Hippocampal volumes and cognitive functions in adult alcoholic patients with adolescent-onset

Sex-Specific Impact of Fkbp5 on Hippocampal Response to Acute Alcohol Injection: Involvement in Alterations of Metabolism-Related Pathways

High levels of alcohol intake alter brain gene expression and can produce long-lasting effects. FK506-binding protein 51 (FKBP51) encoded by Fkbp5 is a physical and cellular stress response gene and has been associated with alcohol consumption and withdrawal severity. Fkbp5 has been previously linked to neurite outgrowth and hippocampal morphology, sex differences in stress response, and epigenetic modification. Presently, primary cultured Fkbp5 KO and WT mouse neurons were examined for neurite outgrowth and mitochondrial signal with and without alcohol. We found neurite specification differences between KO and WT; particularly, mesh-like morphology was observed after alcohol treatment and confirmed higher MitoTracker signal in cultured neurons of Fkbp5 KO compared to WT at both naive and alcohol-treated conditions. Brain regions that express FKBP51 protein were identified, and hippocampus was confirmed to possess a high level of expression. RNA-seq profiling was performed using the hippocampus of naïve or alcohol-injected (2 mg EtOH/Kg) male and female Fkbp5 KO and WT mice. Differentially expressed genes (DEGs) were identified between Fkbp5 KO and WT at baseline and following alcohol treatment, with female comparisons possessing a higher number of DEGs than male comparisons. Pathway analysis suggested that genes affecting calcium signaling, lipid metabolism, and axon guidance were differentially expressed at naïve condition between KO and WT. Alcohol treatment significantly affected pathways and enzymes involved in biosynthesis (Keto, serine, and glycine) and signaling (dopamine and insulin receptor), and neuroprotective role. Functions related to cell morphology, cell-to-cell signaling, lipid metabolism, injury response, and post-translational modification were significantly altered due to alcohol. In summary, Fkbp5 plays a critical role in the response to acute alcohol treatment by altering metabolism and signaling-related genes.

Association of Plasma Pro-Brain-Derived Neurotrophic Factor (proBDNF)/Mature Brain-Derived Neurotrophic Factor (mBDNF) Levels with BDNF Gene Val66Met Polymorphism in Alcohol Dependence

BACKGROUND In a previous study, we reported that pro-brain-derived neurotrophic factor (proBDNF) was involved in the pathology of alcohol dependence, and the single-nucleotide polymorphism (SNP) Val66Met was located at the prodomain of the brain-derived neurotrophic factor gene (BDNF). This polymorphism has been reported to affect intracellular trafficking and activity-dependent secretion of BDNF. Our present research investigated the relationships between the BDNF Val66Met polymorphism and the plasma levels of proBDNF and mature brain-derived neurotrophic factor (mBDNF) in patients with alcohol dependence. MATERIAL AND METHODS The BDNF gene Val66Met polymorphism was genotyped in 59 alcohol-dependent patients and 37 age- and sex-matched controls, and the plasma levels of proBDNF and mBDNF were assessed by enzyme-linked immunosorbent assay in all participants. RESULTS No association was found between the BDNF gene Val66Met polymorphism and alcohol dependence (P>0.05). In comparison with the control group, the level of plasma proBDNF in the alcohol-dependence group was notably increased (Z=-2.228, P=0.026), while the level of mBDNF was remarkedly decreased (Z=-2.014, P=0.044). In the alcohol-dependence group, significant associations were not found between the Val66Met polymorphisms and proBDNF and mBDNF plasma levels (P>0.05). The plasma level of proBDNF was positively correlated with the average daily alcohol consumption in the last month (r=0.344, P=0.008) and drinking history (r=0.317, P=0.014), while the plasma level of mBDNF had negative effects (r=-0.361, P=0.005, with the average daily alcohol consumption; r=-0.427, P=0.001, with drinking history). CONCLUSIONS The BDNF gene Val66Met polymorphism does not appear to affect the secretion of proBDNF and mBDNF in Chinese patients with alcohol dependence. Furthermore, this study reconfirmed that the plasma levels of proBDNF and mBDNF were correlated with the average daily alcohol consumption in the last month and with drinking history.

Functional Activation of Newborn Neurons Following Alcohol-Induced Reactive Neurogenesis

Abstinence after alcohol dependence leads to structural and functional recovery in many regions of the brain, especially the hippocampus. Significant increases in neural stem cell (NSC) proliferation and subsequent "reactive neurogenesis" coincides with structural recovery in hippocampal dentate gyrus (DG). However, whether these reactively born neurons are integrated appropriately into neural circuits remains unknown. Therefore, adult male rats were exposed to a binge model of alcohol dependence. On day 7 of abstinence, the peak of reactive NSC proliferation, rats were injected with bromodeoxyuridine (BrdU) to label dividing cells. After six weeks, rats underwent Morris Water Maze (MWM) training then were sacrificed ninety minutes after the final training session. Using fluorescent immunohistochemistry for c-Fos (neuronal activation), BrdU, and Neuronal Nuclei (NeuN), we investigated whether neurons born during reactive neurogenesis were incorporated into a newly learned MWM neuronal ensemble. Prior alcohol exposure increased the number of BrdU+ cells and newborn neurons (BrdU+/NeuN+ cells) in the DG versus controls. However, prior ethanol exposure had no significant impact on MWM-induced c-Fos expression. Despite increased BrdU+ neurons, no difference in the number of activated newborn neurons (BrdU+/c-Fos+/NeuN+) was observed. These data suggest that neurons born during alcohol-induced reactive neurogenesis are functionally integrated into hippocampal circuitry.

Ethanol-Induced Neuronal and Cognitive/Emotional Impairments are Accompanied by Down-Regulated NT3-TrkC-ERK in Hippocampus

AIMS

Ethanol ingestion affects cognition and emotion, which have been attributed to the dysfunction of specific brain structures. Studies of alcoholic patients and animal models consistently identify reduced hippocampal mass as a key ethanol-induced brain adaptation. This study evaluated how neuroadaptation in the hippocampus (Hip) produced by ethanol contributed to related behavioral deficits in male and female rats.

METHODS

Effects of acute, short-term and long-term ethanol exposure on the anxiety-like behavior and recognition memory on adult male and female Sprague-Dawley rats were assessed using elevated plus maze test and novel object recognition test, respectively. In addition, in order to investigate the direct effect of ethanol on hippocampal neurons, primary culture of hippocampal neurons was exposed to ethanol (10, 30 and 90 mM; 1, 24 and 48 h), and viability (CCK-8) and morphology (immunocytochemistry) were analyzed at structural levels. Western blot assays were used to assess protein levels of NT3-TrkC-ERK.

RESULTS

Acute and short-term ethanol exposure exerted anxiolytic effects, whereas long-term ethanol exposure induced anxiogenic responses in both sexes. Short-term ethanol exposure impaired spatial memory only in female rats, whereas long-term ethanol exposure impaired spatial and recognition memory in both sexes. These behavioral impairments and ethanol-induced loss of hippocampal neurons and decreased cell viability were accompanied by downregulated NT3-TrkC-ERK pathway.

CONCLUSION

These results indicate that NT3-TrkC-ERK signaling in the Hip may play an important role in ethanol-induced structural and behavioral impairments.

Associations of Binge Drinking With Vascular Brain Injury and Atrophy in Older American Indians: The Strong Heart Study

Objectives: American Indians (AIs) generally consume less alcohol than the US general population; however, the prevalence of alcohol use disorder is higher. This is the first large cohort study to examine binge drinking as a risk factor for vascular brain injury (VBI). Methods: We used linear and Poisson regression to examine the association of self-reported binge drinking with VBI, measured via magnetic resonance imaging (MRI), in 817 older AIs who participated in the Strong Heart and Cerebrovascular Disease and Its Consequences in American Indians studies. Results: Any binge drinking at multiple time-points was associated with increased sulcal (β = 0.360, 95% CI [0.079, 0.641]) and ventricle dilatation (β = 0.512, 95% CI [0.174, 0.850]) compared to no binge drinking. Discussion: These observed associations are consistent with previous findings. Identifying how binge drinking may contribute to VBI in older AIs may suggest modifiable health behaviors for neurological risk reduction and disease prevention.

Alcohol Use Disorder, Neurodegeneration, Alzheimer's and Parkinson's Disease: Interplay Between Oxidative Stress, Neuroimmune Response and Excitotoxicity

Alcohol use disorder (AUD) has been associated with neurodegenerative diseases such as Alzheimer's and Parkinson's disease. Prolonged excessive alcohol intake contributes to increased production of reactive oxygen species that triggers neuroimmune response and cellular apoptosis and necrosis via lipid peroxidation, mitochondrial, protein or DNA damage. Long term binge alcohol consumption also upregulates glutamate receptors, glucocorticoids and reduces reuptake of glutamate in the central nervous system, resulting in glutamate excitotoxicity, and eventually mitochondrial injury and cell death. In this review, we delineate the following principles in alcohol-induced neurodegeneration: (1) alcohol-induced oxidative stress, (2) neuroimmune response toward increased oxidants and lipopolysaccharide, (3) glutamate excitotoxicity and cell injury, and (4) interplay between oxidative stress, neuroimmune response and excitotoxicity leading to neurodegeneration and (5) potential chronic alcohol intake-induced development of neurodegenerative diseases, including Alzheimer's and Parkinson's disease.

Hippocampal subfield volumes in abstinent men and women with a history of alcohol use disorder

Alcohol Use Disorder (AUD) has been associated with abnormalities in hippocampal volumes, but these relationships have not been fully explored with respect to sub-regional volumes, nor in association with individual characteristics such as age, gender differences, drinking history, and memory. The present study examined the impact of those variables in relation to hippocampal subfield volumes in abstinent men and women with a history of AUD. Using Magnetic Resonance Imaging at 3 Tesla, we obtained brain images from 67 participants with AUD (31 women) and 64 nonalcoholic control (NC) participants (31 women). The average duration of the most recent period of sobriety for AUD participants was 7.1 years. We used Freesurfer 6.0 to segment the hippocampus into 12 regions. These were imputed into statistical models to examine the relationships of brain volume with AUD group, age, gender, memory, and drinking history. Interactions with gender and age were of particular interest. Compared to the NC group, the AUD group had approximately 5% smaller subiculum, CA1, molecular layer, and hippocampal tail regions. Age was negatively associated with volumes for the AUD group in the subiculum and the hippocampal tail, but no significant interactions with gender were identified. The relationships for delayed and immediate memory with hippocampal tail volume differed for AUD and NC groups: Higher scores on tests of immediate and delayed memory were associated with smaller volumes in the AUD group, but larger volumes in the NC group. Length of sobriety was associated with decreasing CA1 volume in women (0.19% per year) and increasing volume size in men (0.38% per year). The course of abstinence on CA1 volume differed for men and women, and the differential relationships of subfield volumes to age and memory could indicate a distinction in the impact of AUD on functions of the hippocampal tail. These findings confirm and extend evidence that AUD, age, gender, memory, and abstinence differentially impact volumes of component parts of the hippocampus.

Ginsenoside Rg1 alleviates repeated alcohol exposure-induced psychomotor and cognitive deficits

Background

Chronic alcohol consumption disrupts psychomotor and cognitive functions, most of which are subserved by the dysfunction of hippocampus. Dysregulated excitatory glutamatergic transmission is implicated in repeated alcohol induced psychomotor and cognitive impairment. Ginsenoside Rg1, one of the main active ingredient of the traditional tonic medicine Panax ginseng C.A. Meyer (Araliaceae), has been used to treat cognitive deficits. Particularly, Rg1 has been demonstrated to improve hippocampus-dependent learning in mice and attenuate glutamate-induced excitotoxicity in vitro. Thus, in the present research, we sought to investigate the therapeutic effects of Ginsenoside Rg1 on repeated alcohol induced psychomotor and cognitive deficits in hippocampal-dependent behavioral tasks and unravel the underpinnings of its neuroprotection.

Methods

Male ICR (CD-1) mice were consecutively intragastrically treated with 20% (w/v) alcohol for 21 days. Then, behavior tests were conducted to evaluate repeated alcohol induced psychomotor and cognitive deficits. Histopathological changes, and biochemical and molecular alterations were assessed to determine the potential neuroprotective mechanism of Rg1.

Results

The results suggested that Rg1, at the optimal dose of 6 mg/kg, has the potential to ameliorate repeated alcohol induced cognitive deficits by regulating activities of NR2B containing NMDARs and excitotoxic signaling.

Conclusion

Our findings further provided a new strategy to treat chronic alcohol exposure induced adverse consequences.

Hydrogen sulfide improves spatial memory impairment via increases of BDNF expression and hippocampal neurogenesis following early postnatal alcohol exposure

According to experimental and clinical findings, fetal brain development may be interrupted by maternal alcohol consumption during pregnancy. Adult hippocampal neurogenesis is thought to play a role in cognition function (i.e. learning and memory). Recent evidence suggests that ethanol administration causes major apoptotic neurodegeneration in many regions of the rats' developing brain during the synaptogenesis period. Based on the recent studies, H₂S improve learning and memory via increased neurogenesis and antiapoptotic mechanisms in different animal models. In this study, we aimed to evaluate the protective effects of hydrogen sulfide on alcohol-induced memory impairment, hippocampus neurogenesis and neuronal apoptosis in rat pups with postnatal ethanol exposure. Administration of ethanol to male rat pups was performed through intragastric intubation on postnatal days 2-10. The pups were administered 1 mg/kg of NaHS (H₂S donor) on postnatal days 2-10. For examining the spatial memory, Morris water maze test was carried out 36 days after birth. Following the behavioral test, immunohistochemical staining was performed to evaluate the expression levels of BrdU, BDNF and Apoptotic cell death was detected by TUNEL staining. Hydrogen sulfide (H₂S) treatment could significantly improve spatial memory impairment (P < 0.05) and significantly increase the expression of BrdU and BDNF in dentate gyrus area (P < 0.05). It also decreased positive TUNEL cells, compared with the ethanol group (P < 0.01). Based on the findings, H₂S makes significant neuroprotective effects on Ethanol neurotoxicity due to its neurogenesis and anti-apoptotic activity.

Difference in Cognitive Function by First Onset Age of Alcohol Induced Blackout and Its Duration

Objective

Alcohol-induced blackout (blackout) is a typical early symptom of cognitive impairment caused by drinking. However, the first onset age of blackout or the duration after onset of blackout has not been directly compared in previous studies. The purpose of this study was to investigate the differences in cognitive function to the first start age of blackouts and their duration.

Methods

Thirty-one male subjects were included in this study. Their age at the first blackout and the duration after the onset of blackout were investigated. Neuropsychological tests were conducted to determine their attention, memory, and executive function. Subjects were divided into three groups according to their age of the first onset blackout (group O1, < 20 years; group O2, 21–39 years; and group O3, > 40 years). Subjects were also divided into three groups by duration after the onset of blackout (P1, < 10 years; P2, 10–29 years; and P3, > 30 years). We then examined differences in neurocognitive function among these groups.

Results

O1 tended to have a lower memory score than O2 (F = 3.28, p = 0.053). Significant differences were observed in attention and executive function between groups P1 and P3 (Digit Span_backward: F = 6.07, p < 0.05; visual span_forward: F = 4.19, p < 0.05; executive intelligence quotient: F = 3.55, p < 0.05).

Conclusion

Greater memory impairment was detected in subjects having an earlier age of the first blackout. The longer the duration after the onset of blackout, the more impaired their attention and executive function skills.

Cerebrolysin attenuates ethanol-induced spatial memory impairments through inhibition of hippocampal oxidative stress and apoptotic cell death in rats

The present study investigates the potential neuroprotective effect of cerebrolysin (CBL), a combination of neurotrophic factors, on the cognitive and biochemical alterations induced by chronic ethanol administration in rats. The animals were divided into five groups as follows: control; ethanol (4 g/kg, for 30 days) plus normal saline (Ethanol + NS); ethanol plus CBL 1 mL/kg (Ethanol + CBL 1), ethanol plus CBL 2.5 mL/kg (Ethanol + CBL 2.5); and ethanol plus CBL 5 mL/kg (Ethanol + CBL 5). The Morris water maze (MWM) test was performed to assess cognitive impairment. The status of the lipid peroxidation marker MDA, antioxidant capacity, as well as alterations of the apoptotic factors such as Bcl-2, BAX, and cleaved caspase-9 and -3, were evaluated in the hippocampus. The results showed that CBL treatment not only normalized the increased MDA levels in the alcoholic rats and enhanced antioxidant defense, but also reduced the Bax/Bcl-2 ratio and cleaved caspase-9 and -3 in the hippocampus. These results were parallel with improvement in spatial memory performance in the MWM test. The findings of the present study provide evidence for the promising therapeutic effect of CBL in chronic ethanol consumption through counteracting oxidative stress and apoptosis markers.

Hippocampal granule cell loss in human chronic alcohol abusers

Chronic alcohol abuse causes cognitive impairments associated with neurodegeneration and volume loss in the human hippocampus. Here, we hypothesize that alcohol reduces the number of granule cells in the human dentate gyrus and consequently contribute to the observed volume loss. Hippocampal samples were isolated from deceased donors with a history of chronic alcohol abuse and from controls with no alcohol overconsumption. From each case, a sample from the mid-portion of hippocampus was sectioned, immunostained for the neuronal nuclear marker NeuN, and counter stained with hematoxylin. Granule cell number and volume of granular cell layer in the dentate gyrus were estimated using stereology. We found a substantial reduction in granule cell number and also a significantly reduced volume of the granular cell layer of chronic alcohol abusers as compared to controls. In controls there was a slight age-related decline in the number of granule cells and volume of granular cell layer in line with previous studies. This was not observed among the alcoholics, possibly due to a larger impact of alcohol abuse than age on the degenerative changes in the dentate gyrus. Loss of neurons in the alcoholic group could either be explained by an increase of cell death or a reduced number of new cells added to the granular cell layer. However, there is no firm evidence for an increased neuronal death by chronic alcohol exposure, whereas a growing body of experimental data indicates that neurogenesis is impaired by alcohol. In a recent study, we reported that alcoholics show a reduced number of stem/progenitor cells and immature neurons in the dentate gyrus, hence that alcohol negatively affects hippocampal neurogenesis. The present results further suggest that such impairment of neurogenesis by chronic alcohol abuse also results in a net loss of granule cells in the dentate gyrus of hippocampus.

Activation of neural stem cells from quiescence drives reactive hippocampal neurogenesis after alcohol dependence

Neural stem cell-driven adult neurogenesis contributes to the integrity of the hippocampus. Excessive alcohol consumption in alcoholism results in hippocampal degeneration that may recover with abstinence. Reactive, increased adult neurogenesis during abstinence following alcohol dependence may contribute to recovery, but the mechanism driving reactive neurogenesis is not known. Therefore, adult, male rats were exposed to alcohol for four days and various markers were used to examine cell cycle dynamics, the percentage and number of neural progenitor cell subtypes, and the percentage of quiescent versus activated progenitors. Using a screen for cell cycle perturbation, we showed that the cell cycle is not likely altered at 7 days in abstinence. As the vast majority of Bromodeoxyuridine-positive (+) cells were co-labeled with progenitor cell marker, Sox2, we then developed a quadruple fluorescent labeling scheme to examine Type-1, -2a, -2b and -3 progenitor cells simultaneously. Prior alcohol dependence indiscriminately increased all subtypes at 7 days, the peak of the reactive proliferation. An evaluation of the time course of reactive cell proliferation revealed that cells begin proliferating at 5 days post alcohol, where only actively dividing Type 2 progenitors were increased by alcohol. Furthermore, prior alcohol increased the percentage of actively dividing Sox2+ progenitors, which supported that reactive neurogenesis is likely due to the activation of progenitors out of quiescence. These observations were associated with granule cell number returning to normal at 28 days. Therefore, activating stem and progenitor cells out of quiescence may be the mechanism underlying hippocampal recovery in abstinence following alcohol dependence.

ProBDNF/p75NTR/sortilin pathway is activated in peripheral blood of patients with alcohol dependence

Alcohol dependence is a worldwide problem with a great social and economic burden in many countries. A number of studies have suggested that BDNF (mature BDNF) and its precursor (proBDNF) play important roles in the alcohol dependence. However, what roles of the mBDNF/proBDNF pathways play during the pathological process of alcohol dependence are not clearly understood. In our clinical study, peripheral blood was sampled from 30 male patients with alcohol dependence and 50 healthy males (as control). The protein levels of proBDNF, p75NTR, sortilin, mBDNF, TrkB and mRNA levels of BDNF, p75NTR, sortilin, and TrkB were detected in the peripheral blood in our study. We found that the protein levels of proBDNF and p75NTR were increased, but not the sortilin protein level; while the TrkB protein level was decreased in the alcohol dependence patients compared with healthy controls. Moreover, the mRNA levels of p75NTR and sortilin from the lymphocytes were slightly increased; while BDNF and TrkB were significantly decreased. The ELISA results of mBDNF and TrkB were declined in the alcohol dependence group. The levels of mBDNF and TrkB were negatively correlated with the average amount of daily ethanol consumption, and the levels of proBDNF, p75NTR and sortilin were positively correlated with the average amount of ethanol consumption per day. The ratio of proBDNF to mBDNF was altered in alcohol dependence patients. The balance between the proBDNF/p75NTR and mBDNF/TrkB signalling pathways appeared dysregulated in alcohol dependence. Our results suggested that both pathways may participate in the complex processes of alcohol dependence.

Binge Alcohol Exposure Transiently Changes the Endocannabinoid System: A Potential Target to Prevent Alcohol-Induced Neurodegeneration

Excessive alcohol consumption leads to neurodegeneration, which contributes to cognitive decline that is associated with alcohol use disorders (AUDs). The endocannabinoid system has been implicated in the development of AUDs, but little is known about how the neurotoxic effects of alcohol impact the endocannabinoid system. Therefore, the current study investigated the effects of neurotoxic, binge-like alcohol exposure on components of the endocannabinoid system and related N-acylethanolamines (NAEs), and then evaluated the efficacy of fatty acid amide hydrolase (FAAH) inhibition on attenuating alcohol-induced neurodegeneration. Male rats were administered alcohol according to a binge model, which resulted in a transient decrease in [³H]-CP-55,940 binding in the entorhinal cortex and hippocampus following two days, but not four days, of treatment. Furthermore, binge alcohol treatment did not change the tissue content of the three NAEs quantified, including the endocannabinoid and anandamide. In a separate study, the FAAH inhibitor, URB597 was administered to rats during alcohol treatment and neuroprotection was assessed by FluoroJade B (FJB) staining. The administration of URB597 during binge treatment did not significantly reduce FJB+ cells in the entorhinal cortex or hippocampus, however, a follow up "target engagement" study found that NAE augmentation by URB597 was impaired in alcohol intoxicated rats. Thus, potential alcohol induced alterations in URB597 pharmacodynamics may have contributed to the lack of neuroprotection by FAAH inhibition.

Long-Term Effects of Intermittent Adolescent Alcohol Exposure in Male and Female Rats

Alcohol is a serious public health concern that has a differential impact on individuals depending upon age and sex. Patterns of alcohol consumption have recently changed: heavy episodic drinking—known as binge-drinking—has become most popular among the youth. Herein, we aimed to investigate the consequences of intermittent adolescent alcohol consumption in male and female animals. Thus, Wistar rats were given free access to ethanol (20% in drinking water) or tap water for 2-h sessions during 3 days, and for an additional 4-h session on the 4th day; every week during adolescence, from postnatal day (pnd) 28–52. During this period, animals consumed a moderate amount of alcohol despite blood ethanol concentration (BEC) did not achieve binge-drinking levels. No withdrawal signs were observed: no changes were observed regarding anxiety-like responses in the elevated plus-maze or plasma corticosterone levels (pnd 53–54). In the novel object recognition (NOR) test (pnd 63), a significant deficit in recognition memory was observed in both male and female rats. Western Blot analyses resulted in an increase in the expression of synaptophysin in the frontal cortex (FC) of male and female animals, together with a decrease in the expression of the CB2R in the same brain region. In addition, adolescent alcohol induced, exclusively among females, a decrease in several markers of dopaminergic and serotonergic neurotransmission, in which epigenetic mechanisms, i.e., histone acetylation, might be involved. Taken together, further research is still needed to specifically correlate sex-specific brain and behavioral consequences of adolescent alcohol exposure.

Problematic alcohol use and reduced hippocampal volume: a meta-analytic review

BACKGROUND

A number of studies reports reduced hippocampal volume in individuals who engage in problematic alcohol use. However, the magnitude of the difference in hippocampal volume between individuals with v. without problematic alcohol use has varied widely, and there have been null findings. Moreover, the studies comprise diverse alcohol use constructs and samples, including clinically significant alcohol use disorders and subclinical but problematic alcohol use (e.g. binge drinking), adults and adolescents, and males and females.

METHODS

We conducted the first quantitative synthesis of the published empirical research on associations between problematic alcohol use and hippocampal volume. In total, 23 studies were identified and selected for inclusion in the meta-analysis; effects sizes were aggregated using a random-effects model.

RESULTS

Problematic alcohol use was associated with significantly smaller hippocampal volume (d = -0.53). Moderator analyses indicated that effects were stronger for clinically significant v. subclinical alcohol use and among adults relative to adolescents; effects did not differ among males and females.

CONCLUSIONS

Problematic alcohol use is associated with reduced hippocampal volume. The moderate overall effect size suggests the need for larger samples than are typically included in studies of alcohol use and hippocampal volume. Because the existing literature is almost entirely cross-sectional, future research using causally informative study designs is needed to determine whether this association reflects premorbid risk for the development of problematic alcohol use and/or whether alcohol has a neurotoxic effect on the hippocampus.

The Role of Working Memory for Cognitive Control in Anorexia Nervosa versus Substance Use Disorder

Prefrontal cortex executive functions, such as working memory (WM) interact with limbic processes to foster impulse control. Such an interaction is referred to in a growing body of publications by terms such as cognitive control, cognitive inhibition, affect regulation, self-regulation, top-down control, and cognitive–emotion interaction. The rising trend of research into cognitive control of impulsivity, using various related terms reflects the importance of research into impulse control, as failure to employ cognitions optimally may eventually result in mental disorder. Against this background, we take a novel approach using an impulse control spectrum model – where anorexia nervosa (AN) and substance use disorder (SUD) are at opposite extremes – to examine the role of WM for cognitive control. With this aim, we first summarize WM processes in the healthy brain in order to frame a systematic review of the neuropsychological, neural and genetic findings of AN and SUD. In our systematic review of WM/cognitive control, we found n = 15 studies of AN with a total of n = 582 AN and n = 365 HC participants; and n = 93 studies of SUD with n = 9106 SUD and n = 3028 HC participants. In particular, we consider how WM load/capacity may support the neural process of excessive epistemic foraging (cognitive sampling of the environment to test predictions about the world) in AN that reduces distraction from salient stimuli. We also consider the link between WM and cognitive control in people with SUD who are prone to ‘jumping to conclusions’ and reduced epistemic foraging. Finally, in light of our review, we consider WM training as a novel research tool and an adjunct to enhance treatment that improves cognitive control of impulsivity.

Deep Sequencing of 71 Candidate Genes to Characterize Variation Associated with Alcohol Dependence

BACKGROUND

Previous genomewide association studies (GWASs) have identified a number of putative risk loci for alcohol dependence (AD). However, only a few loci have replicated and these replicated variants only explain a small proportion of AD risk. Using an innovative approach, the goal of this study was to generate hypotheses about potentially causal variants for AD that can be explored further through functional studies.

METHODS

We employed targeted capture of 71 candidate loci and flanking regions followed by next-generation deep sequencing (mean coverage 78X) in 806 European Americans. Regions included in our targeted capture library were genes identified through published GWAS of alcohol, all human alcohol and aldehyde dehydrogenases, reward system genes including dopaminergic and opioid receptors, prioritized candidate genes based on previous associations, and genes involved in the absorption, distribution, metabolism, and excretion of drugs. We performed single-locus tests to determine if any single variant was associated with AD symptom count. Sets of variants that overlapped with biologically meaningful annotations were tested for association in aggregate.

RESULTS

No single, common variant was significantly associated with AD in our study. We did, however, find evidence for association with several variant sets. Two variant sets were significant at the q-value <0.10 level: a genic enhancer for ADHFE1 (p = 1.47 × 10^-5 ; q = 0.019), an alcohol dehydrogenase, and ADORA1 (p = 5.29 × 10^-5 ; q = 0.035), an adenosine receptor that belongs to a G-protein-coupled receptor gene family.

CONCLUSIONS

To our knowledge, this is the first sequencing study of AD to examine variants in entire genes, including flanking and regulatory regions. We found that in addition to protein coding variant sets, regulatory variant sets may play a role in AD. From these findings, we have generated initial functional hypotheses about how these sets may influence AD.

Volume of hippocampal subfields in patients with alcohol dependence

Alcohol-induced hippocampal atrophy has been well documented in many studies and is known to affect various subfields. Given the functional heterogeneity of these subfields, we investigated the precise effects of alcohol-induced damage in these areas. Twenty-six male patients with alcohol dependence (alcohol group) and twenty-six age-matched male healthy social drinkers were recruited from a mental health hospital and the community respectively, with the aim of comparing the hippocampal subfields between groups. Each participant underwent a 3T MRI scan. Hippocampal subfield volumes were estimated using an automated procedure and drinking history recorded using Lifetime Drinking History, Alcohol Use Disorder Identification Test, and the Brief Michigan Alcoholism Screening Test. The alcohol group showed a lower total hippocampus volume, specifically in the left presubiculum, fimbria, and bilateral subiculum. Regression analysis assessing the influence of age and group showed that group was a more significant factor than age in most subfields. Our findings suggest that alcohol dependence alters hippocampal subfield volumes. Further longitudinal studies on the interaction of structural and neurocognitive changes would improve our understanding of brain structural changes resulting from long-term alcohol consumption.

Laterality of Brain Activation for Risk Factors of Addiction

Background:

Laterality of brain activation is reported for tests of risk factors of addiction - impulsivity and craving - but authors rarely address the potential significance of those asymmetries.

Objective:

The purpose of this study is to demonstrate this laterality and discuss its relevance to cognitive and neurophysiological asymmetries associated with drug abuse vulnerability in order to provide new insights for future research in drug abuse.

Method:

From published reports, brain areas of activation for two tests of response inhibition or craving for drugs of abuse were compiled from fMRI activation peaks and were tabulated for eight sections (octants) in each hemisphere. Percent asymmetries were calculated (R-L/R+L) across studies for each area.

Results:

For impulsivity, most activation peaks favored the right hemisphere. Overall, the percent difference was 32% (Χ² = 16.026; p < 0.0001) with the greater asymmetry for anterior peaks (46.8%; Χ² = 17.329; p < 0.0001). The asymmetries for cue-induced craving were opposite, favoring the left hemisphere by 6.7% (Χ² = 4.028; p < 0.05). The consistency of left asymmetry was found for almost all drugs. For nicotine, studies where subjects were not allowed to smoke (deprived) prior to measurement had the same left hemisphere activation but those who smoked (satiated) before the fMRI measure showed right asymmetry.

Conclusion:

Brain activation studies demonstrate different left/right hemispheric contributions for impulsivity versus craving - factors related to addiction. Failure to take laterality into consideration is a missed opportunity in designing studies and gaining insight into the etiology of drug abuse and pathways for treatment.

Prefrontal Cortical Thickness Deficit in Detoxified Alcohol-dependent Patients

Alcohol dependence is a serious disorder that can be related with a number of potential health-related and social consequences. Cortical thickness measurements would provide important information on the cortical structural alterations in patients with alcohol dependence. Twenty-one patients with alcohol dependence and 22 healthy comparison subjects have been recruited and underwent high-resolution brain magnetic resonance (MR) imaging and clinical assessments. T1-weighted MR images were analyzed using the cortical thickness analysis program. Significantly thinner cortical thickness in patients with alcohol dependence than healthy comparison subjects was noted in the left superior frontal cortical region, correcting for multiple comparisons and adjusting with age and hemispheric average cortical thickness. There was a significant association between thickness in the cluster of the left superior frontal cortex and the duration of alcohol use. The prefrontal cortical region may particularly be vulnerable to chronic alcohol exposure. It is also possible that the pre-existing deficit in this region may have rendered individuals more susceptible to alcohol dependence.

Chronic Drinking During Adolescence Predisposes the Adult Rat for Continued Heavy Drinking: Neurotrophin and Behavioral Adaptation after Long-Term, Continuous Ethanol Exposure

Previous research has found that adolescent ethanol (EtOH) exposure alters drug seeking behaviors, cognition and neuroplasticity. Using male Sprague Dawley rats, differences in spatial working memory, non-spatial discrimination learning and behavioral flexibility were explored as a function of age at the onset (mid-adolescent vs. adult) of chronic EtOH exposure (CET). Concentrations of mature brain-derived neurotrophic factor (mBDNF) and beta-nerve growth factor (β-NGF) in the prefrontal cortex and hippocampus were also assessed at different time-points: during CET, following acute abstinence (48-hrs), and after protracted abstinence (6-8 wks). Our results revealed that an adolescent onset of CET leads to increased EtOH consumption that persisted into adulthood. In both adult and adolescent onset CET groups, there were significant long-term reductions in prefrontal cortical mBDNF and β-NGF levels. However, only adult onset CET rats displayed decreased hippocampal BDNF levels. Spatial memory, assessed by spontaneous alternation and delayed alternation, was not significantly affected by CET as a function of age of drinking onset, but higher blood-EtOH levels were correlated with lower spontaneous alternation scores. Regardless of the age of onset, EtOH exposed rats were impaired on non-spatial discrimination learning and displayed inflexible behavioral patterns upon reversal learning. Our results indicate that adolescent EtOH exposure changes long-term consumption patterns producing behavioral and neural dysfunctions that persist across the lifespan.

Neurobiological phenotypes associated with a family history of alcoholism

BACKGROUND

Individuals with a family history of alcoholism are at much greater risk for developing an alcohol use disorder (AUD) than youth or adults without such history. A large body of research suggests that there are premorbid differences in brain structure and function in family history positive (FHP) individuals relative to their family history negative (FHN) peers.

METHODS

This review summarizes the existing literature on neurobiological phenotypes present in FHP youth and adults by describing findings across neurophysiological and neuroimaging studies.

RESULTS

Neuroimaging studies have shown FHP individuals differ from their FHN peers in amygdalar, hippocampal, basal ganglia, and cerebellar volume. Both increased and decreased white matter integrity has been reported in FHP individuals compared with FHN controls. Functional magnetic resonance imaging studies have found altered inhibitory control and working memory-related brain response in FHP youth and adults, suggesting neural markers of executive functioning may be related to increased vulnerability for developing AUDs in this population. Additionally, brain activity differences in regions involved in bottom-up reward and emotional processing, such as the nucleus accumbens and amygdala, have been shown in FHP individuals relative to their FHN peers.

CONCLUSIONS

It is critical to understand premorbid neural characteristics that could be associated with cognitive, reward-related, or emotional risk factors that increase risk for AUDs in FHP individuals. This information may lead to the development of neurobiologically informed prevention and intervention studies focused on reducing the incidence of AUDs in high-risk youth and adults.

Sexually dimorphic brain volume interaction in college-aged binge drinkers

BACKGROUND

Binge consumption of alcohol is a major societal problem associated with important cognitive, physiological and neurotoxic consequences. Converging evidence highlights the need to assess binge drinking (BD) and its effects on the developing brain while taking into account gender differences. Here, we compared the brain volumetric differences between genders in college-aged binge drinkers and healthy volunteers.

METHOD

T1-weighted magnetic resonance imaging (MRI) images of 30 binge drinkers (18 males) and 46 matched healthy volunteers (23 males) were examined using voxel-based morphometry. The anatomical scans were covaried with Alcohol Use Disorders Identification Test (AUDIT) scores. Whole brain voxel-wise group comparisons were performed using a cluster extent threshold correction.

RESULTS

Several large clusters qualified with group-by-gender interactions were observed in prefrontal, striatal and medial temporal areas, whereby BD females had more volume than non-BD females, while males showed the inverse pattern of decreased volume in BD males and increased volume in non-BD males. AUDIT scores negatively correlated with volume in the right superior frontal cortex and precentral gyrus.

CONCLUSIONS

These findings dovetail with previous studies reporting that a state effect of BD in college-aged drinkers and the severity of alcohol use are associated with volumetric alterations in the cortical and subcortical areas of the brain. Our study indicates that these widespread volumetric changes vary differentially by gender, suggesting either sexual dimorphic endophenotypic risk factors, or differential neurotoxic sensitivities for males and females.

Adolescent exposure to cocaine increases anxiety-like behavior and induces morphologic and neurochemical changes in the hippocampus of adult rats

Repeated exposure to cocaine during adolescence may affect both physical and psychological conditions in the brain, and increase the risk of psychiatric disorders and addiction behaviors in adulthood. Adolescence represents a critical development period for the hippocampus. Moreover, different regions of the hippocampus are involved in different functions. Dorsal hippocampus (dHP) has been implicated in learning and memory, whereas ventral hippocampus (vHP) plays an important role in emotional processing. In this study, the rats that were exposed to cocaine during adolescence (postnatal days, P28-P42) showed higher anxiety-like behavior in the elevated plus maze test in adulthood (P80), but displayed normal spatial learning and memory in the Morris water maze test. Furthermore, repeated exposure to cocaine during adolescence lead to alterations in morphology of pyramidal neurons, activities of astrocytes, and levels of proteins that involved in synaptic transmission, apoptosis, inflammation and addiction in both dHP and vHP of adult rats. These findings suggest that repeated exposure to cocaine during adolescence in rats may elicit morphologic and neurochemical changes in the hippocampus when the animals reach adulthood. These changes may contribute to the increased susceptibility for psychiatric disorders and addiction seen in adults.

GET73 Prevents Ethanol-Induced Neurotoxicity in Primary Cultures of Rat Hippocampal Neurons

AIMS

N-[(4-trifluoromethyl) benzyl] 4-methoxybutyramide (GET73) may be considered a promising therapeutic agent for the treatment of alcohol use disorders. The compound displayed anti-alcohol and anxiolytic properties in rat. In the present study, an in vitro experimental model of chronic ethanol treatment was used to investigate the ability of the compound to counteract the ethanol-induced neurotoxicity.

METHODS

Primary cultures of rat hippocampal neurons were exposed to ethanol (75 mM; 4 days) and the neuroprotective effects of GET73 were assessed by evaluating cell viability, cell morphology, glutamate levels and reactive oxygen species production.

RESULTS

The exposure to ethanol induced a reduction of cell viability, an alteration of cytoskeleton, a decrease in extracellular glutamate levels and an increase of reactive oxygen species production. The addiction of GET73 (1 and 10 µM) 1 h before and during chronic ethanol exposure prevented all the above ethanol-induced effects. Based on the proposed GET73 mechanism of action, the effects of mGlu5 receptor negative allosteric modulator, 2-methyl-6-(phenylethynyl)-pyridine (MPEP), on ethanol-induced reduction of cell viability were also assessed. The results indicated that the addiction of MPEP (100 µM) 1 h before and during chronic ethanol exposure prevented the ethanol-induced cell viability reduction.

CONCLUSION

The present findings provide the first evidence that GET73 shows a neuroprotective role against ethanol-induced neurotoxicity in primary cultures of rat hippocampal neurons. Together with previous findings, these results suggest that GET73 possesses multifaceted properties thus lending further support to the significance of developing GET73 as a therapeutic tool for use in the treatment of alcohol use disorders.

Chronic ethanol exposure during adolescence through early adulthood in female rats induces emotional and memory deficits associated with morphological and molecular alterations in hippocampus

There is increasing evidence that heavy ethanol exposure in early life may produce long-lasting neurobehavioral consequences, since brain structural maturation continues until adolescence. It is well established that females are more susceptible to alcohol-induced neurotoxicity and that ethanol consumption is increasing among women, especially during adolescence. In the present study, we investigated whether chronic ethanol exposure during adolescence through early adulthood in female rats may induce hippocampal histological damage and neurobehavioral impairments. Female rats were treated with distilled water or ethanol (6.5 g/kg/day, 22.5% w/v) by gavage from the 35(th)-90(th) day of life. Ethanol-exposed animals displayed reduced exploration of the central area and increased number of fecal boluses in the open field test indicative of anxiogenic responses. Moreover, chronic high ethanol exposure during adolescence induced marked impairments on short-term memory of female rats addressed on social recognition and step-down inhibitory avoidance tasks. These neurobehavioral deficits induced by ethanol exposure during adolescence through early adulthood were accompanied by the reduction of hippocampal formation volume as well as the loss of neurons, astrocytes and microglia cells in the hippocampus. These results indicate that chronic high ethanol exposure during adolescence through early adulthood in female rats induces long-lasting emotional and memory deficits associated with morphological and molecular alterations in the hippocampus.

Transcranial Magnetic Stimulation and Deep Brain Stimulation in the treatment of alcohol dependence

Alcohol dependence is a major social, economic, and public health problem. Alcoholism can lead to damage of the gastrointestinal, nervous, cardiovascular, and respiratory systems and it can be lethal, costing hundreds of billions to the health care system. Despite the existence of cognitive-behavioral therapy, psychosocial interventions, and spiritually integrated treatment to treat it, alcohol dependence has a high relapse rate and poor prognosis, albeit with high interindividual variability. In this review, we discuss the use of two neuromodulation techniques, namely repetitive transcranial magnetic stimulation (rTMS) and deep brain stimulation (DBS), and their advantages and disadvantages compared to first-line pharmacological treatment for alcohol dependence. We also discuss rTMS and DBS targets for alcohol dependence treatment, considering experimental animal and human evidence, with careful consideration of methodological issues preventing the identification of feasible targets for neuromodulation treatments, as well as inter-individual variability factors influencing alcoholism prognosis. Lastly, we anticipate future research aiming to tailor the treatment to each individual patient by combining neurofunctional, neuroanatomical and neurodisruptive techniques optimizing the outcome.

Genetic and behavioral determinants of hippocampal volume recovery during abstinence from alcohol

Alcohol-dependent individuals (ALC) have smaller hippocampi and poorer neurocognition than healthy controls. Results from studies on the association between alcohol consumption and hippocampal volume have been mixed, suggesting that comorbid or premorbid factors (i.e., those present prior to the initiation of alcohol dependence) determine hippocampal volume in ALC. We aimed to characterize the effects of select comorbid (i.e., cigarette smoking) and premorbid factors (brain-derived neurotrophic factor [BDNF] genotype [Val66Met rs6265]) on hippocampal volume in an ALC cohort followed longitudinally into extended abstinence. One hundred twenty-one adult ALC in treatment (76 smokers, 45 non-smokers) and 35 non-smoking light-drinking controls underwent quantitative magnetic resonance imaging, BDNF genotyping, and neurocognitive assessments. Representative subgroups were studied at 1 week, 1 month, and at an average of 7 months of abstinence. ALC had smaller hippocampi than healthy controls at all time points. Hippocampal volume at 1 month of abstinence correlated with lower visuospatial function. Smoking status did not influence hippocampal volume or hippocampal volume recovery during abstinence. However, only BDNF Val homozygotes tended to have hippocampal volume increases over 7 months of abstinence, and Val homozygotes had significantly larger hippocampi than Met carriers at 7 months of abstinence. These findings suggest that BDNF genotype, but not smoking status or measures of drinking severity, regulate functionally relevant hippocampal volume recovery in abstinent ALC. Future studies aimed at exploring genetic determinants of brain morphometry in ALC may need to evaluate individuals during extended abstinence after the acute environmental effects of chronic alcohol consumption have waned.

Alcohol and adult hippocampal neurogenesis: promiscuous drug, wanton effects

Adult neurogenesis is now widely accepted as an important contributor to hippocampal integrity and function but also dysfunction when adult neurogenesis is affected in neuropsychiatric diseases such as alcohol use disorders. Excessive alcohol consumption, the defining characteristic of alcohol use disorders, results in a variety of cognitive and behavioral impairments related wholly or in part to hippocampal structure and function. Recent preclinical work has shown that adult neurogenesis may be one route by which alcohol produces hippocampal neuropathology. Alcohol is a pharmacologically promiscuous drug capable of interfering with adult neurogenesis through multiple mechanisms. This review will discuss the primary mechanisms underlying alcohol-induced changes in adult hippocampal neurogenesis including alcohol's effects on neurotransmitters, CREB and its downstream effectors, and the neurogenic niche.

Association of depressive symptoms with hippocampal volume in 1936 adults

Hippocampal atrophy is reported in major depressive disorder (MDD). However, sample sizes were generally modest, and participant characteristics, including age, differed between studies. This study used a community sample to examine relationships between current depressive symptom severity and hippocampal volume across the adult lifespan. A total of 1936 adults with magnetic resonance images of the brain and Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR) scores were included. Brain volumes were quantified using the FSL program. Multiple linear regressions were performed using left, right, and total hippocampal volume as criterion variables, and predictor variables of QIDS-SR total, total brain volume, age, gender, education, psychotropic medications, alcohol use, and race/ethnicity. Post hoc analyses were conducted in participants with QIDS-SR scores 11 (moderate or greater depressive symptom severity) and <11, and older and younger adults. In the primary analysis (sample as a whole) QIDS-SR was inversely associated with total hippocampal volume (b=-0.044, p=0.032, (CI-0.019 to -0.001)) but not with left or right hippocampal volume evaluated individually. In participants with QIDS-SR scores of <11, hippocampal volumes were not associated with QIDS-SR scores. In those with QIDS-SR scores 11 total, right, and left hippocampal volumes were modestly, but significantly, associated with QIDS-SR scores. The association between QIDS-SR scores and the hippocampal volume was much stronger in older persons. Findings suggest smaller hippocampal volumes among those with greater reported depressive symptom severity-an association that is strongest in people with at least moderate depressive symptom levels.

The neuroscience of face processing and identification in eyewitnesses and offenders

Humans are experts in face perception. We are better able to distinguish between the differences of faces and their components than between any other kind of objects. Several studies investigating the underlying neural networks provided evidence for deviated face processing in criminal individuals, although results are often confounded by accompanying mental or addiction disorders. On the other hand, face processing in non-criminal healthy persons can be of high juridical interest in cases of witnessing a felony and afterward identifying a culprit. Memory and therefore recognition of a person can be affected by many parameters and thus become distorted. But also face processing itself is modulated by different factors like facial characteristics, degree of familiarity, and emotional relation. These factors make the comparison of different cases, as well as the transfer of laboratory results to real live settings very challenging. Several neuroimaging studies have been published in recent years and some progress was made connecting certain brain activation patterns with the correct recognition of an individual. However, there is still a long way to go before brain imaging can make a reliable contribution to court procedures.