Robert J. Nijveldt

Modulation of asymmetric dimethylarginine in critically ill patients receiving intensive insulin treatment: A possible explanation of reduced morbidity and mortality?*

Objective:Asymmetric dimethylarginine, which inhibits production of nitric oxide, has been shown to be a strong and independent predictor of mortality in critically ill patients with clinical evidence of organ dysfunction. Interestingly, intensive insulin therapy in critically ill patients improved morbidity and mortality, but the exact mechanisms by which these beneficial effects are brought about remain unknown. Therefore, we aimed to investigate whether modulation of asymmetric dimethylarginine concentrations by intensive insulin therapy is involved in these effects. Design:A prospective, randomized, controlled trial. Setting:A 56-bed predominantly surgical intensive care unit in a tertiary teaching hospital. Patients:From a study of 1,548 critically ill patients who were randomized to receive either conventional or intensive insulin therapy, we included 79 patients who were admitted to the intensive care unit after complicated pulmonary and esophageal surgery and required prolonged (≥7 days) intensive care. Interventions:Determination of asymmetric dimethylarginine concentrations. Measurements and Main Results:Asymmetric dimethylarginine concentrations were determined with high-performance liquid chromatography on the day of admission, on day 2, on day 7, and on the last day at the intensive care unit. Although the asymmetric dimethylarginine levels did not change between day 0 and day 2 in patients receiving intensive insulin treatment, there was a significant increase during this period in the conventionally treated patients (p = .043). Interestingly, the mean daily insulin dose was inversely associated with the asymmetric dimethylarginine concentration on the last day (r = −.23, p = .042), and the asymmetric dimethylarginine concentration on the last day at the intensive care unit was significantly lower in the intensive insulin treatment group (p = .048). Furthermore, asymmetric dimethylarginine was positively associated with duration of intensive care unit stay, duration of ventilatory support, duration of inotropic and vasopressor treatment, number of red cell transfusions, duration of antibiotic treatment, presence of critical illness polyneuropathy, mean Acute Physiology and Chronic Health Evaluation II score, and cumulative Therapeutic Intervention Scoring System-28 score. In addition, asymmetric dimethylarginine levels in patients who died were significantly higher compared with survivors, and changes in the course of asymmetric dimethylarginine plasma concentrations were predictive for adverse intensive care unit outcome. Conclusions:Modulation of asymmetric dimethylarginine concentration by insulin at least partly explains the beneficial effects found in critically ill patients receiving intensive insulin therapy.

Glutamine Alimentation in Catabolic State

Glutamine should be reclassified as a conditionally essential amino acid in the catabolic state because the bodys glutamine expenditures exceed synthesis and low glutamine levels in plasma are associated with poor clinical outcome. After severe stress, several amino acids are mobilized from muscle tissue to supply energy and substrate to the host. Glutamine is one of the most important amino acids that provide this function. Glutamine acts as the preferred respiratory fuel for lymphocytes, hepatocytes and intestinal mucosal cells and is metabolized in the gut to citrulline, ammonium and other amino acids. Low concentrations of glutamine in plasma reflect reduced stores in muscle and this reduced availability of glutamine in the catabolic state seems to correlate with increased morbidity and mortality. Adding glutamine to the nutrition of clinical patients, enterally or parenterally, may reduce morbidity. Several excellent clinical trials have been performed to prove efficacy and feasibility of the use of glutamine supplementation in parenteral and enteral nutrition. The increased intake of glutamine has resulted in lower septic morbidity in certain critically ill patient populations. This review will focus on the efficacy and the importance of glutamine supplementation in diverse catabolic states.

Pattern and incidence of first site recurrences following sentinel node procedure in melanoma patients

Studies of large series of melanoma patients indicated that the average incidence of developing a recurrence during follow-up was 40%. The most frequent first sites of these recurrences were the regional lymph nodes. We hypothesized that the sentinel node (SN) procedure may change the pattern of recurrence by reducing the number of first recurrences in the regional lymph node basin during follow-up to a negligible number, and that locoregional cutaneous and distance metastases are the major future sites of recurrence. We further studied the influence of SN status together with different influential factors on prognosis. An SN procedure with a triple technique was performed in 250 consecutive patients with proven AJCC stages I and II cutaneous melanoma. The median follow-up was 38 months. So far, 44 patients (18%) have developed a recurrence of the disease. The distribution of localization of the first metastases was as follows: 23 patients (52%) with a locoregional cutaneous recurrence; 4 (9%) with recurrence in the regional lymph node basin; 2 (5%) with recurrence in an interval node; and 15 (34%) with distant recurrence. The relative risk of developing recurrence for SN-positive patients is 4.2; for Breslow thickness of 1.51 to 4.00 mm it is 5.5, and thicker than 4.0 mm it is 6.2; for lymphatic invasion 7.6; and for ulceration 3.8. We conclude that the SN procedure changes the pattern of recurrences during follow-up by reducing the number of first recurrences within the regional lymph node basin to a negligible number. High Breslow thickness, lymphatic invasion, and ulceration of the primary melanoma are strong risk factors for recurrence.RésuméL’incidence de récidive de mélanome dans les grandes séries est de l’ordre de 40%. Ces récidives intéressent le plus souvent les ganglions lymphatiques régionaux. Notre hypothèse est que la technique de ganglion sentinelle (GS) réduit le nombre de récidives initiales dans le territoire de drainage direct alors que les récidives sont alors cutanées, locorégionales et à distance. Si cela était vrai, le nombre total de récidives pourrait être diminué. Nous avons étudié l’influence du GS et d’autres facteurs pronostiques. Chez 250 patients atteints de mélanome cutané stades I et II selon la classification AJCC, on a réalisé la technique de GS par la technique triple. La médiane de suivi a été de 38 mois. Jusqu’à présent, 44 patients (18%) ont développé une récidive. La distribution du site de la première métastase a été comme suit: récidive locorégionale cutanée 23 patients (52%), récidive régionale ganglionnaire: quatre (9%); récidive dans un ganglion intermédiaire: deux (5%); et récidive à distance 15 (34%). Le risque relatif (RR) de développer une récidive chez le patient GS positif a été de 4.2, de 5.5 chez le patient ayant un score de Breslow entre 1.51–4.0, et de 6.2 lorsque l’épaisseur a été de plus de 4 mm. Le RR a été de 6.2 en cas d’envahissement lymphatique et de 3.8 en cas d’ulcération. Nous concluons que la technique du GS réduit nettement l’incidence de récidive mais n’empêche pas le patient de développer une récidive. Le risque de développer une récidive lymphatique régionale est devenu rare. L’indexe élevé de Breslow, une invasion lymphatique et l’ulcération du mélanome primaire sont des facteurs prédictifs de récidive importants.ResumenLos estudios sobre grandes series de pacientes con melanoma indican que la tasa promedio de recurrencia primaria en el curso del seguimiento es 40%. El sitio más frecuente de recurrencia primaria es la zona de ganglios regionales. Hemos planteado la hipótesis de que la técnica del ganglio centinela (GC) reduce el número de recurrencias a los ganglios regionales a una cifra mínima, y que las metástasis a los ganglios locales-regionales y a distancia habrán de ser los lugares de recurrencia. Si esto resulta ser cierto, se podría reducir el número total de recurrencias. También estudiamos la influencia del estado del GC y la de otros factores sobre el pronóstico. En 250 pacientes consecutivos con melanoma cutáneo en estados I y II (AJCC) se realizó el procedimiento del GC mediante una técnica triple. El tiempo promedio de seguimiento fue 38 meses. Hasta el momento, 44 pacientes (18%) han desarrollado recurrencia, con la siguiente distribución: 23 pacientes (52%) con recurrencia local-regional cutánea, cuatro (9%) con recurrencia en la zona linfática-regional; 2 (5%) con recurrencia a un ganglio de intervalo; y 15 (34%) con recurrencia a distancia. El riesgo relativo de recurrencia en pacientes con GC positivo es 4.2; en melanomas con espesor de Breslow entre 1.51 y 5.5 mm y de más de 4.0 mm es 6.2; cuando hay invasión linfática el riesgo en 7.6; cuando hay ulceración es 3.8. Nuestra conclusión es que el procedimiento del GC ha reducido claramente la incidencia de recurrencia, aunque ello no quiere decir que prevenga la recurrencia en todos los pacientes. La recurrencia ganglionar local-regional aparece poco común. Un espesor de Breslow grueso, la invasión linfática y la ulceración del melanoma primario son todos factores fuertes de riesgo de recurrencia.

Role of the human erythrocyte in generation and storage of asymmetric dimethylarginine

Proteolytic activity in whole blood may lead to release of the endogenous nitric oxide synthase inhibitor asymmetric dimethylarginine (ADMA). We investigated the role of the human erythrocyte in storage and generation of ADMA in healthy controls (n = 36) and critically ill patients (n = 38). Both free and total (sum of free and protein-incorporated) ADMA were measured. Upon incubation of intact erythrocytes with extracellular ADMA (0 to 40 μmol/l), equilibrium between intra- and extracellular ADMA was reached within 3 h. Compared with controls, patients had significantly higher basal concentrations of ADMA in plasma (0.88 ± 0.75 vs. 0.41 ± 0.07 μmol/l) and erythrocytes (1.28 ± 0.55 vs. 0.57 ± 0.14 μmol/l). Intracellular and plasma ADMA were significantly correlated in the patient group only (r = 0.834). Upon lysis, followed by incubation at 37°C for 2 h, free ADMA increased sevenfold (to 8.60 ± 3.61 μmol/l in patients and 3.90 ± 0.78 μmol/l in controls). In lysates of controls, free ADMA increased further to 9.85 ± 1.35 μmol/l after 18 h. Total ADMA was 15.43 ± 2.44 μmol/l and did not change during incubation. The increase of free ADMA during incubation corresponded to substantial release of ADMA from the erythrocytic protein-incorporated pool (21.9 ± 4.6% at 2 h and 60.8 ± 7.6% at 18 h). ADMA was released from proteins other than hemoglobin, which only occurred after complete lysis and was blocked by combined inhibition of proteasomal and protease activity. Neither intact nor lysed erythrocytes mediated degradation of free ADMA. We conclude that intact erythrocytes play an important role in storage of ADMA, whereas upon erythrocyte lysis large amounts of free ADMA are generated by proteolysis of methylated proteins, which may affect plasma levels in hemolysis-associated diseases.

No Compensatory Upregulation of Placental Dimethylarginine Dimethylaminohydrolase Activity in Preeclampsia

Background/Aims: Placental dysfunction of the asymmetric dimethylarginine (ADMA) degrading enzyme dimethylarginine dimethylaminohydrolase (DDAH) has been suggested as one of the initiating events in the development of preeclampsia (PE). Our primary aim was to investigate the role of the placenta in the metabolism of ADMA during normal pregnancy and PE. Methods: We studied 27 nonpregnant healthy women (C), 15 normotensive pregnant females (P), 16 patients with PE, and 7 patients with the ‘hemolysis, elevated liver enzymes and low platelets’ syndrome (H). Results: There were no significant differences between P and PE with respect to fetomaternal gradient of ADMA, placental DDAH activity and placental ADMA content. During the first stage of labour, mean (±SD) plasma ADMA (μmol/l) was higher in H (0.69 ± 0.22; p < 0.05) compared with C (0.44 ± 0.07), P (0.37 ± 0.06), and PE (0.40 ± 0.06). ADMA was significantly associated with laboratory parameters of hepatic and renal function and with clinical parameters, including systolic and diastolic blood pressure, gestational age, birth weight, and placenta weight. Conclusions: A compensatory upregulation of placental DDAH activity is absent in patients suffering from PE and levels of ADMA in plasma and placenta are normal in patients suffering from PE. However, when the course of PE deteriorates and organ dysfunction (especially liver and kidney) becomes involved, such as during the hemolysis, elevated liver enzymes and low platelets syndrome, ADMA levels increase.

Elevation of asymmetric dimethylarginine (ADMA) in patients developing hepatic failure after major hepatectomy.

BACKGROUND Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of the arginine-nitric oxide pathway. It is conceivable that its concentration is tightly regulated by urinary excretion and degradation by the enzyme dimethylarginine dimethylaminohydrolase, which is highly expressed in the liver. In rats, we showed a high net hepatic uptake of ADMA. Therefore, we aimed to confirm the role of the liver in humans and hypothesized elevated ADMA levels after major liver resection by a reduction of functional liver mass and injury to the remnant liver. METHODS Patients undergoing a major hepatic resection (HEP, n = 17) or major abdominal surgery (MAS, n = 12) were included and followed in time. In addition, ADMA levels were measured in 4 patients having severe hepatic failure after a liver resection. Plasma ADMA concentration was measured by high-performance liquid chromatography. RESULTS Preoperatively and on days 1, 3, and 5, plasma levels of ADMA were higher in HEP patients when compared with MAS patients. In HEP patients with prolonged (>7 days) hepatic injury, ADMA levels were especially elevated. On the first postoperative day, ADMA significantly correlated to bilirubin concentration (r = .528, p < .05) as a marker of postoperative hepatic function. Besides, in patients with severe hepatic failure, ADMA levels were highly elevated. CONCLUSIONS In the present study, evidence was found for the role of the liver in the elimination of ADMA in humans. Increased levels of ADMA occur in the postoperative course after a major hepatic resection, especially when liver function is severely impaired. Further studies need to assess the role of ADMA in the development of complications after liver surgery.

Gut and liver handling of asymmetric and symmetric dimethylarginine in the rat under basal conditions and during endotoxemia.

Abstract: Introduction/Aim: Asymmetric dimethylarginine (ADMA) is an endogenous inhibitor of nitric oxide (NO) synthase enzymes, whereas symmetric dimethylarginine (SDMA) competes with arginine transport. Although both dimethylarginines may be important regulators of the arginine‐NO pathway, their metabolism is largely unknown. In previous studies, evidence was found for the liver in the metabolism of dimethylarginines. We aimed to investigate dimethylarginine handling of the gut and the liver in detail under basal conditions and during endotoxemia.

Arginase release from red blood cells: possible link in transfusion induced immune suppression?

Arginine stimulates lymphocyte function and is degraded by arginase, an enzyme that is abundantly present in red blood cells. Arginase impairs lymphocyte function and responses in vitro. Leakage of arginase from stored red blood cells may be involved in the lymphocyte dysfunction associated in allogenic blood transfusion. In the present study, arginase activity was determined in bags of red cells stored for transfusion. Buffy coat depleted red blood cells were obtained routinely from four healthy donors and stored in bags for a maximum period of five weeks at 4 degrees C. The bags were sampled for determination of arginase, lactate dehydrogenase, and potassium. In addition, a random sample of 36 bags of red blood cells about to be transfused to patients were studied. Levels of arginase, lactate dehydrogenase, and potassium showed a time dependent increase in the bags of the four donors. This time dependent increase in arginase activity could be confirmed in the additional bags sampled (P < 0.0001, r = 0.78). The results for the first time show that arginase is released from red blood cells during storage for transfusion. Arginase infusion may play an important role in the immune suppression observed after blood transfusion.

Glutamine-enriched enteral feeding in trauma patients: reduced infectious morbidity is not related to changes in endocrine and metabolic responses.

BACKGROUND Recently we have shown that glutamine-enriched enteral nutrition in trauma patients reduced the occurrence of pneumonia, bacteremia, and sepsis. In that study, no clear explanation for these results was found except for lower tumor necrosis factor (TNF)-soluble receptors, suggesting immunomodulation. Here we present data on the course of endocrine and metabolic plasma mediators that were analyzed to provide more insight into the working mechanism of glutamine. METHODS Endocrine and metabolic mediators were measured in plasma samples taken on admission (day 0) and on days 1, 2, 3, 7, and 10. Glucose, prealbumin, albumin, alanine, C-reactive protein, alpha1-antitrypsin, complement factors, cortisol, glucagon, insulin, and growth hormone were assessed by standard techniques. RESULTS The rate of feeding, demography, and injury severity did not differ between the glutamine and control group. There was a sustained hyperglycemic response in both groups. Insulin levels rose in the second phase of the period of observation. A moderate cortisol and glucagon response was seen in both groups. There was no alteration in growth hormone levels in either group. C-reactive protein, alpha1-antitrypsin, and complement factors showed similar increases in both groups but levels remained in the normal range. The course of alanine, albumin, and prealbumin also showed no difference between the groups. CONCLUSIONS Glutamine-enriched enteral nutrition had no influence on the endocrine and metabolic response in trauma patients. Therefore, the reduction in infectious morbidity seen in glutamine-supplemented trauma patients is most likely not explained by a modulation of the humoral stress response and its metabolic consequences.

Coagulopathy following major liver resection: the effect of rBPI21 and the role of decreased synthesis of regulating proteins by the liver.

This prospective study investigated the role of reduced hepatic synthesis of regulating proteins in coagulopathy after partial hepatectomy (PH) compared with major abdominal surgery (MAS) without involvement of the liver. Furthermore, we studied the effect of rBPI21, an endotoxin-neutralizing agent, on coagulopathy after PH was studied. Compared with MAS, PH resulted in significantly elevated levels of thrombin-antithrombin-III and plasmin-alpha2-antiplasmin complexes. Levels of antithrombin-3, alpha2-antiplasmin, fibrinogen, plasminogen, alpha2-macroglobulin (alpha2-M), and C1-inhibitor remained lower following PH. Treatment with rBPI21 led to significantly lower levels of tissue-type plasminogen activator (t-PA). Post-operative disseminated intravascular coagulation (DIC) was associated with significantly higher bilirubin and t-PA plasma levels and significantly lower levels of alpha2-M. This study indicates that PH induced hepatic failure results in decreased synthesis of hepatic regulating plasma proteins and subsequent activation of coagulation and fibrinolysis. Prevention of t-PA release by rBPI21 may have important clinical implications. Decreased availability of alpha2-M may be a factor in post-operative DIC.