Tissue-Specific Expression, Developmental Regulation, and Chromosomal Mapping of the Lecithin: Cholesterol Acyltransferase Gene

CD5L-associated gene analyses highlight the dysregulations, prognostic effects, immune associations, and drug-sensitivity predicative potentials of LCAT and CDC20 in hepatocellular carcinoma

BACKGROUND

The dysregulation of CD5L has been reported in hepatocellular carcinoma (HCC). However, its functions in HCC were controversial. In this study, we aimed to identify CD5L-associated pathways and markers and explore their values in HCC diagnosis, prognosis and treatment.

METHODS

HCC datasets with gene expression profiles and clinical data in TCGA and ICGC were downloaded. The immune/stroma cell infiltrations were estimated with xCell. CD5L-associated pathways and CD5L-associated genes (CD5L-AGs) were identified with gene expression comparisons and gene set enrichment analysis (GSEA). Cox regression, Kaplan-Meier survival analysis, and least absolute shrinkage and selection operator (LASSO) regression analysis were performed. The correlations of the key genes with immune/stroma infiltrations, immunoregulators, and anti-cancer drug sensitivities in HCC were investigated. At protein level, the key genes dysregulations, their correlations and prognostic values were validated in clinical proteomic tumor analysis consortium (CPTAC) database. Serum CD5L and LCAT activity in 50 HCC and 30 normal samples were evaluated and compared. The correlations of serum LCAT activity with alpha-fetoprotein (AFP), albumin (ALB) and high-density lipoprotein (HDL) in HCC were also investigated.

RESULTS

Through systemic analyses, 14 CD5L-associated biological pathways, 256 CD5L-AGs and 28 CD5L-associated prognostic and diagnostic genes (CD5L-APDGs) were identified. A risk model consisting of LCAT and CDC20 was constructed for HCC overall survival (OS), which could discriminate HCC OS status effectively in both the training and the validation sets. CD5L, LCAT and CDC20 were shown to be significantly correlated with immune/stroma cell infiltrations, immunoregulators and 31 anti-cancer drug sensitivities in HCC. At protein level, the dysregulations of CD5L, LCAT and CDC20 were confirmed. LCAT and CDC20 were shown to be significantly correlated with proliferation marker MKI67. In serum, no significance of CD5L was shown. However, the lower activity of LCAT in HCC serum was obvious, as well as its significant positive correlations ALB and HDL concentrations.

CONCLUSIONS

CD5L, LCAT and CDC20 were dysregulated in HCC both at mRNA and protein levels. The LCAT-CDC20 signature might be new predicator for HCC OS. The associations of the three genes with HCC microenvironment and anti-cancer drug sensitivities would provide new clues for HCC immunotherapy and chemotherapy.

Defects in a liver-bone axis contribute to hepatic osteodystrophy disease progression

Hepatic osteodystrophy (HOD) is a metabolic bone disease that is often associated with chronic liver disease and is marked by bone loss. Here, we demonstrate that hepatic expression of the phosphatase PP2Acα is upregulated during HOD, leading to the downregulation of expression of the hepatokine lecithin-cholesterol acyltransferase (LCAT). Loss of LCAT function markedly exacerbates the bone loss phenotype of HOD in mice. In addition, we found that alterations in cholesterol levels are involved in the regulation of osteoblast and osteoclast activities. We also found that LCAT improves liver function and relieves liver fibrosis in the mouse HOD model by promoting reversal of cholesterol transport from the bone to the liver. In summary, defects in a liver-bone axis occur during HOD that can be targeted to ameliorate disease progression.

LCAT, ApoD, and ApoA1 Expression and Review of Cholesterol Deposition in the Cornea

Lecithin:cholesterol acyltransferase (LCAT) is an enzyme secreted by the liver and circulates with high-density lipoprotein (HDL) in the blood. The enzyme esterifies plasma cholesterol and increases the capacity of HDL to carry and potentially remove cholesterol from tissues. Cholesterol accumulates within the extracellular connective tissue matrix of the cornea stroma in individuals with genetic deficiency of LCAT. LCAT can be activated by apolipoproteins (Apo) including ApoD and ApoA1. ApoA1 also mediates cellular synthesis of HDL. This study examined the expression of LCAT by epithelial cells, keratocytes, and endothelial cells, the cell types that comprise from anterior to posterior the three layers of the cornea. LCAT and ApoD were immunolocalized to all three cell types within the cornea, while ApoA1 was immunolocalized to keratocytes and endothelium but not epithelium. In situ hybridization was used to detect LCAT, ApoD, and ApoA1 mRNA to learn what cell types within the cornea synthesize these proteins. No corneal cells showed mRNA for ApoA1. Keratocytes and endothelium both showed ApoD mRNA, but epithelium did not. Epithelium and endothelium both showed LCAT mRNA, but despite the presence of LCAT protein in keratocytes, keratocytes did not show LCAT mRNA. RNA sequencing analysis of serum-cultured dedifferentiated keratocytes (commonly referred to as corneal stromal fibroblasts) revealed the presence of both LCAT and ApoD (but not ApoA1) mRNA, which was accompanied by their respective proteins detected by immunolabeling of the cultured keratocytes and Western blot analysis of keratocyte lysates. The results indicate that keratocytes in vivo show both ApoA1 and LCAT proteins, but do not synthesize these proteins. Rather, keratocytes in vivo must take up ApoA1 and LCAT from the corneal interstitial tissue fluid.

EFAD transgenic mice as a human APOE relevant preclinical model of Alzheimer's disease

Identified in 1993, APOE4 is the greatest genetic risk factor for sporadic Alzheimer's disease (AD), increasing risk up to 15-fold compared with APOE3, with APOE2 decreasing AD risk. However, the functional effects of APOE4 on AD pathology remain unclear and, in some cases, controversial. In vivo progress to understand how the human (h)-APOE genotypes affect AD pathology has been limited by the lack of a tractable familial AD-transgenic (FAD-Tg) mouse model expressing h-APOE rather than mouse (m)-APOE. The disparity between m- and h-apoE is relevant for virtually every AD-relevant pathway, including amyloid-β (Aβ) deposition and clearance, neuroinflammation, tau pathology, neural plasticity and cerebrovascular deficits. EFAD mice were designed as a temporally useful preclinical FAD-Tg-mouse model expressing the h-APOE genotypes for identifying mechanisms underlying APOE-modulated symptoms of AD pathology. From their first description in 2012, EFAD mice have enabled critical basic and therapeutic research. Here we review insights gleaned from the EFAD mice and summarize future directions.

Mice lacking β-carotene-15,15'-dioxygenase exhibit reduced serum testosterone, prostatic androgen receptor signaling, and prostatic cellular proliferation

β-Carotene-15,15'-dioxygenase (BCO1) cleaves dietary carotenoids at the central 15,15' double bond, most notably acting on β-carotene to yield retinal. However, Bco1 disruption also impacts diverse physiological end points independent of dietary carotenoid feeding, including expression of genes controlling androgen metabolism. Using the Bco1^-/- mouse model, we sought to probe the effects of Bco1 disruption on testicular steroidogenesis, prostatic androgen signaling, and prostatic proliferation. Male wild-type (WT) and Bco1^-/- mice were raised on carotenoid-free AIN-93G diets before euthanasia between 10 and 14 wk of age. Weights of the prostate and seminal vesicles were significantly lower in Bco1^-/- than in WT mice (-18% and -29%, respectively). Serum testosterone levels in Bco1^-/- mice were significantly reduced by 73%. Bco1 disruption significantly reduced Leydig cell number and decreased testicular mRNA expression of Hsd17b3, suggesting inhibition of testicular testosterone synthesis. Immunofluorescent staining of the androgen receptor (AR) in the dorsolateral prostate lobes of Bco1^-/- mice revealed a decrease in AR nuclear localization. Analysis of prostatic morphology suggested decreases in gland size and secretion. These findings were supported by reduced expression of the proliferation marker Ki-67 in Bco1^-/- prostates. Expression analysis of 200 prostate cancer- and androgen-related genes suggested that Bco1 loss significantly disrupted prostatic androgen receptor signaling, cell cycle progression, and proliferation. This is the first demonstration that Bco1 disruption lowers murine circulating testosterone levels and thereby reduces prostatic androgen receptor signaling and prostatic cellular proliferation, further supporting the role of this protein in processes more diverse than carotenoid cleavage.

The Effect of Natural LCAT Mutations on the Biogenesis of HDL

We have investigated how the natural LCAT[T147I] and LCAT[P274S] mutations affect the pathway of biogenesis of HDL. Gene transfer of WT LCAT in LCAT(-/-) mice increased 11.8-fold the plasma cholesterol, whereas the LCAT[T147I] and LCAT[P274S] mutants caused a 5.2- and 2.9-fold increase, respectively. The LCAT[P274S] and the WT LCAT caused a monophasic distribution of cholesterol in the HDL region, whereas the LCAT[T147I] caused a biphasic distribution of cholesterol in the LDL and HDL region. Fractionation of plasma showed that the expression of WT LCAT increased plasma apoE and apoA-IV levels and shifted the distribution of apoA-I to lower densities. The LCAT[T147I] and LCAT[P274S] mutants restored partially apoA-I in the HDL3 fraction and LCAT[T147I] increased apoE in the VLD/IDL/LDL fractions. The in vivo functionality of LCAT was further assessed based on is its ability to correct the aberrant HDL phenotype that was caused by the apoA-I[L159R]FIN mutation. Co-infection of apoA-I(-/-) mice with this apoA-I mutant and either of the two mutant LCAT forms restored only partially the HDL biogenesis defect that was caused by the apoA-I[L159R]FIN and generated a distinct aberrant HDL phenotype.

HDL biogenesis, remodeling, and catabolism

In this chapter, we review how HDL is generated, remodeled, and catabolized in plasma. We describe key features of the proteins that participate in these processes, emphasizing how mutations in apolipoprotein A-I (apoA-I) and the other proteins affect HDL metabolism. The biogenesis of HDL initially requires functional interaction of apoA-I with the ATP-binding cassette transporter A1 (ABCA1) and subsequently interactions of the lipidated apoA-I forms with lecithin/cholesterol acyltransferase (LCAT). Mutations in these proteins either prevent or impair the formation and possibly the functionality of HDL. Remodeling and catabolism of HDL is the result of interactions of HDL with cell receptors and other membrane and plasma proteins including hepatic lipase (HL), endothelial lipase (EL), phospholipid transfer protein (PLTP), cholesteryl ester transfer protein (CETP), apolipoprotein M (apoM), scavenger receptor class B type I (SR-BI), ATP-binding cassette transporter G1 (ABCG1), the F1 subunit of ATPase (Ecto F1-ATPase), and the cubulin/megalin receptor. Similarly to apoA-I, apolipoprotein E and apolipoprotein A-IV were shown to form discrete HDL particles containing these apolipoproteins which may have important but still unexplored functions. Furthermore, several plasma proteins were found associated with HDL and may modulate its biological functions. The effect of these proteins on the functionality of HDL is the topic of ongoing research.

Characteristic, polymorphism and expression distribution of LCAT gene in a Mongolian gerbil model for hyperlipidemia

This study aims to evaluate the genetic basis and activity of lecithin cholesterol acyltransferase (LCAT) in a novel Mongolian gerbil model for hyperlipidemia. Gerbils may be susceptible to high fat and cholesterol (HF/HC) diets, which can rapidly lead to the development of hyperlipidemia. Approximately 10-30% of gerbils that are over 8months old and fed controlled diets spontaneously develop hyperlipidemia. Using the HF/HC diet model, we detected triglycerides (TG), total cholesterol (TC), HDL (high density lipoprotein)-C, LDL (low density lipoprotein)-C and LCAT in both old (>8months) and young gerbils. The TC and HDL-C levels were two times higher in old gerbils compared with young gerbils (P<0.01). However, in the old group the LCAT activity fell slightly compared with the normal lipidemia group. It is reasonable to hypothesize that this may be associated with single nucleotide polymorphisms of the LCAT gene. We cloned this gene to investigate the sensitivity of the gerbil to the HF/HC diet and spontaneous hyperlipidemia. The entire LCAT gene was cloned by splicing sequences of RACE (rapid amplification of cDNA ends) and nest-PCR products (AN: KC533867.1). The results showed that the 3683base pair gene consists of six exons and five introns. The LCAT protein consists of 444 amino acid (AA) residues, which are analogous to the human LCAT gene, and includes 24 signal peptide AA and 420 mature protein AA. Expression of LCAT was detected in the kidney, spleen and adrenal tissue, apart from the liver, by immunohistochemistry. The abundance of the protein was greater in the older group compared with the control group. Polymorphisms were analyzed by PCR-SSCP (PCR-single-strand conformation polymorphism) but none were found in 444 animals of the ZCLA closed population (a Chinese cultured laboratory gerbil population).

Recombinant human LCAT normalizes plasma lipoprotein profile in LCAT deficiency

Lecithin:cholesterol acyltransferase (LCAT) is the enzyme responsible for cholesterol esterification in plasma. Mutations in the LCAT gene leads to two rare disorders, familial LCAT deficiency and fish-eye disease, both characterized by severe hypoalphalipoproteinemia associated with several lipoprotein abnormalities. No specific treatment is presently available for genetic LCAT deficiency. In the present study, recombinant human LCAT was expressed and tested for its ability to correct the lipoprotein profile in LCAT deficient plasma. The results show that rhLCAT efficiently reduces the amount of unesterified cholesterol (-30%) and promotes the production of plasma cholesteryl esters (+210%) in LCAT deficient plasma. rhLCAT induces a marked increase in HDL-C levels (+89%) and induces the maturation of small preβ-HDL into alpha-migrating particles. Moreover, the abnormal phospholipid-rich particles migrating in the LDL region were converted in normally sized LDL.

Making, baking, and breaking: the synthesis, storage, and hydrolysis of neutral lipids

The esterification of amphiphilic alcohols with fatty acids is a ubiquitous strategy implemented by eukaryotes and some prokaryotes to conserve energy and membrane progenitors and simultaneously detoxify fatty acids and other lipids. This key reaction is performed by at least four evolutionarily unrelated multigene families. The synthesis of this "neutral lipid" leads to the formation of a lipid droplet, which despite the clear selective advantage it confers is also a harbinger of cellular and organismal malaise. Neutral lipid deposition as a cytoplasmic lipid droplet may be thermodynamically favored but nevertheless is elaborately regulated. Optimal utilization of these resources by lipolysis is similarly multigenic in determination and regulation. We present here a perspective on these processes that originates from studies in model organisms, and we include our thoughts on interventions that target reductions in neutral lipids as therapeutics for human diseases such as obesity and diabetes.

Lecithin:cholesterol acyltransferase: old friend or foe in atherosclerosis?

Lecithin:cholesterol acyltransferase (LCAT) is a key enzyme that catalyzes the esterification of free cholesterol in plasma lipoproteins and plays a critical role in high-density lipoprotein (HDL) metabolism. Deficiency leads to accumulation of nascent preβ-HDL due to impaired maturation of HDL particles, whereas enhanced expression is associated with the formation of large, apoE-rich HDL(1) particles. In addition to its function in HDL metabolism, LCAT was believed to be an important driving force behind macrophage reverse cholesterol transport (RCT) and, therefore, has been a subject of great interest in cardiovascular research since its discovery in 1962. Although half a century has passed, the importance of LCAT for atheroprotection is still under intense debate. This review provides a comprehensive overview of the insights that have been gained in the past 50 years on the biochemistry of LCAT, the role of LCAT in lipoprotein metabolism and the pathogenesis of atherosclerosis in animal models, and its impact on cardiovascular disease in humans.

Cholesterol metabolism and transport in the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is the most common neurodegenerative disorder, affecting millions of people worldwide. Apart from age, the major risk factor identified so far for the sporadic form of AD is possession of the epsilon4 allele of apolipoprotein E (APOE), which is also a risk factor for coronary artery disease (CAD). Other apolipoproteins known to play an important role in CAD such as apolipoprotein B are now gaining attention for their role in AD as well. AD and CAD share other risk factors, such as altered cholesterol levels, particularly high levels of low density lipoproteins together with low levels of high density lipoproteins. Statins--drugs that have been used to lower cholesterol levels in CAD, have been shown to protect against AD, although the protective mechanism(s) involved are still under debate. Enzymatic production of the beta amyloid peptide, the peptide thought to play a major role in AD pathogenesis, is affected by membrane cholesterol levels. In addition, polymorphisms in several proteins and enzymes involved in cholesterol and lipoprotein transport and metabolism have been linked to risk of AD. Taken together, these findings provide strong evidence that changes in cholesterol metabolism are intimately involved in AD pathogenic processes. This paper reviews cholesterol metabolism and transport, as well as those aspects of cholesterol metabolism that have been linked with AD.

Quantitative trait locus mapping and identification of Zhx2 as a novel regulator of plasma lipid metabolism

BACKGROUND

We previously mapped a quantitative trait locus on chromosome 15 in mice contributing to high-density lipoprotein cholesterol and triglyceride levels and now report the identification of the underlying gene.

METHODS AND RESULTS

We first fine-mapped the locus by studying a series of congenic strains derived from the parental strains BALB/cJ and MRL/MpJ. Analysis of gene expression and sequencing followed by transgenic complementation led to the identification of zinc fingers and homeoboxes 2 (Zhx2), a transcription factor previously implicated in the developmental regulation of alpha-fetoprotein. Reduced expression of the protein in BALB/cJ mice resulted in altered hepatic transcript levels for several genes involved in lipoprotein metabolism. Most notably, the Zhx2 mutation resulted in a failure to suppress expression of lipoprotein lipase, a gene normally silenced in the adult liver, and this was normalized in BALB/cJ mice carrying the Zhx2 transgene.

CONCLUSIONS

We identified the gene underlying the chromosome 15 quantitative trait locus, and our results show that Zhx2 functions as a novel developmental regulator of key genes influencing lipoprotein metabolism.

Molecular characterization, expression profile and association analysis with carcass traits of porcine LCAT gene

The lecithin cholesterol acyltransferase gene (LCAT) plays an important role in lipoprotein metabolism, especially in the process termed 'reverse cholesterol transport'. In this study, we obtained the 1,434 bp mRNA sequence of porcine LCAT including the full coding region and encoding a protein of 472 amino acids. The sequence was deposited into the GenBank under the accession no. EU717835. The genomic sequence of this gene which contains six exons and five introns, is 3,712 bp in length (GQ379050). Bioinformatic analysis of the 5' regulatory region has revealed that some transcription factor Sp1, AP-1, AP-2 and NF-kappaB were represented in this region. Tissue expression analysis showed that the porcine LCAT gene is ubiquitously expressed in all examined tissues. Phylogenetic tree was constructed by aligning the amino acid sequences of different species. Moreover, we found a single nucleotide polymorphism (SNP, C/G266) in intron 1 of the LCAT gene and association analysis showed that it was significantly associated with ratio of lean to fat (P < 0.05), caul fat weight (P < 0.01), leaf fat weight (P < 0.05), carcass length (P < 0.05) and bone percentage (P < 0.05). Our study will lay the groundwork for the further investigations on the detailed physiological function of LCAT in pig models.

Lecithin: cholesterol acyltransferase--from biochemistry to role in cardiovascular disease

PURPOSE OF REVIEW

We discuss the latest findings on the biochemistry of lecithin : cholesterol acyltransferase (LCAT), the effect of LCAT on atherosclerosis, clinical features of LCAT deficiency, and the impact of LCAT on cardiovascular disease from human studies.

RECENT FINDINGS

Although there has been much recent progress in the biochemistry of LCAT and its effect on high-density lipoprotein metabolism, its role in the pathogenesis of atherosclerosis is still not fully understood. Studies from various animal models have revealed a complex interaction between LCAT and atherosclerosis that may be modified by diet and by other proteins that modify lipoproteins. Furthermore, the ability of LCAT to lower apoB appears to be the best way to predict its effect on atherosclerosis in animal models. Recent studies on patients with LCAT deficiency have shown a modest but significant increase in incidence of cardiovascular disease consistent with a beneficial effect of LCAT on atherosclerosis. The role of LCAT in the general population, however, has not revealed a consistent association with cardiovascular disease.

SUMMARY

Recent research findings from animal and human studies have revealed a potential beneficial role of LCAT in reducing atherosclerosis but additional studies are necessary to better establish the linkage between LCAT and cardiovascular disease.

LCAT synthesized by primary astrocytes esterifies cholesterol on glia-derived lipoproteins

Lipid trafficking in the brain is essential for the maintenance and repair of neuronal membranes, especially after neurotoxic insults. However, brain lipid metabolism is not completely understood. In plasma, LCAT catalyses the esterification of free cholesterol on circulating lipoproteins, a key step in the maturation of HDL. Brain lipoproteins are apolipoprotein E (apoE)-containing, HDL-like particles secreted initially as lipid-poor discs by glial cells. LCAT is synthesized within the brain, suggesting that it may play a key role in the maturation of these lipoproteins. Here we demonstrate that astrocytes are the primary producers of brain LCAT. This LCAT esterifies free cholesterol on nascent apoE-containing lipopoproteins secreted from glia. ApoE is the major LCAT activator in glia-conditioned media (GCM), and both the cholesterol transporter ABCA1 and apoE are required to generate glial LCAT substrate particles. LCAT deficiency leads to the appearance of abnormal approximately 8 nm particles in GCM, and exogenous LCAT restores the lipoprotein particle distribution to the wild-type (WT) pattern. In vivo, complete LCAT deficiency results in a dramatic increase in apoE-HDL and reduced apolipoprotein A-I (apoA-I)-HDL in murine cerebrospinal fluid (CSF). These data show that brain LCAT esterifies cholesterol on glial-derived apoE-lipoproteins, and influences CSF apoE and apoA-I levels.

Developmental changes of protein profiles in the embryonic Sanhuang chicken liver

Understanding embryonic liver development bears the potential to provide important insights into treatments and preventative strategies for paediatric liver disease. Using Sanhuang (SH) chicken as a model system, we sought to identify the proteomic changes associated with embryonic liver development using differential display of proteins with two-dimensional (2-D) polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrometry analysis. Embryonic livers from 200 SH chicken embryos were isolated on days 9, 14 and 19 during incubation and also immediately after hatching. Six hundred and two protein spots were displayed on 2-D gels stained with colloidal Coomassie brilliant blue, of which, 25 protein spots were found to have changes up to threefold in abundance during development. We identified these spots using MALDI-TOF mass spectrometry and found 23 of 25 proteins to be associated with carbohydrate metabolism, cell division, lipid metabolism and signal transduction. Our results provide insight into the biochemical events taking place during the development of SH chicken embryonic liver and highlight the value of proteomics in characterizing complex biochemical processes. Furthermore, the proteome maps may facilitate future studies addressing the effects of genetic and environmental factors and related studies on the development and quality of chicken embryonic liver.

Association of the apolipoprotein A-IV: 360 Gln/His polymorphism with cerebrovascular disease, obesity, and depression in a Brazilian elderly population

The identification of genetic polymorphisms as risk factors for complex diseases can be relevant for their prevention, diagnosis, and prognosis. The apolipoprotein A-IV: 360 Gln/His polymorphism was investigated in 383 elderly individuals, who were participants of a longitudinal study commenced in 1991. The major morbidities that affect elderly people, such as cardiovascular diseases, diabetes, low cognitive function, depression, and obesity, were extensively investigated. DNA was isolated from blood cells, amplified by PCR, and digested with Fnu4HI. In this population the frequency of the His allele was 0.056 and the genotypes were distributed according to Hardy-Weinberg equilibrium. Logistic regression analysis showed a significant association between the presence of His allele and cerebrovascular disease and/or transitory ischemic attack (odds ratio) (OR = 3.070, P = 0.027), obesity (OR = 2.241, P = 0.047), and depression (OR = 2.879, P = 0.005). This study indicates that the presence of the rare allele in elderly people can play a significant role in the occurrence of multifactorial diseases. This is the first study analyzing this polymorphism in elderly people in Brazil. More studies should be encouraged to elucidate the mechanisms involved in these diseases.

Classification of cDNA array genes that have a highly significant discriminative power due to their unique distribution in four brain regions

Novel statistical methods were used to distinguish functionally distinct brain regions using their cDNA array gene expression profiles, and it was found that one of four specific factors is often associated with the most regionally discriminative genes. The gene expression profiles for the substantia nigra (SN), striatum (STR), parietal cortex (PC), and posterolateral cortical amygdaloid nucleus (PLCo) brain regions were determined from each brain region. An F-test identified 339 genes of the 1185 array genes as having a P < or = 0.01 and applied a gene ranking and selection method based on Soft Independent Modeling of Class Analogy (SIMCA) to obtain 59 of the most discriminative genes. Their discriminative power was validated in three steps. The most convincing step showed their ability to correctly predict the brain regional classifications for 18 "test" gene expression sets obtained from the four regions. A two-way Hierarchical Cluster Analysis organized the 59 genes in six clusters according to their expression differences in the brain regions. Expression patterns in the SN and STR regions greatly differed from each other and the PC and PLCo. The closer similarity in the gene expression patterns of the PC and PLCo was probably due to their functional similarity. The important factors in determining differences in the regional gene expression profiles in six clusters were (1) regional myelin/oligodendrocyte levels, (2) resident neuron types, (3) neurotransmitter innervation profiles, and (4) Ca++-dependent signaling and second messenger systems.

Domains of apoE required for binding to apoE receptor 2 and to phospholipids: implications for the functions of apoE in the brain

We have studied the contribution of the carboxy terminal domains of lipid-free apoE isolated from apoE-expressing cell cultures in binding to phospholipids and have determined the affinities of reconstituted POPC-apoE particles for the apoER2. It was found that the initial rate of association of apoE2, apoE3, apoE4, and a mutant form apoE4R158M to multilamellar DMPC vesicles was similar and was reduced and eventually diminished by gradual deletion of the carboxy terminal segments. The truncated apoE forms retained their ability to associate with plasma lipoproteins. Receptor binding studies were performed using the ldlA-7 cells expressing apoER2 and transiently transfected COS-M6 and the appropriate control untransfected cells. Specific binding to apoER2 was obtained by subtracting from the total binding to the receptor-expressing cells the nonspecific binding values of the untransfected cells. POPC-apoE particles generated using apoE3, apoE4, the truncated apoE4-259, apoE4-229, apoE4-202, and apoE-165, and the mutant apoE4R158M all bound tightly to the apoER2 (K(d) range of 12 +/- 3 to 19 +/- 4 microg/mL). POPC-apoE2 bound with reduced affinity (K(d) = 31 +/- 5.3 microg/mL). The findings establish that the apoER2 binding domain of apoE is in the 1-165 amino terminal region, whereas the carboxy terminal 230-299 region of apoE is required for efficient initial association with phospholipids.

Analysis of gene expression following spinal cord injury in rat using complementary DNA microarray

To identify genes that were altered by spinal cord injury (SCI), we used complementary DNA microarray consisting 1176 rat genes. Rats were subjected to contusive injury of the thoracic spinal cord. Sham animals received only a laminectomy. Twenty-four hours later, spinal cord was dissected out, a 32P labeled probe was prepared and hybridized to the microarray. We identified three genes that showed a greater than 2-fold increase in SCI tissue, heat shock 27-kDa protein, tissue inhibitor of metalloproteinase-1 and epidermal fatty acid-binding protein. Seven genes, lecithin:cholesterol acyltransferase, dipeptidyl aminopeptidase related protein, phospholipase C delta 4, plasma membrane Ca2+-ATPase isoform 2, G-protein GO alpha subunit, GABA transporter 3, and neuroendrocrine protein 7B2 were down-regulated greater than 50% in SCI tissue. Changes in expression of these genes were confirmed by reverse transcription-polymerase chain reaction. These genes may play a role in the response to tissue damage or repair following SCI.

Genetic differences in hepatic lipid peroxidation potential and iron levels in mice

Oxidative damage to macromolecules, including lipids, has been hypothesized as a mechanism of aging. One end product of lipid peroxidation, malondialdehyde (MDA), is often quantified as a measure of oxidative damage to lipids. We used a commercial colorimetric assay for MDA (Bioxytech LPO-586, Oxis International, Portland, OR) to measure lipid peroxidation potential in liver tissue from young (2 month) male mice from recombinant inbred (RI) mouse strains from the C57BL/6J (B6)xDBA/2J (D2) series (BXD). The LPO-586 assay (LPO) reliably detected significant differences (P<0.0001) in lipid peroxidation potential between the B6 and D2 parental strains, and yielded a more than two-fold variation across the BXD RI strains. In both B6 and D2 mice, LPO results were greater in old (23 month) mice, with a larger age-related increase in the D2 strain. As the level of iron can influence lipid peroxidation, we also measured hepatic non-heme iron levels in the same strains. Although iron level exhibited a slightly negative overall correlation (r(2)=0.119) with LPO results among the entire group of BXD RI strains, a sub-group with lower LPO values were highly correlated (r(2)=0.704). LPO results were also positively correlated with iron levels from a group of 8 other inbred mouse strains (r(2)=0.563). The BXD RI LPO data were statistically analyzed to nominate quantitaive trait loci (QTL). A single marker, Zfp4, which maps to 55.2 cM on chromosome 8, achieved a significance level of P<0.0006. At least two potentially relevant candidate genes reside close to this chromosomal position. Hepatic lipid peroxidation potential appears to be a strain related trait in mice that is amenable to QTL analysis.

Glucose regulates the transcription of human genes relevant to HDL metabolism: responsive elements for peroxisome proliferator-activated receptor are involved in the regulation of phospholipid transfer protein

Phospholipid transfer protein (PLTP) plays an important role in human plasma HDL metabolism. Clinical data have recently indicated that plasma PLTP activity and mass were both higher in diabetic patients concomitant with hyperglycemia. The present study shows that high glucose increases both PLTP mRNA and functional activity in HepG2 cells, due to a significant increase in the promoter activity of human PLTP gene. The glucose-responsive elements are located between -759 and -230 of the PLTP 5'-flanking region, within which two binding motifs (-537 to -524 and -339 to -327) for either peroxisome proliferator-activated receptor or farnesoid X-activated receptor are involved in this glucose-mediated transcriptional regulation. This finding suggests that high glucose upregulates the transcription of human PLTP gene via nuclear hormone receptors. In addition, high glucose increases mRNA levels for several genes that are functionally important in HDL metabolism, including human ATP-binding cassette transporter A1, apolipoprotein A-I, scavenger receptor BI, and hepatic lipase. The functional promoter activities of these genes are enhanced by high glucose in three cell lines tested, indicating that glucose may also regulate these genes at the transcriptional level. Our findings provide a molecular basis for a role of hyperglycemia in altered HDL metabolism.

The bushlike radiation of muroid rodents is exemplified by the molecular phylogeny of the LCAT nuclear gene

Phylogenetic relationships among 40 extant species of rodents, with an emphasis on the taxonomic sampling of Muridae and Dipodidae, were studied using sequences of the nuclear protein-coding gene LCAT (lecithin cholesterol acyl transferase). Analysis of 804 bp from the exonic regions of LCAT confirmed many traditional groupings in and around Muridae. A strong support was found for the families Muridae (represented by 29 species) and Dipodidae (5 species). Compared with Sciuridae, Gliridae, and Caviomorpha, the Dipodidae family appeared the closest relative of Muridae, confirming the suprafamilial Myodonta concept. Within the speciose family Muridae, the first branching leads to the fossorial Spalacinae and semifossorial Rhyzomyinae. The remaining components of Muridae appear as a polytomy from which are issued Sigmodontinae, Calomyscinae, Arvicolinae, Cricetinae, Mystromyinae, Nesomyinae, and some Dendromurinae (Steatomys and Dendromus). This phylogeny is interpreted as the result of a bushlike radiation at the end of the early Miocene, leading to emergence of most living subfamilies. The separation between three additional taxa, Murinae, Gerbillinae, and "Acomyinae" (which comprises the genera Acomys, Deomys, Uranomys, and Lophuromys), has occurred more recently from a common ancestor issued from the main basal radiation. As previously shown by other molecular studies, the vlei rats, Otomyinae, are nested within Old World Murinae. In the same way, the zokors, Myospalacinae, appear strongly nested within the hamsters, Cricetinae. Finally, we propose a sister group relationship between Malagasy Nesomyinae and south African Mystromyinae.

Astrocyte lipoproteins, effects of apoE on neuronal function, and role of apoE in amyloid-beta deposition in vivo

The genetic association between the E4 isoform of apolipoprotein E (apoE) and increased risk for Alzheimer's disease (AD) has prompted interest in the neurobiology of apoE and the possible relationship between lipoprotein metabolism in the brain and neurodegenerative disease. ApoE, a product of astrocytes, is abundant in brain and in cerebrospinal fluid (CSF) where it is found in lipoproteins the size of large plasma high-density lipoproteins (HDL). Cultured astrocytes also secrete apoE/HDL, although the lipid and apoprotein composition of these nascent particles differs from that found in CSF, suggesting possible functional differences. In vitro studies have demonstrated isoform-specific effects of apoE on neurite outgrowth, neuronal plasticity, neurotoxicity, lipid peroxidation, oxidative injury, binding to cytoskeletal proteins, and interactions with amyloid-beta (Abeta), a primary component of senile plaques in AD. A number of these proposed functions have also been assessed in apoE -/- mice and transgenic mice expressing human apoE3 or apoE4. Importantly, analysis of transgenic mice overexpressing a mutant form of the human amyloid precursor protein (APP(V717F)) in the presence of mouse apoE, no apoE, or human apoE3 or E4 has demonstrated a critical and isoform-specific role for apoE in neuritic plaque formation, a pathologic hallmark of AD. Together, these data have provided important clues as to possible mechanism(s) by which apoE genotype modifies AD risk.

Mouse K-Cl cotransporter KCC1: cloning, mapping, pathological expression, and functional regulation

Although K-Cl cotransporter (KCC1) mRNA is expressed in many tissues, K-Cl cotransport activity has been measured in few cell types, and detection of endogenous KCC1 polypeptide has not yet been reported. We have cloned the mouse erythroid KCC1 (mKCC1) cDNA and its flanking genomic regions and mapped the mKCC1 gene to chromosome 8. Three anti-peptide antibodies raised against recombinant mKCC1 function as immunoblot and immunoprecipitation reagents. The tissue distributions of mKCC1 mRNA and protein are widespread, and mKCC1 RNA is constitutively expressed during erythroid differentiation of ES cells. KCC1 polypeptide or related antigen is present in erythrocytes of multiple species in which K-Cl cotransport activity has been documented. Erythroid KCC1 polypeptide abundance is elevated in proportion to reticulocyte counts in density-fractionated cells, in bleeding-induced reticulocytosis, in mouse models of sickle cell disease and thalassemia, and in the corresponding human disorders. mKCC1-mediated uptake of (86)Rb into Xenopus oocytes requires extracellular Cl(-), is blocked by the diuretic R(+)-[2-n-butyl-6,7-dichloro-2-cyclopentyl-2, 3-dihydro-1-oxo-1H-indenyl-5-yl-)oxy]acetic acid, and exhibits an erythroid pattern of acute regulation, with activation by hypotonic swelling, N-ethylmaleimide, and staurosporine and inhibition by calyculin and okadaic acid. These reagents and findings will expedite studies of KCC1 structure-function relationships and of the pathobiology of KCC1-mediated K-Cl cotransport.

Characterization of Apolipoprotein E-containing Lipoproteins in Cerebrospinal Fluid: Effect of Phenotype on the Distribution of Apolipoprotein E

Background: Apolipoprotein (apo) E, one of the main apolipoproteins in the central nervous system, may play an important role in lipid metabolism; however, the details of its function are poorly understood. In this study, we characterized apoE-containing lipoproteins in cerebrospinal fluid (CSF) and examined the effect of apoE phenotype on the distribution of apoE among the lipoprotein fractions.

Methods: CSF lipoproteins were fractionated by gel filtration and ultracentrifugation, and then characterized by electrophoresis, immunoblot, electron microscopy, and analysis of apoE, total cholesterol, and phospholipid concentrations.

Results: The ratio of sialylated to nonsialylated apoE was higher in CSF than in serum. However, the fundamental forms containing apoE homodimers or heterodimers [such as apo(E-AII) and apo(AII-E2-AII) complexes] were similar in CSF and serum. apoE-containing lipoproteins were fractionated at densities of &lt;1.006, 1.063–1.125, and 1.125–1.21 kg/L. Neither apoE nor apoAI was detected in the fraction with a density range of 1.006–1.063 kg/L. The diameters of the lipoprotein particles with densities of &lt;1.006, 1.063–1.125, and 1.125–1.21 kg/L were 16.7 ± 3.1, 14.0 ± 3.2, and 11.6 ± 2.8 nm (mean ± SD, n = 200), respectively. All of these lipoproteins exhibited a spherical structure. The distribution profile of apoE-containing lipoproteins was affected by the apoE phenotype. A relatively large amount of apoE-containing lipoproteins was isolated from the fraction with a density &gt;1.125 kg/L obtained from CSF associated with apoE2 or apoE3. This tendency was more obvious in CSF associated with apoE2 than in CSF without apoE2. apoE-containing lipoproteins were predominantly observed in the fraction with a density of &lt;1.006 kg/L obtained from CSF associated with apoE4.

Conclusions: The lipoproteins in CSF have a unique composition that is different from that of the lipoproteins in plasma. However, the differences in diameter between the CSF fractions were not as large as for the serum fractions. Our data suggest that the apoE phenotype may affect the distribution profile of apoE-containing lipoproteins in the CSF. This would mean that the metabolism of apoE-containing lipoproteins depends on the apoE isoform present.

Introduction of the human PLTP transgene suppresses the atherogenic diet-induced increase in plasma phospholipid transfer activity in C57BL/6 mice

The human plasma phospholipid transfer protein (PLTP) has been shown to facilitate the transfer of phospholipids between lipoproteins and convert high-density lipoproteins into larger and smaller particles in vitro. To explore the lipid transport function in vivo, transgenic C57BL/6 mice that express the human PLTP gene, driven by its natural promoter, were generated. Little difference in PLTP activity and lipoprotein lipids was observed between transgenic mice and non-transgenic control mice fed the chow diet. In response to an atherogenic high-fat, high-cholesterol, cholic acid containing diet, the PLTP activity increased significantly with time in control mice (62% in males and 34% in females after the high-fat diet for 18 weeks). In contrast, the PLTP activity did not change appreciably in the transgenic mice fed the atherogenic diet. Thus, the introduction of the human transgene suppressed the diet-induced increase in plasma PLTP activity, as evidenced by a decrease in PLTP mRNA in a variety of tissues. High-density lipoprotein levels decreased in mice fed the atherogenic diet, but there was a proportionally greater decrease in transgenic animals than in controls. After 18 weeks on the atherogenic diet, the transgenic animals had high-density lipoprotein-cholesterol and PLTP activity approximately one-half of that of control animals. Non-denaturing gradient gel electrophoresis of plasma indicated that the atherogenic diet decreased the high-density lipoprotein size distribution in control mice. However, high-density lipoprotein particle size distribution of the transgenic mice was shifted to smaller particles compared with control animals (P < 0.001). These findings suggest that PLTP activity can modulate the effects of an atherogenic diet on high-density lipoproteins.

Secretion of lecithin:cholesterol acyltransferase by brain neuroglial cell lines

The ability of different human and rat brain cell lines (neuronal and gliomal) to secrete lecithin:cholesterol acyltransferase (LCAT) was examined. Of these, the strongly secreting human gliomal (U343 and U251) cell lines were selected for a detailed study of enzymatic and structural properties of the secreted LCAT. Both plasma- and brain-derived enzymes are inhibited by DTNB (90%) and are activated by apolipoprotein A-I. LCAT mRNA was measured in these cell lines at levels similar to that found in HepG2 cells. In contrast, apoA-I, apoE, and apoD mRNAs were undetectable in these cell lines. The presence of functional LCAT secreted by cultured nerve cells provides an in vitro model to study the expression and function of LCAT in the absence of others factors of plasma cholesterol metabolism.

Cloning and expression of a novel lysophospholipase which structurally resembles lecithin cholesterol acyltransferase

Lecithin cholesterol acyltransferase (LCAT) is the key enzyme in the esterification of plasma cholesterol and in the reverse cholesterol transport on high-density lipoprotein (HDL). We have found a novel LCAT-related gene among differentially expressed cDNA fragments between two types of foam cells derived from THP-1 cells, which are different in cholesterol efflux ability, using a subtractive PCR technique. The deduced 412-amino-acid sequence has 49% amino acid sequence similarity with human LCAT. In contrast to the liver-specific expression of LCAT, mRNA expression of the gene was observed mainly in peripheral tissues including kidney, placenta, pancreas, testis, spleen, heart, and skeletal muscle. The protein exists in human plasma and is probably associated with HDL. Moreover, we discovered that the recombinant protein hydrolyzed lysophosphatidylcholine (lysoPC), a proatherogenic lipid, to glycerophosphorylcholine and a free fatty acid. We have therefore named this novel enzyme LCAT-like lysophospholipase (LLPL), through which a new catabolic pathway for lysoPC on lipoproteins could be elucidated.

Fatty acids modulate lecithin:cholesterol acyltransferase secretion independently of effects on triglyceride secretion in primary rat hepatocytes

The regulation of plasma lecithin:cholesterol acyltransferase (LCAT) expression is not well understood. Although oleic acid increases both the secretion of triglycerides and LCAT by primary rat hepatocytes, the effect of other fatty acids (FA) on LCAT secretion is not known. This study was designed to examine the effect of FA on the hepatic secretion of LCAT, triglyceride and apolipoprotein A-1 (apoA-1). Primary rat hepatocytes were incubated with serum-free medium, supplemented with individual FA (0-1 mmol/L) for 22-24 h. Preliminary studies indicated a linear secretion of LCAT up to 24 h in both control and FA-treated cells. When hepatocytes were incubated with 1 mmol/L FA, the LCAT secretion increased 50-100% (P < 0.01) in the presence of the 18-carbon FA (stearic, oleic, elaidic and linoleic acids), whereas the presence of butyric, lauric and palmitic acids had no significant effect. LCAT secretion decreased (P < 0.01) in the presence of docosahexaenoic acid (DHA). All FA (except DHA) significantly enhanced triglyceride secretion; however, only the 18 carbon FA significantly stimulated the synthesis and secretion of apoA-1 and secretion of LCAT. The secretion of LCAT correlated with apoA-1 secretion (r = 0.88, P = 0.004) but not with triglyceride secretion (r = 0.55, P = 0.12). Treatment with oleic acid resulted in a 1.5-fold increase in hepatocyte LCAT mRNA accumulation, whereas butyrate and palmitate had no effect. These data indicate that FA that promote the apparent synthesis and secretion of apoA-1 also stimulate the secretion of LCAT in vitro, suggesting a coordinate regulatory mechanism for apoA-1 and LCAT expression.

Molecular basis of fish-eye disease in a patient from Spain. Characterization of a novel mutation in the LCAT gene and lipid analysis of the cornea

The genetic and biochemical basis of fish-eye disease (FED) was investigated in a 63-year-old female proband with low plasma HDL cholesterol. Analyses of corneal and plasma lipids of the proband were consistent with impaired lecithin:cholesterol acyltransferase (LCAT) activity. Free cholesterol and phospholipid levels were elevated relative to control values, whereas cholesteryl ester levels were greatly reduced. Fatty acid compositions of corneal lipids from the proband and control subjects differ from the respective fatty acid compositions of their plasma lipids. This suggests that the metabolic pathways and acyl chain specificities for phospholipid, cholesteryl ester, and triglyceride metabolism within the cornea are distinct from those of plasma. Sequencing of the LCAT gene from the proband revealed a novel mutation at nucleotide 399, corresponding to an Arg99-->Cys substitution. Secretion of LCAT (Arg99-->Cys) by transfected COS-6 cells was approximately 50% of that of the wild type, but its specific activity against reassembled HDL was 93% lower than that of wild-type LCAT. The specific activities of wild-type and LCAT (Arg99-->Cys) against LDL were reduced similarly, suggesting that the appearance of the FED phenotype does not require enhanced activity against LDL. Our data support the hypothesis that FED is a partial LCAT deficiency in which poor esterification in specific types of HDL particles may contribute to the appearance of the corneal opacities.

Cholesteryl ester transfer protein activity enhances plasma cholesteryl ester formation. Studies in CETP transgenic mice and human genetic CETP deficiency

The plasma cholesteryl ester transfer protein (CETP) promotes the removal of HDL cholesteryl esters and is thought to stimulate reverse cholesterol transport (RCT). However, mechanisms by which CETP may stimulate RCT are poorly understood. Thus, we examined the relationship between plasma CETP expression and plasma cholesteryl ester formation in CETP transgenic (Tg) mice, hamsters, and human subjects with genetic CETP deficiency. Incubation of CETP Tg mouse plasma showed a 20% to 40% increase in plasma cholesterol esterification rate (CER, P < .05) compared with control mice. Injection of a neutralizing CETP monoclonal antibody (MAb) (TP2) into natural flanking region CETP Tg mice resulted in an increase in plasma free cholesterol (FC) concentration, FC/CE ratio, FC/phosphatidylcholine ratio, and hepatic CETP mRNA. In hamsters, CETP inhibition also resulted in an increase in plasma FC/phosphatidylcholine ratio and increased CETP mRNA in adipose tissue. In humans with two common CETP gene mutations (an intron 14 splicing defect and a D442G missense mutation), mean plasma CERs were 39 and 60, respectively, compared with 89 nmol x mL-1 x h-1 in normal subjects. By contrast, lecithin:cholesterol acyltransferase (LCAT) mass was normal in CETP-deficient subjects. MAb neutralization of CETP activity in incubated human plasma did not alter the LCAT reaction, even after supplementation with discoidal HDL and VLDL. Thus, genetic alterations in CETP levels lead to secondary changes in the plasma LCAT reaction, possibly because of remodeling of HDL by CETP acting in concert with other factors in vivo. In human genetic CETP deficiency, a moderate impairment in the plasma LCAT reaction may contribute to a defect in RCT, providing a potential mechanism to explain the recently observed excess of coronary heart disease in these subjects.

Alternative splicing in lecithin:cholesterol acyltransferase mRNA: an evolutionary paradigm in humans and great apes

Lecithin:cholesterol acyltransferase (LCAT), an important enzyme affecting reverse cholesterol transport, is expressed in liver and cultured fibroblasts. Sequencing of LCAT cDNA clones demonstrated the coexistence of two mRNA products. In addition to the normal transcript, we identified an alternate message with a splice-mediated insertion of a 95 bp Alu cassette at the junction of exons 5 and 6. In humans, the alternate transcript represents 5-20% of the complete LCAT message in cultured fibroblasts and liver. It is present in humans and the great apes but not in lesser apes (gibbon, siamang) or lower-order primates (e.g., old or new world monkeys). Sequencing of intron 5 of the LCAT locus in several primates revealed a G-->A transition at the splice donor recognition site in the Alu repeat of the gibbon and a G-->A substitution in the last position of the 95 bp Alu sequence of the rhesus monkey, an old world monkey. Both substitutions have been associated with exon skipping in other genes. These results demonstrate that alternative splicing of LCAT mRNA is variant among primates and suggest a potential role of Alu elements in the evolutionary diversity of proteins.

The delta 5-3 beta-hydroxy steroid acyl transferase activities in tissues of the male rat and sheep

Pregnenolone and dehydroepiandrosterone and their sulphate and fatty acid ester derivatives are concentrated in the mammalian brain, as compared to the peripheral organs. Although biological functions have been postulated for the free steroid and sulphate conjugates, the role of steroid fatty acid esters in the central nervous system (CNS) has yet to be established. A comparison of the esterifying capacities of brain and peripheral organs of the male rat and sheep is made here. The male rat brain was found to possess a higher esterifying capacity than all other tissues examined, with 5.32 +/- 2.46 pmol dehydroepiandrosterone fatty acid esters synthesized/mg protein/h and 1.89 +/- 0.42 pmol pregnenolone fatty acid esters synthesized/mg protein/h. Sheep adrenal and sheep liver homogenates were found to have higher esterifying capacities than sheep brain. Within the brain of both species. delta 5-3 beta-hydroxy steroid acyl transferase enzyme(s) were concentrated in the microsomal fraction. The addition of a lecithin:cholesterol acyl transferase inhibitor to incubation assays resulted in a loss in enzyme activity. This effect was more significant in sheep brain microsomes than rat brain microsomes. It is likely that lecithin:cholesterol acyl transferase is more active in the sheep brain than the rat brain. Results from this study indicate that the steroid acyl transferase enzymes that are active in the mammalian brain are substrate specific.

A novel missense mutation (Asn5-->Ile) in lecithin: cholesterol acyltransferase (LCAT) gene in a Japanese patient with LCAT deficiency

We identified a novel missense mutation in the lecithin:cholesterol acyltransferase gene in a new case of lecithin:cholesterol acyltransferase (LCAT) deficiency. The patient was a 64-year-old diabetic Japanese male who showed an extremely low level of serum high-density lipoprotein-cholesterol, corneal opacities, anemia, and proteinuria. Both the patient's LCAT activity and mass were markedly low. DNA sequence analysis of the LCAT gene showed an A-to-T transition at base 97 in exon 1, and predicted a change in asparagine to isoleucine at the 5th amino acid of the protein. Restriction analysis of polymerase chain reaction-amplified DNA using Ase I showed that the patient was homozygous for this mutation. Our results suggested that asparagine 5 was an important amino acid and substitution with isoleucine caused marked reduction of LCAT activity and mass, resulting in LCAT deficiency.

Effects of simvastatin on plasma lipids and apolipoproteins in familial hypercholesterolemic swine

Familial hypercholesterolemia (FHC) in swine, which resembles human familial combined hyperlipidemia, is a complex lipid and lipoprotein disorder associated with the development of severe coronary lesions similar to those occurring in advanced human coronary disease. The disorder is characterized by elevated plasma total cholesterol (TC), triglycerides (TG), LDL-cholesterol (LDL-C), apolipoproteins (apo) B, C-III, and E, and by decreased levels of HDL-cholesterol (HDL-C), apoA-I, and lecithin:cholesterol acyltransferase (LCAT) activity. A dose-response study with simvastatin, a specific inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, was conducted in four treatment groups of FHC animals, exhibiting TC > or = 250 mg/dL. The animals were fed 0, 80, 200, or 400 mg simvastatin daily for 3 weeks. The measured serum parameters included the levels of TC, VLDL-C, LDL-C, HDL-C, TG, lathosterol, apoA-I, B, C-III, and E, as well as LCAT activity. Simvastatin at 200 mg/d significantly decreased the levels of TC (-25%), LDL-C (-27%), lathosterol (-40%), apoB (-22%), apoC-III (-37%), and apoE (-24%) and modestly decreased the levels of HDL-C (-12%) and apoA-I (-11%) (percent relative to the average pretreatment and posttreatment baseline values) but did not affect the levels of TG, VLDL-C, the lathosterol/TC ratio, or LCAT activity. The levels of TC, LDL-C, apoB, and E were also lowered by simvastatin at 80 or 400 mg/d, but to a lesser extent than at 200 mg/d, while the other parameters were not influenced at these doses. The simvastatin-induced decreases of LDL-C, HDL-C, and apoA-I, B, C-III, and E were significantly correlated among each other. These results show that the trend of responses in TC, LDL-C, apoB, apoC-III, and apoE to simvastatin in the FHC swine is similar to that observed in humans, although the drugs is less potent and efficacious in swine, while the results are different from those in humans with regard to the remaining parameters.

Chicken lecithin-cholesterol acyltransferase. Molecular characterization reveals unusual structure and expression pattern

Rapidly growing oocytes in the laying hen are, in addition to the liver, targets of the so-called "reverse cholesterol transport" (RCT) (Vieira, P.M., Vieira, A.V., Sanders, E.J., Steyrer, E., Nimpf, J., and Schneider, W.J. (1995) J. Lipid Res. 36, 601-610), pointing to the importance of this process in nonplacental reproduction. We have begun to delineate the details of this unique transport pathway branch by molecular characterization of the first nonmammalian lecithin-cholesterol acyltransferase (LCAT), the enzyme that catalyzes an early step in RCT. The biological significance of the enzyme is underscored by the high degree of protein sequence identity (73%) maintained from chicken to man. Interestingly, the conservation extends much less to the cysteine residues; in fact, two of the cysteines thought to be important in mammalian enzymes (residues 31 and 184 in man) are absent from the chicken enzyme, providing proof of their dispensability for enzymatic activity. Antibodies prepared against a chicken LCAT fusion protein cross-react with human LCAT and identify a 64-kDa protein present in enzymatically active fractions obtained by hydrophobic chromatography of chicken serum. The developmental and tissue distribution pattern of LCAT in females is striking; during embryogenesis and adolescence, LCAT expression is extremely high in liver but undetectable in brain. Upon onset of laying, however, brain LCAT mRNA increases suddenly and is maintained at levels 5 times higher than in liver, in stark contrast to most mammals. In adult roosters, the levels of LCAT transcripts in brain are lower than in liver. Together with the molecular characterization of chicken LCAT, these newly discovered developmental changes and gender differences in its expression establish the avian oocyte/liver system as a powerful model to delineate in vivo regulatory elements of RCT.