Detection of Ceramide, a Risk Factor for Coronary Artery Disease, in Human Coronary Plaques by Fluorescent Angioscopy

Inflammation: Is It a Healer, Confounder, or a Promoter of Cardiometabolic Risks?

Inflammation is the body's non-specific response to injury or infection. It is a natural defense mechanism that helps to maintain homeostasis and promotes tissue repair. However, excessive inflammation can lead to cellular, tissue, or organ dysfunction, as well as contribute to the development of acute vascular events and diseases like Crohn's disease, psoriasis, obesity, diabetes, and cancer. The initial response to injury involves the activation of platelets and coagulation mechanisms to stop bleeding. This is followed by the recruitment of immune cells and the release of cytokines to promote tissue repair. Over time, the injured tissue undergoes remodeling and returns to its pre-injury state. Inflammation is characterized by the activation of inflammatory signaling pathways involving cytokines, chemokines, and growth factors. Mast cells play a role in initiating inflammatory responses. Pattern recognition receptors (PRRs) such as Toll-like receptors (TLRs) and nucleotide-binding domain (NOD)-like receptors (NLRs) are involved in the activation of these inflammatory pathways. Inflammasomes, which are cytoplasmic complexes, also contribute to inflammation by activating cytokines. Inflammation can also be triggered by factors like dietary components and the composition of the gut microbiota. Dysregulation of the gut microbiome can lead to excessive inflammation and contribute to diseases like atherosclerosis and irritable bowel syndrome (IBS). The immune system and gut-associated lymphoid tissue (GALT) play crucial roles in the inflammatory response and the development of conditions like colorectal cancer. Anti-inflammatory therapy can play a significant role in reducing or inducing the remission of inflammatory diseases such as Crohn's disease and ulcerative colitis. The fetal origin of adult diseases theory suggests that conditions during fetal development, such as low birth weight and maternal obesity, can influence the risk of cardiometabolic diseases later in life. All of the known risk factors associated with cardiometabolic diseases such as hypertension, excess weight, obesity, type-2 diabetes, and vascular diseases are accompanied by chronic low-grade inflammation. Inflammation seems to have a role in precipitating even acute vascular events such as heart attacks and stroke. Common markers of inflammation associated with cardiometabolic disease include interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF-α), C-reactive protein (CRP), and soluble TNF receptors such as sTNFR1 and sTNFR2. These markers serve as indicators of systemic inflammation. However, these markers are not disease-specific but provide an insight into the overall chronic inflammatory status. In fact, inflammation has been identified as a potential target for future treatments to reduce or reverse the risk of atherosclerosis-related complications. The regulation of inflammation is complex, and further research is needed to better understand its mechanisms and develop strategies for managing inflammatory disorders. In summary, inflammation is a natural response to injury or infection, but excessive or prolonged inflammation can lead to the progression of various diseases. Understanding the underlying mechanisms of inflammation is important for developing treatments and preventive measures for inflammatory disorders.

Vitamin D and Ceramide Metabolomic Profile in Acute Myocardial Infarction

Sphingolipids (SLs) influence several cellular pathways, while vitamin D exerts many extraskeletal effects in addition to its traditional biological functions, including the modulation of calcium homeostasis and bone health. Moreover, Vitamin D and SLs affect the regulation of each others' metabolism; hence, this study aims to evaluate the relationship between the levels of 25(OH)D and ceramides in acute myocardial infarction (AMI). In particular, the blood abundance of eight ceramides and 25(OH)D was evaluated in 134 AMI patients (aged 68.4 ± 12.0 years, 72% males). A significant inverse correlation between 25(OH)D and both Cer(d18:1/16:0) and Cer(d18:1/18:0) was found; indeed, patients with severe hypovitaminosis D (<10 ng/mL) showed the highest levels of the two investigated ceramides. Moreover, diabetic/dyslipidemic patients with suboptimal levels of 25(OH)D (<30 ng/mL) had higher levels of both the ceramides when compared with the rest of the population. On the other hand, 25(OH)D remained an independent determinant for Cer(d18:1/16:0) (STD Coeff -0.18, t-Value -2, p ≤ 0.05) and Cer(d18:1/18:0) (-0.2, -2.2, p < 0.05). In light of these findings, the crosstalk between sphingolipids and vitamin D may unravel additional mechanisms by which these molecules can influence CV risk in AMI.

Ceramides and pro-inflammatory cytokines for the prediction of acute coronary syndrome: a multi-marker approach

BACKGROUND

There is a growing body of evidence supporting the significant involvement of both ceramides and pro-inflammatory cytokines in the occurrence and progression of acute coronary syndrome (ACS).

METHODS

This study encompassed 216 participants whose laboratory variables were analysed using standardised procedures. Parameters included baseline serum lipid markers, comprising total cholesterol, low-density lipoprotein-cholesterol, high-density lipoprotein-cholesterol, triglycerides (TGs), lipoprotein(a) (LPa), fasting blood glucose, B-natriuretic peptide and hypersensitive C-reactive protein. Liquid chromatography-tandem mass spectrometry measured the concentrations of plasma ceramides. Enzyme-linked immunosorbent assay quantified tumour necrosis factor-α (TNF-α), interleukin 6 (IL6) and IL8. The correlation between ceramides and inflammatory factors was determined through Pearson's correlation coefficient. Receiver operating characteristic (ROC) curve analysis and multivariate logistic regression evaluated the diagnostic potential of models incorporating traditional risk factors, ceramides and pro-inflammatory cytokines in ACS detection.

RESULTS

Among the 216 participants, 138 (63.89%) were diagnosed with ACS. Univariate logistic regression analysis identified significant independent predictors of ACS, including age, gender, history of diabetes, smoking history, TGs, TNF-α, IL-6, ceramide (d18:1/16:0), ceramide (d18:1/18:0), ceramide (d18:1/24:0), ceramide (d18:1/20:0) and ceramide (d18:1/22:0). Multivariate logistic regression analysis revealed significant associations between gender, diabetes mellitus history, smoking history, LPa, IL-6, ceramide (d18:1/16:0) and ACS. Receiver operating characteristic analysis indicated that model 4, which integrated traditional risk factors, IL-6 and ceramide (d18:1/16:0), achieved the highest area under the curve (AUC) of 0.827 (95% CI 0.770-0.884), compared with model 3 (traditional risk factors and ceramide [d18:1/16:0]) with an AUC of 0.782 (95% CI 0.720-0.845) and model 2 (traditional risk factors and IL-6), with an AUC of 0.785 (95% CI 0.723-0.846) in ACS detection.

CONCLUSIONS

In summary, incorporating the simultaneous measurement of traditional risk factors, pro-inflammatory cytokine IL-6 and ceramide (d18:1/16:0) can improve the diagnostic accuracy of ACS.

Association Between Plasma Ceramides and One-Year Mortality in Patients with Acute Coronary Syndrome: Insight from the PEACP Study

Background

The plasma lipidome profile is likely to improve risk stratification in patients with acute coronary syndrome (ACS) and predict cardiovascular events for secondary disease prevention. Ceramides are involved in the initiation or acceleration of several key pathophysiological processes in atherosclerosis. This study evaluated whether plasma ceramide levels at admission was associated with one-year mortality in patients with ACS.

Methods

In total, 826 patients with ACS from a prospective multicenter study for early evaluation of acute chest pain were enrolled. High-performance liquid chromatography with tandem mass spectrometry (LC/MS) was used to measure the plasma levels of eleven ceramides (C16-C26). The primary outcome was all-cause mortality, and the secondary outcome was cardiac mortality during the one-year follow-up. The relationship between the ceramide levels and mortality was evaluated by Cox regression analysis. The receiver operating characteristic (ROC) curve was established to evaluate discrimination of ceramides.

Results

Eighty-eight (10.7%) patients died after a 12-month follow-up. Five ceramides (C16:0, C18:0, C20:0, C24:1 and C24:2) and their ratios to Cer(d18:1/24:0) were independently associated with the risk of all-cause death and cardiac death. Combining the Global Registry of Acute Coronary Events (GRACE) score with ceramides and their ratios to Cer(d18:1/24:0) had areas under ROC curves ranging from 0.778-0.804 (P<0.001) for all-cause mortality, which was greater than that of the GRACE score alone.

Conclusion

Measurements of long-chain ceramides and very-long-chain ceramides may help in identifying a high risk of mortality beyond traditional assessment tools in patients with ACS.

Trial Registration

clinicaltrials.gov, identifier: NCT04122573.

Ceramides as Mediators of Oxidative Stress and Inflammation in Cardiometabolic Disease

Ceramides, composed of a sphingosine and a fatty acid, are bioactive lipid molecules involved in many key cellular pathways (e.g., apoptosis, oxidative stress and inflammation). There is much evidence on the relationship between ceramide species and cardiometabolic disease, especially in relationship with the onset and development of diabetes and acute and chronic coronary artery disease. This review reports available evidence on ceramide structure and generation, and discusses their role in cardiometabolic disease, as well as current translational chances and difficulties for ceramide application in the cardiometabolic clinical settings.

Ceramides and Cardiovascular Risk Factors, Inflammatory Parameters and Left Ventricular Function in AMI Patients

Background: Ceramides, biologically active lipids correlated to oxidative stress and inflammation, have been associated with adverse outcomes in acute myocardial infarction (AMI). The purpose of this study was to assess the association between ceramides/ratios included in the CERT1 score and increased cardiovascular (CV) risk, inflammatory and left ventricular function parameters in AMI. Methods: high performance liquid chromatography-tandem mass spectrometry was used to identify Cer(d18:1/16:0), Cer(d18:1/18:0), and Cer(d18:1/24:1) levels and their ratios to Cer(d18:1/24:0), in 123 AMI patients (FTGM coronary unit, Massa, Italy). Results: Cer(d18:1/16:0): higher in female patients (<0.05), in patients with dyslipidemia (<0.05), and it directly and significantly correlated with aging, brain natriuretic peptide-BNP, erythrocyte sedimentation rate-ESR and fibrinogen. Cer(d18:1/18:0): higher in females (<0.01) and patients with dyslipidemia (<0.01), and increased according to the number of CV risk factors (considering hypertension, dyslipidemia and diabetes). Moreover, it significantly correlated with BNP, troponin at admission, ESR, C reactive protein-CRP, and fibrinogen. Cer(d18:1/24:1): significantly correlated with aging, BNP, fibrinogen and neutrophils. Cer(d18:1/16:0)/Cer(d18:1/24:0): higher in female patients (<0.05), and in patients with higher wall motion score index-WMSI (>1.7; ≤0.05), and in those with multivessel disease (<0.05). Moreover, it significantly correlated with aging, BNP, CRP, ESR, neutrophil-to-lymphocyte ratio-NRL, and fibrinogen. Cer(d18:1/18:0)/Cer(d18:1/24:0): higher in female patients (<0.001), and increased according to age. Moreover, it was higher in patients with lower left ventricular ejection fraction (<35%, ≤0.01), higher WMSI (>1.7, <0.05), and in those with multivessel disease (0.13 ± 0.06 vs. 0.10 ± 0.05 µM, <0.05), and correlates with BNP, ESR, CRP, fibrinogen and neutrophils, platelets, NLR, and troponin at admission. Multiple regression analysis showed that Cer(d18:1/16:0)/Cer(d18:1/24:0) and Cer(d18:1/18:0)/Cer(d18:1/24:0) remained as independent determinants for WMSI after multivariate adjustment (Std coeff 0.17, T-value 1.9, ≤0.05; 0.21, 2.6, <0.05, respectively). Conclusion: Distinct ceramide species are associated with CV risk, inflammation and disease severity in AMI. Thus, a detailed analysis of ceramides may help to better understand CV pathobiology and suggest these new biomarkers as possible risk predictors and pharmacological targets in AMI patients.

Effects of Dicyclohexyl Phthalate Exposure on PXR Activation and Lipid Homeostasis in Mice

BACKGROUND

Exposure to plastic-associated endocrine disrupting chemicals (EDCs) has been associated with an increased risk of cardiovascular disease (CVD) in humans. However, the underlying mechanisms for this association are unclear. Many EDCs have been shown to function as ligands of the nuclear receptor pregnane X receptor (PXR), which functions as xenobiotic sensor but also has pro-atherogenic effects in vivo.

OBJECTIVE

We sought to investigate the contribution of PXR to the adverse effects dicyclohexyl phthalate (DCHP), a widely used phthalate plasticizer, on lipid homeostasis and CVD risk factors.

METHODS

Cell-based assays, primary organoid cultures, and PXR conditional knockout and PXR-humanized mouse models were used to investigate the impact of DCHP exposure on PXR activation and lipid homeostasis in vitro and in vivo. Targeted lipidomics were performed to measure circulating ceramides, novel predictors for CVD.

RESULTS

DCHP was identified as a potent PXR-selective agonist that led to higher plasma cholesterol levels in wild-type mice. DCHP was then demonstrated to activate intestinal PXR to elicit hyperlipidemia by using tissue-specific PXR-deficient mice. Interestingly, DCHP exposure also led to higher circulating ceramides in a PXR-dependent manner. DCHP-mediated PXR activation stimulated the expression of intestinal genes mediating lipogenesis and ceramide synthesis. Given that PXR exhibits considerable species-specific differences in receptor pharmacology, PXR-humanized mice were also used to replicate these findings.

DISCUSSION

Although the adverse health effects of several well-known phthalates have attracted considerable attention, little is known about the potential impact of DCHP on human health. Our studies demonstrate that DCHP activated PXR to induce hypercholesterolemia and ceramide production in mice. These results indicate a potentially important role of PXR in contributing to the deleterious effects of plastic-associated EDCs on cardiovascular health in humans. Testing PXR activation should be considered for risk assessment of phthalates and other EDCs. https://doi.org/10.1289/EHP9262.

Aggregation Susceptibility of Low-Density Lipoproteins-A Novel Modifiable Biomarker of Cardiovascular Risk

Circulating low-density lipoprotein (LDL) particles enter the arterial intima where they bind to the extracellular matrix and become modified by lipases, proteases, and oxidizing enzymes and agents. The modified LDL particles aggregate and fuse into larger matrix-bound lipid droplets and, upon generation of unesterified cholesterol, cholesterol crystals are also formed. Uptake of the aggregated/fused particles and cholesterol crystals by macrophages and smooth muscle cells induces their inflammatory activation and conversion into foam cells. In this review, we summarize the causes and consequences of LDL aggregation and describe the development and applications of an assay capable of determining the susceptibility of isolated LDL particles to aggregate when exposed to human recombinant sphingomyelinase enzyme ex vivo. Significant person-to-person differences in the aggregation susceptibility of LDL particles were observed, and such individual differences largely depended on particle lipid composition. The presence of aggregation-prone LDL in the circulation predicted future cardiovascular events in patients with atherosclerotic cardiovascular disease. We also discuss means capable of reducing LDL particles' aggregation susceptibility that could potentially inhibit LDL aggregation in the arterial wall. Whether reductions in LDL aggregation susceptibility are associated with attenuated atherogenesis and a reduced risk of atherosclerotic cardiovascular diseases remains to be studied.

Sex differences in the association of sphingolipids with age in Dutch and South-Asian Surinamese living in Amsterdam, the Netherlands

BACKGROUND

Men have a higher risk for cardiovascular disease (CVD) early in life, while women have a higher risk later in life. The sex-related differences in CVD risk, especially by age, could be related to sphingolipid metabolism. We compared plasma sphingolipid concentrations and its increase by age in men and women.

METHODS

Plasma concentrations of 13 types of sphingolipids were measured by liquid chromatography-tandem mass spectrometry in a random subsample of 328 men and 372 women of Dutch and South-Asian Surinamese ethnic origin, participating in the HELIUS study. Sphingolipid concentrations were compared between men and women by age group (18-39, 40-55, and 56-70 years). Multiple linear regression was used to determine sex differences in age trends in sphingolipids stratified by ethnicity. Analyses were performed without adjustment and adjusted for body mass index (BMI) and waist circumference.

RESULTS

At age 18-39 years, sphingolipid concentrations were lower in women than those in men, but at age 56-70 years this was reversed. At higher age, women showed higher concentrations than men. In line, we observed a more rapid increase of sphingolipid concentrations by age in women than in men. The observed sex differences were not explained by BMI or waist circumference. Patterns of sex differences were similar across ethnic groups, although the strength of associations differed.

CONCLUSIONS

Mean sphingolipid concentrations increase more rapidly with age in women than in men. Therefore, plasma lipid concentrations of sphingolipids, although lower in women than in men at younger age, are higher in women than in men at older age.

Relationship between elevated plasma ceramides and plaque rupture in patients with ST-segment elevation myocardial infarction

BACKGROUND AND AIMS

Ceramides (Cer) are an atherogenic substance. However, the associations between specific plasma Cer levels and culprit plaque morphology in ST-segment elevation myocardial infarction (STEMI) patients are unclear.

METHODS

The study consisted of two parallel cohorts. 100 consecutive patients with STEMI were screened as discovery cohort. In the validation cohort, we separately screened 30 normal donors, 30 stable angina pectoris (SAP) and 315 STEMI patients. All STEMI patients underwent emergency percutaneous intervention (PCI) and optical coherence tomography (OCT) examination for culprit plaque. Based on established diagnostic criteria, STEMI patients were classified into plaque rupture (PR) and plaque erosion (PE) group, respectively. Rapid resolution liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (RRLC-Q-TOF/MS) was used to evaluate plasma Cer levels of the screened patients.

RESULTS

STEMI patients had higher plasma Cer(d18:1/16:0), Cer(d18:1/18:0), Cer(d18:1/24:1) and Cer(d18:1/24:0) levels than normal donors and SAP patients (p < 0.001, p < 0.001, p < 0.001, p < 0.001, respectively). Plasma Cer levels were significantly higher in STEMI patients with PR than with PE (p < 0.001, p < 0.001, p = 0.008 and p = 0.006, respectively). The frequency of PR increased with increasing tertiles of plasma Cer (adjusted p for trend = 0.004, 0.044, 0.021 and 0.133, respectively). The fully adjusted per SD odds ratios (95% confidence interval) for PR were 9.375 (2.496-35.215) for Cer(d18:1/16:0), 3.586 (1.588-8.089) for Cer(d18:1/18:0), 8.171 (1.764-37.857) for Cer(d18:1/24:1), and 3.831 (1.288-11.289) for Cer(d18:1/24:10).

CONCLUSIONS

The study documented novel, positive and independent associations between plasma Cer concentrations and the presence of PR, suggesting plasma Cer may act as potential biomarkers for PR to improve risk stratification.

Elevated Plasma Ceramides Are Associated With Antiretroviral Therapy Use and Progression of Carotid Artery Atherosclerosis in HIV Infection

BACKGROUND

Ceramides have been implicated in the pathophysiology of HIV infection and cardiovascular disease. However, no study, to our knowledge, has evaluated circulating ceramide levels in association with subclinical cardiovascular disease risk among HIV-infected individuals.

METHODS

Plasma levels of 4 ceramide species (C16:0, C22:0, C24:0, and C24:1) were measured among 398 women (73% HIV+) and 339 men (68% HIV+) without carotid artery plaques at baseline from the Women's Interagency HIV Study and the Multicenter AIDS Cohort Study. We examined associations between baseline plasma ceramides and risk of carotid artery plaque formation, assessed by repeated B-mode carotid artery ultrasound imaging over a median 7-year follow-up.

RESULTS

Plasma levels of C16:0, C22:0, and C24:1 ceramides were significantly higher in HIV-infected individuals compared with those without HIV infection (all P<0.001), and further analysis indicated that elevated ceramide levels were associated with antiretroviral therapy use, particularly protease inhibitor use, in HIV-infected individuals (all P<0.001). All 4 ceramides were highly correlated with each other ( r=0.70-0.94; all P<0.001) and significantly correlated with total-cholesterol ( r=0.42-0.58; all P<0.001) and low-density lipoprotein cholesterol ( r=0.24-0.42; all P<0.001) levels. Of note, C16:0 and C24:1 ceramides, rather than C22:0 and C24:0 ceramides, were more closely correlated with specific monocyte activation and inflammation markers (eg, r=0.30 between C16:0 ceramide and soluble CD14; P<0.001) and surface markers of CD4⁺ T-cell activation. A total of 112 participants developed carotid artery plaques over 7 years, and higher levels of C16:0 and C24:1 ceramides were significantly associated with increased risk of carotid artery plaques (relative risk [95% CI]=1.55 [1.29, 1.86] and 1.51 [1.26, 1.82] per standard deviation increment, respectively; both P<0.001), after adjusting for demographic and behavioral factors. After further adjustment for cardiovascular disease risk factors and immune activation markers, these associations were attenuated but remained significant. The results were consistent between men and women and between HIV-infected and HIV-uninfected participants.

CONCLUSIONS

In 2 HIV cohorts, elevated plasma levels of C16:0 and C24:1 ceramides, correlating with immune activation and inflammation, were associated with antiretroviral therapy use and progression of carotid artery atherosclerosis.

Ceramides and Ceramide Scores: Clinical Applications for Cardiometabolic Risk Stratification

Ceramides are bioactive lipids that have an important role in many cellular functions such as apoptosis and inflammation. During the past decade emerging clinical data have shown that ceramides are not only of great biochemical interest but may also have diagnostic utility. Ceramides have shown independent predictive value for negative cardiovascular outcomes as well as for the onset of type 2 diabetes. Based on abundant published data, risk score using the concentrations of circulating ceramides have been developed and adapted for routine clinical practice. Currently serum ceramides are used clinically as efficient risk stratifiers for primary and secondary prevention of atherosclerotic cardiovascular disease (CVD). A direct cause-effect relationship between CVD and ceramide has not been established to date. As ceramide-specific medications are being developed, conventional strategies such as lipid lowering agents and lifestyle interventions can be used to reduce overall risk. Ceramides can identify a very high-risk coronary heart disease category of patients in need for more intense medical attention, specifically those patients at higher risk as highlighted in the 2019 European Society of Cardiology guidelines for stable chronic coronary syndrome patients. In addition, the ceramide risk score may be used as a decision-making tool in primary prevention patients with moderate CVD risk. Finally, the ceramide risk score may have a unique utility as a motivational tool to increase patient's adherence to medical therapy and lifestyle changes.

Ceramide Accumulation Is Associated with Declining Verbal Memory in Coronary Artery Disease Patients: An Observational Study

Background:

Biomarkers in cognitively vulnerable populations, like those with coronary artery disease (CAD), may inform earlier intervention in vascular neurodegeneration. Circulating ceramide C18:0 (CerC18:0) is associated with changes in verbal memory in early neurodegeneration and CAD progression.

Objective:

To investigate whether plasma CerC18:0 accumulation is associated with longitudinal declines in verbal memory performance in CAD.

Methods:

In addition to total CerC18:0, we assessed its relative abundance to its precursors as ratios: CerC18:0 to monohexosylceramide C18:0 (MHxCer18:0), CerC18:0 to sphingomyelin C18:0 (SM18:0), and CerC18:0 to sphingosine-1-phosphate (S1P). Verbal memory was assessed using the California Verbal Learning Test 2^nd Ed. Using mixed models in 60 CAD participants, we evaluated associations between baseline CerC18:0 ratios and changes in verbal memory performance, adjusting for age, body mass index, and education. Given that cognitive decline is more rapid following onset of deficits, these associations were compared between those with possible mild vascular neurocognitive disorder (MVND).

Results:

Increased baseline CerC18:0 concentrations correlated with worse verbal memory performance over time (b[SE] = – 0.91[0.30], p = 0.003). Increased baseline CerC18:0/SM18:0 (b[SE] = – 1.11[`], p = 0.03) were associated with worse verbal memory performance over time. These associations were not mediated by whether or not patients had possible MVND at baseline.

Conclusion:

These findings support aberrant CerC18:0 metabolism as an early neurobiological change in vascular neurodegeneration. Future studies should measure enzymes responsible for conversion of sphingolipid precursors into CerC18:0 to assess enzymatic activity.