Endocrine Abstracts

Aim and background: Retinol binding protein 4 (RBP 4) is an adipocyte-secreted molecule causing insulin resistance in transgenic animals. RBP was increased in subjects with impaired glucose tolerance and diabetes type 2. The levels of RBP-4 in PCOS were not investigated till now.

Subjects and methods16 lean PCOS (BMI 21.4 (1.75) kg/m², age 24.1 (4.1) years), 25 obese PCOS (BMI 30.3 (4.8) kg/m², age 26.3 (5.0) years) and 13 healthy women (BMI 21.5 (1.6) kg/m², age 29.4 (7.0) years) were evaluated using euglyceamic hyperinsulinaemic clamp (1 mIU kg⁻¹.min⁻¹) with the determination of insulin sensitivity index (ISI; mmol.kg⁻¹.min^-1 per mIU l⁻¹). In basal sample, RBP-4 levels (mg/l) were determined using ELISA (ImmundiagnostikAG, Bensheim, Germany). Results are given as mean (SD). ANOVA and multiple backward stepwise regression was used for data analysis. NCSS 2002 statistical software was used for calculations.

Results: Insulin sensitivity index was lower only in O-PCOS (33.2(22)) comparing L-PCOS (70.1 (22)) or C (77.4 (22.7)); (P=0.0003). RBP-4 levels were not different between L-PCOS (27.6 (6.8)), C (33.7 (8.2)) or O-PCOS (32.6 (9.9)).

To explain RBP-4 levels in PCOS women, a regression model consisting of ISI, BMI and 17-OHP was suggested. Only ISI (P=0.04) and 17 OHP (P=0.03) influenced significantly and independently RBP-4 levels; explaining 21.9% of the total variability in the dependent variable. When ISI was taken as dependent variable, and testosterone, RBP-4 and BMI as independent variables, final model contained only BMI (P=0.0001) and explained 33.7% of the variability in insulin sensitivity.

In conclusion, RBP-4 levels in PCOS are influenced negatively and independently by both androgen levels and insulin sensitivity. Hence, the RBP-4 levels in PCOS could not be taken as a marker for the description of insulin sensitivity.

Supported by grants of IGA MH CR 8759-3 and GACR 301/04/1085.