Serge Picaud, head of research at Inserm, and his colleagues of the Institut de la Vision have just discovered the origin of this secondary effect and have proposed strategies for limiting it.
They have shown that vigabatrin provokes a marked decrease in the blood level in an amino acid, taurine, resulting in a degeneration of the retina cells induced by light. The researchers therefore suggest that exposure to light should be reduced and a taurine-rich diet introduced in order to curb immediately these secondary effects in children undergoing treatment. As for the validation of an alternative treatment associating vigabatrin and taurine, this will necessitate several years of development.
This work is published in the review Annals of Neurology.
Epilepsy affects 1% of the world's population. With children, its treatment remains extremely restricted, and vigabatrin, (marketed in France under the name of Sabril®), has obtained marketing authorisation for children aged under 2 years. This anticonvulsant, which is also administered to adults in the case of failure of other treatments, is at the same time now being evaluated for the treatment of addiction to heroin, cocaine and methamphetamines.
However, the serious secondary effects of this drug can induce an impairment of the retina and a restriction of the visual field, noted, depending on the studies, in 10% to 40% of patients.
In order to reach an understanding of this drug's modes of actions, and in particular the mechanism of visual function impairment, the Inserm researchers first of all administered vigabatrin to rats over a period of several months and analysed the influence of exposure to light during the treatment. The results show that there is no damage to the retina when the animals are kept in the dark throughout the treatment.
Moreover, since previous work had shown that a deficiency of the organism in taurine (amino acid) triggers the degeneration of the photoreceptors (cells of the retina converting light into nervous signals), the researchers measured, in rodents, the plasma level of 19 amino acids. Whereas the concentration was identical for most of the amino acids in animals under vigabatrin and in non-treated rats, the taurine level turned out to be 67% lower in treated animals
Taurine is essentially contributed by diet. By providing certain of the animals under treatment with a taurine supplementation, the researchers noted that their visual acuity was greater than that of the animals without supplementation. In addition, the amino acid doses administered to six children subject to regular attacks of epilepsy and treated under vigabatrin reveal a taurine level that is far below the normal values reported for children of the same age – and in some cases even undetectable.
On the strength of these various tests, the scientists were able to prove that vigabatrin induces a pronounced reduction of the taurine level in the plasma. This marked fall is responsible for the degeneration of the photoreceptors and thus for the retinal toxicity in the animals exposed to light.
Pending confirmation in the human of the interest of providing patients under vigabatrin with a taurine supplementation, the researchers propose immediate solutions designed to limit the secondary effects in these patients. "In the first instance, care should therefore be taken to ensure that patients under vigabatrin consume a sufficient amount of food containing taurine. It is also important that they should be exposed to as little light as possible (e.g.; no night lights in a baby's bedroom at night) and should be induced to wear sunglasses", says Serge Picaud.
The researchers also emphasise that any taurine supplementation must be subject to medical advice.
To find out more:Firas Jammoul MD1,2, Qingping Wang MD1,2,3, Rima Nabbout MD4,5,6, Caroline Coriat MD1,2, Agnès Duboc PhD1,2, Manuel Simonutti1,2, Elisabeth Dubus1,2, Cheryl M. Craft PhD7, Wen Ye MD3, Stephen D. Collins MD PhD8 , Olivier Dulac MD4,5,6, Catherine Chiron MD4,5,6, José A. Sahel MD1,2,9,10, Serge Picaud PhD1,2,10,11
Priscille Riviere | EurekAlert!
Biofilm discovery suggests new way to prevent dangerous infections
23.05.2017 | University of Texas at Austin
Another reason to exercise: Burning bone fat -- a key to better bone health
19.05.2017 | University of North Carolina Health Care
Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.
The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....
An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.
We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...
Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.
Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...
An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...
In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.
In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...
24.05.2017 | Event News
23.05.2017 | Event News
22.05.2017 | Event News
24.05.2017 | Physics and Astronomy
24.05.2017 | Physics and Astronomy
24.05.2017 | Event News