Adiponectin protects against the development of systolic dysfunction following myocardial infarction

Abstract

There is an association between obesity and heart failure associated with LV dysfunction. Adiponectin is an adipocyte-derived hormone that is downregulated in obesity. Here, we examined the role of adiponectin in cardiac remodeling after myocardial infarction with loss- and gain-of-function genetic manipulations in an experimental model. Myocardial infarction was created in adiponectin-deficient (APN-KO) and wild-type (WT) mice by the permanent ligation of the left anterior descending (LAD) artery. For some experiments, adenoviral vectors expressing adiponectin or beta-galactosidase were delivered systemically. Cardiac structure and function were assessed by echocardiographic and Millar catheter measurements. Myocardial capillary density was assessed by staining with anti-CD31 antibody. Myocyte apoptotic activity was determined by TUNEL-staining. Myocardial interstitial fibrosis was evaluated by Masson's trichrome staining. APN-KO mice showed exacerbated left ventricular (LV) dilation, myocyte hypertrophy and contractile dysfunction compared with WT mice at 4 weeks after LAD ligation. Impaired LV function in APN-KO mice was coupled to myocyte hypertrophy, increased apoptotic activity and interstitial fibrosis in the remote zone, and reduced capillary density in the infarct border zone. No difference in infarct size was observed between WT and APN-KO mice. Administration of adenovirus-mediated adiponectin in WT mice resulted in decreased LV dilatation and improved LV function that was associated with increased capillary density in the infarct border zone and decreased myocyte hypertrophy, diminished myocardial apoptosis and decreased interstitial fibrosis in the remote zone. These data suggest that adiponectin protects against the development of systolic dysfunction after myocardial infarction through its abilities to suppress cardiac hypertrophy and interstitial fibrosis, and protect against myocyte and capillary loss.

Figure 1. Increased myocyte hypertrophy in APN-KO mice subjected to permanent LAD ligation

(A) Schematic illustration of experimental protocol, and survival curves of WT and APN-KO mice after MI. WT: n = 20, KO: n = 14. (B) Left: Heart rate, right: systolic blood pressure in WT and APN-KO mice 4 weeks after sham-operation or MI. (C) Left: Representative Masson’s trichrome-stained cross-sections of the heart from WT (left) and APN-KO (right) mice 4 weeks after MI. Right: Quantification of relative infarct size in WT and APN-KO mice. (D) Left: Heart weight/body weight (HW/BW) ratio in WT and APN-KO mice 4 weeks after sham-operation or MI. Right: Quantitative analysis of cardiomyocyte cross-sectional area in WT and APN-KO mice 4 weeks after sham-operation or MI. (E) Lung wet weight/BW ratio in WT and APN-KO mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 7 mice per experimental group).

Figure 1. Increased myocyte hypertrophy in APN-KO mice subjected to permanent LAD ligation

(A) Schematic illustration of experimental protocol, and survival curves of WT and APN-KO mice after MI. WT: n = 20, KO: n = 14. (B) Left: Heart rate, right: systolic blood pressure in WT and APN-KO mice 4 weeks after sham-operation or MI. (C) Left: Representative Masson’s trichrome-stained cross-sections of the heart from WT (left) and APN-KO (right) mice 4 weeks after MI. Right: Quantification of relative infarct size in WT and APN-KO mice. (D) Left: Heart weight/body weight (HW/BW) ratio in WT and APN-KO mice 4 weeks after sham-operation or MI. Right: Quantitative analysis of cardiomyocyte cross-sectional area in WT and APN-KO mice 4 weeks after sham-operation or MI. (E) Lung wet weight/BW ratio in WT and APN-KO mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 7 mice per experimental group).

Figure 1. Increased myocyte hypertrophy in APN-KO mice subjected to permanent LAD ligation

(A) Schematic illustration of experimental protocol, and survival curves of WT and APN-KO mice after MI. WT: n = 20, KO: n = 14. (B) Left: Heart rate, right: systolic blood pressure in WT and APN-KO mice 4 weeks after sham-operation or MI. (C) Left: Representative Masson’s trichrome-stained cross-sections of the heart from WT (left) and APN-KO (right) mice 4 weeks after MI. Right: Quantification of relative infarct size in WT and APN-KO mice. (D) Left: Heart weight/body weight (HW/BW) ratio in WT and APN-KO mice 4 weeks after sham-operation or MI. Right: Quantitative analysis of cardiomyocyte cross-sectional area in WT and APN-KO mice 4 weeks after sham-operation or MI. (E) Lung wet weight/BW ratio in WT and APN-KO mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 7 mice per experimental group).

Figure 2. Increased LV dilatation and LV dysfunction in APN-KO mice 4 weeks after MI

(A) Left: Representative M-mode echocardiogram for WT and APN-KO mice 4 weeks after sham-operation or MI. Right: LV diastolic dimension (LVDd) in WT and APN-KO mice 4 weeks after sham-operation or MI (n = 7 mice per experimental group). (B) Left: LV end-diastolic pressure (LVEDP) in WT and APN-KO mice 4 weeks after sham-operation or MI. Right: LV dP/dt in WT and APN-KO mice 4 weeks after sham-operation or MI (n = 5 mice per experimental group). Results are presented as mean ± s.d.

Figure 3. Reduced capillary density and increased myocardial apoptosis in APN-KO mice after MI

(A) Left: Representative images of anti-CD31-stained heart sections. Right: Quantitative analysis of CD31-positive capillary density in WT and APN-KO mice 4 weeks after sham-operation or MI. (B) Left: Representative images of TUNEL-stained heart sections from WT and APN-KO mice 4 weeks after sham-operation or MI. Apoptotic nuclei were identified by TUNEL staining (green), cardiac myocytes by staining with anti-α-sarcomeric actin antibody (red), and total nuclei by DAPI counterstaining (blue). Right: Quantitative analysis of apoptotic nuclei in cardiac myocytes from WT and APN-KO mice 4 weeks after sham-operation or MI. TUNEL-positive nuclei are expressed as a percentage of the total number of DAPI-positive nuclei. (C) Left: Representative images of Masson’s trichrome (MT)-stainined heart sections. Right: Quantitative analysis of myocardial interstitial fibrosis in WT and APN-KO mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 5 mice per experimental group).

Figure 3. Reduced capillary density and increased myocardial apoptosis in APN-KO mice after MI

(A) Left: Representative images of anti-CD31-stained heart sections. Right: Quantitative analysis of CD31-positive capillary density in WT and APN-KO mice 4 weeks after sham-operation or MI. (B) Left: Representative images of TUNEL-stained heart sections from WT and APN-KO mice 4 weeks after sham-operation or MI. Apoptotic nuclei were identified by TUNEL staining (green), cardiac myocytes by staining with anti-α-sarcomeric actin antibody (red), and total nuclei by DAPI counterstaining (blue). Right: Quantitative analysis of apoptotic nuclei in cardiac myocytes from WT and APN-KO mice 4 weeks after sham-operation or MI. TUNEL-positive nuclei are expressed as a percentage of the total number of DAPI-positive nuclei. (C) Left: Representative images of Masson’s trichrome (MT)-stainined heart sections. Right: Quantitative analysis of myocardial interstitial fibrosis in WT and APN-KO mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 5 mice per experimental group).

Figure 4. Adenovirus-mediated expression of adiponectin inhibits hypertrophy and cardiac remodeling in WT mice at 4 weeks after MI

(A) Schematic illustration of experimental protocol. (B) Quantification of relative infarct size in Ad-βgal- or Ad-APN-treated mice 4 weeks after MI. (C) Left: HW/BW ratio in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Right: Quantitative analysis of cardiomyocyte cross-sectional area in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. (D) Lung wet weight/BW ratio in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. (E) Left: Representative M-mode echocardiogram for Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Right: LVDd in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. (F) Left: LVEDP in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Right: Left ventricular dP/dt in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 6 mice per experimental group).

Figure 4. Adenovirus-mediated expression of adiponectin inhibits hypertrophy and cardiac remodeling in WT mice at 4 weeks after MI

(A) Schematic illustration of experimental protocol. (B) Quantification of relative infarct size in Ad-βgal- or Ad-APN-treated mice 4 weeks after MI. (C) Left: HW/BW ratio in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Right: Quantitative analysis of cardiomyocyte cross-sectional area in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. (D) Lung wet weight/BW ratio in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. (E) Left: Representative M-mode echocardiogram for Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Right: LVDd in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. (F) Left: LVEDP in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Right: Left ventricular dP/dt in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 6 mice per experimental group).

Figure 5. Adenovirus-mediated expression of adiponectin increases capillary density and diminishes apoptosis in WT mice 4 weeks after MI

(A) Quantitative analysis of capillary density in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. (B) Quantitative analysis of apoptotic nuclei in cardiac myocytes from Ad-βgal- or Ad-APN-treated wild-type mice 4 weeks after sham-operation or MI. (C) Quantitative analysis of myocardial interstitial fibrosis in Ad-βgal- or Ad-APN-treated mice 4 weeks after sham-operation or MI. Results are presented as mean ± s.d. (n = 6 mice per experimental group).