Acipimox attenuates atherosclerosis and enhances plaque stability in ApoE-deficient mice fed a palmitate-rich diet

MG-132 activates sodium palmitate-induced autophagy in human vascular smooth muscle cells and inhibits senescence via the PI3K/AKT/mTOR axis

OBJECTIVE

This study aimed to reveal the role and mechanism of MG-132 in delaying hyperlipidemia-induced senescence of vascular smooth muscle cells (VSMCs).

METHODS

Immunohistochemistry and hematoxylin-eosin staining confirmed the therapeutic effect of MG-132 on arterial senescence in vivo and its possible mechanism. Subsequently, VSMCs were treated with sodium palmitate (PA), an activator (Recilisib) or an inhibitor (Pictilisib) to activate or inhibit PI3K, and CCK-8 and EdU staining, wound healing assays, Transwell cell migration assays, autophagy staining assays, reactive oxygen species assays, senescence-associated β-galactosidase staining, and Western blotting were performed to determine the molecular mechanism by which MG-132 inhibits VSMC senescence. Validation of the interaction between MG-132 and PI3K using molecular docking.

RESULTS

Increased expression of p-PI3K, a key protein of the autophagy regulatory system, and decreased expression of the autophagy-associated proteins Beclin 1 and ULK1 were observed in the aortas of C57BL/6J mice fed a high-fat diet (HFD), and autophagy was inhibited in aortic smooth muscle. MG-132 inhibits atherosclerosis by activating autophagy in VSMCs to counteract PA-induced cell proliferation, migration, oxidative stress, and senescence, thereby inhibiting VSMC senescence in the aorta. This process is achieved through the PI3K/AKT/mTOR signaling pathway.

CONCLUSION

MG-132 activates autophagy by inhibiting the PI3K/AKT/mTOR pathway, thereby inhibiting palmitate-induced proliferation, migration, and oxidative stress in vascular smooth muscle cells and suppressing their senescence.

Palmitic acid in type 2 diabetes mellitus promotes atherosclerotic plaque vulnerability via macrophage Dll4 signaling

Patients with Type 2 Diabetes Mellitus are increasingly susceptible to atherosclerotic plaque vulnerability, leading to severe cardiovascular events. In this study, we demonstrate that elevated serum levels of palmitic acid, a type of saturated fatty acid, are significantly linked to this enhanced vulnerability in patients with Type 2 Diabetes Mellitus. Through a combination of human cohort studies and animal models, our research identifies a key mechanistic pathway: palmitic acid induces macrophage Delta-like ligand 4 signaling, which in turn triggers senescence in vascular smooth muscle cells. This process is critical for plaque instability due to reduced collagen synthesis and deposition. Importantly, our findings reveal that macrophage-specific knockout of Delta-like ligand 4 in atherosclerotic mice leads to reduced plaque burden and improved stability, highlighting the potential of targeting this pathway. These insights offer a promising direction for developing therapeutic strategies to mitigate cardiovascular risks in patients with Type 2 Diabetes Mellitus.

Eicosapentaenoic acid mitigates palmitic acid-induced heat shock response, inflammation and repair processes in fish intestine

Understanding the metabolic effects of fatty acids on fish intestine is critical to the substitution of fish oil with vegetable oils in aquaculture. In this study, the effects of eicosapentaenoic acid (EPA) and palmitic acid (PA) on fish intestine were evaluated in vitro and in vivo. As the first step for in vitro study, an intestinal cell line (SPIF) was established from silver pomfret (Pampus argenteus). Thereafter, the effects of EPA and PA on cell viability, prostaglandin E2 (PGE2) production, and the expression of genes related to heat shock response, inflammation, extracellular matrix (ECM) formation and degradation were examined in SPIF cells. Finally, these metabolic effects of EPA and PA on the intestine were examined in zebrafish (Danio rerio) larvae. Results showed that all tested fatty acids (PA, oleic acid, linoleic acid, α-linolenic acid, arachidonic acid, and docosahexaenoic acid) except EPA reduced SPIF viability to distinct degrees at the same concentrations. PA decreased SPIF viability accompanied by an increase in PGE2 level. Meanwhile, PA increased the expression of genes related to heat shock response (grp78, grp94, hsp70, and hsp90) and inflammation (nf-κb, il-1β, and cox2). Furthermore, PA reduced the expression of collagen type I (col1a1a and col1a1b) and extracellular matrix (ECM) degradation-related gene mmp2, while up-regulating timp2 mRNA expression. In vivo, PA also increased hsp70, il-1β, and cox2 mRNA levels and limited the expression of collagen type I in the larval zebrafish intestine. Interestingly, the combination of EPA and PA partially recovered the PA-induced changes in cell viability, PGE2 production, and mRNA expression in vitro and in vivo. These results suggest that PA may result in heat shock and inflammatory responses, as well as alter ECM formation and degradation in fish intestine, while EPA could at least partially mitigate these negative effects caused by PA.

Suxiaojiuxin pill enhances atherosclerotic plaque stability by modulating the MMPs/TIMPs balance in ApoE-deficient mice

: Suxiaojiuxin pill (SX) is a famous Chinese formulated product, which has been used to treat coronary heart disease and angina pectoris in China. This study was carried out to investigate the effect and possible mechanism of SX on the stability of atherosclerotic plaque in ApoE-deficient mice. ApoE-/- mice of 6-8 weeks old were fed with high-fat diet for developing artherosclerosis. After oral administration of SX for 8 weeks, histopathology of aortic plaque was performed by Sudan III and hematoxylin-eosin staining, and muscle protein was detected by Western blotting (WB). The mRNA and proteins associated with aortic plaque stability were detected by reverse transcription-polymerase chain reaction and WB, respectively. SX treatment could not only reduce serum triglyceride level and plaque area but also increase fibrous cap thickness and collagen content compared with the model group. WB results showed that SX could increase α-smooth muscle actin, tissue inhibitor of metalloproteinase 1 (TIMP-1), and TIMP-2 protein expression, whereas decrease matrix metalloproteinase 2 (MMP-2) and MMP-9 protein expression. Moreover, SX could upregulate the expression of α-smooth muscle actin mRNA and downregulate the expression of vascular endothelial growth factor mRNA. These results showed that SX could enhance atherosclerotic plaque stability in ApoE-deficient mice. The mechanism may be associated with modulating the MMPs/TIMPs balance.

Expression of mammalian target of rapamycin in atherosclerotic plaques is decreased under diabetic conditions: a mechanism for rapamycin resistance

Our previous study demonstrated that diabetes increases in-stent restenosis following rapamycin-eluting stent placement, which was defined as rapamycin resistance. However, the underlying mechanisms of rapamycin resistance remain to be determined. In the present study, male apolipoprotein E-deficient (ApoE-/-) mice were randomly divided into control and diabetic groups. Diabetes was induced by injecting streptozocin (STZ). The hyperglycemic state, defined as a fasting plasma glucose level >13 mmol/l, was maintained for 8 weeks. At the end of the administration, the plasma levels of triglycerides (TG) and total cholesterol (TC) were significantly elevated in the diabetic group compared with the control mice (all P<0.01). The present study revealed that diabetes increased the atherosclerotic plaque size of the aortic root (P<0.01) and the content of vascular smooth muscle cells (VSMCs) in the atherosclerotic lesion (P<0.01). Furthermore, the protein expression and phosphorylation of mammalian target of rapamycin (mTOR), 4E-binding protein 1 and ribosomal S6 kinase 1 (P<0.01) were significantly decreased in the diabetic mice compared with the control group. The decrease in the expression and phosphorylation of mTOR and its downstream kinases may be one of the molecular mechanisms underlying rapamycin resistance.