**6. Conclusion**

We identified a microsatellite in the promoter region of the glutaminase gene that is linked to the development of overt hepatic encephalopathy in patients with cirrhosis. This

3 it can be seen that glutaminase activity is inhibited at 48 hours with differing concentrations

THDP-17 385,175 414,711 408,683 223,631 DON 384,572 323,692 295,361 260,400

Fig. 3. Inhibition of GA activity following 48 hrs incubation with either THDP 17 or DON in

Glutaminase plays a major role in the cause of hepatic encephalopathy. However, a prospective study is required to evaluate the clinical utility of the genetic marker we have identified for predicting overt hepatic encephalopathy before it can be recommended for

In the gut, intestinal glutaminase activity is increased in patients with cirrhosis and correlates with minimal hepatic encephalopathy (Romero-Gomez, Ramos-Guerrero et al. 2004). Glutaminase is also a key factor in the brain. Glutamine synthesis detoxifies ammonia in the brain, but glutaminase transforms glutamine into ammonia, glutamate, and free radicals in the mitochondria, and these byproducts are implicated in mitochondria dysfunction and further neurotransmission impairment (Trojan horse hypothesis) (Albrecht

Studies to date have indicated that OP is safe and patient studies in minimal HE and HE are needed to establish whether OP or glutaminase inhibitors such TPHD-17 (a promising GA inhibitor) could be used as a treatment for this significant complication of liver disease.

We identified a microsatellite in the promoter region of the glutaminase gene that is linked to the development of overt hepatic encephalopathy in patients with cirrhosis. This

0 5 20 100

of THDP-17 and DON (0,5,20 and 100µM).

Activity (mU/ml)

Caco-2 cells

**5. Future research** 

and Norenberg 2006).

**6. Conclusion** 

clinical practice.

promoter is associated with an increase in enzyme activity when the long allele is present. This genetic marker might help identify patients at risk for overt hepatic encephalopathy so that they could be more carefully monitored and could receive intensive treatment and/or define priority in liver transplant waiting list. However, additional studies are needed before this biomarker can be recommended for use in clinical practice.

Our studies support the role of glutaminase in HE and the use of OP, a novel treatment in developing for HE in reducing plasma ammonia. The mechanism by which OP directly reduces ammonia levels in cirrhosis is by increasing muscle GS activity, subsequently trapping and increasing ammonia excretion as phenylacetylglutamine, with the concomitant normalization of gut GA activity. The reduction on ammonia (by OP) leads to a reduction in ICP in ALF and is associated with an improvement in inflammation in the context of chronic liver disease. Moreover, OP modulates iNOS and NFkB mechanisms and prevents LPSinduced brain edema in cirrhotic rats.

And finally, we present a new molecule, THDP-17 as a new therapeutic option for the treatment of hepatic encephalopathy as a GA partial inhibitor that is able to cross the cellular and mitochondrial membranes.

In summary, we believe that further investigation of GA is warranted, because increased knowledge of the pathways involved might lead to the uncovering of new drug targets (such as OP and THDP-17) and other treatments for hepatic encephalopathy. These findings suggest developing approaches to target GA to prevent ammonia release and subsequent HE as a valid therapeutic strategy in the management of patients with liver disease.
