The design of the emulsion interface influences the lipolysis kinetics under in vitro gastric conditions

status: Published onlin

Unraveling the molecular mechanism of in vitro gastric lipolysis through the advanced multi-response modeling technique

status: Published onlin

Pre-duodenal lipid digestion of emulsions: Relevance, colloidal aspects and mechanistic insight

International audienceThe digestion of lipids in the human body has several health and nutritional implications. Lipid digestion is an interfacial phenomenon meaning that water-soluble lipases need to first adsorb to the oil–water interface before enzymatic conversions can start. The digestion of lipids mainly occurs on colloidal structures dispersed in water, such as oil-in-water (o/w) emulsions, which can be designed during food formulation/processing or structured during digestion. From a food design perspective, different in vitro studies have demonstrated that the kinetics of lipid digestion can be influenced by emulsion properties. However, most of these studies have been performed with pancreatic enzymes to simulate lipolysis in the small intestine. Only few studies have dealt with lipid digestion in the gastric phase and its subsequent impact on intestinal lipolysis. In this aspect, this review compiles information on the physiological aspects of gastric lipid digestion. In addition, it deals with colloidal and interfacial aspects starting from emulsion design factors and how they evolve during in vitro digestion. Finally, molecular mechanisms describing gastric lipolysis are discussed

Lipolysis products formation during in vitro gastric digestion is affected by the emulsion interfacial composition

In this work, we report on the effect of the emulsion interfacial composition on the lipid digestion kinetics of in vitro gastric lipolysis. Emulsions (o/w) were formulated with triolein (5%, w/w) and emulsifiers of different chemical nature (1%, w/w). These emulsifiers included different low-molecular-weight surfactants: sodium taurodeoxycholate (NaTDC, ionic), soy lecithin (LEC, zwitterionic), and tween 80 (TW80, non-ionic); as well as biopolymers: soy protein isolate (SPI) and citrus pectin (CP). Emulsions were subjected to static gastric in vitro digestion. Samples were characterized as a function of digestion time in terms of physicochemical properties (droplet charge, microstructure and particle size analysis) and multiple lipolysis products (HPLC coupled to a charged aerosol detector). The kinetic analysis, based on the % of digested triolein, showed that emulsions stabilized by biopolymers did not represent a barrier for gastric lipase adsorption, reaching the highest extents of lipid digestion (25–28%) in the gastric phase. Emulsions stabilized by low-molecular-weight surfactants presented considerable different behaviors under gastric conditions: lipolysis extents of NaTDC- and TW80-based emulsions were low due to early instability or strong interfacial displacement of gastric lipase, respectively; while the LEC-based emulsion presented a higher lipolysis extent (15%) due to its stability and apparent moderate interfacial displacement of gastric lipase. The quantification of multiple lipolysis products allowed the validation of the gastric lipolysis molecular mechanism previously proposed. The results hereby presented constitute advanced insight in the effect of interfacial design on the kinetics of in vitro gastric lipid digestion.status: Published onlin

Enzymatic and chemical conversions taking place during in vitro gastric lipid digestion: The effect of emulsion droplet size behavior

This investigation reports the effect of droplet size behavior on the overall lipolysis profile and molecular lipolysis mechanisms under in vitro gastric conditions. O/W emulsions (5% triolein, 1% sodium taurodeoxycholate) with different initial droplet sizes (fine: 0.58 μm; medium: 1.82 μm; and large: 4.00 μm) were subjected to static in vitro digestion. For the first time, multiple lipolysis products including diolein and monoolein regioisomers were quantified within a single HPLC run. An inverse relation was found between the droplet size and the initial rate and final extent of lipolysis based on the digested triolein. Furthermore, a mechanistic gastric lipolysis model was established based on a reaction scheme including enzymatic and chemical isomerization conversions. The estimated rate of the sn-1/3 hydrolysis was around two- to thirty-fold faster compared to the rates of sn-2 cleavage and isomerization, respectively. These findings resulted in a profound insight in in vitro gastric molecular lipolysis mechanisms.status: Published onlin

On the performance of high frequency radar in the western Mediterranean during the record-breaking storm Gloria

Storm Gloria (January 19–24, 2020) hit the NW Mediterranean Sea with heavy rainfall, strong easterly winds, and very high waves, causing structural damages and 13 fatalities. The low-lying Ebro Delta (ED) region was severely inundated, ruining rice fields and seaside promenades. A variety of Copernicus Marine Environment Monitoring Service (CMEMS) modeling and observational products were jointly used to examine the fingerprint of Gloria and the response of the upper oceanic layer. According to the results, Gloria can be interpreted as a high-impact once-in-a-decade metocean event where various historical records were beaten. The 99th percentile of several parameters (wind speed, significant wave height, wave period, and surface current velocity), derived from long-term observational time series, was persistently exceeded. The atmospheric surge, albeit not negligible, exerted a secondary role in ED. The ability of a high-frequency radar deployed in this region (HFR-ED) to characterize the striking features of the storm was quantified from both waves and circulation aspects. Consistent radar current observations were subsequently compared against the 5-day-ahead forecast of CMEMS Iberia-Biscay-Ireland (IBI) regional ocean model to determine, from an Eulerian perspective, the strengths and shortcomings in its predictive capabilities. Time-averaged maps of surface circulation, superimposed with fields of Instantaneous Rate of Separation (IROS), were derived to resolve flow features and identify areas of elevated particles dispersion, respectively. The mean and P99 values of IROS almost doubled the historical statistics in the vicinity of the northern Ebro hemidelta. Although IBI predicted moderately well basic features of the storm-induced circulation, results suggests that coastal transport processes, likely modulated by wave-current interactions, were not fully captured. Furthermore, current estimations from other two radar systems, overlooking immediate choke points like the Ibiza Channel and the Strait of Gibraltar, evidenced Gloria’s remote-effect in the anomalous circulation patterns observed, that altered the usual water exchanges between adjacent sub-basins. Finally, three-dimensional outcomes from IBI were used to elucidate the impact of this moving storm at different depth levels. Data analyses illustrated that Gloria caused a large increase in kinetic energy and a significant deepening of the mixed layer depth.Peer ReviewedPostprint (published version

Ibiza Absolute Calibration Experiment : Survey and Preliminary Results

International audienceWithin the framework of a project comprising part of the Spanish Space Program related to the JASON-1 CNES (Centre National d'Etudes Spatiales)/NASA (National Aeronautics and Space Administration) mission, a campaign was conducted from June 9-17, 2003, on the Absolute Calibration Site of the island of Ibiza. The objective was to determine the local marine geoid slope under the ascending (187) and descending (248) Jason-1 ground tracks, in order to allow a better extrapolation of the open-ocean altimetric data with on-shore tide gauge locations, and thereby improve the overall precision of the calibration process. For this we have used a catamaran with two GPS antennas onboard, following the Corsica/Senetosa design (Bonnefond et al. 2003a). Five GPS reference stations were deployed in order to reduce the distance between the areas covered by the catamaran and the fixed GPS receiver used in the kinematic process. The geodetic activities (e.g., GPS, leveling) have enabled the building of a very accurate (few mm) network in a reference frame compatible with the satellite altimetry missions (ITRF 2000). The GPS kinematic data were processed using two different software programmes, allowing checking of the consistency of the solutions. If the standard deviation of the differences (3.3 cm) is close to the kinematic process precision, they exhibit some large values (up to 14 cm). These large discrepancies have been reduced using a weighting based on the crossover differences. Inasmuch as the distances between the tide gauges and the areas covered by the GPS catamaran were becoming large, we have used the MOG2D ocean model (Carregravere and Lyard 2003) to correct the sea surface from tides. In the farthest areas, the crossover differences show an improvement by a factor of two. Finally, we also present preliminary results on Jason-1 altimeter calibration using the derived marine geoid. From this analysis, the altimeter bias is estimated to be 120 ± 5 mm. The quality of this first result validates the whole GPS-based marine geoid processing, for which the accuracy is estimated to be better than 3 cm rms at crossovers

INFOGEST inter-laboratory recommendations for assaying gastric and pancreatic lipases activities prior to in vitro digestion studies

International audienceIn vitro digestion studies often use animal digestive enzyme extracts as substitutes of human gastric and pancreatic secretions. Pancreatin from porcine origin is thus commonly used to provide relevant pancreatic enzymes such as proteases, amylase and lipase. Rabbit gastric extracts (RGE) have been recently introduced to provide gastric lipase in addition to pepsin. Before preparing simulated gastric and pancreatic extracts with targeted enzyme activities as described in in vitro digestion protocols, it is important to determine the activities of enzyme preparations using validated methods. The purpose of this inter-laboratory study within the INFOGEST network was to test the repeatability and reproducibility of lipase assays using the pH-stat technique for measuring the activities of gastric and pancreatic lipases from various sources. Twenty-one laboratories having different pH-stat devices received the same protocol with identical batches of RGE and two pancreatin sources. Lipase assays were performed using tributyrin as a substrate and three different amounts (50, 100 and 200 µg) of each enzyme preparation. The repeatability results within individual laboratories were satisfactory with coefficients of variation (CVs) ranging from 4 to 8% regardless of the enzyme amount tested. However, the inter-laboratory variability was high (CV > 15%) compared to existing standards for bioanalytical assays. We identified and weighted the contributions to inter-laboratory variability of several parameters associated with the various pH-stat equipment used in this study (e.g. reaction vessel volume and shape, stirring mode and rate, burette volume for the automated delivery of sodium hydroxide). Based on this, we established recommendations for improving the reproducibility of lipase assays using the pH-stat technique. Defining accurate and complete recommendations on how to correctly quantify activity levels of enzyme preparations is a gateway to promising comparison of in vitro data obtained from different laboratories following the same in vitro digestion protocol