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Monoglyceride hydrolase can be found in blood bound to thrombocytes or as free enzyme after the injection of heparin. Measurement can be performed easily with a new photometric method. The post-heparin activity is decreased in liver disease. This is probably due to the fact, that monoglyceride hydrolase is liberated from the liver's vessels.
Fatty acids and monoglycerides were evaluated in brain heart infusion broth and in milk for antimicrobial activity against the Scott A strain of Listeria monocytogenes. C12:0, C18:3, and glyceryl monolaurate (monolaurin) had the strongest activity in brain heart infusion broth and were bactericidal at 10 to 20 micrograms/ml, whereas potassium (K)-conjugated linoleic acids and C18:2 were bactericidal at 50 to 200 micrograms/ml. C14:0, C16:0, C18:0, C18:1, glyceryl monomyristate, and glyceryl monopalmitate were not inhibitory at 200 micrograms/ml. The bactericidal activity in brain heart infusion broth was higher at pH 5 than at pH 6. In whole milk and skim milk, K-conjugated linoleic acid was bacteriostatic and prolonged the lag phase especially at 4 degrees C. Monolaurin inactivated L. monocytogenes in skim milk at 4 degrees C, but was less inhibitory at 23 degrees C. Monolaurin did not inhibit L. monocytogenes in whole milk because of the higher fat content. Other fatty acids tested were not effective in whole or skim milk. Our results suggest that K-conjugated linoleic acids or monolaurin could be used as an inhibitory agent against L. monocytogenes in dairy foods.
Monoglycerides (MG) are emulsifiers widely used in food and pharmaceutical industries. Current industrial processes for MG production consist of the interesterification of triglycerides with glycerol (GL), in the presence of inorganic catalysts at high temperatures (> 200 degrees C). This reaction is known as glycerolysis and produces a mixture of approx 50% of MG. This level of concentration is suitable for many applications, although, for some specific uses like margarine, shortening, icing, and cream filling, require distilled MGs, which are purified MG (min. 90%) obtained by the molecular distillation process. Therefore, in this work, a 23 factorial design was employed to evaluate the effects of reaction parameters in the MG content after the interesterification reaction of refined soybean oil with GL in the presence of sodium hydroxide as catalyst. After that, the MG content in the reaction product was enhanced through the molecular distillation process in order to obtain distilled MG.
P-glycoprotein (P-gp) is a 170 kDa membrane protein that belongs to the ATP-binding cassette (ABC) transporter superfamily. In normal tissues, P-gp functions as an ATP-dependent efflux pump that excretes highly hydrophobic xenobiotic compounds, playing an important role in protecting the cells/tissues from xenobiotics. In the present study, chemical substances that could directly modulate the intestinal P-gp activity were searched in vegetables and fruits. By using human intestinal epithelial Caco-2 cells as a model of the small intestinal cells, we observed that a bitter melon fraction extracted from 40% methanol showed the greatest increase of the rhodamine-123 accumulation by Caco-2 cells. Inhibitory compounds in the bitter melon fraction were then isolated by HPLC using Pegasil C4 and Pegasil ODS columns. The HPLC fraction having the highest activity was analyzed by (1)H-NMR and FAB-MS, and the active compound was identified as 1-monopalmitin. It is interesting that certain types of monoglyceride might be involved in the drug bioavailability by specifically inhibiting the efflux mediated by P-gp.
Monoglyceride lipase (MGL) has been produced with the baculovirus-insect cell system. The mouse MGL cDNA was subcloned into a baculovirus transfer vector in frame with a sequence encoding an N-terminal stretch of six histidine residues. Purification to apparent homogeneity was obtained by nickel-chelating chromatography. The final yield was 3 mg of pure enzymatically active MGL per liter of Sf9 cell suspension culture. Analysis by SDS-PAGE and mass spectrometry showed that the recombinant histidine-tagged enzyme had the expected molecular mass. With monoolein as substrate, the specific activity and the apparent K(m) were close to those of rat MGL of adipose tissue.
New regulations limit the amount of diglycerol that may be present in partial glycerides used as food emulsifiers. Dimeric glycerol can be easily determined by HPLC on silica columns using acetonitrile: water partition and RI detection. Results for free diglycerol and total diglycerol obtained with a number of monoglyceride samples are given.
Endogenous and postheparin monoglyceride hydrolase (MGH) was studied in 9 patients with acute virus hepatitis and in 25 normal subjects with the use of a new spectrophotometric method. During the 4 weeks of observation the patients had significantly higher endogenous and reduced postheparin MGH levels if compared with the controls (p smaller than 0.001). In the initial phase of hepatitis the alterations were more pronounced and the serum glyceride concentration was raised. The results show that MGM activities in plasma may be greatly influenced by the liver.
The time course of the current following a voltage jump, which is applied to monoglyceride bilayers in the presence of valinomycin, shows two relaxation times. This is basically in agreement with a simple carrier model which has been described in full detail formerly. Relaxation times and amplitudes allow a calculation of the rate constants of the transport model. The presented data supplement an analysis which was hitherto based only on the slower relaxation process and on information derived from the nonlinearity of current-voltage characteristics. The additional resolution of the faster relaxation time allowed an approximate determination of the voltage dependence of the translocation rate constant for carrier-ion-complex and provided evidence for a small voltage dependence of the interfacial reaction. The dependence of the relaxation parameters on the ion concentration in the aqueous phase was interpreted assuming a saturation of the ion concentration at the reaction plane at high bulk concentrations.
The potential of the rectal route for administration of essential fatty acids (EFA) as monoglyceride (MG) was investigated. EFA-deficient rats were supplemented with 14 mg linoleic acid/day for 3 days. Supplementation was either by oral administration as corn oil, orally as corn oil-derived MG or rectally as MG. The patterns of polyunsaturated fatty acids (PUFA) in liver and serum lipids, characteristic of EFA deficiency, were altered in the direction of normalcy in similar magnitude by all modes of supplementation, indicating that the rectal route may be useful for administration of EFA. The amounts of phospholipids (PL) and free fatty acids (FFA) in liver changed by all modes of administration. The magnitude of change of total PL and of FFA in liver depended upon the chemical form in which linoleic acid was administered and the route of administration, indicating that these factors affect lipid metabolism.
Over 40 natural or synthetic lipophilic compounds were screened for antimicrobial activity. Gram (+) bacteria and yeasts but not Gram (-) bacteria were affected by these agents. Epimino and selena fatty acids are more active than their corresponding straight chain unsubstituted fatty acids. The position of selenium influenced the antimicrobial activity of the fatty acids. The presence and position of a double or triple bond, usually an important factor in long chain fatty acids (greater than C14) had little or no effect in C11 fatty acids. Optimum antimicrobial activity was found for fatty acids and their corresponding monoglycerides when the chain lenght was C12. The dilaurin derivative was not active.
2-Arachidonoylglycerol (2-AG) is an endogenous cannabinoid that binds to CB1 and CB2 cannabinoid receptors, inducing cannabimimetic effects. However, the cannabimimetic effects of 2-AG are weak in vivo due to its rapid enzymatic hydrolysis. The enzymatic hydrolysis of 2-AG has been proposed to mainly occur by monoglyceride lipase (monoacylglycerol lipase). Fatty acid amide hydrolase (FAAH), the enzyme responsible for the hydrolysis of N-arachidonoylethanolamide (AEA), is also able to hydrolyse 2-AG. In the present study, we investigated the hydrolysis of endocannabinoids in rat cerebellar membranes and observed that enzymatic activity towards 2-AG was 50-fold higher than that towards AEA. Furthermore, various inhibitors for 2-AG hydrolase activity were studied in rat cerebellar membranes. 2-AG hydrolysis was inhibited by methyl arachidonylfluorophosphonate, hexadecylsulphonyl fluoride and phenylmethylsulphonyl fluoride with ic(50) values of 2.2 nM, 241 nM and 155 microM, respectively. Potent FAAH inhibitors, such as OL-53 and URB597, did not inhibit the hydrolysis of 2-AG, suggesting that 2-AG is inactivated in rat cerebellar membranes by an enzyme distinct of FAAH. The observation that the hydrolysis of 1(3)-AG and 2-AG occurred at equal rates supports the role of MGL in 2-AG inactivation. This enzyme assay provides a useful method for future inhibition studies of 2-AG degrading enzyme(s) in brain membrane preparation having considerably higher MGL-like activity when compared to FAAH activity.
The interaction between beta-lactoglobulin and sonicated aqueous dispersions of the gel phase forming monoglyceride monostearoylglycerol were studied using isothermal titration calorimetry, direct binding experiments, differential scanning calorimetry, leakage of a fluorescent dye and solid-state (31)P- and (2)H-NMR. In the absence of a charged amphiphile, monostearoylglycerol forms a precipitate. Under these conditions, no interaction with beta-lactoglobulin was observed. In the presence of the negatively charged amphiphile dicetylphosphate, the gel phase monostearoylglycerol formed stable and closed, probably unilamellar, vesicles with an average diameter of 465 nm. beta-Lactoglobulin interacts with these bilayer structures at pH 4, where the protein is positively charged, as well as at pH 7 where the protein is negatively charged. Under both conditions of pH, the binding affinity of beta-lactoglobulin is in the micromolar range as observed with ITC and the direct binding assay. At pH 4, two binding modes were found, one of which is determined with ITC while the direct binding assay determines the net result of both. The first binding mode is observed with ITC and is characterized by a large binding enthalpy, a decreased enthalpy of the MSG L(beta) to L(alpha) phase transition and leakage of a fluorescent dye. These characteristics are explained by a beta-lactoglobulin induced partial L(beta) to coagel phase transition that results from a specific electrostatic interaction between the protein and the charged amphiphile. This explanation is confirmed by solid-state (2)H-NMR using 1-monostearoylglycerol with a fully deuterated acyl chain. Upon interaction with beta-lactoglobulin, the isotropic signal in the (2)H-NMR spectrum of the monostearoylglycerol-dicetylphosphate mixture partially transforms into a broad anisotropic signal which could be assigned to coagel formation. The second binding mode probably results from an aspecific electrostatic attraction between the negatively charged bilayer and the positively charged protein and causes the precipitation of the dispersion. At pH 7, only the first binding mode is observed.
Pressure versus distance relations have been obtained for solid (gel) and neat (liquid-crystalline) phase uncharged lipid bilayers by the use of x-ray diffraction analysis of osmotically stressed monoglyceride aqueous dispersions and multilayers. For solid phase monoelaidin bilayers, the interbilayer repulsive pressure decays exponentially from a bilayer separation of approximately 7 A at an applied pressure of 3 x 10(7) dyn/cm2 to a separation of approximately 11 A at zero applied pressure, where an excess water phase forms. The decay length is approximately 1.3 A, which is similar to the value previously measured for gel phase phosphatidylcholine bilayers. This implies that the decay length of the hydration pressure does not depend critically on the presence of zwitterionic head groups in the bilayer surface. For liquid-crystalline monocaprylin, the repulsive pressure versus distance curve has two distinct regions. In the first region, for bilayer separations of approximately 3-8 A and applied pressures of 3 x 10(8) to 4 x 10(6) dyn/cm2, the pressure decays exponentially with a decay length of approximately 1.3 A. In the second region, for bilayer separations of approximately 8-22 A and applied pressures of 4 x 10(6) to 1 x 10(5) dyn/cm2, the pressure decays much more gradually and is inversely proportional to the cube of the distance between bilayers. These data imply that two repulsive pressures operate between liquid-crystalline monocaprylin bilayers, the hydration pressure, which dominates at small (3-8 A) bilayer separations, and the fluctuation pressure, which dominates at larger bilayer separations (greater than 8 A) and strongly influences the hydration properties of the liquid-crystalline bilayers. Thus, due primarily to thermally induced fluctuations, monocaprylin bilayers imbibe considerably more water than do monoelaidin bilayers. For both monoelaidin andmonocaprylin, the measured magnitude of the hydration pressure is found to be proportional to the square of the dipole potential.
We have recently observed that monoglycerides (MGs), a family of lipids consisting of a single fatty acid moiety attached to a glycerol backbone, induce rapid dose-dependent apoptosis in murine thymocytes. In this work, we evaluated the sensitivity of various normal and malignant immune and non-immune cells to MGs. We demonstrate that the propensity to MG-induced death displayed by both T and B lymphocytes is clearly modulated according to their differentiation and activation status. For instance, the earliest T and B cell precursors are refractory to MG-mediated cell death. In the T-cell lineage, immature thymocytes are the most susceptible to MG treatment, while B cells from peripheral lymphoid organs appear more sensitive than B-cell subsets from the bone marrow. On the other hand, both activated T and B cells are more resistant to MG exposure than their non-activated counterparts. In addition, other hematopoietic lineages such as natural killer cells, macrophages, and erythroid cells are quite resistant to MG-induced death. Furthermore, using various immortalized cell lines from different tissues, we found that lymphomas and thymomas are the most sensitive among all lineages tested, while epithelial cells and fibroblasts are unaffected by MG treatment. Finally, MG-induced death was shown to be independent of Fas/Fas ligand (FasL) interactions. Altogether, our findings indicate that there is a cellular specificity related to MG-mediated cell death biased towards T and B lymphocytes. This suggests that MGs could potentially be used in the treatment of specific lymphoid disorders by bypassing the requirement for the Fas/FasL system.
The bactericidal potencies of saturated and unsaturated fatty acids (FAs) and monoglycerides (MGs) against Helicobacter pylori were determined following short incubations with freshly harvested cells over a range of pHs. FAs and their derivatives with an equivalent-carbon number of 12 were the most potent: lauric acid had a minimum bactericidal concentration (MBC) at pH 7.4 of 1 mM, myristoleic and linolenic acid were the most potent unsaturated FAs (MBCs of 0.5 mM, pH 7.4), and monolaurin was the most potent MG (MBC 0.5 mM). Potencies of saturated FAs were increased sharply by lowering pH, and a decrease of only 0.5 pH units can cause a change from non-lethal to lethal conditions. Conversely, the bactericidal action of monolaurin was not pH-dependent. The bactericidal potencies of unsaturated FAs increased with degree of unsaturation. When more than one FA or FA plus MGs were present, their combined action was additive. Urea and endogenous urease did not protect H. pylori from the bactericidal action of FAs. These results suggest that H. pylori present in the stomach contents (but not necessarily within the mucus barrier) should be rapidly killed by the millimolar concentrations of FAs and MGs that are produced by pre-intestinal lipase(s) acting on suitable triglycerides such as milk fat.
Two new lysophosphatidylcholines (1, 2) and four new monoglycerides (5-8) were isolated from the marine sponge Stelletta sp. by bioactivity-guided fractionation. The planar structures of the new compounds were established on the basis of NMR and MS analyses. The stereochemistry was defined by comparison of the optical rotation. The compounds were evaluated for cytotoxicity against a small panel of five human tumor cell lines.
The susceptibilities of three Gram-positive cocci to medium-chain saturated and long-chain unsaturated fatty acids and their one-monoglycerides were studied. The bacteria were incubated with equal volumes of lipid solutions for 10 min. Lauric acid, palmitoleic acid and monocaprin reduced the number of CFU by 6.0 log10 or greater at 5 mM concentration for streptococci of group A (GAS) and group B (GBS). When further compared at lower concentrations and after longer incubation time monocaprin proved to be the most active. Capric acid showed the highest activity against Staphylococcus aureus at 10 mM. However, at lower concentrations monocaprin was the only lipid that showed significant activity against S. aureus. The mode of action of monocaprin against GBS was studied by a novel two-color fluorescent assay of bacterial viability and by electron microscopy. The results indicate that the bacteria are killed by disintegration of the cell membrane by the lipid, leaving the bacterial cell wall intact. The highly lethal effect of monocaprin indicates that this lipid might be useful as a microbicidal agent for prevention and treatment of infections caused by these bacteria.
Normal rats fed an isocaloric sucrose-rich diet (SRD) for 3 weeks developed high levels of triacylglycerol in plasma (P) (mmol triacylglycerol I-1) heart (H) and liver (L) tissues (mumol triacylglycerol mg DNA-1) as compared to control rats fed the standard chow (STD) (X +/- SEM; P: SRD 1.32 +/- 0.06 vs STD 0.49 +/- 0.05, P less than 0.001; H: SRD 2.1 +/- 0.17 vs STD 0.94 +/- 0.01, P less than 0.001; L: SRD 8.48 +/- 1.47 vs STD 1.71 +/- 0.12, P less than 0.001). A simultaneous drop in the activities (mumol glycerol ml-1 hr-1) of several plasma post heparin lipolytic enzymes was observed; total triglyceride lipase (T-TGL): SRD 5.32 +/- 0.34 vs STD 7.48 +/- 0.64, P less than 0.01; lipoprotein lipase (LPL): SRD 1.61 +/- 0.26 vs STD 2.42 +/- 0.41, P less than 0.05; hepatictriglyceride lipase (H-TGL): SRD 3.71 +/- 0.28 vs STD 5.05 +/- 0.69, P less than 0.05 and monoglyceride hydrolase (MGH) (mumol glycerol I-1 min-1): SRD 558 +/- 108 vs STD 1165 +/- 45, P less than 0.001. Rats fed the SRD presented glucose intolerance after i.v. glucose (Kg X 10(-2); 1.06 +/- 0.09 vs 2.61 +/- 0.14 of STD, P less than 0.001) in spite of the presence of hyperinsulinism (sigma plasma IRI microU/ml from 0 to 30 min: 184.6 +/- 23.6 vs 100.5 +/- 9.7 of STD, P less than 0.01) suggesting that a state of insulin resistance had developed.(ABSTRACT TRUNCATED AT 250 WORDS)