Insulin and blood pressure responses to changes in salt intake

In this study we evaluated the role of insulin in hypertension and on salt sensitivity. The study was conducted in 47 consecutive patients attending t he Center for the Detection and Treatment of Cardiovascular and Metabolic R isk factors. The relationships between fasting and post-glucose load insuli n levels and the blood pressure (BP) responses to changes in salt intake, w ere investigated. No correlation was observed between fasting or 2-h post-l oad insulin levels and mean BP (MBP), systolic BP (SBP) or diastolic BP (DB P). The plasma concentrations of insulin were not significantly related to body mass index (BMI) (r(2) = 0.05; P = 0.135). Neither fasting nor 2-h pos t-load insulin predicted the BP response to changes in salt intake. A reduc tion in salt intake from 316 +/- 13 to 26 PM 3 mmoles/day, produced similar BP lowering in subjects with fasting insulin >15 mu U/ml and in subjects w ith normal fasting insulin levels (<15 mu U/ml). In addition, no relationsh ip was observed between the magnitude of the BP responses to salt and the l evels of insulin, either fasting (r(2) = 0.007; P = 0.86) or 2-h after a gl ucose load (r(2) = 0.01; P = 0.213). A very strong association was found be tween body weight or BMI and MBP (r(2) = 0.443; P < 0.0001). In conclusion, our results are against the view of a cause-effect relationship between in sulin and BP levels. In addition, the insulin status of a patient does not predict (nor determines) his (her) vascular reactivity to changes in salt i ntake. Finally, our findings further support the existence of a strong and direct association between body weight and hypertension, and speak against a major role of insulin in the pathogenesis of hypertension associated with obesity.