Life expectancy associated with different ages at diagnosis of type 2 diabetes in high-income countries: 23 million person-years of observation

BACKGROUND

The prevalence of type 2 diabetes is increasing rapidly, particularly among younger age groups. Estimates suggest that people with diabetes die, on average, 6 years earlier than people without diabetes. We aimed to provide reliable estimates of the associations between age at diagnosis of diabetes and all-cause mortality, cause-specific mortality, and reductions in life expectancy.

METHODS

For this observational study, we conducted a combined analysis of individual-participant data from 19 high-income countries using two large-scale data sources: the Emerging Risk Factors Collaboration (96 cohorts, median baseline years 1961-2007, median latest follow-up years 1980-2013) and the UK Biobank (median baseline year 2006, median latest follow-up year 2020). We calculated age-adjusted and sex-adjusted hazard ratios (HRs) for all-cause mortality according to age at diagnosis of diabetes using data from 1 515 718 participants, in whom deaths were recorded during 23·1 million person-years of follow-up. We estimated cumulative survival by applying age-specific HRs to age-specific death rates from 2015 for the USA and the EU.

FINDINGS

For participants with diabetes, we observed a linear dose-response association between earlier age at diagnosis and higher risk of all-cause mortality compared with participants without diabetes. HRs were 2·69 (95% CI 2·43-2·97) when diagnosed at 30-39 years, 2·26 (2·08-2·45) at 40-49 years, 1·84 (1·72-1·97) at 50-59 years, 1·57 (1·47-1·67) at 60-69 years, and 1·39 (1·29-1·51) at 70 years and older. HRs per decade of earlier diagnosis were similar for men and women. Using death rates from the USA, a 50-year-old individual with diabetes died on average 14 years earlier when diagnosed aged 30 years, 10 years earlier when diagnosed aged 40 years, or 6 years earlier when diagnosed aged 50 years than an individual without diabetes. Using EU death rates, the corresponding estimates were 13, 9, or 5 years earlier.

INTERPRETATION

Every decade of earlier diagnosis of diabetes was associated with about 3-4 years of lower life expectancy, highlighting the need to develop and implement interventions that prevent or delay the onset of diabetes and to intensify the treatment of risk factors among young adults diagnosed with diabetes.

FUNDING

British Heart Foundation, Medical Research Council, National Institute for Health and Care Research, and Health Data Research UK.

Well-differentiated gastroenteropancreatic G3 NET: findings from a large single centre cohort

Neuroendocrine neoplasms are known to have heterogeneous biological behavior. G3 neuroendocrine tumours (NET G3) are characterized by well-differentiated morphology and Ki67 > 20%. The prognosis of this disease is understood to be intermediate between NET G2 and neuroendocrine carcinoma (NEC). Clinical management of NET G3 is challenging due to limited data to inform treatment strategies. We describe clinical characteristics, treatment, and outcomes in a large single centre cohort of patients with gastroenteropancreatic NET G3. Data was reviewed from 26 cases managed at Queen Elizabeth Hospital, Birmingham, UK, from 2012 to 2019. Most commonly the site of the primary tumour was unknown and majority of cases with identifiable primaries originated in the GI tract. Majority of cases demonstrated somatostatin receptor avidity. Median Ki67 was 30%, and most cases had stage IV disease at diagnosis. Treatment options included surgery, somatostatin analogs (SSA), and chemotherapy with either platinum-based or temozolomide-based regimens. Estimated progression free survival was 4 months following initiation of SSA and 3 months following initiation of chemotherapy. Disease control was observed following treatment in 5/11 patients treated with chemotherapy. Estimated median survival was 19 months; estimated 1 year survival was 60% and estimated 2 year survival was 13%. NET G3 is a heterogeneous group of tumours and patients which commonly have advanced disease at presentation. Prognosis is typically poor, though select cases may respond to treatment with SSA and/or chemotherapy. Further study is needed to compare efficacy of different treatment strategies for this disease.

Triglyceride-containing lipoprotein sub-fractions and risk of coronary heart disease and stroke: A prospective analysis in 11,560 adults

AIMS

Elevated low-density lipoprotein cholesterol (LDL-C) is a risk factor for cardiovascular disease; however, there is uncertainty about the role of total triglycerides and the individual triglyceride-containing lipoprotein sub-fractions. We measured 14 triglyceride-containing lipoprotein sub-fractions using nuclear magnetic resonance and examined associations with coronary heart disease and stroke.

METHODS

Triglyceride-containing sub-fraction measures were available in 11,560 participants from the three UK cohorts free of coronary heart disease and stroke at baseline. Multivariable logistic regression was used to estimate the association of each sub-fraction with coronary heart disease and stroke expressed as the odds ratio per standard deviation increment in the corresponding measure.

RESULTS

The 14 triglyceride-containing sub-fractions were positively correlated with one another and with total triglycerides, and inversely correlated with high-density lipoprotein cholesterol (HDL-C). Thirteen sub-fractions were positively associated with coronary heart disease (odds ratio in the range 1.12 to 1.22), with the effect estimates for coronary heart disease being comparable in subgroup analysis of participants with and without type 2 diabetes, and were attenuated after adjustment for HDL-C and LDL-C. There was no evidence for a clear association of any triglyceride lipoprotein sub-fraction with stroke.

CONCLUSIONS

Triglyceride sub-fractions are associated with increased risk of coronary heart disease but not stroke, with attenuation of effects on adjustment for HDL-C and LDL-C.

World Health Organization cardiovascular disease risk charts: revised models to estimate risk in 21 global regions

BACKGROUND

To help adapt cardiovascular disease risk prediction approaches to low-income and middle-income countries, WHO has convened an effort to develop, evaluate, and illustrate revised risk models. Here, we report the derivation, validation, and illustration of the revised WHO cardiovascular disease risk prediction charts that have been adapted to the circumstances of 21 global regions.

METHODS

In this model revision initiative, we derived 10-year risk prediction models for fatal and non-fatal cardiovascular disease (ie, myocardial infarction and stroke) using individual participant data from the Emerging Risk Factors Collaboration. Models included information on age, smoking status, systolic blood pressure, history of diabetes, and total cholesterol. For derivation, we included participants aged 40-80 years without a known baseline history of cardiovascular disease, who were followed up until the first myocardial infarction, fatal coronary heart disease, or stroke event. We recalibrated models using age-specific and sex-specific incidences and risk factor values available from 21 global regions. For external validation, we analysed individual participant data from studies distinct from those used in model derivation. We illustrated models by analysing data on a further 123 743 individuals from surveys in 79 countries collected with the WHO STEPwise Approach to Surveillance.

FINDINGS

Our risk model derivation involved 376 177 individuals from 85 cohorts, and 19 333 incident cardiovascular events recorded during 10 years of follow-up. The derived risk prediction models discriminated well in external validation cohorts (19 cohorts, 1 096 061 individuals, 25 950 cardiovascular disease events), with Harrell's C indices ranging from 0·685 (95% CI 0·629-0·741) to 0·833 (0·783-0·882). For a given risk factor profile, we found substantial variation across global regions in the estimated 10-year predicted risk. For example, estimated cardiovascular disease risk for a 60-year-old male smoker without diabetes and with systolic blood pressure of 140 mm Hg and total cholesterol of 5 mmol/L ranged from 11% in Andean Latin America to 30% in central Asia. When applied to data from 79 countries (mostly low-income and middle-income countries), the proportion of individuals aged 40-64 years estimated to be at greater than 20% risk ranged from less than 1% in Uganda to more than 16% in Egypt.

INTERPRETATION

We have derived, calibrated, and validated new WHO risk prediction models to estimate cardiovascular disease risk in 21 Global Burden of Disease regions. The widespread use of these models could enhance the accuracy, practicability, and sustainability of efforts to reduce the burden of cardiovascular disease worldwide.

FUNDING

World Health Organization, British Heart Foundation (BHF), BHF Cambridge Centre for Research Excellence, UK Medical Research Council, and National Institute for Health Research.

Genetic Determination of Coagulation Factor VIIc Levels among Healthy Middle-aged Women

A recent study (1) reported variation among men in clotting factor Vile levels is associated with a genetic polymorphism detected by the restriction enzyme Msp I. The present study determined the Msp I genotype (Arg353, Gln353 alleles) for 189 women (mean age 53) who were subjects in the Healthy Women Study, a population study of CHD risk factor change at menopause. Women with the Arg/Arg genotype (n = 147) had an 16% higher (geometric) mean FVIIc level than those with the Arg/Gln (n = 41) genotype (1.21 vs 1.04 U/ml, p<0.01), while the one subject with the Gln/Gln genotype had an FVIIc level of 1.00 U/ml. These results are consistent with those previously found in healthy men (1). In addition, women carrying the Gin allele did not exhibit the elevation in FVIIc with menopause and use of hormone therapy found among those with the Arg allele, suggesting that genotype may modify the observed rise in factor Vile at menopause. Possibly because of the small sample size this interaction did not reach conventional levels of statistical significance. Results of multiple linear regression analyses controlling for age, hormone use, obesity, (In) triglyceride levels, and family history of CHD found FVIIc levels to be significantly (p<0.001) related to genotype. Thus, genotype appears to be a major determinant of FVIIc levels among women.

Low Plasma Levels of Factor Vile and Antigen Are More Strongly Associated with the 10 Base Pair Promoter (-323) Insertion than the Glutamine 353 Variant

In a group of 705 healthy middle-aged men, we have examined the relationship between plasma levels of Factor VII (FVII) c and Factor VII antigen (FVIIag) and two polymorphisms in the FVII gene. One polymorphism alters arginine at position 353 to glutamine (R/Q), and the other is the result of a 10 base pair (bp) insertion in the promoter region at position -323 from the start of translation (0/1 Obp). The frequency for the Q allele was 0.105 (95% Cl 0.09-0.12) and for the lObp allele was 0.117 (95% Cl 0.10-0.13). Men who were carriers of either of the rare alleles had levels of FVIIc and FVIIag that were approximately 20% lower than non-carriers, and both of these effects were highly statistically significant (p < 0.0001). Strong allelic association was observed between the two polymorphisms, with R and 0 bp being on the same chromosome in 96% of cases, and Q and 10 bp being on the same chromosome in 90% of cases where this could be determined unambiguously (Delta = 0.92, X2 = 1206, p < 0.0001). This strong allelic association created three major genotype groups which were found to have significantly different levels of FVIIc (p < 0.001). In the 547 men homozygous for both common alleles (R/R & 0/0), mean (SD) FVIIc was 101 (29) as compared with 85 (30) in the 20 men with the genotype R/R & 0/10 and 81(23) in the 126 men with the genotype R/Q & 0/10, suggesting a larger lowering effect associated with the 10 bp allele (16%) compared to the Q allele (an additional 4%). The lowering effect on FVII associated with the 10 bp allele remained statistically significant after adjusting for the effect of the Q allele (p = 0.004 for FVIIc and p = 0.06 for FVIIag), but the effect associated with the Q allele was no longer significant after adjusting for the 10 bp allele, suggesting that the strongest effect on levels of FVIIc was associated with the 0/10 bp genotype. In the sample overall, plasma FVIIc was associated positively with serum triglyceride concentration and the slope of this relationship was significantly greater in those with the genotype R/R compared to the other groups combined (0.12 versus 0.02, p = 0.008) with differences of similar size seen in the 0/0 compared to 0/10+10/10 groups. However, using the combined genotypes, the slope of this relationship in the R/R & 0/10 group was 0.38 and was significantly steeper (p = 0 .0 1 ) than in the other two groups who did not differ in this respect (slopes 0.11 and 0.08). This effect was seen on four subsequent annual examinations, and was also evident in the relationship between FVIIag and triglyceride concentration (p = 0.003 for difference between groups measured at baseline only). These data suggest that part of the previously described effects on FVIIc levels associated with the R/Q polymorphism may be explained by genetic variation in the promoter region of the FVII gene.

Elevated Levels of Factor VII Activity in the Postprandial State: Effect of the Factor VII Arg-GIn Polymorphism

A genetic polymorphism (Arg/Gln353) of coagulation factor VII was recently identified and shown to be associated with differences in basal factor VII coagulant activity. Postprandial lipaemia seems to exert an acute but evanescent effect on the activity of factor VII, and the influence of the Arg/Gln353 polymorphism on factor VII activation during postprandial lipaemia was therefore studied in male post-infarction patients [age 48.8 ± 3.3 years (mean ± SD)] with Arg/Arg (n = 23) and Arg/Gln (n = 8) genotypes. Factor VII antigen (VIlag) and activity along with plasma lipoproteins were determined before and after intake of a mixed meal-type of oral fat load. Patients with the Arg/Gln genotype had basal VIlag and activated factor VII (Vila) levels 75% and 48%, respectively, of those of patients homozygous for the Arg allele. In absolute terms, Vila increased more in homozygotes for the Arg allele (AO-6 h Vila 1.76 ± 1.48 ng/ml) than in heterozygotes (0.60 ± 0.27 ng/ml) in response to fat intake, but the percentage increase in Vila molecules did not differ significantly between subjects with Arg/Arg and Arg/Gln genotypes (37 ± 32% versus 27 ± 15%). This suggests that the influence of the Arg/Gln polymorphism on factor VII activity is mainly accounted for by differences in the basal factor VII protein level between genotypes. Since most of our lives are spent in the postprandial state, possession of the factor VII-Gln353 allele is likely to confer protection against coronary heart disease by reducing the amount of Vila produced in response to fat intake.

The Role of β-Fibrinogen Genotype in Determining Plasma Fibrinogen Levels in Young Survivors of Myocardial Infarction and Healthy Controls from Sweden

β-fibrinogen G/A-455 polymorphism genotype was determined in 123 young survivors of myocardial infarction and 86 healthy controls from Sweden. Frequency of the A-455 allele was 0.25 (95% Confidence Interval 0.21–0.29) in both patients and controls, significantly higher than that reported previously (0.19, 95% Cl 0.16–0.22) in 292 men from the UK (1). Mean plasma fibrinogen level was significantly higher in patients (3.6 g/1) than in controls (3.1 g/1), with p <0.001. Genotype was significantly associated with (adjusted) plasma fibrinogen level in controls (p = 0.003). This effect was confined to the smokers (n = 50) where mean fibrinogen level was significantly (p = 0.001) higher in G/A-455 and A/A-455 individuals (3.5 g/1) compared with G/G-455 homozygotes (2.9 g/1). There was a significant interaction between smoking status and genotype in determining plasma fibrinogen levels in the controls. These data provide independent confirmation of the association between β-fibrinogen G/A-455 genotype and plasma fibrinogen levels previously observed in healthy men from the UK (1).

GWAS implicated risk variants in different genes contribute additively to increase the risk of coronary artery disease (CAD) in the Pakistani subjects

Background

Coronary artery disease (CAD) remains the single most important cause of mortality worldwide. Many candidate and GWAS genetic variants have been identified in the recent years. In the current study, we selected six SNPs from various genes that have originally been identified in GWAS studies and examined the association of SNPs individually and as a genetic risk score (GRS) with CAD and blood lipid levels in the Pakistani subjects.

Methods

Six hundred twenty-four (404 cases and 219 controls) subjects were genotyped for variants rs10757274 in CDKN2A gene, rs17465637 in MIA3 gene, rs7025486 in DAB2IP gene, rs17228212 in SMAD3 gene, rs981887 in MRAS gene and rs1746048 in CXCL12 gene, by TaqMan and KASPar allele discrimination techniques. Serum lipid parameters were measured using commercially available kits. Statistical analyses were done using SPSS version 22.

Results

Individually, the single SNPs were not associated with CAD (p < 0.05). However, the combined GRS of 6 SNPs was significantly higher in cases than controls (4.89 ± 0.11 vs 4.58 ± 0.08, p = 0.024). Among blood lipids, GRS showed significant positive association with serum triglycerides levels (p = 0.022).

Conclusion

The GRS was quantitatively associated with CAD risk and showed association with serum triglycerides levels, suggesting that the mechanism of these variants is likely to be in part at least through creating an atherogenic lipid profile in subjects carrying high numbers of risk alleles.

Electronic supplementary material

The online version of this article (10.1186/s12944-018-0736-2) contains supplementary material, which is available to authorized users.

The SNP rs10911021 is associated with oxidative stress in coronary heart disease patients from Pakistan

BACKGROUND

rs10911021 (a single nucleotide polymorphism present upstream of the GLUL gene) affects glutamic acid metabolism, and was shown to be associated with coronary heart disease (CHD) in patients with T2DM but a definite mechanism is unknown. It may affect glutathione cycle, an important effector in the antioxidant defense mechanism, in the cells. We checked the association of this SNP with CHD and oxidative stress biomarkers, malondialdeheyde (MDA), GSH and GSSG in Pakistani patients.

METHODS

A total of 650 subjects (425 CHD cases and 225 controls) were genotyped by TaqMan allelic discrimination technique. The levels of MDA, GSH and GSSG were measured by standard protocols.

RESULTS

The risk allele frequency was higher in cases than controls, but the difference was insignificant (p = 0.55). The SNP was not associated with CHD (p = 0.053) but when the analysis was limited to CHD patients having DM, a significant association (p = 0.03) was observed. The blood levels of MDA and GSSG were higher while that of GSH was significantly lower in the cases than the controls (p < 0.05). Each risk allele increased MDA and GSSG by 0.29 (0.036) mmol/l and 0.4 (0.04) mmol/l, respectively, while decreased GSH by -0.36 (0.03) mmol/l. The SNP was not associated with any of the tested blood lipids.

CONCLUSION

The SNP rs10911021 was associated with CHD only in patients having diabetes, but the SNP was associated with total oxidative stress biomarkers MDA and GSH and GSSG levels. As the SNP rs10911021 showed significant association with oxidative stress parameters and these parameters should an increased oxidative stress in the CHD subjects, it can be concluded that the SNP may have contributed to increase the risk of heart diseases in the diabetic subjects by increasing the oxidative stress.

Fibrinolytic Proteins and Progression of Coronary Artery Disease in Relation to Gemfibrozil Therapy

Impaired fibrinolytic function, mainly due to increased plasma plasminogen activator inhibitor-1 (PAI-1) activity, is common in patients with manifest coronary artery disease (CAD) and a predictor of recurrent cardiovascular events. We investigated the relationships of plasma tissue-type plasminogen activator (tPA) and PAI-1 antigen levels, plasma PAI-1 activity and PAI 4/5-guanosine (4G/5G) genotype to CAD progression in 203 middle-aged men participating in the Lopid Coronary Angiography Trial (LOCAT).

A higher tPA antigen concentration, whether baseline or on-trial, was associated with a more severe global angiographic response (p < 0.05), an association mainly accounted for by progression of diffuse lesions in graft-affected segments (change in per-patient means of average diameters of segments haemodynamically related to bypass grafts). Plasma PAI-1 activity and mass concentration and 4G/5G PAI-1 genotype were unrelated to angiographic outcome measurements. tPA and PAI-1 antigen increased significantly in the gemfibrozil group (+11.3% and + 16.4%, respectively, p < 0.001), whereas there was no treatment effect on PAI-1 activity (median change 0.0%).

It is concluded that fibrinolytic function does not substantially influence progression of CAD as assessed by angiography in middle-aged men. Furthermore, pronounced long-term lowering of serum triglycerides by gemfibrozil treatment does not significantly affect the plasma PAI-1 activity level but increases the plasma tPA and PAI-1 antigen concentrations.

Prothrombin Activation Is Increased among Asymptomatic Carriers of the Prothrombin G20210A and Factor V Arg506Gln Mutations

The risk of venous thrombosis is increased in individuals who carry specific genetic abnormalities in blood coagulation proteins. Among Caucasians, the prothrombin G20210A and factor V Arg506Gln (FV R506Q) mutations are the most prevalent defects identified to date. We evaluated their influence on markers of coagulation activation among participants in the Second Northwick Park Heart Study, which recruited healthy men (aged 50–61 years) from nine general medical practices in England and Wales. They were free of clinical vascular disease and malignancy at the time of recruitment. Genotypes for the two mutations were analyzed using microplate array diagonal gel electrophoresis, and coagulation markers (factor XIIa; activation peptides of factor IX, factor X, and prothrombin; fibrinopeptide A) were measured by immunoassay. Factor VII coagulant activity and factor VIIa levels were determined by a functional clotting assay. Among 1548 men genotyped for both mutations, 28 (1.8%) and 52 (3.4%) were heterozygous for prothrombin G20210A and FV R506Q, respectively. The only coagulation marker that was significantly associated with the two mutations was prothrombin activation fragment F1+2 [mean ± SD, 0.88 ± 0.32 nmol/L in men with prothrombin G20210A (p = 0.002) and 0.89 ± 0.30 in men with FV R506Q (p = 0.0001) versus 0.72 ± 0.24 among non-carriers for either mutation]. This data provides conclusive evidence that heterozygosity for the prothrombin G20210A as well as the FV R506Q mutations in the general population leads to an increased rate of prothrombin activation in vivo.

Regular Exercise, Plasminogen Activator Inhibitor-1 (PAI-1) Activity and the 4G/5G Promoter Polymorphism in the PAI-1 Gene

The aim of this controlled randomised clinical trial was to investigate the effects of regular low to moderate intensity physical activity on plasminogen activator inhibitor-1 (PAI-1) activity during three years while taking into account the 4G/5G polymorphism in the promoter of the PAI-1 gene. Male subjects (age 52-62 years, n = 132) were randomised into an exercise or a (non-intervention) reference group. Aerobic threshold increased by 8.8% (p = 0.025) in the exercise group, and decreased by 1.1% in the non-intervention group, while PAI-1 activity did not change significantly in either study group. However, homozygotes for the 4G allele in the exercise group showed a 36% reduction in PAI-1 (p = 0.025). In conclusion, although regular moderate physical activity did not decrease PAI-1 activity in the whole group, regular exercise may be effective for controlling elevated PAI-1 level in subjects homozygous for the 4G allele.

Rise of circulating thrombopoietin following cardiothoracic surgery is potentiated in patients with coronary atherosclerosis: correlation with a preceding increase in levels of interleukin-6

Thrombopoietin (TPO) is the major regulator of platelet production. Plasma levels of TPO are thought to be regulated by its binding to platelets and megakaryocytes. Here we have used a model of cardiac surgery with cardiopulmonary bypass (CBP) to test the possibility that changes in TPO levels are influenced by the presence of coronary artery disease (CAD) and by changes in interleukin-6 (IL-6). After surgery patients with CAD (n = 22) or with normal coronary arteries (n = 11) showed a significant thrombocytopaenia followed by a reactive thrombocytosis. The platelet recovery was preceded by a significant rise in TPO (from 62.6 ± 9.4 pg/ml at baseline to 129.2 ± 19 pg/ml at 60 h, P <0.001), which in turn was preceded by, and was positively correlated with, a marked increase in circulating IL-6 (from 1.5 ± 0.3 pg/ml at baseline to 269.3 ± 30.6 pg/ml at 3-12 h, P <0.001). The rise of both IL-6 and TPO was significantly larger in patients with CAD. No correlation was found between the post-operative drop in platelet mass and changes in either the TPO or IL-6 levels. These findings suggest that in man circulating TPO levels, besides being controlled by changes in platelet mass, are influenced by inflammatory processes, including the presence of coronary atherosclerosis.

Gene-Environment Interaction in the Determination of Levels of Plasma Fibrinogen

This review will focus on the inflammatory risk factors that may influence changes in plasma fibrinogen levels and that may influence an individual’s risk of ischemic heart disease (IHD). These inflammatory risk factors occur to a different extent in individuals as their environment changes. Although a specific genotype may be associated, in healthy subjects, with modest differences in levels of a risk factor for thrombosis, this effect may be larger or smaller in subgroups of subjects. Documenting such gene-environment interactions is important if genotype information is ever to be used in a clinical or diagnostic setting. Understanding the molecular mechanisms of such interactions is vital to the development of novel therapeutic approaches to reduce risk of myocardial infarction (MI).

We review some of the gene-environment interactions detected to date for the G-455A β-fibrinogen gene promoter polymorphism. Carriers of the A allele, representing roughly 20% of the population, consistently have, on average, 7% to 10% higher fibrinogen levels than those with the genotype GG. Data will be presented to demonstrate interaction between situations of inflammatory stimulation (e.g., smoking habit, presence of ischemic disease, and level of physical exercise) in the determination of the magnitude of the effect of the A allele on plasma fibrinogen levels.

The cytokine interleukin-6 (IL-6) is the likely link between inflammatory processes and IHD. Recently we have identified a functional G/C polymorphism at -174bp in the IL-6 promoter, with the G allele being a 2 to 4 times stronger promoter upon stimulation with interleukin-1 (IL-1) or lipopolysaccharide (LPS). In a small study of healthy subjects, the C allele was associated with significantly lower mean plasma levels of IL-6, an effect which may be protect against the development of IHD. Finally, we describe a rapid throughput genotyping method that is useful for large-scale genetic epidemiology studies.

Gene-environment and Gene-gene Interaction in the Determination of Plasma Homocysteine Levels in Healthy Middle-aged Men

Healthy middle-aged men (n = 1470) from eight general practices across Britain were examined for plasma total homocysteine levels and genotyped for the A222V polymorphism in the methylene-tetrahydrofolate (MTHFR) gene, the 68 bp insertion polymorphism in exon 8 of the cystathionine b synthase (CBS) gene and the D919G polymorphism in the methionine synthase (MS) gene. The median value for plasma homocysteine was 11.90 μmol/l (25–75% Interquartile range 10.10-14.20) for the whole sample. Smokers had significantly higher homocysteine levels than non-smokers (12.90 vs 11.70 μmol/l and p <0.00005) and levels significantly differed according to folate (p-value <0.00005), with men in the lowest quartile of folate having the highest median homocysteine levels. Genotype at all three loci was associated with differences in plasma homocysteine level. Individuals homozygous for the MTHFR V222 allele had 1.6 μmol/l higher median homocysteine levels when compared to the other two genotypes (p <0.00005), while for the CBS and MS genes, individuals carrying one or more of the rare alleles had lower median homocysteine than individuals homozygous for the common allele (0.80 μmol/l, p <0.03, and 0.70 μmol/l, p <0.04 respectively). The raising effect associated with homozygosity for the V222 allele was greater in men in the lowest quartile of folate (interaction between folate and genotype p = 0.02), but none of the genotype effects was significantly modulated by B12 levels. While the raising effects of V222 and MS D919 homozygosity on homocysteine level were essentially additive, the homocysteine lowering effect associated with the CBS 68bp allele was seen most strongly in men homozygous for the V222 allele (MTHFR-CBS genotype interaction p = 0.03) and the D919 allele (MS-CBS interaction p = 0.09). Age, folate, B12 and smoking explained 13.48% of the variance while the three genotypes combined and with interaction terms explained only an additional 2.63%. This interaction between CBS genotype and MTHFR and MS genotype points to a key role of the CBS transulphuration pathway in the metabolism of homocysteine that may be particularly important as a compensatory mechanism in subjects with low dietary folate.

The influence of surface energy on the self-cleaning of insect adhesive devices

The ability of insects to adhere to surfaces is facilitated by the use of adhesive organs found on the terminal leg segments. These adhesive pads are inherently ‘tacky’ and are expected to be subject to contamination by particulates, leading to loss of function. Here, we investigated the self-cleaning of ants and beetles by comparing the abilities of both hairy and smooth pad forms to self-clean on both high and low energy surfaces after being fouled with microspheres of two sizes and surface energies. We focused on the time taken to regain adhesive potential in unrestrained Hymenopterans (Polyrhachis dives and Myrmica scabrinodis) and Coccinellids (Harmonia axyridis and Adalia bipunctata) fouled with microspheres. We found that the reattainment of adhesion is influenced by particle type and size in Hymenopterans, with an interaction between the surface energy of the contaminating particle and substrate. In Coccinellids, reattainment of adhesion was only influenced by particle size and substrate properties. The adhesive organs of Coccinellids appear to possess superior self-cleaning abilities compared with those of Hymenopterans, although Hymenopterans exhibit better adhesion to both surface types.

GPs have key role in detecting familial hypercholesterolaemia

Currently the vast majority of people with familial hypercholesterolaemia (FH) in the U.K. remain undiagnosed, probably 85% of the predicted 120,000 cases. FH is a common inherited disorder of lipid metabolism causing high levels of LDL cholesterol which leads to early CHD. It has an autosomal dominant pattern of inheritance so siblings and children of a patient with FH will have a 50% chance of inheriting the condition. FH is present in the heterozygous form in 1 in 500 of the population. The homozygous form is very rare, affecting 1 in 1,000,000. Around half of men with FH, if untreated, will have developed clinically evident CHD by the age of 55 years, and approximately one third of women by the age of 60. A significant reduction in the mortality and morbidity of the disease can be achieved through changes in lifestyle and the use of statins to lower cholesterol. NICE recommends that clinical management of FH patients should primarily be carried out in lipid clinics. When cascade testing from lipid clinics is underway, GPs will be approached by relatives who have been identified as being at 50% risk of having FH, because they have an affected first-degree relative with the disorder. They will then need to take a blood sample for cholesterol measurement, and often will also be asked to provide a sample for DNA testing. A preliminary investigation in the surgery of a family member would involve a full lipid profile to calculate LDL cholesterol. If this is not elevated in an adult, cut-off value 4.9 mmol/L, FH is highly unlikely. Even if an FH patient is young, currently does not have CHD and may have no other CHD risk factors, the Framingham risk charts should not be used. These individuals are at increased CHD risk which warrants treatment with statins. The vascular health check screening programme recommends that where a total cholesterol of > 7.5 mmol/L is found FH should be considered.

Bayesian methods for meta-analysis of causal relationships estimated using genetic instrumental variables

Genetic markers can be used as instrumental variables, in an analogous way to randomization in a clinical trial, to estimate the causal relationship between a phenotype and an outcome variable. Our purpose is to extend the existing methods for such Mendelian randomization studies to the context of multiple genetic markers measured in multiple studies, based on the analysis of individual participant data. First, for a single genetic marker in one study, we show that the usual ratio of coefficients approach can be reformulated as a regression with heterogeneous error in the explanatory variable. This can be implemented using a Bayesian approach, which is next extended to include multiple genetic markers. We then propose a hierarchical model for undertaking a meta-analysis of multiple studies, in which it is not necessary that the same genetic markers are measured in each study. This provides an overall estimate of the causal relationship between the phenotype and the outcome, and an assessment of its heterogeneity across studies. As an example, we estimate the causal relationship of blood concentrations of C-reactive protein on fibrinogen levels using data from 11 studies. These methods provide a flexible framework for efficient estimation of causal relationships derived from multiple studies. Issues discussed include weak instrument bias, analysis of binary outcome data such as disease risk, missing genetic data, and the use of haplotypes.

RF tumour ablation: Computer simulation and mathematical modelling of the effects of electrical and thermal conductivity

This study determined the effects of thermal conductivity on RF ablation tissue heating using mathematical modelling and computer simulations of RF heating coupled to thermal transport. Computer simulation of the Bio-Heat equation coupled with temperature-dependent solutions for RF electric fields (ETherm) was used to generate temperature profiles 2 cm away from a 3 cm internally-cooled electrode. Multiple conditions of clinically relevant electrical conductivities (0.07-12 S m-1) and 'tumour' radius (5-30 mm) at a given background electrical conductivity (0.12 S m-1) were studied. Temperature response surfaces were plotted for six thermal conductivities, ranging from 0.3-2 W m-1 degrees C (the range of anticipated clinical and experimental systems). A temperature response surface was obtained for each thermal conductivity at 25 electrical conductivities and 17 radii (n=425 temperature data points). The simulated temperature response was fit to a mathematical model derived from prior phantom data. This mathematical model is of the form (T=a+bRc exp(dR) s(f) exp(g)(s)) for RF generator-energy dependent situations and (T=h+k exp(mR)+n?exp(p)(s)) for RF generator-current limited situations, where T is the temperature (degrees C) 2 cm from the electrode and a, b, c, d, f, g, h, k, m, n and p are fitting parameters. For each of the thermal conductivity temperature profiles generated, the mathematical model fit the response surface to an r2 of 0.97-0.99. Parameters a, b, c, d, f, k and m were highly correlated to thermal conductivity (r2=0.96-0.99). The monotonic progression of fitting parameters permitted their mathematical expression using simple functions. Additionally, the effect of thermal conductivity simplified the above equation to the extent that g, h, n and p were found to be invariant. Thus, representation of the temperature response surface could be accurately expressed as a function of electrical conductivity, radius and thermal conductivity. As a result, the non-linear temperature response of RF induced heating can be adequately expressed mathematically as a function of electrical conductivity, radius and thermal conductivity. Hence, thermal conductivity accounts for some of the previously unexplained variance. Furthermore, the addition of this variable into the mathematical model substantially simplifies the equations and, as such, it is expected that this will permit improved prediction of RF ablation induced temperatures in clinical practice.