Relations of plasma fibrinogen level in children to measures of obesity, the (G-455-->A) mutation in the beta-fibrinogen promoter gene, and family history of ischemic heart disease: the Columbia University BioMarkers Study

Adiponectin/resistin levels and insulin resistance in children: a four country comparison study

Background

There are few reports on the effects of ethnicity or gender in the association between adipocytokines and insulin resistance in children of different ages. This study assessed associations between serum concentrations of adiponectin/resistin and parameters of insulin resistance in children from 4 different countries.

Methods

A total of 2,290 children were analyzed in this study; each was from one of 4 different countries (Japan, Thailand, Italy and USA), and grouped according to age (8–11 years old in Group 1 and 12–15 years old in Group 2).

Results

Adioponectin was higher in female than in male children, and in Group 1 than in Group 2. Generally, adiponectin was lower in Asian as compared to Italian and American children. These tendencies remained even after adjustment for body mass index (BMI) or waist circumstance (WC). Among older children (Group 2), resistin was higher in female than in male children. Significant correlations by non-parametric univariate correlation coefficients and Spearman’s rank correlation coefficients were found between adiponectin and homeostasis model assessment of insulin resistance (HOMA-IR), and fasting serum insulin levels in young Japanese, Italian, and American female children(p < 0.01, p < 0.05, p < 0.05, respectively). Correlations between serum adiponectin and HOMA-IR were also found among older male Italian, American, and Thai children (p < 0.05, p < 0.001, p < 0.001, respectively). In multiple regression analysis by forced entry method, adiponectin correlated with HOMA-IR in Italian and American male children, and in all older female children regardless of country of origin. There was no correlation between resistin and markers of insulin resistance in children from any of the countries.

Conclusions

We conclude that serum adiponectin concentrations are lower in Asian as compared to Italian and American children, and that adiponectin but not resistin contributes to differences in markers for insulin resistance in children from different populations.

Efficient distribution estimation for data with unobserved sub-population identifiers

We study efficient nonparametric estimation of distribution functions of several scientifically meaningful sub-populations from data consisting of mixed samples where the sub-population identifiers are missing. Only probabilities of each observation belonging to a sub-population are available. The problem arises from several biomedical studies such as quantitative trait locus (QTL) analysis and genetic studies with ungenotyped relatives where the scientific interest lies in estimating the cumulative distribution function of a trait given a specific genotype. However, in these studies subjects' genotypes may not be directly observed. The distribution of the trait outcome is therefore a mixture of several genotype-specific distributions. We characterize the complete class of consistent estimators which includes members such as one type of nonparametric maximum likelihood estimator (NPMLE) and least squares or weighted least squares estimators. We identify the efficient estimator in the class that reaches the semiparametric efficiency bound, and we implement it using a simple procedure that remains consistent even if several components of the estimator are mis-specified. In addition, our close inspections on two commonly used NPMLEs in these problems show the surprising results that the NPMLE in one form is highly inefficient, while in the other form is inconsistent. We provide simulation procedures to illustrate the theoretical results and demonstrate the proposed methods through two real data examples.

Unbiased and locally efficient estimation of genetic effect on quantitative trait in the presence of population admixture

Population admixture can be a confounding factor in genetic association studies. Family-based methods (Rabinowitz and Larid, 2000, Human Heredity 50, 211-223) have been proposed in both testing and estimation settings to adjust for this confounding, especially in case-only association studies. The family-based methods rely on conditioning on the observed parental genotypes or on the minimal sufficient statistic for the genetic model under the null hypothesis. In some cases, these methods do not capture all the available information due to the conditioning strategy being too stringent. General efficient methods to adjust for population admixture that use all the available information have been proposed (Rabinowitz, 2002, Journal of the American Statistical Association 92, 742-758). However these approaches may not be easy to implement in some situations. A previously developed easy-to-compute approach adjusts for admixture by adding supplemental covariates to linear models (Yang et al., 2000, Human Heredity 50, 227-233). Here is shown that this augmenting linear model with appropriate covariates strategy can be combined with the general efficient methods in Rabinowitz (2002) to provide computationally tractable and locally efficient adjustment. After deriving the optimal covariates, the adjusted analysis can be carried out using standard statistical software packages such as SAS or R. The proposed methods enjoy a local efficiency in a neighborhood of the true model. The simulation studies show that nontrivial efficiency gains can be obtained by using information not accessible to the methods that rely on conditioning on the minimal sufficient statistics. The approaches are illustrated through an analysis of the influence of apolipoprotein E (APOE) genotype on plasma low-density lipoprotein (LDL) concentration in children.

Homocysteine, fibrinogen and anti-ox-LDL antibody levels as markers of atherosclerosis in prepubertal obese children

BACKGROUND

Homocysteine, fibrinogen and antibodies to oxidised LDL were shown to be important markers of atherosclerosis in adults.

AIM

To investigate the levels of these three risk factors in prepubertal obese children.

METHODS

Fasting homocysteine, fibrinogen and antibodies to oxidised LDL, plasma lipids, insulin, HbA1c and blood glucose levels were investigated in 30 prepubertal obese and 28 control children 6-9 years old. Investigations in the obese group were repeated after an oral glucose tolerance test.

RESULTS

Fasting fibrinogen levels of the obese children were found to be significantly higher than those in the controls. Anti-ox-LDL antibody levels increased significantly after an oral glucose tolerance test.

CONCLUSION

Fasting fibrinogen and postload ox-LDL levels which could act as important markers of coronary heart disease in later life could also be important risk factors in prepubertal obese children.

Socioeconomic position and inflammatory and immune biomarkers of cardiovascular disease: applications to the Panel Study of Income Dynamics

Biomarkers are an important aspect of research linking psychosocial stress and health. This article aims to characterize the biological pathways that may mediate the relationship between socioeconomic position (SEP) and cardiovascular disease (CVD) and address opportunities for further research within the Panel Study of Income Dynamics (PSID), with a focus on psychosocial stressors related to SEP. We review the literature on CVD biomarkers, including adhesion and proinflammatory molecules (interleukin-6, other cytokines, C-reactive proteins, fibrinogen, etc.) and microbial pathogens. The impact of socioeconomic determinants and related psychosocial stressors on CVD biomarkers mediated by behavioral and central nervous system pathways are described. We also address measurement and feasibility issues, including specimen collection methods, processing and storage procedures, laboratory error, and within-person variability. In conclusion, we suggest that PSID consider adding important assessments of specific CVD biomarkers and mediating behavioral measures, health, and medications that will ultimately address many of the gaps in the literature regarding the relationship between SEP and cardiovascular health.

Obesity and inflammation in children

Systemic inflammation is present in children and adults with obesity. Inflammation associated with obesity appears to be central to the development of insulin resistance and atherosclerosis and may be important in the pathogenesis of other comorbid conditions. Although generally considered an inert energy storage tissue, white adipose tissue is a metabolically active organ. It produces a number of inflammatory cytokines and acute-phase reactants. Inflammation associated with obesity declines after weight loss and with exercise. It may also be possible to modify obesity-associated inflammation with medications, reducing comorbidities without weight loss. The study of inflammation in the context of excessive adipose tissue is central to understanding obesity and modifying its impact on patients.

Plasma fibrinogen levels and cardiovascular risk factors in Japanese schoolchildren

BACKGROUND

Plasma fibrinogen level has been recognized as an independent risk factor for atherosclerosis and its thrombotic complications in adults. The present study aimed to clarify the association between plasma fibrinogen levels and cardiovascular risk factors in Japanese children.

METHODS

A total of 294 schoolchildren (145 boys and 149 girls) aged 10-13 years in a town in Nagano Prefecture, Japan, were surveyed in 2000 for body mass index (BMI), plasma fibrinogen, serum C-reactive protein (CRP), serum total cholesterol, serum high-density lipoprotein (HDL) cholesterol, hemoglobin (Hb) A1c, and ratio of serum total cholesterol to serum HDL cholesterol (TCHR).

RESULTS

The mean value and standard deviation of plasma fibrinogen level among the schoolchildren was 226.0+/-39.7 mg/dL for boys and 245.3+/-40.9 mg/dL for girls; significantly higher for girls. Among plasma fibrinogen tertiles, serum CRP tended to increase with plasma fibrinogen in both boys and girls. An increasing trend was also found in serum total cholesterol in boys, and in TCHR, HbA1c and BMI in girls. Multiple linear regression analysis revealed significant associations of plasma fibrinogen with serum CRP and HbA1c in both sexes, with TCHR in boys, and with BMI in girls.

CONCLUSIONS

Plasma fibrinogen levels were associated with cardiovascular risk factors such as serum CRP, TCHR, HbA1c, and BMI in Japanese schoolchildren.

Plasma fibrinogen levels are associated with a strong family history of myocardial infarction

Family history of myocardial infarction (MI) is a known risk factor for coronary artery disease (CAD). The aim of the present study was to investigate whether there is a specific risk factor profile for CAD in individuals with a strong family history of MI occurring at any age. The Study of Health in Pomerania is a cross-sectional, population-based study in the north-east of Germany. A random sample was drawn from the population aged 20-79 years. From 3793 subjects with siblings, 34 (0.9%) reported a history of MI in at least one parent and one sibling. We matched these cases with 136 controls (1 : 4 matching for age, sex and presence of sibling). We then compared cases and controls with respect to known risk factors for MI. Subjects with a dual parental and sibling history of MI had higher plasma fibrinogen levels (3.5 versus 3.0 g/l, respectively), and also more often angina pectoris than the matched controls (P < 0.05). Multivariable analysis revealed an independent association between dual parental and sibling history of MI and plasma fibrinogen levels. We conclude that plasma fibrinogen levels may indicate an inheritable risk for CAD in subjects with a strong family history of MI.

Body fat is the main predictor of fibrinogen levels in healthy non-obese men

Previous studies have demonstrated that circulating levels of C-reactive protein (CRP), a marker of cardiovascular risk, are strictly related to body fatness. Elevated fibrinogen levels are also predictive of future cardiovascular events. The metabolic background of this relationship and the predictors of fibrinogen levels have not been well established. We aimed to evaluate whether fibrinogen levels are associated with body fat content and distribution and to determine the independent predictors of fibrinogen levels in a sample of healthy, non-obese, nonsmoking young adult men. Age, anthropometric measures (body mass index [BMI], waist-to-hip ratio [WHR]), total and regional fat content (determined by dual x-ray absorptiometry [DXA]), metabolic variables (total cholesterol [T-Chol], low-density lipoprotein cholesterol [LDL-C], and high-density lipoprotein cholesterol [HDL-C]; triglycerides [TG]; glucose and insulin levels; fasting insulin resistance index [FIRI]; blood pressure), interleukin-6 (IL-6), and acute-phase reactants levels (fibrinogen, highly sensitive [hs]-CRP) were determined in 87 healthy nonsmoking, non-obese subjects. Linear regression analysis was used to evaluate the association between body fat, fibrinogen, and metabolic variables, and multiple regression model analysis was used to examine the independent predictors of fibrinogen levels. Eighty-seven (30.5 +/- 3.5 years) non-obese (mean BMI 24.1 +/- 3.5) men were studied. Fibrinogen levels were strongly associated with measures of body fat and with metabolic variables. Total body fat (P < .0001) and LDL-cholesterol (P < .01) were the independent predictors of fibrinogen levels, accounting for 29.5% and 10.9% of its variance, respectively. Total body fat was the best independent predictor of hs-CRP levels, accounting for 32.5 % of its variance. We conclude that in healthy, non-obese subjects, body fat content is the main predictor of fibrinogen levels, as well of hs-CRP levels. These findings support the speculation that there is a direct mechanism by which adipose tissue might regulate the levels of circulating acute-phase reactants.

Combined segregation and linkage analysis of fibrinogen variability in Israeli families: evidence for two quantitative-trait loci, one of which is linked to a functional variant (-58G > A) in the promoter of the alpha-fibrinogen gene

The association of alpha- and beta-fibrinogen polymorphisms with plasma fibrinogen levels was examined in a sample of 452 family members from 80 Israeli kindreds. The measured genotype analysis indicated that the beta-fibrinogen -455G > A polymorphism was not associated with fibrinogen levels, while the alpha-fibrinogen -58G > A locus showed a significant association with fibrinogen levels (chi2= 17.7; df = 3; p < 0.001), with the -58A allele being associated with higher levels. Segregation analysis in this sample suggested a recessive quantitative-trait locus (QTL) with a major effect that controlled the sex- and age-adjusted fibrinogen levels. Results from a combined segregation/linkage analysis indicated that a single QTL influencing plasma fibrinogen is in gametic equilibrium with the beta-fibrinogen -455G > A and alpha-fibrinogen -58G > A polymorphisms. An extended analysis with a two-QTL model significantly improved the fit of the model (p < or = 0.001), and gave support for linkage between the fibrinogen QTL and the alpha-fibrinogen polymorphism. In vitro analysis with a DNA fragment containing this variant, linked to a reporter gene, showed 2-fold higher expression of the A allele compared to the G allele in the liver cell line HepG2, both under basal conditions and after stimulation with interleukin 6. These results demonstrate that two QTLs are jointly involved in determining plasma fibrinogen levels in this sample of families, one of which is located close to a functional variant in the alpha-fibrinogen locus.

Physical fitness and C-reactive protein level in children and young adults: the Columbia University BioMarkers Study

OBJECTIVE

To examine the association of physical fitness with C-reactive protein (CRP) level in children and young adults.

METHODS

Subjects (N = 205) aged 6 to 24 years were enrolled in the Columbia University BioMarkers Study (1994-1998). Physical fitness was assessed using a non-effort-dependent treadmill testing protocol (physical work capacity at heart rate of 170 beats per minute). CRP level was measured using a high-sensitivity assay.

RESULTS

Subjects were 54% female and 65% of Hispanic origin. Mean fitness level was higher in boys than in girls, but CRP levels did not differ by gender. Fitness level was inversely correlated with CRP (r = -0.22). This relationship was significant in boys (r = -0.32) but not in girls (r = -0.15). After multivariate regression adjustment for age, race/ethnicity, body mass index, and family history of early-onset ischemic heart disease, physical fitness remained inversely associated with CRP level in boys (beta = -0.02; standard error = 0.01).

CONCLUSIONS

These findings indicate that physical fitness is inversely related to CRP level in children and that this relationship is more pronounced in boys than in girls.

Age-related effects of genetic variation on lipid levels: The Columbia University BioMarkers Study

OBJECTIVES

To examine the genotype:phenotype association in children compared with their parents.

METHODS

Variations at 4 key gene loci, namely lipoprotein lipase (LPL S447X), hepatic lipase (HL -480C>T), cholesteryl ester transfer protein (CETP TaqIB), and apolipoprotein CIII (APOC3 -455T>C and -482C>T), were examined in children (n = 495) and their parents (n = 353) in the Columbia University BioMarkers Study, 1994 to 1998.

RESULTS

The frequencies of the rare alleles of the HL -480C>T and APOC3 -455T>C and -482C>T (but not LPL S447X or CETP TaqIB) were significantly lower in non-Hispanic white participants compared with Hispanics. Overall, genotype effects seen in the adults were weaker in the children, although similar trends were seen. In an examination of the effect of body fat on the genotypic effects in the children, there was significant HL -480C>T:sum of skinfold interaction.

CONCLUSIONS

All genotypes were associated with clear relationships to plasma lipid levels in adults, but the effects were weaker in their children, unless stressed by body fat. atherosclerosis, cardiovascular disease, child, lipids, genetics.

Management of hyperlipidemia in children

Atherosclerosis is a major cause of death and disability in adults. Recent investigations suggest that although cardiac end-points such as myocardial infarction and strokes mainly occur in middle-age and older subjects, the pathological basis for atherosclerosis begins in childhood. Hypercholesterolemia is one of the most important risk factors for atherosclerosis in adults and elevated cholesterol in children is associated with sub-clinical deposition of lipids in the aorta and coronary arteries. This report summarizes an approach to the diagnosis and treatment of hyperlipidemia in children. Based on guidelines from the National Cholesterol Education Program, children over 2 years of age should be screened for hypercholesterolemia if there is a family history of premature heart disease or hyperlipidemia. Therapy must be individualized. The majority of children with hyperlipidemia should be managed with a low-saturated fat and low-cholesterol diet. Children over 10 years of age with severe elevations of LDL-cholesterol and who come from high-risk families may be considered for more aggressive dietary therapy or medication in some cases. This is especially true for children with inherited disorders of lipid metabolism such as LDL-receptor deficiency. By identifying high-risk children and instituting therapy during childhood it is hoped that premature onset of adult coronary heart disease can be delayed or avoided altogether.