Swimming exercise training-induced left ventricular hypertrophy involves microRNAs and synergistic regulation of the PI3K/AKT/mTOR signaling pathway.

PURPOSE: Swimming exercise leads to a nonpathological, physiological left ventricular hypertrophy. However, the potential molecular mechanisms are unknown. We investigated the role of microRNAs (miRNA) regulating the cardiac signal cascades were studied in exercised rats.

METHODS: Female Wistar rats were assigned into two groups: (1) sedentary control (SC), (2) swimming exercise (SE). The rats in the SE group completed a 1-h swimming exercise, 5 times/week/8-week with 5 % body overload. miRNA, phosphoinositide-3-kinase catalytic alpha polypeptide (PIK3α), phosphatase and tensin homolog (PTEN) and tuberous sclerosis complex 2 (TSC2) gene expression analysis were performed by real-time PCR in heart muscle. Moreover, we assessed cardiac protein expression of ERK1/2, PI3K/AKT/mTOR, PTEN and TSC2.

RESULTS: Cardiac phospho(ser473)-AKT and phospho(Ser2448)-mTOR were, respectively, increased by 46 and 38 % in the SE group when compared with SC group. miRNAs-21, 144, and 145 were, respectively, up-regulated in the SE group (152 %, 128, and 101 % relative increases), but miRNA-124 was decreased by 38 %. In SE group, PIK3α (targeted by miRNA-124) gene expression increased by 213 %, and Pten (targeted by miRNAs-21 and 144), and TSC2 (targeted by miRNA-145) were, respectively, decreased by 51 and 55 %. In addition, the swimming exercise increased protein levels of PIK3α (36 %) and phospho(Thr1462)-TSC2 (48 %), while it decreased PTEN (37 %) and TSC2 (22 %), which induced activation of PI3K/AKT/mTOR signaling pathway.

CONCLUSION: These findings are consistent with a model in which exercise may induce left ventricular hypertrophy, at least in part, changing the expression of specific miRNAs targeting the PIK3/AKT/mTOR signaling pathway and its negative regulators.