Showing papers on "Fatty acid-binding protein published in 1998"

A novel insulin sensitizer acts as a coligand for peroxisome proliferator-activated receptor-alpha (PPAR-alpha) and PPAR-gamma: effect of PPAR-alpha activation on abnormal lipid metabolism in liver of Zucker fatty rats.

Abstract: We investigated the biological activity of a novel thiazolidinedione (TZD) derivative, KRP-297, and the molecular basis of this activity. When administered to obese Zucker fatty rats (obese rats) at 10 mg/kg for 2 weeks, KRP-297, unlike BRL-49,653, restored reduced lipid oxidation, that is, CO2 and ketone body production from [14C]palmitic acid, in the liver by 39% (P < 0.05) and 57% (P < 0.01), respectively. KRP-297 was also significantly more effective than BRL-49,653 in the inhibition of enhanced lipogenesis and triglyceride accumulation in the liver. To understand the molecular basis of the biological effects of KRP-297, we examined the effect on peroxisome proliferator-activated receptor (PPAR) isoforms, which may play key roles in lipid metabolism. Unlike classical TZD derivatives, KRP-297 activated both PPAR-alpha and PPAR-gamma, with median effective concentrations of 1.0 and 0.8 micromol/l, respectively. Moreover, radiolabeled [3H]KRP-297 bound directly to PPAR-alpha and PPAR-gamma with dissociation constants of 228 and 326 nmol/l, respectively. Concomitantly, KRP-297, but not BRL-49,653, increased the mRNA and the activity (1.5-fold [P < 0.01] and 1.8-fold [P < 0.05], respectively) of acyl-CoA oxidase, which has been reported to be regulated by PPAR-alpha, in the liver. By contrast, KRP-297 (P < 0.05) was less potent than BRL-49,653 (P < 0.01) in inducing the PPAR-gamma-regulated aP2 gene mRNA expression in the adipose tissues. These results suggest that PPAR-alpha agonism has a protective effect against abnormal lipid metabolism in liver of obese rats.

The helical domain of intestinal fatty acid binding protein is critical for collisional transfer of fatty acids to phospholipid membranes

Abstract: Fatty acid binding proteins (FABPs) exhibit a β-barrel topology, comprising 10 antiparallel β-sheets capped by two short α-helical segments. Previous studies suggested that fatty acid transfer from several FABPs occurs during interaction between the protein and the acceptor membrane, and that the helical domain of the FABPs plays an important role in this process. In this study, we employed a helix-less variant of intestinal FABP (IFABP-HL) and examined the rate and mechanism of transfer of fluorescent anthroyloxy fatty acids (AOFA) from this protein to model membranes in comparison to the wild type (wIFABP). In marked contrast to wIFABP, IFABP-HL does not show significant modification of the AOFA transfer rate as a function of either the concentration or the composition of the acceptor membranes. These results suggest that the transfer of fatty acids from IFABP-HL occurs by an aqueous diffusion-mediated process, i.e., in the absence of the helical domain, effective collisional transfer of fatty acids to membranes does not occur. Binding of wIFABP and IFABP-HL to membranes was directly analyzed by using a cytochrome c competition assay, and it was shown that IFABP-HL was 80% less efficient in preventing cytochrome c from binding to membranes than the native IFABP. Collectively, these results indicate that the α-helical region of IFABP is involved in membrane interactions and thus plays a critical role in the collisional mechanism of fatty acid transfer from IFABP to phospholipid membranes.

Fatty acid-binding proteins in the heart.

Abstract: Long-chain fatty acids are important fuel molecules for the heart, their oxidation in mitochondria providing the bulk of energy required for cardiac functioning. The low solubility of fatty acids in aqueous solutions impairs their cellular transport. However, cardiac tissue contains several proteins capable of binding fatty acids non-covalently. These fatty acid-binding proteins (FABPs) are thought to facilitate both cellular uptake and intracellular transport of fatty acids. The majority of fatty acids taken up by the heart seems to pass the sarcolemma through a carrier-mediated translocation mechanism consisting of one or more membrane-associated FABPs. Intracellular transport of fatty acids towards sites of metabolic conversion is most likely accomplished by cytoplasmic FABPs. In this review, the roles of membrane-associated and cytoplasmic FABPs in cardiac fatty acid metabolism under (patho)physiological circumstances are discussed.

Regulation of expression of human intestinal bile acid-binding protein in caco-2 cells

Abstract: Molecular mechanisms of the bile acid active transport system in the ileal enterocytes remain unknown. We examined whether bile acids affect human enterocyte gene expression of intestinal bile acid-binding protein (I-BABP), a component of this transport system. Differentiated Caco-2 cells were incubated in the presence of human bile, bile acids or other lipids. The level of I-BABP expression was evaluated by Northern and Western blot analyses. A 24 h incubation of Caco-2 cells in a medium containing either bile or bile acids resulted in a remarkable 7.5-fold increase in the I-BABP mRNA level over the control level. Neither cholesterol, palmitic acid, phosphatidylcholine nor cholestyramine treated bile showed any difference in I-BABP mRNA expression from the control. Bile acid treatment increased the level of I-BABP mRNA in Caco-2 cells in a time- and dose-dependent manner. Western blot analysis showed that this induction led to increase in cytosolic I-BABP. Chenodeoxycholic acid and deoxycholic acid showed greater induction effects than other hydrophilic bile acids, including their own glycine conjugates. Pretreatment by actinomycin D or cycloheximide completely inhibited the up-regulation of I-BABP expression by bile acid. Bile acids, especially lipophilic bile acids, increase the I-BABP expression in Caco-2-cells, suggesting that luminal bile acids play an important role in regulating the I-BABP gene expression.

Backbone and side chain dynamics of uncomplexed human adipocyte and muscle fatty acid-binding proteins.

Abstract: Adipocyte lipid-binding protein (A-LBP) and muscle fatty acid-binding protein (M-FABP) are members of a family of small (∼15 kDa) cytosolic proteins that are involved in the metabolism of fatty acids and other lipid-soluble molecules. Although highly homologous (65%) and structurally very similar, A-LBP and M-FABP display distinct ligand binding characteristics. Since ligand binding may be influenced by intrinsic protein dynamical properties, we have characterized the backbone and side chain dynamics of uncomplexed (apo) human A-LBP and M-FABP. Backbone dynamics were characterized by measurements of 15N T1 and T2 values and {1H}−15N NOEs. These data were analyzed using model-free spectral density functions and reduced spectral density mapping. The dynamics of methyl-containing side chains were charaterized by measurements of 2H T1 and T1ρ relaxation times of 13C1H22H groups. The 2H relaxation data were analyzed using the model-free approach. For A-LBP, 15N relaxation data were obtained for 111 residues an...

Fatty acid binding protein, a major protein in the flight muscle of migrating Western Sandpipers

Abstract: Migratory flight in birds is fueled primarily by fatty acid oxidation imposing a requirement for high rates of fatty acid: (a) transport; (b) uptake; and (c) delivery to intracellular sites of beta-oxidation. Muscle fatty acid binding protein (M-FABP) is a cytosolic protein involved in the intracellular transport of fatty acids. Its expression appears to be correlated with muscle fatty acid oxidation capacity. The M-FABP was isolated for the first time from a long distance migrant bird using: (i) size exclusion; (ii) anion exchange; and (iii) hydroxyapatite chromatography. M-FABP has a molecular weight of approximately 14,000 Da and an isoelectric point of pH 4.8. A partial amino acid sequence of the protein demonstrated homology to M-FABPs from other species (80% identical to human heart FABP). It was estimated that M-FABP comprises approximately 14 and 21% of total cytosolic protein of the pectoralis and heart, respectively; the highest values yet reported from any vertebrate muscle. The abundance of M-FABP in these tissues suggests that the protein may play a key role in fatty acid supply during endurance flight. Thus, it is proposed that a seasonal increase in M-FABP expression could be a component of physiological preparation for migration.

Cellular differentiation and I-FABP protein expression modulate fatty acid uptake and diffusion

Abstract: The effect of cellular differentiation on fatty acid uptake and intracellular diffusion was examined in transfected pluripotent mouse embryonic stem (ES) cells stably expressing intestinal fatty ac...

Skeletal muscle fatty acid transport and transporters.

Abstract: Long-chain fatty acids (LCFAs) are an important energy source for many tissues. The dogma that LCFAs are freely diffusible has been challenged. It is now known that LCFAs are transported into many tissues. Our studies have shown that LCFAs are also transported into skeletal muscle and into the heart. In recent years a number of putative fatty acid transport proteins have been identified. These are known as plasma membrane fatty acid binding protein (FABPpm, 43 kDa), fatty acid translocase (FAT, 88 kDa) and fatty acid transporter protein (FATP, 63 kDa). All three proteins are present in skeletal muscle and in the heart. The existence of an LCFA transport system in muscle may be essential 1) to facilitate the rapid and regulatable transport of LCFA to meet the metabolic requirements of working muscles and 2) to cope with an increase in circulating LCFAs in some pathological conditions (e.g. diabetes). There is now some evidence that metabolic changes and chronically increased muscle activity can increase the transport of LCFAs and increase the expression of putative LCFA transporters.

Bovine epidermal fatty acid-binding protein : determination of ligand specificity and cellular localization in retina and testis

Abstract: The fatty acid-binding protein (FABP) family consists of small, cytosolic proteins believed to be involved in the uptake, transport, and solubilization of their hydrophobic ligands. Members of this family have highly conserved sequences and tertiary structures. Using an antibody against testis lipid-binding protein, a member of the FABP family, a protein was identified from bovine retina and testis that coeluted with exogenously added docosahexaenoic acid during purification. Amino acid sequencing and subsequent isolation of its cDNA revealed it to be nearly identical to a bovine protein expressed in the differentiating lens and to be the likely bovine homologue of the human epidermal fatty acid-binding protein (E-FABP). From quantitative Western blot analysis, it was estimated that bovine E-FABP comprised 0.9%, 0.1%, and 2.4% of retina, testis, and lens cytosolic proteins, respectively. Binding studies using the fluorescent probe ADIFAB indicated that this protein bound fatty acids of differing levels of saturation with relatively high affinities. Kd values ranged from 27 to 97 nM. In addition, the protein was immunolocalized to the Muller cells in the retina as well as to Sertoli cells in the testis. The location of bovine E-FABP in cells known to be supportive to other cell types in their tissues and the ability of E-FABP to bind a variety of fatty acids with similar affinities indicate that it may be involved in the uptake and transport of fatty acids essential for the nourishment of the surrounding cell types.

Expression of fatty-acid-binding proteins in cells involved in lung-specific lipid metabolism

Abstract: Members of the fatty-acid-binding protein (FABP) family are thought to play an important role in fatty acid transport within the cytosol and thus to be involved in lipid metabolism. As previous data on the occurrence of distinct FABP types in total lung are contradictory, we determined the expression of FABP types in three isolated cell types of rat lung, which are characterised by active lipid metabolism. Alveolar type-II cells synthesise, store and secrete pulmonary surfactant, a phospholipid-rich surface-tension-lowering agent, whereas lung fibroblasts, localised adjacent to the alveolar type-II cells, are assumed to provide neutral lipid substrate to alveolar type-II cells around birth, and alveolar macrophages are known to degrade complex lipids. Initial screening by reverse transcriptase PCR revealed the occurrence of heart (H-), epidermal (E-) and liver FABP in rat lung, the latter being not detectable in the three cell types studied. Cells were analysed by northern and western blotting, then quantitatively by sandwich ELISA, for which recombinant rat E-FABP was prepared. E-FABP mRNA was found in all three cell types, and E-FABP was detected in the following amounts: 240.9 +/- 19.0 ng/mg cytosolic protein in alveolar type-II cells; 172.3 +/- 0.7 ng/mg protein for lung fibroblasts; and 36.9 +/- 3.5 ng/mg protein for alveolar macrophages. This indicates a basic function of E-FABP in cellular lipid metabolism. In contrast, H-FABP probably is involved in the metabolism of neutral lipids because H-FABP mRNA was found only in lung fibroblasts with a corresponding protein level of 315.5 +/- 6.9 ng/mg. Small amounts of H-FABP protein were present in alveolar type-II cells and alveolar macrophages.

Recombinant human heart-type fatty acid-binding protein as standard in immunochemical assays.

Abstract: Cytoplasmic heart-type fatty acid-binding protein has recently gained much attention in clinical diagnosis as a very early marker of acute myocardial infarction. Immunoassays have been developed for determination of this protein in plasma and urine samples. In the present study it is shown that those types of fatty acid-binding proteins which are abundant in tissues other than heart and muscle do not interfere with immunochemical determination of heart-type fatty acid-binding protein. To provide sufficient protein of consistent quality as standard in these immunoassays, human heart-type fatty acid-binding protein was cloned, expressed in Escherichia coli and purified to homogeneity. For quantitation of the recombinant protein its extinction coefficient was determined. Comparison of the recombinant and tissue-derived proteins by a variety of methods revealed both proteins to show similar kinetic as well as equilibrium constants with respect to two monoclonal antibodies currently applied in immunochemical detection of heart-type fatty acid-binding protein. Both preparations were indistiguishable in sandwich-ELISA and immunosensor measurements. A high stability of the recombinant protein was proven by ELISA measurements during storage and several freeze and thaw cycles. Thus, recombinant and tissue-derived heart-type fatty acid-binding proteins are immunochemically equivalent. The recombinant human heart-type fatty acid-binding protein is now available as standard for immunoassays.

Intracellular transport of fatty acids in muscle. Role of cytoplasmic fatty acid-binding protein.

Abstract: Long-chain fatty acids represent a major substrate for energy production in striated muscles, especially in those muscles which have a high oxidative enzymatic capacity. Following their uptake from the extracellular compartment the fatty acids have to translocate through the aqueous cytoplasm of the myocytes to reach the mitochondria where they undergo oxidative degradation. This intracellular transport is assisted by cytoplasmic fatty acid-binding protein (FABPc), a small (15 kD) protein which shows a high affinity for the non-covalent binding of long-chain fatty acids, and of which several types occur. So-called heart-type or muscle-type FABPc is found in muscle cells, and is abundant especially in oxidative fibers. The muscular FABPc content appears to relate to the rate of fatty acid utilization, and also changes in concert to modulations in fatty acid utilization induced by (patho)physiological stimuli (e. g. endurance training, diabetes). The facilitation of intracellular fatty acid transport by FABPc is accomplished by increasing the concentration of the diffusing fatty acids in the aqueous cytoplasm and, most likely, also by interacting directly with membranes to promote transfer of fatty acids to and from the cytosolic binding protein.

Omega-oxidation of monocarboxylic acids in rat brain.

Abstract: The accumulation of dicarboxylic acids is a prominent feature of inborn and toxin induced disorders of fatty acid metabolism which are characterized by impaired mental status. The formation of dicarboxylic acids is also a critical step in liver in the induction of intracellular fatty acid binding proteins and the proliferation of peroxisomes. In order to understand what potential roles dicarboxylic acids have in brain, we examined the extent of omega-oxidation in rat brain. Homogenates of rat brain catalyze the omega-oxidation of monocarboxylic acids with a specific activity of between 0.87 and 5.23 nmol/mg of post-mitochondrial protein/h, depending on the substrate. The activity is remarkably high, between one-fourth and 4 times the activity found in rat liver, depending on the chain length of the substrate. Specific activity increases with increasing chain length of the substrate. The omega-oxidation of palmitic acid is linear over a range of 0.125-3.0 mg of protein and 5-50 microM substrate for up to 45 minutes of incubation. The product of omega-oxidation in brain is almost exclusively dicarboxylic acid. Cultured rat neurons, astrocytes, and oligodendrocytes all contain omega-oxidation activity. Western blots of rat brain homogenate demonstrate a protein that is recognized by antibody to rat liver CYP4A omega-hydroxylase. These results demonstrate that the omega-oxidative pathway is prominent in brain and could play a role in brain fatty acid metabolism.

Fatty acid binding proteins and mammary‐derived growth inhibitor

Abstract: The multigene superfamily of intracellular lipid binding proteins in mammals comprises up to now 13 different types of 14-15kDa proteins. whose foremost high-affinity ligands are long-chain fatty acids, retinoids and bile acids, respectively. The phylogenetically related proteins of highly conserved tertiary structure are encoded by genes. that are canonically structured into four exons and three introns. In addition, these genes are characterized by promoter regions with responsive elements common to many genes encoding lipid-metabolizing enzymes, that interact with nuclear receptors activated by peroxisome proliferators or fatty acids. On the basis of interactions of fatty acids -actually macronutrients - with the ligand activated nuclear receptors and with the fatty acid binding proteins (FABPs) the regulation of FABP-expression and the functions of the various FABP-types in cellular lipid homeostasis, signal transduction and growth regulation will be reviewed.

Cloning and sequencing of complementary DNA for fatty acid binding protein from rainbow trout heart.

Abstract: A cDNA encoding a rainbow trout homologue of mammalian heart fatty acid binding protein (H-FABP) was isolated. The deduced protein sequence is 75% identical to that of rat H-FABP. The structural conservation of H-FABPs and their evolutionary relationship are discussed.