Effect of 7 Days of Grape Seed Extract Supplementation on Cold Pressor Test and Muscle Metaboreflex in Individuals With Elevated and Stage 1 Hypertension

Muscle metatoreflex (MMR) has been known to play an important role in adjusting hemodynamic responses during exercise. The reflex increases sympathetic activity to heart and blood vessels to increase blood supply to contracting skeletal muscles. On the other hand, studies demonstrated that abnormal cardiovascular responses occurred by the overactive MMR in pathological conditions such as hypertension, diabetes, and congestive heart failure. Excessive blood pressure (BP) responses to exercise induce cardiovascular events such as stroke, heart attack, and coronary artery disease. Previously, a study found that dietary supplementation with grape seed extract (GSE) reduced BP response to dynamic exercise in individuals with elevated and stage 1 hypertension (ES1H) and associated with peripheral vasodilation. However, mechanisms underlying this phenomenon are not clear. Purpose: therefore, the purpose of this study is to investigate whether chronic dietary supplementation with GSE can decrease BP responses to exercise and this observation is associated with reduced MMR. Methods: 12 ES1H males were studied. Changes in cardiac output (Q), mean arterial pressure (MAP) and total peripheral resistance (TPR) were compared between the GSE and placebo supplementations during static handgrip exercise (SHE) and post exercise muscular ischemia (PEMI). Participants completed 3 min of SHE at 40% of MVC followed by 2 min of PEMI.

• Grape Seed Extract (Dietary supplement): dietary supplements that rich in polyphenolic compounds
• Placebo (Dietary supplement): Starch

Primary outcomes

• heart rate (bpm) [5 minutes, 3 minutes, and 2 minutes, respectively.]: measured these variables at rest and during static handgrip exercise and muscle metaboreflex
• stroke volume (ml) [5 minutes, 3 minutes, and 2 minutes, respectively.]: measured these variables at rest and during static handgrip exercise and muscle metaboreflex
• cardiac output (l/min) [5 minutes, 3 minutes, and 2 minutes, respectively.]: measured these variables at rest and during static handgrip exercise and muscle metaboreflex
• systolic blood pressure (mmHg) [5 minutes, 3 minutes, and 2 minutes, respectively.]: measured these variables at rest and during static handgrip exercise and muscle metaboreflex
• diastolic blood pressure (mmHg) [5 minutes, 3 minutes, and 2 minutes, respectively.]: measured these variables at rest and during static handgrip exercise and muscle metaboreflex
• total peripheral resistance (mmHg/l/min) [5 minutes, 3 minutes, and 2 minutes, respectively.]: measured these variables at rest and during static handgrip exercise and muscle metaboreflex

Sex: Male, ages: 18 Years to 30 Years, accepts healthy volunteers

Inclusion Criteria:

* systolic blood pressure: 120-139 mmHg and/or a diastolic blood pressure: 80-89 mmHg

Exclusion Criteria:

* taking medications that could affect cardiovascular function or BP

• Jong-Kyung Kim, Ph.D., Principal investigator, California Baptist University