Targeting of eIF6-driven translation induces a metabolic rewiring that reduces NAFLD and the consequent evolution to hepatocellular carcinoma

A postprandial increase of translation mediated by eukaryotic Initiation Factor 6 (eIF6) occurs in the liver. Its contribution to steatosis and disease is unknown. In this study we address whether eIF6-driven translation contributes to disease progression. eIF6 levels increase throughout the progression from Non-Alcoholic Fatty Liver Disease (NAFLD) to hepatocellular carcinoma. Reduction of eIF6 levels protects the liver from disease progression. eIF6 depletion blunts lipid accumulation, increases fatty acid oxidation (FAO) and reduces oncogenic transformation in vitro. In addition, eIF6 depletion delays the progression from NAFLD to hepatocellular carcinoma, in vivo. Mechanistically, eIF6 depletion reduces the translation of transcription factor C/EBPβ, leading to a drop in biomarkers associated with NAFLD progression to hepatocellular carcinoma and preserves mitochondrial respiration due to the maintenance of an alternative mTORC1-eIF4F translational branch that increases the expression of transcription factor YY1. We provide proof-of-concept that in vitro pharmacological inhibition of eIF6 activity recapitulates the protective effects of eIF6 depletion. We hypothesize the existence of a targetable, evolutionarily conserved translation circuit optimized for lipid accumulation and tumor progression.

Discovery and Preliminary Characterization of Translational Modulators that Impair the Binding of eIF6 to 60S Ribosomal Subunits

Eukaryotic initiation factor 6 (eIF6) is necessary for the nucleolar biogenesis of 60S ribosomes. However, most of eIF6 resides in the cytoplasm, where it acts as an initiation factor. eIF6 is necessary for maximal protein synthesis downstream of growth factor stimulation. eIF6 is an antiassociation factor that binds 60S subunits, in turn preventing premature 40S joining and thus the formation of inactive 80S subunits. It is widely thought that eIF6 antiassociation activity is critical for its function. Here, we exploited and improved our assay for eIF6 binding to ribosomes (iRIA) in order to screen for modulators of eIF6 binding to the 60S. Three compounds, eIFsixty-1 (clofazimine), eIFsixty-4, and eIFsixty-6 were identified and characterized. All three inhibit the binding of eIF6 to the 60S in the micromolar range. eIFsixty-4 robustly inhibits cell growth, whereas eIFsixty-1 and eIFsixty-6 might have dose- and cell-specific effects. Puromycin labeling shows that eIF6ixty-4 is a strong global translational inhibitor, whereas the other two are mild modulators. Polysome profiling and RT-qPCR show that all three inhibitors reduce the specific translation of well-known eIF6 targets. In contrast, none of them affect the nucleolar localization of eIF6. These data provide proof of principle that the generation of eIF6 translational modulators is feasible.

Dobutamine echocardiography: usefulness of digital image processing

The present study was undertaken in order specifically to evaluate the usefulness of digital image processing so as to enhance the diagnostic power of dobutamine stress echocardiography. For this purpose 44 dobutamine echocardiographic tests, routinely performed in our echo laboratory, were analysed blindly by two observers using traditional videotape recording and digitized image acquisition. The results obtained from both observers show a trend which suggests that the traditional videotape approach provides more true-positive tests than the digitized approach (27/38 vs 23/38 and 24/38 vs 22/38 for the first and second observer, respectively). True-negative test detection was 6/6 with the videotape and 5/6 with the digitized method for both observers. As a consequence of the discrepancies observed between the two modalities, the videotape indicates that it can provide higher diagnostic accuracy than the digitized approach (72 +/- 9% vs 63 +/- 10%). The tests results concordance (positive or negative) between the two modalities of analysis was 66% for both the observers. The inter-observer agreement on the test results was 84% and 80% for the videotape analysis and the digitized analysis, respectively. On the basis of the results, we consider that digitized analysis applied to dobutamine stress echocardiography does not afford significant diagnostic advantages and should not be considered as an alternative option to traditional videotape analysis. However, it may be considered an extremely useful integrative tool since it produces the on-line image evaluation more easily and faster and allows a more practical form of stress test storage.

[Coronary vasospasm secondary to subcutaneous administration of sumatriptan]

We present the case of a 38-year-old woman with no previous history of coronary heart diseases, who suffered from cluster headaches and had undergone a subcutaneous sumatriptan treatment for two years. With no previous history of underlying ischaemic heart diseases or Prinzmetal's angina or any other significant coronary diseases supported by an angiographic exam, the patient suffered from an episode of coronary vasospasm following a subcutaneous administration of sumatriptan. Therefore particular care should be placed when subcutaneous sumatriptan is administered to patients who experienced chest pain or other related symptoms after the use of the drug.

[Myocardial response to ischemia produced by repeated coronary occlusions: an experimental study]

BACKGROUND

The fact that brief repeated episodes of ischemia may induce prolonged functional depression of the left ventricle is still a matter of debate. During an angioplasty several brief (20-90 sec) coronary occlusions are performed, with the potential risk of inducing myocardial jeopardy.

METHODS

We performed 4 repeated LAD occlusions in 7 open chest pigs under general anesthesia and controlled ventilation. The following parameters were evaluated: mean systemic arterial pressure (MAP), left ventricular peak systolic pressure (LVPSP), heart rate (HR), and peak negative and positive dP/dt (dP/dt- and +). Each parameter was measured in the basal state and every 4 sec, in the expiratory phase, during the coronary occlusion, the first min and after 10 min of reperfusion. The percent change from control values for each parameter was also calculated and, by means of the ANOVA test, the differences among the 4 consecutive occlusions for each parameter were tested.

RESULTS

The results showed that: 1) coronary occlusions significantly depressed dP/dt + and -, MAP and LVPSP, while HR did not change; 2) each variable returned to control values within 1 min of reperfusion; 3) the response to ischemia (percent change) was the same in each of the 4 consecutive occlusions for all parameters at every recording time.

CONCLUSIONS

We can conclude that: 1) each experimental coronary occlusion induces a depression of myocardial function that is reversible in 1 min of reperfusion; 2) four repeated 2 minutes coronary occlusions do not induce cumulative effects on myocardial response to ischemia.

[Effects of low-dose diltiazem on isovolumetric relaxation and contraction]

Calcium entry blockers are commonly believed to have a direct negative inotropic effect, but systolic function of the left ventricle (LV) can be improved when the peripheral vasodilator activity of the drug is present. The aim of our study was to evaluate the effect of diltiazem (D) on isovolumic contraction (IC) and relaxation (IR) at a dosage which is not effective on the peripheral vascular bed. We infused 10 micrograms/Kg/min i.v. of D for a 30 min period in to 12 pigs, anesthetized with ethyl urethane (1250 mg/Kg) and under artificial ventilation. The following variables were evaluated: left ventricular systolic (LVSP) and end-diastolic (LVEDP) pressure, peak - and + dP/dt, mean arterial pressure (MAP), heart rate (HR) and double product. The recordings were obtained in the control condition and 5, 10, 15, 20, 25 and 30 minutes after beginning the infusion. The statistical analysis was performed using the one-way ANOVA test. Our results show: 1) a maximal increase in the peak + dP/dt from 2228 +/- 501 to 2448 +/- 576 mmHg/sec (p less than or equal to 0.01) and of the peak . dP/dt from 1262 +/- 260 to 1348 +/- 272 mmHg/sec (p less than or equal to 0.05); 2) and increase in LVSP from 86 +/- 13 to 90 +/- 10 mmHg (p less than or equal to 0.01) and 3) no changes in HR, PAM, LVEDP and double product. As the indices representing afterload and preload (PAM and LVEDP) remained unchanged during the infusion, we suggest that the increase in dP/dt + and - are due to a direct effect of diltiazem on myocardial function.(ABSTRACT TRUNCATED AT 250 WORDS)

[Amiodarone prophylaxis of ventricular tachycardia in ischemic cardiopathy]

Sustained ventricular tachycardia (VT) in coronary heart disease (CHD) represents a major risk factor for sudden death. The Authors evaluated the prophylactic efficacy of the chronic administration of amiodarone (A) on this arrhythmia and simultaneously the trend of ventricular extrasystole during the antiarrhythmic treatment. Twenty-three patients were examined, 17 with post-infarction cardiopathy and 6 with mixed angina. They showed either 1 or more episodes (2 patients) of sustained VT involving hemodynamic difficulties. The ejection fraction (EF) ranged between 20 and 45% average (35.2 +/- 9). All patients underwent a basal 24 hour ECG 3 days after the VT cardioversion, and every 6 months. All subjects took A orally for a period ranging from 7 to 67 months (average 23.04 +/- 14) at the dose of 800 mg/day 7 for days, and then 200 or 400 mg/day according to the presence or absence of ventricular extrasystoles (VE) greater than or equal to 30/hr and/or Lown's class (L) greater than or equal to 3. No patients died suddenly during the follow-up; 6 of them died for causes other than arrhythmia. Four of them showed only 1 sustained VT relapse after a period of 6 to 11 months. Two of these 4 patients showed a persistent increase of the number of VE and L-class while, in the remaining 2 patients, the number of VE remained substantially unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

[First seconds after acute experimental ischemic: changes in isovolumic contraction and relaxation]

The purpose of this study was to answer the following questions: 1) are isovolumic contraction and relaxation affected in a different way by LAD occlusion? 2) Does proximal and distal LAD coronary occlusion induce different changes in isovolumic contraction and relaxation? In 22 pigs, LAD coronary artery was dissected free right after the first or third diagonal branch and occluded by ligation. The following variables were evaluated: left ventricular systolic and end-diastolic pressure; peak - and + dP/dt, mean arterial and pulmonary pressure. All our data were obtained in the first minute following the occlusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostacyclin effect on cardiovascular system in man evaluated by echocardiography

This was an echocardiographic study of the cardiovascular effects of prostacyclin (PGI2) infused intravenously to human volunteers at the rate of 20 ng . kg-1 . min-1 for 10 minutes. The following parameters were recorded in the steady state, at one-minute intervals throughout infusion and the ensuing recovery period: systolic, diastolic, and mean blood pressure (SBP, DBP, MBP); heart rate (HR); left ventricle end-diastolic (EDD) and end-systolic diameter (ESD); stroke volume index (SVI); cardiac index (CI); peripheral vascular resistance (PVR); left ventricle fractional shortening (FS) and ejection fraction (EF). We detected a progressive reduction of MBP without any HR modification. MBP reduction was associated with a reduction of PVR and a parallel rise of CI and SVI. There was also an increase of FS and EF reflecting a reduced ESD. We conclude that PGI2 infused in man at the rate stated above causes hypotension reflecting an arterial vasodilating effect; a lack of heart rate reflex response to afterload reduction (probably a nerve-mediated effect of PGI2); and no venous vasodilation, judging from the absence of any change in end-diastolic diameter.