Breath Tests

Several breath tests are available from Metabolic Solutions to quantitate liver function. These breath tests use a safe biologic substrate labeled with a non-radioactive isotope of carbon. Breath tests determine the rate of appearance of labeled carbon dioxide to estimate enzyme activity, organ function or presence of disease.

Metabolic Solutions can provide assistance with the following liver function breath tests:

Mitochondrial

Methionine Breath Test: Methionine is an essential amino acid that has important roles in various metabolic processes, including protein synthesis. The Methionine Breath Test uses 1-¹³C-methionine, which is a non-radioactive isotope and is metabolized exclusively by hepatic mitochondria. ¹³C-methionine metabolism within 20 minutes results in an increased concentration of ¹³CO₂ in expired breath. The quantity of ¹³CO₂ measured in breath correlates with liver disease severity. Our studies demonstrate the effectiveness of the Methionine Breath Test in measuring hepatic mitochondrial function in individuals with liver disease. See more information about the Methionine Breath Test.

Octanoate Breath Test: Impairment of mitochondrial beta-oxidation has been reported with several liver diseases such as nonalcoholic steatohepatitis (NASH). Sodium 1-¹³C-octanoate undergoes liver mitochondrial beta-oxidation. The sodium 1-¹³C-octanoate breath test was found to correlate with insulin resistance and predict the presence of NASH.

Cytosolic

Phenylalanine Breath Test: Liver disease is associated with an abnormal elevation of the plasma concentrations of the aromatic amino acids, phenylalanine and tyrosine. The liver is the principal site of aromatic amino acid metabolism, particularly the hydroxylation of phenylalanine to tyrosine and further tyrosine degradation. We showed that the rate of hepatic phenylalanine metabolism can be quantitatively calculated from the appearance of ¹³CO₂ in the breath using the non-radioactive tracer, L-[1-¹³C]phenylalanine. Many studies have demonstrated that the phenylalanine breath test quantitates hepatic cytosolic capacity in end-stage liver disease. See more information about the Phenylalanine Breath Test.

Cytochrome P450 Activity

Methacetin Breath Test: Methacetin is metabolized rapidly by hepatic microsomal enzymes. When ¹³C-methacetin is orally administered, it undergoes extensive liver first-pass clearance. Cytochrome P450 IA2 in liver cells converts methacetin via O-dealkylation to acetaminophen and ¹³CO₂. The ¹³C-methacetin breath test (MBT) has been shown to accurately assess the degree of liver damage. The MBT can reliably distinguish between early cirrhotic and non-cirrhotic patients with 95% sensitivity and 97% specificity. The MBT can be completed within 60 minutes. Custom kits are available for clinical research studies. See more information about the Methacetin Breath Test.

Caffeine Breath Test: The [¹³C]caffeine breath test is highly specific for P4501A2 isoenzyme activity, which catalyzes caffeine 3-N-demethylation. Breath samples are collected over 1 h after oral administration, and the enzyme activity is quantified via analysis of the ratio of ¹³CO₂ to ¹²CO₂ by isotope ratio mass spectrometry. See more information about the Caffeine Breath Test.

Gastric Emptying

Metabolic Solutions, Inc. (MSI) has developed and validated an easy to prepare, low-fat muffin meal along with a simple breath collection system that provides an accurate assessment of solid phase gastric emptying called the Gastric Motility Octanoate Breath Test (GMOBT). The test has been widely used by medical/pharmaceutical researchers to assess delayed gastric emptying (gastroparesis). This technique works well with both human and animal protocols.

Advantages of the MSI Gastric Motility Octanoate Breath Test:

• Non-radioactive and less costly alternative to scintigraphy
• Allows multiple repeat testing on subjects
• Simple to prepare and reproducible caloric meal
• Easy for CROs to study multiple subjects simultaneously
• Custom test kits to meet your needs
• CLIA and GLP compliance (including Part 11)
• Customized reports
• Validated breath assay

The standardized meal in the gastric motility octanoate breath test is a muffin. Muffins are made by adding water and isotope to dry powder ingredients. After mixing the ingredients in the supplied cooking bowl, the ingredients are baked for 2 minutes in a microwave oven. The muffin is made from the combination of two commercially available products. There are no safety concerns with the ingredients. The ingredients of the muffin are kosher certified

The American Gastroenterological Association (AGA) has recommended breath testing to measure gastric emptying rates (AGA position).

Applications with the Octanoate Breath Test

The following examples offer protocols useful for studying gastric emptying:

1. Chey, WD, Shapiro, B, Zawadski, A, and Goodman, K (2001) Gastric emptying characteristics of a novel ¹³C-octanoate-labeled muffin meal.

2. Gonlachanvit, S, Chey, WD, Goodman, KJ and Parkman, HP (2001) Effect of meal size and test duration on gastric emptying and gastric myoelectrical activity as determined with simultaneous [¹³C]octanoate breath test and electrogastrography in normal subjects using a muffin meal.

3. Bromer, MQ, Kantor, SB, Wagner, DA, Knight, LC, Mauer, AH and H.P. Parkman (2002) Simultaneous measurement of gastric emptying with a simple muffin meal using [¹³C]octanoate breath test and scintigraphy in normal subjects and patients with dyspeptic symptoms.

Research, validation studies, procedures and technical information of the Gastric Motility Octanoate Breath Test is provided in our technical paper: Gastric Motility Studies.

Urea Breath Test: The urea breath (UBT) detects urease activity of Helicobacter pylori (H. pylori) in the stomach by administration of ¹³C-urea and monitoring ¹³CO₂ in breath. Levels at a defined cutoff indicate the presence of the infection. The test may also be used to demonstrate that H. pylori has been eliminated by treatment with antibiotics.

Small Intestinal Bacterial Overgrowth: Small intestinal bacterial overgrowth (SIBO) is the overgrowth of bacteria in the small intestines. Normally sterile, the small intestines can be colonized with bacteria that reduce required nutrients from reaching the body and may cause small intestinal inflammation. SIBO is detected by administration of lactulose or glucose and monitoring their fermentation by bacteria to hydrogen and methane gas.

Lactose Breath Test: Lactose intolerance is the inability of the body to breakdown the milk sugar, lactose. This inability causes colonic gas, diarrhea, and abdominal pain. We use the hydrogen breath test for lactose intolerance that detects hydrogen and methane levels after administration of lactose.

Fructose Breath Test: The hallmark of fructose malabsorption is the lack of fructose absorption in the small intestines. Excess fructose reaching the colon can cause bloating, abdominal pain and diarrhea. Fructose malabsorption is detected by the hydrogen breath test after a 25 gram oral load of fructose.

Sucrose Breath Test: The sucrose breath test (SBT) assesses the health and function of the small intestine. Serious health ramifications can result if the functional area of the brush border is significantly reduced by damage caused by infection, surgical trauma, disease, antibiotics, use of certain drugs, and chemotherapy treatments. See more information about the Sucrose Breath Test.

Mixed Triglyceride Breath Test: The mixed triglyceride breath test is the most researched pancreatic function breath test. The breath test uses a triglyceride labeled with a medium chain fatty acid ¹³C-octanoate on the middle position of the glycerol backbone and two longer fatty acids (stearate) on positions 1 and 3. The principle of this breath test is to add the labeled triglyceride to a meal, where it is hydrolyzed to fatty acids by pancreatic lipases in the duodenum. The fatty acids are absorbed and transported to the liver for oxidation to ¹³CO₂.

¹³C Lactose Ureide Breath Test: ¹³C-labeled glycosyl ureides can be used to measure oro-cecal transit time. Intestinal brush border enzymes are not able to split the glycosyl ureide bond between the sugar and urea. However, colonic bacteria are able to split this bond. By using ¹³C-urea, colonic bacteria oxidize this substrate to ¹³CO₂. The initial rise in ¹³CO₂ in the breath determines the oro-cecal transit time.