Glycolipids and their developmental patterns in chick thigh and leg muscles

Ganglioside Composition in Beef, Chicken, Pork, and Fish Determined Using Liquid Chromatography-High-Resolution Mass Spectrometry

Gangliosides (GA) are found in animal tissues and fluids, such as blood and milk. These sialo-glycosphingolipids have bioactivities in neural development, the gastrointestinal tract, and the immune system. In this study, a high-performance liquid chromatography-mass spectrometry (HPLC-MS) method was validated to characterize and quantitate the GA in beef, chicken, pork, and fish species (turbot, snapper, king salmon, and island mackerel). For the first time, we report the concentration of GM3, the dominant GA in these foods, as ranging from 0.35 to 1.1 mg/100 g and 0.70 to 5.86 mg/100 g of meat and fish, respectively. The minor GAs measured were GD3, GD1a, GD1b, and GT1b. Molecular species distribution revealed that the GA contained long- to very-long-chain acyl fatty acids attached to the ceramide moiety. Fish GA contained only N-acetylneuraminic acid (NeuAc) sialic acid, while beef, chicken, and pork contained GD1a/b species that incorporated both NeuAc and N-glycolylneuraminic acid (NeuGc) and hydroxylated fatty acids.

Ethanol-Induced Changes in the Content of Triglycerides, Ceramides, and Glucosylceramides in Cultured Neurons

BACKGROUND

Ethanol induces apoptosis in cultured neurons. To assess the involvement of sphingolipids and neutral lipids in the apoptotic process, ethanol-induced alterations in lipid content and metabolism were examined by using primary cultured rat cerebellar granule neurons (CGNs), human neuroblastoma SK-N-SH cells, and mouse neuroblastoma Neuro2a cells. Ethanol treatment conditions that induced apoptosis in CGNs and SK-N-SH cells but not in Neuro2a cells were used for these experiments.

METHODS

Cultured neurons were treated with and without 100 mM ethanol for one to three days, and the amounts of cellular sphingolipids [ceramide, glucosylceramide (GlcCer), and sphingomyelin] and neutral lipids [cholesterol, triglyceride (TG), and cholesterol ester (ChE)] were analyzed by high-performance thin-layer chromatography, using a Coomassie brilliant blue staining method. The incorporation of [C] acetate into each lipid fraction was measured in CGNs treated with and without ethanol. Also, the effect of delipidated serum, sterols, myriocin (a serine-palmitoyltransferase inhibitor), and desipramine (an acid sphingomyelinase inhibitor) on ethanol-induced lipid changes was studied by using Neuro2a cells.

RESULTS

The most prominent change common to CGN, SK-N-SH, and Neuro2a cells was ethanol-induced TG accumulation. Higher incorporation of radioactivity into TG was also observed in ethanol-treated cultures when cellular lipids were metabolically labeled with [C] acetate in CGNs. In addition, ethanol elevated ceramide levels in all these neurons. However, ethanol induced decreases in GlcCer along with the reduction of cell viability in SK-N-SH cells and CGNs, whereas it increased GlcCer in Neuro2a cells that remained viable. Myriocin, which reduced ceramide levels, attenuated ethanol-induced cell death in SK-N-SH cells. Ethanol-induced accumulation of TG was sterol-independent, whereas changes in ceramide and GlcCer were affected in Neuro2a cells by the presence of sterols in the medium. Staurosporine, which induced cell death in SK-N-SH cells, increased levels of TG, ChE, and ceramides and reduced the level of GlcCer.

CONCLUSIONS

The results showing that ethanol induces accumulation of TG and ceramide in cultured neurons suggest that ethanol enhances lipogenesis and/or reduces fatty acid degradation in neurons, as previously observed in other cell types. Further, ethanol-induced changes in lipid metabolism, specifically those of ceramide and GlcCer, may be related to the ethanol-induced apoptotic pathway.

Alcohol Reduces GM1 Ganglioside Content in the Serum of Inbred Mouse Strains

BACKGROUND

Endogenous and exogenous gangliosides in the plasma affect physiologic and pathologic processes such as angiogenesis and atherogenesis. However, the genetic and environmental factors that regulate the expression of plasma gangliosides are not well known. As shown in the liver and the brain, profiles of gangliosides in the plasma may be strain-specific and can be altered by intake of alcohol. Therefore, we analyzed serum gangliosides derived from inbred mouse strains with and without alcohol treatment.

METHODS

C57BL/6ByJ (B6By) and BALB/cJ mice (60-70 days old) were injected with 20% alcohol (1-6 g/kg) or saline intraperitoneally, and the ganglioside content of the serum, liver, and cerebellum was measured 4 hr after the injection. Also, the effect of oral alcohol self-administration for 18 days with escalating (3-12%) concentrations of alcohol on the serum GM1 content was studied in B6By mice. The quantification of GM1 was performed with a thin-layer chromatography-staining procedure using a cholera toxin B subunit, and the content of other gangliosides was measured after staining with resorcinol reagent.

RESULTS

We found that basal GM1 (containing N-glycolylneuraminic acid) content in the serum of BALB/cJ mice (4.8 +/- 0.26 ng/microl) was 25 times higher than that of B6By mice (0.19 +/- 0.01 ng/microl); the major ganglioside in both strains was GM2. The ganglioside profile in the liver was similar to that of the serum, and the GM1 content in BALB/cJ was nine times higher than that of B6By. Both injection and oral self-administration of alcohol lowered GM1 levels in the serum.

CONCLUSIONS

Endogenous ganglioside profiles in the serum are under genetic control among inbred mouse strains, and they can be altered by acute and chronic alcohol administration. These genetic and alcohol-induced differences in the plasma gangliosides, which appear to reflect ganglioside metabolism in the liver, may affect alcohol-related behaviors and pathologic processes.

Ethanol attenuation of ganglioside sialylation and neuritogenesis

Neurite-producing cultured embryonic chick brain neurons in 96-h culture were exposed chronically to 25 mM ethanol for a 72-h period. Neurital plasma membrane extension was markedly attenuated in the ethanol-exposed neurons as compared with ethanol-free control cultures. The rate of biosynthetic sialylation of gangliosides, which are major structural sialoglycosphingolipid components in the exofacial lipid bilayer of the neurital plasma membrane, decreased to about half that in the alcohol-free neurons. The findings show that ganglioside sialylation in the morphodifferentiating central nervous system neuron is significantly attenuated by chronic exposure to a moderate dose of ethanol. Depression of ganglioside-dependent neuritogenesis may represent a mechanism for development of the central nervous system component of the fetal alcohol syndrome.

Incorporation of very-long-chain fatty acids into sphingolipids of cultured neural cells

We examined effects of exogenous very-long-chain fatty acids on lipids of cultured chick neurons and astrocytes. When chick neurons were incubated in chemically defined medium containing 10 microM nervonic acid (C24:1) for 7 days, it was found that a major fatty acid moiety of gangliosides and sphingomyelin was nervonic acid itself, which was not normally detected in the sphingolipid fraction. This alteration in the fatty acid composition apparently occurred in each ganglioside species. Under these experimental conditions, nervonic acid was not found in the glycerophospholipid fraction, and the amounts of triacylglycerol and free nervonic acid increased. Addition of behenic acid (C22:0) or erucic acid (C22:1) also induced changes in the fatty acid composition of gangliosides. When chick astrocytes were incubated in the presence of 10 microM nervonic acid for 7 days, no significant change was observed in the fatty acid composition of gangliosides. These studies indicate that the manipulation of the fatty acid moiety of sphingolipids in cultured neurons is possible.

Regulation of glycolipid synthesis during differentiation of clonal murine muscle cells

The two clonal murine muscle cell lines G7 and G8, originally derived from the M114 line, represent unique models for comparative studies of myogenesis. Glycolipid synthesis was examined during differentiation using [3H]-galactose and [3H]-glucosamine as precursors. Upon G7 contact glucosylceramide labeling increased and nLcOse5Cer labeling stopped. During membrane fusion, glucosylceramide labeling stopped and lactosylceramide became the major synthetic product. G8 cells presented a different pattern, with increased labeling of GbOse3Cer during myogenesis. The major ganglioside synthesized by both myoblasts was GM3, and more complex structures were observed following completion of myotube formation. Total glycopeptide labeling increased when G8 myoblasts fused and remained elevated in myotubes, whereas no differences during fusion of G7 cells were noted. Upon comparison of the two clonal lines, the only consistent observation was a significant increase in the synthesis of total gangliosides and neutral glycolipid during cell contact and membrane fusion (p less than 0.02). The results suggest that changes in the synthesis of specific glycolipid structures during myogenesis are unique to each muscle cell line examined. However, transient increases in synthesis of total myoblast gangliosides and neutral glycolipids may be a more general phenomenon, possibly by curbing proliferation or by altering myoblast membrane fluidity characteristics during differentiation.

Ganglioside variations in human liver cirrhosis and hepatocellular carcinoma as shown by two-dimensional thin-layer chromatography

Gangliosides isolated from 5 cases of normal liver tissues, 11 cases of liver cirrhosis and 5 cases of hepatocellular carcinoma were compared in their concentrations and compositions. Quantitative analysis revealed no significant change of ganglioside levels between normal and cirrhotic liver tissues or hepatocellular carcinoma. There was also no significant difference (p greater than 0.05) between cirrhotic liver tissues and hepatocellular carcinoma. Two dimensional thin-layer chromatography of the total ganglioside preparations of liver tissues from both liver cirrhosis and hepatocellular carcinoma showed proliferation of GM2, GD3, GD1 and at least two unidentified components, named provisionally spots Nos. 1 and 2 in the present report, and loss of GM3. Sialidase treatment and thin-layer chromatography showed the components of these spots to be sialidase-labile monosialogangliosides and distinctly different from GD3 which was described elsewhere.

Carbohydrate analysis of chicken heart glycolipids

Neutral and acidic glycolipids were extracted from chicken hearts. The neutral and acidic compounds were separated by preparative thin-layer chromatography into eight and two fractions, respectively. Total hydrolysis by mineral acid, permethylation analysis, and sequential cleavage with exoglycosidases showed the presence of glycolipids that belong to the globo- and gala-oligosaccharide series, i.e., the monohexosylceramides Glc-Cer and Gal-Cer, the dihexosylceramides Gal beta 1-4Glc-Cer and Gal alpha 1-4Gal-Cer, the tetrahexosylceramides GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-Cer and GalNAc alpha 1-3GalNAc beta 1-3Gal alpha 1-4Gal-Cer (III3GalNAc alpha-Ga3Cer) and four subfractions of the Forssman glycolipid GalNAc alpha 1-3GalNAc beta 1-3Gal alpha 1-4Gal beta 1-4Glc-Cer. With the notable exception of III3GalNAc alpha 1-Ga3Cer, all glycolipids with terminal GalNAc alpha 1-3GalNAc1 reacted on thin-layer chromatograms with a monoclonal anti-Forssman antibody. The major components of the acidic fraction glycolipids were characterized as the lactose-based gangliosides Glac1 (GM3) and Glac2 (GD3).

The gangliosides of adult human aorta: intima, media and plaque

The composition, structure and localization of gangliosides of aorta taken from subjects who had died after myocardial infarction were studied. Individual gangliosides were purified by high-performance liquid chromatography and high-performance thin-layer chromatography and were characterized on the basis of their chromatographic mobility, carbohydrate composition, neuraminidase hydrolysis and methylation analysis. The main aortic gangliosides were identified as GM3, GM1, GD3, GD1a and GT1b. Significant differences in the ganglioside composition of intima and media were detected and the ganglioside profile of atherosclerotic plaques was found to differ markedly from that of unaffected intima. The latter was characterized by high content of GD3, a ganglioside thought to be associated with membrane permeability, cell interaction, adhesiveness and growth and to suppress unspecific immune responses. Possible implications of the results in low-density lipoprotein binding to the arterial wall and in immunological changes induced by atherosclerotic lesions are discussed.

Glycolipid sialosyltransferase activity in synaptosomes exhibits a product specificity for (2-8)disialosyl lactosyl ceramide (ganglioside GD3)

Intact synaptosomes prepared from 28-day-old rat brains were incubated with CMP-N-acetyl-(14C) neuraminic acid in Krebs-Henseleit buffer in an atmosphere of 95% O2: 5% CO2, at 37 degrees C. The activity of CMP-NANA:ganglioside sialosyltransferase using endogenous acceptors was 0.84 pmoles NANA transferred/mg synaptosomal protein/hr. Analysis of the distribution of labeled sialic acid revealed that GD3 ganglioside (alpha 2----8 disialosyl, alpha 2----3 galactosyl, beta 1----4 glucosyl, beta 1----1-ceramide) was the major product in the membrane carrying 32% of the total lipid bound label. Treatment of the reaction products with Clostridium neuraminidase liberated labeled sialic acid from GD3 and yielded labeled GM3, then unlabeled lactosyl ceramide. Lac-cer and GM3 are present in small amounts in synaptosomes, and GD3 represents less than 2% of the total ganglioside. Our findings indicate that the sialosyltransferase activity of synaptosomes exhibits a preferential product specificity for the small pool of synaptosomal membrane GD3 ganglioside that may be formed in situ, via sialosylation of its precursor (GM3 or lactosyl ceramide) which pre-exists in the synaptosomal plasma membrane. The second major labeled product quantitatively was GD1a whose precursor substrate, GM1, is quite abundant in the membrane, so that the conversion rate of GM1 to GD1a was low in comparison with GD3 formation. Sialosylation of other synaptosomal membrane gangliosides was negligible.

Glycosphingolipid biosynthesis in early chick embryos

Early chick embryos at the age of 22 h (neurula stage) and 48 h (20-25 somite stage) were explanted from eggs and cultured in vitro in the presence of radioactive sugar precursors. Metabolically labelled glycosphingolipids were isolated. Amongst these, neutral and acidic components, the latter including sulfatide and gangliosides, were identified. Cleavage by exoglycosidases, as well as immunostaining with antibodies on thin-layer plates, showed that at both embryonic stages glycosphingolipids were synthesized that belong to the globo series (globoside, Forssman glycolipid), the lacto series (lactoneotetraosylceramide, nLc4Cer, and two nLc4Cer-based gangliosides, a monosialo and a disialo species), and the ganglio series (ganglioside Gtet1a and higher sialylated derivatives).

The effects of phorbol ester on anabolism of lipids of cultured human skin fibroblasts

We have investigated the independent effects of phorbol ester (phorbol 12-myristate 13-acetate) on anabolism of the major lipid components in cultured diploid human skin fibroblasts. When we incubated these cells with [3H]acetate in serum-free medium for 18 h in the presence of 16 nM phorbol ester, [3H]acetate incorporation and the cellular content of cholesterol ester increased, and free cholesterol decreased. Enhancement of [3H]acetate incorporation into cholesterol ester was also observed when the cells were incubated with phorbol ester for 5 h in medium containing lipoprotein-deficient serum. Incorporation of [3H]galactose into glycosphingolipids increased many fold upon exposure of the cells either to fetal calf serum or separately to phorbol ester. Therefore, phorbol ester independently affects cholesterol and glycosphingolipid metabolism in a way that may be similar to that reported for serum low-density lipoproteins and unknown other factors in fetal calf serum. We have observed these effects of phorbol ester in the intact living cell. These findings should provide useful means for the study of metabolism of the plasma membrane lipid components in fibroblasts.

Changes in ganglioside metabolism during in vitro differentiation of quail embryo myoblasts

The metabolism of gangliosides was studied during the in vitro differentiation of both normal quail myoblasts and myoblasts which have been transformed by a temperature-sensitive mutant of Rous sarcoma virus (RSV). These transformed cells can be maintained undifferentiated if incubated at 35 degrees C, but they will differentiate when shifted to 41 degrees C. (D. Montarras and M. Y. Fiszman (1983) J. Biol. Chem. 258, 3882-3888). The analysis of [14C]Glucosamine-labeled gangliosides by two-dimensional thin-layer chromatography reveals variations in the metabolism of the gangliosides during the process of differentiation. During the formation of myotubes, it was observed that the accumulation of GD1a is reduced, while the accumulation of GD3 is increased. Therefore, this results in the variation of the ratio GD3/GD1a which increases from 1.8 to 25 in the case of clones of transformed myoblasts, and from 0.5 to 1.7 in the case of uninfected myoblasts. These variations which have been observed seem to be specific of the myogenic differentiation since they cannot be reproduced when differentiation is inhibited by BUdR treatment or when fibroblasts reach confluency and are blocked in the G1 phase of cell cycle. Furthermore, the transformed myoblasts in vitro are shown to be a good model system since their gangliosides composition is very similar to that of muscle cells in vivo.

Myelin gangliosides in developing rats: the influence of maternal ethanol consumption

The present study examined myelin gangliosides in the developing offspring of rats that were pair-fed control or ethanol liquid diets prior to and during gestation. Between 17 and 31 days of age, we observed an increase in the proportion of GM1 in myelin (from 15% to 38% of ganglioside sialic acid) and a decrease in the proportion of GT1b (from 26% to 4%). GM4 was detected at all ages examined. Between 17 and 31 days of age, there was an increase in the proportion of N-acetylmannosamine-derived radioactivity associated with GM1 (from 16% to 22%) and GM4 (from 5% to 13%), and a decrease in that associated with GT1b (from 24% to 4%). Small, but significant (p less than 0.05), developmentally related differences were found in GD2 and GD3. Detection of GM4 in myelin of young rats in the present study appears to depend on the use of nonpartitioning methods of ganglioside extraction. Although the distribution of myelin gangliosides and radioactivity was near-normal in ethanol-treated pups, there was a consistent decrease in the proportion and radioactivity associated with the major myelin ganglioside, GM1.

Glycosphingolipids of chicken skeletal muscle in early development and genetic dystrophy

The acidic and neutral GSL of chicken pectoral muscle and the activities of relevant sialyltransferase and glycosidases have been examined during embryonic and early post-hatching development. At this stage of myogenesis, a prominent shift to the neutral GSL of longer oligosaccharide length involving Forssman glycolipid most prominently and also globoside and GbOse3Cer occurred but the distribution of muscle-type gangliosides was not obviously affected. The glycosidase and sialyltransferase activities decreased dramatically just prior to or at hatching. The fusion-linked change in GSL suggests a role for terminal galactosamine and/or galactose residues in myoblast aggregation. A parallel developmental study of genetic muscular dystrophy revealed similar GSL levels and enzyme activities. A larger proportion of lactosylceramide in dystrophic muscle throughout development suggests a developmental lag in the mutant.

Studies on glycoconjugate metabolism in developing skeletal muscle membranes

The postnatal development of mammalian skeletal muscle is characterized by changes in the properties of several key membrane glycoprotein enzymes and receptors. In the present study, CMP-sialic acid: fetuin sialyltransferase and CMP-sialic acid: lactosylceramide sialyltransferase activity was characterized in sarcolemma and sarcoplasmic reticulum membranes isolated from neonatal (0-1 week) and adult (8 week) rabbit skeletal muscle. CMP-sialic acid: fetuin sialyltransferase decreased by a factor of 10 in sarcolemma and 6 in sarcoplasmic reticulum during development, whereas CMP-sialic acid: lactosylceramide sialyltransferase activity decreased by a factor of 6 in sarcolemma and 18 in sarcoplasmic reticulum. The Km for CMP-sialic acid using the lipid acceptor declined during the development of sarcoplasmic reticulum (neonate vs. adult: 538 vs. 33 microM), but not in sarcolemma. The carbohydrate composition of sarcolemma was changed only with respect to total sialic acid content (neonate vs. adult: 67 vs. 44 nmol/mg). Similar analysis of sarcoplasmic reticulum carbohydrates showed decreases in total sialic acid, lipid-bound sialic acid, hexosamines and hexoses. The major ganglioside was GM3 for both types of membrane. No qualitative changes were observed in ganglioside composition comparing neonatal and adult membranes.

GM3 and GD3 are the major gangliosides of rat fetal intestine

Gangliosides were extracted from intestine of rat fetuses on each day between 17 days of gestation and 1 day after birth. They were purified from the lipid extract by DEAE-Sephadex chromatography. Two major gangliosides are found at the earliest time: GD3 and GM3. Their contributions to the ganglioside content are, respectively, 48.2 and 33.7%. Between 19 days of gestation and birth, a 3.5-fold increase of the total ganglioside concentration is observed which is due to sharp rise of the GM3 concentration. In GD3 and GM3 of rat fetal intestine, sialic acid is exclusively N-acetylneuraminic acid and fatty acids are all non-hydroxylated.