Oil-in-water emulsions are common vehicles for lipids as nutrients and for the delivery of poorly water-soluble drugs. Enhancing oral bioavailability of these drugs using lipid-based formulations ...(LBF) or self-emulsifying drug delivery systems is one of the current challenges in pharmaceutical industry. Many of the compounds found in LBF (acylglycerols, surfactants with esterified fatty acids, …) are however potential substrates for digestive enzymes. Their digestion (or lipolysis) in the gastrointestinal (GI) tract is critical for drug dissolution and absorption: it can be beneficial (drug solubilization/dispersion) or deleterous (drug precipitation) depending on the drug-LBF association. A better understanding of the fate of LBF in the GI tract is therefore required to engineer efficient lipid-based drug delivery systems. In vitro models for testing simultaneously LBF digestion and drug dispersion are in development to predict drug solubilization and bioavailability, select the best drug-LBF association and obtain better in vitro-in vivo correlations. So far, research in this area has focused on LBF lipolysis under intestinal conditions because the small intestine is the main target for drug delivery and absorption, as well as the main site of digestion by pancreatic enzymes. Lipolysis however starts within the stomach through the action of gastric lipase, the first enzyme involved in fat digestion in humans. In vitro digestion experiments show that most LBFs are submitted to gastric lipolysis, and therefore, both intragastric and intestinal digestions are critical for the fate of LBF and drug solubility.
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•Lipid-based formulations (LBF) allow the oral delivery of poorly water soluble drugs.•Many of the compounds found in LBF are substrates for lipolytic enzymes.•Gastric and intestinal lipolysis of LBF are critical for drug dissolution and absorption.
Developing a mechanistic understanding of the impact of food structure and composition on human health has increasingly involved simulating digestion in the upper gastrointestinal tract. These ...simulations have used a wide range of different conditions that often have very little physiological relevance, and this impedes the meaningful comparison of results. The standardized protocol presented here is based on an international consensus developed by the COST INFOGEST network. The method is designed to be used with standard laboratory equipment and requires limited experience to encourage a wide range of researchers to adopt it. It is a static digestion method that uses constant ratios of meal to digestive fluids and a constant pH for each step of digestion. This makes the method simple to use but not suitable for simulating digestion kinetics. Using this method, food samples are subjected to sequential oral, gastric and intestinal digestion while parameters such as electrolytes, enzymes, bile, dilution, pH and time of digestion are based on available physiological data. This amended and improved digestion method (INFOGEST 2.0) avoids challenges associated with the original method, such as the inclusion of the oral phase and the use of gastric lipase. The method can be used to assess the endpoints resulting from digestion of foods by analyzing the digestion products (e.g., peptides/amino acids, fatty acids, simple sugars) and evaluating the release of micronutrients from the food matrix. The whole protocol can be completed in ~7 d, including ~5 d required for the determination of enzyme activities.
ABSTRACT
Lipase inhibitors are the main anti-obesity drugs prescribed these days, but the complexity of their mechanism of action is making it difficult to develop new molecules for this purpose. The ...efficacy of these drugs is known to depend closely on the physico-chemistry of the lipid-water interfaces involved and on the unconventional behavior of the lipases which are their target enzymes. The lipolysis reaction which occurs at an oil-water interface involves complex equilibria between adsorption-desorption processes, conformational changes and catalytic mechanisms. In this context, surfactants can induce significant changes in the partitioning of the enzyme and the inhibitor between the water phase and lipid-water interfaces. Surfactants can be found at the oil-water interface where they compete with lipases for adsorption, but also in solution in the form of micellar aggregates and monomers that may interact with hydrophobic parts of lipases in solution. These various interactions, combined with the emulsification and dispersion of insoluble substrates and inhibitors, can either promote or decrease the activity and the inhibition of lipases. Here, we review some examples of the various effects of surfactants on lipase structure, activity and inhibition, which show how complex the various equilibria involved in the lipolysis reaction tend to be.
The anti-malarial drug Chloroquine (CQ) and its derivative hydroxychloroquine have shown antiviral activities in vitro against many viruses, including coronaviruses, dengue virus and the biosafety ...level 4 Nipah and Hendra paramyxoviruses. The in vivo efficacy of CQ in the treatment of COVID-19 is currently a matter of debate. CQ is a lysosomotrophic compound that accumulates in lysosomes, as well as in food vacuoles of Plasmodium falciparum. In the treatment of malaria, CQ impairs the digestion and growth of the parasite by increasing the pH of the food vacuole. Similarly, it is assumed that the antiviral effects of CQ results from the increase of lysosome pH and the inhibition of acidic proteases involved in the maturation of virus fusion protein. CQ has however other effects, among which phospholipidosis, characterized by the accumulation of multivesicular bodies within the cell. The increase in phospholipid species particularly concerns bis(monoacylglycero)phosphate (BMP), a specific lipid of late endosomes involved in vesicular trafficking and pH-dependent vesicle budding. It was shown previously that drugs like progesterone, the cationic amphiphile U18666A and the phospholipase inhibitor methyl arachidonyl fluoro phosphonate (MAFP) induce the accumulation of BMP in THP-1 cells and decrease cell infection by human immunodeficiency virus. HIV viral particles were found to be retained into large endosomal-type vesicles, preventing virus spreading. Since BMP was also reported to favour virus entry through hijacking of the endocytic pathway, we propose here that BMP could play a dual role in viral infection, with its antiviral effects triggered by lysosomotropic drugs like CQ.
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•A known effect of Chloroquine (CQ) is phospholipidosis.•The intracellular accumulation of phospholipids is marked by a large increase in BMP, an endosomal specific-lipid.•Other antiviral drugs like progesterone induce BMP accumulation and viral particles sequestration in the cell.•BMP could be associated with the antiviral effects of CQ, at least in vitro.
The development of in vitro digestion models relies on the availability of in vivo data such as digestive enzyme levels and pH values recorded in the course of meal digestion. The variations of these ...parameters along the GI tract are important for designing dynamic digestion models but also static models for which the choice of representative conditions of the gastric and intestinal conditions is critical. Simulating gastric digestion with a static model and a single set of parameters is particularly challenging because the variations in pH and enzyme concentration occurring in the stomach are much broader than those occurring in the small intestine. A review of the literature on this topic reveals that most models of gastric digestion use very low pH values that are not representative of the fed conditions. This is illustrated here by showing the variations in gastric pH as a function of meal gastric emptying instead of time. This representation highlights those pH values that are the most relevant for testing meal digestion in the stomach. Gastric lipolysis is still largely ignored or is performed with microbial lipases. In vivo data on gastric lipase and lipolysis have however been collected in humans and dogs during test meals. The biochemical characterization of gastric lipase has shown that this enzyme is rather unique among lipases: (i) stability and activity in the pH range 2 to 7 with an optimum at pH 4-5.4; (ii) high tensioactivity that allows resistance to bile salts and penetration into phospholipid layers covering TAG droplets; (iii) sn-3 stereospecificity for TAG hydrolysis; and (iv) resistance to pepsin. Most of these properties have been known for more than two decades and should provide a rational basis for the replacement of gastric lipase by other lipases when gastric lipase is not available.
The lipids and some surfactants present in oral lipid-based drug delivery systems are potential substrates for the various lipases involved in gastrointestinal (GI) lipolysis. The levels of these ...enzymes, together with pH and biliairy secretion, are important parameters that condition the fate of lipid-based formulations (LBF) and the dispersion, solubilization and absorption of lipophilic drugs in the GI tract. Since in vitro methods of digestion are now combined with dissolution assays for a better assessment of LBF performance, it is essential to have a basic knowledge on lipase, pH and bile acid (BA) levels in vivo to develop relevant in vitro models. While these parameters and their variations in healthy subjects are today well documented, in vivo data on specific populations (age groups, patients with various diseases, patients with treatment affecting GI tract parameters, …) are scarce and obtaining them from clinical studies is sometimes difficult due to ethical limitations. Here we collected some in vivo data already available on the levels of digestive lipases, gastric and intestinal pH, and BAs at various ages and in patients with exocrine pancreatic insufficiency, a pathological situation that leads to drastic changes in GI tract parameters and impacts pharmacological treatments.
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Biogenesis and fate of lipid droplets Li-Beisson, Yonghua; Carrière, Frédéric
Biochimie,
February 2020, 2020-Feb, 2020-02-00, 20200201, 2020-02, Letnik:
169
Journal Article
Recenzirano
Odprti dostop
Editorial Special issue "Biogenesis and Fate of Lipid Droplets" Intracellular lipid droplets (LDs) are receiving increasing interest from the scientific community, notably because of their link with ...metabolic diseases (obesity, diabetes) and the production of lipid-derived biofuels in microorganisms. Understanding the biogenesis and fate of LDs upon energy mobilization is essential to monitor fat storage in adipose tissue, but also to improve lipid productivity in microalgae under various conditions of growth 1. Intracellular LDs are today considered as individual organelles since they host specific metabolic functions such as the biosynthesis of triacylglycerols (TAGs) and phospholipids 2. In addition to the enzymes involved in these pathways, several proteins have been identified as associated with LDs and their number has been increasing with the progress of proteomics. Some of these proteins presenting hydrophobic patches and a high amphiphilicity are involved in the structure of LDs and together with polar lipids they form the membrane surrounding the neutral lipid core. Some others are involved in the budding of LDs from lipid bilayers and the interactions of LDs with membranes and other organelles. These interactions are important for the transfer of fatty acids and lipid remodelling and homeostasis. The combination of lipidomics and proteomics has led to a better description of LD composition, while microscopy has allowed the visualisation of the specific location of proteins at the surface of LDs. Nevertheless, a better knowledge of the lipid-protein interactions that lead to the biogenesis and fate of LDs is still required. In this context, cellular biologists now adopt principles and methods from biophysics and physical chemistry of lipid emulsions and colloids 3. Emulsions made of TAGs, polar lipids and proteins can serve as models for intracellular LDs. The biodiversity of LDs in animals, plants and microorganisms and their various functions in lipid storage and transport also allows the comparison of data and knowledge from various fields that will help build a global understanding of structure-function relationships. The original articles and reviews of this special issue are a collection of topics presented at the 14th GERLI Lipidomics meeting, which was be held at St Maximin-la-Sainte Baume, France, from September 30th to October 3rd, 2018, with the aim of gathering researchers from various areas with a common interest in LDs, their physical chemistry and metabolism, their association with diseases and various applications in biotechnology, pharmacology and nutrition. The two first mini-reviews are related to lipid metabolism in microalgae. Lupette et al. cover the biosynthesis of fatty acids, acyl-glycero-lipids and sterols in diatoms and show how a metabolic intermediate common to these pathways, like acetyl-CoA, can play an essential role in directing the carbon flux from acyl-lipid to sterol biosynthesis and be determinant for the balance between TAGs and sterols. Prioretti et al. investigate how the target of rapamycin (TOR) signalling pathway could be modulated to enhance TAG production in microalgae. The use of TOR inhibitors increases TAG productivity in the marine diatom Phaeodactylum tricornutum, without stopping growth, while TAG accumulation in microalgae is usually observed under stress conditions with a low growth rate. Yuan et al. report on the characterization of three diacylglycerol acyltransferases (DGATs) from oil palm (Elaeis guineensis), the main source of vegetable oil on Earth. DGATs are key enzymes for the biosynthesis of TAGs and the formation of LDs. Using the heterologous expression of these DGATs in the yeast Saccharomyces cerevisiae, they show that two of them are true DGATs, that could restore TAG synthesis in a yeast TAG-deficient mutant, while the third one is a wax ester synthase.
Fatty acid photodecarboxylase (FAP), one of the few natural photoenzymes characterized so far, is a promising biocatalyst for lipid-to-hydrocarbon conversion using light. However, the optimum ...supramolecular organization under which the fatty acid (FA) substrate should be presented to FAP has not been addressed. Using palmitic acid embedded in phospholipid liposomes, phospholipid-stabilized microemulsions, and mixed micelles, we show that FAP displays a preference for FAs present in liposomes and at the surface of microemulsions. The kinetics of adsorption onto phospholipid and galactolipid monomolecular films further suggests the ability of FAP to bind to and penetrate into membranes, with a higher affinity in the presence of FAs. The FAP structure reveals a potential interfacial recognition site with clusters of hydrophobic and basic residues surrounding the active site entrance. The resulting dipolar moment suggests the orientation of FAP at negatively charged interfaces. These findings provide important clues about the mode of action of FAP and the development of FAP-based bioconversion processes.
Few studies have tested the small intestine microbiota in humans, where most nutrient digestion and absorption occur. Here, our objective was to examine the duodenal microbiota between obese and ...normal volunteers using metagenomic techniques.
We tested duodenal samples from five obese and five normal volunteers using 16S rDNA V6 pyrosequencing and Illumina MiSeq deep sequencing. The predominant phyla of the duodenal microbiota were Firmicutes and Actinobacteria, whereas Bacteroidetes were absent. Obese individuals had a significant increase in anaerobic genera (p < 0.001) and a higher abundance of genes encoding Acyl-CoA dehydrogenase (p = 0.0018) compared to the control group. Obese individuals also had a reduced abundance of genes encoding sucrose phosphorylase (p = 0.015) and 1,4-alpha-glucan branching enzyme (p = 0.05). Normal weight people had significantly increased FabK (p = 0.027), and the glycerophospholipid metabolism pathway revealed the presence of phospholipase A1 only in the control group (p = 0.05).
The duodenal microbiota of obese individuals exhibit alterations in the fatty acid and sucrose breakdown pathways, probably induced by diet imbalance.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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