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PubMed1982

Demonstration of receptors for insulin and insulin-like growth factors on Swarm rat chondrosarcoma chondrocytes. Evidence that insulin stimulates proteoglycan synthesis through the insulin receptor.

The insulin-like growth factor, multiplication stimulating activity (MSA), and insulin were recently shown to stimulate proteoglycan synthesis in monolayer cultures of chondrocytes derived from the Swarm rat chondrosarcoma. Insulin produced significant stimulation at a concentration of less than 1 ng/ml, suggesting that insulin was acting through the insulin receptor rather than through a somatomedin receptor. In this paper we have shown that the insulin-like growth factors IGF-I and IGF-II also are potent stimulators of [35S]sulfate incorporation into macromolecules recovered from the medium and cell layer matrix of the chondrosarcoma chondrocytes. Proinsulin was 3% as potent as insulin in stimulating [35S]sulfate incorporation. We identified receptors for insulin and the insulin-like growth factors, MSA, IGF-I, and IGF-II. Insulin, at concentrations 1000 times the concentration required to produce the biologic response, did not compete for binding of 125I-MSA-II-1 or of 125I-IGF-II and only partially competed for 125I-IGF-I binding. Anti-insulin receptor IgG stimulated proteoglycan synthesis and competed for 125I-insulin binding. Fab fragment prepared from anti-insulin receptor IgG completely blocked the stimulation of [35S]sulfate incorporation into macromolecules by insulin while only partially inhibiting the biologic response to insulin-like growth factors, MSA, IGF-I, and IGF-II. Similarly, the anti-insulin receptor IgG only partially inhibited the binding of 125I-IGF-I and 125I-IGF-II while completely blocking the binding of 125I-insulin. We conclude that insulin stimulates proteoglycan synthesis in the chondrosarcoma chondrocytes by acting through the insulin receptor whereas the insulin-like growth factors probably act through their own receptors.

Animals↗
PubMed2006

Intermediate and long-acting insulins: a review of NPH insulin, insulin glargine and insulin detemir.

OBJECTIVE: To review intermediate- and long-acting insulins with specific emphasis on the newer insulin analogs. METHODS: A MEDLINE search, in English, was conducted with a cut-off of June 30, 2006, using the terms 'NPH insulin', 'insulin analogs', 'insulin glargine', 'insulin detemir' and 'long-acting insulins'. All clinical trials from within the search period were included. RESULTS: The insulin analogs, insulin glargine and insulin detemir, were introduced in an attempt to improve glycemic control among patients with diabetes, without increasing the risk of hypoglycemia. This review indicates that both insulin analogs demonstrate better glycemic control than NPH insulin, based on measurements of HbA1c, fasting glucose and intra-subject variability in blood glucose. This was accomplished with similar or reduced risk of hypoglycemia. Also, insulin detemir appears to be associated with less body weight increase than NPH insulin or insulin glargine. CONCLUSION: The newer long-acting insulin analogs, insulin detemir and glargine, appear to provide better glycemic control than NPH insulin without increasing the risk of hypoglycemia.

Diabetes Mellitus↗
PubMedDate not supplied

Prolonged sulfonylurea administration decreases insulin resistance and increases insulin secretion in non-insulin-dependent diabetes mellitus: evidence for improved insulin action at a postreceptor site in hepatic as well as extrahepatic tissues.

To determine whether long-term sulfonylurea therapy ameliorates glucose homeostasis in patients with NIDDM predominantly by improving insulin secretion or by improving insulin action, we evaluated changes in fasting plasma glucose concentrations, intravenous glucose tolerance, glucose-stimulated insulin secretion, facilitation of glucose disposal by exogenous insulin, and erythrocyte insulin receptor binding before and after prolonged (congruent to 4 mo) administration of tolazamide to 18 patients with NIDDM. Before tolazamide administration, 15 patients had decreased insulin secretion (50 +/- 31 vs 577 +/- 176 microU/ml X 10 min in nondiabetic subjects, P less than 0.05) and insulin resistance (Km 166 +/- 31 vs 58 +/- 3 microU/ml in nondiabetic subjects, P less than 0.05; Vmax 7.3 +/- 0.6 vs 9.8 +/- 0.2 mg/kg/min in nondiabetic subjects, P less than 0.05), whereas the other three patients had comparably impaired insulin secretion (56 +/- 52 microU/ml X min) but were not insulin resistant (Km 70 +/- 6 microU/ml; Vmax 10.8 +/- 0.6 mg/kg/min). The insulin-resistant patients had fasting hyperinsulinemia (19 +/- 4 vs 11 +/- 1 microU/ml in nondiabetic subjects, P less than 0.05), decreased erythrocyte insulin receptor binding (4.8 +/- 0.4 vs 5.8 +/- 0.3%/1.6 X 10(9) cells in nondiabetic subjects, P less than 0.05), and impairment in both insulin-induced suppression of glucose production (Km 97 +/- 31 vs 21 +/- 7 microU/ml in nondiabetic subjects, P less than 0.05), and insulin-induced stimulation of glucose utilization (Km and Vmax 176 +/- 29 microU/ml and 5.8 +/- 0.7 mg/kg/min vs 50 +/- 2 microU/ml and 9.1 +/- 0.6 mg/kg/min in nondiabetic subjects, both P less than 0.05). The nonresistant patients were not hyperinsulinemic (12 +/- micU/ml), had normal insulin receptor binding (5.9 +/- 0.5%/1.6 X 10(9) cells), and were less hyperglycemic than the insulin-resistant patients (128 +/- 11 vs 181 +/- 12 mg/dl, P less than 0.05). After tolazamide administration, both the early phase of glucose-induced insulin secretion (56 +/- 52 vs 141 +/- 68 microU/ml . 10 min) and insulin binding (5.9 +/- 0.5 vs 7.0 +/- 0.5%/1.6 X 10(9) cells) increased in all three nonresistant patients, but there was no consistent improvement in fasting hyperglycemia (128 +/- 11 vs 130 +/- 24 mg/dl), intravenous glucose tolerance (Kivgtt 0.77 +/- 0.18 vs 0.89 +/- 0.29%/min), or facilitation of glucose disposal by insulin (Km 70 +/- 5 vs 64 +/- 5 microU/ml; Vmax 10.8 +/- 0.6 vs 10.1 +/- 0.2 mg/kg/min).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1986

Effects of anti-insulin antibody on insulin binding to liver membranes: evidence against antibody-induced enhancement of insulin binding to the insulin receptor.

In the presence of anti-insulin antibody, 2-to 3-fold enhancement of 125I-insulin binding to liver membranes was observed when binding was estimated by the radioactivity of 125I-insulin bound to the membrane pellets. However, after 125I-insulin was covalently cross-linked to liver membranes using disuccinimidyl suberate in the presence of anti-insulin antibody, sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography showed that 125I-insulin bound to the alpha-subunit of the insulin receptor was inhibited by anti-insulin insulin antibody in an dose-dependent manner. More importantly, at an anti-insulin antibody dilution range between 1:50 and 1:5,000, sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed two 125I-labelled bands of mol wt 62,000 and 27,000, while only one band of mol wt 130,000 was revealed in the absence of anti-insulin antibody. These Mr = 62,000 and Mr = 27,000 bands were found to be the heavy and the light chain of anti-insulin IgG molecules respectively. Pepsin digested anti-insulin serum had only an inhibitory effect on 125I-insulin binding to liver membranes. Non-immunized guinea pig serum or IgG completely abolished the enhanced effect of anti-insulin antibody. Further, this enhanced effect was inhibited by Fc fragment-specific anti-IgG serum or H&L-chain-specific anti-IgG serum in a dose-dependent manner. Protein A also inhibited the effect of anti-insulin antibody. In IM-9 lymphocytes and human red blood cell ghosts, which have no Fc gamma receptors, enhancement of insulin binding was not observed in the presence of anti-insulin antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1997

Glucose-induced insulin secretion is impaired and insulin-induced phosphorylation of the insulin receptor and insulin receptor substrate-1 are increased in protein-deficient rats.

Malnutrition is related to diabetes in tropical countries. In experimental animals, protein deficiency may affect insulin secretion. However, the effect of malnutrition on insulin receptor phosphorylation and further intracellular signaling events is not known. Therefore, we decided to evaluate the rate of insulin secretion and the early molecular steps of insulin action in insulin-sensitive tissues of an animal model of protein deficiency. Pancreatic islets isolated from rats fed a standard (17%) or a low (6%) protein diet were studied for their secretory response to increasing concentrations of glucose in the culture medium. Basal as well as maximal rates of insulin secretion were significantly lower in the islets isolated from rats fed a low protein diet. Moreover, the dose-response curve to glucose was significantly shifted to the right in the islets from malnourished rats compared with islets from control rats. During an oral glucose tolerance test, there were significantly lower circulating concentrations of insulin in the serum of rats fed a low protein diet in spite of no difference in serum glucose concentration between the groups, suggesting an increased peripheral insulin sensitivity. Immunoblotting and immunoprecipitation were used to study the phosphorylation of the insulin receptor and the insulin receptor substrate-1 as well as the insulin receptor substrate-1-p85 subunit of phosphatidylinositol 3-kinase association in response to insulin. Values were greater in hind-limb muscle from rats fed a low protein diet compared with controls. No differences were detected in the total amount of protein corresponding to the insulin receptor or insulin receptor substrate-1 between muscle from rats fed the two diets. Therefore, we conclude that a decreased glucose-induced insulin secretion in pancreatic islets from protein-malnourished rats is responsible, at least in part, for an increased phosphorylation of the insulin receptor, insulin receptor substrate-1 and its association with phosphatidylinositol 3-kinase. These might represent some of the factors influencing the equilibrium in glucose concentrations observed in animal models of malnutrition and undernourished subjects.

Animals↗
PubMed1984

Insulin therapy in obese, non-insulin-dependent diabetes induces improvements in insulin action and secretion that are maintained for two weeks after insulin withdrawal.

The effects of rigorous insulin treatment on insulin action (insulin clamp) and secretion (plasma insulin response to glucose) were studied in 13 obese patients with non-insulin-dependent diabetes mellitus (NIDDM). Improvements were documented in fasting (P less than 0.0001) and postprandial (P less than 0.0001) plasma glucose concentrations, insulin secretion after oral glucose (P less than 0.001), and insulin action (P less than 0.005) after 30 days of therapy. Mean integrated plasma insulin response to glucose increased 2.5-fold after insulin therapy, but this improvement varied considerably from patient to patient. Insulin action also increased with insulin treatment and the resulting values were no longer significantly different from a weight- and age-matched group of subjects with normal glucose tolerance. However, there was considerable patient-to-patient variation in the degree to which insulin action was enhanced. The insulin-induced improvements in glucose tolerance persisted for at least 2 wk after insulin withdrawal, and were associated with continued increased insulin secretion and insulin action. In conclusion, control of hyperglycemia for 1 mo led to improvements in both insulin secretion and action in a series of obese patients with NIDDM that persisted for at least 2 wk after cessation of therapy.

Adult↗
PubMed1999

Insulin aspart (B28 asp-insulin): a fast-acting analog of human insulin: absorption kinetics and action profile compared with regular human insulin in healthy nondiabetic subjects.

OBJECTIVE: To study the pharmacokinetic and pharmacodynamic profile of insulin aspart (a new fast-acting human insulin analog) after subcutaneous administration in the deltoid, abdominal, and thigh sites and to compare this profile with regular human insulin (Novolin; Novo Nordisk A/S, Copenhagen). RESEARCH DESIGN AND METHODS: A total of 20 healthy subjects were studied in a single-center six-period double-blind randomized crossover trial with 6 study days and a washout period of 1 week between each single daily dose of the trial drug. Subjects were randomized to receive a single dose of 0.2 U/kg of insulin aspart or regular insulin on each of the 6 study days in three different sites (the deltoid, the abdomen, and the thigh) during a 10-h euglycemic clamp (two drugs and three injection sites). Pharmacokinetic and pharmacodynamic measurements were derived from blood sample measurements of glucose, insulin, and C-peptide during these clamps. RESULTS: The pharmacodynamic data from the euglycemic clamp study showed that, regardless of injection site, the maximal glucose infusion rate (GIR Cmax) was greater and occurred at an earlier time (GIR Tmax) after administration of insulin aspart than regular insulin (GIR Cmax: abdomen 813 vs. 708, deltoid 861 vs. 736, and thigh 857 vs. 720 g/min, P < 0.05 for all; GIR Tmax: abdomen 94 vs. 173, deltoid 111 vs. 192, and thigh 145 vs. 193 g/min, P < 0.05 for all). Pharmacokinetic parameters were also consistent with faster absorption and higher peak insulin concentrations after insulin aspart administration. From all sites, the peak insulin concentration (Cmax) was higher and occurred earlier (Tmax) after administration of insulin aspart than of regular insulin (Cmax: abdomen 501 vs. 260, deltoid 506 vs. 252, thigh 422 vs. 220 pmol/l, P < 0.001 for all sites; Tmax: abdomen 52 vs. 109, deltoid 54 vs. 98, and thigh 60 vs. 107 min, P < 0.01 for all sites). The absorption and glucose-lowering action of insulin aspart did not differ between sites (similar GIR Cmax, Tmax, and area under the curve parameters). However, the duration of the glucose-lowering effect was up to 34 min shorter (P < 0.01) for the abdomen injections than for the deltoid or thigh injections (lower time of 50% glucose disposal). In addition, the amount of glucose infused was significantly lower by 10-14% in the abdomen than in other sites. CONCLUSIONS: Subcutaneous administration of insulin aspart causes a more rapid and intense maximal effect compared with regular insulin during euglycemic clamp studies in nondiabetic subjects. Abdominal administration of insulin aspart has a shorter duration of glucose-lowering effect compared with administration in the deltoid or thigh.

Absorption↗
PubMed1990

Insulin down-regulates insulin receptor number and up-regulates insulin receptor affinity in cells expressing a tyrosine kinase-defective insulin receptor.

We examined the effect of insulin treatment on HTC cells transfected with large numbers of either normal insulin receptors (HTC-IR) or insulin receptors defective in tyrosine kinase (HTC-IR/M-1030). In both HTC-IR and HTC-IR/M-1030 cells, 20 h of insulin treatment (1 microM) at 37 degrees C resulted in a 65% decrease in the number of binding sites with a reciprocal 6-fold increase in affinity. In contrast, treatment with 10 nM insulin (20 h, 37 degrees C) also increased receptor affinity but had a smaller effect on the number of binding sites. 125I-Insulin binding to soluble receptors from HTC-IR and HTC-IR/M-1030 cells pretreated with insulin showed results similar to those obtained in intact cells. In both HTC-IR and HTC-IR/M-1030 cells, insulin enhanced insulin receptor degradation. In HTC-IR/M-1030 cells a 1-h incubation with insulin did not change receptor number and had only a small effect on receptor affinity; also there was no effect of insulin after a 20-h incubation at 15 degrees C. Inhibiting protein synthesis by pretreatment with cycloheximide (100 microM) did not block either the decrease in receptor number or the increase in receptor affinity. Both HTC-IR and HTC-IR/M-1030 cells exhibited a very slow rate of insulin and insulin receptor internalization and no differences were seen in this parameter when HTC-IR cells were compared to HTC-IR/M-1030 cells. These studies indicate, therefore, that in cells expressing kinase-defective insulin receptors, insulin down-regulates insulin receptor number via enhanced receptor degradation, and up-regulates receptor affinity. These effects were time- and temperature-dependent, but not dependent on new protein synthesis, and suggest that activation of tyrosine kinase may not be a prerequisite for certain mechanisms whereby insulin regulates its receptor.

Animals↗
PubMed1988

Development of insulin antibodies, metabolic control and B-cell function in newly diagnosed insulin dependent diabetic children treated with monocomponent human insulin or monocomponent porcine insulin.

One hundred and thirty eight patients participated in a two-year randomized, double-blind multicentre trial to compare monocomponent human insulin and porcine insulin in the treatment of newly diagnosed insulin dependent diabetic children with respect to development of insulin antibodies, metabolic control and B-cell function. There was no difference between the two patient groups throughout treatment either in the level of IgG insulin binding or the percentage of patients with insulin antibodies (IgG-insulin greater than 0.012 U/l). However, the estimated mean of log insulin binding values in the antibody positive patients alone was significantly lower (p less than 0.05) in the human insulin treated group at all times apart from 1 and 18 months (e.g., human insulin group at one and two years: 0.104 and 0.152 U/l, porcine insulin group at one and two years: 0.162 and 0.212 U/l). The insulin antibodies in both patient groups bound equivalent amounts of human and porcine insulin tracer. Metabolic control, insulin dosage and B-cell function in the two treatment groups were similar throughout the treatment period. It is concluded that in newly diagnosed insulin dependent diabetic children monocomponent human insulin is slightly less immunogenic than monocomponent porcine insulin, and equally effective in overall metabolic control.

Animals↗
PubMed1993

Effect of short- and long-term experimental hyperthyroidism on plasma glucose level and insulin secretion during an intravenous glucose load and on insulin binding, insulin receptor kinase activity, and insulin action in adipose tissue.

Glucose disposal, insulin secretion, and insulin action in adipose tissue were measured in rats treated for 10 or 30 days with high doses of thyroxine (T4). Acutely induced hyperthyroidism produced a high rate of glucose disposal after an intravenous glucose tolerance test (IVGTT), accompanied by a high glucose-stimulated insulin secretion. In addition, in these rats the following phenomena were observed: (1) high insulin binding to isolated adipocytes due to an increase in the insulin receptor number; (2) high insulin binding to partially purified fat insulin receptors; (3) normal tyrosine kinase activity of fat insulin receptors; and (4) high insulin action in isolated adipocytes, such as glucose transport and lipogenesis. Chronically induced hyperthyroidism produced high rates of glucose disposal after an IVGTT, accompanied by an increase of basal and glucose-stimulated insulin secretion. These rats showed (1) normal insulin binding to either isolated adipocytes or partially purified insulin receptors; (2) normal tyrosine kinase activity of fat insulin receptors; (3) normal insulin action in isolated adipocytes. In conclusion, exogenous hyperthyroidism induced an increase in glucose disposal, probably due in part to high insulin secretion. In short-term T4-treated rats an additional increase of insulin action in adipocytes was also observed.

Adipose Tissue↗
PubMed1995

Studies into the identity of the sites of insulin-stimulated insulin receptor serine phosphorylation. Characterization of synthetic peptide substrates for the insulin-stimulated insulin receptor serine kinase.

The identity of the sites of insulin-stimulated serine phosphorylation in the human insulin receptor was examined by synthesizing peptides that together encompassed all the serine residues of the cytosolic portion of the beta-subunit and testing them as substrates for phosphorylation by a preparation of human insulin receptor copurified with insulin-stimulated insulin receptor serine kinase activity. Of the 14 peptides studied, only 4 (1071--1080, 1290--1298, 1253--1271, and 1313--1329) were phosphorylated on serine, with the serine phosphorylation stimulated 2--4-fold by insulin. Peptides 1071--1080 and 1290--1298 were 3--7-fold better substrates for the serine phosphorylation than the other serine-phosphorylated peptides. Peptides 1071--1080 and 1313--1329 also exhibited insulin-stimulated phosphorylation on tyrosine. Two-dimensional thin-layer tryptic mapping of the phosphorylated insulin receptor/insulin-stimulated insulin receptor serine kinase preparation or of insulin receptor phosphorylated in human Hep G2 cells yielded two major peptides, called S1 and S2, that ran as a pair of closely migrating spots, and other lesser peptides that contained phosphoserine. S1 and S2 also contained some phosphotyrosine and gave phosposerine/phosphotyrosine ratios of approximately 6 and 0.96-1.50 for the in vivo and in vitro labeled receptor, respectively. S1 and S2 were not cleaved by V8. Of the serine-phosphorylated peptides, only 1290--1298 and 1071--1080 should be V8 resistant; 1290--1298 contains serine sites 1293/4 and migrated distinctly from S1 and S2 in tryptic maps. Peptide 1071--1080 mimicked the production of S1 and S2 in tryptic maps yielding a doublet of phosphopeptides, each containing phosphoserine and phosphotyrosine, which comigrated exactly with S1 and S2. Comigration was confirmed at a different pH and by mixing experiments. Radiosequenation showed that serine 1078 was phosphorylated. Tyrosine 1075 was also phosphorylated, but it was no more than a minor site in vivo. It is concluded that serine 1078 of the insulin receptor is a major site of insulin-stimulated phosphorylation in vivo and in vitro. The peptide sequences provide a range of substrates to facilitate the study, purification, and characterization of the insulin-stimulated insulin receptor serine kinase or kinases, and the identification of a major site of insulin-stimulated serine phosphorylation will help elucidate the function of the insulin receptor serine phosphorylation.

Amino Acid Sequence↗
PubMed1992

Mutations at the dimer, hexamer, and receptor-binding surfaces of insulin independently affect insulin-insulin and insulin-receptor interactions.

Mutagenesis of the dimer- and hexamer-forming surfaces of insulin yields analogues with reduced tendencies to aggregate and dramatically altered pharmacokinetic properties. We recently showed that one such analogue, HisB10----Asp, ProB28----Lys, LysB29----Pro human insulin (DKP-insulin), has enhanced affinity for the insulin receptor and is useful for studying the structure of the insulin monomer under physiologic solvent conditions [Weiss, M. A., Hua, Q. X., Lynch, C. S., Frank, B. H., & Shoelson, S. E. (1991) Biochemistry 30, 7373-7389]. DKP-insulin retains native secondary and tertiary structure in solution and may therefore provide an appropriate baseline for further studies of related analogues containing additional substitutions within the receptor-binding surface of insulin. To test this, we prepared a family of DKP analogues having potency-altering substitutions at the B24 and B25 positions using a streamlined approach to enzymatic semisynthesis which negates the need for amino-group protection. For comparison, similar analogues of native human insulin were prepared by standard semisynthetic methods. The DKP analogues show a reduced tendency to self-associate, as indicated by 1H-NMR resonance line widths. In addition, CD spectra indicate that (with one exception) the native insulin fold is retained in each analogue; the exception, PheB24----Gly, induces similar perturbations in both native insulin and DKP-insulin backgrounds. Notably, analogous substitutions exhibit parallel trends in receptor-binding potency over a wide range of affinities: D-PheB24 greater than unsubstituted greater than GlyB24 greater than SerB24 greater than AlaB25 greater than LeuB25 greater than SerB25, whether the substitution was in a native human or DKP-insulin background. Such "template independence" reflects an absence of functional interactions between the B24 and B25 sites and additional substitutions in DKP-insulin and demonstrates that mutations in discrete surfaces of insulin have independent effects on protein structure and function. In particular, the respective receptor-recognition (PheB24, PheB25), hexamer-forming (HisB10), and dimer-forming (ProB28, LysB29) surfaces of insulin may be regarded as independent targets for protein design. DKP-insulin provides an appropriate biophysical model for defining structure-function relationships in a monomeric template.

Amino Acid Sequence↗
PubMed1991

Expression of insulin-like growth factor II and receptors for insulin-like growth factor II, insulin-like growth factor I and insulin in isolated and cultured rat hepatocytes.

Insulin-like growth factor II is believed to play an important role in fetal growth and development. The insulin-like growth factor II gene expression is tissue specific and developmentally regulated. We have previously shown an enhanced level of insulin-like growth factor II messenger RNA and protein in human hepatocellular carcinomas. This led to the suggestion that hepatocytes might be involved in insulin-like growth factor II expression. However, previous studies based on in situ hybridization only showed insulin-like growth factor II messenger RNA in liver sinusoidal cells. This paper reports on the analysis of the expression of insulin-like growth factor II and insulin-like growth factor II, insulin-like growth factor I and insulin receptor messenger RNAs in vivo in isolated rat hepatocytes at various stages of development and in vitro in adult rat hepatocytes primary culture. Our study indicates that isolated rat hepatocytes synthesize insulin-like growth factor II messenger RNA with a switch between fetal and adult messenger RNA profiles occurring 21 days after birth. In addition, adult rat hepatocytes in culture expressed insulin-like growth factor II messenger RNA and protein. Insulin-like growth factor II, insulin-like growth factor I and insulin receptor messenger RNAs were also detected. Therefore these results are consistent with the hypothesis that insulin-like growth factor II acts as an autocrine growth factor for hepatocytes in addition to having a paracrine effect. They also indicate that primary culture of hepatocytes is a good model for further studies on insulin-like growth factor II gene regulation.

Animals↗
PubMed1997

Insulin-like growth factor binding protein-1 at the maternal-fetal interface and insulin-like growth factor-I, insulin-like growth factor-II, and insulin-like growth factor binding protein-1 in the circulation of women with severe preeclampsia.

OBJECTIVES: Preeclampsia is characterized by maternal hypertension, proteinuria, edema, and shallow placental invasion. Insulin-like growth factor binding protein-1, abundant in maternal decidua, is believed to play a role in limiting trophoblast invasiveness. In this study we addressed the hypothesis that this binding protein is aberrantly expressed in preeclampsia. We also investigated circulating levels of insulin-like growth factor-I and insulin-like growth factor-II in subjects with severe preeclampsia compared with controls. STUDY DESIGN: Insulin-like growth factor binding protein-1 was investigated by immunohistochemistry at the maternal-fetal interface of eight pregnancies complicated by severe preeclampsia and six controls between 21 and 34 weeks of gestation. Cell types were identified with use of cell-specific markers. Circulating levels of insulin-like growth factor binding protein-1, insulin-like growth factor-I, and insulin-like growth factor-II in 16 patients with severe preeclampsia and 29 controls at the same gestational age were determined by an immunoradiometric assay and correlated with clinical parameters. Data were analyzed by t test and Pearson's method. RESULTS: Insulin-like growth factor binding protein-1 was highly expressed on syncytiotrophoblasts, cytotrophoblasts, and decidual cells but not on placental fibroblasts. Immunostaining was greater at the maternal-fetal interface in severe preeclamptic patients compared with controls. Circulating insulin-like growth factor binding protein-1 levels in subjects with severe preeclampsia were 428.3 +/- 85.9 ng/ml compared with 76.6 +/- 11.8 in controls (p = 0.0007). Circulating insulin-like growth factor-I levels were 80.9 +/- 17.2 ng/ml compared with 179.4 +/- 28.2 ng/ml in controls (p = 0.0001). In contrast, insulin-like growth factor-II levels were not significantly different in the two groups. In subjects with severe preeclampsia insulin-like growth factor binding protein-1 levels correlated with diastolic blood pressure (r = 0.498, p 0.049) and aspartate transcarbamylase (0.621, p = 0.010). CONCLUSIONS: The abundance of insulin-like growth factor binding protein-1 at the maternal-fetal interface in severely preeclamptic pregnancies suggests that the binding protein may participate in the pathogenesis of the shallow placental invasion observed in this disorder. Low circulating insulin-like growth factor-I and elevated insulin-like growth factor binding protein-1 levels may contribute to restricted placental and therefore fetal growth.

Adolescent↗
PubMed2003

A novel insulin analog with unique properties: LysB3,GluB29 insulin induces prominent activation of insulin receptor substrate 2, but marginal phosphorylation of insulin receptor substrate 1.

The potentially enhanced mitogenic activity of insulin analogs represents a safety risk that requires detailed analysis of new analogs considered for therapeutic applications. We assessed the signaling properties and mitogenic potency of two novel rapid-acting insulin analogs, Lys(B3),Glu(B29) insulin (HMR 1964) and Lys(B3),Ile(B28) insulin (HMR 1153) using myoblasts and cardiomyocytes. In myoblasts, both binding and internalization were two- to threefold higher for Asp(B10) insulin and HMR 1153 when compared with HMR 1964 and regular insulin. This finding correlated with a prominent Shc/IGF-I receptor interaction, tyrosine phosphorylation of Shc, activation of extracellular signal-regulated protein kinase (ERK)-1 and -2, and stimulation of DNA synthesis by HMR 1153 and Asp(B10) insulin. In contrast, HMR 1964 produced a marginal activation of the Shc/ERK kinase cascade and was equipotent to insulin in stimulating DNA synthesis in myoblasts. Further, the in vivo growth-promoting activity of this analog was found to be identical to that of regular human insulin. In myoblasts, HMR 1964 produced a minor activation of insulin receptor substrate (IRS)-1 tyrosine phosphorylation, but a prominent activation of IRS-2, with a significantly stronger effect than insulin in human myoblasts. Predominant activation of IRS-2 was also observed in adult cardiomyocytes where HMR 1964 increased 3-O-methylglucose transport and the activation of Akt and glycogen synthase kinase-3 to the same extent as human insulin. We concluded that 1) the mitogenic properties of insulin analogs may result from a series of initial receptor interactions, including internalization and phosphorylation; 2) the mitogenic and metabolic potential of HMR 1964 is identical to that of insulin; and 3) predominant activation of IRS-2 may open new avenues for optimized insulin therapies.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Comparison of an insulin analog, insulin aspart, and regular human insulin with no insulin in gestational diabetes mellitus.

OBJECTIVE: To assess the short-term efficacy of insulin aspart in comparison with regular human insulin in women with gestational diabetes mellitus (GDM) during standardized meal tests. RESEARCH DESIGN AND METHODS: The study included 15 women with GDM who had inadequate diabetes control with diet alone. On 3 consecutive days, breakfast meal tests were performed-the first with no exogenous insulin and the other two after the injection of either regular insulin or insulin aspart. RESULTS: The peak insulin concentration was higher and the peak glucose and C-peptide concentrations were lower with both insulin preparations than with no exogenous insulin. Glucose areas under the curve above baseline were significantly lower with insulin aspart (180-min area, 7.1 mg. h. dl(-1); P = 0.018), but not with regular insulin (30.2 mg. h. dl(-1); P = 0.997), than with no insulin (29.4 mg. h. dl(-1)). CONCLUSIONS: This study demonstrates that effective postprandial glycemic control in women with GDM who required insulin was brought about by insulin aspart through higher insulin peak and lower demand on endogenous insulin secretion.

Adult↗
PubMed1984

Relative roles of insulin clearance and insulin sensitivity in the prebreakfast increase in insulin requirements in insulin-dependent diabetic patients.

During continuous subcutaneous or intravenous insulin infusion therapy, many patients with insulin-dependent diabetes (IDD) require more insulin in the prebreakfast period (0600-0800 h) than earlier in the morning (0100-0300 h). This study was designed to assess whether variations in insulin clearance or insulin sensitivity might contribute to overnight variations in insulin requirements. Euglycemic insulin clamp studies were performed in random sequence from 2400 to 0300 h and from 0500 to 0800 h on successive nights in 10 subjects with IDD. Insulin was infused at a rate of 40 mU/min/m2 and plasma glucose concentration was maintained at 100 mg/dl by a variable rate glucose infusion from a Biostator GCIIS (Miles Laboratories, Elkhart, Indiana). Insulin clearance was (mean +/- SEM) 277 +/- 41 ml/min/m2 between 0700 and 0800 h compared with 256 +/- 41 ml/min/m2 between 0200 and 0300 h (P less than 0.05), while glucose infusion rates were the same [3.86 +/- 0.52 mg/kg/min from 0730 to 0800 h versus 3.99 +/- 0.51 mg/kg/min from 0230 to 0300 h (P = NS)]. All eight patients with a previously documented prebreakfast increase in insulin requirements had higher insulin clearance at this time. These results indicate that differences in insulin clearance between the prebreakfast period and the early morning may account partially for the higher prebreakfast insulin requirements in some subjects with IDD, and the variations in insulin requirements during the night are not due to variations in insulin sensitivity.

Adult↗
PubMedDate not supplied

Attempts to prepare 'insulin-free plasma' from human subjects: effects of serial dilution and insulin recovery studies on immunoreactive insulin activity of partially insulin-free plasma.

The reason for attempts to prepare insulin-free plasma from human plasma is discussed. Binding agent, employed to prepare insulin-free plasma, had a capacity to bind 40% of insulin in the system. Insulin recovery from the filtrate of human standard insulin-binding agent reaction was 60%. Human plasma incubated with binding agent gave a filtrate--partially insulin-free plasma (PIFP)--which contained significantly higher amounts of insulin compared to calculated values. Insulin in PIFP was not augmented by serial dilution. Human standard insulin added to PIFP was recovered in full and the mixture was not dilution augmentable. Incubation of human plasma--human standard insulin (106 microunits/ml) mixture with binding agent gave a PIFP which had 60% of total insulin in the mixture. Dialysis did not alter the immunoreactive insulin activity of plasma. Dialysed samples showed augmentation of insulin activity on serial dilution. These observations strongly suggest the presence of a high molecular-weight, insulin-like inhibitory component in human plasma.

Antigens↗