Vitamin B12 deficiency and altered one-carbon metabolites in early pregnancy is associated with maternal obesity and dyslipidaemia

Vitamin B12 (B12) is a micronutrient essential for one-carbon (1C) metabolism. B12 deficiency disturbs the 1C cycle and alters DNA methylation which is vital for most metabolic processes. Studies show that B12 deficiency may be associated with obesity, insulin resistance and gestational diabetes; and with obesity in child-bearing women. We therefore hypothesised that the associations between B12 deficiency, BMI and the metabolic risk could be mediated through altered 1C metabolites in early pregnancy. We explored these associations in two different early pregnancy cohorts in the UK (cohort 1; n = 244 and cohort 2; n = 60) with anthropometric data at 10–12 weeks and plasma/serum sampling at 16–18 weeks. B12, folate, total homocysteine (tHcy), methionine, MMA, metabolites of 1C metabolism (SAM, SAH) and anthropometry were measured. B12 deficiency (< 150 pmol/l) in early pregnancy was 23% in cohort 1 and 18% in cohort 2. Regression analysis after adjusting for likely confounders showed that B12 was independently and negatively associated with BMI (Cohort 1: β = − 0.260, 95% CI (− 0.440, − 0.079), p = 0.005, Cohort 2: (β = − 0.220, 95% CI (− 0.424, − 0.016), p = 0.036) and positively with HDL cholesterol (HDL-C) (β = 0.442, 95% CI (0.011,0.873), p = 0.045). We found that methionine (β = − 0.656, 95% CI (− 0.900, − 0.412), p < 0.0001) and SAH (β = 0.371, 95% CI (0.071, 0.672), p = 0.017) were independently associated with triglycerides. Low B12 status and alteration in metabolites in 1C metabolism are common in UK women in early pregnancy and are independently associated with maternal obesity and dyslipidaemia. Therefore, we suggest B12 monitoring in women during peri-conceptional period and future studies on the pathophysiological relationship between changes in 1C metabolites and its association with maternal and fetal outcomes on larger cohorts. This in turn may offer potential to reduce the metabolic risk in pregnant women and their offspring

Evaluation of the risk of cardiovascular events with clarithromycin using both propensity score and self-controlled study designs

Aim: Some previous studies suggest a long term association between clarithromycin use and cardiovascular events. This study investigates this association for clarithromycin given as part of Helicobacter pylori treatment (HPT). Methods: Our source population was the Clinical Practice Research Datalink (CPRD), a UK primary care database. We conducted a self-controlled case series (SCCS), a case–time–control study (CTC) and a propensity score adjusted cohort study comparing the rate of cardiovascular events in the 3 years after exposure to HPT containing clarithromycin with exposure to clarithromycin free HPT. Outcomes were first incident diagnosis of myocardial infarction (MI), arrhythmia and stroke. For the cohort analysis we included secondary outcomes all cause and cardiovascular mortality. Results: Twenty-eight thousand five hundred and fifty-two patients were included in the cohort. The incidence rate ratio of first MI within 1 year of exposure to HPT containing clarithromycin was 1.07 (95% CI 0.85, 1.34, P = 0.58) and within 90 days was 1.43 (95% CI 0.99, 2.09 P = 0.057) in the SCCS analysis. CTC and cohort results were consistent with these findings. Conclusions There was some evidence for a short term association for first MI but none for a long term association for any outcome

Segmentation of corpus callosum using diffusion tensor imaging: validation in patients with glioblastoma

Abstract Background This paper presents a three-dimensional (3D) method for segmenting corpus callosum in normal subjects and brain cancer patients with glioblastoma. Methods Nineteen patients with histologically confirmed treatment naïve glioblastoma and eleven normal control subjects underwent DTI on a 3T scanner. Based on the information inherent in diffusion tensors, a similarity measure was proposed and used in the proposed algorithm. In this algorithm, diffusion pattern of corpus callosum was used as prior information. Subsequently, corpus callosum was automatically divided into Witelson subdivisions. We simulated the potential rotation of corpus callosum under tumor pressure and studied the reproducibility of the proposed segmentation method in such cases. Results Dice coefficients, estimated to compare automatic and manual segmentation results for Witelson subdivisions, ranged from 94% to 98% for control subjects and from 81% to 95% for tumor patients, illustrating closeness of automatic and manual segmentations. Studying the effect of corpus callosum rotation by different Euler angles showed that although segmentation results were more sensitive to azimuth and elevation than skew, rotations caused by brain tumors do not have major effects on the segmentation results. Conclusions The proposed method and similarity measure segment corpus callosum by propagating a hyper-surface inside the structure (resulting in high sensitivity), without penetrating into neighboring fiber bundles (resulting in high specificity)

Self-controlled case series methodology

The self-controlled case series method is an epidemiological study design in which individuals act as their own control. The method offers advantages, but has several limitations. This paper outlines the self control case series method and reviews methodological developments that address some of these limitations

Self-controlled case series studies : a modelling guide with R

Self-Controlled Case Series Studies: A Modelling Guide with R provides the first comprehensive account of the self-controlled case series (SCCS) method, a statistical technique for investigating associations between outcome events and time-varying exposures. The method only requires information from individuals who have experienced the event of interest, and automatically controls for multiplicative time-invariant confounders, even when these are unmeasured or unknown. It is increasingly being used in epidemiology, most frequently to study the safety of vaccines and pharmaceutical drugs. Key features of the book include: •A thorough yet accessible description of the SCCS method, with mathematical details provided in separate starred sections. •Comprehensive discussion of assumptions and how they may be verified. •A detailed account of different SCCS models, extensions of the SCCS method, and the design of SCCS studies. •Extensive practical illustrations and worked examples from epidemiology. •Full computer code from the associated R package SCCS, which includes all the data sets used in the book. The book is aimed at a broad range of readers, including epidemiologists and medical statisticians who wish to use the SCCS method, and also researchers with an interest in statistical methodology. The three authors have been closely involved with the inception, development, popularisation and programming of the SCCS method

Use of the self-controlled case series method in vaccine safety studies : review and recommendations for best practice

The self-controlled case-series method was originally developed to investigate potential associations between vaccines and adverse events, and is now commonly used for this purpose. This study reviews applications of the method to vaccine safety investigations in the period 1995–2010. In total, 40 studies were reviewed. The application of the self-controlled case-series method in these studies is critically examined, with particular reference to the definition of observation and risk periods, control of confounders, assumptions and potential biases, methodological and presentation issues, power and sample size, and software. Comparisons with other study designs undertaken in the papers reviewed are also highlighted. Some recommendations are presented, with the emphasis on promoting good practice

Myocardial infarction and cardiac death associated with current use of clarithromycin: cohort study

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Myocardial infarction associated with current use of helicobacter pylori eradication regimen containing clarithromycin: self controlled case series

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Association of maternal vitamin B12 and folate levels in early pregnancy with gestational diabetes: a prospective UK cohort study (PRiDE study)

Aims/hypothesis: The prevalence of gestational diabetes mellitus (GDM) is increasing worldwide in all ethnic groups. Low vitamin B12 and low/high folate levels may contribute to GDM risk, but there is conflicting evidence. Our aim is to assess the relationships of early pregnancy vitamin B12 and folate levels with the risk of GDM status at 26–28 weeks of gestation. Methods: This was a prospective, multi-centre, multi-ethnic cohort study (n = 4746) in the UK. Participants who were eligible to be selectively screened as per the National Institute for Health and Care Excellence (NICE) criteria were included in the study. Results: GDM prevalence was 12.5% by NICE and 14.7% by International Association of Diabetes and Pregnancy Study Groups (IADPSG) criteria. Folate deficiency (1.3%) was rare but B12 insufficiency (42.3% at < 220 pmol/l) and folate excess (36.5%) were common in early pregnancy. Early pregnancy median B12 levels were lower, and folate levels higher, in women who were diagnosed with GDM at 26–28 weeks. B12 was negatively associated with fasting plasma glucose (1 SD: −0.06 mmol/l; 95% CI −0.04, −0.08; p <  0.0001) and 2 h plasma glucose levels (−0.07 mmol/l; 95% CI −0.02, −0.12; p = 0.004). Higher B12 was associated with 14.4% lower RR of IADPSG-GDM (0.856; 95% CI 0.786, 0.933; p = 0.0004) after adjusting for key confounders (age, parity, smoking status, ethnicity, family history, household income and folate status). Approximately half of this association was mediated through BMI. Folate was positively associated with 2 h plasma glucose levels (0.08 mmol/l; 95% CI 0.04, 0.13; p = 0.0005) but its relationship with fasting plasma glucose was U-shaped (quadratic β: 0.011; p = 0.05). Higher folate was associated with 11% higher RR of IADPSG-GDM (adjusted RR 1.11; 95% CI 1.036, 1.182; p = 0.002) (age, parity, smoking status, ethnicity, family history, household income and B12 status). Although no interactions were observed for B12 and folate (as continuous variables) with glucose levels and GDM risk, a low B12–high folate combination was associated with higher blood glucose level and risk of IADPSG-GDM (adjusted RR 1.742; 95% CI 1.226, 2.437; p = 0.003). Conclusions/interpretation: B12 insufficiency and folate excess were common in early pregnancy. Low B12 and high folate levels in early pregnancy were associated with small but statistically significant changes in maternal blood glucose level and higher RR of GDM. Our findings warrant additional studies on the role of unmetabolised folic acid in glucose metabolism and investigating the effect of optimising early pregnancy or pre-conception B12 and folate levels on subsequent hyperglycaemia