Review Article

Endocannabinoid signaling and its regulation

by nutrients

Tiziana Bisogno1,2*

Mauro Maccarrone2,3*

1Endocannabinoid Research Group, Institute of Biomolecular Chemistry,National Research Council, 80078 Pozzuoli, Italy2Center of Integrated Research, Campus Bio-Medico University of Rome,00128 Rome, Italy3European Center of Brain Research/Santa Lucia Foundation, 00143 Rome,Italy

Abstract

Diet plays a central role in maintaining health throughout life

and a controlled food intake is associated to a reduced risk of

certain diseases. A proper diet should include vitamins, miner-

als, carbohydrates, proteins, and fats that have to be optimally

balanced in order to exert their physiological functions. The

endogenous ligands of type-1 and type-2 cannabinoid recep-

tors, N-arachidonoyl-ethanolamine and 2-arachidonoylglycerol,

are arachidonic acid (AA) derivatives whose levels are regu-

lated by the activity of metabolic enzymes, as well as by AA

availability. Since the only sources of AA in mammals are diet

and the enzymatic production in the liver from shorter-chain

essential fatty acids like linoleic acid, it is realistic to hypothe-

size that endocannabinoid levels might be modulated by fatty

acid composition of food. Therefore, in this review we summa-

rize literature data indicating that endocannabinoid levels, and

hence their activity at cannabinoid receptors, might be modu-

lated by food composition. We focused our attention on die-

tary fatty acid content, and on type and esterified form of fatty

acids in the different diets. VC 2014 BioFactors, 00(00):000–000,

2014

Keywords: diet; endocannabinoid system; fatty acids

1. IntroductionNew scientific knowledge regarding the role that diet may playin preventing disease is rapidly emerging, as evidence contin-ues to reveal components within food that not only promotegeneral health and well-being, but can also reduce the risk ofillness. Health food, functional food, dietary supplements, andprobiotics are now terms well-known not only to the scientificcommunity but also to the consumers. It has been well-established that diet plays a central role in maintaining healththroughout life. In the Western world, diet has significantlychanged in recent years and obesity, diabetes, cardiovasculardisease, hypertension, dyslipidemia, and cancer are only someof the pathological conditions that might benefit from a con-trolled food intake. People in developed countries tend to con-sume increasingly palatable food that, together with a diet richin sugars, promotes excess body weight [1].

The endocannabinoid system (ECS) is a ubiquitous lipidsignaling system in which different proteins control or modu-late several physiological processes and impact a huge varietyof human diseases. These include, among others, neurologicaland neuropsychiatric diseases [2,3], obesity and metabolic

Abbreviations: AA, arachidonic acid; AEA, N-arachidonoyl-ethanolamine;2-AG, 2-arachidonoylglycerol; ALA, a-linolenic acid; CB1 and CB2, cannabi-noid receptors type 1 and type 2; CLA, conjugated linoleic acid; DHA,docosahexaenoic acid; DHEA, N-docosahexaenoyl-ethanolamine; eCBs,endocannabinoids; ECS, endocannabinoid system; EPA, eicosapentaenoicacid; EPEA, N-eicosapentaenoyl-ethanolamine; FO, fish oil; KO, krill oil; LA,linolenic acid; NAE, N-acyl-ethanolamine; NAPE, N-arachidonoyl-phosphati-dylethanolamine; OA, oleic acid; OEA, N-oleoylethanolamine PA, palmiticacid, PEA, N-palmitoylethanolamine; PL, phospholipids; PLC, phospholi-pase C; PLD, phospholipase D; PUFA, polyunsaturated fatty acid; TAGs,triacylglycerols.

VC 2014 International Union of Biochemistry and Molecular BiologyVolume 00, Number 00, Month/Month 2014, Pages 00–00

*Address for correspondence: Dr. Tiziana Bisogno, EndocannabinoidResearch Group, Institute of Biomolecular Chemistry, National ResearchCouncil, Via C. Flegrei 34, 80078 Pozzuoli, Italy. Tel.: 139-081 8675093;Fax: 139-081 8041770; E-mail: tbisogno@icb.cnr.it or Prof. Mauro Maccar-rone, Center of Integrated Research, Campus Bio-Medico University ofRome, Via �Alvaro del Portillo 21, 00128 Rome, Italy. Tel.: 139-06225419169; Fax: 139-06 22541456; E-mail: m.maccarrone@unicampus.it.Received 8 April 2014; accepted 8 April 2014DOI 10.1002/biof.1167Published online 00 Month 2014 in Wiley Online Library(wileyonlinelibrary.com)

BioFactors 1

defects [4], as well as cardiovascular disorders [5], cancer [6],and gastrointestinal pathologies [7]. The ECS comprises endog-enous lipid transmitters (known as endocannabinoids, eCBs),their G-protein-coupled receptors (i.e., type 1 (CB1) and type 2(CB2) cannabinoid receptors), and the proteins responsible foreCB biosynthesis, inactivation, transport, and accumulation[8,9]. The main eCBs (Fig. 1), N-arachidonoyl-ethanolamine(anandamide, AEA) and 2-arachidonoylglycerol (2-AG), areproduced by an important n26 dietary polyunsaturated fattyacid (PUFA), that is arachidonic acid (AA), which is also thebiosynthetic precursor of a plethora of other chemical media-tors, overall known as “eicosanoids.” Thus, it is possible topredict that modifications of dietary intake may modulate eCBlevels, and then regulate several physiological functions medi-ated by their signaling. The ECS is implicated in both homeo-static, appetite-triggered, and hedonic (i.e., desire to consumehighly palatable foods that often occurs during periods of rela-tive energy abundance) food intakes [10]. Therefore, under-standing how direct manipulation of nutrients alters ECS activ-ity is a relevant research area, with a potential exploitation fora nutritional approach to treat human diseases. In this review,we summarize the main components of the ECS and discusshow expression and/or activity of its distinct elements might bemodulated by diet.

2. The Endocannabinoid SystemThat Cannabis preparations can stimulate appetite in humans,a phenomenon known as “munchies,” has been known forhundreds of years, but only the identification of the ECS pro-vided the rationale to the phenomenon and suggested a possi-ble interplay between food composition and ECS modulation[11]. Two G-protein-coupled receptors (GPCRs) with high affin-ity and specificity for D9-tetrahydrocannabinol (THC) havebeen cloned to date, CB1 and CB2 [12,13], that are bound andfunctionally activated by several endogenous ligands, termedeCBs. The main members of this group of lipids, AEA [14], and2-AG [15,16], are derived from AA that is hydrolyzed frommembrane phospholipids (PLs) (Fig. 2). Indeed, the direct PLprecursor of AEA is N-arachidonoyl-phosphatidylethanolamine(NAPE), which originates from the trans-acylase-catalyzedtransfer of AA from the sn21 position of PLs to the nitrogenatom of phosphatidylethanolamine [17,18]. NAPE can be con-verted into AEA in a one-step hydrolysis reaction, catalyzed bythe NAPE-specific phospholipase D (NAPE-PLD) [19]. Yet,transgenic mice where the nape-pld gene had been ablated

(NAPE-PLD “knockout,” NAPE-PLD-KO) do not exhibit reducedlevels of AEA in most tissues [20], suggesting that AEA can beformed from NAPE also via other biosynthetic pathways,including: (i) formation of phospho-AEA catalyzed by a phos-pholipase C (PLC) and subsequent action of a protein tyrosinephosphatase N22 [21], that hydrolyzes phospho-AEA to AEA;(ii) phosphodiesterase-mediated hydrolysis of glycerophospho-AEA, which in turn is produced via sequential cleavage of thetwo sn21 and 2-acyl groups of NAPE, catalyzed by a=b-hydrolase 4 (Abdh4) [22]; and (iii) formation of a 2-lyso-NAPEvia a soluble form of phospholipase A2 [23], followed by lyso-PLD-mediated hydrolysis of 2-lyso-NAPEs.

Moreover, by the same biosynthetic pathway responsiblefor AEA formation, other N-acyl-ethanolamines (NAEs), suchas N-palmitoylethanolamine (PEA) or N-oleoylethanolamine(OEA) are formed from palmitic acid (PA) or oleic acid (OA),respectively, esterified at sn21 position of PLs [18]. PEA andOEA do not activate CB receptors and exert their biologicalactivity by interacting with other targets. In particular, theanti-inflammatory mediator PEA acts by activating the nuclearperoxisome proliferator-activated receptor-a (PPAR-a) [24], orby enhancing AEA actions at CB1, transient receptor potentialvanilloid type-1 (TRPV1) channels, or PPAR-c [25]. The ano-rexigenic and neuroprotective agent OEA acts by activatingPPAR-a [26], TRPV1 channels [27], and GPR119 [28]. WhileAEA and other NAEs derive from fatty acids esterified on thesn21 position of PLs, in most cases 2-AG is produced from thehydrolysis of diacylglycerols (DAGs) containing arachidonate inthe 2 position, catalyzed by a DAG lipase that is selective forthe sn21 position [29]. DAGs, in turn, can be produced fromthe hydrolysis of either phosphoinositides (PI), catalyzed by aPI-selective phospholipase C (PI-PLC) [30], or phosphatidic acid(PA) [31], as shown in Fig. 3. The enzymatic inactivation ofAEA and 2-AG occurs through the hydrolysis of their amideand ester bonds, releasing AA and ethanolamine or glycerol,respectively, that are rapidly incorporated into membrane PLs[32,33]. Fatty acid amide hydrolase (FAAH) [34] has been iden-tified as the enzyme mainly responsible for AEA, and to aminor extent for 2-AG, hydrolysis [35]. Additionally, the mono-acylglycerol lipase (MAGL) is the enzyme that most specificallycontrols the levels of 2-AG [36,37]. Even though the latterenzyme is responsible for �85% of the total brain 2-AG degra-dation, two more enzymes, a/b-hydrolase-6 (ABHD6) and a/b-hydrolase-12 (ABHD12), with different subcellular distributionscompared to MAGL, have been suggested to control, togetherwith FAAH, the hydrolysis of distinct pools of 2-AG in the nerv-ous system [38]. From the observations reported above, it canbe anticipated that AEA is a minor component among NAEsand 2-AG is the most abundant among its congeners, reflectingthe relatively little and high amounts of AA esterified to thesn21 or sn22 position of PLs, respectively [39]. Therefore, it isrealistic to hypothesize that FA composition in the diet mightmodulate the amounts of FAs esterified on PLs and, as a con-sequence, the tissue concentrations of eCBs that in turndepend on essential FAs availability. Therefore, in the next

Chemical structures of the main eCBs.FIG 1

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2 Endocannabinoid Signaling and Nutrients

sections, we summarize the available in vitro and in vivo stud-ies, as well as the clinical data, that support this hypothesis.

3. Effect of Dietary Fatty Acids onEndocannabinoid LevelsFatty acids found naturally in the diet are classified accord-ing to the number of carbon atoms in their side chains, andare thus short (<8), medium (8–12), long (14–18), or verylong (�20) chain fatty acids. The double-bonds in natural

unsaturated fatty acids are generally in the cis configuration.The two major families of PUFAs are the n26 (x-6) and then23 (x-3) fatty acids, they are named after the position ofthe first double bond from the x- or n-terminal methyl end ofthe molecule. Linoleic acid (LA) and a-linolenic acid (ALA)are the two traditionally recognized essential fatty acids,which are the 18 carbon atom precursors of the n26 andn23 families, respectively. They include the n26 AA, and then23 eicosapentaenoic acid (EPA) and docosahexaenoic acid(DHA).

Major biosynthetic pathways for anandamide.FIG 2

3

3.1. In Vitro StudiesThe hypothesis that the availability of biosynthetic precursors,rather than the activity of the biosynthetic enzymes, might beresponsible for changes in eCB levels was investigated in vitro inmouse adipocyte cell line, 3T3F442A, supplemented with differ-ent free FAs, like LA, ALA, DHA, AA, OA, and PA [40]. PUFAschanged the amount of AA on the sn22 position of PLs and con-sequently affected the levels of 2-AG. In particular, DHA reducedthe amount of AA esterified on both sn22 and sn21 position ofPLs, but not of triacylglycerols (TAGs), and decreased 2-AG lev-els; instead, AA increased 2-AG levels and the amounts of AAesterified on both TAGs and PLs at the glycerol sn22, but notsn21, carbon [40]. Moreover, while other free FAs had no statis-tically significant effect on 2-AG levels, both PA and OA enhancedthe content of PEA and OEA [40]. In MC3T3-E1 osteoblast-likecells, EPA was reported to modulate distinct elements of theECS, as it reduced NAPE-PLD and CB2 mRNA expression thatincreased during osteoblast maturation, unfortunately the effectof EPA on eCB levels was not addressed in that study [41].Recently, evidence for in vitro formation of n23 (x-3) NAEs, syn-thesized from their corresponding PUFAs has been reported, butthe potential interaction of x-3 NAEs with the ECS remains to beinvestigated. 3T3-L1 adipocytes are indeed able to convert DHA

and EPA to their NAE derivatives N-docosahexaenoyl-ethanola-mine (DHEA) and N-eicosapentaenoyl-ethanolamine (EPEA),respectively, that exert anti-inflammatory properties by decreas-ing Lipopolysaccharide (LPS)-induced Interleukin (IL)-6 andMonocyte chemoattractant protein (MCP)-1 levels in adipocytes[42]. In line with this formation of DHEA and of its putative directbiosynthetic precursor, N-docosahexaenoyl-PE, as well as that ofdidocosahexaenoyl-PC and -PE, has been reported in bovine ret-ina expressing high levels of DHA [43]. DHEA and EPEA werealso endogenously produced following x-3 FAs treatments in dif-ferent human prostate and breast cancer cell lines [44,45] butcell supplementation of DHA or EPA apparently did not signifi-cantly affect 2-AG and AEA levels [44]. Possibly relevant to theabove studies, at least to some extent, is the finding that theavailability of the precursor FAs, supplemented to the cell, ratherthan its incorporation into membrane PLs might be responsiblefor the x-3 NAE formation and for the lack of effect on the n26(x-6) NAE and glycerol levels.

3.2. Animal StudiesThe consumption of n–3 (x-3) and n26 (x-6) essential FAs inWestern diets has changed markedly during the 20th century,with an increase in LA availability from �3% to �8% of energysupply [46]. Since humans cannot synthesize AA de novo, theonly AA source apart from diet is the enzymatic elongationand desaturation of LA precursor [47], hence is also the pre-cursor of eCBs. The hypothesis that LA, might be a diet modu-lator of eCB levels was investigated in mice supplied for 14weeks with various diets, differing in LA content from 1 per-cent of energy (1 en%) to 8 en% [48]. Dietary LA increased tis-sue AA, subsequently elevating 2-AG and AEA levels and pro-moting accumulation of body fat. The adipogenic effect of LAcould be prevented by adding 1 en% EPA and DHA to an 8en% LA diet, able to reduce the AA-PL pool, and to normalizeeCBs tone [48]. In addition, an isocaloric increase of dietaryLA from 1 to 8 en% in both low fat diet (LFD, 12.5 en%) andmedium fat diets (MFD, 35 en%) for 16 weeks elevated livereCB levels and increased the risk to develop obesity [49].Moreover, in a recent study Atlantic salmons (Salmo salar L.)were fed with a high level of LA (8 en%) from soyabean oil(SO) for 6 months, and salmon fillet was used for 16 weeks toproduce food for mice. The replacement of fish oil (FO) withSO in the diet caused an increase in LA, AA, and eCB levels insalmon liver, that subsequently elevated eCB levels in mice fedthe SO salmon diet compared with mice fed the FO salmondiet [49]. The elevated eCB activity in mice was associatedwith increasing weight gain and body weight, supporting therole of dietary LA as a potential key factor in controlling theactivity of the ECS. The presence of LA or conjugated linoleicacid (CLA) in the diet was found to correlate with modulationof eCB levels also in the brain. Indeed, in mice fed with dietscontaining 3% LA or 3% CLA for 4 weeks, the alteration of eCBlevels seemed to be FA-specific, as CLA- but not LA-enricheddiet increased 2-AG but not AEA content selectively in the cer-ebral cortex [50]. Moreover, newborn piglets fed with milk

Major biosynthetic pathways for 2-AG.FIG 3

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4 Endocannabinoid Signaling and Nutrients

formulations enriched in AA and DHA during the first monthof life showed significantly modified concentrations of the cor-responding NAEs in different brain regions, and such altera-tions were accompanied by changes in the distribution ofPUFAs in PLs [51]. A lipidomic analysis of acute 2-week DHAdietary supplementation showed a significant elevation ofDHA, EPA, 2-eicosapentaenoylglycerol (EPG), and DHEA inmurine plasma and brain, with a concomitant reduction ofAEA levels in the brain [52]. Since FA composition in dietmight modulate eCB levels in the brain, and CB1 might medi-ate emotional responses [53], it is reasonable to postulate thatdiets enriched or deprived with either n23 or n26 PUFAsmight produce effects on mood. In particular, maternal dietaryfat was reported to modulate AA incorporation into PLs andeCB production, with potential consequences on hypothalamic-pituitary-adrenal axis modulation during stress in developingpups [54]. Pregnant rats were fed a 5% (controls) or 30% highfat (HF) diet rich in either n26 (HF-n26) or n23 (HF-n23) fatduring the last week of gestation and lactation. On post-natalday 10 of lactation, milk from dams belonging to the HF-n23group displayed a reduced n26/n23 fat ratio compared withcontrol and HF milk, reflecting the composition of maternaldiet. Hypothalamic and hippocampal levels of AA-PLs andeCBs were found to be diet-specific, with positive correlationsin both the hippocampus and hypothalamus for 2-AG, and anegative correlation for AEA in the hypothalamus. Moreover,stress-induced Adreno Cortico Tropic Hormone (ACTH) secre-tion increased upon pre-treatment with CB1/CB2 antagonistsonly in control pumps [54]. More recently, in order to mimiclifelong n26/n23 imbalance of essential PUFAs, mice havebeen fed with n23 deficient diet throughout gestation and lac-tation; after weaning, the offspring received the same dietthroughout the rest of their life [55]. Reduced n23 FA levels inthe diet modified FA composition, and markedly diminishedthe synaptic and behavioral functions of CB1 receptor in twobrain regions that have been implicated in emotional behaviorand mood disorders (i.e., prefrontal cortex and accumbens),without significant alteration of eCB levels in the brain [55].Moreover, a low dietary level of DHA has been associated withincreased risk of developing neuropsychiatric diseases,because nutritional n23 deficiency throughout life causes ananxiety/depressive-like behavior in mice [56]. In particular,mice fed a n23-deficient diet exhibited altered CB1/CB2 signal-ing pathways in prefrontal cortex and hypothalamus, asrevealed by the ability of the CB1/CB2 agonist WIN55,212-2 toactivate MAPK pathway [56].

Does dietary form of fatty acids impact on eCB levels?

Different studies support the hypothesis that the choice of thedietary form of PUFAs may affect their lipid incorporationand/or nutritional activity, overall suggesting that PL-boundEPA and DHA have distinct effects compared to TAG-boundEPA and DHA [57]. In particular, n23 PUFAs are reported tobe mainly bound to PLs in fish products, while in fatty fishsuch as salmon they are bound to PLs and TAGs in a 40:60

ratio; when available as supplement like in FO, n23 PUFAsare almost exclusively bound to TAGs [58]. A relatively newsource rich in n23 PUFAs in the form of PLs (mainly PC)rather than TAGs is krill oil (KO), extracted from Antarctickrill (Euphausia superba) [59]. The proportion of PLs in thetotal lipids of krill has been reported to vary between 30% and60%, and the constitutive presence of a lipid-soluble antioxi-dant like astaxanthin appears to preserve KO from oxidation[60]. Recently, the effects on ectopic fat and inflammation ofeither FO or KO, balanced for EPA and DHA content, wereinvestigated in Zucker rats, a model of obesity and relatedmetabolic dysfunction [61], and were compared with a controldiet devoid of EPA and DHA and with similar contents of OA,LA, and ALA. Rats fed with KO for 4 weeks had significantlylower liver TAGs and reduced peritoneal macrophageresponse to inflammatory stimulus, compared with controlrats. Moreover, a lower concentration of AEA and 2-AG wasfound in the visceral adipose tissue, and of AEA only in theliver and heart [61]. These effects were associated with lowerlevels of AA in membrane PLs, yet not with higher activity ofeCB-degrading enzymes, suggesting that the beneficial effectsof KO might be ascribed to changes in membrane FA composi-tion rather than changes in eCB catabolism [61]. This hypothe-sis was confirmed by measuring eCB levels in different periph-eral tissues, including inguinal and epididymal adipose tissue,liver, gastrocnemius muscle, kidneys, and heart from mice fedfor 8 weeks with HFD diets with different KO content [62]. KOdose-dependently reduced AEA and/or 2-AG levels in almostall the tissues analyzed, by reducing the availability of the bio-synthetic precursors of these compounds. The higher efficacyof n23 PUFAs administered as PLs rather than TAGs was alsoreported by Rossmeisl et al. (2012) [63]. In dietary obese mice,DHA/EPA administered as PLs prevented glucose intoleranceand obesity better than TAGs, and only the PL form reducedplasma insulin and adipocyte hypertrophy, being also moreeffective in reducing hepatic steatosis and low-grade inflam-mation of white adipose tissue (WAT). These beneficial effectswere correlated with reduced 2-AG levels in WAT itself.

4. Human StudiesUnlike in vitro and in vivo animal studies, only a few datahave been reported in humans on the potential modulation ofthe ECS by n23 PUFAs. The effect of 4 weeks dietary treat-ment with KO, menhaden oil (MO), or olive oil (OO) in over-weight or obese individuals has been recently reported [64–66]. KO significantly decreased 2-AG but not AEA plasma lev-els in obese subjects, while MO or OO treatments did not mod-ify eCB levels in either overweight or obese individuals [64].Moreover, as previously observed in mice [62], in overweight/obese subjects the inhibitory effect of KO on eCB levels corre-lated with a reduction of the n26/n23 PUFA ratio in plasmaPLs [64]. In addition, dietary supplementation to obese men ofDHA and EPA for 24 weeks, in the form of krill powder, wasreported to be able to reduce high TAGs content and plasma

5

AEA levels [65]. The reduction of triglyceridemia and eCB lev-els was associated with a decreased waist/hip and visceral fat/skeletal muscle mass ratio [65]. Moreover, data reported abovesuggested that treatments with krill formulations may producedifferent effects on plasma eCB levels depending on differentcohorts of subjects, duration of treatments (4 vs. 24 weeks),and dosage (2 g/day vs. 4 g/day). Furthermore, the use of asheep cheese naturally enriched in ALA, CLA, and vaccenicacid (VA), has been more recently associated to a modulationof eCB profiles in mildly hypercholesterolaemic subjects [66]. A3-week treatment of 42 adult volunteers with control orenriched cheese significantly decreased AEA plasma levels,and after 90 g/per day of enriched cheese, leptin and AEA con-centrations appeared to be strongly correlated [66].

5. Do Spices and Food Plants Modulatethe ECS?The lipid nature of eCB calls for attention on whether and howother dietary fats might modulate eCB levels and their signal cas-cades, and indeed in the last few years several ingredients ofspice or food plant elements (Fig. 4) have emerged for their abil-ity to interact to different extents with ECS. The sesquiterpene(E)-caryophyllene [(E)-BCP] is a major plant volatile aromatic ter-pene found in large amounts in the essential oils of many differ-ent spice and food plants, such as oregano (Origanum vulgareL.), cinnamon (Cinnamomum spp.) and black pepper (Piper nig-rum L.) [67–69]. Because of its weak aromatic taste, (E)-BCP iscommercially used as a food additive. It has been shown that (E)-BCP selectively targets CB2 and produces analgesic and anti-inflammatory effects in vivo [70,71]. Falcarinol [(3R,9Z)21,9-hep-

tadecadiene-4,6-diyn-3-ol] containing vegetables like carrot (Dau-cus carota L.), celery (Apium graveolens L.), fennel (Foeniculumvulgare Mill.), and parsnip (Pastinaca sativa L.) induce pro-allergic effects in skin and exhibit affinity to both human CB1

and CB2 [72]. Several isoprenylated analogs of the naturallyoccurring plant stilbenoid trans-resveratrol, such as arachidin-1[trans-4-(3-methyl-1-butenyl)23,5,30,40-tetrahydroxystilbene] andarachidin-3 [trans-4-(3-methyl-1-butenyl)23,5,40-trihydroxystil-bene], bind to both CB1 and CB2 with low affinity (in the lMrange) [73]. Plant natural products have been also suggested toexert cannabimimetic effects without direct interaction with CB1/CB2 receptors. In particular, genistein and daidzein, found infood sources such as lupin (Lupinus albus, L.), fava (Vicia faba,L.), beans and soybeans (Glycine max L.), inhibit FAAH in a lowmM range [74,75]. Biochanin A, a phytoestrogen present in soy-beans, chickpea (Cicer arietinum), and other legumes, inhibitsFAAH both in vitro and in vivo, and has only modest effects onCB1 and CB2 receptors [76]. Although it is likely that these com-pounds might exert beneficial effects in humans, data on theirestimated daily intake and therapeutic efficacy are still missing.

6. ConclusionsAvailable data summarized in this review highlight the sensitiv-ity of eCB levels to FA composition of the diet. It seems evidentthat the presence in the diet of certain PUFAs has as first conse-quence the alteration of the availability of the eCB biosyntheticprecursors, thus resulting in an alteration of the eCB levels. Thewell-established involvement of the ECS in several central andperipheral human pathologies suggests that any dietary manipu-lation of eCB levels needs to be time- and space-specific, inorder to warrant a correct ECS function and therapeutic exploi-tation. For instance, while obesity and dyslipidemia might bene-fit from a reduction of eCB levels in particular brain areas (i.e.,hypothalamus) or peripheral organs (i.e., adipose tissue or gas-trointestinal tract), the same reduction in other brain regions(i.e., hippocampus or hypothalamus) might support developmentof neuropsychiatric diseases and mood disorders. Further stud-ies are necessary to assess a nutritional approach as alternativetherapy to treat metabolic or emotional diseases. Diet, depend-ing on its FA composition, might reduce (much alike CB1/CB2

antagonists and/or inhibitors of eCB biosynthetic enzymes) orenhance (much alike CB1/CB2 agonists and/or inhibitors of eCBhydrolytic enzymes) the biological activity of eCBs, thus finelytuning its therapeutic potential. On a final note, to fully appreci-ate the relevance of the therapeutic benefit derived from a die-tary modulation of eCB levels, it should be necessary also toevaluate the effect of different diets on the expression and func-tional activity of eCB binding receptors and metabolic enzymes.

AcknowledgementThis investigation was partly supported by Ministero dell’Istru-zione, dell’Universit�a e della Ricerca (PRIN 2010–2011 project)to TB and MM.

Chemical structures of spice and food plant ingre-

dients that interact with the ECS.FIG 4

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6 Endocannabinoid Signaling and Nutrients

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BioFactors

8 Endocannabinoid Signaling and Nutrients