Alcohol en de hersenen*
Wat al in dierenstudies gebleken was dat alcohol hersenschade en veroudering van de hersenen teweeg brengt blijkt nu in deze studie bewezen te worden met onderzoek naar de hersenen van overleden alcoholisten. Alcohol is giftig voor het lichaam en gelukkig moet het eerst door het maagdarmkanaal waar enzymen het voor een groot gedeelte ontgiften voordat het bijv. in de hersenen terecht kan komen. Doch bij grote hoeveelheden ineens of lagere hoeveelheden gedurende langere tijd kan alcohol in de hersenen de hersencellen beschadigen en zelfs doen afsterven. Belangrijk hierbij zijn de insuline en
IGF (insulinegelijkende groeifactor) receptoren, die zorgen voor voldoende energie in de hersencellen. Alcohol zorgt ervoor dat deze receptoren minder effectief worden waardoor de cellen minder actief worden en zelfs af kunnen sterven.
Uit een andere studie blijkt dat het vooraal (veel) wijn is dat de hersenen beschadigd meer dan bijv. bier of sterke drank. In de studie werd gekeken naar de hippocampus, een gebied van de hersenen wat o.m. betrokken is bij het ophalen van herinneringen die nog relatief vers in het geheugen liggen en het bewustzijnsvermogen. Bij niet alcohol gebruikers was de hippocampus 3,85 ml groot, bij bierdrinkers 3,4 ml,bij drinkers van sterke drank 2,9 ml en bij wijndrinkers 2,8 ml.
Alcohol Abuse Can Damage The Brain By Decreasing Insulin And Insulin-Like Growth Factor Receptors
Too much alcohol can cause permanent brain damage, such as Wernicke-Korsakoff syndrome, which is largely related to thiamine deficiency. Previous animal studies have shown that alcohol can also cause brain injury and degeneration by inhibiting insulin and insulin-like growth factor (IGF). A new study using postmortem human brain tissue has found that chronic alcohol abuse can decrease levels of genes needed for brain cells to respond to insulin/IGF, leading to neurodegeneration similar to that caused by Type 2 diabetes mellitus.
Results will be published in the September issue of Alcoholism: Clinical & Experimental Research and are currently available at OnlineEarly.
"Insulin is one of the most important hormones in the body," said Suzanne de la Monte, professor of pathology/ neuropathology and clinical neuroscience at Rhode Island Hospital and the Warren Alpert School of Medicine at Brown University. "It has many functions, including regulation of metabolism. Cells throughout the body depend upon insulin just to stay alive and carry out 'ordinary daily functions.' The best known diseases associated with abnormalities in insulin's availability or actions are Type 1 and Type 2 diabetes." De la Monte is also the study's corresponding author.
During the past several years, she added, there has been growing interest in insulin's effects on brain function. Scientists now believe that deficiencies in insulin, and the loss of brain cells' ability to respond to insulin, are critical factors leading to neurodegeneration, including Alzheimer's dementia. Alcohol may exacerbate the
problem.
"Alcohol is a toxin that clearly can injure or kill brain cells," de la Monte said. "Fortunately, alcohol has to pass through the gastrointestinal tract and liver where enzymes detoxify alcohol, and consequently reduce the levels that reach the brain. However, in either high concentrations, or at lower levels over a longer period of time, alcohol will dissolve some of the lipid in the cell's membrane."
This is where insulin and IGF receptors normally sit, in the cell's membrane, waiting to initiate a signal that tells the cells to make more energy. Earlier animal and tissue research showed that alcohol-related damage causes insulin and IGF receptors to become less accommodating, and the signals needed for cells to increase energy production and stay alive instead become weak and ineffective.
For this study, researchers examined brain tissue from six male chronic alcoholics with a mean age of 57.7 years, and six male "controls" without alcoholism with a mean age of 57.5 years, provided through the New South Wales Tissue Resource Centre at The University of Sydney. Two brain regions were selected for study - the cerebellar cortex in the anterior superior cerebellar vermis region, and the anterior cingulate gyrus in the frontal lobe - as they represent major targets of alcohol's neurotoxicity.
"Our study of human alcoholic brains is really the first of its kind, where we were able to study the effects of chronic alcohol abuse on brain degeneration," said de la Monte. "The subjects had all signed up to donate their brains, and they were included only if alcohol was the only drug used in
life."
The results showed that in chronic alcoholics' brains, there was significant insulin and IGF resistance in those regions known to be highly sensitive to alcohol's toxic effects.
"Insulin and IGF resistance in the cerebellum and frontal lobe was associated with loss of neurons and their connections, and decreased levels of neurotransmitters needed for learning, memory, and motor function," said de la Monte. "The damage that we saw in the cerebellum would account for the poor balance, and increased rates of falling and trauma we see in alcoholics. The insulin and IGF resistance in alcoholics' frontal lobes would account for their associated problems in
memory."
De la Monte added that the insulin resistance their study found was quite similar to what happens in Type 2 diabetes, which means that alcoholic brain disease may be treatable in part by use of drugs that make brain cells more responsive to insulin and IGF.
"Public-health warnings about problems associated with alcohol abuse are fairly prevalent today, but the major emphasis seems to be on the short-term effects related to impairments that cause accidents and promote violence," said de la Monte. "Most people also seem to know that alcohol abuse damages the liver. What I believe is not well known to the public is that, over the long haul, heavy drinking will permanently damage the brain and cause dementia. Some of the dementia is certainly related to a lack of thiamine, also known as Vitamin B1, however, in the majority of cases, thiamine deficiency is not the principal problem. Our study indicates that chronic alcohol abuse causes a Type 2 diabetes effect in certain brain
regions."
De la Monte recommended that readers who are concerned about family or friends having problems with memory or behavior, and are concerned about dementia, to consider prior drinking habits and report this to a professional if warranted. "All dementias are not caused by Alzheimer's disease," she said.
Wine harder on the brain than beer
Scientists say wine damages the brain more than beer or spirits, because it particularly affects the hippocampus, the part of the brain associated with memory and spatial awareness.
The hippocampus is one of the first areas to be affected by Alzheimer's disease.
The psychiatrists who conducted the study compared brain scans from diagnosed alcoholics with those from healthy adults and they say the revelation could explain why millions forget what they are doing mid-task.
The researchers found that wine shrinks the hippocampus and as women tend to drink more wine than beer, they are more likely to be affected; many middle-age drinkers also drink wine for its supposed health benefits.
The team of psychiatrists found the hippocampus, which is located deep within the brain's temporal lobes, was up to 10 per cent smaller in those who drank and they say this is the first study to investigate the impact of the type of preferred beverage on brain-volume shrinkage in patients with alcohol dependence.
The study found that in non-alcoholics the hippocampus was 3.85ml, in beer drinkers it was 3.4ml, in spirit drinkers 2.9ml and for wine drinkers it was the smallest, just 2.8ml; in the case of beer drinkers some had consumed twice as much alcohol as the wine lovers.
The hippocampus controls memory, navigation and spatial awareness and when affected by alcohol it can also cause feelings of disorientation.
The researchers at Germany's Göttingen University found that beer drinkers also had the lowest levels of a compound in the blood called homocysteine a compound found to be linked to higher rates of heart disease, strokes, brain atrophy and dementia.
The researchers from Göttingen University, in Germany suggest that the B vitamins and folate in beer may help to break down homocysteine.
Research in recent years has linked moderate wine drinking to a plethora of health benefits, including reducing cholesterol and high blood pressure and resveratol, a molecule found in the skin of red grapes, has been associated with health benefits including a reduced risk of heart disease, strokes and some cancers.
Other research however has linked moderate alcohol consumption to an increased the risk of bowel cancer and the over-consumption of any alcohol to increased risk of kidney and liver disease, long-term brain damage and organ failure.
The study is published in the medical journal Alcohol and Alcoholism. (Augustus
2008)
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