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J Hebebrand

Publications and source records attributed to J Hebebrand.

At least 91 records · Page 5Linked to original sources
PubMed1999

Significant evidence for linkage of a simulated trait to D1G024--a conclusion reached using multiallelic transmission/disequilibrium tests.

We applied three versions of the transmission/disequilibrium test (TDT) for detecting linkage in nuclear families using the a priori information of possibly present association. For our analyses we employed all marker data for a simulated trait. Results for replicate 11 showed significant linkage to D1G024 using the multiallelic Tmhet statistic and the extended TDT. The TDT for the most frequent parental allele which had been applied successfully in previous studies failed to detect linkage. This result may have happened because the data did not arise from a realistic simulation of the evolution of a real population, where mutations might be expected to occur against a specific haplotype. Simulation studies are required to elucidate the applicability of the TDT for the most frequent parental allele in realistic situations. Furthermore, guidelines have to be developed for how to pool categories in large, sparse contingency tables to obtain larger cell frequencies and lower degrees of freedom.

Alleles↗
PubMed1999

[Body weight regulation in anorexia nervosa with special attention to leptin secretion].

Underweight is a key symptom in anorexia nervosa. In this review we summarize recent findings pertaining to weight regulation in this eating disorder. The observation that a body mass index below 13 kg/m2 upon admission for inpatient treatment is associated with a high mortality rate and chronic persistence of underweight is of obvious clinical relevance. A lowered leptin secretion, which results from the weight loss, is presumably of major importance for the development of amenorrhea. We discuss findings pertaining to a reduced body weight in other psychiatric disorders during adolescence in the light of Kretschmer's findings related to body frame and psychopathology.

Animals↗
PubMed1999

Further evidence for a low body weight in male children and adolescents with Asperger's disorder.

The study explores the common clinical impression and previously reported finding by Hebebrand et al. (7) of reduced body weight in male children and adolescents with Asperger's disorder (AD). Body weight and height of 36 consecutively admitted male patients with AD were retrospectively assessed for the calculation of body mass indices (BMI, kg/m2). The BMIs were transformed to percentile ranks and plotted into BMI-centiles representative for the German population. In addition, comorbid psychopathology was assessed to explore a possible relationship between associated psychopathology and body weight. The mean BMI-centile of all patients was 34.7 +/- 31.8 and, thus, differed significantly from the mean centile of an age- and gender-matched psychiatric control group, which was 52.7 +/- 28.3. Thirteen patients had a BMI below the 10th centile and five even below the third. Three of the latter presented with disturbed eating behaviour. Altogether four patients showed disturbed eating behaviour. They had a significantly lower mean BMI-centile than the rest of the group. The BMI-centiles of patients with other additional psychopathology did not differ significantly from the mean percentile of the whole cohort. The results clearly show an increased risk for underweight and disturbed eating behaviour in patients with Asperger's disorder which should be evaluated in further studies.

Adolescent↗
PubMed1999

No evidence for an involvement of alleles of polymorphisms in the serotonin1Dbeta and 7 receptor genes in obesity, underweight or anorexia nervosa.

The serotonergic (5-hydroxytryptamine, 5-HT) system has been implicated in body weight regulation and in the etiology of anorexia nervosa (AN). Here we describe the screening of the known Phe-124-Cys polymorphism in the 5-HT1Dbeta receptor gene and of the known Pro-279-Leu polymorphism in the 5-HT7 receptor gene. For association tests allele frequencies were compared between up to 393 extremely obese children and adolescents, 142 underweight students and 84 patients with AN. None of the association tests revealed nominal P-values below 0.3. We conclude that a major role of the investigated polymorphisms in body weight regulation or AN appears unlikely.

Adolescent↗
PubMed1999

Serum leptin and gonadotropin levels in patients with anorexia nervosa during weight gain.

Leptin plays an important role in reproductive function. In patients with acute anorexia nervosa, serum leptin levels have repeatedly been shown to be lower than in age-matched controls. We have previously hypothesized that the amenorrhea characteristic of anorexia nervosa is related to this low leptin secretion. In an attempt to address this hypothesis, serum levels of leptin and follicle stimulating hormone (FSH) and luteinizing hormone (LH) of 16 female inpatients with anorexia nervosa or an eating disorder not otherwise specified (atypical anorexia nervosa) were measured on a biweekly basis during weight gain. We hypothesized that a serum leptin level of 1.85 microg L(-1) would be associated with gonadotropin levels at or above the minimal level observed during the menstrual cycle in healthy adult fertile females. Our results revealed that increments of LH levels generally tracked increments of leptin levels during the first weeks of treatment. Similarly, in those patients with low referral leptin levels, FSH initially also tracked leptin levels. In contrast, a relationship between gonadotropin levels and leptin secretion was no longer discernible after LH and FSH levels had peaked. Those patients with exceedingly low leptin levels upon admission revealed a slow increase of gonadotropin levels. Our hypothesis of a threshold leptin level of 1.85 microg L(-1) was supported for LH only.

Adolescent↗
PubMed1999

Plasma leptin levels do not change in healthy humans shortly after a hydrocortisone challenge.

The acute response of plasma leptin levels to a hydrocortisone challenge was measured in 16 healthy volunteers. We additionally asessed insulin which is known to play a regulatory role in the leptin system. While plasma cortisol levels increased significantly after the administration of hydrocortisone, this rise was not associated with any change in leptin and insulin concentrations during the 3.5-hour experimental period. This result corroborates the assumption that glucocorticoid-induced increases in leptin levels, as described in the literature, occur delayed and are due rather to an activation of leptin synthesis than to a mere leptin release.

Adult↗
PubMed1999

Serum leptin levels, body fat deposition, and weight in females with anorexia or bulimia nervosa.

The objective of this retrospective study was to investigate the relation between serum leptin level and fat deposition in patients with eating disorders. 40 female inpatients with anorexia (n=24) or bulimia nervosa (n=16) were assessed for leptin level, body mass index (BMI), and percentage body fat by dual-energy X-ray absorbometry (DXA). The results show that percentage body fat is a better predictor for leptin level and clinical findings in eating disordered patients than BMI. We discuss the necessity for DXA measurements in anorectic patients for prognostic and research purposes.

Absorptiometry, Photon↗
PubMed1999

Phenotypes in three pedigrees with autosomal dominant obesity caused by haploinsufficiency mutations in the melanocortin-4 receptor gene.

Recently, haploinsufficiency mutations in the melanocortin-4 receptor gene (MC4-R) were detected which were assumed to lead to the phenotype of extreme obesity. Previously, we detected three obese carriers among 306 index patients. Here we describe the detection of one haploinsufficiency carrier in an additional study group of 186 obese individuals. We subsequently genotyped and phenotyped 43 family members of these four index patients, two of whom were second-degree cousins. A total of 19 carriers were identified. Extreme obesity was the predominating phenotype. However, moderate obesity occurred in three of the carriers. No other specific phenotypic abnormalities were detected. Female haploinsufficiency carriers were heavier than male carriers in the respective families, a finding similar to findings in MC4-R-knockout mice. In conclusion, our data fully support the etiologic role of MC4-R haploinsufficiency mutations in obesity.

Adolescent↗
PubMed1999

Low body mass indices in adolescents with obsessive-compulsive disorder.

The aim of this study was to evaluate the growth of adolescents with obsessive-compulsive disorder (OCD). Body heights and body mass indices (BMIs; expressed in kg m(-2)) of 51 adolescent patients with OCD were compared with the corresponding anthropometric variables in age- and sex-matched psychiatric controls and in a general population sample, respectively. In accordance with a previous epidemiologically based investigation, body heights and weights were found to be reduced, especially in male patients with OCD. The body mass indices of the patients with OCD were significantly lower than those of age-matched control patients and population controls. However, some of the parameters were also reduced in male psychiatric controls, indicating that the reductions are not entirely specific for adolescent OCD. The results suggest a neuroendocrine dysfunction in adolescent OCD. The low body mass index indicates that psychiatric disorders other than anorexia nervosa are associated with underweight during adolescence.

Adolescent↗
PubMed1999

Several mutations in the melanocortin-4 receptor gene including a nonsense and a frameshift mutation associated with dominantly inherited obesity in humans.

The melanocortin-4 receptor gene (MC4-R) has been implicated in weight regulation. Recently, two independent groups reported frameshift mutations associated with a dominant form of obesity (1, 2). We screened the coding region of the MC4-R in 306 extremely obese children and adolescents (mean body mass index: BMI 34.4 +/- 6.6 kg/m2), 25 healthy underweight students (mean BMI 17.1 +/- 0.8 kg/m2), 52 normal weight individuals (mean BMI 22.0 +/- 1.0 kg/m2), 51 inpatients with anorexia nervosa (AN, DSM IV criteria, mean BMI 14.3 +/- 1.5 kg/m2) and 27 patients with bulimia nervosa (BN, DSM IV criteria, mean BMI 21.7 +/- 5.8 kg/m2) by single strand conformation polymorphism analysis (SSCP). Several mutations were identified, including the frameshift mutation described (1). The mutations were as follows: a) The deletion of 4 bp (delta of CTCT at codon 211) results in a frameshift, thus rendering a truncated protein. This mutation has been assumed to be associated with dominantly-inherited morbid obesity in humans (1). Both the index patient (BMI 42.06 kg/m2, height 171 cm, age 19.6 years) and her mother (BMI 37.55 kg/m2, height 164 cm, age 42.5 years) were heterozygous for the deletion. b) A nonsense mutation at position 35 of the MC4-R was detected in two obese probands (BMI 31.29 kg/m2 and BMI 45.91 kg/m2). This mutation leads to a truncated protein that encompasses the N-terminal extracellular domain. Both carriers additionally showed (c) a missense mutation (Asp-37-Val). In both of these cases Tyr-35-Stop and Asp-37-Val were maternally transmitted, thus these variations form a haplotype. d) e) A male obese proband harbored two missense mutations (Ser-30-Phe, Gly-252-Ser). f)-i) Four different missense mutations (Pro-78-Leu, Thr-112-Met, Arg-165-Trp, Ile-317-Thr) were detected in four different male probands, respectively. All of these mutations (a to i) were found solely in extremely obese individuals whose BMIs were all above the 99th percentile. j) A silent mutation (C-579-T, Val-193-Val) was detected in a male underweight individual. k) A previously described polymorphism (Val-103-Ile; 3) was detected with similar frequencies in all different study groups. 1) We identified a novel polymorphism (Ile-251-Leu) with similar allele frequencies in all groups under study. In conclusion, our data indicate that mutations in the MC4-R are not uncommon. Whereas our data support the evidence for dominantly inherited obesity as revealed by the three obese probands with haplo-insufficiency, the functional significance of the missense mutations remains to be determined.

Adolescent↗
PubMed1999

Missense variants in the human peroxisome proliferator-activated receptor-gamma2 gene in lean and obese subjects.

The peroxisome proliferator-activated receptor-gamma2 (PPARgamma2) is almost uniquely expressed in adipose tissue and is of major importance for fat cell differentiation and lipid metabolism. This study was undertaken to assess whether two missense variants in the PPARgamma2 gene are associated with early-onset obesity. A previously described polymorphism encoding for an amino acid exchange in codon 12 (Pro12Ala) was detected with allele frequencies of 0.13 in 296 markedly obese children and adolescents and 0.14 in 130 lean individuals. A Pro115Gln variant, which had been linked to obesity in Germans in a previous association study, was not detected in any of our obese or lean subjects, who are also of German origin. We conclude from our data that these two variants in the PPARgamma2 gene are unlikely to contribute to the high prevalence of early-onset obesity.

Adolescent↗
PubMed1998

Plasma concentrations of leptin in a bulimic patient.

Recently, the obese gene in the ob/ob mouse was cloned, along with its human homologue. The gene product leptin is important in the regulation of body weight. Excessive food intake during a binge might affect leptin synthesis. Alternatively, fluctuations in leptin synthesis might induce binge eating. Therefore, plasma leptin levels of a patient with bulimia nervosa were determined over a period of 48 hr in a natural setting. Amount, type, time of food intake, and binging and purging episodes were concomitantly assessed. Although binging and purging episodes were quite frequent, leptin levels remained stable and were neither related to food intake nor to binge episodes.

Adult↗
PubMed1998

Sample size calculations for linkage analysis using extreme sib pairs based on segregation analysis with the quantitative phenotype body weight as an example.

One approach to establish linkage is based on allele-sharing methods for sib pairs. Recently, the use of extreme sib pairs (ESP) has been proposed to increase power for mapping quantitative traits in humans. Several approaches have been discussed. In this study, we calculate sample sizes for the various ESP approaches using segregation analyses of quantitative traits. We illustrate this approach by using previously published segregation analyses of body weight despite the fact that the assumptions imposed by these analyses do not hold up for this quantitative phenotype.

Body Weight↗
PubMed1998

Transmission disequilibrium and sequence variants at the leptin receptor gene in extremely obese German children and adolescents.

Genetic determinants of the degree of obesity and body fat distribution have been demonstrated by family studies. The heritability has been estimated to be in the range 0.2-0.7. Mutation leading to obesity in humans has been described for only two genes, one of them the leptin gene. The leptin gene codes for a cytokine secreted by fat cells that binds to the leptin receptor (Lep-R), which exerts some of its biological functions by expression in the brain. Hence, the Lep-R gene appears to be a promising candidate for the determination of obesity in humans. We isolated genomic DNA clones from the Lep-R gene region and identified a new polymorphic microsatellite marker (OBR-CA) within 80 kb of the translation start of Lep-R. We genotyped this and a second, intragenic microsatellite marker (D1S2852) in 130 nuclear families consisting of extremely obese children and adolescents and both parents. Using the most frequent parental allele of both markers, our analysis revealed a significant transmission disequilibrium for the 266-bp allele of D1S2852 (corrected P-value=0.042). No significant result was obtained with the most frequent allele of OBR-CA (corrected P-value=1.0). However, two rare alleles showed transmission disequilibrium and were subsequently used for constructing a haplotype with the 266-bp allele. This haplotype had a transmission rate of 80% (nominal P-value=0.02). In order to identify the underlying mutation, we sequenced all coding exons of Lep-R and the partially overlapping gene encoding the obese receptor gene-related protein (ob-rgrp) in individuals carrying this haplotype. We found one new mutation (Ser675Thr) in the Lep-R gene in one proband and several other mutations known to be not associated with obesity in other study groups. As this new mutation cannot explain our positive linkage result, the transmission disequilibrium of the 266-bp allele and the high transmission rate of the identified haplotype point towards a mutation in close proximity to marker D1S2852.

Adolescent↗
PubMed1998

Screening for mutations in the neuropeptide Y Y5 receptor gene in cohorts belonging to different weight extremes.

OBJECTIVE: The neuropeptide Y (NPY) Y5 receptor is presumed to be involved in the regulation of food intake. DESIGN: To investigate the possible role of this receptor in weight regulation, the whole coding region of the NPY Y5 receptor gene was screened for mutations using temperature gradient gel electrophoresis (TGGE). Detected mutations were screened in extended cohorts. STUDY COHORTS AND METHODS: Cohorts of 87 extremely obese children and adolescents, 15 underweight subjects and 25 patients with anorexia nervosa (AN) were initially screened by TGGE. Extended samples of these cohorts (160 obese children and adolescents; mean body mass index (BMI) 33.5 +/- 6.4 kg/m2, 128 underweight subjects; mean BMI 18.4 +/- 1.0 kg/m2 and 58 patients with AN; mean BMI 14.6 +/- 1.7 kg/m2) were screened to determine the frequencies of a detected mutation and a detected polymorphism in the NPY Y5 receptor gene. In addition, a previously described polymorphism in the first intron of the NPY Y1 receptor gene was analysed. RESULTS: The coding region of the NPY Y5 receptor gene encompasses one exon. A single mutation, which results in a non-conservative amino acid substitution in the first extracellular domain of the receptor (Glu-4-Ala), and one silent polymorphism (Gly-426-Gly-Gly) at nucleotide position 1278 (G-->A) were detected by TGGE. Both tests for association and linkage to the NPY Y1 and NPY Y5 receptor polymorphisms were negative among all cohorts. The Glu-4-Ala mutation was found only in a single patient with AN and her mother. CONCLUSION: The results do not support a major role of the NPY Y5 receptor gene in the variability of body weight in children and adolescents.

Adolescent↗