Emilios C. Kyriakides

Alterations in phosphatidylcholine species and their reversal in pulmonary surfactant during essential fatty-acid deficiency.

Previous studies (Kyriakides, E.C., Beeler, D.A. and Balint, J.A. (1974) Clin. Res. 22, 717a, and Burnell, J.M. and Balint, J.A. (1975) Fed. Proc. 34, 426) have indicated that essential fatty-acid deficiency in rats resulted in significant reduction of palmitate content of lung tissue and lavage phosphatidylcholines. Experiments were, therefore, undertaken to confirm and further characterize these changes and to examine the reversal of these alterations when essential fatty acid deficient rats were fed fat-free diets supplemented with linoleate for 1-14 days. Analysis of the fatty acid composition of liver lipids was used to confirm the presence of essential fatty-acid deficiency in rats that were fed a fat-free diet supplemented with 4% by weight of tripalmitoylglycerol for 14 weeks. Phosphatidylcholines from lung tissue and lavage fluid of essential fatty-acid deficient rats contained significantly less palmitate and significantly more palmitoleate and oleate than those rats receiving linoleate. These changes in fatty acid composition were reflected in a significant reduction of disaturated phosphatidylcholines (predominantly dipalmitoyl) in lung tissue and lavage fluid from essential fatty-acid deficient rats, while the total phosphatidylcholine content remained unchanged. On feeding the diet containing linoleate to the deficient rats, a reversal of these changes began after one day and was nearly complete by 7-14 days.

The relationship of fatty acid composition and surface activity of lung extracts.

Male weanling rats were fed fat-free diets supplemented with 4% (w/w) safflower oil (control) or 4% tripalmitin (essential fatty acid (EFA) deficient) for 14 weeks. Whereas the amount of lecithin in lung lavage material remained unchanged, lung lavage lecithin from EFA-deficient rats contained significantly less palmitic acid (61.4 +/- 2.0% vs. 77.4 +/- 5.8%, P less than 0.01) than that from controls. Surface tension vs. area hysteresis loops were obtained for total lipid extracts (TLE) of lung lavage fluid, intra- and extra-cellular lipoprotein fractions (IBI and IBE) and lipid extracts of those lipoprotein fractions (LBI and LBE). A significant increase in minimal surface tension (gammamin) was found for all samples obtained from EFA-deficient rats as compared to controls. Refeeding of diets containing safflower oil for 7-14 days reversed these changes. Air pressure-volume curves on degassed, excised lungs indicated that greater pressure is required to maintain a given lung volume in EFA-deficient rats. These results support the hypothesis that the fatty acid composition of pulmonary surfactant lecithins is a major determinant of the surface activity of lung extracts.

Hydrophobic surfactant treatment prevents atherosclerosis in the rabbit.

The hypocholesterolemic effect of the hydrophobic surfactant, poloxalene 2930, was studied in the rabbit to determine whether this agent prevents experimentally produced atherosclerosis. Male rabbits were divided into four groups and fed a control diet (group A) or an atherogenic diet (groups B, C, and D) for 10 wk. Diets of groups C and D were supplemented with 0.5 and 1% poloxalene 2930, respectively. Animals in group B developed significantly greater levels of cholesterol in the serum and aorta compared with group A. Addition of poloxalene 2930 to the diets of groups C and D prevented significant elevations in cholesterol concentrations of both serum and aorta compared with group B with values for group D being essentially similar to those observed in group A. Groups C and D also had significant increases of fecal excretion of both neutral fat and neutral steroids as compared with either groups A or B. There were no atherosclerotic lesions of the aortas from group D. Aortas from rabbits in group B had numerous atheromatous plaques while one rabbit each from groups A and C had several very small atheromatous lesions. These results demonstrate that poloxalene 2930 reduces the rise of serum cholesterol in rabbits in response to an atherogenic diet and prevents the development of atherosclerosis. This hypocholesterolemic effect is likely mediated by the effect of this surfactant on the small intestine.

Surfactant Lecithin Fatty Acid Composition and Its Relationship to the Infantile Respiratory Distress Syndrome

Summary: In order to evaluate the role of surfactant lecithin composition in the development of the infantile respiratory distress syndrome (IRDS) we have examined lecithin fatty acid composition from gastric aspirates obtained at the time of delivery from 14 full term healthy infants, 9 control premature infants without respiratory distress, and 16 premature infants who developed IRDS. The latter had significantly reduced concentrations of palmitic acid (48.4 ± 1.8% vs. 65.3 ± 1.5% in fullterm and 59.5 ± 0.8% in control premature infants, P < 0.001). None of the infants in whom palmitic acid was more than 60% of total lecithin fatty acids developed IRDS, whereas 10 of 11 infants with values below 50% did develop this complication. Lecithin from gastric aspirate was shown to be similar in fatty acid composition to lecithins from tracheal washings and amniotic fluid. Palmitic acid concentrations in lecithins of serial tracheal washings paralleled the clinical course of eight infants with IRDS.Speculation: The enzyme systems involved in the biosynthesis of pulmonary surfactant are complex. Failure of maturation of these systems can result in inadequate synthesis of total lecithins or in a selective deficiency of dipalmitoyl lecithin, an essential component of surfactant. Therefore, studies directed to determining the composition of surfactant lecithins may result in better diagnosis, understanding, and management of IRDS.

The pathways of lecithin biosynthesis in essential fatty acid deficiency in hamsters.

Abstract 1. 1. Male hamsters were fed fat-free and chow (control) diets for 12 weeks. At this time they were injected with an isotopic mixture containing 32 P i , [ Me - 14 C]methionine and [ Me - 3 H]choline and killed 1, 2 and 4 h afterwards. The incorporation of these labels into bile and the various fractions of liver phospholipids were studied. 2. 2. In the hamsters receiving the fat-free diet, the incorporation of all three isotopes into hepatic lecithins was increased. There was no change in the pool size of lecithin or of its water soluble phosphorylated precursors. 3. 3. The monoene and triene fractions of hepatic phospholipids from experimental animals were metabolically similar to the diene and tetraene fractions, respectively, of control animals. 4. 4. Cholesterol gallstones were observed in eleven of fifteen hamsters receiving the fat-free diet. None were observed in a similar number of controls. 5. 5. The normal diene lecithin fraction of bile was replaced by a monoene lecithin in the fat-free animals. Biliary phospholipids attained higher specific activities than any hepatic lecithin in control animals while the reverse was the case in the experimental group.

Effect of surfactant poloxalene 2930 on food intake, lipid absorption, and serum cholesterol in rats.

Effect of hydrophobic surfactant, poloxalene 2930, on lipid absorption was studied in rats. Under acute conditions with surfactant infused intraduodenally with a lipid meal absorbed lipid accumulated abnormally in the enterocytes. This effect was quickly reversed after terminating treatment. Long-term administration of poloxalene given in semipurified diets resulted in changes in food intake, weight gain, fecal fat output, and serum cholesterol concentrations. The composition of the diet used as the vehicle for administration had a considerable effect on these results. When semipurified diets were used, food intake and weight gain were greatest when the dietary fat content was at the highest level. When the surfactant was given in ground chow, food intake was not affected and weight gain was only slightly, but significantly, less than the controls as a result of mild fat malabsorption. It is concluded that poloxalene 2930 affects lipid absorption, food intake, and serum cholesterol concentration but that results of this treatment are considerably affected by dietary factors.

Morphological alterations in type II alveolar cells in essential fatty acid deficiency

Abstract Type II epithelial cells from rats on a diet deficient in essential fatty acids demonstrated ultrastructural alterations not heretofore described in this tissue. Mitochondria became enlarged, rounded in outline, and cristae packed the intramitochondrial space. Mitochondrial vesiculation also occurred. The changes did not occur in other cell types, including bronchiolar (Clara) cells, in lung tissue. These events when correlated with biochemical and biophysical data concerning the alveolar surface materials from these animals suggests that a state of essential fatty acid deficiency provides an excellent experimental tool for further study of structural-functional relationships related to synthesis, storage, and secretion of the surface active material from Type II cells onto the alveolar surface.

Desaturation of endogenous and exogenous palmitate in lung tissue in vitro

Lung slices from rats fed a fat-free diet supplemented with safflower oil (control) or tripalmitoyl-glycerol (essential fatty acid [EFA]-deficient) were incubated with [14C] acetate, [14C] palmitate, or [14C] stearate. Of the14C recovered in phospholipids after incubation with [14C] acetate, more than 87% was in 16-carbon fatty acids. Desaturation, as assayed by the percentage of radioactivity in monoenoates in phospholipid fatty acids, was generally double in EFA-deficient slices compared to control slices, regardless of substrate. Desaturation was significantly greater in slices incubated with acetate or octanoate compared to palmitate, indicating that endogenously synthesized palmitate was desaturated more actively than that derived from an exogenous source.