Maternal and fetal outcomes of pregnancy in women with primary systemic vasculitis: A single-center cohort study of 20 patients and 30 pregnancies

OBJECTIVES

To analyze pregnancy outcomes of patients with primary systemic vasculitis followed in a third-level referral center.

METHODS

Retrospective cohort study of all pregnant women with systemic vasculitis followed between 2009 and 2022 at the High-Risk Pregnancy Clinic of the Department of Systemic Autoimmune Diseases of the Hospital Clínic, Barcelona.

RESULTS

Twenty women with primary vasculitis were identified, with a total of 30 pregnancies. Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (n = 7) and Behçet disease (n = 4) were the most frequent types of vasculitis. All women had the diagnosis of vasculitis before pregnancy, with a median time between disease diagnosis and pregnancy of 5.8 years (range: 2 months-29 years). Most were in remission at conception (76.7 %). During pregnancy, a vasculitis flare occurred in 4 (13.3 %) patients (one each with Takayasu arteritis, eosinophilic granulomatosis with polyangiitis [EGPA], IgA vasculitis [IgAV], and Behçet disease [BD]). Four (16.7 %) of the successful pregnancies had post-partum relapses (one each with EGPA, granulomatosis with polyangiitis, IgAV, and BD). Eighty percent of pregnancies resulted in live babies. In four cases (13.3 %), medical termination of pregnancy was decided, considering the mother or baby health risk. There were two spontaneous miscarriages, and no stillbirths or neonatal deaths. Preeclampsia was the most frequent maternal complication (25 %). Newborns were preterm in 24 % and low birthweight in 20 % of cases. No maternal deaths occurred.

CONCLUSIONS

This cohort study shows that vasculitis relapses during pregnancy and post-partum, together with other pregnancy complications, occur in a considerable number of patients with systemic vasculitides, although a final good pregnancy outcome can be expected in most cases. These findings emphasize the convenience of managing these special situations in expert reference centers.

Lysinuric Protein Intolerance and Its Nutritional and Multisystemic Challenges in Pregnancy: A Case Report and Literature Review

Lysinuric protein intolerance (LPI) is a rare inborn error of metabolism (IEM), classified as an inherited aminoaciduria, caused by mutations in the SLC7A7 gene, leading to a defective cationic amino acid transport. The metabolic adaptations to the demands of pregnancy and delivery cause significant physiological stress, so those patients affected by IEM are at greater risk of decompensation. A 28-year-old woman with LPI had experienced 3 early miscarriages. While pregnancy was finally achieved, diverse nutritional and medical challenges emerged (food aversion, intrauterine growth restriction, bleeding risk, and preeclampsia suspicion), which put both the mother and the fetus at risk. Moreover, the patient requested a natural childbirth (epidural-free, delayed cord clamping). Although the existence of multiple safety concerns rejected this approach at first, the application of novel strategies made a successful delivery possible. This case reinforces that the woman's wish for a non-medicated, low-intervention natural birth should not be automatically discouraged because of an underlying complex metabolic condition. Achieving a successful pregnancy is conceivable thanks to the cooperation of interdisciplinary teams, but it is still important to consider the risks beforehand in order to be prepared for possible additional complications.

Correlation of placental lesions in patients with systemic lupus erythematosus, antiphospholipid syndrome and non-criteria obstetric antiphospholipid syndrome and adverse perinatal outcomes

INTRODUCTION

We aimed to describe the pattern of placental injuries in women with systemic lupus erythematosus (SLE), antiphospholipid antibody syndrome (APS) and non-criteria obstetric APS (NC-OAPS), and to correlate the placental findings with the occurrence of adverse perinatal outcomes.

METHODS

The perinatal outcomes and placental findings of pregnancies of women with SLE, APS, and NC-OAPS and gestational-age matched healthy controls were analyzed and classified according to the 2015 Redline - Classification of placental lesions.

RESULTS

91 women with SLE, APS, and NC-OAPS and 91 controls were included. Mean values of placental weight differed between groups, being significantly lower in NC-OAPS and APS groups compared to controls. Furthermore, 14.3% of placentas in the APS group were under the 3rd percentile, which was significantly higher in comparison with other groups. Regarding histopathological placental findings, maternal-side malperfusion was significantly increased in APS (46.4%) compared to NC-OAPS (14.3%) and SLE (9.5%). Fetal-side maldevelopment was significantly increased in NC-OAPS (19.1%) compared to controls (1.1%) and SLE (2.4%). A significantly increased prevalence of adverse perinatal outcomes (APOs) was observed in all studied groups compared to healthy controls (controls 3.3%, SLE 52.4%, NC-OAPS 57.1%, APS 64.3%). Overall, both maternal (OR 6.8, 95%CI 2.1-22) and fetal-side (OR 4.1, 95%CI 1.3-13.5) lesions were significantly associated with APO. Maternal malperfusion and fetal maldevelopment were the lesions most strongly associated with APOs.

DISCUSSION

Pregnant women with SLE, APS, or NC-OAPS showed a different pattern of histopathological findings. Compared to controls, SLE, APS, and NC-OAPS conferred an increased risk of APOs that was strongly associated with placental maternal-side malperfusion and fetal-side maldevelopment.

Expected impact of immunomodulatory agents during pregnancy: A newborn's perspective

The neonatal immune ontogeny begins during pregnancy to ensure that the neonate is well-suited for perinatal life. It prioritizes Th2/M2 and regulatory responses over Th/M1 activity to avoid excessive inflammatory responses and to ensure immune tolerance and homeostasis. Newborns also present increased Th17/Th22 responses providing effective anti-fungal immunity and mucosal protection. Intrauterine exposure to immune modulatory drugs with the placental transfer may influence the natural course of the fetal immune development. The vertical transfer of both biological therapy and small molecules begins during the first trimester through neonatal Fc receptor or placental diffusion, respectively, reaching its maximum transfer potential during the third trimester of pregnancy. Most of the biological therapy have a prolonged half-life in newborn's blood, being detectable in infants up to 12 months after birth (usually 6-9 months). The use of immunomodulators during pregnancy is gaining global interest. Current evidence mainly reports birth-related outcomes without exhaustive analysis of the on-target side effect on the perinatal immune system ontogeny, the infection risk, or the immune dysregulation. The present review will focus on: (1) the main characteristics of the perinatal immune system to understand its specific features and vulnerabilities to immune modulation; (2) the mechanisms of placental transfer of immunomodulators; and (3) the immune changes reported to date in newborns exposed to immunomodulators with emphasis on the current concerns and gaps in knowledge.

Early Prediction of Adverse Pregnancy Outcome in Women with Systemic Lupus Erythematosus, Antiphospholipid Syndrome, or Non-Criteria Obstetric Antiphospholipid Syndrome

A prospectively study of pregnant women with systemic lupus erythematosus (SLE), antiphospholipid syndrome, or non-criteria obstetric antiphospholipid syndrome was conducted to describe the characteristics of women followed in a referral unit and to derive a predictive tool for adverse pregnancy outcome (APO). Demographic characteristics, treatments, SLE activity, and flares were recorded. Laboratory data included a complete blood cell count, protein-to-creatinine urinary ratio (Pr/Cr ratio), complement, anti dsDNA, anti-SSA/Ro, anti-SSB/La, and antiphospholipid antibodies status. A stepwise regression was used to identify baseline characteristics available before pregnancy and during the 1st trimester that were most predictive of APO and to create the predictive model. A total of 217 pregnancies were included. One or more APO occurred in 45 (20.7%) women. A baseline model including non-Caucasian ethnicity (OR 2.78; 95% CI [1.16-6.62]), smoking (OR 4.43; 95% CI [1.74-11.29]), pregestational hypertension (OR 16.13; 95% CI [4.06-64.02]), and pregestational corticosteroids treatment OR 2.98; 95% CI [1.30-6.87]) yielded an AUC of 0.78 (95% CI, [0.70-0.86]). Among first-trimester parameters, only Pr/Cr ratio improved the model fit, but the predictive performance was not significantly improved (AUC of 0.78 vs. 0.81; p = 0.16). Better biomarkers need to be developed to efficiently stratify pregnant women with the most common autoimmune diseases.

Placental damage in pregnancies with systemic lupus erythematosus: A narrative review

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease of unknown cause, which mainly affects women of childbearing age, especially between 15 and 55 years of age. During pregnancy, SLE is associated with a high risk of perinatal morbidity and mortality. Among the most frequent complications are spontaneous abortion, fetal death, prematurity, intrauterine Fetal growth restriction (FGR), and preeclampsia (PE). The pathophysiology underlying obstetric mortality and morbidity in SLE is still under investigation, but several studies in recent years have suggested that placental dysfunction may play a crucial role. Understanding this association will contribute to developing therapeutic options and improving patient management thus reducing the occurrence of adverse pregnancy outcomes in this group of women. In this review, we will focus on the relationship between SLE and placental insufficiency leading to adverse pregnancy outcomes.

Latency to delivery in physical examination-indicated cerclage in twins is similar to that in singleton pregnancies

OBJECTIVE

To compare latency to delivery and perinatal outcomes between twin and singleton pregnancies undergoing physical examination-indicated cerclage.

METHODS

Retrospective observational study (2007-2017) of women who underwent physical examination-indicated cerclage at the Hospital Clinic of Barcelona. Primary outcomes were latency from cerclage to delivery and gestational age at delivery. Secondary outcomes included: neonatal morbidity and mortality, preterm prelabor rupture of membranes, clinical chorioamnionitis and cerclage displacement. Wilcoxon-test and χ² test were used to compare continuous and categorical variables.

RESULTS

Sixty women were included (17 twins and 43 singletons). There were no differences in gestational age at cerclage or presence of bulging membranes between groups. Median (25th;75th percentile) gestational age at delivery was 27.1 (24.5;32.3) weeks in the twin group and 27.6 (25.3;35.3) weeks in the singleton group (P = 0.594). There were no statistically significant differences in latency from cervical cerclage to delivery between the two groups (43 days [21;64] vs. 29 days [16;76], respectively; P = 0.938). There were no differences in neonatal mortality (2/26 [7.7%] vs. 1/33 [3.1%]; P = 0.578) or in composite neonatal morbidity (14 [53.9%] vs. 14 [42.4%]; P = 0.283) between groups, respectively.

CONCLUSION

These results suggest that physical examination-indicated cerclage placement in twins could prolong latency to delivery similarly to singleton pregnancies.

Intra- and interobserver reproducibility of second trimester ultrasound cervical length measurement in a general population

Objectives: To evaluate the reproducibility of ultrasound cervical length (CL) measurement at the second trimester.Methods: A set of 565 cervical ultrasound images were collected at 19 + 0-24 + 6 weeks' gestation. Two senior maternal-fetal specialists measured CL in each image on three occasions 2 weeks apart. In the interval between the first and following two measures, the clinicians reviewed 20 images together to agree on the criteria for measurement. Measurements were analyzed for intra- and inter-observer disagreement. The robustness of patient classification when CL measure was used with different cutoff thresholds was analyzed.Results: Average intra-observer deviation was 2.8 mm for clinician 1 and 3.7 mm for clinician 2. Inter-observer deviation among the two clinicians was 5.2 and 3.2 mm before and after reviewing measurement criteria together. When cutoffs were used to classify as "short" cervix, disagreement ranged from 22 to 70% depending on operator and threshold used.Conclusion: Ultrasound CL measurements by experts showed moderate intra- and inter-observer reproducibility. The use of specific cutoffs to classify patients as high or low risk resulted in wide disagreements. The results stress the importance of training and quality assessments on considering universal screening application of CL measurement.

Cervical consistency index and risk of Cesarean delivery after induction of labor at term

OBJECTIVE

To evaluate the association between the cervical consistency index (CCI) and the risk of Cesarean delivery after planned induction of labor (IOL) at term.

METHODS

This was a prospective observational study of women with a term singleton pregnancy admitted for IOL due to maternal or fetal indication. Ultrasonographic images were obtained before IOL and CCI was calculated offline once recruitment was completed. The main outcome was defined as Cesarean delivery due to failed IOL or arrest of labor. Cesarean deliveries indicated due to maternal or fetal compromise (Van Dillen's grade 1 or 2) were excluded from analysis. Univariate statistical analysis was performed using Fisher's exact test and Student's t-test for categorical and continuous variables, respectively. Multivariate analysis was performed using logistic regression, including CCI and other variables related to the main outcome. Intraclass correlation coefficients were used to estimate intra- and interobserver agreement.

RESULTS

Of 510 women admitted for IOL during the study period and for whom image quality was adequate, 46 were excluded due to emergency Cesarean delivery leaving 464 pregnancies for analysis. Cesarean section due to failed IOL or arrest of labor was performed in 100/464 (21.6%) pregnancies. The mean CCI of women who underwent Cesarean delivery was not significantly different from that in those who had vaginal delivery after IOL (70.1 ± 12.3% vs 70.0 ± 13.1%; P = 0.94). Multivariate analysis also showed absence of statistical association between CCI and Cesarean delivery for failed IOL or arrest of labor. Intraclass correlation coefficients for intra- and interobserver agreement were 0.81 (95% CI, 0.66-0.89) and 0.86 (95% CI, 0.75-0.92), respectively.

CONCLUSION

CCI does not seem to be associated with the risk of Cesarean delivery after IOL. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Clinical and Sonographic Model to Predict Cesarean Delivery after Induction of Labor at Term

OBJECTIVE

To develop a model combining clinical and sonographic features to predict the risk of cesarean delivery after the induction of labor (IOL).

METHODS

We designed a prospective observational study involving women admitted for IOL. The main outcome was defined as cesarean delivery due to failed IOL or arrest of labor. Several clinical and ultrasonographic variables were collected. Seventy percent of the sample was used to build the predictive model, using stepwise logistic regression, while the remaining sample was used for validation. The final model was estimated and calibrated using all participants.

RESULTS

We analyzed 477 pregnancies. The main outcome occurred in 102/477 (21.4%) women. The final model included previous vaginal delivery (odds ratio [OR] 0.088; 95% confidence interval [CI] 0.04-0.21), height (OR 0.904; 95% CI 0.87-0.94), body mass index before delivery (OR 1.084; 95% CI 1.02-1.15), ultrasonographic estimated fetal weight (OR 3.965; 95% CI 2.18-7.22), and ultrasonographic cervical length (OR 1.065; 95% CI 1.04-1.09) as predictors. Area under the receiver operating characteristics curve was 0.826 (95% CI 0.78-0.87). For a 5% false-positive rate, the sensitivity, specificity, and positive and negative likelihood ratios were 44.1%, 94.9%, 8.7, and 0.59, respectively.

CONCLUSION

Our model combining clinical and ultrasonographic features might offer individualized counseling regarding risk of cesarean delivery to women who are candidates for IOL.

Quantitative analysis of cervical texture by ultrasound in mid-pregnancy and association with spontaneous preterm birth

OBJECTIVE

New tools are required to improve the identification of women who are at increased risk for spontaneous preterm birth (sPTB). Quantitative analysis of tissue texture on ultrasound has been used to extract robust features from the ultrasound image to detect subtle changes in its microstructure. This may be applied to the cervix. The aim of this study was to determine if there is an association between quantitative analysis of cervical texture (CTx) on mid-trimester ultrasound and sPTB < 37 + 0 weeks' gestation.

METHODS

This was a single-center nested case-control study of a prospective cohort of 677 consecutive women with singleton pregnancy assessed between 19 + 0 and 24 + 6 weeks' gestation. Women at increased risk for sPTB were included unless they received treatment to prevent sPTB. Women who delivered < 37 + 0 weeks (sPTB) were considered as cases and were matched in a 1: 10 ratio with randomly selected contemporary controls who delivered at term. For each woman, one ultrasound image of the cervix was obtained for which quality was assessed, cervical length (CL) measured offline and a region of interest in the midportion of the anterior cervical lip delineated for use in local binary patterns analysis of CTx. A learning algorithm was developed to obtain the combination of CTx features best associated with sPTB based on feature transformation and discriminant analysis regression. The ability of the learning algorithm to predict sPTB was evaluated using a leave-one-out cross-validation technique, which produced a CTx-based score for each participant. Receiver-operating characteristics (ROC) curves were produced and sensitivity, specificity, and positive and negative likelihood ratios were calculated for the optimal cut-off based on the ROC curve. The results were compared with those obtained for CL. Investigators studying the images were blinded to pregnancy outcome at all times.

RESULTS

Images from 310 women (27 cases and 283 controls) were of sufficient quality and included in the study. Median CTx-based score was significantly lower in cases compared with controls (-1.01 vs -0.07, P ≤ 0.0001). CTx-based score maintained its significant association with sPTB after adjusting for possible confounders (history of sPTB, conization or Müllerian malformation, and CL < 25 mm). CTx-based score was a better predictor of sPTB (AUC, 0.77; 95% CI, 0.66-0.87) than was CL (AUC, 0.60; 95% CI, 0.47-0.72) (P = 0.03). Median CL was similar for cases and controls (37.7 vs 38.6 mm, P = 0.26), although cases were more likely to have CL < 25 mm (18.5% vs 0.4%, P < 0.001).

CONCLUSION

Quantitative analysis of CTx enables the extraction of information relevant to sPTB from ultrasound images to generate a CTx-based score that is associated independently with sPTB. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Mid-trimester sonographic cervical consistency index to predict spontaneous preterm birth in a low-risk population

OBJECTIVES

To investigate the effectiveness of mid-trimester sonographic cervical consistency index (CCI) for the prediction of spontaneous preterm birth (sPTB) in low-risk pregnancies and to compare its performance with that of mid-trimester sonographic cervical-length (CL) measurement.

METHODS

This was a prospective cohort study of women with a singleton pregnancy examined by ultrasound at 19 + 0 to 24 + 6 weeks' gestation. All women underwent transvaginal ultrasound examination of the cervix, but CCI and CL were measured, offline, only in women without a risk factor for sPTB. Staff and participants were blinded to CL and CCI results. CCI was obtained by calculating the ratio between the anteroposterior diameter of the uterine cervix at maximum compression and at rest. The primary outcome was prediction of sPTB before 37 + 0 weeks. Receiver-operating characteristics (ROC) curves were produced and sensitivity and specificity were calculated for the optimal cut-off based on the ROC curve and for the 1^st , 5^th and 10^th centiles of CCI and CL. Intraclass correlation coefficients (ICC) and Bland-Altman plots were used to estimate intra- and interobserver agreement and reliability for measurement of CCI and CL.

RESULTS

Of the 749 women who underwent ultrasound examination of the cervix, 532 were included for analysis. The rates of sPTB before 37 + 0 and before 34 + 0 weeks were 4.1% (22/532) and 1.3% (7/532), respectively. The rates of short cervix < 25 mm and ≤ 20 mm were 0.9% (5/532) and 0.4% (2/532), respectively. The area under the ROC curve (AUC) with regard to predicting sPTB before 37 + 0 weeks was 0.84 (95% CI, 0.75-0.93) for CCI compared with 0.68 (95% CI, 0.56-0.81) for CL (P = 0.03). The optimal cut-off based on the ROC curve was 64.6% for CCI (sensitivity, 77.3%; specificity, 82.7%) and that for CL was 37.9 mm (sensitivity, 72.7%; specificity, 61.2%). The AUC with regard to predicting sPTB before 34 + 0 weeks was 0.87 (95% CI, 0.71-1.0) for CCI compared with 0.71 (95% CI, 0.47-0.94) for CL (P = 0.25). The optimal cut-off based on the ROC curve was 63.6% for CCI (sensitivity, 85.7%; specificity, 84.0%) and that for CL was 37.9 mm (sensitivity, 85.7%; specificity, 61.3%). Intraobserver ICC was > 0.90 both for CCI and CL, while interobserver ICC was 0.89 for CCI and 0.90 for CL.

CONCLUSIONS

Second-trimester CCI is a better predictor of sPTB < 37 weeks in low-risk pregnancies than is CL. External validation is needed as well as studies assessing the value of CCI as a screening tool in unselected and high-risk populations. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Mid-Trimester Cervical Consistency Index and Cervical Length to Predict Spontaneous Preterm Birth in a High-Risk Population

Background  Short cervical length (CL) has not been shown to be adequate as a single predictor of spontaneous preterm birth (sPTB) in high-risk pregnancies. Objective  The objective of this study was to evaluate the performance of the mid-trimester cervical consistency index (CCI) to predict sPTB in a cohort of high-risk pregnancies and to compare the results with those obtained with the CL. Study Design  Prospective cohort study including high-risk singleton pregnancies between 19 ⁺⁰ and 24 ⁺⁶ weeks. The ratio between the anteroposterior diameter of the uterine cervix at maximum compression and at rest was calculated offline to obtain the CCI. Results  Eighty-two high sPTB risk women were included. CCI (%) was significantly reduced in women who delivered <37 ⁺⁰ weeks compared with those who delivered at term, while CL was not. The area under the curve (AUC) of the CCI to predict sPTB <37 ⁺⁰ weeks was 0.73 (95% confidence interval [CI], 0.61-0.85), being 0.51 (95% CI, 0.35-0.67), p  = 0.03 for CL. The AUC of the CCI to predict sPTB <34 ⁺⁰ weeks was 0.68 (95% CI, 0.54-0.82), being 0.49 (95% CI, 0.29-0.69), p  = 0.06 for CL. Conclusion  CCI performed better than sonographic CL to predict sPTB. Due to the limited predictive capacity of these two measurements, other tools are still needed to better identify women at increased risk.

Quantitative Analysis of the Cervical Texture by Ultrasound and Correlation with Gestational Age

OBJECTIVES

Quantitative texture analysis has been proposed to extract robust features from the ultrasound image to detect subtle changes in the textures of the images. The aim of this study was to evaluate the feasibility of quantitative cervical texture analysis to assess cervical tissue changes throughout pregnancy.

METHODS

This was a cross-sectional study including singleton pregnancies between 20.0 and 41.6 weeks of gestation from women who delivered at term. Cervical length was measured, and a selected region of interest in the cervix was delineated. A model to predict gestational age based on features extracted from cervical images was developed following three steps: data splitting, feature transformation, and regression model computation.

RESULTS

Seven hundred images, 30 per gestational week, were included for analysis. There was a strong correlation between the gestational age at which the images were obtained and the estimated gestational age by quantitative analysis of the cervical texture (R = 0.88).

DISCUSSION

This study provides evidence that quantitative analysis of cervical texture can extract features from cervical ultrasound images which correlate with gestational age. Further research is needed to evaluate its applicability as a biomarker of the risk of spontaneous preterm birth, as well as its role in cervical assessment in other clinical situations in which cervical evaluation might be relevant.

Definition of Failed Induction of Labor and Its Predictive Factors: Two Unsolved Issues of an Everyday Clinical Situation

OBJECTIVE

The objectives of this review were to identify the predictive factors of induction of labor (IOL) failure or success as well as to highlight the current heterogeneity regarding the definition and diagnosis of failed IOL.

MATERIALS AND METHODS

Only studies in which the main or secondary outcome was failed IOL, defined as not entering the active phase of labor after 24 h of prostaglandin administration ± 12 h of oxytocin infusion, were included in the review. The data collected were: study design, definition of failed IOL, induction method, IOL indications, failed IOL rate, cesarean section because of failed IOL and predictors of failed IOL.

RESULTS

The database search detected 507 publications. The main reason for exclusion was that the primary or secondary outcomes were not the predetermined definition of failed IOL (not achieving active phase of labor). Finally, 7 studies were eligible. The main predictive factors identified in the review were cervical status, evaluated by the Bishop score or cervical length.

DISCUSSION

Failed IOL should be defined as the inability to achieve the active phase of labor, considering that the definition of IOL is to enter the active phase of labor. A universal definition of failed IOL is an essential requisite to analyze and obtain solid results and conclusions on this issue. An important finding of this review is that only 7 of all the studies reviewed assessed achieving the active phase of labor as a primary or secondary IOL outcome. Another conclusion is that cervical status remains the most important predictor of IOL outcome, although the value of the parameters explored up to now is limited. To find or develop predictive tools to identify those women exposed to IOL who may not reach the active phase of labor is crucial to minimize the risks and costs associated with IOL failure while opening a great opportunity for investigation. Therefore, other predictive tools should be studied in order to improve IOL outcome in terms of health and economic burden.

Insulin and IGF-I receptors in trout adipose tissue are physiologically regulated by circulating hormone levels

In fish, insulin is believed to act on adipose tissue to promote lipid accumulation, but a direct role for insulin in fish adipose tissue lipogenesis has yet to be demonstrated. To investigate the role of insulin and insulin-like growth factor I (IGF-I) in fish adipose tissue function, we have investigated the presence and the regulation of insulin and IGF-I receptors in adipose tissue of brown trout (Salmo trutta). Receptors for insulin and IGF-I were detected in trout adipose tissue, with IGF-I receptors being more abundant (two- to tenfold) and having a higher affinity (twofold) than insulin receptors. In contrast to the situation in mammals, arginine treatment, which elevates the levels of insulin and IGF-I in plasma, increased the number of insulin receptors 1.7-fold and the number of IGF-I receptors 2.3-fold. When plasma levels of insulin and IGF-I were decreased by fasting, insulin receptor numbers fell 3.6-fold and IGF-I receptor numbers fell 2.2-fold. These results demonstrate for the first time the presence of specific insulin and IGF-I receptors in adipose tissue of ectothermic vertebrates and suggest that adipose tissue may be a target for the actions of insulin and IGF-I in fish.

Regulation of plasma insulin-like growth factor-I levels in brown trout (Salmo trutta)

In this study we report that the use of a heterologous radioimmunoassay (RIA) is valid for the detection of insulin-like growth factor-I (IGF-I) levels in plasma of a variety of fish species. Parallelism between standard curves and plasma dilutions were observed and the standard curve obtained with mammalian IGF-I presented the same characteristics as that obtained with coho salmon recombinant IGF-I. The RIA was biologically validated since total plasma IGF-I values were significantly modified by different experimental conditions. Hyperinsulinemia induced either by arginine or insulin injection was accompanied by increases in IGF-I plasma levels in brown trout (Salmo trutta). In contrast, parallel decreases in insulin and IGF-I circulating levels were observed after 45 days of fasting and 20 days after a single streptozotocin injection. Administration of arginine in fasted fish led to a relative increase in insulin and IGF-I plasma concentrations, while arginine injection in fish previously treated with streptozotocin increased IGF-I levels only. The above data suggest that insulin, together with other factors, may act to increase the levels of IGF-I in plasma.

Insulin, insulin-like growth factor-I (IGF-I) and glucagon: the evolution of their receptors

Insulin and glucagon, two of the most studied pancreatic hormones bind to specific membrane receptors to exert their biological actions. Insulin-like growth factors IGF-I and IGF-II are structurally related to insulin, although they are expressed ubiquitously. The biological functions of the IGFs are mediated by different transmembrane receptors, which includes the insulin, IGF-I and IGF-II receptors. The interaction of insulin, insulin related peptides and glucagon with the corresponding receptors has been studied extensively in mammals and continues to be so. At the same time, research on ectothermic animals has made enormous progress in the recent years. This paper summarizes current knowledge on insulin, IGF-I and glucagon receptors, from a comparative point of view with special attention to non-mammalian vertebrates. The review covers adult and mostly typical target tissues, and with very few exceptions, developmental aspects are not considered. Binding characteristics, tissue distribution and structure of insulin and IGF-I receptors will be considered first, because both ligands and receptors are structurally related and have overlapping functions. These sections will be followed by similar distribution of information on glucagon receptors. Readers interested in either structure or functions of insulin, IGFs and glucagon in nonmammalian vertebrates are referred to other reviews (Mommsen TP, Plisetskaya EM. Insulin in fishes and agnathans: history, structure and metabolic regulation. Rev Aquat Sci 1991;4:225-259; Mommsen TP, Plisetskaya EM. Metabolic and endocrine functions of glucagon-like peptides: evolutionary and biochemical perspectives. Fish Physiol Biochem 1993;11:429-438; Duguay SJ, Mommsen TP. Molecular aspects of pancreatic peptides. In: Sherwood NM, Hew CL, editors, Fish Physiology. vol 13. 1994:225-271; Plisetskaya EM, Mommsen TP. Glucagon and glucagon-like peptides in fishes. Int Rev Citol 1996;168:187-257.).

Influence of high-carbohydrate enriched diets on plasma insulin levels and insulin and IGF-I receptors in trout

Insulin and insulin growth factor-I (IGF-I) binding to skeletal muscle semipurified receptors were assessed in rainbow trout (Oncorhynchus mykiss) fed with different enriched carbohydrate diets. The animals were fed for 2 months, either in spring, summer or autumn with a control diet (C, commercial diet containing 21% raw carbohydrates) or with two diets supplied with highly digestible carbohydrates (E1, 22% expanded wheat; and E2, 37% expanded wheat). Insulin and IGF-I receptors were semipurified by affinity chromatography (WGA-agarose). Fish fed with a carbohydrate enriched diet did not show lower growth rates than those fed with the control diet. Independently of the season, rainbow trout fed E1 and E2 presented higher insulin and glucose plasma levels as well as higher tissue glycogen reserves than fish fed C. An increase in the number of insulin receptors during the diet adaptation was observed especially in fish fed with E2. No differences in the affinity of receptors were observed. IGF-I specific binding in skeletal muscle was higher than that of insulin in all groups and in all seasons. Furthermore, IGF-I receptors showed the same tendency as insulin receptors, with increases in their number in experimentally fed fish, especially those fed with E2. Insulin and IGF-I receptors TKA increased only slightly, as a consequence of E1 and E2 diet adaptation. In conclusion, rainbow trout can be fed high-carbohydrate levels and show good rates of growth. This adaptation determines increases in circulating glucose and insulin, and muscle insulin receptors, which indicate an adaptation of the fish to higher levels of glucose supply. The response of IGF-I receptors also suggests a possible role in the regulation of metabolism.

Appearance of insulin and insulin-like growth factor-I (IGF-I) receptors throughout the ontogeny of brown trout (Salmo trutta fario)

Insulin and IGF-I receptors were characterized in glycoprotein fractions prepared by affinity chromatography from different developmental stages of brown trout. The specificity of insulin and IGF-I binding was demonstrated by crossed-competition assays: unlabelled insulin displaced bound radiolabelled insulin at concentrations 45-fold lower than unlabelled IGF-I, whilst unlabelled IGF-I displaced bound radiolabelled IGF-I at concentrations 2,000-fold lower than unlabelled insulin. The affinity of these receptors did not change significantly during trout development. Insulin-specific binding was detectable 3 weeks after spawning, after which it increased to a maximum in fry weighing 0.4 g, and decreased progressively to adult levels. IGF-I specific binding was detectable in newly laid eggs and increased to a maximum during organogenesis in eyed eggs. It then decreased progressively during subsequent stages of development to adult levels. The apparent molecular weight (Mr) of the alpha-subunit of brown trout insulin and IGF-I receptors was smaller than that of the alpha-subunit of the rat insulin receptor. Receptor tyrosine kinase activity was stimulated in a dose-dependent manner by insulin and IGF-I. Insulin and IGF-I stimulated tyrosine kinase activity and reached a maximum of 201 +/- 17.6 and 240 +/- 29.6% of basal phosphorylation, respectively.

Insulin and insulin-like growth factor-I (IGF-I) binding in fish red muscle: regulation by high insulin levels

Insulin and IGF-I binding to semi-purified red muscle receptors was characterized in brown trout, Salmo trutta and the common carp. Cyprinus carpio. The yield of glycoprotein obtained after semipurification of receptors with WGA-agarose affinity chromatography in microgram g-1 initial tissue was 210.6 +/- 21 micrograms g-1 in trout and 108.5 +/- 2.5 micrograms g-1 in carp. IGF-I specific binding (4.72 +/- 0.64%/10 micrograms glycoprotein) was 4-5-times higher than insulin binding (1.04 +/- 0.12%/10 micrograms glycoprotein) in trout red muscle. This difference in binding was due to a higher number and a greater affinity of the IGF-I (Kd, 0.21 +/- 0.03 nM) compared with the insulin (Kd, 0.67 +/- 0.06 nM) receptors in this tissue. Carp red muscle IGF-I binding (9.14 +/- 0.55%/10 micrograms glycoprotein) surpassed insulin binding (2.59 +/- 0.094%/10 micrograms glycoprotein) mainly because of a greater affinity of the IGF-I (Kd, 0.092 +/- 0.027 nM) compared with the insulin (Kd, 0.1515 +/- 0.0285 nM) receptor. IGF-I and insulin binding in carp red muscle were higher than in trout, as a consequence of a higher affinity of carp red muscle receptors. Arginine injection provoked acute hyperinsulinemia in both trout (23.3 +/- 1.01 ng ml-1) and carp (24.3 +/- 1.34 ng ml-1. Specific binding of insulin and IGF-I to the red muscle decreased 4 h after injection. In trout, a decrease of insulin and IGF-I binding of 47.0% and 63.3%, respectively was observed compared with controls, in carp, these values were 44.0% and 45.0%. The number of insulin and IGF-I receptors decreased (42-55%) but affinities did not change suggesting that receptor down-regulation is a consequence of high insulin levels.

Insulin and IGF-I binding in isolated trout cardiomyocytes

Insulin and IGF-I receptor binding were characterized in cardiac muscle cells isolated from the brown trout, Salmo trutta fario. Cardiomyocyte suspensions obtained by perfusion of ventricles with collagenase showed a high degree of viability as judged by trypan blue exclusion, LDH leakage, and morphology. Specific insulin binding was 2.88 +/- 0.28%/10 mg cells after overnight incubation at 4 degrees. Scatchard analysis indicated the presence of high affinity insulin binding sites with an apparent dissociation constant (Kd) of 0.285 +/- 0.043 nM and a binding site density of 1. 61 +/- 0.19 x 10(8)/mg cells. Specificity of insulin binding was determined by displacing labeled insulin with increasing concentrations of IGF-I, and the Kd value obtained was 4.77 +/- 2.82 nM, 17-fold higher than Kd values for displacement of insulin tracer by nonlabeled insulin. The percentage of IGF-I specific binding (6.70 +/- 1.42%/10 mg cells), affinity (Kd = 0.163 +/- 0.023 nM), and binding site density (4.00 +/- 1.13 x 10(8)/mg cells) were higher than those of insulin. Displacement curves of labeled IGF-I with nonlabeled insulin (Kd = 33.6 +/- 9.9 nM), indicated a high specificity of the IGF-I binding site. High concentrations of cold insulin and IGF-I were able to decrease markedly the specific binding to their own receptor. Incubation with cold IGF-I also induced a diminution in insulin binding in agreement with the lower specificity of the insulin receptor. These data suggest that insulin and IGF-I are able to down-regulate their own receptor number in cardiac muscle cells. The present results demonstrate that the isolated cardiac myocyte preparation from brown trout is a useful model for studying insulin and IGF-I binding in fish heart tissue.

Insulin/IGF-I binding ratio in skeletal and cardiac muscles of vertebrates: a phylogenetic approach

Insulin and insulin-like growth factor (IGF-I) receptor binding and tyrosine kinase activity were characterized in cardiac and skeletal muscles of several vertebrates. Specific insulin binding per unit weight of skeletal muscle was clearly higher in pigeon and rat than in ectothermic vertebrates (32 +/- 5 and 25 +/- 2.7%/100 mg initial tissue in pigeon and rat, respectively, vs. 4.4 +/- 0.2%/100 mg in carp samples). Insulin binding clearly predominated over IGF-I binding in skeletal muscle of endotherms (IGF-I binding was 7.7 +/- 0.5%/100 mg in rat). In ectothermic vertebrates the situation was reversed, and IGF-I binding was higher than insulin binding. In cardiac muscle, specific binding of both insulin and especially IGF-I was higher than the values found in skeletal muscle of the same species (IGF-I binding was 60 +/- 4, 103 +/- 2, and 20 +/- 3%/100 mg in carp, turtle, and rat, respectively). The tyrosine kinase activity of insulin and IGF-I receptors of all species studied presented basal phosphotransferase rates (250-1,600 fmol P.micrograms protein-1.30 min-1) and percentage of stimulation (150-520%) with clear differences between species. The present data suggest that insulin and IGF-I binding to skeletal and cardiac muscles change through the vertebrate scale in both quantity and activity.

Up-regulation of insulin binding in fish skeletal muscle by high insulin levels

The effects of insulin titres on regulation of receptor binding were studied in several fish species. Insulin receptors were semi-purified by affinity chromatography (WGA-agarose) from skeletal muscle of carp, brown trout and rainbow trout that had been subjected to increases in insulinemia produced either by arginine injection, food administration, or adaptation to an experimental diet (extruded diet with high-digestibility carbohydrates). Arginine injection provoked acute hyperinsulinemia in both carp and trout. Specific binding of insulin to the skeletal muscle was significantly increased 3 h after injection (from 5.8 +/- 0.3 to 9.6 +/- 0.9%/10 micrograms protein in carp and from 0.8 +/- 0.2 to 1.5 +/- 0.4%/10 micrograms in trout). The same effect was observed in carp liver preparations (from 6.0 +/- 0.75 to 9.9 +/- 1.25%/10 micrograms). No alterations in tyrosine kinase activity of the receptors were detected in either carp or trout preparations: basal activities of the receptors were maintained (3100 +/- 200 fmol P/fmol receptors/30 min and 3700 +/- 400 fmol P/fmol receptors/30 min, in carp and trout, respectively), as were the percentage of stimulation over basal levels obtained by incubation with insulin (227 +/- 25% and 160 +/- 10% respectively). Food ingestion raised plasma insulin levels more steadily. Specific binding also increased in skeletal muscle preparations, especially in carp (from 5.7 +/- 0.3 to 11 +/- 1.7%/10 micrograms at 4 h and 10 +/- 0.7%/10 micrograms at 8 h). Tyrosine kinase activity was maintained without significant changes. Rainbow trout adapted for 2 months to an extruded diet presented higher insulin titres and higher glycogen reserves in liver and muscle. Insulin binding to skeletal muscle preparations was also significantly increased (from 0.36 +/- 0.02 to 0.77 +/- 0.1%/10 micrograms), as was tyrosine kinase activity (from 132 +/- 4% to 156 +/- 6%, without alterations in the basal activity). Results showed that fish can respond to both acute and maintained increases in insulinemia by increasing the number of insulin receptors. Tyrosine kinase activity, in contrast, is only modified after long-term adaptation.