Global longitudinal strain for prediction of mortality in ST-segment elevation myocardial infarction and aortic stenosis patients: two sides of the same coin.

OBJECTIVE: Global longitudinal strain (GLS) predicts major adverse events in ST-segment elevation myocardial infarction (STEMI) and aortic stenosis (AS). Different cut-off values and different end-points have been proposed for prognostic stratification. We aimed to verify whether a single GLS cut-off value can be used to identify increased risk of all-cause death in STEMI and AS. PATIENTS AND METHODS: One-hundred- seventeen successfully treated first STEMI (age 63.8±12.5 yrs, 70% men) and 64 AS (age 80.3±6.9 yrs, 44% men) patients, undergoing echocardiography before discharge and before AS treatment, respectively, were retrospectively analyzed. GLS was analyzed, together with pulmonary artery systolic pressure (PASP), Killip class and Genereux stage. End-point was all-cause death at 6-month follow-up. RESULTS: All-cause death occurred in 4 (3.4%) STEMI and 5 (7.8%) AS patients (p=ns). AS patients who died had GLS similar to died STEMI patients (9.7±2.1 vs. 11.3±1.7, p=ns). GLS cut-off ≤12% predicted death with 89% sensitivity and 70% specificity (AUC 0.84, p=0.001): STEMI and AS patients with GLS ≤12% had worse survival than STEMI and AS patients with GLS >12% (log-rank p=0.001). At multivariate Cox regression analysis, lower GLS values independently predicted death (HR 0.667, 95% CI 0.451-0.986, p=0.042), and the prediction model was improved when GLS was added to old age, significant comorbidities, PASP and Killip/Genereux stage (χ2 6.691 vs. 1.364, p=0.010). CONCLUSIONS: Died patients with STEMI and AS show similar values of GLS. A unique cut-off value of GLS can reliably be used to stratify the risk of all-cause death at 6-month follow-up in both two clinical settings.

Coronary plaque instability assessed by positron emission tomography and optical coherence tomography.

BACKGROUND: Non-ST-elevation myocardial infarction (NSTEMI) and unstable angina (UA) are caused often by destabilization of non-flow limiting inflamed coronary artery plaques. 18F-fluorodeoxyglucose (FDG) uptake with positron emission tomography/computed tomography (PET/CT) reveals plaque inflammation, while intracoronary optical coherence tomography (OCT) reliably identifies morphological features of coronary instability, such as plaque rupture or erosion. We aimed to prospectively compare these two innovative biotechnologies in the characterization of coronary artery inflammation, which has never been attempted before. METHODS: OCT and FDG PET/CT were performed in 18 patients with single vessel coronary artery disease, treated by percutaneous coronary intervention (PCI) with stent implantation, divided into 2 groups: NSTEMI/UA (n = 10) and stable angina (n = 8) patients. RESULTS: Plaque rupture/erosion recurred more frequently [100% vs 25%, p = 0.001] and FDG uptake was greater [TBR median 1.50 vs 0.87, p = 0.004] in NSTEMI/UA than stable angina patients. FDG uptake resulted greater in patients with than without plaque rupture/erosion [1.2 (0.86-1.96) vs 0.87 (0.66-1.07), p = 0.013]. Among NSTEMI/UA patients, no significant difference in FDG uptake was found between ruptured and eroded plaques. The highest FDG uptake values were found in ruptured plaques, belonging to patients with NSTEMI/UA. OCT and PET/CT agreed in 72% of patients [p = 0.018]: 100% of patients with plaque rupture/erosion and increased FDG uptake had NSTEMI/UA. CONCLUSION: For the first time, we demonstrated that the correspondence between increased FDG uptake with PET/CT and morphology of coronary plaque instability at OCT is high.

Ticagrelor and preconditioning in patients with stable coronary artery disease (TAPER-S): a randomized pilot clinical trial.

BACKGROUND: Ticagrelor is a reversibly binding, direct-acting, oral, P2Y12 antagonist used for the prevention of atherothrombotic events in patients with coronary artery disease (CAD). Ticagrelor blocks adenosine reuptake through the inhibition of equilibrative nucleoside transporter 1 (ENT-1) on erythrocytes and platelets, thereby facilitating adenosine-induced physiological responses such as an increase in coronary blood flow velocity. Meanwhile, adenosine plays an important role in triggering ischemic preconditioning through the activation of the A1 receptor. Therefore, an increase in ticagrelor-enhanced adenosine bioavailability may confer beneficial effects through mechanisms related to preconditioning activation and improvement of coronary microvascular dysfunction. METHODS: To determine whether ticagrelor can trigger ischemic preconditioning and influence microvascular function, we designed this prospective, open-label, pilot study that enrolled patients with stable multivessel CAD requiring staged, fractional flow reserve (FFR)-guided percutaneous coronary intervention (PCI). Participants will be randomized in 1:1 ratios either to ticagrelor (loading dose (LD) 180 mg, maintenance dose (MD) 90 mg bid) or to clopidogrel (LD 600 mg, MD 75 mg) from 3 to 1 days before the scheduled PCI. The PCI operators will be blinded to the randomization arm. The primary endpoint is the delta (difference) between ST segment elevations (in millimeters, mm) as assessed by intracoronary electrocardiogram (ECG) during the two-step sequential coronary balloon inflation in the culprit vessel. Secondary endpoints are 1) changes in coronary flow reserve (CFR), index of microvascular resistance (IMR), and FFR measured in the culprit vessel and reference vessel at the end of PCI, and 2) angina score during inflations. This study started in 2018 with the aim of enrolling 100 patients. Based on the rate of negative FFR up to 30% and a drop-out rate up to 10%, we expect to detect an absolute difference of 4 mm among the study arms in the mean change of ST elevation following repeated balloon inflations. All study procedures were reviewed and approved by the Ethical Committee of the Catholic University of Sacred Heart. DISCUSSION: Ticagrelor might improve ischemia tolerance and microvascular function compared to clopidogrel, and these effects might translate to better long-term clinical outcomes. TRIAL REGISTRATION: EudraCT No. 2016-004746-28. No. NCT02701140.  TRIAL STATUS: Information provided in this manuscript refers to the definitive version (n. 3.0) of the study protocol, dated 31 October 2017, and includes all protocol amendments. Recruitment started on 18 September 2018 and is currently ongoing. The enrollment is expected to be completed by the end of 2019. TRIAL SPONSOR: Fondazione Policlinico Universitario A. Gemelli - Roma, Polo di Scienze Cardiovascolari e Toraciche, Largo Agostino Gemelli 8, 00168 Rome, Italy.

Radial artery intima-media ratio predicts presence of coronary thin-cap fibroatheroma: a frequency domain-optical coherence tomography study.

BACKGROUND: Peripheral arterial disease is a risk factor for cardiac mortality but pathophysiologic mechanisms linking atherosclerosis of peripheral arteries with coronary events in the single patient have not been established. METHOD AND RESULTS: We evaluated by frequency-domain optical coherence tomography (FD-OCT) the possible association between culprit coronary plaque characteristics and proximal radial artery features in a cohort of 51 patients symptomatic coronary artery disease undergoing coronary procedures by transradial route. FD-OCT coronary artery analysis included assessment of TCFA and thrombus. FD-OCT radial artery analysis included intimal thickness index (ITI: intimal area/medial area), intima-media ratio (IMR: the maximum intimal thickness/medial thickness), and percentage of luminal narrowing [%LN: (intimal area+medial area)/external elastic membrane area × 100]. Coronary TCFA and thrombus were detected in 19 (37%) and 7 (14%) patients, respectively. TCFA was significantly associated with higher values of radial artery ITI (0.35 vs. 0.26, p=0.02) and IMR (0.45 vs. 0.32, p=0.03), but not with %LN. In contrast, coronary thrombus was only associated with higher %LN (26.7 vs. 22.8, p=0.02). Multivariate logistic regression analysis identified proximal radial artery IMR (OR 16.3, 95% CI 1.1 to 245.1) as an independent predictor of TCFA. CONCLUSIONS: In patients with symptomatic coronary atherosclerosis, vessel wall modifications at the level of the proximal radial artery are associated with adverse coronary features like TCFA and thrombus.

EuroSCORE as predictor of in-hospital mortality after percutaneous coronary intervention.

OBJECTIVE: To date, no common risk stratification system is available to predict the risk of surgical or percutaneous myocardial revascularisation in patients with coronary artery disease (CAD). Thus, we sought to assess the European System for Cardiac Operative Risk Evaluation (EuroSCORE) validity to predict in-hospital mortality after percutaneous coronary intervention (PCI). DESIGN, SETTING AND PARTICIPANTS: EuroSCORE was prospectively and systematically assessed in 1173 consecutive patients undergoing PCI in a high-volume single centre between April 2005 and October 2006. MAIN OUTCOME MEASURE: The receiver-operating characteristics (ROC) curve was used to describe performance and accuracy of the EuroSCORE risk model for the prediction of in-hospital mortality after PCI. RESULTS: The EuroSCORE model demonstrated an overall relation between EuroSCORE rank and the incidence of in-hospital mortality, showing consistency in predicting patient risk across many subgroups and levels of global risk. At multivariable logistic regression analysis the EuroSCORE value was an independent in-hospital mortality predictor (p = 0.002) together with left main disease (p = 0.005), procedural urgency (p = 0.001), ACC/AHA C type lesion (p = 0.02) and PCI failure (p = 0.01). The area under the ROC curve for the EuroSCORE system was 0.91 (95% CI 0.86 to 0.97), indicating a good ability of the model to discriminate patients at risk of dying during the index hospitalisation. CONCLUSION: The EuroSCORE risk model, already extensively validated for the prediction of early mortality following open-heart surgery, can also be efficiently utilised in the setting of PCI. The introduction of the EuroSCORE assessment in patients with documented CAD may help to improve the revascularisation strategy decision-making process.

Sirolimus, Tacrolimus and Zotarolimus eluting stents to treat bifurcated lesions: a 7-month clinical outcome comparison.

AIM: Drug eluting stents (DES) have been shown to reduce restenosis compared with bare metal stents in bifurcated lesions. The aim of this study was to evaluate the long-term clinical outcomes of patients with bifurcated lesions treated by 3 different DES. METHODS: Consecutive patients with symptomatic coronary artery disease on one bifurcated lesion with SB>2.25 mm (on visual estimation) undergoing at the Department of Cardiology of the Catholic University of Rome, Italy were screened. Patients treated with Sirolimus-eluting stent (Cypher Select; SES Group), Tacrolimus-eluting stent (Taxus-Libertè; TA Group) and Zotarolimus-eluting stent (Endeavor Driver; ZOT Group) were enrolled in the study. Clinical and angiographic characteristics of all patients were prospectively recorded. Major adverse clinical events (MACE), including death, acute myocardial infarction (MI) or target lesion revascularization (TVR) by either percutaneous coronary intervention (PCI) or coronary surgery were recorded during the follow-up. Incidence of definite or probable stent thrombosis was calculated according to the ARC criteria. RESULTS: Two hundred and forty-one consecutive patients were enrolled (89 Group CY, 98 Group TA and 54 Group EN). Length of follow-up was 235+/-60 days. Baseline clinical and angiographic characteristic were similar across the groups. The adopted technique for stent implantation was provisional stenting (73.4%), T-stenting technique (7%), crush (7%) and V-stenting (2.6%). The rate of patients finally treated with two stents was similar among groups. The cumulative rate of MACE (9% SES, 12% TA, 11% ZOT: P=0.7) and of TVR (2% SES, 9% TA, 7% ZOT) was similar among groups. No definite stent thrombosis was observed during follow-up, while 1 probable stent thrombosis was observed in TA group. CONCLUSION: The clinical outcome of bifurcated lesions using DES and mainly a technique of single stent implantation is good. In the present observational study, clinical adverse events did not differ in patients with bifurcated lesions treated by Cypher, Taxus or Endeavor stent implantation.

Protein-caloric food restriction affects insulin-like growth factor system in fetal Wistar rat.

We have previously shown that fetuses from protein-caloric undernourished pregnant rats (35% of control diet during the last week of pregnancy) at 21.5 d post coitum exhibit increased beta-cell mass. This alteration is correlated with increased insulinemia and total pancreatic insulin content, a pattern similar to that reported in infants of mild diabetic mothers. In this work, we investigated in undernourished fetuses: 1) whether availability of growth factors such as insulin, GH, and IGFs and their binding proteins (IGFBPs) could be implicated in this alteration, and 2) the beta-cell mitogenic response to IGFs in vitro. The results show that maternal undernutrition increases pancreatic IGF-I expression and islet IGF-I receptor content in undernourished fetuses, whereas hepatic IGF-I expression and serum IGF-I levels were decreased. No changes were observed in serum IGF-II, and its expression was diminished in undernourished pancreases and unchanged in the liver, compared with control fetuses. Serum levels and liver and pancreatic mRNA expression of IGFBP-1 were found to be normal in undernourished fetuses, whereas the serum concentration and abundance of IGFBP-2 mRNA in pancreas were increased. Finally, the beta-cell mitogenic response to IGFs in vitro was significantly increased in undernourished fetal islets, compared with controls. In conclusion, in undernourished fetuses the increased beta-cell mass can be related to the stimulation of replicative beta-cell response due to locally increased pancreatic IGF-I mRNA; this effect is perhaps potentiated or favored by the enhanced islet IGF-I receptor content and pancreatic IGFBP-2 gene expression.

Protein calorie restriction has opposite effects on glucose metabolism and insulin gene expression in fetal and adult rat endocrine pancreas.

We previously demonstrated that fetuses from undernourished pregnant rats exhibited increased beta-cell mass and hyperinsulinemia, whereas keeping food restriction until adult age caused reduced beta-cell mass, hypoinsulinemia, and decreased insulin secretion. Because these alterations can be related to insulin availability, we have now investigated early and long-term effects of protein calorie food restriction on insulin mRNA levels as well as the possible mechanisms that could modulate the endogenous insulin mRNA content. We used fetuses at 21.5 days of gestation proceeding from food-restricted rats during the last week of pregnancy and 70-day-old rats undernourished from day 14 of gestation until adult age and with respective controls. Insulin mRNA levels, glucose transporters, and total glycolysis and mitochondrial oxidative fluxes were evaluated. We additionally analyzed undernutrition effects on signals implicated in glucose-mediated insulin gene expression, especially pancreatic duodenal homeobox-1 (PDX-1), stress-activated protein kinase-2 (p38/SAPK2), and phosphatidylinositol 3-kinase. Undernourished fetuses showed increased insulin mRNA, oxidative glucose metabolism, and p38/SAPK2 levels, whereas undernutrition until adult age provoked a decrease in insulin gene expression, oxidative glucose metabolism, and PDX-1 levels. The results indicate that food restriction caused changes in insulin gene expression and content leading to alterations in glucose-stimulated insulin secretion. The molecular events, increased p38/SAPK2 levels in fetuses and decreased PDX-1 levels in adults, seem to be the responsible for the altered insulin mRNA expression. Moreover, because PDX-1 activation appears to be regulated by glucose-derived metabolite(s), the altered glucose oxidation caused by undernutrition could in some manner affect insulin mRNA expression.

Age-dependent adaptation of the liver thyroid status and recovery of serum levels and hepatic insulin-like growth factor-I expression in neonatal and adult diabetic rats.

The effect of treatment with thyroxine (T(4)) on the hepatic deiodinase (5'D-I) activity and triiodothyronine (T(3)) content and on insulin-like growth factor-I (IGF-I) secretion and mRNA hepatic expression were studied in neonatal and adult diabetic (D) rats and compared with 4 thyroidectomized (Tx) groups: neonatal and adult Tx rats treated or not with T(4). Serum T(3) and T(4) decreased by 92% in both Tx populations and by 80% to 70% in D adults according to the severity of diabetes: -70 mg/kg body weight (BW) (D(70)) or 50 mg/kg BW (D(50)) of streptozotocin (STZ) injected, whereas only a 30% to 33% decrease was found in D neonates. A similar decrease of liver 5'D-I activity and T(3) concentrations was found in neonatal and adult Tx rats, whereas a significant reduction in those parameters was observed only in adult diabetics, either D(70) or D(50), but not in D neonates. Serum levels and liver mRNA expression of IGF-I determined by ribonuclease protection assay, plasma and pituitary growth hormone (GH), plasma insulin, and glycemia were also measured in both D populations. A decrease in circulating IGF-I, previously reported for Tx adult rats, was also found in both D populations. T(4) treatment recovered IGF-I and liver T(3) in both Tx groups and D neonates, but not in D adults. These results show an age-dependent adaptation of the liver thyroid economy in diabetes, as hepatic 5'D-I does not respond to diabetes in neonates and IGF-I is insensitive to T(4) treatment in adult diabetics and suggest a positive correlation between hepatic T(3) content and IGF-I expression in conditions of diabetes and Tx.

Right ventricular dilatation after left ventricular acute myocardial infarction is predictive of extremely high peri-infarctual apoptosis at postmortem examination in humans.

BACKGROUND: Cardiac remodelling after acute myocardial infarction (AMI) is characterised by molecular and cellular mechanisms involving both left and right ventricles, and biventricular failure identifies patients with an extremely unfavourable prognosis. AIMS: To assess whether a link exists between increased myocardial apoptotic rates (AR) at sites of recent infarction and patterns of unfavourable cardiac remodelling, such as biventricular enlargement after left ventricular (LV) infarction. METHODS: Twelve patients with recent AMI involving the LV and not the right ventricle (RV) and with permanent infarct related artery occlusion were selected at necropsy. Gross pathological characteristics, such as LV and RV dilatation, and AR at site of infarction were assessed. Potential false positive results (DNA synthesis and RNA splicing) were excluded from the cell count. RESULTS: RV enlargement, defined as a tricuspidal ring greater than 120 mm, was found in five cases and was associated with LV dilatation. These patients showed significantly higher AR than the others. When the subjects were divided into three groups according to progressive cardiac remodelling (absence of cardiac dilatation, isolated LV dilatation, and biventricular enlargement), the last group had significantly higher ARs than the other two groups, showing that myocardiocyte apoptosis is increased in more unfavourable forms of cardiac remodelling. CONCLUSION: Patients with severely unfavourable cardiac remodelling, such as biventricular enlargement, have extremely high myocardiocyte apoptosis at necropsy, even late after LV myocardial infarction, supporting the role of myocardiocyte loss in determining post-infarction adverse remodelling.

High-risk clinical features predict increased post-infarction myocardial apoptosis and the benefits as a result of an open infarct-related artery.

BACKGROUND: Infarct-related artery (IRA) patency after acute myocardial infarction (AMI) is associated with a more favourable clinical course, in particular in patients with high-risk features. As it has been recently reported that IRA patency is associated with a reduced postinfarction apoptotic rate (AR), the aim of our study was to assess whether IRA status late after AMI had a different impact on AR in high- vs. low-risk patients. METHODS AND RESULTS: Co-localization of TUNEL and caspase-3 was used to calculate the AR at the site of infarction at the time of death in 30 subjects. The Norris coronary prognostic index (NI) was calculated (computing age, presence of pulmonary congestion, heart size and history of previous additional AMI) in order to define the patients' individual risk at the time of hospitalization. According to the NI (< or =7 vs. >7), subjects were divided into low and high risk, as NI >7 carries an approximate threefold higher risk of death. The NI was significantly correlated with the AR at the time of death both in infarct and remote areas. Twenty subjects had IRA occlusion at the time of death, and in these patients AR was significantly higher both in infarct and remote areas (P<0.001 and P=0.009 vs. the others, respectively). However the impact of IRA occlusion on AR was significantly different comparing high- vs. low-risk subjects. In particular, AR at the infarct site was 10-fold higher in the high-risk subjects with IRA occlusion (26.1%[20.4-28.7%]) vs. those with open IRA (2.3%[0.6-3.5%]; P=0.002) and was nonsignificantly different in the low-risk subjects vs. those without IRA occlusion (8.2%[2.5-17.5%] vs. 5.4%[1.5-7.9%]; P=0.48). Similarly, in the high-risk subjects, AR in remote areas was significantly greater in cases with occluded vs. open IRA (0.7%[0.4-0.9%] vs. 0.3%[0.3-0.32%]; P=0.009). CONCLUSION: A significantly higher AR is associated with IRA occlusion late post AMI in subjects with high-risk clinical features, and not in low-risk patients. The diverse impact of IRA occlusion on AR in subjects with different risk profiles may explain the greater benefit associated with coronary reperfusion in high-risk subjects. The overall lower AR in low-risk subjects, independently from the IRA status, may be correlated with the better long-term prognosis after AMI in this case.

Effects of early undernutrition on the brain insulin-like growth factor-I system.

Undernutrition reduces circulating concentrations of insulin-like growth factor (IGF)-I, but how it affects the brain IGF system, especially during development, is largely unknown. We have studied IGF-I, IGF-II, IGF receptor and IGF binding protein (BP)-2 mRNA expression in the hypothalamus, cerebellum and cerebral cortex of neonatal rats that were food restricted beginning on gestational day 16. One group was refed starting on postnatal day 14. Rats were killed on postnatal day 8 or 22. Undernutrition did not produce an overall reduction in brain weight at either age but, at 22 days, both the cerebellum and hypothalamus weighed significantly less. At 8 days, no change was detected in the central IGF axis in response to undernutrition. However, in 22-day-old undernourished rats, IGF-I and IGF receptor mRNA expression were increased in both the hypothalamus and cerebellum, while IGFBP-2 was decreased, but only in the hypothalamus. Refeeding had no effect on any of these parameters. These results suggest that the hypothalamus and cerebellum respond to malnutrition and the decrease in circulating IGF-I, a peptide fundamental for growth and development, by increasing the local production of both the growth factor and its receptor in attempt to maintain normal development.

Influence of hypothyroidism on circulating concentrations and liver expression of IGF-binding proteins mRNA from neonatal and adult rats.

The aim of this work was to study the influence of the endocrine balance between thyroid hormones, insulin and growth hormone (GH) on the regulation of insulin-like growth factor binding proteins (IGFBPs), complementing a study previously reported for insulin-like growth factors (IGFs) in similar populations. Serum concentrations of IGFBPs-1 to -3 were assayed by Western ligand blot and their mRNA expression in the liver assayed by RNase protection assay in the hypothyroid populations: thyroidectomized and mercapto-1-methylimidazole (MMI)-treated neonates, and thyroidectomized adult rats at different periods after thyroidectomy. Serum concentrations of insulin, GH and IGF-I were increased in thyroidectomized neonates and decreased in the other populations. IGFBPs-1 and -2 increased 79% and 50% respectively in thyroidectomized neonatal rats compared with control at 15 days after thyroidectomy, whereas only IGFBP-2 increased (87%) in MMI-treated neonates, which had low serum insulin and GH compared with control on the same days. In thyroidectomized adult rats, IGFBPs-1 and -2 decreased 60% compared with controls on all days studied. Furthermore, when streptozotocin was administered to thyroidectomized neonates and insulin was given to thyroidectomized adult rats to restore insulin to control values in both groups, a differential regulation was found for IGFBPs-1 and -2. The transcriptionally induced decrease in IGFBP-3 (20-25% compared with control in neonates and 50% in adult rats), however, seemed to be regulated by GH and IGF-I. The similarity of changes in IGFBPs found in hypothyroid, undernourished and streptozotocin-induced diabetic neonatal rats suggests that the regulatory effect of insulin or GH on the IGFBPs requires the reduced biologically active thyroid hormone that is found in these three populations.

Increased prevalence of the G20210A prothrombin gene variant in acute coronary syndromes without metabolic or acquired risk factors or with limited extent of disease.

AIMS: To investigate the prevalence of the G20210A prothrombin and G1691A factor V gene variants in patients with acute coronary syndrome stratified according to risk factor profile and to extent of coronary disease, in comparison with matched healthy controls. METHODS AND RESULTS: The 20210 prothrombin and the 1691 factor V loci were genotyped in 247 patients < or =65 years of age (190 myocardial infarction and 57 unstable angina as first presentation of disease) and in 247 healthy age- and sex-matched controls. The prevalence of the 1691A factor V allele was similar in cases and controls. The frequency of heterozygotes for the 20210A prothrombin allele was 6.5% among patients and 2.8% among controls (OR 2.4, 95% CI 1.0-5.9), increasing to 8.7% in patients with a family history of myocardial infarction (OR 3.3, 95% CI 1.2-9.1), to 9.9% in patients (n=81) with < or =1 vessel disease (OR 3.8, 95% CI 1.3-10.8), and to 13.0% in patients who were normocholesterolaemic, non-diabetic, normotensive and non-smokers (OR 5.1, 95% CI 1.2-21.4). CONCLUSIONS: These findings suggest that the 20210A prothrombin allele represents an inherited risk factor for acute coronary syndrome among patients who have limited extent of coronary disease at angiography or who lack major metabolic and acquired risk factors.

Regulation of IGF-I and -II by insulin in primary cultures of fetal rat hepatocytes.

During perinatal development, insulin and nutrients, rather than GH, regulate the IGF system. A selective primary culture of fetal rat hepatocytes has been established in our laboratory to elucidate the molecular mechanism of action of the above regulatory factors on IGF-I and -II gene expression during the late fetal period of the rat. In this model we have previously reported a regulatory role for glucose on IGF-I and -II synthesis and secretion. In the same experimental model, we now report that doses of insulin (0.1-5 microM) within the physiological range in rat fetuses during the last stages of gestation evoke an increase of IGF-I and -II mRNA abundance. Insulin regulated in a parallel manner IGF peptide secretion, and an excellent correlation was observed between IGF-I and -II mRNA and IGF-I and -II peptide levels in the conditioned media in response to the hormone. Finally, the insulin-induced rise in IGF-I and -II mRNA was not mediated by stimulation of gene transcription but by increased transcript stability. The results support the hypothesis that insulin plays a major role in IGF regulation at immature stages of development.

Different role of insulin in GLUT-1 and -4 regulation in heart and skeletal muscle during perinatal hypothyroidism.

Two groups of hypothyroid rats were used; one group was given 2-mercapto-1-methylimidazole (MMI) treatment in the drinking water of the mothers and was killed at 2 and 4 days of life, and the other group was given similar MMI treatment and then was thyroidectomized at 5 days of life and killed at 8 or 20 days. Serum insulin, growth hormone (GH), and insulin-like growth factor I (IGF-I) were decreased in MMI-treated rats but increased in MMI-treated plus thyroidectomized rats. No significant reduction of thyroid hormones was observed in 2-day-old MMI rats. Protein and mRNA expression of GLUT-1 increased, and those of GLUT-4 decreased, in the heart in all populations independent of changes in insulin, GH, and IGF-I levels. However, GLUT-4 protein and mRNA expression in quadriceps and gastrocnemius skeletal muscles decreased at 4 days and increased at 8 and 20 days of life in parallel with insulin, GH, and IGF-I levels. GLUT-1 in the skeletal muscles seemed regulated posttranscriptionally and presented a decrease of mRNA expression in all stages studied. A differential sensitivity to insulin regulation of GLUT-1 and GLUT-4 glucose transporters seems to be one of the causes for the tissue-specific regulation of these glucose transporters in heart and skeletal muscles during the perinatal period.