Liraglutide improves carotid intima-media thickness in patients with type 2 diabetes and non-alcoholic fatty liver disease: an 8-month prospective pilot study

OBJECTIVE

To explore the effects of the glucagon-like peptide-1 receptor analogue liraglutide on subclinical atherosclerosis in diabetic subjects with non-alcoholic fatty liver disease (NAFLD).

RESEARCH DESIGN AND METHODS

In this 8-month prospective study, 29 subjects with type 2 diabetes (T2DM) and NAFLD (16 men and 13 women, mean age: 61 ± 10 years) were matched for age and gender with 29 subjects with T2DM without NAFLD (16 men and 13 women, mean age: 61 ± 8 years). Liraglutide 0.6 mg/day for 2 weeks, followed by 1.2 mg/day, was given in addition to metformin.

MAIN OUTCOME MEASURES

Anthropometric variables, glucometabolic parameters and carotid intima-media thickness (IMT) using B-mode real-time ultrasound were assessed at baseline and 4 and 8 months.

RESULTS

Glycated hemoglobin reduced significantly in both groups. No significant changes were found in body weight, waist circumference and lipids. Carotid IMT decreased significantly in the T2DM patients with NAFLD (from 0.96 ± 0.27 to 0.82 ± 0.17 to 0.85 ± 0.12 mm, p = 0.0325), but not in the T2DM patients without NAFLD (from 0.91 ± 0.23 to 0.88 ± 0.17 to 0.85 ± 0.15 mm, p = 0.4473).

CONCLUSION

Eight months of liraglutide use in patients with T2DM and NAFLD significantly reduced carotid IMT, a surrogate marker of atherosclerosis, independently of glucometabolic changes.

Roles of EGFR and KRAS and their downstream signaling pathways in pancreatic cancer and pancreatic cancer stem cells

Pancreatic cancer is currently the fourth most common cancer, is increasing in incidence and soon will be the second leading cause of cancer death in the USA. This is a deadly malignancy with an incidence that approximates the mortality with 44,000 new cases and 36,000 deaths each year. Surgery, although only modestly successful, is the only curative option. However, due the locally aggressive nature and early metastasis, surgery can be performed on less than 20% of patients. Cytotoxic chemotherapy is palliative, has significant toxicity and improves survival very little. Thus new treatment paradigms are needed desperately. Due to the extremely high frequency of KRAS gene mutations (>90%) detected in pancreatic cancer patients, the roles of the epidermal growth factor receptor (EGFR), Ras/Raf/MEK/ERK and PI3K/PTEN/Akt/mTORC1/GSK-3 pathways have been investigated in pancreatic cancer for many years. Constitutively active Ras can activate both of these pathways and there is cross talk between Ras and EGFR which is believed to be important in driving metastasis. Mutant KRAS may also drive the expression of GSK-3 through Raf/MEK/ERK-mediated effects on GSK-3 transcription. GSK-3 can then regulate the expression of NF-kappaB which is important in modulating pancreatic cancer chemoresistance. While the receptors and many downstream signaling molecules have been identified and characterized, there is still much to learn about these pathways and how their deregulation can lead to cancer. Multiple inhibitors to EGFR, PI3K, mTOR, GSK-3, Raf, MEK and hedgehog (HH) have been developed and are being evaluated in various cancers. Current research often focuses on the role of these pathways in cancer stem cells (CSC), with the goal to identify sites where therapeutic resistance may develop. Relatively novel fields of investigation such as microRNAs and drugs used for other diseases e.g., diabetes, (metformin) and malaria (chloroquine) have provided new information about therapeutic resistance and CSCs. This review will focus on recent advances in the field and how they affect pancreatic cancer research and treatment.

Effects of steatosis on hepatic hemodynamics in patients with metabolic syndrome

The aim of our study was to assess the hemodynamic changes in hepatic and splenic circulation using B-mode ultrasonography and color Doppler ultrasonography, in a population of patients with metabolic syndrome divided with respect to the presence or absence of steatosis diagnosed by ultrasonography. One hundred forty-one patients were included in the study. The severity of non-alcoholic fatty liver disease was classified as mild, moderate or severe. Visceral fat thickness, longitudinal diameter of the spleen, diameter of the portal vein, mean maximum portal vein flow velocity, hepatic artery and splenic artery resistivity indexes and hepatic vein flow phasicity were measured. Non-alcoholic fatty liver disease was detected in 114 of 141 patients, with a prevalence of 80.8%. Patients with steatosis had significantly greater diameters of the portal vein, longitudinal diameters of the spleen, visceral fat thickness and hepatic artery and splenic artery resistivity indexes, whereas their portal vein flow velocities were significantly lower. Non-alcoholic fatty liver disease severity correlated positively with diameter of the portal vein, longitudinal diameter of the spleen and visceral fat thickness and negatively with hepatic artery and splenic artery resistivity indexes and reduced hepatic vein flow phasicity. Our patients with metabolic syndrome and non-alcoholic fatty liver disease had a flattened hepatic vein flow phasicity, greater portal vein diameter, reduction in portal vein flow velocity and intrahepatic arterial vasodilation. The vasodilation of the intrahepatic arterial system was likely activated both by the effect of insulin resistance and as a physiologic adaptation to restore hepatic flow. The increase in spleen volume might be related to the organomegaly typical of obese patients.

Clinical course and management of acute and chronic viral hepatitis during pregnancy

Pregnancy is a para-physiologic condition, which usually evolves without any complications in the majority of women, even if in some circumstances moderate or severe clinical problems can also occur. Among complications occurring during the second and the third trimester very important are those considered as concurrent to pregnancy such as hyperemesis gravidarum, intrahepatic cholestasis of pregnancy, HELLP syndrome and acute fatty liver of pregnancy. The liver diseases concurrent to pregnancy typically occur at specific times during the gestation and they may lead to significant maternal and foetal morbidity and mortality. Commonly, delivery of the foetus, even preterm, usually terminates the progression of these disorders. All chronic liver diseases, such as chronic viral hepatitis, autoimmune hepatitis, Wilson's disease, and cirrhosis of different aetiologies may cause liver damage, independently from pregnancy. In this review we will also comment the clinical implications of pregnancies occurring in women who received a orthotopic liver transplantation (OLT) Therefore, the management of immunosuppressive therapy before and after the delivery in women who received liver transplant is becoming a relevant clinical issue. Finally, we will focus on acute and chronic viral hepatitis occurring during pregnancy, on management of advanced liver disease and we will review the literature on the challenging issue regarding pregnancy and OLT.

Low- and high-density lipoprotein subclasses in subjects with nonalcoholic fatty liver disease

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is associated with increased cardiometabolic risk. Although dyslipidemia represents a key factor in this disease, its impact on serum levels of distinct lipoprotein subfractions is largely unknown.

OBJECTIVE

To assess the full low-density lipoprotein (LDL) and high-density lipoprotein (HDL) profiles in patients with NAFLD.

METHODS

Seven LDL and 10 HDL subfractions were assessed by gel electrophoresis (Lipoprint, Quantimetrix Corporation, USA) in men with biopsy proven NAFLD (simple steatosis [n = 17, age, 34 ± 7 years] and nonalcoholic steatohepatitis [NASH; n = 24, age, 32 ± 6 years]). Exclusion criteria included robust alcohol consumption, infection with hepatitis B or C virus, body mass index ≥ 40 kg/m(2), diabetes mellitus, and hypertension.

RESULTS

Compared with simple steatosis, NASH patients had similar body mass index, homeostasis model assessment of insulin resistance index and plasma lipids, with increased levels of both aspartate aminotransferase and alanine transaminase. NASH subjects had lower levels of larger LDL1 (10 ± 4 vs 13 ± 4%, P = .010) and increased smaller LDL3 and LDL4 particles (9 ± 5 vs 5 ± 5%, P = .017 and 3 ± 3 vs 1 ± 2%, P = .012, respectively). No changes were found in the HDL subclass profile. By multiple regression analysis, we found that NASH was associated only with increased levels of LDL3 (P = .0470).

CONCLUSIONS

The increased levels of small, dense LDL3 and LDL4 in NASH may help to at least partly explain the increased risk for atherosclerosis and cardiovascular diseases in these patients.

Gestational diabetes and the metabolic syndrome: can obesity and small, dense low density lipoproteins be key mediators of this association?

Gestational diabetes mellitus (GDM) represents a condition of glucose intolerance with first appearance or recognition at the time of a pregnancy, associated with an inadequate pancreatic response to the advanced insulin resistance of the later stages of pregnancy, and accompanied by enhancing β-cell mass and secretion of insulin. Women who had GDM exhibit a higher risk for later advent of type 2 diabetes mellitus (T2DM) and cardiovascular diseases (CVD). Additionally, previous GDM has been proposed as independently correlated with higher risk for development of atherosclerosis in a healthy population, similar to the metabolic syndrome (MetS) and independently of the presence of established CVD risk factors. Available data indicate multiple metabolic abnormalities common in women with GDM, including a high small dense low-density lipoprotein (sdLDL) concentration and a resultant high prevalence of CVD and the MetS. Preliminary data indicate that a measurement of sdLDL is worthwhile in women with GDM during pregnancy as well as the postpartum period. A close follow up of these women should be emphasized in clinical practice because GDM could predict not only eventual health risks for these mothers, but also their offspring. Thus, an improvement in care and risk modification of women with GDM may not only contribute towards improved CVD profile, but also potentially prevent adverse outcomes in their offspring. Lifestyle changes should be promoted in order to prevent excessive weight gain during pregnancy and decrease the risk of MetS in the postpartum and long-term.

Uric acid metabolism in pre-hypertension and the metabolic syndrome

In humans uric acid (UA) is the end product of degradation of purines. The handling of UA by the renal system is a complex process which is not fully understood. To date, several urate transporters in the renal proximal tubule have been identified. Among them, urate transporter 1 (URAT1) and a glucose transporter 9 (GLUT9) are considered of greater importance, as potential targets for treatment of hyperuricemia and the potential associated cardio-metabolic risk. Therefore, the recognition of the metabolic pathway of UA and elucidation of occurrence of hyperuricemia may provide important insights about the relationship between UA, pre-hypertension (preHT) and the metabolic syndrome (MetS). We also review the available clinical studies in this field, including experimental studies dealing with the mechanisms of UA transport via different transporters, as well as current treatment options for hyperuricemia in patients with MetS, preHT or cardiovascular risk factors.

Liraglutide reduces oxidative stress and restores heme oxygenase-1 and ghrelin levels in patients with type 2 diabetes: a prospective pilot study

CONTEXT

Liraglutide is a glucagon-like peptide-1 analog and glucose-lowering agent whose effects on cardiovascular risk markers have not been fully elucidated.

OBJECTIVE

We evaluated the effect of liraglutide on markers of oxidative stress, heme oxygenase-1 (HO-1), and plasma ghrelin levels in patients with type-2 diabetes mellitus (T2DM).

DESIGN AND SETTING

A prospective pilot study of 2 months' duration has been performed at the Unit of Diabetes and Cardiovascular Prevention at University of Palermo, Italy. Patients and Intervention(s): Twenty subjects with T2DM (10 men and 10 women; mean age: 57 ± 13 y) were treated with liraglutide sc (0.6 mg/d for 2 wk, followed by 1.2 mg/d) in addition to metformin (1500 mg/d orally) for 2 months. Patients with liver disorders or renal failure were excluded.

MAIN OUTCOME MEASURE(S)

Plasma ghrelin concentrations, oxidative stress markers, and heat-shock proteins, including HO-1 were assessed.

RESULTS

The addition of liraglutide resulted in a significant decrease in glycated hemoglobin (HbA1c) (8.5 ± 0.4 vs 7.5 ± 0.4%, P < .0001). In addition, plasma ghrelin and glutathione concentrations increased (8.2 ± 4.1 vs 13.6 ± 7.3 pg/ml, P = .0007 and 0.36 ± 0.06 vs 0.44 ± 0.07 nmol/ml, P = .0002, respectively), whereas serum lipid hydroperoxides and HO-1 decreased (0.11 ± 0.05 vs 0.04 ± 0.07 pg/ml, P = .0487 and 7.7 ± 7.7 vs 3.6 ± 1.8 pg/ml, P = .0445, respectively). These changes were not correlated with changes in fasting glycemia or HbA1c.

CONCLUSIONS

In a 2-months prospective pilot study, the addition of liraglutide to metformin resulted in improvement in oxidative stress as well as plasma ghrelin and HO-1 concentrations in patients with T2DM. These findings seemed to be independent of the known effects of liraglutide on glucose metabolism.

Cytotoxic activity of the novel small molecule AKT inhibitor SC66 in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is characterized by limited response to current drug therapies. Here, we report that SC66, a novel AKT inhibitor, reduced cell viability in a dose- and time-dependent manner, inhibited colony formation and induced apoptosis in HCC cells. SC66 treatment led to a reduction in total and phospho-AKT levels. This was associated with alterations in cytoskeleton organization, a reduction in expression levels of E-cadherin, β-catenin and phospho-FAK, together with up-regulation of Snail protein levels. All these alterations were coupled with anoikis cell death induction. In addition, SC66 induced the production of reactive oxygen species (ROS) and DNA damage. Pre-treatment with the ROS scavenger N-Acetyl-cysteine (NAC) prevented SC66-induced cell growth inhibition and anoikis. SC66 significantly potentiated the effects of both conventional chemotherapeutic and targeted agents, doxorubicin and everolimus, respectively. In vivo, SC66 inhibited tumor growth of Hep3B cells in xenograft models, with a similar mechanism observed in the in vitro model. Taken together, these data indicate that the AKT inhibitor SC66 had antitumor effects on HCC cells. This was mediated by ROS production, induction of anoikis-mediated cell death and inhibition of the AKT cell survival pathway. Our results provide a rational basis for the use of SC66 in HCC treatment.

Effect of a Natural Supplement Containing Curcuma Longa, Guggul, and Chlorogenic Acid in Patients With Metabolic Syndrome

The impact of a natural supplement (Kepar; Rikrea, Italy), containing several plant extracts such as curcuma longa, silymarin, guggul, chlorogenic acid, and inulin, was evaluated in 78 patients with metabolic syndrome (MetS; 45 men; age: 62 ± 9 years). Kepar at a dose of 2 pills/d was given for 4 months as add-on therapy to the ongoing treatment, maintained at fixed doses for the entire study. Anthropometric variables, plasma lipids, glucose parameters, and oxidative stress were measured at baseline and after 4 months. We found significant reductions in body weight (from 81.1 ± 13.5 to 79.4 ± 12.5 kg, P < .0001), body mass index (from 29.6 [23.7] to 29.3 [21.9] kg/m2, P = .001), and waist circumference (from 105 ± 11 to 102 ± 10 cm, P = .0004) as well as in fasting glucose (from 6.5 [11.7] to 6.4 [7.6] mmol/L, P = .014) and total cholesterol (from 4.8 ± 1.4 to 4.5 ± 1.0 mmol/L, P = .03). No significant changes were found in the other appraised parameters, including oxidative stress. In conclusion, after few months of treatment Kepar seems to exert beneficial effects in patients with MetS. Larger studies with a longer follow-up period are needed to confirm these preliminary findings.

GSK-3 as potential target for therapeutic intervention in cancer

The serine/threonine kinase glycogen synthase kinase-3 (GSK-3) was initially identified and studied in the regulation of glycogen synthesis. GSK-3 functions in a wide range of cellular processes. Aberrant activity of GSK-3 has been implicated in many human pathologies including: bipolar depression, Alzheimer's disease, Parkinson's disease, cancer, non-insulin-dependent diabetes mellitus (NIDDM) and others. In some cases, suppression of GSK-3 activity by phosphorylation by Akt and other kinases has been associated with cancer progression. In these cases, GSK-3 has tumor suppressor functions. In other cases, GSK-3 has been associated with tumor progression by stabilizing components of the beta-catenin complex. In these situations, GSK-3 has oncogenic properties. While many inhibitors to GSK-3 have been developed, their use remains controversial because of the ambiguous role of GSK-3 in cancer development. In this review, we will focus on the diverse roles that GSK-3 plays in various human cancers, in particular in solid tumors. Recently, GSK-3 has also been implicated in the generation of cancer stem cells in various cell types. We will also discuss how this pivotal kinase interacts with multiple signaling pathways such as: PI3K/PTEN/Akt/mTORC1, Ras/Raf/MEK/ERK, Wnt/beta-catenin, Hedgehog, Notch and others.

Non invasive tools for the diagnosis of liver cirrhosis

Liver cirrhosis (LC), the end stage of many forms of chronic hepatitis of different etiologies is a diffuse process characterized by fibrosis and the conversion of normal liver architecture into structurally abnormal nodules surrounded by annular fibrosis. This chronic progressive clinical condition, leads to liver cell failure and portal hypertension, which can favour the onset of hepatocellular carcinoma. Defining the phase of the natural history is crucial for therapeutic choice and prognosis. Liver biopsy is currently considered the best available standard of reference but it has some limits, so alternative tools have been developed to substitute liver biopsy when assessing liver fibrosis. Serum markers offer a cost-effective alternative to liver biopsy being less invasive and theoretically without complications. They can be classified into direct and indirect markers which may be used alone or in combination to produce composite scores. Diagnostic imaging includes a number of instruments and techniques to estimate liver fibrosis and cirrhosis like ultrasound (US), US Doppler, contrast enhanced US and Elastography. US could be used for the diagnosis of advanced LC while is not able to evaluate progression of fibrosis, in this case Elastography is more reliable. This review aims to revise the most recent data from the literature about non invasive methods useful in defining liver fibrosis.

Roles of signaling pathways in drug resistance, cancer initiating cells and cancer progression and metastasis

The EGFR/PI3K/PTEN/Akt/mTORC pathway plays prominent roles in malignant transformation, prevention of apoptosis, drug resistance, cancer initiating cells (CICs) and metastasis. The expression of this pathway is frequently altered in breast and other cancers due to mutations at or aberrant expression of: HER2, EGFR1, PIK3CA, and PTEN as well as other oncogenes and tumor suppressor genes. miRs and epigenetic mechanisms of gene regulation are also important events which regulate this pathway. In some breast cancer cases, mutations at certain components of this pathway (e.g., PIK3CA) are associated with a better prognosis than breast cancers lacking these mutations. The expression of this pathway has been associated with CICs and in some cases resistance to therapeutics. We will review the effects of activation of the EGFR/PI3K/PTEN/Akt/mTORC pathway primarily in breast cancer and development of drug resistance. The targeting of this pathway and other interacting pathways will be discussed as well as clinical trials with novel small molecule inhibitors as well as established drugs that are used to treat other diseases. In this manuscript, we will discuss an inducible EGFR model (v-ERB-B:ER) and its effects on cell growth, cell cycle progression, activation of signal transduction pathways, prevention of apoptosis in hematopoietic, breast and prostate cancer models.

Distribution of liver disease in a cohort of immigrants in Sicily: analysis of day-hospital admissions in a migration medicine unit

The objective of this study was to evaluate the frequency of liver disease and its aetiology in a cohort of immigrants. We retrospectively examined the hospital discharge charts of all the immigrant patients presenting at our day hospital from July 2009 to June 2013, and after evaluating the anamnestic, clinical and laboratory data on these charts we identified subjects with liver disease and its various aetiologies. The total sample population consisted of 1218 patients, of whom 112 (9.2%) had a diagnosis of liver disease. More than two-thirds of the latter (67.8%) came from Africa, while 15.2% were from Asia and 17.0% from Eastern Europe. In most patients the disease was related to HBV (44.6%), followed by alcohol (25%) and then HCV or cryptogenic disease (both 15.2%). Forty-six patients had undergone liver biopsy, which showed eight cases of varying degrees of liver steatosis, 29 cases with a variable severity of chronic liver disease, eight cases with a definite picture of liver cirrhosis and one case of alcoholic hepatitis. These data show that a significant proportion of our immigrant population has liver disease and that the most frequent cause is hepatitis B infection.

Targeting breast cancer initiating cells: advances in breast cancer research and therapy

Over the past 10 years there have been significant advances in our understanding of breast cancer and the important roles that breast cancer initiating cells (CICs) play in the development and resistance of breast cancer. Breast CICs endowed with self-renewing and tumor-initiating capacities are believed to be responsible for the relapses which often occur after various breast cancer therapies. In this review, we will summarize some of the key developments in breast CICs which will include discussion of some of the key genes implicated: estrogen receptor (ER), HER2, BRCA1, TP53, PIK3CA, RB, P16INK1 and various miRs as well some drugs which are showing promise in targeting CICs. In addition, the concept of combined therapies will be discussed. Basic and clinical research is resulting in novel approaches to improve breast cancer therapy by targeting the breast CICs.

Effects of chitosan on plasma lipids and lipoproteins: a 4-month prospective pilot study

Chitosan can favorably modulate plasma lipids, but the available data are not conclusive. We evaluated the effect of chitosan on plasma lipids and lipoproteins in 28 patients with plasma triglyceride levels >150 mg/dL (mean age: 63 ± 12 years), not taking other lipid-lowering agents. All patients received a chitosan derived from fungal mycelium (Xantonet, Bromatech, Italy) at a fixed dose of 125 mg/d in addition to their current medications for 4 months. Polyacrylamide gel electrophoresis was used to measure low-density lipoprotein (LDL) subclasses. After treatment, total cholesterol reduced by 8%, LDL cholesterol by 2%, and triglycerides by 19%, with a concomitant 14% increase in high-density lipoprotein cholesterol. We also found a beneficial effect of chitosan on LDL subclasses, with a significant increase in LDL-2 particles (from 37 ± 8% to 47 ± 8%, P = .0001) and a decrease (although not significant) in atherogenic small, dense LDL. Whether these findings may affect cardiovascular risk remains to be established in future studies.

Heat shock protein 70 serum levels differ significantly in patients with chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma

Members of the heat shock protein 70 (HSP70) family play an important role in assisting protein folding, preventing protein aggregation and transport of proteins across membranes under physiological conditions. Following environmental (i.e., irradiation, chemotherapy), physiological (i.e., cell growth, differentiation), and pathophysiological (i.e., inflammation, tumorigenesis) stress, the synthesis of heat shock proteins (HSPs) is highly up-regulated, whereas protein synthesis in general is reduced. In contrast to normal cells, many tumor entities including hepatocellular carcinoma (HCC) overexpress HSP70, the major-stress-inducible member of the HSP70 family, present it on their cell surface and secrete it into the extracellular milieu. Herein, the prognostic relevance of serum HSP70 levels in patients with chronic hepatitis (CH; n = 50), liver cirrhosis (LC; n = 46), and HCC (n = 47) was analyzed. Similar to other tumor entities, HSP70 is also present on the surface of primary HCC cells. The staining intensity of intracellular HSP70 in HCC tissue is stronger compared to control and cirrhotic liver sections. HSP70 serum levels in all HCC patients were significantly higher compared to a control group without liver disease (n = 40). No significant age- and gender-related differences in HSP70 serum levels were observed in male and female healthy human volunteers (n = 86). Patients with CH (n = 50) revealed significantly higher HSP70 serum levels compared to the control group, however, these values were significantly lower than those of HCC patients (n = 47). Furthermore, a subgroup of patients with LC who subsequently developed HCC (LC-HCC, n = 13) revealed higher HSP70 serum levels than patients with LC (n = 46, p = 0.05). These data indicate that serum HSP70 levels are consecutively increased in patients with CH, LC and liver carcinomas and thus might have a prognostic value.

Nanotechnology applications for the therapy of liver fibrosis

Chronic liver diseases represent a major global health problem both for their high prevalence worldwide and, in the more advanced stages, for the limited available curative treatment options. In fact, when lesions of different etiologies chronically affect the liver, triggering the fibrogenesis mechanisms, damage has already occurred and the progression of fibrosis will have a major clinical impact entailing severe complications, expensive treatments and death in end-stage liver disease. Despite significant advances in the understanding of the mechanisms of liver fibrinogenesis, the drugs used in liver fibrosis treatment still have a limited therapeutic effect. Many drugs showing potent antifibrotic activities in vitro often exhibit only minor effects in vivo because insufficient concentrations accumulate around the target cell and adverse effects result as other non-target cells are affected. Hepatic stellate cells play a critical role in liver fibrogenesis , thus they are the target cells of antifibrotic therapy. The application of nanoparticles has emerged as a rapidly evolving area for the safe delivery of various therapeutic agents (including drugs and nucleic acid) in the treatment of various pathologies, including liver disease. In this review, we give an overview of the various nanotechnology approaches used in the treatment of liver fibrosis.

Should low high-density lipoprotein cholesterol (HDL-C) be treated?

The first observations linking a low serum level of HDL-C to increased risk for cardiovascular disease were made over 50 years ago. High serum levels of HDL-C appear to protect against the development of atherosclerotic disease, while low serum levels of this lipoprotein are among the most important predictors of atherosclerotic disease in both men and women and people of all racial and ethnic groups throughout the world. It has long been assumed that therapeutic interventions targeted at raising HDL-C levels would lower risk for such cardiovascular events as myocardial infarction, ischemic stroke, and death. Even after five decades of intensive investigation, evidence to support this assumption has been fleeting. A number of post hoc analyses of randomized controlled trials and meta-analyses suggest that HDL-C raising, particularly when coupled with aggressive LDL-C reduction, impacts risk for cardiovascular events and rates of progression of atherosclerotic disease. Unfortunately, four recent prospective trials performed with the intent of testing the "HDL hypothesis" (ILLUMINATE, dal-OUTCOMES, AIM-HIGH, and HPS2-THRIVE) failed to meet their primary composite endpoints. These results have lead many clinicians and investigators to question the validity of the assumption that HDL-C raising reduces risk for cardiovascular events. Additional trials with other drugs are underway. In the meantime, HDL-C cannot be considered a target of therapy. Given the complexity of the HDL proteome and lipidome, there is biological plausibility for how HDL particles might exert atheroprotection. We explore the evidence supporting the inverse relationship between HDL-C and cardiovascular disease risk, documented mechanisms by which HDL particles may exert atheroprotection, and the findings either supporting or negating specific therapeutic interventions in patients afflicted with low HDL-C.