Combining SNAC and C10 in oral tablet formulations for gastric peptide delivery: A preclinical and clinical study.

Current oral formulations of macromolecules including peptides typically rely on single permeation enhancer (PE) to promote absorption and thus bioavailability. In this work, we combined two PEs, namely sodium N-[8-(2-hydroxybenzoyl) amino] caprylate (SNAC) and sodium caprate (C10), in one tablet formulation to potentially gain a synergistic effect for enhanced gastric absorption of a GLP-1 analogue and a PCSK9 inhibitor. Permeability tests on a gastric organoids-based cell model showed that the combination of SNAC and C10 can significantly improve peptide permeability compared to either SNAC or C10 alone.

Exploring the complex map of insulin polymorphism: a novel crystalline form in the presence of m-cresol.

In this study, the first crystal structure of a novel crystal form of human insulin bound to meta-cresol in an acidic environment is reported. The combination of single-crystal and powder X-ray diffraction crystallography led to the detection of a previously unknown monoclinic phase (P2). The structure was identified from the powder patterns and was solved using single-crystal diffraction data at 2.

Structures of insect Imp-L2 suggest an alternative strategy for regulating the bioavailability of insulin-like hormones.

The insulin/insulin-like growth factor signalling axis is an evolutionary ancient and highly conserved hormonal system involved in the regulation of metabolism, growth and lifespan in animals. Human insulin is stored in the pancreas, while insulin-like growth factor-1 (IGF-1) is maintained in blood in complexes with IGF-binding proteins (IGFBP1-6). Insect insulin-like polypeptide binding proteins (IBPs) have been considered as IGFBP-like structural and functional homologues.

Structure, Aggregation, and Activity of a Covalent Insulin Dimer Formed During Storage of Neutral Formulation of Human Insulin.

A specific covalently linked dimeric species of insulin high molecular weight products (HMWPs), formed during prolonged incubation of a neutral pharmaceutical formulation of human insulin, were characterized in terms of tertiary structure, self-association, biological activity, and fibrillation properties. The dimer was formed by a covalent link between A21Asn and B29Lys. It was analyzed using static and dynamic light scattering and small-angle X-ray scattering to evaluate its self-association behavior.

High-resolution powder X-ray data reveal the T(6) hexameric form of bovine insulin.

A series of bovine insulin samples were obtained as 14 polycrystalline precipitates at room temperature in the pH range 5.0-7.6.

Insulin analog with additional disulfide bond has increased stability and preserved activity.

Insulin is a key hormone controlling glucose homeostasis. All known vertebrate insulin analogs have a classical structure with three 100% conserved disulfide bonds that are essential for structural stability and thus the function of insulin. It might be hypothesized that an additional disulfide bond may enhance insulin structural stability which would be highly desirable in a pharmaceutical use.

Ligand-controlled assembly of hexamers, dihexamers, and linear multihexamer structures by the engineered acylated insulin degludec.

Insulin degludec, an engineered acylated insulin, was recently reported to form a soluble depot after subcutaneous injection with a subsequent slow release of insulin and an ultralong glucose-lowering effect in excess of 40 h in humans. We describe the structure, ligand binding properties, and self-assemblies of insulin degludec using orthogonal structural methods. The protein fold adopted by insulin degludec is very similar to that of human insulin.

Structural studies of human insulin cocrystallized with phenol or resorcinol via powder diffraction.

The effects of the ligands phenol and resorcinol on the crystallization of human insulin have been investigated as a function of pH. Powder diffraction data were used to characterize several distinct polymorphic forms. A previously unknown polymorph with monoclinic symmetry (P2(1)) was identified for both types of ligand with similar characteristics [the unit-cell parameters for the insulin-resorcinol complex were a = 114.

Novel covalently linked insulin dimer engineered to investigate the function of insulin dimerization.

An ingenious system evolved to facilitate insulin binding to the insulin receptor as a monomer and at the same time ensure sufficient stability of insulin during storage. Insulin dimer is the cornerstone of this system. Insulin dimer is relatively weak, which ensures dissociation into monomers in the circulation, and it is stabilized by hexamer formation in the presence of zinc ions during storage in the pancreatic β-cell.

Engineering of insulin receptor isoform-selective insulin analogues.

Background: The insulin receptor (IR) exists in two isoforms, A and B, and the isoform expression pattern is tissue-specific. The C-terminus of the insulin B chain is important for receptor binding and has been shown to contact the IR just adjacent to the region where the A and B isoforms differ. The aim of this study was to investigate the importance of the C-terminus of the B chain in IR isoform binding in order to explore the possibility of engineering tissue-specific/liver-specific insulin analogues.

Crystallographic characterization of two novel crystal forms of human insulin induced by chaotropic agents and a shift in pH.

Background: Insulin is a therapeutic protein that is widely used for the treatment of diabetes. Its biological function was discovered more than 80 years ago and it has since then been characterized extensively. Crystallization of the insulin molecule has always been a key activity since the protein is often administered by subcutaneous injections of crystalline insulin formulations.

The significance of biochemical and molecular sample integrity in brain proteomics and peptidomics: stathmin 2-20 and peptides as sample quality indicators.

Comparisons of transcriptional and translational expression in normal and abnormal states are important to reach an understanding of pathogenesis and pathophysiology. Maintaining the biochemical, molecular, and structural sample integrity is essential for correct sample comparisons. We demonstrate that both proteins and neuropeptides, including their PTMs, are subjected to massive degradation in the brain already 1 min postmortem.

Binding mode of Thioflavin T in insulin amyloid fibrils.

Amyloid fibrils share various common structural features and their presence can be detected by Thioflavin T (ThT). In this paper, the binding mode of ThT to insulin amyloid fibrils was examined. Scatchard analysis and isothermal titration calorimetry (ITC) showed at least two binding site populations.

Structural characterization of insulin NPH formulations.

Insulin NPH (neutral protamine hagedorn) has for long been one of the most important therapeutic formulations for the treatment of diabetes. The protracted action profile of NPH formulations is gained from crystallizing insulin with zinc in the presence of the basic poly-arginine peptide protamine. In spite of its long history and successful use, the binding mode of the insulin-protamine complex is not known.

Electrostatic calculations and quantitative protein retention models for ion exchange chromatography.

A novel set of protein descriptors has been developed to increase the understanding of protein behavior on chromatographic media. The protein descriptors are pH-dependent and based on electrostatic and hydrophobic properties of mainly the surface of the proteins as revealed by their three-dimensional structure. Interpretable and predictive quantitative structure property relationship (QSPR) models were then obtained for protein retention in ion exchange chromatography at different pH values.

SwePep, a database designed for endogenous peptides and mass spectrometry.

A new database, SwePep, specifically designed for endogenous peptides, has been constructed to significantly speed up the identification process from complex tissue samples utilizing mass spectrometry. In the identification process the experimental peptide masses are compared with the peptide masses stored in the database both with and without possible post-translational modifications. This intermediate identification step is fast and singles out peptides that are potential endogenous peptides and can later be confirmed with tandem mass spectrometry data.