Ahmed Bakillah | SUNY: Downstate Medical Center (original) (raw)
Papers by Ahmed Bakillah
Production de collagene de type quatre et de collagenase quatre par les cellules endotheliales humaines cultivees en presence de differentes concentrations de glucose, et d'hormone de croissance : effets d'un inhibiteur de l'aldose reductase et d'un inhibiteur de proteine kinase c
Http Www Theses Fr, 1994
Rôle de l'interaction de l'apolipoprotéine -B (apoB) avec la protéine microsomiale de transfert des triacyglycérols (MTP) dans l'assemblage et la sécrétion des lipoprotéines
Precipitating factors and targeted therapies in combating the perils of sickle cell disease--- A special nutritional consideration
Nutrition & metabolism, 2016
Nutritional research in sickle cell disease has been the focus in recent times owing to not only ... more Nutritional research in sickle cell disease has been the focus in recent times owing to not only specific nutritional deficiencies, but also the improvements associated with less painful episodes. Though hydroxyurea remains the drug of choice, certain adverse health effects on long term supplementation makes room for researches of different compounds. Macro and micro nutrient deficiencies, along with vitamins, play an important role in not only meeting the calorific needs, but also reducing clinical complications and growth abnormalities. Symptoms of hyper protein metabolism, increased cell turnover, increased cardiac output, and appetite suppression due to enhanced cytokine production, might give us leads for better understanding of the mechanisms involved. Different nutritional approaches comprising of traditional herbal therapies, antioxidants, flavonoids, vitamins, minerals etc., reducing oxidative stress and blood aggregation, have been tried out to increase the health potentia...
Lipids, Nov 1, 1997
We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship... more We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship between intracellular levels and secretion rates of apoB. The assays were based on commercially available antibodies and were specific to human apoB. A monoclonal antibody, 1D1, was immobilized on microtiter wells and incubated with different amounts of low density lipoproteins to obtain a standard curve. Conditioned media were added to other wells in parallel, and the amount of apoB was quantitated from a linear regression curve. To standardize conditions for the measurement of intracellular apoB, cells were homogenized and solubilized with different concentrations of taurocholate. We found that 0.5% taurocholate was sufficient to solubilize all the apoB in HepG2, Caco-2, and McA-RH7777 cells. Next, a standard curve was prepared in the presence of taurocholate and used to determine intracellular levels of apoB in different cell lines. The intracellular levels (pmol/mg cell protein) and the rates of secretion (pmol/mg/h) of apoB100 were positively correlated (r 2 = 0.81, P = 0.0009) in HepG2 cells. Furthermore, a positive correlation (r 2 = 0.88, P < 0.0001) was found between intracellular and secreted apoB42 in stably transfected McA-RH7777 cells. In contrast, no correlation was observed for human apoB28 and apoB18 in stably transfected cells that were secreted either partially associated or completely unassociated with lipoproteins. These studies indicated that the rate of secretion of lipid-associated apoB, but not the lipid-free apoB, was tightly controlled.
Compounds and Methods for Identifying Compounds That Interact with Microsomal Triglyceride Transfer Protein Binding Sites on Apolipoprotein B and Modulate Lipid Biosynthesis
Lysine and Arginine Residues in the N-Terminal 18% of Apolipoprotein B Arecritical for Its Binding to Microsomal Triglyceride Transfer Protein
Biochemistry, 1998
Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are essential for the ... more Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are essential for the efficient assembly and secretion of triglyceride-rich lipoproteins. We have presented evidence for a high-affinity interaction between these proteins [Hussain, M. M., et al. (1997) Biochemistry 36, 13060-13067]. In this study, we used chemically modified low-density lipoproteins (LDL) and recombinant human apoB18 to identify amino acid residues in apoB that are critical for its interactions with MTP. Acetoacetylation of 74% of lysine residues and cyclohexanedione modification of 54% of arginine residues completely abolished the interactions between LDL and MTP. Regeneration of lysine and arginine residues by hydroxylamine treatment completely restored the binding of modified LDL to MTP. Carboxyethylation of all the histidine residues decreased, but did not abolish, apoB-MTP interactions. In contrast, glycine methyl ester modifications of aspartic and glutamic acid residues, up to 38-44%, had no effect on LDL-MTP interactions. Furthermore, modification of lysine and arginine, but not the aspartic and glutamic acid, residues in apoB18 also completely abolished its interactions with MTP. These studies indicated that lysine and arginine, but not aspartic and glutamic acid, residues are critical for apoB-MTP interactions, whereas histidine residues are not as critical. Since lysine and arginine residues in apoB are known to interact with the LDL receptors and heparin, we studied the effect of different glycosaminoglycans on apoB-MTP interactions. Glycosaminoglycans had no significant inhibitory effect on apoB-MTP interactions, suggesting that the lysine and arginine residues crucial for apoB-MTP interactions are different from those that interact with the LDL receptor and heparin. The lysine and arginine residues in apoB18 may directly interact with negatively charged residues in the MTP molecule, or they may function to maintain the conformation of the recognition site.
Human serum preβ1-high density lipoprotein levels are independently and negatively associated with coronary artery diseases
Nutrition & metabolism, 2016
Serum preβ1-high density lipoprotein (preβ1-HDL) was defined by two-dimensional non-denaturing li... more Serum preβ1-high density lipoprotein (preβ1-HDL) was defined by two-dimensional non-denaturing linear gel electrophoresis and apolipoprotein A-I immuno-blotting. Serum preβ1-HDL seems to play an important role in reverse cholesterol transport, a well-known anti-atherosclerosis process. However, there are still debatable questions for its quantification and coronary artery disease (CAD) relevance. We isolated the preβ1-HDL using a new native polyacrylamide gel electrophoresis (PAGE) system and lipid pre-staining serum. We established a two-demensional gel electrophoresis system. We measured the preβ1-HDL in Tangier disease patients and subjects with cholesterol ester transfer protein (CETP) mutation. The preβ1-HDL is clearly separated from lipid-free apoA-I monomer and cannot be converted into other HDL particles under lecithin-cholesterol acyltransferase (LCAT) inhibition. This preβ1-HDL is a spheroidal particle with the highest apoA-1/cholesterol ratio and highest density (≥1.21 g/...
Biochimica Et Biophysica Acta L Lipids and Lipid Metabolism, May 20, 1996
Journal of Lipid Research, 1999
The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apol... more The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apolipoprotein (apo) B-containing lipoproteins. Previous studies have indicated that inhibition of MTP results in decreased apoB plasma levels and decreased hepatic triglyceride secretion. However, the metabolic effects of overexpression of MTP have not been investigated. We constructed a recombinant adenovirus expressing MTP (AdhMTP) and used it to assess the effects of hepatic overexpression of MTP in mice. Injection of AdhMTP into C57BL/6 mice resulted in a 3-fold increase in hepatic microsomal triglyceride transfer activity compared to mice injected with Adnull. On day 4 after virus injection, AdhMTP-injected mice had significantly elevated plasma TG levels as compared to control virus (Adnull)-injected mice. Hepatic TG secretion rates were significantly greater in AdhMTP-injected mice (184 ؎ 12 mg/ kg/h) compared with Adnull-injected mice (65 ؎ 9 mg/kg/ h, P Ͻ 0.001). In addition, hepatic very low density lipoprotein (VLDL) apoB secretion in the AdhMTP-injected group was 74% higher than in the control virus group. Hepatic secretion of apoB-48 and apoB-100 contributed equally to this increase. These results provide the first data that hepatic overexpression of MTP results in increased secretion of VLDL-triglycerides as well as VLDL-apoB in vivo. These results suggest that MTP is rate-limiting for VLDL apoB secretion in wild-type mice under basal chow-fed conditions. -Tietge, U. overexpression of microsomal triglyceride transfer protein (MTP) results in increased in vivo secretion of VLDL triglycerides and apolipoprotein B. J. Lipid Res. 1999. 40: 2134-2139. Supplementary key words recombinant adenovirus expressing MTP • apoB • triglyceride
Mice subjected to aP2-Cre mediated ablation of microsomal triglyceride transfer protein are resistant to high fat diet induced obesity
Nutrition & metabolism, 2016
Microsomal triglyceride transfer protein (MTP) is essential for the assembly of lipoproteins. MTP... more Microsomal triglyceride transfer protein (MTP) is essential for the assembly of lipoproteins. MTP has been shown on the surface of lipid droplets of adipocytes; however its function in adipose tissue is not well defined. We hypothesized that MTP may play critical role in adipose lipid droplet formation and expansion. Plasmids mediated overexpression and siRNA mediated knockdown of Mttp gene were performed in 3T3-L1 pre-adipocytes to evaluate the effects of MTP on cell differentiation and triglyceride accumulation. Adipose-specific knockdown of MTP was achieved in mice bybreeding MTP floxed (Mttp (fl/fl) ) mice with aP2-Cre recombinase transgenic mice. Adipose-specific MTP deficient (A-Mttp (-/-) ) mice were fed 60 % high-fat diet (HFD), and the effects of MTP knockdown on body weight, body fat composition, plasma and tissues lipid composition, glucose metabolism, lipogenesis and intestinal absorption was studied. Lipids were measured in total fasting plasma and size fractionated pla...
Plasma Nitration of High-Density and Low-Density Lipoproteins in Chronic Kidney Disease Patients Receiving Kidney Transplants
Mediators of inflammation, 2015
Background. Functional abnormalities of high-density lipoprotein (HDL) could contribute to cardio... more Background. Functional abnormalities of high-density lipoprotein (HDL) could contribute to cardiovascular disease in chronic kidney disease patients. We measured a validated marker of HDL dysfunction, nitrated apolipoprotein A-I, in kidney transplant recipients to test the hypothesis that a functioning kidney transplant reduces serum nitrated apoA-I concentrations. Methods. Concentrations of nitrated apoA-I and apoB were measured using indirect sandwich ELISA assays on sera collected from each transplant subject before transplantation and at 1, 3, and 12 months after transplantation. Patients were excluded if they have history of diabetes, treatment with lipid-lowering medications or HIV protease inhibitors, prednisone dose > 15 mg/day, nephrotic range proteinuria, serum creatinine > 1.5 mg/dL, or active inflammatory disease. Sera from 18 transplanted patients were analyzed. Four subjects were excluded due to insufficient data. Twelve and eight patients had creatinine < 1.5...
Journal of lipid research, 1999
The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apol... more The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apolipoprotein (apo) B-containing lipoproteins. Previous studies have indicated that inhibition of MTP results in decreased apoB plasma levels and decreased hepatic triglyceride secretion. However, the metabolic effects of overexpression of MTP have not been investigated. We constructed a recombinant adenovirus expressing MTP (AdhMTP) and used it to assess the effects of hepatic overexpression of MTP in mice. Injection of AdhMTP into C57BL/6 mice resulted in a 3-fold increase in hepatic microsomal triglyceride transfer activity compared to mice injected with Adnull. On day 4 after virus injection, AdhMTP-injected mice had significantly elevated plasma TG levels as compared to control virus (Adnull)-injected mice. Hepatic TG secretion rates were significantly greater in AdhMTP-injected mice (184 +/- 12 mg/kg/h) compared with Adnull-injected mice (65 +/- 9 mg/kg/h, P < 0.001). In addition, ...
[Changes in collagen type IV metabolism in diabetes]
Comptes rendus des séances de la Société de biologie et de ses filiales, 1993
In Diabetes Mellitus, type IV collagen biosynthesis is increased: the alpha 1(IV) procollagen spe... more In Diabetes Mellitus, type IV collagen biosynthesis is increased: the alpha 1(IV) procollagen specific mRNA concentration is elevated, particularly in the kidney, and the type IV collagen protein is accumulating is the thickened basement membranes. Aldose reductase inhibitors like sorbinil do prevent basement membrane thickening and type IV collagen overproduction. The latter seems related to intracellular sorbitol accumulation and also to protein kinase C activation. Autocrine or paracrine TGF beta may be involved in the type IV collagen oversecretion. The secreted type IV collagen is subject to posttranslational alterations, especially glycation which leads to advanced glycation end-products and covalent crosslinks. This decreases collagen extractability and susceptibility to collagenases and favours basement membrane thickening. Disaccharide unit-specific alpha-glucosidase activity is inhibited by glucose (Kp = 7.5 mM). Type IV collagenase activity secreted by endothelial cells c...
Lysophosphatidylcholine increases apolipoprotein B secretion by enhancing lipid synthesis and decreasing its intracellular degradation in HepG2 cells
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1998
Free fatty acids and lysophosphatidylcholine (lysoPC) are the major lipids bound to human plasma ... more Free fatty acids and lysophosphatidylcholine (lysoPC) are the major lipids bound to human plasma albumin. The effects of fatty acids on the hepatic production of Apolipoprotein B (apo B) have been studied but those of lysoPC have not. In HepG2 cells, lysoPC increased apo B secretion in different experiments by 50-120%, but did not affect the flotation properties of secreted lipoproteins. LysoPC affected neither the cellular protein levels nor apo A-I secretion suggesting that its effect was specific to apo B. Apo B secretion was maximum after incubating cells for 6 h with 0.2 mM lysoPC as equimolar fatty acid free bovine serum albumin (BSA) complexes. LysoPC was metabolized by cells and its fatty acids were used for the synthesis of phosphatidylcholine and triglycerides (TG). Experiments were performed to understand the mechanism of lysoPC action. LysoPC increased the incorporation of 3H-glycerol into newly synthesized cellular (3-fold) and secreted (4-fold) triglycerides, and increased the synthesis (40%) and secretion (4-fold) of phospholipids. LysoPC did not affect apo B synthesis, but inhibited the intracellular degradation of apo B and increased its secretion. Triacsin C (5 microM), an inhibitor of long chain acyl-CoA synthase, completely inhibited the induction of lipid synthesis and abolished the effect of lysoPC on apo B secretion. These studies indicated that lysoPC increased apo B secretion by inducing lipid synthesis; newly synthesized lipids probably protected apo B from intracellular degradation and enhanced secretion. These studies are consistent with the hypothesis that physiologic concentrations of lysoPC can be an important modulator for hepatic apo B secretion.
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1996
Nutrition & Metabolism, 2014
Nutrition & Metabolism has grown considerably in the ten years since its first article was publis... more Nutrition & Metabolism has grown considerably in the ten years since its first article was published. To see how papers published in the journal had an impact we have identified some of the most popular articles in order to measure their influence, observe which fields are important to our readers, and try to explain what made these articles Nutrition & Metabolism "Classics".
Nutrition & Metabolism, 2013
Lipids, 1997
We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship... more We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship between intracellular levels and secretion rates of apoB. The assays were based on commercially available antibodies and were specific to human apoB. A monoclonal antibody, 1D1, was immobilized on microtiter wells and incubated with different amounts of low density lipoproteins to obtain a standard curve. Conditioned media were added to other wells in parallel, and the amount of apoB was quantitated from a linear regression curve. To standardize conditions for the measurement of intracellular apoB, cells were homogenized and solubilized with different concentrations of taurocholate. We found that 0.5% taurocholate was sufficient to solubilize all the apoB in HepG2, Caco-2, and McA-RH7777 cells. Next, a standard curve was prepared in the presence of taurocholate and used to determine intracellular levels of apoB in different cell lines. The intracellular levels (pmol/mg cell protein) and the rates of secretion (pmol/mg/h) of apoB100 were positively correlated (r 2 = 0.81, P = 0.0009) in HepG2 cells. Furthermore, a positive correlation (r 2 = 0.88, P < 0.0001) was found between intracellular and secreted apoB42 in stably transfected McA-RH7777 cells. In contrast, no correlation was observed for human apoB28 and apoB18 in stably transfected cells that were secreted either partially associated or completely unassociated with lipoproteins. These studies indicated that the rate of secretion of lipid-associated apoB, but not the lipid-free apoB, was tightly controlled.
Journal of Biological Chemistry, 1998
Several studies have demonstrated protein-protein interactions between microsomal triglyceride tr... more Several studies have demonstrated protein-protein interactions between microsomal triglyceride transfer protein (MTP) and apolipoprotein B (apoB). However, the binding sites involved in these interactions have not been elucidated. To identify an MTP binding site in apoB, we have expressed several apoB sequences as fusion proteins with the eight-amino acid FLAG peptide. The chimeras were transiently expressed in COS cells, and conditioned media were used to study the binding of these sequences to either immobilized or soluble MTP. A polypeptide containing amino acids 270 -570 (B: 270 -570), but not 1-300, bound to MTP. AGI-S17, an antagonist of apoB-MTP binding, inhibited the binding of B:270 -570 to MTP but not to M2, a monoclonal antibody that recognizes the FLAG peptide. These data indicated that B:270 -570 contains an MTP binding site. Next, sequences within 270 -570 were subjected to C-terminal truncations at natural proline residues. B:270 -509 bound less efficiently than B:270 -570, whereas, B:270 -430 and other shorter chimeras did not bind to MTP. Furthermore, truncations at amino acids 502 and 509 decreased MTP binding by 73 and 42%, respectively. These data indicate that B:430 -570 in the ␣ 1 -globular domain of apoB plays a crucial role in MTP binding and presumably in the initiation and maturation of apoBcontaining lipoproteins.
Journal of Biological Chemistry, 2001
Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are known to interact ... more Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are known to interact with each other. We evaluated the effect of different lipids on the protein-protein interactions between MTP and apoB100 or its C-terminally truncated forms. Negatively charged lipids decreased protein-protein interactions between apoB and MTP. In contrast, zwitterionic phospholipids enhanced (2-4-fold) the binding of apoB100 to MTP by increasing affinity (1.5-3-fold) between these proteins without affecting the number of binding sites. Similarly, phospholipids augmented (1.5-4-fold) the binding of various C-terminally truncated apoB peptides to MTP. The increased binding was greater for apoB peptides containing lipidbinding domains, such as apoB28 and apoB42. Surprisingly, preincubation of apoB28 with lipid vesicles had no effect on MTP binding. In contrast, incubation of MTP with lipid vesicles resulted in a stable association of MTP with vesicles, and MTP-lipid vesicles bound better (5-fold increase) to LDL than did lipid-free MTP. To determine whether MTP exists stably associated with lipids in cells, microsomal contents from COS cells expressing MTP, HepG2 cells, and mouse liver were ultracentrifuged, and MTP was visualized in different density fractions. MTP was found associated and unassociated with lipids. In contrast, apoB17 and apoB:270 -570 were present unassociated with lipids in COS cells. These studies show that the binding of MTP to lipids results in increased affinity for apoB and that stable MTP-lipid complexes exist in the lumen of the endoplasmic reticulum. Protein-protein interactions between apoB and MTP may juxtapose lipids associated with MTP to lipid-binding domains of apoB and facilitate hydrophobic interactions leading to enhance affinity. We speculate that MTP-lipid complexes may serve as nuclei to form "primordial lipoproteins" and may also play a role in the bulk addition of lipids during the "core expansion" of these lipoproteins.
Production de collagene de type quatre et de collagenase quatre par les cellules endotheliales humaines cultivees en presence de differentes concentrations de glucose, et d'hormone de croissance : effets d'un inhibiteur de l'aldose reductase et d'un inhibiteur de proteine kinase c
Http Www Theses Fr, 1994
Rôle de l'interaction de l'apolipoprotéine -B (apoB) avec la protéine microsomiale de transfert des triacyglycérols (MTP) dans l'assemblage et la sécrétion des lipoprotéines
Precipitating factors and targeted therapies in combating the perils of sickle cell disease--- A special nutritional consideration
Nutrition & metabolism, 2016
Nutritional research in sickle cell disease has been the focus in recent times owing to not only ... more Nutritional research in sickle cell disease has been the focus in recent times owing to not only specific nutritional deficiencies, but also the improvements associated with less painful episodes. Though hydroxyurea remains the drug of choice, certain adverse health effects on long term supplementation makes room for researches of different compounds. Macro and micro nutrient deficiencies, along with vitamins, play an important role in not only meeting the calorific needs, but also reducing clinical complications and growth abnormalities. Symptoms of hyper protein metabolism, increased cell turnover, increased cardiac output, and appetite suppression due to enhanced cytokine production, might give us leads for better understanding of the mechanisms involved. Different nutritional approaches comprising of traditional herbal therapies, antioxidants, flavonoids, vitamins, minerals etc., reducing oxidative stress and blood aggregation, have been tried out to increase the health potentia...
Lipids, Nov 1, 1997
We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship... more We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship between intracellular levels and secretion rates of apoB. The assays were based on commercially available antibodies and were specific to human apoB. A monoclonal antibody, 1D1, was immobilized on microtiter wells and incubated with different amounts of low density lipoproteins to obtain a standard curve. Conditioned media were added to other wells in parallel, and the amount of apoB was quantitated from a linear regression curve. To standardize conditions for the measurement of intracellular apoB, cells were homogenized and solubilized with different concentrations of taurocholate. We found that 0.5% taurocholate was sufficient to solubilize all the apoB in HepG2, Caco-2, and McA-RH7777 cells. Next, a standard curve was prepared in the presence of taurocholate and used to determine intracellular levels of apoB in different cell lines. The intracellular levels (pmol/mg cell protein) and the rates of secretion (pmol/mg/h) of apoB100 were positively correlated (r 2 = 0.81, P = 0.0009) in HepG2 cells. Furthermore, a positive correlation (r 2 = 0.88, P < 0.0001) was found between intracellular and secreted apoB42 in stably transfected McA-RH7777 cells. In contrast, no correlation was observed for human apoB28 and apoB18 in stably transfected cells that were secreted either partially associated or completely unassociated with lipoproteins. These studies indicated that the rate of secretion of lipid-associated apoB, but not the lipid-free apoB, was tightly controlled.
Compounds and Methods for Identifying Compounds That Interact with Microsomal Triglyceride Transfer Protein Binding Sites on Apolipoprotein B and Modulate Lipid Biosynthesis
Lysine and Arginine Residues in the N-Terminal 18% of Apolipoprotein B Arecritical for Its Binding to Microsomal Triglyceride Transfer Protein
Biochemistry, 1998
Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are essential for the ... more Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are essential for the efficient assembly and secretion of triglyceride-rich lipoproteins. We have presented evidence for a high-affinity interaction between these proteins [Hussain, M. M., et al. (1997) Biochemistry 36, 13060-13067]. In this study, we used chemically modified low-density lipoproteins (LDL) and recombinant human apoB18 to identify amino acid residues in apoB that are critical for its interactions with MTP. Acetoacetylation of 74% of lysine residues and cyclohexanedione modification of 54% of arginine residues completely abolished the interactions between LDL and MTP. Regeneration of lysine and arginine residues by hydroxylamine treatment completely restored the binding of modified LDL to MTP. Carboxyethylation of all the histidine residues decreased, but did not abolish, apoB-MTP interactions. In contrast, glycine methyl ester modifications of aspartic and glutamic acid residues, up to 38-44%, had no effect on LDL-MTP interactions. Furthermore, modification of lysine and arginine, but not the aspartic and glutamic acid, residues in apoB18 also completely abolished its interactions with MTP. These studies indicated that lysine and arginine, but not aspartic and glutamic acid, residues are critical for apoB-MTP interactions, whereas histidine residues are not as critical. Since lysine and arginine residues in apoB are known to interact with the LDL receptors and heparin, we studied the effect of different glycosaminoglycans on apoB-MTP interactions. Glycosaminoglycans had no significant inhibitory effect on apoB-MTP interactions, suggesting that the lysine and arginine residues crucial for apoB-MTP interactions are different from those that interact with the LDL receptor and heparin. The lysine and arginine residues in apoB18 may directly interact with negatively charged residues in the MTP molecule, or they may function to maintain the conformation of the recognition site.
Human serum preβ1-high density lipoprotein levels are independently and negatively associated with coronary artery diseases
Nutrition & metabolism, 2016
Serum preβ1-high density lipoprotein (preβ1-HDL) was defined by two-dimensional non-denaturing li... more Serum preβ1-high density lipoprotein (preβ1-HDL) was defined by two-dimensional non-denaturing linear gel electrophoresis and apolipoprotein A-I immuno-blotting. Serum preβ1-HDL seems to play an important role in reverse cholesterol transport, a well-known anti-atherosclerosis process. However, there are still debatable questions for its quantification and coronary artery disease (CAD) relevance. We isolated the preβ1-HDL using a new native polyacrylamide gel electrophoresis (PAGE) system and lipid pre-staining serum. We established a two-demensional gel electrophoresis system. We measured the preβ1-HDL in Tangier disease patients and subjects with cholesterol ester transfer protein (CETP) mutation. The preβ1-HDL is clearly separated from lipid-free apoA-I monomer and cannot be converted into other HDL particles under lecithin-cholesterol acyltransferase (LCAT) inhibition. This preβ1-HDL is a spheroidal particle with the highest apoA-1/cholesterol ratio and highest density (≥1.21 g/...
Biochimica Et Biophysica Acta L Lipids and Lipid Metabolism, May 20, 1996
Journal of Lipid Research, 1999
The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apol... more The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apolipoprotein (apo) B-containing lipoproteins. Previous studies have indicated that inhibition of MTP results in decreased apoB plasma levels and decreased hepatic triglyceride secretion. However, the metabolic effects of overexpression of MTP have not been investigated. We constructed a recombinant adenovirus expressing MTP (AdhMTP) and used it to assess the effects of hepatic overexpression of MTP in mice. Injection of AdhMTP into C57BL/6 mice resulted in a 3-fold increase in hepatic microsomal triglyceride transfer activity compared to mice injected with Adnull. On day 4 after virus injection, AdhMTP-injected mice had significantly elevated plasma TG levels as compared to control virus (Adnull)-injected mice. Hepatic TG secretion rates were significantly greater in AdhMTP-injected mice (184 ؎ 12 mg/ kg/h) compared with Adnull-injected mice (65 ؎ 9 mg/kg/ h, P Ͻ 0.001). In addition, hepatic very low density lipoprotein (VLDL) apoB secretion in the AdhMTP-injected group was 74% higher than in the control virus group. Hepatic secretion of apoB-48 and apoB-100 contributed equally to this increase. These results provide the first data that hepatic overexpression of MTP results in increased secretion of VLDL-triglycerides as well as VLDL-apoB in vivo. These results suggest that MTP is rate-limiting for VLDL apoB secretion in wild-type mice under basal chow-fed conditions. -Tietge, U. overexpression of microsomal triglyceride transfer protein (MTP) results in increased in vivo secretion of VLDL triglycerides and apolipoprotein B. J. Lipid Res. 1999. 40: 2134-2139. Supplementary key words recombinant adenovirus expressing MTP • apoB • triglyceride
Mice subjected to aP2-Cre mediated ablation of microsomal triglyceride transfer protein are resistant to high fat diet induced obesity
Nutrition & metabolism, 2016
Microsomal triglyceride transfer protein (MTP) is essential for the assembly of lipoproteins. MTP... more Microsomal triglyceride transfer protein (MTP) is essential for the assembly of lipoproteins. MTP has been shown on the surface of lipid droplets of adipocytes; however its function in adipose tissue is not well defined. We hypothesized that MTP may play critical role in adipose lipid droplet formation and expansion. Plasmids mediated overexpression and siRNA mediated knockdown of Mttp gene were performed in 3T3-L1 pre-adipocytes to evaluate the effects of MTP on cell differentiation and triglyceride accumulation. Adipose-specific knockdown of MTP was achieved in mice bybreeding MTP floxed (Mttp (fl/fl) ) mice with aP2-Cre recombinase transgenic mice. Adipose-specific MTP deficient (A-Mttp (-/-) ) mice were fed 60 % high-fat diet (HFD), and the effects of MTP knockdown on body weight, body fat composition, plasma and tissues lipid composition, glucose metabolism, lipogenesis and intestinal absorption was studied. Lipids were measured in total fasting plasma and size fractionated pla...
Plasma Nitration of High-Density and Low-Density Lipoproteins in Chronic Kidney Disease Patients Receiving Kidney Transplants
Mediators of inflammation, 2015
Background. Functional abnormalities of high-density lipoprotein (HDL) could contribute to cardio... more Background. Functional abnormalities of high-density lipoprotein (HDL) could contribute to cardiovascular disease in chronic kidney disease patients. We measured a validated marker of HDL dysfunction, nitrated apolipoprotein A-I, in kidney transplant recipients to test the hypothesis that a functioning kidney transplant reduces serum nitrated apoA-I concentrations. Methods. Concentrations of nitrated apoA-I and apoB were measured using indirect sandwich ELISA assays on sera collected from each transplant subject before transplantation and at 1, 3, and 12 months after transplantation. Patients were excluded if they have history of diabetes, treatment with lipid-lowering medications or HIV protease inhibitors, prednisone dose > 15 mg/day, nephrotic range proteinuria, serum creatinine > 1.5 mg/dL, or active inflammatory disease. Sera from 18 transplanted patients were analyzed. Four subjects were excluded due to insufficient data. Twelve and eight patients had creatinine < 1.5...
Journal of lipid research, 1999
The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apol... more The microsomal triglyceride transfer protein (MTP) is essential for the hepatic secretion of apolipoprotein (apo) B-containing lipoproteins. Previous studies have indicated that inhibition of MTP results in decreased apoB plasma levels and decreased hepatic triglyceride secretion. However, the metabolic effects of overexpression of MTP have not been investigated. We constructed a recombinant adenovirus expressing MTP (AdhMTP) and used it to assess the effects of hepatic overexpression of MTP in mice. Injection of AdhMTP into C57BL/6 mice resulted in a 3-fold increase in hepatic microsomal triglyceride transfer activity compared to mice injected with Adnull. On day 4 after virus injection, AdhMTP-injected mice had significantly elevated plasma TG levels as compared to control virus (Adnull)-injected mice. Hepatic TG secretion rates were significantly greater in AdhMTP-injected mice (184 +/- 12 mg/kg/h) compared with Adnull-injected mice (65 +/- 9 mg/kg/h, P < 0.001). In addition, ...
[Changes in collagen type IV metabolism in diabetes]
Comptes rendus des séances de la Société de biologie et de ses filiales, 1993
In Diabetes Mellitus, type IV collagen biosynthesis is increased: the alpha 1(IV) procollagen spe... more In Diabetes Mellitus, type IV collagen biosynthesis is increased: the alpha 1(IV) procollagen specific mRNA concentration is elevated, particularly in the kidney, and the type IV collagen protein is accumulating is the thickened basement membranes. Aldose reductase inhibitors like sorbinil do prevent basement membrane thickening and type IV collagen overproduction. The latter seems related to intracellular sorbitol accumulation and also to protein kinase C activation. Autocrine or paracrine TGF beta may be involved in the type IV collagen oversecretion. The secreted type IV collagen is subject to posttranslational alterations, especially glycation which leads to advanced glycation end-products and covalent crosslinks. This decreases collagen extractability and susceptibility to collagenases and favours basement membrane thickening. Disaccharide unit-specific alpha-glucosidase activity is inhibited by glucose (Kp = 7.5 mM). Type IV collagenase activity secreted by endothelial cells c...
Lysophosphatidylcholine increases apolipoprotein B secretion by enhancing lipid synthesis and decreasing its intracellular degradation in HepG2 cells
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1998
Free fatty acids and lysophosphatidylcholine (lysoPC) are the major lipids bound to human plasma ... more Free fatty acids and lysophosphatidylcholine (lysoPC) are the major lipids bound to human plasma albumin. The effects of fatty acids on the hepatic production of Apolipoprotein B (apo B) have been studied but those of lysoPC have not. In HepG2 cells, lysoPC increased apo B secretion in different experiments by 50-120%, but did not affect the flotation properties of secreted lipoproteins. LysoPC affected neither the cellular protein levels nor apo A-I secretion suggesting that its effect was specific to apo B. Apo B secretion was maximum after incubating cells for 6 h with 0.2 mM lysoPC as equimolar fatty acid free bovine serum albumin (BSA) complexes. LysoPC was metabolized by cells and its fatty acids were used for the synthesis of phosphatidylcholine and triglycerides (TG). Experiments were performed to understand the mechanism of lysoPC action. LysoPC increased the incorporation of 3H-glycerol into newly synthesized cellular (3-fold) and secreted (4-fold) triglycerides, and increased the synthesis (40%) and secretion (4-fold) of phospholipids. LysoPC did not affect apo B synthesis, but inhibited the intracellular degradation of apo B and increased its secretion. Triacsin C (5 microM), an inhibitor of long chain acyl-CoA synthase, completely inhibited the induction of lipid synthesis and abolished the effect of lysoPC on apo B secretion. These studies indicated that lysoPC increased apo B secretion by inducing lipid synthesis; newly synthesized lipids probably protected apo B from intracellular degradation and enhanced secretion. These studies are consistent with the hypothesis that physiologic concentrations of lysoPC can be an important modulator for hepatic apo B secretion.
Biochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, 1996
Nutrition & Metabolism, 2014
Nutrition & Metabolism has grown considerably in the ten years since its first article was publis... more Nutrition & Metabolism has grown considerably in the ten years since its first article was published. To see how papers published in the journal had an impact we have identified some of the most popular articles in order to measure their influence, observe which fields are important to our readers, and try to explain what made these articles Nutrition & Metabolism "Classics".
Nutrition & Metabolism, 2013
Lipids, 1997
We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship... more We have standardized simple but sensitive enzyme-linked immunoassays to understand a relationship between intracellular levels and secretion rates of apoB. The assays were based on commercially available antibodies and were specific to human apoB. A monoclonal antibody, 1D1, was immobilized on microtiter wells and incubated with different amounts of low density lipoproteins to obtain a standard curve. Conditioned media were added to other wells in parallel, and the amount of apoB was quantitated from a linear regression curve. To standardize conditions for the measurement of intracellular apoB, cells were homogenized and solubilized with different concentrations of taurocholate. We found that 0.5% taurocholate was sufficient to solubilize all the apoB in HepG2, Caco-2, and McA-RH7777 cells. Next, a standard curve was prepared in the presence of taurocholate and used to determine intracellular levels of apoB in different cell lines. The intracellular levels (pmol/mg cell protein) and the rates of secretion (pmol/mg/h) of apoB100 were positively correlated (r 2 = 0.81, P = 0.0009) in HepG2 cells. Furthermore, a positive correlation (r 2 = 0.88, P < 0.0001) was found between intracellular and secreted apoB42 in stably transfected McA-RH7777 cells. In contrast, no correlation was observed for human apoB28 and apoB18 in stably transfected cells that were secreted either partially associated or completely unassociated with lipoproteins. These studies indicated that the rate of secretion of lipid-associated apoB, but not the lipid-free apoB, was tightly controlled.
Journal of Biological Chemistry, 1998
Several studies have demonstrated protein-protein interactions between microsomal triglyceride tr... more Several studies have demonstrated protein-protein interactions between microsomal triglyceride transfer protein (MTP) and apolipoprotein B (apoB). However, the binding sites involved in these interactions have not been elucidated. To identify an MTP binding site in apoB, we have expressed several apoB sequences as fusion proteins with the eight-amino acid FLAG peptide. The chimeras were transiently expressed in COS cells, and conditioned media were used to study the binding of these sequences to either immobilized or soluble MTP. A polypeptide containing amino acids 270 -570 (B: 270 -570), but not 1-300, bound to MTP. AGI-S17, an antagonist of apoB-MTP binding, inhibited the binding of B:270 -570 to MTP but not to M2, a monoclonal antibody that recognizes the FLAG peptide. These data indicated that B:270 -570 contains an MTP binding site. Next, sequences within 270 -570 were subjected to C-terminal truncations at natural proline residues. B:270 -509 bound less efficiently than B:270 -570, whereas, B:270 -430 and other shorter chimeras did not bind to MTP. Furthermore, truncations at amino acids 502 and 509 decreased MTP binding by 73 and 42%, respectively. These data indicate that B:430 -570 in the ␣ 1 -globular domain of apoB plays a crucial role in MTP binding and presumably in the initiation and maturation of apoBcontaining lipoproteins.
Journal of Biological Chemistry, 2001
Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are known to interact ... more Apolipoprotein B (apoB) and microsomal triglyceride transfer protein (MTP) are known to interact with each other. We evaluated the effect of different lipids on the protein-protein interactions between MTP and apoB100 or its C-terminally truncated forms. Negatively charged lipids decreased protein-protein interactions between apoB and MTP. In contrast, zwitterionic phospholipids enhanced (2-4-fold) the binding of apoB100 to MTP by increasing affinity (1.5-3-fold) between these proteins without affecting the number of binding sites. Similarly, phospholipids augmented (1.5-4-fold) the binding of various C-terminally truncated apoB peptides to MTP. The increased binding was greater for apoB peptides containing lipidbinding domains, such as apoB28 and apoB42. Surprisingly, preincubation of apoB28 with lipid vesicles had no effect on MTP binding. In contrast, incubation of MTP with lipid vesicles resulted in a stable association of MTP with vesicles, and MTP-lipid vesicles bound better (5-fold increase) to LDL than did lipid-free MTP. To determine whether MTP exists stably associated with lipids in cells, microsomal contents from COS cells expressing MTP, HepG2 cells, and mouse liver were ultracentrifuged, and MTP was visualized in different density fractions. MTP was found associated and unassociated with lipids. In contrast, apoB17 and apoB:270 -570 were present unassociated with lipids in COS cells. These studies show that the binding of MTP to lipids results in increased affinity for apoB and that stable MTP-lipid complexes exist in the lumen of the endoplasmic reticulum. Protein-protein interactions between apoB and MTP may juxtapose lipids associated with MTP to lipid-binding domains of apoB and facilitate hydrophobic interactions leading to enhance affinity. We speculate that MTP-lipid complexes may serve as nuclei to form "primordial lipoproteins" and may also play a role in the bulk addition of lipids during the "core expansion" of these lipoproteins.