Effects, Safety, and Treatment Experience of Advanced Hybrid Closed-Loop Systems in Clinical Practice Among Adults Living With Type 1 Diabetes

BACKGROUND

There are few studies providing a more comprehensive picture of advanced hybrid closed-loop (AHCL) systems in clinical practice. The aim was to evaluate the effects of the AHCL systems, Tandem® t: slim X2™ with Control IQ™, and MiniMed™ 780G, on glucose control, safety, treatment satisfaction, and practical barriers for individuals with type 1 diabetes.

METHOD

One hundred forty-two randomly selected adults with type 1 diabetes at six diabetes outpatient clinics in Sweden at any time treated with either the Tandem Control IQ (TCIQ) or the MiniMed 780G system were included. Glycated hemoglobin A1c (HbA1c) and glucose metrics were evaluated. Treatment satisfaction and practical barriers were examined via questionnaires.

RESULTS

Mean age was 42 years, median follow-up was 1.7 years, 58 (40.8%) were females, 65% used the TCIQ system. Glycated hemoglobin A1c was reduced by 0.6% (6.8 mmol/mol; 95% confidence interval [CI] = 0.5-0.8% [5.3-8.2 mmol/mol]; P < .001), from 7.3% to 6.7% (57-50 mmol/mol). Time in range (TIR) increased with 14.5% from 57.0% to 71.5% (95% CI = 12.2%-16.9%; P < .001). Time below range (TBR) (<70 mg/dL, <3.9 mmol/L) decreased from 3.8% to 1.6% (P < .001). The standard deviation of glucose values was reduced from 61 to 51 mg/dL (3.4-2.9 mmol/L, P < .001) and the coefficient of variation from 35% to 33% (P < .001). Treatment satisfaction increased, score 14.8 on the Diabetes Treatment Satisfaction Questionnaire (DTSQ) (change version ranging from -18 to 18, P < .001). Four severe hypoglycemia events were detected and no cases of ketoacidosis. Skin problems were experienced by 32.4% of the study population.

CONCLUSIONS

Advanced hybrid closed-loop systems improve glucose control with a reasonable safety profile and high treatment satisfaction. Skin problems are common adverse events.

The effect of carbohydrate intake on glycaemic control in individuals with type 1 diabetes: a randomised, open-label, crossover trial

Background

Few studies have examined the effects of lower carbohydrate diets on glucose control in persons with type 1 diabetes (T1D). The objective of the study was to investigate whether a moderate carbohydrate diet improves glucose control in persons with T1D.

Methods

A randomised, multicentre, open-label, crossover trial over 12 weeks. There were 69 individuals assessed for eligibility, 54 adults with T1D and HbA1c ≥ 58 mmol/mol (7.5%) were randomised. Interventions were moderate carbohydrate diet versus traditional diet (30 vs 50% of total energy from carbohydrates) over four weeks, with a four-week wash-out period between treatments. Masked continuous glucose monitoring was used to evaluate effects on glucose control. The primary endpoint was the difference in mean glucose levels between the last 14 days of each diet phase.

Findings

50 individuals were included in the full analysis set with a mean baseline HbA1c of 69 mmol/mol (8.4%), BMI 29 kg/m2, age of 48 years, and 50% were female. The difference in mean glucose levels between moderate carbohydrate and traditional diet was -0.6 mmol/L, 95% CI -0.9 to -0.3, p < 0.001. Time in range increased during moderate carbohydrate diet by 4.7% (68 min/24 h) (95% CI 1.3 to 8.0), p = 0.008. Time above range (>10 mmol/L) decreased by 5.9% (85 min/24 h), 95% CI -9.6 to -2.2, p = 0.003. There were no significant differences in the standard deviation of glucose levels (95% CI -0.3 to 0.0 mmol/L, p = 0.15) or hypoglycaemia in the range <3.9 mmol/L (95% CI -0.4 to 2.9%, p = 0.13) and <3.0 mmol/L (95% CI -0.4 to 1.6%, p = 0.26). Four participants withdrew, none because of adverse events. There were no serious adverse events including severe hypoglycaemia and ketoacidosis. Mean ketone levels were 0.17 (SD 0.14) mmol/L during traditional and 0.18 (SD 0.13) mmol/L during moderate carbohydrate diet (p = 0.02).

Interpretation

A moderate carbohydrate diet is associated with decreases in mean glucose levels and time above range and increases in time in range without increased risk of hypoglycaemia or ketoacidosis compared with a traditional diet in individuals with T1D.

Funding

The Healthcare Board, Region Västra Götaland, The Dr P Håkansson Foundation and the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement [ALFGBG-966173].

Risk factors, mortality trends and cardiovasuclar diseases in people with Type 1 diabetes and controls: A Swedish observational cohort study

BACKGROUND

Historically, the incidence of cardiovascular disease and mortality in persons with Type 1 diabetes (T1D) has been increased compared to the general population. Contemporary studies on time trends of mortality and cardiovascular disease are sparse.

METHODS

In this observational study, T1D persons were identified in the Swedish National Diabetes Registry (n=45,575) and compared with matched controls from the general population (n=220,141). Incidence rates from 2002 to 2019 were estimated with respect to mortality and cardiovascular disease in persons with T1D overall and when stratified for prevalent cardiovascular and renal disease relative to controls.

FINDINGS

Mean age in persons with T1D was 32.4 years and 44.9% (20,446/45,575) were women. Age- and sex- adjusted mortality rates declined over time in both groups but remained significantly higher in those with T1D compared to controls during 2017-2019, 7.62 (95% CI 7.16; 8·08) vs. 2.23 (95% CI 2.13; 2.33) deaths per 1,000 person years. Myocardial infarction, heart failure and stroke decreased over time in both groups, with persistent excess risks in the range of 3.4-5.0 times from 2017 to 2019 in those with T1D. T1D persons ≥45 years without previous renal or cardiovascular complications had standardized mortality rates similar or even lower than controls 5.55 (4.51; 6.60) vs.7.08 (6.75; 7.40) respectively in the last time period.

INTERPRETATION

Excess mortality persisted over time in persons with T1D, largely in patients with cardiorenal complications. Improved secondary prevention with a focus on individualized treatment is needed to close the gap in mortality for individuals with T1D.

FUNDING

This study was financed by grants from the ALF-agreement, NovoNordisk Foundation and the Swedish Heart and Lung Foundation.

Risk factors and incidence over time for lower extremity amputations in people with type 1 diabetes: an observational cohort study of 46,088 patients from the Swedish National Diabetes Registry

AIMS/HYPOTHESIS

The aim of this work was to study the incidence over time of lower extremity amputations and determine variables associated with increased risk of amputations in people with type 1 diabetes.

METHODS

Individuals with type 1 diabetes registered in the Swedish National Diabetes Registry with no previous amputation from 1 January 1998 and followed to 2 October 2019 were included. Time-updated Cox regression and gradient of risk per SD were used to evaluate the impact of risk factors on the incidence of amputation. Age- and sex-adjusted incidences were estimated over time.

RESULTS

Of 46,088 people with type 1 diabetes with no previous amputation (mean age 32.5 years [SD 14.5], 25,354 [55%] male sex), 1519 (3.3%) underwent amputation. Median follow-up was 12.4 years. The standardised incidence for any amputation in 1998-2001 was 2.84 (95% CI 2.32, 3.36) per 1000 person-years and decreased to 1.64 (95% CI 1.38, 1.90) per 1000 person-years in 2017-2019. The incidence for minor and major amputations showed a similar pattern. Hyperglycaemia and renal dysfunction were the strongest risk factors for amputation, followed by older age, male sex, cardiovascular comorbidities, smoking and hypertension. Glycaemic control and age- and sex-adjusted renal function improved during the corresponding time period as amputations decreased.

CONCLUSIONS/INTERPRETATION

The incidence of amputation and of the most prominent risk factors for amputation, including renal dysfunction and hyperglycaemia, has improved considerably during recent years for people with type 1 diabetes. This finding has important implications for quality of life, health economics and prognosis regarding CVD, indicating a trend shift in the treatment of type 1 diabetes.

Characteristics of Continuous Glucose Monitoring Metrics in Persons with Type 1 and Type 2 Diabetes Treated with Multiple Daily Insulin Injections

Background: Although guidelines advocate similar continuous glucose monitoring (CGM) targets for insulin-treated persons with type 1 diabetes (T1D) and type 2 diabetes (T2D), it is unclear how these persons differ with respect to hypoglycemia, glucose variability, and other CGM metrics in clinical practice. Methods: We used data from 2 multicenter randomized-controlled trials (GOLD and MDI-Liraglutide) where 161 persons with T1D and 124 persons with T2D treated with multiple daily injections were included and monitored with masked CGM. Results: Persons from both cohorts had similar mean glucose levels, 10.9 mmol/L (196 mg/dL) in persons with T1D and 10.8 mmol/L (194 mg/dL) in persons with T2D. Time in hypoglycemia (<3.9 mmol/L [70 mg/dL]) was 5.1% and 1.0% for persons with T1D and T2D, respectively (P < 0.001). Corresponding estimates for the standard deviations of mean glucose levels were 4.4 mmol/L (79 mg/dL) versus 3.0 (54 mg/dL) (P < 0.001), for coefficient of variation 41% versus 28% (P < 0.001), and for time in range 38.2% versus 45.3%, respectively (P = 0.004). Mean C-peptide levels were 0.05 nmol/L and 0.67 nmol/L (P < 0.001) for persons with T1D and T2D, respectively. Conclusions: Persons with T1D compared with persons with T2D treated with multiple daily insulin injections spend considerably more time in hypoglycemia, have higher glucose variability, and less "time in range." This needs to be taken into account in daily clinical care and in recommended targets for CGM metrics.

Investigation of early signs of systolic and diastolic dysfunction among persons with type 1 diabetes

Background

Persons with type 1 diabetes have a higher risk to develop heart failure than the general population, and the mechanism behind the increased risk is unclear. In epidemiological studies with hospitalisation for heart failure as endpoint HbA1c, body mass index and decreased kidney function are significant risk factors, but it is unclear how these risk factors influence the development of heart failure.

Methods

In this study, we investigated early signs of systolic and diastolic dysfunction with transthoracic echocardiography. Statistical analysis on correlation of risk factors and early signs of diastolic and systolic dysfunction was made.

Results

In this study population of 287 persons with type 1 diabetes, 160 were men and 127 were women with a mean age of 53.8 (SD 11.6) years and a mean diabetes duration of 36.2 (SD 13.5) years. There were 23 (8.2%) persons who fulfilled the definition of systolic dysfunction (ejection fraction <50% or regional wall motion abnormalities) and 24 persons (9%) the definition for diastolic dysfunction. When comparing the groups with either systolic or diastolic dysfunction to the rest of the population, the only significant risk factor was age in both groups and previous myocardial infarction in the systolic group.

Conclusion

In our study population with type 1 diabetes, we found signs of diastolic dysfunction in 9% and systolic dysfunction in 8.2%. Compared with published data from the general population, this rate is somewhat higher in a younger population. Only age was a significant risk factor in the study.

Risk Factors for Atrial Fibrillation in People With Type 1 Diabetes: An Observational Cohort Study of 36,258 Patients From the Swedish National Diabetes Registry

OBJECTIVE

This study identified variables associated with increased risk of atrial fibrillation in people with type 1 diabetes.

RESEARCH DESIGN AND METHODS

We performed a cohort study of people with type 1 diabetes from the Swedish National Diabetes Registry followed up between 1 January 2001 and 31 December 2013. Median follow-up was 9.7 years (interquartile range 5.2-13.0). The association between potential risk factors and incident atrial fibrillation was investigated using adjusted Cox regression. To compare the impact of each risk factor, the gradient of risk per 1 SD was estimated.

RESULTS

In this cohort of 36,258 patients with type 1 diabetes, 749 developed atrial fibrillation during follow-up. Older age, male sex, renal complications, increased BMI and HbA_1c, coronary artery disease, heart failure, and heart valve disease increased the risk of atrial fibrillation. Age, signs of renal dysfunction with macroalbuminuria, and decreasing estimated glomerular filtration rate were associated with the highest gradient of risk for atrial fibrillation. High blood pressure, severe obesity (BMI >35 kg/m²), and elevated levels of HbA_1c (>9.6%) were associated with increased risk, but no associations were found with hyperlipidemia or smoking.

CONCLUSIONS

The most prominent risk factors for atrial fibrillation in people with type 1 diabetes were older age, cardiovascular comorbidities, and renal complications, while obesity, hypertension, and hyperglycemia had more modest affects.

Influence from polydispersity on the morphology of Voronoi and equilibrium foams

Stochastic foam models are generated from Voronoi spatial partitioning, using the centers of equi-sized hard spheres in random periodic distributions as seed points. Models with different levels of polydispersity are generated by varying the packing of the spheres. Subsequent relaxation is then performed with the Surface Evolver software which minimizes the surface area for better resemblance with real foam structures. The polydispersity of the Voronoi precursors is conserved when the models are converted into equilibrium models. The relation between the sphere packing fraction and the resulting degree of volumetric polydispersity is examined and the relations between the polydispersity and a number of associated morphology parameters are then investigated for both the Voronoi and the equilibrium models. Comparisons with data from real foams in the literature indicate that the used method is somewhat limited in terms of spread in cell volume but it provides a very controlled way of varying the foam morphology while keeping it periodic and truly stochastic. The study shows several strikingly consistent relations between the spread in cell volume and other geometric parameters, considering the stochastic nature of the models.

From efficacy in trials to effectiveness in clinical practice: The Swedish Stroke Prevention Study

Blood pressure treatment has shown great efficacy in reducing cardiovascular events in randomized controlled trials. If this is effective in reducing cardiovascular disease in the general population, is less studied. Between 2001 and 2009 we performed an intervention to improve blood pressure control in the county of Västerbotten, using Södermanland County as a control. The intervention was directed towards primary care physicians and included lectures on blood pressure treatment, a computerized decision support system with treatment recommendations, and yearly feed back on hypertension control. Each county had approximately 255 000 inhabitants. Differences in age and incidence of cardiovascular disease were small. During follow-up, more than 400 000 patients had their blood pressure recorded. The mean number of measurements was eight per patient, yielding a total of 3.4 million blood pressure recordings. The effect of the intervention will be estimated combining the blood pressure data collected from the electronic medical records, with data on stroke, myocardial infarction and mortality from Swedish health registers. Additional variables, from health registers and Statistics Sweden, will be collected to address for confounders. The blood pressure data collected within this study will be an important asset for future epidemiological studies within the field of hypertension.

Generation of periodic stochastic foam models for numerical analysis

Stochastic cellular models of rigid foam based on Voronoi spatial partitioning are generated and investigated for potential use in numerical analysis using finite element methods. Such partitions are deterministic once a distribution of cell nuclei has been defined. A drawback is that the models tend to exhibit a significant share of short edges and small faces. Such small geometrical features are not likely to occur in real foams since they are unfavorable from a surface energy point of view and they also generate problems in numerical analysis due to associated meshing challenges. Through minimization of the surface area, using the computer software Surface Evolver, the Voronoi models are brought to better resemblance with ideal dry foam and the occurrence of small geometrical features is strongly reduced. It is generally seen that different seed point distribution algorithms result in different model topologies. The presented methodology is systematic, parameterized and the results are very promising. Good grounds are provided for modeling of real rigid foam materials, that do not necessarily fully resemble ideal dry foam.

New HTK-N46B cardioplegia provides superior protection during ischemia/reperfusion in failing hearts

AIM

The aim of this paper was to improve operative outcome during open-heart surgery in patients with failing hearts, the composition of cardioplegic solutions has to be further optimized. HTK-N46b, a novel cardioplegic solution, has been developed for efficient protection of the energy state of myocytes as well as endothelial cells. Aim of this study is the evaluation of HTK-N46b in comparison to its precursor Custodiol® (HTK) in failing rat hearts undergoing ischemia/reperfusion.

METHODS

In male Sprague Dawley rats myocardial infarction (MI) was induced by LAD ligation. Six weeks after MI cardiac function was determined by transthoracic echocardiography. Sixteen animals with hearts showing a fractional shortening <25% were randomly assigned to two groups, HTK (N.=8) and HTK-N46b (N.=8). After excision hearts were evaluated in an erythrocyte-perfused isolated working heart model. Cold ischemia (4°C) for 60 minutes was followed by 45 minutes of reperfusion. Cardiac arrest was induced either with HTK or HTK-N46b at the beginning of ischemia.

RESULTS

At similar preischemic fractional shortening (HTK-N46b: 14.41±1.83% vs. HTK: 14.91±1.92%; NS) postischemic recovery of stroke volume and stroke work were significantly improved in the HTK-N46b rat hearts compared to HTK. Concerning recovery of coronary flow there was no difference between groups. At the end of reperfusion the HTK-N46b protected group revealed higher levels of ATP (HTK-N46b: 22.01±0.89 nmol/mg protein vs. HTK: 16.83±1.72 nmol/mg protein; P<0.05) and energy charge (HTK-N46b: 0.82±0.02 vs. HTK: 0.74±0.02; P<0.05).

CONCLUSION

HTK-N46b showed superior cardioprotective properties according to postischemic hemodynamic recovery and biochemical markers compared to HTK in failing rat hearts.

Role of Toll-like receptors 2, 4, and 9 in mediating neutrophil dysfunction in alcoholic hepatitis

Neutrophil dysfunction in alcoholic hepatitis is associated with endotoxemia and an increased incidence of infection, but the mechanism is unclear. We aimed to investigate the role of Toll-like-receptors (TLR)2, 4, and 9 in mediating neutrophil dysfunction in alcoholic hepatitis. Neutrophils from healthy volunteers were incubated with alcoholic hepatitis patients' plasma (n = 12) with and without TLR2, 4, or 9 antagonists and with and without human albumin. TLR2, 4, and 9 expression, neutrophil oxidative burst, phagocytosis, and CXCR1+2 expression were measured by FACS analysis. Patients' plasma increased oxidative burst, decreased CXCR1+2 expression, and decreased phagocytosis of normal neutrophils in association with increased expression of TLR2, 4, and 9 and depletion of ATP. Inhibition of TLR2, 4, and 9 prevented the increase in oxidative burst and the decrease in CXCR1 and CXCR2 expression but did not prevent phagocytic dysfunction. Incubation with albumin completely prevented the patient plasma induced neutrophil dysfunction. Increased expression of TLR2, 4, and 9 is associated with neutrophil dysfunction, endotoxemia, and energy depletion. TLR2, 4, and 9 inhibition does not improve phagocytosis, indicating that TLR overexpression may be the result and not the cause of neutrophil activation. Albumin, an endotoxin scavenger, prevents the deleterious effect of patients' plasma on neutrophil phagocytosis, resting burst, and TLR expression.

Role of Toll-like receptors 2, 4, and 9 in mediating neutrophil dysfunction in alcoholic hepatitis

Neutrophil dysfunction in alcoholic hepatitis is associated with endotoxemia and an increased incidence of infection, but the mechanism is unclear. We aimed to investigate the role of Toll-like-receptors (TLR)2, 4, and 9 in mediating neutrophil dysfunction in alcoholic hepatitis. Neutrophils from healthy volunteers were incubated with alcoholic hepatitis patients' plasma (n = 12) with and without TLR2, 4, or 9 antagonists and with and without human albumin. TLR2, 4, and 9 expression, neutrophil oxidative burst, phagocytosis, and CXCR1+2 expression were measured by FACS analysis. Patients' plasma increased oxidative burst, decreased CXCR1+2 expression, and decreased phagocytosis of normal neutrophils in association with increased expression of TLR2, 4, and 9 and depletion of ATP. Inhibition of TLR2, 4, and 9 prevented the increase in oxidative burst and the decrease in CXCR1 and CXCR2 expression but did not prevent phagocytic dysfunction. Incubation with albumin completely prevented the patient plasma induced neutrophil dysfunction. Increased expression of TLR2, 4, and 9 is associated with neutrophil dysfunction, endotoxemia, and energy depletion. TLR2, 4, and 9 inhibition does not improve phagocytosis, indicating that TLR overexpression may be the result and not the cause of neutrophil activation. Albumin, an endotoxin scavenger, prevents the deleterious effect of patients' plasma on neutrophil phagocytosis, resting burst, and TLR expression.

Nitric oxide homeostasis as a target for drug additives to cardioplegia

The vascular endothelium of the coronary arteries has been identified as the important organ that locally regulates coronary perfusion and cardiac function by paracrine secretion of nitric oxide (NO) and vasoactive peptides. NO is constitutively produced in endothelial cells by endothelial nitric oxide synthase (eNOS). NO derived from this enzyme exerts important biological functions including vasodilatation, scavenging of superoxide and inhibition of platelet aggregation. Routine cardiac surgery or cardiologic interventions lead to a serious temporary or persistent disturbance in NO homeostasis. The clinical consequences are "endothelial dysfunction", leading to "myocardial dysfunction": no- or low-reflow phenomenon and temporary reduction of myocardial pump function. Uncoupling of eNOS (one electron transfer to molecular oxygen, the second substrate of eNOS) during ischemia-reperfusion due to diminished availability of L-arginine and/or tetrahydrobiopterin is even discussed as one major source of superoxide formation. Therefore maintenance of normal NO homeostasis seems to be an important factor protecting from ischemia/reperfusion (I/R) injury. Both, the clinical situations of cardioplegic arrest as well as hypothermic cardioplegic storage are followed by reperfusion. However, the presently used cardioplegic solutions to arrest and/or store the heart, thereby reducing myocardial oxygen consumption and metabolism, are designed to preserve myocytes mainly and not endothelial cells. This review will focus on possible drug additives to cardioplegia, which may help to maintain normal NO homeostasis after I/R.

Diltiazem during reperfusion preserves high energy phosphates by protection of mitochondrial integrity

OBJECTIVE

This study evaluates the effects of diltiazem administered during reperfusion on hemodynamic, metabolic, and ultrastructural postischemic outcome.

METHODS

Hearts of 38 adult White New Zealand rabbits underwent 60 min of global cold ischemia followed by 40 min of reperfusion in an erythrocyte perfused isolated working heart model. Hearts were randomly assigned to four groups and received diltiazem (0.1, 0.25, and 0.5 micromol/l) during reperfusion only, or served as control.

RESULTS

The postischemic time courses of heart rate, aortic flow, and external stroke work clearly reflected the dose-dependent negative chronotropic and inotropic efficacy of diltiazem in the two higher concentrations. High energy phosphates (HEP) determined from myocardial biopsies taken after 40 min of reperfusion were significantly better preserved in all treatment groups compared to control hearts. Similarly ultrastructural grading of mitochondria and myofilaments revealed a significant reduction of reperfusion injury in hearts that received diltiazem compared to control.

CONCLUSIONS

Diltiazem protects mitochondrial integrity and function, thereby preserving myocardial HEP levels. Only low dose diltiazem (0.1 micromol/l) during reperfusion combines both, optimal mitochondrial preservation with minimal changes in hemodynamics.

High-performance liquid chromatographic determination of p-aminohippuric acid and iothalamate in human serum and urine: comparison of two sample preparation methods

A high-performance liquid chromatography method applied to determine p-aminohippuric acid (PAH) and iothalamate (IOT) in serum and urine samples of patients was evaluated according to recovery, reproducibility and linearity utilizing narrow-bore columns. The mobile phase consisted of 0.15 M sodium dihydrogenphosphate with 1.2 mM tetrabutylammonium sulphate, the pH was adjusted to pH 4.6, acetonitrile was added to a final ratio of 95:5 (v/v), the flow-rate was set at 0.3 ml/min. The separation was achieved on a ODS Hypersil column (200 x 2.1 mm I.D.). The UV detector was set at 254 nm. PAH and IOT are used for evaluation of kidney function [effective renal plasma flow (ERPF) and glomerular filtration rate (GFR)]). Under the described chromatographic conditions two sample preparation techniques, ultrafiltration and acetonitrile precipitation were compared. The results demonstrate the accuracy of both methods in evaluation of ERPF and GFR. Due to its cost-effectiveness we recommend the acetonitrile precipitation method in clinical routine.

The erythrocyte-perfused "working heart" model: hemodynamic and metabolic performance in comparison to crystalloid perfused hearts

A brief period of ischemia was used to evaluate an erythrocyte-enriched Krebs-Henseleit (KH) buffer (n=8) compared to KH only (n=8) in an isolated working rabbit heart. Experimental protocol was as follows: preischemic baseline, 5 min of global ischemia followed by 45 min of reperfusion. Preischemic heart rate was identical, coronary flow was significantly lower (2.7 versus 5.6 mL/min/g wet wt, p<0.01), the other hemodynamic and biochemical values were significantly higher in erythrocyte-perfused hearts: aortic flow 23.5 versus 12.0, p<0.01; cardiac output 26.2 versus 17.6, p<0.01; all in mL/min/g wet wt; dp/dt max 1286 versus 997 mmHg/s, p<0.01; myocardial oxygen consumption 3.5 versus 2.3 micromol/min/g wet wt, p<0.05. During early reperfusion, in the erythrocyte-perfused hearts, coronary flow further increased (p<0.003), the other hemodynamic parameters returned to baseline values in both groups. High-energy phosphates showed significantly higher values (ATP 2.0+/-0.1 versus 1.3+/-0.1, p<0.05; CrP 2.0+/-0.2 versus 1.6+/-0.1, p<0.05 all in micromol/g wct wt), water content was significantly lower (81% versus 74%, p<0.05) in erythrocyte-perfused hearts. It can be concluded that the erythrocyte-perfused working heart model provides excellent oxygenation, leading to superior hemodynamic and metabolic performance. Additionally, in the erythrocyte-perfused hearts preservation of coronary flow reserve underlines the physiological competency of this preparation.

Oxidatively modified plasma phospholipids containing reactive carbonyl functions measured by HPLC: evidence for phosphatidylcholine-bound aldehydes in plasma of burn patients

A HPLC method has been developed to measure phosphatidylcholine (PC) containing reactive carbonyl functions in the sn-acyl residue in order to study processes in which such reactive carbonyls can be formed due to e.g. oxidative fragmentation. The method has been applied to determine PC-bound carbonyls as 2,4-dinitrophenylhydrazones (DNPH) in plasma of burn patients. Plasma from healthy volunteers served as controls. Additionally, in vitro oxidation experiments (A: plasma, buffer diluted; B: plasma + iron-EDTA complex and C: plasma + iron-EDTA complex + H2O2) have been performed to obtain and to identify 2,4-dinitrophenylhydrazine derivatizable carbonyl functions in plasma PC. Both, the PC-aldehydes and PC-aldehyde DNPH derivatives were cleavable with phospholipase C. Quantification was based on thin-layer chromatography purified soybean phosphatidylcholine, which was identically oxidized and derivatized as the plasma lipids in vitro.

Desensitization of rat cardiomyocyte adenylyl cyclase stimulation by plasma of noradrenaline-treated patients with septic shock

The purpose of this study was to test the possibility that the mechanisms of catecholamine-induced desensitization of cardiac beta-adrenoceptor stimulation are modified in septic shock. Exposure of neonatal rat cardiomyocytes for 48 hr to plasma of noradrenaline-treated patients with septic shock led to a down-regulation of beta-adrenoceptors by 35%, an increase in the level of inhibitory G protein alpha-subunits by 60%, and a decrease in isoproterenol-stimulated adenylyl cyclase activity by 50% in membranes prepared from the rat cardiomyocytes. Similar alterations were observed following pretreatment of the cells with plasma of adrenaline-treated patients with cardiogenic shock. In contrast, exposure of the cardiomyocytes to plasma of intensive care patients without shock, and to plasma of dopamine-treated patients with septic shock did not induce alterations of the cardiomyocyte adenylyl cyclase system. The dosage of the catecholamines had to be increased within the first two days of treatment in the noradrenaline-treated patients, but not in the dopamine-treated patients with septic shock. Thus, this observed tolerance to noradrenaline in the treatment of septic shock may, in part, be due to a desensitization of cardiac beta-adrenoceptor stimulation induced by the beta-adrenoceptor stimulatory effect of noradrenaline.

The enzymatic and release characteristics of sheep neutrophil elastase: a comparison with human neutrophil elastase

Sheep are often used to study tissue damage following shock after traumatic injury and in the course of other diseases. The processes involved are thought to be caused at least in part by elastase released from polymorphonuclear leukocytes (PMNs). Since little is known about elastase and its role as a mediator of tissue damage in sheep, we studied the biochemical properties and release characteristics to sheep leukocyte elastase (SLE) in comparison of those of human leukocyte elastase (HLE). Both enzymes showed similar molecular masses, amino-acid compositions, N-terminal amino-acid sequences, and abilities to digest elastin substrates. Differences, however, were found in kinetic parameters measured with the elastase-specific substrate N-methoxysuccinyl-(L-alanyl)2-L-prolyl-L- valine-4-nitroanilide (MeoSuc-AAPV-pNa). The Michaelis constant (Km) of ovine elastase was nearly 10 times higher (1.82 mM) than the Km of HLE (0.21 mM). Values of SLE calculated for kcat were 70% and for kcat/Km 8% of corresponding values determined for HLE. In addition, significant differences between sheep and human PMNs were found in in vitro stimulation experiments. In contrast to human PMNs, sheep neutrophils released no active elastase, and only 50 to 70% of the H2O2 produced by human PMNs. This failure to release active elastase could not be explained by a lower elastase content of sheep PMNs, as there were no significant differences found between the elastase contents of sheep and human PMNs. We conclude that elastase liberated by stimulated sheep PMNs is inactivated by a concomitantly released proteinase inhibitor also located within the sheep PMNs.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous determination of myocardial nucleotides, nucleosides, purine bases and creatine phosphate by ion-pair high-performance liquid chromatography

An ion-pair reversed-phase high-performance liquid chromatographic method is described for the separation and quantification of myocardial nucleotides, nucleosides, their metabolites and creatine phosphate-related compounds in a single run. Separation of a standard mixture containing 21 compounds was achieved on a 5-microns Hypersil ODS column with a 5-min isocratic elution (buffer: 0.1 M NaH2PO4, pH 5.5, containing 5.9 mM tetrabutylammonium hydrogen-sulphate) followed by a slow linear gradient to 17% acetonitrile. The method was applied to extracts of freeze-clamped rat heart tissue samples as well as to extracts of neonatal rat heart cardiomyocytes, and it provided good resolution of high-energy phosphates, including creatine phosphate, as well as of their degradation products.

Inhibition of Human, Ovine, and Baboon Neutrophil Elastase with Eglin c and Secretory Leukocyte Proteinase Inhibitor

The association rate constants (kon) of human, ovine, and baboon neutrophil elastase with two recombinant serine proteinase inhibitors (Eglin c, secretory leukocyte proteinase inhibitor) were compared. The association rate constant of sheep leukocyte elastase (SLE) with Eglin c is about 100 times lower (kon = 2.2 x 10(5) M-1s-1) than that of human elastase (kon = 2.4 x 10(7) M-1s-1). Baboon elastase, however, is as effectively blocked with Eglin c (kon = 2.5 x 10(7) M-1s-1) as human elastase. Secretory leukocyte proteinase inhibitor (SLPI) blocks the elastase of all three species with high efficiency; baboon elastase shows the highest association rate constant (kon = 5.6 x 10(7) M-1s-1) followed by human elastase (kon = 4.1 x 10(7) M-1s-1) and finally sheep elastase (kon = 1.2 x 10(7) M-1s-1). These findings demonstrate marked differences in the inhibition kinetic properties of ovine and human elastase. Concerning a future clinical application of proteinase inhibitors, the baboon seems a more suitable model than sheep to evaluate the effects of Eglin c and SLPI, since both inhibitors block baboon and human elastase with comparable efficiency.

Mechanisms in acute septic cardiomyopathy: evidence from isolated myocytes

Although often not considered, the heart is one of the targets of multiple organ failure in sepsis and septic shock, with myocardial depression being a prominent component of this "acute septic cardiomyopathy". Hypotheses concerning the etiology of this depression are increasingly elucidated on a cellular level, including dysfunction of the beta-adrenoceptor/G protein/adenylate cyclase system, calcium channel blockade by cardiodepressant factor, contractile impairment by activated leucocytes, as well as inhibition of protein synthesis by Pseudomonas exotoxin A. In the search for "mechanisms of myocardial depression in sepsis", isolated cardiomyocytes may play a role as research tools with respect to: a) discrimination between direct and indirect cardiodepressant effects; b) identifying not only the acute, but also chronic toxin- and mediator-induced cardiodepression; c) clarification of the mechanism of action of cardiodepressant bacterial toxins and sepsis mediators; d) establishment of in vitro models of leucocyte-mediated cardiodepression in sepsis.

Hyperdynamic sepsis in baboons: I. Aspects of hemodynamics

The baboon has a number of advantages as a shock model, as its physiological as well as its biochemical behaviour is similar to man. Therefore we have tried to set up a model to mimic the early hyperdynamic phase of clinical sepsis. Seven baboons, 21-25 kg body weight were kept under EEG servocontrolled anesthesia for 8 hr. During this time live E. coli (ATC #33985) 2 x 10(10) BW/8 hr were continuously infused intravenously. Adequate fluid supply with Ringer's solution (up to 40 ml/kg/hr) was given to keep the pulmonary artery wedge pressure at baseline levels; this procedure resulted in a hyperdynamic response with a cardiac output (CO) 20-35% above baseline and a decrease (20-39%) in mean arterial pressure (MAP), leading to a 50% decrease in peripheral resistance. The pulmonary vascular changes were reflected in an increase of the mean pulmonary pressure (PA) to 42% above baseline and a marked rise in pulmonary vascular resistance (PVR) to 50% above baseline with no additional changes in pulmonary gas exchange. After 8 hr both CO and MAP were inversely correlated (r = 0.9-1) with dramatically increased catecholamine plasma levels (15 times above baseline). With continuous infusion of live E. coli (blood levels 10(5)-10(6) CFU/ml) and massive fluid supply we have successfully mimicked hyperdynamic sepsis with severe organ failure after an 8-hr observation period.

The cell in shock: the origin of multiple organ failure

The immediate organ damage seen after multiple trauma and in shock is a typical example of non-bacterial inflammation triggered by activation of various mediators of both the humoral and cellular systems. Anaphylatoxins and the low-flow syndrome during the shock phase account for increased PMN* margination, which in turn causes pulmonary leukostasis and may provoke massive mediator release by PMN (oxygen radicals, proteinases, eicosanoids, PAF etc). This probably leads to severe endothelial cell damage, especially in the lung. Adherence of PMN to the endothelium appears to create the micro-environment where high concentrations of proteolytic enzymes and reactive oxygen radicals exert a deleterious effect on the cell membrane. Endothelial cell membrane injury leads to increased vascular permeability and cell edema. The development of the 'organ in shock' may require a few hours and initially cause minor or no functional impairment at all. Only when shock is severe is there early organ failure, which in this stage may still be an expression of non-bacterial inflammation. Numerous studies have reported the existence of shock-induced cardiodepressant substances in association with various forms of circulatory shock. We have determined a net negative inotropic effect of the low-molecular-weight plasma fraction in severe hypovolemic-traumatic shock and have isolated a cardiodepressant factor (CDF), which by blockade of the calcium inward current has a negative inotropic a chronotropic effect. The intestine as a shock organ appears to range first among the organs involved. The translocation of bacteria from the intestinal tract, the 'intestine in shock' represents the trigger reaction that eventually leads from the 'organ in shock', early organ failure to late (septic) organ failure. Here the most prominent factor is endotoxin (LPS) as a basic mediator of gram-negative bacteria, which also triggers the activation of humoral and cellular systems. The posttraumatic hyperdynamic phase commonly starts on days 3-5 and is mainly caused by bacteremia and/or endotoxemia. Macrophages have a major impact on the late phase of organ failure. At present, the most prominent cellular mediator of the lethal effect of endotoxin is thought to be cachectin, which is identical with the tumor necrotising factor (TNF). TNF is secreted by monocytes/macrophages (MO/MA) in response to LPS. Via macrophage derived cytokines and by LPS there is activation of endothelial cells, with increased adhesiveness for PMN. Both due to this increased adhesiveness and the presence of LPS and cytokines, PMN undergo massive activation, which causes mediator release and tissue damage.(ABSTRACT TRUNCATED AT 400 WORDS)

A cardiodepressant factor isolated from blood blocks Ca2+ current in cardiomyocytes

A cardiodepressant factor (CDF) was isolated (salt free) from the plasma of dogs after hypovolemic-traumatic shock by column chromatography. CDF was found to exert a concentration-dependent negative inotropic effect in guinea pig papillary muscle; it reduced the amplitude of cell wall motion, the contraction and relaxation velocity, and the frequency of spontaneously beating rat cardiomyocytes in culture, effects that were rapidly reversible upon washout. By means of electrophysiological methods (whole cell recording with patch electrodes and voltage clamp) we tested the effect of CDF on adult guinea pig cardiomyocytes: application of CDF initially decreased the plateau by 7 mV (150 ms after peak of action potential) and reduced the action potential duration by 93 ms (76% of control action potential duration) at 50% and 88 ms (79%) at 90% of repolarization. The plateau was further reduced by 13 mV and the action potential duration was prolonged by 25 ms (106%) at 50% and was prolonged drastically by 156 ms (137%) at 90% of repolarization compared with control. Voltage-clamp experiments have shown that the most prominent effect of CDF is a strong reduction of ICa accompanied by inhibition of IK and subsequent repolarization. Similar results have been obtained with neonatal rat cardiomyocytes. Blockage of the calcium inward current can explain the negative inotropic and chronotropic effect of CDF in cardiomyocytes.

Net inotropic plasma activity in canine hypovolemic traumatic shock: low molecular weight plasma fraction after prolonged hypotension depresses cardiac muscle performance in vitro

Numerous studies report controversial results about the occurrence and role of cardiodepressant substances in various forms of circulatory shock. We investigated the net inotropic effect of the low molecular weight fraction (mol wt less than or equal to 1,000) of plasma in prolonged canine hypovolemic traumatic shock using an in vitro guinea pig papillary muscle assay (isotonic mode). The shock plasma fractions (ultrafiltrates) after 4 hr of hypotension (mean arterial blood pressure 40-50 mm Hg) and immediately post-reinfusion significantly depressed papillary muscle function (P less than .02). The extent of papillary muscle shortening was decreased by 49.5 +/- 9.9% in pre- and 50.6 +/- 10.0% in post-reinfusion plasma ultrafiltrates (mean values +/- standard error of the mean; n = 6 shock experiments). In contrast, both the plasma ultrafiltrates from ten non-anesthetized healthy dogs and the control ultrafiltrates obtained prior to onset of shock in the experiments (-6.4 +/- 2.6; n = 6) induced no significant change of the in vitro performance of papillary muscle contraction. These results were achieved with plasma fractions in which ionized calcium and pH were adjusted to concentrations equivalent to the bioassay solution. Lactate acidosis and severe hypoglycemia (1.97 +/- 0.43 mM post-reinfusion) occurred in the shock experiments. Lack of energy substrate (glucose) was not responsible for the in vitro depression. Four depressive shock ultrafiltrates with glucose concentrations adjusted to control ultrafiltrate levels induced a 66.6 +/- 8.8% decrease in the extent of papillary muscle shortening. These results suggest that the possible occurrence of high net negative inotropic activity in plasma, especially just post-reinfusion, may play a role in the pathogenesis of irreversible circulatory shock.

Preliminary data on isolation of an elastase-like proteinase and its inhibitor from ovine neutrophil granulocytes

Ovine polymorphonuclear leukocytes (PMNs) were purified by counterflow centrifugation of the buffy coat. The resulting cell preparation was gently sonicated and ultracentrifuged for separation of cytosol and cell organelles. The proteolytic activity of the isolated enzyme was determined with the specific substrate MeO-Suc-Ala-Ala-Pro-Val-Nan (methoxysuccinyl-[L-alanyl]2-L-prolyl-L-valine p-nitroanilide). Elastase-like activity was identified in the insoluble (particular) fraction, while an inhibitor of elastase activity was found in the supernatant (cytosolic fraction). Further purification of the elastase-like enzyme was achieved by cation exchange chromatography (SP-Sephadex C-25 and CM-Sephadex C-25) and gel permeation chromatography (Bio-Gel P-30). Purification of the inhibitor from cytosol was accomplished using anion exchange chromatography (DE32 diethylaminoethyl cellulose) and two gel permeation steps (Sephadex G-75 and TSK-G 2000 SW - HPLC column). Degrees of purity in all separation steps were controlled with SDS-polyacrylamide gel electrophoresis. The molecular mass of the elastase-like enzyme is in a range of 25 to 27 kDa. The isoelectric point is between 8.0 and 9.0. Three isoenzymes were found. The optimal activity lies at pH 8.0. The molecular mass of the inhibitor is about 40 kDa.