Lipoprotein and apolipoprotein abnormalities in familial combined hyperlipidemia: a 20-year prospective study

The toxicity assessment of phosmet on development, reproduction, and gene expression in Daphnia magna

The use of pesticides to control pests, weeds, and diseases or to regulate plant growth is indispensable in agricultural production. However, the excessive use of these chemicals has led to significant concern about their potential negative impacts on health and the environment. Phosmet is one such pesticide that is commonly used on plants and animals against cold moth, aphids, mites, suckers, and fruit flies. Here, we investigated the effects of phosmet on a model organism, Daphnia magna using acute and chronic toxicity endpoints such as lethality, mobility, genotoxicity, reproduction, and gene expression. We performed survival experiments in six-well plates at seven different concentrations (0.01, 0.1, 1, 10, 25, 50, 100 μM) as well as the control in three replicates. We observed statistically significant mortality rates at 25 µM and above upon 24 h of exposure, and at 1 µM and above following 48 h of exposure. Genotoxicity analysis, reproduction assay and qPCR analysis were carried out at concentrations of 0.01 and 0.1 μM phosmet as these concentrations did not show any lethality. Comet assay showed that exposure to phosmet resulted in significant DNA damage in the cells. Interestingly, 0.1 μM phosmet produced more offspring per adult compared to the control group indicating a hormetic response. Gene expression profiles demonstrated several genes involved in different physiological pathways, including oxidative stress, detoxification, immune system, hypoxia and iron homeostasis. Taken together, our results indicate that phosmet has negative effects on Daphnia magna in a dose- and time-dependent manner and could also induce lethal and physiological toxicities to other aquatic organisms.

Endothelial Lipid Metabolism

Endothelial cells (ECs) line all vessels of all vertebrates and are fundamental to organismal metabolism. ECs rely on their metabolism both to transport nutrients in and out of underlying parenchyma, and to support their own cellular activities, including angiogenesis. ECs primarily consume glucose, and much is known of how ECs transport and consume glucose and other carbohydrates. In contrast, how lipids are transported, and the role of lipids in normal EC function, has garnered less attention. We review here recent developments on the role of lipids in endothelial metabolism, with a focus on lipid uptake and transport in quiescent endothelium, and the use of lipid pathways during angiogenesis.

Polygenic architecture and cardiovascular risk of familial combined hyperlipidemia

BACKGROUND AND AIMS

Familial combined hyperlipidemia (FCHL) is one of the most common inherited lipid phenotypes, characterized by elevated plasma concentrations of apolipoprotein B-100 and triglycerides. The genetic inheritance of FCHL remains poorly understood. The goals of this study were to investigate the polygenetic architecture and cardiovascular risk associated with FCHL.

METHODS AND RESULTS

We identified individuals with an FCHL phenotype among 349,222 unrelated participants of European ancestry in the UK Biobank using modified versions of 5 different diagnostic criteria. The prevalence of the FCHL phenotype was 11.44% (n = 39,961), 5.01% (n = 17,485), 1.48% (n = 5,153), 1.10% (n = 3,838), and 0.48% (n = 1,688) according to modified versions of the Consensus Conference, Dutch, Mexico, Brunzell, and Goldstein criteria, respectively. We performed discovery, case-control genome-wide association studies for these different FCHL criteria and identified 175 independent loci associated with FCHL at genome-wide significance. We investigated the association of genetic and clinical risk with FCHL and found that polygenic susceptibility to hypercholesterolemia or hypertriglyceridemia and features of metabolic syndrome were associated with greater prevalence of FCHL. Participants with an FCHL phenotype had a similar risk of incident coronary artery disease compared to participants with monogenic familial hypercholesterolemia (adjusted hazard ratio vs controls [95% confidence interval]: 2.72 [2.31-3.21] and 1.90 [1.30-2.78]).

CONCLUSIONS

These results suggest that, rather than being a single genetic entity, the FCHL phenotype represents a polygenic susceptibility to dyslipidemia in combination with metabolic abnormalities. The cardiovascular risk associated with an FCHL phenotype is similar to that of monogenic familial hypercholesterolemia, despite being ∼5x more common.

Di(isononyl) cyclohexane-1,2-dicarboxylate (DINCH) alters transcriptional profiles, lipid metabolism and behavior in zebrafish larvae

Plasticizers are commonly used in different consumer goods and personal care products to provide flexibility, durability and elasticity to polymers. Due to their reported toxicity, the use of several plasticizers, including phthalates has been regulated and/or banned from the market. Di(isononyl) cyclohexane-1,2-dicarboxylate (DINCH) is an alternative plasticizer that was introduced to replace toxic plasticizers. Increasing global demand and lack of toxicity data and safety assessment of DINCH have raised the concern to human and animal health. Hence, in the present study, we investigated the adverse effects of DINCH (at concentrations ranging from 0.01 to 10 μM) in early developmental stages of zebrafish using different endpoints such as hatching rate, developmental abnormalities, lipid content, behavior analysis and gene expression. We found that DINCH caused hatching delay in a dose-dependent manner and altered the expression of genes involved in stress response. Lipid staining using Oil Red O stain showed a slight lipid accumulation around the yolk, brain, eye and neck with increasing concentration. Genes associated with lipid transport such as fatty acid synthesis, β-oxidation, elongation, lipid transport were significantly altered by DINCH. Genes involved in cholesterol biosynthesis and homeostasis were also affected by DINCH indicating possible developmental neurotoxicity. Behavioral analysis of larvae demonstrated a distinct locomotor activity upon exposure to DINCH. The present data shows that DINCH could induce physiological and metabolic toxicity to aquatic organisms. Hence, further analyses and environmental monitoring of DINCH should be conducted to determine its safety and toxicity levels.

Inflammatory Biomarkers for Cardiovascular Risk Stratification in Familial Hypercholesterolemia

Familial hypercholesterolemia (FH) is a frequent autosomal genetic disease characterized by elevated concentrations of low-density lipoprotein cholesterol (LDL) from birth with increased risk of premature atherosclerotic complications. Accumulating evidence has shown enhanced inflammation in patients with FH. In vessels, the deposition of modified cholesterol lipoproteins triggers local inflammation. Then, inflammation facilitates fatty streak formation by activating the endothelium to produce chemokines and adhesion molecules. This process eventually results in the uptake of vascular oxidized LDL (OxLDL) by scavenger receptors in monocyte-derived macrophages and formation of foam cells. Further leukocyte recruitment into the sub-endothelial space leads to plaque progression and activation of smooth muscle cells proliferation. Several inflammatory biomarkers have been reported in this setting which can be directly synthetized by activated inflammatory/vascular cells or can be indirectly produced by organs other than vessels, e.g., liver. Of note, inflammation is boosted in FH patients. Inflammatory biomarkers might improve the risk stratification for coronary heart disease and predict atherosclerotic events in FH patients. This review aims at summarizing the current knowledge about the role of inflammation in FH and the potential application of inflammatory biomarkers for cardiovascular risk estimation in these patients.

Metabolic disorders and inflammation are associated with familial combined hyperlipemia

BACKGROUND

Familial Combined Hyperlipidemia (FCH) is related to different metabolic disorders. The objective of this study was to evaluate the presence of alterations of hydrocarbonated metabolism and lipid profile together with inflammatory and adhesion molecules in subjects with FCH compared to controls.

METHODS

75 HFC patients and 75 healthy individuals were studied. Glucose, insulin, HOMA-IR index and lipid parameters, in addition to anti-oxidized LDL antibodies (Anti ox-LDL), small and dense LDL (sdLDL) and HDL subfractions, proinflammatory cytokines and adhesion molecules were measured.

RESULTS

FCH patients showed higher levels of hydrocarbonated metabolism parameters, total cholesterol, triglycerides, LDLc, Apolipoprotein B and non-HDLc (p < .001), and lower levels of HDLc (p < .001) and Apolipoprotein AI (p < .05) than controls. In addition, the inflammatory markers hsCRP, IL-6, IL-8, P-selectin, E-selectin and ICAM were all higher with (p < .05) respect to controls. The increase of sdLDL was correlated with the presence of IR and IL-6 levels. Significant differences in diameter and percentage of phenotype B LDL, small HDL subfractions and Anti ox-LDL were also detected between patients and controls.

CONCLUSIONS

The lipid characteristics of FCH are confirmed by IR and a low grade inflammatory state in patients, and are associated with the predominance of sdLDL and Anti ox-LDL.

Studying Lipid Metabolism and Transport During Zebrafish Development

The zebrafish model facilitates the study of lipid metabolism and transport during development. Here, we outline methods to introduce traceable fluorescent or radiolabeled fatty acids into zebrafish embryos and larvae at various developmental stages. Labeled fatty acids can be injected into the large yolk cell prior to the development of digestive organs when the larvae is entirely dependent on the yolk for its nutrition (lecithotrophic state). Once zebrafish are able to consume exogenous food, labeled fatty acids can be incorporated into their food. Our group and others have demonstrated that the transport and processing of these injected or ingested fatty acid analogs can be followed through microscopy and/or biochemical analysis. These techniques can be easily combined with targeted antisense approaches, transgenics, or drug treatments (see Note 1 ), allowing studies of lipid cell biology and metabolism that are exceedingly difficult or impossible in mammals.

Zebrafish lipid metabolism: from mediating early patterning to the metabolism of dietary fat and cholesterol

Lipids serve essential functions in cells as signaling molecules, membrane components, and sources of energy. Defects in lipid metabolism are implicated in a number of pandemic human diseases, including diabetes, obesity, and hypercholesterolemia. Many aspects of how fatty acids and cholesterol are absorbed and processed by intestinal cells remain unclear and present a hurdle to developing approaches for disease prevention and treatment. Numerous studies have shown that the zebrafish is an excellent model for vertebrate lipid metabolism. In this chapter, we review studies that employ zebrafish to better understand lipid signaling and metabolism.

Hypercholesterolemia and microvascular dysfunction: interventional strategies

Hypercholesterolemia is defined as excessively high plasma cholesterol levels, and is a strong risk factor for many negative cardiovascular events. Total cholesterol levels above 200 mg/dl have repeatedly been correlated as an independent risk factor for development of peripheral vascular (PVD) and coronary artery disease (CAD), and considerable attention has been directed toward evaluating mechanisms by which hypercholesterolemia may impact vascular outcomes; these include both results of direct cholesterol lowering therapies and alternative interventions for improving vascular function. With specific relevance to the microcirculation, it has been clearly demonstrated that evolution of hypercholesterolemia is associated with endothelial cell dysfunction, a near-complete abrogation in vascular nitric oxide bioavailability, elevated oxidant stress, and the creation of a strongly pro-inflammatory condition; symptoms which can culminate in profound impairments/alterations to vascular reactivity. Effective interventional treatments can be challenging as certain genetic risk factors simply cannot be ignored. However, some hypercholesterolemia treatment options that have become widely used, including pharmaceutical therapies which can decrease circulating cholesterol by preventing either its formation in the liver or its absorption in the intestine, also have pleiotropic effects with can directly improve peripheral vascular outcomes. While physical activity is known to decrease PVD/CAD risk factors, including obesity, psychological stress, impaired glycemic control, and hypertension, this will also increase circulating levels of high density lipoprotein and improving both cardiac and vascular function. This review will provide an overview of the mechanistic consequences of the predominant pharmaceutical interventions and chronic exercise to treat hypercholesterolemia through their impacts on chronic sub-acute inflammation, oxidative stress, and microvascular structure/function relationships.

A new model system swims into focus: using the zebrafish to visualize intestinal metabolism in vivo

Many fundamental questions remain regarding the cellular and molecular mechanisms of digestive lipid metabolism. One major impediment to answering important questions in the field has been the lack of a tractable and sufficiently complex model system. Until recently, most studies of lipid metabolism have been performed in vitro or in mice, yet each approach possesses certain limitations. The zebrafish (Danio rerio) offers an excellent model system in which to study lipid metabolism in vivo, owing to its small size, genetic tractability and optical clarity. Fluorescent lipid dyes and optical reporters of lipid-modifying enzymes are now being used in live zebrafish to generate visible readouts of digestive physiology. Here we review recent advances in visualizing intestinal lipid metabolism in live larval zebrafish.

Elevated LDL-cholesterol level predicts diabetes in centrally obese women but not men: relative roles of insulin resistance and central obesity

BACKGROUND

The aim was to investigate the sex-specific effect of hypercholesterolemia interacting with abdominal obesity (AO) in predicting Type 2 diabetes mellitus (DM). The 3,048 participants (aged > or =28 years) were free of DM at baseline, a representative sample of Turkish adults and were evaluated prospectively.

METHODS AND RESULTS

As cut-off points for AO were used > or =95 cm in men and > or =91 cm in women, and for hypercholesterolemia > or =5.2 mmol/L. Diabetes was diagnosed using criteria of the American Diabetes Association. Four groups were formed at baseline: Group I subjects had neither AO nor hypercholesterolemia (33.3%), Group II subjects had AO only (27.6%), Group III subjects had hypercholesterolemia only (17.8%), and Group IV subjects had AO combined with hypercholesterolemia (21.3%). Over a mean of 5.9 years, DM developed in 103 women and 116 men. An age-adjusted relative risk (RR) by logistic regression for DM in the 4 groups, using AO as a reference group, disclosed an RR of 1.88 (95% confidence interval 1.14; 3.09) in women and an insignificant RR 1.29 in men (women were predicted to be 1.46 times more likely to develop DM). Hypercholesterolemia alone did not differ significantly from Group I in its ability to predict diabetes. An elevated level of low-density lipoprotein (LDL)-cholesterol (C) (> or =3.4 mmol/L) was delineated as the element associated with diabetes in hypercholesterolemia by multiple logistic regression. The identification of 48 participants with familial-combined hyperlipidemia phenotypes alone could not account for most of the centrally obese and hypercholesterolemic women developing DM.

CONCLUSION

It was suggested that a diminished effectiveness of insulin resistance in centrally obese Turkish women (but not men) might predispose them to an elevation in LDL concentrations, while other features of visceral adiposity still predispose them to DM. In summary, an elevated LDL-C level interacts with AO in Turkish women to enhance the development of diabetes.

Pioglitazone improves myocardial blood flow and glucose utilization in nondiabetic patients with combined hyperlipidemia: a randomized, double-blind, placebo-controlled study

OBJECTIVES

This study's aim was to examine whether treatment with pioglitazone, added to conventional lipid-lowering therapy, would improve myocardial glucose utilization (MGU) and blood flow (MBF) in nondiabetic patients with familial combined hyperlipidemia (FCHL).

BACKGROUND

Thiazolidinediones were found to improve insulin sensitivity and MGU in type 2 diabetes and MBF in Mexican Americans with insulin resistance. Familial combined hyperlipidemia is a complex genetic disorder conferring a high risk of premature coronary artery disease, characterized by high serum cholesterol and/or triglyceride, low high-density lipoprotein (HDL) cholesterol, and insulin resistance.

METHODS

We undertook a randomized, double-blind, placebo-controlled study in 26 patients with FCHL, treated with pioglitazone or matching placebo 30 mg daily for 4 weeks, followed by 45 mg daily for 12 weeks. Positron emission tomography was used to measure MBF at rest and during adenosine-induced hyperemia and MGU during euglycemic hyperinsulinemic clamp at baseline and after treatment.

RESULTS

Whereas no change was observed in the placebo group after treatment, patients receiving pioglitazone showed a significant increase in whole body glucose disposal (3.93 +/- 1.59 mg/kg/min to 5.24 +/- 1.65 mg/kg/min; p = 0.004) and MGU (0.62 +/- 0.26 micromol/g/min to 0.81 +/- 0.14 micromol/g/min; p = 0.0007), accompanied by a significant improvement in resting MBF (1.11 +/- 0.20 ml/min/g to 1.25 +/- 0.21 ml/min/g; p = 0.008). Furthermore, in the pioglitazone group HDL cholesterol (+28%; p = 0.003) and adiponectin (+156.2%; p = 0.0001) were increased and plasma insulin (-35%; p = 0.017) was reduced.

CONCLUSIONS

In patients with FCHL treated with conventional lipid-lowering therapy, the addition of pioglitazone led to significant improvements in MGU and MBF, with a favorable effect on blood lipid and metabolic parameters. (A study to investigate the effect of pioglitazone on whole body and myocardial glucose uptake and myocardial blood flow/coronary vasodilator reserve in patients with familial combined hyperlipidaemia; http://www.controlled-trials.com/mrct/trial/230761/ISRCTN78563659; ISRCTN78563659).

Pioglitazone added to conventional lipid-lowering treatment in familial combined hyperlipidaemia improves parameters of metabolic control: Relation to liver, muscle and regional body fat content

Familial combined hyperlipidaemia (FCHL) is a complex genetic disorder conferring high risk of premature atherosclerosis, characterized by high cholesterol and/or triglyceride, low high density lipoprotein (HDL) cholesterol and insulin resistance. We examined whether pioglitazone, added to conventional lipid-lowering therapy, would favourably affect metabolic parameters and alter body fat content. We undertook a randomized, double blind, placebo-controlled study in 22 male patients with FCHL treated with pioglitazone or matching placebo 30 mg daily for 4 weeks, increasing to 45 mg for 12 weeks. Magnetic resonance imaging and proton magnetic resonance spectroscopy were performed to measure adipose tissue (AT) body content as well as intrahepatocellular lipids (IHCL) and intramyocellular lipids (IMCL) at baseline and after treatment. Significantly improved in the pioglitazone group were: triglyceride/HDL (atherogenic index of plasma) -32.3% (p=0.002), plasma glucose -4.4% (p=0.03), alanine-aminotransferase (ALT) -7.7% (p=0.005) and adiponectin 130.1% (p=0.001). Pioglitazone treatment resulted in a significant increase in total (5.3%, p=0.02) and subcutaneous (7.1%, p=0.003) adipose tissue as well as in soleus-IMCL levels (47.4%, p=0.02) without alteration in intra-abdominal AT or IHCL. Changes in ALT and AST and IHCL were strongly correlated (r=0.72, p<0.01; r=.0.86, p<0.01, respectively). In patients with FCHL on conventional lipid-lowering therapy, the addition of pioglitazone acts favourably on several metabolic parameters.

Five-year follow-up of waist circumference, insulin and ALT levels in familial combined hyperlipidaemia

FCHL (familial combined hyperlipidaemia), an entity with many features of the metabolic syndrome, is characterized by changes in cholesterol and triacylglycerol (triglyceride) phenotype over time. The present study was conducted to investigate the relationship of ALT (alanine aminotransferase) levels, used as a surrogate marker for the amount of hepatic fat, with the switch in triacylglycerol phenotype and the increased susceptibility to develop hypertriglyceridaemia in FCHL. BMI (body mass index), waist circumference and plasma triacylglycerols, insulin and ALT levels were measured in 145 FCHL family members and 54 spouses at baseline and after a 5-year follow-up. A switch from normotriglyceridaemia to hypertriglyceridaemia or vice versa, as observed in 22 of 145 FCHL family members, was associated with changes in plasma ALT levels (P=0.001), but not with insulin levels or waist circumference. At 5 years of follow-up, an intra-individual relationship was observed between waist circumference and plasma triacylglycerols, insulin and ALT levels. For each waist circumference, FCHL patients, but not their NL (normolipidaemic) relatives, exhibited higher triacylglycerol and insulin levels than spouses (P<0.001). Remarkably, both FCHL patients and the NL relatives had higher ALT levels for each waist circumference compared with spouses (P<0.001 for FCHL patients, and P=0.035 for NL relatives). In conclusion, the present study shows that the longitudinal relationship of abdominal obesity–ALT is more specific for all FCHL family members, i.e. patients and their NL relatives, than the relationship of abdominal obesity–triacylglycerols. Additionally, the association of ALT with the switch in triacylglycerol phenotype suggests a central role of the liver in the pathogenesis of FCHL.

Apolipoprotein E polymorphism influences lipid phenotypes in Chinese families with familial combined hyperlipidemia

BACKGROUND

Apolipoprotein E (apoE) polymorphism is associated with changes in the lipoprotein profile of individuals with familial combined hyperlipidemia (FCHL), but its effects on the lipoprotein profiles of members of Chinese families with FCHL remain uncertain.

METHODS AND RESULTS

43 FCHL families (n=449) and 9 normolipidemic families (n=73) were recruited to assess the influence of apoE polymorphism on plasma lipids. The relative frequency of the epsilon4 allele in affected and unaffected FCHL relatives, spouses and normolipidemic members was 13.8%, 5.3%, 9.1% and 6.8%, respectively, with a significantly higher frequency in affected FCHL relatives, compared with unaffected FCHL relatives or normolipidemic members (p=0.0002 or p=0.029). In FCHL relatives, the apoE4 subset (E4/4 and E4/3) exhibited significantly higher levels of apoB, total cholesterol and low-density lipoprotein-cholesterol (LDL-C) than did the apoE3 (E3/3) subset, especially in women (all p<0.05), and there was significant elevation of LDL-C concentrations in men only (p<0.05). In men, the apoE2 (E3/2) subset indicated a decreased level of apoB and increased apoA1 compared with those in the apoE3 subset (p<0.05).

CONCLUSIONS

ApoE polymorphism appears to be associated with variance of the lipoprotein phenotype in Chinese families with FCHL.

The involvement of upstream stimulatory factor 1 in Dutch patients with familial combined hyperlipidemia

Recently, the upstream stimulatory factor 1 gene (USF1) was proposed as a candidate gene for familial combined hyperlipidemia (FCH). In this study, we examined the previously identified risk haplotype of USF1 with respect to FCH and its related phenotypes in 36 Dutch FCH families. The diagnosis of FCH was based on both the traditional diagnostic criteria and a nomogram. The two polymorphisms, USF1s1 and USF1s2, were in complete linkage disequilibrium. No association was found for the individual single nucleotide polymorphisms (SNPs) with FCH defined by the nomogram (USF1s1, P = 0.53; USF1s2, P = 0.53), whereas suggestive associations were found when using the traditional diagnostic criteria for FCH (USF1s1, P = 0.08; USF1s2, P = 0.07). USF1 was associated with total cholesterol (USF1s1, P = 0.05; USF1s2, P = 0.04) and apolipoprotein B (USF1s1, P = 0.06; USF1s2, P = 0.04). Small dense LDL showed a suggestive association (USF1s1, P = 0.10; USF1s2, P = 0.09). The results from the haplotype analyses supported the results obtained for the individual SNPs. In conclusion, the previously identified risk haplotype of USF1 showed a suggestive association with FCH and contributed to the related lipid traits in our Dutch FCH families.

Zebrafish fat-free is required for intestinal lipid absorption and Golgi apparatus structure

The zebrafish fat-free (ffr) mutation was identified in a physiological screen for genes that regulate lipid metabolism. ffr mutant larvae are morphologically indistinguishable from wild-type sibling larvae, but their absorption of fluorescent lipids is severely impaired. Through positional cloning, we have identified a causative mutation in a highly conserved and ubiquitously expressed gene within the ffr locus. The Ffr protein contains a Dor-1 like domain typical of oligomeric Golgi complex (COG) gene, cog8. Golgi complex ultrastructure is disrupted in the ffr digestive tract. Consistent with a possible role in COG-mediated Golgi function, wild-type Ffr-GFP and COG8-mRFP fusion proteins partially colocalize in zebrafish blastomeres. Enterocyte retention of an endosomal lipid marker in ffr larvae support the idea that altered vesicle trafficking contributes to the ffr mutant defect. These data indicate that ffr is required for both Golgi structure and vesicular trafficking, and ultimately lipid transport.

Role of Insulin Resistance in Familial Combined Hyperlipidemia

OBJECTIVE

Insulin resistance is associated with increased triglyceride levels, low high-density lipoprotein cholesterol, small dense low-density lipoprotein (LDL), and increased apolipoprotein B (apoB) levels, all characteristics of familial combined hyperlipidemia (FCH). Therefore, we explored the role of insulin resistance in FCH lipid phenotype expression.

METHODS AND RESULTS

FCH was defined by traditional diagnostic criteria including plasma total cholesterol or triglyceride levels >90th percentile. Insulin resistance was assessed by the Homeostasis Model Assessment (HOMA) index. In total, 132 subjects with FCH, 350 normolipidemic relatives, and 81 spouses who referenced as controls were studied. FCH subjects were significantly more insulin resistant compared with controls and normolipidemic relatives (HOMA index 2.9 [95% CI, 2.6 to 3.2], 2.2 [95% CI, 2.0 to 2.5], and 2.0 [95% CI, 1.9 to 2.2], respectively), even after correction for sex, age, and body mass index (BMI). The degree of insulin resistance was associated with the lipid phenotype expression, and a change in insulin-resistant state was associated with a change in lipid phenotype expression over 5 years. For any level of insulin resistance and degree of obesity, FCH subjects had increased levels of apoB and more small dense LDL compared with controls.

CONCLUSIONS

Insulin resistance is a characteristic feature of FCH, which is not fully explained by their increased BMI and is associated with (change in) lipid phenotype expression. Furthermore, our results support the concept of genetic origin of high apoB and small dense LDL in FCH, which is modulated by insulin resistance and obesity.

Management of atherogenic dyslipidemia of the metabolic syndrome: evolving rationale for combined drug therapy

Atherogenic dyslipidemia is prevalent in various conditions associated with central obesity, hypertension, hyperurecemia, and impaired beta-cell function (ie, the metabolic syndrome). Because of clinical trial evidence, most high-risk patients with atherogenic dyslipidemia require statin therapy. Coadministration of drugs targeted to reduction of low-density lipoprotein precursors, however,is likely to improve the metabolic profile of all non-high-density lipoproteins and produce a significant rise in high-density lipoprotein cholesterol. Large-scale clinical trials with combined drug therapy that show coronary heart disease (CHD) risk reduction or improvement in CHD are needed. It is also possible that new drugs are needed to target fatty acid metabolism and inflammation. As understanding of the metabolic origins of atherogenic dyslipidemia increases, it is possible that new targets of therapy will be identified and that new drug combinations will prove to be even more efficacious than those currently available for treatment of this condition.

Nomogram to Diagnose Familial Combined Hyperlipidemia on the Basis of Results of a 5-Year Follow-Up Study

Background— Familial combined hyperlipidemia (FCH) is traditionally diagnosed by total plasma cholesterol and/or triglyceride levels above the 90th percentile adjusted for age and gender. In a recent study, we showed that the diagnosis of FCH on the basis of these diagnostic criteria was inconsistent in 26% of the subjects over a 5-year period. This result emphasizes the need for reevaluation of the diagnostic criteria for FCH.

Methods and Results— A total of 32 families (299 subjects) were studied in 1994 and 1999. A subject was defined “truly” FCH when diagnosed FCH in 1994 and/or 1999 on the basis of traditional plasma lipid criteria. Additional lipid and lipoprotein parameters, including apolipoprotein B (apoB) and small, dense LDL, were measured at both time points. In total, 121 subjects (40%) were defined as truly FCH. Multivariate analysis revealed that absolute apoB values combined with triglyceride and total cholesterol levels adjusted for age and gender best predicted truly FCH. A nomogram including these parameters is provided to simply and accurately calculate the probability to be affected by FCH. Furthermore, it is shown that when percentiles of triglyceride and total cholesterol adjusted for age and gender are not available in a population, the definition of FCH can be established on the basis of hypertriglyceridemia (>1.5 mmol/L) and hyper-apoB (>1200 mg/L).

Conclusions— The diagnosis of FCH is best predicted by absolute apoB levels combined with triglyceride and total cholesterol levels adjusted for age and gender and can accurately be calculated by a nomogram. This definition is also a good predictor of cardiovascular risk in FCH.

Lipid Metabolism in Zebrafish

Forward genetics is an unbiased methodology to discover new genes or functions of genes. At the present, the zebrafish is one of the few vertebrate systems where large-scale forward genetic studies are practical. Fluorescent lipid labeling of zebrafish larvae derived from families created from ENU-mutagenized fish enabled us to perform a large scale in vivo screen to identify mutants with perturbed lipid processing. With the aid of the zebrafish genome project, positional cloning of mutated genes with abnormal lipid metabolism can be accelerated. MO- and gripNA-based transient gene silencing is feasible in zebrafish embryos and provides a reverse genetic screening strategy to search for important lipid regulators. The advantages of using zebrafish as a vertebrate model to study lipid metabolism include its rapid external development and its optical clarity that enables the monitoring of biological processes. Large scale, high-throughput drug screening in vivo, especially for drugs that inhibit lipid absorption, can be easily achieved in this model. These zebrafish-based assays are important tools to understand aspects of lipid biology with significant clinical implications.

Dyslipidemia in the metabolic syndrome and type 2 diabetes mellitus

Patients with type 2 diabetes mellitus or the metabolic syndrome have a unique dyslipidemia characterized by hypertriglyceridemia; elevated blood levels of apolipoprotein B; small, dense low-density lipoprotein (LDL) cholesterol; and low levels of high-density lipoprotein (HDL) cholesterol, in particular HDL(2)-C. Treatment of the dyslipidemia associated with these disorders should focus on correcting the abnormal lipoprotein levels as well as LDL and HDL heterogeneity. Statins and fibrates are useful for treating elevated LDL in patients with and without diabetes or the metabolic syndrome. In addition, thiazolidinediones or niacin in combination with a statin show promise for correcting defects in LDL and HDL heterogeneity. The ultimate goal of treatment in this patient population is to prevent the development and progression of coronary artery disease.

Effects of atorvastatin on fasting and postprandial complement component 3 response in familial combined hyperlipidemia

VLDL overproduction by enhanced hepatic FFA flux is a major characteristic of familial combined hyperlipidemia (FCHL). The postprandial complement component 3 (C3) response has been associated with impaired postprandial FFA metabolism in FCHL. We investigated the effects of 16 weeks of treatment with atorvastatin on postprandial C3 and lipid changes in 12 FCHL patients. Atorvastatin significantly lowered fasting plasma C3 and triglyceride (TG) in FCHL. Fasting TG and insulin sensitivity were the best predictors of fasting and postprandial C3. Postprandial triglyceridemia and C3 response, estimated as area under the curve (AUC), were significantly lowered by atorvastatin by 19% and 12%, respectively, albeit still elevated, compared with 10 matched controls. Postprandial FFA-AUC and postheparin plasma lipolytic activities remained unchanged after atorvastatin, suggesting no major effect on lipolysis. After atorvastatin, postprandial hydroxybutyric acid-AUC, which was elevated in untreated FCHL patients, was decreased, reaching values similar to those in controls. The present data show reduction of postprandial hepatic FFA flux in FCHL by atorvastatin, providing an additional mechanistic explanation for the reduction of VLDL secretion reported previously for atorvastatin. This was accompanied by a decrease in fasting plasma C3 concentrations and a blunted postprandial C3 response to an acute oral fat load.

Lipoprotein distribution in the metabolic syndrome, type 2 diabetes mellitus, and familial combined hyperlipidemia

Metabolic abnormalities associated with the metabolic syndrome are also present in patients with type 2 diabetes mellitus and in those with familial combined hyperlipidemia (FCHL). These abnormalities include central obesity, insulin resistance with hyperinsulinemia, hypertension, increased plasma triglycerides, and decreased high-density lipoprotein cholesterol levels. Other characteristics associated with FCHL include the presence of small, dense low-density lipoprotein cholesterol and increased apolipoprotein B. Patients with these abnormalities are at an increased risk for premature coronary artery disease. Treatment of the dyslipidemia associated with type 2 diabetes and FCHL with a combination of a statin and a thiazolidinedione or niacin offers the most comprehensive modality to correct the various lipid abnormalities.

Determinants of low HDL levels in familial combined hyperlipidemia

In familial combined hyperlipidemia (FCHL), affected family members frequently have reduced levels of HDL cholesterol, in addition to elevated levels of total cholesterol and/or triglycerides (TGs). In the present study, we focused on those determinants that are important regulators of HDL cholesterol levels in FCHL, and measured postheparin plasma activities of hepatic lipase (HL), lipoprotein lipase, cholesterol ester transfer protein, and phospholipid transfer protein (PLTP) in 228 subjects from 49 FCHL families. In affected family members (n = 88), the levels of HDL cholesterol, HDL2 cholesterol, HDL3 cholesterol, and apolipoprotein A-I were lower than in unaffected family members (n = 88) or spouses (n = 52). The main change was the reduction of HDL2 cholesterol by 25.4% in affected family members (P < 0.001 vs. unaffected family members; P = 0.003 vs. spouses). Affected family members had higher HL activity than unaffected family members (P = 0.001) or spouses (P = 0.013). PLTP activity was higher in affected than unaffected family members (P = 0.025). In univariate correlation analysis, a strong negative correlation was observed between HL activity and HDL2 cholesterol (r = -0.339, P < 0.001). Multivariate regression analysis demonstrated that gender, HL activity, TG, and body mass index have independent contributions to HDL2 cholesterol levels. We suggest that in FCHL, TG enrichment of HDL particles and enhanced HL activity lead to the reduction of HDL cholesterol and HDL2 cholesterol.

Small, dense LDL and elevated apolipoprotein B are the common characteristics for the three major lipid phenotypes of familial combined hyperlipidemia

OBJECTIVE

Familial combined hyperlipidemia (FCHL) is associated with variable lipid and lipoprotein phenotypes arbitrarily defined as type IIa, IIb, and IV based on plasma total cholesterol and triglyceride levels. This study sought to characterize consistent lipoprotein and lipid abnormalities across the 3 lipoprotein phenotypes in 62 patients with documented FCHL (IIa [n=14], IIb [n=19], and IV [n=29]) and 44 healthy individuals.

METHODS AND RESULTS

The lipoprotein cholesterol distribution was determined over 38 fractions obtained by density gradient ultracentrifugation. As expected, FCHL patients with hypertriglyceridemia (IIb and IV) had higher cholesterol levels in VLDL than IIa, whereas IIa showed higher cholesterol in the big, buoyant LDL and in HDL. LDL cholesterol was higher in IIb than IV; most of the increase in LDL cholesterol was associated with big, buoyant LDL rather than small, dense LDL (sdLDL). The differences in lipoproteins between phenotypes were attributable to changes in VLDL and big, buoyant LDL levels. Comparison of the FCHL patients with healthy individuals showed a significant elevation in plasma apolipoprotein B levels and sdLDL in all 3 FCHL phenotypes.

CONCLUSIONS

Although triglyceride and cholesterol levels are variable by lipoprotein phenotype, sdLDL and elevated plasma apolipoprotein B levels are consistent characteristics of FCHL shared by the 3 different lipoprotein phenotypes.

Recent trends in lipid management: raising the bar and shifting the goalposts?

The National Heart Foundation of Australia, in conjunction with the Cardiac Society of Australia and New Zealand, updated its Lipid Guidelines at the end of 2001, but on-going modification is anticipated to stay abreast of the rapid progress in this field. Research at all levels re-affirms the fundamental importance of lipid metabolism in many physiological and pathological processes. In addition, clinical trials such as the recent Heart Protection Study broaden the indications for intervention. The present review summarizes recent advances and analyzes emerging attitudes towards diagnosis and management that will influence future recommendations and practice.

Intra-individual variations of fasting plasma lipids, apolipoproteins and postprandial lipemia in familial combined hyperlipidemia compared to controls

BACKGROUND

The intra-individual variability of plasma lipids and apolipoproteins has not been studied systematically in familial combined hyperlipidemia (FCHL).

METHODS

Intra-individual changes in fasting plasma lipids and apolipoproteins B and AI were determined in 18 untreated FCHL subjects and 16 unrelated, normolipidemic subjects. Participants were matched for gender, age and body mass index. The mean follow-up period of fasting plasma lipids was 48.91 +/- 35.46 (mean +/- S.D.) days. Postprandial lipemia was determined on 3 different days in 1 week in 90 healthy controls and 17 untreated FCHL subjects by the area under the diurnal capillary triglyceride curve (TGc-AUC).

RESULTS

The coefficients of variation (CVs) for fasting plasma TG were similar between FCHL (23.2 +/- 10.2%) and controls (20.4 +/- 8.2%). The CVs for HDL-C, apo B and apo AI were the lowest of all fasting plasma measurements in both groups and there was no significant difference between FCHL (12.8 +/- 8.2%, 13.2 +/- 15.8% and 6.4 +/- 5.2%, respectively) and controls (11.4 +/- 4.3%, 11.3 +/- 10.6% and 7.8 +/- 4.6%, respectively). The CVs for postprandial lipemia were not different between FCHL (15.9 +/- 11.3%) and controls (15.1 +/- 11.0%), and were significantly lower than the CV of fasting capillary TG (TGc) in the same period (36.3 +/- 24.7% and 24.9 +/- 17.2%, respectively).

CONCLUSIONS

Our study does not provide evidence for short-term major changes in fasting or postprandial lipemia or apolipoproteins in FCHL when systematically compared to healthy controls.

Screening for Familial Combined Hyperlipidemia in Children Using Lipid Phenotypes

The purpose of this study was to screen for FCHL in children using serum lipid phenotypes. The subjects were 1190 (599 male, 591 female) children who participated in a screening and care program for life style-related diseases in school children. Total cholesterol, high-density lipoprotein cholesterol and triglyceride were determined, and information on the family history of parents was obtained by questionnaire. Candidates for FCHL were screened by the following criteria; type IIb hyperlipidemia, type IIa hyperlipidemia with positive family history of CHD, hyperlipidemia or both. We informed them of the results by mail. A second series of examinations to diagnose FCHL was performed on volunteer participants, including their parents. The candidates consisted of 9 children with type IIb and 27 with type IIa hyperlipidemia, 11 of whom participated, in the second series of examinations, in which 5 children were diagnosed with FCHL. The prevalence was 0.4%, suggesting that at least half of all individuals with FCHL already demonstrate hyperlipidemia in childhood.