Saliva Test To Diagnose Diabetes And Cancer

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Research could lead to a simple saliva test capable of diagnosing early stage diabetes and cancer, and perhaps neurological disorders and autoimmune diseases. The study, the most comprehensive analysis ever conducted of RNA molecules in human saliva, reveals that saliva contains many of the same disease-revealing molecules that are contained in blood. It was published online by the peer-reviewed journal Clinical Chemistry.

RNA, widely known as a cellular messenger that makes proteins and carries out DNA's instructions to other parts of the cell, is now understood to perform sophisticated chemical reactions and is believed to perform an extraordinary number of other functions, at least some of which are unknown.

The researchers have over the past decade focused on identifying biomarkers in saliva. They discovered that some of the same RNA that is inside human cells are also present in saliva and can be used to detect diseases, a surprising finding, because enzymes in saliva can degrade RNA, making the mouth "a hostile environment".

The researchers analyzed 165 million genetic sequences, and among the many forms of RNA are some unusual ones that live in the mouth and in cells. For example, it wasn't known until very recently that RNA comes in a circular form; the linear form has long been known. But the UCLA scientists identified more than 400 circular RNAs in human saliva, the first discovery of circular RNA in saliva or any body fluid, including 327 forms that were previously unknown.

Circular RNA's function in saliva is not entirely understood, although it does serve as a sponge for tiny RNA molecules called microRNAs, which bind to it. MicroRNAs, which once seemed to be little more than molecular noise, play important roles in many cell types, and have been implicated in cancers and other diseases. One microRNA can regulate hundreds of genes.
 
The scientists compared microRNA levels in saliva to those in the blood and other body fluids, and found the levels of microRNA in blood and in saliva are very similar, indicating that a saliva sample would be a good measure of microRNAs in the body. They also found that saliva contains another class of small RNAs, called piwi-interacting RNAs, or piRNAs, which are produced by stem cells, skin cells and germ cells. There are very few piRNAs in blood and most other body fluids, but the analysis showed that piRNA are abundant in saliva. Although their function is not yet known, they may protect the body from viral infection.
 
The researchers overriding conclusion is that saliva has tremendous medical and scientific value. In the not-too-distant future, dentists might be able to take saliva samples to analyze for a variety of diseases. And the research could lead to a new category of self-diagnostic devices.