Background and aim: The liver plays a crucial role in the metabolism of asymmetric-dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase. ADMA is metabolized via dimethylarginine-dimethylaminohydrolase (DDAH). This study investigated whether changes in serum levels of ADMA occur in a rat model of non-alcoholic steatohepatitis (NASH) and what is the mechanism involved. Materials and methods: NASH was induced in Male Wistar rats by 8 weeks of feeding with an MCD diet (methionine/choline-deficient diet). Blood samples and hepatic biopsies were collected after 1, 2, 3, 4 and 8 weeks. Serum hepatic enzymes (AST, ALT and g-GT) and ADMA were evaluated. Hepatic biopsies were used for in situ NAD(P)H autofluorescence detection and for mRNA expression of DDAH and ADMA transporters (CAT-1) by RT-PCR. Tissue DDAH activity and content of lipid peroxides, glutathione, ATP and ATP/ADP were also quantified. Results: NASH injury was confirmed by altered serum levels of hepatic enzymes. A time-dependent decrease in serum ADMA levels was found in NASH animals as compared with control group. An increase in mRNA expression of DDAH enzyme and CAT-1 transporter were detected. The evaluation of the hepatic DDAH activity showed a decrease associated with a concomitant increase in oxidative stress, as demonstrated by high lipid peroxide levels and low GSH content. A decrease in ATP levels, ATP/ADP and in the NAD(P)Hbound/free ratio reflecting the mitochondria alterations1 were also detected. Conclusions: These results indicate that the oxidative stress observed can contribute to the reduction of DDAH activity. This enzyme is a cysteine hydrolase that may be inhibited by increased reactive oxygen species associated to mitochondria dysfunction. The observed decrease in serum ADMA may be due to the increase in ADMA transporter, CAT-1, supporting previous data on the involvement of this transporter in ADMA changes2. These data confirm and support the crucial role of the liver in the control of ADMA levels by taking up large amounts of ADMA from the systemic circulation. (Supported by Fondazione Cariplo, grant n° 2011-0439). References: 1) Croce et al., Photochem Photobiol Sci, 2005; 2) Li et al., JPET 331:234-243, 2009.
Oxidative stress and alterations in serum levels of aymmetric-dymethylarginine (ADMA) in a rat model of steatohepatitis
CROCE AC;
2014
Abstract
Background and aim: The liver plays a crucial role in the metabolism of asymmetric-dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase. ADMA is metabolized via dimethylarginine-dimethylaminohydrolase (DDAH). This study investigated whether changes in serum levels of ADMA occur in a rat model of non-alcoholic steatohepatitis (NASH) and what is the mechanism involved. Materials and methods: NASH was induced in Male Wistar rats by 8 weeks of feeding with an MCD diet (methionine/choline-deficient diet). Blood samples and hepatic biopsies were collected after 1, 2, 3, 4 and 8 weeks. Serum hepatic enzymes (AST, ALT and g-GT) and ADMA were evaluated. Hepatic biopsies were used for in situ NAD(P)H autofluorescence detection and for mRNA expression of DDAH and ADMA transporters (CAT-1) by RT-PCR. Tissue DDAH activity and content of lipid peroxides, glutathione, ATP and ATP/ADP were also quantified. Results: NASH injury was confirmed by altered serum levels of hepatic enzymes. A time-dependent decrease in serum ADMA levels was found in NASH animals as compared with control group. An increase in mRNA expression of DDAH enzyme and CAT-1 transporter were detected. The evaluation of the hepatic DDAH activity showed a decrease associated with a concomitant increase in oxidative stress, as demonstrated by high lipid peroxide levels and low GSH content. A decrease in ATP levels, ATP/ADP and in the NAD(P)Hbound/free ratio reflecting the mitochondria alterations1 were also detected. Conclusions: These results indicate that the oxidative stress observed can contribute to the reduction of DDAH activity. This enzyme is a cysteine hydrolase that may be inhibited by increased reactive oxygen species associated to mitochondria dysfunction. The observed decrease in serum ADMA may be due to the increase in ADMA transporter, CAT-1, supporting previous data on the involvement of this transporter in ADMA changes2. These data confirm and support the crucial role of the liver in the control of ADMA levels by taking up large amounts of ADMA from the systemic circulation. (Supported by Fondazione Cariplo, grant n° 2011-0439). References: 1) Croce et al., Photochem Photobiol Sci, 2005; 2) Li et al., JPET 331:234-243, 2009.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
