Haemodynamic, endocrine and renal actions of adrenomedullin 5 in an ovine model of heart failure

A refined, minimally invasive, reproducible ovine ischaemia-reperfusion-infarction model using implantable defibrillators: Methodology and validation

Ischaemic heart disease remains a leading cause of premature mortality and morbidity. Understanding the associated pathophysiological mechanisms of cardiac dysfunction arising from ischaemic heart disease and the identification of sites for new therapeutic interventions requires a preclinical model that reproduces the key clinical characteristics of myocardial ischaemia, reperfusion and infarction. Here, we describe and validate a refined and minimally invasive translationally relevant approach to induce ischaemia, reperfusion and infarction in the sheep. The novelty and refinement in the procedure stems from utilization of implantable cardiac defibrillators prior to coronary engagement, balloon angioplasty to induce infarction, and intra-operative anti-arrhythmic drug protocols to reduce adverse arrhythmic events. The protocol is readily adoptable by researchers with access to standard fluoroscopic instrumentation, and it requires minimally invasive surgery. These refinements lead to a substantial reduction of intra-operative mortality to 6.7% from previously published values ranging between 13% and 43%. The model produces key characteristics associated with the fourth universal definition of myocardial infarction, including ECG changes, elevated cardiac biomarkers and cardiac wall motility defects. In conclusion, the model closely replicates the clinical paradigm of myocardial ischaemia, reperfusion and infarction in a translationally relevant large animal setting, and the applied refinements reduce the incidence of intra-operative mortality typically associated with preclinical myocardial infarction models.

Comprehensive expression analysis of hormone-like substances in the subcutaneous adipose tissue of the common bottlenose dolphin Tursiops truncatus

Marine mammals possess a specific subcutaneous fat layer called blubber that not only insulates and stores energy but also secretes bioactive substances. However, our understanding of its role as a secretory organ in cetaceans is incomplete. To exhaustively explore the hormone-like substances produced in dolphin subcutaneous adipose tissue, we performed seasonal blubber biopsies from captive female common bottlenose dolphins (Tursiops truncatus; N = 8, n = 32) and analyzed gene expression via transcriptomics. Analysis of 186 hormone-like substances revealed the expression of 58 substances involved in regulating energy metabolism, tissue growth/differentiation, vascular regulation, immunity, and ion/mineral homeostasis. Adiponectin was the most abundantly expressed gene, followed by angiopoietin protein like 4 and insulin-like growth factor 2. To investigate the endocrine/secretory responses of subcutaneous adipose tissue to the surrounding temperature, we subsequently compared the mean expression levels of the genes during the colder and warmer seasons. In the colder season, molecules associated with appetite suppression, vasodilation, and tissue proliferation were relatively highly expressed. In contrast, warmer seasons enhanced the expression of substances involved in tissue remodeling, immunity, metabolism, and vasoconstriction. These findings suggest that dolphin blubber may function as an active secretory organ involved in the regulation of metabolism, appetite, and tissue reorganization in response to changes in the surrounding environment, providing a basis for elucidating the function of hormone-like substances in group-specific evolved subcutaneous adipose tissue.

Comparison of first-line and second-line terlipressin versus sole norepinephrine in fulminant ovine septic shock

The Surviving Sepsis Guidelines suggest the use of vasopressin in case of catecholamine-refractory septic shock. Terlipressin (TP) as a V₁-selective AVP analogue is a potential alternative, though data regarding the first-line administration in septic shock are scarce. The present study explored and compared the effects of first-line vs. second-line infusion of TP or sole norepinephrine regarding organ function, fluid and norepinephrine requirements and survival in fulminant ovine septic shock. Peritoneal sepsis was induced in 23 ewes after laparotomy and faecal withdrawal from the caecum. After onset of shock, causal and supportive sepsis therapy (antibiotics, peritoneal lavage, fluids and open-label norepinephrine) was performed in all animals. Concurrently, animals were randomized to receive 0.9% sodium chloride (control group) or TP (2 µg∙kg^-1∙h^-1, first-line group) after shock onset. In the second-line TP group, TP (2 µg∙kg^-1∙h^-1) was started once norepinephrine requirements exceeded 0.5 µg∙kg^-1∙min^-1. No significant differences were found between groups regarding survival, haemodynamics as well as fluid- and catecholamine-requirements. Kidney function and electron microscopic kidney injury were comparable between groups. In the present model of fulminant ovine septic shock, first-line TP infusion had no significant effect on fluid and norepinephrine requirements or organ dysfunction as compared to second-line TP infusion or placebo.

Provision of physiological data and reference values in awake and anaesthetized female sheep aged 6-12 months

OBJECTIVE

To provide physiological data and reference values in awake and anaesthetized sheep aged 6-12 months.

STUDY DESIGN

Descriptive study.

ANIMALS

Data from 260 female sheep of the species Ovis orientalis aries aged 6-12 months were extracted from 10 experimental trials.

METHODS

Data from pulmonary arterial thermodilution in awake (cohort 1; n = 109) and anaesthetized animals (cohort 2; n = 81), and transpulmonary thermodilution in anaesthetized animals (cohort 3; n = 70) were analysed. General anaesthesia was induced by intramuscular injection of S-ketamine and midazolam and maintained by inhaled isoflurane. Standard laboratory variables (blood gas and clinical chemistry) were assessed.

RESULTS

A total of 7553 single data entries from 260 healthy sheep were included. Measurement errors or invalid data documentation meant that 313 data entries (4.1%) were excluded. A small confidence interval for median values was calculated for nearly all variables. The median body weight was 39.8 kg (2.5-97.5th percentile 30.6-48.1 kg). A set of reference values (2.5-97.5th percentiles) is provided for common cardiopulmonary and laboratory variables. Compared to awake animals, haemodynamic variables were markedly influenced by anaesthesia, as reflected by a considerably lower stroke volume index in anaesthetized sheep. There were also differences in stroke volume index between the cohorts of pulmonary artery and transpulmonary thermodilution.

CONCLUSIONS AND CLINICAL RELEVANCE

The present work presents a large and consistent database of a variety of physiological variables measured in healthy juvenile female sheep. The data appear to be robust and allow the establishment of standardized inclusion criteria for experimental studies and may help to better evaluate past, present and future research. Differences between pulmonary artery and transpulmonary thermodilution should be assessed in future studies.

Adrenomedullin regulates intestinal physiology and pathophysiology

Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are 2 biologically active peptides produced by the same gene, ADM, with ubiquitous distribution and many physiological functions. Adrenomedullin is composed of 52 amino acids, has an internal molecular ring composed by 6 amino acids and a disulfide bond, and shares structural similarities with calcitonin gene-related peptide, amylin, and intermedin. The AM receptor consists of a 7-transmembrane domain protein called calcitonin receptor-like receptor in combination with a single transmembrane domain protein known as receptor activity-modifying protein. Using morphologic techniques, it has been shown that AM and PAMP are expressed throughout the gastrointestinal tract, being specially abundant in the neuroendocrine cells of the gastrointestinal mucosa; in the enterochromaffin-like and chief cells of the gastric fundus; and in the submucosa of the duodenum, ileum, and colon. This wide distribution in the gastrointestinal tract suggests that AM and PAMP may act as gut hormones regulating many physiological and pathologic conditions. To date, it has been proven that AM and PAMP act as autocrine/paracrine growth factors in the gastrointestinal epithelium, play key roles in the protection of gastric mucosa from various kinds of injury, and accelerate healing in diseases such as gastric ulcer and inflammatory bowel diseases. In addition, both peptides are potent inhibitors of gastric acid secretion and gastric emptying; they regulate the active transport of sugars in the intestine, regulate water and ion transport in the colon, modulate colonic bowel movements and small-intestine motility, improve endothelial barrier function, and stabilize circulatory function during gastrointestinal inflammation. Furthermore, AM and PAMP are antimicrobial peptides, and they contribute to the mucosal host defense system by regulating gut microbiota. To get a formal demonstration of the effects that endogenous AM and PAMP may have in gut microbiota, we developed an inducible knockout of the ADM gene. Using this model, we have shown, for the first time, that lack of AM/PAMP leads to changes in gut microbiota composition in mice. Further studies are needed to investigate whether this lack of AM/PAMP may have an impact in the development and/or progression of intestinal diseases through their effect on microbiota composition.

Adrenomedullin induces pulmonary vasodilation but does not attenuate pulmonary hypertension in a sheep model of acute pulmonary embolism

AIMS

The pulmonary vasodilation induced by adrenomedullin may be beneficial in the acute pulmonary embolism (APE) setting. This study examined effects of adrenomedullin in sheep with microsphere-induced APE.

MAIN METHODS

Twenty four anesthetized, mechanically ventilated sheep were randomly assigned into 3 groups (n=8 per group): animals not subjected to any intervention (Sham), animals with APE induced by microspheres (500 mg, intravenously) treated 30 min later by intravenous physiological saline (Emb group) or intravenous adrenomedullin (50 ng/kg/min) during 30 min (Emb+Adm group). Plasma concentrations of cyclic adenosine (cAMP) and guanosine monophosphate (cGMP) were determined by enzyme immunoassay.

KEY FINDINGS

Variables did not change over time in sham animals. In both embolized groups, microsphere injection significantly (P<0.05) increased pulmonary vascular resistance index (PVRI) and mean pulmonary artery pressure (MPAP) from baseline by 181% and 111-142%, respectively (% change in mean values). Adrenomedullin significantly decreased PVRI (18%-25%) and significantly increased cardiac index (22%-25%) from values recorded 30 min after APE (E30), without modifying MPAP. Adrenomedullin decreased mean arterial pressure (18%-24%) and systemic vascular resistance index (32%-40%). Embolization significantly increased arterial-to-end tidal CO2 gradient, alveolar-to-arterial O2 gradient, and pulmonary shunt fraction from baseline, but these variables were unaffected by adrenomedullin. While adrenomedullin significantly increased plasma cAMP, cGMP levels were unaltered.

SIGNIFICANCE

Adrenomedullin induces systemic and pulmonary vasodilation, possibly via a cAMP mediated mechanism, without modifying the gas exchange impairment associated with APE. The pulmonary anti-hypertensive effect of adrenomedullin may be offset by increases in cardiac index.

Copeptin and MR-proADM in umbilical cord plasma reflect perinatal stress in neonates born to mothers with diabetes and MR-proANP reflects maternal diabetes

AIM

To examine concentrations of three cardiovascular propeptides in umbilical cord plasma of neonates born to mothers with Type 1, Type 2 and gestational diabetes. Measurement of cardiovascular markers in umbilical cord plasma may potentially help identify neonates at risk of postnatal complications. Neonates born to mothers with diabetes have an increased risk of neonatal morbidity and mortality, and measurement of these new biomarkers may potentially help identify neonates at risk of these complications.

SUBJECTS & METHODS

Copeptin, midregional proadrenomedullin (MR-proADM) and mid-regional pro-A-type natriuretic peptide (MR-proANP) were measured in cord plasma of neonates (n = 63) born to mothers with the three types of diabetes. Associations with maternal glycemic control, mode of delivery and neonatal metabolic acidosis were examined.

RESULTS

Umbilical cord plasma copeptin concentrations were lowest in neonates after elective cesarean sections (6.1 pmol/l; interquartile range [IQR]: 4.5-9.1) compared with emergency cesarean sections (156 pmol/l; IQR: 9.6-311; p = 0.019) and vaginal delivery (831 pmol/l; IQR: 107-2407; p < 0.0001). MR-proADM was also affected by mode of delivery; however, this seemed more likely to be caused by an inverse association with the acid-base balance. In this population, only MR-proANP plasma concentrations were related to type of diabetes. Neonates born to mothers with Type 1 diabetes had higher concentrations (median 260 pmol/l; IQR: 222-318) compared with Type 2 diabetes (175 pmol/l; IQR: 169-200; p = 0.003) and gestational diabetes (200 pmol/l; IQR: 149-276; p = 0.009).

CONCLUSION

Umbilical cord plasma copeptin and MR-proADM concentrations primarily reflect perinatal stress associated with mode of delivery and the degree of fetal acidosis, whereas MR-proANP concentrations are higher in neonates born to mothers with Type 1 diabetes.