- Assessment of phase I and phase II detoxification
- Assessment of toxin exposure and impaired liver function
- No hepatotoxic challenge drugs required
- Simple first morning void urine collection
The body continually attempts to eliminate chemical toxins through enzymatic processes in the liver. Urinary D-glucaric acid, a by-product of phase I detoxification, is a valuable indicator of chemical exposure or liver damage. Urinary mercapturic acids are direct end product metabolites of conjugated xenobiotics. Combined assessment of the urinary levels of the two analytes provides valuable information about exposure to xenobiotics and liver disease, and the capability of the liver to eliminate toxins.
Why test liver function?
The production, use and disposal of toxic chemicals and synthetic materials have increased the risk of exposure to health threatening toxins.
Causal relationships between toxic chemicals and diseases have been well established. However many patients endure chronic symptoms that are associated with exposure to toxins before advanced stages of specific diseases are realised. Thus, there is a great demand for noninvasive laboratory tests that can timely assess chemical exposure and the capability of hepatic detoxification.
One process by which the body eliminates toxins is enzymatic detoxification in the liver. A reliable biomarker for exposure to toxic chemicals is urinary D-glucaric acid. Elevated levels of D-glucaric acid indicate induction of cytochrome P-450 enzymes (phase I) as a result of exposure to many xenobiotics (e.g. pesticides, fungicides, petrochemicals, drugs, toluene, formaldehyde, styrenes, etc.) Such exposures induce the glucuronic acid enzymatic pathway and production of D-glucaric acid, thus urinary D-glucaric acid is an indirect by-product of chemical exposure and phase I detoxification reactions.
What do the results indicate?
The urinary level of mercapturic acids indicates quantitatively the degree of activity, or capability of phase II detoxification. Mercapturic acids are the final excretory products of detoxification and include a variety of functionalised xenobiotics that have been conjugated with glutathione or L-cysteine prior to excretion. Low levels of mercapturic acids are consistent with insufficient levels of glutathione and/or cysteine. When the rate of formation of functionalised xenobiotics (phase I) exceeds the capacity of phase II detoxification, more potent toxins accumulate.