Atsushi Nohara

Impacts of Visceral Adipose Tissue and Subcutaneous Adipose Tissue on Metabolic Risk Factors in Middle‐aged Japanese

Regional fat distribution rather than overall fat volume has been considered to be important to understanding the link between obesity and metabolic disorders. We aimed to evaluate the independent associations of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) with metabolic risk factors in apparently healthy middle‐aged Japanese. Participants were 1,119 men and 854 women aged 38–60 years who were not taking medications for diabetes, hypertension, or dyslipidemia. VAT and SAT were measured by use of computed tomography (CT) scanning. VAT and SAT were significantly and positively correlated with each other in men (r = 0.531, P < 0.001) and women (r = 0.589, P < 0.001). In multiple regression analyses, either measure of abdominal adiposity (VAT or SAT) was positively associated with blood pressure, fasting plasma glucose, and log triglyceride (P < 0.001) and inversely with high‐density lipoprotein (HDL)‐cholesterol (P < 0.001). When VAT and SAT were simultaneously included in the model, the association of VAT with triglycerides was maintained (P < 0.001) but that of SAT was lost. The same was true for HDL‐cholesterol in women. For fasting plasma glucose, the association with VAT was strong (P < 0.001) and the borderline association with SAT was maintained (P = 0.060 in men and P = 0.020 in women). Both VAT and SAT were independently associated with blood pressure (P < 0.001). Further adjustment for anthropometric indices resulted in the independent association only with VAT for all risk factors. In conclusion, impacts of VAT and SAT differed among risk factors. VAT showed dominant impacts on triglyceride concentrations in both genders and on HDL‐cholesterol in women, while SAT also had an independent association with blood pressure.

Comparison of waist circumference with body mass index for predicting abdominal adipose tissue

AIMS To compare waist circumference (WC) with body mass index (BMI) for the prediction of abdominal adipose tissues in Japanese men and women. METHODS 1432 men and 1038 women aged 38-60 years were recruited. WC, BMI, visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) using CT scans were measured. RESULTS Women had a lower mean VAT than men (79.3 cm(2) vs. 132.3 cm(2); p<0.001) and a higher mean SAT (196.2 cm(2) vs. 139.7 cm(2); p<0.001). The correlation with WC or BMI was greatest for total adipose tissue (TAT), followed by SAT, and least for VAT. The correlation coefficients were not significantly different between WC and BMI for any adipose tissue except for VAT in men (p<0.05). Age was positively correlated with VAT in both genders (p<0.001). Using multiple regression analyses on VAT, R(2) values using WC and age were 0.45 in men and 0.48 in women. For SAT, the values were 0.57 in men and 0.59 in women. CONCLUSIONS The relationship with WC or BMI was greatest for TAT and SAT, and least for VAT. WC and BMI provided essentially similar estimates of TAT, VAT, and SAT in both genders.

Cholesterol efflux from J774 macrophages and Fu5AH hepatoma cells to serum is preserved in CETP-deficient patients

BACKGROUND The role of CETP in the development of atherosclerosis is debatable, and few data exist regarding the total impact of CETP inhibition on cholesterol efflux. METHODS Acceptor capacities of whole serum and HDL subfractions separated by HPLC were compared using 2 different cell systems. Subjects with CETP deficiency (2 homozygous, 1 compound heterozygous, and 5 heterozygous) were analyzed along with 10 normolipidemic controls. The fractional efflux from cholesterol-labeled Fu5AH hepatoma cells was determined to be SR-BI mediated. The efflux difference between control and liver X receptor (LXR) agonist-induced ABCA1-upregulated J774 macrophages was considered as a measure of ABCA1-mediated efflux. RESULTS For the Fu5AH cell system, the total acceptor capacities of whole serum and HPLC-separated HDL fraction 2 obtained from the homozygous subjects were 38% and 116% higher than the corresponding values for the controls, respectively (p<0.05). For the J774 cell system, the total acceptor capacities of whole serum and HPLC-separated HDL fractions were similar among the CETP-deficient subjects and controls. CONCLUSIONS Serum from homozygous subjects with CETP-null defects exhibited enhanced acceptor capacity via an SR-BI dependent pathway, which is regulated by the middle HPLC-separated HDL fraction. Further, the cholesterol acceptor capacity of serum obtained from patients having complete and partial CETP deficiency was preserved via an ABCA1-dependent pathway.

Formation of preβ1-HDL during lipolysis of triglyceride-rich lipoprotein

Prebeta1-HDL, a putative discoid-shaped high-density lipoprotein (HDL) is known to participate in the retrieval of cholesterol from peripheral tissues. In this study, to clarify potential sources of this lipoprotein, we conducted heparin injection on four Japanese volunteer men and found that serum triglyceride (TG) level decreased in parallel with the increase in serum nonesterified fatty acids and plasma lipoprotein lipase (LPL) protein mass after heparin injection. Plasma prebeta1-HDL showed considerable increases at 15 min after the heparin injection in all of the subjects. In contrast, serum HDL-C levels did not change. Gel filtration with fast protein liquid chromatography system (FPLC) study on lipoprotein profile revealed that in post-heparin plasma, low-density lipoprotein and alphaHDL fractions did not change, whereas there was a considerable decrease in very low-density lipoprotein (VLDL) fraction and an increase in prebeta1-HDL fraction when compared with those in pre-heparin plasma. We also conducted in vitro analysis on whether prebeta1-HDL was produced during VLDL lipolysis by LPL. One hundred microliters of VLDL extracted from pooled serum by ultracentrifugation was incubated with purified bovine milk LPL at 37 degrees C for 0-120 min. Prebeta1-HDL concentration increased in a dose dependent manner with increased concentration of added LPL in the reaction mixture and with increased incubation time, indicating that prebeta1-HDL was produced during lipolysis of VLDL by LPL. Taken these in vivo and in vitro analysis together, we suggest that lipolysis of VLDL particle by LPL is an important source for formation of prebeta1-HDL.

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.

Impact of bezafibrate and atorvastatin on lipoprotein subclass in patients with type III hyperlipoproteinemia: result from a crossover study.

BACKGROUND We elucidated the difference between the effects of bezafibrate and atorvastatin in hypertriglyceridemia with apoE2/2 and 3/3. METHODS An open randomized crossover study consisted of a 4-week treatment period with bezafibrate (400 mg daily) or atorvastatin (10 mg daily) and a 4-week wash-out period. RESULTS Bezafibrate significantly decreased serum concentrations of triglyceride (apoE2/2, E3/3: -49.2%, -39.0%) and significantly increased high-density lipoprotein (HDL) cholesterol (+28.5%, +26.1%) in both apoE phenotypes but did not change serum concentrations of low-density lipoprotein (LDL) cholesterol. Atorvastatin significantly decreased serum concentrations of LDL cholesterol (-34.0%, -30.0%) and triglyceride (-27.6%, -25.8%) in both apoE phenotypes but did not change HDL cholesterol concentrations. Changes in cholesterol in lipoprotein subfractions were not different between apoE2/2 and E3/3. Bezafibrate changed cholesterol distribution from small- to large-sized LDL and from large- to small-sized HDL. On the other hand, atorvastatin decreased cholesterol in all apoB-containing lipoprotein subfractions but did not change any of the HDL subfractions. CONCLUSION Bezafibrate and atorvastatin improve atherogenic dyslipidemia in considerably different ways. Extrapolating from the present data, we presume that the combination of these drugs may contribute to reduce LDL-C/HDL-C ratio effectively as well as lowering concentrations of serum triglyceride.

Familial combined hyperlipidemia

家族性複合型高脂血症は,心筋梗塞患者の10～20%と推定されており,最も頻度の高い高脂血症であるが,その成因は単一でなく,症候群と考えられるため研究が遅れている.確定診断には家族調査が必須となるが,血清CHOL 228mg/dl以上,血清TG 139mg/dl以上, HDL-C 45.5mg/dl以下を同時に満たす症例をFCHLとすることを提案したい.ここでは家族性複合型高脂血症の臨床像,病態を解説し,成因に関する遺伝子異常を明らかにする.さらに本症の治療に関するフィブレート系薬剤の有用性を紹介する.