Stearoyl-CoA desaturase in development and disease.

Stearoyl‐CoA desaturases are ER‐resident enzymes that convert saturated fatty acids into monounsaturated fatty acids and have been studied using whole body, liver, skin, and adipose knockout models, but their specific role in the intestine is not well understood. Stearoyl‐CoA desaturase 1 (SCD1) gene and protein expression increases along the length of the intestine and was found to be induced by fasting followed by refeeding a high sucrose very low‐fat diet, similar to what has been established in liver. In addition to SCD1, stearoyl‐CoA desaturase 2 (SCD2) was also found to be expressed and regulated in a similar manner to SCD1 in the intestine. Intestine specific SCD1 knockout (iKO) mice were generated by crossing SCD1 floxed mice with mice expressing the Cre‐recombinase gene under the villin promoter. These mice have longer intestines and increased lipid absorption compared to floxed counterparts. In addition, iKO mice have increased bile acids, a more hydrophilic bile acid pool, and have increased plasma GLP‐1 and brown adipose tissue (BAT) Iodothyronine Deiodinase 2 (Dio2) gene expression. When placed on a low‐fat diet (10% fat) or a high‐fat diet (45% fat), the iKO mice had increased food intake and energy expenditure while maintaining similar or leaner body weights as their floxed counterparts. The iKO mice showed a trend of improved glucose tolerance. Overall, these results show that stearoyl‐CoA desaturases are expressed and regulated in the intestine. Knocking out SCD1 in an intestine‐specific manner leads to increased bile acids and these increased bile acids may contribute to the increased GLP‐1 and bile acid‐induced thermogenesis in BAT. When fed a high fat diet, iKO mice demonstrated an increased basal metabolic rate, increased food intake, and improved glucose tolerance.

The patterns of cellular fatty acid and sugar composition of 17 strains representing 17 species of rumen bacteria were examined.They were roughly classified into four groups (A, B, C, and D) on the basis of the patterns of their cellular fatty acid composition. Group A had major amounts of even-numbered straight-chain fatty acids besides monounsaturated, 3-hydroxy, and odd-numbered straight-chain fatty acids. Group B had relatively large amounts of fatty aldehydes besides straight-chain saturated and monounsaturated fatty acids. Group C had large amounts of 3-hydroxy and monounsaturated fatty acids besides straight-chain saturated fatty acids. Group D had abundantly iso- and anteiso-methyl- branched fatty acids besides straight-chain saturated fatty acids and fatty aldehydes.The 17 strains of rumen bacteria varied slightly in their patterns of sugar composition mostly. The cells of 10 of the 17 strains contained mostly glucose. Analysis of the cellular fatty acid will help to gain insight into the bacterial community structure in the rumen.

EDITORIAL FOCUSFat for life: new stories on old greaseDong ChengDong ChengPublished Online:01 Jun 2009https://doi.org/10.1152/ajpendo.90993.2008This is the final version - click for previous versionMoreSectionsPDF (40 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations due to the alarming epidemic in the modern world of obesity, dyslipidemia, and the parallel increasing prevalence of the related metabolic and cardiovascular diseases such as type 2 diabetes and atherosclerosis, the neutral lipids triglycerides and cholesteryl esters have a notorious reputation. The excessive accumulation of triglycerides reflects energy surplus, which ultimately causes the excessive adiposity that leads to obesity; in addition, the deposition of cholesteryl esters in the artery walls is an inevitable step for the fatty plaque formation hastening the development of atherosclerosis. Prevention and treatment of neutral lipid-related metabolic and cardiovascular diseases are major challenges for modern medicine.For many years, neutral lipids had been misperceived as “boring grease”. The primary reason is that these lipids are extremely hydrophobic. As a result, the biochemical studies regarding the synthesis and degradation of neutral lipids as well as the elucidation of their metabolic function were largely at the descriptive level. Enzymes involved in the metabolic flux of these lipids are often either intrinsic membrane proteins or favor an extremely hydrophobic environment, which has historically been difficult to isolate through traditional protein purification techniques. Fortunately, in the last two decades, powered with the revolution and the elegant combined use of methodologies in biochemistry, molecular biology, bioinformatics, cell biology, and forward and reverse genetics, we have witnessed an impressive transformation of the neutral lipid field. Today, many steps, if not all, of the neutral lipid metabolic pathways have been revealed in molecular detail. In addition, along with the improved analytic tools, the previously underappreciated complexity of neutral lipids has also started to be revealed. Cases have been identified that establish the relationship between specific species of neutral lipids and specific disease states. The purpose of this review series is to highlight such progress. Because of the richness of the science and the expansion of the field, nine excellent reviews have been divided into four separate parts, each of which will be published in this Journal over the next four consecutive issues.Part I: Pathways for De Novo Triglyceride Synthesis and Assimilation of Exogenous Dietary FatIn eukaryotes, triglycerides are synthesized through two major pathways, the glycerol phosphate pathway and the monoacylglycerol pathway. The glycerol phosphate pathway is believed to be present in the majority of cells and responsible for the de novo synthesis of triglycerides. In contrast, the monoacylglycerol pathway is known to play a major role in the small intestine for the absorption of exogenous dietary fat. The review by Drs. Takeuchi and Reue (7) details the complexity of the biochemistry and genetics of the glycerol phosphate pathway. The first committed step for this pathway is the acylation of glycerol-3-phosphate by glycerol phosphate acyltransferase (GPAT). A second fatty acid moiety is subsequently transferred to lysophosphatidic acid by acylglycerolphosphate acyltransferase (AGPAT) to produce phosphatidate, which in turn is converted to diacylglycerol through the action of phosphatidate phosphatase (PAP). PAP enzyme activity is conferred by the lipin protein family. Diacylglylcerol can either be further acylated by diacylglycerol acyltransferase (DGAT) to synthesize triglyceride or be used in phospholipid synthesis through the Kennedy pathway. In this review, the authors focus on three protein families: GPAT, AGPAT, and PAP enzymes.In the second review, Drs. Iqbal and Hussain (3) discuss the recent progress in the dietary fat absorption pathway. The major species of dietary fat is trigylceride. The remaining portion is comprised of a wide array of polar and nonpolar lipids, such as phospholipids, sterols, and many minor lipids including fat-soluble vitamins. The complicated process of dietary fat digestion and absorption can be divided into four sequential steps: the emulsification and hydrolysis of dietary fat in the lumen of the intestine, the uptake of hydrolyzed products by enterocytes, the resynthesis and packaging of fat into lipoproteins in the enterocytes, and last, the secretion of lipoproteins into circulation. In this context, the authors update the current knowledge pertaining to intestinal lipid absorption.Part II: Membrane Enzymes Crucial for the Synthesis of Triglycerides and Cholesteryl EstersThe second section will contain reviews regarding two types of membrane-associated enzymes known to be critical for the synthesis of triglycerides and cholesteryl esters: membrane-bound acyltransferases, which are intimately involved with the formation of neutral lipids and stearoyl-CoA desaturases (SCDs), whose function is to introduce double bonds to saturated long-chain fatty acids but is also believed to have a profound impact on neutral lipid synthesis. Membrane-bound acyl-CoA:cholesterol acyltransferase (ACAT), acyl-CoA:diacylglycerol acyltransferase (DGAT), and acyl-CoA:monoacylglycerol acyltransferase (MGAT) are enzymes responsible for the synthesis of the neutral lipids cholesteryl ester, triglyceride, and diacylglycerols, respectively. Albeit discovered more than 40 years ago, the molecular elucidation of these enzymes began only about 15 years ago by the landmark molecular cloning of ACAT1. In mammals, two ACAT isoforms exist, ACAT1 and ACAT2, which are encoded by two different genes. ACATs play important roles in cellular cholesterol homeostasis in various tissues. In the first review, Drs. Chang, Li, Chang, and Urano (1) review the current knowledge on ACAT-related research in two areas: 1) ACAT genes and proteins and 2) ACAT enzymes as drug targets for atherosclerosis and for Alzheimer's disease. In the second review, Drs. Shi and Cheng (6) cover the recent progress of molecular and functional elucidation of mammalian DGAT and MGAT enzymes. The metabolic complexity of triglyceride synthesis is reflected by the presence of multiple isoforms of DGAT and MGAT enzymes. To date, two DGATs and three MGATs have been identified, which have distinct catalytic properties, subcellular localization, and tissue distribution and are believed to have multiple functions, such as intestinal fat absorption, lipoprotein assembly, adipose tissue formation, signal transduction, satiety, and lactation. Recent data from studies using knockout mice also indicate that selective inhibition of MGAT or DGAT enzymes may provide novel strategies for treating obesity and related metabolic diseases. The third review, by Drs. Turkish and Sturley (8), highlights the genetic dissections of neutral lipid function in a variety of model systems, including yeast, fly, worm, and mouse. This review provides a philosophical perspective about how and why neutral lipids exist as an important class of lipid for the organism. In addition to triglyceride and cholesteryl ester, two types of neutral lipids that are emphasized in other reviews, the authors also discuss acyl-CoA:wax alcohol acyltransferase (AWAT), another membrane-bound acyltransferase that is responsible for the synthesis of wax esters and which is believed to play an important role in maintaining skin integrity.The last review in Part II, by Drs. Paton and Ntambi (4), covers the topic of SCD. SCD is an enzyme that catalyzes the D9-cis desaturation of a wide range of long-chain fatty acyl-CoA substrates. Characterization of SCD1-deficient mice has revealed the essential role of de novo synthesized oleate in the formation of many neutral lipids, including cholesteryl esters, triglycerides, and wax esters. In addition, SCD1 deletion in mice also leads to a reduction of body weight, decreased adiposity, improved lipid profile, and increased insulin sensitivity, thereby establishing SCD1 as a putative pharmaceutical target for the treatment of diabetes and obesity.Part III: Lipolytic Degradation of Neutral Lipids and Its Metabolic ImplicationIn contrast to the preceding two parts, which focus on the synthesis of neutral lipids, Part III deals with lipolytic degradation pathways for neutral lipids. Depending on the locale of the neutral lipids, they can be degraded either extracellularly, such as in the plasma, or intracellularly, such as within the adipocyte. In the first review in this section, Drs. Wang and Eckel (9) review the current state of knowledge regarding lipoprotein lipase (LPL), an extracellular lipase. Although many tissues synthesize this enzyme, LPL functions in the capillary endothelium. LPL is the primary enzyme responsible for the hydrolysis of the triglyceride core of chylomicrons and very-low-density lipoproteins. The resulting free fatty acids and monoacylglycerols are subsequently taken up by the local adjacent tissues for various functions. Unique to LPL, this lipase exerts critical functions in both the anabolic and catabolic phases of triglyceride metabolism and, hence, is divergently regulated by different metabolic cues in a tissue-specific manner. The mechanisms pertaining to the regulation and physiological implications for LPL have been revealed by various transgenic and knockout models that are systematically reviewed by the authors.The review by Drs. Schweiger, Lass, Zimmermann, and Zechner (5) delves into a recently discovered aspect of the intracellular lipolytic pathway in adipose tissue. The discussion is focused on adipose triglyceride lipase (ATGL) and its regulator CGI-58/ABHD5. For many years, hormone-sensitive lipase (HSL) was thought to be the only significant lipase in white adipose tissue (WAT) responding to catabolic hormones. However, recent cloning and knockout data indicate that ATGL is an additional essential player for lipolysis in WAT. Interestingly, ATGL is activated by its partner CGI-58/ABHD5, an adiposome-associated protein. In their review, the authors present an extended discussion of recent data showing that mutations in ATGL gene and CGI-58/ABHD5 lead to various forms of neutral lipid storage disease (NLSD) in human patients, further indicating that the ATGL-mediated lipolytic system serves a pivotal role in neutral lipid metabolism.Part IV: Analytic Examples of Complexity of Neutral Lipid SpeciesIn the final part of this cluster of reviews on neutral lipids, Drs. Gross and Han (2) discuss the application of shotgun lipidomics, a novel mass spectrometry-based technology, in the elucidation of the previously underappreciated complexity of neutral lipids. The power of shotgun lipidomics lies in its high sensitivity and its exquisite discerning ability. The review first summarizes the basic principles of shotgun lipidomics. The discussion emphasizes the technical breakthroughs for the analysis of neutral lipids, which were previously difficult to analyze by mass spectrometry. In the second part, specific illustrative cases are discussed regarding the identification of subpopulations of lipids and their relationship to the disease or physiological states.I thank Dr. Ta-Yuan Chang for encouragement, advice, and discussion during the course of compiling this Review Series. I also express my gratitude to Drs. Charles Lang and Yuguang Shi for their warm invitation of this Review Series to be published in American Journal of Physiology-Endocrinlogy and Metabolism and to all the contributors for their commitment and dedication to the timely delivery of their excellent reviews.REFERENCES1 Chang TY, Li BL, Chang CC, Urano Y. Acyl-coenzyme A:cholesterol acyltransferases. Am J Physiol Endocrinol Metab (January 13, 2009). doi:10.1152/ajpendo.90926.2008.Link | ISI | Google Scholar2 Gross RW, Han X. Shotgun lipidomics of neutral lipids as an enabling technology for elucidation of lipid-related diseases. Am J Physiol Endocrinol Metab (January 6, 2009). doi:10.1152/ajpendo.90970.2008.Link | ISI | Google Scholar3 Iqbal J, Hussain M. Intestinal lipid absorption. Am J Physiol Endocrinol Metab (January 21, 2009). doi:10.1152/ajpendo.90899.2008.Link | ISI | Google Scholar4 Paton CM, Ntambi JM. Biochemical and physiological function of stearoyl-CoA desaturase. Am J Physiol Endocrinol Metab (December 9, 2008). doi:10.1152/ajpendo.90897.2008.Link | ISI | Google Scholar5 Schweiger M, Lass A, Zimmermann R, Eichmann TO, Zechner R. Neutral lipid metabolism. Am J Physiol Endocrinol Metab (April 28, 2009). doi:10.1152/ajpendo.00099.2009.Link | ISI | Google Scholar6 Shi Y, Cheng D. Beyond triglyceride synthesis: the dynamic functional roles of MGAT and DGAT enzymes in energy metabolism. Am J Physiol Endocrinol Metab (December 30, 2008). doi:10.1152/ajpendo.90949.2008.Link | ISI | Google Scholar7 Takeuchi X, Reue X. Biochemistry, physiology, and genetics of GPAT, AGPAT, and lipin. Am J Physiol Endocrinol Metab (March 31, 2009). doi:10.1152/ajpendo.90958.2008.Link | ISI | Google Scholar8 Turkish AR, Sturley SL. The genetics of neutral lipid biosynthesis, an evolutionary perspective. Am J Physiol Endocrinol Metab (December 30, 2008). doi:10.1152/ajpendo.90898.2008.Link | ISI | Google Scholar9 Wang X, Eckel X. Lipoprotein lipase: from gene to obesity. Am J Physiol Endocrinol Metab (March 24, 2009). doi:10.1152/ajpendo.90920.2008.Link | ISI | Google ScholarAUTHOR NOTESAddress for reprint requests and other correspondence: D. Cheng, Dept. of Metabolic Diseases, Bristol-Myers Squibb Co., PO Box 5400, Princeton, NJ 08543 (E-mail: [email protected]) Download PDF Back to Top Next FiguresReferencesRelatedInformation More from this issue > Volume 296Issue 6June 2009Pages E1181-E1182 Copyright & PermissionsCopyright © 2009 the American Physiological Societyhttps://doi.org/10.1152/ajpendo.90993.2008PubMed19106246History Received 12 December 2008 Accepted 19 December 2008 Published online 1 June 2009 Published in print 1 June 2009 Metrics

Stearoyl-CoA desaturase is a key regulator in fatty acid metabolism that catalyzes the desaturation of stearic acid to oleic acid and controls the intracellular levels of monounsaturated fatty acids (MUFAs). Two stearoyl-CoA desaturases (SCD, Δ9 desaturases) genes were identified in an Antarctic copepod, Tigriopus kingsejongensis, that was collected in a tidal pool near the King Sejong Station, King George Island, Antarctica. Full-length complementary DNA (cDNA) sequences of two T. kingsejongensis SCDs (TkSCDs) were obtained from next-generation sequencing and isolated by reverse transcription PCR. DNA sequence lengths of the open reading frames of TkSCD-1 and TkSCD-2 were determined to be 1110 and 681bp, respectively. The molecular weights deduced from the corresponding genes were estimated to be 43.1kDa (TkSCD-1) and 26.1kDa (TkSCD-2). The amino acid sequences were compared with those of fatty acid desaturases and sterol desaturases from various organisms and used to analyze the relationships among TkSCDs. As assessed by heterologous expression of recombinant proteins in Escherichia coli, the enzymatic functions of both stearoyl-CoA desaturases revealed that the amount of C16:1 and C18:1 fatty acids increased by greater than 3-fold after induction with isopropyl β-D-thiogalactopyranoside. In particular, C18:1 fatty acid production increased greater than 10-fold in E. coli expressing TkSCD-1 and TkSCD-2. The results of this study suggest that both SCD genes from an Antarctic marine copepod encode a functional desaturase that is capable of increasing the amounts of palmitoleic acid and oleic acid in a prokaryotic expression system.

With three-dimensional growth conditions, multicellular tumor spheroids reproduce several parameters of the tumor microenvironment, including oxygen and nutrient gradients, characteristic of poorly vascularized tumor regions. 3D high content screening (HCS) identified compounds that selectively kill tumor cells in the inner core of tumor cell spheroids by targeting the Stearoyl CoA Desaturase 1 (SCD1) pathway. SCD1 catalyzes the rate-limiting step in the production of mono-unsaturated fatty acids (MUFAs). Cancer cells are dependent on higher levels of MUFAs compared to normal cells and SCD1 is highly expressed in multiple tumor types. Changes in the MUFA / SFA (saturated fatty acid) ratio alters lipid biosynthesis and thus triggers cellular (ER) stress and induces the Unfolded Protein Response. Although the lead compound was very effective in vitro, it had unfavorable PK and physical chemistry properties, including low permeability and solubility and very high lipophilicity. This led to insufficient oral bioavailability, which could be overcome by optimization of PK and physical chemistry properties. Here, we report on the in vitro/in vivo effects of our 3D HCS compounds which showed high potency in the 3D spheroid inner core death assay with T47D breast cancer cells. In this in vitro model compound-induced inner core cell death is enhanced by SCD1 substrates palmitic or stearic acid and rescued by the SCD1 products palmitoleic or oleic acid. Furthermore, the effects can be reproduced in 2D cultures, which become increasingly sensitive to inhibition by our 3D HCS compounds with decreasing FBS concentration in the culture medium and this effect can also be rescued by addition of MUFAs but not of palmitic acid. Mode of action analysis showed that our compounds reduced palmitoleoyl- or oleoyl-CoA levels and simultaneously increased saturated fatty acyl-CoAs of palmitate or stearate in several cell lines as well as in vivo. In the sensitive T47D cells, the compounds induced expression of stress response genes and genes related to lipid metabolism. While these results support the SCD1 pathway as target for our 3D HCS compounds, we also observed striking differences to published SCD1 inhibitors suggesting a new cancer target beyond SCD1. Thus, further validation of our inhibitors in vitro and in vivo will be required, but these results suggest that 3D spheroid cultures may be a valuable tool for elucidation of new drug targets for cancer therapy. Citation Format: Sylvia Gruenewald, Carolyn Sperl, Patrick Steigemann, Alexander Walter, Sylvia Zacharias, Uwe Eberspaecher, Roland Neuhaus, Ludwig Zorn, Wolfgang Schwede, Kai Thede, Sven Christian. 3D spheroid screen yields SCD1 pathway inhibitors for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4989. doi:10.1158/1538-7445.AM2017-4989

Lipids are ubiquitous molecules, serving as the structural building blocks for membranes, messengers in cell signaling, or compounds for energy storage. Their functional versatility relies in part on the presence of one or more double bonds in the long lipid carbon chains. The more double bonds there are in a lipid, the more unsaturated it is; and the more unsaturated lipids there are in a membrane, the more flexible the membrane tends to be. Cells take advantage of this property by fine-tuning the levels of saturated and unsaturated fatty acids in membranes to external conditions and required membrane function.

Milkfish, a commercially important culture teleost in Taiwan, are known to be less tolerant to the cold, and the culture industry in this country has often suffered from the mass mortality of winterkills. The membrane lipid desaturation and stearoyl-CoA desaturase expression in milkfish under cold shock were investigated. Milkfish were initially acclimated at 25℃ and then exposed to cold shock of 15℃. The proportions of saturated fatty acids (16: 0 and 18: 0) in the hepatic microsomes of milkfish at 15℃ were lower, while those of monounsaturated fatty acids (16: 1 and 18: 1) were significantly higher than the control fish at 25℃. Δ^9 desaturation index gradually increased in the early period of cold shock and peaked on day 5, followed by slight decrease thereafter. Concurrent changes in Δ^9 desaturation index (16: 1/16: 0 and 18: 1/18: 0) and the proportion of fatty acids in the hepatic microsomes of milkfish were further demonstrated. The trend of stearoyl-CoA desaturase activity changes was found parallel to those of unsaturated fatty acids composition and Δ^9 desaturation index, though 1-day time lag was evident. These parameters are significantly correlated among them, and Δ^9 desaturation index can accordingly be employed to represent the degree of fatty acid desaturation, stearoyl-CoA desaturase activities and membrane fluidity as well. The expression of stearoyl-CoA desaturase mRNA in milkfish is specifically induced by a low temperature, and those in stearoyl-CoA desaturase activities were parallel to the changes in desaturase mRNA transcript. The findings suggested that the increases in the membrane lipid desaturation and stearoyl-CoA desaturase activities in milkfish under cold shock were in accordance with other teleosts being reported elsewhere, and the quantitative compensatory mechanisms are predominantly involved in the acclimation process of cold shock in this species.

BackgroundThe composition of intramuscular fat depends on genetic and environmental factors, including the diet. In pigs, we identified a haplotype of three SNP mutations in the stearoyl-coA desaturase (SCD) gene promoter associated with higher content of monounsaturated fatty acids in intramuscular fat. The second of these three SNPs (rs80912566, C > T) affected a putative retinol response element in the SCD promoter. The effect of dietary vitamin A restriction over intramuscular fat content is controversial as it depends on the pig genetic line and the duration of the restriction. This study aims to investigate changes in the muscle transcriptome in SCD rs80912566 TT and CC pigs fed with and without a vitamin A supplement during the fattening period.ResultsVitamin A did not affect carcass traits or intramuscular fat content and fatty acid composition, but we observed an interaction between vitamin A and SCD genotype on the desaturation of fatty acids in muscle. As reported before, the SCD-TT pigs had more monounsaturated fat than the SCD-CC animals. The diet lacking the vitamin A supplement enlarged fatty acid compositional differences between SCD genotypes, partly because vitamin A had a bigger effect on fatty acid desaturation in SCD-CC pigs (positive) than in SCD-TT and SCD-TC animals (negative). The interaction between diet and genotype was also evident at the transcriptome level; the highest number of differentially expressed genes were detected between SCD-TT pigs fed with the two diets. The genes modulated by the diet with the vitamin A supplement belonged to metabolic and signalling pathways related to immunity and inflammation, transport through membrane-bounded vesicles, fat metabolism and transport, reflecting the impact of retinol on a wide range of metabolic processes.ConclusionsRestricting dietary vitamin A during the fattening period did not improve intramuscular fat content despite relevant changes in muscle gene expression, both in coding and non-coding genes. Vitamin A activated general pathways of retinol response in a SCD genotype-dependant manner, which affected the monounsaturated fatty acid content, particularly in SCD-CC pigs.

Background: Activation of lipid metabolism is an early event of carcinogenesis and a central hallmark of many cancers including breast cancer. Recent findings argue that stearoyl CoA desaturase-1 (SCD1), a key regulator of the fatty acid (FA) composition and the endoplasmic reticulum resident enzyme that converts saturated FA (SFA) into monounsaturated FA (MUFA) is a novel regulator of carcinogenesis. The distinctive lipids composition of membrane in cancer cells and the biological functions of SCD1, however, still remain uncertain. Imaging mass spectrometry (IMS) is a mass spectrometry-based analyzing technique that enables visualization of the individual molecules without requiring antibodies. It allows comprehensive detection of a wide range of biomolecules, such as lipids. We attempted to visualize the localization of lipids in breast cancer by IMS for better understanding of cancer proliferation. Materials and methods: 13 specimens were obtained from the primary breast cancer patients. All were Japanese woman and aged 41–86 years (mean 61.5y.o.). Only one patient received preoperative systematic therapy. 6 were estrogen receptor (ER) and/or progesterone receptor (PgR) positive and human epidermal growth factor receptor 2 (HER2) negative, 2 were ER and/or PgR positive and HER2 positive, 2 were both ER and PgR negative and HER2 positive and 2 were triple negative. IMS: Samples were immediately chilled in liquid Hexan and stored at −80°. All specimens were sliced into 10 mm thin sections, mounted onto one indium-tin oxide-coated glass slides (Bruker Daltonics) and then sprayed by 2,5-Dihydroxybenzoic acid. Matrix assisted laser desorption ionization (MALDI) technique was used as a soft ionization method. We used time of flight (TOF)/TOF type instrument (Ultraflex, Bruker Daltonics) and all the spectrum were acquired automatically using Fleximaging software (Bruker Daltonics). Each spectral intensity at any mass-to-charge ratio (m/z) was measured at 16 regions of interest (ROI); 13 ROI were picked up from cancerous parts and 3 were from non-cancerous parts. Spectral intensities were compared and statistical analysis was performed by Mann Whitney test. The software was also used to create two-dimensional ion-density maps. Results: In the cancerous parts of all the 13 specimens, two distinct peaks of the molecular ions were detected at m/z 798.5 and 810.5, which were not found in the non-cancerous parts. Median intensity of the molecular ions at m/z 798.5 and 810.5 were 38.9 and 3.18 in the cancerous part, while they were 0.84 and 1.02 in the non-cancerous part (p=0.010 and 0.015, respectively). Tandem mass spectrometry analysis for these two molecules revealed that they were two kinds of phosphatidylcholine (PC), PC (16:0/18:1) and PC (18:0/18:1). Localization of the individual PC was visualized by means of IMS, which showed that in cancerous part accumulation of PCs containing MUFA was more pronounced than those containing SFA only. Conclusion: Two kinds of PC containing MUFA were found to highly accumulate in cancerous parts, which may suggest involvement of SCD1 in the membrane composition regulation and cancer proliferation. Further studies may thus be warranted to explore the relation between PC localization and the SCD1 expression. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-05-05.

Stearoyl-CoA desaturase (SCD) is a rate-limiting enzyme in the biosynthesis of monounsaturated fatty acids. It catalyzes the delta 9-cis desaturation of acyl-CoA substrates, the preferred substrates being palmitoyl (C16:0)-CoA and stearoyl(C18:0)CoA, which are converted to palmitoleoyl (C16:1n-7)-CoA and oleoyl-CoA (C18:1n9), respectively (1). These monounsaturated fatty acids are used as substrates for the synthesis of triglycerides, wax esters, cholesteryl esters and membrane phospholipids. The ratio of stearic acid to oleic acid has been implicated in the regulation of cell growth and differentiation through effects on membrane fluidity and signal transduction (2). Monounsaturated fatty acids also influence apoptosis (3) and may have some role in mutagenesis in some tumors (4, 5). Overall, SCD expression affects the fatty acid composition of membrane phospholipids, triglycerides and cholesterol ester, resulting in changes in membrane fluidity, lipid metabolism and obesity (2). Thus, the regulation of SCD is of considerable physiological importance and high SCD activity is associated with a wide range of diseases including cardiovascular disease, obesity, diabetes, neurological disease, skin disease and cancer.

We previously identified stearoyl-CoA desaturase 2 (SCD2) as a new member of the family of genes that are transcriptionally regulated in response to changing levels of nuclear sterol regulatory element binding proteins (SREBPs) or adipocyte determination and differentiation factor 1 (ADD1). A novel sterol regulatory element (SRE) (5'-AGCAGATTGTG-3') identified in the proximal promoter of the mouse SCD2 gene is required for induction of SCD2 promoter-reporter genes in response to cellular sterol depletion (Tabor, D. E., Kim, J. B., Spiegelman, B. M., and Edwards, P. A. (1998) J. Biol. Chem. 273, 22052-22058). In this report, we demonstrate that this novel SRE is both present in the promoter of the SCD1 gene and is critical for the sterol-dependent transcription of SCD1 promoter-reporter genes. Two conserved cis elements (5'-CCAAT-3') lie 5 and 48 base pairs 3' of the novel SREs in the promoters of both the SCD1 and SCD2 murine genes. Mutation of either of these putative NF-Y binding sites attenuates the transcriptional activation of SCD1 or SCD2 promoter-reporter genes in response to cellular sterol deprivation. Induction of both reporter genes is also attenuated when cells are cotransfected with dominant-negative forms of either NF-Y or SREBP. In addition, we demonstrate that the induction of SCD1 and SCD2 mRNAs that occurs during the differentiation of 3T3-L1 preadipocytes to adipocytes is paralleled by an increase in the levels of ADD1/SREBP-1c and that the SCD1 and SCD2 mRNAs are induced to even higher levels in response to ectopic expression of ADD1/SREBP-1c. We conclude that transcription of both SCD1 and SCD2 genes is responsive to cellular sterol levels and to the levels of nuclear SREBP/ADD1 and that transcriptional induction requires three spatially conserved cis elements, that bind SREBP and NF-Y. Additional studies demonstrate that maximal transcriptional repression of SCD2 reporter genes in response to an exogenous polyunsaturated fatty acid is dependent upon the SRE and the adjacent CCAAT motif.

Susceptibility of Podocytes to Palmitic Acid Is Regulated by Stearoyl-CoA Desaturases 1 and 2

Milk fatty acid composition determines milk quality and the health of consumers. Stearoyl-CoA desaturase (SCD) gene controls lipid metabolism in the mammary gland, which plays an essential role in catalyzing saturated fatty acids (SFA) into monounsaturated fatty acids (MUFA). This study aimed to analyze the genetic diversity of the SCD gene and its effect on the milk fatty acid quality of Holstein Friesian (HF). Genetic variants were identified on 226 HF cattle from various dairy breeding Stations in West Java, Central Java, and East Java in Indonesia. Blood samples were extracted and amplified using Real-Time Polymerase Chain Reaction (RT-PCR) technique based on TaqMan Probe to determine the genotype of the SCD gene at g.10153A>G locus. Milk samples were analyzed by Gas Chromatography and Mass Spectrometry (GCMS) on 48 lactating cows. The SCD g.10153A>G produced three genotypes, namely AA (0.112), AG (0.640), and GG (0.271); and two alleles, namely A (0.409) and G (0.591). Genotype polymorphism of the SCD g.10153A>G had a significant effect (p<0.05) on SFA, including propionic acid (C3:0), butyric acid (C4:0), caprylic acid (C8:0), and pentacosylic acid (C25:0); and MUFA including hexadecenoic acid (C16:1) and total fatty acids. The SCD g.10153A>G SNP (AG genotype) could be one of the candidates as a genetic marker to assist selection in reducing SFA and increasing MUFA in the milk content of HF cows in Indonesia.

ENO1 promotes Acute Myeloid Leukemia progression through SCD1-mediated lipid metabolism reprogramming

Hepatic lipid overloading mainly in the form of triglycerides is considered a prerequisite for the development of nonalcoholic fatty liver disease (NAFLD). However, triglyceride accumulation in the liver in response to lipid overflow may represent a protective mechanism against lipotoxicity. Our aims were to assess the fundamental cellular mechanisms that link lipid compartmentation in hepatocytes to liver damage and disease progression in NAFLD by using both in vivo dietary models of NAFLD and in vitro cell models of lipid overloading. Exposure of murine or human hepatocytes to monounsaturated fatty acids (MUFAs) resulted in lipid accumulation without changes in cell viability. In contrast, cell incubation with saturated fatty acids (SFAs) significantly decreased cell viability and increased caspase activation and apoptosis, with only minor lipid droplet accumulation. Genetic or pharmacological inhibition of stearoyl-CoA desaturase-1 (SCD1), the enzyme that converts SFA to MUFA, sensitized cells to SFA-induced apoptosis. Hepatic SCD1 expression increased in experimental steatosis resulting from high fat diet and decreased in a methionine-choline-deficient (MCD) dietary model of steatohepatitis resulting in the latter situation in significantly increased hepatic SFA levels. SCD1(-/-) mice on the MCD diet had decreased steatosis and markedly increased hepatocellular apoptosis, liver injury, and fibrosis compared with the SCD1(+/+), whereas MUFA feeding prevents the MCD-induced injury. In conclusion, this study suggests hepatic SCD1 plays a key role in prevention of steatohepatitis by partitioning excess lipid into MUFA that can be safely stored. This concept has important implications for the development of novel treatment strategies for patients with this condition.