The EIF2AK3 gene region and type I diabetes in subjects from South India

Mutations in the EIF2AK3 gene underlie susceptibility to the Wolcott-Rallison syndrome, which is a monogenic disease associated with insulin-deficient neonatal diabetes. Furthermore, suggestive evidence of linkage between type 1 diabetes (T1DM) and the EIF2KA3 chromosomal region has been reported in Scandinavian families. We have investigated the hypothesis that polymorphic variants in and around the EIF2AK3 gene might partially account for susceptibility to T1DM in South Indian subjects. Excess transmission of the common alleles of two polymorphic markers (D2S1786 and 15INDEL, located within the gene) downstream of EIF2AK3, either singly (D2S1786, P = 0.01) and 15INDEL (P = 0.02) or as a combination (P < 0.001), were found in 234 families with a T1DM proband. There was also a clear paternal effect for the 15INDEL marker (P = 0.005) on disease susceptibility. The presence of the common allele of both markers was found in decreased frequency in the subjects with normal glucose tolerance compared to probands with T1DM (both P <or= 0.0001). Major common mutations of the EIF2AK3 gene in T1DM were excluded. In conclusion, this pilot study demonstrates an association between the region around the EIF2AK3 locus and T1DM susceptibility.

Assessing optimal neural network architecture for identifying disease-associated multi-marker genotypes using a permutation test, and application to calpain 10 polymorphisms associated with diabetes

Biallelic markers, such as single nucleotide polymorphisms (SNPs), provide greater information for localising disease loci when treated as multilocus haplotypes, but often haplotypes are not immediately available from multilocus genotypes in case-control studies. An artificial neural network allows investigation of association between disease phenotype and tightly linked markers without requiring haplotype phase and without modelling any evolutionary history for the disease-related haplotypes. The network assesses whether marker haplotypes differ between cases and controls to the extent that classification of disease status based on multi-marker genotypes is achievable. The network is "trained" to "recognise" affection status based on supplied marker genotypes, and then for each multi-marker genotype it produces outputs which aim to approximate the associated affection status. Next, the genotypes are permuted relative to affection status to produce many random datasets and the process of training and recording of outputs is repeated. The extent to which the ability to predict affection for the real dataset exceeds that for the random datasets measures the statistical significance of the association between multi-marker genotype and affection. This permutation test performs well with simulated case-control datasets, particularly when major gene effects are present. We have explored the effects of systematically varying different network parameters in order to identify their optimal values. We have applied the permutation test to 4 SNPs of the calpain 10 (CAPN10) gene typed in a case-control sample of subjects with type 2 diabetes, impaired glucose tolerance, and controls. We show that the neural network produces more highly significant evidence for association than do single marker tests corrected for the number of markers genotyped. The use of a permutation test could potentially allow conditional analyses which could incorporate known risk factors alongside marker genotypes. Permuting only the marker genotypes relative to affection status and these risk factors would allow the contribution of the markers to disease risk to be independently assessed.

Genetic susceptibility to fibrocalculous pancreatic diabetes in Bangladeshi subjects: a family study

Fibrocalculous pancreatic diabetes (FCPD) is an uncommon cause of diabetes, seen mainly in developing countries. A family-based study was carried out in 67 Bangladeshi families, consisting of a proband with FCPD and both parents, to determine whether an association exists between FCPD susceptibility and either the major histocompatiblity complex (MHC) or insulin gene (INS) loci. HLA-DQB1 typing was done using allele-specific primers, and INS was typed using the restriction enzyme HphI. Three microsatellites (TNFa, TNFc and TNFd), from within and flanking the TNF-LT locus, were used for MHC Class IV typing and a PCR-RFLP assay was used to define the -308G/A TNF promoter polymorphism. The extended transmission disequilibrium test (ETDT) was used for statistical analysis. An overall association was observed between FCPD and HLA-DQB1 (P = 0.003), that was largely due to a positive association with HLA-DQB1*0302 and a negative association with HLA-DQB1*0202. Although no association was found between FCPD and TNF-LT microsatellite markers a trend was observed for TNFc (P = 0.037, Pc = 0.15). No association was found between FCPD and INS (P = 0.26). This study confirms an association between FCPD and the MHC using a family-based study design and the stringent ETDT analysis; a novel protective association was found with HLA-DQB1*0202 in Bangladeshi FCPD subjects. The genetic susceptibility to FCPD has features both similar and dissimilar to T1DM.

Feasibility study of colonoscopy as the primary screening investigation in relatives of patients with colorectal cancer

AIM

Relatives of patients with colorectal cancer are thought to be at a higher risk for this disease than the average population. We aimed to determine whether colonoscopy is a feasible primary screening investigation for this group to identify premalignant and malignant lesions.

METHODS

A total of 449 people underwent colonoscopy and all had one or more relatives with colorectal cancer, of these, 212 were classified as 'asymptomatic' and 237 as being 'symptomatic'. Colonoscopy commenced at 40 years of age or 10 years younger than the youngest affected relative.

RESULTS

Neoplastic change, benign and malignant, was found in 25.5% of the 'asymptomatic' group and 24% of the 'symptomatic' group; in 26% of those with one first degree relative, 39% with two or more first degree relatives and only 19% with second degree relatives. 38% of lesions were out of reach of a flexible sigmoidoscope. No known complications occurred.

CONCLUSIONS

It is feasible to perform colonoscopy as the primary investigation for the first degree relatives of patients with colorectal cancer. The yield of neoplastic lesions is sufficient to make this appropriate.

Evidence that single nucleotide polymorphism in the uncoupling protein 3 (UCP3) gene influences fat distribution in women of European and Asian origin

AIMS/HYPOTHESIS

Uncoupling proteins are mitochondrial transmembrane carriers implicated in the regulation of energy balance. Dysfunction of UCP3 (the predominant uncoupling protein in skeletal muscle) might therefore be expected to reduce thermogenic capacity, alter energy homeostasis and influence predisposition to obesity and Type II (non-insulin-dependent) diabetes mellitus. A variant in the putative promoter region of UCP3 (-55 c-->t) has recently been identified, and an association with obesity reported in French subjects. Our aim was to study the pathophysiological role of this variant in diabetes-related and obesity-related traits using two distinct ethnic populations.

METHODS

The -55 c-->t variant was genotyped in 85 South Indian and 150 European parent-offspring trios ascertained through Type II diabetic probands and in 455 South Indian subjects initially recruited to an urban survey into the prevalence of diabetes.

RESULTS

In South Indian and European parent-offspring trios there was no preferential transmission of either allele at the -55 c-->t polymorphism to diabetic offspring (South Indians, p = 0.60; Europeans, p = 0.15). When family members were analysed for intermediate traits, the t-allele was associated with increased waist-to-hip ratio but only in females (South Indian mothers p = 0.036, daughters p = 0.032: European mothers p = 0.037, daughters p = 0.14). These findings were replicated in South Indian females from the population-based survey (p = 0.039).

CONCLUSION/INTERPRETATION

The consistent association between the t-allele at this locus and increased waist-to-hip ratio in women from three separate data sets indicates that variation at this polymorphism (or another locus with which it is in linkage disequilibrium) influences fat distribution but that this effect is restricted to females.

Pancreatitis in fibrocalculous pancreatic diabetes mellitus is not associated with common mutations in the trypsinogen gene

BACKGROUND

A distinct type of pancreatitis associated with diabetes, termed fibrocalculous pancreatic diabetes (FCPD), has been reported in tropical developing countries including Bangladesh. The molecular basis for autosomal dominant hereditary pancreatitis (HP) has recently been attributed to mutations in exons 2 and 3 of the trypsinogen gene. We have investigated the hypothesis that mutations in the aforementioned exons of this gene might also predispose to FCPD.

METHODS

Seventy Bangladeshi and 50 South Indian unrelated FCPD patients and seven South Indian families with FCPD probands were studied. Pancreatic calcification was confirmed by abdominal X-ray, ultrasound and/or ERCP. Established mutations of exons 2 and 3 of the trypsinogen gene were studied in these subjects by PCR-RFLP analysis and DNA sequencing.

RESULTS

The mutations found in hereditary pancreatitis were not observed in this collection of FCPD subjects, and complete DNA sequencing of exons 2 and 3 of the fourth cationic trypsinogen gene also excluded any new mutations.

CONCLUSIONS

These results indicate that chronic pancreatitis of FCPD is unlikely to be caused by common mutations in the trypsinogen gene.

Family association studies of markers on chromosome 2q and Type 1 diabetes in subjects from South India

BACKGROUND

Several Type 1 diabetes susceptibility loci have been located to chromosome 2q12-21. However, results have not always been consistent and this may reflect study design and the population analysed. We have used a family-based design to look for an association between Type 1 diabetes and markers located to 2q12-21.

METHODS

Ninety-one South Indian families consisting of subjects with Type 1 diabetes and their parents were genotyped for eight polymorphic markers localised to 2q12-21, which includes the interleukin-1 gene cluster. Radiation hybrid mapping was used to localise the map position of D2S308 and D2S363 on 2q12-21. The extended transmission disequilibrium test was used for statistical analysis.

RESULTS

No associations were found between Type 1 diabetes and markers located in and around the interleukin-1 gene cluster or the interleukin-1 Type 1 receptor. In contrast, a suggestive association was found between Type 1 diabetes and two closely-linked markers telomeric of the interleukin-1 gene cluster (D2S308 and D2S363, separated by 3.3 cR) (p=0.004 and p=0.002, respectively).

CONCLUSION

This preliminary study suggests that a locus close to D2S308 and D2S363 is involved in the aetiology of Type 1 diabetes in the South Indian population.

An uncoupling protein 2 gene variant is associated with a raised body mass index but not Type II diabetes

AIMS/HYPOTHESIS

Linkage between markers close to the uncoupling protein 2 and 3 genes (11q13) and resting metabolic rate and a pre-diabetic phenotype have been found. The syntenic region in mouse has been found to be linked to quantitative traits associated with obesity and diabetes. UCP2 and UCP3 could therefore have an important role in body weight regulation and susceptibility to diabetes. We investigated a recently identified variant of the UCP2 gene in exon 8 as a marker for glucose and weight homeostasis.

METHODS

Length variation of the UCP2 exon 8 variant was studied by the polymerase chain reaction and agarose gel electrophoresis. Sequence variants of the UCP3 gene were sought by semi-automated DNA sequencing.

RESULTS

In 453 South Indian subjects, we found an association in women between the UCP2 exon variant and body mass index (p = 0.018). These findings were replicated in a separate group of South Indian subjects (n = 143, p < 0.001) irrespective of sex. Although no association was found between the UCP2 exon 8 variant and overt obesity in British subjects, the UCP2 genotype of obese women (n = 83) correlated with fasting serum leptin concentration (p = 0.006) in the presence of extreme obesity. These observations could not be explained by tight linkage disequilibrium with a coding region variant in the region of the UCP3 gene of biological significance. Lastly, no association was found between UCP2 and Type II (non-insulin-dependent) diabetes using either a family based design (85 families) or case control study (normal glucose tolerance n = 335, impaired glucose tolerance n = 42, Type II diabetes n = 76).

CONCLUSION/INTERPRETATION

We have described a UCP2 gene exon 8 variant that may affect susceptibility to weight gain by influencing regulation of leptin.

HLA-DP and coeliac disease: family and population studies

We investigated polymorphism of HLA-DP genes in three DR3 related diseases, confirming an association of coeliac disease with a Bgl II DP alpha polymorphism (a restriction fragment sized 3.5 kb present in 75% of patients compared to 34% of control subjects, p less than 0.001), and finding a weaker association with dermatitis herpetiformis (57% v 34%, p = 0.01) and no association with insulin dependent diabetes mellitus. The association with coeliac disease was further investigated. Msp I DP beta polymorphism was studied in 52 healthy subjects and 59 patients: a 4.9 kb fragment was present in 51% of patients with coeliac disease compared to 11.5% of control subjects (p less than 0.001). Furthermore, nearly all subjects with the DP alpha 3.5 kb fragment also had the DP beta 4.9 kb fragment. However, disease frequency was still increased in the DP alpha 3.5 positive/DP beta 4.9 negative group. In seven families, each with at least two affected members, while the DP alpha 3.5 fragment was frequently present in patients it did not preferentially segregate with any particular HLA haplotype--for example, those associated with DR3 or DR7--and therefore is not part of an extended haplotype associated with coeliac disease. We therefore conclude that a gene(s) in the HLA-DP region predisposes to coeliac disease independently of the HLA-DR/DQ regions.

Immunoglobulin heavy chain switch region polymorphisms are not associated with type 1 diabetes

In order to ascertain whether the immunoglobulin heavy chain genes are important in the aetiology of Type 1 diabetes, we have used restriction fragment length polymorphism (RFLP) analysis of genomic DNA to study 148 Caucasoid subjects with Type 1 diabetes and 146 normal Caucasoid subjects. A DNA probe homologous to the switch regions for the IgM (S mu) and IgA1 (S alpha 1) genes when used in conjunction with the restriction endonuclease Sst I detects RFLPs at both these loci. There were no significant differences in phenotype or gene frequencies for the alleles of S mu or S alpha 1 in the patients when compared with control subjects; nor were there significant associations of S mu or S alpha 1 with HLA-DR type or gender.

HLA-DR alpha, -DX alpha, and DR beta III gene association studies in DR3 individuals

In this study we have examined the results of probing with synthetic oligomers at the DR beta III locus, together with restriction fragment length polymorphisms defined by BglII digestion and a cDNA DR alpha probe, and Taq 1 digestion and a genomic DQ alpha probe. We have demonstrated heterogeneity of the human leukocyte antigen DR3 and close association of the DR alpha, DR beta III, and DX alpha genes. Two DR3-related preferential allelic associations have been identified, which may prove useful in family analysis as well as for investigations of DR3-related diseases.

DQ beta restriction fragment length polymorphism and its relationship to insulin dependent diabetes mellitus

HLA Class II serological and DQ beta restriction fragment length polymorphisms (RFLPs) were compared in 69 patients with insulin-dependent diabetes mellitus (IDDM) and 81 healthy British Caucasoid controls. The backbone of the analysis was formed by two Taq 1 RFLPs of the DQ beta region designated T2 omega and T6. The two are not allelic and can be inherited individually, together on one, or separately on both, parental haplotypes, the latter almost invariably in association with DR4. In our study the frequency in IDDM patients of both T2 omega and T6 together (relative risk for IDDM = 6.4) is similar to that of DR3/DR4 (relative risk for IDDM = 5.4) with an even higher relative risk for IDDM when they are combined, (relative risk = 18 with 95 per cent confidence limits between 14 and 22). We have thus defined DQ beta RFLPs which tightly associate with IDDM individuals with DR4.

HLA class II alpha chain gene polymorphisms in patients with insulin-dependent diabetes mellitus, dermatitis herpetiformis, and celiac disease

We have investigated DNA polymorphism of the class II alpha chain genes in HLA typed patients with insulin dependent diabetes mellitus (IDDM; n = 79), celiac disease (CD; n = 46), dermatitis herpetiformis (DH; n = 53), and controls (n = 86). Preferential allelic associations of HLA genes and gene products have thus been constructed for susceptibility to these diseases. DR alpha and DQ alpha gene polymorphisms indicated heterogeneity of HLA DR3, DRw6, and DR7, and HLA DR2 and DRw6, respectively. In DR7 positive CD patients a 3.8-kilobase (kb) DR alpha fragment, which correlated with DQw3, was found in only 11% of patients compared with 45% of corresponding controls (P less than 0.05). An increased frequency of a DX alpha genotype UU in all three diseases was found (IDDM 59%, DH 45%, CD 48%, compared to 21% in controls, P less than 0.001), which is not explained solely by the increased frequencies of DR3-DX alpha U. We therefore conclude part of the genetic susceptibility for these three conditions is encoded by genes within the DQ-DX subregion.

Randomized trial of oral adjuvant razoxane (ICRF 159) in resectable colorectal cancer: five-year follow-up

Razoxane is one of the few agents which has shown activity in the treatment of advanced colorectal cancer. The drug has therefore been evaluated in a prospective randomized controlled trial as an adjuvant to surgery for resectable colorectal cancer. The results to median follow-up of 5 years are reported here. Accrual has ceased and a total of 272 patients entered the trial (133 control, 139 treatment). Treated patients received razoxane postoperatively on a continuous, long-term basis while control patients received identical clinical care but no adjuvant chemotherapy. Analysis of the results shows a significant prolongation of the time to recurrence for Dukes' C patients. All other groups including the overall analysis show no benefit although there is a consistent trend in favour of the treated patients except in Dukes' group 'D'. Razoxane is tolerated well by patients and causes minimal side-effects. However acute leukaemia occurred in three patients (2.45 per cent) after prolonged exposure to the drug and further evaluation should be in patients who are at high risk of developing recurrent cancer, in whom such a risk may be acceptable. It is concluded that razoxane is suitable for further evaluation in colorectal cancer and for incorporation into combination chemotherapy regimens.

Prospective serial liver ultrasound scanning in resectable colorectal cancer treated with adjuvant razoxane

Prospective serial ultrasound scanning (U/S) of the liver at 3-monthly intervals has been used to detect the presence of hepatic metastases from successfully resected Dukes' A, B and C grade colorectal carcinomas in a trial of the antimetastatic agent razoxane (ICRF 159). One hundred and twenty-six consecutive patients were randomly allocated to either adjuvant razoxane treatment (61) or to no further treatment (65). Twenty-six patients, 15 in the control group (23 per cent) and 11 in the razoxane treatment group (18 per cent) have developed hepatic metastases. All but three patients in the treated group and four in the controls were detected by U/S. In the control group four patients had definite metastases when metastases were first seen by ultrasound and three more, among the eight who initially had probable metastases, became definite metastases on ultrasound. In the treated group four patients had definite metastases and four more developed them amongst 12 who had probable metastases. The remaining eight of these 12 all regressed completely. This compared with only one complete regression (additionally on 5-FU for lung secondaries) amongst the eight controls who had probable metastases. The median time to development of liver metastases detected by U/S and other means was 59 weeks in the control group and 91 weeks in the razoxane treatment group. Ultrasound has proved to be a safe, sensitive and acceptable serial imaging technique for detecting colorectal liver metastases. Used prospectively, U/S has been valuable in monitoring the natural history of liver metastases and their behaviour during razoxane treatment.

Adjuvant oral razoxane (ICRF-159) in resectable colorectal cancer

One hundred and seventy six patients (81 controls, 95 receiving treatment) have entered a prospective randomized trial of long-term oral adjuvant razoxane (ICRF-159) following removal of a colorectal cancer. The median follow-up is 34 months. The treated patients in Dukes' groups B and C have a significantly longer disease-free interval than the control patients (P = 0.01 'as randomized' and P = 0.004 'as treated'). The differences in survival for Dukes' groups B and C are not significant, although follow-up is short. In Dukes' groups B and C, however, 24 of 56 of the patients in the control group have died (43%), as against only 17 of 64 in the treatment group (27%). The treatment produces very few side-effects, is well tolerated by patients, and is taken orally.