Hagfish Heart Offers Cardiovascular Health Insight: Study

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It is seen by some as among the weirdest of sea creatures and almost certainly the slimiest. But learning how hagfish survive without oxygen could offer valuable insights for cardiovascular research, according to a new study co-led by a University of Guelph professor.

It is the first known study to examine how the isolated hagfish heart functions for extended time periods with little or no oxygen, said Prof. Todd Gillis, Integrative Biology.

Hagfish are ocean bottom-feeders that produce protective slime. They live in low-oxygen environments, including buried in mud on the ocean floor or inside the guts of dead animals, said Gillis, who worked with colleagues at the University of British Columbia (UBC) to learn more about hagfish hearts and metabolism.

The study was published in the December issue of the Journal of Experimental Biology.

“We are a long ways from finding answers to what this means for people. However, learning how the hagfish heart survives without oxygen, in a state of anoxia, can give us insight into human cardiovascular health, and specifically into strategies to protect tissue integrity after cardiac events,” said Gillis, who studies cardiac proteins and physiology.

Studies have found that hagfish can fully recover from 36 hours without oxygen. The human heart becomes rapidly damaged if it is deprived of oxygen for five minutes.

The team reached into the past by using a calorimeter, first used in Britain in the 1950s, to examine the hagfish heart. They modified the device to be able to detect the tiny amount of metabolic heat produced by the excised hagfish heart.

“We wanted to determine if the hagfish heart, deprived of oxygen, was generating any heat. This would mean that it is still metabolically active. We found that even after 16 hours of anoxia that the heart was maintaining metabolic heat production at a level similar to that as with oxygen,” said Gillis.

The researchers found that hagfish use glycogen, a form of energy storage in animals, to keep the heart working. Once the glycogen is depleted, the heart keeps beating, but scientists don’t know how.

That is what Gillis is studying now, along with biomedical sciences professor Glen Pyle, an expert in cardiac function during heart failure.

Both researchers belong to U of G’s Centre for Cardiovascular Investigations, connecting heart researchers from across the Guelph campus.