Effects of a mixed meal on hemodynamics and autonomic control of the heart in patients with type 1 diabetes

The effect of a high fat meal on heart rate variability and arterial stiffness in adolescents with or without type 1 diabetes

AIM

Type 1 diabetes (T1D) is associated with increased arterial stiffness and cardiac autonomic neuropathy. We tested whether those variables are acutely affected by a high fat meal (HFM).

METHODS

Responses to a HFM were measured in adolescents with T1D (N = 14) or without T1D (Control, N = 21). Heart rate variability (HRV), arterial stiffness, blood pressure (BP), and energy expenditure (EE) were measured before (baseline) and four times over 180 min postprandially.

RESULTS

T1D had higher blood glucose and insulin, but the suppression of fatty acids (~40%) and rise in triglycerides (~60%) were similar between groups. T1D had 9% higher EE, but postprandial increase in EE was similar to Controls. T1D had ~7 to 24% lower baseline HRV but a similar postprandial decline of ~8 to 25% as Controls. Both groups had a similar 2 to 5% increase in BP after the meal. Rate pressure product increased postprandially in both groups and was higher in T1D. Pulsewave velocity and augmentation index did not differ between groups or change postprandially.

CONCLUSION

Adolescents with T1D have evidence of cardiac autonomic dysfunction and increased EE, but those variables, along with arterial stiffness, are not acutely made worse by a HFM.

Effect of ingesting a meal and orthostasis on the regulation of splanchnic and systemic hemodynamics and the responsiveness of cardiovascular α1-adrenoceptors

Postprandial orthostasis activates mechanisms of cardiovascular homeostasis to maintain normal blood pressure (BP) and adequate blood flow to vital organs. The underlying mechanisms of cardiovascular homeostasis in postprandial orthostasis still require elucidation. Fourteen healthy volunteers were recruited to investigate the effect of an orthostatic challenge (60°-head-up-tilt for 20 min) on splanchnic and systemic hemodynamics before and after ingesting an 800-kcal composite meal. The splanchnic circulation was assessed by ultrasonography of the superior mesenteric and hepatic arteries and portal vein. Systemic hemodynamics were assessed noninvasively by continuous monitoring of BP, heart rate (HR), cardiac output (CO), and the pressor response to an intravenous infusion on increasing doses of phenylephrine, an α₁-adrenoceptor agonist. Neurohumoral regulation was assessed by spectral analysis of HR and BP, plasma catecholamine and aldosterone levels and plasma renin activity. Postprandial mesenteric hyperemia was associated with an increase in CO, a decrease in SVR and cardiac vagal tone, and reduction in baroreflex sensitivity with no change in sympathetic tone. Arterial α₁-adrenoceptor responsiveness was preserved and reduced in hepatic sinusoids. Postprandial orthostasis was associated with a shift of 500 mL of blood from mesenteric to systemic circulation with preserved sympathetic-mediated vasoconstriction. Meal ingestion provokes cardiovascular hyperdynamism, cardiac vagolysis, and resetting of the baroreflex without activation of the sympathetic nervous system. Meal ingestion also alters α₁-adrenoceptor responsiveness in the hepatic sinusoids and participates in the redistribution of blood volume from the mesenteric to the systemic circulation to maintain a normal BP during orthostasis.NEW & NOTEWORTHY A unique integrated investigation on the effect of meal on neurohumoral mechanisms and blood flow redistribution of the mesenteric circulation during orthostasis was investigated. Food ingestion results in cardiovascular hyperdynamism, reduction in cardiac vagal tone, and baroreflex sensitivity and causes a decrease in α₁-adrenoceptor responsiveness only in the venous intrahepatic sinusoids. About 500-mL blood shifts from the mesenteric to the systemic circulation during orthostasis. Accordingly, the orthostatic homeostatic mechanisms are better understood.

Cortisol, blood pressure, and heart rate responses to food intake were independent of physical fitness levels in women

This research tested the hypothesis that women who had higher levels of physical fitness will have lower hypothalamo-pituitary-adrenal axis (cortisol) and sympatho-adrenal medullary system (blood pressure and heart rate) responses to food intake compared with women who had low levels of physical fitness. Lower fitness (n = 22; maximal oxygen consumption = 27.4 ± 1.0 mL∙kg(-1)·min(-1)) and higher fitness (n = 22; maximal oxygen consumption = 41.9 ± 1.6 mL∙kg(-1)·min(-1)) women (aged 30-50 years; in the follicular phase of the menstrual cycle) who participated in levels of physical activity that met (lower fitness = 2.7 ± 0.5 h/week) or considerably exceeded (higher fitness = 7.1 ± 1.4 h/week) physical activity guidelines made their own lunch using standardised ingredients at 1200 h. Concentrations of cortisol were measured in blood samples collected every 15 min from 1145-1400 h. Blood pressures and heart rate were also measured every 15 min between 1145 h and 1400 h. The meal consumed by the participants consisted of 20% protein, 61% carbohydrates, and 19% fat. There was a significant overall response to lunch in all of the parameters measured (time effect for all, p < 0.01). The cortisol response to lunch was not significantly different between the groups (time × treatment, p = 0.882). Overall, both groups showed the same pattern of cortisol secretion (treatment p = 0.839). Systolic blood pressure, diastolic blood pressure, mean arterial pressure, or heart rate responses (time × treatment, p = 0.726, 0.898, 0.713, and 0.620, respectively) were also similar between higher and lower fitness women. Results suggest that the physiological response to food intake in women is quite resistant to modification by elevated physical fitness levels.

Subclinical myocardial dysfunction and cardiac autonomic dysregulation are closely associated in obese children and adolescents: the potential role of insulin resistance

Background

The prevalence of obesity is increasing among children/adolescents. Subtle cardiovascular abnormalities, responsible for a higher mortality later in life, have been reported in obese children/adolescents. The aims of the study were to evaluate cardiovascular autonomic regulation, by means of spectrum analysis of R-R interval variability, and myocardial function, by means of standard and tissue Doppler echocardiography, in a group of non-hypertensive asymptomatic obese children and adolescents; furthermore, the influence of insulin resistance was tested.

Subjects and Methods

R-R interval variability was analyzed during both the 70° head-up tilt and 24-hour electrocardiographic holter monitoring. Spectrum analysis of R-R interval variability provided the indices of sympathetic (low frequency [LF_RR]) and vagal (high frequency [HF_RR]) modulation of the sinoatrial node. Homeostasis model assessment of insulin resistance (HOMA-IR) was used to classify obese children/adolescents (n=72) as insulin resistant (n=37) and non-insulin resistant (n=35).

Results

In obese subjects: a) left ventricular mass was significantly (p<0.05) increased, whereas both the e/a ratio and the e'/a' ratio were decreased; b) at rest, HF_RR was lower, and the LF_RR/HF_RR ratio was higher; c) during tilting, magnitude of tilt-induced inhibition of HF_RR was lower; d) during 24-hour electrocardiographic holter monitoring, LF_RR and the LF_RR/HF_RR ratio were higher, whereas HF_RR was lower; e) HOMA-IR inversely correlated with both the e'/a' ratio (r=-0.655; p<0.001) and the tilt-induced LF_RR/HF_RR ratio (r=-0.933; p<0.001); and, f) the e'/a' ratio correlated with the tilt-induced LF_RR/HF_RR ratio (r=0.501; p<0.001). Moreover, HF_RR at rest, magnitude of tilt-induced HF_RR reduction, and the e'/a' ratio in insulin resistant obese children/adolescents were markedly lower when compared with the remaining subjects.

Conclusions

Subclinical abnormalities of myocardial function and of cardiac autonomic regulation were closely associated in obese children/adolescents and both correlated with the degree of insulin resistance.

Uncomplicated human type 2 diabetes is associated with meal-induced blood pressure lowering and cardiac output increase

AIMS

Since many type 2 diabetes patients experience postprandial hypotension, the aim of this study was to unravel meal-related changes in systemic hemodynamics and autonomic nervous system (ANS)-balance.

METHODS

Forty-two age-matched males (15 type 2 diabetes; 12 metabolic syndrome; 15 controls) without overt autonomic neuropathy received a standardized high-fat mixed meal after an overnight fast. Hemodynamic variables were measured by finger plethysmography. Fourier analysis was used to calculate the low-/high-frequency (LF/HF)-ratio, a marker of autonomic nervous system-balance, and baroreceptor reflex sensitivity (BRS).

RESULTS

Following the meal, diastolic blood pressure (DBP) decreased in type 2 diabetes patients only, paralleled by a significant decrement in systemic vascular resistance (SVR) and an increase in cardiac index. All groups showed an increase in postprandial heart rate. Controls, but not metabolic syndrome or type 2 diabetes patients, showed a meal-related increase in LF/HF-ratio. When combining all study subjects, homeostatic model assessment-insulin resistance (HOMA-IR) was inversely correlated with changes in DBP, SVR, LF/HF-ratio and BRS.

CONCLUSIONS

Based on these data, we hypothesize that in patients with uncomplicated type 2 diabetes, insulin resistance hampers adequate meal-induced sympathetic activation, leading to a decrease in SVR and resulting in a postprandial drop in DBP.

Cardiac autonomic regulation in response to a mixed meal is impaired in obese children and adolescents: the role played by insulin resistance

CONTEXT

Obesity in children/adolescents has been associated with subtle cardiac abnormalities, including myocardial dysfunction and cardiac autonomic dysregulation at rest, both likely responsible for a higher mortality in adulthood. Food intake induces remarkable adjustments of cardiovascular autonomic activity in healthy subjects.

OBJECTIVE

The objective of the study was to evaluate in obese children/adolescents meal-induced cardiac autonomic response and the role played by insulin resistance.

DESIGN AND SETTING

Sixty-eight obese and 30 matched normal-weight children/adolescents underwent blood sampling and cardiovascular autonomic analysis while recumbent and 20 minutes after a mixed meal ingestion. Spectrum analysis of the R-R interval and systolic blood pressure (SBP) variability provided the indices of sympathetic [low frequency (LFRR)] and vagal [high frequency (HFRR)] modulation of the sinoatrial node and the low frequency component of SBP. The homeostasis model assessment of insulin resistance served to separate insulin resistant (n = 35) from non insulin resistant (n = 33) obese children/adolescents.

RESULTS

At baseline, C-reactive protein, the LFRR to HFRR ratio, SBP, and low frequency oscillatory component of SBP variability in obese children/adolescents were significantly (P < .05) greater than in referent subjects, whereas high-density lipoprotein cholesterol and HFRR were lower; meal-induced increase in the LFRR to HFRR ratio was significantly less than in controls and exaggeratedly scanty (or opposite) among insulin resistant subjects. The homeostasis model assessment of insulin resistance index strongly and inversely correlated (r = -0.871; P < .001) with meal-induced changes in the LFRR to HFRR ratio among obese subjects.

CONCLUSIONS

Autonomic modulation of the heart was impaired after eating in obese children/adolescents. This abnormality was exaggerated among insulin resistant subjects and strongly correlated with the degree of insulin resistance.

Prognostic significance of heart rate turbulence parameters in patients with chronic heart failure

Background

This study is aimed to evaluate the clinical significance of heart rate turbulence (HRT) parameters in predicting the prognosis in patients with chronic heart failure (CHF).

Methods

From June 2011 to December 2012, a total of 104 CHF patients and 30 healthy controls were enrolled in this study. We obtained a 24-hour Holter ECG recording to assess the HRT parameters, included turbulence onset (TO), turbulence slope (TS), standard deviation of N-N intervals (SDNN), and resting heart rate (RHR). The relationships between HRT parameters and the prognosis of CHF patients were determined.

Results

The assessment follow-up period lasted until January 31, 2013. The overall mortality of CHF patients was 9.6% (10/104). Our results revealed that CHF patients had higher levels of TO than those of healthy subjects, but the TS levels of CHF patients were lower than that of the control group. CHF patients with NYHA grade IV had higher HRT_1/2 rate than those with NYHA grade II/III. There were statistical differences in TS, LVEF, SDNN and RHR between the non-deteriorating group and the non-survivor group. Significant differences in TS among the three groups were also found. Furthermore, CHF patients in the non-survivor group had lower levels of TS than those in the deteriorating group. Correlation analyses indicated that TO negatively correlate with SDNN, while TS positively correlated with SDNN and left ventricular ejection fraction (LVEF). We also observed negative correlations between TS and left ventricular end-diastolic cavity dimension (LVEDD), RHR, homocysteine (Hcy) and C-reactive protein (CRP). Multivariate Cox regression analysis further confirmed that LVEF (≤30%), HRT₂, SDNN and RHR were independent risk factors which can indicate poor prognosis in CHF patients.

Conclusions

Our findings indicate that HRT may have good clinical predictive value in patients with CHF. Thus, quantifying HRT parameters could be a useful tool for predicting mortality in CHF patients.

Effect of meal content on heart rate variability and cardiovascular reactivity to mental stress

Little is known about transient effects of foods and nutrients on reactivity to mental stress. In a randomized crossover study of healthy adults (n=20), we measured heart rate variability (respiratory sinus arrhythmia), blood pressure, and other hemodynamic variables after three test meals varying in type and amount of fat. Measurements were collected at rest and during speech and cold pressor tasks. There were significant postmeal changes in resting diastolic blood pressure (-4%), cardiac output (+18%), total peripheral resistance (-17%), and interleukin-6 (-27%). Heart rate variability and hemodynamic reactivity to stress was not affected by meal content. We recommend that future studies control for time since last meal and continue to examine effects of meal content on heart rate variability.