Free fatty acids impair steroidogenesis and promote apoptosis in leydig cells: A new link between metabolic dysfunction and hypogonadism

Abstract

Excess circulating fatty acids contributes to the association between metabolic disorders and hormonal alterations. Indeed, obesity and diabetes mellitus are frequently associated with functional hypogonadism characterised by reduced testosterone levels. Although a high-fat-diet is known to negatively affect testicular function, its specific impact on steroidogenesis remains unclear. Therefore, the aim of this study has been to investigate the effects of different FFAs, with or without human chorionic gonadotropin (hCG) stimulation, on steroidogenesis and apoptosis in a murine Leydig cell line (mLTC1).
mLTC1 cells were exposed with increasing concentrations of palmitate (PA) or oleate (OA), in the presence or absence of 0.2 IU/mL hCG. The expression of the Steroidogenic Acute Regulatory (STAR) protein, a key marker of steroidogenesis, was evaluated by immunoblotting. Testosterone secretion was measured by ELISA, while apoptosis was evaluated by cleaved caspase-3 (C3C) protein expression using immunoblotting.
Exposure to PA significantly reduced hCG-induced STAR protein expression in a dose-dependent manner after 6h and 15h, respectively, compared with PA-free conditions. Similarly, exposure to OA reduced STAR protein expression at all concentrations tested (0.4-1 mM). Prolonged treatment with PA (96 hours) further compromised steroidogenic capacity, leading to a reduction in testosterone production. Furthermore, PA significantly increased C3C levels. Notably, hCG stimulation during the last 6h of incubation significantly reduced PA-induced C3C levels at all concentrations.
In conclusion, both PA and OA impair hCG-induced steroidogenesis, while PA additionally promotes Leydig cell apoptosis. These findings suggest a direct detrimental role of excess FFAs on testicular function in obesity and indicate a potential protective role of hCG in preserving Leydig cell viability under conditions of metabolic stress.