Aug. 13, 2016
Hundreds
of articles published this month further advanced our knowledge of
neuroscience. Lots of new discoveries published in July relate to some of the
most fundamental processes in the brain that shape our daily life, as well as
to the practical problems doctors have to deal with on a regular basis. The
selection of articles presented here reflects my personal opinion about their
importance – there were many more interesting articles that simply could
not be covered by this short review.
In
the beginning of July, scientific community marked the birthday of Alfred
Gilman, who received the 1994 Nobel Prize in Physiology and Medicine for his
work on G-proteins. These days, the description of G-proteins and their
functions can be found in every textbook on physiology and neurology, as they
are heavily involved in the processes of intercellular communication. Even in
this review G-proteins are mentioned in relation to some recent findings.
THE
BEST
Breast-fed
pre-term infants develop higher IQ later in life
New
observational study on pre-term infants confirm the
importance of feeding them with breast milk. The infants who received
predominantly breast milk during the first 28 days of life had higher IQ and
better cognitive and motor functions at age 7. MRI study demonstrated that at
this age the breast-fed children had larger volume of deep nuclear grey matter,
which plays important role in signal processing and connecting different parts
of brain.
Mechanism
of Levodopa-induced dyskinesia uncovered
Levodopa
is essential for treating patients with Parkinson’s disease, but unfortunately
many patients develop undesirable side effects such as dyskinesia, involuntary
rapid repetitive movements, after several years on the drug. Researchers
have uncovered that
the development of dyskinesia is linked to the changes in methylation of
certain genes, as levodopa can change the expression of DNA methylases.
Methylation affects gene expression and results in altered amount of
corresponding proteins, thus disturbing the normal homeostasis. Experiments on
animals show that drug therapies aimed at amending the DNA methylation level
can reduced dyskinesia symptoms.
Slow
action of antidepressants explained
Most
commonly used antidepressant from the serotonin reuptake inhibitors family are
know to take up to 2 months to start producing positive effects in the patients.
Researchers have now discovered the molecular mechanism responsible for this
slow action. It turned out that in people with depression, the signalling
G-protein molecules involved in the response to the drug are bound to the lipid
rafts on the membranes of neurons where they cannot effectively participate in
the signalling response. The study point
to a potential approach that may improve the efficacy of antidepressants.
Anti-cancer
drug promising for treating Alzheimer’s disease
An
FDA-approved anti-cancer drug pazopanib, an inhibitor of tyrosine kinase, was shown to
reduce the level of phosphorylation of tau-protein, one of the key culprits in
the development of Alzheimer’s disease. In laboratory animals, the effect of
the drug led to the improved clearance of toxic proteins from the brain. The
drug is known to penetrate the blood-brain barrier and is effective in the
doses half of those used in cancer treatment. In addition, pazopanib causes few
side effects. The use of pazopanib in human subjects with Alzheimer’s requires
further investigations.
fMRI
helped to visualize brain activity during hypnosis
Hypnosis
gradually emerged as a promising form of psychotherapy, but our knowledge of
brain processes in hypnotized state is still remains in its infancy.
Researchers used fMRI to study the brain of people during hypnosis sessions.
They found that
in hypnotized people the activity of dorsal anterior cingulate is decreased,
the connectivity between dorsolateral prefrontal cortex and the insula is
increased, and the connectivity between dorsolateral prefrontal complex and the
default mode network is reduced. These changes reflect the reduced state of
worrying, increased brain control over processes in the body, and reduced
awareness of one’s actions. Interestingly, these changes were most prominent
only among highly hypnotizable people, which represent around 10% of general
population.
THE
WORST
Antibiotics
increase frequency of manic episodes in psychiatric patients
It
is well established that the composition of bacterial microbiome in the gut
influence the work of our brain – this phenomenon is referred to as the gut
brain axis. It appears that the connection is rather prominent in people with
psychiatric disorders. Recent study suggests
that people with serious mental illnesses such as bipolar syndrome,
schizophrenia or major depression, are more likely to experience manic episode
at the time when they are treated with antibiotics. Antibiotics are known to
disrupt the bacterial flora in the gastrointestinal tract. This disruption may,
in turn, lead to behavioural alterations. Researchers suggest that preventive
treatments minimizing the use of antibiotics in psychiatric patients may reduce
the frequency of manic episodes.
No
link between traumatic brain injury and Alzheimer’s disease
Large
number of previous studies reported association between traumatic brain injury
(TBI) and the development of neurodegenerative diseases such as Alzheimer’s
later in life. The study published
this month questions this conclusion. By analysing data from over 7,000 older
adults (the largest cohort for this kind of study reported so far), researchers
found a strong positive association between TBI and Parkinson’s disease, but no
association between TBI and either Alzheimer’s disease or dementia.
Further work is needed to establish the mechanisms of and the factors
influencing post-TBI neurodegeneration.
Potential
dangers of transcranial direct current stimulation (tDCS)
Transcranial
direct current stimulation (tDCS) is becoming a popular approach to enhance
brain functions. tDSC devices are simple, and the practice of
self-administering them grew in popularity in recent years. This trend alarms
researchers who warned in the open letter that such DIY approach may lead to
unintended consequences. The letter published
by scientists this month points to the fact that the method is still very new
and it is not even known how the stimulation causes positive effects. It is
also not clear how tDCS affects the surrounding areas of the brain that are not
directly targeted, and what are the effects of larger accumulated doses
administered over longer periods of time. The effectiveness of the method also
varies from person to person, and there is a possibility that small changes in
the electrode placement and frequency may lead to undesirable effects.
Link
betwen Alzheimer’s and brain blood vessels problems underestimated
Although
risk factors associated with dementia and Alzheimer’s disease are well studied,
the role of brain blood vessels received very little attention. Recent study demonstrated
that the importance of this factor was clearly underestimated. Atherosclerosis
(plaques in the larger brain arteries) and arteriolosclerosis (hardening of the
smaller artery walls) strongly correlate with the chances of having dementia.
Problems with blood vessels in the brain also correlated significantly with
reduced cognitive abilities and performance in memory tests.
Reduced
physical activity after menopause linked to changes in brain
Post-menopausal
women often experience weight gain. This was often explained by the changes in
hormonal status. New evidences,
however, suggest that this phenomenon is associated with brain changes, more
specifically with the reduction in dopamine signalling level. This leads to
decreased stimulation of pleasure centre and lack of motivation for being more
physically active. Activation of dopamine receptors may potentially reverse
this process.
Bibliography:
Mandy
B. Belfort, MD, MPH et al. Breast Milk Feeding, Brain Development, and
Neurocognitive Outcomes: A 7-Year Longitudinal Study in Infants Born at Less
Than 30 Weeks’ Gestation. The Journal of Pediatrics, July 2016
DOI: 10.1016/j.jpeds.2016.06.045
A.
Figge, K. L. Eskow Jaunarajs, D. G. Standaert. Dynamic DNA Methylation
Regulates Levodopa-Induced Dyskinesia. Journal of Neuroscience,
2016; 36 (24): 6514 DOI: 10.1523/JNEUROSCI.0683-16.2016
Samuel
J. Erb, Jeffrey M. Schappi, Mark M. Rasenick. Antidepressants
Accumulate in Lipid Rafts Independent of Monoamine Transporters to Modulate
Redistribution of the G protein, G?s. Journal of Biological
Chemistry, 2016; jbc.M116.727263 DOI: 10.1074/jbc.M116.727263
Monica
Javidnia, Michaeline Hebron, Hannah J Brown, Charbel E-H Moussa. Pazopanib
Is a Potential Therapeutic for Tauopathies. AAIC 2017, July 16-20,
London. Abstract ID: a8677.
Heidi
Jiang, Matthew P. White, Michael D. Greicius, Lynn C. Waelde, and David
Spiegel. Brain Activity and Functional Connectivity Associated with
Hypnosis. Cerebral Cortex, July 2016 DOI: 10.1093/cercor/bhw220
Robert
Yolken, Maria Adamos, Emily Katsafanas, Sunil Khushalani, Andrea Origoni,
Christina Savage, Lucy Schweinfurth, Cassie Stallings, Kevin Sweeney, Faith
Dickerson. Individuals hospitalized with acute mania have increased
exposure to antimicrobial medications. Bipolar Disorders, 2016;
DOI: 10.1111/bdi.12416
Paul
K. Crane, Laura E. Gibbons, Kristen Dams-O’Connor, Emily Trittschuh, James B.
Leverenz, C. Dirk Keene, Joshua Sonnen, Thomas J. Montine, David A. Bennett,
Sue Leurgans, Julie A. Schneider, Eric B. Larson. Association of
Traumatic Brain Injury With Late-Life Neurodegenerative Conditions and
Neuropathologic Findings. JAMA Neurology, 2016; DOI: 10.1001/jamaneurol.2016.1948
Rachel
Wurzman, Roy H. Hamilton, Alvaro Pascual-Leone, Michael D. Fox. An open
letter concerning do-it-yourself users of transcranial direct current
stimulation. Annals of Neurology, 2016; 80 (1): 1 DOI: 10.1002/ana.24689
Zoe
Arvanitakis, Ana W Capuano, Sue E Leurgans, David A Bennett, Julie A
Schneider. Relation of cerebral vessel disease to Alzheimer’s disease
dementia and cognitive function in elderly people: a cross-sectional study. The
Lancet Neurology, 2016; DOI: 10.1016/S1474-4422(16)30029-1
Young-Min
Park, Jill A. Kanaley, Jaume Padilla, Terese Zidon, Rebecca J. Welly, Matthew
J. Will, Steven L. Britton, Lauren G. Koch, Gregory N. Ruegsegger, Frank W.
Booth, John P. Thyfault, Victoria J. Vieira-Potter. Effects of
intrinsic aerobic capacity and ovariectomy on voluntary wheel running and
nucleus accumbens dopamine receptor gene expression. Physiology
& Behavior, 2016; 164: 383 DOI: 10.1016/j.physbeh.2016.06.006
Viatcheslav Wlassoff, PhD, is a scientific and medical
consultant with experience in pharmaceutical and genetic research. He has an
extensive publication history on various topics related to medical sciences. He
worked at several leading academic institutions around the globe (Cambridge
University (UK), University of New South Wales (Australia), National Institute
of Genetics (Japan). Dr. Wlassoff runs consulting service specialized on
preparation of scientific publications, medical and scientific writing and
editing.
http://brainblogger.com/2016/08/13/best-and-worst-of-neuroscience-and-neurology-july-2016/
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