Levels Of Fatty Acid Synthetase Research Articles

Hsp90α promotes lipogenesis by stabilizing FASN and promoting FASN transcription via LXRα in hepatocellular carcinoma.

Excessive lipid accumulation promotes the occurrence and progression of hepatocellular carcinoma (HCC), accompanied by high levels of fatty acid synthetase (FASN) and more active lipogenesis. Heat shock protein 90 (Hsp90) acts as a chaperone to maintain the stability and activity of the client proteins. Studies have revealed that Hsp90 regulates the lipid metabolism of HCC, but the effect of Hsp90 on FASN still remains unknown. This study aims to discover the mechanism of Hsp90 inhibition on lipid accumulation and investigate the different effects of Hsp90 N-terminal domain inhibitor STA9090 and C-terminal domain inhibitor novobiocin (NB) on FASN protein stability and transcription pathway in HCC. We found that HCC cells tended to store lipids, which could be disrupted by Hsp90 inhibitors in vivo and in vitro. High levels of Hsp90α and FASN in tumor tissue had correlation with poor prognosis of HCC patients and Hsp90α interacted with FASN to maintain its protein stability. Furthermore, N-terminal domain of Hsp90α was essential for process of sterol regulatory element binding protein 1 (SREBP1) to activate FASN transcription and Hsp90α prevented proteasomal degradation of liver X receptor α (LXRα) to upregulate FASN transcription via LXRα/SREBP1 axis. Our data reveals that Hsp90α promotes lipid accumulation by increasing the protein stability and FASN mRNA transcription, and can be alleviated by Hsp90 inhibitors, which provides a theoretical basis for Hsp90-targeted therapy on lipid metabolism in HCC.

Testosterone Inhibits Lipid Accumulation in Porcine Preadipocytes by Regulating ELOVL3.

Castration is commonly used to reduce stink during boar production. In porcine adipose tissue, castration reduces androgen levels resulting in metabolic disorders and excessive fat deposition. However, the underlying detailed mechanism remains unclear. In this study, we constructed porcine preadipocyte models with and without androgen by adding testosterone exogenously. The fluorescence intensity of lipid droplet (LD) staining and the fatty acid synthetase (FASN) mRNA levels were lower in the testosterone-treated cells than in the untreated control cells. In contrast, the mRNA levels of adipose triglycerides lipase (ATGL) and androgen receptor (AR) were higher than in the testosterone-treated cells than in the control cells. Subsequently, transcriptomic sequencing of porcine preadipocytes incubated with and without testosterone showed that the mRNA expression levels of very long-chain fatty acid elongase 3 (ELOVL3), a key enzyme involved in fatty acids synthesis and metabolism, were high in control cells. The siRNA-mediated knockdown of ELOVL3 reduced LD accumulation and the mRNA levels of FASN and increased the mRNA levels of ATGL. Next, we conducted dual-luciferase reporter assays using wild-type and mutant ELOVL3 promoter reporters, which showed that the ELOVL3 promoter contained an androgen response element (ARE); furthermore, its transcription was negatively regulated by AR overexpression. In conclusion, our study reveals that testosterone inhibits fat deposition in porcine preadipocytes by suppressing ELOVL3 expression. Moreover, our study provides a theoretical basis for further studies on the mechanisms of fat deposition caused by castration.

Astaxanthin Alleviates Nonalcoholic Fatty Liver Disease by Regulating the Intestinal Flora and Targeting the AMPK/Nrf2 Signal Axis.

Nonalcoholic fatty liver disease (NAFLD) is among the most prevalent chronic liver diseases around the globe. The accumulation of lipids in the liver and oxidative stress are important pathological mechanisms of NAFLD. Astaxanthin (AT) is a carotenoid extracted from shrimps and crabs with beneficial biological activities, including anti-oxidative and anti-inflammatory activities. 16S microflora sequencing, H&E staining, and the western blot technique were employed to investigate the impacts of AT on a high-fat diet (HFD)-induced NAFLD. Significant mitigation in lipid metabolism-related disorders and decreased oxidative stress in HFD-induced mice were observed due to AT, and significant changes in the gut flora of the model mice were also observed. The in vitro study showed that AT considerably lowered the protein expression level of fatty acid synthetase (FAS), sterol regulatory element-binding protein-1c (SREBP-1c), and acetyl-COA carboxylase (ACC) and increased the protein expression of nuclear factor-E2 associated factor 2 (Nrf2) and AMP-activated protein kinase (AMPK) in oleic acid (OA) and palmitic acid (PA)-induced HepG2 cells. Additionally, mechanistic studies revealed that compound C (AMPK inhibitor, CC) inhibited the regulatory effect of AT on the SREBP-1c and Nrf2 signaling pathways. In conclusion, AT can inhibit the SREBP-1c, FAS, and ACC signaling pathways, activate the AMPK and Nrf2 signaling pathways, and improve the structure of intestinal flora.

Antioxidant and hypolipidemic activities of pectin isolated from citrus canning processing water

In order to make full use of the citrus resource, antioxidant and hypolipidemic activities of pectin isolated from citrus fruit canning processing water were investigated. The crude citrus pectin (CLCP) and its three separated fractions (LCP0, LCP1 and LCP3) possessed considerable DPPH, hydroxyl and ABTS radical scavenging ability. These were also found to effectively decrease ROS level and improve SOD activity in the H2O2-induced oxidative stress HepG2 cell model. In an in vitro simulated gastrointestinal environment, all the four pectins showed remarkable bile acid-binding ability. CLCP, LCP1 and LCP3 exhibited appreciable activity in reducing total cholesterol (TC) and triglyceride (TG) levels in an oleic acid-induced high-fat HepG2 cell model. RT-qPCR assays revealed that pectins effectively down-regulated the mRNA expression level of fatty acid synthetase (FAS) and sterol regulatory element-binding protein (SREBP)-1c. Thus, down-regulation of mRNA expression FAS and SREBP-1c could be important mechanism of the pectins to lower blood lipids. The citrus pectins investigated in this work have potential as ingredients of functional foods due to the antioxidant and hypolipidemic activities.

Study on the Regulation Mechanism of Lipopolysaccharide on Oxidative Stress and Lipid Metabolism of Bovine Mammary Epithelial Cells

The long-term feeding of a high-concentrate diet (the concentrate ratio is greater than 60 %) leads to mammary gland inflammatory response in ruminants and decreased quality in dairy cows and affects the robust development of the dairy industry. The main reason is closely related to elevated lipopolysaccharide (LPS) in the body. In this experiment, a bovine mammary epithelial cell line (MAC-T) was used as a model, and LPS at different concentrations (0 ng/ml, 1 ng/ml, 10 ng/ml, 100 ng/ml, 1000 ng/ml, 10000 ng/ml) was added to the cells. The cell survival rate, oxidative stress indicators, total lipid droplet area, triglyceride content and key genes regulating lipid metabolism were detected by 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT), assay kit, microscope observation and RT-PCR methods to explore the regulatory mechanism of mammary health and milk fat synthesis. The results showed that compared with those of the control group, the survival rates of cells were significantly decreased after 9 h of stimulation with 1000 ng/ml and 10000 ng/ml LPS (P<0.01). The contents of superoxide dismutase (SOD), catalase (CAT) and total antioxidant capacity (T-AOC) in cells were significantly decreased (P<0.05). Compared with that of the control group, the content of malondialdehyde (MDA) in cells was significantly increased (P<0.05) after stimulation with 10000 ng/ml LPS for 9 h. After 9 h of stimulation with 100 ng/ml, 1000 ng/ml and 10000 ng/ml LPS, the total lipid drop area and triglyceride (TG) content of MAC-T cells were significantly decreased (P<0.05). The expression levels of fatty acid synthesis-related genes Acetyl-CoA carboxylase (ACC) and Stearoyl-CoA desaturase 1 (SCD-1) were significantly decreased after 9 h of stimulation with 100 ng/ml, 1000 ng/ml and 10000 ng/ml LPS (P<0.05), while the expression levels of Fatty Acid synthetase (FAS) were significantly decreased after stimulation with 1000 ng/ml and 10000 ng/ml LPS (P<0.05). TG synthesis by the related gene Diacylglycerol acyltransferase-1 (DGAT1) was significantly lower than that of the control group after stimulation with 1000 ng/ml and 10000 ng/ml LPS for 9 h (P<0.05), and Diacylglycerol acyltransferase-2 (DGAT2) also showed a significant decrease after 10000 ng/ml LPS stimulation (P<0.05). In conclusion, adding different concentrations of LPS to MAC-T cells not only led to a decrease in cell activity, resulting in oxidative damage, but also affected fatty acid and TG synthesis, which may ultimately be closely related to the decrease in milk fat synthesis.

Study on the regulation mechanism of lipopolysaccharide on oxidative stress and lipid metabolism of bovine mammary epithelial cells.

The long-term feeding of a high-concentrate diet (the concentrate ratio is greater than 60 %) leads to mammary gland inflammatory response in ruminants and decreased quality in dairy cows and affects the robust development of the dairy industry. The main reason is closely related to elevated lipopolysaccharide (LPS) in the body. In this experiment, a bovine mammary epithelial cell line (MAC-T) was used as a model, and LPS at different concentrations (0 ng/ml, 1 ng/ml, 10 ng/ml, 100 ng/ml, 1000 ng/ml, 10000 ng/ml) was added to the cells. The cell survival rate, oxidative stress indicators, total lipid droplet area, triglyceride content and key genes regulating lipid metabolism were detected by 3-(4,5)-dimethylthiahiazo(-z-y1)-3,5-di-phenytetrazoliumromide (MTT), assay kit, microscope observation and RT-PCR methods to explore the regulatory mechanism of mammary health and milk fat synthesis. The results showed that compared with those of the control group, the survival rates of cells were significantly decreased after 9 h of stimulation with 1000 ng/ml and 10000 ng/ml LPS (P<0.01). The contents of superoxide dismutase (SOD), catalase (CAT) and total antioxidant capacity (T-AOC) in cells were significantly decreased (P<0.05). Compared with that of the control group, the content of malondialdehyde (MDA) in cells was significantly increased (P<0.05) after stimulation with 10000 ng/ml LPS for 9 h. After 9 h of stimulation with 100 ng/ml, 1000 ng/ml and 10000 ng/ml LPS, the total lipid drop area and triglyceride (TG) content of MAC-T cells were significantly decreased (P<0.05). The expression levels of fatty acid synthesis-related genes Acetyl-CoA carboxylase (ACC) and Stearoyl-CoA desaturase 1 (SCD-1) were significantly decreased after 9 h of stimulation with 100 ng/ml, 1000 ng/ml and 10000 ng/ml LPS (P<0.05), while the expression levels of Fatty Acid synthetase (FAS) were significantly decreased after stimulation with 1000 ng/ml and 10000 ng/ml LPS (P<0.05). TG synthesis by the related gene Diacylglycerol acyltransferase-1 (DGAT1) was significantly lower than that of the control group after stimulation with 1000 ng/ml and 10000 ng/ml LPS for 9 h (P<0.05), and Diacylglycerol acyltransferase-2 (DGAT2) also showed a significant decrease after 10000 ng/ml LPS stimulation (P<0.05). In conclusion, adding different concentrations of LPS to MAC-T cells not only led to a decrease in cell activity, resulting in oxidative damage, but also affected fatty acid and TG synthesis, which may ultimately be closely related to the decrease in milk fat synthesis.

Effects of fasting on the activities and mRNA expression levels of lipoprotein lipase (LPL), hormone-sensitive lipase (HSL) and fatty acid synthetase (FAS) in spotted seabass Lateolabrax maculatus.

To investigate the effects of fasting on lipid metabolism in spotted seabass muscle and liver tissues, we analyzed mRNA levels and enzyme activities of lipoprotein lipase (LPL), hormone-sensitive lipase (HSL) and fatty acid synthetase (FAS), and the relationship among fat content, mRNA level, and enzyme activity during fasting of 35days. The results showed that expressions of all the three genes were ubiquitous. During the fasting experiment, the hepatosomatic index (HSI) and fat content of muscle and liver tissues significantly decreased before 5days of fasting (P < 0.05). mRNA levels of LPL increased significantly after 5days of fasting in liver and 7days in muscle. Abundance of HSL transcripts increased significantly after 14days of fasting in both muscle and liver. The activities of LPL and HSL presented a trend that increased firstly, decreased subsequently, and then raised again with the prolonged fasting experiment (P < 0.05). However, activities and mRNA levels of FAS decreased significantly after 1day of fasting in both muscle and liver. Moreover, activities and mRNA levels of FAS showed a moderate correlation in muscle. These results suggested that FAS had a sooner response to fasting than LPL and HSL in both muscle and liver tissues. LPL and HSL played important roles in lipolysis mainly by increasing enzyme activities in the early stage of fasting and mRNA levels in the later stage of fasting in both muscle and liver. Our results also provided useful information on regulating muscle fat content by fasting.

Role of RNA-binding protein HuR in human adipocyte differentiation

Objective To investigate the expressions of RNA-binding protein human antigen R(HuR), fatty acid binding protein type 4(FABP4), fatty acid synthetase(FASN), and lipoprotein lipase(LPL)during the differentiation of human adipocytes, and to explore their possible roles. Methods Human adipose-derived mesenchymal stem cells were induced by adipogenic differentiation, and the adipogenesis of cells was observed by oil red O staining. The expressions of HuR, FABP4, FASN, and LPL mRNA and protein were detected by real-time PCR and Western blotting. After HuR was silenced by siRNA, the change of adipogenesis for human adipose-derived mesenchymal stem cells was observed and the expressions of adipogenic genes were detected. Results The expressions of HuR, FABP4, FASN, and LPL mRNA and protein were significantly increased after human adipose-derived mesenchymal stem cells were induced to differentiate into adipocytes(all P<0.01). After HuR expression was down-regulated by siRNA, the adipogenic level of human adipose-derived mesenchymal stem cells was reduced, with decreased protein levels of FABP4, FASN, and LPL(all P<0.05), which were without changes for their mRNA levels. Conclusion HuR promotes the differentiation of human adipocytes mainly via regulating the changes of FABP4, FASN, and LPL protein levels. (Chin J Endocrinol Metab, 2017, 33: 854-860) Key words: Adipocyte differentiation; RNA binding protein; Human antigen R; Adipocyte fatty acid binding protein; Fatty acid synthase; Lipoprotein lipase

MiR-15b negatively correlates with lipid metabolism in mammary epithelial cells.

Mammary epithelial cells are regulated by steroid hormones, growth factors, and even microRNAs. miR-15b has been found to regulate lipid metabolism in adipocytes; however, its effects on lipid metabolism in mammary epithelial cells, the cells of lipid synthesis and secretion, are as yet unknown. The main purpose of this investigation was to explore the effect of miR-15b on lipid metabolism in mammary epithelial cells, along with the underlying mechanisms. miR-15b was overexpressed or inhibited by miRNA mimics or inhibitors; subsequently, lipid formation in mammary epithelial cells, and proteins related to lipid metabolism, were investigated. Through overexpression or inhibition of miR-15b expression, the current investigation found that miR-15b downregulates lipid metabolism in mammary epithelial cells and is expressed differentially at various stages of mouse and goat mammary gland development. Inhibition of miR-15b expression increased lipid content in mammary epithelial cells through elevation of the lipid synthesis enzyme fatty acid synthetase (FASN), and overexpression of miR-15b reduced lipid content in mammary epithelial cells with decreasing levels of FASN. Moreover, the steroid hormones estradiol and progesterone decreased miR-15b expression with a subsequent increase in lipid formation in mammary epithelial cells. The expression of miR-15b was lower during lactation and negatively correlated with lipid synthesis proteins, which suggests that it may be involved in lipid synthesis and milk production. miR-15b might be a useful target for altering lipid production and milk yield.

Effect of Dietary Surfactin Supplementation on Parameters Related to Lipid Metabolism of Orange-Spotted Grouper

This trial was conducted to investigate the effects of dietary surfactin supplementation on parameters related to lipid metabolism of orange-spotted grouper (Epinephelus coioides) juveniles. Three hundred and sixty fish were randomly divided into 6 treatment groups, and fed dietary surfactin levels: S0 (control group), S25, S50, S100, S150, and S200 mg/kg, respectively. Four replicates with 15 fish per tank were randomly assigned to each group. The trial period was 56 days. The lipid levels in serum, liver, and whole fish, and some lipid metabolism enzymes in the liver were measured. When compared to fish fed no surfactin, fish fed diets supplemented with surfactin presented lower levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, and higher levels of high-density lipoprotein cholesterol in serum; lower lipid levels in whole fish and liver (only 100 and 150 mg/kg surfactin groups) were observed. Dietary 100 mg/kg surfactin supplementation had the most influence on lipids level in serum, whole fish, and liver of orange-spotted grouper juveniles. Lower levels of fatty acid synthetase and higher activity of hepatic lipase and lipoprotein (lipase in liver) were affected only by 100 mg/kg surfactin supplementation in diet. The levels of acetyl CoA carboxylase were similar in all groups. This suggests that appropriate supplementation levels of surfactin in the diet of orange-spotted grouper juveniles might have beneficial effects on lipid metabolism to improve fish health status

Effect of Dietary Surfactin Supplementation on Parameters Related to Lipid Metabolism of Orange-Spotted Grouper

This trial was conducted to investigate the effects of dietary surfactin supplementation on parameters related to lipid metabolism of orange-spotted grouper (Epinephelus coioides) juveniles. Three hundred and sixty fish were randomly divided into 6 treatment groups, and fed dietary surfactin levels: S0 (control group), S25, S50, S100, S150, and S200 mg/kg, respectively. Four replicates with 15 fish per tank were randomly assigned to each group. The trial period was 56 days. The lipid levels in serum, liver, and whole fish, and some lipid metabolism enzymes in the liver were measured. When compared to fish fed no surfactin, fish fed diets supplemented with surfactin presented lower levels of total cholesterol, triglyceride, low-density lipoprotein cholesterol, and higher levels of high-density lipoprotein cholesterol in serum; lower lipid levels in whole fish and liver (only 100 and 150 mg/kg surfactin groups) were observed. Dietary 100 mg/kg surfactin supplementation had the most influence on lipids level in serum, whole fish, and liver of orange-spotted grouper juveniles. Lower levels of fatty acid synthetase and higher activity of hepatic lipase and lipoprotein (lipase in liver) were affected only by 100 mg/kg surfactin supplementation in diet. The levels of acetyl CoA carboxylase were similar in all groups. This suggests that appropriate supplementation levels of surfactin in the diet of orange-spotted grouper juveniles might have beneficial effects on lipid metabolism to improve fish health status

Combination therapy with catechins and caffeine inhibits fat accumulation in 3T3-L1 cells.

Catechins and caffeine, which are green tea components, have a slimming effect; however, the combinational effect of fat metabolism in 3T3-L1 cells remains unclear. In the present study, 3T3-L1 cells were treated with catechins and caffeine in combination, and it was found that combination therapy with catechins and caffeine markedly reduced intracellular fat accumulation, mRNA expression levels of peroxisome proliferator-activated receptor-γ and CCAAT/enhancer-binding protein α in the early stage of cell differentiation were significantly reduced, and mRNA expression of fatty acid synthetase(FAS) andglycerol-3-phosphate dehydrogenase protein expression levels of FAS were downregulated. Noradrenaline-induced lipolysis was enhanced by caffeine, which markedly increased the protein expression of adipose triglyceride lipase and hormone sensitive lipase. These results indicated that combination therapy with catechins and caffeine synergistically inhibited lipid accumulation by regulating the gene and protein expression levels of lipid metabolism-related enzymes. Therefore, catechins and caffeine combination therapy has potential as a functional food that may be used to prevent obesity and lifestyle-associated diseases.

Effects of postprandial starvation on mRNA expression of endocrine-, amino acid and peptide transporter-, and metabolic enzyme-related genes in zebrafish (Danio rerio)

The goal of this study was to systematically evaluate the molecular activities of endocrine-, amino acid and peptide transporters-, and metabolic enzyme-related genes in 35-day-old mixed-sex zebrafish (Danio rerio) after feeding . Zebrafish with initial body weights ranging from 9 to 11mg were fasted for 384h in a controlled indoor environment. Fish were sampled at 0, 3, 6, 12, 24, 48, 96, 192, and 384h after fed. Overall, the present study results show that the regulatory mechanism that insulin-like growth factor I negative feedback regulated growth hormone is conserved in zebrafish, as it is in mammals, but that regulation of growth hormone receptors is highly intricate. Leptin and cholecystokinin are time-dependent negative feedback signals, and neuropeptide Y may be an important positive neuropeptide for food intake in zebrafish. The amino acid/carnitine transporters B(0,+) (ATB(0,+)) and broad neutral (0) amino acid transporter 1(B(0)AT1) mRNA levels measured in our study suggest that protein may be utilized during 24-96h of fasting in zebrafish. Glutamine synthetase mRNA levels were downregulated, and glutamate dehydrogenase, alanine aminotransferase, aspartate transaminase, and trypsin mRNA levels were upregulated after longtime fasting in this study. The mRNA expression levels of fatty acid synthetase decreased significantly (P < 0.05), whereas those of lipoprotein lipase rapidly increased after 96h of fasting. Fasting activated the expression of glucose synthesis genes when fasting for short periods of time; when fasting is prolonged, the mRNA levels of glucose breakdown enzymes and pentose phosphate shunt genes decreased.

When Schwann Cells Conspire with Mitochondria, Neighboring Axons Are under Attack by Glia-Derived Neurotoxic Lipids

In this issue of Neuron, Viader etal. (2013) report on the production of toxic lipids by Schwann cells deficient in mitochondrial respiration, which are capable of destroying neighboring axons. This may have implications for understanding the neurobiology and treatment of mitochondrial neuropathies.

Nutritional and Hormonal Induction of Fatty Liver Syndrome and Effects of Dietary Lipotropic Factors in Egg-type Male Chicks.

This experiment was conducted with male chicks to investigate the influence of hormones and nutrients on the development of fatty liver syndrome (FLS) as well as the effects of dietary lipotropic factors on hepatic fat accumulation and lipogenic enzyme gene expression. A total of two-hundred sixteen 4-wk-old Hy-Line male chicks were divided into six groups and fed an experimental diet (T1, low-energy diet with low levels of lipotropic factors; T2, high-energy diet with low levels of lipotropic factors; T3 and T5, low-energy diet with high levels of lipotropic factors; T4 and T6, high-energy diet with high levels of lipotropic factors) for six weeks. The chicks in T5 and T6 groups were treated with intramuscular injections of estradiol benzoate for three days prior to biopsy and clinical analysis of FLS. Chicks treated with estrogen had significantly greater liver weights than untreated chicks. The abdominal fat contents were increased in chicks consuming high-energy diets as compared to those consuming low-energy diets. Treatment with estrogen significantly increased the concentrations of serum cholesterol, triacylglycerol and phospholipid (p<0.05). The hepatic triacylglycerol levels were tenfold higher in the estrogen treated chicks than in the untreated chicks. There were no significant differences in malondialdehyde levels between the treatment groups. Estrogen treatment dramatically increased the levels of fatty acid synthetase, acetyl-CoA carboxylase and ApoB mRNA. The results indicated that treatment with exogenous estrogen in growing male chicks induced hepatic fat accumulation, which might be partially due to increased lipogenic enzyme gene expression.

A high-glucose, fat-free diet rapidly causes a specific decrease in albumin mRNA even if the diet contains adequate protein

We have shown previously that a high-glucose, fat-free diet decreases the level of liver albumin mRNA in rat even though the diet contains excess protein (30%, w/w). This diet is unique in that it also decreases the higher-order coiling of liver nuclear chromatin. Altered chromatin structure is considered a prerequisite for gene expression. In this study we measured the rate at which liver albumin mRNA is decreased by a high-glucose, fat-free diet. We compared the rate of reduction of albumin mRNA with the rate of dietary induction of two other prominent liver mRNAs. Using RNA-cDNA hybridization, we measured the relative amounts of mRNA for liver albumin, fatty acid synthetase (FAS), and 6-phosphogluconate dehydrogenase (6-PGD) after refeeding a high-glucose, fat-free diet for two hours to 5 days following a 48-hour fast. The results show that a high-glucose, fat-free diet which contains adequate protein causes a maximal decrease in albumin mRNA after 8 hours, coinciding with increases in the levels of FAS and 6-PGD mRNAs. The latter two mRNAs are required for the biosynthesis of fatty acids from the excess carbohydrate. The results indicate that the hepatocyte can coordinately regulate the levels of specific mRNAs, by down-regulating the level of albumin mRNA. The relatively long half-life of the albumin protein may be a factor in the regulation of its mRNA.

Expression of the Progestin-Induced Fatty Acid Synthetase in Benign Mastopathies and Breast Cancer as Measured by RNA In Situ Hybridization

We have shown previously that fatty acid synthetase (FAS) is specifically induced by progestins in human breast cancer cell lines. To test the potential value of FAS as a clinical marker in breast diseases, we measured FAS expression in frozen sections of 22 benign and 27 malignant mammary tumors using in situ hybridization with the [35S]UTP alpha S-labeled FAS anti-sense mRNA. The hybridized RNA was quantified with an IMSTAR computerized image analyzer. We found FAS RNA in epithelial cells, but no labeling was detected in the connective tissue. In breast cancer, we found no correlation between FAS expression and estrogen receptor and progesterone receptor concentrations or status. However, the level of FAS was significantly (P less than .02) higher in premenopausal than in post-menopausal patients and increased with the grade of tumor differentiation (P less than .005 between the poorly and well-differentiated tumors). In benign mastopathies, high levels of FAS RNA were found in some cysts (mostly with apocrine metaplasia). In lobules, the FAS RNA level increased proportionally to the degree of proliferation determined by histological examination (P less than .015) and correlated with the H4 histone level measured in an adjacent section using in situ hybridization (r = 0.85, P less than .001). In ductal structures, a lower correlation (r = 0.64, P less than .01) was found between FAS and H4 RNA levels. We conclude that FAS RNA is overexpressed in some mammary tumors and may be useful in predicting high-risk mastopathies and less aggressive breast cancers.

Metabolism of cis-12-octadecadienic acid and trans-9, trans-12-octsidecadienoic acid and their influence on lipogenic enzyme activities in mouse liver

High carbohydrate (65% glucose) diets containing cis-12-octadecenoic acid (12 c-18:1) or trans-9, trans-12-octadecadienoic acid (9 t,12 t-18:2) were fed to weanling mice to investigate the influence of fatty acid structure on six hepatic enzyme activities involved in lipid metabolism. Results with these diets were compared to those with diets containing no fatty acids, saturated fatty acids; cis-9-octadecenoic acid (9 c-18: l) and cis-9, cis-12-octadecadienoic acid (9 c,12 c-18:2). These comparisons show saturated fatty acids, 9 c-18:1, 12 c-18:1, and 9 t,12 t-8:2, had little or no influence on the activity levels of fatty acid synthetase, malic enzyme (EC 1.1.1.40)citrate cleavage enzyme (EC 4.1.3.8), glucose-6-phosphate dehydrogenase (EC 1.1.1.49), 6-phosphogluconate dehydrogenase (EC 1.1.1.44) and acetyl-CoA carboxylase (EC 6.4.1.2). Neither 12 c-18:1 nor 9 t,12 t-18:2 produced the dramatic enzyme-lowering effect exhibited by the diet containing 9 c,12 c-18:2 when compared to the diet devoid of fat. Thus, both the 9 and 12 bonds must be present in the same molecule. Also, at least one and probably both bonds must be in the cis configuration to depress liver enzyme activities. Capillary gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) were both used for analysis of the methyl esters derived from the hepatic lipids. The GC and GC-MS data provided (a) direct evidence for incorporation of both isomers into hepatic lipids and (b) indirect evidence that 9 t,12 t-18:2 lowered liver Δ 9-desaturase activity. In addition, since these products were found in the complex liver lipids, there is no doubt that the various enzymes concerned with activation and acylation utilize both of these isomeric fatty acids as substrates.

The role of triiodothyronine in the regulation of synthesis rate and translatable mRNA level of fatty acid synthetase in a preadipocyte cell line

Triiodothyronine (T 3) effects on the activity, rate of synthesis and mRNA content of the key lipogenic enzyme, fatty acid synthetase, were studied in differentiating ob 17 preadipocytes cloned from ob/ob mouse epididymal adipose tissue. During differentiation in the presence of insulin, a 6–10-fold increase in both fatty acid synthetase specific activity and synthesis rate were reproducibly observed and occurred concomitantly. The relative synthesis rate exhibited a progressive elevation from 0.5% at confluence to a maximum level of 2% in the presence of insulin. The rate of the enzyme degradation determined by pulse-chase experiments was similar in differentiating cells and insulin-untreated cells of the same age ( t 1 2 , 40–42 h). Furthermore, the increase in the enzyme synthesis rate was preceded by a progressively elevating amount of mRNA encoding for this protein as detected by translation in a reticulocyte lysate cell-free system. It is thus suggested that the increment in total and neosynthesized fatty acid synthetase in essentially due to an increased enzyme synthesis, reflecting an increased relative content of its specific mRNA. T 3 included at a physiological concentration (1.5 nM) in the culture medium enhanced significantly both enzyme synthesis and its specific mRNA. The most important T 3 effect was an acceleration of both processes, a stimulation of the mRNA level being detected as early as day 3 post-confluence and maximum at day 5 when the effect on the synthetase synthesis rate and activity began to be enhanced. This suggests that T 3 would mainly affect fatty acid synthetase as a pretranslational level.

Lack of coordinated regulation of lipogenic enzymes in a human breast cell line, SKBr3

A human breast cell line has been identified which contains prodigious levels of fatty acid synthetase but has a very low capacity for lipogenesis from glucose, lactate or acetate. The fatty acid synthetase from this cell line appears to be structurally and functionally normal, and the low lipogenic capacity of the cells appears to be due to the low activities of other lipogenic enzymes, notably acetyl- CoA carboxylase. Thus, the SKBr3 cell line appears to lack the long-term coordinated control of acetyl-CoA carboxylase and fatty acid synthetase commonly observed in normal lipogenic tissues.