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Sphingolipids are a class of lipids containing a backbone of sphingoid bases, which are a set of aliphatic amino alcohols that includes sphingosine. They were discovered in brain extracts in the 1870s and were named after the mythological sphinx because of their enigmatic nature. These compounds play important roles in signal transduction and cell recognition. Sphingolipidoses, or disorders of sphingolipid metabolism, have particular impact on neural tissue. A sphingolipid with a terminal hydroxyl group is a ceramide. Other common groups bonded to the terminal oxygen atom include phosphocholine, yielding a sphingomyelin, and various sugar monomers or dimers, yielding cerebrosides and globosides, respectively. Cerebrosides and globosides are collectively known as glycosphingolipids.
Fumonisin B1 is the most prevalent member of a family of toxins, known as fumonisins, produced by multiple species of Fusarium molds, such as Fusarium verticillioides, which occur mainly in maize (corn), wheat and other cereals. Fumonisin B1 contamination of maize has been reported worldwide at mg/kg levels. Human exposure occurs at levels of micrograms to milligrams per day and is greatest in regions where maize products are the dietary staple.
Ceramides are a family of waxy lipid molecules. A ceramide is composed of sphingosine and a fatty acid joined by an amide bond. Ceramides are found in high concentrations within the cell membrane of eukaryotic cells, since they are component lipids that make up sphingomyelin, one of the major lipids in the lipid bilayer. Contrary to previous assumptions that ceramides and other sphingolipids found in cell membrane were purely supporting structural elements, ceramide can participate in a variety of cellular signaling: examples include regulating differentiation, proliferation, and programmed cell death (PCD) of cells.
In biochemistry, lipogenesis is the conversion of fatty acids and glycerol into fats, or a metabolic process through which acetyl-CoA is converted to triglyceride for storage in fat. Lipogenesis encompasses both fatty acid and triglyceride synthesis, with the latter being the process by which fatty acids are esterified to glycerol before being packaged into very-low-density lipoprotein (VLDL). Fatty acids are produced in the cytoplasm of cells by repeatedly adding two-carbon units to acetyl-CoA. Triacylglycerol synthesis, on the other hand, occurs in the endoplasmic reticulum membrane of cells by bonding three fatty acid molecules to a glycerol molecule. Both processes take place mainly in liver and adipose tissue. Nevertheless, it also occurs to some extent in other tissues such as the gut and kidney. A review on lipogenesis in the brain was published in 2008 by Lopez and Vidal-Puig. After being packaged into VLDL in the liver, the resulting lipoprotein is then secreted directly into the blood for delivery to peripheral tissues.
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Teleost leptins are a family of peptide hormones found in fish (teleostei) that are orthologs of the mammalian hormone leptin. The teleost and mammalian leptins appear to have similar functions, namely, regulation of energy intake and expenditure.
Ceramide synthase 1 also known as LAG1 longevity assurance homolog 1 is an enzyme that in humans is encoded by the CERS1 gene.
Ceramide synthase 2, also known as LAG1 longevity assurance homolog 2 or Tumor metastasis-suppressor gene 1 protein is an enzyme that in humans is encoded by the CERS2 gene.
Ceramide synthase 3 (CersS3), also known as longevity assurance homologue 3, is an enzyme that is encoded in humans by the CERS3 gene.
Ceramide synthase 5 (CerS5) is the enzyme encoded in humans by the CERS5 gene.
References
- 1 2 Riebeling C, Allegood JC, Wang E, Merrill AH, Futerman AH (October 2003). "Two mammalian longevity assurance gene (LAG1) family members, trh1 and trh4, regulate dihydroceramide synthesis using different fatty acyl-CoA donors". Journal of Biological Chemistry. 278 (44): 43452–43459. doi: 10.1074/jbc.M307104200 . PMID 12912983.
- ↑ Laviad EL, Albee L, Pankova-Kholmyansky I, Epstein S, Park H, Merrill AH, et al. (2008). "Characterization of ceramide synthase 2: tissue distribution, substrate specificity, and inhibition by sphingosine 1-phosphate". Journal of Biological Chemistry. 283 (9): 5677–5684. doi: 10.1074/jbc.M707386200 . PMID 18165233.
- ↑ Schiffmann S, Sandner J, Birod K, Wobst I, Angioni C, Ruckhäberle E, et al. (2009). "Ceramide synthases and ceramide levels are increased in breast cancer tissue". Carcinogenesis. 30 (5): 745–752. doi: 10.1093/carcin/bgp061 . PMID 19279183.
- ↑ Erez-Roman R, Pienik R, Futerman AH (2010). "Increased ceramide synthase 2 and 6 mRNA levels in breast cancer tissues and correlation with sphingosine kinase expression". Biochemical and Biophysical Research Communications. 391 (1): 219–223. doi:10.1016/j.bbrc.2009.11.035. PMID 19912991.
- ↑ Levy M, Futerman AH (2010). "Mammalian ceramide synthases". IUBMB Life. 62 (5): 347–56. doi:10.1002/iub.319. PMC 2858252 . PMID 20222015.
- ↑ Bonzón-Kulichenko E, Schwudke D, Gallardo N, Moltó E, Fernández-Agulló T, Shevchenko A, et al. (2009). "Central leptin regulates total ceramide content and sterol regulatory element binding protein-1C proteolytic maturation in rat white adipose tissue". Endocrinology. 150 (1): 169–78. doi: 10.1210/en.2008-0505 . hdl: 10115/3350 . PMID 18801905.
- ↑ Wang G, Silva J, Dasgupta S, Bieberich E (2008). "Long-chain ceramide is elevated in presenilin 1 (PS1M146V) mouse brain and induces apoptosis in PS1 astrocytes". Glia. 56 (4): 449–56. doi:10.1002/glia.20626. PMID 18205190. S2CID 5324040.