Hypoglycemic effect of peony flowers polyphenols based on gut microbiota and metabolomics

Abstract

Introduction: Type 2 diabetes mellitus (T2DM), remains a significant global public health concern. Peony has a long history of consumption and medicinal in China, and is rich in polyphenols, flavonoids, polysaccharides, and other components. However, the hypoglycemic activity and underlying mechanism of action of peony flowers polyphenols (PP) remain nebulous. Therefore, we investigate the hypoglycemic effect and mechanism of action of PP on T2DM mice.

Methods: PP was extracted and isolated from peony flowers (Paeonia ostii "Fengdan"), the total polyphenol content (TPC) in PP was determined by the Folin-Ciocalteu method and the contents of 17 components in PP were determined by high-performance liquid chromatography. The high-fat diet (HFD) combined with streptozotocin (STZ) was used to establish T2DM mouse model, and the hypoglycemic effect and mechanism of PP based on gut microbiota and metabolomics were investigated.

Results: The TPC in PP was 81.13 ± 2.89%. The results showed that after 8 weeks of intragastric administration, PP significantly reduced the fasting blood glucose (FBG) (P < 0.05), serum insulin level (P < 0.05), and insulin resistance index (P < 0.05), improved impaired glucose tolerance, regulated serum liver and kidney function related indicators, significantly increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) levels (P < 0.05), significantly decreased malondialdehyde (MDA) level (P < 0.05) in the liver, and increased the contents of short-chain fatty acids (SCFAs) in the gut of T2DM mice. The results of 16S rRNA sequencing showed that PP could alter the gut microbiota of T2DM mice, increase the relative abundance of Firmicutes and Bacteroidota, while decrease the relative abundance of Proteobacteria. Non-targeted metabolomics results showed that the high-dose group of PP (PPH) can reverse the metabolic disorders of metabolite markers induced by T2DM in vivo.

Conclusions: Consequently, PP may play a hypoglycemic role by regulating intestinal flora and amino acid metabolism pathway. The research establishes a foundation for using PP as a functional food to prevent or alleviate type 2 diabetes mellitus.

Keywords: SCFAs; T2DM; gut microbiota; metabolomics; peony flowers polyphenols.

Figure 1

HPLC chromatogram of PP and mixed standards. 1—Gallic acid; 2—Methyl gallate; 3—Sinensin; 4—Paeoniflorin; 5—Ethyl gallate; 6—Vitexin glucoside; 7—1,2,3,6-O-Tetragalloyl Glucose; 8—Isovitexin; 9—Luteoloside; 10—Benzoic acid; 11−1,2,3,4,6-O-pentagalloyl glucose; 12—Astragalin; 13—Kaempferol-7-O-glucoside; 14—Apigetrin; 15—Resveratrol; 16—Apigenin; 17—Kaempferide.

Figure 2

Effects of PP on body weight, blood glucose, organ index, OGTT, and serum insulin in T2DM mice. (A) Changes in the body weight over the 8 weeks; (B) Changes in the FBG levers over the 8 weeks; (C) Liver index; (D) Kidney index; (E) OGTT; (F) AUC levels of the OGTT test; (G) Insulin; (H) HOMA-IR.^**P < 0.01 compared with the CON group; ^##P < 0.01 compared with the MOD group.

Figure 3

Effect of PP on serum biochemical indicators in T2DM mice. (A) Serum ALT levels; (B) Serum AST levels; (C) Serum HDL-C levels; (D) Serum LDL-C levels; (E) Serum TC levels; (F) Serum TG levels; (G) Serum ALB levels; (H) Serum CRE levels; (I) Serum TP levels; (J) Serum URER levels.**P < 0.01, *P < 0.05 compared with the CON group; ^##P < 0.01, ^#P < 0.05 compared with the MOD group.

Figure 4

Effect of PP on MDA, GSH-PX, CAT, and MDA activities in liver tissue of T2DM mice. (A) Liver SOD levels; (B) Liver CAT levels; (C) Liver GSH-PX levels; (D) Liver MDA levels. **P < 0.01 compared with the CON group; ^##P < 0.01 compared with the MOD group.

Figure 5

Effects of PP on the histopathological morphology of T2DM mice.

Figure 6

Analysis of serum metabolomics of PP in T2DM mice. (A, B) Scores plots of PCA between the CON, MOD, and PP groups; (C, D) OPLS-DA score plot and displacement test plot for the MOD and CON groups in positive ion mode; (E, F) OPLS-DA score plot and displacement test plot for the MOD and CON groups in negative ion mode; (G, H) OPLS-DA score plot and displacement test plot for the PPH and MOD groups in positive ion mode; (I, J) OPLS-DA score plot and displacement test plot for the PPH and MOD groups in negative ion mode.

Figure 7

(A) Differential metabolite heatmap; (B) KEGG plot of MOD vs. CON; (C) KEGG plot of PPH vs. MOD. (a) Phenylalanine, tyrosine and tryptophan biosynthesis; (b) Galactose metabolism; (c) Alanine, aspartate and glutamate metabolism; (d) Tyrosine metabolism; (e) Arginine biosynthesis; (f) β-Alanine metabolism.

Figure 8

Effects of PP on gut microbiota in T2DM mice. (A) OTU sparse curve; (B) Chao index of OTU level; (C) Shannon index of OTU level; (D) Venn diagram based on OTU; (E) PCoA analysis of mouse gut microbiota; (F) Hierarchical clustering analysis diagram at the door level.

Figure 9

Analysis of gut microbiota structure and species differences. (A) Percent of community abundance on phylum level; (B) Percent of community abundance on genus level; (C) Bacteroidota; (D) Firmicutes(the sum of Firmicutes_A, Firmicutes_B, and Firmicutes_D); (E) Proteobacteria; (F) Escherichia;(G) Klebsiella; (H) Bifidobacterium; (I) LDA scoring plot based on LEfSe analysis; (J) The differential metabolic pathways of PPH on T2DM were predicted using PICRUSt analysis based on the 16SrRNA sequencing data, CON, MOD, and PPH groups. **P < 0.01, *P < 0.05 compared with the CON group; ^##P < 0.01, ^#P < 0.05 compared with the MOD group.

Figure 10

Correlation analysis. (A) Correlation analysis between level gut microbiota and differential metabolites; (B) Correlation analysis of intestinal microflora at genus level and diabetes index components. **P < 0.01, *P < 0.05 compared with the CON group.