Natural astaxanthin enhances testosterone synthesis by improving mitochondrial function and reducing oxidative stress in Leydig cells

This study investigated the effects of astaxanthin (ASTA) on testosterone synthesis and mitochondrial function in testicular Leydig cells of aging roosters. ASTA significantly enhanced Leydig cell viability ( P < 0.05) and increased testosterone production at concentrations of 2.5–20 μg/mL ( P < 0.05), with the optimal effect observed at 5 μg/mL ( P < 0.01). At this concentration, ASTA significantly upregulated the mRNA and protein expression of key steroidogenic enzymes, steroidogenic acute regulatory (StAR), cholesterol side-chain cleavage cytochrome (P450scc), 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD) ( P < 0.01), and steroidogenic factor-1 (SF-1) ( P < 0.05). ASTA also significantly elevated the activities and mRNA expression of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-PX) ( P < 0.01), reduced reactive oxygen species (ROS) levels ( P < 0.05), and decreased malondialdehyde (MDA) content ( P < 0.01). Furthermore, ASTA treatment significantly improved mitochondrial membrane potential (MMP), adenosine triphosphate (ATP) content and mitochondrial DNA (mtDNA) copy number ( P < 0.01), increased the expression of mitochondrial biogenesis regulators peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), nuclear respiratory factor-1 (NRF1), and mitochondrial transcription factor A (TFAM) ( P < 0.01), and significantly suppressed apoptosis ( P < 0.05), as evidenced by increased B-cell lymphoma-2 (Bcl-2) expression ( P < 0.01) and reduced expression of Bcl-2-associated X protein (Bax), cysteinyl aspartate specific proteinase-3 (caspase-3), and apoptosis-inducing factor (AIF) ( P < 0.01). These results indicate that ASTA enhances testosterone synthesis in aging rooster Leydig cells by reducing oxidative stress, improving mitochondrial function and biogenesis, upregulating steroidogenic genes, and inhibiting mitochondrial-related apoptosis.