Mario Siniscalchi

The effect of acute hyperglycaemia on QTc duration in healthy man.

Aims/hypothesis. Prolongation of heart rate-adjusted QT (QTc) is associated with an increased risk of coronary heart disease and sudden death. The objective of this study was to investigate whether acute increases of plasma glucose concentrations in healthy subjects could influence QTc and QTc dispersion. Methods. Plasma glucose concentrations were quickly raised to 15 mmol/l in 20 healthy subjects (10 men/10 women) and maintained for 2 h. On another occasion, and in random order, all subjects underwent the same hyperglycaemic clamp as above and an infusion of the somatostatin analogue octreotide (25 μg as iv bolus followed by a 0.5 g/min infusion) to block the release of endogenous insulin. Results. Systolic and diastolic blood pressures, heart rate and plasma catecholamine concentrations showed significant increases (p < 0.05) starting after 60 min of hyperglycaemia. QTc, QTc dispersion and PR interval also showed significant increments at 120 min of the hyperglycaemic clamp. The infusion of octreotide did not influence QTc duration, QTc dispersion, PR interval and the haemodynamic effects of acute hyperglycaemia. Conclusion/interpretation. The results show that acute hyperglycaemia produces significant increments of QTc and QTc dispersion in normal subjects. In this context, endogenously released insulin during acute hyperglycaemia seems to play a minor part. [Diabetologia (2000) 43: 571–575]

Erectile and endothelial dysfunction in Type II diabetes: a possible link.

Abstract.Aims/hypothesis: The aim of this study was to evaluate the relation between erectile dysfunction and endothelial functions, coagulation activation, peripheral and autonomic neuropathy in men with Type II (non-insulin-dependent) diabetes mellitus. Methods: We studied 30 Type II diabetic patients with symptomatic erectile dysfunction and 30 potent diabetic patients matched for age and disease. Endothelial functions were assessed with the l-arginine test, plasma thrombomodulin and cell adhesion molecules circulating concentrations. Haemostasis was evaluated with markers of thrombin activation and fibrinolysis. Quantitative sensory testing (vibratory, warming, and heat-pain thresholds), cardiovascular reflex tests and 24-h blood pressure monitoring were used to assess peripheral or autonomic neuropathy. Results: Mean erectile score and HbA1 c were 10.5 ± 5.8 and 8.3 ± 1.6 % in patients with erectile dysfunction, and 24.0 ± 0.7 and 6.8 ± 1.4 % in those without erectile dysfunction, respectively (p < 0.001); there was a significant relation between HbA1 c and erectile function score in patients with erectile dysfunction (r = –0.45, p = 0.02). The decrease in blood pressure and platelet aggregation in response to l-arginine was lower (p < 0.05–0.02) in patients with erectile dysfunction, whereas soluble thrombomodulin, P-selectin and intercellular cell ahhesion molecule-1 concentrations were higher (p < 0.05–0.02). Indices of coagulation activation (F1 + 2 and d-dimers) and reduced fibrinolysis (PAI-1) were also found to be higher in erectile dysfunction patients. Heat-pain and warm perception thresholds, as well as cardiovascular reflex tests, were most commonly abnormal in patients with erectile dysfunction (p < 0.05). In multivariate analysis, HbA1 c, MBP response to l-arginine, P-selectin, indices of coagulation, and quantitative sensory testing were independent predictors of erectile function score. Conclusion/interpretation: Erectile dysfunction in diabetic men correlates with endothelial dysfunction. A reduced nitric oxide activity might provide a unifying explanation. [Diabetologia (2001) 44: 1155–1160]

Myocardial lipid accumulation in patients with pressure-overloaded heart and metabolic syndrome

We evaluated the role of sterol-regulatory element binding protein (SREBP)-1c/peroxisome proliferator activated receptor-&ggr; (PPAR&ggr;) pathway on heart lipotoxicity in patients with metabolic syndrome (MS) and aortic stenosis (AS). Echocardiographic parameters of heart function and structural alterations of LV specimens were studied in patients with (n = 56) and without (n = 61) MS undergoing aortic valve replacement. Tissues were stained with hematoxylin-eosin (H and E) and oil red O for evidence of intramyocyte lipid accumulation. The specimens were also analyzed with PCR, Western blot, and immunohistochemical analysis for SREBP-1c and PPAR&ggr;. Ejection fraction (EF) was lower in MS compared with patients without MS (P < 0.001); no difference was found in aortic orifice surface among the groups. H and E and oil red O staining of specimens from MS patients revealed several myocytes with intracellular accumulation of lipid, whereas these alterations were not detected in biopsies from patients without MS. Patients without MS have low levels and weak immunostaining of SREBP-1c and PPAR&ggr; in heart specimens. In contrast, strong immunostaining and higher levels of SREBP-1c and PPAR&ggr; were seen in biopsies from the MS patients. Moreover, we evidenced a significative correlation between both SREBP-1c and PPAR&ggr; and EF and intramyocyte lipid accumulation (P < 0.001). SREBP-1c may contribute to heart dysfunction by promoting lipid accumulation within myocytes in MS patients with AS; SREBP-1c may do it by increasing the levels of PPAR&ggr; protein.

Tight Glycemic Control Reduces Heart Inflammation and Remodeling During Acute Myocardial Infarction in Hyperglycemic Patients

OBJECTIVES We analyzed the molecular mechanisms evoked by tight glycemic control during post-infarction remodeling in human hearts. BACKGROUND The molecular mechanisms by which tight glycemic control improves heart remodeling during acute myocardial infarction (AMI) are still largely unknown. METHODS Eighty-eight patients with first AMI undergoing coronary bypass surgery were studied: 38 normoglycemic patients served as the control group; hyperglycemic patients (glucose >or=140 mg/dl) were randomized to intensive glycemic control (IGC) (n = 25; glucose 80 to 140 mg/dl) or conventional glycemic control (CGC) (n = 25; glucose 180 to 200 mg/dl) for almost 3 days before surgery, with insulin infusion followed by subcutaneous insulin treatment. Echocardiographic parameters were investigated at admission and after treatment period. During surgery, oxidative stress (nitrotyrosine, superoxide anion [O(2)(-)] production, inducible nitric oxide synthase [iNOS]), inflammation (nuclear factor kappa B [NFkappaB], tumor necrosis factor [TNF]-alpha, and apoptosis (caspase-3) were analyzed in biopsy specimens taken from the peri-infarcted area. RESULTS Compared with normoglycemic patients, hyperglycemic patients had higher myocardial performance index (MPI) (p < 0.05), reduced ejection fraction (p < 0.05), more nitrotyrosine, iNOS, and O(2)(-) production, more macrophages, T-lymphocytes, and HLA-DR (Dako, Milan, Italy) cells, and more NFkappaB-activity, TNF-alpha, and caspase-3 levels (p < 0.01) in peri-infarcted specimens. After the treatment period, plasma glucose reduction was greater in the IGC than in the CGC group (p < 0.001). Compared with IGC patients, CGC patients had higher MPI (p < 0.02), had lower ejection fraction (p < 0.05), and had more markers of oxidative stress, more inflammation and apoptosis (p < 0.01) in peri-infarcted specimens. CONCLUSIONS Tight glycemic control, by reducing oxidative stress and inflammation, might reduce apoptosis in peri-infarcted areas and remodeling in AMI patients.

Morning Blood Pressure Peak, QT Intervals, and Sympathetic Activity in Hypertensive Patients

Abstract—We investigated the relation between morning blood pressure (BP) variations, sympathetic activity, and QT intervals in 156 never-treated subjects with essential hypertension and different patterns of morning BP increase. The morning BP peak (MP) was defined as a rise in systolic BP ≥50 mm Hg and/or diastolic BP ≥22 mm Hg during early morning (6:00 to 10:00 am) compared with mean BP during the night. Clinical characteristics of patients with morning BP peak (MP+, n= 69, morning systolic BP=+54±4, diastolic BP=+32±5 mm Hg) did not differ from patients without BP peak (MP−, n= 87, morning systolic BP=+24±5, diastolic BP=+19±3 mm Hg). The daytime (10:00 am to 10:00 pm) and the nighttime (10:00 pm to 6:00 am) BP profile did not differ between the two groups. During daytime and nighttime ECG monitoring, the corrected QT (QTc) interval, and QTc dispersion did not differ significantly between the two groups, whereas during the morning period the QT values were significantly broader in the MP+ group compared with the MP− group (P ≤0.001). Morning LF/HF ratio was significantly higher in MP+ patients than in MP− patients (P ≤0.02). Both systolic and diastolic morning BP, in combination with ratio LF/HF power, were significant predictors of QTc dispersion (adjusted R2=0.59, P ≤0.01) and QTc interval (adjusted R2=0.41, P ≤0.01), whereas inclusion of physical activity and echocardiographic parameters did not add explanatory information. The prolongation of cardiac repolarization times and morning sympathetic overactivity coexist in hypertensive patients with morning BP peaks, and they might contribute to raised cardiovascular risk in these patients.

Circulating microRNA changes in heart failure patients treated with cardiac resynchronization therapy: responders vs. non-responders

MicroRNAs (miRNAs) play an important role in the pathogenesis of structural alterations of the failing heart through their ability to regulate negatively the expression levels of genes that govern the process of adaptive and maladaptive cardiac remodelling. We studied whether LV reverse remodelling after CRT was associated with changes of circulating miRNAs in patients with heart failure (HF) and dyssynchrony.

Morning Blood Pressure Surge as a Destabilizing Factor of Atherosclerotic Plaque Role of Ubiquitin–Proteasome Activity

Whether morning blood pressure surge influences the molecular mechanisms of plaque progression toward instability is not known. Recently, we have demonstrated enhanced activity of the ubiquitin–proteasome system in human plaques and evidenced that it is associated with inflammatory-induced plaque rupture. We evaluated the inflammatory infiltration and ubiquitin–proteasome activity in asymptomatic carotid plaques of hypertensive patients with different patterns of morning blood pressure surge. Plaques were obtained from 32 hypertensive patients without morning blood pressure surge and 28 with morning blood pressure surge enlisted to undergo carotid endarterectomy for extracranial high-grade (>70%) internal carotid artery stenosis. Plaques were analyzed for macrophages, T-lymphocytes, human leukocyte antigen–DR+cells, ubiquitin–proteasome activity, nuclear factor-&kgr;B, inhibitor kB-&bgr;, tumor necrosis factor-&agr;, nitrotyrosine, matrix metalloproteinase-9, and collagen content (immunohistochemistry and ELISA). Compared with plaques obtained from hypertensive patients without morning blood pressure surge, plaques from with morning blood pressure surge had more macrophages, T-lymphocytes, human leukocyte antigen–DR+cells (P<0.001), ubiquitin-proteasome activity, tumor necrosis factor-&agr;, nuclear factor-kB (P<0.001), nitrotyrosine, and matrix metalloproteinase-9 (P<0.01), along with a lesser collagen content and IkB-&bgr; levels (P<0.001). Enhanced ubiquitin–proteasome activity in atherosclerotic lesions of patients with morning blood pressure surge is associated with inflammatory-dependent unstable plaque phenotype. These data suggest a potential interplay between morning blood pressure surge and ubiquitin–proteasome activity in atherosclerosis pathophysiology.

Sirtuin 6 Expression and Inflammatory Activity in Diabetic Atherosclerotic Plaques: Effects of Incretin Treatment

The role of sirtuin 6 (SIRT6) in atherosclerotic progression of diabetic patients is unknown. We evaluated SIRT6 expression and the effect of incretin-based therapies in carotid plaques of asymptomatic diabetic and nondiabetic patients. Plaques were obtained from 52 type 2 diabetic and 30 nondiabetic patients undergoing carotid endarterectomy. Twenty-two diabetic patients were treated with drugs that work on the incretin system, GLP-1 receptor agonists, and dipeptidyl peptidase-4 inhibitors for 26 ± 8 months before undergoing the endarterectomy. Compared with nondiabetic plaques, diabetic plaques had more inflammation and oxidative stress, along with a lesser SIRT6 expression and collagen content. Compared with non-GLP-1 therapy–treated plaques, GLP-1 therapy–treated plaques presented greater SIRT6 expression and collagen content, and less inflammation and oxidative stress, indicating a more stable plaque phenotype. These results were supported by in vitro observations on endothelial progenitor cells (EPCs) and endothelial cells (ECs). Indeed, both EPCs and ECs treated with high glucose (25 mmol/L) in the presence of GLP-1 (100 nmol/L liraglutide) presented a greater SIRT6 and lower nuclear factor-κB expression compared with cells treated only with high glucose. These findings establish the involvement of SIRT6 in the inflammatory pathways of diabetic atherosclerotic lesions and suggest its possible positive modulation by incretin, the effect of which is associated with morphological and compositional characteristics of a potential stable plaque phenotype.

The ubiquitin-proteasome system contributes to the inflammatory injury in ischemic diabetic myocardium: the role of glycemic control.

BACKGROUND Because the ubiquitin-proteasome pathway (UPS) is required for activation of nuclear factor kappa beta (NFkB), a transcription factor that regulates inflammatory genes, we evaluated the UPS activity, NFkB activation, and tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, in ischemic specimens of diabetic myocardium and relate them to the glycemic control (HbA(1c)), oxidative stress (nitrotyrosine, a modified amino acid produced by reactive O(2)), and cardiac outcome (echocardiographic parameters). Moreover, the role of UPS, NFkB, and TNF-alpha in the cardiac tissue injury of acute ischemia/reperfusion (I/R) was evaluated in streptozotocin (STZ)-hyperglycemic rats. Finally, this study aimed to elucidate whether an intervention on UPS with bortezomib, an inhibitor of UPS, may counteract the extensive myocardial infarction and increased inflammatory reaction into the hyperglycemic myocardium. METHODS Ventricular biopsy specimens from 16 nondiabetic and 18 type 2 diabetic patients presenting with unstable angina who underwent coronary artery bypass were collected during coronary bypass surgery. Ejection fraction (EF); myocardial performance index (MPI), which measures both systolic and diastolic function, immunostaining, and cardiac levels of nitrotyrosine; UPS activity; NFkB; and TNF-alpha were investigated in both ischemic human myocardium and heart tissue from STZ-hyperglycemic rats subject to a myocardial ischemia/reperfusion procedure. RESULTS We found that diabetic patients had higher MPI (P<.041) and reduced EF (P<.008) compared with nondiabetic patients. Diabetic specimens had higher nitrotyrosine, UPS activity, NFkB, and TNF-alpha levels compared with nondiabetic patients (P<.001). This was mirrored by consistently high levels of UPS and inflammatory markers in STZ-infarcted hearts, associated with high myocardial damage. In contrast, lesions from normoglycemic animals as well as from hyperglycemic rats treated with bortezomib showed low levels of ubiquitin-proteasome activity, inflammation, and myocardial damage (P<.01). CONCLUSIONS By contributing to the increased inflammation, the UPS overactivity may enhance the risk of complication during myocardial ischemia in diabetic patients.

Autonomic dysfunction is associated with brief episodes of atrial fibrillation in type 2 diabetes.

BACKGROUND AND AIMS This study aimed to investigate the relationship between asymptomatic episodes of atrial fibrillation (AF) and abnormalities of the autonomic nervous system in type 2 diabetic patients who did not have evidence of atrial fibrillation at baseline. METHODS AND RESULTS In a multicentric cross-sectional controlled study, 1992 patients with type 2 diabetes were screened. All underwent ambulatory ECG recording for 48-hour at 3, 6, 9, and 12months. Heart rate variability (HRV) was used as indicator of autonomic activity. One hundred seventy-six diabetics with silent atrial fibrillation episodes (SAFE group) and 288 without silent atrial fibrillation (non-SAFE group) were enrolled. These selected diabetics were matched on clinical and anthropometric data to 120 control subjects without diabetes of the control group. HRV analysis evidenced that LF/HF ratio was significantly higher in the SAFE group than in the non-SAFE group (P<0.05) in the whole period of HM analysis. AF absolute burdens were positively correlated with LF/HF ratio (r=0.31, P<0.001). Multiple regression analysis showed that LF/HF ratio was an independent determinant of AF episodes. CONCLUSIONS This study originally showed a strong relationship between autonomic dysfunction and silent atrial fibrillation in type 2 diabetes.