Ethanol in Human Brain by Magnetic Resonance Spectroscopy: Correlation With Blood and Breath Levels, Relaxation, and Magnetization Transfer

Ethanol Kinetics in the Human Brain Determined by Magnetic Resonance Spectroscopy

In many parts of the world, ethanol is a widely consumed substance that displays its effect in the brain, the target organ for desired, but also negative impact. In a previous study, the ethanol concentrations were analyzed in different regions of the brain by magnetic resonance spectroscopy (MRS). In this study, the same method is used to demonstrate the kinetics of the ethanol concentration in the human brain after oral ethanol uptake. A drinking study was performed with 10 healthy participants. After the uptake of ethanol in a calculated amount leading to a plasma ethanol concentration of 0.92 g/L (19.95 mM corresponding to a blood ethanol concentration of 0.7 g/kg), brain ethanol concentrations were continuously measured by means of MRS on a 3 Tesla human magnetic resonance imaging (MRI) system. For the data acquisition a single-voxel sLASER sequence was used, with the volume of interest located in the occipital cortex. Intermittently, blood samples were taken and plasma was analyzed for ethanol using headspace gas chromatography with flame ionization detection (HS-GC-FID). The obtained MRS brain ethanol curves showed distinct inter-individual differences; however, a good intra-individual correlation of plasma and brain ethanol concentrations was observed. The results suggest a rapid equilibration between blood and brain. The ethanol concentrations measured in the brain were substantially lower than the measured plasma ethanol results, suggesting an MRS visibility of about 63% for ethanol in brain tissue. The maximum individual ethanol concentrations in the brain (normalized to water content) ranged between 7.1 and 14.1 mM across the cohort, while the highest measured plasma concentrations were in the range between 0.35 g/L (9.41 mM) and 0.95 g/L (20.52 mM).

Substance abuse and neurodegenerative diseases: focus on ferroptosis

Psychostimulants and alcohol are widely abused substances with the adverse effects on global public health. Substance abuse seriously harms people's health and causes various diseases, especially neurodegenerative diseases. Neurodegenerative diseases include Alzheimer's disease (AD), Parkinson's disease (PD), and amyotrophic lateral sclerosis (ALS). The pathogenesis of neurodegenerative diseases is complex and diverse, usually involving oxidative stress, mitochondrial dysfunction, metal homeostasis disorder, and neuro-inflammation. The precise molecular mechanisms underlying neurodegeneration remain unclear, which is a major obstacle to therapeutic approaches. Therefore, it is urgent to improve the understanding of the molecular mechanisms of neurodegenerative processes and to identify the therapeutic targets for treatment and prevention. Ferroptosis is a regulatory cell necrosis caused by iron ion catalysis and lipid peroxidation induced by reactive oxygen species (ROS), which is thought to be associated with nervous system diseases, particularly neurodegenerative diseases. This review overviewed the ferroptosis process and explored the relationship of ferroptosis with substance abuse and neurodegenerative diseases, which provides a new way to study the molecular mechanisms of neurodegenerative diseases induced by alcohol, cocaine, and methamphetamine (MA), and also provides the potential therapeutic targets for substance abuse-induced neurodegenerative diseases.

Brain proton magnetic resonance spectroscopy and neurodevelopment after preterm birth: a systematic review

BACKGROUND

Preterm infants are at risk of neurodevelopmental impairments. At present, proton magnetic resonance spectroscopy (¹H-MRS) is used to evaluate brain metabolites in asphyxiated term infants. The aim of this review is to assess associations between cerebral ¹H-MRS and neurodevelopment after preterm birth.

METHODS

PubMed and Embase were searched to identify studies using ¹H-MRS and preterm birth. Eligible studies for this review included ¹H-MRS of the brain, gestational age ≤32 weeks, and neurodevelopment assessed at a corrected age (CA) of at least 12 months up to the age of 18 years.

RESULTS

Twenty papers evaluated ¹H-MRS in preterm infants at an age between near-term and 18 years and neurodevelopment. ¹H-MRS was performed in both white (WM) and gray matter (GM) in 12 of 20 studies. The main regions were frontal and parietal lobe for WM and basal ganglia for GM. N-acetylaspartate/choline (NAA/Cho) measured in WM and/or GM is the most common metabolite ratio associated with motor, language, and cognitive outcome at 18-24 months CA.

CONCLUSIONS

NAA/Cho in WM assessed at term-equivalent age was associated with motor, cognitive, and language outcome, and NAA/Cho in deep GM was associated with language outcome at 18-24 months CA.

IMPACT

In preterm born infants, brain metabolism assessed using ¹H-MRS at term-equivalent age is associated with motor, cognitive, and language outcomes at 18-24 months. ¹H-MRS at term-equivalent age in preterm born infants may be used as an early indication of brain development. Specific findings relating to NAA were most predictive of outcome.

Changes in the brain directly following alcohol consumption-a study of healthy male individuals, with the use of proton magnetic resonance spectroscopy (1HMRS) and diffusion (DWI)

AIMS

To use proton magnetic resonance spectroscopy (1HMRS) and diffusion weighted imaging (DWI) to identify ethanol in the brain directly after consumption, and examine changes in brain metabolite levels and brain microstructure relative to the duration of time following exposure to alcohol.

METHODS

The study involved 44 male volunteers (18-55 years). All brain changes were assessed in the frontal lobes, occipital lobes, basal ganglia and cerebellum, however the detailed analyses focused on the frontal lobes. All participants were examined four times, i.e. before and 0.5-hour, 1 hour and 2 hours after consumption of 150 mL pure vodka (60 g of ethanol).

RESULTS

The highest ethanol levels were identified between 0.5 and 1 hour following alcohol intake. There were significant increases in the concentrations of lipids and lactates approximately one hour after alcohol consumption, and the concentration levels were found to normalise during the following two hours. Some statistically insignificant trends of changes were found for tCr, tCho, mI, GABA, Glc, Glx and tNAA. For the DWI and ADC (Apparent Diffusion Coefficient of water) values, the findings showed statistically insignificant decrease and increase, followed by a tendency towards normalisation. Similar associations in changes of metabolite concentrations and DWI and ADC values were found in the other locations investigated in the study.

CONCLUSION

A single dose of alcohol as used in this experiment produces increases in lipids and lactates in brain tissues that appear reversible.

Development of a Physiologically Based Pharmacokinetic Model for Prediction of Ethanol Concentration-Time Profile in Different Organs

AIMS

A physiologically based pharmacokinetic (PBPK) modeling approach was used to simulate the concentration-time profile of ethanol (EtOH) in stomach, duodenum, plasma and other tissues upon consumption of beer and whiskey under fasted and fed conditions.

METHODS

A full PBPK model was developed for EtOH using the advanced dissolution, absorption and metabolism (ADAM) model fully integrated into the Simcyp Simulator® 15 (Simcyp Ltd., Sheffield, UK). The prediction performance of the developed model was verified and the EtOH concentration-time profile in different organs was predicted.

RESULTS

Simcyp simulation showed ≤ 2-fold difference in values of EtOH area under the concentration-time curve (AUC) in stomach and duodenum as compared to the observed values. Moreover, the simulated EtOH maximum concentration (Cmax), time to reach Cmax (Tmax) and AUC in plasma were comparable to the observed values. We showed that liver is exposed to the highest EtOH concentration, faster than other organs (Cmax = 839.50 mg/L and Tmax = 0.53 h), while brain exposure of EtOH (AUC = 1139.43 mg·h/L) is the highest among all other organs. Sensitivity analyses (SAs) showed direct proportion of EtOH rate and extent of absorption with administered EtOH dose and inverse relationship with gastric emptying time (GE) and steady-state volume of distribution (Vss).

CONCLUSIONS

The current PBPK model approach might help with designing in vitro experiments in the area of alcohol organ damage or alcohol-drug interaction studies.

The Role of Alcohol Metabolism in the Pathology of Alcohol Hangover

The limited number of available studies that examined the pathology of alcohol hangover focused on biomarkers of alcohol metabolism, oxidative stress and the inflammatory response to alcohol as potentially important determinants of hangover severity. The available literature on alcohol metabolism and oxidative stress is reviewed in this article. The current body of evidence suggests a direct relationship between blood ethanol concentration and hangover severity, whereas this association is not significant for acetaldehyde. The rate of alcohol metabolism seems to be an important determinant of hangover severity. That is, fast elimination of ethanol is associated with experiencing less severe hangovers. An explanation for this observation may be the fact that ethanol-in contrast to acetaldehyde-is capable of crossing the blood-brain barrier. With slower ethanol metabolism, more ethanol is able to reach the brain and elicit hangover symptoms. Hangover severity was also significantly associated with biomarkers of oxidative stress. More oxidative stress in the first hours after alcohol consumption was associated with less severe next-day hangovers (i.e., a significant negative correlation was found between hangover severity and malondialdehyde). On the contrary, more oxidative stress at a later stage after alcohol consumption was associated with having more severe next-day hangovers (i.e., a significant positive correlation was found between hangover severity and 8-isoprostane). In conclusion, assessment of biomarkers of alcohol metabolism suggests that fast elimination of ethanol is associated with experiencing less severe hangovers. More research is needed to further examine the complex interrelationship between alcohol metabolism, the role of acetaldehyde and oxidative stress and antioxidants, and the pathology of the alcohol hangover.

Simultaneous edited MRS of GABA, glutathione, and ethanol

The aim of this work was to develop simultaneous edited MRS of γ-aminobutyric acid (GABA), glutathione (GSH), and ethanol (EtOH) using Hadamard encoding and reconstruction of MEGA-edited spectroscopy (HERMES) at 3T. Density-matrix simulations of HERMES were carried out and compared with phantom experiments. In vivo experiments were performed in six healthy volunteers about 30 min after alcohol consumption. Simulations of HERMES showed GABA-, GSH-, and EtOH-edited spectra with low levels of crosstalk and excellent agreement with phantom spectra. In vivo experiments showed well edited GABA signals at 3.0 ppm, GSH at 2.95 ppm, and EtOH at 1.18 ppm in the respective Hadamard combination spectra. Measured integral ratios were 0.082 ± 0.012 for GABA/Cr, 0.037 ± 0.006 for GSH/Cr, and 0.305 ± 0.129 for EtOH/Cr. Simulated, phantom, and in vivo measurements of HERMES show excellent separation of GABA-, GSH-, and EtOH-edited signals with negligible levels of crosstalk. HERMES allows a threefold acceleration of editing while maintaining spectral quality compared with sequentially acquired MEGA-PRESS measurements.

In situ postmortem ethanol quantification in the cerebrospinal fluid by non-water-suppressed proton MRS

Determination of the ethanol concentration in corpses with MRS would allow a reproducible forensic assessment by which evidence is collected in a noninvasive manner. However, although MRS has been successfully used to detect ethanol in vivo, it has not been applied to postmortem ethanol quantification in situ. The present study examined the feasibility of the noninvasive measurement of the ethanol concentration in human corpses with MRS. A total of 15 corpses with suspected alcohol consumption before demise underwent examination in a 3 T whole body scanner. To address the partial overlap of the ethanol and lactate signal in the postmortem spectrum, non-water-suppressed single voxel spectra were recorded in the cerebrospinal fluid (CSF) of the left lateral ventricle via the metabolite cycling technique. The ethanol signals were quantified using the internal water as reference standard, as well as based on a reference signal acquired in a phantom. The measured values were compared with biochemically determined concentrations in the blood (BAC) and CSF (CSFAC). In 8 of the 15 corpses a BAC above zero was determined (range 0.03-1.68 g/kg). In all of these 8 corpses, ethanol was measured in CSF with the proposed MRS protocol. The two applied MRS calibration strategies resulted in similar concentrations. However, the MRS measurements generally overestimated the ethanol concentration by 0.09 g/kg (4%) to 0.72 g/kg (45%) as compared with the CSFAC value. The presented MRS protocol allows the measurement of ethanol in the CSF in human corpses and provides an estimation of the ethanol concentration prior to autopsy. Observed deviations from biochemically determined concentrations are mainly explained by the approximate correction of the relaxation attenuation of the ethanol signal.

Effects of Ethanol Exposure on the Neurochemical Profile of a Transgenic Mouse Model with Enhanced Glutamate Release Using In Vivo 1H MRS

Ethanol (EtOH) intake leads to modulation of glutamatergic transmission, which may contribute to ethanol intoxication, tolerance and dependence. To study metabolic responses to the hyper glutamatergic status at synapses during ethanol exposure, we used Glud1 transgenic (tg) mice that over-express the enzyme glutamate dehydrogenase in brain neurons and release excess glutamate (Glu) in synapses. We measured neurochemical changes in the hippocampus and striatum of tg and wild-type (wt) mice using proton magnetic resonance spectroscopy before and after the animals were fed with diets within which EtOH constituting up to 6.4% of total calories for 24 weeks. In the hippocampus, the EtOH diet led to significant increases in concentrations of EtOH, glutamine (Gln), Glu, phosphocholine (PCho), taurine, and Gln + Glu, when compared with their baseline concentrations. In the striatum, the EtOH diet led to significant increases in concentrations of GABA, Gln, Gln + Glu, and PCho. In general, neurochemical changes were more pronounced in the striatum than the hippocampus in both tg and wt mice. Overall neurochemical changes due to EtOH exposure were very similar in tg and wt mice. This study describes time courses of neurochemical profiles before and during chronic EtOH exposure, which can serve as a reference for future studies investigating ethanol-induced neurochemical changes.

On the Accuracy of In Vivo Ethanol and Acetaldehyde Monitoring, a Key Tile in the Puzzle of Acetaldehyde as a Neuroactive Agent

Over the last 20 years researchers have explored the postulated role of acetaldehyde (ACD) as a mediator of some of the actions of ethanol (EtOH) in the central nervous system (CNS). However, efforts have been hampered mainly by the difficulty of directly measuring in vivo EtOH and ACD levels in the CNS and thus, our knowledge is based on indirect evidences. Although technically challenging, the development of reliable methods for in vivo measurement of ACD and EtOH is of paramount importance to solve the “puzzle of acetaldehyde as a neuroactive agent.” In this short review we discuss the recent advances on brain EtOH pharmacokinetic and state-of-the-art available techniques that could be used for in vivo detect EtOH and ACD both non-invasively (magnetic resonance spectroscopy), and invasively (microdialysis and biosensors). Among the different in vivo sampling techniques described, particular emphasis is paid to the field of enzyme-based amperometric biosensors. Biosensors have gained much attention in recent years for their ability to online monitor biological signals in vivo, and several micro- and nano-structured devices have been successfully used for in vivo studies. Owing to their high temporal and spatial resolution, biosensors could provide the adequate technology for studying in vivo EtOH pharmacokinetic.

Association between overall rate of change in rising breath alcohol concentration and the magnitude of acute tolerance of subjective intoxication via the Mellanby method

OBJECTIVE

The magnitude of acute tolerance is a strong predictor of the development of longer-term chronic tolerance and plays a decisive role in risky decisions (e.g., driving after drinking). Therefore, it is important to identify factors that increase the magnitude of this adaptive process. This study explored whether acute tolerance magnitude varied as a function of the overall rate of increase in breath alcohol concentration (BrAC).

METHODS

Twenty-nine young adult social drinkers (M age = 22.55, SD = 3.10; 62.1% women) consumed a moderate dose of alcohol (men: 0.86 g/kg, women: 0.75 g/kg) in a controlled laboratory setting. Subjective intoxication was assessed at matched BrACs (~0.060 g/dl) on each limb of the BrAC curve.

RESULTS

Hierarchical regression results indicated that faster overall increases in BrAC on the ascending limb were associated with greater acute tolerance for subjective intoxication ratings (p < .01, R²  = .29).

CONCLUSIONS

These results present some of the first evidence that faster increases in BrAC may be associated with greater acute tolerance, as indicated by greater reduction in subjective intoxication across the limbs of the BrAC curve. This greater reduction may, in turn, promote heavier drinking and/or engagement in behaviors for which one is unfit (e.g., driving after drinking).

Lipids and Oxidative Stress Associated with Ethanol-Induced Neurological Damage

The excessive intake of alcohol is a serious public health problem, especially given the severe damage provoked by chronic or prenatal exposure to alcohol that affects many physiological processes, such as memory, motor function, and cognitive abilities. This damage is related to the ethanol oxidation in the brain. The metabolism of ethanol to acetaldehyde and then to acetate is associated with the production of reactive oxygen species that accentuate the oxidative state of cells. This metabolism of ethanol can induce the oxidation of the fatty acids in phospholipids, and the bioactive aldehydes produced are known to be associated with neurotoxicity and neurodegeneration. As such, here we will review the role of lipids in the neuronal damage induced by ethanol-related oxidative stress and the role that lipids play in the related compensatory or defense mechanisms.

Clinical proton MR spectroscopy in central nervous system disorders

A large body of published work shows that proton (hydrogen 1 [(1)H]) magnetic resonance (MR) spectroscopy has evolved from a research tool into a clinical neuroimaging modality. Herein, the authors present a summary of brain disorders in which MR spectroscopy has an impact on patient management, together with a critical consideration of common data acquisition and processing procedures. The article documents the impact of (1)H MR spectroscopy in the clinical evaluation of disorders of the central nervous system. The clinical usefulness of (1)H MR spectroscopy has been established for brain neoplasms, neonatal and pediatric disorders (hypoxia-ischemia, inherited metabolic diseases, and traumatic brain injury), demyelinating disorders, and infectious brain lesions. The growing list of disorders for which (1)H MR spectroscopy may contribute to patient management extends to neurodegenerative diseases, epilepsy, and stroke. To facilitate expanded clinical acceptance and standardization of MR spectroscopy methodology, guidelines are provided for data acquisition and analysis, quality assessment, and interpretation. Finally, the authors offer recommendations to expedite the use of robust MR spectroscopy methodology in the clinical setting, including incorporation of technical advances on clinical units.

Brain proton magnetic resonance spectroscopy of alcohol use disorders

This chapter critically reviews brain proton magnetic resonance spectroscopy ((1)H MRS) studies performed since 1994 in individuals with alcohol use disorders (AUD). We describe the neurochemicals that can be measured in vivo at the most common magnetic field strengths, summarize our knowledge about their general brain functions, and briefly explain some basic human (1)H MRS methods. Both cross-sectional and longitudinal research of individuals in treatment and of treatment-naïve individuals with AUD are discussed and interpreted on the basis of reported neuropathology. As AUDs are highly comorbid with chronic cigarette smoking and illicit substance abuse, we also summarize reports on their respective influences on regional proton metabolite levels. After reviewing research on neurobiologic correlates of relapse and genetic influences on brain metabolite levels, we finish with suggestions on future directions for (1)H MRS studies in AUDs. The review demonstrates that brain metabolic alterations associated with AUDs as well as their cognitive correlates are not simply a consequence of chronic alcohol consumption. Future MR research of AUDs in general has to be better prepared - and supported - to study clinically complex relationships between personality characteristics, comorbidities, neurogenetics, lifestyle, and living environment, as all these factors critically affect an individual's neurometabolic profile. (1)H MRS is uniquely positioned to tackle these complexities by contributing to a comprehensive biopsychosocial profile of individuals with AUD: it can provide non-invasive biochemical information on select regions of the brain at comparatively low overall cost for the ultimate purpose of informing more efficient treatments of AUDs.

Preliminary observation of dynamic changes in alcohol concentration in the human brain with proton magnetic resonance spectroscopy on a 3T MR instrument

PURPOSE

Our purposes were to establish suitable conditions for proton magnetic resonance spectroscopy (MRS) to measure dynamic changes in alcohol concentration in the human brain, to evaluate these changes, and to compare the findings with data from analysis of breath vapor and blood samples.

MATERIALS AND METHODS

We evaluated 4 healthy volunteers (mean age 26.5 years; 3 males, one female) with no neurological findings. All studies were performed with 3-tesla clinical equipment using an 8-channel head coil. We applied our modified single-voxel point-resolved spectroscopy (PRESS) sequence. Continuous measurements of MRS, breath vapor, and blood samples were conducted before and after the subjects drank alcohol with a light meal. The obtained spectra were quantified by LCModel Ver. 6.1, and the accuracy of the MRS measurements was estimated using the estimated standard deviation expressed in percentage (%SD) as a criterion.

RESULTS

Alcohol peaks after drinking were clearly detected at 1.2 ppm for all durations of measurement. Good correlations between breath vapor or blood sample and MRS were found by sub-minute MRS measurement. The continuous measurement showed time-dependent changes in alcohol in the brain and various patterns that differed among subjects.

CONCLUSIONS

The clinical 3T equipment enables direct evaluation of sub-minute changes in alcohol metabolism in the human brain.

Chronic ethanol (EtOH) consumption differentially alters gray and white matter EtOH methyl ¹H magnetic resonance intensity in the primate brain

BACKGROUND

In vivo magnetic resonance spectroscopy (MRS) has previously been used to directly monitor brain ethanol (EtOH). It has been proposed that the EtOH methyl ¹H resonance intensity is larger in EtOH-tolerant individuals than in sensitive individuals. To characterize the relationship between long-term EtOH exposure and the brain EtOH MRS intensity, we present data from a longitudinal experiment conducted using nonhuman primate subjects.

METHODS

In vivo MRS was used to measure the gray matter (GM) and white matter (WM) EtOH methyl ¹H MRS intensity in 18 adult male rhesus macaques at 4 time points throughout the course of a chronic drinking experiment. Time points were prior to EtOH drinking, following a 3-month EtOH induction procedure, and following 6, and 12 subsequent months of 22 h/d of "open access" to EtOH (4% w/v) and water.

RESULTS

The EtOH methyl ¹H MRS intensity, which we observed to be independent of age over the range examined, increased with chronic EtOH exposure in GM and WM. In GM, MRS intensity increased from naïve level following the EtOH induction period (90 g/kg cumulative EtOH intake). In WM, MRS intensity was not significantly different from the EtOH-naïve state until after 6 months of 22-hour free access (110 to 850 g/kg cumulative intake range). The WM MRS intensity in the EtOH-naïve state was positively correlated with future drinking, and the increase in WM MRS intensity was negatively correlated with the amount of EtOH consumed throughout the experiment.

CONCLUSIONS

Chronic exposure to EtOH is associated with brain changes that result in differential increases in EtOH MRS intensity in GM and WM. The EtOH-naïve WM MRS intensity pattern is consistent with its previously proposed relationship to innate tolerance to the intoxicating effects of EtOH. EtOH-dependent MRS intensity changes in GM required less EtOH exposure than was necessary to produce changes in WM. Within WM, an unexpected, potentially age dependent, enhanced sensitivity to EtOH in light drinkers relative to heavy drinkers was observed.

Intravenous ethanol infusion decreases human cortical γ-aminobutyric acid and N-acetylaspartate as measured with proton magnetic resonance spectroscopy at 4 tesla

BACKGROUND

Ethanol modulates glutamate and γ-aminobutyric (GABA) function. However, little is known about the acute pharmacologic effects of ethanol on levels of GABA, glutamate, and other metabolites measurable in the human cortex in vivo with proton magnetic resonance spectroscopy ((1)H-MRS).

METHODS

Eleven healthy social drinkers received two intravenous ethanol infusions that raised breath alcohol levels to a clamped plateau of 60 mg/dL over 60-70 min. The first infusion established tolerability of the procedure, and the second procedure, conducted 15 ± 12 days later, was performed during (1)H-MRS of occipital GABA, glutamate, and other metabolites.

RESULTS

The time course of brain ethanol approximated that of breath ethanol, but venous ethanol lagged by approximately 7 min. The GABA fell 13 ± 8% after 5 min of the ethanol infusion and remained reduced (p = .003) throughout the measurement. The combination of N-acetylaspartate and N-acetylaspartyl glutamate (summed as NAA) fell steadily during the infusion by 8 ± 3% (p = .0036).

CONCLUSIONS

Ethanol reduced cortical GABA and NAA levels in humans. Reductions in GABA levels are consistent with facilitation of GABA(A) receptor function by ethanol. The gradual decline in NAA levels suggests inhibition of neural or metabolic activity in the brain.

Perturbation of the glutamate-glutamine system in alcohol dependence and remission

As acute ethanol exposure inhibits N-methyl-D-aspartate glutamate (Glu) receptors, sudden withdrawal from chronic alcohol use may lead to an increased activation of these receptors with excitotoxic effects. In the longer term, brain levels of Glu and its metabolites, such as glutamine (Gln), are likely to be chronically altered by alcohol, possibly providing a measure of overall abnormal Glu-Gln cycling. However, few studies have assessed concentrations of these metabolites in clinical populations of individuals with alcohol use disorders. Glu and Gln levels were compared in groups of 17 healthy controls and in 13 participants with alcohol dependence. Within the alcohol-dependent group, seven participants had current alcohol use disorder (AUD), and six had AUD in remission for at least 1 year (AUD-R). Neurometabolite concentrations were measured with proton magnetic resonance spectroscopy ((1)H-MRS) in a predominantly gray matter voxel that included the bilateral anterior cingulate gyri. Tissue segmentation provided an assessment of the proportion of gray matter in the (1)H-MRS voxel. The Drinker Inventory of Consequences (DrInC) and Form-90 were administered to all participants to quantify alcohol consequences and use. Glu level was lower and Gln level was higher in the AUD and AUD-R groups relative to the control group; creatine, choline, myo-inositol, and total N-acetyl groups, primarily N-acetylaspartate did not differ across groups. These results were not confounded by age, sex, or proportion of gray matter in the (1)H-MRS voxel. Neurometabolite concentrations did not differ between AUD and AUD-R groups. Subsequent regressions in the combined clinical group, treating voxel gray matter proportion as a covariate, revealed that total score on the DrInC was positively correlated with Gln but negatively correlated with both Glu and gray matter proportion. Regression analyses, including DrInC scores and smoking variables, identified a marginal independent effect of smoking on Gln. The current findings of higher Gln and lower Glu in the combined AUD and AUD-R groups might indicate a perturbation of the Glu-Gln cycle in alcohol use disorders. The absence of differences in mean Glu and Gln between the AUD and AUD-R groups suggests that altered Glu-Gln metabolism may either predate the onset of abuse or persist during prolonged abstinence.

The effect of ethanol on human brain metabolites longitudinally characterized by proton MR spectroscopy

The effect ethanol exerts on the human brain has not yet been addressed by longitudinal magnetic resonance (MR) spectroscopic experiments. Therefore, we longitudinally characterized cerebral metabolite changes in 15 healthy individuals by proton magnetic resonance spectroscopy ((1)H-MRS) subsequent to the ingestion of a standard beverage (mean peak blood alcohol concentration (BAC): 51.43 +/- 10.27 mg/dL). Each participant was examined before, over 93.71 +/- 11.17 mins immediately after and 726.36 +/- 94.96 mins (12.11 +/ -1.58 h) past per os alcohol exposure. Fronto-mesial and cerebellar ethanol concentrations over time were similar as determined by the LCModel analysis of spectral data. Alcohol-induced changes of fronto-mesial creatine, choline, glucose, inositol and aspartate levels at 5.79 +/- 2.94 [corrected] mins upon ingestion as well as cerebellar choline and inositol levels at 8.64 +/- 2.98 [corrected] mins past exposure. Closely associated with ethanol concentrations, supratentorial creatine, choline, inositol and aspartate levels decreased after ethanol administration, whereas glucose levels increased. Similarly, infratentorial choline and inositol concentrations were negatively correlated with ethanol levels over time. There were no changes in N-acetyl-aspartate levels upon alcohol exposure. Furthermore, no influence of ethanol on brain water integrals was detected. Ethanol consumption may directly increase oxidative stress and the neuronal vulnerability to it. In addition, our results are compatible with ethanol-induced cell membrane modifications and alternative energy substrate usage upon alcohol exposure.

Acute tolerance to rate-decreasing effects of single doses of ethanol

Acute tolerance occurs when behavioral impairment is greater at a given blood ethanol concentration (BAC) on the ascending versus descending limb of the BAC-time curve following administration of a single dose of ethanol, however studies utilizing learned behaviors have not been widely reported. We assessed acute tolerance to single doses of ethanol in five Lewis rats responding under a fixed-ratio (FR8) schedule of food presentation. Response rates for food during 1-min components (ending 2, 4, 11, 18, 33, and 57 min after ethanol administration) were determined, and BAC was measured immediately after each component using a rat breathalyzer. Ethanol (0.4, 0.6, 0.8, and 1.2 g/kg, i.p.) produced dose-related decreases in responding for food that tended to recover over time for all but the highest dose tested. Similarly, dose-related increases in BAC were also observed. Using either an analysis that expressed impairment per unit BAC on the ascending limb versus the descending limb (by assessing the area under the curve (AUC) for behavior and BAC on each limb), the slope of the function that relates the behavioral effect to BAC (each expressed as percent maximum effect), or a variant of the Mellanby method (hysteresis), acute tolerance was observed following a dose of 0.4 g/kg ethanol. Though behavior appeared to recover on the descending limb following higher doses (especially 0.6 and 0.8 g/kg), acute tolerance to these doses was not present.

Development of a cone-shape phantom for multi-voxel MR spectroscopy

The purpose of this study was to develop a cone-shape phantom for multi-voxel magnetic resonance spectroscopy (MRS) and to evaluate MR spectra using the cone-shape phantom we developed in this study. A cone-shape MRS phantom was developed with a combination of cone-shape vials. The cylindrical main body was made of acrylic resin and the cone-shape vials were fabricated from poly-ethylene cones. Each cone of the phantom was filled with various metabolite materials. 1.5T GE and 3T Philips systems were used for the single voxel spectroscopy (SVS) as well as for the multi-voxel spectroscopy (MVS). Identification and quantification of the metabolite materials in the cone-shape phantom were done by the SAGE post-program. The MR images and spectra of the cone-shape phantom were obtained from the assigned slice position. The high order shimming control provided enhanced resolution in the SVS and MVS. The area and amplitude were proportional to the metabolite volume in the voxel. The present study demonstrated that the cone-shape phantom was useful for the metabolite quantification. Thus, we propose that the cone-shape phantom can be used for the evaluation of quality control of the MR spectra obtained from SVS and MVS.

In vivo quantification of ethanol kinetics in rat brain

Proton magnetic resonance spectroscopy was used at 3T to measure the uptake and clearance of brain ethanol in rats after bolus intraperitoneal (i.p.) or intragastric (i.g.) alcohol injection, and to estimate the effects of acute alcohol on brain metabolites. The observation duration was 1-1.5 h with temporal resolution of alcohol sampling ranging from 4 s-4 min. The observed time course of alcohol brain concentration followed a consistent pattern characterized by a rapid absorption, an intermediate distribution, and a slower clearance that approached a linear decay. In a sample of eight healthy Wistar rats, the intercept of the linear clearance term, extrapolated back to the time of injection, correlated well with the administered dose per unit of lean body mass. Alcohol concentration estimation based on spectroscopically measured clearance was compared with blood alcohol levels from blood samples at the end of observation, and were in good agreement with the administered dose. Serial proton spectroscopy measurements provide a valid in vivo method for quantifying brain alcohol uptake and elimination kinetics in real time.

Visibility of vascular phenylalanine in dynamic uptake studies in humans using magnetic resonance spectroscopy

In general, vascular contributions to the in vivo magnetic resonance (MR) brain spectrum are too small to be relevant. In cerebral uptake studies, however, vascular contributions may constitute a major confounder. MR visibility of vascular Phe was investigated by recording localized spectra from fully oxygenated and well-mixed whole blood. Blood Phe levels determined by MR spectroscopy (MRS) and ion-exchange chromatography showed excellent correlation. In addition, effects of blood flow were shown to have a small effect on signal amplitude with the MRS methodology used. Hence, blood Phe is almost completely MR visible at 1.5 T, even though it is severely broadened at higher fields. Without appropriate correction, cerebral Phe influx in studies of brain Phe uptake in phenylketonuria patients or healthy subjects would appear to be faster and lead to higher levels. Similar effects are envisaged for studies of ethanol or glucose uptake across the blood-brain barrier.

Ethanol increases nuclear factor-kappa B activity in human astroglial cells

Alcohol abuse adversely affects essentially all the organs of the body, either directly or indirectly. Ethanol may contribute to brain damage via inflammation. Ethanol may also alter CNS immunocompetence and further the progression of certain CNS infections. Nuclear factor (NF)-kappa B helps regulate inflammatory gene expression in glia. It is possible that ethanol effects on CNS pathology are partly a consequence of ethanol modulation of NF-kappa B-associated pathways in glia. We have assessed the effects of 0.5-6 h ethanol exposure on cytokine (5 ng/ml interleukin-1 beta + 100 ng/ml interferon gamma + 30 ng/ml tumor necrosis factor-alpha)-induced NF-kappa B activation in human A172 astroglial cells. Immunoblot analysis indicated that NF-kappa B p65 nuclear translocation occurred within 0.5 h after cytokine stimulation. Stimulation in the presence of ethanol resulted in increased nuclear p65 levels at 3 h, with 200 mM causing a greater increase than 50 mM ethanol. Gel shift assay data suggested that cytokine-induced NF-kappa B binding activity was greatest in cells exposed to 50 mM ethanol, followed by 200 and 0 mM ethanol exposed cells, respectively. Thus, in cytokine-stimulated cells, 200 mM ethanol resulted in greater nuclear p65 levels, yet, 50 mM ethanol exposure resulted in more pronounced DNA binding by NF-kappa B. These findings demonstrate that acute ethanol enhances p65 activity in human astroglia and further support the hypothesis that ethanol-mediated brain pathology involves modulation of NF-kappa B pathways. A better understanding of the mechanistic events involved in ethanol-induced CNS pathology should provide for therapeutic strategies to combat detrimental effects of alcohol on the CNS.

Indirect imaging of ethanol via magnetization transfer at high and low magnetic fields

Ethanol (EtOH) is believed to exert its neurochemical effects through interactions with brain cellular components, which causes a fraction of brain EtOH to have a lower molecular mobility. This facilitates magnetization transfer to other molecules similarly associated with macromolecules, such as water. It was hypothesized that this effect can be used in vivo to image EtOH indirectly via the much stronger brain tissue water resonance. EtOH-containing bovine serum albumin samples were used to demonstrate magnetic coupling between EtOH and water at 7 T and 1.5 T. Spectroscopy and imaging experiments demonstrated that EtOH signal saturation yielded greater water signal reduction than inversion and that this reduction scaled with EtOH concentration in the BSA samples. In human brain at physiologically relevant brain EtOH concentrations, water signal reductions were measurable when saturating the EtOH resonance. Strengths and limitations of indirectly imaging brain EtOH are discussed.

Magnetic resonance spectroscopy and its applications in psychiatry

OBJECTIVE

This paper briefly describes neuroimaging using magnetic resonance spectroscopy (MRS) and provides a systematic review of its application to psychiatric disorders.

METHOD

A literature review (Index Medicus/Medline) was carried out, as well as a review of other relevant papers and data known to the authors.

RESULTS

Magnetic resonance spectroscopy is a complex and sophisticated neuroimaging technique that allows reliable and reproducible quantification of brain neurochemistry provided its limitations are respected. In some branches of medicine it is already used clinically, for instance, to diagnose tumours and in psychiatry its applications are gradually extending beyond research. Neurochemical changes have been found in a variety of brain regions in dementia, schizophrenia and affective disorders and promising discoveries have also been made in anxiety disorders.

CONCLUSION

Magnetic resonance spectroscopy is a non-invasive investigative technique that has provided useful insights into the biochemical basis of many neuropsychiatric disorders. It allows direct measurement, in vivo, of medication levels within the brain and has made it possible to track the neurochemical changes that occur as a consequence of disease and ageing or in response to treatment. It is an extremely useful advance in neuroimaging technology and one that will undoubtedly have many clinical uses in the near future.

[Applications of magnetic resonance spectrometry (MRS) in the study of metabolic disturbances affecting the brain in alcoholism]

The purpose of this article is to provide an overview of the current applications of magnetic resonance spectroscopy (MRS) to the investigation of cerebral metabolism in alcoholic patients. The specific metabolic changes associated with the intoxication process (tolerance, dependance), abstinence and alcohol-related diseases (alcoholic encephalopathy, cirrhosis, Gayet-Wernicke's encephalopathy, Marchiafava-Bignami syndrome) are described.