Lower serum level of miRNA-21 may be considered as a comorbidity-independent characteristic of frailty in cardiovascular patients

We examined the serum level of miRNA-21 in a cohort of frail cardiovascular patients. We have enrolled 261 patients into this ancillary analysis of the FRAPICA trial (ClinicalTrials.org NCT03209414, registered 06/07/20217). The phenotype Fried frailty scale identified 93 robust, 131 pre-frail, and 37 frail patients. The groups differed in terms of demographics, morphology, and clinical characteristics. Frail patients had significantly lower miRNA-21 serum levels (median, 0.022; IQR, 0.0188–0.0351) compared to pre-frail (0.0477; 0.0467–0.0511) and robust patients (0.0477; 0.0428–0.0526), with P < 0.001. In the case of each frailty trait, patients with the presence of this trait had lower miRNA-21 levels than patients without the trait. The comorbidities had no impact on the miRNA-21 level. The miRNA-21 level correlated positively with weight, lean body mass, instrumental activities of daily living score, renal excretory function, expiratory pulmonary function, and hemoglobin concentration.This finding proposes miR-21 as a potential blood circulating biomarker of frailty, indicating that low levels of this miRNA represent a comorbid-independent characteristic of frailty in cardiovascular patients. Future studies are warranted to investigate the prognostic impact of baseline miRNA-21 levels on cardiovascular outcomes, as well as the longitudinal fluctuations of miRNA-21 serum levels and their clinical implications.