Mechanisms of Gene Regulation by Fatty Acids^,

Abstract

Consumption of specific dietary fatty acids has been shown to influence risk and progression of several chronic diseases, such as cardiovascular disease, obesity, cancer, and arthritis. In recent years, insights into the mechanisms underlying the biological effects of fatty acids have improved considerably and have provided the foundation for the emerging concept of fatty acid sensing, which can be interpreted as the property of fatty acids to influence biological processes by serving as signaling molecules. An important mechanism of fatty acid sensing is via stimulation or inhibition of DNA transcription. Here, we focus on fatty acid sensing via regulation of gene transcription and address the role of peroxisome proliferator–activated receptors, sterol regulatory element binding protein 1, Toll-like receptor 4, G protein–coupled receptors, and other putative mediators.

Introduction

Consumption of specific dietary fatty acids has been shown to affect the risk of a wide range of chronic diseases. What traditionally has been lacking is a clear mechanistic framework that links uptake of specific lipids to a biological pathway and disease process. Such a molecular framework should accommodate the often differential effects of fatty acids differing in chain length and saturation on numerous biological parameters. In recent years, insights into the mechanisms underlying the biological effects of fatty acids have progressed rapidly, in part because of the widespread use of in vivo and in vitro gene targeting, and have provided the foundation for the emerging concept of fatty acid sensing. Fatty acid sensing can be interpreted as the property of fatty acids to influence biological processes by serving as signaling molecules. Although it is well established that fatty acid derivatives such as eicosanoids have a major signaling function, there is convincing evidence that fatty acids themselves also carry this property. Part of this regulation occurs via regulation of gene transcription, which is the topic of this review.

Trafficking and cellular sensing of dietary fat

Every day our body processes an amount of fat equivalent to almost one half cup. In the intestine, dietary triglycerides (TG)³ are first hydrolyzed into fatty acids and monoglycerides that, together with bile acids, form into micelles in the intestinal lumen. After being taken up by enterocytes, fatty acids are re-esterified into TG and secreted as part of chylomicrons, initially in the intestinal lymph vessels and from there in the bloodstream. The increase in circulating chylomicrons after a meal gives rise to the postprandial peak in plasma TG. The time course and magnitude of the plasma TG peak may differ among individuals and is increased in obese and diabetic individuals, giving rise to postprandial lipemia. Plasma chylomicrons undergo rapid lipolytic processing via the action of lipoprotein lipase (LPL) anchored to the capillary endothelium, leading to the release of fatty acids and their subsequent uptake by the underlying tissue (1).

One of the major sinks for meal-derived fatty acids is adipose tissue, which acquires most of the absorbed fatty acids via increased local LPL activity. Other tissues that substantially contribute to postprandial clearance of chylomicrons/TGs are skeletal muscle, the heart, and, after conversion to chylomicron remnants, the liver (2). In contrast to plasma TG, circulating levels of adipose tissue–derived nonesterified FFAs decrease rapidly after a mixed meal and again increase at the end of the postprandial period. A considerable portion of circulating FFA are taken up by the liver, where, together with remnant-derived fatty acids and fatty acids produced via de novo lipogenesis, they form the substrate for (re-)esterification and subsequent secretion into plasma as VLDL/TG. Depending on the tissue and feeding status, either plasma FFA or TG-derived fatty acids comprise the major portion of fatty acids for tissue uptake (2). Irrespective of the specific route of delivery, it is evident that the rate of fatty acid uptake by many tissues is very variable and influenced by numerous factors, including tissue metabolic activity, feeding status, fat intake, and the intake of other nutrients, especially carbohydrates. Furthermore, circulating concentration and tissue fluxes of FFA and TG-derived fatty acids are often altered during obesity, type 2 diabetes, or other metabolic disturbances.

A number of proteins are involved in the cellular uptake of FFA, including CD36 and various fatty acid transporters (3). After uptake, fatty acids are bound by fatty acid–binding proteins and can undergo a number of metabolic fates including oxidation in mitochondria and esterification and storage in lipid droplets. In addition, fatty acids can serve as signaling molecules by affecting intra- and extracellular receptor sensor systems either directly or after conversion to specific fatty acid derivatives. An example of these lipid sensors are the nuclear receptors that mediate activation of gene transcription by a variety of hydrophobic compounds, including retinoic acid, steroid hormones, oxysterols, and bile acids (4). This review provides an overview of our current knowledge of the various cellular receptor systems enabling the cell to sense the intra- or extracellular fatty acid concentration and respond by altering gene transcription.

Peroxisome proliferator–activated receptors

The PPARs perhaps compose the best recognized sensor system for fatty acids (Fig. 1). PPARs are transcription factors that are members of the superfamily of nuclear hormone receptors, which also include receptors for fat-soluble vitamins A and D and steroid hormones (5). Nuclear receptors function as ligand-activated transcription factors by binding small lipophilic molecules. They share a modular structure consisting of a DNA- and ligand-binding domain and play a role in a numerous biological processes (6). Three different PPAR subtypes have been cloned, each characterized by a unique tissue expression pattern. PPARα (Nr1c1) is found in many tissues but is predominant in oxidative tissues such as brown adipose tissue, cardiac muscle, skeletal muscle, and liver. PPARδ (Nr1c2) is found in many cell types, whereas PPARγ (Nr1c3) expression is more restricted, with adipocytes and macrophages expressing the highest level (7, 8). Binding of ligand is thought to trigger the physical association of PPARs to specific DNA sequences, called PPAR response elements, in and around target genes. Additionally, ligand binding leads to recruitment of coactivator proteins and loss of corepressor proteins, resulting in activation of DNA transcription (5). Similar to many other nuclear receptors, PPARs bind to DNA as heterodimer with the nuclear receptor retinoid X receptor (RXR), which binds the vitamin A derivative 9-cis retinoic acid.

Figure 1.

General mechanisms of gene regulation by fatty acids (FA). The mechanisms shown mainly apply to hepatocytes. Polyunsaturated fatty acids (PUFA) reduce expression of genes involved in fatty acid and cholesterol synthesis by binding and inactivating UBXD8, thereby inhibiting proteolytic processing of sterol regulatory element binding protein (SREBP) 1. PUFAs reduce expression of L-type pyruvate kinase (glycolysis) in liver, most likely by inhibiting nuclear translocation of MAX-like protein X (MLX)–carbohydrate responsive element binding protein. Various fatty acids, but especially PUFAs, act as ligands for peroxisome proliferator–activated receptors (PPAR). Activation of PPARα by PUFAs in the liver leads to stimulation of fatty acid (FA) catabolism. Docosahexanoic acid has been reported as a ligand for retinoid X receptor. G protein–coupled receptors (GPR) 40–43 and GPR120 are expressed by enterocytes, enteroendocrine cells, and other cell types and serve as membrane receptors for various types of fatty acids including short-chain fatty acids. It is uncertain whether they are involved in the effects of fatty acids on gene expression. Toll-like receptor 4 (TLR4) is present in macrophages and other cell types and has been proposed to be activated by saturated fatty acids (SFA). bHLH, basic helix-loop-helix; ChREBP, carbohydrate-responsive element binding protein; FXR, farnesoid X receptor; HNF4α, hepatocyte nuclear factor 4α; INSIG, insulin induced gene; LXR, liver X receptor; PXR, pregnane X receptor; SCAP, SREBP cleavage activating protein.

PPARs serve as receptors for structurally diverse compounds. Although substantial specificity for 1 particular PPAR subtype has been achieved in the design of synthetic PPAR agonists, there seems to be comparatively little subtype specificity among endogenous PPAR agonists. In several landmark articles from the 1990s, it was demonstrated that all 3 PPARs are able to bind fatty acids with a general preference for long- chain polyunsaturated fatty acids (PUFAs) (9–13). Subsequent studies using a variety of biochemical techniques have firmly corroborated the direct physical association between fatty acids and PPARs and have thus established fatty acids as bona fide PPAR ligands (14–18). In addition, numerous fatty acid–derived compounds and compounds showing a structural resemblance to fatty acids, including acyl-CoAs, oxidized fatty acids (9(S)-HODE and 13(S)-HODE), eicosanoids, endocannabinoids, and phytanic acid, have been shown to activate PPARs (19–26). Whereas the eicosanoid 15-deoxy-delta-12,14-prostaglandin J2 behaves as a specific high-affinity agonist for PPARγ, (8S)-hydroxyeicosatetraenoic acid and prostacylin show preference for PPARα and PPARδ, respectively (9, 27–29). Because the intracellular concentration of fatty acids (free and bound to fatty acid binding proteins) far exceeds the intracellular concentration of eicosanoids and other endogenous PPAR agonists and because fatty acids are able to bind PPARs with high affinity, the question can be raised to what extent do eicosanoids and other fatty acid–derived compounds substantially contribute to the activation of PPARs in vivo. Rather, it can be argued that PPARs serve as general fatty acid sensors with comparatively limited ligand specificity. However, this concept is not universally embraced and has clearly not stopped the quest to identify the potentially elusive single true endogenous PPAR ligand. Recently, Chakravarthy et al. (30) identified the phosphatidylcholine 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine as the lipid compound likely responsible for the activation of PPARα in mice carrying a targeted deletion of the fatty acid synthase gene. Because phosphatidylcholines are abundant in any cell, it is unclear how activation of PPARα by 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine fits into the notion of PPARα being a lipid sensor that responds to changes in metabolic status and lipid fluxes.

As discussed earlier, dietary fatty acids mostly enter the liver as TGs within chylomicron remnants and are liberated after degradation of the remnant particles by hepatic and lysosomal lipase. It has been shown that PPARα is dominant in mediating the effects of dietary fatty acids on hepatic gene expression, including many genes involved in fatty acid catabolism, as revealed by experiments in which wild-type and PPARα^−/− mice were provided with a single oral bolus of synthetic TG consisting of 1 type of fatty acid (17). Lipolysis of circulating lipoproteins, whether hydrolysis of high-density lipoproteins by endothelial lipase or lipolysis of VLDL by LPL, was shown to be an important mechanism for generating ligands for PPARα in endothelial cells (31, 32), whereas hydrolysis of VLDL by hepatic lipase and LPL was shown to provide ligands for PPARδ in hepatocytes and macrophages, respectively (33, 34).

In contrast and very surprisingly, circulating FFAs, which primarily originate from adipose tissue lipolysis, do not seem to be able to activate PPARα, at least in the liver (35, 36). The precise mechanism behind the differential effect of circulating FFAs (“old fat”) versus dietary and endogenously synthesized fatty acids (“new fat”) on hepatic PPARα activation remains unclear but may be related to the existence of distinct intracellular fatty acids pools with distinct metabolic and signaling properties (35). In contrast, hepatic PPARδ can be activated by plasma FFAs (36), and likely the same is true in skeletal muscle, as revealed by the stimulatory effect of increased FFAs on expression of the PPARδ target Angptl4 in skeletal muscle (37, 38).

Interestingly, it was recently proposed that in the mouse heart, PPARα-mediated gene transcription requires the previous esterification of fatty acids and subsequent hydrolysis catalyzed by adipose TG lipase (39). Conversion to TGs and subsequent lipolysis seems to be necessary for fatty acids to become active signaling lipids, but it is unclear whether the specific routing of fatty acids leads to the formation of a specific high-affinity ligand or feeds a distinct intracellular fatty acid pool. In contrast, evidence was also provided that in the liver, adipose TG lipase promotes PPARα activity independently of ligand-induced activation (40).

PPARα acts as a master regulator of hepatic lipid catabolism by inducing the expression of numerous genes involved in mitochondrial and peroxisomal fatty acid oxidation, as well as other lipid-related pathways, inflammatory pathways, and glucose metabolism (41). Accordingly, it can be argued that activation of PPARα by fatty acids in the liver and heart is part of a feed-forward mechanism aimed at promoting oxidation of incoming fuels and thereby preventing the intracellular accumulation and consequent lipotoxicity of fatty acids by stimulating their oxidation. A similar role can be envisioned for PPARδ in skeletal muscle. In addition to stimulation of fatty acid oxidation and possibly by stimulating conversion of fatty acids into TGs (41), activation of PPAR by fatty acids may protect against lipotoxicity by inhibiting LPL-dependent hydrolysis of circulating TGs and consequent uptake of fatty acids via induction of the LPL inhibitor Angptl4 (42).

The role of PPARs in gene regulation by fatty acids is less clear in adipose tissue. Marine oil fatty acids have major effects on adipose tissue function and metabolism as well as on adipose tissue gene regulation (43). Although PUFAs are direct agonists for PPARγ (12), it is unclear to what extent the observed changes in adipose gene expression on chronic PUFA feeding reflect direct ligand activation of PPARγ or other PPARs or are secondary effects conferred by specific eicosanoids or other fatty acid–derived compounds. Activation of PPARγ by fatty acids may be aimed at promoting conversion of incoming fatty acids to TGs and stimulating overall TG storage capacity, thereby protecting against lipotoxicity.

Sterol-regulatory element binding protein 1

Dietary PUFAs suppress hepatic expression of genes involved in fatty acid synthesis (Fig. 1). The underlying mechanism involves a member of the family of basic helix-loop-helix leucine zipper transcription factors named sterol regulatory element binding protein (SREBP) 1 (Srebf1). There are 2 SREBP isoforms, designated SREBP-1c and SREBP-2, which differ in their tissue-specific expression and their target genes selectivity. Although SREBP-1c preferentially activates genes involved in de novo lipogenesis, SREBP-2 has a preference for genes involved in cholesterol synthesis and uptake, at least in the liver (44). Together, SREBPs activate the expression of >30 genes involved in the synthesis and uptake of cholesterol, fatty acids, TGs, and phospholipids.

Although SREBP1 and SREBP2 have both been suggested to be inhibited by PUFAs, there is much more evidence implicating SREBP1 in the down-regulation of gene expression by PUFAs. Studies over the past decade indicated that PUFAs potently lower SREBP-1 mRNA levels and inhibit proteolytic processing of SREBP-1 (45–49). The latter process is required for maturation of precursor membrane-bound SREBP-1 to the mature SREBP-1, which moves to the nucleus and serves as the actual transcription factor. Recently, the target of PUFAs was identified as Ubxd8, an endoplasmic reticulum (ER) membrane–bound protein that facilitates the degradation of Insig-1, which normally sequesters the SCAP-SREBP complex in the ER and prevents its activation (50). Specifically, it was shown that PUFAs inhibit the activity of Ubxd8, thus causing the SCAP-SREBP complex to stay in the ER. In addition to the mechanism described above, evidence has been provided that docosahexanoic acid (DHA) but not other PUFAs stimulate the removal of mature nuclear SREBP-1 via a mechanism dependent on 26S-proteosome and extracellular signal–regulated kinase (51). Down-regulation of SREBP-1 mRNA by PUFAs has been proposed to be mediated by stimulation of SREBP-1 mRNA decay (52), or by antagonizing the activity of the nuclear receptor liver X receptor (LXR) α, a potent inducer of SREBP-1 gene transcription (53, 54). Because a role of LXR in mediating effects of PUFAs is debatable (55), the reduction in SREBP-1 mRNA by PUFA is more likely to be secondary to inhibition of SREBP-1 maturation, which, via autoregulation of SREBP-1 transcriptional activation, leads to reduced SREBP-1 mRNA levels (56).

PUFAs have also been shown to reduce expression of the glycolytic gene pyruvate kinase via a mechanism independent of PPARα (57). This effect may be mediated by inhibiting nuclear translocation of either carbohydrate-responsive element binding protein (MLXIPL) or MAX-like protein X (MLX) (Fig. 1) (58, 59). ChREBP and MLX form a heterodimer functioning as glucose-responsive transcription factor that induces expression of genes involved in glycolysis and lipogenesis, including pyruvate kinase, acetyl-CoA carboxylase 1, and fatty acid synthase. However, additional data need to be collected to more precisely define how PUFAs influence ChREBP or MLX nuclear translocation and what the direct molecular target of PUFAs is.

Hepatocyte nuclear factor 4α and other nuclear receptors

The hepatocyte nuclear factor 4α (HNF4α, Nr2a1) is a nuclear receptor that is exclusively expressed in the gastrointestinal tract, liver, and kidney (7). Targeted disruption of HNF4α leads to early embryonic lethality related to defects in the expression of visceral endoderm proteins required for maintaining gastrulation (60). Using liver-specific HNF4α^−/− mice, it was shown that liver HNF4α is important for hepatocyte differentiation and for governing the expression of genes involved in lipid homeostasis (61). In 1998, evidence was provided that saturated fatty acyl-CoAs may be able to serve as agonists for HNF4α, whereas unsaturated fatty acyl-CoAs were proposed to serve as an antagonistic ligand (62). These data have been contested experimentally and are not widely accepted (63). Elucidation of the molecular structure using X-ray crystallography revealed the presence of a fatty acid that appeared to be constitutively bound (64, 65). More recently, it was shown using affinity isolation/mass-spectrometry that HNF4α is occupied by linoleic acid in COS-7 cells as well as in the liver of fed but not fasted mice, suggesting fatty acid binding is exchangeable. However, no induction of HNF4α targets by linoleic acid was observed in a human colon cancer cell line, raising questions about the purpose of binding of linoleic acid to HNF4α (66). Overall, the binding and especially the activation of HNF4α by fatty acids or acyl-CoAs remains controversial. Indeed, there is only very limited evidence that changes in the concentration of fatty acids or acyl-CoA lead to activation of HNF4α targets.

In addition to PPARs and HNF4α, the nuclear receptors LXR, FXR, and RXR have been proposed to serve as mediators of the effects of fatty acids on gene transcription. With respect to LXR, it was suggested that unsaturated fatty acids suppress Srebp1c gene expression by inhibiting LXR (53). However, another study found that unsaturated fatty acids do not influence LXR-dependent gene regulation in primary rat hepatocytes or in the liver (55).

DHA was originally identified as a ligand for RXR when looking for a factor in brain tissue that activates RXR in a cell-based assay (67). Subsequent experiments showed the direct binding of PUFAs to RXR, with strongest RXR activation observed for DHA and arachidonic acid, followed by linolenic, linoleic, and oleic acids (68). Recent studies confirmed the direct binding of DHA to RXR, although with much lower affinity compared with 9cRA (69). In as much as DHA also binds PPARs and PPARs form permissive heterodimers with RXR, it is technically challenging to distinguish between DHA gene signaling via PPAR versus RXR. Interestingly, using RXR and PPARγ antagonists, it was found that DHA induces expression of adipocyte differentiation-related protein (Plin2) in human choriocarcinoma cells via activation of RXR (70). Recently, effect of DHA on despair behaviors and working memory could be attributed to activation of RXRγ (71).

NF-E2–related factor-2 (NRF2)

An oral lipid load with PUFAs causes rapid up-regulation of numerous oxidative stress genes in several organs, likely representing an adaptive mechanism aimed at preventing cellular lipotoxicity (72). Increased levels of reactive oxygen species and derivatives of fatty acid peroxidation activate the transcription factor NRF2 (NFE2L2), which governs the expression of multiple genes involved in the oxidative stress response. Compounds that activate NRF2, ranging from diphenols to hydroperoxides and heavy metals, are thought to modulate the sulfhydryl group of cysteine residues with KEAP1, which serves as an NRF2-specific adaptor protein for the Cullin-3 ubiquitin ligase complex (73). As a result, these compounds cause the dissociation of Cullin-3 and thereby inhibit NRF2 ubiquitination, leading to stabilization and nuclear translocation of NRF2 and subsequent induction of NRF2 target genes. Studies have shown that oxidation products of linoleic acid, eicosapentanoic acid, and DHA can react with KEAP1, whereas the intact fatty acids cannot (74–76). Thus, the effects of (dietary) PUFAs on the expression of genes involved in the oxidative stress response are likely mediated by specific fatty acid oxidation products via NRF2-dependent

Toll-like receptor 4

Numerous studies have investigated the impact of fatty acids on the inflammatory response in a great variety of cell types and tissues. These studies overwhelmingly point to a proinflammatory effect of saturated fatty acids, whereas (n-3) PUFA exhibit mostly anti-inflammatory properties (77). Most of the modulatory effect of fatty acids on inflammation can probably be attributed to fatty acid metabolites, including prostaglandins, leukotoxins, resolvins, endocannabinoids, ceramides, and diacylglycerols (77). However, there is accumulating evidence that fatty acids may be able to directly activate or suppress inflammatory pathways.

Most of the biological activity of lipopolysaccharides is mediated via its lipid A moiety. It is well established that the fatty acids that are part of lipid A play an important role in ligand recognition and receptor activation of Toll-like receptor 4 (TLR4), leading to the suggestion that saturated fatty acids may promote inflammation by direct activation of TLR4 (Fig. 1). Subsequent studies provided compelling evidence that saturated fatty acids activate nuclear factor-κB and stimulate expression of nuclear factor-κB targets such as cyclooxygenase 2, inducible nitric oxide synthase, and interleukin-1α in macrophages by activating TLR4 signaling in a MyD88-, IRAK-1-, and TRAF6-dependent manner (78–80). In contrast, unsaturated fatty acids are ineffective or may even act as antagonists. It was reported that saturated fatty acids activate TLR4 by promoting its recruitment to lipid rafts via a mechanism involving reactive oxygen species (81). Data showing direct physical binding of saturated fatty acids to TLR4 are still lacking, leaving open the mechanism of TLR4 activation (82). Others have argued against TLR4 activation by saturated fatty acids (83). Using TLR4^−/− macrophages, the role of TLR4 in mediating the inflammatory effects of saturated fatty acids was convincingly demonstrated (84, 85). Loss of TLR4 was also shown to partially protect against diet-induced obesity and insulin resistance, suggesting that TLR4 may be involved in mediating the detrimental effects of chronic high saturated fat consumption (84, 86, 87).

G protein–coupled receptors

Members of the G protein–coupled receptor (GPR) family are involved in mediating the stimulatory effects of fatty acids on insulin secretion by pancreatic β cells and on secretion of various gastrointestinal hormones in the gut (88, 89). These receptors, which include GPR40 (FFA receptor [FFAR]1), GPR41 (FFAR3), GPR43 (FFAR2), GPR84, and GPR120, each exhibit a preference for a specific set of fatty acids. To what extent activation of GPRs by fatty acids directly influences gene transcription remains to be determined (Fig. 1). Nevertheless, because of the emerging importance of GPRs in fatty acid sensing in a variety of tissues, some discussion of GPRs is warranted.

In addition to being activated by short-chain fatty acids (SCFAs) such as acetate, propionate, butyrate, and pentanoate, GPR41 and GPR43 have in common that they are well expressed in the colon, which is exposed to elevated concentrations of SCFAs via bacterial fermentation (88). Furthermore, GPR41 is expressed in numerous immune cells and adipose tissue, where it was shown to be involved in the regulation of leptin production (90). The relative role of GPR41 versus GPR43 as a sensor for SCFAs in the enteroendocrine system is not clear. Recently, it was proposed that GPR41 mediates the effect of gut microbiota on fat mass (91), whereas stimulation of GPR43 by SCFAs was shown to be necessary for the normal resolution of certain inflammatory responses (92).

In contrast to GPR41 and GPR43, GPR40 is activated by medium- and long-chain fatty acids, which include saturated and unsaturated fatty acids. GPR40 is expressed at high levels in pancreatic β cells, where it mediates the stimulatory effect of fatty acids on glucose-stimulated insulin secretion (93, 94). Apart from the pancreatic β cells, GPR40 is known to be expressed in various other cell types such as enteroendocrine cells. In these cells, GPR40 is involved in the stimulation of production of glucagon-like peptide 1 and gastric inhibitory peptide by fatty acids (95).

Other relevant members of the GPR family are GPR84, GPR119, and GPR120. GPR84 is well expressed in bone marrow–derived macrophages and has been proposed as receptor for medium-chain fatty acids (96). GPR119 has an expression pattern similar to that of GPR40, but the receptors shares only little homology. Endogenous ligands of GPR119 have been identified and include the fatty acid derivatives monoacyl glycerol, lysophosphatidylcholine, and oleoylethanolamide (97, 98). GPR120 is activated by saturated and unsaturated fatty acids with ≥12 carbons. GPR120 is most abundant in mouse large intestine, lung, and adipose tissue, but is also expressed in enteroendocrine cells where it mediates the effect of fatty acids on release of glucagon-like peptide 1 and cholecystokinin (99–101). Remarkably, GPR120 was recently proposed to serve as a specific sensor for (n-3) fatty acids in macrophages that may mediate the putative insulin-sensitizing and antidiabetic effects of (n-3) fatty acids in vivo by repressing macrophage-induced tissue inflammation (102). So far, evidence is lacking that shows that activation of these receptors is directly linked to the regulation of gene expression.

Conclusion

Although the importance of dietary fatty acids as determinants of the risk of numerous chronic diseases has been well recognized, only recently have we started to gain appreciation for the vast regulatory functions of dietary fatty acids in the human body. It is now evident that fatty acids, either directly or via its metabolites, act via a great variety of signaling pathways to influence numerous metabolic, inflammatory, and other biological processes. In the past decade, nutrigenomics has provided the ideal conceptual framework and the necessary technological tools to address the global effects of dietary fatty acids and has greatly contributed to a major advancement in our understanding of the molecular action of dietary fatty acids. So far, the focus has been on the molecular characterization of specific signaling routes, coupled with the description of the whole genome effects of dietary fatty acids. In the future, greater emphasis will have to be placed on the functional consequences of specific target gene regulation to fully understand the functional impact of dietary fatty acids and their potentially preventive effect in specific disease conditions. It can be foreseen that nutrigenomics will continue to make a push toward a more mechanistic and genomics-driven approach within the domain of nutritional sciences and further promote the implementation of high-throughput technologies.