Obesity superimposed on aging magnifies inflammation and delays the resolving response after myocardial infarction

Abstract

Polyunsaturated fatty acid (PUFA) intake has increased over the last 100 yr, contributing to the current obesogenic environment. Obesity and aging are prominent risk factors for myocardial infarction (MI). How obesity interacts with aging to alter the post-MI response, however, is unclear. We tested the hypothesis that obesity in aging mice would impair the resolution of post-MI inflammation. PUFA diet (PUFA aging group) feeding to 12-mo-old C57BL/6J mice for 5 mo showed higher fat mass compared with standard lab chow (LC)-fed young (LC young group; 3-5 mo old) or aging alone control mice (LC aging group). LC young, LC aging, and PUFA aging mice were subjected to coronary artery ligation to induce MI. Despite similar infarct areas post-MI, plasma proteomic profiling revealed higher VCAM-1 in the PUFA aging group compared with LC young and LC aging groups, leading to increased neutrophil infiltration in the PUFA aging group (P<0.05). Macrophage inflammatory protein-1γ and CD40 were also increased at day 1, and myeloperoxidase remained elevated at day 5, an observation consistent with delayed wound healing in the PUFA aging group. Lipidomic analysis showed higher levels of arachidonic acid and 12(S)-hydroxyeicosatetraenoic acid at day 1 post-MI in the PUFA aging group compared with the LC aging group (all P<0.05), thereby mediating neutrophil extravasation in the PUFA aging group. The inflammation-resolving enzymes 5-lipoxygenase, cyclooxygenase-2, and heme oxyegnase-1 were altered to delay wound healing post-MI in the PUFA aging group compared with LC young and LC aging groups. PUFA aging magnifies the post-MI inflammatory response and impairs the healing response by stimulating prolonged neutrophil trafficking and proinflammatory lipid mediators.

Keywords: inflammation; lipid mediators; lipidomics; neutrophils; polyunsaturated fatty acids; proteomics.

Fig. 1.

A: study design illustrating the three groups and post-myocardial infarction (post-MI) time points in young and aging mice. The group of mice are shown: lab control diet-fed young (LC young; 3–5 mo, n = 30), lab control diet-fed aging (LC aging group; 17 mo, n = 21), and polyunsaturated fatty acid (PUFA) diet-fed aging (PUFA aging group; 17 mo, n = 21) C57BL/6J mice. B: age-associated changes in the body weight of LC young, LC aging, and PUFA aging C57BL/6J mice. PUFA [10% (wt/wt)] supplementation increased body weight and fat mass in aging mice independent of lean mass. B–E: body weights (B), fat mass (C), lean mass (D), fasting glucose (5 h; E) in LC young, LC aging, and PUFA aging mice. Numbers of mice per group are shown in columns. *P < 0.05 vs. the LC young group; ^¥P < 0.05 vs. LC young and LC aging groups (analyzed by ANOVA).

Fig. 2.

PUFA-induced obesity increased end-diastolic volume (EDV) and reduced ejection fraction in PUFA aging mice at days 1 and 5 post-MI. A: EDV. B: end-systolic volume (ESV). C: ejection fraction. Ejection fraction = [(EDV − ESV)/EDV] × 100. D: infarcted wall. n = 3–8 mice/group per time point. Numbers of mice per group are shown in columns. *P < 0.05 vs. the day 0 control group; ^¥P < 0.05 vs. the LC young group at the respective day (analyzed by ANOVA).

Fig. 3.

PUFA-induced aging amplified proinflammatory analytes compared with LC young and LC aging groups post-MI. A–D: plasma levels of macrophage inflammatory protein (MIP)-1γ (A), CD40 at day 1 (B), and myeloperoxidase (MPO) at day 5 (C) were increased, whereas macrophage chemotactic protein (MCP)-3 (D) was decreased at day 1 post-MI in PUFA aging mice. n = 3–8 mice/group per time point. *P < 0.05 vs. the day 0 control group; ^¥P < 0.05 vs. LC young and LC aging groups; #P < 0.05, PUFA aging group vs. LC aging group at the respective day (analyzed by ANOVA).

Fig. 4.

A: MI-induced left ventricular (LV) neutrophil density was increased in PUFA aging mice compared with LC young and LC aging mice. A: LV tissue stained with anti-mouse neutrophils (Cedarlane). Top, no-MI day 0 control group; bottom, day 1 post-MI (24 h) group. Infiltrated neutrophils are circled. B: quantitation of neutrophil density. n = 5–6 slides/mouse per group. ^¥P < 0.05 vs. LC young and LC aging groups. C: plasma VCAM-1 levels. D: post-MI day 1 infarct area with representative LV midcavities stained with 1% 2,3,5-triphenyltetrazolium chloride. n = 3–8 mice/group per time point. *P < 0.05 vs. the day 0 control group; ^¥P < 0.05 vs. the LC young group at the respective day (analyzed by ANOVA).

Fig. 5.

Liquid chromotography tandem mass spectroscopy-based lipidomic analysis revealed higher levels of plasma arachidonic acid (AA) and 12(S)-HETE at day 1 post-MI in PUFA aging mice. A and B: quantitative measurements of AA (A) and 12(S)-HETE (B). C and D: representative chromatograms of AA at day 0 and 12(S)-HETE at day 1 post-MI in LC aging (C) and PUFA aging (D) groups. n = 3–8 mice/group per time point. *P < 0.05 vs. the day 0 control group; ^¥P < 0.05 vs. the LC aging group at the respective day (analyzed by ANOVA).

Fig. 6.

MI-induced cyclooxygenase (COX)-2 and 5-lipoxygenase (5-LOX) resolved inflammation in LC young and LC aging mice but not in PUFA aging mice. A–D: COX-2 (A and B) and 5-LOX (C and D) immunoblot and densitometry analyses. The densitometry data were normalized to total protein. n = 2 mice in the day 0 control group and 3 mice in the day 1 and 5 post-MI groups. AU, arbitrary units. *P < 0.05 vs. the day 0 control group; ^¥P < 0.05 vs. the LC aging group (analyzed by ANOVA).

Fig. 7.

PUFA aging mice showed reduced inflammation-resolving enzyme heme oxygenase (HO)-1 levels compared with age-matched LC aging and LC young mice post-MI. A and B: HO-1 immunoblot (A) and densitometry (B) measurements. Densitometry data were normalized to total protein. n = 2 mice in the day 0 control group and 3 mice in the day 1 and 5 post-MI groups. *P < 0.05 vs. the day 0 control group; ^¥P < 0.05 vs. the LC young group (analyzed by ANOVA). C: LV HO-1 immunohistochemistry in the day 0 control, day 1 post-MI, and day 5 post-MI groups.

Fig. 8.

Schematic based on major findings. Higher PUFA intake in aging leads to obesity with a higher load of proinflammatory lipid mediators in plasma that aggravates inflammation mediated by increased neutrophil trafficking, thereby impairing the resolution of inflammation in the LV.