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CD36 is an 88-kDa glycoprotein expressed on platelets and monocyte/macrophages (Mphi). CD36 is a multifunctional receptor for collagen, thrombospondin, oxidized low density lipoproteins (LDL), and long-chain fatty acids. The present study was performed to investigate whether CD36 can function as an adhesion molecule which is involved in mediating human macrophages (Mphi) adhesion to type I collagen in vitro. The Mphi of human CD36-deficient as well as normal control subjects were isolated and cultured on the multi-well plates coated with type I collagen, a natural ligand for CD36. Up to 2 h of incubation, the Mphi from CD36-deficient patients showed almost a approximately 55% decrease in adhesion to type I collagen in comparison to those from controls (P0.01). However, there was no significant difference in the adhesion thereafter. Furthermore, the addition of antibody against CD36 into the media of control Mphi significantly inhibited the adhesion by approximately 50% (P0.05). The addition of oxidized LDL (OxLDL) did not alter adhesion of Mphi from both CD36-deficient and controls. These data suggest that CD36 is involved in the adhesion of Mphi to type I collagen, especially in the early stage of adhesion.

Abstract —CD36 is one of the major receptors for oxidized low density lipoproteins belonging to macrophage (Mφ) scavenger receptor (SR) class B and is thought to play an important role in the foam cell formation from monocyte-Mφ in the atherosclerotic lesions. Although it has been hypothesized that smooth muscle cells (SMCs) may be the other origin of foam cells in vivo, supporting data are still very limited. In the present study, we have tested the expression of a variety of SRs, including CD36, in 8 lots of primary human aortic SMCs (HASMCs) explanted from 8 different donors. Functional CD36 was expressed in cultured HASMCs, and the levels of expression were widely ranged between the lots. SR class A (SR-A) was expressed abundantly in CD36-negative lots. Other Mφ markers, such as CD32 and CD68, were expressed in all lots tested. These data suggest that the cultured HASMCs gained an Mφ-like phenotype. To determine the mechanism for the above-described phenotypic change, we have tested the expression of a nuclear receptor, peroxisome proliferator activated receptor-γ, in those cells. This nuclear receptor was abundantly expressed in CD36-positive lots, whereas c- fms was expressed abundantly in CD36-negative/SR-A–positive lots. The synthetic ligand of peroxisome proliferator activated receptor-γ, troglitazone, upregulated the expression of CD36 only in CD36-positive lots. These observations demonstrate that cultured HASMCs can gain an Mφ-like phenotype, possibly classified by the expression of CD36 or SR-A. The present study may support the possibilities of transformation of HASMCs into foam cells in vivo.

Abstract —CD36 is a glycoprotein with an M r of 88 kDa that is expressed on platelets, monocytes/macrophages, capillary endothelial cells, and adipocytes. We previously demonstrated that CD36 is involved in the uptake of oxidized low density lipoprotein (OxLDL) by using CD36-deficient macrophages ( J Clin Invest . 1995;96:1859). However, the regulation of CD36 expression in human monocyte–derived macrophages has not been fully elucidated. The current study attempted to clarify the effect of OxLDL and cytokines, both of which are present in atherosclerotic lesions and may play an important role in atherogenesis, on the expression of CD36. A cell enzyme-linked immunosorbent assay and flow cytometry were used to detect CD36 protein. A ribonuclease protection assay was used to measure CD36 mRNA in human monocyte–derived macrophages. The expression of CD36 was increased during the differentiation of monocytes to macrophages. Incubation of macrophages with 25 μg/mL OxLDL for 24 hours increased the level of CD36 protein by 56% and that of CD36 mRNA by 58%. Lysophosphatidylcholine did not affect the expression of CD36. The effects of OxLDL were demonstrated in macrophages that had already differentiated to the point where CD36 expression was almost maximal. Interferon-γ (IFN-γ) reduced the expression of CD36 in a dose-dependent manner. A concentration of 1000 U/mL IFN-γ significantly reduced the expression of CD36 protein by 57% and that of CD36 mRNA by 30%. In conclusion, CD36 may be important in the formation of foam cells by induction through its ligand (OxLDL). Moreover, some local factors, such as IFN-γ, may suppress CD36 expression on macrophages in human atherosclerotic lesions.

Hyper-low-density lipoprotein (LDL)-cholesterolaemia is a potent risk factor for coronary atherosclerosis. We have recently demonstrated that a cluster of risk factors including insulin resistance, glucose intolerance, hypertriglyceridaemia, and hypertension based on intra-abdominal visceral fat accumulation are closely related to coronary artery disease. In the current study, we evaluated the relationship between visceral fat accumulation and the severity and distribution of coronary atherosclerosis in familial hypercholesterolaemia (FH).The effect of visceral fat accumulation on coronary lesions and risk factors in patients with FH was investigated.Thirty-one male patients with heterozygous FH who underwent coronary angiography.Abdominal fat distribution was estimated by a cross-sectional computed tomographic scan at the umbilical level. Plasma lipid, glucose and insulin concentrations and blood pressure were measured. A 75 g oral glucose tolerance test was also performed.The patients were divided into two groups according to the degree of visceral fat accumulation. Fifteen patients had high visceral fat accumulation (High VF group) and 16 patients had normal visceral fat accumulation (Normal VF group). Body mass index (BMI) and subcutaneous fat area were significantly higher in the high VF group. Baseline serum triglyceride was significantly higher and baseline low-density lipoprotein (LDL)-cholesterol and reduction of LDL-cholesterol during treatment were significantly lower in High VF group. Fasting plasma glucose and insulin concentrations, and systolic and diastolic pressures were significantly higher in the High VF group. Significant correlations were found between visceral fat area and the sum of the glucose and insulin concentration during an oral glucose tolerance test. Visceral fat area was significantly correlated with the severity of coronary stenosis index. Distal coronary lesions were significantly more frequent in the High VF group. Moreover, the correlation between the visceral fat area and coronary stenosis index was found to be independent of age, BMI, and subcutaneous fat area by multiple regression analysis.Visceral fat accumulation is a potent cardiovascular risk factor in heterozygous FH.

Apolipoprotein (apo) E7 was originally identified by Yamamura et al. in subjects with atherosclerotic cardiovascular diseases (J. Clin. Invest. 1984;74:1229). However, the lipoprotein abnormalities associated with apo E7 phenotype have not been elucidated. In the current study, to clarify the physiological roles of apo E7, lipoprotein abnormalities were studied in 12 apo E7 heterozygotes. A total of seven subjects were hyperlipidemic and five subjects were normolipidemic. The apo E phenotype was apo E7/3 in 11 subjects and apo E7/4 in one subject. Polymerase chain reaction revealed that all of the subjects with apo E7 phenotype had the same mutation as that of apo E Suita as reported previously (J. Biochem. 1989;105:249). All the hyperlipidemic subjects were over 40 years of age and two of them also had and severe coronary heart disease. Ultracentrifugal analysis revealed that the cholesterol level both in very low density lipoprotein and in intermediate density lipoprotein (IDL) was substantially higher in hyperlipidemic apo E7 heterozygotes, compared with control subjects and that the IDL cholesterol was also increased even in normolipidemic apo E7 heterozygotes. Polyacrylamide gel electrophoresis of lipoproteins showed a midband, which implies the increase of remnant lipoproteins, in 11 subjects out of 12, irrespective of the presence or absence of hyperlipoproteinemia. In two cases, a broad β pattern was observed similar to that seen in type III hyperlipoproteinemia. Dietary therapy was dramatically effective for the treatment of hyperlipidemia in patients with apo E7. These findings confirm that apo E is crucial for remnant lipoprotein metabolism and that apo E7 is related to the increase in serum remnant lipoproteins, which leads to hyperlipoproteinemia in association with obesity, aging and impaired glucose metabolism.

Cerebrotendinous xanthomatosis (CTX), an autosomal recessive lipid-storage hereditary disorder, is caused by mutations in the sterol 27-hydroxylase gene (CYP 27). A 24-year-old female Japanese CTX patient and her parents were studied for a CYP 27 mutation. Multiple xanthomas were the main complaint of the patient and plasma cholestanol level was markedly elevated. Sterol analysis of a xanthoma biopsy confirmed cholesterol and cholestanol deposition, and the cholestanol accounted for 8.1% of the total setrols. Sterol 27-hydroxylase activity in fibroblasts derived from the patient was undetectable, while the activities in fibroblasts from her mother and father were 54% and 41% of the normal level, respectively. Direct sequence analysis showed a missense mutation of A for G substitution in the CYP 27 gene at codon 362 (CGT 362Arg to CAT 362His) with a homozygous pattern in the patient, and a heterozygous pattern in the parents. The mutation, which eliminates a normal HgaI endonuclease site at position 1195 of the cDNA and is located at the adrenodoxin binding region of the gene, is most probably responsible for the decreased sterol 27-hydroxylase activity in this Japanese CTX family. The combined data strongly support that the primary enzymatic defect in CTX is the disruption of sterol 27-hydroxylase and that the disease is inherited in an autosomal recessive trait.

Cholesteryl ester transfer protein (CETP) plays an important role in regulating the concentration and composi- tion of high density lipoprotein (HDL) and low density lipo- protein (LDL). Although several genetic abnormalities caus- ing CETP deficiency have been identified in the Japanese subjects with a marked hyperalphalipoproteinemia (HALP), there are many CETPdeficient subjects for whom the genetic abnormalities have not been clarified. In the present study, we analyzed the molecular basis of an HALP subject without CETP activity and mass, and found a novel mutation in the CETP gene. This novel mutation (G181X) was a Gto-T sub- stitution at codon 181 of exon 6 which replaced a codon for glycine (GGA) with a premature stop codon (TGA). The G181X mutation created a new cutting site by restriction enzyme MaeIII. To estimate the frequency of G181X, we investigated unrelated 294 HALP (HDL-cholesterol 22.59 mmol/L = 100 mg/dl) subjects by restriction fragment length polymorphism (RFLP) analysis with Mae 111. One (0.34%) HALP subject was homozygous and four (1.36%) were het- erozygous for this mutation. The allelic frequency of a G-to-T substitution at codon 181 of exon 6 was 0.0102 in HALP subjects. From the lipid analysis of the proband and the homozygote, it was clarified that the G181X mutation had dominant effects on HDL and LDL metabolism, similar to a G-to-A substitution at the 5' splice donor site of the intron 14 (1451 + lG + A). 811 In conclusion, the G181X mutation is one of causes of HALP in the Japanese HALP subjects, having dominant effects on lipid metabolism.-Arai, T.

Abstract Hyperalphalipoproteinemia (HALP) has been regarded as a beneficial state accompanied by a longevity syndrome. However, we reported the cases of markedly hyperalphalipoproteinemic subjects with juvenile corneal opacification. These patients had reduced postheparin hepatic triglyceride lipase (HTGL) activities, and one of them has recently been identified to be homozygous for a missense mutation in exon 15 (D442: G) in the cholesteryl ester transfer protein (CETP) gene. In the current study, to elucidate the clinical significance of and atherogenicity in marked HALP, we determined the incidence of atherosclerotic cardiovascular disease (ACD) in patients with marked HALP and characterized the lipoprotein abnormalities in those who had ACD, focusing especially on CETP and HTGL. The subjects were 201 patients (111 males and 90 females) with marked HALP (≥2.58 mmol/L [100 mg/dL]), 67% of whom were demonstrated to have the CETP gene mutations in the intron 14 splice donor site or in exon 15. Their mean age was 54±15 years. Plasma levels of total cholesterol, HDL cholesterol, and triglyceride in all subjects were 6.28±1.78, 3.15±0.90, and 1.08±0.53 mmol/L, respectively. Ten of the male patients (9.0%) and two of the female patients (2.2%) had apparent ACD such as myocardial infarction, angina pectoris, and peripheral vascular diseases. Ten patients with HALP who had ACD were identified to be heterozygotes for CETP deficiency. To further clarify the characteristics of marked HALP in patients with ACD, we compared the plasma lipids, lipoproteins, CETP, and HTGL activities between heterozygotes for CETP deficiency who were with and without ACD. There was no significant difference in plasma lipids, lipoproteins, and CETP between the two groups, whereas HTGL activities were significantly lower in the heterozygotes for CETP deficiency with ACD than in the heterozygotes without ACD and in control subjects. These results suggest that marked HALP may not always be a beneficial state and that people who are heterozygotes for CETP deficiency and who have low HTGL may be susceptible to ACD.

To clarify the physiological roles of CD36 as an oxidized low density lipoprotein (OxLDL) receptor, we analyzed the monocyte-derived macrophages from normal and two CD36-deficient subjects, since we identified the molecular abnormalities (Kashiwagi, H., Y. Tomiyama, Y. Kosugi, M. Shiraga, R. H. Lipsky, Y. Kanayama, Y. Kurata, and Y. Matsuzawa 1994. Blood. 83:3545-3552; and Kashiwagi, H., Y. Tomiyama, S. Honda, S. Kosugi, M. Shiraga, N. Nagao, S. Sekiguchi, Y. Kanayama, Y. Kurata, and Y. Matsuzawa. 1995. J. Clin. Invest. 95:1040-1046). Scatchard analysis of 125I-OxLDL binding showed a linear plot and the maximum binding was lower by approximately 40% in the macrophages from subjects with CD36 deficiency than those from normal controls. Competition studies showed that the uptake of 125I-OxLDL was suppressed by OKM5, an antibody against CD36, by 53% in normal control macrophages, but not in the CD36-deficient macrophages. After incubation with OxLDL for 24 h, cholesteryl ester mass accumulation was reduced by approximately 40% in the macrophages from CD36-deficient subjects than those from normal controls. These results suggest that CD36 is one of the physiological receptors for OxLDL. Since specific binding of OxLDL was only reduced by approximately 40% in spite of the complete deficiency of CD36, several other receptors also may have some role in OxLDL uptake. Further studies will be needed to assess the quantitative role of CD36 in foam cell formation in vivo.

A responsible gene of genetically obese (ob/ob) mouse has recently been isolated. Genetic disruption of ob gene causes massive obesity. To elucidate the pathophysiological regulation of ob gene, we examined the gene expression in fat tissues of a non-genetical obese model, VMH-lesioned rats. The ob mRNA was identified in both subcutaneous and mesenteric fat tissues in the control rats. In VMH-lesioned rats, the abundance of ob mRNA increased after the gain of body weight and marked expression was observed on 15th day after making VMH lesion. These data suggest that ob gene might be upregulated with fat accumulation even in non-genetically obese animals.

We observed two patients with hypercholesterolaemia and tendon xanthomas associated with apolipoprotein (apoE-7) E-7, a rare variant of the apoE isoforms. Both suffered from coronary artery disease and had undergone a coronary bypass operation. Their cholesterol levels were 268 and 310 mg dl-1, respectively. Both patients had marked xanthomas in the Achilles tendons. Both also suffered from diabetes. Although their clinical and laboratory findings were compatible with typical familial hypercholesterolaemia (FH), the analysis of low-density lipoprotein (LDL) receptors in cultured fibroblasts showed no abnormality of binding, internalization or degradation of 125I-LDL. Diabetic control with a low-calorie, low-fat diet led to the rapid reduction of serum cholesterol. Other family members of the patients with apoE-7, who were normoglycaemic, showed normal cholesterol levels and no xanthomas. These findings suggest that coexistent diabetes mellitus may induce overt hyperlipidaemia and accumulation of lipids in tissues in subjects with apoE7.

The purpose of this study was to determine whether lovastatin treatment reduced very low density lipoprotein (VLDL) abnormalities in hypertriglyceridemic subjects. Lovastatin reduced plasma triglyceride levels and the levels of total VLDL, intermediate density lipoprotein (IDL), and low density lipoprotein (LDL) cholesterol. The numbers of VLDL particles of Sf 100-400 and Sf 60-100 but not Sf 20-60 particles were reduced by lovastatin, as was the amount of cholesteryl ester per particle. All VLDL subspecies bound to the LDL receptor of cultured human fibroblasts with similar, high affinities on both placebo and lovastatin, but VLDL Sf 100-400 and VLDL Sf 60-100 caused less suppression of 3-hydroxy-3-methyl glutaryl coenzyme A reductase activity after lovastatin therapy, indicating reduced LDL receptor-mediated cholesterol delivery. The average decrease in reductase suppression by VLDL Sf 100-400 after lovastatin was 32%, similar to the 34% average decrease in cholesteryl ester content of VLDL Sf 100-400 after lovastatin. Although statistical significance was not achieved, there was a trend toward decreased VLDL Sf 100-400-induced rapid, receptor-mediated triglyceride accumulation in P388D1 macrophages after lovastatin. Taken together, these observations suggest that lovastatin may be of potential benefit in decreasing the atherosclerotic complications of hypertriglyceridemia.

Long-term heavy alcohol intake is well known to increase serum high-density lipoprotein (HDL) cholesterol concentrations. Epidemiologic studies have shown that the protective effect of alcohol intake against coronary heart disease (CHD) is observed in moderate alcohol drinkers, but not in heavy ones. To clarify whether heavy alcohol intake may cause abnormalities in lipoprotein metabolism, we analyzed the plasma lipoproteins in eight male chronic heavy alcohol drinkers with marked hyperalphalipoproteinemia. Although their serum HDL cholesterol levels were remarkably high, ranging from 2.67 to 3.58 mmol/L, three patients had CHD and corneal arcus was present in seven patients. Cholesteryl ester transfer protein (CETP) activity was reduced in all subjects (7.3% +/- 4.2%/10 microL/18 h in alcohol drinkers v 20.5% +/- 2.4%/10 microL/18 h in control; mean +/- SD, P < .001). The CETP mass levels were also markedly reduced in these subjects. The analysis of low-density lipoprotein (LDL) on nondenaturing polyacrylamide gradient gel electrophoresis revealed that four subjects with severely low CETP activity (< 25% of control) had polydisperse LDLs, similar to those observed in genetic CETP deficiency. The other four subjects with approximately half the normal CETP activity had homogeneous but smaller-sized LDLs, as compared with control subjects. Particle size of HDL was larger than that of normal control HDL in all subjects. After cessation of alcohol intake, plasma HDL cholesterol levels were decreased and LDLs became more homogeneous and normal in size, in parallel with elevation of CETP activity.(ABSTRACT TRUNCATED AT 250 WORDS)

We have studied the effects of triiodothyronine (T3) on the production of hepatic triacylglycerol lipase (HTGL) in the human hepatocellular carcinoma cell line, HepG2, by measuring its activity and mRNA levels. The HTGL activity released into the medium by heparin, increased after the addition of T3 in a both time- (27% increase after 24 and 75% increase after 48 h) and dose-dependent manner (maximum activity with over 0.2 micrograms/ml of T3 in the medium). Messenger RNA levels of HTGL in cells incubated with T3 for 24 and 48 h were increased by 33% and 98% compared to those of the control. These results suggest that the production of HTGL may be regulated by thyroid hormone at the level of gene expression.

The hypotriglyceridemic action of omega-3 (n-3) fatty acids is attributed primarily to reduction in hepatic triglyceride synthesis and reduced secretion of very-low-density lipoproteins (VLDLs). However, increased catabolism of triglyceride-rich lipoproteins was reported and could be due to increased availability of peripheral lipoprotein lipase (LPL) or hepatic lipase (HL). In this study plasma lipoproteins and postheparin activities of LPL and HL were determined in 12 patients with primary hypertriglyceridemia before and during isocaloric substitution of omega-3 fatty acids (10 g/d) for 4 wk. Omega-3 polyunsaturates resulted in 53% and 61% reductions in plasma triglyceride and VLDL-cholesterol concentrations, respectively (P less than 0.0001). However, low-density-lipoprotein (LDL)-cholesterol concentrations increased by 26% (P less than 0.001). Activities of postheparin LPL and HL essentially remained the same. Thus, in patients with primary hypertriglyceridemia, reduction in plasma triglyceride concentrations and increase in LDL-cholesterol concentrations mediated by omega-3 polyunsaturates seem to occur without an increase in LPL or HL activities.

The first case of 'a metastatic intraluminal myxoma of the aorta' is reported. The patient was a 48-year-old man who had already developed metastases to his skin and brain from a left atrial myxoma. Then, his myxoma grew in his leg and intraluminally in the aorta and caused renovascular hypertension. Surgical removal of the tumor could relieve his hypertension, but he finally died 6 months after surgery. The findings at autopsy were described and previous reports on metastasizing left atrial myxomas were also reviewed.

The effects of lovastatin therapy on concentrations and compositions of lipoproteins were examined in 14 patients with heterozygous familial hypercholesterolemia. The drug lowered plasma levels of cholesterol in total plasma, very low density + intermediate density lipoproteins (VLDL + IDL) and low density lipoproteins (LDL) by 25%, 41%, and 41%, respectively. Plasma total apo B was decreased by 35%. Three VLDL subfractions--VLDL-1, VLDL-2, and VLDL-3--of progressively higher density were examined. Lovastatin therapy reduced only the heaviest--VLDL-3. Concentrations of VLDL-1 and VLDL-2 were unchanged. Total VLDL-cholesterol/apo B was reduced significantly. Drug therapy also altered the composition of LDL as shown by decreasing the cholesterol/apo B. Finally, lovastatin significantly raised HDL-cholesterol concentrations. This study showed that lovastatin modifies the composition of the major apo B-containing lipoproteins as well as reducing their concentrations.

In 1989, we encountered a 68-year-old male patient with marked hyperlipoprotein(a)emia (hyperLp(a)emia), who was being treated for hypertension and arteriosclerotic obliterans (ASO) at an outpatient clinic of our hospital. He began to develop leg edema in 2002 and was referred to the Department of Internal Medicine. It was determined that he had severe hyperlipidemia (total cholesterol, 362 mg/dl), proteinuria, and hypoalbuminemia, suggesting the presence of nephrotic syndrome. On lipoprotein analysis, he was found to have very high levels of Lp(a) in the plasma (329 mg/dl). Severe atherosclerosis was also found: that is, abdominal aortic aneurysm (AAA) and coronary artery disease (CAD) were detected, in addition to ASO. After remission of the nephrotic syndrome, the plasma Lp(a) level decreased to 204 mg/dl and the total cholesterol concentration decreased to 179 mg/dl, while very high levels of Lp(a) persisted. We estimate that the markedly elevated Lp(a) plasma levels in this patient may have played some role in the progression of atherosclerosis.

It has been suggested that oral care is essential for improving the quality of life (QOL). The aim of oral care involves not only maintenance of oral health but also enhancement of mastication and appetite by means of improving taste sensitivity. There are, however, few studies that have investigated the effect of oral care on taste sensitivity. In the present study, we focused on tongue brushing among oral care and examined the changes in taste sensitivities by mild tongue brushing in the nursed elderly. Ninety subjects, over 64 years old with ability to communicate, were divided into 2 groups, one was the cared group (subject's tongue was brushed) and the other was the control group (not brushed but rinsed). The thresholds for four primary tastes such as saltiness, sourness, sweetness and bitterness were measured before and after treatments using the whole mouth method. The mean recognition thresholds for salty and sour tastes significantly decreased after tongue brushing in the cared group, while those for all four tastes were not changed after mouth rinsing in the control group. The present result suggests that mild tongue brushing may enhance taste sensitivity of saltiness and sourness in the nursed elderly.

To elucidate genetic abnormalities in type I CD36 deficiency, we analyzed 28 Japanese subjects whose platelets and monocytes/macrophages lacked CD36 on their surface. We identified two novel mutations in the CD36 gene. One was a complex deletion/insertion mutation, in which 3 bp, GAG, were deleted at nucleotide (nt) 839-841, and 5 bp, AAAAC, were inserted at the same position (839-841del--insAAAAC). Mutation 839-841del--insAAAAC led to a frameshift and appearance of a premature stop codon; it was also accompanied with a marked reduction in the amount of CD36 mRNA. The other was a 12-bp deletion at nt 1438-1449 (1438-1449del) accompanied with or without skipping of exon 9 (nt 959-1028). Mutation 1438-1449del led to an inframe 4-amino-acid deletion, whereas exon 9 skipping led to a frameshift and the appearance of a premature stop codon. Expression assay revealed that both 1438-1449del and exon 9 skipping directly caused impairment of the surface expression of CD36. A survey of the five known mutations including 839-841del--insAAAAC and 1438-1449del in type I CD36-deficient subjects demonstrated that the five mutations covered more than 90% of genetic defects among them and that the substitution of T for C at nt 478 (478C--T) was the most common mutation with more than 50% frequency. However, none of the four subjects that possessed isoantibodies against CD36 had 478C--T, suggesting that 478C--T prevents the production of isoantibodies against CD36.

CD36 and scavenger receptor class A types I and II (SR-AI/II) are major receptors for oxidized low density lipoproteins (OxLDL) expressed on macrophages. To elucidate the role of these two macrophage scavenger receptors in the development of coronary atherosclerosis, we examined the localization of CD36 and SR-AI/II in human coronary atherosclerotic lesions. Serial cryostat sections of 49 coronary arteries obtained from 43 autopsied cases were examined immunohistochemically. Regarding the relationship between the severity of atherosclerosis and immunoreactivities to CD36, there was almost no immunoreactivity to CD36 in regions with diffuse intimal thickening, while the expression of CD36 was accelerated in parallel with the progression of atherosclerosis. In contrast, SR-AI/II was expressed persistently from regions with diffuse intimal thickening to atherosclerotic plaques. We also clarified the differential distribution of CD36 and SR-AI/II in atheromatous plaques. Close to the luminal surface of the intima, macrophages were relatively small in size, contained lesser lipids, and expressed SR-AI/II more abundantly than CD36. In contrast, macrophages in the core region were larger in size, contained more lipids, were strongly positive for CD36 and showed a weaker immunoreactivity to SR-AI/II than those in the luminal surface of the intima. In conclusion, the expression of CD36 and SR-AI/II on macrophages may be regulated differently in the process of coronary atherogenesis.

Abstract —CD36 is 1 of the class B scavenger receptor expressed on monocytes, monocyte-derived macrophages (Mφ), platelets, and adipocytes. In our previous studies, we reported that the uptake of oxidized low density lipoproteins (OxLDLs) is reduced by ≈50% in Mφ from CD36-deficient patients compared with that in control subjects. Recently, we have shown that CD36 is highly expressed in human atherosclerotic aorta. Possibilities have been raised that besides the wide distribution and multifunctional characteristics of CD36, this molecule may also be involved in the mediation of intracellular signaling. The aim of the present study was to elucidate the role of CD36 in cytokine secretion and to investigate the CD36-mediated intracellular signaling stimulated by OxLDL. On addition of OxLDL or thrombospondin-1, the Mφ from CD36-deficient patients secreted significantly less amounts of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) compared with those from controls. RNase protection assay with multiprobe template sets demonstrated that after incubation with OxLDL, the mRNAs of a variety of cytokines, including genes encoding IL-1Ra, IL-1β, IL-6, TNF-α and -β, and interferon (IFN)-γ and -β, were significantly lower in the Mφ of patients. The addition of antibody against CD36 attenuated this OxLDL-induced response in controls. We also observed a reduced response in nuclear factor-κB (NF-κB) activity in OxLDL-stimulated Mφ from CD36-deficient patients. Unlike OxLDL, stimulation by lipopolysaccharide induced an increase in NF-κB activity in Mφ from CD36-deficient patients, suggesting that lipopolysaccharide-mediated signaling was conserved. These results demonstrate that in addition to the reduced OxLDL uptake that we reported previously, CD36-deficient patients may also have an impaired response of OxLDL-induced NF-κB activation and subsequent cytokine expression.

CD36 has been reported to be a receptor for oxidized low density lipoprotein (OxLDL). In the present study, we investigated the pathophysiological role of CD36 on atherogenesis, by using human monocyte-derived macrophages including CD36-deficient macrophages. We also analyzed the distribution of CD36 in human aortic tissues immunohistochemically and studied the regulation of CD36 in macrophages and smooth muscle cells (SMCs). By the addition of OxLDL to macrophages, both the uptake of OxLDL and cholesteryl ester accumulation were reduced in CD36-deficient macrophages. Secretion of TNF-α and IL-1 β in response to OxLDL was remarkably reduced in CD36-deficient macrophages, suggesting the contribution of CD36 in the secretion of cytokines from monocyte/macrophages in addition to forming foam cells. In the immunohistochemical analysis, CD36 and SRA were differently expressed in aortic atherosclerotic lesions. Foamed, large-sized macrophages in atherosclerotic plaques tended to express more abundantly CD36 protein. In the study of regulation of CD36, OxLDL significantly increased the expression of CD36 on macrophages. CD36 was detected in some SMCs and its expression was related to the expression of PPARγ. CD36-positive SMCs did not express SRA, and CD36-negative SMCs expressed SRA. These results suggest that CD36 has an important role on atherogenesis in human.

CD36, a family of scavenger receptor class B (SR-B), is believed to possess multiple functions in vivo. We have reported that CD36 is one of the major receptors for oxidized low density lipoproteins (OxLDL) in vivo by the study with genetic CD36 deficiency. Although it was reported that other SR, SR class A (SR-A), is expressed in vascular smooth muscle cells (VSMCs), one of the major components in the atherosclerotic lesions, it is still unknown whether these cell types do express CD36 or not. In the current study, we have found that cultured human aortic SMCs (HASMCs) from five donors out of eight did express CD36 mRNA with variable levels, determined by RNase protection assay and RT-PCR. Protein expression was confirmed by fluorescence flow cytometry with the specific antibody against human CD36, OKM5. Confocal laser microscopy demonstrated that CD36 immunoreactive mass was detected in the cell surface. The expression was markedly up-regulated by the addition of oxidized LDL(Ox-LDL) and/or troglitazone, a ligand for peroxisome proliferator activator receptor -gamma (PPAR-β). CD36-positive (CD36 (+)) HASMCs have CD36-specific binding for 125I-labeled OxLDL and accumulation of intracellular cholesterol ester (CE). The current study demonstrated that many of VSMCs express CD36 and uptake OxLDL via CD36. We propose that CD36 (+) HASMCs might be one of the origins of foam cells observed in the intima of atherosclerotic lesions.

Abstract —CD36 has been reported to be a receptor for oxidized LDL (Ox-LDL). In our previous study, the uptake of Ox-LDL in CD36-deficient macrophages was reduced by approximately 50% compared with that in control macrophages, suggesting an important role of CD36 as a receptor for Ox-LDL in humans. In the current study, we examined the immunohistochemical localization of CD36 in human aorta in comparison with that of scavenger receptor class A type I and type II (SRA). Cryostat sections were made from aortic tissues. For immunohistochemical staining, the following antibodies were used: (1) FA6-152, anti-CD36 antibody, and (2) SRI-2, which recognizes both type I and type II SRAs. Immunohistochemical staining for CD36 and SRA was performed using labeled streptavidin method. In macrophages scattered in aortic walls without atherosclerotic lesions, the expression of CD36 was hardly observed, whereas that of SRA was detected weakly but consistently. In contrast, in atherosclerotic lesions, macrophages around the core region showed a weak immunoreactivity to CD36 and a strong immunoreactivity to SRA. Furthermore, lipid-laden macrophages, which mainly existed in the core region, had a strongly positive immunoreactivity to CD36, but a low or moderate level of immunoreactivity to SRA. The distributions of CD36 and SRA were different from each other, and especially foamed, large-sized macrophages in atherosclerotic plaques tended to more abundantly express CD36 protein. These data demonstrate, for the first time, that the expression of both CD36 and SRA might be differentially regulated in aortic walls, and might play different roles in the formation of foam cells in atherosclerotic lesions.

Long-chain fatty acids (LCFA) are the major energy substrate for heart and their oxidation is important for achieving maximal cardiac work. However, the mechanism of uptake of LCFA by myocardium has not been clarified. We previously reported that bovine myocardial LCFA transporter has a sequence homology to human CD36. Clinically, total defect of myocardial uptake of radiolabeled long-chain fatty acid analog [123I-BMIPP: Iodine-123 15-(p-iodophenyl)-(R,S)-methylpentadecanoic acid] has been reported in some restricted cases, but the etiology has not been clarified. In the present study, we analyzed CD36 expression and CD36 gene in subjects who showed total lack of myocardial 123I-BMIPP accumulation, and, vice versa, evaluated myocardial 123I-BMIPP uptake in subjects with CD36 deficiency. Four unrelated subjects were evaluated; Two were found to have negative myocardial LCFA accumulation by 123I-BMIPP scintigraphy, after which the expression of CD36 on their platelets and monocytes was analyzed. Remaining two subjects were identified as CD36 deficiency by screening, then 123I-BMIPP scintigraphy was performed. Expression of CD36 on platelets and monocytes was measured by flow cytometric analysis. The molecular defects responsible for CD36 deficiency was detected by allele-specific restriction enzyme analysis. CD36 expression was totally deficient in all 4 subjects on both platelets and monocytes. Two subjects were homozygous for a 478C→T mutation. One was heterozygous for the dinucleotide deletion of exon V and single nucleotide insertion of exon X, and remaining one was considered to be heterozygous for the dinucleotide deletion of exon V and an unknown gene abnormality. All cases demonstrated a completely negative accumulation of myocardial LCFA despite of normal myocardial perfusion, which was evaluated by thallium scintigraphy. In addition, all cases demonstrated apparently normal hepatic LCFA accumulation Thus, these findings suggested that CD36 acts as a major myocardial specific LCFA transporter in humans.

We investigated the relationship between uric acid (UA) metabolism and fat distribution in 36 obese men with a mean +/- SD age of 38 +/- 16 years and mean body-mass index (BMI) of 34 +/- 4 kg/m2. Subjects were divided into two groups: subcutaneous fat obesity (SFO) and visceral fat obesity (VFO), according to their abdominal fat distribution based on the results of computed tomography (CT). SFO was defined as having a ratio of visceral fat area (VFA) to subcutaneous fat area (V/S) of less than 0.4, and VFO was defined as having a V/S ratio > or = 0.4. The levels of serum total cholesterol (T-Chol), triglyceride (TG), and fasting plasma glucose (FPG), and the diastolic blood pressure (dBP) were significantly higher in the VFO group than in the SFO group. Serum UA levels were much higher in both the SFO and VFO groups than in the non-obese control group (492 +/- 107 and 474 +/- 90 v 309 +/- 48 micromol/L, respectively). The 24-hour urinary urate excretion (u-UA24h) and the UA clearance (Cua) to creatinine clearance (Ccr) ratio were significantly higher in the VFO group than in the SFO group (3.75 +/- 1.43 v 2.69 +/- 1.12 mmol/d, P < .05; and 5.9% +/- 2.0% v 3.6% +/- 1.7%, P < .001, respectively). The frequency of hyperuricemia was markedly higher in both the SFO and VFO groups compared with the control group (71% and 73% v 0%, respectively). Although the high serum UA level seemed to be related to low u-UA24h in 80% of SFO subjects with hyperuricemia, this was the case in only 10% of VFO subjects. While 44% of VFO subjects with hyperuricemia were designated as an overproduction type. These results suggest that the mechanism of hyperuricemia in obesity may be affected by the difference in body fat distribution and that the assessment of body fat distribution and types of hyperuricemia is crucial for the treatment of obese patients with hyperuricemia.

The mechanism of severe hyperlipidemia in a 54-year-old woman with multiple myeloma and monoclonal immunoglobulin A (IgA) gammopathy was investigated. Her plasma total cholesterol and triglyceride concentrations were 29.7 mmol/l (1,150 mg/dl) and 11.9 mmol/l (1,060 mg/dl), respectively. Western blot analysis demonstrated that her low density lipoproteins (LDL) contained IgA. This IgA also was shown to bind to control LDL and inhibited 125I-LDL binding to fibroblasts, suggesting that by binding to the LDL, IgA interfered with LDL binding to LDL receptors. These findings indicate that an inhibitory monoclonal IgA against LDL binding may explain, at least in part, the severe hyperlipidemia observed in this case.

Familial hypercholesterolemia (FH) is a genetic disorder characterized by high levels of serum low density lipoprotein (LDL) cholesterol and premature coronary atherosclerosis. In order to elucidate the influence of abnormal glucose metabolism on the development of coronary artery disease (CAD) in FH patients, we examined the prevalence of CAD and characteristics of lipoprotein abnormalities in patients with heterozygous FH who were accompanied by diabetes mellitus (DM) or impaired glucose tolerance (IGT). The subjects of the present study were 150 patients with heterozygous FH, all over 40 years of age. Oral glucose tolerance tests demonstrated that 15 patients had DM and 27 had IGT. The combination of DM or IGT with FH was associated with a further increase in the prevalence of CAD (DM:IGT:normal glucose tolerance (N), 87:59:43%). Furthermore, the prevalence of the stenoses in the distal coronary arteries was significantly higher in the DM group than in the N group, while there was no significant difference in the prevalence of proximal and middle lesions. Serum triglyceride levels were significantly higher in the DM and IGT groups than in the N group (P

Background Heparin-binding epidermal growth factor (EGF)–like growth factor (HB-EGF) is a newly identified member of the EGF family. Our previous in vitro studies showed that HB-EGF is a potent mitogen and chemoattractant for vascular smooth muscle cells (SMCs), suggesting the role of HB-EGF in the pathogenesis of atherosclerosis. The purposes of the present study were to investigate the localization of HB-EGF in both normal and atherosclerotic human coronary arteries and to elucidate the possible roles of this growth factor in the formation of atherosclerotic lesions. Methods and Results The immunohistochemical localization of HB-EGF, SMCs, macrophages, and EGF receptors (EGFRs) was examined in human coronary arteries obtained at autopsy. The medial SMCs of coronary arteries in neonates, infants, and children consistently synthesized HB-EGF protein. In normal adults, however, the relative number of HB-EGF–positive medial SMCs decreased gradually with age after about 30 years of age. In nonatherosclerotic coronary arteries with diffuse intimal thickening, SMCs of the intima, especially those located in the area of the medial side of the intima, were strongly positive for HB-EGF protein. In atherosclerotic plaques of coronary arteries with eccentric intimal thickening, both SMCs and macrophages in and around the core lesions, in addition to the intimal and medial SMCs located adjacent to the plaque, produced HB-EGF protein. A strong immunostaining of EGFRs was observed in these SMCs, suggesting a close association of HB-EGF and EGFR expression. Conclusions These data suggest that HB-EGF might play important roles in the migration of SMCs from the media to the intima, the proliferation of intimal SMCs, and the interaction between SMCs and macrophages in the process of coronary atherogenesis.

A 16-yr-old girl was hospitalized because of amenorrhea and virilism, and was diagnosed with an adrenal tumor on the right side. Her serum androgen levels were markedly elevated, and severe hypocholesterolemia (total cholesterol, 0.59 mmol/L) was observed. After resection of the tumor, her serum cholesterol level dramatically rose to normal, suggesting a role of this tumor in her marked hypocholesterolemia. To investigate the mechanism of hypocholesterolemia in this case, we examined the effects of dehydroepiandrosterone and dehydroepiandrosterone sulfate on the low density lipoprotein (LDL) receptor activity of fibroblasts. These hormones did not have any effect on LDL receptor activity. Northern blot analysis demonstrated that the LDL receptor messenger ribonucleic acid level of this tumor tissue was increased about 8-fold compared with that of normal adrenal cortex. The LDL receptor activity of the cultured cells established from this tumor was 2-fold higher than that of Hep G2 cells. Furthermore, the LDL receptor activity could not be down-regulated by an excessive dose of 25-hydroxycholesterol. These results suggest that increased LDL receptor activity and unrestricted uptake of LDL by the adrenal tumor may have caused the marked hypocholesterolemia in this patient.

It is well known that obesity is frequently associated with low levels of serum high-density lipoprotein (HDL) cholesterol. However, the mechanism for this reduction has not been fully clarified. Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester from HDL to apolipoprotein B-containing lipoproteins and plays an important role in regulating the concentration and composition of HDL. To elucidate the mechanism for the reduction of serum HDL cholesterol in obesity, we analyzed serum lipoproteins, CETP, and postheparin lipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) activities in 30 obese subjects (17 women and 13 men, age 44 +/- 14 years, mean +/- SD). We also investigated the relationship between these variables, total adiposity, and indices of body fat distribution. The average body mass index of the obese subjects was 33.1 +/- 4.8 kg/m2 (range, 26.4 to 43.8 kg/m2). The obese subjects showed significantly lower serum HDL cholesterol levels than control subjects (1.04 +/- 0.28 versus 1.50 +/- 0.34 mmol/L, P < .01). In the obese subjects, both activities and protein mass of CETP and postheparin HTGL activities were significantly increased, whereas postheparin LPL activities were significantly decreased. CETP activities, independent of postheparin HTGL and LPL activities, were correlated negatively with HDL cholesterol (r = -.39, P < .05) and the cholesteryl ester to triglyceride ratio of HDL2 and HDL3 (r = -.36, P < .05; r = -.46, P < .05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum levels of high-density lipoprotein cholesterol are often increased in patients with primary biliary cirrhosis. To elucidate the mechanism of the elevation of high-density lipoprotein cholesterol levels in this disease, lipoprotein abnormalities were analyzed in 10 patients subdivided into two groups according to concentration of high-density lipoprotein cholesterol. Activities and protein masses of lipoprotein lipase, hepatic triglyceride lipase and cholesteryl ester transfer protein were also determined. Serum high-density lipoprotein cholesterol concentration exceeded 90 mg/dl in 5 of 10 patients. Lipoprotein particles in the high-density lipoprotein2 fraction (with density between 1.063 and 1.125 gm/ml) were enriched with apolipoprotein E and larger in size than those of normal controls. In patients with and without hyperalphalipoproteinemia, hepatic triglyceride lipase activity was significantly decreased (p < 0.05); this was due to the reduction of its protein mass. Lipoprotein lipase activity and protein mass were normal. It is noteworthy that increases in cholesteryl ester transfer protein activity and mass were observed. The enhancement of cholesteryl ester transfer protein activity was more remarkable in the patients with hyperalphalipoproteinemia than in those without hyperalphalipoproteinemia. Because a significant positive correlation was demonstrated between activity and protein mass (r = 0.90, p < 0.001), the increase of cholesteryl ester transfer protein activity may be attributed to the increase of its protein mass. These data suggest that the decrease of hepatic triglyceride lipase levels at least partly explains the appearance of apolipoprotein E-rich large high-density lipoprotein particles in patients with primary biliary cirrhosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Summary No major genes responsible for insulin resistance have yet been identified. CD36 is a multifunctional receptor, which plays a part in mediating intracellular signalling as well as in taking up biologically active substances such as long-chain fatty acids. We looked for insulin resistance in genetic CD36 deficiency, which is common in Asian and African populations. The euglycaemic hyperinsulinaemic clamp technique showed insulin resistance in the five CD36–deficient people tested. We conclude that CD36 could be responsible for insulin resistance. The molecular basis for multiple risk-factor-clustering syndromes such as syndrome X1 is unknown. Insulin resistance is the major phenotype in these syndromes, 1 but we have found that accumulation of visceral fat is another phenotype and have proposed the concept of "visceral fat syndrome". 2 Some research suggests that the murine homologue of CD36—-fatty-acid transporter (FAT)—could be related to insulin resistance. 3 Genetic CD36 deficiency is common in Asian and African populations, and was first described in 1990. 4 We have since found three genetic mutations that cause the disorder. CD36 is one of the major receptors for oxidised low-density lipoproteins on macrophages, and metabolism of long chain fatty acids is altered in people with CD36 deficiency. We aimed to find out whether human deficiency of this molecule is associated with insulin resistance.

By equilibrium density gradient ultracentrifugation, we analyzed the chemical composition and particle size of low density lipoproteins (LDLs) in 16 subfractions separated from the LDL fractions (1.019 less than d less than 1.063 g/ml) of two hyperalphalipoproteinemic patients who had a deficiency of cholesteryl ester transfer protein (CETP). The LDLs of these patients comprised a group of heterogeneous lipoprotein particles distributed almost equally in a wide density range from d = 1.025 g/ml to d = 1.053 g/ml, whereas LDLs from normal controls were a homogeneous group of lipoprotein particles distributed in a narrow density range from d = 1.030 g/ml to d = 1.046 g/ml. The LDL in each subfraction derived from the patients' plasma samples was poor in cholesteryl ester and rich in triglycerides and apolipoproteins. Each subfraction of normal control LDL contained only one species of homogeneous LDL particles, which progressively decreased in size with an increase in the density of the fraction. In contrast, each subfraction of patient LDL contained two species of LDL particles: smaller LDLs existed, in addition to those that were found to be identical to the normal control LDL particles observed in the corresponding subfractions. The intermediate density lipoproteins of the two patients were also composed of two species of lipoproteins. From these results, we speculate that two metabolic pathways may exist in the LDL formation process. In this process, the transfer of cholesteryl ester from high density lipoproteins by CETP may convert the smaller lipoprotein particles to the larger ones, forming the homogeneous LDL species.