Jae-Sung Kim, Ph.D., an associate professor in the UF College of Medicine’s department of surgery and head of the Cell Death and Mitochondrial Biology Laboratory, was one of six presenters at the plenary session on basic science at the American Association for the Study of Liver Diseases (AASLD) meeting in Boston last month.
The association is the most prominent organization dedicated to liver study in the world.
Kim was selected out of more than 4,000 applicants to present during the session, he said. He spoke about his research team’s work to understand the causes and effects of impaired liver cell autophagy following surgery. Autophagy, the cell’s cleanup process, allows it to discard or repair abnormal or old components.
Surgery hampers autophagy in liver cells when blood flow to an area is cut off to reduce blood loss, Kim said. Kim and his graduate student, Thomas Biel, Ph.D., have identified a protein, called sirtuin 1, that is reduced in the cells after surgery and which also is a key supporter of optimal liver function.
“We found out that when the tissue is exposed to ischemia, (because) the surgeons are clamping the blood flow to reduce the blood loss, that increases calcium concentration in the tissue,” he explained. “Unfortunately, the increase in the calcium activates a calcium-dependent enzyme that’s called calpain.”
Calpain, in turn, reduces liver-cell levels of sirtuin 1. Sirtuin 1, the team’s research shows, works with a newly identified protein target called mitofusin-2 “to improve liver function after surgery.”
With low levels of sirtuin 1 due to surgery, the liver has trouble functioning as well as it did before surgery.
Kim noted that this research on liver cell function was carried out using both animal and human liver cells, making it more clinically relevant than studies that use only animal cells or models.
Kevin Behrns, M.D., a professor and chair of the department of surgery who is also a liver surgeon, and Ivan Zendejas, M.D., an assistant professor in the department of surgery and a liver transplant surgeon; are co-authors on this research with Kim.
The National Institutes of Health supports Kim’s research on autophagy in liver cells. His RO1 grant, first awarded in 2007, was competitively renewed in September 2014.