Remember those “mighty mitochondria” from your high school biology class? In the last few years, some research studies have focused on these little cellular powerhouses as a potential cause of bipolar disorder.
The mitochondria are organelles - the organ-like components of cells - that through the conversion of glucose provide energy to the rest of the cell. They occur in various numbers, shapes, and sizes in the cytoplasm of all cells in fungi, animals, and plants as well as some unicellular organisms (NCBI, 2004). In addition to this primary function, the mitochondria also play an important regulatory role in other cellular processes such as cellular reproduction, steroid synthesis and heat production to name a few. In short, these structures are vital to the human body.
In the March 1, 2004, edition of Archives of General Psychiatry, researchers at McLean Hospital published findings of a study that may implicate the mitochondria as a cause for bipolar disorder. In individuals with bipolar disorder, something in the energy conversion appears to go awry. This study found that the genes that make the proteins involved in energy transfer were significantly "down-regulated" in the brains of those with bipolar disorder. Dr. Christine Konradi, the lead investigator on this project, writes, “The reduction of these genes indicates that either there are not enough of these 'power plants' in the cells or that these power plants are not efficient. Our study therefore suggests a causal relationship between bipolar disorder and decreased energy transfer. If this is the case, it could completely refocus our approach to the treatment of bipolar disorder."
More recently an article in the journal Molecular Psychiatry also reported a link between bipolar disorder and mitochondria. In this study, the research team genetically engineered mice to have dysfunctioning mitochondria within brain nerve cells. The results included mice with typical behaviors associated with bipolar disorder. The research report, “The mutant mice exhibited characteristic behavioral phenotypes, a distorted day–night rhythm and a robust periodic activity pattern associated with estrous cycle. These abnormal behaviors resembling mood disorder were worsened by tricyclic antidepressant treatment and improved by lithium, a mood stabilizer. We also observed antidepressant-induced mania-like behavior and long-lasting irregularity of activity in some mutant animals. Our data suggest that accumulation of mtDNA defects in brain caused mood disorder-like mental symptoms with similar treatment responses to bipolar disorder.” (Kasahara et al, 2006).
References
Kasahara, T.; Kubota, M.; Miyauchi, T.; Noda, Y.; Mouri, A.;Nabeshima, T. & Kato, T. (2006, April 18). Mice with neuron-specific accumulation of mitochondrial DNA mutations show mood disorder-like phenotypes. Molecular Psychiatry.
Konradi C.; Eaton M.; MacDonald M.L.; Walsh J.; Benes F.M. & Heckers S. (2004, June). Molecular evidence for mitochondrial dysfunction in bipolar disorder. Archives of General Psychiatry.
National Center for Biotechnology Information (NCBI). (2004). What is a cell? A Science Primer.
