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Frederic Carriere - One of the best experts on this subject based on the ideXlab platform.

  • Label free Imaging of Lipase activity on milk fat globules and model systems using DISCO beamline at Synchrotron SOLEIL
    2019
    Co-Authors: Claire Bourlieu-lacanal, Olivia Ménard, Amélie Deglaire, Stephane Pezennec, Didier Dupont, Pierre Villeneuve, Steven Le Feunteun, Jacques Fattacciolli, Frédéric Jamme, Frederic Carriere
    Abstract:

    In their native state, milk lipids are present in the form of dispersed droplets called Milk Fat Globules (MFG, diameter 0.1-20 μm, average = 4 μm in bovine milk) [1,2]. The native MFG is constituted by a triglyceride core covered with an external trilayered membrane inherited from its secretory past. This membrane is mainly based on polar lipids (glycerophospholipids, sphingolipids and glycosphingolipids), proteins (25 % of total membrane with high proportion of glycoproteins and enzymes), neutral lipids and minor components. The major biological function of the MFG is to deliver energy to the mammal newborn, for that, the MFG has to be hydrolyzed in the gastro-intestinal tract by Lipases, in successive steps. The Lipases should interact with the MFG membrane and diffuse into the supramolecular object. The aim of this work was to determine the mechanisms involved in the enzymatic hydrolysis along the digestive process. We used millifluidic cells designed to trap MFG or model droplets and injected successively each Lipase (Gastric, pancreatic related 2, pancreatic triglyceride Lipase) involved in the digestion process and thus mimicking different physiological stages (preterm infant, fullterm infant and adult). Thanks to the deep UV-microscope present at DISCO beamline, the autofluorescence of tryptophan (and tyrosine) of Lipase aminoacids allowed protein observation without external labeling. The Gastric and intestinal neonatal disintegration of milk fat globules (human or bovine) or other model systems (bovine anhydrous milk fat droplets stabilized by bovine milk membrane extracts or soy lecithin) was approached through transmission images recording. The analysis of the number of globules and their state of aggregation/coalescence during digestion (approached via diameter, size, mode and specific surface evolution against time) gave indication on the kinetics and mechanisms of lipolysis. Fluorescence (327-335 nm) image indicated Lipase distribution. Gastric phase was mainly marked by the heterogeneous adsorption of the Gastric Lipase in the MFG membrane. Afterwards, heterogeneous adsorption of pancreatic triglyceride Lipase could also be observed followed by the disappearance of the MFG core. The progression of Lipases fronts was monitored and the kinetics of lipolysis characterized allowing the differentiation of substrate and of in vitro digestion models (full term infant, versus preterm infant versus adult). The microfluidics set up was a very interesting tool to follow sequentially the action of Lipases, to save volume of purified Lipase and to image simultaneously several positions. The high sensitivity of the DISCO beamline allowing the detection of digestive Lipases auto-fluorescence, is a unique tool to unravel their mechanisms of adsorption onto complex substrate using free-label imaging and has generated useful data for infant formula optimization

  • Identification of a new natural Gastric Lipase inhibitor from star anise
    Food and Function, 2019
    Co-Authors: Jannet Kamoun, Renaud Rahier, Imed Koubaa, Pascal Mansuelle, Régine Lebrun, Alexandra Berlioz-barbier, Michele Fiore, Karine Alvarez, Abdelkarim Abousalham, Frederic Carriere
    Abstract:

    The identification and isolation of bioactive compounds are of great interest in the drug delivery field, despite being a difficult task. We describe here an innovative strategy for the identification of a new Gastric Lipase inhibitor from star anise for the treatment of obesity. After plant screening assays for Gastric Lipase inhibition, star anise was selected and investigated by bioactivity guided fractionation. MALDI-TOF mass spectrometry and peptide mass fingerprinting allowed the detection of an inhibitor covalently bound to the catalytic serine of Gastric Lipase. A mass-directed screening approach using UPLC-HRMS and accurate mass determination searching identified the flavonoid myricitrin-5-methyl ether (M5ME) as a Lipase inhibitor. The inhibitory activity was rationalized based on molecular docking, showing that M5ME is susceptible to nucleophilic attack by Gastric Lipase. Overall, our data suggest that M5ME may be considered as a potential candidate for future application as a Gastric Lipase inhibitor for the treatment of obesity

  • INFOGEST static in vitro simulation of gastrointestinal food digestion
    Nature Protocols, 2019
    Co-Authors: André Brodkorb, Marie Alminger, Paula Alvito, Torsten Bohn, Rachel Boutrou, Claire Bourlieu-lacanal, Lotti Egger, Ricardo Assunção, Simon Balance, Frederic Carriere
    Abstract:

    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.

  • lipids in the stomach implications for the evaluation of food effects on oral drug absorption
    Pharmaceutical Research, 2018
    Co-Authors: Frederic Carriere, Mirko Koziolek, Christopher J H Porter
    Abstract:

    Food effects on oral drug bioavailability can have significant impact on the provision of safe and reliable oral pharmacotherapy. A mechanistic understanding of the events that contribute to the occurrence of food effects is therefore critical. An increased oral bioavailability is often seen for poorly water-soluble drugs after co-administration with lipids, including lipids in food, and is commonly explained by the ability of lipids to enhance drug solubility in intestinal luminal fluids. In contrast, the impact of lipids on drug solubilisation in the stomach has received less attention. This is in spite of the fact that lipid digestion is initiated in the stomach by human Gastric Lipase and that Gastric events also initiate emulsification of lipids in the gastrointestinal tract. The stomach therefore acts to ‘pre-process’ lipids for subsequent events in the intestine and may significantly affect downstream events at intestinal drug absorption sites. In this article, the mechanisms by which lipids are processed in the stomach are reviewed and the potential impact of these processes on drug absorption discussed. Attention is also focused on in vitro methods that are used to assess Gastric processing of lipids and their application to better understand food effects on drug release and absorption.

  • Gastric Lipase and other lipolytic enzymes activity in the preterm infant fed raw pasteurized or pasteurized homogenized human milk
    ESPGHAN (European Society for Paediatric Gastroenterology Hepatology and Nutrition) 49. Annual Meeting, 2016
    Co-Authors: S De Oliveira, Frederic Carriere, Olivia Ménard, Didier Dupont, Damien Faurebidegaray, Amandine Bellanger, Emelyne Dirson, Patrick Pladys, Yann Le Gouar, Amélie Deglaire
    Abstract:

    -Objectives and study: Hydrolysis of milk lipids is an essential step in their digestion, initiated in the digestive tract by human Gastric Lipase (HGL). Although limited, Gastric lipolysis has been presented very early as a key phenomenon in efficient fat digestion for newborns. It compensates for the immaturity of exocrine pancreatic function and favours the subsequent action of other lipolytic enzymes such as pancreatic or bile salt dependant Lipases (HPL and BSSL, respectively). Some values of HGL activity have been determined in Gastric aspirates of infants in fasting state or postprandially. High variability was reported probably due to influence of the nature of the meal (infant formula versus human milk), the age of the infant or the analysis method. However, in these studies the HGL output has never been estimated after administration of various types of human milk, nor the potential contribution of non-Gastric lipolytic enzymes. The objective of the present study is thus to determine HGL activity, output and the contribution of other lipolytic enzymes in Gastric aspirates of preterm infants in fasting state or after administration of raw, pasteurized or pasteurizedhomogenized human milk. -Methods: In vivo study was conducted at Rennes Hospital on preterm infants fed by nasoGastric tube (NCT02112331). The infants were included in two independent groups determining the type of meals: A) raw and pasteurized human milk; B) pasteurized and pasteurized-homogenized human milk. After collection (twice a day, six-day sequence), aspirates were immediately blended with glycerol (50:50 v/v) and frozen. Fasted Gastric contents were collected three hours after last meal (up to 12 times per patient to verify intra-individual variation) and postprandial digesta at 35, 60 or 90 min after administrated meal. Gastric volume and pH decrease were monitored. Lipolytic activity was assessed by pH-stat at pH 6 (37°C) using tributyrin as substrate (as detailed by Gargouri et al., 1986), at least on triplicate. A subsequent determination at pH 8 allowed the estimation of non-Gastric Lipases contribution. -Results: Results evidenced high inter and intra-individual variability on estimated Gastric lipolytic activities. In the group A (n=12), lipolytic activity measured at pH 6 ranged from 2 up to 100 U/mL of fasting Gastric content. The determination at pH 8 revealed a contribution of non-Gastric Lipases activity ranging between 0 and 61%: as HGL is not active at such pH, a remaining activity will thus indicate the presence of BSSL or HPL. These contributions were higher in patients fed raw compared to pasteurized human milk in both fasted and postprandial states, probably indicating: i) active BSSL from residual raw human milk contributed to Gastric activity even three hours after meal; ii) the presence of HPL (and hence intestinal content) in the stomach, which confirms the immaturity of motility function in preterms. In patients fed with pasteurized milk the lipolytic activity increased with postprandial time, indicating a HGL secretion induced by the meal. Lipolytic activities from group B are currently been analyzed and will be further detailed. -Conclusion: This study presents a unique set of data illustrating the specificity of preterm infants’ Gastric digestive conditions. These data will be useful to develop relevant in vitro models of infant digestion and analyze the link between Gastric lipolytic activity and lipid digestion.

Martine Armand - One of the best experts on this subject based on the ideXlab platform.

  • The size and interfacial composition of milk fat globules are key factors controlling triglycerides bioavailability in simulated human gastro-duodenal digestion
    Food Hydrocolloids, 2014
    Co-Authors: Cyrielle Garcia, Benoît Robert, Christelle Lopez, Claudine Antona, Martine Armand
    Abstract:

    Lipids organisation might modulate fatty acid bioavailability leading to health implications. We determined whether the size and the interfacial composition of cow milk fat globules could affect triglycerides digestibility. Native fat globules of various sizes covered by their biological membrane (4.2 mm, large LFG 6.6 mm, small SFG 1.7 mm) or homogenised heat-treated (0.3 mm) were digested in Gastric and duodenal conditions simulating human physiology. Lipolysis extents were calculated from the amount of free fatty acids generated, and the fatty acid composition of the products of lipolysis was determined by GC analysis. SFG were more efficiently hydrolysed than LFG by Gastric (13.3 versus 5.6%), Gastric plus pancreatic (62.9 versus 48.7%) and pancreatic (79.6 versus 54.7%) Lipases. A higher lipid interface area with native SFG, that might increase Lipases binding sites, can explain these results. However, the homogenisation, which markedly decreases fat globule size increasing consequently the lipid/water interface area, did not improve Gastric (9%) or duodenal (64.5%) lipolysis probably due to an important change in globule surface composition (proteins versus phospholipids). Interestingly, the size of the milk globule (SFG and HM versus NM and LFG) controls the type of the free fatty acids generated by the human Gastric Lipase, palmitic versus oleic acid, suggesting a different orientation of the accessible mixed triglycerides. Moreover, the type of monoglycerides produced from SFG digestion could be less atherogenic compared to LFG. The size of fat globules governs Gastric and duodenal lipolysis extent when the composition of the interfacial layer is appropriate. It might further control fatty acid bioavailability impacting on Gastric emptying rate via the preferential release of oleic acid, a strong stimulator of CCK.

  • mechanisms of inhibition of triacylglycerol hydrolysis by human Gastric Lipase
    Journal of Biological Chemistry, 2002
    Co-Authors: Yan Pafumi, Paulette Lechene De La Porte, Christine Juhel, Judith Storch, Margit Hamosh, Denis Lairon, Martine Armand
    Abstract:

    Abstract In the human stomach, Gastric Lipase hydrolyzes only 10 to 30% of ingested triacylglycerols because of an inhibition process induced by the long chain free fatty acids generated, which are mostly protonated at Gastric pH. The aim of this work was to elucidate the mechanisms by which free fatty acids inhibit further hydrolysis.In vitro experiments examined Gastric lipolysis of differently sized phospholipid-triolein emulsions by human Gastric juice or purified human Gastric Lipase, under close to physiological conditions. The lipolysis process was further investigated by scanning electron microscopy, and Gastric Lipase and free fatty acid movement during lipolysis were followed by fluorescence microscopy. The results demonstrate that: 1) free fatty acids generated during lipolysis partition between the surface and core of lipid droplets with a molar phase distribution coefficient of 7.4 at pH 5.40; 2) the long chain free fatty acids have an inhibitory effect only when generated during lipolysis; 3) inhibition of Gastric lipolysis can be delayed by the use of lipid emulsions composed of small-size lipid droplets; 4) the release of free fatty acids during lipolysis induces a marked increase in droplet surface area, leading to the formation of novel particles at the lipid droplet surface; and 5) the Gastric Lipase is trapped in these free fatty acid-rich particles during their formation. In conclusion, we propose a model in which the sequential physicochemical events occurring during Gastric lipolysis lead to the inhibition of further triacylglycerol lipolysis.

  • digestion and absorption of 2 fat emulsions with different droplet sizes in the human digestive tract
    The American Journal of Clinical Nutrition, 1999
    Co-Authors: Martine Armand, Berengere Pasquier, Patrick Borel, M Senft, Jacques Salducci, Veronique Jaussan, Jacques Peyrot, Marc Andre, Henri Portugal, Denis Lairon
    Abstract:

    Background: The extent of fat emulsification affects the activity of digestive Lipases in vitro and may govern digestion and absorption of dietary fat. Objective: We investigated the effect of the fat globule size of 2 enteral emulsions on fat digestion and assimilation in humans. Design: Healthy subjects received intraGastrically a coarse (10 mm) and a fine (0.7 mm) lipid emulsion of identical composition in random order. Gastric and duodenal aspirates were collected throughout digestion to measure changes in fat droplet size, Gastric and pancreatic Lipase activities, and fat digestion. Blood lipids were measured postprandially for fat assimilation. Results: Despite an increase in droplet size in the stomach (2.75‐6.20 mm), the fine emulsion retained droplets of smaller size and its lipolysis was greater than that of the coarse emulsion (36.5% compared with 15.8%; P < 0.05). In the duodenum, lipolysis of the fine emulsion was on the whole higher (73.3% compared with 46.3%). The overall 0‐7-h plasma and chylomicron responses given by the areas under the curve were not significantly different between the emulsions, but the triacylglycerol peak was delayed with the fine emulsion (3 h 56 min compared with 2 h 50 min). Conclusions: Fat emulsions behave differently in the digestive tract depending on their initial physicochemical properties. A lower initial fat droplet size facilitates fat digestion by Gastric Lipase in the stomach and duodenal lipolysis. Overall fat assimilation in healthy subjects is not affected by differences in initial droplet size because of efficient fat digestion by pancreatic Lipase in the small intestine. Nevertheless, these new observations could be of interest in the enteral nutrition of subjects suffering from pancreatic insufficiency. Am J Clin Nutr 1999;70:1096‐106.

  • protective function of human milk the milk fat globule
    Seminars in Perinatology, 1999
    Co-Authors: Margit Hamosh, Martine Armand, J A Peterson, Theresa R Henderson, Ciaran D Scallan, Radwin Kiwan, R L Ceriani, Nifin R Mehta, Paul Hamosh
    Abstract:

    Human milk contains many components that protect the newborn against infection at a time when the infant's own defense mechanisms are poorly developed. Fat is one of the major nutrients in human milk. The fat is contained within milk fat globules composed of a core of triglyceride and a membrane consisting of phospholipids, cholesterol, proteins, and glycoproteins. Both the membrane and the core components can provide protection against microorganisms. The major protective membrane glycoproteins, mucin, and lactadherin are resistant to conditions in the newborn's stomach and maintain their structure and function even at low pH and in the presence of the proteolytic enzyme pepsin. The core triglycerides upon hydrolysis by digestive Lipases (especially Gastric Lipase, which is well developed in the newborn) produce free fatty acids and monoglycerides, amphiphylic substances able to lyse enveloped viruses, bacteria, and protozoa. Therefore, in addition to its nutritional value, the fat in human milk has a major protective function.

Robert Verger - One of the best experts on this subject based on the ideXlab platform.

  • use of an inhibitor to identify members of the hormone sensitive Lipase family
    Biochemistry, 2006
    Co-Authors: Yassine Ben Ali, Stefan Petry, Frederic Carriere, Robert Verger, Günter Müller, Régine Lebrun, Henri Chahinian, Luigi Mandrich, Mose Rossi, Giuseppe Manco
    Abstract:

    Hormone-sensitive Lipase (HSL) contributes importantly to the mobilization of fatty acids from the triacylglycerols stored in adipocytes, which provide the main source of energy in mammals. On the basis of amino acid sequence alignments and three-dimensional structures, this enzyme was previously found to be a suitable template for defining a family of serine carboxylester hydrolases. In this study, the HSL family members are characterized rather on the basis of their inhibition by 5-methoxy-3-(4-phenoxyphenyl)-3H-[1,3,4]oxadiazol-2-one (compound 7600). This compound inhibits mammalian HSL as well as other HSL family members, such as EST2 from the thermophilic eubacterium Alicyclobacillus acidocaldarius and AFEST from the hyperthermophilic archaeon Archaeoglobus fulgidus. Various carboxylester hydrolases that are not members of the HSL family were found not to be inhibited by compound 7600 under the same experimental conditions. These include nonlipolytic hydrolases such as Torpedo californica acetylcholinesterase and pig liver esterase, as well as lipolytic hydrolases such as human pancreatic Lipase, dog Gastric Lipase, Thermomyces lanuginosus Lipase, and Bacillus subtilis LipA. When vinyl esters were used as substrates, the residual activity of HSL, AFEST, and EST2 decreased with an increase in compound 7600 concentration in the incubation mixture. The inhibitor concentration at which the enzyme activity decreased to 50% after incubation for 5 min was 70, 20, and 15 nM with HSL, AFEST, and EST2, respectively. Treating EST2 and AFEST with the inhibitor resulted in an increase in the molecular mass, as established by performing matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis. This increase in the molecular mass, which corresponds approximately to the molecular mass of the inhibitor, indicates that a covalent enzyme-inhibitor complex has been formed. Surface-enhanced laser desorption ionization time-of-flight mass spectrometry analysis of a trypsin digest of AFEST treated with the inhibitor or not treated showed the occurrence of an increase in the molecular masses of the "GESAGG"-containing peptide, which is compatible with the formation of a covalent complex with the inhibitor.

  • digestive Lipases from three dimensional structure to physiology
    Biochimie, 2000
    Co-Authors: Nabil Miled, Mireille Riviere, Liliane Dupuis, Alain Roussel, Christian Cambillau, Stéphane Canaan, Frederic Carriere, De Caro A, Robert Verger
    Abstract:

    Abstract Human Gastric Lipase (HGL) is a lipolytic enzyme that is secreted by the chief cells located in the fundic part of the stomach. HGL plays an important role in lipid digestion, since it promotes the subsequent hydrolytic action of pancreatic Lipase in duodenal lumen. Physiological studies have shown that HGL is able of acting not only in the highly acid stomach environment but also in the duodenum in synergy with human pancreatic Lipase (HPL). Recombinant HGL (r-HGL) was expressed in the baculovirus/insect cell system in the form of an active protein with a molecular mass of 45 kDa. The specific activities of r-HGL were found to be similar to that of the native enzyme when tested on various triacylglycerol (TG) substrates. The 3-D structure of r-HGL was the first solved within the mammalian acid Lipase family. This globular enzyme (379 residues) shows a new feature, different from the other known Lipases structures, which consists of a core domain having the α/β hydrolase fold and a cap domain including a putative ‘lid’ of 30 residues covering the active site of the Lipase (closed conformation). HPL is the major lipolytic enzyme involved in the digestion of dietary TG. HPL is a 50 kDa glycoprotein which is directly secreted as an active enzyme. HPL was the first mammalian Lipase to be solved structurally, and it revealed the presence of two structural domains: a large N-terminal domain (residues 1–336) and a smaller C-terminal domain (residues 337–449). The large N-terminal domain belongs to the α/β hydrolase fold and contains the active site. A surface loop called the lid domain (C237–C261) covers the active site in the closed conformation of the Lipase. The 3-D structure of the Lipase-procoLipase complex illustrates how the procoLipase might anchor the Lipase at the interface in the presence of bile salts: procoLipase binds to the C-terminal domain of HPL and exposes the hydrophobic tips of its fingers at the opposite site of its Lipase-binding domain. These hydrophobic tips help to bring N-terminal domain into close conformation with the interface where the opening of the lid domain probably occurs. As a result of all these conformational changes, the open lid and the extremities of the procoLipase form an impressive continuous hydrophobic plateau, extending over more than 50 A. This surface might able to interact strongly with a lipid-water interface. The biochemical, histochemical and clinical studies as well as the 3-D structures obtained will be a great help for a better understanding of the structure-function relationships of digestive Lipases.

  • the specific activities of human digestive Lipases measured from the in vivo and in vitro lipolysis of test meals
    Gastroenterology, 2000
    Co-Authors: Frederic Carriere, Alain De Caro, Francine Ferrato, C Renou, Veronique Lopez, Josiane De Caro, Hans Lengsfeld, R Laugier, Robert Verger
    Abstract:

    Abstract Background & Aims: The lipolytic potential of digestive Lipases in vivo has always been deduced so far from their in vitro activities under nonphysiologic conditions. In the present study, the specific activities of human Gastric Lipase (HGL) and pancreatic Lipase (HPL) were measured on dietary triglycerides (TGs) during test meal lipolysis. Methods: Healthy human volunteers ingested a liquid or solid meal. The specific activities of HGL and HPL were estimated from the Lipase and free fatty acid (FFA) outputs at the postpyloric and duodenal levels, respectively. Based on the in vivo data, lipolysis was also performed in vitro by mixing the meal either with Gastric juice and subsequently with pancreatic juice and bile or with purified HGL and HPL. FFAs were measured by thin-layer chromatography, and the specific activities of HGL and HPL were expressed as micromoles of FFA per minute per milligram of Lipase. Results: In vitro, the specific activities on the liquid meal TGs were 32 (Gastric juice) and 34 (pure Lipase) μmol · min −1 · mg −1 with HGL and 47 (pancreatic juice) and 43 (pure Lipase) μmol · min −1 · mg −1 with HPL. The specific activities on the solid meal TGs were 33 (Gastric juice) and 32 (pure Lipase) μmol · min −1 · mg −1 with HGL and 12 (pancreatic juice) and 15 (pure Lipase) μmol · min −1 · mg −1 with HPL. The in vivo values obtained were in the same range. The secretory Lipase outputs were 21.6 ± 14.5 mg HGL and 253.5 ± 95.5 mg HPL with the liquid test meal and 15.2 ± 5.1 mg HGL and 202.9 ± 96.1 mg HPL with the solid test meal. Conclusions: The specific activities of HGL and HPL on meal TGs were much lower than those measured in vitro under optimized assay conditions (1300–8000). However, these low specific activities are enough for the meal TGs to be completely lipolysed, given the amounts of HGL and HPL secreted during a meal. GASTROENTEROLOGY 2000;119:949-960

  • crystal structure of human Gastric Lipase and model of lysosomal acid Lipase two lipolytic enzymes of medical interest
    Journal of Biological Chemistry, 1999
    Co-Authors: Alain Roussel, Marie-pierre Egloff, Mireille Riviere, Liliane Dupuis, Stéphane Canaan, Robert Verger, Christian Cambillau
    Abstract:

    Abstract Fat digestion in humans requires not only the classical pancreatic Lipase but also Gastric Lipase, which is stable and active despite the highly acidic stomach environment. We report here the structure of recombinant human Gastric Lipase at 3.0-A resolution, the first structure to be described within the mammalian acid Lipase family. This globular enzyme (379 residues) consists of a core domain belonging to the α/β hydrolase-fold family and a “cap” domain, which is analogous to that present in serine carboxypeptidases. It possesses a classical catalytic triad (Ser-153, His-353, Asp-324) and an oxyanion hole (NH groups of Gln-154 and Leu-67). Four N-glycosylation sites were identified on the electron density maps. The catalytic serine is deeply buried under a segment consisting of 30 residues, which can be defined as a lid and belonging to the cap domain. The displacement of the lid is necessary for the substrates to have access to Ser-153. A phosphonate inhibitor was positioned in the active site that clearly suggests the location of the hydrophobic substrate binding site. The lysosomal acid Lipase was modeled by homology, and possible explanations for some previously reported mutations leading to the cholesterol ester storage disease are given based on the present model.

  • crystal structure of human Gastric Lipase and model of lysosomal acid Lipase two lipolytic enzymes of medical interest
    Journal of Biological Chemistry, 1999
    Co-Authors: Alain Roussel, Marie-pierre Egloff, Liliane Dupuis, Stéphane Canaan, Robert Verger, M Riviere, Christian Cambillau
    Abstract:

    Fat digestion in humans requires not only the classical pancreatic Lipase but also Gastric Lipase, which is stable and active despite the highly acidic stomach environment. We report here the structure of recombinant human Gastric Lipase at 3.0-A resolution, the first structure to be described within the mammalian acid Lipase family. This globular enzyme (379 residues) consists of a core domain belonging to the alpha/beta hydrolase-fold family and a "cap" domain, which is analogous to that present in serine carboxypeptidases. It possesses a classical catalytic triad (Ser-153, His-353, Asp-324) and an oxyanion hole (NH groups of Gln-154 and Leu-67). Four N-glycosylation sites were identified on the electron density maps. The catalytic serine is deeply buried under a segment consisting of 30 residues, which can be defined as a lid and belonging to the cap domain. The displacement of the lid is necessary for the substrates to have access to Ser-153. A phosphonate inhibitor was positioned in the active site that clearly suggests the location of the hydrophobic substrate binding site. The lysosomal acid Lipase was modeled by homology, and possible explanations for some previously reported mutations leading to the cholesterol ester storage disease are given based on the present model.

Ménard Olivia - One of the best experts on this subject based on the ideXlab platform.

  • Physico-chemical behaviors of human and bovine milk membrane extracts and their influence on Gastric Lipase adsorption
    'Elsevier BV', 2020
    Co-Authors: Bourlieu Claire, Deglaire Amélie, Ménard Olivia, Pezennec Stéphane, Dupont Didier, Mahdoueni Wafa, Paboeuf Gilles, Gicquel Eric, Bouhallab Said, Carrière Frédéric
    Abstract:

    International audienceMilk fat globule membrane conditions the reactivity and enzymatic susceptibility of milk lipids. The use of bovine membrane extracts to make infant formulas more biomimetic of human milk has been suggested recently. A comparison of the physico-chemical behavior of human and bovine milk membrane extracts and their interaction with Gastric Lipase is here undertaken using biophysical tools. Milk membrane extracts (70% of polar lipids) were obtained either pooling of mature human milk (n = 5) or bovine buttermilk. Human extract contained more anionic glycerophospholipids, less phosphatidylethanolamine and more unsaturated fatty acids (57% versus 46%) than bovine extract. Human extract presented a higher compressibility, with slower increase of surface pressure, than bovine extract. Micronic liquid condensed (LC) domains were evidenced in both extracts at 10 mN/m, but the evolution differs upon compression. Upon Gastric Lipase addition, an adsorption preference for liquid expanded phase (LE) was observed for both extracts. However, insertion was more homogeneous in terms of height level in human extract and impacted less its lipid lateral organization than in bovine extract. Both membrane extracts share close physico-chemical properties, however human membrane higher compressibility may favour Gastric Lipase insertion and higher interfacial reactivity in Gastric conditions

  • Label free Imaging of Lipase activity on milk fat globules and model systems using DISCO beamline at Synchrotron SOLEIL
    HAL CCSD, 2019
    Co-Authors: Bourlieu-lacanal Claire, Deglaire Amélie, Ménard Olivia, Pezennec Stéphane, Le Feunteun Steven, Villeneuve Pierre, Dupont Didier, Fattacciolli Jacques, Jamme Frédéric, Carrière Frédéric
    Abstract:

    International audienceIn their native state, milk lipids are present in the form of dispersed droplets called Milk Fat Globules (MFG, diameter 0.1-20 μm, average = 4 μm in bovine milk) [1,2]. The native MFG is constituted by a triglyceride core covered with an external trilayered membrane inherited from its secretory past. This membrane is mainly based on polar lipids (glycerophospholipids, sphingolipids and glycosphingolipids), proteins (25 % of total membrane with high proportion of glycoproteins and enzymes), neutral lipids and minor components. The major biological function of the MFG is to deliver energy to the mammal newborn, for that, the MFG has to be hydrolyzed in the gastro-intestinal tract by Lipases, in successive steps. The Lipases should interact with the MFG membrane and diffuse into the supramolecular object. The aim of this work was to determine the mechanisms involved in the enzymatic hydrolysis along the digestive process. We used millifluidic cells designed to trap MFG or model droplets and injected successively each Lipase (Gastric, pancreatic related 2, pancreatic triglyceride Lipase) involved in the digestion process and thus mimicking different physiological stages (preterm infant, fullterm infant and adult). Thanks to the deep UV-microscope present at DISCO beamline, the autofluorescence of tryptophan (and tyrosine) of Lipase aminoacids allowed protein observation without external labeling. The Gastric and intestinal neonatal disintegration of milk fat globules (human or bovine) or other model systems (bovine anhydrous milk fat droplets stabilized by bovine milk membrane extracts or soy lecithin) was approached through transmission images recording. The analysis of the number of globules and their state of aggregation/coalescence during digestion (approached via diameter, size, mode and specific surface evolution against time) gave indication on the kinetics and mechanisms of lipolysis. Fluorescence (327-335 nm) image indicated Lipase distribution. Gastric phase was mainly marked by the heterogeneous adsorption of the Gastric Lipase in the MFG membrane. Afterwards, heterogeneous adsorption of pancreatic triglyceride Lipase could also be observed followed by the disappearance of the MFG core. The progression of Lipases fronts was monitored and the kinetics of lipolysis characterized allowing the differentiation of substrate and of in vitro digestion models (full term infant, versus preterm infant versus adult). The microfluidics set up was a very interesting tool to follow sequentially the action of Lipases, to save volume of purified Lipase and to image simultaneously several positions. The high sensitivity of the DISCO beamline allowing the detection of digestive Lipases auto-fluorescence, is a unique tool to unravel their mechanisms of adsorption onto complex substrate using free-label imaging and has generated useful data for infant formula optimizatio

  • Impact des procédés de transformation sur la digestion du lait maternel et des formules infantiles par le nouveau-né.
    2018
    Co-Authors: Deglaire Amélie, Ménard Olivia
    Abstract:

    Malgré les efforts réalisés ces dernières décennies pour rapprocher la composition des formules infantiles de celle du lait humain, d’importantes différences de composition et de structure des constituants demeurent entre ces deux aliments. Le lait humain, véritable « gold standard » pour l’alimentation du nouveau-né présente des structures natives (micelle de caséines, globule gras) qui sont modifiées par les traitements technologiques utilisés lors de la fabrication des formules infantiles. Ces modifications se traduisent par des différences de comportement entre les deux produits dans le tube digestif du nouveau-né (vidange gastrique plus rapide pour le lait humain, cinétiques d’hydrolyse des protéines et des lipides différentes). Les traitements thermiques utilisés lors de la fabrication des formules infantiles entrainent la dénaturation et l’agrégation des protéines laitières affectant leur résistance à l’action des enzymes digestives. Les caséines deviennent plus résistantes à l’hydrolyse tandis que les protéines sériques y sont plus sensibles. L’homogénéisation transforme le globule gras du lait de plusieurs microns de diamètre en petites gouttelettes lipidiques sub-microniques et augmente ainsi la surface spécifique disponible pour la Lipase gastrique entrainant une accélération de la lipolyse. Les conséquences physiologiques pour le nouveau-né restent à établir mais des travaux préliminaires montrent que ces modifications affectent la maturation du système immunitaire et la structuration du microbiote intestinal.Despite the efforts made over the last decades to bring the composition of infant formulas closer to that of human milk, important differences in composition and structure of the constituents remain between these two foods. The human milk, true "gold standard" for the feeding of the newborn, has native structures (casein micelle, fat globule) which are modified by the technological treatments used in the manufacture of infant formulas. These changes result in behavioral differences between the two products in the digestive tract of the newborn (faster Gastric emptying for human milk, differences in kinetics of hydrolysis of proteins and lipids). The heat treatments used in the production of formulas lead to the denaturation and aggregation of milk proteins affecting their resistance to the action of digestive enzymes. Caseins become more resistant to hydrolysis while serum proteins are more sensitive to hydrolysis. Homogenization transforms the fat globule of milk of several microns of diameter into submicron lipid droplets and thus increases the specific surface area available for Gastric Lipase leading to an acceleration of lipolysis. The physiological consequences for the newborn remain to be established but preliminary work shows that these changes affect the maturation of the immune system and the structuring of the intestinal microbiota

  • Impact des procédés de transformation sur la digestion du lait maternel et des formules infantiles par le nouveau-né.
    INRAE, 2018
    Co-Authors: Deglaire Amélie, Ménard Olivia, Dupont Didier
    Abstract:

    Ce numéro est constitué d’articles issus du colloque « Alimentation périnatale, alimentation des séniors: spécificités, impact du microbiote », organisé le 28 mars 2018 à Paris.Despite the efforts made over the last decades to bring the composition of infant formulas closer to thatof human milk, important differences in composition and structure of the constituents remain betweenthese two foods. The human milk, true "gold standard" for the feeding of the newborn, has nativestructures (casein micelle, fat globule) which are modified by the technological treatments used in themanufacture of infant formulas. These changes result in behavioral differences between the twoproducts in the digestive tract of the newborn (faster Gastric emptying for human milk, differences inkinetics of hydrolysis of proteins and lipids). The heat treatments used in the production of formulas leadto the denaturation and aggregation of milk proteins affecting their resistance to the action of digestiveenzymes. Caseins become more resistant to hydrolysis while serum proteins are more sensitive tohydrolysis. Homogenization transforms the fat globule of milk of several microns of diameter into submicronlipid droplets and thus increases the specific surface area available for Gastric Lipase leading toan acceleration of lipolysis. The physiological consequences for the newborn remain to be establishedbut preliminary work shows that these changes affect the maturation of the immune system and thestructuring of the intestinal microbiota.Malgré les efforts réalisés ces dernières décennies pour rapprocher la composition des formulesinfantiles de celle du lait humain, d’importantes différences de composition et de structure desconstituants demeurent entre ces deux aliments. Le lait humain, véritable « gold standard » pourl’alimentation du nouveau-né présente des structures natives (micelle de caséines, globule gras) quisont modifiées par les traitements technologiques utilisés lors de la fabrication des formules infantiles.Ces modifications se traduisent par des différences de comportement entre les deux produits dans letube digestif du nouveau-né (vidange gastrique plus rapide pour le lait humain, cinétiques d’hydrolysedes protéines et des lipides différentes). Les traitements thermiques utilisés lors de la fabrication desformules infantiles entrainent la dénaturation et l’agrégation des protéines laitières affectant leurrésistance à l’action des enzymes digestives. Les caséines deviennent plus résistantes à l’hydrolysetandis que les protéines sériques y sont plus sensibles. L’homogénéisation transforme le globule grasdu lait de plusieurs microns de diamètre en petites gouttelettes lipidiques sub-microniques et augmenteainsi la surface spécifique disponible pour la Lipase gastrique entrainant une accélération de la lipolyse.Les conséquences physiologiques pour le nouveau-né restent à établir mais des travaux préliminairesmontrent que ces modifications affectent la maturation du système immunitaire et la structuration dumicrobiote intestinal

  • A first step towards a consensus static in vitro model for simulating full-term newborn digestion: application to infant formulas
    HAL CCSD, 2017
    Co-Authors: Ménard Olivia, Bourlieu-lacanal Claire, Dupont Didier, De Oliveira, Samira Cássia, Dellarosa N., Capozzi F., Deglaire Amélie
    Abstract:

    Studying food digestion in humans through clinical trials is difficult for economical, ethical and technical reasons. In vitro alternatives are thus used for screening different foods and for a better understanding of the mechanisms of the digestive process. To date, there are only few models for simulating infant digestion and most of them lack of physiological relevance. Thanks to an extensive literature review of the in vivo infant digestive conditions, a gastrointestinal static in vitro model was developed for infants born at term and aged of 28 days. The oral phase was omitted due to the liquid nature of infant formula but also because carbohydrate digestion was not monitored here. The following parameters were determined: pH, ratio of meal to secretions, enzyme units of pepsin and Gastric Lipase (added as rabbit Gastric extract) and of pancreatin (porcine source), and biliary salt molarity. Gastric and intestinal phases lasted 60 min each. The model was applied to the digestion of a commercial infant formula. Kinetics of digestion and end-points were compared with those obtained while submitting the same formula to the adult standardised protocol of in vitro static digestion1.Gastric and intestinal digesta were sampled regularly. Proteolysis kinetics were followed by SDS-PAGE and NMR and lipolysis kinetics by thin layer and gas chromatography. The structure evolution during the Gastric phase was evaluated by confocal laser scanning microscopy and laser light scattering. As a result, the kinetics of proteolysis and lipolysis differed according to the physiological stage likely due to the reduced level of enzymes in the infant model and the higher Gastric pH at the infant stage. This model is of interest for scientists or companies studying the digestion of infant food

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  • Physico-chemical behaviors of human and bovine milk membrane extracts and their influence on Gastric Lipase adsorption
    'Elsevier BV', 2020
    Co-Authors: Bourlieu Claire, Deglaire Amélie, Ménard Olivia, Pezennec Stéphane, Dupont Didier, Mahdoueni Wafa, Paboeuf Gilles, Gicquel Eric, Bouhallab Said, Carrière Frédéric
    Abstract:

    International audienceMilk fat globule membrane conditions the reactivity and enzymatic susceptibility of milk lipids. The use of bovine membrane extracts to make infant formulas more biomimetic of human milk has been suggested recently. A comparison of the physico-chemical behavior of human and bovine milk membrane extracts and their interaction with Gastric Lipase is here undertaken using biophysical tools. Milk membrane extracts (70% of polar lipids) were obtained either pooling of mature human milk (n = 5) or bovine buttermilk. Human extract contained more anionic glycerophospholipids, less phosphatidylethanolamine and more unsaturated fatty acids (57% versus 46%) than bovine extract. Human extract presented a higher compressibility, with slower increase of surface pressure, than bovine extract. Micronic liquid condensed (LC) domains were evidenced in both extracts at 10 mN/m, but the evolution differs upon compression. Upon Gastric Lipase addition, an adsorption preference for liquid expanded phase (LE) was observed for both extracts. However, insertion was more homogeneous in terms of height level in human extract and impacted less its lipid lateral organization than in bovine extract. Both membrane extracts share close physico-chemical properties, however human membrane higher compressibility may favour Gastric Lipase insertion and higher interfacial reactivity in Gastric conditions

  • Label free Imaging of Lipase activity on milk fat globules and model systems using DISCO beamline at Synchrotron SOLEIL
    HAL CCSD, 2019
    Co-Authors: Bourlieu-lacanal Claire, Deglaire Amélie, Ménard Olivia, Pezennec Stéphane, Le Feunteun Steven, Villeneuve Pierre, Dupont Didier, Fattacciolli Jacques, Jamme Frédéric, Carrière Frédéric
    Abstract:

    International audienceIn their native state, milk lipids are present in the form of dispersed droplets called Milk Fat Globules (MFG, diameter 0.1-20 μm, average = 4 μm in bovine milk) [1,2]. The native MFG is constituted by a triglyceride core covered with an external trilayered membrane inherited from its secretory past. This membrane is mainly based on polar lipids (glycerophospholipids, sphingolipids and glycosphingolipids), proteins (25 % of total membrane with high proportion of glycoproteins and enzymes), neutral lipids and minor components. The major biological function of the MFG is to deliver energy to the mammal newborn, for that, the MFG has to be hydrolyzed in the gastro-intestinal tract by Lipases, in successive steps. The Lipases should interact with the MFG membrane and diffuse into the supramolecular object. The aim of this work was to determine the mechanisms involved in the enzymatic hydrolysis along the digestive process. We used millifluidic cells designed to trap MFG or model droplets and injected successively each Lipase (Gastric, pancreatic related 2, pancreatic triglyceride Lipase) involved in the digestion process and thus mimicking different physiological stages (preterm infant, fullterm infant and adult). Thanks to the deep UV-microscope present at DISCO beamline, the autofluorescence of tryptophan (and tyrosine) of Lipase aminoacids allowed protein observation without external labeling. The Gastric and intestinal neonatal disintegration of milk fat globules (human or bovine) or other model systems (bovine anhydrous milk fat droplets stabilized by bovine milk membrane extracts or soy lecithin) was approached through transmission images recording. The analysis of the number of globules and their state of aggregation/coalescence during digestion (approached via diameter, size, mode and specific surface evolution against time) gave indication on the kinetics and mechanisms of lipolysis. Fluorescence (327-335 nm) image indicated Lipase distribution. Gastric phase was mainly marked by the heterogeneous adsorption of the Gastric Lipase in the MFG membrane. Afterwards, heterogeneous adsorption of pancreatic triglyceride Lipase could also be observed followed by the disappearance of the MFG core. The progression of Lipases fronts was monitored and the kinetics of lipolysis characterized allowing the differentiation of substrate and of in vitro digestion models (full term infant, versus preterm infant versus adult). The microfluidics set up was a very interesting tool to follow sequentially the action of Lipases, to save volume of purified Lipase and to image simultaneously several positions. The high sensitivity of the DISCO beamline allowing the detection of digestive Lipases auto-fluorescence, is a unique tool to unravel their mechanisms of adsorption onto complex substrate using free-label imaging and has generated useful data for infant formula optimizatio

  • Impact des procédés de transformation sur la digestion du lait maternel et des formules infantiles par le nouveau-né.
    2018
    Co-Authors: Deglaire Amélie, Ménard Olivia
    Abstract:

    Malgré les efforts réalisés ces dernières décennies pour rapprocher la composition des formules infantiles de celle du lait humain, d’importantes différences de composition et de structure des constituants demeurent entre ces deux aliments. Le lait humain, véritable « gold standard » pour l’alimentation du nouveau-né présente des structures natives (micelle de caséines, globule gras) qui sont modifiées par les traitements technologiques utilisés lors de la fabrication des formules infantiles. Ces modifications se traduisent par des différences de comportement entre les deux produits dans le tube digestif du nouveau-né (vidange gastrique plus rapide pour le lait humain, cinétiques d’hydrolyse des protéines et des lipides différentes). Les traitements thermiques utilisés lors de la fabrication des formules infantiles entrainent la dénaturation et l’agrégation des protéines laitières affectant leur résistance à l’action des enzymes digestives. Les caséines deviennent plus résistantes à l’hydrolyse tandis que les protéines sériques y sont plus sensibles. L’homogénéisation transforme le globule gras du lait de plusieurs microns de diamètre en petites gouttelettes lipidiques sub-microniques et augmente ainsi la surface spécifique disponible pour la Lipase gastrique entrainant une accélération de la lipolyse. Les conséquences physiologiques pour le nouveau-né restent à établir mais des travaux préliminaires montrent que ces modifications affectent la maturation du système immunitaire et la structuration du microbiote intestinal.Despite the efforts made over the last decades to bring the composition of infant formulas closer to that of human milk, important differences in composition and structure of the constituents remain between these two foods. The human milk, true "gold standard" for the feeding of the newborn, has native structures (casein micelle, fat globule) which are modified by the technological treatments used in the manufacture of infant formulas. These changes result in behavioral differences between the two products in the digestive tract of the newborn (faster Gastric emptying for human milk, differences in kinetics of hydrolysis of proteins and lipids). The heat treatments used in the production of formulas lead to the denaturation and aggregation of milk proteins affecting their resistance to the action of digestive enzymes. Caseins become more resistant to hydrolysis while serum proteins are more sensitive to hydrolysis. Homogenization transforms the fat globule of milk of several microns of diameter into submicron lipid droplets and thus increases the specific surface area available for Gastric Lipase leading to an acceleration of lipolysis. The physiological consequences for the newborn remain to be established but preliminary work shows that these changes affect the maturation of the immune system and the structuring of the intestinal microbiota

  • Impact des procédés de transformation sur la digestion du lait maternel et des formules infantiles par le nouveau-né.
    INRAE, 2018
    Co-Authors: Deglaire Amélie, Ménard Olivia, Dupont Didier
    Abstract:

    Ce numéro est constitué d’articles issus du colloque « Alimentation périnatale, alimentation des séniors: spécificités, impact du microbiote », organisé le 28 mars 2018 à Paris.Despite the efforts made over the last decades to bring the composition of infant formulas closer to thatof human milk, important differences in composition and structure of the constituents remain betweenthese two foods. The human milk, true "gold standard" for the feeding of the newborn, has nativestructures (casein micelle, fat globule) which are modified by the technological treatments used in themanufacture of infant formulas. These changes result in behavioral differences between the twoproducts in the digestive tract of the newborn (faster Gastric emptying for human milk, differences inkinetics of hydrolysis of proteins and lipids). The heat treatments used in the production of formulas leadto the denaturation and aggregation of milk proteins affecting their resistance to the action of digestiveenzymes. Caseins become more resistant to hydrolysis while serum proteins are more sensitive tohydrolysis. Homogenization transforms the fat globule of milk of several microns of diameter into submicronlipid droplets and thus increases the specific surface area available for Gastric Lipase leading toan acceleration of lipolysis. The physiological consequences for the newborn remain to be establishedbut preliminary work shows that these changes affect the maturation of the immune system and thestructuring of the intestinal microbiota.Malgré les efforts réalisés ces dernières décennies pour rapprocher la composition des formulesinfantiles de celle du lait humain, d’importantes différences de composition et de structure desconstituants demeurent entre ces deux aliments. Le lait humain, véritable « gold standard » pourl’alimentation du nouveau-né présente des structures natives (micelle de caséines, globule gras) quisont modifiées par les traitements technologiques utilisés lors de la fabrication des formules infantiles.Ces modifications se traduisent par des différences de comportement entre les deux produits dans letube digestif du nouveau-né (vidange gastrique plus rapide pour le lait humain, cinétiques d’hydrolysedes protéines et des lipides différentes). Les traitements thermiques utilisés lors de la fabrication desformules infantiles entrainent la dénaturation et l’agrégation des protéines laitières affectant leurrésistance à l’action des enzymes digestives. Les caséines deviennent plus résistantes à l’hydrolysetandis que les protéines sériques y sont plus sensibles. L’homogénéisation transforme le globule grasdu lait de plusieurs microns de diamètre en petites gouttelettes lipidiques sub-microniques et augmenteainsi la surface spécifique disponible pour la Lipase gastrique entrainant une accélération de la lipolyse.Les conséquences physiologiques pour le nouveau-né restent à établir mais des travaux préliminairesmontrent que ces modifications affectent la maturation du système immunitaire et la structuration dumicrobiote intestinal

  • A first step towards a consensus static in vitro model for simulating full-term newborn digestion: application to infant formulas
    HAL CCSD, 2017
    Co-Authors: Ménard Olivia, Bourlieu-lacanal Claire, Dupont Didier, De Oliveira, Samira Cássia, Dellarosa N., Capozzi F., Deglaire Amélie
    Abstract:

    Studying food digestion in humans through clinical trials is difficult for economical, ethical and technical reasons. In vitro alternatives are thus used for screening different foods and for a better understanding of the mechanisms of the digestive process. To date, there are only few models for simulating infant digestion and most of them lack of physiological relevance. Thanks to an extensive literature review of the in vivo infant digestive conditions, a gastrointestinal static in vitro model was developed for infants born at term and aged of 28 days. The oral phase was omitted due to the liquid nature of infant formula but also because carbohydrate digestion was not monitored here. The following parameters were determined: pH, ratio of meal to secretions, enzyme units of pepsin and Gastric Lipase (added as rabbit Gastric extract) and of pancreatin (porcine source), and biliary salt molarity. Gastric and intestinal phases lasted 60 min each. The model was applied to the digestion of a commercial infant formula. Kinetics of digestion and end-points were compared with those obtained while submitting the same formula to the adult standardised protocol of in vitro static digestion1.Gastric and intestinal digesta were sampled regularly. Proteolysis kinetics were followed by SDS-PAGE and NMR and lipolysis kinetics by thin layer and gas chromatography. The structure evolution during the Gastric phase was evaluated by confocal laser scanning microscopy and laser light scattering. As a result, the kinetics of proteolysis and lipolysis differed according to the physiological stage likely due to the reduced level of enzymes in the infant model and the higher Gastric pH at the infant stage. This model is of interest for scientists or companies studying the digestion of infant food