Muscle Metaboreflex Activation in Young Healthy Men with a Family History of Hypertension

Abstract

Activation of metabolically sensitive skeletal muscle afferents (i.e., the muscle metaboreflex) contributes importantly to the muscle sympathetic nerve activity (MSNA) and pressor responses evoked by static handgrip exercise. Individuals with a positive family history of hypertension (+FHH) have been shown to evoke greater pressor responses to static handgrip exercise however, whether this is due to an exaggerated muscle metaboreflex remains unclear. A recent study demonstrated that young, healthy women with +FHH have an exaggerated muscle metaboreflex activation compared to women with no family history (‐FHH). However, whether men with +FHH also exhibit an augmented muscle metaboreflex response has not been investigated. Therefore, we tested the hypothesis that muscle metaboreflex activation is exaggerated in young men with +FHH. Young, healthy men (+FHH, n=7 and ‐FHH, n=13) performed 2 min of static handgrip exercise at 40% of maximal voluntary contraction followed by a 2 min period of post‐exercise ischemia (PEI) to isolate skeletal muscle metaboreflex activation. In addition, a cold pressor test (CPT) was performed as a generalized, sympathoexcitatory stimulus. Beat‐to‐beat arterial blood pressure (finger photoplethysmography), heart rate (ECG) and MSNA (peroneal nerve microneurography) were measured. Resting mean arterial pressure (MAP; +FHH: 99±3 vs. ‐FHH: 95±2 mmHg, p=0.34) and MSNA (+FHH: 12±1 vs. ‐FHH: 15±3 bursts/min, p=0.56) were similar between groups. The increase in MAP during PEI following 40% handgrip was not different between groups (+FHH: Δ22±3 vs. ‐FHH: Δ23±1 mmHg, p=0.52). However, the MSNA response during PEI was greater in +FHH (Δ20±1 bursts/min) compared to ‐FHH (Δ10±2 bursts/min, p=0.01). No difference was observed in MAP (+FHH: Δ20±5 vs. ‐FHH: Δ19±3 mmHg, p=0.82) or MSNA (+FHH: Δ14±4 vs. ‐FHH: Δ16±5 bursts/min, p=0.75) response to CPT between groups. These preliminary data suggest that a heightened muscle metaboreflex mediated sympatho‐excitation is present in young healthy men with a family history of hypertension.Support or Funding InformationNIH R15‐HL‐130906