Green tea polyphenols to beat liver shortages

New research from the US suggests that drinking green tea may be the answer for patients waiting for a liver transplant.

A liver transplant can be a lifesaving operation for many patients, but a lack of available organs often means that many are unable to receive the treatment they need. Furthermore, many livers are unusable, and primary graft failure, which occurs in five to 15 per cent of cases, often necessitates re-transplantation.

A major source of donor livers is brain-dead accident victims, and accidents are associated overwhelmingly with alcohol. Therefore, alcohol consumption is likely to be a common characteristic of organ donors. Unfortunately, alcohol consumption causes fatty infiltration (deposit of fat within the tissues). Fatty grafts exhibit higher rates of primary graft failure leading to higher death rate; therefore, fatty livers are often not accepted for transplantation.

Previous studies have demonstrated that production of free radicals, an atom or atom group carrying an unpaired electron and no charge, increased in fatty livers after liver transplantation. This increase has been associated with liver graft injury and failure.

Polyphenols are efficient free radical and single oxygen scavengers, and green tea extracts inhibit lipid peroxidation in experimental animals and humans. Green tea contains high levels of polyphenols including catechin, epicatechin, gallocatechin, epigallocatechin, epicatechin gallate and gallocatechin gallate. Considerable epidemiological and experimental evidence shows beneficial effects of green tea extract in reducing the risk of heart disease and cancer, most likely due to the antioxidant property of polyphenols.

The latest research, carried out by Zhi Zhong, John J. Lemasters, Ronald G. Thurman, and their colleagues from the Departments of Cell & Developmental Biology and Pharmacology, University of North Carolina at Chapel Hill, and the Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, North Carolina, tested the hypothesis that green tea extract blocks free radical formation and thus prevents primary graft failure after transplantation of fatty livers from ethanol-fed rats.

The scientists extracted the livers of rats which had been fed alcohol to mimic binge drinking, stored them for 24 hours, then rinsed them with a solution containing green tea extract prior to implantation. They then tested the liver for free radical and lipid peroxidation evidence.

What they discovered was that transaminase or enzyme release after liver transplantation was four-fold higher in rats that received fatty grafts than in rats with healthy control grafts.

While ethanol also caused severe focal necrosis in the liver and decreased survival rates from 88 per cent to 13 per cent, the green tea extract largely blunted graft injury and increased survival of fatty livers to 75 per cent.

The researchers claim that the results of their study, presented at the annual meeting of the American Physiological Society this week, confirm the association of increased free radical formation and graft failure after transplantation of fatty livers from ethanol-treated donors. It also provides evidence that the scavenging of free radicals in fatty livers by green tea extract prevents such liver graft damage and failure.

Green tea polyphenols could thus be an effective therapy to prevent failure of fatty grafts after clinical liver transplantation and lead to the inclusion of previously rejected livers into the pool of organs available for transplantation, they concluded.