Metallothionein-IIA promoter induction alters rat intestinal fatty acid binding protein expression, fatty acid uptake, and lipid metabolism in transfected L-cells

Study on fatty acid binding protein in lipid metabolism of livestock and poultry

Fatty acid binding proteins (FABPs) are key proteins in lipid transport, and 12 family members have been documented in the literature. In recent years, new insights have been gained into the structure and function of FABPs, which are important regulators of lipid metabolic processes in the body and play a central role in coordinating lipid transport and metabolism in various tissues and organs across species. This paper provides a brief overview of the structure and biological functions of FABPs and reviews related studies on lipid metabolism in livestock and poultry to lay the foundation for research on the mechanism underlying the regulatory effect of FABPs on lipid metabolism in livestock and poultry and for the genetic improvement of livestock and poultry.

Sex-Dependent Regulation of Placental Oleic Acid and Palmitic Acid Metabolism by Maternal Glycemia and Associations with Birthweight

Pregnancy complications such as maternal hyperglycemia increase perinatal mortality and morbidity, but risks are higher in males than in females. We hypothesized that fetal sex-dependent differences in placental palmitic-acid (PA) and oleic-acid (OA) metabolism influence such risks. Placental explants (n = 22) were incubated with isotope-labeled fatty acids (13C-PA or 13C-OA) for 24 or 48 h and the production of forty-seven 13C-PA lipids and thirty-seven 13C-OA lipids quantified by LCMS. Linear regression was used to investigate associations between maternal glycemia, BMI and fetal sex with 13C lipids, and between 13C lipids and birthweight centile. Placental explants from females showed greater incorporation of 13C-OA and 13C-PA into almost all lipids compared to males. Fetal sex also influenced relationships with maternal glycemia, with many 13C-OA and 13C-PA acylcarnitines, 13C-PA-diacylglycerols and 13C-PA phospholipids positively associated with glycemia in females but not in males. In contrast, several 13C-OA triacylglycerols and 13C-OA phospholipids were negatively associated with glycemia in males but not in females. Birthweight centile in females was positively associated with six 13C-PA and three 13C-OA lipids (mainly acylcarnitines) and was negatively associated with eight 13C-OA lipids, while males showed few associations. Fetal sex thus influences placental lipid metabolism and could be a key modulator of the impact of maternal metabolic health on perinatal outcomes, potentially contributing toward sex-specific adaptions in which females prioritize survival.

Association of macro-and micro-nutrients dietary intakes with rs2241883 genetic variants of FABP 1 gene in MASHAD study population

INTRODUCTION

There is a relationship between macro-nutrient-intakes and the genes implicated in lipid metabolism. In this study, we assessed the association between macro-and micro-nutrients dietary intakes with rs2241883 genetic variants of the FABP1 gene.

METHODS

For this cross-sectional study 2737 subjects (including 2203 subjects with dyslipidemia and 534 healthy volunteers) were enrolled as part of the Mashhad Stroke and Heart Atherosclerotic Disorder (MASHAD) study cohort. Dyslipidemia was defined based on the National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III). A NanoDrop®-1000 instrument was used to do the quantitation of DNA. The rs2241883 polymorphisms were genotyped using double ARMs PCR reactions. Genotyping reagents were obtained from Applied Biosystems. Dietary intake was evaluated using a food frequency questionnaire (FFQ) and validated by 2 consecutive 24-h food recalls.

RESULTS

The results showed no significant association between subjects with and without dyslipidemia (P > 0.05), except for the zinc to copper ratio, the value for which was higher in the subjects with dyslipidemia (4.78 (1.62)) when compared to subjects without dyslipidemia (4.68 (1.82)) (p = 0.05). Using different genetic models we found that zinc and copper were significantly different in the additive (p = 0.01) and dominant (p = 0.01) genetic models. Although, this association was no longer significant after adjusting for confounding factors.

CONCLUSIONS

There were no associations between macro-and micro-nutrient dietary intakes with rs2241883 genetic variants after adjusting for confounding factors in the MASHAD study population.

n-3 PUFA reduction caused by fabp2 deletion interferes with triacylglycerol metabolism and cholesterolhomeostasis in fish

Fatty acid-binding protein 2 (Fabp2), which is involved in the transport of long-chain fatty acids, is widely studied in mammals. Nevertheless, the role of this protein in teleost fish is mostly unknown. Here, we produced a fabp2^-/- zebrafish (KO) animal model. Compared with wild-type zebrafish (WT), KO had a markedly decreased content of intestinal n-3 poly-unsaturated fatty acids (n-3 PUFAs) and increased levels of intestinal, hepatic, and serum triacylglycerols (TAG). The intestinal transcriptome analysis of KO and WT revealed an obviously disrupted TAG metabolism and up-regulated bile secretion in KO. Expression levels of the genes related to fatty acid transport and cholesterol (CL) absorption in the intestine of KO were significantly lower than those of WT, while the expression levels of genes related to intestinal TAG synthesis and hepatic CL synthesis were in the opposite direction. To confirm these findings, we further established fabp2 transgenic zebrafish (TG). Compared with WT, TG had a markedly increased content of intestinal n-3 PUFAs, a significantly decreased level of hepatic TAG, and significantly higher expression of genes related to fatty acid transport and CL absorption in the intestine. In conclusion, this study suggests that teleost fish fabp2 could promote intestinal n-3 PUFA absorption to mediate TAG synthesis and CL homeostasis, by regulating the genes involved in lipid metabolism.

From fatty-acid sensing to chylomicron synthesis: role of intestinal lipid-binding proteins

Today, it is well established that the development of obesity and associated diseases results, in part, from excessive lipid intake associated with a qualitative imbalance. Among the organs involved in lipid homeostasis, the small intestine is the least studied even though it determines lipid bioavailability and largely contributes to the regulation of postprandial hyperlipemia (triacylglycerols (TG) and free fatty acids (FFA)). Several Lipid-Binding Proteins (LBP) are expressed in the small intestine. Their supposed intestinal functions were initially based on what was reported in other tissues, and took no account of the physiological specificity of the small intestine. Progressively, the identification of regulating factors of intestinal LBP and the description of the phenotype of their deletion have provided new insights into cellular and molecular mechanisms involved in fat absorption. This review will discuss the physiological contribution of each LBP in the main steps of intestinal absorption of long-chain fatty acids (LCFA): uptake, trafficking and reassembly into chylomicrons (CM). Moreover, current data indicate that the small intestine is able to adapt its lipid absorption capacity to the fat content of the diet, especially through the coordinated induction of LBP. This adaptation requires the existence of a mechanism of intestinal lipid sensing. Emerging data suggest that the membrane LBP CD36 may operate as a lipid receptor that triggers an intracellular signal leading to the modulation of the expression of LBP involved in CM formation. This event could be the starting point for the optimized synthesis of large CM, which are efficiently degraded in blood. Better understanding of this intestinal lipid sensing might provide new approaches to decrease the prevalence of postprandial hypertriglyceridemia, which is associated with cardiovascular diseases, insulin resistance and obesity.

Differential liver proteome mapping of control and cadmium-fed rats

A comparative study of proteome maps from control and Cd-exposed rat liver was performed using a new technology of two-dimensional liquid chromatography separation method (PF-2D system, Beckman Coulter). Rats were fed for one month 0 or 100 μg Cd g(-1). The between-replicate and between-sample variations showed good repeatability and suitable reproducibility for the two dimensions of separation of proteins. In this complex mixture, PF-2D led to the separation of two major peaks which differed between control and Cd-exposed rat livers, one being identified by mass spectrometry as Cu/Zn superoxide dismutase (SOD), a well-known biomarker of Cd exposure, the other as phosphatidylethanolamine binding protein (PEBP). SOD content was decreased in Cd-exposed rat liver, compared to the control group which was corroborated by a significant decrease of SOD activity. PEBP content also tended to be decreased after Cd exposure. Present results demonstrate interest but also limitations of proteomic approach using PF-2D system to analyze effects of chemicals on organisms.

Intestinal absorption of long-chain fatty acids: evidence and uncertainties

Over the two last decades, cloning of proteins responsible for trafficking and metabolic fate of long-chain fatty acids (LCFA) in gut has provided new insights on cellular and molecular mechanisms involved in fat absorption. To this systematic cloning period, functional genomics has succeeded in providing a new set of surprises. Disruption of several genes, thought to play a crucial role in LCFA absorption, did not lead to clear phenotypes. This observation raises the question of the real physiological role of lipid-binding proteins and lipid-metabolizing enzymes expressed in enterocytes. The goal of this review is to analyze present knowledge concerning the main steps of intestinal fat absorption from LCFA uptake to lipoprotein release and to assess their impact on health.

An Acute and Coincident Increase in FABP Expression and Lymphatic Lipid and Drug Transport Occurs During Intestinal Infusion of Lipid-Based Drug Formulations to Rats

PURPOSE

To determine a) whether administration of lipid-based formulations can acutely up-regulate the intestinal expression of I-FABP and L-FABP and b) whether this occurs coincidentally with an increase in intestinal lymphatic lipid and drug transport.

METHODS

The expression of I-FABP and L-FABP mRNA (using q-PCR) and protein (using immunohistochemistry and Western blotting) in enterocytes was compared with data describing transport of lipid and drug into intestinal lymph following infusion of a set of lipid-based formulations.

RESULTS

Administration of relatively small amounts of oleic acid (5-20 mg/h) over a 5 h period to rats acutely up-regulated the expression, and altered the intracellular distribution of, I-FABP and L-FABP in the enterocytes of the small intestinal epithelia. The increase in expression of I-FABP and L-FABP correlated well with previous data describing the transport of lipid and drug into intestinal lymph following infusion of the same formulations.

CONCLUSION

The expression and intracellular distribution of I-FABP and L-FABP are acutely influenced by lipid infusion over a time period relevant to feeding or the administration of pharmaceutical lipidic formulations, and these changes occur coincidentally with increased drug transport into the lymphatics.

Effect of branched-chain fatty acid on lipid dynamics in mice lacking liver fatty acid binding protein gene

Although a role for liver fatty acid protein (L-FABP) in the metabolism of branched-chain fatty acids has been suggested based on data obtained with cultured cells, the physiological significance of this observation remains to be demonstrated. To address this issue, the lipid phenotype and metabolism of phytanic acid, a branched-chain fatty acid, were determined in L-FABP gene-ablated mice fed a diet with and without 1% phytol (a metabolic precursor to phytanic acid). In response to dietary phytol, L-FABP gene ablation exhibited a gender-dependent lipid phenotype. Livers of phytol-fed female L-FABP-/- mice had significantly more fatty lipid droplets than male L-FABP-/- mice, whereas in phytol-fed wild-type L-FABP+/+ mice differences between males and females were not significant. Thus L-FABP gene ablation exacerbated the accumulation of lipid droplets in phytol-fed female, but not male, mice. These results were reflected in the lipid profile, where hepatic levels of triacylglycerides in phytol-fed female L-FABP-/- mice were significantly higher than in male L-FABP-/- mice. Furthermore, livers of phytol-fed female L-FABP-/- mice exhibited more necrosis than their male counterparts, consistent with the accumulation of higher levels of phytol metabolites (phytanic acid, pristanic acid) in liver and serum, in addition to increased hepatic levels of sterol carrier protein (SCP)-x, the only known peroxisomal enzyme specifically required for branched-chain fatty acid oxidation. In summary, L-FABP gene ablation exerted a significant role, especially in female mice, in branched-chain fatty acid metabolism. These effects were only partially compensated by concomitant upregulation of SCP-x in response to L-FABP gene ablation and dietary phytol.

Expression of cFABP and PPAR in trophoblast cells: effect of PPAR ligands on linoleic acid uptake and differentiation

Throughout gestation, fetal growth depends, in part, on placental transfer of maternal essential fatty acid (EFA) and long-chain polyunsaturated fatty acid. All fatty acid (FA) can cross lipid bilayer by simple diffusion, such as those in the syncytiotrophoblasts, the multinucleated, terminally differentiated trophoblast cells. The trophoblasts differentiation process is accompanied by an increase of human chorionic gonadotropin (hCG) secretion and an inhibition of Human Achaete-Scute Homologue-2 expression (Hash-2). Furthermore, a number of FA-binding proteins (FABPs) have been identified in membrane and cytoplasm of mammalian cells, which are thought to facilitate the transfer of FA across membranes and their intracellular channeling. Thus, the aim of this study was to investigate the implication of cFABPs in linoleic acid (LA) uptake by human trophoblast cells according to differentiation. Moreover, since peroxisome proliferator-activated receptor (PPARs) regulate the expression of cFABP and play an important role in trophoblast cells differentiation, the effects of PPARs ligands are verified on cFABP expression and differentiation. Herein, we reported the increase of the expression of liver and heart FABP (L- and H-FABP) upon differentiation of trophoblast cells, an inhibition of PPAR alpha and beta, while PPAR gamma levels remains unchanged. The nonselective peroxisome-proliferating agents, bezafibrate and LA, impaired trophoblast differentiation, and reduced L- and H-FABP expression. Furthermore, cobalt, a chemical agent known to mimic hypoxia, inhibits trophoblast cells differentiation and diminishes H-, L-FABP and PPARs expression. Finally, both treatments show no influence on LA uptake by trophoblast cells. In conclusion, this study showed that there is no correlation between the expression of H- and L-FABP and LA uptake by trophoblast cells and that bezafibrate and LA greatly impaired trophoblast cells differentiation.

Double-blind, placebo-controlled study of zinc sulfate in the treatment of attention deficit hyperactivity disorder

BACKGROUND

The most commonly used medications for attention deficit hyperactivity disorder (ADHD) are the psychostimulants. There is, however, considerable awareness in alternative, nonstimulant therapies, because some patients respond poorly to stimulants or are unable to tolerate them. Some studies suggest that deficiency of zinc play a substantial role in the aetiopathogenesis of ADHD. Therefore, to assess the efficacy of zinc sulfate we conducted treatment trial.

METHODS

Patients with a primary DSM-IV diagnosis of ADHD (N=400; 72 girls, 328 boys, mean age=9.61+/-1.7) were randomly assigned in a 1:1 ratio to 12 weeks of double-blind treatment with zinc sulfate (n=202) (150 mg/day) or placebo (n=198). Efficacy was assessed with the Attention Deficit Hyperactivity Disorder Scale (ADHDS), Conners Teacher Questionnaire, and DuPaul Parent Ratings of ADHD. Primary efficacy variables were differences from baseline to endpoint (last observation carried forward) in mean ADHDS and Conners Teacher Questionnaire scores between the zinc sulfate and the placebo groups. Safety evaluations included monitoring of adverse events, vital signs and clinical laboratory values.

RESULTS

Zinc sulfate was statistically superior to placebo in reducing both hyperactive, impulsive and impaired socialization symptoms, but not in reducing attention deficiency symptoms, as assessed by ADHDS. However, full therapeutic response rates of the zinc and placebo groups remained 28.7% and 20%, respectively. It was determined that the hyperactivity, impulsivity and socialization scores displayed significant decrease in patients of older age and high BMI score with low zinc and free fatty acids (FFA) levels. Zinc sulfate was well tolerated and associated with a low rate of side effect.

CONCLUSIONS

Zinc monotherapy was significantly superior to placebo in reducing symptoms of hyperactivity, impulsivity and impaired socialization in patients with ADHD. Although by themselves, these findings may not be sufficient, it may well be considered that zinc treatment appears to be an efficacious treatment for ADHD patients having older age and high BMI score with low zinc and FFA levels.

Sterol carrier protein-2/sterol carrier protein-x expression differentially alters fatty acid metabolism in L cell fibroblasts

Sterol carrier protein-2 (SCP-2) and SCP-x are ubiquitous proteins found in all mammalian tissues. Although both proteins interact with fatty acids, their relative contributions to the uptake, oxidation, and esterification of straight-chain (palmitic) and branched-chain (phytanic) fatty acids in living cells has not been resolved. Therefore, the effects of each gene product on fatty acid metabolism was individually examined. Based on the following, SCP-2 and SCP-x did not enhance the uptake/translocation of fatty acids across the plasma membrane into the cell: i) a 2-fold increase in phytanic and palmitic acid uptake was observed at long incubation times in SCP-2- and SCP-x-expressing cells, but no differences were observed at initial time points; ii) uptake of 2-bromo-palmitate, a nonoxidizable, poorly metabolizable fatty acid analog, was unaffected by SCP-2 or SCP-x overexpression; and iii) SCP-2 and SCP-x expression did not increase targeting of radiolabeled phytanic and palmitic acid to the unesterified fatty acid pool. Moreover, SCP-2 and SCP-x expression enhanced fatty acid uptake by stimulating the intracellular metabolism via fatty acid oxidation and esterification. In summary, these data showed for the first time that SCP-2 and SCP-x stimulate oxidation and esterification of branched-chain as well as straight-chain fatty acids in intact cells.

New insights into the fatty acid-binding protein (FABP) family in the small intestine

The fatty acid-binding protein (FABP) superfamily is constituted by 14-15 kDa soluble proteins which bind with a high affinity either long-chain fatty acids (LCFAs), bile acids (BAs) or retinoids. In the small intestine, three different FABP isoforms exhibiting a high affinity for LCFAs and/or BAs are expressed: the intestinal and the liver-type (I-FABP and L-FABP) and the ileal bile acid-binding protein (I-BABP). Despite of extensive investigations, their respective physiological function(s) are not clearly established. In contrast to the I-FABP, L-FABP and I-BABP share several common structural features (shape, size and volume of the hydrophobic pocket). Moreover, L-FABP and I-BABP genes are also specifically regulated by their respective preferential ligands through a very similar molecular mechanism. Although, they exhibit differences in their binding specificities and location along the small intestine supporting a specialization, it is likely that L-FABP and I-BABP genes exert the same type of basic function(s) in the enterocyte, in contrast to I-FABP.

Control of mitochondrial beta-oxidation flux

The control of mitochondrial beta-oxidation, including the delivery of acyl moieties from the plasma membrane to the mitochondrion, is reviewed. Control of beta-oxidation flux appears to be largely at the level of entry of acyl groups to mitochondria, but is also dependent on substrate supply. CPTI has much of the control of hepatic beta-oxidation flux, and probably exerts high control in intact muscle because of the high concentration of malonyl-CoA in vivo. beta-Oxidation flux can also be controlled by the redox state of NAD/NADH and ETF/ETFH(2). Control by [acetyl-CoA]/[CoASH] may also be significant, but it is probably via export of acyl groups by carnitine acylcarnitine translocase and CPT II rather than via accumulation of 3-ketoacyl-CoA esters. The sharing of control between CPTI and other enzymes allows for flexible regulation of metabolism and the ability to rapidly adapt beta-oxidation flux to differing requirements in different tissues.

Reduced secretion of triacylglycerol in CaCo-2 cells transfected with intestinal fatty acid-binding protein

The fatty acid-binding proteins are hypothesized to be involved in cellular fatty acid transport and trafficking. We established CaCo-2 cells stably transfected with intestinal fatty acid-binding protein (I-FABP) and examined how the expression of this protein may influence fatty acid metabolism. I-FABP expression was detectable in I-FABP-transfected cells, whereas parent CaCo-2 cells as well as mock-transfected cells failed to express detectable levels of I-FABP mRNA or protein at any stage of differentiation. For studies of lipid metabolism, cells were incubated with [14C]oleic acid in taurocholate micelles containing monoolein, and distribution of labeled fatty acid in cellular and secreted lipids was examined. In one transfected cell clone, expressing the highest level of I-FABP, labeled cellular triacylglycerol increased approximately twofold as compared to control cells. The level of intracellular triacylglycerol in two other I-FABP-transfected clones resembled that of control cells. However, secretion of triacylglycerol was markedly reduced in all the I-FABP-expressing cell lines. Our data suggest that increased expression of I-FABP leads to reduced triacylglycerol secretion in intestinal cells.

Fatty-acid-binding proteins do not protect against induced cytotoxicity in a kidney cell model

Intracellular accumulation of fatty acids (FAs) is a well-described consequence of renal ischaemia and may lead to lethal cell injury. Fatty-acid-binding proteins (FABPs) are small cytosolic proteins with high affinity for FAs. They may protect vital cellular functions by binding to and promoting the metabolism of FAs, thereby reducing their intracellular concentration. In this study we investigated the putative cytoprotective role of FABPs in a Madin-Darby canine kidney (MDCK) cell model for renal damage. We studied the effects of transfection with cDNA encoding heart FABP, adipocyte FABP or liver FABP on cytotoxicity induced by chemical anoxia or FAs. Transfection of MDCK type II cells with these cDNA types caused a 5-20-fold increase in FABP content, but did not change the rate or extent of palmitate uptake. After 1 h of incubation with KCN, all cell types showed reduced viability and cellular ATP content and an intracellular accumulation of non-esterified FAs. High extracellular concentrations of oleate, but not palmitate, caused a markedly decreased cell viability and cellular ATP content. Oleate accumulated in non-esterified form in these cells. Simultaneous addition of glucose ameliorated the damaging effects of KCN or oleate, indicating that glycolytic ATP could substitute for uncoupled oxidative phosphorylation. No significant differences in the effects of chemical anoxia or oleate were observed between non-transfected, mock-transfected and FABP-cDNA-transfected cells. Non-esterified FA accumulation was not reduced in any of the FABP-cDNA-transfected cell lines. In conclusion, our data do not provide evidence for a cytoprotective role of FABP in this kidney cell model.

The fatty acid transport function of fatty acid-binding proteins

The intracellular fatty acid-binding proteins (FABPs) comprise a family of 14-15 kDa proteins which bind long-chain fatty acids. A role for FABPs in fatty acid transport has been hypothesized for several decades, and the accumulated indirect and correlative evidence is largely supportive of this proposed function. In recent years, a number of experimental approaches which more directly examine the transport function of FABPs have been taken. These include molecular level in vitro modeling of fatty acid transfer mechanisms, whole cell studies of fatty acid uptake and intracellular transfer following genetic manipulation of FABP type and amount, and an examination of cells and tissues from animals engineered to lack expression of specific FABPs. Collectively, data from these studies have provided strong support for defining the FABPs as fatty acid transport proteins. Further studies are necessary to elucidate the fundamental mechanisms by which cellular fatty acid trafficking is modulated by the FABPs.

Intestinal fatty acid binding protein may favor differential apical fatty acid binding in the intestine

The intestinal mucosa metabolizes fatty acids differently when presented to the lumenal or basolateral membrane. Expression of both liver and intestinal fatty acid binding proteins (L- and I-FABPs) uniquely in the enterocyte offers a possible explanation of this phenomenon. An organ explant system was used to analyze the relative binding of fatty acids to each protein. More fatty acid was bound to L-FABP than to I-FABPs (28% vs. 6% of cytosolic radioactivity), no matter on which side the fatty acid was added. However, a 2-3-fold increase in fatty acid binding to the intestinal paralog was noted after apical addition of palmitic or oleic acid in mucosa from chow fed rats. When oleic acid was added apically, a 1.4-fold increase in binding to I-FABP was observed in mucosa derived from chronically fat fed rats, consistent with the previously observed 50% increase in the content of that protein. Immunocytochemical localization of both FABPs in vivo demonstrated an apical cytoplasmic localization in the fasting state, and redistribution to the entire cytoplasm after fat feeding. These data are consistent with the hypothesis that I-FABP may contribute to the metabolic compartmentalization of apically presented fatty acids in the intestine.

Fatty acid metabolism in human breast cancer cells (MCF7) transfected with heart-type fatty acid binding protein

The human breast cancer cell line MCF7 does not express heart-type fatty acid binding protein (H-FABP), a marker protein for differentiated mammary gland. MCF7 cells transfected with the bovine H-FABP cDNA expressed the corresponding protein and were characterized by growth inhibition and lower tumorgenicity in nude mice [22]. By enzyme linked immunoassay we now determined the amount of bovine H-FABP in these cells as 638 +/- 80 ng/mg protein and used the transfected cells to study the role of H-FABP in fatty acid metabolism. Compared to control cells the uptake of radioactively labelled palmitic acid and oleic acid into MCF7 cells after 30 or 60 min was increased by 67% in H-FABP expressing transfectants, demonstrating a stimulatory role for this FABP-type in fatty acid metabolism. However, preferential targeting of [14C]oleic acid into neutral or phospholipid classes was not observed by the criterion of high performance thin layer chromatography followed by autoradiography. A reason for the modest increase of fatty acid uptake in H-FABP transfected MCF7 cells may be the basal expression of epidermal-type FABP, which was detected for the first time in these cells. It appears that the small amount of E-FABP expressed in MCF7 cells fulfils the need of the cells for a cytosolic fatty acid carrier under culture conditions and that even high concentrations of another FABP do only slightly increase the uptake due to limitations of fatty acid transport through the plasma membrane or of metabolism.

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

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 acid binding protein (I-FABP). Control ES cells, whether differentiated or undifferentiated, did not express I-FABP. The initial rate and maximal uptake of the fluorescent fatty acid, 12-(N-methyl)-N-[(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-octadec anoic acid (NBD-stearic acid), was measured in single cells by kinetic digital fluorescence imaging. I-FABP expression in undifferentiated ES cells increased the initial rate and maximal uptake of NBD-stearic acid 1.7- and 1.6-fold, respectively, as well as increased its effective intracellular diffusion constant (Deff) 1.8-fold as measured by the fluorescence recovery after photobleaching technique. In contrast, ES cell differentiation decreased I-FABP expression up to 3-fold and decreased the NBD-stearic acid initial rate of uptake, maximal uptake, and Deff by 10-, 4.7-, and 2-fold, respectively. There were no significant differences in these parameters between the differentiated control and differentiated I-FABP-expressing ES cell lines. In summary, differentiation and expression of I-FABP oppositely modulated NBD-stearic acid uptake parameters and intracellular diffusion in ES cells.

Differential influence of rat liver fatty acid binding protein isoforms on phospholipid fatty acid composition: phosphatidic acid biosynthesis and phospholipid fatty acid remodeling

The ability of two rat liver fatty acid binding protein (L-FABP) isoforms to influence microsomal phosphatidic acid biosynthesis, a key intermediate in glycerolipid formation, and phospholipid fatty acid remodeling was examined in vitro. Isoform I enhanced microsomal incorporation of [1-14C]-oleoyl-CoA into phosphatidic acid 7-fold while isoform II had no effect relative to basal. In contrast, isoform II enhanced microsomal incorporation of [1-14C]-palmitoyl-CoA into phosphatidic acid 4-fold while isoform I had no effect. These results suggest that each L-FABP isoform selectively utilized different acyl-CoAs for glycerol-3-phosphate esterification. Both isoforms stimulated phosphatidic acid formation by increasing glycerol-3-phosphate acyltransferase activity, not by increasing lysophosphatidic acid acyltransferase activity. Furthermore, the effects of L-FABP on phosphatidic acid biosynthesis could not be correlated with protection from acyl-CoA hydrolysis. L-FABP isoforms also influenced phospholipid fatty acid remodeling in a phospholipid-dependent manner. Isoform I preferentially enhanced oleate and palmitate esterification into phosphatidylethanol-amine, while isoform II stimulated esterification into phosphatidylcholine, phosphatidylserine and sphingomyelin. Taken together, these data demonstrated a unique role of each L-FABP isoform in modulating microsomally derived phospholipid fatty acid composition. (c) 1998 Elsevier Science B.V.