Fatty acids in cell signalling: modulation by lipid binding proteins

The carboxy terminus causes interfacial assembly of oleate hydratase on a membrane bilayer

The soluble flavoprotein oleate hydratase (OhyA) hydrates the 9-cis double bond of unsaturated fatty acids. OhyA substrates are embedded in membrane bilayers; OhyA must remove the fatty acid from the bilayer and enclose it in the active site. Here, we show that the positively charged helix-turn-helix motif in the carboxy terminus (CTD) is responsible for interacting with the negatively charged phosphatidylglycerol (PG) bilayer. Super-resolution microscopy of Staphylococcus aureus cells expressing green fluorescent protein fused to OhyA or the CTD sequence shows subcellular localization along the cellular boundary, indicating OhyA is membrane-associated and the CTD sequence is sufficient for membrane recruitment. Using cryo-electron microscopy, we solved the OhyA dimer structure and conducted 3D variability analysis of the reconstructions to assess CTD flexibility. Our surface plasmon resonance experiments corroborated that OhyA binds the PG bilayer with nanomolar affinity and we found the CTD sequence has intrinsic PG binding properties. We determined that the nuclear magnetic resonance structure of a peptide containing the CTD sequence resembles the OhyA crystal structure. We observed intermolecular NOE from PG liposome protons next to the phosphate group to the CTD peptide. The addition of paramagnetic MnCl2 indicated the CTD peptide binds the PG surface but does not insert into the bilayer. Molecular dynamics simulations, supported by site-directed mutagenesis experiments, identify key residues in the helix-turn-helix that drive membrane association. The data show that the OhyA CTD binds the phosphate layer of the PG surface to obtain bilayer-embedded unsaturated fatty acids.

Feasibility of transient nuclear Overhauser effect imaging in brain at 7 T

PURPOSE

The nuclear Overhauser effect (NOE) quantification from the steady-state NOE imaging suffers from multiple confounding non-NOE-specific sources, including direct saturation, magnetization transfer, and relevant chemical exchange species, and is affected by B₀ and B₁ ⁺ inhomogeneities. The B₀ -dependent and B₁ ⁺ -dependent data needed for deconvolving these confounding effects would increase the scan time substantially, leading to other issues such as patient tolerability. Here, we demonstrate the feasibility of brain lipid mapping using an easily implementable transient NOE (tNOE) approach.

METHODS

This 7T study used a frequency-selective inversion pulse at a range of frequency offsets between 1.0 and 5.0 parts per million (ppm) and -5.0 and -1.0 ppm relative to bulk water peak. This was followed by a fixed/variable mixing time and then a single-shot 2D turbo FLASH readout. The feasibility of tNOE measurements is demonstrated on bovine serum albumin phantoms and healthy human brains.

RESULTS

The tNOE measurements from bovine serum albumin phantoms were found to be independent of physiological pH variations. Both bovine serum albumin phantoms and human brains showed broad tNOE contributions centered at approximately -3.5 ppm relative to water peak, with presumably aliphatic moieties in lipids and proteins being the dominant contributors. Less prominent tNOE contributions of approximately +2.5 ppm relative to water, presumably from aromatic moieties, were also detected. These aromatic signals were free from any CEST signals.

CONCLUSION

In this study, we have demonstrated the feasibility of tNOE in human brain at 7 T. This method is more scan-time efficient than steady-state NOE and provides NOE measurement with minimal confounders.

The interplay of phloem-mobile signals in plant development and stress response

Plants integrate a variety of biotic and abiotic factors for optimal growth in their given environment. While some of these responses are local, others occur distally. Hence, communication of signals perceived in one organ to a second, distal part of the plant and the coordinated developmental response require an intricate signaling system. To do so, plants developed a bipartite vascular system that mediates the uptake of water, minerals, and nutrients from the soil; transports high-energy compounds and building blocks; and traffics essential developmental and stress signals. One component of the plant vasculature is the phloem. The development of highly sensitive mass spectrometry and molecular methods in the last decades has enabled us to explore the full complexity of the phloem content. As a result, our view of the phloem has evolved from a simple transport path of photoassimilates to a major highway for pathogens, hormones and developmental signals. Understanding phloem transport is essential to comprehend the coordination of environmental inputs with plant development and, thus, ensure food security. This review discusses recent developments in its role in long-distance signaling and highlights the role of some of the signaling molecules. What emerges is an image of signaling paths that do not just involve single molecules but rather, quite frequently an interplay of several distinct molecular classes, many of which appear to be transported and acting in concert.

Improvement of Obesity and Dyslipidemic Activity of Amomum tsao-ko in C57BL/6 Mice Fed a High-Carbohydrate Diet

Amomum tsao-ko Crevost et Lemaire (Zingiberaceae) is a medicinal herb found in Southeast Asia that is used for the treatment of malaria, abdominal pain, dyspepsia, etc. The aim of this study was to investigate the effect of an ethanol extract of Amomum tsao-ko (EAT) on obesity and hyperlipidemia in C57BL/6 mice fed a high-carbohydrate diet (HCD). First, the mice were divided into five groups (n = 6/group) as follows: normal diet, HCD, and HCD+EAT (100, 200, and 400 mg/kg/day), which were orally administered with EAT daily for 84 days. Using microcomputed tomography (micro-CT) analysis, we found that EAT inhibited not only body-weight gain, but also visceral fat and subcutaneous fat accumulation. Histological analysis confirmed that EAT decreased the size of fat tissues. EAT consistently improved various indices, including plasma levels of total cholesterol (TC), triglyceride (TG), low-density lipoprotein, high-density lipoprotein, atherogenic index, and cardiac risk factors, which are related to dyslipidemia—a major risk factor for heart disease. The contents of TC and TG, as well as the lipid droplets of HCD-induced hepatic accumulation in the liver tissue, were suppressed by EAT. Taken together, these findings suggest the possibility of developing EAT as a therapeutic agent for improving HCD-induced obesity and hyperlipidemia.

Drug Delivery Strategies for Enhancing the Therapeutic Efficacy of Toxin-Derived Anti-Diabetic Peptides

Toxin peptides derived from the skin secretions of amphibians possess unique hypoglycemic activities. Many of these peptides share cationic and amphipathic structural similarities and appear to possess cell-penetrating abilities. The mechanism of their insulinotropic action is yet not elucidated, but they have shown great potential in regulating the blood glucose levels in animal models. Therefore, they have emerged as potential drug candidates as therapeutics for type 2 diabetes. Despite their anti-diabetic activity, there remain pharmaceutical challenges to be addressed for their clinical applications. Here, we present an overview of recent studies related to the toxin-derived anti-diabetic peptides derived from the skin secretions of amphibians. In the latter part, we introduce the bottleneck challenges for their delivery in vivo and general drug delivery strategies that may be applicable to extend their blood circulation time. We focus our research on the strategies that have been successfully applied to improve the plasma half-life of exendin-4, a clinically available toxin-derived anti-diabetic peptide drug.

FABP4 suppresses proliferation and invasion of hepatocellular carcinoma cells and predicts a poor prognosis for hepatocellular carcinoma

Adipocyte fatty acid-binding protein (FABP4) is abundant in macrophage and adipocyte. It is known to be involved in lipid metabolism. The role of FABP4 has been reported in various cancers, such as non-small cell lung cancer, breast cancer, ovarian cancer, and prostatic cancer. However, its role remains unclear in hepatocellular carcinoma (HCC). In our study, we investigated the expression of FABP4 at both mRNA and protein levels, and by examining 175 cases of patients with cancer of the liver tissue microarray, the significance between the expression of FABP4 and clinical characteristics had been discussed. We found that FABP4 was lowly expressed in HCC tissues compared to the corresponding tissue adjacent, and the expression of FABP4 was significantly associated with the tumor size, PVTT, recurrence-free survival and overall survival. Moreover, multivariate Cox regression analysis indicated that the expression of FABP4, Alb, AFP, HBsAg, and PVTT were independent risk factors for overall survival, and the expression of FABP4, AFP, GGT, tumor size, and encapsulation were independent risk factors for HCC recurrence. In addition, we revealed that FABP4 suppressed HCC cell proliferation and invasion in vitro. Moreover, overexpression of FABP4 led to inhibit tumor growth and decreased tumor volume in vivo. These phenotypes were associated with altered expression of Snail and p-STAT3. Our studies thus suggest that FABP4 could be a potential target for HCC chemotherapy.

Differential Cationization of Fatty Acids with Monovalent Cations Studied by ESI-MS/MS and Computational Approach

RATIONALE

The intercellular and intracellular transport of charged species (Na+ /K+ ) entail interaction of the ions with neutral organic molecules and formation of adduct ions. The rate of transport of the ions across the cell membrane(s) may depend on the stability of the adduct ions, which in turn rely on structural aspects of the organic molecules that interact with the ions.

METHODS

Positive ion ESI mass spectra were recorded for the solutions containing fatty acids (FAs) and monovalent cations (X=Li+ , Na+ , K+ , Rb+ and Cs+ ). Product ion spectra of the [FA+X]+ ions were recorded at different collision energies. Theoretical studies were exploited under both gas phase and solvent phase to investigate the structural effects of the fatty acids during cationization. Stability of [FA+X]+ adduct ions were further estimated by means of AIM topological analyses and interaction energy (IE) values.

RESULTS

Positive ion ESI-MS analyses of the solution of FAs and X+ ions showed preferential binding of the K+ ions to FAs. The K+ ion binding increased with the increase in number of double bonds of FAs, while decreased with increase in the number of carbons of FAs. Dissociation curves of [FA+X]+ ions indicated the relative stability order of the [FA+X]+ ions and it was in line with the observed trends in ESI-MS. The solvent phase computational studies divulged the mode of binding and the binding efficiencies of different FAs with monovalent cations.

CONCLUSIONS

Among the studied monovalent cations, the cationization of FAs follow the order K+ >>Na+ >Li+ >Rb+ >Cs+ . The docosahexaenoic acid showed high efficiency in binding with K+ ion. The K+ ion binding efficiency of FAs depends on the number of double bonds in unsaturated FAs and the carbon chain length in saturated FAs. The cationization trends of FAs obtained from the ESI-MS, ESI-MS/MS analyses were in good agreement with solvent phase computational studies.

Glial Fatty Acid-Binding Protein 7 (FABP7) Regulates Neuronal Leptin Sensitivity in the Hypothalamic Arcuate Nucleus

The hypothalamus is involved in the regulation of food intake and energy homeostasis. The arcuate nucleus (ARC) and median eminence (ME) are the primary hypothalamic sites that sense leptin and nutrients in the blood, thereby mediating food intake. Recently, studies demonstrating a role for non-neuronal cell types, including astrocytes and tanycytes, in these regulatory processes have begun to emerge. However, the molecular mechanisms involved in these activities remain largely unknown. In this study, we examined in detail the localization of fatty acid-binding protein 7 (FABP7) in the hypothalamic ARC and sought to determine its role in the hypothalamus. We performed a phenotypic analysis of diet-induced FABP7 knockout (KO) obese mice and of FABP7 KO mice treated with a single leptin injection. Immunohistochemistry revealed that FABP7⁺ cells are NG2⁺ or GFAP⁺ in the ARC and ME. In mice fed a high-fat diet, weight gain and food intake were lower in FABP7 KO mice than in wild-type (WT) mice. FABP7 KO mice also had lower food intake and weight gain after a single injection of leptin, and we consistently confirmed that the number of pSTAT3⁺ cells in the ARC indicated that the leptin-induced activation of neurons was significantly more frequent in FABP7 KO mice than in WT mice. In FABP7 KO mice-derived primary astrocyte cultures, the level of ERK phosphorylation was lower after leptin treatment. Collectively, these results indicate that in hypothalamic astrocytes, FABP7 might be involved in sensing neuronal leptin via glia-mediated mechanisms and plays a pivotal role in controlling systemic energy homeostasis.

Anti-Obesity Activity of Saringosterol Isolated from Sargassum muticum (Yendo) Fensholt Extract in 3T3-L1 Cells

Saringosterol, a steroid isolated from Sargassum muticum, a brown edible alga widely distributed on the seashores of southern and eastern Korea, has been shown to exhibit anti-obesity effect. In this study, we investigated the anti-obesity activity of saringosterol through various experiments. The inhibitory effect of saringosterol on adipogenesis was evaluated via Oil Red O staining in 3T3-L1 preadipocytes. After confirming that saringosterol is not cytotoxic to these cells by using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay, the effect of saringosterol on the expression of various adipogenesis-related genes was analyzed via quantitative real-time polymerase chain reaction and western blotting. We demonstrated that saringosterol dose dependently inhibited adipocyte differentiation and expression of adipogenic marker genes such as adipocyte fatty acid-binding protein, adiponectin, resistin, and fatty acid synthase in 3T3-L1 cells. In addition, saringosterol significantly inhibited the mRNA and protein expression of peroxisome proliferator-activated receptor γ and CCAAT enhancer-binding protein α in 3T3-L1 cells. Collectively, these findings indicate that saringosterol isolated from S. muticum exhibits anti-obesity effect by inhibiting the expression of adipogenic transcription factors and marker genes and that it may be developed as a drug to suppress adipogenesis. Copyright © 2017 John Wiley & Sons, Ltd.

The combination of three-dimensional and rotary cell culture system promotes the proliferation and maintains the differentiation potential of rat BMSCs

Bone marrow mesenchymal stem cells (BMSCs) are a good candidate for tissue engineering and clinical application. One of the challenges in its cell therapy is how to quickly obtain an adequate number of seed cells and meanwhile maintain suitable differentiation potential. In this study we combined three-dimensional (3D) collagen porous scaffolds with rotary cell culture system (RCCS) (RCCS-3D) to create a stereoscopic dynamic environment for the amplification of rat BMSCs in vitro. The results revealed that this RCCS-3D system could enhance BMSCs' proliferation and colony formation, as well as maintain the differentiation potential compared with conventional static two-dimensional (2D) and 3D cell culture conditions. In addition, high-throughput microarray analysis showed that gene expressions of RCCS-3D system displayed significant differences in cell proliferation and differentiation compared with static-2D conditions. Thus, RCCS-3D system could provide an effective means for BMSCs cell proliferation in vitro and meanwhile maintain differentiation potential in tissue engineering.

Traumatic Acid Reduces Oxidative Stress and Enhances Collagen Biosynthesis in Cultured Human Skin Fibroblasts

Traumatic acid (TA) is a plant hormone (cytokinin) that in terms of chemical structure belongs to the group of fatty acids derivatives. It was isolated from Phaseolus vulgaris. TA activity and its influence on human cells and organism has not previously been the subject of research. The aim of this study was to examine the effects of TA on collagen content and basic oxidative stress parameters, such as antioxidative enzyme activity, reduced glutathione, thiol group content, and lipid peroxidation in physiological conditions. The results show a stimulatory effect of TA on tested parameters. TA caused a decrease in membrane phospholipid peroxidation and exhibited protective properties against ROS production. It also increases protein and collagen biosynthesis and its secretion into the culture medium. The present findings reveal that TA exhibits multiple and complex activity in fibroblast cells in vitro. TA, with its activity similar to unsaturated fatty acids, shows antioxidant and stimulatory effects on collagen biosynthesis. It is a potentially powerful agent with applications in the treatment of many skin diseases connected with oxidative stress and collagen biosynthesis disorders.

Rubus crataegifolius Bunge regulates adipogenesis through Akt and inhibits high-fat diet-induced obesity in rats

Background

Obesity is one of the greatest public health problems and major risk factors for serious metabolic diseases and significantly increases the risk of premature death. The aim of this study was to determine the inhibitory effects of Rubus crataegifolius Bunge (RCB) on adipocyte differentiation in 3 T3-L1 cells and its anti-obesity properties in high fat diet (HFD)-induced obese rats.

Methods

3 T3-L1 adipocytes and HFD-induced obese rats were treated with RCB, and its effect on gene expression was analyzed using RT-PCR and Western blotting experiments.

Results

RCB treatment significantly inhibited adipocyte differentiation by suppressing the expression of C/EBPβ, C/EBPα, and PPARγ in the 3 T3-L1 adipocytes. Subsequently, the expression of the PPARγ target genes aP2 and fatty acid synthase (FAS) decreased following RCB treatment during adipocyte differentiation. In uncovering the specific mechanism that mediates the effects of RCB, we demonstrated that the insulin-stimulated phosphorylation of Akt strongly decreased and that its downstream substrate phospho-GSK3β was downregulated following RCB treatment in the 3 T3-L1 adipocytes. Moreover, LY294002, an inhibitor of Akt phosphorylation, exerted stronger inhibitory effects on RCB-mediated suppression of adipocyte differentiation, leading to the inhibition of adipocyte differentiation through the downregulation of Akt signaling. An HFD-induced obesity rat model was used to determine the inhibitory effects of RCB on obesity. Body weight gain and fat accumulation in adipose tissue were significantly reduced by the supplementation of RCB. Moreover, RCB treatment caused a significant decrease in adipocyte size, associated with a decrease in epididymal fat weight. The serum total cholesterol (TC) and triglyceride (TG) levels decreased in response to RCB treatment, whereas HDL cholesterol (HDL-C) increased, indicating that RCB attenuated lipid accumulation in adipose tissue in HFD-induced obese rats.

Conclusion

Our results demonstrate an inhibitory effect of RCB on adipogenesis through the reduction of the adipogenic factors PPARγ, C/EBPα, and phospho-Akt. RCB had a potent anti-obesity effect, reducing body weight gain in HFD-induced obese rats.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-016-0091-0) contains supplementary material, which is available to authorized users.

Long-Distance Lipid Signaling and its Role in Plant Development and Stress Response

Lipids are important signaling compounds in plants. They can range from small lipophilic molecules like the dicarboxylic acid Azelaic acid to complex phosphoglycerolipids and regulate plant development as well as the response to biotic and abiotic stress. While their intracellular function is well described, several lipophilic signals are known to be found in the plant phloem and can, thus, also play a role in long-distance signaling. Mostly, they play a role in the pathogen response and systemic acquired resistance. This is particularly true for oxylipins, dehydroabietinal, and azelaic acid. However, several phospholipids have now been described in phloem exudates. Their intracellular function as well as implications and a model for long-distance signaling are discussed in this chapter.

FABP4 plasma concentrations are determined by acquired metabolic derangements rather than genetic determinants

BACKGROUND AND AIMS

Circulating FABP4 is strongly associated with metabolic and cardiovascular risk (CVR) and has been proposed as a new risk biomarker. Several FABP4 gene polymorphisms have been associated with protein expression in vitro and metabolic and vascular alterations in vivo. The aim of this study is to evaluate the impact of FABP4 polymorphisms on FABP4 plasma levels and subclinical arteriosclerosis in patients with obesity, metabolic syndrome (MS) or type 2 diabetes (T2DM).

METHODS AND RESULTS

We studied 440 individuals with obesity, MS, T2DM or other cardiovascular risk conditions who attended the vascular medicine and metabolism unit of our hospital. Anamnesis, physical examination and anthropometry data were recorded. Standard biochemical parameters were determined. Plasma FABP4 concentrations were measured. Carotid intima-media thickness (cIMT) was assessed using ultrasonography. The following FABP4 gene single-nucleotide polymorphisms (SNPs) were analyzed: rs3834363, rs16909233, rs1054135, rs77878271, rs10808846 and rs8192688. None of the studied gene allele variants were hyper-represented in patients grouped according the presence of metabolic alterations nor were they associated with the FABP4 concentration. The FABP4 gene variants did not determine cIMT differences between the groups. In a multivariate analysis, gender and BMI, but not gene variants, significantly determined plasma FABP4 concentrations.

CONCLUSIONS

In clinical settings, the circulating FABP4 levels are determined by the acquired metabolic derangements and not genetic variation.

Fatty acid-binding protein 7 regulates function of caveolae in astrocytes through expression of caveolin-1

Fatty acid-binding proteins (FABPs) bind and solubilize long-chain fatty acids, controlling intracellular lipid dynamics. FABP7 is expressed by astrocytes in the developing brain, and suggested to be involved in the control of astrocyte lipid homeostasis. In this study, we sought to examine the role of FABP7 in astrocytes, focusing on plasma membrane lipid raft function, which is important for receptor-mediated signal transduction in response to extracellular stimuli. In FABP7-knockout (KO) astrocytes, the ligand-dependent accumulation of Toll-like receptor 4 (TLR4) and glial cell-line-derived neurotrophic factor receptor alpha 1 into lipid raft was decreased, and the activation of mitogen-activated protein kinases and nuclear factor-κB was impaired after lipopolysaccharide (LPS) stimulation when compared with wild-type astrocytes. In addition, the expression of caveolin-1, not cavin-1, 2, 3, caveolin-2, and flotillin-1, was found to be decreased at the protein and transcriptional levels. FABP7 re-expression in FABP7-KO astrocytes rescued the decreased level of caveolin-1. Furthermore, caveolin-1-transfection into FABP7-KO astrocytes significantly increased TLR4 recruitment into lipid raft and tumor necrosis factor-α production after LPS stimulation. Taken together, these data suggest that FABP7 controls lipid raft function through the regulation of caveolin-1 expression and is involved in the response of astrocytes to the external stimuli. GLIA 2015;63:780-794.

Rubi Fructus (Rubus coreanus) activates the expression of thermogenic genes in vivo and in vitro

OBJECTIVE

To investigate the anti-obesity effect of Rubi Fructus (RF) extract using brown adipose tissue (BAT) and primary brown preadipocytes in vivo and in vitro.

METHODS

Male C57BL/6 J mice (n=5 per group) were fed a high-fat diet (HFD) for 10 weeks with or without RF. Brown preadipocytes from the interscapular BAT of mice (age, post-natal days 1-3) were cultured with differentiation media (DM) including isobutylmethylxanthine, dexamethasone, T3, indomethacin and insulin with or without RF.

RESULTS

In HFD-induced obese C57BL/6 J mice, long-term RF treatment significantly reduced weight gain as well as the weights of the white adipose tissue, liver and spleen. Serum levels of total cholesterol and low-density lipoprotein cholesterol were also reduced in the HFD group which received RF treatment. Furthermore, RF induced thermogenic-, adipogenic- and mitochondria-related gene expressions in BAT. In primary brown adipocytes, RF effectively stimulated the expressions of thermogenic- and mitochondria-related genes. In addition, to examine whether LIPIN1, a regulator of adipocyte differentiation, is regulated by RF, Lipin1 small interfering RNA (siRNA) and RF were pretreated in primary brown adipocytes. Pretreatment with Lipin1 siRNA and RF downregulated the DM-induced expression levels of thermogenic- and mitochondria-related genes. Moreover, RF markedly upregulated AMP-activated protein kinase. Our study shows that RF is capable of stimulating the differentiation of brown adipocytes through the modulation of thermogenic genes.

CONCLUSIONS

This study demonstrates that RF prevents the development of obesity in mice fed with a HFD and that it is also capable of stimulating the differentiation of brown adipocytes through the modulation of thermogenic genes, which suggests that RF has potential as a therapeutic application for the treatment or prevention of obesity.

Rubi Fructus (Rubus coreanus) Inhibits Differentiation to Adipocytes in 3T3-L1 Cells

Rubi Fructus (RF) is known to exert several pharmacological effects including antitumor, antioxidant, and anti-inflammatory activities. However, its antiobesity effect has not been reported yet. This study was focused on the antidifferentiation effect of RF extract on 3T3-L1 preadipocytes. When 3T3-L1 preadipocytes were differentiating into adipocytes, 10-100  μ g/mL of RF was added. Next, the lipid contents were quantified by Oil Red O staining. RF significantly reduced lipid accumulation and downregulated the expression of peroxisome proliferator-activated receptor γ (PPAR γ ), CCAAT0-enhancer-binding proteins α (C/EBP α ), adipocyte fatty acid-binding protein 2 (aP2), resistin, and adiponectin in ways that were concentration dependent. Moreover, RF markedly upregulated liver kinase B1 and AMP-activated protein kinase (AMPK). Interestingly, pretreatment with AMPK α siRNA and RF downregulated the expression of PPAR γ and C/EBP α protein as well as the adipocyte differentiation. Our study shows that RF is capable of inhibiting the differentiation of 3T3-L1 adipocytes through the modulation of PPAR γ , C/EBP α , and AMPK, suggesting that it has a potential for therapeutic application in the treatment or prevention of obesity.

Shikonin suppresses ERK 1/2 phosphorylation during the early stages of adipocyte differentiation in 3T3-L1 cells

Background

The naphthoquinone pigment, shikonin, is a major component of Lithospermum erythrorhizon and has been shown to have various biological functions, including antimicrobial, anti-inflammatory, and antitumor effects. In this study, we investigated the effect of shikonin on adipocyte differentiation and its mechanism of action in 3T3-L1 cells.

Methods

To investigate the effects of shikonin on adipocyte differentiation, 3T3-L1 cells were induced to differentiate using 3-isobutyl-1-methylzanthine, dexamethasone, and insulin (MDI) for 8 days in the presence of 0–2 μM shikonin. Oil Red O staining was performed to determine the lipid accumulation in 3T3-L1 cells. To elucidate the anti-adipogenic mechanism of shikonin, adipogenic transcription factors, the phosphorylation levels of ERK, and adipogenic gene expression were analyzed by Western blotting and quantitative real-time PCR. To further confirm that shikonin inhibits adipogenic differentiation through downregulation of ERK 1/2 activity, 3T3-L1 cells were treated with shikonin in the presence of FGF-2, an activator, or PD98059, an inhibitor, of the ERK1/2 signaling pathway.

Results

Shikonin effectively suppressed adipogenesis and downregulated the protein levels of 2 major transcription factors, PPARγ and C/EBPα, as well as the adipocyte specific gene aP2 in a dose-dependent manner. qRT-PCR analysis revealed that shikonin inhibited mRNA expression of adipogenesis-related genes, such as PPARγ, C/EBPα, and aP2. Adipocyte differentiation was mediated by ERK 1/2 phosphorylation, which was confirmed by pretreatment with PD98059 (an ERK 1/2 inhibitor) or FGF-2 (an ERK 1/2 activator). The phosphorylation of ERK1/2 during the early stages of adipogenesis in 3T3-L1 cells was inhibited by shikonin. We also confirmed that FGF-2-stimulated ERK 1/2 activity was attenuated by shikonin.

Conclusions

These results demonstrate that shikonin inhibits adipogenic differentiation via suppression of the ERK signaling pathway during the early stages of adipogenesis.

Lipidomics of essential fatty acids and oxygenated metabolites

Polyunsaturated fatty acids in mammals may be oxygenated into a myriad of bioactive products through di- and monooxygenases, products that are rapidly degraded to control their action. To evaluate the phenotypes of biological systems regarding this wide family of compounds, a lipidomics approach in function of time and compartments would be relevant. The current review takes into consideration most of the diverse oxygenated metabolites of essential fatty acids at large and their immediate degradation products. Their biological function and life span are considered. Overall, this is a fluxolipidomics approach that is emerging.

Loss of fat with increased adipose triglyceride lipase-mediated lipolysis in adipose tissue during laying stages in quail

The goal of the current study was to investigate regulation of key genes involved in lipid metabolism in adipose and liver to relate lipolytic and lipogenic capacities with physiological changes at the pre-laying, onset of laying, and actively laying stages of quail. Followed by a 50 % increase from pre-laying to onset of laying, adipose to body weight ratio was significantly reduced by 60 % from the onset of laying to the actively laying stage (P < 0.05), mainly resulting from the significantly increased adipocyte size from the pre-laying stage to the onset of laying and reduction of adipocyte size from the onset of laying to the actively laying stage (P < 0.05). In the adipose tissue of actively laying quail, increased protein expression and phosphorylation of adipose triglyceride lipase (ATGL) together with an elevated mRNA expression of comparative gene identification-58, an activator of ATGL, contributes to increased lipolytic activity, as proved by increased amounts of plasma non-esterified fatty acid (P < 0.05). In addition, decreased mRNA expression of fatty acid transport protein in the actively laying quail could contribute to the adipocyte hypotrophy (P < 0.05). In the liver, relative mRNA expression of apo-very low density lipoprotein (VLDL)-II increased significantly from the pre-laying to actively laying stages (P < 0.05), indicating increased apoVLDL-II actively facilitated VLDL secretion in the actively laying quail. These results suggest that the laying birds undergo active lipolysis in the adipocyte, and increase VLDL secretion from the liver in order to secure a lipid supply for yolk maturation.

Lupenone isolated from Adenophora triphylla var. japonica extract inhibits adipogenic differentiation through the downregulation of PPARγ in 3T3-L1 cells

Adenophora triphylla var. japonica (Campanulaceae) is known to have anti-inflammatory and anti-tussive effects. Dysfunction of adipocytes and adipose tissue in obesity is related to various inflammatory cytokines or adipokines. In this study, we investigated whether lupenone isolated from A. triphylla var. japonica extract inhibits adipocyte differentiation and expression of adipogenic marker genes in 3T3-L1 preadipocytes. We demonstrated that lupenone resulted in a significant reduction in lipid accumulation and expression of adipogenic marker genes in a dose-dependent manner. In addition, lupenone decreased the transcriptional activity of peroxisome proliferator-activated receptor γ (PPARγ) induced by troglitazone, and we also demonstrated that lupenone suppressed the PPARγ and CCAAT-enhancer-binding protein α (C/EBPα) protein levels. These findings demonstrated that lupenone isolated from A. triphylla var. japonica extract effectively inhibited adipocyte differentiation through downregulation of related transcription factor, particularly the PPARγ gene.

Identification of lipids and lipid-binding proteins in phloem exudates from Arabidopsis thaliana

The phloem plays a crucial role in assimilate and nutrient transport, pathogen response, and plant growth and development. Yet, few species have yielded pure phloem exudate and, if proteins need to be analysed, those species may not have sequenced genomes, making identification difficult. The enrichment of Arabidopsis thaliana phloem exudate in amounts large enough to allow for metabolite and protein analysis is described. Using this method, it was possible to identify 65 proteins present in the Arabidopsis phloem exudate. The majority of these proteins could be grouped by response to pathogens, stress, or hormones, carbon metabolism, protein interaction, modification, and turnover, and transcription factors. It was also possible to detect 11 proteins that play a role in lipid/fatty acid metabolism (aspartic protease, putative 3-β-hydroxysteroid dehydrogenase, UDP-sulphoquinovose synthase/SQD1, lipase, PIG-P-like protein: phosphatidylinositol-N-acetylglucosaminyltransferase), storage (glycine-rich protein), binding (annexin, lipid-associated family protein, GRP17/oleosin), and/or signalling (annexin, putative lipase, PIG-P-like protein). Along with putative lipid-binding proteins, several lipids and fatty acids could be identified. Only a few examples exist of lipids (jasmonic acid, oxylipins) or lipid-binding proteins (DIR1, acyl-CoA-binding protein) in the phloem. Finding hydrophobic compounds in an aqueous environment is not without precedence in biological systems: human blood contains a variety of lipids, many of which play a significant role in human health. In blood, lipids are transported while bound to proteins. The present findings of lipids and lipid-binding proteins in phloem exudates suggest that a similar long-distance lipid signalling exists in plants and may play an important role in plant growth and development.

New aspects of Phloem-mediated long-distance lipid signaling in plants

Plants are sessile and cannot move to appropriate hiding places or feeding grounds to escape adverse conditions. As a consequence, they evolved mechanisms to detect changes in their environment, communicate these to different organs, and adjust development accordingly. These adaptations include two long-distance transport systems which are essential in plants: the xylem and the phloem. The phloem serves as a major trafficking pathway for assimilates, viruses, RNA, plant hormones, metabolites, and proteins with functions ranging from synthesis to metabolism to signaling. The study of signaling compounds within the phloem is essential for our understanding of plant communication of environmental cues. Determining the nature of signals and the mechanisms by which they are communicated through the phloem will lead to a more complete understanding of plant development and plant responses to stress. In our analysis of Arabidopsis phloem exudates, we had identified several lipid-binding proteins as well as fatty acids and lipids. The latter are not typically expected in the aqueous environment of sieve elements. Hence, lipid transport in the phloem has been given little attention until now. Long-distance transport of hydrophobic compounds in an aqueous system is not without precedence in biological systems: a variety of lipids is found in human blood and is often bound to proteins. Some lipid-protein complexes are transported to other tissues for storage, use, modification, or degradation; others serve as messengers and modulate transcription factor activity. By simple analogy it raises the possibility that lipids and the respective lipid-binding proteins in the phloem serve similar functions in plants and play an important role in stress and developmental signaling. Here, we introduce the lipid-binding proteins and the lipids we found in the phloem and discuss the possibility that they may play an important role in developmental and stress signaling.

Effects of Clostridium difficile Toxin A on the proteome of colonocytes studied by differential 2D electrophoresis

Clostridium difficile is a spore-forming anaerobic pathogen, commonly associated with severe diarrhea or life-threatening pseudomembraneous colitis. Its main virulence factors are the single-chain, multi-domain toxin A (TcdA) and B (TcdB). Their glucosyltransferase domain selectively inactivates Rho proteins leading to a reorganization of the cytoskeleton. To study exclusively glucosyltransferase-dependent molecular effects of TcdA, human colonic cells (Caco-2) were treated with recombinant wild type TcdA and the glucosyltransferase deficient variant of the toxin, TcdA(gd) for 24h. Changes in the protein pattern of the colonic cells were investigated by 2-D DIGE and LCMS/MS methodology combined with detailed proteome mapping. gdTcdA did not induce any detectable significant changes in the protein pattern. Comparing TcdA-treated cells with a control group revealed seven spots of higher and two of lower intensity (p<0.05). Three proteins are involved in the assembly of the cytoskeleton (β-actin, ezrin, and DPYL2) and four are involved in metabolism and/or oxidative stress response (ubiquitin, DHE3, MCCB, FABPL) and two in regulatory processes (FUBP1, AL1A1). These findings correlate well to known effects of TcdA like the reorganization of the cytoskeleton and stress the importance of Rho protein glucosylation for the pathogenic effects of TcdA.

Protein-mediated Fatty Acid Uptake in the Heart

Long chain fatty acids (LCFAs) provide 70-80% of the energy for cardiac contractile activity. LCFAs are also essential for many other cellular functions, such as transcriptional regulation of proteins involved in lipid metabolism, modulation of intracellular signalling pathways, and as substrates for membrane constituents. When LCFA uptake exceeds the capacity for their cardiac utilization, the intracellular lipids accumulate and are thought to contribute to contractile dysfunction, arrhythmias, cardiac myocyte apoptosis and congestive heart failure. Moreover, increased cardiac myocyte triacylglycerol, diacylglycerol and ceramide depots are cardinal features associated with obesity and type 2 diabetes. In recent years considerable evidence has accumulated to suggest that, the rate of entry of long chain fatty acids (LCFAs) into the cardiac myocyte is a key factor contributing to a) regulating cardiac LCFA metabolism and b) lipotoxicity in the obese and diabetic heart. In the present review we i) examine the evidence indicating that LCFA transport into the heart involves a protein-mediated mechanism, ii) discuss the proteins involved in this process, including FAT/CD36, FABPpm and FATP1, iii) discuss the mechanisms involved in regulating LCFA transport by some of these proteins (including signaling pathways), as well as iv) the possible interactions of these proteins in regulating LCFA transport into the heart. In addition, v) we discuss how LCFA transport and transporters are altered in the obese/diabetic heart.

Novel functions of lipid-binding protein 5 in Caenorhabditis elegans fat metabolism

The lipid-binding protein (LBP) family is conserved from Caenorhabditis elegans to mammals and essential for fatty acid homeostasis. RNAi-mediated knockdown of nine C. elegans lbp family members revealed that lbp-5 regulates fat accumulation. C. elegans LBP-5 bound directly to various fatty acids with varying affinities. lbp-5 expression in nhr-49(nr2041) worms was much lower than in N2 worms. Nhr-49 transcriptional activity also decreased with lbp-5 deletion, suggesting that they may work together as functional partners in fat metabolism. In support of this notion, LBP-5 translocated into nuclei, where it appeared to influence C. elegans NHR-49 target genes involved in energy metabolism. Interestingly, LBP-5 is required for stearic acid-induced transcription of NHR-49 target genes. Thus, this knowledge could help identify therapeutic targets to treat obesity and diseases associated with nematode-host interactions.

Molecular cloning and tissue expression of the fatty acid-binding protein (Es-FABP) gene in female Chinese mitten crab (Eriocheir sinensis)

Background

Fatty acid-binding proteins (FABPs), small cytosolic proteins that function in the uptake and utilization of fatty acids, have been extensively studied in higher vertebrates while invertebrates have received little attention despite similar nutritional requirements during periods of reproductive activity.

Results

Therefore, a cDNA encoding Eriocheir sinensis FABP (Es-FABP) was cloned based upon EST analysis of a hepatopancreas cDNA library. The full length cDNA was 750 bp and encoded a 131 aa polypeptide that was highly homologous to related genes reported in shrimp. The 9108 bp Es-FABP gene contained four exons that were interrupted by three introns, a genomic organization common among FABP multigene family members in vertebrates. Gene expression analysis, as determined by RT-PCR, revealed the presence of Es-FABP transcripts in hepatopancreas, hemocytes, ovary, gills, muscle, thoracic ganglia, heart, and intestine, but not stomach or eyestalk. Real-time quantitative RT-PCR analysis revealed that Es-FABP expression in ovary, hemocytes, and hepatopancreas was dependent on the status of ovarian development, with peak expression observed in January.

Conclusions

Evidence provided in the present report supports a role of Es-FABP in lipid transport during the period of rapid ovarian growth in E. sinensis, and indirectly confirms the participation of the hepatopancreas, ovary, and hemocytes in lipid nutrient absorption and utilization processes.

FABP4: a novel candidate gene for polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is a complex multifactorial disorder involving a number of genetic and environmental factors. Adipocyte-fatty acid-binding protein (FABP4) is an adipokine regulating systemic insulin sensitivity, lipid and glucose metabolism. In humans serum FABP4 levels correlate significantly with features of PCOS. Previous researches showed strong evidences that FABP4 impacted the developing of PCOS possibly through its protein alteration or transcription regulation. Thus, the present study is the first attempt to identify the possible genetic role of FABP4 gene in the development of PCOS.

METHODS

About 1000 bp of the promoter region and four exons of FABP4 gene of 178 PCOS patients and 171 healthy controls were directly sequenced.

RESULTS

Three polymorphisms, rs16909225, rs3834363, and rs16909220, were identified, of which rs16909225 and rs16909220 were completely linked (r² = 1) and not associated with the development of PCOS, while the -2-bp/-2-bp genotype of rs3834363 was significantly higher in PCOS than in the controls (χ² = 7.39, df = 1, P = 0.007, OR = 1.80 95% CI: 1.18-2.75).

CONCLUSION

The present study is the first to establish an association between FABP4 gene polymorphisms and the development of PCOS.

Discrete localization of various fatty-acid-binding proteins in various cell populations of mouse retina

Various fatty acids (FAs) are involved as an energy source in many different functions in the organism. They are also essential ingredients of membranous lipids and act as intracellular signaling molecules. Intracellular fatty-acid-binding proteins (FABPs) comprise a family of soluble lipid-binding proteins with low molecular masses and solubilize long-chain FAs to allow intracellular translocation in the aqueous cytosol. To clarify the functions of FABPs in the retina, which is remarkably rich in polyunsaturated FAs, we have investigated the localization of B (brain type)-, H (heart type)-, E (epidermal type)-, and A (adipocyte type)-FABPs in adult mouse retinae by immunohistochemistry. In order to determine the possible involvement of FABPs in retinal degenerative diseases, we have also examined changes in FABP expression in light-induced photoreceptor cell degeneration (photic injury). The discrete localization of B-, H-, E-, and A-FABP species in various cell populations of the retina has been clarified: B-FABP is mainly localized in the cone photoreceptor cells, H-FABP in some populations of amacrine/bipolar/horizontal interneurons, and E-FABP in ganglion cells, with A-FABP-like immunoreactivity being located in resident microglia of normal retinae. E-FABP has further been localized in invasive macrophages in damaged retinae following photic injury, allowing discrete identification of the resident microglia and invasive macrophages by A- and E-FABP immunoreactivity, respectively.

Identification of proteins that interact with podocin using the yeast 2-hybrid system

PURPOSE

As a membrane protein at the insertion site of the slit diaphragm (SD) complex in podocyte foot processes, podocin has been reported to act as a scaffolding protein required to maintain or regulate the structural integrity of the SD. In order to identify proteins that associate or interact with podocin, we screened a mouse kidney complementary DNA (cDNA) library using a yeast 2-hybrid system.

MATERIALS AND METHODS

1) The full-length cDNA of podocin from the mouse kidney was amplified by Polymerase Chain Reaction (PCR), 2) The PCR product was cloned into a pGBKT7 vector, pGBKT7-podocin, 3) After the pGBKT7-podocin was transformed into AH109, the AH109/pGBKT7-podocin product was obtained, 4) The mouse kidney cDNA library was transformed into the AH109/pGBKT7-podocin and screened by selection steps, 5) Next, twelve clones were cultured and isolated, 6) The yeast-purified plasmids were transformed into Escherichia coli (E. coli) by heat shock, and 7) To identify the activation domain (AD)/library inserts, we digested them with Him III, and the fragments were then sequenced.

RESULTS

12 positive clones that interacted with podocin were obtained by screening a mouse kidney cDNA library using pGBKT7-podocin. Among them, only 4 clones were found to function at the podocyte where podocin is present.

CONCLUSION

Additional studies are needed to clarify the role and interaction with podocin and candidates.

A-FABP, a candidate progression marker of human transitional cell carcinoma of the bladder, is differentially regulated by PPAR in urothelial cancer cells

Superficial pT1 bladder tumors are characterized by a high risk of recurrence and progression in grade and stage. Few studies provided evidence that loss of adipocyte-fatty acid binding protein (A-FABP) expression was associated with bladder cancer progression. A-FABP is a lipid binding protein playing a role in intracellular lipid transport and metabolism, as well as in signal transduction. We reported from bladder tumors that decrease of A-FABP transcript level significantly correlated to tumor stage and to histologic grade (p < 0.05). Namely, in poor prognosis high grade pT1 tumors there was a loss of A-FABP expression compared to good prognosis tumors suggesting that re-expression of A-FABP could be a therapeutic approach in early stage bladder cancer to prevent disease progression. We demonstrated for the first time that this marker is upregulated by Peroxisome Proliferator-Activated Receptor (PPAR) alpha, beta and gamma in T24 cells (derived from an undifferentiated grade III carcinoma) and only by PPARbeta in RT4 cells (derived from a well differentiated grade I papillary tumor). This effect occurred through a PPAR-dependent transcriptional mechanism without modifying mRNA stability and interestingly required de novo protein synthesis. Data as a whole suggest a prognostic significance of A-FABP in bladder cancer outcome and the potential utility of overexpression of this protein by PPAR agonists open up new perspectives in the treatment of bladder cancer. (c) 2008 Wiley-Liss, Inc.

Proteome of human T lymphocytes with treatment of cyclosporine and polysaccharopeptide: Analysis of significant proteins that manipulate T cells proliferation and immunosuppression

The aberrant activation of T lymphocyte proliferation is one of the key events in organ transplant recipients and autoimmune disorders. The present study adopted a gel-based proteomics approach to define the proteins representative of the T cell proliferation and to discover the molecules that play critical roles during the suppression of T cell proliferation. Human T lymphocytes were isolated from healthy donors and primed with phytohemagglutinin (PHA) to undergo proliferation. Two medical fungal products with specific T cell activation inhibitory properties, cyclosporine A (CsA) and polysaccharopeptide (PSP), were used to study the proteins that manipulate T cell proliferation. After demonstrating their similar effects on cell proliferation, cell survival and interleuklin-2 (IL-2) secretion, significant quantitative protein alterations were detected between the CsA- and PSP-treated T cell proteome. These altered proteins were identified by MALDI-TOF and classified into 3 categories: (i) proteins affected by both CsA and PSP, (ii) proteins affected by CsA alone, and (iii) proteins affected by PSP alone. Most of these altered proteins have functional significance in protein degradation, the antioxidant pathway, energy metabolism and immune cell regulation.

Cardiac substrate uptake and metabolism in obesity and type-2 diabetes: role of sarcolemmal substrate transporters

Cardiovascular disease is the primary cause of death in obesity and type-2 diabetes mellitus (T2DM). Alterations in substrate metabolism are believed to be involved in the development of both cardiac dysfunction and insulin resistance in these conditions. Under physiological circumstances the heart utilizes predominantly long-chain fatty acids (LCFAs) (60-70%), with the remainder covered by carbohydrates, i.e., glucose (20%) and lactate (10%). The cellular uptake of both LCFA and glucose is regulated by the sarcolemmal amount of specific transport proteins, i.e., fatty acid translocase (FAT)/CD36 and GLUT4, respectively. These transport proteins are not only present at the sarcolemma, but also in intracellular storage compartments. Both an increased workload and the hormone insulin induce translocation of FAT/CD36 and GLUT4 to the sarcolemma. In this review, recent findings on the insulin and contraction signalling pathways involved in substrate uptake and utilization by cardiac myocytes under physiological conditions are discussed. New insights in alterations in substrate uptake and utilization during insulin resistance and its progression towards T2DM suggest a pivotal role for substrate transporters. During the development of obesity towards T2DM alterations in cardiac lipid homeostasis were found to precede alterations in glucose homeostasis. In the early stages of T2DM, relocation of FAT/CD36 to the sarcolemma is associated with the myocardial accumulation of triacylglycerols (TAGs) eventually leading to an impaired insulin-stimulated GLUT4-translocation. These novel insights may result in new strategies for the prevention of development of cardiac dysfunction and insulin resistance in obesity and T2DM.

Incorporation of arachidonic and stearic acids bound to L-FABP into nuclear and endonuclear lipids from rat liver cells

The incorporation of exogenous fatty acids bound to L-FABP into nuclei was studied. Rat liver cell nuclei and nuclear matrices (membrane depleted nuclei) were incubated in vitro with [1-(14)C]18:0 and 20:4n-6 either free or bound to L-FABP, ATP and CoA. FA esterification in whole nuclei and endonuclear lipids was ATP-CoA-dependent, and with specificity regarding fatty acid type and lipid class. 18:0 and 20:4n-6, free or L-FABP bound, showed the same incorporation and esterification pattern in lipids of whole nuclei. Only 20:4n-6 L-FABP bound was less incorporated into TAG with respect to free 20:4n-6. In the nuclear matrix, 18:0 free or L-FABP bound was esterified with a higher specific activity (SA) into: PtdEtn > PtdIns, PtdSer > PtdCho. 20:4n-6 free or L-FABP bound was esterified into: PtdIns > PtdEtn > PtdCho. 20:4n-6:L-FABP was esterified in endonuclear total-PL and PtdIns with a greater SA with respect to free 20:4n-6 and with a minor one as FFA. To summarize, trafficking of FA to nuclei includes esterification of 18:0 and 20:4n-6 either free or L-FABP-bound, into nuclear and endonuclear lipids by an ATP-CoA-dependent pathway. Endonuclear fatty acid esterification was more active than that in whole nuclei, and independent of the nuclear membrane. Esterification patterns of fatty acids L-FABP-bound or free into whole nuclear lipids were the same whereas in the nuclear matrix, L-FABP could play an important role in the mobilization of 20:4n-6 into specific sites of utilization such as the PtdIns pools.

Transcriptional profiling of mesenchymal stromal cells from young and old rats in response to Dexamethasone

Background

Marrow-derived stromal cells (MSCs) maintain the capability of self-renewal and differentiation into multiple lineages in adult life. Age-related changes are recognized by a decline in the stemness potential that result in reduced regeneration potential of the skeleton. To explore the molecular events that underline skeletal physiology during aging we catalogued the profile of gene expression in ex vivo cultured MSCs derived from 3 and 15 month old rats. The ex vivo cultured cells were analyzed following challenge with or without Dexamethasone (Dex). RNA retrieved from these cells was analyzed using Affymetrix Gene Chips to compare the effect of Dex on gene expression in both age groups.

Results

The molecular mechanisms that underline skeletal senescence were studied by gene expression analysis of RNA harvested from MSCs. The analysis resulted in complex profiles of gene expression of various differentiation pathways. We revealed changes of lineage-specific gene expression; in general the pattern of expression included repression of proliferation and induction of differentiation. The functional analysis of genes clustered were related to major pathways; an increase in bone remodeling, osteogenesis and muscle formation, coupled with a decrease in adipogenesis. We demonstrated a Dex-related decrease in immune response and in genes that regulate bone resorption and an increase in osteoblastic differentiation. Myogenic-related genes and genes that regulate cell cycle were induced by Dex. While Dex repressed genes related to adipogenesis and catabolism, this decrease was complementary to an increase in expression of genes related to osteogenesis.

Conclusion

This study summarizes the genes expressed in the ex vivo cultured mesenchymal cells and their response to Dex. Functional clustering highlights the complexity of gene expression in MSCs and will advance the understanding of major pathways that trigger the natural changes underlining physiological aging. The high throughput analysis shed light on the anabolic effect of Dex and the relationship between osteogenesis, myogenesis and adipogenesis in the bone marrow cells.

Microtubular integrity differentially modifies the saturated and unsaturated fatty acid metabolism in cultured Hep G2 human hepatoma cells

The influence of cytoskeleton integrity on the metabolism of saturated and unsaturated FA was studied in surface cultures and cell suspensions of human Hep G2 hepatoma cells. We found that colchicine (COL), nocodazol, and vinblastin produced a significant inhibition in the incorporation of labeled saturated FA, whereas incorporation of the unsaturated FA remained unaltered. These microtubule-disrupting drugs also diminished Delta9-, Delta5-, and Delta6-desaturase capacities. The effects produced by COL were dose (0-50 microM) and time (0-300 min) dependent, and were antagonized by stabilizing agents (phalloidin and DMSO). Dihydrocytochalasin B (20 microM) was tested as a microfilament-disrupting drug and produced no changes in either the incorporation of [14C] FA or the desaturase conversion of the substrates. We hypothesized that the interactions between cytoskeleton and membrane proteins such as FA desaturases may explain the functional organization, facilitating both substrate channeling and regulation of unsaturated FA biosynthesis.

Alterations in intestinal fatty acid metabolism in inflammatory bowel disease

Inflammatory bowel disease (IBD) constitutes a severe intestinal disorder in developed countries with increasing incidence worldwide. Upcoming evidence indicates an important role of intestinal epithelial barrier function in the development of IBD. Fatty acids exert nutritional and protective effects on enterocytes, serve as activators of transcription and constitute precursors of inflammatory mediators. The aim of this study was to investigate differential regulation of genes involved in fatty acid uptake and endogenous fatty acid biosynthesis in IBD. Mucosal biopsy specimens from non-affected regions of the intestine were subjected to DNA microarray analysis. Gene array analysis revealed a variety of genes involved in fatty acid uptake and synthesis to be differentially expressed in ileum and colon of selected IBD patients. To verify these results, real-time RT-PCR was performed for selected regulated candidate genes in larger IBD sample numbers. In single biopsy analysis long chain acyl-CoA synthetase (ACSL) 1 and 4 were upregulated in IBD (P<0.05), while a significant decrease in fatty acid synthase expression was found in ileum and colon of ulcerative colitis patients (P<0.001). Expression of the transcription factor liver X receptor (LXR) which was previously shown to induce fatty acid synthase gene expression was not altered on mRNA level in IBD. However, in cell culture experiments using the human intestinal cell line LS174T induction of fatty acid synthase by the LXR ligand T0901317 was inhibited by TNFalpha. Moreover, these experiments indicated a decrease of LXR protein levels by TNFalpha treatment. These data suggest that the decrease of fatty acid synthase expression in ulcerative colitis patients could be at least partially due to a loss of LXR expression and function in the presence of pro-inflammatory cytokines. Observed alterations in expression of genes of fatty acid metabolism may contribute to the pathophysiology of ulcerative colitis.

Long-chain fatty acid uptake and FAT/CD36 translocation in heart and skeletal muscle

Cellular long-chain fatty acid (LCFA) uptake constitutes a process that is not yet fully understood. LCFA uptake likely involves both passive diffusion and protein-mediated transport. Several lines of evidence support the involvement of a number of plasma membrane-associated proteins, including fatty acid translocase (FAT)/CD36, plasma membrane-bound fatty acid binding protein (FABPpm), and fatty acid transport protein (FATP). In heart and skeletal muscle primary attention has been given to unravel the mechanisms by which FAT/CD36 expression and function are regulated. It appears that both insulin and contractions induce the translocation of intracellular stored FAT/CD36 to the plasma membrane to increase cellular LCFA uptake. This review focuses on this novel mechanism of regulation of LCFA uptake in heart and skeletal muscle in health and disease. The distinct signaling pathways underlying insulin-induced and contraction-induced FAT/CD36 translocation will be discussed and a comparison will be made with the well-defined glucose transport system involving the glucose transporter GLUT4. Finally, it is hypothesized that malfunctioning of recycling of these transporters may lead to intracellular triacylglycerol (TAG) accumulation and cellular insulin resistance. Current data indicate a pivotal role for FAT/CD36 in the regulation of LCFA utilization in heart and skeletal muscle under normal conditions as well as during the altered LCFA utilization observed in obesity and insulin resistance. Hence, FAT/CD36 might provide a useful therapeutic target for the prevention or treatment of insulin resistance.

Loss of expression of the adipocyte-type fatty acid-binding protein (A-FABP) is associated with progression of human urothelial carcinomas

Bladder cancer is the fifth most common malignancy in the world and represents the second most common cause of death among genitourinary tumors. Current prognostic parameters such as grade and stage cannot predict with certainty the long-term outcome of bladder cancer, and as a result there is a pressing need to identify markers that may predict tumor behavior. Earlier we identified the adipocyte fatty acid-binding protein (A-FABP), a small-molecular-mass fatty acid-binding protein that functions by facilitating the intracellular diffusion of fatty acids between cellular compartments as a putative marker of progression based on a limited study of fresh bladder urothelial carcinomas (UCs) (Celis, J. E., Ostergaard, M., Basse, B., Celis, A., Lauridsen, J. B., Ratz, G. P., Andersen, I., Hein, B., Wolf, H., Orntoft, T. F., and Rasmussen, H. H. (1996) Loss of adipocyte-type fatty acid binding protein and other protein biomarkers is associated with progression of human bladder transitional cell carcinomas. Cancer Res.56, 4782-4790). Here we have comprehensively examined the protein expression profiles of a much larger sample set consisting of 153 bladder specimens (46 nonmalignant biopsies, 11 pTa G1, 40 pTa G2, 10 pTa G3, 13 pT1 G3, 23 pT2-4 G3, and 10 pT2-4 G4) by gel-based proteomics in combination with immunohistochemistry (IHC) using a peptide-based rabbit polyclonal antibody that reacts specifically with this protein. Proteomic profiling showed a striking down-regulation of A-FABP in invasive lesions, a fact that correlated well with immunohistochemical analysis of the same samples. The IHC results were confirmed by using a tissue microarray (TMA) containing 2,317 samples derived from 1,849 bladder cancer patients. Moreover, we found that the altered expression of A-FABP in invasive UCs is not due to deregulated expression of peroxisome proliferator-activated receptor gamma (PPARgamma), a trans-activator of A-FABP. Taken together, these results provide evidence that deregulation of A-FABP may play a role in bladder cancer progression and suggest that A-FABP could have a significant prognostic value in combination with other biomarkers.

The tumour-associated antigen EpCAM upregulates the fatty acid binding protein E-FABP

The epithelial cell adhesion molecule, EpCAM, is a transmembrane glycoprotein associated with both benign and malignant proliferation. In cancer cells, expression levels of this tumour-associated antigen correlate positively with the grade of dysplasia and are also a negative prognostic factor for breast cancer patients. De novo expression of EpCAM resulted in the rapid upregulation of the proto-oncogene c-Myc along with enhanced cell proliferation and metabolism. Here, we analyzed the effects of EpCAM onto the proteome of epithelial cells. The epidermal fatty acid binding protein, E-FABP, was identified as a new EpCAM-regulated protein. E-FABP is a major target of c-Myc and was rapidly upregulated upon induction of EpCAM. Additionally, E-FABP levels correlated with the amount of EpCAM in permanent squamous cell carcinoma lines and in vivo in primary head and neck carcinomas. Taken together, these results provide further evidence for the direct involvement of EpCAM in signalling processes, gene regulation, and cellular metabolism supporting its important role in tumour biology.

L-FABP is exclusively expressed in alveolar macrophages within the myeloid lineage

Peroxisome proliferator-activated receptors (PPARs) play a role in inflammation and, in particular, PPARgamma is involved in monocyte/macrophage differentiation. Members of the fatty acid-binding protein (FABP) family have been reported to function as transactivators for PPARs. Therefore, the expression of PPARs and FABPs in the myeloid lineage was investigated by real-time PCR and immunofluorescence analysis. We found adipocyte-, epidermal-, and heart-type FABP to be ubiquitously expressed within the myeloid lineage. In contrast, liver-type FABP was exclusively detected in murine alveolar macrophages (AM), confirmed on protein level by double fluorescence analysis. The PPAR subtypes also showed a temporally and spatially regulated expression pattern in myeloid cells: the beta-subtype was expressed in bone marrow, peritoneal, and alveolar macrophages, whereas it was not detected in dendritic cells (DCs). The gamma1-isoform was present in all cells, however, at different levels, whereas the gamma2-isoform was expressed in alveolar macrophages and dendritic cells. A low level PPARalpha mRNA could be detected in peritoneal macrophages and immature dendritic cells but not in mature dendritic cells and bone marrow macrophages. Interestingly, PPARalpha mRNA was also absent in the alveolar macrophages although liver-type FABP was expressed, indicating that gene expression of liver-type FABP was independent of PPARalpha. Since liver-type FABP is known as transactivator of PPARgamma the simultaneous expression of both proteins may have general implications for the activation of PPARgamma in alveolar macrophages.

Liver fatty acid-binding protein gene ablation inhibits branched-chain fatty acid metabolism in cultured primary hepatocytes

Whereas the role of liver fatty acid-binding protein (L-FABP) in the uptake, transport, mitochondrial oxidation, and esterification of normal straight-chain fatty acids has been studied extensively, almost nothing is known regarding the function of L-FABP in peroxisomal oxidation and metabolism of branched-chain fatty acids. Therefore, phytanic acid (most common dietary branched-chain fatty acid) was chosen to address these issues in cultured primary hepatocytes isolated from livers of L-FABP gene-ablated (-/-) and wild type (+/+) mice. These studies provided three new insights: First, L-FABP gene ablation reduced maximal, but not initial, uptake of phytanic acid 3.2-fold. Initial uptake of phytanic acid uptake was unaltered apparently due to concomitant 5.3-, 1.6-, and 1.4-fold up-regulation of plasma membrane fatty acid transporter/translocase proteins (glutamic-oxaloacetic transaminase, fatty acid transport protein, and fatty acid translocase, respectively). Second, L-FABP gene ablation inhibited phytanic acid peroxisomal oxidation and microsomal esterification. These effects were consistent with reduced cytoplasmic fatty acid transport as evidenced by multiphoton fluorescence photobleaching recovery, where L-FABP gene ablation reduced the cytoplasmic, but not membrane, diffusional component of NBD-stearic acid movement 2-fold. Third, lipid analysis of the L-FABP gene-ablated hepatocytes revealed an altered fatty acid phenotype. Free fatty acid and triglyceride levels were decreased 1.9- and 1.6-fold, respectively. In summary, results with cultured primary hepatocytes isolated from L-FABP (+/+) and L-FABP (-/-) mice demonstrated for the first time a physiological role of L-FABP in the uptake and metabolism of branched-chain fatty acids.

Genetic variation in fatty acid-binding protein-4 and peroxisome proliferator-activated receptor gamma interactively influence insulin sensitivity and body composition in males

Obesity and type 2 diabetes are closely related, multifactorial metabolic conditions characterized by alterations in energy metabolism and glucose homeostasis, respectively. Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-dependent transcription factor that regulates genes involved in lipid and glucose homeostasis, including the adipocyte-specific fatty acid-binding protein (FABP4). In turn, FABP4 binds fatty acids and transports them to the nucleus where the FABP4/fatty acid complex activates PPARgamma in a positive feedback loop. In this study, we tested the hypothesis that the polymorphisms, FABP4-376 and PPARgamma Pro12Ala, interactively influence insulin sensitivity and body composition in nondiabetic, Hispanic and non-Hispanic white males (n = 314) participating in the San Luis Valley Diabetes Study (SLVDS). Although the individual sites were not statistically significantly associated with any of the outcomes, we found statistically significant interaction terms in 2-way analysis of covariance (ANCOVA) models for homeostasis model assessment of insulin resistance (HOMA-IR) (P =.014) and lean mass (P =.019). While the PPARgamma Pro12Ala site was the only statistically significant predictor of fat mass in the 2-way model (P =.012), the FABP4 and PPARgamma main effect terms individually became stronger when considered in one model compared with the analysis of each polymorphism separately. These findings provide evidence that FABP4 and PPARgamma work together to influence a biologic pathway affecting insulin sensitivity and body composition, illustrating the importance of investigating the joint effect of genes in determining susceptibility for complex disease.

Changes in gene expression during chemical-induced nephrocarcinogenicity in the Eker rat

Hydroquinone (HQ) is a rodent carcinogen and a potential human carcinogen. Glutathione conjugation of HQ enhances its biological reactivity, and 2,3,5-tris-(glutathion-S-yl)hydroquinone (TGHQ) is a potent nephrotoxicant and nephrocarcinogen in the Eker rat. Moreover, a single exposure of primary epithelial cells derived from Eker rat kidneys to TGHQ transforms these cells into an immortalized phenotype (quinol-thioether transformed rat renal epithelial (QT-RRE) cells). The Eker rat bears a mutation in one allele of the tuberous sclerosis-2 (Tsc-2) tumor suppressor gene, which predisposes the animals to the development of spontaneous and chemical-induced renal cell carcinoma. Thus, the Eker rat provides a unique model for elucidating the mechanisms of renal tubular epithelial carcinogeneisis. cDNA microarray analysis of QT-RRE3 cells and of tumor tissue derived from the kidneys of Eker rats treated with TGHQ revealed alterations (by threefold or greater) in the expression of a total of 80 genes. Fifteen percent of these genes exhibited similar expression patterns in both QT-RRE cells and tumor tissue. The differentially expressed genes primarily participate in three major areas: (1) signal transduction or in the regulation of signal transduction (extracellular signal regulated kinase 2 (ERK2); protein kinase CK2; protein kinase B; c-jun; NF-kappaB; ras-related GTPases; annexins), (2) stress response, tissue remodeling, and DNA repair (glutathione-S-transferases; procollagen c proteinase enhancer; plasminogen activator; tissue inhibitor of metalloprotease 3; apurinic/apyrimidic endonuclease), and (3) electron transport and energy homeostasis (cytochrome c oxidase subunits). The changes in the expression of many of these genes was confirmed by reverse transcription (RT)-polymerase chain reactions (PCR) using primers specific for the differentially expressed genes. As an example, the annexin I and II genes, implicated in signal transduction, were highly induced in tumor tissue and also in dysplastic lesions isolated from the kidneys of rats treated chronically with TGHQ. The annexin I and II proteins were also upregulated in tumor tissue, which probably play an important role in TGHQ-induced nephrocarcinogenesis. Moreover, in the present study, a tumorigenicity assay using athymic nude mice revealed that QT-RRE cell lines formed tumors when injected in the subcutis of nude mice, providing evidence that the cells are malignantly transformed. Histopathological analysis further indicated that the tumors were composed of neoplastic cells, resembling renal carcinoma cells with varying degrees of atypia, with the presence of apoptotic and mitotic figures.

Variation in the FABP2 promoter alters transcriptional activity and is associated with body composition and plasma lipid levels

The fatty acid-binding proteins (FABPs) are cytoplasmic proteins involved in intracellular fatty acid transport and metabolism. FABP2, the intestinal-type FABP, is expressed exclusively in enterocytes in the small intestine. In previous studies of an Ala54Thr substitution in FABP2, the Thr-allele showed association with increased lipid oxidation, elevated plasma lipids, and impaired insulin sensitivity. We screened roughly 1 kb 5' of the FABP2 initiation codon and identified three insertion/deletion polymorphisms and four single nucleotide polymorphisms (SNPs). Three of the SNPs were in complete linkage disequilibrium with the three insertion/deletion polymorphisms, defining exactly two haplotypes (FABP2p-ID). We tested the hypothesis that this variation alters gene expression by transfecting Caco-2 cells with pGL3-Basic constructs containing opposite FABP2p-ID haplotypes. Luciferase assays showed a statistically significant two-fold increase in gene expression of the pGL3-insertion construct over the pGL3-deletion construct (P<0.001; n=5). We also tested for association between three FABP2 variants and measurements of body composition, plasma lipids, and insulin sensitivity in non-diabetic control subjects from the San Luis Valley Diabetes Study (n=714). The only informative variant, FABP2p-ID, was statistically significantly associated with body mass index (P=0.042) and marginally associated with fat mass (P=0.084), cholesterol (P=0.066), and HOMA IR (a derived measure of insulin resistance; P=0.062) in the entire cohort. Similar associations were seen only in non-Hispanics when the analysis was stratified by ethnicity. Within the non-Hispanic subgroup, the effects of FABP2p-ID on plasma lipids were sex-specific. These results suggest that genetic variation in the 5' region of FABP2 affects transcriptional activity, presumably leading to alterations in body composition and lipid processing.