Upper reference limits of high-sensitivity cardiac troponin T in a general population: comparison with those of sensitive cardiac troponin I.

BACKGROUND: Upper reference limits (97.5th, 99th percentiles) of high-sensitivity and sensitive cardiac troponins (hs-cTn and s-cTn) can be influenced by several factors. Our aim was to study: (1) the ability of hs-cTnT and s-cTnI to detect circulating cTn in a general community population, and (2) the effects of age, renal function, and gender on their 97.5th - 99th percentile values. METHODS: Hs-cTnT and s-cTnI values were measured in 177 subjects. RESULTS: Thirty-six subjects (20%) presented hs-cTnT values above the limit of detection (LoD), whereas no subjects presented detectable s-cTnI values. Men presented more frequently than women with detectable hs-cTnT levels (37% vs. 11%; p = 0.0001). Hs-cTnT was more frequently found in older (> or = 70 years) than in younger subjects (57 vs. 14%; p < 0.0001). Subjects with low estimated glomerular filtration rates (eGFR < 60 mL/min1/ 1.73m2) presented more frequently with detectable hs-cTnT levels than subjects with higher eGFR (71% vs. 17%; p < 0.0001). Hs-cTnT 97.5th - 99th percentiles varied according to selection by age, renal function, and gender; percentile values of s-cTnI were below the LoD of the assay. CONCLUSIONS: Hs-cTnT is more often quantified than s-cTnI in healthy subjects. Age, gender, and eGFR values influence 97.5th - 99th hs-cTnT percentile values.

Arginine-supplemented enteral nutrition in critically ill diabetic and obese rats: a dose-ranging study evaluating nutritional status and macrophage function.

OBJECTIVE: Critically ill diabetic and obese patients are at high risk of complications. Arginine availability is lowered in diabetes and in stress situations, yet arginine is necessary for immune response, mainly by its action through nitric oxide (NO). These facts argue for arginine-supplemented diets in critically ill patients. However, studies have raised concerns about possible adverse effects of such diets in intensive-care patients. We therefore analyzed the metabolic and immunologic effects of an arginine-enriched diet in stressed diabetic-obese rats. METHODS: Zucker Diabetic Fatty rats (fa/fa) were made endotoxemic by an intraperitoneal injection of lipopolysaccharide and then fed 4-d enteral nutrition enriched with arginine (ARG group) or a non-essential amino acid mix (NEAA group). The two groups each were subdivided into three subgroups: the ARG subgroups received 0.5 g (ARG0.5), 2 g (ARG2), and 5 g (ARG5) of arginine per kilogram daily, and the NEAA groups were made isonitrogenous with the corresponding ARG subgroups (NEAA0.5, NEAA2, and NEAA5). Plasma and urinary biomarkers were measured. Cytokine and NO production levels and inducible NO synthase and arginase protein levels were determined from peritoneal macrophages. RESULTS: The survival rate was lower in the ARG5 and NEAA5 subgroups than in all the other subgroups. The nitrogen balance was higher in the ARG5 group than in the NEAA5 group. Plasma triacylglycerol levels were lower in the ARG2 group than in the NEAA2 group. Interleukin-6, tumor necrosis factor-α, and NO production in the macrophages decreased and arginase-1 was upregulated in the ARG-treated rats. CONCLUSIONS: In this model, mortality was increased by the nitrogen burden rather than by arginine per se. Arginine improved nitrogen balance and had an anti-inflammatory action on macrophages by regulating NO production, probably through arginase-1 expression.

Analytical evaluation of a high-sensitivity troponin T assay and its clinical assessment in acute coronary syndrome.

BACKGROUND: The recently developed, highly sensitive cardiac troponin T (hs-cTnT) immunoassay improves the detection of acute myocardial infarction (AMI). However, this assay requires further analytical and clinical evaluation. METHODS: Imprecision, linearity, limits of quantification and interferences were evaluated; hs-cTnT was compared with a conventional cardiac troponin I assay (cTnI), performed on an X-pand(®)HM, in a population of patients with suspected AMI. Finally, the 99th percentile cut-off point for a reference population was explored in 213 healthy control subjects. RESULTS: Imprecision analysis demonstrated coefficients of variation (CVs) below 4%, linearity showed a 0.999 coefficient of correlation, with excellent recovery (99.9%) and a limit of quantification (10%CV) was found at 9.2 ng/L. A negative interference (>20%) with haemolysis was observed when supplemental haemoglobin was above 0.25 g/dL. Patients with suspected AMI more frequently displayed an increased hs-cTnT (83%) than an increased cTnI (55%, P < 0.01). Unstable angina was present in 63% of patients with an increased hs-cTnT associated with no increase in cTnI. The 99th percentile value for our reference population was 16.9 ng/L. In 213 healthy blood donors, hs-cTnT levels were significantly correlated with age (P < 0.0001), and were higher in men than in women (P < 0.0001). CONCLUSIONS: The analytical performance of hs-cTnT complied with the international guidelines for AMI detection. Determining the degree of haemolysis in a sample is of paramount importance to the interpretation of hs-cTnT results. The 99th percentile value of our reference population was established.

Protective effects of glutamine dipeptide and alpha-tocopherol against ischemia-reperfusion injury in the isolated rat liver.

BACKGROUND & AIMS: Glutamine and vitamin E may prevent hepatic ischemia-reperfusion (I/R) injuries. Our aim was to investigate the effects of glutamine, either alone or combined with vitamin E, against I/R in the isolated perfused rat liver. METHODS: Four groups of 8 livers from male Sprague-Dawley rats were isolated and submitted to a 45-min no-flow ischemia and reperfusion in the presence of alanine 2 mM, alanine 2 mM plus vitamin E 150 microM, Alanyl-Glutamine (AlaGln) 2 mM, or AlaGln 2 mM plus vitamin E 150 microM. Six non-perfused livers were studied in parallel. Liver function, metabolic parameters, oxidative stress and inflammatory parameters have been studied. RESULTS: AlaGln was rapidly cleared from the perfusate (436+/-41 nmol min(-1) g(-1)) and lowered transaminase release during reperfusion (ALT: -59%), significantly so in the AlaGln+Vit E group (ALT: -65%, p<0.05). The association of glutamine with vitamin E led to lower degrees NO (-83%, p<0.05) production, better preserved hepatic glutathione content and, as with vitamin E alone, preserved hepatic vitamin A and significantly decreased malondialdehyde (-85%, p<0.05). CONCLUSION: Both glutamine, by attenuating inflammatory response, and vitamin E, via its antioxidative properties, showed complementary protective effects against I/R-induced hepatic injury. These data emphasize the potential benefit of combining glutamine and vitamin E supplementation in hepatic I/R injury.

Protective effects of regulatory amino acids on ischemia-reperfusion injury in the isolated perfused rat liver.

OBJECTIVE: Some amino acids (AAs) display potent regulatory activities on cell metabolism, including via anti-oxidative defences. The aim of this study was to evaluate the protective effect of these AAs on warm ischaemia-reperfusion (I/R) injury in the isolated perfused rat liver. MATERIAL AND METHODS: Livers from fasted male Sprague-Dawley rats were isolated and perfused without (control group) or with (AP group) a mixture of regulatory AAs (glutamine, histidine, leucine, methionine, proline, phenylalanine, tryptophan and alanine). After 45 min of perfusion, warm ischaemia was induced for 45 min by clamping the portal vein catheter; thereafter, reperfusion was performed for 30 min. RESULTS: TNF-alpha production was significantly lower in the AP group during reperfusion ( CONTROL: 39+/-7 versus AP: 16+/-2 pg min-1 g-1, p<0.05), and lactate dehydrogenase (LDH) release decreased significantly during the last 15 min of reperfusion ( CONTROL: 0.13+/-0.03 versus AP: 0.04+/-0.02 IU min-1 g-1, p<0.05), despite similar levels of oxidative stress. The addition of regulatory AAs was not associated with variations in portal flow, bile flow, hepatic glucose or urea metabolism. However, significant changes in intrahepatic glutamine ( CONTROL: 1.4+/-0.2 versus AP: 2.6+/-0.5 micromol g-1, p < 0.05) together with higher glutamate release in the AP group ( CONTROL: 10.2+/-5.4 versus AP: 42.6+/-10.9 nmol min-1 g-1, p < 0.05) indicated modifications in nitrogen metabolism. CONCLUSIONS: Taken together, the lower TNF-alpha production, suggesting decreased inflammatory response, the decrease in LDH release in the AP group, demonstrating a better preservation of liver viability, and the increase in hepatic glutamine indicate that AAs play an important role in the liver's response to I/R.

Evaluation of a glycine-rich amino acid solution for parenteral nutrition in endotoxemic rats.

OBJECTIVE: It has been shown recently that high amounts of glycine might have some pharmacologic effects (reduction of injury and mortality in endotoxemic rats), but its effects on the nutritional status and protein metabolism during injury are still unknown. The aim of this study was to compare the nutritional effects of a glycine-rich amino acid solution for parenteral nutrition (AFD) with a standard one (Vintene) (glycine, 15 vs. 9 g/L) in endotoxemic rats. DESIGN: Laboratory investigation. SETTING: University laboratory. SUBJECTS: Male Wistar rats (198 +/- 11 g). INTERVENTIONS: Rats were operated to receive total parenteral nutrition (250 kcal/kg/day, 2 g N/kg/day) with amino acids supplied by either AFD (n = 9) or Vintene (V, n = 6). One day after surgery, corresponding to day 0 of the experiment and to the first day of full-strength total parenteral nutrition, the AFD and V group rats received an endotoxemic shock by intraperitoneal injection of lipopolysaccharide (Escherichia coli, 8 mg/kg). The rats were then studied over 3 days and compared with a healthy ad libitum-fed group (AL, n = 10). MEASUREMENTS AND MAIN RESULTS: The rats were weighed and urine was collected daily to determine nitrogen balance and 3-methylhistidine excretion. On day 3, the thymus, spleen, liver, intestinal mucosa, and muscles were weighed, and amino acids from plasma and tissues were analyzed. Lipopolysaccharide caused the classic endotoxemic shock, of similar intensity in the V and AFD groups (V and AFD not equal AL, p < .05): no weight gain, decreased nitrogen balance (day 3, AL 558 +/- 21, V 83 +/- 28, AFD 123 +/- 25 mg N/day), increased urinary 3-methylhistidine/creatinine excretion (day 3, AL 51 +/- 2, V 91 +/- 13, AFD 87 +/- 14 mumol/mmol), soleus (V -15% and AFD -26 % vs. AL) and thymus atrophy (V -36% and AFD -33%), and spleen hypertrophy (V 51% and AFD 83%). Compared with V solution, AFD has a reduced content of some essential amino acids and proline and an elevated content of glycine, aspartate, and glutamate. These differences were not reflected in tissue or plasma amino acids, except for plasma glycine, which in the AFD group was restored to the level of the AL group (AL 426 +/- 12 and AFD 379 +/- 50 vs. V 251 +/- 31 mumol/L, p < .05). CONCLUSIONS: In endotoxemic rats, the nutritional effects of a glycine-rich AFD solution are similar to those of a standard amino acid solution for parenteral nutrition.

Does dietary ornithine alpha-ketoglutarate supplementation protect the liver against ischemia-reperfusion injury?

Nutritional supplementation with glutamine, arginine and their precursors has been proposed to contribute to the protection against ischemia-reperfusion-related injuries. The aim of this study was to evaluate in an isolated perfused rat liver model the preventive effect of a 4-day oral ornithine alpha-ketoglutarate (OKG) supplementation against warm ischemia-reperfusion (I-R) injury, and the involvement of nitric oxide synthesis. Rats were fed a controlled regimen supplemented with either OKG (5 g kg(-1); n=15) or an isonitrogenous mixture of non-essential amino acids (Control; n=6) for 4 days. Livers were subsequently prepared for isolated perfusion experiments, including a 45 min no-flow ischemic period. The OKG-treated group was divided into two groups according to the absence (OKG; n=8) or presence of a NO-synthase inhibitor, L-N(omega)-nitro-arginine methyl ester (OKG L-NAME; n=7) during liver perfusion. Liver cytolysis after ischemia was demonstrated by an elevated alanine aminotransferase release during the last 15 min of reperfusion that was significantly higher in the OKG-L-NAME group. Tumor necrosis factor alpha (TNF(alpha)) production was transiently increased only in the control group just after ischemia. At the end of the reperfusion period, liver superoxide dismutase activity was significantly lower in the OKG-L-NAME group compared to control animals. Dietary OKG administration had only a limited effect in this model of mild hepatic I-R, leading mainly to reduced TNF(alpha) production. As the content of lipid peroxidation products was not modified, it seems that OKG acts on the inflammatory response rather than on oxidative reactions. This action can tentatively be attributed to the role of OKG as a glutamine precursor rather than to the synthesis of arginine and nitric oxide.

Arginine and glutamine availability and macrophage functions in the obese insulin-resistant Zucker rat.

Increased susceptibility to infections in obese patients may be related to decreased availability of arginine and glutamine, which may affect immune cell functions. Our aim was to evaluate the in vitro effects of these amino acids on the function of macrophages from obese insulin-resistant Zucker rats. Macrophages, isolated from male Zucker obese or lean rats by peritoneal lavage, were incubated in Dulbecco's modified Eagle medium (DMEM) without arginine or glutamine. Arginine or glutamine was added to the medium at increasing final concentrations (0, 0.25, 0.5, 1 or 2 mM). After stimulation by lipopolysaccharide (LPS) from E. coli (40 microg/ml), productions of tumour necrosis factor alpha (TNFalpha) and of nitric oxide (NO) were measured after 3 or 48 h incubation, respectively. NO production, lower in macrophages from obese rats, decreased in macrophages from lean rats (0 mM: 2,423 +/- 1,174 vs. 2 mM: 198 +/- 31 microM/mg protein/24 h; P < 0.05), but not in those from obese rats, when glutamine was added. TNFalpha production, lower in macrophages from obese rats, was inversely correlated with glutamine concentration. In the presence of arginine, NO production was constantly higher in macrophages from obese rats. It peaked at 0.5 mM arginine and decreased thereafter in both groups. TNFalpha production in macrophages from lean rats was unaffected by arginine, but decreased in macrophages from obese rats (0 mM: 1920 +/- 450 vs. 2 mM: 810 +/- 90 microM/mg protein/3 h; P < 0.05). These results suggest that abnormalities in cell signalling or in arginine and glutamine metabolism in macrophages of obese rats, resulting in decreased TNFalpha production and increased NO release, may contribute to increased susceptibility to infection in insulin-resistant states.