To investigate the quality of different ozone-oxidized surimi gels and their in vitro digestion and absorption characteristics, surimi rinsed with different concentrations of ozonated water (0, 8, 26 mg/L) were prepared. Then, the degree of oxidation and gel structure of surimi were determined, the in vitro digestion and absorption of the gels were simulated, and the digestion and absorption products were analyzed by LC-MS/MS. The results showed that the quality of surimi gels was improved after proper ozone oxidation. After ozone water rinsing, the dry matter digestibility, peptide, and amino acid content increased, and the changes of all three were in line with the Logistic kinetic model (R2 = 0.95-0.99). Caco-2 cell absorption experiments showed that the absorption rate of peptides and amino acids decreased after ozone water rinsing. In summary, ozone oxidation can promote the digestion of surimi gels, but it also reduces the absorption of peptides and amino acids by Caco-2 cells. This study provides a reference for the application of ozone in the food field.

Advanced glycation end products (AGEs), a heterogeneous compound existed in processed foods, are related to chronic diseases when they are accumulated excessively in human organs. Protein-bound Nε-(carboxymethyl) lysine (CML) as a typical AGE, is widely determined to evaluate AGEs level in foods and in vivo. This study investigated the intestinal absorption of three protein-bound CML originated from main food raw materials (soybean, wheat and peanut). After in vitro gastrointestinal digestion, the three protein-bound CML digests were ultrafiltered and divided into four fractions: less than 1 kDa, between 1 and 3 kDa, between 3 and 5 kDa, greater than 5 kDa. Caco-2 cell monolayer model was further used to evaluate the intestinal absorption of these components. Results showed that the absorption rates of soybean protein isolate (SPI)-, glutenin (Glu)-, peanut protein isolate (PPI)-bound CML were 30.18%, 31.57% and 29.5%, respectively. The absorption rates of components with MW less than 5 kDa accounted for 19.91% (SPI-bound CML), 22.59% (Glu-bound CML), 23.64% (PPI-bound CML), respectively, and these samples were absorbed by paracellular route, transcytosis route and active route via PepT-1. Taken together, these findings demonstrated that all three protein-bound CML digests with different MW can be absorbed in diverse absorption pathways by Caco-2 cell monolayer model. This research provided a theoretical basis for scientific evaluation of digestion and absorption of AGEs in food.

Conventional dissolution tests only assess the aqueous release of drugs to ensure quality and performance, without indicating whether absorption occurs through the portal or the lymphatic circulation. To address this issue, this study aimed to develop novel first-generation dissolution models that could investigate the release and uptake of oral lymphotropic drugs and examine relevant formulation issues. Dissolution of three commercial lymphotropic drug products (Terbinafina, Apo-terbinafine, and Lamisil) was done using modified versions of USP Apparatus II and IV. The developed models contained a lymphatic compartment filled with artificial chylomicrons to account for absorption through intestinal lymphatic pathway. The various products exhibited different release profiles into the aqueous media and the lymphatic media across the two tested models. The modified USP IV apparatus demonstrated greater distinction in aqueous release patterns. However, the release pattern into the lymphatic media remained similar in both models. This work represents a progress in meeting the challenges posed by the increasing complexity of pharmaceutical products containing lipophilic drugs or formulations, and has the potential to contribute towards the development of in-vitro bioequivalence standards for formulations targeting intestinal lymphatics.

Intestinal absorption of phosphate is bimodal, consisting of a transcellular pathway and a poorly characterized paracellular mode, even though the latter one contributes to the bulk of absorption under normal dietary conditions. Claudin-3 (Cldn3), a tight junction protein present along the whole intestine in mice, has been proposed to tighten the paracellular pathway for phosphate. The aim of this work was to characterize the phosphate-related phenotype of Cldn3-deficient mice. Cldn3-deficient mice and wildtype littermates were fed standard diet or challenged for 3 days with high dietary phosphate. Feces, urine, blood, intestinal segments and kidneys were collected. Measurements included fecal, urinary, and plasma concentrations of phosphate and calcium, plasma levels of phosphate-regulating hormones, evaluation of trans- and paracellular phosphate transport across jejunum and ileum, and analysis of intestinal phosphate and calcium permeabilities. Fecal and urinary excretion of phosphate as well as its plasma concentration was similar in both genotypes, under standard and high-phosphate diet. However, Cldn3-deficient mice challenged with high dietary phosphate had a reduced urinary calcium excretion and increased plasma levels of calcitriol. Intact FGF23 concentration was also similar in both groups, regardless of the dietary conditions. We found no differences either in intestinal phosphate transport (trans- or paracellular) and phosphate and calcium permeabilities between genotypes. The intestinal expression of claudin-7 remained unaltered in Cldn3-deficient mice. Our data do not provide evidence for a decisive role of Cldn3 for intestinal phosphate absorption and phosphate homeostasis. In addition, our data suggest a novel role of Cldn3 in regulating calcitriol levels.

Magnesium, an essential mineral for various physiological functions, is subject to tight regulation within the body. Understanding its absorption across epithelial cell monolayers is crucial for optimizing dietary magnesium intake and therapeutic strategies. The Caco-2 monolayer model, widely recognized for its relevance to the human intestinal epithelium, provides a suitable platform for this investigation. This protocol covers the step-by-step procedures for the cultivation of Caco-2 monolayer preparation of transwell systems. It provides guidance on the setup of magnesium transport experiments, which involve the application of magnesium salts to the apical side of the Caco-2 monolayer and monitoring their transport to the basolateral side.

OBJECTIVE: Dietary proteins are broken down into peptides across the gastrointestinal tract, with skeletal muscle being a primary deposition site for amino acids in the form of incorporation into, for example, metabolic and structural proteins. It follows that key research questions remain as to the role of amino acid bioavailability, of which protein digestibility and splanchnic sequestration (absorption and utilization) of amino acids are determining factors, impact upon muscle protein synthesis (MPS) in clinical states.
RESULTS: Elevated splanchnic amino acid uptake has been implicated in anabolic resistance (i.e. attenuated anabolic responses to protein intake) observed in ageing, though it is unclear whether this limits MPS. The novel \'dual stable isotope tracer technique\' offers a promising, minimally invasive approach to quantify the digestion of any protein source(s). Current work is focused on the validation of this technique against established methods, with scope to apply this to clinical and elderly populations to help inform mechanistic and interventional insights.
CONCLUSIONS: Considerations should be made for all facets of protein quality; digestibility of the protein, absorption/utilization and subsequent peripheral bioavailability of amino acids, and resultant stimulation of MPS. Stable isotope tracer techniques offer a minimally invasive approach to achieve this, with wide-ranging clinical application.

The nutritional quality of plant-based meat analogues compared to traditional meat products has been questioned in recent commentary, particularly in relation to protein quality and micronutrient bioavailability. However, the attributes of specific products within this category are unclear. We therefore undertook a comprehensive assessment of the compositional and functional attributes of v2food® (Sydney, Australia) plant-based mince, including an assessment of the effects of reformulation, including the addition of amino acids, ascorbic acid, and different forms of elemental iron. The protein digestibility and protein quality of v2food® plant-based mince were comparable to beef mince in the standardized INFOGEST system, and favourable effects on microbiota composition and short-chain fatty acid (SCFA) production were demonstrated in an in vitro digestion system. The use of ferrous sulphate as an iron source improved in vitro intestinal iron absorption by ~50% in comparison to other forms of iron (p < 0.05), although levels were ~3-fold lower than beef mince, even in the presence of ascorbic acid. In conclusion, the current study identified some favourable nutritional attributes of plant-based v2food® mince, specifically microbiota and SCFA changes, as well as other areas where further reformulation could be considered to further enhance the bioavailability of key nutrients. Further studies to assess the effect of plant-based meat analogues on health measures in vivo will be important to improve knowledge in this area.

(1) Background: Proglucagon-derived peptides (PDGPs) including glucagon (Gcg), GLP-1, and GLP-2 regulate lipid metabolism in the liver, adipocytes, and intestine. However, the mechanism by which PGDPs participate in alterations in lipid metabolism induced by high-fat diet (HFD) feeding has not been elucidated. (2) Methods: Mice deficient in PGDP (GCGKO) and control mice were fed HFD for 7 days and analyzed, and differences in lipid metabolism in the liver, adipose tissue, and duodenum were investigated. (3) Results: GCGKO mice under HFD showed lower expression levels of the genes involved in free fatty acid (FFA) oxidation such as Hsl, Atgl, Cpt1a, Acox1 (p < 0.05), and Pparα (p = 0.05) mRNA in the liver than in control mice, and both FFA and triglycerides content in liver and adipose tissue weight were lower in the GCGKO mice. On the other hand, phosphorylation of hormone-sensitive lipase (HSL) in white adipose tissue did not differ between the two groups. GCGKO mice under HFD exhibited lower expression levels of Pparα and Cd36 mRNA in the duodenum as well as increased fecal cholesterol contents compared to HFD-controls. (4) Conclusions: GCGKO mice fed HFD exhibit a lesser increase in hepatic FFA and triglyceride contents and adipose tissue weight, despite reduced β-oxidation in the liver, than in control mice. Thus, the absence of PGDP prevents dietary-induced fatty liver development due to decreased lipid uptake in the intestinal tract.

Docosahexaenoic acid (DHA), an essential omega-3 fatty acid, offers significant health benefits but faces challenges such as distinct odor, oxidation susceptibility, and limited intestinal permeability, hindering its broad application. Microencapsulation, widely employed, enhances DHA performance by facilitating controlled release, digestion, and absorption in the gastrointestinal tract. Despite extensive studies on DHA microcapsules and related delivery systems, understanding the mechanisms governing encapsulated DHA release, digestion, and absorption, particularly regarding the influence of wall materials and DHA sources, remains limited. This review starts with an overview of current techniques commonly applied for DHA microencapsulation. It then proceeds to outline up-to-date advances in the release, digestion and absorption of DHA microcapsules, highlighting the roles of wall materials and DHA sources. Importantly, it proposes strategies for overcoming challenges and exploiting opportunities to enhance the bioavailability of DHA microcapsules. Notably, spray drying dominates DHA microencapsulation (over 90 % usage), while complex coacervation shows promise for future applications. The combination of proteins and carbohydrates or phospholipids as wall material exhibits potential in controlling release and digestion of DHA microcapsules. The source of DHA, particularly algal oil, demonstrates higher lipid digestibility and absorptivity of free fatty acids (FFAs) than fish oil. Future advancements in DHA microcapsule development include formulation redesign (e.g., using plant proteins as wall material and algal oil as DHA source), technique optimization (such as co-microencapsulation and pre-digestion), and creation of advanced in vitro systems for assessing DHA digestion and absorption kinetics.

2-O-β-D-Glucopyranosyl-L-ascorbic acid (AA-2βG) from Lycium barbarum fruits has diverse bioactivities, yet its absorption and digestion are poorly understood. Therefore, the in vivo absorption of AA-2βG in rats was investigated in the present study. After oral administration to SD rats, AA-2βG was absorbed intact, reaching a peak plasma concentration of 472.32 ± 296.64 nM at 90 min, with fecal excretion peaking at 4-8 h and decreasing rapidly by 12-24 h, indicating a prolonged intestinal presence. Furthermore, the digestibility under simulated gastrointestinal conditions and the impact on the gut flora through in vitro fermentation of AA-2βG were investigated. The results reveal that AA-2βG resisted in in vitro simulated digestion, indicating potential interactions with the gut microbiota. The results of in vitro fermentation showed that AA-2βG regulated the composition of the gut microbiota by promoting Oscillospiraceae, Faecalibacterium, Limosilactobacillus, and Fusicatenibacter, while inhibiting Enterococcus, Phocaeicola, Bacteroides, and Streptococcus. Furthermore, at the species level, AA-2βG promoted the growth of Limosilactobacillus mucosae and Faecalibacterium prausnitzii, and inhibited the growth of Enterococcus. F. prausnitzii is a major producer of n-butyric acid, and the results of short-chain fatty acids also demonstrated a significant promotion of n-butyric acid. Therefore, the study on the absorption, excretion, and regulatory effects of AA-2βG on the gut microbiota supported its potential development as a functional food additive to enhance intestinal health and prevent diseases.