Influence of acidosis on lipid peroxidation in brain tissues in vitro

Impact of stress hyperglycemia on outcomes in patients with large ischemic stroke

BACKGROUND

Clinical evidence of the potential influence of stress hyperglycemia ratio (SHR) for patients with large ischemic stroke whether or not receiving endovascular therapy is not clear.

METHODS

This study was a subanalysis of a prospective, multicenter registry, and included 745 patients with large ischemic stroke across 38 centers in China. A total of 427 patients were included in this study, with 285 received endovascular therapy (EVT) and 142 received standard medical therapy (SMT). SHR was defined as glucose (mmol/L)/(1.59 × HbA1C)-2.59. The primary outcome was a moderate neurological outcome (modified Rankin Scale (mRS) score ≤3) at 90 days.

RESULTS

A significant interaction was observed between SHR and whether received EVT (p=0.017). Among patients who received EVT (adjusted OR (aOR) 0.46; 95% CI 0.23 to 0.92; p=0.029), patients in the highest tertile of SHR were significantly less likely to achieve a moderate neurological outcome at 90 days compared with those in the lowest tertile. However, this association was not observed in patients receiving SMT (aOR 2.46; 95% CI 0.74 to 8.21; p=0.142). EVT patients with higher SHR had a significantly higher incidence of symptomatic intracranial hemorrhage compared with lower SHR (aOR 3.29; 95% CI 1.08 to 10.06; p=0.036), while such an association was not observed in the SMT group (aOR 1.52; 95% CI 0.56 to 4.12; p=0.410).

CONCLUSIONS

In patients with large ischemic stroke treated with EVT, SHR is associated with a reduced likelihood of achieving a moderate neurological outcome, as well as an increased risk of symptomatic intracranial hemorrhage.

TRIAL REGISTRATION NUMBER

ChiCTR2100051664.

Anaerobic Glycolysis and Ischemic Stroke: From Mechanisms and Signaling Pathways to Natural Product Therapy

Ischemic stroke is a serious condition that results in high rates of illness and death. Anaerobic glycolysis becomes the primary means of providing energy to the brain during periods of low oxygen levels, such as in the aftermath of an ischemic stroke. This process is essential for maintaining vital brain functions and has significant implications for recovery following a stroke. Energy supply by anaerobic glycolysis and acidosis caused by lactic acid accumulation are important pathological processes after ischemic stroke. Numerous natural products regulate glucose and lactate, which in turn modulate anaerobic glycolysis. This article focuses on the relationship between anaerobic glycolysis and ischemic stroke, as well as the associated signaling pathways and natural products that play a therapeutic role. These natural products, which can regulate anaerobic glycolysis, will provide new avenues and perspectives for the treatment of ischemic stroke in the future.

Association of Admission Glucose and Outcomes After Endovascular Treatment for Acute Stroke: Data From the ANGEL-ACT Registry

BACKGROUND

The association between admission glucose levels and clinical outcomes after stroke has not been effectively elucidated. This study assessed the association among admission glucose levels, admission hyperglycemia, diabetes mellitus, and 90-day neurological outcomes in patients with acute ischemic stroke undergoing endovascular therapy.

METHODS

The ANGEL-ACT registry enrolled adults with acute ischemic stroke undergoing endovascular therapy between 2017 and 2019 in China and patients with available admission glucose data were included. Restricted cubic spline regression was used to determine the knots of blood glucose levels. Binary or ordinal logistic regression models were used to examine the impact of different admission glucose levels on neurological outcomes and 90-day mortality.

RESULTS

In total, 1684 participants with available admission glucose concentrations were evaluated. The admission glucose level was divided into 4 levels according to the restricted cubic spline curves: level 1 (<5.3 mmol/L), level 2 (5.3 to 7.0 mmol/L), level 3 (7.0 to 11.6 mmol/L), and level 4 (≥11.6 mmol/L). Level 4 admission glucose was associated with a decreased incidence of a modified Rankin scale score of 0 to 2 (hazard ratio, 0.59; 95% CI, 0.40-0.87) and an increased risk of mortality (hazard ratio, 1.74; 95% CI, 1.06-2.85). Levels 3 and 4, hyperglycemia, and diabetes mellitus independently predicted symptomatic intracranial hemorrhage (sICH). Admission glucose levels showed J-shaped relationships with sICH.

CONCLUSIONS

Higher admission glucose levels (≥11.6 mmol/L) were associated with a decreased likelihood of a modified Rankin scale score of 0 to 2 and an increased risk of mortality and sICH.

Association between stress hyperglycemia and outcomes in patients with acute ischemic stroke due to large vessel occlusion

AIMS

This study aimed to evaluate the association between stress hyperglycemia ratio (SHR) and clinical outcomes at 90 days in acute ischemic stroke due to large vessel occlusion receiving endovascular treatment.

METHODS

The RESCUE BT trial was a multicenter, randomized, double-blind, placebo-controlled clinical trial, consisting of 948 stroke patients from 55 centers in China. A total of 542 patients with glucose and glycated hemoglobin (HbA1C) values at admission were included in this analysis. SHR, measured by glucose/HbA1C, was evaluated as both a tri-categorical variable (≤1.07 vs. 1.08-1.29 vs. ≥1.30) and a continuous variable. The primary outcome was a favorable functional outcome (modified Rankin Scale [mRS] score ≤2) at 90 days. The secondary outcome included excellent functional outcome (mRS score ≤1) and safety outcomes, such as 90-day mortality and intracranial hemorrhage. The study was registered with Chictr.org.cn (ChiCTR-INR-17014167).

RESULTS

Compared with patients in the lowest tertile of SHR, the highest tertile group had significantly lower odds of achieving favorable functional outcome of mRS score of 0-2 (adjusted odds ratio, 0.44; 95% confidence interval, 0.28-0.69; p < 0.001) and excellent clinical outcome of mRS score of 0-1 (adjusted odds ratio, 0.48; 95% confidence interval, 0.29-0.79; p = 0.004) at 90 days after adjusting for potential covariates. Similar results were observed after further adjustment for preexisting diabetes and Alberta Stroke Program Early Computed Tomography Score (ASPECTS).

CONCLUSION

Stress hyperglycemia ratio, as measured by the glucose/HbA1C, was associated with a decreased odds of achieving a favorable functional outcome in patients with acute large vessel occlusion stroke at 90 days.

Stress hyperglycemia is predictive of clinical outcomes in patients with spontaneous intracerebral hemorrhage

Background

Stress hyperglycemia is a common condition in patients suffering from critical illness such as spontaneous intracerebral hemorrhage (ICH). Our study aimed to use glucose-to-glycated hemoglobin (HbA1c) ratio to investigate the impact of stress hyperglycemia on clinical outcomes in patients with ICH.

Methods

A sample of eligible 586 patients with spontaneous intracerebral hemorrhage from a multicenter, hospital-based cohort between 2014 and 2016 were recruited in our study. Stress hyperglycemia was evaluated by the index of the glucose-to-HbA1c ratio that was calculated by fasting blood glucose (mmol/L) divided by HbA1c (%). Patients were divided into two groups based on the median of the glucose-to-HbA1c ratio. The main outcomes were poor functional outcomes (modified Rankin Scale score of 3–6) at discharge and 90 days. Multivariable logistic regression and stratified analyses were performed to explore the association of stress hyperglycemia with poor prognosis of ICH.

Results

On multivariable analysis, higher glucose-to-HbA1c ratio (≥1.02) was independently correlated with poor functional outcomes at discharge (adjusted OR = 3.52, 95%CI: 1.98–6.23) and 90 days (adjusted OR = 2.27, 95%CI: 1.38–3.73) after adjusting for potential confounding factors. The correlation between glucose-to-HbA1c ratio and worse functional outcomes still retained in patients with or without diabetes mellitus.

Conclusions

Stress hyperglycemia, calculated by glucose-to-HbA1c ratio, was independently correlated with worse functional outcomes at discharge and 90 days in patients with ICH. Moreover, glucose-to-HbA1c ratio, might not only be used as a simple and readily available index to predict clinical outcomes of ICH but also provide meaningful insight into future analysis to investigate the optimal range of glucose levels among ICH patients and develop tailored glucose-lowering strategies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02760-9.

Impact of Stress Hyperglycemia on Early Neurological Deterioration in Acute Ischemic Stroke Patients Treated With Intravenous Thrombolysis

Background and Purpose

It has been widely reported that stress hyperglycemia contributes to poor prognosis in patients experiencing acute ischemic stroke (AIS). However, its predictive value for early neurological deterioration (END) after intravenous administration of recombinant tissue-type plasminogen activator (IV-rtPA) in AIS patients is still unclear. The aim of this study was to evaluate the impact of stress hyperglycemia on the risk of END after IV-rtPA.

Methods

A total of 798 consecutive patients treated with IV-rtPA were included in this study. The stress hyperglycemia ratio (SHR) was calculated as fasting plasma glucose level at admission (mg/dl)/glycosylated hemoglobin (HbAlc) (%). END was defined as a National Institutes of Health Stroke Scale Score (NIHSS) ≥ 4 points 24 h after IV-rtPA, and poor functional outcome at discharge was defined as a modified Rankin Scale (mRS) score of 3–6 at discharge. Patients with a prior history of diabetes or HbAlc ≥ 6.5% were considered to have diabetes mellitus. Patients were grouped according to SHR values. Multivariate logistical regression was used to evaluate the risk of END for patients within specific SHR categories.

Results

In total, 139 (17.4%) patients had END. After adjusting for confounders, the highest tertile group had higher risks of END and poor functional outcome at discharge than those of patients in the lowest tertile group (OR, 1.95; 95% CI, 1.21–3.15; p = 0.006) (OR, 1.85; 95% CI, 1.163–2.941; p = 0.009), and the predictive value of high SHR for END was also significant in patients with diabetes mellitus (OR, 3.05; 95% CI, 1.29–7.21; p = 0.011). However, a significant association of high SHR and poor functional outcome was only found in patients without diabetes (OR, 1.85; 95% CI, 1.002–3.399; p = 0.045).

Conclusion

A higher SHR predicted that patients with severe stress hyperglycemia had higher risks of END and poor functional outcome at discharge after IV-rtPA.

Effects of Glycemic Gap on Post-Stroke Cognitive Impairment in Acute Ischemic Stroke Patients

Background: Post-stroke hyperglycemia is a frequent finding in acute ischemic stroke patients and is associated with poor functional and cognitive outcomes. However, it is unclear as to whether the glycemic gap between the admission glucose and HbA1c-derived estimated average glucose (eAG) is associated with post-stroke cognitive impairment (PSCI). Methods: We enrolled acute ischemic stroke patients whose cognitive functions were evaluated three months after a stroke using the Korean version of the vascular cognitive impairment harmonization standards neuropsychological protocol (K-VCIHS-NP). The development of PSCI was defined as having z-scores of less than −2 standard deviations in at least one cognitive domain. The participants were categorized into three groups according to the glycemic gap status: non-elevated (initial glucose − eAG ≤ 0 mg/dL), mildly elevated (0 mg/dL < initial glucose − eAG < 50 mg/dL), and severely elevated (50 mg/dL ≤ initial glucose − eAG). Results: A total of 301 patients were enrolled. The mean age was 63.1 years, and the median National Institute of Health Stroke Scale (NIHSS) score was two (IQR: 1–4). In total, 65 patients (21.6%) developed PSCI. In multiple logistic regression analyses, the severely elevated glycemic gap was a significant predictor for PSCI after adjusting for age, sex, education level, initial stroke severity, Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification, and left hemispheric lesion (aOR: 3.65, p-value = 0.001). Patients in the severely elevated glycemic gap group showed significantly worse performance in the frontal and memory domains. Conclusions: In conclusion, our study demonstrated that an elevated glycemic gap was significantly associated with PSCI three months after a stroke, with preferential involvement of frontal and memory domain dysfunctions.

Tissue Acidosis Associated with Ischemic Stroke to Guide Neuroprotective Drug Delivery

Simple Summary

Ischemic stroke is caused by the blockade of a blood vessel in the brain. Consequently, the brain region supplied by the blocked vessel suffers brain damage and becomes acidic. Here we provide a summary of the causes and consequences of acid accumulation in the brain tissue. Ischemic stroke requires immediate medical attention to minimize the damage of brain tissue, and to save function. It would be desirable for the medical treatment to target the site of injury selectively, to enrich the site of ongoing injury with the protective agent, and to avoid undesirable side effects at the same time. We propose that acid accumulation at the sight of brain tissue injury can be used to delineate the region that would benefit most from medical treatment. Tiny drug carriers known as nanoparticles may be loaded with drugs that protect the brain tissue. These nanoparticles may be designed to release their drug cargo in response to an acidic environment. This would ensure that the therapeutic agent is directed selectively to the site where it is needed. Ultimately, this approach may offer a new way to treat stroke patients with the hope of more effective therapy, and better stroke outcome.

Abstract

Ischemic stroke is a leading cause of death and disability worldwide. Yet, the effective therapy of focal cerebral ischemia has been an unresolved challenge. We propose here that ischemic tissue acidosis, a sensitive metabolic indicator of injury progression in cerebral ischemia, can be harnessed for the targeted delivery of neuroprotective agents. Ischemic tissue acidosis, which represents the accumulation of lactic acid in malperfused brain tissue is significantly exacerbated by the recurrence of spreading depolarizations. Deepening acidosis itself activates specific ion channels to cause neurotoxic cellular Ca²⁺ accumulation and cytotoxic edema. These processes are thought to contribute to the loss of the ischemic penumbra. The unique metabolic status of the ischemic penumbra has been exploited to identify the penumbra zone with imaging tools. Importantly, acidosis in the ischemic penumbra may also be used to guide therapeutic intervention. Agents with neuroprotective promise are suggested here to be delivered selectively to the ischemic penumbra with pH-responsive smart nanosystems. The administered nanoparticels release their cargo in acidic tissue environment, which reliably delineates sites at risk of injury. Therefore, tissue pH-targeted drug delivery is expected to enrich sites of ongoing injury with the therapeutical agent, without the risk of unfavorable off-target effects.

Stress hyperglycemia is predictive of worse outcome in patients with acute ischemic stroke undergoing intravenous thrombolysis

No study investigated the possible detrimental effect of stress hyperglycemia on patients affected acute ischemic stroke (AIS) undergoing intravenous thrombolysis (IVT). A new index, the glucose-to-glycated hemoglobin ratio (GAR), has been developed for assessing stress hyperglycemia. We retrospectively analyzed data from a prospectively collected database of consecutive patients admitted to the Udine University Hospital with AIS that were treated with IVT from January 2015 to December 2019. Four hundred and fourteen consecutive patients with AIS undergoing IVT entered the study. The patients were then stratified into four groups by quartiles of GAR (Q1-Q4). The higher GAR index was, the more severe stress hyperglycemia was considered. Prevalence of 3 months poor outcome (37.7% for Q1, 34% for Q2, 46.9% for Q3, and 66.7% for Q4, p for trend = 0.001), 3 months mortality (10.5% for Q1, 7.5% for Q2, 11.2% for Q3, and 27.1% for Q4, p for trend = 0.001), and symptomatic intracranial hemorrhage (0.9% for Q1, 0.9% for Q2, 5.1% for Q3, and 17.7% for Q4, p for trend = 0.001) was significant different among the four groups. AIS patients with severe stress hyperglycemia had a significantly increased risk of 3 months poor outcome (OR 2.43, 95% CI 1.14-5.22, p = 0.02), 3 months mortality (OR 2.38, 95% CI 1.01-5.60, p = 0.04), and symptomatic intracranial hemorrhage (OR 16.76, 95% CI 2.09-134.58, p = 0.008) after IVT. In conclusion, we demonstrated that stress hyperglycemia, as measured by the GAR index, is associated to worse outcome in AIS patients undergoing IVT.

An integrative approach to the regulation of mitochondrial respiration during exercise: Focus on high-intensity exercise

During exercise, muscle ATP demand increases with intensity, and at the highest power output, ATP consumption may increase more than 100-fold above the resting level. The rate of mitochondrial ATP production during exercise depends on the availability of O₂, carbon substrates, reducing equivalents, ADP, P_i, free creatine, and Ca²⁺. It may also be modulated by acidosis, nitric oxide and reactive oxygen and nitrogen species (RONS). During fatiguing and repeated sprint exercise, RONS production may cause oxidative stress and damage to cellular structures and may reduce mitochondrial efficiency. Human studies indicate that the relatively low mitochondrial respiratory rates observed during sprint exercise are not due to lack of O₂, or insufficient provision of Ca²⁺, reduced equivalents or carbon substrates, being a suboptimal stimulation by ADP the most plausible explanation. Recent in vitro studies with isolated skeletal muscle mitochondria, studied in conditions mimicking different exercise intensities, indicate that ROS production during aerobic exercise amounts to 1-2 orders of magnitude lower than previously thought. In this review, we will focus on the mechanisms regulating mitochondrial respiration, particularly during high-intensity exercise. We will analyze the factors that limit mitochondrial respiration and those that determine mitochondrial efficiency during exercise. Lastly, the differences in mitochondrial respiration between men and women will be addressed.

Physiological stress against simulated 200-m and 500-m sprints in world-class boat paddlers

To characterize physiological stress response against simulated short-distance sprints among world-class paddlers. Thirteen dragon boat gold medalists performed 200-m and 500-m simulated race trials on a kayak ergometer in a randomized, counter-balanced, crossover fashion. During the 200-m and 500-m sprints, oxygen consumption (VO₂) increased from 8.7 to 31.2 ml/kg/min and from 8.0 to 32.7 ml/kg/min within 60 s, respectively. A plateau of 35 ml/kg/min below maximal VO₂(VO_2max) (39.7 ± 6.3 ml/kg/min) was reached at 75 s during the 500-m sprint. Respiratory exchange ratio dropped from 1.21 ± 0.16 to 1.07 ± 0.12 and 1.28 ± 0.13 to 1.06 ± 0.16 at 45 s, and resurged to 1.17 and 1.28 at the end of 200-m and 500-m sprints with lactate concentration reached 13 ± 2 and 15 ± 2 mM. Aerobic energy contribution to paddling power increases from ~10% for the first 15 s to ~80% for the last 15 s during the 500-m trial. Postexercise plasma thiobarbituric acid reactive substances increased by 376% and 543% above baseline after 200-m and 500-m trials (P < 0.001, between trials), respectively, followed by quick returns to baseline in 30 min (P < 0.001). Increased plasma creatine kinase (+48%) was observed only after the 500-m trial (P < 0.001, between trials), not 200-m trial. Our data suggest that muscle damage occurred only when maximal sprinting exceeding 2 min, highlighting an importance of volume than intensity on exercise-induced muscle damage.

Acidosis Maintains the Function of Brain Mitochondria in Hypoxia-Tolerant Triplefin Fish: A Strategy to Survive Acute Hypoxic Exposure?

The vertebrate brain is generally very sensitive to acidosis, so a hypoxia-induced decrease in pH is likely to have an effect on brain mitochondria (mt). Mitochondrial respiration (JO₂) is required to generate an electrical gradient (ΔΨm) and a pH gradient to power ATP synthesis, yet the impact of pH modulation on brain mt function remains largely unexplored. As intertidal fishes within rock pools routinely experience hypoxia and reoxygenation, they would most likely experience changes in cellular pH. We hence compared four New Zealand triplefin fish species ranging from intertidal hypoxia-tolerant species (HTS) to subtidal hypoxia-sensitive species (HSS). We predicted that HTS would tolerate acidosis better than HSS in terms of sustaining mt structure and function. Using respirometers coupled to fluorimeters and pH electrodes, we titrated lactic-acid to decrease the pH of the media, and simultaneously recorded JO₂, ΔΨm, and H⁺ buffering capacities within permeabilized brain and swelling of mt isolated from non-permeabilized brains. We then measured ATP synthesis rates in the most HTS (Bellapiscus medius) and the HSS (Forsterygion varium) at pH 7.25 and 6.65. Mitochondria from HTS brain did have greater H⁺ buffering capacities than HSS mt (∼10 mU pH.mg_protein ^-1). HTS mt swelled by 40% when exposed to a decrease of 1.5 pH units, and JO₂ was depressed by up to 15% in HTS. However, HTS were able to maintain ΔΨm near -120 mV. Estimates of work, in terms of charges moved across the mt inner-membrane, suggested that with acidosis, HTS mt may in part harness extra-mt H⁺ to maintain ΔΨm, and could therefore support ATP production. This was confirmed with elevated ATP synthesis rates and enhanced P:O ratios at pH 6.65 relative to pH 7.25. In contrast, mt volumes and ΔΨm decreased downward pH 6.9 in HSS mt and paradoxically, JO₂ increased (∼25%) but ATP synthesis and P:O ratios were depressed at pH 6.65. This indicates a loss of coupling in the HSS with acidosis. Overall, the mt of these intertidal fish have adaptations that enhance ATP synthesis efficiency under acidic conditions such as those that occur in hypoxic or reoxygenated brain.

Skeletal muscle signaling, metabolism, and performance during sprint exercise in severe acute hypoxia after the ingestion of antioxidants

The aim of this study was to determine if reactive oxygen species (ROS) could play a role in blunting Thr¹⁷²-AMP-activated protein kinase (AMPK)-α phosphorylation in human skeletal muscle after sprint exercise in hypoxia and to elucidate the potential signaling mechanisms responsible for this response. Nine volunteers performed a single 30-s sprint (Wingate test) in two occasions while breathing hypoxic gas ([Formula: see text] = 75 mmHg): one after the ingestion of placebo and another following the intake of antioxidants (α-lipoic acid, vitamin C, and vitamin E), with a randomized double-blind design. Vastus lateralis muscle biopsies were obtained before, immediately after, and 30- and 120-min postsprint. Compared with the control condition, the ingestion of antioxidants resulted in lower plasma carbonylated proteins, attenuated elevation of the AMP-to-ATP molar ratio, and reduced glycolytic rate (P < 0.05) without significant effects on performance or V̇o₂ The ingestion of antioxidants did not alter the basal muscle signaling. Thr¹⁷²-AMPKα and Thr^184/187-transforming growth factor-β-activated kinase 1 (TAK1) phosphorylation were not increased after the sprint regardless of the ingestion of antioxidants. Thr²⁸⁶-CaMKII phosphorylation was increased after the sprint, but this response was blunted by the antioxidants. Ser⁴⁸⁵-AMPKα1/Ser⁴⁹¹-AMPKα2 phosphorylation increased immediately after the sprints coincident with increased Akt phosphorylation. In summary, antioxidants attenuate the glycolytic response to sprint exercise in severe acute hypoxia and modify the muscle signaling response to exercise. Ser⁴⁸⁵-AMPKα1/Ser⁴⁹¹-AMPKα2 phosphorylation, a known mechanism of Thr¹⁷²-AMPKα phosphorylation inhibition, is increased immediately after sprint exercise in hypoxia, probably by a mechanism independent of ROS.NEW & NOTEWORTHY The glycolytic rate is increased during sprint exercise in severe acute hypoxia. This study showed that the ingestion of antioxidants before sprint exercise in severe acute hypoxia reduced the glycolytic rate and attenuated the increases of the AMP-to-ATP and the reduction of the NAD⁺-to-NADH.H⁺ ratios. This resulted in a modified muscle signaling response with a blunted Thr²⁸⁶-CaMKII but similar AMP-activated protein kinase phosphorylation responses in the sprints preceded by the ingestion of antioxidants.

Diabetes and hyperglycemia as risk factors for postoperative outcome in maxillofacial surgery

BACKGROUND

Aim of this study was to investigate the frequency of complications in maxillofacial surgery in-patients in correlation to diabetes mellitus or a pathologically altered glucose metabolism.

MATERIALS AND METHODS

All patients' electronic health records were analyzed retrospectively. Diabetes mellitus anamnesis, the treatment regime, blood glucose levels, and the duration of inpatient treatment were recorded. Glucose readings ≥200 mg/dL measured at any time and fasting glucose levels of ≥110 mg/dL were defined as hyperglycemic. Noted complications were infection, dehiscence, swelling, and necrosis.

RESULTS

8.7% out of 1374 patients had a known diabetes diagnosis. 13.0% had high fasting glucose and 11.4% aberrant maximum glucose readings. Complications did not occur more often in patients with a previously known diabetes but more often in patients with high maximum blood glucose levels. Of these patients, only 56.3% were known diabetics.

CONCLUSIONS

Diabetes mellitus does not necessarily lead to higher frequency of complications in surgical patients. Moreover, patients with well-controlled diabetes seem to have a similar outcome compared to nondiabetics. Hyperglycemia however has an important impact on treatment outcome.

Comprehensive interpretation of hyperglycemia and hyperosmolality on the clinical outcomes among ischemic stroke patients

BACKGROUND

Hyperglycemia and hyperosmolality are associated with poor outcomes among acute ischemic stroke (AIS) patients.

OBJECTIVES

We evaluated the association between hyperglycemia and hyperosmolality, as a combination measure, with poor outcome among AIS patients.

METHODS

We conducted a retrospective study of AIS patients admitted to the study hospital emergency department between January and December 2014. Hyperglycemia was defined as serum glucose >144 mg/dL, and hyperosmolality was defined as a serum osmolality >295 mOsm/kg. After excluding hypoglycemia and hypoosmolality, the enrolled patients were classified into the following 4 subgroups: normoglycemia-normoosmolality, hyperglycemia-normoosmolality (HGNO), normoglycemia-hyperosmolality (NGHO), and hyperglycemia-normoosmolality (HGHO). The primary outcome was poor neurological status at 6 months, which was defined as a modified Rankin scale score ≥2.

RESULTS

Six hundred seven patients were included. The primary outcome was 336 (55.4%), and it was highest in the HGNO group (69.6%, 103/148), followed by the HGHO group (67.9%, 53/78), the NGHO group (57.3%, 43/75) and the normoglycemia-normoosmolality group (44.7%, 137/306). The multivariable logistic regression analysis revealed that HGNO and HGHO remained significant factors, with primary outcomes (adjusted odds ratio, 2.08; 95% confidence interval, 1.16-3.71) and 2.93 (1.45-5.91), respectively), whereas NGHO was not a significant factor. Cases of extremely high sodium levels were few in the NGHO and HGHO groups, whereas considerable cases of extremely high glucose level were observed in the HGHO group.

CONCLUSION

Hyperglycemia was associated with poor outcome, even after excluding the effect of hyperosmolality. However, hyperosmolality without hyperglycemia was not associated with poor outcome. An additive effect, likely reflecting severe hyperglycemia, was observed.

Development of a normothermic extracorporeal liver perfusion system toward improving viability and function of human extended criteria donor livers

Donor organ shortages have led to an increased interest in finding new approaches to recover organs from extended criteria donors (ECD). Normothermic extracorporeal liver perfusion (NELP) has been proposed as a superior preservation method to reduce ischemia/reperfusion injury (IRI), precondition suboptimal grafts, and treat ECD livers so that they can be successfully used for transplantation. The aim of this study was to investigate the beneficial effects of a modified NELP circuit on discarded human livers. Seven human livers that were rejected for transplantation were placed on a modified NELP circuit for 8 hours. Perfusate samples and needle core biopsies were obtained at hourly intervals. A defatting solution that contained exendin-4 (50 nM) and L-carnitine (10 mM) was added to the perfusate for 2 steatotic livers. NELP provided normal temperature, electrolytes, and pH and glucose levels in the perfusate along with physiological vascular flows and pressures. Functional, biochemical, and microscopic evaluation revealed no additional injuries to the grafts during NELP with an improved oxygen extraction ratio (>0.5) and stabilized markers of hepatic injury. All livers synthesized adequate amounts of bile and coagulation factors. We also demonstrated a mild reduction (10%) of macroglobular steatosis with the use of the defatting solution. Histology demonstrated normal parenchymal architecture and a minimal to complete lack of IRI at the end of NELP. In conclusion, a modified NELP circuit preserved hepatocyte architecture, recovered synthetic functions, and hepatobiliary parameters of ECD livers without additional injuries to the grafts. This approach has the potential to increase the donor pool for clinical transplantation. Liver Transplantation 22 979-993 2016 AASLD.

Metabolic reprogramming by the pyruvate dehydrogenase kinase-lactic acid axis: Linking metabolism and diverse neuropathophysiologies

Emerging evidence indicates that there is a complex interplay between metabolism and chronic disorders in the nervous system. In particular, the pyruvate dehydrogenase (PDH) kinase (PDK)-lactic acid axis is a critical link that connects metabolic reprogramming and the pathophysiology of neurological disorders. PDKs, via regulation of PDH complex activity, orchestrate the conversion of pyruvate either aerobically to acetyl-CoA, or anaerobically to lactate. The kinases are also involved in neurometabolic dysregulation under pathological conditions. Lactate, an energy substrate for neurons, is also a recently acknowledged signaling molecule involved in neuronal plasticity, neuron-glia interactions, neuroimmune communication, and nociception. More recently, the PDK-lactic acid axis has been recognized to modulate neuronal and glial phenotypes and activities, contributing to the pathophysiologies of diverse neurological disorders. This review covers the recent advances that implicate the PDK-lactic acid axis as a novel linker of metabolism and diverse neuropathophysiologies. We finally explore the possibilities of employing the PDK-lactic acid axis and its downstream mediators as putative future therapeutic strategies aimed at prevention or treatment of neurological disorders.

Pyruvate Dehydrogenase Kinase-mediated Glycolytic Metabolic Shift in the Dorsal Root Ganglion Drives Painful Diabetic Neuropathy

The dorsal root ganglion (DRG) is a highly vulnerable site in diabetic neuropathy. Under diabetic conditions, the DRG is subjected to tissue ischemia or lower ambient oxygen tension that leads to aberrant metabolic functions. Metabolic dysfunctions have been documented to play a crucial role in the pathogenesis of diverse pain hypersensitivities. However, the contribution of diabetes-induced metabolic dysfunctions in the DRG to the pathogenesis of painful diabetic neuropathy remains ill-explored. In this study, we report that pyruvate dehydrogenase kinases (PDK2 and PDK4), key regulatory enzymes in glucose metabolism, mediate glycolytic metabolic shift in the DRG leading to painful diabetic neuropathy. Streptozotocin-induced diabetes substantially enhanced the expression and activity of the PDKs in the DRG, and the genetic ablation of Pdk2 and Pdk4 attenuated the hyperglycemia-induced pain hypersensitivity. Mechanistically, Pdk2/4 deficiency inhibited the diabetes-induced lactate surge, expression of pain-related ion channels, activation of satellite glial cells, and infiltration of macrophages in the DRG, in addition to reducing central sensitization and neuroinflammation hallmarks in the spinal cord, which probably accounts for the attenuated pain hypersensitivity. Pdk2/4-deficient mice were partly resistant to the diabetes-induced loss of peripheral nerve structure and function. Furthermore, in the experiments using DRG neuron cultures, lactic acid treatment enhanced the expression of the ion channels and compromised cell viability. Finally, the pharmacological inhibition of DRG PDKs or lactic acid production substantially attenuated diabetes-induced pain hypersensitivity. Taken together, PDK2/4 induction and the subsequent lactate surge induce the metabolic shift in the diabetic DRG, thereby contributing to the pathogenesis of painful diabetic neuropathy.

Hyperglycaemia in patients with no history of diabetes presenting to Internal Medicine Departments

AIMS

Stress hyperglycaemia during hospitalisation may be the first sign of diabetes mellitus (DM). Most hospitals routinely measure blood glucose, which may enable early diagnosis. This study measured the prevalence of hyperglycaemia in hospitalised adults with no history of diabetes, and whether the discharge summary recommended work-up.

METHODS

Files with at least one random blood glucose (RBG) sample were included and reviewed for specific discharge recommendations concerning elevated blood glucose. Hyperglycaemia was defined as serum glucose > 200 mg/dl. Length of stay, in-hospital mortality and 3-year mortality were examined.

RESULTS

Among 5274 discharged patients, 1479 had DM. They were older and had a higher incidence of cerebrovascular risk factors. Among 3714 patients without known DM, 211 (5.7%) had at least one RBG > 200 mg/dl. Of these patients, 31 died and 24 left against medical advice. Of the remaining 156, 25(16%) files included instructions to the family physician. These patients were younger, more overweight and less frequently diagnosed with dementia or other mental illness. Patients with RBG > 200 mg/dl had prolonged hospital stay (6.5 ± 5.3 vs. 4.0 ± 4.8; p < 0.001). In-hospital mortality and 3-year mortality were increased by 5.1 and 1.89, respectively (p < 0.001 for both parameters) compared to those without RBG ≤ 200 mg/dl. RBG > 200 mg/dl emerged as a significant, independent predictor of prolonged hospital stay and death.

CONCLUSIONS

Random blood glucose > 200 mg/dl is common in medical departments and is associated with increased in-hospital and 3-year out-hospital mortality.

Protective effects of taurine against closed head injury in rats

Taurine, an abundant amino acid in the nervous system, is reported to reduce ischemic brain injury in a dose-dependent manner. This study was designed to investigate whether taurine protected the brain against closed head injury (CHI) in rats. Taurine was administered intravenously 30 min after CHI. It was found that taurine lessened body-weight loss and improved neurological functions at 7 days after CHI. Moreover, it lowered brain edema and blood-brain barrier permeability, enhanced activity of superoxide dismutase and the level of glutathione, and reduced levels of malondialdehyde and lactic acid in traumatic tissue 24 h after CHI. In addition, it attenuated neuronal cell death in hippocampal CA1 and CA3 subfields 7 days after CHI. All of these effects were dose dependent. These data demonstrated the dose-dependent protection of taurine against experimental CHI and suggest that taurine treatment might be beneficial in reducing trauma-induced oxidative damage to the brain, thus showing the potential for clinical implications.

Chikusetsu Saponin IVa Ameliorates Cerebral Ischemia Reperfusion Injury in Diabetic Mice via Adiponectin-Mediated AMPK/GSK-3β Pathway In Vivo and In Vitro

Diabetes mellitus substantially increases the risk of stroke and enhances brain's vulnerability to ischemia insult. In a previous study, Chikusetsu saponin IVa (CHS) pretreatment was proved to protect the brain from cerebral ischemic in normal stroke models. Whether CHS could attenuate cerebral ischemia/reperfusion (I/R) injury in diabetic mice and the possible underlying mechanism are still unrevealed. Male C57BL/6 mice were injected streptozotocin to induce diabetes. After that, the mice were pretreated with CHS for 1 month, and then, focal cerebral ischemia was induced following 24-h reperfusion. The neurobehavioral scores, infarction volumes, and some cytokines in the brain were measured. Apoptosis was analyzed by caspase-3, Bax, and Bcl-2 expression. Downstream molecules of adiponectin (APN) were investigated by Western blotting. The results showed that CHS reduced infarct size, improved neurological outcomes, and inhibited cell injury after I/R. In addition, CHS pretreatment increased APN level and enhanced neuronal AdipoR1, adenosine monophosphate-activated protein kinase (AMPK), and glycogen synthase kinase 3 beta (GSK-3β) expression in a concentration-dependent manner in diabetic mice, and these effects were abolished by APN knockout (KO). In vitro test, CHS treatment also alleviated PC12 cell injury and apoptosis, evidenced by reduced tumor necrosis factor alpha (TNF-α), malondialdehyde (MDA) and caspase-3 expression, and Bax/Bcl-2 ratio in I/R injured cells. Moreover, CHS enhanced AdipoR1, AMPK, and GSK-3β expression in a concentration-dependent manner. Likewise, short interfering RNA (sinRNA) knockdown of liver kinase B1 (LKB1), an upstream kinase of AMPK, reduced the ability of CHS in protecting cells from I/R injury. Furthermore, this LKB1-dependent cellular protection resulted from AdipoR1 and APN activation, as supported by the experiment using sinRNA knockdown of AdipoR1 and APN. Thus, CHS protected brain I/R in diabetes through AMPK-mediated phosphorylation of GSK-3β downstream of APN-LKB1 pathway.

Early hyperglycaemia and the early-term death in patients with spontaneous intracerebral haemorrhage: a meta-analysis

BACKGROUND AND AIMS

Stroke is often accompanied by hyperglycaemia, and this has an important impact on prognosis. The aim of this study was to investigate the relationship between early hyperglycaemia and the outcome of spontaneous intracerebral haemorrhage (sICH).

METHODS

A systematic literature search on PubMed, Embase, Cochran, WANFANG DATA, VIP and CNKI databases was conducted, and eight eligible studies were retrieved. Relative risks and 95% confidence interval (CI) in the hyperglycaemia group compared with the non-hyperglycaemia group were calculated and meta-analysed when possible.

RESULTS

Eight controlled trials and cohort studies totalling 3756 patients addressing early hyperglycaemia and the outcome of sICH were compiled for this meta-analysis. Cut-off points for defining hyperglycaemia was 6.1-8.3 mmol/L, and the median cut-off value was 7.5 mmol/L. Studies were assigned to one of the two subgroups: the group A (for studies with the values of glucose concentrations above the median cut-off) and the group B (for studies with the values of glucose concentrations below the median cut-off). The RR for short-term death associated with hyperglycaemia was 3.65 (95% confidence interval (CI) (3.08, 4.33); P < 0.0001). In the subgroup analysis, the relative risk values were 3.46 (95% CI (1.66, 7.20); P = 0.0009) and 3.53 (95% CI (2.92, 4.26); P < 0.00001) for the groups A and B respectively. The publication bias showed that Egger's test (P > 0.1), Begg's test (P > 0.05) and Nfs0.05 exceeded included studies.

CONCLUSIONS

Early hyperglycaemia can significantly increase the rate of early-term death in patients with sICH, independent of the cut-off points for hyperglycaemia.

Role of iron, zinc and reduced glutathione in oxidative stress induction by low pH in rat brain synaptosomes

Brain ischemia leads to a decrease in pH_o. We have shown previously in synaptosomes that the extracellular acidification induces depolarization of mitochondria followed by synthesis of superoxide anions and oxidative stress. Here, we investigated the effects of lowered pH_o on oxidative stress and membrane potentials in synaptosomes treated by the iron chelator deferoxamine and zinc chelator TPEN. We demonstrated that chelating of metals has no impact on superoxide anion synthesis and intrasynaptosomal mitochondria depolarization. Meanwhile, deferoxamine was able to inhibit oxidative stress induced by low pH_o and hydrogen peroxide application. Compared to deferoxamine, TPEN was less effective but it decreased the DCF fluorescence induced by pH_o 6.0 which had no effects in other oxidative stress models. We found that the chelators were able to inhibit slightly plasma membrane depolarization. Synaptosomes preincubation at low pH_o caused no effects on the reduced glutathione level. Depletion of glutathione by CDNB produced no additional increase in the DCF fluorescence induced by pH_o 7.0. Our results suggest that free iron is crucial for the development of oxidative stress elicited by acidification in synaptosomes. Chelating of this metal seems to be a promising strategy for protecting the neuronal presynaptic terminals against oxidative stress developed at stroke.

Adrenomedullin deficiency and aging exacerbate ischemic white matter injury after prolonged cerebral hypoperfusion in mice

Adrenomedullin was originally isolated from pheochromocytoma cells and reduces insulin resistance by decreasing oxidative stress. White matter lesions induced by aging and hyperglycemia play a crucial role in cognitive impairment in poststroke patients. Here, we examine whether adrenomedullin deficiency and aging exacerbate ischemic white matter injury after prolonged cerebral hypoperfusion. Adrenomedullin heterozygous, wild-type young/aged mice were subjected to prolonged hypoperfusion. Prolonged cerebral hypoperfusion followed by immunohistochemical analysis was used to evaluate white matter injury. After prolonged hypoperfusion, white matter damage progressed in a time-dependent manner in AM^+/− group compared with the wild-type group. The number of oligodendrocyte progenitor cells gradually increased after prolonged hypoperfusion, whereas oligodendrocytes decreased following a transient increase, but the ratio of increase was mild in the AM^+/− group (P < 0.05). Oxidative stress was detected in oligodendrocytes, with a larger increase in the AM^+/− group (P < 0.05). Aged mice showed the same tendency, but white matter damage was worse, especially in the aged AM^+/− group. Our results demonstrated that white matter injury was increased in adrenomedullin deficiency, which induced oxidative stress. White matter injury was more exacerbated because of hyperglycemia in aged AM^+/− group. Adrenomedullin may be an important target in the control of ischemic white matter injury.

Citicoline protects brain against closed head injury in rats through suppressing oxidative stress and calpain over-activation

Citicoline, a natural compound that functions as an intermediate in the biosynthesis of cell membrane phospholipids, is essential for membrane integrity and repair. It has been reported to protect brain against trauma. This study was designed to investigate the protective effects of citicoline on closed head injury (CHI) in rats. Citicoline (250 mg/kg i.v. 30 min and 4 h after CHI) lessened body weight loss, and improved neurological functions significantly at 7 days after CHI. It markedly lowered brain edema and blood-brain barrier permeability, enhanced the activities of superoxide dismutase and the levels of glutathione, reduced the levels of malondialdehyde and lactic acid. Moreover, citicoline suppressed the activities of calpain, and enhanced the levels of calpastatin, myelin basic protein and αII-spectrin in traumatic tissue 24 h after CHI. Also, it attenuated the axonal and myelin sheath damage in corpus callosum and the neuronal cell death in hippocampal CA1 and CA3 subfields 7 days after CHI. These data demonstrate the protection of citicoline against white matter and grey matter damage due to CHI through suppressing oxidative stress and calpain over-activation, providing additional support to the application of citicoline for the treatment of traumatic brain injury.

Proton-dependent zinc release from intracellular ligands

In cultured cortical and hippocampal neurons when intracellular pH drops from 6.6 to 6.1, yet unclear intracellular stores release micromolar amounts of Zn(2+) into the cytosol. Mitochondria, acidic organelles, and/or intracellular ligands could release this Zn(2+) . Although exposure to the protonophore FCCP precludes reloading of the mitochondria and acidic organelles with Zn(2+) , FCCP failed to compromise the ability of the intracellular stores to repeatedly release Zn(2+) . Therefore, Zn(2+) -releasing stores were not mitochondria or acidic organelles but rather intracellular Zn(2+) ligands. To test which ligands might be involved, the rate of acid-induced Zn(2+) release from complexes with cysteine, glutathione, histidine, aspartate, glutamate, glycine, and carnosine was investigated; [Zn(2+) ] was monitored in vitro using the ratiometric Zn(2+) -sensitive fluorescent probe FuraZin-1. Carnosine failed to chelate Zn(2+) but did chelate Cu(2+) ; the remaining ligands chelated Zn(2+) and upon acidification were releasing it into the medium. However, when pH was decreasing from 6.6 to 6.1, only zinc-cysteine complexes rapidly accelerated the rate of Zn(2+) release. The zinc-cysteine complexes also released Zn(2+) when a histidine-modifying agent, diethylpyrocarbonate, was applied at pH 7.2. Since the cytosolic zinc-cysteine complexes can contain micromolar amounts of Zn(2+) , these complexes may represent the stores responsible for an acid-induced intracellular Zn(2+) release. This study aimed at identifying intracellular stores which release Zn(2+) when pHi drops from 6.6 to 6.1. It was found that these stores are not mitochondria or acidic organelles, but rather intracellular Zn(2+) ligands. When the pH was decreasing from 6.6 to 6.1, only zinc-cysteine complexes showed a rapid acceleration in the rate of Zn(2+) release. Therefore, the stores responsible for an acid-induced intracellular Zn(2+) release in neurons may be the cytosolic zinc-cysteine complexes.

Insulin for glycaemic control in acute ischaemic stroke

BACKGROUND

People with hyperglycaemia concomitant with an acute stroke have greater mortality, stroke severity, and functional impairment when compared with those with normoglycaemia at stroke presentation. This is an update of a Cochrane Review first published in 2011.

OBJECTIVES

To determine whether intensively monitoring insulin therapy aimed at maintaining serum glucose within a specific normal range (4 to 7.5 mmol/L) in the first 24 hours of acute ischaemic stroke influences outcome.

SEARCH METHODS

We searched the Cochrane Stroke Group Trials Register (September 2013), CENTRAL (The Cochrane Library 2013, Issue 8), MEDLINE (1950 to September 2013), EMBASE (1980 to September 2013), CINAHL (1982 to September 2013), Science Citation Index (1900 to September 2013), and Web of Science (ISI Web of Knowledge) (1993 to September 2013). We also searched ongoing trials registers and SCOPUS.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing intensively monitored insulin therapy versus usual care in adults with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

We obtained a total of 1565 titles through the literature search. Two review authors independently selected the included articles and extracted the study characteristics, study quality, and data to estimate the odds ratio (OR) and 95% confidence interval (CI), mean difference (MD) and standardised mean difference (SMD) of outcome measures. We resolved disagreements by discussion.

MAIN RESULTS

We included 11 RCTs involving 1583 participants (791 participants in the intervention group and 792 in the control group). We found that there was no difference between the treatment and control groups in the outcomes of death or dependency (OR 0.99, 95% CI 0.79 to 1.23) or final neurological deficit (SMD -0.09, 95% CI -0.19 to 0.01). The rate of symptomatic hypoglycaemia was higher in the intervention group (OR 14.6, 95% CI 6.6 to 32.2). In the subgroup analyses of diabetes mellitus (DM) versus non-DM, we found no difference for the outcomes of death and disability or neurological deficit. The number needed to treat was not significant for the outcomes of death and final neurological deficit. The number needed to harm was nine for symptomatic hypoglycaemia.

AUTHORS' CONCLUSIONS

After updating the results of our previous review, we found that the administration of intravenous insulin with the objective of maintaining serum glucose within a specific range in the first hours of acute ischaemic stroke does not provide benefit in terms of functional outcome, death, or improvement in final neurological deficit and significantly increased the number of hypoglycaemic episodes. Specifically, those people whose glucose levels were maintained within a tighter range with intravenous insulin experienced a greater risk of symptomatic and asymptomatic hypoglycaemia than those people in the control group.

Free radicals and sprint exercise in humans

Sprint exercise ability has been critical for survival. The remarkably high-power output levels attained during sprint exercise are achieved through strong activation of anaerobic, and to a lesser extent, aerobic energy supplying metabolic reactions, which generate reactive oxygen and nitrogen species (RONS). Sprint exercise may cause oxidative stress leading to muscle damage, particularly when performed in severe acute hypoxia. However, with training oxidative stress is reduced. Paradoxically, total plasma antioxidant capacity increases during the subsequent 2 h after a short sprint due to the increase in plasma urate concentration. The RONS produced during and immediately after sprint exercise play a capital role in signaling the adaptive response to sprint. Antioxidant supplementation blunts the normal AMPKα and CaMKII phosphorylation in response to sprint exercise. However, under conditions of increased glycolytic energy turnover and muscle acidification, as during sprint exercise in severe acute hypoxia, AMPKα phosphorylation is also blunted. This indicates that an optimal level of RONS-mediated stimulation is required for the normal signaling response to sprint exercise. Although RONS are implicated in fatigue, most studies convey that antioxidants do not enhance sprint performance in humans. Although currently controversial, it has been reported that antioxidant ingestion during training may jeopardize some of the beneficial adaptations to sprint training.

Effect of oxidative stress on sympathetic and renal vascular responses to ischemic exercise

Reactive oxygen species (ROS), produced acutely during skeletal muscle contraction, are known to stimulate group IV muscle afferents and accentuate the exercise pressor reflex (EPR) in rodents. The effect of ROS on the EPR in humans is unknown. We conducted a series of studies using ischemic fatiguing rhythmic handgrip to acutely increase ROS within skeletal muscle, ascorbic acid infusion to scavenge free radicals, and hyperoxia inhalation to further increase ROS production. We hypothesized that ascorbic acid would attenuate the EPR and that hyperoxia would accentuate the EPR. Ten young healthy subjects participated in two or three experimental trials on separate days. Beat-by-beat measurements of heart rate (HR), mean arterial pressure (MAP), muscle sympathetic nerve activity (MSNA), and renal vascular resistance index (RVRI) were measured and compared between treatments (saline and ascorbic acid; room air and hyperoxia). At fatigue, the reflex increases in MAP (31 ± 3 versus 29 ± 2 mmHg), HR (19 ± 3 versus 20 ± 3 bpm), MSNA burst rate (21 ± 4 versus 23 ± 4 burst/min), and RVRI (39 ± 12 versus 44 ± 13%) were not different between saline and ascorbic acid. Relative to room air, hyperoxia did not augment the reflex increases in MAP, HR, MSNA, or RVRI in response to exercise. Muscle metaboreflex activation and time/volume control experiments similarly showed no treatment effects. While contrary to our initial hypotheses, these findings suggest that ROS do not play a significant role in the normal reflex adjustments to ischemic exercise in young healthy humans.

High glucose induces apoptosis and suppresses proliferation of adult rat neural stem cells following in vitro ischemia

Background

Post-stroke hyperglycemia appears to be associated with poor outcome from stroke, greater mortality, and reduced functional recovery. Focal cerebral ischemia data support that neural stem cells (NSCs) play an important role in post-ischemic repair. Here we sought to evaluate the negative effects of hyperglycemia on the cellular biology of NSCs following anoxia, and to test whether high glucose affects NSC recovery from ischemic injury.

Results

In this study, we used immortalized adult neural stem cells lines and we induced in vitro ischemia by 6 h oxygen and glucose deprivation (OGD) in an anaerobic incubator. Reperfusion was performed by returning cells to normoxic conditions and the cells were then incubated in experimental medium with various concentrations of glucose (17.5, 27.75, 41.75, and 83.75 mM) for 24 h. We found that high glucose (≥27.75 mM) exposure induced apoptosis of NSCs in a dose-dependent manner after exposure to OGD, using an Annexin V/PI apoptosis detection kit. The cell viability and proliferative activity of NSCs following OGD in vitro, evaluated with both a Cell Counting kit-8 (CCK-8) assay and a 5-ethynyl-2’-deoxyuridine (EdU) incorporation assay, were inhibited by high glucose exposure. Cell cycle analysis showed that high glucose exposure increased the percentage of cells in G0/G1-phase, and reduced the percentage of cells in S-phase. Furthermore, high glucose exposure was found to significantly induce the activation of c-Jun N-terminal protein kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) and suppress extracellular signal-regulated kinase 1/2 (ERK1/2) activity.

Conclusions

Our results demonstrate that high glucose induces apoptosis and inhibits proliferation of NSCs following OGD in vitro, which may be associated with the activation of JNK/p38 MAPK pathways and the delay of G1-S transition in the cells.

Acidosis, magnesium and acetylsalicylic acid: effects on thrombin

Thrombin, an enzyme from the hydrolase family, is the main component of the blood coagulation system. In ischemic stroke it acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin forming blood clots in the brain. It has been found to phosphoresce at room temperature in the millisecond and microsecond ranges. The phosphorescence of thrombin was studied under physiological conditions, in acidosis (decrease of pH from 8.0 to 5.0) and on the addition of salts (magnesium sulfate and sodium chloride) and of acetylsalicylic acid, and its connection with thrombin function is discussed. Acidosis significantly increased the internal dynamics of thrombin. We propose that lactate-acidosis plays a protective role in stroke, preventing the formation of clots. The addition of NaCl and MgSO(4) in different concentrations increased the internal dynamics of thrombin. Also, the addition of MgSO(4) decreased thrombin-induced platelet aggregation. However, magnesium sulfate and acetylsalicylic acid in the therapeutic concentrations used for treatment of ischemic stroke had no effect on thrombin internal dynamics. The data obtained will help to elucidate the conformational stability of thrombin under conditions modulating lactate-acidosis and in the presence of magnesium sulfate.

Influence of intra- and extracellular acidification on free radical formation and mitochondria membrane potential in rat brain synaptosomes

Brain ischemia is accompanied by lowering of intra- and extracellular pH. Stroke often leads to irreversible damage of synaptic transmission by unknown mechanism. We investigated an influence of lowering of pH(i) and pH(o) on free radical formation in synaptosomes. Three models of acidosis were used: (1) pH(o) 6.0 corresponding to pH(i) decrease down to 6.04; (2) pH(o) 7.0 corresponding to the lowering of pH(i) down to 6.92: (3) 1 mM amiloride corresponding to pH(i) decrease down to 6.65. We have shown that both types of extracellular acidification, but not intracellular acidification, increase 2',7'-dichlorodihydrofluorescein diacetate fluorescence that reflects free radical formation. These three treatments induce the rise of the dihydroethidium fluorescence that reports synthesis of superoxide anion. However, the impact of amiloride on superoxide anion synthesis was less than that induced by moderate extracellular acidification. Superoxide anion synthesis at pH(o) 7.0 was almost completely eliminated by mitochondrial uncoupler carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone. Furthermore, using fluorescent dyes JC-1 and rhodamine-123, we confirmed that pH(o) lowering, but not intracellular acidification, led to depolarization of intrasynaptosomal mitochondria. We have shown that pH(o) but not pH(i) lowering led to oxidative stress in neuronal presynaptic endings that might underlie the long-term irreversible changing in synaptic transmission.

Ischemia-induced hyperglycemia: consequences, neuroendocrine regulation, and a role for RAGE

Many patients that present with cerebral ischemia exhibit moderate to severe hyperglycemia. Although many hyperglycemic patients suffer from diagnosed or previously undiagnosed diabetes a further subset of individuals is hyperglycemic without diabetes. Hyperglycemia during cerebral ischemia is associated with high levels of mortality and morbidity and limits the effective treatment interventions available. Controlling hyperglycemia with insulin treatment in critical care situations improves overall outcomes, although it is not without risk. Therefore it is critically important to understand the basic mechanisms that underlie both the induction of hyperglycemia and the consequences of it for ischemic outcomes. In this manuscript, the neuroendocrine mediators, and mechanisms of hyperglycemia exacerbated inflammation, glucose dysregulation and ischemic outcomes are discussed. The possibility that the advanced glycation end product (AGE) and receptor for AGE (RAGE) axis mediates the deleterious effects of hyperglycemia on inflammation and neuronal damage is discussed.

Onion (Allium cepa) extract attenuates brain edema

OBJECTIVE

This study investigated the potential beneficial effects of onion extract on brain ischemia-induced edema and blood-brain barrier (BBB) dysfunction. The possible underlying mechanisms are investigated, especially those linked to the antioxidant effects of the onion extract.

METHODS

Brain ischemia was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion in mice. Mice were treated intravenously with onion extract 30 min before MCAO. Brain edema and BBB hyperpermeability were evaluated by the measurement of the brain water content and Evans blue extravasation, respectively. The disruption of tight junction proteins was examined by immunohistochemical staining. The level of malondialdehyde was determined using the thiobarbituric acid method. The activities of glutathione peroxidase and catalase were determined by spectrophotometric assay.

RESULTS

Brain water content in the ischemic hemisphere was significantly reduced by treatment with onion extract. Onion extract also had a significant effect on both the decrease in Evans blue extravasation and the inhibition of zonula occludens-1 and occludin disruption caused by brain ischemia. In addition, onion extract significantly prevented brain ischemia-induced reduction in catalase and glutathione peroxidase activities and elevation of malondialdehyde level in the brain tissue.

CONCLUSION

The results from this study demonstrate that onion extract prevents brain edema, BBB hyperpermeability, and tight junction proteins disruption, possibly through its antioxidant effects in the mouse MCAO model. This study suggests that onion extract may be a beneficial nutrient for the prevention of BBB function during brain ischemia.

"Moderate intensive insulin therapy" is associated with remission of high intracranial pressure in patients with vascular or infectious central nervous system diseases

Intensive insulin therapy (IIT), targeting blood glucose between 80 mg/dL and 110 mg/dL ("strict IIT"), has been associated with rapid remission of high intracranial pressure (ICP), but its use is limited due to a high risk of hypoglycemia. The aim of this retrospective study was to assess whether "moderate IIT" (target range for blood glucose: 80-140 mg/dL) could have the same beneficial effect on ICP with a lower risk of hypoglycemia. We retrospectively analyzed the records of 64 patients with high ICP due to vascular or infectious central nervous system diseases. Patients treated with moderate IIT (n=32) after 2005 were compared with patients treated with a conventional approach (n=32, target <180 mg/dL) before 2005. We assessed daily ICP during the first 14 days. Secondary endpoints were the rate of hypoglycemic events and outcome. ICP was significantly lower during the second week in patients treated with moderate IIT (mean±standard deviation [SD] daily ICP on days 8-14: 16±5 mmHg compared to 12±4 mmHg, p<0.001). The risk of hypoglycemic events (<40 mg/dL) did not differ significantly between the groups (0 vs. 1 patient, p=0.5). Moderate IIT is associated with remission of high ICP. In contrast to strict IIT, its use seems not to be limited by an increased risk of severe hypoglycemia.

Different neuroprotective responses of Ginkgolide B and bilobalide, the two Ginkgo components, in ischemic rats with hyperglycemia

Ginkgo biloba extracts show neuroprotective effects during cerebral ischemia, but with various components, the mechanisms of action remain unclear. In this study, we tested the effects of Ginkgolide B (GB) and bilobalide (BB) on normoglycemic and hyperglycemic rats subjected to transient cerebral ischemia. Rats were administered p.o. with different Ginkgo components GB (6 mg/kg) or BB (6 mg/kg) once daily for 7 days. Hyperglycemia was made by jugular vein infusion of glucose and transient middle cerebral artery occlusion/reperfusion was induced by a suture insertion technique. Results showed that both GB and BB exerted neuroprotection under normoglycemia, as determined by infarct volume and neurological deficit scores. Yet, BB showed less protective effects during hyperglycemic cerebral ischemia. Cerebral blood flow (CBF) was evaluated during occlusion and the first hour of reperfusion. BB but not GB caused acute increase in CBF after reperfusion, especially in hyperglycemia. Reactive oxygen species and malondialdehyde levels were reduced by GB in both models but BB were not effective in reactive oxygen species or malondialdehyde control in hyperglycemia ischemic rats. These results suggested that CBF plays crucial roles during early stage of reperfusion in the presence of hyperglycemia. Administration of compound that improves CBF may have little effect in hyperglycemic stroke.

Hemorrhagic transformation induced by acute hyperglycemia in a rat model of transient focal ischemia

Hemorrhagic transformation (HT) is a major factor limiting the use of tissue plasminogen activator for stroke. HT has been found in animals undergoing transient focal cerebral ischemia with hyperglycemia. This study examined the incidence rate, location and content of HT.Rats were divided into two groups: the hyperglycemic group and normoglycemic group. Rats received an injection of 50% glucose (6 ml/kg, i.p.) or an equivalent volume of saline 15 min before 2-h transient middle cerebral artery occlusion (tMCAO) with reperfusion. Rats were killed 4, 8 or 24 h later and used for blood-brain barrier permeability, hemoglobin content, brain edema, and infarct volume measurements. Mortality and HT incidence rates were also evaluated. We found that all hyperglycemic rats had HT, and two out of six normoglycemic rats had HT 24 h after tMCAO. Hyperglycemic rats had more severe Evans blue leakage (p<0.05) and brain edema (p<0.05) in the ipsilateral hemisphere. However, infarct volumes were the same in hyperglycemic and normoglycemic rats. In conclusion, acute hyperglycemia reliably and consistently resulted in hemorrhagic transformation in a rat model of transient focal cerebral ischemia. The model is useful for experimental assessment of new therapies for HT.

Insulin for glycaemic control in acute ischaemic stroke

BACKGROUND

Patients with hyperglycaemia concomitant with an acute stroke have greater stroke severity and greater functional impairment when compared to those with normoglycaemia at stroke presentation.

OBJECTIVES

To determine whether maintaining serum glucose within a specific normal range (4 to 7.5 mmol/L) in the first 24 hours of acute ischaemic stroke influences outcome.

SEARCH STRATEGY

We searched the Cochrane Stroke Group Trials Register (June 2010), CENTRAL (The Cochrane Library 2010, Issue 2), MEDLINE (1950 to June 2010), EMBASE (1980 to June 2010), CINAHL (1982 to June 2010), Science Citation Index (1900 to June 2010), and Web of Science (ISI Web of Knowledge) (1993 to June 2010). In an effort to identify further published, unpublished and ongoing trials we searched ongoing trials registers and SCOPUS.

SELECTION CRITERIA

Eligible studies were randomised controlled trials comparing intensively monitored insulin therapy versus usual care in adult patients with acute ischaemic stroke.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted the study characteristics, study quality, and data to estimate the odds ratio (OR) and 95% confidence interval (CI), mean difference (MD) and standardised mean difference (SMD) of outcome measures.

MAIN RESULTS

We included seven trials involving 1296 participants (639 participants in the intervention group and 657 in the control group). We found that there was no difference between treatment and control groups in the outcome of death or disability and dependence (OR 1.00, 95% CI 0.78 to 1.28) or final neurological deficit (SMD -0.12, 95% CI -0.23 to 0.00). The rate of symptomatic hypoglycaemia was higher in the intervention group (OR 25.9, 95% CI 9.2 to 72.7). In the subgroup analyses of diabetes mellitus (DM) versus non-DM, we found no difference for the outcomes of death and dependency or neurological deficit.

AUTHORS' CONCLUSIONS

With the current evidence, we found that the administration of intravenous insulin with the objective of maintaining serum glucose within a specific range in the first hours of acute ischaemic stroke does not provide benefit in terms of functional outcome, death, or improvement in final neurological deficit and significantly increased the number of hypoglycaemic episodes. Specifically, those who were maintained within a more tight range of glycaemia with intravenous insulin experienced a greater risk of symptomatic and asymptomatic hypoglycaemia than those individuals in the control group.

Modelling of pH dynamics in brain cells after stroke

The identification of salvageable brain tissue is a major challenge at stroke presentation. Standard techniques used in this context, such as the perfusion-diffusion mismatch, remain controversial. There is thus a need for new methods to help guide treatment. The potential role of pH imaging in this context is currently being investigated. Intracellular pH varies as a function of local perfusion, intracellular energy stores and time. Low pH triggers the production of free radicals and affects the calcium balance of the cells, which may lead to apoptosis and cell death. Thus, the characterization of pH dynamics may have predictive value for cell death after stroke, particularly when combined with novel imaging techniques. Therefore, we have extended an existing model of brain cellular metabolism to simulate the pH response of cells to ischaemia. Simulation results for conditions of reduced cerebral blood flow show good agreement for the evolution of intracellular pH with previously reported measurements and encourage the development of quantitative pH imaging to validate the predictive value of pH.

Hypercapnia causes cellular oxidation and nitrosation in addition to acidosis: implications for CO2 chemoreceptor function and dysfunction

Cellular mechanisms of CO2 chemoreception are discussed and debated in terms of the stimuli produced during hypercapnic acidosis and their molecular targets: protons generated by the hydration of CO2 and dissociation of carbonic acid, which target membrane-bound proteins and lipids in brain stem neurons. The CO2 hydration reaction, however, is not the only reaction that CO2 undergoes that generates molecules capable of modifying proteins and lipids. Molecular CO2 also reacts with peroxynitrite (ONOO-), a reactive nitrogen species (RNS), which is produced from nitric oxide (*NO) and superoxide (*O2-). The CO2/ONOO- reaction, in turn, produces additional nitrosative and oxidative reactive intermediates. Furthermore, protons facilitate additional redox reactions that generate other reactive oxygen species (ROS). ROS/RNS generated by these redox reactions may act as additional stimuli of CO2 chemoreceptors since neurons in chemosensitive areas produce both *NO and *O2- and, therefore, ONOO-. Perturbing *NO, *O2-, and ONOO- activities in chemosensitive areas modulates cardiorespiration. Moreover, neurons in at least one chemosensitive area, the solitary complex, are stimulated by cellular oxidation. Together, these data raise the following two questions: 1) do pH and ROS/RNS work in tandem to stimulate CO2 chemoreceptors during hypercapnic acidosis; and 2) does nitrosative stress and oxidative stress contribute to CO2 chemoreceptor dysfunction? To begin considering these two issues and their implications for central chemoreception, this minireview has the following three goals: 1) summarize the nitrosative and oxidative reactions that occur during hypercapnic acidosis and isocapnic acidosis; 2) review the evidence that redox signaling occurs in chemosensitive areas; and 3) review the evidence that neurons in the solitary complex are stimulated by cellular oxidation.

Effects of deferoxamine on brain injury after transient focal cerebral ischemia in rats with hyperglycemia

Hemorrhagic transformation (HT) is a major factor limiting the use of tissue plasminogen activator (tPA) for stroke patients. This study examined the role of deferoxamine (DFX) in brain injury and HT in a rat model of transient focal ischemia with hyperglycemia. Rats received an injection of 50% glucose (6 mL/kg, i.p.) 15 min before undergoing transient middle cerebral artery occlusion (tMCAO; 2 h occlusion) with reperfusion. Rats were treated with DFX (100 mg/ kg, i.m.) or vehicle immediately after tMCAO. Rats were killed at 4, 8 and 24 h later and used for brain edema, blood-brain barrier permeability, hemorrhage volume, hemoglobin content, and infarct volume measurements. Mortality rate was also evaluated. DFX treatment reduced mortality at 24 h (4% vs. 24% in the vehicle-treated group, p<0.05). DFX also reduced infarct volume (85.1+/-56.3 vs. 164.3+/-93.4 mm(3) in vehicle, p<0.05) and swelling in the basal ganglia (p<0.05) 24 h after tMCAO. The total hemorrhage volume in the ipsilateral hemisphere at 8 h post tMCAO was less in DFX-treated animals (p<0.05). However, blood-brain barrier permeability was same in DFX- and vehicle-treated groups. DFX attenuates death rate, hemorrhagic transformation, infarct volume, and brain swelling in a rat transient focal ischemia with hyperglycemia model, suggesting that DFX could be potential treatment to reduce the hemorrhagic transformation for stroke patients.