Wednesday, December 21, 2016

Diet as medicine in mitochondrial diseases

EMBO: Researchers from the University of Helsinki, Finland, found that diet could have a strong impact on the progression of mitochondrial disease. In their study, published in EMBO Molecular Medicine, low-carbohydrate diet aggravated muscle damage in patients with a mitochondrial muscle disease called “progressive external ophthalmoplegia” (PEO). However, damage was not permanent. The patients recovered quickly and short-term muscle damage eventually resulted in a modest improvement of muscle strength in the long run. However, more research is needed before diet change is used as a tool in therapeutic strategy.

Mitochondrial diseases are a group of disorders that result from defects in mitochondria, specialized cellular compartments that convert nutrition into chemical energy the cell can use. In PEO, the muscles of the eyes are affected, leading to limitations in eye movement and drooping eyelids. In addition, patients often suffer from weakness of muscles in the arms or legs, particularly during exercise.

“Since mitochondria turn the food we eat into energy, we expected that diet should have an impact on disease progression,” said Anu Suomalainen, senior author of the publication. After promising results from mouse experiments, Suomalainen and her colleagues set out to test this notion in a small pilot trial comprising five PEO patients and ten control subjects.

All participants were switched to a high-fat, low-carbohydrate “modified Atkins” diet. Contrary to the researchers’ expectations, the primary reaction of the patients to the diet was detrimental. They suffered from progressive muscle pain and showed signs of muscle damage so that the trial was prematurely discontinued after a maximum of 11 days on the diet. However, the patients recovered quickly and 2.5 years later, they had actually gained in muscle strength as compared to pre-diet state. Apparently, the short-term muscle damage induced by diet had a modest beneficial impact in the long run.

A thorough examination of the patients allowed the researchers to explain this devious route to improvement. They showed that modified Atkins diet selectively kills muscle fibers that were already damaged through disease-related mitochondrial dysfunction. Whereas most body cells can use a broad range of biomolecules as fuel, pre-damaged fibers apparently depend on carbohydrates. If carbohydrates are not provided in the diet the fibers die, explaining the short-term adverse reactions of the patients. The scientists speculate that this could stimulate muscle regeneration:  healthy satellite cells - muscle stem cells - are activated; they divide and eventually fuse with existing muscle fibers, supplying them with healthy mitochondria.

The results point to the potential of using dietary change as a therapeutic strategy, although in a carefully controlled clinical setting. In fact, caution is required. Low-carbohydrate diet can lead to long-term improvement but can also cause muscle damage. This observation also casts light on the alleged safety of low-carbohydrate diets as a means of weight loss. For some people with subclinical mitochondrial diseases, it may have adverse side effects on muscles.

Modified Atkins diet induces subacute selective ragged-red-fiber-lysis in mitochondrial myopathy patients
Ahola S, Auranen M, Isohanni P, Niemisalo S, Urho N, Buzkova J, Velagapudi V, Lundbom N, Hakkarainen A, Muurinen T, Piirilä P, Pietiläinen KH, Suomalainen A.

Read the paper:
doi: 10.15252/emmm.201606592