Novel Mechanisms Responsible for Postmenopausal Hypertension

Abstract

Abstract-Blood pressure increases in many women after menopause. Hypertension is one of the major risk factors for cardiovascular disease. However, the mechanisms responsible for the postmenopausal increase in blood pressure are yet to be elucidated. Various humoral systems have been proposed to play a role in postmenopausal hypertension, such as changes in estrogen/androgen ratios, increases in endothelin and oxidative stress, and activation of the renin-angiotensin system (RAS). In addition, obesity, type II diabetes, and activation of the sympathetic nervous system are common in postmenopausal women and may also play important roles. However, progress in elucidating the mechanisms responsible for postmenopausal hypertension has been hampered by the lack of a suitable animal model. The aging female spontaneously hypertensive rat (SHR) exhibits many of the characteristics found in postmenopausal women. In this review, some of the possible mechanisms that could play a role in postmenopausal hypertension are discussed, as well as the characteristics of the aged female SHR as a model to study. Key Words: endothelin Ⅲ renin-angiotensin system Ⅲ oxidative stress Ⅲ obesity Ⅲ diabetes mellitus Ⅲ sympathetic nervous system B efore menopause, blood pressure is typically lower in women than in age-matched men. 1 In aging men and women, systolic and diastolic blood pressures increase, although in later years the diastolic plateaus or even declines. [1][2][3] However, in postmenopausal women, the prevalence of hypertension and cardiovascular disease risk increases regardless of ethnic origin. Results from the National Health and Nutrition Examination Survey (NHANES III) showed that in Hispanic women and non-Hispanic black women, the prevalence of hypertension was similar to, or higher than, that in men by age 60 years. 4 In non-Hispanic white populations, the prevalence of hypertension was higher in women than in men by age 70 years. 4 The increase in blood pressure in postmenopausal women does not occur as soon as the ovary becomes senescent, but rather over a number of years. 5 The mechanisms responsible for the increased blood pressure in women after menopause are not known. This review focuses on the use of the spontaneously hypertensive rat as a model of postmenopausal hypertension and evaluates the possible mechanistic roles of the sex hormones, oxidative stress, endothelin, renin-angiotensin system (RAS), weight gain, and sympathetic activation in postmenopausal hypertension. Animal Model for the Study of Postmenopausal HypertensionThe elucidation of mechanisms responsible for postmenopausal hypertension has been stunted by lack of an animal model. Sheep, rabbits, nonhuman primates, rats, and mice have been used as models of various menopausal changes; 6 however, to our knowledge, there is no animal model of naturally occurring postmenopausal hypertension. There have been attempts to mimic menopause by ovariectomizing animals; 7,8 however, these have rarely taken into account the effect of aging and cessation of ova...

Sex difference in blood pressure among South Asian diaspora in Europe and North America and the role of BMI: a meta-analysis

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