Multiple urinary peptides are associated with hypertension: a link to molecular pathophysiology.

OBJECTIVES: Hypertension is a common condition worldwide; however, its underlying mechanisms remain largely unknown. This study aimed to identify urinary peptides associated with hypertension to further explore the relevant molecular pathophysiology. METHODS: Peptidome data from 2876 individuals without end-organ damage were retrieved from the Human Urinary Proteome Database: general population (discovery) or type 2 diabetic (validation) cohorts. Participants were divided based on systolic blood pressure (SBP) and diastolic BP (DBP) into hypertensive (SBP ≥140 mmHg and/or DBP ≥90 mmHg) and normotensive (SBP <120 mmHg and DBP <80 mmHg, without antihypertensive treatment) groups. Differences in peptide abundance between the two groups were confirmed using an external cohort (n = 420) of participants without end-organ damage, matched for age, BMI, eGFR, sex, and the presence of diabetes. Furthermore, the association of the peptides with BP as a continuous variable was investigated. The findings were compared with peptide biomarkers of chronic diseases and bioinformatic analyses were conducted to highlight the underlying molecular mechanisms. RESULTS: Between hypertensive and normotensive individuals, 96 (mostly COL1A1 and COL3A1) peptides were found to be significantly different in both the discovery (adjusted) and validation (nominal significance) cohorts, with consistent regulation. Of these, 83 were consistently regulated in the matched cohort. A weak, yet significant, association between their abundance and standardized BP was also observed. CONCLUSION: Hypertension is associated with an altered urinary peptide profile with evident differential regulation of collagen-derived peptides. Peptides related to vascular calcification and sodium regulation were also affected. Whether these modifications reflect the pathophysiology of hypertension and/or early subclinical organ damage requires further investigation.

Early vascular ageing phenotypes and urinary targeted metabolomics in children and young adults: the ExAMIN Youth SA and African-PREDICT studies.

Some individuals are susceptible to accelerated biological ageing, resulting in premature alterations in arterial structure and function. Identifying early-onset vascular ageing characterised by arterial stiffening is vital for intervention and preventive strategies. We stratified and phenotyped healthy children (5-9 yrs) and young adults (20-30 yrs) into their vascular ageing extremes established by carotid-femoral pulse wave velocity (cfPWV) percentiles (i.e., healthy vascular ageing (HVA) and early vascular ageing (EVA)). We compared anthropometric, cardiovascular, and metabolomic profiles and explored associations between cfPWV and urinary metabolites. Children and adults in the EVA groups displayed higher levels of adiposity, cardiovascular, and lifestyle risk factors (adults only) (all p ≤ 0.018). In adults, several urinary metabolites were lower in the EVA group (all q ≤ 0.039) when compared to the HVA group, with no differences observed in children. In multiple regression analysis (adults only), we found inverse associations between cfPWV with histidine (adj. R2 = 0.038; ß = -0.192; p = 0.013) and beta-alanine (adj. R2 = 0.034; ß = -0.181; p = 0.019) in the EVA group, but with arginine (adj. R2 = 0.021; ß = -0.160; p = 0.024) in the HVA group. The inverse associations of beta-alanine and histidine with cfPWV in the EVA group is suggestive that asymptomatic young adults who present with an altered metabolomic and less desired cardiovascular profile in combination with unfavourable lifestyle behaviours may be predisposed to early-onset vascular ageing. Taken together, screening on both a phenotypic and metabolic level may prove important in the early detection, prevention, and intervention of advanced biological ageing.

Urinary metabolomics, dietary salt intake and blood pressure: the African-PREDICT study.

In Black populations excessive salt intake may exacerbate the genetic predisposition to hypertension and promote the early onset of cardiovascular disease. Ethnic differences in the interaction between sodium intake and the metabolome may play a part in hypertension and cardiovascular disease development. We determined (1) urinary amino acid and acylcarnitine profiles of young Black and White adults according to low, moderate, and high dietary salt intake, and (2) investigated the triad of salt intake, systolic blood pressure (SBP), and the associated metabolomics profile. This study included 447 White and 380 Black adults aged 20-30 years from the African-PREDICT study. Estimated salt intake was determined from 24-hour urinary sodium levels. Urinary amino acids and acylcarnitines were measured using liquid chromatography-tandem mass spectrometry. Black adults exhibited no significant differences in SBP, amino acids, or acylcarnitines across low (<5g/day), moderate (5-10g/day), and high (>10g/day) salt intake. White adults with a high salt intake had elevated SBP compared to those with low or moderate intakes (p < 0.001). Furthermore, gamma-aminobutyric acid (GABA) (q = 0.020), citrulline (q = 0.020), glutamic acid (q = 0.046), serine (q = 0.054) and proline (q = 0.054) were lowest in those with higher salt intake. Only in White and not Black adults did we observe inverse associations of clinic SBP with GABA (Adj. R2 = 0.34; Std. ß = -0.133; p = 0.003), serine (Adj. R2 = 0.33; Std. ß = -0.109; p = 0.014) and proline (Adj. R2 = 0.33; Std. ß = -0.109; p = 0.014). High salt intake in White, but not in black adults, were related to metabolomic changes and may contribute to pathophysiological mechanisms associated with increased BP.

Identifying a metabolomics profile associated with masked hypertension in two independent cohorts: Data from the African-PREDICT and SABPA studies.

Individuals with masked hypertension (MHT) have a greater risk of adverse cardiovascular outcomes than normotensive (NT) individuals. Exploring metabolomic differences between NT and MHT individuals may help provide a better understanding of the etiology of MHT. We analyzed data from 910 young participants (83% NT and 17% MHT) (mean age 24 ± 3 years) from the African-PREDICT and 210 older participants (63% NT and 37% MHT) from the SABPA (mean age 42 ± 9.6 years) studies. Clinic and ambulatory blood pressures (BPs) were used to define BP phenotypes. Urinary amino acids and acylcarnitines were measured using liquid chromatography time-of-flight mass spectrometry in SABPA and liquid chromatography tandem mass spectrometry in the African-PREDICT studies. In the SABPA study, amino acids (leucine/isoleucine, valine, methionine, phenylalanine), free carnitine (C0-carnitine), and acylcarnitines C3 (propionyl)-, C4 (butyryl)-carnitine and total acylcarnitine) were higher in MHT than NT adults. In the African-PREDICT study, C0- and C5-carnitines were higher in MHT individuals. With unadjusted analyses in NT adults from the SABPA study, ambulatory SBP correlated positively with only C3-carnitine. In MHT individuals, positive correlations of ambulatory SBP with leucine/isoleucine, valine, methionine, phenylalanine, C0-carnitine and C3-carnitine were evident (all p < 0.05). In the African-PREDICT study, ambulatory SBP correlated positively with C0-carnitine (r = 0.101; p = 0.006) and C5-carnitine (r = 0.195; p < 0.001) in NT adults and C5-carnitine in MHT individuals (r = 0.169; p = 0.034). We demonstrated differences between the metabolomic profiles of NT and MHT adults, which may reflect different stages in the alteration of branched-chain amino acid metabolism early on and later in life.

Elevated blood pressure positively associates with alpha-1 microglobulin in prepubescent children: the ExAMIN Youth SA study.

OBJECTIVES AND METHODS: Hypertension is a growing health concern in childhood populations and individuals of African descent. As the kidneys play a significant role in blood pressure regulation, we compared alpha-1 microglobulin (A1M) as a marker of proximal tubular function between young healthy black and white children (n = 957; aged: 5-9 years) and explored its association with blood pressure. RESULTS: The black children had higher levels of A1M (P < 0.001) and higher DBP (P < 0.001) when compared with their white counterparts. In multiple regression analysis, SBP (adj. R2 = 0.173, ß = 0.151; P < 0.001) and DBP (adj. R2 = 0.110, ß = 0.179; P < 0.001) associated positively with A1M in the black children. In binary logistic regression, each standard deviation increase in A1M increased the odds of having elevated blood pressure by 28% (P = 0.002) in the black group, independent of age, sex, BMI z-score and body height. No significance was reached in the white children. CONCLUSION: Our findings highlight the importance of a marker of proximal tubular function, especially in children of black ethnicity, in the setting of elevated blood pressure. Early childhood screening for elevated blood pressure remains essential in order to promote primary prevention of hypertension and early onset kidney damage in children.

The association between serum vitamin D and body composition in South African HIV-infected women.

BACKGROUND: HIV and antiretroviral therapy (ART) alter vitamin D metabolism, and may be associated with bone loss. OBJECTIVES: The aim of this study was to determine the association between serum 25-hydroxyvitamin D (25(OH)D) and body composition in postmenopausal South African women living with HIV and on ART. METHOD: In this 2-year longitudinal study on 120 women conducted in the North West province of South Africa, serum 25(OH)D concentration, bone mineral density (BMD) at three sites, lean mass and percentage of body fat (%BF) were measured by dual-energy X-ray absorptiometry (DXA). Multivariable linear mixed models were used to assess the association between serum 25(OH)D and body composition over 2 years. Linear mixed models were also used to determine the longitudinal association between lean mass, %BF and BMD. RESULTS: Vitamin D deficiency and insufficiency increased from baseline (10.2% and 19.5%) to 11.5% and 37.5%, respectively, after 2 years. Serum 25(OH)D decreased significantly, however, with a small effect size of 0.39 (P = 0.001), whilst total BMD (effect size 0.03, P = 0.02) and left hip femoral neck (FN) BMD (effect size 0.06, P = 0.0001) had significant small increases, whereas total spine BMD did not change over the 2 years. Serum 25(OH)D had no association with any BMD outcomes. Lean mass had a stronger positive association with total spine and left FN BMD than %BF. CONCLUSION: Serum 25(OH)D was not associated with any BMD outcomes. Maintenance of lean mass could be important in preventing bone loss in this vulnerable group; however, longer follow-up may be necessary to confirm the association.

Urinary proteomics combined with home blood pressure telemonitoring for health care reform trial: rational and protocol.

BACKGROUND: Hypertension and diabetes cause chronic kidney disease (CKD) and diastolic left ventricular dysfunction (DVD) as forerunners of disability and death. Home blood pressure telemonitoring (HTM) and urinary peptidomic profiling (UPP) are technologies enabling prevention. METHODS: UPRIGHT-HTM (Urinary Proteomics Combined with Home Blood Pressure Telemonitoring for Health Care Reform [NCT04299529]) is an investigator-initiated 5-year clinical trial with patient-centred design, which will randomise 1148 patients to be recruited in Europe, sub-Saharan Africa and South America. During the whole study, HTM data will be collected and freely accessible for patients and caregivers. The UPP, measured at enrolment only, will be communicated early during follow-up to 50% of patients and their caregivers (intervention), but only at trial closure in 50% (control). The hypothesis is that early knowledge of the UPP risk profile will lead to more rigorous risk factor management and result in benefit. Eligible patients, aged 55-75 years old, are asymptomatic, but have ≥5 CKD- or DVD-related risk factors, preferably including hypertension, type-2 diabetes, or both. The primary endpoint is a composite of new-onset intermediate and hard cardiovascular and renal outcomes. Demonstrating that combining UPP with HTM is feasible in a multicultural context and defining the molecular signatures of early CKD and DVD are secondary endpoints. EXPECTED OUTCOMES: The expected outcome is that application of UPP on top of HTM will be superior to HTM alone in the prevention of CKD and DVD and associated complications and that UPP allows shifting emphasis from treating to preventing disease, thereby empowering patients.

Vascular function and cardiovascular risk in a HIV infected and HIV free cohort of African ancestry: baseline profile, rationale and methods of the longitudinal EndoAfrica-NWU study.

BACKGROUND: People living with the Human Immunodeficiency Virus (PLHIV) have an increased susceptibility to develop non-communicable diseases such as cardiovascular disease (CVD). Infection with HIV contributes to the development of CVD independent of traditional risk factors, with endothelial dysfunction being the central physiological mechanism. While HIV-related mortality is declining due to antiretroviral treatment (ART), the number of deaths due to CVD is rising in South Africa - the country with the highest number of PLHIV and the world's largest ART programme. The EndoAfrica study was developed to determine whether HIV infection and ART are associated with cardiovascular risk markers and changes in vascular structure and function over 18 months in adults from different provinces of South Africa. This paper describes the rationale, methodology and baseline cohort profile of the EndoAfrica study conducted in the North West Province, South Africa. METHODS: In this case-control study, conducted between August 2017 and June 2018, 382 volunteers of African descent (276 women; 106 men), comprising of 278 HIV infected and 104 HIV free individuals were included. We measured health behaviours, a detailed cardiovascular profile, and performed biomarker analyses. We compared baseline characteristics, blood pressure, vascular function and biochemical markers between those infected and HIV free. RESULTS: At baseline, the HIV infected participants were older (43 vs 39 years), less were employed (21% vs 40%), less had a tertiary education (7% vs 16%) and their body mass index was lower (26 vs 29 kg/m2) than that of the HIV free participants. While the cardiovascular profile, flow-mediated dilation and pulse wave velocity did not differ, glycated haemoglobin was lower (p = 0.017) and total cholesterol, high density lipoprotein cholesterol, triglycerides, gamma-glutamyltransferase and tobacco use were higher (all p < 0.047) in PLHIV. CONCLUSION: Despite PLHIV being older, preliminary cross-sectional analysis suggests that PLHIV being treated with ART do not have poorer endothelial or vascular function compared to the HIV free participants. More detailed analyses on the baseline and follow-up data will provide further clarity regarding the cardiovascular profile of South Africans living with HIV.

Urinary Metabolites and Their Link with Premature Arterial Stiffness in Black Boys: The ASOS Study.

BACKGROUND AND AIMS: Black boys (6-8 years of age) were shown to have higher pulse wave velocity with potential early vascular compromise. We aimed to compare predefined urinary metabolites in black and white boys to explore associations of pulse wave velocity with these metabolites. METHODS AND RESULTS: We included 40 white and 40 black apparently healthy boys between the ages of 6 and 8 years. Femoral pulse wave velocity was measured along with various metabolites using liquid chromatography tandem mass spectrometry (LC-MS/MS) and gas chromatography-time of flight-mass spectrometry (GC-TOF-MS) methods. Pulse wave velocity and diastolic blood pressure were higher in the black compared to the white boys (both p ≤ 0.002). Isovalerylcarnitine was lower and 1-metylhistidine tended to be lower (p = 0.002 and p = 0.073, respectively), whereas L-proline levels tended to be higher (p = 0.079) in the black compared to the white boys. In single, partial, and multiple regression analyses, pulse wave velocity correlated inversely with ß-alanine (ß = -0.414; p = 0.008) and 1-methylhistidine (ß = -0.347; p = 0.032) and positively with L-proline (ß = 0.420; p = 0.008), threonic acid (ß = 0.977; p = 0.033), and malonic acid (ß = 0.348; p = 0.030) in black boys only. CONCLUSION: Our study is the first to discover the associations of pulse wave velocity with ß-alanine, 1-methylhistidine, and L-proline in children from South Africa, which may suggest potential early compromise in cardiac protective metabolic pathways in black boys as young as 6 years of age.

Defensive coping and essential amino acid markers as possible predictors for structural vascular disease in an African and Caucasian male cohort: The SABPA study.

Defensive coping (DefS), oxidative stress, inflammation, and related amino acids (phenylalanine [Phe] and tyrosine [Tyr]) have been implicated in cardiovascular disease. This study assessed whether inflammation, oxidative stress, changes in essential amino acids, and altered coping strategies are correlated with subclinical vascular changes in African (n = 82) and Caucasian (n = 100) men from the Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study. The Coping Strategy Indicator questionnaire identified DefS participants. Ambulatory blood pressure (BP) was monitored for 24 h, whereas carotid intima media thickness (CIMT) and cross-sectional wall area (CSWA) were determined ultrasonically. Essential amino acids were analyzed with a liquid chromatography tandem mass spectrometry method. Oxidative-inflammatory markers were measured by spectrophotometry. African men had poorer health than Caucasian men, including higher alcohol abuse, elevated BP, abdominal obesity, physical inactivity, and elevated inflammation. Phe (p < .001) and Phe/Tyr ratio (p = .006) as well as CIMT (p = .032) were higher in African men. DefS African men had higher levels of Phe (p = .002) and Phe/Tyr (p = .009) compared to DefS Caucasian men; these differences were not observed in non-DefS men. Systolic BP and inflammation (C-reactive protein) were positively associated with left (L-) CSWA, while Phe/Tyr was negatively associated with L-CSWA in DefS African men. African males presented with elevated Phe and Phe/Tyr ratio, catecholamine precursors, worsening during DefS-possibly driven by inflammation and BP contributing to structural vascular abnormalities.

Association of 25-hydroxyvitamin D and parathyroid hormone with the metabolic syndrome in black South African women.

The relationship between 25 hydroxyvitamin D (25(OH)D), parathyroid hormone (PTH) and metabolic traits appear to differ among ethnicities and may be influenced by obesity. The aim of the study was to examine the association of serum 25(OH)D or PTH with metabolic syndrome (MetS) while controlling for adiposity in black women. Using a cross-sectional study design, 209 urban black women aged ≥ 43 years from the North West Province, South Africa, were included. Multiple regression models were used to explore the relationship between 25(OH)D or PTH and body composition. To explore the association between 25(OH)D or PTH and MetS, a separate variable was created including at least 3 of the MetS criteria, but excluding elevated waist circumference as a diagnostic criterion in a logistic regression model. The majority of the women (69.9%) were overweight or obese and 65.5% of the women had excessive adiposity using the age-specific cut-off points for body fat percentage. All body composition variables were positively associated with PTH, whereas body mass index and waist circumference, but not body fat percentage, had negative associations with 25(OH)D also after adjusting for confounders. Before and after adjusting for age, body fat, habitual physical activity, tobacco use, season of data collection, and estimated glomerular filtration rate, neither 25(OH)D nor PTH showed significant associations with MetS. Although PTH was positively associated and 25(OH)D was negatively associated with adiposity in black women, there was no association between either 25(OH)D or PTH and MetS in this study population, nor did adiposity influence these relationships.

Masked hypertension and its associated cardiovascular risk in young individuals: the African-PREDICT study.

Hypertension prevalence is increasing globally, yet little is known about the occurrence of masked hypertension (MHT) in young, sub-Saharan African adults, and how it relates to elevated cardiovascular risk. The African-PREDICT study (recruitment based on normotensive clinic blood pressure (BP)) determined the frequency of MHT and its relationship with arterial stiffness and biochemical markers of inflammation and endothelial activation. We included men and women (n=352), 20-30 years, screened for normotensive clinic BP (54% white, 40% men). Clinic BP, ambulatory blood pressure monitoring (ABPM), central systolic pressure, aortic pulse wave velocity (aPWV), augmentation index, anthropometry, physical activity and biochemical markers of cardiovascular risk were assessed (lipids, glucose, insulin, markers of endothelial activation and inflammation). Eighteen percent of the study population had MHT (60% white, 68% men). Those with MHT had increased adiposity, clinic-, ABPM- (24-h, day and night) and central-BP (within normal ranges), heart rate, aPWV and biochemical markers of cardiovascular risk, compared with normotensives (all P<0.05). Using multivariable adjusted odds ratios, we found that MHT was associated with increased likelihood for higher aPWV (odds ratio (OR)=1.567, P=0.010), insulin (OR=1.499, P=0.049), monocyte chemoattractant protein-1 (OR=1.499, P=0.026), vascular cellular adhesion molecule (OR=1.409, P=0.042) and C-reactive protein (OR=1.440, P=0.044). In a young adult (supposedly healthy) cohort, the occurrence of MHT is alarming, especially since MHT further demonstrated elevated cardiovascular risk via increased adiposity, arterial stiffness, endothelial activation and inflammation. Detection of MHT is crucial to increase awareness of elevated cardiovascular risk, and to ensure the required lifestyle and/or pharmaceutical interventions.

Testosterone and acute stress are associated with fibrinogen and von Willebrand factor in African men: the SABPA study.

BACKGROUND: Low testosterone, acute and chronic stress and hypercoagulation are all associated with hypertension and hypertension-related diseases. The interaction between these factors and future risk for coronary artery disease in Africans has not been fully elucidated. In this study, associations of testosterone, acute cardiovascular and coagulation stress responses with fibrinogen and von Willebrand factor in African and Caucasian men in a South African cohort were investigated. METHODS: Cardiovascular variables were studied by means of beat-to-beat and ambulatory blood pressure monitoring. Fasting serum-, salivary testosterone and citrate coagulation markers were obtained from venous blood samples. Acute mental stress responses were evoked with the Stroop test. RESULTS: The African group demonstrated a higher cardiovascular risk compared to Caucasian men with elevated blood pressure, low-grade inflammation, chronic hyperglycemia (HbA1c), lower testosterone levels, and elevated von Willebrand factor (VWF) and fibrinogen levels. Blunted testosterone acute mental stress responses were demonstrated in African males. In multiple regression analyses, higher circulating levels of fibrinogen and VWF in Africans were associated with a low T environment (R(2) 0.24-0.28; p≤0.01), but only circulating fibrinogen in Caucasians. Regarding endothelial function, a low testosterone environment and a profile of augmented α-adrenergic acute mental stress responses (diastolic BP, D-dimer and testosterone) were associated with circulating VWF levels in Africans (Adj R(2) 0.24; p<0.05). CONCLUSIONS: An interdependence between acute mental stress, salivary testosterone, D-dimer and vascular responses existed in African males in their association with circulating VWF but no interdependence of the independent variables occurred with fibrinogen levels.

Carotid cross-sectional wall area is significantly associated with serum leptin levels, independent of body mass index: the SABPA study.

Hypertension and obesity are serious health burdens in sub-Saharan Africa. Urbanized Africans seem to be more susceptible to the development of these diseases than Caucasians. Current research suggests that leptin may be an important contributor to the development of hypertension and atherosclerosis. The aim of this study was to investigate leptin levels and their associations with cardiovascular function in urbanized Africans and Caucasians. Serum leptin, ambulatory blood pressure and carotid intima-media thickness were measured, and the cross-sectional wall area (CSWA) was calculated. The results showed that Africans had higher leptin levels (P<0.001), ambulatory blood pressure (P<0.001), carotid intima-media thickness (P<0.01) and CSWA (P<0.01) than Caucasians. As we found no interaction between ethnicity and gender for the association between leptin and the cardiovascular variables, we focused mainly on the total group of Africans and Caucasians. In single, partial and multiple regression analyses, positive associations of ambulatory systolic blood pressure (ß=0.256; P<0.001), diastolic blood pressure (ß=0.143; P=0.012), pulse pressure (ß=0.327; P<0.001) and CSWA (ß=0.107; P=0.038) with leptin were observed. Even after adjusting for body mass index (BMI), the association between CSWA (ß=0.107; P=0.038) and leptin remained. Our findings therefore suggest that leptin may contribute to the development of atherosclerosis, independent of BMI.