Richard Havel, Howard Eder, and the evolution of lipoprotein analysis

Eating habits, sleep, and a proxy for circadian disruption are correlated with dyslipidemia in overweight night workers

OBJECTIVE

The aim of this study was to evaluate the relationship between proxy for circadian disruption, eating habits, sleep characteristics, and dyslipidemic parameters.

METHODS

This was a randomized, double-blind, crossover controlled clinical trial, and for this study, only baseline data were used. The sample was composed of 36 overweight female nurses who worked on a fixed night shift (12 × 36 h). Linear regression models were used to assess the relationship between the mentioned variables.

RESULTS

The participants' average age was 39.4 y (Standard error (SE) 1 y) and the average nighttime sleep duration was 5.76 h (SE 0.16 h). The average chronotype indicated a moderate early type (03:03 h; SE 20 min) and the average social jetlag was 03:42 h (SE 10 min). It was found that 1 h less of nighttime sleep increased very-low-density lipoprotein cholesterol levels by 2.75 mg/dL and triacylglyceride levels by 3.62 mg/dL. Additionally, higher social jetlag was associated with higher low-density lipoprotein cholesterol levels. On the other hand, each additional hour in the chronotype increased high-density lipoprotein cholesterol levels by 3.06 mg/dL and a time interval >2 h between the last meal and sleep onset was associated with higher high-density lipoprotein cholesterol levels.

CONCLUSION

Short duration of nighttime sleep and high social jetlag are risk factors for dyslipidemia, whereas the late type and the longer time interval between the last meal and sleep onset appear to be protective factors for dyslipidemia.

The early years of lipoprotein research: from discovery to clinical application

This review outlines major milestones in the first four decades of lipoprotein research beginning with their discovery nearly 90 years ago. It focuses on the contributions of some of the key investigators during this era, and findings that set the stage for widespread clinical implementation of lipoprotein testing for evaluation and management of CVD risk.

Assessing the functional properties of high-density lipoproteins: an emerging concept in cardiovascular research

Although plasma concentrations of high-density lipoprotein (HDL) cholesterol correlate inversely with the incidence of atherosclerotic cardiovascular disease, results from recent epidemiological, genetic and pharmacological intervention studies resulted in a shift of concept. Rather than HDL cholesterol mass levels, the functionality of HDL particles is increasingly regarded as potentially clinically important. This review provides an overview of four key functional properties of HDL, namely cholesterol efflux and reverse cholesterol transport; antioxidative activities; anti-inflammatory activities; and the ability of HDL to increase vascular nitric oxide production resulting in vasorelaxation. Currently available assays are put into context with different HDL isolation procedures yielding compositional heterogeneity of the particle. Gathered knowledge on the impact of different disease states on HDL function is discussed together with potential underlying causative factors modulating HDL functionalities. In addition, a perspective is provided regarding how a better understanding of the determinants of (dys)functional HDL might impact clinical practice and the future design of rational and specific therapeutic approaches targeting atherosclerotic cardiovascular disease.

Comparison of lipoprotein separation and lipid analysis methodologies for human and cynomolgus monkey plasma samples

To assess cardiovascular risk in both clinical and basic research settings, it is imperative to be able to accurately measure plasma lipid levels. Here, methods commonly used to measure lipoproteins and lipids: ultracentrifugation (UC), fast protein liquid chromatography (FPLC), Roche auto-analyzer, and enzymatic assays were tested and compared. Plasma samples from 20 healthy humans and 22 cynomolgus monkeys were analyzed for their total cholesterol (TC), cholesterol in low density lipoproteins (LDL) and high density lipoproteins (HDL), and triglycerides (TG). Major lipid classes from UC and FPLC separated lipoprotein fractions from human plasma were further characterized by liquid chromatography-mass spectrometry analysis. All the tested methods showed acceptable performance with Roche analyzer among the best in approximate dilution linearity and recovery for most lipids as well as in repeatability between measurements of the same samples. TC, LDL, HDL, and TG values measured in human vs. monkey were-183.9 ± 35.5 (mean ± SD) vs. 105.6 ± 24.6 mg/dl, 106.0 ± 30.1 vs. 42.8 ± 13.0 mg/dl, 50.0 ± 11.4 vs. 53.4 ± 14.8 mg/dl, and 107.6 ± 50.7 vs. 58.0 ± 52.3 mg/dl. While no single method was uniformly the best, we recommend the Roche analyzer for routine measurements. UC or FPLC separation is needed for further functional characterization for specific lipid fraction. We have shown athero-protective profile in cynomolgus monkey compared with humans.

Triglyceride-rich lipoproteins and plasma lipid transport

This memoir provides a history of the triglyceride-rich lipoproteins of blood plasma over the last half-century. As precursors of low-density lipoproteins and in their own right, triglyceride-rich lipoproteins are essential to the formation of atherosclerotic plaques and to consequent ischemic vascular disease. The author recounts research at the National Heart Institute during 1953 to 1956 and continuing thereafter at the University of California San Francisco. Emphasis is placed on key insights arising from investigations of human disease, the interplay of fatty acid and triglyceride-transport involving the liver, small intestine, adipose tissue and muscle, and the role of the liver in the synthesis and catabolism of atherogenic lipoproteins.

Improved cholesterol phenotype analysis by a model relating lipoprotein life cycle processes to particle size

Increased plasma cholesterol is a known risk factor for cardiovascular disease. Lipoprotein particles transport both cholesterol and triglycerides through the blood. It is thought that the size distribution of these particles codetermines cardiovascular disease risk. New types of measurements can determine the concentration of many lipoprotein size-classes but exactly how each small class relates to disease risk is difficult to clear up. Because relating physiological process status to disease risk seems promising, we propose investigating how lipoprotein production, lipolysis, and uptake processes depend on particle size. To do this, we introduced a novel model framework (Particle Profiler) and evaluated its feasibility. The framework was tested using existing stable isotope flux data. The model framework implementation we present here reproduced the flux data and derived lipoprotein size pattern changes that corresponded to measured changes. It also sensitively indicated changes in lipoprotein metabolism between patient groups that are biologically plausible. Finally, the model was able to reproduce the cholesterol and triglyceride phenotype of known genetic diseases like familial hypercholesterolemia and familial hyperchylomicronemia. In the future, Particle Profiler can be applied for analyzing detailed lipoprotein size profile data and deriving rates of various lipolysis and uptake processes if an independent production estimate is given.

A brief history of lipid and lipoprotein measurements and their contribution to clinical chemistry

The study of modern lipid chemistry began in the 17th and 18th centuries with early observations by Robert Boyle, Poulletier de la Salle, Antoine François de Fourcroy and others. The 19th century chemist, Chevreul, identified several fatty acids, suggested the name 'cholesterine' for the fatty substance in gallstones, coined the word 'glycerine', and showed that fats were comprised of glycerol and fatty acids. The 20th century brought many advances in the understanding of lipoprotein structure and function, and explored relationships between lipoproteins and disease states. The development of the ultracentrifuge and other lipoprotein separation techniques, and reagents for accurate, standardized quantitative measurement have steadily increased our understanding of the important role of lipoprotein metabolism in both healthy and disease states.