Cardiac autonomic dysinnervation and myocardial blood flow in long-term Type 1 diabetic patients

Individuals with impaired glucose tolerance demonstrate normal cardiac sympathetic innervation using I-123 mIBG scintigraphy

BACKGROUND

Impaired glucose tolerance (IGT) is associated with an increased risk of type 2 diabetes (T2DM) and cardiovascular disease. Some but not all studies have reported cardiac autonomic dysfunction in subjects with IGT and there is only one direct study of cardiac innervation in subjects with IGT. The purpose of this study was to assess global and regional cardiac sympathetic innervation and cardiac autonomic function in individuals with IGT.

METHODS AND RESULTS

We undertook (123)I-mIBG scintigraphy and cardiac autonomic function in 15 subjects with IGT and 15 age and sex-matched healthy controls. Early heart to mediastinum ratio (HMR) (1.71 ± 0.17 vs 1.67 ± 0.13, P = .49), late HMR (1.73 ± 0.18 vs 1.73 ± 0.16, P = .97) and washout rate (WR) (18.6 ± 4.2 vs 19.1 ± 7.6%, P = .84), did not differ between subjects with IGT and control subjects. More detailed regional analysis revealed reduced tracer uptake at the apex, base and inferior wall in all subjects and the anterior wall in a minority of subjects. There were no differences in total score (56.6 ± 4.0 vs 53.3 ± 8.4, P = .193), modified score (48.5 ± 3.3 vs 46.2 ± 6.0, P = .215), anterior wall score (10.2 ± 1.3 vs 10.1 ± 1.6, P = .898), inferior wall score (8.9 ± 1.9 vs 7.7 ± 2.6, P = .163), basal score (18.7 ± 1.9 vs 18.2 ± 3.3, P = .636) and tests of cardiac autonomic function between the groups.

CONCLUSION

Global and regional measures of MIBG uptake and washout as well as cardiac autonomic function did not differ between subjects with IGT and healthy controls.

Risk evaluation for coronary artery disease in patients with impaired glucose tolerance after a successful coronary intervention

PURPOSE

Patients with coronary artery disease (CAD) often have risk factors that may influence endothelial function. The purpose of this study was to evaluate the endothelial function and its association with coronary risk factors after percutaneous coronary intervention (PCI).

MATERIALS AND METHODS

A total of 14 patients with impaired glucose tolerance and CAD underwent positron emission tomography with N-13 ammonia to measure myocardial blood flow (MBF) at rest and during a cold pressor test (CPT), to estimate endothelial function as a percent increase (%increase) of MBF. The results were compared among normal segments (normal), reperfused segments with PCI (PCI), and nonculprit CAD segments without PCI (non-PCI). Correlations between the %increase and major risk factors were also investigated.

RESULTS

CPT induced significant increase in MBF in all groups. The %increase of normal, non-PCI, and PCI groups were 33% ± 22%, 21% ± 23%, and 26% ± 23%, respectively. Comparison with risk factors demonstrated significant correlations only in the non-PCI group. Specifically, there were negative correlations between %increase and fasting blood sugar (r = -0.64, P < 0.05), hemoglobin A1c (r = -0.74, P < 0.05), total cholesterol (r = -0.87, P < 0.05), triglyceride (r = -0.71, P < 0.05), and low-density lipoprotein cholesterol (r = -0.92, P < 0.005), respectively.

CONCLUSIONS

Although impaired glucose tolerance patients with a PCI-treated coronary stenosis showed preserved response to CPT, the %increase negatively correlated with risk factors in the non-PCI segments. Therefore, coronary risk factors may affect CAD lesions in PCI-treated patients.

Impact of type 2 diabetes on nitric oxide and adrenergic modulation of myocardial perfusion

Type 2 diabetic patients are characterized by a reduced adenosine-induced hyperemic myocardial perfusion, which may contribute to their increased cardiovascular morbidity. We hypothesized that the reduced hyperemia can be explained by functional changes in endothelial or autonomic nervous regulation. In 12 type 2 diabetic patients without signs of ischemic heart disease and 14 age-matched control subjects, myocardial perfusion was measured at rest, during adenosine, and during adenosine and alpha-receptor blockade (phentolamine) using positron emission tomography on two separate days: 1) with, and 2) without nitric oxide (NO) inhibition with N(G)-nitro-L-arginine methyl ester. Myocardial perfusion during adenosine was lower in type 2 diabetic patients compared with control subjects (P = 0.05). No significant effect of NO inhibition on myocardial perfusion during adenosine was found in any of the groups. In control subjects, alpha-receptor blockade increased hyperemic myocardial vascular resistance during NO inhibition, whereas no effect was observed in type 2 diabetic patients. At rest, a significant correlation was observed between rate-pressure product and myocardial perfusion in control subjects. NO inhibition and type 2 diabetes abolished this correlation. Endothelial and cardiac autonomic nerve function seems to play only a minimal role in the reduced hyperemic myocardial perfusion in type 2 diabetic patients. However, the linear correlation between resting perfusion and cardiac work appears to be abolished in type 2 diabetes and during NO synthase inhibition.

Foam cell death induced by 7beta-hydroxycholesterol is mediated by labile iron-driven oxidative injury: mechanisms underlying induction of ferritin in human atheroma

Human atherosclerotic lesions typically contain large amounts of ferritin associated with apoptotic macrophages and foam cells, although the reasons are unknown. In the present investigation, we studied the relationship between ferritin induction and occurrence of apoptosis in 7beta-hydroxycholesterol (7beta-OH)-treated monocytic cells and macrophages. We found that 7beta-OH enlarges the intracellular labile iron pool, increases formation of reactive oxygen species (ROS), and induces ferritin and cytosolic accumulation of lipid droplets, lysosomal destabilization, and apoptototic macrophage death. Since ferritin is a phase II-type protective protein, our findings suggest that ferritin upregulation here worked as an inefficient defense mechanism. Addition to the culture medium of both a membrane-permeable iron chelator 10-phenanthroline and the non-membrane-permeable iron chelators apoferritin and desferrioxamine afforded significant protection against the 7beta-OH-induced effects. Consequently, endocytosed iron compounds dramatically augmented 7beta-OH-induced cytotoxicity. We conclude that oxidized lipid 7beta-OH causes not only foam cell formation but also oxidative damage with abnormal metabolism of cellular iron. The findings suggest that modulation of iron metabolism in human atheroma may be a potential therapeutic strategy against atherosclerosis.

Functional Neuroimaging of Sympathetic Innervation of the Heart

Many concepts about acute and chronic effects of stress depend on alterations in sympathetic nerves supplying the heart. Physiologic, pharmacologic, and neurochemical approaches have been used to evaluate cardiac sympathetic function. This article describes a fourth approach that is based on nuclear scanning to visualize cardiac sympathetic innervation and function and relationships between the neuroimaging findings and those from other approaches. Multiple-system atrophy with orthostatic hypotension (formerly the Shy-Drager syndrome) features normal cardiac sympathetic innervation and normal entry of norepinephrine into the coronary sinus (cardiac norepinephrine spillover), in contrast to Parkinson disease with orthostatic hypotension, which features neuroimaging and neurochemical evidence for loss of cardiac sympathetic nerves. This difference may have important implications not only for diagnosis but also for understanding the etiology of Parkinson disease. By analysis of curves relating myocardial radioactivity with time (time-activity curves) after injection of a sympathoneural imaging agent, it is possible to obtain information about cardiac sympathetic function. Abnormal time-activity curves are seen in common disorders such as heart failure and diabetic neuropathy and provide an independent, adverse prognostic index. Analogous abnormalities might help explain increased cardiovascular risk in psychiatric disorders such as melancholic depression.

Intensification of therapeutic approaches reduces mortality in diabetic patients with acute myocardial infarction: the Munich registry

OBJECTIVE

The myocardial infarction (MI) registry of the Academic Schwabing Hospital, Munich, investigates the hospital course of diabetic and nondiabetic patients with acute MI. The aim of this study was to improve quality care management and to compare hospital mortality and therapeutic approaches (i.e., PTCA, stenting, GPIIb/IIIa receptor antagonists, glucose-insulin infusion).

RESEARCH DESIGN AND METHODS

Data of diabetic patients and nondiabetic patients were analyzed. All diabetic and nondiabetic subjects who were admitted in 1999 and 2001 were included: 1999, 126 (38%) diabetic and 204 (62%) nondiabetic patients; 2001, 91 (31%) diabetic and 205 (59%) nondiabetic patients.

RESULTS

In 1999, coronary angiography (P < 0.01), percutaneous transluminal coronary angioplasty (PTCA) (P < 0.001), and stenting (P < 0.001) were performed less frequently in diabetic than in nondiabetic patients. During this period, total hospital mortality (29 vs. 16%, P < 0.01) and mortality within 24 h after admission (14 vs. 5%, P = 0.01) were higher in diabetic than in nondiabetic patients. In 2001, frequencies of coronary angiography, PTCA, and stenting were increased in diabetic patients (P < 0.001 vs. 1999), and the interventions were comparable with those performed in nondiabetic patients. Furthermore, glucose-insulin infusion was administered in 46% of diabetic subjects. In 2001, total hospital mortality decreased to 17% in diabetic subjects (P = 0.028 vs. 1999) and mortality within 24 h after admission declined to 4% (P = 0.027 vs. 1999). Logistic regression analysis revealed that an increase in the number of therapeutic approaches (also when adjusted for clinical variables) is associated with a reduction in mortality of diabetic patients with acute MI (adjusted odds ratio 0.14, P < 0.0001).

CONCLUSIONS

Intensification of multiple advanced therapeutic strategies in diabetic patients with acute MI enables a substantial reduction in hospital mortality. The enforcement leads to rates of hospital mortality that are comparable to those of nondiabetic patients.