Saliva-based detection of metabolic changes simpler and less invasive .

Testing for health conditions usually involves needles, X-rays and other invasive or uncomfortable measures. To make diagnostics less burdensome for patients, scientists are developing alternatives, looking for disease markers in urine—and even spit. Now a study, appearing in ACS’ Journal of Proteome Research, demonstrates for the first time that individuals may have saliva “fingerprints.” The finding suggests that identifying changes in these baseline fingerprints could someday be a reliable way to detect disease.

Saliva is an important physiological fluid that contains a complex mixture of analytes that may produce a characteristic individual signature.

Saliva testing is a diagnostic technique that involves laboratory analysis of saliva to identify markers of endocrine, immunologic, inflammatory, infectious, and other types of conditions. Saliva is a useful biological fluid for assaying steroid hormones such as cortisol, genetic material like RNA, proteins such as enzymes and antibodies, and a variety of other substances, including natural metabolites, including saliva nitrite, a biomarker for nitric oxide status (see below for Cardiovascular Disease, Nitric Oxide: a salivary biomarker for cardio-protection). Saliva testing is used to screen for or diagnose numerous conditions and disease states, including Cushing’s disease, anovulation, HIV, cancer, parasites, hypogonadism, and allergies. Salivary testing has even been used by the U.S. government to assess circadian rhythm shifts in astronauts before

Saliva testing is used to screen for or diagnose numerous conditions and disease states, including Cushing’s disease, anovulation, HIV, cancer, parasites, hypogonadism, and allergies. Salivary testing has even been used by the U.S. government to assess circadian rhythm shifts in astronauts before flight and to evaluate hormonal profiles of soldiers undergoing military survival training.

NASA Space Applications

Blood-based measurements are effective, but saliva-based detection of metabolic changes would be simpler and less invasive for use in spaceflight. If the results support testing saliva for the presence of biological markers, future automated devices could rapidly test saliva instead of blood samples before, during and after space missions.

Earth Applications
If saliva can be used as a reliable indicator of bone and muscle health, it may also be used as a simple, automated, non-invasive clinical tool on Earth. Salivary markers could be used to test for certain medical conditions in settings where blood samples are difficult or impossible, including in remote areas, for young children, or for large-scale screening of a general population.

Description

The research focuses on the use of saliva and urine as a non-invasive tool to monitor some of the metabolic changes secondary to the microgravity-induced reduction in bone/muscle mass.

A number of previous observations show that exposure to microgravity results in a reduction of bone and muscle mass.  These effects are a limiting step in the duration of space mission.  Similar effects on bone  and muscle mass are induced by prolonged bed-rest, that is, by the experimental condition which is used to simulate microgravity on Earth.  The reduction in bone and muscle mass is associated with changes in blood levels and, secondarily, in urine levels, of several substances, which are used in research and clinical practice, as markers of bone or muscle metabolism.  A recent program of the Italian Space Agency (ASI) included a set of bed-rest experiments which confirmed and extended these previous observations.

Saliva and urine are biological fluids which can be easily and repeatedly collected without risks.  Past and recent data from different laboratories consistently indicate that the chemical composition of saliva and urine reflects, in many aspects, the chemical composition of blood.  This is true also for some markers of bone or muscle conditions.  In fact, saliva, urine, and blood tend to have similar levels of bone mineral components (calcium and phosphate), of bone-related vitamins (vitamin D), and of end-products of muscle protein (urea), etc.

The research includes pre-flight procedures, in-flight procedures, and post-flight procedures.

Pre-flight and post-flight measurements of bone/muscle mass  serve to verify the presence of the expected mass reduction after the space mission.   This set of measurements is done by leg peripheral Quantitative Computed Tomography, an X-ray based method which is currently used in medical practice (pQCT, Stratec, Germany).

Biological samples are collected pre-flight (blood, urine, and saliva), in flight (urine and saliva), and post-flight (blood, urine and saliva).  They will be rapidly frozen for later laboratory work-up on specific markers of bone/muscle metabolism.

In-flight urinary samples will be compared to pre-flight urinary samples to verify the presence of expected modifications in those markers due to microgravity exposure during the space mission.  In-flight saliva samples and pre-flight saliva samples are compared to assess if some of the modifications in urinary markers are present and detectable in saliva also.  Pre-flight and post-flight blood samples will serve as reference for urinary samples and as comparator with previous data.

Credit : NASA