The classification of diabetes mellitus and the tests used for its diagnosis were brought into order by the National Diabetes Data Group of the USA and the second World Health Organization Expert Committee on Diabetes Mellitus in 1979 and 1980. Apart from minor modifications by WHO in 1985, little has been changed since that time. There is however considerable new knowledge regarding the aetiology of different forms of diabetes as well as more information on the predictive value of different blood glucose values for the complications of diabetes. A WHO Consultation has therefore taken place in parallel with a report by an American Diabetes Association Expert Committee to re-examine diagnostic criteria and classification. The present document includes the conclusions of the former and is intended for wide distribution and discussion before final proposals are submitted to WHO for approval. The main changes proposed are as follows. The diagnostic fasting plasma (blood) glucose value has been lowered to > or =7.0 mmol l(-1) (6.1 mmol l(-1)). Impaired Glucose Tolerance (IGT) is changed to allow for the new fasting level. A new category of Impaired Fasting Glycaemia (IFG) is proposed to encompass values which are above normal but below the diagnostic cut-off for diabetes (plasma > or =6.1 to or =5.6 to <6.1 mmol l(-1)). Gestational Diabetes Mellitus (GDM) now includes gestational impaired glucose tolerance as well as the previous GDM. The classification defines both process and stage of the disease. The processes include Type 1, autoimmune and non-autoimmune, with beta-cell destruction; Type 2 with varying degrees of insulin resistance and insulin hyposecretion; Gestational Diabetes Mellitus; and Other Types where the cause is known (e.g. MODY, endocrinopathies). It is anticipated that this group will expand as causes of Type 2 become known. Stages range from normoglycaemia to insulin required for survival. It is hoped that the new classification will allow better classification of individuals and lead to fewer therapeutic misjudgements.

Definition, diagnosis and classification of diabetes mellitus and its complications. Part 1: diagnosis and classification of diabetes mellitus provisional report of a WHO consultation.

The human insulin receptor cDNA: The structural basis for hormone-activated transmembrane signalling

We have investigated the effects of ligation of the fibronectin receptor (FnR) on gene expression in rabbit synovial fibroblasts. Monoclonal antibodies to the FnR that block initial adhesion of fibroblasts to fibronectin induced the expression of genes encoding the secreted extracellular matrix-degrading metalloproteinases collagenase and stromelysin. That induction was a direct consequence of interaction with the FnR was shown by the accumulation of mRNA for stromelysin and collagenase. Monoclonal antibodies to several other membrane glycoprotein receptors had no effect on metalloproteinase gene expression. Less than 2 h of treatment of the fibroblasts with anti-FnR in solution was sufficient to trigger the change in gene expression, and induction was blocked by dexamethasone. Unlike other inducers of metalloproteinase expression, including phorbol diesters and growth factors, addition of the anti-FnR in solution to cells adherent to serum-derived adhesion proteins or collagen produced no detectable change in cell shape or actin microfilament organization. Inductive effects were potentiated by cross-linking of the ligand. Fab fragments of anti-FnR were ineffective unless cross-linked or immobilized on the substrate. Adhesion of fibroblasts to native fibronectin did not induce metallo-proteinases. However, adhesion to covalently immobilized peptides containing the arg-gly-asp sequence that were derived from fibronectin, varying in size from hexapeptides up to 120 kD, induced collagenase and stromelysin gene expression. This suggests that degradation products of fibronectin are the natural inductive ligands for the FnR. These data demonstrate that signals leading to changes in gene expression are transduced by the FnR, a member of the integrin family of extracellular matrix receptors. The signaling of changes in gene expression by the FnR is distinct from signaling involving cell shape and actin cytoarchitecture. At least two distinct signals are generated: the binding of fibronectin-derived fragments and adhesion-blocking antibodies to the FnR triggers events different from those triggered by binding of the native fibronectin ligand. Because the genes regulated by this integrin are for enzymes that degrade the extracellular matrix, these results suggest that information transduced by the binding of various ligands to integrins may orchestrate the expression of genes regulating cell behavior in the extracellular environment.

https://rupress.org/jcb/article-pdf/109/2/877/1058190/877.pdf

Signal transduction through the fibronectin receptor induces collagenase and stromelysin gene expression.

I. Introduction IN THE fasted state, glucose homeostasis depends upon the balance between hepatic glucose production and glucose utilization by the major insulin-dependent tissues, such as liver, adipose, and muscle, and by insulin-independent tissues, such as brain and kidney. This balance is tightly regulated by pancreatic hormones. Thus, in normal individuals, the response to increased plasma glucose levels is an increase in secretion of insulin from β-cells of the pancreatic islets. This increase in circulating insulin levels stimulates glucose transport into peripheral tissues and inhibits hepatic gluconeogenesis. In type II diabetes there are at least two fundamental defects: one is a decrease in the ability of peripheral tissues to respond to insulin (insulin resistance), and the second is impaired β-cell function, which results from long-term hyperglycemia. It appears that both genetic and environmental factors are responsible for the progression from normal glucose tolerance to type II diabetes (...

Insulin Action and the Insulin Signaling Network

Three recent advances pertinent to the mechanism of insulin action include (i) the discovery that the insulin receptor is an insulin-dependent protein tyrosine kinase, functionally related to certain growth factor receptors and oncogene-encoded proteins, (ii) the molecular cloning of the insulin proreceptor complementary DNA, and (iii) evidence that the protein tyrosine kinase activity of the receptor is essential for insulin action. Efforts are now focusing on the physiological substrates for the receptor kinase. Experience to date suggests that they will be rare proteins whose phosphorylation in intact cells may be transient. The advantages of attempting to dissect the initial biochemical pathway of insulin action include the wealth of information about the metabolic consequences of insulin action and the potential for genetic analysis in Drosophila and in man.

https://science.sciencemag.org/content/sci/237/4821/1452.full.pdf

After insulin binds.

Exposure of adipocytes to antibodies to the insulin receptor results in a blockade of 125I-labeled insulin binding, stimulation of glucose oxidation, and many more insulin-like effects. Allowing for differences in purity, antireceptor antibody is equipotent with insulin on a molar basis. Both the bivalent F(ab′)2 and monovalent Fab′ fragments of the antireceptor antibody are fully active in inhibiting 125I-labeled insulin binding. Bivalent F(ab′)2 also retains its insulin-like effects. In contrast, the monovalent Fab′ loses almost all ability to stimulate glucose oxidation and acts as a competitive antagonist of insulin-stimulated glucose oxidation. Addition of anti-F(ab′)2 antisera, which crosslink the Fab′-receptor complexes, results in a restoration of the insulin-like activity of the antibody. Similarly, when cells are exposed to submaximal doses of insulin, addition of anti-insulin antibodies at low concentration enhances the biological activity of insulin. These data suggest that receptor occupancy by ligand is not sufficient for signal generation and that the insulin-like effects of antireceptor antibody (and perhaps insulin itself) require receptor aggregation or clustering. This aggregation, however, appears to be independent of microfilaments or microtubules because the insulin-like effects of antireceptor antibody, and in fact, of insulin itself, are unaffected by agents that are known to disrupt these structures.

https://www.pnas.org/content/pnas/75/9/4209.full.pdf

Direct demonstration that receptor crosslinking or aggregation is important in insulin action.

Autoantibodies to the insulin receptor have been detected in the sera of several patients with the Type B syndrome of insulin resistance and acanthosis nigricans. In this study we have used three of these sera (B-1, B-2, and B-3) as probes of the insulin receptor in isolated rat adipocytes. Preincubation of adipocytes with each of the three sera resulted in an inhibition of subsequent [125I]insulin binding. 50% inhibition of binding occurred with serum dilutions of 1:5 to 1:7,500. As in our previous studies with other tissues, Scatchard analysis of the insulin-binding data was curvilinear consistent with negative cooperativity. Computer analysis suggested that in each case the inhibition of binding was due to a decrease in receptor affinity rather than a change in available receptor number.

In addition to the effects on insulin binding, adipocytes pretreated with antireceptor sera also showed alterations in biological responses. All three sera produced some stimulation of basal glucose oxidation. With serum B-3, maximal stimulation of glucose oxidation occurred at a serum concentration that inhibited binding by only 10-15%, whereas with serum B-2 the dilution curves for inhibition of binding and stimulation of glucose oxidation were superimposable. Serum B-1 behaved as a partial agonist; that is, it inhibited binding more effectively than it stimulated glucose oxidation. Cells pretreated with this serum in a concentration which inhibited binding by 80% also showed a five-fold shift to the right in the dose response of insulin-stimulated glucose oxidation, whereas spermine-stimulated glucose oxidation was unaffected. Serum B-2, which contained the highest titer of antireceptor antibodies, also stimulated 2-deoxy-glucose transport, as well as glucose incorporation into lipid and glycogen.

Both the ability of the serum to inhibit binding and stimulate glucose utilization were enriched in purified immunoglobulin fractions and retained in the F(ab′)2 fragment of the IgG. In addition, the bioactivity was blocked by antihuman IgG but not by anti-insulin antibodies. Enzymatic digestion of adipocytes with trypsin resulted in a complete loss of insulin-stimulated bioactivity of serum B-3, but had only minor effects on the glucose oxidation produced by serum B-1 or B-2.

These data suggest that the antibodies present in these three sera bind to different determinants on the insulin receptor. Thus, these antibodies may be useful probes of receptor structure and function.

/pdf/effects-of-autoantibodies-to-the-insulin-receptor-on-elwumsb8ja.pdf

Effects of Autoantibodies to the Insulin Receptor on Isolated Adipocytes: STUDIES OF INSULIN BINDING AND INSULIN ACTION

Publisher Summary Insulin exerts a wide spectrum of effects at the cellular level. These include effects at the membrane level, for example, the stimulation of glucose and amino acid uptake; effects on both membrane and cytoplasmic enzymes; and effects on protein synthesis, DNA synthesis, cell growth, and differentiation. This is the reason why unraveling the mechanism of insulin action has been difficult. This chapter describes insulin receptors, receptor antibodies, and the mechanism of insulin action. In addition, the effects of insulin vary both in time course and dose–response. Some effects of insulin, such as the stimulation of glucose transport, occur within seconds after hormone exposure, whereas others, such as the stimulation of DNA synthesis, require hours; effects on most cytoplasmic enzymes lie somewhere between these two extremes. It is well known that insulin stimulates glucose transport, and this effect persists in membrane vesicles even after the cell is broken. Several new probes have become available that have shed some light on the problem of insulin action. These include cultured cell systems, which are highly responsive to insulin; new methods for studying receptor structure; mutant cell lines that possess defects in either the insulin receptor or pathways of insulin action; and antibodies to the insulin receptor that block insulin binding and mimic insulin action.

Insulin receptors, receptor antibodies, and the mechanism of insulin action.

Glucocorticoid excess in vivo has been shown to cause decreases in insulin sensitivity and insulin receptor binding in target tissues. It has not been previously possible to produce all of these changes in vitro because of limitations of the isolated rat adipocyte as an experimental model. We have studied the effects of glucocorticoid hormones on insulin binding and insulin action in differentiated mouse 3T3-L1 fatty fibroblasts, in an attempt to develop a complete in vitro model of the insulin resistance associated with glucocorticoid excess. Exposure of 3T3-L1 cells to dexamethasone, a synthetic glucocorticoid, resulted in decreased binding of insulin to its receptor and decreased insulin stimulation of 2-deoxyglucose uptake. Although some effect of dexamethasone on these parameters was observed after 24 h, more than 3 days were required for maximal inhibition of both binding and biological response. The magnitude of these changes was concentration dependent over a range of 0.1 –100 nM dexamethasone. Ex...

Glucocorticoid-induced insulin resistance in vitro: evidence for both receptor and postreceptor defects.

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2881%2980773-9

Kathleen L. Baird

Papers

Direct demonstration that receptor crosslinking or aggregation is important in insulin action.

Effects of Autoantibodies to the Insulin Receptor on Isolated Adipocytes: STUDIES OF INSULIN BINDING AND INSULIN ACTION

Insulin receptors, receptor antibodies, and the mechanism of insulin action.

Glucocorticoid-induced insulin resistance in vitro: evidence for both receptor and postreceptor defects.

Role of valence and the cytoskeleton in the insulin-like activity of concanavalin A