Masayuki Tsuchida

Altered metabolism of low-density lipoprotein and very-low-density lipoprotein remnant in autosomal recessive hypercholesterolemia: results from stable isotope kinetic study in vivo.

Background— Autosomal recessive hypercholesterolemia (ARH) exhibits different responsiveness to statins compared with that in homozygous familial hypercholesterolemia (FH). However, few data exist regarding lipoprotein metabolism of ARH. Therefore, we aimed to clarify lipoprotein metabolism, especially the remnant lipoprotein fractions of ARH before and after statin therapy. Methods and Results— We performed a lipoprotein kinetic study in an ARH patient and 7 normal control subjects, using stable isotope methodology (10 mg/kg of [2H3]-leucine). These studies were performed at baseline and after the 20 mg daily dose of atorvastatin. Tracer/tracee ratio of apolipoprotein B (apoB) was determined by gas chromatography/mass spectrometry and fractional catabolic rates (FCR) were determined by multicompartmental modeling, including remnant lipoprotein fractions. FCR of low-density lipoprotein (LDL) apoB of ARH was significantly lower than those of control subjects (0.109 versus 0.450±0.122 1/day). In contrast, the direct removal of very-low-density lipoprotein remnant was significantly greater in ARH than those in control subjects (47.5 versus 2±2%). Interestingly, FCR of LDL apoB in ARH dramatically increased to 0.464 1/day, accompanying reduction of LDL cholesterol levels from 8.63 to 4.22 mmol/L after treatment with atorvastatin of 20 mg/d for 3 months. Conclusions— These results demonstrate that ARH exhibits decreased LDL clearance associated with decreased FCR of LDL apoB and increased clearance for very-low-density lipoprotein remnant. We suggest that increased clearance of remnant lipoprotein fractions could contribute to the great responsiveness to statins, providing new insights into the lipoprotein metabolism of ARH and the novel pharmacological target for LDLRAP1.

Comparison of Effects of Pitavastatin and Atorvastatin on Plasma Coenzyme Q10 in Heterozygous Familial Hypercholesterolemia: Results From a Crossover Study

An open, randomized, four‐phased crossover study using 4 mg of pitavastatin or 20 mg of atorvastatin was performed to compare their efficacy and safety, especially regarding plasma levels of coenzyme Q10 (CoQ10) in 19 Japanese patients with heterozygous familial hypercholesterolemia. Pitavastatin and atorvastatin caused significant and almost comparable reductions in serum levels of total cholesterol (−35.4 vs. −33.8%), low‐density lipoprotein cholesterol (−42.8 vs. −40.7%), and triglyceride (−26.1 vs. −29.4%), and significantly increased serum levels of high‐density lipoprotein cholesterol (12.1 vs. 11.4%). Under these conditions, plasma levels of CoQ10 were reduced by atorvastatin (−26.1%, P=0.0007) but not by pitavastatin (−7.7%, P=0.39), although no adverse events or abnormalities of liver and muscle enzyme were observed after either statin treatment. It remains to be seen whether the observed changes in CoQ10 levels are related to the long‐term safety of this drug.

A novel method for determining functional LDL receptor activity in familial hypercholesterolemia: Application of the CD3/CD28 assay in lymphocytes

BACKGROUND The objective of this study was to develop a new and simple method for measuring low-density lipoprotein receptor (LDLR) activity using peripheral lymphocytes enabling us to clinically diagnose familial hypercholesterolemia (FH) and ascertain the involved mutations (such as K790X mutation), that might not be clearly detected in the conventional method. METHODS Our method comprised the following 2 features: first, we used anti-CD3/CD28 beads to stimulate T-lymphocytes to obtain a uniform fraction of lymphocytes and maximum up-regulation of LDLR. Second, we excluded the possibility of overestimation of lymphocyte signals bound only to its surface, by adding heparin to the cultured lymphocytes used for the LDLR assay. RESULTS Based on the genetic mutation, the FH subjects were divided into 2 groups, K790X, (n=20) and P664L, (n=5), and their LDLR activities was measured by this method, which was found to be 55.3+/-8.9% and 63.9+/-13.8%, respectively, of that of the control group (n=15). In comparison, the LDLR activity was 86.1+/-11.6% (K790X) and 73.3+/-6.3% (P664L) of that of the control group when measured by the conventional method, indicating that impairment of LDLR function in FH K790X subjects was much more clearly differentiated with our method than with the conventional method (paired t-test, p<0.0001). The levels of LDLR expression also showed similar tendencies, that is, 89.4+/-13.2% (K790X) and 76.9+/-17.4% (P664L) of that of the control group when measured by the conventional method, and 78.1+/-9.7% (K790X) and 70.3+/-26.5% (P664L) when measured by our new method. In addition, we confirmed that there was little influence of statin treatment on LDLR activity among the study subjects when our method was used. CONCLUSION These results demonstrate that our new method is applicable for measuring LDLR activity, even in subjects with an internally defective allele, and that T-lymphocytes of the FH K790X mutation possess characteristics of that allele.

Apolipoprotein B gene mutations and fatty liver in Japanese hypobetalipoproteinemia

BACKGROUND Familial hypobetalipoproteinemia (FHBL) is a hereditary disorder characterized by decreased plasma concentrations of low-density lipoprotein cholesterol. The best-characterized causes of FHBL are apolipoprotein B (apoB) gene mutations, which produce truncated apoB proteins. Fatty liver is thought to be frequent in FHBL, owing to impaired secretion of very-low-density lipoprotein from the liver. Homozygotes for FHBL present with extremely low concentrations of plasma lipids, and may suffer from deficiencies of fat-soluble vitamins. The objectives of this study were to identify apoB-defective FHBL subjects and investigate fatty liver in Japanese population. METHODS We screened 14 hypocholesterolemic subjects for apoB gene mutations by PCR-SSCP and performed liver ultrasonography in a Japanese population. RESULTS We identified an apoB-82 homozygote in one subject and an apoB-13.7 heterozygote in another subject. Four of 6 individuals with FHBL presented with fatty liver in those 2 FHBL families. Liver biopsy of the apoB-13.7 heterozygote, which had obesity and insulin resistance, showed severe fatty liver. The apoB-82 homozygote was asymptomatic with fat-soluble vitamin concentrations being normal, possibly due to spared secretion of apoB-48 from the intestine and increased plasma concentrations of high-density lipoprotein cholesterol. CONCLUSION ApoB gene mutations might not be rare and that fatty liver might be frequent in Japanese FHBL.

High Frequency of a Retinoid X Receptor γ Gene Variant in Familial Combined Hyperlipidemia That Associates With Atherogenic Dyslipidemia

Objective—The genetic background of familial combined hyperlipidemia (FCHL) has not been fully clarified. Because several nuclear receptors play pivotal roles in lipid metabolism, we tested the hypothesis that genetic variants of nuclear receptors contribute to FCHL. Methods and Results—We screened all the coding regions of the PPAR&agr;, PPAR&ggr;2, PPAR&dgr;, FXR, LXR&agr;, and RXR&ggr; genes in 180 hyperlipidemic patients including 60 FCHL probands. Clinical characteristics of the identified variants were evaluated in other 175 patients suspected of coronary disease. We identified PPAR&agr; Asp140Asn and Gly395Glu, PPAR&ggr;2 Pro12Ala, RXR&ggr; Gly14Ser, and FXR −1g−>t variants. Only RXR&ggr; Ser14 was more frequent in FCHL (15%, P<0.05) than in other primary hyperlipidemia (4%) and in controls (5%). Among patients suspected of coronary disease, we identified 9 RXR&ggr; Ser14 carriers, who showed increased triglycerides (1.62±0.82 versus 1.91±0.42 [mean±SD] mmol/L, P<0.05), decreased HDL-cholesterol (1.32±0.41 versus 1.04±0.26, P<0.05), and decreased post-heparin plasma lipoprotein lipase protein levels (222±85 versus 149±38 ng/mL, P<0.01). In vitro, RXR&ggr; Ser14 showed significantly stronger repression of the lipoprotein lipase promoter than RXR&ggr; Gly14. Conclusion—These findings suggest that RXR&ggr; contributes to the genetic background of FCHL.

An Enhanced Device for Transluminal Retrieval of Vascular Stents Without Surgical Procedures: Experimental Studies

BACKGROUND Although efforts have been focused on developing endovascular procedures by which intravascular devices such as stents could be effectively deployed, few data exist regarding devices for the nonsurgical retrieval of deployed stents. Therefore, we designed to enable retrieval of deployed stents without a surgical procedure. METHODS The device consisted of four components: ultra-low profile forceps with 2.0 mm in diameter, conducting shaft with 1.8 mm in diameter, control handle by which the forceps is opened or closed, and a covering sheath. This device was designed to advance into the vessel lumen along a 0.014-inch guidewire by over the wire fashion. RESULTS The forceps could firmly catch nonexpanded as well as expanded tubular-type stents with open cells in an in vitro model that was 4.0 mm in diameter. Then, we used this device in porcine renal arteries with 2.5-5.0 mm in diameter. At first, a fragmented 0.014-inch guidewire could be safely removed without vessel damage that was confirmed by intravascular ultrasound. This device could successfully remove four of five inappropriately and 11 of 14 appropriately deployed stents. Under these conditions, intravascular ultrasound demonstrated minor vessel wall dissection in two-third of cases. CONCLUSIONS These results demonstrate that the present device can be used for transluminal removal of foreign bodies such as nonexpanded as well as expanded stents in acute phase. Further miniaturization may enable using this type of device in the renal as well as coronary arteries.

P-214 Clinical Impact of Heterozygous Carrier of Autosomal Recessive Hypercholesterolemia on Asymptomatic Hyperlipidemic Patients

Velocity (baPWV) and conventional coronary risk factors. The relationship between this new parameter and coronary artery sclerosis was evaluated in comparison with other indexes. Results: CAD patients were characteristic of more hypertensive and diabetic with higher CAVI and baPWV than nonCAD subjects. Multivariate logistic analysis after adjustment for hypertension, diabetes mellitus, Dyslipidemia, current smoke, sex and age, still verified that CAD risk was significantly related to CAVI (OR; 3.60, for the difference between the first and the fourth quartile [95% Confidence Interval; 1.60 8.10, p = 0.002]), whereas the same relationship with baPWV statistically diminished (OR; 1.99, 95% Confidence Interval; 0.88 4.49, p = 0.097). CAVI also showed a more remarkable ability to predict CAD than baPWV and age among patients without hypertension and diabetes mellitus under age of 70 (CAVI; OR = 3.98, p = 0.020, baPWV; OR = 0.90, p = 0.631, age; OR = 1.15, p = 0.043). Conclusions: CAVI is more useful in predicting coronary artery stenosis than baPWV in all CAD-suspected subjects and even in their relative low-risk groups, which may lead to a possibility of CAVI for helping detecting CAD among those who are not easily screened out by coronary risk factors and baPWV.