Helena Fonseca Raposo

Fatty acid synthase inhibition with Orlistat promotes apoptosis and reduces cell growth and lymph node metastasis in a mouse melanoma model

Fatty acid synthase (FASN) is the enzyme responsible for the endogenous synthesis of the saturated fatty acid palmitate. In contrast to most normal cells, malignant cells depend on FASN activity for growth and survival. In fact, FASN is overexpressed in a variety of human cancers including cutaneous melanoma, in which its levels of expression are associated with a poor prognosis and depth of invasion. Here, we show that the specific inhibition of FASN activity by the antiobesity drug Orlistat or siRNA is able to significantly reduce proliferation and promote apoptosis in the mouse metastatic melanoma cell line B16‐F10. These results prompted us to verify the effect of FASN inhibition on the metastatic process in a model of spontaneous melanoma metastasis, in which B16‐F10 cells injected in the peritoneal cavity of C57BL/6 mice metastasize to the mediastinal lymph nodes. We observed that mice treated with Orlistat 48 hr after the inoculation of B16‐F10 cells exhibited a 52% reduction in the number of mediastinal lymph node metastases, in comparison with the control animals. These results suggest that FASN activity is essential for B16‐F10 melanoma cell proliferation and survival while its inactivation by Orlistat significantly reduces their metastatic spread. The chemical inhibition of FASN activity could have a potential benefit in association with the current chemotherapy for melanoma.

The Fatty Acid Synthase Inhibitor Orlistat Reduces the Growth and Metastasis of Orthotopic Tongue Oral Squamous Cell Carcinomas

Fatty acid synthase (FASN) is the biosynthetic enzyme responsible for the endogenous synthesis of fatty acids. It is downregulated in most normal cells, except in lipogenic tissues such as liver, lactating breast, fetal lung, and adipose tissue. Conversely, several human cancers, including head and neck squamous cell carcinomas (HNSCC), overexpress FASN, which has been associated with poor prognosis and recently suggested as a metabolic oncoprotein. Orlistat is an irreversible inhibitor of FASN activity with cytotoxic properties on several cancer cell lines that inhibits tumor progression and metastasis in prostate cancer xenografts and experimental melanomas, respectively. To explore whether the inhibition of FASN could impact oral tongue squamous cell carcinoma (OTSCC) metastatic spread, an orthotopic model was developed by the implantation of SCC-9 ZsGreen LN-1 cells into the tongue of BALB/c nude mice. These cells were isolated through in vivo selection, show a more invasive behavior in vitro than the parental cells, and generate orthotopic tumors that spontaneously metastasize to cervical lymph nodes in 10 to 15 days only. SCC-9 ZsGreen LN-1 cells also exhibit enhanced production of MMP-2, ERBB2, and CDH2. The treatment with orlistat reduced proliferation and migration, promoted apoptosis, and stimulated the secretion of VEGFA165b by SCC-9 ZsGreen LN-1 cells. In vivo, the drug was able to decrease both the volume and proliferation indexes of the tongue orthotopic tumors and, importantly, reduced the number of metastatic cervical lymph nodes by 43%. These results suggest that FASN is a potential molecular target for the chemotherapy of patients with OTSCC. Mol Cancer Ther; 13(3); 585–95. ©2013 AACR.

Inhibition of fatty acid synthase in melanoma cells activates the intrinsic pathway of apoptosis

Fatty acid synthase (FASN) is the metabolic enzyme responsible for the endogenous synthesis of the saturated long-chain fatty acid, palmitate. In contrast to most normal cells, FASN is overexpressed in a variety of human cancers, including cutaneous melanoma, in which its levels of expression are associated with tumor invasion and poor prognosis. We have previously shown that FASN inhibition with orlistat significantly reduces the number of spontaneous mediastinal lymph node metastases following the implantation of B16-F10 mouse melanoma cells in the peritoneal cavity of C57BL/6 mice. In this study, we investigate the biological mechanisms responsible for the FASN inhibition-induced apoptosis in B16-F10 cells. Both FASN inhibitors, cerulenin and orlistat, significantly reduced melanoma cell proliferation and activated the intrinsic pathway of apoptosis, as demonstrated by the cytochrome c release and caspase-9 and -3 activation. Further, apoptosis was preceded by an increase in both reactive oxygen species production and cytosolic calcium concentrations and independent of p53 activation and mitochondrial permeability transition. Taken together, these findings demonstrate the mitochondrial involvement in FASN inhibition-induced apoptosis in melanoma cells.

Fibrates and fish oil, but not corn oil, up-regulate the expression of the cholesteryl ester transfer protein (CETP) gene☆

Cholesteryl ester transfer protein (CETP) is a plasma protein that reduces high density lipoprotein (HDL)-cholesterol (chol) levels and may increase atherosclerosis risk. n-3 and n-6 polyunsaturated fatty acids (PUFAs) are natural ligands, and fibrates are synthetic ligands for peroxisome proliferator activated receptor-alpha (PPARα), a transcription factor that modulates lipid metabolism. In this study, we investigated the effects of PUFA oils and fibrates on CETP expression. Hypertriglyceridemic CETP transgenic mice were treated with gemfibrozil, fenofibrate, bezafibrate or vehicle (control), and normolipidemic CETP transgenic mice were treated with fenofibrate or with fish oil (FO; n-3 PUFA rich), corn oil (CO, n-6 PUFA rich) or saline. Compared with the control treatment, only fenofibrate significantly diminished triglyceridemia (50%), whereas all fibrates decreased the HDL-chol level. Elevation of the CETP liver mRNA levels and plasma activity was observed in the fenofibrate (53%) and gemfibrozil (75%) groups. Compared with saline, FO reduced the plasma levels of nonesterified fatty acid (26%), total chol (15%) and HDL-chol (20%). Neither of the oil treatments affected the plasma triglyceride levels. Compared with saline, FO increased the plasma adiponectin level and reduced plasma leptin levels, whereas CO increased the leptin levels. FO, but not CO, significantly increased the plasma CETP mass (90%) and activity (23%) as well as increased the liver level of CETP mRNA (28%). In conclusion, fibrates and FO, but not CO, up-regulated CETP expression at both the mRNA and protein levels. We propose that these effects are mediated by the activation of PPARα, which acts on a putative PPAR response element in the CETP gene.

Efeito dos ácidos graxos n-3 e n-6 na expressão de genes do metabolismo de lipídeos e risco de aterosclerose

Atherosclerosis, the main cause of myocardial infarction, stroke, gangrene and other peripheral vascular diseases, also persists as the main cause of morbidity and mortality in Western populations. Roughly 17.5 million people died from cardiovascular diseases in 2005, representing 30% of the causes of death in that year, and in 2015, another 20 million people will die of cardiovascular diseases around the world. The n-3 fatty acids, especially the long-chain n-3 found in fish, have been shown to be particularly effective in the prevention and treatment of diseases such as dyslipidemias, diabetes mellitus and obesity, presenting an important cardioprotective effect. In this context, studies have found that at least some of the cardiovascular benefits associated with eicosapentaenoic and docosahexaenoic fatty acids regard the modulation of genes that respond to the peroxisome proliferator-activated receptors involved in lipid metabolism. This review will discuss some of the mechanisms of action of some n-3 and n-6 fatty acids on the metabolism of lipids and lipoproteins. In conclusion, many aspects that contribute to the risk of cardiovascular diseases are affected by n-3 intake. N-3 fatty acids not only reduce triglycerides, but also promote factors that increase adiponectin, reduce blood cholesterol levels and improve the reverse cholesterol transport, and all of these contribute to reducing the risk of atherosclerosis. However, additional studies are still necessary to elucidate all the cellular and molecular mechanisms responsible for the cardioprotective effect of n-3 fatty acids.

Apolipoprotein CIII Overexpression-Induced Hypertriglyceridemia Increases Nonalcoholic Fatty Liver Disease in Association with Inflammation and Cell Death

Nonalcoholic fatty liver disease (NAFLD) is the principal manifestation of liver disease in obesity and metabolic syndrome. By comparing hypertriglyceridemic transgenic mice expressing apolipoprotein (apo) CIII with control nontransgenic (NTg) littermates, we demonstrated that overexpression of apoCIII, independent of a high-fat diet (HFD), produces NAFLD-like features, including increased liver lipid content; decreased antioxidant power; increased expression of TNFα, TNFα receptor, cleaved caspase-1, and interleukin-1β; decreased expression of adiponectin receptor-2; and increased cell death. This phenotype is aggravated and additional NAFLD features are differentially induced in apoCIII mice fed a HFD. HFD induced glucose intolerance together with increased gluconeogenesis, indicating hepatic insulin resistance. Additionally, the HFD led to marked increases in plasma TNFα (8-fold) and IL-6 (60%) in apoCIII mice. Cell death signaling (Bax/Bcl2), effector (caspase-3), and apoptosis were augmented in apoCIII mice regardless of whether a HFD or a low-fat diet was provided. Fenofibrate treatment reversed several of the effects associated with diet and apoCIII expression but did not normalize inflammatory traits even when liver lipid content was fully corrected. These results indicate that apoCIII and/or hypertriglyceridemia plays a major role in liver inflammation and cell death, which in turn increases susceptibility to and the severity of diet-induced NAFLD.

Taioba (Xanthosoma sagittifolium) Leaves: Nutrient Composition and Physiological Effects on Healthy Rats

Several studies have shown that fruits and vegetables contribute to protect against degenerative pathologies such as cardiovascular diseases, diabetes, and cancer, mainly due to the presence of dietary fiber (DF) and polyphenols. Taioba (Xanthosoma sagittifolium) is an edible aroid widely grown in many parts of Africa, America, and Asia. The tubers portions of taioba are widely consumed; however, the leafy portions are generally discarded, despite their high nutritive value. In this study, we have partly characterized the DF of lyophiized taioba leaf (LTL), and assessed the possible protective effects on biochemical parameters and on bile acid (BA) production in colon and cecum, when fed to healthy rats for 4 wk. Forty-five Wistar rats were assigned to either of 5 groups: group 1 received AIN 93G diet (CG: Control); group 2 received AIN 93G containing 2.5% of cellulose + 2.5% inulin (CEIN_5%); group 3 received AIN 93G containing 2.5% of cellulose + 2.5% taioba fiber (CETA_5%); group 4 received AIN 93G containing 5% cellulose + 2.5% taioba fiber (CETA_7.5%); group 5 received AIN 93G containing 5% cellulose + 2.5% of inulin (CEIN_7.5%). LTL showed high contents of total fiber, predominantly comprising insoluble DF with glucose as the major monomer. Rats receiving LTL had increased fecal mass and fat excretion, and improved BA profiles by diminishing the proportion of secondary acids, thus suggesting that consumption of taioba leaf may have the property of lowering the risk of colon cancer.

Chia oil supplementation changes body composition and activates insulin signaling cascade in skeletal muscle tissue of obese animals

OBJECTIVE Chia seed oil is the richest source of plant-based ω-3 fatty acid, α-linolenic acid, but its potential and mechanisms of action to treat obesity are unclear. The aim of the study was to evaluate the effects of chia oil (ChOi) supplementation on body composition and insulin signaling in skeletal muscles of obese mice. METHODS Male C57 BL/6 mice (n = 8/group) were fed regular control chow or a high-fat diet (HFD) for 135 d. Another HFD group additionally received ChOi from 90 to 135 d. RESULTS Consumption of ChOi reduced fat mass accumulation and increased lean mass as evidenced by nuclear magnetic resonance. Moreover, obese mice treated with ChOi showed higher tyrosine phosphorylation of insulin receptor substrate 1, greater activation of protein kinase B, and increased translocation of glucose transporter type 4 in skeletal muscle tissue in response to insulin. ChOi supplementation improved glucose levels and insulin tolerance; decreased serum insulin, leptin, and triacylglycerols; and increased blood high-density lipoprotein cholesterol levels. All these effects caused by the use of ChOi seemed to be independent of the resolution of inflammation because the markers of inflammation were not altered in animals fed the HFD. CONCLUSION The molecular effects observed in muscle tissue together with changes in body composition may have contributed to the increased glucose tolerance and to the healthy phenotype presented by obese animals treated with ChOi.

Cholesteryl ester transfer protein (CETP) enhances interscapular brown adipose tissue (iBAT) temperature and induces a greater increment in iBAT mass when exposed to cold

Abstract Cholesteryl ester transfer protein CETP is a plasma protein that mediates the exchange of triglycerides for esterified cholesterol from HDL to the apoB containing lipoproteins. In this way, CETP promotes reduction of plasma HDLcholesterol and, thus, increases the risk of atherosclerosis. Recently, we identified a new role for CETP, in that CETP may modulate adiposity. Previous data from our group shows that CETP expression reduces adipose tissue mass (~30%) and leptinemia (40%), what cannot be explained by differences in fat intake or excretion. The effect on adiposity is explained by increased lipolysis rates and whole body energy expenditure EE(50 and 10%, respectively). Here, we show that CETP expressing transgenic mice have similar spontaneous activity, and citrate synthase activity (mitochondria number marker) is not increased in liver, muscle and iBAT. Although rectal temperature is reduced in CETP group, the iBAT temperature was increased (more than 1oC). Moreover, cold exposure (4 oC) for 10 days increased iBAT mass 15% more in CETP group than in NTg group. During this period, growth and food intake were similar between groups. These findings suggest that the increase in EE in CETP expressing mice might be due to interscapular brown adipose tissue (iBAT) activity, what leads to the adiposity reduction effect of CETP.