Evaluation of a web-based ECG-interpretation programme for undergraduate medical students.

BACKGROUND: Most clinicians and teachers agree that knowledge about ECG is of importance in the medical curriculum. Students at Karolinska Institute have asked for more training in ECG-interpretation during their undergraduate studies. Clinical tutors, however, have difficulties in meeting these demands due to shortage of time. Thus, alternative ways to learn and practice ECG-interpretation are needed. Education offered via the Internet is readily available, geographically independent and flexible. Furthermore, the quality of education may increase and become more effective through a superior educational approach, improved visualization and interactivity. METHODS: A Web-based comprehensive ECG-interpretation programme has been evaluated. Medical students from the sixth semester were given an optional opportunity to access the programme from the start of their course. Usage logs and an initial evaluation survey were obtained from each student. A diagnostic test was performed in order to assess the effect on skills in ECG interpretation. Students from the corresponding course, at another teaching hospital and without access to the ECG-programme but with conventional teaching of ECG served as a control group. RESULTS: 20 of the 32 students in the intervention group had tested the programme after 2 months. On a five-graded scale (1- bad to 5 - very good) they ranked the utility of a web-based programme for this purpose as 4.1 and the quality of the programme software as 3.9. At the diagnostic test (maximal points 16) by the end of the 5-month course at the 6th semester the mean result for the students in the intervention group was 9.7 compared with 8.1 for the control group (p = 0.03). CONCLUSION: Students ranked the Web-based ECG-interpretation programme as a useful instrument to learn ECG. Furthermore, Internet-delivered education may be more effective than traditional teaching methods due to greater immediacy, improved visualisation and interactivity.

Effect of C-peptide on diabetic neuropathy in patients with type 1 diabetes.

Recent results indicate that proinsulin C-peptide, contrary to previous views, exerts important physiological effects and shows the characteristics of a bioactive peptide. Studies in type 1 diabetes, involving animal models as well as patients, demonstrate that C-peptide in replacement doses has the ability to improve peripheral nerve function and prevent or reverse the development of nerve structural abnormalities. Peripheral nerve function, as evaluated by determination of sensory nerve conduction velocity and quantitative sensory testing, is improved by C-peptide replacement in diabetes type 1 patients with early stage neuropathy. Similarly, autonomic nerve dysfunction is ameliorated following administration of C peptide for up to 3 months. As evaluated in animal models of type 1 diabetes, the improved nerve function is accompanied by reversal or prevention of nerve structural changes, and the mechanisms of action are related to the ability of C-peptide to correct diabetes-induced reductions in endoneurial blood flow and in Na+ K+-ATPase activity and modulation of neurotrophic factors. Combining the results demonstrates that C-peptide may be a possible new treatment of neuropathy in type 1 diabetes.

Evaluation of multi-modal high salt binding ion exchange materials.

The performance and selectivity of novel cation and anion exchange multi-modal chromatographic materials were evaluated. Desorption profiles of 13 proteins possessing a range of properties (e.g. size, charge and hydrophobicity) were determined on the cation exchange materials. Batch experiments were carried out by loading individual proteins on each resin at low salt, and examining the desorption of the proteins during sequential washes with increasing salt concentrations. While all of the resins exhibited some binding of proteins at elevated salt concentrations, this effect was more pronounced on the resins with aromatic ligands as compared to the materials with aliphatic ligands. As expected, materials with higher ionic capacities exhibited higher binding at elevated salts. In addition, some proteins exhibited high binding at elevated salt concentrations to all of the resins. The combined effect of charge and other secondary interactions with these multi-modal chromatographic materials enables high salt binding of a range of proteins as well as unique selectivities for the recovery of certain classes of proteins. Since the anion exchange materials all exhibited high binding at elevated salt concentrations the work with these materials focused on a study of elution strategies to remove proteins from these aromatic based materials. After evaluating various elution protocols, a combined strategy of pH change and chaotropic salt were shown to minimize electrostatic and hydrophobic interactions and was found to be an effective elution strategy for this class of anion exchange materials using peanut lectin as a model protein.

C-Peptide replacement therapy and sensory nerve function in type 1 diabetic neuropathy.

OBJECTIVE: C-peptide replacement in animals results in amelioration of diabetes-induced functional and structural abnormalities in peripheral nerves. The present study was undertaken to examine whether C-peptide administration to patients with type 1 diabetes and peripheral neuropathy improves sensory nerve function. RESEARCH DESIGN AND METHODS: This was an exploratory, double-blinded, randomized, and placebo-controlled study with three study groups that was carried out at five centers in Sweden. C-peptide was given as a replacement dose (1.5 mg/day, divided into four subcutaneous doses) or a dose three times higher (4.5 mg/day) during 6 months. Neurological examination and neurophysiological measurements were performed before and after 6 months of treatment with C-peptide or placebo. RESULTS: The age of the 139 patients who completed the protocol was 44.2 +/- 0.6 (mean +/- SE) years and their duration of diabetes was 30.6 +/- 0.8 years. Clinical neurological impairment (NIA) (score >7 points) of the lower extremities was present in 86% of the patients at baseline. Sensory nerve conduction velocity (SCV) was 2.6 +/- 0.08 SD below body height-corrected normal values at baseline and improved similarly within the two C-peptide groups (P < 0.007). The number of patients responding with a SCV peak potential improvement >1.0 m/s was greater in C-peptide-treated patients than in those receiving placebo (P < 0.03). In the least severely affected patients (SCV < 2.5 SD below normal at baseline, n = 70) SCV improved by 1.0 m/s (P < 0.014 vs. placebo). NIA score and vibration perception both improved within the C-peptide-treated groups (P < 0.011 and P < 0.002). A1C levels (7.6 +/- 0.1% at baseline) decreased slightly but similarly in C-peptide-and placebo-treated patients during the study. CONCLUSIONS: C-peptide treatment for 6 months improves sensory nerve function in early-stage type 1 diabetic neuropathy.

Quantitative determination of the ligand content in Benzamidine Sepharose 4 Fast Flow media with ion-pair chromatography.

A quantitative hydrochloric acid hydrolysis-HPLC method was developed for the analysis of the ligand content of Benzamidine Sepharose 4 Fast Flow media. The method requires about 100 mg of dried sample and simple reaction vials can be utilised. Release of the ligand (p-aminobenzamidine) from the base matrix (Sepharose 4 Fast Flow) was obtained after hydrolysis for 180min at 70 degrees C in concentrated hydrochloric acid. When Benzamidine Sepharose 4 Fast Flow media were treated this way p-aminobenzoic acid and p-aminobenzamidine were the only products released from the ligand. A chromatographic system based on ion-pair reversed phase separation was used to quantify these ligand products. The mobile phase was made acidic enough to make p-aminobenzoic acid and p-aminobenzamidine positively charged in order to make ion-pair formation with hexanesulfonic acid possible. The relative standard deviation of th e method was below 2% and no systematic errors could be detected when the results were compared to an independent method based on elemental analysis (nitrogen). The new HPLC method was used to analyse ligand densities in the range of 2-20 micromol/ml medium.

C-peptide prevents glomerular hypertrophy and mesangial matrix expansion in diabetic rats.

BACKGROUND: There is accumulating evidence that C-peptide exerts beneficial renal effects in type-1 diabetes by reducing glomerular hyperfiltration, albuminuria and glomerular hypertrophy in the early stage of nephropathy. The aim of this study was to clarify further the effects of C-peptide on renal structural changes in type-1 diabetic rats. METHODS: The effects of C-peptide or placebo on glomerular volume, mesangial expansion, glomerular basement membrane thickness, albuminuria and glomerular filtration rate (GFR) were studied in three groups of rats: a non-diabetic group (N, n=9) and two groups that, during 8 weeks of diabetes, were left untreated for 4 weeks and then given a subcutaneous infusion of either placebo (D, n=11) or C-peptide (DCp, n=11) during the next 4 weeks. Furthermore, GFR was studied after 4 weeks of diabetes in an additional diabetic group (D-early, n=9) and in an age-matched non-diabetic group (N-early, n=9). RESULTS: After 4 weeks, GFR in the D-early group was 102% higher than in the N-early group. GFR after 8 weeks did not differ between the study groups. The D group presented with a 33% larger glomerular volume than the N group (P<0.001), while glomerular volume in the DCp group was similar to that in the N-group. Total mesangial and mesangial matrix fractions were increased by 46% (P<0.001) and 133% (P<0.001), respectively, in the D group. The corresponding values in the DCp group did not differ from those for the non-diabetic animals. Neither the thickness of the glomerular basement membrane nor the level of albuminuria differed significantly between the study groups. CONCLUSIONS: C-peptide administration in replacement dose to streptozotocin-diabetic rats serves to limit or prevent the glomerular hypertrophy and the mesangial matrix expansion seen in the post-hyperfiltration phase of early diabetic nephropathy.

Surface chemical analysis of carbohydrate materials used for chromatography media by time-of-flight secondary ion mass spectrometry.

The surface chemical structure of two raw materials (agarose and dextran) and four base matrixes used in the manufacture of chromatography media were analyzed using time-of-flight secondary ion mass spectrometry (TOF-SIMS). The results show that the small differences in molecular structure between these materials result in significant differences in the TOF-SIMS spectra and that these differences can be identified and quantified using either of two different approaches. In a novel approach, fragment ion distributions were extracted from the TOF-SIMS spectra for each material, providing an immediate and systematic overview of the spectral features. Difference fragment distributions were used to highlight spectral differences between the materials. The results of the fragment ion distribution analysis, in terms of identification and quantification of spectral variations between different materials, were found to be in agreement with the results from a principal component analysis using the same set of data. Both methods were found capable of (i) distinguishing between agarose and dextran and (ii) detecting and quantifying the degree of cross-linking present in the four base matrix materials. In addition, using a deuterated chemical cross-linker, it was possible to identify spectral features specifically connected to the cross-link molecular structure.

C-peptide and captopril are equally effective in lowering glomerular hyperfiltration in diabetic rats.

BACKGROUND: C-peptide has been shown to reduce glomerular hyperfiltration, glomerular hypertrophy and urinary albumin excretion in type 1 diabetes, but its effect has not been compared with that of an angiotensin-converting enzyme inhibitor (ACEI) in the early stage of renal involvement in diabetes. METHODS: Glomerular filtration rate (GFR) was measured in terms of inulin clearance and renal blood flow, using ultrasound technique, in four groups of streptozotocin-induced diabetic rats before and after a 60 min infusion of C-peptide (D-Cp), captopril (D-ACEI), C-peptide and captopril (D-Cp-ACEI) or placebo (D-placebo). In addition, a non-diabetic control group was studied before and after captopril infusion (C-ACEI). RESULTS: GFR was 37-51% higher in the diabetic groups than in the control animals. GFR decreased after treatment in the D-Cp, D-ACEI and D-Cp-ACEI groups, but did not change in the D-placebo group. Blood flow increased by 26-32% in the three groups receiving captopril and by 5% in the diabetic groups treated with C-peptide alone or placebo. The increase in blood flow in the three ACEI-treated groups was significantly greater than in the D-placebo group. Filtration fraction fell significantly in all groups, but only in the combined D-Cp-ACEI group did it fall significantly more than in the D-placebo group. CONCLUSIONS: C-peptide and captopril lower diabetes-induced glomerular hyperfiltration to a similar extent, but the influence of captopril on blood flow is greater than that of C-peptide, suggesting different mechanisms of action. No statistically significant additive effects of C-peptide and captopril were shown in this acute infusion study.

Chemical characterisation of different separation media based on agarose by static time-of-flight secondary ion mass spectrometry.

In this paper, the novel application of time-of-flight secondary ion mass spectrometry (TOF-SIMS) for qualitative and semi-quantitative investigation of the surface chemistry of separation media based on beaded agarose is reported. Five different media were studied: DEAE Sepharose Fast Flow, Q Sepharose Fast Flow, SP Sepharose Fast Flow, Phenyl Sepharose Fast Flow at ligand densities between 7 and 33% (w/w) and the base matrix Sepharose 6 Fast Flow. The obtained TOF-SIMS spectra reveal significant chemical information regarding the ligands (DEAE, Q, SP and Phenyl) which are covalently attached to the agarose-based matrix Sepharose 6 Fast Flow. For the anion-exchange media (DEAE and Q Sepharose Fast Flow), the positive TOF-SIMS spectra yielded several strong characteristic fragment peaks from the amine ligands. Structural information was obtained, e.g. from the peak at m/z 173.20, originating from the ion structure [(C2H5)2NCH2CH2NH(C2H5)2l+, which shows that the ligand in DEAE Sepharose Fast Flow is composed of both tertiary and quaternary amines. The positive spectrum of Phenyl Sepharose Fast Flow contained major fragments both from the base matrix and the ligand. The cation-exchanger (SP Sepharose Fast Flow) gave rise to a positive spectrum resembling that of the base matrix (Sepharose 6 Fast Flow) but with a different intensity pattern of the matrix fragments. In addition, peaks with low intensity at m/z 109.94, 125.94 and 139.95 corresponding to Na2SO2+, Na2SO3+ and Na2SO3CH2+, respectively, were observed. The positive TOF-SIMS spectrum of Sepharose 6 Fast Flow contains a large number of fragments in the mass range up to m/z 200 identified as CxHyOz and CxHy structures. The results clearly show that positive TOF-SIMS spectra of different media based on Sepharose 6 Fast Flow are strongly influenced by the ligand coupled to the matrix. The negative TOF-SIMS spectra contained several ligand-specific, characteristic peaks for the cation-exchanger, having sulphonate as the ion-exchange group. Negative fragments such as S-, SO-, SO2-, SO3-, C2H3SO3-, C3H5SO3- and OC3H5SO3- were observed. Phenyl Sepharose Fast Flow, which has an uncharged group (Phenyl) coupled to the agarose matrix yielded one ligand-related peak corresponding to the C6H5O- fragment. DEAE and Q ligands could only be identified by the appearance of the fragments CN- and CNO- in the negative spectrum. However, a strong peak corresponding to the counter ion (Cl-) was observed. TOF-SIMS analysis can also be used for the investigation of residues from the coupling procedure that bonds the ligands to the matrix. One example is the observation of bromine peaks in the negative spectrum of Q Sepharose Fast Flow. Furthermore, it has also been shown that different ligand concentrations of Phenyl Sepharose Fast Flow can easily be detected by TOF-SIMS analysis. Information regarding the difference between the ligand density on the surface of the beads and in the bulk can also be obtained. However, spectra registered on the outermost surface and on the pore surface (crushed beads) of DEAE Sepharose Fast Flow clearly show that the agarose and the DEAE groups are homogeneously distributed in the beads.

C-peptide improves adenosine-induced myocardial vasodilation in type 1 diabetes patients.

Patients with type 1 (insulin-dependent) diabetes show reduced skeletal muscle blood flow and coronary vasodilatory function despite intensive insulin therapy and good metabolic control. Administration of proinsulin C-peptide increases skeletal muscle blood flow in these patients, but a possible influence of C-peptide on myocardial vasodilatory function in type 1 diabetes has not been investigated. Ten otherwise healthy young male type 1 diabetic patients (Hb A1c 6.6%, range 5.7-7.9%) were studied on two consecutive days during normoinsulinemia and euglycemia in a double-blind, randomized, crossover design, receiving intravenous infusion of C-peptide (5 pmol.kg-1.min-1) for 120 min on one day and saline infusion on the other day. Myocardial blood flow (MBF) was measured at rest and during adenosine administration (140 microg.kg-1.min-1) both before and during the C-peptide or saline infusions by use of positron emission tomography and [15O]H2O administration. Basal MBF was not significantly different in the patients compared with an age-matched control group, but adenosine-induced myocardial vasodilation was 30% lower (P < 0.05) in the patients. During C-peptide administration, adenosine-stimulated MBF increased on average 35% more than during saline infusion (P < 0.02) and reached values similar to those for the healthy controls. Moreover, as evaluated from transthoracal echocardiographic measurements, C-peptide infusion resulted in significant increases in both left ventricular ejection fraction (+5%, P < 0.05) and stroke volume (+7%, P < 0.05). It is concluded that short-term C-peptide infusion in physiological amounts increases the hyperemic MBF and left-ventricular function in type 1 diabetic patients.

Preparation and characterization of prototypes for multi-modal separation media aimed for capture of negatively charged biomolecules at high salt conditions.

Several prototypes of multi-modal ligands suitable for the capture of negatively charged proteins from high conductivity (28 mS/cm) mobile phases were coupled to Sepharose 6 Fast Flow. These new prototypes of multi-modal anion-exchangers were found by screening a diverse library of multi-modal ligands and selecting anion-exchangers resulting in elution of test proteins at high ionic strength. Candidates were then tested with respect to breakthrough capacity of BSA in a buffer adjusted to a high conductivity (20 mM Piperazine and 0.25 M NaCl, pH 6.0). The recovery of BSA was also tested with a salt step (from 0.25 to 2.0 M NaCl using 20 mM Piperazine as buffer, pH 6.0) or with a pH-step to pH 4.0. We have found that non-aromatic multi-modal anion-exchange ligands based on primary or secondary amines (or both) are optimal for the capture of proteins at high salt conditions. Furthermore, these new multi-modal anion-exchange ligands have been designed to take advantage not only of electrostatic but also hydrogen bond interactions. This has been accomplished through modification of the ligands by the introduction of hydroxyl groups in the proximity of the ionic group. Experimental evidence on the importance of the relative position of the hydroxyl groups on the ligand in order to improve the breakthrough capacity of BSA has been found. Compared to strong anion-exchangers such as Q Sepharose Fast Flow the new multi-modal weak anion-exchangers have breakthrough capacities of BSA at mobile phases of 28 mS/cm and pH 6.0 that are 20-30 times higher. The new multi-modal anion-exchangers can also be used at normal anion-exchange conditions and with either a salt step or a pH-step to acidic pH can accomplish the elution of proteins. In addition, the functional performance of the new anion-exchangers was found to be intact after treatment in 1.0 M sodium hydroxide solution for 1 week. A number of multi-modal anion-exchange ligands based on aromatic amines exhibiting high breakthrough capacity of BSA have been found. With these ligands recovery was often found to be low due to strong non-electrostatic interactions. However, for phenol derived anion-exchange media the recovery can be improved by desorption at high pH.

Preparation and characterization of prototypes for multi-modal separation aimed for capture of positively charged biomolecules at high-salt conditions.

Several prototypes of aromatic (Ar) and non-aromatic (NoAr) cation-exchange ligands suitable for capture of proteins from high conductivity (ca. 30 mS/cm) mobile phases were coupled to Sepharose 6 Fast Flow. These new prototypes of multi-modal cation-exchangers were found by screening a diverse library of multi-modal ligands and selecting cation-exchangers resulting in elution of test proteins at high ionic-strength. Candidates were then tested with respect to breakthrough capacity of bovine serum albumin (BSA), human IgG and lysozyme in buffers adjusted to a high conductivity. By applying a salt-step or a pH-step the recoveries were also tested. We have found that aromatic multi-modal cation-exchanger ligands based on carboxylic acids seem to be optimal for the capture of proteins at high-salt conditions. Experimental evidence on the importance of the relative position of the aromatic group in order to improve the breakthrough capacity at high-salt conditions has been found. It was also found that an amide group on the alpha-carbon was essential for capture of proteins at high-salt conditions. Compared to a strong cation-exchanger such as SP Sepharose Fast Flow the best new multi-modal weak cation-exchangers have breakthrough capacities of BSA, human IgG and lysozyme that are 10-30 times higher at high-salt conditions. The new multi-modal cation-exchangers can also be used at normal cation-exchange conditions and with either a salt-step or a pH-step (to pH-values where the proteins are negatively charged) to accomplish elution of proteins. In addition, the functional performance of the new cation-exchangers was found to be intact after treatment in 1.0 M sodium hydroxide solution for 10 days. For BSA it was also possible to design cation-exchangers based on non-aromatic carboxyl acid ligands with high capacities at high-salt conditions. A common feature of these ligands is that they contain hydrogen acceptor groups close to the carboxylic group. Furthermore, it was also possible to obtain high breakthrough capacities for lysozyme and BSA of a strong cation-exchanger (SP Sepharose Fast Flow) if phenyl groups were attached to the beads. Varying the ligand ratio (SP/Phenyl) could be used for optimizing the function of mixed-ligand ion-exchange media.

C-peptide increases forearm blood flow in patients with type 1 diabetes via a nitric oxide-dependent mechanism.

Proinsulin C-peptide has been shown to increase muscle blood flow in type 1 diabetic patients. The underlying mechanism is not fully understood. The aim of this study was to evaluate if the vasodilator effect of C-peptide is mediated by nitric oxide (NO). Eleven type 1 diabetic patients were studied two times and randomized to administration of intravenous and intra-arterial infusion of C-peptide or saline. Forearm blood flow (FBF) was measured by venous occlusion plethysmography during infusion of C-peptide or saline before, during, and after NO synthase (NOS) blockade. Endothelium-dependent and -independent vasodilatation was evaluated by administration of acetylcholine and sodium nitroprusside, respectively. FBF increased by 35% during intravenous C-peptide (P < 0.01) but not during saline infusion (-2%, not significant). NOS blockade resulted in a more pronounced reduction in FBF during intravenous C-peptide than during saline infusion (-41 vs. -26%, P < 0.05). Intra-arterial C-peptide failed to increase FBF during NOS blockade. However, when C-peptide was given after the recovery from NOS blockade, FBF rose by 30% (P < 0.001). The vasodilator effects of acetylcholine and nitroprusside were not influenced by C-peptide. It is concluded that the stimulatory effect of C-peptide on FBF in type 1 diabetic patients is mediated via the NO system and that C-peptide increases basal endothelial NO levels.

Amelioration of sensory nerve dysfunction by C-Peptide in patients with type 1 diabetes.

Studies have demonstrated that proinsulin C-peptide stimulates the activities of Na(+),K(+)-ATPase and endothelial nitric oxide synthase, both of which are enzyme systems of importance for nerve function and known to be deficient in type 1 diabetes. The aim of this randomized double-blind placebo-controlled study was to investigate whether C-peptide replacement improves nerve function in patients with type 1 diabetes. Forty-nine patients without symptoms of peripheral neuropathy were randomized to either 3 months of treatment with C-peptide (600 nmol/24 h, four doses s.c.) or placebo. Forty-six patients (15 women and 31 men, aged 29 years, diabetes duration 10 years, and HbA(1c) 7.0%) completed the study. Neurological and neurophysiological measurements were performed before and after 6 and 12 weeks of treatment. At baseline the patients showed reduced nerve conduction velocities in the sural nerve (sensory nerve conduction velocity [SCV]: 50.9 +/- 0.70 vs. 54.2 +/- 1.2 m/s, P < 0.05) and peroneal nerve (motor nerve conduction velocity: 45.7 +/- 0.55 vs. 53.5 +/- 1.1 m/s, P < 0.001) compared with age-, height-, and sex-matched control subjects. In the C-peptide treated group there was a significant improvement in SCV amounting to 2.7 +/- 0.85 m/s (P < 0.05 compared with placebo) after 3 months of treatment, representing 80% correction of the initial reduction in SCV. The change in SCV was accompanied by an improvement in vibration perception in the patients receiving C-peptide (P < 0.05 compared with placebo), whereas no significant change was detectable in cold or heat perception. In conclusion, C-peptide administered for 3 months as replacement therapy to patients with early signs of diabetic neuropathy ameliorates nerve dysfunction.

Loss of temporal lobe beta power in young adults with type 1 diabetes mellitus.

Cognitive defects have been reported in type 1 diabetes mellitus with possible correlation to recurrent episodes of hypoglycemia. The purpose of the present study was to identify signs of brain dysfunction with quantitative EEG in adults with insulin-dependent (type 1) diabetes. Patients (n = 49) with type 1 diabetes and controls (n = 51) were recruited. All patients had good glycemic control, no diabetic polyneuropathy and a minor history of severe hypoglycaemia. EEG was recorded for 15 min following a standardized protocol, power spectra were obtained from 236-584 s of artefact-free EEG from each subject and EEG was repeated in diabetic patients after 3 and 9 months. The most pronounced finding was a loss of fast oscillations (alpha, beta and gamma activity) in both posterior temporal regions, with p< 0.001 for beta and p< 0.05 or 0.01 for alpha and gamma activity in the diabetes patients. A decrease in beta activity was also present bilaterally in the anterior temporal and occipital regions (p< 0.05 or 0.01). The alpha peak frequency was lower in patients than in controls, with reductions bilaterally in the temporo-central regions (p< 0.01). These changes were not found to correlate to a previous history of hypoglycaemia. The alpha and beta power showed a high test-retest reliability at both 3 and 9 months (0.88-0.92). The focal decrease in temporal lobe fast activity suggests that these brain regions are preferentially affected by type 1 diabetes. This abnormality may be related to the mechanism underlying the cognitive dysfunction described in diabetes.

C-peptide exerts beneficial effects on myocardial blood flow and function in patients with type 1 diabetes.

Myocardial dysfunction, perfusion abnormalities, and the extent to which these abnormalities may be reversed by C-peptide administration was assessed in type 1 diabetic patients. Eight patients were studied before and during a 0.84-mg/kg dipyridamole administration using a randomized double-blind crossover protocol with infusion of C-peptide (6 pmol x kg(-1) x min(-1)) or saline during 60 min on two different days. Myocardial function was measured as peak myocardial velocity during systole (Vs) and early diastole (Vd) by pulsed tissue Doppler imaging. Myocardial contrast echocardiography was used for assessment of myocardial blood volume (SI(max)) and myocardial blood flow index (MBFI) calculated from the relation between trigger interval and signal intensity. Eight age-matched healthy volunteers served as control subjects. In the basal state, Vd (13.8 +/- 0.6 vs. 15.6 +/- 0.5 cm/s, P < 0.04) and SI(max) (6.6 +/- 0.6 vs. 8.2 +/- 0.6 a.u. P < 0.04) were reduced in patients compared with control subjects. Dipyridamole administration significantly increased indexes of myocardial function and blood flow to a similar extent in patients and control subjects. During C-peptide administration, Vs and Vd increased by 12% (P = 0.03), SI(max) increased from 6.6 +/- 0.6 to 8.1 +/- 0.7 a.u. (P < 0.02), and MBFI increased from 3.3 +/- 0.4 to 5.3 +/- 0.9 (P < 0.05). The results demonstrate that type 1 diabetic patients have impaired myocardial function and perfusion in the basal state that can be improved by short-term replacement of C-peptide.

Insulin, but not proinsulin C-peptide, enhances platelet fibrinogen binding in vitro in Type 1 diabetes mellitus patients and healthy subjects.

INTRODUCTION: Insulin treatment is essential in Type 1 diabetes mellitus (DM). However, previous studies have shown complex effects of insulin on platelet function. Proinsulin C-peptide has shown beneficial effects in Type 1 DM, but it is not known if it can affect platelet activation. We thus investigated how insulin, C-peptide, and their combination influence platelets from DM patients and healthy subjects. MATERIALS AND METHODS: Hirudinized blood from patients (n = 10) and healthy subjects (n = 10) was preincubated in the absence or presence of insulin (10 and 100 microU/ml), C-peptide (0.3, 1, and 10 nM), or the combination (1 nM C-peptide + 100 microU/ml insulin or 10 nM C-peptide + 100 microU/ml insulin) and further incubated without or with 10(-6) M ADP. Platelet activation was monitored by platelet fibrinogen binding and P-selectin expression using whole blood flow cytometry. Data are presented as binding index (BI), which integrates the percentage of activated cells and their mean fluorescence intensity. RESULTS: Insulin enhanced ADP-induced platelet fibrinogen binding in both Type 1 DM patients and healthy subjects. For example, ADP-stimulated platelet fibrinogen BI increased from 4.25 +/- 0.74 to 8.63 +/- 2.00 with 10 microU/ml insulin (P < .05) in Type 1 DM patients. However, insulin did not increase platelet P-selectin expression. Proinsulin C-peptide did not influence platelet fibrinogen binding or P-selectin expression in either Type 1 DM patients or healthy subjects. The combination of C-peptide and insulin had similar effects as insulin alone. CONCLUSIONS: Insulin at physiological concentrations enhances platelet fibrinogen binding in both Type 1 DM patients and healthy subjects, whilst C-peptide does not influence platelet activation.

In vivo biodistribution and pharmacokinetics of (18)F-labeled human C-peptide: evaluation in monkeys using positron emission tomography.

The recently observed beneficial effects exerted by C-peptide in insulin-dependent diabetes patients (IDDM) have instigated research into the mechanisms of C-peptide action as well as the location for it. Here we report in vivo biodistribution studies performed in monkeys using positron emission tomography (PET) and C-peptide labeled in the N-terminal with fluorine-18. Following iv injection of the radiotracer, dynamic decay data were collected over the chest and/or abdomens of the monkeys. The radioactivity distributed mainly to the kidneys, less to the heart and to some extent to the liver. Excretion of radioactivity into the urinary bladder was observed. Brain uptake was not detected in a static emission scan of the head performed at late times. Accumulation of radioactivity in the skeleton as a result of in vivo defluorination was not observed. Pharmacokinetic modeling of the regional concentrations of radioactivity over time resulted, for most organs, in two-compartment models. The organs with the highest radioactivity concentrations have been identified, enabling dose estimations for studies in humans with low or no C-peptide.

Combined endothelin receptor blockade evokes enhanced vasodilatation in patients with atherosclerosis.

Endothelin (ET)-1 causes vasoconstriction via ET(A) and ET(B) receptors located on vascular smooth muscle cells and vasodilatation via ET(B) receptors on endothelial cells. Studies in vitro indicate an upregulation of ET(B) receptors in atherosclerosis. The present study investigated the vascular effects evoked by endogenous ET-1 in atherosclerotic patients. Forearm blood flow (FBF) was measured with venous occlusion plethysmography in 10 patients with atherosclerosis and in 10 healthy control subjects during intra-arterial infusion of selective ET receptor antagonists. The ET(B) receptor antagonist BQ788 evoked a significant increase in FBF (31+/-13%) in the patients, whereas a 20+/-9% reduction was observed in the control subjects. The ET(A) receptor antagonist BQ123 combined with BQ788 evoked a marked increase in FBF (102+/-25%) in the patients compared with no effect in the control subjects (-3+/-9%, P<0.001 versus patients). The ET(A) receptor antagonist BQ123 increased FBF to a similar degree in patients (39+/-11%) as in control subjects (41+/-11%). The increase in FBF evoked by selective ET(A) receptor blockade was significantly (P<0.05) less than that evoked by combined ET(A)/ET(B) receptor blockade in the atherosclerotic patients. These observations suggest an enhanced ET-1-mediated vascular tone in atherosclerotic patients, which is at least partly due to increased ET(B)-mediated vasoconstriction.

Enhanced vasoconstrictor effect of big endothelin-1 in patients with atherosclerosis: relation to conversion to endothelin-1.

The enhanced production of endothelin-1 (ET-1) in atherosclerotic arteries may be related to increased activity of the endothelin converting enzyme (ECE) which converts big ET-1 to ET-1. The purpose of the present study was to investigate whether the vasoconstrictor activity of big ET-1 is altered as a result of increased conversion to ET-1 in patients with atherosclerosis. Big ET-1 was infused into the brachial artery of nine patients with atherosclerosis and nine healthy controls. Forearm blood flow (FBF) was measured with venous occlusion plethysmography. Big ET-1 (15 and 50 pmol/min) evoked more pronounced reduction in FBF in the patients than in the controls (P<0.01). The low dose big ET-1 elevated local venous plasma ET-1 (from 2.8+/-0.3 to 9.0+/-1.6 pmol/l; P<0.01) and the net formation of ET-1 (from -6.6+/-8.6 to 50.5+/-16.0 fmol/min; P<0.01) in the patients but not in the controls. Furthermore, histological examination revealed ECE immunoreactivity in the fibrous cap of atherosclerotic plaques in addition to the endothelium and smooth muscle cells of radial arteries. In conclusion, administration of big ET-1 results in enhanced vasoconstriction and increased formation of ET-1 in patients with atherosclerosis as compared to healthy controls which may be due to increased activity of ECE.