Endothelial function, insulin sensitivity and inflammatory markers in hyperprolactinemic pre-menopausal women

BACKGROUND

Hyperprolactinemia has been reported to be associated with abnormalities of carbohydrate metabolism. The aim of this study was to evaluate the effects of hyperprolactinemia and bromocriptine (Brc) treatment on endothelial function, insulin sensitivity and inflammatory markers in pre-menopausal women.

METHODS

Sixteen hyperprolactinemic pre-menopausal women with pituitary adenomas were recruited and 20 healthy subjects were included as controls. Patients were given Brc in doses of 2.5-20 mg/dl until normal levels of prolactin were reached. Prior to treatment and 2 months after prolactin levels were normalized, the following tests were performed. Insulin sensitivity was determined by an oral glucose tolerance test based on a formula named the insulin sensitivity index (ISI composite). Endothelial function was measured as flow-mediated dilatation (FMD) on a brachial artery using high resolution ultrasound.

RESULTS

Serum glucose, insulin, estrogen, highly sensitive C-reactive protein (hsCRP), fibrinogen, homocysteine and uric acid levels were measured. Calculated ISI composite and FMD were significantly lower in the hyperprolactinemic group in comparison with the controls and improved after Brc treatment. Serum homocysteine, hsCRP and uric acid levels were significantly higher in hyperprolactinemic patients than in the controls and returned to normal levels with Brc treatment. Serum prolactin concentrations were inversely correlated with FMD measurements (r=-0.68; P<0.0001), ISI composite (r=-0.48; P<0.005) and serum estrogen (r=-0.54; P<0.005), and positively correlated with serum homocysteine concentrations (r=0.55; P<0.0001) in the hyperprolactinemic group.

CONCLUSIONS

The hyperprolactinemic state is associated with impaired endothelial function and decreased insulin sensitivity, which are early markers of atherosclerosis. These alterations may predispose to the development of atherosclerosis in non-treated cases. Correction of the hyperprolactinemic state is associated with improved endothelial function and insulin sensitivity.

Effect of angiotensin-converting enzyme inhibition on endothelial function and insulin sensitivity in hypertensive patients

INTRODUCTION

Evidence suggests an association between insulin resistance, hypertension and impaired endothelial function. Studies have shown that insulin resistance precedes the development of hypertension. By improving insulin sensitivity, it may be possible to improve hypertension and the subsequent damage to vessel walls. Some data indicates beneficial effects of angiotensin-converting enzyme (ACE) inhibitors on insulin sensitivity and endothelial function. We aimed to investigate these effects of ACE inhibition in the same group of patients with essential hypertension.

MATERIALS AND METHODS

Nine non-smoking, untreated hypertensive patients (38.3+9 years, 4/5 male/female) and 12 age-matched healthy subjects (35.2+6.7 years, 5/7 male/female) were included in the study. Hypertensive patients were given enalapril maleate (5 40 mg/day) for six months. The following parameters were studied at baseline and at the end of treatment period. Whole body insulin sensitivity was measured by a formula derived from an oral glucose tolerance test and named as the insulin sensitivity index (ISI). Insulin was measured by chemiluminescence and glucose by a glucose oxidase method. Endothelial function was evaluated as flow-mediated dilatation (FMD) of the brachial artery by ultrasonography and expressed as a percentage change relative to baseline diameter. Endothelial- independent vasodilatation was measured after sublingual nitroglycerine.

RESULTS

FMD was impaired in the hypertensive group compared with healthy subjects (7.3+3.1% vs. 15.3+4.8%, p<0.0005), and ISI values were 1.18+0.6 vs. 4.4+0.9 (p<0.0001) respectively. Both insulin sensitivity and FMD improved after the treatment period compared with baseline values, FMD increased from 7.3+3.1% to 16.0+2.9% (p<0.0005) and ISI from 1.18+0.6 to 4.2+1.0 (p<0.0001). FMD and ISI showed a significant positive correlation (r=0.67, p<0.001) in the hypertensive group.

CONCLUSIONS

Patients with essential hypertension have impaired endothelial function and decreased whole body insulin sensitivity compared with healthy subjects. Treatment for six months with enalapril maleate seems to improve both FMD and ISI. This study confirms the beneficial effects of ACE inhibition on both endothelial function and insulin sensitivity tested in the same group of essential hypertensive patients. The mechanism of these favourable effects of ACE inhibition needs to be clarified.