Human milk-specific fat components enhance the secretion of ghrelin by MGN3-1 cells

Triacylglycerols (TAGs) are a major fat component in human milk. Since gastric lipase produces 1,2-diacylglycerol from TAGs, we focused on the bioactivity of human milk-derived diacylglycerols in stomach cells. Ghrelin is produced in the stomach and acts as an important regulator of growth hormone secretion and energy homeostasis. In this study, we showed that 1-oleoyl-2-palmitoylglycerol (OP) increased ghrelin secretion, whereas 1,3-dioleoyl-2-palmitoylglycerol (OPO), a major component of human milk TAGs, did not increase ghrelin levels in the ghrelin-secreting cell line, MGN3-1. Therefore, diacylglycerol OP may directly contribute to the regulation of ghrelin secretion. We also found that 2-palmitoylglycerol and 1- and 2-oleoylglycerol increased ghrelin secretion. Finally, we demonstrated that the intracellular cAMP levels and preproghrelin and ghrelin O-acyl transferase expression levels were enhanced by OP treatment in MGN3-1 cells. This may represent an example of a novel mother-infant interaction mediated by fat components derived from human breast milk.

Gac Fruit Oils Encapsulated by Palm Oil-based Monoacylglycerols: The Effect of Drying Methods

Lyotropic liquid crystals (LLCs) are interesting wall-materials for encapsulation technology, in which monoacylglycerols (MAGs) are considered as potential ingredient for LLC formulation. This study, therefore, applied palm oil-based MAGs to encapsulate Gac fruit oils and compared the effect of two drying methods (freeze-drying and spray-drying) on the quality of products during storage. Wall-materials were prepared by ultrasound dispersing MAGs/water mixtures (40/60, w/w) into Pluronic solution (2%, w/w) to formulate LLC dispersions. Then, Gac fruit oils were encapsulated by freeze-drying and spray-drying. Various technologies were applied to characterize the properties of dispersions, the encapsulated powder morphology and the loading capacity. Obtained results showed that LLC dispersions made of palm oilbased MAG were micro- and nano-emulsions which were very convenient for encapsulating Gac fruit oils. For both drying methods, β-carotene of Gac fruit oils was successfully entrapped by MAGs with a high loading capacity (200 µg β-carotene/g powder). The degradation of encapsulated β-carotene after four storage weeks was 10 - 40% and freeze-dried samples showed a better protection effect in comparison to spray-dried samples.

Characterization of Palm Fatty Acid Distillate, Diacylglycerol Regioisomers, and Esterification Products Using High-Performance Size Exclusion Chromatography

High-performance size exclusion chromatography (HPSEC) equipped with an evaporative light scattering detector (ELSD) was utilized for characterization of palm fatty acid distillate (PFAD) and its esterified products, with a particular focus on lipid profiles and diacylglycerol (DAG) regioisomers. The separation of triacylglycerol (TAG), DAG, monoacylglycerol (MAG), and free fatty acid (FFA) was achieved through a single 100-Å Phenogel column, coupled with a 2-cm C18 guard, utilizing toluene/acetic acid (100:0.25, v/v) as the mobile phase. This separation was based on size sieving principles and the interactions between the hydroxyl group(s) and the Phenogel matrix. The limit of detection (LOD) and limit of quantification (LOQ) for the esterified PFAD products analyzed by this method fell within the range of 4.8-5.5 μg/mL and 14.7-16.7 μg/mL, respectively. Additionally, the same column, paired with a 2-cm silica guard and a mobile phase comprised of toluene/isooctane/acetic acid (35:65:0.15, v/v/v), was used for the characterization of DAG regioisomers within the esterified PFAD. LODs and LOQs for sn-1,3-DAG and sn- 1,2-DAG were determined to be 39.2 and 118.7 μg/mL, and 32.8 and 99.5 μg/mL, respectively. Investigation of esterified PFAD products prepared using 4% H2SO4 at 120°C. After 2 h, the analysis revealed the highest MAG content at 31.85%, accompanied by 51.54% DAG, 2.35% TAG, and a residual 14.27% FFA. Notably, as the reaction time extended, the MAG content decreased, while both DAG and TAG levels exhibited an increasing trend. Further examination of DAG regioisomers during PFAD esterification, under varying catalyst concentrations (2-10%) and reaction temperatures (80-140°C), demonstrated a significant increase in the percentage of sn-1,3-DAG, inversely correlated with the reduction in FFA from 2% H 2 SO 4 and 80°C onwards. Remarkably, the percentage of sn-1,2-DAG remained relatively stable regardless of changes in catalyst concentrations or temperatures, confirming its susceptibility to isomerization into the thermodynamically more stable sn-1,3-DAG form. This study provides valuable insights into the composition and behavior of esterified PFAD products.

Alterations of gut microbiome and metabolism induced by inulin associated with weight loss in obese female mice

Our previous work revealed the microbiota-dependent beneficial effects of inulin in obese male mice, but the effects in obese female mice were not determined. High-fat diet (HFD)-induced obese female mice were switched to normal diets and gavaged with normal saline or inulin for 10 weeks. Inulin supplementation significantly accelerated weight loss and reversed HFD-induced gut microbiota dysbiosis in obese female mice, and also reduced the ratio of Firmicutes/Bacteroidetes and enriched the abundance of norank_f_Muribaculaceae and Alistipes. In addition, 52 key serum metabolites were distinctly altered after inulin supplementation. Among them, andrographolide and monoacylglycerols (18:4) increased more than 9-fold and 14-fold, respectively, while phosphatidylcholine (PC) (18:1e/2:0), PC (20:1/20:2) and PC (19:1/19:1) decreased. In conclusion, gut microbiota and metabolites were closely associated with the beneficial effects of inulin in accelerating weight loss in obese female mice.

Nostochopcerol, a new antibacterial monoacylglycerol from the edible cyanobacterium Nostochopsis lobatus

A new antibacterial 3-monoacyl-sn-glycerol, nostochopcerol (1), was isolated from a cultured algal mass of the edible cyanobacterium Nostochopsis lobatus MAC0804NAN. The structure of compound 1 was established by the analysis of NMR and MS data while its chirality was established by comparison of optical rotation values with synthetically prepared authentics. Compound 1 inhibited the growth of Bacillus subtilis and Staphylococcus aureus at MIC of 50 μg/mL and 100 μg/mL, respectively.

Monoacylglycerol O-acyltransferase 1 lowers adipocyte differentiation capacity in vitro but does not affect adiposity in mice

OBJECTIVE

Monoacylglycerol O-acyltransferase 1 (Mogat1), a lipogenic enzyme that converts monoacylglycerol to diacylglycerol, is highly expressed in adipocytes and may regulate lipolysis by re-esterifying fatty acids released during times when lipolytic rates are low. However, the role of Mogat1 in regulating adipocyte fat storage during differentiation and diet-induced obesity is relatively understudied.

METHODS

Here, adipocyte-specific Mogat1 knockout mice were generated and subjected to a high-fat diet to determine the effects of Mogat1 deficiency on diet-induced obesity. Mogat1 floxed mice were also used to develop preadipocyte cell lines wherein Mogat1 could be conditionally knocked out to study adipocyte differentiation in vitro.

RESULTS

In preadipocytes, it was found that Mogat1 knockout at the onset of preadipocyte differentiation prevented the accumulation of glycerolipids and reduced the differentiation capacity of preadipocytes. However, the loss of adipocyte Mogat1 did not affect weight gain or fat mass induced by a high-fat diet in mice. Furthermore, loss of Mogat1 in adipocytes did not affect plasma lipid or glucose concentrations or insulin tolerance.

CONCLUSIONS

These data suggest Mogat1 may play a role in adipocyte differentiation in vitro but not adipose tissue expansion in response to nutrient overload in mice.

Conversion of Pulse Protein Foam-Templated Oleogels into Oleofoams for Improved Baking Application

The food industry has long been searching for an efficient replacement for saturated-fatty-acid-rich fats for baking applications. Although oleogels have been considered a potential alternative for saturated and trans fats, their success in food application has been poor. The present study explored the use of oleofoams obtained by whipping the pulse protein foam-templated oleogels for cake baking. Oleogels were prepared at room temperature by adding canola oil containing high-melting monoglyceride (MAG) or candelilla wax (CW) to the freeze-dried pea or faba bean protein-stabilized foams. Oleogels were then whipped to create the oleofoams; however, only the oleogels containing MAG could form oleofoams. CW-oleogel could not form any oleofoam. The most stable oleofoams with the highest overrun, stability, and storage modulus were obtained from 3% MAG+pulse protein foam-templated oleogels. The MAG plus protein foam-templated oleogels showed smaller and more packed air bubbles than MAG-only oleofoam, which was ascribed to the protein's ability to stabilize air bubbles and provide a network in the continuous oil phase to restrict air bubble movement. A novel batter preparation method for oleofoam was developed to increase air bubble incorporation. The X-ray microtomography images of the cakes showed a non-homogeneous distribution of larger air bubbles in the oleofoam cake compared to the shortening cake although their total porosity was not much different. The oleofoam cakes made with the new method yielded similar hardness and chewiness compared to the shortening cakes. By improving rheology and increasing air incorporation in the batter, high-quality cakes can be obtained with MAG-containing oleofoams made from pulse protein foam-templated oleogels.

α/β-Hydrolase Domain-Containing 6 (ABHD6)- A Multifunctional Lipid Hydrolase

α/β-hydrolase domain-containing 6 (ABHD6) belongs to the α/β-hydrolase fold superfamily and was originally discovered in a functional proteomic approach designed to discover monoacylglycerol (MAG) hydrolases in the mouse brain degrading the endocannabinoid 2-arachidonoylglycerol. Subsequent studies confirmed that ABHD6 acts as an MAG hydrolase regulating cannabinoid receptor-dependent and -independent signaling processes. The enzyme was identified as a negative modulator of insulin secretion and regulator of energy metabolism affecting the pathogenesis of obesity and metabolic syndrome. It has been implicated in the metabolism of the lysosomal co-factor bis(monoacylglycerol)phosphate and in the surface delivery of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors. Finally, ABHD6 was shown to affect cancer cell lipid metabolism and tumor malignancy. Here, we provide new insights into the experimentally derived crystal structure of ABHD6 and its possible orientation in biological membranes, and discuss ABHD6's functions in health and disease.

Two AMP-Binding Domain Proteins from Rhizophagus irregularis Involved in Import of Exogenous Fatty Acids

Arbuscular mycorrhizal fungi (AMF) colonize roots, where they provide nutrients in exchange for sugars and lipids. Because AMF lack genes for cytosolic fatty acid de novo synthase (FAS), they depend on host-derived fatty acids. AMF colonization is accompanied by expression of specific lipid genes and synthesis of sn-2 monoacylglycerols (MAGs). It is unknown how host-derived fatty acids are taken up by AMF. We describe the characterization of two AMP-binding domain protein genes from Rhizophagus irregularis, RiFAT1 and RiFAT2, with sequence similarity to Saccharomyces cerevisiae fatty acid transporter 1 (FAT1). Uptake of ¹³C-myristic acid (14:0) and, to a lesser extent, ¹³C-palmitic acid (16:0) was enhanced after expression of RiFAT1 or RiFAT2 in S. cerevisiae Δfat1 cells. The uptake of ²H-labeled fatty acids from ²H-myristoylglycerol or ²H-palmitoylglycerol was also increased after RiFAT1 and RiFAT2 expression in Δfat, but intact ²H-MAGs were not detected. RiFAT1 and RiFAT2 expression was induced in colonized roots compared with extraradical mycelium. ¹³C-label in the AMF-specific palmitvaccenic acid (16:1Δ11) and eicosatrienoic acid (20:3) were detected in colonized roots only when ¹³C₂-acetate was supplemented but not ¹³C-fatty acids, demonstrating that de novo synthesized, host-derived fatty acids are rapidly taken up by R. irregularis from the roots. The results show that RiFAT1 and RiFAT2 are involved in the uptake of myristic acid (14:0) and palmitic acid (16:0), while fatty acids from MAGs are only taken up after hydrolysis. Therefore, the two proteins might be involved in fatty acid import into the fungal arbuscules in colonized roots.[Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Glycerophosphodiesterase 3 (GDE3) is a lysophosphatidylinositol-specific ectophospholipase C acting as an endocannabinoid signaling switch

Endocannabinoid signaling plays a regulatory role in various (neuro)biological functions. 2-arachidonoylglycerol (2-AG) is the most abundant endocannabinoid, and although its canonical biosynthetic pathway involving phosphoinositide-specific phospholipase C and diacylglycerol lipase α is known, alternative pathways remain unsettled. Here, we characterize a noncanonical pathway implicating glycerophosphodiesterase 3 (GDE3, from GDPD2 gene). Human GDE3 expressed in HEK293T cell membranes catalyzed the conversion of lysophosphatidylinositol (LPI) into monoacylglycerol and inositol-1-phosphate. The enzyme was equally active against 1-acyl and 2-acyl LPI. When using 2-acyl LPI, where arachidonic acid is the predominant fatty acid, LC-MS analysis identified 2-AG as the main product of LPI hydrolysis by GDE3. Furthermore, inositol-1-phosphate release into the medium occurred upon addition of LPI to intact cells, suggesting that GDE3 is actually an ecto-lysophospholipase C. In cells expressing G-protein-coupled receptor GPR55, GDE3 abolished 1-acyl LPI-induced signaling. In contrast, upon simultaneous ex-pression of GDE3 and cannabinoid receptor CB2, 2-acyl LPI evoked the same signal as that induced by 2-AG. These data strongly suggest that, in addition to degrading the GPR55 LPI ligand, GDE3 can act as a switch between GPR55 and CB2 signaling. Coincident with a major expression of both GDE3 and CB2 in the spleen, spleens from transgenic mice lacking GDE3 displayed doubling of LPI content compared with WT mice. Decreased production of 2-AG in whole spleen was also observed, supporting the in vivo relevance of our findings. These data thus open a new research avenue in the field of endocannabinoid generation and reinforce the view of GPR55 and LPI being genuine actors of the endocannabinoid system.

Antimicrobial Lipids from Plants and Marine Organisms: An Overview of the Current State-of-the-Art and Future Prospects

In the actual post-antibiotic era, novel ways of rethinking antimicrobial research approaches are more urgent than ever. Natural compounds with antimicrobial activity such as fatty acids and monoacylglycerols have been investigated for decades. Additionally, the interest in other lipid classes as antimicrobial agents is rising. This review provides an overview on the research about plant and marine lipids with potential antimicrobial activity, the methods for obtaining and analyzing these compounds, with emphasis on lipidomics, and future perspectives for bioprospection and applications for antimicrobial lipids. Lipid extracts or lipids isolated from higher plants, algae or marine invertebrates are promising molecules to inactivate a wide spectrum of microorganisms. These lipids include a variety of chemical structures. Present and future challenges in the research of antimicrobial lipids from natural origin are related to the investment and optimization of the analytical workflow based on lipidomics tools, complementary to the bioassay-guided fractionation, to identify the active compound(s). Also, further work is needed regarding the study of their mechanism of action, the structure-activity relationship, the synergistic effect with conventional antibiotics, and the eventual development of resistance to lipids, which, as far as is known, is unlikely.

Retinol-binding protein 2 (RBP2): biology and pathobiology

Retinol-binding protein 2 (RBP2; originally cellular retinol-binding protein, type II (CRBPII)) is a 16 kDa cytosolic protein that in the adult is localized predominantly to absorptive cells of the proximal small intestine. It is well established that RBP2 plays a central role in facilitating uptake of dietary retinoid, retinoid metabolism in enterocytes, and retinoid actions locally within the intestine. Studies of mice lacking Rbp2 establish that Rbp2 is not required in times of dietary retinoid-sufficiency. However, in times of dietary retinoid-insufficiency, the complete lack of Rbp2 gives rise to perinatal lethality owing to RBP2 absence in both placental (maternal) and neonatal tissues. Moreover, when maintained on a high-fat diet, Rbp2-knockout mice develop obesity, glucose intolerance and a fatty liver. Unexpectedly, recent investigations have demonstrated that RBP2 binds long-chain 2-monoacylglycerols (2-MAGs), including the canonical endocannabinoid 2-arachidonoylglycerol, with very high affinity, equivalent to that of retinol binding. Crystallographic studies establish that 2-MAGs bind to a site within RBP2 that fully overlaps with the retinol binding site. When challenged orally with fat, mucosal levels of 2-MAGs in Rbp2 null mice are significantly greater than those of matched controls establishing that RBP2 is a physiologically relevant MAG-binding protein. The rise in MAG levels is accompanied by elevations in circulating levels of the hormone glucose-dependent insulinotropic polypeptide (GIP). It is not understood how retinoid and/or MAG binding to RBP2 affects the functions of this protein, nor is it presently understood how these contribute to the metabolic and hormonal phenotypes observed for Rbp2-deficient mice.

Monoacylglycerol of 7,10-Dihydroxy-8(E)-octadecenoic Acid Enhances Antibacterial Activities against Food-Borne Bacteria

Conversion of free fatty acids into monoacylglycerol gives rise to new structural properties, particularly amphipathic property. Therefore, monoacylglycerols are widely used in pharmaceutical and food industries and are also reported to facilitate better absorption into the human body. A functional fatty acid when transformed into a monoacylglycerol will possibly conserve both the original functionality and amphipathic property. The compound 7,10-dihydroxy-8(E)-octadecenoic acid (DOD) was generated from oleic acid by Pseudomonas aeruginosa PR3 and was known to contain antimicrobial activities against a broad range of food-borne and plant pathogenic bacteria. Here, we attempted to convert DOD into its monoacylglycerol form using lipase for producing an amphipathic antibacterial agent. Consequently, the monoacylglycerol of DOD (DOD-MAG) was successfully produced by coincubating DOD, glycerol, and lipase at 30 °C. The maximum conversion yield reached 70% after 12 h of incubation. Antibacterial activity of DOD-MAG was enhanced by 8 times from the original activity of DOD against food-borne bacteria.

Removal of organochlorines from vegetable oils and its benefits in preventing formation of monochloropropanediol diesters

This paper reports the first results on depleting certain organochlorines from vegetable oils without the use of any solvent in order to mitigate monochloropropanediol diesters (MCDPE). The concept is based on separating the organochlorines from the bulk oil by using trapping agents (e.g. monoacylglycerols) that can be easily separated from the oil. The process starts by mixing and homogenizing crude vegetable oils with the trapping agent and subsequently separating the trapping agent from the oil bulk via crystallization. The proof-of-concept of the approach is demonstrated on a spiked sunflower model system, solvent extracted crude sunflower oil, industrially produced crude soybean and corn oils. The depletion of organochlorines in the crude oils and its beneficial effect on the MCPDE content in the heat treated samples is measured by LC-MS. The depletion efficacy of the monitored organochlorines was estimated to be in the 60-95 % range. Both the melting point and polarity of the trapping agents affected the depletion efficacy of the organochlorines. Trapping agents with higher melting point and polarity, such as monostearin were more effective in comparison to high melting point but less polar agents such as palm stearin or agents rich in polar but low melting point monolinolein/monoolein. The effect of organochlorine depletion on the subsequent MPCDE levels in heat treated oil was in the range of 60-90 % reduction depending on the type of the studied oil.

Lipid metabolism alterations in the neuronal response to A53T α-synuclein and Fe-induced injury

Pathological α-synuclein (α-syn) overexpression and iron (Fe)-induced oxidative stress (OS) are involved in the death of dopaminergic neurons in Parkinson's disease (PD). We have previously characterized the role of triacylglycerol (TAG) formation in the neuronal response to Fe-induced OS. In this work we characterize the role of the α-syn variant A53T during Fe-induced injury and investigate whether lipid metabolism has implications for neuronal fate. To this end, we used the N27 dopaminergic neuronal cell line either untransfected (UT) or stably transfected with pcDNA3 vector (as a transfection control) or pcDNA-A53T-α-syn (A53T α-syn). The overexpression of A53T α-syn triggered an increase in TAG content mainly due to the activation of Acyl-CoA synthetase. Since fatty acid (FA) β-oxidation and phospholipid content did not change in A53T α-syn cells, the unique consequence of the increase in FA-CoA derivatives was their acylation in TAG moieties. Control cells exposed to Fe-induced injury displayed increased OS markers and TAG content. Intriguingly, Fe exposure in A53T α-syn cells promoted a decrease in OS markers accompanied by α-syn aggregation and elevated TAG content. We report here new evidence of a differential role played by A53T α-syn in neuronal lipid metabolism as related to the neuronal response to OS.

Re-evaluation of mono- and di-glycerides of fatty acids (E 471) as food additives

The EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of mono- and di-glycerides of fatty acids (E 471) when used as a food additive. The Panel considered that it is very likely that hydrolysis of mono- and di-glycerides of fatty acids by lipases in the gastrointestinal tract would occur, resulting in the release of glycerol and fatty acids. Glycerol (E 422) and fatty acids (E 570) have been re-evaluated and the Panel concluded that there was no safety concern regarding their use as food additives. Toxicological studies with mono- and di-glycerides rich in unsaturated fatty acids were considered for the re-evaluation of E 471. No evidence for adverse effects was reported in short-term, subchronic studies, chronic, reproductive and developmental toxicity studies. Neither carcinogenic potential nor a promotion effect in initiation/promotion was reported. The available studies did not raise any concern with regard to genotoxicity. The refined estimates were based on 31 out of 84 food categories in which E 471 is authorised. The Panel noted that the contribution of E 471 represented at the mean only 0.8-3.5% of the recommended daily fat intake. Based on the approach described in the conceptual framework for the risk assessment of certain food additives re-evaluated under Commission Regulation (EU) No 257/2010 and taking into account the considerations mentioned above, the Panel concluded that there was no need for a numerical acceptable daily intake (ADI) and that the food additive mono- and di-glycerides of fatty acids (E 471) was of no safety concern at the reported uses and use levels. The Panel recommended some modifications of the EU specifications for E 471.

Monoacylglycerol signalling and ABHD6 in health and disease

Lipid metabolism dysregulation underlies chronic pathologies such as obesity, diabetes and cancer. Besides their role in structure and energy storage, lipids are also important signalling molecules regulating multiple biological functions. Thus, understanding the precise lipid metabolism enzymatic steps that are altered in some pathological conditions is helpful for designing better treatment strategies. Several monoacylglycerol (MAG) species are only recently being recognized as signalling lipid molecules in different tissues. Recent studies indicated the importance of the ubiquitously expressed serine hydrolase α/β-hydrolase domain 6 (ABHD6), which is a MAG hydrolase, in regulating signalling competent MAG in both central and peripheral tissues. The central and peripheral function of the endocannabinoid 2-arachidonoylglycerol, which is a 2-MAG, and its breakdown by both ABHD6 and classical MAG lipase has been well documented. ABHD6 and its substrate MAG appear to be involved in the regulation of various physiological and pathological processes including insulin secretion, adipose browning, food intake, neurotransmission, autoimmune disorders, neurological and metabolic diseases as well as cancer. Diverse cellular targets such as mammalian unc13-1 (Munc13-1), PPARs, GPR119 and CB1/2 receptors, for MAG-mediated signalling processes have been proposed in different cell types. The purpose of this review is to provide a comprehensive summary of the current state of knowledge regarding ABHD6/MAG signalling and its possible therapeutic implications.

Modified Gas Chromatographic Method to Determine Monoacylglycerol and Diacylglycerol Contents in Edible Fats and Oils

Monoacylglycerol (MAG) and diacylglycerol (DAG) are minor components of edible fats and oils, and they relate to the quality of these foods. The AOCS official method Cd 11b-91 has been used to determine MAG and DAG contents in fats and oils. There are, however, difficulties in the determination of MAG and DAG using this analytical procedure. Therefore, we improved this method by modifying the trimethylsilyl derivatization procedure and replacing the internal standard (IS) material. In our modified method, TMS-HT (mixture of hexamethyldisilazane and trimethylchlorosilane) was used for derivatization of MAG and DAG, which was followed by liquid-liquid extraction with water and n-hexane solution containing the IS, tricaprin. Using the modified method, we demonstrated superior repeatability in comparison with that of the AOCS method by reducing procedural difficulties. The relative standard deviation of distearin peak areas was 1.8% or 2.9% in the modified method, while it was 5.6% in the AOCS method. In addition, capillary columns, such as DB-1ht and DB-5ht could be used in this method.

The Plant Polyester Cutin: Biosynthesis, Structure, and Biological Roles

Cutin, a polyester composed mostly of oxygenated fatty acids, serves as the framework of the plant cuticle. The same types of cutin monomers occur across most plant lineages, although some evolutionary trends are evident. Additionally, cutins from some species have monomer profiles that are characteristic of the related polymer suberin. Compositional differences likely have profound structural consequences, but little is known about cutin's molecular organization and architectural heterogeneity. Its biological importance is suggested by the wide variety of associated mutants and gene-silencing lines that show a disruption of cuticular integrity, giving rise to numerous physiological and developmental abnormalities. Mapping and characterization of these mutants, along with suppression of gene paralogs through RNA interference, have revealed much of the biosynthetic pathway and several regulatory factors; however, the mechanisms of cutin polymerization and its interactions with other cuticle and cell wall components are only now beginning to be resolved.

MGL2/YMR210w encodes a monoacylglycerol lipase in Saccharomyces cerevisiae

In silico analysis of the uncharacterized open reading frame YMR210w in Saccharomyces cerevisiae revealed that it possesses both an α/β hydrolase domain (ABHD) and a typical lipase (GXSXG) motif. The purified protein displayed monoacylglycerol (MAG) lipase activity and preferred palmitoyl-MAG. Overexpression of YMR210w in the known MAG lipase mutant yju3Δ clearly revealed that the protein had MAG lipase activity, hence we named the ORF MGL2. Overexpression of YMR210w decreased the cellular triacylglycerol levels. Analysis of the overexpressed strains showed reduction in the lipid droplets number and size. Phenotype studies revealed that the double deletion yju3Δmgl2Δ displayed a growth defect that was partially restored by MGL2 overexpression.

Molecular and biochemical characterizations of the monoacylglycerol lipase gene family of Arabidopsis thaliana

Monoacylglycerol lipase (MAGL) catalyzes the last step of triacylglycerol breakdown, which is the hydrolysis of monoacylglycerol (MAG) to fatty acid and glycerol. Arabidopsis harbors over 270 genes annotated as 'lipase', the largest class of acyl lipid metabolism genes that have not been characterized experimentally. In this study, computational modeling suggested that 16 Arabidopsis putative MAGLs (AtMAGLs) have a three-dimensional structure that is similar to a human MAGL. Heterologous expression and enzyme assays indicated that 11 of the 16 encoded proteins indeed possess MAG lipase activity. Additionally, AtMAGL4 displayed hydrolase activity with lysophosphatidylcholine and lysophosphatidylethanolamine (LPE) substrates and AtMAGL1 and 2 utilized LPE as a substrate. All recombinant AtMAGLs preferred MAG substrates with unsaturated fatty acids over saturated fatty acids and AtMAGL8 exhibited the highest hydrolase activities with MAG containing 20:1 fatty acids. Except for AtMAGL4, -14 and -16, all AtMAGLs showed similar activity with both sn-1 and sn-2 MAG isomers. Spatial, temporal and stress-induced expression of the 16 AtMAGL genes was analyzed by transcriptome analyses. AtMAGL:eYFP fusion proteins provided initial evidence that AtMAGL1, -3, -6, -7, -8, -11, -13, -14 and -16 are targeted to the endoplasmic reticulum and/or Golgi network, AtMAGL10, -12 and -15 to the cytosol and AtMAGL2, -4 and -5 to the chloroplasts. Furthermore, AtMAGL8 was associated with the surface of oil bodies in germinating seeds and leaves accumulating oil bodies. This study provides the broad characterization of one of the least well-understood groups of Arabidopsis lipid-related enzymes and will be useful for better understanding their roles in planta.

A First Attempt into the Production of Acylglycerol Mixtures from Echium Oil

Enzymatic glycerolysis of Echium oil (Echium plantagineum) has been carried out in the presence of four commercial lipases. Different pretreatments of the reaction mixture, such as high pressure homogenization and addition of food grade monoolein as an emulsifier, were evaluated to test their influence on the glycerolysis reaction. In addition, the impact of reducing temperature and the utilization of a solvent generally recognized as safe as a flavoring agent, such as limonene, were also investigated. Conversion of ca. 60-70% of triacylglycerols and production of ca. 25-30% of monoacylglycerols (MAGs) were attained. Finally, at the best reaction conditions, the glycerolysis reaction was scaled up at pilot plant and the product mixture obtained was fractionated via molecular distillation. From this stage, two products were attained: a distillate containing 80% of MAGs and a residue containing approximately 50% of diacylglycerols and 50% of triacylglycerols. All these mixtures can be utilized as self-emulsifying vehicles for the formulation of bioactive substances and also as precursors for the production of structured bioactive lipids.

Effect of emulsifier and viscosity on oil separation in ready-to-use therapeutic food

Oil separation is a common food quality problem in ready-to-use therapeutic food (RUTF), the shelf-stable, peanut-based food used to treat severe acute malnutrition in home settings. Our objective was to evaluate the effect on oil separation of three emulsifiers at different concentrations in RUTF. We also assessed two viscosity measurements. A scale-up experiment was carried out during full-scale RUTF production in Malawi. Results indicate that viscosity is inversely correlated with oil separation, and that the Bostwick consistometer is a simple, useful tool to predict viscosity. Oil separation in RUTF may be mitigated by use of an emulsifier, which increases the viscosity of the product. The emulsifier that reduced oil separation to the greatest extent was a mixture of high and low monoacylglycerol (MAG) emulsifiers. Proper raw material quality control to achieve consistent ingredient fat level and fat type, and production temperature and shearing control should be a focus in RUTF manufacturing.

'Hit and run' serial femtosecond crystallography of a membrane kinase in the lipid cubic phase

The lipid-based bicontinuous cubic mesophase is a nanoporous membrane mimetic with applications in areas that include medicine, personal care products, foods and the basic sciences. An application of particular note concerns it use as a medium in which to grow crystals of membrane proteins for structure determination by X-ray crystallography. At least two variations of the mesophase exist. One is the highly viscous cubic phase, which has well developed long-range order. The other so-called sponge phase is considerably more fluid and lacks long-range order. The sponge phase has recently been shown to be a convenient vehicle for delivering microcrystals of membrane proteins to an X-ray free-electron laser beam for serial femtosecond crystallography (SFX). Unfortunately, the sponge phase approach calls for large amounts of protein that are not always available in the case of membrane proteins. The cubic phase offers the advantage of requiring significantly less protein for SFX but comes with its own challenges. Here, we describe the physico-chemical bases for these challenges, solutions to them and prospects for future uses of lipidic mesophases in the SFX arena.

The influence of fat and monoacylglycerols on growth of spore-forming bacteria in processed cheese

Highly undesirable microbial contaminants of processed cheese are endospore-forming bacteria of the genera Bacillus and Clostridium. Survival of Bacillus subtilis, B. cereus, Clostridium butyricum and C. sporogenes was examined in model processed cheese samples supplemented with monoacylglycerols. In processed cheese samples, monoacylglycerols of undecanoic, undecenoic, lauric and adamantane-1-carboxylic acid at concentration of 0.15% w/w prevented the growth and multiplication of both Bacillus species throughout the storage period. The two species of Clostridium were less affected by monoacylglycerols in processed cheese samples and only partial inhibition was observed. The effect of milk fat content on microbial survival in processed cheese was also evaluated. The growth of Bacillus sp. was affected by the fat level of processed cheese while population levels of Clostridium sp. did not differ in processed cheese samples with 30, 40 and 50% fat in dry matter.

Classical endocannabinoid-like compounds and their regulation by nutrients

Endocannabinoid-like compounds are structurally related to the true endocannabinoids but do not contain highly unsaturated fatty acids, and they do not bind the cannabinoid receptors. The classical endocannabinoid-like compounds include N-acylethanolamines and 2-monoacylglycerols, and their structural resemblance to the endocannabinoids makes them players in the endocannabinoid system, where they can interfere with the actions of the true endocannabinoids, because they in several cases engage the same synthesizing and degrading enzymes. In addition they have pharmacological actions of their own, which are particularly interesting in a nutritional and metabolic context. Exogenously supplied oleoylethanolamide, palmitoylethanolamide, and linoleoylethanolamide have anorexic effects, and the endogenous formation of these N-acylethanolamines in the small intestine may serve an important role in regulating food intake, through signaling via PPARα and the vagus nerve to the brain appetite center. A chronic high-fat diet will decrease intestinal levels of these anorectic N-acylethanolamines and this may contribute to the hyperphagic effect of high-fat diet; 2-monoacylglycerols mediate endocrine responses in the small intestine; probably trough activation of GPR119 on enteroendocrine cells, and diet-derived 2-monoacylglycerols, for example, 2-oleoylglycerol and 2-palmitoylglycerol might be important for intestinal fat sensing. Whether these 2-monoacylglycerols have signaling functions in other tissues is unclear at present.

Urgineaglyceride A: a new monoacylglycerol from the Egyptian Drimia maritima bulbs

One new compound, (2S)-1-O-(Z)-tetracos-6-enoate glycerol (1) named urgineaglyceride A, along with six known compounds, 3,5,7,3',5'-pentahydroxydihydroflavonol (2), stigmasterol (3), (25S)-5β-furostane-3β-22α-26-triol (4), scillaridin A (5), (2S)-(+)-2-hydroxynaringenin-4'-O-β-D-glucopyranoside (6) and quercetin-3'-O-β-D-glucopyranoside (7), were isolated from the EtOAc fraction of Drimia maritima (L.) Stearn bulbs. Their structures were secured based on their IR, UV, 1D and 2D NMR data, in addition to HR-MS data and comparison with the literature data. The isolated compounds were evaluated for their in vitro growth inhibitory activity against A549 non-small cell lung cancer (NSCLC), U373 glioblastoma (GBM) and PC-3 prostate cancer cell lines. Compounds 2 and 3 displayed variable activities against the tested cancer cell lines. Compound 2 was a selective inhibitor of the NSCLC cell line with an IC₅₀ of 2.3 μM, whereas 3 was selective against GBM with IC₅₀ of 0.5 μM and against PC-3 with 2.0 μM.

Fatty acid specificity of T1 lipase and its potential in acylglycerol synthesis

BACKGROUND

T1 lipase has received considerable attention due to its thermostability. Fatty acid specificity of T1 lipase (crude and purified) was investigated, and its potential in the synthesis of acylglycerols was also evaluated.

RESULTS

Fatty acid specificity of T1 lipase (crude and purified) was investigated in the esterification of fatty acids (C6:0 to C18:3), suggesting that crude and purified T1 lipase had the lowest preference for C18:0 [specificity constant (1/α) = 0.08] followed by C18:1 (1/α = 0.12) and showed the highest preference for C8:0 (1/α = 1). A structural model was constructed to briefly explore interactions between the lipase and its substrate. Furthermore, crude T1 lipase-catalysed synthesis of diacylglycerols (DAGs) and monoacylglycerols (MAGs) by esterification of glycerol with C18:1 was studied for evaluating its potential in acylglycerols synthesis. The optimal conditions were glycerol/oleic acid molar ratio 5:1, the lipase concentration 9.7 U g(-1) of substrates, water content 50 g kg(-1) of substrates and temperature 50 °C, which yielded 42.25% DAGs, 26.34% MAGs and 9.18% triacylglycerols at 2 h.

CONCLUSION

DAGs and MAGs were synthesised in good yields although C18:1 (a much poorer substrate) was used. Our work demonstrates that T1 lipase, which was discovered to show 1,3-regio-selectivity, is a promising biocatalyst for lipids modification.

Anti-inflammatory potential of monogalactosyl diacylglycerols and a monoacylglycerol from the edible brown seaweed Fucus spiralis Linnaeus

A monoacylglycerol (1) and a 1:1 mixture of two monogalactosyl diacylglycerols (MGDGs) (2 and 3) were isolated from the brown seaweed Fucus spiralis Linnaeus. The structures were elucidated by spectroscopic means (NMR and MS) and by comparison with the literature. Compound 1 was composed of a glycerol moiety linked to oleic acid (C18:1 Ω9). Compounds 2 and 3 contained a glycerol moiety linked to a galactose unit and eicosapentaenoic acid (C20:5 Ω3) combined with octadecatetraenoic acid (C18:4 Ω3) or linolenic acid (C18:3 Ω3), respectively. The isolated compounds were tested for their cytotoxic and anti-inflammatory activity in RAW 264.7 macrophage cells. All of them inhibited NO production at non-cytotoxic concentrations. The fraction consisting of compounds 2 and 3, in a ratio of 1:1, was slightly more effective than compound 1 (IC₅₀ of 60.06 and 65.70 µg/mL, respectively). To our knowledge, this is the first report of these compounds from F. spiralis and on their anti-inflammatory capacity.

Transcriptional and biochemical responses of monoacylglycerol acyltransferase-mediated oil synthesis and associated senescence-like responses in Nicotiana benthamiana

Triacylglycerol (TAG) accumulates in plant seeds as a major renewable source of carbon for food, fuel and industrial feedstock. Approaches to enhance TAG content by altering lipid pathways and genes in vegetative parts have gained significant attention for biofuel and other applications. However, consequences of these modifications are not always studied in detail. In an attempt to increase TAG levels in leaves we previously demonstrated that a novel substrate, monoacylglycerol (MAG), can be used for the biosynthesis of diacylglycerol (DAG) and TAG. Transient expression of the Mus musculus monoacylglycerol acyltransferases MGAT1 and 2 in the model plant Nicotiana benthamiana increased TAG levels at 5 days post-infiltration (dpi). Here we show that increased TAG and DAG levels can be achieved as early as 2 dpi. In addition, the MGAT1 infiltrated areas showed senescence-like symptoms from 3 dpi onwards. To unravel underlying molecular mechanisms, Illumina deep sequencing was carried out (a) for de-novo assembling and annotation of N. benthamiana leaf transcripts and (b) to characterize MGAT1-responsive transcriptome. We found that MGAT1-responsive genes are involved in several processes including TAG biosynthesis, photosynthesis, cell-wall, cutin, suberin, wax and mucilage biosynthesis, lipid and hormone metabolism. Comparative analysis with transcript profiles from other senescence studies identified characteristic gene expression changes involved in senescence induction. We confirmed that increased TAG and observed senescence-symptoms are due to the MAG depletion caused by MGAT1 activity and suggest a mechanism for MGAT1 induced TAG increase and senescence-like symptoms. The data generated will serve as a valuable resource for oil and senescence related studies and for future N. benthamiana transcriptome studies.

The bioaccessibility of eicosapentaenoic acid was higher from phospholipid food products than from mono- and triacylglycerol food products in a dynamic gastrointestinal model

The bioaccessibility of eicosapentaenoic acid (EPA) in the forms of monoacylglycerol (EPA-MAG), triacylglycerol (EPA-TAG), and phospholipid (EPA-PL) during gastrointestinal passage was compared in this study using a dynamic gastrointestinal model (TIM system). The TIM system simulated the average upper gastrointestinal tract conditions of healthy human adults after intake of a meal (fed state conditions). In this study, the three EPA-rich oils were separately homogenized with full fat milk to obtain oil-in-water emulsions. Plain yogurt was added into the mixture at an emulsion/yogurt ratio of 4:1 (w/w) as the food matrix of the test products. The results show that the test meals containing EPA-PL left the stomach compartment most efficiently in comparison with the gastric emptying of EPA-MAG and EPA-TAG. The PLs also showed a significantly (P < 0.05) higher bioaccessibility of EPA (75-80%) in comparison with MAG (30%) and TAG (38%). The better gastric emptying of EPA-PL was likely related to the more stable emulsion of EPA-PL in the test meal. EPA-PL was delivered within the meal matrix into the duodenum instead of floating on the top of the test meal matrix. EPA-MAG had the highest amount of EPA that did not leave the stomach (68% of the test meal). The results from this work indicate that EPA-PL is a more effective form of EPA for a higher lipid bioaccessibility than MAG and TAG under the test conditions.

The actions and metabolism of lysophosphatidylinositol, an endogenous agonist for GPR55

Lysophosphatidylinositol (LPI) is a subspecies of lysophospholipid and is assumed to be not only a degradation product of phosphatidylinositol (PI), but also a bioactive lysophospholipid mediator. However, not much attention has been directed toward LPI compared to lysophosphatidic acid (LPA), since the receptor for LPI has not been identified. During screening for an agonist for the orphan G protein coupled receptor GPR55, we identified LPI, 2-arachidonoyl LPI in particular, as an agonist for GPR55. Our efforts to identify an LPI receptor facilitated research on LPI as a lipid messenger. In addition, we also found that DDHD1, previously identified as phosphatidic acid-preferring phospholipase A1, was one of the synthesizing enzymes of 2-arachidonoyl LPI. Here, we summarized the background for discovering the LPI receptor, and the actions/metabolism of LPI. We also referred to the biosynthesis of PI, a 1-stearoyl-2-arachidonoyl species, since the molecule is the precursor of 2-arachidonoyl LPI. Furthermore, we discussed physiological and/or pathophysiological processes involving LPI and GPR55, including the relevance of LPI-GPR55 and cannabinoids, since GPR55 was previously postulated to be another cannabinoid receptor. Although there is no doubt that GPR55 is the LPI receptor, we should re-consider whether or not GPR55 is in fact another cannabinoid receptor.

Different functions of intestinal and liver-type fatty acid-binding proteins in intestine and in whole body energy homeostasis

It has long been known that mammalian enterocytes coexpress two members of the fatty acid-binding protein (FABP) family, the intestinal FABP (IFABP) and the liver FABP (LFABP). Both bind long-chain fatty acids and have similar though not identical distributions in the intestinal tract. While a number of in vitro properties suggest the potential for different functions, the underlying reasons for expression of both proteins in the same cells are not known. Utilizing mice genetically lacking either IFABP or LFABP, we directly demonstrate that each of the enterocyte FABPs participates in specific pathways of intestinal lipid metabolism. In particular, LFABP appears to target fatty acids toward oxidative pathways and dietary monoacylglycerols toward anabolic pathways, while IFABP targets dietary fatty acids toward triacylglycerol synthesis. The two FABP-null models also displayed differences in whole body response to fasting, with LFABP-null animals losing less fat-free mass and IFABP-null animals losing more fat mass relative to wild-type mice. The metabolic changes observed in both null models appear to occur by nontranscriptional mechanisms, supporting the hypothesis that the enterocyte FABPs are specifically trafficking their ligands to their respective metabolic fates.

A methodology for radiolabeling of the endocannabinoid 2-arachidonoylglycerol (2-AG)

The metabolic intermediate and endocannabinoid signaling lipid 2-arachidonoylglycerol (2-AG) has not been readily labeled, primarily because of its instability toward rearrangement. We now detail a synthetic method that easily gives tritiated 2-AG from [5,6,8,9,11,12,14,15-(3)H(N)]arachidonic acid in two steps. We utilized a short chain 1,3-diacylglycerol and proceeded through the "structured lipid" [5'',6'',8'',9'',11'',12'',14'',15''-(3)H(N)]2-arachidonoyl-1,3-dibutyrylglycerol, a triacylglycerol that was conveniently deprotected in ethanol with acrylic beads containing Candida antarctica lipase B to give [5'',6'',8'',9'',11'',12'',14'',15''-(3)H(N)]2-arachidonoylglycerol ([(3)H]2-AG). The flash chromatographic separation necessary to isolate the labeled 2-acylglycerol [(3)H]2-AG resulted in only 4% of the rearrangement byproducts that have been a particular problem with previous methodologies. This reliable "kit" method to prepare the radiolabeled endocannabinoid as needed gave tritiated 2-arachidonoylglycerol [(3)H]2-AG with a specific activity of 200 Ci/mmol for enzyme assays, metabolic studies, and tissue imaging. It has been run on unlabeled materials on over 10 mg scales and should be generally applicable to other 2-acylglycerols.

Uptake of Lipids by the Entomophilic Nematode Romanomermis culicivorax

Romanomermis culicivorax juveniles were dissected out of Aedes aegypti larvae 7 days after infection and incubated under controlled conditions in isotonic saline containing a (1)C-labeled fatty acid (palmitic acid), monoacylglycerol (glycerol monoolein), or triacylglycerol (glycerol tripalmate) nutrient source. The mermithid absorbed each of these lipids from the incubation medium, the rate of uptake being greatest for glycerol monoolein. No lipase activity was detected in whole nematode homogenates or in the media in which the nematodes were incubated. It is suggested that the nematode transports complex lipid molecules across its outer cuticle intact.