Relationship between lipoprotein(a) levels, oxidative stress, and blood pressure levels in patients with essential hypertension

Cardiac markers: Role in the pathogenesis of arterial hypertension

Cardiac biomarkers may play unique roles in the prognostic evaluation of patients with hypertension, as many cardiac biomarker levels become abnormal long before the onset of obvious cardiovascular disease (CVD). There are numerous cardiac markers. However, this review article only reported the roles of creatinine kinase-MB, cardiac troponins, lipoprotein a, osteopontin, cardiac extracellular matrix, C-reactive protein, cardiac matrix metalloproteinases, cardiac natriuretic peptides, myoglobin, renin, and dynorphin in the pathogenesis of hypertension. This article explained recent major advances, as well as discoveries, significant gaps, and current debates and outlined possible directions for future research. Further studies are required to determine the association between myoglobin and other cardiac markers in hypertension. Moreover, therapeutic approaches are required to determine the early control of these cardiac markers, which ultimately reduce the prevalence of CVDs.

Oral Cholecalciferol Supplementation in Sahara Black People with Chronic Kidney Disease Modulates Cytokine Storm, Oxidative Stress Damage and Athero-Thromboembolic Risk

The 25-hydroxyvitamin D3 (25OHD3) deficiency in chronic kidney disease (CKD) is associated with immune system dysfunction (pro-inflammatory cytokines storm) through macrophages renal infiltration, oxidative stress (OxS) damage and athero-thromboembolic risk. Conversely, cholecalciferol supplementation (25OHD-S) prevents kidney fibrosis by inhibition of vascular calcification and nephrotic apoptosis (nephrons reduction). The objective of this study was to investigate the pleiotropic effects of 25OHD-S on immunomodulation, antioxidant status and in protecting against thromboembolic events in deficiency CKD Black and White individuals living in the Southern Sahara (SS). The oral 25OHD-S was evaluated in 60,000 IU/month/36 weeks versus in 2000 IU/day/24 weeks in Black (n = 156) and White (n = 150). Total serum vitamin D was determined by liquid chromatography-tandem mass spectrometry. All biomarkers of pro-inflammatory cytokines (PIC) were assessed by ELISA tests. OxS markers were assessed by Randox kits. Homocysteine and lipoproteine (a) were evaluated by biochemical methods as biomarkers of atherothromboembolic risk. All statistical analyses were performed with Student’s t-test and one-way ANOVA. The Pearson test was used to calculate the correlation coefficient. The means will be significantly different at a level of p value < 0.05. Multiple logistic regressions were performed using Epi-info and Statview software. Vitamin D deficiency alters the PIC profile, OxS damage and atherothrombogenic biomarkers in both SS groups in the same manner; however, these disorders are more acute in Black compared to White SS individuals. The results showed that the serum 25OHD3 concentrations became normal (>75 nmol/L or >30 ng/mL) in the two groups. We have shown that the dose and duration of 25OHD-S treatment are not similar in Black SS residents compared to White SS subjects, whilst the same inhabit the south Sahara environment. It appears that a high dose intermittent over a long period (D60: 36 weeks) was more efficient in Black people; while a lower dose for a short time is sufficient (D2: 24 weeks) in their White counterparts. The oral 25OHD-S attenuates PIC overproduction and OxS damage, but does not reduce athero-thromboembolic risk, particularly in Black SS residents.

Lipoprotein (a) and Hypertension

PURPOSE OF REVIEW

To provide an overview of the associations between elevated blood pressure and lipoprotein (a) and possible causal links, as well as data on the prevalence of elevated lipoprotein (a) in a cohort of hypertensive patients.

RECENT FINDINGS

Elevated lipoprotein (a) is now considered to be an independent and causal risk factor for atherosclerotic cardiovascular disease and calcific aortic valve disease. Despite this, there are limited data demonstrating an association between elevated lipoprotein (a) and hypertension. Further, there is limited mechanistic data linking lipoprotein (a) and hypertension through either renal impairment or direct effects on the vasculature. Despite the links between lipoprotein (a) and atherosclerosis, there are limited data demonstrating an association with hypertension. Evidence from our clinic suggests that ~ 30% of the patients in this at-risk, hypertensive cohort had elevated lipoprotein (a) levels and that measurement of lipoprotein (a) maybe useful in risk stratification.

Lipid Profile Modulates Cardiometabolic Risk Biomarkers Including Hypertension in People with Type-2 Diabetes: A Focus on Unbalanced Ratio of Plasma Polyunsaturated/Saturated Fatty Acids

Type 2 diabetes mellitus (T2DM) is associated with lipid metabolism disorder, particularly elevated plasma levels of non-esterified free fatty acids (NEFFA) and an increased cardiovascular disease risk, such as essential hypertension (H). The plasma unbalance of saturated fatty acid (SFA)/polyunsaturated fatty acid (PUFA) ratio is a likely contributor, but the mechanisms involved are not clearly elucidated. The aim of this study is to explore the association between plasma SFA/PUFA ratio and the clusters of cardiometabolic syndrome (CMS), including the atherogenic biomarkers, inflammatory status, feeding patterns, and physical activity in people with T2DM with or without essential hypertension. The study was conducted on 784 adult male and female participants, aged between 30 and 50 years, and divided into 3 groups: 100 T2DM without hypertension (D); 368 T2DM with hypertension (DM); and 316 hypertensive participants without T2DM (H). All Participants were phenotyped regarding CMS clusters according to the NCEP/ATPIII criteria. Insulin resistance was assessed by Homeostasis model assessment (HOMA model). Metabolic, atherogenic, and inflammatory parameters were analyzed by biochemical methods; NEFFA by microfluorimetry; SFA, PUFA-n6 and PUFA-n3 by gas phase chromatography. Dietary lipids and physical activity were analyzed through the use of validated questionnaires. The clusters of CMS were found in all groups. Dyslipidemia was correlated with accretion NEFFA levels in all groups, but more accentuated in the DH group (r = +0.77; p < 0.001). Similarly, plasma PUFA/SFA ratio and PUFA-3 level was lower, concomitantly with a higher plasma ApoB100/ApoA1 (p < 0.001), lipoprotein (a), homocysteine (p < 0.001), and pro-inflammatory cytokines (TNFα, IL-6, IL1-β) in the DH group. Likewise, the depletion of PUFA-n3/PUFA-n6 ratio is associated with the decrease of omega 3-DHA (docosahexaenoic acid) and omega 3-EPA (eicosapentaenoic acid) (p < 0.001). It appears that the PUFAs-n3 ratio modulates cardiometabolic risk, inflammatory state and atherogenic biomarkers. The plasma unbalanced ratio of SFA/PUFA reflects dietary fatty acids intake. The contribution of dietary lipids is undisputed. Nutritional recommendations are required to determine the fatty acids ratio (saturated and unsaturated) provided in the diet.

Genome-wide association study of nocturnal blood pressure dipping in hypertensive patients

Background

Reduced nocturnal fall (non-dipping) of blood pressure (BP) is a predictor of cardiovascular target organ damage. No genome-wide association studies (GWAS) on BP dipping have been previously reported.

Methods

To study genetic variation affecting BP dipping, we conducted a GWAS in Genetics of Drug Responsiveness in Essential Hypertension (GENRES) cohort (n = 204) using the mean night-to-day BP ratio from up to four ambulatory BP recordings conducted on placebo. Associations with P < 1 × 10^− 5 were further tested in two independent cohorts: Haemodynamics in Primary and Secondary Hypertension (DYNAMIC) (n = 183) and Dietary, Lifestyle and Genetic determinants of Obesity and Metabolic Syndrome (DILGOM) (n = 180). We also tested the genome-wide significant single nucleotide polymorphism (SNP) for association with left ventricular hypertrophy in GENRES.

Results

In GENRES GWAS, rs4905794 near BCL11B achieved genome-wide significance (β = − 4.8%, P = 9.6 × 10^− 9 for systolic and β = − 4.3%, P = 2.2 × 10^− 6 for diastolic night-to-day BP ratio). Seven additional SNPs in five loci had P values < 1 × 10^− 5. The association of rs4905794 did not significantly replicate, even though in DYNAMIC the effect was in the same direction (β = − 0.8%, P = 0.4 for systolic and β = − 1.6%, P = 0.13 for diastolic night-to-day BP ratio). In GENRES, the associations remained significant even during administration of four different antihypertensive drugs. In separate analysis in GENRES, rs4905794 was associated with echocardiographic left ventricular mass (β = − 7.6 g/m², P = 0.02).

Conclusions

rs4905794 near BCL11B showed evidence for association with nocturnal BP dipping. It also associated with left ventricular mass in GENRES. Combined with earlier data, our results provide support to the idea that BCL11B could play a role in cardiovascular pathophysiology.

Electronic supplementary material

The online version of this article (10.1186/s12881-018-0624-7) contains supplementary material, which is available to authorized users.

When should we measure lipoprotein (a)?

Recently published epidemiological and genetic studies strongly suggest a causal relationship of elevated concentrations of lipoprotein (a) [Lp(a)] with cardiovascular disease (CVD), independent of low-density lipoproteins (LDLs), reduced high density lipoproteins (HDL), and other traditional CVD risk factors. The atherogenicity of Lp(a) at a molecular and cellular level is caused by interference with the fibrinolytic system, the affinity to secretory phospholipase A2, the interaction with extracellular matrix glycoproteins, and the binding to scavenger receptors on macrophages. Lipoprotein (a) plasma concentrations correlate significantly with the synthetic rate of apo(a) and recent studies demonstrate that apo(a) expression is inhibited by ligands for farnesoid X receptor. Numerous gaps in our knowledge on Lp(a) function, biosynthesis, and the site of catabolism still exist. Nevertheless, new classes of therapeutic agents that have a significant Lp(a)-lowering effect such as apoB antisense oligonucleotides, microsomal triglyceride transfer protein inhibitors, cholesterol ester transfer protein inhibitors, and PCSK-9 inhibitors are currently in trials. Consensus reports of scientific societies are still prudent in recommending the measurement of Lp(a) routinely for assessing CVD risk. This is mainly caused by the lack of definite intervention studies demonstrating that lowering Lp(a) reduces hard CVD endpoints, a lack of effective medications for lowering Lp(a), the highly variable Lp(a) concentrations among different ethnic groups and the challenges associated with Lp(a) measurement. Here, we present our view on when to measure Lp(a) and how to deal with elevated Lp(a) levels in moderate and high-risk individuals.

Lipoprotein (a): More than a bystander in the etiology of hypertension? A study on essential hypertensive patients not yet on treatment

BACKGROUND

Hypertension (HTN) is a very common disorder with a substantial impact on public health because of its complications.

OBJECTIVES

To study the association of serum lipoprotein(a) [Lp(a)] elevation with essential hypertension (eHTN).

PATIENTS AND METHODS

This study was conducted on a group of essential hypertensive patients. Laboratory exams consisting of serum creatinine and Lp(a) were measured.

RESULTS

Ninety five essential hypertensive patients were enrolled to the study. Serum LP (a) in patients was 46.5±20. In patients an inverse correlation between serum Lp(a) andcreatinine clearance was seen (r = -0.175 p<0.05). There was a significant correlation between serum Lp(a) and age (r =0.191 p<0.05) or duration of HTN (known duration of hypertension period) (r =0.362 p<0.05).

CONCLUSIONS

Our data suggest that Lp(a) may be involved as a cofactor in essential hypertension, with a mechanism that remains to be elucidated.

Serum bilirubin and lipoprotein-a: how are these associated with whole blood viscosity?

BACKGROUND

It has been demonstrated that oxidative stress can induce red blood cell rigidity and haemolysis, which in turn can cause hyperviscosity and hyperbilirubinaemia, respectively. However, haemolysis may be associated with a low level of haemoglobin, which reduces whole blood viscosity (WBV). Bilirubin can behave as antioxidant or oxidant, and one uncharted course for diagnostic pathology is how or whether bilirubinaemia and viscosity are associated. Further, oxidative stress is now being assessed using lipoprotein-a (Lp(a)), among other things but whether it is associated with blood viscosity has not been established.

AIM

This study investigates the association and correlation of haemoglobin level and WBV with serum Lp(a) and bilirubin levels in a general population of patients.

MATERIALS AND METHODS

Sixty-eight cases that were tested for Lp(a), concomitantly with full blood count and liver function, in our archived clinical pathology database were used in this study. WBV levels were determined using a validated formula. Multivariate and univariate analyses as well as correlation were performed.

RESULTS

WBV was found to be significantly associated with bilirubin (P<0.02), but not with Lp(a). Haemoglobin concentration was inversely correlated with Lp(a) (P<0.04), but not with bilirubinaemia.

CONCLUSION

This pilot study suggests that hyperbilirubinaemia and hyperviscosity are associated and positively correlated. Consideration of whether serum bilirubin (as an indirect index of oxidative stress) can be used in combination with WBV (as index of macrovascular effect of oxidative stress) to assess oxidative damage is recommended.

Efficacy of optimal long-term management of multiple cardiovascular risk factors (CVD) on walking and quality of life in patients with peripheral artery disease (PAD): protocol for randomized controlled trial

Peripheral artery disease (PAD) is an understudied chronic illness most prevalent in elderly individuals. PAD patients experience substantial walking impairment due to symptoms of limb ischemia that significantly diminishes quality of life (QOL). Cardiovascular disease (CVD) morbidity and mortality is increased in this population because of aggressive atherosclerosis resulting from untreated CVD risk factors. Despite current national guidelines recommending intensive CVD risk factor management for PAD patients, untreated CVD risk factors are common. Interventions that bridge this gap are imperative. The Vascular Insufficiency - Goals for Optimal Risk Reduction (VIGOR(2)) study is a randomized controlled trial (RCT) that examines the effectiveness of a long-term multifactor CVD risk reduction program on walking and quality of life in patients with PAD. The purpose of this article is to provide a detailed description of the design and methods of VIGOR(2). Clinical Trial Registration - URL: http://clinicaltrials.gov/ct2/show/NCT00537225.

Insulin resistance explains the relationship between novel cardiovascular risk factors and hypertension. The Telde Study

BACKGROUND

Most studies describing an association between hypertension and an inflammatory/pro-thrombotic state do not assess insulin resistance.

AIM

To examine the association between hypertension and new cardiovascular risk factors when considering both classical risk factors and insulin resistance.

METHODS

In a population-based sample of 1030 subjects, clinical information and blood samples were obtained. Subjects were classified according to the presence or absence of hypertension, and insulin resistance was estimated using the homeostasis model of assessment (HOMA). To identify variables independently associated with hypertension, a four-model multiple logistic regression was performed: model 1 included novel risk factors (Plasminogen Activator Inhibitor- 1 [PAI-1], fibrinogen, von Willebrand Factor [vWF], lipoprotein(a), homocysteine and C-reactive Protein [CRP]); model 2, novel risk factors plus HOMA; model 3 included both classical (smoking, triglycerides, HDL cholesterol, total cholesterol, waist circumference and diabetes) and novel risk factors and model 4, model 3 plus HOMA. All were adjusted for age, BMI and gender and compared using Akaike's Information Criterion (AIC).

RESULTS

In model 1, only PAI-1, age and BMI showed association with hypertension.When HOMA and classical risk factors were also included, PAI-1 was replaced by triglyceride, smoking and diabetes. The lowest AIC value (best adjustment) was displayed by model 4, comprising all of the variables. Only age, BMI, HOMA and smoking remained significantly associated with hypertension.

CONCLUSIONS

The novel cardiovascular risk factors assessed do not add information as markers of hypertension when classical risk factors or insulin resistance are included in the evaluation.

The PON1192RR genotype is associated with a higher prevalence of arterial hypertension

OBJECTIVE

To investigate whether genetic polymorphism of paraoxonase (PON1192), an enzyme which protects low density lipoprotein from oxidation, is related to the prevalence of arterial hypertension.

METHODS

Two groups of carefully selected subjects of both sexes were enrolled and compared. The first group comprised 219 healthy controls (mean age 46.5 +/- 14.7 years) whereas the second comprised 119 hypertensive patients (mean age 47.9 +/- 10.5 years) with untreated essential arterial hypertension. Anthropometric and biochemical parameters were within the normal range in both groups. The PON1192 polymorphism was determined by a polymerase chain reaction-restriction fragment length polymorphism approach.

RESULTS

In hypertensive patients, a significant increase of the frequency of PON1192RR genotype with respect to healthy controls (14.3 versus 5.0%, P = 0.003) was found. Logistic regression analyses also showed that the PON1192RR genotype was independently associated with a four-fold increase in susceptibility to arterial hypertension (odds ratio = 4.31; 95% confidence interval = 1.63-11.43, P = 0.003).

CONCLUSIONS

The finding that PON1192RR genotype is associated with a higher prevalence of arterial hypertension may contribute to improving the stratification of cardiovascular risk within a population aged 30-60 years. Determination of the PON1192 polymorphism may help to identify those individuals who are prone to developing cardiovascular diseases at an early stage, suggesting the need for close monitoring of cardiovascular risk factors before the onset of cardiovascular disease.

Therapy of hyper-Lp(a)

Lipoprotein (a) [Lp(a)] appears to be one of the most atherogenic lipoproteins. It consists of a low-density lipoprotein (LDL) core in addition to a covalently bound glycoprotein, apolipoprotein (a) [apo(a)]. Apo(a) exists in numerous polymorphic forms. The size polymorphism is mediated by the variable number of kringle-4 Type-II repeats found in apo(a). Plasma Lp(a) levels are determined to more than 90% by genetic factors. Plasma Lp(a) levels in healthy individuals correlate significantly high with apo(a) biosynthesis and not with its catabolism. There are several hormones known to have a strong impact on Lp(a) metabolism. In certain diseases, such as kidney disease, Lp(a) catabolism is impaired leading to up to fivefold elevations. Lp(a) levels rise with age but are otherwise influenced only little by diet and lifestyle. There is no safe and efficient way of treating individuals with elevated plasma Lp(a) concentrations. Most of the lipid-lowering drugs have either no significant influence on Lp(a) or exhibit a variable effect in patients with different forms of primary and secondary hyperlipoproteinemia. There is without doubt a strong need to concentrate on the development of specific medications to selectively target Lp(a) biosynthesis, Lp(a) assembly and Lp(a) catabolism. So far only anabolic steroids were found to drastically reduce Lp(a) plasma levels. This class of substance cannot, of course, be used for treatment of patients with hyper-Lp(a). We recommend that the mechanism of action of these drugs be studied in more detail and that the possibility of synthesizing derivatives which may have a more specific effect on Lp(a) without having any side effects be pursued. Other strategies that may be of use in the development of drugs for treatment of patients with hyper-Lp(a) are discussed in this review.

Oxidative stress in white coat hypertension; role of paraoxonase

Oxidative stress in sustained hypertension was shown with several biochemical parameters. Oxidized low-density lipoprotein (oxLDL) plays an important role during the atherosclerosis process and paraoxonase (PON1) can significantly inhibit lipid peroxidation. Serum PON1 activity, oxLDL and malondialdehyde (MDA) concentrations and their relationship with serum lipid parameters and systolic and diastolic blood pressures (SBP and DBP) were determined in subjects with white coat hypertension (WCH), sustained hypertension (HT) and normotension (NT). The study group consisted of a total of 86 subjects, 30 with WCH (14 male, 16 female subjects), 30 with HT (13 male, 17 female subjects) and 26 with NT (12 male, 14 female subjects). Both white coat hypertensive and hypertensive subjects had significantly higher levels of MDA than normotensives (P<0.026 and P<0.001, respectively). The oxLDL level of the HT group was significantly higher than the NT group (P<0.023). The WCH group had an oxLDL level similar to both hypertensive and normotensive groups. HT and WCH groups had significantly lower PON1 levels than the normotensive group (P<0.001). oxLDL correlated with MDA positively (P=0.008), and PON1 negatively (P=0.008). A negative correlation between MDA and PON1 (P=0.014) was detected. MDA correlated positively with both SBP and DBP (P=0.001), while PON1 correlated with both of them negatively (P=0.01 and P=0.008, respectively). OxLDL correlated with diastolic blood pressure positively (P=0.008). Our data demonstrate that oxidative stress increase in WCH is associated with a decrease in PON1 activity. The reduction in PON1 activity may be one of the factors leading to an increase in oxidative status in WCH.

Lipoprotein(a): still an enigma?

PURPOSE OF REVIEW

Lipoprotein(a) belongs to the class of the most atherogenic lipoproteins. Despite intensive research - in the last year more than 80 papers have been published on this topic - information is still lacking on the physiological function of lipoprotein(a) and the site of its catabolism. Important advances have been made in the knowledge of these points, which may have some therapeutic implications.

RECENT FINDINGS

The association of high lipoprotein(a) values with an increase in risk for coronary events has been documented in further prospective studies. This increased risk may relate to recent findings that apolipoprotein(a) is produced in situ within the vessel wall. In addition, lipoprotein(a) binds and inactivates the tissue factor pathway inhibitor and induces plasminogen activator inhibitor type 2 expression in monocytes. A new antisense oligonucleotide strategy has been proposed which efficiently inhibits apolipoprotein(a) expression in vitro and in vivo. Apolipoprotein(a), however, suppresses angiogenesis and thus may interfere with the infiltration of tumor cells. Finally, the enzymatic activity leading to the formation of apolipoprotein(a) fragments in plasma and their catabolism have been further elucidated.

SUMMARY

We are still far away from understanding the pathways involved in lipoprotein(a) catabolism, and the physiological function of this lipoprotein. Recent findings, however, provide new insight into pathomechanisms in patients with increased lipoprotein(a) related to hemostasis, which may serve as a basis for designing new treatment strategies.