Regional serotonin transporter availability and depression are correlated in Wilson's disease

Assessment and factors affecting quality of life among patients with Wilson's disease

Wilson's disease is caused by abnormal copper metabolism resulting in deposition in various organs, including the brain, liver, and cornea, thus disrupting organ function. It is characterized by encephalopathy, extrapyramidal symptoms, progressive liver failure, and copper ring deposition in the cornea. Management of this disease should include quality of life maintenance; however, relevant studies on this topic are lacking. This study aimed to assess the factors affecting the quality of life (QoL) of patients with Wilson's disease. A cross-sectional survey using convenience sampling was conducted between July 2020 and March 2021 at the hospital. Data on patient characteristics, 36-item Short-Form General Health Survey, Uniform Wilson Disease Rating Scale, and Hamilton Depression Rating Scale scores were collected. Associations among quality of life depression, anxiety, and Wilson's disease progression were examined using Pearson correlation analysis. Factors affecting the quality of life of patients, including depression, anxiety, liver function, clinical symptoms, diet, liver function, brain magnetic resonance imaging (MRI) findings, disease duration, Barthel Index, and Morse scores were examined using multivariate linear regression analysis. This study included 134 patients with Wilson's disease whose mean age was 29.12 ± 8.59 years. The mean QoL score in the patient group was 71.38 ± 9.55 points and was negatively correlated with anxiety (r = - 0.883, P = 0.000), depression (r = - 0.852 P = 0.000), and clinical symptoms (r = - 0.542, P = 0.000) scores. Anxiety, depression, and clinical symptoms severity are vital factors for the QoL of patients with Wilson's disease. The study provides foundational evidence to design novel interventions, including symptom management, diet, and self-care ability, which can help in improving the quality of life in patients with Wilson's disease and decreasing the burden associated with this disease.

Major Depressive Disorder in an International Multisite Wilson Disease Registry

BACKGROUND AND AIMS

Psychiatric symptoms are frequently reported in Wilson disease (WD); however, systematic assessments with validated measures are lacking.

OBJECTIVE

We aim to report the prevalence and clinical correlates for major depressive disorder (MDD) as resulting from a multisite international WD registry.

METHODS

All patients enrolled in the WD registry received structured psychiatric evaluations (Mini International Neuropsychiatric Interview, Patient Health Questionnaire-9, Generalized Anxiety Disorder-7 scale, Perceived Stress Scale), laboratory tests, hepatology, and neurological assessments. We present the analysis of the data collected at enrollment for the first 3 years (N = 62).

RESULTS

Thirty-seven percent (23) had a lifetime history (MDD), and 6% (4) met the criteria for an active major depressive episode. Depression was self-reported in 30.51% (19) at WD diagnosis. Patients with MDD had worse mental health quality-of-life (QOL) scores (median 43 vs 53.6, P = 0.006), higher severe anxiety (13.04% vs 0), higher perceived stress (median 18 vs 9, P < 0.003), and higher levels of neuroticism (median 8 vs 5.0, P = 0.002). We found no significant difference in physical health QOL and severity of neurological or liver disease. There was no significant difference in copper parameters or liver tests in those with MDD and without. The limitations of our study consist of the small sample size, the cross-sectional report, and the lack of brain copper measurements.

CONCLUSIONS

Lifetime MDD is highly prevalent in WD and associated with worse mental health QOL. We did not find a significant association among liver disease, neurological disease laboratory tests, and MDD. Screening for depression should be considered in patients with WD.

BMI Modifies the Association Between Depression Symptoms and Serum Copper Levels

Depression is one of the most common mental disorders which dramatically threatens public health and wellness. Copper has been known to be involved in many biological processes that could help explaining the occurrence of depression. However, studies focusing on its effect have yielded mixed results. The present study aims to evaluate the association between serum copper levels and depression symptoms. It also investigates the effect of modification of BMI (body mass index) on depression symptoms. A total of 5419 US adults aged 20 years or older from the National Health and Nutrition Examination Survey (NHANES) 2011-2016 participated in the cross-sectional study. Logistic regression models were applied using depression levels as the outcome and serum cooper/selenium/zinc categories as the main predictor, with the adjustments of gender, age, marital status, race, education, family income level, alcohol drinking, cigarette smoking, diabetes, pressure, stroke, and BMI. The interaction terms for copper levels and other covariates were further incorporated into the model to assess their roles in predicting depression symptoms. The prevalence of depression symptoms was significantly higher in samples with a high copper level. Among the levels of serum copper, selenium, and zinc, only the association between depression symptoms and serum copper levels was observed to be significant in the unadjusted model (P = 0.002). Individuals with a high copper level (114-134 μg/dL) and a very high copper level (≥ 134 μg/dL) had 1.85 (95% CI 1.24, 2.77)- and 1.72 (95% CI 1.21, 2.44)-fold higher odds ratio of depression symptoms, respectively, compared to those with a normal serum copper level. Although the association was not significant in the adjusted models, in which confounders were added, the interaction of copper level, including high and very high copper levels, and obesity (BMI ≥ 30 kg/m²) exhibited significantly higher odds ratio (4.12 (95% CI 1.38, 12.27) and 4.53 (95% CI 1.87, 10.96)) of having depression symptoms. The concentration of serum copper was positively associated with the prevalence of depression symptoms. Obesity exacerbated the risk of having depression symptoms in people with high serum copper levels.

Nuklearmedizinische Diagnostik beim Morbus Wilson

Wilson's disease is an autosomal recessive disorder of copper metabolism and is caused by a genetic defect on chromosome 13. Nuclear medicine methods can prove the metabolic defect and contribute to the assessment of central neurological deficits.With high specificity and sensitivity, the intravenous radiocopper test enables the diagnosis to be confirmed as the basis for initiating treatment. The oral radiocopper test is used to monitor zinc treatment.[¹²³I]β-CIT-SPECT and [¹²³I]IBZM-SPECT provide functional information of the nigrostriatal system.[¹²³I]β-CIT-SPECT also allows the determination of SERT availability in the hypothalamus/brain stem as a surrogate parameter of depression.Metabolic parameters of the cortex, basal ganglia and cerebellum can be assessed by [¹⁸F]FDG-PET studies.SPECT and [¹⁸F]FDG-PET studies show significant differences between neurological and non-neurological Wilson patients. Overall, only noninvasive in vivo nuclear medicine enables a deeper insight into the pathophysiology of neurological processes in Wilson's disease.

Wilson's Disease: Clinical, Genetic and Pharmacological Findings

Wilson's disease (WD) is an autosomal recessive disorder characterized by copper accumulation and toxicity in the liver and in other tissues. WD presents with liver disease, neurological or psychiatric disturbances or other less common clinical features. Diagnosis of WD is often difficult and may be formulated through clinical, biochemical, imaging, histochemical and genetic evaluations. Pharmacological approach in WD consists in copper chelating agents such as D-penicillamine, trientine, dimercaprol and tetrathiomolybdate. In 1997 zinc was approved for maintenance therapy of WD by the U.S. FDA. Orthotopic Liver Transplantation is indicated in fulminant hepatic failure, progressive hepatic insufficiency despite therapy, cirrhosis with complications of portal hypertension. However the most appropriate therapy, including OLT, remains controversial in WD and further studies are needed especially in order to differentiate the possibility of specific therapies for different WD phenotypes.

Quality of Life and Psychiatric Symptoms in Wilson's Disease: the Relevance of Bipolar Disorders

INTRODUCTION

Wilson's disease is an inherited disorder caused by a gene located on chromosome 13, which involved copper transportation across cell membranes. The disease can cause a reduced incorporation of copper into ceruloplasmin resulting in accumulation of this metal in the liver, central nervous system, kidneys and other organs. The objective is to define the frequencies of psychiatric disorders in WD, the amount of impairment of Quality of Life [QoL] in patients with WD and the relevance of the psychiatric disorders in the QoL of people suffering by WD.

METHODS

This is a systematic review. The search of the significant articles was carried out in PubMed using specific key words.

RESULTS

Such other neurological diseases, WD is characterized by chronic course and need of treatments, impairment of functional outcomes and high frequency of psychiatric symptoms, although a specific association between Bipolar Disorders and WD was recently found. Despite this, since today few studies are carried on WD patients' quality of life related to psychiatric symptoms. Some new reports showed a link between presence of Bipolar Disorders diagnosis, cerebral damage and low Qol.

CONCLUSION

Prospective studies on large cohorts are required to establish the effective impact of psychiatric disorders comorbidity, particularly Bipolar Disorders, on quality of life in WD and to clarify the causal link between brain damage, psychiatric disorders and worsening of QoL.

Bipolar disorders and Wilson's disease

BACKGROUND

The aim of this study was to determine the risk for Bipolar Disorder (BD) in Wilson's disease (WD) and to measure the impaired Quality of Life (QL) in BD with WD using standardized psychiatric diagnostic tools and a case control design.

METHODS

This was a case control study. The cases were 23 consecutive patients with WD treated at the University Hospital in Cagliari, Italy, and the controls were 92 sex- and age-matched subjects with no diagnosis of WD who were randomly selected from a database used previously for an epidemiological study. Psychiatric diagnoses according to DSM-IV criteria were determined by physicians using structured interview tools (ANTAS-SCID). QL was measured by means of SF-12.

RESULTS

Compared to controls, WD patients had lower scores on the SF-12 and higher lifetime prevalence of DSM-IV major depressive disorders (OR = 5.7, 95% CI 2.4-17.3) and bipolar disorders (OR = 12.9, 95% CI 3.6-46.3). BD was associated with lower SF-12 in WD patients.

CONCLUSIONS

This study was the first to show an association between BD and WD using standardized diagnostic tools and a case control design. Reports in the literature about increased schizophrenia-like psychosis in WD and a lack of association with bipolar disorders may thus have been based on a more inclusive diagnosis of schizophrenia in the past. Our findings may explain the frequent reports of loss of emotional control, hyperactivity, loss of sexual inhibition, and irritability in WD patients. This study was limited by a small sample size.

Distribution volume ratio of serotonin and dopamine transporters in euthymic patients with a history of major depression - a dual-isotope SPECT study

Serotonin transporter (SERT) and dopamine transporter (DAT) levels differ in patients with major depression who are in a depressed state in comparison with healthy controls. The aim of this study was to examine the distribution volume ratios (DVRs) of SERT and DAT in drug-free and euthymic patients with a history of major depression. Subjects comprised 13 patients with a history of major depression and 26 sex- and age-matched healthy controls. The euthymic state of depression was defined as a score of 7 or less on the Hamilton Depression Rating Scale. The DVRs of SERT and DAT were approximated using SPECT, with [(123)I] 2-((2-((dimethylamino)methyl)phenyl)thio)-5-iodophenylamine (ADAM) and [(99m)Tc] TRODAT-1 as the ligands, respectively. There were no significant differences in the DVRs of SERT or DAT between healthy subjects and euthymic patients with a history of major depression; hence, the SERT and DAT DVRs may not therefore be trait markers for patients with major depression, which helps us to understand more about the pathophysiology of depression.

Dopamine transporter imaging in adult patients with attention-deficit/hyperactivity disorder

The aim of this study was to provide in vivo evidence for the hypothesis that dopaminergic neurotransmission is altered in adult patients with attention-deficit/hyperactivity disorder (ADHD). We used high-resolution brain-dedicated single-photon emission computed tomography and the dopamine transporter (DAT) marker [(123)I]FP-CIT in 17 adult treatment-naïve ADHD patients and 14 age-matched controls. Magnetic resonance imaging-based region of interest analysis was performed to quantify the DAT availability (expressed as a ratio of specific to non-displaceable binding, V(3)'') in the striatum. Additionally, the specific radiotracer binding was assessed in the thalamus and the midbrain/brainstem regions (reflecting also the availability of the serotonin transporter to which [(123)I]FP-CIT binds with moderate affinity). In the striatal areas of the ADHD patients, a significantly reduced specific tracer binding was found (V(3)'': 5.18+/-0.98; controls 6.36+/-1.34). In contrast, the specific [(123)I]FP-CIT binding did not differ from controls in the thalamus and midbrain/brainstem areas. These data indicate a reduced dopaminergic but not serotonergic transmitter reuptake function in adult ADHD. Further studies will have to deal with the question of whether these findings have the potential to influence treatment decisions in this complex disorder.

High ceruloplasmin levels are associated with obsessive compulsive disorder: a case control study

Background

Alterations in ceruloplasmin are currently assumed as one of the mechanisms underlying the development of a number of neurodegenerative disorders. Several studies indicate that elevated serum ceruloplasmin levels may play a role in schizophrenia by exacerbating or perpetuating dopaminergic dysregulation. No study investigating the relationship between ceruloplasmin and obsessive-compulsive disorder (OCD) has been published to date. Nowadays OCD is increasingly speculated to be a different disorder than other anxiety disorders, and rather is considered to be more similar to psychotic disorders. The objective of this study to explore whether there is an association of ceruloplasmin with OCD as in schizophrenia.

Method

26 pure OCD and 9 co-morbid OCD patients from Gaziantep University Sahinbey Research Hospital, Psychiatry Clinics, diagnosed according to the DSM IV and 40 healthy controls were included in the study. Blood samples were collected; ceruloplasmin levels were measured.

Results

The mean ceruloplasmin level in pure OCD patients, co-morbid OCD patients, and control group persons were 544.46 ± 26.53, 424.43 ± 31.50 and 222.35 ± 8.88 U/L respectively. Results of all 3 groups differ significantly. Positive predictive value of ceruloplasmin for that cut-off point is 31/31 (100%) and negative predictive value is 40/44 (91%) in our group.

Conclusion

Although the nature of relationship is not clear there was an association between ceruloplasmin levels and OCD in our study.

Is major depressive disorder a metabolic encephalopathy?

Metabolic encephalopathy is an acute disturbance in cellular metabolism in the brain evoked by conditions of hypoxia, hypoglycaemia, oxidative stress and/or inflammation. It usually develops acutely or subacutely and is reversible if the systemic disorder is treated. If left untreated, however, metabolic encephalopathy may result in secondary structural damage to the brain. Most encephalopathies are present with neuropsychiatric symptoms, one in particular being depression. However, mood disorders are often co-morbid with cardiovascular, liver, kidney and endocrine disorders, while increasing evidence concurs that depression involves inflammatory and neurodegenerative processes. This would suggest that metabolic disturbances resembling encephalopathy may underscore the basic neuropathology of depression at a far deeper level than currently realized. Viewing depression as a form of encephalopathy, and exploiting knowledge gleaned from our understanding of the neurochemistry and treatment of metabolic encephalopathy, may assist in our understanding of the neurobiology of depression, but also in realizing new ideas in the pharmacotherapy of mood disorders.

Psychopathology and personality traits in patients with treated Wilson disease grouped according to gene mutations

Wilson disease (WD) is a recessively inherited copper storage disorder mainly affecting liver and brain. Genotype/phenotype correlations have been report ed but as yet not regarding psychic symptoms. Our aim was to investigate if a correlation might exist between genotype and phenotype concerning psychopathology and/or personality traits in patients with treated WD. Nine homozygous and three compound heterozygous Swedish patients were retrospectively investigated, representing four different mutation settings. Psychopathological symptoms were studied using the Comprehensive Psychopathological Rating Scale (CPRS), personality traits using the Karolinska Scales of Personality (KSP) and mutations were analyzed by manifold sequencing. Psychopathological symptoms: Patients with the Trp779Stop mutation had the lowest scores on the total CPRS, due to less pronounced reported CPRS items, as compared to the other three groups of patients. Compound heterozygotes for the His1069Gln/Arg1319Stop mutation showed the highest total CPRS scores. Personality traits: Patients homozygous for the Trp779Stop and the Thr977Met mutations had high scores on Psychopathy related scales whereas patients with His1069Gln/Arg1319Stop mutations had the lowest scores on these scales. Serum ceruloplasmin levels were undetectable in all patients with the Trp779Stop and Thr977Met mutations. The results show a trend towards a genotype/phenotype correlation regarding psychopathological symptoms and personality traits in treated patients with WD. If replicable, these results might contribute to the elucidation of the possible clinical importance of functionally deleterious gene mutations in WD psychopathology and personality traits.

Copper induced oxidation of serotonin: analysis of products and toxicity

Serotonin is a major neurotransmitter that controls many functions, ranging from mood and behaviour through to sleep and motor functions. The non-enzymatic oxidation of serotonin is of significant importance as some oxidation products are considered to be neurotoxic. An interaction between copper and serotonin has been suggested by symptoms observed in a number of neurodegenerative diseases such as Wilson's and Prion diseases. Using PC12 cells as a model of neuronal cells, we show that the interaction between copper and serotonin is toxic to undifferentiated cells. The toxicity is largely due to reactive oxygen species as cell death is significantly reduced in the presence of the antioxidant mannitol. Differentiation of the PC12 cells also confers resistance to the oxidative process. In vitro oxidation of serotonin by copper results in the eventual formation of a coloured pigment, thought to be a melanin-like polymeric species. Using spectroscopic methods we provide evidence for the formation of a single intermediate product. This dimeric intermediate was identified and characterized as 5,5'-dihydroxy-4,4'-bitryptamine. These results indicate that copper structurally alters serotonin and this process may play a role in copper related neurodegenerative diseases.

Reduced midbrain serotonin transporter availability in drug-naïve patients with depression measured by SERT-specific [(123)I] nor-beta-CIT SPECT imaging

Earlier results have indicated that serotonin transporter (SERT) availability is altered in major depression. We examined SERT density with a more serotonin-specific ligand and with a larger number of patients than in previous studies. Twenty-nine antidepressant-naïve patients with major depressive disorder (MDD) and 19 healthy age- and sex-matched controls were studied with SPECT using [(123)I] nor-beta-CIT as a ligand. The patients had a significantly lower (-10%) binding potential in the midbrain region than controls. No correlation with depression severity was found. These findings indicate that SERT availability in the midbrain area is reduced in depression, and that interindividual variation is considerable in both patients and controls.

Possible impact of dopamine SPECT on decision-making for drug treatment in Parkinsonian syndrome

Single-photon emission computed tomography (SPECT) markers allow measuring the integrity of the brain dopaminergic system in vivo. We used dopamine transporter (DAT) SPECT with [(123)I]FP-CIT and dopamine D(2)/D(3) receptor SPECT with [(123)I]IBZM to evaluate whether there is a reduction of DAT and/or D(2)/D(3) receptor SPECT in treated and untreated patients with Parkinsonian syndrome (PS). We found that almost a quarter of our patients treated with anti-Parkinsonian medication prior to SPECT imaging did not show evidence of a presynaptic dopaminergic deficit while 37% of untreated patients were diagnosed as having Parkinson's disease. 17% of treated patients had additional loss of D(2)/D(3) receptor binding capacity in concordance with the clinical follow-up diagnoses of multiple system atrophy, progressive nuclear palsy, and vascular Parkinsonism. Apart from 38% clinically uncertain cases, SPECT was in concordance with 75% of initial clinical diagnoses. 25% were reclassified as indicated by SPECT findings and confirmed by a 1.5-year clinical follow-up. We conclude that dopamine SPECT may support establishing or refuting the clinical diagnosis and, therefore, help to make the decision for or against dopaminomimetic treatment in cases with PS.

Sex differences in diencephalon serotonin transporter availability in major depression

BACKGROUND

Major depression is more prevalent in women than men. The present study evaluated if previous findings that demonstrated decreased 5-hydroxytryptamine (5-HT) transporter availability in depressed patients would be confirmed in a larger sample and also evaluated sex differences.

METHODS

Depressed (n = 32) and healthy subjects (n = 32), including 16 pairs of women and men, participated in an iodine-123-2 beta-carbomethoxy-3beta-(4-iodophenyltropane) ([(123)I]beta-CIT) single photon emission computed tomography (SPECT) and a magnetic resonance imaging (MRI) scan. Participants were administered [(123)I]beta-CIT (225.7 +/- 3.7 MBq) and imaged 23.0 +/- 1.6 hours later. Statistical analyses included analysis of variance and a regression analysis of the main and interactive effects of age, sex, and depression.

RESULTS

Overall, depressed patients demonstrated 12% lower diencephalon and no change in striatal or brainstem [(123)I]beta-CIT uptake. Significant age by sex, sex by depression, and age by sex by depression interactions were noted due to 22% lower diencephalon [(123)I]beta-CIT uptake in depressed women compared with less than a 1% decrease in depressed men.

CONCLUSIONS

As observed previously, diencephalon 5-HT transporter availability is decreased in depressed patients. However, the decrease appears to be sex-specific and age-dependent. These findings suggest that serotonergic mechanisms mediating depressed mood differ between men and women in an age-dependent manner and may explain why young women respond better to treatment with selective serotonin reuptake inhibitor (SSRI) antidepressants.

Wilson disease

Wilson disease (WD) is an autosomal recessive inherited disorder of copper metabolism, resulting in pathological accumulation of copper in many organs and tissues. The hallmarks of the disease are the presence of liver disease, neurologic symptoms, and Kayser-Fleischer corneal rings. The leading neurologic symptoms in WD are dysathria, dyspraxia, ataxia, and Parkinsonian-like extrapyramidal signs. Changes in the basal ganglia in brain magnetic resonance imaging (MRI) are characteristic features of the disease. In presence of liver cirrhosis, some features may resemble hepatic encephalopathy. Symptoms and MRI abnormalities may be fully reversible on treatment with zinc or copper chelators. Improvement can be monitored by serial recording of brain-stem-evoked responses. The basic defect is an impaired trafficking of copper in hepatocytes. ATP7B is the gene product of the WD gene located on chromosome 13 and resides in hepatocytes in the trans-Golgi network, transporting copper into the secretory pathway for incorporation into apoceruloplasmin and excretion into the bile. While about 40% of patients preset with neurologic symptoms, little is known about the role of copper and ATP7B in the central nervous system. In some brain areas, like in the pineal gland, ATP7B is expressed and functionally active. Increasing evidence supports an important role for metals in neurobiology. Two proteins related to neurodegeneration are copper-binding proteins (1) the amyloid precursor protein (APP), a protein related to Alzheimer's disease, and (2) the Prion protein, related to Creutzfeldt-Jakob disease. A major source of free-radical production in the brain derives from copper. To prevent metal-mediated oxidative stress, cells have evolved complex metal transport systems. APP is a major regulator of neuronal copper homeostasis and has a copper-binding domain (CuBD). The surface location of this site, structural homology of CuBD to copper chaperones, and the role of APP in neuronal copper homeostasis are consistent with the CuBD acting as a neuronal metallotransporter. There are several copper-containing enzymes in the brain, like dopamine beta hydroxylase or Cu/Zn superoxide dismutase (SOD1). Their function may be altered because of copper overload. WD appears to be associated with a dopaminergic deficit. Mutations in the SOD1gene cause familial amyotrophic lateral sclerosis. Survival of transgenic mice with a mutant SOD1 which fails to incorporate Cu((2+)) in its active site was improved by copper depletion. Wilson disease (WD) is an autosomal recessive inherited disorder in which copper pathologically accumulates primarily within the liver and subsequently in the neurologic system and many other organs and tissues. Presence of liver disease, neurologic symptoms, and Kayser-Fleischer corneal rings are the hallmarks of the disease.

Serotonin and dopamine transporter imaging in patients with obsessive-compulsive disorder

In obsessive-compulsive disorder (OCD), the success of pharmacological treatment with serotonin re-uptake inhibitors and atypical antipsychotic drugs suggests that both the central serotonergic and dopaminergic systems are involved in the pathophysiology of the disorder. We applied [123I]-2beta-carbomethoxy-3beta-(4-idiophenyl)tropane (beta-CIT) and a brain-dedicated high-resolution single photon emission computed tomography (SPECT) system to quantify dopamine transporter (DAT) and serotonin transporter (SERT) availability. By comparing 15 drug-naïve patients with OCD and 10 controls, we found a significantly reduced availability (corrected for age) of striatal DAT and of thalamic/hypothalamic, midbrain and brainstem SERT in OCD patients. Severity of OCD symptoms showed a significant negative correlation with thalamic/hypothalamic SERT availability, corrected for age and duration of symptoms. Our data provide evidence for imbalanced monoaminergic neurotransmitter modulation in OCD. Further studies with more selective DAT and SERT radiotracers are needed.

Trafficking of the plasma membrane gamma-aminobutyric acid transporter GAT1. Size and rates of an acutely recycling pool

Plasma membrane neurotransmitter transporters rapidly traffic to and from the cell surface in neurons. This trafficking may be important in regulating neuronal signaling. Such regulation will be subject to the number of trafficking transporters and their trafficking rates. In the present study, we define an acutely recycling pool of endogenous gamma-aminobutyric acid transporters (GAT1) in cortical neurons that comprises approximately one-third of total cellular GAT1. Kinetic analysis of this pool estimates exocytosis and endocytosis time constants of 1.6 and 0.9 min, respectively, and thus approximately one-third of the recycling pool is plasma membrane resident in the basal state. Recent evidence shows that GAT1 substrates, second messengers, and interacting proteins regulate GAT1 trafficking. These triggers could act by altering trafficking rates or by changing the recycling pool size. In the present study we examine three GAT1 modulators. Calcium depletion decreases GAT1 surface expression by diminishing the recycling pool size. Sucrose increases GAT1 surface expression by blocking clathrin- and dynamin-dependent endocytosis, but it does not change the recycling pool size. Protein kinase C decreases surface GAT1 expression by increasing the endocytosis rate, but it does not change the exocytosis rate or the recycling pool size. Based upon estimates of GAT1 molecules in cortical boutons, the present data suggest that approximately 1000 transporters comprise the acutely recycling pool, of which 300 are on the surface in the basal state, and five transporters insert into the plasma membrane every second. This insertion could represent the fusion of one transporter-containing vesicle.

Brain serotonin transporter availability predicts treatment response to selective serotonin reuptake inhibitors

BACKGROUND

Few studies have investigated the predictive value of central serotonin transporter (SERT) availability for treatment response to serotonin reuptake inhibitors (SSRIs). This study used brain imaging to examine the relationship between pretreatment brain SERT availability and transporter occupancy by SSRIs with treatment response in two independent depressed populations.

METHODS

Study 1: Twenty-three patients with major depression underwent a single photon emission computed tomography (SPECT) measurement of brain SERT availability using [123I]beta-CIT ([123I]methyl 3beta-(4-iodophenyl) tropane-2beta-carboxylate. The SERT availability was correlated with treatment response to fluoxetine (20 mg/day) assessed with weekly Hamilton Depression Rating Scale (HDRS) for 6 weeks. Study 2: The second group included 10 depressed patients who received 6 weeks of paroxetine treatment (20 mg/day) and serial SPECT scans (baseline, during, and after the treatment).

RESULTS

In Study 1, higher pretreatment diencephalic SERT availability significantly predicted better treatment response 4 weeks later. Similar results were found in Study 2 and supported Study 1 findings. The data showed that greater occupancy of diencephalic transporters by paroxetine correlated with better treatment response.

CONCLUSIONS

Higher pretreatment availability and greater occupancy of SERT in diencephalon may predict better treatment course in response to SSRIs.