Abstract
Oxidative stress, one of the most common biological dysfunctions, is usually associated with pathological conditions and multiple diseases in humans and animals. Chinese olive fruit (Canarium album L.) extracts (OE) are natural plant extracts rich in polyphenols (such as hydroxytyrosol, HT) and with antioxidant, anti-hyperlipidemia, and anti-inflammatory potentials. This study was conducted to investigate the antioxidant capacity of OE supplementation and its related molecular mechanism in mice. Mice (25.46 ± 1.65 g) were treated with 100 mg/kg body weight (BW) OE or saline solution for 4 weeks, and then the antioxidant and anti-inflammatory capacities of mice were examined. The results showed that OE supplement significantly increased the serum antioxidative enzyme activities of total antioxidant activity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase and decreased the serum malondialdehyde (MDA) level, indicating that OE treatment enhanced the antioxidant capacity in mice. qPCR results showed that the transcriptional expression of antioxidant SOD1, CAT, Gpx1, and Gpx2 were significantly down-regulated in the small intestine (jejunum and ileum) after OE administration. Meanwhile, OE treatment significantly decreased the T-AOC and increased the MDA level in the small intestine. Furthermore, OE administration dramatically reduced the mRNA expression of pro-inflammatory cytokines (TNF-α and IL-1β), which confirmed its antioxidant and anti-inflammatory capacities with OE administration. Using amplicon sequencing technology, 16S rRNA sequencing results showed that OE supplement significantly increased the colonic Firmicutes/Bacteroidetes ratio, which also had a negative correlation with the serum MDA level and positively correlated with serum GSH-Px activity through Pearson correlation analysis. Besides that, Alloprevotella was negatively correlated with serum T-AOC. Colidextribacter was positively correlated with serum MDA and negatively correlated with serum T-AOC, SOD, and GSH-Px levels. In summary, this study showed that treatment with 100 mg/kg BW polyphenol-rich OE could alter colonic microbiota community, which was strongly associated with improved antioxidant capacity in mice.
Highlights
Oxidative stress is regarded as a result of the imbalance of oxidants and antioxidants, which can cause damage to important cellular macromolecules, such as DNA, lipid, and protein, and, in turn, lead to toxicity, chronic inflammation, and diseases, acting as a serious threat to animal and human health [1,2,3]
Oral administration with OE for 4 weeks had no significant effects on the body weight (P > 0.05) and average daily feed intake in mice compared with the mice in the Con group (P > 0.05; Figure 1)
Studies being conducted both in animal models and humans have revealed the significant role of oxidative stress in the pathogenesis of various diseases, including neurodegenerative and metabolic diseases and cancer [3, 33,34,35]
Summary
Oxidative stress is regarded as a result of the imbalance of oxidants and antioxidants, which can cause damage to important cellular macromolecules, such as DNA, lipid, and protein, and, in turn, lead to toxicity, chronic inflammation, and diseases, acting as a serious threat to animal and human health [1,2,3]. Polyphenols are natural compounds present in plants with numerous biological activities, which have been proposed to be useful as adjuvant therapy for their potential antioxidant effect, associated with the anti-inflammatory activity [11]. Increasing evidence has indicated that olive extracts rich in polyphenolic compounds have powerful antioxidant and anti-inflammatory effects in mammalian cells, rats, and humans [14,15,16,17]. Some studies have shown that olive extracts have anti-bacterial and anti-inflammation effects [21,22,23] It is well-established that these beneficial health properties of olive extracts are related to one of the polyphenolic compounds named hydroxytyrosol (HT) [24,25,26]. Olive extracts enriched with various polyphenols (especially HT) may be an effective prevention against disorders related to oxidative stress
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