Nagahiko Sakuma

Identification of a gene, ABCG5, important in the regulation of dietary cholesterol absorption.

The molecular mechanisms regulating the amount of dietary cholesterol retained in the body, as well as the bodys ability to exclude selectively other dietary sterols, are poorly understood. An average western diet will contain about 250–500 mg of dietary cholesterol and about 200–400 mg of non-cholesterol sterols. About 50–60% of the dietary cholesterol is absorbed and retained by the normal human body, but less than 1% of the non-cholesterol sterols are retained. Thus, there exists a subtle mechanism that allows the body to distinguish between cholesterol and non-cholesterol sterols. In sitosterolemia, a rare autosomal recessive disorder, affected individuals hyperabsorb not only cholesterol but also all other sterols, including plant and shellfish sterols from the intestine. The major plant sterol species is sitosterol; hence the name of the disorder. Consequently, patients with this disease have very high levels of plant sterols in the plasma and develop tendon and tuberous xanthomas, accelerated atherosclerosis, and premature coronary artery disease. We previously mapped the STSL locus to human chromosome 2p21 (ref. 4) and further localized it to a region of less than 2 cM bounded by markers D2S2294 and D2S2291 (M.-H.L. et al., manuscript submitted). We now report that a new member of the ABC transporter family, ABCG5, is mutant in nine unrelated sitosterolemia patients.

HDL3 EXERTS MORE POWERFUL ANTI-OXIDATIVE, PROTECTIVE EFFECTS AGAINST COPPER-CATALYZED LDL OXIDATION THAN HDL2

OBJECTIVE To evaluate which HDL subfraction, HDL2 or HDL3 exerts the greater preventive effect on the Cu(2+)-induced LDL oxidation. METHODS LDL was incubated for 6 h with 2.5 microM Cu2+ in phosphate-buffered saline alone, or in the presence of HDL2 or HDL3 at various protein concentrations. Each sample was subjected to agarose gel electrophoresis, and the amount of lipid hydroperoxide in each sample of LDL was measured. RESULTS There was no significant difference in the levels of LPO between the LDL and LDL + HDL2 cases, whereas a significant reduction was apparent with LDL + HDL3. Both HDL2 and HDL3 significantly inhibited oxidative modification of LDL, as assessed by electrophoretic mobility, in a concentration dependent manner, but this effect was much more pronounced with HDL3. CONCLUSION HDL3 may play an important role in the prevention of atherosclerosis in vivo, more effectively inhibiting oxidation of LDL than HDL2.

Fine mapping of a gene responsible for regulating dietary cholesterol absorption; founder effects underlie cases of phytosterolaemia in multiple communities.

Sitosterolaemia (also known as phytosterolaemia, MIM 210250) is a rare recessive autosomal inherited disorder, characterised by the presence of tendon and tuberous xanthomas, accelerated atherosclerosis and premature coronary artery disease. The defective gene is hypothesised to play an important role in regulating dietary sterol absorption and biliary secretion, thus defining a molecular mechanism whereby this physiological process is carried out. The disease locus was localised previously to chromosome 2p21, in a 15 cM interval between microsatellite markers D2S1788 and D2S1352 (based upon 10 families, maximum lodscore 4.49). In this study, we have extended these studies to include 30 families assembled from around the world. A maximum multipoint lodscore of 11.49 was obtained for marker D2S2998. Homozygosity and haplotype sharing was identified in probands from non-consanguineous marriages from a number of families, strongly supporting the existence of a founder effect among various populations. Additionally, based upon both genealogies, as well as genotyping, two Amish/Mennonite families, that were previously thought not to be related, appear to indicate a founder effect in this population as well. Using both homozygosity mapping, as well as informative recombination events, the sitosterolaemia gene is located at a region defined by markers D2S2294 and Afm210xe9, a distance of less than 2 cM.

Coexisting type III hyperlipoproteinemia and familial hypercholesterolemia: A case report

A 39-year-old man presented with type III hyperlipoproteinemia in association with heterozygous familial hypercholesterolemia (FH). He had extensive tuberous xanthomas over the knees and elbows and xanthomas in the Achilles tendons. He also had palmar xanthomas. He exhibited severe hypercholesterolemia and hypertriglyceridemia. This patient was heterozygous for FH, as evidenced by low low-density lipoprotein (LDL) receptor function on lymphocytes, and had type III hyperlipoproteinemia, as determined by apolipoprotein (apo) E phenotype 2/2 in isoelectric focusing of the E isoproteins and the presence of a broad beta band on electrophoresis. Because therapy consisting of diet restrictions and lipid-lowering agents such as clinofibrate and niceritrol did not decrease serum total cholesterol ([TC] 15.26 mmol/L) and triglyceride ([TG] 10.79 mmol/L) levels effectively, the patient underwent plasmapheresis once every 2 weeks using a dextran sulfate-cellulose column. Repeated plasmapheresis markedly reduced serum TC and TG and induced complete regression of the palmar xanthoma after 6 months. The severity of tuberous xanthomas on the knees and elbows was reduced after 2.5 years. After plasmapheresis, TC decreased to 1.94 mmol/L from 10.40 mmol/L and TG decreased to 0.33 mmol/L from 7.90 mmol/L. Plasmapheresis performed with a dextran sulfate-cellulose column was highly effective in removing the lipoprotein-remnant particles in this patient, leading to generalized improvement in the lipoprotein profile.

Changes of HDL subfraction concentration and particle size by intralipid in vivo.

The effects of the artificial triglyceride-phospholipid emulsion (10% intralipid) on HDL subfraction were studied in vivo. After a 14-h fast, subjects received intralipid via a 4-h infusion. Serum lipoproteins were analyzed before and at 4 and 6 h after the start of the infusion. At 4-h the following acute changes by infusion were observed. Triglyceride, phospholipid, free cholesterol, and esterified cholesterol in chylomicrons and VLDL increased. HDL2 as well as triglyceride, phospholipid, free cholesterol and protein within the HDL2 increased, while HDL3 decreased. An increase in HDL3 triglyceride was observed. The masses of apo A-I and A-II in the HDL2 density interval rose while these parameters fell in HDL3. There were decreases of apo C-II and C-III in the HDL subfractions and elevations in chylomicrons and VLDL. The particle size of the HDL subfractions increased. However, most of these acute changes at 4 h tended to disappear by 6 h. These results suggest that there is exchange of lipids and reversible transfer of apo C-II and C-III between HDL subfractions and intralipid, and conversion of HDL3 to HDL2 followed by the reverse conversion of HDL2 to HDL3 as the synthetic emulsion is cleared from the plasma.

Assessment of functional low-density-lipoprotein receptors on lymphocytes by a simplified method using culture medium with lipoprotein-free fetal calf serum and pravastatin

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Takayasu's arteritis accompanied with massive pericardial effusion--a case report.

A 40-year-old woman who had been treated for Takayasus arteritis was admitted to the hospital with fever, fatigue, malaise, and severe chest pain. Computed tomography of the chest demonstrated massive pericardial effusion and bilateral pleural effusion. In laboratory data, the C-reactive protein was high at 22.0 mg/dL, and erythrocyte sedi mentation rate was also high at 80 mm/hr. The diagnosis was pericarditis with a recur rence of the systemic inflammatory process of Takayasus arteritis. The patient was treated with methylprednisolone pulse therapy. Her massive pericardial effusion disap peared without pericardiocentesis.

Effects of vitamin C and vitamin E on plasma levels of lipid hydroperoxides and thiobarbituric acid reactive substance in humans

Abstract A study was conducted to investigate the effects of vitamin C and vitamin E on plasma levels of lipid hydroperoxides (LPO) and thio-barbituric acid reactive substance (TBARS) in human volunteers to identify the step in the lipid peroxidation cascade at which these vitamins act. Forty subjects (20 men and 20 women) were randomly assigned to receive either vitamin C or vitamin E. Twenty subjects received 500 mg of vitamin C daily for 4 weeks, and 20 subjects received 300 mg of vitamin E daily for 4 weeks. Blood samples were collected before and 4 weeks after vitamin treatment, in the morning, after the subjects had fasted for 12 hours. Plasma levels of LPO and TBARS were determined. Plasma levels of lipids, apolipoproteins, vitamin C, and vitamin E were also measured. Vitamin C significantly reduced plasma levels of LPO and TBARS. Vitamin E significantly increased plasma levels of LPO and significantly reduced plasma levels of TBARS. Plasma concentrations of vitamin C and vitamin E significantly increased after 4 weeks of vitamin treatment. There were no significant changes in the plasma levels of lipids except LPO, TBARS, and apolipoproteins. From these results, it was concluded that vitamin C reduced LPO and TBARS levels, and vitamin E increased LPO levels and reduced TBARS levels.

Excretion of urinary epidermal growth factor in non-insulin dependent diabetes mellitus

Morning urine samples were assayed for human EGF (hEGF) in 137 non-insulin dependent diabetic patients with normal serum creatinine and beta 2-microglobulin levels. Serving as controls, 80 age- and sex-matched healthy subjects were also examined. A significant positive correlation between hEGF excretion and the level of hemoglobin A1C (HbA1c) was present in those patients with a HbA1c value exceeding 8% (r = 0.37; p = 0.003) but not in the overall patients. The urinary hEGF level did not correlate with the concentration of glucose in urine or plasma. The mean urinary hEGF level of diabetic patients was significantly lower than that of healthy subjects. The mean urinary hEGF level was significantly lower in the patients with a diabetic history that exceeded five years as compared with those with a history below five years. The mean urinary hEGF level was significantly lower in the patients with retinopathy vs. those without retinopathy. In the patients with HbA1c value below 8%, the mean urinary hEGF level was lower in the patients whose urinary albumin level exceeded 1.7 mg/mmol.creatinine as compared with those whose urinary albumin excretion was below 1.7 mg/mmol.creatinine. These findings suggest that urinary hEGF excretion may decrease with the progression of diabetic complications in the patients with well-controlled glycemia, and that inadequate glycemic control may lead to an increased excretion of urinary hEGF in the early disease stage.

Transforming growth factor - α activity in effusions: Comparison of radioimmunoassay and radioreceptorassay

Transforming growth factor-alpha (TGF-alpha) in pleural and peritoneal effusions was assayed by homologous radioimmunoassay (RIA) and radioreceptor assay (RRA) using human placental membrane. Effusions were obtained from 24 patients with and 17 patients without cancer. Most of the effusions were found to contain TGF-alpha by RIA and RRA, but immunoreactive epidermal growth factor (EGF) was not detected. Effusions were chromatographed on Bio-Gel P-60 with several peaks of TGF-alpha activity by both RIA and RRA. A discrepancy in the chromatographic pattern of TGF-alpha between RIA and RRa suggested the existence of EGF-like substances capable of binding to EGF receptors which lack immunoreactivity for EGF or TGF-alpha. The TGF-alpha concentration of the acetic acid-extracted malignant effusions assayed by RRA significantly exceeded the value obtained from benign effusions (17.0 +/- 8.7 vs. 9.2 +/- 6.3 ng/ml; mean +/- SD: p < 0.02). However, the concentrations obtained by RIA did not differ.