Reprinted with the kind permission of Life Extension.
October 23 2017. The September 5, 2017 issue of Cell Metabolism reported research findings from the University of Utah School of Medicine that reveal a role for carnitine in the body’s response to cold temperatures.
“Cold-induced thermogenesis is an energy-demanding process that protects endotherms against a reduction in ambient temperature,” Judith Simcox, PhD, and colleagues write. “We found that the liver undergoes a metabolic switch to provide fuel for brown fat thermogenesis by producing acylcarnitines.”
“Cold stimulates white adipocytes to release free fatty acids that activate the nuclear receptor HNF4?, which is required for acylcarnitine production in the liver and adaptive thermogenesis,” they continue. “Once in circulation, acylcarnitines are transported to brown adipose tissue, while uptake into white adipose tissue and liver is blocked.”
Acylcarnitines are fatty acyl esters of L-carnitine that were found to increase in young mice during cold adaptation. “It was surprising to see acylcarnitines in the bloodstream,” Dr Simcox remarked. “The dogma was that once cells generated them, they used them right away.”
With aging comes a decline in the ability to adapt to cold exposure. In the current study, researchers found that a single dose of L-carnitine or palmitoylcarnitine improved aging-related cold sensitivity in mice. Because activating cold adaptation burns calories, improving the process be useful for more than the ability to tolerate cold environments.
“This work is putting a new face on an old character,” Dr Simcox stated. “We’re changing how we think about cold-induced thermogenesis.”