Effect of dietary fat composition on rat colon plasma membranes and fecal lipids.

The present study was designed to examine the effect of dietary fat composition on the structure of colon mucosal plasma membranes and fecal lipids. Rats were fed a purified diet containing 14% of either highly saturated fat (beef fat or butterfat) or highly polyunsaturated oil (safflower) in addition to 2% corn oil for 4 wk. Colon mucosal membranes were prepared and examined for lipid composition and protein pattern. Saturated fatty acid feeding resulted in the loss of some protein bands from plasma membranes compared to feeding polyunsaturated fatty acids. Within the saturated fatty acid--rich fats, feeding beef fat caused a greater loss than did feeding butterfat. Dietary fat composition had no effect on membrane content of phospholipid and cholesterol. Saturated fatty acid feeding resulted in an increase in the percentage of 18:1 in plasma membrane lipids compared to feeding safflower oil. The observed changes in the structure of colon mucosal membrane of animals fed the saturated fats were associated with an increase in fecal free fatty acids. There was a 4-fold and 2-fold increase in fecal free fatty acids with feeding the beef fat and butterfat diets, respectively, compared to the safflower oil diet. Alterations in fecal bile acid and free fatty acid composition were also noticed with feeding saturated fatty acids. The results obtained suggest that feeding saturated fatty acids as the main source of fat in the diet could influence the structure of colon mucosa, and this could be mediated through fecal free fatty acids.

Effect of dietary saturated fatty acids on hormone-sensitive lipolysis in rat adipocytes.

The objective of this work was to examine the mechanism by which dietary saturated fatty acids, as compared with polyunsaturated fatty acids, lower hormone-sensitive lipolysis in rat adipocytes. Rats were fed a purified diet containing 14% of a fat with a high concentration of either saturated fatty acids (coconut oil or beef fat) or polyunsaturated fatty acids (safflower oil) as a control. In addition, each diet contained 2% corn oil. The animals were fed these diets for 4 wk. Norepinephrine-stimulated lipolysis was 50% lower when diets rich in saturated fatty acids, regardless of their chain length, were fed than when a diet containing a high concentration of polyunsaturated fatty acids was fed. The specific activities of adenylate cyclase, 3',5'-cyclic nucleotide (cAMP) phosphodiesterase and hormone-sensitive lipase were lower when saturated fatty acids were fed than when polyunsaturated fatty acids were fed. Accumulation of cAMP upon stimulation with 10(-5) M norepinephrine was lower when saturated fatty acids were fed than when polyunsaturated fatty acids were fed. Moreover, adipocytes were larger when saturated fatty acids were fed than when polyunsaturated fatty acids were fed. The data obtained suggest that dietary saturated fats exert their inhibitory effect on hormone-stimulated lipolysis by influencing several points in the lipolytic cascade.

Effect of dietary saturated fatty acids on intracellular free fatty acids and kinetic properties of hormone-sensitive lipase of rat adipocytes.

Experiments were conducted to examine the effects of dietary saturated fatty acids on the intracellular free fatty acid concentration and composition and on the kinetic parameters of hormone-sensitive lipase of rat adipocytes. Animals were fed for 4 wk 14% coconut oil, beef fat or safflower oil and 2% corn oil in a purified diet. Adipocytes of animals fed the coconut oil diet contained higher basal level of intracellular free fatty acids than those of animals fed other beef fat or safflower oil diets. Norepinephrine (10(-5) M) stimulated the basal intracellular free fatty acid concentration by 2.3-3.4-fold in adipocytes from animals fed saturated fatty acids, compared with 6.4-fold in those of animals fed the safflower oil diet. The concentrations of intracellular free fatty acids in adipocytes of experimental animals after stimulation with 10(-5) M norepinephrine, however, were not significantly different. The intracellular free fatty acid pool of adipocytes of animals fed the saturated fatty acids had more palmitic acid and less linoleic acid than those of safflower oil-fed animals. The results indicate that type of dietary fat had no effect on kinetic properties of hormone-sensitive lipase.

Effect of dietary fats on the lipid composition and enzyme activities of rat cardiac sarcolemma.

The effect of dietary lipids on the lipid composition and the activities of some enzymes of cardiac sarcolemma were studied. Feeding rats coconut oil--rich diet for 4 weeks resulted in a significant decrease in 5'-nucleotidase, phosphodiesterase I and p-nitrophenylphosphatase activity of cardiac sarcolemma as compared with feeding rats safflower oil. Sarcolemma from animals fed coconut oil diet contained a significantly lower concentration of total polyunsaturated fatty acids and a higher concentration of total monounsaturated fatty acids than that from rats fed safflower oil. Most of the alterations in polyunsaturated fatty acids were found in 20:4, whereas those of the monounsaturates were found in 18:1. Among all the phosphoglycerides, the fatty acid composition of the phosphatidylcholine exhibited the largest alterations as a result of coconut oil feeding. No dietary effect was observed in the sarcolemma content of cholesterol and phospholipid. These studies clearly indicate that manipulation of dietary lipids influences both the fatty acid composition and some functional properties of the sarcolemma membranes.

Developmental alterations in 5'-nucleotidase kinetics and lipid composition of rat heart sarcolemma.

The objective of these studies was to examine the mechanism by which the specific activity of heart sarcolemma 5'-nucleotidase decreases as function of age. We examined the kinetic properties and the lipid composition of the sarcolemma from animals with different ages. The age groups used were 1 month, 6-8 months and 13-15 months. It was found that the Km of this enzyme increases as the animal develops from 1 month to 6-15 months. The opposite was true with 5'-nucleotidase Vmax. There was no significant difference between the middle age and the older age groups in those parameters. The results of these experiments suggest that the increase in Km in sarcolemma 5'-nucleotidase could be due to the reduction of the sarcolemmal polyunsaturated fatty acid concentration, the only lipid alteration observed.

Alteration of rat heart sarcolemma lipid composition by dietary elaidic acid.

Male weanling rats were fed a semisynthetic diet containing 5% of either elaidic acid or oleic acid for 4 weeks. The heart sarcolemma were isolated and examined for purity by using marker enzymes. The sarcolemma preparations were enriched in phosphodiesterase I, 5'-nucleotidase and p-nitrophenyl phosphatase as compared with the heart homogenates. Succinic dehydrogenase activity was not detected in these preparations. The lipids of sarcolemma fractions from animals fed the trans fatty acids were enriched with the fatty acid fed. Most of this incorporation was found to be associated with the two major phospholipids, phosphatidylcholine and phosphatidylethanolamine. The incorporation of elaidic acid into the membranes resulted in an increase in membrane cholesterol without affecting either membrane phospholipid content or profile. The alterations induced in the lipid composition of heart sarcolemma by feeding this dietary trans fatty acid suggest some functional alterations in these membranes.

Evaluation of mycobacillin and versicolin as agricultural fungicides. III. Growth pattern and antibiotic production in soil by Aspergillus versicolor.

Soil supports the growth of a jute pathogen Colletotrichum gloeosporioides but only to a limited extent that of its antagonist Aspergillus versicolor. The growth of the sensitive pathogen is considerably checked by the antagonist in mixed soil culture although versicolin production could not be demonstrated within the limits of assay. Both the sensitive and the antagonistic organisms grow well in soil-compost medium and versicolin production by the latter is also enhanced. The antagonistic effect of Aspergillus versicolor on Colletotrichum gloeosporioides is expectedly more marked in soil-compost medium than in soil medium.