Defense against oxidative stress in Caenorhabditis elegans by dark tea

Abstract

Dark tea, rich in nutricines including tea polyphenols and free amino acids, is a kind of post-fermented tea. The potential application of nutricines against oxidative damage and senescence, which drives animal health maintenance and disease prevention, has attracted considerable interest. In this study, the effect of dark tea and its effects on longevity and defense against oxidative stress was investigated in the Caenorhabditis elegans (C. elegans) model. Under normal conditions, dark tea extended the lifespan without significant impairment of propagation. It also improved the motility, alleviated the fat accumulation and apoptosis. Additionally, orally administered dark tea could significantly decrease the level of reactive oxygen species (ROS) and resulted in a superior lifespan in H₂O₂-induced oxidative stressed C. elegans. In antioxidant assays in vitro, dark tea was found to be rich in strong hydroxyl, DPPH and ABTS+ free radical scavenging capacity. Interestingly, mRNA sequence analyses further revealed that dark tea may catalyze intracellular relevant oxidative substrates and synthesize antioxidants through synthetic and metabolic pathways. These results suggest that dark tea is worth further exploration as a potential dietary supplement for the maintenance of animal health and the prevention of related diseases.

Keywords: Caenorhabditis elegans; dark tea; longevity; mRNA sequencing analysis; oxidative stress.

Figure 1

Effects of various concentrations of dark tea (A, Brick Tea; B, Pu’er Tea; C, Liubao Tea) on the lifespan in C. elegans.

Figure 2

Effects of dark tea on the lifespan in C. elegans under oxidative damage conditions.

Figure 3

Effects of dark tea on the ROS levels in C. elegans. (A) ROS fluorescence plot in the normal state. (B) ROS fluorescence plot in the oxidative damage state. (C) Quantitative analysis plot of ROS fluorescence intensity in the normal state. (D) Quantitative analysis plot of ROS fluorescence intensity in the oxidative damage state. **** indicates p < 0.0001.

Figure 4

Effects of dark tea on the free radicals scavenging capacity. (A) -OH. (B) DPPH. (C) ABTS+.

Figure 5

Effects of dark tea on the reproductive capacity in C. elegans. (A) The number of offspring daily in each groups in the pawning period. (B) The total of number of offspring in each group in the pawning period.

Figure 6

Effects of dark tea on the motility in C. elegans. (A) Frequency of head bobbing in 1 min. (B) Degree of body bending in 20 s. * indicates p < 0.05, ** indicates p < 0.01, *** indicates p < 0.001.

Figure 7

Effects of dark tea on the fat content in C. elegans. (A) Plot of fat staining. (B) Plot of quantitative analysis of staining intensity. ** indicates p < 0.01, **** indicates p < 0.0001.

Figure 8

Effects of dark tea on the apoptosis in C. elegans. (A) Apoptosis fluorescence graph. (B) Quantitative analysis graph of apoptosis fluorescence intensity. **** indicates p < 0.0001.

Figure 9

Distribution of genes identified in dark tea. (A) Volcano plot of differentially expressed genes. The horizontal coordinate indicates the logarithmic value of the fold difference in expression of a gene in the two samples and the vertical coordinate indicates the negative logarithmic value of the statistical significance of the change in gene expression. Red dots indicate up-regulation and blue dots indicate down-regulation. (B) Up-regulated and down-regulated genes. (C) Venn diagram of the set of differential genes (fold change≥2).

Figure 10

GO annotation categorization statistical chart. (A) Brick Tea. (B) Pu’er Tea (C) Liubao Tea. The horizontal coordinate is the GO classification, the vertical coordinate is the number of genes, and different colors represent the different primary classifications to which they belong.

Figure 11

Bubble chart of genes enriched in KEGG pathways. (A) Brick Tea. (B) Pu’er Tea (C) Liubao Tea. The bubble size represents the number of genes in the enriched pathway terms, and the bubble color represents the p value.