Effect of dietary fatty acid structure and composition on postprandial lipid metabolism
In this thesis effects of dietary fatty acid
composition and of positional distribution of fatty acids
in dietary TAG, on postprandial lipid and hormone
responses, were investigated.
A6 week fish oil supplementation period (2.7 g n-3
fatty acids per day) decreased fasting TAG and increased TC
(p<0.05) and LDL-C (p<0.05) levels in normal subjects.
Postprandial plasma TAG responses to a test meal were also
significantly reduced following the fish oil supplementation
period (area under the response curves, p<0.001).
Apolipoproteins A-I and B responses did not alter in
response to chronic fish oil supplementation. Type II
diabetics responded differently to normal subjects to fish
oil supplementation. Fasting lipid and apolipoprotein
levels were not significantly altered, and the postprandial
TAG response to a test meal showed a trend towards higher
values following the fish oil supplementation period.
In the study of effects of dietary TAG structure on
postprandial lipid apolipoprotein (A-I, B), hormone
(insulin, GIP) and glucose responses, no effect of test
meals differing in the positional distribution of palmitic
acid at the sn-2 or the sn-3 positions of the TAG molecule
In a study of acute effects of dietary fatty acid
composition in healthy male subjects, a fish oil test meal
(40 g fish oil concentrate), significantly reduced plasma
TAG postprandial responses compared with a mixed oil meal
(containing 40 g of a mixture of oils high in SFA and
mimicking the current U. K. dietary fat intake), p<0.05.
Post-heparin LPL activity was also significantly increased
12 hours following the fish oil test meal (p<0.01). A 40
g corn oil test meal did not have any significant effect on
postprandial lipid, hormone (insulin and GIP), and retinyl
palmitate levels (the latter was administered with each
test meal-700 I. U. /kg of body weight) compared with the
other two test meals.
A feeding study, using a rat model, showed that
following two weeks of a fish oil diet (5%, w/w) the postprandial
incorporation of [U-t4C]glucose into hepatic total
lipids and TAG measured in vitro, was significantly reduced
compared with rates measured in animals on a mixed oil diet
(p<0.05). In the presence of the two anabolic hormones,
insulin and GIP, in vitro rates of hepatic cholesterogenesis
increased (p<0.05), and these effects of hormones
were independent of the type of the diet fed. In addition,
plasma TAG levels were significantly lower in the fish oil
group compared with levels in the mixed oil and corn oil
dietary groups (p<0.05), and plasma insulin levels were
significantly higher in the mixed oil dietary group than in
the other two groups (p<0.001).