Martin Pfohl

Noninvasive determination of endothelium-mediated vasodilation as a screening test for coronary artery disease: Pilot study to assess the predictive value in comparison with angina pectoris, exercise electrocardiography, and myocardial perfusion imaging

BACKGROUND Peripheral endothelial dysfunction (ED) quantified by the determination of flow-mediated dilation (FMD%) of the brachial artery with the use of high-resolution ultrasound is an early marker of atherosclerosis. Although a positive correlation with coronary artery disease (CAD) has been reported, the unanswered clinical question is the validity of FMD% as a screening test in patients with clinical suspicion of CAD. Thus the aim of this study was to determine the predictive value of FMD% compared with angina pectoris, exercise electrocardiography, and myocardial perfusion imaging. METHODS AND RESULTS In this pilot study, we measured ED in 122 patients scheduled for coronary angiography by using high-resolution ultrasound (13 MHz). We defined ED as FMD% </=4.5%. The presence of CAD was defined as angiographically detectable atherosclerotic vessel alterations of any degree. Exercise electrocardiography and myocardial perfusion imaging had been performed on an outpatient basis. Statistical analysis was conducted by analysis of variance and Mantel-Haenszel chi-square test. Patients with CAD (n = 101) had a significantly lower FMD% than patients without CAD (n = 21; 3.7% +/- 4.1% vs 7.01% +/- 3.5%, P <.001). A sensitivity of 71%, a specificity of 81% with a positive predictive value of 0.95 (72 of 76), and a negative predictive value of 0.41 (17 of 46) was calculated. In comparison to angina pectoris (sensitivity 95%, specificity 47.6%), exercise electrocardiography (sensitivity 82.4%, specificity 57.1%) and myocardial perfusion imaging (sensitivity in our study group 100%) had the best specificity, and a high sensitivity for FMD% was found. CONCLUSIONS The determination of ED was found to be a sensitive and specific screening test to predict the presence of CAD. Because this is a noninvasive, nonradioactive, and cost-effective approach, it warrants further evaluation to determine its value in daily clinical practice as an additional screening test in the diagnosis of CAD.

Preserved endothelial function in IDDM patients, but not in NIDDM patients, compared with healthy subjects.

OBJECTIVE To examine endothelial function (EF) noninvasively in IDDM and NIDDM patients with long diabetes duration. RESEARCH DESIGN AND METHODS We studied EF in 17 IDDM patients without diabetic complications and in 25 NIDDM patients with comparable glycemic control and with diabetic complications and compared both with nondiabetic control subjects matched for age, sex, and lumen diameter. Using high-resolution ultrasound, we measured the endothelialdependent (FAD%) and independent vasodilation (GTN%); the blood flow at rest, postocclusive, and after application of 400 μg glyceroltrinitrate of the brachial artery; and the intima media thickness (IMT) of the common carotid artery. RESULTS In the IDDM patients, neither FAD% (8.2 ± 4.6 vs. 7.6 ± 4.2%), GTN% (16.3 ± 4.9 vs. 18.4 ± 6.4%), nor postocclusive blood flow (40.6 ± 19.1 vs. 39.3 ± 23.6 cm/s) differed from the control subjects. IMT (0.59 ± 0.10 vs. 0.55 ± 0.14 mm) was slightly, but not significantly, elevated. In contrast, the NIDDM patients showed an impaired FAD% (3.8 ± 3.3 vs. 6.9 ± 4.4%, P < 0.01), no difference in GTN%, and a decreased postocclusive blood flow (18.5 ± 13.8 vs. 32.7 ± 20.0 cm/s, P < 0.01). IMT was significantly increased in NIDDM patients (0.77 ± 0.14 vs. 0.62 ± 0.10 mm, P < 0.001). CONCLUSIONS In contrast to NIDDM patients with cardiovascular complications, IDDM patients with long diabetes duration and good long-term metabolic control do not have impaired EF compared with control subjects.

Upregulation of cholesterol synthesis after acute myocardial infarction—is cholesterol a positive acute phase reactant?

Acute myocardial infarction is associated with profound alterations in the plasma lipoprotein profile. The mechanism of these alterations is not clear, and both cholesterol biosynthesis up- and downregulation could possibly be a consequence of acute myocardial infarction. We determined plasma lipids, lipoproteins, apolipoproteins, and lathosterol-which is regarded as an estimate of whole body cholesterol biosynthesis in humans-concentrations in 34 patients (age 68+/-10 years, 24 male, 10 female) admitted to our hospital with acute MI and with onset of symptoms within the last 12 h. Samples were taken immediately after admission to the hospital, and 1, 2, and 10 days after admission. On the first day after admission there was a decrease in total cholesterol (C) by 14.1%, (P = 0.01), in LDL-C by 14.4% (P = 0.03), in HDL-C by 9.3% (NS), and in triglycerides by 19.5% (NS). Apolipoprotein B100 was reduced by 18.3% (P = 0.008), and apolipoprotein AI by 12.3% (NS). The lathosterol/cholesterol ratio was increased by 23.1% after 1 day, and by 28.7% after 2 days (P = 0.05). After 10 days, all variables except the apolipoproteins had essentially returned to baseline values. In conclusion, the changes in the plasma lipid profile after acute myocardial infarction are associated with a profound increase of whole body cholesterol biosynthesis as judged by the lathosterol/cholesterol ratio. These changes may possibly enhance the delivery of cholesterol to cells involved in tissue repair mechanisms after acute myocardial infarction.

Insertion/Deletion Polymorphism of the Angiotensin I-Converting Enzyme Gene Is Associated With Coronary Artery Plaque Calcification As Assessed by Intravascular Ultrasound

OBJECTIVES We evaluated the influence of the insertion/deletion (I/D) polymorphism of the angiotensin I-converting enzyme (ACE) gene on coronary plaque morphology and calcification in patients with angiographically documented coronary artery disease (CAD). BACKGROUND The ACE I/D polymorphism has been associated with an increased risk of myocardial infarction in patients with the DD genotype but not with the presence of native CAD. METHODS We studied 146 patients undergoing percutaneous transluminal coronary angioplasty for stable angina pectoris by means of preinterventional intravascular ultrasound (IVUS). Qualitative and quantitative criteria were used to classify the target lesions as poorly or highly echoreflective or as calcified. Genomic deoxyribonucleic acid was analyzed by polymerase chain reaction (PCR) to identify the I/D polymorphism, with a second insertion-specific PCR in DD genotypes to prevent mistyping. RESULTS The ACE genotype groups (DD 46, ID 68, II 32) were well matched for the basic characteristics. Patients with the DD genotype had significantly more calcified lesions (DD 80%, ID 57%, II 66%; unadjusted odds ratio [OR] 2.88, 95% confidence interval [CI] 1.30 to 6.92, p = 0.008) and more calcifications >180 degrees of the vessel circumference (DD 22%, ID 10%, II 6%; OR 2.80, 95% CI 1.05 to 7.63, p = 0.03). The prevalence of myocardial infarction was not significantly associated with coronary calcification (OR 1.44, 95% CI 0.72 to 2.88, p = 0.31). CONCLUSIONS Patients with CAD and the ACE DD genotype have a significantly higher incidence and greater extent of coronary lesion calcification, as determined by IVUS. This finding indicates that the ACE I/D gene polymorphism is related to the development or progression of atherosclerotic plaque calcification.

Nachweis diabetischer Mikrozirkulationsveränderungen mittels Kapillaroskopie und Laser-Doppler-Anemometrie

ZusammenfassungHintergrund: Während funktionelle Störungen der kutanen Mikrozirkulation bei diabetischen Patienten deutlich ausgeprägt sind, wurden kapillaroskopisch nur geringe Veränderungen der Hautkapillarmorphologie beobachtet. Wir untersuchten die Wechselbeziehungen zwischen morphologischen und funktionellen kutanen Mikrozirkulationsstörungen bei Patienten mit Typ-1- und Typ-2-Diabetes sowie den Einfluss der Diabetesdauer auf die Kapillarmorphologie. Patienten und Methodik: Bei 16 Patienten mit Typ-1- und 19 mit Typ-2-Diabetes wurden die Dichte, Maße und Morphologie von Nagelfalzkapillaren mittels Kapillaroskopie im Vergleich mit Kontrollgruppen gleicher Alters- und Geschlechtsverteilung untersucht. Die Messungen der kapillären Blutzellgeschwindigkeit erfolgten dorsal an der Mittelphalanx des vierten Fingers mittels Laser-Doppler-Anemometrie in Ruhe und nach dreiminütiger suprasystolischer Stauung. Ergebnisse: Die diabetischen Patienten unterschieden sich hinsichtlich der Kapillardichte und -weite sowie des Durchmessers des arteriellen Kapillarschenkels nicht von den Kontrollpersonen. Die Gesamtgruppe der an Typ-1- und Typ-2-Diabetes erkrankten Personen wies jedoch größere Durchmesser der Apexregion und des venösen Schenkels der Kapillaren auf (Apex: 19,2±0,6 μm vs. 17,4±0,6 μm, p = 0,0243; venöser Schenkel: 17,3±0,5 μm vs. 15,9±0,4 μm, p = 0,0238). Kapillartorquierungen ließen sich bei Patienten mit Typ-1- (n = 13 vs. n = 7, p = 0,028) und Typ-2-Diabetes (n = 16 vs. n = 9, p = 0,017) häufiger als bei den Kontrollpersonen nachweisen. Bei Patienten mit Typ-1-Diabetes fand sich eine negative Korrelation zwischen Kapillardichte und kapillärer Blutzellgeschwindigkeit in Ruhe (r = −0,52; p = 0,019). In der Gruppe der an Typ-2-Diabetes erkrankten Personen fiel eine positive Korrelation zwischen dem kapillären Apexdurchmesser und der maximalen postokklusiven kapillären Blutzellgeschwindigkeit auf (r = 0,49; p = 0,017). Bei Patienten mit Type-2-Diabetes ließ sich mit zunehmender Erkrankungsdauer eine Abnahme des Durchmessers des arteriellen Schenkels (r = −0,48; p = 0,020) und der Weite der Kapillaren (r = −0,48; p = 0,018) beobachten. Schlussfolgerung: Im Rahmen dieser Pilotstudie fanden sich bei Patienten mit Diabetes mellitus kapillaroskopisch Hinweise auf erhöhte Prävalenzen von Torquierungen und Dilatationen der Hautkapillaren als möglicher Ausdruck einer diabetischen Mikroangiopathie. Diabetische Mikrozirkulationsstörungen führen zu einer Beeinträchtigung der postokklusiven reaktiven Hyperämie und können mit Hilfe der Laser-Doppler-Anemometrie erstmals in Einzelkapillaren außerhalb des Nagelfalzes quantifiziert werden. Morphologische und funktionelle Mikrozirkulationsalterationen bei diabetischen Patienten beeinflussen sich möglicherweise gegenseitig über Hämodynamikveränderungen, die von der Diabetesdauer abhängen.AbstractBackground: Only minor changes of skin capillary morphology have been described in diabetic patients by means of capillaroscopy, whereas cutaneous microvascular dysfunction is well known. We examined correlations between functional and morphological abnormalities of the capillaries in Type 1 and 2 diabetic patients and the influence of diabetes duration on capillary morphology. Patients and Methods: Density, diameters and morphology of nailfold capillaries were investigated in diabetic patients, 16 Type 1 and 19 Type 2 and compared to age- and sex-matched control groups. Capillary blood cell velocities (CBV) during rest and after 3-minute arterial occlusion were measured in the dorsal middle phalangeal area of the left ring finger by means of laser Doppler anemometry. Results: Capillary density, width and arterial limb diameter were similar in Type 1 and 2 diabetic patients compared to their controls. Capillary diameters of the apical part and the venous limb were enlarged in the combined analysis of Type 1 and 2 diabetic patients compared to the control group (apex: 19.2±0.6 μm vs 17.4±0.6 μm, p = 0,0243; venous limb: 17.3±0.5 μm vs 15.9±0.4 μm, p = 0.0238). Tortuous capillaries were more often observed in Type 1 (n = 13 vs n = 17, p = 0.028) and 2 diabetic patients (n = 16 vs n = 9, p = 0.019) than in controls. In Type 1 diabetic patients an inverse correlation (r = −0.52; p = 0.019) was found between capillary density and resting CBV. In Type 2 diabetic patients capillary apex diameter correlated positively with peak CBV (r = 0.49; p = 0.017). Disease duration correlated inversely with arterial limb diameter (r = −0.48; p = 0.020) and width of the capillaries (r = −0.48; p = 0.018) in Type 2 diabetic patients. Conclusion: Tortuous and dialated capillaries, indicating microangiopathy, were found in the skin of diabetic patients by means of capillaroscopy. Using laser Doppler anemometry it is possible to assess impairment of postocclusive reactive hyperemia, due to diabetic microvascular dysfunction, in single capillaries. Correlations between morphological and functional microcirulatory alterations in diabetes may be explained by hemodynamic changes, depending on diabetes duration.BACKGROUND Only minor changes of skin capillary morphology have been described in diabetic patients by means of capillaroscopy, whereas cutaneous microvascular dysfunction is well known. We examined correlations between functional and morphological abnormalities of the capillaries in Type 1 and 2 diabetic patients and the influence of diabetes duration on capillary morphology. PATIENTS AND METHODS Density, diameters and morphology of nailfold capillaries were investigated in diabetic patients, 16 Type 1 and 19 Type 2, and compared to age- and sex-matched control groups. Capillary blood cell velocities (CBV) during rest and after 3-minute arterial occlusion were measured in the dorsal middle phalangeal area of the left ring finger by means of laser Doppler anemometry. RESULTS Capillary density, width and arterial limb diameter were similar in Type 1 and 2 diabetic patients compared to their controls. Capillary diameters of the apical part and the venous limb were enlarged in the combined analysis of Type 1 and 2 diabetic patients compared to the control group (apex: 19.2 +/- 0.6 microns vs 17.4 +/- 0.6 microns, p = 0.0243; venous limb: 17.3 +/- 0.5 microns vs 15.9 +/- 0.4 microns, p = 0.0238). Tortuous capillaries were more often observed in Type 1 (n = 13 vs n = 7, p = 0.028) and 2 diabetic patients (n = 16 vs n = 9, p = 0.019) than in controls. In Type 1 diabetic patients an inverse correlation (r = -0.52; p = 0.019) was found between capillary density and resting CBV. In Type 2 diabetic patients capillary apex diameter correlated positively with peak CBV (r = 0.49; p = 0.017). Disease duration correlated inversely with arterial limb diameter (r = -0.48; p = 0.020) and width of the capillaries (r = -0.48; p = 0.018) in Type 2 diabetic patients. CONCLUSION Tortuous and dilated capillaries, indicating microangiopathy, were found in the skin of diabetic patients by means of capillaroscopy. Using laser Doppler anemometry it is possible to assess impairment of postocclusive reactive hyperemia, due to diabetic microvascular dysfunction, in single capillaries. Correlations between morphological and functional microcirculatory alterations in diabetes may be explained by hemodynamic changes, depending on diabetes duration.

Evaluation of the Insertion/Deletion ACE Gene Polymorphism as a Risk Factor for Carotid Artery Intima-Media Thickening and Hypertension in Young Type 1 Diabetic Patients

OBJECTIVE To study the distribution of the insertion/deletion polymorphism of the ACE gene in young type 1 diabetic patients and to evaluate possible associations between the ACE genotype, arterial hypertension, and intima-media thickness (IMT) of the common carotid artery. RESEARCH DESIGN AND METHODS Study participants were 148 type 1 diabetic patients (56 men and 92 women), aged 14–44 years, with a diabetes duration of ≥2 years. HbA1c, albuminuria, and lipid status were assessed by standard laboratory techniques; the ACE genotypes were assessed by polymerase chain reaction. The patients were categorized according to the presence or absence of hypertension, nephropathy, and retinopathy. The IMT, which can be used to estimate early stages of atherosclerosis, was measured by high-resolution ultrasonography. RESULTS The ACE genotypes were distributed as follows: 21% II, 37% ID, 42% DD. The IMT values did not differ among patients with various ACE genotypes (0.63 ± 0.15 mm), but the prevalence of hypertension was significantly higher in patients with DD (odds ratio, 4.26 versus II ± ID; 95% CI, 1.64–11.06). Multiple linear regression analysis showed that only age, hypertension, and sex were determinants for the IMT. CONCLUSIONS Our results suggest a relationship between the prevalence of hypertension and the deletion polymorphism of the ACE gene in young type 1 diabetic patients, but we could not find an association between carotid artery IMT and ACE genotype in this population.

Screening and identification of familial defective apolipoprotein B-100 in clinical samples by capillary gel electrophoresis

Familial defective apolipoprotein B-100 (FDB) is a dominantly inherited disorder. It is characterized by a decreased affinity of low density lipoprotein (LDL) for the LDL receptor, as a consequence of a substitution of adenine by guanine in exon 26 of the apolipoprotein B-100 gene, coding for the putative LDL receptor-binding domain of the mature protein. This disorder is associated with a strikingly high incidence of arteriosclerosis and tends to cause disease and premature death. In this communication we describe a rapid capillary gel electrophoretic method in combination with molecular biology techniques to facilitate the diagnosis of FDB. Mutation screening for FDB is performed by an allele-specific amplification followed by capillary gel electrophoresis (CGE). For the combined polymerase chain reaction (PCR)-CGE method, a total analysis time of only 3 h is needed, a period that is normally necessary for the run and for staining of the gel only, not including the time for PCR, gel casting, etc. In our pilot study 4 of 43 hypercholesterolemic patients were found to have the predominant apoB 3500 codon mutation. The verification is demonstrated by DNA-sequencing. This pilot study will be followed by a large cohort analysis of the south-west German population to determine the frequency of FDB in this area. The PCR-CGE method on the Dionex capillary electrophoresis system (CES I) allows rapid, fully automated detection of the mutation resulting in the unequivocal diagnosis of FDB.

Upregulation of cholesterol synthesis after acute reduction of low density lipoprotein by apheresis in normocholesterolaemic subjects : Evidence for a threshold effect

The influence of low density lipoproteins (LDL) in the plasma on the regulation of cholesterol biosynthesis is not clear. We studied the changes in plasma mevalonic acid (MVA) concentration and the lathosterol/cholesterol (L/C) ratio, which are well established indices of whole body cholesterol synthesis, in four normocholesterolaemic subjects after each had undergone LDL apheresis on two occasions. LDL apheresis of 75% of the calculated plasma volume reduced LDL-cholesterol by 44% to 1.5 +/- 0.2 mmol/l without changing plasma MVA levels or L/C ratios. Apheresis of 125% of the calculated plasma volume decreased plasma LDL-cholesterol by 69% to 0.9 +/- 0.2 mmol/l, with significant increases in plasma MVA and L/C ratio on the day after the procedure. These results imply that LDL-cholesterol is an integral part of the sterol regulatory pool and suggest that plasma levels cannot be lowered below 1-1.4 mmol/l in normal subjects without upregulating cholesterol biosynthesis.

Downregulation of β-adrenergic receptors by low density lipoproteins and its prevention by β-adrenergic receptor antagonists

Objective: Vasodilation by β-adrenergic receptors of smooth muscle cells appears to be impaired early after the onset of hypercholesteremia. The aim of this study was to analyze the modulation of β-adrenergic receptor density and adenylyl cyclase activity in the presence of moderately elevated concentrations of LDL. The effects of β1- and β2-adrenergic receptor antagonists on LDL-induced receptor changes were studied. Methods and results: Media explants of porcine coronary arteries were incubated with moderately elevated LDL concentrations (0.7–3.9 mmol/l). The density of β-adrenergic receptors was determined in plasma membranes using the radioligand [125I]iodocyanopindolol. LDL (3.9 mmol/l) resulted in a decrease of β-adrenergic receptor density (control 137±5 vs. 89±7 fmol/mg protein, P <0.01). After removal of LDL and cultivation for an additional 3 days β-adrenergic receptors increased to 129±5 fmol/mg. In the presence of the β1- or β2-adrenergic receptor antagonists the LDL-mediated decrease was inhibited. Addition of metoprolol after 3 days of LDL incubation caused a restoration of receptor density. The basal, isoproterenol- and forskolin-stimulated adenylyl cyclase activities were increased after LDL incubation by 180, 110 or 80%, respectively. Conclusion: Moderately elevated LDL levels decreased β-adrenergic receptor density while adenylyl cyclase activity was simultaneously increased. β1- or β2-adrenergic receptor antagonists prevented this receptor decrease and might preserve the β-adrenergic receptor density in the presence of moderately elevated LDL levels.

Antikrper gegen Glutamatdecarboxylase und Tyrosinphosphatase-hnliches Protein IA-2 in der Klassifikation von unselektionierten Diabetespatienten

ZusammenfassungHintergrund: Die Klassifikation eines Diabetes mellitus lässt sich in selektionierten Patientengruppen über die Bestimmung der Glutamatdecarboxylase- und Tyrosinphosphatase-ähnliches-Protein-Antikörper (GAD-Ak und IA-2-Ak) mit relativ hoher Sensitivität und Spezifität vornehmen. Patienten und Methodik: Da die Ergebnisse aus solchen selektionierten Patientengruppen sich nur bedingt auf den klinischen Alltag übertragen lassen, untersuchten wir den Einsatz dieser Antikörperbestimmung in einer Querschnittsstudie an 157 unselektierten Patienten unserer Diabetesambulanz. Die Prävalenz der verschiedenen Antikörper wurde in Relation zu den klinisch diagnostizierten Diabetestypen und auch zur jeweiligen Diabetesdauer gesetzt. Ergebnisse: Bei den Patienten mit klinisch diagnostizierten Diabetes mellitus Typ 1 waren die GAD-Ak bei 44% eindeutig und bei 10% fraglich positiv, die IA-2-Ak waren bei 36% dieser Patienten positiv oder fraglich positiv. Die Rate an antikörperpositiven Patienten nahm mit zunehmender Diabetesdauer ab. Im Gegensatz hierzu waren bei den Patienten mit klinsch diagnostiziertem Diabetes mellitus Typ 2 die GAD-Ak bei 25,2% eindeutig und bei 13,1% fraglich positiv, die IA-2-Ak nur bei 4,7% positiv. Die GAD-Ak-positiven Patienten ließen sich klinisch nur teilweise dem “latent autoimmune diabetes in adults” (LADA) zuordnen, da einige erst nach > 10-jähriger Diabetesdauer insulinpflichtig wurden. Die Prävalenz von GAD-Ak bei den Typ-2-/LADA-Patienten war unabhängig von der Diabetesdauer. Schlussfolgerung: Zusammenfassend erscheint in klinischen Zweifelsfällen zur Unterscheidung zwischen einem Diabetes mellitus Typ 2 und einem LADA zunächst die Bestimmung der GAD-Ak zur weiteren Klassifikation sinnvoll. Für die Differenzierung zwischen einem Diabetes mellitus Typ 2 und einem LADA bietet die Bestimmung der IA-2-Ak im Vergleich zu den GAD-Ak in der Regel nur wenig zusätzliche Informationen.AbstractBackground: The determination of glutamic acid decarboxylase and tyrosine phosphatase-like antibodies (GAD-AB and IA-2-AB) may be useful for the classification of diabetes, and in selected patient groups the measurement of these autoantibodies has been shown to be rather sensitive and specific. Patients and Methods: In this study we examined the use of these antibody determination in a clinical setting of 157 diabetic outpatients recruited randomly from our diabetes clinic. The prevalence of the different antibodies was set in relation to the clinically classified diabetes type and to diabetes duration. Results: Among the patients with a clinical diagnosis of type 1 diabetes, the GAD-AB were clearly positive in 44% and borderline positive in 10%, whereas the IA-2-AB were positive or borderline positive in 36% of these patients. The prevalence of positive autoantibodies declined with increasing duration of type 1 diabetes. Among the patients with clinically diagnosed type 2 diabetes, the GAD-AB were clearly positive in 25.2% and borderline positive in 13.1%, IA-2-AB were only found in 4.7%. Patients with a clinical diagnosis of type 2 diabetes but positive for GAD-AB could not clearly be identified as having latent autoimmune diabetes in adults (LADA), since some of them did not need insulin therapy up to 10 years after the diagnosis of diabetes. The prevalence of GAD-AB in type 2 diabetic/LADA patients did not depend on diabetes duration. Conclusion: We conclude that the determination especially of GAD-AB may be useful for the classification of diabetes in clinically unclear cases. The additional determination of IA-2-AB appears to provide only limited additional information.