High-Density Lipoprotein Subfractions: Much Ado about Nothing or Clinically Important?

Untargeted lipidomics reveals novel HDL metabotypes and lipid-clinical correlates

Plasma high-density lipoprotein (HDL), originally studied for its role in lipid transport, is now appreciated to have wide-ranging biological functions that become defective during disease. While >200 lipids have collectively been detected in HDL, published HDL lipidomic analyses in different diseases have commonly been targeted to prespecified subsets of lipids. Here, we report the results of untargeted lipidomic analysis of HDL isolated from 101 subjects referred for computed tomographic coronary imaging for whom multiple additional clinical and lipoprotein metadata were measured. Unsupervised clustering of the total HDL lipidome revealed that the subjects fell into one of two discrete groups, herein referred to as HDL "metabotypes." Patients in metabotype 1 were likelier to be female and tended to have a less atherogenic lipoprotein profile, higher HDL cholesterol efflux capacity (CEC), and lower-grade non-calcified burden on coronary imaging than metabotype 2 counterparts. Specific lipids were relatively enriched in metabotype 1 HDL. Linear modeling revealed that several of these lipids were positively associated with CEC, statin use, HDL size, and HDL particle number, and positively correlated with HDL apolipoprotein A-1, suggesting that they may be informative HDL biomarkers. Taken together, we posit a novel, clinically relevant categorization for HDL revealed by systems biology.

HDL Levels as a Novel Predictor of Long-Term Adverse Outcomes in Patients with Heart Failure: A Retrospective Cohort Study

Background

The role of high-density lipoprotein cholesterol (HDL-C) in heart failure (HF) outcomes is contentious. We aimed to assess HDL-C's prognostic value in HF patients.

Methods

In this retrospective cohort study (2012-2022) at the First Affiliated Hospital of Xinjiang Medical University, we analyzed 4442 patients, categorized by HDL-C quartiles. We applied the Cox proportional hazards model to assess survival and report hazard ratios (HR) with 95% confidence intervals (CI).

Results

Over a decade, we recorded 1354 fatalities (42.3%) and 820 readmissions. The third HDL-C quartile (0.93-1.14 mmol/L) showed the lowest mortality rates, with reduced risks in the second and third quartiles compared to the first (Q2 HR=0.809, 95% CI 0.590-1.109; Q3 HR=0.794, 95% CI 0.564-1.118). The fourth quartile presented a lower mortality risk compared to the first (Q4 HR=0.887, 95% CI 0.693-1.134). A significant correlation existed between HDL-C levels and cardiovascular risk (HR=0.85, 95% CI 0.75-0.96, p<0.01).

Conclusion

HDL-C levels exhibit a complex association with mortality in HF, indicating the importance of HDL-C in HF prognosis and the need for tailored management strategies.

Association between the proportion of HDL-cholesterol subclasses and the severity of coronary artery stenosis in patients with acute myocardial infarction

BACKGROUND

Past research has shown an inverse correlation between high-density lipoprotein (HDL) and coronary heart disease (CHD), while recent studies have shown that extremely high or low HDL levels increase the risk of cardiovascular death.

OBJECTIVE

To explore the relationships between HDL subtypes and the degree of coronary artery stenosis in patients with acute myocardial infarction (AMI).

METHODS

This was a single-center cross-sectional study. Ultimately, we included 1,200 adult participants with AMI hospitalized from 2017 to 2023. Patients were classified into mild and moderate-severe groups according to their Gensini score. Restricted cubic spline and multivariate logistic regression models were used to explore the associations between HDL subclasses and the severity of coronary stenosis.

RESULTS

The adjusted odds ratios (ORs), 95% confidence intervals (CIs), and p values for HDL subclasses in the multivariate logistic model (adjusted for age, gender, hypertension status, diabetes status, stroke status, and kidney disease status) were as follows: HDL-2b: 0.97 (0.95-1.00, p= 0.018) and HDL-3: 0.98 (0.97-0.99, p= 0.008). Subgroup analysis revealed that HDL-3 exhibited a statistically significant impact on the severity of coronary stenosis among individuals <75 years of age and among men, and the influence of HDL-2b on the severity of coronary stenosis was statistically significant only in individuals aged ≥75 years.

CONCLUSION

The relationship between reduced levels of HDL-2b and HDL-3 and the risk of coronary stenosis exhibited a linear pattern and was significantly modified by age. Subgroup analysis identified specific populations that warrant attention regarding HDL-2b and HDL-3.

Association between HDL-C and intensive blood pressure control in patients with hypertension: A post-hoc analysis of SPRINT

Previous studies in patients with hypertension have demonstrated that there is a U-shaped association between HDL-C (high-density lipoprotein cholesterol) and the risk of cardiovascular events in male patients with hypertension. However, to the best of our knowledge, the relationship between HDL-C and intensive blood pressure control in specific cardiovascular events has never been investigated. To fill this knowledge gap, the authors analyzed the relationship between HDL-C levels and cardiovascular events in hypertensive patients within the Systolic Blood Pressure Intervention Trial (SPRINT). The SPRINT evaluated the impact of intensive blood pressure control (systolic blood pressure < 120 mm Hg) versus standard blood pressure control (systolic blood pressure < 140 mm Hg). The Cox proportional risk regression was used to investigate the association between different HDL-C status and clinical outcomes. Additional stratified analyzes were performed to evaluate the robustness of sex difference. A total of 9323 participants (6016 [64.53%] males and 3307 [35.47%] females) with hypertension from the SPRINT research were included in the analysis. The median follow-up period was 3.26 years. Our population was divided into five groups based on the HDL-C plasma levels: HDL-C < 30 mg/dL, HDL-C between 30 and 40 mg/dL, HDL-C between 40 and 60 mg/dL, HDL-C between 60 and 80 mg/dL and HDL-C > 80 mg/dL. Sensitivity analyzes showed that in the SPRINT, women in the HDL-C high population had a higher risk of mortality from all causes than men. In this cohort study, results suggest that patients with HDL-C levels higher than 80 mg/dL had lower risk of SPRINT primary outcome, cardiovascular death, and stroke, but this study tested association, not causation. HDL-C levels were associated with composite cardiovascular outcomes in male but not female patients. Our results demonstrated that in patients with hypertension, the association between HDL-C and risk of cardiovascular events is L-shaped.

A decreased level of high-density lipoprotein is a possible risk factor for type 2 diabetes mellitus: A review

Introduction

Type 2 diabetes mellitus (T2DM) is characterized primarily by dyslipidemia and hyperglycemia due to insulin resistance. High-density lipoprotein (HDL) play a significant role in preventing the incidence of dyslipidemia and its complications. HDL has different protective functions, such as reducing oxidation, vascular inflammation, and thrombosis; additionally, its anti-diabetic role is one of the most significant recent discoveries about HDL and some of its constituent lipoproteins.

Methods

This research reviews ongoing studies and preliminary investigations into the assessment of relation between decreased level of HDL and T2DM.

Results

The levels of HDL and its functions contribute to glucose hemostasis and the development of T2DM through four possible mechanisms, including insulin secretion by beta cells, peripheral insulin sensitivity, non-insulin-dependent glucose uptake, and adipose tissue metabolic activity. Additionally, the anti-oxidant properties of HDL protect beta cells from apoptosis caused by oxidative stress and inflammation induced by low-density lipoprotein, which facilitate insulin secretion.

Conclusion

Therefore, HDL and its compositions, especially Apo A-I, play an important role in regulating glucose metabolism, and decreased levels of HDL can be considered a risk factor for DM. Different factors, such as hypoalphalipoproteinemia that manifests as a consequence of genetic factors, such as Apo A-I deficiency, as well as secondary causes arising from lifestyle choices and underlying medical conditions that decrease the level of HDL, could be associated with DM. Moreover, intricate connections between HDL and diabetic complications extend beyond glucose metabolism to encompass complications like cardiovascular disease and kidney disease. Therefore, the exact interactions between HDL level and DM should be evaluated in future studies.

Association of Lipoprotein Subfractions With Presence and Severity of Coronary Artery Disease in Patients Referred for Coronary Angiography

Lipoprotein subfractions (LS) can be used for better risk stratification in subjects deemed not at high risk for coronary artery disease (CAD). In this study, we evaluated the correlation between LS with CAD presence and severity. This is a prospective case-control study of 157 patients referred for coronary angiography who were not on lipid-lowering therapy and had LS measured by nuclear magnetic resonance spectroscopy. Synergy between PCI with Taxus and Cardiac Surgery (SYNTAX) scores were calculated to estimate CAD severity. Univariate and multivariable regression analysis was performed to determine correlation of LS with CAD presence and severity and acute coronary syndrome (ACS). There was significant association of certain LS (positive for total low-density lipoprotein particle [LDL-P], small LDL-P and apolipoprotein B, negative for large high-density lipoprotein particle [HDL-P] and apolipoprotein A1 [ApoA1]) with the presence of obstructive CAD and CAD severity. Small LDL-P and HDL-P were still predictive for obstructive CAD after adjusting for traditional risk factors, 10-year atherosclerotic cardiovascular disease risk score and in those with low-density lipoprotein cholesterol <100 mg/100 ml. Total LDL-P and ApoA1 were predictive of CAD severity on multivariable analysis. Higher small LDL-P and lower large HDL-P were associated with ACS presence, although only large HDL-P had a significant inverse correlation with ACS on adjusted analysis (odds ratio 0.74 95% confidence interval 0.58, 0.95) In conclusion, in our cohort of patients referred for coronary angiography, total LDL-P, small LDL-P, and apolipoprotein B had significant direct correlation, and large HDL-P and ApoA1 had significant inverse correlation with obstructive CAD and CAD severity.

Association of HDL Subfraction Profile with the Progression of Insulin Resistance

Type 2 diabetes mellitus (T2DM) is a major global public health problem, as it is associated with increased morbidity, mortality, and healthcare costs. Insulin resistance (IR) is a condition characterized by disturbances in carbohydrate and lipid metabolism that precedes T2DM. The aim of the present study was to investigate the association between HDL and its subfraction profile and the progression of IR, as assessed by the Homeostatic Model Assessment for IR (HOMA-IR) index, and to define cut-off values to identify an increased risk of IR. Individuals with a HOMA-IR greater than 3.63 were considered to have IR. The HDL subfractions were separated using the Lipoprint system, which identifies ten subfractions (HDL-1-10) in three subclasses as large (HDL-L), intermediate (HDL-I) and small (HDL-S). Analyses were performed on samples from 240 individuals without IR and 137 with IR from the Hungarian general and Roma populations. The HDL-1 to -6 subfractions and the HDL-L and -I classes showed a significant negative association with the progression and existence of IR. Among them, HDL-2 (B = -40.37, p = 2.08 × 10-11) and HDL-L (B = -14.85, p = 9.52 × 10-10) showed the strongest correlation. The optimal threshold was found to be 0.264 mmol/L for HDL-L and 0.102 mmol/L and above for HDL-2. Individuals with HDL-L levels below the reference value had a 5.1-fold higher risk of IR (p = 2.2 × 10-7), while those with HDL-2 levels had a 4.2-fold higher risk (p = 3.0 × 10-6). This study demonstrates that the HDL subfraction profile (especially the decrease in HDL-2 and -L) may be a useful marker for the early detection and intervention of atherogenic dyslipidemia in subjects with impaired glucose and insulin metabolism.

Fatty fish consumption reduces lipophilic index in erythrocyte membranes and serum phospholipids

BACKGROUND AND AIMS

Lipophilic index (LI) has been introduced to assess the overall fatty acid lipophilicity and as a simple estimate of membrane fluidity. However, little is known on effect of diet on LI. We tested if Camelina sativa oil (CSO) high in ALA, fatty fish (FF) or lean fish (LF) affect LI as compared to control diet and, secondarily, if the LI is associated with HDL lipids and functionality and LDL lipidome.

METHODS AND RESULTS

We used data from two randomized clinical trials. The AlfaFish intervention lasted 12 weeks and 79 subjects with impaired glucose tolerance were randomized to FF, LF, CSO or control group. In the Fish trial, 33 subjects with myocardial infarction or unstable ischemic heart attack were randomized to FF, LF or control group for 8 weeks. LI was calculated from erythrocyte membrane fatty acids in AlfaFish and from serum phospholipids in Fish trial. HDL lipids were measured using high-throughput proton nuclear magnetic resonance spectroscopy. There was a significant decrease in LI in the FF group in the AlfaFish (fold change 0.98 ± 0.03) and in the Fish trial (0.95 ± 0.04) and the decrease differed from that of control group in both trials and from CSO group in the AlfaFish study. There were no significant changes in LI in LF or CSO groups. The mean diameter of HDL particles and concentration of large HDL particles were inversely associated with LI.

CONCLUSION

FF consumption decreased LI indicating better membrane fluidity in subjects with impaired glucose tolerance or coronary heart disease.

High HDL (High-Density Lipoprotein) Cholesterol Increases Cardiovascular Risk in Hypertensive Patients

BACKGROUND

Emerging evidence suggests that elevated circulating levels of HDL-C (high-density lipoprotein cholesterol) could be linked to an increased mortality risk. However, to the best of our knowledge, the relationship between HDL-C and specific cardiovascular events has never been investigated in patients with hypertension.

METHODS

To fill this knowledge gap, we analyzed the relationship between HDL-C levels and cardiovascular events in hypertensive patients within the Campania Salute Network in Southern Italy.

RESULTS

We studied 11 987 patients with hypertension, who were followed for 25 534 person-years. Our population was divided in 3 groups according to the HDL-C plasma levels: HDL-C<40 mg/dL (low HDL-C); HDL-C between 40 and 80 mg/dL (medium HDL-C); and HDL-C>80 mg/dL (high HDL-C). At the follow-up analysis, adjusting for potential confounders, we observed a total of 245 cardiovascular events with a significantly increased risk of cardiovascular events in the low HDL-C group and in the high HDL-C arm compared with the medium HDL-C group. The spline analysis revealed a nonlinear U-shaped association between HDL-C levels and cardiovascular outcomes. Interestingly, the increased cardiovascular risk associated with high HDL-C was not confirmed in female patients.

CONCLUSIONS

Our data demonstrate that there is a U-shaped association between HDL-C and the risk of cardiovascular events in male patients with hypertension.

Anthracycline-induced cardiotoxicity: targeting high-density lipoproteins to limit the damage?

Doxorubicin (DOX) is an anthracycline antibiotic frequently used against a wide range of cancers, including breast cancer. Although the drug is effective as a treatment against cancer, many patients develop heart failure (HF) months to years following their last treatment with DOX. The challenge in preventing DOX-induced cardiotoxicity is that symptoms present after damage has already occurred in the myocardium. Therefore, early biomarkers to assess DOX-induced cardiotoxicity are urgently needed. A better understanding of the mechanisms involved in the toxicity is important as this may facilitate the development of novel early biomarkers or therapeutic approaches. In this review, we discuss the role of high-density lipoprotein (HDL) particles and its components as possible key players in the early development of DOX-induced cardiotoxicity. HDL particles exist in different subclasses which vary in composition and biological functionality. Multiple cardiovascular risk factors are associated with a change in HDL subclasses, resulting in modifications of their composition and physiological functions. There is growing evidence in the literature suggesting that cancer affects HDL subclasses and that healthy HDL particles enriched with sphingosine-1-phosphate (S1P) and apolipoprotein A1 (ApoA1) protect against DOX-induced cardiotoxicity. Here, we therefore discuss associations and relationships between HDL, DOX and cancer and discuss whether assessing HDL subclass/composition/function may be considered as a possible early biomarker to detect DOX-induced cardiotoxicity.

Association between Lipoprotein Subfractions, Hemostatic Potentials, and Coronary Atherosclerosis

Background. Dyslipidemias are associated with atherosclerotic plaque formation and a prothrombotic state, thus increasing the risk of both atherosclerotic vascular disease and atherothrombotic adverse events. We sought to explore the association between lipoprotein subfractions, overall hemostasis, and coronary calcifications in individuals at intermediate cardiovascular risk. Methods. Consecutive statin-naive individuals at intermediate cardiovascular risk referred for coronary artery calcium score (CACS) scanning were included. CACS was assessed using a 128-slice dual-source CT scanner. Traditional lipid profile, high-density lipoprotein (HDL) subfractions 2 and 3, and small dense low-density lipoproteins (sdLDL) were measured with commercially available assays. Overall hemostatic (OHP) and coagulation potentials (OCP) were measured spectrophotometrically, using fibrin aggregation curves after exposure to thrombin and recombinant tissue-type plasminogen activator, respectively. Overall fibrinolytic potential (OFP) was calculated as a difference between the two areas under curves. Results. We included 160 patients (median age 63 (interquartile range (IQR), 56-71 years, 52% women, and median CACS 8, IQR 0-173 Agatston units). HDL3 levels—but not sdLDL or hemostatic potentials—were significantly associated with CACS zero, even after adjusting for age, sex, arterial hypertension, dyslipidemia, diabetes, and smoking history (OR 0.980 (0.962-0.999), $p=0.034$ ). HDL3 was also significantly associated with OCP ( $r=-0.232$ , $p$ adjusted for age and sex 0.037). Conclusions. In patients at intermediate cardiovascular risk, HDL3 is associated with both subclinical atherosclerosis and overall coagulation. Our findings are in line with studies reporting on an inverse relationship between HDL3 and atherosclerosis and provide one possible mechanistic explanation for the association between novel lipid biomarkers and coagulation derangements.