Inhibition of growth of microbial mutants by trans-octadecenoates

Lipid nutrition: "In silico" studies and undeveloped experiments

This review examines lipids and lipid-binding sites on proteins in relation to cardiovascular disease. Lipid nutrition involves food energy from ingested fatty acids plus fatty acids formed from excess ingested carbohydrate and protein. Non-esterified fatty acids (NEFA) and lipoproteins have many detailed attributes not evident in their names. Recognizing attributes of lipid-protein interactions decreases unexpected outcomes. Details of double bond position and configuration interacting with protein binding sites have unexpected consequences in acyltransferase and cell replication events. Highly unsaturated fatty acids (HUFA) have n-3 and n-6 motifs with documented differences in intensity of destabilizing positive feedback loops amplifying pathophysiology. However, actions of NEFA have been neglected relative to cholesterol, which is co-produced from excess food. Native low-density lipoproteins (LDL) bind to a high-affinity cell surface receptor which poorly recognizes biologically modified LDLs. NEFA increase negative charge of LDL and decrease its processing by "normal" receptors while increasing processing by "scavenger" receptors. A positive feedback loop in the recruitment of monocytes and macrophages amplifies chronic inflammatory pathophysiology. Computer tools combine multiple components in lipid nutrition and predict balance of energy and n-3:n-6 HUFA. The tools help design and execute precise clinical nutrition monitoring that either supports or disproves expectations.

Influence of heated and nonheated partially hydrogenated dietary fats on ileal chyme fat and fatty acid composition of ileal mucosa in pigs

In this study the effects of partially hydrogenated chemically processed fats (CPF) and non-CPF on the ileal chyme fat and the fatty acid (FA) profile of the ileal mucosa and the subcutaneous tissue were analyzed. Samples were collected via an ileocutaneous fistula. For three months pigs were fed a control meal or diets containing either non-CPF high on 16:0, non-CPF high on 18:2 n6, CPF with 50% trans-18:1 or 20% trans-18:1. The latter fat was used after heat treatment. With both CPF diets, the fat content in the ileal chyme was three times higher than with non-CPF. In contrast to subcutaneous tissue reflecting dietary composition, changes in FA profile of ileal mucosa were restricted. Each non-CPF resulted in an increase of the characteristic major dietary FA. Both CPF increased the mucosal trans-FA percentage from 0 to 12% on average, although dietary composition was different. This study suggests: (1) less effects of trans-FA on the regulation of intraluminal fat load compared to saturated and cis-polyunsaturated FA, and (2) higher mucosal incorporation of trans-FA with heated CPF. This may play a role in the development of epithelial lesions in the ileum, which are known following ingestion of these fats.

Distribution of dietary trans-octadecenoate among acyl-CoA and other lipid fractions of rat liver and heart

Groups of rats were fed diets containing 10% of either corn oil, partially hydrogenated soybean oil, or a mixture of the two. The partially hydrogenated oil contained a high level of trans-octadecenoate and a low level of linoleate, and all diets were adjusted to contain similar levels of cis-octadecenoate. The fatty acid compositions of five tissue lipid fractions from liver and heart (non-esterified fatty acids, acyl-CoA, diacylglycerols, triacylglycerols and phospholipids) were analyzed to measure the effect of the dietary supply on the accumulation of trans-octadecenoates and other fatty acids at different steps of glycerolipid synthesis. Although trans-octadecenoate was increased in all of the lipid fractions when the dietary supply was increased, the accumulation did not exceed 15% of the acyl chains in any of the lipid pools even when the dietary trans acid accounted for 46% of the fatty acids supplied in the diet. The trans-octadecenoate accumulated in a similar manner in the lipids of both liver and heart, and the amounts found in the acyl-CoA esters of both tissues were relatively low compared to the diet. A high dietary supply of trans-octadecenoate appeared to diminish the relative content of stearate in the acyl-CoA and phospholipid fractions. The level of cis-octadecenoate maintained in tissue phospholipids was similar to that in the acyl-CoA fractions, whereas the trans-octadecenoate content in phospholipids more closely resembled that in the diacylglycerols. Normal proportions of arachidonate were maintained in the tissue phospholipids during high intake of trans acids, even though lower levels were observed in the acyl-CoA and diacylglycerols of liver.

Selective loss of mitochondrial genome can be caused by certain unsaturated fatty acids

Various unsaturated fatty acids had different effectiveness for maintaining the continued replication of functional mitochondria in an unsaturated fatty acid auxotroph of Saccharomyces cerevisiae (KD115). Certain isomers of octadecenoic acid (i.e., cis-9) and eicosatrienoic acid (i.e.,cis-8,11,14) permitted continued replication of mitochondria and provided cultures that contained only 4 to 5% cells that formed petite colonies. On the other hand, cultures grown with cis-12- or cis-13-octadecenoic acid or cis-11,14,17-eicosatrienoic acid, produced a 12- to 16-fold greater frequency of petite mutants (50-60%) after 8 to 10 generations of growth. The production of the petite mutants occurred despite adequate incorporation of these unsaturated fatty acids into cellular phospholipids and an apparently normal ability to undergo the initial steps in the induction of cellular respiration. The evidence suggests that some cellular processes necessary for continued mitochondrial replication depend on the structural features of the fatty acyl chains as well as the overall content of unsaturated fatty acids in membrane phospholipids. Impairment of that process by certain inadequate fatty acids or by an inadequate supply of a suitable fatty acid leads to a permanent loss of the mitochondrial genome from the cells of subsequent generations.

Occurrence of octadecenoic fatty acid isomers from hydrogenated fats in human tissue lipid classes

The level of trans-18:1 isomers in several isolated lipid classes of human liver, heart, red blood cells and plasma was determined. Phospholipids contained substantially fewer trans-18:1 isomers than triglycerides. The double bond distribution of the cis and trans octadecenoate fraction of triglycerides and phosphatidylcholines from human liver and heart was determined. Whereas the double bond distribution of the triglycerides correlated closely with the pattern found in dietary hydrogenated vegetable oils, the phosphatidylcholine fraction showed evidence of selective incorporation or metabolism of specific trans positional isomers. In general, isomers with double bonds near the methyl terminus were present at levels higher than expected from their relative abundance in the diet. Refinements in methodology needed to analyze octadecenoate double bond configuration and location in human tissues are presented.

Peripheral nerve cells in culture rich in Schwann cells incorporate and metabolize trans-unsaturated fatty acid (elaidic acid) as well as physiological dis isomer (oleic acid)

A culture of peripheral nerve cells enriched in Schwann cells was obtained from sciatic nerve in normal and demyelinating trembler mutant. These cells incorporated and metabolized a non-physiological trans fatty acid (elaidic aid) as well as the physiological cis isomer (oleic acid). Both acids were incorporated similarly in all lipids studied (phosphatidylcholine was a very potent acceptor) only cholesterol-esters' formation was slightly reduced from elaidic acid. Both acids were partially degradates into sub-units, in turn used for synthesis of new fatty acids. However elaidic acid was less degraded by the cells thus providing more C14:1, C16:1 fatty acids and less cholesterol. The sub-units were also used to provide very long chains, saturated and mono-unsaturated; only synthesis of nervonic acid was at variance when using oleic and elaidic acids. The presence of elaidic acid diminished the elongation-desaturation of essential fatty acids. No major differences were found between control and trembler cells, however cholesterol-esters' synthesis was slightly enhances in the mutant cells, when using both acids.

Phospholipid synthesis in S. cerevisiae strain GL7 grown without unsaturated fatty acid supplements

In the absence of exogenous unsaturated fatty acids (UFA), Saccharomyces cerevisiae strain GL7 synthesizes low levels of UFA and large amounts of decanoic, dodecanoic and tetradecanoic fatty acids. Supplementation with hemin leads to slightly higher levels of UFA, but synthesis of the medium-chain saturated fatty acids (SFA) continues. Under these conditions of limited UFA availability, strain GL7 incorporates most of its UFA into phosphatidylethanolamine (PE), whereas phosphatidylcholine (PC) and phosphatidylserine + phosphatidylinositol (PS+PI) are enriched with the medium-chain SFA. The association of specific fatty acids with the various phospholipids is not accompanied by changes in the proportions of newly synthesized phospholipids, demonstrating that the fatty acid composition of PE can be modulated independently of the other phospholipids. The effect of sterol structure on the fatty acid composition of cells grown with limiting UFA was also examined. Yeast cells grown with either ergosterol or stigmasterol contained less UFA and more medium-chain SFA in their phospholipids than did cholesterol-grown cells, suggesting that the former sterols allow strain GL7 to grow with a lower UFA content.

Effects of feeding oleic acid or hydrogenated vegetable oils to lactating cows

In feeding trials to clarify the mechanism by which unsaturated oils depress milk fat percentage, oleic acid at 250 or 500 ml per cow per day did not reduce milk fat percentage significantly. At 500 ml these changes were significant (control, oleic): rumen acetate 61.6, 60.3%; rumen propionate 19.4, 21.0%; milk fat content of 18:1 trans fatty acid 3.0, 8.0%; and of 18:2 cis fatty acid 2.2, 1.4%. Feeding hydrogenated vegetable oil containing 13% trans acid at 454 g per cow per day decreased slightly milk fat percentage and elevated plasma cholesterol 190 to 245 mg/100 ml and 18:1 trans fatty acid in milk fat 4.2 to 6.2%. Hydrogenated vegetable oil containing 49% 18:1 trans acid at 454 g daily decreased milk fat 3.9 to 3.1%. Milk fat triglycerides decreased in short chain fatty acids and increased in 18:1 trans 2.6 to 11.2%, 18:1 cis 22.9 to 29.0%, and 18:2 trans .2 to 1.8%. Milk phospholipids decreased 14.1 to 9.6% in 14:0 fatty acid and increased .3 to 3.1% in 18:1 trans and 20.5 to 31.4% in 18:1 cis. Blood cholesterol esters were increased 152 to 195 mg/100 ml. The data lend support to the concept that trans acids or compounds produced in the rumen during their formation from polyunsaturated fatty acids are responsible for the milk fat depression from unsaturated oils.

Chain elongation of trans-octadecenoic acid isomers in rat liver microsomes

The chain elongations of trans-octadecenoic acid isomers with double-bond positions delta 4 to delta 15 were studied with rat liver microsomes. The delta 7 and delta 9, trans isomers were converted to trans-9 and trans-11-eicosenoic acids, respectively, at about 40% of the rate of conversion of cis-9-octadecenoic acid to cis-11-eicosenoic acid. The rates of conversion of delta 8, delta 10, delta 11, and delta 12 trans isomers were lower than those of delta 7 and delta 9 trans isomers, but the delta 4, delta 5, delta 6, delta 13, delta 14, and delta 15 trans isomers were not elongated at rates exceeding experimental error.

Incorporation of deuterium-labeled cis- and trans-9-octadecenoic acids in humans: plasma, erythrocyte, and platelet phospholipids

The objective of this study was to follow the uptake and distribution of oleic and elaidic acids into human erythrocytes, platelets, and plasma phospholipids. The use of dual and triple labeling methodology permitted a precise comparison of elaidic and oleic acid utilization. Elaidic acid (EI) was selectively concentrated in all the plasma phospholipids except for lysophosphatidylcholine. Three times more elaidic than oleic acid (OI) accumulated in the 1-acyl position of phosphatidylcholine, as determined by hydrolysis with phospholipase A2. Rapid incorporation and removal of elaidate were observed for all samples. These results support the concept that enzymes responsible for acylation of phospholipids are sensitive to double bond configuration and the physical properties of the fatty acid moieties. Labeled fatty acid levels in red cell and platelet phospholipids were much lower than for plasma phospholipids, indicating a relatively slow rate for the in vivo incorporation of fatty acids into blood cell membrane phospholipids. No isotope effect was found when oleic acid labeled with deuterium on the double bond was used.

Incorporation, metabolism and positional distribution of trans-unsaturated fatty acids in developing and mature brain. Comparison of elaidate and oleate administered intracerebrally

Mixtures of [1-14C]elaidic acid and [9,10-3H]oleic acid, as well as [1-14C]elaidic or [1-14C]oleic acid alone, were administered by intracerebral injection to 10-day old and adult rats to examine the relative incorporation and metabolism of trans- and cis-monounsaturated fatty acids in developing and mature brain. Rates and extents of total incorporation of label from trans- and cis-acid into complex lipids were similar. Maximum labeling of the neutral lipid, mainly triacylglycerol and cholesterol, occurred prior to 4 h after injection whereas phospholipid, mainly choline phosphoglyceride, was maximally labeled at 4--8 h after injection. The decrease in labeled phospholipid from 24 to 90 h was greater with elaidate than with oleate. At 8 h labeled elaidic acid was preferentially esterified in the 1-position of all phosphoglycerides whereas labeled oleic acid, in contrast to the positional distribution of endogenous oleate, was randomly distributed. Label from elaidate found in palmitate increased with time to 26% of the total recovered label by 48 h. Thus, although some of the trans-fatty acid is oxidized and its labeled carbon is redistributed, most is incorporated unaltered into complex lipid of brain at rates similar to those for its cis-isomer. The developing central nervous system, therefore, does not metabolically exclude the trans-acid, elaidic acid, from membrane lipids.

Metabolism of linoleate versus linoelaidate in the laying hen

The metabolic fate in the laying hen of linolaidic acid, the trans,trans-geometric isomer of linoleic acid, was compared to that of the naturally occurring cis,cis linoleate. In two experiments, mixtures of radioisotope-labeled linoleate and linoelaidate were orally administered to a set of three laying hens. A third mixture consisting of linoleate-3H and linoleate-14C was fed to three hens to measure biological isotope effects. Isotopic ratios (3H/14C) of the neutral lipid and phospholipid fractions isolated from egg yolks and of the octadecadienoic acids from these fractions were compared to those of the administered mixtures. The 3H/14C ratios indicate that linoelaidic acid and linoleic acid are equally incorporated into egg yolk neutral lipids and phospholipids. Arachidonic acid was found exclusively in the phospholipid fraction and was radiolabeled with the isotope from the cis,cis octadecadienoate isomer only. Further detailed analysis of individual neutral lipid components indicated: (a) discrimination against the trans,trans isomer in cholesteryl esters and (b) no discrimination against either isomer in triacylglycerols.

Quantitative effects of unsaturated fatty acids in microbial mutants. VII. Influence of the acetylenic bond location on the effectiveness of acyl chains

The ability of a series of 18 carbon acetylenic fatty acids to fulfill the unsaturated fatty acid requirements of Escherichia coli and Saccharomyces cerevisiae was investigated. Despite their high melting points (greater than 40 degrees C), several isomers of the acetylenic fatty acids were as efficient or more efficient in supporting growth than the analogous fatty acid having a cis-double bond. The efficiencies of the different positional isomers in supporting cell proliferation varied from essentially 0 cells per fmol for the 2-5 and 13-17 isomers to high values when the acetylenic bond was near the center of the chain: e.g. 45 E. coli and 5.5 S. cerevisiae cells/fmol for the 10 isomer. A striking ineffectiveness of the 9 isomer was observed with E. coli. The 7, 8 and 10 isomers were at least 10-fold more efficient than any of the other positional isomers in supporting the growth of E. coli. In contrast, the 9 isomer was among the most effective acetylenic fatty acids tested with the yeast mutant. Chromatographic analysis of the extracted lipids indicated that each of the acetylenic isomers tested (except delta2 and delta3) could be esterified by the prokaryotic and eukaryotic microorganisms. The content of unsaturated plus cyclopropane acids observed when growth ceased in E. coli cultures supplemented with growth-limiting concentrations of the acetylenic fatty acids ranged from approx. 15 mol% for the 8 isomer to approx. 35 mol% for the 14 and 17 isomers. The 8-11 isomers were observed to be esterified predominantly at the two position in phosphatidylethanolamine of E. coli and in phosphatidylcholine of S. cerevisiae.

A shift from phospholipid to triglyceride synthesis when cell division is inhibited by trans-fatty acids

The yeast mutant Saccharomyces cerevisiae (KD 46) requires added unsaturated fatty acid for growth. When cell growth was inhibited by the presence of trans-acids there was a marked inhibition of oleate esterification into phospholipids accompanying continued incorporation into triglycerides. Apparently some control point in phospholipid synthesis associated with the cell cycle occurs after the stage of phosphatidate biosynthesis.