Separation of postprandial lipoproteins: improved purification of chylomicrons using an ApoB100 immunoaffinity method

Elevated levels of triglyceride-rich lipoproteins (TRLs), both fasting and postprandial, are associated with increased risk for atherosclerosis. However, guidelines for treatment are defined solely by fasting lipid levels, even though postprandial lipids may be more informative. In the postprandial state, circulating lipids consist of dietary fat transported from the intestine in chylomicrons (CMs; containing ApoB48) and fat transported from the liver in VLDL (containing ApoB100). Research into the roles of endogenous versus dietary fat has been hindered because of the difficulty in separating these particles by ultracentrifugation. CM fractions have considerable contamination from VLDL (purity, 10%). To separate CMs from VLDL, we produced polyclonal antibodies against ApoB100 and generated immunoaffinity columns. TRLs isolated by ultracentrifugation of plasma were applied to these columns, and highly purified CMs were collected (purity, 90–94%). Overall eight healthy unmedicated adult volunteers (BMI, 27.2 ± 1.4 kg/m2; fasting triacylglycerol, 102.6 ± 19.5 mg/dl) participated in a feeding study, which contained an oral stable-isotope tracer (1-13C acetate). We then used this technique on plasma samples freshly collected during an 8 h human feeding study from a subset of four subjects. We analyzed fractionated lipoproteins by Western blot, isolated and derivatized triacylglycerols, and calculated fractional de novo lipogenesis. The results demonstrated effective separation of postprandial lipoproteins and substantially improved purity compared with ultracentrifugation protocols, using the immunoaffinity method. This method can be used to better delineate the role of dietary sugar and fat on postprandial lipids in cardiovascular risk and explore the potential role of CM remnants in atherosclerosis.

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249 ROLE OF DE NOVO LIPOGENESIS IN GROWING VERY LOW BIRTH WEIGHT BREASTFED INFANTS.

Journal of Investigative Medicine ◽

10.1136/jim-52-suppl1-249 ◽

2004 ◽

Vol 52 (Suppl 1) ◽

pp. S122.6-S123

Author(s):

M. Garg ◽

C. Bell ◽

L. Rogers ◽

S. Bassilian ◽

W. N.P. Lee

Keyword(s):

Birth Weight ◽

Low Birth Weight ◽

Very Low Birth Weight ◽

De Novo ◽

De Novo Lipogenesis ◽

Breastfed Infants

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A Narrative Review on the Role of AMPK on De Novo Lipogenesis in Non-Alcoholic Fatty Liver Disease: Evidence from Human Studies

Cells ◽

10.3390/cells10071822 ◽

2021 ◽

Vol 10 (7) ◽

pp. 1822

Author(s):

Christian von Loeffelholz ◽

Sina M. Coldewey ◽

Andreas L. Birkenfeld

Keyword(s):

Liver Disease ◽

Fatty Liver ◽

Fatty Liver Disease ◽

Mammalian Cells ◽

De Novo ◽

Adenosine Monophosphate ◽

De Novo Lipogenesis ◽

Alcoholic Fatty Liver ◽

Alcoholic Fatty Liver Disease

5′AMP-activated protein kinase (AMPK) is known as metabolic sensor in mammalian cells that becomes activated by an increasing adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratio. The heterotrimeric AMPK protein comprises three subunits, each of which has multiple phosphorylation sites, playing an important role in the regulation of essential molecular pathways. By phosphorylation of downstream proteins and modulation of gene transcription AMPK functions as a master switch of energy homeostasis in tissues with high metabolic turnover, such as the liver, skeletal muscle, and adipose tissue. Regulation of AMPK under conditions of chronic caloric oversupply emerged as substantial research target to get deeper insight into the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Evidence supporting the role of AMPK in NAFLD is mainly derived from preclinical cell culture and animal studies. Dysbalanced de novo lipogenesis has been identified as one of the key processes in NAFLD pathogenesis. Thus, the scope of this review is to provide an integrative overview of evidence, in particular from clinical studies and human samples, on the role of AMPK in the regulation of primarily de novo lipogenesis in human NAFLD.

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TAMI-37. STEAROYL-COA DESATURASE 1 IS ESSENTIAL FOR THE GROWTH OF IDH MUTANT GLIOMA

Neuro-Oncology ◽

10.1093/neuonc/noab196.821 ◽

2021 ◽

Vol 23 (Supplement_6) ◽

pp. vi206-vi206

Author(s):

Tomohiro Yamasaki ◽

Lumin Zhang ◽

Tyrone Dowdy ◽

Adrian Lita ◽

Mark Gilbert ◽

...

Keyword(s):

Glioma Cell ◽

De Novo ◽

Glioma Cells ◽

Model Systems ◽

De Novo Lipogenesis ◽

Wild Type ◽

Knock Out ◽

Stearoyl Coa Desaturase ◽

Scd1 Expression

Abstract BACKGROUND Increased de novo lipogenesis is a hallmark of cancer metabolism. In this study, we interrogated the role of de novo lipogenesis in IDH1 mutated glioma’s growth and identified the key enzyme, Stearoyl-CoA desaturase 1 (SCD1) that provides this growth advantage. MATERIALS ANDMETHODS We prepared genetically engineered glioma cell lines (U251 wild-type: U251WT and U251 IDHR132H mutant: U251RH) and normal human astrocytes (empty vector induced-NHA: NHAEV and IDHR132H mutant: NHARH). Lipid metabolic analysis was conducted by using LC-MS and Raman imaging microscopy. SCD1 expression was investigated by The Cancer Genome Atlas (TCGA) data analysis and Western-blotting method. Knock-out of SCD1 was conducted by using CRISPR/Cas9 and shRNA. RESULTS Previously, we showed that IDH1 mut glioma cells have increased monounsaturated fatty acids (MUFAs). TCGA data revealed IDH mut glioma shows significantly higher SCD1 mRNA expression than wild-type glioma. Our model systems of IDH1 mut (U251RH, NHARH) showed increased expression of this enzyme compared with their wild-type counterpart. Moreover, addition of D-2HG to U251WT increased SCD1 expression. Herein, we showed that inhibition of SCD1 with CAY10566 decreased relative cell number and sphere forming capacity in a dose-dependent manner. Furthermore, addition of MUFAs were able to rescue the SCD1 inhibitor induced-cell death and sphere forming capacity. Knock out of SCD1 revealed decreased cell proliferation and sphere forming ability. Decreasing lipid content from the media did not alter the growth of these cells, suggesting that glioma cells rely on de novo lipid synthesis rather than scavenging them from the microenvironment. CONCLUSION Overexpression of IDH mutant gene altered lipid composition in U251 cells to enrich MUFA levels and we confirmed that D-2HG caused SCD1 upregulation in U251WT. We demonstrated the glioma cell growth requires SCD1 expression and the results of the present study may provide novel insights into the role of SCD1 in IDH mut gliomas growth.

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Role of human liver lipogenesis and reesterification in triglycerides secretion and in FFA reesterification

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1998.274.2.e321 ◽

1998 ◽

Vol 274 (2) ◽

pp. E321-E327 ◽

Cited By ~ 13

Author(s):

Frederique Diraison ◽

Michel Beylot

Keyword(s):

Turnover Rate ◽

De Novo ◽

Plasma Free Fatty Acid ◽

Normal Subjects ◽

De Novo Lipogenesis ◽

Deuterated Water ◽

Extrahepatic Tissues ◽

Almost All ◽

State 1

To measure 1) the contribution of hepatic de novo lipogenesis (DNL) and plasma free fatty acid (FFA) reesterification to plasma triglyceride (TG) secretion, and 2) the role of oxidation and hepatic and extrahepatic reesterification in FFA utilization, five normal subjects drank deuterated water and were infused (postabsorptive state) with [1-13C]palmitate and [1,2,3-2H5]glycerol. Total lipid oxidation (Lox) was measured by indirect calorimetry. FFA oxidation (2.76 ± 0.65 μmol ⋅ kg−1 ⋅ min−1) accounted for 45% of FFA turnover rate (Rt) (1.04 μmol ⋅ kg−1 ⋅ min−1) and 91% of Lox; FFA reesterification was 3.27 ± 0.54 μmol ⋅ kg−1 ⋅ min−1. Fractional and absolute TG Rt were 0.21 ± 0.02 h−1 and 0.11 ± 0.05 μmol ⋅ kg−1 ⋅ min−1. DNL accounted for 3.9 ± 0.9% of TG secretion, and hepatic FFA reesterification accounted for 49.4 ± 5.7%; this last process represented a utilization of FFA of 0.16 ± 0.02 μmol ⋅ kg−1 ⋅ min−1. We conclude that, in the postabsorptive state, 1) DNL and FFA reesterification account for only 50–55% of TG secretion, the remaining presumably being provided by stored lipids or lipoproteins taken up by liver, 2) most reesterification occurs in extrahepatic tissues, and 3) oxidation and reesterification each contribute about one-half to FFA utilization; FFA oxidation accounts for almost all Lox.

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Loss of regulation of lipogenesis in the Zucker diabetic (ZDF) rat

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.2000.279.2.e425 ◽

2000 ◽

Vol 279 (2) ◽

pp. E425-E432 ◽

Cited By ~ 33

Author(s):

W.-N. Paul Lee ◽

Sara Bassilian ◽

Shu Lim ◽

Laszlo G. Boros

Keyword(s):

High Fat Diet ◽

Leptin Receptor ◽

De Novo ◽

De Novo Lipogenesis ◽

Chain Elongation ◽

Deuterated Water ◽

High Fat ◽

Macronutrient Composition ◽

Zdf Rat

We present here a study on the role of leptin in the regulation of lipogenesis by examining the effect of dietary macronutrient composition on lipogenesis in the leptin receptor-defective Zucker diabetic fatty rat (ZDF) and its lean litter mate (ZL). Animals were pair fed two isocaloric diets differing in their fat-to-carbohydrate ratio providing 10 and 30% energy as fat. Lipogenesis was measured in the rats using deuterated water and isotopomer analysis. From the deuterium incorporation into plasma palmitate, stearate, and oleate, we determined de novo synthesis of palmitate and synthesis of stearate by chain elongation and of oleate by desaturation. Because the macronutrient composition and the caloric density were controlled, changes in de novo lipogenesis under these dietary conditions represent adaptation to changes in the fat-to-carbohydrate ratio of the diet. De novo lipogenesis was normally suppressed in response to the high-fat diet in the ZL rat to maintain a relatively constant amount of lipids transported. The ZDF rat had a higher rate of lipogenesis, which was not suppressed by the high-fat diet. The results suggest an important hormonal role of leptin in the feedback regulation of lipogenesis.

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