Blood pressure, insulin, and C-peptide levels in San Luis Valley, Colorado

To explore the associations between blood pressure and both fasting insulin and C-peptide levels.

A cross-sectional analysis was conducted of 895 normoglycemic members of a bi-ethnic community in Colorado who were selected from a control group recruited for a geographically based study of diabetes mellitus prevalence and risk factors. All subjects included in this study had normal glucose tolerance as judged by a 75-g oral glucose tolerance test interpreted using World Health Organization criteria. None of the subjects were taking antihypertensive medication. Multiple linear regression analysis was used to examine relationships between fasting insulin and C-peptide levels and blood pressure.

Among all subjects, diastolic blood pressure was found to significantly increase with increasing levels of both hormones (insulin coefficient = 0.197, P = 0.013; C-peptide coefficient = 0.0436, P = 0.004), whereas systolic blood pressure was significantly related to fasting C-peptide level (coefficient = 0.0295, P = 0.050). These relationships were similar in magnitude for both Hispanic and non-Hispanic white subjects, but were diminished among women and subjects with a higher body mass index.

Higher fasting insulin and C-peptide levels are associated with higher blood pressure, but these relationships are modified by sex and degree of obesity.