Cardiovascular disease in insulin dependent diabetes mellitus: similar rates but different risk factors in the US compared with Europe.
BACKGROUND: Cardiovascular disease (CVD) in insulin dependent diabetes mellitus (IDDM) has been linked to renal disease. However, little is known concerning international variation in the correlations with hyperglycaemia and standard CVD risk factors. METHODS: A cross-sectional comparison was made of prevalence rates and risk factor associations in two large studies of IDDM subjects: the Pittsburgh Epidemiology of Diabetes Complications Study (EDC) and the EURODIAB IDDM Complications Study from 31 centres in Europe. Subgroups of each were chosen to be comparable by age and duration of diabetes. The EDC population comprises 286 men (mean duration 20.1 years) and 281 women (mean duration 19.9 years); EURODIAB 608 men (mean duration 18.1 years) and 607 women (mean duration 18.9 years). The mean age of both populations was 28 years. Cardiovascular disease was defined by a past medical history of myocardial infarction, angina, and/or the Minnesota ECG codes (1.1-1.3, 4.1-4.3, 5.1-5.3, 7.1). RESULTS: Overall prevalence of CVD was similar in the two populations (i.e. men 8.6% versus 8.0%, women 7.4% versus 8.5%, EURODIAB versus EDC respectively), although EDC women had a higher prevalence of angina (3.9% versus 0.5%, P < 0.001). Multivariate modelling suggests that glycaemic control (HbA1c) is not related to CVD in men. Age and high density lipoprotein cholesterol predict CVD in EURODIAB, while triglycerides and hypertension predict CVD in EDC. For women in both populations, age and hypertension (or renal disease) are independent predictors. HbA1c is also an independent predictor-inversely in EURODIAB women (P < 0.008) and positively in EDC women (P = 0.03). Renal disease was more strongly linked to CVD in EDC than in EURODIAB. CONCLUSIONS: Despite a similar prevalence of CVD, risk factor associations appear to differ in the two study populations. Glycaemic control (HbA1c) does not show a consistent or strong relationship to CVD. (+info)
Hereditary juvenile haemochromatosis: a genetically heterogeneous life-threatening iron-storage disease.
Juvenile haemochromatosis is a rare inborn error of iron metabolism with clinical manifestations before 30 years of age. Unlike adult haemochromatosis which principally affects men, juvenile haemochromatosis affects the sexes equally; it causes early endocrine failure, dilated cardiomyopathy and joint disease. We report four patients (two of each sex) from three pedigrees affected by juvenile haemochromatosis with a mean onset at 22 years (range 14-30). All had endocrine deficiency with postpubertal gonadal failure secondary to pituitary disease; two suffered near-fatal cardiomyopathy with heart failure. Mean time to diagnosis from the first clinical signs of disease was 9.8 years (range 0.5-20) but general health and parameters of iron storage responded favourably to iron-depletion therapy. A 24-year-old man listed for heart transplantation because of cardiomyopathy [left ventricular (LV) ejection fraction 16%] responded to intravenous iron chelation with desferrioxamine combined with phlebotomy (ejection fraction 31%). A 27-year-old woman with subacute biventricular heart failure refractory to medication required orthotopic cardiac transplantation before the diagnosis was established (LV ejection fraction 25%). Genetic studies showed that these two patients with cardiomyopathy from unrelated families were heterozygous for the HFE 845G-->A (C282Y) mutation and wild-type at the H63D locus: complete sequencing of the intron-exon boundaries and entire coding sequence of the HFE gene failed to identify additional lesions. Two siblings in a pedigree without cardiomyopathy were wild-type at the HFE C282Y locus; although the brother harboured a single copy of the 187C-->G (H63D) allele, segregation analysis showed that in neither sibling was the iron-storage disease linked to MHC Class I markers on chromosome 6p. Juvenile haemochromatosis is thus a genetically heterogenous disorder distinct from the common adult variant. (+info)
Constitutional genetic variation at the human aromatase gene (Cyp19) and breast cancer risk.
The activity of the aromatase enzyme, which converts androgens into oestrogens and has a major role in regulating oestrogen levels in the breast, is thought to be a contributing factor in the development of breast cancer. We undertook this study to assess the role of constitutional genetic variation in the human aromatase gene (Cyp19) in the development of this disease. Our genotyping of 348 cases with breast cancer and 145 controls (all Caucasian women) for a published tetranucleotide repeat polymorphism at intron 4 of the Cyp19 gene revealed the presence of six common and two rare alleles. Contingency table analysis revealed a significant difference in allelic distribution between cases and controls (chi2 5df = 13.52, P = 0.019). The allele measuring 171 bp was over-represented in cases; of 14 individuals homozygous for this allele, 13 were cases. These individuals had a higher incidence of cancer in family members and an earlier age at diagnosis than other cases. In sequencing Cyp19's coding exons and regulatory regions, we discovered a perfect association between a silent polymorphism (G-->A at Val80) and the high-risk genotype. Our conclusion is that constitutional genetic variation at the Cyp19 locus is associated with the risk of developing breast cancer, with the 171-bp allele serving as the high-risk allele. (+info)
Cancer risk in close relatives of women with early-onset breast cancer--a population-based incidence study.
Inherited susceptibility to breast cancer is associated with an early onset and bilateral disease. The extent of familial risks has not, however, been fully assessed in population-based incidence studies. The purpose of the study was to quantify the risks for cancers of the breast, ovary and other sites of close relatives of women in whom breast cancer was diagnosed at an early age. Records collected between 1943 and 1990 at the Danish Cancer Registry were searched, and 2860 women were found in whom breast cancer was diagnosed before age 40. Population registers and parish records were used to identify 14 973 parents, siblings and offspring of these women. Cancer occurrence through to 31 December 1993 was determined within the Cancer Registry's files and compared with national incidence rates. Women with early-onset breast cancer were at a nearly fourfold increased risk of developing a new cancer later in life (268 observed vs. 68.9 expected). The excess risk was most evident for second cancer of the breast (181 vs. 24.5) and for ovarian cancer (20 vs. 3.3). For mothers and sisters, risks for cancers of the breast and ovary were significantly increased by two- to threefold. Bilateral breast cancer and breast-ovarian cancer were very strong predictors of familial risks, with one in four female relatives predicted to develop breast and/or ovarian cancer by age 75. Mothers had a slightly increased risk of colon cancer, but not endometrial cancer. The risk for breast cancer was also increased among fathers (standardized incidence ratio 2.5; 95% CI 0.5-7.4) and especially brothers (29; 7.7-74), although based on small numbers. The risk for prostatic cancer was unremarkable. In this large population-based survey, the first-degree relatives of women who developed breast cancer before age 40 were prone to ovarian cancer as well as male and female breast cancer, but not other tumours that may share susceptibility genes with breast cancer. (+info)
Age of onset in Huntington disease: sex specific influence of apolipoprotein E genotype and normal CAG repeat length.
Age of onset (AO) of Huntington disease (HD) is known to be correlated with the length of an expanded CAG repeat in the HD gene. Apolipoprotein E (APOE) genotype, in turn, is known to influence AO in Alzheimer disease, rendering the APOE gene a likely candidate to affect AO in other neurological diseases too. We therefore determined APOE genotype and normal CAG repeat length in the HD gene for 138 HD patients who were previously analysed with respect to CAG repeat length. Genotyping for APOE was performed blind to clinical information. In addition to highlighting the effect of the normal repeat length upon AO in maternally inherited HD and in male patients, we show that the APOE epsilon2epsilon3 genotype is associated with significantly earlier AO in males than in females. Such a sex difference in AO was not apparent for any of the other APOE genotypes. Our findings suggest that subtle differences in the course of the neurodegeneration in HD may allow interacting genes to exert gender specific effects upon AO. (+info)
Multipoint oligogenic analysis of age-at-onset data with applications to Alzheimer disease pedigrees.
It is usually difficult to localize genes that cause diseases with late ages at onset. These diseases frequently exhibit complex modes of inheritance, and only recent generations are available to be genotyped and phenotyped. In this situation, multipoint analysis using traditional exact linkage analysis methods, with many markers and full pedigree information, is a computationally intractable problem. Fortunately, Monte Carlo Markov chain sampling provides a tool to address this issue. By treating age at onset as a right-censored quantitative trait, we expand the methods used by Heath (1997) and illustrate them using an Alzheimer disease (AD) data set. This approach estimates the number, sizes, allele frequencies, and positions of quantitative trait loci (QTLs). In this simultaneous multipoint linkage and segregation analysis method, the QTLs are assumed to be diallelic and to interact additively. In the AD data set, we were able to localize correctly, quickly, and accurately two known genes, despite the existence of substantial genetic heterogeneity, thus demonstrating the great promise of these methods for the dissection of late-onset oligogenic diseases. (+info)
Analysis of affected sib pairs, with covariates--with and without constraints.
Covariate models have previously been developed as an extension to affected-sib-pair methods in which the covariate effects are jointly estimated with the degree of excess allele sharing. These models can estimate the differences in sib-pair allele sharing that are associated with measurable environment or genes. When there are no covariates, the pattern of identical-by-descent allele sharing in affected sib pairs is expected to fall within a small triangular region of the potential parameter space, under most genetic models. By restriction of the estimated allele sharing to this triangle, improved power is obtained in tests for genetic linkage. When the affected-sib-pair model is generalized to allow for covariates that affect allele sharing, however, new constraints and new methods for the application of constraints are required. Three generalized constraint methods are proposed and evaluated by use of simulated data. The results compare the power of the different methods, with and without covariates, for a single-gene model with age-dependent onset and for quantitative and qualitative gene-environment and gene-gene interaction models. Covariates can improve the power to detect linkage and can be particularly valuable when there are qualitative gene-environment interactions. In most situations, the best strategy is to assume that there is no dominance variance and to obtain constrained estimates for covariate models under this assumption. (+info)
Identification of a C/G polymorphism in the promoter region of the BRCA1 gene and its use as a marker for rapid detection of promoter deletions.
Reduced expression of BRCA1 has been implicated in sporadic breast cancer, although the mechanisms underlying this phenomenon remain unclear. To determine whether regulatory mutations could account for the reduced expression, we screened the promoter region by sequencing in 20 patients with sporadic disease. No mutations were detected; however, a new polymorphism consisting of a C-to-G base change within the beta-promoter was identified, with the frequency of the G allele being 0.34. Close to complete linkage disequilibrium was found between this marker and the Pro871 Leu polymorphism, situated in exon 11, which has previously been shown not to be associated with breast or ovarian cancer. This indicates that the C/G polymorphism is also unlikely to play a role in either disease. However, the strength of linkage disequilibrium between these markers permitted their use for rapid screening for genomic deletions within BRCA1. A series of 214 cases with familial breast cancer were analysed using this approach; 88/214 were heterozygous for the promoter polymorphism, thereby excluding a deletion in this region. Among the remaining patients, one hemizygous case reflecting a promoter deletion was successfully identified. Therefore, this study indicates that deletions within the beta-promoter region of BRCA1 are an uncommon event in familial breast cancer. Furthermore, it suggests that mutations within the BRCA1 promoter are unlikely to account for the reported decreased expression of BRCA1 in sporadic disease. (+info)