Proinflammatory status, genetics and atherosclerosis

Over the last decade, C-reactive protein concentration analyzed by the high sensitivity method (hsCRP) has been proven as a marker of premature atherosclerosis. Concentration exceeding 2 mg/l represents an increased individual risk of myocardial infarction and stroke but strict application of this borderline is complicated by relations of CRP concentrations to other risk factors of cardiovascular diseases. In a large 1 % representative sample of the Czech population, a positive relation of hsCRP to BMI, a waist circumference and triglyceride concentration was documented. Substantial sex differences were found in its relationship to age. Whereas it is continuously increasing in men, this increase appears in women only after menopause. A substantial decrease of body weight and visceral fat volume by increased physical activity is accompanied by significant decrease of hsCRP in young obese women. This decrease was not related to a change of interleukin-6 concentration, although it is supposed to regulate CRP production. CRP concentration is partly under genetic control as a higher concentration in young siblings of probands with proved coronary atherosclerosis was documented. The participation of genes related to lipoprotein metabolism (genes for apolipoprotein CI and apolipoprotein E) influence hsCRP concentrations. We hypothesized that an increased concentration of hsCRP represents a certain marker of proinflammatory status related to central obesity and triglyceride metabolism and it might be related to individual properties of monocytes in atherogenesis.

Prague hereditary hypercholesterolemic (PHHC) rat - a model of polygenic hypercholesterolemia

Prague hereditary hypercholesterolemic (PHHC) rat - rat strain crossbred from Wistar rats - is a model of hypercholesterolemia induced by dietary cholesterol. Importantly, no bile salts and/or antithyroid drugs need to be added to the diet together with cholesterol to induce hypercholesterolemia. PHHC rats have only modestly increased cholesterolemia when fed a standard chow and develop hypercholesterolemia exceeding 5 mmol/l on 2 % cholesterol diet. Most of the cholesterol in hypercholesterolemic PHHC rats is found in VLDL that become enriched with cholesterol (VLDL-C/VLDL-TG ratio > 1.0). Concurrently, both IDL and LDL concentrations rise without any increase in HDL. PHHC rats do not markedly differ from Wistar rats in the activities of enzymes involved in intravascular remodelation of lipoproteins (lipoprotein and hepatic lipases and lecithin:cholesterol acyltransferase), LDL catabolism, cholesterol turnover rate and absorption of dietary cholesterol. The feeding rats with cholesterol diet results in development of fatty liver in spite of suppression of cholesterol synthesis. However, even though cholesterolemia in PHHC rats is comparable to human hypercholesterolemia, the PHHC rats do not develop atherosclerosis even after 6 months on 2 % cholesterol diet. Importantly, the crossbreeding experiments documented that hypercholesterolemia of PHHC rats is polygenic. To identify the genes that may be involved in pathogenesis of hypercholesterolemia in this strain, the studies of microarray gene expression in the liver of PHHC rats are currently in progress.

Life style change and reverse cholesterol transport in obese women

HDL cholesterol resp. apolipoprotein A1 concentrations are tools to estimate individual CVD risk, although only a part of HDL particles participate in reverse cholesterol transport (RCT). This discrepancy was analyzed in life style change based on increase of physical activity and dietary counseling. Efflux of cholesterol from pre-labeled macrophages to plasma acceptors of tested individuals was used as an RCT measure. Changes of lipoprotein parameters, glucose, fasting insulin concentrations and RCT were analyzed in 15 obese women after 9-week intervention consisted of 5 sessions of increased physical activity per week. Controlled increase in physical activity for 9 weeks induced a decrease of body weight averaging 9 kg (ranged from 2.3 to 15.5 kg). The intervention leads to significant decreases of triglycerides, apoprotein A1 and apoprotein B concentration, whereas total cholesterol, LDL cholesterol and HDL cholesterol did not change significantly. The increase of RCT was not significant, but there was highly significant negative correlation between individual decrease of body weight and an increase of RCT. Significant increase of RCT was found in 13 persons with a weight reduction more than 3.5 kg. Substantial weight loss is necessary to increase RCT.

Why we are not able to find the coronary heart disease gene - apoE as an example

The apoprotein E gene ranks among the most discussed candidate genes for cardiovascular disease. We studied whether the association between apoprotein E gene polymorphism and manifestation of acute coronary syndrome is modulated by the presence/absence of traditional cardiovascular risk factors. The population under study were 1066 patients (men under 65 years) admitted between 2006- 2009 to five coronary care units in Prague (GENetic DEtermination of Myocardial Infarction in Prague) and the control population (1066 age-matched men selected from the Czech population sample). The frequency of disadvantage genotype E4+ was significantly higher (P < 0.01) in acute coronary syndrome patients (22.38 %) than in controls (16.76 %). When the acute coronary syndrome group was step by step limited to non-smokers, non-diabetics and normotensive individuals, the odds ratio displayed a gradual increase from 1.35 (for the entire group) through 1.48 (non-smokers), 1.53 (non-smokers+non-diabetics) to 1.71 (non-smokers+non-diabetics+normotensives). The effect of the apoprotein E gene on the individual risk of acute coronary syndrome is nonhomogenous within the patient groups. This association of apoprotein E gene with acute coronary syndrome is strongly modified by the presence/absence of traditional cardiovascular factors of atherosclerosis in a high-risk Czech population.

Antiatherogenic Effect of Simvastatin Is Not Due to Decrease of LDL Cholesterol in Ovariectomized Golden Syrian Hamster

The changes of the composition of blood lipoproteins caused by menopause could also change the effect of hypolipidemic therapy. Using an experimental model we studied the changes of serum lipids and the effect of immediate or delayed treatment with simvastatin on atherosclerosis after surgical menopause. Female golden Syrian hamster aged 6 months were fed hypercholesterolemic diet during the whole study. Atherosclerotic changes in thoracic and abdominal aortas were assessed by stereomicroscopic method after 12 weeks. Four experimental groups were studied: sham-operated animals (n=5), ovariectomized animals (n=9), ovariectomized animals treated for 12 weeks (n=10), and ovariectomized animals treated 4 weeks after ovariectomy for 8 weeks (n=9). The dose of simvastatin was 10 mg/kg of body weight. After 12 weeks, ovariectomized animals had tenfold higher concentration of triglycerides in LDL fraction and significantly higher prevalence of atherosclerosis than animals without ovariectomy. Treatment with simvastatin substantially decreased the prevalence of atherosclerotic changes, but otherwise did not change individual serum lipids including LDL cholesterol. However, it improved proportions of pro- and antiatherogenic serum lipids mainly by the increase of HDL cholesterol. The timing of simvastatin treatment had no significant effect on atherosclerotic changes or lipid parameters. Simvastatin treatment partly prevented atherosclerotic changes induced by ovariectomy. This effect was not mediated by decrease of LDL cholesterol, but by increase in HDL cholesterol.

May alcohol-induced increase of HDL be considered as atheroprotective?

It is well known that the consumption of moderate doses of alcohol leads to the increase of HDL-cholesterol (HDL-C). Atheroprotectivity of HDL particles is based primarily on their role in reverse cholesterol transport (RCT). In the study with a cross-over design 13 male volunteers were studied in two different regimens: i) drinking of 36 g alcohol daily and ii) drinking only non-alcoholic beverages, to test whether alcohol-induced increase of HDL cholesterol can affect cholesterol efflux (CHE) from cell culture of labeled human macrophages. Alcohol consumption induced significant (p < 0.05) increases of HDL cholesterol from 1.25 +/- 0.32 to 1.34 +/- 0.38 mmol/l and Apo A1 from 1.34 +/- 0.16 to 1.44 +/- 0.19 g/l. These changes were combined with a slight increase of cholesterol efflux from 13.8 +/- 2.15 to 14.9 +/- 1.85 % (p = 0.059). There were significant correlations between individual changes of HDL-C and Apo A1 concentrations and individual changes of CHE (0.51 and 0.60, respectively). In conclusion, moderate alcohol consumption changes the capacity of plasma to induce CHE only at a border line significance.

No relation between angiotensin‐converting enzyme gene polymorphism and smoking dependence

BACKGROUND

Smoking as a major risk factor for development of cancer and cardiovascular disease is thought to be partially genetically determined. The aim of this study was to investigate whether there is an association between insertion/deletion (I/D) polymorphism in angiotensin-converting enzyme (ACE) and smoking status and the number of cigarettes smoked per week.

METHODS

Using polymerase chain reaction, I/D polymorphism was evaluated in the ACE gene in 1204 male and 1375 female representative Caucasians. Information about smoking status and number of cigarettes smoked per week was collected via a questionnaire.

RESULTS

Frequencies of the alleles and genotypes of ACE I/D polymorphism did not differ between smokers, past smokers and individuals who had never smoked. No association was found between ACE I/D polymorphism and the number of cigarettes smoked per week, either in males or in females.

CONCLUSION

I/D polymorphism in the ACE gene does not play any role in genetic determination of predisposition to smoking.

Proinflammatory status, genetics and atherosclerosis

Over the last decade, C-reactive protein concentration analyzed by the high sensitivity method (hsCRP) has been proven as a marker of premature atherosclerosis. Concentration exceeding 2 mg/l represents an increased individual risk of myocardial infarction and stroke but strict application of this borderline is complicated by relations of CRP concentrations to other risk factors of cardiovascular diseases. In a large 1 % representative sample of the Czech population, a positive relation of hsCRP to BMI, a waist circumference and triglyceride concentration was documented. Substantial sex differences were found in its relationship to age. Whereas it is continuously increasing in men, this increase appears in women only after menopause. A substantial decrease of body weight and visceral fat volume by increased physical activity is accompanied by significant decrease of hsCRP in young obese women. This decrease was not related to a change of interleukin-6 concentration, although it is supposed to regulate CRP production. CRP concentration is partly under genetic control as a higher concentration in young siblings of probands with proved coronary atherosclerosis was documented. The participation of genes related to lipoprotein metabolism (genes for apolipoprotein CI and apolipoprotein E) influence hsCRP concentrations. We hypothesized that an increased concentration of hsCRP represents a certain marker of proinflammatory status related to central obesity and triglyceride metabolism and it might be related to individual properties of monocytes in atherogenesis.

Apolipoprotein E Arg136 --> Cys in individuals with premature myocardial infarction

Coronary artery disease is a serious health problem worldwide caused by interactions between genetic and environmental risk factors. One of the candidate genes is the gene for apolipoprotein E. We present a case report of two young smoking and obese carriers (man 45 years and woman 32 years old) of the apolipoprotein E (p.Arg136Cys) mutation, but with no severe dyslipidaemias detected among 1,671 survivors (1,483 men, 188 women, aged 21-75 years) of acute coronary syndrome screened for genetic and traditional cardiovascular risk factors. Between acute coronary syndrome survivors, the mutation has not yet been described. Even though this mutation raises suspicion to be a risk factor for cardiovascular disease (based on previous publications), its frequency was very low and similar to the control population (12 detected carriers of the mutation within the 9,386 screened individuals). Therefore, whether this rare mutation is causal for the development of myocardial infarction needs to be further evaluated.

Apolipoprotein A5 in health and disease

High plasma levels of triglycerides (TG) are an independent risk factor in the development of cardiovascular disease, with about 50 % of the final levels being determined genetically. Apolipoprotein A5 (APOA5) is the last discovered member of the apolipoprotein APOA1/C3/A4 gene cluster, found by comparative sequencing analysis. The importance of APOA5 gene for determination of plasma triglyceride levels has been suggested after development of transgenic and knock-out mice (transgenic mice displayed significantly reduced TG, whereas knock-out mice had high TG). In Czech population, alleles C-1131 and Trp19 are associated with elevated levels of plasma TG and higher risk of myocardial infarction development. These alleles also play some role in nutrigenetics and actigenetics of lifestyle interventions leading to the plasma cholesterol changes as well as in the pharmacogenetics of statin treatment. On the contrary, APOA5 mutations detected in Czech population did not show strict effect on plasma TG levels. Val153 → Met variant exhibit the sexspecific effect of HDL-cholesterol levels. The suggested roles of APOA5 variants in determination of the plasma remnant particles, plasma concentrations of C-reactive protein or some anthropometrical parameters were excluded.

Changes of plasma lipids during weight reduction in females depends on APOA5 variants

BACKGROUND

Apolipoprotein A5 (APOA5) is a determinant of plasma lipids, and its role in body mass index (BMI) determination is discussed. This study was aimed at the investigation of the relationship between common APOA5 gene variants and body weight/plasma lipid decrease in overweight females.

METHODS

We analyzed 98 unrelated overweight and obese nondiabetic Czech females (BMI >27.5). APOA5 T-1131-->C and Ser19-->Trp variants were genotyped. Before and after 9 weeks of lifestyle modification, biochemical and anthropometrical measurements and assessment of nutritional intake were performed. The lifestyle modification program consisted of a reduction in energy intake and an exercise program (aerobic exercise 4 times per week, 60 min each).

RESULTS

The mean age of the participants was 30.7 +/- 3.7 years, the mean BMI before the intervention was 31.4 +/- 3.8 and the weight loss was 5.9 +/- 2.5 kg (7 +/- 3%). There were 86 T-1131T homozygotes and 12 carriers of the C-1131 allele and 82 Ser19Ser homozygotes and 16 carriers of the Trp19 allele, respectively; 72 females had the commonest T-1131T/Ser19Ser haplotype. No significant association between BMI decrease and APOA5 variants was found, but T-1131T carriers have a significantly higher body weight both before and after the intervention (p < 0.05; p = not significant for BMI). The fasting glycemia was significantly higher in Trp19 carriers both before and after the intervention (p < 0.01). Further, plasma triglyceride levels decreased in Ser19Ser homozygotes but increased in Trp19 carriers (1.42 +/- 0.62 to 1.28 +/- 0.48 vs. 1.15 +/- 0.47 to 1.41 +/- 0.80 mmol/l; p < 0.05 for differences between the groups). Similarly, in carriers of at least 1 less common APOA5 allele (n = 26), plasma low-density lipoprotein cholesterol levels did not decrease as they did in T-1131T/Ser19Ser carriers (3.11 +/- 0.70 to 3.27 +/- 0.81 vs. 3.39 +/- 0.81 to 3.16 +/- 0.86 mmol/l; p < 0.05 for differences between the groups).

CONCLUSIONS

APOA5 gene variants have effects on the decrease in plasma triglyceride and low-density lipoprotein cholesterol level in females in a model combining their dietary habits and physical activity changes.

Replacement of dietary saturated FAs by PUFAs in diet and reverse cholesterol transport

Dietary intervention is the first and usually successful approach in the treatment of high LDL cholesterol (LDL-C) concentration, but it is frequently accompanied by a decrease in HDL concentration. We studied 14 male volunteers on two different diets, high saturated fatty acid (SFA) and high PUFA, in a crossover design to test whether a decrease in HDL can affect reverse cholesterol transport from relabeled macrophages. A significant decrease of LDL-C (in mmol/l) after a PUFA diet compared with an SFA diet from 3.15 +/- 0.65 to 2.80 +/- 0.56 (P < 0.01) was accompanied by a significant decrease of HDL cholesterol (HDL-C) (in mmol/l) from 1.21 +/- 0.30 to 1.10 +/- 0.32 (P < 0.05). These changes did not affect cholesterol efflux (CHE) from macrophages (9.74 +/- 1.46% vs. 9.53 +/- 1.41%). There was no correlation between individual changes of HDL-C and changes of CHE. It is concluded that the decrease of HDL-C after successful dietary intervention of LDL-C is not accompanied by a decrease of CHE.

Differences in expression of cholesterol 7alpha-hydroxylase between PHHC and Wistar rats

PHHC rats represent a suitable experimental model of polygenic hypercholesterolemia. It has been found that its metabolic defect is not related to alimentary cholesterol absorption and LDL clearance. We have tested possible changes in cholesterol clearance from the liver to bile acids by analysis of the expression of the cholesterol 7alpha-hydroxylase (cyp7A1) gene in PHHC (N = 20) and Wistar (controls) (N = 19) male rats. The animals were fed standard laboratory diet (CD) or control diet containing 5% fat and 2% cholesterol (HCD) for two weeks. SSCP and RT-PCR were used for mutation analysis and study of gene expression, respectively. Although the basal cholesterolemia in PHHC was similar to controls (1.80 +/- 0.48 and 1.52 +/- 0.39 mmol/l, respectively), it rose in rats fed on HCD to 9.81 +/- 1.65 mmol/l in PHHC rats and only to 2.19 +/- 0.41 mmol/l in controls. Similarly to the basal cholesterol concentration, the gene expression of cyp7A1 in the liver of rats on CD was the same in both compared groups on the control diet. In controls on HCD, cyp7A1 gene expression increased almost 4-fold immediately on the first day and achieved up to approximately 20-multiple basal expression in the end of the feeding period. Compared to the controls, after switching to HCD the cyp7A1 gene expression in PHHC rats did not change dramatically. These results suggest that the cyp7A1 gene plays an important role in development of hypercholesterolemia in PHHC rats.