Up-regulation Of stearoyl-CoA Desaturase Research Articles

Upregulation of SCD1 by ErbB2 via LDHA promotes breast cancer cell migration and invasion.

The incidence of breast cancer ranks at the top of female malignant tumors in China. Metastasis remains the main cause of death among breast cancer patients. The overexpression of ErbB2 is closely related to the metastasis and poor prognosis of breast cancer patients. Therefore, ErbB2 is an important clinical therapeutic target of breast cancer. However, the molecular mechanism of ErbB2 promoting breast cancer metastasis has not been studied clearly. Stearoyl-CoA desaturase 1 (SCD1) is a key enzyme in catalyzing the conversion of saturated fatty acids (SFAs) into monounsaturated fatty acids (MUFAs). SCD1 is overexpressed in breast cancer, and its overexpression is an indicator of poor prognosis in breast cancer patients. However, the role of SCD1 in ErbB2-overexpressing breast cancer metastasis has not been reported. In this study, we investigated the role of SCD1 in the migration and invasion of ErbB2-overexpressing breast cancer cells and its molecular mechanism. First, we demonstrated that ErbB2 upregulates the expression of SCD1. Second, we found that SCD1 and its catalytic product oleic acid played crucial roles in migration and invasion of ErbB2-overexpressing breast cancer cells. Finally, we found that in breast cancer cells, ErbB2 upregulated SCD1 through lactate dehydrogenase A (LDHA). To sum up, upregulation of SCD1 by ErbB2 via LDHA promotes the migration and invasion of breast cancer cells.

TMET-03. STEAROYL-COA DESATURASE INHIBITOR SUPPRESSES IDH MUTANT GLIOMA GROWTH VIA ENHANCING LIPOLYSIS

Abstract BACKGROUND Mutant isocitrate dehydrogenase (IDH) produces 2-hydroxyglutarate (D2HG) and causes metabolic reprograming, but so far, little is known about the role of mutant IDH and D2HG in de novo lipogenesis and fatty acids synthesis. In this study, to develop a feasible drug for IDH mutant glioma, we targeted Stearoyl-CoA desaturase 1 (SCD1) catalyzing the biosynthesis of monosaturated fatty acids (MUFA) to suppress IDH mutant glioma progression. Materials and METHODS We prepared genetically engineered glioma cell lines (U251 wild type: U251WT and U251 IDHR132H mutant: U251RH), normal human astrocytes (empty vector induced-NHA: NHAEV and IDHR132H mutant: NHARH) and patient derived cell lines. Lipid metabolic analysis was conducted by using LC-MS, and functional analysis for the role of SCD1 expression was investigated by RNA sequence and Western-blotting. RESULTS LC-MS analysis of extracted Endoplasmic Reticulum revealed that there was significantly higher amount of MUFA in IDH mutant than wild type. SCD1 expression was increased in IDH mutant compared to wild type due to D2HG-mediated upregulation of SCD1 in IDH mutant. Therefore, IDH mutant in which SCD1 expression level was higher than wild type indicated high sensitivity to SCD inhibitor, and apoptosis was highly induced in IDH mutant compared to wild type. RNA sequencing was performed in U251RH treated with SCD inhibitor compared to U251RH treated with DMSO, and lipid droplet metabolism-associated RNA expression was significantly changed in SCD inhibitor-treated U251RH. Based on the RNA sequence data, we checked lipid droplet in U251RH with presence or absence of SCD inhibitor, and lipolysis was induced by SCD inhibitor treatment, suggesting that SCD inhibition is associated with the apoptosis in IDH mutant via enhanced lipolysis mechanism. CONCLUSIONS D2HG produced in IDH mutant glioma directly induces SCD1 expression and enhances sensitivity to SCD inhibitor, which suggests that SCD inhibitor would be IDH mutant glioma-specific treatment strategy.

Early-life exposure to bisphenol A induces dysregulation of lipid homeostasis by the upregulation of SCD1 in male mice

Exposure of Bisphenol A (BPA) is closely associated with an increased prevalence of obesity-related metabolic syndrome. However, the potential mechanism of BPA-induced adipogenesis remains to be fully elucidated. Herein, potential mechanisms of BPA-induced adipogenesis in 3T3-L1 preadipocytes were evaluated using RNA-Seq. Then, using an early-life BPA exposure model, we further evaluated the effects of BPA exposure on lipid and glucose homeostasis. The results showed that lipid content in 3T3-L1 adipocytes was significantly increased after BPA exposure (p < 0.01) and male C57BL/6 mice with the dose of 500 μg/kg/day BPA by once-a-day oral administration for 8 weeks displayed a NAFLD-like phenotype. RNA-Seq analysis of preadipocytes showed that BPA exposure affected multiple biological processes including glycosphingolipid biosynthesis, regulation of lipolysis in adipocytes, PPAR signaling pathway and fatty acid metabolism. The dysregulation in a series of genes of mice was associated to de novo lipogenesis and lipid transport, which was linked to obesity. Importantly, we also found a significant expression increase of stearoyl-CoA desaturase 1 (SCD1) and a significant decrease of apolipoprotein D (APOD) in both fat (p < 0.01) and livers (p < 0.01) of male mice. Besides, the dysregulation of pro-inflammatory genes (TNF-α,IL-6 and SAA3) showed that BPA exposure promoted progression of hepatic inflammation. In conclusion, this study elucidated a novel mechanism in which obesity associated with BPA exposure by targeting SCD1. Exposure to BPA should be carefully examined in the chronic liver metabolic diseases.

Low glycaemic diets alter lipid metabolism to influence tumour growth.

Dietary interventions can change metabolite levels in the tumour microenvironment, which might then affect cancer cell metabolism to alter tumour growth1-5. Although caloric restriction (CR) and a ketogenic diet (KD) are often thought to limit tumour progression by lowering blood glucose and insulin levels6-8, we found that only CR inhibits the growth of select tumour allografts in mice, suggesting that other mechanisms contribute to tumour growth inhibition. A change in nutrient availability observed with CR, but not with KD, is lower lipid levels in the plasma and tumours. Upregulation of stearoyl-CoA desaturase (SCD), which synthesises monounsaturated fatty acids, is required for cancer cells to proliferate in a lipid-depleted environment, and CR also impairs tumour SCD activity to cause an imbalance between unsaturated and saturated fatty acids to slow tumour growth. Enforcing cancer cell SCD expression or raising circulating lipid levels through a higher-fat CR diet confers resistance to the effects of CR. By contrast, although KD also impairs tumour SCD activity, KD-driven increases in lipid availability maintain the unsaturated to saturated fatty acid ratios in tumours, and changing the KD fat composition to increase tumour saturated fatty acid levels cooperates with decreased tumour SCD activity to slow tumour growth. These data suggest that diet-induced mismatches between tumour fatty acid desaturation activity and the availability of specific fatty acid species determine whether low glycaemic diets impair tumour growth.

Macrophage-activating lipopeptide-2 and corticotropin-releasing hormone stimulate the inflammatory signalling in human sebocytes through activation of stearoyl-CoA desaturase and fatty acid desaturase 2.

The macrophage-activating lipopeptide-2 (MALP-2) activates cells carrying a functional Toll-like receptor (TLR)-2/6. Human sebocytes express functional TLR-2, TLR-4 and CD14. Upregulation of stearoyl-CoA desaturase (SCD) and fatty acid desaturase-2 (FADS2) expression induces pro-inflammatory sebaceous activity. On the other hand, corticotropin-releasing hormone (CRH) is likely to serve as an autocrine stress hormone in human sebocytes. In addition to its antiproliferative, lipogenetic and androgen-activating functions, CRH exhibits a pro-inflammatory action and its expression is upregulated in acne-involved sebaceous glands. Determination of the pro-inflammatory function of MALP-2 and CRH and clarification of the option that MALP-2 and/or CRH activity on human sebocytes might be mediated through SCD and/or FADS2. SZ95 sebocytes were treated with MALP-2, CRH and the SCD inhibitor/ligand FPCA. SCD, FADS2, TLR-2 mRNA and protein levels and IL-6 and IL-8 secretion were investigated. Intracellular CRH levels were assessed under treatment with CRH, MALP-2, linoleic acid and arachidonic acid. Phorbol 12-myristate 13-acetate and dexamethasone served as positive and negative controls, respectively. MALP-2 upregulated SCD, FADS2, TLR-2 mRNA and protein levels and IL-6 and IL-8 secretion from SZ95 sebocytes. Co-incubation of SZ95 sebocytes with MALP-2/FPCA did not affect the MALP-2-induced SCD mRNA upregulation but reduced FADS2 mRNA levels and inhibited IL-8 secretion. CRH induced an early, low-level SCD and FADS2 upregulation and TLR-2 and IL-8 secretion. High intracellular CRH concentrations could be detected early after CRH treatment and persisted up to 24h. MALP-2 stimulated intracellular CRH levels. MALP-2 stimulates the inflammatory signalling in human sebocytes through SCD and FADS2 activation. Inhibition of FADS2 mRNA levels and IL-8 secretion through MALP-2/FCPA co-incubation and diminution of fatty acid unsaturation might lead to a reduction of pro-inflammatory sebaceous lipids. CRH upregulates inflammatory signalling via the SCD/FADS2 pathway, and MALP-2 selectively enhances CRH levels in human sebocytes.

Maternal High-Fat Diet Leads to Non-alcoholic Fatty Liver Disease Through Upregulating Hepatic SCD1 Expression in Neonate Rats.

Non-alcoholic fatty liver disease (NAFLD) has become the leading cause of liver disease in children, with evidence that the maternal diet and the early life nutritional environment are potential risk for such disease. This study was aimed to investigate the effects of maternal high-fat diet (HFD) on the occurrence of NAFLD in offspring rats and the underlying mechanisms. In this study, the incidence of NAFLD was compared in F1 offspring rats between the maternal HFD group and standard chow (SC) group. In addition, the expression levels of inflammatory cytokines in the placenta, in the umbilical cord blood, and in the livers of neonate offsprings were compared between two groups. HepG2 cells were treated with recombinant IL6 (rIL6) to assess stearoyl-CoA desaturase 1 (SCD1) expression and lipid synthesis in an inflammatory condition. Lipid accumulation was assayed in both SCD1 overexpression and interference HepG2 cells as well as in neonatal rats. Our results showed that HFD exposure before and throughout the pregnancy induced the elevated hepatic TG content of F1 neonates. The levels of inflammatory cytokines in the placenta, umbilical cord blood, and the livers of HFD F1 neonates were significantly higher than those of the SC group. In addition, rIL6 treatment led to TG accumulation accompanied by the upregulation of SCD1 in HepG2 cell lines. Overexpression of SCD1 led to the accumulation of TG contents in HepG2 cells, whereas Scd1 knockdown attenuated the effects of rIL6 treatment. Overexpression of SCD1 in F1 neonatal rats led to hepatic lipid accumulation. Our study indicated that maternal HFD led to intrauterine inflammation, which subsequently caused transgenerationally abnormal hepatic lipid metabolism of F1 neonates. This modulation might be mediated by upregulating SCD1 expression in hepatic cells.

Downregulation of CPT2 promotes tumorigenesis and chemoresistance to cisplatin in hepatocellular carcinoma

BackgroundCancer cells often have characteristic changes in metabolism. Besides Warburg effect, abnormal lipid metabolism is also considered as one of the most typical metabolic symbols of cancer. Thus, understanding the mechanisms of cell metabolic reprogramming may provide a potential avenue for cancer treatment.Materials and methodsIn total, 41 pairs of matched samples of primary hepatocellular carcinoma (HCC) and adjacent non-cancerous liver tissues were collected. Afterward, we performed quantitative reverse transcriptase polymerase chain reaction to investigate carnitine palmitoyltransferase-2 (CPT2) expression and then systematically analyzed its relationship with clinicopathologic features. We further performed proliferation, colony formation, migration and invasion, drug resistance, and lipogenesis assays to determine the function of CPT2 in HCC.ResultsIn this study, we have identified CPT2 which is the rate-limiting enzyme of fatty acid oxidation, downregulated in HCC and was significantly associated with tumor histological differentiation and venous invasion. In vitro studies demonstrated that knockdown of CPT2 remarkably enhanced the tumorigenic activity and metastatic potential of hepatoma cells. In addition, CPT2 silencing induced chemoresistance to cisplatin. Mechanistically, low expression of CPT2 promoted cancer cell lipogenesis via upregulation of stearoyl-CoA desaturase-1, the key enzyme involved in the synthesis of monounsaturated fatty acids, at both mRNA and protein levels in hepatoma cell line.ConclusionAltogether, our findings demonstrate that CPT2 has a critical role in HCC progression and chemoresistance and may potentially serve as a novel prognostic marker and therapeutic target for HCC treatment.

Lung fibroblasts promote metastatic colonization through upregulation of stearoyl-CoA desaturase 1 in tumor cells.

As a rate-limiting step in metastasis, metastatic colonization requires survival signals from supportive stroma. However, the mechanisms driving this process are incompletely understood. Here, we showed that the proliferation of B16F10 cells was promoted when cocultured with lung fibroblasts. Meanwhile, co-injection of B16F10 tumor cells with mouse lung fibroblasts significantly increased lung metastasis. Based on GEO database, we identified stearoyl-CoA desaturase 1 (SCD1) as a novel factor promoting metastatic colonization. Importantly, we found that fibroblast-secreted cathepsin B (CTSB) induced the upregulation of SCD1 in B16F10 through Annexin A2 (ANXA2) and PI3K/Akt/mTOR pathway. The elevated SCD1 induced a higher ratio of monounsaturated fatty acids to saturated fatty acids in B16F10 cells. The changes in fatty acid composition contributed to tumor cell proliferation and metastatic colonization. Furthermore, targeting SCD1 effectively inhibited lung metastasis and prolonged the overall survival of mice. Meanwhile, the expression of SCD1 was negatively correlated with disease-free survival in five types of cancer patients. Collectively, our study identifies SCD1 as a critical modulator of tumor cell proliferation that is activated by cathepsin B, secreted by lung fibroblasts at the metastatic niche. Our novel findings provide potential therapeutic targets to prevent tumor metastasis.

Chronic consumption of fructose in combination with trans fatty acids but not with saturated fatty acids induces nonalcoholic steatohepatitis with fibrosis in rats.

Consumption of Western diet high in fat and fructose has been attributed to the recent epidemic of nonalcoholic fatty liver disease (NAFLD). However, the impact of specific fatty acids on the progression of NAFLD to nonalcoholic steatohepatitis (NASH) is poorly understood. In the present study, we investigated the chronic effects of consumption of fructose in combination with saturated fatty acids (SFA) or trans fatty acids (TFA) on the development of NAFLD. Male Sprague-Dawley rats were randomly assigned to six isocaloric starch/high fructose (44% of calories), high fat (39% calories) diet containing either starch-peanut oil, fructose-peanut oil, fructose-palmolein, fructose-clarified butter, fructose-coconut oil or fructose-partially hydrogenated vegetable oil and fed for 24weeks. Palmolein, clarified butter and coconut oil were used as the source of SFA whereas partially hydrogenated vegetable oil was used as the source of TFA. Peanut oil was used as the reference oil. Long-term feeding of fructose in combination with SFA or TFA induced hepatic steatosis of similar extent associated with upregulation of stearoyl CoA desaturase-1. In contrast, fructose in combination with TFA induced NASH with fibrosis as evidenced by upregulation of hepatic proinflammatory cytokine and fibrogenic gene expression, increased hepatic oxidative stress and adipocytokine imbalance. Histopathological analysis revealed the presence of NASH with fibrosis. Further, peanut oil prevented the development of NAFLD in fructose-fed rats. Fructose in combination with TFA caused NASH with fibrosis by inducing oxidative stress and inflammation, whereas, fructose in combination with SFA caused simple steatosis, suggesting that the type of fatty acid is more important for the progression of NAFLD.

High-fructose corn syrup-55 consumption alters hepatic lipid metabolism and promotes triglyceride accumulation

High-fructose corn syrup-55 (HFCS-55) has been suggested to be more lipogenic than sucrose, which increases the risk for nonalcoholic fatty liver disease (NAFLD) and dyslipidemia. The study objectives were to determine the effects of drinking different sugar-sweetened solutions on hepatic gene expression in relation to liver fatty acid composition and risk of NAFLD. Female rats were randomly assigned (n=7 rats/group) to drink water or water sweetened with 13% (w/v) HFCS-55, sucrose or fructose for 8 weeks. Rats drinking HFCS-55 solution had the highest (P=.03) hepatic total lipid and triglyceride content and histological evidence of fat infiltration. Rats drinking HFCS-55 solution had the highest hepatic de novo lipogenesis indicated by the up-regulation of stearoyl-CoA desaturase-1 and the highest (P<.001) oleic acid (18:1n-9) content. This was accompanied by reduced β-oxidation indicated by down-regulation of hepatic peroxisome proliferator–activated receptor α. Disposal of excess lipids by export of triglyceride-rich lipoprotein from the liver was increased as shown by up-regulation of gene expression of microsomal triglyceride transfer protein in rats drinking sucrose, but not HFCS-55 solution. The observed lipogenic effects were attributed to the slightly higher fructose content of HFCS-55 solution in the absence of differences in macronutrient and total caloric intake between rats drinking HFCS-55 and sucrose solution. Results from gene expression and fatty acid composition analysis showed that, in a hypercaloric state, some types of sugars are more detrimental to the liver. Based on these preclinical study results, excess consumption of caloric sweetened beverage, particularly HFCS-sweetened beverages, should be limited.

PPARγ Agonists Attenuate Palmitate-Induced ER Stress through Up-Regulation of SCD-1 in Macrophages.

BackgroundClinical trials have shown that treatment of patients with type 2 diabetes with pioglitazone, a peroxisome proliferator-activated receptor (PPAR)γ agonist, reduces cardiovascular events. However, the effect of PPARγ agonists on endoplasmic reticulum (ER) stress that plays an important role in the progression of atherosclerosis has not been determined. We sought to determine the effect of PPARγ agonists on ER stress induced by palmitate, the most abundant saturated fatty acid in the serum.Methods and ResultsProtein expression of ER stress marker was evaluated by Western blot analysis and stearoyl-CoA desaturase1 (SCD-1) mRNA expression was evaluated by qRT-PCR. Macrophage apoptosis was detected by flowcytometry. Pioglitazone and rosiglitazone reduced palmitate-induced phosphorylation of PERK, a marker of ER stress, in RAW264.7, a murine macrophage cell line. Pioglitazone also suppressed palmitate-induced apoptosis in association with inhibition of CHOP expression, JNK phosphorylation and cleavage of caspase-3. These effects of pioglitazone were reversed by GW9662, a PPARγ antagonist, indicating that PPARγ is involved in this process. PPARγ agonists increased expression of SCD-1 that introduces a double bond on the acyl chain of long-chain fatty acid. 4-(2-Chlorophenoxy)-N-(3-(3-methylcarbamoyl)phenyl)piperidine-1-carboxamide, an inhibitor of SCD-1, abolished the anti-ER stress and anti-apoptotic effects of pioglitazone. These results suggest that PPARγ agonists attenuate palmitate-induced ER stress and apoptosis through SCD-1 induction. Up-regulation of SCD-1 may contribute to the reduction of cardiovascular events by treatment with PPARγ agonists.

Stearoyl-CoA desaturase 1 and paracrine signal involvement in the promotion of breast cancer cell migration induced by cancer-associated fibroblasts

Despite the acknowledged impact of the tumor stroma on breast cancer development and progression, the molecular basis of such effects remain partially unexplained. We previously reported that breast cancer-associated fibroblasts (CAFs) induced epithelial-mesenchymal transition and an increase in cell membrane fluidity and migration speed in poorly (MCF-7) and highly invasive (MDA-MB-231) breast cancer cells. More recently, in order to better define the mechanisms responsible for the CAF-promoted tumor cell migration, we investigated the role of Stearoyl-CoA desaturase 1 (SCD1), the main enzyme regulating membrane fluidity, and demonstrated its CAF-triggered up-regulation as well as its crucial role in the migratory ability of the above tumor cells. Besides SCD1 induction, a CAF-promoted enhancement in the protein level and/or activity of the SCD1 transcription factor, the sterol regulatory element-binding protein 1 (SREBP1), was observed. Moreover, the influence of stroma-derived signals in cancer cell migration speed was proved by cell tracking analysis in the presence of neutralizing antibodies to hepatocyte growth factor, transforming growth factor-β or basic fibroblast growth factor, where a marked reduction or abolishment of the fibroblast-triggered increase in cancer cell migration speed was observed. In the last part of this study, in order to verify if soluble CAF-derived factors stimulate breast cancer cell migration in a SCD1-dependent manner, tumor cells were exposed to CAF-conditioned medium (CM) and their migration evaluated by scratch assay in the presence of a small molecule inhibitor of SCD1. Moreover, to assess if the induction of SCD1 expression by CAFs might occur via SREBP1, the desaturase levels were also determined in SREBP1-inhibited tumor cells. These latest investigations indicate that SCD1 contributes to the promotion of breast cancer cell migration by CAF-derived soluble factors, since the desaturase inhibition completely suppressed the stimulatory effect of CAF-CM on tumor cell migration. SREBP1 inhibition impaired CAF-mediated up-regulation of SCD1 in poorly invasive but not in highly invasive tumor cells, in which SREBP1-independent mechanisms may account for the enhancement of SCD1 levels. These results provide further insights in understanding the role of CAFs in promoting tumor cell migration, which may help to design new stroma-based therapeutic strategies.

Abstract 1706: Estrogen induces stearoyl-CoA desaturase expression in human MCF-7 breast carcinoma cells.

Abstract Approximately 95% of breast cancers are estrogen-dependant. Estrogen plays a crucial role in many cellular processes in estrogen-sensitive breast cancer such as carcinogenesis, production of growth factors, angiogenesis and growth stimulation. To sustain cell growth, many cancer cells exhibit an altered metabolism that is characterized by increased glycolysis and lipogenesis. We observed for the first time an up regulation of stearoyl-CoA desaturase-1 (SCD1) in response to estrogen in the hormone-dependent MCF7 human breast carcinoma cell line. SCD1 is a key enzyme in the production of monounsaturated fatty acids that are essential for membrane biogenesis. Using estrogen-starved MCF7 cells, treatment with 2 nM of estrogen induced cell proliferation, increased SCD-1 gene expression measured by qPCR (2.6±0.1 fold increase, p&amp;lt;0.05) and SCD-1 protein expression (7.2 fold increase) determined by immunoblot analysis, compared to control cells. Estrogen-induced SCD1 expression was accompanied by important changes in cellular fatty acid compositions with significant increases in the monounsaturated fatty acid content in membrane phospholipids and in SCD-1 product/substrate ratios with a 4.3±0.03 fold increase in the 16:1n-7/16:0 ratio and a 1.9±0.01 fold increase in the 18:1n-9/18:0 ratio compared to untreated cells (both p&amp;lt;0.05). Treatment of estrogen-stimulated cells with a selective SCD1 inhibitor inhibited estrogen-induced cell proliferation and prevented the estrogen-induced changes in membrane lipid composition. Overall, these results show for the first time that estrogen induces SCD-1 expression in breast carcinoma cells and suggests a crucial role for SCD1 in estrogen dependent cancer cell proliferation. SCD1 may therefore represent a potential therapeutic target for estrogen-dependent cancer. (This work was supported by the Canadian Institutes of Health Research and the Canada Research Chairs Program). Citation Format: Anissa Belkaid, Rodney J. Ouellette, Marc E. Surette. Estrogen induces stearoyl-CoA desaturase expression in human MCF-7 breast carcinoma cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1706. doi:10.1158/1538-7445.AM2013-1706

Increased Stearoyl-CoA Desaturase Index and Triglyceride Content in the Liver of Rats after a Single Bout of Swimming Exercise

Up-regulation of stearoyl-CoA desaturase (SCD) is closely related to improved insulin resistance. We investigated whether the SCD indices in tissues were influenced by a single-endurance exercise and low content of dietary medium-chain fatty acid (FA). Wistar rats were fed a long-chain (S) or medium- and long-chain FA (M) diet for 2 weeks. At the end of the experiment, the rats were further assigned to two sub-groups (sedentary, Sed; exercise, Ex). These groups were defined as S-Sed, S-Ex, M-Sed, and M-Ex. The rats in the exercise groups were subjected to swimming exercise for 4 h, and tissue samples were obtained. The exercise significantly increased the triglyceride (TG) content and SCD index only in the liver. In contrast, no such changes were apparent by intake of the M diet. A single bout of endurance exercise increased the hepatic TG content and SCD index which might be effective in protecting against insulin resistance.

Epithelium-stroma reciprocal influence in breast cancer. Focus on plasma membrane features related to cell migratory/invasive ability

Interactions occurring between malignant cells and stromal microenvironment greatly influence progression of breast cancer. In a previous study, we co-cultured mammary cancer cells exhibiting different degrees of metastatic potential (MDA-MB- 231>MCF-7) with fibroblasts isolated from breast healthy skin (normal fibroblasts, NFs) or breast tumor stroma (cancer-associated fibroblasts, CAFs). In this system, we demonstrated the influence exerted in particular by CAFs on malignant cells, leading to the acquisition of a more aggressive/invasive phenotype (i.e. reduced adhesion, epithelial-mesenchymal transition, enhanced plasma membrane fluidity and migration velocity/directness). In the present study, we evaluated the reciprocal effect of breast tumor cells and fibroblasts in co-culture on the expression of the main enzyme regulating the fatty acids membrane composition, Stearoyl-CoA desaturase 1 (SCD1). Abnormally high levels of SCD1 have been reported in different cancers and transformed cells and the enzyme has been recently raised to the role of key regulator of cell growth, programmed cell death and carcinogenesis. In our experience, Western blot analysis demonstrated a strong increase in SCD1 expression in both MCF-7 and MDA-MB-231 cells, resulting from their interaction with CAFs and, at a lesser extent, with NFs. High levels of SCD1 were also observed in both NFs and CAFs when co-cultured with MCF-7 cells. MDA-MB-231 cells more slightly up-regulated the enzyme expression in NFs or even induced a certain inhibition in CAFs. The fibroblast-triggered up-regulation of SCD1 in cancer cells could reasonably be considered the molecular event underlying the increase of membrane fluidity, previously observed in tumor cells co-cultured with NFs and, notably, with CAFs. This change might downstream promote the previously described increase in tumor cell motility.

Effects of Perfluorinated Fatty Acids with Different Carbon Chain Length on Fatty Acid Profiles of Hepatic Lipids in Mice

Alterations by perfluorinated fatty acids (PFCAs) with a chain length of 6-9 carbons in the fatty acid profile of hepatic lipids of mice were investigated. The characteristic changes caused by all the PFCAs examined were increases in the contents and proportions of oleic acid (18 : 1), palmitoleic acid (16 : 1) and 8,11,14-eicosatrienoic acid (20 : 3) in hepatic lipids. Hepatic contents of palmitic acid were also increased by the treatments with the PFCAs. These effects were almost dependent on the hepatic concentrations of PFCA molecules regardless of their carbon chain length. Perfluorooctanoic acid elevated the expressions of mRNA encoding acetyl-CoA carboxylase, fatty acid synthase, malic enzyme, stearoyl-CoA desaturase (SCD) (SCD1 and 2), chain elongase (ELOVL5), Δ6 desaturase (Fads2), 1-acylglycerophosphocholine acyltransferase (LPCAT) (LPCAT3). The four PFCAs examined induced microsomal SCD and LPCAT in hepatic concentration-dependent manners regardless of carbon chain length. One linear regression line was confirmed between LPCAT activity and hepatic concentration of PFCA at wide range of the concentration, whereas the induction of SCD was saturable at relatively low concentration of PFCAs. These results suggest (i) that PFCAs with a chain length of 6-9 carbons change the fatty acid profile of hepatic lipids by increasing contents and proportions of 16 : 1, 18 : 1 and 20 : 3, (ii) that these alterations in fatty acid profile are caused by up-regulation of SCD, de novo fatty acid synthesis, chain elongase and Δ6 desaturase and (iii) that the mechanism underlying SCD induction is, in part, mediated through peroxisome proliferator-activated receptor α.

Unsaturated Fatty Acids in Fish Oil Play a Role in Adequate Fat Distribution to Plasma, Liver and White Adipose Tissue

The components bringing the effects of fish oil on glucose and lipid metabolism are unclear. We used hydrogenated fish oil, which has saturated fatty acids with the same carbon chain lengths as the unsaturated fatty acids in fish oil, to clarify the functions of these unsaturated fatty acids on the improvements in lipid and glucose metabolism in mice. Mice divided into 3 groups were fed different diets: fish oil diet (FO), hydrogenated fish oil diet (HFO), and soybean oil diet (SBO) as a control. Body weight gain and white adipose tissue weight in the HFO and FO groups were significantly decreased compared with those in the SBO group. However, in the HFO group, the triglyceride (TG) levels in plasma were significantly decreased, while the lipids levels in the liver were remarkably increased compared with those in the FO group. Regarding the fatty acid composition in the liver and white adipose tissue in the HFO group, in parallel with the up-regulation of stearoyl-CoA desaturase 1 mRNA, relative amounts of C16 : 1 and C18 : 1 were significantly increased. By contrast, blood glucose levels in the oral glucose tolerance test had not deteriorated in the HFO group. Our results indicate that unsaturated fatty acids in the FO diet decrease lipid levels in the liver and maintain the balance of lipid levels in plasma, liver and white adipose tissue; in addition, in the HFO group, C16 : 1 and C18 : 1 synthesized in the liver and white adipose tissue may improve glucose tolerance and lipid metabolism.

Up-regulation of stearoyl-CoA desaturase 1 and elongase 6 genes expression in rat lipogenic tissues by chronic food restriction and chronic food restriction/refeeding

Successful treatment of obesity and related diseases by chronic food restriction requires the understanding of the effect of such nutritional therapy on the expression of genes which have been implicated to be involved in some diseases associated with obesity. The purpose of this study was to examine the effect of chronic food restriction and chronic food restriction/refeeding on lipogenic enzymes, especially the expression of genes encoding the stearoyl-CoA desaturase 1 (Scd1) and elongase6 (Elovl6) in rat liver and adipose tissue. We found that both chronic food restriction and chronic food restriction/refeeding caused increased expression of the Scd1 and Elovl6 genes in both the liver and adipose tissue. The increase was more pronounced in case of chronic food restriction/refeeding (several-fold increase) than that in chronic food restriction alone (two to threefold increase). Essentially, similar results were obtained when the expression of fatty acid synthase, acetyl-CoA carboxylase, ATP-citrate lyase, and malic enzyme genes was studied. Moreover, we found that chronic food restriction and short-term fasting exert opposite effects on the expression of lipogenic enzymes genes. The increased expression of the genes encoding Scd1, Elovl6, and other key lipogenic enzymes may favor fat storage after chronic food restriction/refeeding and may be part of the molecular mechanism by which food restriction/refeeding increases body weight and enhances susceptibility to insulin resistance.

Corn oil or corn grain supplementation to steers grazing endophyte-free tall fescue. II. Effects on subcutaneous fatty acid content and lipogenic gene expression1

Twenty-eight Angus steers (289 kg) were finished on a high-concentrate diet (85% concentrate: 15% roughage; CONC), or endophyte-free tall fescue pastures with corn grain supplement (0.52% of BW; PC), corn oil plus soybean hull supplement (0.10% of BW corn oil plus 0.45% of BW soybean hulls; PO), or no supplement (pasture only; PA). Subcutaneous adipose tissues were processed for total cellular RNA extraction and fatty acid composition by GLC. Relative expression of genes involved in lipogenesis [fatty acid synthase (FASN), acetyl-CoA carboxylase, lipoprotein lipase, stearoyl-CoA desaturase (SCD)] and activators of transcription [(peroxisome proliferator-activated receptor-gamma), C/EBPalpha, sterol regulatory binding protein-1, signal transducer and activator of transcription-5, and Spot-14] was determined by real-time quantitative PCR. Housekeeping gene (glyceraldehyde 3-phosphate dehydrogenase and beta-actin) expression was used in analysis to normalize expression data. Total fatty acid content was greatest (P < 0.001) for CONC and least (P < 0.001) for PA. Supplementation of grazing cattle increased (P < 0.001) total fatty acid content compared with PA, but concentrations were less (P < 0.001) than for CONC. Myristic and palmitic acid contents were greater (P < 0.001) for CONC than for PO and PC, which were greater (P < 0.001) than for PA. Stearic acid content was greater (P < 0.01) for PO than for CONC, PC, and PA. Finishing on CONC increased (P < 0.001) total MUFA content by 68% compared with PA. Corn grain supplementation increased (P < 0.001) MUFA content compared with PA; in contrast, MUFA content did not differ (P > 0.05) between PO and PA. Corn oil supplementation increased (P < 0.001) trans-11 vaccenic acid content in subcutaneous fat by 1.2-, 1.7- and 5.6-fold relative to PA, PC, and CONC, respectively. Concentrations of the cis-9, trans-11 CLA isomer were 54, 58, and 208% greater (P < 0.01) for PO than for PA, PC, and CONC, respectively. Corn grain supplementation to grazing steers did not alter (P > 0.05) the cis-9, trans-11 CLA isomer compared with PA. Oil supplementation increased (P < 0.001) linoleic acid (C18:2) content by 56, 98 and 262% compared with CONC, PC, and PA, respectively. Relative mRNA expression of SCD was upregulated (P < 0.001) by 46-, 18- and 7-fold, respectively, for CONC, PC, and PO compared with PA. Relative FASN mRNA expression was also upregulated (P = 0.004) by 9- and 5-fold, respectively, for CONC and PC compared with PA. Grain feeding, either on CONC or supplemented on pasture, upregulated FASN and SCD mRNA to increase MUFA and de novo fatty acids in subcutaneous adipose tissue. Upregulation of SCD with grain feeding and reduced tissue CLA concentrations suggest that the decreased CLA concentrations were the result of limited substrate (trans-11 vaccenic acid) availability.

Increased Fatty Acid Desaturation and Enhanced Expression of Stearoyl Coenzyme A Desaturase Protects Pancreatic β-Cells from Lipoapoptosis

Increased availability of fatty acids causes cell death and dysfunction in beta-cell lines, isolated islets, and animal models of diabetes. From the MIN6 beta-cell line, we selected two subpools that are resistant to palmitate-induced apoptosis. Protection was not universal because palmitate-resistant cells remained sensitive to cytokine- and streptozotocin-induced apoptosis. Palmitate oxidation and incorporation into cholesterol ester (but not triglycerides) were significantly higher in palmitate-resistant cells than in control cells. Consistent with these findings, transcript profiling revealed increased expression in palmitate-resistant cells of several beta-oxidation genes as well as a 2.8-fold upregulation of stearoyl-CoA desaturase 1 (SCD1). Correspondingly, the oleate-to-palmitate ratio of palmitate-resistant cells was double that of palmitate-pretreated control cells. At least some of this additional oleate in palmitate-resistant cells was incorporated into cholesterol ester stored in the form of large cytosolic lipid bodies. However, blocking cholesterol ester formation did not render palmitate-resistant cells sensitive to palmitate-induced apoptosis. On the other hand, an inhibitor of SCD1, 10,12-conjugated linoleic acid, dose dependently overcame the resistance of palmitate-resistant cells to lipoapoptosis. Our results suggest that desaturation per se is more important in protecting beta-cells from the cytotoxic effects of palmitate than is the nature of neutral lipid storage pool thus generated.