The prevalence of o2 allele is increased in individuals with hypertriglyceridemia [9,10] and clearance of
triglyceride rich particles is prolonged also in nor- molipidemic individuals with one or two o2 alleles
[11,12]. E22 phenotype is an obligatory, but not the only, prerequisite for the development of human type
III hyperlipidemia, characterised by accumulation of remnants of triglyceride rich lipoprotein particles in
plasma [13]. However, this rare condition alone fails to explain the o2-hypertriglyceridemia association. A
few studies suggest that o4 carriers also have higher serum triglyceride values than o3 homozygotes [14 –
18], and the meta-analysis by Dallongeville and co- workers shows that subjects with apo E2 phenotype
and apo E4 heterozygotes have higher serum triglyce- ride concentrations than E3 homozygotes [19].
To analyse the effects of the apo E phenotypes on serum triglyceride values in breast-fed and recently
weaned infants, serum triglyceride values and apo E phenotypes were determined in a large population of
7- and 13-month-old infants in Finland, a country with an exceptionally high prevalence of the o4 allele.
2. Methods
2
.
1
. Subjects This study comprises a part of the participants of
the STRIP project Special Turku Coronary Risk Factor Intervention Project, which is a randomised,
prospective trial aimed at decreasing exposure of chil- dren to known environmental atherosclerosis risk fac-
tors. The ongoing project was launched in Turku, Finland, in 1990. Details of the study design have
been published [20]. In brief, 1062 infants were ran- domised to intervention n = 540 and control n =
522 groups at the age of 7 months. This study comprises those infants from whom blood was suc-
cessfully drawn at the ages of 7 months n = 745 and 13 months n = 859. Blood samples from 671 infants
were available at both ages.
2
.
2
. Counselling The intervention families visited the counselling
team a paediatrician and a dietician at infant’s ages of 7, 8, 10 and 13 months. Infant’s fat intake was not
restricted, but saturated fatty acids were suggested to be replaced by polyunsaturated and monounsaturated
fatty acids to approach a ratio of polyunsaturated to monounsaturated to saturated fatty acids of 1:1:1. In-
fant foods low in saturated fat and cholesterol were thus recommended. A daily cholesterol intake of less
than 200 mg was also proposed. Solid foods were introduced to all infants at 3 – 6 months of age; all
infants received breast milk or formula to the age of 1 year. The intervention infants then had skim milk
as their primary milk source. The intervention parents were advised to add two to three teaspoonfuls 10 – 15
g vegetable oil or soft margarine into the infant’s daily diet to confirm an adequate supply of energy
and fat 30 – 35 of total energy.
The control families visited the same counselling team at the infant’s ages of 7 and 13 months. They
received no individualised dietary counselling about the amount or quality of fat in the child’s diet. Solid
foods were introduced to control infants at 3 – 6 months of age. The control infants consumed breast
milk or formula also until the age of 1 year but changed then to milk with at least 1.9 fat, as was
counselled at the well baby clinics in Finland at that time.
2
.
3
. Ethics The STRIP project has been approved by the Joint
Commission on Ethics of the Turku University and the Turku University Central Hospital.
2
.
4
. Biochemical determinations and weight measurement
Non-fasting blood samples were drawn between 08:00 and 17:00 h under cutaneous anaesthesia Emla,
Astra, So¨derta¨lje, Sweden from an antecubital vein. The mean time interval between the infant’s previous
meal and sampling was 2.29 9 0.98 h at 7 months of age and 2.19 9 0.90 h at 13 months of age; the time
interval was similar among carriers of different apo E phenotypes. Serum was separated by low-speed cen-
trifugation 3400 × g, for 12 min after clotting at room temperature and was stored for B 1 month at
−
25°C. Serum triglyceride concentration was determined
with a fully enzymatic colorimetric GPO-PAP method Boehringer, Mannheim, Germany using a Kone CD
analyser. Serum HDL cholesterol concentration was measured using a fully enzymatic method after precip-
itation of LDL and VLDL with dextran sulphate 500 000 as described [21]. Apo E phenotypes were
determined
using isoelectric
focusing and
im- munoblotting of delipidated serum [7]. All analyses
were performed in the laboratory of the Research and Development Unit of Social Insurance Institution in
Turku.
The weight of the infants was measured to the nearest 0.01 kg with a baby scale Seca
®
725, Ham- burg, Germany and expressed as relative weight, i.e.
as deviation in percentages from the mean weight of healthy Finnish children of the same height and sex
[22].
2
.
5
. Statistical analysis The results are expressed as means 9 S.D. Serum
triglyceride concentrations were log-transformed for statistical analyses because of skewness of the data.
Differences between two groups were tested with a two-sample t-test. One- or two-way analysis of variance
was used in analyses of overall differences between the apo E phenotypes. In some analyses, subjects with apo
E34 and 44 phenotypes were analysed together as the apo E4
+
group. Similarly, in some analyses apo E23 and apo E33 children were combined to form the apo
E4
−
group. Pearson’s correlation coefficient r was calculated for serum triglyceride values at the two age
points and for correlation between concentrations of serum HDL cholesterol and triglycerides. P-values B
0.05 were considered significant. Statistical analyses were performed using SAS release 6.12 program pack-
age SAS Institute, Cary, NC.
3. Results
