Insulin resistance and reduced nocturnal fall of blood pressure as risk factors for atherosclerosis in salt sensitive hypertension

ABSTRACT

Recent studies reported that salt sensitive [SS] hypertensive models are more susceptible to atherosclerotic complications than non-salt sensitive [NSS], and some other studies showed that a link may exist between salt sensitivity, reduced nocturnal fall of blood pressure and insulin resistance. The aim of the present study was to confirm these findings and to study the possible role of insulin resistance and reduced nocturnal fall of blood pressure in the suspected increase of atherosclerotic complications in SS hyertensive patients. This study was carried out on 26 patients with essential hypertension classified as 12 SS and 14 NSS. SS patients were at a significantly higher risk of being non-dippers than NSS [OR=11, 95% CI=1.35-114.75] and there was a significant negative correlation between salt sensitivity index [SSI] and nocturnal fall of blood pressure during high salt intake [r=-0.61, p<0.001]. Moreover, there was a significant positive correlation between SSI and both insulin resistance index [IRI] and insulin level during high salt intake [r=0.623, p<0.001 and r=0.621, p<0.001 respectively] and a significant negative correlation between nocturnal fall of blood pressure and both IRI and insulin level during high salt intake [r=0.517, p<0.01 and r=-0.486, p<0.05 respectively]. Nocturnal fall of blood pressure was preserved in SS patients during low salt intake and IRI and insulin level were significantly lower in SS patients during low salt intake compared to that during high salt intake [3.57 +/- 1.02 versus 5.64 +/- 1.67 and 15.92 +/- 3.82 micro lU/mL versus 23.5 +/- 5.99 micro lU/mL]. Carotid intima-media thickness [IMT] was significantly higher in SS patients compared to NSS [0.84 +/- 0.21 mm versus 0.65 +/- 0.16 mm] [p<0.05] and there was a significant positive correlation between carotid IMT and both IRI and insulin level [r=0.773, p<0.001 and r=0.700, p<0.001 respectively] and a significant negative correlation between carotid IMT and nocturnal fall of blood pressure [r=-0530, p<0.01]. It was concluded that insulin resistance, salt induced increase in blood pressure and reduced nocturnal fall of blood pressure are associated with each other in patients with essential hypertension. Insulin resistance and reduced nocturnal fall of blood pressure are closely related to atherosclerotic complications in hypertensive patients and are implicated, at least in part, in the increased atherosclerotic complications in SS patients. Dietary salt restriction can cause improvement of insulin sensitivity in SS patients and shift of circadian blood pressure rhythm from a non-dipper to dipper pattern