Influence of flavonols and quercetin derivative compounds on MA-10 Leydig cells steroidogenic genes expressions.

Androgen are mainly synthesized and secreted from testicular Leydig cells and play critical roles in testis development, normal masculinization, spermatogenesis, and male fertility. The rate-limiting step in testosterone biosynthesis involves the import of cholesterol inside mitochondria by the steroidogenic acute regulatory (Star) protein. Cholesterol is then converted to pregnenolone by the steroidogenic enzyme Cyp11a1, followed by a chemical transformation to testosterone using other steroidogenic enzymes. Interestingly, levels of Star protein within adult Leydig cells decrease during aging, resulting in defective mitochondrial cholesterol transfer and reduced testosterone production. Such decline may be delayed by increasing Star and/or Cyp11a1 gene expressions using supplementation with flavonoids, a group of the polyphenolic compounds widely distributed in fruits and vegetables. In this study, we examined whether the distribution of hydroxyl groups and/or acetylation or methylation of flavonols could influence their potency to stimulate steroidogenesis within Leydig cells. Low levels of quercetin, myricetin and pentaacetylquercetin (10μM) stimulated cAMP-dependent Star, Cyp11a1 and Fdx1 promoters' activations and may increase steroidogenesis within Leydig cells. Indeed, pentaacetylquercetin successfully increased cAMP-dependent accumulation of progesterone from MA-10 Leydig cells, possibly through activation of Star and Cyp11a1 transcriptions. Thus, dietary supplementation of pentaacetylquercetin could be potentially effective to maintain testosterone production within aging males.