Astragaloside IV Alleviates Depression in Rats by Modulating Intestinal Microbiota, T‑Immune Balance, and Metabolome

This study aims to explore the effects of Astragaloside IV (AS-IV) on abnormal behaviors, intestinal microbiota, intestinal T-immune balance, and fecal metabolism of a model of depression in rats. Herein, we integrally applied 16S rRNA sequencing, molecular biological techniques, and ¹H NMR-based fecal metabolomics to demonstrate the antidepression activity of AS-IV. The results suggested that AS-IV regulated the depression-like behaviors of rats, which are presented by an increase of body weight, upregulation of sucrose preference rates, and a decrease of immobility time. Additionally, AS-IV increased the abundances of beneficial bacteria (Lactobacillus and Oscillospira) in a model of depression in rats. Moreover, AS-IV regulated significantly the imbalance of Th17/Treg cells, and the abnormal contents of both anti-inflammatory factors and pro-inflammatory factors. Besides, fecal metabolomics showed that AS-IV improved the abnormal levels of short-chain fatty acids and amino acids. Collectively, our research supplemented new data, supporting the potential of AS-IV as an effective diet or diet composition to improve depression-like behaviors, dysfunctions of microbiota, imbalance of T immune, and the abnormality of fecal metabolome. However, the causality of the other actions was not proven because of the experimental design and the methodology used. The current findings suggest that AS-IV could function as a promising diet or diet composition to alleviate depressed symptoms.