Cuticular lipids of insects: V. Cuticular wax esters of secondary alcohols from the grasshoppersMelanoplus packardii andMelanoplus sanguinipes

Wax esters of secondary alcohols constitute 18–20% of the cuticular lipid extract ofMelanoplus packardii and 26–31% of the cuticular lipids ofMelanoplus sanguinipes. The total number of carbons in the wax esters range from 37–54 with 41 predominating in both species. The fatty acids ofM. packardii wax esters are 16∶0, 18∶0, 14∶0, 20∶0 and 12∶0 in decreasing quantity. The fatty acids ofM. sanguinipes wax esters are 18∶0, 20∶0, 16∶0 22∶0, 14∶0, 19∶0 and 17∶0 in decreasing quantity. The secondary alcohols from the wax esters ofM. packardii are C₂₅, C₂₃ and C₂₇ in decreasing quantity, and the secondary alcohols of theM. sanguinipes are C₂₃, C₂₅, C₂₁, C₂₇, C₂₄, C₂₂ and C₂₆ in decreasing quantity. Each secondary alcohol consists of two to four isomers with the hydroxyl group located near the center of the chain. Montana Agriculture Experiment Station, Journal Series No. 332.     

Occurrence of wax esters and 1-O-alkyl-2,3-diacylglycerols in goat epididymal sperm plasma membrane

Two unusual lipid classes were detected by thin-layer chromatography in the neutral lipids derived from goat cauda-epididymal sperm plasma membrane. The lipids were identified as wax esters and 1-O-alkyl-2,3-diacylglycerols based on chromatographic properties, identity of their hydrolysis products, and infrared/¹H nuclear magnetic resonance spectral evidence. The membrane containedca. 3 and 5 μg/mg protein of wax esters and alkyldiacylglycerols, respectively. The relative proportions of wax esters and alkyldiacylglycerols in the total neutral lipids were 1.5% and 2.4%, respectively. The lipids contained fatty acids with chain lengths of C₁₄ to C₂₂. The major fatty acids of the wax esters were 14∶0, 16∶0, 16∶1ω7, 18∶0 and 18∶1ω9. The fatty acids in alkyldiacylglycerol were 16∶0, 18∶0, 22∶5ω3 and 22∶6ω3. Alkyldiacylglycerol was particularly rich in docosahexaenoic acid 22∶6ω3) representing 30% of the total fatty acids. The alcohols of wax ester were all saturated with C₂₀–C₂₉ carbon chains. The deacylated products derived from alkyldiacylglycerols were identified as hexadecyl, octadecyl and octadec-9′-enyl glycerol ethers.     

The effect of lyophilization on the solvent extraction of lipid classes,fatty acids and sterols from the oysterCrassostrea gigas

The lipid class compositions of adult Pacific oysters [Crassostrea gigas (Thunberg)] were examined using latroscan thin-layer chromatography/flame-ionization detection (TLC/FID), and fatty acid compositions determined by capillary gas chromatography and gas chromatography/mass spectrometry (GC/MS). The fatty acid methyl esters were separated using argentation TLC and also analyzed as their 4,4-dimethyloxazoline derivatives using GC/MS. Major esterified fatty acids inC. gigas were 16∶0, 20∶5n−3, and 22∶6n−3. C₂₀ and C₂₂ nonmethylene interrupted (NMI) fatty acids comprised 4.5 to 5.9% of the total fatty acids. The NMI trienoic fatty acid 22∶3(7,13,16) was also identified. Very little difference was found in the proportions of the various lipid classes, fatty acids or sterols between samples of adult oysters of two different sizes. However, significant differences in some of the lipid components were evident according to the method of sample preparation used prior to lipid extraction with solvents. Lyophilization (freeze drying) of samples led to a significant reduction in the amounts of triacylglycerols (TG) extracted by solvents in two separate experiments (7.0 and 52.5% extracted). Extracts from lyophilized samples had less 16∶0, C₁₈ unsaturated fatty acids, and 24-ethylcholest-5-en-3β-ol, while C₂₀ and C₂₂ unsaturated fatty acids comprised a higher proportion of the total fatty acids. There was no significant change in the amounts of polar lipids, total sterols, free fatty acids or hydrocarbons observed in extracts from lyophilized samples relative to extracts from nonlyophilized samples. Addition of water to the freezedried samples prior to lipid extraction greatly improved lipid yields and resulted in most of the TG being extracted.     

The Di- and triesters of the lipids of steer and human meibomian glands

Three groups of diesters have been isolated and identified in the lipids of steer meibomian glands. The first group, designated as α Type I, with the abbreviated formula FA-αOHFA-FA1c, consisted of α-hydroxy fatty acids esterified to fatty acids and fatty alcohols in the approximate molar ratio 1∶1∶1. The second group, designated as ω Type I-St, with the abbreviated formula FA-ωOHF A-St, consisted of ω-hydroxy fatty acids esterified to fatty acids and sterols in the approximate molar ratio 1∶1∶1. The third group, designated as α,ω Type II, with the abbreviated formula FA-α,ωdiol-FA, consisted of α,ω-diols esterified to 2 moles of fatty acids. The sum of the different diesters comprised about 9% of total steer meibomian lipids. Capillary GLC of the fatty acids of αType I diesters showed the fatty acids to be a family with a two-cluster profile, one at C₁₂ to C₂₀ and the other at C₂₁ to C₃₁, with anteiso chains predominating. Fatty acids from ωType I-St and α,ωType II diesters gave mainly a one-cluster profile in the short long chain, C₂₃ to C₃₀, with anteiso chains predominating, while the α-hydroxy fatty acids were short chain C₁₃ to C₁₈ acids with C₁₆ predominating. The sterols in diesters ωType I-St were cholesterol (∼60%), Δ7 cholestenol (∼35%) and an unidentified compound (∼5%) with a GLC retention time slightly longer than Δ7 cholestenol on SE-30 phase. The ω-hydroxy fatty acids and α,ω-diols both were of exceedingly long chain lengths, C₂₉−C₃₈, and showed similar GLC profiles. Two types of triesters comprising approximately 1% of total steer meibomian lipids have been isolated but incompletely characterized. In terms of molar ratios, one group of triesters gave fatty acids:ω-hydroxy fatty acids:α-hydroxy fatty acids:sterols + fatty alcohols as approximately 1∶1∶1∶1. The other contained fatty acids, α-hydroxy fatty acids and α,ω-diols in what appears to be a complex mixture of several triesters. Diesters ωType I and α,ωType II also were found in human meibum. Hitherto these two diesters have not been found in any animal tissue.     

Mass spectrometric analysis of the fatty acids and nonsaponifiable lipids ofEimeria tenella oocysts

The fatty acids and nonsaponifiable lipids ofEimeria tenella oocysts were analyzed by gas liquid chromatography and combined gas liquid chromatographymass spectrometry. The fatty acids detected were identified as C_14∶0, C_16∶0, C_16∶1, C_18∶0, C_18∶1, and C_18∶2. Though the wt of the fatty acid fraction decreased during sporulation from 91 μg per 10⁶ oocysts to 47 μg per 10⁶ oocysts, the relative amounts of these fatty acids did not change appreciably. The nonsaponifiable lipids ofE. tenella consisted of cholesterol and unbranched primary alcohols of 22, 24, 26, 28, 30, and 32 carbons. Mass fragmentography demonstrated that each species of alcohol consisted of saturated and monounsaturated derivatives. Trimethylsilyl ethers of fatty alcohols were found to offer several important advantages over free alcohols for mass spectrometric characterization. Before sporulation, most fatty alcohols were in the oocyst wall. During sporulation, the wt of the nonsaponifiable lipids increased from 16 μg per 10⁶ oocysts of 44 μg per 10⁶ oocysts due largely to synthesis of C₂₄ and C₂₆ alcohols. The newly synthesized fatty alcohols were not deposited in the oocyst wall.     

Linear, steroidal, and triterpene esters, and steryl glycosides from Festuca argentina

Ester waxes and steryl glycosides of the grass Festuca argentina were studied. Saponification of the waxes from the petroleum ether extract led to n-hexacosanol as the major single linear alcohol, along with pentacyclic triterpenols, such as β-amyrin, germanicol, isobaurenol, lupeol, hopenol-a and hopeol, and low amounts of sterols, such as cholesterol, campesterol, stigmasterol, sitosterol and dihydrositosterol, identified by gas chromatography/mass spectrometry (GC/MS). Fatty acids were identified as methyl esters as C_12∶0, C_14∶0, C_16∶0, C_18∶0, C_18∶2, and C_20∶0. The occurrence of a wide chainlength range of fatty acids and a single linear alcohol closely matched for other reports on the tribe Festuceae. On the contrary, pentacyclic triterpenols with a variety of skeletons, especially isobauerenol, are not usual as esters of fatty acids in the Gramineae. Low amounts of steryl glycosides were also obtained from the methylene chloride percolate of the methanol extract. Upon acetylation followed by hydrolysis, aglycones were identified by capillary gas-liquid chromatography (GLC) and GC/MS. As Δ⁷-cholesterol, campesterol, stigmasterol, sitosterol, dihydrositosterol, and the sugars as glucose, xylose, and arabinose by GLC of the respective alditol acetates. This is the first report on the linear, steryl, and triterpenyl esters of F. argentina. It is noteworthy that Δ⁷-steryl glycosides are rare, and steryl monoarabinosides have not been proviously reported on the family Gramineae.     

The fatty acids ofEntomophthora coronata

The total lipids and fatty acid composition ofEntomophthora coronata were determined. The fungus was grown on a chemically defined medium and a chemically nondefined medium (Sabouraud dextrose yeast extract) for a period of 26 days. The organism contained from 16.2% to 44.6% total lipids depending upon the days of growth. The major fatty acids were 12∶0 (5.5–9.0%), 13∶0 (1.2–8.2%), 14∶0 (33.5–43.5%), 16∶0 (9.7–13.9%), 18∶1₉ (20.4–22.4%), and 18∶2_9,12 (3.5–10.5%). Lesser amounts of 15∶0, 16∶1, 16∶2, 17∶0, 18∶0, two other 18∶2 (both having conjugated double bonds), 18∶3_6,9,12, another 18∶3 (conjugated double bonds), 20∶3_8,11,14, 20∶4_5,8,11,14, another 20∶4 (conjugated double bonds), and 24∶1 acids were found. Trace amounts of 20∶0, 20∶1, 20∶2, 22∶0 and 24∶0 were also present. The relative percentage of most of the fatty acids did not vary appreciably with growth. However, 18∶2_9,12 and 20∶4_5,8,11,14 increased with age of the chemically defined culture. Peak E (18∶2, conjugated double bonds) increased and 13∶0 and 18∶3_6,9,12 decreased with age of the chemically nondefined culture. The fatty acids were predominately saturated (56.9–69.1%) and contained a high percentage of shorter chain fatty acids (C 12 to C 15). The fatty acids of the chemically defined culture were more unsaturated than the Sabouraud culture and the unsaturation increased with age of the culture.     

Lipid,sterol and fatty acid composition of antarctic krill (Euphausia superba Dana)

The lipid classes, fatty acids of total and individual lipids and sterols of Antarctic krill (Euphausia superba Dana) from two areas of the Antarctic Ocean were analyzed by thin layer chromatography (TLC), gas liquid chromatography (GLC) and gas liquid chromatography/mass spectrometry (GLC/MS). Basic differences in the lipid composition of krill from the Scotia Sea (caught in Dec. 1977) and krill from the Gerlache Strait (caught in Mar. 1981) were not observed. The main lipid classes found were: phosphatidylcholine (PC) (33–36%), phosphatidylethanolamine (PE) (5–6%), triacylglycerol (TG) (33–40%), free fatty acids (FFA) (8–16%) and sterols (1.4–1.7%). Wax esters and sterol esters were present only in traces. More than 50 fatty acids could be identified using GLC/MS, the major ones being 14∶0, 16∶0, 16∶1(n−7), 18∶1(n−9), 18∶1(n−7), 20∶5(n−3) and 22∶6(n−3). Phytanic acid was found in a concentration of 3% of total fatty acids. Short, medium-chain and hydroxy fatty acids (C≤10) were not detectable. The sterol fraction consisted of cholesterol, desmosterol and 22-dehydrocholesterol.     

The lipids of the oriental hornet,Vespa orientalis F.

Analysis of the hornet’s hemolymph revealed the presence of C₁₆ and C₁₈ fatty acids (70%), which were accompanied by minor quantities (ranging from 0.1% to 0.6%) of the following acids: C_10∶0, C_11∶0, C_12∶0, C_13∶0, C_14∶0, C_15∶0, C_16∶0, and C_17∶0. The hemolymph of the queen larvae contained more C_18∶1 than the hemolymph of the worker larvae, and the percentage of C_16∶1 was higher in the fat body and the midgut than in the hemolymph. The significance of these results is discussed.     

Fatty acid composition of rat hearts as influenced by age and dietary fatty acids

Fatty acid composition of neutral and polar lipid fractions from rat hearts was determined in rats of different ages as their diet source changed. Piebald rats were weaned at 21 days and were fed standard lab chow. Lipids from rat hearts, mothers milk and lab chow were purified on a Sephadex G-25 fine column and separated into neutral and polar lipid fractions by silicic acid column chromatography. These lipid fractions were then hydrolyzed and methylated with BF₃ in methanol, prior to gas liquid chromatographic separation on a 1/8 in. × 10 ft aluminum column of 15% EGS on 80–100 mesh acid-washed Chromosorb W. Three major fatty acids in the neutral lipid fraction comprised 72% of total neutral lipid fatty acids from young hearts. At sexual maturity (at least 74 days old) C_18∶1 was the major fatty acid, followed by C_16∶0 and C_18∶0. The same three fatty acids comprised 83% of total polar lipid fatty acids, but C_18∶0 was the major fatty acid, followed by C_16∶0 and C_18∶1. The fatty acid composition of dietary lipids influenced the total neutral lipid fatty acid composition of the rat heart, but had little influence on the fatty acid composition of the polar lipid fraction. Presented in part at the AOCS Meeting, New Orleans, April 1970.     

Neutral lipids of chickpea flour and protein isolates

The neutral lipids composition of defatted chickpea flour and two types of protein isolates has been studied. The main compounds in neutral lipids are triacylglycerols, free fatty acids, and diacylglycerols. Other compounds present are wax esters, free fatty alcohols, and free sterols. The main fatty acids in neutral lipids are C_18:2 and C_18:1 among the unsaturated, and C_16:0 and C_18:0 among the saturated acids. Free and esterified alcohols range from C_16:0 to C_28:0, the majority being those with an even number of carbon atoms. Sterols observed are β-sito-sterol, campesterol, stigmasterol, and δ-5-avenasterol. Triacyl-glycerols are partially hydrolyzed, and the amounts of unsaturated sterols and unsaturated fatty acids are reduced as a result of the chemical treatment during production of the protein isolates.     

Varietal difference in lipid content and fatty acid composition of highbush blueberries

Lipids from five cultivars of highbush blueberries (Vaccinium corymbosum L.) were extracted and fractionated into neutral lipids (60–66%), glycolipids (20–22%) and phospholipids (14–18%). The major fatty acids in all fractions were palmitic (16∶0), oleic (18∶1), linoleic (18∶2), and linolenic (18∶3) acids. All lipid classes had a large concentration of C₁₈ polyunsaturated acids (84–92%), indicating that blueberries are a rich source of linoleic and linolenic acids. Changes in the fatty acid composition of neutral lipids and phospholipids were not significantly different among the five cultivars, but significant differences were noted in the ratios of linoleic and linolenic acids in the glycolipids fraction.     

Neutral lipid and fatty acid composition of earthworms (Lumbricus terrestris)

Earthworms (Lumbricus terrestris) were extracted with chloroform-methanol (2∶1) and examined primarily for neutral lipids and fatty acids. TLC showed spots for sterols, hydrocarbons, free fatty acids, phospholipids and pigments but none for glycerides (tri-, di- or mono). Saponification of the crude lipid extract yielded 32% fatty acids, 25% unsaponifiables and 43% unidentified. The lipid contained 3% hydrocarbon and 16% sterols. GLC of the hydrocarbons showed at least 13 components. GLC of the sterol fraction showed peaks corresponding to cholesterol (the major component), γ-sitosterol, β-sitosterol, stigmasterol, campesterol, and ergosterol. GLC showed that at least 38 fatty acids were present, with 18∶1, 18∶2, 18∶0, 20∶1 and 17∶0 predominanting. Abstracted in part from the Ph.D. dissertation of J. Cerbulis, Rutgers, The State University, 1966.     

Changes in lipids of pigeon “milk” in the first week of its secretion

Pigeon “milk” (PM) collected from the crop of 1- to 5-day-old squabs was analyzed to examine whether there were changes in lipid composition during the first week of secretion. The high PM fat content (9–11%) remained fairly constant in the first 5 days of secretion. The mean percentage of neutral lipids, glycolipids and phospholipids was 80, 12 and 8%, respectively. Unlike the content of neutral lipids, glycolipid and phospholipid levels increased significantly between day 1 and day 5 of secretion. Triglycerides, the major neutral lipids, decreased by 24% between day 1 and day 5, while free sterols, monoglycerides and hydrocarbons increased by 8%, 11% and 2.5%, respectively, during the same period; diglycerides and sterol esters, however, remained unchanged. The ratio of saturated to unsaturated fatty acids was 0.27 and it remained unchanged. Medium-chain (C₁₀, C₁₂ and C₁₄) and oddchain (C₁₅ and C₁₇) fatty acid contents were low. Fatty acids longer than C₂₀ were absent. Palmitic acid, the major saturated fatty acid, increased by 42% from day 1 to day 5, whereas stearic acid decreased by 48% during the same period. Oleic acid, the predominant unsaturated fatty acid, also decreased from 51 to 45% between the first and fifth day of PM secretion. Polyunsaturated acids (18∶2, 18∶3 and 20∶4) accounted for 26% and 30% of the total fatty acids on day 1 and day 5, respectively. Although lipid changes in the crop of squabs prior to collection of samples cannot totally be ruled out, the nature of lipid changes is likely to reflect cellular breakdown that precedes PM secretion by parent pigeons.     

Trans-6-hexadecenoic acid and the corresponding alcohol in lipids in the sea anemoneMetridium dianthus

Trans-6-hexadecenoic acid was found in polar lipids, triglycerides, was esters and diacylglyceryl ethers of the sea anemoneMetridium dianthus from Passamaquoddy Bay. The corresponding alcomaquoddy Bay. The corresponding alcohol also apparently occurs in the wax esters of this species. The long-chain (C₂₀, C₂₂) monoethylenic alcohols reported for other species of sea anemones from neighboring waters were absent and the major alcohol and glyceryl ether chain both had 16∶0 structures. The isomers of C₁₈ and C₂₀ monoethylenic fatty acids in polar lipids and triglycerides were unusual in their high proportion of theω ₇ isomer. These two lipids also contained higher proportion of the polyunsaturated fatty acids than the others.     

Polyunsaturated fatty glyceride syntheses by microbial lipases

The degree of glyceride syntheses by lipase TOYO (Chromobacterium viscosum) and lipase OF (Candida cylindracea) using individual free fatty acids C_18∶1, C_18∶2, C_18∶3, C_18∶4, C_20∶4, C_20∶5 and C_22∶6 were compared. Lipase TOYO incorporated each of the fatty acids into glycerol at levels of greater than 89%. Lipase OF incorporated most of the fatty acids at levels above 70% (docosahexaenoic acid incorporation was 63%). It was concluded that these two lipases are feasible for producing glycerides from unsaturated fatty acids.     

Lipid composition of yoshida ascites hepatoma and of livers and blood plasma from host and normal rats

The lipid composition of Yoshida ascites hepatoma cells was analyzed together with that of ascitic plasma and of livers and blood plasma from host and normal rats. In comparison to normal livers, host livers showed no significant differences in the content of the various lipid classes, but contained a higher percentage of palmitic acid and a lower proportion of arachidonic acid in the major phospholipid classes. In addition, tumor growth induced a marked hypertriglyceridemia in host animals; changes in the concentration of other plasma lipid classes were not statistically significant. The ascitic plasma contained small amounts of lipids mainly constituted by cholesteryl esters and phospholipids. Yoshida hepatoma cells contained less phospholipids in comparison to both host and normal liver, while the increased level of triglycerides and the decrease of free fatty acids were not statistically significant. Hepatoma cells showed appreciable amounts of ether-linked lipids associated in part to neutral lipids (as glyceryl ether diesters) and, in part, to ethanolamine and choline phosphoglycerides. The alkyl groups in GEDE as well as in ethanolamine and choline phosphoglycerides were mainly constituted by C_16∶0 and C_18∶0 followed by C_18∶1. The alk-1-enyl groups in ethanolamine and choline phosphoglycerides were C_16∶0 and C_18∶0 with only a minor proportion of C_18∶1. In comparison to both host and normal liver, Yoshida hepatoma cells showed significant changes in the fatty acid composition of neutral lipids and phospholipids. Some of the major changes consisted of an increase of monoenoic acids associated with a decrease of arachidonic and docosahexaenoic acids in phosphatidylethanolamine, phosphatidylcholine, and phosphatidylinositol.     

Arachidonic, eicosapentaenoic, and biosynthetically related fatty acids in the seed lipids from a primitive gymnosperm, Agathis robusta

The fatty acid composition of the seeds from Agathis robusta, an Australian gymnosperm (Araucariaceae), was determined by a combination of chromatographic and spectrometric techniques. These enabled the identification of small amounts of arachidonic (5,8,11,14–20∶4) and eicosapentaenoic (5,8,11,14,17–20∶5) acid for the first time in the seed oil of a higher plant. They were apparently derived from γ-linolenic (6,9,12–18∶3) and stearidonic (6,9,12,15–18∶4) acids, which were also present, via chain elongation and desaturation, together with other expected biosynthetic intermediates [bis-homo-γ-linolenic (8,11,14–20∶3) and bishomo-stearidonic (8,11,14,17–20∶4) acids]. Also present were a number of C₂₀ fatty acids, known to occur in most gymnosperm families, i.e., 5,11–20∶2, 11,14–20∶2 (bishomo-linoleic), 5,11,14–20∶3 (sciadonic), 11,14,17–20∶3 (bishomo-α-linolenic), and 5,11,14,17–20∶4 (juniperonic) acids. In contrast to most other gymnosperm seed lipids analyzed so far, A. robusta seed lipids did not contain C₁₈ Δ5-desaturated acids [i.e., 5,9–18∶2 (taxoleic), 5,9,12–18∶3 (pinolenic), or 5,9,12,15–18∶4 (coniferonic)]. These structures support the simultaneous existence of Δ6- and Δ5-desaturase activities in A. robusta seeds. The Δ6-ethylenic bond is apparently introduced into C₁₈ polyunsaturated acids, whereas the Δ5-ethylenic bond is introduced into C₂₀ polyunsaturated acids. A general metabolic pathway for the biosynthesis of unsaturated fatty acids in gymnosperm seeds is proposed. When compared to Bryophytes, Pteridophytes (known to contain arachidonic and eicosapentaenoic acids), and species from other gymnosperm families (without such acids), A. robusta appears as an “intermediate,” with the C₁₈ Δ6-desaturase/C₁₈→C₂₀ elongase/C₂₀ Δ5-desaturase system in common with the former subphyla, and the unsaturated C₁₈→C₂₀ elongase/C₂₀ Δ5-desaturase system specific to gymnosperms. The following hypothetical evolutionary sequence for the C₁₈ Δ6/Δ5-desaturase class in gymnosperm seeds is suggested: Δ6 (initial)→Δ6/Δ5 (intermediate)→Δ5 (final).     

cis-5-olefinic unusual fatty acids in seed lipids of gymnospermae and their distribution in triacylglycerols

Open-tubular gas chromatographic analysis of fatty acids in the lipids from the seeds of 20 species of Gymnospermae showed that they all contained nonmethylene-interrupted polyenoic (NMIP) acids as minor components and palmitic, oleic, linoleic and α-linolenic acids as major components. The NMIP acids have an additional 5,6-ethylenic bond in ordinary plant unsaturated fatty acids and the following C₂ elongation acids:cis-5,cis-9-octadecadienoic acid (5,9–18∶2) (I); 5,9,12–18∶3 (II); 5,9,12,15–18∶4, 5,11–20∶2, 5,11,14–20∶3 (III); and 5,11,14,17–20∶4 (IV). The main NMIP acids found in neutral lipids are I in two species ofTaxus, II in seven species of Pinaceae, III in two species of Podocarpaceae,Torreya nucifera, Cycas revoluta, andGinkgo biloba, and III and IV in each of three species of Taxodiaceae, and Cupressaceae. The polar lipids constitute the minor fraction of seed lipids in general. The content and composition of NMIP acids in these lipids differe considerably from those in neutral lipids. Analysis of the partial cleavage products of triacylglycerols showed that the NMIP acids distribute mainly in the 1,3-position.     

Long chain fatty acid deficits in brain myelin sphingolipids of undernourished rat pups

A restricted maternal dietary intake (40% of ad libitum intake) is known to cause myelin deficit that is accompanied by decreased amounts of individual phospholipids and sphingolipids in brain myelin of suckling rats. This communication reports the effects of the same nutritional stress on the fatty acid composition of brain myelin lipids. In myelin of 19-day-old normally fed rats, palmitate (16∶0), stearate (18∶0) and oleate (18∶1) accounted for 80–90% of all fatty acids in phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine. Maternal dietary restriction resulted in deficits of total fatty acid content, but did not affect the proportional distribution of individual fatty acids among phospholipids. By contrast, longer chain (22- and 24-carbon) fatty acids accounted for more than half the fatty acid content of myelin cerebroside and sulfatide from the 19-day-old control rat pups. In undernourished rats of that age, proportions of lignocerate (24∶0) and nervonate (24∶1) in cerebroside and sulfatide were 40–50% lower than those in control rats. This, together with higher proportions of 16∶0, 18∶0 and 18∶1 and a higher ratio of C₁₆−C₂₀ to C₂₂−C₂₄ in under-nourished than in control rats, suggests an impairment in fatty acid chain elongation. Ten days of nutritional rehabilitation failed to restore the fatty acid imbalances; however, after an additional 5 days of ad libitum feeding, the experimental and control values were similar. The undernutrition results in hypomyelination, which is characterized by a proportional decrease in lignoceric and nervonic acids of sphingolipids.