Fructose stimulated de novo lipogenesis is promoted by inflammation.
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ABSTRACT:
SUBMITTER: Todoric J
PROVIDER: S-EPMC8018782 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Dietary free sugars have received much attention over the past few years. Much of the focus has been on the effect of fructose on hepatic de novo lipogenesis (DNL). Therefore the aim of the present study was to investigate the effects of meals high and low in fructose on postprandial hepatic DNL and fatty acid partitioning and dietary fatty acid oxidation. Sixteen healthy adults (eight men, eight women) participated in this randomised cross-over study; study days were separated by a 4-week wash-out period. Hepatic DNL and dietary fatty acid oxidation were assessed using stable-isotope tracer methodology. Consumption of the high fructose meal significantly increased postprandial hepatic DNL to a greater extent than consumption of the low fructose meal and this effect was evident in women but not men. Despite an increase in hepatic DNL, there was no change in dietary fatty acid oxidation. Taken together, our data show that women are more responsive to ingestion of higher amounts of fructose than men and if continued over time this may lead to changes in hepatic fatty acid partitioning and eventually liver fat content.
| S-EPMC6164310 | biostudies-literature
Project description:Consumption of sugar is associated with obesity, type 2 diabetes mellitus, nonalcoholic fatty liver disease, and cardiovascular disease. The conversion of fructose to fat in liver (de novo lipogenesis [DNL]) may be a modifiable pathogenetic pathway. We determined the effect of 9 days of isocaloric fructose restriction on DNL, liver fat, visceral fat (VAT), subcutaneous fat, and insulin kinetics in obese Latino and African American children with habitual high sugar consumption (fructose intake >50 g/d).Children (9-18 years old; n = 41) had all meals provided for 9 days with the same energy and macronutrient composition as their standard diet, but with starch substituted for sugar, yielding a final fructose content of 4% of total kilocalories. Metabolic assessments were performed before and after fructose restriction. Liver fat, VAT, and subcutaneous fat were determined by magnetic resonance spectroscopy and imaging. The fractional DNL area under the curve value was measured using stable isotope tracers and gas chromatography/mass spectrometry. Insulin kinetics were calculated from oral glucose tolerance tests. Paired analyses compared change from day 0 to day 10 within each child.Compared with baseline, on day 10, liver fat decreased from a median of 7.2% (interquartile range [IQR], 2.5%-14.8%) to 3.8% (IQR, 1.7%-15.5%) (P < .001) and VAT decreased from 123 cm3 (IQR, 85-145 cm3) to 110 cm3 (IQR, 84-134 cm3) (P < .001). The DNL area under the curve decreased from 68% (IQR, 46%-83%) to 26% (IQR, 16%-37%) (P < .001). Insulin kinetics improved (P < .001). These changes occurred irrespective of baseline liver fat.Short-term (9 days) isocaloric fructose restriction decreased liver fat, VAT, and DNL, and improved insulin kinetics in children with obesity. These findings support efforts to reduce sugar consumption. ClinicalTrials.gov Number: NCT01200043.
| S-EPMC5813289 | biostudies-literature
Project description:The role of carbonic anhydrase in de novo lipid synthesis was examined by measuring [1-14C]acetate incorporation into total lipids, fatty acids and non-saponifiable lipids in freshly isolated rat hepatocytes. Two carbonic anhydrase inhibitors, trifluoromethylsulphonamide (TFMS) and ethoxozolamide (ETZ) decreased incorporation of 14C into total lipids. Both fatty acid and non-saponifiable lipid components of the total lipid were inhibited to approximately the same extent by 100 microM TFMS (29 +/- 0.3% and 35 +/- 0.3% of control respectively in replicate studies). However, neither drug significantly affected ATP concentrations or the transport activity of Na+/K(+)-ATPase, two measures of cell viability. To establish the site of this inhibition, water-soluble 14C-labelled metabolites from perchloric acid extracts of the radiolabelled cells were separated by ion-exchange chromatography. TFMS inhibited 14C incorporation into citrate, malate, alpha-oxoglutarate and fumarate, but had no effect on incorporation of 14C into acetoacetate. Since ATP citrate-lyase, the cytosolic enzyme that catalyses the conversion of citrate into acetyl-CoA, catalyses an early rate-limiting step in fatty acid synthesis, levels of cytosolic citrate may be rate controlling for de novo fatty acid and sterol synthesis. Indeed citrate concentrations were significantly reduced to 37 +/- 6% of control in hepatocytes incubated with 100 microM TFMS for 30 min. TFMS also inhibited the incorporation of 14C from [1-14C]pyruvate into malate, citrate and glutamate, but not into lactate. This supports the hypothesis that TFMS inhibits pyruvate carboxylation, i.e. since all of the 14C from [1-14C]pyruvate converted into citric acid cycle intermediates must come via pyruvate carboxylase (i.e. rather than pyruvate dehydrogenase). Our findings indicate a role for carbonic anhydrase in hepatic de novo lipogenesis at the level of pyruvate carboxylation.
| S-EPMC1135873 | biostudies-other
Project description:Patients with nonalcoholic fatty liver disease (NAFLD) are reported to have low growth hormone (GH) production and/or hepatic GH resistance. GH replacement can resolve the fatty liver condition in diet-induced obese rodents and in GH-deficient patients. However, it remains to be determined whether this inhibitory action of GH is due to direct regulation of hepatic lipid metabolism. Therefore, an adult-onset, hepatocyte-specific, GH receptor (GHR) knockdown (aLivGHRkd) mouse was developed to model hepatic GH resistance in humans that may occur after sexual maturation. Just 7 days after aLivGHRkd, hepatic de novo lipogenesis (DNL) was increased in male and female chow-fed mice, compared with GHR-intact littermate controls. However, hepatosteatosis developed only in male and ovariectomized female aLivGHRkd mice. The increase in DNL observed in aLivGHRkd mice was not associated with hyperactivation of the pathway by which insulin is classically considered to regulate DNL. However, glucokinase mRNA and protein levels as well as fructose-2,6-bisphosphate levels were increased in aLivGHRkd mice, suggesting that enhanced glycolysis drives DNL in the GH-resistant liver. These results demonstrate that hepatic GH actions normally serve to inhibit DNL, where loss of this inhibitory signal may explain, in part, the inappropriate increase in hepatic DNL observed in NAFLD patients.
| S-EPMC4542445 | biostudies-literature
Project description:Membrane lipid composition is central to the highly specialized functions of neurological tissues. In the retina, abnormal lipid metabolism causes severe forms of blindness, often through poorly understood neuronal cell death. Here, we demonstrate that deleting the de novo lipogenic enzyme fatty acid synthase (FAS) from the neural retina, but not the vascular retina, results in progressive neurodegeneration and blindness with a temporal pattern resembling rodent models of retinitis pigmentosa. Blindness was not rescued by protection from light-evoked activity; by eating a diet enriched in palmitate, the product of the FAS reaction; or by treatment with the PPAR? agonist fenofibrate. Vision loss was due to aberrant synaptic structure, blunted responsiveness to glial-derived neurotrophic factor and ciliary neurotrophic factor, and eventual apoptotic cell loss. This progressive neurodegeneration was associated with decreased membrane cholesterol content, as well as loss of discrete n-3 polyunsaturated fatty acid- and saturated fatty acid-containing phospholipid species within specialized membrane microdomains. Neurotrophic signaling was restored by exogenous cholesterol delivery. These findings implicate de novo lipogenesis in neurotrophin-dependent cell survival by maintaining retinal membrane configuration and lipid composition, and they suggest that ongoing lipogenesis may be required to prevent cell death in many forms of retinopathy.
| S-EPMC5821215 | biostudies-literature
Project description:Fate and behavior of neural progenitor cells are tightly regulated during mammalian brain development. Metabolic pathways, such as glycolysis and oxidative phosphorylation, that are required for supplying energy and providing molecular building blocks to generate cells govern progenitor function. However, the role of de novo lipogenesis, which is the conversion of glucose into fatty acids through the multienzyme protein fatty acid synthase (FASN), for brain development remains unknown. Using Emx1Cre-mediated, tissue-specific deletion of Fasn in the mouse embryonic telencephalon, we show that loss of FASN causes severe microcephaly, largely due to altered polarity of apical, radial glia progenitors and reduced progenitor proliferation. Furthermore, genetic deletion and pharmacological inhibition of FASN in human embryonic stem cell-derived forebrain organoids identifies a conserved role of FASN-dependent lipogenesis for radial glia cell polarity in human brain organoids. Thus, our data establish a role of de novo lipogenesis for mouse and human brain development and identify a link between progenitor-cell polarity and lipid metabolism.
| S-EPMC8764667 | biostudies-literature
Project description:Fate and behaviour of neural progenitor cells is tightly regulated during mammalian brain development. Metabolic pathways, such as glycolysis and oxidative phosphorylation, that are required for supplying energy and providing molecular building blocks to generate cells, govern progenitor function. However, the role of de novo lipogenesis, which is the conversion of glucose into fatty acids through the multi-enzyme protein fatty acid synthase (FASN), for brain development remains unknown. Using Emx1Cre-mediated, tissue-specific deletion of Fasn in the mouse embryonic telencephalon, we show that loss of FASN causes severe microcephaly, largely due to altered polarity of apical, radial glia progenitors (APs) and reduced progenitor proliferation. Further, genetic deletion and pharmacological inhibition of FASN in human embryonic stem cell (ESC)-derived forebrain organoids identifies a conserved role of FASN-dependent lipogenesis for radial glia cell polarity and progenitor expansion in the developing human forebrain. Thus, our data establish a role of de novo lipogenesis for mouse and human brain development and identify a link between progenitor cell polarity and lipid metabolism.
2022-01-14 | PXD026110 | Pride
Project description:To investigate the effects of tacrolimus (TC) and everolimus (EV) on non-alcoholic steatohepatitis (NASH) induced by high fat, high cholesterol and fructose (fast food) diet in C57BL/6J mice.C57BL/6J mice were divided into four groups (n=8). 1) Standard Chow (SC); 2) Fast food (FF) diet; 3) FF + Tacrolimus (TC, 1mg/kg) and; 4) FF + Everolimus (EV, 1mg/kg) and treated for 16 weeks. Serum and tissue samples were analyzed for evidence of inflammation, fibrosis, lipogenesis, and apoptosis.TC and EV treatments significantly reduced the hepatic lipid accumulation, improved liver-body weight ratio, blood biochemistry, and insulin resistance in mice fed with FF diet. However, inflammation, enlarged portal tracts, and fibrosis were pronounced in EV treated group. The lipogenic parameters, Peroxisome proliferator-activated receptor gamma (PPAR-?), Sterol regulatory element-binding protein 1(SREBP-1), mammalian target of rapamycin (m-TOR), Stearoyl-CoA desaturase-1 (SCD-1) and fatty acid translocase (CD36) were significantly down-regulated in livers of TC and EV treated groups as compared to FF group. TC improved Bcl2/Bax ratio, decreased apoptosis, CYP2E1 protein expression and liver fibrosis levels, however, EV offered no such protection. Further, in an In-vitro model of lipotoxicity using the mouse hepatocyte (AML-12) cell line, treatment with TC and EV significantly reduced lipid accumulation and lipogenic and apoptotic markers induced with palmitic acid.In FF diet induced model of NASH, both TC and EV inhibited hepatic lipid accumulation and improved metabolic parameters such as insulin resistance and dyslipidemia. However, mice administered with EV exhibited inflammatory and fibrotic responses despite reduced hepatic steatosis.
| S-EPMC5768335 | biostudies-literature
Project description:Increased de novo lipogenesis is being increasingly recognized as a hallmark of cancer. Despite recent advances in fluorescence microscopy, autoradiography and mass spectrometry, direct observation of de novo lipogenesis in living systems remains to be challenging. Here, by coupling stimulated Raman scattering (SRS) microscopy with isotope labeled glucose, we were able to trace the dynamic metabolism of glucose in single living cells with high spatial-temporal resolution. As the first direct visualization, we observed that glucose was largely utilized for lipid synthesis in pancreatic cancer cells, which occurs at a much lower rate in immortalized normal pancreatic epithelial cells. By inhibition of glycolysis and fatty acid synthase (FAS), the key enzyme for fatty acid synthesis, we confirmed the deuterium labeled lipids in cancer cells were from de novo lipid synthesis. Interestingly, we also found that prostate cancer cells exhibit relatively lower level of de novo lipogenesis, but higher fatty acid uptake compared to pancreatic cancer cells. Together, our results demonstrate a valuable tool to study dynamic lipid metabolism in cancer and other disorders.
| S-EPMC4212242 | biostudies-other
Project description:AMP-activated protein kinase (AMPK) is a heterotrimeric kinase that regulates cellular energy metabolism by affecting energy-consuming pathways such as de novo lipid biosynthesis and glucose production as well as energy-producing pathways such as lipid oxidation and glucose uptake. Accordingly, compounds that activate AMPK represent potential drug candidates for the treatment of hyperlipidemia and type 2 diabetes. Screening of a proprietary library of AMP mimetics identified the phosphonic acid 2 that bears little structural resemblance to AMP but is capable of activating AMPK with high potency (EC50 = 6 nM vs AMP EC50 = 6 ?M) and specificity. Phosphonate prodrugs of 2 inhibited de novo lipogenesis in cellular and animal models of hyperlipidemia.
| S-EPMC4007905 | biostudies-other