A key gene that helps to explain an underlying cause of incurable bowel disorders, which affect around 300,000 people in the UK, has been identified by scientists.
A study found that blocking the effects of the beneficial gene can harm vital parts of the cell and lead to bowel disease.
The findings boost understanding of the cause of these lifelong conditions and could lead to new treatments, scientists say.
Inflammatory Bowel Disease (IBD) includes disorders such as Crohn's Disease and Ulcerative Colitis. The causes of these conditions are unknown and there is currently no cure.
The gene, known as MDR1, governs an important extractor system for toxins in the gut, removing damaging substances from intestinal cells, scientists said.
A research team, led by the University of Edinburgh, showed that MDR1 function was lower in people with inflamed IBD compared with those without inflammation.
Experts then showed that mice without MDR1 had faulty mitochondria, parts of the cell known as "batteries", which play a vital role in energy generation and cell health.
This mitochondrial dysfunction then resulted in colitis, inflammation of the inner lining of the bowel - a defining feature of IBD.
Researchers involved in the study analysed genetic data from 90,000 people, 40,000 of whom had IBD.
The university study also revealed that a drug called Mitoquinone, which protects the mitochondria against toxins, can reduce colitis and promote bowel recovery in the mice lacking MDR1. Scientists have described this as a "significant step forward".
Lead author Dr Gwo-Tzer Ho, honorary consultant gastroenterologist at the University of Edinburgh's MRC Centre for Inflammation Research, said: "IBD has a serious impact on quality of life, with 6,000 new cases diagnosed per year in the UK.
"We have shown that MDR1 and mitochondrial function are important jigsaw pieces in the complex causes of IBD.
"Our studies highlight the importance of shielding the mitochondria from damage. This will open new approaches to drug targets that focus on the mitochondria to better design treatments for patients."
The study, carried out with researchers at the University of Bristol and in the USA and Japan, was funded by the Medical Research Council and Crohn's and Colitis UK.
It is published in the journal Mucosal Immunology.