Addition of heart score to high-sensitivity troponin T versus conventional troponin T in risk stratification of patients with chest pain at the coronary emergency rooms.

Patients with chest pain have a large impact on available resources in coronary emergency rooms (CER). Clinical judgement, ECG, risk scores and biomarkers guide in risk stratification. We investigated if high-sensitivity troponin T (HsT) and the HEART Score could contribute to risk stratification at the CER. All patients with chest pain, without elevated conventional troponin levels at presentation, were included. HsT levels were determined at admission (T1), at 4-6 h (T2) and 8-10 h after symptom onset (T3). The HEART Score was calculated as risk score for the occurrence of a major adverse cardiac event (MACE). Thirty days after discharge, occurrence of MACE was registered. Eighty-nine patients were included (overall mean age 61 years (range 20-90)). At presentation, 68 patients (76 %) had a HsT below cut-off value of 14 ng/l (mean HEART Score 3.7, range 1-9). Thirty-one of these 68 patients had a HEART Score between 1-3, no MACE occurred in this group. For 3 patients (4 %) HsT levels increased above 14 ng/l. These 3 patients had a HEART Score between 4-6. The majority of patients with chest pain can be safely discharged within 4-6 h after onset of symptoms using HsT and the HEART Score. In contrast, patients with initially normal HsT but a high HEART Score need longer follow-up and repeat HsT determination.

Preoperative fasting plasma C-peptide level may help to predict diabetes outcome after gastric bypass surgery.

BACKGROUND: To evaluate whether preoperative measurement of fasting plasma C-peptide levels is useful to predict diabetes outcome after Roux-en-Y gastric bypass (RYGB) surgery. MATERIALS AND METHODS: Diabetes outcome after RYGB was evaluated in 126 obese patients: 41 non-diabetic controls (NDC), 29 with impaired glucose tolerance (IGT) and 56 had type 2 diabetes mellitus (T2DM). Body weight, fasting plasma glucose, fasting C-peptide levels, and HbA1c were measured at baseline and 3.6 ± 0.16 years after GBS. Complete resolution of diabetes was defined as: fasting glucose <7.0 mmol/l, HbA1c <6.5 %, achieved without anti-diabetic medication. RESULTS: Patients with complete resolution of diabetes had a more recent diagnosis of T2DM, lower preoperative HbA1c levels and lower daily doses of metformin and insulin use. These parameters were related to postoperative HbA1c levels but they failed to mark the specific patients who had not reached complete resolution of T2DM. Fasting preoperative C-peptide levels had better predictive power: 90 % of T2DM patients with preoperative fasting C-peptide levels >1.0 nmol/l achieved a postoperative HbA1c <6.5 %, and 74 % achieved complete resolution of their diabetes. In contrast, none of the T2DM patients with a preoperative fasting C-peptide <1.0 nmol/l attained these goals. CONCLUSIONS: A preoperative fasting plasma C-peptide level <1.0 nmol/l in severely obese T2DM patients indicates partial ß-cell failure, and is associated with a markedly reduced chance of complete resolution of T2DM after RYGB. We therefore advocate measuring C-peptide levels in all diabetic patients up for bariatric surgery to improve the prediction of outcome.

IRS-1 tyrosine phosphorylation reflects insulin-induced metabolic and mitogenic responses in 3T3-L1 pre-adipocytes.

We determined the involvement of Tyr-1158 within the regulatory loop of the insulin receptor (IR) in the generation of insulin-specific responses in situ. For this purpose chimeric receptors with an epidermal growth factor (EGF) receptor extracellular domain and an IR cytoplasmic domain (EIR) were constructed, which allow activation of the cytoplasmic IR domain without activation of endogenous wt-IRs. Tyr-1158 of the chimera EIR was exchanged for Phe, creating a mutant chimeric receptor (EIR-Y1158F). Chimeric receptors were expressed in 3T3-L1 pre-adipocytes, which do not show insulin-specific responses upon EGF stimulation. We found that pre-adipocytes expressing EIR-Y1158F were impaired in their ability to stimulate glycogen synthesis and DNA synthesis upon maximal stimulation with EGF. EIR-Y1158F was impaired in its ability to phosphorylate insulin receptor substrate (IRS)-1 and induce downstream signals of IRS-1 phosphorylation, such as the association of IRS-1 with phosphatidyl-inositol-3'-kinase and the activation of protein kinase B (Akt). In contrast with the phosphorylation of IRS-1, the phosphorylation of IRS-2 and extracellular regulated protein kinase-1/-2 was normal in EIR-Y1158F expressing cells. These observations suggest that the level of IRS-1 phosphorylation rather than the level of IRS-2 phosphorylation mediates insulin-induced glycogen synthesis and DNA synthesis in 3T3-L1 pre-adipocytes.

Identification of Ser(1275) and Ser(1309) as autophosphorylation sites of the human insulin receptor in intact cells.

In a previous report we described Ser(1275) and Ser(1309) as autophosphorylation sites of the human insulin receptor (IR) tyrosine kinase (TK) in vitro. The question remained whether the observed phosphorylation was exclusive for the in vitro activated receptor or a more general, mechanism of the activated receptor in situ. In this study, we determined the intrinsic activity of the IR to phosphorylate both serine residues in intact cells. For this purpose CHO-09 and NIH-3T3 derived cell-lines expressing the human IR were metabolically labelled with [(32)P]orthophosphate, followed by hormone stimulation of the receptor. The IR was isolated by immunoprecipitation and SDS-PAGE and subsequently analysed for serine phosphorylation by phosphopeptide mapping of HPLC-purified tryptic phosphopeptides. Activation of the IR in the intact cell appeared to result in phosphate incorporation into Ser(1275) and Ser(1309), providing strong evidence that both serine residues are phosphorylation sites of the activated receptor in intact cells.

The insulin receptor tyrosine kinase domain in a chimaeric epidermal growth factor-insulin receptor generates Ca2+ signals through the PLC-gamma1 pathway.

The receptors for insulin (IR) and epidermal growth factor (EGFR) are members of the tyrosine kinase receptor (TKR) family. Despite homology of their cytosolic TK domains, both receptors induce different cellular responses. Tyrosine phosphorylation of insulin receptor substrate (IRS) molecules is a specific IR post-receptor response. The EGFR specifically activates phospholipase C-gamma1 (PLC-gamma1). Recruitment of substrate molecules with Src homology 2 (SH2) domains or phosphotyrosine binding (PTB) domains to phosphotyrosines in the receptor is one of the factors creating substrate specificity. In addition, it has been shown that the TK domains of the IR and EGFR show preferences to phosphorylate distinct peptides in vitro, suggesting additional mechanisms of substrate recognition. We have examined to what extent the substrate preference of the TK domain contributes to the specificity of the receptor in vivo. For this purpose we determined whether the IR TK domain, in situ, is able to tyrosine-phosphorylate substrates normally used by the EGFR. A chimaeric receptor, consisting of an EGFR in which the juxtamembrane and tyrosine kinase domains were exchanged by their IR counterparts, was expressed in CHO-09 cells lacking endogenous EGFR. This receptor was found to activate PLC-gamma1, indicating that the IR TK domain, in situ, is able to tyrosine phosphorylate substrates normally used by the EGFR. These findings suggest that the IR TK domain, in situ, has a low specificity for selection and phosphorylation of non-cognate substrates.