Impaired HDL function in obese adolescents: impact of lifestyle intervention and bariatric surgery

Anti-inflammatory function of apolipoprotein B-depleted plasma is impaired in non-alcoholic fatty liver disease

Background

Non-alcoholic fatty liver disease (NAFLD) is associated with an increased risk of cardiovascular events. HDL exerts various protective functions on the cardiovascular system including anti-inflammatory activity by suppressing adhesion molecules expression in inflammation-induced endothelial cells. This study was designed to search if the anti-inflammatory capacity of apolipoprotein B-depleted plasma (apoB-depleted plasma) is altered in NAFLD patients.

Methods

A total of 83 subjects including 42 NAFLD and 41 control subjects were included in this cross-sectional study. Anti-inflammatory function of HDL was determined as the ability of apoB-depleted plasma to inhibit tumor necrosis factor-α (TNF-α)-induced expression of adhesion molecules in human umbilical vein endothelial cells (HUVECs).

Results

Incubation of inflammation-stimulated HUVECs with the NAFLD patients’ apo-B depleted plasma led to higher levels of expression of adhesion molecules compared to the control subjects’ plasma samples, reflecting an impaired anti-inflammatory capacity of apoB-depleted plasma in the NAFLD patients. Impaired anti-inflammatory capacity of apoB-depleted plasma was correlated with fatty liver and obesity indices. After adjustment with obesity indices, the association of anti-inflammatory capacity of apoB-depleted plasma with NAFLD remained significant.

Conclusion

Impaired anti-inflammatory activity of apoB-depleted plasma was independently associated with NAFLD.

Environmental Factors Modifying HDL Functionality

BACKGROUND

Currently, it has been recognized that High-Density Lipoproteins (HDL) functionality plays a much more essential role in protection from atherosclerosis than circulating HDL-cholesterol (HDL-C) levels per se. Cholesterol efflux from macrophages to HDL, cholesterol efflux capacity (CEC) has been shown to be a key metric of HDL functionality. Thus, quantitative assessment of CEC may be an important tool for the evaluation of HDL functionality, as improvement of HDL function may lead to a reduction of the risk for Cardiovascular disease (CVD).

INTRODUCTION

Although the cardioprotective action of HDLs is exerted mainly through their involvement in the reverse cholesterol transport (RCT) pathway, HDLs also have important anti-inflammatory, antioxidant, antiaggregatory and anticoagulant properties that contribute to their favorable cardiovascular effects. Certain genetic, pathophysiologic, disease states and environmental conditions may influence the cardioprotective effects of HDL either by inducing modifications in lipidome and/or protein composition or in the enzymes responsible for HDL metabolism. On the other hand, certain healthy habits or pharmacologic interventions may actually favorably affect HDL functionality.

METHOD

The present review discusses the effects of environmental factors, including obesity, smoking, alcohol consumption, dietary habits, various pharmacologic interventions, as well as aerobic exercise, on HDL functionality.

RESULT

Experimental and clinical studies or pharmacological interventions support the impact of these environmental factors in the modification of HDL functionality, although the mechanisms that are mediated are poorly understood.

CONCLUSION

Further research should be conducted to unreal the underlying mechanisms of these environmental factors and to identify new pharmacologic interventions, capable of enhancing CEC, improving HDL functionality and potentially improving cardiovascular risk.

Pro-inflammatory HDL in women with obesity and nonalcoholic steatohepatitis

BACKGROUND

Individuals with non-alcoholic fatty liver disease (NAFLD), which includes non-alcoholic steatohepatitis (NASH), are at increased risk for cardiovascular events, independent of traditional risk factors. Limited data on pro-inflammatory high density lipoprotein (HDL) in NASH exists in the literature. We hypothesized that HDL from individuals with NASH would be more pro-inflammatory than HDL from individuals without NASH.

METHODS

Study participants were individuals with obesity who had undergone bariatric surgery with wedge liver biopsy. Using HDL isolated from serum obtained from study participants at the time of surgery, HDL-elicited macrophage cytokine expression (TNF-α, IL-1β, and IL-6) from THP-1 macrophages, HDL-associated receptor expression (ABCA1 and ABCG1) from apolipoprotein E deficient (apo E^-/-) mouse peritoneal macrophages, and isolevuglandin (isoLG) modified HDL were measured.

RESULTS

11 women with NASH and 15 women without NASH were included in the study. Both TNF-α (P = 0.032) and IL-1β (P = 0.029) were significantly more expressed by THP-1 macrophages exposed to HDL from women with NASH compared to women without NASH. ABCA1 and ABCG1 expression by apo E^-/- mouse peritoneal macrophages was not significantly different when exposed to HDL from either women with NASH or women without NASH. IsoLG-modified HDL isolated from the serum of women with NASH trended higher than women without NASH.

CONCLUSION

Our study suggests a more pro-inflammatory HDL in women with obesity and NASH compared to women with obesity and without NASH.

LDL and HDL Oxidative Modification and Atherosclerosis

Low-density lipoprotein (LDL) and high-density lipoprotein (HDL) are two kinds of common lipoproteins in plasma. The level of LDL cholesterol in plasma is positively correlated with atherosclerosis (AS), which is related to the complex macromolecular components, especially the easy oxygenation of protein and lipid components. However, the plasma HDL cholesterol level is negatively correlated with AS, but the results of recent studies show that the oxidative modified HDL in pathological state will not reduce and may aggravate the occurrence and development of AS. Therefore, the oxidative modification of lipoproteins is closely related to vascular homeostasis, which has become a hot research area for a long time.

Interaction between adipocytes and high-density lipoprotein:new insights into the mechanism of obesity-induced dyslipidemia and atherosclerosis

Obesity is the most common nutritional disorder worldwide and is associated with dyslipidemia and atherosclerotic cardiovascular disease. The hallmark of dyslipidemia in obesity is low high density lipoprotein (HDL) cholesterol (HDL-C) levels. Moreover, the quality of HDL is also changed in the obese setting. However, there are still some disputes on the explanations for this phenomenon. There is increasing evidence that adipose tissue, as an energy storage tissue, participates in several metabolism activities, such as hormone secretion and cholesterol efflux. It can influence overall reverse cholesterol transport and plasma HDL-C level. In obesity individuals, the changes in morphology and function of adipose tissue affect plasma HDL-C levels and HDL function, thus, adipose tissue should be the main target for the treatment of HDL metabolism in obesity. In this review, we will summarize the cross-talk between adipocytes and HDL related to cardiovascular disease and focus on the new insights of the potential mechanism underlying obesity and HDL dysfunction.

Altered proteome of high-density lipoproteins from paediatric acute lymphoblastic leukemia survivors

Acute lymphoblastic leukemia (ALL) is the most frequent malignancy in children. With the use of more modern, efficient treatments, 5-year survival has reached more than 90% in this population. However, this achievement comes with many secondary and long-term effects since more than 65% of the survivors experience at least one severe complication, including the metabolic syndrome and cardiovascular diseases. The main objective of the present work was to characterize the composition of HDL particles isolated from pediatric ALL survivors. HDLs from 8 metabolically healthy ALL survivors, 8 metabolically unhealthy ALL survivors and 8 age- and gender-matched controls were analyzed. The HDL fraction from the survivors contained less cholesterol than the controls. In addition, proteomic analyses revealed an enrichment of pro-thrombotic (e.g., fibrinogen) and pro-inflammatory (e.g., amyloid A) proteins in the HDLs deriving from metabolically unhealthy survivors. These results indicate an alteration in the composition of lipid and protein content of HDL from childhood ALL survivors with metabolic disorders. Although more work is needed to validate the functionality of these HDLs, the data seem relevant for survivor health given the detection of potential biomarkers related to HDL metabolism and functionality in cancer.

Weight loss after bariatric surgery in obese adolescents: a systematic review and meta-analysis

Of adolescents in the United States, 20% have obesity and current treatment options prioritize intensive lifestyle interventions that are largely ineffective. Bariatric surgery is increasingly being offered to obese adolescent patients; however, large-scale effectiveness data is lacking. We used MEDLINE, Embase, and Cochrane databases, and a manual search of references to conduct a systematic review and meta-analysis on overall weight loss after gastric band, gastric sleeve, and gastric bypass in obese adolescent patients (age ≤19) and young adults (age ≤21) in separate analyses. We provided estimates of absolute change in body mass index (BMI, kg/m²) and percent excess weight loss across 4 postoperative time points (6, 12, 24, and 36 mo) for each surgical subgroup. Study quality was assessed using a 10 category scoring system. Data were extracted from 24 studies with 4 having multiple surgical subgroups (1 with 3, and 3 with 2 subgroups), totaling 29 surgical subgroup populations (gastric band: 16, gastric sleeve: 5, gastric bypass: 8), and 1928 patients (gastric band: 1010, gastric sleeve: 139, gastric bypass: 779). Mean preoperative BMI (kg/m²) was 45.5 (95% confidence interval [CI]: 44.7, 46.3) in gastric band, 48.8 (95%CI: 44.9, 52.8) in gastric sleeve, and 53.3 (95%CI: 50.2, 56.4) in gastric bypass patients. The short-term weight loss, measured as mean (95%CI) absolute change in BMI (kg/m²) at 6 months, was -5.4 (-3.0, -7.8) after gastric band, -11.5 (-8.8, -14.2) after gastric sleeve, and -18.8 (-10.9, -26.6) after gastric bypass. Weight loss at 36 months, measured as mean (95%CI) absolute change in BMI (kg/m²) was -10.3 (-7.0, -13.7) after gastric band, -13.0 (-11.0, -15.0) after gastric sleeve, and -15.0 (-13.5, -16.5) after gastric bypass. Bariatric surgery in obese adolescent patients is effective in achieving short-term and sustained weight loss at 36 months; however, long-term data remains necessary to better understand its long-term efficacy.

Predictors of Impaired HDL Function in HIV-1 Infected Compared to Uninfected Individuals

OBJECTIVE

High-density lipoprotein (HDL) function rather than absolute level may be a more accurate indicator for cardiovascular disease (CVD). Novel methods can measure HDL function using patient samples. The objective of this study is to identify factors that may contribute to HDL dysfunction in chronic treated HIV-1 infection.

DESIGN

Retrospective study of HDL function measured in 2 ways in HIV-1-infected men with low overall CVD risk and healthy men with no known CVD risk matched by race to the HIV-1-infected participants.

METHODS

We examined patient-level factors associated with 2 different measures of HDL dysfunction: reduced antioxidant function (oxidized HDL, HDLox) and reduced HDL-apoA-I exchange (HAE), a measure of HDL remodeling, in the HIV infected and control men. Multivariable-adjusted linear regression analyses were used adjusting for false discovery rate, age, race, body mass index (BMI), CD4 count, viremia, CVD risk, smoking, lipids, apoA-I, and albumin.

RESULTS

In multivariate analysis among HIV-1-infected men (n = 166) (median age 45 years, CD4 T-cell count 505 cells/mm, 30.1% were viremic), higher BMI, lower apoA-I, and lower albumin were among the most notable correlates of higher HDLox and lower HAE (P < 0.05). In HIV-1 uninfected participants, lower albumin and higher BMI were associated with lower HAE and higher HDLox, respectively (P ≤ 0.05). HDLox was inversely related to HAE in HIV-1-infected individuals (P < 0.001).

CONCLUSIONS

Increased HDLox correlates with reduced HAE in chronic HIV-1 infection. Higher BMI, lower apoA-I, and albumin were identified as factors associated with HDL dysfunction in chronic HIV-1 infection using 2 independent methods.

Improvement of High-Density Lipoprotein Function in Patients With Early Rheumatoid Arthritis Treated With Methotrexate Monotherapy or Combination Therapies in a Randomized Controlled Trial

OBJECTIVE

Abnormal function of high-density lipoprotein (HDL) has been implicated as a potential mechanism for the increased incidence of cardiovascular (CV) disease in patients with rheumatoid arthritis (RA). This study was undertaken to evaluate changes in HDL function and HDL-associated proteins over 2 years of follow-up in patients with early RA receiving either methotrexate (MTX) monotherapy, MTX + etanercept (ETN) combination therapy, or MTX + sulfasalazine (SSZ) + hydroxychloroquine (HCQ) triple therapy in the Treatment of Early Aggressive Rheumatoid Arthritis (TEAR) trial.

METHODS

The antioxidant capacity of HDL, paraoxonase 1 (PON-1) activity, and levels of HDL-associated haptoglobin (Hp), HDL-associated apolipoprotein A-I (Apo A-I), and myeloperoxidase (MPO) were measured in 550 TEAR participants at 4 time points (time 0 [pretreatment] and at 24, 48, and 102 weeks of treatment). Repeated-measures analysis using mixed-effects linear models with an autoregressive covariate structure was performed to model the within-subject covariance over time.

RESULTS

Mixed-effects models, which were controlled for traditional CV risk factors, treatment regimen, prednisone use, and statin use, demonstrated significant associations between RA disease activity, measured using the Disease Activity Score in 28 joints, erythrocyte sedimentation rate, or C-reactive protein level, and the profile of HDL function over time. Specifically, decreases in RA disease activity over time were associated with increases in PON-1 activity and levels of HDL-associated Apo A-I, and decreases in the HDL inflammatory index and levels of MPO and HDL-associated Hp.

CONCLUSION

Reduced disease activity in patients with early RA treated with MTX monotherapy, MTX + ETN combination therapy, or MTX + SSZ + HCQ triple therapy in the TEAR trial was associated with improvements in the HDL function profile. Additional studies are warranted to evaluate abnormal HDL function as a potential mechanism and therapeutic target for CV risk in patients with RA.

Impact of Lifestyle Intervention on HDL-Induced eNOS Activation and Cholesterol Efflux Capacity in Obese Adolescent

Background. Endothelial dysfunction occurs in obese children and adolescent and is regarded as a key step in the development of atherosclerosis. Important components for the development of endothelial dysfunction are reduced activity of endothelial nitric oxide synthase (eNOS) and an increase in cholesterol deposition in the vessel wall, due to reduced reverse cholesterol transport (RCT) activity. High density lipoprotein (HDL) exhibits antiatherosclerotic properties including modulation of eNOS activity and cholesterol efflux capacity. Lifestyle intervention programs can modify endothelial dysfunction in obese adolescents, but their impact on HDL-mediated eNOS activation and RCT is unknown so far. Methods. Obese adolescents (15 ± 1 years, BMI > 35 kg/m²) where randomized either to an intervention group (IG, n = 8; restricted diet and exercise) or to a usual care group (UC, n = 8). At the beginning and after 10 months of treatment HDL-mediated eNOS phosphorylation and cholesterol efflux capacity were evaluated. Results. Ten months of treatment resulted in a substantial weight loss (−31%), an improvement of endothelial function, and an increase in HDL-mediated eNOS-Ser¹¹⁷⁷ phosphorylation and RCT. A correlation between change in eNOS-Ser¹¹⁷⁷ phosphorylation or RCT and change in endothelial function was noted. Conclusion. A structured lifestyle intervention program improves antiatherosclerotic HDL functions, thereby positively influencing endothelial function.

Weight loss surgery in adolescents corrects high-density lipoprotein subspecies and their function

Background/Objective

Youth with obesity have an altered HDL subspecies profile characterized by depletion of large apoE rich HDL particles and an enrichment of small HDL particles. The goal of this study was to test the hypothesis that this atherogenic HDL profile would be reversed and that HDL function would improve with metabolic surgery.

Methods

Serum samples from adolescent males with severe obesity mean ± SD age of 17.4 ± 1.6 years were studied at baseline and 1 year following vertical sleeve gastrectomy (VSG). HDL subspecies and HDL function were evaluated pre and post VSG using paired t-tests. A lean group of adolescents was included as a reference group.

Results

After VSG, BMI decreased by 32% and insulin resistance as estimated by HOMA-IR decreased by 75% (both p<0.01). Large apoE rich HDL subspecies increased following VSG (p<0.01) and approached that of lean adolescents despite participants with considerable residual obesity. Additionally, HDL function improved compared to baseline (cholesterol efflux capacity increased by 12%, HDL lipid peroxidation potential decreased by 30%, and HDL anti-oxidative capacity improved by 25%, all p<0.01).

Conclusions

Metabolic surgery results in a significant improvement in the quantity of large HDL subspecies and HDL function. Our data suggest metabolic surgery may improve cardiovascular risk in adolescents and young adults.

Childhood obesity-related endothelial dysfunction: an update on pathophysiological mechanisms and diagnostic advancements

Childhood obesity jeopardizes a healthy future for our society's children as it is associated with increased cardiovascular morbidity and mortality later on in life. Endothelial dysfunction, the first step in the development of atherosclerosis, is already present in obese children and may well represent a targetable risk factor. Technological advancements in recent years have facilitated noninvasive measurements of endothelial homeostasis in children. Thereby this topic ultimately starts to get the attention it deserves. In this paper, we aim to summarize the latest insights on endothelial dysfunction in childhood obesity. We discuss methodological advancements in peripheral endothelial function measurement and newly identified diagnostic markers of vascular homeostasis. Finally, future challenges and perspectives are set forth on how to efficiently tackle the catastrophic rise in cardiovascular morbidity and mortality that will be inflicted on obese children if they are not treated optimally.

Rapid and body weight-independent improvement of endothelial and high-density lipoprotein function after Roux-en-Y gastric bypass: role of glucagon-like peptide-1

BACKGROUND

Roux-en-Y gastric bypass (RYGB) reduces body weight and cardiovascular mortality in morbidly obese patients. Glucagon-like peptide-1 (GLP-1) seems to mediate the metabolic benefits of RYGB partly in a weight loss-independent manner. The present study investigated in rats and patients whether obesity-induced endothelial and high-density lipoprotein (HDL) dysfunction is rapidly improved after RYGB via a GLP-1-dependent mechanism.

METHODS AND RESULTS

Eight days after RYGB in diet-induced obese rats, higher plasma levels of bile acids and GLP-1 were associated with improved endothelium-dependent relaxation compared with sham-operated controls fed ad libitum and sham-operated rats that were weight matched to those undergoing RYGB. Compared with the sham-operated rats, RYGB improved nitric oxide (NO) bioavailability resulting from higher endothelial Akt/NO synthase activation, reduced c-Jun amino terminal kinase phosphorylation, and decreased oxidative stress. The protective effects of RYGB were prevented by the GLP-1 receptor antagonist exendin9-39 (10 μg·kg(-1)·h(-1)). Furthermore, in patients and rats, RYGB rapidly reversed HDL dysfunction and restored the endothelium-protective properties of the lipoprotein, including endothelial NO synthase activation, NO production, and anti-inflammatory, antiapoptotic, and antioxidant effects. Finally, RYGB restored HDL-mediated cholesterol efflux capacity. To demonstrate the role of increased GLP-1 signaling, sham-operated control rats were treated for 8 days with the GLP-1 analog liraglutide (0.2 mg/kg twice daily), which restored NO bioavailability and improved endothelium-dependent relaxations and HDL endothelium-protective properties, mimicking the effects of RYGB.

CONCLUSIONS

RYGB rapidly reverses obesity-induced endothelial dysfunction and restores the endothelium-protective properties of HDL via a GLP-1-mediated mechanism. The present translational findings in rats and patients unmask novel, weight-independent mechanisms of cardiovascular protection in morbid obesity.

Hepatic ABCA1 expression improves β-cell function and glucose tolerance

Low HDL is a risk factor for the development of type 2 diabetes. Hepatic ABCA1 is the rate-limiting protein in HDL biogenesis, and mice lacking hepatic ABCA1 (ABCA1(-l/-l)) have very low plasma HDL concentrations. To investigate the role of hepatic ABCA1 in glucose tolerance and β-cell function, we used ABCA1(-l/-l) mice, which showed impaired glucose tolerance without changes in insulin sensitivity. Insulin secretion was reduced following glucose gavage. Ex vivo, glucose stimulated insulin secretion from β-cells from wild-type (WT) and ABCA1(-l/-l) mice was similar. Insulin secretion was, however, reduced upon addition of ABCA1(-l/-l) serum to the medium compared with WT serum, whereas islets lacking β-cell ABCA1 were not affected differently by ABCA1(-l/-l) or WT serum. After high-fat feeding, WT and ABCA1(-l/-l) mice showed no difference in glucose tolerance or insulin secretion, and serum from ABCA1(-l/-l) and WT mice fed a high-fat diet did not affect insulin secretion differently. We conclude that hepatic ABCA1 improves glucose tolerance by improving β-cell function through both HDL production and interaction with β-cell ABCA1. The beneficial effect of hepatic ABCA1 is decreased under metabolic stress. Increasing hepatic ABCA1 may represent a novel therapeutic strategy for improving glucose homeostasis in diabetes.

Alteration of HDL functionality and PON1 activities in acute coronary syndrome patients

OBJECTIVE

The functionality of HDL has been suggested as an important factor in the prevention of cardiovascular and coronary artery diseases. The objective of the present study was to investigate the functionality of HDL and the factors that may affect the anti-atherogenic properties of HDL in ACS patients.

METHODS AND RESULTS

One hundred healthy subjects and 205 ACS patients were recruited. HDL functionality was evaluated by measuring their capacity to mediate cholesterol efflux from J774 macrophages. Oxidative stress status was determined by measuring plasma malondialdehyde (MDA), protein carbonyl, and vitamin E levels by HPLC. The PON1 Q192R polymorphism status and PON1 paraoxonase and arylesterase activities of the healthy subjects and ACS patients were also determined. The HDL of ACS patients displayed a limited capacity to mediate cholesterol efflux, especially via the ABCA1-pathway. MDA (7.06±0.29 μM) and protein carbonyl (9.29±0.26 μM) levels were significantly higher in ACS patients than in healthy subjects (2.29±0.21 μM and 3.07±0.17 μM, respectively, p<0.0001), while α- and γ-tocopherol (vitamin E) levels in ACS patients were 8-fold (p<0.001) and 2-fold (p<0.05) lower than in healthy subjects. Paraoxonase, arylesterase and HDL-corrected PON1 activities (PON1 activity/HDL ratio) were significantly lower in ACS patients. Logistic regression analyses showed that high PON1 paraoxonase and arylesterase activities had a significant protective effect (OR=0.413, CI 0.289-0.590, p<0.001; OR=0.232 CI 0.107-0.499, p<0.001, respectively) even when adjusted for HDL level, age, BMI, and PON1 polymorphism.

CONCLUSION

The results of the present study showed that the functionality of HDL is impaired in ACS patients and that the impairment may be due to oxidative stress and an alteration of PON1 activities.

Effects of bariatric surgery on HDL structure and functionality: results from a prospective trial

BACKGROUND

In addition to high-density lipoprotein cholesterol (HDL-C) levels, HDL quality appears also very important for atheroprotection. Obese patients with metabolic syndrome have significantly reduced HDL-C levels and are usually at increased risk for coronary heart disease. Despite that weight loss benefits these patients, its effects on HDL quality and functionality is currently poorly studied.

OBJECTIVES

We investigated how rapid weight loss affects HDL structure and its antioxidant potential in patients undergoing a malabsorptive bariatric procedure.

METHODS

Fasting plasma samples were collected the day before and 6 months after the bariatric procedure from 20 morbidly obese patients with body mass index >50, then HDL was isolated and analyzed by biochemical techniques.

RESULTS

We report a dramatic alteration in the apolipoprotein ratio of HDL that was accompanied by the presence of more mature HDL subspecies and a concomitant increase in the antioxidant potential of HDL. Interestingly, our obese cohort could be distinguished into 2 subgroups. In 35% of patients (n = 7), HDL before surgery had barely detectable apolipoprotein (apo) A-I and apoCIII, and the vast majority of their HDL cholesterol was packed in apoE-containing HDL particles. In the remaining 65% of patients (n = 13), HDL before surgery contained high levels of apoA-I and apoCIII, in addition to apoE. In both subgroups, surgical weight loss resulted in a switch from apoE to apoA-I-containing HDL.

CONCLUSIONS

Rapid weight loss exerts a significant improvement in HDL structure and functionality that may contribute to the documented beneficial effect of malabsorptive bariatric procedures on cardiovascular health.

15-lipoxygenase-mediated modification of HDL3 impairs eNOS activation in human endothelial cells

Caveolae are cholesterol and glycosphingolipids-enriched microdomains of plasma membranes. Caveolin-1 represents the major structural protein of caveolae, that also contain receptors and molecules involved in signal transduction pathways. Caveolae are particularly abundant in endothelial cells, where they play important physiological and pathological roles in regulating endothelial cell functions. Several molecules with relevant functions in endothelial cells are localized in caveolae, including endothelial nitric oxide synthase (eNOS), which regulates the production of nitric oxide, and scavenger receptor class B type I (SR-BI), which plays a key role in the induction of eNOS activity mediated by high density lipoproteins (HDL). HDL have several atheroprotective functions, including a positive effect on endothelial cells, as it is a potent agonist of eNOS through the interaction with SR-BI. However, the oxidative modification of HDL may impair their protective role. In the present study we evaluated the effect of 15-lipoxygenase-mediated modification of HDL3 on the expression and/or activity of some proteins localized in endothelial caveolae and involved in the nitric oxide generation pathway. We found that after modification, HDL3 failed to activate eNOS and to induce NO production, due to both a reduced ability to interact with its own receptor SR-BI and to a reduced expression of SR-BI in cells exposed to modified HDL. These findings suggest that modification of HDL may reduce its endothelial-protective role also by interfering with vasodilatory function of HDL.

Effect of bariatric surgery on microvascular dysfunction associated to metabolic syndrome: a 12-month prospective study

OBJECTIVE

To prospectively evaluate the effect of weight loss after bariatric surgery on microvascular function in morbidly obese patients with and without metabolic syndrome (MetS).

METHODS

A cohort of morbidly obese patients with and without MetS was studied before surgery and after 12 months of surgery. Healthy lean controls were also examined. Microvascular function was assessed by postocclusive reactive hyperemia (PORH) at forearm skin evaluated by laser Doppler flowmetry (LDF). Cutaneous vascular conductance (CVC) was calculated from laser-Doppler skin blood flow and blood pressure. Regression analysis was performed to assess the contribution of different clinical, metabolic and biochemical parameters to microvascular function.

RESULTS

Before surgery, 62 obese patients, 39 with MetS and 23 without MetS, and 30 lean control subjects were analyzed. The absolute area under the hyperemic curve (AUC(H)) CVC of PORH was significantly decreased in obese patients compared with lean control subjects. One year after surgery, AUC(H) CVC significantly increased in patients free of MetS, including patients that had MetS before surgery. In contrast, AUC(H) CVC did not significantly change in patients in whom MetS persisted after surgery. Stepwise multivariate regression analysis showed that only changes in HDL cholesterol (HDL-C) and oxidized LDL (oxLDL) independently predicted improvement of AUC(H) after surgery. These two variables together accounted for 40.9% of the variability of change in AUC(H) CVC after surgery.

CONCLUSIONS

Bariatric surgery could significantly improve microvascular dysfunction in obese patients, but only in patients free of MetS after surgery. Improvement of microvascular dysfunction is strictly associated to postoperative increase in HDL-C levels and decrease in oxLDL levels.

Functionally defective high-density lipoprotein and paraoxonase: a couple for endothelial dysfunction in atherosclerosis

The endothelium is the primary target for biochemical or mechanical injuries caused by the putative risk factors of atherosclerosis. Endothelial dysfunction represents the ultimate link between atherosclerotic risk factors that promote atherosclerosis. HDL-C is thought to exert at least some parts of its antiatherogenic facilities via stimulating endothelial NO production, nearby inhibiting oxidative stress and inflammation. HDL-C is capable of opposing LDL's inductive effects and avoiding the ox-LDL's inhibition of eNOS. Paraoxonase 1 (PON1) is an HDL-associated enzyme esterase which appears to contribute to the antioxidant and antiatherosclerotic capabilities of HDL-C. "Healthy HDL," namely the particle that contains the active Paraoxonase 1, has the power to suppress the formation of oxidized lipids. "Dysfunctional HDL," on the contrary, has reduced Paraoxonase 1 enzyme activity and not only fails in its mission but also potentially leads to greater formation of oxidized lipids/lipoproteins to cause endothelial dysfunction. The association of HDL-C PON1 and endothelial dysfunction depends largely on the molecules with exact damaging effect on NO synthase coupling. Loss of nitric oxide bioavailability has a pivotal role in endothelial dysfunction preceding the appearance of atherosclerosis. Analyses of HDL-C and Paraoxonase1 would be more important in the diagnosis and treatment of atherosclerosis in the very near future.