Extracting the urine: Metabolic profile

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  • Published: Sep 15, 2013
  • Author: David Bradley
  • Channels: Chemometrics & Informatics
thumbnail image: Extracting the urine: Metabolic profile

The "urinome"

The chemical composition of urine is of particular interest to physicians, nutritionists and environmental scientists because it allows them to uncover critical information not only about a person's health, what they have eaten, what they drank, any drugs they have taken, prescription or otherwise, and even to which environmental pollutants they might have been exposed.

A sophisticated research project at the University of Alberta, Canada, brings together nuclear magnetic resonance spectroscopic data, mass spectrometry and liquid chromatography to identify the 3000 or so chemical metabolites in 230 classes that can be present in a sample of human urine. The work is the culmination of more than seven years effort and involved a team comprising almost twenty individual scientists. The researchers anticipate that their detailed chemical profile of urine will have considerable implications for medical, nutritional, drug and environmental testing.

Although one might imagine that everything there was to say about urine had already been said, from its use in kick-starting a compost heap to the alchemists' attempts to use it to create an elixir of eternal youth, there is, turns out, a lot more to be said. "Urine is an incredibly complex biofluid," explains U of Alberta's David Wishart. "Until our systematic study, we had no idea that we could be flushing so many different chemicals down our toilets."

Taking more than the P

Their complex analysis of a wide range of human urine samples has led to the identification and quantification of hundreds of compounds. To support the experimental data, the team used computer-based data mining techniques to scour more than a century of the scientific literature. This has allowed them to build a chemical inventory of urine, aggregating chemical names, synonyms, descriptions, structures, concentrations and disease associations for thousands of urinary metabolites. The associated database is freely available and is called the Urine Metabolome Database, or UMDB, a worldwide reference used for clinical, drug and environmental analyses of urine. The UMDB is maintained by The Metabolomics Innovation Centre, Canada's national metabolomics core facility.

The Human Genome Project attracted much attention and much hype surrounded its purported benefits. However, metabolites, the products of the chemical processing of the proteins encoded by the genes in our genome is nearer the proverbial coal face of human health and disease studies where data mining comes into its own. "While the human genome project certainly continues to capture most of the world's attention, I believe that these studies on the human metabolome are already having a far more significant and immediate impact on human health," adds Wishart.

Heading up metabolomic research

The chemical composition of urine is of particular interest to physicians, nutritionists and environmental scientists because it allows them to uncover critical information not only about a person's health, what they have eaten, what they drank, any drugs they have taken, prescription or otherwise, and even to which environmental pollutants they might have been exposed. Analysis of urine for medical purposes dates back more than 3,000 years. In fact, up until the late 1800s, urine analysis using colour, smell and even taste (uroscopy) was a primary analytical approach to medical diagnosis of disease. Even today, millions of chemically based urine tests are performed every day to identify metabolic disorders in newborns, to diagnose diabetes, to monitor kidney function, confirm bladder infections and detect illicit drug use in sport and crime.

Wishart points out that the majority of medical textbooks cite a list of just 50 to 100 chemicals to be found in urine and tests usually only assess six or seven compounds. This is, it appears, a mere drop in the ocean. "Expanding the list of known chemicals in urine by a factor of 30 and improving the technology so that we can detect hundreds of urine chemicals at a time could be a real game-changer for medical testing," Wishart says. This new study has particular significance because it will allow developers to market a whole new generation of fast, cheap and painless medical tests for diagnosis and monitoring that will be far less invasive than the usual round of blood samples and tissue biopsies.

In particular, he notes that new urine-based diagnostic tests for colon cancer, prostate cancer, celiac disease, ulcerative colitis, pneumonia and imminent organ transplant rejection are now being developed or are about to enter the marketplace, thanks in part to this work.

"This is certainly not the final word on the chemical composition of urine," Wishart adds. "As new techniques are developed and as more sensitive instruments are produced, I am sure that hundreds more urinary compounds will be identified. In fact, new compounds are being added to the UMDB almost every day. Previously, the same team described the chemical composition of human cerebrospinal fluid (2008) and in 2011 the chemical composition of human blood.

Related Links

PLOS one, 2013, 8(9): e73076: "The Human Urine Metabolome"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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