Two patterns of LDL metabolism in normotriglyceridemic patients with hypoalphalipoproteinemia

Different emergence phenology of European grapevine moth (Lobesia botrana, Lepidoptera: Tortricidae) on six varieties of grapes

The phenology of insect emergence affects reproductive success and is especially critical in short-lived species. An increasing number of studies have documented the effects of thermal and other climatic variations and of unpredictable habitats on the timing of adult insect emergence within and between populations and years. Numerous interacting factors may affect the phenology of adult emergence. Host-plant quality and availability is a key factor that has been largely neglected in studies of the phenology of phytophagous insects. The purpose of this study was to determine the effect of host plant characteristics on the rate of larval growth and the pattern of emergence in a wild population of Lobesia botrana (European grapevine moth), a significant pest in European vineyards. The phenology of emergence differed significantly among the six tested varieties of grapes. The percentage of bunches harboring pupae was similar among the different grape varieties, and the total number of pupae collected was similar to the number of emerging adults per bunch. Among the six varieties of grapes, 0-25 pupae were produced on each bunch. Each of the grape varieties had a single wave of emergence, in which males emerged before females, but their emergence phenology differed significantly in Chardonnay, Chasselas, and Pinot grapes. Both genders had extended durations of emergence in Merlot grapes. Together, the present results show that the characteristics of the grape host plant affect the emergence phenology of L. botrana.

Reference distributions for apolipoproteins AI and B and B/AI ratios: comparison of a large cohort to the world's literature

Limiting the clinical utility of apolipoproteins AI (apo AI) and B (apo B) and the apo B/AI ratios until the last decade has been the lack of satisfactory methods for quantifying serum levels and credible reference materials. Great technological strides have been made in the last few years. The remaining barrier to more relevant and cost-effective use of serum protein data for diagnosis and prognosis has been the availability of widely recognized reliable reference intervals from birth to old age for both males and females. A total of 82 publications reporting reference intervals have been identified that meet most of the same inclusion criteria used in our prior six studies. These have been analyzed statistically and compared to similar studies, i.e., sufficient number, listed subject criteria, method, and reference material, in general terms. Published smaller studies with constrained age ranges, agree on average with our large series of life-long reference intervals that range from less than one year to over 80 years. This study was performed to assess the degree of agreement between smaller reference interval studies to our large population analysis. This meta-analysis provides support and reassurance that many of the smaller reference intervals published previously fall within reasonable limits of out large population.

Hypercholesterolemia and Dyslipidemia

Disorders of cholesterol and lipoprotein metabolism are at the heart of atherosclerosis and coronary artery disease (CAD). CAD, however, is a metabolic disorder that involves a complex interaction between genetic susceptibility and environmental conditions. Despite considerable success in the treatment of hypercholesterolemia, atherosclerosis remains the leading cause of death in most Western countries. Although cholesterol-lowering trials have revealed a 25% to 30% reduction in clinical events, most patients continue to have events even when treated successfully with cholesterol-lowering medications (Fig. 1). This less-than-optimal result is partly because atherosclerosis is a multifactorial disease. Although disorders of lipoprotein metabolism are found in more than 80% of patients with CAD, these disorders are very heterogeneous, and single-drug therapy aimed at one disorder should not be expected to improve the disease status in most patients. Metabolic treatment still requires identification and treatment of patients with high cholesterol levels, but the focus has shifted to identifying high-risk patients in groups previously thought to be low risk, or to identifying disorders coexistent with high cholesterol levels that are not corrected by standard cholesterol-lowering medications (Table 1). The ability to detect high-risk CAD traits, which are often inherited, and to predict response to treatment has substantially improved in the past few years. These improvements allow identification of metabolic subgroups of patients, which can alter risk prediction and response to specific treatments. Sophisticated laboratory methods permit physicians to apply this knowledge to patient care and to enter a new era of CAD risk factor detection and treatment. These advances allow for a more scientific approach than did the previously standard epidemiologic risk factors and routine blood lipid profiles. The current state-of-the-art method of diagnosing and treating lipoprotein disorders has progressed beyond the standard "lipid profile," which includes total, low-density lipoprotein (LDL), and high-density lipoprotein (HDL) cholesterol along with fasting triglyceride levels. Incorporating aspects of the atherogenic lipid profile (ALP), LDL subclass distribution, HDL subclass distribution, apo E isoforms, and lipoprotein (a) provides the interested clinician with the tools to create a more detailed and accurate diagnosis of lipoprotein disorders. Sophisticated laboratory tests are available to clinicians through technology transfer programs, as exemplified by the Lawrence Berkeley National Laboratory/Berkeley HeartLab collaboration, and allow clinicians access to research-quality laboratory tools. This has significant clinical relevance because the presence of these disorders guides treatment specific to the disorder(s). Appropriate treatment is more beneficial in subgroups exhibiting the disorder that the therapy is most likely to correct. A single drug or lifestyle therapy is no longer appropriate for all patients. The treatment must match the disorder.

Effect of lifibrol on the metabolism of low density lipoproteins and cholesterol

Lifibrol is a powerful cholesterol-lowering drug of unknown mechanism of action. This investigation was carried out to determine whether the major action of lifibrol is to enhance clearance of low density lipoproteins (LDL) through the LDL-receptor pathway, and if so, whether the drug exerts its action by altering the excretion of bile acids (acidic steroids), the absorption of cholesterol, or the synthesis of cholesterol. In a first study, in two patients with complete absence of LDL receptors, lifibrol therapy had essentially no effect on plasma LDL concentrations; in two others who had a marked reduction in LDL-receptor activity, response to the drug was attenuated. These findings suggest that lifibrol requires an intact LDL-receptor pathway to exert its action. In a second study, in patients with primary moderate hypercholesterolemia, isotope kinetic studies showed that lifibrol enhanced the fractional catabolic rate of LDL-apolipoprotein B (apo B), but had no effect on transport rates of LDL; these observations likewise support the probability that lifibrol acts mainly to increase the activity of the LDL-receptor pathway. However, in a third study in hypercholesterolemic patients, lifibrol therapy failed to increase acidic steroid excretion, inhibit cholesterol absorption, or reduce net cholesterol balance. Furthermore, lifibrol treatment did not significantly reduce urinary excretion of mevalonic acid. In contrast, in a parallel study, simvastatin therapy, which is known to inhibit cholesterol synthesis, gave the expected decrease in net cholesterol balance and reduction in urinary excretion of mevalonic acid. Thus, lifibrol, like statins, appears to increase the activity of LDL receptors; but in contrast to findings with statins, it was not possible to detect a significant decreased synthesis of cholesterol, either from balance studies or from urinary excretion of mevalonic acid. This finding raises the possibility that lifibrol activates the LDL-receptor pathway through a different mechanisms which remains to be determined.

The role of cholesterol management in coronary disease risk reduction in elderly patients

This article discusses the various factors that must be taken into account and balanced when making decisions about particular therapies for the management of high-serum cholesterol in older persons.

Abnormal metabolism of free fatty acids in hypertriglyceridaemic men: apparent insulin resistance of adipose tissue

OBJECTIVE

There is growing evidence that endogenous hypertriglyceridaemia is frequently accompanied by a state of insulin resistance. The present study was performed to determine whether patients with primary endogenous hypertriglyceridaemia commonly have abnormalities in plasma concentrations and turnover rates of free fatty acids (FFA), which could reflect a state of insulin resistance in adipose tissue and could account for raised plasma triglycerides.

DESIGN

Hypertriglyceridaemic and normotriglyceridemic control patients underwent measurements of plasma concentrations and turnover rates of FFA. Fat weights in both groups were determined by hydrodensitometry, and fat distribution was assessed by skin-folds and measurement of waist and hip circumferences. Other measurements included plasma glucose, insulin, lipids, and lipoproteins.

SUBJECTS

Fifteen men with normal plasma triglycerides and 21 men with primary endogenous hypertriglyceridaemia were studied. Men in both groups varied in body weights and total fat weights, but total fat weights were entirely overlapping for the two groups. Waist-to-hip ratios and waist circumferences also were similar for the two groups.

RESULTS

For any total body fat content or waist circumference, most hypertriglyceridaemia patients had higher mean plasma concentrations of FFA and higher turnover rates (flux) for FFA than did normotriglyceridemic patients. Hypertriglyceridaemic patients also had higher fasting insulin concentrations for a given body fat content. In general, both FFA flux and plasma insulin levels were positively correlated with plasma concentrations of triglyceride and inversely with high density lipoprotein (HDL) cholesterol.

CONCLUSIONS

These studies indicate that many patients with primary endogenous hypertriglyceridaemia have increased flux of FFA and hyperinsulinemia that cannot be explained either by increased total body fat content or by greater waist circumferences than observed in normotriglyceridemic patients.

Hypertriglyceridemia, atherogenic dyslipidemia, and the metabolic syndrome

The importance of high serum cholesterol, especially a high level of low-density lipoprotein (LDL) cholesterol, as a risk factor for coronary artery disease is well established. Likewise, efficacy for decreasing risk for coronary artery disease by LDL-lowering therapy has recently been documented through clinical trials. However, many high-risk patients manifest elevated serum triglyceride levels, and the role of hypertriglyceridemia in causation of coronary artery disease remains to be elucidated. Nonetheless, there is growing evidence that hypertriglyceridemia is a marker for increased risk for coronary artery disease; in fact, it can serve as a marker for several atherogenic factors. These factors include increased concentrations of atherogenic triglyceride-rich lipoproteins; the atherogenic lipoprotein phenotype, or lipid triad; and the metabolic syndrome. The lipid triad consists of elevated serum triglycerides, small LDL particles, and low high-density lipoprotein (HDL) cholesterol. The metabolic syndrome includes the coexistence of the lipid triad, elevated blood pressure, insulin resistance (plus glucose intolerance), and a prothrombotic state. Many previous studies indicate that hypertriglyceridemia is strongly associated with all of these atherogenic factors. The clinical approach to treatment of patients with hypertriglyceridemia thus requires a broad-based strategy that includes reduction of atherogenic triglyceride-rich lipoproteins, reversal of the lipid triad, and favorable modification of the metabolic syndrome. The development of therapeutic regimens to effect these changes poses a challenge for future research on the problem of hypertriglyceridemia.