Vulnerable atherosclerotic plaque rupture is the principal mechanism that accounts for myocardial infarction and stroke. High matrix metalloproteinase-9 (MMP-9) expression and activity have been proven to lead to plaque instability. Metformin, a first-line treatment for type 2 diabetes, is beneficial to plaque vulnerability. However, the mechanism underlying its anti-atherogenic effect remains unclear. Molecular docking and surface plasmon resonance experiments showed that metformin directly interacts with MMP-9, and incubated MMP-9 overexpressing HEK293A cells with metformin (1 μmol·L⁻¹) significantly attenuates MMP-9’s activity using zymography and MMP activity assays. Moreover, metformin treatment drives MMP-9 degradation. Next, we constructed a carotid artery atherosclerotic plaque model and administered consecutive 14-day metformin (200 mg·kg⁻¹·d⁻¹) treatment by intragastric gavage. Immunofluorescence staining of the right carotid common artery and serum MMP activity assay results showed that metformin treatment decreased local plaque MMP-9 protein level and circulating MMP-9 activity, respectively. Histochemical staining revealed that after metformin treatment, the collagen content in plaque was significantly preserved, and the plaque vulnerability index decreased. These findings suggested that metformin improved atherosclerotic plaque stability by directly binding to MMP-9 and driving its degradation.

High density lipoprotein (HDL) has been proved to be a protective factor for coronary heart disease. Notably, HDL in atherosclerotic plaques can be nitrated (NO2-oxHDL) and chlorinated (Cl-oxHDL) by myeloperoxidase (MPO), likely compromising its cardiovascular protective effects. Here we determined the effects of NO2-oxHDL and Cl-oxHDL on SMC migration using wound healing and transwell assays, proliferation using MTT and BrdU assays, and apoptosis using Annexin-V assay in vitro, as well as on atherosclerotic plaque stability in vivo using a coratid artery collar implantation mice model. Our results showed that native HDL promoted SMC proliferation and migration, whereas NO2-oxHDL and Cl-oxHDL inhibited SMC migration and reduced capacity of stimulating SMC proliferation as well as migration, respectively. OxHDL had no significant influence on SMC apoptosis. In addition, we found that ERK1/2-phosphorylation was significantly lower when SMCs were incubated with NO2-oxHDL and Cl-oxHDL. Furthermore, transwell experiments showed that differences between native HDL, NO2-oxHDL and Cl-oxHDL was abolished after PD98059 (MAPK kinase inhibitor) treatment. In aortic SMCs from scavenger receptor BI (SR-BI) deficient mice, differences between migration of native HDL, NO2-oxHDL and Cl-oxHDL treated SMCs vanished, indicating SR-BI’s possible role in HDL-associated SMC migration. Importantly, NO2-oxHDL and Cl-oxHDL induced neointima formation and reduced SMC positive staining cells in atherosclerotic plaque, resulting in elevated vulnerable index of atherosclerotic plaque. These findings implicate MPO-catalyzed oxidization of HDL may contribute to atherosclerotic plaque instability by inhibiting SMC proliferation and migration through MAPK-ERK pathway which was dependent on SR-BI.

Exercise has proven cardiac benefits, but the underlying mechanisms of exercise that protect the heart from acute sympathetic stress injuries remain unknown. In this study, adult C57BL/6J mice and their AMP-activated protein kinase α2 knockout (AMPKα2^−/−) littermates were either subjected to 6 weeks of exercise training or housed under sedentary conditions and then treated with or without a single subcutaneous injection of the β-adrenergic receptor (β-AR) agonist isoprenaline (ISO). We investigated the differences in the protective effects of exercise training on ISO-induced cardiac inflammation in wild-type (WT) and AMPKα2^−/− mice using histology, enzyme-linked immunosorbent assay (ELISA) and Western blotting analyses. The results indicated that exercise training alleviated ISO-induced cardiac macrophage infiltration, chemokines and the expression of proinflammatory cytokines in wild-type mice. A mechanism study showed that exercise training attenuated the ISO-induced production of reactive oxygen species (ROS) and the activation of NLR Family, pyrin domain-containing 3 (NLRP3) inflammasomes. In cardiomyocytes, the ISO-induced effects on these processes were inhibited by AMP-activated protein kinase (AMPK) activator (metformin) pretreatment and reversed by the AMPK inhibitor (compound C). AMPKα2^−/− mice showed more extensive cardiac inflammation following ISO exposure than their wild-type littermates. These results indicated that exercise training could attenuate ISO-induced cardiac inflammation by inhibiting the ROS-NLRP3 inflammasome pathway in an AMPK-dependent manner. Our findings suggested the identification of a novel mechanism for the cardioprotective effects of exercise.

Heart failure (HF) is a global concern, particularly HF with preserved ejection fraction (HFpEF), lacking effective treatments. Understanding the differences of metabolic profiles between HFpEF and HFrEF (heart failure with reduced ejection fraction) patients is crucial for therapeutic advancements. In this study, pseudotargeted metabolomics was employed to analyze for disparities of plasma metabolic profiles between HFpEF and HFrEF in two cohorts: discovery (n = 514) and validation (n = 3368). Plasma-free carnitine levels were significant changed in HF patients. A non-linear and U-shaped (for HFpEF) or J-shaped (for HFrEF) association between circulating free carnitine levels and the composite risk of cardiac events were observed. Interestingly, HFpEF patients with low free carnitine (≤40.18 μmol/L) displayed a poorer survival, contrasting with HFrEF where higher levels (≥35.67 μmol/L) were linked to poorer outcomes, indicating distinct metabolism pathways. In conclusion, these findings offer insights into HFpEF metabolic profiles, suggesting potential therapeutic targets.

Lecithin cholesterol acyltransferase (LCAT) plays a pivotal role in acyl-esterifying cholesterol intravascularly, but its function in metabolic dysfunction-associated steatotic liver disease (MASLD) or steatohepatitis (MASH) has remained uncertain both in murine models and humans for decades, which is largely attributable to the distinct differences in cholesterol metabolism between mice and humans. Previously, we created a novel golden Syrian hamster model deficient in LCAT activity. Herein, we explored the influence of LCAT on the development of MASLD and MASH. A cross-sectional clinical study of LCAT activity and free cholesterol (FC) levels in healthy and MASLD patients was performed. LCAT knockout (LCAT KO) hamsters were used to explore the characteristics of cholesterol homeostasis and MASLD and MASH development. Lipidomics, mRNA-seq, and qPCR were employed to investigate the underlying mechanisms involved. MASLD patients displayed reduced LCAT activity, elevated FC levels, and ratio of FC/TC. Serum FC levels were positively correlated with triglyceride (TG), total cholesterol (TC), and apoB100 levels. In hamsters, LCAT deficiency resulted in increased FC levels and decreased high-density lipoprotein levels. Apolipoprotein profiles revealed increased ApoB100/48 and apoE but decreased apoAI. Increases in serum FC levels were primarily observed in LCAT-deficient hamster. Interestingly, LCAT KO hamsters presented mild TG species deposition in the liver even when fed a chow diet indicated by lipidomics. These increased TG species included TG (16:0/18:1/18:2), TG (16:0/18:1/18:3), and TG (16:0/16:1/18:1). On a high-fat and high-cholesterol diet, LCAT-deficient hamsters developed severe liver ballooning, inflammation, and fibrosis. Using HepG2 cells and primary hepatocytes confirmed that FC increased intracellular lipogenesis and promoted inflammatory response, which was reversed by a NLRP3 inhibitor. In summary, LCAT deficiency in hamsters promotes liver lipid deposition and MASH progression, thus highlighting the therapeutic role of LCAT in MASLD and MASH.