Table 3.

Liver mitochondrial breath tests: substrates and evidence for potential clinical applications.

Substrate/Clinical Applications	Information
KICA
ALD	Effect of acute alcohol consumption (even low-moderate doses) [171]
ALD	Discrimination between chronic alcohol consumption and nonalcoholic chronic liver disease [173]
ALD	Monitoring and ascertaining of alcohol withdrawal [173]
NAFLD	Discrimination between simple steatosis and steatohepatitis (NASH) and between low-grade and high-grade fibrosis [147] (Figure 6)
HCC	Effect of treatment (thermoablation, chemoembolization) and prediction of tumour recurrence after local treatment. Comparison with methacetin [158]
Drugs	Evaluation of acute drug toxicity [171]
Methionine
Healthy subjects	Validation studies with 2 mg/kg body weight (methyl-13C)-methionine. Breath 13CO2 enrichment measured at base line and every 15 min thereafter for 180 min. [174]
Healthy subjects	Effect of alcohol consumption (30 min after the ingestion of ethanol 0.3 g/kg body weight). Decreased excretion with ethanol, due to impaired mitochondrial oxidation [175].
Liver cirrhosis	Discrimination between different degree of chronic liver damage [175]
ALD	Diagnosis of acute alcohol ingestion [174]
NAFLD	Discrimination between simple steatosis and NASH [176]
HCV	Discrimination between HCV infected patients and healthy subjects and toxicity of pegylated interferon plus ribavirin treatment [177]
Drugs	Evaluation of chronic drug toxicity [178]
Friedriech’s ataxia	Diagnosis of neurological disorders [179]
Octanoate
NAFLD	Evaluation of altered lipid metabolism [180]
NASH	Total β-oxidation of octanoic acid remained normal between controls and NASH patients, although cumulative 13CO2 recovery was higher in women than men [181]

Abbreviations: ALD = alcoholic liver disease; HCC = hepatocellular carcinoma; HCV = hepatitics C virus; KICA= α-ketoisocaproic acid; NAFLD= nonalcoholic fatty liver disease; NASH = nonalcoholic steatohepatitis.