Bipolar disorder (BD) is a common psychiatric
disorder with a lifetime prevalence of approximately 1%. It is characterized by mood swings between positive
manic/hypomanic and negative/depressive states.
studies indicate that genetic components contribute to BD development,
several genome-wide association studies (GWASs) identified limited
number of susceptibility (risk) genes for BD, most of which are yet
‘A novel risk gene (FADS1 and FADS2) for bipolar disorder has been identified by researchers.’
Collaborative research in Japan, under the guidance of the principle
investigators from Fujita Health University and RIKEN, led to the
identification of a novel risk gene (FADS1 and FADS2) for bipolar
disorder via GWAS performed using samples collected in Japan (2,964
cases and 61,887 comparison subjects).
The function of this gene is well
established: metabolism of lipids, including blood lipids (e.g.,
cholesterol and triglyceride) and omega3/6 polyunsaturated fatty acids
(PUFA). Previous epidemiological surveys have shown that prevalence of
hyperglycemia or metabolic syndrome in patients with BD was higher than
that of the general population; hence, the researchers concluded that
lipid abnormality may be involved in BD pathophysiology.
To maximize the sample size, the researchers then conducted a
meta-analysis between their samples and results from the publicly
available BD GWAS database (Psychiatric GWAS Consortium). They
identified an additional novel gene for BD (NFIX) and supported three
previously implicated genes (ODZ4, MAD1L1, and TRANK1).
The sample size analyzed in this study is one of the largest,
especially as samples were collected in Asian populations. However,
because of the extremely small effect size of the BD risk (i.e., odds
ratio ~1.2), Prof. Nakao Iwata says, "a large number of risk genes are
still unidentified. Therefore further study is essential."
In addition, he says, "We cannot use this information in the clinical
setting yet. After elucidating a concrete association of these genes
with BD, in terms of their function, new therapeutic strategies may be
developed, including the development of new drugs."