Short-term Hyperglycemia Research Articles

Hyperglycemia-independent neonatal streptozotocin-induced retinopathy (NSIR) in rats.

Introduction: Chemicals, such as MNU (N-methyl-N-nitrosourea) and NaIO3 (sodium iodate), are widely used to induce retinal degeneration in rodents. Streptozotocin (STZ) is an analog of N-acetyl glucosamine in which an MNU moiety is linked to a hexose and has a special toxic effect on insulin-producing pancreatic β-cells. It is commonly used to induce hyperglycemia to model diabetes. While intracerebroventricular injection of STZ can produce Alzheimer's disease independent of hyperglycemia, most retinal studies using STZ focus on the effects of hyperglycemia on the retina, but whether STZ has any impact on retinal cells independent of hyperglycemia is unknown. We aimed to investigate the role of cytotoxicity of STZ in rat retina. Methods: Intravitreal or subcutaneous injection of STZ was performed on newborn rats. Electroretinogram (ERG) and H&E staining investigated retinal function and morphological changes. Retinal cell types, cell death, proliferation, inflammation, and angiogenesis were studied by immunostaining. RNA sequencing was performed to examine the transcriptome changes of retinal cells after intravitreal injection of STZ. Results: Intravitreal (5μg or 10μg) or subcutaneous (30mg/kg) injection of STZ at the early stage of newborn rats couldn't induce hyperglycemia but caused NSIR (Neonatal STZ-induced retinopathy), including reduced ERG amplitudes, retinal rosettes and apoptosis, cell cycle arrest, microglial activation, and delayed retinal angiogenesis. STZ did not affect the early-born retinal cell types but significantly reduced the late-born ones. Short-term and long-term hyperglycemia had no significant effects on the NSIR phenotypes. RNA sequencing revealed that STZ induces oxidative stress and activates the p53 pathway of retinal cells. Locally or systemically, STZ injection after P8 couldn't induce SINR when all retinal progenitors exit the cell cycle. Conclusion: NSIR in rats is independent of hyperglycemia but due to STZ's direct cytotoxic effects on retinal progenitor cells. NSIR is a typical reaction to STZ-induced retinal oxidative stress and DNA damage. This significant finding suggests that NSIR may be a valuable model for studying retinal progenitor DNA damage-related diseases, potentially leading to new insights and treatments.

P-787 Gestational diabetes in mice induces embryonic fibro-adipogenic progenitors memory that impedes the recovery of injured skeletal muscle in adult offspring

Abstract Study question Whether and how intrauterine hyperglycemia induced by Gestational diabetes steadily influences the function and fate of mesenchymal stem cells, specifically fibro-adipogenic progenitors. Summary answer Gestational diabetes in mice caused declines in self-renewal and paracrine in fibro-adipogenic progenitors, prompted adipogenesis and fibrosis, destroyed recovery after muscular injury in adult offspring. What is known already Gestational diabetes contributed to the increased susceptibility to metabolic disorders, cardiovascular diseases and atherosclerosis. Intrauterine hyperglycemia promoted placental inflammation and endowed the hematopoietic stem and progenitor cells. As an important mesenchymal stem cell, fibro-adipogenic progenitors (FAPs) play a key role in the process of “replace, repair, regeneration, restore and regress”. When acute injury happens to skeletal muscle, the fibro-adipogenic progenitors cluster start to renew itself and differentiate into functional cells like fibroblasts or adipocytes, secrete cytokines to nearby myoblasts, inducing myotube formation and muscle regeneration by cell-cell communication. Study design, size, duration Pregnant mice were randomly divided into control (CTR) and gestational diabetes (GDM) groups, GDM group was intraperitoneally injected with 100 mg/kg streptozotocin on gestational days (GDs) 6.5 and 12.5, while CTR group was treated with vehicle buffer. Only when random blood glucose level was higher than 16.8 mmol/L beginning on GD13.5 were regarded as the GDM group. At 8 weeks of offspring, we intramuscular injected cardiotoxin (CTX) to induce acute tibialis anterior muscle injury. Participants/materials, setting, methods 7 days after CTX intramuscular injection (CTX-D7) in offspring, mice were sacrificed and tiabialis anterior muscle was selected. Perilipin immunochemical and immunofluorescent staining, MASSON and Sirius Red staining were used to evaluate the recovery extent between CTR and GDM groups. Then we used fluorescence-activated cell sorting to evaluate the self proliferation of fibro-adipogenic cells at CTX-D3. We also collected FAPs to perform induced differentiation in vitro, co-culture with myoblast and SMART-sequence to explore underlying mechanism. Main results and the role of chance 7 days after cardiotoxin injection (CTX-D7), we used WGA to mark injured myofibers, eMHC to mark regenerated myofibers. Immunofluorescence and hematoxylin-eosin staining showed the muscle fibers in GDM male were still severe damaged and inadequate recovered when compared to CTR group. Perilipin immunochemical staining demonstrated more lipids deposition in GDM male muscle. MASSON and Sirius Red staining also revealed increased accumulation of collagen fibers in GDM group. Fluorescence-activated cell sorting firstly displayed depletion in numbers of Lineage-VCAM-Sca-1+ fibro-adipogeneic progenitors (FAPs) compartment in GDM group at CTX-D3 compared to CTR group. Using α-SMA to mark collagen fibers, perilipin to mark adiposity cells, we also observed activation of the FAPs into fibrosis or adipogenesis by in vitro induced differentiation. Myotubes formation experiment showed that myotubes were thinner and fusion extent was worse in myoblasts co-cultured with GDM FAPs rather than CTR FAPs. Finally, we performed SMART-sequence of FAPs between groups. Regarding p < 0.05 and the absolute of log2 foldchange >1 as significance, we totally found 1572 down-regulated genes, 1527 up-regulated genes in GDM FAPs. And the GO term analysis showed us that WNT signaling pathway, cell surface receptor signaling pathway were most highly affected. Limitations, reasons for caution We haven’t found out the key molecule in WNT signaling pathway, and how intrauterine hyperglycemia steadily affected FAP’s function remains to be explored. Also, whether other mesenchymal stem cells are influenced by short-term intrauterine hyperglycemia needs to be clarified. Wider implications of the findings Fibro-adipogenic progenitors is an important part of mesenchymal stem cells. These results demonstrated GDM in mice might induce mesenchymal memory that affects the long-term health of the offspring, which reminds us the stemness of GDM progenitors or stem cells might be destroyed and its cell-cell function may be also damaged. Trial registration number ZJU20210047

Short- and long-term exposure to high glucose induces unique transcriptional changes in osteoblasts in vitro.

Bone is increasingly recognized as a target for diabetic complications. In order to evaluate the direct effects of high glucose on bone, we investigated the global transcriptional changes induced by hyperglycemia in osteoblasts in vitro. Rat bone marrow-derived mesenchymal stromal cells were differentiated into osteoblasts for 10days, and prior to analysis, they were exposed to hyperglycemia (25 mM) for the short-term (1 or 3days) or long-term (10 days). Genes and pathways regulated by hyperglycemia were identified using mRNA sequencing and verified with qPCR. Genes upregulated by 1-day hyperglycemia were, for example, related to extracellular matrix organization, collagen synthesis and bone formation. This stimulatory effect was attenuated by 3days. Long-term exposure impaired osteoblast viability, and downregulated, for example, extracellular matrix organization and lysosomal pathways, and increased intracellular oxidative stress. Interestingly, transcriptional changes by different exposure times were mostly unique and only 89 common genes responding to glucose were identified. In conclusion, short-term hyperglycemia had a stimulatory effect on osteoblasts and bone formation, whereas long-term hyperglycemia had a negative effect on intracellular redox balance, osteoblast viability and function.

Transient albuminuria in the setting of short-term severe hyperglycemia in type 1 diabetes

In a cohort of 1817 children with type 1 diabetes (T1D), short-term hyperglycemia was associated with transient albuminuria (11 % during new-onset T1D without diabetic ketoacidosis (DKA), 12 % during/after DKA, 6 % during routine screening). Our findings have implications regarding future risk of diabetic kidney disease and further investigation is needed.

Short- and Long-Term Effects on Glucose Control of Nonadherence to Insulin Therapy in People With Type 2 Diabetes An In Silico Study.

Strict adherence to multiple daily insulin (MDI) therapy is a cornerstone for the achievement of good glucose control in people with advanced type 2 diabetes (T2D). Here, we aim to in silico assess glucose control in T2D subjects with poor adherence to MDI therapy. We tuned the Padova T2D Simulator, originally describing early-stage T2D physiology, around advanced T2D people. One hundred in silico advanced T2D subjects were generated and equipped with optimal MDI therapy: specifically, basal and bolus insulin amounts and injection times were individualized for each subject by applying titration algorithms that iteratively update insulin dose based on glucose deviation from its target. Then, the effect of nonadhering to MDI therapy was assessed using standard glucose control metrics calculated in two 6-month 3-meal/day in silico scenarios: in Scenario 1, subjects received the optimal basal and prandial insulin bolus at each meal; in Scenario 2, subjects received optimal basal insulin and randomly delayed or skipped the prandial insulin bolus in 3 lunches during working days and 1 dinner during weekends. A statistically significant degradation was found in all glucose control outcome metrics in Scenario 2 versus Scenario 1: e.g., percent time above 180 mg/dL increased by 22.2% and glucose management index by 0.2%. Impaired adherence to MDI therapy in T2D leads to glucose control deteriorations in both short and long terms. Interestingly, short-term hyperglycemia seems being contrasted by residual endogenous insulin secretion, which statistically increased by 3-fold after delayed/skipped insulin boluses compared with optimal ones.

305-OR: Short-Term Hyperglycemia Impacts Mouse Skeletal Muscle in a Sex-Specific Manner

Cardiorespiratory Fitness (CRF) a universal predictor of cardiovascular and all-cause mortality, is lower in people with diabetes. Skeletal muscle is a key determinant of CRF, in particular mitochondrial content, function and oxygen extraction. Hyperglycemia is implicated in the dysfunction of microvascular blood flow. Our previous work demonstrated lower mitochondrial density/fiber and capillary mean flow velocity (MFV) with 4 weeks of hyperglycemia in males and females. Treadmill running resulted in greater capillary MFV and mitochondrial density in only hyperglycemic females. We hypothesize that along with alterations in mitochondrial density and blood flow, there is a disruption in skeletal muscle mitochondrial function with hyperglycemia, and that these parameters will respond to nitrite (NO2-) treatment in a sex-specific manner. We used a model of short-term hyperglycemia with tamoxifen inducible β-cell deletion of glucokinase. Two weeks after induction, blood flow in the gastrocnemius (gastroc) was measured using intravital microscopy, and the gastroc was collected from male (M) and female (F) mice with blood glucose >400mg/dl (HG) and euglycemic controls (EG). A subset of mice received NO2- treatment for 1-2 weeks prior to gastroc measurements. Immunofluorescence imaging of gastroc were analyzed for expression of COX1 (mitochondrial marker), Dystrophin (muscle fiber sarcolemma boundary), and CD31 (capillary marker). Mitochondrial respiration was measured in gastroc fibers using Oroboros O2k. Mitochondrial respiration was lower in HG compared to EG (p<0.0009), but only respiration in M appeared to respond to NO2- treatment (p=0.0252). No difference was observed in mitochondrial density in EG versus HG. Capillary MFV was greater with HG and mitigated by NO2-treatment. NO2- targets mitochondrial function by improving capillary blood flow, but only in males. Our combined data sets suggest HG-associated mitochondrial defects need to be treated in a sex-specific manner. Disclosure N.A.Hulett: None. L.Knaub: None. G.Pott: None. D.Ramirez: None. A.Johnston: None. R.L.Scalzo: None. J.E.B.Reusch: Advisory Panel; Medtronic. Funding U.S. Department of Veterans Affairs (BX002046, CX001532); National Institutes of Health (P30DK116073, 5T32AG000279-20)

Abstract 37: Acute Hyperglycemia At Stroke Onset Is Associated With Abnormal Red Blood Cells

Background: Acute hyperglycemia at stroke onset is a common clinical problem and is an independent predictor of mortality and long-term disability. Abnormal red blood cells (RBCs) have long been recognized as a stroke risk factor and are associated with poor stroke outcome. Recent evidence has shown that short term hyperglycemia exposure can intensify oxidative stress in RBCs and cause hemolysis. We hypothesize that acute hyperglycemia may induce RBC dysfunction in stroke patients, which may be related to the poor outcome in those patients. Method: 93 stroke patients were consecutively recruited in accordance with IRB protocol. Patients with diabetes, prediabetes or HbA1C ≥ 5.7% were excluded. None of the patients had preexisting anemia. Hyperglycemia was defined as blood glucose > 110 mg/dL at admission. RBC indices were documented for all the patients. Patients with major hemorrhagic events and multiple blood draws were excluded from the study. Clinical outcome was determined by mRankin Scale at 3 month (good: ≤ 2; poor: > 2). Result: 45 (48.4%) were hyperglycemic and 48 (51.6%) were normoglycemic. Hyperglycemic patients showed gradually decreased RBC counts and hemoglobin content, while RBC distribution width (RDW) was gradually elevated (Fig. A). Subgroup analyses showed that the association of hyperglycemia with RBC alterations was not affected by sex and age, two factors that are known to affect RBC function (Fig. B). More importantly, patients with abnormally low RBC count, low hemoglobin and high RDW were at increased risk of developing poor outcome (Fig. C). These results remained robust after adjusting for other risk factors (Fig. C), suggesting that abnormal RBC parameters are independent predictors of poor stroke outcome. Conclusion: Our results revealed that acute hyperglycemia at stroke onset is associated with abnormal RBC indices, which are predictive of poor stroke outcome. Studies in a larger patient cohort with extended time course are still ongoing.

1069-P: A National Physician Survey of Perspectives on Deintensifying Diabetes Medications

Deintensifying diabetes medications rarely occurs for older adults with type 2 diabetes (T2D) despite many being tightly controlled with hypoglycemia-inducing medications. We conducted a national survey of US physicians to understand their perspectives on deintensification for older adults with T2D. The survey was designed by a team of patients, caregivers, and physicians, and distributed to a random sample of physicians in general medicine, geriatrics, and endocrinology in three mailing waves. Respondents rated the importance of deintensifying, and of switching to a medication with a better risk/benefit profile, on 5-point Likert scales; the frequency of these actions in the past 3 months; and barriers/facilitators. We received 427 completed surveys to date, response rate 27%. The Figure shows physicians’ responses. Our findings show that the vast majority of US physicians view deintensifying diabetes medications as important to the care of older adults, although they accomplish this infrequently. Major barriers were physicians’ views that patients were reluctant to change medications or to allow their glucose to be higher. Adverse events, especially hypoglycemia, were strong facilitators, as was reducing cost of therapy. Geriatricians reported deintensifying more often than other specialties. Endocrinologists switched medications more often and were more concerned about short-term hyperglycemia. Disclosure S.J.Pilla: None. I.J.Wang: None. N.Schoenborn: None. C.Boyd: Other Relationship; Dynamed, UpToDate. S.Golden: Advisory Panel; Abbott Diabetes, Medtronic. N.N.Mathioudakis: None. N.M.Maruthur: Other Relationship; Johns Hopkins HealthCare Solutions. Funding National Institutes of Health (1R24AG064025 and 1K23DK128572)

1372-P: Hyperglycemia Impacts Mouse Skeletal Muscle in a Sex-Specific Manner

Functional Exercise Capacity (FEC) , a universal predictor of cardiovascular and all-cause mortality, is lower in adults and youth with diabetes for reasons that are poorly understood. Skeletal muscle is key determinant of FEC. We hypothesized that skeletal muscle capillary and mitochondrial density are lower with hyperglycemia and respond to exercise training. To test this hypothesis we generated a model of short-term hyperglycemia (HG) with inducible beta cell deletion of glucokinase (GKlox/lox;PdxCreER) . Male (M) and female (F) HG mice and euglycemic littermate controls (EG) completed 3 weeks of treadmill training (Ex) or remained sedentary (Sed) . The gastrocnemius was collected 24 hours after the final exercise bout. Expression of COX1 (mitochondrial marker) , Dystrophin (muscle fiber sarcolemma boundary marker) , and CD31 (capillary marker) was detected by immunofluorescence. Sirtuin 3 (SIRT3) , an NAD+ dependent deacetylase (mitochondrial homeostasis) was measured using the JESS system. (Fig 1) Mitochondrial density (mitochondria per fiber as quantified by fluorescence intensity units per fiber [FIU/fiber]) was significantly lower in HG vs. EG (p<0.0001) and differed by sex (p=0.0048 sex x glycemia interaction) . Ex resulted in greater mitochondrial density (p=0.0265) independent of sex and glycemia. Capillary density and SIRT3 were unchanged. Sex-differences in muscle response to HG warrant further investigation. Disclosure L.Knaub: None. G.Pott: None. N.A.Hulett: None. S.Hull: None. R.L.Scalzo: None. J.Reusch: Advisory Panel; Medtronic. Funding VA Merit (BX002046)

Hyperglycemia Augmented Neuropathic Pain Involving the HMGB1/TLR4 Inflammatory Axis

<p>Peripheral neuropathy, accompanied by chronic neuropathic pain, is among the frequent and debilitating complications of diabetes. Hyperglycemia is a risk factor for neuropathic pain, but the pathological mechanisms are unclear. The high mobility group box 1 (HMGB1)/toll-like receptor 4 (TLR4) inflammatory axis is strongly implicated in the pathogenesis of neuropathic pain,so we examined how hyperglycemia influences the HMGB1/TLR4 axis and behavioural manifestations of hyperalgesia in the Sprague-Dawley rat sciatic nerve chronic constriction injury (CCI) model. Short-term hyperglycemia induced by streptozotocin significantly augmented mechanical allodynia and thermal hyperalgesia in CCI model rats compared to normoglycemic CCI model rats.These augmented nociceptive behaviours were associated with increased immune cell infiltration and activation, cytokine production and expression levels of TLR4 and HMGB1, as well as with reduced Sirt1 expression in spinal cord dorsal horn and sciatic nerve. High glucose also enhanced HMGB1/TLR4 inflammatory axis activity and cytokine production in lipopolysaccharide-stimulated RAW264.7 macrophages. Our results suggest that hyperglycemia predisposes individuals with peripheral nerve injury to neuropathic pain, in part through enhancement of Sirt1/HMGB1/TLR4 signalling and ensuing neuroinflammation.</p> <p> </p>

Adiponectin accumulation in the retinal vascular endothelium and its possible role in preventing early diabetic microvascular damage

Adiponectin (APN), a protein abundantly secreted from adipocytes, has been reported to possess beneficial effects on cardiovascular diseases in association with its accumulation on target organs and cells by binding to T-cadherin. However, little is known about the role of APN in the development of diabetic microvascular complications, such as diabetic retinopathy (DR). Here we investigated the impact of APN on the progression of early retinal vascular damage using a streptozotocin (STZ)-induced diabetic mouse model. Our immunofluorescence results clearly showed T-cadherin-dependent localization of APN in the vascular endothelium of retinal arterioles, which was progressively decreased during the course of diabetes. Such reduction of retinal APN accompanied the early features of DR, represented by increased vascular permeability, and was prevented by glucose-lowering therapy with dapagliflozin, a selective sodium-glucose co-transporter 2 inhibitor. In addition, APN deficiency resulted in severe vascular permeability under relatively short-term hyperglycemia, together with a significant increase in vascular cellular adhesion molecule-1 (VCAM-1) and a reduction in claudin-5 in the retinal endothelium. The present study demonstrated a possible protective role of APN against the development of DR.

The impact of short-term hyperglycemia and obesity on biventricular and biatrial myocardial function assessed by speckle tracking echocardiography in a population of women with gestational diabetes mellitus

Background and aimsTo compare biventricular and biatrial myocardial strain indices assessed by two-dimensional speckle tracking echocardiography (2D-STE) in women with gestational diabetes mellitus (GDM) and those with uncomplicated pregnancy at the third trimester of pregnancy and in post-partum. Methods and results30 consecutive GDM women and 30 age-, ethnicity- and gestational week-matched controls without any comorbidity were examined in this prospective case–control study. All women underwent obstetric visit, blood tests and transthoracic echocardiography (TTE) implemented with 2D-STE analysis of all cardiac chambers at 36–38 weeks’ gestation. TTE and 2D-STE were repeated at 6–10 weeks after delivery.At 36–38 weeks’ gestation, GDM women, compared to controls, had significantly higher body mass index (BMI), blood pressure values and inflammatory markers. TTE showed increased left ventricular (LV) mass and impaired LV diastolic function in GDM women, whereas there was no significant difference between the groups in ejection fraction. 2D-STE revealed that biventricular global longitudinal strain (GLS) and biatrial reservoir strain indices were significantly lower in GDM women than controls. Third trimester BMI was inversely correlated with LV-GLS (r = −0.86) and was independently associated with reduced LV-GLS (less negative than −20%) in GDM women in post-partum (OR 1.81, 95%CI 1.14–2.89). A BMI value ≥ 30 kg/m2 had 100% sensitivity and 99.5% specificity for identifying GDM women with impaired LV-GLS in post-partum (AUC = 0.97). ConclusionWomen with GDM, compared to women with uncomplicated pregnancy, have significantly lower biventricular and biatrial myocardial deformation indices. These abnormalities may be persistent in post-partum in GDM women with obesity.

The effects of short term hyperglycemia on human red blood cells studied using Raman spectroscopy and optical trap.

Management of postprandial hyperglycemia is important for preventing severe complications like cardiovascular disease in diabetes patients. The associated glycemic instability in postprandial hyperglycemia may also cause disorders in circulating red blood cells (RBCs). Therefore, effects of short-term hyperglycemic stress on RBCs such as occur in the postprandial condition, have been studied here ex vivo using single-cell Raman spectroscopy and optical trapping. RBCs incubated in high glucose containing media relevant to postprandial hyperglycemia were studied for changes with respect to controls by analyzing the single-cell Raman spectra acquired with Raman optical tweezers with 532nm excitation light. Use of 532nm light for exciting Raman spectra also results in simultaneous photoreduction of intracellular hemoglobin (Hb). The level of photoreduction was noticed to be limited in hyperglycemia-exposed cells in comparison to the control. Since this suggests formation of permanently oxidized Hb in hyperglycemia-exposed RBCs, a fluorescence study was performed which showed elevated levels of oxidative stress in these cells. The changes in the RBC membrane, which may result due to higher levels of oxidative stress, were investigated using optical stretching experiments under the laser trap. The results indicated a loss of elasticity for the RBC membrane due to hyperglycemic exposure.

Systemic Administration of Insulin Receptor Antagonist Results in Endothelial and Perivascular Adipose Tissue Dysfunction in Mice.

Hyperglycemia linked to diabetes results in endothelial dysfunction. In the present work, we comprehensively characterized effects of short-term hyperglycemia induced by administration of an insulin receptor antagonist, the S961 peptide, on endothelium and perivascular adipose tissue (PVAT) in mice. Endothelial function of the thoracic and abdominal aorta in 12-week-old male C57Bl/6Jrj mice treated for two weeks with S961 infusion via osmotic pumps was assessed in vivo using magnetic resonance imaging and ex vivo by detection of nitric oxide (NO) production using electron paramagnetic resonance spectroscopy. Additional methods were used to analyze PVAT, aortic segments and endothelial-specific plasma biomarkers. Systemic disruption of insulin signaling resulted in severe impairment of NO-dependent endothelial function and a loss of vasoprotective function of PVAT affecting the thoracic as well as abdominal parts of the aorta, however a fall in adiponectin expression and decreased uncoupling protein 1-positive area were more pronounced in the thoracic aorta. Results suggest that dysfunctional PVAT contributes to vascular pathology induced by altered insulin signaling in diabetes, in the absence of fat overload and obesity.

Does Hyperglycemia Cause Oxidative Stress in the Diabetic Rat Retina?

Diabetes, being a metabolic disease dysregulates a large number of metabolites and factors. However, among those altered metabolites, hyperglycemia is considered as the major factor to cause an increase in oxidative stress that initiates the pathophysiology of retinal damage leading to diabetic retinopathy. Diabetes-induced oxidative stress in the diabetic retina and its damaging effects are well known, but still, the exact source and the mechanism of hyperglycemia-induced reactive oxygen species (ROS) generation especially through mitochondria remains uncertain. In this study, we analyzed precisely the generation of ROS and the antioxidant capacity of enzymes in a real-time situation under ex vivo and in vivo conditions in the control and streptozotocin-induced diabetic rat retinas. We also measured the rate of flux through the citric acid cycle by determining the oxidation of glucose to CO2 and glutamate, under ex vivo conditions in the control and diabetic retinas. Measurements of H2O2 clearance from the ex vivo control and diabetic retinas indicated that activities of mitochondrial antioxidant enzymes are intact in the diabetic retina. Short-term hyperglycemia seems to influence a decrease in ROS generation in the diabetic retina compared to controls, which is also correlated with a decreased oxidation rate of glucose in the diabetic retina. However, an increase in the formation of ROS was observed in the diabetic retinas compared to controls under in vivo conditions. Thus, our results suggest of diabetes/hyperglycemia-induced non-mitochondrial sources may serve as major sources of ROS generation in the diabetic retina as opposed to widely believed hyperglycemia-induced mitochondrial sources of excess ROS. Therefore, hyperglycemia per se may not cause an increase in oxidative stress, especially through mitochondria to damage the retina as in the case of diabetic retinopathy.

Endothelial Dysfunction, Atherosclerosis, and Increase of von Willebrand Factor and Factor VIII: A Randomized Controlled Trial in Swine.

It is well known that high von Willebrand factor (VWF) and factor VIII (FVIII) levels are associated with an increased risk of cardiovascular disease. It is still debated whether VWF and FVIII are biomarkers of endothelial dysfunction and atherosclerosis or whether they have a direct causative role. Therefore, we aimed to unravel the pathophysiological pathways of increased VWF and FVIII levels associated with cardiovascular risk factors. First, we performed a randomized controlled trial in 34 Göttingen miniswine. Diabetes mellitus (DM) was induced with streptozotocin and hypercholesterolemia (HC) via a high-fat diet in 18 swine (DM + HC), while 16 healthy swine served as controls. After 5 months of follow-up, FVIII activity (FVIII:C) was significantly higher in DM + HC swine (5.85 IU/mL [5.00-6.81]) compared with controls (4.57 [3.76-5.40], p = 0.010), whereas VWF antigen (VWF:Ag) was similar (respectively 0.34 IU/mL [0.28-0.39] vs. 0.34 [0.31-0.38], p = 0.644). DM + HC swine had no endothelial dysfunction or atherosclerosis during this short-term follow-up. Subsequently, we performed a long-term (15 months) longitudinal cohort study in 10 Landrace-Yorkshire swine, in five of which HC and in five combined DM + HC were induced. VWF:Ag was higher at 15 months compared with 9 months in HC (0.37 [0.32-0.42] vs. 0.27 [0.23-0.40], p = 0.042) and DM + HC (0.33 [0.32-0.37] vs. 0.25 [0.24-0.33], p = 0.042). Both long-term groups had endothelial dysfunction compared with controls and atherosclerosis after 15 months. In conclusion, short-term hyperglycemia and dyslipidemia increase FVIII, independent of VWF. Long-term DM and HC increase VWF via endothelial dysfunction and atherosclerosis. Therefore, VWF seems to be a biomarker for advanced cardiovascular disease.

SIRT1 Activation by Polydatin Alleviates Oxidative Damage and Elevates Mitochondrial Biogenesis in Experimental Diabetic Neuropathy.

Mitochondrial dysfunction has been implicated as a one of the major factors linked to the development of painful diabetic neuropathy (DN). Several studies have demonstrated that sirtuin (SIRT1) activation recuperates nerve function by activating mitochondrial biogenesis. Polydatin, a resveratrol glycoside, has been explored to improve mitochondrial function via SIRT1 activation. However, the neuroprotective effects of polydatin in DN remain elusive. In this study, polydatin (25 and 50mg/kg, oral) was administered for last 2weeks of 8-week study to diabetic Sprague-Dawley rats weighing 250-300g (post 6-weeks of streptozotocin 55mg/kg, intraperitoneal). Treatment with polydatin significantly attenuated mechanical and thermal hyperalgesia in diabetic rats. Treated diabetic rats also showed improvement in motor/sensory nerve conduction velocities and nerve blood flow. For in vitro studies, Neuro2a cells were exposed to high-glucose (30mM) condition to simulate short-term hyperglycemia. Polydatin was evaluated for its role in SIRT1 and Nrf2 activation at a dose of 5, 10, and 20µM concentrations. Polydatin exposure normalized the mitochondrial superoxides, membrane potentials and improved neurite outgrowth in high-glucose-exposed Neuro2a cells. Increased SIRT1 activation by polydatin resulted in peroxisome proliferator activated receptor-gamma coactivator-1α (PGC-1α) directed mitochondrial biogenesis. SIRT1 activation also facilitated Nrf2-directed antioxidant signaling. Study results inferred that decline in mitochondrial biogenesis and oxidative function in diabetic rats and high-glucose-exposed Neuro2a cells, could be counteracted by polydatin administration, postulated via enhancing SIRT1 and Nrf2 axis.

COVID-19, diabetes mellitus and ACE2: The conundrum

COVID-19, diabetes mellitus and ACE2: The conundrum

Oxidative status of erythrocytes, hyperglycemia, and hyperlipidemia in diabetic cats.

BackgroundErythrocytes of diabetic cats have decreased superoxide dismutase activity, possibly indicative of oxidative stress.HypothesisErythrocytes of diabetic cats undergo oxidative stress, which is caused by hyperglycemia and hyperlipidemia, and improves with treatment.AnimalsTwenty‐seven client‐owned cats with diabetes mellitus, 11 matched healthy cats, and 21 purpose‐bred healthy cats.MethodsProspective study. Advanced oxidized protein products, carbonyls (protein oxidation by‐products), and thiols (antioxidants) were quantified in erythrocyte membrane, thiobarbituric acid reactive substances (TBAR, lipid peroxidation by‐products), and thiols in erythrocyte cytoplasm of all cats. Comparison were performed between diabetic and matched healthy cats, between diabetic cats achieving remission or not, and among purpose‐bred cats after 10 days of hyperglycemia (n = 5) or hyperlipidemia (n = 6) versus controls treated with saline (n = 5) or untreated (n = 5).ResultsCompared with controls, erythrocytes of diabetic cats initially had higher median membrane carbonyls (4.6 nmol/mg total protein [range: 0.1‐37.7] versus 0.7 [0.1‐4.7], P < .001) and lower cytoplasmic TBAR (1.9 nmol/mg [0.5‐2.4] versus 2.4 [1.4‐3.5] P < .001), and thiols (419 nmol/mg [165‐621] versus 633 [353‐824], P < 0.001). After 12‐16 weeks of treatment in diabetic cats, carbonyls decreased by 13% (P < .001), but remained higher (P < .001) and TBAR and thiols lower (P = .02, P < .001) than those in controls. No differences were observed between diabetic cats achieving remission or not, and among purpose‐bred cats.Conclusions and Clinical ImportanceDiabetes mellitus is associated with increased protein oxidation and reduced antioxidant defenses, which persist during treatment and remission, although mild improvement in protein oxidation occurs. Short‐term hyperglycemia or hyperlipidemia does not cause oxidative stress. The reason for decreased TBAR remains unknown.

574-P: Recurrent Short-Term Hypoglycemia and Hyperglycemia Enhance Apoptosis and Oxidative Stress through Polyol Pathway and Endoplasmic Reticulum Stress Pathway in Schwann Cells

It is demonstrated that glucose fluctuations, such as postprandial hyperglycemia, and hypoglycemia due to diabetes treatment could be implicated in the development of diabetic complications. There is evidence for the involvement of oxidative stress in the pathogenesis of diabetic neuropathy. It has been elucidated that hyperglycemia induced oxidative stress and caused peripheral nerve dysfunction. However, the effects of hypoglycemia and blood glucose fluctuation on diabetic neuropathy remain unclear. In the present study, we investigated the mechanisms of recurrent short-term hypoglycemia and hyperglycemia on apoptosis and oxidative stress in Schwann cells, and we also examined the involvement of polyol pathway and endoplasmic reticulum (ER) stress pathway in these abnormalities. Immortalized adult mouse Schwann cells were exposed to five different glucose treatments over 3 days: 1) normal glucose (NG), 2) constant low glucose (LG), 3) constant high glucose (HG), 4) intermittent low glucose (ILG; 1 h three times per day), 5) intermittent high glucose (IHG; 1 h three times per day). Cell viability was reduced not only HG, but also LG. Furthermore, either IHG or ILG also decreased cell viabilities. TBARS levels were increased by HG, LG, IHG, and ILG. High glucose (HG and IHG) and low glucose (LG and ILG) increased the expression of cleaved caspase-3 and reduced that of Bcl-2. Epalrestat, an aldose reductase inhibitor, as well as 4-PBA, an ER stress inhibitor, recovered cell death and oxidative stress which were induced by LG, HG, ILG and IHG. These results suggest that intermittent hypoglycemia and hyperglycemia enhanced apoptosis and oxidative stress through both polyol pathway and ER stress pathway in Schwann cells, and that not only hyperglycemia, but also hypoglycemia and glucose fluctuations might cause nerve dysfunction in diabetes, resulting in the onset and progression of diabetic neuropathy. Disclosure A. Kato: None. Y. Tatsumi: None. H. Yako: None. T. Himeno: None. M. Kondo: None. Y. Kato: Speaker's Bureau; Self; Merck &amp; Co., Inc. H. Kamiya: Speaker's Bureau; Self; Astellas Pharma Inc., Eli Lilly Japan K.K., MSD K.K., Novartis Pharma K.K., Novo Nordisk Oharma Ltd., Ono Pharmaceutical Co., Ltd., Sanofi K.K. K. Sango: None. J. Nakamura: Research Support; Self; Astellas Pharma Inc., Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Japan Tobacco Inc., Kissei Pharmaceutical Co., Ltd., Merck Sharp &amp; Dohme Corp., Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sanofi K.K., Sumitomo Dainippon Pharma Co., Ltd., Taisho Pharmaceutical Co., Ltd., Takeda Pharmaceutical Company Limited. Speaker's Bureau; Self; Astellas Pharma Inc., AstraZeneca, Boehringer Ingelheim Pharmaceuticals, Inc., Daiichi Sankyo Company, Limited, Eli Lilly and Company, Kowa Pharmaceu. Co. Ltd., Merck Sharp &amp; Dohme Corp., Mitsubishi Tanabe Pharma Corporation, Novartis Pharmaceuticals Corporation, Novo Nordisk Inc., Ono Pharmaceutical Co., Ltd., Sanofi K.K., Takeda Pharmaceutical Company Limited, Terumo Medical Corporation. K. Kato: None. Funding Japan Society for the Promotion of Science