A review on the hypoglycemic effect, mechanism and application development of natural dietary polysaccharides

A review of in vitro antioxidant and antidiabetic polysaccharides: Extraction methods, physicochemical and structure-activity relationships

Nowadays, various plant polysaccharides have been successfully extracted which exhibited strong biological activities and might be useful for diabetes management. However, the effect of extraction methods, physicochemical and the structural-activity relationships of polysaccharides to exhibit antioxidants and antidiabetics were inadequate to explain their mechanism in action. The uses of advance extraction methods might be preferred to obtain higher antioxidants and antidiabetic activities of polysaccharides compared to conventional methods, but the determination of optimal extraction conditions might be crucial to preserve their structure and biological functions. Other than that, the physicochemical and structural properties of polysaccharides were closely related to their biological activities such as antioxidant and antidiabetic activities. Therefore, this review addressed the research gap of the influence of extraction methods, physicochemical and structural relationships of polysaccharides to biological activities, pointing out the challenges and limitations as well as future prospects to the current findings.

Effects of chitosan guanidine on blood glucose regulation and gut microbiota in T2DM

Diabetes mellitus (DM) is a chronic metabolic disease characterized by hyperglycemia. Type 2 diabetes mellitus (T2DM) represents approximately 90 % of all DM cases and is primarily caused by an imbalance in blood glucose homeostasis due to inadequate insulin secretion or insulin resistance. This study explores the potential therapeutic effects of chitosan guanidine (CSG) on a T2DM mouse model. The findings reveal that CSG significantly enhances oral glucose tolerance (OGTT) and insulin sensitivity (ITT), reduces fasting blood glucose (FBG) levels, and suppresses the expression of proinflammatory cytokines in T2DM mice. These changes improve insulin resistance and diminish inflammation. Additionally, CSG markedly ameliorates lipid metabolism disorders, lowers total cholesterol (TC) and triglyceride (TG) levels, and inhibits hepatic fat accumulation. 16S rRNA and Spearman correlation analyses indicate that CSG promotes the relative abundance of probiotic genera such as Bacteroidota, Patescibacteria, Actinobacteria, and Cyanobacteria. These bacteria are positively correlated with short-chain fatty acids (SCFAs) and high-density lipoprotein cholesterol (HDLC) levels. Conversely, CSG reduces the relative abundance of pathogenic bacteria, including Proteobacteria and Ralstonia, leading to an improved intestinal microbial community composition in T2DM mice and alleviating T2DM symptoms. These results suggest that CSG holds significant potential as a non-insulin therapeutic agent for diabetes management.

Effect of steam explosion pretreatment on the fermentation characteristics of polysaccharides from tea residue

Green tea residues are the by-product of tea processing and they contain a large number of bioactive ingredients. Steam explosion has been recognized as one of the most innovative pretreatments for modifying the physicochemical characteristic of polysaccharides from lignocellulosic materials. However, the comparison of biological activity of steam exploded (SE-GTR) and unexploded (UN-GTR) green tea residue polysaccharides was still unclear, which prompted the determination of the efficacy of steam explosion in tea residue resource utilization. In this study, the effects of two extracted polysaccharides UN-GTR and SE-GTR on human gut microbiota in vitro fermentation were conducted. The results showed that after steam explosion pretreatment, SE-GTR displayed more loose and porous structures, resulting in higher polysaccharide content (2483.44±0.5 μg/mg) compared to UN-GTR (1903.56±2.6 μg/mg). In addition, after 24 h fermentation, gut microbiota produced more beneficial metabolites by SE-GTR. The largest SCFAs produced among samples was acetic acid, propionic acid and butyric acid. Furthermore, SE-GTR could regulate the composition and diversity of microbial community, increasing the abundance of beneficial bacteria, such as Bifidobacterium. These results revealed that steam explosion pretreatment could be a promising and efficient approach to enhance the antioxidant activity and bioavailability of polysaccharides isolated from tea residues.

Natural hypoglycaemic bioactives: Newer avenues and newer possibilities

The incidences of endocrine and metabolic disorders like diabetes have increased worldwide. Several proposed molecular pathways mechanisms for the management of diabetes have been identified, but glycaemic control is still a challenging task in the drug discovery process. Most of the drug discovery processes lead to numerous scaffolds that are prominent in natural products. The review deals with the natural bioactives as an α-amylase inhibitors, α-glucosidase inhibitors, protein tyrosine phosphatase-1B inhibitors, dipeptidyl peptidase-IV inhibitors, G-protein coupled receptors-40 agonists, PPAR-γ agonists and the activators of 5'-adenosine monophosphate-activated protein kinase and glucokinase. So, in this review, we focused on the hypoglycaemic bioactives, which will assist scientific developers, traditional medicinal practitioners, and readers to discover some potent antidiabetic molecules. Strategies like chemometric approaches, scaffold hopping, and total synthesis of natural products by group modification or ring opening/closing mechanism could be useful for the development of novel hit/lead antidiabetic molecules. The study concludes that each phyto molecule inherits a potential to get explored by repurposing techniques for various antidiabetic targets and offer an alternative antidiabetic therapeutic medicinal potential.

Structural characterization and hypoglycemic effect of polysaccharides of Polygonatum sibiricum

Polygonatum sibiricum polysaccharide (PSP) was extracted and purified from raw material obtained from P. sibiricum. The structural features of PSP were investigated by Congo red, circular dichroism spectrum, high-performance gel permeation chromatography, scanning electron microscope, atomic force microscope, ultraviolet spectroscopy, and Fourier transform infrared spectroscopy analysis. In vitro simulations were conducted to investigate the kinetics of PSP enzyme inhibition. Moreover, a type II diabetes mouse model (T2DM) with streptozotocin-induced insulin resistance was established, and the indexes of lipid quadruple, insulin resistance index, oral glucose tolerance (OGTT), organ index, and pancreatic morphology of model mice were measured. The results showed that PSP mainly consists of monosaccharides, such as mannose, glucose, galactose, xylose, and arabinose. It also has a β-glycosidic bond of a pyranose ring and an irregular reticulated aggregated structure with a triple helix. In vitro enzyme inhibition assays revealed that PSP acts as a reversible competitive inhibitor of α-glucosidase and α-amylase. Furthermore, PSP was found to reduce insulin resistance index, increase OGTT and serum insulin levels, decrease free fatty acid content to improve lipid metabolism, and lower glycated serum protein content to enhance glucose metabolism in T2DM mice, thereby leading to a reduction in blood glucose concentration. Additionally, PSP exhibited reparative effects on the damaged liver tissue cells and pancreatic tissue in T2DM mice. The experiment results provide a preliminary basis for the therapeutic mechanism of PSP about type II diabetes and a theoretical reference for application in food and pharmaceutical development.

Prospects of yam (Dioscorea) polysaccharides: Structural features, bioactivities and applications

Yam (Dioscorea) is a tuber crop cultivated for food security, revenue, and medicinal purposes. It has been used to treat diabetes, asthma, diarrhea, and other diseases. The main active ingredients in yam, polysaccharides, are regarded to be the important reason for its widespread applications. Now, a comprehensive review of research developments of yam polysaccharides (YPs) was presented to explore their prospects. We outlined the structural characteristics, biological activities, structure-activity relationships, and potential applications. Around 13 neutral components and 17 acidic components were separated. They exhibited various bioactivities, including immunomodulatory, hypoglycemic, hypolipidemic, antioxidant, gastrointestinal protective, anti-fatigue, and senile disease treatment activities, as well as prebiotic effect. Structure-activity relationships illustrated that unique structural properties, chemical modifications, and carried biopolymers could influence the bioactivities of YPs. The potential applications in medicine, food, and other fields have also been summarized.

Carbohydrate polymer degradation derivatives as possible natural mannanase inhibitors

The role of mannanases is diverse and they are used in many industrial applications, in animal feed, in the food industry and in healthcare. They are also applied in biomass processing, because they play an important role in the breakdown of hemicellulose. Among the mannanase inhibitors, heavy metal ions and general enzyme inhibitors are mainly mentioned. Unfortunately, almost no data are available on carbohydrate-based natural inhibitors of mannanases. According to the literature, carbohydrates do not play an important role in the inhibition of mannanases, so neither do oligosaccharides. This is in contrast to the action and inhibition of other O-glycosyl hydrolases. My hypothesis is that mannanases, like other polysaccharide-degrading enzymes, work in the same way and can be inhibited by oligosaccharides. Evidence from docking and modeling results supports and makes probable the hypothesis that oligosaccharides can inhibit the activity of mannanases, similar to the inhibition of other O-glycosyl hydrolases. Among natural carbohydrate oligomers, several potential mannanase inhibitors have been identified and characterized. In addition to expensive research, it is very important to use research based on cheaper modeling to explore the processes. The results obtained are novel and forward-looking, enabling in-depth and targeted research to be carried out.

Natural polysaccharides regulate intestinal microbiota for inhibiting colorectal cancer

The gastrointestinal tract is an important part of the human immune system. The gut microbiome, which constitutes a major component of the gastrointestinal tract, plays a crucial role in maintaining normal physiological functions and influences the development, diagnosis, and immunotherapy of colorectal cancer (CRC). Natural polysaccharides can be extracted from animals, plants, and traditional Chinese medicines. They serve as an essential energy source for the gut microbiome, promoting probiotic proliferation and regulating the intestinal microecological balance. Moreover, polysaccharides exhibit anti-tumor effects due to their immune regulatory functions and low toxicity. This review focuses on discussing these anti-tumor effects in CRC, along with improving gut microbiome dysbiosis and regulating the tumor immune microenvironment, providing evidence for effective therapeutic strategies against CRC.

Dendrobium officinale regulate lipid metabolism in diabetic mouse liver via PPAR-RXR signaling pathway: Evidence from an integrated multi-omics analysis

Dendrobium officinale (DEN) is recognized as a kind of functional food that can effectively ameliorate endocrine and metabolic disruptions. This study delved into the pharmacological mechanism of DEN on hepatic lipotoxicity associated with Type II diabetes mellitus (T2DM). In vivo study experiments on db/db mice indicated that DEN treatment notably enhanced liver function, decreased blood lipid levels, and improved insulin sensitivity. Non-targeted metabolomics analysis revealed that DEN significantly ameliorated metabolism pathways, including lipoic acid, linoleic acid, bile secretion, and the alanine/aspartate/glutamate metabolism, as well as taurine and hypotaurine metabolism. Transcriptomics analysis demonstrated DEN treatment could modulate the expression of genes such as Cpt1b, Scd1, G6pc2, Fos, Adrb2, Atp2a1, Ppp1r1b, and Cyp7a1. Furthermore, Proteomics analysis indicated that the beneficial effect of DEN on lipid metabolism was linked to pathways like AMPK and PPAR signaling. The integrative analysis of multi-omics revealed that the PPAR-RXR signaling was critical to the therapeutic effect of DEN on T2DM-induced fatty liver. Additionally, in vitro study on AML-12 cells confirmed that DEN counteract PA-induced lipid accumulation by activating the PPAR-RXR pathway. Overall, these findings suggested that DEN exhibited the potential to mitigate T2DM-induced hepatic lipo-toxicity and manage lipid imbalances in T2DM.