Hiroshige Itakura’s research while affiliated with Ibaraki University and other places

Background We recently reported distinct nature of high-density lipoproteins (HDL) subgroup particles with apolipoprotein (apo) A-I but not apoA-II (LpAI) and HDL having both (LpAI:AII) based on the data from 314 Japanese. While plasma HDL level almost exclusively depends on concentration of LpAI having 3 to 4 apoA-I molecules, LpAI:AII appeared with almost constant concentration regardless of plasma HDL levels having stable structure with two apoA-I and one disulfide-dimeric apoA-II molecules (Sci. Rep. 6; 31,532, 2016). The aim of this study is further characterization of LpAI:AII with respect to its role in atherogenesis. Methods Association of LpAI, LpAI:AII and other HDL parameters with apoB-lipoprotein parameters was analyzed among the cohort data above. Results ApoA-I in LpAI negatively correlated with the apoB-lipoprotein parameters such as apoB, triglyceride, nonHDL-cholesterol, and nonHDL-cholesterol + triglyceride, which are apparently reflected in the relations of the total HDL parameters to apoB-lipoproteins. In contrast, apoA-I in LpAI:AII and apoA-II positively correlated to the apoB-lipoprotein parameters even within their small range of variation. These relationships are independent of sex, but may slightly be influenced by the activity-related CETP mutations. Conclusions The study suggested that LpAI:AII is an atherogenic indicator rather than antiatherogenic. These sub-fractions of HDL are to be evaluated separately for estimating atherogenic risk of the patients.

Plasma concentration of apoA-I, apoA-II and apoA-II-unassociated apoA-I was analyzed in 314 Japanese subjects (177 males and 137 females), including one (male) homozygote and 37 (20 males and 17 females) heterozygotes of genetic CETP deficiency. ApoA-I unassociated with apoA-II markedly and linearly increased with HDL-cholesterol, while apoA-II increased only very slightly and the ratio of apoA-II-associated apoA-I to apoA-II stayed constant at 2 in molar ratio throughout the increase of HDL-cholesterol, among the wild type and heterozygous CETP deficiency. Thus, overall HDL concentration almost exclusively depends on HDL with apoA-I without apoA-II (LpAI) while concentration of HDL containing apoA-I and apoA-II (LpAI:AII) is constant having a fixed molar ratio of 2 : 1 regardless of total HDL and apoA-I concentration. Distribution of apoA-I between LpAI and LpAI:AII is consistent with a model of statistical partitioning regardless of sex and CETP genotype. The analysis also indicated that LpA-I accommodates on average 4 apoA-I molecules and has a clearance rate indistinguishable from LpAI:AII. Independent evidence indicated LpAI:A-II has a diameter 20% smaller than LpAI, consistent with a model having two apoA-I and one apoA-II. The functional contribution of these particles is to be investigated.

The Japan EPA Lipid Intervention Study (JELIS) reported a 19% reduction of the risk for coronary artery disease after long-term use of pure eicosapentaenoic acid (EPA) in Japanese patients with hypercholesterolemia. The variation in plasma fatty acid composition influenced the risk of coronary events. The aim of this study was to examine in JELIS participants the possible correlation of changes in plasma fatty acids with those of serum lipids. The coefficient for the correlation between the absolute change in plasma fatty acid concentrations and the changes in serum lipids was calculated in 13,901 JELIS participants. Low-density lipoprotein (LDL) cholesterol exhibited a positive correlation with docosahexaenoic acid (DHA; r=0.117 in control group, r=0.155 in EPA group) and linoleic acid (r=0.139 in control group, r=0.177 in EPA group), but the correlation coefficients with EPA (r=0.097 in control group, r=-0.032 in EPA group) were less than 0.1. We distributed the patients into 9 groups according to tertiles of the change in EPA and DHA. The average absolute decrease of LDL cholesterol and L/H ratio in each group was significantly smaller (p<0.001) in the DHA-high tertile, but not in any EPA tertile. The changes in DHA, but not in EPA, showed a positive correlation with the changes in LDL-cholesterol.

The present study examined the importance of reducing non-high-density lipoprotein cholesterol (non-HDL-C) for the primary prevention of the occurrence of coronary artery disease (CAD) in the JELIS, and the effects of EPA. The patients were distributed into 4 subgroups using the lipid management goal for LDL-C recommended by the Japan Atherosclerosis Society guideline (2007) and the goal for non-HDL-C defined as 30 mg/dL higher than LDL-C: A) achieved both goals; B) achieved the LDL-C but not non-HDL-C goal; C) achieved the non-HDL-C but not LDL-C goal; and D) did not attain either goal. The incidences of CAD in the 4 subgroups were compared, and the effects of eicosapentaenoic acid (EPA) on the risk of CAD in these subgroups were examined. In the non-EPA group, the incidence of CAD in patients who did not achieve the goals for LDL-C or non-HDL-C was higher than in patients who achieved those goals. Patients in subgroups B, C, and D were at higher risk for CAD than those in subgroup A (B, HR 2.31; C, HR 1.90; D, HR 2.47). EPA reduced the risk of CAD by 38% in subgroups B, C, and D (p= 0.007). We reconfirmed non-HDL-C as a predictor of the risk for CAD and a residual risk marker of CAD after LDL-C-lowering therapy. EPA was useful to reduce the occurrence of CAD in patients who did not achieve the goals for LDL-C and/or non-HDL-C.

The long-term event monitoring (LEM) study evaluated the lipid-lowering efficacy and safety of fluvastatin in Japanese patients with hypercholesterolemia. The present sub-analysis focused on the impact of risk factors on event prevention. In the LEM study, patients (n=21,139) who started fluvastatin between 2000/4/1 and 2002/3/31 in Japan were prospectively registered and followed up for 3 years (secondary prevention cohort) or 5 years (primary prevention cohort). Of the patients registered, 19,084 were included in this sub-analysis. The secondary prevention group, demonstrated 8.27- and 2.89-fold higher incidence in cardiac events and cerebral events, respectively compared with the primary prevention group (P < 0.001). Complications of cerebrovascular disease demonstrated a 2.22- and 5.29-fold higher incidence in cardiac events and cerebral events (P < 0.01 and P < 0.001, respectively). Presence of diabetes mellitus (DM) in patients without complication significantly increased the incidence in both cardiac events (2.37) and cerebral events (2.15) as compared with non-DM patients for primary prevention (P < 0.001 and P < 0.01, respectively). For the secondary prevention, DM patients with complication of cardiac disease showed a significantly higher incidence in both cardiac events (1.59) and cerebral events (3.79) compared with non-DM patients (P < 0.05 and P < 0.01, respectively). In contrast, DM patients with complications of cerebrovascular disease showed a significantly higher incidence in cerebral events (2.58, P < 0.05), but not cardiac events compared with non-DM patients. Similarly, the presence of hypertension significantly increased the incidence in both cardiac (1.64) and cerebral events (1.81) for primary prevention (P < 0.01 and P < 0.05, respectively). For secondary prevention, hypertension in patients with complication of cardiac or cerebrovascular disease did not affect incidence in both cardiac and cerebral events. In the patients without complication, high triglycerides and low high density lipoprotein cholesterol (HDL-C), but not low density lipoprotein cholesterol (LDL-C), increased cerebral events, while only LDL-C significantly increased cardiac events. For secondary prevention, high triglycerides or low HDL-C, but not LDL-C, significantly increased the relative risk of cardiac events in the patients with complication of cardiac disease. The LEM study, a large-scale prospective study of long-term fluvastatin treatment for hypercholesterolemia in Japanese patients, demonstrated high impact of complications such as DM and hypertension as well as high triglycerides or low HDL-C on cardiac and cerebral events. After long-term statin treatment, the control of other factors rather than LDL-C alone might be important to avoid vascular events.

Background/PurposeDiagnosis and management of the metabolic syndrome (MetS) are beneficial for successful aging. In spite of several criteria for MetS, there is little information on cardiometabolic risk clustering in elderly Japanese. The purpose of this study was, therefore, to determine the relationship between age-associated changes in obesity and metabolic components in the Japanese.