lactate/N-acetylaspartate Research Articles

Early assessment of injury with optical markers in a piglet model of neonatal encephalopathy

BackgroundOpportunities for adjunct therapies with cooling in neonatal encephalopathy are imminent; however, robust biomarkers of early assessment are lacking. Using an optical platform of broadband near-infrared spectroscopy and diffuse correlation spectroscopy to directly measure mitochondrial metabolism (oxCCO), oxygenation (HbD), cerebral blood flow (CBF), we hypothesised optical indices early (1-h post insult) after hypoxia-ischaemia (HI) predicts insult severity and outcome.MethodsNineteen newborn large white piglets underwent continuous neuromonitoring as controls or following moderate or severe HI. Optical indices were expressed as mean semblance (phase difference) and coherence (spectral similarity) between signals using wavelet analysis. Outcome markers included the lactate/N-acetyl aspartate (Lac/NAA) ratio at 6 h on proton MRS and TUNEL cell count.ResultsCBF-HbD semblance (cerebrovascular dysfunction) correlated with BGT and white matter (WM) Lac/NAA (r2 = 0.46, p = 0.004, r2 = 0.45, p = 0.004, respectively), TUNEL cell count (r2 = 0.34, p = 0.02) and predicted both initial insult (r2 = 0.62, p = 0.002) and outcome group (r2 = 0.65 p = 0.003). oxCCO-HbD semblance (cerebral metabolic dysfunction) correlated with BGT and WM Lac/NAA (r2 = 0.34, p = 0.01 and r2 = 0.46, p = 0.002, respectively) and differentiated between outcome groups (r2 = 0.43, p = 0.01).ConclusionOptical markers of both cerebral metabolic and vascular dysfunction 1 h after HI predicted injury severity and subsequent outcome in a pre-clinical model.ImpactThis study highlights the possibility of using non-invasive optical biomarkers for early assessment of injury severity following neonatal encephalopathy, relating to the outcome.Continuous cot-side monitoring of these optical markers can be useful for disease stratification in the clinical population and for identifying infants who might benefit from future adjunct neuroprotective therapies beyond cooling.

Interleukin-33 and Soluble ST2 Levels in Infants with Hypoxic-Ischemic Encephalopathy

Introduction: Interleukin (IL)-33 and its receptor ST2L play key roles in the IL-33/ST2 signaling pathway. Soluble ST2 (sST2) inhibits the proper function of IL-33. sST2 levels are increased in patients with several neurological diseases, but in infants with hypoxic-ischemic encephalopathy (HIE), IL-33 and sST2 levels have not been studied. This study aimed to investigate whether serum levels of IL-33 and sST2 are useful as biomarkers of HIE severity and prognostic factors for infants with HIE. Methods: Twenty-three infants with HIE and 16 controls (gestational age ≥36 weeks and ≥1,800 g birth weight) were enrolled in this study. Serum levels of IL-33 and sST2 were measured at <6 h, 1–2, 3, and 7 days of age. Hydrogen-1 magnetic resonance spectroscopy was performed, and ratios of peak integrals of lactate/N-acetylaspartate (Lac/NAA) were calculated as objective indicators of brain damage. Results: In the moderate and severe HIE, serum sST2 concentrations were increased and there was a good correlation between serum sST2 and HIE severity on days 1–2, whereas no variation was observed in serum IL-33. Serum sST2 levels were positively correlated with Lac/NAA ratios (Kendall’s rank correlation coefficient = 0.527, p = 0.024), and both sST2 and Lac/NAA ratios were significantly higher in HIE infants with neurological impairment (p = 0.020 and <0.001, respectively). Conclusions: sST2 may be a useful predictor of severity and later neurological outcomes in infants with HIE. Further investigation is required to elucidate the relationship between the IL-33/ST2 axis and HIE.

Pseudoprogression in GBM versus true progression in patients with glioblastoma: A multiapproach analysis

Background and purposeTo investigate the feasibility of using a multiapproach analysis combining clinical data, diffusion- and perfusion-weighted imaging, and 3D magnetic resonance spectroscopic imaging to distinguish true tumor progression (TP) from pseudoprogression (PSP) in patients with glioblastoma. Materials and methodsProgression was suspected within 6 months of radiotherapy in 46 of the 180 patients included in the Phase-III SpectroGlio trial (NCT01507506). Choline/creatine (Cho/Cr), choline/N-acetyl aspartate (Cho/NAA) and lactate/N-acetyl aspartate (Lac/NAA) ratios were extracted. Apparent diffusion coefficient (ADC) and cerebral blood volume (CBV) maps were calculated. ADC, relative CBV values and tumor volume (TV) were collected at relapse. Differences between TP and PSP were evaluated using Mann–Whitney tests, and p values were adjusted with Bonferroni correction. ResultsPatients with suspected progression underwent a new MRI scan 1 month after the first one. Of these, 28 were classified as PSP, and 18 as TP. After a median follow-up of 41 months, median overall survival was higher in PSP than in TP (25.2 vs 20.3 months; p = 0.0092). Lac/NAA and Cho/Cr ratios were higher in TP than in PSP (1.2 vs 0.5; p = 0.006; and 3 vs 2.2; p = 0.021). After multivariate regression analysis, TV was the most significant predictor of TP vs PSP, and the only one retained in the model (p = 0.028). ConclusionThree spectroscopic ratios could be used to differentiate PSP from TP. TV at relapse was the most predictive factor in the multivariate analysis, and overall survival was higher in PSP than in TP.

Short-term outcomes of remote ischemic postconditioning 1 h after perinatal hypoxia-ischemia in term piglets.

We aimed to assess remote ischemic postconditioning (RIPC) as a neuroprotective strategy after perinatal hypoxia-ischemia (HI) in a piglet model. Fifty-four newborn piglets were subjected to global HI for 45 min. One hour after HI, piglets were randomized to four cycles of 5 min of RIPC or supportive treatment only. The primary outcome was brain lactate/N-acetylaspartate (Lac/NAA) ratios measured by magnetic resonance spectroscopy at 72 h. Secondary outcomes included diffusion-weighted imaging and neuropathology. RIPC was associated with a reduction in overall and basal ganglia Lac/NAA ratios at 72 h after HI, but no effect on diffusion-weighted imaging, neuropathology scores, neurological recovery, or mortality. The selective effect of RIPC on Lac/NAA ratios may suggest that the metabolic effect is greater than the structural and functional improvement at 72 h after HI. Further studies are needed to address whether there is an add-on effect of RIPC to hypothermia, together with the optimal timing, number of cycles, and duration of RIPC. RIPC after HI was associated with a reduction in overall and basal ganglia Lac/NAA ratios at 72 h, but had no effect on diffusion-weighted imaging, neuropathology scores, neurological recovery, or mortality. RIPC may have a selective metabolic effect, ameliorating lactate accumulation without improving other short-term outcomes assessed at 72 h after HI. We applied four cycles of 5 min RIPC, complementing existing data on other durations of RIPC. This study adds to the limited data on RIPC after perinatal HI and highlights that knowledge gaps, including timing and duration of RIPC, must be addressed together with exploring the combined effects with hypothermia.

Quantification of the severity of hypoxic-ischemic brain injury in a neonatal preclinical model using measurements of cytochrome-c-oxidase from a miniature broadband-near-infrared spectroscopy system.

.We describe the development of a miniaturized broadband near-infrared spectroscopy system (bNIRS), which measures changes in cerebral tissue oxyhemoglobin () and deoxyhemoglobin ([HHb]) plus tissue metabolism via changes in the oxidation state of cytochrome-c-oxidase ([oxCCO]). The system is based on a small light source and a customized mini-spectrometer. We assessed the instrument in a preclinical study in 27 newborn piglets undergoing transient cerebral hypoxia-ischemia (HI). We aimed to quantify the recovery of the HI insult and estimate the severity of the injury. The recovery in brain oxygenation (), blood volume (), and metabolism () for up to 30 min after the end of HI were quantified in percentages using the recovery fraction (RF) algorithm, which quantifies the recovery of a signal with respect to baseline. The receiver operating characteristic analysis was performed on bNIRS-RF measurements compared to proton () magnetic resonance spectroscopic (MRS)-derived thalamic lactate/N-acetylaspartate (Lac/NAA) measured at 24-h post HI insult; Lac/NAA peak area ratio is an accurate surrogate marker of neurodevelopmental outcome in babies with neonatal HI encephalopathy. The -RF cut-off threshold of 79% within 30 min of HI predicted injury severity based on Lac/NAA with high sensitivity (100%) and specificity (93%). A significant difference in thalamic Lac/NAA was noticed () between the two groups based on this cut-off threshold of 79% -RF. The severe injury group () had smaller recovery in -RF () and no significant difference was observed in -RF between groups. At 48 h post HI, significantly higher -MRS-measured inorganic phosphate/exchangeable phosphate pool (epp) () and reduced phosphocreatine/epp () were observed in the severe injury group indicating persistent cerebral energy depletion. Based on these results, the bNIRS measurement of the oxCCO recovery fraction offers a noninvasive real-time biomarker of brain injury severity within 30 min following HI insult.

Proton magnetic resonance spectroscopy lactate/N-acetylaspartate within 2 weeks of birth accurately predicts 2-year motor, cognitive and language outcomes in neonatal encephalopathy after therapeutic hypothermia

ObjectiveBrain proton (1H) magnetic resonance spectroscopy (MRS) lactate/N-acetylaspartate (Lac/NAA) peak area ratio is used for prognostication in neonatal encephalopathy (NE). At 3 Tesla in NE babies, the objectives were to...

DHA and therapeutic hypothermia in a short-term follow-up piglet model of hypoxia-ischemia: Effects on H+MRS biomarkers.

BackgroundTherapeutic hypothermia has become the standard of care for newborns with hypoxic-ischemic encephalopathy in high and middle income countries. Docosahexaenoic acid (DHA) has neuroprotective properties of reducing excitotoxicity, neuroinflammation and apoptosis in rodent models. We aim to study whether post hypoxic administration of i.v. DHA will reduce H+MRS biomarkers and gene expression of inflammation and apoptosis both with and without hypothermia in a large animal model.MethodsFifty-five piglets were randomized to severe global hypoxia (N = 48) or not (Sham, N = 7). Hypoxic piglets were further randomized by factorial design: Vehicle (VEH), DHA, VEH + Hypothermia (HT), or DHA + HT. 5 mg/kg DHA was given intravenously 210 min after end of hypoxia. Two-way ANOVA analyses were performed with DHA and hypothermia as main effects.ResultsCortical lactate/N-acetylaspartate (Lac/NAA) was significantly reduced in DHA + HT compared to HT. DHA had significant main effects on increasing N-acetylaspartate and glutathione in hippocampus. Therapeutic hypothermia significantly reduced the Lac/NAA ratio and protein expression of IL-1β and TNFα in hippocampus and reduced Troponin T in serum. Neuropathology showed significant differences between sham and hypoxia, but no differences between intervention groups.ConclusionDHA and therapeutic hypothermia significantly improve specific H+MRS biomarkers in this short-term follow up model of hypoxia-ischemia. Longer recovery periods are needed to evaluate whether DHA can offer translational neuroprotection.

Systemic pro-inflammatory cytokine status following therapeutic hypothermia in a piglet hypoxia-ischemia model

BackgroundInflammatory cytokines are implicated in the pathogenesis of perinatal hypoxia-ischemia (HI). The influence of hypothermia (HT) on cytokines after HI is unclear. Our aim was to assess in a piglet asphyxia model, under normothermic (NT) and HT conditions: (i) the evolution of serum cytokines over 48 h and (ii) cerebrospinal fluid (CSF) cytokine levels at 48 h; (iii) serum pro/anti-inflammatory cytokine profile over 48 h and (iv) relation between brain injury measured by magnetic resonance spectroscopy (MRS) and brain TUNEL positive cells with serum cytokines, serum pro/anti-inflammatory cytokines and CSF cytokines.MethodsNewborn piglets were randomized to NT (n = 5) or HT (n = 6) lasting 2–26 h after HI. Serum samples were obtained 4–6 h before, during and at 6–12 h intervals after HI; CSF was obtained at 48 h. Concentrations of interleukin (IL)-1β, −4, −6, −8, −10 and TNF-α were measured and pro/anti-inflammatory status compared between groups. White matter and thalamic voxel lactate/N-acetyl aspartate (Lac/NAA) (a measure of both oxidative metabolism and neuronal loss) were acquired at baseline, after HI and at 24 and 36 h.ResultsLac/NAA was reduced at 36 h with HT compared to NT (p = 0.013 basal ganglia and p = 0.033 white matter). HT showed lower serum TNF-α from baseline to 12 h (p < 0.05). Time-matched (acquired within 5 h of each other) serum cytokine and MRS showed correlations between Lac/NAA and serum IL-1β and IL-10 (all p < 0.01). The pro/anti-inflammatory ratios IL-1β/IL-10, IL-6/IL-10, IL-4/IL-10 and IL-8/IL-10 were similar in NT and HT groups until 36 h (24 h for IL-6/IL-10); after this, 36 h pro/anti-inflammatory cytokine ratios in the serum were higher in HT compared to NT (p < 0.05), indicating a pro-inflammatory cytokine surge after rewarming in the HT group. In the CSF at 48 h, IL-8 was lower in the HT group (p < 0.05). At 48 h, CSF TNF-α correlated with Lac/NAA (p = 0.02) and CSF IL-8 correlated with white matter TUNEL positive cell death (p = 0.04).ConclusionsFollowing cerebral HI, there was a systemic pro-inflammatory surge after rewarming in the HT group, which is counterintuitive to the putative neuroprotective effects of HT. While serum cytokines were variable, elevations in CSF inflammatory cytokines at 48 h were associated with MRS Lac/NAA and white matter cell death.

MRI and spectroscopy in (near) term neonates with perinatal asphyxia and therapeutic hypothermia

BackgroundPrevious studies have demonstrated the association of abnormalities on diffusion-weighted MRI (DW-MRI) and proton magnetic resonance spectroscopy (1H-MRS) in infants with perinatal asphyxia. The use of therapeutic hypothermia might change...

Prognostic Accuracy of Thalamic Proton Magnetic Resonance Spectroscopy Following Therapeutic Hypothermia in Neonatal Encephalopathy

Background and aims: Deep grey matter lactate/N-acetylaspartate (Lac/NAA) peak area ratio on proton magnetic resonance spectroscopy (1H MRS) is the best predictor of neurological outcome following neonatal encephalopathy (NE). We evaluated the prognostic accuracy following therapeutic hypothermia (TH).Methods: We performed magnetic resonance imaging (MRI) in consecutive term babies with NE, over a 3 year period before and after introduction of TH. Death or severe neurodisability (BSID 3) at 12 months was considered as an unfavourable outcome.Results: Of 28 babies studied, 11 babies received TH. The median (range) age at MRI was 10 (5,12) days. Thalamic Lac/NAA (>0.29) had 100% sensitivity and specificity for predicting adverse outcome in both normothermic babies and cooled infants (Table 1). The mean (SD) Lac/NAA was high in infants who had unfavorable outcome (Figure 1)Table Full size tableConclusions: The prognostic accuracy of 1H MRS deep gray matter Lac/NAA peak area ratios is unaltered by TH.

Cerebral Magnetic Resonance Biomarkers in Neonatal Encephalopathy: A Meta-analysis

Accurate prediction of neurodevelopmental outcome in neonatal encephalopathy (NE) is important for clinical management and to evaluate neuroprotective therapies. We undertook a meta-analysis of the prognostic accuracy of cerebral magnetic resonance (MR) biomarkers in infants with neonatal encephalopathy. We reviewed all studies that compared an MR biomarker performed during the neonatal period with neurodevelopmental outcome at > or =1 year. We followed standard methods recommended by the Cochrane Diagnostic Accuracy Method group and used a random-effects model for meta-analysis. Summary receiver operating characteristic curves and forest plots of each MR biomarker were calculated. chi(2) tests examined heterogeneity. Thirty-two studies (860 infants with NE) were included in the meta-analysis. For predicting adverse outcome, conventional MRI during the neonatal period (days 1-30) had a pooled sensitivity of 91% (95% confidence interval [CI]: 87%-94%) and specificity of 51% (95% CI: 45%-58%). Late MRI (days 8-30) had higher sensitivity but lower specificity than early MRI (days 1-7). Proton MR spectroscopy deep gray matter lactate/N-acetyl aspartate (Lac/NAA) peak-area ratio (days 1-30) had 82% overall pooled sensitivity (95% CI: 74%-89%) and 95% specificity (95% CI: 88%-99%). On common study analysis, Lac/NAA had better diagnostic accuracy than conventional MRI performed at any time during neonatal period. The discriminatory powers of the posterior limb of internal capsule sign and brain-water apparent diffusion coefficient were poor. Deep gray matter Lac/NAA is the most accurate quantitative MR biomarker within the neonatal period for prediction of neurodevelopmental outcome after NE. Lac/NAA may be useful in early clinical management decisions and counseling parents and as a surrogate end point in clinical trials that evaluate novel neuroprotective therapies.

Is brain lactate increased in Huntington's disease?

Impaired brain energy metabolism with increased regional brain lactate may play a role in the pathogenesis of Huntington's disease (HD). Magnetic resonance spectroscopy (MRS) has provided conflicting evidence, however, regarding metabolic changes. Our objective was to evaluate the potential contribution of CSF lactate to the changes observed with MRS in HD. We performed single voxel MRS at 3 T in 23 patients with HD and 28 age-matched control subjects using a method to segment voxels into grey matter, white matter, and CSF, and to extrapolate regional lactate content to a hypothetical voxel containing 100% brain in order to control for differences in CSF lactate. Lactate/creatine and lactate/N-acetyl aspartate (Lac/NAA) ratios were significantly increased in parieto-occipital (p<0.05) and cerebellar (p<0.01) voxels in HD patients. After extrapolating group Lac/NAA results to a theoretical voxel containing 100% brain, this ratio was greater in the HD group than the control group, suggesting possibly increased lactate in this predicted voxel, although the difference between groups did not reach statistical significance. These results suggest an increase in brain lactate content in manifest HD, in a regionally non-specific fashion, although the possibility of a CSF contribution to this increase cannot be ruled out. Regardless, this supports the possibility of impaired mitochondrial function resulting in abnormal brain energy metabolism in HD.

CEREBRAL METABOLISM OF NEWBORN PIGLETS FOLLOWING HYPOXIA- ISCHEMIA AND NITRIC OXIDE SYNTHASE INHIBITION, EXAMINED USING PROTON AND PHOSPHOROUS MAGNETIC RESONANCE SPECTROSCOPY. • 1729

Increased production of nitric oxide, a free radical with a potential for tissue damage, in cerebral tissue during hypoxia-ischemia (HI) and reperfusion has been demonstrated previously. The present study tests thehypothesis that inhibition of nitric oxide synthase (NOS) during cerebral HI reduces hypoxia-induced lactate production and changes in intracellular pH (pHi), phosphocreatine/ inorganic phosphate(PCr/Pi) ratios in cortical tissue of newborn piglets. Methods: Following anesthesia, 8 newborn piglets aged 1-3 days were instrumented, including placement of inflatable carotid occluders, and ventilated. The animals were placed in a 4.7 T magnet for examination of cerebral metabolism using 31P and 1H-MRS. Measurements were performed every 15 min throughout the experiment. One hour after the i.v. administration of 40 mg/kg Nω-nitro-L- arginine (n=4, NNLA-Hx group) or normal saline (n=4, Hx group), HI was induced by decreasing the FiO2 to 0.08 and carotid occlusion. After one hour, occluders were deflated, and resuscitation was started with an FiO2 sufficient to obtain PaO2 levels of 80-100 mmHg. pHi, PCr/Pi and lactate/N-acetylaspartate (Lac/NAA) ratios were calculated.Results: baseline pHi, PCr/Pi and Lac/NAA ratios(mean ± S.D.) were 7.22 ± 0.08, 2.80 ± 0.32, 0 in the Hx group and 7.12 ± 0.05, 2.46 ± 0.41, and 0 in the NNLA-Hx group, respectively (group differences not significant). After 1 hour of HI pHi, PCr/Pi and Lac/NAA were 6.79 ± 0.26, 1.13± 0.67, 1.10 ± 0.40 in the Hx group and 6.24 ± 0.31, 0.09± 0.06, and 2.07 ± 1.07 in the NNLA-Hx group. These differences are significant (P<0.05). Following 1 hour of resuscitation, pHi, PCr/Pi and Lac/NAA of the Hx group were 7.24 ± 0.18, 2.62 ± 0.36, and 0.34 ± 0.49, whereas in the NNLA-Hx group these values were 6.72 ± 0.44, 0.73 ± 0.93, and 1.11 ± 0.32, respectively. These differences are also significant (P<0.05).Conclusion: inhibition of NOS by NNLA during HI and reperfusion deteriorated cerebral energy metabolism in newborn piglets, which is in contrast with our hypothesis. We speculate that NO mediated effects on cerebral perfusion are important for cerebral energy metabolism following HI and reperfusion. Supported by the Wilhelmina Children's Hospital Research Fund

Effects of hyperglycemia on the time course of changes in energy metabolism and pH during global cerebral ischemia and reperfusion in rats: correlation of 1H and 31P NMR spectroscopy with fatty acid and excitatory amino acid levels.

The effects of hyperglycemia on the time course of changes in cerebral energy metabolite concentrations and intracellular pH were measured by nuclear magnetic resonance (NMR) spectroscopy in rats subjected to temporary complete brain ischemia. Interleaved 31P and 1H NMR spectra were obtained every 5 min before, during, and for 2 h after a 30-min bilateral carotid occlusion preceded by permanent occlusion of the basilar artery. The findings were compared with free fatty acid and excitatory amino acid levels as well as with cations and water content in funnel-frozen brain specimens. One hour before occlusion, nine rats received 50% glucose (12 ml/kg i.p.) and five received 7% saline (12 ml/kg i.p.). Before ischemia, there were no differences in cerebral metabolite levels or pH between hyperglycemic rats and controls. During the carotid occlusion, the lactate/N-acetylaspartate (Lac/NAA) peak ratio was higher (0.73-1.48 vs. 0.56-0.82; p less than 0.05) and pH was lower (less than 6.0 vs. 6.45 +/- 0.05; p less than 0.05) in the hyperglycemic rats than in the controls. Phosphocreatine and adenosine triphosphate were totally depleted in both groups. Within 5-15 min after the onset of reperfusion, the Lac/NAA peak ratio increased further in all rats; however, only in extremely hyperglycemic rats (serum glucose greater than 960 mg/dl) did the lactic acidosis progress rather than recover later during reperfusion. Total free fatty acid and excitatory amino acid levels, but not cation concentration or water content, in brain correlated with serum glucose levels during and after ischemia and with NMR findings after 2 h of reperfusion. Although profound hyperglycemia (serum glucose of 970-1,650 mg/dl) appears to be associated with progression of anaerobic glycolysis and failure of cerebral energy metabolism to recover after temporary complete brain ischemia and with postischemic excitotoxic and lipolytic reactions thought to participate in delayed cellular injury, severe hyperglycemia (490-720 mg/dl) was associated with recovery of energy metabolism.