Fatty Acid Synthase Protein Levels Research Articles

Association of fatty-acid synthase polymorphisms and expression with outcomes after radical prostatectomy.

Fatty-acid synthase (FASN), selectively overexpressed in prostate cancer (PCa) cells, has been described as linked to the aggressiveness of PCa. Constitutional genetic variation of the FASN gene and the expression levels of FASN protein in cancer cells could thus be expected to predict outcome after radical prostatectomy (RP). This study evaluates the associations of malignant tissue status, neoadjuvant androgen deprivation therapy (NADT) and single-nucleotide polymorphisms (SNPs) of FASN with FASN protein expression in prostate tissue. The study then examines the associations of FASN SNPs and gene expression with three measures of post-prostatectomy outcome. Seven tagging FASN SNPs were genotyped in 659 European American men who underwent RP at Roswell Park Cancer Institute between 1993 and 2005. FASN protein expression was assessed using immunohistochemistry. The patients were followed for an average of 6.9 years (range: 0.1-20.6 years). Outcome was assessed using three end points: biochemical failure, treatment failure and development of distant metastatic PCa. Cox proportional hazards analyses were used to evaluate the associations of the tagging SNPs and FASN expression with these end points. Bivariate associations with outcomes were considered; the associations also were controlled for known aggressiveness indicators. Overall, no SNPs were associated with any known aggressiveness indicators. FASN staining intensity was stronger in malignant than in benign tissue, and NADT was associated with decreased FASN staining in both benign and malignant tissue. The relationships of FASN SNPs and staining intensity with outcome were less clear. One SNP, rs4246444, showed a weak association with outcome. FASN staining intensity also showed a weak and seemingly contradictory relationship with outcome. Additional study with longer follow-up and populations that include more metastatic patients is warranted.

Diets high in monounsaturated and polyunsaturated fatty acids decrease fatty acid synthase protein levels in adipose tissue but do not alter other markers of adipose function and inflammation in diet-induced obese rats

This study investigates the effects of monounsaturated and polyunsaturated fatty acids from different fat sources (High Oleic Canola, Canola, Canola–Flaxseed (3:1 blend), Safflower, or Soybean Oil, or a Lard-based diet) on adipose tissue function and markers of inflammation in Obese Prone rats fed high-fat (55% energy) diets for 12 weeks. Adipose tissue fatty acid composition reflected the dietary fatty acid profiles. Protein levels of fatty acid synthase, but not mRNA levels, were lower in adipose tissue of all groups compared to the Lard group. Adiponectin and fatty acid receptors GPR41 and GPR43 protein levels were also altered, but other metabolic and inflammatory mediators in adipose tissue and serum were unchanged among groups. Overall, rats fed vegetable oil- or lard-based high-fat diets appear to be largely resistant to major phenotypic changes when the dietary fat composition is altered, providing little support for the importance of specific fatty acid profiles in the context of a high-fat diet.

Modulation of Fatty Acid Synthase Degradation by Concerted Action of p38 MAP Kinase, E3 Ligase COP1, and SH2-Tyrosine Phosphatase Shp2

The Src-homology 2 (SH2) domain-containing tyrosine phosphatase Shp2 has been known to regulate various signaling pathways triggered by receptor and cytoplasmic tyrosine kinases. Here we describe a novel function of Shp2 in control of lipid metabolism by mediating degradation of fatty acid synthase (FASN). p38-phosphorylated COP1 accumulates in the cytoplasm and subsequently binds FASN through Shp2 here as an adapter, leading to FASN-Shp2-COP1 complex formation and FASN degradation mediated by ubiquitination pathway. By fasting p38 is activated and stimulates FASN protein degradation in mice. Consistently, the FASN protein levels are dramatically elevated in mouse liver and pancreas in which Shp2/Ptpn11 is selectively deleted. Thus, this study identifies a new activity for Shp2 in lipid metabolism.

Maturation and Activity of Sterol Regulatory Element Binding Protein 1 Is Inhibited by Acyl-CoA Binding Domain Containing 3

Imbalance of lipid metabolism has been linked with pathogenesis of a variety of human pathological conditions such as diabetes, obesity, cancer and neurodegeneration. Sterol regulatory element binding proteins (SREBPs) are the master transcription factors controlling the homeostasis of fatty acids and cholesterol in the body. Transcription, expression, and activity of SREBPs are regulated by various nutritional, hormonal or stressful stimuli, yet the molecular and cellular mechanisms involved in these adaptative responses remains elusive. In the present study, we found that overexpressed acyl-CoA binding domain containing 3 (ACBD3), a Golgi-associated protein, dramatically inhibited SREBP1-sensitive promoter activity of fatty acid synthase (FASN). Moreover, lipid deprivation-stimulated SREBP1 maturation was significantly attenuated by ACBD3. With cell fractionation, gene knockdown and immunoprecipitation assays, it was showed that ACBD3 blocked intracellular maturation of SREBP1 probably through directly binding with the lipid regulator rather than disrupted SREBP1-SCAP-Insig1 interaction. Further investigation revealed that acyl-CoA domain-containing N-terminal sequence of ACBD3 contributed to its inhibitory effects on the production of nuclear SREBP1. In addition, mRNA and protein levels of FASN and de novo palmitate biosynthesis were remarkably reduced in cells overexpressed with ACBD3. These findings suggest that ACBD3 plays an essential role in maintaining lipid homeostasis via regulating SREBP1's processing pathway and thus impacting cellular lipogenesis.

Cassia tora (Leguminosae) seed extract alleviates high-fat diet-induced nonalcoholic fatty liver

The aim of this study was to examine the effects of Cassia tora seeds on high-fat diet (HFD)-induced hepatic steatosis, and elucidate the molecular mechanisms behind its effects. After being fed a HFD for two weeks, rats were orally dosed with Cassia seed ethanol extract (CSEE) (100, 200, or 300mg/kg) once daily for 8weeks. CSEE induced dose-dependent reductions in plasma lipid levels, as well as decreased the over hepatic lipid accumulation. Furthermore, CSEE treatment improved HFD-induced hepatic histological lesions. CSEE enhanced the phosphorylation of AMP-activated protein kinase (AMPK) and its primary downstream targeting enzyme, acetyl-CoA carboxylase, up-regulated the gene expression of carnitine palmitoyl transferase 1, and down-regulated sterol regulatory element binding protein 1 and fatty acid synthase protein levels in the livers of HFD-fed rats. AMPK inhibition by compound C retarded CSEE-induced reduction in triglyceride accumulation in HepG2 cells stimulated by insulin. Our findings suggest that CSEE may regulate hepatic lipid homeostasis related with an AMPK-dependent signaling pathway. Targeting AMPK activation with CSEE may represent a promising approach for the prevention and treatment of obesity-related non-alcoholic fatty liver disease.

Reduction of lipid accumulation in white adipose tissues by Cassia tora (Leguminosae) seed extract is associated with AMPK activation

Natural herbal medications may be one answer to the worldwide epidemic of obesity. This study examines the effects of Cassia seed ethanol extract (CSEE) upon lipid accumulation in white adipose tissue (WAT). CSEE exhibited a significant concentration-dependent decrease in the intracellular accumulation of trigycerides in 3T3-L1 adipocytes. After being fed a high-fat diet (HFD) for 2weeks, rats were fed CSEE (100, 200 or 300mg/kg) once daily for 8weeks. CSEE caused dose-related reductions in body weight gain (as well as plasma lipid levels and epididymal WAT sizes in HFD-fed rats). CSEE enhanced the phosphorylation of AMP-activated protein kinase (AMPK) and its primary downstream targeting enzyme, acetyl-CoA carboxylase, up-regulated gene expression of carnitine palmitoyl transferase 1, and down-regulated sterol regulatory element-binding protein 1 and fatty acid synthase protein levels in epididymal WAT of HFD-fed rats. CSEE could attenuate lipid accumulation in WAT via AMPK signaling pathway activation.

Emodin Protects against High-Fat Diet-Induced Obesity via Regulation of AMP-Activated Protein Kinase Pathways in White Adipose Tissue

Emodin is an active herbal component traditionally used in China for treating a variety of diseases. The aim of this study was to examine the effect of emodin on the reducing lipid accumulation in white adipose tissue of high-fat diet-fed rats, and on the regulation of the expression of the genes involved in lipid metabolism to elucidate the mechanisms. After being fed a high-fat diet for two weeks, rats were dosed orally with emodin (20, 40, 80 mg/kg/day) or pioglitazone (20 mg/kg/day), once daily for eight weeks. Changes in body weight, feeding pattern, serum lipids, coronary artery risk index, and atherogenic index were investigated. Subcutaneous white adipose tissues were isolated for pathology histology and Western blot analyses. Changes of triglyceride accumulation in differentiated 3 T3-L1 adipocytes were also investigated. Emodin exhibited a significant concentration-dependent decrease in the intracellular accumulation of triglyceride in 3 T3-L1 adipocytes. Emodin (80 mg/kg/day) displayed similar characteristics to pioglitazone (20 mg/kg/day) in reducing body weight gain and plasma lipid levels as well as the coronary artery risk and atherogenic indices of high-fat diet-fed rats. Emodin also caused dose related reductions in epididymal white adipose tissue sizes in high-fat diet-fed rats. Emodin and pioglitazone enhanced the phosphorylation of AMP-activated protein kinase and its primary downstream targeting enzyme, acetyl-CoA carboxylase, upregulated gene expression of carnitine palmitoyl transferase 1, and downregulated sterol regulatory element binding protein 1 and fatty acid synthase protein levels in the epididymal white adipose tissue of high-fat diet-fed rats. Our findings suggest that emodin could attenuate lipid accumulation in white adipose tissue through AMP-activated protein kinase activation.

Abstract 5157: Prolactin plays a role in regulating fatty acid synthesis and metabolism in the prostate cancer cell line PC-3

Abstract Introduction: Prostate cancer (PCa) metabolism is unique from other cancers due to a high reliance on fatty acid (FA) break down for energy. This phenomenon of FA dependence is exemplified clinically by poor tumor detection by PET scanning, which makes proteins involved in FA synthesis and metabolism interesting therapeutic targets in PCa. Two important proteins for fat metabolism are fatty acid synthase (FASN) and carnitine palmitoyl-transferase I (CPT1). FASN is responsible for de novo synthesis of long-chain (LC) FA and its activation is tightly regulated. CPT1 is a rate-limiting enzyme, which shuttles LC-FA into the mitochondria for beta-oxidation. The hormone prolactin (PRL) plays a role in the normal prostate by increasing energy metabolism and citrate production. The receptor for PRL (PRLR) has 5 isoforms, which are speculated to have different signaling capabilities. Our lab has shown the ability of PRL to increase CPT1A, but not FASN, mRNA and protein levels in human breast cancer cells. We hypothesized that PRL plays a similar role in PCa FA synthesis and metabolism due to the known presence of PRLR in these cells. The objectives of this study were to 1) identify which PRLR isoforms are expressed 2) determine if mRNA or protein levels of FASN and CPT1A change in response to PRL dosing and 3) establish if PRLR isoform expression plays a role in the results obtained in objective #2. Methods: PNT1A (normal prostate epithelial) and PC-3 (PCa) cells were dosed with 0, 50 or 100 ng/ml PRL. The mRNA levels for CPT1A and FASN were measured with RT-qPCR. For protein expression of FASN and CPT1A 30 ug of protein was loaded onto SDS-PAGE gels, followed by transfer to PVDF membranes, incubated in primary and then secondary antibodies and finally ECL reagent was added to the membranes for band detection. Over-expression studies were performed using lipofectamine 2000 to transiently over-express the long form or a shorter truncated version of the PRLR that were cloned into an expression vector. Over-expression studies were analyzed using Western blotting for FASN and CPT1A as mentioned above. Results: Both PNT1A and PC-3 cell lines express various PRLR isoforms. PRL did not have a significant effect on FASN or CPT1A mRNA levels in either cell type. Western blotting revealed significant changes for FASN and CPT1A protein levels in PC-3 cells at the 100 ng/ml dose. PRLR isoform over-expression studies indicated that isoform expression does appear to be an important variable in how PRL affects FASN and CPT1A protein levels. Conclusion: This project indicates a role for PRL in regulating FA synthesis and metabolism in the PCa cell line PC-3. Regulation at the protein level appears to be influenced by the PRLR isoform that is predominately expressed. These results suggest that PRL and/or its receptors could be a therapeutic target in treating prostate cancer. This project was supported by funding provided from CIHR to GS. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5157. doi:1538-7445.AM2012-5157

Effect of lipid extracts from edible blue‐green algae, Nostoc commune var. Sphaeroides Kützing and Spirulina Platensis, on the regulation of genes for cholesterol and lipid metabolism in HepG2 cells

We previously demonstrated that lipid extract (LE) from an edible blue‐green alga, Nostoc commune var. Sphaeroides Kützing (NO), inhibited the expression of genes involved in lipogenesis, cholesterol synthesis and LDL uptake by repressing maturation of sterol regulatory element binding protein 1 (SREBP‐1) and SREBP‐2 in HepG2 cells. To compare the effect of NO with Spirulina Platensis (SP), the most common BGA for human consumption, LE was prepared with dichloromethane/methanol (2:1) from two blue‐green algae species and HepG2 cells were incubated with the algal LE for 24 hr. Both algal LE decreased mRNA levels of LDL receptor (LDLR), HMG‐CoA reductase (HMGR) and SREBP‐2 in a dose‐dependent manner (0–100 g/ml). Protein levels of the genes were also diminished by algal LE except mature SREBP‐2 protein in NO LE‐treated cells. Fatty acid synthase (FAS) and stearoyl CoA desaturase mRNA as well as FAS protein levels were significantly lowered by NO and SP LE with concomitant decreases in SREBP‐1c mRNA and its mature protein. The results suggest NO and SP LE contain bioactive components that inhibit SREBP‐1c expression and maturation to repress lipogenic gene expression; and different mechanism may mediate the repressive effect of NO and SP LE on the expression of LDLR and HMGR because mature SREBP‐2 protein was not diminished by NO LE whereas SP LE markedly reduced the protein levelsGrant Funding Source: NIH R21AT005152

Emodin, a Naturally Occurring Anthraquinone Derivative, Ameliorates Dyslipidemia by Activating AMP-Activated Protein Kinase in High-Fat-Diet-Fed Rats

The aim of this study was to investigate the antiobesity and antihyperlipidaemic effects of emodin on high-fat diet (HFD)-induced obese rats, and on the regulation of the expression of the genes involved in lipid metabolism to elucidate the mechanisms. After being fed HFD for two weeks, Wistar rats were dosed orally with emodin (40 and 80 mg kg−1) or pioglitazone (20 mg kg−1), once daily for eight weeks. Emodin (80 mg kg−1 per day) displayed similar characteristics to pioglitazone (20 mg kg−1 per day) in reducing body weight gain, plasma lipid levels as well as coronary artery risk index and atherogenic index of HFD-fed rats. Emodin also caused dose related reductions in the hepatic triglyceride and cholesterol contents and lowered hepatic lipid droplets accumulation in HFD-fed rats. Emodin and pioglitazone enhanced the phosphorylation of AMP-activated protein kinase (AMPK) and its primary downstream targeting enzyme, acetyl-CoA carboxylase, up-regulated gene expression of carnitine palmitoyl transferase 1, and down-regulated sterol regulatory element binding protein 1 and fatty acid synthase protein levels in hepatocytes of HFD-fed rats. Our findings suggest emodin could attenuate lipid accumulation by decreasing lipogenesis and increasing mitochondrial fatty acid β-oxidation mediated by activation of the AMPK signaling pathway.

Effect of hepatitis B virus X protein on expression of lipid metabolism-related genes in HepG2 cells

To investigate the effect of Hepatitis B Virus X Protein (HBx) on the expression of lipid metabolism-related genes and its role in pathogenesis of hepatocyte fatty degeneration. Hepatitis B Virus X gene eukaryon expression vector pIRES2-eGFP-HBx was transfected into HepG2 cells to establish HepG2/HBx cell model for HBx expression. HepG2 cells transfected with pIRES2-eGFP (HepG2/pIRES2 cell) and non-transfected were used as controls. At 24, 48 and 72 hours after transfection, the expression of green fluorescent protein (GFP) was observed by fluorescence microscope and the triglyceride(TG) content was detected. RT-PCR and Western blot were applied to detect the levels of sterol regulatory element binding protein-1 (SREBP-1), liver x receptor alpha (LXRalpha) mRNA and the levels of HBx, LXRalpha and fatty acid synthase (FAS) protein. At 24, 48 and 72 hours after transfection, the expression of GFP was found in HepG2/HBx and HepG2/pIRES2 cells, and increased gradually. The expression of HBx was detected only in HepG2/HBx cells, and was increased with time after transfection (F = 32.21, P less than 0.01). These suggested successful obtaining of HepG2-HBx cell model for HBx expression. At 24h, 48h and 72h after transfection, the expression levels of LXRalpha mRNA (0.386+/-0.055, 0.505+/-0.071, 0.649+/-0.058 ) and SREBP-1 mRNA (0.395+/-0.055, 0.548+/-0.047, 0.795+/-0.058), as well as the levels of LXRalpha protein(0.178+/-0.036, 0.263+/-0.047, 0.347+/-0.058) and FAS protein(0.436+/-0.055, 0.608+/-0.053, 0.827+/-0.046) in HepG2-HBx group were dramatically higher than those in the controls at the same time points (all P less than 0.05/0.01), and were gradually increased with time (all P less than 0.05/0.01). A positive correlationship was observed between HBX protein level and the LXRalpha, SREbP-1 mRNA and LXRalpha, FAS protein levels. The difference of TG content between HepG2/HBx group and control groups was not statistically significant (P more than 0.05). HBx-LXRalpha-SREBP-1/FAS pathway suggested regulating transcription and expression of lipid metabolism-related genes, which might be one of the important molecular mechanism causing hepatocyte fatty degeneration.

Angiotensin II type 2 receptor blockade inhibits fatty acid synthase production through activation of AMP-activated protein kinase in pancreatic cancer cells

The lipogenesis-promoting enzyme fatty acid synthase is highly expressed in pancreatic ductal adenocarcinoma. Angiotensin II, which is the principal hormone of the renin angiotensin system, is generated actively in the pancreas and has been shown to increase the expression of fatty acid synthase. The angiotensin II type 2 receptor has been proposed to play an important role in lipogenesis and fat deposition. In this study, we explored the potential role of the angiotensin II type 2 receptor in fatty acid synthase regulation in pancreatic ductal adenocarcinoma cells, and we evaluated the mechanisms involved. Fatty acid synthase messenger RNA and protein in pancreatic ductal adenocarcinoma cell lines treated with or without angiotensin II (10(-6) to 10(-8) mol/L) in the presence or absence of the angiotensin II type 2 receptor blocker PD123319 (10(-4) to 10(-6) mol/L) were analyzed by real-time polymerase chain reaction and Western blotting. The total-AMP-activated protein kinase and phospho-AMP-activated protein kinase, total-acetyl CoA carboxylase and phospho-acetyl CoA carboxylase, and LKB1/STK11 were analyzed by Western immunoblotting. The tissue localization of the angiotensin II type 2 receptor was examined by immunohistochemistry in invasive pancreatic ductal adenocarcinoma lesions and matching normal tissue. Angiotensin II type 2 receptor treatment increased fatty acid synthase expression and promoter activity in significantly pancreatic ductal adenocarcinoma cells; these effects were blocked significantly in the presence of PD123319. Interestingly, angiotensin II also induced angiotensin II type 2 receptor expression in pancreatic ductal adenocarcinoma cells. PD123319, C75, and AICAR decreased fatty acid synthase protein levels, but only PD123319 increased LKB1/STK11 levels. All 3 agents activated AMP-activated protein kinase differentially and inhibited acetyl CoA carboxylase. Angiotensin II type 2 receptor messenger RNA levels were upregulated significantly in 20 of the 25 neoplastic tissues examined (80%) when compared with matching controls. Angiotensin II type 2 receptor protein was localized in the malignant ducts and in the stromal cells. Our data demonstrate a previously unknown involvement of the angiotensin II type 2 receptor in pancreatic ductal adenocarcinoma cell fatty acid synthesis and suggest that its blockade has potential as a novel chemopreventive and antilipogenic mechanism for human pancreatic ductal adenocarcinoma through the activation of AMP-activated protein kinase, which could have detrimental effects on cancer cell survival.

Abstract 64: Differences in lipogenesis between cancer cells in culture and solid tumors

Abstract Elevated lipogenesis is a characteristic feature of cancer. Fatty acid synthase (FASN) overexpression has been found in many human cancers. Tumor cells in culture and solid tumor models are essential tools to study cancer biology. A comparison of the models can reveal tumor microenvironmental influences on lipogenesis. Here we have characterized differences in lipid components such as total fatty acid (tFA) and phosphatidylcholine (PtCho) levels between tumor cells in culture and solid tumors, with 1H MR spectroscopy (MRS) of lipid-soluble cell or tumor extracts derived from breast and prostate cancer cell lines. MCF-12A, nonmalignant human mammalian epithelial cells, MDA-MB-231, an estrogen receptor (ER)/progesterone receptor (PR)-negative metastatic human breast cancer cell line and MCF-7, an ER/PR-positive poorly metastatic human breast cancer cell line, as well as PC-3 and DU-145, which are both androgen independent malignant human prostate cell lines were used in this study. Fully relaxed 1H MR spectra of lipid-soluble extracts from cells in culture and tumors were acquired on a Bruker Avance 500 MR spectrometer using tetramethylsilane (TMS) as an internal concentration standard. Total FA and PtCho levels were quantified as A.U./cell or A.U./g using integrals of the 1.3 ppm and 3.2 ppm signals in the 1H NMR spectra, respectively, normalized to the cell number or tumor weight (g). Patterns of PtCho and tFA levels were similar in cells, but different in tumors. Both PtCho and tFA levels were significantly higher in MCF-7 cells compared to MCF-12A and MDA-MB-231 cells. Interestingly, the levels of PtCho and tFA in nonmalignant MCF-12A cells and malignant MDA-MB-231 cells were comparable. However, the level of tFA in MDA-MB-231 tumors was significantly higher than in MCF-7 tumors. It has been known that hypoxia and low pH conditions activate FASN activity. FASN or/and other lipogenic enzymes in MDA-MB-231 tumors may be more sensitive to those microenvironmental factors. The tFA level of DU-145 cells was significantly higher compared with PC-3 cells. However, PtCho and tFA levels in PC-3 and DU-145 tumors were not significantly different. FASN protein levels in MCF-12A and MCF-7 cells were not significantly different. Since MCF-12A medium contains epidermal growth factor, which activates FASN, we need to further investigate the involvement of FASN without its activators and with only de novo fatty acid. Our results revealed that tFA levels of cells and tumors do not show similar patterns. The differences between cells and tumors can arise from environmental factors found in solid tumors such as depletion of nutrients and oxygen, changes in pH, as well as cancer cell and stromal/endothelial cell interactions. Additional studies are necessary to unravel the tumor microenvironmental factors responsible for the differences in lipid metabolism observed between cells grown in culture as compared to the same cells grown as solid tumors. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 64.

Effects of farnesoid X receptor on the expression of the fatty acid synthetase and hepatic lipase

The farnesoid X receptor (FXR) is a nuclear receptor that regulates gene expression in response to bile acids (BAs). FXR plays an important role in the homeostasis of bile acid, cholesterol, lipoprotein and triglyceride. In this report, we identified fatty acid synthase (FAS) and hepatic lipase (HL) genes as novel target genes of FXR. Human hepatoma HepG2 cells were treated with chenodeoxycholic acid, the natural FXR ligand, and the messenger RNA and protein levels of FAS and HL were determined by RT-PCR and Western blot analysis, respectively. Chenodeoxycholic acid (CDCA) down-regulated the expression of FAS and HL genes in a dose and time-dependent manner in human hepatoma HepG2 cells. In addition, treatment of mice with CDCA significantly decreased the expression of FAS and HL in mouse liver and the activity of HL. These results demonstrated that FAS and HL might be FXR-regulated genes in liver cells. In view of the role of FAS and HL in lipogenesis and plasma lipoprotein metabolism, our results further support the central role of FXR in the homeostasis of fatty acid and lipid.

The Gene Expression of the Main Lipogenic Enzymes is Downregulated in Visceral Adipose Tissue of Obese Subjects

Contradictory findings regarding the gene expression of the main lipogenic enzymes in human adipose tissue depots have been reported. In this cross-sectional study, we aimed to evaluate the mRNA expression of fatty acid synthase (FAS) and acetyl-CoA carboxilase (ACC) in omental and subcutaneous (SC) fat depots from subjects who varied widely in terms of body fat mass. FAS and ACC gene expression were evaluated by real time-PCR in 188 samples of visceral adipose tissue which were obtained during elective surgical procedures in 119 women and 69 men. Decreased sex-adjusted FAS (-59%) and ACC (-49%) mRNA were found in visceral adipose tissue from obese subjects, with and without diabetes mellitus type 2 (DM-2), compared with lean subjects (both P < 0.0001). FAS mRNA was also decreased (-40%) in fat depots from overweight subjects (P < 0.05). Indeed, FAS mRNA was significantly and positively associated with ACC gene expression (r = 0.316, P < 0.0001) and negatively with BMI (r = -0.274), waist circumference (r = -0.437), systolic blood pressure (r = -0.310), serum glucose (r = -0.277), and fasting triglycerides (r = -0.226), among others (all P < 0.0001). Similar associations were observed for ACC gene expression levels. In a representative subgroup of nonobese (n = 4) and obese women (n = 6), relative FAS gene expression levels significantly correlated (r = 0.657, P = 0.034; n = 10) with FAS protein values. FAS protein levels were also inversely correlated with blood glucose (r = -0.640, P = 0.046) and fasting triglycerides (r = -0.832, P = 0.010). In conclusion, the gene expression of the main lipogenic enzymes is downregulated in visceral adipose tissue from obese subjects.

P63 Promotes Cell Survival through Fatty Acid Synthase

There is increasing evidence that p63, and specifically ΔNp63, plays a central role in both development and tumorigenesis by promoting epithelial cell survival. However, few studies have addressed the molecular mechanisms through which such important function is exerted. Fatty acid synthase (FASN), a key enzyme that synthesizes long-chain fatty acids and is involved in both embryogenesis and cancer, has been recently proposed as a direct target of p53 family members, including p63 and p73. Here we show that knockdown of either total or ΔN-specific p63 isoforms in squamous cell carcinoma (SCC9) or immortalized prostate epithelial (iPrEC) cells caused a decrease in cell viability by inducing apoptosis without affecting the cell cycle. p63 silencing significantly reduced both the expression and the activity of FASN. Importantly, stable overexpression of either FASN or myristoylated AKT (myr-AKT) was able to partially rescue cells from cell death induced by p63 silencing. FASN induced AKT phosphorylation and a significant reduction in cell viability was observed when FASN-overexpressing SCC9 cells were treated with an AKT inhibitor after p63 knockdown, indicating that AKT plays a major role in FASN-mediated survival. Activated AKT did not cause any alteration in the FASN protein levels but induced its activity, suggesting that the rescue from apoptosis documented in the p63-silenced cells expressing myr-AKT cells may be partially mediated by FASN. Finally, we demonstrated that p63 and FASN expression are positively associated in clinical squamous cell carcinoma samples as well as in the developing prostate. Taken together, our findings demonstrate that FASN is a functionally relevant target of p63 and is required for mediating its pro-survival effects.

Activation of liver X receptor regulates fatty acid synthase expression in diabetic liver

To investigate the effects of liver X receptor (LXR) on the expression of fatty acid synthase (FAS) in diabetic liver. Sixteen-week-old male db/db mice with C57BL/6 background were administered via gavaging of T0901317 (TO), a LXR synthetic agonist, at the dose of 3 mg x kg(-1) x d(-1) or dimethyl sulfide (DMSO), a vehicle alone for 7 days. Then the mice were killed with their livers taken out to undergo immunohistochemistry to observe the distribution of FAS protein. Human hepatocellular liver carcinoma cell of the line HepG2 were cultured with TO (10 micromol/L) or DMSO for 24 hours. Another HepG2 cells were transfected with mouse FAS promoter-luciferase reporter recombinants with or without pcDNA3.1, LXR expression vector, or an active sterol regulatory element binding protein-1c (SREBP-1c) expression vector for 12 hours. Real-time PCR and Western blotting were used to detect the levels of mRNA and protein of FAS and SREBP-1c respectively. Luciferase reporter assay was utilized to examine the activity of mouse FAS promoter. FAS was abundantly expressed in the mouse livers, especially in the cytoplasm of liver cells. The FAS mRNA levels of the livers of the db/db mice was about 5.5 times as high as that of the db/m mice (P < 0.01). The FAS protein levels in the livers of db/db and db/m mice treated with TO were 1.7 and 3.5 times higher than those of the control mice (both P < 0.05). The SREBP-1 mRNA levels in the liver of the db/m and db/db mice treated with TO were 2.4 and 2.1 times higher compared with the control mice (P < 0.05, P < 0.01). Luciferase test showed that the FAS promoter activity of the HepG2 cells treated with TO was 1.5 times that of the control cells (P < 0.01). The FAS promoter activities of the HepG2 cells transfected with LXR and SREBP-1c were 1.9 and 1.6 times those of the control cells (botn P < 0.01). LXRE directly or indirect (via SREBP-lc) upregulates the expression of FAS gene in the diabetic liver. LXR may mediate the lipid accumulation in liver of diabetes.

The antiadipogenic effect of macrophage-conditioned medium depends on ERK1/2 activation

The proatherogenic state of obesity is associated with hypertrophied adipocytes that may arise because of deficient adipogenesis. Macrophages infiltrate adipose tissue as a function of obesity and may release factors that attenuate adipogenesis. Macrophage-conditioned medium inhibits human and 3T3-L1 adipocyte differentiation in culture, but underlying molecular mechanisms have yet to be defined. Exposure of 3T3-L1 cells throughout the 8-day period of differentiation to medium conditioned by THP-1 macrophages (THP-1-MacCM) blocked adipogenesis. Triacylglycerol (TG) accumulation and induction of peroxisome proliferator–activated receptor γ and fatty acid synthase protein levels were inhibited by 59% (n = 4, P < .001), 29% (n = 4, P < .01), and 47% (n = 4, P < .01), respectively. THP-1-MacCM had no effect when added after the first 2 days of differentiation, indicating that early exposure of its targets must be needed to inhibit 3T3-L1 adipogenesis. Cell enumeration revealed a 44% decrease in clonal expansion compared with standard differentiation (n = 3, P < .01). Addition of THP-1-MacCM to 3T3-L1 preadipocytes increased ERK1/2 phosphorylation by 6.5-fold (n = 3, P < .01). PD98059 (an inhibitor of the ERK1/2 pathway) impaired the negative effect of THP-1-MacCM on TG accumulation, indicated by an inhibition of 25% vs 69% (n = 3, P < .001), without altering fatty acid synthase or peroxisome proliferator–activated receptor γ levels. Our data implicate ERK1/2 as an important signaling mediator for the inhibitory effect of THP-1-MacCM on TG accumulation during 3T3-L1 adipogenesis.

Effect of an enriched cholesterol diet during gestation on fatty acid synthase, HMG-CoA reductase and SREBP-1/2 expressions in rabbits

Pregnancy is associated with hyperlipidemia and hypercholesterolemia in humans. These changes take place to support fetal growth and development, and modifications of these maternal concentrations may influence lipids and cholesterol synthesis in the dam, fetus and placenta. Administration of a 0.2% enriched cholesterol diet (ECD) during rabbit gestation significantly increased cholesterol and triglyceride (TG) levels in maternal livers and decreased fetal weight by 15%. Here we used Western blot analysis to examine the impact of gestation and 0.2% ECD on the expression levels of fatty acid synthase (FAS), HMGR and SREBP-1/2, which are involved in either lipid or cholesterol synthesis. We confirmed that gestation modifies the hepatic and circulating lipid profile in the mother. Our data also suggest that the maternal liver mainly supports lipogenesis, while the placenta plays a key role in cholesterol synthesis. Thus, our data demonstrate a decrease in HMGR protein levels in dam livers by feeding an ECD. In the placenta, SREBPs are highly expressed, and the ECD supplementation increased nuclear SREBP-1/2 protein levels. In addition, our results show a decrease in FAS protein levels in non-pregnant liver and in the liver of offspring from ECD-treated animals. Finally, our data suggest that the placenta does not modify its own cholesterol synthesis in response to an increase in circulating cholesterol. However, the dam liver compensates for this increase by essentially decreasing the level of HMGR expression. Because HMGR and FAS expressions do not correlate with the circulating lipid profile, it would be interesting to find which genes are then targeted by SREBP-1/2 during gestation.

Fatty acid synthase gene expression in human adipose tissue: association with obesity and type 2 diabetes

Increased expression and activity of the lipogenic pathways in adipose tissue may contribute to the development of obesity. As a central enzyme in lipogenesis, the gene encoding fatty acid synthase (FASN) was identified as a candidate gene for determining body fat. In the present study we tested the hypothesis that increased FASN expression links metabolic alterations of excess energy intake, including hyperinsulinaemia, dyslipidaemia and altered adipokine profile to increased body fat mass. In paired samples of visceral and subcutaneous adipose tissue from 196 participants (lean or obese), we investigated whether FASN mRNA expression (assessed by PCR) in adipose tissue is increased in obesity and related to visceral fat accumulation, measures of insulin sensitivity (euglycaemic-hyperinsulinaemic clamp) and glucose metabolism. FASN mRNA expression was increased by 1.7-fold in visceral vs subcutaneous fat. Visceral adipose tissue FASN expression was correlated with FASN protein levels, subcutaneous FASN expression, visceral fat area, fasting plasma insulin, serum concentrations of IL-6, leptin and retinol-binding protein 4 (RBP4), and inversely with measures of insulin sensitivity, independently of age, sex and BMI. Moreover, we found significant correlations between FASN expression and markers of renal function, including serum creatinine and urinary albumin excretion. Increased FASN gene expression in adipose tissue is linked to visceral fat accumulation, impaired insulin sensitivity, increased circulating fasting insulin, IL-6, leptin and RBP4, suggesting an important role of lipogenic pathways in the causal relationship between consequences of excess energy intake and the development of obesity and type 2 diabetes.