Treatment with activin type ii receptor antibody improves cardiac function in mice after myocardial infarction

Background

Activin type ii receptor (ActRII) binding to its natural ligands including myostatin, activin, and growth development factor 11 negatively regulates muscle growth. Blockade of the ligands/ActRII signaling with human ActRII monoclonal antibody has been shown to increase body lean mass and reduce fat mass in patients with type 2 diabetes. However, the blockade effect on the ligands/ActRII signaling in heart failure with or without cardiac cachexia remains controversial. We hypothesized that the blockade effect on the ligands/ActRII signaling with a murine ActRII monoclonal antibody would improve cardiac function in a mouse model of heart failure.

Methods

Under anesthesia with isoflurane in oxygen, C57BL/6 mice were subjected to sham surgery or myocardial infarction (MI) by ligation of left anterior descending coronary artery to induce heart failure. Mice were randomized into treatment groups based on ejection fraction measured by Vevo 3100 Imaging System two weeks after MI. MI mice were treated weekly with vehicle (n=11), 10 mg/kg (n=12), or 20 mg/kg (n=12) ActRII antibody by subcutaneous injection for 8 weeks. Cardiac function was determined by Vevo 3100 Imaging system at 4, 8 weeks post-treatment, respectively. Body lean and fat mass were determined by Bruker's Whole Body Composition Analyzer. Myocardial infarct size was determined by Masson's trichrome staining on heart sections.

Results

Myocardial infarction markedly impaired cardiac function in mice. Ejection fraction reduced to 21.3±1.9% in MI mice compared to 56.3±1.2% in sham-operated mice (p<0.0001). Weekly treatment with 10 mg/kg or 20 mg/kg antibody significantly improved ejection fraction to 32.1±2.8%, and 35.9±2.9%, respectively (p<0.01 and p<0.001). Antibody treatment in MI mice also reduced MI-induced lung congestion by 5% and 8% (p<0.01), respectively. However, heart weight and myocardial infarct size in antibody treated mice were comparable to those in vehicle-treated mice. Moreover, antibody treatment dose-dependently increased body weight, which is further confirmed by increases in muscle mass and body lean mass measured by gravimetric analysis and body composition analyzer.

Conclusion

ActRII antibody dose-dependently improved cardiac function independent of myocardial infarct size post-MI. Although antibody significantly increased body weight and lean mass, it did not significantly increase heart weight, indicating that antibody treatment did not cause adverse remodeling post-MI while it remarkably improved cardiac function. Our data suggest that ActRII antibody could be a novel treatment for heart failure with reduced ejection fraction and may be particularly beneficial in patients with cachexia.

Funding Acknowledgement

Type of funding sources: None.

Early steroid withdrawal in pediatric renal transplant on newer immunosuppressive drugs

Steroids have been a cornerstone in renal transplant immunosuppression. New immunosuppressive drugs have led to protocols using early steroid withdrawal or complete avoidance. A prospective protocol in 23 pediatric renal transplant (ages 2-14 yr) who received decreasing steroid doses stopping at day 7 post-Tx, FK, and MMF were compared with a CsA, AZT, historically matched steroid-based control group. Basiliximab was used in two doses. Anthropometric, biochemical variables, AR rates, and CMV infection were evaluated and compared using Student's t-test and regression analysis. A better growth pattern was seen in steroid withdrawal group. GFR rate and serum glucose were similar in both groups. Total serum cholesterol levels were significantly lower in steroid withdrawal group. The incidence of AR at 12 months was 4.3% in steroid withdrawal group vs. 8.6% in steroid-based group (p = ns). No difference in CMV infection was observed. Hemoglobin levels were low during the first months in both groups; reached normal values after six months. SBP became higher at 12 months in steroid-based group. Patient and graft survival was 98% in both groups at one-yr post-transplant. Early steroid withdrawal was efficacious, safe, and did not increase risk of rejection, preserving optimal growth, renal function, and reducing cardiovascular risk factors.