Metabolic Syndrome Is Associated with Increased Plasma Fibroblast Growth Factor 21 (FGF21) in Postmenopausal Breast Cancer Survivors: Implications for Therapy and Diagnosis

Background: Fibroblast growth factor 21 (FGF21) is a peptide hormone that is synthesized by several organs and regulates energy homeostasis, including reducing fat mass and lowering hyperglycemia, insulin resistance and dyslipidemia. It also increased metabolic syndrome (MS) and cardiovascular risk in breast cancer (BC) survivors treated with aromatase inhibitors (AIs) aimed at reducing cancer recurrence. We evaluated whether blood FGF21 concentration is associated with MS and its five criteria in postmenopausal women treated with AIs, and whether this persists after multimodal interventions that reduce MS. Methods: A quasi-experimental longitudinal study in 31 postmenopausal women with localized BC on Ais, assessed via a 12-week multimodal program. Their MS was evaluated per the NCEP-ATP III guidelines (waist circumference, blood pressure, fasting glucose, triglycerides, HDL-cholesterol). Plasma FGF21 was measured pre/post-intervention via fasting blood samples, centrifugation, and ELISA assay. Results: Pre-intervention FGF21 median: 377.62 pg/mL (38.40–1616.42). Plasma FGF21 concentrations positively correlated with MS criteria number pre- and post-intervention (all p < 0.05). Linear regression confirmed pre-intervention MS criteria (β = 127.262, p = 0.006) and antihypertensive drugs as predictors of post-FGF21 levels. Analysis of individual MS criteria revealed significant associations with blood pressure (p = 0.028 and p = 0.022 for systolic and diastolic pressure, respectively) and fasting glucose changes (p = 0.008). Conclusions: Plasma FGF21 may act as a biomarker for monitoring exercise-based interventions which reduce MSs, particularly hypertension and hyperglycemia, in AI-treated BC survivors.