Modulation of rat preadipocyte adipose conversion by androgenic status: involvement of C/EBPs transcription factors

Androgenic status affects rat preadipocyte adipose conversion from two deep intra-abdominal (epididymal and perirenal) fat depots differently. The aim of this study was to establish whether these site-specific alterations of adipogenesis are related to altered expressions of the transcriptional fact ors regulating proliferation and differentiation of preadipocytes, c-myc an d CCAAT/enhancer binding proteins (C/EBPs: C/EBP alpha and beta). The increased proliferation of epididymal and perirenal preadipocytes from castrated rats was not linked to variations in c-myc mRNA and protein level s. The expression of the early marker of adipogenesis, lipoprotein lipase (LPL ), was decreased by androgenic deprivation in epididymal cells but remained insensitive to the androgenic status in perirenal preadipocytes. In contra st, LPL expression increased in subcutaneous preadipocytes from castrated r ats, an effect which was partly corrected by testosterone treatment. Expression of C/EBP beta was unaffected by androgenic status whatever the a natomical origin of die preadipocytes. In contrast, the mRNA and protein le vels of C/EBP alpha were greatly decreased by androgenic deprivation in epi didymal cells, an alteration which could not be corrected by in vivo testos terone administration. Altogether these results demonstrated that in preadipocytes androgenic depr ivation affects site-specifically the expression of LPL, an early marker of adipogenesis and of C/EBP alpha, a master regulator of adipogenesis. These observations contribute to an explanation of why castration induces defect ive adipose conversion in rat epididymal preadipocytes specifically.