Shinichi Usui

Low-density lipoprotein receptor-related protein 5 (LRP5) is essential for normal cholesterol metabolism and glucose-induced insulin secretion

A Wnt coreceptor low-density lipoprotein receptor-related protein 5 (LRP5) plays an essential role in bone accrual and eye development. Here, we show that LRP5 is also required for normal cholesterol and glucose metabolism. The production of mice lacking LRP5 revealed that LRP5 deficiency led to increased plasma cholesterol levels in mice fed a high-fat diet, because of the decreased hepatic clearance of chylomicron remnants. In addition, when fed a normal diet, LRP5-deficient mice showed a markedly impaired glucose tolerance. The LRP5-deficient islets had a marked reduction in the levels of intracellular ATP and Ca2+ in response to glucose, and thereby glucose-induced insulin secretion was decreased. The intracellular inositol 1,4,5-trisphosphate (IP3) production in response to glucose was also reduced in LRP5−/− islets. Real-time PCR analysis revealed a marked reduction of various transcripts for genes involved in glucose sensing in LRP5−/− islets. Furthermore, exposure of LRP5+/+ islets to Wnt-3a and Wnt-5a stimulates glucose-induced insulin secretion and this stimulation was blocked by the addition of a soluble form of Wnt receptor, secreted Frizzled-related protein-1. In contrast, LRP5-deficient islets lacked the Wnt-3a-stimulated insulin secretion. These data suggest that Wnt/LRP5 signaling contributes to the glucose-induced insulin secretion in the islets.

Circadian Changes in Subfoveal Choroidal Thickness and the Relationship with Circulatory Factors in Healthy Subjects

PURPOSEnTo investigate circadian changes in subfoveal choroidal thickness (SFCT) and the relation to systemic factors in healthy subjects.nnnMETHODSnThirty-eight eyes of 19 healthy volunteers were enrolled. SFCT was measured by using prototype high-penetration optical coherence tomography. Intraocular pressure (IOP), systolic blood pressure (SBP), diastolic blood pressures (DBP), and heart rate (HR) were measured every 3 hours over a 24-hour period. Circadian changes in the mean arterial pressure (MAP) and mean ocular perfusion pressure (MOPP) were calculated. The difference between the maximal and minimal SFCTs was analyzed, and correlations between the SFCT and other systemic factors were evaluated.nnnRESULTSnThere was a significant circadian variation in SFCT (P < 0.0001). The total mean SFCT was 280.3 ± 106.1 μm. At 6 PM, the mean SFCT (271.9 ± 103.5 μm) was the thinnest and at 3 AM it was the thickest (290.8 ± 110.8 μm). The SFCTs in 32 of 38 eyes were thickest between 3 and 9 AM and in 27 of 38 eyes, thinnest between 3 and 9 PM. The mean SFCT was significantly negatively correlated with the mean SBP (R(2) = 0.59, P = 0.02) in all eyes. There were no significant correlations between the mean SFCT and the mean DBP, MAP, HR, IOP, and MOPP in all eyes.nnnCONCLUSIONSnWe investigated the circadian change of choroidal thickness using high-penetration optical coherence tomography in healthy volunteers. The significant diurnal change was found and the choroid was thicker at night and thinner in daytime. Fluctuations in the choroidal thickness may be related to SBP.

Severe hypercholesterolemia, impaired fat tolerance, and advanced atherosclerosis in mice lacking both low density lipoprotein receptor-related protein 5 and apolipoprotein E.

LDL receptor-related protein 5 (LRP5) plays multiple roles, including embryonic development and bone accrual development. Recently, we demonstrated that LRP5 is also required for normal cholesterol metabolism and glucose-induced insulin secretion. To further define the role of LRP5 in the lipoprotein metabolism, we compared plasma lipoproteins in mice lacking LRP5, apolipoprotein E (apoE), or both (apoE;LRP5 double knockout). On a normal chow diet, the apoE;LRP5 double knockout mice (older than 4 months of age) had ∼60% higher plasma cholesterol levels compared with the age-matched apoE knockout mice. In contrast, LRP5 deficiency alone had no significant effects on the plasma cholesterol levels. High performance liquid chromatography analysis of plasma lipoproteins revealed that cholesterol levels in the very low density lipoprotein and low density lipoprotein fractions were markedly increased in the apoE;LRP5 double knockout mice. There were no apparent differences in the pattern of apoproteins between the apoE knockout mice and the apoE;LRP5 double knockout mice. The plasma clearance of intragastrically loaded triglyceride was markedly impaired by LRP5 deficiency. The atherosclerotic lesions of the apoE;LRP5 double knockout mice aged 6 months were ∼3-fold greater than those in the age-matched apoE-knockout mice. Furthermore, histological examination revealed highly advanced arthrosclerosis, with remarkable accumulation of foam cells and destruction of the internal elastic lamina in the apoE;LRP5 double knockout mice. These data suggest that LRP5 mediates both apoE-dependent and apoE-independent catabolism of plasma lipoproteins.

Evaluation of the choroidal thickness using high-penetration optical coherence tomography with long wavelength in highly myopic normal-tension glaucoma.

PURPOSEnTo evaluate the choroidal thickness by high-penetration optical coherence tomography (OCT) using long wavelength in highly myopic normal-tension glaucoma (NTG).nnnDESIGNnCross-sectional retrospective study.nnnMETHODSnnnnSETTINGSnInstitutional.nnnPARTICIPANTSnTwelve eyes from 8 patients under 45 years old, diagnosed as NTG without any other ocular diseases, spherical equivalent refractive error between -6 and -12 diopters, and axial length greater than 26.5 mm; and 12 eyes of matched healthy volunteers.nnnINTERVENTIONnChoroid was imaged with prototype high-penetration OCT and its thickness was measured.nnnMAIN OUTCOME MEASURESnChoroidal thickness at the fovea and 5 locations: 2 mm superior, temporal, and inferior to the center of the optic nerve head, and 2 mm superior (superotemporal) and 2 mm inferior (inferotemporal) to the temporal location.nnnRESULTSnOverall, the choroidal thickness in the NTG group was approximately 50% that in controls. Mean choroidal thickness in the NTG group was significantly thinner in the control group at the fovea (166 vs 276 μm, P < .001), superior (172 vs 241 μm, P < 0.05), superotemporal (161 vs 244 μm, P < .01), temporal (110 vs 161 μm, P < .01), and inferotemporal (115 vs 159 μm, P < .05) to the optic nerve head. Stepwise analysis disclosed that the foveal choroidal thickness is the most influential factor on the occurrence of NTG (P < .0001, R(2) = 0.4).nnnCONCLUSIONSnChoroidal thickness in highly myopic NTG is significantly thinner than in controls, at least in some specific locations. Choroidal thinning is somehow related with highly myopic NTG and may be a useful diagnostic parameter for myopic NTG.

Choroidal thickness in central serous chorioretinopathy.

Purpose: To study the choroidal thickness profile using high-penetration optical coherence tomography in central serous chorioretinopathy (CSC). Methods: Thirty-five eyes of 27 subjects with CSC and 35 healthy, age-matched control eyes were included. We observed the choroid using the prototype high-penetration optical coherence tomography. Fluorescein angiography and indocyanine green angiography were performed to identify the CSC location and activity. The choroidal thicknesses was measured manually in various conditions or locations, and the choroidal thickness maps were obtained from cube scans and calculating software and composed of nine sectors in the Early Diabetic Retinopathy Study chart. Results: The subfoveal choroidal thicknesses in all eyes with CSC were significantly (P < 0.01) greater than that in the control eyes. The choroidal thickness at the fovea and the fluorescein points of leakage were significantly (P < 0.01 for both comparisons) greater in eyes with CSC than the corresponding locations in the fellow eyes in patients with unilateral disease. Dilatation of the choroidal large vessels was significantly (P < 0.01) more common in CSC. The foveal choroidal thickness was significantly greater in eyes with venous dilatation (P < 0.01) than those without. The mean choroidal thickness was significantly (P < 0.05) greater in all sectors of the Early Diabetic Retinopathy Study chart except for the inner (P = 0.087) and outer (P = 0.053) inferior sectors. The percent mean choroidal thicknesses compared with the normal controls in the nasal sector were significantly (P < 0.05 and P < 0.01, respectively) greater in the inner and outer circles than in the superior, temporal, and inferior sectors. Conclusion: The choroid is diffusely thickened in CSC likely because of the choroidal vascular dilatation. The nasal macula undergoes the greatest alterations in choroidal thickness compared with the other areas.

Virus-mediated Transduction of Apolipoprotein E (ApoE)-Sendai Develops Lipoprotein Glomerulopathy in ApoE-deficient Mice

Lipoprotein glomerulopathy (LPG) is a unique renal disease characterized by thrombus-like substances in markedly dilated glomerular capillaries, dysbetalipoproteinemia, and elevated plasma concentrations of apoE. Recent studies identified several apoE mutations in patients with LPG, including apoE2(R145P) Sendai (apoE-Sendai). Virus-mediated transduction of apoE-Sendai in apoE-deficient hypercholesterolemic mice resulted in insufficient correction of hypercholesterolemia and a marked and temporal induction of plasma triglyceride levels. In vitro binding studies showed that apoE-Sendai has a reduced affinity for the low density lipoprotein receptor, suggesting that dysbetalipoproteinemia in LPG is caused by the apoE mutation. Furthermore, histological examination revealed marked intraglomerular depositions of apoE-containing lipoproteins in mice injected with apoE-Sendai virus. These LPG-like depositions were detected 6 days after virus injection and were sustained for at least 60 days. Our results demonstrated that apoE-Sendai is an etiological cause of LPG.

Relation between RLP-triglyceride to RLP-cholesterol ratio and particle size distribution in RLP-cholesterol profiles by HPLC

Remnant-Like Particles (RLP) isolated by an immunoseparation method are heterogeneous in their physical and biochemical properties. The objective of this study was to examine the relation between RLP-triglyceride (RLP-TG) to RLP-cholesterol (RLP-C) ratio and particle size distribution in RLP-C profiles from patients with hyperlipoproteinemia by HPLC. RLP were isolated from serum samples from 147 subjects. RLP-C and RLP-TG were quantified by respective enzymatic methods. Particle sizes of the RLP were measured using HPLC with 4 connected TSKgel LipopropakXL columns. Based on HPLC profiles of RLP-C from individual subjects, three different types were classified: predominantly LDL, predominantly VLDL, and mostly VLDL types. All patients with type III hyperlipidemia were mostly VLDL type but with smaller particle size of VLDL (32 nm) than other subjects. Severe hypertriglyceridemic (TG>4.52 mmoll(-1)) subjects were mostly VLDL type with large particle size (41 nm). As for all subjects (n=105) without predominantly LDL type, a significant correlation between RLP particle size and RLP-TG to RLP-C ratio (r=0. 432, P<0.001) was obtained, but not in case of serum TG to RLP-C ratio (r=0.062). It suggests that RLP-TG to RLP-C ratio might be used for discrimination of atherogenic smaller-sized lipoprotein from larger-sized TG-rich lipoprotein remnants.

Effect of Probucol in Lecithin-Cholesterol Acyltransferase–Deficient Mice: Inhibition of 2 Independent Cellular Cholesterol–Releasing Pathways In Vivo

Abstract —Cellular cholesterol release takes place by at least 2 distinct mechanisms: the lecithin-cholesterol acyltransferase (LCAT)-driven net efflux by cholesterol diffusion and the generation of high density lipoprotein (HDL) with cellular cholesterol and phospholipid on the cell-apolipoprotein interaction. Therefore, LCAT deficiency impairs the former pathway, and the latter can be inhibited by probucol, which interferes with the apolipoprotein-cell interaction. Hence, probucol was given to the LCAT-deficient mice in the attempt to suppress both of these pathways. The mice were fed low (0.2%) and high (1.2%) cholesterol diets containing 0.5% probucol for 2 weeks. LCAT deficiency and probucol markedly decreased plasma HDL, and the effects were synergistic. Tissue cholesterol content was lower in the adrenal glands and ovaries in the LCAT-deficient mice and in the probucol-treated mice, suggesting that HDL is a main cholesterol provider for these organs. It was also moderately decreased in the spleen of the low cholesterol–fed female mice and in the thyroid gland of the low cholesterol–fed male mice. On the other hand, the esterified cholesterol content in the liver was substantially increased by the probucol treatment with a high cholesterol diet in the LCAT-deficient mice but not in the wild-type mice. Among the groups, there was no significant difference in the tissue cholesterol levels in other organs, such as the liver, spleen, thymus, brain, erythrocytes, thyroid gland, testis, and aorta, resulting from either LCAT deficiency or probucol. Thus, the apolipoprotein-mediated mechanism plays a significant role in the export of cellular cholesterol in the liver, indicating that the liver is a major site of the HDL assembly. Otherwise, tissue cholesterol homeostasis can largely be maintained in mice even when the assembly of new HDL is inhibited by probucol in the absence of LCAT. Nonspecific diffusion of cholesterol perhaps adequately maintains the homeostasis in the experimental condition.

Changes in axial length and choroidal thickness after intraocular pressure reduction resulting from trabeculectomy

Purpose To evaluate changes in axial length and choroidal thickness after trabeculectomy. Patients and methods Fourteen patients under 80 years of age with glaucoma, were enrolled. The choroid was imaged using prototypical high-penetration optic coherence tomography (OCT) and the thickness was measured. Axial length, choroidal thickness, and intraocular pressure (IOP) were measured bilaterally at 3 pm 1 day before and 6 days after trabeculectomy. The choroidal thickness was measured at the fovea and four other locations (2 mm superior, temporal, inferior, and nasal to the center of the optic nerve head). Results The IOP and axial length significantly decreased in eyes that underwent trabeculectomy (P < 0.0001 for the IOP; P < 0.001 for axial length comparisons). The mean choroidal thicknesses significantly increased in eyes that underwent trabeculectomy compared to preoperatively (P < 0.0001 for the fovea; P < 0.01 for four locations around the optic disc). The mean magnitude of change in IOP was correlated positively with the mean magnitude of change in axial length, but not correlated with the mean magnitude of change in choroidal thickness at the fovea that underwent trabeculectomy. The sum of the axial length and subfoveal choroidal thickness in eyes decreased significantly postoperatively (P < 0.05). Conclusion The axial length shortened, the choroid thickened, and the sum of the axial length and subfoveal choroidal thickness decreased with IOP reduction early after trabeculectomy.

Effects of bezafibrate and pravastatin on remnant-like lipoprotein particles and lipoprotein subclasses in type 2 diabetes.

The effects of bezafibrate and pravastatin on remnant-like lipoprotein particles (RLPs) and lipoprotein subclasses were compared in type 2 diabetes. Bezafibrate (400 mg/day) and pravastatin (10 mg/day) were given to 27 Japanese diabetics in a randomized crossover design. RLP cholesterol (RLP-C) and RLP triglyceride (RLP-TG) were measured by an immunoseparation technique. LDL and HDL were separated each into three subclasses (large, medium, small) and their cholesterol (C) contents were measured by an HPLC method. RLP-C was reduced more effectively by pravastatin (bezafibrate -16.0% vs. pravastatin -40.6%, P < 0.05), whereas RLP-TG was reduced more effectively by bezafibrate (-55.2% vs. -35.0%, P < 0.05). Further, pravastatin decreased large and small LDL-C levels equally (large; -23.6%; medium; -17.2%, small; -21.0%), while bezafibrate produced a relatively larger reduction in small LDL-C (-12.1; -16.9; -21.5%). Whereas bezafibrate significantly decreased large HDL-C and increased medium and small HDL-C (-49.6; 34.1; 35.8%), pravastatin significantly increased only medium HDL-C (5.2; 9.4; 5.9%). Bezafibrate reduced RLP-C and RLP-TG more effectively in patients with high TG levels, whereas pravastatins effect was not markedly influenced by the initial TG level. Thus measurements of RLP-C, RLP-TG, and HPLC subclasses revealed that bezafibrate and pravastatin differently influence the lipoprotein status in type 2 diabetes.