Integrated untargeted and targeted testicular metabolomics to reveal the regulated mechanism of Gushudan on the hypothalamic‐pituitary‐gonadal axis of kidney‐yang‐deficiency‐syndrome rats

Modern studies have shown that neuroendocrine disorders caused by the dysfunction of the hypothalamic-pituitary-gonadal (HPG) axis are one of the important pathogenetic mechanisms of kidney-yang-deficiency-syndrome (KYDS). The preventive effect of Gushudan on KYDS has been reported, but its regulatory mechanisms on the HPG axis have not been elucidated. In this study, we developed an integrated untargeted and targeted metabolomics analysis strategy to investigate the regulatory mechanism of Gushudan on the HPG axis in rats with KYDS. In untargeted metabolomics, we screened 14 potential biomarkers such as glycine, lysine, and glycerol that were significantly associated with the HPG axis. To explore the effect of changes in the levels of potential biomarkers on KYDS, all of them were quantified in targeted metabolomics. With the quantitative results, correlations between potential biomarkers and testosterone, a functional indicator of the HPG axis, were explored. The results showed that oxidative stress, inflammatory response, and energy depletion, induced by metabolic disorders in rats, were responsible for the decrease in testosterone levels. Gushudan improves metabolic disorders and restores testosterone levels, thus restoring HPG axis dysfunction. This finding elucidates the special metabolic characteristics of KYDS and the therapeutic mechanism of Gushudan from a new perspective.