Urea and Minerals Monitoring in Space Missions by Spot Samples of Saliva and Urine

Abstract

BACKGROUND: Microgravity induces redistribution of body fluids and reductions in muscle and bone mass. These effects correlate with changes in lab test results, including urea and bone minerals. Difficulties with collecting blood and urine during space missions limit the available data. This pilot study investigated metabolic changes during a space mission using untimed spot samples of urine and saliva. Untimed spot urine was used for urinalysis with data normalization per creatinine concentration. Saliva was proven useful as an index of serum urea and phosphorus.METHODS: Two astronauts collected urine and saliva samples 75 ± 5 d before launch (baseline) and 3–5 times during a 6-mo space mission. Samples were collected 3 h after morning breakfast. Urine was collected using a standard NASA device. Saliva was collected using a Salivette™ synthetic swab. Samples were kept frozen using automated biochemistry until lab work-up. Anthropometric data were collected at baseline and after the mission.RESULTS: For astronauts 1 and 2, respectively, total bone mineral density decreased (−1.4% and −0.9%). In-flight changes were as follows: transiently decreased urine urea/creatinine ratio (−32% and −24%), transiently decreased urine phosphorus/creatinine ratio (−52% and −30%), increased urine calcium/creatinine ratio (up to +116% and +27%), and transient increases in saliva urea (up to +48% and +195%) and phosphorus (up to +29% and +46%). The astronaut with greater changes in urine minerals had greater reduction in bone mineral density.DISCUSSION: The results support the hypothesis that untimed samples of urine and saliva are useful for investigation of metabolic changes during space missions. Changes in urine and saliva minerals suggested down-regulation of parathyroid gland activity during the space mission.Bilancio G, Cavallo P, Lombardi C, Guarino E, Cozza V, Giordano F, Cirillo M. Urea and minerals monitoring in space missions by spot samples of saliva and urine. Aerosp Med Hum Perform. 2019; 90(1):43–47.

Oral Tissue Responses to Travel in Space

“…Analyses of saliva of cosmonauts during long-term spaceflight showed levels of cortisol below baseline [43], whereas salivary cortisol biorhythms and concentrations were preserved in astronauts onboard Spacelab [44] and cosmonauts on the International Space Station (ISS) [45]. Transient increases in saliva urea and phosphate concentrations, monitored in 2 astronauts during 6 months on the ISS, were consistent with serum concentrations reported in earlier studies [46]. Although studied in astronaut plasma, not saliva, in the NASA Twin Study, EGF and NGF levels were altered during a 340-day flight and after landing [47].…”

Saliva for assessing creatinine, uric acid, and potassium in nephropathic patients

“…This is an observational study that was performed in accordance with the ethical principles of the Declaration of Helsinki and was approved by the local institutional Ethics Committees (n. 5/2012 and 4/2013). The study was included in a collaboration project developed by the Italian Space Agency ( Agenzia Spaziale Italiana , ASI) and the National Aeronautics and Space Administration (NASA) for investigation on the use of saliva in the monitoring of metabolic changes during space mission (https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=304), [19, 20]. The study enrolled healthy volunteers of the department personnel for analyses on methodological aspects and patients with chronic kidney disease (CKD) of the outpatient clinic of the University Hospital for analyses on associations saliva/plasma as previously reported [19].…”

“…The study was included in a collaboration project developed by the Italian Space Agency ( Agenzia Spaziale Italiana , ASI) and the National Aeronautics and Space Administration (NASA) for investigation on the use of saliva in the monitoring of metabolic changes during space mission (https://www.nasa.gov/mission_pages/station/research/experiments/explorer/Investigation.html?#id=304), [19, 20]. The study enrolled healthy volunteers of the department personnel for analyses on methodological aspects and patients with chronic kidney disease (CKD) of the outpatient clinic of the University Hospital for analyses on associations saliva/plasma as previously reported [19]. CKD patients were selected for analyses on associations saliva/plasma because kidney disease is known to induce sizeable increases in plasma concentrations of all analytes under study.…”

“…Samples of saliva were collected always 1–2 min after blood. To comply with the restraints of space missions, saliva was collected with the use of a synthetic swap (Salivette, Sarstedt, Germany) and without timing or stimulation with paraffin or other agents [19]. Blood contamination was controlled by macroscopic inspection only [18].…”

“…Analyses on methodological aspects included five objectives: differences between blind duplicates of standard samples; differences between standard samples simultaneously collected in two different sites (i.e., right vestibulum oris and left vestibulum oris); differences between standard samples of different days (day-to-day variability); differences between standard samples and mid-morning samples (i.e., samples collected 3-h after the completion of breakfast); differences between standard samples and frozen/thawed samples. The timing of mid-morning samples was selected to match the schedule of experiments in space mission [19]. In experiments on frozen/thawed saliva, standard samples were divided in two aliquots: one was maintained at 2–4 °C for one hour while the other one was frozen and thawed at 2–4 °C.…”