Japanese soybean paste miso lessens sympathovagal imbalance and attenuates brain sodium sensitivity in mice with pressure overload

Miso is a traditional Japanese food that is made from fermented soybeans, and it can attenuate salt-induced hypertension in salt-sensitive hypertensive rats. We also recently demonstrated that regular miso intake inhibits salt-sensitive sympathoexcitation in mice with pressure overload (CPO). In this context, sympathoexcitation contributes to the pathogenesis of hypertension, including salt-sensitive hypertension. Therefore, we hypothesized that miso might be able to improve sympathovagal imbalance, thereby attenuating salt-induced hypertension. We first treated mice with an intraperitoneal (IP) injection of miso supernatant that was suspended in a 0.28 M sodium solution. Five hours after the miso injection, the mice's systolic blood pressure and heart rate had decreased, with a lower ratio of low frequency (LF) to high frequency (HF) power of heart rate variability. However, an IP injection of high-sodium saline solution (0.28 M sodium) alone had no effects on these parameters. To evaluate the effects of miso on sodium sensitivity in CPO-mice, we also performed aortic banding. At 4 weeks after the surgery, the mice received an IP injection of miso supernatant or high-sodium saline. The ratio of LF/HF increased after the high-sodium saline injection, although not after the miso injection, which indicated that miso inhibited the enhanced sodium sensitivity for sympathetic activity in CPO-mice. We also pre-treated CPO-mice with an intracerebroventricular infusion of miso supernatant to evaluate its effect on increased cerebrospinal fluid (CSF) sodium-induced hypertension. Diluted miso supernatant (in a 0.14 M sodium solution) attenuated the increased CSF sodium-induced hypertension, although pre-treatment with normal-sodium (0.14 M) saline failed to change the hypertension. These results suggest that miso acts on the brain to sway the sympathovagal balance towards a parasympathetic nerve dominant state, and to attenuate the brain sodium sensitivity for sympathoexcitation in CPO-mice.