Model Of Type 2 Diabetes Research Articles

Proteome profiling of whole plasma and plasma-derived extracellular vesicles facilitates the detection of tissue biomarkers in the non-obese diabetic mouse.

The mechanism by which pancreatic beta cells are destroyed in type 1 diabetes (T1D) remains to be fully understood. Recent observations indicate that the disease may arise because of different pathobiological mechanisms (endotypes). The discovery of one or several protein biomarkers measurable in readily available liquid biopsies (e.g. blood plasma) during the pre-diabetic period may enable personalized disease interventions. Recent studies have shown that extracellular vesicles (EVs) are a source of tissue proteins in liquid biopsies. Using plasma samples collected from pre-diabetic non-obese diabetic (NOD) mice (an experimental model of T1D) we addressed if combined analysis of whole plasma samples and plasma-derived EV fractions increases the number of unique proteins identified by mass spectrometry (MS) compared to the analysis of whole plasma samples alone. LC-MS/MS analysis of plasma samples depleted of abundant proteins and subjected to peptide fractionation identified more than 2300 proteins, while the analysis of EV-enriched plasma samples identified more than 600 proteins. Of the proteins detected in EV-enriched samples, more than a third were not identified in whole plasma samples and many were classified as either tissue-enriched or of tissue-specific origin. In conclusion, parallel profiling of EV-enriched plasma fractions and whole plasma samples increases the overall proteome depth and facilitates the discovery of tissue-enriched proteins in plasma. If applied to plasma samples collected longitudinally from the NOD mouse or from models with other pathobiological mechanisms, the integrated proteome profiling scheme described herein may be useful for the discovery of new and potentially endotype specific biomarkers in T1D.

Efficacy and Mechanism of Pueraria lobata and Pueraria thomsonii Polysaccharides in the Treatment of Type 2 Diabetes.

Diabetes is called a “wasting and thirsting disorder” in Chinese traditional medicine because there is a depletion of vital substances in the body independent of the intake of food or water and an inability to reintroduce fluids through drinking. Pueraria lobata (Willd.) Ohwi (GG) and Pueraria thomsonii Benth. (FG) are traditional Chinese herbal medicines used in the treatment of wasting-thirst that reduce blood glucose levels. Flavonoids are the main pharmacodynamic components of GG and FG, and they are also the most studied components at present, but polysaccharides are also active components of GG and FG, which, however, are less studied. Therefore, this study aimed to investigate the effect of Pueraria polysaccharides (GG and FG polysaccharides) on type 2 diabetes (T2D), as well as their related mechanisms of action in terms of both intestinal flora and metabolomics. The C57BL/KsJ-db/db mouse model, a well-established model of obesity-induced T2D, was used in this study. The metabolomic analysis showed that Pueraria polysaccharides improved the metabolic profile of diabetic mice and significantly regulated metabolites and metabolic pathways. Both GG and FG polysaccharides regulated insulin resistance in mice by regulating PPAR signaling pathway so as to treat T2D. Additionally, Pueraria polysaccharides regulated the structure of gut microbiota and improved the diabetes-related metabolic pathway. Therefore, this study discovered the antidiabetic effects and potential mechanisms of Pueraria polysaccharides through multiple pathways involving gut microbiota and metabolites, providing a theoretical basis for further studies on their effects in the treatment of T2D.

Proteomic examination of Cornus officinalis stimulated 1.1B4 human pancreatic cells reveals activation of autophagy and Keap1/Nrf2 pathway

Type 1 diabetes (T1D) is an autoimmune disease initiated by genetic predisposition and environmental influences culminating in the immunologically mediated destruction of pancreatic β-cells with eventual loss of insulin production. Although T1D can be accurately predicted via autoantibodies, therapies are lacking that can intercede autoimmunity and protect pancreatic β-cells. There are no approved interventional modalities established for this purpose. One such potential source for clinical agents of this use is from the frequently utilized Cornus officinalis (CO) in the field of ethnopharmacology. Studies by our lab and others have demonstrated that CO has robust proliferative, metabolic, and cytokine protective effects on pancreatic β-cells. To identify the molecular mechanism of the biological effects of CO, we performed a proteomic and phosphoproteomic analysis examining the cellular networks impacted by CO application on the 1.1B4 pancreatic β-cell line. Our label-free mass spectrometry approach has demonstrated significant increased phosphorylation of the selective autophagy receptor of p62 (Sequestosome-1/SQSTM1/p62) and predicted activation of the antioxidant Kelch-like ECH-associated protein 1 (Keap1)/Nuclear factor-erythroid factor 2-related factor 2 (Nrf2) pathway. Further validation by immunoblotting and immunofluorescence revealed markers of autophagy such as increased LC3-II and decreased total p62 along with nuclear localization of Nrf2. Both autophagy and the Keap1/Nrf2 pathways have been shown to be impaired in human and animal models of T1D and may serve as an excellent potential therapeutic target stimulated by CO.

Role of adropin in arterial stiffening associated with obesity and type 2 diabetes.

Adropin is a peptide largely secreted by the liver and known to regulate energy homeostasis; however, it also exerts cardiovascular effects. Herein, we tested the hypothesis that low circulating levels of adropin in obesity and type 2 diabetes (T2D) contribute to arterial stiffening. In support of this hypothesis, we report that obesity and T2D are associated with reduced levels of adropin (in liver and plasma) and increased arterial stiffness in mice and humans. Establishing causation, we show that mesenteric arteries from adropin knockout mice are also stiffer, relative to arteries from wild-type counterparts, thus recapitulating the stiffening phenotype observed in T2D db/db mice. Given the above, we performed a set of follow-up experiments, in which we found that 1) exposure of endothelial cells or isolated mesenteric arteries from db/db mice to adropin reduces filamentous actin (F-actin) stress fibers and stiffness, 2) adropin-induced reduction of F-actin and stiffness in endothelial cells and db/db mesenteric arteries is abrogated by inhibition of nitric oxide (NO) synthase, and 3) stimulation of smooth muscle cells or db/db mesenteric arteries with a NO mimetic reduces stiffness. Lastly, we demonstrated that in vivo treatment of db/db mice with adropin for 4 wk reduces stiffness in mesenteric arteries. Collectively, these findings indicate that adropin can regulate arterial stiffness, likely via endothelium-derived NO, and thus support the notion that "hypoadropinemia" should be considered as a putative target for the prevention and treatment of arterial stiffening in obesity and T2D.NEW & NOTEWORTHY Arterial stiffening, a characteristic feature of obesity and type 2 diabetes (T2D), contributes to the development and progression of cardiovascular diseases. Herein we establish that adropin is decreased in obese and T2D models and furthermore provide evidence that reduced adropin may directly contribute to arterial stiffening. Collectively, findings from this work support the notion that "hypoadropinemia" should be considered as a putative target for the prevention and treatment of arterial stiffening in obesity and T2D.

Sustained inhibition of NPY/AgRP neuronal activity by FGF1.

In rodent models of type 2 diabetes (T2D), central administration of FGF1 normalizes elevated blood glucose levels in a manner that is sustained for weeks or months. Increased activity of NPY/AgRP neurons in the hypothalamic arcuate nucleus (ARC) is implicated in the pathogenesis of hyperglycemia in these animals, and the ARC is a key brain area for the antidiabetic action of FGF1. We therefore sought to determine whether FGF1 inhibits NPY/AgRP neurons and, if so, whether this inhibitory effect is sufficiently durable to offer a feasible explanation for sustained diabetes remission induced by central administration of FGF1. Here, we show that FGF1 inhibited ARC NPY/AgRP neuron activity, both after intracerebroventricular injection in vivo and when applied ex vivo in a slice preparation; we also showed that the underlying mechanism involved increased input from presynaptic GABAergic neurons. Following central administration, the inhibitory effect of FGF1 on NPY/AgRP neurons was also highly durable, lasting for at least 2 weeks. To our knowledge, no precedent for such a prolonged inhibitory effect exists. Future studies are warranted to determine whether NPY/AgRP neuron inhibition contributes to the sustained antidiabetic action elicited by intracerebroventricular FGF1 injection in rodent models of T2D.

Heterogeneity and altered β-cell identity in the TallyHo model of early-onset type 2 diabetes

A primary underlying defect makes β-cells "susceptible" to no longer compensate for the peripheral insulin resistance and to trigger the onset of type 2 diabetes (T2D). New evidence suggests that in T2D, β-cells are not destroyed but experience a loss of identity, reverting to a progenitor-like state and largely losing the ability to sense glucose and produce insulin. We assessed (using fluorescence microscopy and histomorphometry correlated with the glycaemic status) the main β-cell identity modifications as diabetes progresses in the TallyHo/JngJ (TH) male mice, a polygenic model of spontaneous T2D, akin to the human phenotype. We found that: 1) conversion to overt diabetes is paralleled by a progressive reduction of insulin-expressing cells and expansion of a glucagon-positive population, together with alteration of islet size and shape; 2) the β-cell population is highly heterogeneous in terms of insulin content and specific transcription factors like PDX1 and NKX6.1, that are gradually lost during diabetes progression; 3) GLUT2 expression is altered early and strongly reduced at late stages of diabetes; 4) an endocrine developmental program dependent on NGN3-expressing progenitors is revived when hyperglycaemia becomes severe; and 5) the re-expression of the EMT-associated factor vimentin occurs as diabetes worsens, representing a possible regenerative response to β-cell loss. Based on these results, we formulated additional hypotheses for the β-cell identity alteration in the TH model, together with several limitations of the study, that constitute future research directions.

Comparison of therapeutic effects of mesenchymal stem cells from umbilical cord and bone marrow in the treatment of type 1 diabetes

BackgroundThe therapeutic potential of mesenchymal stem cells (MSCs) in type 1 diabetes (T1D) has been demonstrated in both preclinical and clinical studies. MSCs that have been used in research on T1D are derived from various tissue sources, with bone marrow (BM) and umbilical cord (UC) tissues being the most commonly used. However, the influence of tissue origin on the functional properties and therapeutic effects of MSCs in T1D remains unclear. This study aimed to compare the therapeutic efficacy of UC-MSCs and BM-MSCs in a mouse model of T1D as well as in patients with T1D.MethodsIn non-obese diabetic (NOD) mice, the development of diabetes was accelerated by streptozotocin injections. Thereafter, diabetic mice were randomized and treated intravenously with UC-MSCs, BM-MSCs or phosphate-buffered saline as a control. Blood glucose and serum insulin were measured longitudinally after transplantation. At 14 days post-transplantation, pancreatic tissues were collected to assess insulitis and the β-cell mass. Flow cytometry was performed to evaluate the composition of T lymphocytes in the spleen and pancreatic lymph nodes of the NOD mice. In our retrospective study of patients with T1D, 28 recipients who received insulin therapy alone or a single transplantation of UC-MSCs or BM-MSCs were enrolled. The glycaemic control and β-cell function of the patients during the first year of follow-up were compared.ResultsIn NOD mice, UC-MSC and BM-MSC transplantation showed similar effects on decreasing blood glucose levels and preserving β cells. The regulation of islet autoimmunity was examined, and no significant difference between UC-MSCs and BM-MSCs was observed in the attenuation of insulitis, the decrease in T helper 17 cells or the increase in regulatory T cells. In patients with T1D, MSC transplantation markedly lowered haemoglobin A1c (HbA1c) levels and reduced insulin doses compared to conventional insulin therapy. However, the therapeutic effects were comparable between UC-MSCs and BM-MSCs, and they also exerted similar effects on the endogenous β-cell function in the patients.ConclusionIn conclusion, both UC-MSCs and BM-MSCs exhibited comparable therapeutic effects on improving glycaemic control and preserving β-cell function in T1D. Considering their abundance and higher cell yields, UC-MSCs appear to be more promising than BM-MSCs in clinical applications.Trial registration NCT02763423. Registered on May 5, 2016—Retrospectively registered, https://www.clinicaltrials.gov/.

In silico identification and verification of ferroptosis-related genes in type 2 diabetic islets.

Type 2 diabetes (T2D) is a major global public health burden, with β-cell dysfunction a key component in its pathogenesis. However, the exact pathogenesis of β-cell dysfunction in T2D is yet to be fully elucidated. Ferroptosis, a recently discovered regulated form of non-apoptotic cell death, plays a vital role in the development of diabetes and its complications. The current study aimed to identify the key molecules involved in β-cell ferroptosis3 in patients with T2D using the mRNA expression profile data of GSE25724 by bioinformatic approaches. The differentially expressed mRNAs (DE-mRNAs) in human islets of patients with T2D were screened using the islet mRNA expression profiling data from the Gene Expression Omnibus and their intersection with ferroptosis genes was then obtained. Ferroptosis-related DE-mRNA functional and pathway enrichment analysis in T2D islet were performed. Using a protein-protein interaction (PPI) network constructed from the STRING database, Cytoscape software identified ferroptosis-related hub genes in the T2D islet with a Degree algorithm. We constructed a miRNA-hub gene network using the miRWalk database. We generated a rat model of T2D to assess the expression of hub genes. A total of 1,316 DE-mRNAs were identified in the islet of patients between T2D and non-T2D (NT2D), including 221 and 1,095 up- and down-regulated genes. Gene set enrichment analysis revealed that the ferroptosis-related gene set was significantly different in islets between T2D and NT2D at an overall level. A total of 33 ferroptosis-related DE-mRNAs were identified, most of which were significantly enriched in pathways including ferroptosis. The established PPI network with ferroptosis-related DE-mRNAs identified five hub genes (JUN, NFE2L2, ATG5, KRAS, and HSPA5), and the area under the ROC curve of these five hub genes was 0.929 in the Logistic regression model. We constructed a regulatory network of hub genes and miRNAs, and the results showed that suggesting that hsa-miR-6855-5p, hsa-miR-9985, and hsa-miR-584-5p could regulate most hub genes. In rat model of T2D, the protein expression levels of JUN and NFE2L2 in pancreatic tissues were upregulated and downregulated, respectively. These results contribute to further elucidation of ferroptosis-related molecular mechanisms in the pathogenesis of β-cell dysfunction of T2D.

ICAM-1 Abundance Is Increased in Pancreatic Islets of Hyperglycemic Female NOD Mice and Is Rapidly Upregulated by NF-κB in Pancreatic β-Cells.

Type 1 diabetes (T1D) is classified as an autoimmune disease where pancreatic β-cells are specifically targeted by cells of the immune system. The molecular mechanisms underlying this process are not completely understood. Herein, we identified that the Icam1 gene and ICAM-1 protein were selectively elevated in female NOD mice relative to male mice, fitting with the sexual dimorphism of diabetes onset in this key mouse model of T1D. In addition, ICAM-1 abundance was greater in hyperglycemic female NOD mice than in age-matched normoglycemic female NOD mice. Moreover, we discovered that the Icam1 gene was rapidly upregulated in response to IL-1β in mouse, rat, and human islets and in 832/13 rat insulinoma cells. This early temporal genetic regulation requires key components of the NF-κB pathway and was associated with rapid recruitment of the p65 transcriptional subunit of NF-κB to corresponding κB elements within the Icam1 gene promoter. In addition, RNA polymerase II recruitment to the Icam1 gene promoter in response to IL-1β was consistent with p65 occupancy at κB elements, histone chemical modifications, and increased mRNA abundance. Thus, we conclude that β-cells undergo rapid genetic reprogramming by IL-1β to enhance expression of the Icam1 gene and that elevations in ICAM-1 are associated with hyperglycemia in NOD mice. These findings are highly relevant to, and highlight the importance of, pancreatic β-cell communication with the immune system. Collectively, these observations reveal a portion of the complex molecular events associated with onset and progression of T1D.

Hepatocyte Rap1a contributes to obesity- and statin-associated hyperglycemia.

SUMMARYExcessive hepatic glucose production contributes to the development of hyperglycemia and is a key feature of type 2 diabetes. Here, we report that activation of hepatocyte Rap1a suppresses gluconeogenic gene expression and glucose production, whereas Rap1a silencing stimulates them. Rap1a activation is suppressed in obese mouse liver, and restoring its activity improves glucose intolerance. As Rap1a′s membrane localization and activation depends on its geranylgeranylation, which is inhibited by statins, we show that statin-treated hepatocytes and the human liver have lower active-Rap1a levels. Similar to Rap1a inhibition, statins stimulate hepatic gluconeogenesis and increase fasting blood glucose in obese mice. Geranylgeraniol treatment, which acts as the precursor for geranylgeranyl isoprenoids, restores Rap1a activity and improves statin-mediated glucose intolerance. Mechanistically, Rap1a activation induces actin polymerization, which suppresses gluconeogenesis by Akt-mediated FoxO1 inhibition. Thus, Rap1a regulates hepatic glucose homeostasis, and blocking its activity, via lowering geranylgeranyl isoprenoids, contributes to statin-induced glucose intolerance.

Disrupted and Elevated Circadian Secretion of Glucagon-Like Peptide-1 in a Murine Model of Type 2 Diabetes.

Metabolism and circadian rhythms are intimately linked, with circadian glucagon-like peptide-1 (GLP-1) secretion by the intestinal L-cell entraining rhythmic insulin release. GLP-1 secretion has been explored in the context of obesogenic diets, but never in a rodent model of type 2 diabetes (T2D). There is also considerable disagreement regarding GLP-1 levels in human T2D. Furthermore, recent evidence has demonstrated decreased expression of the β-cell exocytotic protein secretagogin (SCGN) in T2D. To extend these findings to the L-cell, we administered oral glucose tolerance tests at 6 time points in 4-hour intervals to the high-fat diet/streptozotocin (HFD-STZ) mouse model of T2D. This revealed a 10-fold increase in peak GLP-1 secretion with a phase shift of the peak from the normal feeding period into the fasting-phase. This was accompanied by impairments in the rhythms of glucose, glucagon, mucosal clock genes (Arntl and Cry2), and Scgn. Immunostaining revealed that L-cell GLP-1 intensity was increased in the HFD-STZ model, as was the proportion of L-cells that expressed SCGN; however, this was not found in L-cells from humans with T2D, which exhibited decreased GLP-1 staining but maintained their SCGN expression. Gcg expression in isolated L-cells was increased along with pathways relating to GLP-1 secretion and electron transport chain activity in the HFD-STZ condition. Further investigation into the mechanisms responsible for this increase in GLP-1 secretion may give insights into therapies directed toward upregulating endogenous GLP-1 secretion.

A critical role of the mechanosensor PIEZO1 in glucose-induced insulin secretion in pancreatic β-cells

Glucose-induced insulin secretion depends on β-cell electrical activity. Inhibition of ATP-regulated potassium (KATP) channels is a key event in this process. However, KATP channel closure alone is not sufficient to induce β-cell electrical activity; activation of a depolarizing membrane current is also required. Here we examine the role of the mechanosensor ion channel PIEZO1 in this process. Yoda1, a specific PIEZO1 agonist, activates a small membrane current and thereby triggers β-cell electrical activity with resultant stimulation of Ca2+-influx and insulin secretion. Conversely, the PIEZO1 antagonist GsMTx4 reduces glucose-induced Ca2+-signaling, electrical activity and insulin secretion. Yet, PIEZO1 expression is elevated in islets from human donors with type-2 diabetes (T2D) and a rodent T2D model (db/db mouse), in which insulin secretion is reduced. This paradox is resolved by our finding that PIEZO1 translocates from the plasmalemma into the nucleus (where it cannot influence the membrane potential of the β-cell) under experimental conditions emulating T2D (high glucose culture). β-cell-specific Piezo1-knockout mice show impaired glucose tolerance in vivo and reduced glucose-induced insulin secretion, β-cell electrical activity and Ca2+ elevation in vitro. These results implicate mechanotransduction and activation of PIEZO1, via intracellular accumulation of glucose metabolites, as an important physiological regulator of insulin secretion.

Delivery of Dissociated Islets Cells within Microporous Annealed Particle Scaffold to Treat Type 1 Diabetes.

Type 1 diabetes (T1D) is caused by the autoimmune loss of insulin-producing beta cells in the pancreas. The only clinical approach to patient management of blood glucose that doesn't require exogenous insulin is pancreas or islet transplantation. Unfortunately, donor islets are scarce and there is substantial islet loss immediately after transplantation due, in part, to the local inflammatory response. The delivery of stem cell-derived beta cells (e.g., from induced pluripotent stem cells) and dissociated islet cells hold promise as a treatment for T1D; however, these cells typically require re-aggregation in vitro prior to implantation. Microporous scaffolds have shown high potential to serve as a vehicle for organization, survival, and function of insulin-producing cells. In this study, we investigated the use of microporous annealed particle (MAP) scaffold for delivery of enzymatically dissociated islet cells, a model beta cell source, within the scaffold's interconnected pores. We found that MAP-based cell delivery enables survival and function of dissociated islets cells both in vitro and in an in vivo mouse model of T1D.

Machine Learning-Derived Prenatal Predictive Risk Model to Guide Intervention and Prevent the Progression of Gestational Diabetes Mellitus to Type 2 Diabetes: Prediction Model Development Study.

BackgroundThe increasing prevalence of gestational diabetes mellitus (GDM) is concerning as women with GDM are at high risk of type 2 diabetes (T2D) later in life. The magnitude of this risk highlights the importance of early intervention to prevent the progression of GDM to T2D. Rates of postpartum screening are suboptimal, often as low as 13% in Asian countries. The lack of preventive care through structured postpartum screening in several health care systems and low public awareness are key barriers to postpartum diabetes screening.ObjectiveIn this study, we developed a machine learning model for early prediction of postpartum T2D following routine antenatal GDM screening. The early prediction of postpartum T2D during prenatal care would enable the implementation of effective strategies for diabetes prevention interventions. To our best knowledge, this is the first study that uses machine learning for postpartum T2D risk assessment in antenatal populations of Asian origin.MethodsProspective multiethnic data (Chinese, Malay, and Indian ethnicities) from 561 pregnancies in Singapore’s most deeply phenotyped mother-offspring cohort study—Growing Up in Singapore Towards healthy Outcomes—were used for predictive modeling. The feature variables included were demographics, medical or obstetric history, physical measures, lifestyle information, and GDM diagnosis. Shapley values were combined with CatBoost tree ensembles to perform feature selection. Our game theoretical approach for predictive analytics enables population subtyping and pattern discovery for data-driven precision care. The predictive models were trained using 4 machine learning algorithms: logistic regression, support vector machine, CatBoost gradient boosting, and artificial neural network. We used 5-fold stratified cross-validation to preserve the same proportion of T2D cases in each fold. Grid search pipelines were built to evaluate the best performing hyperparameters.ResultsA high performance prediction model for postpartum T2D comprising of 2 midgestation features—midpregnancy BMI after gestational weight gain and diagnosis of GDM—was developed (BMI_GDM CatBoost model: AUC=0.86, 95% CI 0.72-0.99). Prepregnancy BMI alone was inadequate in predicting postpartum T2D risk (ppBMI CatBoost model: AUC=0.62, 95% CI 0.39-0.86). A 2-hour postprandial glucose test (BMI_2hour CatBoost model: AUC=0.86, 95% CI 0.76-0.96) showed a stronger postpartum T2D risk prediction effect compared to fasting glucose test (BMI_Fasting CatBoost model: AUC=0.76, 95% CI 0.61-0.91). The BMI_GDM model was also robust when using a modified 2-point International Association of the Diabetes and Pregnancy Study Groups (IADPSG) 2018 criteria for GDM diagnosis (BMI_GDM2 CatBoost model: AUC=0.84, 95% CI 0.72-0.97). Total gestational weight gain was inversely associated with postpartum T2D outcome, independent of prepregnancy BMI and diagnosis of GDM (P=.02; OR 0.88, 95% CI 0.79-0.98).ConclusionsMidgestation weight gain effects, combined with the metabolic derangements underlying GDM during pregnancy, signal future T2D risk in Singaporean women. Further studies will be required to examine the influence of metabolic adaptations in pregnancy on postpartum maternal metabolic health outcomes. The state-of-the-art machine learning model can be leveraged as a rapid risk stratification tool during prenatal care.Trial RegistrationClinicalTrials.gov NCT01174875; https://clinicaltrials.gov/ct2/show/NCT01174875

Neuroprotective Substances: Are they Able to Protect the Pancreatic Beta- Cells Too?

Growing pieces of evidence demonstrate a close relationship between type 2 diabetes (T2D) and neurodegenerative disorders such as Alzheimer's disease. The similarity of physiological and pathological processes occurring in pancreatic β-cells and neurons over the course of these pathologies allows raising the question of the practicability of studying neuroprotective substances for their potential antidiabetic activity. This review analyzes studies of antidiabetic and cytoprotective action on pancreatic β- cells of the neuroprotective compounds that can attenuate the oxidative stress and enhance the expression of neurotrophins: low-molecular-weight NGF mimetic compound GK-2, selective anxiolytic afobazole, antidepressants lithium chloride, and lithium carbonate on the rat streptozotocin model of T2D. It was found that all the above-listed neuroprotective substances have a pronounced antidiabetic activity. The decrease in the β-cells number, the average area of the pancreatic islets, as well as the violation of their morphological structure caused by the streptozotocin was significantly weakened by the therapy with the investigated neuroprotective substances. The extent of these morphological changes clearly correlates with the antihyperglycemic effect of these compounds. The presented data indicate that the neuroprotective substances attenuating the damaging effect of oxidative stress and neurotrophins deficit cannot only protect neurons but also exert their cytoprotective effect towards pancreatic β-cells. These data may provide a theoretical basis for the further study of neuroprotective drugs as potential therapeutic options for T2D prevention and treatment.

Mouse models of type 1 diabetes and their use in skeletal research.

In this review, we describe the three primary mouse models of insulin-deficiency diabetes that have been used to study the effects of type 1 diabetes (T1D) on skeletal outcomes. These models include streptozotocin (chemically)-induced diabetes, autoimmune-mediated diabetes (the nonobese diabetes mouse), and a mutation in the insulin gene (the Akita mouse). We then describe the skeletal findings and/or skeletal phenotypes that have been delineated using these models. Humans with T1D have decreased bone mineral density and an increased risk for fragility fracture. Mouse models of insulin-deficiency diabetes (hereafter denoted as T1D) in many ways recapitulate these skeletal deficits. Utilizing techniques of microcomputed tomography, bone histomorphometry, biomechanical testing and fracture modeling, bone biomarker analysis, and Raman spectroscopy, mouse models of T1D have demonstrated abnormalities in bone mineralization, bone microarchitecture, osteoblast function, abnormal bone turnover, and diminished biomechanical properties of bone. Mouse models have provided significant insights into the underlying mechanisms involved in the abnormalities of bone observed in T1D in humans. These translational models have provided targets and pathways that may be modifiable to prevent skeletal complications of T1D.

Femoral Skeletal Perfusion is Reduced in Male Mice with Type 1 Diabetes

The bone vasculature and blood flow are critical for bone modeling, remodeling, and regeneration. Vascular complications are one of the major health concerns of people with type 1 diabetes (T1D). Moreover, people with T1D have lower bone mineral density and increased bone fragility. The goal of this study was to understand whether bone perfusion was altered in a mouse model of T1D and how this related to changes in bone mass. T1D was induced via the administration of streptozotocin in 12-week-old C57BL/6NHsd male mice. The assessment of bone perfusion utilized the injection of fluorescent microspheres with assessment of levels in the bone. Femoral blood flow and VEGF-A expression in the cortical bone shafts were lower in the T1D mice, compared to healthy controls, in this pattern followed that of changes in bone mass. These data demonstrate a possible association between reduced skeletal perfusion and reduced bone mass in the setting of T1D.

823-P: The Long-Acting Dual Amylin and Calcitonin Receptor Agonist KBP Has Increased Efficacy on Weight Loss and Glucose Control Compared with Cagrilintide in Obese and Diabetic Rats

Long-acting dual amylin and calcitonin receptor agonists (DACRAs) are novel candidates for treatment of type 2 diabetes (T2D) and obesity due to their beneficial effects on both body weight, glucose control and insulin action. Cagrilintide, which is currently in clinical trials, has shown promising effects on weight loss. In this study we compared a new long-acting DACRA (KBP) to cagrilintide in pre-clinical models of obesity and T2D. In vitro potencies were assessed using receptor assays. In vivo efficacies were investigated head-to-head in high fat diet (HFD) fed obese and T2D (ZDF) rat models. In vitro data showed that both peptides active both the amylin and the calcitonin receptor, with KBP being more potent on both receptors. This was further confirmed in vivo by assessment of acute effects on food intake and CTX suppression. KBP (1.5, 4.5 and 13.5 nmol/kg) and cagrilintide (10, 30 and 100 nmol/kg) induced a potent and dose-dependent weight loss in HFD rats, with the highest dose of KBP being superior to cagrilintide. In diabetic ZDF rats, DACRA treatment improved glucose control and preserved plasma insulin compared to vehicle. Interestingly, despite similar levels of plasma insulin, KBP treatment was superior to cagrilintide in improving glucose control. This was further reflected in the HbA1c levels at study end, where KBP treatment resulted in significantly lower levels compared to cagrilintide. In summary, both DACRAs induced weight loss and improved glucose tolerance, insulin action as well as glucose control. However, KBP treatment results in superior efficacy on both weight loss and glucose control. These findings highlight KBP as a promising once-weekly agent for treatment of obesity and T2D. Disclosure A.T.Larsen: Employee; Nordic Bioscience. N.Sonne: None. K.Mohamed: None. E.Bredtoft: None. F.Andersen: None. M.A.Karsdal: Employee; Nordic Bioscience A/S, Nordic Bioscience A/S, Nordic Bioscience A/S. K.Henriksen: Employee; Nordic Bioscience A/S, Stock/Shareholder; Nordic Bioscience A/S.

258-LB: ICAM-1 Abundance Is Increased in Pancreatic Islets of Hyperglycemic NOD Mice and Is Rapidly Upregulated by NF-kB in Pancreatic Beta Cells

Type 1 diabetes (T1D) is an autoimmune disease strongly associated with immune cell targeting of pancreatic β-cells, which ultimately produces insulin insufficiency. We identified the Icam1 gene and ICAM-1 protein, which facilitate interaction with immune cells, as elevated in female NOD mice relative to male mice. This observation is consistent with a greater frequency of diabetes onset in female mice in this well-established model of T1D. In addition, ICAM-1 protein abundance was greater in hyperglycemic female NOD compared with age-matched normoglycemic female NOD mice. Upon examining islet β-cell responses to immune cell-derived cytokines, we discovered that the Icam1 gene was rapidly (within 3h) and strongly (> 20-fold) upregulated in mouse, rat, and human islets as well as 832/13 rat insulinoma cells in response to IL-1β (p < 0.01) . Using chromatin immunoprecipitation (ChIP) assays, we identified rapid recruitment (within 30 minutes) of the p65 transcriptional subunit of NF-κB to κB genomic elements within the Icam1 gene promoter (3-fold; p < 0.05 relative to isotype control) . ChIP assays also revealed elevated RNA polymerase II recruitment to the Icam1 gene promoter (within 30 min) in response to IL-1β (7-fold, p < 0.05) . Finally, using single-cell RNA-Sequencing, we discovered that only a few clusters of β-cells expressed Icam1 at very low abundance in the basal (unstimulated) condition, while the majority of β-cell clusters in the IL-1β (3 h) stimulated condition presented with strong Icam1 positive (mRNA expressing) cells. Thus, we conclude that most, if not all, β-cells undergo rapid genetic reprogramming by IL-1β to enhance expression of the Icam1 gene and promote accumulation of the ICAM-1 protein. These findings illustrate the importance of pancreatic β-cell communication with the immune system and reveal inducible events at the β-cell level that are linked with onset and progression of T1D. Disclosure T. Martin: None. S. Burke: None. S. Ghosh: None. M. D. Karlstad: None. J. Collier: None. Funding National Institutes of Health (R03 AI151920-02)

Metformin does not prevent the alteration of reticulum-mitochondria Ca2+ coupling and the progression towards early diabetic cardiomyopathy with HFpEF in a diet-induced mouse model of T2D

Diabetic cardiomyopathy, as a major complication of type 2 diabetes (T2D), shows a rising prevalence nowadays. Reticulum-mitochondria Ca2+ uncoupling was recently reported as an early but reversible trigger of cardiac dysfunction using a diet-induced murine model of DCM with heart failure and preserved ejection fraction (HFpEF). Metformin is the first-line treatment prescribed to treat T2D patients, with known protective effects against myocardial infarction. We here aimed to determine if metformin could hinder the alteration of the reticulum-mitochondria Ca2+ coupling and the cardiac dysfunction induced by a high-fat high-sucrose diet (HFHSD) in mice. Mice were either fed a HFHSD or a standard diet for 16 weeks. During the last 6 weeks of diet, HFHSD mice received a daily oral gavage with either metformin or vehicle. Reticulum-mitochondria Ca2+ coupling was assessed: 1) structrally by proximity ligation assay between IP3R and VDAC; and 2) functionally by Ca2+ imaging of the mitochondrial Ca2+ sensor, 4mtD3cpv, expressed by intramyocardial adenoviral injection. Echocardiography was perfomed on lightly anesthetized animals to assess systolic function and hypertrophy. Metformin rescued the glucose tolerance and insulinemia in HFHSD mice, but partially for the cardiac insulin resistance. However, in the HFHSD cardiomyocyte, metformin did not preclude the reduction of the proximity between IP3R and VDAC, and of the histamine-driven reticulum-mitochondria Ca2+ transfer through the IP3R-VDAC complex. Echocardiography also revealed no prevention of HFHSD-induced cardiac hypertrophy and strain rate reduction. Our data report that 6 weeks of metformin treatment did not preserve the reticulum-mitochondria Ca2+ coupling in the diabetic heart and did not prevent the progression towards early DCM with HFpEF.