Rapid and safe determination of human apolipoprotein E genotypes by miniaturised SDS-PAGE in non-insulin dependent diabetes mellitus

Expression of the human apoE2 isoform in adipocytes: altered cellular processing and impaired adipocyte lipogenesis

Expression of apoE in adipocytes has been shown to have an important role in modulating adipocyte triglyceride (TG) metabolism and gene expression that is independent of circulating and extracellular apoE. The impact of adipocyte expression of common human apoE isoforms was evaluated using adipocytes harvested from human apoE2, -3, and -4 knock-in mice. Expression of the apoE2 isoform was associated with an increase in adipocyte apoE gene expression and apoE synthesis. Newly synthesized apoE2 was unstable in adipocytes and demonstrated increased degradation and decreased secretion. ApoE2-expressing mice were hyperlipidemic, and had increased size of gonadal fat pads and of adipocytes, compared with apoE3 mice. In isolated cells, however, expression of the apoE2 isoform produced defective lipogenesis and increased TG hydrolysis. Incubation of adipose tissue with apoE3-containing TG-rich lipoproteins resulted in a significant increase in TG in adipose tissue from apoE3 and -E4 mice, but not apoE2 mice. Reduced capacity to internalize FFA as lipogenic substrate contributed to defective lipogenesis. Newly synthesized apoE2 is unstable in adipocytes and results in decreased adipocyte TG synthesis and defective FA uptake. These changes recapitulate those observed in apoE knockout adipocytes and have implications for understanding metabolic disturbances in humans expressing the E2 isoform.

Apolipoprotein E allele distribution in trisomy 13, 18, and 21 conceptuses in a Hungarian population

Reports documented a higher frequency of apolipoprotein E (apoE) allele epsilon 4 among mothers of children diagnosed with Down syndrome. We studied the prevalence of apoE alleles among 56 conceptuses with trisomy 13, trisomy 18, or trisomy 21. The presence of the 3 most common apoE alleles (epsilon 2, epsilon 3, epsilon 4) was determined by polymerase chain reaction-restriction fragment length polymorphism, and trisomy status was detected by fluorescent polymerase chain reaction followed by DNA fragment analysis and by conventional cytologic methods. We found no significant difference in the distribution of apoE alleles in the group of trisomy 21 fetuses compared with samples from healthy blood donors. The odds of having trisomy 18 for the apoE epsilon 4 group was 3-fold as high as for apoE epsilon 3 allele compared with the healthy control group. Furthermore, a statistically significant association was found for those with trisomy 18 and apoE epsilon 4, while for those with trisomy 13 and apoE epsilon 4, the test showed no significant association. The observed apoE allele epsilon 3 frequencies among patients with Down syndrome and healthy control subjects may help explain and support previous work that did not find high rates of atherosclerosis among these persons. The role of apoE alleles in the development of trisomies needs further study.

Relationship between altered postprandial lipemia and insulin resistance in normolipidemic and normoglucose tolerant obese patients

OBJECTIVE

Although there are changes in the postprandial lipid responses of obese patients, these are closely associated with high fasting triglycerides (TG). This study of 17 normotriglyceridemic, normoglucose-tolerant android obese subjects (body mass index, BMI = 34.3 +/- 3.1 kg/m2) and 33 normal-weight controls (BMI = 21.8 +/- 1.6 kg/m2) was done to examine their postprandial responses to an oral fat loading test containing retinol (890 calories, 85% fat) and to evaluate the possible association between clinical and biological features of obesity and/or insulin resistance and postprandial lipemia.

SUBJECTS AND MEASUREMENTS

Blood samples were taken before giving the fat load and at 2,3,4,5,6 and 8 h after it. Insulin sensitivity was assessed using HOMA, and TG and retinyl palmitate (RP) in the plasma, chylomicrons and non-chylomicron fractions were measured each time.

RESULTS

The areas under the curves (AUC) of chylomicron TG for the obese and controls were not different, indicating adequate lipolytic activity. By contrast, the AUC for non-chylomicron TG was significantly greater in the obese than in the controls (512 +/- 135 vs 429 +/- 141 mmol/lmin, P < 0.01). In addition, the AUC for RP in this same fraction was significantly lower in the obese than in the controls (103 +/- 55 vs 157 +/- 88 mg/l min, P < 0.05), suggesting that the TG from endogenous lipoproteins accounted for most of the increase in TG in the non chylomicron fraction. Parameters related to obesity showed no relationship with these postprandial abnormalities, whereas HOMA, which discriminated between the groups, partly explained (r2= 23%, P < 0.01) the significant increase in non-chylomicron TG.

CONCLUSIONS

Android obese patients with a fasting TG in the normal range and not different from the fasting TG of lean controls had an abnormal postprandial lipemia response, indicated by a significantly greater TG in the non-chylomicron subfraction than in controls. These alterations may be partly due to postprandial changes in endogenous lipoproteins as a consequence of insulin resistance.

Apolipoprotein E gene polymorphism frequencies in a sample of healthy Hungarians

Apolipoprotein E (apo E) has been found to play an important role in lipid metabolism and has been associated with cardiovascular and neurodegenerative conditions. Hungarians have some of the highest rates of cardiovascular morbidity and mortality in the world. This study examines the distribution of apo E alleles and genotypes in a population of healthy ethnic Hungarian blood donors (n = 302). Male (n = 152) and female (n = 150) subjects ranging from 18 to 62 years of age (mean 37.0) were involved. To determine the frequency of apo E alleles, polymerase chain reaction followed by restriction length polymorphism was applied. The analyses of data showed that apo E allele epsilon3 had the greatest frequency in this group (0.807), followed by apo epsilon2 (0.104) and apo epsilon4 (0.087). The highest genotype frequency was found to be epsilon3/3 at 65.2% (n = 197) followed by genotype epsilon3/4 at 15.9% (n = 48), genotype epsilon2/3 at 15.2% (n = 46), genotype epsilon2/2 at 2.3% (n = 7), genotype epsilon2/4 at 1.0% (n = 3) and genotype epsilon4/4 at 0.4% (n = 1). The apo E frequencies found in this study appear to differ from an earlier study of blood donors, where the results are based on apo E phenotyping.

Apolipoprotein E alleles in women with severe pre-eclampsia

This study investigated the frequency of apolipoprotein E (apoE) alleles among women with severe pre-eclampsia. The presence of the three most common apoE alleles (epsilon 2, epsilon 3, epsilon 4) was determined by polymerase chain reaction-restriction fragment length polymorphism in three groups of white women: non-pregnant healthy (n = 101), pregnant healthy (n = 52), and pregnant with a diagnosis of severe pre-eclampsia (n = 54). The frequency of apo epsilon 2 was highest among women with severe pre-eclampsia (16.6%) followed by non-pregnant women (12.9%), and those experiencing a healthy pregnancy (10.6%). The higher frequency of the apo epsilon 2 allele detected among women with severe pre-eclampsia suggests that apoE may play a role in the development of pre-eclampsia.