Construction of a Fusion Peptide 5rolGLP-HV and Analysis of its Therapeutic Effect on Type 2 Diabetes Mellitus and Thrombosis in Mice

Phellinus igniarius Polysaccharides Ameliorate Hyperglycemia by Modulating the Composition of the Gut Microbiota and Their Metabolites in Diabetic Mice

Gut microbiota dysbiosis has been reported as a risk factor in the development of type 2 diabetes mellitus (T2DM). Polysaccharides from Phellinus igniarius (P. igniarius) possess various properties that help manage metabolic diseases; however, their underlying mechanism of action remains unclear. Therefore, in this study, we aimed to evaluate the effect of P. igniarius polysaccharides (SH-P) on improving hyperglycemia in mice with T2DM and clarified its association with the modulation of gut microbiota and their metabolites using 16S rDNA sequencing and liquid chromatography-mass spectrometry. Fecal microbiota transplantation (FMT) was used to verify the therapeutic effects of microbial remodeling. SH-P supplementation alleviated hyperglycemia symptoms in T2DM mice, ameliorated gut dysbiosis, and significantly increased the abundance of Lactobacillus in the gut. Pathway enrichment analysis indicated that SH-P treatment altered metabolic pathways associated with the occurrence and development of diabetes. Spearman's correlation analysis revealed that changes in the dominant bacterial genera were significantly correlated with metabolite levels closely associated with hyperglycemia. Additionally, FMT significantly improved insulin sensitivity and antioxidative capacity and reduced inflammation and tissue injuries, indicating improved glucose homeostasis. These results indicate that the ameliorative effects of SH-P on hyperglycemia are associated with the modulation of gut microbiota composition and its metabolites.

Cordyceps cicadae polysaccharides alleviate hyperglycemia by regulating gut microbiota and its mmetabolites in high-fat diet/streptozocin-induced diabetic mice

Introduction

The polysaccharides found in Cordyceps cicadae (C. cicadae) have received increasing academic attention owing to their wide variety of therapeutic activities.

Methods

This study evaluated the hypoglycemic, antioxidant, and anti-inflammatory effects of polysaccharides from C. cicadae (CH-P). In addition, 16s rDNA sequencing and untargeted metabolomics analysis by liquid chromatography-mass spectrometry (LC-MS) were used to estimate the changes and regulatory relationships between gut microbiota and its metabolites. The fecal microbiota transplantation (FMT) was used to verify the therapeutic effects of microbial remodeling.

Results

The results showed that CH-P treatment displayed hypoglycemic, antioxidant, and anti-inflammatory effects and alleviated tissue damage induced by diabetes. The CH-P treatment significantly reduced the Firmicutes/Bacteroidetes ratio and increased the abundance of Bacteroides, Odoribacter, Alloprevotella, Parabacteroides, Mucispirillum, and significantly decreased the abundance of Helicobacter and Lactobacillus compared to the diabetic group. The alterations in the metabolic pathways were mostly related to amino acid biosynthesis and metabolic pathways (particularly those involving tryptophan) according to the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Correlation analysis showed that Bacteroides, Odoribacter, Alloprevotella, Parabacteroides, and Mucispirillum were positively correlated with indole and its derivatives, such as 5-hydroxyindole-3-acetic acid. Indole intervention significantly improved hyperglycemic symptoms and insulin sensitivity, and increased the secretion of glucagon-like peptide-1 (GLP-1) in diabetic mice. FMT reduced blood glucose levels, improved glucose tolerance, and increased insulin sensitivity in diabetic mice. However, FMT did not significantly improve GLP-1 levels.

Discussion

This indicates that C. cicadae polysaccharides alleviate hyperglycemia by regulating the production of metabolites other than indole and its derivatives by gut microbiota. This study provides an important reference for the development of novel natural products.

Islet MC4R Regulates PC1/3 to Improve Insulin Secretion in T2DM Mice via the cAMP and β-arrestin-1 Pathways

Melanocortin-4 receptor (MC4R) plays an important role in energy balance regulation and insulin secretion. It has been demonstrated that in the pancreas, it is expressed in islet α and β cells, wherein it is significantly correlated with insulin and glucagon-like peptide-1 (GLP-1) secretion. However, the molecular mechanism by which it regulates islet function is still unclear. Therefore, in this study, our aim was to clarify the signaling and target genes involved in the regulation of insulin and GLP-1 secretion by islet MC4R. The results obtained showed that in islet cells, the expression of prohormone convertase 1/3 (PC1/3), which is correlated with islet GLP-1 and insulin secretion, increased significantly under the action of the MC4R agonist, NDP-α-MSH, but decreased under the action of the MC4R antagonist, AgRP. Additionally, we observed that to exert their regulatory functions in the islets, cAMP and β-arrestin-1 acted as important signaling mediators of MC4R, and compared with control islets, the cAMP, PKA, and β-arrestin-1 levels corresponding to NDP-α-MSH-treated islets were significantly elevated; however, in AgRP-treated islets, their levels decreased significantly. Islets treated with the PKA inhibitor, H89, and the ERK1/2 inhibitor, PD98059, also showed significant decreases in PC1/3 expression level, indicating that the cAMP and β-arrestin-1 pathways are significantly correlated with PC1/3 expression. These findings suggest that islet MC4R possibly affects PC1/3 expression via the cAMP and β-arrestin-1 pathways to regulate GLP-1 and insulin secretion. These results provide a new theoretical basis for targeting the molecular mechanism of type 2 diabetes mellitus.