Expression and Activity of 20α-Hydroxysteroid Dehydrogenase (AKR1C1) in Abdominal Subcutaneous and Omental Adipose Tissue in Women

We examined the expression and activity of 20α-hydroxysteroid dehydrogenase (20α-HSD) in abdominal adipose tissue in women. This recently characterized enzyme from the aldoketoreductase 1C family is responsible for the conversion of progesterone into 20α-hydroxyprogesterone. Abdominal sc (SC) and omental (OM) adipose tissue biopsies were obtained from a sample of 32 women aged 47.7 ± 5.9 yr (body mass index 27.6 ± 5.0 kg/m2) undergoing abdominal hysterectomies. Body composition and body fat distribution measurements were performed before the surgery by dual-energy x-ray absorptiometry and computed tomography, respectively. The expression of 20α-HSD was determined by real-time RT-PCR, and its activity was measured in whole-tissue homogenates. mRNA and activity of the enzyme were detected in both the SC and OM fat depots, the two measures being significantly higher in the SC compartment. Women characterized by a visceral adipose tissue area of 100 cm2 or greater had an increased 20α-HSD conversion rate in their OM adipose tissue, compared with women without visceral obesity (13.99 ± 2.07 vs. 7.92 ± 0.83 fmol/μg protein per 24 h, P < 0.05). Accordingly, a positive correlation was found between OM adipose tissue 20α-HSD activity and computed tomography-measured visceral adipose tissue area (r = 0.36, P < 0.05). Significant positive correlations were also found between OM 20α-HSD activity and OM adipocyte diameter (r = 0.49, P < 0.05) and OM adipose tissue LPL activity (r = 0.36, P = 0.06). In conclusion, 20α-HSD activity and mRNA were detected in SC and OM adipose tissue in women, and OM 20α-hydroxylation of progesterone was highest in women with visceral obesity. Additional studies are required to establish whether local conversion of progesterone may impact on the metabolism and function of adipocytes located within the abdominal cavity.