Biomedical subjects

In Kyoon Lyoo

Publications and source records attributed to In Kyoon Lyoo.

At least 19 recordsLinked to original sources

PubMed2026

Fyn signaling in the medial prefrontal cortex regulates resistance to stress-induced object recognition impairments in male rats.

Genome-wide association studies on patients with depression have identified FYN and FYB, an FYN-binding protein, as being linked to depression. We have reported that experimental manipulations in gene expression in the medial prefrontal cortex (mPFC) alter stress-induced object recognition impairments in animals. Therefore, we examined the impact of alterations in FYN and FYB expression in the mPFC of adult male rats on resistance to stress-induced impairments in object recognition. Animals with virus-mediated knockdown or overexpression of Fyn in the mPFC were subjected to either a brief 20-min restraint with 20 intermittent tail shocks, which does not induce object recognition impairment, or a prolonged 60-min restraint with 60 intermittent tail shocks, which does. In an object recognition task, control rats maintained intact object recognition following a brief stress, whereas rats with Fyn knockdown or overexpression in the mPFC showed impaired object recognition. Prolonged stress impaired object recognition in both control rats and rats with Fyn knockdown or overexpression. Additionally, rats with Fyn knockdown in the mPFC exhibited fewer c-Fos-positive cells in the mPFC in response to brief stress, accompanied by a trend toward increased c-Fos in the amygdala compared with control rats. Fyn knockdown also reduced Fyb expression in the mPFC. Furthermore, Fyb knockdown in the mPFC impaired object recognition following brief stress, suggesting that the observed effects are consistent with involvement of a coupled Fyn-Fyb signaling axis rather than Fyn alone. These findings suggest that altered Fyn-related signaling in the mPFC may underlie the resistance to stress-induced object recognition impairments.

Animals↗

PubMed2007

Asymmetrically altered integrity of cingulum bundle in posttraumatic stress disorder.

Previously, our group reported the altered white matter tract integrity of the left anterior cingulate in posttraumatic stress disorder (PTSD) in whole-brain exploration. Current study intended to explore whether the alteration was more prominent in any specific regions of the cingulum bundle. Diffusion tensor images of 21 PTSD subjects and 21 healthy comparison subjects were acquired. Eight isocubic regions of interest (ROIs), i.e. bilateral rostral, subgenual, dorsal, and upper cingulum bundle, were selected. Fractional anisotropy values in each ROI, which indicate the white matter tract integrity, were measured and compared between groups. Relative to comparison subjects, PTSD subjects had significantly smaller fractional anisotropy values in the left side of rostral, subgenual and dorsal cingulum bundle (26.7, 25.0, 22.2% decrease, respectively), but not in the right side ROIs. We report an asymmetrical alteration of the cingulum bundle in PTSD.

Adult↗

PubMed2006

Decreased frontal white-matter integrity in abstinent methamphetamine abusers.

This study explored differences in frontal white-matter (WM) integrity between methamphetamine (MA) abusers and healthy comparison subjects using diffusion tensor imaging (DTI). Fractional anisotropy (FA) values, which indicate WM integrity, were calculated for regions-of-interest in frontal WM on diffusion tensor images of 32 MA abusers and 30 healthy comparison subjects. Frontal executive functions were also assessed by the Wisconsin Card Sorting test (WCST). MA abusers had significantly lower FA values in bilateral frontal WM at the anterior commissure-posterior commissure (AC-PC) plane and the right frontal WM 5 mm above the AC-PC plane relative to healthy comparison subjects. MA abusers had more total, perseveration and non-perseveration errors in the WCST relative to healthy comparison subjects. FA values of the right frontal WM 5 mm above the AC-PC plane negatively correlated with the number of total and non-perseveration errors in the WCST in MA abusers. In the sub-analysis for gender differences, lower FA values in frontal WM and more errors in the WCST were found only in male MA abusers, not in female MA abusers, relative to comparison subjects of the respective gender. We report that frontal WM integrity of MA abusers is compromised. This finding may also be related to impairment in frontal executive function. In addition, the neurotoxic effect of MA on frontal WM may be less prominent in women than in men, possibly due to oestrogen's neuroprotective effect.

Adult↗

PubMed2006

Decreased GABA levels in anterior cingulate and basal ganglia in medicated subjects with panic disorder: a proton magnetic resonance spectroscopy (1H-MRS) study.

The purpose of this study was to investigate the brain gamma-aminobutyric acid (GABA) concentration and its relationship with clinical variables in patients with panic disorder (PD). Single voxel proton magnetic resonance spectroscopy ((1)H-MRS) scan was performed on 22 medicated subjects with PD and 25 age and sex-matched healthy comparison subjects. GABA and other metabolite levels were measured in the anterior cingulate cortex (ACC) and basal ganglia. GABA levels were significantly lower in the ACC and basal ganglia of PD patients relative to comparison subjects. Lactate and choline concentrations in the ACC in PD patients were also higher than in the comparison subjects. Our data suggested in part that alterations of the GABA function and the energy metabolism in ACC and basal ganglia may play an important role in the pathophysiology of panic disorder.

Adult↗

PubMed2006

Relationship between N-acetyl-aspartate in gray and white matter of abstinent methamphetamine abusers and their history of drug abuse: a proton magnetic resonance spectroscopy study.

OBJECTIVE: Altered concentrations of the brain metabolites, including N-acetyl-aspartate (NAA) and myo-inositol (MI), may indicate neurotoxicity associated with drug abuse. In this study, the authors explored differences in brain metabolites between abstinent methamphetamine (MA) abusers and healthy comparison subjects and the associations between metabolite concentrations and clinical characteristics. METHOD: Proton magnetic resonance spectroscopy (MRS) was performed on 30 abstinent MA abusers and 20 healthy comparison subjects. Two sets of MA user subgroups were defined depending on abstinence duration (greater or less than 6 months) or the total cumulative MA dose (greater or less than 100 g lifetime). NAA and other metabolites were measured in the frontal gray and white matter and compared between MA abuser groups and healthy comparison subjects. RESULTS: MI concentrations were higher for the MA abusers relative to healthy comparison subjects. NAA concentration was lower in frontal white matter of MA abusers with a 'large' cumulative dose relative to those with a 'small' cumulative dose and to healthy comparison subjects. Additionally, in MA abusers NAA concentrations in frontal white matter correlated inversely with the cumulative MA dose. In contrast, there was no significant difference in frontal gray matter NAA concentration among the three groups. However, frontal gray matter NAA concentrations for MA abusers correlated negatively with the total cumulative MA dose and positively with the duration of abstinence. There were no differences between the different MA user groups for MI. CONCLUSIONS: The current findings suggest that MA-induced metabolic alterations of frontal gray and white matter are dose-dependent, for primarily male subjects. Additionally, these findings potentially suggest that the MA-related abnormalities may, in part, recover with abstinence in gray matter, but not in the white matter regions.

Adult↗

PubMed2006

Mania, glutamate/glutamine and risperidone in pediatric bipolar disorder: a proton magnetic resonance spectroscopy study of the anterior cingulate cortex.

BACKGROUND: The purpose of this study was to investigate the anterior cingulate cortex (ACC) glutamate/glutamine (Glx) to creatine ratio (Glx/Cr) in two groups of children with Bipolar Disorder (BPD): those exhibiting manic symptoms requiring treatment and those being stably treated with the atypical antipsychotic risperidone. Atypical antipsychotics have been shown to increase serum glutamate levels and ACC Glx/Cr in subjects with schizophrenia. In this study, we hypothesized that the children with BPD in need of treatment would have lower Glx/Cr compared with the children with BPD being stably treated with risperidone. METHODS: Proton MR spectra were acquired, at 1.5 T, from the ACC of eighteen subjects with a DSM-IV diagnosis of BPD: ten (11.10+/-3.48 years; five female) were manic and not medicated with any antipsychotic and eight (10.88+/-2.99 years; one female) were medicated with the atypical antipsychotic risperidone. RESULTS: Children with BPD exhibiting manic symptoms requiring treatment had lower Glx/Cr than children with BPD being stably treated with the atypical antipsychotic risperidone. The children treated with risperidone also had significantly lower YMRS and CGI-Mania scores than the children not treated with risperidone. Both YMRS and CGI-Mania scores correlated negatively with ACC Glx/Cr levels. LIMITATIONS: The cross-sectional design, small sample size, the use of Glx rather than glutamate or glutamine and the use of Cr ratios rather than absolute concentrations are limitations of this study. CONCLUSIONS: Children with mania have lower Glx/Cr levels than children with BPD being stably treated with the atypical antipsychotic risperidone. Mania may be associated with reduced glutamate/glutamine levels in the ACC: other imaging studies have shown mania associated with hypometabolism in the ACC. These reductions in glutamate/glutamine may be increased following successful treatment with glutamatergic agents.

Adolescent↗

PubMed2006

Personality, dopamine receptor D4 exon III polymorphisms, and academic achievement in medical students.

This study investigated the relationships between genetic polymorphisms, personality traits, and academic achievement in medical school students. Study subjects were 220 1st-year medical students at Korea University Medical School during two consecutive academic years (2003-2004). Grade-point averages (GPA) during the second semester of the 1st year of the medical school were obtained as a measure of academic achievement. In addition, all participants completed the Temperament and Character Inventory and questionnaires on depression and anxiety. The polymorphisms in exon III of the dopamine D4 receptor (DRD4) were determined using the polymerase chain reaction. Our results revealed that both male and female subjects with a higher GPA may be characterized as having higher persistence and lower novelty seeking traits. In addition, male subjects with high GPA had higher scores in self directedness and female subjects with a higher GPA may be characterized as having higher scores in harm avoidance. Male students with 4-repeat alleles had a significantly lower GPA than male students without 4-repeat alleles. This relationship also remained after controlling for the personality variables, none of which showed a relationship with the polymorphism after Bonferroni correction. For females, however, no associations could be found between GPA and the polymorphism. Thus, the present study demonstrated for the first time a possible influence of the DRD4 48 bp variable number of tandem repeats polymorphism on academic achievement and proved that this was not mediated by performance-associated personality traits.

Adult↗

PubMed2006

Serum homocysteine, folate level and methylenetetrahydrofolate reductase 677, 1298 gene polymorphism in Korean schizophrenic patients.

High homocysteine serum level has been regarded as one of the important factors that influence the development of schizophrenia. Genetic variations of methylenetetrahydrofolate reductase, which is a main enzyme reducing homocysteine level, are reported in schizophrenic patients. We measured the serum level of homocysteine/folate and methylenetetrahydrofolate reductase C677T/A1298C gene polymorphism in 235 patients with schizophrenia. Plasma homocysteine levels were higher and folate levels were lower in patients than in comparison subjects. Variations of C677T were more frequent in patients than in comparison subjects. Patients with the 677TT genotype showed higher homocysteine levels than patients with the CC and CT genotypes. These findings suggest that folate supplement may be beneficial to some schizophrenic patients with homocysteinemia due to the genetic defect of methylenetetrahydrofolate reductase.

Case-Control Studies↗

PubMed2006

Effects of catechol-O-methyltransferase Val158Met polymorphism on the cognitive stability and aggression in the first-onset schizophrenic patients.

We assessed catechol-O-methyltransferase (COMT) polymorphism in 132 first-onset schizophrenic patients and 80 healthy controls. The relationship between COMT polymorphism and cognitive function, aggression and psychiatric symptoms was tested in the schizophrenic group. COMTL carrier had higher digit span score and lower similarity score than COMTH homozygote. COMTL carrier had higher attention and delusion scores and lower inappropriate affect scores than COMTH homozygote. Attention and delusion scores of COMTL allele were higher than COMTH allele. COMTL group had higher aggression than COMTH homozygote. Our results support the theory that COMTL allele was related with increased tonic dopamine activity and cognitive 'stability', which may induce cognitive inflexibility in schizophrenia.

Adult↗

PubMed2006

The relationship between the biogenetic temperament and character and psychopathology in adolescents.

BACKGROUND: This study was conducted to investigate the relationship between patterns of temperament and character and self-reported psychopathology in adolescents from the community. SAMPLING AND METHODS: The Junior Temperament and Character Inventory (JTCI) and Youth Self-Report (YSR) instruments were administered to 623 Korean middle school students (boys/girls = 331/292; age = 13.3 +/- 0.9 years old). Multiple linear regression analyses were used to evaluate the relationship between temperament and character based on Cloninger's biogenetic theory of personality and youth psychopathology of internalizing and externalizing problems. RESULTS: Internalizing problems of the YSR (withdrawn, somatic complaint and anxious/depressed scales) were significantly related to high Harm Avoidance and low Reward Dependence (JTCI temperament) and low Self-Directedness and high Self-Transcendence (JTCI character). Externalizing problems of the YSR (delinquency and aggression) were significantly associated with high Novelty Seeking and high Harm Avoidance (JTCI temperament) and low Self-Directedness, low Cooperativeness and high Self-Transcendence (JTCI character). CONCLUSIONS: Findings of the current study suggest that specific patterns of temperament and character potentially influence adolescents' psychopathology in the community.

Adolescent↗

PubMed2006

Advances in magnetic resonance imaging methods for the evaluation of bipolar disorder.

This article reviews the current state of magnetic resonance imaging techniques as applied to bipolar disorder. Addressed are conventional methods of structural neuroimaging and recently developed techniques. This latter group comprises volumetric analysis, voxel-based morphometry, the assessment of T2 white matter hyperintensities, shape analysis, cortical surface-based analysis, and diffusion tensor imaging. Structural analysis methods used in magnetic resonance imaging develop exponentially, and now present opportunities to identify disease-specific neuroanatomic alterations. Greater acuity and complementarity in measuring these alterations has led to the generation of further hypotheses regarding the pathophysiology of bipolar disorder. Included in the summary of findings is consideration of a resulting neuroanatomic model. Integrative issues and future directions in this relatively young field, including multi-modal approaches enabling us to produce more comprehensive results, are discussed.

Bipolar Disorder↗

PubMed2006

The relationship between temperament and character and psychopathology in community children with overweight.

This study investigated the relationship between temperament and character and psychopathology in at risk of overweight and overweight children. The Child Behavior Checklist (CBCL) and the Junior Temperament and Character Inventory (JTCI) questionnaires were administered to 453 children (10-12 years of age, 203 boys and 250 girls) in Kimpo, South Korea. Subjects were divided into three groups; (1) nonoverweight children (n = 345), (2) children at risk of overweight (n = 72), and (3) overweight children (n = 36). CBCL and the JTCI scores were compared among three groups. In addition, the relationships between subscales of the CBCL and the JTCI were evaluated. On the CBCL, overweight children had higher scores in social problems, delinquent problems, and total problems compared to nonoverweight children. Children at risk of overweight showed higher scores only in social problems compared to nonoverweight children. On the JTCI, lower persistence and tendency of higher novelty seeking was observed in overweight children compared to nonoverweight children. Persistence scores were negatively correlated with scores of delinquent problems, externalizing problems, and total problems in overweight children. Compared to nonoverweight and children at risk of overweight, overweight children had distinct patterns of temperament and character that were related to the specific psychopathology.

Body Mass Index↗

PubMed2006

Regional cerebral cortical thinning in bipolar disorder.

OBJECTIVE: This study was conducted to explore differences in cortical thickness between subjects with bipolar disorder and healthy comparison subjects using cortical surface-based analysis. METHODS: Brain magnetic resonance images were acquired from 25 subjects with bipolar disorder and 21 healthy comparison subjects. Cortical surface-based analysis was conducted using the Freesurfer application. Group differences in cortical thickness, defined by the distance from gray/white boundary to the pial surface, were assessed using statistical difference maps. RESULTS: Subjects with bipolar disorder exhibited significantly decreased cortical thickness in left cingulate cortex, left middle frontal cortex, left middle occipital cortex, right medial frontal cortex, right angular cortex, right fusiform cortex and bilateral postcentral cortices, relative to healthy comparison subjects (all p < 0.001). Duration of illness in bipolar subjects was inversely correlated with the cortical thickness of the left middle frontal cortex. CONCLUSIONS: Cortical thinning was present in multiple prefrontal cortices in bipolar disorder. There was also cortical thinning in sensory and sensory association cortices, which has not been reported in previous studies using region-of-interest or voxel-based morphometry methods. Cortical thinning observed in the current study may be related to impairment of emotional, cognitive, and sensory processing in bipolar disorder but longitudinal studies will be necessary to test this hypothesis.

Adult↗

PubMed2006

Basal ganglia shape alterations in bipolar disorder.

OBJECTIVE: Shape differences in the caudate heads and putamen were compared between drug-naive and drug-treated patients with bipolar disorder and healthy comparison subjects by using spherical harmonic (SPHARM) techniques. On the basis of previous studies, the authors hypothesized that the drug-naive patients would exhibit shape differences of the caudate heads and putamen, especially on the right side, relative to the healthy comparison subjects, and that shape differences, relative to healthy comparison subjects, would differ between drug-naive and drug-treated patients. METHOD: Brain magnetic resonance images were acquired from 49 bipolar disorder patients (21 drug-naive and 28 drug-treated patients) and 37 healthy comparison subjects. Volumetric measurements were obtained, and SPHARM descriptions were used to measure between-group radius differences in the surfaces of the caudate heads and putamen. RESULTS: Although no significant between-group volume differences were found in the striatal structures, significant shape differences in the anterior and ventral surfaces of the striatum were observed. Specifically, shape differences, more prominent for the right side, were found for drug-naive bipolar disorder patients, relative to the healthy comparison subjects, but not for drug-treated bipolar disorder subjects. CONCLUSIONS: The findings suggest that drug-naive bipolar disorder patients have shape differences of the striatum, relative to healthy comparison subjects, and that these differences may be modulated by treatment. The findings more generally demonstrate the sensitivity of the SPHARM analytic technique for detecting subtle anatomical shape differences in small brain regions in the absence of volume differences.

Adult↗

PubMed2006

Brain white-matter hyperintensities and treatment outcome in major depressive disorder.

BACKGROUND: An increased incidence of brain white-matter hyperintensities has been described in major depressive disorder, butthe impact of such hyperintensities on treatment outcome is still controversial. AIMS: To investigate the relationship of brain white-matter hyperintensities with cardiovascular risk factors and with treatment outcome in younger people with major depressive disorder. METHOD: We assessed brain white-matter hyperintensities and cardiovascular risk factors in 84 people with major depressive disorder prior to initiating antidepressant treatment. We also assessed hyperintensities in 35 matched controls. RESULTS: We found no significant difference in the prevalence of white-matter hyperintensities between the depression and the control groups. Left-hemisphere subcortical hyperintensities correlated with lower rates of treatment response. We found no correlation between global hyperintensity measures and clinical outcome. Brain white-matter hyperintensities correlated with hypertension and age and withtotal cardiovascular risk score. CONCLUSIONS: Subcortical white-matter hyperintensities in the left hemisphere (but notin other brain areas) maybe associated with poor response to antidepressant treatment in major depression.

Adolescent↗

PubMed2006

Effects of type 1 diabetes on gray matter density as measured by voxel-based morphometry.

The effects of type 1 diabetes and key metabolic variables on brain structure are not well understood. Sensitive methods of assessing brain structure, such as voxel-based morphometry (VBM), have not previously been used to investigate central nervous system changes in a diabetic population. Using VBM, we compared type 1 diabetic patients aged 25-40 years with disease duration of 15-25 years and minimal diabetes complications with an age-matched, nondiabetic control group. We investigated whether lower than expected gray matter densities were present, and if so, whether they were associated with glycemic control and history of severe hypoglycemic events. In comparison with control subjects, diabetic patients showed lower density of gray matter in several brain regions. Moreover, in the patient group, higher HbA(1c) levels and severe hypoglycemic events were associated with lower density of gray matter in brain regions responsible for language processing and memory. Our study represents the first comprehensive study of gray matter density changes in type 1 diabetes and suggests that persistent hyperglycemia and acute severe hypoglycemia have an impact on brain structure.

Adolescent↗

PubMed2005

Brain MRI white matter hyperintensities and one-carbon cycle metabolism in non-geriatric outpatients with major depressive disorder (Part I).

The objective of the present work was to study the interrelationship between white matter hyperintensities (WMHs), cardiovascular risk factors and elements of the one-carbon cycle including serum folate, vitamin B12, and homocysteine levels in a relatively young sample of outpatients with major depressive disorder (MDD), and to compare the severity of white matter hyperintensities in MDD patients and healthy volunteers. Fifty MDD outpatients (34% women, age 40.6+/-10.3 years), free of psychotropic medications for at least 2 weeks before enrollment, underwent magnetic resonance imaging (MRI) scans of the brain to detect T2 WMHs and also had (1) serum folate, vitamin B12, homocysteine and cholesterol levels measured, and (2) cardiovascular risk factors assessed during the same study visit. Thirty-five healthy comparison subjects (40% women, age 39.2+/-9.8 years) also underwent brain MRI scans. Hypofolatemia, hypertension and age independently predicted a greater severity of total brain WMHs. Separately, the same factors also predicted a greater severity of subcortical WMHs. Hypofolatemic and hypertensive patients had more severe WMHs than normal controls. In light of the adverse impact of WMHs on a number of health-related outcomes later in life, hypofolatemia and hypertension may represent modifiable risk factors to prevent the occurrence of such adverse outcomes.

Adolescent↗

PubMed2005

Prefrontal and temporal gray matter density decreases in opiate dependence.

RATIONALE: There have been only a few structural brain-imaging studies, with varied findings, of opiate-dependent subjects. Voxel-based morphometry (VBM) is suitable for studying whole brain-wise structural brain changes in opiate-dependent subjects. OBJECTIVES: The objective of the current study is to explore gray matter density in opiate-dependent subjects. METHODS: Gray matter density in 63 opiate-dependent subjects and 46 age- and sex-matched healthy comparison subjects was compared using VBM. RESULTS: Relative to healthy comparison subjects, opiate-dependent subjects exhibited decreased gray matter density in bilateral prefrontal cortex [Brodmann areas (BA) 8, 9, 10, 11, and 47], bilateral insula (BA 13), bilateral superior temporal cortex (BA 21 and 38), left fusiform cortex (BA 37), and right uncus (BA 28). CONCLUSIONS: This study reports that opiate-dependent subjects have gray matter density decreases in prefrontal and temporal cortex, which may be associated with behavioral and neuropsychological dysfunction in opiate-dependent subjects.

Adult↗