BACKGROUND: A major worldwide health issue is the rising frequency of resistance of bacteria.Drug combinations are a winning strategy in fighting resistant bacteria and might help in protecting the existing drugs.Monolaurin is natural compound extracted from coconut oil and has a promising antimicrobial activity against Staphylococcus.aureus. This study aims to examine the efficacy of monolaurin both individually and in combination with β-lactam antibiotics against Staphylococcus aureus isolates.
METHODS: Agar dilution method was used for determination of minimum inhibitory concentration (MIC) of monolaurin against S.aureus isolates. Scanning electron microscope (SEM) was used to detect morphological changes in S.aureus after treatment with monolaurin. Conventional and Real-time Polymerase chain reaction (RT-PCR) were performed to detect of beta-lactamase (blaZ) gene and its expressional levels after monolaurin treatment. Combination therapy of monolaurin and antibiotics was assessed through fractional inhibitory concentration and time-kill method.
RESULTS: The antibacterial activity of monolaurin was assessed on 115 S.aureus isolates, the MIC of monolaurin were 250 to 2000 µg/ml. SEM showed cell elongation and swelling in the outer membrane of S.aureus in the prescence of 1xMIC of monolaurin. blaZ gene was found in 73.9% of S.aureus isolates. RT-PCR shows a significant decrease in of blaZ gene expression at 250 and 500 µg/ml of monolaurin. Synergistic effects were detected through FIC method and time killing curve. Combination therapy established a significant reduction on the MIC value. The collective findings from the antibiotic combinations with monolaurin indicated synergism rates ranging from 83.3% to 100%.In time-kill studies, combination of monolaurin and β-lactam antibiotics produced a synergistic effect.
CONCLUSIONS: This study showed that monolaurin may be a natural antibacterial agent against S. aureus, and may be an outstanding modulator of β-lactam drugs. The concurrent application of monolaurin and β-lactam antibiotics, exhibiting synergistic effects against S. aureus in vitro, holds promise as potential candidates for the development of combination therapies that target particularly, patients with bacterial infections that are nearly incurable.

The objective of the present study was to evaluate the effects of a tributyrin and monolaurin blend compared to high ZnO levels in weaned piglets under field conditions. In Trial 1, piglets (n = 168) were assigned to 1 of 2 treatments: 1) control (CON; diet supplemented with 3000 g ZnO/t of feed; n = 8 replicates); 2) tributyrin and monolaurin blend - Porcestin™ (PR; diet supplemented with basal level of ZnO at 150 g/t and with the tested blend at 5 kg/t of feed; n = 8 replicates). In Trial 2, piglets (n = 244) were assigned to the same two treatments (n = 10 replicates). The study duration was 4 (Trial 1) and 6 (Trial 2) weeks post-weaning. In both trials, growth performance was similar between treatments (P > 0.05). In Trial 1, faecal counts of Lactobacillus spp. increased in pigs of PR group (P < 0.05). In both trials, histomorphometrical analysis of jejunum and ileum samples showed a thicker intestinal mucosa in favor of the PR treatment (P < 0.01), and Foxp3-positive regulatory T cells increased together with a concomitant decrease of MPO-positive granulocytes in jejunal mucosa of piglets from the PR treatment (P < 0.01). Overall, supplementation of monolaurin and tributyrin blend compared to high ZnO levels resulted in similar growth performance. Moreover, beneficial effects on small intestinal morphometry and immune cells responses indicate its ability to attenuate inflammatory processes. Further research is necessary to optimize the use of tested product.

To improve the quality of cultured large yellow croaker (Larimichthys crocea), this study was performed to study the impacts of glycerol monolaurate (GML) on the nutritional value, growth performance, muscle texture, and taste intensity of L. crocea. The results showed that GML as a feed additive significantly increased the crude lipid content and reduced the diameters of muscle fibers, which in turn markedly altered the flesh texture in terms of cohesiveness. Moreover, the taste indicators (umami and richness) and flavor-related amino acid (glutamic acid, glycine, and proline) contents of L. crocea muscle were significantly higher in the GML group. Metabolomic and gene expression analyses showed that GML supplementation could significantly improve amino acid biosynthesis and metabolism, promote protein and lipid synthesis, and activate myogenic-related signaling pathways of L. crocea. Consequently, adding an appropriate amount of GML to fish feed would be conducive to providing healthy, nutrient-rich and acceptably flavored aquatic-products.

OBJECTIVE: The aim of the study was to test the hypothesis that 5% monolaurin vaginal gel, a naturally occurring monoglyceride shown to have antimicrobial effects on vaginal pathogens without affecting Lactobacillus species, cures bacterial vaginosis (BV).
METHODS: This was a multicenter, double-blinded, randomized controlled trial comparing 5% monolaurin vaginal gel to vehicle placebo (glycol-based) gel administered twice daily for 3 days. Nonpregnant, nonbreastfeeding women between ages 18 and 50 years were recruited and BV confirmed. Primary outcome was clinical cure assessed by resolution of all 4 Amsel criteria. Secondary outcomes included safety and tolerability assessed by solicited urogenital adverse events. Exploratory outcomes included colony counts for vaginal microbes associated with healthy vaginal flora (Lactobacillus species) and the dysbiosis often associated with BV (Gardnerella species and Mobiluncus species). A 2:1 test article to placebo randomization scheme was planned.
RESULTS: One hundred nine women participated with 73 randomized to the treatment arm and 36 to the placebo arm. There was no significant difference in clinical cure for BV (p = .42) with 17% of the monolaurin group and 25% of the placebo group achieving clinical cure. Lactobacilli species counts increased in the monolaurin group compared with placebo (1.0 × 10 vs -5.2 × 10). Two thirds of both groups reported solicited urogenital adverse events, but these were mild to moderate with no significant difference between groups (p = .24).
CONCLUSIONS: Monolaurin was no more clinically or microbiologically effective than placebo in curing BV. Future research should explore whether monolaurin may be used to increase Lactobacilli species.

Fluidity of lipid membranes is known to play an important role in the functioning of living organisms. The fluorescent probe Laurdan embedded in a lipid membrane is typically used to assess the fluidity state of lipid bilayers by utilizing the sensitivity of Laurdan emission to the properties of its lipid environment. In particular, Laurdan fluorescence is sensitive to gel vs liquid⁻crystalline phases of lipids, which is demonstrated in different emission of the dye in these two phases. Still, the exact mechanism of the environment effects on Laurdan emission is not understood. Herein, we utilize dipalmitoylphosphatidylcholine (DPPC) and dioleoylphosphatidylcholine (DOPC) lipid bilayers, which at room temperature represent gel and liquid⁻crystalline phases, respectively. We simulate absorption and emission spectra of Laurdan in both DOPC and DPPC bilayers with quantum chemical and classical molecular dynamics methods. We demonstrate that Laurdan is incorporated in heterogeneous fashion in both DOPC and DPPC bilayers, and that its fluorescence depends on the details of this embedding.

The study of surfactant and bio membranes interaction is particularly complex due to the diversity in lipid composition and the presence of proteins in natural membranes. Even more difficult is the study of this interaction in vivo since cellular damage may complicate the interpretation of the results, therefore for most of the studies in this field either artificial or model systems are used. One of the model system most used to study biomembranes are erythrocytes due to their relatively simple structure (they lack nuclei and organelles having only the plasma membrane), their convenient experimental manipulation and availability. In this context, we used rabbit erythrocytes as a model membrane and Laurdan (6-lauroyl-2-dimethylaminonaphthalene) as the fluorescent probe to study changes promoted in the membrane by the interaction with the sucrose monoester of myristic acid, β-d-fructofuranosyl-6-O-myristoyl-α-d-glucopyranoside (MMS). Surfactant and erythrocytes interaction was studied by measuring hemoglobin release and the changes in water content in the membrane sensed by Laurdan. Using two-photon excitation, three types of measurements were performed: Generalized Polarization (analyzed as average GP values), Fluorescence Lifetime Imaging, FLIM (analyzed using phasor plots) and Spectral imaging (analyzed using spectral phasor). Our data indicate that at sublytical concentration of surfactant (20μM MMS), there is a decrease of about 35% in erythrocytes size, without changes in Laurdan lifetime or emission spectra. We also demonstrate that as hemolysis progress, Laurdan lifetime increased due to the decrease in hemoglobin (strong quencher of Laurdan emission) content inside the erythrocytes. Under these conditions, Laurdan spectral phasor analyses can extract the information on the water content in the membrane in the presence of hemoglobin. Our results indicate an increase in membrane fluidity in presence of MMS.

Arsenic exposure has been associated with low birth weight. However, the underlying mechanisms are not well understood. Alterations to metabolites may act as causal mediators of the effect of arsenic exposure on low birth weight. This pilot study aimed to explore the role of metabolites in mediating the association of arsenic exposure on infant birth weight. Study samples were selected from a well-established prospectively enrolled cohort in Bangladesh comprising 35 newborns and a subset of 20 matched mothers. Metabolomics profiling was performed on 35 cord blood samples and 20 maternal peripheral blood samples collected during the second trimester of pregnancy. Inorganic arsenic (iAs) exposure was evaluated via cord blood samples and maternal toenail samples collected during the first trimester. Multiple linear regression and mediation analyses were used to explore the relationship between iAs exposure, metabolite alterations, and low birth weight. Cord blood arsenic level was correlated with elevated levels of 17-methylstearate, laurate (12:0) and 4-vinylphenol sulfate along with lower birth weight. Prenatal maternal toenail iAs level was associated with two peripheral blood metabolites (butyrylqlycine and tartarate), which likely contributed to higher cord blood iAs levels both independently and interactively. Findings of this pilot study indicate that both intrauterine and maternal peripheral blood metabolites appear to influence the toxic effect of inorganic arsenic exposure on low birth weight.

The fluorescent marker Laurdan and its new derivative, C-Laurdan, have been investigated by means of theoretical calculations in a DOPC lipid bilayer membrane at room temperature, and a comparison is made with results from fluorescence experiments. Experimentally, the latter probe is known to have a higher sensitivity to the membrane polarity at the lipid headgroup region and has higher water solubility. Results from Molecular Dynamics (MD) simulations show that C-Laurdan is oriented with the carboxyl group toward the head of the membrane, with an angle of 50° between the molecular backbone and the normal to the bilayer, in contrast to the orientation of the Laurdan headgroup whose carbonyl group is oriented toward the polar regions of the membrane and which describes an angle of ca. 70-80° with the membrane normal. This contrast in orientation reflects the differences in transition dipole moment between the two probes and, in turn, the optical properties. QM/MM results of the probes show little differences for one- (OPA) and two-photon absorption (TPA) spectra, while the second harmonic generation (SHG) beta component is twice as large in Laurdan with respect to C-Laurdan probe. The fluorescence anisotropy decay analysis of the first excited state confirms that Laurdan has more rotational freedom in the DOPC membrane, while C-Laurdan experiences a higher hindrance, making it a better probe for lipid membrane phase recognition.

Using LAURDAN spectral imaging and spectral phasor analysis we concurrently studied the growth and hydration state of subcellular organelles (lamellar body-like, LB-like) from live A549 lung cancer cells at different post-confluence days. Our results reveal a time dependent two-step process governing the size and hydration of these intracellular LB-like structures. Specifically, a first step (days 1 to 7) is characterized by an increase in their size, followed by a second one (days 7 to 14) where the organelles display a decrease in their global hydration properties. Interestingly, our results also show that their hydration properties significantly differ from those observed in well-characterized artificial lamellar model membranes, challenging the notion that a pure lamellar membrane organization is present in these organelles at intracellular conditions. Finally, these LB-like structures show a significant increase in their hydration state upon secretion, suggesting a relevant role of entropy during this process.

The binding of monomeric and aggregated variants of 1-83 N-terminal fragment of apolipoprotein A-I with substitution mutations G26R, G26R/W@8, G26R/W@50 and G26R/W@72 to the model lipid membranes composed of phosphatidylcholine and its mixture with cholesterol has been investigated using fluorescent probes pyrene and Laurdan. Examination of pyrene spectral behavior did not reveal any marked influence of apoA-I mutants on the hydrocarbon region of lipid bilayer. In contrast, probing the membrane effects by Laurdan revealed decrease in the probe generalized polarization in the presence of aggregated proteins. suggesting that oligomeric and fibrillar apoA-I species induce increase in hydration degree and reduction of lipid packing density in the membrane interfacial region. These findings may shed light on molecular details of amyloid cytotoxicity.