Marinobufagenin is related to elevated central and 24-h systolic blood pressures in young black women: the African-PREDICT Study

Hypertension in sub-Saharan Africa: the current profile, recent advances, gaps, and priorities

Recent global and regional reports consistently confirm the high and increasing prevalence of hypertension in sub-Saharan Africa (SSA), with poor detection, treatment, and control rates. This narrative review summarises the burden of hypertension in SSA and recent findings from community-based hypertension management strategies. We further outline prominent risk factors according to recent data and associated underlying mechanisms for hypertension development. An extensive review of literature showed that most countries have reported on the prevalence of hypertension during 2017-2023, despite limitations linked to the lack of nationally representative studies, heterogeneity of sampling and data collection methods. Task-shifting approaches that assign roles to model patients and community health workers reported improved linkage to healthcare services and adherence to medication, with inconsistent findings on blood pressure (BP)-lowering effects over time. The regularly reported risk factors include unhealthy diet, sedentary lifestyle, increased adiposity and underweight, ageing, level of education, and/or income as well as psychosocial factors. Newer data on the pathophysiological mechanisms leading to hypertension and potential areas of intervention are reported from children and adults and include, among others, salt-handling and volume overload, endothelial function, BP dipping patterns and the role of human immunodeficiency virus . To conclude, significant strides have been made in data reporting from SSA on the burden of hypertension in the region as well as biomarker research to improve understanding and identification of areas of intervention. However, gaps remain on linkage between knowledge generation, translation, and implementation research. Coordinated studies addressing both discovery science and public health are crucial to curb hypertension development and improve management in SSA.

New Insights on the Role of Marinobufagenin from Bench to Bedside in Cardiovascular and Kidney Diseases

Marinobufagenin (MBG) is a member of the bufadienolide family of compounds, which are natural cardiac glycosides found in a variety of animal species, including man, which have different physiological and biochemical functions but have a common action on the inhibition of the adenosine triphosphatase sodium-potassium pump (Na+/K+-ATPase). MBG acts as an endogenous cardiotonic steroid, and in the last decade, its role as a pathogenic factor in various human diseases has emerged. In this paper, we have collated major evidence regarding the biological characteristics and functions of MBG and its implications in human pathology. This review focused on MBG involvement in chronic kidney disease, including end-stage renal disease, cardiovascular diseases, sex and gender medicine, and its actions on the nervous and immune systems. The role of MBG in pathogenesis and the development of a wide range of pathological conditions indicate that this endogenous peptide could be used in the future as a diagnostic biomarker and/or therapeutic target, opening important avenues of scientific research.

Traditional and Emerging Sex-Specific Risk Factors for Cardiovascular Disease in Women

Cardiovascular disease (CVD) remains a major health threat in women. While traditional CVD risk factors such as hypertension, hyperlipidemia, diabetes, and smoking have been recognized for over 50 years, optimal control of these risk factors remains a major challenge. Unique sex-specific risk factors such as adverse pregnancy outcomes, premature menopause and low estrogen states, and chronic autoimmune inflammatory disorders also contribute to increased CVD risk in women. In addition, psychological risk factors such as stress, depression, and social determinants of health may have a disproportionately adverse impact in women. An improved understanding of traditional and emerging sex-specific CVD risk factors and management of modifiable factors is critical for clinicians who provide care for women. Early recognition and treatment of risk factors may alter the trajectory of adverse CVD events. A multi-disciplinary approach with team-based care involving multiple specialists and improved, targeted educational efforts are needed to reduce CVD risk factors and its adverse consequences in women.

Endogenous Mammalian Cardiotonic Steroids-A New Cardiovascular Risk Factor?-A Mini-Review

The role of endogenous mammalian cardiotonic steroids (CTS) in the physiology and pathophysiology of the cardiovascular system and the kidneys has interested researchers for more than 20 years. Cardiotonic steroids extracted from toads or plants, such as digitalis, have been used to treat heart disease since ancient times. CTS, also called endogenous digitalis-like factors, take part in the regulation of blood pressure and sodium homeostasis through their effects on the transport enzyme called sodium–potassium adenosine triphosphatase (Na/K-ATPase) in renal and cardiovascular tissue. In recent years, there has been increasing evidence showing deleterious effects of CTS on the structure and function of the heart, vasculature and kidneys. Understanding the role of CTS may be useful in the development of potential new therapeutic strategies.

The association of PAI-1 with 24 h blood pressure in young healthy adults is influenced by smoking and alcohol use: The African-PREDICT study

BACKGROUND AND AIMS

The association between plasminogen activator inhibitor-1 (PAI-1) and blood pressure is well established, but it is debatable whether raised PAI-1 levels precede or result from raised blood pressure. Furthermore, it is unclear whether this association already exists in the absence of overt hypertension and to what degree it is influenced by health behaviours. Our aim was to investigate the association of 24 h blood pressure with PAI-1 activity (PAI-1_act) in a young, healthy cohort, and to assess the influence of alcohol consumption and smoking on these associations.

METHODS AND RESULTS

Healthy black and white men and women (aged 20-30 years, n = 1156) were cross-sectionally analysed. Statistical analysis was performed first split by ethnicity and sex and then by alcohol consumption and smoking. Regression analyses adjusted for age revealed positive associations of 24 h blood pressure with PAI-1_act in most groups (p < 0.05). In multivariate-adjusted analyses, significance was lost in all groups except black men, who also had higher monocyte chemoattractant protein-1 (MCP-1) and von Willebrand factor antigen (vWF_ag) compared to white men (both p < 0.001). Analyses in black men, split by self-reported alcohol use and smoking, revealed 24 h blood pressure-PAI-1_act associations only in alcohol users (24 h SBP [B = 4.22, p < 0.001], DBP [B = 2.04, p = 0.015] and PP [B = 2.18, p = 0.013]) and smokers (24 h SBP [B = 6.10, p < 0.001] and PP [B = 4.33, p = 0.001]).

CONCLUSION

Our findings support a positive association between 24 h blood pressure and PAI-1, particularly in individuals with higher MCP-1 and vWF_ag levels. Furthermore, smoking and alcohol consumption play an important role in modifying the association between blood pressure and PAI-1.

Predicting Nonalcoholic Fatty Liver Disease through a Panel of Plasma Biomarkers and MicroRNAs in Female West Virginia Population

(1) Background: Nonalcoholic fatty liver disease (NAFLD) is primarily characterized by the presence of fatty liver, hepatic inflammation and fibrogenesis eventually leading to nonalcoholic steatohepatitis (NASH) or cirrhosis. Obesity and diabetes are common risk factors associated with the development and progression of NAFLD, with one of the highest prevalence of these diseased conditions in the West Virginia population. Currently, the diagnosis of NAFLD is limited to radiologic studies and biopsies, which are not cost-effective and highly invasive. Hence, this study aimed to develop a panel and assess the progressive levels of circulatory biomarkers and miRNA expression in patients at risk for progression to NASH to allow early intervention strategies. (2) Methods: In total, 62 female patients were enrolled and blood samples were collected after 8–10 h of fasting. Computed tomography was performed on abdomen/pelvis following IV contrast administration. The patients were divided into the following groups: Healthy subjects with normal BMI and normal fasting blood glucose (Control, n = 20), Obese with high BMI and normal fasting blood glucose (Obese, n = 20) and Obese with high fasting blood glucose (Obese + DM, n = 22). Based on findings from CT, another subset was created from Obese + DM group with patients who showed signs of fatty liver infiltration (Obese + DM(FI), n = 10). ELISA was performed for measurement of plasma biomarkers and RT-PCR was performed for circulating miRNA expression. (3) Results: Our results show significantly increased levels of plasma IL-6, Leptin and FABP-1, while significantly decreased level of adiponectin in Obese, Obese + DM and Obese + DM(FI) group, as compared to healthy controls. The level of CK-18 was significantly increased in Obese + DM(FI) group as compared to control. Subsequently, the expression of miR-122, miR-34a, miR-375, miR-16 and miR-21 was significantly increased in Obese + DM and Obese + DM(FI) group as compared to healthy control. Our results also show distinct correlation of IL-6, FABP-1 and adiponectin levels with the expression of miRNAs in relation to the extent of NAFLD progression. (4) Conclusion: Our results support the clinical application of these biomarkers and miRNAs in monitoring the progression of NAFLD, suggesting a more advanced diagnostic potential of this panel than conventional methods. This panel may provide an appropriate method for early prognosis and management of NAFLD and subsequent adverse hepatic pathophysiology, potentially reducing the disease burden on the West Virginia population.

Monoclonal Antibody to Marinobufagenin Downregulates TGFβ Profibrotic Signaling in Left Ventricle and Kidney and Reduces Tissue Remodeling in Salt-Sensitive Hypertension

Background Elevated levels of an endogenous Na/K-ATPase inhibitor marinobufagenin accompany salt-sensitive hypertension and are implicated in cardiac fibrosis. Immunoneutralization of marinobufagenin reduces blood pressure in Dahl salt-sensitive (Dahl-S) rats. The effect of the anti-marinobufagenin monoclonal antibody on blood pressure, left ventricular (LV) and renal remodeling, and gene expression were investigated in hypertensive Dahl-S rats. Methods and Results Dahl-S rats were fed high NaCl (8%, HS; n=14) or low NaCl (0.1%, LS; n=14) diets for 8 weeks. Animals were administered control antibody (LS control antibody, LSC; HS control antibody, HSC; n=7 per group) or anti-marinobufagenin antibody once on week 7 of diet intervention (n=7 per group). Levels of marinobufagenin, LV, and kidney mRNAs and proteins implicated in profibrotic signaling were assessed. Systolic blood pressure was elevated (211±8 versus 133±3 mm Hg, P<0.01), marinobufagenin increased 2-fold in plasma (P<0.05) and 5-fold in urine (P<0.01), LV and kidney weights increased, and levels of LV collagen-1 rose 3.5-fold in HSC versus LSC. Anti-marinobufagenin antibody treatment decreased systolic blood pressure by 24 mm Hg (P<0.01) and reduced organ weights and level of LV collagen-1 (P<0.01) in hypertensive Dahl salt-sensitive rats with anti-marinobufagenin antibody versus HSC. The expression of genes related to transforming growth factor-β-dependent signaling was upregulated in the left ventricles and kidneys in HSC versus LSC groups and became downregulated following administration of anti-marinobufagenin antibody to hypertensive Dahl-S rats. Marinobufagenin also activated transforming growth factor-β signaling in cultured ventricular myocytes from Dahl-S rats. Conclusions Immunoneutralization of heightened marinobufagenin levels in hypertensive Dahl-S rats resulted in a downregulation of genes implicated in transforming growth factor-β pathway, which indicates that marinobufagenin is an activator of profibrotic transforming growth factor-β-dependent signaling in salt-sensitive hypertension.

The Na+K+-ATPase Inhibitor Marinobufagenin and Early Cardiovascular Risk in Humans: a Review of Recent Evidence

PURPOSE OF REVIEW

This review synthesizes recent findings in humans pertaining to the relationships between marinobufagenin (MBG), a steroidal Na+/K+-ATPase inhibitor and salt-sensitivity biomarker, and early cardiovascular risk markers.

RECENT FINDINGS

Twenty-four-hour urinary MBG strongly associates with habitual salt intake in young healthy adults (aged 20-30 years). Furthermore, in young healthy adults free of detected cardiovascular disease, MBG associates with increased large artery stiffness and left ventricular mass independent of blood pressure. These findings in human studies corroborate mechanistic data from rat studies whereby stimulation of MBG by a high salt intake or MBG infusion increased vascular fibrosis and cardiac hypertrophy. Twenty-four-hour urinary MBG may be a potential biomarker of early cardiovascular risk. Adverse associations between MBG-which increases with salt consumption-and early cardiovascular risk markers support the global efforts to reduce population-wide salt intake in an effort to prevent and control the burden of non-communicable diseases.

Acute salt loading and cardiotonic steroids in resistant hypertension

The study addresses the association of marinobufagenin (MBG), a natriuretic and vasoconstrictor steroid, and Na/K-ATPase (NKA) activity with pressor response to salt-loading and arterial stiffness in resistant hypertension (RH). Thirty-four patients (18 males and 16 females; 56±8 years) with RH on a combined (lisnopril/amlodipine/hydrochlorothiazide) therapy and 11 healthy age-matched normotensive subjects (7 males and 4 females; 54±2 years) were enrolled in this study. Salt-loading was performed via intravenous infusion of 1000mL saline (0.9% NaCl) for 1h. Arterial stiffness was measured by Sphygmocor Px device with a calculation of pulse-wave velocity (PWV). Activity of NKA was measured in erythrocytes. We demonstrated that plasma levels of MBG and magnitude of NaCl-induced MBG-dependent NKA inhibition are associated with PWV, and that this association has gender- and age-specific fashion in RH patients.

Autonomic activity and its relationship with the endogenous cardiotonic steroid marinobufagenin: the African-PREDICT study

Aim: Marinobufagenin (MBG), a cardiotonic steroid and a natriuretic hormone, is elevated in response to high salt diet consumption. In animal models salt intake stimulates adrenocortical MBG secretion via increased angiotensin II, sympathetic activity and aldosterone. No evidence in humans exists to suggest the involvement of the angiotensinergic-sympatho-excitatory pathway in MBG production. We investigated whether MBG is related to indices of autonomic activity in men and women. Methods: This cross-sectional study included 680 black and white, men and women from the African-PREDICT study (aged 20-30 years). Continuous 24 hr ECG recordings were used to obtain low and high frequency (LF, HF) heart rate variability (HRV). We measured 24 hr urinary MBG excretion and serum aldosterone. Results: We found a positive association of MBG excretion with estimated salt intake (P < 0.001) and aldosterone (P < 0.001) in women and men. In women only, a positive relationship was evident between MBG excretion and LF HRV in multivariate adjusted regression analyses (Adj. R ²= 0.33; β = 0.11; P = 0.030). In men, MBG excretion associated positively with HF HRV in similar regression analyses (R ² = 0.36; β = 0.12; P = 0.034). Sex-specific results were corroborated only in blacks, namely, a positive association of MBG excretion with LF HRV in black women (R ² = 0.38; β = 0.13; P = 0.036), and negative association with HF HRV in black men (R ² = 0.40; β = 0.18; P = 0.045). No relationships were evident in white women (P = 0.58) or men (P = 0.27). Conclusion: Our findings in this human cohort support suggested mechanisms whereby MBG is elevated as a result of increased salt intake, including autonomic activity, previously demonstrated in Dahl salt-sensitive hypertension.

The African Prospective study on the Early Detection and Identification of Cardiovascular disease and Hypertension (African-PREDICT): Design, recruitment and initial examination

Background

Globally hypertension is stabilising, but in sub-Saharan Africa the incidence of hypertension remains on an increase. Although this might be attributed to poor healthcare and ineffective antihypertensive treatment, there is a limited understanding of population and individual-specific cardiovascular pathophysiology – necessary for effective prevention and treatment strategies in Africa. As there is a lack of longitudinal studies tracking the early pathophysiological development of hypertension in black populations, the African-PREDICT study was initiated. The purpose of this paper is to describe the detailed methodology and baseline cohort profile of the study.

Methods and results

From 2013 to 2017, the study included 1202 black (N = 606) and white (N = 596) men and women (aged 20–30 years) from South Africa – screened to be healthy and clinic normotensive. At baseline, and each 5-year follow-up examination, detailed measures of health behaviours, cardiovascular profile and organ damage are taken. Also, comprehensive biological sampling for the ‘omics’ and biomarkers is performed. Overall, the baseline black and white cohort presented with similar ages, clinic and 24-hour blood pressures, but black adults had lower socioeconomic status and higher central systolic blood pressure than white individuals.

Conclusions

The prospective African-PREDICT study in young black and white adults will contribute to a clear understanding of early cardiovascular disease development.

Large artery stiffness is associated with marinobufagenin in young adults: the African-PREDICT study

OBJECTIVES

The cardiotonic steroid, marinobufagenin (MBG), has been shown to play a physiological natriuretic role in response to salt intake. However, recent studies in clinical and animal models demonstrated possible links between elevated levels of endogenous MBG and increased arterial stiffness. Large artery stiffness is a known predictor of future cardiovascular disease. We, therefore, investigated whether large artery stiffness relates to 24-h urinary MBG excretion in young apparently healthy black and white adults.

METHODS

This study included data of 711 participants (black 51%, men 42%, mean age 24.8 ± 3.02 years). We measured the carotid-femoral pulse wave velocity (cfPWV), 24-h urinary MBG and sodium excretion.

RESULTS

In single, partial and multivariable adjusted (Adj.) regression analyses, we found a persistent positive association between cfPWV and MBG excretion in women [Adj. R = 0.23; standardized (std.) β = 0.15; P = 0.002], but not men (Adj. R = 0.17; std. β = 0.06; P = 0.31). Multiple regression models were adjusted for ethnicity, age, waist-to-height ratio, mean arterial pressure, high-density lipoprotein cholesterol, C-reactive protein, γ-glutamyl transferase and glucose.

CONCLUSION

In conclusion, already at a young age heightened endogenous MBG levels may contribute to large artery stiffness in women via pressure-independent mechanisms, increasing their risk for future cardiovascular disease.

Dietary Sodium Restriction Reduces Arterial Stiffness, Vascular TGF-β-Dependent Fibrosis and Marinobufagenin in Young Normotensive Rats

High salt (HS) intake stimulates the production of marinobufagenin (MBG), an endogenous steroidal Na/K-ATPase ligand, which activates profibrotic signaling. HS is accompanied by a blood pressure (BP) increase in salt-sensitive hypertension, but not in normotensive animals. Here, we investigated whether HS stimulates MBG production and activates transforming growth factor-beta (TGF-β) profibrotic signaling in young normotensive rats, and whether these changes can be reversed by reducing salt to a normal salt (NS) level. Three-month old male Sprague–Dawley rats received NS for 4 and 8 weeks (0.5% NaCl; NS4 and NS8), or HS for 4 and 8 weeks (4% NaCl; HS4 and HS8), or HS for 4 weeks followed by NS for 4 weeks (HS4/NS4), n = 8/group. Systolic BP (SBP), pulse wave velocity (PWV), MBG excretion, aortic collagen 1α2, collagen 4α1 and TGF-β, Smad2, Smad3, Fli-1 mRNA, and total collagen abundance were measured at baseline (BL), and on weeks 4 and 8. Statistical analysis was performed using one-way ANOVA. SBP was not affected by HS (125 ± 5 and 126 ± 6 vs. 128 ± 7 mmHg, HS4 and HS8 vs. BL, p > 0.05). HS increased MBG (164 ± 19 vs. 103 ± 19 pmol/24 h/kg, HS4 vs. BL, p < 0.05) and PWV (3.7 ± 0.2 vs. 2.7 ± 0.2 m/s, HS4 vs. NS4, p < 0.05). HS8 was associated with a further increase in MBG and PWV, with an increase in aortic Col1a2 80%), Col4a1 (50%), Tgfb1 (30%), Smad2 (30%) and Smad3 (45%) mRNAs, and aortic wall collagen (180%) vs. NS8 (all p < 0.05). NS following HS downregulated HS-induced factors: in HS4/NS4, the MBG level was 91 ± 12 pmol/24 h/kg (twofold lower than HS8, p < 0.01), PWV was 3.7 ± 0.3 vs. 4.7 ± 0.2 m/s (HS4/NS4 vs. HS8, p < 0.05), aortic wall Tgfb1, Col1a2, Col4a1, Smad2, Smad3 mRNAs, and collagen abundance were reversed by salt reduction to the BL levels (p < 0.05). HS was associated with an activation of TGF-β signaling, aortic fibrosis and aortic stiffness accompanied by an MBG increase in the absence of SBP changes in young normotensive rats. The reduction of dietary salt following HS decreased MBG, PWV, aortic wall collagen and TGF-β. Thus, HS-induced aortic stiffness in normotensive animals occurred in the context of elevated MBG, which may activate SMAD-dependent TGF-β pro-fibrotic signaling. This data suggests that a decrease in salt consumption could help to restore aortic elasticity and diminish the risk of cardiovascular disease by reducing the production of the pro-fibrotic factor MBG.

Marinobufagenin and left ventricular mass in young adults: The African-PREDICT study

Background The endogenous steroidal inhibitor of sodium-potassium-dependent adenosine triphosphate and natriuretic hormone, marinobufagenin, plays a physiological role in ionic homeostasis. Animal models suggest that elevated marinobufagenin adversely associates with cardiac and renal, structural and functional alterations. It remains uncertain whether marinobufagenin relates to the early stages of target organ damage development, especially in young adults without cardiovascular disease. We therefore explored whether elevated 24-hour urinary marinobufagenin excretion was related to indices of subclinical target organ damage in young healthy adults. Design This cross-sectional study included 711 participants from the African-PREDICT study (black 51%, men 42%, 24.8 ± 3.02 years). Methods We assessed cardiac geometry and function by two-dimensional echocardiography and pulse wave Doppler imaging. 24-Hour urinary marinobufagenin and sodium excretion were measured, and the estimated glomerular filtration rate determined. Results Across marinobufagenin excretion quartiles, left ventricular mass ( P < 0.001), end diastolic volume ( P < 0.001), stroke volume ( P = 0.004) and sodium excretion ( P < 0.001) were higher within the fourth compared with the first quartile. Partial regression analyses indicated that left ventricular mass ( r = 0.08, P = 0.043), end diastolic volume ( r = 0.10, P = 0.010) and stroke volume ( r = 0.09, P = 0.022) were positively related to marinobufagenin excretion. In multivariate-adjusted regression analysis, left ventricular mass associated positively with marinobufagenin excretion only in the highest marinobufagenin excretion quartile (adjusted R²= 0.20; β = 0.15; P = 0.043). This relationship between left ventricular mass and marinobufagenin excretion was evident in women (adjusted R²= 0.06; β = 0.127; P = 0.015) but not in men (adjusted R²= 0.06; β = 0.007; P = 0.92). Conclusions Left ventricular mass positively and independently associates with marinobufagenin excretion in young healthy adults with excessively high marinobufagenin excretion. Women may be more sensitive to the effects of marinobufagenin on early structural cardiac changes.

Low to Normal Plasma Levels of Marinobufagenin 24 Hours or More after an Ischemic Stroke: A Pilot Study

Background

Numerous studies have demonstrated a strong relationship between circulating levels of marinobufagenin (MBG) and salt-sensitivity. Since salt-sensitive hypertensives have increased plasma levels of MBG and are known to be at a higher risk of having cardiovascular events, stroke and increased mortality, we evaluated the possibility of an association between MBG and ischemic stroke. In this pilot study, we determined plasma MBG levels in patients after surviving an ischemic stroke compared to similar age and gender groups of treated hypertensives and normotensive controls.

Methods

We measured plasma MBG levels in a total of 40 participants subdivided into three groups: After an ischemic stroke STR (n = 13), participants with a diagnosis of hypertension receiving blood pressure medication HT (n = 14) and normotensive control subjects CTL (n = 13). We used inferential statistics (parametric or non-parametric) and ordered logistic regression models (unadjusted and adjusted) and all statistical analyses were performed using Stata 14.

Results

We did not include a subject from the CTL group because of a diagnosis of glucose-6-phosphate dehydrogenase deficiency and an extreme plasma MBG value of 2,246 pmol/L. Participants' mean age was 60.4 ± 11.5 years; 56% were male. There was no significant difference between study groups (p > 0.05) for gender, age, and body mass index. HbA1c levels were significantly higher in the STR as compared to the CTL p < 0.05). In the STR group MBG levels were below the normal range (< 200 pmol/L) in three (23%), eight (61%) were in the normal range (200-400 pmol/L), while two (16%) had increased MBG values (> 400 pmol/L). Also, among the STR, the plasma MBG levels did not differ between those receiving and not receiving thrombolytic therapy (p > 0.05). From the 14 HT participants, six (43%) had MBG plasma levels within the normal range, and eight (57%) had high concentrations (> 400 pmol/L). Four (29%) of the treated hypertensives had extreme MBG levels (> 1,000 pmol/L) and normal values of blood pressure.

Conclusion

There was no significant elevation of plasma MBG in survivors 24 h or more after an ischemic stroke. The extreme values of plasma MBG in 29% of the treated hypertensives suggests the presence of salt-sensitivity and a possible side effect of a specific combination of medications. Both of these findings contribute new knowledge to the design of studies to define if there is an MBG molecular mechanism underlying the complex associations among salt-sensitivity, hypertension, and ischemic stroke.