Hyperglycemic Changes Research Articles

407 Glucose activates STAT3, promoting XRCC1 expression and increased DNA repair after exogenous challenge

OBJECTIVES/GOALS: Inflammation-promoting exposures, including hyperglycemia and inflammatory cytokines, are common in the development and progression of multiple cancers. Here, we determine if high glucose drives the dysregulation of XRCC1, changing BER/SSBR capacity, and increasing resistance to DNA damaging agents. METHODS/STUDY POPULATION: Here, we acutely exposed cell lines models with 30 mM glucose to mimic hyperglycemic changes and monitored the gene and protein expression of STAT3 and XRCC1. We selected the osteosarcoma cell line U2OS, with high STAT3 activation before glucose challenge, and the non-tumorigenic human embryonic kidney cell line HEK293T, with low STAT3 activation before glucose challenge, to dissect the role STAT3 plays in dysregulating DNA repair. We also examined changes in STAT3 occupancy at the XRCC1 promoter following glucose challenge using chromatin immunoprecipitation (ChIP). Finally, we measured changes in the sensitivity to the alkylating agent methyl methanesulfonate (MMS) induced by the glucose challenge using cell survival and DNA strand break analysis. RESULTS/ANTICIPATED RESULTS: High glucose challenge increases the phosphorylation and activation of STAT3 and subsequently increases XRCC1 gene and protein content in the cell. Acute high glucose activated STAT3, driving the subsequent expression of XRCC1 in U2OS and HEK293T cells through increased STAT3 occupancy at the XRCC1 promoter. High glucose also reduced sensitivity to MMS, increasing cell survival. The most significant increase in resistance to MMS occurred in the HEK293T, which also showed the largest increase in XRCC1 protein expression following the glucose challenge. Increased survival correlated with the faster resolution of DNA strand breaks in glucose-challenged cell lines. DISCUSSION/SIGNIFICANCE: This work has identified a novel regulatory mechanism by which high glucose drives the expression of XRCC1 through STAT3 activation, increasing DNA repair and resistance to the DNA damaging agent MMS. These data suggest dietary choices induce sustained XRCC1 expression and may contribute to chemoresistance and poor survival outcomes in cancers.

The Investigation of the Effect of Hyperglycemic Changes on Psychophysical Measurements of Visual Function in Pseudophakic People Living with Diabetes Mellitus.

PurposeThe purpose of this study was to show the effect of increasing blood glucose level (BGL) on psychophysical visual function represents by visual acuity and contrast sensitivity in pseudophakic people living with diabetes (PDM).Study DesignThis was quasi-experimental, quantitative study using a pretest–posttest approach.MethodsThe study was conducted at Gamalakhe community health centre located in Gamalakhe township and included a sample of 50 pseudophakic people living without diabetes mellitus (PWDM) and 50 pseudophakic PDM. BGL as well as psychophysical measurements of visual function were measured preprandial and postprandial. Visual acuity (VA) was measured at distance (4 m) and near (40 cm) using logMAR VA charts, and contrast sensitivity (CS) was measured at 50 cm using a Mars chart. The data collected were captured and subsequently analyzed using SPSS version 25.ResultsGlycemic changes measured preprandial and postprandial observed a mean increase of 2.06±1.35 mmol/L (p=0.350) and 1.08±0.47 mmol/L (p=0.291) in pseudophakia PDM and pseudophakic PWDM, respectively. CS showed a mean increase of 0.01±0.10 (p=0.23) and 0.002±0.02 (p=0.19) log units in PDM and PWDM, respectively; however, the independent t-test showed this was insignificant between PDM and PWDM (p=0.27). A insignificant mean increase of 0.01±0.04 log units (p=0.25) and 0.001±0.01 (p=0.32) in distance VA of pseudophakic PDM and PWDM was found, respectively. A mean increase of 0.001±0.01 log units (p=0.32) and 0.01±0.03 (p=0.06) near logMAR VA of pseudophakic PDM and PWDM was found, respectively.ConclusionAcute hyperglycemic changes do not result in overall significant changes in visual acuity and contrast sensitivity in pseudophakic PDM and PWDM for an increase in glycemia of 2 mmol/L. We recommend studies investigate if changes occur for glycemic increases exceeding 2 mmol/L.

THE MEASUREMENT OF THE CHOROIDAL THICKNESS DURING ORAL GLUCOSE TOLERANCE TESTS IN PREDIABETIC SUBJECTS: A SPECTRAL DOMAIN OPTICAL COHERENCE TOMOGRAPHY STUDY

Objective: The aim of this study is to investigate how acute hyperglycaemic changes affect the choroid in patients with prediabetes. Material and Method: Each subject underwent a 75 g oral glucose tolerance test (OGTT) after overnight fasting. The measurement of choroidal thickness (ChT) was done with new generation spectral domain optical coherence tomography (SD-OCT). Results: Fasting Plasma Glucose (FPG) levels of the patients with only isolated Impaired Fasting Glucose (IGT) patients are higher (all p<0.0001). Mean insulin levels were also higher in patients with prediabetes than in healthy volunteers during the entire experiment (all p<0.0001). Changes in ChT differed between the groups, a transient increase was observed in the mean ChT as well as subfoveal, nasal and temporal locations at the 500 µm distance to fovea in prediabetes individuals. While the subfoveal ChT difference was 1.52±4.11 µm (range, -11.00/24.00 µm) in prediabetes, -0.22±1.74 µm (range -2.00/8.00 µm) in the control group at the first hour of the OGTT. A transient choroidal thickening occurred in the prediabetes group, while there was no change in the healthy volunteers. Conclusion: Detecting acute hyperglycemic changes with instant measurements may help us to better understand the effect of the disease on ocular structures. 

Effects of β-glucan and Folium mori Extract Combinations in STZ-induced Diabetic Rats: Effectiveness of Various BGFM Complex Compositions in Treating Diabetes

Background: The hypoglycaemic effects of β-glucan (BG) extracts from some mushrooms and Folium mori (FM) has been reported. Objective: To determine the most effective composition of combined β-glucan originated from Aureobasidium and Folium mori extract (BGFM) for treating diabetes and complicated hepatopathy and nephropathy using streptozotocin (STZ)-induced diabetic rats. Methods: Six days after STZ dosing, rats (n = 5 per group) were selected based on body weight and blood glucose levels. BGFM was orally administered once a day for 28 days (Qd × 28), and changes in blood glucose levels, body weight, liver and kidney weight, and levels of serum blood urea nitrogen (BUN), creatinine, aspartate aminotransferase (AST), and alanine aminotransferase (ALT) were measured. Results: The diabetic control group exhibited dramatic decreases in body weight, and increase in liver and kidney weight, and blood glucose, serum BUN, creatinine, AST, and ALT levels compared to the non-diabetic sham group. However, these hyperglycaemic changes were markedly reduced in the Folium mori extract single group (S-FM) and some groups that received a mixed composition. Additionally, the changes related to the complicated hepatopathy and nephropathy of body weight were attenuated in the β-glucan single (S-BG) and some mixed groups compared to the diabetic control group. The anti-diabetic effects of β-glucan composition increased with its dose, and similarly, the hypoglycaemic effects of FM composition increased with its dose. Of the 11 types of mixed composition and single formulations, the BG:FM 1:4 composition was considered most effective for dual efficacy in terms of its hypoglycaemic and anti-diabetic effects. Conclusion: The greatest synergistic effects of the BGFM complex in treating the hyperglycaemic and complicated hepatopathy and nephropathy of STZ were obtained using a BG:FM 1:4 ratio.

Response of lactate metabolism in brain glucosensing areas of rainbow trout (Oncorhynchus mykiss) to changes in glucose levels.

There is no evidence in fish brain demonstrating the existence of changes in lactate metabolism in response to alterations in glucose levels. We induced in rainbow trout through intraperitoneal (IP) treatments, hypoglycaemic or hyperglycaemic changes to assess the response of parameters involved in lactate metabolism in glucosensing areas like hypothalamus and hindbrain. To distinguish those effects from those induced by peripheral changes in the levels of metabolites or hormones, we also carried out intracerebroventricular (ICV) treatments with 2-deoxy-D-glucose (2-DG, a non-metabolizable glucose analogue thus inducing local glucopenia) or glucose. Finally, we also incubated hypothalamus and hindbrain in vitro in the presence of increased glucose concentrations. The changes in glucose availability were in general correlated to changes in the amount of lactate in both areas. However, when we assessed in these areas the response of parameters related to lactate metabolism, the results obtained were contradictory. The increase in glucose levels did not produce in general the expected changes in those pathways with only a minor increase in their capacity of lactate production. The decrease in glucose levels was, however, more clearly related to a decreased capacity of the pathways involved in the production and use of lactate, and this was especially evident after ICV treatment with 2-DG in both areas. In conclusion, the present results while addressing the existence of changes in lactate metabolism after inducing changes in glucose levels in brain glucosensing areas only partially support the possible existence of an astrocyte-neuron lactate shuttle in hypothalamus and hindbrain of rainbow trout relating glucose availability to lactate production and use.

Evaluating the Role of Serum 1,5-Anhydroglucitol Concentrations as an Indicator of Hyperglycemic Changes in Diabetic and Non Diabetic Surgical Patients

Purpose: We investigated the relationship between plasma glucose and serum 1,5-anhydroglucitol (1,5-AG) concentrations in surgical patients to determine the role of 1,5-AG concentrations in perioperative glycemic control. Methods: We enrolled 57 patients (19 with and 38 without diabetes) in the study, who underwent hepatectomy under general anesthesia with sevoflurane and remifentanil. Plasma glucose and serum 1,5-AG concentrations were measured and their correlations were evaluated. Results: In all patients, plasma glucose concentrations increased significantly during hepatectomy, but serum 1,5-AG concentrations declined after surgery. Linear regression analysis revealed a weak but significant correlation between the decrease rate of 1,5-AG concentrations and the increase rate of plasma glucose concentrations. Regression analyses revealed this correlation to be more intense in patients without diabetes than in all patients, whereas no correlation was observed in patients with diabetes. These results suggest that serum 1,5- AG concentrations decrease significantly in proportion to increase in plasma glucose concentrations in patients without diabetes, but are less sensitive to such changes in patients with diabetes. Consequently, this indicates that preoperative serum 1,5-AG concentrations in patients with diabetes are too low to be influenced by glycemic fluctuations. In both patient groups, decreased 1,5-AG concentrations did not normalize until 72 h after initiation of surgery. Conclusion: Measurement of 1,5-AG concentrations may be a useful for evaluating glycemic control during anesthesia in patients with normal glycemic metabolism; however, this approach may not be as useful in patients with diabetes as in those without diabetes.

In This Issue

HomeCirculation ResearchVol. 110, No. 8In This Issue Free AccessIn BriefPDF/EPUBAboutView PDFView EPUBSections ToolsAdd to favoritesDownload citationsTrack citationsPermissions ShareShare onFacebookTwitterLinked InMendeleyReddit Jump toFree AccessIn BriefPDF/EPUBIn This Issue Originally published13 Apr 2012https://doi.org/10.1161/RES.0b013e3182571a16Circulation Research. 2012;110:1035Lack of Neutrophil-Derived CRAMP Reduces Atherosclerosis in Mice (p 1052)Döring et al reveal how neutrophils promote atherosclerosis, and suggest a way to stop it.Download figureDownload PowerPointAtherosclerosis is a chronic inflammatory disorder associated with lipid accumulation in the vessel wall. Although the inflammation is known to be promoted, at least in part, by neutrophils, the precise mechanism by which these cells contribute to atherogenesis remains unclear. When activated, neutrophils release secretory vesicles called granules, and certain granule proteins, such as CRAMP (or LL37 in humans), are able to recruit other inflammatory cell types. To determine whether this happens during atherosclerotic lesion formation, Döring et al examined atherosclerosis-prone mice lacking CRAMP. Sure enough, these mice had fewer inflammatory cells adhering to their blood vessel walls, which resulted in smaller atherosclerotic plaques containing a reduced proportion of macrophages. CRAMP previously has been detected in endothelial cells and macrophages, but the team showed that in atherosclerotic vessels, CRAMP was specifically upregulated in neutrophils. The team also found that CRAMP promotes inflammatory cell recruitment by interacting with their formyl-peptide membrane receptors. Blocking these receptors, or indeed CRAMP activity, may be an avenue toward atherosclerosis therapies, as suggested by the authors.Sensing Gene-Regulatory Hyperglycemic Changes by Set7 in Vascular Endothelial Cells (p 1067)Histone modifier, Set7, activates proinflammatory genes in response to high blood glucose, reportOkabe et al.Download figureDownload PowerPointHistone proteins in chromatin can be posttranslationally modified in a number of different ways, and these modifications can be indicative of particular states of gene expression. For example, the addition of a methyl group to lysine 4 of histone H3 is associated with gene activation. Okabe et al were studying the activation of proinflammatory genes in response to hyperglycemia and wondered if such H3 methylation might be involved. They examined Set7, an H3-methylating enzyme, and found that when human epithelial cells were exposed to high glucose, the enzyme relocated to the nucleus. There, Set7 activated two proinflammatory genes, IL-8 and HMOX1. However, only IL-8 displayed H3 methylation, suggesting Set7 can activate genes independent of its methylation activity. In mice subjected to transient hyperglycemia, the same gene activation and histone methylation were observed. And, interestingly, the histone modification lasted at least 1 week. This persistence, say the authors, might explain “hyperglycemic memory,” the observation that even transient spikes in blood glucose levels can activate pathophysiological pathways leading to diabetes and atherosclerosis.Revascularization of Ischemic Skeletal Muscle by Estrogen-Related Receptor-γ (p 1087)Transcription factor ERRγ prompts new blood vessel growth in ischemic muscle, report Matsakas et al.Download figureDownload PowerPointSkeletal muscle ischemia is a common disorder that often accompanies obesity, diabetes, atherosclerosis, and other cardiovascular and metabolic diseases. In severe cases, it can lead to tissue death and limb amputation. Besides adopting a healthier lifestyle, undergoing vascular surgery is among the few available treatment options. Thus, noninvasive treatments are desperately needed. Matsakas et al now suggest that boosting muscle ERRγ levels might be one such noninvasive approach. ERRγ is known to activate a network of proangiogenic and oxidative metabolism factors in mouse skeletal muscle, but whether it could actually promote vascular recovery was unknown. To find out, the team occluded blood vessels in the hind limbs of mice to induce muscle ischemia. Within 1 or 2 weeks, mice that overexpressed ERRγ showed improved revascularization, blood perfusion, and reversal of myofiber damage compared with their wild-type counterparts. The transgenic mice also displayed higher expression levels of proangiogenic factors in the ischemic muscle. The authors suggest that boosting ERRγ levels might be a potential therapy not only for ischemia of the muscle but also for that of the heart or brain.Written by Ruth Williams. Previous Back to top Next FiguresReferencesRelatedDetails April 13, 2012Vol 110, Issue 8 Advertisement Article InformationMetrics © 2012 American Heart Association, Inc.https://doi.org/10.1161/RES.0b013e3182571a16 Originally publishedApril 13, 2012 PDF download Advertisement

Distinguishing Hyperglycemic Changes by Set7 in Vascular Endothelial Cells

Epigenetic changes are implicated in the persisting vascular effects of hyperglycemia. The precise mechanism whereby chromatin structure and subsequent gene expression are regulated by glucose in vascular endothelial cells remain to be fully defined. We have studied the molecular and functional mechanism whereby the Set7 methyltransferase associates with chromatin formation and histone methylation in vascular cells in response to current and previous exposure to glucose. To characterize the molecular and functional identity of the Set7 protein, we used vascular cells overexpressing or lacking Set7. Chromatin fractionation for mono-methylation of lysine 4 on histone H3 identified methyltransferase activity. Immunofluorescence experiments strongly suggest that Set7 protein accumulates in the nucleus in response to hyperglycemia. Moreover, activation of proinflammatory genes by high glucose is dependent on Set7 but distinguished by H3K4m1 gene patterns. We show that transient hyperglycemia regulates the expression of proinflammatory genes in vascular endothelial cells in vitro and the persistent increase in glucose-induced gene expression in the aorta of nondiabetic mice. This study uncovers that the response to hyperglycemia in vascular endothelial cells involves the H3K4 methyltransferase, Set7. This enzyme appears to regulate glucose-induced chromatin changes and gene expression not only by H3K4m1-dependent but also H3K4m1-independent pathways. Furthermore, Set7 appears to be responsible for sustained vascular gene expression in response to prior hyperglycemia and is a potential molecular mechanism for the phenomenon of hyperglycemic memory.

Quantitative proteomic analysis of single pancreatic islets

Technological developments make mass spectrometry (MS)-based proteomics a central pillar of biochemical research. MS has been very successful in cell culture systems, where sample amounts are not limiting. To extend its capabilities to extremely small, physiologically distinct cell types isolated from tissue, we developed a high sensitivity chromatographic system that measures nanogram protein mixtures for 8 h with very high resolution. This technology is based on splitting gradient effluents into a capture capillary and provides an inherent technical replicate. In a single analysis, this allowed us to characterize kidney glomeruli isolated by laser capture microdissection to a depth of more than 2,400 proteins. From pooled pancreatic islets of Langerhans, another type of "miniorgan," we obtained an in-depth proteome of 6,873 proteins, many of them involved in diabetes. We quantitatively compared the proteome of single islets, containing 2,000-4,000 cells, treated with high or low glucose levels, and covered most of the characteristic functions of beta cells. Our ultrasensitive analysis recapitulated known hyperglycemic changes but we also find components up-regulated such as the mitochondrial stress regulator Park7. Direct proteomic analysis of functionally distinct cellular structures opens up perspectives in physiology and pathology.

Requirement of Aldose Reductase for the Hyperglycemic Activation of Protein Kinase C and Formation of Diacylglycerol in Vascular Smooth Muscle Cells

Activation of protein kinase C (PKC) has been linked to the development of secondary diabetes complications. However, the underlying molecular mechanisms remain unclear. We examined the contribution of aldose reductase, which catalyzes the first, and the rate-limiting, step of the polyol pathway of glucose metabolism, to PKC activation in vascular smooth muscle cells (VSMCs) isolated from rat aorta and exposed to high glucose in culture. Exposure of VSMCs to high glucose (25 mmol/l), but not iso-osmotic mannitol, led to an increase in total membrane-associated PKC activity, which was prevented by the aldose reductase inhibitors tolrestat or sorbinil or by the ablation of aldose reductase by small interfering RNA (siRNA). The VSMCs were found to express low levels of sorbitol dehydrogenase, and treatment with the sorbitol dehydrogenase inhibitor CP-166572 did not prevent high-glucose-induced PKC activation. Stimulation with high glucose caused membrane translocation of conventional (alpha, beta1, beta2, and gamma) and novel (delta and epsilon) isoforms of PKC. Inhibition of aldose reductase prevented membrane translocation of PKC-beta2 and -delta and delayed the activation of PKC-beta1 and -epsilon, whereas membrane translocation of PKC-alpha and -gamma was not affected. Treatment with tolrestat prevented phosphorylation of PKC-beta2 and -delta. High glucose increased the formation of diacylglycerol (DAG) and enhanced phosphorylation of phospholipase C-gamma1 (PLC-gamma1). Inhibition of aldose reductase prevented high glucose-induced DAG formation and phosphorylation of PLC-gamma1 and PLC-beta2 and -delta. Inhibition of phospholipid hydrolysis by D609, but not by the synthetic alkyl-1-lysophospholipid 1-O-octadecyl-2-O-methyl-rac-glycerophosphocholine, or edelfosine, prevented DAG formation. Treatment with sorbinil decreased the levels of reactive oxygen species in high-glucose-stimulated VSMCs. Hence, inhibition of aldose reductase, independent of sorbitol dehydrogenase, appears to be effective in diminishing oxidative stress and hyperglycemic changes in signaling events upstream to the activation of multiple PKC isoforms and PLC-gamma1 and may represent a useful approach for preventing the development of secondary vascular complications of diabetes.

Endogenous glucose production in type I glycogen storage disease

The adaptive mechanisms that protect some patients with Type I glycogen storage disease from fasting hypoglycemia were examined in two young adults. Both maintained low normal fasting plasma glucose concentrations even during 3 day fasts; blood lactate concentrations increased during the first 12 hr and then decreased to normal during the second and third days. Acute hyperglycemic responses to glucagon nearly doubled after three days of starvation when compared with responses following 12 hr fasts. Enhanced glucagon-induced hyperglycemic changes also were observed following the administration of alcohol or glucocorticoids. However, fructose infusions failed to demonstrate hyperglycemic responses after a 3 day fast, alcohol or glucocorticoids. The present studies demonstrate endogenous glucose production in our patients despite an absence of the enzyme glucose-6-phosphatase. These findings could explain why some patients with Type I glycogen storage disease are protected from fasting hypoglycemia.

Carbohydrate utilization during amytal anesthesia.

Page1 has shown that anesthesia produced by amytal is not associated with the hyperglycemic changes which usually accompany anesthesia. Numerous investigators have employed this anesthetic in experiments involving various phases of carbohydrate metabolism.A comparison has been made of the response to intravenous glucose administration in six dogs with and without amytal anesthesia. The authors2 have previously observed a marked constancy in the response of any one animal to repeated glucose injections. The amytal was administered in doses of 60 mg. per kilo body weight intraperitoneally or 100 to 110 mg. per kilo body weight subcutaneously. The depth of the narcosis during the course of the experiment varied in different animals from light to deep surgical anesthesia. The method employed for studying the response was the same as previously described.2 A thirty per cent solution of glucose was injected intravenously by means of a Woodyatt pump at a rate of 4 grams per kilo body weight per hour for several ...