Marco Catalano

Polymorphism within the promoter of the serotonin transporter gene and antidepressant efficacy of fluvoxamine

Depression with psychotic features has been shown to respond to selective serotonin reuptake inhibitors (SSRIs). The serotonin transporter (5-HTT) is a prime target for SSRIs. A functional polymorphism within the promoter region of the 5-HTT gene, leading to different transcriptional efficiency, was recently reported. We tested the hypothesis that allelic variation of the 5-HTT promoter could be related to the antidepressant response to fluvoxamine and/or augmentation with pindolol (a serotonin autoreceptors antagonist) which has been suggested as an augmentation therapy for nonresponders. One hundred and two inpatients with major depression with psychotic features were randomly assigned to treatment with a fixed dose of fluvoxamine and either placebo or pindolol for 6 weeks. Depression severity was assessed once a week using the Hamilton Depression Rating Scale. Allelic variation in each subject was determined using a PCR-based method. Data were analyzed with a three-way repeated measures analysis of variance. Both homozygotes for the long variant (l/l) of the 5-HTT promoter and heterozygotes (l/s) showed a better response to fluvoxamine than homozygotes for the short variant (s/s). In the group treated with fluvoxamine plus pindolol all the genotypes acted like l/l treated with fluvoxamine alone. Fluvoxamine efficacy in delusional depression seems to be related to allelic variation within the promoter of the 5-HTT gene. Even though other factors may be implicated, genotyping at 5-HTT promoter may represent a promising tool to individualize the pharmacological treatment of depression.

Distribution of a novel mutation in the first exon of the human dopamine D4 receptor gene in psychotic patients

Disturbances in dopaminergic transmission have been implicated in the etiology of psychotic disorders. Interindividual differences in deoxyribonucleic acid (DNA) sequences coding for dopamine receptor proteins might contribute to the genetic background of these diseases. We have identified a variation in exon 1 of the dopamine D4 receptor (DRD4) gene, which is characterized by a polymorphic 12 base pair (bp) repeat. This repeat codes for a sequence of four amino acids in the extracellular N-terminal part of the receptor, which borders the first putative transmembrane domain. The 12bp repeat occurs as a two-fold repeat in the more common variant (A1 allele) and is represented only once in the rarer one (A2 allele). The frequency of this DNA polymorphism was determined in a sample of 59 patients suffering from delusional disorder, in 79 schizophrenic patients, and in 75 control subjects. Sixteen (27%) of the 59 patients with delusional disorder carried the A2 allele compared with six (8%) of the controls. The observed difference in genotype frequencies between patients with delusional disorder and controls was highly significant. There were no significant differences in genotype frequencies between schizophrenics and controls: Our results strongly suggest the involvement of genetic variation in the DRD4 gene in conferring susceptibility to delusional disorder.

Serotonin transporter linked polymorphic region in anorexia nervosa and bulimia nervosa.

SIR – Strong genetic liability and common etiopathogenetic background have been suggested for Eating Disorders (ED). Several lines of evidence support a possible involvement of serotonin (5-HT) pathways in modulating eating behavior, since alteration in 5-HT activity has been consistently demonstrated in ED. Moreover, 5-HT disturbances seem to persist after recovery. These findings and the efficacy of 5-HT reuptake inhibitors in the treatment of ED suggest the serotonin transporter (5-HTT) gene as a good candidate for genetic studies. A deletion (short variant = s)/insertion (long variant = l) functional polymorphism has been described within the promoter region of the 5-HTT gene (5-HTTLPR). Studies of transfected cells in culture show that the long and short variants exhibit different transcriptional properties. In particular, basal transcriptional activity of the long variant is more than twice that of the short form. We studied this polymorphism in a sample of 50 bulimic (BN), 56 anorexic (AN) patients (19 restricting and 37 binge-eating type) and 120 healthy controls, closely questioned to exclude any psychiatric disorder. Informed consent was obtained from all the subjects, females, unrelated and of Italian descent. Patients fulfilled DSM-IV diagnostic criteria and were sequentially recruited at the Eating Disorder Clinic and Research Unit at San Raffaele University Hospital, Milan. Genomic DNA was extracted from whole blood and the polymorphism was analyzed as previously described. Statistical analysis was performed with x statistics and power calculation with the EPINFO program (version 6.04b, 1997). Table 1 shows the distribution of 5-HTTLPR alleles and genotypes in our sample. Genotype frequencies in controls and both subtypes of AN patients are in Hardy–Weinberg (H–W) equilibrium, while the BN group shows a significant deviation due to a lowerthan-expected frequency of the l/l genotype.

SSRIs antidepressant activity is influenced by Gβ3 variants

Abstract The aim of the present study was to test a possible effect of the G-protein β3-subunit (Gβ3) C825T gene variant on the antidepressant activity of selective serotonin reuptake inhibitors (SSRIs) in a sample of major and bipolar depressives, with or without psychotic features. Four hundred and ninety inpatients were treated with fluvoxamine 300 mg/day ( n =362) or paroxetine 40 mg/day ( n =128) and either placebo or pindolol in a double-blind design for 6 weeks. The severity of depressive symptoms was weekly assessed with the Hamilton Rating Scale for Depression. Gβ3 allelic variants were determined in each subject using a PCR-based technique. Subjects with Gβ3 T/T variants showed better response to treatment ( P =0.009) and this effect was independent from analyzed demographic and clinical variables. These results confirm preliminary reports and shed further light on the genetics of the response to antidepressant treatments.

Amino acid patterns in schizophrenia: Some new findings

Blood concentrations of various amino acids were measured in schizophrenic patients and control subjects. Significantly higher blood concentrations of glycine, glutamate, and serine were found in the schizophrenic patients. Glycine was abnormally elevated in subjects with paranoid or undifferentiated schizophrenia, but not in disorganized patients. Since glutamate, glycine, and serine play a complex role in the regulation of N-methyl-D-aspartate (NMDA) receptors, which are important in the control of normal cognitive processes, we hypothesized that the elevated levels of these amino acids might disrupt the normal functioning of NMDA receptors and might be involved in the pathophysiology of schizophrenia.

Plasma Tryptophan to Large Neutral Amino Acids Ratio and Therapeutic Response to a Selective Serotonin Uptake Inhibitor

The molar ratio of total plasma tryptophan (Trp) to the sum of the other large neutral amino acids (LNAAs), thought to reflect brain serotonin (5-HT) formation, was estimated in 47 patients with major depression (unipolar and bipolar) before and after 6 weeks of treatment with a serotonin uptake inhibitor, fluvoxamine. We found a significant difference between responders (n = 39) and nonresponders (n = 8) for the pre- and in-treatment plasma Trp to LNAAs ratios. In contrast, there were no differences between the two groups for the mean plasma steady-state fluvoxamine levels. These findings suggest that a specific plasma amino acid profile may be a useful indicator of good clinical response to a selective 5-HT uptake inhibitor.

An association study between 5-HTTLPR polymorphism, COMT polymorphism, and Tourette's syndrome.

Several lines of evidence suggest that a genetic component underlies Tourettes syndrome (TS). We investigated both the role of the insertion/deletion polymorphism in the promoter region of the serotonin transporter gene (5-HTTLPR) and that of the Val-158-Met substitution in the catechol-O-methyl-transferase (COMT) gene in conferring susceptibility to TS. Fifty-two TS patients were recruited and compared with a control group of 63 healthy subjects. Neither a genotypic nor an allelic association was found; subdividing TS patients according to clinical variables, such as a co-diagnosis of obsessive-compulsive disorder (OCD) and a positive family history for obsessive compulsive disorder or tics, also failed to reveal a significant association. The lack of significance for 5-HTTLPR and COMT polymorphisms in conferring liability to TS does not exclude a role of different functional polymorphisms in genes coding for serotonergic or dopaminergic structures in the etiology of TS. In fact, TS is a complex disorder and these genes most likely have only a minor genetic effect in its etiology.

Identification of two novel polymorphisms and a rare deletion variant in the human dopamine D4 receptor gene.

We report two novel polymorphisms and a rare deletion variant in the human dopamine D4 receptor gene. The two polymorphisms are characterized by single base pair substitutions, namely a G→C transversion changing codon 11 from GGG (encoding Gly) to CGG (encoding Arg) and a C→T transition in position −11 upstream from the start codon. The Arg11 variant occurs at a frequency of about 1% and the C→T transition at a frequency of about 7% in German control subjects (n = 148). Allele frequencies observed in patients suffering from schizophrenia (n = 256) and bipolar affective disorder (n = 99) were similar. The deletion variant is characterized by a 21 bp deletion affecting codons 36 to 42 coding for amino acids Ala-Ala-Leu-Val-Gly-Gly-Val located in the first transmembrane domain of the dopamine D4 receptor. The mutation was identified in a single individual suffering from obsessive-compulsive disorder and panic disorder. We were unable to detect the deletion in patients with schizophrenia and bipolar affective disorder, nor in healthy controls.

Psychoimmunoendocrine Investigation in Anorexia nervosa

Immunological and neuroendocrine parameters were examined in 11 women with anorexia nervosa, 6 restricted and 5 bulimic-anorectics, 17-43 years old with 2-15 years duration of the disease, and in 11 age- and sex-matched psychophysically healthy controls. The T lymphocyte proliferative response to phytohemagglutinin (PHA), plasma adrenocorticotropic hormone (ACTH), cortisol and beta-endorphin (beta-EP) levels was examined in basal conditions and after corticotropin-releasing hormone (CRH) stimulation. Cortisol inhibition by dexamethasone (DST), and basal growth hormone (GH) and prolactin (PRL) levels were also examined. The immune study did not reveal significant differences between patients and controls. ACTH and cortisol basal levels were significantly higher in anorectics, while beta-EP, GH and PRL concentrations did not differ in the two groups. ACTH, beta-EP and cortisol responses to CRH were blunted in anorectics and the DST impaired in 55% of the patients. No correlations were observed between neuroendocrine impairments and the T lymphocyte response to PHA, or between the immunological neuroendocrine parameters and the body mass index of either patients or controls.

Systematic screening for mutations in the coding region of the human serotonin transporter (5‐HTT) gene using PCR and DGGE

Dysfunctions in serotonergic pathways may underlie several psychiatric disorders. The reuptake of serotonin (5-HT) from synaptic terminals is mediated by a specific transporter (5-HTT). Genetic variation in the gene coding for the 5-HTT protein might be involved in the predisposition to psychiatric disorders. A systematic screening of the whole coding sequence of the 5-HTT gene in mood disorder (MD) and obsessive-compulsive disorder (OCD) patients, as well as in healthy controls, using PCR and denaturing gradient gel electrophoresis (DGGE) revealed the presence of two mutations. The first was in intron 4, and the second was a C-->A transversion leading to an amino-acid exchange (Leu-->Met) in position 255 of the deduced protein sequence. No further occurrence of this substitution was found in an extended sample of patients and controls. Therefore, structural modifications of the 5-HTT gene do not seem to play either a major or minor role in the genetic predisposition to MD or OCD.