Increase In Lipogenesis Research Articles

Hepatocellular Carcinoma-Associated Protein TD26 Interacts and Enhances Sterol Regulatory Element-Binding Protein 1 Activity to Promote Tumor Cell Proliferation and Growth.

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide. Increased lipogenesis has been reported to play a critical role in HCC progression. However, the underlying mechanism contributing to lipogenesis increase in HCC remains elusive. Here, we show that HCC-associated protein TD26 (TD26) was highly expressed in HCC tumor tissues compared to matched normal tissues. From the clinicopathologic analyses of two independent HCC cohorts, we demonstrate that TD26 expression was positively correlated with tumor size and was an independent predictor of overall survival (OS) and recurrence-free survival (RFS) in HCC patients. Our metabolomics assays demonstrate that TD26 had no effect on glycometabolism, but significantly increased lipogenesis in HCC cells. In addition, our functional assays indicate that TD26 promoted HCC cell proliferation and tumor growth. We further demonstrate that TD26-mediated increase in lipogenesis and tumor cell proliferation was SREBP1 dependent. Mechanistically, we demonstrate that, through its C-terminus (amino acids [aa] from 121 to 198), TD26 interacted with the truncated nuclear sterol regulatory element-binding protein 1 (SREBP1) form (nSREBP1), but not full-length SREBP1 (flSREBP1), to block adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)-mediated inhibition on SREBP1 activity, resulting in increased lipogenesis, elevated tumor cell proliferation, and enhanced tumor progression. Conclusion: We propose that TD26 is a positive regulator on SREBP1 transactivity, and the interaction between TD26 and SREBP1 can serve as a potential therapeutic target for HCC treatment.

Vitamin D deficiency aggravates the liver metabolism and inflammation in ovariectomized mice

AimsA prevalence of vitamin D deficiency has been reported in association with the postmenopause. Thus, we aimed to experimentally study the effect of the vitamin D deficiency and ovariectomy, alone or combined, in the liver damage. Main methodsThree-months-old female mice C57BL/6 with bilateral ovariectomy (Ovx group, n = 30) or a sham procedure (n = 30) were separated feeding control diet (C, n = 15) or a diet restricted in vitamin D (D-, n = 15) during additional 12 weeks. Key findingsBody mass (BM) and blood pressure (BP) were higher in Ovx than in C animals, but highest in Ovx (D-) that also showed glucose intolerance/ insulin resistance. Plasmatic lipids, alanine aspartase transferase, and hepatic steatosis were increased because of the combination of Ovx and D-. However, D- had little implication in the changes of the BM and BP, but affected hepatic steatosis. Gene and protein expressions demonstrated an impaired glucose uptake in the liver because of Ovx and D-, and an increase in lipogenesis and decrease in beta-oxidation in the liver associated more to the Ovx, but also evident in D-. Also, interleukin 6 and tumor necrosis factor alpha showed an enhancement due to dietary restriction of vitamin D. SignificanceThe findings demonstrated that ovariectomy and dietary restriction of vitamin D are inducers of harmful effects on the liver of mice, enhancing lipogenesis and inflammation and compromising beta-oxidation. The treatment of vitamin D deficiency is simple and not costly and can reduce the impact of menopause on metabolism and especially the liver.

Diet-induced thermogenesis: fake friend or foe?

Diet-induced thermogenesis (DIT) is energy dissipated as heat after a meal, contributing 5-15% to total daily energy expenditure (EE). There has been a long interest in the intriguing possibility that a defect in DIT predisposes to obesity. However, the evidence is conflicting; DIT is usually quantified by indirect calorimetry, which does not measure heat. Using gas exchange, indirect calorimetry measures total post-prandial EE, which comprises heat energy produced from brown adipose tissue (BAT) and energy required for processing and storing nutrients. We questioned whether DIT is reliably quantified by indirect calorimetry by employing infrared thermography to independently assess thermogenesis. Thermogenic activity of BAT was stimulated by cold and by a meal that induced a parallel increase in energy production. These stimulatory effects on BAT thermogenesis were inhibited by glucocorticoids. However, glucocorticoids enhanced postprandial EE in the face of reduced BAT thermogenesis and stimulated lipid synthesis. The increase in EE correlated significantly with the increase in lipogenesis. As energy cannot be destroyed (first law of thermodynamics), the energy that would have been dissipated as heat after a meal is channeled into storage. Post-prandial EE is the sum of heat energy that is lost (true DIT) and chemical energy that is stored. Indirect calorimetry does not reliably quantify DIT. When estimated by indirect calorimetry, assumed DIT can be a friend or foe of energy balance. That gas exchange-derived DIT reflects solely energy dissipation as heat is a false assumption likely to explain the conflicting results on the role of DIT in obesity.

FTO promotes SREBP1c maturation and enhances CIDEC transcription during lipid accumulation in HepG2 cells

The fat mass and obesity-associated (FTO) gene is tightly related to body weight and fat mass, and plays a pivotal role in regulating lipid accumulation in hepatocytes. However, the mechanisms underlying its function are poorly understood. Sterol regulatory element binding protein-1c (SREBP1c) is a transcription factor that regulates lipogenesis. Cell death-inducing DFFA (DNA fragmentation factor-α)-like effector c (CIDEC) plays a crucial role in lipid droplets (LDs) size controlling and lipid accumulation. In this report, we first observed that FTO overexpression in HepG2 cells resulted in an increase of lipogenesis and up-regulation of SREBP1c and CIDEC, two key regulatory factors in lipogenesis. In contrast, FTO knockdown in HepG2 cells resulted in a decrease of lipogenesis and down-regulation of SREBP1c and CIDEC expression. Moreover, SREBP1c knockdown resulted in a decrease of lipogenesis in HepG2 cells with FTO overexpression. In addition, FTO demethylation defect mutant presented less transcription of the key genes, and less nuclear translocation and maturation of SREBP1c. Further investigation demonstrated that overexpression of SREBP1c in HepG2 cells also promoted high CIDEC expression. Luciferase reporter assays showed that SREBP1c significantly stimulated CIDEC gene promoter activity. Finally, CIDEC knockdown reduced SREBP1c-induced lipogenesis. In conclusion, our studies suggest that FTO increased the lipid accumulation in hepatocytes by increasing nuclear translocation of SREBP1c and SREBP1c maturation, thus improving the transcriptional activity of LD-associated protein CIDEC. Our studies may provide new mechanistic insight into nonalcoholic fatty liver disease (NAFLD) mediated by FTO.

Abstract B82: Metabolomic analysis reveals association between leucine and lipogenesis for the formation of lipid rafts in the membrane of primary breast tumor samples

Abstract Introduction: Upregulation of lipogenesis, via FASN, represents a nearly-universal phenotypic alteration in most malignancies. Experimental studies indicated that leucine deprivation decreased expression of lipogenic gene FASN, saturated fatty acid (SFA) synthesis, and induced apoptosis in breast cancer cells. However, the association between lipogenesis and leucine is not well understood in breast cancer. Methods: In this sense, metabolomics analysis was performed from primary breast cancer and adjacent tissue samples from cohort of 96 breast cancer patients from the Institut Gustave-Roussy and Institute Curie – Paris, University of Debrecen – Hungary, and University of Tartu – Estonia. The Biocrates Life Science® company performed the metabolomics analysis using the Absolute IDQ p180 kit. Statistical analysis was performed by MetaboAnalyst 3.0 software (p <0.05). We performed the combined analysis of genes from public database (GEO) with genes of interest related to metabolic pathways. Differently expressed genes analyses between breast tumor and normal breast tissue were performed by TMev program using TestT student (p< 0.05). We selected only differently expressed genes related with leucine metabolism and lipogenesis for further analyses. Results: Indeed, in the tumor tissue we observed an increase of lipogenesis, and BCAA (branched chain amino acid) uptake and catabolism. The amino acids valine and isoleucine were used for the synthesis of succinyl and alpha ketoglutarate to meet the increased demand for the TCA (tricarboxylic acid) cycle. Surprisingly, the leucine metabolites indicated that it was used for cholesterol synthesis. Moreover, in tumor tissue samples an increase of SFA synthesis was observed, such as palmitic acid, sphingolipids, and phosphatidylcolines SFA enriched. Together with increased synthesis of cholesterol (via leucine), these data suggest an increase of lipid rafts in the breast tumor cells membrane when compared to normal breast adjacent tissue. To validate these data, we found 12 genes differently expressed genes related to leucine/cholesterol/lipogenesis/lipid rafts from public database. Conclusion: Our results indicate that lipogenic phenotype is associated with leucine metabolism to promote survival and proliferation, through lipid rafts increase, necessary to receptors (i.e., HER2, EGFR) location and activation within the breast tumor cells membrane. Citation Format: Jéssica Reis, Ismael Dale, Angela Logullo, Maria Mitzi, Dan Waitzberg, Graziela Ravacci. Metabolomic analysis reveals association between leucine and lipogenesis for the formation of lipid rafts in the membrane of primary breast tumor samples [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; São Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr B82.

Glucocorticoids suppress brown adipose tissue function in humans: A double-blind placebo-controlled study.

To investigate the effect of glucocorticoids on brown adipose tissue (BAT) function in humans. In a randomized double-blind cross-over design, 13 healthy adults underwent 1 week of oral prednisolone treatment (15 mg/d) and placebo with an intervening 2-week wash-out period. BAT function was assessed in response to cooling (19°C) and to a standardized meal, by measuring fluoro-deoxyglucose (FDG) uptake using positron emission tomography-computed tomography and skin temperatures overlying the supraclavicular (SCL) BAT depots using infrared thermography. Postprandial energy and substrate metabolism was assessed by indirect calorimetry. During cooling, prednisolone significantly reduced BAT FDG uptake (standardized uptake value, SUVmax, 6.1 ± 2.2 vs 3.7 ± 1.2; P < .05) and SCL temperature (-0.45 ± 0.1 vs -1.0 ± 0.1°C; P < .01) compared to placebo. Postprandially, prednisolone significantly blunted the rise in SCL temperature (+0.2 ± 0.1 vs -0.3 ± 0.1°C; P < .05), enhanced energy production (+221 ± 17 vs +283 ± 27 kcal/d; P < .01) and lipid synthesis (+16.3 ± 3.2 vs +23.6 ± 4.9 mg/min; P < .05). The prednisolone-induced reduction in SCL temperature significantly correlated with the reduction in FDG uptake (r = 0.65, P < .05), while the increase in energy production significantly correlated with the increase in lipogenesis (r = 0.6, P < .05). Prolonged exposure to glucocorticoid suppresses the function of human BAT. The enhancement of energy production and lipogenesis in the face of reduced dissipation of energy as heat suggests that glucocorticoids channel energy towards fat storage after nutrient intake. This is a novel mechanism of glucocorticoid-induced obesity.

Sleep restriction induced energy, methylation and lipogenesis metabolic switches in rat liver.

Sleep curtailment is ubiquitous in modern day society. Sleep debt is associated with maladaptive physiological changes that can lead to cardiometabolic and neuropsychiatric pathologies. Recent literature has shown the effects of sleep restriction (SR) on systemic metabolic profiles in biofluids, implying that tissue-specific metabolomes are impacted by SR. To test this hypothesis, we assessed hepatic metabolic profiles of rats after 5days of SR using UPLC-MS based metabolomics analysis and gene expression analysis. Our data suggests distinctive effects of SR on the liver metabolic profile of rats compared to forced-activity control animals. We observed specific impacts of SR on NAD metabolism through NAD accumulation and upregulation of Nampt, the rate determining step of NAD salvage. Additional multi-omic changes were observed in methionine metabolism, with an elevated SAM:SAH ratio under SR. This effect on one carbon metabolism is indicative of increased methylation potential. Changes in TCA cycle intermediates and ATP-citrate lyase (Acly) gene expression were observed that may be related to altered circulatory lipid profiles previously reported documenting the chrono-metabolic connection. Taken together with previous investigations, these observations are consistent with a model of decreased TCA activity with concomitant increase in lipogenesis induced by SR. These tissue-specific mechanistic insights into metabolic effects of SR provide a springboard to future metabolic intervention studies.

Cyp1b1 deletion and retinol deficiency coordinately suppress mouse liver lipogenic genes and hepcidin expression during post-natal development

Cyp1b1 deletion and gestational vitamin A deficiency (GVAD) redirect adult liver gene expression. A matched sufficient pre- and post-natal diet, which has high carbohydrate and normal iron content (LF12), increased inflammatory gene expression markers in adult livers that were suppressed by GVAD and Cyp1b1 deletion. At birth on the LF12 diet, Cyp1b1 deletion and GVAD each suppress liver expression of the iron suppressor, hepcidin (Hepc), while increasing stellate cell activation markers and suppressing post-natal increases in lipogenesis. Hepc was less suppressed in Cyp1b1−/− pups with a standard breeder diet, but was restored by iron supplementation of the LF12 diet. Conclusions. The LF12 diet delivered low post-natal iron and attenuated Hepc. Hepc decreases in Cyp1b1−/− and GVAD mice resulted in stellate activation and lipogenesis suppression. Endothelial BMP6, a Hepc stimulant, is a potential coordinator and Cyp1b1 target. These neonatal changes in Cyp1b1−/− mice link to diminished adult obesity and liver inflammation.

TRIENNIAL GROWTH AND DEVELOPMENT SYMPOSIUM: Molecular mechanisms related to bovine intramuscular fat deposition in the longissimus muscle.

The intramuscular fat (IMF) content of the LM, also known as marbling, is particularly important in determining the price of beef in Korea, Japan, and the United States. Deposition of IMF is influenced by both genetic (e.g., breed, gender, and genotype) and nongenetic factors (e.g., castration, nutrition, stressors, animal weight, and age). Castration of bulls markedly increases deposition of IMF, resulting in improved beef quality. Here, we present a comparative gene expression approach between bulls and steers. Transcriptomic and proteomic studies have demonstrated that the combined effects of increases in lipogenesis, fatty acid uptake, and fatty acid esterification and decreased lipolysis are associated with increased IMF deposition in the LM. Several peripheral tissues (LM, adipose tissues, and the liver) are involved in lipid metabolism. Therefore, understanding the significance of the tissue network in lipid metabolism is important. Here, we demonstrate that lipid metabolism in LM tissues is crucial for IMF deposition, whereas lipid metabolism in the liver plays only a minor role. Metabolism of body fat and IMF deposition in bovine species has similarities with these processes in metabolic diseases, such as obesity in humans and rodents. Extensive studies on metabolic diseases using epigenome modification (DNA methylation, histone modification, and microRNA), microbial metagenomics, and metabolomics have been performed in humans and rodents, and new findings have been reported using these technologies. The importance of applying "omics" fields (epigenomics, metagenomics, and metabolomics) to the study of IMF deposition in cattle is described. New information on the molecular mechanisms of IMF deposition may be used to design nutritional or genetic methods to manipulate IMF deposition and to modify fatty acid composition in beef cattle. Applying nutrigenomics could maximize the expression of genetic potential of economically important traits (e.g., marbling) in animals.

Physiological Suppression of Lipotoxic Liver Damage by Complementary Actions of HDAC3 and SCAP/SREBP

Liver fat accumulation precedes non-alcoholic steatohepatitis, an increasing cause of end-stage liver disease. Histone deacetylase 3 (HDAC3) is required for hepatic triglyceride homeostasis, and sterol regulatory element binding protein (SREBP) regulates the lipogenic response to feeding, but the crosstalk between these pathways is unknown. Here we show that inactivation of SREBP by hepatic deletion of SREBP cleavage activating protein (SCAP) abrogates the increase in lipogenesis caused by loss of HDAC3, but fatty acid oxidation remains defective. This combination leads to accumulation of lipid intermediates and to an energy drain that collectively cause oxidative stress, inflammation, liver damage, and, ultimately, synthetic lethality. Remarkably, this phenotype is prevented by ectopic expression of nuclear SREBP1c, revealing a surprising benefit of de novo lipogenesis and triglyceride synthesis in preventing lipotoxicity. These results demonstrate that HDAC3 and SCAP control symbiotic pathways of liver lipid metabolism that are critical for suppression of lipotoxicity.

(S)YS-51, a novel isoquinoline alkaloid, attenuates obesity-associated non-alcoholic fatty liver disease in mice by suppressing lipogenesis, inflammation and coagulation

Obesity-associated non-alcoholic fatty liver disease (NAFLD) increases coagulation and inflammation. We hypothesized that (S)YS-51, an agent found to be beneficial in animal models of sepsis, may reduce NAFLD in high-fat diet (HFD) mice by reducing coagulation and inflammation. C57BL/6 mice were fed either a chow diet or HFD and each was supplemented with or without (S)YS-51 (10mg/kg, daily, i.p.) for 16 weeks. The results showed that HFD caused significant increases in lipogenesis [CD36, fatty acid synthase (FAS) and sterol response element binding protein (SREBP)-1c mRNA and protein], inflammation [monocyte chemotactic protein (MCP)-1, tumor necrosis factor (TNF)-α, intercellular cell adhesion molecule-1 (ICAM-1), TGF-β, and procollagen type 1 mRNA, macrophage infiltration] and coagulation [tissue factor (TF) and plasminogen activator inhibitor-1 (PAI-1) mRNA and thrombin antithrombin complex (TAT)] in the liver, adipose tissue and serum, which were significantly reduced by (S)YS-51. These results of (S)YS-51 were accompanied by significant reduction of weight gain, liver size, hepatic steatosis and fibrosis, blood cholesterol, hepatic triglyceride, and macrophage infiltration and inflammatory cytokines in adipose tissue without affecting food intake in HFD mice. Interestingly, (S)YS-51 increased SIRT1 mRNA and protein and AMPK expression in the liver of HFD mice by increasing both NAD+/NADH ratio and LKB1 phosphorylation. In HepG2 cells, (S)YS-51 activated SIRT1 followed by AMPK. Finally, (S)YS-51 improved glucose tolerance and insulin resistance in HFD mice. We concluded that (S)YS-51 attenuates NAFLD and insulin resistance in HFD mice by, at least, activation of SIRT1/AMPK signals. Thus, (S)YS-51 may be beneficial in NAFLD treatment.

Differential modulation of cytosolic lipases activities in liver and adipose tissue by high-carbohydrate diets.

Several studies have demonstrated that a high-fructose (FRUC) diet induces metabolic and haemodynamic abnormalities, known as the metabolic syndrome, which are characterised by obesity, glucose intolerance, insulin resistance, dyslipidaemia and hypertension. In this study, the effect of a FRUC diet (60% fructose) for 8weeks on the metabolism of lipids in liver and epididymal adipose tissue from Wistar rats was compared with the AIN-93M diet and the effects of the AIN-93M diet were compared with a chow diet. The FRUC diet induced marked increases in both hepatocyte lipid droplet volume and postprandial serum levels of triacylglycerol (TAG), but reduced the postprandial serum levels of insulin. The AIN-93M diet induced marked increases in the hepatocyte lipid droplet volume and the serum levels of insulin, without affecting the serum levels of TAG. We found that isocaloric substitution of cornstarch, dextrinised cornstarch and sucrose (AIN-93M diet) for fructose did not affect the hepatic VLDL-TAG secretion and adipose tissue glucose uptake, lipolysis and cytosolic lipases activities in rats. However, the high-fructose diet induced a severe steatosis in liver accompanied by a decrease in cytosolic lipases activities. In adipose tissue, the FRUC diet induced a decrease in the lipoprotein lipase activity, and an increase in lipogenesis. FRUC and AIN-93M diets induced changes in lipid homeostasis in liver and adipose tissue by distinct biochemical mechanisms.

Advanced Glycation End Products (AGE) Potently Induce Autophagy through Activation of RAF Protein Kinase and Nuclear Factor κB (NF-κB)

Advanced glycation end products (AGE) accumulate in diabetic patients and aging people because of high amounts of three- or four-carbon sugars derived from glucose, thereby causing multiple consequences, including inflammation, apoptosis, obesity, and age-related disorders. It is important to understand the mechanism of AGE-mediated signaling leading to the activation of autophagy (self-eating) that might result in obesity. We detected AGE as one of the potent inducers of autophagy compared with doxorubicin and TNF. AGE-mediated autophagy is inhibited by suppression of PI3K and potentiated by the autophagosome maturation blocker bafilomycin. It increases autophagy in different cell types, and that correlates with the expression of its receptor, receptor for AGE. LC3B, the marker for autophagosomes, is shown to increase upon AGE stimulation. AGE-mediated autophagy is partially suppressed by inhibitor of NF-κB, PKC, or ERK alone and significantly in combination. AGE increases sterol regulatory element binding protein activity, which leads to an increase in lipogenesis. Although AGE-mediated lipogenesis is affected by autophagy inhibitors, AGE-mediated autophagy is not influenced by lipogenesis inhibitors, suggesting that the turnover of lipid droplets overcomes the autophagic clearance. For the first time, we provide data showing that AGE induces several cell signaling cascades, like NF-κB, PKC, ERK, and MAPK, that are involved in autophagy and simultaneously help with the accumulation of lipid droplets that are not cleared effectively by autophagy, therefore causing obesity.

Hepatocyte β-Klotho regulates lipid homeostasis but not body weight in mice.

β-Klotho (β-Kl), a transmembrane protein expressed in the liver, pancreas, adipose tissues, and brain, is essential for feedback suppression of hepatic bile acid synthesis. Because bile acid is a key regulator of lipid and energy metabolism, we hypothesized potential and tissue-specific roles of β-Kl in regulating plasma lipid levels and body weight. By crossing β-kl(-/-) mice with newly developed hepatocyte-specific β-kl transgenic (Tg) mice, we generated mice expressing β-kl solely in hepatocytes (β-kl(-/-)/Tg). Gene expression, metabolomic, and in vivo flux analyses consistently revealed that plasma level of cholesterol, which is over-excreted into feces as bile acids in β-kl(-/-), is maintained in β-kl(-/-) mice by enhanced de novo cholesterogenesis. No compensatory increase in lipogenesis was observed, despite markedly decreased plasma triglyceride. Along with enhanced bile acid synthesis, these lipid dysregulations in β-kl(-/-) were completely reversed in β-kl(-/-)/Tg mice. In contrast, reduced body weight and resistance to diet-induced obesity in β-kl(-/-) mice were not reversed by hepatocyte-specific restoration of β-Kl expression. We conclude that β-Kl in hepatocytes is necessary and sufficient for lipid homeostasis, whereas nonhepatic β-Kl regulates energy metabolism. We further demonstrate that in a condition with excessive cholesterol disposal, a robust compensatory mechanism maintains cholesterol levels but not triglyceride levels in mice.

Early redox imbalance is associated with liver dysfunction at weaning in overfed rats.

Neonatal overfeeding induced by litter size reduction leads to further obesity and other metabolic disorders, such as liver oxidative stress and microsteatosis at adulthood. We hypothesized that overfeeding causes an early redox imbalance at weaning, which could programme the animals to future liver dysfunction. Thus, we studied lipogenesis, adipogenesis, catecholamine status and oxidative balance in weaned overfed pups. To induce early overfeeding, litters were adjusted to three pups at the 3rd day of lactation (SL group). The control group contained 10 pups per litter until weaning (NL group). Peripheral autonomic nerve function was determined in vivo at 21 days old. Thereafter, pups were killed for further analysis. Differences were considered significant when P < 0.05. The SL pups presented with a higher visceral adipocyte area, higher content of lipogenic enzymes (ACC, FAS) and with a lower content of adipogenic factors (CEBP, PPARγ) in visceral adipose tissue (VAT). Although autonomic nerve activity and adrenal catecholamine production were not significantly altered, catecholamine receptor (β3ADR) content was lower in VAT. The SL pups also presented with higher triglyceride, PPARγ, PPARα and PGC1α contents in liver. In plasma and liver, the SL pups showed an oxidative imbalance, with higher lipid peroxidation and protein oxidation. The SL group presented with a higher serum alanine aminotransferase (ALT). The early increase in lipogenesis in adipose tissue and liver in weaned overfed rats suggests that the higher oxidative stress and lower catecholamine content in VAT are associated with the early development of liver dysfunction and adipocyte hypertrophy.

Activated α2-Macroglobulin Binding to Human Prostate Cancer Cells Triggers Insulin-like Responses

Ligation of cell surface GRP78 by activated α2-macroglobulin (α2M*) promotes cell proliferation and suppresses apoptosis. α2M*-treated human prostate cancer cells exhibit a 2-3-fold increase in glucose uptake and lactate secretion, an effect similar to insulin treatment. In both α2M* and insulin-treated cells, the mRNA levels of SREBP1-c, SREBP2, fatty-acid synthase, acetyl-CoA carboxylase, ATP citrate lyase, and Glut-1 were significantly increased together with their protein levels, except for SREBP2. Pretreatment of cells with α2M* antagonist antibody directed against the carboxyl-terminal domain of GRP78 blocks these α2M*-mediated effects, and silencing GRP78 expression by RNAi inhibits up-regulation of ATP citrate lyase and fatty-acid synthase. α2M* induces a 2-3-fold increase in lipogenesis as determined by 6-[(14)C]glucose or 1-[(14)C]acetate incorporation into free cholesterol, cholesterol esters, triglycerides, free fatty acids, and phosphatidylcholine, which is blocked by inhibitors of fatty-acid synthase, PI 3-kinase, mTORC, or an antibody against the carboxyl-terminal domain of GRP78. We also assessed the incorporation of [(14)CH3]choline into phosphatidylcholine and observed similar effects. Lipogenesis is significantly affected by pretreatment of prostate cancer cells with fatostatin A, which blocks sterol regulatory element-binding protein proteolytic cleavage and activation. This study demonstrates that α2M* functions as a growth factor, leading to proliferation of prostate cancer cells by promoting insulin-like responses. An antibody against the carboxyl-terminal domain of GRP78 may have important applications in prostate cancer therapy.

The role of glycerol-3-phosphate dehydrogenase 1 in the progression of fatty liver after acute ethanol administration in mice

Acute ethanol consumption leads to the accumulation of triglycerides (TGs) in hepatocytes. The increase in lipogenesis and reduction of fatty acid oxidation are implicated as the mechanisms underlying ethanol-induced hepatic TG accumulation. Although glycerol-3-phosphate (Gro3P), formed by glycerol kinase (GYK) or glycerol-3-phosphate dehydrogenase 1 (GPD1), is also required for TG synthesis, the roles of GYK and GPD1 have been the subject of some debate. In this study, we examine (1) the expression of genes involved in Gro3P production in the liver of C57BL/6J mice in the context of hepatic TG accumulation after acute ethanol intake, and (2) the role of GPD1 in the progression of ethanol-induced fatty liver using GPD1 null mice. As a result, in C57BL/6J mice, ethanol-induced hepatic TG accumulation began within 2h and was 1.7-fold greater than that observed in the control group after 6h. The up-regulation of GPD1 began 2h after administering ethanol, and significantly increased 6h later with the concomitant escalation in the glycolytic gene expression. The incorporation of 14C-labelled glucose into TG glycerol moieties increased during the same period. On the other hand, in GPD1 null mice carrying normal GYK activity, no significant increase in hepatic TG level was observed after acute ethanol intake. In conclusion, GPD1 and glycolytic gene expression is up-regulated by ethanol, and GPD1-mediated incorporation of glucose into TG glycerol moieties together with increased lipogenesis, is suggested to play an important role in ethanol-induced hepatic TG accumulation.

A systems approach to determine the effect of changes in gene expression in adipose tissue on productive and reproductive efficiency in dairy cattle

In order to assess the patterns of metabolism that affect efficiency, an existing mechanistic metabolic model of dairy cows (Molly) was expanded to include transcriptional control of metabolism in adipose tissue and reproductive processes. Our objective was to test the effects of changes in gene transcription in adipose tissue on patterns of metabolism, reproductive processes and efficiency. The model describes the substrate sensitivity and maximum velocity for lipogenesis, esterification and lipolysis. Data were collected from first and second parity cows from various studies, and included nutrient intake, milk component output, changes in adipose tissue lipid, visceral and body protein and lipid, and metabolism rates in adipose tissue and gene transcription. The lipogenic pathways were primarily controlled by transcriptional changes, whereas lipolysis varied primarily by post-translational control. We used the difference in transcriptional and post-translational metabolic control to alter Vmax and Ks for lipogenesis and lipolysis; in addition, we modelled a range of energy costs for ion transport and protein turnover in liver, muscle and adipose tissues. Changing rates of lipogenesis and lipolysis (~four-fold) did not affect milk production or feed intake, but altered maintenance costs, fat accretion, energetic efficiency and reproduction. Increases in lipogenesis decreased postpartum interval to first ovulation; increases in rates of lipolysis increased the interval. Changes in metabolic rate from changing either adipose tissue metabolism or rate of ion transport and protein turnover affected rates of oestrogen and progesterone degradation, which affected follicular growth and corpus luteum function. This model may be used to help interpret genomic and transcriptomic data to pinpoint the most effective ways to select and manage for changes in productive and reproductive efficiency.

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.

Insulin‐dependent and ‐independent regulation of sterol regulatory element‐binding protein‐1c

Insulin‐dependent and ‐independent regulation of sterol regulatory element‐binding protein‐1c