Hypertension after the Menopause: What Can We Learn from Experimental Studies?

Hypertension is the most prevalent cardiovascular disease of the adult population and is closely associated with serious cardiovascular events. The burden of hypertension with respect to vascular and other organ damage is greater in women. These sex differences are not fully understood. The unique feature in women is their transition to menopause accompanied by profound hormonal changes that affect the vasculature that are also associated with changes of blood pressure. Results from studies of hormone replacement therapy and its effects on the cardiovascular system are controversial, and the timing of treatment after menopause seems to be important. Therefore, revealing potential sex- and sex hormone-dependent pathophysiological mechanisms of hypertension in experimental studies could provide valuable information for better treatment of hypertension and vascular impairment, especially in postmenopausal women. The experimental rat models subjected to ovariectomy mimicking menopause could be useful tools for studying the mechanisms of blood pressure regulation after menopause and during subsequent therapy.

Acute responses of hepatic fat content to consuming fat, glucose and fructose alone and in combination in non-obese non-diabetic individuals with non-alcoholic fatty liver disease.

We have recently demonstrated that a high-fat load can induce immediate increase in hepatic fat content (HFC) and that such an effect can be modified differently by co-administration of fructose or glucose in healthy subjects. Therefore, we addressed the question how consumption of these nutrients affects changes in HFC in subjects with non-alcoholic fatty liver disease (NAFLD). Eight male non-obese non-diabetic patients with NAFLD underwent 6 experiments each lasting 8 hours: 1. fasting, 2. high-fat load (150 g of fat (dairy cream) at time 0), 3. glucose (three doses of 50 g at 0, 2, and 4 hours), 4. high-fat load with three doses of 50 g of glucose, 5. fructose (three doses of 50 g at 0, 2, and 4 hours), 6. high-fat load with three doses of 50 g of fructose. HFC was measured using magnetic resonance spectroscopy prior to meal administration and 3 and 6 hours later. Plasma triglycerides, non-esterified fatty acids, glucose and insulin were monitored throughout each experiment. HFC increased by 10.4 ± 6.9% six hours after a high-fat load and by 15.2 ± 12.5% after high-fat load with fructose. When co-administering glucose with fat, HFC rose only transiently to return to baseline at 6 hours. Importantly, NAFLD subjects accumulated almost five times more fat in their livers than healthy subjects with normal HFC. Consumption of a high-fat load results in fat accumulation in the liver of NAFLD patients. Fat accumulation after a fat load is diminished by glucose but not fructose co-administration.

The role of connexin 37 polymorphism in spontaneous abortion.

Among unique cardiovascular risk factors in women are complications during pregnancy, including miscarriage. Important risk factor is also genetic background. One of powerful candidate genes for cardiovascular disease of atherosclerotic origin (aCVD) is gene for connexin 37 (Cx37) with strong gene-environment interaction including smoking status, that is also strong risk factor for complications in pregnancy including spontaneous abortion (SA). We analyzed association between SA and Cx37 gene polymorphism (1019C>T; Pro319Ser) in 547 fetuses and its potential interaction with smoking status of mothers. Using genetic analyses from women from general population as controls, ORs for T allele, found in our previous studies to be protective against aCVD, were calculated. T allele carriers (fetuses), had OR 0.91 (95 % CI 0.72-1.14) and no interaction with smoking was observed. In conclusion, no significant association between Cx37 polymorphism and SA was observed and no modifying effect of smoking status on this association was detected.

Intraventricular placement of a spring expander does not attenuate cardiac atrophy of the healthy heart induced by unloading via heterotopic heart transplantation.

An important complication of the prolonged left ventricle assist device support in patients with heart failure is unloading-induced cardiac atrophy which proved resistant to various treatments. Heterotopic heart transplantation (HTx) is the usual experimental model to study this process. We showed previously that implantation of the newly designed intraventricular spring expander can attenuate the atrophy when examined after HTx in the failing heart (derived from animals with established heart failure). The present study aimed to examine if enhanced isovolumic loading achieved by implantation of the expander would attenuate cardiac post-HTx atrophy also in the healthy heart. Cardiac atrophy was assessed as the ratio of the transplanted-to-native heart weight (HW) and its degree was determined on days 7, 14, 21 and 28 after HTx. The transplantation resulted in 32±3, 46±2, 48±3 and 46±3 % HW loss when measured at the four time points; implantation of the expander had no significant effect on these decreases. We conclude that enhanced isovolumic loading achieved by intraventricular implantation of the expander does not attenuate the development of cardiac atrophy after HTx in the healthy heart. This indicates that such an approach does not represent a useful therapeutic measure to attenuate the development of unloading-induced cardiac atrophy.

Glucose added to a fat load suppresses the postprandial triglyceridemia response in carriers of the -1131C and 56G variants of the APOA5 gene.

Apolipoprotein A-V plays an important role in the determination of plasma triglyceride (TG) concentration. We aimed to determine whether polymorphisms -1131T>C (rs662799) and 56C>G (rs3135506) of the APOA5 gene have an impact on the course of postprandial lipemia induced by a fat load and a fat load with added glucose. Thirty healthy male volunteers, seven heterozygous for the -1131C variant and three for the 56G variant (HT) carriers, and 20 wild-type (WT) carriers underwent two 8-hour tests of postprandial lipemia - one after an experimental breakfast consisting of 75 g of fat and second after a breakfast consisting of 75 g of fat and 25 g of glucose. HT carriers had a higher postprandial response after fat load than WT carriers (AUC TG: 14.01+/-4.27 vs. 9.84+/-3.32 mmol*h/l, respectively, p=0.016). Glucose added to the test meal suppressed such a difference. Heterozygous carriers of the variants of APOA5 (-1131C and 56G) display more pronounced postprandial lipemia after pure fat load than WT carriers. This statistically significant difference disappears when glucose is added to a fat load, suggesting that meal composition modulates the effect of these polymorphisms on the magnitude of postprandial lipemia.

Lost in menopausal transition: the timing of atherosclerosis prevention in women.

Advanced atherosclerotic changes can often resist even to very aggressive treatment. Although basic mechanisms of its origin and development are known, some important steps in this process are still waiting for more detailed explanation. Therefore, in addition to already proved aggressive lowering of LDL cholesterol, appropriate timing of atherosclerosis treatment is of the essence. Revealing different stages of atherosclerotic process, less or more sensitive to treatment is of primary importance; however, its detection is complicated by several facts including not exactly identifiable periods of quiescence and progression of atherosclerotic process. One of populations, study of which could add valuable information regarding this problem, are women in menopausal transition. Previously unsuccessful therapy with hormone replacement therapy is restudied with focus on the time of/after menopause. Now, it is supposed to be favorable in women soon, approximately less than 8 years, after menopause. In addition, the same principle - optimal timing of the intervention of traditional cardiovascular risk factors, especially lipids, could be also of importance. Therefore, menopausal transition could be optimal period for the intervention in women at risk. However, this approach is to be proved by evidence from controlled prospective studies focused on lifestyle and/or pharmacological intervention.

Traditional risk factors of acute coronary syndrome in four different male populations - total cholesterol value does not seem to be relevant risk factor.

Cardiovascular diseases are the most common cause of mortality and morbidity in most populations. As the traditional modifiable risk factors (smoking, hypertension, dyslipidemia, diabetes mellitus, and obesity) were defined decades ago, we decided to analyze recent data in patients who survived acute coronary syndrome (ACS). The Czech part of the study included data from 999 males, and compared them with the post-MONICA study (1,259 males, representing general population). The Lithuanian study included 479 male patients and 456 age-matched controls. The Kazakhstan part included 232 patients and 413 controls. In two countries, the most robust ACS risk factor was smoking (OR 3.85 in the Czech study and 5.76 in the Lithuanian study), followed by diabetes (OR 2.26 and 2.07) and hypertension (moderate risk elevation with OR 1.43 and 1.49). These factors did not influence the ACS risk in Kazakhstan. BMI had no significant effect on ACS and plasma cholesterol was surprisingly significantly lower (P<0.001) in patients than in controls in all countries (4.80+/-1.11 vs. 5.76+/-1.06 mmol/l in Czechs; 5.32+/-1.32 vs. 5.71+/-1.08 mmol/l in Lithuanians; 4.88+/-1.05 vs. 5.38+/-1.13 mmol/l in Kazakhs/Russians). Results from our study indicate substantial heterogeneity regarding major CVD risk factors in different populations with the exception of plasma total cholesterol which was inversely associated with ACS risk in all involved groups. These data reflect ethnical and geographical differences as well as changing pattern of cardiovascular risk profiles.

Circulating microparticles as a predictor of vascular properties in patients on mechanical circulatory support; hype or hope?

Microparticles are small circulating vesicles originating from circulatory system and vascular wall cells released during their activation or damage. They possess different roles in regulation of endothelial function, inflammation, thrombosis, angiogenesis, and in general, cellular stress. Microparticles are the subject of intensive research in pulmonary hypertension, atherosclerotic disease, and heart failure. Another recently emerging role is the evaluation of the status of vasculature in end-stage heart failure patients treated with implantable ventricular assist devices. In patients implanted as destination therapy, assessment of the long-term effect of currently used continuous-flow left ventricular assist devices (LVADs) on vasculature might be of critical importance. However, unique continuous flow pattern generated by LVADs makes it difficult to assess reliably the vascular function with most currently used methods, based mainly on ultrasound detection of changes of arterial dilatation during pulsatile flow. In this respect, the measurement of circulating microparticles as a marker of vascular status may help to elucidate both short- and long-term effects of LVADs on the vascular system. Because data regarding this topic are very limited, this review is focused on the advantages and caveats of the circulating microparticles as markers of vascular function in patients on continuous-flow LVADs.

Titin antibodies in "seronegative" myasthenia gravis--A new role for an old antigen.

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies targeting the neuromuscular junction of skeletal muscles. Triple-seronegative MG (tSN-MG, without detectable AChR, MuSK and LRP4 antibodies), which accounts for ~10% of MG patients, presents a serious gap in MG diagnosis and complicates differential diagnosis of similar disorders. Several AChR antibody positive patients (AChR-MG) also have antibodies against titin, usually detected by ELISA. We have developed a very sensitive radioimmunoprecipitation assay (RIPA) for titin antibodies, by which many previously negative samples were found positive, including several from tSN-MG patients. The validity of the RIPA results was confirmed by western blots. Using this RIPA we screened 667 MG sera from 13 countries; as expected, AChR-MG patients had the highest frequency of titin antibodies (40.9%), while MuSK-MG and LRP4-MG patients were positive in 14.6% and 16.4% respectively. Most importantly, 13.4% (50/372) of the tSN-MG patients were also titin antibody positive. None of the 121 healthy controls or the 90 myopathy patients, and only 3.6% (7/193) of other neurological disease patients were positive. We thus propose that the present titin antibody RIPA is a useful tool for serological MG diagnosis of tSN patients.

Gene variants at FTO, 9p21, and 2q36.3 are age-independently associated with myocardial infarction in Czech men.

AIM: Cardiovascular disease (CVD) is a major cause of morbidity and mortality in developed countries. This study aimed to confirm the effect of common putative CVD-associated gene variants (FTO rs17817449, KIF6 rs20455, 9p21 rs10757274 and 2q36.3 rs2943634) on CVD manifestation, and determine whether this effect differs between younger (< 50 years) and older CVD patients. METHODS: 1191 controls and 1889 MI patients were analyzed. All participants were Caucasian Czech males aged <65 years (532 were <50 years) who were examined at cardiology clinics in Prague, Czech Republic. Variants of FTO, 9p21, 2q36.3, and KIF-6 were genotyped using PCR-RFLP or TaqMan assay. RESULTS: Variants of FTO (OR 1.48; 95% CI, 1.19-1.84 in a TT vs. GG comparison, p=0.0005); 9p21 (OR 1.74; 95% CI, 1.41-2.14 in an AA vs. GG comparison, p=0.0001); and 2q36.3 (OR 1.34; 95%CI, 1.09-1.65 in an AA vs. +C comparison, p=0.006) were significantly associated with MI in the male Czech population. In contrast, genotype frequencies of KIF-6 (rs20455) were the same in patients and controls (P=1.00). Nearly identical results were observed when a subset of young MI patients (N=532, aged <50 years) was analyzed. CONCLUSION: We confirmed the importance of determining FTO, 9p21, and 2q36.3 variants as part of the genetic determination of MI risk in the Czech male population.

Determinants of preclinical atherosclerosis are different in type 1 and type 2 diabetic women.

Diabetes mellitus type 2 ranks among the strongest predictors of cardiovascular diseases (CVD) while the association of type 1 diabetes with CVD is more complex. We studied differences between type 1 and 2 diabetic women regarding association of cardiovascular risk factors with preclinical atherosclerosis expressed as intima-media thickness of common carotid (IMT CCA) and femoral arteries (IMT CFA) measured by high resolution ultrasound. Women with type 1 (n=203) and type 2 diabetes (n=123) were examined with regard to the presence of cardiovascular risk factors. In type 1 diabetic women strong association between IMT CCA and body mass index, waist circumference, and total body fat was found in contrast to type 2 diabetic women. In type 2 diabetic women strong association between IMT CCA and fasting glucose, glycated hemoglobin, and atherogenic index of plasma (log TG/HDL cholesterol) was observed in contrast to type 1 diabetic women. In type 1 diabetic women, IMT CFA was associated with body fat in contrast to type 2 diabetic women. Preclinical atherosclerosis in type 1 diabetic women was strongly associated with factors reflecting body fat and its distribution, while in type 2 diabetic women preclinical atherosclerosis was associated with markers reflecting glucose and lipid metabolic disorders.

Fasting and nonfasting triglycerides in cardiovascular and other diseases.

Moderately elevated plasma/serum triglycerides (2-10 mmol/l) signalize increased risk for cardiovascular disease or presence of non-alcoholic steatohepatitis. Extremely elevated triglycerides (more than 10 mmol/l) signalize increased risk for pancreatitis and lipemia retinalis. The concentration of triglycerides is regulated by many genetic and nongenetic factors. Extremely elevated triglycerides not provoked by nutritional factors, especially inappropriate alcohol intake are more likely to have a monogenic cause. On the contrary, mildly to moderately elevated triglycerides are often caused by polygenic disorders; these could be also associated with central obesity, insulin resistance, and diabetes mellitus. Concentration of triglycerides is also closely interconnected with presence of atherogenic remnant lipoproteins, impaired reverse cholesterol transport and more atherogenic small LDL particles. In general, there is tight association between triglycerides and many other metabolic factors including intermediate products of lipoprotein metabolism which are frequently atherogenic. Therefore, reliable evaluation of the independent role of triglycerides especially in atherosclerosis and cardiovascular disease is difficult. In individual cases values of HDL cholesterol, non-HDL cholesterol (total minus HDL cholesterol), non-HDL/nonLDL cholesterol (total minus HDL minus LDL cholesterol, especially in nonfasting status), atherogenic index of plasma and/or apolipoprotein B could help in decisions regarding aggressiveness of treatment.

The effect of glucose when added to a fat load on the response of glucagon-like peptide-1 (GLP-1) and apolipoprotein B-48 in the postprandial phase.

Increased and prolonged postprandial lipemia has been identified as a risk factor of cardiovascular disease. However, there is no consensus on how to test postprandial lipemia, especially with respect to the composition of an experimental meal. To address this question of how glucose, when added to a fat load, affects the selected parameters of postprandial lipemia, we carried out a study in 30 healthy male volunteers. Men consumed an experimental meal containing either 75 g of fat + 25 g of glucose (F+G meal) or 75 g of fat (F meal) in a control experiment. Blood was taken before the meal and at selected time points within the following 8 h. Glucose, when added to a fat load, induced an increase of glycemia and insulinemia and, surprisingly, a 20 % reduction in the response of both total and active glucagon-like peptide-1 (GLP-1) concentration. The addition of glucose did not affect the magnitude of postprandial triglyceridemia and TRL-C and TRL-TG concentrations but stimulated a faster response of chylomicrons to the test meal, evaluated by changes in apolipoprotein B-48 concentrations. The addition of glucose induced the physiological response of insulin and the lower response of GLP-1 to the test meal during the early postprandial phase, but had no effect on changes of TRL-cholesterol and TRL-TG within 8 h after the meal.

Association of intima-media thickness of carotid arteries with remnant lipoproteins in men and women.

The subclass of triglyceride-rich lipoproteins - remnant-like particles (RLP) seems to be strong and independent risk factor for cardiovascular disease. We evaluated the role of RLP and other risk factors (RF) with sonographically measured intima-media thickness of carotid arteries (IMT CCA) in a cohort of Czech population including women defined according to the time after menopause. We investigated relation of IMT CCA to age, weight, central obesity, plasma lipids including remnant-like particles cholesterol (RLP-C) and triglycerides (RLP-TG) in 136 men and 160 women. Using multiple linear regression analysis, significant association between IMT CCA and RLP-C was found in women 1-7 years after menopause. In the whole group of women, only age and fasting blood glucose were independently associated with IMT CCA. In men only age significantly correlated with IMT CCA. Significant decrease of all plasma lipids between 1988 and 1996 in men was detected, while in women significant increase in triglycerides and no change in non-HDL cholesterol was observed. RLP-C was the strongest independent RF for atherosclerosis in postmenopausal women but its association with IMT CCA was limited to several years after menopause. In conclusion, women changing reproductive status could be more sensitive to atherogenic impact of remnant lipoproteins.

Is the amount of coronary perivascular fat related to atherosclerosis?

Interesting and stimulating data about the effect of the perivascular adipose tissue size on atherogenesis are based mainly on CT findings. We studied this topic by directly analyzing perivascular adipose tissue in explanted hearts from patients undergoing transplantation. Ninety-six consecutive patients were included, including 58 with atherosclerotic coronary heart disease (CHD) and 38 with dilation cardiomyopathy (DCMP). The area of perivascular fat, area of the coronary artery wall, and ratio of CD68-positive macrophages within the perivascular fat and within the vascular wall were quantified by immunohistochemistry. There was no significant difference in the perivascular adipose tissue size between the two groups. Nevertheless, there was a significantly higher number of macrophages in the coronary arterial wall of CHD patients. In addition, we found a close relationship between the ratio of macrophages in the arterial wall and adjacent perivascular adipose tissue in the CHD group, but not in the DCMP group. According to our data interaction between macrophages in the arterial wall and macrophages in surrounding adipose tissue could be more important mechanism of atherogenesis than the size of this tissue itself.

Effect of exercise on markers of vascular health in renal transplant recipients.

The cornerstone of cardiovascular risk management is lifestyle intervention including exercise which could exert favorable impact also in renal transplant recipients. Nevertheless, reliable assessment of the effect of lifestyle interventions is complicated and the available data in this population are not consistent. The aim of the study was to evaluate the effect of physical activity on selected laboratory markers of vascular health including circulating stem cells, endothelial progenitor cells, microparticles, and plasma asymmetric dimethyl arginine in renal transplant recipients. Nineteen men and 7 women were recruited in 6-month program of standardized and supervised exercise. Control group consisted of 23 men and 13 women of similar age and body mass index not included into the program. One year after the transplantation, the main difference between intervention and control group was found in the change of endothelial progenitor cells (p=0.006). Surprisingly, more favorable change was seen in the control group in which endothelial progenitor cells significantly increased compared to the intervention group. The explanation of this finding might be a chronic activation of reparative mechanisms of vascular system in the population exposed to multiple risk factors which is expressed as relatively increased number of endothelial progenitor cells. Therefore, their decrease induced by exercise might reflect stabilization of these processes.

MuSK autoantibodies in myasthenia gravis detected by cell based assay--A multinational study.

Seronegative myasthenia gravis (MG) presents a serious gap in MG diagnosis and understanding. We applied a cell based assay (CBA) for the detection of muscle specific kinase (MuSK) antibodies undetectable by radioimmunoassay. We tested 633 triple-seronegative MG patients' sera from 13 countries, detecting 13% as positive. MuSK antibodies were found, at significantly lower frequencies, in 1.9% of healthy controls and 5.1% of other neuroimmune disease patients, including multiple sclerosis and neuromyelitis optica. The clinical data of the newly diagnosed MuSK-MG patients are presented. 27% of ocular seronegative patients were MuSK antibody positive. Moreover, 23% had thymic hyperplasia suggesting that thymic abnormalities are more common than believed.

Endothelial dysfunction expressed as endothelial microparticles in patients with end-stage heart failure.

Left ventricular assist devices (LVAD), currently used in treatment of terminal heart failure, are working on principle of rotary pump, which generates continuous blood flow. Non-pulsatile flow is supposed to expose endothelial cells to high stress and potential damage. Therefore, we investigated longitudinal changes in concentration of circulating endothelial microparticles (EMP) as a possible marker of endothelial damage before and after implantation of LVAD. Study population comprised 30 patients with end-stage heart failure indicated for implantation of the Heart Mate II LVAD. Concentrations of microparticles were measured as nanomoles per liter relative to phosphatidylserine before and 3 months after implantation. At 3 months after implantation we observed significant decrease in concentration of EMP [5.89 (95 % CI 4.31-8.03) vs. 3.69 (95 % CI 2.70-5.03), p=0.03] in the whole group; there was no difference observed between patients with ischemic etiology of heart failure (n=18) and with heart failure of non-ischemic etiology (n=12). In addition, heart failure etiology had no effect on the rate of EMP concentration decrease with time. These results indicate possibility that LVAD do not cause vascular damage 3 months after implantation. Whether these results suggest improvement of vascular wall function and of endothelium is to be proved in long-term studies.

Bilateral oophorectomy may have an unfavorable effect on glucose metabolism compared with natural menopause.

The incidence of diabetes mellitus is rising worldwide. The aim of this prospective epidemiological study was to compare the effects of natural and surgical menopause on parameters of glucose metabolism. In a group of 587 repeatedly examined women, with a baseline age of 45-55 years, the following subgroups of women were separated: those after bilateral oophorectomy (BO, n=37) and those in natural menopause (NAT, n=380) including women menopausal already at baseline (POST, n=89). The study parameters including glycemia, insulinemia, HOMA-IR and beta-cell function using HOMA-beta were determined at baseline and 6 years later. Over the study period, there was a marked rise in prediabetic and diabetic values of fasting glycemia; the percentage of women with diabetic values increased in the NAT (from 0.8 % to 3.9 %) and POST (from 2.2 % to 9.0 %) subgroups, with the highest prevalence in the BO subgroup (from 8.1 % to 10.8 %). While, among women with non-diabetic fasting glycemia, an increase in fasting glycemia was observed in all study subgroups, it was more marked in the BO subgroup than in the NAT and POST ones (p=0.02 both). This difference between NAT and BO was also found in the long-term trend of development of glycemia in non-diabetic women (p=0.014). Compared with natural menopause, bilateral oophorectomy may have an adverse effect on glucose metabolism.

Relation between preclinical atherosclerosis and venous thromboembolism in patients with thrombophilias - longitudinal study.

Preclinical atherosclerosis may represent a risk factor for venous thromboembolism (VTE). In longitudinal study we followed longitudinally 96 patients (32 men) with thrombophilias with (n=51) and without (n=45) history of VTE. In both groups we studied the changes of preclinical atherosclerosis at peripherally located arteries detected by ultrasound. In addition, we assessed changes in selected risk factors of atherosclerosis. During the mean follow-up of 56.0+/-7.62 months we did not find significant change in preclinical atherosclerosis defined as Belcaro score in either group (-3 % in the VTE group vs 0 % in non VTE group). Significant increase in body mass index (1.03+/-1.98 kg*m(-2), resp. 1.21+/-1.67 kg*m(-2), p<0.01) and non-significant increase in systolic blood pressure were detected in both groups. Waist circumference increased significantly only in patients without VTE (4.11+/-7.84 cm, p<0.05). No differences in changes of risk factors under study between both groups were detected. In summary, patients with thrombophilia and history of VTE showed no evidence of greater progression of atherosclerosis or increase in traditional risk factors of atherosclerosis than patients with thrombophilia without history of VTE. Unfavorable changes of body mass index, waist circumference and systolic blood pressure were detected in both groups during study period.