Insulins with built-in glucose sensors for glucose responsive insulin release.

Derivatization of insulin with phenylboronic acids is described, thereby equipping insulin with novel glucose sensing ability. It is furthermore demonstrated that such insulins are useful in glucose‐responsive polymer‐based release systems. The preferred phenylboronic acids are sulfonamide derivatives, which, contrary to naïve boronic acids, ensure glucose binding at physiological pH, and simultaneously operate as handles for insulin derivatization at LysB29. The glucose affinities of the novel insulins were evaluated by glucose titration in a competitive assay with alizarin. The affinities were in the range 15–31 mM (K_d), which match physiological glucose fluctuations. The dose‐responsive glucose‐mediated release of the novel insulins was demonstrated using glucamine‐derived polyethylene glycol polyacrylamide (PEGA) as a model, and it was shown that Zn(II) hexamer formulation of the boronated insulins resulted in steeper glucose sensitivity relative to monomeric insulin formulation. Notably, two of the boronated insulins displayed enhanced insulin receptor affinity relative to native insulin (113%–122%) which is unusual for insulin LysB29 derivatives. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.     

猪B_0L-丙氨酰胰岛素和猪B_1L-亮氨酰胰岛素的制备及性质研究

 猪胰岛素经与MSC·ONsu选择性反应,得到[MSC]A_(21)B_(29)胰岛素,再与BOC-L-Ala·TTT缩合,去保护后得到[L-Ala]B_0胰岛素,将得到的[MSC]A_(21)B_(29)胰岛素经Edman降解,再与BOC-L-Leu·TTT缩合、去保护后得到[L-Leu]B_1胰岛素。样品经N-末端分析,醋酸纤维素薄膜电泳、氨基酸组成分析和紫外吸收光谱鉴定,确定它们分别为均一的[L-Ala]B_0胰岛素和[L-Leu]B_1胰岛素。放射免疫法分析[L-Al_a]B_0肽岛素和[L-Leu]B_1胰岛素的免疫活性分别相当于天然胰岛素的30％和47％,小鼠惊厥法分析表明[L-Ala]B_6胰岛素与[L-Leu]B_1胰岛素的生物活力为19.7国际单位/mg和19.1国际单位/mg,相当于天然胰岛素的76％和73％。     

Human insulin

The two human insulins of clinical importance are (a) semisynthetic human insulin prepared from pork pancreas by enzymatically substituting threonine for alanine-the last amino acid in the beta chain-thereby transforming pork insulin in vitro to human insulin; and (b) biosynthetic human insulin synthesized biotechnologically in Escherichia coli-K12. Using this latter technique, it is possible to produce mass quantities of highly purified insulin for the treatment of insulin-dependent diabetics, avoiding the problems inherent in supplies of insulin produced from animal pancreas. It has been suggested that to avoid confusion the two human insulins should be called semisynthetic human insulin of pork origin and biosynthetic human insulin of E. coli origin, respectively. These insulins have four advantages over highly purified animal insulins: (a) they induce lower titers of circulating insulin antibodies; (b) their subcutaneous injection is associated with fewer skin reactions; (c) they are absorbed more rapidly from the injection site; and (d) less degradation occurs at the site of injection. These data indicate that newly diagnosed insulin-dependent diabetes, particularly in children, should be treated with either of the two human insulins. The warranty against inadequate supplies of insulin offered by biosynthetic human insulin makes the use of pork insulins unnecessary and beef insulins totally useless.     

Toward understanding the role of insulin alpha-helix II in the growth-promoting activity of insulin.

For further understanding the contribution of the alpha-helix II (alphaII) in the growth-promoting activity of insulin, the residues A2Ile, A5Gln, and A8Thr located in alphaII were mutated to Leu, Glu, and Tyr, respectively. Three mutant insulins, [A2Leu]human insulin, [A5Glu]human insulin, and [A8Tyr]human insulin, were prepared by means of site-directed mutagenesis. The in vitro growth-promoting activities of the three mutant insulins, measured using GR2H6 cells, were 7.5%, 291%, and 250% of that of native insulin, respectively. Their receptor-binding activities to the insulin receptor were 2.3%, 46.7%, and 138.7%, respectively, compared with native insulin. Both the growth-promoting and receptor-binding activities of [A2Leu]human insulin and [A3Leu]insulin (Shi et al., 1997) were parallel and greatly decreased compared with native insulin. The results demonstrate that the residues A2Ile and A3Val in the alphaII are essential for the growth-promoting activity of insulin, and the growth-promoting function of insulin might be performed through, or mainly through, binding to the insulin receptor. The growth-promoting activities of [A5Glu]human insulin and [A8Tyr]human insulin were increased 6-fold and 2-fold, respectively, compared with native insulin, indicating that their growth-promoting activities might be expressed by, or mainly by, binding to the IGF-1 receptor.     

Mouse antibodies to the insulin receptor developing spontaneously as anti-idiotypes. I. Characterization of the antibodies

Mice immunized to ungulate insulins were found to develop antibodies of two specificities: insulin antibodies that were mostly IgG1 and IgG2 antibodies that acted both as anti-idiotypes to specific mouse insulin antibodies and as antibodies to the insulin receptor. There was a negative association between the presence of anti-idiotypic receptor antibodies and insulin antibodies bearing the specific idiotype; the specific idiotypic antibodies were confined to the early phase of the primary response while the anti-idiotypic receptor antibodies were detected only after the idiotypic antibodies had disappeared. To map the insulin epitope that triggered the specific idiotypic response, we chemically altered the insulin molecule so as to inhibit its interaction with the insulin receptor. The altered insulins triggered high titers of antibodies binding to antigenic determinants on native insulin, but no anti-idiotypic receptor antibodies. Thus, the epitope responsible for the specific idiotypic-anti-idiotypic network was probably the part of the insulin molecule whose conformation is recognized by the insulin receptor.     

Isolation, primary structure, and biological and immunological properties of pink and chum salmon insulins

1. Insulins have been isolated from islet tissue of pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon. The primary structure of chum and pink salmon insulins was found to be identical. Compared to the amino acid sequence of human insulin, the salmon insulins under study differed at 14 positions. 2. Biological activity of pink salmon insulin was 83% of that of standard porcine insulin. 3. The immunological properties of fish insulins were investigated in specific radioimmunoassay (RIA) systems, based on porcine and pink salmon insulins. 4. A significant difference in the antigenic determinants of these fish and mammalian hormones was revealed.     

Sequence-specific 1H-NMR assignments for the aromatic region of several biologically active, monomeric insulins including native human insulin

The aromatic region of the 1H-FT-NMR spectrum of the biologically fully-potent, monomeric human insulin mutant, B9 Ser----Asp, B27 Thr----Glu has been investigated in D2O. At 1 to 5 mM concentrations, this mutant insulin is monomeric above pH 7.5. Coupling and amino acid classification of all aromatic signals is established via a combination of homonuclear one- and two-dimensional methods, including COSY, multiple quantum filters, selective spin decoupling and pH titrations. By comparisons with other insulin mutants and with chemically modified native insulins, all resonances in the aromatic region are given sequence-specific assignments without any reliance on the various crystal structures reported for insulin. These comparisons also give the sequence-specific assignments of most of the aromatic resonances of the mutant insulins B16 Tyr----Glu, B27 Thr----Glu and B25 Phe----Asp and the chemically modified species des-(B23-B30) insulin and monoiodo-Tyr A14 insulin. Chemical dispersion of the assigned resonances, ring current perturbations and comparisons at high pH have made possible the assignment of the aromatic resonances of human insulin, and these studies indicate that the major structural features of the human insulin monomer (including those critical to biological function) are also present in the monomeric mutant.     

Ionization behavior of native and mutant insulins: pK perturbation of B13-Glu in aggregated species

Upscale titration from pH 2.5 to 11.2 is used as a means for probing solvent accessibility of ionizing groups in zinc-free preparations of native and mutant insulins. Stoichiometry and pK alpha values of ionizing groups in the titration curves are determined by iterative curve fitting. Under denaturing conditions, the titration curve of human insulin is in good agreement with that predicted from the sum of unperturbed titrations of the constituent ionizing groups and yields an apparent isoionic point of 5.3. Under nondenaturing conditions where aggregation and precipitation occur, titrations show that only five out of six carboxylate residues of human insulin ionize in the expected region. Consequently, one carboxylate ionization is masked and the apparent isoionic point located at pH 6.4. Correlation between ionization behavior and patterns of aggregation and solubility is established by titrations of mutant insulins and of dilute native insulin. Titration of an unusually soluble species, B25-Phe----His, shows that precipitation is not responsible for the masked carboxylate ionization of native insulin. Titrations of mutants B13-Glu----Gln and B9-Ser----Asp show that the masked ionization probably originates from monomer-monomer interactions in the insulin dimer. We conclude that the B13-Glu side chain is responsible for the masked carboxylate ionization in aggregated forms of human insulin.     

Sequence and evolution of guinea pig preproinsulin DNA

Guinea pig insulin exhibits an unusually high degree of divergence from the conserved insulins of other mammals. cDNA clones encoding guinea pig preproinsulin were isolated, and their nucleic acid sequences were determined. Comparisons of the nucleic acid sequence and its predicted amino acid sequence with sequences encoding insulins of other species revealed that the gene encoding guinea pig preproinsulin evolved from the same ancestral mammalian gene as other known mammalian insulin genes.     

Effects of fully synthetic human insulin in comparison to porcine insulin in normal subjects

Fully synthetic human insulin (CGP 12'831) was compared to porcine insulin in identical and non-identical formula by intravenous insulin tolerance tests in 12 volunteers. The half-lives of the three insulins tested did not differ (t 1/2: 5.5 +/- 0.2 minutes), though acid porcine insulin exhibited lower serum peak values. The hypoglycemic effects of the three insulins were identical. Human insulin produced a significantly smaller decrease in serum potassium (2p less than 0.01). The secretion of serum C-peptide was less inhibited by human insulin (2p less than 0.05). The counter-regulatory hormonal response of cortisol and growth hormone was lower after hypoglycemia induced by human insulin (2p less than 0.05). It is suggested that the hormonal effects of hypoglycemia are modified by insulin and depend in part on the molecular structure of insulin.     

Effects of fully synthetic human insulin in comparison to porcine insulin in normal subjects

Fully synthetic human insulin (CGP 12'831) was compared to porcine insulin in identical and non-identical formulation by intravenous insulin tolerance tests in 12 volunteers. The half-lives of the three insulins tested did not differ (t 1/2: 5.5 +/- 0.2 minutes), though acid porcine insulin exhibited lower serum peak values. The hypoglycemic effects of the three insulins were identical. Human insulin produced a significantly smaller decrease in serum potassium (2p less than 0.01). The secretion of serum C-peptide was less inhibited by human insulin (2p less than 0.05). The counter-regulatory hormonal response of cortisol and growth hormone was lower after hypoglycemia induced by human insulin (2p less than 0.05). It is suggested that the hormonal effects of hypoglycemia are modified by human insulin and depend in part on the molecular structure of insulin.     

Soluble, prolonged-acting insulin derivatives. I. Degree of protraction and crystallizability of insulins substituted in the termini of the B-chain

Hydrophilic insulins, more positively charged than human insulin at neutral pH, have been prepared by substitution with basic amino acids at the termini of the B-chain and by blocking the C-terminal carboxyl group of the B-chain. The isoelectric pH of the insulin is thereby moved from 5.4 towards physiological levels. Slightly acid solutions of derivatives, in which charge has been added in the C-terminus of the B-chain, have a prolonged action in vivo, in particular if the carboxyl group is blocked. It is found that the prolonged-acting hydrophilic insulins crystallize instantly when the pH is adjusted to 7. The prolonged action is ascribed to this readiness to crystallization combined with a low solubility, which may be further decreased by increased concentration of zinc ions. Hydrophobic insulins have a prolonged action independent of the site of substitution even if the derivative is soluble at physiological pH. Some derivatives were prepared from porcine insulin by tryptic transpeptidation. N-terminal B-chain substituted insulins were prepared by alkylation of a biosynthetic single-chain insulin precursor, followed by tryptic transpeptidation rendering the double chain insulin derivative. The observed blood glucose lowering in the rabbits implies that neither N- nor C-terminal B-chain substitution results in substantial deterioration of biological potency. An index for the degree of protraction based on the blood glucose data is used to compare the insulins.     

Isolation and amino acid sequence of insulins and C-peptides of European bison (Bison bonasus) and fox (Alopex lagopus)

Insulins and C-peptides were extracted and purified from bison and fox pancreatic glands. The insulins were reduced and pyridylethylated, and the derived A- and B-chains separated by HPLC. Amino acid sequence determinations of the pyridylethylated A- and B-chains proved bisontine insulin to be identical to bovine insulin and fox insulin to be identical to dog and porcine insulin. Bisontine C-peptide proved to be identical to bovine C-peptide. The isolated fox C-peptide comprises 23 amino acid residues and probably represents a major tryptic fragment of a larger C-peptide. The fox C-peptide fragment is identical to the dog C-peptide (9-31) except for residue 3 (residue 11 in the dog C-peptide), which is aspartic acid as compared with glutamic acid in the dog C-peptide.     

Specific insulin binding to chloroplasts isolated from Acetabularia mediterranea]

Kinetics of insulin fixation to chloroplasts, exponential dissociation of bound hormone, competition between radioactive and native insulins for binding and for release indicate that chloroplasts possess insulin receptors.     

Role of B13 Glu in insulin assembly. The hexamer structure of recombinant mutant (B13 Glu-->Gln) insulin.

The assembly of the insulin hexamer brings the six B13 glutamate side-chains at the centre into close proximity. Their mutual repulsion is unfavourable and zinc co-ordination to B10 histidine is necessary to stabilize the well known zinc-containing hexamers. Since B13 is always a carboxylic acid in all known sequences of hexamer forming insulins, it is likely to be important in the hormone's biology. The mutation of B13 Glu-->Gln leads to a stable zinc-free hexamer with somewhat reduced potency. The structures of the zinc-free B13 Gln hexamer and the 2Zn B13 insulin hexamer have been determined by X-ray analysis and refined with 2.5 A and 2.0 A diffraction data, respectively. Comparisons show that in 2Zn B13 Gln insulin, the hexamer structure (T6) is very like that of the native hormone. On the other hand, the zinc-free hexamer assumes a quaternary structure (T3/R3) seen in the native 4Zn insulin hexamer, and normally associated only with high chloride ion concentrations in the medium. The crystal structures show the B13 Gln side-chains only contact water in contrast to the B13 glutamate in 2Zn insulin. The solvation of the B13 Gln may be associated with this residue favouring helix at B1 to B8. The low potency of the B13 Gln insulin also suggests the residue influences the hormone's conformation.     

Mutational Analysis of the Absolutely Conserved B8Gly： Consequence on Foldability and Activity of Insulin

B8Gly is absolutely conserved in insulins during evolution. Moreover, its corresponding position is always occupied by a Gly residue in other members of insulin superfamily. Previous work showed that Ala replacement of B8Gly significantly decreased both the activity and the foldability of insulin. However, the effects of substitution are complicated, and different replacements sometimes cause significantly different results. To analyze the effects of B8 replacement by different amino acids, three new insulin/single-chain insulin mutants with B8Gly replaced by Ser, Thr or Leu were prepared by protein engineering, and both their foldability and activity were analyzed. In general, replacement of B8Gly by other amino acids causes significant detriment to the foldability of single-chain insulin： the conformations of the three B8 mutants are essentially different from that of wild-type molecules as revealed by circular dichroism; their disulfide stabilities in redox buffer are significantly decreased; their in vitro refolding efficiencies are decreased approximately two folds; the structural stabilities of the mutants with Set or Thr substitution are decreased significantly, while Leu substitution has little effect as measured by equilibrium guanidine denaturation. As far as biological activity is concerned, Ser replacement of B8Gly has only a moderate effect： its insulin receptor-binding activity is 23% of native insulin. But Ttir or Leu replacement produces significant detriment： the receptorbinding potencies of the two mutants are less than 0.2% of native insulin. The present results suggest that Gly is likely the only applicable natural amino acid for the B8 position of insulin where both foldability and activity are concerned.     

The amino acid sequence of human insulin-like growth factor I and its structural homology with proinsulin

The complete amino acid sequence of human insulin-like growth factor I (IGF-I), a polypeptide isolated from serum, has been determined. IGF-I is a single chain polypeptide of 70 amino acid residues cross-linked by three disulfide bridges. The calculated molecular weight is 7649. IGF-I displays obvious homology to proinsulin: positions 1 to 29 are homologous to insulin B chain and positions 42 to 62 to insulin A chain. A shortened "connecting" peptide with 12 residues (positions 30 to 41) compared to 30 to 35 in proinsulins shows no homology to proinsulin C peptide. An octapeptide sequence at the COOH-terminal end is also a feature not found in proinsulins. The number of differences in amino acid positions between IGF-I and insulins suggests that duplication of the gene of the common ancestor of proinsulin and IGF occurred before the time of appearance of the vertebrates. Of the 19 residues known to be invariant in all insulins so far sequenced, only glutamine A5 and asparagine A21 are replaced in IGF-I by glutamic acid and alanine, respectively. The fact that all half-cystine and glycine residues and most nonpolar core residues of the insulin monomer are conserved is compatible with a three-dimensional structure of IGF-I similar to that of insulin.     

When a unit of insulin is not a unit: Detemir dosing and insulin cost in type 2 diabetes mellitus

Background: Increasing acceptance of basal-bolus insulin therapy for the control of diabetes mellitus (DM) has led to newer formulations of basal insulin analogues. The newest one is detemir.Objectives: Clinical evidence suggests that patients with type 2 DM require higher doses of detemir than other basal insulins to achieve equivalent glycemic control. This study examines evidence for greater dosing requirements and the implications of higher doses on the cost of insulin treatment.Methods: We performed a MEDLINE search for randomized, prospective studies comparing detemir with other basal insulins in patients with type 2 DM that were published in English between January 2000 and November 2008. The mean daily doses of basal and bolus insulin and the mean total daily insulin doses were determined. Overall weighted mean doses of the insulins were used to estimate the mean total daily insulin doses required for a 100-kg patient, and published 2008 US retail prices were used to estimate the retail costs of basal-bolus and basal-only insulin regimens.Results: Seven trials involving 3311 patients were identified in the literature search. The mean total daily insulin dose was 0.80 unit/kg for detemir-based regimens and 0.58 unit/kg for comparison regimens. For basal-bolus regimens, the estimated retail cost of the mean total daily insulin dose was $11.24 for detemir-based regimens compared with $8.99 for glargine-based regimens and $6.41 for neutral protamine Hagedorn (NPH)-based insulins. For basal-only regimens, the estimated retail cost of the mean total daily insulin dose was $8.23 for detemir compared with $5.19 for glargine and $2.35 for NPH.Conclusions: It is important for health care providers and patients to know that patients with type 2 DM may require substantially higher doses of detemir than other basal insulins. This should be considered when titrating the dose as well as in cost-benefit analyses of detemir versus other insulins.     

Intramolecular cross-linking of insulin. Preparation and properties of oxalyl- and malonyl-bis(methionyl) insulin

The bifunctional reagents, oxalyl-(Met-ONp)2 and malonyl-(Met-ONp)2 have been prepared and investigated as reversible cross-linking reagents for insulin and model compounds. The removal of the cross-linking residues was demonstrated by the cyanogen bromide cleavage of oxalyl-(Met-Phe-OMe)2 and malonyl-(Met-Phe-OMe)2. Zinc-insulin reacted with a molar equivalent of oxalyl-(Met-ONp)2 or malonyl-(Met-ONp)2 in presence of excess triethylamine to yield oxalyl-(Met)2-insulin and malonyl-(Met)2-insulin, respectively. In these derivatives the N-terminal phenylalanine (B1 residue) was free. Thus the cross-link was between A1 and B29 residues in insulin. All three disulfide bonds of these insulin derivatives undergo reduction with tributylphosphine to give six sulfhydryls. Air-oxidation of reduced oxalyl-(Met)2-insulin and malonyl-(Met)2-insulin in 0.05 M disodium phosphate, pH 9.5, yielded products which were indistinguishable from oxalyl-(Met)2-insulin and malonyl-(Met)2-insulin respectively, as measured by physicochemical and biological methods. Cyanogen bromide cleavage of reduced and reoxidized malonyl-(Met)2-insulin in 70% formic acid regenerated insulin quantitatively, but only 40% of insulin was determined from similar treatment of oxalyl-(Met)2-insulin. The regenerated insulins exhibited the biological activity of native insulin. These studies strongly suggest that disulfide bonds formed during oxidation of reduced oxalyl-(Met)2-insulin and malonyl-(Met)2-insulin are identical to those found in insulin.     

Correlation between HbA1c, purified insulins, diabetic control, and insulin antibodies in diabetic children

Insulin antibodies were determined in sera from 38 children diagnosed as having juvenile diabetes for a duration of 0.7-15.2 years (median = 4.9 years). 8 children were treated with purified porcine insulins from the beginning of their disease, 16 children with bovine insulin NPH alone, and 14 children with non-purified, of whom 9 were later transferred to purified insulins. Serum insulin antibodies were measured by non-specific and specific methods using beef (B) and pork (P) antigens as described by Welborne and Sebriakova, respectively. 12/38 children had insulin binding levels similar to those of normal children, irrespective of the type of insulin used. The concentration of antibodies using radiolabelled B or P insulins as antigens were strongly correlated, by both the non-specific (p less than 0.01) and the specific (p less than 0.01) methods. Children with better score for diabetic control had significantly lower levels of insulin antibodies against B (p less than 0.05) and P (p less than 0.05) than those with poor diabetic control. There was also a significant positive correlation between mean HbA1c concentration and both B and P mean insulin antibody concentration (p less than 0.01). Finally, patients treated with purified porcine insulin had significantly lower levels of antibodies than patients with non-purified bovine insulin (p less than 0.05).