Gw. Power et al., THE EFFECT OF DIETARY-LIPID MANIPULATION ON HEPATIC MITOCHONDRIAL PHOSPHOLIPID FATTY-ACID COMPOSITION AND CARNITINE PALMITOYLTRANSFERASE-I ACTIVITY, Biochemistry and molecular biology international, 34(4), 1994, pp. 671-684
The maximal activity of the overt form of carnitine palmitoyltransfera
se I (CPT I; EC 2.3.1.21) and its sensitivity to inhibition by malonyl
CoA were measured in mitochondria prepared from the livers of rats wh
ich had been fed for 10 weeks on either a low fat diet (LF; 2.4% fat b
y weight) or on one of four high fat diets which contained 20% by weig
ht of either hydrogenated coconut oil (HCO), olive oil (OO), safflower
oil (SO) or menhaden (fish) oil (MO). CPT I activity (i.e. activity p
er g of liver tissue), was elevated in animals fed the the OO, SO or M
O diets compared with those fed the LF or HCO diets. Feeding the HCO d
iet did not result in elevation of CPT I activity compared with feedin
g the LF diet. CPT I specific activity (i.e. activity per mg mitochond
rial protein) was elevated in animals fed SO diet, but not in animals
fed any of the other high fat diets. These observations suggest that a
n elevated fat load is not solely responsible for increasing CPT I act
ivity, but that the fatty acid composition of the diet also plays a ro
le. Hepatic CPT I activity of rats fed the LF diet was most sensitive
to inhibition by malonyl CoA ([I-50]= 0.53 mu M). Each of the high fat
diets decreased the sensitivity of CPT I to inhibition by malonyl CoA
; CPT I activity in the livers from animals fed the MO diet was the le
ast sensitive to malonyl CoA inhibition ([1(50)]= 1.8 mu M). The fatty
acid compositions of the major mitochondrial membrane phospholipids,
phosphatidylcholine, phosphatidylethanolamine and cardiolipin were mod
ified according to the fatty acid composition of the diet. Each of the
se phospholipids had a distinct fatty acid composition and similar eff
ects of dietary lipid manipulation on the fatty acid compositions were
observed. Feeding the SO diet resulted in fatty acid compositions whi
ch were most similar to those found after feeding the LF diet. Feeding
the HCO and OO diets increased the proportions of stearic and oleic a
cids, respectively, while decreasing the proportion of linoleic acid.
Feeding the MO diet resulted in increased proportions of palmitic, pal
mitoleic, eicosapentaenoic and docosahexaenoic acids and decreased pro
portions of linoleic and arachidonic acids in each of the phospholipid
s. It is proposed that the effects of dietary lipid manipulation upon
CPT I activity and sensitivity to inhibition by malonyl CoA are due to
alterations in the fatty acid composition of the phospholipids in the
mitochondrial membrane where CPT I resides.