Endogenous Fatty Acid Synthesis Research Articles

Vitamin D deficiency promotes nonalcoholic steatohepatitis through impaired enterohepatic circulation in animal model.

Vitamin D deficiency (VDD) or insufficiency is recognized for its association with nonalcoholic steatohepatitis (NASH), whereas the underlying mechanism remains unknown. Using animal models, we found that vitamin D deficiency promoted the high-fat diet (HFD)-initiated simple steatosis into typical NASH, characterized by elevated hepatic inflammation and fat degeneration. The NASH derived from VDD + HFD was related to poor retention of bile acids in the liver and biliary tree, in line with downregulation of the ileal apical sodium-dependent bile acid cotransporter (iASBT). The impediment of hepatic bile acids by the VDD + HFD mice was related to increased expression of hepatic SREBP-1c and fatty acid synthase, suggesting that VDD may upregulate endogenous fatty acid synthesis into NASH through impaired enterohepatic circulation. Administration of 1,25(OH)2VD3 (calcitriol) corrected the NASH phenotypes in line with restoration of iASBT, promotion of bile filling in the biliary tree, suppression of hepatic lipogenesis, and inflammation. Moreover, administration of a bile acid-sequestering agent suppressed ileal fibroblast growth factor 15 expression, leading to increased iASBT expression to restore bile filling in the liver and biliary tree, which ameliorates steatosis and inflammation in the liver. These results suggest a novel mechanism for NASH development, by which VDD downregulates iASBT expression, resulting in a poor bile acid pool and elevation of hepatic lipogenesis and inflammation. In conclusion, vitamin D and bile acid sequestration may be explored as new strategies to treat or prevent NASH.

Alpha-2-glycoprotein 1(AZGP1) regulates biological behaviors of LoVo cells by down-regulating mTOR signaling pathway and endogenous fatty acid synthesis.

AZGP1 is a multifaceted protein associated with lipid mobilization, a process that is regulated by FASN and other metabolic pathways such as mTOR signaling. The active mTOR signaling pathway has been found to be involved in a variety of tumors. However, it remains unclear whether it is involved in the regulation of AZGP1 and FASN. An AZGP1-expressing plasmid was transfected into a human colorectal cancer cell line (LoVo) with a low expression of AZGP1. The expression of AZGP1, FASN, eIF4E, p-mTOR, p-S6,and S6K1 were measured by Western blot analysis, and target genes were detected by RT-PCR. Cell proliferation was studied using the MTT and colony formation assays. The analysis of apoptosis and the cell cycle phase were assessed by flow cytometry. The capacity of cell migration was investigated using the transwell migration assay. We found that the expression of AZGP1 was up-regulated while the expression of FASN, eIF4E, p-mTOR, p-S6, and S6K1 were down-regulated in LoVo cells after AZGP1 was expressed. The proliferation of malignant cells was reduced in AZGP1-overexpression cells, which is consistent with an increased in the G2-arrest and apoptosis rate. Furthermore, the migration of AZGP1-overexpression cells was decreased. The overexpression of AZGP1 suppressed the activation of the mTOR pathway and endogenous FASN-regulated fatty acid synthesis, mitigating the malignant phenotype of LoVo cells. Herein, we provide evidence that AZGP1 may constitute a novel tumor suppressor for LoVo colorectal cancer cells.

Common genetic variants and risk of brain injury after preterm birth.

The role of heritable factors in determining the common neurologic deficits seen after preterm birth is unknown, but the characteristic phenotype of neurocognitive, neuroanatomical, and growth abnormalities allows principled selection of candidate genes to test the hypothesis that common genetic variation modulates the risk for brain injury. We collected an MRI-linked genomic DNA library from 83 preterm infants and genotyped tag single nucleotide polymorphisms in 13 relevant candidate genes. We used tract-based spatial statistics and deformation-based morphometry to examine the risks conferred by carriage of particular alleles at tag single nucleotide polymorphisms in a restricted number of genes and related these to the preterm cerebral endophenotype. Carriage of the minor allele at rs2518824 in the armadillo repeat gene deleted in velocardiofacial syndrome (ARVCF) gene, which has been linked to neuronal migration and schizophrenia, and rs174576 in the fatty acid desaturase 2 gene, which encodes a rate-limiting enzyme for endogenous long chain polyunsaturated fatty acid synthesis and has been linked to intelligence, was associated with white matter abnormality measured in vivo using diffusion tensor imaging (P = .0009 and P = .0019, respectively). These results suggest that genetic variants modulate white matter injury after preterm birth, and known susceptibilities to neurologic status in later life may be exposed by the stress of premature exposure to the extrauterine environment.

Role of brain stearoyl‐CoA desaturase‐1 in metabolism, obesity, and glucose homeostasis (605.2)

The high prevalence of obesity, coupled with its potential to develop into serious health issues including type II diabetes, insulin resistance and coronary artery disease, reveals it is a significant health problem. To investigate how excess adipose tissue manifests into these health issues, we have observed the effects of a disruption in stearoyl‐CoA desaturase 1 (SCD1), which is involved in the synthesis of endogenous monounsaturated fatty acids from saturated fatty acids. We have previously demonstrated that whole‐body deficiency of SCD1 in mice protects from high‐fat diet‐induced obesity, hepatic steatosis and insulin resistance. However, the tissue‐specific contribution of SCD1 to these phenotypes remains to be fully elucidated. In the current study, we investigated the role of brain SCD1 in mediating the metabolic consequences of a high‐fat diet (HFD). We fed nestin‐cre+;SCD1 flox/flox brain‐specific SCD1 knockout (BKO) mice a HFD for 18 weeks. We observed that both male and female BKO mice weighed significantly less than Lox controls. In addition, male BKO mice had lower hepatic triglyceride levels than Lox mice, and enhanced glucose tolerance relative to Lox mice. Overall, these results indicate brain SCD1 plays a role in HFD‐induced adiposity and glucose homeostasis.

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.

Obez Kişilerde Plazma Yağ Asit Kompozisyonu, Desatüraz ve Elongaz Enzim Aktivitelerinin Değerlendirilmesi

Obesity is associated with an increased risk of insulin resistance, diabetes, hyperlipidemia, hypertension and elevated circulating fatty acids. Some of those abnormalities may be caused by an altered fatty acid metabolism. Increased plasma fatty acids in obese individuals may contribute to accelerate of β-oxidation and may also affect insulin sensivity. Fatty acid composition is used as an indicator of disease risk, because its alteration has been related to metabolic disease and cardiovascular disease. Desaturase are involved in the endogenous synthesis of polyunsaturated fatty acids. The delta 9, 6 and 5 desaturases introduce a double bond at specific positions on long chain fatty acids. Fatty acids of the enzymes responsible for chain extension process is called the elongase. In this paper, we review estimated, addressing the recent studies, plasma fatty acid composition, desaturase and elongase activity in obese people

Fatty acid synthase overexpression in adult testicular germ cell tumors: potential role in the progression of non-seminomatous germ cell tumors

Overexpression of fatty acid synthase (FASN), which is a key enzyme responsible for the endogenous synthesis of fatty acids, and its association with multistep progression have been demonstrated in various human malignant tumors. We aimed to clarify the potential role of FASN overexpression in the development and progression of adult testicular germ cell tumors (TGCTs). From the primary sites of a cohort of 113 TGCT cases, we obtained 221 histological components: 53 intratubular germ cell neoplasias, unclassified (IGCNUs), 84 seminomas, 32 embryonal carcinomas, seven choriocarcinomas, 21 yolk sac tumors, and 24 teratomas. Samples were analyzed for overexpression of FASN by immunohistochemistry. Intensities of immunoreactivity and the fraction of positive cells were classified into each four categories (intensity, 0 to 3; fraction, 0-10% = 1, 11-50% = 2, 51-80% = 3, and >80% = 4). The overall score was determined by multiplication of both scores and overall scores greater than 6 were considered FASN overexpression. On a component basis, FASN overexpression was detected in 8% of seminomas but not in IGCNUs (0%) and was detected frequently in non-seminomatous germ cell tumors (NSGCTs) (88% of embryonal carcinomas, all choriocarcinomas, 81% of yolk sac tumors, and 54% of teratomas). There were no cases of a mixed tumor (i.e., a tumor with multiple histological components) that overexpressed FASN in seminoma components but not in co-existing NSGCT components, suggesting sequential progression. Our immunohistochemical data suggest that FASN overexpression occurs as a late event during the progression from IGCNUs/seminomas to NSGCTs.

Fatty acid synthase plays a role in cancer metabolism beyond providing fatty acids for phospholipid synthesis or sustaining elevations in glycolytic activity

Fatty acid synthase is over-expressed in many cancers and its activity is required for cancer cell survival, but the role of endogenously synthesized fatty acids in cancer is unknown. It has been suggested that endogenous fatty acid synthesis is either needed to support the growth of rapidly dividing cells, or to maintain elevated glycolysis (the Warburg effect) that is characteristic of cancer cells. Here, we investigate both hypotheses. First, we compared utilization of fatty acids synthesized endogenously from 14C-labeled acetate to those supplied exogenously as 14C-labeled palmitate in the culture medium in human breast cancer (MCF-7 and MDA-MB-231) and untransformed breast epithelial cells (MCF-10A). We found that cancer cells do not produce fatty acids that are different from those derived from exogenous palmitate, that these fatty acids are esterified to the same lipid and phospholipid classes in the same proportions, and that their distribution within neutral lipids is not different from untransformed cells. These results suggest that endogenously synthesized fatty acids do not fulfill a specific function in cancer cells. Furthermore, we observed that cancer cells excrete endogenously synthesized fatty acids, suggesting that they are produced in excess of requirements. We next investigated whether lipogenic activity is involved in the maintenance of high glycolytic activity by culturing both cancer and non-transformed cells under anoxic conditions. Although anoxia increased glycolysis 2–3 fold, we observed no concomitant increase in lipogenesis. Our results indicate that breast cancer cells do not have a specific qualitative or quantitative requirement for endogenously synthesized fatty acids and that increased de novo lipogenesis is not required to sustain elevations in glycolytic activity induced by anoxia in these cells.

Sterol regulatory element binding protein 1 and its target gene networks

Sterol regulatory element binding protein 1 (SREBP-1) is one of the important nuclear transcription factors. SREBP-1 can maintain lipids dynamic equilibrium by regulating the expression of enzymes required for synthesis of endogenous cholesterol, fatty acids, triglycerides and phospholipids. Anomalies of SREBP-1 and its target genes can cause a series of metabolic diseases such as insulin resistance, type Ⅱ diabetes, heart dysfunction, vascular complications and hepatic steatosis. In these years, the development of high-throughput technologies has greatly expanded our knowledge about SREBP-1 target genes and the pattern of transcriptional regulation. Here we reviewed recent research progress of SREBP-1, with a focus on the protein structure, activation process, DNA binding sites and target genes. Most importantly, we showed the transcriptional regulatory networks based on omics datasets, which will contribute to a better understanding of the role of SREBP-1 in lipid metabolism and provide new clues for the treatment of lipid metabolism disorders.

Dietary Fats And Metabolic Syndrome

The quantity and quality of fats consumed in the diet can have important effects on prevention and/or improvement clustering metabolic abnormalities of the metabolic syndrome. Fatty acids as food ingredients regulate cholesterol homeostasis and concentrations of blood lipoproteins, and affect the levels of other cardiometabolic risk factors, such as blood pressure, haemostasis, and body weight, through various mechanisms. There is convincing evidence that exchanging dietary saturated fat with monounsaturated fat produces beneficial effects on metabolic control, i.a. it lowers LDL-cholesterol concentrations, improves the postprandial lipid profile and lowers the blood pressure. Serum fatty acid composition mainly reflects dietary fat intake, but also endogenous fatty acid synthesis catalyzed by desaturases. Furthermore, high fat intake and serum fatty acid profile may influence the progression of obesity and insulin sensitivity. This review highlights current dietary guidance of fats quality recommendation in health and cardio metabolic risk.

Phenotyping the effect of diet on non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is associated with the growing incidence of metabolic syndrome. Diet is an important contributor to the pathogenesis of NAFLD. In this review, we focused on recent publications reporting on the effect of macro- and micronutrients on development and progression of NAFLD. In general, saturated fat and fructose seem to stimulate hepatic lipid accumulation and progression into NASH, whereas unsaturated fat, choline, antioxidants, and high-protein diets rich in isoflavones seem to have a more preventive effect. Knowledge of the underlying mechanisms by which diet affects NAFLD is expanding, not in the least due to innovative techniques, such as genomics tools that provide detailed comprehensive information on a large high-throughput scale. Although most nutrients seem to interfere with the balance between hepatic de novo lipogenesis (endogenous synthesis of fatty acids) and lipid oxidation (burning fat for energy), there are also indications that diet can trigger or prevent hepatic lipid accumulation by influencing the interaction between liver, gut, and adipose tissue. This review now gives a current detailed overview of diet-mediated mechanisms underlying NAFLD development and progression and summarizes recent results of genomics (transcriptomics, proteomics and metabolomics) studies that contribute to improved staging, monitoring and understanding of NAFLD pathophysiology.

Abstract 5154: Fatty acids mediated regulation of cancer metabolism

Abstract Although fatty acids have been shown to modulate progression, growth and invasiveness of cancer cells, it remains unclear how saturated and unsaturated fatty acids affect metabolic reprogramming of aggressive and nonaggressive cancer metabolism. In this study, we tested the hypothesis that fatty acids induce differential competitive effects on glucose oxidation in aggressive and nonaggressive ovarian cancer cells. Normal cells rely mainly on mitochondrial oxidative phosphorylation for their required energy supply, however, cancer cells utilize aerobic glycolysis pathway for their energetic need. We hypothesized that high fat diet could deregulate this metabolic alteration in cancer cells. Such as glucose, fatty acids are an influential source of ATP, energy currency, within a cell. In our study, using metabolic footprinting we studied the affect of both saturated (stearic and palmitic acid) and unsaturated fatty acids (linoleic and oleic) on glycolysis, pentose phosphate pathway and TCA cycle. Moreover, we also studied the effect of glucose on fatty acid oxidation, uptake and endogenous fatty acid synthesis. Metabolic flux analysis was done for comparative metabolic profiling under various nutritional conditions. We observed that fatty acids differentially regulate highly invasive ovarian cancer (SKOV3 and SKOV3ip) cells than less invasive ovarian cancer (OVCAR3) cells. Interestingly, we found strong effect of fatty acids on glycolysis in less invasive cancer cells. In contrast, our study showed that glucose has dominant effect on aggressive cells compared to less aggressive cells. Our studies emphasize the role of fatty acids in ovarian cancer growth, invasion and migration and underlie the need to develop therapy based on high fat diet synergistically with existing chemotherapeutics and cancer drugs. 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 5154. doi:1538-7445.AM2012-5154

Global mapping of protein phosphorylation events identifies Ste20, Sch9 and the cell-cycle regulatory kinases Cdc28/Pho85 as mediators of fatty acid starvation responses in Saccharomyces cerevisiae

Synthesis, degradation, and metabolism of fatty acids are strictly coordinated to meet the nutritional and energetic needs of cells and organisms. In the absence of exogenous fatty acids, proliferation and growth of the yeast Saccharomyces cerevisiae depends on endogenous synthesis of fatty acids, which is catalysed by fatty acid synthase. In the present study, we have used quantitative proteomics to examine the cellular response to inhibition of fatty acid synthesis in Saccharomyces cerevisiae. We have identified approximately 2000 phosphorylation sites of which more than 400 have been identified as being regulated in a temporal manner in response to inhibition of fatty acid synthesis by cerulenin. By bioinformatic analysis of these phosphorylation events, we have identified the cell cycle kinases Cdc28 and Pho85, the PAK kinase Ste20 as well as the protein kinase Sch9 as central mediators of the cellular response to inhibition of fatty acid synthesis.

Lipid alterations in human colon epithelial cells induced to differentiation and/or apoptosis by butyrate and polyunsaturated fatty acids

The present study highlights the important association between lipid alterations and differentiation/apoptotic responses in human colon differentiating (FHC) and nondifferentiating (HCT-116) cell lines after their treatment with short-chain fatty acid sodium butyrate (NaBt), polyunsaturated fatty acids (PUFAs), and/or their combination. Our data from GC/MS and LC/MS/MS showed an effective incorporation and metabolization of the supplemented arachidonic acid (AA) or docosahexaenoic acid (DHA), resulting in an enhanced content of the respective PUFA in individual phospholipid (PL) classes and an altered composition of the whole cellular fatty acid spectrum in both FHC and HCT-116 cells. We provide novel evidence that NaBt combined with PUFAs additionally modulated AA and DHA cellular levels and caused their shift from triacylglycerol to PL fractions. NaBt increased, while AA, DHA and their combination with NaBt decreased endogenous fatty acid synthesis in FHC but not in HCT-116 cells. Fatty acid treatment also altered membrane lipid structure, augmented cytoplasmic lipid droplet accumulation, reactive oxygen species (ROS) production and dissipation of the mitochondrial membrane potential. All these parameters were significantly enhanced by combined NaBt/PUFA treatment, but only in FHC cells was this accompanied by highly increased apoptosis and suppressed differentiation. Moreover, the most significant changes of ROS production, differentiation and apoptosis among the parameters studied, the highest effects of combined NaBt/PUFA treatment and a lower sensitivity of HCT-116 cells were confirmed using two-way ANOVA. Our results demonstrate an important role of fatty acid-induced lipid alterations in the different apoptotic/differentiation response of colon cells with various carcinogenic potential.

Translational control of the sterol-regulatory transcription factor SREBP-1 mRNA in response to serum starvation or ER stress is mediated by an internal ribosome entry site

SREBPs (sterol-regulatory-element-binding proteins) are a family of transcription factors that modulate the expression of several enzymes implicated in endogenous cholesterol, fatty acid, triacylglycerol and phospholipid synthesis. In the present study, evidence for SREBP-1 regulation at the translational level is reported. Using several experimental approaches, we have demonstrated that the 5'-UTR (untranslated region) of the SREBP-1a mRNA contains an IRES (internal ribosome entry site). Transfection experiments with the SREBP-1a 5'-UTR inserted in a dicistronic reporter vector showed a remarkable increase in the downstream cistron translation, through a cap-independent mechanism. Insertion of the SREBP-1c 5'-UTR in the same vector also stimulated the translation of the downstream cistron, but the observed effect can be ascribed, at least in part, to a cryptic promoter activity. Cellular stress conditions, such as serum starvation, caused an increase in the level of SREBP-1 precursor and mature form in both Hep G2 and HeLa cells, despite the overall reduction in protein synthesis, whereas mRNA levels for SREBP-1 were unaffected by serum starvation. Transfection experiments carried out with a dicistronic construct demonstrated that the cap-dependent translation was affected more than IRES-mediated translation by serum starvation. The thapsigargin- and tunicamycin-induced UPR (unfolded protein response) also increased SREBP-1 expression in Hep G2 cells, through the cap-independent translation mediated by IRES. Overall, these findings indicate that the presence of IRES in the SREBP-1a 5'-UTR allows translation to be maintained under conditions that are inhibitory to cap-dependent translation.

ErbB receptors and fatty acid synthase expression in aggressive head and neck squamous cell carcinomas

Overexpression of ErbB receptors is frequent in head and neck squamous cell carcinomas (HNSCC) and seems to be correlated with tumor progression and metastasis. Fatty acid synthase (FASN), the key lipogenic enzyme responsible for the endogenous synthesis of fatty acids, is regulated by ErbB2 and overexpressed in several human malignancies. This study was performed to examine the immunohistochemical expression patterns of ErbB1, ErbB2, ErbB3, ErbB4, and FASN in a tissue microarray, containing 33 representative areas from aggressive primary HNSCC (whose patients had distant metastasis), and 21 matched lung metastasis. Strong correlation among the expression of ErbB family receptors was found (ErbB1-ErbB2 P = 0.008, ErbB1-ErbB4 P = 0.018, EbB2-ErbB3 P = 0.001, ErbB2-ErbB4 P = 0.006, ErbB3-ErbB4 P=0.012) in the HNSCC. FASN expression was significantly associated with ErbB2 (P = 0.024). Lymphatic permeation was correlated with ErbB3 (P = 0.033) and histological grade with ErbB4 staining (P = 0.050). ErbB1 and ErbB2 were found mainly in patients with smoking habit (P = 0.011 and P = 0.027), and ErbB2 was associated with alcohol consumption and clinical stage (P = 0.014 and P = 0.031). Finally, FASN was overexpressed in lung metastasis, in comparison with matched HNSCC samples (P = 0.006). The results showed that high FASN immunohistochemical expression is a feature of HNSCC lung metastasis, and ErbB1-ErbB2, ErbB1-ErbB4, ErbB2-ErbB3, ErbB2-ErbB4, and ErbB3-ErbB4 expression levels are correlated in the respective primary tumors, being ErbB2 the preferred coexpression partner of all the other ErbB receptors.

Calorie restriction increases fatty acid synthesis and whole body fat oxidation rates

Calorie restriction (CR) increases longevity and retards the development of many chronic diseases, but the underlying metabolic signals are poorly understood. Increased fatty acid (FA) oxidation and reduced FA synthesis have been hypothesized to be important metabolic adaptations to CR. However at steady state, FA oxidation must match FA intake plus synthesis; FA intake is low, not high, during CR. It is therefore not clear how FA dynamics are altered during CR. Accordingly, we measured food intake patterns, whole‐body fuel selection, endogenous FA synthesis and gene expression in mice on CR. Within two days of starting CR, a shift occurred to a cyclic pattern of whole‐body FA metabolism, with an initial phase of elevated endogenous FA synthesis (respiratory exchange ratio [RER]>1.10, lasting 4–6 hours after food provision), followed by a prolonged phase of FA oxidation (RER=0.70, lasting 18–20 hours). CR mice oxidized four times as much fat per day as ad libitum fed (AL) controls (367 vs 97 mg/d) despite reduced fat intake. This increase in FA oxidation was balanced by a 3‐fold increase in adipose tissue FA synthesis. We conclude that CR induces a surprising metabolic pattern characterized by periods of elevated FA synthesis alternating with periods of FA oxidation disproportionate to dietary FA intake. This pattern may have implications for understanding the reduced oxidative damage and disease risk in CR animals.Grant Funding Source: NIH

Calorie restriction increases fatty acid synthesis and whole body fat oxidation rates

Calorie restriction (CR) increases longevity and retards the development of many chronic diseases, but the underlying metabolic signals are poorly understood. Increased fatty acid (FA) oxidation and reduced FA synthesis have been hypothesized to be important metabolic adaptations to CR. However, at metabolic steady state, FA oxidation must match FA intake plus synthesis; moreover, FA intake is low, not high, during CR. Therefore, it is not clear how FA dynamics are altered during CR. Accordingly, we measured food intake patterns, whole body fuel selection, endogenous FA synthesis, and gene expression in mice on CR. Within 2 days of CR being started, a shift to a cyclic, diurnal pattern of whole body FA metabolism occurred, with an initial phase of elevated endogenous FA synthesis [respiratory exchange ratio (RER) >1.10, lasting 4-6 h after food provision], followed by a prolonged phase of FA oxidation (RER = 0.70, lasting 18-20 h). CR mice oxidized four times as much fat per day as ad libitum (AL)-fed controls (367 +/- 19 vs. 97 +/- 14 mg/day, P < 0.001) despite reduced energy intake from fat. This increase in FA oxidation was balanced by a threefold increase in adipose tissue FA synthesis compared with AL. Expression of FA synthase and acetyl-CoA carboxylase mRNA were increased in adipose and liver in a time-dependent manner. We conclude that CR induces a surprising metabolic pattern characterized by periods of elevated FA synthesis alternating with periods of FA oxidation disproportionate to dietary FA intake. This pattern may have implications for oxidative damage and disease risk.

Clinicopathological significance of ubiquitin-specific protease 2a (USP2a), fatty acid synthase (FASN), and ErbB2 expression in oral squamous cell carcinomas

Overexpression of fatty acid synthase (FASN) and ErbB2 has been described in oral squamous cell carcinomas (OSCC). FASN is the key lipogenic enzyme responsible for the endogenous synthesis of fatty acids and its expression can be regulated by ErbB2. The deubiquitinating enzyme (DUB) ubiquitin-specific protease 2a (USP2a) plays a critical role in prostate cancer cell survival by stabilizing the FASN protein. This study investigates whether the gene expression and the immunohistochemical status of FASN, ErbB2, and USP2a correlate with the clinicopathological characteristics of OSCC cases. A strong positive correlation among ErbB2, FASN, and USP2a expression (p=0.001) was observed by qRT-PCR in laser capture microdissected OSCC samples. Perineural infiltration was associated with ErbB2 mRNA expression (p=0.046). The presence of metastatic cervical lymph nodes was associated with FASN (p=0.002), ErbB2 (p=0.001), and USP2a (p=0.006) mRNA levels. ErbB2 staining at the cell membranes was stronger in well-differentiated lesions while a cytoplasmic positivity was found in poorly differentiated tumors. Most of the OSCC (97.06%) that showed a high positivity for FASN were also labeled for ErbB2 at the cell membranes (p=0.001). FASN and ErbB2 positivity was associated with tumor thickness and lymphatic embolization (p=0.006 and p=0.035, p=0.006 and p=0.024 respectively). The membrane expression of ErbB2 as well as FASN and Ki-67 staining were significantly associated with a high risk of recurrence by predicting both disease free survival (log-rank test, p=0.0056, p=0.0011, and p=0.0004, respectively) and overall survival (log-rank test, p=0.0005, p=0.0062, and p=0.0001, respectively). Taken together, the results presented here suggest a molecular connection among FASN, ErbB2, and USP2a in OSCC since their mRNA and protein levels were associated with tumor progression and poor prognosis.

Lower estimates of δ-5 desaturase and elongase activity are related to adverse profiles for several metabolic risk factors in young Japanese women

Little is known about the relation between the activities of certain enzymes involved in endogenous fatty acid synthesis and metabolic risk factors, particularly in young adults and non-Western populations. In this cross-sectional study, we examined the associations between estimated desaturase and elongase activities and metabolic risk factors in young Japanese women. The subjects were 640 female Japanese dietetic students aged 18 to 22 years. Body height and weight, from which body mass index (BMI) was derived, waist circumference, and blood pressure were measured. Fasting blood samples were collected for biochemical and fatty acid measurements. Desaturase and elongase enzyme activities were estimated as the ratio of product to precursor of individual fatty acids in serum lipids. delta-9 desaturase activity was positively associated with BMI, diastolic blood pressure, total and low-density lipoprotein cholesterol, and triacylglycerol and was negatively associated with high-density lipoprotein cholesterol (P <or= .019). delta-6 desaturase activity showed positive associations with BMI, systolic blood pressure, triacylglycerol, and the homeostasis model assessment of insulin resistance (P <or= .045). delta-5 desaturase activity showed independent negative associations with BMI, systolic blood pressure, triacylglycerol, insulin, and the homeostasis model assessment of insulin resistance (P <or= .007). Elongase activity was associated negatively with BMI, systolic and diastolic blood pressures, and triacylglycerol and was positively associated with high-density lipoprotein cholesterol (P <or= .026). In conclusion, increased estimates of delta-9 and delta-6 desaturase activity and decreased estimates of delta-5 desaturase and elongase activity were associated with adverse profiles for several metabolic risk factors in young Japanese women.