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T D Spector

Publications and source records attributed to T D Spector.

At least 19 recordsLinked to original sources

SHP-2 and PI3-kinase genes PTPN11 and PIK3R1 may influence serum apoB and LDL cholesterol levels in normal women.

Insulin regulates apoB metabolism via activation of PI3K or regulation of MTP via MAPK/ERK signalling. SHP-2 enhances both pathways through increased IRS-1 phosphorylation. We hypothesized that variants in the SHP-2 gene PTPN11 and PI3K p85alpha subunit gene PIK3R1 may influence fasting levels of plasma apoB and/or LDL cholesterol. We tested association of tagging SNPs (tSNPs) in each gene with serum lipids in a large sample of unselected population-based Caucasian female twins (n=2771, mean age 47.4+/-12.5 years) and then tested interaction between tSNPs in determining apoB and LDL levels. PTPN11 tSNP rs11066322 was associated with apoB (P=0.007) and rs11066320 was associated with LDL cholesterol (P=0.016). PIK3R1 tSNP rs251406 was associated with apoB (P=0.0003) and rs706713 was associated with LDL cholesterol (P=0.009). PTPN11 tSNP rs11066322 interacted with PIK3R1 tSNP rs251406 in determining serum apoB levels (P=0.012) and with PIK3R1 tSNP rs40318 in determining LDL cholesterol levels (P=0.009). Association of single tSNPs with both apoB and LDL cholesterol as well as interactions between the two genes suggest that variants influencing SHP-2 activity may modulate the acute pathway by which insulin regulates these lipids.

Adult↗

Prevalence of premature ovarian failure in monozygotic and dizygotic twins.

BACKGROUND: Premature ovarian failure (POF) before 40 years of age from natural causes affects approximately 1% of adult women, with minor variations between ethnic groups. A recent case of ovarian transplantation between young monozygotic (MZ) twins in which one had undergone unexplained POF at 14 years has prompted a study of the prevalence of POF. METHODS: Menopausal ages of 832 Australian and UK female twin-pairs were extracted from volunteer national twin registry databases containing medical, reproductive and lifestyle data surveyed by mail questionnaire. Surgical menopause was an exclusion criterion. RESULTS: The prevalence of POF in both MZ and dizygotic (DZ) twins was similar in both registries and 3- to 5-fold greater than the general population at age thresholds 40 and 45 years. No specific factors were found to account for the higher risk of early menopause. Some twins of both zygosities were highly discordant for menopausal age (>or=10 years). Nevertheless, there was significant intra-twin dependence, especially for MZ twins, and the average age difference at last menses was greater in DZ twin-pairs. CONCLUSION: Both MZ and DZ twins are at higher risk of POF. Despite some striking differences within MZ twin-pairs, menopausal ages were more concordant than for DZ twin-pairs, confirming that the timing of menopause has a heritable component.

Adult↗

Reduction of leucocyte telomere length in radiographic hand osteoarthritis: a population-based study.

BACKGROUND: Although age is the strongest predictor of osteoarthritis, the exact mechanism underlying this disorder remains elusive. OBJECTIVE: To examine the association between leucocyte telomere length (LTL), a bio-indicator of ageing, and radiographic hand osteoarthritis. METHODS: An unselected, predominantly female sample from the TwinsUK Adult Twin Registry (Twin Research and Genetic Epidemiology Unit, St Thomas Hospital, London, UK) was studied. Radiographs of both hands were obtained with a standard posteroanterior view and assessed for radiographic osteoarthritis according to the Kellgren/Lawrence (K/L) score. Individual radiographic features including osteophytes and joint space narrowing (JSN) were also assessed on a four-point scale using a standard atlas. Hand osteoarthritis was defined radiographically as having >or=3 osteoarthritis-affected joints of both hands (K/L score>or=2). Severity of hand osteoarthritis was indicated semiquantitatively by total K/L scores, osteophytes, JSN scores and proportion of joints affected. Mean LTL was measured by the terminal restriction fragment length using the Southern blot. RESULTS: A total of 1086 Caucasian subjects (mean (SD) age 55 (8.0) years) were studied. LTL was 6.95 (0.64) kb and was inversely correlated with age. After adjustment for age, sex, body mass index and smoking, LTL was significantly shorter by 178 bp in subjects with hand osteoarthritis (n = 160) than in those without (n = 926; p = 0.04). LTL was also significantly associated with semicontinuous measures of osteoarthritis (eg, total K/L score, JSN score, osteophyte score and proportion of joints affected) after adjustment (all p<or=0.02) in a dose-response fashion. CONCLUSION: Shorter LTL equivalent to around 11 years of annual loss in normal people is associated with radiographic hand osteoarthritis and disease severity, suggesting potential shared mechanisms between osteoarthritis and ageing, and implicating oxidative stress and low-level chronic inflammation in both conditions.

Adult↗

Genetic influence on the progression of radiographic knee osteoarthritis: a longitudinal twin study.

OBJECTIVE: Genetic influences on rates of osteoarthritis (OA) progression are unknown. Our aim was to estimate the heritability of progression of radiographic knee OA using a longitudinal twin study. METHODS: Unselected monozygotic (MZ) and dizygotic (DZ) twin pairs from the TwinsUK registry were utilized. Anteroposterior radiographs were performed on both knees at baseline and follow-up using the same protocol. Radiographic features of knee OA including osteophyte and joint space narrowing (JSN) were assessed on a four-point scale using a standard atlas. Progression of knee osteophyte and JSN was defined as the difference in the corresponding score between follow-up and baseline > or =1. Liability threshold modelling using logistic regression was utilized for heritability estimation. RESULTS: A total of 114 MZ pairs and 195 DZ pairs were studied. The average follow-up time was 7.2 years. Medial progression of osteophyte and JSN was more common than lateral progression. Prevalence of progression was generally higher in the MZs than the DZs. Similarly, concordances and tetrachoric correlations for both osteophyte and JSN were higher in the MZs than the DZs although only significant for overall and medial JSN and osteophyte. The heritability estimates were 69% [95% confidence interval (CI) 42-97%] and 80% (95% CI 50-100%) for medial osteophyte and JSN, respectively. The estimates were reduced by 7-15% after adjustment for age, body mass index (BMI), and the severity of osteophyte/JSN at baseline. CONCLUSION: Our data documented a substantial genetic influence on the progression of knee OA--as seen in the medial compartment, providing a solid basis to search for genes involved in this highly relevant clinical trait.

Aged↗

The big finger: the second to fourth digit ratio is a predictor of sporting ability in women.

BACKGROUND: The second to fourth finger length ratio (2d:4d) is thought to be related to diverse traits including cognitive ability, disease susceptibility, and sexuality. OBJECTIVE: To examine the relationship between 2d:4d and sports ability in women. METHODS: Hand radiographs from 607 women (mean age 54 years) were used to estimate 2d:4d. Ranking of sports ability was on a scale (1-5). RESULTS: The highest achieved level of participation in any sport was significantly negatively associated with 2d:4d (b = -4.93, p = 0.01) as was the relationship between 2d:4d and running level (b = -6.81, p = 0.034). Ability in other sports also showed a negative relationship albeit non-significant. CONCLUSIONS: These results suggest that a low 2d:4d ratio is related to increased female sports ability. It can be postulated that this ratio may predict potential sports ability. Understanding the mechanisms underpinning this relationship may give important insights into musculoskeletal fitness, health and disease.

Adult↗

Phosphatidylinositol 3-kinase p85alpha regulatory subunit gene PIK3R1 haplotype is associated with body fat and serum leptin in a female twin population.

AIMS/HYPOTHESIS: Phosphatidylinositol 3-kinase (PI3K) couples the leptin and insulin signalling pathways via the insulin receptor substrates IRS1 and IRS2. Hence, defective activation of PI3K could be a novel mechanism of peripheral leptin or insulin resistance. We investigated associations of tagging single-nucleotide polymorphisms (tSNPs) in the PI3K p85alpha regulatory subunit gene PIK3R1 with anthropometry, leptin, body fat and insulin sensitivity in a female twin population of European extraction. MATERIALS AND METHODS: Eight tSNPs were genotyped in 2,778 women (mean age 47.4+/-12.5 years) from the St Thomas' UK Adult Twin Registry (Twins UK). RESULTS: SNP rs1550805 was associated with serum leptin (p=0.028), BMI (p=0.025), weight (p=0.019), total fat (p=0.004), total fat percentage (p=0.002), waist circumference (p=0.025), central fat (p=0.005) and central fat percentage (p=0.005). SNPs rs7713645 and rs7709243 were associated with BMI (p=0.020 and p=0.029, respectively), rs7709243 with weight, total and central fat (p=0.026, p=0.031 and p=0.023, respectively) and both SNPs with fasting glucose (p=0.003 and p=0.001, respectively) and glucose 2-h post OGTT (p=0.023 and p=0.007, respectively). Subjects with haplotype 222 (frequency 7.2%) showed higher serum leptin concentration (p=0.007) and body fat measures (p< or =0.001 for all), and those with haplotype 221 (frequency 38.7%) showed higher fasting and 2-h glucose (p=0.035 and p=0.021, respectively) compared with subjects with the most common haplotype, 111 (frequency 45.5%). CONCLUSIONS/INTERPRETATION: Association of the PIK3R1 SNP rs1550805 with serum leptin and body fat may reflect a diminished ability of PI3K to signal via IRS1 or IRS2 in response to leptin.

Adipose Tissue↗

Heritability of DNA-damage-induced apoptosis and its relationship with age in lymphocytes from female twins.

Apoptosis is a physiological form of cell death important in normal processes such as morphogenesis and the functioning of the immune system. In addition, defects in the apoptotic process play a major role in a number of important areas of disease, such as autoimmune diseases and cancer. DNA-damage-induced apoptosis plays a vital role in the maintenance of genomic stability by the removal of damaged cells. Previous studies of the apoptotic response (AR) to radiation-induced DNA damage of lymphoid cells from individuals carrying germline TP53 mutations have demonstrated a defective AR compared with normal controls. We have also previously demonstrated that AR is reduced as individuals age. Results from the current study on 108 twins aged 18-80 years confirm these earlier findings that the AR of lymphoid cells to DNA damage is significantly reduced with increasing age. In addition this twin study shows, for the first time, that DNA-damage-induced AR has a strong degree of heritability of 81% (95% confidence interval 67-89%). The vital role of DNA-damage-induced apoptosis in maintaining genetic stability, its relationship with age and its strong heritability underline the importance of this area of biology and suggest areas for further study.

Adolescent↗

AMP-kinase alpha2 subunit gene PRKAA2 variants are associated with total cholesterol, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol in normal women.

BACKGROUND: 5'-AMP-activated protein kinase (AMPK) inactivates critial ensymes in fatty acid and cholesterol synthesis. We hypothesised that the serum lipid profile may be influenced by genetic variation in the AMPK catalytic alpha2 subunit. METHOD: We examined association of 5 tagging SNPs (tSNPs) in the PRKAA2 gene with serum lipids in 2777 normal Caucasian females (mean age 47.4+/-12.5 years). RESULTS: All tSNPs were associated with total- and LDL-cholesterol, (p<0.001 to 0.034), explaining variances of 0.13-0.59% and 0.11-0.55% respectively. One haplotype (frequency 34.7%) showed lower total- and LDL-cholesterol compared with the most common haplotype (frequency 45.7%) (p< or =0.001), explaining 0.78% of total- and 0.75% of LDL-cholesterol. Another haplotype (frequency 10.5%) was significantly associated with lower HDL-cholesterol (p = 0.005), explaining 0.59% of variance. CONCLUSIONS: PRKAA2 gene variants are significantly associated with serum lipoproteins in a large sample of normal female Caucasians.

AMP-Activated Protein Kinases↗

Common polymorphisms in SOCS3 are not associated with body weight, insulin sensitivity or lipid profile in normal female twins.

AIMS/HYPOTHESIS: Inhibition of signal transduction by suppressor of cytokine signalling-3 (SOCS-3) potentially influences resistance to insulin and leptin. The aim of this study was to test the association between three single-nucleotide polymorphisms (SNPs) representative of common linkage disequilibrium clusters in SOCS3 (rs4969169, rs12953258 and rs8064821) and obesity measures, insulin sensitivity measures and serum lipids in the general population. METHODS: The three SNPs, which had rare allele frequencies >0.06, were genotyped in 2,777 female twins of European extraction (mean age 47.4+/-12.5 years) from the St Thomas' UK Adult Twin Registry (Twins UK). RESULTS: Minor allele frequencies were as follows: rs4969169=0.067, rs12953258=0.097 and rs8064821=0.101. Individual SOCS3 SNPs were not associated with general or central obesity, or with two indices of insulin sensitivity (homeostasis model assessment and insulin sensitivity measure). CONCLUSIONS/INTERPRETATION: The results do not indicate that any of the three SNPs studied are associated with obesity, insulin measures or lipid measures.

Adult↗

The effects of social status on biological aging as measured by white-blood-cell telomere length.

Low socio-economic status (SES) is associated with a shortened life expectancy, but its effect on aging is unknown. The rate of white-blood-cell (WBC) telomere attrition may be a biological indicator of human aging. We tested the hypothesis that SES is associated with telomere attrition independent of known risk factors influencing the aging process. We studied 1552 female twins. A venous blood sample was taken from each twin and isolated WBCs used for extraction of DNA. Terminal restriction fragment length (TRFL) was measured. Questionnaire data were collected on occupation, education, income, smoking, exercise, height and weight. Standard multiple linear regression and multivariate analyses of variance tested for associations between SES and TRFL, adjusting for covariates. A discordant twin analysis was conducted on a subset to verify findings. WBC telomere length was highly variable but significantly shorter in lower SES groups. The mean difference in TRFL between nonmanual and manual SES groups was 163.2 base pairs (bp) of which 22.9 bp (approximately 14%) was accounted for by body mass index, smoking and exercise. Comparison of TRFL in the 17 most discordant SES twin pairs confirmed this difference. Low SES, in addition to the harmful effects of smoking, obesity and lack of exercise, appears to have an impact on telomere length.

Adolescent↗

Obesity is associated with genetic variants that alter dopamine availability.

Human and animal studies have implicated dopamine in appetite regulation, and family studies have shown that BMI has a strong genetic component. Dopamine availability is controlled largely by three enzymes: COMT, MAOA and MAOB, and by the dopamine transporter SLC6A3, and each gene has a well-characterized functional variant. Here we look at these four functional polymorphisms together, to investigate how heritable variation in dopamine levels influences the risk of obesity in a cohort of 1150, including 240 defined as obese (BMI > or = 30). The COMT and SLC6A3 polymorphisms showed no association with either weight, BMI or obesity risk. We found, however, that both MAOA and MAOB show an excess of the low-activity genotypes in obese individuals (MAOA:chi2= 15.45, p = 0.004; MAOB:chi2= 8.05, p = 0.018). Additionally, the MAOA genotype was significantly associated with both weight (p = 0.0005) and BMI (p = 0.001). When considered together, the 'at risk genotype'--low activity genotypes at both the MAOA and MAOB loci--shows a relative risk for obesity of 5.01. These results have not been replicated and, given the experience of complex trait genetics, warrant caution in interpretation. In implicating both the MAOA and MOAB variants, however, this study provides the first indication that dopamine availability (as opposed to other effects of MAOA) is involved in human obesity. It is therefore a priority to assess the associations in replication datasets.

Body Mass Index↗

Predicting the risk of fracture at any site in the skeleton: are all bone mineral density measurement sites equally effective?

The ability to assess a patient's risk of fracture is fundamental to the clinical role of bone densitometry. Fracture discrimination is quantified by the relative risk (RR), defined as the increased risk of fracture for a 1 standard deviation decrease in bone mineral density (BMD). The larger the value of RR, the more effective measurements are at identifying patients at risk of fracture. Epidemiological studies show that RR values for predicting the risk of any fracture are approximately the same for all BMD measurement sites. In this study, we show theoretically that this interesting observation is predictable and a consequence of two related observations: (1) that fracture prediction by BMD measurement sites distant from the fracture site is quantitatively explained by the correlation of BMD measurements and (2) that all correlation coefficients between distant BMD sites are comparable, with values in the range r = 0.55-0.65. The first of these conditions (referred to as the correlation hypothesis) is important because it sets a lower limit on the RR values at distant BMD sites on the assumption that measurements at these sites contain no independent information about fracture risk over and above that provided by their correlation with the fracture site BMD. If the correlation hypothesis is true, the present study points to the importance of the correlation coefficient between BMD sites as a key index that is indicative of the ability of different types of measurement to predict fracture risk. If, on the contrary, the correlation hypothesis is not valid, there is scope to improve bone densitometry by further studies to better identify those measurements that do provide independent information about fracture risk and how best to integrate this information with existing techniques to improve decision making.

Absorptiometry, Photon↗

The relation between progressive osteoarthritis of the knee and long term progression of osteoarthritis of the hand, hip, and lumbar spine.

BACKGROUND: The association between progression of knee osteoarthritis and progression of osteoarthritis at sites distant from the knee is unclear because of a lack of multisite longitudinal progression data. OBJECTIVE: To examine the association between radiological progression of knee osteoarthritis and osteoarthritis of the hands, hips, and lumbar spine in a population based cohort. METHODS: 914 women had knee x rays taken 10 years apart, which were read for the presence of osteophytes and joint space narrowing (JSN). Progression status was available for hand, hip, and lumbar spine x rays over the same 8 to 10 year period. The association between progression of knee osteoarthritis and osteoarthritis at other sites was analysed using odds ratios (OR) and 95% confidence intervals (CI) in logistic regression models. RESULTS: 89 of 133 women had progression of knee osteoarthritis based on osteophytes, and 51 of 148 based on JSN definition. Progression of JSN in the knee was predicted by progression in lumbar spine disc space narrowing (OR = 2.9 (95% CI 1.2 to 7.5)) and hip JSN (OR = 2.0 (1.0 to 4.2)). No consistent effects were seen for hand osteoarthritis. The associations remained after adjustment for age and body mass index. CONCLUSIONS: Progression of knee osteoarthritis is associated with progression of lumbar spine and hip osteoarthritis. This may have implications for trial methodology, the selection of patients for osteoarthritis research, and advice for patients on prognosis of osteoarthritis.

Adult↗

Haplotypes of the low-density lipoprotein receptor-related protein 5 (LRP5) gene: are they a risk factor in osteoarthritis?

OBJECTIVE: Several genome-wide scans have revealed an osteoarthritis (OA)-susceptibility locus on chromosome 11q in close proximity to the low-density lipoprotein receptor-related protein 5 (LRP5) gene. The regulation of bone mass is under the control of LRP5 and since increased bone mass is thought to play a role in the pathology of OA we examined LRP5 polymorphisms and haplotypes to determine if variants of this locus may predispose to OA. METHODS: A UK control population of 187 individuals was examined for five commonly occurring polymorphisms against a cohort of 158 DNAs from patients with knee OA. An additional UK cohort was also examined to confirm the findings of the first study; this second group consisted of 110 knee OA patients. Haplotype analysis was also performed on patient and control DNAs. RESULTS: A study of individual polymorphisms revealed no association with disease. However, haplotype analysis of the initial two populations revealed a common haplotype (C-G-C-C-A) that provided a 1.6-fold increased risk of OA (P(c)=0.021). The data obtained from the second cohort confirmed the initial findings, with a 1.6-fold increased risk observed within this cohort for the risk haplotype (P=0.012). CONCLUSIONS: A closer investigation of LRP5 and associated Wnt signalling molecules in OA will help determine disease aetiology and the development of novel treatment strategies that specifically target the bone compartment.

Aged↗

Interaction between two quantitative trait loci affects fetal haemoglobin expression.

The biological mechanisms controlling complex quantitative traits are likely to be affected by interactions between genetic factors, sometimes referred to as epistasis. The identification of interacting loci through genetic analyse faces many challenges, and few examples of replicated findings of interaction exist for humans and model system organisms. The replication of an interaction, or the non-independence, of two quantitative trait loci (QTL) affecting the developmental switch from the expression of fetal to adult haemoglobin is reported here. Fetal haemoglobin expression in adults is a highly heritable, yet complex, phenotype. Using a sample of 874 dizygotic twin pairs of European descent, we found linkage to a QTL on chromosome 8 to be conditional on the twin pairs' genotypes at a polymorphism in the beta-globin complex; an interaction originally identified in a large Asian Indian kindred. The beta-globin polymorphism has been previously shown to be associated with fetal haemoglobin levels in adults. This study reports the first known replication of a genetic interaction between QTLs influencing a complex human trait.

Chromosomes, Human, Pair 8↗

Linkage to the FOXC2 region of chromosome 16 for varicose veins in otherwise healthy, unselected sibling pairs.

BACKGROUND: The FOXC2 gene on 16q24 is mutated in lymphoedema distichiasis (LD), in which varicose veins (VV) are a common feature. We hypothesised that this gene might be implicated in the development of VV in the normal population, therefore, after performing a classical twin study, we tested for linkage and association in white women. We also tested for linkage with haemorrhoids (H), as a separate venous anomaly at the same locus. METHODS: A total of 2060 complete female twin pairs aged 18-80 years from the St Thomas' Adult UK Twin registry replied to questions on VV and H as part of a broader postal survey of 6600 twins (62% response rate). Dizygotic female twin pairs were tested for linkage and association to the candidate marker D16S520 (1903 individuals genotyped), which is located about 80 kb from FOXC2. RESULTS: Casewise concordance rates were significantly higher for monozygotic than dizygotic twins for both phenotypes (VV 67% v 45%; p = 2.2x10(-6); H 68% v 59%; p = 0.01; H including during pregnancy 73% v 64%; p = 2.1x10(-4)), corresponding to additive genetic heritabilities in liability of 86% (95% confidence interval (CI) 73% to 99%) for VV and 56-61% for H (95% CI 43% to 73%). The presence of VV and H were significantly correlated. We found significant evidence of linkage to the marker for VV (MLS(ASP) = 1.37, p = 0.01; GLM(ASP/DSP) Z = 3.17 p = 0.002), but no association. Both linkage and association tests were negative for H. The combined phenotype of having VV and H did not show any evidence of linkage or association. CONCLUSION: These results demonstrate VV and H to be heritable, related conditions, and the data strongly suggest FOXC2 to be implicated in the development of VV in the general population.

Adolescent↗

The effect of moderate alcohol consumption on bone mineral density: a study of female twins.

BACKGROUND: Osteoporosis is associated with morbidity and mortality, particularly in postmenopausal women. The effect of moderate alcohol intake on bone mineral density (BMD) and fracture risk remains unclear. OBJECTIVE: To carry out a twin study to investigate this effect while controlling for genetic effects and other confounding variables. METHODS: BMD was determined at the hip and lumbar spine in 46 pairs of monozygotic twins discordant for alcohol consumption. Biochemical evidence of altered bone metabolism was sought. RESULTS: A positive association between alcohol consumption and BMD was shown, in contrast to the negative effect of smoking on BMD. Markers of bone turnover were not associated with alcohol or BMD. CONCLUSIONS: Moderate alcohol consumption is not harmful to bone health in women and may even be beneficial. Beneficial effects do not appear to be mediated through an action on bone metabolism.

Alcohol Drinking↗

Extended haplotypes and linkage disequilibrium in the IL1R1-IL1A-IL1B-IL1RN gene cluster: association with knee osteoarthritis.

The interleukin-1 gene cluster is a key regulator in a number of chronic disease processes. We explored the linkage between nine polymorphic loci in the IL1R1 promoter, eight in the IL1A-IL1B-IL1RN gene complex, and their association with osteoarthritis (OA), a common complex disease associated with low-level inflammation. Using 195 healthy controls, we identified eight novel polymorphisms in the IL1R1 exon 1A region. We found limited LD between IL1R1 and the IL1A-IL1B-IL1RN cluster, although LD within these two individual groups was high. To test association with knee OA, we genotyped 141 patients from Bristol (UK) at the 17 loci. IL1R1 promoter haplotypes showed no association with disease. However, within the IL1A-IL1B-IL1RN complex, we identified a common haplotype conferring a four-fold risk of OA (P=0.00043; Pc=0.0043) and one IL1B-IL1RN haplotype conferring a four-fold reduced risk (P=0.0036; Pc=0.029). To replicate these associations, we subsequently examined 163 knee OA patients from London. Here, the effects of the haplotypes were confirmed: the risk IL1A-IL1B-IL1RN haplotype conferred a two-fold risk of OA (P=0.02), and the protective IL1B-IL1RN haplotype conferred a five-fold reduced risk of OA (P=0.0000008). These results may help to explain the genome-wide scan linkage data and functional observations concerning association between IL-1 and OA.

Aged↗