Apolipoprotein E genotype and cholesterogenesis in polygenic hypercholesterolemia

Apolipoprotein E polymorphism and changes in serum lipids during a family-based counselling intervention

OBJECTIVE

To compare serum lipids and their changes during a family-based health education in children aged 6-17 years with or without the epsilon4 allele of the gene encoding apolipoprotein E (apoE).

DESIGN

An intervention study.

SETTING

A family-based prevention of risk factors of coronary heart disease in Eastern Finland. The programme consisted of two counselling meetings at children's schools and three at children's homes.

SUBJECTS

Four hundred and thirty-nine children with a family history of cardiovascular diseases (CVD) participated in a family-based health education. The children were divided into two groups according to apoE genotype. The risk group consisted of 143 children having apoE epsilon4 allele (genotype epsilon3/4 or epsilon4/4) and the non-risk group of 296 children without apoE epsilon4 allele (epsilon2/3 or epsilon3/3). The final sample of the follow-up study included 354 (81%) children (114 and 240, respectively).

RESULTS

Baseline differences were found in low-density lipoprotein cholesterol (LDL-C) (P=0.007) and LDL-C/high-density lipoprotein cholesterol (HDL-C) ratio (P=0.030) among boys and in total cholesterol (TC)/HDL-C (P=0.008) and LDL-C/HDL-C ratios (P=0.006) among girls. Differences between groups in changes during the follow-up were observed only for TC/HDL-C ratio (P-value adjusted for age=0.049) among boys.

CONCLUSIONS

At baseline, children with apoE epsilon4 allele had on average a more unfavourable lipid profile than those without apoE epsilon4 allele. However, the effect of about 33 months' family-based health education on plasma lipids did not depend on apoE genotype in children with a family history of CVD.

Microcrystalline Chitosan is Ineffective to Decrease Plasma Lipids in both Apolipoprotein E epsilon4 Carriers and Non-Carriers: A Long-Term Placebo-Controlled Trial in Hypercholesterolaemic Volunteers

Chitosan is a deacetylated product of chitin. Microcrystalline form of chitosan has a large adsorption area claimed to decrease gastrointestinal absorption of cholesterol. However, the long-term effect of chitosan on plasma lipids is variable, the averaged influence being negligible or lacking in mildly-to-moderately hypercholesterolaemic (4.8-6.8 mmol/l) subjects. We evaluated whether this variation and inefficacy depend on apolipoprotein E genotype. 130 middle-aged, otherwise healthy men (n=55) and women (n=75) were randomized into two treatment groups for a 7 month trial. During a 1 month run-in period all participants received placebo. Subsequently, one half first took placebo twice daily for 3 months and then 1.2 g chitosan twice daily for 3 months, and the other half vice versa in a cross-over way. Altogether 84 participants completed the study. Plasma lipids and glucose were determined at the end of each phase of the study, and all subjects undergone to the cross-over phases were apolipoprotein E genotyped. Chitosan altered plasma total, low- and high density cholesterol, triglycerides, and blood glucose in neither apolipoprotein E epsilon 4 allele carriers (n=29) nor non-carriers (n=55), compared to placebo. In conclusions, chitosan is ineffective to decrease plasma lipids in apolipoprotein E epsilon 4 carrier and non-carrier phenotypes with mildly-to-moderately increased plasma cholesterol.

Urinary excretion and serum concentration of mevalonic acid during acute intake of alcohol

The influence of 2 different alcoholic beverages containing an equal amount of alcohol (48 g), 1 with mevalonic acid (beer) and 1 without (vodka), on the urinary excretion and serum concentration of mevalonic acid was investigated in 7 healthy subjects. Drinking 1 L of beer at night containing 608 microg/L mevalonic acid more than doubled the urinary excretion of mevalonic acid the following 12 hours, on average from 103 +/- 15 microg/12 h to 211 +/- 17 microg/12 h (P < .001; 18% of the administered dose). Drinking the same amount of alcohol as vodka had no effect, but urinary mevalonic acid output increased slightly the following day (7 AM to 7 PM) after ingestion of both alcoholic beverages. Serum concentrations of mevalonic acid were significantly increased the following morning after ingestion of beer (from 3.22 +/- 0.20 ng/mL to 6.79 +/- 0.58 ng/mL) or vodka (from 3.23 +/- 0.37 ng/mL to 5.36 +/- 0.55 ng/mL, P < .002 for both). An increase in the ratio of lathosterol to cholesterol in serum, another indicator of 3beta-hydroxy-3beta-methylglutaryl coenzyme A reductase activity in the liver, was also observed (+18% and +25%, respectively). After oral administration of [13C2] mevalonic acid at night, 20% +/- 0.7% of the dose was excreted in urine the following 12 hours, and only trace amounts thereafter. No [13C2] mevalonic acid could be detected in serum the following morning. We conclude that the absorption of dietary mevalonic acid and alcohol-induced mevalonic acid synthesis affects the urinary excretion and serum concentration of this cholesterol precursor. Therefore, studies using mevalonic acid as a marker of cholesterol synthesis must be carefully monitored regarding dietary mevalonic acid intake and alcohol consumption.

Low levels of serum cholesterol and systolic blood pressure in Japanese with the apolipoprotein E3/2 genotype

Apolipoprotein E (apoE) plays an important role in lipoprotein and cholesterol metabolism. An association between serum cholesterol and blood pressure has been suggested by epidemiological and experimental studies. But it is still not clear whether the apoE polymorphism plays a role in regulating blood pressure. The present study was undertaken to determine the association among apoE genotype, serum cholesterol and blood pressure in 303 healthy Japanese workers. Amplified fragments of DNA by the polymerase chain reaction were digested with HhaI and analyzed by 3% agarose-gel electrophoresis. Individuals with the apoE3/2 genotype had significantly lower levels of total cholesterol and systolic blood pressure than either the apoE3/3 individuals or the apoE3/4 + 4/4 individuals (P <0.05). The hypothesis that apoE indirectly influences systolic blood pressure through total serum cholesterol was supported by a covariance analysis of linear structural equations.