Insulin resistance induced by hyperinsulinemia coincides with a persistent alteration at the insulin receptor tyrosine kinase domain.

Insulin resistance, the diminished response of target tissues to insulin, is associated with the metabolic syndrome and a predisposition towards diabetes in a growing proportion of the worldwide population. Under insulin resistant states, the cellular response of the insulin signaling pathway is diminished and the body typically responds by increasing serum insulin concentrations to maintain insulin signaling. Some evidence indicates that the increased insulin concentration may itself further dampen insulin response.

Improved glucose metabolism in vitro and in vivo by an allosteric monoclonal antibody that increases insulin receptor binding affinity.

Previously we reported studies of XMetA, an agonist antibody to the insulin receptor (INSR). We have now utilized phage display to identify XMetS, a novel monoclonal antibody to the INSR. Biophysical studies demonstrated that XMetS bound to the human and mouse INSR with picomolar affinity.

Inhibition of insulin receptor function by a human, allosteric monoclonal antibody: a potential new approach for the treatment of hyperinsulinemic hypoglycemia.

Novel therapies are needed for the treatment of hypoglycemia resulting from both endogenous and exogenous hyperinsulinema. To provide a potential new treatment option, we identified XMetD, an allosteric monoclonal antibody to the insulin receptor (INSR) that was isolated from a human antibody phage display library. To selectively obtain antibodies directed at allosteric sites, panning of the phage display library was conducted using the insulin-INSR complex.

XOMA 052, an anti-IL-1β monoclonal antibody, prevents IL-1β-mediated insulin resistance in 3T3-L1 adipocytes.

Objective: Interleukin-1β (IL-1β) has recently been implicated as a major cytokine that is involved in the pancreatic islet inflammation of type 2 diabetes mellitus. This inflammation impairs insulin secretion by inducing beta-cell apoptosis. Recent evidence has suggested that in obesity-induced inflammation, IL-1β plays a key role in causing insulin resistance in peripheral tissues.

Chromium supplementation in non-obese non-diabetic subjects is associated with a decline in insulin sensitivity.

Background: The use of chromium supplements is widespread for the prevention and treatment of diabetes mellitus but there are conflicting reports on efficacy, possibly reflecting discrepant effects across different populations. In the present studies, we test the hypothesis that chromium supplementation raises serum chromium levels and correspondingly improves insulin sensitivity.

Methods: A double blind placebo-controlled randomized trial was conducted on 31 non-obese, normoglycemic subjects.

A fully human, allosteric monoclonal antibody that activates the insulin receptor and improves glycemic control.

Many patients with diabetes mellitus (both type 1 and type 2) require therapy to maintain normal fasting glucose levels. To develop a novel treatment for these individuals, we used phage display technology to target the insulin receptor (INSR) complexed with insulin and identified a high affinity, allosteric, human monoclonal antibody, XMetA, which mimicked the glucoregulatory, but not the mitogenic, actions of insulin. Biophysical studies with cultured cells expressing human INSR demonstrated that XMetA acted allosterically and did not compete with insulin for binding to its receptor.

Insulin resistance in non-obese subjects is associated with activation of the JNK pathway and impaired insulin signaling in skeletal muscle.

Background: The pathogenesis of insulin resistance in the absence of obesity is unknown. In obesity, multiple stress kinases have been identified that impair the insulin signaling pathway via serine phosphorylation of key second messenger proteins. These stress kinases are activated through various mechanisms related to lipid oversupply locally in insulin target tissues and in various adipose depots.

Inhibitory effects of nordihydroguaiaretic acid (NDGA) on the IGF-1 receptor and androgen dependent growth of LAPC-4 prostate cancer cells.

Background: Nordihydroguaiaretic acid (NDGA) is an inhibitor of the IGF-1 receptor (IGF-1R) in breast and other cancers, and concomitantly inhibits tumor growth both in cultured cells and animals. The current study evaluates the effect of NDGA on the androgen-stimulated growth of human prostate cancer cells.

Methods: LAPC-4 prostate cancer cells in tissue culture were androgen starved for 3 days, 1 nM dihydrotestosterone (DHT) and other androgens were then added for up to 7 days, and cell proliferation measured.

The role of membrane glycoprotein plasma cell antigen 1/ectonucleotide pyrophosphatase phosphodiesterase 1 in the pathogenesis of insulin resistance and related abnormalities.

Insulin resistance is a major feature of most patients with type 2 diabetes mellitus (T2D). A number of laboratories have observed that PC-1 (membrane [corrected] glycoprotein plasma cell antigen 1; also termed [corrected] ectonucleotide pyrophosphatase phosphodiesterase 1 or ENPP1) [corrected] is either overexpressed or overactive in muscle, adipose tissue, fibroblasts, and other tissues of insulin-resistant individuals, both nondiabetic and diabetic. Moreover, PC-1 (ENPP1) overexpression [corrected] in cultured cells in vitro and in transgenic mice in vivo, [corrected] impairs insulin stimulation of insulin receptor (IR) activation and downstream signaling.

Nordihydroguaiaretic acid (NDGA), an inhibitor of the HER2 and IGF-1 receptor tyrosine kinases, blocks the growth of HER2-overexpressing human breast cancer cells.

We have reported that nordihydroguaiaretic acid (NDGA) inhibits the tyrosine kinase activities of the IGF-1 receptor (IGF-1R) and the HER2 receptor in breast cancer cells. Herein, we studied the effects of NDGA on the growth of estrogen receptor (ER) positive MCF-7 cells engineered to overexpress HER2 (MCF-7/HER2-18). These cells are an in vitro model of HER2-driven, ER positive, tamoxifen resistant breast cancer.

Nordihydroguaiaretic acid inhibits insulin-like growth factor signaling, growth, and survival in human neuroblastoma cells.

Neuroblastoma is a common pediatric malignancy that metastasizes to the liver, bone, and other organs. Children with metastatic disease have a less than 50% chance of survival with current treatments. Insulin-like growth factors (IGFs) stimulate neuroblastoma growth, survival, and motility, and are expressed by neuroblastoma cells and the tissues they invade.

Parallel synthesis of diarylureas and their evaluation as inhibitors of insulin-like growth factor receptor.

Diarylurea (DAU) compounds, particularly species composed of a heteroaryl ring system conjugated through a urea linkage to a substituted arene, were previously identified by the screening of a diverse chemical library to be active against the insulin growth factor receptor (IGF-1R). DAU compounds 4{a,b} were synthesized in parallel by the coupling of aryl amines 2{a} with aryl isocyanates 3{b}. Preparative RP-HPLC purification was found necessary to remove an impurity 5{b}, the symmetric urea resulting from the hydrolytic degradation of aryl isocyanates.

IGF-binding protein-1 levels are related to insulin-mediated glucose disposal and are a potential serum marker of insulin resistance.

Objective: IGF-binding protein (IGFBP)-1 is negatively regulated by insulin. We determined whether the measurement of IGFBP-1 in serum is a useful marker of insulin resistance.

Research Design And Methods: Twenty-three subjects underwent a euglycemic insulin clamp.

Diarylureas are small-molecule inhibitors of insulin-like growth factor I receptor signaling and breast cancer cell growth.

In breast and certain other cancers, receptor tyrosine kinases, including the insulin-like growth factor I receptor (IGF-IR), play an important role in promoting the oncogenic process. The IGF-IR is therefore an important target for developing new anti-breast cancer therapies. An initial screening of a chemical library against the IGF-IR in breast cancer cells identified a diaryl urea compound as a potent inhibitor of IGF-IR signaling.

Overexpression of the insulin receptor inhibitor PC-1/ENPP1 induces insulin resistance and hyperglycemia.

The ectoenzyme PC-1 is an insulin receptor inhibitor that is elevated in cells and tissues of humans with type 2 diabetes (T2D). We have recently shown that acute PC-1 overexpression in liver causes insulin resistance and glucose intolerance in mice (3), but the chronic effects of PC-1 overexpression on these functions are unknown. Herein we produced transgenic mice overexpressing the potent q allele of human PC-1 in muscle and liver.

Nordihydroguaiaretic acid (NDGA) inhibits the IGF-1 and c-erbB2/HER2/neu receptors and suppresses growth in breast cancer cells.

Nordihydroguaiaretic acid (NDGA) is a phenolic compound isolated from the creosote bush Larrea divaricatta that has anti-cancer activities both in vitro and in vivo. We can now attribute certain of these anti-cancer properties in breast cancer cells to the ability of NDGA to directly inhibit the function of two receptor tyrosine kinases (RTKs), the insulin-like growth factor receptor (IGF-1R) and the c-erbB2/HER2/neu (HER2/neu) receptor. In MCF-7 human breast cancer cells, low micromolar concentrations of NDGA inhibited activation of the IGF-1R, and downstream phosphorylation of both the Akt/PKB serine kinase and the pro-apoptotic protein BAD.

Variants of ENPP1 are associated with childhood and adult obesity and increase the risk of glucose intolerance and type 2 diabetes.

We identified a locus on chromosome 6q16.3-q24.2 (ref.

The molecular basis for oxidative stress-induced insulin resistance.

Reactive oxygen and nitrogen molecules have been typically viewed as the toxic by-products of metabolism. However, accumulating evidence has revealed that reactive species, including hydrogen peroxide, serve as signaling molecules that are involved in the regulation of cellular function. The chronic and/or increased production of these reactive molecules or a reduced capacity for their elimination, termed oxidative stress, can lead to abnormal changes in intracellular signaling and result in chronic inflammation and insulin resistance.

Analysis of insulin-stimulated insulin receptor activation and glucose transport in cultured skeletal muscle cells from obese subjects.

Obesity is associated with impaired insulin-stimulated glucose disposal in the skeletal muscle, but whether this is an intrinsic or acquired factor is unknown. In many patients with type 2 diabetes mellitus (T2D) and their nondiabetic relatives, who have a genetic predisposition for diabetes, insulin resistance is maintained in cultured muscle cells. To study the association of obesity with defects in insulin action, we investigated insulin stimulation of both insulin receptor (IR) autophosphorylation and subsequent glucose transport in primary skeletal muscle cell cultures obtained from both nonobese and obese nondiabetic subjects.

Increased hepatic levels of the insulin receptor inhibitor, PC-1/NPP1, induce insulin resistance and glucose intolerance.

The ectoenzyme, plasma cell membrane glycoprotein-1 (PC-1), is an insulin receptor (IR) inhibitor that is elevated in cells and tissues of insulin-resistant humans. However, the effects of PC-1 overexpression on insulin action have not been studied in animal models. To produce mice with overexpression of PC-1 in liver, a key glucose regulatory organ in this species, we injected them with a PC-1 adenovirus vector that expresses human PC-1.

Structure-based de novo design of ligands using a three-dimensional model of the insulin receptor.

For the first time, a three-dimensional model of the insulin receptor is used in the de novo design of novel ligands that potentially mimic interactions of insulin at its receptor. Compound 4 competed with insulin as seen in autophosphorylation assays and inhibited up to 68% of IR autophosphorylation at 300 microM of 4 in 3T3IR cells induced by 1 nM insulin. This model provides a basis for the design of potent insulin receptor ligands.

Are oxidative stress-activated signaling pathways mediators of insulin resistance and beta-cell dysfunction?

In both type 1 and type 2 diabetes, diabetic complications in target organs arise from chronic elevations of glucose. The pathogenic effect of high glucose, possibly in concert with fatty acids, is mediated to a significant extent via increased production of reactive oxygen species (ROS) and reactive nitrogen species (RNS) and subsequent oxidative stress. ROS and RNS directly oxidize and damage DNA, proteins, and lipids.

Oxidative stress and stress-activated signaling pathways: a unifying hypothesis of type 2 diabetes.

In both type 1 and type 2 diabetes, the late diabetic complications in nerve, vascular endothelium, and kidney arise from chronic elevations of glucose and possibly other metabolites including free fatty acids (FFA). Recent evidence suggests that common stress-activated signaling pathways such as nuclear factor-kappaB, p38 MAPK, and NH2-terminal Jun kinases/stress-activated protein kinases underlie the development of these late diabetic complications. In addition, in type 2 diabetes, there is evidence that the activation of these same stress pathways by glucose and possibly FFA leads to both insulin resistance and impaired insulin secretion.

Decreased insulin receptor (IR) autophosphorylation in fibroblasts from patients with PCOS: effects of serine kinase inhibitors and IR activators.

Insulin resistance is characteristic of many patients with polycystic ovary syndrome (PCOS). Several studies have suggested that a decrease in insulin receptor (IR) autophosphorylation is a significant component of this resistance. In this study, we have used a highly sensitive ELISA to measure IR tyrosine phosphorylation in fibroblasts from patients with PCOS and healthy control women.

Regulation of insulin receptor function by a small molecule insulin receptor activator.

In type 2 diabetes mellitus, impaired insulin signaling leads to hyperglycemia and other metabolic abnormalities. TLK19780, a non-peptide small molecule, is a new member of a novel class of anti-diabetic agents that function as activators of the insulin receptor (IR) beta-subunit tyrosine kinase. In HTC-IR cells, 20 microm TLK19780 enhanced maximal insulin-stimulated IR autophosphorylation 2-fold and increased insulin sensitivity 2-3-fold.