Role of insulin resistance in the genesis of sodium sensitivity in essential hypertension

Abstract

We recently showed that cardiovascular morbidity was higher in sodium sensitive type of essential hypertension than in the non-sodium sensitive type. It was examined whether sodium sensitivity was associated with insulin resistance, an important atherosclerotic cardiovascular risk factor in essential hypertension. Fifty-three patients with essential hypertension, who had normal (n = 12) and impaired (n = 41) glucose tolerance, were placed on high (12–15 g NaCl/day) and low (1–3 g) sodium diets for 1 week each to determine sodium sensitivity. Fasting plasma glucose and insulin concentrations were measured on a regular sodium diet. The homeostasis model assessment insulin resistance index (fasting glucose [mmol/L] × fasting insulin [mU/L]/22.5) was 1.40 ± 0.10 and 1.47 ± 0.14 in non-sodium sensitive and sodium sensitive groups. The insulin resistance index was positively correlated with the sodium sensitivity index, while was negatively correlated with fractional excretion of sodium (FE_Na) obtained during a high sodium diet. In addition, the insulin resistance index had a positive relationship with overall creatinine clearance. Sodium sensitivity index was also negatively correlated with FE_Na obtained during a high sodium diet. These results showed that insulin resistance might participate in the genesis of sodium sensitivity in essential hypertension by enhancing tubular sodium reabsorption, as reflected in decreased FE_Na and augmented creatinine clearance. Insulin resistance seemed elevated in sodium sensitive state of essential hypertension, leading to future cardiovascular events.