The average human lifespan is around 73.4 years. The Greenland shark’s potential lifespan surpasses 500 years, making that number seem pretty insignificant by comparison. These sharks, which inhabit the cold depths of the North Atlantic and Arctic Oceans, can live longer than any known vertebrate species. Looking at that number, the oldest Greenland sharks were alive when Galileo made his first telescope. Some could have even been mere pups when Shakespeare wrote Hamlet.
It turns out that these creatures could, aside from being living history, reveal insights beneficial for human health and the conservation of vulnerable species in the face of climate change.
During the Society for Experimental Biology Annual Conference in Prague, researchers revealed that the metabolic activity of the Greenland shark’s muscles remains constant as they age. This discovery contrasts sharply with most other species, where metabolic rates typically decrease over time, leading to aging and associated health issues.
Aside from being interesting from an oceanographic standpoint, the finding could hit closer to humans’ out-of-water homes. The discovery could answer some cardiovascular health questions.
Delving Deep into Shark Metabolism
“We want to understand what adaptations they have that allow (Greenland sharks) to live so long,” says Ewan Camplisson, a PhD student at the University of Manchester. “Most species show variation in their metabolism when they age. We want to determine if Greenland sharks also show this traditional sign of aging or if their metabolism remains unaltered over time.”
Previously, scientists assumed the shark’s lengthy lifetime was due to its frigid environment and limited movement. But the mechanisms causing this species’ extraordinary longevity appear to be significantly more complex.
Camplisson and his team tested muscle samples to see how active certain enzymes were. They looked at samples from Greenland sharks of different ages and from various temperatures. Surprisingly, they found that the enzyme activity stayed the same, regardless of the shark’s age. This suggests that the sharks’ metabolism doesn’t slow down as they get older, which might help explain their long lifespans.
“This is quite different to most animals which tend to show some variation in their metabolic enzyme activity as they age,” Camplisson said. “The results support our hypothesis that the Greenland shark does not show the same traditional signs of aging as other animals.”
Additionally, the study showed that the metabolic enzymes of Greenland sharks exhibited higher activity levels in warmer temperatures. This indicates that their muscle metabolism is not adapted explicitly for polar environments, which could affect their survival as climate change warms their natural habitats.
Implications for Human Health
The effects of this research extend beyond marine biology.
“By studying the Greenland shark and its heart, we may be able to better understand our own cardiovascular health,” he says. “These are issues that become progressively more common and severe with increasing age.”
Human and shark hearts are built differently — shark hearts have two chambers, while human hearts have four. However, on a cellular level, there are similarities that might offer valuable new knowledge. If scientists can figure out what makes Greenland sharks’ hearts avoid the usual age-related decline, they could use their discovery to improve human heart health, especially in treating heart diseases.
Heart diseases often stem from the breakdown of heart tissues and a drop in metabolic efficiency. By applying what scientists glean from Greenland sharks, researchers could develop treatments to keep heart muscles functioning well. And this could potentially reduce heart disease risk in older adults.
Further, learning how Greenland sharks maintain stable metabolism without usual signs of aging could lead to advancements in treating age-related conditions in humans. For example, researchers might develop treatments to keep elderly humans’ metabolism healthy, which reduces the risk of heart diseases.
Researchers could also study the particular enzymes that remain active in Greenland sharks to understand their structure and function better. If scientists can replicate or mimic these enzymes in humans, they could help maintain muscle and heart health, slowing the aging process in human tissues.
Exploring the genetic reasons behind the Greenland shark’s long life and stable metabolism could also uncover key genes or pathways that promote longevity and health. These genetic factors could lead to new gene therapies or drugs targeting these pathways in humans, helping the medical community maintain heart health and metabolic functions as we age.
Conservation Concerns
However, the study also highlights the Greenland shark’s vulnerability to climate change. As the oceans warm, these sharks, which do not reach sexual maturity until around 150 years old, face significant threats to their survival. Their slow reproduction rate and long generation times make them particularly susceptible to environmental changes.
“(W)ith such a long generation time, the species will have far less of a chance to adapt to anthropogenic changes in their environment,” Camplisson said.
In a world with rapidly changing climate conditions, long-lived species that cannot adapt may be the most at risk of extinction.
Camplisson plans to expand his research to test more enzymes and tissue types to better understand the shark’s metabolic activity.
“My ultimate goal is to protect the species, and the best way to do this is to better understand them,” he said.
By comprehensively studying these sharks, scientists hope to develop strategies to mitigate climate change’s impacts and other threats. Understanding the Greenland shark’s longevity and resilience can offer broader insight into biological aging and adaptation.
