Circadian rhythm of the autonomic nervous system in insulin resistant subjects with normoglycemia, impaired fasting glycemia, impaired glucose tolerance, type 2 diabetes mellitus

Abstract

BackgroundIn type 2 diabetes mellitus both insulin resistance and hyperglycemia are considered responsible for autonomic dysfunction. The relation between the autonomic activity, impaired fasting glycemia and impaired glucose tolerance is, however, unclear. The purpose of this study was to evaluate and compare the circadian autonomic activity expressed as heart rate variability (HRV) measured by 24-hours ECG recording in insulin resistant subjects (IR) with characteristics as follow: IR subjects with normal oral glucose tolerance test results, IR subjects with impaired fasting glucose, IR subjects with impaired glucose tolerance and subjects with type 2 diabetes mellitus.MethodsEighty Caucasian insulin resistant subjects (IR) and twenty five control subjects were recruited for the study. IR subjects were divided into four groups according to the outcoming results of oral glucose tests (OGTTs): IR subjects with normal glucose regulation (NGR), IR subjects with impaired fasting glycemia (IFG), IR subjects with impaired glucose tolerance (IGT) and subjects with type 2 diabetes mellitus (DM). Autonomic nervous activity was studied by 24-hours ECG recording. Heart rate variability analysis was performed in time and frequency domains: SDNN, RMS-SD, low frequency (LF) and high frequency (HF) were calculated.ResultsThe total SDNN showed statistically significant reduction in all four groups with insulin resistant subjects (IR) when compared to the control group (p <0,001). During night LF normalized units (n.u.) were found to be higher in all four groups including IR subjects than in the control group (all p < 0,001) and subjects with normal glucose regulation (NGR), with impaired fasting glycemia (IFG) and with impaired glucose tolerance (IGT) were found to have higher LF n.u. than those in the type 2 diabetes mellitus group. The linear regression model demonstrated direct association between LF values and the homeostasis model assessment-index (HOMA-I), in the insulin resistant group (r = 0,715, p <0,0001).ConclusionThe results of our study suggest that insulin resistance might cause global autonomic dysfunction which increases along with worsening glucose metabolic impairment. The analysis of sympathetic and parasympathetic components and the sympathovagal balance demonstrated an association between insulin resistance and sympathetic over-activity, especially during night. The results indicated that the sympathetic over-activity is directly correlated to the grade of insulin resistance calculated according to the HOMA-I. Since increased sympathetic activity is related to major cardiovascular accidents, early diagnosis of all insulin resistant patients should be contemplated.

Heart rate variability and endothelial function after sleep deprivation and recovery sleep among male shift and non-shift workers

“…Shift and non-shift workers also showed significant differences in HRV parameters: SDNN, RMSSD, and SDSD were significantly lower and LF/HF was significantly higher among the shift workers. Lower SDNN, RMSSD, and SDSD reflect a lower variance and higher LF/HF indicates higher sympathetic and/or lower parasympathetic activity, both factors being associated with a higher risk of CVD (13,15,17). The current findings thus support the idea of increased cardiovascular risk among shift workers.…”

“…In addition, the cardiac sympathetic/parasympathetic balance, is thought to be reflected in the low frequency/high frequency (LF/HF) ratio. A lower variance (eg, lower SDNN) in the ECG and a shift towards a higher LF/HF ratio (ie, higher sympathetic and/or lower parasympathetic activation) has been strongly associated with CVD and related conditions such as stress, metabolic syndrome, and diabetes (12)(13)(14)(15)(16)(17)(18).…”

Improvements in heart rate variability with exercise therapy

“…However, it is possible that a completely different mechanism is responsible for autonomic denervation in this group (39). diabetes mellitus Impaired autonomic nervous function among patients with diabetes as assessed by HRV has been observed in otherwise healthy adults (41,42), as well as in children (43) and adolescents (41,44). Both short-term (45-47) and 24 h (48,49) assessments have revealed the prognostic significance of HRV among individuals with type 1 and/or type 2 diabetes (Table 2).…”

Autonomic nervous system activity is independently associated with the risk of shift in the non-dipper blood pressure pattern

“…[15][16][17] In addition, information regarding introduction of an antihypertensive treatment (angiotensin-converting enzyme or angiotensin-receptor blocker, b-blockers, diuretics, calcium channel blockers or other antihypertensive drugs) between the two examinations was collected at the second examination.…”