffected by diet and genotype, indicating these susceptible groups can still receive adequate levels of insulin following INL delivery. Our findings support the involvement of brain insulin signaling in cognition and highlight continuing efforts investigating mechanisms resulting from treatment with INL insulin.

Bruton's tyrosine kinase (BTK) inhibitors alter blood glucose and insulin in obese mice but reduce inflammation independent of BTK.

Obesity is associated with metabolic inflammation, which can contribute to insulin resistance, higher blood glucose, and higher insulin indicative of prediabetes progression. The nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome is a metabolic danger sensor implicated in metabolic inflammation. Many features of metabolic disease can activate the NLRP3 inflammasome; however, it is not yet clear which upstream triggers to target, and there are no clinically approved NLRP3 inflammasome inhibitors for metabolic disease. Bruton's tyrosine kinase (BTK) mediates activation of the NLRP3 inflammasome. Ibrutinib is the most-studied pharmacological inhibitor of BTK, and it can improve blood glucose control in obese mice. However, inhibitors of tyrosine kinases are permissive, and it is unknown if BTK inhibitors require BTK to alter endocrine control of metabolism or metabolic inflammation. We tested whether ibrutinib and acalabrutinib, a new generation BTK inhibitor with higher selectivity, require BTK to inhibit the NLRP3 inflammasome, metabolic inflammation, and blood glucose in obese mice. Chronic ibrutinib administration lowered fasting blood glucose and improved glycemia, whereas acalabrutinib increased fasting insulin levels and increased markers of insulin resistance in high-fat diet-fed CBA/J mice with intact Btk. These metabolic effects of BTK inhibitors were absent in CBA/CaHN-Btkxid/J mice with mutant Btk. However, ibrutinib and acalabrutinib reduced NF-κB activity, proinflammatory gene expression, and NLRP3 inflammasome activation in macrophages with and without functional BTK. These data highlight that the BTK inhibitors can have divergent effects on metabolism and separate effects on metabolic inflammation that can occur independently of actions on BTK.NEW & NOTEWORTHY Bruton's tyrosine kinase (BTK) is involved in immune function. It was thought that BTK inhibitors improve characteristics of obesity-related metabolic disease by lowering metabolic inflammation. However, tyrosine kinase inhibitors are permissive, and it was not known if different BTK inhibitors alter host metabolism or immunity through actions on BTK. We found that two BTK inhibitors had divergent effects on blood glucose and insulin via BTK, but inhibition of metabolic inflammation occurred independently of BTK in obese mice.

The GLP-1 Receptor Agonist Liraglutide Decreases Primary Bile Acids and Serotonin in the Colon Independently of Feeding in Mice.

Liraglutide, a glucagon-like peptide 1 analog used to treat type 2 diabetes and obesity, is a potential new treatment modality for bile acid (BA) diarrhea. Here, we show that administration of liraglutide significantly decreased total BAs, especially the primary BAs, including cholic acid, chenodeoxycholic acid, taurocholic acid, taurochenodeoxycholic acid, glycocholic acid, and β-muricholic acid, in the liver and feces. In addition, liraglutide significantly decreased tryptophan metabolites, including L-tryptophan, serotonin, 5-hydroxy indole-3-acetic acid, L-kynurenine, and xanthurenic acid, in the colon, whereas it significantly increased indole-3-propionic acid. Moreover, the administration of liraglutide remarkably decreased the expression of apical sodium-dependent bile acid transporter, which mediates BA uptake across the apical brush border member in the ileum, ileal BA binding protein, and fibroblast growth factor 15 in association with decreased expression of the BA-activated nuclear receptor farnesoid X receptor and the heteromeric organic solute transporter Ostα/β, which induces BA excretion, in the ileum. Liraglutide acutely decreased body weight and blood glucose levels in association with decreases in plasma insulin and serotonin levels in food-deprived mice. These findings suggest the potential of liraglutide as a novel inhibitor of primary BAs and serotonin in the colon.

Thymidylate synthase disruption to limit cell proliferation in cell therapies

Stem and progenitor cells hold great promise for regenerative medicine and gene therapy approaches. However, transplantations of living cells entail a fundamental risk of unwanted growth, potentially exacerbated by CRISPR-Cas9 or other genetic manipulations. Here, we describe a safety system to control cell proliferation while allowing robust and efficient cell manufacture, without any added genetic elements. Inactivating TYMS, a key nucleotide metabolism enzyme, in several cell lines resulted in cells that proliferate only when supplemented with exogenous thymidine. Under supplementation, TYMS-/--pluripotent stem cells proliferate, produce teratomas and successfully differentiate into potentially therapeutic cell types such as pancreatic beta-cells. Our results suggest that supplementation with exogenous thymidine affects stem cell proliferation, but not the function of stem cell-derived cells. After differentiation, postmitotic cells do not require thymidine in vitro or in vivo, as shown by the production of functional human insulin in mice up to 5 months after implantation of stem-cell derived pancreatic tissue.

Catalpol improves insulin resistance and lipid metabolism disorder in diabetic mice by inhibiting microRNA-101-3p to up-regulate FOS-related antigen 2.

Disorders of glucose and lipid metabolism are important causes of type 2 diabetes mellitus (T2DM). Defining the molecular mechanisms of metabolic disorders and exploring drug targets are key to the treatment of T2DM. The study discovered the effects of catalpol on insulin resistance (IR) and lipid metabolism disorder (LMD) in type 2 diabetes mellitus (T2DM). A T2DM mouse model was established by a high-fat diet and a single intraperitoneal injection of streptozotocin. and injected with catalpol at 10 mg/kg for 12 weeks, and the lentiviral vector of miR-101-3p or Fos-related antigen 2 (FOSL2) expression was interfered with intravenously mouse insulin resistance (IR) and lipid metabolism disorder (LMD)-related indices were then measured. Pancreatic histopathology was observed by hematoxylin and eosin (HE) staining and TUNEL staining. The miR-101-3p and FOSL2 were detected by RT-qPCR or Western blot. In results: catalpol improved IR and LMD (both P<0.05) in diabetic mice, and alleviated the histopathological changes in the pancreas. miR-101-3p was upregulated (P<0.05), and FOSL2 was downregulated (P<0.05) in T2DM mice, while catalpol rescued their expression pattern (both P<0.05). The miR-101-3p targeted FOSL2. Down-regulating miR-101-3p or up-regulating FOSL2 improved IR and LMD (all P<0.05) in diabetic mice, and alleviated pancreatic histopathological changes. Overexpressing miR-101-3p or suppressing FOSL2 weakened the ameliorative effects of catalpol in T2DM mice (all P<0.05). We conclude that catalpol improves IR and LMD in diabetic mice by inhibiting miR-101-3p to up-regulate FOSL2.

Bioinformatic analysis and construction of competitive endogenous RNA network reveals protective effect of Jiangtang Sanhao Formula on the liver of diabetic mice

IntroductionJiangtang Sanhao Formula (JTSHF), composed of Panax ginseng, Atractylodes macrocephala, Coptis chinensis, Salvia miltiorrhiza and several other herbs, is a traditional Chinese medicine formula commonly used to treat type 2 diabetes. This compound shows significant clinical efficacy in the treatment of diabetic, however, its target and pharmacological mechanism are still unclear. The present study explored the therapeutic effect of JTSHF on diabetic mice and conducted RNA sequencing to investigate the potential mechanism. MethodsThe T2DM mice model was established using a high-fat diet combined with an intraperitoneal injection of low-dose STZ. Fasting blood glucose (FBG), serum insulin, glucose tolerance, and blood lipids in mice from different groups were examined. Then the effects of JTSHF on oxidative stress and liver histopathology in diabetic mice were observed. Next, transcriptome analysis was performed to identify differentially expressed genes (DEG), which were validated using real-time quantitative PCR (RT-qPCR). By using pathway enrichment analysis, we identified several key pathways which are essential in the JTSHF effect on T2DM. Finally, we constructed ceRNA network to illustrate the regulatory effect of JTSHF on transcriptional profile in diabetic liver. ResultsJTSHF reduced FBG level and blood lipid contents, ameliorated glucose tolerance and improved insulin sensitivity in diabetic mice. It also showed protective effects on fatty livers induced by high-fat diet and diabetes. For the first time, we revealed that JTSHF exerts anti-T2DM role in the liver of diabetic mice, which is associated with multiple molecular targets and signaling pathways. Enrichment analysis and treatment-based mRNA-ncRNA-miRNA ceRNA networks revealed that JTSHF might exerts therapeutic effect by modulating lipid metabolism. DiscussionOur research found that JTSHF exerts anti-T2DM effect by affecting multiple pathways. Among these, lipid metabolism and oxidative stress might be involved. The present study provided novel insights for the mechanism of JTSHF, and the differentially expressed genes identified can be potential therapeutic targets in the treatment of T2DM in future.

Silencing ANGPTL8 reduces mouse preadipocyte differentiation and insulin signaling

ANGPTL8, expressed mainly in the liver and adipose tissue, regulates the activity of lipoprotein lipase (LPL) present in the extracellular space and triglyceride (TG) metabolism through its interaction with ANGPTL3 and ANGPTL4. Whether intracellular ANGPTL8 can also exert effects in tissues where it is expressed is uncertain. ANGPTL8 expression was low in preadipocytes and much increased during differentiation. To better understand the role of intracellular ANGPTL8 in adipocytes and assess whether it may play a role in adipocyte differentiation, we knocked down its expression in normal mouse subcutaneous preadipocytes. ANGPTL8 knockdown reduced adipocyte differentiation, cellular TG accumulation and also isoproterenol-stimulated lipolysis at day 7 of differentiation. RNA-Seq analysis of ANGPTL8 siRNA or control siRNA transfected SC preadipocytes on days 0, 2, 4 and 7 of differentiation showed that ANGPTL8 knockdown impeded the early (day 2) expression of adipogenic and insulin signaling genes, PPARγ, as well as genes related to extracellular matrix and NF-κB signaling. Insulin mediated Akt phosphorylation was reduced at an early stage during adipocyte differentiation. This study based on normal primary cells shows that ANGPTL8 has intracellular actions in addition to effects in the extracellular space, like modulating LPL activity. Preadipocyte ANGPTL8 expression modulates their differentiation possibly via changes in insulin signaling gene expression.

Vitamin D Alleviates Type 2 Diabetes Mellitus by Mitigating Oxidative Stress-Induced Pancreatic β-Cell Impairment.

Type 2 diabetes mellitus (T2DM) is a common metabolic disorder with rising incidence worldwide. This study explored the anti-T2DM role of vitamin D, thereby providing novel therapeutic strategies. C57BL/6 J mice and MIN6 cells were used to induce in vivo T2DM and damaged β-cell models, respectively. Body weights, fasting blood glucose, and fasting insulin were measured in mice. Oral glucose tolerance test (OGTT) and insulin tolerance test (ITT) were conducted on mice. Lipid indices (TG, TC, LDL-C, and HDL-C) were detected in mouse serum. Hematoxylin-eosin staining was used to evaluate pancreatic tissue injury. ELISA was used to assess insulin and oxidative stress (OS) markers (MDA, GSH, and SOD) in mice and MIN6 cells. Production of ROS was detected in islet β-cells and MIN6 cells. Cell viability and apoptosis were evaluated using CCK-8 and flow cytometry, respectively. QRT-PCR and western blotting were used to detect pro-inflammatory factors (TNF-α and IL-6) and endoplasmic reticulum stress (ERS) markers (CHOP and GRP78), respectively. Vitamin D reduced body weights, fasting blood glucose, and insulin and ameliorated glucose tolerance and insulin sensitivity in T2DM mice. Besides, vitamin D decreased serum TG, TC, LDL-C, and increased HDL-C in T2DM mice. Vitamin D inhibited pancreatic histopathological injury, cell apoptosis, OS, and β-cell decline in T2DM mice. Moreover, vitamin D alleviated cell death, insufficient insulin secretion, inflammation, OS, and ERS in damaged MIN6 cells. Notably, N-acetyl-L-cysteine (an OS inhibitor) enhanced these effects of vitamin D. Vitamin D relieved T2DM symptoms by alleviating OS-induced β-cell impairment.

D4 Dopamine Receptors Regulate Insulin and Salt Sensitivities in Mice

D4 Dopamine Receptors Regulate Insulin and Salt Sensitivities in Mice

Ablation of diacylglycerol kinase ε promotes whitening of brown adipose tissue under high fat diet feeding

Adipose tissue (AT) comprises distinct fat depots such as white AT and brown AT. White and brown adipocytes exhibit different morphological and physiological properties. White adipocytes containing large single lipid droplet (LD) provide energy on demand whereas brown adipocytes loaded with multilocular LDs consume energy to generate heat or dissipate excess energy. Recent studies have shown that multilocular brown-like cells emerge in white AT under certain conditions. These cells termed beige adipocytes participate in energy expenditure and heat generation. In the process of lipolysis, TG is broken down into free fatty acid and diacylglycerol (DG). In this regard, DG also serves as a signaling molecule activating some proteins such as protein kinase C. Therefore, DG kinase (DGK), an enzyme which phosphorylates DG into phosphatidic acid (PA), plays a pivotal role in integrating energy homeostasis and intracellular signaling. Recently, we described that DGKε-KO mice exhibit increased adiposity in visceral white AT accompanied with impaired glucose tolerance early (40 days) in the course of high fat diet (HFD) feeding, although these mice exhibit “browning or beiging” in visceral white AT associated with improved glucose tolerance after longer term HFD feeding (180 days). This study was conducted to understand the overall features of adipose tissues and investigate changes in subcutaneous (inguinal) white AT and interscapular brown AT of DGKε-KO mice during the course of HFD feeding. Results demonstrated that fat accumulation is promoted in all fat depots under 40 days of HFD feeding conditions. Remarkably, “whitening” of brown adipocytes was identified in DGKε-deficient brown AT during the course of HFD feeding, suggesting brown adipocyte dysfunction. In addition, insulin levels were considerably elevated in DGKε-KO mice under 180 days of HFD feeding conditions. Collectively, these findings suggest that brown adipocytes are dysfunctional in DGKε-KO mice, which promotes browning or beiging in visceral white AT. Beige adipocytes may take over energy disposal and contribute to improving glucose tolerance with the aid of high levels of insulin in DGKε-KO mice upon excess feeding.

Exercise ameliorates skeletal muscle insulin resistance by modulating GRK4-mediated D1R expression.

Exercise has been recommended as a nonpharmaceutical therapy to treat insulin resistance (IR). Previous studies showed that dopamine D1-like receptor agonists, such as fenoldopam, could improve peripheral insulin sensitivity, while antipsychotics, which are dopamine receptor antagonists, increased susceptibility to Type 2 diabetes mellitus (T2DM). Meanwhile, exercise has been proved to stimulate dopamine receptors. However, whether the dopamine D1 receptor (D1R) is involved in exercise-mediated amelioration of IR remains unclear. We found that the D1-like receptor antagonist, SCH23390, reduced the effect of exercise on lowering blood glucose and insulin in insulin-resistant mice and inhibited the contraction-induced glucose uptake in C2C12 myotubes. Similarly, the opposite was true for the D1-like receptor agonist, fenoldopam. Furthermore, the expression of D1R was decreased in skeletal muscles from streptozotocin (STZ)- and high-fat intake-induced T2DM mice, accompanied by increased D1R phosphorylation, which was reversed by exercise. A screening study showed that G protein-coupled receptor kinase 4 (GRK4) may be the candidate kinase for the regulation of D1R function, because, in addition to the increased GRK4 expression in skeletal muscles of T2DM mice, GRK4 transgenic T2DM mice exhibited lower insulin sensitivity, accompanied by higher D1R phosphorylation than control mice, whereas the AAV9-shGRK4 mice were much more sensitive to insulin than AAV9-null mice. Mechanistically, the up-regulation of GRK4 expression caused by increased reactive oxygen species (ROS) in IR was ascribed to the enhanced expression of c-Myc, a transcriptional factor of GRK4. Taken together, the present study shows that exercise, via regulation of ROS/c-Myc/GRK4 pathway, ameliorates D1R dysfunction and improves insulin sensitivity.

Probiotic Escherichia coli Nissle 1917-derived outer membrane vesicles modulate the intestinal microbiome and host gut-liver metabolome in obese and diabetic mice.

Obesity and diabetes are common chronic metabolic disorders which can cause an imbalance of the intestinal flora and gut-liver metabolism. Several studies have shown that probiotics, including Escherichia coli Nissle 1917 (EcN), promote microbial balance and metabolic health. However, there are no studies on how EcN outer membrane vesicles (EcN-OMVs) influence the intestinal microflora and affect the metabolic disorders of obesity and diabetes. In this study, we evaluated the effects of EcN-OMVs on high-fat diet (HFD)-induced obesity and HFD + streptozotocin (STZ)-induced diabetes. EcN-OMVs could reduce body weight, decrease blood glucose, and increase plasma insulin in obese mice. Similarly, EcN-OMVs treatment could modify the ratio of Firmicutes/Bacteroidetes in the gut, elevate intestinal short-chain fatty acid (SCFA)-producing flora, and influence the SCFA content of the intestine. Furthermore, the intestinal metabolites ornithine and fumaric acid, hepatic ω-6 unsaturated fatty acids, and SCFAs were significantly increased after administering EcN-OMVs. Overall, this study showed that EcN-OMVs might act as post-biotic agents that could modulate gut-liver metabolism and ameliorate the pathophysiology of obesity and diabetes.

Supplementation with CO induces lipogenesis in adipose tissue, leptin and insulin resistance in healthy Swiss mice

The consumption of saturated fatty acids (SFA), the main compound in coconut oil (CO), can promote insulin and leptin resistance and are associated with inflammation and obesity. We investigated the effects of CO supplementation on leptin signaling in healthy mice. Swiss male mice received oral supplementation for eight weeks with 300 μL of water for the control group (CV) or CO (100 or 300 μL). Sensitivity to leptin/insulin was evaluated after eight weeks of supplementation. The CO induced endoplasmic reticulum stress and leptin resistance in the hypothalamus, as demonstrated by reduced effect on the energy expenditure, hypothalamic pJAK2 and pSTAT3, and POMC expression. In the adipose tissue, lipogenesis was favored and STAT3 and JAK2 signaling was impaired after CO supplementation. Furthermore, the supplementation with CO reduced pAKT in the hypothalamus, liver and white adipose tissue. These results show that CO induces hypothalamic and peripheral resistance to leptin and insulin in healthy mice.

236-OR: Pancreatic ß-Cell TRAPδ Deficiency Reduces Insulin Production but Improves Insulin Sensitivity

The endoplasmic reticulum (ER) membrane protein translocon-associated protein-δ (TRAPδ, also known as SSR4) is involved in insulin biosynthesis in pancreatic β cell lines. However, its pathophysiological significance for the maintenance of islet β cell function and glucose homeostasis is unclear. Herein, we generated a mouse line with pancreatic β cell-specific deletion of TRAPδ (TRAPδ βKO), and found that TRAPδ βKO led to decreased circulating insulin in mice fed with either normal chow diet or high fat diet. Multiple independent experiments confirmed that, although TRAPδ deletion decreased insulin content in the islets, it did not affect composition of islet cells, insulin gene expression, insulin/proinsulin ratio, nor the expression and glycosylation of the prohormone enzymes involved in proinsulin processing. These data suggest that TRAPδ does not play a critical role in the transcription of insulin gene and processing of proinsulin. Importantly, untranslocated preproinsulin was significantly increased when the islets were treated with a proteasomal inhibitor, suggesting that TRAPδ deficiency impaired preproinsulin translocation, resulting in a rapid degradation of untranslocated preproinsulin that accounts for the decreased insulin production. Interestingly, the moderate decrease in the circulating insulin level in TRAPδ βKO mice did not cause impaired glucose tolerance and elevated fasting blood glucose, suggesting that compensatory mechanisms may account for maintaining glucose homeostasis. The insulin tolerance tests confirmed improvement of insulin sensitivity accompanied with upregulation of phosphorylated AKT in the peripheral insulin target tissues of TRAPδ βKO mice. Together, these data uncover a critical role of TRAPδ in preproinsulin translocation and insulin biosynthesis. The moderately decreased circulating insulin promotes insulin sensitivity in the insulin target tissues. Disclosure J.Guo: None. Y.Huang: None. M.Liu: None. Y.Yang: None. N.Xu: None. Y.Yang: None. W.Feng: None. Y.Ye: None. X.Li: None. X.Xu: None. J.Cui: None. Funding National Natural Science Foundation of China (81830025, 82220108014, 82270864, 82070854); National Key R&amp;D Program of China (2019YFA0802502, 2022YFE0131400); Tianjin Municipal Health and Health Committee (TJWJ2021ZD00); Tianjin Key Medical Discipline (Specialty) Construction Project (TJYXZDXK-030A)