The influence of ethnicity and glucose tolerance status on subjective hunger sensations and prospective food intake in overweight and obese Asian and European Australians

AIMS

To examine the influence of ethnicity and glucose tolerance status on subjective sensations and food intake in overweight/obese Asian and European Australians.

METHODS

18 Asians and 26 Europids were classified as normal glucose tolerance (NGT) and impaired glucose tolerance (IGT) based on serial measures of finger-prick glucose following an oral glucose tolerance test (OGTT). Subjective sensations of hunger and satiety were measured before and every 15min after the OGTT using a visual analogue scale (VAS). Food intake was measured covertly from consumption of a buffet style lunch and from self-maintained 24h food records. All serial measurements were converted into total area under the curve (TAUC) and comparisons adjusted for age, fat and fat-free mass.

RESULTS

There was a significant difference interaction between ethnicity (ETH) and glucose tolerance (GTT) for subjective fullness, desire for food and prospective food intake. IGT Asians had significantly greater sensations of fullness, but lesser prospective food and desire to eat, as compared to other groups. However there were no differences in calorie and macronutrient intake at buffet lunch or over 24-h.

CONCLUSION

Interactions between ethnicity and glucose tolerance status in subjective sensations did not transcribe to differences in prospective food intake.

InterRett—The application of bioinformatics to International Rett syndrome research

InterRett, International Rett Syndrome Association (IRSA) Rett Phenotype Database, is a unique international project funded by the IRSA, which brings together child neurologists, geneticists, paediatricians, epidemiologists, researchers and families of affected children. The principal aim of InterRett is to increase the clinical understanding of Rett syndrome throughout the world and with the statistical power of large case numbers, determine any correlations between genotype and the phenotypic characteristics. Since establishment of the database in January 2003, InterRett has registered 286 cases from 24 countries, with family questionnaire data submitted on 242 cases and clinician data on 116 cases. Collated de-identified data gathered from families and clinicians have been incorporated into a searchable online database allowing simple and complex interrogation of the clinical phenotype information. InterRett will also serve as a clearing house for data to encourage inter-country collaboration between researchers and negotiations are in place with several countries for data contributions in excess of 1000 cases. The resulting online database will be an invaluable resource for understanding the nature and management of Rett syndrome, as well as providing a model for other rare childhood disorders.

Investigating genotype-phenotype relationships in Rett syndrome using an international data set

BACKGROUND

Rett syndrome is an uncommon neurodevelopmental disorder with an incidence of 1:9,000 live female births. The principal genetic cause was first reported in 1999 when the association with mutations in the methyl-CpG-binding protein 2 (or MECP2) gene was identified. This study uses data from a large international database, InterRett, to examine genotype-phenotype relationships and compares these with previous findings in a population-based cohort.

METHOD

The data set for these analyses was derived from a subset of InterRett cases with subject information collected from the family, the clinician, or both. Individual phenotypic characteristics and clinical severity using three scales were compared among those with eight known recurrent pathogenic MECP2 mutations as well as those with C-terminal deletions (n = 272).

RESULTS

Overall, p.R270X and p.R255X were the most severe and p.R133C and p.R294X were the mildest mutations. Significant differences by mutation were seen for individual phenotypic characteristics such as hand use, ambulation, and language.

CONCLUSIONS

This multicenter investigation into the phenotypic correlates of MECP2 mutations in Rett syndrome has provided a greater depth of understanding than hitherto available about the specific phenotypic characteristics associated with commonly occurring mutations. Although the modifying influence of X inactivation on clinical severity could not be included in the analysis, the findings confirm clear genotype-phenotype relationships in Rett syndrome and show the benefits of collaboration crucial to effective research in rare disorders.

Development of a Video-based Evaluation Tool in Rett Syndrome

This paper describes the development of a video-based evaluation tool for use in Rett syndrome (RTT). Components include a parent-report checklist, and video filming and coding protocols that contain items on eating, drinking, communication, hand function and movements, personal care and mobility. Ninety-seven of the 169 families who initially agreed to participate returned a videotape within 8 months of the first request. Subjects whose videos were returned had a similar age profile to those who did not provide a video but were more likely to have classical than atypical RTT. Evidence of the content and social validity and inter-rater reliability on 11 videos is provided. Video may provide detailed, objective assessment of function and behaviour in RTT.

Predictors of scoliosis in Rett syndrome

Scoliosis is a common clinical manifestation of Rett syndrome, a neurodevelopmental disorder that almost exclusively affects girls. Following apparently normal development, these girls typically regress and lose previously attained cognitive, social, and motor skills. Severe intellectual and physical disabilities remain throughout life. Mutations in the methyl-CpG-binding protein 2 gene, MECP2, are detected in approximately 80% of cases and are associated with phenotypic variability. Population-based data on Australian cases were used to study the association between early developmental and genetic factors and the onset of scoliosis. The median age at scoliosis onset was 9.80 years, and three quarters of subjects had developed scoliosis by 13 years of age. Children with compromised early development before 6 months, those who were less mobile at 10 months, and those who never walked were more likely to have an earlier onset of scoliosis. When seven common point mutations and large genomic and C-terminal deletions were compared, the R294X mutation appeared to provide some protective effect against the development of scoliosis.

Genotype and early development in Rett syndrome: the value of international data

BACKGROUND

Rett syndrome is a neurodevelopmental disorder mostly affecting females and caused by mutations in the MECP2 gene. Originally the syndrome was characterised as having a normal prenatal and perinatal period with later regression. Previous work has speculated that the girl with Rett syndrome may not be normal at birth.

AIMS

to examine whether early development between birth and ten months varies by genotype in Rett syndrome.

METHODS

cases were sourced from two databases, the Australian Rett Syndrome Database (est. 1993) and the newly formed InterRett - IRSA Rett Phenotype Database. Data available on 320 cases included information provided by parents on perinatal problems, early developmental behaviour and mobility. Problem scores, mobility scores and a total composite score for each mutation were generated and compared.

RESULTS

overall, 58% of respondents noted unusual behaviour during the first six months and 70.6% from the period between 6 and 10 months of life. Statistically significant differences were detected between some of the common mutations. Infants with R294X (P=0.05) and R133C (P=0.03) were less likely than those with R255X to have problems in the perinatal period. The most severe profile overall for early development was associated with mutations R255X and R270X.

CONCLUSION

This is the largest study to date examining the effects of individual mutations in Rett syndrome. With the ongoing case ascertainment and expansion of InterRett, sample size will increase rapidly and provide improved statistical power for future analyses. Results from this study will contribute to understanding the mechanism of early development in Rett syndrome and determining if and at which time(s) early intervention might be feasible.

InterRett and RettBASE: International Rett Syndrome Association databases for Rett syndrome

In 2001, the International Rett Syndrome Association funded the establishment of a World Wide Web-based database to collect and display the genetic data of children and adults with Rett syndrome from around the world. RettBASE (<http://mecp2.chw.edu.au>) encompasses both published and unpublished data; includes pathogenic mutations, benign polymorphisms, and sequence variations of uncertain significance; and has a range of query capabilities, allowing for simple or complex interrogation of the database. To undertake genotype-phenotype correlations and to identify the likely subtle differences in phenotype, detailed phenotype data on large samples will be provided by the International Rett Syndrome Association International Phenotype database InterRett. InterRett is under development by the Australian Rett syndrome study group at the Telethon Institute for Child Health Research in Perth, Western Australia. It will collect data from clinicians and families and provide deidentified, collated data on the Internet (<http://www.ichr.uwa.edu.au/rett/irsa>). Data records will be linked with RettBASE through a common unique identifier. An international reference panel is advising on the development of the database. Data collection procedures from families and clinicians are currently being piloted. Full data collection from both groups began in the second half of 2003. Concurrently, the output database will be developed to provide deidentified individual records and collated data for clinicians and researchers and collated data for families and the general public. This Web-based database will be an invaluable resource for understanding the nature of the disorder and managing children and adults with Rett syndrome.

Hand preference, extent of laterality, and functional hand use in Rett syndrome

Residual hand use in functional tasks, extent of laterality, and right or left preference were studied in 145 2- to 24-year-old, postregression Australian subjects with Rett syndrome via parent questionnaire. Hand use was markedly restricted, more for complex than simple and for external (touching food and objects) than internal tasks (scratching, rubbing eyes), suggesting a deficit in cerebral control of external, goal-oriented hand use, which is perhaps genetically determined because there is significantly greater restriction of external tasks in subjects with demonstrated MECP2 mutations. Overall, 33.6% of patients were reported with a left-hand preference, 40.7% with a right-hand preference, and 25.7% with an equal hand preference. Extent of laterality was greater for external than internal and for complex than simple external tasks. Older subjects showed less functional hand use and possibly more overall laterality. However, their hand preference was similar to younger subjects. The anomalous pattern of hand preference in Rett syndrome may be linked to the primary apraxic deficit in this disorder rather than to late manifestation of laterality.

Describing the phenotype in Rett syndrome using a population database

BACKGROUND

Mutations in the MECP2 gene have been recently identified as the cause of Rett syndrome, prompting research into genotype-phenotype relations. However, despite these genetic advances there has been little descriptive epidemiology of the full range of phenotypes.

AIMS

To describe the variation in phenotype in Rett syndrome using four different scales, by means of a population database.

METHODS

Using multiple sources of ascertainment including the Australian Paediatric Surveillance Unit, the development of an Australian cohort of Rett syndrome cases born since 1976 has provided the first genetically characterised population based study of Rett syndrome. Follow up questionnaires were administered in 2000 to families and used to provide responses for items in four different severity scales.

RESULTS

A total of 199 verified cases of Rett syndrome were reported between January 1993 and July 2000; 152 families provided information for the follow up study. The mean score using the Kerr scale was 22.9 (SD 4.8) and ranged from 20.5 in those under 7 years to 24.2 in those over 17 years. The mean Percy score was 24.9 (SD 6.6) and also increased with age group from 23.0 to 26.9. The mean Pineda score was 16.3 (SD 4.5) and did not differ by age group. The mean WeeFIM was 29.0 (SD 11.9), indicating extreme dependence, and ranged from 18 to 75.

CONCLUSION

We have expanded on the descriptive epidemiology of Rett syndrome and shown different patterns according to the severity scale selected. Although all affected children are severely functionally dependent, it is still possible to identify some variation in ability, even in children with identified MECP2 mutations.

Using the Internet to pilot a questionnaire on childhood disability in Rett syndrome

There is increasing use of the Internet for the transfer and sharing of medical information. Opportunities to pilot surveys online are now also available. An online HTML questionnaire allowed us to pilot a questionnaire about functional ability and the use of health services in Rett syndrome, a rare neurological disorder. Subscribers to a list server completed the online questionnaire and returned data by CGI script-formatted e-mail. Text boxes were provided for open-ended questions. Eighty-six questionnaires were returned from 224 subscribers with 76% returned within the first week. Almost all respondents were Caucasian, well educated and English speaking. The issue of selection bias and the need for mechanisms to validate the diagnosis are important considerations in any research facilitated through the Internet. However, we were able to contact an otherwise inaccessible group in a fast and cost-efficient manner and effectively pilot our survey without tapping into our own study population.

Functional status, medical impairments, and rehabilitation resources in 84 females with Rett syndrome: a snapshot across the world from the parental perspective

PURPOSE

Rett syndrome is a neurological disorder almost exclusively affecting females. Information on its genetic basis has recently become available. However there is little information on the burden and impact of this disorder on the family despite the apparent variability in phenotype. The purpose of this study was to obtain information on the burden and impact of Rett syndrome by examining the functional abilities, medical needs and use of medical, therapy and accommodation services in the sample.

METHOD

We used the internet to access an opportunistic sample of parents of 86 females with Rett syndrome. Data on functional status (using the Wee FIM in questionnaire format) morbidity patterns and use of services were collected.

RESULTS

The response indicated that the instrument used would be appropriate for tracking these parameters in a population-based cohort. Subjects with Rett syndrome in this pilot sample were completely or partially dependent in all functional domains and significantly more so than children with Down syndrome.

CONCLUSION

The complexity of dependency with need for quality medical surveillance throughout adolescence and adulthood requires accessible centres of excellence linking families and skilled professionals. We plan to use this instrument to obtain a more comprehensive profile of the health, functioning and service use of a total population of children with Rett syndrome.

Family data in Rett syndrome: association with other genetic disorders

BACKGROUND

Rett syndrome is a neurological disorder, almost exclusively affecting girls.

METHODOLOGY

Between 1993 and 1995 pedigree data were obtained from families of girls registered with the Australian Rett syndrome database.

RESULTS

Although 21 individual disorders were reported to be present in family members of affected girls, there was no apparent clustering of the same disorder in different families. However it was certain that a geneticist had been involved in only 10.9% of cases.

CONCLUSIONS

Mutations in the MECP2 gene have now been reported in a proportion of sporadic cases. Thus, it will be important to examine this phenotype-genotype correlation in the Australian cohort. Where a mutation is found, prenatal diagnosis in a subsequent pregnancy will be a possibility. Using the Australian population database and in conjunction with the clinical genetic services in each state it is planned to contact families with an affected girl to offer testing and counselling.

Using genetic epidemiology to study Rett syndrome: the design of a case-control study

Rett syndrome is a neurological disorder that is seen almost exclusively in females. Although generally considered to have a genetic basis, the underlying mechanism remains obscure. One favoured hypothesis is that the syndrome is an X-linked dominant disorder, lethal or non-expressed in males. Genealogical research has also suggested that the mode of transmission in Rett syndrome may involve a premutation which over several generations is converted to a full mutation. Geographical clustering has been reported, and it has also been proposed that Rett syndrome is a clinically variable condition and that other neurological disorders may be occurring more commonly in families with Rett syndrome. Other studies have found an apparent increase in intellectual disability and seizures in the extended families of girls with Rett syndrome. The science of genetic epidemiology can be used to identify familial aggregation, which is the clustering of a disorder within a family. We have used a case-control study design to investigate both fetal wastage and familial aggregation of other disorders in families of girls with Rett syndrome. The Australian Rett Syndrome Database provided the source of cases, and control probands were girls of a similar age with normal development. This paper describes the methodology for a case-control study of this rare condition using pedigree data and discusses issues in the collection and evaluation of such data. The use of a control population is an important feature. Both the strengths and the shortcomings of our design are identified, and recommendations are made for future research.

Patterns of pregnancy loss, perinatal mortality, and postneonatal childhood deaths in families of girls with Rett syndrome

Rett syndrome is a neurodevelopmental disorder that occurs predominantly in girls and results in severe physical and intellectual handicap. A popular genetic mechanism is an X-linked dominant disorder, lethal in males. A case control study design was used to investigate fetal wastage as indicated by reported miscarriage and stillbirth prevalence, and the prevalence and cause of reported neonatal and other childhood deaths. There was no disturbance in the sibling sex ratio when case and control families were compared. In the parental generation and in the proband generation miscarriages were reported in similar proportions in case and control families. The reported stillbirth rates in case families was almost double that in control families and reported perinatal loss was more common on the maternal side in case families than in control families. Stillbirths and neonatal deaths affected slightly more boys in the parental and proband generations of case families (19 of 30) than in control families (10 of 21). Childhood deaths also occurred a little more commonly in Rett syndrome families. Sudden infant death syndrome was reported in three siblings of Rett syndrome probands but in no control siblings. Confirmation of this pattern of perinatal loss and infant mortality could indicate an alternative expression of the Rett syndrome gene.

A population-based approach to the investigation of osteopenia in Rett syndrome

This study compares bone mass in a national sample of girls with Rett syndrome (RS) with a sample of control children. The Australian RS Database was the source of cases for this population-based study. Hand radiographs were available from 101 of 137 subjects (74% of the known Australian population of girls with RS aged < or = 20 years). Control radiographs matched for age, sex, and laterality were obtained from hospital radiology departments. A measure of cortical thickness was made from the difference between the outer diameter and the medullary space in the second metacarpal bone. A mean z-score value for cortical thickness and percentage cortical area for each individual was calculated. The mean cortical thickness (z score) for girls with RS was -1.94 compared with -0.38 for control children (P<0.001). In girls with RS, the mean cortical thickness decreased with age (P<0.001). In girls who were taking epilepsy medication it was -2.21 compared with -1.23 in those not taking epilepsy medication (P<0.001). There was no evidence of a beneficial effect of increased calcium intake on cortical thickness. A similar pattern was obtained when percentage cortical area was estimated. In multivariate analysis, increasing age and use of anticonvulsant medication were associated with decreased cortical thickness and only use of anticonvulsant medication with decreased percentage cortical area. Fractures had occurred in one-third of cases and it was estimated that just over 40% of girls would sustain a fracture by the age of 15 years. Girls with RS may be at increased risk of fractures and their bone quality compromised as determined by cortical thickness and percentage cortical area measurements from the second metacarpal.

Metacarpophalangeal pattern profile and bone age in Rett syndrome: further radiological clues to the diagnosis

Hand radiographs of 100 girls representing 73% of the known Australian population of girls with Rett syndrome, age 20 years or less, were available for this study. Control radiographs were matched for age, sex, and laterality. Bone age was assessed against standard radiographs in Greulich and Pyle [1959: Radiographic Atlas of Skeletal Development of the Hands and Wrist, 2nd ed.]. A metacarpophalangeal pattern (MCPP) profile comparing the relative lengths of the hand bones with mean population norms by age was produced by converting the length of each of the 19 metacarpal and phalangeal bones into a Z score. In girls less than 15 years old, bone age was more advanced in Rett syndrome than in age-matched control girls (left hand P = 0.03, right hand 0.004), but was most advanced in the younger group and normalized with age. In Rett syndrome, the mean Z score for the 19 metacarpal and phalangeal bones was 1.0 in children under 5 years, -0.27 in those aged 5-11 years, and -1.7 in those aged 12 years and over. This variation between age groups was much greater than in the controls. The dips in the MCPP profile occurred at MC2 and D1, and the peaks at M5, P5, and M4. An MCPP profile may provide an additional aid to diagnosis in cases of Rett syndrome where all the criteria are not met, but in children under age 5 years, advanced bone age may be more helpful as a marker.

Familial aggregation in Rett syndrome: what is the evidence for clustering of other disorders in families of affected girls?

Rett syndrome is a neurodevelopmental disorder of unknown cause which affects girls almost exclusively. Apparently normal development in the first year of life is usually followed by loss of skills and the development of stereotypic hand movements. This study has used genetic epidemiological methods including a case control design to examine the evidence for aggregation of other disorders in families of girls with Rett syndrome. In one family there were two sisters with a condition consistent with Rett syndrome. Intellectual disability was not reported more commonly in case families (P = 0.46). However, "learning problems" were slightly commoner (P = 0.05) especially in the parental generation (P = 0.02) and these findings warrant further investigation. Mental illness and seizures were not reported at an increased prevalence. However, we would recommend the use of other strategies to collect information about psychiatric illness. Spinal curvature was reported more commonly in case families (P = 0.07) but no mechanism for clinical verification of this was included in the study. There was an apparent increase in bowel problems in the parents (P = 0.04). The major weaknesses of our study were our inability to validate any diagnosis clinically and the lack of power (due to the comparative rarity of the outcomes). The strengths are that we have been able to collect pedigree data on the families of a substantial proportion of a total population of girls with Rett syndrome and to collect comparative data from a control population. Our reported findings warrant further investigation in a larger study.

Diagnosis of Rett syndrome: can a radiograph help?

Rett syndrome (RS), a neurodevelopmental disorder almost exclusively affecting girls, is associated with severe intellectual and motor disability. In the absence of biological markers, diagnosis is determined by a set of clinical criteria. In a previous study in Scotland, shortening of the fourth metatarsal was reported clinically in 20% of classical RS cases aged 5 years or older. The Australian Rett Syndrome Study database has facilitated a population-based radiological study of the hands and feet of girls with RS. Straight radiographs of hands and feet were available from 94 cases, representing 70.1% of the known RS population in Australia. Control radiographs were matched for age, sex, and laterality. Relative shortening of the fourth metacarpal/metatarsal was assessed using the sign method. A short ulna (negative ulna variance) was defined as the distal articular surface of the ulna being at least 5mm proximal to the distal articular surface of the radius. A positive metacarpal sign was twice as common in verified cases of RS than in controls in the right but not the left hand. A short ulna was more common in subjects with RS than in controls. A short fourth metatarsal was also more common among subjects with RS. More than half (56.6%) the girls with RS over the age of 4 years had a negative ulnar variance in either wrist or a metatarsal sign in either foot. These findings will assist with the diagnosis of RS and may help direct research towards the location of the molecular defect.

Skeletal abnormalities in Rett syndrome: increasing evidence for dysmorphogenetic defects

The presence of metatarsal and metacarpal abnormalities in some individuals has raised the possibility that Rett syndrome is, in fact, a multiple congenital abnormalities/mental retardation (MCA/MR) syndrome. We have conducted radiological examination of 17 cases of Rett syndrome in Western Australia. Short fourth and/or fifth metatarsals were identified in 65% of cases and short fourth and/or fifth metacarpals in 57%. Metatarsal (P = 0.045) and metacarpal (P = 0.006) shortness were significantly more common in girls 14 years or older. Negative ulnar variance (found in 79% of cases) appeared to be independent of age. Reduced bone density in the hands was found in 86% of cases. A nationwide study using the Australian Rett Syndrome Database is planned to follow up these findings and compare them with findings from a control group. The confirmation of these abnormalities in a high proportion of cases may provide morphologic markers to assist in the diagnosis of Rett syndrome and perhaps provide a further avenue of research into the pathogenesis of this disorder.

Over-synthesis and instability of sigma protein in a merodiploid strain of Escherichia coli

We have used two different methods to study the rates of RNA polymerase subunit synthesis in haploid Escherichia coli K12, and a KLF10 rPOB, C+ merodiploid derivative, when grown in glucose-minimal medium at 37 degrees C. Our results indicate that the haploid strain produces beta, beta', alpha and sigma in the molar ratios 1.01:0.99: less than or equal to 2.90:0.26; and that all these subunits are reasonably stable during subsequent growth. The merodiploid produces alpha at the same rate as the haploid, beta and beta' at a 42% higher rate, and sigma at twice the rate. Some 40% of the newly synthesised beta and beta' is degraded within one hour; the residuum is as stable as in the haploid. Alpha is stable throughout. By contrast, sigma is subject to a marked and continuous turnover in the merodiploid. These results are discussed in terms of gene dosage and regulatory effects.