Takao Maruyama

Molecular mechanisms, lipoprotein abnormalities and atherogenicity of hyperalphalipoproteinemia.

Hyperalphalipoproteinemia (HALP) is caused by a variety of genetic and environmental factors. Among these, plasma cholesteryl ester transfer protein (CETP) deficiency is the most important and frequent cause of HALP in the Asian populations. CETP facilitates the transfer of cholesteryl ester (CE) from high density lipoprotein (HDL) to apolipoprotein (apo) B-containing lipoproteins, and is a key protein in the reverse cholesterol transport system. The deficiency of CETP causes various abnormalities in the concentration, composition, and function of both HDL and low density lipoprotein (LDL). The significance of CETP in terms of atherosclerosis had been controversial. However, the in vitro evidence showed large CE-rich HDL particles in CETP deficiency are defective in cholesterol efflux. Similarly, scavenger receptor BI (SR-BI) knockout mice show a marked increase in HDL-cholesterol but accelerated atherosclerosis in atherosclerosis-susceptible mice. Recent epidemiological studies in Japanese-Americans and in Omagari area where HALP subjects with the intron 14 splicing defect of CETP gene are markedly frequent, have demonstrated an increased incidence of coronary atherosclerosis in CETP-deficient patients. Thus, CETP deficiency is a state of impaired reverse cholesterol transport which may possibly lead to the development of atherosclerosis. The current review will focus on the molecular mechanisms and atherogenicity of HALP, especially CETP deficiency.

Prevalence and phenotypic spectrum of cholesteryl ester transfer protein gene mutations in Japanese hyperalphalipoproteinemia.

A patient with cholesteryl ester transfer protein (CETP) deficiency presents with marked hyperalphalipoproteinemia (HALP). To investigate the contribution of CETP deficiency to the cause of HALP (HDL-C> or =1.94 mmol/l, 75 mg/dl), we investigated the CETP activities and the prevalence of genetic CETP mutations among 624 Japanese HALP subjects. The subjects were screened for four known genetic CETP mutations (intron 14 splicing defect (In14), exon 15 missense mutation (Ex15), intron 10 splicing defect (In10) and exon 6 nonsense mutation (Ex6)). We found the frequency of the patients with reduced CETP activity (<75% of normal controls) to be 55.5 and 64.1% in a high HDL group (1.94< or =HDL-C<2.59 mmol/l) and a marked HALP group (HDL-C> or =2.59 mmol/l, 100 mg/dl), respectively. At least one of the four mutations was identified in 65.7% of subjects with reduced CETP activities and 57.5% of subjects with marked HALP. The In14 and Ex15 mutations were very common in HALP subjects and the frequency of In10 mutation and Ex6 mutation was quite low. To investigate the impact of genetic CETP mutation on the phenotypes, we compared the plasma lipid levels and CETP activities between the subjects with two common mutations. All In14 homozygotes showed marked HALP, while marked HALP is less frequent (64.3%) in Ex15 homozygotes. HDL-C levels in Ex15 heterozygotes were significantly higher than those of In14 heterozygotes, suggesting the mutation has dominant negative effects on CETP activity in vivo. Some cases with In14 (5.7%) or Ex15 (7.2%) mutation showed low HDL-C levels. We conclude that CETP deficiency is a major cause of HALP; nevertheless CETP deficiency is not necessarily HALP.

High-density lipoproteins from probucol-treated patients have increased capacity to promote cholesterol efflux from mouse peritoneal macrophages loaded with acetylated low-density lipoproteins.

To elucidate the anti‐atherogenic effect of probucol, high‐density lipoprotein (HDL) was isolated from probucol‐treated patients (nu2003=u200314) and compared with that from control subjects (nu2003=u200312). The HDL obtained from probucol‐treated patients was low in cholesteryl ester (CE) in comparison with that from control subjects (21.3u2003±u20033.9 mol per cent vs. 27.6u2003±u20033.2 mol% of total lipids, Pu2003<u20030.001), and the peak diameters of patients HDL were significantly smaller than those of control subjects on 4–30% non‐denaturing polyacrylamide gradient gel electrophoresis (10.6u2003±u20030.6u2003nm vs. 12.1u2003±u20030.4u2003nm, Pu2003<u20030.001). These data may be explained by the increased cholesteryl ester transfer protein (CETP) activities of probucol‐treated patients (129u2003±u200312% of control subjects, Pu2003<u20030.001). The in vitro ability of HDL to remove CE from lipid‐laden macrophages induced by incubation with acetylated low‐density lipoprotein (Ac‐LDL) was studied. The small and CE‐poor HDL obtained from probucol‐treated patients had a greater capacity to promote CE efflux from macrophages than did control HDL (59.8u2003±u20036.9% vs. 44.2u2003±u20035.4%, Pu2003<u20030.01). Furthermore, the ability of HDL to promote cholesterol efflux correlated negatively with the CE content and particle diameter of HDL (ru2003=u2003−0.561 and ru2003=u2003−0.583 respectively; Pu2003<u20030.01). When the inhibitory effect of HDL on the incorporation of [14C]‐oleate into cellular cholesteryl ester was compared, the HDL from patients and control subjects inhibited CE formation to a similar extent. The enhanced ability of probucol‐treated patients HDL may, therefore, be involved in the acceleration of hydrolysis of the CE pool in macrophages. Taken together, we conclude that CETP plays a crucial role in making HDL more active in its anti‐atherogenic function by reducing CE and making HDL smaller, and that probucol may enhance reverse cholesterol transport by activating CE transfer in vivo. The current study demonstrated, for the first time, that HDL modified by enhanced CETP activity in vivo is potentially anti‐atherogenic.

Novel LPL mutation (L303F) found in a patient associated with coronary artery disease and severe systemic atherosclerosis.

Background Patients with lipoprotein lipase (LPL) deficiency had been generally thought to be spared accelerated atherosclerosis in spite of a marked elevation of plasma triglyceride levels. However, it has been recently reported that some heterozygous and homozygous LPL‐deficient patients are associated with premature atherosclerosis. In this paper, we report a 55‐year‐old type I hyperlipidaemic patient with a novel missense mutation in the LPL gene.

Morphology of gingival capillaries adjacent to complete crowns

Clinically normal gingivae adjacent to natural teeth did not exhibit dilated capillaries. The morphologies of the capillary loops were of the normal and mixed types. More than one fourth of the capillary loops in the gingivae adjacent to the complete crowns showed dilatation. The capillary loops were of the mixed and complex forms. Dilatation and complex capillary loops were found in the clinically normal gingivae adjacent to the complete crowns. The capillary microscope is an aid in the diagnosis of gingivae adjacent to complete crowns.