HIGHLIGHTED TOPIC Mechanisms of Sympathetic Regulation in Cardiovascular Disease Altered hemodynamics during muscle metaboreflex in young type 1 diabetes patients

Roberto S, Marongiu E, Pinna M, Angius L, Olla S, Bassareo P, Tocco F, Concu A, Milia R, Crisafulli A. Altered hemodynamics during muscle metaboreflex in young type 1 diabetes patients. J Appl Physiol 113: 1323–1331, 2012. First published June 14, 2012; doi:10.1152/japplphysiol.00280.2012.—A reduction in catecholamine levels during exercise has been described in young subjects with type 1 diabetes mellitus (DM1). It has been suggested that type 1 diabetes per se is associated with the loss of sympathetic response before any clinical evidence. Considering that an increase in sympathetic drive is required for normal cardiovascular response to muscle metaboreflex, the aim of this study was to assess the hemodynamics during metaboreflex in DM1 patients. Impedance cardiography was used to measure hemodynamics during metaboreflex activation, obtained through postexercise ischemia in 14 DM1 patients and in 11 healthy controls (CTL). Principal results were: 1) blunted blood pressure response during metaboreflex was observed in DM1 patients compared with the CTL; 2) reduced capacity to increase systemic vascular resistance was also witnessed in DM1 subjects; 3) DM1 subjects reported higher stroke volumes as a consequence of reduced cardiac afterload compared with the CTL, which led to a more evident cardiac output response, which partially compensated for the lack of vasoconstriction. These facts suggest that cardiovascular regulation was altered in DM1 patients and that there was a reduced capacity to increase sympathetic tone, even in the absence of any overt clinical sign. The metaboreflex test appears to be a valid tool to detect early signs of this cardiovascular dysregulation.