Insulin Resistant Women Exhibit Abnormal Vascular Reactivity To Mental Challenge

Abstract

Insulin resistant women have reduced blood flow to working muscles. Whether other autonomic responses are different from women possessing normal insulin levels is undetermined. PURPOSE: To examine the hemodynamic implications of insulin resistance (IR). METHODS: Seven normotensive, insulin-resistant women and 11 age-matched healthy women with normal fasting insulin with respect to mental challenge response were compared. During 10 min of the Stroop task heart rate, blood pressure, cardiac output, systemic vascular resistance, vascular resistance, and vascular conductance were assessed using impedance cardiography and venous occlusion. Peak oxygen uptake was measured using open-circuit spirometry. RESULTS: The IR and control groups were of similar weight (64 versus 69 kg), BMI (24 versus 26 kg/m2), age (21.9 versus 22.8 years), blood pressure (115/69 versus 117/67 mmHg), and peak aerobic power (32.1 versus 28.2 ml·kg-1·min-1). The IR group possessed significantly higher fasting insulin (49.8 versus 11.7 μU/ml) and HOMA-IR (9.8 versus 2.5). During Stroop forearm vascular resistance significantly increased for the IR compared to controls (+12.5 versus −11.7 ml·100 ml tissue-1·min-1), whereas forearm vascular conductance change was significantly decreased (−0.4 versus +0.7 ml·100 ml tissue-1·min-1). Controls demonstrated increased cardiac output (.8 L/min) and a small increase in vascular resistance (+13 dyne.s.cm-5), whereas IR subjects demonstrated a smaller increase in cardiac output (.2 L/min) and a significantly larger increase in systemic vascular resistance (+197 dyne.s.cm-5). CONCLUSIONS: IR women showed a blunted cardiac output and an exaggerated systemic vascular resistance response to mental challenge. This pattern of cardiac output and vascular resistance response may be a marker for future hypertension in young normotensive, hyperinsulinemic women.