In the evolutionary chain, scientists suggest that early mammals evolved from being cold-blooded to warm-blooded in order to survive but they paid a high cost. This leaves us vulnerable to heart attacks.
"Many of the lower vertebrates can regenerate body parts and organs, including the heart, but most mammals cannot. This feature was lost somewhere in the ectotherm-to-endotherm transition," said Guo Huang, Ph.D., investigator at UCSF's Cardiovascular Research Institute, assistant professor of physiology and senior author of the new study, published March 7 in the journal Science.
The connection between endothermy and heart tissues (a so-called Faustian evolutionary bargain) lies in the thyroid hormone according to the study.
The thyroid gland produces a pair of well-studied hormones that are known to regulate body temperature, metabolic rate and normal heart function. But Huang's study revealed that these hormones are also responsible for shutting off cardiac cell division, thus preventing heart tissue from repairing itself after an injury.
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