scholarly journals NaCT (SLC13A5) facilitates citrate import and metabolism under nutrient-limited conditions

2021 ◽  
Author(s):  
Avi Kumar ◽  
Thekla Cordes ◽  
Anna E Thalacker-Mercer ◽  
Ana M Pajor ◽  
Anne N Murphy ◽  
...  
Keyword(s):  
Cortical Neurons ◽  
De Novo ◽  
Hepatic Metabolism ◽  
Acid Synthesis ◽  
Huh7 Cell ◽  
De Novo Lipogenesis ◽  
Pediatric Epilepsy ◽  
Citrate Transporter ◽  
Huh7 Cells ◽  
Rat Cortical Neurons

Citrate lies at a critical node of metabolism linking tricarboxylic acid metabolism and fatty acid synthesis via acetyl-coenzyme A. Recent studies have linked the sodium citrate transporter (NaCT), encoded by SLC13A5, to dysregulated hepatic metabolism and pediatric epilepsy. To examine how NaCT-mediated citrate metabolism contributes to the pathophysiology of these diseases we applied 13C isotope tracing to SLC13A5-deficient hepatocellular carcinoma (HCC) cell lines and primary rat cortical neurons. Exogenous citrate contributed to intermediary metabolism at appreciable levels only under hypoxic conditions. In the absence of glutamine, citrate supplementation increased de novo lipogenesis and growth of HCC cells. Knockout of SLC13A5 in Huh7 cells compromised citrate uptake and catabolism. Citrate supplementation rescued Huh7 cell viability in response to glutamine deprivation and Zn2+ treatment, and these effects were mitigated by NaCT deficiency. Collectively, these findings demonstrate that NaCT-mediated citrate uptake is metabolically important under nutrient limited conditions and may facilitate resistance to metal toxicity.

Effect of carbohydrate intake on de novo lipogenesis in human adipose tissue

1987 ◽  
Vol 253 (6) ◽  
pp. E664-E669 ◽  
Author(s):  
C. Chascione ◽  
D. H. Elwyn ◽  
M. Davila ◽  
K. M. Gil ◽  
J. Askanazi ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
De Novo ◽  
Acid Synthesis ◽  
De Novo Lipogenesis ◽  
Whole Body ◽  
High Intake ◽  
Carbohydrate Diet ◽  
Triglyceride Synthesis ◽  
High Carbohydrate

Rates of synthesis, from [14C]glucose, of fatty acids (de novo lipogenesis) and glycerol (triglyceride synthesis) were measured in biopsies of adipose tissue from nutritionally depleted patients given low- or high-carbohydrate intravenous nutrition. Simultaneously, energy expenditure and whole-body lipogenesis were measured by indirect calorimetry. Rates of whole-body lipogenesis were zero on the low-carbohydrate diet and averaged 1.6 g.kg-1.day-1 on the high-carbohydrate diet. In vitro rates of triglyceride synthesis increased 3-fold going from the low to the high intake; rates of fatty acid synthesis increased approximately 80-fold. In vitro, lipogenesis accounted for less than 0.1% of triglyceride synthesis on the low intake and 4% on the high intake. On the high-carbohydrate intake, in vitro rates of triglyceride synthesis accounted for 61% of the rates of unidirectional triglyceride synthesis measured by indirect calorimetry. In vitro rates of lipogenesis accounted for 7% of whole-body lipogenesis. Discrepancies between in vitro rates of fatty acid synthesis from glucose, compared with acetate and citrate, as reported by others, suggest that in depleted patients on hypercaloric high-carbohydrate diets, adipose tissue may account for up to 40% of whole-body lipogenesis.

scholarly journals Hepatic GH Receptor Signaling Directly Suppresses Hepatic Steatosis and De Novo Lipogenesis, Independent of Changes in Plasma IGF1 and Insulin

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. A48-A48
Author(s):  
Maria del Carmen Vazquez Borrego ◽  
Mercedes del Rio Moreno ◽  
Andre Sarmento-Cabral ◽  
Mariyah Mahmood ◽  
Papasani V Subbaiah ◽  
...  
Keyword(s):  
Hepatic Steatosis ◽  
Target Genes ◽  
De Novo ◽  
Acid Synthesis ◽  
De Novo Lipogenesis ◽  
Mrna Levels ◽  
Male Mice ◽  
Alcoholic Fatty Liver ◽  
Insulin Levels ◽  
Triglyceride Accumulation

Abstract A reduction in GH, as well as IGF1, is associated with non-alcoholic fatty liver disease (NAFLD). However, the relative contribution of changes in circulating GH and IGF1, to hepatic triglyceride accumulation (steatosis), remains to be clearly defined. To study the direct actions of GH on hepatocyte metabolism, we have utilized a mouse model of adult-onset, hepatocyte-specific, GHR knockdown (aHepGHRkd; 10–12 week-old, GHRfl/fl male mice, treated with AAV8-TBGp-Cre). In this and previous reports, we have observed that aHepGHRkd male mice rapidly develop steatosis (after 7 days) associated with enhanced de novo lipogenesis (DNL; measured by deuterated H2O labeling, 10h after 0800h food removal), and low ketone levels, suggestive of reduced hepatic β-oxidation. Of note, aHepGHRkd also reduces plasma IGF1 levels to >80% of GHR-intact controls (GHRfl/fl mice treated with AAV8-TBGp-Null), leading to a rise in GH, due to loss of IGF1 negative feedback to the pituitary/hypothalamus. This reciprocal shift in IGF1/GH is associated with an increase in insulin levels. Therefore, it is possible that the steatosis that develops in aHepGHRkd mice is the consequence of systemic insulin resistance supplying excess substrates (glucose and NEFA) for hepatic lipogenesis. However, inconsistent with this theory is the fact that glucose and NEFA levels are not altered after aHepGHRkd. To tease out the indirect (perhaps driven by high insulin levels) vs. direct effects of GH on hepatocyte lipid accumulation, male aHepGHRkd mice were injected with a vector expressing rat IGF1 (AAV8-TBGp-rIGF1). Reconstitution of hepatocyte IGF1 in aHepGHRkd mice, raised plasma IGF1 and normalized GH, insulin and ketone levels, but hepatic steatosis and DNL remained greater than that of GHR-intact controls, indicating GH directly suppresses hepatic fat accumulation. RNAseq analysis of livers from aHepGHRkd mice showed expression of genes related to carbohydrate metabolism (Gck, Khk) and fatty acid synthesis (Fasn, Srebf1, Usf1), processing (Scd1) and uptake (Cd36) were increased, while genes related to gluconeogenesis (Pck1, Fbp1, G6pc) were reduced. Remarkably, IGF1 reconstitution had no major impact on the hepatic transcriptome of aHepGHRkd mice, with the exception of reducing the expression of Srebf1, consistent with the reduction in circulating insulin levels. Interestingly, carbohydrate-responsive element-binding protein (CHREBP) levels, but not mRNA levels, were greater in aHepGHRkd mice with or without IGF1 reconstitution, consistent with upregulation of CHREBP target genes (Khk and Fasn among others). Taken together, these results suggest GH directly regulates steatosis, at least in part, by suppressing carbohydrate-driven DNL, where additional studies are underway to test this hypothesis.

scholarly journals Sterol regulatory element binding protein and dietary lipid regulation of fatty acid synthesis in the mammary epithelium

2010 ◽  
Vol 299 (6) ◽  
pp. E918-E927 ◽  
Author(s):  
Michael C. Rudolph ◽  
Jenifer Monks ◽  
Valerie Burns ◽  
Meridee Phistry ◽  
Russell Marians ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Mammary Gland ◽  
Fatty Acid ◽  
Fatty Acid Synthesis ◽  
De Novo ◽  
Regulatory Element ◽  
Acid Synthesis ◽  
De Novo Lipogenesis ◽  
Mrna Levels ◽  
Sterol Regulatory Element

The lactating mammary gland synthesizes large amounts of triglyceride from fatty acids derived from the blood and from de novo lipogenesis. The latter is significantly increased at parturition and decreased when additional dietary fatty acids become available. To begin to understand the molecular regulation of de novo lipogenesis, we tested the hypothesis that the transcription factor sterol regulatory element binding factor (SREBF)-1c is a primary regulator of this system. Expression of Srebf1c mRNA and six of its known target genes increased ≥2.5-fold at parturition. However, Srebf1c-null mice showed only minor deficiencies in lipid synthesis during lactation, possibly due to compensation by Srebf1a expression. To abrogate the function of both isoforms of Srebf1, we bred mice to obtain a mammary epithelial cell-specific deletion of SREBF cleavage-activating protein (SCAP), the SREBF escort protein. These dams showed a significant lactation deficiency, and expression of mRNA for fatty acid synthase ( Fasn), insulin-induced gene 1 ( Insig1), mitochondrial citrate transporter ( Slc25a1), and stearoyl-CoA desaturase 2 ( Scd2) was reduced threefold or more; however, the mRNA levels of acetyl-CoA carboxylase-1α ( Acaca) and ATP citrate lyase ( Acly) were unchanged. Furthermore, a 46% fat diet significantly decreased de novo fatty acid synthesis and reduced the protein levels of ACACA, ACLY, and FASN significantly, with no change in their mRNA levels. These data lead us to conclude that two modes of regulation exist to control fatty acid synthesis in the mammary gland of the lactating mouse: the well-known SREBF1 system and a novel mechanism that acts at the posttranscriptional level in the presence of SCAP deletion and high-fat feeding to alter enzyme protein.

scholarly journals Suppressed de novo lipogenesis by plasma membrane citrate transporter inhibitor promotes apoptosis in HepG2 cells

FEBS Open Bio ◽  
2018 ◽  
Vol 8 (6) ◽  
pp. 986-1000 ◽  
Author(s):  
Phornpun Phokrai ◽  
Wan‐angkan Poolsri ◽  
Somrudee Suwankulanan ◽  
Narinthorn Phakdeeto ◽  
Worasak Kaewkong ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Hepg2 Cells ◽  
De Novo ◽  
De Novo Lipogenesis ◽  
Citrate Transporter

scholarly journals The Effect of Fructose Feeding on Intestinal Triacylglycerol Production and De Novo Fatty Acid Synthesis in Humans

Nutrients ◽  
2020 ◽  
Vol 12 (6) ◽  
pp. 1781
Author(s):  
Simon Steenson ◽  
Fariba Shojaee-Moradie ◽  
Martin B. Whyte ◽  
Kim G. Jackson ◽  
Julie A. Lovegrove ◽  
...  
Keyword(s):  
De Novo ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Acid Synthesis ◽  
Acute Effect ◽  
De Novo Lipogenesis ◽  
Fructose Intake ◽  
High Fructose ◽  
Catabolic Rate

A high fructose intake exacerbates postprandial plasma triacylglycerol (TAG) concentration, an independent risk factor for cardiovascular disease, although it is unclear whether this is due to increased production or impaired clearance of triacylglycerol (TAG)-rich lipoproteins. We determined the in vivo acute effect of fructose on postprandial intestinal and hepatic lipoprotein TAG kinetics and de novo lipogenesis (DNL). Five overweight men were studied twice, 4 weeks apart. They consumed hourly mixed-nutrient drinks that were high-fructose (30% energy) or low-fructose (<2% energy) for 11 h. Oral 2H2O was administered to measure fasting and postprandial DNL. Postprandial chylomicron (CM)-TAG and very low-density lipoprotein (VLDL)-TAG kinetics were measured with an intravenous bolus of [2H5]-glycerol. CM and VLDL were separated by their apolipoprotein B content using antibodies. Plasma TAG (p < 0.005) and VLDL-TAG (p = 0.003) were greater, and CM-TAG production rate (PR, p = 0.046) and CM-TAG fractional catabolic rate (FCR, p = 0.073) lower when high-fructose was consumed, with no differences in VLDL-TAG kinetics. Insulin was lower (p = 0.005) and apoB48 (p = 0.039), apoB100 (p = 0.013) and non-esterified fatty acids (NEFA) (p = 0.013) were higher after high-fructose. Postprandial hepatic fractional DNL was higher than intestinal fractional DNL with high-fructose (p = 0.043) and low-fructose (p = 0.043). Fructose consumption had no effect on the rate of intestinal or hepatic DNL. We provide the first measurement of the rate of intestinal DNL in humans. Lower CM-TAG PR and CM-TAG FCR with high-fructose consumption suggests lower clearance of CM, rather than elevated production, may contribute to elevated plasma TAG, possibly due to lower insulin-mediated stimulation of lipoprotein lipase.

Effects of pregnancy and ovarian steroids on fatty acid synthesis and uptake in Syrian hamsters

1991 ◽  
Vol 260 (1) ◽  
pp. R153-R158 ◽  
Author(s):  
A. J. Bhatia ◽  
G. N. Wade
Keyword(s):  
Fatty Acids ◽  
Adipose Tissue ◽  
Fatty Acid ◽  
White Adipose Tissue ◽  
Fatty Acid Synthesis ◽  
De Novo ◽  
Acid Synthesis ◽  
De Novo Lipogenesis ◽  
Ovarian Steroids ◽  
Syrian Hamsters

The effects of pregnancy and ovarian steroids on the in vivo distribution of newly synthesized fatty acids (incorporation of tritium from 3H2O into fatty acid) in Syrian hamsters (Mesocricetus auratus) were examined. During late, but not early, gestation hamsters had reduced levels of newly synthesized fatty acids in heart, liver, uterus, and white adipose tissues (parametrial and inguinal fat pads). Treatment of ovariectomized hamsters with estradiol + progesterone significantly decreased fatty acid synthesis-uptake in heart, liver, and inguinal white adipose tissue. Treatment with either estradiol or progesterone alone was without significant effect in any tissue. Pretreatment of hamsters with Triton WR-1339 (tyloxapol), an inhibitor of lipoprotein lipase activity and tissue triglyceride uptake, abolished the effects of estradiol + progesterone in white adipose tissue and heart but not in liver. Thus hamsters lose body fat during pregnancy in part because of decreased de novo lipogenesis. The effect of pregnancy on lipogenesis is mimicked by treatment with estradiol + progesterone but not by either hormone alone. Furthermore, it appears that the liver is the principal site of estradiol + progesterone action on lipogenesis in Syrian hamsters.

Ketogenic diet in combination with voluntary exercise impacts markers of hepatic metabolism and oxidative stress in male and female Wistar rats

2020 ◽  
Vol 45 (1) ◽  
pp. 35-44 ◽  
Author(s):  
Mary P. Moore ◽  
Rory P. Cunningham ◽  
Taylor J. Kelty ◽  
Luigi R. Boccardi ◽  
Nhu Y. Nguyen ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Energy Homeostasis ◽  
De Novo ◽  
Hepatic Metabolism ◽  
De Novo Lipogenesis ◽  
Female Rats ◽  
Female Wistar Rats ◽  
Amp Activated Protein Kinase ◽  
Hepatic Markers ◽  
And Oxidative Stress

Ketogenic diets (KDs) are shown to benefit hepatic metabolism; however, their effect on the liver when combined with exercise is unknown. We investigated the effects of a KD versus a “western” diet (WD) on markers of hepatic lipid metabolism and oxidative stress in exercising rats. Male and female Wistar rats with access to voluntary running wheels were randomized to 3 groups (n = 8–14 per group): standard chow (SC; 17% fat), WD (42% fat), or KD (90.5% fat) for 7 weeks. Body fat percentage (BF%) was increased in WD and KD versus SC, although KD females displayed lower BF% versus WD (p ≤ 0.05). Liver triglycerides were higher in KD and WD versus SC but were attenuated in KD females versus WD (p ≤ 0.05). KD suppressed hepatic markers of de novo lipogenesis (fatty acid synthase, acetyl coenzyme A carboxylase) and increased markers of mitochondrial biogenesis/content (peroxisome proliferator activated receptor-1α, mitochondrial transcription factor A (TFAM), and citrate synthase activity). KD also increased hepatic glutathione peroxidase 1 and lowered oxidized glutathione. Female rats exhibited elevated hepatic markers of mitochondrial biogenesis (TFAM), mitophagy (light chain 3 II/I ratio, autophagy-related protein 12:5), and cellular energy homeostasis (phosphorylated 5′AMP-activated protein kinase/5′AMP-activated protein kinase) versus males. These data highlight that KD and exercise beneficially impacts hepatic metabolism and oxidative stress and merits further investigation. Novelty KD feeding combined with exercise improved hepatic oxidative stress, suppressed markers of de novo lipogenesis, and increased markers of mitochondrial content versus WD feeding. Males and females responded similarly to combined KD feeding and exercise. Female rats exhibited elevated hepatic markers of autophagy/mitophagy and energy homeostasis compared with male rats.

scholarly journals Central Resistin Regulates Hypothalamic and Peripheral Lipid Metabolism in a Nutritional-Dependent Fashion

Endocrinology ◽  
2008 ◽  
Vol 149 (9) ◽  
pp. 4534-4543 ◽  
Author(s):  
María J. Vázquez ◽  
C. Ruth González ◽  
Luis Varela ◽  
Ricardo Lage ◽  
Sulay Tovar ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Lipid Metabolism ◽  
Mrna Expression ◽  
Fatty Acid Synthase ◽  
De Novo ◽  
Acid Synthesis ◽  
Inhibitory Effect ◽  
De Novo Lipogenesis ◽  
Dependent Manner ◽  
Fed State

Evidence suggests that the adipocyte-derived hormone resistin (RSTN) directly regulates both feeding and peripheral metabolism through, so far, undefined hypothalamic-mediated mechanisms. Here, we demonstrate that the anorectic effect of RSTN is associated with inappropriately decreased mRNA expression of orexigenic (agouti-related protein and neuropeptide Y) and increased mRNA expression of anorexigenic (cocaine and amphetamine-regulated transcript) neuropeptides in the arcuate nucleus of the hypothalamus. Of interest, RSTN also exerts a profound nutrition-dependent inhibitory effect on hypothalamic fatty acid metabolism, as indicated by increased phosphorylation levels of both AMP-activated protein kinase and its downstream target acetyl-coenzyme A carboxylase, associated with decreased expression of fatty acid synthase in the ventromedial nucleus of the hypothalamus. In addition, we also demonstrate that chronic central RSTN infusion results in decreased body weight and major changes in peripheral expression of lipogenic enzymes, in a tissue-specific and nutrition-dependent manner. Thus, in the fed state central RSTN is associated with induced expression of fatty acid synthesis enzymes and proinflammatory cytokines in liver, whereas its administration in the fasted state does so in white adipose tissue. Overall, our results indicate that RSTN controls feeding and peripheral lipid metabolism and suggest that hepatic RSTN-induced insulin resistance may be mediated by central activation of de novo lipogenesis in liver.

Abstract 20: Tribbles1 (Trib1) is a Novel Regulator of in vivo Hepatic Fatty Acid Lipogenesis in the Mouse.

2013 ◽  
Vol 33 (suppl_1) ◽  
Author(s):  
Robert C Bauer ◽  
Jian Cui ◽  
Anthony P Kent ◽  
Daniel J Rader
Keyword(s):  
Fatty Acid ◽  
Transcriptional Control ◽  
De Novo ◽  
Association Studies ◽  
Liver Weight ◽  
Acid Synthesis ◽  
De Novo Lipogenesis ◽  
Pcr Analysis ◽  
Genome Wide Association Studies

Tribbles1 (TRIB1) was recently identified in genome-wide association studies as being strongly linked to plasma levels of VLDL, HDL, LDL, and TG as well as coronary artery disease in humans. Previous experiments in mice using AAV-mediated hepatic overexpression of Trib1 confirmed this association, as mice overexpressing Trib1 exhibited reductions of 45% and 57% in plasma total cholesterol (TC) and TG, respectively ( Burkhardt et al, 2010 ). Here we report a Trib1 liver-specific knockout mouse (Trib1_LSKO) created through AAV-mediated delivery of Cre recombinase into adult mice with a floxed version of Trib1. Four weeks after infection, Trib1_LSKO mice exhibited 21% and 70% increases in TC and TG, respectively ( p =0.01 and 0.02), as compared to floxed Trib1 littermates infected with null virus (Controls). Trib1_LSKO animals also exhibited a 25% increase in liver weight ( p <0.01), and histological analysis revealed steatotic livers in LSKO mice. Real-time PCR analysis revealed >2-fold increases in the hepatic transcription of genes involved in fatty acid synthesis in Trib1_LSKO mice as compared to Controls. Examination of hepatic lipids revealed a 78% increase in hepatic TG content ( p <0.001) of Trib1_LSKO mouse livers, while no significant change in hepatic cholesterol was observed. When de novo lipogenesis was measured using [3H]-acetate, Trib1_LSKO animals exhibited significantly increased production of TG (3.6-fold, p <0.001), fatty acids (2.2-fold, p =0.02), diacylglycerol (1.8-fold, p <0.01), and phospholipids (2-fold, p =0.05). Microarray analysis of Trib1_LSKO livers compared to Controls revealed greater than 1,600 genes that were significantly altered between the two groups (fold change>1.5, FDR<10%). Pathway analysis suggested that the altered gene set was enriched for genes downstream of C/EBP and C/EBP. Western blot analysis of liver extracts showed increases in both C/EBP and C/EBP levels in Trib1_LSKO mice compared to Controls. In conclusion, Trib1 is a novel regulator of de novo lipogenesis in mice, presumably through the regulation of lipogenic gene transcription. This transcriptional control may be regulated by increased levels of C/EBP and/or C/EBP, or an as yet undetermined target of Trib1.

scholarly journals Combination of Mitochondrial and Plasma Membrane Citrate Transporter Inhibitors Inhibits De Novo Lipogenesis Pathway and Triggers Apoptosis in Hepatocellular Carcinoma Cells

2018 ◽  
Vol 2018 ◽  
pp. 1-15 ◽  
Author(s):  
Wan-angkan Poolsri ◽  
Phornpun Phokrai ◽  
Somrudee Suwankulanan ◽  
Narinthorn Phakdeeto ◽  
Pattamaphorn Phunsomboon ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Plasma Membrane ◽  
Fatty Acid ◽  
Cancer Therapy ◽  
Cell Apoptosis ◽  
Hepg2 Cells ◽  
Cytotoxic Effect ◽  
De Novo ◽  
De Novo Lipogenesis ◽  
Citrate Transporter

Increased expression levels of both mitochondrial citrate transporter (CTP) and plasma membrane citrate transporter (PMCT) proteins have been found in various cancers. The transported citrates by these two transporter proteins provide acetyl-CoA precursors for the de novo lipogenesis (DNL) pathway to support a high rate of cancer cell viability and development. Inhibition of the DNL pathway promotes cancer cell apoptosis without apparent cytotoxic to normal cells, leading to the representation of selective and powerful targets for cancer therapy. The present study demonstrates that treatments with CTP inhibitor (CTPi), PMCT inhibitor (PMCTi), and the combination of CTPi and PMCTi resulted in decreased cell viability in two hepatocellular carcinoma cell lines (HepG2 and HuH-7). Treatment with citrate transporter inhibitors caused a greater cytotoxic effect in HepG2 cells than in HuH-7 cells. A lower concentration of combined CTPi and PMCTi promotes cytotoxic effect compared with either of a single compound. An increased cell apoptosis and an induced cell cycle arrest in both cell lines were reported after administration of the combined inhibitors. A combination treatment exhibits an enhanced apoptosis through decreased intracellular citrate levels, which consequently cause inhibition of fatty acid production in HepG2 cells. Apoptosis induction through the mitochondrial-dependent pathway was found as a consequence of suppressed carnitine palmitoyl transferase-1 (CPT-1) activity and enhanced ROS generation by combined CTPi and PMCTi treatment. We showed that accumulation of malonyl-CoA did not correlate with decreasing CPT-1 activity. The present study showed that elevated ROS levels served as an inhibition on Bcl-2 activity that is at least in part responsible for apoptosis. Moreover, inhibition of the citrate transporter is selectively cytotoxic to HepG2 cells but not in primary human hepatocytes, supporting citrate-mediating fatty acid synthesis as a promising cancer therapy.

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