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Abstract Background Type 2 diabetes mellitus (T2DM) is a major global health issue and a significant risk factor for atherosclerosis. Atherosclerosis in T2DM patients has been associated with inflammation, insulin resistance, hyperglycemia, dyslipidemia, and oxidative stress. Identifying molecular features of atherosclerotic plaques in T2DM patients could provide valuable insights into the pathogenesis of the disease. Methods The MASCADI (Arachidonic Acid Metabolism in Carotid Stenosis Plaque in Diabetic Patients) study aimed to investigate the increase of 2-arachidonoyl-lysophatidylcholine (2-AA-LPC) in carotid plaques from T2DM and control patients and to explore its association with plaque vulnerability as well as with blood and intra-plaque biomarkers altered during diabetes. Results In a population of elderly, polymedicated patients with advanced stage of atherosclerosis, we found that T2DM patients had higher systemic inflammation markers, such as high-sensitivity C-reactive protein (hsCRP) and IL-1β, higher levels of oxysterols, increased triglyceride levels, and decreased HDL levels as compared to control patients. Furthermore, 2-AA-LPC was significantly enriched in plaques from diabetic patients, suggesting its potential role in diabetic atherosclerosis. Interestingly, 2-AA-LPC was not associated with systemic markers related to diabetes, such as hsCRP, triglycerides, or HDL cholesterol. However, it was significantly correlated with the levels of inflammatory markers within the plaques such as lysophospholipids and 25-hydroxycholesterol, strengthening the link between local inflammation, arachidonic acid metabolism and diabetes. Conclusion Our study is in line with a key role for inflammation in the pathogenesis of diabetic atherosclerosis and highlights the involvement of 2-AA-LPC. Further research is needed to better understand the local processes involved in the alteration of plaque composition in T2DM and to identify potential therapeutic targets. Trial registration The MASCADI was registered on ClinicalTrials.gov (clinical registration number: NCT03202823).

Recent studies have highlighted an important role for lysophosphatidylcholine acyltransferase 3 (LPCAT3) in controlling the PUFA composition of cell membranes in the liver and intestine. In these organs, LPCAT3 critically supports cell-membrane-associated processes such as lipid absorption or lipoprotein secretion. However, the role of LPCAT3 in macrophages remains controversial. Here, we investigated LPCAT3's role in macrophages both in vitro and in vivo in mice with atherosclerosis and obesity. To accomplish this, we used the LysMCre strategy to develop a mouse model with conditional Lpcat3 deficiency in myeloid cells (Lpcat3KOMac). We observed that partial Lpcat3 deficiency (approximately 75% reduction) in macrophages alters the PUFA composition of all phospholipid (PL) subclasses, including phosphatidylinositols and phosphatidylserines. A reduced incorporation of C20 PUFAs (mainly arachidonic acid [AA]) into PLs was associated with a redistribution of these FAs toward other cellular lipids such as cholesteryl esters. Lpcat3 deficiency had no obvious impact on macrophage inflammatory response or endoplasmic reticulum (ER) stress; however, Lpcat3KOMac macrophages exhibited a reduction in cholesterol efflux in vitro. In vivo, myeloid Lpcat3 deficiency did not affect atherosclerosis development in LDL receptor deficient mouse (Ldlr−/−) mice. Lpcat3KOMac mice on a high-fat diet displayed a mild increase in hepatic steatosis associated with alterations in several liver metabolic pathways and in liver eicosanoid composition. We conclude that alterations in AA metabolism along with myeloid Lpcat3 deficiency may secondarily affect AA homeostasis in the whole liver, leading to metabolic disorders and triglyceride accumulation.

Summary: Low-grade inflammation is constitutive of atherosclerosis, and anti-inflammatory therapy inhibiting interleukin-1β (IL-1β) reduces the rate of cardiovascular events. While cholesterol accumulation in atheroma plaque and macrophages is a major driver of the inflammatory process, the role of the LXR cholesterol sensors remains to be clarified. Murine and human macrophages were treated with LXR agonists for 48 h before Toll-like receptor (TLR) stimulation. Unexpectedly, we observe that, among other cytokines, LXR agonists selectively increase IL1B mRNA levels independently of TLR activation. This effect, restricted to human macrophages, is mediated by activation of HIF-1α through LXR. Accordingly, LXR agonists also potentiate other HIF-1α-dependent pathways, such as glycolysis. Treatment of human macrophages with carotid plaque homogenates also leads to induction of IL1B in an LXR-dependent manner. Thus, our work discloses a mechanism by which cholesterol and oxysterols trigger inflammation in atherosclerosis. This suggests perspectives to target IL-1β production in atherosclerotic patients.