Proteomic-Biostatistic Integrated Approach for Finding the Underlying Molecular Determinants of Hypertension in Human Plasma

Abstract

1 has shown that despite the availability of several effective blood pressure (BP)-lowering drugs, the burden of disease caused by hypertension rather than decreasing has continuously incremented worldwide. This indicates limitations of the diagnostic and therapeutic strategies to date implemented in managing hypertension and underscores the urgent need of new strategies for overcoming these limitations and reducing their consequences on public health.Under the diagnostic aspect, hypertension is identified on the simple basis of several BP measurements taken under standard conditions, but it is well-known that BP is extremely variable, and its measurements are scarcely reproducible.2 This has brought to a long-lasting and continuing discussion on the Abstract-Despite advancements in lowering blood pressure, the best approach to lower it remains controversial because of the lack of information on the molecular basis of hypertension. We, therefore, performed plasma proteomics of plasma from patients with hypertension to identify molecular determinants detectable in these subjects but not in controls and vice versa. Plasma samples from hypertensive subjects (cases; n=118) and controls (n=85) from the InGenious HyperCare cohort were used for this study and performed mass spectrometric analysis. Using biostatistical methods, plasma peptides specific for hypertension were identified, and a model was developed using least absolute shrinkage and selection operator logistic regression. The underlying peptides were identified and sequenced offline using matrix-assisted laser desorption ionization orbitrap mass spectrometry. By comparison of the molecular composition of the plasma samples, 27 molecular determinants were identified differently expressed in cases from controls. Seventy percent of the molecular determinants selected were found to occur less likely in hypertensive patients. In cross-validation, the overall R 2 was 0.434, and the area under the curve was 0.891 with 95% confidence interval 0.8482 to 0.9349, P<0.0001. The mean values of the cross-validated proteomic score of normotensive and hypertensive patients were found to be −2.007±0.3568 and 3.383±0.2643, respectively, P<0.0001. The molecular determinants were successfully identified, and the proteomic model developed shows an excellent discriminatory ability between hypertensives and normotensives. The identified molecular determinants may be the starting point for further studies to clarify the molecular causes of hypertension. 2 Although the use of these subtypes of hypertension has become popular in the management of hypertension, there are no agreements yet on strategies for their management.3 Under the therapeutic aspect, several classes and compounds have been shown to effectively lower BP, thus reducing cardiovascular disease risk. 4,5 However, each of these classes is known to be effective only in a proportion of hypertensive patients, and in the absence of proven predictors of their effect, they are commonly prescribed by a trial and error str...

Proteomic Analysis of Longitudinal Changes in Blood Pressure

“…Studies evaluating the association between circulating proteomics and BP progression are rare. Two previous cross-sectional studies have used mass spectrometry based proteomics to discriminate between hypertensive and normotensive individuals [60,61]. Xu et al studied serum from 47 patients with essential hypertension and 47 healthy controls, and identified differences between those groups in multiple proteins [60].…”

“…Xu et al studied serum from 47 patients with essential hypertension and 47 healthy controls, and identified differences between those groups in multiple proteins [60]. Gajjala et al used a similar design to investigate 118 hypertensive persons and 85 controls [61]. Both studies are limited by their cross-sectional design, small sample sizes and lack of replication.…”

Novel plasma peptide markers involved in the pathology of CKD identified using mass spectrometric approach

“…Peptides that were selected by the model were identified off-line from the reconstituted samples by MALDI-time of flight (TOF)/TOF fragment ion analysis as well as by LTQ Orbitrap XL mass spectrometry. One microliter of sample and α-4-hydroxycinnamic acid matrix was spotted on the target (MTP AnchorChip 400/384; Bruker-Daltonics, Germany) using dried droplet method α-4-hydroxycinnamic acid (Sigma-Aldrich, Germany) as described previously [12]. All measurements were performed on a Bruker Ultraflex-III TOF/TOF mass spectrometry (Bruker-Daltonics, Germany) that was equipped with a Smart Beam Laser operated at a repetition rate of 100–200 Hz and operated in positive mode.…”

“…The value of the LC-MS technique as a tool for identifying biomolecules such as peptides or metabolites is shown by recent studies in different renal diseases [8–12]. Using a mass spectrometric approach, we identified both peptides accumulating and peptides showing reduced concentrations with decreasing renal function, as these peptides may be of interest for establishing new therapeutic targets and/or new markers of CKD progression.…”

Utilizing proteomics to understand and define hypertension: where are we and where do we go?

“…An exemption is a recent study Gajjala et al [69] who employed a complex proteomic workflow to discover plasma peptides that are differentially expressed between normotensive and hypertensive subjects. A proteomic score has been developed to differentiate between patients and controls and includes a total of 27 molecular determinants, such as phosphoinositide 3-kinase regulator 1, osteocalcin, and nexilin.…”