This study was conducted to investigate cellular mechanisms that could explain the sexual dimorphsim observed in fat distribution. For that purpose, twenty normal-weight and healthy premenopausal women and twelve men were recruited to undergo body fat distribution measures by computed tomography and the analysis of adipocyte cellularity and preadipocyte cell kinetics through adipose tissue biopsies taken from the upper (abdominal subcutaneous) and lower (lateral thigh) body. Results confirmed the expected sex differences in body composition revealing that women had more subcutaneous and less intra-abdominal (visceral) fat than men. There was a greater abundance of early-differenciated adipocytes in the stromavascular fraction (SVF) in women compared to men, especially in the femoral depot (≈35%). By measuring key transcription factors involved in differentiation such as peroxisome proliferator-activated receptor (PPAR)-g and Ccaat-enhancer-binding proteins (C/EBP)-a, the authors found lower PPAR-g mRNA abundance in cultured femoral compared to abdominal subcutaneous preadipocytes in women, but not in men. There were no gender differences in the amount of C/EBP-a mRNA and preadipocyte proliferation. Thus these results suggest that mechanisms causing gender differences in body fat distribution are not due to inherent properties of preadipocytes, but probably differences in the microenvironment of fat depots that include sex steroids, macrophages and various cell types present in fat tissue.
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