Exercise induces excessive normetanephrine responses in hypertensive diabetic patients

Exaggerated sympathoadrenal function has been accused of contributing to hypertension in type-2 diabetes. Recently, plasma unconjugated (free) metanephrines were reported to be stable markers of catecholamine hypersecretion. Thus, we aimed to examine whether unconjugated metanephrines are reliable markers of stress response induced by standardized cycling exercise and to identify differences in such stress responses between hypertensive and/or diabetic patients.

Type-2 diabetic patients with (DM/H; n= 8, 50 +/- 7 years, HbA1c: 7.7 +/- 0.6%) or without hypertension (DM/N; n = 6, 48 +/- 10 years, 7.5 +/- 1.8%) and nondiabetic hypertensive patients (H; n = 8, 56 +/- 4 years) were studied during incremental cycling exercise (15 min) to 75% of individual VO(2)max and during recovery (60 min). Plasma catecholamines and unconjugated metanephrines were measured by high-performance liquid chromatography with electrochemical detection. Hormone responses were quantified from the areas under the concentration-time curves and compared with those of age-, sex- and BMI-matched healthy volunteers (CON, n= 22).

Blood pressure responses of DM/H and H, but not DM/N, were greater than those of CON (P < 0.01), whereas heart rates increased similarly in all groups. Unconjugated normetanephrine responses were only increased (P = 0.04) in DM/H (2156 vs. 1133 pg mL(-1) min(-1) but not in DM/N (1528 vs. 1300 pg mL(-1) min(-1) and H (1960 vs. 1425 pg mL(-1) min(-1) when compared with respective CON. Unconjugated metanephrines did not change from baseline, whereas catecholamine responses were comparable in all groups.

The excessive response of plasma unconjugated normetanephrine to cycling may serve as a marker of exaggerated sympathoadrenal function in hypertensive type-2 diabetic patients.