Autonomic nervous system and risk factors for vascular disease. Effects of autonomic unbalance in schizophrenia and Parkinson’s disease

Dopamine D4 receptor subtype activation reduces the rat cardiac parasympathetic discharge

The dopaminergic system influences the heart rhythm by inhibiting the rat cardiac sympathetic and parasympathetic neurotransmissions through activation of D₂-like receptors (encompassing the D₂, D₃, and D₄ subtypes). Whereas D₂ receptor subtype activation results in cardiac sympatho-inhibition, the dopamine receptor subtypes involved in rat cardiac vago-inhibition remain unknown. Hence, this study investigated the specific functional role of the D₂-like receptor subtypes (D₂, D₃, and/or D₄) inhibiting the rat heart cholinergic drive. For this purpose, male Wistar rats were pithed and prepared for cardiac vagal stimulation. Bradycardic responses were obtained by electrical stimulation of vagal fibres (3, 6, 9 Hz; n = 100) or i.v. acetylcholine (ACh; 1, 5, 10 μg/kg; n = 15). Expression of D₂, D₃, and D₄ receptors was studied in left and right atrium samples by PCR (n = 4). Intravenous injections of quinpirole (D₂-like agonist; 1-30 μg/kg), but not of SFK-38393 (D₁-like agonist; 1-30 μg/kg), dose-dependently inhibited the vagally induced bradycardia. The vago-inhibition induced by quinpirole (which failed to affect the bradycardia to i.v. ACh) was unchanged after i.v. injections of the antagonists L-741,626 (D₂; 100 μg/kg) or SB-277011-A (D₃; 100 μg/kg), but it was abolished by L-745,870 (D₄; 100 μg/kg). mRNA levels of D₂, D₃, and D₄ receptor subtype were detected in the left and right rat atria. Our results suggest that the quinpirole-induced vagolytic effect involves prejunctional D₄ receptor subtypes, located in the left and right atria. This provides new evidence on the relevance of D₄ receptor modulating the heart parasympathetic control.

Influence of Acute Antipsychotic Treatment on Cardiorespiratory Coupling and Heart Rate Variability

A major contributing factor associated with increased cardiac mortality in patients with schizophrenia (SCZ) seems to be a dysfunction of the autonomic nervous system (ANS). The link between ANS dysfunction and SCZ is multifactorial, but some reports suggest that the use of antipsychotics could be implicated. This case illustrates the time course of autonomic improvement in response to antipsychotic treatment in an inpatient with SCZ in acute psychosis. To this end, we documented markers of autonomic function during hospitalization. Heart rate variability (HRV; cardiac autonomic modulation) analysis showed an increased variability over time (from Day 1 to Day 3), with strongest reaction at Day 3. The respiration analysis showed an increased respiratory variability over time (from Day 1 to Day 3) suggesting improved autonomic modulation in response to the pharmacotherapy. Cardiorespiratory coupling (CRC; surrogate of cardiorespiratory synchrony and cardiovagal modulation) showed an increasing influence of heart rate on respiration and increased from Day 1 to Day 3. The concurrent improvement of psychosis and autonomic function in response to antipsychotic treatment in this patient suggest a potential cardio protective role of antipsychotics in the acute setting. Prospective trials aimed at examining the cardiovascular implications of acute psychosis treatment in patients with schizophrenia are warranted.

Higher mortality after myocardial infarction in patients with severe mental illness: a nationwide cohort study

OBJECTIVES

The aim of this study was to explore the impact of severe mental illness (SMI) on myocardial infarction survival and determine the influence of risk factor burden, myocardial infarction severity and different treatments.

DESIGN, SETTING AND PARTICIPANTS

This population-based cohort study, conducted in Sweden during the period 1997-2010, included all patients with a first diagnosis of myocardial infarction in the Swedish nationwide myocardial infarction register SWEDEHEART (n = 209 592). Exposure was defined as a diagnosis of SMI (i.e. bipolar disorder or schizophrenia) in the national patient register prior to infarction. Bias-minimized logistic regression models were identified using directed acyclic graphs and included covariates age, gender, smoking, diabetes, previous cardiovascular disease, myocardial infarction characteristics and treatment.

MAIN OUTCOME MEASURES

The outcomes were 30-day and 1-year mortality, obtained through linkage with national population registers.

RESULTS

Patients with bipolar disorder (n = 442) and schizophrenia (n = 541) were younger (mean age 68 and 63 years, respectively) than those without SMI (n = 208 609; mean age 71 years). The overall 30-day and 1-year mortality rates were 10% and 18%, respectively. Compared with patients without SMI, patients with SMI had higher 30-day [odds ratio (OR) 1.99, 95% confidence interval (CI) 1.55-2.56] and 1-year mortality (OR 2.11, 95% CI 1.74-2.56) in the fully adjusted model. The highest mortality was observed amongst patients with schizophrenia (30-day mortality: OR 2.58, 95% CI 1.88-3.54; 1-year mortality: OR 2.55, 95% CI 1.98-3.29).

CONCLUSION

SMI is associated with a markedly higher mortality after myocardial infarction, also after accounting for contributing factors. It is imperative to identify the reasons for this higher mortality.

Hyperlipidemia in patients with schizophrenia: a national population-based study

OBJECTIVE

The objective was to examine hyperlipidemia among Taiwanese patients with schizophrenia.

METHODS

We obtained a random sample of 766,427 subjects aged ≥18 years in 2005. Subjects with at least one primary diagnosis of schizophrenia and with a primary or secondary diagnosis of hyperlipidemia or medication for hyperlipidemia were identified. We compared the prevalence and incidence of hyperlipidemia in schizophrenic patients with the general population.

RESULTS

The prevalence of hyperlipidemia in patients with schizophrenia was higher than that in the general population (8.15% vs. 8.10%; odds ratio 1.17; 95% confidence interval, 1.04-1.31) in 2005. Compared with the general population, schizophrenic patients had a higher prevalence of hyperlipidemia in individuals aged <50 years, among those with higher insurance amount, and among persons living in northern and central regions and in urban areas. The average annual incidence of hyperlipidemia in schizophrenic patients with second-generation antipsychotic use from 2006 to 2008 was higher than that in the general population (1.57% vs. 1.29%; odds ratio 1.31; 95% confidence interval, 1.11-1.55).

CONCLUSIONS

Patients with schizophrenia had a much higher prevalence of hyperlipidemia in young adulthood than that in the general population. Schizophrenic patients with second-generation antipsychotic exposure had a higher incidence of hyperlipidemia than individuals in the general population.

Serum adiponectin levels in advanced-stage Parkinson's disease patients

Patients with advanced Parkinson's disease (PD) experience body weight loss and reductions in the most common cardiovascular risk factors. At present, the pathogenetic mechanisms involved have not been elucidated. Increased serum concentrations of adiponectin, which possesses antiatherogenic and anti-inflammatory properties, are associated with a reduction in cardiovascular risk. The objective of this study was to determine adiponectin serum concentrations in PD patients. Thirty PD patients underwent a full nutritional status assessment, including the determination of adiponectin serum concentrations. Mean ± SD adiponectin concentrations were 9.59 ± 5.9 μg/mL (interquartile range: 5.92–12.9 μg/mL). In PD patients, adiponectin serum levels were similar to those in normal-weight, healthy, young subjects and significantly higher than that in an aged-matched group of morbidly obese subjects. Further studies are warranted to establish the role of adiponectin in the management of PD patients.

Insulin resistance and metabolic profile in antipsychotic naïve schizophrenia patients

OBJECTIVES

Several studies have suggested insulin resistance related to dyslipidemia and body weight in drug treated schizophrenia patients. Although, insulin resistance or impaired glucose tolerance is also reported in antipsychotic naïve schizophrenia patients, their relationship with dyslipidemic changes and body weight is not well established. The present study was undertaken to examine insulin resistance in antipsychotic naïve schizophrenia patients of this region and to evaluate any association between lipid parameters and body weight with their insulin resistance, if any.

METHOD

Plasma glucose, total serum cholesterol and its LDL, HDL fractions, and serum insulin levels were measured from fasting blood samples of newly diagnosed, antipsychotic naïve schizophrenia patients (n=30) and matched control group (n=25) in a hospital based case control study. Homoeostatic model assessment (HOMA) was done to evaluate insulin resistance.

RESULTS

Means of plasma glucose, total serum cholesterol and its LDL, HDL fractions did not vary significantly (p>0.05) between cases and control. Insulin resistance was significantly increased (p<0.05) in drug naïve cases. Multiple linear regression analyses did not show any association (p>0.05) between insulin resistance and lipid parameters.

CONCLUSIONS

Newly diagnosed schizophrenia patients were more prone to insulin resistance in our study population. This was not associated with any dyslipidemic changes as the lipid parameters were not elevated in them compared to the healthy controls. It was not dyslipidemia, but some other common genetic or risk factors that might be responsible for the increased insulin resistance in antipsychotic naïve schizophrenia patients in our study population.