#899 The effect of exercise training on microRNAs in patients undergoing hemodialysis

Abstract

Abstract Background and Aims Physical inactivity is a risk factor for mortality and morbidity in patients undergoing hemodialysis (HD). Therefore, physical exercise (PE) is recommended as part of the management of HD patients. Although the benefits of PE for HD patients have been well documented in the literature, the pathophysiological mechanism still needs to be fully understood. Recently, microRNAs (miRNAs) have come to light as potential mediators of PE's therapeutic effects in healthy individuals. Currently, no information is available about how PE affects the expression of miRNAs in HD patients, mainly for osteogenic differentiation, a critical process in forming vascular calcification. Therefore, this observational longitudinal study aims to assess the expression of miR-9 and miR-30b, two regulators of the osteogenic commitment from endothelial progenitor cells, in HD patients engaged in an interdialytic exercise program. Method Male HD patients aged between 50 and 80 could walk for at least six meters were enrolled. Exclusion criteria were uncorrected anemia, acute infectious disease, uncontrolled hyperparathyroidism, active oncologic disease, and severe cardio-respiratory, musculoskeletal, or neurological conditions inhibiting exercise training. Patients were engaged in a structured interdialytic program supervised by an exercise facilitator. Exercise training was performed at home or the dialysis centre based on the patient's needs and preferences. It consisted of a 10-minute session/day of low-intensity walking and/or resistance exercises. The speed was increased weekly and controlled with a metronome application on the patient's smartphone. The maximum distance covered evaluates the patients' physical performance, as measured by the 6-minute walking test (6MWT). It was assessed at baseline and the 6-month follow-up. Blood samples for miRNA analysis were collected during the short interdialytic period at baseline and at the 6-month follow-up. MiRNAs will be extracted from serum samples using the miRNeasy Serum/Plasma Advanced Kit. Statistical analysis will be performed using SPSS 21.0. The difference between the two groups was assessed using a t-test for paired data. P-values<0.05 were considered statistically significant. Results Patients’ characteristics at baseline are shown in Table 1. Five patients were enrolled in the study, three undergoing exercise training at the dialysis centre and two at home. At six months, miR-30b expression appeared significantly upregulated in all patients (p<0.03) (Fig. 1). At the same time, the upregulation of miR-9 did not reach significance (p = 0.07). In one patient, miR-9 was not detected (Fig. 2). The mean distance covered during the 6MWT did not improve at six months (255 ± 129 meters) compared to baseline (235 ± 118 meters) (p = 0.49). Conclusion Preliminary results of this longitudinal observational study show that miR-30b was upregulated in patients engaged in the exercise training period at the 6-month follow-up despite no improvement in physical performance. The upregulation of miR-30b levels can potentially reduce the dedifferentiation of vascular smooth muscle cells into an osteoblastic-like phenotype. At the end of our study, novel evidence concerning the potential effect of exercise training on miRNA expressions correlated to the vascular calcification process in HD patients will be available.