Usefulness of serum apolipoprotein B levels for screening children with primary dyslipoproteinemias

The association of plasma homocysteine levels with serum leptin and apolipoprotein B levels in childhood obesity

BACKGROUND

An elevated plasma total homocysteine (tHcy) level has recently been established as an independent risk factor for thrombosis and vascular disease. However, the relationship between hyperhomocysteinemia and cardiovascular disease and obesity remains controversial. The aim of the study was to investigate a possible relationship between plasma tHcy levels and measures of childhood obesity.

SUBJECTS AND METHODS

Forty children and adolescents with exogenous obesity and 20 non-obese subjects in an age-and sex-matched control group were investigated. Fasting samples were collected for plasma tHcy, serum insulin, leptin, vitamin B12, folate, creatinine and lipid parameters. Anthropometric characteristics and body compositions were assessed in both groups.

RESULTS

The obese patients had significantly higher tHcy levels than the non-obese controls (14.3+/-11.8 micromol/L vs 8.7+/-5.9 micromol/L; P=0.017). In both groups, plasma tHcy was positively related to serum leptin, but serum apolipoprotein B (apo B) levels were positively related to plasma tHcy levels only in obese patients.

CONCLUSIONS

Our study demonstrates for the first time that leptin and apo B are main correlates of tHcy in obese children and adolescents and suggests that hyperleptinemia and increased apo B may contribute to impairment of tHcy metabolism in childhood obesity.

Apolipoprotein B as a Marker of Familial Hyperlipoproteinemia

AIMS

Families with 10-12-year-old schoolchildren were informed about and asked to participate in a study to identify children with hyperlipoproteinemia. We hypothesised that children and families with familial blood lipid abnormalities, specifically those with familial hypercholesterolemia (FH) and familial combined hyperlipidemia (FCHL), could be identified by the child's apolipoprotein B level exceeding the 95th percentile.

METHODS

Written information and consent was distributed to the families. Families whose child had an apoB concentration exceeding the 95th percentile were further examined. Children and parents were divided into normal, high and very high low density lipoprotein cholesterol (LDLC) groups. In adults a high LDLC level was defined as > 4.1-4.9, a very high as > 4.9 mmol/l, in children as > 3.4-4.1 and > 4.1 mmol/l, respectively. The triglyceride level was regarded as high when > 3.6 mmol/l.

RESULTS

Of 2,855 families, 2,186 agreed to participate. The 95th percentile apoB level was for boys 0.98 and girls 1.07 g/l. Of the 131 children with an apoB level above the 95th percentile, 109 families accepted further examinations. Of 109 hyperapoB children 23 were obese. Normal LDLC was found in 28 hyperapo B children of whom six parents had high/very high LDLC and one high triglyceride concentrations. A high LDLC level was found in 52 children of whom 23 parents had higy/very high LDLC and another five high LDLC and/or high triglyceride concentrations. A very high LDLC level was found in 29 children, in two of them due to hypothyroidism, 17 had a parent with high/very high LDLC and another two parents a high triglyceride concentration. Familial hypercholesterolemia, defined as a LDLC concentration above twice the normal one in the child and a very high level in a parent, was suspected in six families, five having a relative with premature CHD. The families with FCHL should be included in the 20 families with hyperapoB and a child with high-very high LDLC and a parent with very high LDLC or TG levels.

CONCLUSION

Of the 109 children examined due to the child's increased apoB concentration, about 20% were obese and 75% had an increased LDLC concentration. A familial occurrence of hyperlipoproteinemia was evident in about 50% of the families with an hyperapoB child. Six families probably suffer from familial hypercholesterolemia. The definite number of FCHL families could not be defined since extended pedigrees were not available. A high suspicion of FCHL was evident in 20 families. ApoB is an important marker of hyperlipoproteinemia of familial occurrence identifying families in need of primary CHD prevention.