Polyunsaturated fatty acid deficiency affects sulfatides and other sulfated glycans in lysosomes through autophagy-mediated degradation.

Metabolic changes in sulfatides and other sulfated glycans have been related to various diseases, including Alzheimer's disease (AD). However, the importance of polyunsaturated fatty acids (PUFA) in sulfated lysosomal substrate metabolism and its related disorders is currently unknown. We investigated the effects of deficiency or supplementation of PUFA on the metabolism of sulfatides and sulfated glycosaminoglycans (sGAGs) in sulfatide-rich organs (brain and kidney) of mice. A PUFA-deficient diet for over 5 weeks significantly reduced the sulfatide expression by increasing the sulfatide degradative enzymes arylsulfatase A and galactosylceramidase in brain and kidney. This sulfatide degradation was clearly associated with the activation of autophagy and lysosomal hyperfunction, the former of which was induced by suppression of the Erk/mTOR pathway. A PUFA-deficient diet also activated the degradation of sGAGs in the brain and kidney and that of amyloid precursor proteins in the brain, indicating an involvement in general lysosomal function and the early developmental process of AD. PUFA supplementation prevented all of the above abnormalities. Taken together, a PUFA deficiency might lead to sulfatide and sGAG degradation associated with autophagy activation and general lysosomal hyperfunction and play a role in many types of disease development, suggesting a possible benefit of prophylactic PUFA supplementation.

Targeted lipidomics and metabolomics evaluations of cortical neuronal stress in schizophrenia.

BACKGROUND: Cortical neuronal dysfunction has been proposed to underlie the psychopathology and cognitive dysfunction of schizophrenia. Previously we have reported altered sphingolipid and N-acylphosphatidylserine (NAPS) metabolism in the frontal cortex in schizophrenia. We continue to expand these investigations to define the biochemical basis for these critical neuropathologies. METHODS: We undertook a targeted high resolution mass spectrometric analysis to validate our previous reports of elevated sphingolipids and NAPS in the frontal cortex of a new cohort of schizophrenia subjects. Furthermore we expanded these analyses to include ceramides, N-acylphosphatidylethanolamines (NAPE), and N-acylethanolamines (NAE). In the same tissue samples we examined N-acetylaspartylglutamate (NAAG), a modulator of excitatory amino acid transmission, hypothesized to be involved in the pathology of schizophrenia. RESULTS: We repeated our observations of elevated sulfatides in the frontal cortex in schizophrenia. An in-depth analysis of other sphingolipids revealed decrements in ceramide levels and increased levels of lactosylceramides. NAPS also were found to be augmented in schizophrenia as we previously reported. In addition, levels of NAPES, established biomarkers of neuronal stress, were elevated while their metabolites, NAEs were decreased. With regard to excitatory amino acid neurotransmission, NAAG levels were decreased by 50% while the metabolic precursor, N-acetylaspartate was unaltered. CONCLUSIONS: Our data support the concept of cortical neuronal dysfunction in schizophrenia as indicated by altered metabolism of structural sphingolipids and NAAG, a modulator of excitatory amino acid neurotransmission.

γ-Aminobutyric Acid Attenuates High-Fat Diet-Induced Cerebral Oxidative Impairment via Enhanced Synthesis of Hippocampal Sulfatides.

Long-term high-fat diet (HFD) in rats triggered cerebral oxidative stress, reflected by reactive oxygen species accumulation and antioxidant decline in peripheral and cerebral tissues, together with hippocampal lipid disturbance, particularly for triglyceride accumulation and sulfatide deficiency. Hippocampal formation and cerebral cortex also exhibited pathological changes, characterized by neurofibrillary tangle and reduced Nissl bodies. Sulfatides were noted to protect hippocampal neurons from oxidative damage through the clearance of ß-amyloid protein, with apolipoprotein E transporting and low-density lipoprotein receptor binding. Delightedly, we found γ-aminobutyric acid (GABA) supplement delivered by rice bran to rats significantly promoted hippocampal sulfatide synthesis and reversed the HFD-induced sulfatide deficiency and oxidative-triggered cerebral impairment. Elevated GABA concentration in hippocampus and the activation of GABA B-type receptors might be the primary contributors. This study demonstrated the potential of GABA-enriched rice bran as a novel dietary supplement to enhance a sulfatide-based therapeutic approach for neurodegenerative diseases in the early stages.

Sulfatides Primarily Exist in the Substantia Nigra Region of Mouse Brain Tissue.

Lipid distribution in the brain is important for many biological functions and has been associated with some brain diseases. The aim of this study was to investigate lipid distribution in different regions of brain tissue in mice. To this end, substantia nigra (SN), caudate putamen (CPu), hippocampus (Hip), hypothalamus (Hyp), and cortex (Cx) tissues of mice were analyzed using direct infusion nanoelectrospray-ion trap mass spectrometry and multivariate analyses. The SN, CPu, Hip, Hyp, and Cx groups showed clear differences in lipid distribution using principal component analysis and a partial least-squares discriminant analysis score plot, and lipid levels were significantly different in different brain regions. In particular, sulfatides were mainly distributed in the SN region. Our results could be used to help understand the functions and mechanisms of lipids in various brain diseases.

Dysfunctional glycosynapses in schizophrenia: disease and regional specificity.

BACKGROUND: Our previous lipidomics studies demonstrated elevated sulfatides, plasmalogens, and N-acylphosphatidylserines in the frontal cortex of schizophrenia subjects. These data suggest that there may be an abnormal function of glycosynapses in schizophrenia. We further examined the disease and anatomical specificity of these observations. METHODS: We undertook a targeted lipidomics analysis of plasmalogens, sulfatides, and N-acyl-phosphatidylserines in the frontal cortex obtained from schizophrenia, bipolar, and ALS subjects and the cerebellum of schizophrenia subjects. RESULTS: We demonstrate that sulfatides, plasmalogens, and N-acyl-phosphatidylserines are significantly elevated in the frontal cortex of patients suffering from schizophrenia and bipolar depression but not in ALS patients. These lipids were unchanged in the cerebellum of subjects with schizophrenia. CONCLUSIONS: Our data suggest that dysfunction of oligodendrocyte glycosynapses may be specific to limbic circuits in schizophrenia and that this dysfunction is also detected in bipolar depression, suggesting that these disorders possess several common pathophysiological features.

Age- and brain region-specific effects of dietary vitamin K on myelin sulfatides.

Dysregulation of myelin sulfatides is a risk factor for cognitive decline with age. Vitamin K is present in high concentrations in the brain and has been implicated in the regulation of sulfatide metabolism. Our objective was to investigate the age-related interrelation between dietary vitamin K and sulfatides in myelin fractions isolated from the brain regions of Fischer 344 male rats fed one of two dietary forms of vitamin K: phylloquinone or its hydrogenated form, 2',3'-dihydrophylloquinone (dK), for 28 days. Both dietary forms of vitamin K were converted to menaquinone-4 (MK-4) in the brain. The efficiency of dietary dK conversion to MK-4 compared to dietary phylloquinone was lower in the striatum and cortex, and was similar to that in the hippocampus. There were significant positive correlations between sulfatides and MK-4 in the hippocampus (phylloquinone-supplemented diet, 12 and 24 months; dK-supplemented diet, 12 months) and cortex (phylloquinone-supplemented diet, 12 and 24 months). No significant correlations were observed in the striatum. Furthermore, sulfatides in the hippocampus were significantly positively correlated with MK-4 in serum. This is the first attempt to establish and characterize a novel animal model that exploits the inability of dietary dK to convert to brain MK-4 to study the dietary effects of vitamin K on brain sulfatide in brain regions controlling motor and cognitive functions. Our findings suggest that this animal model may be useful for investigation of the effect of the dietary vitamin K on sulfatide metabolism, myelin structure and behavior functions.

The Yin and Yang of lactosylceramide metabolism: implications in cell function.

Although lactosylceramide (LacCer) plays a pivotal role in the biosynthesis of nearly all the major glycosphingolipids, its function in regulating cellular function has begun to emerge only recently. Our current opinion is that several physiologically critical molecules such as modified/oxidized LDL, growth factors, pro-inflammatory cytokines and fluid shear stress converge upon and activate lactosylceramide synthase to generate LacCer. In turn, LacCer activates an "oxygen-sensitive" signaling pathway involving superoxides, nitric oxide, p21 Ras GTP loading, kinase cascade, PI3kinase/Akt activation, nuclear factor up-regulation ultimately contributing to phenotypic changes such as cell proliferation, adhesion, migration and angiogenesis. Since dys-regulation of such phenotypic changes constitute a hallmark in several diseases of the cardiovascular system, proliferative disorders such as cancer, polycystic kidney disease and inflammatory diseases, LacCer synthase and LacCer provide novel targets for the development of therapeutics aimed at these health conditions.

Endosomes and lysosomes play distinct roles in sulfatide-induced neuroblastoma apoptosis: potential mechanisms contributing to abnormal sulfatide metabolism in related neuronal diseases.

Alterations in sulfatide metabolism, trafficking and homoeostasis are present at the earliest clinically recognizable stages of Alzheimer's disease and are associated with metachromatic leukodystrophy. However, the role of sulfatide in these disease states remains unknown. In the present study, we investigated the sequelae of NB (neuroblastoma) cells upon sulfatide supplementation and the biochemical mechanisms contributing to the sulfatide-induced changes. By using shotgun lipidomics, we showed dramatic accumulations of sulfatide, ceramide and sphingosine in NB cells in a time- and dose-dependent manner. Further studies utilizing subcellular fractionation and shotgun lipidomics analyses demonstrated that most of the increased ceramide content was generated in the endosomal compartment, whereas sulfatides predominantly accumulated in lysosomes. In addition, we determined that the sulfatide-mediated increase in endosomal ceramide content mainly resulted from beta-galactosidase activity, which directly hydrolyses sulfatide to ceramide without a prior desulfation step. Substantial cell apoptosis occurred in parallel with the accumulation of sulfatides and ceramides, as revealed by mitochondrial membrane depolarization, by phosphatidylserine translocation and by the TUNEL (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labelling) assay. These findings were also demonstrated with primary neuron cultures. Collectively, our results demonstrate that abnormal sulfatide metabolism can induce cell apoptosis due to endosome-mediated ceramide generation and the accumulation of cytotoxic levels of sulfatides in lysosomes.

Altered thalamic membrane phospholipids in schizophrenia: a postmortem study.

BACKGROUND: Membrane lipids are important mediators of neuronal function. In a postmortem study, we measured membrane lipid components in the left thalamus of schizophrenic patients. This region might play an important role in the pathophysiology of schizophrenia and has not been studied thus far with respect to its membrane lipid composition. METHODS: The study included 18 chronic schizophrenic patients and 23 healthy control subjects. Using lipid extraction and thin-layer chromatography, we measured membrane phospholipids, galactocerebrosides 1 and 2, and sulfatides in thalamus homogenate. RESULTS: The main membrane phospholipid phosphatidylcholine and the major myelin membrane components sphingomyelin and galactocerebrosides 1 and 2 were found to be decreased in schizophrenic patients. In contrast, phosphatidylserine was increased. These lipid contents did not correlate with postmortem intervals and medication doses. There was no difference in the membrane phospholipids lysophosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol, and phosphatidylglycerol or in sulfatides. CONCLUSIONS: Our results confirm findings of magnetic resonance imaging, postmortem, and gene expression studies. They support the notion of an increased phospholipid breakdown in schizophrenia as a sign for decreased myelination and oligodendrocyte dysfunction.

Multi-specificity of a Psathyrella velutina mushroom lectin: heparin/pectin binding occurs at a site different from the N-acetylglucosamine/N-acetylneuraminic acid-specific site.

An N-acetylglucosamine (GlcNAc)/N-acetylneuraminic acid-specific lectin from the fruiting body of Psathyrella velutina (PVL) is a useful probe for the detection and fractionation of specific carbohydrates. In this study, PVL was found to exhibit multispecificity to acidic polysaccharides and sulfatides. Purified PVL and a counterpart lectin to PVL in the mycelium interact with heparin neoproteoglycans, as detected by both membrane analysis and solid phase assay. The pH-dependencies of the binding to heparin and GlcNAc5-6 differ. The heparin binding of PVL is inhibited best by pectin, polygalacturonic acid, and highly sulfated polysaccharides, but not by GlcNAc, colominic acid, or other glycosaminoglycans. Sandwich affinity chromatography indicated that PVL can simultaneously interact with heparin- and GlcNAc-containing macromolecules. Extensive biotinylation was found to suppress the binding activity to heparin while the GlcNAc binding activity is retained. On the other hand, biotinyl PVL binds to sulfatide and the binding is not inhibited by GlcNAc, N-acetylneuraminic acid, or heparin. These results indicate that PVL is a multi-ligand adhesive lectin that can interact with various glycoconjugates. This multispecificity needs to be recognized when using PVL as a sugar-specific probe to avoid misleading information about the nature of glycoforms.

Vitamin K status influences brain sulfatide metabolism in young mice and rats.

The established role of vitamin K in nutrition is as a cofactor in the post-translational conversion of specific glutamyl to gamma-carboxyglutamyl (Gla) residues in a limited number of proteins. Administration of the vitamin K antagonist warfarin has previously been shown to decrease brain sulfatide concentrations and decrease brain galactocerebroside sulfotransferase (GST) activity in young mice. A dietary deficiency of vitamin K has now been shown to decrease (P < 0.01) brain sulfatide concentrations of 30-d-old mice significantly (by 21%). Male 21-d-old rats fed an excess of vitamin K for 7 or 14 d had 26 and 31% (P < 0.05) greater GST activity and 15 and 18% (P < 0.05) greater brain sulfatide concentrations, respectively, than controls fed a vitamin K-deficient diet. Male 21-d-old rats fed a diet containing 500 mg of phylloquinone/kg diet had an intermediate response and were vitamin K sufficient by normal criteria. The vitamin K response was observed when either phylloquinone or menaquinone-4 was fed as a source of the vitamin. These data suggest that in addition to its recognized role in Gla synthesis, vitamin K status is important in the maintenance of normal complex lipid sulfatide metabolism in young rats and mice.

Changes in whole brain membranes of rats following pre- and post-natal exposure to ethanol.

The chronic effects of ethanol on the fatty acid composition of rats that have been exposed to ethanol in utero were examined. Ten female Wistar rats were fed a nutritionally adequate liquid diet for 3 weeks before mating, throughout gestation and until the offspring reached the 10th or 20th post-natal day. Whole brain lipid changes were examined at these 2 time points. On day 10, a decrease in 18:1 lipid content was found, indicating tolerance development. However, by day 20 an increase in polyunsaturated fatty acid content (20:4) was detected, indicating that ethanol may be causing an increase in membrane fluidity. Although these results are contrary to those found in adult rats following chronic ethanol administration, it seems likely that, in the immature animal, the brain is still undergoing rapid development and therefore may be affected differentially by ethanol.

Vesicular transport of sulfatide in the myelinating mouse brain. Functional association with lysosomes?

Sulfatide synthesis and its subcellular distribution kinetics was followed in the myelinating brain of 17-day-old mice. Pulse-labeling-chasing conditions were achieved by an intraperitoneal injection of (35S)sulfate followed 2 h later by a second injection of a high dose of unlabeled sulfate. At 1, 2, 3, 4, and 6 h after the (35S)sulfate injection, the brains were removed, homogenized, and subcellular fractions were obtained by differential and discontinuous sucrose gradient centrifugation (Eichberg, J., Whittaker, V. P., and Dawson, R. M. (1964) Biochem. J. 92, 91-100). The microsomal membranes were further subfractionated (Siegrist, H. P., Burkart, T., Wiesmann, U. N., Herschkowitz, N. N., and Spycher, M. A. (1979) J. Neurochem. 33, 497-504) into light myelin, plasma membranes, Golgi vesicles, endoplasmic reticulum membranes, and heavy vesicles associated with acid hydrolase activities. The [35S]sulfatide-labeling kinetics was measured in all subcellular fractions. The results indicate that sulfatides are synthesized in the Golgi-endoplasmic reticulum complex and transferred in vesicles at least partially associated with lysosomes to the myelin membranes. The association of sulfatides with lysosomes could explain the existence of the previously described labile pool of newly synthesized sulfatides (Burkart, T., Hofmann, K., Siegrist, H. P., Herschkowitz, N. N., and Wiesmann, U. N. (1981) Dev. Biol. 83, 42-48) and also could be a form of vesicular transport to the myelin.

Effect of early postnatal dietary sterculate on the fatty acid composition of rat liver and brain lipids.

Pregnant rats were fed a high carbohydrate diet containing either 1% trilinolein or 1% trilinolein with 0.2% methyl sterculate from 18 day gestation to 21 day postpartum. The pups were weaned at 21 days and continued on the same diet for an additional 10 days. The microsomal stearyl CoA desaturase activities of the liver were effectively inhibited. Liver triglycerides showed increases in the saturated fatty acids concentrations at the expense of the corresponding monoenes. The concentration of cis 6-7 octadecenoic acid was elevated. In liver phospholipids, the concentration of stearic acid was increased without a corresponding decrease in the oleic acid content. A drastic decrease in the nervonic acid (24:1, n-9) concentration of liver sphingomyelin was observed. The lipids of the brain did not contain sterculic acid, and brain desaturase activity was unaffected. There was no significant change in the concentration of monoenoic acids from 16:1 to 22:1. However, nervonic acid was decreased by 32%. These results suggest that brain nervonic acid may be derived from a precursor other than oleic acid.