Remarkable quantitative and qualitative differences in HDL after niacin or fenofibrate therapy in type 2 diabetic patients

Effects of niacin and omega-3 fatty acids on HDL-apolipoprotein A-I exchange in subjects with metabolic syndrome

HDL-apolipoprotein A-I exchange (HAE) measures a functional property associated with HDL's ability to mediate reverse cholesterol transport. HAE has been used to examine HDL function in case-control studies but not in studies of therapeutics that alter HDL particle composition. This study investigates whether niacin and omega-3 fatty acids induce measurable changes in HAE using a cohort of fifty-six subjects with metabolic syndrome (MetS) who were previously recruited to a double-blind trial where they were randomized to 16 weeks of treatment with dual placebo, extended-release niacin (ERN, 2g/day), prescription omega-3 ethyl esters (P-OM3, 4g/day), or the combination. HAE was assessed at the beginning and end of the study. Compared to placebo, ERN and P-OM3 alone significantly increased HAE by 15.1% [8.2, 22.0] (P<0.0001) and 11.1% [4.5, 17.7] (P<0.0005), respectively, while in combination they increased HAE by 10.0% [2.5, 15.8] (P = 0.005). When HAE was evaluated per unit mass of apoA-I ERN increased apoA-I specific exchange activity by 20% (2, 41 CI, P = 0.02) and P-OM3 by 28% (9.6, 48 CI, P<0.0006). However the combination had no statistically significant effect, 10% (-9, 31 CI, P = 0.39). With regard to P-OM3 therapy in particular, the HAE assay detected an increase in this property in the absence of a concomitant rise in HDL-C and apoA-I levels, suggesting that the assay can detect functional changes in HDL that occur in the absence of traditional biomarkers.

The Impact of the Mediterranean Diet and Lifestyle Intervention on Lipoprotein Subclass Profiles among Metabolic Syndrome Patients: Findings of a Randomized Controlled Trial

Metabolic syndrome (MetS) is associated with alterations of lipoprotein structure and function that can be characterized with advanced lipoprotein testing (ADLT). The effect of the Mediterranean diet (MedDiet) and weight loss on the lipoprotein subclass profile has been scarcely studied. Within the PREDIMED-Plus randomized controlled trial, a sub-study conducted at Bellvitge Hospital recruiting center evaluated the effects of a weight loss program based on an energy-reduced MedDiet (er-MedDiet) and physical activity (PA) promotion (intervention group) compared with energy-unrestricted MedDiet recommendations (control group) on ADLT-assessed lipoprotein subclasses. 202 patients with MetS (n = 107, intervention; n = 95, control) were included. Lipid profiles were determined, and ADLT was performed at baseline, 6, and 12 months. Linear mixed models were used to assess the effects of intervention on lipoprotein profiles. Compared to the control diet, at 12 months, the er-MedDiet+PA resulted in a significant additional 4.2 kg of body weight loss, a decrease in body mass index by 1.4 kg/m2, reduction in waist circumference by 2.2 cm, decreased triglycerides, LDL-cholesterol and non-HDL-cholesterol, and increased HDL-cholesterol. In er-MedDiet+PA participants, ADLT revealed a decrease in small dense-LDL-cholesterol (sd-LDL-C), intermediate-density lipoproteins, VLDL-triglyceride, and HDL-Triglyceride, and an increase in large LDL and large VLDL particles. In conclusion, compared to an ad libitum MedDiet (control group), er-MedDiet+PA decreased plasma triglycerides and the triglyceride content in HDL and VLDL particles, decreased sd-LDL-C, and increased large LDL particles, indicating beneficial changes against cardiovascular disease.

High-density lipoprotein revisited: biological functions and clinical relevance

Previous interest in high-density lipoproteins (HDLs) focused on their possible protective role in atherosclerotic cardiovascular disease (ASCVD). Evidence from genetic studies and randomized trials, however, questioned that the inverse association of HDL-cholesterol (HDL-C) is causal. This review aims to provide an update on the role of HDL in health and disease, also beyond ASCVD. Through evolution from invertebrates, HDLs are the principal lipoproteins, while apolipoprotein B-containing lipoproteins first developed in vertebrates. HDLs transport cholesterol and other lipids between different cells like a reusable ferry, but serve many other functions including communication with cells and the inactivation of biohazards like bacterial lipopolysaccharides. These functions are exerted by entire HDL particles or distinct proteins or lipids carried by HDL rather than by its cholesterol cargo measured as HDL-C. Neither does HDL-C measurement reflect the efficiency of reverse cholesterol transport. Recent studies indicate that functional measures of HDL, notably cholesterol efflux capacity, numbers of HDL particles, or distinct HDL proteins are better predictors of ASCVD events than HDL-C. Low HDL-C levels are related observationally, but also genetically, to increased risks of infectious diseases, death during sepsis, diabetes mellitus, and chronic kidney disease. Additional, but only observational, data indicate associations of low HDL-C with various autoimmune diseases, and cancers, as well as all-cause mortality. Conversely, extremely high HDL-C levels are associated with an increased risk of age-related macular degeneration (also genetically), infectious disease, and all-cause mortality. HDL encompasses dynamic multimolecular and multifunctional lipoproteins that likely emerged during evolution to serve several physiological roles and prevent or heal pathologies beyond ASCVD. For any clinical exploitation of HDL, the indirect marker HDL-C must be replaced by direct biomarkers reflecting the causal role of HDL in the respective disease.

Therapeutic Potential of Emerging NAD+-Increasing Strategies for Cardiovascular Diseases

Cardiovascular diseases are the leading cause of death worldwide. Aging and/or metabolic stress directly impact the cardiovascular system. Over the last few years, the contributions of altered nicotinamide adenine dinucleotide (NAD+) metabolism to aging and other pathological conditions closely related to cardiovascular diseases have been intensively investigated. NAD+ bioavailability decreases with age and cardiometabolic conditions in several mammalian tissues. Compelling data suggest that declining tissue NAD+ is commonly related to mitochondrial dysfunction and might be considered as a therapeutic target. Thus, NAD+ replenishment by either genetic or natural dietary NAD+-increasing strategies has been recently demonstrated to be effective for improving the pathophysiology of cardiac and vascular health in different experimental models, as well as human health, to a lesser extent. Here, we review and discuss recent experimental evidence illustrating that increasing NAD+ bioavailability, particularly by the use of natural NAD+ precursors, may offer hope for new therapeutic strategies to prevent and treat cardiovascular diseases.

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

High-density lipoproteins (HDL) are a heterogenous group of plasma molecules with a large variety in composition. There is a wide specter in lipid content and the number of different proteins that has been associated with HDL is approaching 100. Given this heterogeneity and the fact that the total amount of HDL is inversely related to the risk of coronary heart disease (CHD), there has been increasing interest in the function of specific HDL subgroups and in what way measuring and quantifying these subgroups could be of clinical importance in determining individual CHD risk. If certain subgroups appear to be more protective than others, it may also in the future be possible to pharmacologically increase beneficial and decrease harmful subgroups in order to reduce CHD risk. In this review we give a short historical perspective, summarize some of the recent clinical findings regarding HDL subclassifications and discuss why such classification may or may not be of clinical relevance.

Dysfunctional High-Density Lipoproteins in Type 2 Diabetes Mellitus: Molecular Mechanisms and Therapeutic Implications

High density lipoproteins (HDLs) are commonly known for their anti-atherogenic properties that include functions such as the promotion of cholesterol efflux and reverse cholesterol transport, as well as antioxidant and anti-inflammatory activities. However, because of some chronic inflammatory diseases, such as type 2 diabetes mellitus (T2DM), significant changes occur in HDLs in terms of both structure and composition. These alterations lead to the loss of HDLs’ physiological functions, to transformation into dysfunctional lipoproteins, and to increased risk of cardiovascular disease (CVD). In this review, we describe the main HDL structural/functional alterations observed in T2DM and the molecular mechanisms involved in these T2DM-derived modifications. Finally, the main available therapeutic interventions targeting HDL in diabetes are discussed.

Efficacy of oral rosuvastatin intervention on HDL and its associated proteins in men with type 2 diabetes mellitus

PURPOSE

High-density lipoprotein (HDL) undergoes structural and functional modification in patients with type 2 diabetes mellitus (T2DM). There are limited data on effect of rosuvastatin on HDL-associated proteins and the antiatherogenic effects of rosuvastatin. The present study intended to study the efficacy of rosuvastatin intervention on HDL-associated proteins and its other antiatherogenic effects in men with T2DM.

METHODS

Men with T2DM on oral antidiabetic treatment, with LDL-C levels > 75 mg/dL and willing for rosuvastatin intervention (20 mg/day orally for a period of 12 weeks), were included. Fasting glucose, lipid profile were measured using standard methods. Oxidized low-density lipoprotein (oxLDL), oxidized HDL (oxHDL), paraoxonase-1 (PON-1), tumour necrosis factor-α (TNF-α) and lecithin:cholesterol acyltransferase (LCAT) in serum were measured by ELISA; serum myeloperoxidase (MPO) by spectrophotometric method and cholesterol efflux by fluorometric assay. Carotid intima-media thickness (cIMT) measurement to assess vascular health status was done using doppler.

RESULTS

Rosuvastatin produced a significant decrease (p < 0.05) in lipids (total cholesterol, triglycerides, LDL-C); oxidative stress (oxLDL, oxHDL, MPO); inflammation (TNF-α); LCAT concentration; cIMT; significant increase in antiatherogenic HDL and cholesterol efflux (p < 0.05) and no change in apoA-I levels from baseline to 12 weeks of follow-up. A decrease in MPO activity was found to be independently associated with an increase in cholesterol efflux.

CONCLUSIONS

Post intervention there is a quantitative and qualitative improvement in HDL, which helps in its reverse cholesterol transport (RCT) and antioxidant functions. Improvement in HDL functions and suppression of inflammation by rosuvastatin lead to regression in cIMT, which is beneficial in decreasing the progression of cardiovascular disease (CVD) in men with diabetes.

Pharmacological Management of Cardiac Disease in Patients with Type 2 Diabetes: Insights into Clinical Practice

BACKGROUND

Type 2 Diabetes Mellitus (T2DM) has emerged as a growing pandemic. Cardiovascular disease (CVD) constitutes another major health problem, with coronary heart disease being the leading cause of cardiovascular death. Patients with T2DM require a multilevel therapeutic approach, both for primary and secondary prevention of CVD.

OBJECTIVE

To present and summarize the most recent, highest level evidence retrieved from literature, relevant to the pharmaceutical management of CVD in T2DM.

METHODS

We conducted a comprehensive search of the literature on MEDLINE from its inception till today, primarily for relevant systematic reviews, meta-analyses and randomized controlled trials.

RESULTS

There is a trend towards more intensified therapeutic interventions in T2DM, concerning glycemic, lipid and blood pressure control. New drugs, such as sodium-glucose co-transporter 2 (SGLT-2) inhibitors, glucagon-like peptide-1 receptor agonists (GLP-1RAs) and proprotein convertase subtilisin/ kexin type 9 (PCSK9) inhibitors might evolve as key players in the management of diabetes and its complications within the next years. Classic drugs, such as those targeting the renin-angiotensinaldosterone system, statins and aspirin remain first-line treatment options, both for primary and secondary prevention of CVD. Lifestyle interventions should always be integrated into a complete therapeutic strategy in diabetic patients. Novel drugs, such as finerenone and LCZ696 have provided significant results in cardiovascular outcome studies; however, their role in T2DM has to be further elucidated.

CONCLUSION

Pharmaceutical approach of CVD in T2DM is multilevel and complex. Drug classes featuring pleiotropic effects may boost our armamentarium in the fight against CVD.

Altered HDL metabolism in metabolic disorders: insights into the therapeutic potential of HDL

Metabolic disorders are associated with an increased risk of cardiovascular disease (CVD), and are commonly characterized by a low plasma level of high-density lipoprotein cholesterol (HDL-C). Although cholesterol lowering medications reduce CVD risk in these patients, they often remain at increased risk of CVD. Therapeutic strategies that raise HDL-C levels and improve HDL function are a potential treatment option for reducing residual CVD risk in these individuals. Over the past decade, understanding of the metabolism and cardioprotective functions of HDLs has improved, with preclinical and clinical studies both indicating that the ability of HDLs to mediate reverse cholesterol transport, inhibit inflammation and reduce oxidation is impaired in metabolic disorders. These cardioprotective effects of HDLs are supported by the outcomes of epidemiological, cell and animal studies, but have not been confirmed in several recent clinical outcome trials of HDL-raising agents. Recent studies suggest that HDL function may be clinically more important than plasma levels of HDL-C. However, at least some of the cardioprotective functions of HDLs are lost in acute coronary syndrome and stable coronary artery disease patients. HDL dysfunction is also associated with metabolic abnormalities. This review is concerned with the impact of metabolic abnormalities, including dyslipidemia, obesity and Type 2 diabetes, on the metabolism and cardioprotective functions of HDLs.

The Circulating GRP78/BiP Is a Marker of Metabolic Diseases and Atherosclerosis: Bringing Endoplasmic Reticulum Stress into the Clinical Scenario

BACKGROUND

Glucose-regulated protein 78/Binding immunoglobulin protein (GRP78/BiP) is a protein associated with endoplasmic reticulum stress and is upregulated by metabolic alterations at the tissue-level, such as hypoxia or glucose deprivation, and it is hyper-expressed in fat tissue of obese individuals.

OBJECTIVE

To investigate the role of the GRP78/BiP level as a metabolic and vascular disease biomarker in patients with type 2 diabetes (DM), obesity and metabolic syndrome (MS).

METHODS

Four hundred and five patients were recruited, of whom 52.5% were obese, 72.8% had DM, and 78.6% had MS. The intimae media thickness (cIMT) was assessed by ultrasonography. The plasma GRP78/BiP concentration was determined, and its association with metabolic and vascular parameters was assessed. Circulating GRP78/BiP was also prospectively measured in 30 DM patients before and after fenofibrate/niacin treatment and 30 healthy controls.

RESULTS

In the cross-sectional study, the GRP78/BiP level was significantly higher in the patients with obesity, DM, and MS. Age-, gender- and BMI-adjusted GRP78/BiP was directly associated with LDL-cholesterol, non-HDL-cholesterol, triglycerides, apoB, and cIMT. GRP78/BiP was positively associated to carotid plaque presence in the adjusted model, irrespective of obesity, DM and MS. In the prospective study, nicotinic acid treatment produced a significant reduction in the GRP78/BiP levels that was not observed with fenofibrate.

CONCLUSIONS

GRP78/BiP plasma concentrations are increased in patients with both metabolic derangements and subclinical atherosclerosis. GRP78/BiP could be a useful marker of metabolic and cardiovascular risk.

HDL Triglycerides: A New Marker of Metabolic and Cardiovascular Risk

While cholesterol content in high-density lipoproteins (HDLs) is a well-established inverse marker of cardiovascular risk, the importance of HDL–triglyceride (HDL-TG) concentration is not well known. We aim to examine plasma HDL-TG concentrations, assessed by ¹H-NMR, in patients with metabolic diseases and their association with classical biomarkers. In this cross-sectional study, we included 502 patients with type 2 diabetes or metabolic syndrome attending the lipid unit of our University Hospital. The presence of arteriosclerotic plaques was assessed by ultrasonography. A complete lipoprotein profile was performed by ¹H-NMR (Liposcale test). HDL-TG was strongly positively correlated with total triglycerides, glycerol, and fatty liver index, while a strong negative correlation was observed with HDL-cholesterol (HDL-C) and HDL-particle number (HDL-P). HDL-TG was associated with all triglyceride-rich lipoprotein parameters and had an opposite association with HDL-C and HDL-P. It was also significantly correlated with circulating cholesterol ester transfer protein (CETP). HDL-TG concentrations were higher as metabolic syndrome components increased. HDL-TG was also higher with worsening glucose metabolism. Patients with carotid plaques also showed higher HDL-TG. In contrast to HDL-C, HDL-TG is directly associated with metabolism and arteriosclerotic vascular alterations. HDL-TG should be considered a biomarker of metabolic and cardiovascular risk and could be a marker of HDL dysfunction.

HDL: Fact, fiction, or function? HDL cholesterol and cardiovascular risk

The measurement of high-density lipoprotein cholesterol is highly utilized by clinicians to help predict cardiovascular risk, but this measure is not causally associated with atherosclerotic cardiovascular disease events. The use of Mendelian randomization studies has led to a change in investigative attention from the high-density lipoprotein cholesterol concentration to its physiological functions. High-density lipoprotein plays key roles in important pathways related to the development of atherosclerotic disease including reverse cholesterol transport, oxidation and inflammation, and endothelial function as well as in other physiological systems including immune system modulation, cellular apoptosis, and endothelial progenitor cell homeostasis. The identification of dysfunctional high-density lipoprotein may better predict future cardiovascular events compared to numerical high-density lipoprotein cholesterol and aid in enhanced clinical risk stratification. The emergence of discrete physiological measurements of high-density lipoprotein, such as cholesterol efflux capacity and the high-density lipoprotein inflammatory index, may provide an opportunity for clinical application in the future. However, the validity of these measurements and their commercial availability remain barriers to a realistic transition to clinical medicine.

Cholesterol efflux capacity of large, small and total HDL particles is unaltered by atorvastatin in patients with type 2 diabetes

BACKGROUND AND AIMS

Research on the biologic activities of HDL, such as cholesterol efflux capacity and HDL composition, has allowed the understanding of the effect of interventions directed to improve cardiovascular risk. Previously, statin therapy has shown conflicting results about its effects on cholesterol efflux capacity of HDL; the underlying mechanisms are unclear but studies with positive effects are associated with an increase of HDL-cholesterol levels. We investigated if 10 weeks of atorvastatin therapy changes HDL efflux capacity and the chemical composition of its subpopulations.

METHODS

In a before-after design basis, HDL-cholesterol levels, chemical composition and cholesterol efflux capacity from HDL subpopulations isolated by isophynic ultracentrifugation were assessed in plasma samples from 60 patients with type 2 diabetes mellito (T2DM) at baseline and after 10 weeks of treatment with 20 mg atorvastatin. Cholesterol efflux was measured from human THP-1 cells using large, light HDL2b and small, dense 3c subpopulations as well as total HDL as acceptors. Changes of cholesterol efflux and chemical composition of HDL after treatment were analyzed. Correlations among variables potentially involved in cholesterol efflux were evaluated.

RESULTS

A significant decrease of 4% in HDL-cholesterol levels was observed from 47 (42-54) to 45 (39-56) mg/dL, p = 0.02. Cholesterol efflux from total-HDL and HDL2b and 3c subfractions was maintained unchanged after treatment. The total mass of HDL remained unaffected, except for the HDL3a subpopulation accounted for by a significant increase in total protein content. No significant correlations for variables previously known to be associated with cholesterol efflux were found in our study.

CONCLUSIONS

Short therapy of 10 weeks with 20 mg of atorvastatin does not modify the cholesterol efflux capacity neither the total mass of HDL2b, HDL3c and total HDL. The discrepancy with previous reports may be due to the selective effects among different classes of statins or differences in the approaches to measure cellular cholesterol efflux.

Inhibition of JNK signalling mediates PPARα-dependent protection against intrahepatic cholestasis by fenofibrate

BACKGROUND AND PURPOSE

Fenofibrate, a PPARα agonist, is the most widely prescribed drug for treating hyperlipidaemia. Although fibrate drugs are reported to be beneficial for cholestasis, their underlying mechanism has not been determined.

EXPERIMENTAL APPROACH

Wild-type mice and Pparα-null mice were pretreated orally with fenofibrate for 3 days, following which α-naphthylisothiocyanate (ANIT) was administered to induce cholestasis. The PPARα agonist WY14643 and JNK inhibitor SP600125 were used to determine the role of PPARα and the JNK pathway, respectively, in cholestatic liver injury. The same fenofibrate regimen was applied to investigate its beneficial effects on sclerosing cholangitis in a DDC-induced cholestatic model.

KEY RESULTS

Fenofibrate, 25 mg·kg^-1 twice a day, totally attenuated ANIT-induced cholestasis and liver injury as indicated by biochemical and histological analyses. This protection occurred in wild-type, but not in Pparα-null, mice. Alterations in bile acid synthesis and transport were found to be an adaptive response rather than a direct effect of fenofibrate. WY14643 attenuated ANIT-induced cholestasis and liver injury coincident with inhibition of JNK signalling. Although SP600125 did not affect cholestasis, it inhibited liver injury in the ANIT model when the dose of fenofibrate used was ineffective. Fenofibrate was also revealed to have a beneficial effect in the sclerosing cholangitis model.

CONCLUSIONS AND IMPLICATIONS

These data suggest that the protective effects of fenofibrate against cholestasis-induced hepatic injury are dependent on PPARα and fenofibrate dose, and are mediated through inhibition of JNK signalling. This mechanism of fenofibrate protection against intrahepatic cholestasis may offer additional therapeutic opportunities for cholestatic liver diseases.

Lipoprotein hydrophobic core lipids are partially extruded to surface in smaller HDL: "Herniated" HDL, a common feature in diabetes

Recent studies have shown that pharmacological increases in HDL cholesterol concentrations do not necessarily translate into clinical benefits for patients, raising concerns about its predictive value for cardiovascular events. Here we hypothesize that the size-modulated lipid distribution within HDL particles is compromised in metabolic disorders that have abnormal HDL particle sizes, such as type 2 diabetes mellitus (DM2). By using NMR spectroscopy combined with a biochemical volumetric model we determined the size and spatial lipid distribution of HDL subclasses in a cohort of 26 controls and 29 DM2 patients before and after two drug treatments, one with niacin plus laropiprant and another with fenofibrate as an add-on to simvastatin. We further characterized the HDL surface properties using atomic force microscopy and fluorescent probes to show an abnormal lipid distribution within smaller HDL particles, a subclass particularly enriched in the DM2 patients. The reduction in the size, force cholesterol esters and triglycerides to emerge from the HDL core to the surface, making the outer surface of HDL more hydrophobic. Interestingly, pharmacological interventions had no effect on this undesired configuration, which may explain the lack of clinical benefits in DM2 subjects.