This blog does try to be based on evidence, but sometimes you do have to question the validity of what appears in peer reviewed journals. It might concern what does, or does not cross the blood brain barrier, or what works in vivo versus in vitro.
Two interesting papers were recently brought to my attention regarding Bumetanide.
With a pinch of salt is an English idiom which means
to view something with skepticism
In Tyler’s paper it was rats with epilepsy showing big improvements when taking Bumetanide.
In Agnieszka’s paper, involving mice and Chinese hamsters, researchers are making the point that so little Bumetanide crosses into the brain that its therapeutic value is limited.
So which is true?
Well it seems that in some humans with autism enough bumetanide crosses the blood brain barrier (BBB) to show a positive effect. Perhaps if a more penetrative analogue of Bumetanide was developed, it would show even greater effect, otherwise adjunct therapies may be needed (Acetazolamide, potassium bromide, estradiol etc) to gain the full benefit of lowering intracellular chloride.
In the past I have made the case for bumetanide possibly reducing the incidence of epilepsy developing in autism and that this really would be important. This does not mean that one person with autism might not develop epilepsy around the same time he started taking bumetanide. In the study below the rats with seizures seemed to be protected by bumetanide and the number of harmful neural connections detected in the brain was significantly reduced.
Multiple blood-brain barrier transport mechanisms limit bumetanide accumulation, and therapeutic potential, in the mammalian brain.
There is accumulating evidence that bumetanide, which has been used over decades as a potent loop diuretic, also exerts effects on brain disorders, including autism, neonatal seizures, and epilepsy, which are not related to its effects on the kidney but rather mediated by inhibition of the neuronal Na-K-Cl cotransporter isoform NKCC1. However, following systemic administration, brain levels of bumetanide are typically below those needed to inhibit NKCC1, which critically limits its clinical use for treating brain disorders. Recently, active efflux transport at the blood-brain barrier (BBB) has been suggested as a process involved in the low brain:plasma ratio of bumetanide, but it is presently not clear which transporters are involved. Understanding the processes explaining the poor brain penetration of bumetanide is needed for developing strategies to improve the brain delivery of this drug. In the present study, we administered probenecid and more selective inhibitors of active transport carriers at the BBB directly into the brain of mice to minimize the contribution of peripheral effects on the brain penetration of bumetanide. Furthermore, in vitro experiments with mouse organic anion transporter 3 (Oat3)-overexpressing Chinese hamster ovary cells were performed to study the interaction of bumetanide, bumetanide derivatives, and several known inhibitors of Oats on Oat3-mediated transport. The in vivo experiments demonstrated that the uptake and efflux of bumetanide at the BBB is much more complex than previously thought. It seems that both restricted passive diffusion and active efflux transport, mediated by Oat3 but also organic anion-transporting polypeptide (Oatp) Oatp1a4 and multidrug resistance protein 4 explain the extremely low brain concentrations that are achieved after systemic administration of bumetanide, limiting the use of this drug for targeting abnormal expression of neuronal NKCC1 in brain diseases.
Prolonged epileptic seizures may cause serious problems that will continue for the rest of a patient's life. As a result of a seizure, neural connections of the brain may be rewired in an incorrect way. This may result in seizures that are difficult to control with medication. Mechanisms underlying this phenomenon are not entirely known, which makes current therapies ineffective in some patients.
A study conducted with a rat epilepsy model at the Neuroscience Center of the University of Helsinki showed that a change in the function of gamma-aminobutyric acid (GABA), a main neurotransmitter in the brain, is an underlying cause in the creation of harmful neural connections.
After a prolonged convulsive seizure, instead of the usual inhibitory effect of the transmitter, GABA accelerates brain activity. This, in turn, creates new, harmful neural connections, says Research Director Claudio Rivera.
The accelerating effect of GABA was blocked for three days with a drug called bumetanide given soon after a seizure. Two months after the seizure, the number of harmful connections detected in the brain was significantly lower.
"Most importantly, the number of convulsive seizures diminished markedly," says Claudio Rivera.
In this study, new indications may be found for bumetanide in the treatment of epilepsy. Bumetanide is a diuretic already in clinical use. Extensive clinical studies have already been conducted with bumetanide regarding its ability to reduce the amount of convulsions or prevent them entirely in the acute phase of seizures. This, however, is the first time that bumetanide has been found to have a long-term effect on the neural network structure of the brain.
Further study of the newly found mechanism may eventually help limit the exacerbation of epilepsy and prevent the onset of permanent epilepsy after an individual serious seizure. It may also be possible that a similar mechanism is responsible for the onset of epilepsy after a traumatic brain injury.
"The next step is to study bumetanide both by itself and in combination with other clinically used drugs. We want to find out the ways in which it may offer additional benefits in the treatment of epilepsy in combination with and even in place of currently used antiepileptic drugs," says Claudio Rivera.
Vitamin D and Autism
Two medical readers of this blog highlighted this recent paper showing an apparent universal benefit of vitamin D supplementation in autism.
Is it too good to be true? Time for the pinch of salt?
One important point to note is that this study was in Egypt and, although sunny, are children there eating food that has already been fortified with vitamin D, like it is in Western countries?
Autism spectrum disorder (ASD) is a frequent developmental disorder characterized by pervasive deficits in social interaction, impairment in verbal and nonverbal communication, and stereotyped patterns of interests and activities. It has been previously reported that there is vitamin D deficiency in autistic children; however, there is a lack of randomized controlled trials of vitamin D supplementation in ASD children.
This study is a double-blinded, randomized clinical trial (RCT) that was conducted on 109 children with ASD (85 boys and 24 girls; aged 3-10 years). The aim of this study was to assess the effects of vitamin D supplementation on the core symptoms of autism in children. ASD patients were randomized to receive vitamin D3 or placebo for 4 months. The serum levels of 25-hydroxycholecalciferol (25 (OH)D) were measured at the beginning and at the end of the study. The autism severity and social maturity of the children were assessed by the Childhood Autism Rating Scale (CARS), Aberrant Behavior Checklist (ABC), Social Responsiveness Scale (SRS), and the Autism Treatment Evaluation Checklist (ATEC).
Supplementation of vitamin D was well tolerated by the ASD children. The daily doses used in the therapy group was 300 IU vitamin D3/kg/day, not to exceed 5,000 IU/day. The autism symptoms of the children improved significantly, following 4-month vitamin D3 supplementation, but not in the placebo group. This study demonstrates the efficacy and tolerability of high doses of vitamin D3 in children with ASD.
This study is the first double-blinded RCT proving the efficacy of vitamin D3 in ASD patients. Depending on the parameters measured in the study, oral vitamin D supplementation may safely improve signs and symptoms of ASD and could be recommended for children with ASD. At this stage, this study is a single RCT with a small number of patients, and a great deal of additional wide-scale studies are needed to critically validate the efficacy of vitamin D in ASD.