Neuroimaging shows genetics and environment affect different regions of brain.


It is known that glucose is an essential fuel for brain energy metabolism as well as oxygen.  Functional activation of neurons is normally associated with increases in the local cerebral glucose utilization and blood flow.  However, factors influencing variations in cerebral metabolism itself have not been investigated yet.  Now, a study from researchers at Osaka University shows that genetic influence on cerebral glucose metabolism plays a major role in the bilateral parietal lobes and the left temporal lobe of the human brain, while environmental influences after birth dominated in other regions.  The opensource study is published in The Journal of Nuclear Medicine.

Previous studies show that the patterns of glucose metabolism appear to be influenced by various factors, including genetic and environmental ones.  The magnitude and proportion of these influences remains unclear.  To help with this dilemma, twins have long been part of the quest to determine the influences of nature vs. environment, or nurture.  With earlier studies examining more than half a century of research collected on 14.5 million pairs of twins concluding that the nature versus nurture debate is a draw.  Findings showed that both have nearly identical influences on a person’s traits and diseases.  However, researchers still didn’t know specifically how nature and environment can affect the human brain.

The current study investigated 40 identical and 18 fraternal twin pairs, ages 30 or older; eighteen control pairs matched genetically unrelated individuals of the same age and gender as the twins in the study.  The lab used positron emission tomography (PET) scans with the radiopharmaceutical 2-deoxy-2-F-18-fluoro-D-glucose (FDG) targeting regional cerebral glucose metabolism.

The team evaluated the F-18 FDG uptake in each cerebral lobe for the identical and fraternal twins as well as the controls. Results show that by comparing differences, they could estimate the genetic and environmental contributions.

The lab note that previous studies have revealed strong genetic influence on the volume of frontal gray matter, whereas their data findings show that frontal glucose metabolism is preferentially influenced by environmental factors. They go on to conclude that knowing which areas of the brain are more influenced by the environment will help with understanding particular neurological and psychiatric disorders.

The team surmise that the frontal lobes of monozygotic twins are anatomically identical, however, they are metabolically and functionally different under environmental influences. For the future, the researchers state that their twin-imaging technique can be applied to amyloid imaging in Alzheimer’s disease and neurotransmitter-receptor imaging in psychiatric disorders where genetic, epigenetic and environmental influences remain unknown, to identify specific environmental risk factors.

Source: The Society of Nuclear Medicine and Molecular Imaging (SNMMI)

 

Similarity images of dizygotic and monozygotic pairs compared by control pairs. Average difference in SUV ratio (as percentage difference in control pairs) between members of dizygotic twins and monozygotic twins is displayed pixel by pixel on standard MR brain atlas in color scale. Average difference in SUV ratio between members of control pairs was set to be 100%.  Genetic and Environmental Influences on Regional Brain Uptake of 2-deoxy-2-18F-fluoro-D-glucose: a PET Study in Monozygotic and Dizygotic Twins.  Watanabe et al 2016.

Similarity images of dizygotic and monozygotic pairs compared by control pairs. Average difference in SUV ratio (as percentage difference in control pairs) between members of dizygotic twins and
monozygotic twins is displayed pixel by pixel on standard MR brain atlas in color scale. Average difference in SUV ratio between members of control pairs was set to be 100%. Genetic and Environmental Influences on Regional Brain Uptake of 2-deoxy-2-18F-fluoro-D-glucose: a PET Study in Monozygotic and Dizygotic Twins. Watanabe et al 2016.

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