Serum Insulin Levels, 24-Hour Blood Pressure Profile, and Left Ventricular Mass in Nonobese Hypertensive Patients

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Abstract
Abstract In essential hypertensive patients, considered to be insulin-resistant, a blunted decline in nocturnal blood pressure is associated with increased adrenergic tone and left ventricular mass. Since insulin stimulates the sympathetic system, we tested whether insulin resistance and insulinemia influence left ventricular mass and the 24-hour blood pressure profile. We studied 29 nonobese hypertensive patients with office diastolic pressure between 95 and 110 mm Hg and normal oral glucose tolerance test after a 4-month washout period. They were then assigned to M-mode echocardiographic evaluation and 24-hour ambulatory blood pressure monitoring. The glucose and insulin responses to a 75-g oral glucose load were compared with those obtained in 16 weight-matched normotensive control subjects. During the oral glucose tolerance test the hypertensive patients compared with control subjects presented higher levels of glucose at 60 minutes (138.7±30.3 versus 108.7±35.7 mg/dL; P <.05) and 90 minutes (114.0±23.8 versus 94.8±31.1 mg/dL; P <.05) and insulin at 60 minutes (287.1±259.4 versus 142.1±83.9 pmol/L; P <.05). However, peak insulin levels after glucose load did not correlate with ambulatory blood pressure values or left ventricular mass index. Left ventricular mass index showed significant correlation with mean sleeping systolic pressure ( r s =.56, P <.05) and diurnal systolic pressure ( r s =.37, P <.05) but not with mean diurnal or sleeping diastolic pressures. In conclusion, our results indicate that in nonobese hypertensive patients, insulin resistance does not have any influence on the 24-hour blood pressure profile or on left ventricular mass index. Blood pressure levels during sleep in these patients seem to contribute to increases in left ventricular mass.