Context. Studies of platelet function in diabetics are inconsistent, some studies reporting higher platelet reactivity, while others showed no change.Objective. We aimed to evaluate platelet indices and in vitro platelet aggregation in rats with long-lasting (28 weeks) diabetes mellitus.Design. Twelve controls and 14 diabetic rats were investigated. Diabetes was induced in 11-week-old rats using streptozotocin (60 mg/kg,i.p.). Platelet indices and in vitro adenosine diphosphate (ADP)-, protease-activated receptor 4 (PAR4) agonist-, and arachidonic acid (AA)-induced platelet aggregation were assessed at the age of 38 weeks.Results. Compared to controls, diabetic rats presented lower platelet count and plateletcrit (both p≤0.001), and higher mean platelet volume (p<0.01). ADP-(p=0.04) and AA-induced (p<0.01) platelet aggregation were lower in diabetic compared with control rats, whereas PAR4 agonistinduced platelet aggregation was similar between the two groups (p=1.00).Conclusions. This study demonstrates a paradox of high intrinsic platelet reactivity and low in vitro ADP-and AA-induced platelet aggregation in diabetic rats compared with non-diabetic controls. The relevance of in vitro platelet aggregation to the contribution of platelets to in vivo thromboembolic events in diabetic rats remains questionable.

Funding Acknowledgements Type of funding sources: None. Background The involvement of apolipoprotein B (apoB) in atherogeneis is well known because of its role in the metabolism of lipids. Elevated levels of apoB have been found not only to be correlated with clinical atherosclerosis, but also with sub-clinical forms. Cardiovascular risk can be estimated based on clinical risk scores. However, the main limitation of these risk score models is to estimate only traditional risk factors and not other important factors such as apoB. Purpose To assess the interactive effects of apoB in asymptomatic patients, and its link to cardiovascular risk. Methods This prospective observational study included 811 asymptomatic participants. According to the median apoB value (set at 130 mg/ dl) the study population was divided into two groups as follows: group 1 – 713 patients with low apoB values and group 2 – 98 patients with high apoB. Also, for each patient personal data, such as family history of premature cardiovascular disease, smoker status, personal history of heart failure or atherosclerotis were obtained. Regarding the subclinical atherosclerosis the carotid thickness of intima-media was measured. Results Patients with high apoB are more frequent males (p=0.008) with a mean age of 57.6 ± 11.9 years old (p&lt;0.0001) and smokers (p=0.01). The apoB level was not higher in patients with known atherosclerosis or with traditional risk factors such as diabetes melitus, history of stroke, myocardial infarction, or hypertension. Although, subclinical atherosclerosis, expressed by the presence of carotid plaques is more frequent found in patients with elevated apoB levels (p=0.0001). A higher total cholesterol (p&lt;0.0001), triglycerides (p&lt;0.0001) and LDL-cholesterol levels (p&lt;0.0001) were identified in patients from group 2 compared with those form group 1. Moreover, the uric acid was observed to be correlated with the apoB serum level (5.2 ±1.5 vs. 6.2 ±1.7, p=0.001). The risk of diabetes melitus was also found to be higher in group 2 compared with group 1, expressed by the glycosylate haemoglobin (5.6 ± 0.7 vs 5.9 ± 1.1, p&lt;0.0001). Conclusions Apolipoprotein B level is correlated with subclinical atherosclerosis and worse outcomes expressed by a higher lipid profile and risk of diabetes melitus development. These findings highlighted that the determination of the apoB is therefore mandatory for a better stratification of cardiovascular risks in primary prevention of atherosclerosis.

No abstract

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI Background The autonomic control of the pacemaker current, If, and the molecular mechanisms underlying parasympathetic If modulation are well understood. Conversely, the effects of chronic If blockade on the parasympathetic nervous system and on the heart rate (HR) response to acute parasympathetic changes are still largely unknown. Such interactions could significantly influence the course of patients undergoing chronic therapy with the If blocker ivabradine. Purpose We aimed to assess the effects of long-term If blockade using ivabradine on cardiac autonomic modulation and on the cardiovascular response to acute in vivo and in vitro parasympathetic stimulation. Methods Radiotelemetry ECG transmitters were implanted in 6 Control and 10 ivabradine-treated male Wistar rats (IVA; 3 weeks, 10 mg/kg/day); sympathetic and parasympathetic heart rate variability parameters were assessed. At the end of the study, the right atrium was removed and right atrial HCN(1-4) RNA expression levels were analyzed. The HR and systolic blood pressure (SBP) responses to in vivo electrical stimulation of the right vagus nerve (2–20 Hz) and the spontaneous sinus node discharge rate (SNDR) response to in vitro cholinergic receptors stimulation using carbamylcholine (10-9–10-6 mol/L) were assessed in 6 additional Control and 10 IVA rats. Results At the end of the study, mean 24-h HR was significantly lower in the IVA compared with the Control rats (301.3 ± 7.5 bpm vs. 341.5 ± 8.3 bpm; p&lt; 0.01). Ivabradine administration led to a significant increase in vagal tone and shifted the sympatho-vagal balance towards vagal dominance (awake, asleep, and over 24-h; all p&lt; 0.05). In the Control rats, in vivo vagus nerve stimulation induced a progressive decrease in both the SBP (p = 0.0001) and the HR (p&lt; 0.0001). Meanwhile, in the IVA rats, vagal stimulation had no effect on the HR (p = 0.16) and induced a significantly lower drop in SBP (p&lt; 0.05). Ivabradine-treated rats also presented a significantly lower SNDR drop in response to carbamylcholine (p&lt; 0.01) and significantly higher HCN4 expression (p = 0.02). Conclusion Long-term If blockade using ivabradine caused a significant increase in vagal tone and shifted the autonomic balance towards vagal dominance in rats. Given the highly proarrhythmic effects of vagal activation at the atrial level, these findings could provide an explanation for the increased risk of atrial fibrillation associated with ivabradine use in clinical trials. In addition, ivabradine reduced the HR response to direct muscarinic receptors stimulation, canceled the cardioinhibitory response and blunted the hemodynamic response to in vivo vagal stimulation, and led to significant sinus node HCN4 up-regulation. These data suggest that ivabradine-induced HCN4 and the consequent If up-regulation could render the sinus node less sensitive to acute vagal inputs and could thus protect against excessive bradycardia induced by acute vagal activation.

Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS - UEFISCDI, within PNCDI III Background Numerous long-term pharmacologic manipulations of cardiac ion channels have shown potential to modify the expression of genes encoding proteins for those channels. Purpose We aimed to investigate whether long-term pharmacologic inhibition of the hyperpolarization-activated inward current (If) using ivabradine affects the right atrial expression of genes encoding for hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, responsible for If. Methods The right atrial mRNA expression of HCN1, HCN2, and HCN4, and of the neuron-specific HCN3 isoform was quantified in 6 control (Control) and 12 ivabradine-treated (IVA; 10 mg/kg, 4 weeks) adult male Wistar rats. The expression levels of the target genes were normalized with GAPDH housekeeping gene levels and compared between the two groups. Results Right atrial HCN1 and HCN2 expression levels were both similar (both p &gt;0.05) between the IVA and the Control rats. There was also no significant difference in the right atrial expression of the neuron-specific HCN3 isoform between the two groups (p = 0.22). However, the right atrial expression of HCN4, the most highly expressed HCN isoform in the sinus node, was significantly higher in the ivabradine-treated compared to the non-treated rats (p = 0.02). Conclusions Our study shows that chronic If blockade using ivabradine significantly up-regulates right atrial HCN4 expression. Although the examined samples contained both nodal and non-nodal tissue, since HCN4 is highly expressed in the nodal pacemaker cells and only sparsely in the remaining atrial myocardium, it is likely that the HCN4 changes observed in our study reflect sinus node alterations. HCN4 and a consequent If up-regulation could render the sinus node less sensitive to acute vagal inputs and protect against excessive vagal-induced bradycardia. Further studies will have to evaluate this hypothesis.