| 1. Armuzzi, A. Marcoccia,
S., Zocco, M.A., De Lorenzo, A., Grieco, A., Tondi,
P., Pola, P., Gasbarrini, G. and Gasbarrini, A. (2000)
Scand J Gastroenterol 35:650-3.
Mitochondrial metabolism is essential for liver function,
and the availability of simple and non-invasive tests
able to assess hepatic mitochondrial function could
be extremely useful. Since the amino acid methionine
is oxidized by liver mitochondria, this study investigated
the feasibility of a breath test with 13C-methionine
in healthy subjects to assess hepatic mitochondrial
function before and after ethanol-induced oxidative
stress. Twenty healthy male volunteers received 2 mg/kg
body weight [methyl-13C]-methionine. Breath 13CO2
enrichment was measured at baseline and every 15 min
thereafter for 180 min. Forty-eight hours later the
test was repeated 30 min after the ingestion of ethanol
(0.3 g/kg body weight). After oral administration of
methionine, 13CO2 excretion reached
a peak (4.76% ± 0.9%) within 30-60 min and then decreased
progressively. The cumulative 13CO2
excretion within 3 h was 7.81% ± 0.66%. After ethanol-induced
oxidative stress, 13CO2 excretion
increased slowly, with a delayed and significantly decreased
peak (2.13% ± 0.45%; p<0.05). The results indicate
that the 13C-methionine breath test acts
as a marker to estimate the oxidative capacity of liver
mitochondria in healthy subjects.
2. Ishii, Y., Asai, S., Kohno,
T., Takahashi, Y., Nagata, T., Suzuki, S., Kohno, T.,
Iwai, S. and Ishikawa, K. (2001) Evaluation of liver
regeneration using the L-[1-13C] methionine
breath test. J Surg Res 95:195-9.
The purpose of the study was to examine the relationship
between changes in the liver weight/body weight percentage,
amount of hepatic tissue total DNA, and the results
of the [1-13C] methionine breath test during
hepatic regeneration in a rat model of 70% hepatectomy.
Male Wistar rats (230-290 g) were subjected to 70% hepatectomy
under anesthesia. One, 2, 3, 7, and 14 days postoperatively,
40 mg/kg 13C methionine was intravenously
injected into the femoral vein, and the increase in
exhaled 13CO2 was measured for
15 min. Simple laparotomy was performed in control rats.
Following the breath test, the regenerated liver was
removed and weighed. The amount of DA was determined
in the liver tissue. The correlation coefficient (r)
between liver weight/body weight and the results of
the methionine breath test were 0.892. The correlation
between DNA and the results of the methionine breath
test was 0.800. In conclusion, the 13C methionine
breath test is considered to be very useful for assessing
liver regeneration.
3. Spahr, L., Negro, F., Rubbia-Brandt,
L., Marinescu, O., Goodman, K., Jordan, M., Frossard,
J.L. and Hadengue, A. (2001) Acute valproate-associated
microvesicular steatosis: Could the [13C]
methionine breath test be useful to assess liver mitochondrial
function? Dig Dis Sci 46:2758-61.
Microvesicular steatosis is a potentially severe manifestation
of valproic acid Hepatotoxicity due to an acquired impairment
of mitochondrial function. Testing currently used to
investigate mitochondrial function are cumbersome and
cannot be used routinely. We report on a noninvasive
breath test using [13C] methionine for estimation
of mitochondrial function in a case of pure severe valproic
acid overdose-induced microvesicular changes. The initially
abnormal breath test improved together with the recovery
of liver failure. In conclusion, this observation suggests
that the [13C] methionine breath test may
provide a noninvasive estimate of hepatic mitochondrial
function in vivo.
4. Russmann, S., Junker, E. and
Lauterberg, B.H. (2002) Remethylation and transsulfuration
of methionine in cirrhosis: Studies with L-[H3-methyl-1-13C]
methionine. Hepatology 36:1190-6.
Disturbances of the methionine cycle may result in liver
injury. Patients with alcohol-induced liver disease
often exhibit hypermethioninemia and a delayed clearance
(CL) of methionine, but the extent to which transsulfuration
and remethylation pathways of the cyclic methionine
metabolism are affected is unknown. Methionine turnover
was determined in 7 healthy volunteers and 6 patients
with alcohol-induced cirrhosis after oral administration
of 2 mg/kg L-[H3-methyl-1-13C]
methionine, which permitted us to follow transsulfuration
by its decarboxylation to 13CO2
and remethylation by replacement of the labeled methyl
group by an unlabeled one. Basal plasma concentrations
of endogenous methionine (50 ± 5 vs. 25 ± 2 mmol/l,
mean ± SEM, p<0.001) were significantly higher in
patients with cirrhosis and its CL was significantly
decreased (774 ± 103 vs. 2050 ± 141 ml/min, p<0.001).
Methionine turnover amounted to 42 ± 4 vs. 27 ± 3 mmol/kg/h
(p<0.05) in controls and patients with cirrhosis,
respectively. The fraction of administered methionine
undergoing remethylation was lowered in patients with
cirrhosis (7.6 ± 1.5 vs. 14.1 ± 1.1%, p<0.005). However,
because of the larger pool of circulating methionine,
the total flux of methionine through the remethylation
pathway was similar in both groups. A significantly
lower fraction of the administered dose appeared in
the form of 13CO2 in breath in
patients with cirrhosis (2.2 ± 0.4 vs. 11.0 ± 0.8%,
p <0.001). In conclusion, the data indicate that
the liver with cirrhosis compensates for a decreased
activity of remethylating enzymes by operating higher
concentrations of methionine. In contrast, transsulfuration
is impaired in patients with alcohol-induced cirrhosis
such that an assessment of transsulfuration by a simple
breath test may provide a clinically useful estimate
of hepatic function.
5. Spahr, L., Negro, F., Leandro,
G., Marinescu, O., Goodman, K.J., Rubbia-Brandt, L.,
Jordan, M. and Hadengue, A. (2001) Impaired hepatic
mitochondrial oxidation using the [13C] methionine
breath test in patients with macrovesicular steatosis
and patients with cirrhosis. Med Sci Monit 9:CR6-11.
In cirrhosis, hepatic mitochondria exhibit morphological
and functional abnormalities. In human steatosis, ultrastructural
changes are reported in the absence of ethanol. Routine
evaluation of mitochondrial function is difficult. We
used the methionine breath test to explore hepatic mitochondrial
oxidation in vivo. The 13C methionine breath
test was performed in healthy subjects (n=15), patients
with cirrhosis (n=25) and patients with biopsy-proven
severe (>40% involved hepatocytes), non-alcoholic
macrovesicular steatosis (n=18). After oral administration
of 200 mg 1-13C methionine, hepatic mitochondrial
decarboxylation was measured by breath 13CO2
enrichment, expressed as % dose oxidized/h. At 60 minutes,
patients with steatosis had reduced exhalation of 13CO2
as compared to healthy subjects (-47%, 18.8 ± 12 vs.
36 ± 6.1 % dose/hr, p<0.05). Cirrhotics had even
lower values as compared to patients with steatosis
(-60%, 7.5 ± 3.4 vs. 18.8 ± 12 % dose/hr, p<0.05).
In cirrhosis, dose/h correlated (r=0.68) to aminopyrine
breath test values, a microsomal function test, and
was inversely correlated (r=-0.48) to the Child-Pugh
score. In conclusion, hepatic mitochondrial oxidation
as reflected by the 13C methionine breath
test is impaired both in patients with pure non alcohol-related
severe macrovesicular steatosis and in patients with
cirrhosis of mixed etiologies. This non-invasive test
can be used to monitor hepatic mitochondrial function
in vivo.
6. Di Campli, C., Angelini, G.,
Armuzzi, A., Nardo, B., Zocco, M.A., Candelli, M., Santoliquido,
A., Cavallari, A., Bernardi, M. and Gasbarrini, A. (2003)
Quantitative evaluation of liver function by the methionine
and aminopyrine breath tests in the early stages of
liver transplantation.
The early phase after liver transplant is considered
the period of greatest risk for graft failure. The aminopyrine
breath test could be useful for evaluating the liver
viable mass, and the methionine breath test could be
used to evaluate oxidative capacity of liver mitochondria.
We performed these tests in the early phase following
liver transplant in order to correlate the time course
of these tests to the outcome of transplantation. Twenty-three
patients undergoing liver transplant were enrolled.
The methionine and aminopyrine breath tests were performed
on the days 1, 3, and 5, and 2, 4, and 6, respectively,
after transplant. All but two transplants were successful
in the short term and the cumulative percentage of the
dose of 13C progressively increased after
transplantation, reaching values not significantly different
from controls (methionine at day 5). In two patients,
primary non-function occurred; in these patients the
cumulative percentage of the 13C dose did
not increase after ortotopic liver tansplant and the
results of both breath tests indicated that it always
remained significantly lower compared to that of the
other patients. In conclusion, a combination of breath
tests, exploring both mitochondrial and microsomal function,
could be useful in the early phase after liver transplant
in order to evaluate the graft outcome.
7. Milazzo, L., Riva, A., Sangaletti,
O., Piazza, M., Antinori, S. and Moroni, M. (2004) 13C
methionine breath test detects liver mitochondrial impairment
in HIV-infected patients with antiretroviral drug-related
hyperlactatemia. J Acquir Immune Defic Syndr 35:429-32.
A fundamental issue in the management of HIV-infected
patients is long-term toxicity of antiretroviral therapy
(ART). Hyperlactatemia is often asymptomatic, whereas
lactic acidosis represents a potentially fatal condition.
We used the 13C-methionine breath test to
investigate hepatic mitochondrial oxidation in HIV-1
infected patients on ART. 13C methionine
breath tests were performed in healthy subjects (n=10),
ART-naïve HIV infected patients (n=10), HIV-infected
patients on ART (n=15) and HIV-infected patients on
ART with hyperlactatemia (n=5). The 4 studied groups
showed significantly different 13CO2
exhalation curves (p=0.001). No difference emerged between
naïve HIV-infected patients and healthy controls. HIV-infected
patients on ART with normolactatemia had reduced 13CO2
exhalation compared to healthy subjects. HIV patients
with hyperlactatemia had even lower 13CO2
values compared to normolactatemia treated patients.
In 4 hyperlactatemic patients, the methionine breath
test 3-8 weeks after ART discontinuation and reduction
of serum lactate showed a significantly higher 13CO2
exhalation. In conclusion, the 13C methionine
breath test revealed mitochondrial impairment in antiretroviral
treated patients, more prominent in those with hyperlactatemia.
Drug suspension caused an amelioration of the mitochondrial
respiratory chain by increasing 13CO2
exhalation. This non-invasive test is useful to monitor
ART mitochondrial toxicity in vivo.
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