genes

Alzheimer's expressed differently in carriers and noncarriers of the Alzheimer’s gene

July, 2010
  • A new study reveals that having the 'Alzheimer's gene' doesn't simply increase your risk of developing Alzheimer's, but affects how the brain is damaged.

A comprehensive study reveals how the ‘Alzheimer's gene’ (APOE ε4) affects the nature of the disease. It is not simply that those with the gene variant tend to be more impaired (in terms of both memory loss and brain damage) than those without. Different parts of the brain (and thus different functions) tend to be differentially affected, depending on whether the individual is a carrier of the gene or not. Carriers displayed significantly greater impairment on tests of memory retention, while noncarriers were more impaired on tests of working memory, executive control, and lexical access. Consistent with this, carriers showed greater atrophy in the mediotemporal lobe, and noncarriers greater atrophy in the frontoparietal area. The findings have implications both for diagnosis and treatment.

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Gene variant may protect memory and thinking skills in older people

April, 2010

The role of the dopamine-regulating COMT gene in cognitive function has been the subject of debate. Now a large study of older adults has revealed that the Met variant of the COMT gene was linked to a greater decline in cognitive function. This effect was more pronounced for African-Americans.

The role of the catechol-O-methyltransferase (COMT) gene in cognitive function has been the subject of some debate. The gene, which affects dopamine, comes in two flavors: Val and Met. One recent study found no difference between healthy carriers of these two gene variants in terms of cognitive performance, but did find differences in terms of neural activity. Another found that, although the gene did not affect Alzheimer’s risk in its own, it acted synergistically with the Alzheimer’s gene variant to do so. Now an eight-year study of nearly 3000 adults in their 70s has revealed that the Met variant of the COMT gene was linked to a greater decline in cognitive function. This effect was more pronounced for African-Americans. This is interesting because it has been the Val genotype that in other research has been shown to have a detrimental effect. It seems likely that this genotype must be considered in its context (age, race, gender, and ApoE status have all been implicated in research).

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Obesity gene, carried by more than a third of the US population, leads to brain tissue loss

April, 2010
  • A variant of a gene called the fat mass and obesity associated (FTO) gene causes people to gain weight and puts them at risk for obesity.
  • A new study suggests that this gene variant is also associated with loss of brain tissue, in that, if you have this gene variant, your weight is associated with neuron loss, and if you don't, it isn’t.

A variant of a gene called the fat mass and obesity associated (FTO) gene causes people to gain weight and puts them at risk for obesity. The gene variant is found in nearly half of all people in the U.S. with European ancestry, around one-quarter of U.S. Hispanics, 15 percent of African Americans and 15 percent of Asian Americans. A new study involving 206 healthy elderly subjects from around the U.S. now suggests that this gene variant is also associated with loss of brain tissue. It’s not clear why, but the gene is highly expressed in the brain. Those with the "bad" version of the FTO gene had an average of 8% less tissue in the frontal lobes, and 12% less in the occipital lobes. The brain differences could not be directly attributed to other obesity-related factors (cholesterol levels, hypertension, or the volume of white matter hyperintensities), which didn’t vary between carriers and non-carriers. But if you have this gene variant, your weight is associated with neuron loss, and if you don't, it isn’t. The finding emphasizes the need for those with the gene to fight weight gain (and brain loss) by exercising and eating healthily.

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