Melatonin inhibits testosterone synthesis in Roosters Leydig cells by regulating lipolysis of lipid droplets.

Leydig cells are important component of testis cells, which can synthesize testosterone with free cholesterol derived from lipid droplets (LDs). It is well known that melatonin could regulate synthesis of testosterone. However, it is still unclear whether melatonin participates in the synthesis of testosterone by regulating the lipolysis of LDs in Leydig cells. The purpose of this study was to elucidate the effect of melatonin on synthesis of testosterone in roosters Leydig cells by regulating lipolysis of LDs. The results showed that melatonin decreased synthesis of testosterone and intracellular free cholesterol in roosters Leydig cells. Exogenous addition of 22-OH-Cholesterol counteracted the inhibitory effect of melatonin on synthesis of testosterone. Furthermore, melatonin increased the LDs content and expression of perilipin 1 (PLIN1), and decreased expression of hormone-sensitive lipase (HSL) and triacylglycerol hydrolase (ATGL) in roosters Leydig cells. In addition, silencing PLIN1 reversed the inhibitory effect of melatonin on synthesis of testosterone in roosters Leydig cells by increasing free cholesterol content and expression of HSL and ATGL, and decreasing the lipid droplet content. Activation of cAMP/PKA pathway by using the pathway activators Forskolin and 8-Bromo-cAMP attenuated the inhibitory effect of melatonin on synthesis of testosterone accompanied by increasing level of free cholesterol content and expression of HSL and ATGL, and decreasing level of lipid droplet content and expression of PLIN1 in roosters Leydig cells. These results suggested that melatonin could inhibit the synthesis of testosterone in roosters Leydig cells by reducing the content of intracellular free cholesterol in which expression of PLIN1 and cAMP/PKA pathway were inhibited to reduce the lipolysis of LDs.