Effects of nicotinic acid on insulin sensitivity and blood pressure in healthy subjects

Insulin resistance and hyperinsulinaemia are associated with hypertension a lthough a causative relationship has not been established. The aim of this study was to determine whether a short term reduction in insulin sensitivit y induced by nicotinic acid treatment (NA) would alter blood pressure. The study was a double-blind randomised placebo-controlled cross-over study, Se ven healthy volunteers, three males and four females were randomised to pla cebo or NA 500 mg daily for 7 days then 1 g daily for a further 7 days, Hyp erinsulinaemic euglycaemic clamp, indirect calorimetry, 24-h ambulatory blo od pressure monitoring (ABPM) and forearm blood flow measurement (FABF) wer e performed at day 14 of each treatment phase. NA significantly reduced the glucose Infusion rate required to maintain euglycaemia in all subjects (pl acebo vs NA; 31.5 +/- 4.2 vs 26.2 +/- 4.6 mu mol/kg/min, P = 0.002) associa ted with a decrease in non-oxidative glucose disposal. NA did not significa ntly alter 24-h mean systolic or diastolic blood pressure. Fasting glucose, insulin and non-esterified free fatty acid (NEFA) levels remained unchange d, energy expenditure and substrate oxidation were not altered by NA. These results suggest a short term reduction in insulin sensitivity with NA is n ot accompanied by a change in blood pressure. This may relate to the short duration of treatment, to a dissociation between insulin resistance and hyp ertension or to other homeostatic mechanisms which prevent blood pressure r ising in subjects not predisposed to hypertension.