Combining a nontargeted and targeted metabolomics approach to identify metabolic pathways significantly altered in polycystic ovary syndrome

Abstract

Objective Polycystic ovary syndrome (PCOS) is a condition of androgen excess and chronic anovulation frequently associated with insulin resistance. We combined a nontargeted and targeted metabolomics approach to identify pathways and metabolites that distinguished PCOS from metabolic syndrome (MetS). Methods Twenty obese women with PCOS were compared with 18 obese women without PCOS. Both groups met criteria for MetS but could not have diabetes mellitus or take medications that treat PCOS or affect lipids or insulin sensitivity. Insulin sensitivity was derived from the frequently sampled intravenous glucose tolerance test. A nontargeted metabolomics approach was performed on fasting plasma samples to identify differentially expressed metabolites, which were further evaluated by principal component and pathway enrichment analysis. Quantitative targeted metabolomics was then applied on candidate metabolites. Measured metabolites were tested for associations with PCOS and clinical variables by logistic and linear regression analyses. Results This multiethnic, obese sample was matched by age (PCOS, 37 ± 6; MetS, 40 ± 6 years) and body mass index (BMI) (PCOS, 34.6 ± 5.1; MetS, 33.7 ± 5.2 kg/m2). Principal component analysis of the nontargeted metabolomics data showed distinct group separation of PCOS from MetS controls. From the subset of 385 differentially expressed metabolites, 22% were identified by accurate mass, resulting in 19 canonical pathways significantly altered in PCOS, including amino acid, lipid, steroid, carbohydrate, and vitamin D metabolism. Targeted metabolomics identified many essential amino acids, including branched-chain amino acids (BCAA) that were elevated in PCOS compared with MetS. PCOS was most associated with BCAA (P = .02), essential amino acids (P = .03), the essential amino acid lysine (P = .02), and the lysine metabolite α-aminoadipic acid (P = .02) in models adjusted for surrogate variables representing technical variation in metabolites. No significant differences between groups were observed in concentrations of free fatty acids or vitamin D metabolites. Evaluation of the relationship of metabolites with clinical characteristics showed 1) negative associations of essential and BCAA with insulin sensitivity and sex hormone–binding globulin and 2) positive associations with homeostasis model of insulin resistance and free testosterone; metabolites were not associated with BMI or percent body fat. Conclusions PCOS was associated with significant metabolic alterations not attributed exclusively to androgen-related pathways, obesity, or MetS. Concentrations of essential amino acids and BCAA are increased in PCOS, which might result from or contribute to their insulin resistance.

Metabolic Analysis in Women with Polycystic Ovary Highlight Specific Biomarkers of Insulin Resistance

“…Creatine, serine, lactate, glycine, dodecanedioic acid and threonine were glucose metabolism related metabolites found decreased in IR PCOS compared with controls or non-IR PCOS women [14][15][16][17]. Although, lactate was also found increased in IR PCOS women comparatively with non-IR PCOS patients [16].…”

“…However, lysine, leucine, tyrosine, α-aminoadipic acid and phenylalanine were the amino acid metabolism related metabolites, correlated to IR PCOS women compared with control/ non-IR PCOS women. Nonetheless, argininesuccinic acid, 5-methoxysalicylic-acid and indoxyl sulfate were reported as decreased in IR PCOS women [14][15][16][17].…”

“…Other metabolites corelated to IR PCOS women were linoleic acid, vaccenic acid, palmitic acid, trans-2hexenoyl-coa, myristic acid. Only lyso -phosphatidylcholine and palmitic acid are invers proportional correlated to IR of PCOS women [14][15][16][17].…”

“…The following characteristics were considered: number of participants, control group characteristics, study design, PCOS diagnostic method used, inclusion/exclusion criteria, metabolomic technique used, sample used for metabolomics, the metabolites identified to have been altered in IR PCOS patients compared to either non-IR PCOS or controls. Data summarizing is presented in Tables 1 and 2 [16] and 37±6 [17].…”

Nontargeted discovery of xenobiotics in human urine by MALDI-TOF/TOF-MS

“…However, the metabolites identified in nontargeted analysis can be further quantified in targeted analysis. (22) In addition, the metabolic profiles of biological samples obtained in the nontargeted analysis can be used to compare different groups of samples, e.g., patients with a disease and the healthy individuals. The differentiation of sample groups is achieved by statistical analysis of the metabolite profiles.…”