Beneficial effects of increasing monounsaturated fat intake in adolescents with type 1 diabetes.

This study aimed to increase the monounsaturated fat content in the diet of outpatient adolescents with type 1 diabetes and to examine the metabolic effects after 12 weeks. Twenty-three adolescents were randomly allocated to either a high monounsaturated fat diet or a control diet. Their mean age was 16.9 (S.D. 2.1) years and median HbA(1c) was 9.1% [IQR 7.9-10.4%]. Dietary targets were not reached judged by their 4-day food diaries. However, the whole study group had a significant increase in monounsaturated fat as indexed by red cell phospholipid fatty acids (RCFAs), with an increase of n-9 RCFAs from 14.9% [IQR: 14.5-21.7%] to 21.7% [IQR: 18.8-25.6%] (P=0.002). Changes in n-9 RCFAs were inversely related to changes in HbA(1c) (R(2)=0.26, P=0.02), such that a 10% increase in n-9 RCFAs corresponded to a 0.64% improvement (decrease) in HbA(1c). Changes in n-9 RCFAs were also inversely related to changes in plasma total cholesterol (R(2)=0.38, P=0.002) and plasma LDL cholesterol (R(2)=0. 21, P=0.03). These changes were not associated with changes in insulin dose, body weight or physical activity. Overall, the results demonstrate that a modest increase in the monounsaturated fat content of an adolescent diet has the potential to improve glycaemic control and lipid profile.

Changes in the immunoreactivity of Apo A-I during storage.

We assayed apolipoprotein (Apo) A-I levels in re-constituted standard sera, and in serum samples and dried blood samples spotted onto filter-paper, taken from 4 healthy adults. An ELISA method was used to study changes in immunoreactivity after storage at different temperatures, for periods of up to 2 yr. For standard Apo A-I sera, immunoreactivity increased significantly with both time and temperature of storage after reconstitution. Immunoreactivity of Apo A-I in sera of healthy adults was stable on storage at -16 degrees C and -70 degrees C for 43 days, at 4 degrees C for 21 days, and at room temperature for only 10 days, after which there was a considerable increase. Dried blood spot Apo A-I immunoreactivity was also stable at -16 degrees C for at least 43 days, but not at 4 degrees C. Storage at room temperature caused significantly increased immunoreactivity from day 2. These changes could result from temperature and time-dependent structural or compositional changes in high density lipoprotein particles leading to exposure of more Apo A-I antigenic sites. The results define the conditions of time and temperature of storage of samples and standards necessary for Apo A-I assays using ELISA methodology.

Screening for familial hypercholesterolemia in 5000 neonates: a recall study.

To investigate the feasibility of screening for familial hypercholesterolemia, apolipoprotein B (Apo B) levels were determined in dried blood spot samples on neonatal screening cards from 5000 consecutively born neonates, by radial immunodiffusion assay. The 103 infants with Apo B levels in the top 2% were recalled for repeat dried blood spot Apo B determinations. Forty-five of the 103 infants were retested, and serum lipid profiles and Apo B levels were determined for both parents of 43 of these infants, and for the mother only for the other two infants. The recalled "top 2%" group had a higher proportion of females, a higher mean birth weight, a higher mean gestational age and a higher proportion of infants sampled initially on day 5 than in the total screened population, consistent with our previously determined influence of these factors on Apo B levels at screening. The retested group (n = 45) was representative of the total recalled group (n = 103) with respect to Apo B levels at screening, sex, birth weight, gestational age, and age at sampling for screening. The infants' mean +/- SD age at retesting was 12.3 +/- 3.3 months. Their mean Apo B value on retesting was 0.65 +/- 0.20 g/liter of whole blood (range 0.30 to 1.16 g/liter). Two fathers had had coronary bypass surgery by the age of 40 and had type II lipid profiles and elevated serum Apo B levels. For both, their child had elevated Apo B levels at recall (both 1.05 g/liter of whole blood).(ABSTRACT TRUNCATED AT 250 WORDS)

A neonatal screening approach to the detection of familial hypercholesterolaemia and family-based coronary prevention.

We measured by radial immunodiffusion apolipoprotein B (ApoB) as a genetic marker for familial hypercholesterolaemia in heel prick blood spot samples on filter paper routinely collected from 5000 3- to 5-day-old neonates for current screening programmes. Dried blood spot ApoB levels were distributed continuously and were 9% higher in female neonates than in males (0.246 +/- 0.085 versus 0.225 +/- 0.079 g/L of whole blood, mean +/- SD, p less than 0.0001). Neonates of birth weight under 2.5 kg had lower levels than the population mean in both sexes but levels did not change with birth weight within this range; in those with the birth weights greater than 2.5 kg levels increased with increasing birth weight. Sex and birth weight could account for 5.7% of the variability of ApoB. Levels had largely stabilized by day 3 of life. Of parents of neonates whose ApoB levels were among the top 2%, 45 families were available for study when the infants were aged 12.3 +/- 3.3 months. In 6 of these families there was a persisting elevation of ApoB both in the infants (levels greater than 0.7 g/L of whole blood) and in one parent who also had elevated ApoB and a lipid profile of familial hypercholesterolaemia phenotype, results indicating an ascertainment rate of between 1 in 365 and 1 in 830 of the screened population. These studies have defined the variables affecting neonatal ApoB levels and establish that neonatal screening for familial hypercholesterolaemia is feasible. Primary prevention of vascular disease in young families with the gene should be possible with this approach.

Variables affecting apolipoprotein B measurements in 3- to 5-day-old babies: a study of 4491 neonates.

To investigate the feasibility of establishing a neonatal screening program for familial type II hypercholesterolemia, we assayed apolipoprotein B (Apo B), using a radial immunodiffusion assay, in dried blood spot samples from 4491 consecutively born, 3- to 5-day-old neonates. We explored factors influencing levels at the time of sampling and factors associated with the handling of the dried blood spot samples before assay which could affect the assayed value. Assayed Apo B levels were distributed continuously and decreased with increasing delay and temperature of storage of the samples before assay. Female neonates had significantly higher mean Apo B levels than males (p less than 0.0001), with their respective means +/- SD being 0.246 +/- 0.085 g/liter (n = 2086) and 0.225 +/- 0.079 g/liter of whole blood (n = 2390). In both sexes mean Apo B levels were significantly lower in low birth weight (less than or equal to 2.5 kg) and in low gestational age (less than or equal to 36 wk) neonates. For neonates with birth weight greater than 2.5 kg and gestational age more than 36 wk, Apo B levels increased with increasing birth weight and gestational age. Sex, birth weight, and gestational age could account for 5.7% of the variability of Apo B. After adjustments for these variables, the neonate's age at sampling did not influence Apo B levels significantly. Apo B levels were not affected by different dietary regimens, whether breast-fed, formula-fed, or breast-fed with formula complement.(ABSTRACT TRUNCATED AT 250 WORDS)

Radial immunodiffusion assay of apolipoprotein B in blood dried on filter paper--a potential screening method for familial type II hypercholesterolaemia.

In the search for an effective neonatal screening programme for familial type II hypercholesterolaemia, we have developed and validated a radial immunodiffusion assay for measuring, in dried blood spots, the concentration of apolipoprotein B. The method has advantages over previously described methods, being cheaper, more robust, and suitable for partial automation. In 34 adults there was a close linear relationship between capillary and venous blood spot apolipoprotein B concentrations (r = 0.94), between capillary blood spot and serum apolipoprotein B also measured by radial immunodiffusion (r = 0.90), and between capillary blood spot apolipoprotein B and LDL cholesterol measured by ultracentrifugation (r = 0.85). Apolipoprotein B levels in serum and LDL cholesterol also correlated closely (r = 0.95, n = 40). In 30 normal 3- to 5-day old babies, heel prick blood spot apolipoprotein B levels were 280 +/- 70 mg/l (mean +/- SD) and 790 mg/l in one presumed heterozygote for familial hypercholesterolaemia. We conclude that serum apolipoprotein B measured by radial immunodiffusion accurately reflects adult LDL cholesterol levels, and that the assay, using dried blood spots on filter paper should permit both neonatal and adult screening programmes to detect familial hypercholesterolaemia.