Effects of surface-deacetylated chitin nanofibers on non-alcoholic steatohepatitis model rats and their gut microbiota

Nanochitin From Crab Shells: Production, Chemical Modification, Composite Materials, and Physiological Functions

Large quantities of crab shells are generated in food-processing plants. In this review, the authors summarize a series of research findings on the production of nanochitin, its physical properties, chemical modifications, and functions, which have not been fully addressed in existing literature. Nanochitin, which has a width of 10 nm, is derived from chitin, the main component of crab shells, using a technology similar to that used to produce nanocellulose from wood. Unlike conventional chitin, nanochitin is well dispersed in water, making it easy to mold and process into various products for different applications. They can also be modified for specific uses through processes such as acylation and etherification to enhance their physical properties and add functionality. Nanochitin, which are known for their exceptional mechanical strength, can be blended with resins to create composite films with improved strength and elasticity. These films maintain the transparency of the resin, reduce its thermal expansion, and offer reinforcement. Chitin and its derivative chitosan are used as wound dressings, hemostatic agents, and health foods. Nanochitin and its deacetyl derivatives have diverse functions such as topical medicine for the skin, ingestion as a health food, and use as pesticides or fertilizers for plants.

Heat-Processed Diet Rich in Advanced Glycation End Products Induced the Onset and Progression of NAFLD via Disrupting Gut Homeostasis and Hepatic Lipid Metabolism

Epidemiologic studies have suggested an association between the consumption of dietary advanced glycation end products (dAGEs) and the incidence of nonalcoholic fatty liver disease (NAFLD). However, the precise mechanism by which dAGEs induce NAFLD development, particularly the pathogenic role of the gut-liver axis, remains poorly understood. In this study, by establishing a high-AGE diet (HAD)-fed C57BL/6 mouse model, we employed multiomics approaches combined with a series of biological analyses to investigate the effect of HAD on NAFLD in vivo. Our results showed that exposure to HAD led to fat accumulation, oxidative stress, inflammation, and fibrosis in the liver of mice. Transcriptome analysis further revealed that HAD exposure disrupted lipid metabolism and activated inflammation-related signaling pathways in the liver. Additionally, exposure to HAD induced perturbations in gut homeostasis, as evidenced by the compromised gut barrier function, reduced probiotic abundance, and increases in pathogenic bacterial proportions. Dysbiosis of gut homeostasis may further act as a trigger for the initiation and progression of NAFLD via the gut-liver axis. This study sheds light on the underlying mechanisms through which dAGEs contribute to the development of NAFLD and helps to understand the detrimental effects of food ultraprocessing products in modern diets. Future studies are needed to explore the in-depth mechanisms related to the gut-liver axis to consolidate our conclusions.

Direct activation of Toll-like receptor 2 signaling stimulated by contact with the interfacial structures of chitin nanofibers

The innate immune system, which eliminates pathogens and abnormal cells, is involved in the pathogenesis of various diseases and infections, where Toll-like receptors (TLRs) play a critical regulatory role. In this study, we investigated the potential of chitin nanofiber (CtNF) to induce an immune response, which is expected to act as an agonist of TLR2. Crab-derived CtNF, surface-deacetylated CtNF, and surface-carboxylated cellulose NF were employed as TLR2-mediated immune stimulator, signal regulator, and cell adhesion promoter, respectively, to fabricate cell culture scaffolds for HEK293 cells with TLR2 and human monocyte THP-1 cells with or without TLR2. Surface deacetylation of CtNF drastically diminished the immunological response of HEK293 cells, suggesting that the N-acetyl groups on the solid CtNF surface were pivotal for TLR2-mediated stimulation. A comparison of wild-type and TLR2-KO THP-1 cells on cell culture substrates with N-acetyl groups ranging from 0 to 1.39 mmol g-1 revealed that immune signaling for nuclear factor-κB and interferon regulatory factor pathways was strongly dependent on the surface N-acetyl group content. The immunostimulatory level at the interface of solid CtNF and immune cells could be regulated by simply mixing CtNF and surface-deacetylated CtNF, which is a significant advantage for its potential use as a novel immunostimulant.

Structural Color of Partially Deacetylated Chitin Nanowhisker Film Inspired by Jewel Beetle

Nanochitin was developed to effectively utilize crab shells, a food waste product, and there is ongoing research into its applications. Short nanowhiskers were produced by sonicating partially deacetylated nanochitin in water, resulting in a significant decrease in viscosity due to reduced entanglement of the nanowhiskers. These nanowhiskers self-assembled into a multilayered film through an evaporation technique. The macro- and nanoscale structures within the film manipulate light, producing vibrant and durable structural colors. The dried cast film exhibited green and purple stripes extending from the center to the edge formed by interference effects from the multilayer structure and thickness variations. Preserving structural colors requires maintaining a low ionic strength in the dispersion, as a higher ionic strength reduces electrostatic repulsion between nanofibers, increasing viscosity and potentially leading to the fading of color. This material's sensitivity to environmental changes, combined with chitin's biocompatibility, makes it well-suited for food sensors, wherein it can visually indicate freshness or spoilage. Furthermore, chitin's stable and non-toxic properties offer a sustainable alternative to traditional dyes in cosmetics, delivering vivid and long-lasting color.

Nanoformulations for the diagnosis and treatment of metabolic dysfunction-associated steatohepatitis

Metabolic dysfunction-associated steatohepatitis (MASH) is a progressive phase of metabolic dysfunction-associated steatotic liver disease (MASLD) that develops into irreversible liver cirrhosis and hepatocellular carcinoma, ultimately necessitating liver transplantation as the sole life-saving option. However, given the drawbacks of liver transplantation, including invasiveness, chronic immunosuppression, and a lack of donor livers, prompt diagnosis and effective treatment are indispensable. Due to the limitations of liver biopsy and conventional imaging modalities in diagnosing MASH, as well as the potential hazards associated with liver-protecting medicines, numerous nanoformulations have been created for MASH theranostics. Particularly, there has been significant study interest in artificial nanoparticles, natural biomaterials, and bionic nanoparticles that exhibit exceptional biocompatibility and bioavailability. In this review, we summarized extracellular vesicles (EVs)-based omics analysis and Fe3O4-based functional magnetic nanoparticles as magnetic resonance imaging (MRI) contrast agents for MASH diagnosis. Additionally, artificial nanoparticles such as organic and inorganic nanoparticles, as well as natural biomaterials such as cells and cell-derived EVs and bionic nanoparticles including cell membrane-coated nanoparticles, have also been reported for MASH treatment owing to their specific targeting and superior therapeutic effect. This review has the potential to stimulate advancements in nanoformulation fabrication techniques. By exploring their compatibility with cell biology, it could lead to the creation of innovative material systems for efficient theragnostic uses for MASH. STATEMENT OF SIGNIFICANCE: People with metabolic dysfunction-associated steatohepatitis (MASH) will progress to fibrosis, cirrhosis, or even liver cancer. It is imperative to establish effective theragnostic techniques to stop MASH from progressing into a lethal condition. In our review, we summarize the advancement of artificial, natural, and bionic nanoparticles applied in MASH theragnosis. Furthermore, the issues that need to be resolved for these cutting-edge techniques are summarized to realize a more significant clinical impact. We forecast the key fields that will advance further as nanotechnology and MASH research progress. Generally, our discovery has significant implications for the advancement of nanoformulation fabrication techniques, and their potential to be compatible with cell biology could lead to the creation of innovative materials systems for effective MASH theragnostic.

Recent Progress of Oral Functional Nanomaterials for Intestinal Microbiota Regulation

The gut microbiota is closely associated with human health, and alterations in gut microbiota can influence various physiological and pathological activities in the human body. Therefore, microbiota regulation has become an important strategy in current disease treatment, albeit facing numerous challenges. Nanomaterials, owing to their excellent protective properties, drug release capabilities, targeting abilities, and good biocompatibility, have been widely developed and utilized in pharmaceuticals and dietary fields. In recent years, significant progress has been made in research on utilizing nanomaterials to assist in regulating gut microbiota for disease intervention. This review explores the latest advancements in the application of nanomaterials for microbiota regulation and offers insights into the future development of nanomaterials in modulating gut microbiota.

Optimization of Chitin Nanofiber Preparation by Ball Milling as Filler for Composite Resin

Chitin nanofiber is a nanomaterial produced by pulverizing chitin, the main component of crab shells. Since it has excellent mechanical properties, it is expected to be used as a reinforcing material to strengthen materials. Chitin was mechanically ground in water using a ball mill to prepare nanofibers. The ball size, total ball weight, and milling time were varied, and the resulting water dispersion and the cast film were analyzed to optimize the conditions for efficient preparation. The length and width of the nanofibers were also measured by SEM and AFM observations. The size of the balls affected the level of grinding and the intensity of impact energy on the chitin. The most efficient crushing was achieved when the diameter was 1 mm. The total ball weight directly affects the milling frequency, and milling proceeds as the total weight increases. However, if too many balls occupy the container, the grinding efficiency decreases. Therefore, a total ball weight of 300 g was optimal. Regarding the milling time, the chitin becomes finer depending on the increase of that time. However, after a specific time, the shape did not change much. Therefore, a milling time of approximately 150 min was appropriate.

Production of chitin nanoparticles by bottom-up approach from alkaline chitin solution

Most of the series of nanochitins have been produced by the break-down process. In this study, chitin nanoparticles were prepared by a bottom-up process. Chitin was treated with sodium hydroxide to obtain an alkaline chitin aqueous solution. The alkaline chitin was regenerated by neutralization and then vigorously stirred to obtain chitin nanoparticles. The average particle size of the chitin nanoparticles was 7 nm. The individual particles were stably dispersed in water. Chitin nanoparticles had lower crystallinity than the raw material chitin and the surface of the chitin nanoparticles regenerated in water were presumed to be hydrophilic. The low crystallinity and the high hydrophilicity of the surface contributed to the high dispersibility of the chitin nanoparticles in water. Chitin nanoparticles had higher heat resistance than the raw material chitin, suggesting a large change in the higher-order structure associated with dissolution and subsequent regeneration of chitin. Since chitin nanoparticles interact with each other less than chitin nanofibers produced by mechanical treatment, the viscosity of nanoparticles was smaller than that of nanofibers. Therefore, it can be prepared at a high concentration. In addition, the chitin nanoparticles can be easily redispersed in water after being concentrated by centrifugation.

Optimum Preparation Conditions for Highly Individualized Chitin Nanofibers Using Ultrasonic Generator

α-Chitin derived from crab shells was treated with 30% sodium hydroxide to prepare partially deacetylated chitin with a deacetylation degree of 36%. Partially deacetylated chitin nanofibers were prepared by applying weak ultrasonic energy generated by a domestic ultrasonic cleaner. The deacetylated chitin was easily disintegrated into nanofibers with the aid of electrostatic repulsion and osmotic pressure effect of amino cations on the chitin surfaces. The nanofibers were characterized in terms of yield, morphology, crystallinity, viscosity, and dispersibility. After a series of characterizations, ultrasonication with 45 kHz frequency and 20 min treatment was found to be the optimum conditions for obtaining fine nanofibers with a high yield.

Sacran, a sulfated polysaccharide, suppresses the absorption of lipids and modulates the intestinal flora in non-alcoholic steatohepatitis model rats

AIMS

The objective of this study was to investigate the effects of administering sacran, a sulfated polysaccharide, on liver biology, gut microbiota, oxidative stress, and inflammation on stroke-prone spontaneously hypertensive (SHRSP5/Dmcr) rats that develop fibrotic steatohepatitis with histological similarities to that of non-alcoholic steatohepatitis (NASH).

MAIN METHODS

Four groups of 8-week-old SHRSP5/Dmcr rats were fed a high fat-cholesterol (HFC) diet for 4 and 8 weeks and administered either sacran (80 mg/kg/day) or a non-treatment, respectively. Liver function was evaluated by biochemical and histopathological analyses. Hepatic inflammatory markers were measured using mRNA expression. Fecal microbial profiles were determined via 16S rRNA sequencing. A triglyceride (TG) absorption test was administered to the 8-week-old Sprague-Dawley (SD) rats.

KEY FINDING

Sacran administration was observed to decrease the extent of oxidative stress and hepatic biochemical parameters in serum and hepatic injury with the levels of transforming growth factor-beta (TGF-β1) and tumor necrosis factor-alpha (TNF-α), being increased compared to those of the non-treatment group. At the genus level, sacran administration caused a significant decrease in the harmful Prevotella genus, and a significant increase in the useful Blautia genus was observed. Sacran administration also decreased the serum TG increase that was induced by administering corn oil to the SD rats.

SIGNIFICANCE

We conclude that sacran administration has the potential to reduce the absorption of lipids into blood and to improve several gut microbiotas, in the gastrointestinal tract, thereby inhibiting the subsequent development of oxidative stress and hepatic markers in the systematic circulation on NASH.

Chitin and Chitosan Derivatives as Biomaterial Resources for Biological and Biomedical Applications

Chitin is a long-chain polymer of N-acetyl-glucosamine, which is regularly found in the exoskeleton of arthropods including insects, shellfish and the cell wall of fungi. It has been known that chitin can be used for biological and biomedical applications, especially as a biomaterial for tissue repairing, encapsulating drug for drug delivery. However, chitin has been postulated as an inducer of proinflammatory cytokines and certain diseases including asthma. Likewise, chitosan, a long-chain polymer of N-acetyl-glucosamine and d-glucosamine derived from chitin deacetylation, and chitosan oligosaccharide, a short chain polymer, have been known for their potential therapeutic effects, including anti-inflammatory, antioxidant, antidiarrheal, and anti-Alzheimer effects. This review summarizes potential utilization and limitation of chitin, chitosan and chitosan oligosaccharide in a variety of diseases. Furthermore, future direction of research and development of chitin, chitosan, and chitosan oligosaccharide for biomedical applications is discussed.

Recent Advances in Marine-Based Nutraceuticals and Their Health Benefits

The oceans have been the Earth's most valuable source of food. They have now also become a valuable and versatile source of bioactive compounds. The significance of marine organisms as a natural source of new substances that may contribute to the food sector and the overall health of humans are expanding. This review is an update on the recent studies of functional seafood compounds (chitin and chitosan, pigments from algae, fish lipids and omega-3 fatty acids, essential amino acids and bioactive proteins/peptides, polysaccharides, phenolic compounds, and minerals) focusing on their potential use as nutraceuticals and health benefits.