SCD5 expression correlates with prognosis and response to neoadjuvant chemotherapy in breast cancer.

Neoadjuvant chemotherapy (NACT) represents a standard option for breast cancer. Unfortunately, about 55-80% of breast cancer patients do not have a favorable response to chemotherapy. Highly specific tumor biomarker that can predict the pathological response to neoadjuvant chemotherapy is lacking. Stearoyl-CoA desaturase 5 (SCD5) is an integral membrane protein of the endoplasmic reticulum that participates in lipid metabolism. Previous studies on the role of SCD5 in human cancers drew different conclusions. Therefore, the role of SCD5 in breast cancer remains unclear. Our study aims to understand its expression signature, prognosis value and correlation with pathological response to NACT in breast cancer using bioinformatics from public databases. Analysis of samples from public databases showed that SCD5 expression was down-regulated in some human cancers including breast cancer, and low expression of SCD5 was associated with more aggressive breast cancer phenotypes. Survival analysis revealed that SCD5 expression was related to prognosis in breast cancer. Integrated analysis of multiple public datasets indicated that SCD5 expression signature was associated with pathological response to NACT, particularly in TNBC. Based on functional enrichment analysis, the most affected biological functions in high SCD5-expressing breast cancer tissues were involved in negative regulation of cell cycle. Moreover, a significantly negative correlation between SCD5 expression and several cell cycle regulators was noted. Taken together, SCD5 was involved in the development and progression of breast cancer and might be a predictive biomarker for response to NACT. In conclusion, SCD5 could serve as a predictive biomarker of pathological response to NACT and play a carcinostatic role in breast cancer. These results provided us with clues to better understand SCD5 from the perspective of bioinformatics and highlighted the clinical importance of SCD5 in breast cancer, especially triple negative breast cancer (TNBC).

High-fructose diet-induced hepatic expression of the Scd1 gene is associated with increased acetylation of histones H3 and H4 and the binding of ChREBP at the Scd1 promoter in rats.

Stearoyl-CoA desaturase-1 (SCD1) is a key enzyme in the biosynthesis of monounsaturated fatty acids, and the expression of the Scd1 gene is induced by the intake of the lipogenic sugar fructose. We examined the effects of a high-fructose diet on hepatic acetylation of histones H3 and H4 and the binding of carbohydrate response element-binding protein (ChREBP) on the Scd1 gene promoter in rats. Rats were fed a control diet or a high-fructose diet for 10 days. The intake of a high-fructose diet significantly increased histone H3 and H4 acetylation and ChREBP binding to the Scd1 gene promoter as well as the amount of triglyceride and the expression of the Scd1 gene. These results suggest that short-term intake of high fructose upregulates expression of Scd1 by enhancing acetylation of histones H3 and H4 and binding of ChREBP at the Scd1 promoter.

Metabolic rerouting via SCD1 induction impacts X-linked adrenoleukodystrophy.

X-linked adrenoleukodystrophy (ALD) is a progressive neurodegenerative disease caused by mutations in ABCD1, the peroxisomal very long-chain fatty acid (VLCFA) transporter. ABCD1 deficiency results in accumulation of saturated VLCFAs. A drug screen using a phenotypic motor assay in a zebrafish ALD model identified chloroquine as the top hit. Chloroquine increased expression of stearoyl-CoA desaturase-1 (scd1), the enzyme mediating fatty acid saturation status, suggesting that a shift toward monounsaturated fatty acids relieved toxicity. In human ALD fibroblasts, chloroquine also increased SCD1 levels and reduced saturated VLCFAs. Conversely, pharmacological inhibition of SCD1 expression led to an increase in saturated VLCFAs, and CRISPR knockout of scd1 in zebrafish mimicked the motor phenotype of ALD zebrafish. Importantly, saturated VLCFAs caused ER stress in ALD fibroblasts, whereas monounsaturated VLCFA did not. In parallel, we used liver X receptor (LXR) agonists to increase SCD1 expression, causing a shift from saturated toward monounsaturated VLCFA and normalizing phospholipid profiles. Finally, Abcd1-/y mice receiving LXR agonist in their diet had VLCFA reductions in ALD-relevant tissues. These results suggest that metabolic rerouting of saturated to monounsaturated VLCFAs may alleviate lipid toxicity, a strategy that may be beneficial in ALD and other peroxisomal diseases in which VLCFAs play a key role.

Interplay between Thyroid Hormones and Stearoyl-CoA Desaturase 1 in the Regulation of Lipid Metabolism in the Heart.

Stearoyl-CoA desaturase 1 (SCD1), an enzyme that is involved in the biosynthesis of monounsaturated fatty acids, induces the reprogramming of cardiomyocyte metabolism. Thyroid hormones (THs) activate both lipolysis and lipogenesis. Many genes that are involved in lipid metabolism, including Scd1, are regulated by THs. The present study used SCD1 knockout (SCD1-/-) mice to test the hypothesis that THs are important factors that mediate the anti-steatotic effect of SCD1 downregulation in the heart. SCD1 deficiency decreased plasma levels of thyroid-stimulating hormone and thyroxine and the expression of genes that regulate intracellular TH levels (i.e., Slc16a2 and Dio1-3) in cardiomyocytes. Both hypothyroidism and SCD1 deficiency affected genomic and non-genomic TH pathways in the heart. SCD1 deficiency is known to protect mice from genetic- or diet-induced obesity and decrease lipid content in the heart. Interestingly, hypothyroidism increased body adiposity and triglyceride and diacylglycerol levels in the heart in SCD1-/- mice. The accumulation of triglycerides in cardiomyocytes in SCD1-/- hypothyroid mice was caused by the activation of lipogenesis, which likely exceeded the upregulation of lipolysis and fatty acid oxidation. Lipid accumulation was also observed in the heart in wildtype hypothyroid mice compared with wildtype control mice, but this process was related to a reduction of triglyceride lipolysis and fatty acid oxidation. We also found that simultaneous SCD1 and deiodinase inhibition increased triglyceride content in HL-1 cardiomyocytes, and this process was related to the downregulation of lipolysis. Altogether, the present results suggest that THs are an important part of the mechanism of SCD1 in cardiac lipid utilization and may be involved in the upregulation of energetic metabolism that is associated with SCD1 deficiency.

Sodium Orthovanadate Changes Fatty Acid Composition and Increased Expression of Stearoyl-Coenzyme A Desaturase in THP-1 Macrophages.

Vanadium compounds are promising antidiabetic agents. In addition to regulating glucose metabolism, they also alter lipid metabolism. Due to the clear association between diabetes and atherosclerosis, the purpose of the present study was to assess the effect of sodium orthovanadate on the amount of individual fatty acids and the expression of stearoyl-coenzyme A desaturase (SCD or Δ9-desaturase), Δ5-desaturase, and Δ6-desaturase in macrophages. THP-1 macrophages differentiated with phorbol 12-myristate 13-acetate (PMA) were incubated in vitro for 48 h with 1 µM or 10 µM sodium orthovanadate (Na3VO4). The estimation of fatty acid composition was performed by gas chromatography. Expressions of the genes SCD, fatty acid desaturase 1 (FADS1), and fatty acid desaturase 2 (FADS2) were tested by qRT-PCR. Sodium orthovanadate in THP-1 macrophages increased the amount of saturated fatty acids (SFA) such as palmitic acid and stearic acid, as well as monounsaturated fatty acids (MUFA)-oleic acid and palmitoleic acid. Sodium orthovanadate caused an upregulation of SCD expression. Sodium orthovanadate at the given concentrations did not affect the amount of polyunsaturated fatty acids (PUFA) such as linoleic acid, arachidonic acid, eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA), and docosahexaenoic acid (DHA). In conclusion, sodium orthovanadate changed SFA and MUFA composition in THP-1 macrophages and increased expression of SCD. Sodium orthovanadate did not affect the amount of any PUFA. This was associated with a lack of influence on the expression of FADS1 and FADS2.

Engineering of Chinese hamster ovary cell lipid metabolism results in an expanded ER and enhanced recombinant biotherapeutic protein production.

Chinese hamster ovary (CHO) cell expression systems have been exquisitely developed for the production of recombinant biotherapeutics (e.g. standard monoclonal antibodies, mAbs) and are able to generate efficacious, multi-domain proteins with human-like post translational modifications at high concentration with appropriate product quality attributes. However, there remains a need for development of new CHO cell expression systems able to produce more challenging secretory recombinant biotherapeutics at higher yield with improved product quality attributes. Amazingly, the engineering of lipid metabolism to enhance such properties has not been investigated even though the biosynthesis of recombinant proteins is at least partially controlled by cellular processes that are highly dependent on lipid metabolism. Here we show that the global transcriptional activator of genes involved in lipid biosynthesis, sterol regulatory element binding factor 1 (SREBF1), and stearoyl CoA desaturase 1 (SCD1), an enzyme which catalyzes the conversion of saturated fatty acids into monounsaturated fatty acids, can be overexpressed in CHO cells to different degrees. The amount of overexpression obtained of each of these lipid metabolism modifying (LMM) genes was related to the subsequent phenotypes observed. Expression of a number of model secretory biopharmaceuticals was enhanced between 1.5-9 fold in either SREBF1 or SCD1 engineered CHO host cells as assessed under batch and fed-batch culture. The SCD1 overexpressing polyclonal pool consistently showed increased concentration of a range of products. For the SREBF1 engineered cells, the level of SREBF1 expression that gave the greatest enhancement in yield was dependent upon the model protein tested. Overexpression of both SCD1 and SREBF1 modified the lipid profile of CHO cells and the cellular structure. Mechanistically, overexpression of SCD1 and SREBF1 resulted in an expanded endoplasmic reticulum (ER) that was dependent upon the level of LMM overexpression. We conclude that manipulation of lipid metabolism in CHO cells via genetic engineering is an exciting new approach to enhance the ability of CHO cells to produce a range of different types of secretory recombinant protein products via modulation of the cellular lipid profile and expansion of the ER.

Let-7c regulates proliferation and osteodifferentiation of human adipose-derived mesenchymal stem cells under oxidative stress by targeting SCD-1.

Osteoporosis is a progressive bone disease characterized by decreased bone mass and density, which usually parallels a reduced antioxidative capacity and increased reactive oxygen species formation. Adipose-derived mesenchymal stem cells (ADMSCs), a population of self-renewing multipotent cells, are a well-recognized source of potential bone precursors with significant clinical potential for tissue regeneration. We previously showed that overexpressing stearoyl-CoA desaturase 1 (SCD-1) promotes osteogenic differentiation of mesenchymal stem cells. Micro-RNAs (miRNAs) are noncoding RNAs recently recognized to play key roles in many developmental processes, and miRNA let-7c is downregulated during osteoinduction. We found that let-7c was upregulated in the serum of patients with postmenopausal osteoporosis compared with healthy controls. Levels of let-7c during osteogenic differentiation of ADMSCs were examined under oxidative stress in vitro and found to be upregulated. Overexpression of let-7c inhibited osteogenic differentiation, whereas inhibition of let-7c function promoted this process, evidenced by increased expression of osteoblast-specific genes, alkaline phosphatase activity, and matrix mineralization. The luciferase reporter assay was used to validate SCD-1 as a target of let-7c. Further experiments showed that silencing of SCD-1 significantly attenuated the effect of let-7c inhibitor on osteoblast markers, providing strong evidence that let-7c modulates osteogenic differentiation by targeting SCD-1. Inhibition of let-7c promoted the translocation of ß-catenin into nuclei, thus activating Wnt/ß-catenin signaling. Collectively, these data suggest that let-7c is induced under oxidative stress conditions and in osteoporosis, reducing SCD-1 protein levels, switching off Wnt/ß-catenin signaling, and inhibiting osteogenic differentiation. Thus, let-7c may be a potential therapeutic target in the treatment of osteoporosis and especially postmenopausal osteoporosis.

Inhibition of Stearoyl-CoA desaturase 1 reverts BRAF and MEK inhibition-induced selection of cancer stem cells in BRAF-mutated melanoma.

BACKGROUND: Combination therapy with BRAF and MEK inhibitors significantly improves survival in BRAF mutated melanoma patients but is unable to prevent disease recurrence due to the emergence of drug resistance. Cancer stem cells (CSCs) have been involved in these long-term treatment failures. We previously reported in lung cancer that CSCs maintenance is due to altered lipid metabolism and dependent upon Stearoyl-CoA-desaturase (SCD1)-mediated upregulation of YAP and TAZ. On this ground, we investigated the role of SCD1 in melanoma CSCs. METHODS: SCD1 gene expression data of melanoma patients were downloaded from TCGA and correlated with disease progression by bioinformatics analysis and confirmed on patient's tissues by qRT-PCR and IHC analyses. The effects of combination of BRAF/MEKi and the SCD1 inhibitor MF-438 were monitored by spheroid-forming and proliferation assays on a panel of BRAF-mutated melanoma cell lines grown in 3D and 2D conditions, respectively. SCD1, YAP/TAZ and stemness markers were evaluated in melanoma cells and tissues by qRT-PCR, WB and Immunofluorescence. RESULTS: We first observed that SCD1 expression increases during melanoma progression. BRAF-mutated melanoma 3D cultures enriched for CSCs overexpressed SCD1 and were more resistant than 2D differentiated cultures to BRAF and MEK inhibitors. We next showed that exposure of BRAF-mutated melanoma cells to MAPK pathway inhibitors enhanced stemness features by upregulating the expression of YAP/TAZ and downstream genes but surprisingly not SCD1. However, SCD1 pharmacological inhibition was able to downregulate YAP/TAZ and to revert at the same time CSC enrichment and resistance to MAPK inhibitors. CONCLUSIONS: Our data underscore the role of SCD1 as prognostic marker in melanoma and promote the use of SCD1 inhibitors in combination with MAPK inhibitors for the control of drug resistance.

Errors in protein synthesis increase the level of saturated fatty acids and affect the overall lipid profiles of yeast.

The occurrence of protein synthesis errors (mistranslation) above the typical mean mistranslation level of 10-4 is mostly deleterious to yeast, zebrafish and mammal cells. Previous yeast studies have shown that mistranslation affects fitness and deregulates genes related to lipid metabolism, but there is no experimental proof that such errors alter yeast lipid profiles. We engineered yeast strains to misincorporate serine at alanine and glycine sites on a global scale and evaluated the putative effects on the lipidome. Lipids from whole cells were extracted and analysed by thin layer chromatography (TLC), liquid chromatography-mass spectrometry(LC-MS) and gas chromatography (GC). Oxidative damage, fatty acid desaturation and membrane fluidity changes were screened to identify putative alterations in lipid profiles in both logarithmic (fermentative) and post-diauxic shift (respiratory) phases. There were alterations in several lipid classes, namely lyso-phosphatidylcholine, phosphatidic acid, phosphatidylethanolamine, phosphatidylinositol, phosphatidylserine, and triglyceride, and in the fatty acid profiles, namely C16:1, C16:0, C18:1 and C18:0. Overall, the relative content of lipid species with saturated FA increased in detriment of those with unsaturated fatty acids. The expression of the OLE1 mRNA was deregulated, but phospholipid fluidity changes were not observed. These data expand current knowledge of mistranslation biology and highlight its putative roles in human diseases.

DHA upregulates FADS2 expression in primary cortical astrocytes exposed to vitamin A.

The fads2 gene encoding delta6-desaturase, the rate-limiting enzyme of the LCPUFA biosynthesis is expressed in astrocytes. Dietary fatty acids, which cross the blood-brain barrier, may regulate the transcription of lipogenic enzymes through activation of transcription factors such as peroxisome proliferator-activated receptors (PPARs). The PPARs form the transcription complex with retinoid X receptors (RXRs) that are activated by 9-cis retinoic acid, a metabolite of vitamin A (VA). The study examines whether challenge of astrocytes with VA, prior 24-h treatment with palmitic acid (PA), alpha-linolenic acid (ALA) or docosahexaenoic acid (DHA) has the effect on the FADS2 expression. RT-qPCR showed that in astrocytes not challenged with VA, PA increased fads2 gene expression and DHA decreased it. However, in VA-primed astrocytes, PA doubled the FADS2 mRNA levels, while DHA increased fads2 gene expression, oppositely to non-primed cells. Furthermore, similar changes were seen in VA-primed astrocytes with regard to delta6-desaturase protein levels following PA and DHA treatment. ALA did not have any effect on the FADS2 mRNA and protein levels in either VA-primed or non-primed astrocytes. These findings indicate that in the presence of vitamin A, DHA upregulates fads2 gene expression in astrocytes.

Protein engineering: Regulatory perspectives of stearoyl CoA desaturase.

Stearoyl Co A desaturase (SCD) is a rate-limiting lipogenic enzyme that plays an integral role in catalyzing the synthesis of monounsaturated fatty acids, chiefly oleate and palmitoleate. Both contribute a major part of the biological membrane. Numerous SCD isoforms exist in mouse and humans, i.e., SCD-1 to SCD-4 and SCD-1 and SCD-5, respectively. From the biological viewpoint, hyperexpression of SCD1 cause many metabolic disorders including obesity, insulin resistance, hypertension, and hypertriglyceridemia, etc. Herein, an effort has been made to highlight the value of protein engineering in controlling the SCD-1 expression with the involvement of different inhibitors as therapeutic agents. The first part of the review describes Stearoyl CoA desaturase index and different SCD isoforms. Various regulatory aspects of SCD are reviewed in four subsections, i.e., (1) hormonal regulation, (2) regulation by dietary carbohydrates, (3) regulation by green tea, and (4) regulation via polyunsaturated fatty acids (PUFAs). Moreover, the regulation of Stearoyl CoA desaturase expression in the metabolism of fats and carbohydrates is discussed. The third part mainly focuses on natural and synthetic inhibitors. Towards the end, information is also given on potential future considerations of SCD-1 inhibitors as metabolic syndrome therapeutics, yet additional work is required.

Increased expression of the gene encoding stearoyl-CoA desaturase 1 in human bladder cancer.

Bladder cancer is a common disease and a significant cause of death worldwide. There is thus great interest in identifying a diagnostic and prognostic biomarker, as well as gaining an understanding of the molecular basis of bladder cancer. Stearoyl-CoA desaturase 1 gene (SCD1) is highly overexpressed in many human cancers. However, the expression of SCD1 has not yet been investigated in patients with bladder cancer. Here, we document that (a) the SCD1 is highly overexpressed in human bladder cancer; (b) high expression of SCD1 is more frequently observed in the late stage of disease and patients with lymph node metastasis; (c) bladder cancer patients with a higher SCD1 mRNA level have a poorer survival rate than those with normal SCD1 expression. Overall, this is the first report to indicate an association between SCD1 mRNA level and clinical indicators of human bladder cancer. Our study has provided evidence supporting the potential role of SCD1 as a biomarker for human bladder cancer prognosis.

Identification of cytochrome b5 CYTB-5.1 and CYTB-5.2 in C. elegans; evidence for differential regulation of SCD.

Unsaturated fatty acids (UFAs) play crucial roles in living organisms regarding development, energy metabolism, stress resistance, etc. The biosynthesis of UFAs starts from the introduction of the first double bond by stearoyl-CoA desaturase (SCD), converting saturated fatty acids (SFAs) to monounsaturated fatty acids (MUFAs). This desaturation is considered to be an aerobic process that requires cytochrome b5 reductase, cytochrome b5 and SCD. However, this enzyme system remains elusive in Caenorhabditis elegans. Here, we show that inactivation by RNAi knockdown or mutation (gk442189) of putative cytochrome b5 genes cytb-5.1 led to reduced conversion of C18:0 to C18:1(n-9) by SCD desaturases FAT-6/7 in C. elegans. On the contrary, cytb-5.2RNAi and cytb-5.2(gk113588) mutant worms showed decreased conversion of C16:0 to C16:1(n-7) by FAT-5 desaturase. Dietary supplementation with C18:1(n-9) and C18:2(n-6) also showed that CYTB-5.1 is likely required for the activity of FAT-6/7 desaturases, but not for FAT-1 to FAT-4 desaturases. Interestingly, co-immunoprecipitation (Co-IP) demonstrated that either FAT-7 or FAT-5 has ability to interact with both CYTB-5.1 and CYTB-5.2. Moreover, RNAi knockdown of cytb-5.1 upregulates the transcriptional and translational expression of fat-5 to fat-7, which may be due to the feedback induction by reduced C18:1(n-9) and downstream fatty acids. Furthermore, both CYTB-5.1 and CYTB-5.2 are involved in fat accumulation, fertility and lifespan in worms, which may be independent of changes in fatty acid compositions. Collectively, these findings for the first time reveal the differential regulation of various SCDs by distinct cytochrome b5 CYTB-5.1 and CYTB-5.2 in the biosynthesis of UFAs in C. elegans.

Hair Growth Cycle Is Arrested in SCD1 Deficiency by Impaired Wnt3a-Palmitoleoylation and Retrieved by the Artificial Lipid Barrier.

Stearoyl-CoA desaturase 1 (SCD1) is the dominant member of the SCD-isozyme family, regarded as a major regulator of lipid and energy metabolism in liver and adipose tissue. SCD1 deficiency impairs the desaturation of de novo-synthesized palmitoyl- and stearoyl-CoA to palmitoleoyl- and oleoyl-CoA. Scd1-/- mice develop metabolic waste syndrome and skin lesions: epidermal barrier disruption, alopecia, and degeneration of sebaceous glands. The unifying molecular link between the two divergent traits remains incompletely understood. Here we show the absence of palmitoleic acid (9Z-16:1) in the lipidome of the scd1-null mouse, which prohibits posttranslational O-palmitoleoylation of Wnt3a protein, essential for Wnt3a/ß-catenin signaling in stem cell lineage decision in development of the epidermal barrier, hair growth cycle, and sebaceous glands. Substitution of the disrupted epidermal lipid barrier by an inert hydrocarbon coat prevents excessive transepidermal water loss, normalizes thermogenesis and metabolic parameters, and surprisingly leads to the activation of hair bulge progenitor cells and reprograming of a regular hair growth cycle and development of a regular fur in scd1-/- mice. Progenitor sebocytes are not activated. Independent of age, application or removal of the artificial lipid barrier allows the reversible telogen-anagen reentry and exit of the hair growth cycle.

A Caenorhabditis elegans model for ether lipid biosynthesis and function.

Ether lipids are widespread in nature, and they are structurally and functionally important components of membranes. The roundworm, Caenorhabditis elegans, synthesizes numerous lipid species containing alkyl and alkenyl ether bonds. We isolated C. elegans strains carrying loss-of-function mutations in three genes encoding the proteins required for the initial three steps in the ether lipid biosynthetic pathway, FARD-1/FAR1, ACL-7/GNPAT, and ADS-1/AGPS. Analysis of the mutant strains show that they lack ether lipids, but possess the ability to alter their lipid composition in response to lack of ether lipids. We found that increases in de novo fatty acid synthesis and reduction of stearoyl- and palmitoyl-CoA desaturase activity, processes that are at least partially regulated transcriptionally, mediate the altered lipid composition in ether lipid-deficient mutants. Phenotypic analysis demonstrated the importance of ether lipids for optimal fertility, lifespan, survival at cold temperatures, and resistance to oxidative stress.Caenorhabditis.

Individual CLA Isomers, c9t11 and t10c12, Prevent Excess Liver Glycogen Storage and Inhibit Lipogenic Genes Expression Induced by High-Fructose Diet in Rats.

This study assessed the effects of individual conjugated linoleic acid isomers, c9t11-CLA and t10c12-CLA, on nonalcoholic fatty liver disease (NAFLD) and systemic endothelial dysfunction in rats fed for four weeks with control or high-fructose diet. The high-fructose diet hampered body weight gain (without influencing food intake), increased liver weight and glycogen storage in hepatocytes, upregulated expression of fatty acid synthase (FAS) and stearoyl-CoA desaturase-1 (SCD-1), and increased saturated fatty acid (SFA) content in the liver. Both CLA isomers prevented excessive accumulation of glycogen in the liver. Specifically, t10c12-CLA decreased concentration of serum triacylglycerols and LDL + VLDL cholesterol, increased HDL cholesterol, and affected liver lipid content and fatty acid composition by downregulation of liver SCD-1 and FAS expression. In turn, the c9t11-CLA decreased LDL+VLDL cholesterol in the control group and downregulated liver expression of FAS without significant effects on liver weight, lipid content, and fatty acid composition. In summary, feeding rats with a high-fructose diet resulted in increased liver glycogen storage, indicating the induction of gluconeogenesis despite simultaneous upregulation of genes involved in de novo lipogenesis. Although both CLA isomers (c9t11 and t10c12) display hepatoprotective activity, the hypolipemic action of the t10c12-CLA isomer proved to be more pronounced than that of c9t11-CLA.

In situ characterizing membrane lipid phenotype of breast cancer cells using mass spectrometry profiling.

Lipid composition in cell membrane is closely associated with cell characteristics. Here, matrix-assisted laser desorption/ionization- Fourier transform ion cyclotron resonance mass spectrometry was employed to in situ determine membrane components of human mammary epithelial cells (MCF-10 A) and six different breast cancer cell lines (i.e., BT-20, MCF-7, SK-BR-3, MDA-MB-231, MDA-MB-157, and MDA-MB-361) without any lipid extraction and separation. Partial least-square discriminant analysis indicated that changes in the levels of these membrane lipids were closely correlated with the types of breast cell lines. Elevated levels of polyunsaturated lipids in MCF-10 A cells relative to six breast cancer cells and in BT-20 cells relative to other breast cancer cell lines were detected. The Western blotting assays indicated that the expression of five lipogenesis-related enzymes (i.e., fatty acid synthase 1(FASN1), stearoyl-CoA desaturase 1 (SCD1), stearoyl-CoA desaturase 5 (SCD5), choline kinase α (CKα), and sphingomyelin synthase 1) was associated with the types of the breast cells, and that the SCD1 level in MCF-7 cells was significantly increased relative to other breast cell lines. Our findings suggest that elevated expression levels of FASN1, SCD1, SCD5, and CKα may closely correlated with enhanced levels of saturated and monounsaturated lipids in breast cancer cell lines.

17ß-estradiol induces stearoyl-CoA desaturase-1 expression in estrogen receptor-positive breast cancer cells.

BACKGROUND: To sustain cell growth, cancer cells exhibit an altered metabolism characterized by increased lipogenesis. Stearoyl-CoA desaturase-1 (SCD-1) catalyzes the production of monounsaturated fatty acids that are essential for membrane biogenesis, and is required for cell proliferation in many cancer cell types. Although estrogen is required for the proliferation of many estrogen-sensitive breast carcinoma cells, it is also a repressor of SCD-1 expression in liver and adipose. The current study addresses this apparent paradox by investigating the impact of estrogen on SCD-1 expression in estrogen receptor-α-positive breast carcinoma cell lines. METHODS: MCF-7 and T47D mammary carcinomas cells and immortalized MCF-10A mammary epithelial cells were hormone-starved then treated or not with 17ß-estradiol. SCD-1 activity was assessed by measuring cellular monounsaturated/saturated fatty acid (MUFA/SFA) ratios, and SCD-1 expression was measured by qPCR, immunoblot, and immunofluorescence analyses. The role of SCD-1 in cell proliferation was measured following treatment with the SCD-1 inhibitor A959372 and following SCD-1 silencing using siRNA. The involvement of IGF-1R on SCD-1 expression was measured using the IGF-1R antagonist AG1024. The expression of SREBP-1c, a transcription factor that regulates SCD-1, was measured by qPCR, and by immunoblot analyses. RESULTS: 17ß-estradiol significantly induced cell proliferation and SCD-1 activity in MCF-7 and T47D cells but not MCF-10A cells. Accordingly, 17ß-estradiol significantly increased SCD-1 mRNA and protein expression in MCF-7 and T47D cells compared to untreated cells. Treatment of MCF-7 cells with 4-OH tamoxifen or siRNA silencing of estrogen receptor-α largely prevented 17ß-estradiol-induced SCD-1 expression. 17ß-estradiol increased SREBP-1c expression and induced the mature active 60 kDa form of SREBP-1. The selective SCD-1 inhibitor or siRNA silencing of SCD-1 blocked the 17ß-estradiol-induced cell proliferation and increase in cellular MUFA/SFA ratios. IGF-1 also induced SCD-1 expression, but to a lesser extent than 17ß-estradiol. The IGF-1R antagonist partially blocked 17ß-estradiol-induced cell proliferation and SCD-1 expression, suggesting the impact of 17ß-estradiol on SCD-1 expression is partially mediated though IGF-1R signaling. CONCLUSIONS: This study illustrates for the first time that, in contrast to hepatic and adipose tissue, estrogen induces SCD-1 expression and activity in breast carcinoma cells. These results support SCD-1 as a therapeutic target in estrogen-sensitive breast cancer.

Lipopolysaccharide derived from the rumen down-regulates stearoyl-CoA desaturase 1 expression and alters fatty acid composition in the liver of dairy cows fed a high-concentrate diet.

BACKGROUND: Dairy cows are often fed a high-concentrate diet to meet lactating demands, yet long-term concentrate feeding induces subacute ruminal acidosis (SARA) and leads to a decrease in milk fat. Stearoyl-CoA desaturase1 (SCD1) participates in fatty acid biosynthesis in the liver of lactating ruminants. Here, we conducted this study to investigate the impact of lipopolysaccharide derived from the rumen on SCD1 expression and on fatty acid composition in the liver of dairy cows fed a high-concentrate diet. Eight multiparous mid-lactating Holstein cows (455 ± 28 kg) were randomly assigned into two groups in the experiment and were fed a low-concentrate diet (LC) or high-concentrate diet (HC) for 18 weeks. RESULTS: The results showed that the total volatile fatty acids and lactic acid accumulated in the rumen, leading to a decreased rumen pH and elevated lipopolysaccharides (LPSs) in the HC group. The long chain fatty acid profile in the rumen and hepatic vein was remarkably altered in the animals fed the HC diet. The triglyceride (TG), non-esterified fatty acid (NEFA) and total cholesterol (TCH) content in the plasma was significantly decreased, whereas plasma glucose and insulin levels were increased. The expression of SCD1 in the liver was significantly down-regulated in the HC group. In regards to transcriptional regulators, the expression of sterol regulatory element binding transcription factors (SREBF1c, SREBF2) and SREBP cleavage activating protein (SCAP) was down-regulated, while peroxisome proliferator-activated receptor α (PPARα) was up-regulated. CONCLUSIONS: These data indicate that lipopolysaccharide derived from the rumen down-regulates stearoyl-CoA desaturase 1 expression and alters fatty acid composition in the liver of dairy cows fed a high-concentrate diet.

An SCD gene from the Mollusca and its upregulation in carotenoid-enriched scallops.

Carotenoids are a diverse group of red, orange, and yellow pigments that act as vitamin A precursors and antioxidants. Animals can only obtain carotenoids through their diets. Amongst the carotenoids identified in nature, over one third are of marine origin, but current research on carotenoid absorption in marine species is limited. Bivalves possess an adductor muscle, which is normally white in scallops. However, a new variety of Yesso scallop (Patinopecten yessoensis), the 'Haida golden scallop', can be distinguished by its adductor muscle's orange colour, which is caused by carotenoid accumulation. Studying the genes related to carotenoid accumulation in this scallop could benefit our understanding of the mechanisms underlying carotenoid absorption in marine organisms, and it could further improve scallop breeding for carotenoid content. Stearoyl-CoA desaturase (SCD) is the rate-limiting enzyme in the production of monounsaturated fatty acids, which enhance carotenoid absorption. Here, the full-length cDNA and genomic DNA sequences of the SCD gene from the Yesso scallop (PySCD) were obtained. The PySCD gene consisted of four exons and three introns, and it contained a 990-bp open reading frame encoding 329 amino acids. It was ubiquitously expressed in adult tissues, embryos and larvae of both white Yesso scallops and 'Haida golden' scallops. Although the expression pattern of PySCD in both types of scallops was similar, significantly more PySCD transcripts were detected in the 'Haida golden' scallops than in the white scallops. Elevated PySCD expression was found in tissues including the adductor muscle, digestive gland, and gonad, as well as in veliger larvae. This study represents the first characterisation of an SCD gene from the Mollusca. Our data imply that PySCD functions in multiple biological processes, and it might be involved in carotenoid accumulation.