Novel 1-L polyethylene glycol + ascorbate versus high-volume polyethylene glycol regimen for colonoscopy cleansing: a multicenter, randomized, phase IV study

BACKGROUND AND AIMS

Adequate bowel cleansing is critical to ensure quality and safety of a colonoscopy. A novel 1-L polyethylene glycol plus ascorbate (1L-PEG+ASC) regimen was previously validated against low-volume regimens but was never compared with high-volume regimens.

METHODS

In a phase IV study, patients undergoing colonoscopy were randomized 1:1 to receive split-dose 1L PEG+ASC or a split-dose 4-L PEG-based regimen (4L-PEG) in 5 Italian centers. Preparation was assessed with the Boston Bowel Preparation Scale (BBPS) by local endoscopists and centralized reading, both blinded to the randomization arm. The primary endpoint was noninferiority of 1L-PEG+ASC in colon cleansing. Secondary endpoints were superiority of 1L-PEG+ASC, patient compliance, segmental colon cleansing, adenoma detection rate, tolerability, and safety.

RESULTS

Three hundred eighty-eight patients (median age, 59.8 years) were randomized between January 2019 and October 2019: 195 to 1L-PEG+ASC and 193 to 4L-PEG. Noninferiority of 1L-PEG+ASC was demonstrated for cleansing in both the entire colon (BBPS ≥ 6: 97.9% vs 93%; relative risk [RR], 1.03; 95% confidence interval [CI], 1.001-1.04; P superiority = .027) and in the right-sided colon segment (98.4% vs 96.0%; RR, 1.02; 95% CI, .99-1.02; P noninferiority = .013). Compliance was higher with 1L-PEG+ASC than with 4L-PEG (178/192 [92.7%] vs 154/190 patients [81.1%]; RR, 1.10; 95% CI, 1.05-1.12), whereas no difference was found regarding safety (moderate/severe side effects: 20.8% vs 25.8%; P = .253). No difference in adenoma detection rate (38.8% vs 43.0%) was found.

CONCLUSIONS

One-liter PEG+ASC showed noninferiority compared with 4L-PEG in achieving adequate colon cleansing and provided a higher patient compliance. No differences in tolerability and safety were detected. (Clinical trial registration number: NCT03742232.).

Per-Oral Endoscopic Myotomy for Esophagogastric Junction Outflow Obstruction: A Multicenter Pilot Study

Esophagogastric junction outflow obstruction (EGJOO) is a rare but increasingly recognized diagnosis as described by The Chicago Classification of Esophageal Motility Disorders version 3.0 (version 3.0).¹ On high-resolution manometry (HRM), EGJOO is characterized by increased integrated relaxation pressure (IRP) of the lower esophageal sphincter (LES), yet with some preserved esophageal peristalsis.^2-4 Little consensus exists on the preferred therapeutic approach.³ Although conceptually per-oral endoscopic myotomy (POEM) should address the measurable dysfunction in the LES, few data exist to support this.⁵ Thus, we aimed to evaluate the safety and efficacy of POEM for the treatment of symptomatic EGJOO.

Influence of gemfibrozil on sulfate transport in human erythrocytes during the oxygenation-deoxygenation cycle

The effects of gemfibrozil (GFZ), an antihyperlipidemic agent, on the anionic transport of the human red blood cells (RBC) during the oxygenation-deoxygenation cycle were examined. Gemfibrozil clearly plays a role in the modulation of the anionic flux in erythrocytes; in fact it causes a strong increment of anions transport when the RBCs are in the high-oxygenation state (HOS). Such an effect is remarkably reduced in the low-oxygenation state (LOS). With the aim of identifying the dynamics of fibrate action, this effect has been investigated also in human ghost and chicken erythrocytes. These latter, in fact, are known to possess a B3 (anion transporter or Band 3) modified at the cytoplasmic domain (cdb3) which plays a significant role in the metabolic modulation of red blood cells. The results were analyzed taking into account the well-known interactions between fibrates and both conformational states of hemoglobin i.e. the T state (deoxy-conformation) and the R state (oxy-conformation). The effect of gemfibrozil on anionic influx appears to be due to a wide interaction involving a "multimeric" Hb-GFZ-cdb3 macromolecular complex.

Band 3 protein function in teleost fish erythrocytes: effect of oxygenation-deoxygenation

During vertebrate evolution, structural changes in red blood cells (RBC) and hemoglobin (Hb), have probably resulted in the importance of blood carbon dioxide transport. The chloride/bicarbonate exchange across the RBC membrane, which is an integral part of the blood CO(2) transport process in vertebrates, has been examined on two different species of teleost fish, Euthynnus alletteratus and Thunnus thynnus, at several oxygenation states of erythrocyte HOS (high-oxygenation state, about 90 % of saturation) and LOS (low-oxygenation state, about 15 % of saturation). The results were compared with those observed in human RBC under the same experimental conditions and with the chicken (Gallus gallus) erythrocytes, which have particular modifications at the N-terminus of the band 3 protein (B3). In fish the kinetic measurements have shown a different anion transport in several oxygenation states of erythrocytes, indicating that also at lower levels of vertebrate evolution there exists a modulation of the anionic flow affected by oxygen. The functional correlation of anion transport to changes of parts of the hemoglobin sequence responsible for alterations in the interactions with the cytoplasmic domain of band 3 protein (cdb3) allowed us to suggest a hypothesis about fish physiology. The highest values of kinetic measurements observed in fish have been attributed to the metabolic need of the RBC in response to the removal of CO(2) that in teleosts is also of endogenous origin.

Enzymatic urea adaptation: lactate and malate dehydrogenase in Elasmobranchii

Lactate dehydrogenase (LDH) and malate dehydrogenase (MDH) electrophoretic tissue patterns of two different orders of Elasmobranchii: Carchariniformes (Galeus melanostomus and Prionace glauca) and Squaliformes (Etmopterus spinax and Scymnorinus licha) were studied. The number of loci expressed for these enzymes was the same of other elasmobranch species. Differences in tissue distribution were noted in LDH from G. melanostomus due to the presence of an additional heterotetramer in the eye tissue. There were also differences in MDH. In fact, all the tissues of E. spinax and G. melanostomus showed two mitochondrial bands. Major differences were noted in the number of isozymes detected in the four compared elasmobranchs. The highest polymorphism was observed in E. spinax and G. melanostomus, two species that live in changeable environmental conditions. The resistance of isozymes after urea treatment was examined; the resulting patterns showed a quite good resistance of the enzymes, higher for LDH than MDH, also at urea concentration much greater than physiological one. These results indicated that the total isozyme resistance can be considered higher in urea accumulators (such as elasmobranchs) than in the non-accumulators (such as teleosts).

Two proline-rich peptides from pig (Sus scrofa) salivary glands generated by pre-secretory pathway underlying the action of a proteinase cleaving ProAla bonds

The primary structures of two salivary proline-rich peptides (PRP-SP-A, M 6156.0 amu and PRP-SP-B, M 1905.0 amu), from pig (Sus scrofa) were determined. The PRP-SP-B peptide, 21 residues long, overlaps with a sequence repeated 43 times in three deposited cDNAs coding for PRP proteins cloned from porcine parotid glands (Swiss-Prot codes: Q95JC9, Q95JD1, Q95JD0). PRP-SP-A peptide, 56 amino acid residues long, overlaps with the N-terminus repeats of Q95JC9 and Q95JD1 and it is phosphorylated at Ser 12 and 14. The two peptides were found both in whole saliva and in granules from pig parotid glands. The biosynthesis of the two peptides implies the action of a proteinase responsible for Pro downward arrow Ala cleavage in the pre-secretory process.

Role of polyols in thermal inactivation of shark ornithine transcarbamoylase

The ability of activity modulators of ornithine transcarbamoylase (OCT) from the liver of the thresher shark Alopias vulpinus to stabilize the enzyme against thermal denaturation was investigated in the tri-buffer at pH 7.8, at temperatures ranging from 60 to 70 (o)C, in the presence of polyhydroxylic molecules such as glycerol and sugars. The study indicated that in the presence of 0.5 M sugars and 1.6 M glycerol in the preincubation medium the OCT activity increases. When trehalose is introduced directly in the reaction mixture in a range of concentration of 0.25-0.5 M, the activity is lower than that with maltose, glycerol and buffer alone. Kinetic data for carbamoyl phosphate and ornithine with and without maltose and glycerol are similar, whereas trehalose increases the kinetic values. Arrhenius plots show an increase of activation energy due to trehalose, whereas values obtained with maltose and glycerol are similar to the control.

Purification and properties of ornithine carbamoyltransferase from loggerhead turtle liver

Ornithine carbamoyltransferase has been purified from the liver of the loggerhead turtle Caretta caretta by a single-step procedure using chromatography on an affinity column to which the transition-state analogue, delta-N-(phosphonoacetyl)-L-ornithine (delta-PALO), was covalently bound. The procedure employed yielded an enzyme which was purified 373-fold and was judged to be homogeneous by nondenaturing and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme showed a specific activity of 224. The molar mass of the C. caretta enzyme was approximately 112 kDa, the single band obtained by SDS-PAGE indicated a subunit molar mass of 39.5 kDa; hence, the enzyme is a trimer of identical subunits. It catalyzes an ordered sequential mechanism in which carbamoyl phosphate binds first, followed by L-ornithine. The Michaelis constants were 0.858 mM for L-ornithine and 0.22 mM for carbamoyl phosphate, the dissociation constant of the enzyme-carbamoyl phosphate complex was 0.50 mM.

Glycated human hemoglobin (HbA1c): functional characteristics and molecular modeling studies

A minor hemoglobin component of human red blood cell hemolysate, HbA1c, is the result of the non-enzymatic reaction of glucose with the alpha-amino groups of the valine residues at the N-terminus of the beta-chains of human hemoglobin. In this paper, the effect of protons, chloride and 2,3-diphosphoglycerate (DPG) on the functional properties of HbA1c has been investigated in some details. Moreover, the structural modifications induced on the native molecule by the sugar moieties, studied by computer modeling, do agree with the observed functional alterations. In particular, the functional results indicate that: (a) the low-affinity conformation (or T-state) of HbA1c is destabilized by the chemical modification per se; (b) the Bohr effect is reduced with respect to that of native HbA0; (c) the affinity of the T-state of HbA1c for 2,3-diphosphoglycerate is about 2.6 x lower than that of the corresponding conformational state of HbA0, while the R-state is less affected with, the affinity being 1.7 x lower. At the structural level, computer modeling studies show that the two sugar moieties are asymmetrically disposed within the 2,3-diphosphoglycerate binding site. In addition, molecular mechanics and dynamics calculations concerning the interaction with 2,3-diphosphoglycerate indicate that while in HbA0 the effector can assume two different stable orientations, in glycated Hb only one orientation is possible. All together, the results show that glycation of the Val 1 residues of both beta-chains does not impair the binding of DPG but imposes a different mode of binding by changing the internal geometry of the complex and the surface distribution of the positive electrostatic potential within the binding pocket.

Characterization of Cu,Zn superoxide dismutase from the bathophile fish, Lampanyctus crocodilus

Cu,Zn SOD from the bathophile teleost Lampanyctus crocodilus (LSOD) shows a high degree of homology with the sequence of the enzymes from other teleostean fish species. The catalytic properties of LSOD are very similar to those of the bovine enzyme, albeit with higher sensitivity to thermal denaturation. The apparent molecular mass of LSOD (37.6 KDa) is higher than the other Cu,Zn SOD variants studied. The aminoacid sequence of LSOD reveals interesting substitutions compared to the bovine enzyme. These are discussed in view of the particular environmental conditions to which L. crocodilus is adapted.

Diving behaviour and haemoglobin function: the primary structure of the alpha- and beta-chains of the sea turtle (Caretta caretta) and its functional implications

The amino acid sequence of the alpha- and beta-chains of haemoglobin (Hb) from the loggerhead sea turtle (Caretta caretta) has been determined. Comparison with that of human Hb shows differences in several residues involved in both alpha 1 beta 1 and alpha 1 beta 2 packing contacts. On the whole, in spite of the mutations, the essential characteristics of both interfaces seem to be maintained. The functional properties of the sea turtle Hb have been investigated at different temperatures and as a function of proton, chloride and organic phosphate concentrations. In addition to overall similarities shared with most of the vertebrate Hbs previously described, this molecule shows significant differences which could be related to the life behaviour of the turtle. In fact, while the shape of the Bohr-effect curve is well adapted for gas exchange during prolonged dives, the very small enthalpy change for O2 binding ensures that O2 delivery becomes essentially insensitive to the temperature changes of the environment. Moreover, and similarly to the case of emperor penguin Hb, the small alkaline Bohr effect appears to be only choride-linked, since the pH dependence of the O2 affinity is abolished in the absence of this ion. These functional characteristics are discussed on the basis of the primary structure of alpha- and beta-chains.

Molecular modeling and electrostatic potential calculations on chemically modified Cu,Zn superoxide dismutases from Bos taurus and shark Prionace glauca: role of Lys134 in electrostatically steering the substrate to the active site

The three-dimensional structure of Cu,Zn superoxide dismutase (SOD) from the shark Prionace glauca was homology modeled on the structure of the bovine enzyme used as a template. Shark SOD displays the conservative substitution of one of the residues involved in the electrostatic guidance of superoxide toward the active site of the enzyme, i.e., Lys134, which is replaced by arginine. The association rate, calculated by brownian dynamics simulations incorporating electrostatic terms, and the enzyme reaction rate, measured by the pulse radiolysis method, were found to be identical for both bovine and shark SODs. In order to quantify the role of Lys134 in electrostatically steering the superoxide to the active site, chemical modification of the lysine residues by carbamoylation was carried out on both bovine and shark SODs. Experimental determination of the enzymatic reaction rate indicated that the charge located on the residue 134 gives 19% contribution to the guidance of superoxide anion at low ionic strength. This value matches the association rates predicted by brownian dynamics.

Structural studies on the loggerhead sea turtle (Caretta caretta) myoglobin

The primary structure of myoglobin from the loggerhead sea turtle (Caretta caretta) has been determined; the protein consists of 153 amino acid residues. The ferric loggerhead sea turtle myoglobin has been crystallized in a form suitable for X-ray structural investigations. The crystals were grown at pH 8.0, in 0.05 M tris/HCl buffer, using 3.2 M ammonium sulfate as precipitating agent, at 4 degrees C, and belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell constants a = 37.2 A, b = 61.1 A, c = 75.2 A (one molecule, 17,000 M(r), in the asymmetric unit). A molecular replacement solution was found for the loggerhead sea turtle myoglobin crystals using sperm whale myoglobin structure as search model. The R-factor value, after molecular replacement, is 0.387, for the data in the 15-3.3 A resolution range. The results here reported are the basis for the first X-ray crystallographic investigation on a reptile myoglobin, and indicate a strong overall structural similarity between the loggerhead sea turtle and mammalian (i.e. sperm whale) myoglobins.

Reduced sensitivity of O2 transport to allosteric effectors and temperature in loggerhead sea turtle hemoglobin: functional and spectroscopic study

The functional and spectroscopic (EPR and absorbance) properties of the adult loggerhead sea turtle (Caretta caretta) hemoglobin have been studied with special reference to the action of allosteric effectors and temperature. Present results indicate that turtle Hb displays a very low O2 affinity and a very small sensitivity to allosteric effectors and temperature. Furthermore, the amplitude of the Bohr effect for O2 binding is strongly reduced. In parallel, EPR and absorbance spectroscopic properties of the nitrosylated derivative of turtle Hb suggest that the hemoprotein is in a low-affinity conformation, even in the absence of allosteric effectors. These findings suggest the existence of unusual molecular mechanisms modulating the basic reaction of Hb with O2, which may be linked to specific physiological needs related to the diving behavior of the turtle.

Dolphin ceruloplasmin: the first proteolytically stable mammalian ceruloplasmin

1. Ceruloplasmin, the blue protein of the plasma of vertebrates, was isolated from dolphin, a marine mammal. The protein showed overall physico-chemical parameters very similar to those of all other mammalian ceruloplasmins. The spectroscopic properties indicated a conservation of the copper binding sites. 2. Non-denaturing electrophoresis revealed a conformation similar to that of other mammalian ceruloplasmins. EPR spectroscopy and calorimetric analyses indicated a three-domain arrangement of the protein typical of "aged" ceruloplasmin. 3. Dolphin ceruloplasmin is the only mammalian ceruloplasmin insensitive to trypsin, plasmin or chymotrypsin. This property, however, does not result in a higher conformational stability of the molecule. Thus, susceptibility of ceruloplasmin to aging is not directly related to the lability to proteases, which is typical of all other mammalian ceruloplasmins so far studied.

Unusual stability properties of a reptilian ceruloplasmin

Ceruloplasmin from the turtle Caretta caretta was isolated to purity by using the single-step procedure recently developed by us to purify sheep and chicken ceruloplasmin. It has a Mr of ca. 145,000 and a total copper content of 5.1 +/- 0.2 atoms of copper per molecule, 50% of which are detectable by EPR. The spectroscopic features include an absorption maximum at 603 nm in the electronic spectrum and the total absence of any resonance attributable to Type 2 copper in the EPR spectrum. Turtle ceruloplasmin was found to be unusually resistant to aging and proteolysis, when compared to ceruloplasmins isolated from other species. p-Phenyl-endiamine oxidase activity measurements revealed an unusually low catalytic efficiency, while the kinetic parameters of Fe(II) oxidation were consistent with those reported for other species of ceruloplasmin.

Substitution of arginine for lysine 134 alters electrostatic parameters of the active site in shark Cu,Zn superoxide dismutase

The complete amino acid sequence was determined for the Cu,Zn superoxide dismutase from the shark Prionace glauca. The active site region shows the substitution of an Arg for Lys at position 134, which is important for electrostatic facilitation of the diffusion of O2- to the catalytically active copper. This change may be related to observed alterations of electrostatic parameters of the enzyme (pK of the pH dependence of the enzyme activity, rate of inactivation by H2O2), although it preserves a high efficiency of dismutation at neutral pH.

Isolation and characterization of Cu,Zn superoxide dismutase of the shark Prionace glauca

A Cu,Zn superoxide dismutase was purified for the first time from an elasmobranch species (Prionace glauca) and showed the following differences with respect to other animal superoxide dismutases. The enzyme displays a low isoelectric point. The enzyme activity is unusually independent of ionic strength. The isolated enzyme has 30% of its copper in the reduced state.

Sheep ceruloplasmin: isolation and characterization

Ceruloplasmin has been isolated from sheep plasma by a procedure involving two chromatographic steps and (NH4)2SO4 fractionation. The ovine protein is similar to ceruloplasmins from other species previously described (human, bovine), having a single chain of about 125 Kdal with a very high degree of homology in the amino acid composition. It differs, however, from human and bovine ceruloplasmin because of its lower copper content and its higher specific enzyme activity. The oxidase activity as well as the spectroscopic properties were found to be pH range 5-8 with a pH optimum for activity of 6.3.