Effects of nateglinide on the secretion of glycated insulin and glucose tolerance in type 2 diabetes

Aims: Glycation of insulin has been demonstrated within pancreatic beta-cells and the resulting impaired bioactivity may contribute to insulin resistance in diabetes. We used a novel radioimmunoassay to evaluate the effect of nateglinide on plasma concentrations of glycated insulin and glucose tolerance in type 2 diabetes. Methods. Ten patients (5 M/5 F, age 57.8 +/- 1.9 years, HbA(1c), 7.6 +/- 0.5%,, fasting plasma glucose 9.4 +/- 1.2 mmol/l, creatinine 81.6 +/- 4.5 mumol/l) received oral nateglinide 120 mg or placebo, 10 min prior to 75 g oral glucose in a random, single blind, crossover design, 1 week apart. Blood samples were taken for glycated insulin, glucose, insulin and C-peptide over 225 min. Results: Plasma glucose and glycated insulin responses were reduced by 9% (P = 0.005) and 38% (P = 0.047), respectively, following nateglinide compared with placebo. Corresponding AUC measures for insulin and C-peptide were enhanced by 36% (P = 0.005) and 25% (P = 0.007) by nateglinide. Conclusions: Glycated insulin in type 2 diabetes is reduced in response to the insulin secretagogue nateglinide, resulting in preferential release of native insulin. Since glycated insulin exhibits impaired biological activity, reduced glycated insulin release may contribute to the anti hyperglycaemic action of nateglinide. (C) 2003 Elsevier Ireland Ltd. All rights reserved.

Structure-Based Mutational Analysis of eIF4E in Relation to sbm1 Resistance to Pea Seed-Borne Mosaic Virus in Pea

Background: Pea encodes eukaryotic translation initiation factor eIF4E (eIF4E(S)), which supports the multiplication of Pea seed-borne mosaic virus (PSbMV). In common with hosts for other potyviruses, some pea lines contain a recessive allele (sbm1) encoding a mutant eIF4E (eIF4E(R)) that fails to interact functionally with the PSbMV avirulence protein, VPg, giving genetic resistance to infection.

Ocular blood flow analysis detects microvascular abnormalities in impaired glucose tolerance.

Objective: Waveform analysis has been used to assess vascular resistance and predict cardiovascular events. We aimed to identify microvascular abnormalities in patients with impaired glucose tolerance (IGT) using ocular waveform analysis. The effects of pioglitazone were also assessed. Methods: Forty patients with IGT and twenty-four controls were studied. Doppler velocity recordings were obtained from the central retinal, ophthalmic and common carotid arteries, and sampled at 200 Hz. A discrete wavelet-based analysis method was employed to quantify waveforms. The resistive index (RI),was also determined. Patients with IGT were randomised to pioglitazone or placebo and measurements repeated after 12 weeks treatment. Results: In the ocular waveforms, significant differences in power spectra were observed in frequency band four (corresponding to frequencies between 6.25 and 12.50 Hz) between groups (p

Altered Toll-like Receptor 2-mediated Endotoxin Tolerance Is Related to Diminished Interferon β Production

Induction of endotoxin tolerance leads to a reduced inflammatory response after repeated challenge by LPS and is important for resolution of inflammation and prevention of tissue damage. Enterobacterial LPS is recognized by the TLR4 signaling complex, whereas LPS of some non-enterobacterial organisms is capable of signaling independently of TLR4 utilizing TLR2-mediated signal transduction instead. In this study we report that Porphyromonas gingivalis LPS, a TLR2 agonist, fails to induce a fully endotoxin tolerant state in a human monocytic cell line (THP-1) and mouse bone marrow-derived macrophages. In contrast to significantly decreased production of human IL-8 and TNF-alpha and, in mice, keratinocyte-derived cytokine (KC), macrophage inflammatory protein-2 (MIP-2), and TNF-alpha after repeated challenge with Escherichia coli LPS, cells repeatedly exposed to P. gingivalis LPS responded by producing less TNF-alpha but sustained elevated secretion of IL-8, KC, and MIP-2. Furthermore, in endotoxin-tolerant cells, production of IL-8 is controlled at the signaling level and correlates well with NF-kappa B activation, whereas TNF-alpha expression is blocked at the gene transcription level. Interferon beta plays an important role in attenuation of chemokine expression in endotoxin-tolerized cells as shown in interferon regulatory factor-3 knock-out mice. In addition, human gingival fibroblasts, commonly known not to display LPS tolerance, were found to be tolerant to repeated challenge by LPS if pretreated with interferon beta. The data suggest that the inability of the LPS-TLR2 complex to induce full endotoxin tolerance in monocytes/macrophages is related to diminished production of interferon beta and may partly explain the involvement of these LPS isoforms in the pathogenesis of chronic inflammatory diseases.

Mutation altering the miR-184 seed region causes keratoconus with cataract

MicroRNAs (miRNAs) bind to complementary sequences within the 3? untranslated region (UTR) of mRNAs from hundreds of target genes, leading either to mRNA degradation or suppression of translation. We found that a mutation in the seed region of miR-184 (MIR184) is responsible for familial severe keratoconus combined with early-onset anterior polar cataract, by deep sequencing of a linkage region known to contain the mutation. The mutant form fails to compete with miR-205 (MIR205) for overlapping target sites on the 3? UTRs of INPPL1 and ITGB4. Although these target genes and miR-205 are expressed widely, the phenotype is restricted to the cornea and lens because of the very high expression of miR-184 in these tissues. Our finding highlights the tissue-specificity of a gene network regulated by a miRNA. Awareness of the important function of miRNAs may aid identification of susceptibility genes and new therapeutic targets for treatment of both rare and common diseases.

Investigating the effects of physiological bile acids on GLP-1 secretion and glucose tolerance in normal and GLP-1R(-/-) mice

Physiological secretion of bile acids has previously been linked to the regulation of blood glucose. GLP-1 is an intestinal peptide hormone with important glucose-lowering actions, such as stimulation of insulin secretion and inhibition of glucagon secretion. In this investigation, we assessed the ability of several bile acid compounds to secrete GLP-1 in vitro in STC-1 cells. Bile acids stimulated GLP-1 secretion from 3.3- to 6.2-fold but some were associated with cytolytic effects. Glycocholic and taurocholic acids were selected for in vivo studies in normal and GLP-1R(-/-) mice. Oral glucose tolerance tests revealed that glycocholic acid did not affect glucose excursions. However, taurocholic acid reduced glucose excursions by 40% in normal mice and by 27% in GLP-1R(-/-) mice, and plasma GLP-1 concentrations were significantly elevated 30 min post-gavage. Additional studies used incretin receptor antagonists to probe involvement of GLP-1 and GIP in taurocholic acid-induced glucose lowering. The findings suggest that bile acids partially aid glucose regulation by physiologically enhancing nutrient-induced GLP-1 secretion. However, GLP-1 secretion appears to be only part of the glucose-lowering mechanism and our studies indicate that the other major incretin GIP is not involved.

Specificity enhancement of polyclonal antisera by the induction of tolerance to unwanted cross-reacting determinants

Steroids form a structurally closely related group. As a result, antibodies produced for use in immunoassays regularly show unwanted cross-reactivities, These may be reduced by altering hapten-protein coupling procedures, thereby reducing the exposure of the determinants giving rise to the undesirable cross-reaction. However, these procedures carl prove to be complex, expensive and nor totally predictable in outcome. Exploitation of the clonal selection theory is an attractive alternative approach. The host is primed with the interfering cross-reactant coupled to a non-immunogenic amino acid copolymer to inactivate the B-lymphocyte clones specific for this steroid, producing a specific immunotolerance. Then, 3 days Inter, the host is immunized with the steroid against which nn antibody is required. The clones producing antibody to this immunogen are unaffected and the cross-reactivity is significantly reduced or deleted The technique has been applied to the reduction of endogenous sex steroid cross-reactivity from antibodies prepared against synthetic and semi-synthetic androgens (17 alpha-methyltestosterone, 19-nor-beta-testosterone) and the progestogen medroxyprogesterone. Antibodies prepared against the synthetic oestrogen zeranol using this technique have significantly reduced its undesirable cross-reactivity with the fungal metabolite 7 alpha-zearalenol. Highly specific antisera have been generated in all cases, the only adverse effect being a reduction in the titres achieved in comparison with rabbits receiving the conventional immunizing regime.