Bumetanide – a prescription drug for oedema (the build-up of fluid in the body) – improves some of the symptoms in young children with autism spectrum disorders and has no significant side effects, confirms a new study from researchers in China and the UK. Published today in Translational Psychiatry, the study demonstrates for the first time that the drug improves the symptoms by decreasing the ratio of the GABA to glutamate in the brain. GABA and glutamate are both neurotransmitters – chemical messengers that help nerve cells in the brain communicate.
This study is important and exciting, because it means that there is a drug that can improve social learning and reduce autism spectrum disorder symptoms during the time when the brains of these children are still developing
Barbara Sahakian
Autism spectrum disorder (ASD) is a neurodevelopmental disorder estimated to affect one in 160 children worldwide. It is characterised by impairments in social communication, which manifest as problems with understanding emotions and with non-verbal communication, such as eye contact and smiling, and in failures to develop, maintain and understand social relationships.
Although the biological mechanisms underlying ASD remain largely unknown, previous research has suggested that it may result from changes in brain development early in life, and in particular in relation to GABA, a neurotransmitter, a chemical in the brain that controls how nerve cells communicate. In the adult brain, GABA is inhibitory, which means it switches nerve cells ‘off’. In fetal life and early postnatal development, it is mostly excitatory, switching nerve cells ‘on’ and making them fire, playing a key role in the development and maturation of nerve cells. Alterations in the GABA-switch (from excitatory to inhibitory) can cause a delay in when the developing neural circuits reach functional maturity, with consequences for network activity. This implies that intervening at an early age may help reduce some of the symptoms that can make life challenging for people with ASD.
Current treatments for ASD at preschool age are mainly behavioural interventions, such as using play and joint activities between parents and their child to boost language, social and cognitive skills. However, with limited resources there is an inequality in access to these treatments across the globe, particularly in developing countries.
Previous studies in rats and small clinical trials involving children with ASD suggest that the drug bumetanide, which has been approved for use in oedema, a condition that results in a build-up of fluid in the body, could help reduce symptoms of ASD.
Now, an international collaboration between researchers at a number of institutions across China and at the University of Cambridge, UK, has shown that bumetanide is safe to use and effective at reducing symptoms in children as young as three years old. ASD can be reliably diagnosed at age 24 months or even as early as 18 months of age.
To understand the mechanisms underlying the improvements, the researchers used a brain imaging technique known as magnetic resonance spectroscopy to study concentrations of neurotransmitters within the brain. They found that in two key brain regions – the insular cortex (which plays a role in emotions, empathy and self-awareness) and visual cortex (responsible for integrating and processing visual information) – the ratio of GABA to glutamate decreased over the three-month period in the treatment group. GABA and glutamate are known to be important for brain plasticity and promoting learning.
The team say the discovery that bumetanide changes the relative of concentrations of GABA to glutamate could provide a useful biomarker – a tell-tale biological measure – of how effective a treatment is. However, they cautioned that further research is needed to confirm the effectiveness of bumetanide as a treatment for ASD.
To read the full article, please visit the University of Cambridge website