Phospholipids acid ester content

Another technique for determination of the fatty acid ester content of phosphatidylcholine is through the use of infrared spectrometry. The fatty acid ester groups in the native phospholipid and the methyl esters derived from this phospholipid absorb quite strongly at 1750-1730 cm-1. This latter absorption... 

Simultaneously, some of the phospholipids and the apo A apolipoproteins are transferred from the chylomicron particle onto HDL. The newly formed particle, the chylomicron remnant, contains 80% to 90% of the triglyceride content of the original chylomicron. Because of the presence of apo B-48 and apo E on its surface, the chylomicron remnant can be recognized by specific hepatic remnant receptors and internalized by endocytosis. The components of the particle are then hydrolyzed in the lysosomes. The cholesterol released can form bile acids, be incorporated into newly synthesized lipoprotein, or be stored as cholesteryl ester. Furthermore, the cholesterol from these remnants can down regulate HMG-CoA reductase, the rate-hmiting enzyme of cholesterol biosynthesis (see earlier section on cholesterol synthesis). 

Cholesterol and triglycerides, as the major plasma hpids, are essential substrates for cell membrane formation and hormone synthesis and provide a source of free fatty acids. Hyperlipidemia is defined as an elevation of one or more of cholesterol, cholesterol esters, phospholipids, or triglycerides. Lipids, being water immiscible, are not present in free form in the plasma but rather circulate as hpoproteins. Hyperlipoproteinemia describes an increased concentration of the lipoprotein macromolecules that transport lipids in the plasma. The density of plasma lipoproteins is determined by their relative content of protein and lipid. Density, composition, size, and electrophoretic mobility divide lipoproteins into four classes (Table 21-1). 

An uncontrolled study (Christophe et al., 1994) in patients with cystic fibrosis demonstrated an increase in vital capacity after 4 wk of supplementation with 1500 mg of borage oil (330 mg of GLA) daily. AA content of serum phospholipids was increased, although they would be expected to decrease based on results of other studies. AA, DGLA, and linoleic acid content of cholesterol esters also increased. 

The serum phospholipids and red cell membrane phospholipids of children with SCD have an altered fatty acid composition. We and others (2123) have shown that children with SCD have lower percentages of the long-chain n-3 PUFA and increased percentages of saturated fatty acids in their phospholipids. In addition, Connor and co-workers (22) documented that the red cell membrane phospholipids of children with SCD have a higher proportion of saturated and monounsaturated fatty acids and a lower proportion of PUFA in the sn-2 position. This abnormality in fatty acid content can be reversed by supplementation with PUFA, as demonstrated by Muskeit and co-workers (23) who found an increase in the level of n-3 fatty acids in both plasma cholesterol esters and red blood cell phospholipids of children with SCD after supplementation with fish oil. 

Stern and Shapiro (1954) incubated the intact mesenteric fat of starved rats with serum and observed a deerease in the total serum esterified fatty acid content but no decrease in the phospholipid or cholesterol ester fraction. When mesenteric adipose tissue was incubated with sodium stearate-1-C or sodium oleate, a significant uptake could be demonstrated and the fatty acids that disappeared from the medium could be recovered in good yield inside the tissue. Of the stearate absorbed, 20-30% was found in the tissue in a combined form, presumably in ester linkage. Stern and Shapiro (1954) also showed that adipose tissue can absorb fatty acids from emulsions of triolein, sorbitan-monolaurate, sorbitan-monopalmitate, and... 

As with the male rat, the early reports that erucic acid somehow interfered with reproduction in the female rat are difficult to assess because the diets that were used may have been low in essential fatty acids (Carroll and Noble, 1957). Decreased numbers of pregnancies, resorption, and pseudopregnancies were observed in female rats fed diets supplemented with either erucic or oleic acids. Somewhat more plausible are the reports that the ovarian cholesterol content is increased in rats fed a HEAR oil containing diet (Carroll and Noble, 1952). When rats were fed ethyl erucate mixed with corn oil which is high in essential fatty acids, there were no noticeable reproductive abnormalities in the females (Walker eta/., 1972). As in the adrenal gland, the erucic acid in the ovaries accumulated as the cholesterol ester. Also, the cholesterol esters of 20 4 n-6, 22 4 n-6, and 24 1 n-9 were increased in the ovaries from these rats. An interesting observation by these authors was that rats fed an olive oil containing diet with no erucic acid accumulated appreciable quantities of esterified erucic acid, i.e., 3.1% of the cholesterol ester fraction and 1.4% of the phospholipid fraction. It was... 

The average lipid content of the rat heart is about 3% of the fresh weight. The phospholipids comprise 60-70% of the total lipids, the remainder consists of triglycerides (—25%), cholesterol (—6%), cholesteryl ester (—2%) and minor amounts of diglycerides and free fatty acids (Simon and Rouser, 1969 Kramer, 1980). A detailed compositional analysis of the rat heart phospholipids was published by Simon and Rouser (1969) and shown in Table II. The structure of the phospholipids is also given in Table II. 

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