Salt sensitivity correlates positively with insulin sensitivity in healthy volunteers

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.

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).

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.

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.