The relation of glucose metabolism to left ventricular mass and function and sympathetic nervous system activity in obese subjects with metabolic syndrome.

Journal of Clinical Endocrinology and Metabolism

PubMedID: 23271752

Straznicky NE, Grima MT, Sari CI, Karapanagiotidis S, Wong C, Eikelis N, Richards KL, Lee G, Nestel PJ, Dixon JB, Lambert GW, Schlaich MP, Lambert EA. The relation of glucose metabolism to left ventricular mass and function and sympathetic nervous system activity in obese subjects with metabolic syndrome. J Clin Endocrinol Metab. 2013;98(2):E227-37.
CONTEXT
Altered cardiac structure and function have been reported in prediabetic and diabetic populations; however, the contribution of the sympathetic nervous system (SNS) to these changes has yet to be delineated.

OBJECTIVE
Our objective was to examine interrelationships between glucose metabolism, left ventricular mass and function, and SNS activity in obese metabolic syndrome subjects.

PARTICIPANTS AND METHODS
Unmedicated impaired glucose tolerant (IGT) (n = 31) or treatment-naive type 2 diabetic (T2D) (n = 25) subjects, matched for age (mean 58 ± 1 years), gender, body mass index (32.2 ± 0.5 kg/m(2)), and blood pressure, participated. They underwent echocardiography and assessments of whole-body norepinephrine kinetics, muscle sympathetic nerve activity, and insulin sensitivity by euglycemic clamp (M value).

RESULTS
T2D subjects had higher left ventricular mass index (LVMI) (93.6 ± 3.5 vs 77.2 ± 3.4 g/m(2), P = .002) and Doppler-derived isovolumetric relaxation and deceleration times (both P < .05) and lower early/late transmitral inflow velocities (E/A) (P = .02) compared with IGT. Total muscle sympathetic nerve activity and arterial norepinephrine concentration were higher in the T2D group (by 18% and 32%, respectively, both P = .05), whereas plasma norepinephrine clearance was reduced (1.94 ± 0.11 vs 2.26 ± 0.10 L/min, P = .02). M value correlated inversely with left ventricular septal thickness (r = -0.46, P = .007). Whole-body noradrenaline spillover rate correlated with LVMI in the T2D subgroup (r = 0.47, P = .03). In the pooled cohort, LVMI was independently predicted by pulse pressure (r = 0.38, P = .004) and E/A ratio by 2-hour glucose (r = -0.38, P = .005).

CONCLUSIONS
Transition from IGT to T2D is associated with cardiac enlargement and diastolic dysfunction, which relate to metabolic, hemodynamic, and SNS alterations.