Sympathovagal balance and 1-h postload plasma glucose in normoglucose tolerant hypertensive patients

AIMS: Normoglucose tolerant (NGT) subjects with a 1-h postload plasma glucose (PLPG) value ≥155 mg/dL have an increased risk of type-2 diabetes and subclinical organ damage. Heart rate variability (HRV) reflects cardiac autonomic balance, frequently impaired in course of diabetes. At this time, no data support the association between 1-h PLPG and HRV; thus, we investigated the possible association between 1-h PLPG and HRV. METHODS: We enrolled 92 never-treated hypertensive subjects (56 women, 36 men), aged 55 ± 9.8 years. During OGTT, the patients underwent electrocardiographic recordings to evaluate HRV in the time domain (SDNN). Insulin sensitivity was assessed by Matsuda index. RESULTS: Among participants, 56 were NGT, 20 had impaired glucose tolerance (IGT), and 16 had type-2 diabetes. According to the 1-h PLPG cutoff point of 155 mg/dL, we divided NGT subjects into: NGT < 155 (n = 38) and NGT ≥ 155 (n = 18). Glucose tolerance status was associated with a significant (P < 0.0001) increase in PLPG and insulin and the reduction in Matsuda index. In all groups, the SDNN values significantly (P < 0.0001) decreased during the first hour of OGTT. A complete recovery in NGT groups was observed at the end of the second hour; in IGT and type-2 diabetes, SDNN remained significantly lower with respect to baseline values. At multiple regression analysis, Matsuda index resulted in the only determinant of SDNN modification, explaining the 12.3 % of its variability. CONCLUSIONS: Our data demonstrate that during OGTT, sympathovagal balance is acutely affected by both glucose and insulin modifications. Particularly, NGT ≥ 155 subjects behave in the same way of IGT and type-2 diabetes patients.