Neonatal hyperglycemia alters the neurochemical profile,dendritic arborization and gene expression in the developing rat hippocampus

Hyperglycemia (blood glucose concentration >150 mg/dL) is common in extremely low gestational age newborns (ELGANs; birth at <28 week gestation). Hyperglycemia increases the risk of brain injury in the neonatal period. The long‐term effects are not well understood. In adult rats, hyperglycemia alters hippocampal energy metabolism. The effects of hyperglycemia on the developing hippocampus were studied in rat pups. In Experiment 1, recurrent hyperglycemia of graded severity (moderate hyperglycemia (moderate‐HG), mean blood glucose 214.6 ± 11.6 mg/dL; severe hyperglycemia (severe‐HG), 338.9 ± 21.7 mg/dL; control, 137.7 ± 2.6 mg/dL) was induced from postnatal day (P) 3 to P12. On P30, the hippocampal neurochemical profile was determined using in vivo ¹H MR spectroscopy. Dendritic arborization in the hippocampal CA1 region was determined using microtubule‐associated protein (MAP)‐2 immunohistochemistry. In Experiment 2, continuous hyperglycemia (mean blood glucose 275.3 ± 25.8 mg/dL; control, 142.3 ± 2.6 mg/dL) was induced from P2 to P6 by injecting streptozotocin (STZ) on P2. The mRNA expression of glycogen synthase 1 (Gys1), lactate dehydrogenase (Ldh), glucose transporters 1 (Glut1) and 3 (Glut3) and monocarboxylate transporters 1 (Mct1), 2 (Mct2) and 4 (Mct4) in the hippocampus was determined on P6. In Experiment 1, MRS demonstrated lower lactate concentration and glutamate/glutamine (Glu/Gln) ratio in the severe‐HG group, compared with the control group (p < 0.05). Phosphocreatine/creatine ratio was higher in both hyperglycemia groups (p < 0.05). MAP‐2 histochemistry demonstrated longer apical segment length, indicating abnormal synaptic efficacy in both hyperglycemia groups (p < 0.05). Experiment 2 showed lower Glut1, Gys1 and Mct4 expression and higher Mct1 expression in the hyperglycemia group, relative to the control group (p < 0.05). These results suggest that hyperglycemia alters substrate transport, lactate homeostasis, dendritogenesis and Glu‐Gln cycling in the developing hippocampus. Abnormal neurochemical profile and dendritic structure due to hyperglycemia may partially explain the long‐term hippocampus‐mediated cognitive deficits in human ELGANs.     

Accurate prediction of hypoxic-ischaemic encephalopathy at delivery: a cohort study

Objective: Hypoxic-ischaemic encephalopathy (HIE) is a major acute neurologic manifestation of perinatal asphyxia associated with significant mortality and morbidity. The study aimed to develop a simple, accurate method of predicting HIE at delivery. Methods: Between January 2003 and December 2009, all HIE cases were identified from the 38,404 deliveries at a single tertiary centre. Receiver operating curve (ROC) analysis and multivariate logistic regression assessed the ability of clinical and biochemical assessments to predict HIE. Results: Sixty neonates met the HIE criteria: 39 were moderate-severe HIE. Univariate analyses identified clinical neonatal markers (Apgar scores and neonatal resuscitation level) to be better HIE predictors than biochemical markers (umbilical artery pH, base excess and lactate values). Multivariable models using two to four predictors had areas under ROC curves up to 0.98, sensitivities up to 93% and specificities up to 99%. For moderate-severe HIE, the most effective predictor was neonatal resuscitation level and arterial lactate (ROC 0.98, sensitivity 85%, specificity 99%). Conclusion: The combination of umbilical arterial lactate and neonatal resuscitation level provides a rapid and accurate method of predicting moderate-severe HIE that can identify neonates at birth that may benefit from tertiary care and neuroprotective therapies.     

Neuronal lactate levels depend on glia-derived lactate during high brain activity in Drosophila

Lactate/pyruvate transport between glial cells and neurons is thought to play an important role in how brain cells sustain the high-energy demand that neuronal activity requires. However, the in vivo mechanisms and characteristics that underlie the transport of monocarboxylates are poorly described. Here, we use Drosophila expressing genetically encoded FRET sensors to provide an ex vivo characterization of the transport of monocarboxylates in motor neurons and glial cells from the larval ventral nerve cord. We show that lactate/pyruvate transport in glial cells is coupled to protons and is more efficient than in neurons. Glial cells maintain higher levels of intracellular lactate generating a positive gradient toward neurons. Interestingly, during high neuronal activity, raised lactate in motor neurons is dependent on transfer from glial cells mediated in part by the previously described monocarboxylate transporter Chaski, providing support for in vivo glia-to-neuron lactate shuttling during neuronal activity.     

肝炎肝硬化外周血细胞变化与乳酸脱氢酶的相关性分析

目的探讨肝炎肝硬化患者外周血细胞变化与血清乳酸脱氢酶水平的相关性。为早期发现骨髓病态造血、早期诊治及判断预后提供依据。方法对227例肝炎肝硬化患者的外周血血红蛋白、中性粒细胞、血小板、网织红细胞、血清丙氨酸转移酶(ALT)、血清乳酸脱氢酶(LDH)进行检测和分析。结果肝炎肝硬化LDH水平与外周血三系血细胞水平呈显著负相关(r=-0.789,P0.05),而与网织红细胞增高呈显著正相关(r=0.576,P0.05),与预后不良呈显著正相关(r=0.778,P0.05)。结论肝炎肝硬化患者血清LDH升高可以作为早期病态造血的客观指标,是早期防治及判断预后的依据。     

Ratiometric analysis in hyperpolarized NMR (I): test of the two‐site exchange model and the quantification of reaction rate constants

Conventional methods for the analysis of in vivo hyperpolarized ¹³C NMR data from the lactate dehydrogenase (LDH) reaction usually make assumptions on the stability of rate constants and/or the validity of the two‐site exchange model. In this study, we developed a framework to test the validity of the assumption of stable reaction rate constants and the two‐site exchange model in vivo via ratiometric fitting of the time courses of the signal ratio L(t)/P(t). Our analysis provided evidence that the LDH enzymatic kinetics observed by hyperpolarized NMR are in near‐equilibrium and satisfy the two‐site exchange model for only a specific time window. In addition, we quantified both the forward and reverse exchange rate constants of the LDH reaction for the transgenic and mouse xenograft models of breast cancer using the ratio fitting method developed, which includes only two modeling parameters and is less sensitive to the influence of instrument settings/protocols, such as flip angles, degree of polarization and tracer dosage. We further compared the ratio fitting method with a conventional two‐site exchange modeling method, i.e. the differential equation fitting method, using both the experimental and simulated hyperpolarized NMR data. The ratio fitting method appeared to fit better than the differential equation fitting method for the reverse rate constant on the mouse tumor data, with less relative errors on average, whereas the differential equation fitting method also resulted in a negative reverse rate constant for one tumor. The simulation results indicated that the accuracy of both methods depends on the width of the transport function, noise level and rate constant ratio; one method may be more accurate than the other based on the experimental/biological conditions aforementioned. We were able to categorize our tumor models into specific conditions of the computer simulation and to estimate the errors of rate quantification. We also discussed possible approaches to the development of more accurate rate quantification methods for hyperpolarized NMR. Copyright © 2013 John Wiley & Sons, Ltd.     

A subconvulsive dose of kainate selectively compromises astrocytic metabolism in the mouse brain in vivo

Despite the well-established use of kainate as a model for seizure activity and temporal lobe epilepsy, most studies have been performed at doses giving rise to general limbic seizures and have mainly focused on neuronal function. Little is known about the effect of lower doses of kainate on cerebral metabolism and particularly that associated with astrocytes. We investigated astrocytic and neuronal metabolism in the cerebral cortex of adult mice after treatment with saline (controls), a subconvulsive or a mildly convulsive dose of kainate. A combination of [1,2-¹³C]acetate and [1-¹³C]glucose was injected and subsequent nuclear magnetic resonance spectroscopy of cortical extracts was employed to distinctively map astrocytic and neuronal metabolism. The subconvulsive dose of kainate led to an instantaneous increase in the cortical lactate content, a subsequent reduction in the amount of [4,5-¹³C]glutamine and an increase in the calculated astrocytic TCA cycle activity. In contrast, the convulsive dose led to decrements in the cortical content and ¹³C labeling of glutamate, glutamine, GABA, and aspartate. Evidence is provided that astrocytic metabolism is affected by a subconvulsive dose of kainate, whereas a higher dose is required to affect neuronal metabolism. The cerebral glycogen content was dose-dependently reduced by kainate supporting a role for glycogen during seizure activity.     

HR‐MAS MRS of the pancreas reveals reduced lipid and elevated lactate and taurine associated with early pancreatic cancer

The prognosis for patients with pancreatic cancer is extremely poor, as evidenced by the disease's five‐year survival rate of ~5%. New approaches are therefore urgently needed to improve detection, treatment, and monitoring of pancreatic cancer. MRS‐detectable metabolic changes provide useful biomarkers for tumor detection and response‐monitoring in other cancers. The goal of this study was to identify MRS‐detectable biomarkers of pancreatic cancer that could enhance currently available imaging approaches. We used ¹H high‐resolution magic angle spinning MRS to probe metabolite levels in pancreatic tissue samples from mouse models and patients. In mice, the levels of lipids dropped significantly in pancreata with lipopolysaccharide‐induced inflammation, in pancreata with pre‐cancerous metaplasia (4 week old p48‐Cre;LSL‐Kras^G12D mice), and in pancreata with pancreatic intraepithelial neoplasia, which precedes invasive pancreatic cancer (8 week old p48‐Cre LSL‐Kras^G12D mice), to 26 ± 19% (p = 0.03), 19 ± 16% (p = 0.04), and 26 ± 10% (p = 0.05) of controls, respectively. Lactate and taurine remained unchanged in inflammation and in pre‐cancerous metaplasia but increased significantly in pancreatic intraepithelial neoplasia to 266 ± 61% (p = 0.0001) and 999 ± 174% (p < 0.00001) of controls, respectively. Importantly, analysis of patient biopsies was consistent with the mouse findings. Lipids dropped in pancreatitis and in invasive cancer biopsies to 29 ± 15% (p = 0.01) and 26 ± 38% (p = 0.02) of normal tissue. In addition, lactate and taurine levels remained unchanged in inflammation but rose in tumor samples to 244 ± 155% (p = 0.02) and 188 ± 67% (p = 0.02), respectively, compared with normal tissue. Based on these findings, we propose that a drop in lipid levels could serve to inform on pancreatitis and cancer‐associated inflammation, whereas elevated lactate and taurine could serve to identify the presence of pancreatic intraepithelial neoplasia and invasive tumor. Our findings may help enhance current imaging methods to improve early pancreatic cancer detection and monitoring. Copyright © 2014 John Wiley & Sons, Ltd.     

Impact of exogenous lactate on survival and radioresponse of carcinoma cells in vitro

Purpose:?Tumour lactate levels have been shown to correlate with high radioresistance in tumour models in?vivo. The study aimed to evaluate the impact of pathophysiological extracellular lactate concentrations and acidosis on the in?vitro survival and radioresponse of various cancer cell lines.

Materials and methods:?HCT-116, HT29 (colorectal) and FaDu (HNSCC) carcinoma cells were studied. Lactate release rates were determined, and expression of the monocarboxylate transporter MCT1 and its cofactor CD147 were monitored by immunofluorescence and flow cytometry. Colony formation was compared for cells exposed to 20?mM exogenous lactate, acidosis (pH 6.4) and lactate plus acidosis relative to control and dose response curves (0.5–10?Gy) were documented.

Results:?All cell lines expressed MCT1 and CD147 and showed comparable lactate release rates. High lactate levels and acidosis slightly decreased HCT-116 colony forming capacity. This effect was neither additive nor did it affect radioresponse. Clonogenic survival of HT29 cells, however, was critically reduced in a lactate-enriched or acidic milieu and a synergistic effect was observed. Here, both conditions enhanced radiosensitivity. Exogenous lactate also impaired colony formation of FaDu cells but acidosis was ineffective. This cell line was more susceptible to irradiation under lactate exposure independent of pH.

Conclusions:?Tumour cell behaviour and radioresponse in a lactate environment is multifaceted. The consideration of lactate accumulation as a parameter affecting radiotherapeutic intervention and as a target for new therapeutic strategies is interesting but requires extended mechanistic studies.