Seaweed Dietary Fiber Sodium Alginate Suppresses the Migration of Colonic Inflammatory Monocytes and Diet-Induced Metabolic Syndrome via the Gut Microbiota

Ginseng-DF ameliorates intestinal mucosal barrier injury and enhances immunity in immunosuppressed mice by regulating MAPK/NF-κB signaling pathways

PURPOSE

Dietary fiber (DF) has a good application prospect in effectively restoring the integrity of the intestinal mucosal barrier. Ginseng-DF has good physicochemical properties and physiological activity and shows positive effects in enhancing immunity. The aim of this study was to investigate the protective effect of Ginseng-DF on intestinal mucosal barrier injury induced by cyclophosphamide (CTX) in immunosuppressed mice and its possible mechanism.

METHODS

The effects of Gginseng-DF on immune function in mice were studied by delayed-type hypersensitivy, lymphocyte proliferation assay and NK cytotoxicity assay, the T lymphocyte differentiation and intestinal barrier integrity were analyzed by flow cytometry and western blot.

RESULTS

Ginseng-DF (2.5% and 5%) could attenuate the inhibition of DTH response by CTX, promote the transformation and proliferation of lymphocytes, and stimulate NK effector cell activity. At the same time, Ginseng-DF could restore the proportion of CD4+/CD8+ T lymphocytes induced by CTX to different extents, improved spleen tissue damage, promoted the secretion of immunoglobulin IgG, and enhanced body immunity. More importantly, Ginseng-DF could up-regulate the contents of TNF-α, IFN-γ, IL-6 and IL-1β in serum and intestine of immunosuppressed mice to maintain the balance between Th1/Th2 cytokines, and improve the permeability of intestinal mucosal barrier. Meanwhile, Ginseng-DF could reduce intestinal epithelial cell apoptosis and improve intestinal adaptive immunity in CTX-induced immunosuppressed mice by regulating MAPK/NF-κB signaling pathway.

CONCLUSION

Ginseng-DF can be used as a safe dietary supplement to enhance body immunity and reduce intestinal mucosal injury caused by CTX.

Evaluation of antioxidant, antidiabetic and antiobesity potential of phenylpropanoids (PPs): Structure-activity relationship and insight into action mechanisms against dual digestive enzymes by comprehensive technologies

Phenylpropanoids (PPs), a group of natural compounds characterized by one or more C6-C3 units, have exhibited considerable potential in addressing metabolic disease. However, the comprehensive investigation on the relationship of compound structures and involved activity, along with the action mechanisms on the drug target is absent. This study aimed to evaluate the antioxidant and inhibitory activities of 16 PPs against two digestive enzymes, including α-glucosidase and pancreatic lipase, explore the structure-activity relationships and elucidate the mechanisms underlying enzyme inhibition. The findings revealed the similarities in the rules governing antioxidant and enzyme inhibitory activities of PPs. Specifically, the introduction of hydroxyl groups generally exerted positive effects on the activities, while the further methoxylation and glycosylation were observed to be unfavorable. Among the studied PPs, esculetin exhibited the most potent antioxidant activity and dual enzymes inhibition potential, displaying IC50 values of 0.017 and 0.0428 mM for DPPH and ABTS radicals scavenging, as well as 1.36 and 6.67 mM for α-glucosidase and lipase inhibition, respectively. Quantification analysis indicated esculetin bound on both α-glucosidase and lipase successfully by a mixed-type mode. Further analyses by UV-Vis, FT-IR, fluorescence spectra, surface hydrophobicity, SEM, and molecular docking elucidated that esculetin could bind on the catalytic or non-catalytic sites of enzymes to form complex, impacting the normal spatial conformation for hydrolyzing the substrate, thus exhibiting the weakened activity. These results may shed light on the utilization value of natural PPs for the management of hyperglycemia and hyperlipemia, and afford the theoretical basis for designing drugs with stronger inhibition against the dual digestive enzymes based on esculetin.

Unraveling the bioactive interplay: seaweed polysaccharide, polyphenol and their gut modulation effect

Seaweed is rich in many unique bioactive compounds such as polyphenols and sulfated polysaccharides that are not found in terrestrial plant. The discovery of numerous biological activities from seaweed has made seaweed an attractive functional food source with the potential to be exploited for human health benefits. During food processing and digestion, cell wall polysaccharide and polyphenols commonly interact, and this may influence the nutritional properties of food. Interactions between cell wall polysaccharide and polyphenols in plant-based system has been extensively studied. However, similar interactions in seaweed have received little attention despite the vast disparity between the structural and chemical composition of plant and seaweed cell wall. This poses a challenge in extracting seaweed bioactive compounds with intact biological properties. This review aims to summarize the cell wall polysaccharide and polyphenols present in brown, red and green seaweed, and current knowledge on their potential interactions. Moreover, this review gives an overview of the gut modulation effect of seaweed polysaccharide and polyphenol.

Bioinspired pH-Responsive Microalgal Hydrogels for Oral Insulin Delivery with Both Hypoglycemic and Insulin Sensitizing Effects

The oral form of insulin is more convenient and has better patient compliance than subcutaneous or intravenous insulin. Current oral insulin preparations, however, cannot overcome the enzyme barrier, chemical barrier, and epithelial barrier of the gastrointestinal tract completely. In this study, a microalgae-based oral insulin delivery strategy (CV@INS@ALG) was developed using Chlorella vulgaris (CV)-based insulin delivery system cross-linking with sodium alginate (ALG). CV@INS@ALG could overcome the gastrointestinal barrier, protect insulin from harsh gastric conditions, and achieve a pH-responsive drug release in the intestine. CV@INS@ALG might contribute to two mechanisms of insulin absorption, including direct insulin release from the delivery system and endocytosis by M cells and macrophages. In the streptozotocin (STZ)-induced type 1 diabetic mouse model, CV@INS@ALG showed a more effective and long-lasting hypoglycemic effect than direct insulin injection and did not cause any damage to the intestinal tract. Additionally, the long-term oral administration of the carrier CV@ALG effectively ameliorated gut microbiota disorder, and significantly increased the abundance of probiotic Akkermansia in db/db type 2 diabetic mice, thereby enhancing the insulin sensitivity of mice. Microalgal insulin delivery systems could be degraded and metabolized in the intestinal tract after oral administration, showing good biodegradability and biosafety. This insulin delivery strategy based on microalgal biomaterials provides a natural, efficient, and multifunctional solution for oral insulin delivery.

Durvillaea antarctica: A Seaweed for Enhancing Immune and Cardiometabolic Health and Gut Microbiota Composition Modulation

Durvillaea antarctica is the seaweed that is the most consumed by the Chilean population. It is recognized worldwide for its high nutritional value in protein, vitamins, minerals, and dietary fiber. This is a narrative review in which an extensive search of the literature was performed to establish the immunomodulator, cardiometabolic, and gut microbiota composition modulation effect of Durvillaea antarctica. Several studies have shown the potential of Durvillaea antarctica to function as prebiotics and to positively modulate the gut microbiota, which is related to anti-obesity, anti-inflammatory, anticancer, lipid-lowering, and hypoglycemic effects. The quantity of Bacteroides was negatively correlated with that of inflammatory monocytes and positively correlated with the levels of several gut metabolites. Seaweed-derived polysaccharides modulate the quantity and diversity of beneficial intestinal microbiota, decreasing phenol and p-cresol, which are related to intestinal diseases and the loss of intestinal function. Additionally, a beneficial metabolic effect related to this seaweed was observed, mainly promoting the decrease in the glycemic levels, lower cholesterol levels and cardiovascular risk. Consuming Durvillaea antarctica has a positive impact on the immune system, and its bioactive compounds provide beneficial effects on glycemic control and other metabolic parameters.

An exploration of alginate oligosaccharides modulating intestinal inflammatory networks via gut microbiota

Alginate oligosaccharides (AOS) can be obtained by acidolysis and enzymatic hydrolysis. The products obtained by different methods have different structures and physiological functions. AOS have received increasing interest because of their many health-promoting properties. AOS have been reported to exert protective roles for intestinal homeostasis by modulating gut microbiota, which is closely associated with intestinal inflammation, gut barrier strength, bacterial infection, tissue injury, and biological activities. However, the roles of AOS in intestinal inflammation network remain not well understood. A review of published reports may help us to establish the linkage that AOS may improve intestinal inflammation network by affecting T helper type 1 (Th1) Th2, Th9, Th17, Th22 and regulatory T (Treg) cells, and their secreted cytokines [the hub genes of protein-protein interaction networks include interleukin-1 beta (IL-1β), IL-2, IL-4, IL-6, IL-10 and tumor necrosis factor alpha (TNF-α)] via the regulation of probiotics. The potential functional roles of molecular mechanisms are explored in this study. However, the exact mechanism for the direct interaction between AOS and probiotics or pathogenic bacteria is not yet fully understood. AOS receptors may be located on the plasma membrane of gut microbiota and will be a key solution to address such an important issue. The present paper provides a better understanding of the protecting functions of AOS on intestinal inflammation and immunity.

Hornification: Lessons learned from the wood industry for attenuating this phenomenon in plant-based dietary fibers from food wastes

A significant amount of waste is annually generated worldwide by the supply chain of the food industry. Considering the population growth, the environmental concerns, and the economic opportunities, waste recovery is a promising solution to produce valuable and innovative ingredients for food and nonfood industries. Indeed, plant-based wastes are rich in dietary fibers (DF), which have relevant technical functionalities such as water/oil holding capacity, swelling capacity, viscosity, texture, and physiological properties such as antioxidant activity, cholesterol, and glucose adsorption capacities. Different drying technologies could be applied to extend the shelf life of fresh DF. However, inappropriate drying technologies or process conditions could adversely affect the functionalities of DF via the hornification phenomenon. Hornification is related to the formation of irreversible hydrogen bindings, van der Waals interactions, and covalent lactone bridges between cellulose fibrils during drying. This review aims to capitalize on the knowledge developed in the wood industry to tackle the hornification phenomenon occurring in the food industry. The mechanisms and the parameters affecting hornification as well as the mitigation strategies used in the wood industry that could be successfully applied to foods are summarized. The application of conventional drying technologies such as air or spray-drying increased the occurrence of hornification. In contrast, solvent exchange, supercritical drying, freeze-drying, and spray-freeze-drying approaches were considered effective strategies to limit the consequences of this phenomenon. In addition, incorporating capping agents before drying attenuated the hornification. The knowledge summarized in this review can be used as a basis for process design in the valorization of plant-based wastes and the production of functional DF that present relevant features for the food and packaging industries.

Alginate Alleviates Dextran Sulfate Sodium-Induced Colitis by Promoting Bifidobacterium animalis and Intestinal Hyodeoxycholic Acid Synthesis in Mice

Alginate (ALG) is known to alleviate intestinal inflammation in inflammatory bowel disease, but its mechanism of action remains elusive. In the present study, we studied the involvement of the intestinal microbiota and bile acid (BA) metabolism in ALG-mediated anti-inflammatory effects in mice. A combination of 16S rRNA gene amplicon sequencing, shotgun metagenomic sequencing, and targeted BA metabolomic profiling was employed to investigate structural and functional differences in the colonic microbiota and BA metabolism in dextran sulfate sodium (DSS)-treated mice with or without dietary supplementation of ALG. We further explored the role of the intestinal microbiota as well as a selected ALG-enriched bacterium and BA in DSS-induced colitis. Dietary ALG alleviated DSS-mediated intestinal inflammation and enriched a small set of bacteria including Bifidobacterium animalis in the colon (P < 0.05). Additionally, ALG restored several bacteria carrying secondary BA-synthesizing enzymes such as 7α-hydroxysteroid dehydrogenase and BA hydrolase to healthy levels in DSS-treated mice. Although a majority of BAs were suppressed by DSS, a few secondary BAs such as hyodeoxycholic acid (HDCA) were markedly enriched by ALG. Furthermore, ALG significantly upregulated the expression of a major BA receptor, the farnesoid X receptor, while suppressing NF-κB and c-Jun N-terminal kinase (JNK) activation. Depletion of the intestinal microbiota completely abrogated the protective effect of ALG in DSS-treated mice. Similar to ALG, B. animalis and HDCA exerted a strong anti-inflammatory effect in DSS-induced colitis by downregulating inflammatory cytokines (interleukin-1β [IL-1β], IL-6, and tumor necrosis factor alpha [TNF-α]). Taken together, these results indicated that ALG achieves its alleviating effect on intestinal inflammation through regulation of the microbiota by enriching B. animalis to promote the biosynthesis of specific secondary BAs such as HDCA. These findings have revealed intricate interactions among the intestinal microbiota, BA metabolism, and intestinal health and further provided a novel strategy to improve intestinal health through targeted manipulation of the intestinal microbiota and BA metabolism. IMPORTANCE ALG has been shown to ameliorate inflammatory bowel disease (IBD), but little is known about the mechanism of its anti-inflammatory action. This study was the first to demonstrate that ALG provided a preventive effect against colitis in an intestinal microbiota-dependent manner. Furthermore, we confirmed that by selectively enriching intestinal B. animalis and secondary BA (HDCA), ALG contributed to the attenuation of DSS-induced colitis. These findings contribute to a better understanding of the mechanism of action of ALG on the attenuation of colitis and provide new approaches to IBD therapy by regulating gut microbial BA metabolism.

Nutrition, Immunosenescence, and Infectious Disease: An Overview of the Scientific Evidence on Micronutrients and on Modulation of the Gut Microbiota

The immune system is key to host defense against pathogenic organisms. Aging is associated with changes in the immune system, with a decline in protective components (immunosenescence), increasing susceptibility to infectious disease, and a chronic elevation in low-grade inflammation (inflammaging), increasing the risk of multiple noncommunicable diseases. Nutrition is a determinant of immune cell function and of the gut microbiota. In turn, the gut microbiota shapes and controls the immune and inflammatory responses. Many older people show changes in the gut microbiota. Age-related changes in immune competence, low-grade inflammation, and gut dysbiosis may be interlinked and may relate, at least in part, to age-related changes in nutrition. A number of micronutrients (vitamins C, D, and E and zinc and selenium) play roles in supporting the function of many immune cell types. Some trials report that providing these micronutrients as individual supplements can reverse immune deficits in older people and/or in those with insufficient intakes. There is inconsistent evidence that this will reduce the risk or severity of infections including respiratory infections. Probiotic, prebiotic, or synbiotic strategies that modulate the gut microbiota, especially by promoting the colonization of lactobacilli and bifidobacteria, have been demonstrated to modulate some immune and inflammatory biomarkers in older people and, in some cases, to reduce the risk and severity of gastrointestinal and respiratory infections, although, again, the evidence is inconsistent. Further research with well-designed and well-powered trials in at-risk older populations is required to be more certain about the role of micronutrients and of strategies that modify the gut microbiota-host relationship in protecting against infection, especially respiratory infection.

Potential Food and Nutraceutical Applications of Alginate: A Review

Alginate is an acidic polysaccharide mainly extracted from kelp or sargassum, which comprises 40% of the dry weight of algae. It is a linear polymer consisting of β-D-mannuronic acid (M) and α-L-guluronic acid (G) with 1,4-glycosidic linkages, possessing various applications in the food and nutraceutical industries due to its unique physicochemical properties and health benefits. Additionally, alginate is able to form a gel matrix in the presence of Ca²⁺ ions. Alginate properties also affect its gelation, including its structure and experimental conditions such as pH, temperature, crosslinker concentration, residence time and ionic strength. These features of this polysaccharide have been widely used in the food industry, including in food gels, controlled-release systems and film packaging. This review comprehensively covers the analysis of alginate and discussed the potential applications of alginate in the food industry and nutraceuticals.

Cooperative action of gut-microbiota-accessible carbohydrates improves host metabolic function

Microbiota-accessible carbohydrates (MACs) exert health-promoting effects, but how each MAC impacts gut microbiota and regulates host physiology remains unclear. Here, we show that l-arabinose and sucrose cooperatively act on gut microbiota and exert anti-obesogenic effects. Specifically, l-arabinose, a monosaccharide that is poorly absorbed in the gut and inhibits intestinal sucrase, suppresses diet-induced obesity in mice in the presence of sucrose. Additionally, the suppressive effect of l-arabinose on adiposity is abrogated in mice lacking the short-chain fatty acid (SCFA) receptors GPR43 and GPR41. Mechanistically, l-arabinose increases the relative abundance of acetate and propionate producers (e.g., Bacteroides), while sucrose enhances SCFA production. Furthermore, l-arabinose and sucrose activate the glycolytic and pentose phosphate pathways of Bacteroides, respectively, indicating that they synergistically promote acetate production through distinct pathways. These findings suggest that each MAC has a unique property and thus may serve as a precision gut-microbiota modulator to promote host homeostasis.

Gut Microbiota of Individuals Could Be Balanced by a 14-Day Supplementation With Laminaria japonica and Differed in Metabolizing Alginate and Galactofucan

Laminaria japonica is rich in alginate (Alg) and galactofucan (GF) which have both been reported to regulate gut microbiota composition. To reveal the effect of L. japonica on human gut microbiota, the fecal microbiota of 12 volunteers before and after 14-day L. japonica intake was sequenced and compared, and the capabilities of the gut microbiota to utilize Alg and GF were also investigated. The 16S rRNA gene sequencing results demonstrated that Firmicutes/Bacteroidetes ratio could be balanced by L. japonica supplementation. The ability of gut microbiota to utilize Alg was significantly enhanced by L. japonica supplementation. Furthermore, the multiple linear regression analysis suggested that bacteria from Bacteroidaceae and Ruminococcaceae were positively correlated with Alg utilization while those from Erysipelotrichaceae, Bacteroidaceae, and Prevotellaceae participated in GF degradation. Moreover, the production of acetic acid and the total short-chain fatty acids (SCFAs) in fermentation were consistent with the consumption of Alg or GF, and propionic acid content was positively correlated with Alg consumption. In addition, the percentage of monosaccharides in the consumed GF after the fermentation suggested that gut microbiota from individuals could consume GF with different monosaccharide preferences. These findings shed a light on the impacts of dietary L. japonica on human health.