Successful treatment of renovascular hypertension has no effect on insulin sensitivity.

BACKGROUND

The association of insulin resistance (IR) and essential hypertension is well known, but a causal relationship has not been proven. Patients with secondary hypertension as a result of renal artery stenosis (RAS) usually do not reveal IR, but no study has addressed the effect of blood pressure reduction after successful treatment of RAS on insulin sensitivity and glucose effectiveness.

PATIENTS AND METHODS

The insulin sensitivity index (SI) and glucose effectiveness (SG) were measured before and after successful intervention of an angiographically proven significant RAS in 18 out of 23 patients (eight males/10 females; mean age 51.5 +/- 13.1 years) in which improvement/cure of arterial hypertension was achieved. After a mean of 10.7 months, patients were reevaluated for 24-h blood-pressure measurement, kidney function, adrenaline, noradrenaline, plasma-renin-activity (PRA), aldosterone, atrial natriuretic peptide (ANP) and cyclic guanosine monophosphate (cGMP), and glucose metabolism parameters such as basal insulin, glucose disappearance constant (K-value), SI and SG. For calculation of SI and SG, insulin and glucose data from the modified frequent sampling intravenous glucose tolerance test (FSIGT) were submitted to the MINMOD program.

RESULTS

After intervention, systolic 24-h blood pressure had decreased from 156.1 +/- 16.4 mmHg to 139.9 +/- 15.1 mmHg, and diastolic 24-h blood pressure from 97.1 +/- 14.7 mmHg to 87.3 +/- 13.4 mmHg. No significant change in SI (before 4.3 +/- 2.0, after 4.8 +/- 2.0 min(-1) per microU mL(-1)) or SG (before 1.55 +/- 0.42x10(-2) min(-1), after 1.8 +/- 0.48x10(-2) min(-1)) was observed. Aldosterone decreased from 246.7 +/- 180.7 to 115 +/- 61.4 (P=0.009) as PRA decreased from 12.4 +/- 11.4 to 4.2 +/- 7.6 ng mL h(-1) (P=0.01). Creatinine clearance, and adrenaline and noradrenaline levels as well as ANP and cGMP did not change after treatment for RAS. Subsequent to the definition of IR (SI < or =3.2x10(-4) min(-1) per microU mL(-1)) some differences among these two subgroups (SI < or =3.2, or SI>3.2) could be found. Patients with IR (n=8) were characterized by a higher body mass index (BMI), higher basal insulin values and significantly lower cGMP values. Only the group without IR (n=10) developed significant improvement of systolic blood pressure.

CONCLUSION

We conclude that blood pressure reduction by treatment of RAS does not alter insulin action and that there is no link between the circulating concentrations of renin/aldosterone and glucose metabolism in renovascular hypertension (RVH). The results do not support the hypothesis of a direct link between blood pressure in RVH and the individual state of insulin sensitivity. However, patients with a normal SI are more likely to experience an almost normalization of arterial blood pressure after treatment for RAS.