phenylthiourea and Schizophrenia

Reports suggesting that schizophrenia participants are more likely to be phenylthiocarbamide (PTC) non-tasters when compared to controls have recently been controversial. If supported, a genetic-based phenotypic variation in PTC taster status is implicated, suggesting a greater illness risk for those participants with recessive alleles for the TAS2R38 receptor. Should PTC insensitivity be a schizophrenia endophenotype, then it would be expected in follow-up of ultra high-risk for psychosis participants who later develop schizophrenia (UHR-S). UHR-S was hypothesised to show reduced PTC sensitivity compared to those who were previously at risk, but did not transition (UHR-NP). PTC perception was assessed in 219 UHR participants at long-term follow-up, of whom 53 had transitioned to psychosis (UHR-P) during the follow-up period. Fifteen of the 219 participants were diagnosed with schizophrenia. Seventy-eight had a family history of psychotic disorder. No differences in PTC taster status were found in UHR participants based upon transition to psychosis status, schizophrenia diagnosis, or family history of schizophrenia. This report indicates that schizophrenia development among UHR participants is not associated with PTC tasting deficits and fails to support previous findings that inability to detect the bitter taste of PTC is a schizophrenia endophenotype.

Topics: Adolescent; Adult; Disease Progression; Endophenotypes; Female; Humans; Male; Phenylthiourea; Psychiatric Status Rating Scales; Psychotic Disorders; Schizophrenia; Schizophrenic Psychology; Taste Perception

Phenylthiocarbamide (PTC) taste sensitivity is an inherited trait determined primarily by allelic variation of the taste-receptor gene TAS2R38 on chromosome 7q. Results of prior studies examining the ability to taste PTC in patients with schizophrenia have been mixed because of the difficulties in measuring PTC taste sensitivity behaviorally. In the current study, we examined the TAS2R38 genotypes of schizophrenia patients to determine whether the increased prevalence of nontasters in this patient population was indicative of a specific genetic association. Our a-priori hypothesis was that schizophrenia patients would show an increased prevalence of the nontaster phenotype compared with controls. The genotypes of two nonsynonymous coding single-nucleotide polymorphisms in TAS2R38 were assayed for 176 schizophrenia patients and 229 healthy control individuals, and the two-allele haplotypes were estimated. There was an over-representation of the major PTC nontaster haplotype among patients of European descent, relative to control individuals of similar ancestry. Patients and controls of African ancestry did not differ. The PTC nontaster haplotype is a genetic marker that may be used to identify subsets of schizophrenia patients who potentially harbor vulnerability genes in this region of chromosome 7q.

Topics: Adult; Chromosomes, Human, Pair 7; Female; Haplotypes; Humans; Male; Middle Aged; Phenylthiourea; Receptors, G-Protein-Coupled; Schizophrenia; Taste Buds

The inability to taste phenylthiocarbamide (PTC; "taste-blindness") has been associated with a number of medical and neurological illnesses not typically related to taste. We examined PTC sensitivity in 67 schizophrenia patients, 30 healthy controls, and 30 first-degree relatives to determine whether taster status could represent a simple vulnerability marker. A higher prevalence of non-tasters was seen in patients and family members relative to healthy controls. Among patients, non-tasters exhibited increased levels of negative and first-rank symptoms as well as poorer right nostril odor identification skills relative to PTC tasters. These differences were not explained by age, sex, education, smoking, or intensity differences. Phenotypic variation in PTC sensitivity is thought to be genetic in origin and suggests greater illness risk for those subjects with recessive taster alleles.

Topics: Adult; Female; Genes, Recessive; Humans; Male; Middle Aged; Phenylthiourea; Psychiatric Status Rating Scales; Psychophysics; Reference Values; Risk Factors; Schizophrenia; Schizophrenic Psychology; Schizotypal Personality Disorder; Smell; Statistics as Topic; Taste Threshold

This study sought to replicate recent findings that both patients and relatives are significantly more likely to be phenylthiocarbamide (PTC) nontasters than healthy controls, and that within the patient group, nontasters have more severe positive and/or negative symptoms than tasters. Associations between PTC-tasting status and olfactory identification scores also were examined.. PTC perception and olfactory identification were assessed in 48 patients with schizophrenia or schizoaffective disorder, 28 first-degree relatives, and 32 healthy volunteers.. The three groups did not differ in PTC taste sensitivity. Findings did not change after: a sensitivity analysis that re-categorized participants who "possibly" tasted PTC, excluding Caucasian participants, or restricting the sample of patients to only those with schizophrenia. Among the patients, tasters and nontasters did not differ with regard to positive, negative, or general psychopathology symptoms. In the combined sample and the three groups separately, there were no associations between PTC-tasting status and olfactory identification scores.. This study, conducted specifically as an attempt to replicate previously reported findings, failed to provide support for PTC perception as an endophenotypic marker for schizophrenia. Further research is warranted.

Topics: Adult; Control Groups; Diagnostic and Statistical Manual of Mental Disorders; Dysgeusia; Family; Female; Genetic Markers; Humans; Male; Phenotype; Phenylthiourea; Psychiatric Status Rating Scales; Schizophrenia; Schizophrenic Psychology; Taste Threshold

The inability to taste phenylthiocarbamide (PTC) has been associated with medical and neurological illnesses not typically related to taste. The authors examined PTC sensitivity in schizophrenia patients and their non-ill relatives to determine whether this represented a vulnerability marker.. PTC sensitivity was assessed in 42 schizophrenia patients, 23 healthy comparison subjects, and 12 first-degree relatives of the patients.. More nontasters were found among patients and family members than healthy comparison subjects. Among patients, nontasters had more positive symptoms. Differences were not explained by sex, age, medication, smoking, or cognitive impairment.. The prevalence of PTC nontasters was greater among schizophrenia patients and non-ill first-degree family members. Phenotypic variation in PTC sensitivity is genetic in origin. This suggests a higher risk for illness among subjects with recessive alleles.

Topics: Adult; Comorbidity; Discrimination, Psychological; Family; Female; Genes, Recessive; Genetic Predisposition to Disease; Genetic Variation; Humans; Male; Pedigree; Phenotype; Phenylthiourea; Prevalence; Schizophrenia; Taste; Taste Disorders; Taste Threshold

Topics: Adolescent; Adult; Aged; Child; Child, Preschool; Epilepsy; Eye; Female; Functional Laterality; Genetics, Population; Hair; Hand; Humans; Infant; Infant, Newborn; Male; Middle Aged; Pedigree; Phenylthiourea; Pigmentation; Schizophrenia; Sex Ratio; Tajikistan; Taste

Topics: Alcoholism; Bipolar Disorder; Black or African American; Chromosome Mapping; Epilepsy; Female; Genes; Genetics, Medical; Humans; Intellectual Disability; Male; Mental Disorders; Phenylthiourea; Schizophrenia; Sex Factors; Taste; White People