HDL subspecies in young adult twins: heritability and impact of overweight

Lipoprotein Insulin Resistance Score and Mortality Risk Stratification in Heart Failure

BACKGROUND

Higher total serum cholesterol is associated with lower mortality in heart failure. Evaluating associations between lipoprotein subfractions and mortality among people with heart failure may provide insights into this observation.

METHODS

We prospectively enrolled a community cohort of people with heart failure from 2003 to 2012 and assessed vital status through 2021. Plasma collected at enrollment was used to measure lipoprotein subfractions via nuclear magnetic resonance spectroscopy. A composite score of 6 lipoprotein subfractions was generated using the lipoprotein insulin resistance index (LP-IR) algorithm. Using covariate-adjusted proportional hazards regression models, we evaluated associations between LP-IR score and all-cause mortality.

RESULTS

Among 1382 patients with heart failure (median follow-up 13.9 years), a one-standard-deviation (SD) increment in LP-IR score was associated with lower mortality (hazard ratio [HR] 0.93; 95% confidence interval [CI], 0.97-0.99). Among LP-IR parameters, mean high-density lipoprotein (HDL) particle size was significantly associated with lower mortality (HR per 1-SD decrement in mean HDL particle size = 0.83; 95% CI, 0.78-0.89), suggesting that the inverse association between LP-IR score and mortality may be driven by smaller mean HDL particle size.

CONCLUSIONS

LP-IR score was inversely associated with mortality among patients with heart failure and may be driven by smaller HDL particle size.

Cardiometabolic Traits in Adult Twins: Heritability and BMI Impact with Age

Background: The prevalence of obesity and cardiometabolic diseases continues to rise globally and obesity is a significant risk factor for cardiometabolic diseases. However, to our knowledge, evidence of the relative roles of genes and the environment underlying obesity and cardiometabolic disease traits and the correlations between them are still lacking, as is how they change with age. Method: Data were obtained from the Chinese National Twin Registry (CNTR). A total of 1421 twin pairs were included. Univariate structural equation models (SEMs) were performed to evaluate the heritability of BMI and cardiometabolic traits, which included blood hemoglobin A1c (HbA1c), fasting blood glucose (FBG), systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), triglycerides (TGs), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C). Bivariate SEMs were used to assess the genetic/environmental correlations between them. The study population was divided into three groups for analysis: ≤50, 51−60, and >60 years old to assess the changes in heritability and genetic/environmental correlations with ageing. Results: Univariate SEMs showed a high heritability of BMI (72%) and cardiometabolic traits, which ranged from 30% (HbA1c) to 69% (HDL-C). With age increasing, the heritability of all phenotypes has different degrees of declining trends. Among these, BMI, SBP, and DBP presented significant monotonous declining trends. The bivariate SEMs indicated that BMI correlated with all cardiometabolic traits. The genetic correlations were estimated to range from 0.14 (BMI and LDL-C) to 0.39 (BMI and DBP), while the environmental correlations ranged from 0.13 (BMI and TC/LDL-C) to 0.31 (BMI and TG). The genetic contributions underlying the correlations between BMI and SBP and DBP, TC, TG, and HDL-C showed a progressive decrease as age groups increased. In contrast, environmental correlations displayed a significant increasing trend for HbA1c, SBP, and DBP. Conclusions: The findings suggest that genetic and environmental factors have essential effects on BMI and all cardiometabolic traits. However, as age groups increased, genetic influences presented varying degrees of decrement for BMI and most cardiometabolic traits, suggesting the increasing importance of environments. Genetic factors played a consistently larger role than environmental factors in the phenotypic correlations between BMI and cardiometabolic traits. Nevertheless, the relative magnitudes of genetic and environmental factors may change over time.

Age dependent association between remnant cholesterol and cardiovascular disease

Background and aims

High remnant cholesterol is associated with cardiovascular disease (CVD), but whether CVD risk attributable to remnant cholesterol vary between young and later adults remains unknown. The study aimed to assess age differences in the association between remnant cholesterol and CVD.

Methods

This prospective study included 95 663 participants without CVD and lipid-lowering treatment at baseline, including 16 254 young adults (age 18-39 years) and 79 409 later adults (age ≥40 years). Individuals were grouped by clinically meaningful remnant cholesterol concentrations of <0.50, 0.50-0.99, 1.00-1.49, and ≥1.50 mmol/L. Multivariable Cox regressions were performed to calculate hazard ratio (HR).

Results

During a median follow-up of 11.01 years, 164 incident CVD were identified in young adults, and 6081 cases in later adults. After multivariate adjustment, the association between remnant cholesterol and CVD was more pronounced in young adults than later adults (P for interaction=0.0019), the HR was 2.24 (95% confidence interval [CI], 1.45-3.47) for young individuals with remnant cholesterol ≥1.50 mmol/L, compared to individuals with remnant cholesterol <0.50 mmol/L, while the corresponding HR was 1.21 (95% CI, 1.13-1.29) for later adults. Furthermore, the population attributable risk percentage for remnant cholesterol < 1.50 vs ≥ 1.50 mmol/L was also higher in young (14.8%) than later adults (4.2%).

Conclusions

Despite a lower incidence risk of CVD among young adults compared later adults, the stronger association and greater attributable risk of remnant cholesterol among young adults highlight the importance of preventive efforts across the adult life course.

Association between daily egg intake and lipid profiles in adults from the Henan rural cohort study

BACKGROUND AND AIMS

The association between daily egg intake and dyslipidemia remains a contentious issue. Therefore, our study was aimed to explore the relation of daily egg intake to lipid profile; and whether the association was mediated by body mass index (BMI).

METHODS AND RESULTS

A total of 39,021 participants (18-79 years) were enrolled from the Henan Rural Cohort Study. Data on egg consumptions and blood lipid indices were collected with standardized processes. Logistic regression and restricted cubic splines were used to estimate the odds ratio (OR) and 95% confidence intervals (95% CI). Mediation analysis using bootstrap was performed to examine the contribution of BMI to daily egg intake and HDL-C. The participants were divided into 3 egg intake groups (＜26.79 g/d, 26.79-62.50 g/d, ＞62.5 g/d). According to our results, comparing with the low daily egg consumption group, medium and high egg intake tertiles were related with increased high-TC (OR_medium = 1.546, 95%CI (1.417,1.688); OR_high = 1.902,95%CI (1.703, 2.124)), high LDL-C (OR_medium = 1.224, 95%CI (1.121, 1.337); OR_high = 1.368,95%CI (1.220, 1.534)) and non-HDL-C(OR_medium = 1.486,95%CI(1.358,1.625); OR_high = 1.715,95%CI (1.499, 1.888)), as well as inversely associated with high-TG (OR_medium = 0.825, 95% CI(0.778, 0.875); OR_high = 0.778,95%CI(0.718,0.844)) and low HDL-C (OR_medium = 0.914, 95%CI (0.858, 0.973); OR_high = 0.756,95%CI(0.693,0.825)). Moreover, mediation analysis showed that both of BMI and WC partly mediated the relationship between daily egg intake and HDL-C.

CONCLUSIONS

Our results suggested that the daily egg intake may have a role in effect on lipid profiles, and the effect of daily egg intake on HDL-C may be partly mediated by BMI and WC.

FinnTwin16: A Longitudinal Study from Age 16 of a Population-Based Finnish Twin Cohort

The purpose of this review is to provide a detailed and updated description of the FinnTwin16 (FT16) study and its future directions. The Finnish Twin Cohort comprises three different cohorts: the Older Twin Cohort established in the 1970s and the FinnTwin12 and FT16 initiated in the 1990s. FT16 was initiated in 1991 to identify the genetic and environmental precursors of alcoholism, but later the scope of the project expanded to studying the determinants of various health-related behaviors and diseases in different stages of life. The main areas addressed are alcohol use and its consequences, smoking, physical activity, overall physical health, eating behaviors and eating disorders, weight development, obesity, life satisfaction and personality. To date, five waves of data collection have been completed and the sixth is now planned. Data from the FT16 cohort have contributed to several hundred studies and many substudies, with more detailed phenotyping and collection of omics data completed or underway. FT16 has also contributed to many national and international collaborations.

Associations of Blood Pressure and Cholesterol Levels During Young Adulthood With Later Cardiovascular Events

BACKGROUND

Blood pressure (BP) and cholesterol are major modifiable risk factors for cardiovascular disease (CVD), but effects of exposures during young adulthood on later life CVD risk have not been well quantified.

OBJECTIVE

The authors sought to evaluate the independent associations between young adult exposures to risk factors and later life CVD risk, accounting for later life exposures.

METHODS

The authors pooled data from 6 U.S. cohorts with observations spanning the life course from young adulthood to later life, and imputed risk factor trajectories for low-density lipoprotein (LDL) and high-density lipoprotein cholesterols, systolic and diastolic BP starting from age 18 years for every participant. Time-weighted average exposures to each risk factor during young (age 18 to 39 years) and later adulthood (age ≥40 years) were calculated and linked to subsequent risks of coronary heart disease (CHD), heart failure (HF), or stroke.

RESULTS

A total of 36,030 participants were included. During a median follow-up of 17 years, there were 4,570 CHD, 5,119 HF, and 2,862 stroke events. When young and later adult risk factors were considered jointly in the model, young adult LDL ≥100 mg/dl (compared with <100 mg/dl) was associated with a 64% increased risk for CHD, independent of later adult exposures. Similarly, young adult SBP ≥130 mm Hg (compared with <120 mm Hg) was associated with a 37% increased risk for HF, and young adult DBP ≥80 mm Hg (compared with <80 mm Hg) was associated with a 21% increased risk.

CONCLUSIONS

Cumulative young adult exposures to elevated systolic BP, diastolic BP and LDL were associated with increased CVD risks in later life, independent of later adult exposures.

Disease Heritability Inferred from Familial Relationships Reported in Medical Records

Heritability is essential for understanding the biological causes of disease but requires laborious patient recruitment and phenotype ascertainment. Electronic health records (EHRs) passively capture a wide range of clinically relevant data and provide a resource for studying the heritability of traits that are not typically accessible. EHRs contain next-of-kin information collected via patient emergency contact forms, but until now, these data have gone unused in research. We mined emergency contact data at three academic medical centers and identified 7.4 million familial relationships while maintaining patient privacy. Identified relationships were consistent with genetically derived relatedness. We used EHR data to compute heritability estimates for 500 disease phenotypes. Overall, estimates were consistent with the literature and between sites. Inconsistencies were indicative of limitations and opportunities unique to EHR research. These analyses provide a validation of the use of EHRs for genetics and disease research.

Heritability and responses to high fat diet of plasma lipidomics in a twin study

Lipidomics have a great potential as clinical tool for monitoring metabolic changes in health and disease. Nevertheless hardly anything is known about the heritability of lipids. Therefore, it is necessary to clarify how and how much we can affect these progresses in individuals. In our interventional twin study (46 healthy, non-obese twin pairs) we investigated the lipid profile in plasma samples after switching from a low fat diet to an isocaloric high fat diet (HFD) to characterize the metabolic adaptation. Additionally we used the ACE model for Additive genetics, Common and unique Environment as well as linear mixed modelling to analyse the heritability of lipids. The heritability of lipids varied between 0–62% and applied to lipid species rather than to lipid classes. Phospholipids showed the highest inheritance. In addition, sex, body mass index (BMI) and age were important modifiers. The lipid profile changed already after one week of HFD and diverged further after 5 weeks of additional HFD. Basal concentrations of specific lipids within phospholipids are strongly inherited and are likely to be associated with heritable disease risks. BMI, sex and age were major modifiers. Nutrition strongly alters specific lipid classes, and has to be controlled in clinical association studies.

Comparison of serum biochemical parameters between two broiler chicken lines divergently selected for abdominal fat content

In humans, obesity is associated with increased or decreased levels of serum biochemical indicators. However, the relationship is not as well understood in chickens. Due to long-term intense selection for fast growth rate, modern broilers have the problem of excessive fat deposition, exhibiting biochemical or metabolic changes. In the current study, the Northeast Agricultural University broiler lines divergently selected for abdominal fat content (NEAUHLF) were used to identify differences in serum biochemical parameters between the 2 lines. A total of 18 serum biochemical indicators were investigated in the 16th, 17th, and 18th generation populations of NEAUHLF, and the genetic parameters of these serum biochemical indicators were estimated. After analyzing the data from these 3 generations together, the results showed that the levels of 16 of the tested serum biochemical parameters were significantly different between the lean and fat birds. In the fat birds, serum concentrations of high-density lipoprotein cholesterol (HDL-C), HDL-C:low-density lipoprotein cholesterol (LDL-C), total bile acid, total protein, albumin, globulin, aspartate transaminase (AST):alanine transaminase (ALT), γ-glutamyl transpeptidase (GGT), uric acid, and creatinine were very significantly higher (P < 0.01), whereas LDL-C, albumin:globulin, glucose, AST, ALT, and free fatty acids concentrations in serum were very significantly lower than those in the lean birds (P < 0.01). Of these 16 serum biochemical parameters, 5 (LDL-C, HDL-C:LDL-C, total bile acid, albumin, and albumin:globulin) had high heritabilities (0.58 ≤ h2 ≤ 0.89), 6 (HDL-C, total protein, globulin, AST:ALT, GGT, and creatinine) had moderate heritabilities (0.29 ≤ h2 ≤ 0.48), and the remaining 5 had low heritabilities (h2 < 0.20). Serum HDL-C, HDL-C:LDL-C, and glucose had higher positive genetic correlation coefficients (rg) with abdominal fat traits (0.30 ≤ rg ≤ 0.80), whereas serum globulin, AST, and uric acid showed higher negative genetic correlations with abdominal fat traits (–0.62 ≤ rg ≤ –0.30). The remaining 10 serum biochemical parameters had lower genetic correlations with abdominal fat traits (–0.30 < rg < 0.30). In conclusion, we identified serum HDL-C and HDL-C:LDL-C levels as potential biomarkers for selection of lean birds. These findings will also be useful in future studies for investigating obesity and lipid metabolism in humans as well as in other animal species.

Abdominal obesity and circulating metabolites: A twin study approach

OBJECTIVE

To investigate how obesity, insulin resistance and low-grade inflammation link to circulating metabolites, and whether the connections are due to genetic or environmental factors.

SUBJECTS AND METHODS

Circulating serum metabolites were determined by proton NMR spectroscopy. Data from 1368 (531 monozygotic (MZ) and 837 dizygotic (DZ)) twins were used for bivariate twin modeling to derive the genetic (rg) and environmental (re) correlations between waist circumference (WC) and serum metabolites. Detailed examination of the associations between fat distribution (DEXA) and metabolic health (HOMA-IR, CRP) was performed among 286 twins including 33 BMI-discordant MZ pairs (intrapair BMI difference ≥3 kg/m(2)).

RESULTS

Fat, especially in the abdominal area (i.e. WC, android fat % and android to gynoid fat ratio), together with HOMA-IR and CRP correlated significantly with an atherogenic lipoprotein profile, higher levels of branched-chain (BCAA) and aromatic amino acids, higher levels of glycoprotein, and a more saturated fatty acid profile. In contrast, a higher proportion of gynoid to total fat associated with a favorable metabolite profile. There was a significant genetic overlap between WC and several metabolites, most strongly with phenylalanine (rg=0.40), glycoprotein (rg=0.37), serum triglycerides (rg=0.36), BCAAs (rg=0.30-0.40), HDL particle diameter (rg=-0.33) and HDL cholesterol (rg=-0.30). The effect of acquired obesity within the discordant MZ pairs was particularly strong for atherogenic lipoproteins.

CONCLUSIONS

A wide range of unfavorable alterations in the serum metabolome was associated with abdominal obesity, insulin resistance and low-grade inflammation. Twin modeling and obesity-discordant twin analysis suggest that these associations are partly explained by shared genes but also reflect mechanisms independent of genetic liability.

Serum fatty acid and lipoprotein subclass concentrations and their associations in prepubertal healthy Norwegian children

INTRODUCTION

The lipid metabolism is one of the most important and complex processes in the body. Serum concentrations of 18 fatty acids (FAs) and 24 lipoprotein features, i.e. concentrations of lipoprotein main and subclasses and average particle size in main classes, in 195 ethnic Norwegian children from the rural Fjord region were quantified by chromatography.

OBJECTIVES

To assess gender differences in prepubertal children and reveal predictive FA patterns for lipoprotein features.

METHODS

Lipoprotein features were modelled from FA profiles using multivariate regression.

RESULTS

Contrary to observations for adults from the same region, gender differences in prepubertal children were generally small. However, higher concentrations of C16-C18 FAs for girls compared to boys correlated to higher concentrations of triglycerides (TG) and very low density lipoprotein (VLDL) particles and larger average size of VLDL particles. Concentrations of high density lipoprotein (HDL) and its subclass of medium particle size were higher in boys than in girls. These findings are opposite to observations in adults from the same region, but reflect that prepubertal boys are more physically active than girls. Furthermore, children possessed only half the serum levels of eicosapentaenoic acid and docosahexaenoic acid measured in adults. Since sampling was done after 12 h of fasting, these differences may reflect higher rate of utilization of these crucial FAs in children.

CONCLUSION

Good predictive models were obtained for TGs, VLDL and chylomicrons with C14-C18 FAs as major contributors. Weak predictive associations were observed for HDL and Apolipoprotein A1 (ApoA1) with C20-C24 FAs as contributors.

Epigenetics in adaptive evolution and development: the interplay between evolving species and epigenetic mechanisms: extract from Trygve Tollefsbol (ed.) (2011) Handbook of epigenetics--the new molecular and medical genetics. Chapter 26. Amsterdam, USA: Elsevier, pp. 423-446

By comparing epigenetics of current species with fossil records across evolutionary transitions, we can gauge the moment of emergence of some novel mechanisms in evolution, and recognize that epigenetic mechanisms have a bearing on mutation. Understanding the complexity and changeability of these mechanisms, as well as the changes they can effect, is both fascinating and of vital practical benefit. Our most serious pandemics of so-called 'non-communicable' diseases - mental and cardiovascular disorders, obesity and diabetes, rooted in the 'metabolic syndrome' - are evidently related to effects on our evolutionary mechanisms of agricultural and food industrialization, modern lifestyle and diet. Pollution affects us directly as well as indirectly by its destruction of ecologically essential biosystems. Evidently such powerful conditions of existence have epigenetic effects on both our health and our continuing evolution. Such effects are most profound during reproductive and developmental processes, when levels of hormones, as affected by stress particularly, may be due to modern cultures in childbearing such as excessive intervention, separation, maternal distress and disruption of bonding. Mechanisms of genomic imprinting seem likely to throw light on problems in assisted reproductive technology, among other transgenerational effects.

Association of cholesteryl ester transfer protein genotypes with paraoxonase-1 activity, lipid profile and oxidative stress in type 2 diabetes mellitus: A study in San Luis, Argentina

Aims/Introduction

Diabetic dyslipidemia is common in type 2 diabetes. The TaqIB polymorphism in cholesteryl ester transfer protein (CETP; B1 and B2 alleles; rs708272) is associated with changes in enzyme activity and lipid concentrations. The aim of the present study was to assess associations of CETP genotypes with lipoprotein profile, oxidant/anti-oxidant status and the plasma activity of paraoxonase-1 (PON-1) in a population of diabetic patients living in San Luis, Argentina.

Materials and Methods

For oxidative stress status parameters, thiobarbituric acid-reactive substances (TBARS) and nitric oxide (NO) levels, and catalase and PON-1 activity were assessed in 40 patients with type 2 diabetes mellitus and 30 healthy participants. CETP polymorphism was analyzed by polymerase chain reaction-based methods.

Results

Type 2 diabetes mellitus had significantly higher concentrations of oxidative stress parameters: TBARS (P < 0.0001) and catalase activity (P < 0.0001). PON-1 activity and NO levels were significantly lower in diabetics (P = 0.0002 and P = 0.0008, respectively). The CETP genotypes distribution among study groups was not significantly different. The B2 carriers of the TaqIB CETP polymorphism are associated with higher high-density lipoprotein cholesterol levels and PON-1 activity in control and type 2 diabetes mellitus patients. Linear regression analysis showed that there was a significant and positive correlation between the changes of PON-1 activity and high-density lipoprotein cholesterol levels in non-B1B1 (B2 carriers) in controls (r = 0.83, P < 0.0001) and diabetic patients (r = 0.39, P = 0.0003).

Conclusions

The results of the current study show that type 2 diabetes mellitus is characterized by intense oxidative stress, and that the alterations observed in the lipoprotein profile and PON-1 activity might be related to the higher CETP activity in diabetic patients as a consequence of insulin resistance.

Transgenerational healing: Educating children in genesis of healthy children, with focus on nutrition, emotion, and epigenetic effects on brain development

Although our continuing evolution can never achieve our perfection, we long for our children's birth and health to be near-perfect. Many children are born healthy, though fewer than is possible. Birthing and health rapidly improved generally due to modern housing, sanitation and medicine, as well as birth interventions. Arguably interventions have exceeded the optimal level, without enough regard for natural physical and intuitive resources. Conception, often too easy, receives too little personal preparation unless a couple has problems. Nurturing the health of sperm and ovum seems hard to focus on, yet is needed by both parents - and even by the four grandparents. What are the key factors? Positive: The fields of hormones/emotions and of nutrition/metabolism. Negative: stress, poor nutrition, toxins, diseases; much being due to poverty. Positive and negative both have structural and also epigenetic effects. Interventions, essential or inessential, are seldom without negative side effects. Health can best, and most economically, be generated at the beginning of life, through healthy conception, gestation and birth. Understanding prime needs improves initial health. It also informs therapy of any early-life problems. Healing is therefore more efficient when transgenerational, and much more powerful than individual healing. My vision of healing is safeguarding our evolution in progress. Children's choices - eating, exercise, emotional attitudes and relationships - are already profoundly affecting any children they may have, their mental and physical health. The most practical starting point seems to be educating boys as well as girls. Childhood is therefore the time to educate them in choices. The correction of often unnoticed problems- nutrient deficits, toxins, uro-genital disease - has enabled nearly nine out of ten couples to bear fully healthy babies, even following severe problems - infertility, miscarriages, stillbirths and malformations. Correcting problems before conception prevents both structural faults and wrong setting of gene-switches. Children's habits set. Once courting most are preoccupied and many pregnant unintentionally. Childhood is the time to be adopting a healthy lifestyle, the way to healthy babies The mother's nutritional and emotional status throughout pregnancy continues to affect her child's future physical and mental health, behaviour and ability. Before conception a woman needs to build her appropriate body stores - vitamins and minerals, proteins, docosahexaenoic acid. Before bearing another child, a replenishment time of 3 years is desirable. A return to childbearing in the 20s and early 30s could reduce risks that have risen with the recent shift towards conception by school children and by women in their late 30s or more. Governments, schoolteachers, health professionals, need to adopt this policy of transgenerational health. Empowerment with knowledge is the one way to fend off the growing pandemic of mental ill health and related disorders and to make the most of a nation's genetic potential. Financially there could be no better investment, let alone in enhancing people's lives. Childhood is the most appropriate time for education in this way to generating a healthy, able and peaceful human race. Essential to our amazing genetic systems are the resources of land, sea and air. We are one with our biosphere. We need urgently to follow up the vital work of Developmental Origins of Health and Disease, and of Far East initiatives in sea-bed and sea husbandry.

Acquired liver fat is a key determinant of serum lipid alterations in healthy monozygotic twins

OBJECTIVE

The effects of acquired obesity on lipid profile and lipoprotein composition in rare BMI-discordant monozygotic (MZ) twin pairs were studied.

DESIGN AND METHODS

Abdominal fat distribution, liver fat (magnetic resonance imaging and spectroscopy), fasting serum lipid profile (ultracentrifugation, gradient gel-electrophoresis, and colorimetric enzymatic methods), and lifestyle factors (questionnaires and diaries) were assessed in 15 BMI-discordant (within-pair difference [Δ] in BMI >3 kg/m2) and nin concordant (ΔBMI <3 kg/m2) MZ twin pairs, identified from two nationwide cohorts of Finnish twins.

RESULTS

Despite a strong similarity of MZ twins in lipid parameters (intra-class correlations 0.42-0.90, P < 0.05), concentrations of apolipoprotein B (ApoB), intermediate-density lipoprotein cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein 3a% (HDL3a%), and HDL3c% were higher (P < 0.05) and those of HDL cholesterol, HDL2-C, and HDL2b% were lower (P < 0.01) in the heavier co-twins of BMI-discordant pairs. The composition of lipoprotein particles was similar in the co-twins. When BMI-discordant pairs were further divided into liver fat-discordant and concordant (based on median for Δliver fat, 2.6%), the adverse lipid profile was only seen in those heavy co-twins who also had high liver fat. Conversely, BMI-discordant pairs concordant for liver fat did not differ significantly in lipid parameters. In multivariate analyses controlling for Δsubcutaneous, Δintra-abdominal fat, sex, Δsmoking and Δphysical activity, Δliver fat was the only independent variable explaining the variation in ΔApoB, Δtotal cholesterol, and ΔLDL-C concentration.

CONCLUSIONS

Several pro-atherogenic changes in the amounts of lipids but not in the composition of lipoprotein particles were observed in acquired obesity. In particular, accumulation of liver fat was associated with lipid disturbances, independent of genetic effects.

High-density lipoprotein (HDL) particle subpopulations in heterozygous cholesteryl ester transfer protein (CETP) deficiency: maintenance of antioxidative activity

Cholesteryl ester transfer protein (CETP) deficiency causes elevated high-density lipoprotein-cholesterol (HDL-C) levels; its impact on HDL functionality however remains elusive. We compared functional and compositional properties of HDL derived from 9 Caucasian heterozygous CETP mutation carriers (splice-site mutation in intron 7 resulting in premature truncation) with those of 9 age- and sex-matched normolipidemic family controls. As expected, HDL-C levels were increased 1.5-fold, and CETP mass and activity were decreased by −31% and −38% respectively, in carriers versus non-carriers. HDL particles from carriers were enriched in CE (up to +19%, p<0.05) and depleted of triglycerides (TG; up to −54%, p<0.01), resulting in a reduced TG/CE ratio (up to 2.5-fold, p<0.01). In parallel, the apoA-I content was increased in HDL from carriers (up to +22%, p<0.05). Both the total HDL fraction and small, dense HDL3 particles from CETP-deficient subjects displayed normal antioxidative activity by attenuating low-density lipoprotein oxidation with similar efficacy on a particle mass basis as compared to control HDL3. Consistent with these data, circulating levels of systemic biomarkers of oxidative stress (8-isoprostanes) were similar between the two groups. These findings support the contention that HDL functionality is maintained in heterozygous CETP deficiency despite modifications in lipid and protein composition.

Genome-wide association study to identify common variants associated with brachial circumference: a meta-analysis of 14 cohorts

Brachial circumference (BC), also known as upper arm or mid arm circumference, can be used as an indicator of muscle mass and fat tissue, which are distributed differently in men and women. Analysis of anthropometric measures of peripheral fat distribution such as BC could help in understanding the complex pathophysiology behind overweight and obesity. The purpose of this study is to identify genetic variants associated with BC through a large-scale genome-wide association scan (GWAS) meta-analysis. We used fixed-effects meta-analysis to synthesise summary results across 14 GWAS discovery and 4 replication cohorts comprising overall 22,376 individuals (12,031 women and 10,345 men) of European ancestry. Individual analyses were carried out for men, women, and combined across sexes using linear regression and an additive genetic model: adjusted for age and adjusted for age and BMI. We prioritised signals for follow-up in two-stages. We did not detect any signals reaching genome-wide significance. The FTO rs9939609 SNP showed nominal evidence for association (p<0.05) in the age-adjusted strata for men and across both sexes. In this first GWAS meta-analysis for BC to date, we have not identified any genome-wide significant signals and do not observe robust association of previously established obesity loci with BC. Large-scale collaborations will be necessary to achieve higher power to detect loci underlying BC.

"My parents died of myocardial infarction: is that my destiny?"

This article presents an overview of clinical and molecular genetics of myocardial infarction (MI). Discussion includes the partial overlapping of risk factors for myocardial infarction and atherosclerosis, the impact of a positive family history on the risk of MI, the "familial" nongenetic, environmental factors, the inherited risk associated with the low-dose input of many genes, and a simple approach to stratify the individual risk in genetic counseling.

Heritability and familiality of type 2 diabetes and related quantitative traits in the Botnia Study

AIMS/HYPOTHESIS

To study the heritability and familiality of type 2 diabetes and related quantitative traits in families from the Botnia Study in Finland.

METHODS

Heritability estimates for type 2 diabetes adjusted for sex, age and BMI are provided for different age groups of type 2 diabetes and for 34 clinical and metabolic traits in 5,810 individuals from 942 families using a variance component model (SOLAR). In addition, family means of these traits and their distribution across families are calculated.

RESULTS

The strongest heritability for type 2 diabetes was seen in patients with age at onset 35-60 years (h (2) = 0.69). However, including patients with onset up to 75 years dropped the h (2) estimates to 0.31. Among quantitative traits, the highest h (2) estimates in all individuals and in non-diabetic individuals were seen for lean body mass (h (2) = 0.53-0.65), HDL-cholesterol (0.52-0.61) and suppression of NEFA during OGTT (0.63-0.76) followed by measures of insulin secretion (insulinogenic index [IG(30)] = 0.41-0.50) and insulin action (insulin sensitivity index [ISI] = 0.37-0.40). In contrast, physical activity showed rather low heritability (0.16-0.18), whereas smoking showed strong heritability (0.57-0.59). Family means of these traits differed two- to fivefold between families belonging to the lowest and highest quartile of the trait (p < 0.00001).

CONCLUSIONS/INTERPRETATION

To detect stronger genetic effects in type 2 diabetes, it seems reasonable to restrict inclusion of patients to those with age at onset 35-60 years. Sequencing of families with extreme quantitative traits could be an important next step in the dissection of the genetics of type 2 diabetes.

Dietary omega-3 polyunsaturated fatty acid intake is related to a protective high-density lipoprotein subspecies profile independent of genetic effects: a monozygotic twin pair study

BACKGROUND

Studies on diet and high-density lipoprotein (HDL) subspecies distribution are limited.

OBJECTIVE

We examined the relationship between macronutrient composition and lipoprotein particle size and HDL subspecies independent of genetic effects by studying monozygotic (MZ) twins.

METHODS

24 healthy MZ twin pairs aged 23-33 years were identified from two longitudinal population-based studies, FinnTwin16 and FinnTwin12. Total energy and nutrient intake were assessed with 3-day food records and physical activity was measured by the Baecke index. HDL subspecies distribution was determined by non-denaturing gradient gel electrophoresis. Associations between diet composition and HDL mean particle size were determined by multivariate nutrient density models adjusted for confounding variables.

RESULTS

Substituting one energy percentage from omega-3 polyunsaturated fatty acids (n-3 PUFAs) for a corresponding amount of energy from other type of fats was related to changes in the relative proportions of the HDL subspecies 2b, 3a and 3b toward a larger mean particle size in men (β ± SE: 1.00 ± 0.26 nm, p = 0.004) and women (β ± SE: 0.90 ± 0.21 nm, p = 0.001). This association remained significant in analyses controlling for genetic and shared environmental influences using within-pair differences of the measures in MZ twin pairs (β ± SE: 0.37 ± 0.14 nm, p = 0.019). Twins with the higher n-3 PUFA intake had significantly higher proportions of large HDL(2b) particles and lower proportions of smaller-sized HDL(3a) and HDL(3b) particles as compared to their co-twins with lower intakes (p < 0.05).

CONCLUSIONS

Our data suggest that n-3 PUFA intake is associated with a favorable change in the distribution of HDL subspecies towards larger particles independent of genetic and shared environmental factors.

Large-scale candidate gene analysis of HDL particle features

Background

HDL cholesterol (HDL-C) is an established marker of cardiovascular risk with significant genetic determination. However, HDL particles are not homogenous, and refined HDL phenotyping may improve insight into regulation of HDL metabolism. We therefore assessed HDL particles by NMR spectroscopy and conducted a large-scale candidate gene association analysis.

Methodology/Principal Findings

We measured plasma HDL-C and determined mean HDL particle size and particle number by NMR spectroscopy in 2024 individuals from 512 British Caucasian families. Genotypes were 49,094 SNPs in >2,100 cardiometabolic candidate genes/loci as represented on the HumanCVD BeadChip version 2. False discovery rates (FDR) were calculated to account for multiple testing. Analyses on classical HDL-C revealed significant associations (FDR<0.05) only for CETP (cholesteryl ester transfer protein; lead SNP rs3764261: p = 5.6*10⁻¹⁵) and SGCD (sarcoglycan delta; rs6877118: p = 8.6*10⁻⁶). In contrast, analysis with HDL mean particle size yielded additional associations in LIPC (hepatic lipase; rs261332: p = 6.1*10⁻⁹), PLTP (phospholipid transfer protein, rs4810479: p = 1.7*10⁻⁸) and FBLN5 (fibulin-5; rs2246416: p = 6.2*10⁻⁶). The associations of SGCD and Fibulin-5 with HDL particle size could not be replicated in PROCARDIS (n = 3,078) and/or the Women's Genome Health Study (n = 23,170).

Conclusions

We show that refined HDL phenotyping by NMR spectroscopy can detect known genes of HDL metabolism better than analyses on HDL-C.

ATHENA: A knowledge-based hybrid backpropagation-grammatical evolution neural network algorithm for discovering epistasis among quantitative trait Loci

BACKGROUND

Growing interest and burgeoning technology for discovering genetic mechanisms that influence disease processes have ushered in a flood of genetic association studies over the last decade, yet little heritability in highly studied complex traits has been explained by genetic variation. Non-additive gene-gene interactions, which are not often explored, are thought to be one source of this "missing" heritability.

METHODS

Stochastic methods employing evolutionary algorithms have demonstrated promise in being able to detect and model gene-gene and gene-environment interactions that influence human traits. Here we demonstrate modifications to a neural network algorithm in ATHENA (the Analysis Tool for Heritable and Environmental Network Associations) resulting in clear performance improvements for discovering gene-gene interactions that influence human traits. We employed an alternative tree-based crossover, backpropagation for locally fitting neural network weights, and incorporation of domain knowledge obtainable from publicly accessible biological databases for initializing the search for gene-gene interactions. We tested these modifications in silico using simulated datasets.

RESULTS

We show that the alternative tree-based crossover modification resulted in a modest increase in the sensitivity of the ATHENA algorithm for discovering gene-gene interactions. The performance increase was highly statistically significant when backpropagation was used to locally fit NN weights. We also demonstrate that using domain knowledge to initialize the search for gene-gene interactions results in a large performance increase, especially when the search space is larger than the search coverage.

CONCLUSIONS

We show that a hybrid optimization procedure, alternative crossover strategies, and incorporation of domain knowledge from publicly available biological databases can result in marked increases in sensitivity and performance of the ATHENA algorithm for detecting and modelling gene-gene interactions that influence a complex human trait.