Low Density Lipoprotein Cholesterol Decreases the Expression of Adenosine A2A Receptor and Lipid Rafts-Protein Flotillin-1: Insights on Cardiovascular Risk of Hypercholesterolemia

High blood levels of low-density lipoprotein (LDL)-cholesterol (LDL-C) are associated with atherosclerosis, mainly by promoting foam cell accumulation in vessels. As cholesterol is an essential component of cell plasma membranes and a regulator of several signaling pathways, LDL-C excess may have wider cardiovascular toxicity. We examined, in untreated hypercholesterolemia (HC) patients, selected regardless of the cause of LDL-C accumulation, and in healthy participants (HP), the expression of the adenosine A2A receptor (A2AR), an anti-inflammatory and vasodilatory protein with cholesterol-dependent modulation, and Flotillin-1, protein marker of cholesterol-enriched plasma membrane domains. Blood cardiovascular risk and inflammatory biomarkers were measured. A2AR and Flotillin-1 expression in peripheral blood mononuclear cells (PBMC) was lower in patients compared to HP and negatively correlated to LDL-C blood levels. No other differences were observed between the two groups apart from transferrin and ferritin concentrations. A2AR and Flotillin-1 proteins levels were positively correlated in the whole study population. Incubation of HP PBMCs with LDL-C caused a similar reduction in A2AR and Flotillin-1 expression. We suggest that LDL-C affects A2AR expression by impacting cholesterol-enriched membrane microdomains. Our results provide new insights into the molecular mechanisms underlying cholesterol toxicity, and may have important clinical implication for assessment and treatment of cardiovascular risk in HC.

Factors Predicting Statin Initiation During Childhood in Familial Hypercholesterolemia: Importance of Genetic Diagnosis

OBJECTIVE

To identify childhood and parental factors associated with initiation of statin therapy in children with heterozygous familial hypercholesterolemia (HeFH), including underlying genetic diagnosis or parental premature atherosclerotic cardiovascular disease (ASCVD).

STUDY DESIGN

This multicenter cohort study included 245 HeFH child-parent pairs from the REFERCHOL national register (2014-2020). Demographic and clinical characteristics at the last visit were collected. Vascular disease in parents was defined as a history of ASCVD, and/or a coronary artery calcium score >100, and/or stenosis of >50% in at least carotid artery. Statistical analyses included descriptive analysis, logistic regression for univariate and multivariate effects of statins, and a sensitivity analysis combining the characteristics of children and parents.

RESULTS

Among the 245 children in the study cohort, 135 (58%), with a mean age of 14 ± 3 years, were treated with a statin. In multivariable analysis, the predictive childhood factors associated with statin treatment were genetic diagnosis (OR, 2.5; 95% CI, 1.3 to 4.9; P = .01), older age (OR, 4.4; 95% CI, 1.8-10.6; P = .01), more than 2 visits (OR, 2.36; 95% CI, 1.18-4.73; P = .015), and longer duration of follow-up (OR, 1.3; 95% CI, 1.1-1.6; P < .001). The predictive parental factor associated with childhood treatment was the presence of vascular disease (OR, 2.4; 95% CI, 1.0-5.7; P = .04).

CONCLUSIONS

HeFH confirmed by DNA testing during childhood and a history of vascular disease in parents were independently associated with statin treatment in children with HeFH. Genetic diagnosis may be useful for cardiovascular prevention in children.

A Rare Mutation in LMNB2 Associated with Lipodystrophy Drives Premature Cell Senescence

Many proteins are causative for inherited partial lipodystrophies, including lamins, the essential constituents of the nuclear envelope scaffold called the lamina. By performing high throughput sequencing on a panel of genes involved in lipodystrophies, we identified a heterozygous mutation in LMNB2 gene (c.700C > T p.(Arg234Trp)) in a female patient presenting early onset type II diabetes, hypertriglyceridemia, and android fat distribution. This mutation is rare in the general population (frequency 0.013% in GnomAD) and was predicted pathogenic by a set of pathogenicity prediction software. Patient-derived fibroblasts showed nuclear shape abnormalities and premature senescence features, which are two typical cellular phenotypes associated with laminopathies. Moreover, we observed an atypical aggregation of lamin B2 in nucleoplasm, which co-distributes with emerin and lamin A/C, along with an abnormal distribution of lamin A/C at the nuclear envelope. Finally, reducing lamin B2 expression level by siRNA targeted toward LMNB2 transcripts resulted in decreased nuclear anomalies and senescence-associated beta-galactosidase, suggesting a role of the mutated protein in the occurrence of the observed cellular phenotype. Altogether, these results suggest that mutations in lamin B2 could produce premature senescence and partial lipodystrophy features as observed with certain mutants of lamin A/C.

Unraveling Host-Gut Microbiota Dialogue and Its Impact on Cholesterol Levels

Disruption in cholesterol metabolism, particularly hypercholesterolemia, is a significant cause of atherosclerotic cardiovascular disease. Large interindividual variations in plasma cholesterol levels are traditionally related to genetic factors, and the remaining portion of their variance is accredited to environmental factors. In recent years, the essential role played by intestinal microbiota in human health and diseases has emerged. The gut microbiota is currently viewed as a fundamental regulator of host metabolism and of innate and adaptive immunity. Its bacterial composition but also the synthesis of multiple molecules resulting from bacterial metabolism vary according to diet, antibiotics, drugs used, and exposure to pollutants and infectious agents. Microbiota modifications induced by recent changes in the human environment thus seem to be a major factor in the current epidemic of metabolic/inflammatory diseases (diabetes mellitus, liver diseases, inflammatory bowel disease, obesity, and dyslipidemia). Epidemiological and preclinical studies report associations between bacterial communities and cholesterolemia. However, such an association remains poorly investigated and characterized. The objectives of this review are to present the current knowledge on and potential mechanisms underlying the host-microbiota dialogue for a better understanding of the contribution of microbial communities to the regulation of cholesterol homeostasis.

Lipoprotein-apheresis in familial hypercholesterolemia: Long-term patient compliance in a French cohort

BACKGROUND AND AIMS

Lipoprotein apheresis (LA) is a complex therapeutic option and poor compliance can adversely affect treatment outcome. The aim of this study was to describe long-term compliance to treatment in patients undergoing regular LA therapy and to investigate factors related to low compliance.

METHODS

We analysed 11,391 prescribed procedures of LA performed between 1990 and 2007 in 51 patients with familial hypercholesterolemia. Regular LA treatment was initiated in patients presenting with either homozygous familial hypercholesterolemia (n = 21), or severe heterozygous familial hypercholesterolemia (n = 30) with elevated LDL-cholesterol levels and who did not respond adequately to diet and drug therapy; the majority of these patients (n = 30) had cardiovascular disease at initiation of therapy.

RESULTS

The overall observed compliance rate based on the number of achieved/programmed procedures was 87.5%. Neither cardiovascular history nor subtypes of hypercholesterolemia was associated with compliance. In addition, there was no impact of patient demography on compliance. Treatment frequency alone significantly impacted non-compliance (i.e. patient with weekly procedures were less compliant). Interestingly, a non-significant decrease in compliance was observed among patients aged <20 years.

CONCLUSIONS

Despite the complexity of the LA procedure and its impact on the organisation of patients' daily lives, overall compliance was very high. The choice of an appropriate and adequate frequency of treatment significantly impacted patient compliance.

Glycemic disorders in melanoma patients treated with anti-PD1

9525

Background: Anti-PD1 are now the backbone of immunotherapy (IT) of metastatic melanoma (MM). Although they are overall well- tolerated, a number of severe immune-related adverse events (IRAE) have been described, among which type 1 diabetes. We observed 3 cases of fulminant diabetes (FD) in our center, and also had the impression that diabetics patients became more difficult to manage when receiving anti-PD1. Methods: Retrospective analysis of blood glucose samples collected before, during and after anti-PD1 treatment (trt ) in all mm patients (pts) receiving anti-PD1 in our department over a 36-month period. Study of FD cases observed. Results: A total of 163 pts were treated with 1920 cures of anti-PD1 including 27 treated within clinical trials. Anti-PD1 was the 1st line of IT in 70% of cases. As a whole, 1470 glycaemia were available. There was no significant difference between the median pre and post-trt glycaemia (5.37 +/-1.6 vs 5.6 +/-1.3 mmol/L (p = 0.033)). In the 28 pts with a type I (n = 0) or II (n = 28) diabetes prior to trt, there was very slight drift toward an increase of glycaemia along with the successive trt infusions (+0.05mmol/L/Cure, p = 0.004 with linear regression tendency test) .Three pts (1.84%) developed a FD revealed by a severe episode of ketosis with acute polyuria polydipsia, hyperglycaemia until 50mmol/L and weight loss. Two additional cases of FD were observed in pts treated within clinical trial comparing anti-PD1 with anti-CTLA4 in adjuvant and metastatic situation (imputability of anti-PD1 likely but uncertain until unblinding). None of these pts had any glucose increase in weeks prior to FD diagnosis. Four out of 5 FD cases had an HLA group at risk for type 1 diabetes development (HLA DRB3/4), a rare group in general population (1%). Conclusions: We could not document any systematic tendency to glycemic disorder in mm pts treated by anti-PD1. In diabetic pts prior to trt, a slight drift toward increase of glycaemia may be explained by other interfering factors (diet, metastatic disease itself, corticosteroids, anxiety etc). FD is not exceptional (2% of patients in our series) and does not seem to be announced by any minor preliminary glycemic disorder. Despite apparently stochastic onset, FD may be associated with HLA DRB3/4 subgroup.

[Statin and cardiovascular diseases after 75 years]

Statin prescription in persons older than 75 years or with frailty signs raises questions on the role of cholesterol in the genesis of atherosclerosis in this population, on the benefit of this treatment in primary or secondary prevention, and on their side effects in a context of multiple pathology and multiple medications. These questions are approached with the available literature data for this population. In secondary prevention, statin prescription is recommended whatever the age although intensive treatment should be avoided. In primary prevention, in the absence of consensus, their prescription depends on both geriatric and cardiovascular risk assessment.

Abstract 307: Influence of Dendritic Cells on Cholesterol Absorption and Excretion: Implication in Atherogenesis

Atherosclerosis represents the chronic pathophysiological process implicated in the majority of cardiovascular (CV) diseases and constitutes one of the leading causes of death in the world. The development of atherosclerotic lesions is characterized by an accumulation of extracellular and intracellular lipids in the arterial wall. These phenomena are associated with a strong local immuno-inflammatory response characterized by the recruitment of various populations of leucocytes including monocytes, macrophages and dendritic cells (DCs).

DCs are central to the regulation of immunity and the polarization of the immune response. We recently demonstrated that the longevity/depletion of DCs directly impacts plasma cholesterol levels, which is the main risk factor for atherosclerosis.

To gain insight into the cellular and molecular mechanisms underlying the inverse relationship between DC numbers and cholesterolemia, we have evaluated the impact of DCs on cholesterol homeostasis, using CD11c-hBcl2/apoE KO mice, in which specific DC-expression of the anti-apoptotic transgene hBcl2 increase their longevity and numbers. Firstly, we quantified DC populations in the liver and in the intestine, which are the main organs involved in cholesterol metabolism. Secondly, we measured the rates of dietary cholesterol absorption, tissue cholesterol content and sterol and bile salt excretion. Thirdly, we analysed the expression of genes associated with cholesterol metabolism in the liver and the intestine.

We found an increase of DC numbers in the liver and in the intestine in the CD11c-hBcl2 apoE KO mice relative to control apoE KO mice. This increase of DC numbers was associated with reduced intestinal cholesterol absorption and fecal bile acid excretion, but also with greater fecal excretion of sterols. Finally, there were no differences in the cholesterol content of the intestine and the liver. Our results suggest that the decrease in plasma cholesterol level in CD11c-hBcl2 apoE KO mice relative to apoE KO mice could be due to both a decrease of intestinal cholesterol absorption and an increase in sterol excretion. The role of intestinal DCs in dietary cholesterol absorption and excretion is presently under investigation but the present study reveal that DCs are central to the atherosclerotic process, because they are implicated in cholesterol metabolism.

Abstract 344: Bcl-x Inactivation in Macrophages Accelerates Progression of Advanced Atherosclerotic Lesions in Apoe -/- Mice

Background: Bcl-x is the most abundantly expressed member of the Bcl-2 gene family in macrophages but its role in macrophage apoptosis during atherogenesis is unknown.

Methods and results: We previously reported dual pro- and anti-atherogenic effects of macrophage survival in early versus advanced atherosclerotic lesions respectively, potentially reflecting growing impairment of efferocytosis during plaque progression. Here, we specifically inactivated Bcl-x in macrophages and evaluated its impact on atherosclerotic lesion formation in Apoe -/- mice at various stages of the disease. Bcl-x deficiency in macrophages increased susceptibility to apoptosis, resulting in the depletion of tissue macrophages in vivo, including its major pool, Küppfer cells in the liver. We also observed increased cholesterol levels, that was however not associated with any acceleration of early atherosclerotic plaque progression. This observation, suggests that the atheroprotective effect of macrophage apoptosis at that stage of disease was counterbalanced by enhanced cholesterol levels. Bcl-x KOmac/Apoe -/- mice exhibited significantly larger advanced lesions than control mice. These lesions showed vulnerable traits. Such enhanced lesion size may occur as a result not only of apoptotic cell accumulation but also of elevated cholesterol levels.

Conclusions: Modulation of macrophage resistance to apoptosis through targeted deletion of Bcl-x has a major impact on the entire macrophage cell population in the body, including Küpffer cells. Macrophage survival may, therefore, not only influence atherosclerotic plaque development and vulnerability but also cholesterol metabolism.

Bcl-x inactivation in macrophages accelerates progression of advanced atherosclerotic lesions in Apoe(-/-) mice

OBJECTIVE

Bcl-x is the most abundantly expressed member of the Bcl-2 gene family in macrophages, but its role in macrophage apoptosis during atherogenesis is unknown.

METHODS AND RESULTS

We previously reported dual pro- and antiatherogenic effects of macrophage survival in early versus advanced atherosclerotic lesions, respectively, potentially reflecting growing impairment of efferocytosis during plaque progression. Here, we specifically inactivated Bcl-x in macrophages and evaluated its impact on atherosclerotic lesion formation in Apoe(-/-) mice at various stages of the disease. Bcl-x deficiency in macrophages increased their susceptibility to apoptosis, resulting in the depletion of tissue macrophages in vivo, including its major pool, Küppfer cells in the liver. We also observed increased cholesterol levels that were, however, not associated with any acceleration of early atherosclerotic plaque progression. This observation suggests that the atheroprotective effect of macrophage apoptosis at that stage of disease was counterbalanced by enhanced cholesterol levels. Bcl-x KO(mac)/Apoe(-/-) mice exhibited significantly larger advanced lesions than control mice. These lesions showed vulnerable traits. Such enhanced lesion size may occur as a result not only of apoptotic cell accumulation but also of elevated cholesterol levels.

CONCLUSIONS

Modulation of macrophage resistance to apoptosis through targeted deletion of Bcl-x has a major impact on the entire macrophage cell population in the body, including Küpffer cells. Macrophage survival may, therefore, not only influence atherosclerotic plaque development and vulnerability but also cholesterol metabolism.

Fasting apoprotein B-48 level and coronary artery disease in a population without frank fasting hypertriglyceridemia

The aim of this study was to test the hypothesis that fasting apoprotein B-48 level might be a surrogate marker of postprandial lipemia in evaluating the risk of coronary artery disease (CAD) in a population without frank abnormality in fasting lipid profile. One hundred twenty-three patients tested by coronary angiography were selected on the criteria of absence of treatment with hypolipidemic drugs, obvious hypertriglyceridemia (>2.85 mmol/L), or other conditions that may interfere with lipoprotein metabolism except diabetes. CAD was defined by more than 50% narrowing of vessel lumen, and its severity is determined by the number of arteries involved. Fasting apoprotein B-48 was measured by a competitive enzyme-linked immunosorbent assay method. There was no difference in fasting apoprotein B-48 levels between the groups with and without CAD (0.123+/-0.096 vs 0.136+/-0.125 microg/mL, respectively), whatever the sex or whether with or without diabetes. The apoprotein B-48 level was not related to the presence or the severity of CAD. There was also no correlation between fasting apoprotein B-48 levels and age, sex, body mass index, and usual fasting lipid parameters in both patients with and without angiographically proven CAD. Finally, among the features of metabolic syndrome, apoprotein B-48 was correlated with fasting triglyceride levels (r=0.357, P<.01) only. In conclusion, the present study shows that in the absence of any major fasting abnormality in plasma lipid parameters, fasting apoprotein B-48 level, which has been associated with postprandial hyperlipidemia, does not predict the risk of CAD.