Lipoprotein lipase and hepatic lipase: their relationship with HDL subspecies Lp(A-I) and Lp(A-I,A-II)

ANGPTL3 impacts proteinuria and hyperlipidemia in primary nephrotic syndrome

Background

It is unclear why primary nephrotic syndrome (PNS) patients often have dyslipidemia. Recent studies have shown that angiopoietin-like protein 3 (ANGPTL3) is an important regulator of lipid metabolism. In this study, we explored how ANGPTL3 impacts dyslipidemia during PNS development.

Methods

We measured the serum levels of ANGPTL3 in PNS patients (n=196). Furthermore, the degree of proteinuria and lipid metabolism were examined in angptl3-overexpressing transgenic (angptl3-tg) mice at different ages. Moreover, in this study, we used the clustered regularly interspaced short palindromic repeats-associated protein 9 (CRISPR/Cas9) system to create angptl3-knockout (angptl3-/-) mice to investigate lipopolysaccharide (LPS)-induced nephrosis.

Results

Compared with that in the healthy group, the serum level of ANGPTL3 in the PNS group was significantly increased (32 (26.35-39.66) ng/ml vs. 70.44 (63.95-76.51) ng/ml, Z =-4.81, P < 0.001). There were significant correlations between the serum level of ANGPTL3 and the levels of cholesterol (r=0.34, P < 0.001), triglycerides (r= 0.25, P = 0.001) and low-density lipoprotein (r= 0.50, P < 0.001) in PNS patients. With increasing age, angptl3-tg mice exhibited increasingly severe hypertriglyceridemia and proteinuria. The pathological features of angptl3-tg mice included rich lipid droplet deposition in hepatocytes and diffuse podocyte effacement. Compared to wild-type mice, angptl3-/- mice showed significantly lower degrees of lipid dysfunction and proteinuria after stimulation with LPS. The effects of ANGPTL3 on nephrotic dyslipidemia were confirmed in cultured hepatocytes subjected to angptl3 knockdown or overexpression. Finally, significant alterations in lipoprotein lipase (LPL) levels were observed in liver tissues from Angptl3-/- and wild-type mice stimulated with LPS.

Conclusions

ANGPTL3 could be involved in the development of dyslipidemia, as well as proteinuria, during PNS pathogenesis. Inhibition of LPL expression may the mechanism by which ANGPTL3 induces hyperlipidemia in PNS.

Small-Molecule Inhibitors Targeting Lipolysis in Human Adipocytes

Chronically elevated circulating fatty acid levels promote lipid accumulation in nonadipose tissues and cause lipotoxicity. Adipose triglyceride lipase (ATGL) critically determines the release of fatty acids from white adipose tissue, and accumulating evidence suggests that inactivation of ATGL has beneficial effects on lipotoxicity-driven disorders including insulin resistance, steatohepatitis, and heart disease, classifying ATGL as a promising drug target. Here, we report on the development and biological characterization of the first small-molecule inhibitor of human ATGL. This inhibitor, designated NG-497, selectively inactivates human and nonhuman primate ATGL but not structurally and functionally related lipid hydrolases. We demonstrate that NG-497 abolishes lipolysis in human adipocytes in a dose-dependent and reversible manner. The combined analysis of mouse- and human-selective inhibitors, chimeric ATGL proteins, and homology models revealed detailed insights into enzyme–inhibitor interactions. NG-497 binds ATGL within a hydrophobic cavity near the active site. Therein, three amino acid residues determine inhibitor efficacy and species selectivity and thus provide the molecular scaffold for selective inhibition.

C4BPA: A Novel Co-Regulator of Immunity and Fat Metabolism in the Bovine Mammary Epithelial Cells

The C4b binding protein alpha (C4BPA) chain primarily engages in critical inflammatory and coagulation processes. The previous transcriptomic analysis showed that C4BPA is a differentially expressed gene in lower and higher fat content mammary gland cell lines from Chinese Holstein. This study aimed to investigate the effects of C4BPA on the inflammation and milk fat synthesis in bMECs by C4BPA knockdown and overexpression. The results highlighted that knockdown of C4BPA in bMECs could suppress the mRNA and protein expression of IL-6, IL-8, IL-12, and the TLR-4/NF-κB pathway-related genes and promote the expression of complement and coagulation cascade pathways related genes as well as TNF-α. Moreover, knockdown of C4BPA expression in bMECs reduced the content of triglyceride (TG) and cholesterol (CHOL) in bMECs, increased NEFA content, reduced mRNA and protein expression of ACSL1 and PPARA, and increased the mRNA and protein expression of ELOVL6, FADS1, and LPL. The bMECs, with the overexpression of C4BPA, showed the enhanced expression of TLR-4/NF-κB linked genes, IL-6, IL-8, IL-12, and mRNA and protein level while reduced mRNA expression of TNF-α, compliment, and coagulation cascade related genes was observed. In bMECs, overexpression of C4BPA enhanced the content of TG and CHOL while reducing NEFA and stimulated the mRNA and protein expression of ACSL1, PPARA, and PPARG genes while inhibiting the mRNA and protein expression of FADS1 and LPL genes. Our results show that C4BPA not only regulates the lipid metabolism through the PPAR signaling pathway in bMECs but also contributes to the inflammatory response through TLR-4/NF-κB and the complement and coagulation cascade pathways. This study, for the first time, provides the primary basis for understanding the role of C4BPA in immunity and fat metabolism, which enables the researchers for innovative direction to investigate genes associated with fat metabolism and immunity. This study also advocates that the breeders must pay attention to such type of genes with multiple functions during animal breeding.

CSL112 (Apolipoprotein A-I [Human]) Strongly Enhances Plasma Apoa-I and Cholesterol Efflux Capacity in Post-Acute Myocardial Infarction Patients: A PK/PD Substudy of the AEGIS-I Trial

Introduction:

Cholesterol efflux capacity (CEC) is impaired following acute myocardial infarction (AMI). CSL112 is an intravenous preparation of human plasma-derived apoA-I formulated with phosphatidylcholine (PC). CSL112 is intended to improve CEC and thereby prevent early recurrent cardiovascular events following AMI. AEGIS-I (ApoA-I Event Reducing in Ischemic Syndromes I) was a multicenter, randomized, double-blind, placebo-controlled, dose-ranging phase 2b study, designed to evaluate the hepatic and renal safety of CSL112. Here, we report an analysis of a pharmacokinetic (PK) and pharmacodynamic (PD) substudy of AEGIS-I.

Methods:

AMI patients were stratified by renal function and randomized 3:3:2 to 4, weekly, 2-hour infusions of low- and high-dose (2 g and 6 g) CSL112, or placebo. PK/PD assessments included plasma concentrations of apoA-I and PC, and measures of total and ABCA1-dependent CEC, as well as lipids/lipoproteins including high density lipoprotein cholesterol (HDL-C), non-HDL-C, low density lipoprotein cholesterol (LDL-C), ApoB, and triglycerides. Inflammatory and cardio-metabolic biomarkers were also evaluated.

Results:

The substudy included 63 subjects from AEGIS-I. CSL112 infusions resulted in rapid, dose-dependent increases in baseline corrected apoA-I and PC, which peaked at the end of the infusion (Tmax ≈ 2 hours). Similarly, there was a dose-dependent elevation in both total CEC and ABCA1-mediated CEC. Mild renal impairment did not affect the PK or PD of CSL112. CSL112 administration was also associated with an increase in plasma levels of HDL-C but not non-HDL-C, LDL-C, apoB, or triglycerides. No dose-effects on inflammatory or cardio-metabolic biomarkers were observed.

Conclusion:

Among patients with AMI, impaired CEC was rapidly elevated by CSL112 infusions in a dose-dependent fashion, along with an increase in apoA-I plasma concentrations. Findings from the current sub-study of the AEGIS-I support a potential atheroprotective benefit of CSL112 for AMI patients.

Sedentary Time and Metabolic Risk in Extremely Active Older Adults

OBJECTIVE

Increasing evidence suggests that time spent sedentary predicts increasing cardiometabolic risk independent of other physical activity. We objectively measured activity levels in active older adults and examined the association between sedentary behavior and the continuous metabolic syndrome risk score (cMSy).

RESEARCH DESIGN AND METHODS

Older adults (age ≥65 years) were recruited from the Whistler Masters ski team, a group of active older adults who undergo organized group training. Daily activity levels were recorded with accelerometers (SenseWear) worn for 7 days. A compositional approach was used to determine proportion of the time spent sedentary as compared with all other nonsedentary behaviors (isometric log-ratio transformation for time spent sedentary [ILR1]). Waist circumference, triglycerides, HDL, systolic blood pressure, and fasting glucose were measured, and cMSy was calculated using principal component analysis (sum of eigenvalues ≥1.0).

RESULTS

Fifty-four subjects (30 women and 24 men, mean ± SE age 71.4 ± 0.6 years) were recruited. Subjects demonstrated high levels of physical activity (2.6 ± 0.2 h light activity and 3.9 ± 0.2 h moderate/vigorous activity). In our final parsimonious model, ILR1 showed a significant positive association with increasing cMSy (standardized β = 0.368 ± 0.110, R ² = 0.40, P = 0.002), independent of age and biological sex.

CONCLUSIONS

Despite high levels of activity, ILR1 demonstrated a strong association with cMSy. This suggests that even in active older adults, sedentary behavior is associated with increasing cardiometabolic risk.

Apolipoproteins E and CIII interact to regulate HDL metabolism and coronary heart disease risk

BACKGROUND

Subspecies of HDL contain apolipoprotein E (apoE) and/or apoCIII. Both proteins have properties that could affect HDL metabolism. The relation between HDL metabolism and risk of coronary heart disease (CHD) is not well understood.

METHODS

Eighteen participants were given a bolus infusion of [D3]L-leucine to label endogenous proteins on HDL. HDL was separated into subspecies containing apoE and/or apoCIII and then into 4 sizes. Metabolic rates for apoA-I in HDL subspecies and sizes were determined by interactive modeling. The concentrations of apoE in HDL that contain or lack apoCIII were measured in a prospective study in Denmark including 1,949 incident CHD cases during 9 years.

RESULTS

HDL containing apoE but not apoCIII is disproportionately secreted into the circulation, actively expands while circulating, and is quickly cleared. These are key metabolic steps in reverse cholesterol transport, which may protect against atherosclerosis. ApoCIII on HDL strongly attenuates these metabolic actions of HDL apoE. In the epidemiological study, the relation between HDL apoE concentration and CHD significantly differed depending on whether apoCIII was present. HDL apoE was associated significantly with lower risk of CHD only in the HDL subspecies lacking apoCIII.

CONCLUSIONS

ApoE and apoCIII on HDL interact to affect metabolism and CHD. ApoE promotes metabolic steps in reverse cholesterol transport and is associated with lower risk of CHD. ApoCIII, when coexisting with apoE on HDL, abolishes these benefits. Therefore, differences in metabolism of HDL subspecies pertaining to reverse cholesterol transport are reflected in differences in association with CHD.

TRIAL REGISTRATION

Clinicaltrials.gov NCT01399632.

FUNDING

This work was supported by NIH grant R01HL095964 to FMS and by a grant to the Harvard Clinical and Translational Science Center (8UL1TR0001750) from the National Center for Advancing Translational Science.

Metabolic effects of fluvastatin extended release 80 mg and atorvastatin 20 mg in patients with type 2 diabetes mellitus and low serum high-density lipoprotein cholesterol levels: a 4-month, prospective, open-label, randomized, blinded-end point (probe) trial

BACKGROUND

Diabetic dyslipidemia is characterized by greater triglyceridation of all lipoproteins and low levels of plasma high-density lipoprotein cholesterol (HDL-C). In this condition, the serum level of low-density lipoprotein cholesterol (LDL-C) is only slightly elevated. The central role of decreased serum HDL-C level in diabetic cardiovascular disease has prompted the establishment of a target of ≥50 mg/dL in patients with diabetes mellitus (DM).

OBJECTIVE

The aim of the study was to assess the effects of once-daily administration of fluvastatin extended release (XL) 80 mg or atorvastatin 20 mg on serum HDL-C levels in patients with type 2 DM and low levels of serum HDL-C.

METHODS

This 4-month, prospective, open-label, randomized, blinded-end point (PROBE) trial was conducted at Endocrinology and Diabetology Service, L. Sacco-Polo University Hospital (Milan, Italy). Patients aged 45 to 71 years with type 2 DM receiving standard oral antidiabetic therapy, with serum HDL-C levels <50 mg/dL, and with moderately high serum levels of LDL-C and triglycerides (TG) were enrolled. After 1 month of lifestyle modification and dietary intervention, patients who were still showing a decreased HDL-C level were randomized, using a 1:1 ratio, to receive fluvastatin XL 80-mg tablets or atorvastatin 20-mg tablets, for 3 months. Lipoprotein metabolism was assessed by measuring serum levels of LDL-C, HDL-C, TG, apolipoprotein (apo) A-I (the lipoprotein that carries HDL), and apo B (the lipoprotein that binds very low-density lipoprotein cholesterol, intermediate-density lipoprotein, and LDL on a molar basis). Patients were assessed every 2 weeks for treatment compliance and subjective adverse events. Serum creatine phosphokinase and liver enzymes were assessed before the run-in period, at the start of the trial, and at 1 and 3 months during the study.

RESULTS

One hundred patients were enrolled (50 patients per treatment group; fluvastatin XL group: 33 men, 17 women; mean [SD] age, 58 [12] years; atorvastatin group: 39 men, 11 women; mean [SD] age, 59 [11] years). In the fluvastatin group after 3 months of treatment, mean (SD) LDL-C decreased from 149 (33) to 95 (25) mg/dL (36%; P < 0.01), TG decreased from 437 (287) to 261 (164) mg/dL (40%; P < 0.01), and HDL-C increased from 41 (7) to 46 (10) mg/dL (12%; P < 0.05). In addition, apo A-I increased from 118 (18) to 124 (15) mg/dL (5%; P < 0.05) and apo B decreased from 139 (27) to 97 (19) mg/dL (30%; P < 0.05). In the atorvastatin group, LDL-C decreased from 141 (25) to 84 (23) mg/dL (40%; P < 0.01) and TG decreased from 411 (271) to 221 (87) mg/dL (46%; P < 0.01). Neither HDL-C (41 [7] vs 40 [6] mg/dL; 2%) nor apo A-I (117 [19] vs 114 [19] mg/dL; 3%) changed significantly. However, apo B decreased significantly, from 131 (20) to 92 (17) mg/dL (30%; P < 0.05). Mean changes in HDL-C (+5 [8] vs -1 [2] mg/dL; P < 0.01) and apo A-I (+6 [18] mg/dL vs -3 [21] mg/dL; P < 0.01) were significantly greater in the fluvastatin group than in the atorvastatin group, respectively. However, the decreases in LDL-C (54 [31] vs 57 [32] mg/ dL), TG (177 [219] vs 190 [65] mg/dL), and apo B (42 [26] vs 39 [14] mg/dL) were not significantly different between the fluvastatin and atorvastatin groups, respectively. No severe adverse events were reported.

CONCLUSIONS

Fluvastatin XL 80 mg and atorvastatin 20 mg achieved mean serum LDL-C (≤ 100 mg/dL) and apo B target levels (≤ 100 mg/dL) in the majority of this population of patients with type 2 DM, but mean serum HDL-C level was increased significantly only with fluvastatin-16 patients (32%) in the fluvastatin group compared with none in the atorvastatin group achieved HDL-C levels ≥50 mg/dL. The increase in HDL-C in the fluvastatin-treated patients was associated with an increase in apo A-I, suggesting a potential pleiotropic and selective effect in patients with low HDL-C levels.

The effect of hepatic lipase on coronary artery disease in humans is influenced by the underlying lipoprotein phenotype

Increased or decreased hepatic lipase (HL) activity has been associated with coronary artery disease (CAD). This is consistent with the findings that gene variants that influence HL activity were associated with increased CAD risk in some population studies but not in others. In this review, we will explain the conditions that influence the effects of HL on CAD. Increased HL is associated with smaller and denser LDL (sdLDL) and HDL (HDL(3)) particles, while decreased HL is associated with larger and more buoyant LDL and HDL particles. The effect of HL activity on CAD risk is dependent on the underlying lipoprotein phenotype or disorder. Central obesity with hypertriglyceridemia (HTG) is associated with high HL activity that leads to the formation of sdLDL that is pro-atherogenic. In the absence of HTG, where large buoyant cholesteryl ester-enriched LDL is prominent, elevation of HL does not raise the risk for CAD. In HTG patients, drug therapy that decreases HL activity selectively decreases sdLDL particles, an anti-atherogenic effect. Drug therapy that raises HDL(2) cholesterol has not decreased the risk for CAD. In trials where inhibition of cholesterol ester transfer protein (CETP) or HL occurs, the increase in HDL(2) most likely is due to inhibition of catabolism of HDL(2) and impairment of reverse cholesterol transport (RCT). In patients with isolated hypercholesterolemia, but with normal triglyceride levels and big-buoyant LDL particles, an increase in HL activity is beneficial; possibly because it increases RCT. Drugs that lower HL activity might decrease the risk for CAD only in hypertriglyceridemic patients with sdLDL by selectively clearing sdLDL particles from plasma, which would override the potentially pro-atherogenic effect on RCT. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Role of plasma phospholipid transfer protein in lipid and lipoprotein metabolism

The understanding of the physiological and pathophysiological role of PLTP has greatly increased since the discovery of PLTP more than a quarter of century ago. A comprehensive review of PLTP is presented on the following topics: PLTP gene organization and structure; PLTP transfer properties; different forms of PLTP; characteristics of plasma PLTP complexes; relationship of plasma PLTP activity, mass and specific activity with lipoprotein and metabolic factors; role of PLTP in lipoprotein metabolism; PLTP and reverse cholesterol transport; insights from studies of PLTP variants; insights of PLTP from animal studies; PLTP and atherosclerosis; PLTP and signal transduction; PLTP in the brain; and PLTP in human disease. PLTP's central role in lipoprotein metabolism and lipid transport in the vascular compartment has been firmly established. However, more studies are needed to further delineate PLTP's functions in specific tissues, such as the lung, brain and adipose tissue. Furthermore, the specific role that PLTP plays in human diseases, such as atherosclerosis, cancer, or neurodegenerative disease, remains to be clarified. Exciting directions for future research include evaluation of PLTP's physiological relevance in intracellular lipid metabolism and signal transduction, which undoubtedly will advance our knowledge of PLTP functions in health and disease. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Glimepiride increases high-density lipoprotein cholesterol via increasing adiponectin levels in type 2 diabetes mellitus

The aims of the present study are to investigate the effect of glimepiride 1 mg/d on plasma adiponectin and to assess the contribution of adiponectin in changing high-density lipoprotein cholesterol (HDL-c) levels after glimepiride treatment. Forty patients with type 2 diabetes mellitus were included. Plasma adiponectin, fasting plasma glucose, insulin, hemoglobin A(1c), and cholesterol were measured at study entry and after 3 months of treatment with glimepiride. Both plasma adiponectin level (7.5 +/- 4.5 vs 8.3 +/- 4.5 microg/mL, P = .040) and HDL-c level increased significantly (50 +/- 11 vs 53 +/- 10 mg/dL, P = .041) in the all-subjects group. In the low-adiponectin group (initial plasma adiponectin level <6 microg/mL), both plasma adiponectin level (4.5 +/- 0.9 vs 5.9 +/- 2.0 microg/mL, P = .004) and HDL-c level increased significantly (44 +/- 8 vs 49 +/- 9 mg/dL, P = .011). There was no significant change in the high-adiponectin group (initial plasma adiponectin level >or=6 microg/mL). Change in plasma adiponectin level was an independent factor for change in HDL-c level after adjustment for other factors (beta = .574, P = .009, R(2) = 0.524, P = .036). In conclusion, glimepiride improved plasma adiponectin level, especially in the subjects with type 2 diabetes mellitus with low adiponectin level before treatment, and may directly contribute to improving HDL-c level.

Oral but not transdermal estrogen replacement therapy changes the composition of plasma lipoproteins

The role of hormone replacement therapy and estrogen replacement therapy (ERT) in cardiovascular disease prevention has not been unambiguously defined yet. The metabolic effects of estrogens may vary depending upon the route of administration. Therefore, we compared the impact of unopposed oral or transdermal ERT on plasma lipids and lipoproteins in 41 hysterectomized women. This was an open-label, randomized, crossover study (with 2 treatments and 2 periods). The 41 hysterectomized women were randomized to receive oral or transdermal 17beta-estradiol in the first or second of two 12-week study periods. Plasma lipid and lipoprotein levels were assayed before and after each treatment using standard automated methods. Lipid content of lipoprotein subclasses was assessed by sequential ultracentrifugation. The atherogenic index of plasma (AIP) was calculated as log(triglyceride [TG]/high-density lipoprotein [HDL] cholesterol). The difference between the 2 forms of administration was tested using a linear mixed model. The change from baseline for each of the forms was tested using paired t test. Oral ERT resulted in a significant increase in HDL cholesterol and apolipoprotein A-I levels, whereas it significantly decreased total and low-density lipoprotein (LDL) cholesterol and increased TG concentrations. Transdermal ERT had no such effect. Oral ERT led to a significant TG enrichment of HDL (0.19 +/- 0.06 vs 0.27 +/- 0.07 mmol/L, P < .001) and LDL particles (0.23 +/- 0.08 vs 0.26 +/- 0.10 mmol/L, P < .001) compared with baseline, whereas transdermal therapy did not have any effect on lipoprotein subclasses composition. The difference between the 2 treatments was statistically significant for HDL-TG and LDL-TG (0.27 +/- 0.07 vs 0.19 +/- 0.05 mmol/L, P < .001 and 0.26 +/- 0.10 vs 0.22 +/- 0.07 mmol/L, P< .001, respectively). The transdermal but not oral ERT significantly reduced the AIP compared with baseline (-0.17 +/- 0.26 vs -0.23 +/- 0.25, P = .023), making the difference between the therapies statistically significant (-0.23 +/- 0.25 vs -0.18 +/- 0.22, P = .017). Oral administration of ERT resulted in TG enrichment of LDL and HDL particles. Transdermal ERT did not change the composition of the lipoproteins and produced a significant improvement of AIP. Compared with transdermal ERT, orally administered ERT changes negatively the composition of plasma lipoproteins.

Plasma phospholipid transfer protein activity, a determinant of HDL kinetics in vivo

OBJECTIVE

Phospholipid transfer protein (PLTP) is an important regulator in the transport of surface components of triglyceride-rich lipoprotein (TRL) to high density lipoprotein (HDL) during lipolysis and may therefore play an important role in regulating HDL transport. In this study we investigated the relationship of plasma PLTP activity with HDL metabolism in men.

DESIGN AND METHODS

The kinetics of HDL LpA-I and LpA-I:A-II were measured using intravenous administration of [D3]-leucine, gas chromatography-mass spectrometry (GCMS) and a new multicompartmental model for HDL subpopulation kinetics (SAAM II) in 31 men with wide-ranging body mass index (BMI 18-46 kg/m2). Plasma PLTP activity was determined as the transfer of radiolabelled phosphatidylcholine from small unilamellar phosphatidylcholine vesicles to ultracentrifugally isolated HDL.

RESULTS

PLTP activity was inversely associated with LpA-I concentration and production rate (PR) after adjusting for insulin resistance (P < 0.05). No significant associations were observed between plasma PLTP activity and LpA-I fractional catabolic rate (FCR). In multivariate analysis, including homeostasis model assessment score (HOMA), triglyceride, cholesteryl ester transfer protein (CETP) activity and PLTP activity, PLTP activity was the only significant determinant of LpA-I concentration and PR (P = 0.020 and P = 0.016, respectively).

CONCLUSIONS

Plasma PLTP activity may be a significant, independent determinant of LpA-I kinetics in men, and may contribute to the maintenance of the plasma concentration of these lipoprotein particles in setting of hypercatabolism of HDL.

Effects of fluvastatin slow-release (XL 80 mg) versus simvastatin (20 mg) on the lipid triad in patients with type 2 diabetes

The lipid triad is the association of small, dense (sd) low-density lipoprotein (LDL), low high-density lipoprotein (HDL), and hypertriglyceridemia, all of which play a role in coronary artery disease in patients with type 2 diabetes. Although statins have demonstrated clear positive effects on cardiovascular morbidity/mortality in patients with diabetes and on single components of the lipid triad, it remains controversial whether they affect all components of the triad in these patients. Therefore, we performed a single-center, parallel-group, prospective, randomized, open-label, blinded-endpoint (PROBE)-type comparison of fluvastatin extended-release (XL) 80 mg (n=48) and simvastatin 20 mg (n=46), each given once daily for 2 months to patients with type 2 diabetes with the lipid triad, who were enrolled after a 1-month lifestyle modification and dietary intervention program. After fluvastatin therapy, LDL (-51%; P<.01), apolipoprotein B (ApoB; -33%; P<.01), intermediate-density LDL (idLDL) (-14.3%; P<.05), sdLDL (-45%; P<.01), and triglycerides (-38%; P<.01) were significantly decreased, and HDL (+14.3%; P<.05) and apolipoprotein A-I (ApoA-I; +7%; P<.05) were increased; large buoyant (lb) LDL did not change (P=NS). Simvastatin therapy decreased LDL (-55.1%; P<.01), ApoB (-46%; P<.01), lbLDL (-33.3%; P<.05), idLDL (-22.7%; P<.05), sdLDL (-33.3%; P<.05), and triglycerides (-47.9%; P<.01); HDL was not changed (P=NS) after simvastatin, but ApoA-I was increased (+11.3%; P<.01). HDL increases (P<.01) and sdLDL decreases (P<.01) were significantly greater after fluvastatin compared with simvastatin therapy; LDL, triglycerides, ApoB, and idLDL changes were similar after both therapies (P=NS), and lbLDL decreases were greater with simvastatin therapy (P<.05). With both treatments, classic mean LDL and ApoB target levels were achieved in most patients. We conclude that the lipid triad can be controlled with fluvastatin XL 80 mg in patients with type 2 diabetes.

Low plasma adiponectin levels are associated with increased hepatic lipase activity in vivo

OBJECTIVE

Hepatic lipase plays a key role in hydrolyzing triglycerides and phospholipids present in circulating plasma lipoproteins. Plasma hepatic lipase activity is known to be regulated by several hormonal and metabolic factors, but hepatic lipase responsiveness to insulin is still controversial. Hypoadiponectinemia is known to be associated with insulin resistance, diabetes, and obesity. These conditions are often characterized by high plasma triglyceride and low HDL cholesterol levels, and they have been shown to be associated with high plasma hepatic lipase activity. We therefore raised the question whether adiponectin may be associated with plasma hepatic lipase activity in vivo.

RESEARCH DESIGN AND METHODS

We measured plasma adiponectin and postheparin hepatic lipase activity in 206 nondiabetic men and in a second group of 110 patients with type 2 diabetes. The correlation of these parameters with markers of insulin resistance and systemic inflammation was investigated.

RESULTS

In nondiabetic patients, adiponectin levels were significantly inversely correlated with plasma hepatic lipase activity (r = -0.4, P < 0.01). These results were confirmed in the group of patients with type 2 diabetes (r = -0.32, P = 0.004). Multivariate analysis revealed that adiponectin was the strongest factor influencing hepatic lipase activity. The association was independent of age, sex, BMI, plasma triglycerides, insulin, HDL cholesterol, and high-sensitivity C-reactive protein and accounted for approximately 10 and 12% of the variation in hepatic lipase activity in the two different patient cohorts, respectively.

CONCLUSIONS

These results demonstrate for the first time a significant inverse association between adiponectin and postheparin plasma hepatic lipase activity that is independent of other factors such as markers of insulin resistance or inflammation. Therefore, adiponectin, rather than insulin, may represent an important factor contributing to the regulation of hepatic lipase activity in both nondiabetic individuals and patients with type 2 diabetes. The effect of adiponectin on hepatic lipase activity may also help to explain the HDL cholesterol-elevating action of adiponectin.

Effects of peroxisome proliferator-activated receptor alpha/delta agonists on HDL-cholesterol in vervet monkeys

The objective of this study was to demonstrate the efficacy of a novel peroxisome proliferator-activated receptor (PPAR) agonist and known PPARalpha and PPARdelta agonists to increase HDL-cholesterol (HDL-C) in the St. Kitts vervet, a nonhuman primate model of atherosclerosis. Four groups (n = 6) were studied and each group was assigned one of the following "treatments": a) vehicle only (vehicle); b) the PPARdelta selective agonist GW501516 (GW); c) the PPARalpha/delta agonist T913659 (T659); and d) the PPARalpha agonist TriCor (fenofibrate). No statistically significant changes were seen in body weight, total plasma cholesterol, plasma triglycerides, VLDL-C, LDL-C, or apolipoprotein B (apoB) concentrations. Each of the PPARalpha and PPARdelta agonists investigated in this study increased plasma HDL-C, apoA-I, and apoA-II concentrations and increased HDL particle size in St. Kitts vervets. The maximum percentage increase in HDL-C from baseline for each group was as follows: vehicle, 5%; GW, 43%; T659, 43%; and fenofibrate, 20%. Treatment with GW and T659 resulted in an increase in medium-sized HDL particles, whereas fenofibrate showed increases in large HDL particles. These data provide additional evidence that PPARalpha and PPARdelta agonists (both mixed and selective) have beneficial effects on HDL-C in these experimental primates.

Emerging roles for phospholipid transfer protein in lipid and lipoprotein metabolism

PURPOSE OF REVIEW

This review highlights the recent key advances in our understanding of the role of phospholipid transfer protein in lipid and lipoprotein metabolism.

RECENT FINDINGS

The overexpression of human phospholipid transfer protein in mice is associated with an increase in atherosclerosis. This is consistent with earlier studies using mouse models suggesting that phospholipid transfer protein was pro-atherogenic. The presence of phospholipid transfer protein in macrophages and atherosclerotic lesions suggests that it could be either anti-atherogenic by facilitating lipid efflux or pro-atherogenic by facilitating lipid retention. Phospholipid transfer protein may also be a key player in reverse cholesterol transport, as it interacts with the adenosine triphosphate-binding cassette transporter A1 and facilitates lipid efflux from peripheral cells. Both the release of chymase, a neutral protease, from mast cells and the oxidation of HDL by hypochlorous acid can impair the function of phospholipid transfer protein in reverse cholesterol transport. Studies of phospholipid transfer protein-mediated phospholipid transfer activity in humans support a role for phospholipid transfer protein in hypertriglyceridemia, obesity, diabetes, inflammation and coronary artery disease, and in the modulation of LDL particle density and size. Furthermore, recent evidence suggests that phospholipid transfer protein may play a role in reproductive processes, in lipid and lipoprotein metabolism in the central nervous system, and in neurodegenerative disease.

SUMMARY

Phospholipid transfer protein is emerging as a multifaceted and multifunctional player in lipid and lipoprotein metabolism, but much additional work will be required to understand the significance of these recent findings for clinical practice.