Tag: schizophrenia

Categories : Mental Health NeurologyTags :

Schizophrenia Associated with 12-hour Gene Cycles in the Brain

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In the open-access journal PLOS Biology, researchers present the first evidence of 12-hour cycles of gene activity in the human brain. Led by Madeline R. Scott, the study also reveals that some of those 12-hour rhythms are missing or altered in the postmortem brains of patients with schizophrenia.

Schizophrenia patients are known to have disturbances in several types of 24-hour bodily rhythms, including sleep/wake cycles, hormone levels, and gene activity in the prefrontal cortex of the brain. However, virtually nothing is known about gene activity in the brain for cycles that are shorter than the usual 24-hour circadian rhythm. A few years ago, researchers discovered that certain genes in the body were associated with 12-hour bodily rhythms, which may have an origin in the 12-hour cycle of ocean tides.

As it is not possible to measure gene transcript levels in living brains, the new study instead used a time-of-death analysis to search for 12-hour rhythms in gene activity within postmortem brains. They focused on the dorsolateral prefrontal cortex as it is associated with cognitive symptoms and other abnormalities in gene expression rhythms that have been observed in schizophrenia.

Numerous genes in the normal dorsolateral prefrontal cortex were found to have 12-hour rhythms in activity. Among them, gene activity levels related to building connections between neurons peaked in the afternoon/night, while those related to mitochondrial function (and therefore cellular energy supply) peaked in the morning/evening.

In contrast, postmortem brains from patients with schizophrenia contained fewer genes with 12-hour activity cycles, and those related to neural connections were missing entirely. Additionally, although the mitochondria-related genes did maintain a 12-hour rhythm, their activity did not peak at the normal times. Whether these abnormal rhythms underlie the behavioural abnormalities in schizophrenia, or whether they result from medications, nicotine use, or sleep disturbances should be examined in future studies.

Co-author Colleen A. McClung adds: “We find that the human brain has not only circadian (24 hour) rhythms in gene expression but also 12-hour rhythms in a number of genes that are important for cellular function and neuronal maintenance. Many of these gene expression rhythms are lost in people with schizophrenia, and there is a dramatic shift in the timing of rhythms in mitochondrial-related transcripts which could lead to suboptimal mitochondrial function at the times of day when cellular energy is needed the most.”

Source: ScienceDaily

Categories : Immune System Mental HealthTags :

Autoimmune Clue in Some Schizophrenia Cases

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Mirror symbolising schizophrenia
Source: Vince Fleming on Unsplash

Schizophrenia, which affects how people interact with reality, is difficult to treat because it has many possible causes. In a study published in Cell Reports Medicine, Japanese researchers have identified an autoantibody – an antibody which attacks the body’s own tissues – in some patients with schizophrenia.

Notably, they also found that this autoantibody caused schizophrenia-like behaviours and changes in the brain when they injected it into mice.

When considering possible autoantibodies that might cause schizophrenia, researchers from Tokyo Medical and Dental University (TMDU) had a specific protein in mind. Previous research has suggested that neural cell adhesion molecule (NCAM1), which helps facilitate synaptic connections, may have a role in the development of schizophrenia.

“We decided to look for autoantibodies against NCAM1 in around 200 healthy controls and 200 patients with schizophrenia,” explained lead author of the study Hiroki Shiwaku. “We only found these autoantibodies in 12 patients, suggesting that they may be associated with the disorder in just a small subset of schizophrenia cases.”

The research went on to find out whether these autoantibodies could cause any changes that commonly occur in schizophrenia, so they purified autoantibodies from some of the patients and injected them into the brains of mice.

“The results were impressive,” said the study’s senior author, Hidehiko Takahashi. “Even though the mice only had these autoantibodies in their brains for a short time, they had changes in their behaviour and synapses that were similar to what is seen in humans with schizophrenia.”

The mice given the patient autoantibodies had cognitive impairment and changes in their regulation of the startle reflex, which are both seen in other animal models of schizophrenia. They also had fewer synapses and dendritic spines, which are structures that are important for the connections between brain cells, and are also affected in schizophrenia.

The study findings hold promise for the diagnosis and treatment of schizophrenia can present very differently among patients and is often resistant to treatment. If schizophrenia is indeed caused by autoantibodies against NCAM1 in some patients, this will lead to important improvements in their diagnosis and treatment.

Source: Tokyo Medical and Dental University

Categories : Mental HealthTags :

Researchers Hit upon a Possible Biomarker for Schizophrenia

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Investigators at Sanford Burnham Prebys have discovered that a certain protein circulating in blood could be a potential biomarker for schizophrenia. The activity of this protein, present in both the brain and blood, affects neural connections in human brains and is uniquely imbalanced in people with schizophrenia. 

The study, an international collaboration among groups at Yokohama City University Graduate School of Medicine in Japan and the Department of Psychiatry at Harvard Medical School in Belmont, Massachusetts, was recently published in PNAS.

“This study examined the activity of CRMP2, a protein found in the brain (called a ‘cytoskeletal protein’) that regulates how neurons make connections with each other,” said co-senior author of the study Evan Y Snyder, MD, PhD, director of the Center for Stem Cells and Regenerative Medicine at Sanford Burnham Prebys. “CRMP2 also happens to be expressed in lymphocytes in the blood and can therefore be readily sampled in people by doing nothing more than a simple venipuncture.

“There was an abundance of CRMP2 levels in samples from people with schizophrenia compared to people without the disorder. We also saw structural abnormalities in the dendrites of neurons that could potentially be disabling because dendrites play an important role in receiving impulses from other nerve cells in the brain.”

In previous research, most people were found to maintain an even proportion of the two forms of CRMP2: its active, non-phosphorylated form and its inactive, phosphorylated form. Postmortem brain tissue and then blood samples from people with schizophrenia were examined and compared these levels to those in people without the disorder.

The findings indicated that the amount of active CRMP2 was too high in people with schizophrenia and, at least in young people with schizophrenia, was not balanced by an appropriate amount of increased inactive CRMP2. That imbalance between active and inactive CRMP2 could account for some dysfunctions in neural connections.

Testing blood for high levels of active CRMP2, along with low levels of inactive CRMP2, could support schizophrenia diagnosis.

“Schizophrenia can be challenging to diagnose early on or in young patients for a number of reasons,” explained Dr Snyder. “Pairing a blood test with psychiatric and neurobehavioral exams could help doctors distinguish schizophrenia from other conditions that have somewhat similar symptomologies, such as the manic phase of bipolar disorder or other behavioral, personality, or thought disorders.

“Our results were most striking in people under the age of 40, and even more so in people under the age of 30. An early diagnosis could improve the clinical management of affected individuals as well as accelerate the development of new therapeutic options,” Dr Snyder added.

As a next step, the researchers want to delve into the molecular biology of the disease to discover the ‘regulator’  that balances most people’s CRMP2 levels. They also want to conduct a larger, multi-centre clinical study that compares schizophrenia with other psychiatric disorders, which would include participants from more ethnicities and age groups.

Source: Sanford Burnham Prebys Medical Discovery Institute

Journal information: Munetaka Nomoto el al., “Clinical evidence that a dysregulated neural network modulator may aid in diagnosing schizophrenia,” PNAS (2021). www.pnas.org/cgi/doi/10.1073/pnas.2100032118

Categories : Mental HealthTags :

Dietary Supplement Treats Schizophrenia in Mouse Model

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A study has found that a simple dietary supplement reduces behavioral symptoms in mice with a genetic mutation that causes schizophrenia. 

Schizophrenia is estimated to affect about 1 in 100 people globally and is one of the top 15 leading causes of disability worldwide.

The study examined the role of betaine in schizophrenia, as it is known to be reduced in the brains of schizophrenia patients. Betaine, often associated with sweetness or umami flavours, was first isolated from sugar beets and is acquired through the diet and also produced in the body. Betaine supplements are already used clinically to treat the metabolic disease homocystinuria.

“I don’t encourage anyone to take betaine for no reason, if a doctor has not recommended it. But, we know this drug is already used clinically, so repurposing it to treat schizophrenia should be safe,” said study leader Professor Nobutaka Hirokawa, MD, PhD, from the University of Tokyo Graduate School of Medicine.
“There are treatments for schizophrenia, but they have side effects and unfortunately there is still no effective drug for patients to take that we can explain biochemically why it works,” Prof Hirokawa added.

Genetic studies have found possible links between schizophrenia and variations in the kinesin family 3b (kif3b) gene as well as another gene involved in the body’s production of betaine. The researchers categorised all 45 members of the kinesin superfamily of genes in mammals, most of which encode motor proteins that move materials throughout the cell. Together with another protein kinesin superfamily, the KIF3B protein transports cargo throughout a neuron, travelling up and down the cell’s skeleton.

The researchers mice used to model schizophrenia which had only one functional copy of the kif3b gene. These mice have different behaviours to normal mice such as avoiding social interactions and being less startled by a sound test. The Kif3b mutant mice that were raised on a diet with triple the normal amount of betaine had normal behaviour.

To work out why betaine had this effect on mice, researchers grew nerve cells with the kif3b mutation in the laboratory and added fluorescent labels so they could watch the development of cellular skeleton.

Kif3b mutant neurons grown in the lab have an unusual, overly branched structure with too many dendrites, unlike the normal tree-like shape of healthy neurons. Similar overly branched neurons are also seen in brain samples donated by people with schizophrenia, regardless of any treatments or medications they took while alive.

During healthy neuron development, the cell’s main body fills with a skeleton component called tubulin. Meanwhile, the cell’s front growth cone builds outwards in a spiky, erratic dance due to the movements of another skeleton component known as filamentous actin. In kif3b mutants, this dancing movement, which experts refer to as lamellipodial dynamics, is reduced and the distinction between tubulin and actin is blurred.

Chemical analyses of the brains of kif3b mutant mice and human schizophrenia patients reveal significant chemical damage to CRMP2, a protein which helps assemble actin. This damage causes the proteins to clump together. However, betaine is known to prevent the kind of chemical damage, carbonyl stress, responsible for CRMP2 dysfunction.

“In postmortem brains of schizophrenia patients, CRMP2 is the protein in the brain with the most carbonyl stress. Betaine likely eliminates the carbonyl stress portion of the schizophrenia equation,” said Hirokawa.

It appears that by shielding CRMP2 from damage, betaine treatment allows kif3b mutant neurons to build normal structures, allowing the remaining functional KIF3B protein can shuttle cargo around the cell. Other in vitro experiments showed that KIF3B and CRMP2 can bind together, but their exact relationship remains unclear.

“We know that the amount of betaine decreases in schizophrenia patients’ brains, so this study strongly suggests betaine could be therapeutic for at least some kinds of schizophrenia,” said Hirokawa.

Source: Medical Xpress

Journal information: Shogo Yoshihara et al. Betaine ameliorates schizophrenic traits by functionally compensating for KIF3-based CRMP2 transport, Cell Reports (2021). DOI: 10.1016/j.celrep.2021.108971