Subgroups of participants
To assess the levels of fructose and uric acid in various metabolic states and the impact of clinical characteristics on cases and controls, the study population was further subdivided according to PCOS-related metabolic alterations, including obesity, insulin resistance, dyslipidemia, metabolic syndrome.
According to the WHO-defined diagnostic criteria for lean, overweight, and obese individuals in Asia,13 we categorized the participants into the following three subgroups: lean (BMI < 23 kg/m2), overweight (23 kg/m2 ≤ BMI < 25 kg/m2), and obese (BMI ≥ 25 kg/m2) (Table S1).
The degree of insulin resistance was estimated using a homeostasis model (HOMA-IR). We calculated the HOMA-IR index as follows: FPG (mM) × FSI (mIU/l)/22.5; insulin resistance could be defined as HOMA-IR > 2.5; this threshold value has been widely used earlier (Table S2).14
Participants were classified as dyslipidemia and normolipidemia groups based on the following criteria: TC ≥ 6.2 mmol/l; TG ≥ 2.3 mmol/l; LDL-C ≥ 4.1 mmol/l; and HDL-C < 1.0 mmol/l, fulfilling at least one of the above criteria (Table S3).15
According to the criteria proposed by the American Association of Clinical Endocrinologists/American College of Endocrinology, the manifestation of three or more of the following factors is sufficient for the diagnosis of metabolic syndrome16:BMI ≥ 25 kg/m2; TG ≥ 1.70 mmol/l; HDL-C < 1.29 mmol/l; blood pressure ≥ 130/85 mmHg; plasma glucose after a 2-h load > 7.8 mmol/l, 6.1 mmol/l ≤ FPG ≤ 7. 0 mmol/l; other risk factors included type 2 diabetes, PCOS, sedentary lifestyle, old age, family history of hypertension or cardiovascular disease, and ethnicity with a high risk of type 2 diabetes or cardiovascular disease (Table S4).