LncRNA DANCR promotes macrophage lipid accumulation through modulation of membrane cholesterol transporters

The progression of atherosclerosis (AS), the pathological foundation of coronary artery disease (CAD), is featured by massive lipid deposition in the vessel wall. LncRNAs are implicated in lipid disorder and AS, whereas the specific role of lncRNA DANCR in atherogenesis remains unknown. Here, we demonstrated that DANCR promotes macrophage lipid accumulation by regulating the expression of membrane cholesterol transport proteins. qPCR showed that compared to control groups, CAD patients and atherosclerotic mice had higher DANCR levels. Treating human THP-1 macrophages and mouse RAW264.7 macrophages with ox-LDL significantly upregulated the expression levels of DANCR. Oil Red O staining showed that the silence of DANCR robustly reduced, while overexpression of DANCR significantly increased the numbers and size of lipid droplets in ox-LDL-treated THP-1 macrophages. In contrast, the opposite phenomena were observed in DANCR overexpressing cells. The expression of ABCA1, ABCG1, SR-BI, and NBD-cholesterol efflux was increased obviously by DANCR inhibition and decreased by DANCR overexpression, respectively. Furthermore, transfection with DANCR siRNA induced a robust decrease in the levels of CD36, SR-A, and Dil-ox-LDL uptake, while DANCR overexpression amplified the expression of CD36, SR-A and the uptake of Dil-ox-LDL in lipid-laden macrophages. Lastly, we found that the effects of DANCR on macrophage lipid accumulation and the expression of membrane cholesterol transport proteins were not likely related to miR-33a. The present study unraveled the adverse role of DANCR in foam cell formation and its relationship with cholesterol transport proteins. However, the competing endogenous RNA network underlying these phenomena warrants further exploration.

Postprandial plasma lipidome responses to a high-fat meal among healthy women

Postprandial lipemia consists of changes in concentrations and composition of plasma lipids after food intake, commonly presented as increased levels of triglyceride-rich lipoproteins. Postprandial hypertriglyceridemia may also affect high-density lipoprotein (HDL) structure and function, resulting in a net decrease in HDL concentrations. Elevated triglycerides (TG) and reduced HDL levels have been positively associated with risk of cardiovascular diseases development. Here, we investigated the plasma lipidome composition of 12 clinically healthy, nonobese and young women in response to an acute high-caloric (1135 kcal) and high-fat (64 g) breakfast meal. For this purpose, we employed a detailed untargeted mass spectrometry-based lipidomic approach and data was obtained at four sampling points: fasting and 1, 3 and 5 h postprandial. Analysis of variance revealed 73 significantly altered lipid species between all sampling points. Nonetheless, two divergent subgroups have emerged at 5 h postprandial as a function of differential plasma lipidome responses, and were thereby designated slow and fast TG metabolizers. Late responses by slow TG metabolizers were associated with increased concentrations of several species of TG and phosphatidylinositol (PI). Lipidomic analysis of lipoprotein fractions at 5 h postprandial revealed higher TG and PI concentrations in HDL from slow relative to fast TG metabolizers, but not in apoB-containing fraction. These data indicate that modulations in HDL lipidome during prolonged postprandial lipemia may potentially impact HDL functions. A comprehensive characterization of plasma lipidome responses to acute metabolic challenges may contribute to a better understanding of diet/lifestyle regulation in the metabolism of lipid and glucose.

Insulin Rescued MCP-1-Suppressed Cholesterol Efflux to Large HDL2 Particles via ABCA1, ABCG1, SR-BI and PI3K/Akt Activation in Adipocytes

Purpose

Intracellular cholesterol imbalance plays an important role in adipocyte dysfunction of obesity. However, it is unclear whether obesity induced monocyte chemoattractant protein-1 (MCP-1) causes the adipocyte cholesterol imbalance. In this study, we hypothesize that MCP-1 impairs cholesterol efflux of adipocytes to HDL2 and insulin rescues this process.

Methods

We recruited coronary artery disease (CAD) patients with obesity and overweight to analyze the association between MCP-1 and HDL2-C by Pearson correlation coefficients. We performed [³H]-cholesterol efflux assay to demonstrate the effect of MCP-1 and insulin on cholesterol efflux from 3T3-L1 adipocytes to large HDL2 particles. Western blot, RT-qPCR, cell-surface protein assay, and confocal microscopy were performed to determine the regulatory mechanism.

Results

Plasma MCP-1 concentrations were negatively correlated with HDL2-C in CAD patients with obesity and overweight (r = −0.60, p < 0.001). In differentiated 3T3-L1 adipocytes, MCP-1 reduced cholesterol efflux to large HDL2 particles by 55.4% via decreasing ATP-binding cassette A1 (ABCA1), ABCG1, and scavenger receptor class B type I (SR-BI) expression. Intriguingly, insulin rescued MCP-1 mediated-inhibition of cholesterol efflux to HDL2 in an Akt phosphorylation-dependent manner. The rescue efficacy of insulin was 138.2% for HDL2. Moreover, insulin increased mRNA and protein expression of ABCA1, ABCG1, and SR-BI at both transcriptional and translational levels via the PI3K/Akt activation.

Conclusions

These findings indicate that MCP-1 impairs cholesterol efflux to large HDL2 particles in adipocytes, which is reversed by insulin via the upregulation of ABCA1, ABCG1, and SR-BI. Therefore, insulin might improve cholesterol imbalance by an anti-inflammatory effect in adipocytes. Clinical trial registration number: ChiCTR2000033297; Date of registration: 2020/05/ 27; Retrospectively registered.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10557-021-07166-2.

The Alcohol-High-Density Lipoprotein Athero-Protective Axis

Ingestion of alcohol is associated with numerous changes in human energy metabolism, especially that of plasma lipids and lipoproteins. Regular moderate alcohol consumption is associated with reduced atherosclerotic cardiovascular disease (ASCVD), an effect that has been attributed to the concurrent elevations of plasma high-density lipoprotein-cholesterol (HDL-C) concentrations. More recent evidence has accrued against the hypothesis that raising plasma HDL concentrations prevents ASCVD so that other metabolic processes associated with alcohol consumption have been considered. This review explored the roles of other metabolites induced by alcohol consumption-triglyceride-rich lipoproteins, non-esterified free fatty acids, and acetate, the terminal alcohol metabolite in athero-protection: Current evidence suggests that acetate has a key role in athero-protection but additional studies are needed.

Postprandial remodeling of high-density lipoprotein following high saturated fat and high carbohydrate meals

BACKGROUND

Humans spend most of the time in the postprandial state, yet most knowledge about high-density lipoproteins (HDL) derives from the fasted state. HDL protein and lipid cargo mediate HDL's antiatherogenic effects, but whether these HDL constituents change in the postprandial state and are affected by dietary macronutrients remains unknown.

OBJECTIVES

This study aimed to assess changes in HDL protein and lipid composition after the consumption of a high-carbohydrate or high saturated fat (HSF) meal.

METHODS

We isolated HDL from plasma collected during a randomized, cross-over study of metabolically healthy subjects. Subjects consumed isocaloric meals consisting predominantly of either carbohydrate or fat. At baseline and at 3 and 6 hours postprandial, we quantified HDL protein and lipid composition by liquid chromatography-mass spectrometry.

RESULTS

A total of 15 subjects were included (60% female, aged 34 ± 15 years, body mass index: 24.1 ± 2.7 kg/m2). Consumption of the HSF meal led to HDL enrichment in total lipid (P = .006), triglyceride (P = .02), and phospholipid (P = .008) content and a corresponding depletion in protein content. After the HSF meal, 16 of the 25 measured phosphatidylcholine species significantly increased in abundance (P values range from .027 to <.001), along with several sphingolipids including ceramides (P < .004), lactosylceramide (P = .023), and sphingomyelin-14 (P = .013). Enrichment in apolipoprotein A-I (P = .001) was the only significant change in HDL protein composition after the HSF meal. The high-carbohydrate meal conferred only minimal changes in HDL composition.

CONCLUSION

Meal macronutrient content acutely affects HDL composition in the postprandial state, with the HSF meal resulting in enrichment of HDL phospholipid content with possible consequences for HDL function.

Impact of a one-year lifestyle modification program on cholesterol efflux capacities in men with abdominal obesity and dyslipidemia

Cholesterol efflux capacities (CECs) are negatively associated with cardiovascular disease risk, irrespective of plasma high-density lipoprotein (HDL) cholesterol levels. Whether interventions targeting lifestyle improve HDL-CECs is unknown. Our objective was to determine whether improving dietary quality and increasing physical activity levels improves HDL-CECs in men with abdominal obesity and dyslipidemia. Our study sample included men (48 ± 8.5 yr) with an elevated waist circumference (≥90 cm) associated with dyslipidemia (triglycerides ≥1.69 and/or HDL cholesterol <1.03 mmol/l); 113 men completed a 1-yr intervention, consisting of a healthy eating and physical activity/exercise program, and 32 were included in a control group. An oral lipid tolerance test (OLTT) was performed in a subsample of 28 men who completed the intervention, and blood was collected every 2 h for 8 h. HDL-CECs were measured using [³H]cholesterol-labeled J774 macrophages and HepG2 hepatocytes. The lifestyle modification program led to an overall improvement in the cardiometabolic risk profile, increases in J774-HDL-CEC by 14.1% (+0.88 ± 1.09%, P < 0.0001), HepG2-HDL-CEC by 3.4% (+0.17 ± 0.75%, P = 0.01), and HDL cholesterol and apolipoprotein A-1 levels (13.5%, P < 0.0001 and 14.9%, P < 0.0001, respectively). J774-HDL-CECs and HepG2-HDL-CECs did not change in the control group. The best predictor for changes in HDL-CEC was apolipoprotein A-1 level. The lifestyle modification program also improved HDL-CEC response in postprandial lipemia during an OLTT. HDL-CEC did not change during the OLTT. Our results suggest that increasing physical activity levels and improving diet quality can have a positive impact on both HDL quantity and quality in men with abdominal obesity and dyslipidemia.

High-Density Lipoprotein Subfractions and Cholesterol Efflux Capacity Are Not Affected by Supervised Exercise but Are Associated with Baseline Interleukin-6 in Patients with Peripheral Artery Disease

OBJECTIVE

To quantify the association between high-density lipoprotein (HDL) subfractions, efflux capacity, and inflammatory markers at baseline and the effect of supervised exercise on these HDL parameters in patients with peripheral artery disease (PAD).

METHODS

The study to improve leg circulation (SILC) was a randomized trial of supervised treadmill exercise, leg resistance training, or control in individuals with PAD. In a post hoc cross-sectional analysis, we quantified the associations between baseline HDL subfraction concentrations (HDL2 and HDL3), HDL-C efflux capacity, and inflammatory markers [C-reactive protein (CRP) and interleukin-6 (IL-6)]. We then examined the effect of supervised exercise on changes in these lipoprotein parameters and inflammatory markers in 88 patients from SILC.

RESULTS

Baseline HDL-C efflux capacity was associated with baseline concentrations of HDL2 (β = 0.008, p = 0.0106), HDL3 (β = 0.013, p < 0.0001), and IL-6 (β = -0.019, p = 0.03). Baseline HDL3 concentration was inversely associated with IL-6 concentration (β = -0.99, p = 0.008). Compared to control, changes in HDL2, HDL3, normalized HDL-C efflux capacity, CRP, or IL-6 were not significantly different at 6 months following the structured exercise intervention.

CONCLUSION

HDL efflux and HDL3 were inversely associated with IL-6 in PAD patients. Structured exercise was not associated with changes in HDL subfractions, HDL-C efflux capacity, CRP, and IL-6 in PAD patients. Our preliminary findings support the theory that inflammation may adversely affect HDL structure and function; however, further studies are needed to evaluate these findings.

Dysfunctional high-density lipoproteins in coronary heart disease: implications for diagnostics and therapy

Low plasma levels of high-density lipoprotein (HDL) cholesterol are associated with increased risks of coronary heart disease. HDL mediates cholesterol efflux from macrophages for reverse transport to the liver and elicits many anti-inflammatory and anti-oxidative activities which are potentially anti-atherogenic. Nevertheless, HDL has not been successfully targeted by drugs for prevention or treatment of cardiovascular diseases. One potential reason is the targeting of HDL cholesterol which does not capture the structural and functional complexity of HDL particles. Hundreds of lipid species and dozens of proteins as well as several microRNAs have been identified in HDL. This physiological heterogeneity is further increased in pathologic conditions due to additional quantitative and qualitative molecular changes of HDL components which have been associated with both loss of physiological function and gain of pathologic dysfunction. This structural and functional complexity of HDL has prevented clear assignments of molecules to the functions of normal HDL and dysfunctions of pathologic HDL. Systematic analyses of structure-function relationships of HDL-associated molecules and their modifications are needed to test the different components and functions of HDL for their relative contribution in the pathogenesis of atherosclerosis. The derived biomarkers and targets may eventually help to exploit HDL for treatment and diagnostics of cardiovascular diseases.

Postprandial decrease in LDL-cholesterol in men with metabolic syndrome

BACKGROUND

In some epidemiological studies, blood lipids are determined at non-fasting state, which may impact cardiovascular risk estimation. The aim of this study was to evaluate postprandial LDL-C changes in men with newly diagnosed metabolic syndrome (MetSy).

METHODS

36 male patients were examined: 12 men with and 24 men without MetSy. The fat tolerance test was performed before and after a three-month hypolipidemic treatment. Serum lipids were measured using routine methods, lipid peroxides (LPO) colorimetrically, apolipoproteins A-I, B, and hsCRP immunoturbidimetrically.

RESULTS

The postprandial increase in triglycerides was associated with a decrease in LDL-C and a small decrease in apo B. In men with MetSy, the mean change in LDL-C (-19.5 ± 2.3 mg/dl) was greater than in healthy men (-5.7 ± 3.8 mg/dl). All lipid changes (ΔTG, ΔLDL-C and ΔLPO) were linearly dependent on the postprandial non-LDL-cholesterol. After three months of hypolipidemic treatment, in all men with MetSy, the apoB/apoA-I ratio remained the same as before the therapy.

CONCLUSION

In men diagnosed with MetSy, postprandial decreases in LDL-cholesterol may cause underestimation of cardiovascular risk. After three months of hypolipidemic treatment, there was only a partial reduction in this risk, as the apoB/apoA-I ratio remained the same.

Enhanced cholesterol efflux to HDL through the ABCA1 transporter in hypertriglyceridemia of type 2 diabetes

OBJECTIVE

Our objective was to examine the role of hypertriglyceridemia on the capacity of HDL to facilitate ABCA-1 mediated cholesterol efflux in type 2 diabetes (T2DM).

METHODS

HDL mediated cholesterol efflux through the ABCA-1 transporter was measured using BHK cell lines in samples of 71 participants with T2DM in the presence or absence of high triglyceride levels (TG). Additionally, HDL mediated efflux was measured in 13 diabetic and non-diabetic participants fasting and four hours after a high-fat test challenge.

RESULTS

HDL mediated cholesterol efflux function was increased in participants with T2DM with hypertriglyceridemia when compared to participants with T2DM without hypertriglyceridemia (efflux ratio mean±standard deviation (SD), T2DM+TG: 1.17±0.25 vs. T2DM - TG: 1.03±0.19, p=0.0098). In the fat challenge study, we observed a significant increase in ABCA-1 mediated cholesterol efflux capacity following an ingestion of high-fat test meal by participants in both groups of T2DM (n=6, efflux ratio, mean±SD, pre: 0.86±0.4 vs. post: 1.34±0.6, p=0.01) and non-diabetic participants (n=7, efflux ratio mean±SD pre: 1.24±0.31 vs. post: 1.39±0.42, p=0.04) that was partly explained by the difference in CETP activity (r=0.6, p=0.03).

CONCLUSION

Our study suggests that high triglyceride levels facilitate ABCA-1 mediated efflux function of HDL in part by activating CETP.

Acute coronary syndrome remodels the protein cargo and functions of high-density lipoprotein subfractions

OBJECTIVES

This study examined alterations in the functions and proteome of high-density lipoprotein (HDL) subfractions (HDL2 and HDL3) isolated from patients with acute coronary syndrome (ACS) compared with control subjects.

METHODS

We measured HDL subfraction cholesterol efflux capacity, inflammatory index (HII), paraoxonase-1 (PON1) activity, and lipid hydroperoxide (LOOH) levels in both male age-matched controls and the ACS group (n = 40/group). Additionally, proteomic analysis was used to monitor changes in the HDL subfraction proteome between controls and ACS subjects.

RESULTS

Both HDL2 and HDL3 from ACS patients had greater HII and LOOH levels compared with controls (P<0.001); PON1 activity and cholesterol efflux capacity in both HDL2 and HDL3 from the ACS group were significantly less than those of controls (P<0.001). Using proteomic analysis, we demonstrated that, compared with the control group, nine proteins were selectively enriched in HDL3 from subjects with ACS, and ras-related protein Rab-7b was decreased in HDL3. Additionally, in the ACS subjects, 12 proteins were decreased in HDL2 and 4 proteins were increased in HDL2.

CONCLUSIONS

Functional HDL subfractions shifted to dysfunctional HDL subfractions during ACS, and the functional impairment was linked to remodeled protein cargo in HDL subfractions from ACS patients.

High-density lipoprotein subclasses and their relationship to cardiovascular disease

OBJECTIVE

To assess the clinical utility of measuring high-density lipoprotein (HDL) subfractions to assess coronary heart disease (CHD) risk.

METHODS

Literature review of 80 published investigations.

RESULTS

Measurements of HDL2b by gradient gel electrophoresis provided more consistent evidence of CHD risk than measurement of HDL2 cholesterol. Five of the seven studies that compared the extent or progression of atherosclerosis with gradient gel electrophoresis estimates of HDL subclasses (71%) assigned statistical significance to HDL2b. Ten of the 11 case-control comparisons (91%) reported lower HDL2b in cases. In contrast, of the 16 association studies relating HDL2 cholesterol and HDL3 cholesterol to extent of disease, five reported no significant relationships with either subfraction, two reported significant relationships with both HDL2 and HDL3 cholesterol, four reported significant relationships with HDL2 but not HDL3 cholesterol, and five reported relationships with HDL3 but not HDL2 cholesterol. Forty-five percent of the case-control comparisons reported that both HDL2 cholesterol and HDL3 cholesterol were significantly lower in cases than controls, 17% failed to find significance for either subfraction, and the remainder reported significantly lower values in cases for HDL2 cholesterol only (26%) or HDL3 cholesterol only (11%). On average, the case-control differences were similar for HDL2 (-0.12 ± 0.01 mmol/L) and HDL3 cholesterol (-0.10 ± 0.02 mmol/L), although relative to controls, the percent reduction was twice as great for HDL2 (-25.7 ± 2.9%) than HDL3 cholesterol (-12.1 ± 1.5%). Eight prospective studies were identified and four reported that both HDL2 and HDL3 predicted lower risk for CHD, one reported reductions in risk for HDL2 but not HDL3 cholesterol, and three reported reductions in risk for HDL3 but not HDL2 cholesterol. None of the prospective studies show that measurements of HDL cholesterol subfractions improve the identification of persons at risk.

CONCLUSIONS

HDL2 and HDL3 cholesterol do not distinguish cardioprotective differences between HDL subclasses. More extensive characterization of HDL particles by one or two dimensional gel electrophoresis, ion mobility, or ultracentrifugation may provide more specific information about CHD risk than the measurement of HDL cholesterol, HDL3 cholesterol, or HDL2 cholesterol.

A reduction of CETP activity, not an increase, is associated with modestly impaired postprandial lipemia and increased HDL-cholesterol in adult asymptomatic women

Background

The relationship between CETP and postprandial hyperlipemia is still unclear. We verified the effects of varying activities of plasma CETP on postprandial lipemia and precocious atherosclerosis in asymptomatic adult women.

Methods

Twenty-eight women, selected from a healthy population sample (n = 148) were classified according to three CETP levels, all statistically different: CETP deficiency (CETPd ≤ 4.5%, n = 8), high activity (CETPi ≥ 23.8, n = 6) and controls (CTL, CETP ≥ 4.6% and ≤ 23.7%, n = 14). After a 12 h fast they underwent an oral fat tolerance test (40 g of fat/m² of body surface area) for 8 hours. TG, TG-rich-lipoproteins (TRL), cholesterol and TRL-TG measurements (AUC, AUIC, AR, RR and late peaks) and comparisons were performed on all time points. Lipases and phospholipids transfer protein (PLTP) were determined. Correlation between carotid atherosclerosis (c-IMT) and postprandial parameters was determined. CETP TaqIB and I405V and ApoE-ε3/ε2/ε4 polymorphisms were examined. To elucidate the regulation of increased lipemia in CETPd a multiple linear regression analysis was performed.

Results

In the CETPi and CTL groups, CETP activity was respectively 9 and 5.3 higher compared to the CETPd group. Concentrations of all HDL fractions and ApoA-I were higher in the CETPd group and clearance was delayed, as demonstrated by modified lipemia parameters (AUC, AUIC, RR, AR and late peaks and meal response patterns). LPL or HL deficiencies were not observed. No genetic determinants of CETP deficiency or of postprandial lipemia were found. Correlations with c-IMT in the CETPd group indicated postprandial pro-atherogenic associations. In CETPd the regression multivariate analysis (model A) showed that CETP was largely and negatively predicted by VLDL-C lipemia (R² = 92%) and much less by TG, LDL-C, ApoAI, phospholipids and non-HDL-C. CETP (model B) influenced mainly the increment in ApoB-100 containing lipoproteins (R² = 85% negatively) and phospholipids (R² = 13%), at the 6^thh point.

Conclusion

The moderate CETP deficiency phenotype included a paradoxically high HDL-C and its sub fractions (as earlier described), positive associations with c-IMT, a postprandial VLDL-C increment predicting negatively CETP activity and CETP activity regulating inversely the increment in ApoB100-containing lipoproteins. We hypothesize that the enrichment of TG content in triglyceride-rich ApoB-containing lipoproteins and in TG rich remnants increases lipoproteins' competition to active lipolysis sites,reducing their catabolism and resulting on postprandial lipemia with atherogenic consequences.

Differences and similarities of postprandial lipemia in rodents and humans

Background

The rat has been a mainstay of physiological and metabolic research, and more recently mice. This study aimed at characterizing the postprandial triglyceride profile of two members of the Muridae family: the Wistar rats (Rattus norvegicus albinus) and C57BL/6 mice (Mus musculus) plus comparing them to the profile obtained in humans.

Methods

Thirty-one male and twelve female Wistar rats, ten C57BL/6 male and nine female mice received a liquid meal containing fat (17%), protein (4%) and carbohydrates (4%), providing 2 g fat/Kg. Thirty-one men and twenty-nine women received a standardized liquid meal containing fat (25%), dextromaltose (55%), protein (14%), and vitamins and minerals (6%), and providing 40 g of fat per square meter of body surface. Serial blood samples were collected at 2, 4, 6, 8 and 10 h after the ingestion in rats, at 1, 2, 3, 4, 5 and 6 h in mice and in humans at 2, 4, 6 and 8 h. Wilcoxon and Mann-Whitney tests were used.

Results/Discussion

The triglyceride responses were evaluated after the oral fat loads. Fasting and postprandial triglyceridemia were determined sequentially in blood sample. AUC, AUIC, AR, RR and late peaks were determined.

Conclusions

Rats are prone to respond in a pro-atherogenic manner. The responses in mice were closer to the ones in healthy men. This study presents striking differences in postprandial triglycerides patterns between rats and mice not correlated to baseline triglycerides, the animal baseline body weight or fat load in all animal groups.