Structural characterization and tartary buckwheat polysaccharides alleviate insulin resistance by suppressing SOCS3-induced IRS1 protein degradation

Preliminary characterization of Ramaria botrytoides polysaccharide RB-P1-1 and analysis of its hypoglycemic effects by altering the gut microbiota and metabolites in mice with type 2 diabetes mellitus

Gut microbiota has a symbiotic relationship with the host and is closely linked to the development of type 2 diabetes mellitus (T2DM). Polysaccharides are natural bioactive compounds with beneficial effects on T2DM; however, the mechanisms underlying their effects remain unclear. This study investigated the hypoglycemic effects of a purified polysaccharide, RB-P1-1, from Ramaria botrytoides and assessed its association with gut microbiota and metabolite changes using 16S rDNA sequencing and liquid chromatography-mass spectrometry, respectively. Hypoglycemic effects were evaluated after microbial community restoration via fecal microbiota transplantation. RB-P1-1 significantly improved hyperglycemia profiles and reshaped gut microbiota, increasing the abundance of Alistipes, Bacteroides, Ruminococcus, Odoribacter, Akkermansia, and Turicibacter. RB-P1-1 modulated microbiota metabolites associated with hypoglycemic effects, including pyridoxamine, L-histidine, quercetin, 3-phosphonopropionic acid, oleoylethanolamide, 3-ketocholanic acid, 4-phenylbutyric acid, LysoPC(P-16:0/0:0), LysoPC(18:2), and short-chain fatty acids, and altered various metabolic pathways involved in T2DM development. Gut microbiota that showed altered abundance were correlated with metabolites that showed altered concentration. Gut microbiota isolated from the RB-P1-1-treated group alleviated the symptoms associated with T2DM. These results suggest RB-P1-1 is an effective active ingredient in the treatment of T2DM by modulating gut microbiota and metabolites.

The regulatory mechanism of natural polysaccharides in type 2 diabetes mellitus treatment

Diabetes is a complex, multifactorial disease that is caused by a pathological combination of insulin resistance and pancreatic islet dysfunction. Polysaccharides are extensively dispersed in nature and have a very complicated structure with various biological properties. Natural polysaccharides have potentially extraordinary beneficial health effects on managing metabolic diseases such as diabetes, obesity and cardiovascular disease. Thus, a systematic review of the latest research into and possible regulatory mechanisms of natural polysaccharides for type 2 diabetes mellitus treatment is of great significance for a better understanding of their pharmaceutical value. We discuss the regulatory mechanisms of natural polysaccharides for the treatment of diabetes, and especially their role in reshaping dysfunctional gut microbiota. Natural polysaccharides could be developed as new and safe antidiabetic drugs, and detailed mechanistic studies could further clarify the molecular targets of polysaccharides in the treatment of diabetes.

The effect of Helicobacter pylori-derived extracellular vesicles on glucose metabolism and induction of insulin resistance in HepG2 cells

Helicobacter pylori infection has been associated with the development of insulin resistance (IR). This study aimed to examine the effect of H. pylori-derived extracellular vesicles (EVs) on IR induction. EVs were derived from two H. pylori strains, and characterised by transmission electron microscopy and dynamic light scattering. Different concentrations of insulin were added to HepG2 cells to induce IR model. HepG2 cells were exposed to various concentrations of H. pylori-derived EVs to assess IR development. The gene expression of IRS1, AKT2, GLUT2, IL-6, SOCS3, c-Jun and miR-140 was examined using RT-qPCR. Glucose uptake analysis revealed insulin at 5 × 10 -7 mol/l and EVs at 50 µg/ml induced IR model in HepG2 cells. H. pylori-derived EVs downregulated the expression level of IRS1, AKT2, and GLUT2, and upregulated IL-6, SOCS3, c-Jun, and miR-140 expression in HepG2 cells. In conclusion, our findings propose a novel mechanism by which H. pylori-derived EVs could potentially induce IR.

Polysaccharides extracted from common buckwheat (Fagopyrum esculentum) attenuate cognitive impairment via suppressing RAGE/p38/NF-κB signaling and dysbiosis in AlCl3-treated rats

Patients may find it challenging to accept several FDA-approved drugs for Alzheimer's disease (AD) treatment due to their unaffordable prices and side effects. Despite the known antioxidant, anti-inflammatory, and microbiota-regulating effects of common buckwheat (Fagopyrum esculentum) polysaccharides (FEP), their specific role in preventing AD has not been determined. Here, this study investigated the preventive effects of FEP on AD development in AlCl3-treated rats. The physical properties of FEP were evaluated using X-ray diffraction, FTIR, TGA, DSC, monosaccharide composition, molecular weight, and scanning electron microscopy. The results demonstrated that FEP administration improved memory and learning ability in AlCl3-treated rats. Additionally, AD pathological biomarkers (APP, BACE1, Aβ1-42, and p-TauSer404), inflammatory-associated proteins (IL-1β, IL-6, TNF-α, and Iba1), and MDA and the RAGE/p38/NF-κB pathway were elevated in AlCl3-treated rats. Moreover, these effects were reversed by the upregulation of LRP1, anti-inflammatory cytokines (IL-4 and IL-10), antioxidant enzymes (SOD and catalase), and autophagy proteins (Atg5, Beclin-1, and LC3B). Furthermore, FEP treatment increased the levels of short-chain fatty acids (SCFAs) and the abundance of SCFAs-producing microbes ([Eubacterium]_xylanophilum_group, Lachnospiraceae_NK4A136_group, Lactobacillus). Overall, FEP mitigated oxidative stress, RAGE/p38/NF-κB-mediated neuroinflammation, and AD-associated proteins by upregulating autophagy and SCFA levels, which led to the amelioration of cognitive impairment through microbiota-gut-brain communication in AlCl3-treated rats.

Phenolic Constituents from Black Quinoa Alleviate Insulin Resistance in HepG2 Cells via Regulating IRS1/PI3K/Akt/GLUTs Signaling Pathways

Quinoa is a nutrient-rich pseudocereal with a lower glycemic index and glycemic load. However, its therapeutic potency and underlying mechanism against insulin resistance (IR) have not been fully elucidated. In this work, network pharmacology was applied to screen IR targets and their related pathways. The efficacy and mechanism of black quinoa polyphenols (BQP) on IR improvement were evaluated and uncovered based on the IR model in vitro combined with molecular docking. Ten phenolic constituents of BQP were detected, and the network pharmacology results show that PI3K/Akt pathways are the main pathways in BQP against IR. The in vitro assay proved that BQP increases the glucose consumption and glycogen synthesis via upregulating insulin receptor substrate 1 (IRS1)/PI3K/Akt/glucose transporters (GLUTs) signaling pathways to alleviate IR. Rutin, resveratrol, and catechin show lower binding energy docking with IRS1, PI3K, Akt, and GLUT4 proteins, indicating better interactions. It might be an effective constituent against IR. Hence, BQP could become a potential functional food source for blood glucose management among insulin-resistant people.

Research progress on the hypoglycemic activity and mechanisms of natural polysaccharides

The incidence of diabetes, as a metabolic disease characterized by high blood sugar levels, is increasing every year. The predominantly western medicine treatment is associated with certain side effects, which has prompted people to turn their attention to natural active substances. Natural polysaccharide is a safe and low-toxic natural substance with various biological activities. Hypoglycemic activity is one of the important biological activities of natural polysaccharides, which has great potential for development. A systematic review of the latest research progress and possible molecular mechanisms of hypoglycemic activity of natural polysaccharides is of great significance for better understanding them. In this review, we systematically reviewed the relationship between the hypoglycemic activity of polysaccharides and their structure in terms of molecular weight, monosaccharide composition, and glycosidic bonds, and summarized underlying molecular mechanisms the hypoglycemic activity of natural polysaccharides. In addition, the potential mechanisms of natural polysaccharides improving the complications of diabetes were analyzed and discussed. This paper provides some valuable insights and important guidance for further research on the hypoglycemic mechanisms of natural polysaccharides.

Fagopyrum tataricum ethanol extract ameliorates symptoms of hyperglycemia by regulating gut microbiota in type 2 diabetes mellitus mice

Type 2 diabetes mellitus (T2DM) is typically accompanied by sudden weight loss, dyslipidemia-related indicators, decreased insulin sensitivity, and altered gut microbial communities. Fagopyrum tataricum possesses many biological activities, such as antioxidant, hypolipidemic, and hypotensive activities. However, only a few studies have attempted to elucidate the regulatory effects of F. tataricum ethanol extract (FTE) on intestinal microbial communities and its potential relationships with T2DM. In this study, we established a T2DM mouse model and investigated the regulatory effects of FTE on hyperglycemia symptoms and intestinal microbial communities. FTE intervention significantly improved the levels of fasting blood glucose, the area under the curve of oral glucose tolerance test (OGTT), and glycosylated serum protein, as well as pancreas islet function correlation index. In addition, FTE effectively improved hepatic and cecum injuries and insulin secretion due to T2DM. It was also revealed that the potential hypoglycemic mechanism of FTE was involved in the regulation of protein kinase B (AKT-1) and glucose transporter 2 (GLUT-2). Furthermore, compared with the Model group, the FTE-H intervention exhibited a significantly decreased ratio of Firmicutes to Bacteroidetes at the phylum level, reduced relative abundance of pernicious bacteria at the genus level, such as Desulfovibrio, Oscillibacter, Blautia, Parabacteroides, and Erysipelatoclostridium, and ameliorated inflammatory response and insulin resistance. Moreover, the correlation between gut microbiota and hypoglycemic indicators was predicted. The results showed that Lachnoclostridium, Lactobacillus, Oscillibacter, Bilophila, and Roseburia have the potential to be used as bacterial markers for T2DM. In conclusion, our research showed that FTE alleviates hyperglycemia symptoms by regulating the expression of AKT-1 and GLUT-2, as well as intestinal microbial communities in T2DM mice.

Tartary buckwheat root polysaccharides ameliorate non-alcoholic fatty liver disease via the IL6-SOCS3-SREBP1c pathway

Our previous study demonstrated that Tartary buckwheat root polysaccharides (TBRP) could reduce insulin resistance in diabetes mellitus by inhibiting SOCS3-stimulated IRS1 protein degradation. However, whether TBRP has the efficiency to treat non-alcoholic fatty liver disease (NAFLD) is still undetermined. This investigation aimed to examine the effects of TBRP on a high-fat diet (HFD)-triggered NAFLD, and elucidate the underlying molecular mechanisms. Briefly, TBRP toxicity in hepatoma (BEL7404) and pancreatic cancer (BxPC3) cells and zebrafish embryos developmental models, were evaluated in-vitro and in-vivo, respectively. TBRP inhibited cellular lipid accumulation by suppressing fat synthesis, furthermore, it improved body weight gain, liver weight, liver-to-body weight ratio, serum lipids triglyceride, total cholesterol, ALT, LDL-C, HDL-C, and AST levels in the NAFLD mice model. Additionally, TBRP treatment also lowered the nitric oxide content. The qPCR assay revealed that mRNA expression of TNF, IL1β, and IL6 was also markedly reduced in TBRP-treated NAFLD mice. The expression of SOCS3, SREBP1c, and STAT3 was elucidated by western blot analysis, which indicated that TBRP markedly decreased the gene expression for de novo fat synthesis by the SOCS3-SREBP1c pathway. These findings reveal that TBRP ameliorates NAFLD via the IL6-SOCS3-SREBP1c signaling pathway and therefore, may represent a promising approach for NAFLD treatment.

Extraction, Isolation, Screening, and Preliminary Characterization of Polysaccharides with Anti-Oxidant Activities from Oudemansiella raphanipies

Response surface methodology (RSM) was used to find the optimal extraction process of Oudemansiella raphanipies polysaccharides (ORPs). The results showed that the optimal extraction parameters were an alkali concentration of 0.02 mol/L, a ratio of material to liquid of 1:112.7 g/mL, an extraction temperature of 66.0 °C, and an extraction time of 4.0 h. Under the optimal conditions, the yield of ORPs was raised to 16.2 ± 0.1%. The antioxidant activities of ORPs-I~V were determined and compared, and ORPs-V was further purified by chromatography, with an average molecular weight (Mw) of 18.86 kDa. The structure of ORPs-V was determined by Fourier transform-infrared spectroscopy (FT-IR), monosaccharide analysis, and nuclear magnetic resonance (NMR) spectroscopy. The ORPs-V comprised fucose, rhamnose, arabinose, glucose, galactose, mannose, xylose, fructose, galacturonic acid, and glucuronic acid at a ratio of 1.73:1.20:1.13:2.87:8.71:2.89:1.42:0.81. Compared to other ORPs, ORPs-V showed the strongest antioxidant activities (ABTS radical cation, hydroxyl radical and DPPH scavenging activities, and reducing power), and were able to significantly increase the activities of superoxide dismutase, catalase, lactate dehydrogenase, and glutathione peroxidase. However, they reduced the malondialdehyde content in mice fed a high-fat diet. These results indicate that ORPs-V may be good anti-oxidant agents to be applied in functional foods.

Alternative to Sugar, Honey Does Not Provoke Insulin Resistance in Rats Based on Lipid Profiles, Inflammation, and IRS/PI3K/AKT Signaling Pathways Modulation

Insulin resistance (IR) is the central link to metabolic syndrome (MS), and IR prevention has become the key to overcoming this worldwide public health problem. A diet rich in simple sugars is an important pathogenic factor in IR development. To investigate the effect of honey on IR compared to the sugar-water diet, we analyzed phenolics and oligosaccharides in jujube honey and rape honey based on LC-MS and silane derivatization/GC-MS. The effects of different diets on glucose and lipid profile, histopathology and IR-related mechanism pathways were analyzed and compared by equal sugar levels intervention of fructose, fructose + glucose and two kinds of unifloral honey (high-/low-dose) in rats. The results suggested that sugar-equivalent honey, which differs from sugar solution, especially 17.1 g/kg BW jujube honey rich in phenolics (1.971 mg/100 g of isoquercitrin) and oligosaccharides (2.18 g/100 g of turanose), suppressed IR via maintaining glucose (OGTT and ITT) and lipid (TC, TG, LDL-C, HDL-C, and NEFA) homeostasis, improving histological structural abnormalities of the liver, adipose and skeletal muscle, reducing oxidative stress (GSH-Px and MDA) and inflammation (IL-6 and TNF-α), modulating the NF-κB (NF-κB gene expression was down-regulated to 0.94) and IRS/PI3K/AKT signaling pathways (e.g., AKT and GLUT2 expression in liver increased by 4.56 and 13.37 times, respectively) as well as reshaping the gut microbiota. These revealed a potential nutritional contribution of substituting honey for simple sugar in the diet, providing a theoretical basis for controlling IR development via dietary modification and supplementation.