Laura López-Simón

Leptin and adiponectin levels in pubertal children: relationship with anthropometric variables and body composition.

Abstract Background: Adipocytokines play an important role in controlling energy homeostasis, and in various metabolic processes related to obesity. The aim of this study was to describe serum leptin and adiponectin concentrations in a sample of pubertal Spanish children and to evaluate their association with anthropometric parameters and body composition. Methods: The study included 833 pubertal boys and girls. Serum leptin and adiponectin concentrations were determined by ELISA. Results: Leptin concentrations were significantly higher (p<0.0001) in obese or overweight (OW) children compared with children with normal weight (NW). Adiponectin was significantly lower (p<0.01) in obese or OW girls compared with girls of NW, although these findings were not the same for boys. Weight, body mass index (BMI), waist circumference (WC), hip circumference (HC), and waist to hip ratio were significantly correlated (p<0.01) with leptin concentrations in both genders. Correlation of leptin with fat mass and % fat mass was strong, particularly in boys. The association of adiponectin concentrations with anthropometric variables was weaker in both genders. No significant correlations were found between adiponectin concentrations and fat mass or % fat mass. Conclusions: In summary, our study showed that, in pubertal children, leptin is related to weight, BMI, WC and HC and correlates even more strongly with % fat mass. However, adiponectin was weakly related to anthropometric variables and was not correlated with body fat. Clin Chem Lab Med 2010;48:707–11.

Sex hormone-binding globulin and lipid profile in pubertal children.

Men and women have different lipid profiles throughout life, related to changes in sex hormones; and this has been associated with sex-related differences in the prevalence of coronary heart disease. The influence of sex hormone changes during puberty on the lipid profile has been reported, but levels of sex hormone-binding globulin (SHBG) (the specific plasma binding protein of sex hormones) have not been evaluated even though its regulatory role might be crucial. The aim of this study was to analyze the relationship between sex hormones and SHBG and changes in plasma lipid levels during puberty. Our population-based sample included 370 healthy schoolchildren (175 male and 195 female), ranging from 12 to 15 years old. High-density lipoprotein cholesterol (HDL-C) levels were significantly lower in 15-year-olds than in younger boys, and apolipoprotein (apo) A-I levels steeply decreased across the studied age groups. Parallel to these changes, testosterone levels increased whereas SHBG decreased as age increases in boys. In girls, no significant differences were observed in these variables among the age groups. Testosterone and SHBG were highly correlated with anthropometric variables. Sex hormone-binding globulin was negatively associated with triglycerides (TG) in both sexes, remaining statistically significant after further adjustment for age and body mass index (BMI) in girls. Sex hormone-binding globulin was the only predictive variable for HDL-C and TG in multiple linear regression analysis, after adjustment by BMI, in both sexes, accounting for 10% of the variance of HDL-C in boys and for around 5% of the variance of TG in both sexes. In boys, testosterone and SHBG remained significantly correlated to apo A-I levels, even after adjusting for age and BMI, and were the most important predictive variables for apo A-I in multiple linear regression analysis. In conclusion, SHBG levels are related to a decrease in HDL-C and apo A-I levels during puberty in boys and to a decrease in TG levels during puberty in both sexes.

Sex‐specific association between leptin receptor polymorphisms and leptin levels and BMI in healthy adolescents

Aim:  To examine the relationship of three common polymorphisms in the leptin receptor (LEPR) gene, implicated in the regulation of body weight, with leptin levels and obesity‐related phenotypes in a population‐based sample of healthy pubertal children in Spain.

Sex hormone‐binding globulin levels and metabolic syndrome and its features in adolescents#

Oya I, Schoppen S, Lasunción MA, Lopez‐Simon L, Riestra P, Oya M, Garcés C. Sex hormone‐binding globulin levels and metabolic syndrome and its features in adolescents.

Fat Intake Influences the Effect of the Hepatic Lipase C-514T Polymorphism on HDL-Cholesterol Levels in Children:

Polymorphisms in the hepatic lipase gene have been associated with variability in plasma HDL-C concentrations, but contradictory results have been reported regarding the effect of diet on this association in adults. In our study, we examined whether dietary fat intake modified the association between lipid levels and the C-514T polymorphism in the hepatic lipase gene (LIPC C-514T) in prepubescent children. The LIPC C-514T polymorphism was determined by PCR and restriction analysis in 1260 healthy school children, aged 6–8. Information on the children’s nutrient intake was obtained by means of a validated food frequency questionnaire. We found that regardless of gender, carriers of the minor allele had significantly higher apo A-I levels compared to noncarrier subjects. The effect of the polymorphism, however, was modified by dietary fat intake. In boys, the presence of the LIPC C-514T polymorphism was associated with significantly higher HDL-C among children within the highest tertiles of total, saturated, monounsaturated, or polyunsaturated fat intake. Apo A-I levels were significantly higher in carriers of the LIPC C-514T polymorphism, but only among boys who consumed high total as well as monounsaturated fat and among girls who consumed high total, saturated, monounsaturated, and polyunsaturated fat. Our data show that dietary fat intake modifies the effect of the LIPC C-514T polymorphism on plasma HDL-C and apo A-I levels in prepubescent children, being associated with higher levels of HDL-C and apo A-I only when fat intake is high. This significant gene-nutrient interaction could help to explain inter-individual variations in the plasma lipid response to fat intake.

Hormone levels in 12- to 15-year-old boys and girls in Spain and their relationship with anthropometric variables.

OBJECTIVE To determine hormone levels in a population-based sample of pubertal children and evaluate their association with anthropometric parameters. METHODS Sex steroid levels were assessed using RIA and IRMA. RESULTS In boys, changes in weight and height across the period were accompanied by changes in testosterone and SHBG. In girls, anthropometric variables did not change and were not correlated with estradiol. CONCLUSIONS We observed an association between hormone levels and anthropometric changes when active growth associated with puberty was taking place.

Genetic determinants of plasma HDL-cholesterol levels in prepubertal children

INTRODUCTION Genetic determinants have been related to variation of high-density lipoprotein cholesterol (HDL-C) levels, but the extension of this association remains controversial. In our study, we analyzed the contribution of several polymorphisms on HDL-C-related genes to variation of plasma HDL-C in prepubertal children. METHODS We studied 1269 (641 males and 628 females) 6-8 years old healthy children, who participated in a cross-sectional study examining cardiovascular risk factors in Spain. Common genetic variants in the apolipoprotein AI, apolipoprotein AII, cholesteryl ester transfer protein (CETP), hepatic lipase, ATP-binding cassette transporter A1, and paraoxonase genes were determined by PCR. RESULTS CETP TaqI B2 carrier girls had significantly higher HDL-C levels than B1B1 girls. B2B2 boys had significantly higher (p<0.001) HDL-C than B1B1and B1B2 boys. In linear regression analysis, CETP TaqIB appears as the main predictor of HDL-C plasma levels, accounting for 4.5% and 1.8% of HDL-C variation in girls and boys respectively. CONCLUSIONS Our data showed that among the studied polymorphisms only the CETP TaqIB polymorphism contributes to the variation in HDL-C levels in prepubertal children, particularly in girls, but overall these polymorphisms explain a small part of the variation of HDL-C plasma levels at this age.

High-density lipoprotein cholesterol and paraoxonase 1 (PON1) genetics and serum PON1 activity in prepubertal children in Spain.

Abstract Background: Oxidative stress plays an important role in atherosclerosis. Paraoxonase 1 (PON1) is a high-density lipoprotein (HDL)-associated enzyme that inhibits low-density lipoprotein (LDL) oxidation and may play a protective role against coronary heart disease. The aim of this study was to analyze the relationship between HDL-cholesterol (HDL-C) and PON1 in a Spanish prepubertal population with high plasma HDL-C levels. Methods: The study population included 1266 children between the ages of 6 and 8 years. Serum PON1 activity was measured by the hydrolysis of paraoxon. PON1 192Q/R and PON1 55L/M polymorphisms were analyzed by PCR and restriction analysis. Results: The prevalence of the less common PON1 192R and PON 55M alleles in this population was 30% and 38%, respectively. No significant correlations between serum PON1 activity and lipid profile were observed. Multiple linear regression analysis showed that the PON1 192Q/R polymorphism accounts for 69% of PON1 activity in the children in the study, with the PON1 55L/M polymorphism accounting for an additional 5% of this variation in boys, and for an additional 3% together with HDL-C concentration in girls. Conclusions: PON1 192Q/R polymorphism is the main determinant of PON1 activity in the prepubertal population in this study, accounting for around 70% of serum PON1 activity. HDL-C concentration has a small contribution to serum PON1 activity in girls. Clin Chem Lab Med 2008;46:809–13.

Análisis de la actividad paraoxonasa (PON1) y de los polimorfismos PON1 192 y PON1 55 en la población prepuberal del Estudio Cuatro Provincias

Introduccion La paraoxonasa 1 (PON1) es una ester hidrolasa presente en las lipoproteinas de alta densidad (HDL), relacionada con la eliminacion de componentes oxidados de las lipoproteinas de baja densidad (LDL) y por ello con el riesgo cardiovascular. Nuestro estudio analiza la actividad PON1 y los polimorfismos 192 y 55 del gen PON1 en los ninos de edad prepuberal integrantes del Estudio Cuatro Provincias. Metodos La poblacion de estudio la constituyen 1.275 ninos de 6 a 8 anos. La actividad PON1 en suero se determino mediante la hidrolisis de paraoxon. Los polimorfismos geneticos PON1 192Q/R y PON1 55M/L se analizaron mediante amplificacion por reaccion en cadena de la polimerasa (PCR) y posterior analisis de restriccion. Resultados En nuestra poblacion la frecuencia de los alelos PON192R y PON55M es del 30 y el 38%, respectivamente, sin diferencias significativas entre provincias. La actividad PON1 es mas elevada en Orense y mas baja en Murcia, tanto en la poblacion total como para cada uno de los genotipos. En la provincial de Orense se observaron correlaciones significativas entre la actividad PON1 y los valores plasmaticos de colesterol total (CT), colesterol unido a HDL (cHDL) y apolipoproteina AI (apo AI). El analisis de regresion muestra que el polimorfismo PON1 192Q/R es el principal determinante de la actividad PON1 en nuestra poblacion. Conclusiones La frecuencia de los polimorfismos PON192 y PON55 no difiere significativamente entre provincias. Sin embargo, a pesar de que el polimorfismo PON192 es el principal determinante de la actividad PON1, Orense presenta la actividad PON1 mas alta y Murcia la mas baja, lo que sugiere que ya a esta edad existen factores que regulan esa actividad dentro de cada genotipo.

Relationship between leptin and insulin levels and homeostatic model assessment (HOMA) index in Spanish pubertal children

Leptin plays a central role in the maintenance of energy balance. Leptin concentrations have been shown to be directly proportional to the amount of body fat. However, it is well known that disruption of leptin signalling in the hypothalamus results in obesity. Hyperleptinaemia and/or leptin resistance may play an important role in insulin resistance by participating in its origin. The association between plasma leptin and insulin among adults has been examined, but studies in pubertal children are scarce. The aim of the present study was to determine the relationship between plasma leptin and insulin levels and HOMA index in pubertal Spanish boys and girls of normal weight (NW) and overweight (OW). The study included 356 healthy schoolchildren (165 male and 191 female) from the Comunidad de Madrid, with a mean age of 13.7 years, ranging from 12–15 years, who participated in the follow up of a voluntary survey, the Four Provinces Study, a large-scale crosssectional study in Spain examining cardiovascular risk factors in four large metropolitan areas of the country. The girls and boys were classified into NW and OW children according to Cole et al.. Obese children were included in the OW group because of their low number. Fasting (12 h) venous blood samples were obtained by venipuncture in Vacutainer tubes. Once centrifuged, fractions were separated and frozen at 70 C. Plasma leptin was determined by ELISA using a commercially-available kit (EIA-2395; DRG Instruments GmbH, Marburg, Germany). Serum insulin concentrations were measured by radioimmunoassay using a commercial kit (BI-Insulin IRMA; Bio-Rad Laboratories, Hercules, CA, USA). HOMA index was calculated (fasting insulin (mU/ml) · fasting glucose (mmol/l)/ 22.5). Leptin levels were significantly higher in girls than in boys in NW and OW groups (P<0.0001). Insulin levels and HOMA index were higher in NW girls than NW boys but levels were not different between OW girls and boys. Leptin levels were highly correlated with anthropometric variables in NW and OW girls, while in boys (NW and OW) correlations were weaker, being significant only with BMI. In these pubertal children plasma leptin levels were associated with insulin levels and HOMA index in girls and boys. The correlations were especially strong in girls.