Kaneo Ishii

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.

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.

Apolipoprotein E polymorphism and hyperlipemia in type II diabetics.

The relationship between apolipoprotein E (apoE) polymorphism and plasma lipids and hyperlipemia was investigated in 105 male type II diabetics and 111 male nondiabetics. ApoE phenotypes were determined by a one-dimensional rapid flat gel isoelectric focusing method as described previously. The apoE phenotype frequency in diabetics was similar to that in nondiabetics. The frequency of hyperlipemia was higher in diabetics (56.2%) than in nondiabetics (32.4%). It was highest in the apoE3/2 group of diabetics and nondiabetics, followed by the apoE4/3 and apoE3/3 groups in the order described, indicating that the susceptibility to hyperlipemia differs among the apoE phenotype groups. ApoE3/2 diabetics had significantly higher levels of apoE and very-low-density lipoprotein (VLDL) cholesterol (chol)/VLDL triglyceride (TG) ratios than apoE3/3 diabetics. The effects of diabetes mellitus on plasma lipid levels differed among the various apoE phenotype groups: i.e., plasma total chol and low-density lipoprotein (LDL) chol increased only in apoE3/2 and apoE4/3 diabetics and plasma high-density lipoprotein chol decreased only in apoE3/3 diabetics, as compared with the corresponding apoE phenotype groups of nondiabetics, whereas plasma TG, VLDL TG, and VLDL chol increased in the three apoE phenotype diabetics. Furthermore, an increase of apoEII; apoEIII ratio was observed in apoE3/3 diabetics, particularly in those with hypertriglyceridemia. This study has also shown that the increased apoEII: apoEIII ratio is due to increased sialation of apoE based on the study of sialidase digestion of apo VLDL. We conclude that apoE polymorphism should be taken into consideration when plasma lipoprotein patterns are studied in type II diabetics and that increased sialation of apoE may at least partly contribute to an increased frequency of hypertriglyceridemia in type II diabetics.

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.

Increased frequency of apolipoprotein epsilon 4 allele in type II diabetes with hypercholesterolemia.

The apolipoprotein E (apoE) phenotype and allele frequencies were examined in type II (non-insulindependent) diabetic patients with normolipidemia (n = 134) and hypercholesterolemia (type IIa hyperlipoproteinemia, n = 35; type lib hyperlipoproteinemia, n = 42). The frequencies of apoE4-present phenotypes (apoE4/3, apoE4/4, and apoE4/2) were highest in the type IIa group (51.4%), followed by the type Mb group (38.1%) and the normolipidemic group (16.4%), respectively, whereas the frequency of the most common phenotype, apoE3/3, was lowest in the type IIa group (48.6%), followed by the type lib group (61.9%) and the normolipidemic group (79.9%), respectively. There were significant differences in the apoE phenotype frequencies between the normolipidemic group and the type IIa and Mb groups. The frequency of the ∈4 allele was significantly higher in the type IIa (28.6%) and Mb (20.2%) groups than in the normolipidemic group (8.9%), whereas the frequency of the ∈3 allele was significantly lower in the type IIa (71.4%) and Mb (78.6%) groups than in the normolipidemic group (89.2%). The frequency of the ∈2 allele tended to be lower in diabetic patients with hypercholesterolemia. In addition, these frequencies were also examined in nondiabetic subjects (n = 59). The frequency of the ∈4 allele tended to be higher in hypercholesterolemic diabetic subjects (24.1%) than in hypercholesterolemicnondiabetic subjects (15.3%). These data suggest that diabetic patients with the ∈4 allele may be more susceptible to hypercholesterolemia than diabetic patients without the ∈4 allele and possibly nondiabetic subjects with the ∈4 allele, although the underlying mechanism is unknown.

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.

Apolipoprotein E allele frequencies in non-insulin-dependent diabetes mellitus with hypertriglyceridemia (type IIb, III, IV, and V hyperlipoproteinemia)☆

We examined apolipoprotein E (apo E) allele frequencies in non-insulin-dependent diabetes mellitus (NIDDM) patients with normolipidemia or various types of hypertriglyceridemia to elucidate the association of the apo E alleles with hypertriglyceridemia in NIDDM. NIDDM patients with normolipidemia (N = 134) or hypertriglyceridemia [type IIb hyperlipoproteinemia (HLP) (N = 42), III HLP (N = 7), IV HLP (N = 96), and V HLP (N = 8)] were randomly selected from our Diabetic Clinics. Apo E phenotypes (genotypes) were determined by our rapid flat-gel isoelectric focusing method. The frequency of the epsilon 4 allele was significantly higher in the type IIb (20.2%, P less than .01) and V (25.0%, P less than .05) HLP patients than in the normolipidemic patients (8.9%), whereas the frequency of the epsilon 3 allele was significantly (P less than .025) lower in the type IIb HLP patients (78.6%) than in the normolipidemic patients (89.2%). The frequency of the epsilon 2 allele was significantly higher in the type III (64.3%, P less than .001) and IV (5.2%, P less than .05) HLP patients than in the normolipidemic patients (1.9%), whereas the frequency of the epsilon 3 allele was significantly lower in the type III (28.6%, P less than .001) and IV (82.8%, P less than .05) HLP patients than in the normolipidemic patients. Thus, it has proven that the epsilon 2 allele is related to type III and IV HLP in NIDDM, whereas the epsilon 4 allele is related to type IIb and V HLP in NIDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolic and morphological changes of the heart in Chinese hamsters (CHAD strain) with spontaneous long-term diabetes

We studied the effect of spontaneous long-term (9-10 months) diabetes on the heart of Chinese hamsters (CHAD strain) to elucidate the relationship between diabetes mellitus and cardiomyopathy. The diabetic hamsters, aged approximately 11 months, showed body weight loss, hyperglycemia (mean fasting plasma glucose 402 mg/dl), hypoinsulinemia, hyperlipidemia and ketonemia. The diabetic hamsters showed reduced activities of cytoplasmic glycolytic key enzymes; hexokinase, pyruvate kinase and phosphofructokinase, increases in cardiac glycogen and glucose-6-phosphate contents and a 40% decrease in cardiac ATP content, indicating decreased energy production. An accumulation of myocardial triglyceride and cholesterol was found in the diabetic hamsters. In addition, the cardiac norepinephrine content was increased in the diabetic hamsters, suggesting the presence of autonomic nervous disorder. Increased heart weight and thickening of the septum and both ventricular walls were found in the diabetic hamsters. Light-microscopic analysis revealed that 42.9% of the diabetic hamsters had myocardial degeneration without any vascular lesion of extramural large and intramural small vessels, whereas the non-diabetic controls had no myocardial or vascular lesions. These data suggest that the diabetic Chinese hamsters had cardiomyopathy, which is possibly caused by extravascular factors such as metabolic or autonomic nervous disorder although conclusive evidence is lacking.

Insulin and glucagon response of the diabetic Chinese hamster in the Asahikawa colony

The relationship between pancreatic hormone content and pattern of hormone release has not been completely elucidated because of heterogeneity in diabetes. Accordingly, this study was performed to establish the relationship, using spontaneously diabetic Chinese hamsters in the Asahikawa colony, a newly discovered experimental model resembling insulin-deficient diabetes in humans. As a result of investigations of insulin and glucagon responses to glucose or arginine in vivo and in vitro using isolated islets obtained by the collagenase procedure, a decreased insulin response and paradoxical glucagon response to glucose, and an excessive glucagon response to arginine were found in the diabetic animals. While the yield of isolated islets tended to decrease, a decreased pancreatic insulin content and increased pancreatic glucagon content were found as the diabetic state advanced. It may be suggested, therefore, that the relationship between pancreatic hormone content and pattern of hormone release in diabetic animals in the Asahikawa colony is based on the disruption of islets, disruption or dysfunction of B-cells and hyperplasia or hypertrophy of A-cells by some cause genetically determined.