Differential Associations for Salivary Sodium, Potassium, Calcium, and Phosphate Levels with Carotid Intima Media Thickness, Heart Rate, and Arterial Stiffness

Abstract

Salivary biomarkers may offer a noninvasive and easy sampling alternative in cardiovascular risk evaluation. The aim of the present study was to establish associations of salivary potassium, sodium, calcium, and phosphate levels with the cardiovascular phenotype determined by carotid ultrasound and carotid-femoral pulse wave velocity and to identify possible covariates for these associations. N = 241 samples of nonstimulated whole buccal saliva were obtained from subjects with (n = 143; 59%) or without (n = 98; 41%) hypertension. The potassium concentrations were 10-fold higher in saliva compared with plasma, whereas sodium concentrations exhibited the reverse relation between saliva and blood. There were no significant correlations between the levels of sodium, potassium, or calcium in saliva and plasma. All salivary electrolytes, except sodium, were significantly associated with age. In age-adjusted analyses, salivary potassium was significantly associated with carotid artery intima media thickness (cIMT) and carotid-femoral pulse wave velocity, and these associations were at the limit of significance in multivariate analyses including prevalent cardiovascular disease and risk factors. Body mass index was a significant confounder for salivary potassium. Salivary phosphate was significantly associated with cIMT in the multivariate analysis. Salivary potassium, calcium, and phosphate levels were significantly associated with heart rate in the univariate age-adjusted as well as in two different multivariate models, whereas no significant associations between sodium and heart rate were observed. In conclusion, the differential association of salivary electrolytes with cardiovascular phenotypes indicates that these electrolytes should be further studied for their predictive value as noninvasive biomarkers for cardiovascular risk evaluation.

Wireless, Flexible, Ion-Selective Electrode System for Selective and Repeatable Detection of Sodium

“…While real-time detection was enabled by deploying a Bluetooth low-energy module, a thin selective membrane electrode directly formed on a Cu contact pad on the flexible circuit showed excellent selectivity and long-term stability of sensitivity desired for repeatable use. The flexible sodium sensor exhibited near-Nernstian sensitivity of 56 mV/decade in sodium concentrations from 10 −4 to 1 M, covering a typical spectrum of saliva [5,6,36,37]. on calibration protocols and corresponding saliva detection, multiple times.…”

“…As illustrated in Figure 1c, the resulting saliva concentration was in the range of the reported values analyzed by commercial bulky devices. Specifically, normal saliva sodium level is in the range of 4 to 37 mM [36,37] and 6 to 35 mM [5,6] via photonic and electrochemical detection, respectively. The measured sodium concentration from our sensor ranged from 6.5 to 11.8 mM (7 times), which was consistent with the reported range.…”

“…Unlike the case of bulky devices, the thin-film ISE in this work showed great applicability for a wearable, portable system, along with wireless data acquisition, mechanical flexibility, and repeatable sensing capabilities. Comparison of measured sodium levels between commercial bulky devices (1-4) and our wireless system, where reference 1: 8.7-24 mM (generally known) [36], reference 2:4-37 mM (photometer) [37], reference 3:6-35 mM (electrochemical luminescence) [5], reference 4:10-13 mM (electrochemical ISE) [6], and our wireless film ISE: 6.5-11.8 mM. Figure 2 shows fabrication procedures for the film ISE, and verification strategies for the flexible structural designs.…”

“…Wireless, flexible film-based ion-selective electrodes (ISEs) have great potential for replacing existing bulky equipment with a miniaturized and mobile system for many clinical applications based on noninvasive measurements [1][2][3]. Selective detection of sodium in sweat and saliva, correlated to its level in blood [4], has been used for disease diagnosis (e.g., cystic fibrosis and cardiovascular risk) [5,6]. However, it is still very challenging for flexible film ISEs to offer repeatable and accurate measurements over an extended period since they are vulnerable to chemical and mechanical deformation.…”

“…(b) Repeated measurements of signal voltages in calibration sodium solutions (concentrations: 10 −4 , 10 −2 , 10 −1 , and 1 M) and human saliva. (c) Comparison of measured sodium levels between commercial bulky devices (1-4) and our wireless system, where reference 1: 8.7-24 mM (generally known)[36], reference 2: 4-37 mM (photometer)[37], reference 3: 6-35 mM (electrochemical luminescence)[5], reference 4: 10-13 mM (electrochemical ISE)[6], and our wireless film ISE: 6.5-11.8 mM.…”