C-mirna Expression Responses To Whole-body Vibration And Resistance Exercise In Postmenopausal Women

Abstract

Circulating microRNAs (c-miRNA, miR) are potential biomarkers for age-related changes in musculoskeletal function. There is a paucity of data on c-miRNA responses to exercise, especially in postmenopausal women (PMW). Evaluating alterations in the expression of c-miRNA may provide deeper insight into the benefits of exercise for bone health in aging populations. PURPOSE: The purpose of this study was to characterize the effects of acute bouts of resistance exercise (RE) and whole-body vibration (WBV) on selected c-miRNAs that regulate bone metabolism (miR-21-5p, -23a-3p, -133a-3p, -148a-3p) in PMW (n=10). METHODS: Subjects performed a high intensity RE condition and a WBV condition in random order. RE consisted of 3 sets, 10 reps, 70% 1RM for leg press, shoulder press, lat pulldown, leg extension, and hip adduction isotonic exercises. For WBV, 5-1 min bouts were performed (20 Hz, 3.38 mm peak-to-peak displacement) each separate by 1 min rest on a Galileo vibration platform. Morning blood samples after an overnight fast were collected pre, immediately-post (IP), 60 min, 24 hrs, and 48 hrs after exercise to measure c-miRNA and TRAP5b. C-miRNA expression was corrected for plasma volume (PV) shifts using the equation: %ΔPV = (log(100)/(log(100) – log(Hct Pre)) * log(100)*((log(Hct Pre) – log(Hct Post))/log(Hct Post)). The correction factor was subtracted from the Cq values for each exercise sample. RESULTS: PV significantly decreased for both conditions at IP (p=0.04), thus serum variables were corrected for PV shifts. There was a significant condition × time interaction for miR-21 (p=0.019), which decreased in relative expression from 60p (1.61 ± 0.31) to 24h (0.80 ± 0.16) after WBV but not after RE. MiR-23a-3p, -133a-3p, -148a-3p showed no significant expression changes for either exercise condition. TRAP5b concentrations significantly decreased 24h (WBV -7.56% ± 5.27, RE -3.44% ± 4.33) after exercise (p<0.01) even after correcting for PV shifts (p<0.01). CONCLUSION: C-miR-21-5p was downregulated at 24 hrs in response to an acute bout of WBV. Both types of exercise also decreased serum TRAP5b 24 hrs post-exercise, indicating decreased bone resorption. This is the first known study to correct c-miRNA expression for PV shifts.