Non-Invasive Estimation of Hydration Status Changes through Tear Fluid Osmolarity during Exercise and Post-Exercise Rehydration

Background/aimsSARS-CoV-2 is highly contagious. More evidence concerning extrapulmonary transmission routes such as the eyes is urgently needed. Although the humoral immune response is important in the viral containment, the local response in tears has not yet been studied. The aim of our study was twofold: to assess the prevalence of both SARS-CoV-2 RNA and antibodies in tear fluid.MethodsIn a first series, nasopharyngeal sampling and tear sampling by Schirmer test strips were performed in 26 acutely ill patients with COVID-19 to assess the presence of SARS-CoV-2 RNA by reverse transcription PCR. In a second series, IgG and IgA responses to SARS-CoV-2 spike protein in serum and tear fluid of convalescent individuals (n=22) were compared with control individuals (n=15) by ELISA.ResultsSARS-CoV-2 RNA was detected in tears of 7/26 (26.9%) patients with COVID-19. None of them had ocular symptoms. Convalescent individuals displayed a significant higher ratio of IgG (p<0.0001) and IgA (p=0.0068) in tears compared with control individuals. A sensitivity of 77.3% and specificity of 93.3% was observed for IgG, and 59.1% and 100% for IgA.ConclusionsOur results demonstrate the presence of SARS-CoV-2 RNA and a local IgG and IgA immune response in tear fluid. These data confirm the possibility of SARS-CoV-2 transmission through tear fluid and the importance of the eye as a first defence against SARS-CoV-2, indicating the potential of tears as a non-invasive surrogate for serum in monitoring the host immune response.

Download Full-text

The (in)dependency of blood and sweat sodium, chloride, potassium, ammonia, lactate and glucose concentrations during submaximal exercise

European Journal of Applied Physiology ◽

10.1007/s00421-020-04562-8 ◽

2020 ◽

Author(s):

L. Klous ◽

C. J. de Ruiter ◽

S. Scherrer ◽

N. Gerrett ◽

H. A. M. Daanen

Keyword(s):

Sodium Chloride ◽

Submaximal Exercise ◽

Blood Composition ◽

Maximum Heart Rate ◽

Post Exercise ◽

Non Invasive ◽

Potassium Lactate ◽

Blood Potassium ◽

Sweat Composition ◽

Sweat Sodium

Abstract Purpose To reduce the need for invasive and expensive measures of human biomarkers, sweat is becoming increasingly popular in use as an alternative to blood. Therefore, the (in)dependency of blood and sweat composition has to be explored. Methods In an environmental chamber (33 °C, 65% relative humidity; RH), 12 participants completed three subsequent 20-min cycling stages to elicit three different local sweat rates (LSR) while aiming to limit changes in blood composition: at 60% of their maximum heart rate (HRmax), 70% HRmax and 80% HRmax, with 5 min of seated-rest in between. Sweat was collected from the arm and back during each stage and post-exercise. Blood was drawn from a superficial antecubital vein in the middle of each stage. Concentrations of sodium, chloride, potassium, ammonia, lactate and glucose were determined in blood plasma and sweat. Results With increasing exercise intensity, LSR, sweat sodium, chloride and glucose concentrations increased (P ≤ 0.026), while simultaneously limited changes in blood composition were elicited for these components (P ≥ 0.093). Sweat potassium, lactate and ammonia concentrations decreased (P ≤ 0.006), while blood potassium decreased (P = 0.003), and blood ammonia and lactate concentrations increased with higher exercise intensities (P = 0.005; P = 0.007, respectively). The vast majority of correlations between blood and sweat parameters were non-significant (P > 0.05), with few exceptions. Conclusion The data suggest that sweat composition is at least partly independent of blood composition. This has important consequences when targeting sweat as non-invasive alternative for blood measurements.

Download Full-text

Proteins and microRNAs are differentially expressed in tear fluid from patients with Alzheimer’s disease

Scientific Reports ◽

10.1038/s41598-019-51837-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 6

Author(s):

Aidan Kenny ◽

Eva M. Jiménez-Mateos ◽

María Ascensión Zea-Sevilla ◽

Alberto Rábano ◽

Pablo Gili-Manzanaro ◽

...

Keyword(s):

Alzheimer’S Disease ◽

Alzheimer's Disease ◽

Unmet Need ◽

Cost Effective ◽

Specific Protein ◽

Tear Fluid ◽

Initiation Factor ◽

Non Invasive ◽

A Genome ◽

Potential Biomarker

Abstract Alzheimer’s disease (AD) is characterized by a progressive loss of neurons and cognitive functions. Therefore, early diagnosis of AD is critical. The development of practical and non-invasive diagnostic tests for AD remains, however, an unmet need. In the present proof-of-concept study we investigated tear fluid as a novel source of disease-specific protein and microRNA-based biomarkers for AD development using samples from patients with mild cognitive impairment (MCI) and AD. Tear protein content was evaluated via liquid chromatography-mass spectrometry and microRNA content was profiled using a genome-wide high-throughput PCR-based platform. These complementary approaches identified enrichment of specific proteins and microRNAs in tear fluid of AD patients. In particular, we identified elongation initiation factor 4E (eIF4E) as a unique protein present only in AD samples. Total microRNA abundance was found to be higher in tears from AD patients. Among individual microRNAs, microRNA-200b-5p was identified as a potential biomarker for AD with elevated levels present in AD tear fluid samples compared to controls. Our study suggests that tears may be a useful novel source of biomarkers for AD and that the identification and verification of biomarkers within tears may allow for the development of a non-invasive and cost-effective diagnostic test for AD.

Download Full-text

P1185LUNG COMETS AND EVALUATION OF HYDRATION STATUS IN PERITONEAL DIALYSIS PATIENTS

Nephrology Dialysis Transplantation ◽

10.1093/ndt/gfaa142.p1185 ◽

2020 ◽

Vol 35 (Supplement_3) ◽

Author(s):

Robert Ekart ◽

Lucijan Lucic Srajer ◽

Katharina Marko ◽

Nina Hojs ◽

Sebastjan Bevc ◽

...

Keyword(s):

Body Composition ◽

Peritoneal Dialysis ◽

The Body ◽

Whole Body ◽

Fluid Distribution ◽

Hydration Status ◽

Non Invasive ◽

Fluid Status ◽

Multifrequency Bioimpedance ◽

Dialysis Vintage

Abstract Background and Aims Assessment of optimal hydration status in patients with end-stage renal disease (ESRD) on peritoneal dialysis (PD) is a challenge. Multiple diagnostic options to determine hydration status in PD patients are available. Multifrequency bioimpedance spectroscopy (MBIS) is a cheap, simple and non-invasive method of estimating body composition, including estimates of total body water (TBW), extracellular water (ECW), intracellular water (ICW) and the ratio between both spaces (ECW/ICW). Lung ultrasonography (LUS) and lung B-lines (lung comets) can be used for the evaluation of extravascular lung water. Ultrasound evaluation of inferior vena cava (UIVC) provides rapid, non-invasive assessment of a patient's hemodynamic and volume status. N-terminal pro-brain natriuretic peptide (NT-proBNP) is related to fluid status and fluid distribution. The aim of our study was to assess fluid status in PD patients comparing four different methods: MBIS, LUS, UIVC and NT-proBNP. Method We performed a single-centre cohort study in 19 PD patients. The body composition was measured using the portable whole-body MBIS device, Body Composition Monitor-BCM(®) (Fresenius Medical Care, Bad Homburg, Germany), LUS with portable US device (VScan, General Electrics Corporate), UIVC index with SonoSite US device. NT-proBNP was measured in a one-step sandwich chemiluminescent immunoassay (Dimension Vista® System 1500, Siemens Healthcare Diagnostics Inc., Newark, NJ, USA). Results The mean age of patients was 54 ± 10 years, mean dialysis vintage 53 (10-194) months, 63% were men. Thirteen (68.4%) patients had fluid overload (FO) > 1.1 L. Data of patients are presented in table 1. We found a statistically significant correlation between the number of lung comets and ECW/ICW ratio (r = 0.496, P = 0.031) and NT-proBNP (r = 0.759, P < 0.0001). In contrast, there was no significant correlation between the number of lung comets and UIVC (r = 0.221, P < 0.364). Conclusion According to our results, LUS with lung comets, MBIS with ECW/ICW ratio and NT-proBNP are useful and complementary methods for evaluation of fluid status in PD patients.

Download Full-text

Tear Fluid Osmolarity as a Potential Marker of Hydration Status

Yearbook of Sports Medicine ◽

10.1016/j.yspm.2011.08.060 ◽

2012 ◽

Vol 2012 ◽

pp. 330-332

Author(s):

R.J. Shephard

Keyword(s):

Tear Fluid ◽

Hydration Status ◽

Potential Marker

Download Full-text

The Utility of Thirst as a Measure of Hydration Status Following Exercise-Induced Dehydration

Nutrients ◽

10.3390/nu11112689 ◽

2019 ◽

Vol 11 (11) ◽

pp. 2689 ◽

Cited By ~ 4

Author(s):

William M. Adams ◽

Lesley W. Vandermark ◽

Luke N. Belval ◽

Douglas J. Casa

Keyword(s):

Body Mass ◽

Prolonged Exercise ◽

Recovery Period ◽

Fluid Replacement ◽

Hydration Status ◽

Post Exercise ◽

Visual Analog Scales ◽

Hot Environment ◽

Ad Libitum ◽

Exercise Induced

The purpose of this study was to examine the perception of thirst as a marker of hydration status following prolonged exercise in the heat. Twelve men (mean ± SD; age, 23 ± 4 y; body mass, 81.4 ± 9.9 kg; height, 182 ± 9 cm; body fat, 14.3% ± 4.7%) completed two 180 min bouts of exercise on a motorized treadmill in a hot environment (35.2 ± 0.6 °C; RH, 30.0 ± 5.4%), followed by a 60 min recovery period. Participants completed a euhydrated (EUH) and hypohydrated (HYPO) trial. During recovery, participants were randomly assigned to either fluid replacement (EUHFL and HYPOFL; 10 min ad libitum consumption) or no fluid replacement (EUHNF and HYPONF). Thirst was measured using both a nine-point scale and separate visual analog scales. The percent of body mass loss (%BML) was significantly greater immediately post exercise in HYPO (HYPOFL, 3.0% ± 1.2%; HYPONF, 2.6% ± 0.6%) compared to EUH (EUHFL, 0.2% ± 0.7%; EUHNF, 0.6% ± 0.5%) trials (p < 0.001). Following recovery, there were no differences in %BML between HYPOFL and HYPONF (p > 0.05) or between EUHFL and EUHNF (p > 0.05). Beginning at minute 5 during the recovery period, thirst perception was significantly greater in HYPONF than EUHFL, EUHNF, and HYPOFL (p < 0.05). A 10 min, ad libitum consumption of fluid post exercise when hypohydrated (%BML > 2%), negated differences in perception of thirst between euhydrated and hypohydrated trials. These results represent a limitation in the utility of thirst in guiding hydration practices.

Download Full-text