Clinical outcomes and predictors of success with Impella weaning in cardiogenic shock: a single-center experience

Introduction

Cardiogenic shock (CS) is a severe syndrome with poor prognosis. Short-term mechanical circulatory support with Impella devices has emerged as an increasingly therapeutic option, unloading the failing left ventricle (LV) and improving hemodynamic status of affected patients. Impella devices should be used for the shortest time necessary to allow LV recovery because of time-dependent device-related adverse events. The weaning from Impella, however, is mostly performed in the absence of established guidelines, mainly based on the experience of the individual centres.

Methods

The aim of this single center study was to retrospectively evaluate whether a multiparametrical assessment before and during Impella weaning could predict successful weaning. The primary study outcome was death occurring during Impella weaning and secondary endpoints included assessment of in-hospital outcomes.

Results

Of a total of 45 patients (median age, 60 [51-66] years, 73% male) treated with an Impella device, 37 patients underwent impella weaning/removal and 9 patients (20%) died after the weaning. Non-survivors patients after impella weaning more commonly had a previous history of known heart failure (p = 0.054) and an implanted ICD-CRT (p = 0.01), and were more frequently treated with continuous renal replacement therapy (p = 0.02). In univariable logistic regression analysis, lactates variation (%) during the first 12-24 h of weaning, lactate value after 24 h of weaning, left ventricular ejection fraction (LVEF) at the beginning of weaning, and inotropic score after 24 h from weaning beginning were associated with death. Stepwise multivariable logistic regression identified LVEF at the beginning of weaning and lactates variation (%) in the first 12-24 h from weaning beginning as the most accurate predictors of death after weaning. The ROC analysis indicated 80% accuracy (95% confidence interval = 64%-96%) using the two variables in combination to predict death after weaning from Impella.

Conclusions

This single-center experience on Impella weaning in CS showed that two easily accessible parameters as LVEF at the beginning of weaning and lactates variation (%) in the first 12-24 h from weaning begin were the most accurate predictors of death after weaning.

Momordica cochinchinensis (Gấc) Seed Extracts Induce Apoptosis and Necrosis in Melanoma Cells

Momordica cochinchinensis is a herbal medicine used throughout Asia and this study investigated the antimelanoma potentials and molecular mechanisms of M. cochinchinensis seed with emphasis on extraction to optimise bioactivity. Overall, the aqueous extract was superior, with a wider diversity and higher concentration of proteins and peptides that was more cytotoxic to the melanoma cells than other extraction solvents. The IC50 of the aqueous extract on melanoma cells were similar to treatment with current anticancer drugs, vemurafenib and cisplatin. This cytotoxicity was cancer-specific with lower cytotoxic effects on HaCaT epidermal keratinocytes. Cytotoxicity correlated with MAPK signalling pathways leading to apoptosis and necrosis induced by triggering tumour necrosis factor receptor-1 (TNFR1), reducing the expression of nuclear factor kappa B (NF-kB), and suppression of BRAF/MEK. This efficacy of M. cochinchinensis seed extracts on melanoma cells provides a platform for future clinical trials as potent adjunctive therapy for metastatic melanoma.

Phytochemical Constituents and Derivatives of Cannabis sativa; Bridging the Gap in Melanoma Treatment

Melanoma is deadly, physically impairing, and has ongoing treatment deficiencies. Current treatment regimens include surgery, targeted kinase inhibitors, immunotherapy, and combined approaches. Each of these treatments face pitfalls, with diminutive five-year survival in patients with advanced metastatic invasion of lymph and secondary organ tissues. Polyphenolic compounds, including cannabinoids, terpenoids, and flavonoids; both natural and synthetic, have emerging evidence of nutraceutical, cosmetic and pharmacological potential, including specific anti-cancer, anti-inflammatory, and palliative utility. Cannabis sativa is a wellspring of medicinal compounds whose direct and adjunctive application may offer considerable relief for melanoma suffers worldwide. This review aims to address the diverse applications of C. sativa's biocompounds in the scope of melanoma and suggest it as a strong candidate for ongoing pharmacological evaluation.

Ultrasound-Stimulated Microbubbles Enhance Radiation-Induced Cell Killing

Recent in vivo studies using ultrasound-stimulated microbubbles as a localized radiosensitizer have had impressive results. While in vitro studies have also obtained similar results using human umbilical vein endothelial cells (HUVEC), studies using other cell lines have had varying results. This study was aimed at investigating any increases in radiation-induced cell killing in vitro using two carcinoma lines not previously investigated before (metastatic follicular thyroid carcinoma cells [FTC-238] and non-small cell lung carcinoma cells [NCI-H727]), in addition to HUVEC. Cells were treated using a combination of 1.6% (v/v) microbubbles, ∼90 s of 2-MHz ultrasound (mechanical index = 0.8) and 0-6 Gy of kilovolt or MV X-rays. Cell viability assays obtained 72 h post-treatment were normalized to untreated controls, and analysis of variance was used to determine statistical significance. All cells treated with combined ultrasound-stimulated microbubbles and radiation exhibited decreased normalized survival, with statistically significant effects observed for the NCI-H727 cells. No statistically significant differences in effects were observed using kV compared with MV radiation. Further studies using increased microbubble concentrations may be required to achieve statistically significant results for the FTC-238 and HUVEC lines.

Temporal trend mortality and in-hospital mortality predictors in an ischemic cardiogenic shock population: a 10 years single-centre retrospective study

Background

Cardiogenic shock (CS) after acute myocardial infarction (AMI) is a life-threatening condition with an high rate of in-hospital mortality.

Purpose

This study aims to 1) describe predictors of in-hospital mortality; 2) evaluate ten years mortality temporal trend in our Cardiac Intensive Care Unit (CICU); 3) assess the feasibility of CARDSHOCK risk score in our population; 4) elaborate a simpler version of CARDSHOCK risk score.

Methods

All consecutive patients with CS after AMI admitted at our CICU from March 2012 to July 2021 were included in this single-centre retrospective study.

Results

We included 167 patients [males 67%; age 71 (61–80) years] with ischemic CS. Patients had severe LV dysfunction in 66%. Baseline serum lactate was 5.2 (3.1–8.8) mmol/L. All patients required inotropes: 71% required dopamine [mean dose 5.6 (2.4–11,3) mcg/kg/min], 65% required noradrenaline [mean dose 0.10 (0.05–0.18) mcg/kg/min], 32% required dobutamine [mean dose 4.5 (2.2–15.9) mcg/kg/min]; 17.4% received levosimendan alone [mean dose 0.1 mcg/kg/min]. Mechanical cardiac support (MCS) was pursued in 91.1% [65% IABP, 23% Impella CP, 4% VA-ECMO]. From March 2012 to July 2021 we observed a significative temporal trend mortality reduction (OR=0.90, 95% CI: 0.84–0.96, p=0.0015), in particular in-hospital mortality has reduced from 57% of first time-quartile to 29% of the fourth quartile (Figure 1). In addition we also noted a significant increase in Impella catheter use (p=0.0005) with a consequent reduction of IABP (p=0.01), a reduction in dopamine administration (p=0.0007) and a greater use of dobutamine and levosimendan (p=0.015 and p=0.0001). In our population of AMI-CS patients CARDSHOCK risk score was a reliable in-hospital mortality predictor tool (OR 1.11; 95% CI, 1.06–1.17; p=0.00011). After the multivariate analysis only ejection fraction (EF) at baseline (OR=0.99, 95% CI: 0.98–0.99, p=0.009), lactate level at presentation (OR=1.03, 95% CI: 1.01–1.06, p=0.015) and presence of three-vessels coronary artery disease (OR=0.73, 95% CI: 0.59–0.90, p=0.0038) resulted to be in-hospital mortality predictors. For this reason, a prediction model composed by those three variables was created which exhibited better predictive performance for in-hospital mortality than Cardshock risk score (AUC of 0.94 vs AUC of 0.72 respectively, p=0.015) (Figure 2).

Conclusions

In our retrospective single-centre study a significant reduction of mortality through the years is observed, probably due to more extensive use of micro axial pumps and better manipulation of inotropic drug therapies. The use of Cardshock risk score has been proven to be a feasible tool in prediction on in-hospital mortality also in our sample composed only of AMI-CS patients. In addition, a more simplified risk score made up of only three clinical variables demonstrates at least the same predictive performance. Future validation in a larger population could be advisable to validate the simplified score.

Funding Acknowledgement

Type of funding sources: None.

P370 INNOVATIVE TELEMONITORED MODEL OF PHYSICAL EXERCISE PRESCRIPTION IN SECONDARY PREVENTION DURING THE QUARANTINE

Introduction

COVID–19 pandemic induced the emanation of extraordinary measures like quarantine, that can be considered a risk factor for both physical and mental health in the population. In particular, gym’s closure and the need to stay home didn’t allow people to perform physical activity easily, with a consequent worsening of cardiovascular risk factors. During quarantine some general recommendations have been disseminated, but little is known about specific guidelines for home–based exercise prescription in patients with cardiovascular disease. Therefore, the purpose of this study is to develop home–based physical exercise programs for cardiac patients referred to the Center for Exercise Science and Sports of University of Ferrara.

Methods

On the basis of exercise capacity obtained from the last functional evaluation, performed in presence before the closure, three structured workouts were realized following the guidelines. They are composed as follows: warm–up, strenght and balance exercises alternate to indoor walking, cool–down. Patients received an explicative iconographic via e–mail or smartphone. Some domiciliary sessions were supervised by an operator through video connection.

Results

All patients showed excellent compliance with the proposed program. Adherence has been verified through biweekly recalls. No adverse events occurred.

Conclusions

Telemonitored exercise prescription in cardiac outpatients was effective and safe, helping to prevent negative consequences of the abrupt cessation of physical activity due to COVID–19 pandemic. These evidence could be useful even after the end of pandemic, for all those patients that are less likely to participate in traditional cardiovascular rehabilitation programs because of difficulties in reaching facilities or leaving home.

P401 REMOTE COUNSELING ROLE DURING COVID–19 PANDEMIC IN SECONDARY PREVENTION AFTER ACUTE CORONARY SYNDROME

Introduction

Patients affected by acute coronary syndrome are usually referred to center–based secondary prevention programs where they are enrolled in physical activity programs and received indications about cardiovascular risk factors control. COVID–19 pandemic induced the emanation of restrictions in people’s mobility, ban on gathering and the obligation of social distancing. This made it difficult to maintain such group meetings in presence.

Methods

After hospitalization for acute coronary syndrome in Cardiology Unit of the AUSL of Ferrara, patients equipped with electronic devices were allowed to participate to remote counseling meetings on the digital platform LifesizeC. To improve participation, meetings were organized monthly (in order to gradually include new discharged patients) and involving caregivers (if patients weren’t able to access the web app). Information on regular physical activity benefits were provided. In particular, the F.I.T.T. principle (Frequency, Intensity, Type, Time) has been explained and Borg’s exertion scale was illustrated to be used in autonomy. Furthermore, there were provided recommendations about the need of a proper warm– up/cool–down, the possibility to wear a heart rate monitor and the early recognition of symptoms and warning signs. To complete health education, there were given information about correct nutrition, risk factors control and correct assumption of pharmacological therapy.

Results

All patients showed interest in the topics analyzed, asking various questions during the meetings. They also stated that they were strongly motivated to undertake regular physical activity having received convincing explanations on its usefulness and safety.

Conclusions

Remote counseling meetings obtained a high approval rating and the moments of discussion with the speakers were particularly well attended. The prescription of physical exercise in secondary prevention can follow innovative telemonitored approaches, which could be maintained even after COVID–19.

P422 EARLY EXERCISE PRESCRIPTION AFTER ACUTE CORONARY SINDROME. A NEW MODEL FROM BEDSIDE TO THE COMMUNITY

Purpose

Physical inactivity is a major risk factor and negative prognostic index of cardiovascular disease. It is necessary to define effective strategies to direct patients after an acute coronary syndrome (ACS) to physically active lifestyle. The aim of this study was to examin efficacy, feasibility and long term adherence of a new physical activity prescription, adapted to patients (pts) early after ACS.

Methods

34 pts, mean age 67years, hospitalized for ACS, were enrolled consecutively and randomized 2:1 in treatment (TR) group (n = 23) or in control (CT) group. All pts were evaluated before discharge from hospital (T0) through Quality of Life (QoL) SF12 questionnaire, determination of physical activity during free time, six–minute walking test (6MWT). All pts were orally advised about the importance of changing life–style as recommended by current international guidelines. At T0, pts in the TR group performed a 500m moderate and perceptually–regulated (11–13 on the 6–20 Borg scale) treadmill walking test (500–m TWT) to estimate peak oxygen uptake (VO2peak). A home–based physical activity based on walking, was provided to pts in the TR group: it was recommended to maintain the level of perceived intensity of effort as indicated during 500m–TWT. These pts also received a reinforce phone–call at 2 and 4 weeks (T1 and T2), that allowed monitoring the adherence to the programme. All pts were finally evaluated 8 weeks after enrollment (T3) through the same tests performed at T0.

Results

Pts of the TR group at T3 reported significative improvement, compared to T0, in 6MWT (+79 m, p < 0.001), QoL (expressed in the items of SF12), usual physical activity during free time (+13MET/h/week, p < 0.001), VO2peak (+4 mL/kg/min, p < 0.001). Compliance to the programme resulted optimal since all TR group pts continued the planned physical activity for all the follow–up.

Conclusions

Results of this study on efficacy, feasibility and compliance of a new model of secondary prevention programme, suggest the importance of implementing programmes of tailored physical activity schedules, based on walking, that can be safetly started soon after clinical stabilization of ACS.

Adherence to a guided walking program with amelioration of cognitive functions in subjects with schizophrenia even during COVID-19 pandemic

Background

Aim of the study was to enrol a group of individuals with schizophrenia in a long-term moderate-intensity physical activity program and to evaluate its effects on their cognitive functions and cardiovascular risk factors. An additional aim of the study was the comparison of the adherence to the physical activity program before and during the COVID-19 pandemic.

Methods

Forty sedentary patients diagnosed with schizophrenia (mean age 46.4 ± 9.6) followed by the Public Mental Health Department of Ferrara were included in the study. 28 of them followed a 1-year walking program consisting of two guided walking sessions/week, while 12 maintained their sedentary lifestyle and followed the usual Cognitive Rehabilitation program. To the participants following the walking program VO₂ peak and walking speed were assessed at baseline and at the end of the program. All participants were evaluated on blood pressure and anthropometric variable. Cognitive functions were assessed with the Screen for Cognitive Impairment in Psychiatry (SCIP) and with the Frontal Assessment Battery (FAB) questionnaires.

Results

The 20 participants completing the walking program displayed significant improvements in cognitive functions (d_ppc2 0.35 for SCIP and 0.26 for FAB), with a positive correlation between SCIP score and the number of sessions attended (R = 0.86, p < 0.001), evident in the patients attending to at least 75 of the 100 walking sessions. Walking speed and VO₂peak increased significantly and a decrease of body weight, BMI, systolic and diastolic blood pressure was also observed. The adherence to the walking program registered during Covid-19 period did not differ from that observed before the pandemic. The 12 CG (Control Group) patients maintaining the sedentary lifestyle did not display improvements of cognitive functions.

Conclusions

The main finding of this study is the improvement of cognitive functions which is significantly related to the number of walking sessions attended by participants with schizophrenia. The walking program, guided by exercise specialists, proved to be an enjoyable activity for people with mental disorder feasible even during the COVID-19 pandemic.

Trial registration Retrospectively registered on ISRCTN as non-randomized trial (n. ISRCTN14763786).

Sex sub analysis from observational multicenter registry of patients treated with Impella mechanical circulatory support device in Italy: the IMP-IT women

Background

Women-specific data on safety, effectiveness, and outcomes for mechanical support in the setting of cardiogenic shock (CS) and high-risk percutaneous coronary intervention (HR-PCI) are still unsettled. The IMP-IT study was a multicenter observational national registry that enrolled all patients treated with Impella 2.5, Impella CP, Impella 5.0 and Impella RP, both for CS and HR-PCI indications, across 17 Italian centers from 2004 to June 2018

Purpose

To analyze the characteristics of female population enrolled in IMP-IT registry and to assess differences in presentation, timing to interventions and outcomes between men and women.

Methods

The Women-IMP-IT study is a multicenter observational national registry focusing on female population enrolled in IMP-IT study. Baseline, procedural and hemodynamics characteristics, such as outcome were collected. Differences between men and women were examined.

Results

Mean age of female population was 66.9±16.1 years, Body mass index was 26.3±5.5 kg/m2. There was a higher rate of cardiogenic shock (66.7% vs. 49.1%; p=0.06), NSTEMI (18% vs 9%, p=0.03) and acute myocarditis (9.6% vs 1.4%, p=0.01) in women vs men, associated with a lower rate of protected PCI (33.3% vs 50.9%, p=0.06). We did not observed a statistically difference in device related complications (27.4% vs 23.3%; p=0.50), respectively in women compared to men. In particular, no differences were observed in access site bleedings (10.8% vs 9%; p=0.70) and life threatening or severe bleeding (15.3% vs 11.4%; p=0.40). At one year, all-cause death rate was 45.1% in women vs 30.1% in men (p=0.016), and cardiac death rate was 42.5% in women and 27.5% in men (p=0.013). At 1-year no significant difference was observed in the rate of myocardial infarction (3.7% vs 2.3%; p=0.44), stroke (3.7% vs 2.6%; p=0.70), heat-failure hospitalization (7.7% vs 7.5%; p=1.0), need for left ventricular assist device or heart transplantation (1.3% vs 5.5%; p=0.21).

Conclusions

In our series, use of Impella is CS and HR-PCI is increasing in female population. Sex-differences in mortality are mostly explained by clinical differences at presentation.

Funding Acknowledgement

Type of funding source: Private grant(s) and/or Sponsorship. Main funding source(s): EAPCI Education and Training Grants

Differential Effects on Haemostatic Markers by Metformin and the Contraceptive Pill: A Randomized Comparative Trial in PCOS

Background Polycystic ovarian syndrome (PCOS) affects up to 18% of reproductive-aged women with increased risks of cardiovascular disease and venous thromboembolic disease, related to metabolic and hormonal features, obesity and an apparent hypofibrinolytic state, possibly exacerbated by current PCOS treatments.

Objective To investigate and compare haemostatic impacts of common pharmacological treatments and explore relationships with hormonal and metabolic variables in PCOS.

Patients/Methods This mechanistic sub-study using biobanked samples from a 6-month randomized comparative trial of pharmacological treatments assessed pro- and anti-thrombotic markers and overall haemostatic activity. Overweight women of mean age 33.9 ± 6.7 years and mean BMI (body mass index) of 36.5 ± 7.0 kg/m2 with PCOS (n = 60) were randomized to either metformin, higher-dose oral contraceptive pill (OCP) or low-dose OCP + spironolactone (OCP + S). Primary outcome measures included changes in plasminogen activator inhibitor 1 (PAI-1), asymmetric dimethylarginine (ADMA), prothrombin fragments 1 and 2 (PF1 and 2), plasminogen, tissue plasminogen activator (tPA), thrombin activatable fibrinolysis inhibitor (TAFI) and thrombin generation (TG).

Results PAI-1 activity fell in all groups, ADMA fell in higher-dose OCP, PF1 and 2 increased with metformin and higher-dose OCP, TG rose and tPA fell in both OCP groups, plasminogen increased in all and TAFI increased after higher-dose OCP.

Conclusion Endothelial function (primary haemostasis) improved with higher dose with some improvement in low-dose OCP + S and metformin. Aberrant coagulation was noted in both OCP groups, but not with metformin. Fibrinolysis was reduced with higher-dose OCP. Our work suggests an additional dimension of treatment (haemostatic system effects) that favours metformin treatment over the OCP in PCOS.

Non-invasive evaluation of the myocardial substrate of cardiac amyloidosis by gadolinium cardiac magnetic resonance

OBJECTIVE

To investigate the prevalence and distribution of gadolinium (Gd) enhancement at cardiac magnetic resonance (CMR) imaging in patients with cardiac amyloidosis (CA) and to look for associations with clinical, morphological, and functional features.

PATIENTS AND DESIGN

21 patients with definitely diagnosed CA (nine with immunoglobulin light chain amyloidosis and 12 transthyretin related) underwent Gd-CMR.

RESULTS

Gd enhancement was detected in 16 of 21 (76%) patients. Sixty six of 357 (18%) segments were enhanced, more often at the mid ventricular level. Transmural extension of enhancement within each patient significantly correlated with left ventricular (LV) end systolic volume (r = 0.58). The number of enhanced segments correlated with LV end diastolic volume (r = 0.76), end systolic volume (r = 0.6), and left atrial size (r = 0.56). Segments with > 50% extensive transmural enhancement more often were severely hypokinetic or akinetic (p = 0.001). Patients with > 2 enhanced segments had significantly lower 12 lead QRS voltage and Sokolow-Lyon index. No relation was apparent with any other clinical, morphological, functional, or histological characteristics.

CONCLUSION

Gd enhancement is common but not universally present in CA, probably due to expansion of infiltrated interstitium. The segmental and transmural distribution of the enhancement is highly variable, and mid-ventricular regions are more often involved. Enhancement appears to be associated with impaired segmental and global contractility and a larger atrium.

Multidetector CT: a new gold standard in the diagnosis of pulmonary embolism? State of the art and diagnostic algorithms

PURPOSE

From the early 90s, spiral CT technology has considerably changed the diagnostic capability of Pulmonary Embolism (PE), giving a direct vision of intravascular thrombi. Further technological progress has strengthened its diagnostic impact leading to an essential role in clinical practice. The advent of Multi-Detector CT (MDCT) has subsequently increased the reliability of this technique to the point of undermining the role of pulmonary angiography as the gold standard and occupying a central position in diagnostic algorithms. The aim of this paper is to appraise this evolution by means of a meta-analysis of the relevant literature from 1995 to 2004.

RESULTS

The review of the literature showed the sensitivity and specificity of CT to have increased from 37-94% and 81-100% (single-detector CT) to 87-94% and 94-100% (4-channel multidetector CT), especially thanks to the possibility of depicting subsegmental clots, with an interobserver agreement of 0.63-0.94 (k).

CONCLUSIONS

CT is one of the most reliable and effective methods in the diagnosis is PE, with the advantage of being extremely fast and providing alternative diagnoses. Recent improvements in MDCT technology confers the highest value of diagnostic accuracy with respect to other imaging modalities such as scintigraphy, angiography, MRI, D-dimer assay and Doppler US.

The effects of insulin on transport and metabolism of glucose in skeletal muscle from hyperthyroid and hypothyroid rats

The effects of insulin on the rates of glucose disposal were studied in soleus muscles isolated from hyper- or hypothyroid rats. Treatment with triiodothyronine for 5 or 10 days decreased the sensitivity of glycogen synthesis but increased the sensitivity of lactate formation to insulin. The sensitivity of 3-O methylglucose to insulin was increased only after 10 days of treatment and was accompanied by an increase in the sensitivity of 2-deoxyglucose phosphorylation; however, 2-deoxyglucose and glucose 6-phosphate in response to insulin remained unaltered. In hypothyroidism, insulin-stimulated rates of 3-O-methylglucose transport and 2-deoxyglucose phosphorylation were decreased; however, at basal levels of insulin, 3-O-methylglucose transport was increased, while 2-deoxyglucose phosphorylation was normal. In these muscles, the sensitivity of lactate formation to insulin was decreased; this defect was improved after incubation of the muscles with prostaglandin E2. The results suggest: (a) in hyperthyroidism, insulin-stimulated rates of glucose utilization in muscle to form lactate are increased mainly because of a decrease in glycogen synthesis; when hyperthyroidism progresses in severity, increases in the sensitivity of glucose transport to insulin and in the activity of hexokinase may also be involved; (b) in hypothyroidism, the decrease in insulin-stimulated rates of glucose utilization is caused by decreased rates of glycolysis; (c) prostaglandins may be involved in the changes in sensitivity of glucose utilization to insulin observed in muscle in altered thyroid states.

Effects of glucocorticoid excess on the sensitivity of glucose transport and metabolism to insulin in rat skeletal muscle

GENBANK/dy examines the mechanisms of glucocorticoid-induced insulin resistance in rat soleus muscle. Glucocorticoid excess was induced by administration of dexamethasone to rats for 5 days. Dexamethasone decreased the sensitivity of 3-O-methylglucose transport, 2-deoxyglucose phosphorylation, glycogen synthesis and glucose oxidation to insulin. The total content of GLUT4 glucose transporters was not decreased by dexamethasone; however, the increase in these transporters in the plasma membrane in response to insulin (100 m-units/litre) was lessened. In contrast, the sensitivity of lactate formation to insulin was normal. The content of 2-deoxyglucose in the dexamethasone-treated muscle was decreased at 100 m-units/litre insulin, while the contents of glucose 6-phosphate and fructose 2,6-bisphosphate were normal at all concentrations of insulin studied. The maximal activity of hexokinase in the soleus muscle was not affected by dexamethasone; however, inhibition of this enzyme by glucose 6-phosphate was decreased. These results suggest the following. (1) Glucocorticoid excess causes insulin resistance in skeletal muscle by directly inhibiting the translocation of the GLUT4 glucose transporters to the plasma membrane in response to insulin; since the activity of hexokinase is not affected, the changes in the sensitivity of glucose phosphorylation to insulin seen under these conditions are secondary to those in glucose transport. (2) The sensitivity of glycogen synthesis and glucose oxidation to insulin is decreased, but that of glycolysis is not affected: a redistribution of glucose away from the pathway of glycogen synthesis and glucose oxidation could maintain a normal rate of lactate formation although the rate of glucose transport is decreased.

Cellular uptake and release of the immunomodulating fungal toxin gliotoxin

Uptake of the immunomodulating agent gliotoxin into a panel of cells using biosynthetically radiolabelled 35S toxin showed rapid association of the toxin with all cell types studied with 70-85% of the total counts in the media becoming cell associated. A difference in kinetics was observed for cell lines when compared to the primary cells thymocytes, activated T-cells and macrophages. In the latter uptake was maximal after 10-15 min and radiolabel was lost from the cells as early as 100 min. In the cell lines studied, uptake was complete in less than 1 min with no loss of label after 100 min. The exception to this was a Wilms tumour line. Analysis of the fate of gliotoxin taken up into sensitive (activated T-cells) and resistant (human fibroblast) cells by HPLC showed: (a) up to 30% of the original gliotoxin taken up by sensitive cells was released as free gliotoxin over a 22 hr period. The remainder was metabolized to inorganic sulphate; (b) in T-cells gliotoxin is reduced to the dithiol form in significant amounts and this reduction may be modulated by glutathione; and (c) no reduced gliotoxin could be detected in the resistant fibroblast cell line 27Sk even though up to 50% of the original gliotoxin was still present in the free form in these cells at 22 hr. Gliotoxin became covalently associated with macromolecules in both cell types studied. Very little free gliotoxin is released into extracellular medium by the fibroblast cell line. Gliotoxin at 500 nM was found to induce apoptosis or programmed cell death in the Wilms tumour cell line but not in any other cell line studied, and this may account for the different kinetics of release of the toxin from the Wilms tumour cell line.

Studies on the effects of growth hormone administration in vivo on the rates of glucose transport and utilization in rat skeletal muscle

The effects of growth hormone (GH) administration to rats in vivo on the sensitivity of the rate of glucose utilization to insulin were studied in soleus muscles isolated from these rats. A single injection of GH did not increase the rate of glucose transport within 1-2 h. However, 12 h after, the rate of glucose transport was increased at 10 mU insulin l-1 and was accompanied by a similar increase in the rate of lactate formation but no change in the rate of glycogen synthesis. Prolonged treatment with GH decreased the rate of glucose transport and glycogen synthesis and increased the content of glucose 6-phosphate at physiological levels of insulin but did not affect the rate of lactate formation. These results suggest that: (a) GH does not increase the rate of glucose transport acutely; however, after several hours, the sensitivity of glucose transport and glycolysis to insulin are increased; (b) prolonged elevations of the level of GH in plasma decrease the sensitivity of the rate of glucose transport and glycogen synthesis to insulin. However, redirection of glucose residues away from the pathway of glycogen synthesis towards that of glycolysis and a possible increase in the rate of glycogenolysis maintain a normal rate of lactate formation, although the rate of glucose transport is decreased.

Effects of insulin-like growth factor I on the rates of glucose transport and utilization in rat skeletal muscle in vitro

1. The effects of insulin-like growth factor I (IGF-I) on the rates of glucose transport and utilization and its interaction with insulin were investigated in rat soleus muscle in vitro. IGF-I increased the rates of glucose transport, lactate formation, glycogen synthesis and the flux of glucose to hexose monophosphate, but it had no effect on the rate of glucose oxidation or glycogenolysis. 2. In the absence of insulin, low levels of IGF-I (0-30 ng/ml) increased the rate of glycolysis and the content of fructose 2,6-bisphosphate, but the content of glucose 6-phosphate remained unaltered; at higher levels of IGF-I (300-3000 ng/ml) the rate of glycolysis and the content of fructose 2,6-bisphosphate showed a further modest increase, but the content of glucose 6-phosphate doubled. Similar changes were seen when the level of insulin was increased from basal (0-0.4 ng/ml) to maximal (40 ng/ml). 3. Neither IGF-I nor insulin affected the contents of ATP, ADP, AMP, phosphocreatine or citrate. 4. Maximal concentrations of IGF-I increased the rate of lactate formation to a greater extent than did maximal concentrations of insulin. 5. In the presence of IGF-I, the rate of glucose utilization was less responsive to insulin. 6. The results suggest that, in rat skeletal muscle: (a) IGF-I increases the rates of glucose transport and utilization independently of insulin, and has a preferential effect on the rate of lactate formation; (b) the effects of IGF-I and insulin are not additive; (c) in addition to its effects on glucose transport, IGF-I increases the rate of glycogen synthesis and may stimulate glycolysis at the level of 6-phosphofructokinase; (d) changes in the content of fructose 2,6-bisphosphate may be part of the mechanism to regulate glycolytic flux in skeletal muscle in response to either IGF-I or insulin.