HDL as Bidirectional Lipid Vectors: Time for New Paradigms

High-Density Lipoproteins from Coronary Artery Disease and Aortic Valve Stenosis Patients Differentially Regulate Gene Expression in a Model of Cardiac Adipocytes

Previous reports have described a statistical association between high-density lipoproteins (HDL) subclasses and the expression of genes coding for pro-calcifying proteins in the epicardial adipose tissue of patients with coronary artery disease (CAD) and aortic valvular stenosis (AVS). These results suggest a causal relationship between HDL and the regulation of gene expression in epicardial adipose tissue. However, there is no experimental evidence that supports this causal relationship. Therefore, we explored the effect of HDL isolated from CAD or AVS patients on the expression of OPN, BMP2, and BMP4, genes coding for proteins related to calcification, osteopontin, and bone morphogenetic proteins -2 and -4, respectively, and LEP, UCP, and PER, coding for leptin, uncoupling protein-1, and perilipin-2, respectively, proteins that confer phenotypic characteristics to adipocytes. The experiments were performed using a novel model of cardiac adipocytes differentiated in vitro from stromal cells of rabbit cardiac adipose tissue. AVS or CAD patients' HDL differentially modulated the expression of BMP4 and LEP, whereas HDL from both kinds of patients upregulated the OPN gene expression. A high concentration of triglycerides associated to small HDL and a higher concentration of phospholipids of large HDL from CAD patients than those from AVS individuals were the most remarkable structural differences. Finally, we demonstrated that cholesterol from reconstituted HDL was internalized to the adipocytes. The regulation of genes related to the secretory activity of cardiac adipocytes mediated by HDL has clinical implications as a potential therapeutic target for the prevention and treatment of CAD and AVS. In summary, the HDL isolated from the CAD and AVS patients differentially regulated gene expression in adipocytes by a mechanism that seems to be dependent on HDL lipid internalization to the cells and structural characteristics of the lipoproteins.

Relationship of SOD-1 Activity in Metabolic Syndrome and/or Frailty in Elderly Individuals

INTRODUCTION

Although aging is a natural phenomenon, in recent years it has accelerated. One key factor implicated in the aging process is oxidative stress. Oxidative stress also plays a role in frailty (frail) and metabolic syndrome (MetS).

METHODS

A total of 66 elderly persons (65 years old and older) with no acute or severe chronic disorders were assessed for waist circumference (WC), arterial blood pressure, glycemia, glycated hemoglobin (HbA1c), plasma lipids, and activity of erythrocyte superoxide dismutase (SOD-1). Patients were classified as NonMetS-Nonfrail (n = 19), NonMetS-frail (n = 20), MetS-Nonfrail (n = 17), or MetS-frail (n = 10).

RESULTS

There were no significant differences in superoxide dismutase activity among investigated elderly groups. However, the data suggest that MetS individuals, both frail and nonfrail, have higher risk factors for cardiovascular disease compared to NonMetS individuals. The correlations analyses of SOD-1 and other metabolic indices suggest that SOD-1 levels may be influenced by age, total cholesterol, HDL cholesterol, and fasting glucose levels in certain groups of seniors.

CONCLUSIONS

Aging is associated with decreased antioxidant enzyme SOD-1 activity with glucose alteration in frailty syndrome as well as with lipids disturbances in metabolic syndrome. These factors provide a nuanced view of how frailty and metabolic syndrome interact with various health parameters, informing both clinical practice and future research directions.

Inflammation and Oxidative Stress Induced by Obesity, Gestational Diabetes, and Preeclampsia in Pregnancy: Role of High-Density Lipoproteins as Vectors for Bioactive Compounds

Inflammation and oxidative stress are essential components in a myriad of pathogenic entities that lead to metabolic and chronic diseases. Moreover, inflammation in its different phases is necessary for the initiation and maintenance of a healthy pregnancy. Therefore, an equilibrium between a necessary/pathologic level of inflammation and oxidative stress during pregnancy is needed to avoid disease development. High-density lipoproteins (HDL) are important for a healthy pregnancy and a good neonatal outcome. Their role in fetal development during challenging situations is vital for maintaining the equilibrium. However, in certain conditions, such as obesity, diabetes, and other cardiovascular diseases, it has been observed that HDL loses its protective properties, becoming dysfunctional. Bioactive compounds have been widely studied as mediators of inflammation and oxidative stress in different diseases, but their mechanisms of action are still unknown. Nonetheless, these agents, which are obtained from functional foods, increase the concentration of HDL, TRC, and antioxidant activity. Therefore, this review first summarizes several mechanisms of HDL participation in the equilibrium between inflammation and oxidative stress. Second, it gives an insight into how HDL may act as a vector for bioactive compounds. Third, it describes the relationships between the inflammation process in pregnancy and HDL activity. Consequently, different databases were used, including MEDLINE, PubMed, and Scopus, where scientific articles published in the English language up to 2023 were identified.

The role of atherogenic lipoproteins in diabetes: Molecular aspects and clinical significance

Dyslipidaemia plays a prominent role in the genesis of atherosclerotic plaque and the increased cardiovascular risk in diabetes. Macrophages readily take up atherogenic lipoproteins, transforming into foam cells and amplifying vascular damage in the presence of endothelial dysfunction. We discuss the importance of distinct lipoprotein subclasses in atherogenic diabetic dyslipidaemia as well as the effects of novel anti-diabetic agents on lipoprotein fractions and ultimately on cardiovascular risk prevention. In patients with diabetes, lipid abnormalities should be aggressively identified and treated in conjunction with therapeutical agents used to prevent cardiovascular disease. The use of drugs that improve diabetic dyslipidaemia plays a prominent role in conferring cardiovascular benefit in individuals with diabetes.

Eicosapentaenoic and Docosahexaenoic Acid Supplementation Increases HDL Content in n-3 Fatty Acids and Improves Endothelial Function in Hypertriglyceridemic Patients

High-density lipoproteins (HDLs) are known to enhance vascular function through different mechanisms, including the delivery of functional lipids to endothelial cells. Therefore, we hypothesized that omega-3 (n-3) eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content of HDLs would improve the beneficial vascular effects of these lipoproteins. To explore this hypothesis, we performed a placebo-controlled crossover clinical trial in 18 hypertriglyceridemic patients without clinical symptoms of coronary heart disease who received highly purified EPA 460 mg and DHA 380 mg, twice a day for 5 weeks or placebo. After 5 weeks of treatment, patients followed a 4-week washout period before crossover. HDLs were isolated using sequential ultracentrifugation for characterization and determination of fatty acid content. Our results showed that n-3 supplementation induced a significant decrease in body mass index, waist circumference as well as triglycerides and HDL-triglyceride plasma concentrations, whilst HDL-cholesterol and HDL-phospholipids significantly increased. On the other hand, HDL, EPA, and DHA content increased by 131% and 62%, respectively, whereas 3 omega-6 fatty acids significantly decreased in HDL structures. In addition, the EPA-to-arachidonic acid (AA) ratio increased more than twice within HDLs suggesting an improvement in their anti-inflammatory properties. All HDL-fatty acid modifications did not affect the size distribution or the stability of these lipoproteins and were concomitant with a significant increase in endothelial function assessed using a flow-mediated dilatation test (FMD) after n-3 supplementation. However, endothelial function was not improved in vitro using a model of rat aortic rings co-incubated with HDLs before or after treatment with n-3. These results suggest a beneficial effect of n-3 on endothelial function through a mechanism independent of HDL composition. In conclusion, we demonstrated that EPA and DHA supplementation for 5 weeks improved vascular function in hypertriglyceridemic patients, and induced enrichment of HDLs with EPA and DHA to the detriment of some n-6 fatty acids. The significant increase in the EPA-to-AA ratio in HDLs is indicative of a more anti-inflammatory profile of these lipoproteins.

HDL metabolism and functions impacting on cell cholesterol homeostasis are specifically altered in patients with abdominal aortic aneurysm

Background

The etiopathogenesis of abdominal aortic aneurysm (AAA) is still unclarified, but vascular inflammation and matrix metalloproteases activation have a recognized role in AAA development and progression. Circulating lipoproteins are involved in tissue inflammation and repair, particularly through the regulation of intracellular cholesterol, whose excess is associated to cell damage and proinflammatory activation. We analyzed lipoprotein metabolism and function in AAA and in control vasculopathic patients, to highlight possible non-atherosclerosis-related, specific abnormalities.

Methods

We measured fluorometrically serum esterified/total cholesterol ratio, as an index of lecithin-cholesterol acyltransferase (LCAT) activity, and cholesteryl ester transfer protein (CETP) activity in patients referred to vascular surgery either for AAA (n=30) or stenotic aortic/peripheral atherosclerosis (n=21) having similar burden of cardiovascular risk factors and disease. We measured high-density lipoprotein (HDL)-cholesterol efflux capacity (CEC), through the ATP-binding cassette G1 (ABCG1) and A1 (ABCA1) pathways and serum cell cholesterol loading capacity (CLC), by radioisotopic and fluorimetric methods, respectively.

Results

We found higher LCAT (+23%; p < 0.0001) and CETP (+49%; p < 0.0001) activity in AAA sera. HDL ABCG1-CEC was lower (−16%; p < 0.001) and ABCA1-CEC was higher (+31.7%; p < 0.0001) in AAA. Stratification suggests that smoking may partly contribute to these modifications. CEC and CETP activity correlated with CLC only in AAA.

Conclusions

We demonstrated that compared to patients with stenotic atherosclerosis, patients with AAA had altered HDL metabolism and functions involved in their anti-inflammatory and tissue repair activity, particularly through the ABCG1-related intracellular signaling. Clarifying the relevance of this mechanism for AAA evolution might help in developing new diagnostic parameters and therapeutic targets for the early management of this condition.