Andrea Tedde

5-HT2A receptor gene polymorphisms in anorexia nervosa and bulimia nervosa.

To examine the distribution of different polymorphisms in genes of the 5-HT system in patients with anorexia nervosa (AN) and bulimia nervosa (BN), we analyzed the distribution of a polymorphism (-1438G/A) and the presence of known mutations in 5-HT2A and 5-HT2C receptor genes in 168 Italian female patients affected by AN and BN. Patients with AN restricting type (ANr) only, unlike those with AN binge eating/purging type (ANp) and BN purging type (BNp), showed a statistically significant difference in 5-HT2A-1438A/A genotype frequency with respect to controls. With regard to the other polymorphisms, no differences were found in the studied groups with respect to controls. 5-HT2A promoter polymorphism is probably implicated in the susceptibility to eating disorders and its involvement is more significant in ANr, when compared with ANp and BNp.

5-HT2A promoter polymorphism in anorexia nervosa

A study has shown an association between a polymorphism (–1438G/A) in the promoter region of the 5-HT2A gene and anorexia nervosa. Two independent groups failed to replicate these data. We studied this polymorphism in two clinical subtypes of anorexia nervosa and in controls. We analysed the segregation of this polymorphism in 77 female patients with anorexia nervosa, according to DSM-IV criteria (43 restricting-type, body-mass index [BMI] 14·9 [SD 2·6] kg/m, and 34 purging type, BMI 16·0 [1·9] kg/m, 15–34 years (mean age 24·58 [5·75] years). All patients or their parents gave their informed written consent. We also studied 107 normal female age-matched controls (age 15–36 years, mean age 25·33 [5·57] years), obtained from the DNA bank of the CNR (National Research Council, Florence, Italy). All controls were carefully assessed to exclude any neurological or psychiatric disorders. DNA from affected and non-affected individuals was extracted from transformed lymphoblasts or peripheral blood samples with the phenolchloroform procedure. Amplification from 200 ng of genomic DNA was done with a Thermal Cycler 9600 (Perkin Elmer). The 1438G/A polymorphism was analysed as previously described. The frequencies of 1438G/A alleles were estimated by gene counting. Statistical analysis was done with the 2 test. The table shows the distribution of 1438G/A alleles and genotypes in the different groups. The distribution of 1438G/A genotypes in all groups followed HardyWeinberg equilibrium. A significant difference in the distribution of 1438A/A genotype was observed in anorexia patients compared with the control group (p 0·1). Our data independently confirm and extend previous results, suggesting a role of the 5-HT2A gene in anorexia. Two other groups have reported negative results. However, one study had no controls and did not report the 1438A/A genotype in anorexia nervosa. Indeed, the 1438A/A genotype is similar in all series of anorexia patients (0·3, 0·25, and 0·29), but Campbell’s study showed a very high frequency in the control group (0·2) compared with the other series (0·12 and 0·9 in our study). This difference in controls may explain the difference in results. Our results also suggest that restricting and purging types of anorexia nervosa have a different involvement of the 5-HT2A gene promoter polymorphism. This finding may lead to a better understanding of the two types of this severe psychiatric disease and suggests a different implication of the serotonergic system in the pathogenesis and possibly in treatment of anorexia nervosa. 1 Collier DA, Arranz MJ, Li T, Mupita D, Brown N, Treasure J. Association between the 5-HT2A gene promoter polymorphism and anorexia nervosa. Lancet 1997; 350: 412. 2 Hinney A, Ziegler A, Nothen MA, Remschmidt H, Hebebrand J. 5-HT2A receptor gene polymorphism, anorexia nervosa, and obesity. Lancet 1997; 350: 1324–25. 3 Campbell DA, Sundaramurthy D, Markham AF, Pieri LF. Lack of association between 5-HT2A gene promoter polymorphism and susceptibility to anorexia nervosa. Lancet 1998; 351: 499.

Screening for mutations in the neurofibromatosis type 2 (NF2) gene in sporadic meningiomas

Meningiomas are benign tumors of the central nervous system. They are usually sporadic but can also occur associated with the neurofibromatosis type 2 (NF2) syndrome. The gene responsible for NF2, recently isolated from chromosome 22, encodes a membrane-organizing protein that shows high sequence homology to a protein family thought to link the cytoskeleton with membrane proteins. Mutations of the NF2 gene have been described in sporadic meningiomas, exclusively in tumors that show loss of heterozygosity (LOH) of 22q. These preliminary results indicate that the NF2 gene is involved in the pathogenesis of at least a subset of meningiomas, where it does indeed behave as a tumor suppressor gene. In order to characterize better the role of the NF2 gene in the genesis of meningiomas we have examined the entire coding sequence of the gene in 125 meningiomas by single-strand conformational polymorphism analysis; furthermore, LOH analysis for markers of 22q has been carried out. Inactivating mutations were identified in 30% of our samples, all of which also showed LOH of 22q. The majority of mutations identified were frameshifts and nonsense mutations, which are predicted to produce a truncated or non-functional protein. We also found two missense and three in-frame deletions that may pinpoint specific regions of the protein critical to its function. Furthermore, the distribution of mutations throughout the gene, suggested that exons 2, 3, 5, 11 and 13 are more frequently involved. Our results reconfirm the importance of the NF2 gene in the pathogenesis of meningiomas and also suggest that there may be a nonrandom clustering of mutations throughout the gene.

Association between 5-HT2A receptor polymorphism and psychotic symptoms in Alzheimer’s disease

Abstract Background: The aim of this study is to analyze the segregation of the 102T/C polymorphism in the serotonin 2A receptor gene in patients affected by sporadic and familial Alzheimer’s disease (FAD) with and without psychotic symptoms. Methods: The polymorphism was analyzed in 275 subjects. A semistructured interview was used to obtain information about delusions, hallucinations, and other specific behavioral signs occurring during the disease. Results: Fifty-two percent of AD patients with psychotic symptoms were homozygous for the C102 allele, as compared with 6.9% of AD patients without psychosis. Similarly, the C102/C102 genotype was significantly more frequent in FAD patients with psychosis than in FAD patients without (46.5% vs. 7.8%). Conclusions: Our data strongly confirm and extend to FAD previous studies suggesting that the genetic variation at this locus is associated with prominent psychotic features in AD and that the 102C allele could play an important role in late-onset AD.

Brain metabolic decreases related to the dose of the ApoE e4 allele in Alzheimer’s disease

Objectives: Declines in brain glucose metabolism have been described early in Alzheimer’s disease (AD), and there is evidence that a genetic predisposition to AD contributes to accelerate this process. The epsilon4 (e4) allele of the apolipoprotein E (ApoE) gene has been implicated as a major risk factor in this process. The aim of this FDG-PET study was to assess the ApoE e4 dose related effect on regional cerebral glucose metabolism (METglc) in clinical AD patients, with statistical voxel based methods. Methods: Eighty six consecutive mild to moderate AD patients included in the Network for Efficiency and Standardisation of Dementia Diagnosis database underwent FDG-PET scans at rest. PCR was used to determine the ApoE genotype. Patients were grouped as e4 non-carriers (n = 46), e3/e4 (n = 27) and e4/e4 (n = 13) carriers. A voxel-based mapping program was used to compare each AD subgroup with a database of 35 sex and age matched controls (p<0.001, corrected for cluster extent) and also to compare between the subgroups (p<0.001, uncorrected). Results: No difference was found as to age at examination, age at onset, sex, disease duration, educational level, or severity of dementia between AD subgroups. Compared with controls, all AD subgroups had equivalent METglc reductions in the precuneus, posterior cingulate, parietotemporal, and frontal regions. Direct comparisons between AD subgroups indicated that patients with at least one e4 allele had METglc reductions within additional associative and limbic areas compared with e4 non-carriers. Conclusions: The present FDG-PET study showed different metabolic phenotypes related to the ApoE genotype in clinical AD patients, as revealed with voxel based statistical methods. The results suggest a generalised disorder in e4 carriers impairing metabolism globally, in addition to the more localised changes typical of AD patients.

Cholesteryl ester transfer protein (CETP) I405V polymorphism and longevity in Italian centenarians.

A common polymorphism (I405V) in exon 14 of the cholesteryl ester transfer protein (CETP) gene has been recently associated to healthy aging in Ashkenazi Jewish. In order to study this genetic effect in long-lived individuals with a different ethnicity, we analyzed the allele and genotype distributions of the CETP polymorphism a sample of Italian centenarians. Our result does not confirm the association between the I405V CETP variation and the healthy aging phenotype described in the Ashkenazi Jewish population and suggests that other gene environment interactions contribute to longevity.

Brain-derived neurotrophic factor, apolipoprotein E genetic variants and cognitive performance in Alzheimer's disease.

Since greater attention has been paid to the direct link of genetic variation to cognition and memory performance, apolipoprotein E (ApoE) and brain-derived neurotrophic factor (BDNF) have been the two most frequently studied genes. To investigate the effect of BDNF and ApoE polymorphisms on the cognitive profile of mild-moderate Alzheimers disease (AD) cases, AD patients, genotyped for ApoE and BDNF polymorphisms, underwent extensive neuropsychological investigation. The effect of either ApoE epsilon4 allele and BDNF genetic variant on the neuropsychological pattern of mental impairment was examined both in terms of group differences in performance on the neuropsychological tests between carriers and non-carriers of each variant and by selecting the best predictor of cognitive performance among demographic and genetic factors by means of a multiple regression analysis. Our data confirm a specific effect caused by the presence and amount of ApoE epsilon4 allele, while they suggest that BDNF genetic variants are not a susceptibility factor to AD.

KIBRA gene variants are associated with episodic memory performance in subjective memory complaints.

The KIBRA gene encodes a cytoplasmatic protein, a member of the signal transduction protein family, expressed mainly in the brain. Recent studies have implicated the involvement of a genetic variation in the KIBRA gene (T allele) in human memory in normal subjects and in the risk of developing Alzheimers disease (AD). We report here the distribution of the KIBRA genetic variant and the Apolipoprotein E (ApoE) epsilon4 allele and their association with neuropsychological measures in older adults reporting problems with everyday memory (subjective memory complaints, SMC). We found that SMC subjects with the CT/TT genotype performed more poorly than those with the CC genotype on long-term memory tests. Thus, in our opinion, these data suggest that the KIBRA genotype could affect memory performance in a different way in those that complain of memory deficits compared to those that do not.

Brain-derived neurotrophic factor genetic variants are not susceptibility factors to Alzheimer's disease in Italy

Several lines of evidences have suggested an involvement of the brain-derived neurotrophic factor (BDNF, 11p13) in the pathogenesis of neurodegenerative disorders, in particular, in Alzheimer’s disease (AD). Recently, positive associations between two BDNF polymorphisms (the Val66Met[G196A] and 270C/T) and AD have suggested a possible effect of BDNF genetic variations on the risk of AD. In light of these findings, we analyzed the segregation of the Val66Met(G196A) and 270C/T BDNF and apolipoprotein E (ApoE) genes polymorphisms in Italian patients with AD. We analyzed a sample of 128 Italian patients with sporadic AD (45 men and 83 women; mean age, 71.1 8.5; age at onset, 65.7 8.6 mean SD, with age of onset defined as the onset of first cognitive changes) enrolled at the Department of Neurology, University of Florence and 97 healthy controls (36 men and 61 women; mean age, 72.9 24 years). All subjects were carefully assessed with a rigorous diagnostic evaluation to exclude diagnosis of any neurological disorder. Clinical assessments of patients were done according to published guidelines and the AD diagnosis fulfilled the National Institute of Neurological and Communicative Disorders and Stroke Alzheimer’s disease and related Disorders Association criteria for probable AD. The local ethical committee approved the protocol of the study and the written consent for genetic screening was obtained from all subjects or, where appropriate, their relative or legal representative. All the gene polymorphisms were analyzed by polymerase chain reaction followed by appropriate restriction enzyme digestion. Allele frequencies were estimated by gene counting. Comparisons of genotype and allele frequencies distribution between patients and controls were assessed by 2 test. Both polymorphisms followed a distribution in Hardy– Weinberg equilibrium and did not significantly differ from that of controls (p 0.1) (Table). In addition, no correlation was observed between age at onset, sex, or any BDNF genotype. Stratification of data irrespective of the ApoE status (data not shown) did not show an epistatic effect of the two genes. It could be speculated that, in previous studies, the analyzed populations were not matched for their ethnic background, a major confounding factor when studying polymorphisms. Several nonmutually exclusive factors can produce conflicting results in association studies of common complex diseases including the presence of genetic, clinical, and population heterogeneity. Our data suggest that BDNF genetic variants are not a susceptibility factor for AD, nor do they mitigate the effect of ApoE ε4 allele on AD risk.

Association of IL10 promoter polymorphism in Italian Alzheimer's disease

Recent studies have reported a genetic association between single nucleotide polymorphisms (SNPs) in the promoter region of Interleukin (IL) 10 and Alzheimers disease (AD) with conflicting results. To further investigate the proposed association and to clarify the role of cytokines as a potential cause for AD susceptibility, we analyzed genotypes, allele distributions and haplotypes of IL10 promoter polymorphisms -1082 (rs1800896) and -819 (rs1800871) in an Italian sample of 222 sporadic AD patients and 179 normal controls. All 401 subjects were also genotyped for the Apolipoprotein E (ApoE) polymorphism. We reported a positive association between the -819T/C polymorphism and AD. Moreover, we found a significant difference for this SNP in the ApoE varepsilon4 non-carrier AD patients compared to the ApoE varepsilon4 non-carrier control group. For the -1082A genotype and allele distribution, no significant association was found in AD patients, although it was detected within the AT haplotype. Our results indicate that IL10 polymorphisms may be involved in the risk of developing AD.