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recently published study demonstrates a link
between telomere length, which is a mark of biological aging, and bipolar risk.
The research helps to explain why bipolar disorder often comes hand-in-hand
with other age-related diseases.
Individuals
with bipolar disorder carry the hallmarks of increased cellular aging.
Individuals
with bipolar
disorder, which is sometimes referred to as manic depression, experience
shifts in mood from feeling extremely energized and elated, to hopeless and
depressed. It affects an estimated 2.6 percent of adults in the United States each year.
Aside
from the psychological disruption, bipolar disorder is linked to a range of
other diseases normally associated with advanced age, such as cardiovascular
disease, type 2 diabetes, and obesity.
Recently,
researchers from King's College London in the United Kingdom and the Icahn
School of Medicine at Mount Sinai in New York City, NY, set out to probe this
relationship further. The team were particularly interested in telomeres, which
are features of chromosomes that reflect the age of an organism.
Their
findings are published in the journal Neuropsychopharmacology.
Telomeres and biological aging
Telomeres
act as protective caps on the ends of DNA strands. Each time a cell divides,
the telomere becomes shorter, until it is so short that the cell can no longer
replicate.
In
this way, telomere length can be used as a measure of biological aging and
susceptibility to disease. In older people, telomeres are generally shorter.
However, biological aging is different from chronological aging.
Various genetic and environmental factors can
influence the rate of biological aging, meaning that two people of the same
chronological age might be different ages biologically.
Telomere
length is currently being investigated as a biomarker for neuropsychiatric
conditions. For instance, shortened telomeres have been found in individuals
with major depressive disorder, schizophrenia,
and dementia.
An
association has also been found between telomere length and the structure of
the hippocampus, which is an area of the brain involved in memory and mood
regulation. Similarly, shorter telomeres are associated with reduced
memory function.
Lithium reduces bipolar-related aging
For
the new study, scientists took DNA samples from 63 patients with bipolar
disorder, 74 first-degree relatives, and 80 unrelated healthy individuals.
Relatives of individuals with bipolar disorder were included because telomere
length is known to be heritable.
They
found that, in the first-degree relatives, telomere length was significantly
shorter than in the healthy controls. In the bipolar group, telomere length was
dependent on another factor: lithium.
Lithium
is a drug commonly used to treat bipolar disorder. Individuals with the
condition who had taken this drug did not have significantly shorter telomeres,
but those that had not taken the medication showed the same reduced length as
their relatives.
This suggests that lithium prevents or minimizes the
premature aging associated with bipolar disorder, backing up previous findings.
Telomere length and the hippocampus
To
investigate the relationship between telomere length and brain structure, the
researchers conducted MRI scans on the
participants. As predicted, the team found that shorter telomeres were
associated with reduced hippocampal volume.
"Our study provides the first
evidence that familial risk for bipolar disorder is associated with shorter
telomeres, which may explain why bipolar disorder patients are also at a
greater risk for aging-related diseases."
First
author Dr. Timothy Powell, King's College London
These
findings are interesting in their own right, but they open up a range of new
questions to be answered. Dr. Powell gives an example, asking, "For instance,
do those at risk for bipolar disorder carry genes predisposing them to faster
biological aging, or are they more likely to partake in environmental factors
which promote aging (e.g. smoking, poor diet)? Identifying modifiable risk
factors to prevent advanced aging would be a really important next step."
These
findings may open up new avenues of research into new interventions. In fact,
co-senior author Dr. Sophia Frangou says that the results suggest "that
proteins which protect against telomere shortening may provide novel treatment
targets for people with bipolar disorder and those predisposed to it."
There
is much work to be done, but the links between telomeres, premature aging, and
neuropsychiatric conditions are sure to yield fascinating and useful results
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