John D. Brunzell

Shotgun proteomics implicates protease inhibition and complement activation in the antiinflammatory properties of HDL.

HDL lowers the risk for atherosclerotic cardiovascular disease by promoting cholesterol efflux from macrophage foam cells. However, other antiatherosclerotic properties of HDL are poorly understood. To test the hypothesis that the lipoprotein carries proteins that might have novel cardioprotective activities, we used shotgun proteomics to investigate the composition of HDL isolated from healthy subjects and subjects with coronary artery disease (CAD). Unexpectedly, our analytical strategy identified multiple complement-regulatory proteins and a diverse array of distinct serpins with serine-type endopeptidase inhibitor activity. Many acute-phase response proteins were also detected, supporting the proposal that HDL is of central importance in inflammation. Mass spectrometry and biochemical analyses demonstrated that HDL3 from subjects with CAD was selectively enriched in apoE, raising the possibility that HDL carries a unique cargo of proteins in humans with clinically significant cardiovascular disease. Collectively, our observations suggest that HDL plays previously unsuspected roles in regulating the complement system and protecting tissue from proteolysis and that the protein cargo of HDL contributes to its antiinflammatory and antiatherogenic properties.

Lipoprotein Management in Patients With Cardiometabolic Risk Consensus statement from the American Diabetes Association and the American College of Cardiology Foundation

Risk factors for type 2 diabetes and cardiovascular disease (CVD) often cluster, including obesity (particularly central), insulin resistance, hyperglycemia, dyslipoproteinemia, and hypertension. These conditions can also occur in isolation, and they are exaggerated by physical inactivity and smoking. Since each of these factors increases risk of CVD, the concept of global cardiometabolic risk (CMR) (Fig. 1) is of value (1). Lipoprotein abnormalities, including elevated triglycerides, low HDL cholesterol, and increased numbers of small dense LDL particles, are common findings in patients with CMR. Clinical entities with increased CMR include type 2 diabetes, familial combined hyperlipidemia, familial hypoalphalipoproteinemia, and polycystic ovary syndrome (2). These disorders often share the CMR characteristics of central obesity, insulin resistance, dyslipoproteinemia, and hypertension. There are stringent lipid treatment goals for patients with type 2 diabetes or CVD; however, guidelines for treatment of dyslipoproteinemia in high-risk subjects without diabetes or CVD are less intense and are based primarily on LDL cholesterol concentrations, with non-HDL concentrations a secondary consideration in some subjects. Numerous trials have demonstrated that therapies (primarily statins) directed at LDL cholesterol lowering clearly reduce risk of CVD events in patients with diabetes and in those without diabetes but with other CVD risk factors; yet, a number of questions remain. Even with adequate LDL cholesterol lowering, many patients on statin therapy have significant residual CVD risk. It is unclear whether lipoprotein parameters other than LDL or non-HDL cholesterol provide clinically significant additional prognostic information regarding CVD risk, yield more information about the effectiveness of therapy, or indicate more appropriate treatment targets. Many patients with CMR or diabetes have relatively normal levels of LDL cholesterol but increased numbers of small dense LDL particles and other atherogenic lipoproteins. Some have advocated that assessment of other lipoprotein parameters might be more helpful than assessment limited to LDL or non-HDL …

Lipoprotein Management in Patients With Cardiometabolic Risk : Consensus Conference Report From the American Diabetes Association and the American College of Cardiology Foundation

Risk factors for type 2 diabetes and cardiovascular disease (CVD) often cluster, including obesity (particularly central), insulin resistance, hyperglycemia, dyslipoproteinemia, and hypertension. These conditions can also occur in isolation, and they are exaggerated by physical inactivity and

[8] Single vertical spin density gradient ultracentrifugation

Publisher Summary Density gradient ultracentrifugation in the swing out rotor has been successfully applied to fractionation of the major lipoprotein species and their subspecies; however, it requires a minimum of 24–36 h to complete the separation of the major lipoprotein fractions in plasma. This chapter describes 13 separate vertical spin procedures for the preparative separation of a number of different plasma lipoproteins and a method for the quantitative analysis of lipoprotein cholesterol from plasma separated by single vertical spin (SVS) density gradient ultracentrifugation. The vertical rotor works on the principle that compression of the gradient geometry by the vertical rotor when at speed shortens spin time over more conventional ultracentrifugation techniques without loss of resolution. The single vertical spin procedure has a number of advantages over the more conventional methods including decreased spin time, decreased lipoprotein degradation, and good resolution. But there are certain disadvantages of this method also, such as wall adherence of VLDL and albumin, resolution, and plasma volume limit per rotor. However, the chapter addresses solutions to the problems of single vertical spin ultracentrifugation such as angled-head rotors.

Evidence for a Common, Saturable, Triglyceride Removal Mechanism for Chylomicrons and Very Low Density Lipoproteins in Man

Hypertriglyceridemic subjects were fed diets in which dietary fat calories were held constant, but carbohydrate calories were varied. Three subjects with fasting chylomicronemia (Type V) were given less carbohydrate and four subjects without fasting chylomicronemia (Type IV) were fed diets with more calories as carbohydrate. The restricted carbohydrate intake led to disappearance of chylomicronemia in those subjects who had chylomicronemia on a normal diet (Type V to IV). In those subjects without chylomicronemia, chylomicronemia appeared in response to increased carbohydrate intake (Type IV to V). Thus chylomicron concentrations in plasma were altered even though fat intake and presumably chylomicron input into plasma was kept constant. These findings provide evidence for saturation of chylomicron removal mechanisms by alteration of endogenous triglyceride-rich lipoprotein concentrations. They suggest that chylomicrons compete with very low density lipoproteins for similar removal mechanisms. The relationship between endogenous triglyceride concentration and the lipolytic activity in plasma following heparin was then evaluated with the use of long-term heparin infusions to release and maintain lipolytic activity in the circulation. 10 subjects were placed on fatfree diets to remove circulating dietary fat. The plasma lipolytic rate during the heparin infusion was measured consecutively on different days in individuals whose triglyceride concentrations were varied by either increasing or decreasing calories. The lipolytic rate was curvilinearly related to the plasma triglyceride concentrations. This curvilinear relationship followed Michaelis-Menton saturation kinetics over a wide range of triglyceride concentrations on fat-free, high-carbohydrate diets, in multiple studies in a group of individuals. These studies suggest that endogenous and exogenous triglyceride compete for a common, saturable, plasma triglyceride removal system related to lipoprotein lipase.

Effect of ritonavir on lipids and post-heparin lipase activities in normal subjects

BackgroundIntensive therapy of HIV infection with highly active antiretroviral therapy (HAART) dramatically reduces viral loads and improves immune status. Abnormalities of lipid levels, body fat distribution, and insulin resistance have been commonly reported after starting HAART. Whether the lipid abnormalities result from changes in metabolism after an improvement in HIV status or are partly attributable to the effects of protease inhibitor use is unknown. MethodsTwenty-one healthy volunteers participated in a 2 week double-blind, placebo-controlled study on the effect of the protease inhibitor ritonavir on total lipids, apolipoproteins, and post-heparin plasma lipase activities. ResultsThose taking ritonavir (n = 11) had significantly higher levels of plasma triglyceride, VLDL cholesterol, IDL cholesterol, apolipoprotein B, and lipoprotein (a) compared with placebo (n = 8). HDL cholesterol was lower with therapy as a result of a reduction in HDL3 cholesterol. Post-heparin lipoprotein lipase (LpL) activity did not change but hepatic lipase activity decreased 20% (P < 0.01) in those taking ritonavirrcompared with placebo. Although all lipoprotein subfractions became triglyceride enriched, most of the increase in triglyceride was in VLDL and not in IDL particles. ConclusionTreatment with ritonavir in the absence of HIV infection or changes in body composition results in hypertriglyceridemia that is apparently not mediated by impaired LpL activity or the defective removal of remnant lipoproteins, but could be caused by enhanced formation of VLDL. Long-term studies of patients with HIV infection receiving HAART will be necessary to determine the impact of these drugs and associated dyslipidemia on the risk of coronary artery disease.

Sweet tooth reconsidered: Taste responsiveness in human obesity

Taste responses of normal-weight, obese, and formerly obese individuals for sucrose and fat containing stimuli were examined using a mathematical modelling technique known as the Response Surface Method. The subjects accurately rated intensities of sweetness, fatness, and creaminess of 20 different mixtures of milk, cream, and sugar, and no mixture phenomena or inter-group differences were observed. In contrast, hedonic taste responses varied across subject groups, and were affected differentially by the sucrose and lipid content of the stimuli. Normal-weight subjects optimally preferred stimuli containing 20% lipid and less than 10% sucrose. Obese subjects preferred high-fat stimuli (greater than 34% lipid) that contained less than 5% sucrose, while formerly obese subjects showed enhanced responsiveness to both sugar and fat. Hedonic responsiveness as measured by the optimal sugar/fat ratio was negatively correlated with the degree of overweight (body mass index: weight/height). We hypothesize that sensory preferences for dietary sugars and fats aren determined by body-weight status and may affect the patterns of food consumption.

Evidence for a New Pathophysiological Mechanism for Coronary Artery Disease Regression Hepatic Lipase–Mediated Changes in LDL Density

BACKGROUND Small, dense LDL particles are associated with coronary artery disease (CAD) and predict angiographic changes in response to lipid-lowering therapy. Intensive lipid-lowering therapy in the Familial Atherosclerosis Treatment Study (FATS) resulted in significant improvement in CAD. This study examines the relationship among LDL density, hepatic lipase (HL), and CAD progression, identifying a new biological mechanism for the favorable effects of lipid-altering therapy. METHODS AND RESULTS Eighty-eight of the subjects in FATS with documented coronary disease, apolipoprotein B levels >/=125 mg/dL, and family history of CAD were selected for this study. They were randomly assigned to receive lovastatin (40 mg/d) and colestipol (30 g/d), niacin (4 g/d) and colestipol, or conventional therapy with placebo alone or with colestipol in those with elevated LDL cholesterol levels. Plasma hepatic lipase (HL), lipoprotein lipase, and LDL density were measured when subjects were and were not receiving lipid-lowering therapy. LDL buoyancy increased with lovastatin-colestipol therapy (7.7%; P<0.01) and niacin-colestipol therapy (10.3%; P<0.01), whereas HL decreased in both groups (-14% [P<0.01] and -17% [P<0.01] with lovastatin-colestipol and niacin-colestipol, respectively). Changes in LDL buoyancy and HL activity were associated with changes in disease severity (P<0.001). In a multivariate analysis, an increase in LDL buoyancy was most strongly associated with CAD regression, accounting for 37% of the variance of change in coronary stenosis (P<0.01), followed by reduction in apolipoprotein Bl (5% of variance; P<0.05). CONCLUSIONS These studies support the hypothesis that therapy-associated changes in HL alter LDL density, which favorably influences CAD progression. This is a new and potentially clinically relevant mechanism linking lipid-altering therapy to CAD improvement.

Evaluation and treatment of hypertriglyceridemia: an Endocrine Society clinical practice guideline.

OBJECTIVE The aim was to develop clinical practice guidelines on hypertriglyceridemia. PARTICIPANTS The Task Force included a chair selected by The Endocrine Society Clinical Guidelines Subcommittee (CGS), five additional experts in the field, and a methodologist. The authors received no corporate funding or remuneration. CONSENSUS PROCESS Consensus was guided by systematic reviews of evidence, e-mail discussion, conference calls, and one in-person meeting. The guidelines were reviewed and approved sequentially by The Endocrine Societys CGS and Clinical Affairs Core Committee, members responding to a web posting, and The Endocrine Society Council. At each stage, the Task Force incorporated changes in response to written comments. CONCLUSIONS The Task Force recommends that the diagnosis of hypertriglyceridemia be based on fasting levels, that mild and moderate hypertriglyceridemia (triglycerides of 150-999 mg/dl) be diagnosed to aid in the evaluation of cardiovascular risk, and that severe and very severe hypertriglyceridemia (triglycerides of > 1000 mg/dl) be considered a risk for pancreatitis. The Task Force also recommends that patients with hypertriglyceridemia be evaluated for secondary causes of hyperlipidemia and that subjects with primary hypertriglyceridemia be evaluated for family history of dyslipidemia and cardiovascular disease. The Task Force recommends that the treatment goal in patients with moderate hypertriglyceridemia be a non-high-density lipoprotein cholesterol level in agreement with National Cholesterol Education Program Adult Treatment Panel guidelines. The initial treatment should be lifestyle therapy; a combination of diet modification and drug therapy may also be considered. In patients with severe or very severe hypertriglyceridemia, a fibrate should be used as a first-line agent.

Myocardial infarction in the familial forms of hypertriglyceridemia

Among 74 hypertriglyceridemic patients who were referred for study because of hypertriglyceridemia, family investigations detected 19 with familial hypertriglyceridemia and 24 with familial combined hyperlipidemia. The frequency of myocardial infarction among adult living hyperlipidemic relatives of patients with familial combined hyperlipidemia was 17.5% (10/57). Five of these relatives had their infarct between the ages of 40 and 50 yr of age, and five before the age of 40 yr. The frequency of myocardial infarction in living hyperlipedemic relatives with familial hypertriglyceridemia was 4.7% (2/43) and was similar to the frequency of myocardial infarction among normolipidemic relatives (4.5%) or among spouse controls (5.2%). Mortality data due to myocardial infarction among relatives of index patients failed to contribute meaningful information.