Association of physiological stress markers at the emergency department to readmission and death within 90 days: a prospective observational study

Background

Predicting the risk of readmission or death in patients at the emergency department (ED) is essential in identifying patients who would benefit the most from interventions. We aimed to explore the prognostic value of mid-regional proadrenomedullin (MR-proADM), mid-regional pro-atrial natriuretic peptide (MR-proANP), copeptin, and high-sensitivity troponin T (hs-TnT) to identify patients with a higher risk of readmission and death among patients presenting with chest pain (CP) and/or shortness of breath (SOB) in the ED.

Methods

This single-center prospective observational study included non-critically ill adult patients with a chief complaint of CP and/or SOB who visited the ED at Linköping University Hospital. Baseline data and blood samples were collected, and patients were followed up for 90 days after inclusion. The primary outcome was a composite of readmission and/or death from non-traumatic causes within 90 days of inclusion. Binary logistic regression was used and receiver operating characteristics (ROC) curves were constructed to determine the prognostic performance for predicting readmission and/or death within 90 days.

Results

A total of 313 patients were included and 64 (20.4%) met the primary endpoint. MR-proADM > 0.75 pmol/L (odds ratio [OR]: 2.361 [95% confidence interval [CI]: 1.031 - 5.407], P = 0.042) and multimorbidity (OR: 2.647 [95% CI: 1.282 - 5.469], P = 0.009) were significantly associated with readmission and/or death within 90 days. MR-proADM increased predictive value in the ROC analysis to age, sex, and multimorbidity (P = 0.006).

Conclusions

In non-critically ill patients with CP and/or SOB in the ED, MR-proADM and multimorbidity may be helpful for the prediction of the risk of readmission and/or death within 90 days.

Copeptin in Growth Hormone-Treated Patients

Growth hormone (GH) changes body composition, including increasing body water. GH is known to have an anti-natriuretic effect in the kidney, but little is known of its effect on arginine-vasopressin (AVP) release. We studied the effect of GH on AVP release by measurement of copeptin, a fragment from the same precursor protein, in GH-treated patients with GH deficiency. The study was designed as a retrospective cohort study of biobank samples from 34 patients substituted with GH between 1999 and 2004. Copeptin and insulin-like growth factor 1 (IGF-1) results were compared with previously obtained data. An increase in IGF-1 and copeptin was seen at 3 and 6 months’ treatment compared to baseline. Between the 3 and 6 months follow up, copeptin levels were stable. There was a difference in HbA1c between 3 and 6 months (p < 0.01) and between baseline and 6 months (p = 0.042), with higher levels at 6 months. In addition, LDL levels were lower at the 6 months follow up (p = 0.046). The waist circumference at 3 months was lower (p = 0.02). To conclude, three months of GH treatment increased the levels of copeptin and the increase remained at 6 months. This could be a compensatory mechanism balancing the anti-natriuretic effect of GH treatment seen in previous studies.

Admission of patients with chest pain and/or breathlessness from the emergency department in relation to risk assessment and copeptin levels - an observational study

BACKGROUND

One of the most critical decisions that emergency department (ED) physicians make is the discharge versus admission of patients. We aimed to study the association of the decision in the ED to admit patients with chest pain and/or breathlessness to a ward with risk assessment using the Rapid Emergency Triage and Treatment System (RETTS), the National Early Warning Score (NEWS), and plasma levels of the biomarkers copeptin, midregional proadrenomedulin (MR-proADM), and midregional proatrial natriuretic peptide (MR-proANP).

METHODS

Patients presenting at the ED with chest pain and/or breathlessness with less than one week onset were enrolled. Patients were triaged according to RETTS. NEWS was calculated from the vital signs retrospectively.

RESULTS

Three hundred and thirty-four patients (167 males), mean age 63.8 ± 16.8 years, were included. Of which, 210 (62.8%) patients complained of chest pain, 65 (19.5%) of breathlessness, and 59 (17.7%) of both. Of these, 176 (52.7%) patients were admitted to a ward, and 158 (47.3%) patients were discharged from the ED. In binary logistic models, age, gender, vital signs (O₂ saturation and heart rate), NEWS class, and copeptin were associated with admission to a ward from the ED. In receiver-operating-characteristics (ROC) analysis, copeptin had an incremental predictive value compared to NEWS alone (P = 0.002).

CONCLUSIONS

Emergency physicians' decisions to admit patients with chest pain and/or breathlessness from the ED to a ward are related to age, O₂ saturation, heart rate, NEWS category, and copeptin. As an independent predictive marker for admission, early analysis of copeptin might be beneficial when improving patient pathways at the ED.

Plasma mid-regional pro-atrial natriuretic peptide predicts cardiovascular events in patients with type 2 diabetes independently of subclinical organ damage

AIM

The aim of this study was to investigate the association between plasma MR-proANP and cardiovascular disease (CVD) in a middle-aged population with type 2 diabetes.

METHODS

MR-proANP was measured in 690 patients with type 2 diabetes participating in the epidemiological study CARDIPP (Cardiovascular Risk Factors in Patients with Diabetes-a Prospective Study in Primary Care). The outcome variables were incident major adverse cardiovascular events (MACE) and all-cause mortality. Patients were followed using the national Swedish Cause of Death Registry and the Inpatient Register.

RESULTS

During the mean follow-up period of 10.8 years, MACE occurred in 111 patients and 102 patients died. The hazard ratio for an increment of MR-proANP of 1 pmol/l adjusted for sex, age, current smoking, previous CVD, HbA1c, serum cholesterol, eGFR, systolic blood pressure, C-reactive protein, aortic pulse wave velocity, left ventricular mass and intima media thickness in the carotid arteries was 1.007 (95% CI 1.000-1.013, P = 0.042) for MACE and 1.008 (95% CI 1.001-1.014, P = 0.017) for all-cause mortality.

CONCLUSIONS

Elevated MR-proANP levels predict an increased risk for MACE and all-cause mortality in patients with type 2 diabetes independently of CVD risk factors and markers for subclinical organ damage.

Toe brachial index predicts major acute cardiovascular events in patients with type 2 diabetes independently of arterial stiffness

OBJECTIVE

Our aim was to analyze the predictive value of toe brachial index (TBI) as a risk marker for future major adverse cardiovascular events (MACE) and all-cause mortality in patients with type 2 diabetes (T2D).

METHODS

TBI was measured in 741 patients with T2D in 2005-2008. Conventional risk factors for vascular disease as well as non-invasive measurements such as pulse-wave velocity (PWV) and intima-media thickness (IMT) of the carotid arteries were estimated. MACE was defined as cardiovascular death or hospitalization for non fatal myocardial infarction or non fatal stroke. Patients were followed for incidence of MACE using the national Swedish Cause of Death Registry and the Inpatient Register.

RESULTS

During the follow-up for a period of 9 years MACE occurred in 97 patients and 85 patients died. TBI tertile, 1 versus 3, was significantly related to MACE (HR 2.67, 95%CI 1.60-4.50; p < 0.001) and to all-cause mortality (HR 1.98, 95%CI 1.16-3.83; p = 0.01). TBI tertile 1 as compared to TBI tertile 3 predicted MACE, but not all-cause mortality, independently of age, sex, diabetes duration and treatment, antihypertensive treatment, previous cardiovascular diseases, office systolic blood pressure, HbA1c, LDL cholesterol, estimated glomerular filtration rate, body mass index, current smoking PWV, IMT and carotid plaque presence (HR 3.39, 95%CI 1.53-7.51; p = 0.003 and HR 1.81, 95%CI 0.87-3.76; p = 0.1, respectively).

CONCLUSIONS

Low TBI predicts an increased risk for MACE independently of arterial stiffness in patients with type 2 diabetes.

TRIAL REGISTRATION

Clinical Trials.gov number NCT01049737. Registered January 14, 2010.

Association of Insulin-like Growth Factor-1, Bone Mass and Inflammation to Low-energy Distal Radius Fractures and Fracture Healing in Elderly Women Attending Emergency Care

OBJECTIVE

Elderly patients suffer fractures through low-energy mechanisms. The distal radius is the most frequent fracture localization. Insulin-like growth factor-1 (IGF1) plays an important role in the maintenance of bone mass and its levels decline with advancing age and in states of malnutrition. Our aim was to investigate the association of IGF1 levels, bone mass, nutritional status, and inflammation to low-energy distal radius fractures and also study if fracture healing is influenced by IGF1, nutritional status, and inflammation.

METHODS

Postmenopausal women, 55 years or older, with low-energy distal radius fractures occurring due to falling on slippery ground, indoors or outdoors, were recruited in the emergency department (ED) and followed 1 and 5 weeks after the initial trauma with biomarkers for nutritional status and inflammation. Fractures were diagnosed according to standard procedure by physical examination and X-ray. All patients were conservatively treated with plaster casts in the ED. Patients who needed interventions were excluded from our study. Fracture healing was evaluated from radiographs. Fracture healing assessment was made with a five-point scale where the radiological assessment included callus formation, fracture line, and stage of union. Blood samples were taken within 24 h after fracture and analyzed in the routine laboratory. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA).

RESULTS

Thirty-eight Caucasian women, aged 70.5 ± 8.9 years (mean ± SD) old, were recruited. Nutritional status, as evaluated by albumin (40.3 ± 3.1 g/L), IGF1 (125.3 ± 39.9 μg/L), body mass index (26.9 ± 3.6 kg/m² ), arm diameter (28.9 ± 8.9 cm), and arm skinfold (2.5 ± 0.7 cm), was normal. A positive correlation was found between IGF1 at visit 1 and the lowest BMD for hip, spine, or radius (r = 0.39, P = 0.04). High sensitive C-reactive protein (hsCRP) and leukocytes were higher at the fracture event compared to 5 weeks later (P = 0.07 and P < 0.001, respectively). Fracture healing parameters (i.e. callus formation, fracture line, and stage of union) were positively correlated with the initial leukocyte count and to difference in thrombocyte count between visit 1 and 3.

CONCLUSIONS

In elderly women with low-energy distal radius fractures, an association between IGF1 and lowest measures of BMD was found, indicating that low IGF1 could be an indirect risk factor for fractures. Fracture healing was associated with initial leukocytosis and a lower thrombocyte count, suggesting that inflammation and thrombocytes are important components in fracture healing.

Insulin-Like Growth Factor-1 at Diagnosis and during Subsequent Years in Adolescents with Type 1 Diabetes

BACKGROUND

Type 1 diabetes (T1D) in adolescents is associated with alterations in the insulin-like factor system probably caused both by a deranged metabolism and insulinopenia in the portal vein.

OBJECTIVE

To study how the circulating IGF-1 is affected at diagnosis and during subsequent years in adolescents with T1D.

METHODS

Ten girls and ten boys with type 1 diabetes (T1D), aged 13.0 ± 1.4 (mean ± SD) years at diagnosis, took part in the study. Blood samples were drawn at diagnosis and after 3, 9, 18, and 48 months. HbA1c, total IGF-1, and C-peptide were measured.

RESULTS

At diagnosis, the patients had high HbA1c, low IGF-1, and measurable C-peptide. After the start of insulin treatment, maximal improvement in glycemic control and IGF-1 occurred within 3 months and then both tended to deteriorate, that is, HbA1c to increase and IGF-1 to decrease. C-peptide decreased with time, and after 4 years, half of the patients were C-peptide negative. At diagnosis, C-peptide correlated positively to IGF-1 (r = 0.50; p < 0.03). C-peptide correlated negatively with insulin dose (U/kg) after 18 and 48 months from diagnosis (r = -0.48; p < 0.03 and r = -0.72; p < 0.001, resp.).

CONCLUSIONS

In conclusion, our results show that in newly diagnosed adolescents with type 1 diabetes and deranged metabolism, the IGF-1 level is low and rapidly improves with insulin treatment but later tends to decrease concomitantly with declining endogenous insulin secretion.

Different Effects of Intraperitoneal and Subcutaneous Insulin Administration on the GH-IGF-1 Axis in Type 1 Diabetes

CONTEXT

In type 1 diabetes mellitus, low levels of insulin-like growth factor -1 (IGF-1) and IGF binding protein-3 (IGFBP-3) and high levels of GH and IGFBP-1 are present, probably due to portal vein insulinopenia.

OBJECTIVE

To test the hypothesis that continuous ip insulin infusion (CIPII) has a more pronounced effect than sc insulin therapy on regulation of the GH-IGF-1 axis.

DESIGN

This was a prospective, observational case-control study. Measurements were performed twice at a 26-week interval.

SETTING

Two secondary care hospitals in the Netherlands participated in the study.

PATIENTS

There were a total of 184 patients, age- and gender-matched, of which 39 used CIPII and 145 sc insulin therapy for the past 4 years.

OUTCOMES

Primary endpoint included differences in IGF-1. Secondary outcomes were differences in GH, IGFBP-1, and IGFBP-3.

RESULTS

IGF-1 was higher with CIPII as compared to SC insulin therapy: 124 μg/liter (95% confidence interval [CI], 111-138) vs 108 μg/liter (95% CI 102-115) (P = .035). Additionally, IGFBP-3 concentrations were higher and IGFBP-1 and GH concentrations were lower with CIPII as compared to SC insulin therapy: 3.78 mg/liter (95% CI, 3.49-4.10) vs 3.31 mg/liter (95% CI, 3.17-3.47) for IGFBP-3, 50.9 μg/liter (95% CI, 37.9-68.2) vs 102.6 μg/liter (95% CI, 87.8-119.8) for IGFBP-1 and 0.68 μg/liter (95% CI, 0.44-1.06) vs 1.21 μg/liter (95% CI, 0.95-1.54) for GH, respectively. In multivariate analysis, IGF-1 had no significant association with HbA1c.

CONCLUSIONS

The GH-IGF-1 axis may be affected by the route of insulin administration with CIPII counteracting dysregulation of the GH-IGF1 axis present during sc insulin therapy.

After 6years of intraperitoneal insulin administration IGF-I concentrations in T1DM patients are at low-normal level

OBJECTIVE

Low concentrations of insulin-like growth factor-I (IGFI) have been reported in type 1 diabetes mellitus (T1DM), suggested to be due to low insulin concentrations in the portal vein. The aim was to describe the long-term course of IGFI concentrations among T1DM subjects treated with continuous intraperitoneal (IP) insulin infusion (CIPII).

DESIGN

Nineteen patients that participated in a randomized cross-over trial comparing CIPII and subcutaneous (SC) insulin therapy in 2006 were followed until 2012. IGF-I measurements were performed at the start of the 2006 study, after the 6 month SC- and CIPII treatment phase in 2006 and during CIPII therapy in 2012. Z-scores were calculated to compare the IGF-I concentrations with age-specific normative range values of a non-DM reference population.

RESULTS

In 2012, IGF-I Z-scores (-0.7; 95% confidence interval -1.3, -0.2) were significantly higher than at the start of the 2006 study (-2.5; -3.3, -1.8), the end of the SC (-2.0; -2.6, -1.5) and CIPII (-1.6; -2.1, -1.0) treatment phase with a mean difference of: 1.8 (0.9, 2.7), 1.3 (0.5, 2.1) and 0.8 (0.1, 1.6), respectively.

CONCLUSION

After 6 years of treatment with CIPII, IGF-I concentrations among T1DM patients increased to a level that is higher than during prior SC insulin treatment and is in the lower normal range compared to a non-DM reference population. The results of this study suggest that long-term IP insulin administration influences the IGF system in T1DM.

Insulin and IGF1 receptors in human cardiac microvascular endothelial cells: metabolic, mitogenic and anti-inflammatory effects

Diabetes is associated with microcirculatory dysfunction and heart failure and changes in insulin and IGF1 levels. Whether human cardiac microvascular endothelial cells (HMVEC-Cs) are sensitive to insulin and/or IGF1 is not known. We studied the role of insulin receptors (IRs) and IGF1 receptors (IGF1Rs) in metabolic, mitogenic and anti-inflammatory responses to insulin and IGF1 in HMVEC-Cs and human umbilical vein endothelial cells (HUVECs). IR and IGF1R gene expression was studied using real-time RT-PCR. Receptor protein expression and phosphorylation were determined by western blot and ELISA. Metabolic and mitogenic effects were measured as glucose accumulation and thymidine incorporation. An E-selectin ELISA was used to investigate inflammatory responses. According to gene expression and protein in HMVEC-Cs and HUVECs, IGF1R is more abundant than IR. Immunoprecipitation with anti-IGF1R antibody and immunoblotting with anti-IR antibody and vice versa, showed insulin/IGF1 hybrid receptors in HMVEC-Cs. IGF1 at a concentration of 10(-8) mol/l significantly stimulated phosphorylation of both IGF1R and IR in HMVEC-Cs. In HUVECs IGF1 10(-8) mol/l phosphorylated IGF1R. IGF1 stimulated DNA synthesis at 10(-8) mol/l and glucose accumulation at 10(-7) mol/l in HMVEC-Cs. TNF-α dramatically increased E-selectin expression, but no inflammatory or anti-inflammatory effects of insulin, IGF1 or high glucose were seen. We conclude that HMVEC-Cs express more IGF1Rs than IRs, and mainly react to IGF1 due to the predominance of IGF1Rs and insulin/IGF1 hybrid receptors. TNF-α has a pronounced pro-inflammatory effect in HMVEC-Cs, which is not counteracted by insulin or IGF1.

Increased IGF1 levels in relation to heart failure and cardiovascular mortality in an elderly population: impact of ACE inhibitors

OBJECTIVE

There are conflicting results regarding the association of circulating IGF1 with cardiovascular (CV) morbidity and mortality. We assessed the relationship between IGF1 levels and heart failure (HF), ischemic heart disease (IHD), and CV mortality in an elderly population taking into account the possible impact of angiotensin converting enzyme (ACE) inhibitors.

DESIGN AND METHODS

A total of 851 persons aged 66-81 years, in a rural Swedish municipality, were subjected to medical history, clinical examination, electrocardiography, echocardiography, and fasting plasma samples. They were then followed for 8 years.

RESULTS AND CONCLUSION

Patients on ACE inhibitors had higher IGF1 levels compared with those without ACE inhibitors. In patients on ACE inhibitors, higher IGF1 values were found in patients with an ejection fraction (EF) <40% compared with EF ≥40%, in patients with higher proBNP levels in quartile 4 vs 1, and in patients with IHD when compared to those without ACE inhibitors (P<0.001). In patients without ACE inhibitors, no relationship was found between IGF1 levels and HF or IHD. In multivariate regression, only ACE inhibitors, ECG changes characteristic for IHD, and gender had a significant impact on IGF1. Patients with higher IGF1 levels in quintiles 4 and 5 compared to quintiles 1 and 2 had a 50% higher risk for CV death (P=0.03). This was significant after adjustment for well-known CV risk factors and ACE inhibitors (P=0.03).

CONCLUSIONS

Our results show that treatment with ACE inhibitors in an elderly population is associated with increased IGF1 levels, especially in patients with impaired cardiac function or IHD. High IGF1 levels tend to be associated with an increased risk for CV mortality.

Human aortic smooth muscle cells are insulin resistant at the receptor level but sensitive to IGF1 and IGF2

Whether insulin, at physiological concentrations, has direct effects on vascular smooth muscle cells (VSMCs) remains controversial. Our aim was to characterize the mechanism for insulin resistance in VSMCs. For comparison, the effects of IGF1 and IGF2 were also studied. Cultured human aortic smooth muscle cells (HASMC) were used. Receptor mRNA was analyzed by quantitative reverse transcription PCR and receptor protein by ELISA and western blot. Biological effects were studied by thymidine incorporation and glucose accumulation. In HASMC, both mRNA and protein expression of IGF1 receptors (IGF1R) were fivefold higher compared to insulin receptor (IR). IR isoform A mRNA was 13-fold more expressed than IR isoform B. IR and IGF1R co-precipitated, indicating the presence of hybrid IR/IGF1R. Phosphorylation of the IGF1R beta-subunit was obtained by IGF1 10(-9)-10(-8) mol/l and IGF2 10(-8) mol/l. IR beta-subunit was phosphorylated by IGF1 10(-8) mol/l but not by insulin. IGF1 stimulated IR substrate-1 and AKT at 10(-8) mol/l and extracellular signal-regulated kinases 1 and 2 at 10(-9)-10(-8) mol/l respectively. IGF1 and 2 at a concentration of 10(-8)-10(-7) mol/l significantly stimulated (3)H-thymidine incorporation, whereas insulin did not. (14)C-Glucose accumulation was stimulated by IGF1 or IGF2 10(-8)-10(-7) mol/l, and also by insulin 10(-7) mol/l. Our results suggest that IGF1R and hybrid IR/IGF1R are activated by physiological concentrations of IGF1 and 2 in HASMC and this propagates downstream signaling and biological effects, while insulin has no effect on its receptor or downstream signaling probably due to a preponderance of IGF1R and incorporation of IR into hybrid IR/IGF1R.

Differential lipid profile and hormonal response in type 2 diabetes by exogenous insulin aspart versus the insulin secretagogue repaglinide, at the same glycemic control

Our aim was to study, at the same glycemic control, how treatment with either the insulin secretagogue repaglinide or exogenous insulin aspart affects endogenous insulin secretion, plasma insulin and IAPP (islet amyloid polypeptide) levels, GH-IGF (growth hormone-insulin-like growth factor) axis and plasma lipoprotein concentrations in patients with type 2 diabetes. Five patients, age 65.0+/-4.1 years (mean+/-SE), body weight 82.5+/-5.0 kg, BMI (body mass index) 27.7+/-1.5 kg/m(2) were treated for 10 weeks with repaglinide or insulin aspart in a randomized, cross-over study. At the end of each treatment a 24-h metabolic profile was performed. Blood glucose, C-peptide, free human insulin, free total (human and analogue) insulin, proinsulin, IAPP, IGF-I, IGFBP-1 (IGF binding protein-1), GHBP (growth hormone binding protein) and plasma lipoprotein concentrations were measured. Similar 24-h blood glucose profiles were obtained with repaglinide and insulin aspart treatment. During the repaglinide treatment, the meal related peaks of C-peptide and free human insulin were about twofold higher than during treatment with insulin aspart. Proinsulin, GHBP were higher and IAPP levels tended to be higher during repaglinide compared to insulin aspart. Postprandial plasma total cholesterol, triglycerides and apolipoprotein B concentrations were higher on repaglinide than on insulin aspart treatment. Our results show that, at the same glycemic control, treatment with exogenous insulin aspart in comparison with the insulin secretagogue repaglinide result in a lower endogenous insulin secretion, and a tendency towards a less atherogenic postprandial lipid profile.

Human microvascular endothelial cells are sensitive to IGF-I but resistant to insulin at the receptor level

Human microvascular endothelial cells (HMVEC) are sensitive to IGF-I but insulin resistant and express several times more IGF-I receptors (IGF-IR) than insulin receptors (IR). Our aim was to investigate the mechanism of this insulin resistance in cultured HMVEC by studying receptor activation and signal propagation downstream. The IGF-IR beta-subunit and the IR beta-subunit were detected and found to co-precipitate. IRA was the major IR isoform expressed in HMVEC. IGF-I 10(-9) to 10(-8)M phosphorylated its cognate receptor beta-subunit. IGF-I also phosphorylated the IR beta-subunit at 10(-9)M. Phosphorylation of insulin receptor substrate 1 was obtained by IGF-I 10(-9) to 10(-8)M. Akt was phosphorylated by IGF-I at 10(-8) to 10(-7)M and by insulin 10(-7)M. IGF-I at 10(-8) to 10(-6)M significantly increased DNA-synthesis. We conclude that microvascular endothelial cells are sensitive to IGF-I but resistant to insulin due to a preponderance of IGF-I receptors and sequestration of insulin receptors into insulin/IGF-I hybrid receptors.

Characterisation of receptors for IGF-I and insulin; evidence for hybrid insulin/IGF-I receptor in human coronary artery endothelial cells

OBJECTIVE

Coronary artery disease is a prevalent cause of morbidity and mortality in diabetes. Little is known about insulin-like growth factor-I receptors (IGF-IR) and insulin receptors (IR) in human coronary endothelium. Our aim was to characterize IGF-IR and IR in human coronary artery endothelial cells (HCAEC).

DESIGN

Cultured human coronary artery endothelial cells were used. Gene expression was measured by quantitative real-time RT-PCR analysis and receptor affinity by ligand binding. Receptor protein, phosphorylation of IGF-IR and IR beta-subunit as well as the presence of hybrid insulin receptor/Insulin-like growth factor-I receptor (Hybrid IR/IGF-IR) was analyzed by immunoprecipitation and Western blot. Postreceptor effects of insulin and IGF-I were assed by (3)H-thymidine incorporation.

RESULTS

The gene expression of IGF-IR was several folds higher than that of IR. and insulin receptor isoform A (IR-A) was 20-fold more expressed than insulin receptor isoform B (IR-B) in HCAEC. The specific binding of (125)I-IGF-I was higher than that of (125)I-insulin. Insulin and the new long acting insulin analog, glargine, interacted with the IGF-IR with over thousand and 100-fold less potency than IGF-I itself, whereas IGF-II had 6 times lower potency than IGF-I. Phosphorylation of the IGF-IR beta-subunit was obtained by concentrations of 10(-10)-10(-8)M IGF-I, 10(-6)M of insulin, inconsistently by 10(-8)M insulin and not at all by 10(-10)-10(-9)M insulin. The IR beta-subunit was phosphorylated by insulin and IGF-I at concentrations of 10(-9)-10(-8)M. When immunoprecipitating with specific monoclonal anti-IR or anti-IGF-IR alpha-subunit antibodies we found bands situated in slightly different positions suggesting the presence of Hybrid IR/IGF-IR. IGF-I, IGF-II and insulin (10(-9)-10(-7)M) had no significant effect on (3)H-thymidine incorporation into DNA.

CONCLUSIONS

Human coronary endothelial cells express more IGF-IR than IR, mainly IR-A, and also Hybrid IR/IGF-IR. Both IGF-I and insulin phosphorylate their receptors, but only IGF-I seems to phosphorylate Hybrid IR/IGF-IR. Our study provides experimental evidence for a possible role of IGF-IR, IR and Hybrid IR/IGF-IR in human coronary artery endothelial cells.

Expression and function of receptors for insulin-like growth factor-I and insulin in human coronary artery smooth muscle cells

AIMS/HYPOTHESIS

Hyperinsulinaemia and insulin resistance, as well as low IGF-I, have been implicated in the pathogenesis of cardiovascular disease. Little is known about direct effects of IGF-I and insulin on human coronary artery smooth muscle cells (HCASMCs). Our aim was to characterise the expression and function of IGF-I receptor (IGF-IR) and insulin receptor (IR) in HCASMCs.

MATERIALS AND METHODS

Cultured HCASMCs were used. mRNA expression was measured by quantitative real-time RT-PCR analysis. Receptor proteins, phosphorylation of beta-subunits and the presence of hybrid IR/IGF-IR were analysed by immunoprecipitation and western blotting. DNA synthesis and glucose metabolism were assessed using [3H]thymidine incorporation and D-[U-14C]glucose accumulation respectively.

RESULTS

The mRNA expression of IGF-IR was approximately eight-fold higher than that of IR in HCASMCs. The presence of IGF-IR and IR could be demonstrated by immunoprecipitation and western blot analysis. Phosphorylation of the IGF-IR beta-subunit was obtained by IGF-I at 10(-10)-10(-8) mol/l and insulin at 10(-8) mol/l. Insulin and IGF-I at 10(-10)-10(-9) mol/l phosphorylated the IR beta-subunit. When immunoprecipitated with monoclonal anti-IR alpha-subunit or IGF-IR alpha-subunit antibodies, we found bands in slightly different positions, suggesting the presence of hybrid IR/IGF-IR. IGF-I at 10(-9)-10(-8) mol/l significantly stimulated [3H]thymidine incorporation and at a concentration of 10(-9)-10(-7) mol/l also D-[U-14C]glucose accumulation in HCASMCs. Insulin at 10(-9)-10(-7) mol/l had no effect on DNA synthesis, but increased glucose accumulation at 10(-7) mol/l.

CONCLUSIONS/INTERPRETATION

Our study provides experimental evidence that IGF-IR and possibly hybrid IR/IGF-IR play a role in HCASMCs.

IGF-I/insulin hybrid receptors in human endothelial cells

Vascular complications are common in diabetes. IGF-I receptors (IGF-IR) and insulin receptors (IR) in endothelial cells might respond to altered levels of IGF-I and insulin, resulting in altered endothelial function in diabetes. We therefore studied IGF-IR and IR gene expression, ligand binding, receptor protein, and phosphorylation in human umbilical vein endothelial cells (HUVEC). IGF-IR mRNA was more abundant than IR mRNA in freshly isolated HUVEC (IGF-IR/IR ratio 7.1 +/- 1.5) and in cultured HUVEC (ratio 3.5 +/- 0.51). Accordingly, specific binding of (125)I-IGF-I (0.64 +/- 0.25%) was higher than that of (125)I-insulin (0.25 +/- 0.09%). Protein was detected for both receptors and IGF-I/insulin hybrid receptors. IGF-IR phosphorylation was stimulated by 10(-10) to 10(-8) M IGF-I. IR were activated by 10(-9) to 10(-8) M insulin and IGF-I. We conclude that HUVEC express more IGF-IR than IR, and also express hybrid receptors. Both IGF-I and insulin phosphorylate their own receptors but only IGF-I seems to phosphorylate hybrid receptors.

Insulin-like growth factor I receptors are more abundant than insulin receptors in human micro- and macrovascular endothelial cells

Micro- and macroangiopathy are major causes of morbidity and mortality in patients with diabetes. Our aim was to characterize IGF-I receptor (IGF-IR) and insulin receptor (IR) in human micro- and macrovascular endothelial cells. Cultured human dermal microvascular endothelial cells (HMVEC) and human aortic endothelial cells (HAEC) were used. Gene expression was measured by quantitative real-time RT-PCR and receptor protein by ligand-binding assay. Phosphorylation of IGF-IR beta-subunit was analyzed by immunoprecipitation and Western blot. Glucose metabolism and DNA synthesis was assessed using [(3)H]glucose and [(3)H]thymidine incorporation, respectively. We detected gene expression of IGF-IR and IR in HAEC and HMVEC. IGF-IR gene expression was severalfold higher than that of IR. The specific binding of (125)I-IGF-I was higher than that of (125)I-insulin in HAEC and HMVEC. Insulin and the new, long-acting insulin analog glargine interacted with the IGF-IR with thousand- and hundred-fold less potency than IGF-I itself. Phosphorylation of the IGF-IR beta-subunit was shown in HAEC for IGF-I (10(-8) M) and insulin (10(-6) M) and in HMVEC for IGF-I and glargine (10(-8) M, 10(-6) M). IGF-I 10(-7) M stimulated incorporation of [(3)H]thymidine into DNA, and 10(-9)-10(-7) M also the incorporation of [(3)H]glucose in HMVEC, whereas glargine and insulin had no significant effects at 10(-9)-10(-7) M. Human micro- and macrovascular endothelial cells express more IGF-IR than IR. IGF-I and high concentrations of glargine and insulin activates the IGF-IR. Glargine has a higher affinity than insulin for the IGF-IR but probably has no effect on DNA synthesis at concentrations reached in vivo.