Masaaki Eto

Reciprocal effects of apolipoprotein E alleles (ε2 AND ε4) on plasma lipid levels in normolipidemic subjects

A significantly lower frequency of the ε2 allele and a significantly higher frequency of the ε3 allele were found in the normolipidemic Japanese population than those in the normolipidemic Caucasian populations. We have compared plasma lipid variables among the apolipoprotein (apo) E phenotype groups and estimated the average effects of the three common alleles (ε2, ε3 and ε4) on plasma lipid levels in normolipidemic subjects. Plasma triglyceride (TG), very low density lipoprotein (VLDL)‐TG, VLDL‐cholesterol (C) and apo E levels were high in the apo E3/2 group, intermediate in the apo E3/3 group and low in the apo E4/3 group, whereas plasma total cholesterol (TC), low density lipoprotein (LDL)‐C and high density lipoprotein (HDL)‐C levels were low in the apo E3/2 group, intermediate in the apo E3/3 group and high in the apo E4/3 group. Furthermore, the ε2 allele had an effect to increase the TG, VLDL‐TG, VLDL‐C and apo E levels and decrease the TC, LDL‐C and HDL‐C levels, whereas the ε4 allele had an effect opposite to the el allele. These results indicate that the ε2 and ε4 alleles have the reciprocal effects on plasma lipid, lipoprotein and apo E levels.

A racial difference in apolipoprotein E allele frequencies between the Japanese and Caucasian populations

We have examined the apo E phenotype frequencies in the Japanese population (n = 576, 16–78 years of age). Apo E phenotypes were determined by the rapid flat gel isoelectric focusing method that we previously reported. The apo E phenotype frequencies in the Japanese were 0.3% for E2/2, 6.1% for E3/2, 71.9% for E3/3, 0.7% for E4/2, 19.3% for E4/3 and 1.7% for E4/4. The apo E allele frequencies were 0.037, 0.846 and 0.117 for the e2, e3 and e4 alleles, respectively. These frequencies were compared with those in the Caucasian populations (n = 3033) reported by Sing & Davignon (1985). There was a significant difference in the apo E phenotype frequencies between the Japanese and Caucasian populations. In addition, a significantly lower frequency of the e2 and e4 alleles and a significantly higher frequency of the e3 allele were found in the Japanese than those reported for the Caucasian populations. It is concluded that there is a racial difference in the apo E allele frequencies between the Japanese and Caucasian populations.

Increased frequencies of apolipoprotein ε2 and ε4 alleles in patients with ischemic heart disease

It has been demonstrated that the genetic polymorphism of apolipoprotein (apo) E is associated with atherosclerosis. Thus, in this study, we have examined the apo E allele frequencies in 109 patients with ischemic heart disease (IHD) and 576 Japanese people as controls, and we have compared these frequencies between patients with IHD and controls. The frequencies of the ε2 and ε4 alleles were significantly higher in patients with IHD than in the controls (ε2: 8.2% vs 3.7%, ε4: 17.0% vs 11.7%), whereas the frequency of the ε3 allele was significantly lower in patients with IHD than in the controls (74.8% vs 84.6%). The ε2‐carrying patients with IHD were characterized by type III (43.8%) and IV (25.0%) hyperlipoproteinemia (HLP), whereas the ε4‐carrying patients with IHD were characterized by hypercholesterolemia (type IIb HLP: 42.8%, type IIa HLP: 28.6%). It is concluded that both ε2 and ε4 alleles are more associated with IHD than the ε3 allele.

Familial hypercholesterolemia and apolipoprotein E4

The purpose of this study was to elucidate the relationship between two genetic factors associated with raised blood cholesterol, i.e. familial hypercholesterolemia (FH) and apolipoprotein (apo) E4. A group of 50 unrelated heterozygous FH patients aged 33-71 years were studied together with 129 normolipidemic subjects. A significantly higher frequency of apo E4 phenotypes was found in FH patients (30.0%) than in normolipidemic subjects (15.5%). FH patients were divided into two groups with and without apo E4. Plasma total cholesterol (Chol) and triglyceride (TG) levels were significantly higher, and plasma low density lipoprotein-cholesterol (LDL-Chol) level tended to be higher in FH patients with apo E4 than in those without apo E4. In addition, the prevalence of ischemic heart disease (IHD) was significantly higher in FH patients with apo E4 (73.3%) than in those without apo E4 (31.4%). No significant difference was noted in age and in the prevalence of obesity, diabetes, hypertension and smoking between the FH groups with and without apo E4. These results suggest that apo E4 is associated with higher levels of total Chol and TG and, at least in part, contributes to the predisposition to IHD in FH.

Increased frequency of apolipoprotein ε2 allele in non‐insulin dependent diabetic (NIDDM) patients with nephropathy

The genetic polymorphism of apolipoprotein E (ε2, ε3 and ε4) is associated with lipid abnormalities. It has been suggested that lipid abnormalities may contribute to the development and progression of kidney diseases, including diabetic nephropathy. Thus, in this study we compared the apo E allele frequencies among 146 non‐insulin‐dependent diabetic (NIDDM) patients with nephropathy, 135 NIDDM patients without nephropathy and 576 of the general Japanese population. The ε2 allele frequency was significantly higher in diabetic patients with nephropathy (7.2%) and with renal failure (9.7%) than in diabetic patients without nephropathy (2.6%) and in the general Japanese population (3.7%). It is concluded that there is a possibility that the ε2 allele is associated with nephropathy in NIDDM.

A rapid flat gel isoelectric focusing method for the determination of apolipoprotein E phenotypes and its application

A rapid flat gel isoelectric focusing method has been developed for the determination of apolipoprotein E phenotypes. Isoelectric focusing in 5% polyacrylamide flat gel with 8 mol/l urea and 2.8% pharmalyte (pH 4-6.5) was carried out at 3,000 V and 4 degrees C for 1 h under a constant power of 30 W. The separation of apolipoprotein E isoproteins was good and the isoelectric points were determined. Using this method, the apolipoprotein E phenotype frequency was examined in the Japanese population, and a higher frequency of phenotype E3/3 and a lower frequency of phenotype E3/2 were found in Japanese than those reported for the German, American or English population. In our focusing system the cut-off point of apolipoprotein E2/E3 ratio between the phenotype E3/3 and E3/2 was assumed to be approximately 0.9. These results indicate that this method may be useful for the determination of apolipoprotein E phenotypes.

Apolipoprotein E2, renal failure and lipid abnormalities in non-insulin-dependent diabetes mellitus

The association of apolipoprotein E (apo E) genetic polymorphism, particularly apo E2, with renal failure (plasma creatinine > or = 1.4 mg/dl, and urinary albumin excretion index > or = 300 mg/g.creatinine and/or persistent proteinuria) was investigated in 57 non-insulin-dependent diabetic (NIDDM) patients. Apo E2 allele frequency was significantly higher in diabetic patients with renal failure (9.6%) than in diabetic patients without renal failure (3.2%) and in the general Japanese population (3.7%). This finding suggests that apo E2 is associated with renal failure in NIDDM. In addition, to elucidate the association of apo E2 with lipid abnormalities, plasma lipid and lipoprotein levels were compared among the apo E2 (E2/2 and E3/2) and E3/3 groups of NIDDM with renal failure (n = 27) and the apo E2 (E3/2) and E3/3 groups of NIDDM with normoalbuminuria (n = 34). In diabetic patients, the apo E2 group with renal failure had significantly higher levels of plasma total cholesterol (T-chol), very-low-density lipoprotein (VLDL)-chol, triglyceride (TG), VLDL-TG and apo E than the apo E3/3 group with renal failure, and had significantly higher levels of plasma T-chol, VLDL-chol, TG and VLDL-TG than the apo E2 and E3/3 groups with normoalbuminuria. Furthermore, the apo E2 group with renal failure had significantly higher ratios of VLDL-(chol/TG) and VLDL-chol/TG (an index of remnants in plasma) than the apo E3/3 group with renal failure and the apo E2 and E3/3 groups with normoalbuminuria. These results suggest that apo E2 leads to the accumulation of TG-rich lipoprotein and remnants in plasma. It is concluded that apo E2 is associated with renal insufficiency in NIDDM and that apo E2 may be a factor that aggravates lipid abnormalities in NIDDM with renal failure.

Effects of probucol on plasma lipids and lipoproteins in familial hypercholesterolemic patients with and without apolipoprotein E4

It has been reported that total cholesterol (Chol) response to probucol is greater in familial hypercholesterolemic (FH) patients with apo E4 than in those without apo E4. We further examined the effect of probucol on plasma triglyceride (TG) and lipoprotein-Chol levels as well as total Chol levels in heterozygous FH patients with apo E4 (n = 14 for apo E4/3, n = 1 for apo E4/4) and without apo E4 (n = 31 for apo E3/3). Probucol was administered in a dosage of 500 mg twice daily for 3 months. The reduction in total Chol levels was significantly greater in FH patients with apo E4 (-90 mg/dl, -27.5%) than in those without apo E4 (-41 mg/dl, -13.7%). The reduction in low density lipoprotein (LDL)-Chol levels was also significantly greater in FH patients with apo E4 (-73 mg/dl vs. -34 mg/dl). There was a significant difference in the change in TG and very low density lipoprotein (VLDL)-Chol levels with treatment between the FH patients with apo E4 (-37 and -8 mg/dl, respectively) and without apo E4 (+8 and +2 mg/dl, respectively). However, there was no significant difference in the reduction in HDL-Chol levels between the 2 groups (-9 mg/dl vs. -9 mg/dl). It is concluded that FH patients with apo E4 showed the greater reduction in plasma TG levels as well as total Chol levels with probucol treatment than those without apo E4, and that the greater reduction in total Chol levels in them, as reported previously, was mainly due to the greater reduction in LDL-Chol levels and slightly due to that in VLDL-Chol levels.

Apolipoprotein E polymorphism and susceptibility to early- and late-onset sporadic Alzheimer's disease in Hokkaido, the northern part of Japan

Apolipoprotein E (ApoE) phenotypes and corresponding allele frequencies were examined in 72 patients (50-90 years of age) with sporadic Alzheimers disease (AD) and 83 elderly controls (61-96 years of age) in Hokkaido, the northern part of Japan. The frequency of the ApoE-epsilon 4 allele was significantly higher in the patients with either early-onset (age < 65 years) AD (0.40) or late-onset AD (0.26) than in controls (0.07), while the patients developing AD before 50 years of age had no epsilon 4 allele. The mean age at onset of AD was significantly lower in the ApoE-epsilon 4 homozygotes compared to that in the patients with either one or no epsilon 4 allele (60.2, 71.3 and 70.3 years, respectively). Our results indicate that the ApoE-epsilon 4 allele is associated with susceptibility to Japanese sporadic AD developing after 50 years of age and homozygosity for the epsilon 4 allele shifts the onset to earlier age.

Apolipoprotein E alleles and hyperlipoproteinemia in Japan

Genetic polymorphism of apolipoprotein (apo) E has been demonstrated to be associated with hyperlipoproteinemia (HLP). There are few reports on this association in Japan. Thus, in this study, we have examined the apo E allele frequencies in normolipidemia (n = 129), nonfamilial hypercholesterolemic (FH) type IIa HLP (n=40), non‐FH type IIb HLP (n = 35), type III HLP (n = 17), type IV HLP (n = 59), type V HLP (n = 19) and heterozygous FH (n = 51) in Japan, and compared these frequencies between normolipidemia, and different types of HLP and FH. The frequency of the 4 allele was significantly higher in type IIa (18.7%), IIb (21.4%) and V (29.0%) HLP and FH (16.6%) than in normolipidemia (8.9%), whereas the frequency of the σ2 allele was significantly higher in type III (70.6%) and IV (11.0%) HLP than in normolipidemia (3.1%). These results indicate that the σ4 allele is associated with non‐FH hypercholesterolemia (type IIa and IIb HLP), type V HLP and FH, whereas the ɛ2 allele is associated not only with type III HLP but also with type IV HLP.