Anne Zanchi

Poly(ADP-Ribose) Polymerase Is Activated in Subjects at Risk of Developing Type 2 Diabetes and Is Associated With Impaired Vascular Reactivity

Background—We have previously shown that endothelial function is impaired not only in diabetes but also in subjects at risk of developing type 2 diabetes. We hypothesized that changes in the expression or activity of the endothelial isoform of nitric oxide synthase (eNOS), the receptor for advanced glycation end products (RAGE), and poly(ADP-ribose) polymerase (PARP) are related to this impairment. Methods and Results—We included a control group of 21 healthy subjects, a group of 22 healthy individuals with parental history of type 2 diabetes, a group of 23 subjects with impaired glucose tolerance, and a group of 21 type 2 diabetic patients. Two 2-mm forearm skin biopsies were taken from each participant and used for measurements. The percentage of PARP-positive endothelial nuclei was higher in the group with parental history of type 2 diabetes and diabetic patients compared with the controls (P <0.001). Immunoreactivity for nitrotyrosine (a marker of reactive nitrogen species) was higher in the diabetic group compared with all other groups (P <0.01). No differences in the expression of eNOS and RAGE were found among all 4 groups. The polymorphism of the eNOS gene was also studied and was not found to influence eNOS expression or microvascular functional measurements. Conclusions—PARP activation is present in healthy subjects at risk of developing diabetes as well as in established type 2 diabetic patients, and it is associated with impairments in the vascular reactivity in the skin microcirculation.

Blockade of the renin-angiotensin-aldosterone system : a key therapeutic strategy to reduce renal and cardiovascular events in patients with diabetes

Diabetes (particularly type 2 diabetes) represents a global health problem of epidemic proportions. Individuals with diabetes are not only more likely to develop hypertension, dyslipidemia, and obesity, but are also at a significantly higher risk for coronary heart disease, peripheral vascular disease, and stroke. Angiotensin II plays a key pathophysiological role in the progression of diabetic renal disease, and blockade of the renin–angiotensin system with angiotensin-converting enzyme inhibitors (ACEi) or angiotensin II antagonists has therefore become an important therapeutic strategy to reduce renal and cardiovascular events in patients with diabetes. Several studies have demonstrated the effects of angiotensin II antagonists on the reduction of albuminuria and the progression of renal disease from microalbuminuria to macroalbuminuria. More importantly, several endpoint trials have shown that the antiproteinuric effects of losartan and irbesartan translate into cardiovascular and renoprotective benefits beyond blood pressure lowering, thereby delaying the need for dialysis or kidney transplantation by several years. These and other studies indicate that angiotensin II antagonists not only improve survival and quality of life of patients with diabetic nephropathy, but also have the potential to reduce the substantial healthcare burden associated with managing these patients. ACEi also appear to exert similar beneficial effects in diabetic patients, but whether clinically significant differences in renoprotection or mortality exist between angiotensin II antagonists and ACEi in patients with type 2 diabetes remains to be fully investigated in appropriate head-to-head studies.

Aortic Connexin43 Is Decreased During Hypertension Induced by Inhibition of Nitric Oxide Synthase

Connexin43 (Cx43), the predominant gap junction protein in vessels and heart, is involved in the control of cell-to-cell communication and is thought to modulate the contractility of the vascular wall and the electrical coupling of cardiac myocytes. We have investigated the effects of arterial hypertension induced by inhibition of nitric oxide synthase on the expression of Cx43 in aorta and heart as well as on the distensibility of the carotid artery. Administration of 0.4 g/L NG-nitro-L-arginine methyl ester (L-NAME) to rats in their drinking water for 4 weeks increased intra-arterial mean blood pressure, wall thickness of aorta and carotid artery (25%), and heart weight (17%). Analysis of heart mRNA demonstrated increased expression of the fetal skeletal alpha-actin and of atrial natriuretic peptide but not of Cx43. In contrast, Cx43 mRNA and protein were decreased by 50% in the aortas of L-NAME-treated rats that did not show increased carotid distensibility. Because these data contrasted with those obtained in the 2-kidney, 1 clip model of rat hypertension, which is characterized by increased arterial distensibility and Cx43 expression in aorta, we investigated by Western blot analysis the posttranslational modifications of Cx43. We found that Cx43 was more phosphorylated in the aorta of 2-kidney, 1 clip rats than in that of L-NAME or control rats, which indicated a differential regulation of Cx43 in different models of hypertension. The data suggest that the cell-to-cell communication mediated by Cx43 channels may help regulate the elasticity of the vascular wall.

Endothelial function of the mesenteric arteriole and mechanical behaviour of the carotid artery in rats with insulin resistance and hypercholesterolaemia.

Objective To examine whether insulin resistance and hypercholesterolaemia in obese Zucker rats are associated with a modification of the mechanical behaviour of a conductance (carotid) artery and with an altered endothelium-dependent response to acetylcholine of a small resistance (mesenteric) artery. Design Male obese Zucker rats, 6–8 months old, were compared with age-matched lean heterozygous and control Zucker rats. Methods The mechanical behaviour of the carotid artery was examined in anaesthetized rats by simultaneously monitoring the internal diameter with an A-mode ultrasonic echo-tracking device and the intra-arterial pressure with a computerized data-acquisition system. Furthermore, histometric measurements of the carotid artery were carried out after death. The response to acetylcholine was examined in vitro with a Mulvany dual myograph on precontracted isolated segments of the third-generation mesenteric artery. Results Obese Zucker rats exhibited high plasma insulin and cholesterol levels. Blood pressure was the same in the obese and control animals. There was no hypertrophy or change in the mechanical behaviour of the carotid arterial wall. Heart weight was slightly higher in the obese rats than in the controls, but smaller in relation to body weight. The relaxation to acetylcholine was significantly attenuated in isolated small mesenteric arteries obtained from the obese strain. Conclusion Hyperinsulinaemia and hypercholesterolaemia in obese Zucker rats are associated with an abnormal response to acetylcholine in the mesenteric arterioles. This metabolic state does not, however, alter the mechanical behaviour or the geometry of the carotid artery.

Time Course Changes of the Mechanical Properties of the Carotid Artery in Renal Hypertensive Rats

Distensibility of the carotid artery is not altered 2 weeks after renal artery clipping despite adaptive vascular hypertrophy related to hypertension. The purpose of this study was to assess arterial wall behavior with hypertension persisting for a longer period. Male Wistar rats were examined 1, 5, 9, and 24 weeks after renal artery clipping (two-kidney, one clip renal hypertension; n = 40) or after sham operation (n = 39). Mean blood pressure increased significantly to 132 +/- 4, 143 +/- 4, 153 +/- 4, and 144 +/- 4 versus 98 +/- 2, 107 +/- 2, 115 +/- 3, and 108 +/- 3 mm Hg, respectively, in 1-, 5-, 9-, and 24-week hypertensive rats and age-matched controls. Cardiac and vascular hypertrophy increased in parallel and were correlated to mean blood pressure. Wall stress at mean blood pressure did not differ between the hypertensive and normotensive groups (3.79 +/- 0.24, 4.60 +/- 0.34, 4.49 +/- 0.27, and 4.14 +/- 0.28 versus 3.15 +/- 0.12, 4.14 +/- 0.25, 4.80 +/- 0.28, and 4.69 +/- 0.32 10(3) dyne/cm2, respectively, in 1-, 5-, 9-, and 24-week hypertensive rats and age-matched controls). Distensibility-pressure data from the two groups fell on a common curve for all study periods. The intrinsic properties of the wall constituents were similar in controls and hypertensive rats at 1 and 5 weeks. However, the arteries became stiffer in the 9- and 24-week hypertensive rats, as illustrated by a shift to higher levels of the incremental elastic modulus-stress curve. Wall stress remains constant at mean blood pressure as a result of the increase in wall tissue mass. With time, even though the distensibility-pressure curve is not shifted downward, the thickened wall becomes stiffer in the hypertensive rats, which may predispose them to accelerated alterations of the wall material.

Vascular acetylcholine response during chronic NO synthase inhibition : in vivo versus in vitro

OBJECTIVE The aim of this study was to compare the response to NO-mediated vasodilators in vivo and in vitro during chronic NO synthase inhibition. METHODS NG-Nitro-L-arginine-methyl ester (L-NAME, 0.4 g/l) or vehicle was administered in the drinking water for 6 weeks to male Wistar rats weighing 220-240 g. The effect of acetylcholine and sodium nitroprusside was examined in vivo, on systemic blood pressure and heart rate and in vitro, on the precontracted isolated mesenteric artery. The in vivo response to both vasodilators was examined in awake rats monitored by an indwelling catheter in the femoral artery. Isolated segments of the third-generation mesenteric artery were examined in vitro with a Mulvany dual myograph after precontraction with noradrenaline. RESULTS In isolated mesenteric arteries obtained from rats chronically treated with L-NAME, the initial relaxant response to acetylcholine was significantly decreased whereas that to sodium nitroprusside was enhanced. A late acetylcholine-induced contractile response was present and abolished by indomethacin. In vivo, the hypotensive action of sodium nitroprusside was also enhanced in the L-NAME-treated rats. Acetylcholine reduced blood pressure in the L-NAME-treated hypertensive animals more than in normotensive controls, but less than in control rats infused intravenously with noradrenaline at a dose increasing their blood pressure to hypertensive levels. CONCLUSIONS The NO-mediated vasodilation induced by acetylcholine is attenuated during chronic NO synthase inhibition, both in vivo and in vitro. The blunted hypotensive response to acetylcholine can be demonstrated only if blood pressure of control rats is acutely increased to hypertensive levels.

Antidiabetic drugs and kidney disease - Recommendations of the Swiss Society for Endocrinology and Diabetology

Patients with diabetes are at risk of early renal function decline. Therefore, kidney function needs monitoring at least once per year. Once the glomerular filtration rate (GFR) is less than 60 ml/min, the pharmacokinetics of antidiabetic drugs may be altered. Sulfonylurea and glinide therapies are associated with a risk of hypoglycaemia which is increased in the presence of renal impairment. Most sulfonylureas must be discontinued once GFR is <60 ml/min. Some glinides may be continued beyond this threshold, in particular repaglinide, which may be used in dialysis patients. In the absence of comorbidities, metformin can be continued at lower doses until a GFR of 45 ml/min, but must be withdrawn in case of dehydration or during the administration of a nephrotoxic drug including dye for radiological investigations. Glitazones may worsen water and sodium retention in patients with renal impairment. The pharmacokinetics of all DPP-IV inhibitors except linagliptin are altered with impaired renal function. Only sitagliptin, saxagliptin and linagliptin may be used in advanced kidney disease, but experience is as yet very limited. GLP-1 agonists are contraindicated in moderate to advanced kidney disease.

Age-related changes of the mechanical properties of the carotid artery in spontaneously hypertensive rats

Background We had previously demonstrated that the distensibility of the carotid artery in spontaneously hypertensive rats (SHR) aged 18 weeks does not differ from that of the carotid artery in normotensive animals for common pressure levels, despite vascular hypertrophy in SHR. Objective To examine the time-course effects of hypertension on the geometry and the mechanical properties of the carotid artery in SHR. Methods The mechanical behavior of the carotid arteries of anesthetized SHR, stroke-prone SHR (SHRSP), and Wistar–Kyoto (WKY) rats aged 4, 8, 12, 16, and 32 weeks was examined by simultaneously measuring the internal diameter with an A-mode ultrasonic echotracking device and the intra-arterial pressure with a computerized data-acquisition system. Histometric measurements of the carotid artery were performed after death of rats. Results Blood pressure increased with time in rats of the two genetic hypertensive models. However, it rose earlier and to higher levels in the SHRSP. Cardiac hypertrophy was comparable in the two hypertensive groups whereas vascular hypertrophy was less pronounced in the SHRSP than it was in the SHR. There was an age-related decrease in arterial distensibility in rats of all groups that was more pronounced in the SHRSP than it was in the SHR compared with that in WKY rats (decreases of 57 and 36%, respectively, versus WKY rats aged 32 weeks; P < 0.05). For rats of all ages studied, although aging affected differently the vascular properties of the distinct animal strains, arterial distensibility was increased in the SHR and SHRSP compared with that in control animals for similar blood pressure levels, implying a rightward shift of the distensibility–pressure curves in the two hypertensive models. However, there was a significant reduction in arterial distensibility in rats of the two hypertensive strains at their respective mean blood pressues, compared with that in control animals.

Activation of electrical triggers of atrial fibrillation in hyperthyroidism.

CONTEXT A shortening of the atrial refractory period has been considered as the main mechanism for the increased risk of atrial fibrillation in hyperthyroidism. However, other important factors may be involved. OBJECTIVE Our objective was to determine the activity of abnormal supraventricular electrical depolarizations in response to elevated thyroid hormones in patients without structural heart disease. PATIENTS AND DESIGN Twenty-eight patients (25 females, three males, mean age 43+/-11 yr) with newly diagnosed and untreated hyperthyroidism were enrolled in a prospective trial after exclusion of heart disease. Patients were followed up for 16 +/- 6 months and studied at baseline and 6 months after normalization of serum TSH levels. MAIN OUTCOME MEASURES The incidence of abnormal premature supraventricular depolarizations (SVPD) and the number of episodes of supraventricular tachycardia was defined as primary outcome measurements before the start of the study. In addition, heart rate oscillations (turbulence) after premature depolarizations and heart rate variability were compared at baseline and follow-up. RESULTS SVPDs decreased from 59 +/- 29 to 21 +/- 8 per 24 h (P = 0.003), very early SVPDs (so called P on T) decreased from 36 +/- 24 to 3 +/- 1 per 24 h (P < 0.0001), respectively, and nonsustained supraventricular tachycardias decreased from 22 +/- 11 to 0.5 +/- 0.2 per 24 h (P = 0.01) after normalization of serum thyrotropin levels. The hyperthyroid phase was characterized by an increased heart rate (93 +/- 14 vs. 79 +/- 8 beats/min, P < 0.0001) and a decreased turbulence slope (3.6 vs. 9.2, P = 0.003), consistent with decreased vagal tone. This was confirmed by a significant decrease of heart rate variability. CONCLUSION Hyperthyroidism is associated with an increased supraventricular ectopic activity in patients with normal hearts. The activation of these arrhythmogenic foci by elevated thyroid hormones may be an important causal link between hyperthyroidism and atrial fibrillation.

Blockade of the renin-angiotensin system and renal tissue oxygenation as measured with BOLD-MRI in patients with type 2 diabetes.

AIM To assess whether blockade of the renin-angiotensin system (RAS), a recognized strategy to prevent the progression of diabetic nephropathy, affects renal tissue oxygenation in type 2 diabetes mellitus (T2DM) patients. METHODS Prospective randomized 2-way cross over study; T2DM patients with (micro)albuminuria and/or hypertension underwent blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) at baseline, after one month of enalapril (20 mgqd), and after one month of candesartan (16 mgqd). Each BOLD-MRI was performed before and after the administration of furosemide. The mean R₂* (=1/T₂*) values in the medulla and cortex were calculated, a low R₂* indicating high tissue oxygenation. RESULTS Twelve patients (mean age: 60 ± 11 years, eGFR: 62 ± 22 ml/min/1.73 m(2)) completed the study. Neither chronic enalapril nor candesartan intake modified renal cortical or medullary R₂* levels. Furosemide significantly decreased cortical and medullary R₂* levels suggesting a transient increase in renal oxygenation. Medullary R₂* levels correlated positively with urinary sodium excretion and systemic blood pressure, suggesting lower renal oxygenation at higher dietary sodium intake and blood pressure; cortical R₂* levels correlated positively with glycemia and HbA1c. CONCLUSION RAS blockade does not seem to increase renal tissue oxygenation in T2DM hypertensive patients. The response to furosemide and the association with 24 h urinary sodium excretion emphasize the crucial role of renal sodium handling as one of the main determinants of renal tissue oxygenation.