Background: The aim of the study was to assess the relationship between insulin sensitivity and salt sensitivity in healthy subjects who display a wide range of insulin sensitivity. As a secondary objective, we assessed the relationship between salt sensitivity and the other characteristics of the insulin resistance syndrome.
Study design: Forty-seven normotensive volunteers (age 34 +/- 15 years) with a normal glucose tolerance test were selected. We measured insulin sensitivity using the hyperinsulinaemic euglycaemic clamp (50 mU kg-1 h-1), blood pressure, waist-to-hip ratio, fasting insulin levels, serum lipids and uric acid levels. In a subset of 21, representing a wide range of insulin sensitivity, salt sensitivity was determined as the difference in mean arterial blood pressure (MAP) at the end of a high-salt diet (10 g of NaCl per day for 1 week) vs. a low-salt diet (2 g of NaCl per day for 1 week).
Results: Insulin sensitivity (M/I value, range 0.49-4.41 mg kg-1 min-1 per pmol L-1 x 100) was negatively correlated with MAP (r = -0.54, P < 0. 001) and waist-to-hip ratio (r = - 0.59, P < 0.001) but positively correlated with salt sensitivity (r = 0.47, P = 0.03). Salt sensitivity also correlated with high-density lipoprotein (HDL)-cholesterol (r = 0.46, P = 0.038) but not with waist-to-hip ratio, fasting insulin levels, low-density lipoprotein cholesterol, serum triglycerides or serum uric acid.
Conclusions: In healthy normotensive subjects who display a wide range of insulin sensitivity, as measured with the euglycaemic clamp technique, salt sensitivity correlates positively with insulin sensitivity and HDL-cholesterol, but not with the other characteristics of the insulin resistance syndrome.