PTSD linked to low levels of adiponectin

Researchers have reported a biological mechanism that might explain why individuals with post-traumatic stress disorder (PTSD) relive past traumas again and again.

The School of Medicine at The University of Texas (UT) Health Science Centre at San Antonio has filed for patent protection on the finding because it may eventually lead to a drug to treat PTSD.

The new research centres on the hormone adiponectin, which is secreted by fat cells called adipocytes.

The scientists studied a mouse model of PTSD. These mice were trained to associate a setting, such as a box, with a mild unpleasant stimulus. As expected, they showed a fear response when re-exposed to the setting.

Mice deficient for adiponectin and its receptor formed fearful memories just like healthy mice, but when placed again in the same setting minus the unpleasant stimulus, were slower to let go of the fear.

Injecting adiponectin prior to this training prompted faster learning to overcome fear, the measurements showed.

“Once the threat is no longer there, the fear should go away, but in PTSD it keeps flashing back,” said Xin-Yun Lu, M.D., Ph.D., professor of pharmacology and a member of the Barshop Institute for Aging and Longevity Studies at the UT Health Science Centre. “In the PTSD animal model, the circulating adiponectin is low, data suggest. If the genes encoding adiponectin and its receptor are disrupted, the mice extinguish fear responses much slower. If adiponectin levels are elevated in the brain, the mice get extinction faster.”

People with low adiponectin levels might be more prone to developing PTSD

Adiponectin impairment is implicated in metabolic diseases such as obesity and type 2 diabetes. The new research shows the hormone has a role beyond its metabolic control, Dr Lu said.

“It is interesting that this hormone promotes fear extinction,” she said. “Increasing adiponectin levels or activating its specific receptors might facilitate extinction-based exposure treatments for PTSD and other trauma- and stress-related disorders.”

Dr Lu said people who have low levels of the hormone might be more prone to developing PTSD symptoms if they are exposed to a traumatic event. She noted that it will take years of work to learn if adiponectin can be translated into a therapy for human PTSD.

“To date, medication treatments for PTSD have been of limited benefit,” said Alan L. Peterson, Ph.D., ABPP, professor of psychiatry at the UT Health Science Centre and director of the STRONG STAR Consortium and the Consortium to Alleviate PTSD. “Dr Xin-Yun Lu’s work holds significant promise for the development of new, more effective medication treatments for PTSD.”