Relationship of plasma insulin concentration and insulin sensitivity to blood pressure. Is it modified by obesity?

To investigate the relationship between insulin level, insulin sensitivity and blood pressure in normoglycaemic men (n = 51) and women (n = 64) aged 53-61 years who were not receiving blood pressure medication and were participants in a previous population-based study.

Insulin sensitivity was estimated by the minimal model from a frequently sampled intravenous glucose tolerance test.

Systolic blood pressure (SBP) did not correlated significantly with fasting insulin level, 2 h insulin level or insulin sensitivity. Diastolic blood pressure (DBP) correlated positively with fasting insulin level but not with 2 h insulin level or insulin sensitivity. However, the positive association between fasting insulin level and DBP was not significant after adjustment for obesity and age. The relationship between high fasting insulin concentration and high DBP was stronger in lean than in obese subjects. The positive correlation between fasting insulin level and DBP was significant in lean but not in obese subjects.

The relationships between decreased insulin sensitivity and compensatory hyperinsulinaemia and blood pressure were rather weak. It is possible that different mechanisms may control blood pressure in lean and obese subjects, with a weaker association between insulin level and blood pressure in obese subjects. Alternatively, in obese subjects long-standing hyperinsulinaemia might increase blood pressure by mechanisms such as sympathetic activation and effects of vasculature, which may mask the underlying contribution of hyperinsulinaemia.