This study was completed in mouse models and in human HF patients.
Animals
Two transgenic (TG) strains of mice with cardiomyocyte-restricted overexpression of either β2- adrenergic receptor (β2- AR TG) or Mammalian sterile 20-like kinase 1 (Mst1 TG) were used in the present study. Our previous works have characterized cardiomyopathic phenotypes of both models [16, 18-20]. All strains of mice were from the same C57Bl/6 genetic background. Only male mice were studied. Age-matched non-transgenic (nTG) littermates were used as controls. Mice were housed in standard conditions with food and water provided ad libitum. All experimental procedures were approved by a local animal ethics committee in compliance with both the Australian Code for the Care and Use of Animals for Scientific Purposes (8th edition) and the ARRIVE guidelines.
Subjects
This protocol was approved by the ethics committee of the First Affiliated Hospital of Xi'an Jiaotong University (Shaanxi 710061, China) and was in accordance with the Helsinki Declaration's guidelines. Informed consent was obtained for all participants. The cohort study consisted of chronic HF patients, aged between 18–80 years, who were diagnosed with heart failure with reduced ejection fraction (HFrEF) in the Department of Cardiovascular Medicine at Xunyi Hospital and Jingyang Hospital from May 2014 to May 2015. Patients were then followed up for a period of 50 months and were evaluated for the development of major adverse cardiovascular events (MACEs). Patients were excluded from the present study if they had acute HF, active neoplasia, acute myocardial infarction, acute or chronic liver disease (alanine aminotransferase level >5 times the upper normal limit), acute stroke, serious kidney disease, chronic consumption disease, thyroid dysfunction, fibrotic pathologies (e.g., pulmonary fibrosis, collagenases), and/or cancer. Following these exclusion criteria, a total of 166 HF patients were recruited. All participants were divided into two groups (group 1 and group 2) according to their Gal-3 levels. Then, based on their clinical features, patients from each group were further divided into two subgroups, with coronary-heart-disease (CHD) group and without CHD group.
Histological and plasma analyses in mice
Blood was collected in heparin-containing vials when mice were killed, centrifuged at 4°C (3,000 rpm in 20 min), and stored at −80°C. Plasma Gal-3 levels were detected by a mice Galectin-3 Quantikine ELISA Kit (R&D Systems Inc., Minneapolis, MN, USA) in twin duplicates wells , following protocols provided by the manufacturer. And then Paraffin-embedded LV sections (6 μm) were prepared and used for Gal-3 immunofluorescent staining. For Gal-3 immunofluorescent staining, after samples had been dewaxed, heat-induced antigen retrieval and permeabilization were carried out (with 10 mM of Na-citrate buffer containing 0.05% Tween 20; pH 6.0; 95°C for 25 min) followed by blocking with DAKO Protein Block (X0909, Agilent, 1 h at room temperature). Sections were incubated with primary goat anti-mouse Gal-3 (1:100, AF1197, R&D Systems) overnight at 4°C, after which they were incubated with the secondary antibody, Alexa Fluor 594 donkey anti-goat IgG (1:200, A11058, Invitrogen by Thermo Fisher Scientific). The cardiomyocyte boundary was revealed by wheat-germ-agglutinin FITC staining (1:80, FL-1021, Vector Labs, 1 h at room temperature). Images were acquired with an Olympus BX61 fluorescent microscope.
Clinical measurements
Investigators and a trained interviewer collected all of the clinical data. The trained interviewer collected patient information, including demographic data, past medical history, history of cardiovascular diseases, the Minnesota Living with Heart Failure Questionnaire (MLHFQ), New York Heart Association (NYHA) functional class, smoking behavior, and alcohol abuse. Smoking was defined as smoking cigarettes within one month of the indexed hospital admission. Hypertension was defined as a cuff blood pressure ≥140/90 mmHg and/or the current use of antihypertensive medications. Subjects were also questioned about their past histories of diabetes mellitus and their current use of anti-diabetic drugs. Diagnosis of diabetes was confirmed if plasma fasting glucose was ≥7.0 mM (or if the 2-h postprandial glucose was > 11.1 mM) or if there was current use of anti-diabetic medication. Anthropometric measurements, such as body weight (kg) and height (m), were taken during the first visit. Body mass index (BMI) was calculated as weight divided by height squared.
Analysis of patients blood parameters
Blood was collected from each patient at admission. After overnight fasting, between 6–7 a.m., blood from the median cubital vein was drawn into ethylenediaminetetraacetic acid (EDTA)-containing tubes. Plasma was separated within 2 h after collection. Blood parameters were measured at the Central Clinical Laboratory of the First Affiliated Hospital of Xi'an Jiaotong University, including hemoglobin (HB), creatinine (CR), urea nitrogen (BUN), alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Plasma samples for later analyses (i.e., to detect Gal-3 levels) were collected in EDTA-containing vials, centrifuged at 4°C (3,000 rpm in 10 min), and stored at −80°C.
Plasma Gal-3 levels were detected by a Human Galectin-3 Quantikine ELISA Kit (R&D Systems Inc., Minneapolis, MN, USA) in duplicates wells, following protocols provided by the manufacturer; the mean serum Gal-3 value was calculated as the final level. The detection range of the plasma Gal-3 immunoassay was 0–4,000 pg/mL. Plasma TIMP-1 levels were detected by a human TIMP-1 Quantikine ELISA Kit (Abbkine, Inc., China) in duplicates wells, following protocols provided by the manufacturer, the mean serum TIMP-1 value was calculated as the final level. The calibration range of serum TIMP-1 was 31.25–2,000 ng/mL, and the limit of detection was 16 ng/mL.
Echocardiographs and electrocardiograms
Echocardiographs were performed with a Phillips iE33 system by a single trained operator blinded to the Gal-3 plasma concentration of each subject. All echo data were analyzed by a single operator to limit inter-observer variability. The left ventricular ejection fraction (LVEF) was calculated by the Simpson biplane model. The following standard parameters were collected: left ventricular end-systolic and end-diastolic volumes (LVESV and LVEDV); left ventricular end-systolic and end-diastolic dimensions (LVESD and LVEDD); and left ventricular fraction shortness (LVFS). The 12 electrocardiographic leads were made up of three standard limb leads (I, II, and III), augmented limb leads (aVR, aVL and aVF), and six precordial leads (V1, V2, V3, V4, V5, and V6). The QT interval was best measured between the beginning of the Q wave until the end of the T wave in lead II.
Treatments and evaluations of patient outcomes
All HF patients were actively followed up at average times of 1, 3, 6, and 50 months after the initiation of treatments. Follow-up information was completed for all 166 patients (100%). Information was obtained by face-to-face interviews or telephone conversations. Information regarding secondary cardiovascular events and treatments since the start of the treatment in the present study was obtained. Cardiovascular events were defined as either MACEs as the main cause of death, re-hospitalization because of HF, or composite endpoint events. All patients received β-blockers, as well as angiotensin-converting enzyme inhibitors (ACEI) or angiotensin receptor blockers (ARB), according to the China HF guidelines of 2014, unless there were contraindications to these drugs. Mineralocorticoid-receptor antagonists, diuretics, and digoxin were prescribed to patients who had corresponding indications according to the China HF guidelines of 2014.
Statistical analysis
Analyses were performed using SPSS version 13.0. Normally distributed values are presented as mean±standard deviations (SDs), and differences between groups were determined using Student’s t tests. Variables with a skewed normal distribution are presented as medians (inter-quartile range), and between-group differences for these variables were determined using Rank-Sum tests. Categorical variables are presented as percentages, and differences between groups were tested using Chi-squared tests. MACE-rate estimates were generated via the Kaplan-Meier method. Cox proportional hazards modeling was used to assess the relative importance of baseline risk factors to the resulting endpoints. Hazard ratios (HR) are presented, with 95% CIs, to show the risk of an event when a given factor was present. Significance was defined at the 5% level using a two-tailed statistical test.