The following abstract suggests some properties of saturated fat
in comparison to polyunsaturated fat.  It's technical, but skip
to the end for the bottom line.

Todd Moody
[log in to unmask]

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Atherosclerosis 1998 Dec;141(2):321-32

Effect of the fat composition of a single meal on the composition
and cytotoxic potencies of lipolytically-releasable free fatty
acids in postprandial plasma.

Chung BH, Hennig B, Cho BH, Darnell BE

Department of Medicine, University of Alabama at Birmingham,
35294-0012, USA.  [log in to unmask]

[Medline record in process]

Ingestion of a meal increases plasma levels of triglyceride
(TG)-rich lipoproteins through the secretion of intestine-derived
chylomcirons and liver-derived very low density lipoproteins
(VLDL). We have determined the effects of the fat composition of
a single meal on the composition of TG in TG-rich lipoproteins
(VLDL + chylomicrons) and circulating and
lipolytically-releasable free fatty acids (FFA) in postprandial
(PP) plasma and on the cytotoxic potencies of the
lipolytically-released FFA to cultured arterial wall cells. PP
lipemia was induced by feeding fasted normolipidemic human
subjects with a meal rich in saturated fat (SF) and another meal
rich in polyunsaturated fat (PUF), or vice versa; each meal
provided 65% of energy as fat, and polyunsaturated to saturated
fatty acid ratios (P/S) of the SF and PUF in the meals were 0.40
and 2.49, respectively. The mean P/S of TG in TG-rich
lipoproteins (1.43) and circulating FFA (1.46) in 4 h PP plasma
of PUF were significantly higher than those in PP plasma of SF
(0.44 and 0.59, respectively) in fasting plasma (0.52 and 0.53,
respectively). In vitro lipolysis of fasting and PP serum by
purified bovine milk lipoprotein lipase (LpL) resulted in a
marked (8.8-12.3-fold) increase in the serum FFA level. The P/S
of serum FFA in postlipolysis fasting and PP serum were
consistently higher than that of FFA or that of TG associated
with TG-rich lipoproteins in prelipolysis fasting and PP serum,
indicating that polyunsaturated TG in VLDL and/or chylomicrons is
more susceptible than saturated TG to lipolysis. When
postlipolysis serum was interacted with cultured endothelial
cells and mouse peritoneal macrophages (MPM), the
lipolytically-released FFA in PP serum of SF and PUF disrupted
the barrier function of endothelial cells and were cytotocxic to
cultured MPM; FFA in postlipolysis fasting serum was not
cytotoxic. FFA in postlipolysis PP serum of PUF were consistently
more potent than that in postlipolysis PP serum of SF. Further
study showed that all long-chain monounsaturated FFA and
polyunsaturated FFA, but not saturated FFA, incorporated into
lipoproteins (LDL) were cytotoxic to cultured MPM. In conclusion,
despite the generally well-accepted belief that SF is more
atherogenic than PUF, the present study provides in vitro
evidence that the lipolytic remnant products of TG-rich
lipoproteins produced after a meal rich in PUF are more injurious
to arterial wall cells than those produced after a meal rich in
SF.

UI: 99076997