Importance of Dendrobium officinale in improving the adverse effects of high-fat diet on mice associated with intestinal contents microbiota

Abstract

A growing body of evidence suggests that the disturbance of intestinal microbiota induced by high-fat diet is the main factor causing many diseases. Dendrobium officinale (DO), a medicinal and edible homologous Chinese herbal medicine, plays essential role in regulating intestinal microbiota. However, the extent of DO on the intestinal contents microbiota in mice fed with a high-fat diet still remains unclear. Therefore, this study explored the role of intestinal contents microbiota in the regulation of adverse effects caused by high-fat diet by DO from the perspective of intestinal microecology. Twenty-four mice were randomly distributed into the normal saline-treated basal diet (bcn), normal saline-treated high-fat diet (bmn), 2.37 g kg^-1 days^-1 DO traditional decoction-treated high-fat diet (bdn) and 1.19 g kg^-1 days^-1 lipid-lowering decoction-treated high-fat diet (bjn) groups for 40 days. Subsequently, we assessed the changes in body weight, serum total cholesterol (TC), total triacylglycerol (TG), low density lipoprotein-cholesterol (LDL-C), high density lipoprotein-cholesterol (HDL-C) levels, and the characteristics of intestinal contents microbiota. Results demonstrated that DO exerted the modulating effect on the changes in body weight, TG, TC, LDL-C, and HDL-C levels. Besides, DO decreased the richness and diversity of intestinal contents microbiota, and altered the structure as a whole. Dominant bacteria, Ruminococcus and Oscillospira, varied significantly and statistically. Moreover, DO influenced the carbohydrate, amino acid, and energy metabolic functions. Furthermore, Ruminococcus and Oscillospira presented varying degrees of inhibition/promotion of TG, TC, LDL-C, and HDL-C. Consequently, we hypothesized that Ruminococcus and Oscillospira, as dominant bacteria, played key roles in the treatment of diseases associated with a high-fat diet DO.

Keywords: Dendrobium officinale; diversity; dominant bacteria; high-fat diet; intestinal contents microbiota.

Figure 1

Experimental flow chart.

Figure 2

Effects of DO on the changes in body weight of mice fed high-fat diet. Data were mean ± SD, n = 6, ^*p < 0.05. ΔM₂₁ = body weight of mice on the 7th day-body weight of mice on the 0th day; ΔM₃₁ = body weight of mice on the 14th day-body weight of mice on the 0th day; ΔM₄₁ = body weight of mice on the 21th day-body weight of mice on the 0th day; ΔM₅₁ = body weight of mice on the 28th day-body weight of mice on the 0th day; ΔM₆₁ = body weight of mice on the 35th day-body weight of mice on the 0th day. bcn: normal saline-treated basal diet group; bmn: normal saline-treated high-fat diet group; bdn: DO traditional decoction-treated high-fat diet group; bjn: lipid-lowering decoction-treated high-fat diet group. (A) Weight changes of female mice. (B) Weight changes of male mice.

Figure 3

Sequencing data quality assessment of intestinal contents microbiota. (A) Sequence length distribution diagram. (B) The effective sequence quantity of each sample. (C) Dilution curve of Chaos 1. (D) Dilution curve of Shannon. (E) Species accumulation curve. bcn: normal saline-treated basal diet group; bmn: normal saline-treated high-fat diet group; bdn: DO traditional decoction-treated high-fat diet group; bjn: lipid-lowering decoction-treated high-fat diet group.

Figure 4

OTU number and diversity of intestinal contents microbiota. (A) Venn diagram. (B) Rank abundance distribution curve. The longer the folded line, the greater the number of OTUs in the sample. The gentler the curve, the better the uniformity of the community; the steeper the curve, the lower the homogeneity of the community. (D) OTU number of each sample at different classification levels. (C) OTU in each sample at each classification level. (D) Chaos 1 index; ACE index; Shannon index; Simpson index. (E) PCA analysis. (F) NMDS analysis. Data were mean ± SD, n = 3, p > 0.05. bcn: normal saline-treated basal diet group; bmn: normal saline-treated high-fat diet group; bdn: DO traditional decoction-treated high-fat diet group; bjn: lipid-lowering decoction-treated high-fat diet group.

Figure 5

Dominant bacteria and differential bacteria of intestinal contents microbiota. Data were mean ± SD, n = 3, ^*p < 0.05. (A) Intestinal contents microbiota composition in the phylum level. (B) Intestinal contents microbiota composition in the genus level. (C) Genus levels of dominant bacteria. (D) LDA scores plot. The horizontal coordinates were the logarithmic scores of LDA for each classification unit. The vertical coordinates were the classification units with significant differences between groups. The longer the length, the more significant the difference was. (E) Cladogram diagram. The circles radiating from the inner to the outer layers of the diagram represented the taxonomic hierarchy of species from phylum to species. Nodes indicated a taxonomic unit at the taxonomic level. Letters identified the names of taxonomic units with significant differences between groups. bcn: normal saline-treated basal diet group; bmn: normal saline-treated high-fat diet group; bdn: DO traditional decoction-treated high-fat diet group; bjn: lipid-lowering decoction-treated high-fat diet group.

Figure 6

Functional analysis of intestinal contents microbiota. (A) Predicted abundance of KEGG function. (B) Histogram of metabolic function. (C) Interaction network of “Ruminococcus-metabolic function”. (D) Interaction network of “Oscillospira-metabolic function.” Solid line represented positive correlation, dotted line represented negative correlation. The thickness of the line indicated the strength of the correlation. bcn: normal saline-treated basal diet group; bmn: normal saline-treated high-fat diet group; bdn: DO traditional decoction-treated high-fat diet group; bjn: lipid-lowering decoction-treated high-fat diet group.

Figure 7

Correlation analysis. (A) “Ruminococcus-dominant bacteria” interaction network at the genus level. (B) “Ochrobactrum-dominant bacteria” interaction network at the genus level. Solid line represented positive correlation, dotted line represented negative correlation. The thickness of the line indicated the strength of the correlation. (C) RDA analysis. Different colored arrows represented the dominant bacteria and environmental factors. Dots of different colors represented samples from different groups. The Angle between the arrow lines represented correlation, an acute angle represented positive correlation, and an obtuse angle represented negative correlation. bcn: normal saline-treated basal diet group; bmn: normal saline-treated high-fat diet group; bdn: DO traditional decoction-treated high-fat diet group; bjn: lipid-lowering decoction-treated high-fat diet group.