Alterations in nonesterified free fatty acid trafficking rather than hyperandrogenism contribute to metabolic health in obese women with polycystic ovary syndrome.

Objective: To determine whether alterations in nonesterified fatty acid (NEFA) dynamics or degree of hyperandrogenism (HA) contribute to the difference in insulin sensitivity between women with metabolically healthy obese polycystic ovary syndrome (PCOS) (MHO-PCOS) and women with metabolically unhealthy obese PCOS (MUO-PCOS).

Design: Prospective cross-sectional study.

Setting: Tertiary-care academic center.

Patients: One hundred twenty-five obese women with PCOS.

Intervention: Consecutive obese (body mass index [BMI] ≥ 30 kg/m) oligo-ovulatory women (n = 125) with PCOS underwent an oral glucose tolerance test and a subgroup of 16 participants underwent a modified frequently sampled intravenous glucose tolerance test to determine insulin-glucose and -NEFA dynamics.

Main Outcome Measures: Degree of insulin resistance (IR) in adipose tissue (AT) basally (Adipo-IR) and dynamically (the nadir in NEFA levels observed [NEFA], the time it took for NEFA levels to reach nadir [TIME], and the percent suppression in plasma NEFA levels from baseline to nadir [%NEFA]); peak lipolysis rate (S) and peak rate of NEFA disposal from plasma pool (K); whole-body insulin-glucose interaction (acute response of insulin to glucose [AIRg], insulin sensitivity index [Si], glucose effectiveness [Sg], and disposition index [Di]); and HA (hirsutism score, total and free testosterone levels, and dehydroepiandrosterone sulfate levels).

Results: A total of 85 (68%) women were MUO-PCOS and 40 (32%) were MHO-PCOS using the homeostasis model of assessment of IR. Subjects with MUO-PCOS and MHO-PCOS did not differ in mean age, BMI, waist-to-hip ratio, HA, and lipoprotein levels. By a modified frequently sampled intravenous glucose tolerance test, eight women with MUO-PCOS had lesser Si, K, and the percent suppression in plasma NEFA levels from baseline to nadir (%NEFA) and greater TIME, NEFA, and baseline adipose tissue IR index (Adipo-IR) than eight subjects with MHO-PCOS, but similar fasting NEFA levels and S. Women with MUO-PCOS had a higher homeostasis model of assessment-β% and fasting insulin levels than women with MHO-PCOS. In bivalent analysis, Si correlated strongly and negatively with Adipo-IR and NEFA, weakly and negatively with TIME, and positively with K and %NEFA, in women with MUO-PCOS only.

Conclusion: Independent of age and BMI, women with MUO-PCOS have reduced NEFA uptake and altered insulin-mediated NEFA suppression, but no difference in HA, compared with women with MHO-PCOS. Altered insulin-mediated NEFA suppression, rather than HA or lipolysis rate, contributes to variations in insulin sensitivity among obese women with PCOS.