Intronic polymorphism in the fatty acid transport protein 1 gene is associated with increased plasma triglyceride levels in a French population

FATP4 deletion in liver cells induces elevation of extracellular lipids via metabolic channeling towards triglycerides and lipolysis

Evidence from mice with global deletion of fatty-acid transport protein4 (FATP4) indicates its role on β-oxidation and triglycerides (TG) metabolism. We reported that plasma glycerol and free fatty acids (FA) were increased in liver-specific Fatp4 deficient (L-FATP4-/-) mice under dietary stress. We hypothesized that FATP4 may mediate hepatocellular TG lipolysis. Here, we demonstrated that L-FATP4-/- mice showed an increase in these blood lipids, liver TG, and subcutaneous fat weights. We therefore studied TG metabolism in response to oleate treatment in two experimental models using FATP4-knockout HepG2 (HepKO) cells and L-FATP4-/- hepatocytes. Both FATP4-deificient liver cells showed a significant decrease in β-oxidation products by ∼30-35% concomitant with marked upregulation of CD36, FATP2, and FATP5 as well as lipoprotein microsomal-triglyceride-transfer protein genes. By using 13C3D5-glycerol, HepKO cells displayed an increase in metabolically labelled TG species which were further increased with oleate treatment. This increase was concomitant with a step-wise elevation of TG in cells and supernatants as well as the secretion of cholesterol very low-density and high-density lipoproteins. Upon analyzing TG lipolytic enzymes, both mutant liver cells showed marked upregulated expression of hepatic lipase, while that of hormone-sensitive lipase and adipose-triglyceride lipase was downregulated. Lipolysis measured by extracellular glycerol and free FA was indeed increased in mutant cells, and this event was exacerbated by oleate treatment. Taken together, FATP4 deficiency in liver cells led to a metabolic shift from β-oxidation towards lipolysis-directed TG and lipoprotein secretion, which is in line with an association of FATP4 polymorphisms with blood lipids.

Fatty Acyl Coenzyme A Synthetase Fat1p Regulates Vacuolar Structure and Stationary-Phase Lipophagy in Saccharomyces cerevisiae

During yeast stationary phase, a single spherical vacuole (lysosome) is created by the fusion of several small ones. Moreover, the vacuolar membrane is reconstructed into two distinct microdomains. Little is known, however, about how cells maintain vacuolar shape or regulate their microdomains. Here, we show that Fat1p, a fatty acyl coenzyme A (acyl-CoA) synthetase and fatty acid transporter, and not the synthetases Faa1p and Faa4p, is essential for vacuolar shape preservation, the development of vacuolar microdomains, and cell survival in stationary phase of the yeast Saccharomyces cerevisiae. Furthermore, Fat1p negatively regulates general autophagy in both log- and stationary-phase cells. In contrast, Fat1p promotes lipophagy, as the absence of FAT1 limits the entry of lipid droplets into the vacuole and reduces the degradation of liquid droplet (LD) surface proteins. Notably, supplementing with unsaturated fatty acids or overexpressing the desaturase Ole1p can reverse all aberrant phenotypes caused by FAT1 deficiency. We propose that Fat1p regulates stationary phase vacuolar morphology, microdomain differentiation, general autophagy, and lipophagy by controlling the degree of fatty acid saturation in membrane lipids. IMPORTANCE The ability to sense environmental changes and adjust the levels of cellular metabolism is critical for cell viability. Autophagy is a recycling process that makes the most of already-existing energy resources, and the vacuole/lysosome is the ultimate autophagic processing site in cells. Lipophagy is an autophagic process to select degrading lipid droplets. In yeast cells in stationary phase, vacuoles fuse and remodel their membranes to create a single spherical vacuole with two distinct membrane microdomains, which are required for yeast lipophagy. In this study, we discovered that Fat1p was capable of rapidly responding to changes in nutritional status and preserving cell survival by regulating membrane lipid saturation to maintain proper vacuolar morphology and the level of lipophagy in the yeast S. cerevisiae. Our findings shed light on how cells maintain vacuolar structure and promote the differentiation of vacuole surface microdomains for stationary-phase lipophagy.

Withaferin A Promotes White Adipose Browning and Prevents Obesity Through Sympathetic Nerve-Activated Prdm16-FATP1 Axis

The increasing prevalence of obesity has resulted in demands for the development of new effective strategies for obesity treatment. Withaferin A (WA) shows a great potential for prevention of obesity by sensitizing leptin signaling in the hypothalamus. However, the mechanism underlying the weight- and adiposity-reducing effects of WA remains to be elucidated. In this study, we report that WA treatment induced white adipose tissue (WAT) browning, elevated energy expenditure, decreased respiratory exchange ratio, and prevented high-fat diet-induced obesity. The sympathetic chemical denervation dampened the WAT browning and also impeded the reduction of adiposity in WA-treated mice. WA markedly upregulated the levels of Prdm16 and FATP1 (Slc27a1) in the inguinal WAT (iWAT), and this was blocked by sympathetic denervation. Prdm16 or FATP1 knockdown in iWAT abrogated the WAT browning-inducing effects of WA and restored the weight gain and adiposity in WA-treated mice. Together, these findings suggest that WA induces WAT browning through the sympathetic nerve-adipose axis, and the adipocytic Prdm16-FATP1 pathway mediates the promotive effects of WA on white adipose browning.

The Role of Lipid Metabolism in T Lymphocyte Differentiation and Survival

The differentiation and effector functions of both the innate and adaptive immune system are inextricably linked to cellular metabolism. The features of metabolism which affect both arms of the immune system include metabolic substrate availability, expression of enzymes, transport proteins, and transcription factors which control catabolism of these substrates, and the ability to perform anabolic metabolism. The control of lipid metabolism is central to the appropriate differentiation and functions of T lymphocytes, and ultimately to the maintenance of immune tolerance. This review will focus on the role of fatty acid (FA) metabolism in T cell differentiation, effector function, and survival. FAs are important sources of cellular energy, stored as triglycerides. They are also used as precursors to produce complex lipids such as cholesterol and membrane phospholipids. FA residues also become incorporated into hormones and signaling moieties. FAs signal via nuclear receptors and their channeling, between storage as triacyl glycerides or oxidation as fuel, may play a role in survival or death of the cell. In recent years, progress in the field of immunometabolism has highlighted diverse roles for FA metabolism in CD4 and CD8 T cell differentiation and function. This review will firstly describe the sensing and modulation of the environmental FAs and lipid intracellular signaling and will then explore the key role of lipid metabolism in regulating the balance between potentially damaging pro-inflammatory and anti-inflammatory regulatory responses. Finally the complex role of extracellular FAs in determining cell survival will be discussed.

Metabolic reprogramming through fatty acid transport protein 1 (FATP1) regulates macrophage inflammatory potential and adipose inflammation

Objective

A novel approach to regulate obesity-associated adipose inflammation may be through metabolic reprogramming of macrophages (MΦs). Broadly speaking, MΦs dependent on glucose are pro-inflammatory, classically activated MΦs (CAM), which contribute to adipose inflammation and insulin resistance. In contrast, MΦs that primarily metabolize fatty acids are alternatively activated MΦs (AAM) and maintain tissue insulin sensitivity. In actuality, there is much flexibility and overlap in the CAM-AAM spectrum in vivo dependent upon various stimuli in the microenvironment. We hypothesized that specific lipid trafficking proteins, e.g. fatty acid transport protein 1 (FATP1), would direct MΦ fatty acid transport and metabolism to limit inflammation and contribute to the maintenance of adipose tissue homeostasis.

Methods

Bone marrow derived MΦs (BMDMs) from Fatp1^−/− and Fatp1^+/+ mice were used to investigate FATP1-dependent substrate metabolism, bioenergetics, metabolomics, and inflammatory responses. We also generated C57BL/6J chimeric mice by bone marrow transplant specifically lacking hematopoetic FATP1 (Fatp1^B−/−) and controls Fatp1^B+/+. Mice were challenged by high fat diet (HFD) or low fat diet (LFD) and analyses including MRI, glucose and insulin tolerance tests, flow cytometric, histologic, and protein quantification assays were conducted. Finally, an FATP1-overexpressing RAW 264.7 MΦ cell line (FATP1-OE) and empty vector control (FATP1-EV) were developed as a gain of function model to test effects on substrate metabolism, bioenergetics, metabolomics, and inflammatory responses.

Results

Fatp1 is downregulated with pro-inflammatory stimulation of MΦs. Fatp1^−/− BMDMs and FATP1-OE RAW 264.7 MΦs demonstrated that FATP1 reciprocally controled metabolic flexibility, i.e. lipid and glucose metabolism, which was associated with inflammatory response. Supporting our previous work demonstrating the positive relationship between glucose metabolism and inflammation, loss of FATP1 enhanced glucose metabolism and exaggerated the pro-inflammatory CAM phenotype. Fatp1^B−/− chimeras fed a HFD gained more epididymal white adipose mass, which was inflamed and oxidatively stressed, compared to HFD-fed Fatp1^B+/+ controls. Adipose tissue macrophages displayed a CAM-like phenotype in the absence of Fatp1. Conversely, functional overexpression of FATP1 decreased many aspects of glucose metabolism and diminished CAM-stimulated inflammation in vitro. FATP1 displayed acyl-CoA synthetase activity for long chain fatty acids in MΦs and modulated lipid mediator metabolism in MΦs.

Conclusion

Our findings provide evidence that FATP1 is a novel regulator of MΦ activation through control of substrate metabolism. Absence of FATP1 exacerbated pro-inflammatory activation in vitro and increased local and systemic components of the metabolic syndrome in HFD-fed Fatp1^B−/− mice. In contrast, gain of FATP1 activity in MΦs suggested that Fatp1-mediated activation of fatty acids, substrate switch to glucose, oxidative stress, and lipid mediator synthesis are potential mechanisms. We demonstrate for the first time that FATP1 provides a unique mechanism by which the inflammatory tone of adipose and systemic metabolism may be regulated.

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FATP1-mediated activation of fatty acids is a novel approach to limit inflammation.

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Fatp1 deficiency primed macrophages for pro-inflammatory activation.

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Lack of Fatp1 led to greater HFD-induced adipose inflammation.

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Fatp1^−/− adipose tissue macrophages were classically activated.

Fatty acid transport proteins in disease: New insights from invertebrate models

The dysregulation of lipid metabolism has been implicated in various diseases, including diabetes, cardiopathies, dermopathies, retinal and neurodegenerative diseases. Mouse models have provided insights into lipid metabolism. However, progress in the understanding of these pathologies is hampered by the multiplicity of essential cellular processes and genes that modulate lipid metabolism. Drosophila and Caenorhabditis elegans have emerged as simple genetic models to improve our understanding of these metabolic diseases. Recent studies have characterized fatty acid transport protein (fatp) mutants in Drosophila and C. elegans, establishing new models of cardiomyopathy, retinal degeneration, fat storage disease and dermopathies. These models have generated novel insights into the physiological role of the Fatp protein family in vivo in multicellular organisms, and are likely to contribute substantially to progress in understanding the etiology of various metabolic disorders. Here, we describe and discuss the mechanisms underlying invertebrate fatp mutant models in the light of the current knowledge relating to FATPs and lipid disorders in vertebrates.

The beta-3 adrenergic agonist (CL-316,243) restores the expression of down-regulated fatty acid oxidation genes in type 2 diabetic mice

Background

The hallmark of Type 2 diabetes (T2D) is hyperglycemia, although there are multiple other metabolic abnormalities that occur with T2D, including insulin resistance and dyslipidemia. To advance T2D prevention and develop targeted therapies for its treatment, a greater understanding of the alterations in metabolic tissues associated with T2D is necessary. The aim of this study was to use microarray analysis of gene expression in metabolic tissues from a mouse model of pre-diabetes and T2D to further understand the metabolic abnormalities that may contribute to T2D. We also aimed to uncover the novel genes and pathways regulated by the insulin sensitizing agent (CL-316,243) to identify key pathways and target genes in metabolic tissues that can reverse the diabetic phenotype.

Methods

Male MKR mice on an FVB/n background and age matched wild-type (WT) FVB/n mice were used in all experiments. Skeletal muscle, liver and fat were isolated from prediabetic (3 week old) and diabetic (8 week old) MKR mice. Male MKR mice were treated with CL-316,243. Skeletal muscle, liver and fat were isolated after the treatment period. RNA was isolated from the metabolic tissues and subjected to microarray and KEGG database analysis.

Results

Significant decreases in the expression of mitochondrial and peroxisomal fatty acid oxidation genes were found in the skeletal muscle and adipose tissue of adult MKR mice, and the liver of pre-diabetic MKR mice, compared to WT controls. After treatment with CL-316,243, the circulating glucose and insulin concentrations in the MKR mice improved, an increase in the expression of peroxisomal fatty acid oxidation genes was observed in addition to a decrease in the expression of retinaldehyde dehydrogenases. These genes were not previously known to be regulated by CL-316,243 treatment.

Conclusions

This study uncovers novel genes that may contribute to pharmacological reversal of insulin resistance and T2D and may be targets for treatment. In addition, it explains the lower free fatty acid levels in MKR mice after treatment with CL-316,243 and furthermore, it provides biomarker genes such as ACAA1 and HSD17b4 which could be further probed in a future study.

Electronic supplementary material

The online version of this article (doi:10.1186/s12986-015-0003-8) contains supplementary material, which is available to authorized users.

SLC27 fatty acid transport proteins

The uptake and metabolism of long chain fatty acids (LCFA) are critical to many physiological and cellular processes. Aberrant accumulation or depletion of LCFA underlie the pathology of numerous metabolic diseases. Protein-mediated transport of LCFA has been proposed as the major mode of LCFA uptake and activation. Several proteins have been identified to be involved in LCFA uptake. This review focuses on the SLC27 family of fatty acid transport proteins, also known as FATPs, with an emphasis on the gain- and loss-of-function animal models that elucidate the functions of FATPs in vivo and how these transport proteins play a role in physiological and pathological situations.

Fatty acid transport proteins, implications in physiology and disease

Uptake of long-chain fatty acids plays pivotal roles in metabolic homeostasis and human physiology. Uptake rates must be controlled in an organ-specific fashion to balance storage with metabolic needs during transitions between fasted and fed states. Many obesity-associated diseases, such as insulin resistance in skeletal muscle, cardiac lipotoxicity, and hepatic steatosis, are thought to be driven by the overflow of fatty acids from adipose stores and the subsequent ectopic accumulation of lipids resulting in apoptosis, ER stress, and inactivation of the insulin receptor signaling cascade. Thus, it is of critical importance to understand the components that regulate the flux of fatty acid between the different organ systems. Cellular uptake of fatty acids by key metabolic organs, including the intestine, adipose tissue, muscle, heart, and liver, has been shown to be protein mediated and various unique combinations of fatty acid transport proteins (FATPs/SLC27A1-6) are expressed by all of these tissues. Here we review our current understanding of how FATPs can contribute to normal physiology and how FATP mutations as well as hypo- and hypermorphic changes contribute to disorders ranging from cardiac lipotoxicity to hepatosteatosis and ichthyosis. Ultimately, our increasing knowledge of FATP biology has the potential to lead to the development of new diagnostic tools and treatment options for some of the most pervasive chronic human disorders. This article is part of a Special Issue entitled Triglyceride Metabolism and Disease.

Association of FATP1 gene polymorphisms with chicken carcass traits in Chinese meat-type quality chicken populations

In this study, we aimed to detect the single nucleotide polymorphisms (SNPs) of the chicken FATP1 gene and discern the potential association between FATP1 SNPs and chicken carcass traits. A total of 620 meat-type quality chickens from six commercial pure lines (S01, S02, S03, S05, S06 and D99) and two cross lines (S05 × S01 and S06 × S01) were screened by using the single-strand conformational polymorphism analysis (SSCP) and DNA sequencing. Five SNPs [g.49360G > A, g.48195G > A, g.46847A > G, g.46818A > G, and g.46555A > G] were identified in chicken FATP1 gene. SNP g.46818 A > G was a rare variant and was not considered in the subsequent analysis. Sixteen haplotypes were reconstructed on the basis of the other four SNPs. The linear regression model analysis indicated that there were significant associations of certain diplotypes with part of carcass traits, such as live weight (LW), carcass weight (CW), and semi-eviscerated weight (SEW) (P < 0.05). In particular, diplotype H2H4 had a negative effect on LW, CW, SEW, and abdominal fat weight (AW); diplotype H6H10 had the highest reducing effect on subcutaneous fat thickness (SFT). Our results suggested that FATP1 gene polymorphisms were associated with chicken carcass traits or was linked with the major gene. The SNPs in this gene may be utilized as potential markers for marker-assisted selection (MAS) during chicken breeding.

Long-chain polyunsaturated fatty acid (LC-PUFA) transfer across the placenta

Fetal long-chain polyunsaturated fatty acid (LC-PUFA) supply during pregnancy is of major importance, particularly with respect to docosahexaenoic acid (DHA) that is an important component of the nervous system cell membranes. Growing evidence points to direct effects of DHA status on visual and cognitive outcomes in the offspring. Furthermore, DHA supply in pregnancy reduces the risk of preterm delivery. Because of limited fetal capacity to synthesize LC-PUFA, the fetus depends on LC-PUFA transfer across the placenta. Molecular mechanisms of placental LC-PUFA uptake and transport are not fully understood, but it has been clearly demonstrated that there is a preferential DHA transfer. Thus, the placenta is of pivotal importance for the selective channeling of DHA from maternal diet and body stores to the fetus. Several studies have associated various fatty acid transport and binding proteins (FATP) with the preferential DHA transfer, but also the importance of the different lipolytic enzymes has been shown. Although the exact mechanisms and the interaction of these factors remains elusive, recent studies have shed more light on the processes involved, and this review summarizes the current understanding of molecular mechanisms of LC-PUFA transport across the placenta and the impact on pregnancy outcome and fetal development.

Identification of 14 new single nucleotide polymorphisms in the bovineSLC27A1gene and evaluation of their association with milk fat content

The solute carrier family 27 member 1 (SLC27A1) is an integral membrane protein involved in the transport of long-chain fatty acids across the plasma membrane. This protein has been implicated in diet-induced obesity and is thought to be important in the control of energy homeostasis. In previous reports, our group described the isolation and characterization of the bovineSLC27A1gene. The bovine gene is organized in 13 exons spanning over more than 40 kb of genomic DNA and maps in BTA 7 where several quantitative trait loci for fat related traits have been described. Because of its key role in lipid metabolism and its genomic localization, in the present work the search for variability in the bovineSLC27A1gene was carried out with the aim of evaluating its potential association with milk fat content in dairy cattle. By sequencing analysis of all exons and flanking regions 14 new single nucleotide polymorphisms (SNPs) were identified: 1 in the promoter, 7 in introns and 6 in exons. Allele frequencies of all the SNPs were calculated by minisequencing analysis in two groups of Holstein-Friesian animals with highest and lowest milk-fat content estimated breeding values as well as in animals of two Spanish cattle breeds, Asturiana de los Valles and Menorquina. In the conditions assayed, no significant differences between Holstein-Friesian groups were found for any of the SNPs, suggesting that theSLC27A1gene may have a poor or null effect on milk fat content. In Asturiana and Menorquina breeds all the positions were polymorphic with the exception of SNPs 1 and 8 in which C allele was fixed in both of them.

Protein-mediated fatty acid uptake: novel insights from in vivo models

Long-chain fatty acids are both important metabolites as well as signaling molecules. Fatty acid transport proteins are key mediators of cellular fatty acid uptake and recent transgenic and knockout animal models have provided new insights into their contribution to energy homeostasis and to pathological processes, including obesity and insulin desensitization.

Impact on fatty acid metabolism and differential localization of FATP1 and FAT/CD36 proteins delivered in cultured human muscle cells

We compared the intracellular distribution and regulatory role of fatty acid transporter protein (FATP1) and fatty acid translocase (FAT/CD36) on muscle cell fatty acid metabolism. With the use of adenoviruses, FATP1 and FAT genes were delivered to primary cultured human muscle cells. FATP1 and FAT moderately enhanced palmitate and oleate transport evenly at concentrations of 0.05, 0.5, and 1 mM. Long-term (16 h) consumption of palmitate and oleate from the media, and particularly incorporation into triacylglyceride (TAG), was stimulated equivalently by FATP1 and FAT at all fatty acid concentrations tested. In contrast, long-term CO(2) production was reduced by FATP1 and FAT at all doses of palmitate and at the lower concentrations of oleate. Neither FATP1 nor FAT markedly altered the production of acid-soluble metabolic intermediates from palmitate or oleate. The intracellular localization of fusion constructs of FATP1 and FAT with enhanced green fluorescent protein (EGFP) was examined. Independently of fatty acid treatment, FATPGFP was observed throughout the cytosol in a reticular pattern and concentrated in the perinuclear region, partly overlapping with the Golgi marker GM-130. FATGFP was found in the extracellular membrane and in cytosolic vesicles not coincident with GM-130. Neither FATP1 nor FAT proteins colocalized with lipid droplets in oleate-treated cells. We conclude that whereas FAT is localized on the extracellular membrane, FATP1 is active in the cytosol and imports fatty acids into myotubes. Overall, both FATP1 and FAT stimulated transport and consumption of palmitate and oleate, which they channeled away from complete oxidation and toward TAG synthesis.

Role of FATP in parenchymal cell fatty acid uptake

Long-chain fatty acids (LCFAs) represent key metabolites for energy generation and storage. Transport and metabolism of LCFA are believed to be regulated by membrane-associated proteins that bind and transport LCFA. Identifying the postulated fatty acid transporters is of considerable interest since altered fatty acid uptake has been implicated in disease such as insulin resistance and obesity. Recently, a family of membrane associated proteins, termed fatty acid transport proteins (FATPs), have been described that enhance uptake of LCFAs. Until today, six members of this family, designated FATP1-6, have been characterized. This review will focus on FATP structure, expression patterns, regulation, mechanism of transport and clinical implications.

Analysis of candidate genes in Polish families with obesity

This study analyzes the relationship between risk factors related to overweight/obesity, insulin resistance, lipid tolerance, hypertension, endothelial function and genetic polymorphisms associated with: i) appetite regulation (leptin, melanocortin-3-receptor (MCR-3), dopamine receptor 2 (D2R)); ii) adipocyte differentiation and insulin sensitivity (peroxisome proliferator-activated receptor-gamma2 (PPAR-gamma2), tumor necrosis factor-alpha (TNF-alpha)); iii) thermogenesis and free fatty acid (FFA) transport/catabolism (uncoupling protein-1 (UCP1), lipoprotein lipase (LPL), beta2- and beta3-adrenergic receptor (beta2AR, beta3AR), fatty acid transport protein-1 (FATP-1) and iv) lipoproteins (apoliprotein E (apoE), apo CIII). The 122 members of 40 obese Caucasian families from southern Poland participated in the study. The genotypes were analyzed by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR) or by direct sequencing. Phenotypes related to obesity (body mass index (BMI), fat/lean body mass composition, waist-to-hip ratio (WHR)), fasting lipids, glucose, leptin and insulin, as well as insulin during oral glucose tolerance test (OGTT) (4 points within 2 hours) and during oral lipid tolerance test (OLTT) (5 points within 8 hours) were assessed. The insulin sensitivity indexes: homeostasis model assessment of insulin resistance, whole body insulin sensitivity index, hepatic insulin sensitivity and early secretory response to an oral glucose load (HOMA-IR, ISI-COMP, ISI-HOMA and DELTA) were calculated. The single gene mutations such as C105 T OB and Pro115 Gln PPAR-gamma2 linked to morbid obesity were not detected in our group. A weak correlation between obesity and certain gene polymorphisms was observed. Being overweight (25 < BMI > or = 30 kg/m2) significantly correlated with worse FFA tolerance in male PPAR-gamma2 12Pro, LPL-H (G) allele carriers. Insulin resistance was found in female PPAR-gamma2 Pro12, TNF-alpha (-308A) and LPL-H (G) allele carriers. Hypertension linked to the PPAR-gamma2 Pro allele carriers was characterized by high leptin output during OLTT. We conclude that the polymorphisms we investigated were weakly correlated with obesity but significantly modified the risk factors of the metabolic syndrome.

Common gene polymorphisms and nutrition: emerging links with pathogenesis of multifactorial chronic diseases (review)

Rapid progress in human genome decoding has accelerated search for the role of gene polymorphisms in the pathogenesis of complex multifactorial diseases. This review summarizes the results of recent studies on the associations of common gene variants with multifactorial chronic conditions strongly affected by nutritional factors. Three main individual sections discuss genes related to energy homeostasis regulation and obesity, cardiovascular disease (CVD), and cancer. It is evident that several major chronic diseases are closely related (often through obesity) to deregulation of energy homeostasis. Multiple polymorphic genes encoding central and peripheral determinants of energy intake and expenditure have been revealed over the past decade. Food intake control may be affected by polymorphisms in the genes encoding taste receptors and a number of peripheral signaling peptides such as insulin, leptin, ghrelin, cholecystokinin, and corresponding receptors. Polymorphic central regulators of energy intake include hypothalamic neuropeptide Y, agouti-related protein, melanocortin pathway factors, CART (cocaine- and amphetamine-regulated transcript), some other neuropeptides, and receptors for these molecules. Potentially important polymorphisms in the genes encoding energy expenditure modulators (alpha- and beta- adrenoceptors, uncoupling proteins, and regulators of adipocyte growth and differentiation) are also discussed. CVD-related gene polymorphisms comprising those involved in the pathogenesis of atherosclerosis, blood pressure regulation, hemostasis control, and homocysteine metabolism are considered in a separate section with emphasis on multiple polymorphisms affecting lipid transport and metabolism and their interactions with diet. Cancer-associated polymorphisms are discussed for groups of genes encoding enzymes of xenobiotic metabolism, DNA repair enzymes, factors involved in the cell cycle control, hormonal regulation-associated proteins, enzymes related to DNA methylation through folate metabolism, and angiogenesis-related factors. There is an apparent progress in the field with hundreds of new gene polymorphisms discovered and characterized, however firm evidence consistently linking them with pathogenesis of complex chronic diseases is still limited. Ways of improving the efficiency of candidate gene approach-based studies are discussed in a short separate section. Successful unraveling of interaction between dietary factors, polymorphisms, and pathogenesis of several multifactorial diseases is exemplified by studies of folate metabolism in relation to CVD and cancer. It appears that several new directions emerge as targets of research on the role of genetic variation in relation to diet and complex chronic diseases. Regulation of energy homeostasis is a fundamental problem insufficiently investigated in this context so far. Impacts of genetic variation on systems controlling angiogenesis, inflammatory reactions, and cell growth and differentiation (comprising regulation of the cell cycle, DNA repair, and DNA methylation) are also largely unknown and need thorough analysis. These goals can be achieved by complex simultaneous analysis of multiple polymorphic genes controlling carefully defined and selected elements of relevant metabolic and regulatory pathways in meticulously designed large-scale studies.

A common polymorphism in the fatty acid transport protein-1 gene associated with elevated post-prandial lipaemia and alterations in LDL particle size distribution

The fatty acid transport proteins (FATPs) have been implicated in facilitated cellular uptake of non-esterified fatty acids (NEFAs), thus having the potential to regulate local and systemic NEFA concentrations and metabolism. Hypothesising that genetic variation within the FATP genes may affect lipid metabolism, we investigated a G/A substitution at position 48 in intron 8 of the fatty acid transport-1 (FATP1) gene with respect to associations with fasting and post-prandial plasma lipid and lipoprotein variables in 628 healthy 50-year-old Swedish men and 426 Swedish women, aged 37-65 years. A subset of 105 men with the apoE3/E3 genotype underwent an oral fat tolerance test. Although fasting plasma TG concentrations were not different, male A/A individuals had significantly higher post-prandial TG concentrations and VLDL(1) (S(f) 60-400 apoB100)-to-VLDL(2) (S(f) 20-60 apoB100) ratio compared to male G/A and G/G individuals. A/A individuals apparently failed to suppress plasma NEFA concentrations during the oral fat tolerance test. Furthermore, fasting plasma concentrations of the largest, most buoyant LDL subfraction (LDL-I) were significantly lower in carriers of the A allele in the male cohort. Electromobility shift assays and reporter gene studies indicated that binding of nuclear factors and effect on transcriptional activity differ between the intron 8 alleles. These findings suggest that through regulation of NEFA trafficking, FATP1 might play a role in post-prandial lipid metabolism and development of cardiovascular disease.

Placental regulation of fatty acid delivery and its effect on fetal growth--a review

More than 90 per cent of the fat deposition in the fetus occurs in the last 10 weeks of pregnancy during which it increases exponentially to reach a rate of accretion of around 7 g/day close to term. All of the n -3 and n -6 fatty acid structure acquired by the fetus has to cross the placenta and fetal blood is enriched in long chain polyunsaturated fatty acids (LCPUFA) relative to the maternal supply. The placenta may regulate its own fatty acid substrate supply via the action of placental leptin on maternal adipose tissue. Fatty acids cross the microvillous and basal membranes by simple diffusion and via the action of membrane bound and cytosolic fatty acid binding proteins (FABPs). The direction and magnitude of fatty acid flux is mainly dictated by the relative abundance of available binding sites. The fatty acid mix delivered to the fetus is largely determined by the fatty acid composition of the maternal blood although the placenta is able to preferentially transfer the important PUFA to the fetus as a result of selective uptake by the syncytiotrophoblast, intracellular metabolic channelling of individual fatty acids, and selective export to the fetal circulation. Placental FABP polymorphisms may affect these processes. There is little evidence to suggest that placental delivery of fatty acids limits normal fetal growth although the importance of the in utero supply may be to support post-natal development as most of the LCPUFA accumulated by the fetus is stored in the adipose tissue for use in early post-natal life.

Fatty acid transport: the roads taken

Efficient uptake and channeling of long-chain fatty acids (LCFAs) are critical cellular functions. Although spontaneous flip-flop of nonionized LCFAs from one leaflet of a bilayer to the other is rapid, evidence is emerging that proteins are important mediators and/or regulators of trafficking of LCFAs into and within cells. Genetic screens have led to the identification of proteins that are required for fatty acid import and utilization in prokaryotic organisms. In addition, functional screens have elucidated proteins that facilitate fatty acid import into mammalian cells. Although the mechanisms by which these proteins mediate LCFA import are not well understood, studies in both prokaryotic and eukaryotic organisms provide compelling evidence that uptake of LCFAs across cellular membranes is coupled to esterification by acyl-CoA synthetases. This review will summarize results of studies of non-protein-mediated and protein-mediated LCFA transport and discuss how these different mechanisms may contribute to cellular metabolism.

Placental nutrient transfer capacity and fetal growth

The objective of this study was to determine whether the ability of the human placenta to transfer glucose and fatty acids is related to normal fetal growth. The intrinsic nutrient transport capacity of the placenta was measured under standardized conditions during in vitro perfusion of 30 human term placentas and related to birth weight (range 2640-4640g), birth weight centile (8th-99th), ponderal index (2.43-3.69), placental weight (418-1030g) and placental:fetal weight (0.14-0.31). There was no statistically significant change in the rate of nutrient transfer per placenta or per kg fetal weight, with birth weight, birth weight centile, ponderal index, placental weight and placental:fetal weight. There was a weak but significant relationship (P=0.020, r(2)=9 per cent) between the ratio of glucose to fatty acid transport and birth weight centile, largely due to the high ratio found in the lowest birth weight quartile where the babies are thinnest. This study provides no evidence that placental nutrient transport capacity limits fetal growth across a wide range of birth weights in normal pregnancies. It is proposed that the fetus itself may regulate placental nutrient transport in vivo via the fetal cardiac output and the rate of fetal nutrient utilization.

Mouse fatty acid transport protein 4 (FATP4): characterization of the gene and functional assessment as a very long chain acyl-CoA synthetase

FATP4 (SLC27A4) is a member of the fatty acid transport protein (FATP) family, a group of evolutionarily conserved proteins that are involved in cellular uptake and metabolism of long and very long chain fatty acids. We cloned and characterized the murine FATP4 gene and its cDNA. From database analysis we identified the human FATP4 genomic sequence. The FATP4 gene was assigned to mouse chromosome 2 band B, syntenic to the region 9q34 encompassing the human gene. The open reading frame was determined to be 1929 bp in length, encoding a polypeptide of 643 amino acids. Within the coding region, the exon-intron structures of the murine FATP4 gene and its human counterpart are identical, revealing a high similarity to the FATP1 gene. The overall amino acid identity between the deduced murine and human FATP4 polypeptides is 92.2%, and between the murine FATP1 and FATP4 polypeptides is 60.3%. Northern analysis showed that FATP4 mRNA was expressed most abundantly in small intestine, brain, kidney, liver, skin and heart. Transfection of FATP4 cDNA into COS1 cells resulted in a 2-fold increase in palmitoyl-CoA synthetase (C16:0) and a 5-fold increase in lignoceroyl-CoA synthetase (C24:0) activity from membrane extracts, indicating that the FATP4 gene encodes an acyl-CoA synthetase with substrate specificity biased towards very long chain fatty acids.