Subclinical postoperative atrial fibrillation: a randomized trial

Background

Postoperative atrial fibrillation (POAF) is the most common complication of cardiac surgery, requiring interventions and prolonging hospital stay. POAF is associated with increased mortality and a higher rate of systemic thrombo-embolism. The rates of recurrent AF, optimal follow-up and management remain unclear. We aimed to evaluate the incidence of recurrent atrial fibrillation (AF) events, during long term follow-up in patients with POAF following cardiac surgery.

Methods

Patients with POAF and a CHA₂DS₂-VASc score of ≥2 were randomized in a 2:1 ratio to either implantation of a loop recorder (ILR) or ECG monitoring using periodic Holters. Participants were followed prospectively for 2 years. The primary end point was the occurrence of AF longer than 5 min.

Results

The final cohort comprised of 22 patients, of whom 14 received an ILR. Over a median follow up of 25.7 (IQR of 24.7-44.4) months, 8 patients developed AF, representing a cumulative annualized risk of AF recurrence of 35.7%. There was no difference between ILR (6 participants, 40%) and ECG/Holter (2 participants, 25% p = 0.917). All 8 patients with AF recurrence were treated with oral anticoagulation. There were no cases of mortality, stroke or major bleeding. Two patients underwent ILR explantation due to pain at the implantation site.

Conclusions

The rate of recurrent AF in patients with POAF after cardiac surgery and a CHA₂DS₂-VASc score of ≥2 is approximately 1 in 3 when followed systematically. Further research is need to assess the role of ILRs in this population.

Elevated Native T1 Values in The Remote Myocardium Supplied by Obstructive Non-infarct Related Coronary Arteries in post-STEMI CMR

Introduction: Native T1 mapping values are elevated in acutely injured myocardium. We sought to study whether native T1 values, in the non-infarct related myocardial territories, might differ when supplied by obstructive or non-obstructive coronary arteries. Methods: Consecutive patients (N = 60, mean age 59 years) with first STEMI following primary percutaneous coronary intervention (PCI), underwent Cardiac MRI (CMR) within 5 ± 2 days. A retrospective review of coronary angiography reports classified coronary arteries as infarct related coronary artery (IRA) and non-IRA. Obstructive coronary artery disease (CAD) was defined as stenosis ≥ 50%. Native T1 values were presented using a 16-segment AHA model according to the three main coronary territories, left anterior descending (LAD), left circumflex (LCX) right coronary artery (RCA). Results: The cutoff native T1 value for predicting obstructive non-IRA LAD was 1309 msec with a sensitivity and specificity of 67% and 82%, respectively (AUC 0.76 ,95% CI 0.57 - 0.95, p = 0.04). The cutoff native T1 value for predicting obstructive non-IRA RCA was 1302 msec with a sensitivity and specificity of 83% and 55%, respectively (AUC 0.7 95% CI 0.52-0.87, p = 0.05). Logistic regression model adjusted for age and infarct size demonstrated that native T1 was an independent predictor for the obstructive non-IRAs LAD (OR 4.65; 1.32 – 26.96, p = 0.05) and RCA (OR 3.70; 1.44 - 16.35, p = 0.03). Conclusion: Elevated native T1 values are independent predictors of obstructive Non-IRA in STEMI patients. These results suggest the presence of concomitant remote myocardial impairment in the non-infarct territories with obstructive CAD.

The association between fasting plasma glucose and glycated hemoglobin in the prediabetes range and future development of hypertension

Background

Prediabetes is a well-established risk factor for progression to overt diabetes mellitus (DM), which is in turn associated with development of hypertension (HTN) and vice versa. However, the role of prediabetes and HbA1c in particular as an independent risk factor for the development of hypertension is unclear.

Aim

In this current study, we aimed to evaluate the association between both fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) levels in the prediabetes range and development of HTN among a large cohort of normotensive subjects.

Design and methods

We investigated 5016 normotensive participants without DM and other cardiovascular risk factors who were annually screened in a tertiary medical center. Subjects were divided into normoglycemic and prediabetic groups. Normoglycemia was defined as HbA1c < 5.7% and FPG < 100 mg/dl. Prediabetes was defined according to the ADA criteria, i.e., 6.5% > HbA1c ≥ 5.7% or impaired fasting glucose (IFG):126 mg/dl > FPG ≥ 100 mg/dl. Subgroup analysis was made by dividing participants into four groups according to FPG and HbA1C levels, i.e., normoglycemia, impaired HbA1c only, IFG only, and both parameters impaired.

Results

During a follow-up of 3.7 ± 2.9 years, 318 (6.3%) subjects developed HTN. A cumulative hazard function for the development of hypertension showed a 2.89-fold ([95% CI 2.19–3.83], p < .0001) increased risk for HTN in the prediabetic population. In a multivariable Cox proportional hazard regression model adjusted to common confounding risk factors for HTN, prediabetes was found to be independently associated with a 1.95-fold ([95%, CI 1.43–2.52] p < .0001) increased risk for hypertension. Impaired HbA1C only was not found to be independently associated with HTN, while IFG only showed a 2.13-fold (95%, [CI 1.46–3.11] p < .0001) increased risk for HTN compared to normoglycemic, and a 2.55-fold ([95% CI 1.85–3.51] p < .0001) increased risk for HTN when both parameters impaired.

Conclusion

Our study demonstrates that FPG in the prediabetes range, albeit not glycated hemoglobin, is independently and significantly associated with future development of HTN. Therefore, our findings further highlight the pivotal predictive role of IFG for HTN development as opposed to the limited independent role of abnormal HbA1c levels.

Electronic supplementary material

The online version of this article (10.1186/s12933-019-0859-4) contains supplementary material, which is available to authorized users.

Molecular mechanisms of antioxidant enzyme expression in lung during exposure to and recovery from hyperoxia

Manganese superoxide dismutase (MnSOD) activity falls approximately 50% in lung during 48 h of exposure of adult rats to > 95% O2 (L. B. Clerch and D. Massaro. J. Clin. Invest. 91: 499-508, 1993). We now show that hyperoxia also decreased MnSOD activity in lungs of adult baboons, making the phenomenon potentially more important to humans. In rats, a decrease in lung MnSOD activity during an initial 48 h of exposure to > 95% O2 and its increase during an immediately subsequent 24 h in air were due to decreases and increases, respectively, in MnSOD specific activity and synthesis rate; the latter was due to altered translational efficiency. The concentration in the lung of copper-zinc superoxide dismutase mRNA, catalase mRNA, and glutathione peroxidase mRNA, unchanged during the initial 48 h of exposure to O2, rose approximately twofold during reexposure to O2 after 24 h in air. The demonstration that the fall in MnSOD activity is translationally and posttranslationally regulated during the initial exposure to hyperoxia suggests that gene transfer to increase MnSOD activity in hyperoxic lungs may also require therapy that maintains translational efficiency and MnSOD specific activity.

Radiation-initiated, immortal Syrian hamster embryo fibroblasts release elevated levels of H2O2 and show divergent MnSOD and catalase activities

To characterize molecular events associated with the neoplastic conversion of primary cells by ionizing radiation, we studied the activities and mRNA expression of manganese superoxide dismutase (MnSOD) and catalase (CAT) in Syrian hamster embryo fibroblasts during the early stages of immortalization after treatment with gamma-rays. The irradiated cells showed divergent MnSOD and CAT responses relative to unirradiated controls. At passage 6, MnSOD activity was increased about 50-fold, although the concentration of MnSOD mRNA increased only 1.6-fold. By contrast, CAT activity diminished 2-fold despite an increase of 1.6-fold in the concentration of CAT mRNA. This divergence between the MnSOD and CAT activities was maintained upon culturing and, at passage 12, MnSOD was 35-fold increased and CAT 3.7-fold decreased, relative to unirradiated cells. The amount of H2O2 released into the culture medium by the radiation-initiated cells was 6-fold greater than in control media. Because H2O2 is a causative agent in the induction of malignant transformation in vitro, our results suggest that the elevated production of H2O2 caused by the imbalance between the activities of MnSOD and CAT may participate in the immortalization and subsequent malignant conversion of Syrian hamster embryo fibroblasts by ionizing radiation.

Pertussis toxin alters the concentration and turnover of manganese superoxide dismutase in rat lung

Treatment of rats with pertussis toxin (PTX) decreases the activity of manganese superoxide dismutase (Mn-SOD) in the lung and results in oxygen toxicity in air (L. B. Clerch, G. Neithardt, U. Spencer, J. A. Melendez, G. D. Massaro, and D. Massaro. J. Clin. Invest. 93: 2482-2489, 1994). To examine aspects of the mechanism of the PTX-induced fall in Mn-SOD activity, we injected rats with PTX (50 micrograms/kg), killed the rats 72 h later, and measured the activity, concentration, specific activity, and turnover of Mn-SOD in the lung. Treatment with PTX caused an approximately 50% fall in Mn-SOD activity and Mn-SOD concentration but no change in Mn-SOD specific activity. PTX also caused an increase in Mn-SOD mRNA concentration, a fall in Mn-SOD synthesis, and an increase in the half-life of Mn-SOD and general proteins. We conclude the PTX-induced low concentration of Mn-SOD is due to a decrease of translational efficiency. We suggest that, under normoxic conditions, signal transduction via heterotrimeric guanine nucleotide binding proteins regulates the expression of Mn-SOD at the level of translation and Mn-SOD degradation.

Inhibitory effect of ODN, a naturally occurring processing product of diazepam binding inhibitor, on secretagogues-induced insulin secretion

Diazepam binding inhibitor (DBI1-86) is a peptide that is present in large amounts in the intestine and pancreas and which inhibits glucose-stimulated insulin release from both perfused pancreas and isolated islets in low nanomolar concentrations. Here, DBI33-50 (also known as ODN, octadecaneuropeptide), one of the naturally occurring processing products of DBI1-86, and certain synthetic modified derivatives, have been shown to inhibit glucose and glibenclamide-stimulated insulin secretion from isolated rat islets and glibenclamide-stimulated insulin secretion from hamster-insulinoma (HIT-T15) beta-cell line. DBI17-50 (TTN; triakontatetraneuropeptide), another prominent processing product of DBI, had no effect. The 50% inhibitory concentration (IC50) for the effect of ODN on insulin secretion induced by 8.3 of 16.7 mM glucose was approximately the same: 5 to 6 nM. Moreover, ODN inhibited insulin release induced by 0.01 or 1 microM glibenclamide with a similar IC50 (8 to 10 nM) in both isolated pancreatic islets and in HIT-T15 beta-cells. At concentration up to 1 microM, ODN had no effect on insulin secretion induced by PACAP (pituitary adenylate cyclase polypeptide), BAYK 8644 (methyl-(1,4-dihydro-2,6-dimethyl-3-nitro-4,2-trifluoromethylphenyl) pyridine-5-carboxylate), and only marginally it affected IBMX-(isobutylmethylxanthine) induced insulin secretion. This indicates that ODN does not act directly on ATP-regulated K+ channels, voltage dependent Ca2+ channels or cAMP production. In contrast, ODN inhibited insulin secretion induced by sodium nitroprussiate in a manner that is independent from the presence of extracellular Ca2+. These results suggest that ODN or ODN-like peptide fragments of DBI, may inhibit glucose or glibenclamide-induced insulin secretion via a signaling pathway that regulate the cytoplasmic free Ca2+ concentration.

The role of diazepam binding inhibitor and its processing products at mitochondrial benzodiazepine receptors: regulation of steroid biosynthesis

The rate-limiting step in the biosynthesis of steroids is the transport of the substrate cholesterol from the outer to the inner mitochondrial membrane, where cholesterol is metabolized to pregnenolone. This transport is markedly stimulated by the action of hormones, such as adrenocorticotropic hormone (ACTH) and luteinizing hormone (LH) for adrenocortical and testicular Leydig cells, respectively. Recently, it was demonstrated that the peripheral-type or mitochondrial benzodiazepine receptor, abundant in steroidogenic tissues, is involved in the regulation of steroid biosynthesis. In search for an endogenous ligand for mitochondrial benzodiazepine receptors, regulating steroidogenesis, the effects of Diazepam Binding Inhibitor (DBI) were studied. The model systems used were the Y-1 adrenocortical and the MA-10 Leydig cell lines, previously shown to be valid steroidogenic models. Both cell lines contain significant levels of immunoreactive DBI. Purified DBI from rat brain, at high nanomolar concentrations, increased formation of pregnenolone, when added to mitochondrial preparations of both cell types; but at concentrations of DBI above 1 microM, a decrease in the stimulation was observed. Flunitrazepam, a benzodiazepine which binds to mitochondrial benzodiazepine receptors, with high nanomolar affinity, inhibited the stimulatory action of DBI on the formation of mitochondrial pregnenolone, indicating that DBI exerts its stimulatory effects through an action on mitochondrial benzodiazepine receptors. In order to determine the biologically active amino acid sequence in the DBI molecule, various fragments of DBI were synthesized and tested; also, peptides structurally unrelated to DBI were tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Diazepam binding inhibitor and its processing products stimulate mitochondrial steroid biosynthesis via an interaction with mitochondrial benzodiazepine receptors

A recognition site for benzodiazepines structurally different from that linked to various gamma-aminobutyric acid A (GABAA) receptor subtypes is located on the outer mitochondrial membranes of steroidogenic cells. This protein has been signified to be important in the regulation of steroid biosynthesis. Because of its location it is designated herein as the mitochondrial benzodiazepine receptor (MBR). A putative endogenous ligand for MBR is the peptide diazepam binding inhibitor (DBI), previously shown to displace drugs from MBR and to be expressed and stored in steroidogenic cells rich in MBR. The two model systems used to study steroidogenic regulation by DBI were the Y-1 adrenocortical and MA-10 Leydig cell lines previously shown to be applicable in studies of mitochondrial steroidogenesis. Both cell lines contain DBI as well as DBI processing products, including the DBI fragments that on reverse phase HPLC coelute with the naturally occurring triakontatetraneuropeptide [TTN; DBI-(17-50)] and octadecaneuropeptide [DBI-(33-50)]. When DBI purified from rat brain was added to mitochondria prepared from Y-1 and MA-10 cell lines, it increased the rates of pregnenolone formation in a dose-related manner. In both cell lines, maximal stimulation (3-fold) of mitochondrial steroidogenesis was obtained with 0.33 microM DBI, with an EC50 of approximately 0.1 microM. However, DBI concentrations higher than 1 microM caused a smaller increase in pregnenolone formation. Flunitrazepam, a benzodiazepine that binds with high nanomolar affinity to MBR, was recently shown to act as an antagonist of ACTH and LH/hCG-induced steroidogenesis and was found in the present studies to inhibit DBI-stimulated mitochondrial steroidogenesis. During the incubation with mitochondria, DBI was partially processed to different peptide fragments, including octadecaneuropeptide and TTN. To determine whether DBI processing products influence mitochondrial steroid biosynthesis, several DBI fragments and other peptides structurally unrelated to DBI were tested. Among these, only TTN stimulated mitochondrial steroid synthesis in a dose-dependent manner similar to DBI.

A study of diazepam binding inhibitor (DBI) processing products in human cerebrospinal fluid and in postmortem human brain

Diazepam binding inhibitor (DBI) is a neuropeptide of 11 kDa molecular size and is unevenly distributed in human and rat brain. It appears to function as a negative allosteric modulator of GABAA receptors. In the present paper, using antibodies directed against several synthetic peptides, which correspond to selective regions of human DBI (DBI 51-70, DBI 37-50, DBI 81-101), it is shown that DBI is processed into at least 6 peptide fragments in both postmortem human brain and in cerebrospinal fluid (CSF). One of these fragments was identified as the synthetic DBI 51-70 fragment (an eikosaneuropeptide, ENP) by combined chromatographic procedures. Immunoblotting analysis of the other fragments, by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE), revealed an apparent molecular size, ranging from 3-4 kDa for four of them and a larger molecular form of 8 kDa. On the basis of the immunological properties, a tentative amino acid sequence was deduced.

A natural processing product of rat diazepam binding inhibitor, triakontatetraneuropeptide (diazepam binding inhibitor 17-50) contains an alpha-helix, which allows discrimination between benzodiazepine binding site subtypes

Synthetic peptides related to triakontatetraneuropeptide (TTN) [17TQPTDEEMLFIYSHFKQATVGDVNTDRPGLLDLK50; diazepam binding inhibitor (DBI) 17-50], a natural brain processing product of rat DBI, were analyzed for their physicochemical and ligand-receptor interaction characteristics. The ability of TTN and TTN-related fragments to displace [3H]flumazenil (ethyl-8-fluoro-5,6-dihydro-5-methyl-6-oxo-4H-imidazol[1,5a] [1,4]-benzodiazepine-3-carboxylate) or [3H]Ro 5-4864 [7-chloro-1,3-dihydro-1-methyl-5-(p-chlorophenyl)-2H-1, 4-benzodiazepine-2-one] from their respective benzodiazepine (BZ) binding site subtypes was tested in intact cerebellar culture neurons or in homogenates of cultured astrocytes. These studies indicate that the C-terminal region of TTN, which is also present in DBI 22-50, eicosapentaneuropeptide (DBI 26-50), and octadecaneuropeptide (ODN) (DBI 33-50), but not in DBI 19-41, is essential for interaction with the BZ recognition sites. When the C-terminal lysine of ODN is blocked with an NH2 group, the ability of ODN to interact with the binding of [3H]flumazenil is lost. A comparison analysis of the binding data with the secondary structure characteristics of the peptides demonstrated that TTN (DBI 17-50) and DBI 22-50, which have hydrophobic portions and marked tendencies to produce alpha-helicity, specifically displace (apparent Ki, 5-6 microM) [3H] Ro 5-4864 from astroglial cell binding sites. Peptides (ODN, eicosapentaneuropeptide, OND-NH2) with very low tendencies to form alpha-helices and with virtually no hydrophobic structure were not able to displace Ro 5-4864 at concentrations of up to 100 microM. In contrast, ODN was a good displacer of [3H]flumazenil from intact neurons, with an apparent IC50 of 5 microM. These data suggest that the alpha-helical portion of TTN may be important for BZ receptor recognition and BZ receptor subtype discrimination.

DBI (diazepam binding inhibitor): the precursor of a family of endogenous modulators of GABAA receptor function. History, perspectives, and clinical implications

Biochemical, electrophysiological, and lately, molecular biological techniques have shown that GABAA receptors are heterogeneous supramolecular complexes and can be divided into at least three major subgroups: GABAA1, GABAA2, and GABAA3. They differ mainly in the structural and functional properties of the allosteric modulatory center associated with each one of them. This paper will review the present state of research based on the evidence that DBI (diazepam binding inhibitor) and its natural processing products can selectively modulate GABAergic transmission at different GABAA receptor subtypes. Furthermore, the possibility that the DBI family of peptides represents a novel and meaningful neurochemical correlate for neuropsychiatric pathology, sustained by an alteration of GABAergic transmission, will be discussed.

Isolation and characterization of a rat brain triakontatetraneuropeptide, a posttranslational product of diazepam binding inhibitor: specific action at the Ro 5-4864 recognition site

This report describes the purification and characterization from rat brain of triakontatetraneuropeptide (TTN, DBI 17-50), a major biologically active processing product of diazepam binding inhibitor (DBI). Brain TTN was purified by immunoaffinity chromatography with polyclonal octadecaneuropeptide, DBI 33-50) antibodies coupled to CNBr-Sepharose 4B followed by two reverse-phase HPLC steps. The amino acid sequence of the purified peptide is: Thr-Gln-Pro-Thr-Asp-Glu-Glu-Met-Leu-Phe-Ile-Tyr-Ser-His-Phe-Lys-Gln-Ala-Thr-Val - Gly-Asp-Val-Asn-Thr-Asp-Arg-Pro-Gly-Leu-Leu-Asp-Leu-Lys. Synthetic TTN injected intracerebroventricularly into rats induces a proconflict activity (IC50 0.8 nmol/rat) that is prevented by the specific "peripheral" benzodiazepine (BZ) receptor antagonist isoquinoline carboxamide, PK 11195, but not by the "central" BZ receptor antagonist imidazobenzodiazepine, flumazenil. TTN displaces [3H]Ro 5-4864 from synaptic membranes of olfactory bulb with a Ki of approximately 5 microM. TTN also enhances picrotoxinin inhibition of gamma-aminobutyric acid (GABA)-stimulated [3H]flunitrazepam binding. These data suggest that TTN, a natural DBI processing product acting at "Ro 5-4864 preferring" BZ binding site subtypes, might function as a putative neuromodulator of specific GABAA receptor-mediated effects.

Determination of oil oxidation by an aldehyde-requiring mutant of luminous bacteria

A simple, rapid bioluminescence test (BT) for the determination of lipid oxidation is described. The test utilizes an aldehyde-requiring dark mutant of Vibrio harveyi (M42) that emits light in the presence of long chain (C8-C16) aliphatic aldehydes. The procedure consists of treating the oil or fat with CO2+ ion in ethanolic medium at alkaline pH. This treatment facilitates the decomposition of the hydroperoxides into long-chain aldehydes, part of which is used by the bacteria to produce light. The test was evaluated with corn, soybean and safflower oils, and shows excellent correlation with the commonly used peroxide value assay.

The nucleotide sequence of the mRNA encoding the fusion protein of measles virus (Edmonston strain): a comparison of fusion proteins from several different paramyxoviruses

Membrane fusion is the primary cytopathic effect observed in cells infected with measles virus. The viral protein responsible for this process has previously been defined as the fusion (F) protein. Fusion is activated by the proteolytic cleavage of a precursor molecule (F0) to yield two disulfide-linked polypeptides (F1 and F2). In this paper the mRNA for the membrane fusion protein has been cloned and the resulting cDNAs were sequenced. A mRNA composed of 2377 nucleotides was found to contain one open reading frame which could potentially code for a protein of 550 amino acids. This corresponding gene product was identified as the fusion protein through use of antibodies directed against a synthetic peptide which was constructed from the deduced amino acid sequence. A long and rather G-C rich 5' terminus was found on the mRNA and this noncoding region may play some role in regulation of protein synthesis at the translational level. Protein sequence data derived from the cDNA clones revealed a highly conserved F1 amino terminus which is characteristic of most paramyxoviruses. Very little amino acid homology (except for the conservation of the F1 terminus and 9 cysteines) was evident when the sequence was compared to other paramyxovirus fusion proteins. However an overall hydrophobic nature was characteristic of all the F proteins and hydrophobicity plots for the fusion proteins of 4 different paramyxoviruses were very similar. Computer analysis was also employed to analyze the secondary structure of the measles virus F protein. Large stretches of alpha helix were characteristic of the regions which purportedly interact with membranes. The functional domains of the F protein and their similarity to those of the influenza hemagglutinin protein are discussed in this communication. We concluded that the distribution of hydrophobic regions capable of spanning biological membranes determines the fusogenic nature of the F protein.

Use of antibodies directed against synthetic peptides for identifying cDNA clones, establishing reading frames, and deducing the gene order of measles virus

A number of cDNA clones complementary to measles virus mRNA and 50S genome RNA have been generated. These clones have been mapped by restriction enzyme analysis and were subsequently sequenced by the method of Maxam and Gilbert (A. M. Maxam and W. Gilbert, Methods Enzymol. 65:499-560, 1980). Computer analysis of these DNA sequences revealed open reading frames which potentially could code for a number of gene products. Portions of these putative polypeptides were synthesized, and rabbit antibodies directed against peptide-hemocyanin conjugates were produced. These antibodies were used to immunoprecipitate virus-specific polypeptides which were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. For each of the antisera tested, a unique protein was precipitated whose migration on polyacrylamide gels corresponded to standard gene products identified by monoclonal antibodies and antisera against measles virus. By using this method, we were able to assign the coding regions of cDNA clones to specific protein products and, subsequently, to order the genes of the 3'-terminal third of measles genome RNA.