analyses. Other metabolic variables for which prior hypotheses existed were also tested in multiple regres-
sion analyses. The observed average difference in total cholesterol between saturated and polyunsaturated fat
periods was compared with the predicted value on the basis of reported dietary change and the metaanalyses
of Clarke and colleagues [36].
6. Results
Thirty two females, mean 9 S.D. age, 46 11 years and 23 males, 45 8 years completed the study. Mean
9 S.D. weight and body mass index were 69.9 11.6 kg and 26.6 4.4 kgm
2
for women and 80.5 10.5 kg and 26.6 2.7 kgm
2
for men. Body weight fluctuated slightly but did not change significantly throughout the
study period. Reported total energy intake, percentage of energy derived from macronutrients, total daily
cholesterol and ratio of polyunsaturated to saturated P:S fatty acids are shown in Table 1. Average intakes
suggest a high overall level of compliance with dietary advice; reported intakes of saturated fatty acids were
decreased to approximately half, and P:S ratio in- creased about five-fold on the polyunsaturated com-
pared with the saturated fatty acid periods. Total fat, carbohydrate and protein intakes remained fairly con-
stant throughout the four experimental periods. The mole percent contribution of selected fatty acids to
total triglyceride fatty acids on the different diets is shown in Table 2. Plasma triglyceride linoleate was
higher on the polyunsaturated than the saturated diets and lauric, myristic and palmitic acids higher on the
saturated than the polyunsaturated diets.
Table 3 summarises, for the entire study group, the levels of total, HDL and LDL cholesterol at the time of
screening, before the start of the study baseline and on each of the experimental periods. For each individ-
ual the value for a given diet is taken as the mean of the two measurements made during the final week of the
dietary period. The average difference between total cholesterol measured on the 2 days was 0.05 mmoll.
Mean levels of total and LDL cholesterol were signifi- cantly lower on the polyunsaturated than the saturated
diet periods. The observed average difference in total cholesterol on the saturated and polyunsaturated fat
Table 1 Mean 9 S.D. intakes of total energy and various nutrients before the start of the study baseline and on each experimental period
a
P2 S2
P1 S1
Baseline Screening
7652 1994 9264 2438
Energy kJday 9411 2454
8858 2252 9607 2827
9177 2649 Energy from
45 8 44 8
46 7 43 8
Carbohydrate 49 10
45 7 15 3
15 4 16 3
17 3 15 3
Protein 16 3
36 7 37 6
36 7 28 7
37 6 Total fat
35 7 11 3
20 5 11 3
21 5 Saturated fat
11 4 16 4
10 3 3 1
10 4 5 1
Polyunsaturated fat 5 2
3 2 12 3
9 3 9 3
Monounsaturated 11 3
10 3 11 2
0.3 0.4
0.2 P:S ratio
1.1 0.2
1.0 323 130
304 113 248
236 109 307 173
Cholesterol mgday 219 112
120
a
S1, S2 and P1, P2 represent the first and second periods on high saturated and polyunsaturated fatty acid diets, respectively. Means significantly greater on S1 and S2 than P1 and P2, PB0.001.
Means significantly greater on P1 and P2 than S1 and S2, PB0.001. Means significantly lower on P1 than S1, PB0.001, and on P2 than S2, PB0.01.
Table 2 Mean 9 S.D. mole percentage contribution of linoleic, lauric, myristic and palmitic acids to total triglyceride fatty acids on each experimental
diet
a
S1 P1
S2 P2
11.01 3.74 18.81 7.29
Linoleic acidC18:2n-6 18.28 6.39
11.79 4.11 0.89 1.32
Lauric acid C12.0 0.32 0.23
0.79 1.01 0.35 0.25
Myristic acid C14.0 4.23 2.08
2.69 0.96 3.99 1.67
2.85 1.06 Palmitic acid C16.0
29.88 3.38 26.50 4.25
29.46 3.61 26.89 3.90
a
S1, S2 and P1, P2 represent the first and second periods of high saturated and polyunsaturated fatty acids respectively. Means significantly greater on P1 and P2 than S1 and S2, PB0.005.
Means significantly greater on S1 and S2 than P1 and P2, PB0.001.
Table 3 Mean 9 S.D. concentrations of total, LDL and HDL cholesterol and triglycerides during the study. Values are in mmoll
Baseline S1
P1 Screening
S2 P2
Total cholesterol 6.05 0.82
6.31 0.71 6.60 1.07
5.94 0.81 6.44 0.95
6.08 0.97 4.17 0.76
4.46 0.96 3.92 0.75
4.28 0.71 4.41 0.90
LDL cholesterol 4.09 0.91
1.32 0.34 HDL cholesterol
1.18 0.32 1.39 0.36
1.34 0.32 1.360.41
1.30 0.29 1.57 0.54
1.63 0.64 1.48 0.53
Triglyceride 1.49 0.63
1.53 0.56 1.51 0.66
Means significantly greater on S1 and S2 than P1 and P2, PB0.001. Baseline HDL cholesterol significantly lower than HDL cholesterol at all other times, PB0.01.
Table 4 Change in plasma lipids and lipoproteins and baseline characteristics of subjects in the cholesteryl ester transfer protein CETP TaqB genotypes
a
CETP TaqB1B1 n = 17 CETP TaqB1B2+B2B2 n = 38
Difference 95 CI Change
0.74 0.50 TC mmoll
0.40 0.49 −
0.34 −0.05, −0.63 LDL-C mmoll
0.33 0.56 0.68 0.56
− 0.34 −0.08, −0.61
0.05 0.24 0.02 0.25
0.03 −0.09, 0.15 HDL-C mmoll
0.05 0.37 TAG mmoll
0.04 0.45 −
0.01 −0.18, 0.15 10 8
SAFA energy 9 6
− 1 −5, 3
7 4 8 4
− 1 −2, 2
PUFA energy 5.9 5.7
TAG 18:2 mol 7.0 8.2
1.1 −2.1, 4.2 Baseline
CET nmolmlhr 36.7 11.2
34.1 11.2 −
2.6 −9.1, 4.0 45 11
Age years −
3 −9, 3 48 8
26.9 4.0 26.1 3.3
0.7 −1.5, 2.9 BMI kgm
2
6.01 1.04 TC mmoll
6.07 0.71 0.06 −0.42, 0.54
LDL-C mmoll 4.15 0.86
4.18 0.72 0.03 −0.42, 0.48
1.20 0.36 1.13 0.21
0.07 −0.12, 0.25 HDL-C mmoll
1.63 0.66 TAG mmoll
1.55 0.48 −
0.08 −0.40, 0.24 Dense LDL mgdl
74 56 64 39
− 10 −35, 17
a
Values are mean 9 S.D. unless stated otherwise.
diets 0.57 mmoll is similar to the change predicted on the basis of reported dietary change 0.59 mmoll.
HDL cholesterol and triglyceride levels did not change significantly throughout the experimental period, but
HDL cholesterol levels were significantly lower on the baseline diet than at all other times during the study.
Genotype distributions were as expected according to Hardy – Weinburg equilibrium. Table 4 shows the aver-
age differences in plasma lipids, lipoproteins and in- dices of dietary compliance on the three dietary
cross-overs and baseline characteristics in subjects with the CETPB1B1 and CETPB1B2 + B2B2 genotypes.
Changes in plasma cholesterol and LDL cholesterol were
significantly greater
in subjects
with the
CETPB1B1 genotype compared with those with one or more B2 alleles. Change in indices of dietary compli-
ance and baseline characteristics did not differ signifi- cantly between subjects in the CETP genotypes. Plasma
CET activity tended to be higher in those with the CEPTB1B1 genotype but not significantly so P =
0.17. Eight of the subjects with the CEPTB1B1 geno- type
also had
one or
more apoE4
alleles. Polymorphisms of apoB signal peptide, apoCIII, apoE
or lipoprotein lipase did not significantly influence plasma cholesterol response to type of dietary fat
Table 5, though there was a trend toward greater cholesterol responses in those with apoE3E4 and lipo-
protein lipase X447 + compared with those with other genotypes. Plasma cholesterol response to dietary
change was similar in men and women.
Table 6 examines the extent to which various mea- sures of dietary compliance, baseline body mass index
BMI and biochemical measurements predict the mag- nitude of the differences in cholesterol between diets
high and low in saturated fat. Change in reported saturated and polyunsaturated fat intake, as assessed by
3-day diet records and change in plasma triglyceride linoleate, explained some individual variation in these
univariate analyses. HDL cholesterol at screening was also predictive of change in plasma total cholesterol in
univariate analyses.
The model shown in Table 7 suggests that CETP and LPL S447X genotypes are the most powerful determi-
nants of cholesterol change. Individuals with the CETP genotype B1B1 and the LPL X447 + allele showed a
0.44 95 CI: 0.22, 0.66 and 0.45 95 CI: 0.18, 0.72
Table 5 Mean 9 S.D. difference in cholesterol between diets high and low in saturated fat on the three crossovers in individuals with different apoB
signal peptide, apoCIII, apoE or lipoprotein lipase genotypes Mean cholesterol difference
Difference 95 CI n
Apo B 0.51 0.60
32 0.01 −0.25, 0.27
Signal peptide 2727 0.50 0.38
Signal peptide 2424 or 2724 23
Apo CIII CC
0.51 0.49 29
0.01 −0.30, 0.27 0.50 0.55
26 CT+TT
Apo E 0.37 0.55
5 E2E3
0.46 0.54 E3E3
a
0.10 −0.39, 0.59 30
0.66 0.43 0.29 −0.20, 0.78
18 E3E4
a
Lipoprotein lipase Hind III 0.48 0.50
23 0.05 −0.23, 0.33
H+H+ H−H+H−H−
32 0.53 0.53
Lipoprotein lipase, S
447
X S447S447
47 0.47 0.51
0.27 −0.08, 0.63 0.74 0.48
X447+ 8
a
Compared to apoE2E3.
mmoll greater change in total cholesterol respectively than those with one or more CETP B2 allele or ho-
mozygous for the LPL S447 allele when other factors were held constant. Each 1 change in total energy
from SAFA resulted in an average change of 0.02 mmoll in total cholesterol and a mole percent change
in plasma triglyceride linoleate in an average change in cholesterol of 0.03 mmoll. Cholesterol level at the time
of initial screening was also an independent predictor of response. The variables identified by the model in Table
7 accounted for just under a third of the variation in response. Similar estimates for the influence of the
CETP gene 0.40 95 CI 0.19, 0.61 mmoll and LPL haplotypes 0.35 95 CI 0.12, 0.58 mmoll on choles-
terol response was obtained by regressing cholesterol measurements at the end of each diet period on the
corresponding cholesterol levels at the beginning of each period and including effects for treatment, dietary
SAFA
and PUFA
in each
dietary period
and interaction.
In the last part of the analysis, a number of addi- tional variables for which prior hypotheses existed were
included in the model to see whether their inclusion affected the estimates. None of these other variables
gender, dense LDL, CET activity, apo B or any other genotypes appeared to influence change in cholesterol
or the strength of the associations demonstrated in Table 7. Substitution of apolipoprotein E genotype for
screening plasma cholesterol demonstrated a similar predictive power with no diminution of the effects of
CETP and LPL genotypes or for reported change in dietary saturated fatty acids or for triglyceride linoleate.
It is interesting to note that Apo E2E3 individuals had a screening total cholesterol of 5.79 mmoll n = 5, apo
E3E3 individuals, 6.26 mmoll n = 30 and apo E4E3 individuals, 6.52 mmoll n = 18. Finally we considered
interactions between the LPL and CETP genes and
Table 6 Simple correlation between change in plasma total cholesterol and
several measures of dietary compliance change in reported intake of saturated fatty acids, DSAFA; change in reported intake of polyun-
saturated fatty acids, DPUFA; change in ratio of reported intake of polyunsaturated:saturated fatty acid, DP:S; change in triglyceride
linoleate, baseline BMI and metabolic variables
Potential determinants of response P
r n
Compliance measure 53
0.36 0.00
DSAFA 0.06
53 DPUFA
0.22 53
DP:S 0.14
0.16 55
0.21 Dplasma triglyceride linoleate
0.07 53
Total cholesterol screening 0.20
0.08 HDL cholesterol
53 0.24
0.04 53
LDL cholesterol 0.11
0.22 Triglycerides
53 −
0.03 0.42
0.13 0.17
55 Total cholesterol baseline
55 HDL cholesterol
0.12 0.19
LDL cholesterol 55
0.14 0.15
55 Triglycerides
0.11 −
0.17 55
0.20 Apo B
0.12 55
Dense LDL 0.13
0.18 55
Cholesterol ester tranfer protein activity −
0.10 0.23
55 −
0.13 0.17
BMI The P values were adjusted for multiple observations for each
person.
Table 7 Multiple regression model including those variables explaining a significant proportion of individual variation in response
Robust S.E. Coefficient
a
95 CI 0.52
− 0.60
Constant 0.11
Cholesterol ester transfer protein genotypeTaqB1B1 0.22–0.66
0.44 0.14
0.45 0.18–0.72
Lipoprotein lipase S447XX447+ DSAFA
0.01 0.02
0.01–0.03 0.01
0.03 0.01–0.04
Dplasma triglyceride linoleate 0.08
− 0.01–0.32
Screening total cholesterol 0.16
R
2
= 0.28
a
The coefficient is a measure of the change in total cholesterol for a unit change in the variable concerned. PB0.005.
PB0.01. P = 0.06.
triglyceride linoleate. Although there was an interaction between LPL S447X and plasma triglyceride linoleate,
this did not add significantly to the explanatory power of the model P = 0.09. The difference between the linear
effects difference between the slopes for LPL S447S447 and LPLX447 + individuals was significant P = 0.002.
The coefficients for the plasma triglyceride linoleate terms were 0.08 95CI: 0.03, 0.13 for LPL X447 +
individuals and 0.02 95CI: 0.01, 0.03 for individuals homozygous for the S447 allele. The interaction between
CETP and plasma triglyceride linoleate did not add to the explanatory power of the model P = 0.79.
7. Discussion
