One role of the hormone insulin is to transport glucose to cells to be used as energy. Insulin resistance occurs when the cells do not take in/accept glucose. The glucose then remains in the blood stream and cells have inadequate energy which generates fatigue. Obesity, and excess belly fat are the primary causes of insulin resistance. Obesity, is associated with decreased activity of insulin receptors, a decreased number of insulin receptors and with post-receptor failure to activate tyrosine kinase.
Insulin resistance is the primary disease driver of metabolic syndrome. Several mechanisms connect insulin resistance and metabolic syndrome with hypertension. Data indicates that insulin stimulates renal (kidney) sodium re-absorption. Insulin resistance is also associated with the development of salt-sensitive hypertension through the anti-natriuretic effect of insulin. An anti-natriuretic agent causes the body to retain sodium. Essentially, high insulin levels cause the body to hold salt, which increases blood volume. High blood volume causes the heart and arteries to work harder to push blood through circulatory system. As such, the increase in blood volume contributes to high blood pressure.
High serum insulin levels are also associated with an increase in circulating endothelin-1 in healthy and insulin-resistant individuals. Endothelin-1 is a blood vessel tightening (vasocontrictor) peptide. Elevated levels of endothelin-1 have been demonstrated in various disease conditions that are characterized by sodium retention and/or renal vasoconstriction.
Obesity and excess belly fat stimulate high insulin levels. The high insulin levels then contribute to vasoconstriction, increased intravascular fluid, and decreased vasodilatation, which contribute to the development of hypertension. The good news is that for those with excess weight and/or excess belly fat, weight loss can substantially lessen the bioactive mechanisms that lead to the development of insulin resistance and hypertension.
Sources:
Abnormalities of renal sodium handling in the metabolic syndrome. Results of the Olivetti Heart Study. Strazzullo P, Barbato A, Galletti F
J Hypertens 2006, 24:1633-1639
The underlying mechanisms for the development of hypertension in the metabolic syndrome.
Hidekatsu Yana, Yoshiharu Tomona
Nutrition Journal 2008
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