STZ-treated Mice Research Articles

Inhibition of selective factor Xa suppresses type 1 diabetes development in mice via the CXCL16 chemokine

Type 1 diabetes mellitus (T1DM) is associated with enhanced thrombosis potential. This research aims to investigate the role of coagulation system activation and CXCL16 in T1DM progression and the possible preventive effect of the selective Factor Xa inhibitor, Fondaparinux (Fond). Forty male Wistar albino mice were classified into 4 groups. Control, Fond, Streptozotocin (STZ), and Fond + STZ groups. Biochemical, hematological, and histopathological parameters, expressions of CXCL16, insulin, fibrinogen, and PAR-2, were investigated. A significant increase in blood glucose level and expressions of CXCL16, fibrinogen, and PAR-2, together with histological and nuclear changes in the pancreatic islets, was observed in STZ-treated mice, accompanied by a reduction in the serum insulin level. Fond improved the deleterious effects resulting from STZ treatment. In conclusion, coagulation system activation and CXCL16 play a critical role in the initiation of T1DM and could be used as therapeutic targets for T1DM prevention.

Genetic deletion of calcium-independent phospholipase A2γ protects mice from diabetic nephropathy.

Calcium-independent phospholipase A2γ (iPLA2γ) is localized in glomerular epithelial cells (GECs)/podocytes at the mitochondria and endoplasmic reticulum, and can mediate release of arachidonic acid and prostanoids. Global knockout (KO) of iPLA2γ in mice did not cause albuminuria, but resulted in mitochondrial structural abnormalities and enhanced autophagy in podocytes. In acute glomerulonephritis, deletion of iPLA2γ exacerbated albuminuria and podocyte injury. This study addresses the role of iPLA2γ in diabetic nephropathy. Hyperglycemia was induced in male mice with streptozotocin (STZ). STZ induced progressive albuminuria in control mice (over 21 weeks), while albuminuria did not increase in iPLA2γ KO mice, remaining comparable to untreated groups. Despite similar exposure to STZ, the STZ-treated iPLA2γ KO mice developed a lower level of hyperglycemia compared to STZ-treated control. However, there was no significant correlation between the degree of hyperglycemia and albuminuria, and even iPLA2γ KO mice with greatest hyperglycemia did not develop significant albuminuria. Mortality at 21 weeks was greatest in diabetic control mice. Sclerotic glomeruli and enlarged glomerular capillary loops were increased significantly in diabetic control compared to diabetic iPLA2γ KO mice. Glomerular matrix was expanded in diabetic mice, with control exceeding iPLA2γ KO. Glomerular autophagy (increased LC3-II and decreased p62) was enhanced in diabetic iPLA2γ KO mice compared to control. Treatment of cultured GECs with H2O2 resulted in increased cell death in control GECs compared to iPLA2γ KO, and the increase was slightly greater in medium with high glucose compared to low glucose. H2O2-induced cell death was not affected by inhibition of prostanoid production with indomethacin. In conclusion, mice with global deletion of iPLA2γ are protected from developing chronic glomerular injury in diabetic nephropathy. This is associated with increased glomerular autophagy.

Alpha- to Beta-Cell Transdifferentiation in Neonatal Compared with Adult Mouse Pancreas in Response to a Modest Reduction in Beta-Cells Using Streptozotocin.

Following the near-total depletion of pancreatic beta-cells with streptozotocin (STZ), a partial recovery of beta-cell mass (BCM) can occur, in part due to the alpha- to beta-cell transdifferentiation with an intermediary insulin/glucagon bi-hormonal cell phenotype. However, human type 2 diabetes typically involves only a partial reduction in BCM and it is not known if recovery after therapeutic intervention involves islet cell transdifferentiation, or how this varies with age. Here, we used transgenic mouse models to examine if islet cell transdifferentiation contributes to BCM recovery following only a partial depletion of BCM. Cell lineage tracing was employed using Glucagon-Cre/yellow fluorescent protein (YFP) transgenic mice treated with STZ (25 mg/kg-neonates; 70 mg/kg-adults) or vehicle alone on 3 consecutive days. Mice were euthanized 2-30 days later with a prior glucose tolerance test on day 30, and immunofluorescence histology performed on the pancreata. Beta-cell abundance was reduced by 30-40% two days post STZ in both neonates and adults, and subsequently partially recovered in adult but not neonatal mice. Glucose tolerance recovered in adult females, but not in males or neonates. Bi-hormonal cell abundance increased 2-3-fold in STZ-treated mice vs. controls in both neonates and adults, as did transdifferentiated cells expressing insulin and the YFP lineage tag, but not glucagon. Transdifferentiated cell presence was an order of magnitude lower than that of bi-hormonal cells. We conclude that alpha- to beta-cell transdifferentiation occurs in mice following only a moderate depletion in BCM, and that this was accompanied by a partial recovery of BCM in adults.

7765 Exploring the Synergistic Effect of GHRH Receptor Agonist MR-409 and Incretin-based Therapies in Type 1 Diabetes Using a Low-dose Streptozotocin Model

Abstract Disclosure: M. Gonzalez Medina: None. R. Louzada: None. V. Pita-Grisanti: None. M. Blandino: None. T. Cui: None. W. Sha: Owner/Co-Owner; Self; WS. is co-inventor on GHRH agonists MR-409 patent, assigned to the University of Miami and the Veterans Affairs. R. Cai: Owner/Co-Owner; Self; R.C. is co-inventor on GHRH agonists MR-409 patent, assigned to the University of Miami and the Veterans Affairs. A.V. Schally: Owner/Co-Owner; Self; A.V.S. is co-inventor on GHRH agonists MR-409 patent, assigned to the University of Miami and the Veterans Affairs.. E. Bernal-Mizrachi: None. Patients with type 1 diabetes (T1D) have decreased functional β-cell mass due to inflammatory cell infiltration and cytokine-induced β-cell death. Clinical trials using a combination of immunomodulatory agents and β-cell protecting medications such as GLP1-R agonists (GLP1-Ra) are being considered. A potential limitation for the clinical efficacy of GLP1-R agonists is the loss of GLP-1-R at the cell surface in states of hyperglycemia. Hence, novel agents that enhance β-cell survival and proliferation through parallel pathways could improve responses to GLP1-R agonists and/or synergistically potentiate β-cell responses. Previous studies have demonstrated beneficial effects of growth hormone-releasing hormone receptor agonists (GHRH-Ra), such as MR-409 on islet preconditioning in transplantation models. Our previous studies showed that GHRH-Ra protects β-cells from autoimmune injury in vitro and improves glucose levels in a model of high-dose streptozotocin-induced diabetes via stimulation of the cAMP/PKA/CREB/IRS2 axis. However, the effects of combination of incretin-based therapy with GHRHRa on β-cell survival in T1D models have not yet been explored. Using the low-dose STZ model in C57/B6 mice, we investigated how MR-409 alone or in combination with GLP1-R agonists (Exendin-4 or Ex-4) promotes β-cell survival and prevents T1D. Low-dose STZ treated mice received daily MR-409 and Ex-4 injections, either alone or in combination for six weeks. We found that, STZ-treated mice that received either MR-409, Ex-4 or combination exhibited better glucose homeostasis while the combination failed to induce any additional effect. Interestingly, glucose tolerance and insulin levels were improved only in the MR-409-treated mice. β-cell mass was similarly increased in mice that received MR-409, Ex-4 and combination groups compared to the vehicle-treated. Further, treatment of human islets with MR-409 and/or Ex-4 induced insulin receptor substrate 2 (IRS2) expression, a master regulator of survival and growth in β-cells, while the combination of both therapies did not have any additional effect. Experiments in human islets exposed to proinflammatory cytokines treatment demonstrated that MR-409 and/or Ex-4 was associated with a decrease in β-cell death and improved insulin secretory function by activation of the cAMP/PKA/CREB/IRS2 axis. These studies demonstrate that although there was no evidence for a synergistic effect between MR-409 and Ex-4, MR-409 appears to have more potent effects on improving glucose tolerance and insulin levels when compared to the long-term effect of Ex-4 in a low-dose STZ model, suggesting that MR-409 could be an alternative therapeutic agent in the treatment of β-cell death in T1D. Presentation: 6/2/2024

Diabetic Mice Spleen Vulnerability Contributes to Decreased Persistence of Antibody Production after SARS-CoV-2 Vaccine.

During the COVID-19 pandemic, diabetic and obese patients experienced higher rates of hospital admissions, severe illness, and mortality. However, vaccinations failed to provide those vulnerable populations the same level of protection against COVID-19 severity as those without diabetic and obese phenotypes. Our study aimed to investigate how diabetes mellitus (DM) impacts the immune response following vaccination including the artificially designed trimeric SARS-CoV-2 spike (S)-protein. By using two diabetic mouse models, ob/ob mice (obese, hyperglycemic, and insulin-resistant) and STZ-treated mice (insulin-deficient and hyperglycemic), we observed a significant reduction in S-protein-specific IgG antibody titer post-vaccination in both diabetic models compared to wild-type (WT) mice. Both diabetic mouse models exhibited significant abnormalities in spleen tissue, including marked reductions in splenic weight and the size of the white pulp regions. Furthermore, the splenic T-cell and B-cell zones were notably diminished, suggesting an underlying immune dysfunction that could contribute to impaired antibody production. Notably, vaccination with the S-protein, when paired with an optimal adjuvant, did not exacerbate diabetic cardiomyopathy, blood glucose levels, or liver function, providing reassurance about the vaccine's safety. These findings offer valuable insights into potential mechanisms responsible for the decreased persistence of antibody production in diabetic patients.

Establishment and characterization of a mouse model for studying kidney repair in diabetes.

The prognosis of acute kidney injury (AKI) is markedly worse in diabetic patients. Diabetes not only exaggerates the severity of AKI but may also prevent kidney repair or recovery from AKI. Little is known about the cellular and molecular basis of defective kidney repair in diabetes. One obstacle in studying kidney repair in diabetes is the lack of suitable animal models. Specifically, diabetes increases AKI severity, making it difficult to induce the same level of AKI in diabetic and non-diabetic animals to compare their kidney repair. Here, we have identified a time-window of 4 days immediately after the completion of streptozotocin (STZ) treatment in mice when blood glucose has yet to rise. Within this time-window, renal ischemia-reperfusion injury (IRI) induced the same level of AKI in STZ-treated mice [127.2±12.82 mg/dL blood urea nitrogen (BUN), 2.275±0.4728 serum creatinine] and vehicle solution-treated mice (128.6±11.83 mg/dL BUN, 2.087±0.4748 mg/dL serum creatinine]. By day 5-6, the post-AKI kidney entered into the phase of kidney repair when diabetic hyperglycemia started in STZ-treated mice, providing the opportunity to study the effect of diabetes on kidney repair without affecting initial AKI. In this model, kidney repair was indeed impaired by diabetes (116.5±8.052 mg/dL BUN and 1.382±0.2732 mg/dL serum creatinine in IR+vehicle group; 136.6±8.740 mg/dL BUN and 1.916±0.3756 mg/dL serum creatinine in IR+STZ group). The impairment was associated with decreased tubular cell proliferation and increased tubular cell senescence, peritubular capillary (PTC) rarefaction, inflammation, and 40.90% more interstitial fibrosis.

Characterization of MSCs expressing islet neogenesis associated protein (INGAP): INGAP secretion and cell survival in vitro and in vivo

Mesenchymal stem/stromal cells (MSCs) are emerging as a new therapy for diabetes. Here we investigate the properties of MSCs engineered to express Islet Neogenesis Associated Protein (INGAP) previously shown to reverse diabetes in animal models and evaluate their potential for anti-diabetic applications in mice. Mouse bone marrow-derived MSCs retrovirally transduced to co-express INGAP, Firefly Luciferase and EGFP (INGAP-MSCs), were characterized in vitro and implanted intraperitoneally (IP) into non-diabetic and diabetic C57BL/6 mice (Streptozotocin model) and tracked by live bioluminescence imaging (BLI). Distribution and survival of IP injected INGAP-MSCs differed between diabetic and non-diabetic mice, with a rapid clearance of cells in the latter, and a stronger retention (up to 4 weeks) in diabetic mice concurring with homing towards the pancreas. Interestingly, INGAP-MSCs inhibited the progression of hyperglycemia starting at day 3 and lasting for the entire 6 weeks of the study. Pursuing greater retention, we investigated the survival of INGAP-MSCs in hydrogel matrices. When mixed with Matrigel™ and injected subcutaneously into non-diabetic mice, INGAP-MSCs remained in the implant up to 16 weeks. In vitro tests in three matrices (Matrigel™, Type I Collagen and VitroGel®-MSC) demonstrated that INGAP-MSCs survive and secrete INGAP, with best results at the density of 1–2 x 106 cells/mL. However, all matrices induced spontaneous adipogenic differentiation of INGAP-MSCs in vitro and in vivo, which requires further investigation of its potential impact on MSC therapeutic properties. In summary, based on their ability to stop the rise in hyperglycemia in STZ-treated mice, INGAP-MSCs are a promising therapeutic tool against diabetes but require further research to improve cell delivery and survival.

Canagliflozin Mitigated Cognitive Impairment in Streptozotocin-Induced Sporadic Alzheimer's Disease in Mice: Role of AMPK/SIRT-1 Signaling Pathway in Modulating Neuroinflammation.

Sporadic Alzheimer's disease (SAD) represents a major health concern especially among elderly. Noteworthy, neuroinflammation and oxidative stress are highly implicated in AD pathogenesis resulting in enhanced disease progression. Moreover, most of the available anti-Alzheimer drugs have several adverse effects with variable efficacy, therefore new strategies, including agents with anti-inflammatory and antioxidant effects, are encouraged. Along these lines, canagliflozin (CAN), with its anti-inflammatory and anti-apoptotic activities, presents a promising candidate for AD treatment. Therefore, this study aimed to evaluate the therapeutic potential of CAN via regulation of AMPK/SIRT-1/BDNF/GSK-3β signaling pathway in SAD. SAD model was induced by intracerebroventricular streptozotocin injection (ICV-STZ;3mg/kg, once), while CAN was administered (10mg/kg/day, orally) to STZ-treated mice for 21 days. Behavioral tests, novel object recognition (NOR), Y-Maze, and Morris Water Maze (MWM) tests, histopathological examination, total adenosine monophosphate-activated protein kinase (T-AMPK) expression, p-AMPK, and silent information regulator-1 (SIRT-1) were evaluated. Furthermore, brain-derived neurotrophic factor (BDNF), glycogen synthase kinase-3β (GSK-3β), acetylcholinesterase (AChE), Tau protein, insulin-degrading enzyme (IDE), nuclear factor erythroid-2 (Nrf-2), interleukin-6 (IL-6), nuclear factor kappa-B-p65 (NFκB-p65), beta-site APP cleaving enzyme 1 (BACE-1), and amyloid beta (Aβ) plaque were assessed. CAN restored STZ-induced cognitive deficits, confirmed by improved behavioral tests and histopathological examination. Besides, CAN halted STZ-induced neurotoxicity through activation of p-AMPK/SIRT-1/BDNF pathway, subsequently reduction of GSK-3β, Tau protein, AChE, NFκB-p65, IL-6, BACE-1, and Aβ plaque associated with increased IDE and Nrf-2. Consequentially, our findings assumed that CAN, via targeting p-AMPK/SIRT-1 pathway, combated neuroinflammation and oxidative stress in STZ-induced AD. Thus, this study highlighted the promising effect of CAN for treating AD.

Renal ischemia/reperfusion induces prominent progressive kidney disease in diabetic mice.

Acute kidney injury (AKI) is a public health concern associated with high rates of mortality, even in milder cases. One of the reasons for the difficulty in managing AKI in patients is due to its association with pre-existing comorbidities, such as diabetes. In fact, diabetes increases the susceptibility to develop more severe AKI after renal ischemia. However, the long-term effects of this association are not known. Thus, an experimental model was designed to evaluate the chronic effects of renal ischemia/reperfusion (IR) in streptozotocin (STZ)-treated mice. We focused on the glomerular and tubulointerstitial damage, as well as kidney function and metabolic profile. It was found that pre-existing diabetes may potentiate progressive kidney disease after AKI, mainly by exacerbating proinflammatory and sustaining fibrotic responses and altering renal glucose metabolism. To our knowledge, this is the first report that highlights the long-term effects of renal IR on diabetes. The findings of this study can support the management of AKI in clinical practice.NEW & NOTEWORTHY This study demonstrated that early diabetes potentiates progressive kidney disease after ischemia/reperfusion (IR)-induced acute kidney injury, mainly by exacerbating pro-inflammatory and sustaining fibrotic responses and altering renal glucose metabolism. Thus, these findings will contribute to the therapeutic support of patients with type 1 diabetes with eventual renal IR intervention in clinical practice.

Dopamine signalling in pancreatic islet cells and role in adaptations to metabolic stress.

Dopamine and related receptors are evidenced in pancreatic endocrine tissue, but the impact on islet β-cell stimulus-secretion as well as (patho)physiological role are unclear. The present study has evaluated islet cell signalling pathways and biological effects of dopamine, as well as alterations of islet dopamine in rodent models of diabetes of different aetiology. The dopamine precursor l-DOPA partially impaired glucose tolerance in mice and attenuated glucose-, exendin-4, and alanine-induced insulin secretion. The latter effect was echoed by the attenuation of glucose-induced [Ca2+]i dynamics and elevation of ATP levels in individual mouse islet cells. l-DOPA significantly decreased β-cell proliferation rates, acting predominantly via the D2 receptor, which was most abundant at the mRNA level. The administration of streptozotocin (STZ) or high-fat diet (HFD) in mice significantly elevated numbers of dopamine-positive islet cells, with HFD also increasing colocalization of dopamine with insulin. At the same time, colocalization of dopamine with glucagon was increased in STZ-treated and pregnant mice, but unaffected by HFD. These findings highlight a role for dopamine receptor signalling in islet cell biology adaptations to various forms of metabolic stress.

Curcumin Mitigates Streptozotocin-Induced Genotoxicity In Vivo by Activating P53 Protein and Inhibiting Oxidative Stress and Chromosomal Aberration.

Genotoxins are chemical constituents that damage DNA or chromosomal architecture, leading to alterations in the genetic level. Streptozotocin, a monofunctional nitrosourea derivative, is often utilized to induce diabetes mellitus in laboratory animals because of its detrimental effects on pancreatic cells. The purpose of this work was to investigate possible protective efficacy against the genotoxic effects of Streptozotocin. This study examines the potentiality of curcumin, a phytoproduct with anti-genotoxic and anti-diabetic qualities, against streptozotocin-induced chromosomal abnormalities and DNA damage. The study evaluates the possible protective efficacy of curcumin, exploring a variety of biochemical and molecular biology techniques in murine models. The experiment involves a control group, the administration of Streptozotocin (Group S), and a curcumin-pretreated STZ group (Group SC) in mice. The effects of curcumin on DNA damage and chromosomal aberrations were investigated by histopathology, immunofluorescence, evaluation of chromosomal aberrations, detection of Reactive oxygen species, cell viability analysis, and DNA laddering assay. The results demonstrated a significant reduction in DNA damage, chromosomal anomalies, and a decrease in the expression of the p53 protein in the curcumin-treated animals compared to that of STZ-treated mice. The overall results show that curcumin can reduce chromosomal aberrations and DNA damage by altering the expression of p53 repair proteins. This suggests that curcumin has a promising future as a therapeutic agent, especially when it comes to drug-induced toxicity and the development of novel therapeutics.

Enrichment of Bioactive Lipids in Urinary Extracellular Vesicles and Evidence of Apoptosis in Kidneys of Hypertensive Diabetic Cathepsin B Knockout Mice after Streptozotocin Treatment.

Cathepsin B (CtsB) is a ubiquitously expressed cysteine protease that plays important roles in health and disease. Urinary extracellular vesicles (uEVs) are released from cells associated with urinary organs. The antibiotic streptozotocin (STZ) is known to induce pancreatic islet beta cell destruction, diabetic nephropathy, and hypertension. We hypothesized that streptozotocin-induced diabetic kidney disease and hypertension result in the release of bioactive lipids from kidney cells that induce oxidative stress and renal cell death. Lipidomics was performed on uEVs isolated from CtsB knockout mice treated with or without STZ, and their kidneys were used to investigate changes in proteins associated with cell death. Lysophosphatidylethanolamine (LPE) (18:1), lysophosphatidylserine (LPS) (22:6), and lysophosphatidylglycerol (LPG) (22:5) were among the bioactive lipids enriched in uEVs from CtsB knockout mice treated with STZ compared to untreated CtsB mice (n = 3 uEV preparations per group). Anti-oxidant programming was activated in the kidneys of the CtsB knockout mice treated with STZ, as indicated by increased expression of glutathione peroxidase 4 (GPX4) and the cystine/glutamate antiporter SLC7A11 (XCT) (n = 4 mice per group), which was supported by a higher reactivity to 4-hydroxy-2-nonenal (4-HNE), a marker for oxidative stress (n = 3 mice per group). Apoptosis but not ferroptosis was the ongoing form of cell death in these kidneys as cleaved caspase-3 levels were significantly elevated in the STZ-treated CtsB knockout mice (n = 4 mice per group). There were no appreciable differences in the pro-ferroptosis enzyme acyl-CoA synthetase long-chain family member 4 (ACSL4) or the inflammatory marker CD93 in the kidneys (n = 3 mice per group), which further supports apoptosis as the prevalent mechanism of pathology. These data suggest that STZ treatment leads to oxidative stress, inducing apoptotic injury in the kidneys during the development of diabetic kidney disease and hypertension.

Mitochondria-derived peptide is an effective target for treating streptozotocin induced painful diabetic neuropathy through induction of activated protein kinase/peroxisome proliferator-activated receptor gamma coactivator 1alpha -mediated mitochondrial biogenesis.

Painful Diabetic Neuropathy (PDN) is a common diabetes complication that frequently causes severe hyperalgesia and allodynia and presents treatment challenges. Mitochondrial-derived peptide (MOTS-c), a novel mitochondrial-derived peptide, has been shown to regulate glucose metabolism, insulin sensitivity, and inflammatory responses. This study aimed to evaluate the effects of MOTS-c in streptozocin (STZ)-induced PDN model and investigate the putative underlying mechanisms. We found that endogenous MOTS-c levels in plasma and spinal dorsal horn were significantly lower in STZ-treated mice than in control animals. Accordingly, MOTS-c treatment significantly improves STZ-induced weight loss, elevation of blood glucose, mechanical allodynia, and thermal hyperalgesia; however, these effects were blocked by dorsomorphin, an adenosine monophosphate-activated protein kinase (AMPK) inhibitor. In addition, MOTS-c treatment significantly enhanced AMPKα1/2 phosphorylation and PGC-1α expression in the lumbar spinal cord of PDN mice. Mechanistic studies indicated that MOTS-c significantly restored mitochondrial biogenesis, inhibited microglia activation, and decreased the production of pro-inflammatory factors, which contributed to the alleviation of pain. Moreover, MOTS-c decreased STZ-induced pain hypersensitivity in PDN mice by activating AMPK/PGC-1α signaling pathway. This provides the pharmacological and biological evidence for developing mitochondrial peptide-based therapeutic agents for PDN.

Toward once-monthly insulin therapy via synergy in two pharmacokinetic protractors: Fc-conjugation and fatty acid acylation.

Pharmacokinetic properties and duration of therapeutic action of a pharmaceutical agent can be significantly extended through the combination of two distinct strategies aimed at increasing plasma half-life: fatty acid acylation and Fc-conjugation. Using insulin as a case study, we demonstrate that a doubly protracted insulin analog produces a substantial prolongation of pharmacodynamic effect to lower blood glucose in STZ-treated mice when compared to the Fc-only counterparts. This enhancement is further corroborated by direct pharmacokinetic measurements in rat and dog models, demonstrating the potential for once-monthly insulin therapy. The results suggest that this approach might have broad application across a diverse spectrum of peptide- and protein-based therapeutics.

Genetic lineage tracing identifies adaptive mechanisms of pancreatic islet β cells in various mouse models of diabetes with distinct age of initiation.

During the pathogenesis of type 1 diabetes (T1D) and type 2 diabetes (T2D), pancreatic islets, especially the β cells, face significant challenges. These insulin-producing cells adopt a regeneration strategy to compensate for the shortage of insulin, but the exact mechanism needs to be defined. High-fat diet (HFD) and streptozotocin (STZ) treatment are well-established models to study islet damage in T2D and T1D respectively. Therefore, we applied these two diabetic mouse models, triggered at different ages, to pursue the cell fate transition of islet β cells. Cre-LoxP systems were used to generate islet cell type-specific (α, β, or δ) green fluorescent protein (GFP)-labeled mice for genetic lineage tracing, thereinto β-cell GFP-labeled mice were tamoxifen induced. Single-cell RNA sequencing (scRNA-seq) was used to investigate the evolutionary trajectories and molecular mechanisms of the GFP-labeled β cells in STZ-treated mice. STZ-induced diabetes caused extensive dedifferentiation of β cells and some of which transdifferentiated into a or δ cells in both youth- and adulthood-initiated mice while this phenomenon was barely observed in HFD models. β cells in HFD mice were expanded via self-replication rather than via transdifferentiation from α or δ cells, in contrast, α or δ cells were induced to transdifferentiate into β cells in STZ-treated mice (both youth- and adulthood-initiated). In addition to the re-dedifferentiation of β cells, it is also highly likely that these "α or δ" cells transdifferentiated from pre-existing β cells could also re-trans-differentiate into insulin-producing β cells and be beneficial to islet recovery. The analysis of ScRNA-seq revealed that several pathways including mitochondrial function, chromatin modification, and remodeling are crucial in the dynamic transition of β cells. Our findings shed light on how islet β cells overcome the deficit of insulin and the molecular mechanism of islet recovery in T1D and T2D pathogenesis.

574-P: A Ketogenic Diet Improves Aerobic Capacity in Hyperglycemic Mice by Sex-Dependent Mechanisms

Hyperglycemia is associated with lower aerobic exercise capacity (VO2peak) in humans and rodent models. We tested whether reducing blood glucose levels with a dietary intervention can restore VO2peak in hyperglycemic mice. Male and female CD-1 mice were injected with low dose streptozotocin (STZ) to induce moderate hyperglycemia (>200 mg/dL). Hyperglycemic mice were randomized to receive a standard diet (STZ-CHOW) or a ketogenic diet (STZ-KETO). KETO significantly reduced blood glucose in STZ-treated mice. Next, both groups underwent similar volumes of exercise training by voluntary wheel running, or remained sedentary for 8 wks. In males, VO2peak during maximal exercise testing was similar in sedentary mice, regardless of diet. However, with training, VO2peak was significantly improved in STZ-KETO, but not STZ-CHOW males (see Figure). In females, KETO significantly increased VO2peak in sedentary mice, with no additional increase in response to training. Improved VO2peak with KETO in females was associated with a 50% increase in skeletal muscle mitochondrial ATP synthase protein. In contrast, ATP synthase was not regulated by diet in males. Our data demonstrate that a ketogenic diet can improve VO2peak in mice with hyperglycemia. In males, improved VO2peak with KETO was exercise-dependent, while in females, the beneficial effects of KETO on VO2peak and mitochondrial content were exercise-independent. Disclosure P.Pattamaprapanont: None. M.Formato: None. R.Nogueira soares: None. S.J.Lessard: None.

1549-P: scEMC10 Promotes Glucose Intolerance via the Inhibition of PKA-Mediated Insulin Secretion

It has been shown recently that overexpression of the secreted isoform of endoplasmic reticulum membrane complex subunit 10 (scEMC10) impairs, whereas Emc10 knockout (KO) or antibody neutralization of circulating scEMC10 improves glucose tolerance in mice fed with high fat diet. In humans, serum scEMC10 levels correlate positively with fasting plasma glucose and HbA1c. The mechanism underlying the regulation of glucose metabolism by scEMC10 remains largely unknown. In this study, alation of EMC10 significantly improved glucose tolerance in chow diet-fed mice, which was attributed to increased glucose-stimulated insulin secretion (GSIS), but not improved insulin sensitivity evaluated by euglycemic-hyperinsulinemic clamp. Using an adeno-associated virus, either reconstitution of scEMC10 in Emc10 KO mice or overexpression of scEMC10 in wildtype mice significantly decreased glucose tolerance accompanied by blunted GSIS. Recombinant scEMC10 inhibited GSIS in both INS-1 cells and isolated primary islets in vitro. Mechanistically, we presented evidence that extracellular scEMC10 can be transported into beta cells where it binds to the catalytic subunit of PKA and inhibits phosphorylations of PKA substrates including phosphorylated CREB, along with reduced PDX-1 expression. Furthermore, antibody neutralization of circulating scEMC10 alleviated hyperglycemia in both STZ-treated mice and ob/ob mice. This work identifies scEMC10 as a suppressor of insulin secretion via the inhibition of PKA signaling in islet beta cells and suggests scEMC10 neutralizing antibody as a promising pharmaceutical agent to treat diabetes. Disclosure J.Dai: None. S.Liu: None. K.Chen: None. S.Jin: None. Y.Wang: None. L.Chen: None. X.Wang: None. Funding National Natural Science Foundation of China (81873645); Science and Technology Commission of Shanghai Municipality (22140902700)

404-P: Single-Cell RNA Profiling Changes in Glomerular Cells in Diabetic Nephropathy (DN)

Hyperglycemia, the main risk factor for DN, causes complex pathological damages in glomeruli. To characterize detail changes in cell differentiation and gene expressions induced by diabetes, we performed unbiased single-cell RNA sequencing (scRNA-seq) on glomerular cells from diabetic and nondiabetic mice of long duration. Glomerular cells were isolated from C57 mice after 7-months of STZ-induced diabetes, when clear glomerular pathologies have been documented. Total number of 48,337 high-qualitied glomerular cells were isolated and sequenced from WT and STZ-treated mice. Based on clustering analysis and cell-type specific markers, 12 different cell types were identified, including endothelial cells (EC), podocytes, mesangial cells (MC), proximal tubule cells, parietal epithelial cells (PEC), collecting duct cells, ascending loop of Henle, macrophages, B cells, T cells, NK cells and neutrophils. Over 90% of the cells were from glomeruli (41% EC, 34 % podocytes, 14% MC, 2% of PEC), and 6% immune cells. Interestingly, gene profiling identified 9 clusters of EC, 5 clusters of MC and 7 clusters of podocytes. Diabetes did not change the total cell numbers for EC, MC and podocytes, although macrophage and B cell numbers were increased from 2.2% to 4.8% and 0.35% to 1%, respectively. Cluster subset analysis of EC, MC and podocytes showed that diabetes induced substantial changes. For podocytes, diabetes increased those clusters (5% to 37%) with high expressions of stressed proteins such as Hspa1a, Hspa1b and Hsp90aa1, while decreased those clusters with high expressions of ECM production and CDC42 GTPase cycle, that were involved in cytoskeleton stabilization and foot process formation. Findings from scRNA-seq of glomeruli showed there were multiple subsets of podocytes, EC and MC, which appear to have different functions and their distributions were changed by diabetes. Understanding the mechanism for the distribution changes of the subsets may provide new insight in the pathogenesis of DN. Disclosure J. Fu: None. Q. Li: None. K. Park: None. Q. Huang: None. I. Wu: None. G.L. King: Research Support; Janssen Research & Development, LLC.

292-LB: Cholesterol Accumulation in Islets Exacerbates Insulin Secretory Defects in a Model of Mild ß-Cell Dysfunction

Hypercholesterolemia is common in diabetes. We sought to determine whether cholesterol (Chol) can exacerbate impaired insulin secretion in islets from a mouse model of mild β-cell dysfunction. To induce β-cell dysfunction, C57BL/6J male mice were treated with low-dose (30 mg/kg, i.p.) streptozotocin (STZ) or vehicle (VEH) once daily on 3 consecutive days. Mice were then fed a 9% fat diet for 4 weeks, after which islets were isolated and cultured for 24 h ± Chol prior to endpoint measures. After 4 weeks, body weight (STZ 28.9±1.0 vs VEH 29.1±1.1 g) and fed glucose (STZ 191.2±11.0 vs VEH 177.8±8.2 mg/dl) did not differ. When cultured with 0 mM Chol, isolated islets from STZ-treated mice showed reduced glucose (20 mM)-stimulated insulin secretion (GSIS: 973.9±191.7 vs 1714.8±384.6 pM, n=5, p<0.05) and a trend for lower insulin content (180.6±18.2 vs 230.4±22.9 nM, n=5, p=0.06), compared to islets from VEH-treated mice. Having established STZ-induced β-cell dysfunction, islets from STZ-treated mice were cultured ± 0.5 mM Chol, then Chol content and GSIS measured. Culture in 0.5 mM (vs 0 mM) Chol resulted in increased islet Chol content (58.9 ± 4.3 vs 17.6 ± 3.0 µg/mg protein; n=3, p<0.01). A trend for increased basal insulin secretion (2.8 mM glucose: 185.8±64.7 vs 32.8±3.5 pM, n=5, p=0.09) and reduced GSIS (305.3±60.3 vs 973.9±191.7 pM, n=5, p<0.05) were observed in islets cultured with 0.5 mM Chol. Insulin content was also reduced (125.8±10.8 vs 180.6±18.2 nM, n=5, p<0.01) with 0.5 mM Chol culture. In sum, we have developed a STZ-based, euglycemic mouse model of subclinical β-cell dysfunction. Chol treatment of islets from these mice exacerbates β-cell dysfunction, in keeping with a deleterious effect of Chol. This model now provides the ability to determine whether hypercholesterolemia in vivo results in further impairment of β-cell dysfunction and the development of hyperglycemia, an observation that would be relevant to the progression of prediabetes to diabetes and diabetes per se. Disclosure R. Akter: None. B. Barrow: None. R. L. Hull-meichle: Employee; Veterans Administration, Research Support; Casma Therapeutics, Cystic Fibrosis Foundation, NIH - National Institutes of Health, Veterans Administration. S. Zraika: None. S. E. Kahn: Advisory Panel; Anji Pharmaceuticals, Bayer Inc., Boehringer Ingelheim Inc., Eli Lilly and Company, Merck & Co., Inc., Other Relationship; Novo Nordisk. Funding U.S. Department of Veterans Affairs (I01BX001060); National Institutes of Health (P30DK017047); Diabetes Research Connection (46)

1576-P: Hepatic Ketogenesis Insufficiency Improves Glycemia in Type 1 Diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease and is increasing by approximately 2-3% per year. One characteristic feature of T1D is the increased production of ketone bodies. However, the role of ketone bodies and/or ketogenesis in the pathogenesis of T1D remains unknown. We generated mice with conditional ketogenic insufficiency by knocking out the ketogenic enzyme 3-hydroxy methylglutaryl CoA synthase 2 (Hmgcs2) in the liver. Six to eight-week-old Hmgcs2ΔLiv and Hmgcs2F/F(littermates that do not express Alb-Cre) were injected with tamoxifen @200 mg/kg body weight. One week later, Hmgcs2ΔLiv and Hmgcs2F/F mice were injected with strep tozotocin (STZ; 50mg/kg B.W for 5 consecutive days) to induce hyperglycemia. We found that Hmgcs2ΔLiv mice had significantly lower blood glucose than their littermate controls. The improvement in glycemia is not due to a change in food intake or body weight. Moreover, no difference in serum insulin levels and Akt phosphorylation in the liver suggested that ketogenic insufficiency does not improve glycemia in T1D via the insulin signaling pathway. When we assessed glucose production by pyruvate tolerance test, Hmgcs2ΔLiv mice showed lower glucose levels. Further, the mRNA and protein levels of gluconeogenic genes such as G6PCand PCK1 were significantly decreased in the livers of Hmgcs2ΔLivmice. We also observed a significant reduction in PGC-1α, the transcriptional regulator of gluconeogenesis, suggesting that ketogenic insufficiency in T1D reduces hepatic gluconeogenesis. The metabolism of ketone bodies in peripheral tissues impairs their ability to utilize glucose. Our indirect calorimetry analysis showed a trend toward increased respiratory exchange ratio (RER) in STZ-treated Hmgcs2ΔLiv mice, suggesting that ketogenic insufficiency increases carbohydrate metabolism in T1D. Our data show that ketogenesis may contribute to hyperglycemia in T1D by regulating hepatic glucose production and peripheral glucose utilization. Disclosure R.Mooli: None. S.Ramakrishnan: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (DK110537)