An Extracellular Domain of the Insulin Receptor β-Subunit with Regulatory Function on Protein-Tyrosine Kinase

Abstract Anti-insulin receptor monoclonal antibody MA-10 inhibits insulin receptor autophosphorylation of purified rat liver insulin receptors without affecting insulin binding (Cordera, R., Andraghetti, G., Gherzi, R., Adezati, L., Montemurro, A., Lauro, R., Goldfine, I. D., and De Pirro, R. (1987) Endocrinology 121, 2007-2010). The effect of MA-10 on insulin receptor autophosphorylation and on two insulin actions (thymidine incorporation into DNA and receptor down-regulation) was investigated in rat hepatoma Fao cells. MA-10 inhibits insulin-stimulated receptor autophosphorylation, thymidine incorporation into DNA, and insulin-induced receptor down-regulation without affecting insulin receptor binding. We show that MA-10 binds to a site of rat insulin receptors different from the insulin binding site in intact Fao cells. Insulin does not inhibit MA-10 binding, and MA-10 does not inhibit insulin binding to rat Fao cells. Moreover, MA-10 binding to down-regulated cells is reduced to the same extent as insulin binding. In rat insulin receptors the MA-10 binding site has been tentatively localized in the extracellular part of the insulin receptor beta-subunit based on the following evidence: (i) MA-10 binds to insulin receptor in intact rat cells; (ii) MA-10 immunoprecipitates isolated insulin receptor beta-subunits labeled with both [35S]methionine and 32P; (iii) MA-10 reacts with rat insulin receptor beta-subunits by the method of immunoblotting, similar to an antipeptide antibody directed against the carboxyl terminus of the insulin receptor beta-subunit. Moreover, MA-10 inhibits autophosphorylation and protein-tyrosine kinase activity of reduced and purified insulin receptor beta-subunits. The finding that MA-10 inhibits insulin-stimulated receptor autophosphorylation and reduces insulin-stimulated thymidine incorporation into DNA and receptor down-regulation suggests that the extracellular part of the insulin receptor beta-subunit plays a role in the regulation of insulin receptor protein-tyrosine kinase activity

C-Reactive Protein Levels at the Midpregnancy Can Predict Gestational Complications

Although essential for a successful pregnancy, a growing body of evidence suggests that maternal inflammation, when dysregulated, may represent a risk factor for both maternal and neonatal outcomes. Here, we assessed the accuracy of maternal C-reactive protein (CRP) concentrations at the middle phase of pregnancy in the identification of maternal adverse outcomes (MAO) until delivery. A correlation between CRP and a complicated pregnancy including both maternal and neonatal adverse outcomes has been investigated, too. In this retrospective study, conducted at the Diabetology Unit of IRCCS Ospedale Policlinico San Martino, Genoa (Italy), 380 outpatient pregnant women have been enrolled at the prenatal visit before performing a 75 g oral glucose tolerance test at 24th-26th gestational week for gestational diabetes mellitus (GDM) screening. Demographic, medical, and reproductive history has been obtained by verbal interview. Data about pregnancy and delivery have been retrieved from medical records. The median value of maternal baseline serum CRP was 3.25 \u3bcg/mL. Women experiencing MAO were older, more frequently suffering from hypertension, and showed higher CRP concentrations, with a cutoff value >1.86 \u3bcg/mL found by a ROC curve analysis to be accurately predictive for MAO. By a logistic regression analysis, serum CRP levels >1.86 \u3bcg/mL have been found to predict MAO also considering maternal age, hypertension, and GDM. Maternal CRP levels have been positively associated with overall pregnancy adverse outcomes (maternal and neonatal), too. In conclusion, in pregnant women serum levels of CRP can early recognize subjects at higher risk for maternal and neonatal complications needing a more stringent follow-up

Restoration of acute insulin response in T2DM subjects 1 month after biliopancreatic diversion

objective: Biliopancreatic diversion (BPD) restores normal glucose tolerance in a few weeks in morbid obese subjects with type 2 diabetes, improving insulin sensitivity. However, there is less known about the effects of BPD on insulin secretion. We tested the early effects of BPD on insulin secretion in obese subjects with and without type 2 diabetes. Methods and Procedures: Twenty-one consecutive morbid obese subjects, 9 with type 2 diabetes (T2DM) and 12 with normal fasting glucose (NFG) were evaluated, just before and 1 month after BPD, by measuring body weight (BW), glucose, adipocitokines, homeostasis model assessment of insulin resistance (HOMA-IR), acute insulin response (AIR) to e.v. glucose and the insulinogenic index adjusted for insulin resistance ([∆I5/∆G5]/HOMA-IR). Results: Preoperatively, those with T2DM differed from those with NFG in showing higher levels of fasting glucose, reduced AIR (57.9 ± 29.5 vs. 644.9 ± 143.1 pmol/l, P < 0.01) and reduced adjusted insulinogenic index (1.0 ± 0.5 vs. 17.6 ± 3.9 1/mmol 2 , P < 0.001). One month following BPD, in both groups BW was reduced (by ~11%), but all subjects were still severely obese; HOMA-IR and leptin decreased significanlty, while high-molecular weight (HMW) adiponectin and adjusted insulinogenic index increased. In the T2DM group, fasting glucose returned to non-diabetic values. AIR did not change in the NFG group, while in the T2DM group it showed a significant increase (from 58.0 ± 29.5 to 273.8 ± 47.2 pmol/l, P < 0.01). In the T2DM group, the AIR percentage variation from baseline was significantly related to changes in fasting glucose (r = 0.70, P = 0.02), suggesting an important relationship exists between impaired AIR and hyperglycaemia. Discussion: BPD is able to restore AIR in T2DM even just 1 month after surgery. AIR restoration is associated with normalization of fasting glucose concentrations

Serum Leptin and Adiponectin Concentration in Type 2 Diabetes Patients in the Short and Long Term Following Biliopancreatic Diversion.

A deranged adipokine system is implicated in obesity and in type 2 diabetes mellitus (T2DM), and the lack of remission of T2DM after bariatric surgery could be also accounted for by the postoperative persistence of this condition. METHODS: Thirty T2DM patients undergoing biliopancreatic diversion (BPD) with a wide range of baseline body mass index (BMI) were evaluated prior to and at 1 and 5 years following BPD. Besides the usual clinical evaluations, acute insulin response (AIR) to intravenous glucose load as a parameter of insulin secretion and the serum leptin and adiponectin concentration were measured throughout the follow-up period in all patients. RESULTS: A long-term T2DM remission was observed in 21 patients (70 %). Serum leptin level reduced at the first year and remained substantially unchanged at a long term in both the remitter and non-remitter patients, while following the operation, a progressive significant increase of serum adiponectin level was observed only in remitter patients (from 9.2 to 12.3 \u3bcg/mL at 1 year and to 15.18 \u3bcg/mL at 5 years in the remitters and from 8.8 to 8.75 \u3bcg/mL at 1 year and to 11.8 \u3bcg/mL at 5 years in the non-remitters). Serum leptin mean values were positively associated with the BMI ones both prior to and following BPD (p\u2009<\u20090.005), while serum adiponectin values were positively related (p\u2009<\u20090.04) to the postoperative AIR data. CONCLUSIONS: The improvement of the pattern of cytokine production, as evidenced by postoperative rise in serum adiponectin concentration, might play a role in T2DM remission after bariatric surgery

High-molecular weight adiponectin isoforms increase after biliopancreatic diversion in obese subjects.

High-molecular weight adiponectin isoforms increase after biliopancreatic diversion in obese subjects. Obesity. 2006;14:1511\u20131514. Objective: Our objective was to test the effect of biliopancreatic diversion (BDP) in adiponectin multimerization. Adiponectin, the major protein secreted by adipose tissue, circulates in plasma in different isoforms. The most clinically relevant oligomers are high-molecular weight (HMW) multimers and low-molecular weight (LMW) trimers. Contrasting data on the effect of weight loss on adiponectin isoforms have been reported. Research Methods and Procedures: We measured total plasma adiponectin and HMW and LMW adiponectin oligomers (by Western blot analysis) before and 1 month after BPD, in 18 severely obese subjects. Results: One month after BPD, body weight decreased 11%. Total adiponectin showed significant increase after BPD. In addition, we found a significant increase in HMW (percentage) adiponectin oligomers. We found a significant inverse correlation between HMW (percentage) and BMI before and after BPD. Homeostasis model of assessmentinsulin resistance decreased significantly after the BPD, without any significant correlation with total serum adiponectin and adiponectin oligomers. A moderate weight loss after BPD increases total and HMW adiponectin oligomers. The significant correlation between BMI and HMW (percentage) adiponectin oligomers but not between BMI and total adiponectin might indicate a role of body fat mass in regulation of adiponectin multimerization. These data suggest that HMW oligomers represent a very sensitive parameter to short-term BMI changes after BPD

Beta-cell function improvement after biliopancreatic diversion in subjects withtype 2 diabetes and morbid obesity.

In subjects with obesity and type 2 diabetes mellitus (T2DM), biliopancreatic diversion (BPD) improves glucose stimulated insulin secretion, whereas the effects on other secretion mechanisms are still unknown. Our objective was to evaluate the early effects of BPD on nonglucose-stimulated insulin secretion. In 16 morbid obese subjects (9 with T2DM and 7 with normal fasting glucose (NFG)), we measured insulin secretion after glucose-dependent arginine stimulation test and after intravenous glucose tolerance test (IVGTT) before and 1 month after BPD. After surgery the mean weight lost was 13% in both groups. The acute insulin response during IVGTT was improved in T2DM after BDP (from 55 +/- 10 to 277 +/- 91 pmol/l, P = 0.03). A reduction of insulin response to arginine was observed in NFG, whereas opposite was found in T2DM. In particular, acute insulin response to arginine at basal glucose concentrations (AIR(basal)) was reduced but insulin response at 14 mmol/l of plasma glucose (AIR(14)) was increased. Therefore, after BPD any statistical difference in AIR(14) between NFG and T2DM disappeared (1,032 +/- 123 for NFG and 665 +/- 236 pmol/l for T2DM, P = ns). The same was observed for Slope(AIR), a measure of glucose potentiation, reduced in T2DM before BPD but increased after surgery, when no statistically significant difference resulted compared with NFG (Slope(AIR) after BPD: 78 +/- 11 in NFG and 56 +/- 18 pmol/l in T2DM, P = ns). In conclusion, in obese T2DM subjects 1 month after BPD we observed a great improvement of both glucose- and nonglucose-stimulated insulin secretions. The mechanisms by which BDP improve insulin secretion are still unknown

Microgram amounts of abscisic acid in fruit extracts improve glucose tolerance and reduce insulinemia in rats and in humans

2-Cis,4-trans-abscisic acid (ABA) is a plant hormone that is present also in animals. Several lines of evidence suggest that ABA contributes to the regulation of glycemia in mammals: nanomolar ABA stimulates insulin release from \u3b2-pancreatic cells and glucose transporter-4-mediated glucose uptake by myoblasts and adipocytes in vitro; plasma ABA increases in normal human subjects, but not in diabetic patients, after a glucose load for an oral glucose tolerance test (OGTT). The presence of ABA in fruits prompted an exploration of the bioavailability of dietary ABA and the effect of ABA-rich fruit extracts on glucose tolerance. Rats underwent an OGTT, with or without 1 \ub5g/kg ABA, either synthetic or present in a fruit extract. Human volunteers underwent an OGTT or a standard breakfast and lunch, with or without a fruit extract, yielding an ABA dose of 0.85 or 0.5 \ub5g/kg, respectively. Plasma glucose, insulin, and ABA were measured at different time points. Oral ABA at 0.5-1 \ub5g/kg significantly lowered glycemia and insulinemia in rats and in humans. Thus, the glycemia-lowering effect of low-dose ABA in vivo does not depend on an increased insulin release. Low-dose ABA intake may be proposed as an aid to improving glucose tolerance in patients with diabetes who are deficient in or resistant to insulin.-Magnone, M., Ameri, P., Salis, A., Andraghetti, G., Emionite, L., Murialdo, G., De Flora, A., Zocchi, E. Microgram amounts of abscisic acid in fruit extracts improve glucose tolerance and reduce insulinemia in rats and in humans

Impaired increase of plasma abscisic acid in response to oral glucose load in type 2 diabetes and in gestational diabetes

The plant hormone abscisic acid (ABA) is present and active in humans, regulating glucose homeostasis. In normal glucose tolerant (NGT) human subjects, plasma ABA (ABAp) increases 5-fold after an oral glucose load. The aim of this study was to assess the effect of an oral glucose load on ABAp in type 2 diabetes (T2D) subjects. We chose two sub-groups of patients who underwent an oral glucose load for diagnostic purposes: i) 9 treatment-naive T2D subjects, and ii) 9 pregnant women with gestational diabetes (GDM), who underwent the glucose load before and 8-12 weeks after childbirth. Each group was compared with matched NGT controls. The increase of ABAp in response to glucose was found to be abrogated in T2D patients compared to NGT controls. A similar result was observed in the women with GDM compared to pregnant NGT controls; 8-12 weeks after childbirth, however, fasting ABAp and ABAp response to glucose were restored to normal in the GDM subjects, along with glucose tolerance. We also retrospectively compared fasting ABAp before and after bilio-pancreatic diversion (BPD) in obese, but not diabetic subjects, and in obese T2D patients, in which BPD resulted in the resolution of diabetes. Compared to pre-BPD values, basal ABAp significantly increased 1 month after BPD in T2D as well as in NGT subjects, in parallel with a reduction of fasting plasma glucose. These results indicate an impaired hyperglycemia-induced ABAp increase in T2D and in GDM and suggest a beneficial effect of elevated ABAp on glycemic control