To investigate insulin sensitivity and the influence of level of physical fitness in men with a family history of hypertension and in control subjects.Design
Insulin sensitivity was determined and physical fitness estimated in 39 normotensive, glucose-tolerant men with a family history of hypertension (Relatives group) and in 29 age- and body mass index-matched normotensive men with no such family history (Controls group).Methods
The euglycaemic hyperinsulinaemic clamp technique (steady-state insulin concentration approximately 100mU/I) was used to determine insulin sensitivity. Physical fitness, measured as maximal oxygen uptake, was estimated from the heart rate response to a submaximal exercise test.Results
Insulin sensitivity index and estimated maximal oxygen uptake were lower in the Relatives than in the Controls. There was a positive correlation between insulin sensitivity and maximal oxygen uptake in both groups. In the Controls there was a negative correlation between insulin sensitivity and waist: hip ratio, but this relationship was not found in the Relatives.Conclusions
The present findings indicate that reduction of insulin sensitivity precedes the development of high blood pressure and may be coupled to low physical fitness. As abdominal fat distribution seems not to be related to insulin sensitivity in subjects with a family history of hypertension, changes in muscle fibre composition or muscle glucose metabolism, or both, might explain the lower insulin sensitivity and physical fitness in the Relatives.