Effect of hyperglycemia on reperfusion-associated recovery of intracellular pH and high energy phosphates after transient cerebral ischemia in gerbils

Suppression of Inner Mitochondrial Membrane Peptidase 2-Like (IMMP2L) Gene Exacerbates Hypoxia-Induced Neural Death Under High Glucose Condition

It is known that diabetes hyperglycemia enhances cerebral ischemia and reperfusion induced damage. We have previously shown that mutation of inner mitochondrial membrane peptidase 2-like (IMMP2L) increases brain damage caused by transient cerebral ischemia. In this study, we attempt to examine the impact of IMMP2L deficiency on an in vitro model that mimics the diabetic hypoxic conditions. Normal IMMP2L wild type and IMMP2L gene deleted HT22 cells were cultured. Hypoxia was induced under high glucose and acidic conditions with 4 h of oxygen deprivation. Cell viability was assessed by CCK-8 assay and cell death was determined using Annexin V/7-AAD assay. Superoxide production was measured using dihydroethidium staining and mitochondrial membrane potential was detected using JC-1 probe. Suppression of IMMP2L reduced the cell viability, increased the ROS production and decreased the mitochondrial membrane potential. In conclusion, our study demonstrated that deficiency of IMMP2L in cells, cultured under hypoxia, high glucose and acidic conditions, exacerbated neuronal death under a condition that mimics in vivo cerebral ischemia in diabetic condition.

Cerebral metabolic alterations in rats with diabetic ketoacidosis: effects of treatment with insulin and intravenous fluids and effects of bumetanide

OBJECTIVE

Cerebral edema is a life-threatening complication of diabetic ketoacidosis (DKA) in children. Recent data suggest that cerebral hypoperfusion and activation of cerebral ion transporters may be involved, but data describing cerebral metabolic alterations during DKA are lacking.

RESEARCH DESIGN AND METHODS

We evaluated 50 juvenile rats with DKA and 21 normal control rats using proton and phosphorus magnetic resonance spectroscopy (MRS). MRS measured cerebral intracellular pH and ratios of metabolites including ATP/inorganic phosphate (Pi), phosphocreatine (PCr)/Pi, N-acetyl aspartate (NAA)/creatine (Cr), and lactate/Cr before and during DKA treatment. We determined the effects of treatment with insulin and intravenous saline with or without bumetanide, an inhibitor of Na-K-2Cl cotransport, using ANCOVA with a 2 x 2 factorial study design.

RESULTS

Cerebral intracellular pH was decreased during DKA compared with control (mean +/- SE difference -0.13 +/- 0.03; P < 0.001), and lactate/Cr was elevated (0.09 +/- 0.02; P < 0.001). DKA rats had lower ATP/Pi and NAA/Cr (-0.32 +/- 0.10, P = 0.003, and -0.14 +/- 0.04, P < 0.001, respectively) compared with controls, but PCr/Pi was not significantly decreased. During 2-h treatment with insulin/saline, ATP/Pi, PCr/Pi, and NAA/Cr declined significantly despite an increase in intracellular pH. Bumetanide treatment increased ATP/Pi and PCr/Pi and ameliorated the declines in these values with insulin/saline treatment.

CONCLUSIONS

These data demonstrate that cerebral metabolism is significantly compromised during DKA and that further deterioration occurs during early DKA treatment--consistent with possible effects of cerebral hypoperfusion and reperfusion injury. Treatment with bumetanide may help diminish the adverse effects of initial treatment with insulin/saline.

Dexamethasone for intracranial neurosurgery and anaesthesia

Dexamethasone is frequently administered to patients with brain tumours having neurosurgery, and is often given for other purposes by anaesthetists. This review outlines the rationale for its use by both specialities, and discusses its potential adverse effects.

Effect of hyperglycemia on progressive paraparesis in a rat metastatic spinal tumor model

Object

Hyperglycemia has been shown to potentiate ischemic injury of the spinal cord by quenching vasodilators and potentiating tissue acidosis and free radical production. Steroid-induced hyperglycemia is a common event in the surgical management of metastatic epidural spinal cord compression (MESCC). The goal in this study was to determine whether experimentally induced hyperglycemia accelerates neurological decline in an established animal model of MESCC.

Methods

Sixteen Fischer 344 rats underwent a transabdominal approach for implantation of a CRL-1666 breast adenocarcinoma cell line within the vertebral body of L-6. After 72 hours of recovery from tumor implantation, the animals received intraperitoneal injections every 12 hours of either 2 g/kg dextrose in 5 ml 0.09% saline (hyperglycemia, 8 rats) or 5 ml 0.09% saline alone (normoglycemia, 8 rats). Weights were taken daily, and the hindlimb function was tested daily after tumor implantation by using the Basso-Beattie-Bresnahan (BBB) scale (score range 1–21). Animals were killed at time of paralysis (BBB Score < 7), and the volume of epidural tumor growth within the spinal canal was measured. To determine the degree of hyperglycemia induced by this dextrose regimen, a surrogate group of 10 Fischer 344 rats underwent intraperitoneal injections of 2 g/kg dextrose (5 rats) or 0.09% saline (5 rats) every 12 hours, and serum glucose levels were assessed 1, 3, 6, 8, 10, and 12 hours after injections for 24 hours.

Results

Dextrose versus saline injections resulted in elevated mean serum glucose at 3 (259 vs 103 μg/dl), 6 (219 vs 102 μg/dl), 8 (169 vs 102 μg/dl), and 10 hours (118 vs 99 μg/dl) after injection, returning to normal levels by 12 hours (96 vs 103 μg/dl) just prior to subsequent injection. All rats had normal hindlimb function for the first 8 days after tumor implantation. Hyperglycemic versus normoglycemic rats demonstrated a worsened median BBB score by postimplantation Day 9 (Score 20 vs 21, p = 0.023) through Day 16 (Score 8 vs 12, p = 0.047). Epidural tumor volume demonstrated a near-linear growth rate across both groups; however, hyperglycemic rats developed paralysis earlier (median 15.5 vs 17.5 days, p = 0.0035), with significantly less epidural tumor volume (2.75 ± 0.38 cm3 vs 4 ± 0.41 cm3, p < 0.001) at time of paralysis.

Conclusions

In a rat model of metastatic epidural spinal cord compression, rats maintained in a hyperglycemic state experienced accelerated time to paralysis. Also, less epidural tumor volume was required to cause paralysis in hyperglycemic rats. These results suggest that hyperglycemic states may contribute to decreased spinal cord tolerance to compression resulting from MESCC. Clinical studies evaluating the effect of aggressive glucose control in patients with MESCC may be warranted.

PERSISTENT OUTPATIENT HYPERGLYCEMIA IS INDEPENDENTLY ASSOCIATED WITH DECREASED SURVIVAL AFTER PRIMARY RESECTION OF MALIGNANT BRAIN ASTROCYTOMAS

OBJECTIVE

Patients with malignant brain astrocytomas are at high risk for developing hyperglycemia secondary to frequent corticosteroid administration. Several clinical studies have shown that hyperglycemia is associated with poor outcome in multiple disease states. Furthermore, hyperglycemia augments in vitro astrocytoma growth, whereas hypoglycemia attenuates in vitro astrocytoma cell growth. We hypothesized that persistent hyperglycemic states in the outpatient setting may serve as a prognostic marker of decreased survival in patients with malignant brain astrocytomas.

METHODS

We retrospectively reviewed 367 cases of craniotomy for malignant brain astrocytomas (World Health Organization Grade III or IV). Persistent hyperglycemia was defined as serum glucose greater than 180 mg/dL occurring three or more times between 1 and 3 months postoperatively. Isolated hyperglycemia was defined as an isolated occurrence of serum glucose greater than 180 mg/dL. The independent association of outpatient glucose levels and recorded clinical and treatment variables with overall survival was assessed via multivariate proportional-hazards regression analysis.

RESULTS

A total of 367 craniotomies (209 primary, 158 secondary) were performed for malignant brain astrocytomas (glioblastoma multiforme, 297; anaplastic astrocytomas, 70); 68 (19%) and 28 (8%) of the patients experienced isolated or persistent outpatient hyperglycemia, respectively. Patients experiencing persistent hyperglycemia were older (59 ± 13 versus 51 ± 14 yr), were diabetic more frequently (7 [25%] versus 10 [3%]), continued to receive corticosteroids more frequently (21 [75%] versus 35 [10%]); and received temozolomide less often (4 [14%] versus 116 [34%]). Adjusting for intergroup differences and variables associated with survival in this model, age (P = 0.001), Karnofsky Performance Scale score (P = 0.001), tumor grade (P = 0.001), primary versus secondary resection (P = 0.008), temozolomide (P = 0.007), subsequent resection (P = 0.07), and continued outpatient dexamethasone therapy, persistent outpatient hyperglycemia (relative risk, 1.79; 95% confidence interval, 1.05–3.05, P = 0.03) remained independently associated with decreased survival. Median survival for persistently hyperglycemic versus normal-glycemic cohorts was 5 and 11 months, respectively.

CONCLUSION

In our experience, persistent outpatient hyperglycemia was associated with decreased survival in patients undergoing surgical resection for malignant astro- cytomas and was independent of the degree of disability, tumor grade, diabetes, prolonged dexamethasone use, or subsequent treatment modalities. Increased glucose control is warranted in this patient population and may contribute to improved outcomes in the treatment of malignant brain astrocytomas.

Predictors of ambulatory function after decompressive surgery for metastatic epidural spinal cord compression

OBJECTIVE

Metastatic epidural spinal cord compression (MESCC) is a relatively common and debilitating complication of metastatic disease that often results in neurological deficits. This study was designed to explore associations with maintaining and regaining ambulatory function after decompressive surgery for MESCC.

METHODS

Seventy-eight patients undergoing decompressive surgery for MESCC at an academic tertiary care institution between 1995 and 2005 were retrospectively reviewed. Fisher's exact analysis was used to compare preoperative ambulatory and nonambulatory patients. Multivariate Cox proportional hazards regression was used to identify associations with either maintaining or regaining the ability to walk.

RESULTS

Patients were followed for 7.1 +/- 1.6 (mean +/- standard deviation) months after surgery. Preoperative nonambulatory patients required more extensive surgery (increased operative spinal levels and number of laminectomies) and had more surgical site complications (wound dehiscences and cerebrospinal fluid leaks) compared with preoperative ambulatory patients. From the multivariate analysis, preoperative ability to walk (relative risk [RR], 2.320; 95% confidence interval [CI], 1.301-4.416; P < 0.01) independently increased the likelihood of ambulation at the last follow-up evaluation 2.3-fold. Pathological vertebral compression fracture at presentation (RR, 0.471; 95% CI, 0.235-0.864; P = 0.01) independently decreased the likelihood of ambulation at the time of the last follow-up evaluation 2.1-fold. For patients unable to walk at the time of surgery, preoperative radiation therapy (RR, 0.406; 95% CI, 0.124-0.927; P = 0.03) decreased the likelihood of regaining the ability to walk 2.5-fold. Symptoms present for less than 48 hours (RR, 2.925; 95% CI, 1.133-2.925; P = 0.02) and postoperative radiotherapy (RR, 2.595; 95% CI, 1.039-8.796; P = 0.04) independently increased the likelihood of regaining ambulatory ability 2.9- and 2.6-fold, respectively, by the time of last follow-up evaluation.

CONCLUSION

The identification of these associations with neurological outcome may help guide in the preservation or return of ambulation after surgery for patients with MESCC.

Induced hippocampal neuron protection in an optimized gerbil ischemia model: insult thresholds for tolerance induction and altered gene expression defined by ischemic depolarization

Preconditioning of hippocampal CA1 neurons was evaluated in a gerbil model of transient global ischemia using extracellular recording of DC potential shifts characteristic of ischemic depolarization to precisely define the duration of both priming and test insults. Brief ischemia resulting in depolarizations of 2.5 to 3.5 minutes consistently induced maximal tolerance (95% protection) against subsequent challenges 2 days later with an approximate doubling of the insult duration required for complete CA1 neuron loss from 6 to 12 minutes depolarization when evaluated 1 week after the test insult. Significant protection persisted at 2 months survival, although the apparent injury threshold regressed to approximately 8 minutes, indicating delayed progression of injury after longer test insults. In situ hybridization was used to evaluate depolarization thresholds for induction of mRNAs encoding the 70 kDa heat shock/stress protein, hsp72, as well as several immediate-early genes (c-fos, c-jun, junB, and junD). Immediate-early genes were prominently expressed after short insults inducing tolerance, whereas appreciable hsp72 induction only occurred after insults approaching the threshold for neuron injury. These results establish an ischemic preconditioning model with the predictability needed for mechanistic studies and demonstrate that prior transcriptional activation of the postischemic heat shock response is not required for expression of delayed tolerance.

Is neuroprotective efficacy of nNOS inhibitor 7-NI dependent on ischemic intracellular pH?

The purpose of this study was to test the hypothesis that the efficacy of 7-nitroindazole (7-NI), a selective neuronal nitric oxide (NO) synthase (NOS) inhibitor, is pH dependent in vivo during focal cerebral ischemia. Wistar rats underwent 2 h of focal cerebral ischemia under 1% halothane anesthesia. 7-NI, 10 and 100 mg/kg in 0.1 ml/kg DMSO, was administered 30 min before occlusion. Ischemic brain acidosis was manipulated by altering serum glucose concentrations. Confirmation of the effects of these serum glucose manipulations on brain intracellular pH (pH(i)) was confirmed in a group of acute experiments utilizing umbelliferone fluorescence. The animals were euthanized at 72 h for histology. 7-NI significantly (P < 0.05) reduced infarction volume in both the normoglycemic by 93.3% and hyperglycemic animals by 27.5%. In the moderate hypoglycemic animals, the reduction in infarction volume did not reach significance because moderate hypoglycemia in itself dramatically reduced infarction volume. We hypothesize that a mechanism to explain the published discrepancies on the effects of neuronal NOS inhibitors in vivo may be due to the effects by differences in ischemic brain acidosis on the production of NO.

Brain energetics of cardiopulmonary cerebral resuscitation

Recovery of normal brain energetic conditions during and after resuscitation from cardiac arrest is critical for survival and good neurologic outcome. This review emphasizes the glucose-driven metabolic processes during and after ischemia and on the post-resuscitation development of secondary energy derangements. It also explores some potential therapeutic interventions designed to attenuate these energy derangements. The article summarizes some bench research and is not intended to provide treatment strategies for clinical application.

Preischemic blood glucose supply to the brain modulates HSP(72) synthesis and neuronal damage in gerbils

Preischemic hyperglycemia is known to aggravate brain damage caused by transient forebrain ischemia. Because heat shock proteins (HSPs) 72 have been proposed to play a protective role against ischemic neuronal injury, we studied the HSP(72) mRNA expression and protein synthesis in gerbils subjected to 10 min bilateral carotid occlusion under normoglycemic, hyperglycemic and fasting conditions. HSP(72) mRNA expression and HSP(72) synthesis were studied using in situ hybridization and immunostaining, respectively. After 8 h of blood recirculation, HSP(72) mRNAs were expressed in all the hippocampal subfields of the three different groups, with higher expression in the hyperglycemic gerbils. After 48 h of reperfusion, HSP(72) mRNAs had almost completely disappeared in the hyper- and normoglycemic groups, and were more strongly expressed in the CA(1) neurons of the fasted group. At this time, fasted gerbils exhibited intense HSP(72) immunoreactivity in the CA(1), whereas an absence of immunoreactivity was observed in that area in the other groups. Finally, ischemia was also associated with marked astrocytic activation, as evidenced by GFAP immunostaining. Overall results indicate that preischemic differences in blood glucose supply to the brain are related to HSP(72) mRNA expression (in terms of duration) and to HSP(72) protein induction (in terms of intensity) in the vulnerable CA(1) neurons of the hippocampus. Ability of CA(1) neurons to synthesize HSP(72) proteins was associated with higher neuronal survival in the fasted group after 48 h of reflow, suggesting a protective role of HSP(72), even though evaluation of neuronal damage at 7 days indicated that neuronal death was mainly delayed in the time.